ft I I Digitized by tine Internet Arciiive in 2007 witin funding from IVIicrosoft Corporation littp://www.arcliive.org/details/anatomyofliumanboOOcruvricli ib THE ANATOMY OF THE HUmAM BODY. BY J. CRUVEILHIER, n07X8S0B OF ANATOMY TO THE FACULTY OF MEDICINE OF PARIS, PHYSICIAN TO THE HOSPITAL Of 8ALPETBIEBE, AND PRESIDENT OF THE ANATOMICAL SOCIETY OF PARIS. THE FIRST AMERICAN, FROM THP USJ" .^ARIS EDITION. Edited by GRANVILLE SHARP PATTISON, M.D., VK07ESSOR OF ANATOMY IN THE UNIVEItSITY OF NEW-YORK, MEMBER OF THE MEDIC0-CHIRUR0IC4I SOCIETY OF LONDON, OF THE WARNF.RIAN SOCIETY OF NATURAL HISTORY OF EDINBURGH, OF THE SOCIETE MEDICALS D'EMULATION, AND SOCIETE PHILOMATIQUE OF PARIS. THIRD EDITION. NEW-YORK: HARPER & BROTHERS, PUBLISHERS 329 & 331 PEARL STREET, FRANKLIN SQUARE. 1853. 1\ Entered, according to Act of Congress, in the year 1844, by Harper & Brothers, In the Clerk's Office of the Southern District of New-TC ork » . EDITOR'S PREFACE. Numerous and excellent as the works on Anatomy are which have lately been reprinted in this country, still they are, all of them, so de- cidedly inferior to the " Svstem op Anatomy by Cruveilhier," that the editor feels it unnecessary to offer any apology for having under- taken its republication. Occupying, however, as he does the Chair of Anatomy in the Metropolitan University of the United States, the pro- fession may perhaps think that it would have been more becoming of him to have published a System of Anatomy of his own, rather than to have undertaken the humble office of editing the work of a European anatomist. The reasons which have influenced him in the course he has pur- sued are the following : The science of Anatomy, viewed abstractly, and without reference to its connexion with Physiology, Pathology, and the Practice of Med- icine and Surgery, is to the student just commencing a very dry and uninteresting study. Yet in this way it is generally taught in the schools, each system being demonstrated separately, without refer- ence to the others, or to the Physiological and Pathological facts which its demonstrations tend to illustrate. The course followed by the editor, as a teacher of Anatomy, as his numerous students are aware, is very difierent. His great object has always been to endeavour to give interest to every lesson, by making it not a mere lecture on Anatomy, but a discourse illustrating Physiological and Pathological science, and elucidating the principles which should guide the practitioner in the practice of his profession. For the editor to have prepared a mere system of Anatomy would have been, in fact, merely to have undertaken the work of a compiler ; originality was out of the question, and no industry nor effort could have enabled him to have produced, on this plan, a better work tha^ the systems of Wilson, Quain, or the numerous other systematic trea- tises on Anatomy which have already been published. The editor having been a teacher of Anatomy for more than thirty years, from his experience is fully aware of the vast importance to the successful performance of his duties as an anatomical professor, of his being en- abled to interest his pupils and to fix and enchain their attention, that he is very unwilling to do anything which could have the effect of taking from the intoi'(>Ht or diminishing the freshness of his lectures. To pub- 13430 IV EDITOR 8 PREFACE. lish a system of Anatomy on the same plan as that adopted in his lec- tures, he would, of necessity, require to imbody in it the same Phys- iological, Pathological, and practical views with which they are illus- trated ; and to have done so> he cannot doubt but that the interest of his lectures would have been diminished, and that he would in future have found it much more difficult to fix the attention of his pupils. This consideration has decided him never to publish, so long as he is engaged in the duties of teaching, an original work on Anatomy. The system of Anatomy of Cruveilhier has recommended itself to the editor for publication : First, on account of its decided superiority to any other work on Anatomy which has ever been published ; and, secondly, from its being prepared, in some measure, in accordance with the plan which he follows in his lectures, many of its details be- ing illustrated by Physiological and Pathological references. In republishing the work, the editor has so restricted himself in the performance of liis task that he feels it can neither add to nor take from his reputation. He has merely furnished to the members of the profession in the United States The System of Anatomy op Cru- veilhier. Several reasons have influenced him in being sparing in the introduction of notes or additional matter. First. The work is in itself so perfect as not to require them. Secondly. It is very volumi- nous, and to have increased its size would have been to have diminish- ed its value. Thirdly. The editor has ever thought that an inde- pendent mind will shrink from mixing up and incorporating his thoughts with those of another. If a man wishes to obtain reputation as an author, let him publish an original work, and not attempt to gain popularity by illustrating and enlarging the labours of another. Since the English edition of Cruveilhier has been published in Lon- don, the first and second volumes of a second edition of the work have been published by the author in Paris. The editor has carefully com- pared the second edition with the fi»st, so far as it has been published, and has incorporated in the American edition whatever he thought could increase its value. He has, however, only followed the second edition when he thought that the changes introduced were improve- ments. In many instances, with the view of keeping down the size o^ the book, he has condensed into a few short paragraphs the substance of several pages. In the department of Myology the author has in his second edition made very numerous alterations from the first. As these, in the opinion of the editor, have rather diminished than in- creased the value of the work, he has only in a very few instances adopt- ed them. The student, he feels satisfied, will find the description of the muscles sufficiently minute. The subdivisions introduced, and the minutiae which are added to their descriptions in the second edition. EDITOR :> l'Rt:rACF would tend rather to embarrass than to piuiuure their improvement; he has, therefore, very generally preferred to follow the first edition in the description of the muscles. In the original work there are no engravings ; this is a great desidera- tum, which has been removed in the English edition by the introduc- tion of numerous woodcuts, selected with care from the best anatomi- cal engravings, and marked with letters of reference. This greatly enhances the value of the work. The translation, which is an excel- lent one, was made by Dr. Madden. Systems of Anatomy generally offer little interest except to the anatomical student. This cannot be said of the system of Anatomy of Cruveilhier. It imbodies a fund of information, in connexion with Physiology and Pathology, which will, in the opinion of the editor, pro- cure for it a place in the library of every physician and surgeon who feels any interest in his profession. If the members of the profession only procure the book and peruse it, he cannot doubt but that the cause of Anatomical science will be greatly promoted in the United States ; and should this be the case, the editor will be amply repaid for any trouble he may have had in undertaking the republication of Cru- veilhier. University of New-York, Sept. Ist, l^A^. k AUTHOR'S PREFACE. The study of man offers three very different objects for contemplation ; viz., his or- ganization, his vital functions, and his moral and intellectual faculties. The organization or structure of man is the object of anatomy, a science which in- vestigates every distinguishable material condition of the different parts that enter into the construction of his frame. Anatomy is a science of observation, and is, in this re- spect, susceptible of mathematical precision and physical certainty. The vital functions of man are the objects of physiology, which reveals to us the ac- tions of organs, with whose structure anatomy has previously made us acquainted. The science of physiology inquires into the various motions that occur within the human body, just as anatomy investigates the form of its component parts. All that we know, in fact, concerning material objects, may be resolved into a knowledge of their motions and their forms. As a moral and intellectual being, man is the object of the science of psychology, which contemplates him in the exercise of thought and volition, analyzes the operations of his mind and will, and classifies them according to their supremacy. A perfect acquaintance with man necessarily presupposes a combination of all that is taught by these three sciences ; and it is because his anatomy, his physiology, and his moral and intellectual endowments have not been studied by the same class of philoso- phers, that in the sciences relating to himself so much yet remains to be desired. Anatomy — the immediate object of this work — constitutes the foundation of medicine. In order to discover the precise seat of a defect in some complicated machine, and the means to be adopted for the reparation of its disordered mechanism, it is necessary to be acquainted with the relative importance, and the particular action of all its constitu- ent parts. " The human body," says Bacon, " may be compared, from its complex and delicate organization, to a musical instrument of the most perfect construction, but ex- ceedingly liable to derangement." And the whole science of medicine is therefore re- duced to a knowledge of the means by which that harmonious instrument, the human frame, may be so tuned and touched as to yield correct and pleasing sounds. But since anatomy forms, as it were, the vestibule of medical science, it is of im- portance that he who is entering upon its pursuit should fully understand the path he is about to tread ; it is necessary, therefore, to assign, on the one hand, the rank which medicine holds as a natural science, and, on the other, the position of anatomy among the various sciences relating to medicine. The term science, according to the admirable definition of the Roman orator, signifies certain knowledge, deduced from certain principles — cognitio certa ex principiis certis ex- orta. Sciences are divided into the metaphysical, the mathematical, and the natural ; but since the two former are not connected with our present subject, we shall direct atten- tion to the natural sciences only. The object of the natural sciences, or of physics, taken in its widest signification, is a knowledge of the materials of which the universe is composed, and of the laws by which they are governed. They are subdivided into the physical, and the physiological or zoo- logical. The physical sciences take into consideration all the phenomena presented by inor- ganic bodies; they comprise, 1. Astronomy, which studies the heavenly bodies as they revolve in space, and estimates, by the aid of numbers, the laws by which their move- ments are governed ; 2. Physics, properly so called, or the study of the properties of matter in general ; in aid of which, experiments are performed in order to exhibit phe- nomena in every possible light, and calculation is employed to render fruitful the results of experiment ; 3. Geology, or that science which studies the surface of the globe, and the successive strata which are met with in its interior ; which goes back far beyond all historical traditions, brings to light, as it were, the very depths of the earth, and traces, with a sure hand, the history of the globe, and the various revolutions it has undergone ; 4. Chemistry, which consists in the study of the reciprocal actions of bodies, when re- duced to their atomic condition. The zoological or physiological sciences embrace all the phenomena presented by living bodies. The science of botany examines into the structure and functions of plants ; but zoology, properly so called, investigates the organization and the life of animals. The examination into structure or organization constitutes anatomy. Physiology embraces the study of functions or of life. The facts presented to us in the zoological are of a totally different character from those comprised in the physical sciences, Inorganic bodies, in fact, are governed by constant and immutable laws, acting in perfect harmony with each other ; but living bodies are subject not only to physical, but also to vital laws, the latter of which are constantly struggling against the former. This struggle constitutes life ; death is the triumph of the physical over the vital laws. In consequence, however, of this continual strife, derangements of structure and disordered functions very often occur ; and these become more frequent and more complicated, in proportion as the organization is more highly developed, and the animal more elevated in the scale of creation. A knowledge of these derangements and of the proper means for restoring both or vui author's preface. ganization and life to a healthy condition, constitutes the science of medicine ; and the station which I have just assigned to this most important branch of zoological science will prove, better than any arguments, that the study of the physiological or healthy state of organization and of life should precede that of their pathological or diseased conditions ; and that anatomy forms the first link in the chain of medical science. Each science has its own methods of investigation, and its peculiar elements of cer- tainty. Metaphysics and moral philosophy have a metaphysical and moral certainty. The mathematical sciences set out from a small number of self-evident propositions or axioms founded upon the nature of things, proceed gradually from the known to the un- known, and trust to problems already demonstrated as to so many axioms, by means of which, as steps, they again ascend towards new truths. The natural sciences, again, are founded upon observation, and observation is merely the evidence of our senses ; hence arises the necessity of exercising them, in order to increase their acuteness and their activity. Facts, therefore, constitute the elements of the natural sciences ; and then reasoning follows, founded upon those facts and upon analogy. It would be absurd to study the natural sciences after the same method as metaphysics. It may readily be understood, that as the purely physical sciences are based upon con- stant phenomena, mathematics are directly applicable to them, and hence they are termed physico-mathematical sciences; but in the zoological sciences, effects are continually varying, according to their causes. Any attempts, therefore, to apply the art of numbers to the elements of medicine, would be to imitate the philosopher, Condorcet, who enter- tained the whimsical notion of subjecting moral probabilities to the test of mathematical precision ; who was anxious to substitute a-\-b for either oral or written legal testimony ; who admitted half proofs and fractional proofs, and then reduced them to equations, by means of which he supposed he could arrive at arithmetical decisions, regarding the lives, the fortunes, and the characters of his fellow-men. It must, however, be reluctantly confessed, that we can acquire a knowledge only of the surfaces of a body ; and that to say we are acquainted with its texture, is to state, in other words, that we have a knowledge of the smallest surfaces comprised within its general surface. Sight, touch, &c., the only means of investigation by which we can appreciate the qualities of matter in general, can recognise nothing but surfaces, appear- ances, and relative properties. Absolute properties they are unable to detect. With our organization, we shall never know of what material objects essentially consist, but only what they are in relation to ourselves. This work being essentially of an elementary nature, and in some measure adapted for the lecture-room, I have endeavoured to confine myself within narrow limits, and strictly to avoid all considerations which are not inunediately connected with the anato- my of organs. At the same time I have not forgotten that this work was intended for the student of medicine, and not for the naturalist ; I have, therefore, been induced, in the following pages, if not expressly to indicate, at least to direct attention to the more immediate applications of anatomy to physiology, surgery, and medicine. The objects which I have constantly had in view have been to exhibit the actual state of the science of anatomy ; to present its numerous facts in their most natural order ; to describe each fact clearly, precisely, and methodically ; to adopt such a method as would form an easy guide to the student, and not involve him in confusion ; and, lastly, to give to each detail its peculiar value, by invariably directing particular attention to the more important points, instead of confounding them with matters of less consequence, in an indigested and monotonous enumeration of facts. The following is the order in which the principal divisions of the subject have been treated. The first division comprises Osteology, Arthrology or Syndesmology, and Odontology. 1. Osteology, which, notwithstanding the great number of works on the subject, seema always to offer some new facts to those who study it with zeal, has been treated with the attention it deserves, as forming the basis of anatomical knowledge. An account of the development of the osseous system has appeared to me necessary for the comple- tion of its history. I have therefore considered the following points in connexion with the development of each bone : the number of ossific points ; the time of appearance of the primitive and complementary ossific points ; the periods at which the several points unite, and the changes occurring in the bone subsequently to its growth. By adopting this method, the most complicated ossifications are reduced to a few propositions easily retained in the memory. The inconvenience arising from including in a description of the bones all the attach- ments of the muscles, and nearly the whole anatomy of the part, is so totally at variance with a methodical arrangement of facts, that it is unnecessary to offer an apology for the changes made in this respect. Occasionally, however, I have mentioned those muscu- lar attachments which might serve to characterize the osseous surfaces on which they are situated. 2. Under the title of Syndesmology, or Arthrology, are united all the articulations of the human body. Assummg as the only basis of classification the form of the articula- ted surfaces, which is always in aocordanoc with the means of union and tlic movements of tlie joint. I have bnen iu'liieofl tn mo lify thi- division.'^ nsuallv adopted. Tlic runilt'Li- AUTHOR S PREFACE. IX throsis, or comyloid arliculaium, and the articulation by mutiial reception, form quite as natural genera as the enarthrosis and the arthrodia. It will, perhaps, be found that the characters of the different kinds of articulation, and in particular those of the anpxlar ginglymus, which I have called the trochlear articulation, and those of the lateral gingly- mus, or the trochoid articulation of the ancients, are more clearly defined than in other anatomical works. The mechanism, t. e., the movements of a joint, is so intimately connected with its anatomy, that it was impossible to pass it over in silence ; on the other hand, it was sometimes difficult to determine the limit which ought to distinguish an anatomical from a physiological treatise. I have endeavoured to avoid both extremes, by confining my- self strictly to the mechanism of each joint in particular, referring to works on physiol- ogy for the principal movements of locomotion, and of animal statics, such as waUiing, running, standing, &c. 3. Odontology, or the description of the teeth, concludes the first division. I have ta- ken care to point out that this juxtaposition of the bones and the teeth was founded upon their common indestructibility, and not upon the identity of their nature ; the bones be- ing organs composed of living tissues, while the hard portion of the teeth, on the other hand, is but the solidified product of secretion.* The second division includes Myology, Aponeurology, and Splanchnology. 1. In treating of Myology, I have preferred the topographical to the physiological ar- rangement of the muscles, for this reason only, that it admits of all of them being studied upon the same subject. To unite, as far as was practicable, the undoubted advantages possessed by both methods, I have given, at the conclusion of myology, a general sketch of the muscles, arranged according to their physiological relations ; and by grouping them, not after their order of super-imposition, but according to their several actions, I have arranged them around the articulations to which they may belong, and have point- ed out the extensors, the flexors, &c. A muscle being known when its attachments are ascertained, I have thought it advi- sable to commence the description of each by a brief announcement of its origin and in- sertion, as a sort of definition or summary. The particular details concerning its mode of insertion, whether it be aponeurotic or fleshy, and concerning the direction of its fibres, complete the description of each muscle considered by itself ; the history of which is concluded by an examination of its relations to neighbouring parts, and of its uses. The individual or combined action of the muscles, for the production of simple movements, follows so naturally after their description, and presupposes so correct and positive a knowledge of their anatomy, that it can be treated of with propriety only in a work on anatomy. The compound movements necessary for the consecutive or simultaneous action of a great number of muscles come within the province of physiology. 2. The aponeuroses, those important appendages of the muscular system, are separ- ately noticed, in connexion with the muscles to which they belong ; but I have also de- scribed them together under the head of Aponeurology. This combination of analogous parts possesses the twofold advantage of simplifying the science, by enabling one part to elucidate the structure of another, and of permitting us to discover the general laws according to which these structures are disposed. 3. With some modification, I have adopted that old division of anatomy, which treats of the viscera and organs, and which is known by the name of Splanchnology. The brain and the organs of the senses, which were included in this division in all anatomical works preceding those of Soemmering and Bichat, have been removed from it, and described with the other portions of the nervous system. The description of the heart, in like manner, will be found with that of the other organs of circulation. In short, the old classification of the viscera, according to their locality, that is, into those of the head, the neck, the chest, &c., has been replaced by a more physiological arrange- ment. Splanchnology will therefore comprehend a description of the organs of digestion and their appendages, of the organs of respiration (among which is included the larynx, or the organ of voice), and, lastly, the genito-urinary organs. To the inquiry why I have departed from the usual custom of placing splanchnology at the end of anatomy, I reply that, in order to study, with advantage, the vessels and the nerves, it is necessary to have a previous acquaintance with the organs to which they are distributed. The importance of the parts described in this division, and the practical results which flow from even the most superficial knowledge of their forms, connexions, and intimate structure, are at once my reason and excuse for extending, to so great a length, this portion of the work ; and, moreover, it is necessary to state, that there are many medi- cal practitioners who learn anatomy only from elementary works. The third and the last division treats of the organs of circulation, viz., the heart, arter- ies, veins, and lymphatics ; and of the sensory apparatus, viz., the organs of the senses, the brain, and the nerves. 1 . No part of anatomy, perhaps, has been better known than the arteries, since the appearance of Haller's admirable works ; I could neither have followed a better guide nor a more perfect model. * See n.ilr. n. 1S3. u X author's peeface. 2. The study of the vei?is has acquired an unexpected degree of importance, in conse- quence of the works of various physicians on phlebitis ; and our knowledge of them has been mucli extended by the researches of M. Dupuytren into the veins of the spine, and the excellent plates of this order of vessels published by M. Breschet. 3. The study of the lymphatics has been almost abandoned since the very remarkable publications of Mascagni : I have endeavoured to ascertain what credit was to be given to the assertions of some modern writers concerning the frequent communication be- tween the veins and the lyniphatics. 4. The work of Soemmering on the organs of the senses constitutes, perhaps, the high- est title to fame possessed by that great anatomist ; and it might even be said that he has left nothing for his successors to accomplish, did not the constant study of a science of observation unceasingly proclaim this important truth, that it is in the power of no man to declare, beyond this limit thou shalt not pass. The brain and the nerves, to which so many able and laborious inquirers have lately directed their attention, have been my favourite objects of investigation ; on account of their importance, and perhaps, also, from the difficulties attending their study. Not sat- isfied with simply tracing the nerves to the various organs in the body, I have studied them in the interior of those organs, and have endeavoured to ascertain the precise branches that are distributed to each particular part. I may add, that, in order to facilitate the dissection of the nervous system, and, indeed, of all the other parts of the body, I have presented, whenever it was necessary, a short account of the best method of preparation. With regard to the general spirit of this work, I have been anxious to render it clas- sical ; and have avoided, most scrupulously, that species of induction and analogical rea- soning, which, in a great measure, constitutes philosophical anatomy. To this kind of anatomy I have never even introduced any allusions, except when its general ideas and views (almost always ingenious, but usually bold and speculative) might elucidate our own subjects. All the descriptions have been made from actual dissections. It was only after hav- ing completed from nature the account of each organ that I consulted writers, whose imposing authority could then no longer confine my thoughts, but always excited me to renewed investigations wherever any discrepancy existed. Anatomy being, as already stated, the basis of medical science, we should greatly misapprehend its nature did we not consider it the chief of the accessory sciences of medicine. Without it, the physiologist rears his structure upon sand ; for physiology is nothing more than the interpretation of anatomy. It is anatomy that guides the eye and the hand of the surgeon ; that inspires him with that ready confidence, which leads him to search among structures, whose lesion would be dangerous or mortal, for some vessel that must be tied, or for a tumour which must be extirpated. Nor is it less indispensa- ble to the physician, to whom it reveals the seat of diseases, and the changes of form, size, relation, and texture, which the affected organs have undergone. Anatomy is, moreover, the science which, of all others, excites the greatest curiosity. If the mineralogist and the botanist are so eager, the one to determine the nature of a stone, the other to ascertain the characters of a flower ; if the love of their particular science induces them to undertake the most dangerous voyages, in order to enrich it with a new species, what ought to be our ardour in pursuing the study of man, that masterpiece of creation, whose structure, possessed of both delicacy and strength, ex- hibits so much harmony as a whole, and displays so much perfection in its parts ! And while contemplating this marvellous organization, in which all has been provided and prearranged with such intelligence and wisdom, that no single fibre can acquire the slightest addition, or undergo the least diminution of power, without the equilibrium be- ing destroyed and disorder being induced — what anatomist is there who would not feel tempted to exclaim, with Galen, that a work on anatomy is the most beautiful hymn which man can chant in honour of his Creator !* May this work inspire among students an ever-increasing ardour for the study of the organization of man, which, even if it were not the most eminently useful, would still be the most interesting, and the most beautiful of all the sciences. And what more powerful motive for emulation can present itself to a generous mind, than the idea, "that every acquisition of knowledge is a conquest achieved for the relief of suffering humanity !" Let it never be forgotten that, without anatomy, there is no physiology, no surgery, no medicine ; that, in a word, all the medical sciences are grafted upon anato- my as upon a stock ; and that the deeper its roots descend, the more vigorous will be its branches, and the more abundantly laden with flowers and with fruit. I must here express my acknowledgments to M. Chassaignac, the anatomical assist- ant to the Faculty, who has distinguished himself in several concours, and who has as- sisted me with the greatest zeal in the execution of this work. * " Sacrum sermonem quem ego Conditoris nostri verum hyranum compono, existimoque in hoc veram esse pietatem, non si tauroruni hecatombas ei sacrificaverim. et casias, aliaque sexcenta odoramenta ac unguenta suffumigaverim, sod si noverini ipse primus, deiude ct aliis exposuerim quffinam sit ipsius sapicntia.quce virtus. ciUii! bomtas."— (Galen, De usu part., lib iii.) CONTENTS. INTRODUCTION. Object and Division of Anatomy. — General View of the Human Frame. — Apparatus of Sensation— of lo- comotion— of Nutrition— of Reproduction. — General Plan of tlie Worli Page 1 APPARATUS OF LOCOMOTION. OSTEOLOGY. Of the Bones in Oeneral. The Bones— Importance of their Study.— General View of the Skeleton. — Number of the Bones.— Method of Description.— Nomenclature.— Situation in general.— Direction.— Size, Weight, and Density of Bones. — Figure. — Distinction into long, broad, and flat Bones. — Regions of Bones. — Eminences and Cavities. — Internal Conformation. — Texture. — Development, or Osteogeny.— Nutrition 5 The Vertebral Column. General Characters of the Vertebrse. — Characters peculiar to the Vertebrse of each Region. — Characters proper to certain Vertebrae. — Vertebree of the Sacro-coccygeal Region. — The Vertebral Column in general. — Development 18 The Scull. Composed of the Cranium and Face. — Cranial Bones — Occipital — Frontal — Sphenoid — CEthmoid — Parietal — Temporal. — The Cranium in general. — Development. — Bones of the Face— Superior Maxillary. — Palate. — Malar. — Nasal. — Lachrymal — Inferior turbinated. — Vomer— Inferior Maxillary. — The Face in general. — Cavities. — Development 33 The Thorax, or Chest. The Sternum.— Ribs.— Costal Cartilages.— The Thorax in general.— Development 64 The Superior, or Thoracic Extremities. The Shoulder.— Clavicle.— Scapula.— The Shoulder in general.— Development.— Humerus.— Ulna.— Radius. —The Hand— The Carpus and Carpal Bones.— The Metacarpus and Metacarpal Bones.— The Fingers.— General Development of the Superior Extremities 73 The Inferior, or .Abdominal Extremities. The Haunch.— Os Coxse.— The Pelvis.— Development.— Femur.— Patella.— Tibia.— Fibula.— The Foot.— The Tarsus and Tarsal Bones. — The Metatarsus and Metatarsal Bones.— The Toes. — Development of the Lower ExUemities. — Comparison of the Upper and Lower Extremities. — Os Hyoides . . . .87 The .Articulations, or Arthrology. General Observations. — Articular Cartilages. — Ligaments. — Synovial Membranes. — Classification of the Joints,— Diarthroses. — Synarthroses. — Amphiarthroses, or Symphyses Ill .Articulations of the Vertebral Column. Articulations of the Vertebra with each other. — Those peculiar to certain Vertebra;. — Sacro-vertebral. Sa- cro-coccygeal, and Coccygeal Articulations. — Articulations of the Cranium— of the Face — of the Tho- rax 115 Articulations of the Superior or Thoracic Extremities. Articulations of the Shoulder. — Scapulo-humeral. — Humero-cubital. — Radio-cubital. — Radio-carpal. — Of the Carpus and Metacarpus. — Of the Fingers 135 Articulations of the Inferior or Abdominal Extremities. Articulations of the Pelvis.— Coxo-femoral. — Knee-joint.— Peroneo-tibial. — Ankle-joint.— Of the Tarsus.— Tarso-metatarsal. — Of the Toes 154 ODONTOLOGY. Circumstances in which the Teeth differ from Bones. — Number. — Position.— External Conformation.— Gen- eral Characters. — Classification— Incisor — Canine— Molar.— Structure. — Development . . . .177 MYOLOGY. The Muscles in general. — Nomenclature. — Number. — Volume and Substance. — Figure. — Dissection. — Rela- tions. — Attachments. — Structure. — Uses. — Preparation. — Order of Description . . . .190 Muscles of the Posterior Region of the TVunk. The Trapezius.— Latissimus Dorsi and Teres Major.— Rhomboideus. — Levator Anguli Scapula.- Serrati , Postici. — Splenius. — Posterior Spinal Muscles. — Complexus. — Inter-spinales Colli. — Recti Capitis Postici, | Major et Minor. — Obliqui Capitis, Major et Minor. — General View and Action of the Posterior Spinal Muscles 198 Muscles of the Anterior Abdominal Region. The Obliquus Externus Abdominis. — Obliquuslntemus and Cremaster. — Transversalis Abdominis. — Rectus Abdominis.— Pyramidalis 208 Diaphragmatic Region 212 Lumbar Region. The Psoas and lUacus. — Psoas Parvus. — Ciuadratus Lumborum . . 214 ^ Lateral Vertebral Region. Tholnter-transversales and Rectus Capitis Lateralis.— Scaleni .217 # XU CONTENTS. Deep Anterior Cervical, or Prevertebral, Region. The Recti Capitis Antici, Major et Minor.— Longus Colli.— Action of these Muscles . . . Page 318 Thoracic Region. The Pectoralis Major.— Pectoralis Minor.— Sub-clavius.—Serratus Magnus. — Intercostalei.— Supra-costales. — Infra-costales. — Triangularis Sterni 220 Superficial Anterior Cervical Region. The Platysma Myoides. — Sterno-cleido-itiastoideus 234 Muscles of the Infra-hyoid Region. The Sterno-hyoideus. — Scapulo- or Omo-hyoideus. — Sterno-thyroideus. — Thyrohyoideus . . . 5^ Muscles of the Supra-hyoid Region. The Digastricus — Stylo-hyoideus. — Mylo-hyoideus. — Genio-hyoideus.— Their Action .... 228 Muscles of the Cranial Region. Occipito-frontalis. — Auricular Muscles 230 Muscles of the Palpebral Region. Orbicularis Palpebrarum. — Superciliaris. — Levator Palpebrae Superioris .... . . 231 JVasal Region. The Pjramidalis Nasi.— Levator Labii Superioris Alaeque Nasi.— TransTersalis, or Triangularis Nasi^— De pressor Alie Nasi. — N^so-labialis 233 Muscles of the Labial Region. The Orbicularis Oris. — Buccinator. — Levator Labii Superioris. — Caninus. — Zygontatici, Major et Minor. Triangularis. — Quadratus Menti. — Levator Labii Superioris. — Movements of the Lips and those of the Face 234 Muscles of the Temporo-maxillary Region. The Masseter and Temporalis 339 The Pterygo-maxillary Region. The Pterygoideiu Intemus. — The Pterygoideus Kxternus 240 Muscles of the Shoulder. The Deltoideus. — Supraspinatus. — Infra-spinatug and Teres Minor. — Sub-scapularis .... 341 Muscles of the Arm. The Biceps. — Brachialis Anticus. — Coraco-brachialis. — ^Triceps Extensor Cubiti 244 Muscles of the Forearm 349 Muscles of the Hand. The Abductor Brevis Pollicis. — Opponens Pollicis. — Flexor Brevis Pollicis. — Adductor PoIIicis. — Palmaris Brevis. — Abductor Digit! Minimi. — Flexor Brevis Digiti Minimi. — Opponens Digiti Minimi. — ^The Interos- seous Muscles, Dorsal and Palmar 260 Muscles of the Pelvis. The GIutsBi Maximus, Medius, et Minimus. — Pyriformis. — Obturator Intemus. — Gemelli, Superior et Inferior. ^^iuadratus Femoris. — Obturator Extern us. — Action of these Muscles 364 Muscles of the Thigh. The Biceps Cruris. — Semi-tendinosus. — Semi-membranosus. — Tensor Vagina Femoris. — Sartorius. — Triceps Extensor Cruris. — Gracilis. — Adductor Muscles of the Thigh 369 Muscles of the Leg. The Tibialis Anticus. — The Extensor Communis Digitorum. — Extensor Proprius Pollicis. — Peronei Longus et Brevis. — Gastrocnemius, Plantaris and Solaris. — Popliteus. — Tibialis Posticus. — Flexor Longus Pol- licis 377 Muscles of the Fbot. The Extensor Brevis Digitorum. — Abductor Pollicis Pedis. — Flexor Brevis Pollicis Pedis. — Adductor Pollicis Pedis. — Transveisus Pollicis Pedis. — Abductor Digiti Minimi.— Flexor Brevis Digiti Minimi. — Flexor Bre- vis Digitorum. — Flexor Accessorius. — Lumbricales. — Interossei 386 APONEUROLOGY. Geaeral Observations on the Aponeuroses. — Structure. — Uses 294 Particular Aponeuroses. Superficial Fascia. — Aponeuroses of the Cranium — of the Face — of the Neck — of the Thorax — of the Abdo- men— of the Pelvis — of the Thigh, Leg, and Foot — of the Shoulder, Arm, Forearm, and Hand . . 397 SPLANCHNOLOGY. General Observations on the Viscera.— External Conformation.- tructure.— Development.— Functions.— Dissection 330 Tbk Qsgans of Digestion and theik Aitendages. Alimentary or Digestive Canal. General Observations. — Division. — Mouth and its Appendages. — Lips.— Cheeks. — Hard and soft Palate. — Tonsils. — Tongue. — Salivary Glands. — Buccal Mucous Membrane. — Pharynx. — CEsophagus. — Stomach. — Small Intestine. — Large Intestine. — Muscles of the Perineum. — Development of the Intestinal Canal . 333 Appendages of the Alimentary Canal. Tlie Liver and its Excretory Apparatus.— The Pancreas. — ^The Spleen 384 The Organs of Respiration General Observations.— The Lungs and Pleura;.— The Trachea and Bronchi.— Development of the Lungs. —The Larynx— its Structure, Development, and Functions.— The Thyroid Gland .... 409 CONTENTS. XUl The Genito-Urinaey Organs. Tlie Urinary Organs. DiTiskw.— The Kidneys and Ureters.— The Bladder.— The Supra-renal Capsnles . . . Page 435 The Generative Organs. The Oenerative Organs of the Male. The Testicles and their Coverings.— The Epididymis, the Vasa Deferentia, and Vealcalsi Seminallte.— The Penis.— The Urethra.— The Prostate and Cowper's Glands 446 The Generative Organs of the Female. The Ovaries.- The FalloiMan Tubes.— The Uterus.— The Vagina.— The Urethra.— The Vulva . . 461 The Mammte. Number.— Situation. — Size.— Form. — Structure.— Development 473 The Peritoneum. The Sub-ombiUcal Portion. — The Supra-umbilical Portion.— General Description and Structure . . 479 ANGEIOLOGY. Definition and Objects of Angeiology 479 The Heart. General Description. — External and Internal Conformation. — Structure. — Development.— Functions. — The Pericardium . 479 The Arteries. Definition. — Nomenclature. — Origin. — Varieties. — Course. — Anastomoses. — Form and Relations. — Termina- tion. — Structure. — Preparation 496 Description of the Arteries. The Pulmonary Artery. Preparation. — Description. — Relations. — Size. — Development 499 The Aorta. Preparation.-Definition.— Situation. — Direction.— Size. — Division into the Arch of the Aorta, the Thoracic Aorta, and the Abdominal Aorta 501 Collateral Branches of the Aorta. Ehiumeration and Classification. — Arteries arising from the Aorta at its Origin, viz., the Coronary or Car- diac.^Arteries arising from the Thoracic Aorta, viz., the Bronchial, the (Esophageal, the Intercostal.— Arteries arising from the Abdominal Aorta, viz., the Lumbar, the Inferior Phrenic, the CcBliac Axis, in- cluding the Coronary of the Stomach, the Hepatic, and the Splenic, the Superior Mesenteric, the Inferior Mesenteric, the Spermatic, the Renal, and the Supra-renal or Capsular . . . . . .503 Arteries arising from the Arch of the Aorta. Enumeration and Varieties. — The Common Carotids. — ^The External Carotid — the Superior Thyroid — the Facial — the Lingual — the Occipital — the Posterior Auricular — the Parotid — the ascending Pharyngeal — the Temporal — the Internal Maxillary. — ^The Internal Carotid— the Ophthalmic — the Cerebral Branches of the Internal Carotid. — Summary of the Distribution of the Common Carotids. — Artery of the Upper Extremity.— The Brachio-cephalic. — The Right and Left Sub-clavians— the Vertebral and its Cerebral Branches, with Remarks on the Arteries of the Brain, Cerebellum, and Medulla — the Inferior Thyroid — the Supra-scapular — the Posterior Scapular — the Internal Mammary — the deep Cervical — the Superior Litercostal. — ^The Axillary — the Acromio-thoracic — the Long Thoracic — the Sub-scapular — the Posterior Circumflex— the Anterior Circumflex. — ^The Brachial and its Collateral Branches. — The Radial, its Col- lateral Branches, and the deep Palmar Arch. — The Ulnar, its Collateral Branches, and the Superficial Palmar Arch. — General Remarks on the Arteries of the Upper Extremity 513 Arteries arising from the Termination of the Aorta. Enumeration. — The Middle Sacral.— The Common Iliacs. — The Internal Iliac, or Hypogastric — ^the Umbil- ical — the Vesical — the middle Haemorrhoidal — the Uterine — the Vaginal — the Obturator — the Ilio-lurabar —the Lateral Sacral — the Glutsal — the Sciatic — the Internal Pudic. — Summary of the Distribution of the Internal Iliac. — Artery of the Lower Extremity. — The External Iliac — the Epigastric— the Circumflex Iliac. — The Femoral — the Superficial Epigastric — the External Pudic — the Muscular — the deep Femoral, its Circumflex and Perforating Branches. — The Popliteal, and its Collateral Branches. — The Anterior Tibial and the Dorsal Artery of the Foot. — The Tibio-peronenl — Peroneal — Posterior Tibial, and the In- ternal and External Plantar. — Comparison between the Arteries of the Upper and Lower Extremities . 552 The Veins. Definition.— The Venous System. — Origin of the Veins.— Course. — Anastomoses and Plexuses. — Varieties. — Termiaation. — Valves. — Structure. — Preparation. — Method of Description 573 Description op the Veins. The Pulmonary Veins Preparation.— Description.— Relations.— Size.— Peculiarities 577 The Veins of the Heart. The Great Coronaiy or Cardiac Vein.— The Small Cardiac Veins 577 The Superior, or Descending Vena Cava and its Branches, The Superior Vena Cava. — The Brachio-cephalic Veins — the Inferior Thyroid — the Internal Mammary — the Superior Phrenic, the Thymic, Pericardiac, and Mediastinal— the Vertebral. — ^The Jugular Veins, viz., the External — the Anterior — and the Internal. — The Encephalic Veins, and the Sinuses of the Diuu Mater, viz., the Lateral — the Superior Longitudinal — the Straight — the Superior and Inferior Petrosal — the Cavernous — the Coronary — and the Anterior and Posterior Occipital Sinuses — the Conflux of the Sinuses.— The Branches of Origin of the Jugular Veins— the Facial— tlie Temporo-maxiilarv- the Pos- k XIT CONTENTS. terior Auricular— the Occipital— the Lingual— the Pharyngeal— the Superior and Midcile ThsToid— the Veins of the Dipioe. — Summary of the Distribution of the Veins of the Head. — The deep Veins of the Upper Extremity — the Palmar, Radial, Ulnar, Brachial, and Axillary — the Sub-clavian. — The Superficial Veins of the Upper Extremity — in the Hand — in the Forearm — at the Elbow— €uid in the Arm. — General Remarks on these Superficial Veins Page 578 The Inferior, or Ascending Vena Cava and its Branches. The Inferior Vena Cava — the Lumbar or Vertebro-lumbar Veins — the Renal — the Middle Supra-renal — the Spermatic and Ovarian — the Inferior Phrenic. — The Portal System of Veins — the Branches of Origin of tlie Vena Porta— the Vena Portae — the Hepatic Veins. — The Common liiacs — the Internal Iliac — the Hemorrhoidal Veins and Plexuses — the Pelvic Veins and Plexuses in the Male and in the Female. — ^The deep Veins of the Lower Extremity — the Plantar, Posterior Tibial, Peroneal, Dorsal, Anterior Tibial, and Popliteal — the Femoral — the External Iliac. — The Superficial Veins of the Lower Extremity — the Inter- nal Saphenous — the External Saphenous 596 The Veins of the Spine. General Remarks. — The Superficial Veins of the Spine. — The Anterior Superficial Spinal Veins, viz., the Greater Azygos — the Lesser Azygos — the Left Superior Vertebro-costals — the Right Vertebro-costals — the Vertebro-lumbar — the Ilio-lurabar, and Middle and Lateral Sacral — the Anterior Superficial Spinal Veins in the Neck. — The Posterior Superficial Spinal Veins. — The deep Spinal or Intra-spinal Veins — the Anterior Longitudinal, and the Transverse Veins or Plexuses, and the Veins of the Vertebrte — the Posterior and the Posterior and Lateral Transverse Veins or Plexuses — the Medullary Veins. — General Remarks on the Veins of the Spine 605 The Lymphatic System. Definition, History, and general View of the Lymphatic System. — Origin. — Course. — Termination and Structure of the Lymphatic Vessels. — The Lymphatic Glands. — Preparation of the Lymphatic Vessels and Glands 611 Description of the Lymphatic System. The Thoracic Duct — the Right Thoracic Duct. — The Lymphatic System of the Lower Extremity — of t e Pelvic and Lumbar Regions — of the Liver — of the Stomach, Spleen, and Pancreas— of the Intestines — of the Thorax — of the Head — of the Cervical Regions — of the Upper Extremity and Upper Part of the Trunk 620 NEUROLOGY. The Organs of the Senses. The Skin — its External Characters, Structure, and Appendages. — The Tongue considered as the Orgaa of Taste. — The Organ of Smell — the Nose— the Pituitary Membrane. — The Organ of Sight — the Eyebrows — the Eyelids — the Muscles of the Orbit — the Lachrymal Apparatus — the Globe of the Eye, its Mem- branes and Humours — the Vessels and Nerves of the Eye. — The Organ of Hearing — the External Ear — the Middle Ear or Tympanum — the Internal Ear or Labyrinth — the Nerves and Vessels of the Ear . 62fl The Cerebro-spinal Axis. General Observations 681 The Membranes of the Cerebro-spinal Axis. General Remarks. — The Dura Mater — the Cranial Portion, its Structure and Uses— the Spinal Portion. — The Arachnoid — its Cranial Portion — its Spinal Portion — the Sub-arachnoid Fluid — their Uses. — The Pia Mater — its External Cerebral Portion 682 The Spinal Cord, and the Medulla Oblongata. General View of the Cord — its Limits and Situation — the Ligamentum Denticulatum. — Size of the Spinal Cord — Form, Directions, and Relations — the Cord in its Proper Membrane — the Proper Membrane, or Neurilemma of the Cord — the Cord deprived of its Proper Membrane. — Internal Structure of the Cord — Sections — Examination by means of Water, and when hardened in Alcohol — the Cavities or Ventricles of the Cord. — ^The Medulla Oblongata — Situation — External Conformation — Anterior Surface, the Ante- rior Pyramids and the Olivary Bodies — the Posterior Surface — the Lateral Surfaces — the Internal Struc- ture — Sections — Examination by Dissection, and under Water. — Development of the Spinal Cord.— De- velopment of the Medulla Oblongata. — Comparative Anatomy of the Spinal Cord. — Comparative Anatomy of the Medulla Oblongata 693 The Isthmus of the Encephalon. General Description and Division. — The Pons Varolii and Middle Peduncles of the Cerebellum — the Pedun- cles of the Cerebrum — the Superior Peduncles of the Cerebellum and the Valve of Vieussens — the Cor- pora Quadrigemina. — Internal Structure of the Isthmus, viz., of its Inferior, Middle, and Superior Strata. — Sections. — Development. — Comparative Anatomy 710 The Cerebellum. General Description. — External Characters and Conformation — Furrows, Lobules, Lamins, and Lamellte. — Internal Conformation — the Fourth Ventricle, its Fibrous Layers, its Inferior Orifice, and its Choroid Plexus. — Sections of the Cerebellum, Vertical and Horizontal. — Examination by Means of Water, and of the hardened Cerebellum. — General Viev% nf the Organ. — Development. — Comparative Anatomy . 715 The Cerebrum, or Brain Proper. Definition — Situation — Size and Weight — General Form. — The Superior or Convex Surtice. — 1 ne Inferior Surface or Base — its Median Region, containing the Inter-peduncular Space, the Corpora Albicantia, the Optic Tracts and Commissure, the Tuber Cinereum, Infundibuluni, and Pituitary Body, the Anterior Part of the Floor of the Third Ventricle, the reflected Part of the Corpus Callosum, the Anterior Part of the Longitudinal Fissure, the Posterior Part of the Longitudinal Fissure, the Posterior Extremity of the Corpus Callosum and Median Portion of the Transverse Fissiu-e, and the Transverse Fissure. — The Lateral Re- gions, including the Fissiu-e of Sylvius and the Lobes of the Brain. — The Convolutions and Anfractuosi- ties of the Brain, upon its Inner Surface, its Base, and its Convex Surface — Uses of the Convolutions and Anfractuosities. — The Internal Structure of the Brain — Examination by Sections — Horizontal Sections showing the Corpus Callosum, the Septum Luciduni, the Fornix and Corpus Fimbriatum, the Velum In- terpositum, the Middle or Third Ventricle, the Aqueduct of Sylvius, the Pineal Gland, the Lateral Ven- tricle?, their Superior and Inferior Portions, the Choroid Plexus, and the Lining Membrane and the Fluid of the Ventriclus — Mrdlan Vertical Section — Transverse Vertical Sections — Section of Willis. — General CONTENTS. XV Remirks on this Method of examining the Brain.— Methods of Varolius, Vienssens, and Gall.— Gall and Spurzheim's Views on the Structure of the Brain. — General Idea of the Brain.— Development. — Compar- ative Anatomy ... Page 725 The Nerves, ob the Peripheral Portion of the Nervous System. General Remarks. — History and Classification. — Origin, or Central Extremity. — Different Kinds. — Course, Plexuses, and Anastomoses. — Direction, Relations, and Mode of Division. — Termination. — Nervous Gan- glia, and the great Sympathetic System.— Conne.\ions of the Ganglia with each other, and with the Spi- nal Nerves.— Structure of Nerves.— Structure of Ganglia.— Preparation of Nerves . . . .759 Description of the Nerves. General Remarks.— Division into Spinal, Cranial, and Sympathetic Nerves 769 TVke Spinal JVerves. Enumeration and Classification. — ^The Central Extremities, or Origins of the Spinal Nerves — Apparent Ori- gins — Deep or real Origins. — The Posterior Branches of the Spinal Nerves — Common Characters — the Posterior Branches of the Cervical Nerves, their Common and Proper Characters — the Posterior Branches of the Dorsal, Lumbar, and Sacral Nerves. — The Anterior Branches of the Spinal Nerves — their General Arrangement 770 The interior Branches of the Cervical JVerves. Dissection. — Anterior Branch of the First, Second, Third, and Fourth Cervical Nerves. — The Cervical Plexus— its Anterior Branch, the Superficial Cervical— its Ascending Branches, the great Auricular and the External or Lesser Occipital— its Superficial Descending Branches, the Supra-clavicular— its deep De scending Branches, the Nerve to the Descendens Noni and the Phrenic — its deep Posterior Branches. — The Anterior Branches of the Fifth, Sixth, Seventh, and Eighth Cervical, and First Dorsal Nerves. — The Brachial Plexus — its Collateral Branches above the Clavicle — its Muscular Branches, Posterior Thoracic, Supra-scapular — opposite to the Clavicle the Thoracic, below the Clavicle the Circumflex — its Terminal Branches, the Internal Cutaneous and its Accessory, the Musculo-cutaneous, the Median, the Ulnar, the Musculo-spiral or Radial. — Summary of the Distribution of the Branches of the Brachial Plexus . 776 The interior Branches of the Dorsal JVerves, or the Intercostal JVerves. Dissection. — Enumeration. — Common Characters. — Characters proper to each 794 The interior Branches of the Lumbar JVerves. Enumeration.— The Lumbar Plexus.— Collateral Branches, Abdominal and Inguinal.— Terminal Branches — the Obturator Nerve— the Crural Nerve and its Branches, viz., the Musculo-cutaneous— the Accessory of the Internal Saphenous— the Branch to the Sheath of the Vessels— the Muscular Branches— the Inter- nal Saphenous 796 The Anterior Branches of the Sacral M'erves. Dissection. — Enumeration. — The Sacral Plexus. — Collateral Branches, viz., the Visceral Nerves — the Mus- cular Nerves — the Inferior Hemorrhoidal — the Internal Pudic and its Branches — the Superior Gluteal Nerve— the Inferior Gluteal, or Lesser Sciatic Nerve — the Nerves for the Pyramidalis, (iuadratus Fe- moris, and Gemelli. — Terminal Branch of the Sacral Plexus, or the great Sciatic Nerve. — The External Popliteal and its Branches — the Peroneal, Saphenous, Cutaneous, and Muscular Branches — the Musculo- cutaneous — the Anterior Tibial. — The Internal Popliteal and its Branches — the Tibial or External Saphe- nous — Muscular and Articular Branches — the Internal Plantar — the External Plantar. — Summary of the Nerves of the Lower Extremity. — Comparison of the Nerves of the Upper with those of the Lower Ex- tremity 804 T%e Cranial JVerves. Definition and Classification. — ^The Central Extremities of the Cranial Nerves, viz., of the Olfactory— of the Optic — of the Common Motor Oculi — of the Pathetic — of the Trigeminal — of the External Motor Oculi — of the Portio Dura and Portio Mollis of the Seventh — of the Glosso-pharyngeal, Pneumogastric, and Spinal Accessory Divisions of the Eighth — and of the Ninth Nerves 816 Distribution of the Cranial JVerves. The First Pair, or Olfactory Nerves. — ^The Second, or Optic Nerves. — The Third, or Common Mdlor Nerves. — The Fourth, or Pathetic Nerves. — The Fifth, or Trigeminal Nerves — the Ophthalmic Division of the Fifth, and its Lachrymal, Frontal, and Nasal Branches — the Ophthalmic Ganglion — the Superior Maxil- lary Division of the Fifth, and its Orbital Branch — the Spheno-palatine Ganglion, and its Palatine, Spheno- palatine, and Vidian Branches — the Posterior and Anterior Dental, and the Terminal Branches of the Su- perior Maxillary Nerve — the Inferior Maxillary Division of the Fifth — its Collateral Branches, viz., the deep Temporal, the Masseteric, Buccal, and Internal Pterygoid, and Auriculo-temporal — its Terminal Branches, viz., the Lingual and Inferior Dental — the Otic Ganglion. — The Sixth Pair, or External Motor Nerves. — The Seventh Pair — the Portio Dura, or the Facial Nerve — its Collateral Branches — its Terminal Branches, viz., the Temporo-facial and Cervico-facial — the Portio Mollis, or Auditory Nerve. — The Eighth Pair — its First Portion, or the Glosso-pharyngeal' Nerve — its Second Portion, or the Pneumogastric Nerve, divided into a Cranial, Cervical, Thoracic, and Abdominal Part— its Third Portion, or the Spinal Acces- sory Nerve.— The Ninth Pair, or the Hypoglossal Nerves.— General View of the Cranial Nerves . 824 The Sympathetic System of JVerves. €eneral Remarks.— The Cervical Portion of the Sympathetic. — The Superior Cervical Ganglion — its Supe- rior Branch, Carotid Plexus, and Cavernous Plexus — its Anterior, External, Inferior, and Internal Branch- es.— The Middle Cervical Ganglion. — The Inferior Cervical Ganglion. — The Vertebral Plexus. — The Cardiac Nerves ; Right, Superior, Middle, and Inferior ; Left.— The Cardiac Ganglion and Plexuses.— The Thoracic Portion of the Sympathetic- The External and Internal Branches.— The Splanchnic Nerves, Great and Small.— The Visceral Ganglia and Plexuses in the Abdomen, viz., the Solar Plexus and Semi- lunar Ganglia.— The Diaphragmatic and Supra-renal, the Coeliac, the Superior Mesenteric, the Inferior Mesenteric, and the Renal, Spermatic, and Ovarian Plexuses.— The Lumbar Portion of the Sympathetic. —The Communicating, External, and Internal Branches.— The Lumbar Splanchnic Nerves and Visceral Plexuses in the Pelvis. — The Sacral Portion of the Sympathetic. — General View of the Sympathetic System 854 DESCRIPTIVE ANATOMY. INTRODUCTION. Object and Division of Anatomy. — General View of the Human Frame. — Apparatus of Sen- sation — of Locomotion — of Nutrition — of Reproduction. — General Plan of the Work. Considered in its most extended signification, Anatomy* is the science which has for its object the structure of Uving beings. Living beings are divided into two great classes, vegetables and animals ; there is, therefore, a vegetable anatomy and an animal anatomy. When anatomy embraces, in one general view, the whole series of animals, comparing the same organs as they exist in ^he different species, it receives the name of zoological, or comparative anatomy. Zoological anatomy is denominated philosophical or transcendental, when from the com- bination and comparison of particular facts it deduces general results, and laws of orga- nization. When anatomy is confined to the examination of one species only, it receives the name of special ; such as the anatomy of man, the anatomy of the horse, &c. Physio- logical anatomy considers the organs in their healthy state. Pathological anatomy regards them as altered by disease. \Vhen physiological anatomy is confined to the examination of the external conforma- tion of organs, that is to say, of aU their qualities which may be ascertained without di- vision of their substance, it is called descriptive anatomy. If, on the contrary, it pene- trates into the interior of organs, in order to determine their constituent or elementary parts, it receives the name general anatomy, or of the anatomy of textures. Descriptive anatomy informs us of the names of organs {anatomical nomenclature), their number, situation, direction, size, colour, weight, consistence, figure, and relations ; it traces, in fact, the topography of the hmnan body. In more than one respect, it is to medicine what geography is to history. The anatomy used by painters and sculptors may be regarded as one of its dependances, and may be defined to be the knowledge of the external surface of the body, in the different attitudes of repose, and in its various move- ments. On this subject it may be observed, that the precise determination of the ex- ternal eminences and depressions may afford most important indications regarding the situation and state of deeply-seated parts, and is therefore worthy the attention of the physician. Descriptive anatomy, in the sense here meant, has arrived at a high degree of perfec- tion. It is to this branch that reference is made by those who affirm that nothing now remains to be done in anatomy. But although descriptive anatomy may be all that the surgeon requires to enable him to comprehend the lesions which most commonly fall under his notice, and to perform operations, it will by no means suffice for the physician or the physiologist. For their purposes, anatomical investigations must not be confined to the surface, but penetrate into, and analyze the substance of organs. Now such is the object of general or textural anatomy. By its means the different organs are re- solved into their component tissues : these tissues, again, are reduced to their simple elements, which are then studied by themselves, independently of the organs which they form ; and subsequently, by considering the elementary constituents as combined in va- rious proportions, the organization of even the most comphcated and dissimilar parts is made manifest. There is one species of anatomy which has of late been cultivated with the greatest success. I mean the anatomy of the fatus. The anatomy of the fatus, or the anatomy of the body at different periods of life, naiMcd the anatomy of evolution, has for its object the study of the development of organs, their successive modifications, and sometimes even the metamorphoses which they undergo, from the time of their first appearance until they arrive at perfection. Lastly, there is a species of anatomy to which the term of " applied anatomy''' may be given, because it comprehends all the practical applications of the science to medicine * The word Anatomy is derived from the Greek [ava, up, and rtuvai, I cut). It is, in fact, by means of dissection principally that we are enabled to separate and study the different organs. But injections, desicca- tion, the action of alcohol, concentrated acids, &c., are also means employed by the anatomist A 2 INTRODUCTION. and surgery. With this view, the body is divided into regions or departments, and each region into successive layers. The relation of the different layers is pointed out, and in each layer the parts Avhich compose it. In a word, the constant object is the solution of the following question : A region, or any part of the surface of the body being given, to determine the subjacent parts which correspond to it at different depths, and their order of superposition. This has generally been denominated the anatomy of regions, topographical or surgical anatomy, because it has hitherto been studied only with refer- ence to its uses in surgery. It may easily be shown, however, that with the exception of the limbs or extremities, the anatomical knowledge of which has few applications to medicine, properly so called, the study of regions is no less important to the physician than to the surgeon. To give it, therefore, a name corresponding with its use, it should be called medico-chirurgical topographical anatomy. Such are the different aspects under which anatomy may be regarded. The following work is essentially devoted to descriptive anatomy.* General View of the Human Body. Before entering on a detailed description of the munerous organs which enter into the composition of the human body, it is advisable to present a rapid sketch of the whole. Such general views, instead of embarrassing the mind, at once enlighten and satisfy it, by exhibiting the objects of its research in their true relations, and showing the end to be attained. There is one general covering, which, like a garment, envelops the whole body, and is moulded, at it were, round all its parts. This covering is the skin, of which the nails and hair are dependances. The skin presents a certain number of apertures, by means of which a communication is established between the exterior and the interior of the body. These apertures, however, are not formed by a mere perforation or breach of continuity in the skin ; on the contrary, this membrane passes inward at the circumference of these openings, and having undergone certain important modifications in its structure, forms the mucous membranes, a kind of internal tegument, which may be considered as a prolongation of the external envelope. We might, therefore, strictly speaking, regard the human body as essentially composed of a skin folded back upon itself This idea is, indeed, realized in some of the inferior animals, which consist of a mere tube or canal. In proportion, however, as we ascend in the scale, we find the layers which separate these two teguments become more and more increased in thickness, and cavities are at length formed between them. Nevertheless, however widely these membranes may be separated from each other, and however different they may be in external aspect, there are abundant analogies to establish unequivocally their common origin. Under the skin there is a layer of adipose cellular tissue, which gently elevates it, fiUa up the depressions, and contributes to impart that roundness of form which character- izes all animals, and particularly the human species. In some parts, there are muscles inserted into the skin, which are intended for its movement ; these are the cutaneoua muscles. In man they are very inconsiderable, and are confined to the neck and face, where they play an important part in giving expression to the physiognomy ; but in the larger animals they line the whole skin, and in certain classes, of very simple organiza- tion, they constitute the entire locomotive apparatus. The superficial veins and lymphatics traverse the subcutaneous cellular tissue : tlie latter, at various parts of their course, pass through enlargements denominated lymphatic ganglions, or lymphatic glands, which are grouped together in certain regions. Below the cellular tissue are the muscles, red, fleshy bundles, arranged in many layers. In the centre of all these structures are placed the bones, inflexible columns, v/hich serve for a support to all that surrounds them. The vessels and the nerves are in the immediate neighbourhood of the bones, and, consequently, removed as much as possible from external injury. Lastly, around the muscles and under the subcutaneous adipose tissue are certain strong membranes, which bind the parts together, and which, by pro longations detached from their internal surface, separate and retain in their situation the different muscular layers, frequently each particular muscle : these envelopes are the aponeuroses. Such is the general structure of the limbs or extremities. If next we examine the trunk, we find in its parietes a similar structure, but more in ternally are cavities lined by thin transparent membranes, named serous, on account of a liquid or serosity with which they are moistened. In these cavities are situated or- gans of a complex structure, called viscera, of which we shall give a rapid enumeration m an order conformable to the offices they perform in the animal economy. The hmnan body, as well as that of other organized beings, is composed of certain parts, denominated organs {bpyavov, an instrument), which differ from each other in * Descriptive anatomy ought, in strictness, to be confined to the consideration of the external characters ol organs, or what is understood by the term external conformation ; nevertheless, in order to present a complete view of each organ, after having described its exterior, we shall give a short account of its texture and deveJ- onment. GENERAL VIEV^'6'p¥kte' HUMAN BODY. 3 their structure and use, but are all combined, for the double purpose of the preservation of the individual, and the continuance of the species. To accomplish these purposes, the organs are distributed in a certain number of groups or series, each of which has a definite end to fulfil. This end is denominated a function : the series of organs receives the name of an apparatus. Of those necessary for the preservation of the individual, some are designed to place him in relation with external objects, and these constitute the apparatus of relation : the others are destined to repair the loss which the parts of the body are constantly suffering ; they form the apparatus of nutrition. The apparatus of relation may be subdivided into two classes : 1. The apparaius of sensation. 2. The apparatus of motion. Apparatus of Sensation. — The apparatus of sensation consists, 1. Of the organs of sense ; 2. Of the nerves ; 3. Of the brain and spinal cord. The organs of the senses are, 1. The skin, which possesses sensibility, the exercise of which constitutes tact. The skin being placed under the direction of the will, and rendered mobile in consequence of the peculiar mechanism of the human hand, is called the organ of touch. 2. The organ of taste, the seat of which is in the cavity of the mouth, that is, at the entrance of the digestive canal. 3. The organ of smell, placed in the nasal fossee, the commencement of the respiratory passages, by which we are en- abled to recognise the odorous emanations of bodies. 4. The organ of hearing, con- structed in accordance with the principles of acoustics, and placed in relation with the vibrations of the air. 5. TTie organ of sight, which bears relation to the hght, and ex- hibits a construction in harmony with the most important laws of dioptrics. The organs of sense receive impressions from without. Four of them occupy the face, and are, therefore, placed in the vicinity of the brain, to which they transmit im- pressions with great rapidity and precision ; and that organ seems, in its turn, to extend into them, so to speak, by means of the nerves. Indeed, the impressions received by the external organs would be arrested in them, were it not for certain conductors of such impressions : these conductors are the nerves — white, fasciculated cords, one ex- tremity of which passes into the organs, while the other is connected to the spinal mar- row and the brain, which are the central parts of the nervous system, the nerves con- stituting the peripheral part. Apparatus of Locomotion. — The apparatus of locomotion consists, 1. Of an active or contractile portion, the muscles. These are terminated by tendons, organs of a pearly white colour, which direct upon a single point the action of many forces ; 2. Of a pas- sive portion, the bones, true levers, which constitute the framework of the body, and tlie extremities of which, by their mutual contact, form the articulations : in the latter we perceive (a) the cartilages, compressible, elastic substances, which deaden the violence of shocks, and render the contact uniform ; (jb) an unctuous liquid, the synovia, secreted by membranes denominated synovial : this liquid performs the office of the grease em- ployed in the wheel- work of machinery ; (c) bands or ligaments, which maintain the con- nexion of the bones. Such is the apparatus designed to establish the relation between man and external objects. Apparatus of Nutrition. — The apparatus which performs in the human body the im- portant office of nutrition consists of the following parts : A. The digestive apparatus, which consists essentially of a continuous tube or canal, denominated the alimentary canal. This canal has not the same form and structure throughout the whole extent : on the contrary, it is composed of a series of vei7 dissim- ilar organs, all, however, contributing to the formation of one common passage. These organs are, 1. The mouth; 2. The pharynx; 3. The msophagus, or gullet; 4. The stom- ach ; 5. The intestines ; which are farther subdivided into the small intestines, consisting of the duodenum, jejunum, and ileum, and the large intestines, comprising the cacum, colon, and rectum. To this long tube, the greater part of which is contained in the abdomen, where it forms numerous reduplications, are annexed, 1. The liver, a glandular organ, whose office it is to secrete the bile, and which occupies the superior and right portion of the abdomen ; 2. The spleen, whose functions are involved in great obscurity, but which may, perhaps, be termed an appendix to the liver, on the left side ; 3. The pancreas, which pours a fluid into the duodemmi, by an orifice common to it and the biliary duct. B. On the internal surface of the digestive canal, and particularly that portion of it which bears the name of the small intestine, certain vessels open by numerous orifices or mouths,* and carry otfthe nutritive fluids prepared by the process of digestion : these are the chyliferous or absorbent vessels, which are also called lacteal vessels, on account of the white, milky aspect presented by their contents while absorption is going on. The absorbent appai'atus consists, also, of another set of vessels denominated lymphatics, be- cause they contain a colourless liquid named lymph, which they collect from a,H parts ol * (This must not be understood literally. See account of the lacteals, infni.l 4 INTRODUCTION. the body. All the absorbent vessels, of whatever order they may be, traverse at differ^ ent parts of their course certain grayish bodies, called lymphatic gangUmis or glands, and finally terminate in the venous system. C. The venous system arises from all parts of the body : it takes up, on the one hand, all those matters which, having been employed a sufficient time as part of the body, must be eliminated from it ; and, on the other hand, all those substances which are carried into the system, to contribute to its reparation : it is composed of vessels denominated veins which at various distances are provided with valves, and at last unite in forming two large veins called vena cavce, of which one, the superior, receives the blood from the upper part of the body ; the other, the inferior, brings back that which has circulated in the lower portion. These two venae cavae terminate in the central organ of the circalation, the heart, a hollow muscle, containing four contractile cavities : two on the right side, the right au- ricle and ventricle, and two on the left, the left auricle and ventricle. D. Next to these in order of function is the respiratory apparatus, composed of two spongy sacs, placed on each side of the heart, and occupying almost the whole of the chest : these are the lungs. They receive the air from a common tube, the trachea, which is surmounted by a vibratile organ, the larynx, which opens externally by the nose and mouth, and constitutes the organ of voice. E. From that cavity of the heart which is called the left ventricle, arises a large ves- sel, the aorta : this forms the principal and primitive trunk of the whole class of vessels named arteries, whose office it is to convey red blood to all parts of the body, to main- tain their heat and life. F. There still remains one other portion of the nutritive system, the urinary appara- tus, consisting of, 1. The kidneys, organs which secrete the urine : 2. The ureters, by means of which the urine, as soon as secreted, passes off into a spacious receptacle, the bladder, from whence it is at intervals expelled along a passage which has received the name of urethra. Apparatus of Reproduction. — ^The apparatus above mentioned is destined for individual preservation : the organs which secure the continuance of the species constitute the generative or reproductive apparatus. They differ in the male and in the female. In the male they are, 1 . The testicles, which prepare the spermatic or fecundating fluid , 2. The vasa deferentia, tubes which transmit this fluid from the testicle where it is se- creted to the vesiculse seminales ; 3. The vesicula. seminales, or receptacles of semen ; 4. The cjaculatory ducts, through which the semmal fluid passes into the urethra ; 5. The prostate and Cowpefs glands, glandular appendages of the organs for the transmission of the semen ; 6. The penis, by means of which the fecundating fluid is conveyed into the interior of the genital organs of the female. The generative apparatus in the female is composed of the following organs : 1. The ovaries, the function of which is to produce, or keep in readiness, the ovulum or germ ; 2. The uterine tubes, which transmit the germ, when fecundated, to the uterus ; 3. The uterus or womb, in which the product of conception remains and is developed during the period of gestation ; 4. The vagina, a canal which permits the passage of the foetus at its final expulsion ; 5. As appertaining to the system should be mentioned the mammary glands, which secrete the milk destined for the nourishment of the new-bom infant. Genkral Plan of the Work. There are two methods by which the numerous facts that come within the range of anatomy may be explained. The different organs may be studied in their order of super- position, or in the topographic order, a capite ad calcem ; in this way the most dissimilar parts are brought together, while others are separated which have the greatest analogy ; or they may be considered in a physiological order, i. e., an order founded upon the same grounds as serve for the classification of functions. This is clearly the most rational, because it has the incontestable advantage of preparing for the study of the functions by that of the organs. It may be easily seen, however, that this physiological arrangement should be modified according to the relative difficulty in the study of the different parts of the body ; for the great aim in a work of instruction should be to conduct the mind, by degrees, from simple and easy objects to those which are more complicated. It is for this reason that the consideration of the nervous system, which, in strict accordance with physiological arrangement, should be placed near to that of the locomotive appara- tus, is deferred. The object proposed has been to adopt an arrangement which would, as far as possible, reconcile both these views, and, at the same time, be compatible with the greatest economy of subjects for dissection ; and this appears to be secured by the method generally adopted, at least with a few slight modifications. The following table presents a view of the general plan of this work : f 1 . Of the bones— Osteology. , • . , , ^ 1 2. Of the articulations — SyndeHHology. 1. Apparatus of locomotion S 3. Of the muscles-Myology. 14. Of the aponeuroses — Aponeurolog . GENERAL OBSERVATIONS. B. Apparatus of digestion, apparams of respiration, ) Splanchnoloffv genito-urinary apparatus ....)' f Heart T 3. Apparatus of the circulation .... 'S Veins'*^ [ >Angeiology. I Lymphatics J f Organs of the senses'! 4, Apparatus of sensation and innervation . , < jj^^^ ""'^ ' ' > Neurology. LNerves . . .J APPARATUS OF LOCOMOTION. OSTEOLOGY. OF THE BONES IN GENER.4.L. The Bones — Importance of their Study. — General View of the Skeleton. — Number of the Bones. — Method of Description. — Nomenclature. — Situation in general. — Direction. — Size, Weight, and Density of Bones. — Figure. — Distinction into Long, Broad, and Flat Banes. — Regions of Bones. — Eminences and Cavities. — Internal Cofiformation. — Texture. — De- velopment of Osteogeny. — Nutrition. The bones are parts of a stony hardness, but yet organized and living. They serve as a support to all other parts of the body, are a means of protection to many, and aiford points of attachment to the muscles, in the midst of which they are situated. All the hard parts of the body, however, are not bones. The fundamental character of a bone consists in its being at once hard and organized. As the bones receive vessels for the purpose of nutrition at every part of their surface, they are surrounded on all sides by a membrane which is fibrous and vascular, named the Periosteum (nepl, around ; dareov, a bone). According to this definition, the teeth, horns, nails, and, in articulated animals, the ex- terior skeleton, are not to be considered as bones, but merely ossiform concretions. We may add, that true bones belong exclusively to vertebrated animals. The study of the bones constitutes Osteology, which may be regarded as the basis of anatomy, for without a knowledge of the bones it is impossible to become acquainted with the muscular insertions, or the exact relations between the muscles, nerves, vis- cera, and, above all, the vessels, for which the bones afford the anatomist invariable points of reference. Osteology has, therefore, ever since the time of the Alexandrian school, formed the commencement of the study of anatomy. In the present day, the transcendental anatomists have particularly engaged in the study of the osseous system, doubtless on account of the facility with which it may be investigated ; and from their labours, though in many respects speculative, a more ac- curate knowledge has been obtained of some of the nicer points of osteology, which had scarce attracted notice from the older anatomists. Lastly, from the admirable researches of Cuvier respecting fossil animals, osteology has become one of the most important bases of comparative anatomy and geology. By the study of bones the anatomist has been enabled to determine genera and species, no longer existing on the face of the globe, and to give, as it were, new life to these old and disjointed relics of the antediluvian animal kingdom. Thus the fossil bones, deposited in an invariable order of superposition in the crust of the earth, have been transformed into monuments more authentic than historical records. General View of the Skeleton. — ^The bones form a system or whole, of which the different parts are contiguous, and united to each other. The only exception to this rule is the OS hyoides, and yet the ligaments by which it is connected with the rest of the system are evidently the representatives of the osseous pieces, which in the lower animals con- nect this bone with the temporal. The assemblage of the bones constitutes the skeleton. It is called a natural skeleton when its different parts are connected by their own ligaments ; an artificial skeleton, on the other hand, is one of which the bones are joined together by artificial connexions, such as metallic wires, &c. The result of this union is a symmetrical and regular structure, essentially composed of a central column, denominated the vertebral column or spine, which terminates superi- orly in a considerable enlargement, the cranium, and inferiorly in certain immovably united vertebrae, which constitute the sacrum and coccyx. To this column the following appendages are attached : 1. In front of and below the cranium, a complicated osseous structure, the face, divided into two maxillce, the superior and inferior. 2. On each side twelve bony arches, flexible, elastic, and curved — the ribs, which are united in front to another column, the sternum. These parts, taken together, form the thorax. 3. Four prolongations, called limbs or extremities : two superior, or thoracic, as they are termed, because they correspond with the chest or thorax ; and two inferior or pelvic, so named g 6 OSTEOLOGY. on account of their connexion with the basin or pelvis, but better uamed^ abdominal a tremities. The thoracic and abdominal extremities are evidently modifications of the same fundamental type, and are essentially composed of the same number of analogous parts, viz. : 1. An osseous girdle, the superior constituted by the bones of the shoulder, the inferior by the pelvis. 2. A part Avhich may be in some measure regarded as the body of the limb, viz., the humerus, in the thoracic extremity, the femur in the abdominal. 3. A manubrium or handle, to use an expression of Galen, above the forearm, below the leg. 4. Lastly, digitated appendages which form the extremities, properly so called, viz., the hand and the /oof. Number of the Bones. — Authors do not agree respecting the number of the bones. Some, for instance, describe the sphenoid and the occipital as forming only one bone, while most anatomists consider them two distinct bones. Some admit three pieces in the sternum, which they describe separately. Many, after the example of the older writers, divide the haunch into three distinct bones — ^the pubes, the ischium, and the ileum : others recognise five pelvic or sacral vertebrae ; three or five parts of the os hyoides ; and, lastly, the ossa sesamoidea and the ossa wormiana- are omitted by some, but by others are reckoned in the enumeration of the bones. The ideas of certain modem authors with respect to the development of the bones, in- stead of dispelling the uncertainty which attaches to the enumeration of the parts of the skeleton, have tended not a little to increase the confusion, because many of them have made no distinction between bones, properly so called, and pieces of ossification. All doubt, however, in this respect will cease, provided we consider as distinct bones only those portions of the skeleton which are separable at the time of complete development. The time at which the osseous system arrives at its perfect development is between the twenty-fifth and thirtieth year. According to these views, we may count in the human body 198 bones, viz. : Vertebral column, including the sacrum and coccyx .... 26 Cranium 8 Face 14 Os hyoides 1 Thorax (ribs, sternum) 25 Superior extremities, each 32, viz., shoulder, arm, forearm, and hand 64 Inferior extremities, each 30, viz., pelvis, thigh, leg, and foot . 60 198 This enumeration does not include the ossa wormiana, nor the ossa sesamoidea, among which we include the patella. Of these 198 bones, 34 only are single : all the others are in pairs, which reduces the number to be studied to 116. Before proceeding to examine each piece of the skeleton in particular, we shall state the method we intend to pursue in the description. The chief points embraced by de- tailed descriptions of a bone are, 1. Its name; 2. Its general situation; 3. Its direction ; 4. Its bulk and weight ; 5. Its figure ; 6. Its regions ; 7. Its relations ; 8. Its internal conformation ; 9. Its intimate texture ; 10. Its development. Nomenclature. — Osteological nomenclature has many imperfections. Persuaded of the importance of a suitable choice of language in the study of all the sciences, some anatomists have endeavoured to introduce reforms, but with little success, the old de- nominations being still for the most part retained. From these modern systems of no- menclature we shall adopt only such terms as Eire strikingly appropriate, or such as have already been sanctioned by usage. We may here observe that the denominations of bones have been derived, 1. From their situation ; as the frontal, which is so called be- cause it is situated in the forehead : 2. From a resemblance, usually very obscure, to some well-known object, as the bones named tibia, scaphoid, malleus, incus, stapes ; or to some geometrical figure, as the cuboid : 3. From their size ; as the os magnum of the carpus, and the small bones or ossicula of the ear : 4. From some circumstance of their external conformation ; as the cribriform or ethmoid bone, the unciform or hooked bone : 5. From the name of the author who first most carefully described them ; as the ossicles of Ber tin, of Morgagni — swings of Jngrassias, &c. General Situation of Bones. — The situation of a bone is determined by comparing the place which it occupies with that occupied by other bones of the skeleton. In order to make this comparison, the skeleton is supposed to be surrounded by certain planes, which are thus denominated : 1 . A7i anterior plane, passing before the forehead, the breast, and the feet ; 2. A posterior plane, passing behind the occiput and the heels ; 3. A superior plane, placed horizontally above the head ; 4. An inferior plane, which passes be- low the soles of the feet ; 5 and 6. The two lateral planes, which complete the sort of case or parallelepiped with which we suppose the skeleton to be surrounded. Lastly, the skeleton being symmetrical, i. e., exactly divisible into two similar halves, we admit a seventh imaginary plane, the median or antero-posterior, separating these two halves. By the term median line is understood an imaginary line traced so as to mark exteriorly the division of all the symmetrical bone" of the skeleton into two similar halves. GENEEAL OBSERVATIONS. 7 These points being understood, nothing is more easy than to determine the position of a bone. If it approach nearer to the anterior plane than others with which it is com- pared, it is said to be anterior to them ; if it be nearer the posterior plane, it is said to be posterior to them. Let us take, for example, the malar or cheek bones. With respect to the whole face, they are placed at the anterior, superior, and in some degree the lateral part; relatively to the neighbouring bones, they are situated, 1. Below the frontal; 2. Above and a little external to the maxillary ; 3. Before the great wings of the sphenoid and the zygomatic process of the temporal. Direction of Bones. — The direction of a bone is absolute or relative. The absolute di- rection is expressed by the terms straight, curved, angular, or twisted ; in a word, it is the direction of a bone considered by itself, or independently of its situation in the skeleton. The long bones are never quite straight : sometimes they present a shght degree of cur- vature, as the femur ; sometimes their extremities are curved in opposite directions, like the letter S, as the clavicle : sometimes, again, they are twisted upon their own axes, as the humerus, the fibula, &c. The relative direction is determined by reference to .the planes which circumscribe the skeleton. Viewed in this manner, a bone is vertical, horizontal, or oblique. It is needless to enter into any explanation of the terms vertical and horizontal ; but with re- gard to the oblique direction, it may be stated that this is determined by the respective situations of its two extremities. For example, a bone is oblique when one extremity approximates the superior, the median, and the posterior planes, while the other ap- proaches nearer to the inferior, lateral, and anterior planes ; such a bone is said to be obhque from above downward, from within outward, and from behind forward. It is easy to see that in this way the situation of a bone relatively to the different planes may be determined with the greatest exactness. It should be observed, that in describing the direction of a bone, we should always set out from the same point. Thus, if the direc- tion of a bone from above downward is spoken of in determining its obhquity from be- fore backward, and from vrithin outward, we should always commence with the supe rior extremity. \^ Size, Weight, and Density of Bones. — The size of a bone may be measured by the ex- /* tent of its three dimensions ; but as an exact estimate is not in general required, it is sufficient to indicate the voliftne of each bone relatively to others, whence has arisen the division of bones into great, middle-sized, and small ; a distinction, however, altogeth- er vague and futile, since from the largest to the smallest bones there is so regular a gradation that the limits assigned must be quite arbitrary. The weight, or the mass of the skeleton compared with the rest of the body, the weight of each bone, and the comparative weight of different bones, are points of little inter- est ; such, however, is not the case with the specific weight or density of bones. In respect of density, viz., the number of molecules in a given volume, the bones are the heaviest of all organs. The truth of this assertion is by no means contradicted by the lightness of certain bones, which is only apparent, and which is caused by vacant spaces or cells in their substance. This density varies in different kinds of bones, in bones of the same kind, and even in different parts of the same bone. Thus, in the long bones, the greatest density is in the middle : the extremities of the long bones and the short bones have a much lower density. The broad or flat bones hold a middle place between the shaft of long bones and the short bones. Of these broad bones, those of the cranium are heavier than those of the pelvis. Age has a remarkable influence upon the specific weight of bones. It has been said that the bones of the aged are specificcdly more heavy than those of the adult, just as the bones of the adult are specifically heavi- er than those of the infant ; and this assertion appears the more probable, from it being generally admitted, as a law of organization, that the phosphate of lime increases in bones with the progress of age ; and it is well known that the weight of bones depends, in part, on the presence of this calcareous phosphate. But on this point, as on many others, experience has refuted these preconceived opinions. Thus, it is certain that the specific, as well as the absolute weight of bones, is much less considerable in the old person than in the adult ; and this difference depends upon the loss of substance which the bones undergo, in common with all other tissues, during the progress of age : thus, in aged subjects, the walls of the cylinder of the long bones are remarkably diminished in thickness, while the medullary cavity is proportionally increased. We rnay even af- firm, with Chaussier, that the medullary cavity of the shaft of long bones has a greater diameter, in proportion as the individual is advanced in age. In like manner, the cells of the spongy tissue become much larger, and their w-alls acquire an extreme tenuity. It may, nevertheless, be contended, that the weight of the osseous fibre, or, rather, of the osseous molecules of the old people, is gieater, comparatively, than that of the same parts in the adult ; and this presumption is ahnost converted into certainty by chemical iinalysis, which shows an excess of phosphate of lime in the bones of the aged : to re- move all doubts upon this point, it would he necessary to grind an adult bone and an old one, and to weigh in the balance an equal bulk of each powder. In this way the contra- dictory statements of certain authors might be reconciled. -K 8 OSTEOLOGY. The increasing fragility of bones, and the consequent frequency of fractures in old age, are CEisily explained, since along with the accumulation of phosphate of lime, which di- minishes the elasticity while it increases the brittleness, there occurs a diminution of bulk, and, consequently, there is less resistance. It is with respect to the quantity of calcareous phosphate alone that the osseous system can be said to preponderate in old age. Shape of Bones. — The shape of a bone is determined, 1. By comparison either with different known objects, or with geometrical figures : thus the frontal bone has been compared to the scallop-shells of pilgrims, the sphenoid to a bat with extended wings, &c. It may be readily conceived that, notwithstanding its want of exactness, this meth- od of comparison, so familiar to the ancients, cannot be altogether proscribed. The comparison of bones whose forms are so irregular with the regular solid figures of which geometry treats is no less inaccurate than the preceding ; nevertheless, we shall con- tinue, like other anatomists, to speak of the short bones as cuboidal, the shafts of long bones as being prismatic and triangular, the lower maxdlaj parabolic, &c. We shall speak of spheres, of cones, of ovoids, of cylinders, &c. 2. The symmetry or want of synmietry of bones is a fundamental point in the deter- mination of their figure : thus, some bones are divisible into two halves exactly resem- bling each other ; these are the syimnetrical or azygos bones, also called median, be- cause they always occupy the middle line. The others can not be divided into two sim- ilar parts : these are the asymmetrical bones, called also lateral or corresponding, because they are always in pairs, and situated on opposite sides of the median line. 3. The figure of a bone comprehends, also, the proportion which its three dimensions bear to each other. When the three dimensions, length, breadth, and thickness, are nearly equal, the bone is said to be short ; when the length and breadth are almost the same, and both greater than the thickness, the bone is called broad or fiat. Lastly, the predominance of one dimension over the two others constitutes the character of long bones. The distinction here drawn, however, is not altogether exact, because there are certain mixed bones which partake at the seime time of the character of the long and the broad bones. Some general observations upon the three great classes will not be out of place here, as they will be applicable in the description of the individual bones. Ge?ieral Characters of Long, Flat, and Short Bones. Of Long Bones. — The long bones are situated in the extremities, in the centre of which they form a set of pillars or levers placed upon each other. The bones of the abdominal extremities are generally longer and larger than those of the thoracic. The longest bones are in the upper part of the limbs ; it may be said, indeed, that the length of bones is in the direct ratio of their proximity to the trunk. The diameter of the long bones is smallest in their middle. From this part, as from a centre, they gradually increase in volume, and at their extremities are much enlarged, so as to present a diameter doubld or treble that of the shaft. Every long bone, therefore, presents a biconical form, i. e., is shaped like two cones united by their summits. A long bone consists of a shaft and extremities. The shaft of the long bones is almost always prismatic and triangular ; so much so, that in this respect the bones seem to be an exception to the general rule of organized bodies, which have usually a rounded form, and to approach nearer that of the mineral kingdom, the characteristic shape of which is angular. The extremities of long bones are enlarged, that they may serve, 1. For articula- tions ; 2. For the insertion of ligaments and muscles ; 3. For the reflection of tendons, the direction of which they alter. Each extremity presents a smooth articular surface, covered with cartilage in the fresh state, and not perforated by any foramina, and a non-articular portion, rough, pierced with apertures, and covered with eminences and depressions. Of Broad or Flat Bones. — These bones, intended to form the parietes of cavities, are more or less curved, and present for consideration a circumference and two surfaces ; the internal concave, the external convex. No single broad bone constitutes a cavity ; there are always a certain number united for this purpose. Some broad bones are alter- nately concave and convex on the same surface, as the haunch bones. In flat or broad bones there is no accurate correspondence between the inequalities, ridges, or depres- sions of the two surfaces. Thus, the iliac portion of the haunch bones, instead of pre senting a convexity on the inner surface, to correspond with the external iliac fossa, is hoUowed out into another depression, the internal iliac fossa. In like manner, in the cranium certain impressions and eminences exist on the internal surface, whUe the ex- ternal is uniformly convex, and almost smooth. The parietal, and even the occipital protuberances, would be twice or three times more prominent if the interior concavity were faithfully represented by a corresponding external prominence, and if this concav- ity were not in a great measure hollowed out from the substance of the bone. The circumference of broad bones being intended either for articulations or for inser- tions, is for this purpose greatly thickened. Thus the parietal bones, which are very GENERAL OBSERVAT[ONS. 9 thin at their centre, become considerably thicker at the circumterence. The broad bones present at their circumference sometimes a simple enlargement, when it is in- tended for muscular insertions only ; for example, the haunch bones : sometimes indent- ations of various kinds, and sinuosities, when it is to serve the purpose of articulation ; for instance, the bones of the cranium. Of Short Bones. — These are principally met with in the vertebral column, the carpus, and the tarsus ; in fact, wherever great solidity is required in connexion with slight mo- bility : several of them are always grouped together ; their form is extremely irregular, but generally cuboid ; they have also numerous facettes for articulation. The non-artic- ular portion is rough, for the insertion of ligaments and tendons. Regions of Bones. — There are so many objects to be considered on the surface of a bone, that it is necessary, in order to prevent the omission of any essential detail in the description, to divide the surface into a certain number of parts or regions, which should be successively examined. These different parts or regions have been denom- inated faces, borders, and angles. Thus, in the prismatic and triangular shafts of long bones, there are three faces and three borders to be considered ; in the flat bones, two faces and a circumference, which is again subdivided into borders and angles formed by the meet- ing of these borders. There are six faces in the short bones. These faces and borders are named sometimes, from their situation, superior, inferior, anterior, posterior, &c. ; some- times from the parts which they contribute to form, such as the orbital and palatine fa- ces of the superior maxillary bone ; sometimes from their relations to other parts, as the cerebral and cutaneous face of the bones of the cranium, the frontal, occipital, and tem- poral borders of the parietal bones. When the borders give insertion to a great number of muscles, it has been deemed advisable to divide these into three parts or parallel lines : the middle is then called the interstice, and the two lateral are named lips, the in- ternal and external lip ; the superior border of the haunch bone, and the linea aspera of the femur, are examples. Eminences and Cavities of Bones. — ^The bones present certain eminences and cavities, of which it is proper to take a general survey in this place. Eminences of Bones. — The osseous eminences or processes were divided by the an- cients into two great classes, apophyses and epiphyses, distinguished by the difference of their mode of development. According to their view, some of these eminences arise from the body of the bone, appearing to be nothing more than prolongations or vege- tations of its substance : these they called apophyses ; others, on the contrary, are formed by separate osseous centres or nuclei, which make their appearance at various times during the process of the development of bone : to these they gave the name of epiphyses. This distinction, however, founded upon incomplete observation, has been totally rejected, since the researches of M. Serres on Osteogeny have rendered it evi- dent that almost aU the osseous eminences are developed from isolated nodules ; so that an eminence, which at one time is an epiphysis, becomes afterward an apophysis. If, therefore, the majority of eminences are formed from separate osseous points, the dif- ference between them can apply only to the relative periods at which they become uni- ted to the body of the bone. A far more important distinction is that by which the eminences are divided into articular and non-articular. The articular eminences have received different names. 1. They are called dentic- ulations when they form angular eminences resembling the teeth of a saw ; these are best seen in the bones of the cranium. This kind of eminence is employed only in im- movable articulations. The others belong to joints which admit of motion, and have received the folloMing names : 1. They are called heads when they represent a portion of a sphere supported by a more contracted portion, to which the name of neck is given ; for example, the head and neck of the femur. 2. The term condyle is applied to them when they resemble an elongated head, or a portion of an ovoid cut parallel to its greatest diameter ; for exsim- ple, the condyles of the inferior maxilla. The non-articular eminences are, for the most part, designed for muscular insertions. Their appellations are in general derived from their shape. Thus, they are denominated, 1 . Prominences. When they are but slightly elevated, smooth, and almost equally ex- tended in all directions ; as the parietal and frontal eminences. 2. Mamillary Processes. When they resemble papillas ; for instance, the mamillary processes of the internal surface of the bones of the cranium. 3. Tuberosities. When they are of a larger size, round, but uneven ; for example, the occipital protuberance, the bicipital tuberosity (or tubercle) of the radius. 4. Spines or Spinous Processes. When, from their acuminated, but generaUy rugged form, they bear some resemblance to a thorn ; as the spine of the tibia, the spinous pro- cesses of the vertebrae. 5. Lines. When their length greatly exceeds their breadth ; as the semicircular lines of the occipital bone. When these lines are more prominent, and covered with asper- ities, they receive the name of linear asperae ; as the hnea aspera of the femur. B 10 OSTEOLOGY. 6. Crests. When they are elevated, and have a sharp edge ; as the external and inter nal crest of the occipital bone, the crest of the tibia. One of these eminences has been denominated the crista galli, because it bears some resemblance to the comb of a cock. 7. The term apophyses (or processes) has been retained for those eminences which are of a certain size, and appear to form, as it were, a little bone superadded to that from which they spring ; they are distinguished, for the most part, by epithets derived from their shape. Thus, the clinoid processes of the sphenoid are so called from their supposed resemblance to the supporters of a bed {kMvjj, a bed ; ehhc, shape). Pterygoid processes are those wliich are like wings (Trrcptf, a wing). Mastoid, such as resemble a nipple (fiaardc, manrmia). Zygomatic, such as have the form of a yoke {Cvyoc, a yoke). Styloid, such as are like a style. Coronoid, such as are shaped like one of the angular projec- tirns of a diadem.* Odontoid, such as resemble a tooth ; as the odontoid process of the second cervical vertebra. Coracoid, such as have the form of a raven's beak («dpaf, a raven) ; as the coracoid process of the scapula. Malleoli, euch as are like a hammer (malleus, a hammer). Some processes have received names, 1 . From the parts they contribute to form — orbitar processes, malar processes, olecranon {uTiivrj, the elbow ; Kpdvov, head) : 2. From their direction ; as the ascending process of the superior maxilla : 3. From their uses ; as the trochanters (jpoxau, to turn), because they serve for the insertion of muscles, which rotate the leg on its own axis. No part of the language of osteology, perhaps, is more faulty than the nomenclature of the eminences. Thus, how unlike is the spine of the scapula to the spinous processes of the vertebrae, or the styloid process of the temporal to the diminutive projection call- ed styloid of the radius ! Many eminences which perform analogous offices have re- ceived different names : thus, the eminences of the humerus, which give attachment to its rotating muscles, are called the great and small tuberosities ; while the correspond- ing parts of the femur have been denominated trochanters. While, therefore, we retain the names consecrated by usage, we shall be careful to point out the more rational terms substituted by modern anatomists, and particularly by Chaussier. The size of the eminences of insertion is in general proportional to the number and strength of the muscles and ligaments which are attached to them. To be convinced of this fact, it is only necessary to compare the male and female skeleton, or that of a man of sedentary habits and that of a person devoted to athletic exercises. This re- markable correspondence between the size of osseous eminences and the strength of the muscles which are inserted into them, has given rise to the opinion that these eminences are formed by muscular traction. It is easy to refute this notion, and without entering into details which belong to general anatomy, we shall prove, by facts, that the osseous projections enter into the primordial plan of organization, so much so, that they would have doubtless existed, even though the muscles had never exercised any traction upon the bones. I have twee had occasion to dissect the thoracic extremities of individuals, who, in consequence of convulsions during their earliest infancy, had suffered complete paralysis of these parts. The limb affected had scarcely the proportions of that of a child of eight or nine years, while the opposite hmb was perfectly developed. Never- theless, in this atrophied limb, the smallest as well as the largest projections were per- fectly marked. Moreover, very powerful muscles are often inserted into cavities, as, for instance, the pterygoid cavity of the sphenoid. Cavities of Bones. — Besides the great cavities of the skeleton, cavities in the formation of which many bones concur, and which are destined to lodge and defend the organs most important to Ufe, there are a great number of smaller excavations formed in the substance of the bone itself. These cavities, like the eminences, are divided into two great classes, articular and non-articular. The articular cavities have received different names. 1. The term cotyloid designates the articular cavity in the haunch bone, because it is deep and round, like a vessel known by the ancients under the name of kotvIt]. 2. The name glenoid (from y7ir)vr]) is applied to many articular cavities, which are more shallow ; for example, the glenoid cavity of the scapula, the glenoid cavity of the temporal bone. 3. The term al- veoli has been assigned to the cells or sockets in which the roots of the teeth are lodged. It is not correct, however, to consider as an articulation the union of the teeth with the jaws, because, as we shall afterward show, the teeth are not true bones. The non-articular cavities are to be considered with reference both to their figure and their uses. From their figure, they have received the following denominations : 1. Fossa, or pits, are cavities largely excavated, wider at the margin than at the bottom ; e. g., the parietal fossaj. 2. Sinuses are cavities with a narrow entrance ; as the sphenoidal sinus, maxillary sinus, &c. 3. The term cells is applied when the cavities are small, but nu- merous, and communicating with each other ; as the ethmoidal cells, &c. 4. Channels {gutters) are cavities which resemble an open semi-cyhndrical canal ; as the channels for the longitudinal and lateral sinuses of the scull. 5, These take the name of grooves * [Also from Kopiivt], a wow — like a crow's beak.] GENERAL OBSERVATIONS. 11 (coulisses) when they are lined by a thin layer of cartilage, for the passage of tendons ; as the bicipital groove of the humerus. The terra pulley or trochlea is applied to grooves which have their two borders also covered with cartilage. 6. Furrows are superficial impressions, long, but very narrow, and intended for the lodgment of vessels or nerves, as the furrows for the middle meningeal artery. 7. When more deeply excavated than the last, and angular at the bottom, they are named by the Frencli anatomists Rainures. 8. A notch {incisura) is a cavity cut in the edge of a bone.* The cavities wliich we have described exist only on one surface of a bone ; those which perforate its substance are usually denominated foramina or holes. 1. When a foramen has an irregular, and, as it were, lacerated orifice, it is named a foramen lacerum. 2. When its orifice is very small and irregular, it is called hiatus ; when the opening is long, narrow, and resembling a crack or slit, it is denominated a fissure ; as the sphenoidal fissure, the glenoid fissure, &c. 3. If the perforation runs some way through the substance of a bone, it is called a conduit or canal ; as the Vidian canal, carotid canal, &c. There are some canals which lodge the vessels intended for the nourishment of the bone : these are called nutritious canals. They are divided into three kinds. The first, which belong exclusively to the shafts of long bones, and to some broad bones, penetrate the substance of the bone very obUquely. These are the nutritious canals prop- erly so called. Anatomists carefully point out their situation, size, and direction, in de- scribing each bone. The second kind are seen on the extremities of long bones, on the borders, or adjoin- ing the borders, of broad bones. Cansds of this kind are generally near the articular sur- faces. Their number is always considerable. Bichat has counted 140 on the lower end of the thigh bone, twenty upon a vertebra, and fifty upon the os calcis. The third kind of nutritious canals are exceedingly small, and might be denominated the capillary canals of bones. They are found in great numbers on the surfaces of all bones. They may be easily seen by the aid of a good magnifying glass ; their presence is also indicated by the drops of blood which appear upon the surface of a bone on tear- ing off the periosteum ; for example, on the internal surface of the cranium, after sep- arating the dura mater. The diameter of these little canals has been calculated to be about the l-20th of a line. The farther progress of the above-mentioned canals is as follows : those of the first kind, which belong to the long bones, soon divide into two secondary canals, one ascend- ing, the other descending, and communicating with the central or medullary cavity. Tliose which are situated in the broad bones form winding passages, which run for a considerable distance in the substance of the bone. The canals of the second kind sometimes pass completely through the bone (as in the bodies of the vertebrae), and they communicate with the spongy tissue. The canals of the third kind terminate at a greater or less depth, in the compact substance of the long bones, and in the spongy tissue of the short bones. Such are the forms and general ar- rangement of all the cavities which exist on the surface of the bone ; the following are their uses : 1. They serve for the reception and protection of certain organs ; ex., the occipital fossa;, which receive a portion of the cerebellum. 2. For insertion or surfaces of attachment, as those on which muscular fibres are implanted, as the temporal and pterygoid foss£e. 3. For the transmission of certain organs, such as vessels and nerves which have to pass into or out of an osseous cavity ; such are the fissures, canals, fora- mina, &.C. 4. For increasing the extent of surface ; as the sinuses and cells connected with the organ of smelling, the surface of which they greatly enlarge by their numerous anfractuosities.t 5. For the easy passage of tendons, and sometimes for their reflec- tion, so that the original direction of the force is changed. To this class belong the bi- cipital groove of the humerus, that for the tendon of the obturator intemus, &c. They are generally converted into canals by means of fibrous tissue, which lines and com- pletes them. 6. For the nutrition of bones, such being the use of the three orders of nutritious canals already described. We must mention, along with these osseous cavi- ties, other markings or impressions seen on the surface of many bones ; for example, the shallow depressions in the lower jaw bone for the sub-lingual and sub-maxillary glands, the impressions named digital on the internal surface of the cranium. As the eminences of bones have been attributed to the mechanical effect of muscular traction, so the various impressions and VEiscular furrows upon the internal surface of the cranium have been considered to be the result of pressure and pulsation ; but it would be more correct to limit ourselves to the simple statement, that the impressions and eminences on the inside of the cranial bones exactly correspond with the elevations and depressions on the surface of the brain, and also that the osseous furrows for the middle meningeal artery correctly represent the ramifications of that vessel. * [There is great latitude amo!ig anatomical writers in the use of these terms.] t [Whatever other purpose tliey may serve, such cells and sinuses are, in most instances, to be regard- ed as a provision for increasing the bulk and strength of bones without a corresponding augmentation ol weight.T \ 12 OSTEOLOGY. We may here point out certain rules to be followed in describing the external confor- mation of bones. 1 . In describing the surface of a bone, it should be so divided that the description may comprehend but few objects at a time. Thus, a broad bone is to be di- vided into two surfaces, into angles and borders, which are to be successively studied. 2. The bone being thus subdivided into regions, each of these is then examined, care being taken regularly to proceed from one part to its opposite, i. e., to pass from the su- perior to the inferior surface, and from the anterior to the posterior. This is the only method which, in a long description, will guard against omissions and avoid tiresome repetitions. 3. It is also of great importance, in considering the objects presented by each region or surface, to follow an invariable and regularly progressive order. Thus, after exposing the objects placed in front, the examination should be continued uninter- ruptedly from this point backward. 4. In the symmetrical bones, it is advisable to de- scribe, first, the objects situated in the median line, and afterward those placed lateraDy. Internal Conformation of Bones. — The tissue of bones, like that of most other organs, presents the appearance of fibres, whose properties are throughout identical, but which, by certain differences in their mode of arrangement, give rise to two forms or modifica- tions of structure. To one of these the name of compact substance has been given ; to the other, that of sjioncry or cancellated substance. A subordinate modification of the lat- ter has long been described under the name of reticular tissue. The spongy or cellular substance has the appearance of cells and areola?, of an irregu- lar shape and variable size, all of which communicate with each other, and their walls are partly fibrous, partly lamellar. The compact substance seems to consist of fibres strongly compressed, so as to form a close, firm tissue. It is both fibrous and areolar. By means of careful inspection, softening the bone in nitric acid, and studying its devel- opment, it has been clearly proved that it is fibrous, and that in long bones the fibres are arranged longitudinally, v.hile in broad bones they seem to diverge like rays from the centre to every part of the circumference ; and that in the short bones they are disposed irregularly, so as to form a superficial layer or crust. The researches of Malpighi have conclusively shown that it is also areolar or spongy. By examining a bone softened by nitric acid, or studying it in the fcetal state, it may be seen that, in fkct, the compact tis- sue is nothing more than an areolar substance, the meshes of which are extremely close and much elongated. Accidental ossifications, and the diseases of bone which so fre- quently exhibit the compact tissue converted into spongy, and the spongy changed into compact, complete the demonstration.* In strictness, therefore, but one form of osseous tissue can be admitted, namely, the areolar, which presents itself under two aspects, sometimes being close, compact, and fasciculated ; sometimes spongy and cellular. Having thus become acquainted with these two forms of osseous tissue, their general arrangement in the different kinds of bones is next to be examined. Internal Structure of Long Bones. — A vertical section of a long bone presents, in the body or shaft, a cylindrical cavity, which, in the fresh state, is filled with a soft, fatty substance, named the marrow. This cavity, or medullary canal, is of greatest diameter at the middle of the shaft ; and, as it recedes from this point, it is narrowed and inter- sected at various parts by lamellae detached from the sides, and forming a sort of incom- plete partitions. Sometimes, however, there is a complete partition ; thus, I have seen the cylinder of a femur divided into two distinct halves by a horizontal partition situa- ted precisely in the middle of the bone. The medullary canal is not regularly cylindri- cal, nor does it correspond in figure with the external surface of the bone. It commu- nicates with the exterior by means of the nutritious canals, which sometimes run, for a considerable distance in the substance of the bone, parallel to the medullary cavity, with which they communicate by numerous apertures, and transmit the vessels as far as the extremities of the bone. Some have supposed that the cavity existed only in order to receive the man-ow, while, on the other hand, it has been maintained that the marrow existed only to fill up the cavity. Whatever be the uses of the marrow, it is certain that the existence of a cavity in the centre of long bones is an advantageous provision for strength ; for it is proved in physics, that, of two cylinders, composed of the same material in equal quantity, the one which is hollow, and whose diameters are, conse- quently, greater, will offer greater resistance than that which is solid. By the contri vance, therefore, of the medullary canal, there is an increase of strength without aug- * [The description in the text applies to the more obvious structure of bone ; but, when examined with the microscope, the osseous substance, both compact and spongy, is seen to consist of exceedingly fine lamell» laid on one another. In the compact external crust of bones, these lamellae run parallel with the surface ; they also surround, concentrically, the small cavities of the compact substance aad the cells of the spongy texture, the parietes of which they form. They are not to be confounded with the coarser layers and plates described in the compact substance by Gagliardi, Monro, and others of the older writers. Along with the la- mellce there are minute, opaque, white bodies, with extremely fine lines irregularly branching out from thera. These bodies, which can be seen only with the aid of the microscope, are named the osseous corpuscules ; they obviously contain ralcareous matter, and are, probably, minute ramified cavities lined with earthy salts. The earthy matter of bone, however, is not confined to the corpuscules, for the intermediate substance is »lfx) impregnated with it. For a representation of the minute structure of bone, see Mullefs Physiology, translated by Baly, pkte 1.] GENERAL OBSERVATIONS. 13 mentation of weight. There is another advantage in this arrangement, viz., the in- crease of volume without corresponding increase of weight ; for, since the bones are intended to give insertion to numerous muscles, it is necessary that their surfaces should not be reduced to too small dimensions ; but this must have been the result had the walls of the hollow cylinder been compressed so as to form a solid rod. The mar- row consists of two distinct parts : 1. The medullary membrane, which lines the walls of the canal. 2. The fatty tissue, properly so called, or the medullary hquid. The membrane, highly vascular, serves to nourish the internal layers of the bone : it possesses great sensibility and a high degree of vitality. The fatty tissue, on the con- trary, is altogether insensible. If a probe be introduced into the centre of the meduUa of a long bone in a living animal, no sign of pain is evinced so long as the instrument does not touch the walls of the cavity ; but whenever the walls are rubbed or scratched, the pain becomes excessive, and is manifested by piercing cries and violent struggles. The proportion between the thickness of the walls of the cylinder and the diameter ot the medullary canal varies not only in different individuals, but in the same person at dif- ferent periods of life. In the aged, the thickness of the walls is proportionally much less than in the adult : this is one cause of the great fragility of the bones in old age. Some- times in the adult the walls are so thin, that the bone breaks by the slightest force : in such cases, there is in some sort hypertrophy of the medulla and atrophy of the bone. It is in such cases that fractures occur from the simple effect of muscular contraction, or even from moving in bed. It is in the central canal of long bones that those very deUcate osseous filaments are observed, which, interlacing with each other, and forming large meshes, give rise to that variety of spongy tissue wliich has received the name of reticular, and which appears in- tended to give support to the medulla. The compact tissue diminishes, and the cells increase in number, the greater the distance from the centre of the bone, so that the ex- tremities are entirely composed of spongy substance covered by a thin layer of compact tissue. It appears that the compact tissue which fonns the shafts of the bones divides and subdivides into lamellae, in order to form the cells of the extremities. It is easy to perceive the advantage of a spongy structure in the usually voluminous extremities of the long bones : they could not have been compact without a great increase of weight, while the additional strength thus acquired would have been redundant, and altogether useless. The cells of the spongy substance are filled by an adipose tissue, similar to that which exists in the bodies of long bones : from its greater fluidity, it has been denominated meiullary juice. Internal Structure of Broad Bones. — If the surface of a broad bone be scraped, or if the bone be sawn across perpendicularly or obliquely, it will be found to consist of two lamellcB or tables, separated by a greater or less thickness of spongy tissue. Hence the two plates are insulated, and one may be fissured or broken without injury to the other. The thick- ness of the compact laminae and of the spongy tissue is not uniform throughout the whole extent of a broad bone. At the centre, for example, there is scarcely any spongy tissue, and hence the transparency of the bone at this part. Towards the circumference, on the contrary, the spongy tissue forms a very thick layer. In the bones which form the vault of the cranium, the spongy substance takes the name of diplo'e {6in?.6og, double), because it occupies the interval between the two tables. From what has been said regarding the internal structure of broad bones, it is evident that their distinctive character depends as much upon their internal as their external conformation, and therefore the ribs, which, according to their external characters, seem rather to belong to the long bones, have been classed among the broad, because they exhibit in their internal structure the characters of the latter kind of bones. Internal Structure of Short Bones. — The extremity of a long bone, if separated from the shaft, would represent a short bone, both in its external and internal conformation ; for a short bone is a spongy mass, covered by a thin layer of compact tissue. To their spongy structure the short bones, as well as the extremities of the long, owe their specific lightness. It should be observed, that what has been said concerning the internal structure of bones applies, in strictness, only to those of the adult, because the younger the subject, the less are the cells of the spongy tissue developed. And, in like manner, as the walls of the cylinder of long bones diminish in thickness, and the medullary cavity increases in diam- eter in the aged, so by the progress of age the walls of the cells become extremely thin, and the cells themselves very large. In some cases of disease, for example, after white swelling of the ankle-joint, I have observed true medullary canals in the cuboid bone and calcaneum ; and I have remarked in one case of cancer of the breast, that the ribs adjoining the tumour were hollowed out by a sort of medullary canal. It is to this dimi- nution of the osseous substance, this kind of atrophy of the bone, that I am disposed to attribute the fragility so often observed in the whole osseous system in cancerous diseases. Chemical Composition of Bones. — The bony tissue consists essentially of two distinct elements, one inorganic, the other organized. When a bone is subjected to the action of dUute nitric acid, the salts are removed ; it becomes flexible and elastic like cartilage, and though retaining its original bulk and form, it is found to have lost a great part of T^ OSTEOLOGY. its weight. By this process its saline ingredients have been dissolved, and nothing re- mains but its organic constituents, which, being subjected to boiling, present all the characters of gelatine. On the other hand, if a bone be calcined, the whole of its organic matter is destroyed, giving out during the process the odour of burned horn. A substance remains which preserves exactly the shape and size of the original bone, but at the same time is very light, porous, and so friable that it crumbles to powder under the slightest pressure. If the calcination be complete, the bone is rendered perfectly white, but it is black when the burning has not been carried sufficiently far ; it m^y even be vitrified by a more in- tense heat applied for a longer time. Prolonged exposure to the action of air and moist- ure in like manner remove the organized substance, and leave only a calcareous residue. The two elements of bone do not bear the same proportion at different ages. Certain diseases greatly affect the predominance of one or the other, producing almost the ssune effects as chemical agents. To the inorganic matter the bones owe their hardness and durability ; to the organized substance they are indebted for their vitality and the slight degree of flexibility and elas- ticity which they possess. The following are the results furnished by the cKemical analysis of M. Berzelius : 1. Okganized Part \ ^ Animal matter reduced to gelatine by boiling . 32-17 12. Insoluble animal matter rlS {Phosphate of lime 51'04 Carbonate of lime ....... ll'SO Fluate of lime 2'0 Phosphate of magnesia ri6 Soda and chloride of sodium 1"20 The bones are furnished with vessels : by one set arterial blood is transmitted, by another venous blood is returned. 1. The arteries are of three orders, corresponding with the osseous canals, which have been described in speaking of the cavities of bones. First Order, or Arteries of the Medullary Canal of Long Bones. — In each medullary canal there is at least one principal artery which enters by the nutritious canal and divides almost immediately into two branches, one ascending, the other descending. These subdivide into an infinite number of small branches, the interlacements of which form that vascular network called the medullary membrane. With this network the vessels of the second order freely anastomose after their entrance at the extremities of the bone. In consequence of this important communication, the vessels, notwithstanding the great difference in the manner of their entering the bone, can reciprocally supply each other with blood. In illustration of this, Bichat relates a singular case, in which the nutritious foramen of a tibia was completely obliterated, and yet the nutrition of the bone was un- impaired. The medullary artery gives off the twigs for those layers of compact tissue which form the parietes of the medullary cavity. The arteries of the second order, destined for the spongy tissue, enter the bones by the nutritious foramina of the second order ; but their number by no means corresponds with that of the foramina, which are for the most part destined for the transmission of veins. These arteries communicate hoth with the medullary artery already mentioned and vdth the arteries of the periosteum. The arteries of the third order, or the periosteal arteries, are exceedingly numerous. This class comprehends the innumerable httle arteries which, after ramifying in the perioste- um, enter the bone by the minute canals of the third order. These small vessels, spe- cially distributed to the exterior layers of compact substance, anastomose with the two preceding orders of vessels. 2. The veins of bones follow the course of the arteries. But there are peculiar venous canals in the interior of the broad and the short bones, and in the spongy extremities of the long bones. These canals were first described by M. Dupuytren in the cranial bones, where they are very obvious : they are perforated with lateral openings, by which they receive blood from the adjoining parts ; their parietes are formed by a very thin plate of compact tissue, and they are lined by a prolongation of the internal membrane of the veins. We shall afterward see that there is a complete analogy between these venous canals and the sinuses of the dura mater, the only difference being in the nature of their parietes, which are fibrous in the sinuses, but bony in the canals in question. I have remarked, that in the foetus and new-bom infants, the cells of the spongy tissue, which subsequently contain adipose matter, are filled with venous blood. Lymphatic vessels have not yet been actually demonstrated in the bony tissue ; but it is probable that they really exist there ; at least, the process of nutrition in bones, and certain morbid phenomena which they present, lead to the beUef of their existence. The cellular tissue also enters into the composition of the bones : it contributes to form their fibrous structure. Nerves can be demonstrated in connexion with most of the bones of the skeleton. But it is necessary to distinguish those nerves which merely pass through the bones from those which are distributed on their substance. DEVELOPMENT OF BONES. J|^ Development of Bones, or Osteogeny. From the time of their first appearance in the foetus, to the period of their complete development, the bones pass through a series of changes, which constitute one of the most important circumstances in their history. The investigation of these changes, or of the successive periods of development, is the object o{ osteogeny. The development of the bones, considered generally, presents three phases or periods, designated by the name mucous, cartilaginous, and osseous stage. 1. The mucous stage. The mucous condition, the cellular of some authors, has not been well defined. Some apply the term to that period of formation in which the bonea and the other organs of the body form but one homogeneous mass of a mucous aspect others use the term to signify a more advanced stage, in which the bones, acquiring a greater consistence than the surrounding parts, begin to show their development through these more transparent tissues. In the latter sense, the mucous stage is obviously no- thing but the commencement of the cartilaginous, and therefore the first acceptation is the only one to be retained. 2. The cartilaginous stage succeeds the mucous, though the time of the transition from the one to the other has not been precisely ascertained. Several anatomists are of opin- ion, with Mr. Howship, that the cartilaginous state does not necessarily intervene be- tween the mucous and osseous conditions ; that its occurrence is only satisfactorily de- monstrated in such bones as are late in ossifying, and that it constitutes a sort of provis- ional condition, in which the cartilage is employed to perform the office of bone. Bui when we take into consideration, in the first place, the rapid transition from the cartila- ginous to the osseous stage in certain bones, and, secondly, the translucency of newly- formed cartilage when of inconsiderable thickness, as in the cranium, where the carti- lage is scarcely to be distinguished from the two membranes between which it is placed, we can conceive that the cartilaginous stage may easily have been overlooked. On the other hand, the constant result of my observations proves that, in the natural process of ossification, every bone passes through the state of cartilage. When the different pieces of the skeleton assume the cartilaginous condition, the change occurs throughout their whole substance at once. The notion of central points of cartilaginification, corresponding with the points of ossification, is purely hypotheti- cal : a bone becomes cartilaginous in all parts simultaneously, and never by insulated points. The cartilage has the same figure as the future bone. Bones which are to be permanently united by intermediate cartilage, are formed from m ;. imitive piece of cartilage, as those of the cranium and face : those, on the other haau, which are connected together only by ligaments, are distinct and separable while in the cartilaginous -state. 3. The osseous stage. The cartilaginous condition of the skeleton is completed by the end of the second month ;* but ossification conunences in several places long before this period. The first point of ossification appears after the fourth week in the clavicle ; the second, in the lower jaw. From the thirty-fifth to the fortieth day points of ossifica- tion appear sometimes successively, in other cases simultaneously, in the thigh-bone, the humerus, the tibia, and upper jaw-bone. From the fortieth to the fifty-fifth day, points of ossification appear at short intervals in the annular portion of the uppermost vertebrse, in the bodies of the dorsal vertebrae, in the ribs, the tabular bones of the scull, the fibula, the scapula, the ilium, the nasal, palatine, and metacarpal bones, the phalan- ges of the fingers and toes, the metatarsus, &c. Once commenced, the ossification pro- ceeds with more or less rapidity in the different bones during the remainder of intra- uterine hfe. In the child at birth, the shafts of the long, as well as the broad bones, are far advan- ced in development. As to the short bones, the vertebrae are scarcely less early in their evolution than the long and broad bones ; the calcaneum, cuboid, and sometimes the as- tragalus, have points of ossification, but only commencing. The extremities of the long bones, with a single exception, the lower end of the femur, are as yet without ossifying points. The remaining short bones and extremities of long bones ossify subsequently. Of the tarsal bones, the scaphoid is the last to ossify ; the pisiform is the latest among the carpal bones ; the patella is ossified at the age of three years. In regard to the process of ossification, a question of the highest interest presents it- self, viz.. Is the successive appearance of the centres of ossification governed by any general law? The order of commencement of the points of ossification is in no way dependant on the size of the bones. It is true that the smaller bones, excepting the ossicles of the ear, are later in appearing ; but, at the same time, it is not the largest bones that are the earliest ; thus, the bones of the pelvis appear long after the clavicle. * [The relative time of ossification of the different bones, or, at least, the order in which it commences in them, is easily determined ; but owing to the uncertainty respecting the age of the embryo in its early stages, the absolute time of foetal life at which each bone begins to ossify is very uncertain, and, accordingly, the statements of many anatomists differ from that given in the text : thus the seventh week is assigned by some as the period when ossification commences in the clavicle. The age fixed by the author appears too early.] 16 OSTEOLOGY. Proximity to the heart or great vessels has no effect on the precocity of development. Though the ribs vt'hich are near the heart ossify speedily, the breast-bone, on the other hand, which is still nearer, is one of the bones latest in ossifying. Again, the anterior and inferior angle of the parietal, which is close to the anterior branch of the middle meningeal artery, is the part of the bone which last ossifies. The femoral artery lies on the confines of the os pubis and ilium, which at that part long remain cartilaginous. The true law which governs the order of appearance of the points of ossification is this, viz., that the period of formation is earlier or later in the several bones according to the period at which they are required to fulfil their oflice in the economy. Thus, the jaws being required to act immediately after birth, are ossified before the other bones of the head. In the same way, the ribs, destined for a function which must commence from the moment of birth, are for this purpose completely ossified : the vertebrae and bones of the cranium appear early, because of their use as protecting the spinal cord and brain ; and it is thus that the pretended correspondence between the rapidity of ossifica- tion and proximity to the nervous centres is explained. Although several of the bones are completed solely by an extension of the primitive nuclei of ossification, the greater number acquire, in addition to these principal or es- sential pieces, complementary points of ossification named epiphyses. Thus, while in the frontal the two original points of ossification suffice by their extension for the- com- pletion of the bone, the vertebrse, on the other hand, have three primary osseous nuclei, one for the body, and two for the laminae and processes ; and five complementary pieces of ossification, namely, two for the body, and one each for the tips of the spinous and transverse processes. The transition from the state of cartilage to bone is attended with the following phenom- ena : the cartilage becomes more dense ; its colour is at first a dull white, but subse- quently changes to deep yellow ; small irregular cavities are formed in its substance ; red vessels show themselves ; a bony point appears in the midst of these vessels, and this bony nucleus is spongy and penetrated with blood. The ossification spreads by lit- tle and little, always preceded by a great development of vessels ; so that, in attentively examining an ossifying cartilage, we find first an osseous point, then a red zone, next an opaque layer of cartilage which is permeated by canals, and, lastly, the remaining car- tilage traversed only by a few vascular canals which run towards the point of ossifica- tion. Moreover, it is always at some aepth within the substance of the cartilage that the first osseous points appear, and never at the surface. It is only in cases of accident- al or diseased ossification, as in the cartilages of the ribs, that it occasionally begins at the surface. It is unnecessary to pursue farther the immediate process of ossification • nor need we here discuss the purely speculative question, whether the bone is really a new part essentially distinct from the cartilage, which is absorbed and gives place to it, or merely a deposite of earthy phosphate in a cartilaginous tissue. In admitting that ossification is always preceded and accompanied by a great devel- opment of vessels, a fact proved incontestably by Haller and Bichat, I must, neverthe- less, decidedly dissent from the opinion that the appearance of blood in a cartilage is a constant indication of approaching ossification; for several cartilages have naturally bloodvessels, as may be seen in the cartilages of the ribs and larynx. Tlie study of the development of the bones does not consist merely in determining the number and time of appearance of their points of ossification : it comprehends, also, the ulterior changes which take place in the osseous system, viz., the union of the primitive points of ossification, and the appearance and junction of the complementary points of ossifica- tion. It is to be remarked, that the order of development and union of the points of os- sification does not always correspond with that in which they originally appear ; nay, it is often the reverse. Thus, the lower epiphysis of the femur is the earliest in appearing, and it is the last in joining ; while, on the other hand, the upper end of the radius is one of the latest of the epiphyses in appearing, but is joined to the bone before all, or nearly all, the rest. The junction of the pieces of ossification is not complete till about the age of twenty-five years, at which time the lower epiphysis of the femur unites with the body of the bone. General Mode of Ossification of Eminences and Cavities. — M. Serres, in a very remarka- ble work, has given, under the title of General Laws of Osteogeny, the results of his ob- servations concerning the development of azygos or median bones, and of eminences and cavities ; and with a rapid notice of these, we shall conclude what is to be said on the points of ossification. 1. By the law of symmetry, which, according to M. Serres, governs the development of all bones situated on the median line, every such bone is originally double, that is, composed of two separate halves, which, advancing to meet each other, are at last join- ed. Thus there are originally two osseous halves of the spinal column, and two demi- sterna. The basilar portion of the occipital, the body of the sphenoid, the cribriform plate of the ethmoid, the vomer, and the spinous processes of the vertebrae, have, ac- cording to this view, originally been double. But this law has many exceptions. Thus, although some of the pieces of the sternum are conunonly formed from two lateral DEVELOPMENT OF BONES. iT points, the first and the last are always, or almost always, developed from a single point in their middle. The bodies of the vertebrae are most commonly formed from a single primitive nucleus : the same is the case with the basilar portion of the occipital, the per- pendicular plate of the ethmoid, the vomer, and the spinous processes of the vertebrae. Instances of incomplete division of bones on the median Une must not be adduced in proof of the existence of two primitive points of ossification. 2. Every eminence, according to M. Serres, is developed by a special point of ossifi- cation. This is true generally : but how many eminences are formed merely by the ex- tension of ossification from the piece which supports them ! Where, it may be asked, is the special point of ossification for the articular processes of the vertebrae, the coronoid process of the ulna, the external and internal protuberances of the occipital, &c. 1 There are even double eminences developed from a single point, £is the condyles of the femur. SPEvery cavity is formed by the union of at least two pieces of ossification ; so that, when a bone furnished with a cavity consists of several pieces, the place of junction of these pieces is at the cavity. Thus, the three pieces of the os innominatum meet together at the cotyloid cavity. The same law, according to M. Serres, regulates the formation of the foramina and osseous canals of every kind, as the medullary cavity of the long bones, all the canals for vessels and nerves, as the carotid, vidian, &c. : according to the same law, all the foramina in the bones of the scuU are formed originally of two halves. But the facts are opposed to this doctrine when applied so universally. Progress of Ossification in the three Kinds of Bones. — 1. In the loTig hones. Ossifica- tion commences in their middle part. A small cylinder of bone appears, narrow in the middle, expanded at the ends, tubular within, perforated already with the nutritious fo- ramen, which is very obvious, and receives very large vessels. This Uttle cylinder grows gradually thicker and longer, extending towards the extremities of the bone, which it reaches about the time of birth ; while at this period the ossification is so far advanced in the body of the long bones, their extremities are not yet osseous. It is only at later periods, varying in different bones, that an osseous nucleus appears in the cartilaginous extremities, increasing and encroaching upon the portion of cartilage which separates it from the bony shaft, until that cartilaginous partition, gradually becoming thinner, is at last itself invaded by the ossification. All the long bones have two essential or princi- pal epiphyses, to which complementary epiphyses are sometimes added. The phalan- ges* are an exception ; they have only one. It is this process which is named junction of the epiphyses. The time of its completion is not confined to any very definite limits, but it is over by twenty or twenty-five years. Throughout the whole time of development the growth in length takes place, chiefly by ossification of the intermediate cartilage, which separates the epiphyses from the shaft, but partly, also, by longitudinal expansion of the ossified shaft itself The former mode of increase has been satisfactorily established by Hunter ; the latter is proved by the following experiment of Duhamel : Three needles being fixed in the shaft of a long bone of a bird, at measured distances, it is found that after a certain time they become farther separated, which proves that the osseous cylinder has undergone an elongation. 2. In the broad bones. 1. Among the broad bones, those which are symmetrical often conmience by two points placed one on each side of the median line. 2. The asymmet- rical bones are developed sometimes from a single point of ossification, as the parietal ; sometimes by several, as the temporal. One of the most remarkable circumstances in the development of broad bones is the sort of radiation by which the deposition of calcareous phosphate extends, which spreads from the centre where the first osseous point was deposited, and advances by divergent rays to all points of the circumference, forming bony striae separated by intervals, which are soon filled up by new osseous rays. As these rays are of unequal length, and are separated at the circumference by intervals of greater or less extent, it follows that a broad bone in the process of ossification must have at its circumference a scalloped or jagged border, like the toothed edge of a comb. It is this form of ossification which gives rise to the serratures of the sutures. The broad bones are proportionally much thinner in the early periods of ossification than subsequently, because at first the spongy texture is scarcely developed. At the time of birth, the primary pieces of ossification not having united except in very few places, and the ossification which spreads from the centre of the bones not having yet reached the limits of their circumference, it follows that the constituent parts of bones, and the edges of different bones which are destined in the end to meet together, are at this period separated by cartilaginous, and, in some measure, membranous intervals, which in the cranium constitute the fontanelles. After birth, ossification spreads more and more in the broad bones ; at the same time they increase in hardness and thickness, appearing as if to separate into two plates or tables, the interval between which be- comes filled with spongy tissue. The epiphysary or complementary points of ossification of some of the broad bones * [Also the clavicle, the metatarsal, and usually the metacarpal bones.] c 1 8 OSTEOLOGY. represent, in a certain degree, the epiphyses of the long bones. They occupy the cu- cumference, and are thence named marginal epiphyses. Thus, in the cartilaginous bor- der of the haunch-bone, which represents the crest of the ilium, a point of ossification commences, and extending along its whole length, forms a marginal epiphysis, which subsequently joins the rest of the bone, and in this respect is perfectly analogous to the epiphyses at the extremities of the long bones. The epiphyses, then, are not an exclu- sive attribute of the long bones, as Bichat maintained. They are found, also, in some of the short bones. But it would be indulging in a false analogy to class the Wormian bones, formed during the development of the cranium, with the epiphyses of the long and the broad bones ; for they have peculiarities which are never found in true epiphy- ses. Thus, 1. They are not joined by osseous union, as is the case with epiphyses, but always by suture. 2. There is no constancy in their time of appearance, nor in ^eir figure, which is irregular, nor in their size, which is, in general, greater the earlierlftey have appeared, because they have then had longer time to extend themselves before meeting the neighbouring bones. From what has been said, we conclude that the broad bones have a twofold mode of mcrease in breadth, namely, the successive addition of bony substance to their borders, and the formation of marginal epiphyses. In every broad bone which is formed from several pieces, and which has on its surface a part for articulation, this last becomes the centre in which the different pieces meet, and are ultimately joined when the ossi fication is completed. 3. In the short bones. These are the latest in being ossified ; a great number of them are still cartilaginous at birth. The short bones are not destitute of epiphyses, as is proved by the ossification of the vertebrae and calcaneum. Their ossification, in fine, presents the same phases, and follows the same progress, as that of the extremities of the long bones, which they resemble in so many respects. Changes which take place in Bones after Maturity. To obtain a complete notion of the development of the bones, we must not rest satis- fied with ascertaining the number of points of ossification, their successive appearance, and their mode of junction ; we must also study the changes which they undergo after they have attained their full growth. The increase of the bones in height teraiinates when their several pieces have become united : the time when this is accomplished varies from the age of twenty to thirty years ; but they continue to increase in thickness for a considerable time longer. In proof of this, we need only compare the bones of a young man with those of an adult of forty. In old age the bones still undergo important changes : the medullary canal of the long bones augments in width, and the tliickness of its parietes diminishes in proportion ; and something similar takes place in the broad and the short bones. Another important fact to be here mentioned is, that the relative proportion of calca- reous phosphate and animal matter undergoes continual changes in the course of life. Thus, by an analysis of Dr. I. Davy, it was shown that the proportion of calcareious phos- phate was a fifth less in a child of fifteen years than in the adult. The same chemist found that the proportion of phosphate of lime in an adult occipital was to that in an occipital bone of an aged person as sixty-four to sixty-nine. JSTutrition of Bones. The fact of the nutrition of bones, and the process of composition and decomposition in which it consists, appear to me to be demonstrated by the experiment with madder. If an animal is fed for some time with food impregnated with thfe juice of madder, its bones soon become coloured red, as may be ascertained by ampirfttfang a limb ; but, by suspending the use of that substance for some time, the bones recover their natural col- our. In this experiment, there is no doubt that the calcareous phosphate is the vehicle of the colouring matter, for the bones are the only parts that become coloured ; aU that is cartilaginous remains free from colour. We may infer from this that a twofold move- ment continually goes on in bones, by which new molecules are first deposited and then removed, after they have for a longer or shorter period formed part of these organs.* The administration of madder, moreover, demonstrates a fact, which was proved by Duhamel du Monceau in a very curious set of experiments, namely, that the growth of bones takes place by the successive deposition of new layers, formed by the undermost or contiguous layers of the periosteum. Thus, let a pigeon be fed with food impregnated with madder, suspend the use of the madder for a time, then renew it ; after this, the bones, when cut through, exhibit a red layer next their surface, then a white layer, then a red layer again. Thus the bones grow in two ways, namely, by the interstitial mode of groAvth, or by intussusception, which they have in common with the other tissues ; and, secondly, by juxtaposition. * A somewhat subtle objection would be the following : May not the colouring matter be deposited and again carried off without the particles of phosphate of lime being necessarily subject to the same vicissitudes ! THE VERTEBRAL COLUMN. 19 THE VERTEBRAL COLUMN. Gene-al Characters of the Vertehra. — Characters peculiar to the Vertehra of each Region. — Characters proper to certain Vertcbree. — Vertebrae of the Sacro-Coccygeal Regvm. — Tht Vertebral Column in general. — Development. The vertebral column (from the Latin word vertere, to turn, because ^' *• the body turns round this as an axis), spine, or rachis, is that long, flex- c _; ^^^ the transverse suture, which results from the articulation of the body of the sphenoid with the truncated inferior angle of the occipital bone, the spheno-occipital suture. On each side we observe the inferior occipital pro- tuberances, presenting certain variations in size in different subjects, to which Gall has attached great importance in his craniological system. These pro THE CRANIUM IN GENERAL. 47 tuberances are bounded above by the superior semicircular line of the occipital bone (J); they are crossed in the middle by the inferior semicircular Une {g), which is separated from the preceding by muscular impressions. Between the inferior semicircular line and the occipital foramen are also a number of inequalities for the attachment of mus- cular fibres. Still more anteriorly is the posterior condyloid fossa, and occasionally the posterior condyloid foramen {g). Outside the condyles are the jugular surface (t), the eminence of the same name, and the petro-occipital suture, running obliquely from behind forward and inward (i k), without any indentations, or even complete juxtaposition of the bones, and terminating behind in a large irregular opening (before i), the foramen lacerum postcrius, which is divided into two parts by a tongue of bone : the anterior is the smaller, and transmits the eighth pair of nerves ; the posterior is larger, and is call- ed the jugular fossa, from its receiving the enlarged commencement {sinus or diverticu- lum) of the jugular vein. The petro-occipital suture terminates in front in another irreg- ularly triangular opening, the foramen lacerum. anterius (k), which is closed by cartilage, and forms, in fact, a fontanelle between the edges of the occipital, temporal, and sphe- noid bones. In front of the petro-occipital suture is the inferior surface of the petrous bone, with its numerous asperities ; then, still proceeding from behind forward, we find the mastoid process (Z), the digastric groove (m), the stylo-mastoid foramen (7), the sty- loid and vaginal processes, the inferior orifice of the carotid canal (»), and the petro-sphe- noidal suture, at the external termination of which the osseous portion of the Eustachian tube opens by an orifice directed obliquely for\vard and downward. Thus all the sutures of the posterior half of the base of the cranium meet in the fora- men lacerum anterius. From its internal angle, the spheno-occipital suture stretches across to the same part of the opposite foramen. The petro-sphenoidal suture sets out from the external angle, and becomes continuous with the fissure of Glasserius ; and the petro-occipital suture extends from the posterior angle to the occipito-mastoid suture, which it joins at an obtuse angle : all these sutures are formed by juxtaposition, and not by mutual reception, as those of the roof of the scull. The lateral regions of the cranium are bounded, behind, by the lambdoid suture ; in front, by the external orbital process ; and above, by the temporal ridge. This region, more or less rounded in different subjects, is, nevertheless, the flattest part of the vault of the scull. Proceeding from behind forward, we observe, 1, the mastoid region, comprehend- ing the mastoid foramen (9, Jig. 21), the external auditory meatus, the glenoid cavity, and the transverse root of the zygomatic process ; 2, the temporal region or fos&a, con- cave in front, convex behind, bounded below by the zygomatic arch, which projects con- siderably from the head, more especially in carnivorous animals, and by a ridge which separates it from the zygomatic fossa. The temporal fossa is traversed by numerous sutures, arranged in the following manner : The fronto-parietal or coronal suture (c b. Jig. 22) descends vertically ; from its inferior extremity two others proceed, one in front, the sphe no-frontal, the other behind, the sphcno-parietal. Each of these soon divides into two branches. From the spheno-parietal the spheno-temporal descends, and terminates in the fissure of Glasserius ; the temporo-parietal (b i d) passes horizontally, and becomes continuous with the lambdoidal suture {df). The spheno-temporal and temporo-parie- tal sutures are, each, part of the squamous suturk. From the spheno-frontal suture the two following proceed : the fronto-jugal,* running horizontally, and the spheno-jugal, which passes downward ; the denominations of these sutures indicate at once the bones by which they are formed. The explanation which we have given appears the most Ukely to facilitate the recollection of these numerous sutures, by connecting them with each other. The following table exliibits a summary of all that has been stated : I^Spheno-frontaJ { gpheno-jugal. All these sutures are remarkable, from the circumstance that the bones which enter into their formation are cut obliquely like scales, and for the most part the edge of the bone above is overlapped by the edge of the bone below, so that each inferior scale, like the abutment of an arch, prevents the superior one which corresponds to it from being forced outward. (Vide Mechanism of the Cranium. Sy\desmology.) Internal Surface of the Cranium. In order to examine the internal surface of the cranium, it is necessary to make two sections, one horizontally from the occipital protuberance to the glabella {Jig. 23), the other vertically along the median line from before backward {Jig. 22). In the median line, proceeding from before backward, we observe the frontal crest or ridge, and the longitudinal groove, stretching from the frontal crest, along the roof of the scull to the internal occipital protuberance. In this groove, which is of no great depth, we find aline which indicates the place of union of the two pieces of the frontal hone during the earJy ♦ Tho malar bone is often called the jvigal bone, and hence the names of fronto-jugal and spheno-jugaL OSTEOLOGY. Fig. 23. Fig. 22. periods of life, and the internal surface of the sagittal suture. It receives the superior longi- tudinal sinus in its entire extent, and contains the internal orifices of the parietal foramina. On each side are the frontal fossae, correspond- ing to the protuberances of the same name, and the internal surface of the fronto-parietal (coronal) suture {be, Jig. 22); the encephalic surface of the parietal bone (^i dfc), and the parietal fossa; the lambdoid suture {df), and the superior occipital fossa. We may remark that the fossce are deeper than would "seem to be indicated by the external prominences, be cause they are partly formed at the expense of the bone itself; and that the sutures are less deeply denticulated on their internal than on their external aspect. Lastly, the whole internal surface of the vault of the cranium, but especially that of the parietal bones, is traversed by ramified grooves (i i), partly for veins, partly for ar- teries ; the venous grooves, which are not perceptible in all subjects, but which are very large in some, are distinguished from the arterial, as M. Breschet has pointed out, by their being perforated by numerous foramina. The base of the cranium {fig. 23), presents three series of fossae, or three regions, ar- ranged, as it were, in steps upon an inclined plane, from before backward, and from above downward. They are described as the anterior, middle, and posterior regions. Anteriw or cthmoido-frontal region. In this region we observe, in the middle, the eth- moidal fossa, in which is the foramen caecum ; tl^e crista gaUi (a) ; the ethmoidal grooves, and the for- amina with which they are perforated ; the ethmoi dal fissure, for the ethmoidal or nasal branch of the ophthalmic nerve ; the ethmoido-frontal sutures, run- ning from before backward ; the orifices of the inter- nal orbitary foramina ; and the trace of the ethnw-sphe- noidal suture, running transversely. Behind the eth- moidal fossa, the surface of the sphenoid is slightly impressed by the passage forward of the olfactory nerves. Laterally, we see the orbital plates {b), remarkable for the prominence of their mammillary projections, and traversed by small grooves for the ramifications of the middle meningeal artery ; and the fronto-sfhe- Twidal sutures (before c), which mark the union of the lesser wings of the sphenoid (c), with the orbital por- tion of the frontal bone {b). The orbital plates sup- port the anterior lobes of the brain. The middle region exhibits in the centre a fossa, in which we observe the depression for the olfactory nerves, the optic groove, and olivary process (before d) ; the pituitary fossa (d), deeply excavated behind ; the quadrilateral plate (behind d) ; the cavernous grooves ; and the anterior and posterior clinoid processes. On the sides we find very deep fossae, which correspond with the middle lobes of the brain, called middle lateral fossa of the base of the cranium; they are broad externally, narrow inter- nally, and are bounded in front by the posterior edge of the lesser wings of the sphenoid (c), and behind by the superior border of the petrous portion of the temporal bone (/«)• They are formed by the superior surface of the petrous portion, the internal surface of the squa- mous portion of the temporal, and the superior surface of the great wings of the sphe- noid. They present, successively from before backward, the sphenoidal fissure (or for- amen lacerum orbitale) ; the foramen rotundum, or superior maxillary '(2) ; the foramen ovale (3) ; the foramen spinosum (4) ; the internal orifices of the foramen lacerum an- terius and carotid canal (before 5), and the hiatus Fallopii. We see here, also, the union of the sphenoid with the squamous and petrous portions of the temporal bone, forming the sphcno-tcmporal {i and c) and pctro-sphe?ioidal sutures. This fossa is traversed from be- hind forward and outward by a groove {i 4), which commences at the foramen spinosum, passes along the external border of the sphenoid, or, rather, is hollowed out from the spheno-temporal suture, and divides into two branches ; the anterior, the larger, pro- ceeds to the anterior inferior angle of the parietal bone, with the anterior ramified groove m which it becomes continuous ; the posterior is directed horizontally backward to the posterior inferior angle of the parietal bone. In some cases, the portion of the groove which extends from the foramen spinosum to the summit of the lesser wing of the sphe- noid, almost equals in diameter the lateral grooves, and it is then almost always pierced by foramina : it contains the middle meningeal artery, and a large vein THE CEANIUM IN GENERAL. 49 Posterior region of the base of the cranium. This region presents in the middle the ba- silar groove (k) ; the spheno-occipital suture, the foramen magnum (m), the anterior con- dyloid foramina (8) {Ji,fig. 22), the internal occipital ridge, and protuberance {o,fig. 21). Laterally, the inferior oceipital fossa, the deepest in the scull, which are formed by the posterior surface of the petrous portion of the temporal bone, almost the whole of the en- cephalic surface of the occipital bone, and the posterior inferior angle of the parietal. We find here the foramen lacerum posterius (7), the suture which unites the temporal to the occipital bone, and along the petro-occipital suture, a smedl groove named inferior pe- trosal (on each side of A:), The inferior occipital fossa is bounded above by a broad and deep groove (n), intend- ed to lodge the lateral sinus, and called the lateral groove. It commences at the internal occipital protuberance (o), and proceeds horizontedly outward to the base of the petrous portion, where it is again enlarged, and passes roimd, extending downward and inward along the occipital fossa, until it arrives at the occipito-meistoid suture (r), where it rises and terminates in the foramen lacerum posterius. The inferior occipital fossa is divi- ded into two parts by this groove : an anterior, formed by the posterior face of the pars petrosa, and a posterior, formed by the occipital bone. In this groove, the mastoid fora- men, the posterior condyloid foramen, when it exists, and the superior and inferior petrosal grooves open. The dimensions of the lateral grooves are extremely variable ; inost commonly the left is smaller and shallower than the right, especially in its horizontal portion. Of the eminences and depressions on the internal surface of the cranium, the most deeply marked are those situated upon the base. This is more especially the case with regard to the orbital plates and the middle and lateral fossae. Since the publication of the works of Gall and Spurzheim, anatomists have re-adopted the opinion of the an- cients, who regarded these eminences and depressions as corresponding respectively with the anfractuosities and the convolutions of the brain : the cranium, in fact, is mould- ed upon the brain ; to be convinced of which, it is only necessary to repeat the following experiment, which I have often made for this purpose. Remove the brain from the cavity of the cranium, and supply its place by plaster of Paris ; when dry, this substance will present a faithful model of the convolutions and anfractuosities of the brain. In cases of chronic hydrocephalus, where the inequalities of the brain are effaced by the accumulation of fluid, the internal surface of the cranium shows scarcely any vestiges of eminences and depressions. The osseous tissue, notwithstanding its hardness, is easily moidded around organs, and yields with facility to the compression which soft parts exercise upon it. It is very uncommon to open the cranium of a subject, some- what advanced in years, without observing in some points a more or less considerable absorption of the parietes of the scull, occasioned either by clusters of certain smaU white bodies, called glandulae Pacchioni, or by dilated veins. One anatomical fact worthy of notice is the want of any configuration of the external surface conformable in its details with that of the internal surface : compare, for in- stance, the roof of the orbit with the cranial surface of the orbital plate of the frontal bone. This difference is due to the circumstance that the digital impressions encroach on the diploe, and are, in part, excavated from the space otherwise occupied by it. The two compact laminag which form the bones of the cranium are in some measure inde- pendent of each other ; the internal one belongs, so to speak, to the brain ; the exter- nal to the locomotive system. The diploe is the limit of these two laminae. This ana- tomical fact is at variance with the doctrine of Gall respecting the protuberances ; it proves that the cerebral convolutions are not faithfully represented by external prominences. In order to complete the anatomical history of the cranium, it yet remains to consider, 1. Its general development; 2. The connexion of its several parts. (For this latter subject, see Syndesmology.) As to the analogies which have been so ingeniously established between the cranium and the vertebral column, a detailed analysis of them would be out of place in an ele- mentarv work like the present. Development of the Cranium. The cranium is remarkable for the early period at which its development commences. As soon as ihe embryo is sufficiently advanced in growth to exhibit any distinction oi parts, the head, under the form of an ovoid vesicle, greatly exceeds the magnitude of the whole body With regard to the order in which the different parts are ossified, we may remark, that the bones of the roof precede those of the base, in like manner as in the vertebrae the laminae are ossified before the bodies. In both cases the evolution is most prompt in those parts which are especially destined to protect import£uit organs. Cranial Bones at Birth. The bones of the roof of the scull appear before those of the base, but at birth ossifi- cation is less advanced in the roof than in the base ; accordingly, in a foetus at the full time, the bones of the base form a solid whole, and are immovable, while those of the G W OSTEOLGOY. roof are separated by membranous intervals, which permit of pretty extensive move- ments, so that at this period the roof of the cranium yields, in a great degree, to pressure. At birth, there is nothing resembling the mode of union called suture. Nevertheless, each bone presents denticulations like the teeth of a comb round the circumference. The existence of these indentations before the period when the bones come into con- tact, proves that they are not the result of any mechanical action produced by their meeting; the only influence of this kind to which they are subjected during their forma tion, is the deviation of opposing denticulations. The frontal suture is the first developed. Another peculiarity of this stage of development is the existence of those membra- nous intervals denominated fontanelles. They are produced in the following manner : the process of ossification commences in the centre of the bone, and advances from that point to the circumference, the most distant parts of the bone being, of course, the last to be ossified. These points, in broad or flat bones, are the angles, and, consequently, at the place where several angles of diflferent bones ultimately unite, there must exist an unossified space at this time : these spaces are the fontanelles. They have all been pointed out in the description of the cranial bones ; they are of especial importance to the accoucheur, on account of the indications which they furnish for determining the position of the child. All traces of the fontanelles are completely obliterated at the age of four years. The Wormian Bones. The Wormian bones should be regarded as supplementary points or centres, developed when the general ossification proceeds somewhat slowly ; and we therefore consider it proper to include a description of them in the account of the development of the cranium. The Wormian bones, so called because the first description of them has been assigned to Wormius, a physician in Copenhagen, are also denominated exacted bones, ossa trique- tra, or complimentary bones of the scull. They are extremely variable, both in situation, number, and size ; but they are most common in the lambdoid suture, i. e., in the most rugged of all the sutures, the asperities of which they tend to increase. This fact should not be overlooked in examining fractures of the cranium. The most remarkable of all the Wormian bones is the one which sometimes supplies the place of the superior angle of the occipital, and which Blasius has called the triangular bone ; it is the epactal bone properly so called. It is not uncommon to find a Wormian bone in the sagittal su- ture, and this may be compared to the inter-parietal bone of some animals. Bertin has described a quadrangular bone occupying the situation of the anterior fontanelle, and resembling it in figure : I have myself met with such a fonnation. The anterior inferior angle of the parietal is sometimes formed by a Wormian bone ; I have seen one in the squamous suture. In some sculls the whole of the occipital bone above the occipital protuberance is formed by these bones. Generally both tables of the bone enter into the formation of the Wormian bones ; but there are instances in which they are confined to the external, and others to the internal table. The Wormian bones are not always visible in the interior of the cranium : in some cases they are, as it were, incrusted in the substance of the bone, at the circumference of which they are observed. Their mode of development resembles that of the broad bones, i. c., it proceeds by ra- diation from the centre to the circumference. According to Beclard, they are not devel- oped until five or six months after birth : at their junction with the surrounding bones they form sutures, which are the first to become effaced in after life. From all that has been said regarding this class of bones (which are in a manner acci- dental, for they are neither constant in number nor in their existence), it is evident that they can be only considered as supplementary points of ossification, and not as performing an important office in contributing to the solidity of the cranium, as the name cles de voiUe, given to them by some anatomists, would seem to indicate. Progress of Development in the Adult and the Aged. The cartilaginous lamina which separates the bones at first, gradually becomes ossi- fied. The sutures become so serrated that it is almost impossible to separate the bones without breaking some of their teeth. At the same time that the bones increase in breadth, they augment in thickness ; the diploe, which at first did not exist, is developed between the two plates. In the adult, several bones already begin to join by osseous union ; of this we have an example in the sphenoid and occipital, which at an early pe- riod form one bone. In the aged, the traces of the sutures are in a great measure effaced, so that in cer- tain cases the whole scull would seem to be composed of one entire piece. The con- tinuity of some bones is occasionally such, that the venous canals of the one communi- cate and open directly into those of the other. It is not uncommon to find the bones of an old subject thin and translucent like horn, in a greater or less extent. This diminu- tion of thickness, added to the increasing fragility of the osseous tissue, affords an ex- SUPERIOR MAXILLARY BONES. 51 planation of the ease with which the sculls of old people may be broken : and the con- tinuity of the bones explains the possibility of the fracture being much extended. The greatest variety exists as to the thickness and density of the bones of the scull in old age, Generally they are as brittle as glass, but in some instances they are so soft and spongy that, although easily depressed, they can scarcely be fractured by the blow of a hammer. I have frequently, in old people, seen the teeth of the parietal and lamb- doidal sutures soft, placed in juxtaposition, and merely joined by a soft fibrous sub- stance, which admitted of their being separated without difficulty. The lambdoidal su- ture is the one which the most frequently presents this disposition, and in all the in- stances of this kind which I have met with, the superior borders of the occipital overlap the corresponding borders of the parietal. The F^ce. The face is tnat very complicated osseous structure, which is situated at the anterior and inferior part of the head, and is hollowed out into deep cavities for the reception of the organs of sight, smell, and taste, and for the apparatus of mastication. The face is divided into two portions, the upper and the lower jaw. The lower jaw is formed by one bone only ; the upper jaw consists of thirteen bones. But, although this circumstance tends to establish a great difference between the two, yet it must be re- marked, that all the parts of the upper jaw are so immovably united, that in appearance they form only one bone ; and, moreover, that it is essentially formed by one fundamental piece, the superior maxillary bone, to which all the others are attached as accessory parts. Of the fourteen bones which constitute the face, two only are median or single : viz., the vomer, and the inferior maxilla. All the others are double, and form six pairs, viz., the superior maxillary, the malar, palate, and proper nasal bones, the ossa unguis, and the inferior turbinated bones. The Superior Maxillary Bones {figs. 24 and 25, with the Palate Bones). They are two in number, united, to a certain extent, in the median line, and form al- most the whole of the upper jaw. Their figure is very irregular : they belong to the class of short bones. They have three surfaces, an external, an internal, and a superi- or ; and three borders, an anterior, a posterior, and an inferior. External or Facial Surface {fig. 24). — Proceeding from before backward, we observe a small fossa in which the myrtiform muscle {depressor labii supe- rioris et alee nasi) is inserted, and which is bounded externally by the ridge which forms the alveolus of the canine tooth ; a deeper fossa, named fossa canina, or infra orhitalis, surmounted by the orifice of the infra orbitary canal (o) ; and, more posteri- orly, a vertical ridge, which separates the fossa canina from the maxillary tuberosity (m). This protuberance, which is most prominent before the appearance of the wisdom tooth, is trav- ersed by small canals, the posterior and superior dental, which transmit vessels and nerves of the same name. From the an- terior part of this region, a long vertical process arises, the as- cending or nasal process {a b) of the superior maxilla. It is of a pyramidal shape, and flat- tened. Its external surface is smooth, and presents the openings of certain vascular ca- nals which communicate with the interior of the nasal fossae, and some inequalities for the insertion of the common elevator of the upper lip and ala of the nose. On the inter- nal surface {fig. 25) we observe, in succession from above downward, a rough surface, which assists in closing the anterior cells of the ethmoid ; a horizontal ridge, to which the middle turbinated bone is attached ; a concave surface, which forms part of the mid- dle meatus of the nose ; and another horizontal ridge for articulation with the inferior turbinated bone : like the external, this surface also is perforated by foramina, and mark- ed by arterial furrows. Its anteriw edge {a b,figs. 24, 25) thin, and bevelled internally, i& applied to the nasal bone. The posterior edge is thick, and marked by the lachrymo-nasal g'oove, which forms part of the lachrymal groove above, and of the nasal duct below. It has two edges or lips : the internal, which is very thin, articulates with the os unguis and the inferior turbinated bone ; the external, which is rounded, gives attachment to the straight tendon and some fibres of the orbicularis palpebrarum muscle. The direc- tion of the lachrymo-nasal groove is slightly curved ; the convexity being internal and in front, the concavity external and behind. The summit of the nasal process is trun- cated and serrated for articulation with the nasal notch of the frontal bone. Superior or Orbital Surface {c,fig. 24). — This is the smallest of the three surfaces. It forms almost the entire floor of the orbit : it is triangular, and slightly oblique from within outward, and from above downward, and presents a groove behind, which is continuous with the infra-orbitary canal. This last-named passage, at first a mere channel, after- ward a complete canal, passes from behind forward and inward, bends down and opens at the upper part of the canine fossa. Before its termination, it gives off a small canal, the anterior and superior dental, which runs in the anterior wall of the maxiUary sinus, 53 OSTEOLOGY. and transmits the vessels and nerves which are distributed to the incisor and canine teeth. Sometimes this branch of the canal opens into the maxillary sinus. In many subjects I have seen it curve backward, and conduct a communicating branch between the infra-orbitary and palatine nerves as far as the maxillary tuberosity. The orbiial surface is bounded by an external edge, which forms part of the spheno-maxillary fissure ; by an internal edge, which articulates with the os unguis, the os planum of the ethmoid, and the palate bone ; and by an anterior edge, which forms part of the rim of the orbit. At the external termination of this edge is a very irregular eminence, appearing as if part of the bone had been broken off: this is the malar process, which corresponds with the sum- mit of the maxillary sinus, and is articulated with the malar bone. At the internal ex- tremity of the orbital edge, we find the ascending process already described. Internal or Naso-palatine Surface {Jig. 25). — This surface is divided into two unequal parts by a horizontal square plate, which intersects it at right angles. This plate is the palatine process {t), the superior surface of which, smooth and hollow, is broader posteriorly than anteri- orly, and forms part of the floor of the nasal fossae : its inferior surface is rough, and forms part of the roof of the palate : its internal border (t) is very thick in front, and articulates with the corresponding edge of the opposite bone. This border is surmounted by a crest, which contributes to form the furrow into which the vomer is received, and which presents, at the junction of its anterior with the two posterior thirds, a groove (r) running obliquely upward and backward. This groove, when united with a similar one on the opposite bone, forms the anterior palatine or incisive ca- nal, which is single below and double above. The anterior edge of the palatine process is very narrow, and forms part of the anterior opening of the nasal fossae : the posterior edge, bevelled at the expense of the superior table, supports the horizontal portion of the palate bone. That part (to) of the internal surface of the maxillary bone which is situated below the palatine process, is of no great extent : it forms part of the arch of the palate. A furrow more or less deep, and bounded by projecting edges, runs along the external bor- der of the palatine process, and protects the posterior palatine vessels and nerves. The raucous membrane of the palate covers this region of the bone. The part of the inter- nal surface (n) of the superior maxillary bone which is above the palatine process, be- longs to the nasal fossa : it is covered by the pituitary membrane. We observe here from before backward, 1, the internal surface (c) of the ascending process (a) ; 2, below the inferior ridge, a smooth surface which forms part of the inferior meatus of the nose ; 3, the inferior orifice (behind c) of the lachrymo-nasal groove, sometimes converted into a complete canal by a bridge of bone ; 4, the opening of the maxillary sinus (s), which appears wide in a detached bone, but in its natural connexion is contracted by prolonga- tions of the palate bone, the ethmoid, the inferior turbinated bone, and the os unguis, all of which are articulated with the circumference of this opening ; it is still farther dimin- ished when the bones are covered by their pituitary membrane. At its lower part, this orifice presents a fissure in which a lamina belonging to the palate bone is received : this method of articulation has received the name of Schindylesis. At the upper part are small cells, which unite with the ethmoid ; behind the orifice is a rough surface, which articulates with the palate bone ; and, lastly, a groove, which forms part of the posterior palatine canal. The orifice which we have just described leads into the interior of a cavity denom- inated maxillary sinus, or antrum of Highmore, although it had been before very accurate- ly described by Vesalius. It is hollowed out from the substance of the maxillary bone, and has the form of a pyramid, the base of which corresponds with the internal surface of the bone ; the summit with the malar process ; the superior wall with the floor of the ojbit ; the anterior wall with the fossa carina, and the posterior with the maxillary tuber- osity. These two last-mentioned walls are traversed by linear projections or ridges, which correspond with the anterior and posterior dental canals. There is also one ridge upon the superior wall : it indicates the passage of the infra-orbitary canal. The ex- treme tenuity of this superior or orbitary wall is an anatomical fact of great importance, because it explains the influence which tumours developed in the sinus exert upon the organs contained in the cavity of the orbit. The septum between the sinus and the bot- tom of the alveoli is also so thin, that an instrument can easily penetrate into the sinus in this situation. This remark applies particularly to the alveolus of the canine tooth. The anterior harder {g a, figs. 24 and 25) of the superior maxilla presents, below, a ver- tical portion (g- d), surmounted by a small eminence called the nasal spine (a) : it is then hollowed out into a deep notch (a h), to form half the anterior orifice of the nasal fossae ; and, lastly, becomes continuous with the anterior edge (h a) of the ascending process. The posterior harder is vertical and very thick : it articulates below with the pterygoid process, through the medium of the palate-bone : above, it forms part of the pteiygo- maxillary fissure. • PALATE BONES. 53 The inferior or alveolar border {g k) is the thickest and strongest part, being, in some respects, the base of the bone. It is hollowed into conical cavities separated by thin septa. These cavities are the alveoli or sockets of the teeth : they are proportioned in dimensions to the size of the fangs vi^hich they are intended to lodge, and in like man- ner are subdivided into two, three, or four secondary cavities. The bottom of these al- veoU is in apposition with the maxillary sinus, into which they occasionally open. This border presents, especiaUy in front, flutings or projections which correspond with the alveoli, and depressions which mark the inter-alveolar septa. In young subjects we may observe, chiefly behind the incisor teeth, some very remark- able foramina, to which much importance has been attached as connected with the phe- nomena of dentition. Internal Structure. — This bone is remarkably light for its size, on account of the larg« cavity which it encloses. It is more compact than most of the short bones, and has spongy tissue only in the alveolar border, the maxillary tuberosity, and the malar eminence. Connexions. — The superior maxilla is articulated with two bones of the cranium, the frontal and the ethmoid, and with all the bones of the face. It lodges eight of the teeth of the upper jaw. Development. — Anatomists are not at all agreed respecting the number and arrange- ment of the osseous points which concur in forming the superior maxilla. In the maxillary bone of the fcetus, and sometimes even in that of the adult, there are, as I can attest from observation, two very remarkable fissures, which would seem to in- dicate the primitive separation of the bone into three pieces. 1. The first fissure, which may be called the incisive fissure, is visible on each side of the arch of the palate. It commences at the septum, which divides the alveoli of the canine tooth and lateral incisor, is continued backward to the anterior palatine canal, and is prolonged above on the internal surface of the ascending process. This fissure is apparent only on the internal surface of the superior maxilla : it either does not exist at all upon the external surface, or is so early obliterated that it can scarcely ever be met with. The portion of the maxilla circumscribed by this fissure sustains the incisor teeth, and represents the incisor or inter-maxillary bone of the lower animals. In hare- lip, the solution of continuity is in the situation of this fissure. It is therefore probable that this anterior portion of the maxillary bone is developed from a special point. Bertin asserts this, and Meckel and Beclard admit it. I have not been able to observe such independent development at any period of foetal life at which I have examined the max- illary bone. 2. A second and equally constant fissure is visible in the situation of the infra-orbital canal, and is prolonged from the edge of the orbit in the form of a small suture to the anterior orifice of this canal : it may be called the orbital fissure. This fissure, like the preceding, has always seemed to me incomplete, and not occasioned by the separation of a distinct piece. The superior maxillary bone is one of the earliest in making its appearance. Ossifi- cation commences in it from the thirtieth to the thirty-fifth day, in the situation of the alveolar arch. At birth the superior maxilla has little height, but a considerable extent from before backward. At this period it is chiefly formed by the alveolar border, which is almost con- tiguous to the floor of the orbit. The maxillary sinus is already very apparent. In the adult, the vertical dimensions increase by enlargement of the sinus. In the aged, the al- veolar process becomes flattened, and diminished in height. The Palate Bones (Jigs. 24, 25, 26, and 27). The palate bones are situated at the posterior part of the nasal fossae and the palatine arch ; they are two in number, sjrmmetrical, and each pig. 26. Fig. ar. composed of two thin quadrilateral laminae, one of which is horizontal, the other vertical, and which are joined to- gether at right angles. The horizcmtal plate {b c, figs. 26 and 27), the only one known to the ancients, and named by them the as quad- ratum, presents a superior surface (jif), smooth and con- tinuous with the floor of the nasal fossae, of which it forms the broadest part : an inferior surface {b c), which com- pletes the arch of the palate : it is rough, slightly concave in front, and presents behind and to the outside a trans- verse ridge for the insertion of the tensor palati muscle ; and in front of this ridge is the inferior orifice of the pos- terior palatine canal. The anterior edge of this plate is cut obliquely, so as to rest upon the posterior edge of the palatine process of the superior maxillary. The posterior edge is concave, and very thin ; it gives attachment to the velum palati. The internal edge is sunnounted by a crest, which forms one of the sides of the vomer, and terminates be aind by a sharp process (d), which, when united to the corresponding part of the opposite M OSTEOLOGY. bone, constitutes the posterior nasal spine, which gives attachment to the levator muscle of the uvula (azygos uvulae). The external edge is united to the vertical portion of the bone. The vertical portion, or lamina (a b), is slightly inclined inward, quadrilateral, longer, broader, and thinner than the preceding. On it we observe, 1. An internal surface (mf and 2, fig. 25), which contributes to form the external wall of the nasal fossae, and which presents from above downward a horizontal ridge for articulation with the middle tur- binated bone ; a groove belonging to the middle meatus ; another ridge for articulation with the inferior turbinated bone (e and 2, fig. 25) ; and another groove which makes part of the inferior meatus (e/and l,fig. 25). 2. An external surface (s b,fig. 26, and p b, fig. 27), very irregular, which contributes to form the bottom of the zygomatic fossa above, and which is rough in front for union with the superior maxillary. This surface is traversed by a vertical groove, which, by itself, forms £dmost the entire extent of the posterior palatine canal {g g, fig. 26). 3. An anterior or maxillary border {i, fig. 27), very thin and irregular, which advances so far forward as to contract the entrance into the maxillary sinus, and presents a tongue of bone, which is received into the fissure already described as existing at this orifice. 4. A posterior or pterygoid border {I, fig. 26), which is applied to the inner plate of the pterygoid process. There is below, at the angle form- ed by its union with the posterior edge of the horizontal portion, a very considerable pro- cess for the size of the bone : this has been called palatine process, or tuberosity of the os palati (3, fig. 25 ; lb, fig. 26), but is better named pterygoid or pyramidal process : its base is continuous with the test of the bone, and from this point passes downward, and is, as it were, enclosed in the bifurcation of the pterygoid process of the sphenoid. Its upper surface is traversed by three grooves, the middle of which forms part of the pterygoid fossa, and the lateral ones are rough, and receive the simimits of the two pterygoid plates. Below, the pyreunidal process exhibits the orifices of the accessory ducts of the posterior palatine canal. Externally it presents a rough surface, which articulates above with the tuberosity of the superior maxilla, and which is free in the rest of its extent, and forms part of the zygomatic fossa. The middle of this process is grooved in a vertical direc- tion, for the posterior palatine canal. 5. The inferior border of the vertical portion is continuous with the external edge of the horizontal plate. 6. The superior or sphenmdal border is connected with the sphenoid in almost the whole of its extent. It presents a deep notch, forming three fourths or sometimes the entire spheno-palatine foramen {G,fig. 25 ; 0, figs. 26, 27 ; n, fig. 37), which corresponds with the spheno-palatine ganglion, and gives passage to the vessels and nerves of the same name. This border is surmounted by two processes, an anterior or orbital (4, fig. 25 ; a, figs. 26, 27), and a posterior or sphe- noidal {5, fig. 25 ; m,figs. 26, 27). The sphenoidal process is the broader, particularly at its base, but is not so elevated as the anterior : it presents three facettes — an internal, which forms part of the nasal fossa ; an external, which is visible in the zygomatic fossa ; and a superior, which articulates with the sphenoid, and presents a groove, which con- tributes to form the ptcrygo-palatine canal. The orbital process, inclined outward, and supported by a constricted portion or neck, has five facettes. Three of these are articular, viz., the internal {n,fig. 27), which is concave, and unites with the ethmoid, covering and completing its cells ; the anterior {p, fig. 27), which joins the maxillary bone ; and the posterior (q, fig. 26), which is united to the sphenoid by certain asperities surrounding a cell, which exists in the substance of the process, and com- municates with the sphenoidal sinus. The other tico are non-articular, viz., the superior (r, fig. 26), which forms the deepest part of the floor of the orbit, and the external (s, fig. 26), which forms part of the zygomatic fossa, and is separated from the preceding by ,a small edge, which constitutes a portion of the spheno-maxillary fissure. Internal Structure. — The palate bone is compact throughout, excepting in the palatine process, where it is thick and cellular. Connexions. — The palate bone articulates with its fellow on the opposite side, with the maxillary, the sphenoid, the ethmoid, the inferior turbinated bone, and the vomer. Development. — This bone is developed from a single point of ossification, which ap- pears from the fortieth to the fiftieth day, at the point of union of the vertical and hori- zontal portions, and the pyramidal process. During its development, the bone appears as it were crushed down, so that the vertical portion is shorter than the horizontal, and there is a marked predominance in the antero-posterior diameter. This disposition is in accordance with the shortness of the vertical diameter of the superior maxilla. ^s-^- The Malar Bones {fig. 28). The malar hones, called also cheek, jugal, or zygomatic bones, are situated in the superior and lateral part of the face : their form is that of a very irregular four-sided figure. They have thn e sur- faces, an anterior, a posterior, and a superior ; four borders, and four angles. The anterior or cutaneous surface (a) looks outward, is convex and smooth, and presents the openings of several foramina {h). NASAL BONES. 55 named malar, which are intended for nerves and vessels. This surface gives attach- ment below to the zygomaticus major muscle. It forms the most prominent part of the cheek, and is covered only by the skin and orbicularis palpebrarum muscle : it is, conse- quently, much exposed to injury. The superior or orbital surface (jb) is supported by a thick curved process, the orbital pro- cess, which arises from the bone almost at a right angle. This surface is concave, and of small extent : it forms part of the orbit, exhibits the internal openings of one or more malar foramina, and terminates behind by a rough, serrated edge, which articulates above with the frontal and sphenoid bone, and below with the superior maxillary. The same maxiUary edge presents in the middle a retiring, smooth angle, which constitutes the anterior extremity of the spheno maxillary fissure. The posterior or temporal surface is concave, and presents a smooth surface Ijehind, which contributes to form the temporal fossa, and on which one or more malar foramina open ; and a rough surface in front, which unites with the malar process of the superior maxilla. Of the /our borders, two are superior ; of these, the anterior or orbital {d e) is semi-lunar, rounded and blunt, and forms the external third of the base of the orbit ; the posterior or temporal {e f) is thin, and curved like the letter S, and bounds the temporal fossa in front. Of the two inferior borders, the anterior or maxillary (d g) is very rough and articulates with the maxillary bone ; the posterior or masseteric (gf) is horizontal, thick, and tubercular, and gives attachment to the masseter muscle. Of the/oMr angles, the superior ox frontal (e), which is much elongated, and vertical, is the tliickest part of the bone, and articulates with the external angular process of the frontal bone : the posterior or zygomatic (/), broader and thinner than the preceding, is serrated, and slants downward and backward, for articulation with the zygomatic process of the temporal bone, which rests upon it. The internal or orbital angle {d) looks in- ward and forward, is very acute, and articulates with the superior maxillary near the infra-orbitary canal. The inferior or malar angle {g) looks downward, is obtuse, and unites with the outer part of the malar or jugal process of the superior maxillary. Internal Structure. — Tlie malar bone is almost entirely compact, possessing spongy tissue only in the anterior and inferior edge, and in the part where the orbital portion is given off. It is constantly traversed by a canal called zygomatic. This passeige is gen- erally simple, but sometimes double or even multiple, and opens by at least three orifices. The superior or orbital orifice is visible on the surface of the same name ; the next or external zygomatic foramen is on the cutaneous surface of the bone ; and the third or internal zygomatic on the inner surface of the vertical portion. Connexions. — The malar bone is articulated with the superior maxillary, the frontal, the sphenoid, and the temporal. Development. — It is developed from one point of ossification, which appears about the fiftieth day of fcetal life. The ulterior changes which it undergoes do not require par- ticular notice. The Masai Bones {fgs. 29, 30). The nasal bones are two in number, asymmetrical, and very small in the human sub- Fig. 29. Fig. 30. ject ; they are closely contiguous to each other, sometimes united into one piece superiorly. They are situated at the upper and middle part of the face, and form, as their name indicates, the osseous part of the nose, of which they constitute the root. They are directed obliquely downward and forward, but with various degrees of inclination in dif- ferent subjects ; and hence the varieties in the shape and prominence of the middle or bridge of the nose. Their figure is rectangular and oblong ; they are thick and narrow above, broad and thin below ; and have two surfaces, an anterior and a posterior, and four edges. The anterior or cutaneous surface {fig. 29) is covered only by the skin and pyramidalis nasi muscle, and hence the ease with which these bones are fractured : it is concave above, flat or even convex below : the orifice of a vascular canal is always very distinctly seen, which is variable in its situation, sometimes single, but often accompanied by others of smaller size. The posterior or pituitary surface (fig. 30) is concave, and forms the anterior part of the roof of the nostrils : it is marked by vascular and nervous furrows, and in the fresh state is covered by the pituitary membrane. Of the four edges, the superior (a, figs. 29, 30), short, thick, and serrated, articulates with the nasal notch of the frontal bone. The inferior (d), very thin, and more elonga- ted, has a slight notch in the centre for the passage of a nervous filament, and forms part of the anterior orifice of the nasal fossae : it unites with the lateral cartilage of the nose. The internal (b) edge is thick above, and bevelled, so that, when approximated to the other bone, the two constitute a fiirrow, in which the nasal spine of the frontal and the perpendicular lamella of the ethmoid bone are received. The external (c) edge is some- what longer than the internal, is slightly bevelled on the outer table, and indented for articulation with the ascending process of the superior maxilla, which rests upon it. 66 . OSTEOLOGY. Connexions. — The two bones are articulated together : they unite also with the frontal, the ethmoid, and the superior maxiUa, and likewise with the lateral cartilages cf the nose : they afford passage to the vessels which establish a communication between the skin of the nose, and the mucous membrane of the nasal fossae. Internal Structure. — The nasal bones are thick and cellular in their upper parts, thin dnd entirely compact in their lower, and are traversed by nervous and vascular grooves. Development. — The nasal bone is developed from one single osseous point, which ap- pears before the end of the second month. Ossa Unguis^ or Lachrymal Bones {figs. 31, 32). These are the smallest bones of the face : they are thin, like paper, and have the trans Fig. 31. Fig 32. parence, tenuity, and even the shape of a nail, from which circum- stance one of their names has been derived. They are situated at the internal and anterior part of the orbit : their figure is irregularly . quadrilateral : they are two in number, and, therefore, asymmetri- If '7r cal. They have two surfaces and four edges. ' j,i#^ The external or orbital surface {fig. 32) is divided into two unequal parts by a vertical ridge (a b), which terminates below in a sort of '^ hook. The portion anterior to the ridge is narrow, and marked by a porous groove (c), which, when joined to the channel on the ascending process of the superior maxilla, forms the lachrymal groove (hence the name of lachrymal bone).* The portion {d) of the os unguis, which is posterior to the ridge, completes the inner wall of the orbit. The internal or ethmoidal surface {fig. 31) presents a furrow (a' b), which corresponds to the external ridge ; the portion {c') in front of the furrow forms part of the middle meatus ; behind is a rough surface {d'), which covers the anterior cells of the ethmoid. Of the four borders, the supcrior{a a) is rough, and articulates with the internal angu- lar process of the frontal bone ; the inferior {b h') articulates with the inferior turbinated bone by a small tongue which passes backward, and which contributes to form the nasal canal, and with the internal edge of the orbital surface of the superior maxillary. The anterior edge {e e') unites with the ascending process of the maxillary bone ; and the ■posterior edge {f f), slightly denticulated, joins the orbital portion or lamina papyracea ,^mhe ethmoid. ^^ Connexions. — The os unguis articulates with the frontal, the ethmoid, the superior maxillary, and the inferior turbinated bone : they assist in the formation of the lachrymal sac, the nasal canal, and the internal wall of the orbit. Structure. — The os unguis consists of a very thin layer of compact tissue, and is the inost brittle of all the bones. It is of importance to note its tenuity and fragility, be- , Hji^aase it is concerned in the operation for fistula lachrymalis. Development. — The os unguis is ossified at the commencement of the third month, from one single point. The Inferior Turbinated or Inferior Spongy Bones (figs. 33, 34, and d, fig- 37). The inferior turbinated bones, so called on account of their curved figure, are situated Figs 33 34. ^^ *^^ lower part of the external wall of the nasal fossae {d, ' ' fig. 35), below the ethmoid, whence the name sub-ethmoidal turbinated bones. They are two in number, asymmetrical, and their greatest diameter is directed from before backward. They have two surfaces, two edges, and two extremities. The internal surface {fig. 34, and d,fig. 37) is convex, and looks towards the nose, which it sometimes touches when that part deviates from the straight direction ; the external sur- face {fig. 33) is concave, and forms part of the middle meatus. Both are rough, and, as it were, spongy, which has given rise to the assertion that these bones form an exception to the general rule of the spongy tissue being in the interior of bones : this appearance, however, is owing to the multi- plicity of canals intended for nerves, and more particularly for the veins which expand over the bone. The superior or articular edge {abed, figs. 33, 34) is very irregular, and presents from before backward, 1. A thin edge {a b), which articulates with the ascend- ing process df the superior maxilla. 2. A small eminence bearing the name of nasal or lachrymal process (5), which articulates by its apex with the os unguis, and by its two edges with the two lips of the ascending process of the superior maxillary, to complete the nasal canal. 3. A curved pkte, called auricular process (e, fig. 33) by Bertin, who com- pared it to the ear of a dog : this plate is directed downward, and applied partially upon the orifice of the maxillary sinus, which it assists in closing. 4. Behind this process * The existence of lachryma) bones is subordinate to that of the lachrymal secretion. The;r are not met with in those animals -which bve in the water, and which have neither lachrymal glands nor ptjssages. VOMER. INFERIOR MAXILLA. 57 we find a thin edge (c d, figs. 33, 34), which articulates with a small ridge on the palate bone. 5. Between the auricular and the lachrymal processes are small prominences which unite with tlie ethmoid. The inferior or free border (a d) is convex, and thicker in the middle than at its ex tremities : it is separated from the floor of the nostrils by an interval (m o, fig. 37) of un- certain extent, a circumstance to be remembered during the introduction of instruments into the nasal fossae. The anterior extremity (a) is a little less pointed than the posterior {d), which distin- guishes the bone of the right from that of the left side. Connexions. — The inferior turbinated bones articulate with the superior maxillary, the palate bones, the ethmoid, and the ossa unguis : they have important relations with the inferior orifice of the nasal canal, which they defend from the contact of foreign bodies. Structure. — ^Their external spongy appearance depends upon the multitude of canals with which their surface is furrowed, but they are almost exclusively formed of compact tissue. Development. — Their ossification commences about the fifth mftith of foetal life, by a point situated in the centre. The Vomer {jig. 35, and 10, fig. 22). The vomer is so called from its supposed resemblance to a ploughshare. It is situated in the median plane, and forms the posterior part of the sep- jVe'. 35. tmn of the nostrils. It is thin, flat, and quadrilateral, and has two surfaces and four edges. The surfaces are placed laterally (as at a, fig. 35), and are generally plane, but they are often bent to one side or the other, and are then convex and concave in opposite directions : they are always smooth, and covered by the pituitary membrane, and present small vascular and nervous furrows. The superior or sphenoidal border {Jb, fig. 35, and 3, fig. 22) is the shortest and thickest : it is marked by a deep groove, which receives the in- ferior crest of the sphenoid ; the two lips of the groove are bent outward, and received into furrows on the inferior surface of the same bone, and thus complete a small chan- nel for the passage of vessels and nervous filaments. The inferior or maxillary (c) bor- der is the longest, and is received into the furrow which is formed by the union of the two palate bones behind and of the two superior maxiUary in front : it sometimes termi- nates by a more or less prominent process behind the anterior nasal spine. The anterior or ethmoidal border {d, fig. 35, and 3 4, fig. 22) presents the continuation of the groove on the superior edge, and receives the inferior bcujder of the perpendicular plate of the eth- moid. There is no groove where it is attach" to the cartilaginous septum. The pos- terior or guttural edge {e,fig. 35, and t, 10, fig. 22) is free : it is thin and sharp, and in- clines downward and forward : it separates the posterior openings of the nasal fossae. Connexions. — The vomer is articulated with the sphenoid, the ethmoid, the superior maxillary, the palate bones, and the cartilage of the septum. Internal Structure. — ^The vomer is composed of two very thin compact laminae, which are distinct above, but united below. Some anatomists have called these plates alee of the vomer. Development. — It is developed from one point of ossification, which is situated at the lower part of the bone, and appears before the end of the second month. It then pre- sents the form of a deep groove, embracing the cartilage just as, at a future period, it embraces the sphenoidal crest. At birth the vomer is still only a groove ; afterward this condition is confined to the sphenoidal and ethmoidal edges of the bone. It is not uninteresting to note the peculiar and uncommon manner in which the ossification pro- ceeds from the surface to the interior of the cartilage. Inferior Maxilla {fig. 36). While, as w^ have before observed, a considerable nimiber of bones to enter into the formation of the upper jaw, the lower jaw consists of one pig. 36, bone only. The inferior maxilla occupies the lower part of the face. From the number and importance of the practi- cal points connected with this bone, too much attention cannot be bestowed on the study of its form and connex- ions. It has the shape of a parabolic curve, the two ex- tremities of which, called rami, form a right angle with the middle portion or body. Of the body or middle portion (a). — The body represents a curved plate, convex in front and concave behind. It of- fers to our notice an anterior and a posterior surface, and a superior and inferior border. The anterior surface has in the middle a vertical line, called symphysis menti (c d) ; it H 9i OSTEOLOGY. marks the place of union of the two pieces of \jfhich this bone is composed in young subjects, and which, in a great number of animals, remain distinct through life.* The mode in which the two halves of the body of the inferior maxilla are united, forming an arch instead of an angle, as in other animals, constitutes one of the distinc live characters of the human species ; and the vertical direction of the symphysis, com- pared Avith its very oblique inclination downward and backward, or almost horizontal position in the lower animals, is a no less characteristic mark of man, who alone can be said to possess a chin.\ In front the symphysis terminates by a triangular eminence called mental 'process (d). Behind, it presents below four small tubercles, two superior and two inferior, known by the collective appellation of genial processes {yivcLov, the chin), and give attachment to the genio-hyoid and genio-glossal muscles. On each side of the symphysis, we observe on the anterior or cutaneous surface of the body of the inferior maxilla, 1. A small depression for the attachment of muscles, named mental fossa (e c). 2. A line, which commences at the mental process, passes obliquely upward, and becomes' continuous with the anterior edge of the ramus of the jaw : it is named the external oblique, or external maxillary line (c/), and is also intended for muscu- lar insertions. 3. Above this line, the mental foramen (_g), the orifice of the inferior dental canal, which transmits the mental vessels and nerves. 4. The anterior surface of the alveolar arch (c h), marked by a series of projections corresponding to the alveoli, and separated by vertical depressions, which point out the situation of the inter-alveolar sep- ta. 5. Below the external oblique line, a smooth surface (a), separated from the skin by the platysma myoides muscle. The posterior or lingual surface is in some measure moulded upon the tongue : it pre- sents, 1. The mylo-hjoidcan line (k) (jivXog, dens molaris), called also internal oblique or in- ternal tnaxillary, which commences at the genial processes, and passes upward and back- ward, becoming more prominent opposite the last molar tooth. 2. Below this line, a broad but superficial depression, which lodges the sub-maxillary gland. 3. Above the oblique line, and near the symphysis, a fossa, which lodges the sub-lingual gland, and a sracfoth surface covered by the mucous membrane of the mouth and gums. These two lines, the external and internal oblique, divide the body of the inferior max- illa into two parts, a superior or alveolar, and an inferior or basilar. The first named constitutes almost the entire body of the bone in the foetus and the infant ; in the adult it forms only two thirds of the depth of the bone, the other third being the basilar portion : last- ly, in the aged, the alveolar portion almost entirely disappears, and the basilar only is left. The superior or alveolar border describes a smaller curve than the corresponding alveo- lar edge of the superior maxilla ; so that, in a regular conformation of the parts, the in- ferior incisor teeth are overlapped by thgl, superior. This border is less tliick in front than behind, where it projects inward : it is pierced by a series of sockets or alveoli, re- sembling those of the superior maxilla, and, like them, variable according to the kind of teeth which they are intended to receive. The inferior border or base of the jaw {d m) is the thickest part of the bone ; it forms part of a larger curve than the superior border, so that the jaw projects forward in some measure at the lower part : this projection varies much in different subjects. Rami of the iyiferior maxilla {b b). — These are quadrilateral, and present, 1. An external surface (A) covered by the masseter muscle, which is inserted into it, especially below, where we may observe depressions and ridges, and where the bone itself is more or less bent outward ; in front of these ridges is a slight mark, which corresponds with the situation of the facial artery. 2. An internal or pterygoid surface, also rough, for the at- tachment of the internal pterygoid muscle, and on which is observed the superior orifice (I) of the inferior dental canal, which is wide, and has a sort of spine, to which the in- ternal lateral ligament of the temporo-maxillary articulation is attached : a small groove passes from this orifice in the same direction as the canal, and bears the name of mylo- hyoidean furrow, because it lodges the nerve of that name. 3. A posterior or parotid edge, which is round, and gives attachment below to the stylo-maxillary ligament : it is era- braced by the parotid gland. 4. An anterior edge (r), marked by a groovi^ which is the continuation of the alveolar border ; the anterior and posterior lips of this groove being formed by the external and internal oblique lines. 5. A superior edge, very thin, and hol- lowed out into gi deep notch, called sigmoid notch (n o), on account of its shape, giving peissage to nerves and vessels. 6. An inferior edge, which is nothing more than a con- tinuation of the inferior border of the body of the bone. The angle which the rami form with the body of the bone is named the angle of the jaw (m). It is a right angle in the adult, but very obtuse in the infant, as also in the * In serpents these pieces form a movable joint ; and as a similar arrangement obtains between the two halves of the upper jaw, these reptiles are enabled to swallow an object much larger than their head, or even than their body. t It is interesting to remark the difference in the dissection of the symphysis in the Caucasian and Ethi- opian varieties of the human family. In the former it is placed nearly vertically, slightly oblique from above to below, and from behind to before. In the latter it is oblique from before to behind, and in this respect re- sembles the conformation in the inferior animals, more especially in the Simiie. INFEBIOE MAXILLA. ^ «iaruivora and some of the rodentia^ this disposition enabling its muscles to act with ' greater power. The rami of the inferior maxilla are terminated above by two processes : the anterior; called the coronoid process (n) ; the posterior, named the condyle (p). The coronoid process is triangular, and inclined forward ; broad at its base, and pointed at its summit ; it gives attachment to the temporal muscle. The size of this process in the different species of animals bears an exact and constant proportion, both to the depth and extent of the temporal fossa, and to the strength and curvature of the zygomatic arch. The condyle articulates with the glenoid cavity of the temporal bone ; it is an oblong eminence, the greatest dizuneter of which is directed sUghtly inward and backward. It is supported by a contracted portion, called the neck of the condyle {^cervix) (o). This neck is turned inward in such a manner that the condyle, which it supports, does not project beyond the external plane of the ramus of the jaw ; it is also pr§tty deeply excavated internally, to afford attachment to the external pterygoid muscle. The neck of the con- dyle is the weakest part of the inferior maxilla. Connexions. — The inferior maxilla articidates with the temporal bone, and lodges the lower range of teeth. Structure. — The external surface of the inferior maxUla is composed of compact tis- sue ; the interior of the bone assumes the form of diploe, and is traversed for a great part of its extent by the dental or inferior maxillary canal, which transmits the vessels and nerves that are distributed upon the teeth of this jaw. This canal commences at the middle of the ramus, by a groove covered with a fibrous lamina, the only use of which, as it appears to me, is to protect the vessels and nerves, and to separate them from the internal pterygoid muscle. From this point it proceeds forward and inward be- low the mylo-hyoidean line, the curvature of which it follows ; it gradually becomes con- tracted in diameter ; and in the situation of the second smaU molar or bicuspid tooth, it divides into two canals, the larger of which is very short, and opens upon the external surface of the body of the bone at the mental foramen already described ; the other, very minute, pursues the original track, and is lost near the middle incisor tooth. In its pas- sage the inferior dental canal communicates with the alveoli, by one, and sometimes two foramina, through which the vessels and nerves of the teeth are transmitted. The sit- uation of the dental canal varies much in different periods of life. In the new-bom in- fant, before the appearance of the teeth, it occupies the lowest portion of the jaw ; after the second dentition, it corresponds pretty nearly with the mylo-hyoidean line ; and after loss of the teeth, it runs along the alveolar border. In the inferior maxilla of the old subject, the anterior orifice of the dental canal, or the mental foramen, is close to the su- perior border of the bone. The dimensions of the dental canal are no less remarkable for their variations ; it is very large in the foetus, and in the child before the appearance of the second set of teeth ; it diminishes during adult age, and is much contracted in the old subject. Development. — The inferior maxilla is developed by two points of ossification, one for each lateral half Antenrieth admits, in addition, three complementary points ; one for the condyle, one for the coronoid process, and one for the angle ; but I have never ob- served them. The case is different, however, with a point of ossification described and figured by Spix, which forms the inner side of the alveolar border, or, rather, of the den- tal canal. In a foetus of about fifty or sixty days, I have seen a kind of bony spiculum, which passed along the internal surface of the body and ramus of the bone ; on the one half of the maxillary bone this spiculum was entirely free ; but that of the other side ad- hered by the internal third of its length. The spine which surmounts the dental canal is nothing more than the extremity of this bony spiculum. It follows, therefore, that the inferior maxilla is developed from four points of ossification. The inferior maxilla takes precedence of all the bones of the head in its development, and, indeed, of all the bones of the skeleton, excepting the clavicle. The inferior edge of the body of the bone appears as early as the thirtieth or thirty-fifth day ; this extends backward to form the ramus, and in front to form the portion which supports the incisor teeth ; it is probable that the osseous point of the dental caned, mentioned above, appears at the same time. From the fiftieth to the sixtieth day, each half of the bone appears already marked by a groove common to the dental canal and the alveoli. At a later period, the groove becomes very considerable, and is divided into alveoli by septa, which at first are incomplete, but afterward become perfect ; the alveoli and their septa occupy at this time the entire depth of the bone. The point of ossification described by Spix is united to the rest of the bone from the fiftieth to the sixtieth day. (Spix aflirms that it remains separate until the fourth month.) The two halves of the maxilla are joined together during the first year after birth. The traces of this union exist for some time, but are afterward effaced ; in the lower animals the suture remains throughout life. The changes which the inferior maxilla undergoes after birth, relate, 1- To the angle which the ramus forms with the body of the bone, which is very obtuse at birth, and be- oomes a right angle after devetopment is completed. 2. To the alterations effected in 60 OSTEOLOGY. the booy of the bone, by the first and second dentitions, the loss of teeth in liie aged, and the subsequent absorption and disappearance of the alveoli. The Face in general. The fourteen bones which we have described, united to each other, and joined to the bones of the cranium, form a piece of bony sculpture, symmetrical, extremely complica- ted, destined to lodge the organs of smell, sight, and taste, and to be the instrument of mastication. This bony sculpture forms the face, which is situated below the cranium, above the neck, and in front of the vertebral column, from which it is separated by the pharynx, and is bounded on each side by the zygomatic arches. Dimensions of the Face. In order to form a just idea of the dimensions of the face, it is necessary to examine a scull cut vertically from before backward (as in fig. 22). We then perceive that the face is comprised within a triangular space, which is bounded above by an irregular line that separates it from the cranium ; in front by the face, properly so called ; and below, by a line passing below the symphysis menti. If a line be drawn above the inferior maxilla, and under the arch of the palate, when prolonged backward, it will be in the plane of the foramen magnum ; for the cranium having much less depth in front than behind, a horizontal line, which touches the cranium behind, is separated from it in front by the entire height of the upper jaw. The vertical diameter, which extends from the frontal protuberance to the chin, is the longest of all the diameters of the face. It gradually diminishes from before backward. The transverse diameter is of considerable extent in the situation of the cheeks, but di- minishes above and below this point. The antero-posterior diameter stretches above from the nasal spine to the basilar process ; below it is greatly contracted ; and at the level of the chin only measures the thickness of the symphysis. With regard to the dimensions of the face as a whole, we shall only refer to what has been already stated concerning the inverse proportion of the area of the cranium, and that of the face, in different species of animals.* The face represents a triangular pyramid, and offers for consideration three surfaces or regions : an anterior, a superior, and an inferior. Anterior or Facial Region. The numerous anatomical differences which this region presents form distinctive characters, not only of different nations, but also of different individuals. It is bounded above by the forehead, below by the base of the inferior maxilla, and laterally by a line which passes along the external angular process, the malar bone, and the ridge which separates the canine fossa from the tuberosity of the maxilla. In this region we observe, in the median line, the nasal eminence ; a transverse suture, formed by the union of the proper nasal bones with the os frontis, the fronto-nasal suture ; below this suture, the nose, a pyramidal eminence, narrow above or at its root, broad below or at its base, and formed by two bones, which are united together by juxtaposition in the median hne, and externally to the ascending process of the superior maxilla. Below this eminence is the anterior orifice of the nasal fossa, which has the form of a heart on playing cards, and presents at the bottom the anterior nasal spine, and below this a ver- tical suture, the maxillary, the interval which separates the middle incisor teeth, the opening of the mouth, and the symphysis menti. On each side, we find the opening or base of the orbit, directed obliquely outward, of an irregular square form, and presenting above the supra-orlitary foramen ; below, the infra-orhitary foramen ; on the outside, the fronto-jugal suture ; and, on the inside, the fronto-maxillary suture. Below the opening of the orbit is the canine fossa, then the alveoli and teeth of the two jaws, the extemsd oblique line, the mental foramen, and the base of the inferior maxilla. Superior or Cranial Region. This region is so united with the inferior surface of the cranium, that the scull and the superior maxilla form only one piece, and cannot be removed from each other. It presents, in the median line, counting from behind forward, the articulation of the vomer with the sphenoid, in which articulation there is a mutual reception of parts, the sphe- noidal crest being received between the laminae of the vomer, and these, in their turn, being lodged in corresponding fissures in the sphenoid ; the articulation of the vomer with the posterior edge of the perpendicular plate of the ethmoid ; the articulation of this perpendicular plate with the nasal spine of the frontal bone ; and the articulation of this spine with the proper bones of the nose. On each side, proceeding from within out- ward, we observe, 1. The roof of the nasal fossae, formed behind by the inferior surface of the body of the sphenoid ; in the middle by tlie cribriform plate of the ethmoid ; and in front by the pusterior surface of the nasal bones. 2. More externally, the base of the ' Vide of the cranium in general ; of the facial angle of Camper ; the occipital angle of Danbenton, and the measurement of Cuvier, p. 45 THE FACE IN GENERAL. 01 pterygoid processes, the articulation of the palate bone with the sphenom, the pterygo- palatine canal, and the spheno-palatine foramen. 3. The articulation of the lateral mass- es of the ethmoid with the sphenoid behind, and with the frontal bone in front. 4. The articulation of the internal angular process of the frontal bone with the os unguis. 5. The articulation of the nasal notch of the frontal bone with the ascending process of the su- perior maxilla, and the proper bones of the nose. 6. More externally still, the roof of the orbit, bounded externally by the articulation of the frontal with the malar bone and the sphenoid, and by the sphenoidal fissure. 7. The anterior surface of the great wing of ^ the sphenoid, which forms the largest portion of the external wall of the orbit ; 8. Out- side the orbit, the zygomatic arch. Inferior or Guttural Region. This region forms part of the pharynx and cavity of the mouth. It presents from be- hind forward, 1. A vertical portion; 2. A horizontal portion ; and, 3. Another vertical portion. The vertical portion {fig. 21) exhibits in the median line the posterior edge of the sep- tum narium, formed by the vomer ; the posterior extremity of the articulation of the vo- mer with the sphenoid (o, fig. 21) ; and the posterior nasal spine. On each side, the pos- terior opening of the nasal fossa {k o, y), which is quadrilateral, longer in its vertical than in its transverse diameter, and formed internally by the vomer, externally by the ptery- goid process (r), above by the sphenoid united with the palate bone, and below by the ualate bone. More externally is the pterygoid fossa (r), formed by the sphenoid, and a small part of the palate bone. Still more externally, we find a deep fossa, or, rather, a large space bounded internally by the external plate of the pterygoid process and th# tu- berosity of the maxillary bone, and externally by the ramus of the inferior maxilla ; it is known by the name of the zygomatic fossa. The horizontal portion is the aixh of the palate {i x y, fig. 21). It is of a parabolic form, extremely rough, and, in the fresh state, covered by the palatine mucous membrane. It is constituted by the palatine processes of the maxillary bones (x), and by the horizontal portions of the palate bones (y), and presents, in consequence, a crucial suture, at the cen- tral point of which the vomer is attached : hence the piece of anatomical nicety which consisted in Eisking at what part of the skeleton it is possible to touch five bones at once with the point of a needle. The arch of the palate is pierced by several foramina ; we find here the inferior opening of the anterior palatine canal (1), which is single below, but double above, so as to open into each nostril separately ; the posterior palatine canals (2), which open at the posterior and external part of the arch of the palate ; and a groove, which runs along the external edge of the arch, and lodges the posterior palatine vessels and ner\'es at their exit from their canals. The third portion is also vertical : it presents, 1. In the median line, the suture of the two superior maxillary bones, the interval between the middle incisor teeth of each jaw, the symphysis menti, and the genial processes. 2. On each side, the posterior surface of the alveolar border of the upper jaw, and the two rows of teeth which lie across each , other like the blades of scissors in the middle, but meet posteriorly. 3. The posterior surface of the inferior maxilla, the internal oblique line, the sub-lingual and sub-maxillary fossae, and, lastly, the base of the inferior maxilla. Zygomatic or Lateral Regions. These regions are bounded above and on the outside by the zygomatic arch ; above and on the inside by the transverse ridge which separates the temporal from the zygo- matic fossa. They present first a plane surface, formed by the ramus of the inferior maxilla ; when this part is removed, we observe the zygomatic fossa, the superior wall of which is formed by the inferior surface of the great wing of the sphenoid, the anterior by the maxillary tuberosity, the internal by the outer plate of the pterygoid process, and the external by the ramus of the inferior maxilla. The posterior and inferior walls are wanting. At the bottom of this fossa, between the maxiUary bone and the anterior surface of the pterygoid process, is a large vertical fissure, named by Bichat the pterygo-maxillary fissure ; this opening leads into a sort of fossa, denominated by the older anatomists bot- tom of the zygomatic fossa, and by Bichat spheno-maxillary fossa, which it is important to study carefully, because five foramina or canals open into it, viz., three behind ; thefora' men rotundum, the vidian or pterygoid, and the ptery go-palatine canals : a fourth on the in- side, the spheno-palatine ; and a fifth below, the superior orifice o{the posterior palatine canal. Lastly, the spheno-maxillary fossa presents, at the union of its superior with its ante- rior wall, the spheno-maxillary fissure [fig. 21, before 3), which, on the one hand, makes an acute angle with the sphenoidal fissure (or foramen lacerum orbitale), and, on the other, a right angle with the pterygo-maxillary fissure. The spheno-maxillary fissure, which is traversed solely by some nerves and vessels, is formed internally by the max- illary and palate bones, externally by the sphenoid, and at its anterior extremity, which is very broad, it is completed by the malar bone. 62 OSTEOLOGY. ■' Cavities of the Face. ---i. >*»..:•,. TTie study of those bones which we have been engaged in examining has made us ac- quainted with the existence of a great number of cavities, which considerably augment the size of the face, and multiply its internal surfaces, without proportionally increasing the weight. All the cavities of the face may be reduced to three principal : viz., 1. The orbital cav- ities ; 2. The nasal fossae, of which ail the sinuses are dependances ; and, 3. The buc- cal cavitv, or mouth. The Orbits. These cavities, two in number, have the form of quadrangular pyramids, the axes of which, prolonged backward, would intersect each other in the situation of the sella tur- cica. It shoidd, at the same time, be remarked, that the internal wall of the orbit does not participate in this obliquity, but is directed straight from before backward. We have to consider in each orbit, a superior, an inferior, an external, and an internal wall ; four angles which correspond to the intersection of these surfaces ; a base and an apex. The superior wall, or roof of the orbit, formed by the frontal bone in front, and by the orbital or lesser wing of the sphenoid behind, is concave, and presents from before back- ward, 1 . Towards the outside, the lachrymal fossa. 2. On the inside, the slight depres- sion in which the pulley for the superior oblique muscle is attached. 3. The suture be- tween the lesser wing of the sphenoid and the orbital plate of the frontal.bone. 4. The foramen opticum. The inferior wall, or floor, forms a plane inclined outward and downward, and pre- senll from before backward, 1. The infra-orbital canal. 2. A suture which marks the union of the malar bone with the superior maxilla. 3. The orbital surface of the superior maxilla. 4. A suture which marks the union of the superior maxilla with the palate bone. 5. The orbital facette of the palate bone. The external wall, formed by the sphenoid and the malar bone, presents an almost ver- tical suture, which indicates internally the spheno-jugal suture. The internal wall, formed by the os unguis, the ethmoid, and the sphenoid, presents two vertical sutures : in front, that which unites the os unguis to the ethmoid, and be- hind, that which unites the ethmoid to the sphenoid. In front of these sutures is the lachrymal groove, formed by the union of the os unguis and the ascending process of the superior maxilla ; at the lower part of this groove we find the wide and very oblique ori- fice of the nasal canal or duct, which opens into the middle meatus of the nose, and es- tablishes a direct communication between the orbital and nasal cavities. Of the four angles, two are superior and two infetior. Of the two superior, one is in- ternal, the other external. The external superior angle presents the sphenoidal fissure behind, and the inner aspect of the spheno-frontal and fronto-jugal sutures. The internal superior angle presents the suture of union of the frontal bone with the ethmoid behind, and with the os unguis in front. The orifices of the two internal orbital foramina are seen in the situation of this suture. Of the two inferior angles, the external presents the spheno-maxillary fissure, a portion of the malar bone, and the opening of the jugal canal. The internul presents an uninter- rupted horizontal suture, which unites in front the maxillary bone to the os unguis ; more posteriorly, the maxillary bone, and then the palate bone, to the ethmoid. The base of the orbit is cut obhquely from within outward, and from before backward ; its ver- tical diameter is, for the most part, quite perpendicular to the horizon, but is sometimes rendered slightly oblique by the projection of the frontal sinuses. At the apex of the or bit is the union of the sphenoidal, the spheno-maxillary, and pterygo-maxillary fissures. The Nasal Fossa. These fossae are two in number, separated from each other by a vertical septum di- rected from before backward ; they are situated in the middle of the face, and are pro- longed into the interior of several of the bones of the face and cranium by means of the cavities called sinuses. To describe their situation more exactly, we may say that they are placed below the anterior and middle part of the base of the cranium, above the cav- ity of the mouth, between the orbits, and the canine and zygomatic fossae of each side. In order to have an exact idea, either of the dimensions or the shape of the nasal fossae, it is necessary to have recourse to horizontal and vertical sections, of which the latter should be made both from before backward and from side to side. With regard to their dimensions, the nasal fossae (see figs. 22 and 37) present, 1. A vertical diameter, larger in the middle than before or behind. 2. A transverse diameter much shorter than the other two, and gradually contracted* from the lower to the upper part, on account of the obliquity of the external wall. 3. An antero-posterior diameter, which measures the whole of the interval between the anterior and posterior openings of the nares. * This pro^essivo contraction of the nasal fosss from below upward, and the obliquity of the externa! wall, ought to be remembered during the introduction of instruments into the nose. THE FACE IN GENERAL. ^ ■ The nasal fossae have a horizontal direction, but are nevertheless slightly inclined backward and downward ; this is caused by the sloping of the inferior wall and the ob- liquity of the body of the sphenoid, which fonns part of the superior wall. They are irregular cavities, and have four walls ; a superior, an inferior, an internal, and an ex- ternal ; and two orifices, an anterior and a posterior. The superior wall or roof of the nasal fosses presents a concavity looking downward : it o : :rraefl 1 In front by the proper bones of the nose, and in a small degree by the na- sal spine of tne frontal bone. 2. In the middle, by the cribriform plate of the ethmoid. 3. Behind, by the body of the sphenoid. In this wall are two transverse sutures, name- ly : before, the suture which indicates the union of the nasal and frontal bones, and be- hind, that which marks the union of the ethmoid and sphenoid. At the back part of this wall the opening of the sphenoidal sinus is seen. The inferior wall or floor, much broader but shorter than the superior, presents a trans- verse concavity ; it is directed from before backward, and slightly from above downward, which arrangement concurs in determining the obliquity of the nasal fossae. It is form- ed, in front by the superior maxilla ; behind, by the palate bone ; a transverse suture marks the union of these bones. Near its anterior extremity, and at the side of the me- dian line, the floor of the nasal fossa? shows the superior orifice of each branch of the an- terior palatine canal {g, fig. 22, and o, fig. 37). The internal wall (see fig. 22) formed by the septum is generally flat, but sometimes concave or convex, according as it is bent to one or the other side.* We find here the suture which indicates the union of the vomer with the perpendicu- ' lar plate of the ethmoid (3 4, fig. 22) ; the septum in the skeleton is deeply notched in front, and this notch (14 8), which is formed above by the perpendicular plate of the eth- moid, and below by the vomer, is occupied in the fresh state by a cartilage, called the cartilage of the septum. The external wall {fig. 37), remarkable for its anfractuosities, is formed by the ethmoid (,6 c), the OS unguis, the palate bone (m y), the superior maxillary p^ 37_ (* ic o), and the inferior turbinated bone (d). It presents from above downward, 1. The superior turbinated bone, superior concha, or concha of Morgagni (i), in front of which is a rough square sur- face. 2. The superior meatus (between b and c), at the back part of which we find the spheno-palatine foramen (n), and the open- ing of the posterior ethmoidal cells. 3. Below the superior mea- tus, the middle turbinated bone, or middle concha (c). 4. Below, the middle meatus (between c and d), at the back of which is the open- ing of the maxillary sinus already described {s-ee maxillary bone, Jig. 25) ; and in front, the infundibulum (s, fig. 37), which leads into the anterior ethmoidal cells. 5. The inferior turbinated bone, or inferior concha (d). 6. The inferior meatus (m o), in which we find the inferior orifice of the nasal canal. The anterior and posterior openings of the nasal fossae have been described with the anterior and inferior regions of the face. General DevelopTnent of the Face. The development of the face is not effected solely by an equable increase of its dimen- sions ; for certain regions are at one period of life predominant, at another period rela- tively smaller, which circumstances give rise to very characteristic differences of form at different ages. State of the interior Region of the Face at different Periods of Life. In the Foetus. — The upper part of the face shows a remarkable predominance, depend- ant upon the early development of the frontal bone and the great capacity of the orbits. The middle portion, or the superior maxilla, on the contrary, is very much contracted by the absence of the maxillary sinus and canine fossa ; the vertical dimensions of the superior maxilla and of the palate bone are so small, that the edge of the orbit and the alveolar border are almost contiguous. We should mention here that the prominence of the alveolar border, which still encloses all the germs of the teeth, is the principal cause of the absence of the canine fossa. Lastly, the inferior maxilla is contracted in its vertical diameter, like the superior, and, like it, presents a decided prominence in front, by reason of its enclosing the germs of the teeth in the alveoli. The inclusion of the dental germs also, by causing the alveolar border to project, produces a degree of obliquity downward and backward of the symphysis ; to these causes of the small extent of the vertical dimension of the face, we must add also the inconsiderable height of the ethmoid at this period. * Sometimes the deviation of the septum is so considerable that the internal touches the external wall, and, consequently, there is great difficulty in th« passage of the air. This circumstance has given nse ir some cases to a suspicion of the existence of polypus. i 64 OSTEOLOGV. The transverse dimensions of the face are very considerable at the level of the orbits , at the lower part of the face, on the contrary, they are proportionally much less than in the adult. The characteristics, then, of the face of the foetus are, 1. The smallness of its verti- cal dimension. 2. The predominance in size of its upper over its lower part. In the adult, the development of the maxillary sinus, the widening and vertical exten- sion of the alveolar arches, give to the face the expression which characterizes it at that period of life. In the aged, the loss of the teeth, and the disappearance of the alveolar edge, partly restore to the face the expression which it had in tlie foetus ; but the elongation and prom- iuence of the chin, which, from the diminution of the vertical diameter, approaches the nose, and the symphysis of which is now oblique from behind forward and downward, impress upon it a peculiar character. The obliquity of the cliin, just mentioned, is pre- cisely the reverse of that which exists in the foetus. State of the Lateral Regions in different jjges. These regions undergo the fewest changes of all ; for if, on the one hand, the devel- opment of the maxillary sinus tends to increase the prominence of the maxillary tuber- osity in the adult, on the other, the inclusion of the dental germs in the superior max- illa, during foetal life, compensates for the want of the sinus. State of the Posterior Region of the Face at different ^ges. In the guttural portion, this region presents, in the foetus and the infant, the foUowmg circumstances : the posterior borders of the rami of the jaw are very oblique, instead oi being almost vertical, as in the adult ; the pterygoid processes, and the posterior nasal openings, are also directed very obliquely downward and forward, instead of vertically, on account of the absence as yet of the maxillary sinus, which, during its development, carries them backward. From the obliquity of the posterior border of the ramus of the jaw, it follows that the articular surface of the condyle which surmounts it looks back ward instead of upward. In the horizontal or palatine portion, the inferior region of the face has proportionally less extent from before backward than in the adult, on account of the obliquity of the pterygoid process, and the slight development of the maxillary sinus. We perceive, then, how great an influence the varying conditions of these sinuses exercise over the whole configuration of the face, at the different periods of life. It may be easily conceived that the cavities of the face must undergo important chan ges during these alterations in the shape of the face which we have been describing. The most remarkable is the tardy development of the nasal fossae compared with that of the orbits. It may even be said that they proceed in an inverse ratio. The orbital cavity, intended to receive the globe of the eye, which is already highly developed at the time of birth, is of great capacity. This magnitude it owes entirely to the rapid growth of the frontal and sphenoid bones ; because the malar bone and the superior maxilla con- tribute but little towards it, and the height of the ethmoid is so small, that the vertical diameter of the orbit, which depends upon that of the ethmoid, is less considerable than its transverse diameter. The nasal fossas, which are very small in the foetus, gradually acquire an increased extent of surface, by the growth in height of the ethmoid, the pal- ate bone, the superior maxillary, and the vomer, and by the augmented size of the turbi- nated bones ; and their surface is still farther extended by the enlargement of the max- illary, sphenoidal, and frontal sinuses, and the ethmoidal cells. The development of the frontal sinus, it may be observed, is owing chiefly to the separation of the two tables of the bone, the anterior of which is almost always thrown forward, the posterior remain- ing stationary. There are, however, some examples on record, in which it was evident that the sinus was formed almost exclusively by the retrocession of the posterior table. THE THORAX, OR CHEST. The Sternum. — Ribs. — Costal Cartilages. — The Thorax in general. — Development. The thorax {■&upa^, the chest) is a sort of bony cage intended to contain and protect the principal organs of respiration and circulation. The parts which enter into its com- position are twelve dorsal vertebrae behind, the sternum in front, and twelve flexible bones named ribs, on each side. We have already described the dorsal vertebrae, and have now, therefore, only to notice the sternum and the ribs. The Sternum (a b c,fig. 38). The sternmn, so named from the Greek word arepvov, the breast, is a kind of flat- tened, symmetrical, bony column, which occupies the anterior and middle part of the thorax. It is situated between the ribs, which support it like props. The clavicles, 6S and through them the upper extremities, rest upon its upper part as a basis, during their movements. The sternum is not immovably fixed in its place; it is raised and de- pressed, as we shall point out in describing the mechanism of the thorax. The length of the sternum, which is proportionally smaller in the female than in the male, varies from 5^ to 7i inches. At its upper part its breadth is from IHo 2 inches ; it then becomes contracted, then again expands, and terminates below in a very nar- row extremity. Its thickness above is about 6 lines ; at its lower part it is much thin- ner, never exceeding 3 hues. With regard to figure, the sternum was compared by the ancients to the sword of a gladiator, and from this have arisen the denominations given to its various parts. The upper part {a), which is broadest, has been called the handle (manubrium) ; the middle part (J), the body {mucro) ; and the lower extremity (c), the poini ; xipJioid appendix {pro- cessus cnsiformis). This division of the bone into three parts has been retained by some modern anatomists, who describe the three pieces of the sternum separately as so many distinct bones. We shall adhere to it only, however, in speaking of the development of the bone. The sternum presents two surfaces, two borders, and two extremities. 1. The anterior or cutaneous surface is shghly convex, and forms an oblique plane down- ward and forward ; it presents three or four projecting transverse lines, which are tra- ces of the union of the original pieces of the bone, and divide it into surfaces of unequal size. The line which marks the union of the first two pieces of the bone is the most remarkable ; it causes a projection of variable size in different individuals, which has been sometimes mistaken for a fracture or exostosis. At the lower part of this surface, we find in some subjects a foramen which perforates the bone : sometimes, in place ot this foramen, there is a considerable aperture, to which much importance has been attached, as affording a proof of the primitive separation of the bone in the median hne. The existence of this opening explains how purulent matter, deposited behind the ster- num, may in certain cases make its way outward without any absorption of the bone. The anterior surface of the sternum is covered by the skin, and an interlacement of very numerous aponeurotic fibres. 2. The posterior, mediastinal, or cardiac surface (a b c), is slightly concave from above downward, and presents, in young subjects, lines (e e) corresponding to those which occupy the anterior ; but all which, excepting the one between the first and second pieces of the bone, are effaced at a more advanced age. This surface is in relation with many organs contained in the chest, and especially the heart, in front of which the sternum forms a kind of shield.* At the lower part of this surface are several nutritious foramina. 3. The borders, very thick and sinuous, present seven articular cavities {d d, &c.), sep- arated from each other by semilunar notclies, which are longer above than below, where the facettes closely approach one another. The uppermost of these seven cavities is shallow, triangular, and at an early age becomes ingrained with the cartilage of the first rib ; those which follow are d^Sfttu angular, and situated at the extremities of each of the lines (e e) above mentionfd:^J^ey are all intended to articulate with the cartilages of the first seven ribs. WhenjgiSmined in a dried specimen, they appear more angiSar and deeper in proportion to the^buth of the subject. 4. The superior or clavicular extremity is the broadest and thickest part of the whole bone, presenting a notch, transversely concave, which bears the name of fourchette (/) of the sternum (or semilunar notch) ; on each side {g g) is an oblong articular surface, concave from without inward, convex from before backward, articulated with the clav- icle, and surrounded with inequalities for the insertion of muscles and ligaments. It frequently happens that the two clavicular facettes are not at the same height ; a fact which was noticed by Morgagni, and which I have attributed to the unequal wearing of the two articular surfaces. 5. The inferior or abdomj^nal extremity is formed by the xiphoid appendix (c) {^i^o^, a sword), called also xiphoid'^ ensiform cartilage, because it often remains cartilaginous to Hdult age. In length, shape, and direction, it presents numerous varieties ; it is fre- quently bifid, sometimes pierced by a foramen, and is accasionally bent forward, or to one side, and, in certain cases, much depressed : its summit gives attachment to an ap- oneurotic structure, called the linea alba ; behind, it indirectly corresponds with the stomach, which rests upon it when the body is placed in a prone position.! * This use of the bone is eiemplified in many animals which are provided with a sternum, though they hav« no ribs ; for example, the frog. This bone has attracted much of the attention of the modem transcendentalists. By them it is regarded as a vertebral column anterior to the intestinal canal in man, and inferior to it in the lower animals. Many of them have conceived that they have found in it a cervical, a dorsal, and a lumbar regfion, &c., &c. M. Cruveilhier, in the opinion of the editor, with much propriety, in the first edition of his work, took no notice of the idle and fanciful speculations of the transcendentalists, either in reference to the sternum, or to the analogy which exists between the bones of the cranium and the vertebrae. Although he lias, in the sec- ond edition, introduced some notices in reference to the analogy which these gentlemen have attempted to establish between the cranium and the vertebral column, believing that they only increase the size of the book without adding to its value, we have excluded them. — Ed. t In front this appendix is sub-cutaneous, and the skin which covers it is so sensible that the slightest con- I 66 OSTEOLOGY. Connexions. — The sternum articulates with sixteen bones, viz., fourteen ribs through the medium of their cartilages, and the two clavicles. Structure. — It consists of two very thin compact laminae, with an intervening spongy substance, the cells of which are very large, and have very delicate parietes ; it is one of the most spongy bones of the body, and to this circumstance the frequency of its dis- eases is doubtless attributable. Development. — The sternum is one of the slowest bones in its ossification ; up tc the sixth month of fcEtal life, the broad cartilage of which it is composed exhibits no bony points. It is also, of aU the bones, the one in which the phenomena of ossification pro- ceed with least regularity. For the sake of simplicity, we shall study in succession the development of the three parts which we have indicated, under the names of manubrium, body, and xiphoid appendix. 1. Ossification of the Manubrium. — This part of the bone sometimes presents a single nucleus, rounded, and transversely oblong ; sometimes it presents two nuclei, and, in this case, they may be either placed one above the other, or side by side. In the former case, the uppermost nucleus is the larger ; in the latter, both may be symmetrical and of equal size, or, what is far more common, they may be of unequal magnitude. Lastly, the manubrium occasionally presents more than two osseous points. Albinus found three in one subject and four in another. It should be remarked, that in the case of plurality of osseous points, the largest are generally situated above : the exceptions to this rule are very rare. The osseous points make their appearance from the fifth to the sixth month of foetal life. 2. Of the Body. — The osseous nuclei which enter into the composition of the body of the sternum have generally a rounded form when they are single, and are situated in the median line ; when they exist in pairs, or are placed laterally, they are more elongated, but smaller, and appear to represent only the half of one of the single nodules. These different osseous points are always so arranged as to be situated between two costo- sternal articulations, so that a portion of the sternum is developed in each of the inter- vals comprised between two ribs. The last piece is the only exception, being common to the articulation of the sixth and seventh ribs. If there be more osseous points than one in an intercostal space, these, as Albinus has remarked, are invariably placed laterally, not one above the other. There are, therefore, four primitive pieces in the body of the sternum, and each of these is sometimes formed by one point of ossification ; at other times, by two lateral points. The following is the order in which the ossification of the body of the sternum pro- ceeds : the two upper pieces first appear from the fifth to the sixth month of foetal life ; the third is visible at the sixth month ; the fourth most conunonly makes its appearance after birth, but sometimes towards the end of gestation. In the ossification of the body of the sternum, we more frequently find examples of two symmetrical nodules placed on opposite sides of the median line, than in the develop- ment of the manubrium, f^*^ Union of the Points of Ossification of the Body. — In cqjteidering the union of the differ- ent parts which compose the body of the sternum, it i?|i|Mpssary to make a distinction between the lateral conjunction, that is, the union of the osseous points which are situated on each side of the median line, and the vertical conjunction, or the union of the pieces of the sternum properly so called. The lateral conjunction, or the union of those osseous germs which form a pair in the same interval, always precedes the vertical conjunction. The vertical conjunction, oj the union of the pieces of the body of the sternum together, commences with the two inferior portions. After this union, the body of the bone con- sists only of three parts. The second piece then unites with the lower ; the sternal foramen is found sometimes at the junction of these last-mentioned parts, sometimes at the place where the two lateral points of the fourth and of the third portion of the body are united. The first piece of the body is not united to the two others until from the twentieth to the twenty-fifth year. It should be observed, that the union of the divisions of the body of the sternum takes place precisely in the inverse order of their appearance. In fact, the appearance of the osseous points proceeds from above downward, their union from below upward ; a fact which verifies an assertion formerly made, viz., that the order of development of osseous points is not always correlative to the order of conjunction. 3. Ossification of the Appendix. — This is generally accomplished by one nodule : some- tusion produces, even in the most powerful men, syncope.* This fact may explain the importance which has been«ttached to the configuration of this process, and to the names "pit of the stomach," " scrobiculus cordis," " pracordittm," which have been given to the region which corresponds to it. Much has been said of the dis- placement of the Kiphoid appendix, and of the accidents to which this has given place ; but, in reality, these displacements hare never been observed, and the accidents which have been attributed to them have most cer- tainly depended on&n injury inflicted on the parts situated behind it. * We do not believe that the skin situated over this appendix is more sensible than the skin elsewhere. The syncope which follows a blow here is, in our opinion, produced by the impression it produces on the in» temal organs. — Ed. THE RIBS. 6¥' tunes there are two, and then they are rarely symmetrical. The process commences in the upper part of the cartilage, and very rarely extends through the whole. The time of appearance of the osseous point is extremely variable ; sometimes it is visible to- wards the third or fourth year ; sometimes not until the twelfth, or even the eigh- teenth year. In adult age, the sternum is composed of the three parts the development of which I have just noticed, and which the ancients considered and described as distinct bones. From the fortieth to the fiftieth year, and sometimes later, the appendix becomes united to the body, which very rarely joins the manubrium ; when such is the case, the union is more apparent than real ; for if the bone be cut verticdly, the articulation is apparent, under a very thin layer of osseous matter. From what has been said of the numerous varieties of ossification, it will be evident that it is impossible to assign to this bone a limited number of osseous points. To those which have been noticed I would add two others, described by Beclard under the name of supra-sternal points, which I have seen once only in the sternum of an adult, in the form of pisiform nodules, placed on each side of the semilunar notch of the stemiun. The Ribs (1 to 12, Jig. 38). The ribs (^costce, from custodes, as if, according to the explanation of Monro, they were the guardians of the organs of the chest) ^^^^ 3g are osseous arches stretched from the ver- tebral column to the sternum. Their pos- terior four fifths consist of bone ; the ante- rior fifth is cartilaginous. The osseous portion is the rib, properly so called ; the cartilaginous portion is named the costal cartilage. The ribs are 24 in number, 12 (1 to 12) on each side. Sometimes there are 26, thirteen being on each side, and then these supernumerary ribs are formed either from a part of the transverse process of the sev- enth cervical vertebra, or of the transverse process of the first lumbar, which affords an evident proof of the analogy existing be- tween these parts. Sometimes, but more rarely, there are only 22 ribs, an anomaly pointed out by Galen. In this case, we sometimes find two adjacent ribs united throughout their entire length, sometimes the first rib in a rudimentary state, being properly formed posteriorly, but having its anterior extremity lost in the>substance of the scaleni muscles, or united to the second rib, and through it joined to the sternum.* The ribs are divided into two classes : 1. Those which extend from the vertebrae to the sternum, the true ribs, sternal or ver- tebrosternal ribs (1 to 7). 2. Those which do not reach the sternum, the false, aster- nal, or vertebral ribs (8 to 12). The last two false ribs (11 12) are called floating, because their anterior extremity is movable in the fleshy parietes of the abdomen. The ribs are designated numerically ;5rs^, second, &c., counting from above downward. It should, however, be observed, that in many surgi- cal works, the ribs are counted from below upward, which is the easiest method on the living subject. The ribs have certain general characters which distinguish them from all other bones and certain proper characters, by which one is known from another. General Characters of the Ribs. The ribs resemble flattened bony arches of about six lines in breadth, and one in thick- ness, and of lengths varying according to their situation. The first rib is almost hori- lontal, and the others in succession slope gradually more obliquely from behind forward, and from above downward, their anterior extremities being on a much lower plane than the posterior. Considered with regard to their axes, i. e., their absolute direction, the ribs represent portions of a circle which successively increase to the eighth, and dimin- * la a subject prepared for my lectures, the transverse processes of the second, third, and fourth lumbar vertebrae were elongated, so as to form supernumerary ribs, while the transverse process of the first was un- changed. 09}, OSTEOLOGY. ish again to the twelfth ; their curvature is not regular, the posterior part representing the segment of a much smaller circle than the anterior. They are generally tvnsted upon themselves, so that their two extremities cannot rest at once upon the same horizontal plane. The point where this torsion exists is marked on the convex surface by an ob- lique projecting line, called the angle (Ji) of the rib ; but it is not correct to consider the angle of the rib as resulting from this torsion ; it appears to me simply intended for mus- cular insertions. The ribs have a body and two extremities. The posterior or vertebral extremity is Fig. 39. thicker than the rest of the bone, whence it has received the name of head (i) {capitulum casta), and presents two half surfaces (c c, fig. 39), of which the upper is smaller than the lower, separated by a horizontal ridge. These two facettes articulate with corresponding surfaces on the bodies of the dorsal vertebrae {d rf, fig. 39). The head is supported by a constricted portion, the neck (k, fig. 38), which is flattened from before backward, and is the weakest part of the bone. It presents behind some inequalities which correspond to the _ transverse process of the dorsal- vertebra below. Externally to the neck is an eminence known as the tubercle \l I) of the rib ; it is divided into two parts, which are united at an angle, viz., an internal and inferior portion {I), smooth and convex, which articulates with the transverse process of the vertebra below the particu- lar rib examined ; and an external rough portion (Z), which gives attachment to liga- ments. The tubercle is in general most prominent in the upper ribs. That part of the rib which is included between the head and the tubercle {neck, cervix) is directed from within outward, and slightly from above downward, so as to reach the summit of the transverse process of the vertebra below. Beyond the tubercle, the rib still follows the same direction for not more than fifteen lines ; it is then bent decidedly forward. The situation of this curve, which corresponds with the torsion of the edges above mentioned, is at the angle of the rib. The interval which separates the tuberosity from the angle is the thickest and strongest part of the rib. The rest of the rib which is before the angle becomes broader and thinner, and is di- rected forward, so that, as Haller expresses it, the line which it describes represents in some measure the tangent of the posterior curve. The anterior extremity (m) has a hollowed oval facette for receiving the cartilage. Besides the objects we have already described, we observe, near the anterior extremity of the rib, an oblique line, analogous to that which forms the angle, but much less marked. This line may be considered as forming the anterior angle of the ribs, and, like the posterior, it is intended for muscular insertions. From what has been said, we perceive that the ribs present, 1. A posterior extremity or head, supported by a neck ; S. An anterior extremity united to the costal cartilage ; 3. A body, having an external, or cutaneous surface, which is convex ; and an internal, or pul- monary surface, which is smooth and concave ; a superior edge, which is curved, thick, and rounded ; and an inferior edge, which has a greater dujprature than the superior, is thin and sharp, and marked by a groove or furrow on the inner surface, called the groove of the ribs {e, fig. 39), which receives and protects the intercostal vessels and nerves. Lastly, the ribs have a double curvature, one of the surfaces, another of the edges ; this last is the curvature of torsion. Connexions. — The ribs are articulated, behind, with the dorsal vertebrae ; in front, with the costal cartilages. Structure. — The external aspect of a rib resembles a long bone ; but the internal con- formation is analogous to that of flat bones. The compact and spongy substances are so distributed that these bones enjoy a certain degree of flexibility, with great power of resistance. In young subjects, the compact substance is in excess ; in the aged, and in certain diseases, the opposite is the case ; hence the extreme fragility of these bones, which are then broken by the least effort. Development of the Ribs. — The ribs are among the earliest developed of the bones, the 'ossification of their bodies commencing from the fortieth to the fiftieth day after concep- tion. They are developed by three osseous points : one primitive, and two epiphysary. The primitive point by itself forms the body of the bone. Of the two epiphysary points, one is intended to form the hccid of the rib, the other the tubercle. They appear from the sixteenth to the twentieth year, and they unite with the rest of the bone about the twenty-fifth year. These epiphysary points do not exist in the two lower ribs, which, consequently, have only one point of ossification. Special Characters of different Ribs. The differential characters of the ribs have reference, first, to the length, which increas- es gradually from the first to the seventh, and diminishes again to the twelfth ; secondly, to the curvature, the four upper ribs being parts of much smaller circles than the rest, and thus forming the summit of the cone of the chest, while the lower ribs constitute its COST'XL CAST ILAGES. 18^ ISase ; and, lastly, to certain peculiarities of conformation in the first, second, third, elev enth, and twelfth ribs, which require special description. The first rib {\,fig. 38, and^. 40) is the shortest, and proportionally the broadest of all the ribs, thus forming an imperfect hd to the bony case which p- ^q constitutes the thorax. Its edges are curved, but its surfaces are flat. The curve which it describes forms part of the circum- ference of a much smaller circle than any of the other ribs. The posterior extremity has a small head with a single convex facette r^M ^^^k (a, fig. 40), supported by a long, thin, and cylindrical neck (b). The tubercle (c) is very prominent ; it occupies the external bor- der, and gives an angular appearance to this rib. The anterior extremity {d) is broader than that of any other rib. Of the two surfaces, one is directed upward and slightly outward, the other downward and a little inward. The superioi surface {fi^. 40) has two depressions separated by a tuberosity (e). The anterior corre- sponds to the subclavian vein ; the posterior to the artery of the same name. The tu- berosity which separates them gives attachment to the anterior scalenus muscle. The internal edge (a e d) is concave ; the external (a c d) is convex, and has no groove. The first rib has neither a curvature of torsion, nor an angle ; so that the whole of it can rest upon the same horizontal plane. The superior surface presents, also, near its anterior -extremity, a depression, which appears to result from pressure by the clavicle, which I have seen, in some cases, immediately articulated with this bone. The second rib (2, fig- 38) preser\'es many of the characters of the preceding, but dif- fers essentially in its length, which is at least double ; it belongs to a much larger circle : it has no curvature of torsion, and can rest upon the same plane with its two ends ; the angle is scarcely visible. The external surface is directed upward ; it presents in the middle a very rough eminence for the attachment of the serratus magnus muscle. The internal surface looks obliquely downward ; near the tubercle it has a very smtill groove. The third rib (3, fig. 38) differs from the second by its great length, by the presence of the angle, and by a curvature of torsion sufficient to prevent the two ends from rest- ing at once upon the same horizontal plane. The eleventh and twelfth ribs (11 l^,fig- 38) differ from all the others by the following characters: 1. They form segments of much larger circles than any of the others; 2. Their heads have only one articular facette, and this is flattened ; 3. They have no neck, properly so called ; 4. They have no tubercle : 5. They have no groove ; 6. They have a very thin and pointed anterior extremity. These two ribs differ from each other only in length, the twelfth being the shorter. The Costal Cartilages (T to \1\jig. 38). The flexibility and elasticity of the ribs is partly owing to their structure, but more ' especially to the costal cartilages which prolong them in front. There are twelve cos- tal cartilages, distinguished niunerically as first, second, third, &c. ; they are separated from each other by intervals, which are very considerable at the upper part of the tho- rax, but gradually diminish as we proceed downward : it is not very uncommon to meet with thirteen cartilages on one side ; at other times there are only eleven. We some- times find two cartilages which are joined together, and articulated with the sides of the sternum ; when there are thirteen cartilages, the supernumerary one generally exists between the third and fourth ribs ; it is thin, and, as it were, rudimentary ; it does not form the continuation of any rib, and terminates insensibly in the muscles. The first seven cartilages (1 to 7) articulate immediately with the sternum ; and hence the name of sternal given to the ribs with which they are connected. Of the other five cartilages, the last two (11 12) have no connexion with those that precede them; and, from this circumstance, the navae floating has been given to the last two ribs. General Characters of the Costal Cartilages. All the costal cartilages are flattened like the ribs, and precisely resemble, in breadth and thickness, the bones to which they are attached. The external end is received into a cavity hollowed out in the anterior extremity of the rib : their internal or sternal ex- tremity, which is much narrower than the external, is angular, and articulates with the corresponding angular facettes of the sternum. Their anterior or cutaneous surfaces are slightly convex, and covered by the muscles of the anterior region of the trunk, to many of which they give attachment. Their posterior or mediastinal surfaces are slightly concave. Their superior and inferior edges bound the intercostal spaces, and give attachment to the muscles of the same name. They are altogether distinct from articular cartilages, and have a peculiar tendency to ossify, this process taking place partly on the surface, and partly from within outward. Differential Characters of the Costal Cartilages. The costal cartilages increase in length from the first to the seventh, and sometimes to the eighth, which in this case articulates with the sternum ; they diminish in length 70 OSTEOLOGY. from the seventh to the twelfth. This difference depends on the circumstance that the osseous parts of the upper ribs terminate anteriorly in a line directed obhquely from above downward, and from within outward, and that the sternum is only about half the length of the lateral wall of the thorax, so that only the first four or five cartilages could join this bone, did not the others bend upward, so as to reach its sides or join the lower edge of the cartilage above ; the first three cartilages alone, therefore, follow the same direction as the bony rib. The first cartilage differs from all the others by its shortness, its thickness and breadth, and its tendency to ossify ; it is ahnost always bony in the ■ adult ; it is often continuous with the sternum, but is sometimes only contiguous, in which case its articulation to this bone presents a great difference as respects motion. The second and third costal cartilages cannot be distinguished from each other, but they differ from the rest in being joined at right angles with the sternum, in not being bent, and in being as broad at their sternal as at their costal extremities. The fourth carti- lage becomes bent upward, after having followed the direction of the rib for a little way. The length and curvature of the cartilages of the fifth, sixth, and seventh ribs progres- sively increase : the seventh is at least three inches long, whUe the fifth is not more than thirteen or fourteen hues ; their inner ends become successively narrowed, so as to correspond with the diminishing cavities on the edges of the sternum ; the borders of the fifth, sixth, seventh, and eighth costal cartilages articulate together, and present, for this purpose, articular facettes, supported by eminences. The cartilages of the eighth, ninth, and tenth ribs gradually diminish in length ; externally they have the same breadth as the rib, and decrease as they pass inward, so as to terminate by a pointed extremity, which is applied to the lower edge of the rib above. The cartilages of the eleventh and twelfth ribs are extremely short, especiaUy that of the twelfth, which is only a few lines in length ; their internal free extremity loses itself, so to speak, in the substance of the abdominal parietes, so that they are altogether unconnected with the other cartilages. The Thorax in genekal. The sternum, the ribs, and the whole dorsal region of the vertebral column, form the framework of a large visceral cavity, the thorax, intended to contain and protect the chief organs of respiration and circulation. It occupies the upper part of the trunk, be- tween the thoracic extremities ; its boundaries are very well defined above, but below there is not any line of demarcation in the skeleton between the cavities of the thorax and abdomen ; or, rather, the bony thorax is common to the thoracic and abdominal vis- cera. We shall see afterward, that these two cavities are separated from each other by a movable and muscular septum called the diaphragm. With regard to capacity, the thorax holds a middle place between the cavity of the cranium and that of the abdomen. In each individual, the capacity of the thor2ix is ex- actly proportional to the volume of the lungs ; and as, in general, voluminous lungs co- exist with a highly-developed muscular apparatus, it follows that the size of the thorax is no equivocal sign of a vigorous constitution. The thorax differs much from the ab- dominal cavity in regard to its extensibility, being only capable of very Umited alternate movements of dilatation and contraction. In the structure of the thorax, we find the twofold condition of solidity and mobility in so perfect a degree,, that the framework of which it is composed is equally fitted to serve as a protecting structure and a respira- tory apparatus. This limited dilatabihty contrasts, on the one hand, with the almost in- definite extensibility of the abdominal cavity, and, on the other, with the absolute want of extensibility in the cranium. We should form a very incorrect idea of the dimensions and shape of the thorax, if we were to judge of them by its external aspect while still covered by the soft parts, and surrounded by that species of girdle which is formed by the shoulder round its upper part ; for we should then conclude it to be a truncated cone, with the base above. On the contrary, when the surrounding parts are removed, the thorax represents a cone, the base of which is in precisely the opposite direction, that is, below. The height of Ihe thorax cannot be measured with exactness, because it varies according to the de- pression or elevation of the muscular septum, which intervenes between the thoracic and the abdominal cavities. We can only say, that the bony framework should be di- vided into two parts, a superior or supra-diaphragmatic, which belongs to the chest, prop- erly so called, and contains the lungs and heart ; and an inferior, which forms part of the cavity of the abdomen, and contains the liver, the spleen, the kidneys, the stomach, the duodenum, and part of the colon. It should be also remarked, that the supra and sub-diaphragmatic portions of the thorax constantly vary in their respective proportions ; and that these variations of height principally take place at the sides, the middle remain- ing always nearly the same. The transverse diameters increase rapidly from the upper to the lower part of the thorax. The same is true of the antero-posterior diameters, and these also sensibly increase opposite the concavity of the dorsal region of the spine. The antero-posterior diameters are much greater laterally than in the median line, where they are diminished by the considerable projection of the bodies of the dorsal ver- THE THORAX IN GENERAL. 71 tebrae. This shortness of the antero-posterior diameters between the sternum and the vertebral column is in proportion to the small size of the heart, which is situated in this region, as compared with that of the lungs, which occupy the sides. Antero-posterior Flattening. — The cone represented by the thorax is flattened from be- fore backward. This flattening appears to be connected with the existence of the clav- icle, for we meet with it in all animals provided with this bone, while in those in which it does not exist the flattening is lateral, i. e., from one side to the other. The shape of the thorax is subject to many varieties, as respects different individuals, age, sex, &c. Of the individual varieties, some are compatible with health, others are pathological, and constitute malformations, the history of which belongs to the subject of diseases of the chest. Sometimes they are congenital ; at other times they are the result of accidental circumstances which have modified the primitive conformation. In some subjects the lateral exceeds the antero-posterior flattening, and the sternum is prominent, as we habitually see it in the thorax of phthisical patients. Many individual varieties of conformation of the thorax are the effect of frequently repeated, or permanent compressions exercised on the bony cavity. I have seen infants in whom the thorax was perfectly well formed at birth, but had been deformed and flat- tened on the sides by pressure from the hands of the nurse. If there be, in fact, a time when the slightest external pressure may be productive of permanent deformity, it is during the first years of life. The effects of a strong and permanent constriction are also manifest in a very evident manner, in the alterations of the form of the thorax con- sequent upon the use of stays. This species of constriction affects principally the lower part of the chest ; so that the fifth, sixth, seventh, eighth, ninth, and tenth ribs are press- ed forward and inward, because the length and flexibility of their cartilages allow them to yield readily ; and all the viscera which correspond to this species of girdle undergo very marked alterations in their direction, and even in their figure and position. Thus the liver, the spleen, and the stomach are forced upward and compress the lungs, which, in their turn, are pushed to the upper part of the chest, and have a tendency to pass con- siderably beyond the level of the first rib ; 2. The stomach becomes more oblique ; 3. The transverse arch of the colon is often forced downward ; the pregnant uterus acquires an oblique direction. In an old female, whose thorax was so contracted below as to present the appearance of a barrel, and bore witness to the use of a very tight corset, the cartilage of the seventh rib, on the right side, was in contact with that of the oppo- site rib ; the xiphoid appendix was strongly depressed, and pushed behind the cartilages of the seventh and eighth ribs, which touched each otlier. Some varieties of conforma- tion depend upon deviations of the vertebral column ; they evidently belong to patholo- gic2il anatomy, and need not occupy our attention. In the female, the chest resembles a cone, with a larger base, but of less height than in the male. There are certain varieties at different ages, which will be noticed in the history of the general development of the thorax. As the thorax does not form a regular cone, when we speak of its axis being directed obhquely from above downward, and from behind forward, we only refer to its anterior wall, the posterior and latereil being altogether devoid of this obliquity. We shall now consider in detail the external and the internal surface of the thorax ; the inferior circumference or base, and the superior circumference or summit, resulting from its conical form. External Surface of the Thorax. On this surface we find an anterior, a posterior, and two lateral regions. The anterior or sternal region, much wider below than above, forms a plane inclined from above downward, and from behind forward, and more or less projecting according to the general conformation of the thorax. It presents, 1. In the middle, the cutaneous surface of the sternum; 2. On the sides, the series of articulations of the cartilages of the ribs with the sternum ; 3. The costal cartilages, those being the longest which ap- pertain to the lower ribs ; 4. Between the cartilages, certain intervals named intercostal spaces ; 5. Externally to the cartilages, an oblique line running from above downward, and from within outward, and marking the series of articulations of the costal cartilages with the ribs ; 6. Still more externally, another oblique line, wliich has not been pointed out, and which is formed by the anterior angles of the ribs ; it corresponds in obhquity with the chondro-stemal Hne, and forms the boundary of the anterior region. The posterior or vertebral region presents, in the median line, the series of dorsal spi- nous processes ; on the sides, 1. The vertebral grooves ; 2. The series of dorsal trans- verse processes ; 3. Their articulation with the tubercles of the ribs ; 4. A series of surfaces, of which the lower are the largest, and which are comprised between the angle and the tubercle of each rib ; 5. Lastly, an oblique line, running from above downward, and from within outward, formed by the posterior angles of the ribs. The lateral or costal regions resemble a sort of curved grate, more convex behind than in front, and showing the series of ribs and intercostal spaces in the same manner as the anterior and posterior regions. They increase in width from above downward, and 72 OSTEOLOGY, form a sort of inclined plane, with a curved surface, and obliquely directed from above downvi^ard, and from within outward. The first two intercostal spaces are both the broadest and the shortest ; the third and fourth are broader in front than behind ; the following are of almost uniform width through their whole extent : on the whole, tue breadth of the spaces diminishes from above downward, or, as Bertin remarks, tlie edge? of the lower ribs are almost in contact. The last two intercostal spaces form the onlj exception, for they are nine lines in width, while those in the middle of the chest are only about four. It should, moreover, be remarked, that the intercostal spaces are broader in front than behind ; a fact which may be easily shown by comparing the dis- . tance which separates the anterior extremities of the first and second ribs with that which intervenes between their posterior terminations. The length of the intercostal spaces increases from the first to the sixth ; it then diminishes to the last two, where it is very small. Internal Surface of the Thorax. This surface, like the external, is divided into four regions. The anterior region ex- actly resembles the anterior region of the external surface, with this difference only, that it is concave instead of being convex. • The -posterior region presents, 1. In the median line, the dorsal portion of the spinal coliuntm, which, like an incomplete septum, forms a projection in the interior of the tho- racic cavity, and divides it into two equal parts ; 2. On the sides, two deep grooves, which are contracted above, but gradually enlarge towards the lower part. These grooves, which lodge the posterior convex portions of the lungs, exist only in the human subject ; they allow part of the weight of the body to be throwTi backward — an arrange- ment which is very advantageous for preserving the equilibrium in standing, and is a proof that man is destined to the erect posture. The lateral regions form an inclined plane on the inside, resembling that which exists on the outside, only they are concave instead of being convex. Superior and Inferior Circumferences. The superior circumference or summit is narrow in comparison with the inferior, and slopes obliquely from above downward and forward ; it is wider transversely than in the antero-posterior direction, and resembles the shape of a heart on playing cards. The circumference of this opening is formed, in front, by the upper end of the sternum ; be- hind, by the first dorsal vertebra ; on the sides, by the first ribs and their cartilages. This opening, which is contracted in its dimensions by the clavicles, gives passage to the following organs : the trachea, the oesophagus, the thoracic duct, the large arteries and veins of the head, neck, and thoracic extremities, the apex of the lungs, and several muscles of the neck. The inferior circumference or hase is very wide, at least four times larger than the pre- ceding, and, like it, broader transversely than from before backward. It presents, 1. In front, a wide notch, the borders of which are formed by the cartilages of the seventh, eighth, ninth, and tenth ribs, but are incomplete between the tenth and eleventh, as also between the eleventh and twelfth ; at the apex of this notch is the ensiform cartilage. 2. Behind, we find on each side of the vertebral column a notch of much smaller dinien- sions than that in front ; it is caused by the great obliquity of the twelfth rib, which forms an acute angle with the spine. The inferior circumference of the thorax is con- nected with muscles by numerous attachments. The great mobility enjoyed by the lower aperture of the thorax, which, as we have seen, is subjected to alternate movements of dilatation and contraction, contrasts remarkably with the almost absolute immutability of the superior aperture. The lower opening pre- sents certain varieties in dimension which are observed chiefly during inspiration, or are occasioned by accidental causes of dilatation, such as pregnancy or the accumulation of fluids in the abdominal cavity. This variability of its dimensions has reference to the compressibility and dilatability of the abdominal viscera. Such an alteration at the upper opening would have caused serious inconvenience by compressing the trachea and the vessels. General Development of the Thorax. The shape and dimensions of the thorax vary considerably at different periods of Ufe ; it is of great importance to be well acquainted with these, because they bear constant relation to changes in the organs contained within the cavity. One of the most remarkable characteristics of the fcetal thorax is the predominance of the antero-posterior over the transverse diameter ; at this age we find the sternum very far separated from the spine, and forming a considerable projection in front. This ar- rangement coincides with the largely-developed state of the heart, and an organ denom- inated the thymus gland, which are both situated in the middle of the thorax ; and also with the small size of the lungs, which are situated laterally. Another marked feature in the chest of the foetus is the absence, or, at least, the slight depth, of those grooves which we have described as peculiar to man, and intended to lodge the posterior edge of THE LIMBS. 73 the lungs. The absence of these pulmonary grooves produces, as a necessary conse- quence, a want of those external projections on the back of the thorax, which we find in the adult corresponding with the grooves on the interior. These two characteristics, viz., the predominance of the antero-posterior diameter, and the absence of the grooves, both depend on the same cause, viz., the shght degree of curvature of the ribs in the foetus. At a more advanced period the curvatures increase, the posterior grooves are gradu- ally developed, the antero-posterior diameter is diminished, and the transverse propor- tionally increased, so that there is less difference in the absolute capacity of the thorax than would at first sight appear, for the differences we have noticed are in a great measure referrible to the comparative predominance of one or other diameter. We should also remark, that in the foetus, the vertical diameter, particularly at the sides, is much shorter^ on account of the unexpanded state of the lungs, and the elevation of the diaphragm by the abdomind viscera. The two circumferences likewise present remarkable differences. In the foetus, the superior opening has a greater extent from before backward than transversely, which is precisely the opposite of what is observed in the adult. The inferior aperture is ex- tremely wide in every direction ; and this accords with the large size of many of the abdominal viscera at this age, and particularly of the Uver. At birth there is a sudden enlargement of the chest, because the access of air increases the lungs to a double or threefold extent, which, up to this period, were much contract- ed. At puberty, the thorax participates in the great development which the respiratory apparatus undergoes. It is at this time, eiIso, that malformations of this cavity most fre- quently become obvious. In adult age, the thorax still grows, but in an sdmost insen- sible manner. In the aged, the different pieces of the sternum become united by osseous union : the cartilages are ossified ; the thorax has a tendency, in some degree, to form only one piece, which does not permit the different parts to move upon one another. THE LIMBS. The vertebral column alone, in many animals, is the organ of locomotion, and the jaws the organ of prehension ; but all animals so constituted either live in water or crawl on the earth. The vertebral column, however, in man, and in those animals which live in the air, is not constructed in such a way as to allow of the performance of a complete locomotion, and thence the necessity of limbs, which are only connected to the trunk by their superior extremities, and which, along the rest of their length, are completely iso- lated from the body. They are also denominated extremities, because they are the parts which are most distant from the centre of the body. They are four in number : two supe- rior, or thoracic, so called because they are directly connected with the thorax ; and two in- ferior, or abdominal, because they are continuous with the abdominal cavity. These last are intended to support the weight of the body like two pillars, and to transport it from place to place : the thoracic hmbs are intended to seize objects or to repel them. The extremities present in their structure certain general circumstances which are essen- tially characteristic. We shaU particularly notice the following : 1. As regards their form. The bones of the extremities differ in many respects both from those of the trunk and those of the head. They generally have the appearance of cylindrical and elongated levers, superimposed so as to form a column, the parts of which are movable upon each other. 2. The continuity of the extremities with the trunk is established by means of osseous zones or girdles, viz., the shoulder for the thoracic limbs, the pelvis for the abdominal. 3. The bones of the extremities diminish in size and length from the proximal to the distal, or free end. 4. The nimiber of the bones in the limbs augments as we proceed towards their free extremity. 5. As a necessary consequence of the augmented number of bones, and of their pro- gressively diminished size, the articulations become more numerous and smaller towards the distal end of the limb. The thoracic and abdominal extremities being constructed upon the same fundamental type, we should never forget, in describing them, that they have numerous analogies, while, at the same time, we notice the differences in each which are connected with its peculiar ofiice. THE SUPERIOR OR THORACIC EXTREMITIES. The Shoulder. — Clavicle. — Scapula. — The Shoulder in general. — Development. — Humerm. — Ulna. — Radius. — The Hand. — The Carpus and Carpal Bones. — The Metacarpus an4 Metacarpal Bones. — The Fingers. — General Development of the Superior Extremities. ;, The thoracic extremities arQ divided into four parts, which, proceeding from the central Dwards the distal end, are, 1. The shoulder ; 2. The arm ; 3. The fore-ann ; 4. The hand K 'i4 OSTEOLOGY. ■;„*?r":t The Shoulder. ^mfiX- • ^^ .,» ..J ;..' The shoulder, situated at the posterior and lateral part of the chest, is composed of two bones, which form by their union a sort of angular lever with a horizontal and a ver- indeed, the most slender of all the long bones, and may be at once recognised by this character. Its direction is vertical, with a slight in- chnation outward at its lower part. It is the most twisted on itself of all the long bones, and is a remarkable exemplification of that law of osteology, viz., that the torsion of bones is always connected with the changes of direction of tendons, or vessels. It is divided into a body and two extremities. The body has the form of a triangular prism. In order rightly to comprehend its shape, it is necessary to be aware that the muscles which are placed on its external surface above turn round to the posterior aspect below, from which it is easy to under- stand how the four upper fifths of the external surface look outward, and the lower fifth backward. The external surface (n) is marked by a deep groove which runs along it, and gives at- tachment to the peroneus longus, and pcroneus brevis. The lower part, which is turned back- ward, is smooth. The internal surface is divided into two unequal parts by a longitudi- nal ridge, to which the interosseous ligament is attached. The portion of the surface in front of the ridge is narrower than the other, being in some subjects not more than two lines in breadth ; it gives attachment to the muscles on the fore part of the leg : the por- tion beliind the ridge is larger, and gives attaclunent to the tibialis posticus. This sur- face becomes anterior at its lower part (o). * We have hitherto deemed it unnecessary to indicate the position in which each bone should be studied, Decause a glance at an articulated skeleton would suffice to enable the student at once to place the bones aright. The fibula, however, forms an exception, on account of its remarkable torsion. In order, then, to 8t:5y this bone conectly, it is necessary to place the flattened end (u ») downward, taking care that the artic- ular surface on that part be turned inward, and that the thin edge (u) of the eminence which forms this Jow- "r end should look forward. v >^^' • THE FOOT. 99 The posterior surface of the fibula is narrow above, and expanded below, where it looks inward, and terminates by a rough part, to which ligaments that unite it to the tibia are attached. The whole of this surface gives attachment to muscles. We observe on it the principal nutritious canal, which passes obliquely downward. This canal is some- times placed on the internal surface of the bone. The three edges participate in the deviations of the surfaces. Thus, the miter edge (r) becomes posterior below ; the anterior edge (s) becomes external, and is bifurcated ; the internal edge becomes anterior, and after being thus changed, forms the continuation of the ridge for the interosseous ligament, which we noticed upon the inner surface. All the edges give attachment to muscles and aponeurotic processes, and are remark- able for their prominence. The superior extremity or head (t) of the fibula presents an articular facette (near t\ slightly concave, which unites with a corresponding surface on the tibia : on the outside are some irregular impressions for the insertion of the biceps muscle, and the externa! lateral Ugament of the knee. At the back part of this head we observe the styloid pro* cess of the fibula (below t) for the tendon of the biceps. The lower extremity or external malleolus (w v) passes much below the inferior articu- lar surface of the tibia ; it is longer and thicker than the internal malleolus. It is flat- tened on the outside and the inside, and presents, 1. An external surface (uv), convex and sub-cutaneous. 2. An inlerTial surface, which articulates with the astragalus hy means of a facette, which completes on the outside the sort of mortise fgrjneci by tha union of the lower ends of the tibia and fibula ; below and behind this ^urfeioc is a, deep, rough excavation, which gives attachment to a ligament. .3.^Aji aut^erion ^ige (u) for the insertion of a Ugament. 4. A posterior edge (c), thicker, ■jrarlied by a superficial -groovG for the passage of the tendons of the peronei muscles. t&. A summit, which gives airaclj ment to one of the external lateral ligaments of the ankle-jciu*^. Connexions. — The fibula forms the outer part of rh*? le?, and a^liculr.tes with the tibia and the astragalus. ' - > ^ Internal Structure. — The shaft is compact, and has a very small medullary canal, and the extremities are spongy. Development. — The fibiSa is developed from three points : one for the body, and one for each extremity. The osseous point of the body appears a little after that of the shaft of the tibia, from the fortieth to the fiftieth day. At birth, the two extremities are still car- tilaginous. An osseous point appears in the lower end during the second year ; that of the upper end about the fifth. The extremities are united to the shaft of the bone when the development is completed, viz., from twenty to twenty-five years : the lower end is the first to become joined. The Foot {figs. 54, 55, and 56). The foot is the part of the lower extremity which is analogous to the hand in the up per. They are both but varieties of the same type of organization, with certain differ- ences which have reference to their respective uses. In the foot, for example, which is intended to support the body, the conditions necessary for solidity are principally mani- fest, while the hand is chiefly remarkable for the mobility of its parts. The foot is composed of twenty-six bones, which, by their imion, form three distinct parts, viz., 1. The tarsus (c if, fig. 54), a bony mass, consisting of seven pieces closely articu- lated ; 2. The metatarsus, composed of five sep- arate columns {m m", figs. 54 and 55) ; and, 3. The toes, formed each of three columns (n o r), excepting the first, or most internal, which has only two {71" r"). The size of the foot varies in different indi- viduals. It exceeds the hand in thickness and length, but is not so broad. Its direction is horizontal from before backward, and it forms a right angle with the leg, differing much in this respect from the hand, which is in the same line as the forearm. It is flattened from above downward, is hollow below {fig. 56), nar- row behind, where it is of considerable height, and thinner and broader in front, at which part jilso it is digitated. It presents, 1 . A superior or dorsal surface, which is convex, dorsum pedis, ( fig. 54) ; 2. An inferior or plantar surface, which is concave transversely, and likewise in the an- tero-posterior direction, sole of the foot {fig. 55) ; 3. An internal or tibial edge {fig. 56), which is very thick, and corresponds to the great toe ; 4. An external or fibular edge, which corre- 100 OSTEOLOGY. sponds to the little toe ; 5. A ■posterior extremity or heel ; 6. An anterxar or digital exttemity. We shall describe in succession the tarsus, the metatarsus, and the '.oes. The Tarsus {figs. 54, 55, and 56). The tarsus is an analogous structure to the carpus, but differs from it in forming the Pig^ 56. posterior half of the foot, while the carpus only constitutes about a sixth of the hand. Its antero-posterior diameter surpasses by more than double its transverse, precisely the opposite of what obtains in the carpus. It resembles a vaulted arch, the convexity of which (c a j, fig. 56) looks upward, and which is excavated below {d i) both trans- versely and from before backward. The weight of the leg falls upon the smnmit of this arch. This form of the foot is not de- signed merely for securing the advantages derived from the mechanism of arches, but is especially intended to afford a protecting excavation for the organs which could not with impunity be compressed in standing and progression. The posterior and free extremity of the tarsus is narrow, and progressively enlarges forward. The tarsus is composed of seven bones, disposed in two rows. The/r«^ or tibial raw iS formed b/'twp bones only, the os calcis (c) and the astragalus (a) ; the second or meta- tarsal row cenoists Qffiv& bones, viz., the scaphoid (g), the cuboid (/), and the three cune- iform bones (i j I). The bo|ies. of the first row, instead of being placed in the same trans- verse line, like those of the, flust, row of the carpus, rest one upon the other. The astrag- iilus'is the oniy JJipne /)f the tarsus which enters into the formation of the ankle-joint. ' ' ' ■ " "'■'^o .Fiiist ,cri 'J!iJ)ial Row of the Tarsus. " " ■ ♦ The Astragalus [a). The astragalus is placed below the tibia, above the os calcis, on the inside of the mal- leolar extremity of the fibula, and behind the scaphoid ; it is irregularly cuboid in its fig- ure, is the second largest bone of the tarsus, and heis six surfaces : 1. The superior oi tibial surface (a, fig. 54) is articular, and shaped like a trochlea or pulley, which fits ex- actly to the lower surface of the tibia. In front and behind the trochlea are inequalities for the attachment of ligaments. 2. The inferior or calcaneal surface (a, fig. 55) presents two facettes, separated by a very deep furrow, running obliquely backward and inward, and broadest in front, which gives insertion to a ligament. The facette behind the groove is the larger ; it is concave and oblong in the same direction as the groove. The facette in front is flat, and often divided into two smaller surfaces. Both articulate with the OS calcis. 3. The internal lateral surface {fig. 56) is articular for a considerable por- tion of its upper part, and corresponds to the internal malleolus ; below, there is a rough depression, which gives attachment to the internal lateral ligament of the ankle-joint. 4. The exterTud lateral surface is triangular, like the corresponding surface of the external malleolus, with which it articulates. It should be remarked, that both the lateral articu- lar surfaces of the astragalus are continuous with the trochlea or upper surface, without mterruption. 5. The anterior or scaphoid surface is convex, and has been called the head of the astragalus ; it is articular, and continuous, below, with the anterior facette of the lower surface of the bone already described. This head is supported by a contracted portion, or neck (i, fig. 54 and 56), to which ligaments are attached. 6. The posterior surface is very small ; it consists simply of a groove, slanting downward and inward, along which the tendon of the flexor longus poUicis pedis glides. The Os Calcis (c). The OS calcis, or calcaneum, situated below the astragalus, and at the lower and back part of the foot, is the largest bone of the tarsus. Its form is irregularly cuboid, with the greatest diameter from before backward ; it is flattened transversely. Its size and its length have reference to the double ofl5ce which it serves, of transmitting the weight of the body to the ground, and of acting as a lever for the extensor muscles of the foot. I should remark, that its large posterior extremity forms the heel (d, figs. 55, 56), the horizontal direction of which, in man, is one of the most advantageous arrangements for the vertical position of the body. The OS calcis has six surfaces : 1. The superior surface {fig. 54) presents, in front, two, or often three, articular facettes, which correspond with those on the lower surface ol the astragalus. The posterior facette is the larger, convex, and separated from the an terior by a groove, which is shallower than the corresponding one of the astragalus, but follows the same direction backward and inward. The whole of the non-articular por- tion of this surface projects behind the astragalus ; it is flattened on the sides, and slight- ly concave from before backward. Its length varies in different individuals, and is tho cause of the varieties in the projection of the heel. 2. Tlie lower oi plantar surface {fig THE CUBOID AND SCAPHOID BONES. 101 55) is rather an edge than a true surface ; it is directed obliquely upward and forward. We observe here, at the back part, two tuberosities, the internal of which is much larger than the external ; both serve as places of insertion for muscles, but their principal use is to support the weight of the body behind, and they essentially constitute the heel (d. Jig. 56) in the human subject. 3. The external surface is superficial, which accounts for the frequency of injuries of this bone on its outside, and explains, also, the ])ossibility of reaching it with surgical instruments. It is convex, and narrow in front, where it pre- sents two superficial grooves separated by a tubercle (s, figs. 54 and 55). These grooves afford a passage to the tendons of the peroneus longus and brevis. On the anterior and superior part of this surface we find, also,'tinother tubercle, which is a guide to the sur- geon in the partial amputation of the foot recommended by Chopart. 4. The internal sur- face {fig. 56) is deeply grooved for the passage of several tendons, and also for the nerves and vessels which are distributed to the sole of the foot. It presents, in front and above, a projecting eminence, like a blunt hook, in a shallow groove, below which the tendon of the flexor longus pollicis pedis glides. This eminence has been called the small process of the os calcis (e, fig. 56), also sustentaculum tali, because the anterior and internal articular surface, which supports the astragalus, is on its upper part. 5. The anterior or cuboid surface is the smallest. It is concave from above downward, and articulates with the cuboid. It is surmounted on the inside by a short projection, direct- ed horizontally forward,* above which the third articular surface for the astragalus is situated when it exists. The whole portion of the os calcis which supports the anterior or cuboid surface bears the name of great process of the os calcis {t,figs. 54 and 55). 6. The posterior surface is shaped like a triangle, with the base downward ; its lower part is rough and irregular, and gives attachment to the tendo Achillis, the upper part, over which the same tendon glides, being smooth and polished like ivory. Second Row of the Tarsus. The bones of the second row are five in number : on the outside it is formed by the cuboid alone, but on the inside it is subdivided into two secondary rows ; a posterior, formed by the scaphoid ; and an anterior, composed of the three cuneiform bones. This subdivision of the inner portion of the tarsus, by multiplying the articulations, has the effect of diminishing the violence of shocks, or of pressure upon the foot, especially on the inner side, to which they are principally applied. The Cuboid Bone [ffigs. 54 and 55). Tho cuboid, which ranks £is the third bone of the tarsus in point of size, is situated at the outside of the foot, and appears like-a continuation of the great process of the os calcis. It is more regularly cuboid than any of the other tarsal bones, and has six surfaces : 1. The upper or dorsal surface {fig. 54) is covered by the extensor brevis digitorum pedis, and looks somewhat outward. 2. The lower or plantar surface {fig. 55) presents on its fore part a deep groove (/), running obliquely inward and forward, for the tendon of the peroneous longus. Behind this groove, the posterior lip of which is very prominent, are impres- sions for the ligament which connects the cuboid and the os calcis. 3. The posterior or calcaneal surface is sinuous, directed obliquely inward and backward, and adapted to the OS calcis in such a way that there is a mutual reception of the surfaces of the two bones. At the inside of this surface, we observe a process which is directed inward and back- ward, and strengthens the union with the os calcis. It occasionally becomes an obstacle to the disarticulation of the foot, after Chopart's method. 4. The anterior or metatarsal surface looks obhquely inward and forward ; it articulates with the fourth and fifth meta tarsal bones. 5. The internal surface articulates with the third cuneiform bone, and fre- quently also with the scaphoid ; it presents, besides, some impressions for the insertiop. of ligaments. 6. The external surface is rather an edge; its extent from before back- ward scarcely equals half the length of the internal surface. We observe on it the com- mencement of the groove for the tendon of the peroneus longus. The Scaphoid {g,Jigs. 54, 55, and 56). The scaphoid or navicular hone, so named from its supposed resemblance to a boat, is situated on the inner side of the tarsus ; it is flattened from before backward, and is thicker above than below, irregularly elliptical, with the long diameter placed transverse- ly. It has two surfaces and a circumference : 1. The posterior surface is concave, and receives, thougn incompletely, the head of the astragalus. 2. The anterior surface pre- sents three articular facettes, which correspond to the three cuneiform bones. 3. The circumference is convex above, inclined inward, and rough for ligamentous insertions. It is much smaller below, where also it gives attachment to ligaments. On the i?iside it presents, at its lower part, a large process, process of the scaphoid (at g), which may be easily felt under the skin, and serves as a guide in performing Chopart's amputation. This process gives attachment to the tendon of the tibialis posticus. It is frequently * This small prolongation, which might be called imaZi anterior process of the os calcis, in contradistinction to the one on the internal surface already mentioned, merits notice in the performance of Chopart's operation. 102 OSTEOLOGY. very large, and may, and, indeed, has been mistaken for an exostosis of the bone. On the outside the circumference is irregular, gives attachment to some hgamentous fibres, and often presents a small surface which articulates with the cuboid : this surface is continuous with the facettes for the three cuneiform bones. The Three Cuneiform Bones. These bones, so named from their shape, are three in number: they are called ^rsf, second, and third, counting from the inside of the foot. Tliey are also distinguished by their size, into the great, middle-sized, and small.* The First Cuneiform Bone (t, figs. 54, 55, and 56). The first or internal cuneiform bone is the largest. It is placed on the inside of the others, in front of the scaphoid, and behind the first metatarsal bone. It is shaped like a wedge with the base below, which is precisely contrary to what obtains with the other two. We observe oa it, 1. An internal surface {fig. 56), which is subcutaneous, and forms part of the inner edge of the foot. 2. An external surface, which presents an an- gular articular facette for union with the second cuneiform bone behind, and the second metatarsal bone before ; the non-articular portion of the external surface of the first cuneiform bone is rough, and gives attachment to ligaments. 3. A posterior surface, which is concave, and articulates with the most internal and largest facette on the an- terior surface of the scaphoid. 4. An anterior or metatarsal surface, which is plane, or, rather, shghtly convex, of a semilunar form, the convexity being to the inside, and the greatest diameter vertical ; it is broad below and narrow above, and articulates with , the first metatarsal bone. 5. An inferior surface {fig. 55), which forms the base of the wedge ; it is rough, with a tubercle behind for the attachment of the tibialis anticus. 6. An upper part {fig. 54), which forms the point of the wedge ; it is an angular border, running forward and upward, and thicker in front than behind, where it contributes to form the convexity of the foot. The Second or Middle Cuneiform Bone {j,fig. 54, 55, and 56). The second coneiform bone is the smallest of the three : it ^ placed between the two others, and corresponds to the scaphoid behind, and the second metatarsal bone in front. The wedge wliich it represents has the base turned upward ; its length from behind for- ward is very inconsiderable. It presents, 1. An internal surface, which is triangular, and articulates with the first cuneiform bone : 2. An external surface, which articulates with the third or external cuneiform bone : 3. A posterior or scaphoid surface, which is concave, and articulates with the middle facette on the anterior surface of the scaphoid : 4. An anterior or metatarsal surface, which is triangular, and nan'ower than the posterior ; it articulates with the second metatarsal bone : 5. A superior surface {fig. 54), or lase of the wedge, which is irregularly square, and rough for the attachment of ligamentous fibres : 6. An apex {fig. 55), which is very thin, and gives attachment to some hgaments. The Third or External Cuneiform Bone {I, figs. 64 and 55). This bone, which is the third as regards position, and the second in point of size, has, like the preceding, the form of a wedge with the base turned upward. Its internal sur- face articulates behind with a corresponding surface on the preceding bone, and in front with the second metatarsal. This last portion completes the kind of recess or mortise into which the head of the second metatarsal bone is received ; its inner side being formed by the first cuneiform bone, and the bottom by the second. The external surface articulates with the cuboid : the posterior surface is continuous with the two lateral ones, and articulates with the most external of the three facettes on the scaphoid : the ante- rior surface is triangular, and articulates with the end of the third metatarsal bone : the base {fig. 54) is rough, and forms part of the convexity of the foot : the apex {fig. 55) is more obtuse than the same part of the second cuneiform bone, and passes considerably below it. Structure of the Banes of the Tarsus. — The bones of the tarsus present the structure common to all short bones, viz., a mass of spongy tissue surrounded by a layer of com- pact substance. I have remarked, that in some cases of white swelling of the ankle- joint, the OS calcis contained in its interior a cavity analogous to the medullary canal of long bones. This cavity, however, must be looked upon as Edtogether abnormal. Development of the Tarsal Bones. — ^With the exception of the os calcis, which has two osseous germs, all the bones of the tarsus are developed from single points. The os calcis first becomes ossified. A bony nodule appears in the centre of its cartilage, about the middle of the sixth month of foetal life, according to most osteogonists ; in the fifth, or even the fourth month, according to others. It is placed much nearer the anterior than the posterior extremity of the future bone. Another osseous germ is formed in the posterior extremity of the os calcis, from the eighth to the tenth year, and is much thicker at its lower than at its upper part. The astragalus is developed from one point, * Also, by position, into internal, middle, and external. THE METATARSUS. 103 which appeara from the fifth to the sixth month of intra-uterine life. According to Bfe- clard, the cuboid is not ossified until some months after birth ; I have observed the pro- cess to be already commenced in a foetus at the full term. Meckel says that it begins after the eighth month of foetal life. Blumenbach, on the contrary, makes the time of its ossification a year and a half, or two years after birth ; and Albinus, who has been followed in this respect by the generality of anatomists, affirms that in the foetus at the full period, all the bones of the tarsus, excepting the os calcis and the astragalus, still re- main cartilaginous. The cuneiform bones are developed in the following order : The first is ossified to wards the end of the first year ; the second and the third appear almost simultaneously about the fourth year ; the os calcis being the only bone of the tarsus which has more than one point of ossification, is also the only bone in which we have to examine the or der of union. The two points which form it are not united until the fifteenth year. The Metatarsus {m m'^figs. 54, 55, and 56). The metatarsus forms the second portion of the foot. Like the metacarpus, its anal ogous part in the hand, it consists of five long bones, parallel to each other, forming a sort of quadrilateral grating, the intervals of which, called interosseous spaces, are in- creased by the disproportion between the ends and the shafts of the bones. The meta- tarsus presents, 1. An inferior or plantar surface {fig. 55), with a marked transverse con- cavity ; 2. A superior or dorsal surface {fig. 54), which is convex^ and answers to the back of the foot ; 3. An internal or tibial edge (m', fig. 56), which is very thick, and cor- responds to the great toe ; 4. An external or fibular edge, which is thin, and corresponds to the little toe ; 5. A posterior or tarsal extremity, which presents a waved articular line ; 6. An anterior or digital extremity, presenting five heads flattened on the sides, which as- sist in forming five separate articulations. The bones of the metatarsus have certain characters which distinguish them from all others, besides some peculiar marks by which they may be known from each other, and from the metacarpal bones, with which they have many analogies. General Characters of the Metatarsal Bones. The metatarsal bones belong to the class of long bones, both in shape and structure. Each consists of a body and two extremities. The body is prismatic and triangular, and sUghtly curved, with the concavity below. Two of its surfaces are lateral, and corre- spond to the interosseous spaces ; the third, so narrow that it resembles an edge, is on the dorsum of the foot. Two of the edges are lateral ; the third is below, on the plantar aspect of the foot. The posterior or tarsal extremity is much expanded, and presents five surfaces, two of which are non-articular, and three articular. Of the two non-articular surfaces, one is su- perior, and the other inferior ; both give attachment to ligaments. Of the three articu- lar surfaces, one is posterior, that is, on the extremity of the bone ; in general it is tri- angular, and articulates with a corresponding surface on one of the tarsal bones. The other two are lateral, partly articular, and partly non-articular. The articular surfaces are small, and often consist of more than one ; they join the contiguous metatarsal bones. The tarsal extremity is wedge-shaped ; the upper or dorsal surface being very broad, represents the base of the wedge ; the lower surface, being narrow, forms the point. The anterior or digital extremity presents a head or condyle, flattened on the sides, and oblong from above downward ; the articular surface extends much farther on the lower aspect, or in the direction of flexion, than on the upper, or the direction of extension. On the inside and outside of the condyle there is a depression, and a projection behind it for the lateral ligament of the joint. Characters of the different Metatarsal Bones. The first or metatarsal bone of the great toe (m', figs. 54, 55, 56) is remarkable for its great size. It is the only one which, in this respect, resembles the tarsus ; its body is shaped like a triangular prism ; its digital extremity is marked on the plantar aspect by a double furrow for two sesamoid bones (*, fig. 56). (Vide Articulation of the Foot.) Its tarsaL extremity presents a semilunar concave surface, with its greatest diameter verti- cal, which articulates with the internal cuneiform bone. There is no articular surface on the circumference of the first metatarsal bone. In this point it resembles the first metacarpal bone, and by this and its great size it is distinguished from all the others. The fifth metatarsal bone (m, fig. 54, 55) is the shortest after the first ; it has only one lateral articular face on its tarsal extremity. On the opposite side of this extremity, viz., on the outside, we observe a large process, process of the fifth inetatarsal bone, shaped like a triangular pyramid, and directed obliquely backward and outward, into which the peroneus brevis is inserted. This process may be easily felt under the skin, and serves as a guide in the partial amputation of the foot at the tarso-metatarsal articulation. Another charact^iristic of the fifth metatarsal bone is the great obliquity outward and backward of the %rticular face on its posterior extremity. 104 OSTEOLOGY. The second, third, and fourth metatarsal bones are distinguished from each other by the following characters. The second is the longest, and also the largest after the first ; it articulates with the three cuneiform bones by its posterior extremity, which is dovetailed with them. The third and the fourth metatarsal bones are of almost equal length ; their apparent difference in an articulated foot depends chiefly on the fact that the articulation of the fourth with the cuboid is on a plane posterior to that of the third with the external cuneiform bone. Lastly, they may be known from each other by the presence of two surfaces, on the in- side of the posterior extremity of the fourth metatarsal ; one being for the external cu- neiform bone, and the other for the third metatarsal bone. Development. — The metatarsal bones are developed from two points ; one for the body, and one for the anterior or digital extremity. The first metatarsal bone is the only ex- ception to this rule, for its epiphysary point is situated at the posterior extremity.* The osseous point of the body appears first during the third month, according to the majority of authors, but about the forty-fifth day, according to the observations of Blumenbach and Beclard. It is completely developed in the foetus at the full period. The epiphysary point makes its appearance during the second year. The union of these parts does not take place until the eighteenth or nineteenth year, and is not simultaneous in all the bones of the metatarsus. The epiphysis of the first metatarsal bone is the first to unite with the body. An interval of a year sometimes intervenes between the union of this epiphysis and those of the other four metatarsal bones. The Toes [n o r, n r, Jigs. 54, 55). The resemblance between the phalanges of the fingers and those of the toes is so com- plete, that we cannot do better than refer to the description already given of the former for details respecting the latter. At the same time, it should be remarked, that the pha- langes of the toes appear, as it were, atrophied, or stinted in growth, when compared with those of the fingers, excepting the great toe, which, in all its parts, preserves the large dimensions of the inner side of the foot. The first or metatarsal phalanx {n to n') resembles closely the metacarpal phalanx of the fingers. The middle phalanx (o) is remarkably small and short ; it would almost ap- pear to consist of the extremities alone, the body being absent. At first sight it might be t£iken for a pisiform bone, or, rather, for one of the pieces of the coccyx ; but the presence of anterior and posterior articular faces is sufficient to mark the distinction. The ungual phalanges (r r') of the toes resemble in form, but are much smaller than the corresponding parts of the fingers. This remark, however, only applies to the last four, for the ungual phalanx of the great toe is in size at least double that of the thumb. I cannot conclude this description without remarking, that the articular surface of the posterior extremity of the metatarsal phalanges, as well as of the anterior extremity of the metatarsal bones, is prolonged farther upward than the corresponding surfaces on the metacarpal bones and phalanges of the fingers ; this arrangement allows a greater extension of the toes, and is an important element in the mechanism of progression. Development. — The first, second, and third phalanges are developed from two points of ossification ; one for the body, and one for the metatarsal extremity. The epiphysary points of the second and third phalanges are so small, that their existence has been doubted by many anatomists. The osseous points of the bodies of the first phalanges are much later in appearing than those of the metatarsal bones, not being visible, in general, until from the second to the fourth month ; the first phalanx of the great toe is an exception, its ossification concmiencihg from the fiftieth to the sixtieth day. The epiphysary point of the first phalanges does not appear until the fourth year. The bodies of the second phalanges are ossified almost at the same time as those of the first ; the epiphysary point of their posterior extremity is not visible until from the sixth to the sev- enth year. The bodies of the third phalanges are ossified before those of the second and the first ; an osseous point appears in them about the forty-fifth day, excepting in the lit- tle toe, where it is much later. The ungual phalanx of the great toe is remarkable as be- ing ossified before all the other phalanges of the toes. It is developed from a point which does not occupy the centre, but the summit of the phalanx. The epiphysary point of the posterior extremity appears about the fifth year in the great toe, and about the sixth year in the othei four. The epiphysary points of the phalanges are not united to the bodies until the age of seventeen or eighteen years. General Development of the Inferior Extremity. The most characteristic feature of the lower extremity in the foetus is the comparative Sateness of its development, which is most remarkable at the early periods. We have * This exception corresponds entirely with that observed in the hand, and renders the analogy between the metatarsal bone of the great toe and the metacarpal of the thumb extremely close ; for the same reason, both of these bones resemble tke first phalanges of the fingers. I may add, that, in some subjects, it has appeared to me that there was a very thin epiphysary point at the digital extremity of this bone, which soon united tn the body COMPARISON Oi' THE EXTREMITIES. 106 already stated the periods at which each point of ossification appears in the diiferent bones, and the times at which they are united, and it now only remains for us to point out some peculiarities of development which have not been included in the description of the bones. From the observations of Bichat, it is generally admitted that the neck of the femur in the foetus and the newly-born infant is proportionally shorter than in the adult, and forms ahnost a right angle with the shaft of the bone ; that the body of the femur is al- most straight ; and that its extremities are proportionally much larger than they become subsequently. As we before observed with regard to the upper extremities, all these assertions are at variance with the results of our observations. The same reflections apply equally to the bones of the leg, the torsion of which we believe to exist to the same degree in the foetus and in the new-bom infant as in the adult. After birth, the development of the lower limbs proceeds more rapidly than that of the upper, and the final proportions are not attained until the age of puberty. In the aged, the phalanges of the toes are often anchylosed ; but this union, like the dislocations of the toes, and some deformities of the tarsus and metatarsus, are the results of pressure upon the foot occasioned by tight shoes, and the more or less complete immobility in which the parts are maintained.* Comparison of the Superior and Inferior Extremities. We have hitherto omitted the applications of that species of comparative anatomy by which different organs of the same animal are compared with one another. Those anal- ogies which exist between the various parts that compose the trunk could not, with pro- priety, be included in a work on descriptive anatomy. But we do not deem it proper to apply the same rule to the parallel between the upper and lower extremities ; for that is founded on such numerous and striking points of analogy, and has become so much a subject of instruction, that we should consider it a serious omission did we here neglect giving a brief notice of it. The upper and the lower extremities are evidently constructed after the same type, but present certain modifications corresponding to the difference of their functions. I should remark in this place, that some of these analogies are very manifest and satis- factory, and greatly facilitate the remembrance of important anatomical details ; while others are far-fetched, and wholly destitute of useful application : these will be passed over with a simple notice. We shall now compare in succession the shoulder and the haunch, the humerus and the femur, the forearm and the leg, the hand and the foot. Comparison of the Shoulder and the Pelvis. Before the time of Vicq-d'Azyr, anatomists were in the habit of considermg the clavi- cle and the scapula among the bones of the upper extremity, but regarded the os innom- inatum or haunch as belonging to the trunk ; and yet the most simple reflection is suf- ficient to establish the analogy between the shoulder and the haunch. In order the more readily to appreciate the points of resemblance and difference between these parts, it is advisable to follow the method adopted by Vicq-d'Azyr, of studying the shoulder reversed ; or, what is the same thing, to compare the aspect of the shoulder which cor- responds to the head, with that of the pelvis which answers to the coccyx ; remember- ing, at the same time, that, for a long period after birth, the haimch bone is formed of three distinct pieces, the ilium, the ischium, and the pubes. 1. The shoulders form an osseous girdle, intended to form a point of support for the upper extremities, in the same manner as the haunch does for the lower extremities. The girdle formed by the shoulders is interrupted in front in the situation of the sternum, and behind, opposite the vertebral column ; hence there are two shoulders, while the haunch bones constitute one united whole. The shoulder, therefore, and, consequently, the arm of one side, are completely independent of those of the other, but the two lower extremities have a sohd bond of union. 2. The second point of difference relates to the comparative dimensions of the pelvis and the shoulder. The great size of the pelvis, the thickness of its edges, the depth of its notches, and the prominence of its eminences, contrast strongly with the slender construction of the shoulder, and the thin edges of the scapula, and are in harmony with the uses of the lower extremities. 3. The broad portion of the scapula is analogous to the iliac portion of the os innom- inatum ; the internal iliac fossa is analogous to the subscapular fossa. 4. The supra and infra-spinous fossae correspond to the external iliac fossa ; but the iliimi has no part analogous to the spine of the scapula. 5. The axillary border of the scapula answers to the anterior edge of the os innomi- natum. The spinal border is analogous to the crest of the ilium. The superior border * On thi» subject the reader may consult a very curious memoir, by Camper, on the inconveniences arising from tight shoes, to which he attributes, 1. The shortening of the second toe ; 2. The partial luxation of some of the tarsal bones. To this vie may add the luxation, outward, of the first phalanx of the great toe ; and the luxation, inward, of the first phalanx of the second, and sometimes of the third toe. o 106 OSTEOLOGY. of the scapula corresponds to the posterior border of the os innominatuin ; and the cora^ coid notch on this border, with the coracoid hgament which converts it into a foramen, are analogous to the sciatic notch, and the sacro-sciatic ligaments. 6. The glenoid cavity is evidently analogous to the acetabulum ; according to Vicq- d'Azyr, the coracoid and the acromion processes are represented by the tuberosity of the ischium and the pubes, with this remarkable difference only, that the two processes of the shoulder are separated from each other by the large acromio-coracoid notch, while in the pelvis the iscliium and the pubes are united, and, instead of including a notch, form the circumference of a foramen, the obturator. This analogy is not universally admitted ; for the ischium, being intended to sustain the weight of the body when sit- ting, bears no resemblance in this respect to the shoulder. One of the most striking analogies between the shoulder and the pelvis is that of the clavicle and the horizontiS portion of the pubes ; with this difference, that the clavicle is articulated with the scap- ula, while the pubes is united by bone to the ilium. Without forcing an analogy, we may trace a similitude between the symphysis pubis, and the union of the clavicles by means of the interclavicular ligament. Comparison of the Arm Bone and the Thigh. In order to make the parallel exact, we must remember the relative situation of the&o two bones, and compare the right femur with the left humerus ; and the side of flexion, that is, the posterior aspect of the first, with the side of flexion, or the anterior aspect of the second. This being determined, we must place the linea aspera of the femur in front, and the himierus in its natural position. The humerus is much smaller than the femur, being about a third shorter, and only half the weight and bulk. The humerus is placed vertically, and almost parallel to the axis of the trunk ; in this it contrasts with the marked obliquity of the thigh bones, which touch each other at their lower ends. The humeri are separated from each other by a greater distance than the femora ; this differ- ence depends on the conformation of the human thorax, which is flattened in front and behind, while in quadrupeds it is flattened on the sides, and permits the approximation of the humeri, which serve as pillars of support to the fore part of the trunk. The humerus is not curved like the femur, but, on the other hand, it is much more twisted, and presents an oblique groove, which does not exist in the femur. We shall compare in succession the shafts and the extremities of these bones. 1. Comparison of the Shafts. — -The posterior surface of the humerus exactly corresponds to the anterior surface of the femur, being, like it, smooth and rounded. The external surface resembles the external plane of the femur, with some differences ; the impres- sion for the gluteus maximus is evidently analogous to the deltoid impression. The in- ternal surface is in contact with the brachial artery, as is the internal surface of the femur with the femoral artery. The anterior edge is a sort of linea aspera, analogous to that of the femur, and, like it, terminating by a bifurcation at its upper part. 2. Comparison of the Loicer Ends of the Bones. — Although the differences between these parts are very marked, we can yet detect, in the one bone, traces of all the more important points of structure observed in the other. Thus, the internal and external tuberosities of the humerus evidently resemble those of the femur, and they are both intended for the insertion of muscles and ligaments. The trochlea of the humerus re- sembles that of the femur, with this difference, that, in the femur, the two borders of the pulley diverge from each other behind, while in the humerus they are parallel through- out. In front and behind the femoral trochlea, we find depressions, wliich are manifestly analogous to the coronoid and olecranal fossae of the humeral trochlea. Lastly, without admitting any fundamental difference, we may explain the existence of the small head of the humerus, for which there is no representative in the femur, by a reference to the fact, that both bones of the forearm unite with the humerus, while only one bone of the leg articulates with the femur. Comparison of the Upper Ends. — As in the femur, we find in the humerus a segment of a spheroid, or a head, supported by a neck, of which, however, there is only a trace ; and two tuberosities, which are analogous to the trochanters, and, like them, give at- tachment to the rotator muscles of the Umb. In the humerus, however, the two pro- cesses are much more closely approximated, being only separated by the bicipital groove. Lastly, the great tuberosity of the humerus causes the prominence of the shoulder, in the same manner as the great trochanter causes the prominence of the hip. Comparison of the Leg and Forearm. The forearm is that portion of the upper extremity which is represented by the leg in the lower. Each is composed of two bones ; but while the leg is essentially constitu- ted by the tibia, which alone enters into the formation of the knee-joint, and the greater part of the ankle-joint, both the radius and the ulna contribute, almost in an equal degree, to that of the forearm ; and although the ulna forms the greater part of the elbow-joint, the radius, by a sort of compensation, is the chief bone of the wrist-joint. Although the general analogy between the forearm and leg is sufficiently striking, it js COMPARISON OP THE EXTREMITIES. 107 not so easy to trace the corresponding parts in detail. Anatomists are much at variance on this subject, particularly as to which bone of the forearm corresponds to the tibia. Vicq-d'Azyr, from a consideration of the elbow and the knee joints, came to the con- clusion that the ulna is analogous to the tibia, and the radius to the fibula. M. de Blain- Tille, on the contrary, reflecting on the relations between the leg and foot, and the fore arm and hand, and considering that the tibia is placed on the same line with the great toe, and the radius with the thumb, and also that in the forearm the radius constitutes the chief part of the wrist-joint, and that in the leg the tibia is most concerned in the ankle- joint, is of opinion that the tibia and the radius are analogous parts. We shall adopt what is true in either opinion, and reject what appears to us too un conditionally stated or incorrect ; and, therefore, considering, 1. That neither of the bones of the leg resembles, by itself, one of the bones of the foreann ; 2. That each bone of the leg has some characters, both of the ulna and of the radius ; 3. That the natural position of the forearm being that of pronation, and that the leg being in a state of constant pro- nation, it is incorrect to compare the forearm when supinated with the leg when in the opposite position ; 4. That comparative anatomy has shown, in ruminating animals, the upper extremity of the ulna to be blended with the radius, and a slender process on the external aspect of the forearm resembUng the fibula, we are inclined to believe that the upper end of the tibia is represented by the upper lialf of the ulna, and the lower half of the tibia by the lower half of the radius ; while the fibula is represented by the upper part of the radius and the lower part of the ulna. If we enter into details, we shaU see how plausible this comparison is in reality. Comparison of the Upper Half of the Ulna and the Upper Half of the Tibia. The horizontal portion of the great sigmoid cavity of the ulna is represented by the upper end of the tibia, and the crest which separates the two surfaces of the cavity is analogous to the spine of the tibia. The patella and the olecranon are constructed after the same type ; the mobility of the first, and the fixture of the last, are not essential dif- ferences. The body of the ulna is prismatic and triangular, like that of the tibia ; its in- ternal surface is superficial and almost subcutaneous, like the anterior surface of the tibia ; its posterior edge (crest of the ulna) is prominent, and represents the crest of the tibia ; it is equally superficial, and serves as a guide in the diagnosis and coaptation of fractures. As in the tibia, the crest of the ulna is continuous with a triangular tuberosity, which may be called the posterior tuberosity of the ulna, and is analogous to the anterior tuberosity of the tibia. Comparison of the Lower Part of the Radius and the Lower Part of the Tibia. The quadrangular lower end of the radius corresponds to the equally quadrangulai lower extremity of the tibia. The inferior articular surface of both is divided into two parts, by an antero-posterior ridge. The ulnar side of the lower end of the radius is hollowed into an articular cavity, in the same way as the fibular side of the lower end of the tibia. The styloid process of the radius answers to the internal malleolus of the tibia. Both extremities exhibit furrows for the passage of tendons. Comparison of the Hand and Foot. The back of the foot corresponds with the back of the hand, the sole with the palm, the tibial edge of the one with the radial edge of the other ; the fibular and the ulnar borders are analogous ; the tarsal extremity of the foot corresponds with the carpal extremity of the hand, and each has a digital extremity. But amid these features of resemblance, which are sufficient to establish the old adage, pes altera manus, we find also great dif- ferences. Thus the foot exceeds the hand both in size and weight, being longer and thicker, though it is narrower : this excess of volume does not affect the toes, which are mcomparably smaller than the fingers ; nor the metatarsus, but is confined to the tarsus, of which the carpus seems little more than a vestige. A second characteristic differ- ence is the absence of the power of opposition in the great toe. As far as regards func- tion, indeed, it may be truly said, that the want of this power constitutes a foot, and the Eossession of it a hand. A third difference results from the mode of articulation of the jg with the foot, for the leg does not articulate with the posterior extremity of the tar- sus, but Avith its upper surface, so that a part of the tarsus projects behind the joint, and the axis of the foot forms a right angle with that of the leg. These remarks will suffice to show the general differences between the hand and the foot. Comparison of the Bones of the Carpus and Tarsus. While the carpus scarcely forms the eighth part of the hand, the tarsus constitutes half the foot. Its antero-posterior diameter, which is five or six inches, is three times greater than the transverse diameter, precisely contrary to what is the case in the hand. The tarsus resembles a vault, concave below, both in the antero-posterior and transverse directions, and receives the leg upon its summit. The carpus is nothing more than a groove for tendons. It is manifest that the carpus is only the rudiment of the tarsus, which is not surprising, if we consider that the former is truly the fundamental part of lOS OSTEOLOGY. the foot, and the basis of support to the whole body. We shall examine in detail the analogies and the differences of these two constituent parts of the foot and the hand. They differ in the following respects : 1. There are eight bones in the carpus : there are only seven in the tarsus. 2. Each of the two rows of the carpus is composed of four bones : the first row of the tarsus consists of two bones, and the second of five ; 3. The bones of the first row of the tarsus are placed one above the other, not arranged side by side as in the first row of the carpus. 4. One tarsal bone only enters into the formation of the ankle-joint, while three of the carpal bones are concerned in the wrist-joint : last- ly, the second row of the tarsus is subdivided into two secondary rows on the inside, a posterior, formed by the scaphoid, and an interior, formed by the three cuneiform bones. We shall now compare the bones of these two regions, and for the want of their re- semblance in shape, we shall have recourse to that of their mode of connexion — a meth- od which is, perhaps, more constant and important than that which is founded upon a character so variable as figure. Comparison of the Metatarsal Row of the Tarsus with the Metacarpal Row of the Carpus. The metatarsal and the metacarpal rows are evidently more analogous to each other than the first rows of each region, and have, therefore, been chosen for the purpose of establishing the parallel. 1. The cuboid is manifestly analogous to the os unciforme ; their relative positions are the same ; their forms are, in a great measure, similar ; and while the cuboid is at- tached to the last two metatarsal bones, the os unciforme articulates with the last two metacarpal. This analogy being admitted, we shall find in the three cuneiform bones the representatives of the three other bones of the second row of the carpus, viz., the trapezium, the trapezoid, and the os magnum. 2. We must admit here that the analogies now become much less evident. Never- theless, the third cuneiform bone, which, from being in contact with the cuboid, should represent the os magnum, which is contiguous to the os unciforme, does so far agree, that it articulates with the third metatarsal bone, as the os magnum does with the third metacarpal ; and, what is sufficiently remarkable, the third cuneiform has a slight con- nexion with the second metatarsal, as the os magnum has with the second metacarpal. Although, therefore, we do not find in the third cuneiform bone anything approaching to the size of the os magnum, or resembling the remarkable head of that bone, we should not, on that account, hastily conclude that they have no analogy. We shall explain af- terward how this fact should be interpreted : we only wish it to be admitted in this place, that the base or metacarpal portion of the os magnum is represented by the third cuneiform bone. 3. The second cuneiform bone, which corresponds to the trapezoid, supports the sec- ond metatarsal, as the trapezoid supports the second metacarpal. 4. The first cuneiform bone, which supports the first metatarsal, corresponds to the trapezium, which supports the first bone of the metacarpus. All these analogies, it must be confessed, are very imperfect, and founded rather upon the connexions than the forms of the different bones. In fact, what resemblance is there between the three large cu- neiform bones all cut into facette-like wedges, and all so like each other in shape, and the bones of the carpus, to which we have compared them 1 Above all, what compari- son can be established between the third cuneiform, which exactly resembles a wedge, and the os magnum, which has a rounded head 1 There is nothing in the metatarsal range of the tarsus which represents the rounded head which belongs to the metacarpal row of the carpus ; but the following considerations, which did not escape the notice of Vicq-d'Azyr, will serve to solve the difficulty. 1. It is an observation which apphes with sufficient generality to the whole skeleton, that when two bones move upon each other, one being provided with a head, and the other with a cavity, the head moves upon the cavity, not the cavity on the head. Thus, the femur moves upon the os innominatum ; the humerus upon the scapula. 2. The hand, in the performance of its functions, almost always moves upon the forearm. In the move- ments of the hand, the metacarpal row of the carpus moves upon the first row, and therefore the metacarpal row presents the head. On the contrary, in the movements of the bones of the tarsus during progression, the bones of the first row always move upon those of the second or metatarsal row ; and consequently, instead of finding a rounded head in the second row, we meet with it in the first. Proceeding thus by the method of exclusion, it now only remains for us to establish the analogy between the bones of the first row of the carpus on the one hand, and the scaphoid, the os calcis, and astragalus on the other. The analogies here are very equiv ocal, and are not agreed upon among anatomists. Comparison of the First Row of the Tarsus with the First Rmo of the Carpus. As there are only three bones in the posterior row of Uie tarsus which correspond to the antibrachial or superior row of the carpus, it might be supposed, d priori, that one of these would correspond to two of the bones of the first row of the carpus. A verv slight COMPARISON OP THE EXTREMITIES. 109 examination of the tarsus and the carpus in a quadruped will show at once that the pisiform bone is represented by that part of the os calcis which projects behind the as- tragalus. The OS calcis is the only bone of the tarsus which is developed from two points ; and this establishes a strong presumption in favour of the opinion that it repre- sents two bones. If we admit the analogy of the back part of the os calcis with the pi- siform bone, the anterior portion of this bone would represent the cuneiform or pyram- idal bone of the carpus ; and as this last articulates with the os unciforme, so the an- terior portion of the os calcis unites with its representative, the cuboid. The os calcis, then, may be considered as representing the cuneiform and the pisiform bones blended together, and much augmented in size. It remains, then, to establish the analogy between the scaphoid and semilunar bones of the hand, and the astragalus and scaphoid of the foot. The scaphoid of the hand resembles the scaphoid of the foot, both in form and con- nexions. The similarity of shape has led to the identity of name ; and, with regard to connexions, we find that the scaphoid of the foot is attached to the three cuneiform bones, and that of the hand to the trapezium, the trapezoid, and the os magnum, which represent the three cuneiform bones ; and, lastly, we observe that the scaphoid bone of the foot is placed on the same side as the great toe, and that the scaphoid bone of the hand is placed on the same side as the thumb. There is, however, one remarkable dif- ference between them, viz., that the scaphoid bone of the hand articulates with the fore- arm, while that of the foot has no connexion with the leg. "We have now only to discover in the tarsus the representative of the semilunar bone. All the rest of the bones being now excluded, we can only conclude, with Vicq-d'Azyr, that the astragalus is its counterpart, with the mere addition of a rounded head. Comparison of the Metacarpus and the Metatarsus. Five small long bones, arranged parallel to eacli other, form both the metacarpus and the metatarsus. In both there are four interosseous spaces : these are larger in the hand than in the foot, because there is a greater disproportion between tlie bulk of the extremities and shafts of the metacarpal than of the metatarsal bones : the metacarpus, from being shorter, appears broader than the metatarsus. The most distinguishing char- acter of the metacarpus is the fact, that the metacarpal bone of the thumb is the short- est of the whole, and is situated on a plane anterior to the others, and that its direction is oblique, aU which circumstances bear reference to the movement of opposition, which is peculiar to the hand. The characteristic mark of the inetatarsus is the size of the first metatarsal bone, which greatly exceeds that of all the others. The great size of the tarsus is continued in this bone and the great toe, on account of the important part they perform in the mechanism of standing. There is so great a resemblance between the other metacarpal and metatarsal bones, that some attention is necessary in order to distinguish between them. 1. The metatarsal bones gradually diminish in size from their tarsal to their digited extremities ; the metacarpal bones, on the contrary, are most expanded at their digital ends. The metacarpal are shorter and thicker ; the metatar- sal longer and more slender. The shaft of the metacarpal bones is pretty regularly pris- matic and triangular ; that of the metatarsal, on the contrary, is compressed or flatten- ed on the sides. 2. There are no well-marked differences between the carpal extremi- ties of the metacarpal bones and the tarsal extremities of the metatarsal ; but the lat- ter are larger than the former, which agrees with the greater dimensions of the tarsus. 3. The tarsal extremities are more regularly cuneiform than the corresponding ends of the metacarpal bones. The most characteristic differences, however, of these two series of bones are found in the digital extremities, which are incomparably larger in the metacarpus than in the metatarsus, the fingers being the chief part of the hand, while the tarsus is the principal portion of the foot. We should also remark, that the convex articular surfaces of the digital ends of the metatarsal bones are prolonged farther on the dorsal aspect than the corresponding surfaces of the metacarpal bones. Comparison of the Phalanges of the Fingers and Toes. The fingers, being the essential organs of prehension and the fundamental part of the hand, greatly exceed the toes both in length and thickness, and the latter may be looked upon as representing in rudhnent the former, being precisely analogous in structure. The phalanges of the toes may, therefore, be regarded as phalanges of the fingers in a state of atrophy ; but the great toe forms a remarkable exception to this rule, for its phalanges are much larger in proportion to the other toes than the phalanges of the thumb are to the other fingers. This magnitude of the great toe corresponds to the size of its metatarsal bone, and accords with its destination, as constituting the principal sup- ■^rt for the weight of the body in front. The first phalanx of the toes exactly resembles the first phalanx of the fingers in all things but volume. The middle phalanx of the toes can scarcely be recognised, from its diminutive size : it may be said to want the shaft al- together, the extremities being in contact. As we have already^remarked, it might at 110 OSTEOLOGY. first sight be confounded with a pisiform, or a sesamoid bone, or still more readily with a piece of the coccyx. Comparison of the Upper and Lower Extremities with regard to Development. The development of the lower extremities is proportionally less rapid than that of the upper. The clavicle and the scapula are ossified before the os innominatum. The os- sification of the skeleton commences in the clavicle ; in this bone, the osseous nodule is visible from the twenty-fifth to the thirtieth day ; it appears in the scapula about the for- tieth day. The osseous point of the ilium is visible about the forty-fifth day, that of the ischium in the third month, and that of the pubes in the fifth month. The scapula is completely ossified at the age of twenty years ; the marginal process of the crest of the ilium is scarcely united until the twenty-fifth year. The bony centres of the shafts of the femur and humerus are almost simultaneous in their appearance. The germ of the lower end of the femur always exists at birth ; that of the lower end of the humerus does not appear until the end of the first year ; but this latter unites with the bone at eighteen years, while the former is still separate at twenty years. The tibia is ossified a little be- fore the bones of the forearm, the fibula a little after them. The ossification of the leg and the forearm is completed almost about the same time. The ossification of the bones of the tarsus precedes that of the carpus by a considerable period. Thus, at from foui and a half to five months of foetal life, a bony point is visible in the os calcis, and some days after in the astragalus ; the os magnum and os cuneiforme (which, however, ar« not the representatives of the preceding) do not show ossific points until a year after birth. The pisiform bone is not ossified until the twelfth year ; while the latest of the tarsal bones, the scaphoid, is converted into bone at the fifth year. Nevertheless, the epiphysary point of the os calcis (which we have shown to be analogous to the pisiform bone) does not become visible until the tenth year ; this fact strengthens the analogy between the pisiform bone and the epiphysary lamina of the os calcis. The metatarsal bones are developed in exactly the same manner as the metacarpal, only at a somewhat later period. The union of the epiphyses takes place a little earlier in the metatarsus than in the metacarpus. The toes are ossified at a later period than the fingers ; especicdly the ungual and the second phalanges, which are much later than those of the fingers. It is, no doubt, impossible to state the precise reason for these differences ; but it is sufficient to find a positive relation between the rate of development of these parts, and the offices they are intended to fulfil. The Os Hyoides, or the Hyoid Apparatus* (fig. 57). The OS hyoides has a parabolic form, resembling the upsilon of the Greeks, whence its name. It is the only bone which is detached from the rest or Fig. 57. ^ the skeleton ; it is connected only by ligaments and muscles, and is situated between the base of the tongue and the larynx. It is larger in the male than in the female. It is placed almost hori- zontally, the concavity of its curve looking backward, and the convexity forward. This bone is divided into five parts ; viz., a body or middle part (a), ani four cornua, two large (J) and two small (c). This multiplicity of parts, which is much greater in some animals, es- pecially fishes, justifies the name of " hyoid apparatus," which we have adopted.! The body of the os hyoides (a) is quadrilateral, elongated, and curved, with the cavity behind. Its anterior surface looks upward, and presents a crucial projection, the vestige of a process which in many animals is prolonged into the substance of the tongue. This projection gives attachment to several muscles, the insertions of which are marked by transverse lines, interrupted by tubercles. The posterior surface, more or less excavated in different individucds, is sometimes connected with a yellow ceUular tissue, which sep- arates it from the epiglottis, and is sometimes covered by a synovial membrane. Its ex- cavation, which is never very great in man, is the vestige of the enormous cavity which exists in the hyoid of the Howler monkey. The lower edge gives attachment to the thy- ro-hyoid muscle only. The upper edge gives insertion to a yeUow membrane, a sort ol ligament which stretches into the tongue ; and also to the yeUow thyro-hyoid ligament, which has been incorrectly stated to be inserted into the lower edge of the bone. The extremities of the body of the os hyoides are covered by cartilage for articulation with the great cornua. The great cornua or rami {b) are much longer than the body, and flattened above and below, while the body is compressed from before backward. They are expanded at the place where they articulate with the body, pass backward, and, after being contracted * I have introduced the description of the os hyoides into this place, because, although chiefly belonging to the tongue, it gives attachment to several muscles, and, therefore, should be previously knovfn to the student t Vide M QeofFroy Saint-Hilaire, on the anterior bones of the chest. — {Philos. Anat., vol. i., p. 139.) THE ARTICULAR CARTILAGES. HI and flattened, terminate in a rounded tubercle, which is sometimes surmounted by an epiphysis. ♦ The little comua (c) are called also styloid cornua, because they are connected with the styloid process by means of a ligament. They are two pisiform nodules at the point of junction of the great comua with the body of the hyoid {ossa pisiformia lingualia of Soemmering). They surmount the upper edge of the bone, and are directed upward and outward ; their length is very variable. In the lower animals, the prolongations which correspond to these httle cornua are much longer than the great cornua in man. They articulate by their lower end with the body and the great cornua. Their upper part gives attachment to a ligament, which unites it with the styloid process. This ligament which is sometimes ossified in man, is always a bony connexion in the lower animals.* Internal Structure. — The hyoid bone is composed chiefly of compact tissue ; but there is a small quantity of spongy tissue in the thick parts of the body and the great cornua. Development. — The os hyoides is developed from five points ; one for the body, two for the great comua, and two for the little cornua.. Some anatomists admit two points for the body, and make the whole number six. The ossification of the great cornua precedes that of the body, which becomes bony soon afl;er birth ; the little cornua are not ossified until some months afl;er. All the pie- ces are at first separated by considerable portions of cartilage, afterward by a very thin layer, which sometimes remains during life, and gives the different parts of the bone a great degree of mobility. THE ARTICULATIONS, OR ARTHROLOGY. General Observations. — Articular Cartilages. — Ligaments. — Synovial Membranes. — Classi- fication of the Joints. — Diarthroses. — Synarthroses. — Amphiarthroses, or Symphyses. The bones are united together by the joiTits or articulations. The study of these parts is the object of syndesmology, or, more properly, of arthrology {apdpov, a joint). In exam- ining each joint, it is necessary to consider, 1. The contiguous surfaces of the bones, or the articular surfaces ; 2. The uniting medium, or the ligaments ; 3. The means or condi- tions which facilitate the motion of the parts, the syiwvial membranes ; and, 4. The move- ments of which the joint is capable, t It is impossible to insist too much upon the importance of a careful study of the artic- ulations. There is no part of anatomy a thorough knowledge of which is more indis- pensable both to the physiologist and the surgeon ; without it the former cannot form a correct idea of the animal mechanism, nor can the latter appreciate the nature of those numerous injuries and diseases of which the articulations are the seat. Before describing the forms and the motions of the different joints, it is necessary to give a general idea of the articular cartilages, the synovial membranes, the hgaments, &c. ; in short, of all the means which contribute to secure the solidity and mobility of the articulations. The Articular Cartilages. It has been observed,t that when two osseous surfaces in immediate contact rub upon each other, they are gradually absorbed in such a manner as to render the movements between them diflicult and painful. In order to avoid these injurious effects in the joints, the contiguous surfaces of the bones are covered by a layer of cartilage (the incrusting or articular cartilage), a substance which unites in itself the qualities of solidity, pliability, and elasticity in a high degree, yielding when compressed, and returning to its former state when the pressure is removed. These articular cartilages exist in all the mova- ble joints. The extent of surface which they cover is generally proportioned to the ex- tent of motion in the joints. Their thickness is generally greatest when the bones which they cover are most movable,' and most subjected to pressure. An articular car- tilage is not of uniform thickness throughout. Thus, on convex surfaces, the cartilagi- nous layer is thicker in the centre than at the circumference ; and, on the other hand, the cartilages of articular cavities are thickest at the circumference. The most perfect co- aptation results from this arrangement. It should also be remarked, that the most vio- lent shocks are applied to the centre of the heads of the bones, and to the circumference of the cavities. The articular cartilages present, 1. A free surface, perfectly smooth and polished, which is in the interior of the articulation ; 2. An adherent surface, which is so closely attached * In the lower animals, the styloid process is detached from the cranium, and forms one of the hyoid chain of bones, which is composed, 1. Of the five pieces of the os hyoides ; 2. Of the bones which supply the place of the styloid ligaments ; 3. Of the styloid processes, or, rather, bones : nine pieces in all. t Three of these, viz., the configuration of the articular surfaces, the ligaments, and the niovements of the joint, are essentially related to each other; so that we may deduce, cles been relaxed. What has been said above of the manner in which the ribs withstand violence is not however, applicable to the false ribs, which, having no fixed point on the stemui.l are depressed into the abdominal cavity. Mechanism of the Thorax with reference to Mobility. The thorax is not equally movable throughout. The middle portion, which corresponds to the heart, and which is formed by the sternum and vertebral column, has a very limit- ed degree of mobility, vvhile the sides which correspond to the lungs are endowed with the power of extensive motion. The movements of the thorax consist of alternate dilatations and contractions, from which its mechanism has been compared to that of a pair of bellows. They result from the motions which take place at the costo-vertebral and chondro-sternal articulations, and at the articulations of the cartilages with each other. We cannot explain the move- ments of each rib, and of the entire thorcix, without first analyzing the motions at each of the above joints. Movements of the Costo-vertebral Articulations. These articulations permit only very limited gliding motions. In these movements, each rib represents a lever, which moves upon the fulcrum afforded by the vertebral col- umn. It may describe the movements, 1. Of elevation; 2. Of depression ; 3. It may be carried inward ; 4. It may be carried outward ; 5. It may perform a revolving motion around the cord of the arc which it represents. These different movements, which are very obscure in the immediate neighbourhood of the joint, are more evident the gieater the distance is from the posterior end of the rib. The means of union between the ribs and vertebrae are so strong, that luxation of the ribs is impossible ; and the causes which would tend to produce it would break the neck of the rib. Each rib is capable of performing all these motions ; but, as they vary in degree in the different ribs, we must examine them comparatively in the series of costo-vertebral ar- ticulations. The eleventh and the twelfth ribs possess the most extensive power of motion. They owe this, 1. To the circumstance of their being scarcely at aU united to the very small transverse processes ; 2. To the loose state of their ligaments ; and, 3. To the almost perfect flatness of their articulated surfaces. The extent of their move- ments inward and outward should also be noticed. We shall find these movements but less pronounced, in the eighth, ninth, and tenth ribs, they scarcely exist in the first seven ribs. The shape of the head of the first rib is undoubtedly favourable to mobility, and has suggested the idea that it is the most movable of all the ribs ; but the articulation of its tubercle with the transverse process of the first dorsal vertebra, and the tightness of its ligaments, suflSiciently explain why this opinion is erroneous. The movements which take place in the second, third, fourth, filth, sixth, and seventh costo-vertebral articulations do not differ sufficiently to require any special mention. Movements of the Chondro-sternal Articulations. In these articulations there is even less gUding than in the preceding. The anterior extremity of the first rib, or, rather, of the cartilage which forms its continuation, is the least movable of all ; more commonly, it is completely fixed on account of its continu- ity with the sternum, a circumstance which neutralizes the favourable conditions for mobility presented by its posterior extremity. The eleventh and twelfth ribs, whose anterior extremities are connected only to soft parts, are the most movable. The mo- bility of the ribs in front decreases from the lower to the upper part of the thorax ; to this rule the second rib is an exception, chiefly on account of tlie two synovial mem- branes at its chondro-sternal articulation, which permit of greater motion. This, how- ever, is variable, depending as it does on the absence or presence of an articulation be- tween the first and second bones of the sternum, and upon the more or less variable mode in which these two pieces are articulated. Movements of the Cartilages upon each other. The movements of this kind are restricted to the sixth, seventh, eighth, ninth, and tenth ribs, the cartilages of which alone are articulated to each other. They are simple, gliding motions, and this gliding is proportionate to the looseness of the ligaments. Hence it follows, that the ribs wliich I have just mentioned are always moved simul- taneously as they gUde slightly upon each other ; whereas the superior ribs are inde- pendent in their movements. This independence, however, is not as great as it might appear at first sight, on account of the interosseous aponeuroses, the interosseous mus- cles, and the superior transverso-costal ligament, which is very narrow above, and forms below large and shining aponeurotic laminae. It results, from the facts above stated, that the most movable ribs are the twelfth and the eleventh, which may be moved upward and downward, and, at the same time, 134 ARTHROLOGY. enjoy, in the highest degree, the movements of projection inward and outward ; that the first rib is the least movable of all ; that the superior ribs may be moved isolatedly ; that the inferior ribs are moved all together. Movements of the entire Rib. Since we now know all the elements of which the movement of the ribs is composed, we shall easily comprehend the play of each of those bones isolatedly, and the play of the whole thorax. The movements of the entire rib are composed, 1. Of those which take place at the sternal and vertebral articulations ; and, 2. Of those which result from its own flexibility and elasticity. We shall endeavour to reduce the subject to its most simple elements. Let us suppose, then, that the ribs are straight, inflexible levers : from their oblique po- sition in reference to the vertical axis of the spinal column, their elevation will increase the width of the intercostal spaces ; for it is a law of physics, that lines which are ob- lique with regard to another line, and parallel to each other, become farther separated when they are placed perpendicularly to that line. Hence it follows, that the contact or the overlapping of the ribs is impossible during the movement upward of these bones. A second effect of the elevation of this oblique lever is the advancement of the anterior extremity of the rib, which movement increases proportionately to the length of the le- ver ; hence results an increase of the antero-posterior diameter of the thorax. But as the ribs are curved levers, and not rectilinear, in assuming the horizontal position, their concavity must come to be directed perpendicularly to the median plane formed by the mediastinum. It may be shown, geometrically, that the concavity of an arc which falls perpendicularly upon a plane, includes a greater space than when it falls obliquely. From the elevation of the ribs results, therefore, an increase of the transverse diameter of the thorax.* The arcs of the ribs, however, have not all the same curvature : each rib has its own peculiar perimeter, and it may be proved that the more curved the rib, the greater is the projection outward which it forms when elevated. Lastly, as in some ribs the upper border forms the segment of a smaller circle than the lower, the movement of projection outward is proportionally greater in these than in the other ribs. This assertion may be experimentally proved by imitating the movements of elevation and depression on the second rib. I- The greater the disproportion between the curvature of the superior and that of the inferior border, the more marked will be the projection gjitward. This is the reason why the elevation of the second and third ribs, when they are bent at once, both by their faces and their borders, produce such a remarkable increase of the thoracic capacity. If the ribs and their cartilages were inflexit)le levers, the movements of elevation would be much restrained ; but, by a mechanism, of which we find no instance elsewhere, the flexibility of these levers introduces into the problem a power which is most impor- tant and very variable, so that their movements are much more marked than would arise from the mobility of the articular surfaces. These movements cannot be determined by calculation. Now this flexibility, whence results a movement of torsion in the rib, or of rotation round an axis, represented by the cord of the arc which the rib forms, is in a direct ratio to the length of the ribs and their cartilages, and the flexibility of either. Indeed, the movements of the ribs are much more considerable in children and women than in old men ; and the deficiency of mechanical power in regard to breathing, which corresponds to the smallness of the power of locomotion in old men, explains the sever- ity which characterizes asthma and all the diseases of the lungs at this age. We shall now examine the movements of the thorax in genercil. Movements of the Thorax in general. The general movements of the thorax, which result from those partial motions we have been engaged in considering, are, 1. A movement of dilatation, corresponding with the act of inspiration ; 2. A movement of contraction, corresponding with that of expi- ration. 1 . The dilatation of the thorax is caused by the elevation of the ribs. By this move- ment, the anterior extremity of each rib is carried forward, and the antero-posterior di- ameter of the thorax is thus increased ; the most eccentric portion of the rib is carried outward, and the transverse diameter of the thorax is thereby augmented. There is a sort of antagonism between the upper and lower part of the thorax, with regard to the direction in which the increase of its capacity is effected : in the upper part the trans- verse diameter is most augmented ; in the lower, the antero-posterior diameter. The most movable point in the superior ribs is at the centre of the curvature ; the most movable point of the inferior ribs is at the junction of the ribs and the cartilages But the columns to which the extremities of the ribs are attached are not equ£iUy mo- * BoreUi, t. ii., p. 177. t From measurements taken by Haller, it appears that the second rib is the most elevated during inspira- tion ; and if this may be doubted, it cannot be denied that its eccentric movement is greater than that of ant »f the other ribs. ARTICULATIONS OF THE SHOULDER. 135 vable : if the posterior extremity is fixed, the anterior extremity may be moved from its place. This circimistance does not oppose the transverse enlargement being produced by the elevation of the arcs of the ribs, though it introduces a new condition into the problem, to wit, the elevation of the anterior column or the sternum. So long as the movement of elevation of the ribs is limited to the costo-vertebrcd articulations and a slight flexibility of the ribs and their cartilages, the sternum scarcely participates in the motion ; but when the elevation is carried beyond a certain point, when all the powers of inspiration are in activity, when there is an integral movement of the thorax, which has not been sufficiently distinguished from the partijd movement, then the sternum is carried upward with the ribs, then the first two ribs, which we have represented as the essential props of the sternum, are themselves elevated, and this elevation must be the Scune as that of all the other ribs, and must, therefore, be proportionately more consider- able. Does the sternum perform an angular motion during its elevation, as Haller ima- gined 1 On placing the thorax between two parallel planes, and on executing a forci- ble movement of inspiration, we feel at the inferior portion a pressure, which seems to indicate, in this inferior portion, a movement of projection forward. The lever formed by the inferior ribs being longer, it seems, indeed, as though there ought to be an angular motion ; but it will be observed that there is no pression tending to diminish the curve which is described by the ribs ; that therefore the two halves of the arc which the curves represent do not recede from each other, and that the powers of elevation simply draw all the anterior extremities of the ribs upward ; indeed, the sternum is simply elevated near the cervic£d region, retaining; its primitive direction, as Borelli had previously well pointed out ; considering the flexibility of the cartilages, the angular motion is almost impossible. The enlargement of the thorax is effected by the elevation of the ribs, and takes place either transversely forward or backward. The enlargement of the thorax in a vertical direction is produced by a totally different mechanism, the contraction of the diaphragm, of which we shall speak hereafter. 2. Let us now speak of the contraction of the thortix. This contraction is effected by the depression of the ribs. In the first stage, the contraction is passive, because it re- sults from the elasticity of the cartilages, which, on account of the relaxing of the eleva- tor muscles, cease to be maintained in a state of torsion, and therefore react and restore the rib to its primitive position, so that the rib and cartilage, according to the ingenious remark of Haller, are alternately the cause of their respective movements. It ought to be remarked, that the movement of depression is much more limited than the movement of elevation ; and I may justly regard the superior transverso-costal hgament as being destined to impose particular limits to that depression, during which the intercostal spaces are narrowed. We may regard as a powerful auxiliary of the depression and the contraction of the thorax the movement of projection inward, especially in the last five ribs, which are in certain respects depending upon each other. This movement of pro- jection inward is opposed to the transverse dilatation or the movement of projection out- ward, which takes place especially at the superior portion, as has been seen above, and as is shown every day by the use of the corsets. Afterward we shall see that the great inspiratory powers, or powers of elevation, occupy the superior portion of the thorax, as the great expiratory powers occupy the inferior portion. To the integral elevation of the thorax, in the most considerable degree of contraction, corresponds an integral de- pression, and this depression of the ribs is directly produced by muscles which bear the name of expiratory muscles. ARTICULATIONS OF THE SUPERIOR OR THORACIC EXTREMITIES. Articvlaiions of the Shoulder. — Scapulo-humeral, — ■Humero-cuhital. — Radio-cubital. — Radio- carpal. — Of the Carpus and Metacarpus. — Of the Fingers. Articulations of the Shoulder. The two bones of the shoulder are articulated together ; the clavicle is also united with the sternum and the first rib. There are, therefore, two orders of articulations : 1 The intrinsic articulations of the shoulder, viz., the acromio- and coraco-clavicular artic- ulations ; 2. The extrinsic, or the sterno- and costo-clavicular. The Acromio- and Coraco-clavicular Articulations. The clavicle is articulated, 1. With the acromion by its external extremity, the acro- mio-clavicular articulation ; 2. With the coracoid process by its lower surface, the coraco- clavicular articulation. Preparation. — Remove the skin, the cellular tissue, and the muscles which surround the joints ; separate the acromion from the spine of the scapula ; remove, in succession, the different layers of the superior acromio-clavicular ligament, so as to be able to judge of its thickness. Make a vertical section of the acromio-clavicular articulation, so as to be able to observe the thickness of the ligaments and articular cartilages. 136 ARTHROLOGY. Aeromio-clavicular Articulation {fig- 69). Articular Surfaces. — ^The clavicle and the acromion process oppose to each other a plane, elliptical surface, with its greatest diameter directed from before backward. The articular surface of the clavicle looks somewhat obliquely downward and outward, the acromial facette looks obliquely upward and inward. The extent of these surfaces va- ries greatly in individued cases, dependant on the degree of exercise to which the joint is subjected.* Means of Union and Promsion for facilitating Motion. — These are, 1. An intcr-articidar cartilage, first pointed out by Weitbrecht ; it is by no means constant, and, when it does exist, occupies only the upper half of the articulation. 2. An orbicular fibrous capsule {d, fig. 69), which is very thick above and behind, and very thin below. It is composed of distinct bundles, which are much longer behind than in front, and are strengthened by some fibres belonging to the aponeurosis of the trapezius muscle ; it is not only attached to the upper edge of the articular surface, but also to some inequalities upon the upper surface of the acromion. It is composed of several layers, the deepest being the shortest. 3. A synovial membrane, of a very simple construction, supported below by adipose tissue. Coraco-clavicular Articulation {fig. 69). There can be no doubt concerning the existence of an articulation, where two surfaces are contiguous, and capable of a gliding motion on each other ; one of them, the coracoid, being almost always covered with carti- lage and a synovial membrane ; and the other, the clavicular, presenting some- times a considerable process for this ar- ticulation. The means of union are two ligaments, or, rather, two distinct ligamentous bun- dles, a posterior and an anterior : they are called coraco-clavicular. 1. The posterior ligament, named also the conoid or radiated (c, fig. 69), is trian- gular, and directed vertically ; it com- mences by a narrow extremity, at the base of the coracoid process, and is inserted into a series of tubercles on the posterior edge of the clavicle, near its outer extremity. 2. The anterior ligament (/) {trapezoid ligament of Boyer) arises from the internal edge of the coracoid process, and from the whole extent of the rough projection on the base of this process ; from this it proceeds very obliquely to the ridge on the lower surface, near the external end of the clavicle. The two coraco-clavicular ligaments are continuous, and can only be distinguished by the direction of their fibres. We might with propriety range among the means of union of this joint an aponeurotic lamina, to which much importance has been attached in surgical anatomy, and which is known by the name of the costo-clavicular aponeurosis, or costo-coracoid ligament. It may be easily felt under the pectoralis major in emaciated individuals : it extends from the inner edge of the coracoid process to the lower surface of the clavicle, and converts the groove for the subclavius muscle into a canal. Mechanism of the Acromio- and Coraco-clavicular Articulations. The acromio- and coraco-clavicular articulations perform well-marked gliding move- ments ; and, in addition, the scapula rotates forward and backward upon the clavicle to a considerable extent. In order to have a correct idea of these motions and their mecha- nism, it is necessary to procure a shoulder with the ligaments still attached, and to ro- tate the scapula backward and forward. It will be then seen that the scapula turns round an imaginary axis passing through its middle. The looseness of the posterior half of the orbicular and of the coraco-clavicular ligaments permits this rotatory motion ; of the two coraco-clavicular ligaments, one limits the rotation forward, while the other, which, as we have observed, runs in an opposite direction, hmits the rotation backward. Although these motions are pretty extensive, they never give rise to dislocation, which can only be produced by falls on the top of the shoulder, the coraco-clavicular ligaments being lacerated if the luxation be complete. Incomplete luxations may, however, take place without laceration of these ligaments. The Sterno-clavicular Articulation {fig. 69). The articulation of the inner end of the clavicle is composed of the sterna-clavicular and the costo-clavicular articulations. Preparation. — Saw through the clavicles vertically at their middle, and also the first ribs at corresponding points ; and meet these two sections by a horizontal division of the * In indiyiduals who have excrciscil the upper extremities very much, these surfaces are uneven, and unequally incrusted '"•th np^lv-fonned cartilage. ARTICULATIONS OF THE SHOULDER. 1^7 Sternum. In order to see the interior of the sterno-clavicular joint, open the fibrous cap- sule along the edge of the sternum above, or, rather, make a horizontal cut, which will divide it into two parts, an upper and an under. In order to examine the costo-clavicular articulation, open the synovial membrane be- hind. The sterno-clavicular articulation belongs to those which are formed by rmitual reception. Articular Surfaces. — The articular surface of the sternum is transversely oblong con- cave in the same direction, and convex from before backward ; it looks obliquely upward and outward, and is situated on the side of the notch on the upper part of the sternum. 1. The articular surface of the clavicle is oblong from before backward, slightly concave in the same direction, and convex transversely. From the respective configuration of these surfaces a mutual jointing results, and the short diameter of the one corresponds to the long diameter of the other ; so that the end of the clavicle overlaps the surface of the sternum in front and behind, and the surface of the sternum projects beyond that of the clavicle on the inside and the outside.* 2. There is an inter-articular lamina of cartilage (i. Jig. 69) between the articular sur- faces, which is moulded upon them, and is very tliick, especially at the edges. It is sometimes perforated in the centre. + It is so closely united by its circumference to the orbicular Hgament that it is impossible to separate them : it adheres below to the carti- lage of the first rib, and above and behind to the clavicle. Means of Union. — These are, 1. The orbicular ligament {I, fig. 69). This name may be given to the fibrous capsule which surrounds the joint in all directions. The fibres which compose it have been regarded as forming two distinct bundles, known by the name of anterior and posterior ligaments ; but it is impossible to distinguish between them. Fi- bres proceed from all parts of the circumference of the articular surface of the clavicle, obliquely downward and inward, to the circumference of the articular surface of the ster- num. The capsule is not of equal thickness throughout ; it is thinner, and somewhat looser, in front than behind, which may partly account for the more frequent luxations of the clavicle forward than backward. 2. The inter-clavicular ligament (wi, Jig. 69), consisting of a very distinct bundle stretch ing horizontally above the fourchette of the sternum, from the upper part of the innei end of one clavicle to the inner end of the other. This ligament, which is much nearer the posterior than the anterior part of the joint, establishes a sort of continuity between the clavicles. It is the only direct means of union between the two shoulders. 3. There are two synovial capsules in this joint. That which is between the sternum and the inter-articular cartilage is more loose than that between the cartilage and the clavicle. The Costo-clavicular Articulation {Jig. 69). The articulation between the clavicle and the cartilage of the first rib is an arthrodia. It is formed between an articular surface, which almost always exists on the lower sur- face of the clavicle, and a corresponding facette on the upper surface of the inner end of the first rib, at its junction with the cartilage. There is, in this articulation, a syno- vial membrane, which is loose, especially behind. There is only one ligament, the cos- to-clavicular {g, Jig. 66), a thick, strong bundle of fibres, quite distinct from the tendon of the subclavius muscle, which is placed in front of it. It is fixed to the inner part of the first costal cartilage, and is directed very obliquely upward and outward, to be inserted into the under surface of the clavicle, to the inner side of the articular facette. Mechanism of the Sterno-clavicular Articulation. This articulation is the movable centre of the motions of the shoulder and of the whole upper extremity ; and hence the utility of an inter-articular cartilage, to obviate tte effects of blows or pressure : hence, also, the wearing away of this cartilage, the de- formity and wasting of the articular surfaces, the depression of the right sternal facette, and, lastly, the difference in the size of the sternal extremities of the right and left clavicles. This articuation, like all those effected by mutual reception, admits of motions in every direction : viz., upward, downward, forward, backward ; and of circumduction, resulting from the preceding, but not of rotation. 1. Movement of Elevation. — In this the sternal facette of the clavicle glides downward upon the corresponding surface of the sternum ; the inter-clavicular ligament is relaxed ; the cartilage of the first rib comes in contact with the inner extremity of the clavicle, limits the degree of elevation, and prevents displacement. 2. Movement of Depression. — In this the sternal end of the clavicle glides in the oppo site direction ; the articular surfaces of the costo-clavicular articulation press strongly * Bichat considers that this arrangement of the articular surfaces predisposes to luxation ; it appears to ma to have a precisely opposite effect, as it permits tho surfaces to move upon each other to a considerable extent without being separated. i,- i, i, t In a great number of cases this ligament is found partially wasted by the continued pressure to which the joint is subjected. s 138 ARTHBOLOGY. against each other, and limit the extent of this movement. It should be remarked, that in this movement the subclavian artery is compressed betvi^een the clavicle and the first rib, sometimes so completely as to arrest the circulation in the limb. 3. In the movement of the shoulder backward, the inner end of the clavicle glides for- ward upon the surface of the sternum ; the anterior part of the orbicular capsule is stretched ; and if the movement is carried beyond a certain point, the capsule is torn, and the clavicle dislocated forward. 4. In the foricard movement of the shoulder, the inner end of the clavicle glides back- ward. The anterior part of the orbicular ligament is relaxed, and the posterior part stretched ; as, also, the inter-clavicular ligament, which, as we have seen, is nearer the back than the front of the joint. In this motion luxation may take place backward. It may be remarked that, of all the movements of the shoulder, the one described, in which the clavicle is likely to be dislocated backward, is the most uncommon. The movement of circumduction is more extensive forward and upward than backward. The motions at the sterno-clavicular articulation are very circumscribed in themselves , but when transmitted by the lever of the clavicle, they become very considerable at the apex of the shoulder. Mechanism of the Costo-clavicular Articulation. This articulation, which may be regarded as a dependance of the sterno-clavicular, admits of very limited motions, subordinate to those of the joint last described. The Scapulo-humeeal Articulation {figs. 69 and 70). Preparation. — Separate the upper extremity from the trunk, either by disarticulating the clavicle at its sternal end, or by dividing it through the middle ; 2. Detach the del- toid from its origin ; 3. Detach the supra and infra spinati muscles, the teres minor and subscapularis, proceeding from the scapula to the humerus ; 4. Observe the adhesion of the tendons of these muscles to the capsular ligament ; 5. Divide the capsule trans- versely, after having studied its external aspect. The scapulo-humeral articulation belongs to the class of enarthroses. Articular Surfaces. — These are the glenoid cavity of the scapula, slightly concave, of an oval form, with the large end downward, and looking directly outward ; and the head of the humerus, consisting of about a third of a sphere, and presenting a surface three or four times more extensive than the glenoid cavity. The axis of the head of the hume- rus forms a very obtuse angle with that of the shaft of the bone.* These two surfaces are covered by a layer of cartilage, which, on the head of the hu- merus, is thicker at the centre than at the circumference ; while the reverse obtains in the glenoid cavity. Glenoid Ligament (a, fig. 70). — This is a fibrous circle, which surrounds the margin of Fig. 70. the glenoid cavity, and appears to be formed by the bifur- cation of the tendon of the long head of the biceps ; but it is also partly composed of fibres proper to itself, which stretch along the margin, arising from one point and ter- minating in another. Notwithstanding this addition, the head of the humerus is still too large to be received into the cavity, so that a portion of it is always in contact with the capsular ligament ; an inconvenience that is obviated, in some measure, by the existence of a supplementary cavity, as we shall presently see. The scapulo-humeral ar- ticulation is therefore one formed by juxtaposition, and not by reception ; from which arrangement it has lately been classed among the arthrodial articulations. Means of Union. — Like all enarthroses, there is here a fibrous capsule, or capsular lig- ament (r, figs. 69 and 70), a sac with two openings, which extends from the margin of the glenoid cavity to the anatomical neck of the humerus, t This capsule is remarkable for its laxity. In fact, it is so capacious that it could lodge a head twice as large as that of the humerus, and is so long that it will allow the articular surfaces to be separated for more than an inch ; the only example of so great a separation without laceration of the ligament.t There is this peculiarity in the fibrous capsule of the shoulder-joint, that it is incom- plete in one part, its place being there supplied by the tendons of the surrounding mus- cles. In no joints, in fact, have the muscles and tendons more effect in strengthening the articulation : they are, in a manner, identified with it. There are a great many varie- .ies in this respect. The fibrous capsule is so much stronger, as it is less adherent to the * Such is the shortness of the neck of the humerus, that its head, which looks upward and inward, would 6e almost entirely included between the prolonged planes of the body of the humerus. t It should be remarked, however, that the fibrous capsule does not terminate directly at the anatomical neck of the humerus, but is prolonged a little downward, and becomes blended with the insertions of the ten- dons of the supra and infra spinati and subscapularis. i In paralysis of the deltoid, the head of the humerus is so far separated from the glenoid cavity thai two fingers may be inserted betweeu the articular surfaces. AKTICULATtONS OF THE SHOULDER. 189 surrounding tendons. The following are the relations of the capsule : 1. Below, in the variable space between the subscapularis and teres minor, it corresponds to the cellular tissue of the axilla, or, rather, to the thin edges of the muscles just mentioned : the head of the humerus may, therefore, be easily felt by the fingers introduced deeply into the axilla. 2. Above and on the outside, it is in contact with the tendon of the supra-spi- natus, from which it is difficult to separate it, and is also in relation, though not immedi- ately, with the arch formed by the acromion and clavicle with the deltoid muscle. 3. In front, it corresponds to the subscapular muscle, from which it may be easily separated. 4. Behind, it corresponds to the tendons of the supra and infra spinatus, which are more or less adherent to it, and the teres minor, which does not adhere to it. As to its struc- ture, it is composed of fibres stretched irregularly from the neck of the humerus to the circumference of the glenoid cavity. Its thickness is not great, nor is it equal through- out, being most considerable below and in front ; but the capsule is strengthened above by a considerable bundle of fibres (s, fig. 69), called the coracoid ligament, coraco-humeral ligament, or accessory ligament of the fibrous capsule, which arises from the anterior edge of the coracoid process, and spreads out on the capsule. This capsule always presents an opening or an interruption above and before,* on a level with the superior border of the subscapularis, which covers the opening in part ; or, rather, between this border and the coracoid process. This opening is of an oval form ; its greatest diameter is horizontal ; its large extremity is turned outward, and its small extremity inward. The circumference of this opening, which is large enough to admit the point of the index fin- , ger, is perfectly smooth, thick, and looks like mother-of-pearl, especially in its inferior half. This opening is traversed by a considerable prolongation of the synovial mem- brane, which reaches the basis of the coracoid process, and then extends between the tendon of the subscapularis and the cavity which bears the same name. This cone- shaped prolongation is variable with respect to its extent, and appears to have no other object except to facilitate the gliding of the tendon of the subscapularis under the cora- coid arch and against the border of the glenoid cavity. By distending the articular cap- sule in several subjects, Mr. Bonamy has demonstrated this disposition to my perfect satisfaction. I have been able to see that the synovial prolongation is sometimes divi- ded into several cells by incomplete walls, by which this distended prolongation acquires a crimpled aspect. Sometimes several of these cells are totally distinct from the syno- vial membrane. Inter-articular Ligament. — This name may, with propriety, be applied to the tendon (t, fig. 70) of the long head of the biceps, which, arising from the upper part of the glenoid cavity, turns like a cord over the head of the humerus, and passes along the bicipital groove. It acts by keeping the head of the humerus applied to the glenoid cavity, and forms a sort of arch that supports the bone when it is forced upward. In two subjects, I found this tendon terminating by a strong adhesion in the bicipital groove, and thus justifying the name of inter-articular ligament, which I have applied to it : the tendon for the long head of the biceps took its origin from the same groove. I consider this division of the tendon to have been accidental, for the bicipital groove was depressed, and the inter-articular ligament flattened, and, as it were, lacerated. The synovial capsule is the simplest of all in regard to its disposition. It lines the fibrous capsule and the tendons which replace it, and is reflected, on one side, on the neck of the humerus, and, on the other, upon the border of the glenoid cavity, to be lost upon the circumference of the articular cartilages. It is remarkable, inasmuch as, 1. It forms a fold round the tendon of the biceps, which is prolonged into the bicipital groove, and terminates below by a cul-de-sac or circular fold, which prevents the effusion of the synovia ; 2. It is open in one or two points,+ and presents two prolongations communi- cating with the synovial bursse of the subscapularis and infra-spinatus. Supplementary Cavity. — ^We may regard as a dependance of the scapulo-humeral artic- ulation the vaulted arch formed by the coracoid and acromion processes, and the liga- ment which unites them. In shape it corresponds to the head of the humerus, and is so constructed that the coracoid process prevents displacement inward ; the acromion pre- vents it upward and outward ; and the ligament between them opposes dislocation di- rectly upward. This provision evidently compensates for the incomplete reception of the head of the humerus in the glenoid cavity. A circumstance which proves the use fulness of this vault, and the frequent contacts which it must have with the humerus, is the presence of a synovial capsule, situated between the coraco-acromion vault on one * I have seen this opening divided into two unequal portions by a fibrous bundle, strong, looking like mother- of-pearl, and resemliling a little tendon. Often 1 have met a second interruption of the fibrous capsule on a level with the concave border of the acromion process, which concave border acts as a real retum-puHey for the infra-spinatus muscle, and is analogous to the return-pulley presented by the basis of the coracoid process to the subscapularis muscle. When the capsule is perforated at this point, the synovial membrane gives oflf a prolongation, which serves as a gliding capsule for the tendon of the infra-spinatus. t [Although the synovial capsule of the shoulder-joint is thus occasionally prolonged into the bursoe mucosal connected with the tendons of these muscles, it must not, therefore, be supposed that it is an exception to the general rule that membranes of this nature always form shut sacs ; in such cases, the three structures consti- tute one coiitiiiuuus cavity.] 140 - " • . ARTHROLOGY. side, and, on the other, the tendon of the infra-spinatus and the great trochanter of the humerus. The study of the coraco-acromion vault cannot, therefore, be separated from the study of the scapulo-humeral articulation, either under an anatomical and physiolo- gical or surgical point of view. The Coraco-acromial Ligament. This ligament (m, figs. 69 and 70) forms part of the vault we have described : it is a triangular bundle of radiating fibres, which extends from the apex of the acromion to the A^hole length of the posterior edge of the coracoid process. Its external edge becomes Ainner, and is continued into an aponeurotic lamina below the deltoid muscle, and sep- arating that muscle from the joint. Its anterior and its posterior bundles are very thick, folded upon each other, and look like mother-of-pearl ; its middle bundles are much less thick. It is lined below by a synovial membrane, and is separated from the clavicle by fatty tissue.* Mechanism of the Scapulo-humeral Articulation. The scapulo-humeral articulation admits of the most extensive movements of any joint in the body : it is capable of every kind of motion, viz., forward and backward, and also those of adduction, abduction, circumduction, and rotation. Forward and Backward Motions. — In these the head of the humerus rolls upon the gle- noid cavity, and moves round the axis of the neck of the humerus, while the lower extrem- ity of the bone describes the arc of a circle, of which the centre is at the joint, the radius being represented by the humerus.! The forward movement is very extensive, and may be carried so far that the humerus may take a vertical direction exactly opposite to the natural one. The motion backward is produced by the same mechanism ; the head of the humerus turns upon its axis. This movement is limited by the contact of the head of the humerus with the coracoid process, without which dislocation forward would be very easily produced. It should be remarked that, in any considerable movement of the humerus forward, the scapula is also moved, performing that sort of rotation which we spoke of when considering the mechanism of the shoulder. And this combination of the movement forward of the arm and the movement of rotation of the shoulder renders every kind of displacement extremely difficult in exercising the movements of the arm forward. The movement outward, or abduction, is the most remarkable. It belongs exclusively to animals possessed of a clavicle. In it the head of the humerus does not turn upon an axis ; it glides downward upon the glenoid cavity, and presses upon the lower part of the capsule. The shape of the glenoid cavity, which has its long diameter vertical, and its broad part below, is advantageous as regards this motion. When abduction is car- ried so far that the humerus forms a right angle with the axis of the trunk, a great part of the head of the bone is below the glenoid cavity. If, while in this condition, the arm be moved forward or backward, the great tuberosity of the humerus rubs against the coraco-acromial arch, and forms with it a sort of supplementary articulation, lubricated by the bursa situated between the coraco-acromion vault and this great trochanter.^ The movement of abduction may be carried so far as to allow the arm to touch the head without dislocation ; for the capsular ligament is sufficiently loose, especially below, to receive almost the whole head of the bone without being torn. It should be remarked, that during abduction the scapula is fixed, which explains the frequency of luxations of the humerus downward. Adduction is limited by the arm meeting with the thorax. When it is combined with the forward motion, the upper and back part of the capsule, and the muscles which cover it, are considerably stretched. The scapula does not participate in this movement, du- ring which luxation can be occasioned only by a very strong impulse on the arm upward and backward. Circumduction is nothing more than the transition of the humerus from one to another of these motions. The cone which it describes is much more extensive in front than behind, a circumstance tending greatly to facilitate the prehension of external objects, which is the chief purpose of the upper extremities. This predominance of the forward motions has been already noticed in the sterno-clavicular articulation, and will be found also in many others. * [This is the ligamentum proprium anterius of authors ; but the author has taken no notice of another liga- ment proper to the scapula, viz., the ligamentvm proprium posterius, a thin band of fibres stretched across the notch at the base of the coracoid process, which it thus converts into a foramen. The supra-scapular nerve generally passes below, and the artery above it.] t It is through this ingenious and simple mechanism, of which we shall soon see another example in the articulation of the femur with the os innominatnm, that the movement forward of the humerus maybe carried far enough to describe a demi-circle, without the bone being displaced. X If theory has led us to believe that the coraco-acromion vault contributed to luxation, by offering a point of support to the lever represented by the humerus abducted from the body, a more careful observation, on the contrary, has demonstrated that this supporting of the humerus was impossible, as the anterior border of the coraco-acromion ligament is alone pressing against the humerus in the forcible abduction, and luxation is al- ways produced in a middle abduction of the urni. ARTICULATIONS OF THE ELBOW. 141 Fig.n. Fig. 72. Rotation. — In this movement the humerus does not turn upon its own, but upon an imaginary axis, directed from the head of the humerus to the epi-trochlea, parallel to the bone. The manner in which the rotatory muscles embrace the head of the humerus is highly favourable to this motion, by compensating for the shortness of the neck, which serves as a lever for the rotatory movements. The Humero-cubital Articulation, or Elbow-joint {figs. 71 and 72). Preparation. — 1. Remove carefully the brachialis anticus muscle ; 2. Detach the ten- don of the triceps from above downward, without opening the synovial capsule ; 3. Re- move the muscles which are attached to the internal and external tuberosities, keeping in mind that the lateral ligaments are intimately connected with the tendons of these muscles. This articulation belongs to the class of trochlear joints (angular ginglymi). Articular Surfaces. — On the humerus we find, 1. An almost perfect trochlea or puUey presenting two edges, of which the internal is the more prominent, so that, when the end of the bone rests upon a horizontal plane, its shaft is directed very obliquely from above downward and inward ; 2. The small head, or articidar condyle, separated from the trochlea by a furrow, which is also articular ; 3. Two cavities, a pos- terior, which is very deep, and is intended to receive the olecranon process, and an anterior, which is shal- lower, and receives the coronoid. The articular surfaces of the forearm are, 1. The greater sigmoid cavity of the ulna, which exactly em- braces the trochlea ;* 2. The glenoid cavity of the ra- dius, which receives the small head of the humerus. The means of union consist of four ligaments, two lateral, an anterior, and a posterior. 1. The external lateral ligament (a, Jigs. 71, 72) is blended with the ten- don of the supinator brevis ; it is of a triangular form, and stretches from the external tuberosity of the hu- merus to the annular ligament, with which it becomes continuous, and which seems to be in part formed by it. Some fibres of this ligament are also inserted into the outer part of the sigmoid cavity of the ulna. This connexion of the lateral with the annular ligament is of great importance with reference to the production of luxations of the upper end of the radius, t 2. The internal lateral ligaments are two in number ; one internal, properly so called, or humero-cormioidian ; the other internal and posterior, humero-olecranian. The former, or humero-coronoidian, which is partly confounded with the aponeurotic tendon of the superficial flexor muscle of the fingers, is a thick, rounded bundle, which arises below the internal tuberosity of the humerus, and is inserted into the whole internal side of the coracoid process, and more especially in its tubercle. The second, or humero-olecranian, which might be described as a posterior ligament of the articulation, is thin and radiating ; it arises from the posterior portion of the epi- trochlea, and irradiates to be inserted into the whole extent of the internal border of the olecranon ; the inferior bundles are the strongest, and come in part from the humero- coronoidian ligament. The superior bundles are thin and slender, and reach beyond the olecranon, in order to expand over the synovial membrane. 3. The anterior ligament (c) is a very thin layer, in which, however, three orders of fibres can be recognised. The first, directed vertically, fonn a bundle which extends from the upper part of the coronoid cavity to the lower part of the coronoid process ; the second are transverse, and intersect the first at right angles ; and, lastly, the third are obliquely directed downward and outward to the annular ligament, t We shall see, hereafter, that the brachialis anticus renders an anterior resisting ligament entirely use- less ; moreover, the most inferior and deepest fibres of this muscle are directly inserted in this anterior hgament. * Tbere is here, indeed, a hinge : it is the most remarkable example of a hin?e in the system ; it is the most perfect angular ginglymoid. The two articular surfaces present a sinuous surface, wliich is alternately concave and convex, a sort of catching which is seen nowhere else. t These relations between the annular ligament and the external lateral ligament are so intimate that these two ligaments are seldom torn independently of each other ; hence the consecutive dislocation "f the radius .pon the cubitus in the luxations of the elbow ; hence, also, the luxations of the radius upon the humerus, the ulna remaining in its place. (See an example of the luxation backward of the radius upon the humerus, the ulna remaining in its place, Anat. Pathol., with plates, 8th number.) t It should be remarked, that none of these ligaments of the elbow-joint are attached directly to the radius, but that the fibres which are- directed towards this bone join the annular ligament. This arrangement allows the radius to rotate with perfect freedom within its ring, which would have been impossible had the fibr>^ been directly inserted into the bone. 142 ARTHROLOGY. 4. The posterior ligament {d,fig. 72). The place of the posterior Hgament is occupied by the olecranon and the tendon of the triceps. There are some fibres, however, which sxtend from the external to the internal tuberosity of the humerus, which are in relation with the synovial membrane in front, and the tendon of the triceps behind. The princi- pal posterior ligamentous fibres are those which seem to arise from the humero-olecra- nian hgament. The synovial membrane covers the posterior surface of the anterior ligament ; from this it is reflected upon the coronoid cavity, covers the olecranon cavity behind, and is prolonged a little between the tendon of the triceps and the back of the humerus. In this place it is widest and most loose. Below, it forms a prolongation, which extends into the radio-cubital articulation, covering the whole inner surface of the annular liga- ment, and forming a circular cul-de-sac below it, which prevents the effusion of the sy- novia.* There is some synovial adipose tissue round the points of reflection, and also at the margin of the coronoid and olecranon cavities. Mechanism of the Humero-cuhital Articulation. Extension and flexion, the only motions performed by this joint, are executed by it with remarkable precision and rapidity. The precision of these movements depends, 1 . Upon the exact fitting of the articular surfaces ; 2. Upon the great extent of the transverse di- ameter, round which the movements of flexion and extension are performed as round an axis ; 3. Upon the shortness of the antero-posterior diameter of the inferior extremity of the humerus, and, consequently, on the smallness of the circle to which the curve of the humeral trochlea belongs. 1. Flexion. — In this motion, which is very extensive, the radius and ulna move as a sin- gle bone from behind forward, on the small head and trochlea of the humerus. It should be observed that, in this movement, the obliquity of the trochlea from behind forward, and from without inward, throws the forearm, when bent, in front of the thorax, and the hand in front of the mouth. This motion is limited by the meeting of the coronoid process with the coronoid cavity. When this motion is carried to the greatest extent, the upper end of the olecranon descends to the level of the lowest part of the trochlea, and is, con- sequently, below the line which passes through the two tuberosities, or condyles, of the humerus. In this motion, the back part of the trochlea and the olecranal fossa are cov- ered only by the tendon of the triceps, so that instruments can readily enter the joint at this place. The flexion of the elbow, which constitutes a fundamental movement in pre- hension of bodies, may be carried as far as possible, even so far as to cause the forearm to meet the arm, without any risk of luxation, as any sort of dislocation here is impossi ble, however extensive this movement may be. 2. Extension. — In this movement, the radius and ulna roll backward upon the humerus. This motion can only be carried so far that the forearm and the arm form a right line, for then the upper part of the olecranon comes in contact with the bottom of the olecra nal fossa. The anterior ligament and the anterior and middle bundles of the internal lat- eral hgament are put on the stretch, and thus concur in limiting the movement of exten- sion, which is already limited by the olecranon coming in contact with the bottom of the olecranon cavity. There is no appreciable lateral motion of this joint, the exact fitting of the articular surfaces effectually preventing it.+ The Radio-cubital Articulations {figs. 71 to 75). In these articulations, the radius and the ulna are united, 1. By their upper ends {supe- rior radio-cubital articulation) ; 2. By their lower ends {inferior radio-cubital articulation) ; 3. By the interosseous ligament through a great part of their extent. Superior Radio-cubital Articulation. Preparation. — Remove with care the anconeus and the supinator brevis, and separate the forearm from the arm. The articular surfaces are the edge of the head of the radius, which is of unequal height in different parts, and the lesser sigmoid cavity of the ulna, which is oblong from before backward, broader in the middle than at the ends, and which forms the bony portion of the osteo-fibrous ring in which the head of the radius rolls. The means of union consist of the annular ligament of the radius {e, figs. 71 and 72) * [According to the common opinion, the articular surfaces of the radius and ulna are, of course, also cov- ered by the synovial membrane.] t A glance at the articulation of the elbow, surrounded by its ligaments, is sufficient to convince us of the facility with which the dislocation of the humerus forward takes place, favoured as it is by the smallness of the antero-posterior diameter of the articulation, and by the deficiency in the resistance of the anterior liga- ment. This dislocation is, next to that of the humerus, the most frequent, notwithstanding the resistance of the brachialis anticus, which, being an active ligament, supports the anterior portion of the articulation, with which it is so closely identified, that, in this dislocation, it is always torn, at least incompletely. This dislo- cation forward is, moreover, favoured in the movement of extension by the point of the olecranon meeting the bottom of the olecranon cavity of the humerus. In a fall upon the wrist, the forearm being extended, the hu- merus becomes a lever of the first kind, whose point of support is represented by the- olecranon cavity of the humerus strongly pressed against by the point of the olecranon ; the lever of power is represented by the whole length of the humerus ; the lever of resistance, by the short portion of the humerus below the olecranon cavity RADIO-CUBITAL ARTICULATIONS. 143 This ligament is a band forming three fourths of a ring, which is completed by the lesser sigmoid cavity of the ulna ; it is attached, by its two ends, to the fore and back part of this cavity. Its internal surface, which is smooth and shining like mother-of-pearl, is in contact with the articular border of the head of the radius. The external lateral ligament is attached to its outer surface, and evidently becomes continuous with its posterior half. This arrangement has doubtless given rise to the assertion, that the external lateral lig- ament is attached to the ulna. Those fibres of the anterior ligament which are directed obliquely downward and outward are also inserted into the annular ligament. All these ligamentous attachments retain the annular ligament in its proper position ; when they are divided, it is manifestly retracted towards the neck of the radius, and exposes the ar- ticular edge of the bone. The breadth of the annular ligament is from three to four lines, and its upper circumference is wider than the lower, which construction tends to main- tain the head of the radius in its situation more accurately. With regard to its structure, I would observe, that it is much thicker behind, where it receives the insertion of the ex- ternal lateral ligament, than in front, where it may be much more easily ruptured ; and I am persuaded that, in luxation of the elbow, it is not the external lateral ligament which is most commonly torn, but rather the anterior portion of the annular. The synovial capsule is a sort of diverticulum from that of the elbow-joint, which is prolonged upon the inner surface of the annular ligament, and is reflected upward from its lower margin, so as to form a sort of cul-de-sac below it. Inferior Radio-cubital Articulation. Preparation. — 1. Remove the muscles on both aspects of the forearm. 2. Separate the hand from the forearm so as to expose the lower surface of the triangular ligament, or fibro-cartilage. 3. In order to examine the interior of the joint, saw through the middle of the forearm ; divide the anterior and posterior ligaments ; separate the two bones of the forearm ; cut through the triangular ligament at its insertion into the ulna. The articular surfaces are a small sigmoid cavity on the radius, analogous to that which we have described at the upper end of the ulna, and the external two thirds of the cir- cumference of the head of the ulna. This articulation, therefore, is precisely the re- verse of the upper, since in this the ulna furnishes tl\e head, and the radius the sigmoid cavity, while a precisely opposite arrangement obtains in the upper joint. The means of union are, 1. Some fibres stretched in front and behind the joint, and call- ed anterior (/, Jigs. 71 and 75) and posterior (ff, Jigs. 72 and 74) ligaments. They form a very imperfect annular ligament. They extend from the anterior and posterior margins of the sigmoid cavity of the radius to the anterior and posterior surfaces of the little head of the ulna, in the neighbourhood of its styloid process. 2. The triangular ligament, or, rather, cartilage* {i,Jigs. 7i and 73). This is a triangu- lar lamina of cartilage, the apex of which is fixed into the angle formed by the head and styloid process of the ulna, and its base into the lower edge of the sigmoid cavity of the radius. It is thin at the base and the centre, and thick at the apex and the circumfer- ence. It concurs in maintaining the union of the radius and ulna, and performs the office of those inter-articular cartilages which we have noticed as peculiar to such joints as are most exposed to shocks and friction ; and, above all, it restores the level of the inferior radio-cubital surface by filling up the vacancy caused by the projection of the radius be- low the ulna. There is a separate synovial membrane for this joint (see above, i. Jig. 75), (often called membrana sacciformis). It covers the upper surface of the triangular ligament, and the sort of incomplete ring which circumscribes the head of the ulna. It forms very loose folds at the places of reflection, which admit of very extensive rotation. This synovial membrane is common to the articulation of the ulna with the radius, and to the articula- tion of the ulna with the inter-articular cartilage ; it is entirely independent of the syno- \ial membrane of the wrist-joint. Middle Radio-cubital Articulation, or Interosseous Ligament. The interosseous ligament {I, figs. 71, 72), improperly so called, is an aponeurosis which occupies the interval between the radius and ulna, and which appears to serve princi- pally for the insertion of muscles. It is broader in the middle than at the ends, and does not reach the extremities of the interosseous space, for there is an interval above and below, which serves the purpose of giving passage to nerves and vessels, and also per- mits more free motion between the two bones. The fibres which compose it are direct- ed obhquely downward and inward, i. e., from the radius to the ulna. We generally ob- serve on its anterior aspect several bundles running downward and outward ; the supe- * This is the only example in the system of an inter-articulary cartilage serving as a means of union be- tween the bones. Can its principal use be to prevent the dislocation of the ulna in the movements of rotation 1 The following experiment will show that this cartilage does not oppose the forcible movements of pronation and supination : Saw the bones of the forearm at their middle line, separate the forearm from the wrist, ro- tate with the utmost force the radius upon the ulna, and it will be sedn that, during these movements, the in- ter-articular cartilage remains unstrained in all its points. This cartilage is attached to the groove of the sty loid process of the ulna by fibrous tissue ; what it called the summit of the triangular cartilage is, therefore Dothing else than a very short and strong little ligament, by which the cartilage is attached to the ulna. 144 ARTHEOLOGY. rior and the strongest of these is called the round ligament, or the ligamentous cord of Weitbrecht (m, Jig. 71). It extends obliquely downward and outward, from the outside of the coronoid process of the ulna to the lower part of the bicipital tuberosity of the ra- dius. Its direction is, therefore, precisely the inverse of that of the fibres of the inter- osseous ligament. Mechanism of the Radio-cubital Articulations. These articulations, like all trochlear joints, only admit of one kind of motion, viz., rotation, which is here called by a peculiar name. Rotation forward is denominated ■pronation. ; rotation backward is called sjipination. We must examine these in both the upper and the lower radio-cubital articulations. Mechanism of the Superior Radio-cubital Articulations. Pronation. — In this movement, the inner part of the head of the radius rolls backward upon the lesser sigmoid cavity of the ulna, and may be carried so far that the radius may describe half a circle upon its axis. Notwithstanding the obstacles to displacement re- sulting from the strength of the back part of the annular ligaments, and the presence of the two little hooks, one in front and the other behind the lesser sigmoid cavity of the ulna, and, lastly, notwithstanding the advantage produced by the reception of the small head of the humerus in the cup-like cavity of the upper end of the radius, in violent pro- nation the head of the radius is frequently luxated backward. Perhaps no dislocation is more common in infancy than the incomplete luxation backward of the upper end of the radius, on account of the greater looseness of the annular ligament, and the less com- plete reception of the small head of the humerus in the cupula of the radius. The cause occasioning this displacement is forced pronation, so frequent when infants are held by the hand, in attempting to save them from falling. In supination, the head of the radius turns upon its axis in a different direction, i. e., its inner part ghdes forward upon the lesser sigmoid cavity of the ulna. If it be carried too far, dislocation forward may be the consequence.* Mechanism of the Inferior Radio-cubital Articulations. The movements of pronation and supination, at the lower radio-cubital articulation, are produced by a mechanism which is precisely the inverse of the former ; for the ra- dius, instead of rotating upon its own axis, turns round the head of the ulna by a move- ment of circumduction. This difference results partly from the curvature of the radius, and partly from the great transverse diameter of its lower end, which forms the radius of the arc of the circle which it describes round the ulna. In pronation, the little sig- moid cavity roUs forward on the articular edge of the head of the ulna ; in supination, it glides in the opposite direction, that is, backward. We see, then, that in the lower ar- ticulation, a concave surface moves upon a convex, while the contrary takes place at the upper. • Does the inter-articular cartilage limit these motions, as it has been asserted 1 The experiment which I have indicated above shows that this cartilage is in the same con- ditions in regard to the articular surfaces, both in pronation and supination, and that the small ligament which attaches it to the groove of the styloid process of the ulna, expe- riences neither tension nor relaxation. The anterior and posterior ligaments alone are able to limit the movements of rotation by their resistance ; but, in forcible pronation, these may be broken, and the head of the ulna dislocated backward ; in forcible supina- tion, it may be dislocated forward. It should be remarked that, in cases of luxation of the ulna, the head of this bone does not lacerate the capsule, but the capsule is torn upon it ; for, as we shall afterward see, the ulna is immovable at the cubito-carpal joint, and takes no share in the partial motions of the forearm. Mechanism of the Radio-cubital Articulations, considered with reference to the Bodies of the two Bones. In the movement of pronation, the radius crosses the ulna at an acute angle, so that its lower part is carried in front of the ulna, while the upper remains on the outside. The movement of supination consists in the return of the radius to its state of parallel- ism with the ulna. In pronation, the interosseous ligament is relaxed ; in supination, it is stretched : its absence at the upper part of the forearm, where its place is supphed by the ligament of Weitbrecht, allows more extensive rotatory movements, t * This displacement is very uncommon, on account of the hook-like projection at the anterior extremity of the sigmoid cavity, and doubtless, also, because forcible supination is very rjjre. Professor Dng^es informs me that he has seen an instance of this dislocation of the radius, and proved its existence by inspection after death. I have myself recMitly met with a case of an incomplete dislocation forward in a child ; a slight pres- sure from before backward upon the superior extremity of the radius was sufficient to reduce the dislocation, which took place on a sudden, while the child was being dressed. t If the interosseous ligament, the fibres of which pass downward from the radius to the ulna, had besn prolonged to the upper part of the interosseous space, it would have much impeded the motions of supination, l)y limiting the movements of the bicipital tuberosity, into which one of the supinator muscles of the forearm, viz., the biceps, is inserted ; but the round ligament being inserted below the bicipital tuberosity, and passing dojwQward from the ulna to the radius, can have no effect in limiting the extent of rotation RADIO-CARPAL ARTICULATION. 145 The existence of the interosseous space is an indispensable condition for the peiform- ance of pronation and supination ; and, therefore, every curative plan for the treatment of fractures of the forearm which does not provide for the preservation of this space should at once be rejected. In the explanation we have given of the mechanism of the radio-cubital articulations the ulna has been considered as an immovable axis, round which the radius executes below certain movements of circumduction ; but many authors have maintained the opinion that the ulna also takes part in these motions. Without discussing the different theories which have been successively proposed on this subject, we shall mention an experiment which is at once decisive of the question. If all the articulations of the arm be exposed from the shoulder to the hand, and the humerus be immovably fixed in a vice, it will be seen that, when the forearm is pronated or supinated, the radius moves upon the ulna, which remains altogether imdisturbed ; and, also, that any lateral motion of the ulna is absolutely impossible, from its perfect jointing with the humerus at the elbow. When the humerus is not completely fixed, it also rotates in conjunction with the bones of the forearm. Lastly, it should be observed that, when the radius is rotated during semiflexion of the forearm, the motion is accompanied by slight degrees of flexion and extension at the elbow-joint. Radio-carpal Articulation {figs. 73 to 75). Preparation. — Divide the fibrous sheaths of the flexor and extensor tendons, and care- fully remove those tendons ; bearing in mind the fact that the fibrous sheaths closely ad- here to the ligaments, or, rather, are identified with them, and may be considered as an appurtenance of the ligamentous apparatus of the joint. This articulation belongs to the class of condylarthroses. The articular surfaces (fig. 73) are those of the scaphoid, the semilunar, and the cunei- form, which together form a condyle, oblong transversely, and covered by articular car- tilages, which are prolonged farther on the posterior than on the anterior aspect of the bones, and the transversely oblong concave, articular surface, formed by the lower ends of the radius and ulna. The radius, which forms by itself two thirds of the surface, cor- responds to the scaphoid and semilunar, and presents an antero-posterior ridge, and a slight contraction from before backward, opposite the interval between these two bones. The ulna corresponds to the cuneiform bone, with the intervention of an inter-articular cartilage, viz., the triangular cartilage already described, which performs the part both of a hgament and an inter-articular cartilage. The concave surface presented by the lower part of the forearm is completed at the sides by the styloid processes of the radius and ulna. Means of Union. — There are for this joint an external lateral hgament, an internal lat- eral, two anterior, and one posterior hgament. The external lateral ligament {a, figs. 73, 74, 75) stretches from the summit, and forms the neighbouring parts of the styloid process of the radius to the outer part of the scapho- id, where it is inserted by a broad attachment immediately on the outside of the radial ar- ticular surface of that bone. This ligament, which is not very thick, is continuous with the anterior and the posterior ligament, without any line of demarcation being perceived. The internal lateral ligament. It is uncovered immediately after the tendinous sheath of the extensor carpi ulnaris has been divided. It is lined by the synovial membrane of this sheath. It is a cylindrical chord, commencing at the styloid process, of which it seems to be a continuation, and dividing inferiorly into two fasciculi, one of which is at- tached to the pisiform, the other, which is more considerable, to the posterior surface of the cuneiform bone. This chord first appears very thick ; but, on dividing it, it is seen perforated by a cavity communicating inferiorly with the radio-carpal articulation, and its superior extremity is not attached to the summit of the styloid process of the ulna, but to the middle point of this process, in the form of a demi-capsule. The summit of this pro- cess is articular, and surrounded with a thick layer of cartilage ; it is farther contained in the synovial membrane of the wrist, and is in direct relation with the cuneiform bone. The styloid process of the ulna is therefore the only portion of this bone which enters di- rectly into the wrist-joint. The anterior ligaments are two in number, one radial, the other ulnar. The radio-carpal hgament forms a broad layer resembling mother-of-pearl, which ap- pears as soon as the flexor tendons have been removed. It is composed of bundles, which are often separated by adipose cellular tissue and vessels, so that I considered it neces- sary, in the former edition of this work, to describe three anterior radial bundles, an ex- ternal, a middle, and an internal ; I have abandoned this distinction, because it does not appear of any use. This ligament arises from the whole breadth of the anterior border of the inferior extremity of the radius around the articular surface ; it also arises from the anterior border of the styloid process of this bone. Hence its fibres stretch from above downward, and from without inward, approximating to a horizontal position, in proportion as they are more elevated. The most external fibres go to the os unciforme and the os magnum ; those which come next are inserted into the scaphoid bone ; others, again, into T 146 ARTHEOLOGY. the cuneiform and the pisiform bones. The most elevated fibres, which ire the most in- ternal, seem to be continuous with the anterior ligament of the inferior "adio-cubital ar- ticulation. The most external bundles of this ligament are tl e thickest. This ligament is composed of several layers of fibres, the most superficial cf which are the longest. The ulnar-carpal ligament has probably been conjfounded by authors with the internal lateral Ugament ; or perhaps it may have escaped their notice altogether, on account of its being deeply seated. This ligament arises, by a narrow extremity, from the groove which separates the styloid process from the little head of the ulna, in front of the small ligament which forms the summit of the inter-articular cartilage ; thence it goes down- ward and outward, passes under a few fibres of the anterior radio-carpal ligament, and ■ lost by irradiating. The horizontal superior fibres describe a curve beneath the head o- the idna, and are inserted into the anterior border of the radius, where they are confound- ed with the fibres of the radio-carpal ligament ; the inferior fibres descend almost verti- cally downward, externally to the pisiform bone, and terminate in the os cuneiforme. The posterior ligament cannot possibly be separated from the fibrous sheath of the ex- tensor and radial tendons, with which it is continuous. There is but one posterior liga- ment ; it is much weaker and narrower than the anterior radio-carpal ligament, and stretches obhquely from the posterior border of the radius to the posterior faces of the cuneiform and the semilunar bones. The bundle which goes to the cuneiform is the stronger. This ligament covers about the third portion of the joint, while the radio-car- pal ligament covers the whole of the anterior surface. It should be observed, that there is a marked predominance of the anterior over the posterior ligaments, both in the artic- ulation of the hand with the forearm, and in the articulations of the carpus. With regard to the anterior and posterior ligaments of the radio-carpal articulation, I shall make an observation which may be of some interest : it is, that all these ligaments, with the exception of the cubito-carpal, come from the radius, and closely unite the inferior extremity of that bone to the first range of the carpus, and, consequently, to the hand. The synovial membrane (see Jig. 73) is loose behind, where it is only partially covered by the ligaments we have described ; throughout the whole of the remaining circumfer- ence of the joint it is strengthened by scattered ligamentous fibres, which some anato- mists have described as a capsular ligament. This synovial membrane sometimes com- municates with that of the lower radio-cubital articulation, by an opening at the place o union of the triangular cartilage with the lower edge of the sigmoid cavity of the radius. It also sometimes communicates with the general synovial membrane of the carpus, by the interosseous spaces which separate the bones of the first carpal row. Besides the means of union which we have described, the flexor tendons in front, and the extensor tendons behind, should be noticed, as serving to increase the strength of the joint. Mechanism of the Radio-carpal Articulation. This articulation belongs to the condyloid class, and has, therefore, four motions, viz., flexion, extension, abduction, and adduction, and by passing from one of these to the other, it can perform circumduction. 1. Flexion. — In this motion, the condyle formed by the first row of the carpus glides Ibackward upon the lower end of the forearm. The posterior ligaments and the exten- :Sor tendons are put on the stretch. When the movement of flexion is carried too far, luxation may take place by laceration of the posterior ligament, and then the lower end of the two bones of the forearm pass in front of the articular surface of the bones of the first row of the carpus. The possibility of dislocation of this joint has been doubted ; but I have seen two instances of this kind of dislocation, which were incontestable. 2. In extension, the condyle formed by the carpus roUs forward upon the lower end of the forearm ; and as the articular surface of the carpus reaches farther on the back than in .front, it follows that extension may be carried farther than flexion: it is limited by the strong anterior ligaments, and also by the lateral ligaments, which, as is generally observed, are attached nearer to the side- of flexion than to that of extension. It should also be remarked, that extension is the easiest motion of the hand upon the forearm : this may be readily understood from the great power which the hand possess- es when it forms a right angle behind with the forearm.* 3. In abduction, the condyle formed by the carpus rolls in the direction of its length, t. c, transversely and from without inward, while the radial edge of the hand is inchned towards the radial edge of the forearm : this motion is limited by the mutual meeting of the styloid process of the radius, and the external process of the scaphoid. 4. In adduction, the ulnar edge of the hand is bent towards the ulnar edge of the fore- ; arm ; the motion is limited by the meeting of the summit of the styloid process of the ulna and the cuneiform bone, and also by the tension of the external lateral ligamsnt. It may be easily conceived, that in the lateral movements, which are performed in * We should observe that it is almost impossible to separate the mechanism of the carpal articulations irom that of the radio-carpal joint ; the latter is noticed here by itself only in order to conform with the ana toicical divisions. ARTICULATIONS OF THE CARPUS. 147 the direction of the long diameter of the articular surfaces, dislocation must be very dif ficult, and that, when it does occur, it must be incomplete. The movement of circumduction is nothing more than a succession of the different m» tions which have been already pointed out. The hand describes a cone, of greater ex tent behind, that is, in the direction of extension, than in front, or in the direction o» flexion. It is also still more restricted in adduction and abduction. Articulations of the Carpus (figs. 73 to 75). These articulations comprise, 1. The articulations of the bones of each row together and, 2. The articulations of the two rows. Articulations of the Bones of each Row. Preparation. — 1. Remove the extensor and the flexor tendons ; 2. Separate the hand from the forearm, then the first row from the second, and, lastly, the bones of both rows from each other, examining their means of union before completing the separation. Articular Surfaces. — The articulations of the bones of each row are amphi-arthroses, and, consequently, present one part continuous and another contiguous. The bones of the first row correspond to each other by oblique surfaces, those of the second row by vertical and more extensive surfaces. Means of Union. — Two classes of ligaments belong to these joints : the one is extend- ed between the corresponding surfaces, the interosseous ligaments; the other set are peripheral, and are divided into palmar and dorsal. The palmar and dorsal ligaments are fibrous bundles, stretched transversely or oblique- ly from each of the bones of the carpus to those which are contiguous to it. The dorsal are much thinner than the palmar. The interosseous ligaments are not disposed in an exactly similar manner in the two rows, and we shall, therefore, examine them separate- ^ 73 ly. 1 . The interosseous Ugaments of the first row (e e, fig. 73) occupy only the upper part of the corresponding u facettes ; they are nothing more than small fibrous bun- \' dies, one extending from the scaphoid (1) to the semi- lunar (2) ; the other from the semilunar to the cunei- form (3) ; they are sometimes partially interrupted, and present openings, which establish a communication be- tween the general synovial membrane of the carpus and that of the radio-carpal articulation. These inter- osseous ligaments are reddish, scarcely fascicidated, very loose, so as to admit of pretty extensive gliding motions. 2. The interosseous ligaments {d d d) of the second row are much thicker than those of the first ; the whole non-articular portion of the corresponding facettes gives insertion to these Ugaments, which are very compact, and of a much more dry and close tex- ture than the reddish tissue connecting together the bones of the fii-st row. It follows, therefore, that the bones of the second row are more firmly united than those of the first, whose interosseous ligaments are loose, and permit a certain degree of mobility. The articulation of the pisiform bone with the cuneiform merits a special description. Articulation of the Pisiform and Cuneiform Bodies. For this articulation, the pisiform bone presents a single articular surface, which unites with the auterior facette of the cuneiform bone. There are four ligaments in this little joint, which is nothing else but a loose arthrodia : 1. Two inferior {e,fig. 75), which are very strong, viz., an external, stretched obliquely from the pisiform to the hook-like process of the unciform bone ; and an internal, vertical, which is inserted into the upper end of the fifth metacarpal bone. These two ligaments appear partly to re- sult from the bifurcation of the tendon of the flexor carpi ulnaris, this tendon being in the place of the superior ligament, which is wanting. The internal lateral ligament of the radio-carpal articulation may also be considered as entering into the structure of the superior ligament. 2. An anterior and a posterior ligament, thin and radiating, which strengthen the synovial capsule in front and behind. The synovial capsule is, most commonly, a small isolated pouch ; and sometimes it is a prolongation of the radio-carpal synovial membrane. This capsule is ver>' loose, and the ligaments are not very tight ; hence the great mobility of the articulation. Articulation of the two Rows of Carpus together. The articulation of the two rows of the carpus together presents an enarthrosis in the middle, and an arthrodia on each side. The articular surfaces consist of a head or spherical eminence received into a cavity, constituting the enarthrosis, and of plane surfaces on the inside and the outside, whick form a double arthrodia. The head is formed by the os magnum (6cted by means of "the sacrum, which rests upon the ossa innominata. We should add, that a small portion of the weight is directly trans- mitted to the femurs by the iliac bones, which support the viscera of the abdomen. TQbe following arrangements should be noted, as being concerned in the transmission of the weight by means of the sacrum : 1. The great size of that bone, affording evidence of the destination of man for the erect posture. 2. The obtuse angle at which the sacrum unites with the vertebral column, peculiar to the human species, and which becomes the seat of a decomposition of the force transmitted by the spine. Part of the momentum acting in the direction of the axis of the column has no other effect than that of increas- ing the sacro- vertebral angle, at the expense of the flexibility of the inter-articular car- tilage ; the rest is transmitted to the sacrum, and then to the lower extremities. 3. The double wedge shape of the sacrum itself. In order to understand the advantage arising from this form, it is necessary to remark, first, that the weight of the trunk is transmit- ted in the axis of the upper half of the sacrum, and, consequently, in the direction of a line sloping downward and backward ; from this it follows, that the sacrum must have a tendency to be displaced either downward or backward, but the displacement downr ward is prevented by the position of the ossa innominata, which are nearer to each other below than above. The displacement backward is obviated by the oblique direction of the articular surfaces of the same bones backward and inward, while the obliquity of the sacrum itself is in the opposite direction, for it is broader in front than behind.* 4. The distance intervening between the sacro-iliac and the coxo-femoral articulations. The articulation of the vertebral column with the pelvis being situated at the back part of that cavity, while those of the femurs are situated towards the front and the side, the distance between them increases the space in which the centre of gravity can oscillate, without being carried so far forward as to pass beyond the perpendicular let fall from the coxo- femoral articulation to the base of support. In man alone is found a large pelvian basis of support, and thus the erect posture has been rendered possible in him, without an ex- cessive extension in front. In quadrupeds, the antero-posterior diameter of the bones of the ilium is rather short, and their haunch bones are elongated behind, and placed in almost the same plane as the vertebral column. The foetus and new-born infant somewhat resemble the lower animals in this respect, and, therefore, in the human subject there is a great tendency to assume the attitude of a quadruped during the first year of existence. The weight received by the sacrum and transmitted to the haunch bones is divided, sometimes equally and sometimes unequally, between the sacro-iliac symphyses. One portion of the impulse calls into action the mobility of the symphyses, and the remainder is transmitted to the cotyloid cavities. It should be remarked, that this transmission is effected along the triangular prismatic columns, which form the sides of the inlet of the pelvis, and are the thickest and strongest parts of that structure. At the foot oi these * Without admitting- that the influences to which the sacrum is subjected have a tendency to force it back- ward as well as downward, it is impossible to explain either the use of its being- shaped like a wedge, with the base turned forward, or of that powerful apparatus of posterior ligaments which can oidy resist its disloca- tion backward. The idea that these forces tend to press it forward is manifestly at variance with the naturt of the uniting media ; for the sacro-iliac symphyses are only maintained in front by a very thin ligamentous layer, and the breadth of the space between the iliac bones is also greater in front than behind; ciicumstaa- ces that ■\\ould evidently facilitate displacement forward. ARTHROLOGY. columns, which form cmres, we find, dug, as it were, into their substances, the cotyloid cavities, to which the weight of the trunk is transmitted. During the sitting posture, the weight of the body is transmitted to the tuberosities of the ischia, which, from their great size, are well fitted to support it. As these processes are a little anterior to the cotyloid cavities, and, therefore, situated in a plane very near the front of the pelvis, the centre of gravity of the trunk has a tendency to fall behind the basis of support represented by them ; and, therefore, it is easy to push an individual backward when in the sitting pos- ture, inasmuch as in front the basis for the support of the pelvis is increased by the length of tlie femurs and the length of the foot while man is seated on a chair, and the whole length of the abdominal extremity while he is seated on a horizontal plane. The mode in which the pelvis resists violence appUed to the tuberosities of the ischia in falls, is some- what connected with its mechanism as adapted to the sitting posture. The shock is, in these cases, transmitted directly upward in the dh-ection of the acetabula, the lower hem- ispheres of which offer resistance like two arches : from the acetabula the impulse is communicated backward, by the thick columns extending from behind these cavities, to the sacro-iliac symphyses ; and forward, to the symphysis pubis ; so that falls upon the tuberosities are dmost always accompanied with painful concussion both of the sacro- iliac and pubic symphyses. In order to complete our account of the mechanism of the pelvis in standing, we must examine its mode of resistance in falls upon the knees or soles of the feet. In this case, the shock is communicated from below upward to the upper halves of the cotyloid cavi- ties, wliich are supported by the prismatic columns already described. The anterior part of each acetabulum presents a large notch, and is altogether unconcerned in the transmission of these shocks ; so, also, is the very thin lamina constituting the bottom or inner wall of the cavity, which can only suffer compression in falls upon the great tro- chanter. The great difference existing between a fall upon the knees and the tuberosi- ties of the ischia, and the fall upon the points of the feet, with regard to a commotion of the brain and the spinal marrow, may be easily conceived. While standing on one 4»ot the weight of the trunk is transmitted to the femur by the sacro-iliac symphyses, and by the curve-shaped column of the side which bears upon the ground. In this position a fall readily takes place, on account of the facihty with which the centre of gravity passes the basis of support. During progression, the pelvis affords to each thigh alternately a solid fulcrum, and re- ceives itself a fixed point of support from the femur of that leg which rests upon the ground. While onp side of the pelvis is thus supported upon one of the thigh bones, the other side is projected forward. These alternate movements of projection of either side of the pelvis take place at the coxo-femoral articulation of the extremity which rests upon the ground. The alternate movements of projection increase in proportion to the breadth of the pelvis. It is for this reason that women, in walking, move the hips more than men. The remark of a witty author, that " running is the only thing which women are unable to do gracefully," is an allusion to this rather awkward motion of the pelvis. We may form a correct idea of the share which the pelvis takes in the act of walking by studying the mode of progression of persons with wooden legs. In these unfortunate beings the lateral inclinations of the pelvis are sufficient for progression by transporting the centre of gravity alternately to the two inflexible columns substituted for the lower extremities. 3. Mechanism of the Pelvis with regard to Parturition. — The art of midwifery depends, in a great measure, upon the study of the pelvis ; it is impossible to form a true concep- tion of the mechanism of natural labour without being acquainted with the axes of the pelvis, its dimensions as compared with the size of the foetus, the sacro- vertebral angle, the inclined planes of the true pelvis, the diameters of the brim and the outlet, and the malformations to which it is liable. Any lengthened details upon these points would be out of place here. I shall only remark, I. That the existence of the arch of the pubes is pecidiar to the human species ; and, 2. That the sciatic notches and the obturator foramina are not only useful from economizing weight, but also because, corresponding as they do to the oblique diameters of the head of the foetus during parturition, they ren- der less painful the pressure attendant upon that process ; 3. That the pyramidales, the mtemal obturators, and the psoae and iliaci muscles perform, so to speak, the office of mat- tresses in the pelvic cavity ; 4. That parturition, consisting in the expulsion of the foetus along the line of the pelvis, natural parturition, provided the expulsive power exists in its normal conditions, depends partly on a true conformation of the pelvis, and partly on a true conformation and position of the foetus ; 5. That a general idea of all the defects which may occur in the conformation of the pelvis may be expressed by stating, that this cavity is liable to all the malformations which may result from a pressure upon its whole brim or only a part of it, from above downward, from below upward, from before backward, or from side to side. 4. Mechanism of the Pelvis with regard to its own Movements. — The intrinsic movements of the pelvis are very obscure, being confined to mere gliding or swinging motions, the production of which destroys part of the momentum from any external violence. By COXO-FEMOEAL AETICULATION. 159i some admirable contrivance, the mobility of the intrinsic articulations of the pelvis is considerably increased during the latter periods of pregnancy, so that the coccyx may be pressed backward, causing an increase of five or six lines in the antero-posterior diam- eter of the outlet ; wliile the symphysis pubis* becomes susceptible of a slight separa- tion, which increases (in a very slight degree, it is true, but sufficiently to merit notice) the dimensions of the brim of this cavity. This mobiUty, which is especially remarkable in a narrow pelvis, favours the process of labour in a singular degree. The natural mobil- ity of the symphysis pubis has suggested the operation of symphyseotomy, by which the diameters of the pelvis, however, are but little increased, unless the severing of the bones of the pubes should be carried far enough to result in a separation of the sacro- iliac symphysis. A relaxation taking place in the symphysis of the pelvis may give rise to strange errors in diagnosis. The extrinsic movements of the pelvis are those of flexion, extension, lateral inclina- tion, and rotation : these motions, which are all very hmited, have been indicated in describing the mechanism of the vertebral column. The motions of the pelvis upon the thighs are very considerable : they will be examined with the mechanism of the hip-joint. CoxO-FEMOEAL ARTICULATION {fig. 76). Preparation. — Remove with care all the muscles that surround the joint, preserving the reflected tendon of the rectus femoris. The psoas and iliacus muscles, the synovial capsule of which so often communicates with the articular synovial membrane, must be removed with particular care. After the fibrous capsule has been studied upon its exter- nal surface, a circular division should be made round its middle portion, for the purpose of uncovering the deep-situated parts. This articulation is the type of the order enar- throsis, being a true ball and socket joint. The articular surfaces are the globular head of the femur, and the cotyloid cavity of the OS innominatum. There is a striking difference between this joint and that of the shoul- der, as far as regards the size of the articular head and the depth of the articular cavity. While the head of the humerus and the glenoid cavity are simply in juxtaposition with- out any reception of the former into the latter, so that the scapulo-humeral articulation has for a long time been, and is now considered as an arthrodia, there is a deep and com- plete fitting of the head of the femur into the cotyloid cavity, which we have pronoun- ced to be the deepest articular cavity of the body. Both of the surfaces above named are covered with cartilage, with the exception of two depressions, one of which is situa- ted on the head of the femur, the other at the bottom of the cotyloid cavity : the latter is filled with a reddish adipose tissue, improperly called the cotyloid gland. It is analo- gous to the adipose tissue found in the neighbourhood of all the joints ; its use is not well known. I have often asked myself the question, Why should there be this poste- rior cotyloid cavity ! On submitting the joint to an antero-posterior vertical section, shghtly encroaching on the margin of the posterior cotyloid cavity, it will be seen that the object of this cavity is to protect the round ligament in all the possible positions of the head of the femur ; and that, without this cavity, the round ligament could not have existed \vithout its being compressed between the articular surfaces. Now, as the intra- articular vessels enter this cavity, and go to the head of the femur along the round lig- ament, it is not impossible but that the exclusive use of this posterior cotyloid cavity should be to protect the vessels destined to the head of the femur, and that the round hgament itself should have no other use than to support these vessels, and to transmit them to the head of the femur. The cotyloid adipose tissue does not seem to have any other object, except to fill the empty space of this posterior cavity. It appears to me that the round ligament of the coxo-femoral articulation of the poste- rior cotyloid cavity serves the same purpose as the space between the condyles of the lower end of the femur and the crucial ligaments of the knee-joint. Means of Union. — The cotyloid ligament {n, fig. 76). This band, improperly called co- tyloid ligament, is attached to the margin of the acetabulum, which it, as it were, com- pletes ; it augments the depth of the cavity, and renders smooth its sinuous and notched circumference. It is of greater size at the notches than in any other part : by its means the irregularities of the edge of the acetabulum are effaced, and the deep- notch in front and below is converted into a foramen for the passage of vessels to the fatty tissue, the inter-artiailar ligament, and the head of the femur. The cotyloid band is much thicker above and behind than below and in front, and it is precisely against the first two points that the head of the femur constantly presses. It is also remarkable, in this respect, that the diameter of its free borders is smaller than that by which it is attached ; and this circumstance assists, in some degree, in retaining the head of the femur in the cotyloid cavity, t It consists of fibres which arise succes- * In a female seventy-nine years of age, the mother of nineteen children, I found the symphysis pubis ex- tremely movable : the two articular surfaces of the pubes were contiguous ; the interosseous ligament had disappeared ; and a very thick, fibrous capsule, of recent formation, surrounded the articular surfaces in front, above and below, being inserted at some distance from them. It was a symphysis changed to a loose arthrodia. t I have never seen this disposition better exhibited than in a subject in which the cotyloid band was OSM- fied in its whole extent, except at the place on a level with the anterior and inferior notch. The head of thfl 160 ARTHROLOGY. sively from all points of the circumference of the acetabulum, and interlace at very acute angles. This interlacement is especially visible in the situation of tlie great anterior notch, where the fibres may be seen arising from each side of the notch, and passing across each other. The orUcular ligament, or Jibrous capsule (p, Jig. 76). This represents a fibrous sac, having two openings, by one of which it embraces the acetabulum, outside the cotyloid ligament, while the other surrounds the neck of the femur. The femoral insertion of the capsular ligament requires to be carefully studied, for the purpose of explaining the difference between fractures within, and fractures beyond, the capsule. This insertion is so arranged, that at the upper part and in front of the joint it corresponds with the base of the neck of the femur, while beneath and behind it is situated at the junction of the external wich the two internal thirds of the neck. The insertion of the capsule in front takes place not only at the base of the neck of the femur, but also internally to this base, to the extent of several lines, as may be ascertained by an incision being made along this insertion in the direction of the axis of the neck. The length of tlie orbicular ligament is exactly equal to the distance between its insertions, excepting at the inner part, where it is much more loose. Hence the extent of the motion of abduction, which is so remarkable in some jugglers, that they are able to separate their legs until they form right angles with the body, without producing dislocation. The thickness of this ligament is not equal throughout : it is greatest above and on the outside, where the reflected tendon of the rectus muscle is situated ; it is yet very considerable in front and above ; it is less thick behind, and still thinner on the inside. In some subjects the thickness of the superior part of the capsule is to that of the inferi- or as five to one. In front, the capsule is strengthened by a bundle of fibres stretched Dbliquely, like a sling, from the anterior inferior spinous process of the ilium to the inside of the base of the neck of the femur. It is called by Bertin the anterior and superior lig- ament (r, fig. 76). This band, which serves as a re-enforcement to the capsule, lies un- der that portion of the iliacus muscle which arises from the anterior spinous process of the ilium, and follows the direction of this muscle ; it is composed of pardlel fibres, and closely adheres to the capsule, without adhering in the least to the muscle. Within this bundle the capsule is often imperfect, and permits a communication between the synovial membrane of the joint and the bursa of the psoas and iliacus muscles. This last syno- vial membrane may be considered as a prolongation of the articular synovial membrane ; this prolongation is analogous to the one which we have described at the scapulo-hume- ral articulation for the subscapularis muscle. In one subject that I dissected, the com- municating orifice was so large, that the common tendon of these muscles was in imme- diate contact with a considerable portion of the head ofthe femur ; the tendon itself be- ing split into several bands, some of which had been lacerated, and, as it were, worn away by friction. The external surface of the capsular ligament is in relation with the psoas and iliacus muscles in front, being separated from them by a bursa at the upper part, in those cases where the fibrous capsule is not interrupted, and giving insertion to many of their fibres below. On the inside, it is in relation with the obturator externus and the pectineus ; on the outside, with the gluteus minimus ; behind, with the quadratus femoris, the ge- melli, the pyi-iformis, and the obturator intemus. Several of these muscles send fortify- ing bundles of fibres to the capsule. I may point out an aponeurotic expansion coming from the gluteus minimus, which establishes a close connexion between this muscle and the capsule ; a second expansion, furnished by the pyriformis and the gemelli ; and a third, which is furnished to the capsule by the tendon of the vastus externus. The internal surface is lined by the synovial membrane. The orbicular ligament ofthe hip-joint differs from the generality of such structures in being of a dull white instead of a pearly white colour, and in being composed of ir- regularly interlaced fibres, except the superficial fibres, which are disposed in parallel lines. I have also observed a very remarkable fact, apparently overlooked by anatomists, viz., that it is extremely thin at its inferior orifice, but especially behind ; and that near this insertion it is strengthened by some circular fibres which embrace the neck of the bone like a collar, but without adhering to it ; and that in its different movements this sort of collar rolls round the neck, but is retained in its place by small bundles of fibres, reflected from the capsule upon the neck of the bone, which raise the synovial mem- brane from the surface. The intcr-articular, which is improperly called round ligament (t, fig. 76). This ligament arises, under the form of a fibrous band, folded backward upon itself, from the depression on the head of the femur, which depression is not entirely filled by it. It is twisted around this head, and is divided into three bands, one of which, after having again been subdivided, traverses the adipose tissue and is fixed into the bottom of the cotyloid cav- ity, while the two others are attached to the two edges ofthe cotyloid notch, below the cotyloid band, by which this insertion, with which it is often continuous, is concealed. femur wis mechanically and solidly retained in the acetabulum, whose bottom, being partly worn out ani] pressed inward, fonned a prominence in the interior face of the pelvis. COXO-FEMORAL ARTICULATION. 161 In one case a prolongation of this ligament traversed the cotyloid notch, and was at- tached to the part nearest the capsule. The thickness and the strength of this inter-ar ticular ligament are extremely variable : sometimes it is extremely strong, sometimes very weak ; sometimes it adheres to one edge only of the notch ; sometimes it consists mere- ly of a few ligamentous fibres, contained within the substance of the reflected synovial membrane ; sometimes in its place is found a fold of that membrane, which may be torn by the slightest force ; and, lastly, it is not uncommon to find that it is altogether wanting. The synovial membrane lines the whole internal surface of the capsular ligament the two non-adhering surfaces of the cotyloid ligament, and that part of the neck of the fe- mur contained within the joint ; it embraces the round ligament, and sends off a pro- longation from it to a quantity of fatty matter at the bottom of the acetabulum;* an ar- rangement which led the older anatomists to believe that the round ligament was in- serted into the bottom of the cotyloid cavity. Mechanism, of the Coxo-femoral Articulation. Like all enarthroses, the coxo-femoral articulation can execute movements of flexion, extension, abduction, adduction, circumduction, and rotation. 1. Inflexion, the head of the femur roUs in the cotyloid cavity around an imaginary axis corresponding with that of the neck of the bone, while the lower end of the femur is carried from behind forward, and describes the segment of a circle, whose radius is represented by the shaft of the bone. In the mechanism of this movement, the neck of the femur has the effect of substituting a rotatory motion of the head of that bone upon a fixed point, without changing the relation of the head with the acetabulum, and, con- sequently, without any tendency to displacement, for a very extensive movement back- ward and forward, which would otherwise have been necessary, and in which the sur- faces would have been liable to separation from each other. We can, indeed, scarcely believe that luxation would be possible during this motion, although it can be carried so far that the front of the thigh and the fore part of the abdomen may be brought in contact 2. Extension is effected by the same mechanism, the head and the neck of the femur rolling upon themselves from behind forward, while large arcs of a circle, from before backward, are described by the body of the bone ; but such is the obliquity of the acetab- ulum, which looks both forward, outward, and downward, that when the femur is in the vertical direction, the head projects and carries forward the fibrous capsule. The anterior re-enforcing bundle is stretched. The psoas and iliacus muscles perform the office of an active ligament. Luxations of the femur forward are not common, for the movement of extension is limited by the meeting of the edge of the acetabulum and the back part of the neck of the femur ; and the ligament and muscles above named also tend to counteract it. 3 and 4. The mechanism of adduction and abduction is altogether different from that of the preceding movements, where the articulation forms the centre of a circle descri- bed by the femur, the radius of which is measured by a line stretched from the head of the bone to the space between the condyles. In abduction, the head of the femur presses against the inner part of the capsular ligament ; and, on account of the looseness of this ligament, the obliquity of the acetabulum, and the arrangement of the inter-articular lig- ament, this movement may be carried very far without displacement, and is only limited by the meeting of the upper edge of the neck of the femur with the rim of the cotyloid cavity. But this very niceting may itself become the cause of luxation, and then the edge of the cotyloid cavity may be regarded as the fulcrum of a lever of the first order with unequal arms, the whole length of the femur being the arm, to which the power is applied, and the neck of the bone, that by which the resistance acts. In adduction, the femur moves in precisely the opposite direction : this motion is lim- ited by the mutual contact of the two thighs, but, by means of slight flexion, it may be carried so far as to throw one over the other. The great depth of the upper and exter- nal part of the cotyloid cavity, and the strength of the capsular ligament in the same di- rections, would seem to oppose all displacement. But it should be observed, that falls upon the knees almost always happen during adduction of the thighs, for this is an in- stinctive movement of preservation. However slight the adduction may be, the inter- articular ligament is of necessity stretched ; and from this it follows, as my colleague, M. Gerdy, has ingeniously remarked, that the head of the femur is detached from the bottom of the cavity by a kind of rolling of the round ligament upon it, and comes to press against the fibrous capsule. The rupture of the inter-articular ligament is not al- ways necessary in luxation. I have seen several instances of a so-called incomplete lux- ation inward, without this hgament being torn. 5. Circumduction consists in the transition from one of these motions to another. The * The synovial membrane is often seen, being interposed and descending- between the adipose substance and the posterior cotyloid cavity. I may also point out semilunar folds, which are often formed by tne syno rial membrane round the neck of the femur. These folds are supported by some detached fibres of the cap- Bule, so that the neck, on a level with those fibres, is lined with synovial membrane only in the neighbour hood of the head of the femur. The synovial folds appear to me destined to conduct vessels to the margin of the head of the femur. Round the head of the femur, at its point of union with the neck, are constants found very small adipose bundles. v • - • • X 162 ' "' ' ■ ARTHROLOGY. femur circumscribes a cone, of which the apex is in the joint, while the base is described by the lower end of that bone. The axis of the cone is represented by aline drawn from the head of the femur to the interval between the condyles ; and the length of the femur accounts for movements which are scarcely felt at the coxo-femoral articulation, being so considerable at the lower end of the bone. 6. Independently of the movements above described, the coxo-femoral articulation per- forms motions of rotation, arising by no means from its enarthrodial shape, but from the presence of the neck of the femur. Generally no movement appears to require a greater expenditure of power on the part of nature than the rotatory movements, and these move- ments are not always regulated by the same mechanism. We have already seen an ex- ample of this movement in the atlo-axoidian articulation, where a cylinder forme 1 by tho odontoid process rolls in the partly osseous and partly fibrous ring of the atlas, as an axle tree in a wheel. Here the arrangement is quite different ; the rotatory movement is ob tained simply by the lever being bent like an elbow in such a manner as to make the rota tory movements of the femur upon its axis result from the movements forward or backward of the bent portion. This movement should be studied both at the upper and at the lower part of the femur. At the upper part it is a motion of horizontal displacement, the radi- us being represented by the head and neck of the bone ; at the lower part it is a rotatory motion of the femur, not precisely upon itself, but upon an imaginary axis placed on the inside of, and parallel to, the shaft. It follows that there can be no rotation in cases of fracture of the neck of the bone, and this is one of the diagnostic signs of that accident Lastly, it may be observed that rotation is perfonned from without inward, or from within outward : the latter is the more extensive and more natural movement ; it is produced by a great number of muscles, and, therefore, during repose, the point of the foot is slightly inclined outward. The Knee-joint (Jigs. 78 to 81). Preparation. — 1. Make a crucied incision in front of the knee and dissect back the flaps. 2. Detach the aponeurosis of the thigh, preserving the fibrous band, which forms the con- tinuation of the tensor vagina femoris, and which forms, as it were, a superficial ligament. 3. Remove the aponeurosis of the triceps on the sides of the patella, taking care to avoid opening the synovial capsule. 4. Remove the tendon of the biceps, and turn downward the tendons of the sartorius, gracilis, and semitendinosus. 5. Remove the popliteal ves- sels and nerves behind, and also the gastrocnemii. 6. After having studied the ligaments situated around the synovial capsule, isolate the latter as much as possible by dissecting off the lateral ligaments, and the ligamentum patellae. 7. Open the synovial capsule above the palate. 8. Make a horizontal section of the femur immediately above the con- dyles, and a vertical section from before backward between the condyles These two sections are intended to expose the crucial ligaments. The articulation of the knee belongs to the class of angular ginglymi ; it is the largest and most complicated joint in the human body ; it is, perhaps, the most important, both in regard to the part which it plays in the mechanism of the animal economy, and the fre- quency and the gravity of the maladies which it is liable to. Articular Surfaces. — The lower end of the femur and the upper end of the tibia are the essential constituents of this joint, which is completed in front by the patella. The ar- ticular surface of the femur is formed in front by the trochlea, and behind by the two condyles, separated by the intercondyloid fossa ; the articular surface of the tibia con- sists of the glenoid cavities, separated by the spine of the til)ia, in front of and behind which are some irregular projections. The patella presents two concave surfaces, sep- arated from each other by a vertical ridge corresponding to the groove of the trochlea. These surfaces are aU covered with a thick layer of cartilage. It should be remarked, with regard to the knee-joint, 1. That the articular surfaces are rather placed in juxta- position than jointed together ; 2. That the articulation is in some measure double, since two very distinct condyles correspond to two equally distinct cavities. These two con- dyles being turned in opposite directions, viz., the external backward and outward, the internal backward and inward, they are opposed to each other ; like the articulation oi the two condyles of the occipital bone with the atlas, which are opposed both to the lat- eral and the rotatory motions, and, in regard to these motions, constitutes an angulai ginglymus, so in the case in the knee, its two condyles constituting, as it were, a double condylian articulation, transformed into an angular ginglymus. Inter-articular Cartilages. — Like all joints that are exposed to much pressure, the knee is provided with inter-articular cartilages. They are two in number, and are named, from their figure, semilunar or falciform cartilages (a, b, fig. 78). Their upper surfaces, corresponding to the convexity of the condyles, are concave ; their external circumfer- ence is very thick, and the internal sharp and thin : they therefore assist in deepening the concave surfaces of the tibia. The section of tlicse cartilages forms an elongated isoscele triangle, with its base outward. The external inter-articular cartilage (a) gov ers almost the whole of the external glenoid cavity of the tibia, fonning nearly a com- plete circle ; while the internal cartilage (4), which is, indeed, semilunar, leaves a great ARTICULATIONS OP THE KNEE-JOINT. '-.H^'UnMt* . 1^.78. part of the corresponding cavity uncovered.* In this respect the inter-articular cartilages of the knee differ from all others of the S2uiie kind, for they do not establish a complete separ- ation of the articular surfaces, between which they are placed. « hese falciform cartilages are inserted into the tibia by means of ligaments, which deserve a particular description. Ligaments of the External Semilunar Cartilage. — These are two : the one anterior, and the other posterior ; both of them are very strong. The anterior is inserted in front of the spine of the tibia, outside of the anterior crucial ligament, into a deep depression situated near the external glenoid cavity of the tibia. This anterior ligament of the external semilunar cartilage sends off a bundle which intermingles with the ante- rior crucial ligament. The posterior is inserted into the spine of the tibia, in the unequally-divided interval situated between the two prominences of the spine. The posterior ligament sends off a considerable bundle of fibres to be inserted into the posterior crucial ligament. The circular form of the external semilunar cartilage is owing to the insertions of the two an- teiior and posterior ligaments being separated from each other only by a few lines. Ligaments of the Internal Semilunar Cartilage. — These are much weaker than the foi- mer. The anterior is inserted a good deal before its fellow, the anterior ligament of the external semilunar cartilage, and the posterior is inserted a good deal behind the corresponding ligament of the externed semilunar cartilage ; hence the semilunar shape of the internal semilunar cartilage, which does not send off any fibrous prolongation to the anterior or posterior crucial ligaments. The ligaments of the inter-articular cartila- ges being inserted into the tibia, these cartilages follow the tibia throughout its course Means of Union of the Knee-joint are two lateral hgaments, a posterior and an anterior, two crucial ligaments, and a synovial capsule. 1. Lateral Ligaments. — The external lateral ligament {a, figs. 79 and 80) appears as a rounded cord ; it is inserted into the exter- nal tuberosity of the femur, at the point of union of the five anterior sixths with the first posterior, on the prolongation of the line of the fibula ; the precise point of this insertion is a small eminence surmounting a depression which is destined to the tendon of the popli- teus muscle, and is situated in front of an- al other depression destined to the external ge- A meUus ; thence this ligament descends, in a '^ vertical line, to be inserted into the external face of the head of the fibula. This ligament has the appearance of a tendon ; it extends along the anterior border of the tendon of the biceps, with which it may be readily con- founded. We should have but an incomplete idea of the means of union which the knee-joint pos- sesses on the outside, if we did not add to the number of its ligaments the tendon of the bi- ceps, which unites in some sort its inferior insertions with those of the external lateral ligament, and the small band of the fascia lata inserted into the anterior tubercle of the tibia, and sending to the external edge of the rotula an expansion, which unites with the tendon of the vastus externus. The internal lateral ligament (J c, figs. 79 and 80), which is much longer than the exter- nal, has the shape of a broad, thin, pearly- coloured band, arising from the posterior part Fig. 79. Fig. 80. * On asking- myself the question why there should be this difference between the two semilunar cartilages, I have come to the conclusion that the external condyle of the femur, pressing much more upon the tiliia than the internal, on account of the external following the axis of the femur, while the internal is turned away from it , t. »»■ l f ♦ to the inside, the externa! inter-articular cartilage had to protect a greater portion of the articular «unace ol thti tibia 164 ARTHROLOGY. of the internal tuberosity of the femur, on a level with the external lateral ligament, im- mediately below the tubercle into which the third adductor muscle is inserted ; it is turned downward, and a little outward ; it widens in its course, and is inserted, by a broad surface, into the internal border and the anterior surface of the tibia : at this in- sertion, which is at least an inch wide, it is covered by the tendons of the sartorius^ gracilis, and semitendinosus muscles, which glide over this ligament by means of an in tervening synovial bursa. Its deep surface is applied to the anterior or reflected tendon of the semi-membrano sus, to the internal semilunar cartilage, to which it intimately adheres, and to the inter nal inferior articular vessels, which are protected by it. When the layers of this ligament are removed in succession, it will be seen that the deepest fibres are attached to the superior part of the internal tuberosity of the tibia, and adhere to the synovial membrane. The lateral ligaments are situated much nearer to the flexing or the back part, than to the extending or the fore part of the joint, so that they are stretched during extension, and assist in limiting that motion, but are re- laxed during flexion, to the performance of which they offer no obstacle. The posterior ligament, or ligament of Winslow (c, figs. 79 and 81), is much complicated, and is composed, 1. Of a fibrous capsule for each condyle ; 2. Of a median posterior hg- ament, the only one which has been described by authors. 1. Fibrous Capsule of the Cmidyles. — Each condyle is enveloped with a fibrous husk , that of the external condyle is covered by the external origin of the gemellus, and thai of the internal condyle by the internal. The fibrous capsule of the internal condyle is completed by the internal origin of the gemellus turning around the highest and most in- ternal portion of this condyle. The semi-membranosus muscle sends a fibrous expansion from above downward to this same internal capsule ; the external head of the gemellus is still much more than the internal identified wath the corresponding fibrous capsule, which furnishes a great number of insertions to that muscle. When there is a sesa- moid bone in the external gemellus, it is found in the substance of the external capsule. 2. The Median Posterior Ligament. — It is composed of several sets of fibres : 1. Some pass obliquely upward and outward, being formed by a considerable expansion of the semi-membranosus ; 2. Others proceed from the tendons of the popliteus and the ge- melli ; and, lastly, 3. Some fibrous bundles, partly vertical and partly oblique, arise from above the condyles of the femur, and are attached to the tibia. Frotn this collection of fibres running in different directions, there results an irregularly-interwoven ligament, perforated by foramina that transmit the ramifications of tlie middle articular artery ; several of the most deeply-seated ligamentous bundles are inserted into the edges of the inter-articular cartilages. 3. Anterior Ligament, or Ligamentum Patellm {d,figs. 80 and 81). — This name is given to that portion of the tendon of the extensor muscles which ex- tends from the patella to the tibia. This ligament has the thape of a very broad, thick, almost triangular band. Its fibres arise by a broad insertion, of from five to six lines, from the apex of the patella and from the anterior surface of this bone ; they are parallel, pearly-white, and become nearer to each other as they approach the most prominent and lower portion of the anterior tuberosity of the tibia, to which tuberosity they are attached. It should be remarked, tliat this ligament is by no means inserted into the rugged projections which are found on the back part of the apex of the patella. Behind this ligament is a considerable mass of adipose tissue {e,fig. 81), which separates the hgament from the articular synovial capsule , a synovial bursa if, fig. 81) separates it from the anterior portion of the tuberosity over which it glides. This synovial bursa sometimes communicates with the articular synovial capsule, and sometimes is totally dis- tinct from it.* Crucial or Interosseous Ligaments. — In the interior of the knee- * I should remark that this bursa extends partly over the ligament, which it covers from side to side, ana partly over the anterior tuberosity of the tibia, vfhich is at this point completely deprived of inter-articular car. tilage , so that the facility with which the synovial membrane of the tibia is removed contrasts with the diffi- culty which is experienced in dissecting the synovial membrane which covers the inter-articular cartilages, provided it exists there. The ligamentum patella; forms only a part of the anterior ligament of the knee-joint , this anterior ligament is completed by the rotula and by the united tendons of the rectus femoris, the vastus mtemus and extemus, of which united tendons the ligamentum patellae is evidently a continuation. We see here a very remarkable application of this law, by mea>is of which the articular ligaments are fortified by ten dons, and sometimes completely replaced by ftem ; and I have taken care to observe that it is generally the trochlear joints which exhibit examples of this replacing of ligaments by tendons in regard to extension, be- cause, in the movement of extension, a ligament, being a purely passive means of union, was not sufficient. What would take place if an ordinary ligament were to be substituted for the tendon of the extensor muscles t In the first place, this ligament would have to be extremely long to permit flexion ; but in case it should be long enough for flexion, what would become of it in the movement of extension ? Unless it were endowed witn the extensibility and the elasticity of the yellow ligaments, it would become folded, and would thrust itself between the articular surfaces. It is for this reason that a ligament was required which might be short ARTICULATIONS OF THE KNEE-JOINT. Ifffe joint there are two interosseous ligaments {g i,fig- 78), so arranged as to admit of the most extensive flexion, but to limit the movement of extension. They are called cniciaU because they cross each other like the letter X. They are situated in the deep inter- condyloid fossa, whose sole destination appears to be that of protecting them. The an- terior {g,Jigs. 78 and 81) arises from the external condyle, and passes to the fore part of the spine of the tibia. The •posterior (t, fig. 78) arises from the internal condyle, and is fixed to the back part of the spine. Both are continuous, by a distinct bundle, with the external inter-articular cartilage ; never with the internal. The names anterior and posterior have been given these ligaments, from their inferior insertion ; for superiorly they arise on the same level. Here follows a more minute description of their inser- tions above and below, and of their direction. The anterior crucial ligament arises, as a little band flattened from side to side, from the semilunar depression, which is concave superiorly, and is situated on the internal or median surface of the external condyle ; thence it extends from above downward, from without inward, and from behind forward, flattens from before backward, and is inserted in front of the spine of the tibia, upon which spine it encroaches a little by means of some insertions which it takes between the two articular projections constituting the spine. From the external edge of this ligament a few fibres are given off, which extend into the external part of the semilunar cartilage. The posterior crucial ligament arises from the external or median surface of the inter- nal condyle in a semilunar depression, entirely similar to the one which is destined to the anterior crucial ligament ; like the latter, it presents a threefold obliquity from above down- ward, from before backward, and from within outward ; it sends a considerable expan- sion to the external inter-articular cartilage, and is inserted back of the spine of the tibia. Thence it follows that the crucial ligaments present a double crossing : 1. A crossing in an antero-posterior direction, and this alone has been observed with attention ; 2. A crossing in a transverse direction ; when the tibia is rotated from within outward, the crossing of these two ligaments increases to such an extent that these two ligaments, strongly pressed against each other, limit the motion ; in the movement of rotation from without inward, on the contrary, as the crossing diminishes, they become relaxed and parallel ; both are stretched during extension, and relaxed during flexion ; there is an exception for the most anterior fibres of the anterior crucial ligament, which are relaxed in the middle state of extension, and stretched during flexion ; but when the extension is considerable, the anterior crucial ligament is also stretched in its anterior fibres, which, being pressed by the condyles, describe a curve anteriorly concave. The synovial capsule of this joint is the largest and the most complicated of all that ex- ist in the body. In tracing it from the upper edge of the patella, we find, behind the ten- don of the extensor muscles, a large cul-de-sac {s,fig. 81), sometimes replaced by a dis- tinct synovial capsule, interposed between that tendon and the surface of the femur. In many subjects, this bursa communicates with the synovial capsule of the knee-joint by a more or less considerable opening, and in such cases a circular constriction forms the only trace of separation. On each side of the patella the synovial membrane extends beneath the two vasti, and is sometimes elevated from one and a half to two inches above the articular surfaces ; the prolongation under the vastus externus is much more considerable than that under the vastus internus. The existence of these two prolonga- tions affords an explanation of the sweUings observed at the sides of the knee in dropsy of this joint ; and the greater extent of the external prolongation explains, also, the great- er size of the prominence on the outside. In the inter-condyloid notch the synovial mem- brane envelops the crucial ligaments ; then it is reflected upon the posterior ligament, the lateral ligaments, the semilunar cartilages, the articular surfaces of the tibia, and, lastly, the back of the ligamentum pateUae ; it next sends off a prolongation, containing a few ligamentous fibres, and extending from the lower border of the patella to the front of the inter-condyloid notch. This fold has been incorrectly termed the adipose ligament ened or elongated as might be necessary, a tendon being the continuation of a muscle, that is, of an organ at once capable of extension, contraction, and endowed with elasticity. Besides this, a bone was required that might complete the articulation on the outside, that might fill the large space which, during the movement of flexion, would have remained empty between the articular surfaces, and might glide without injury ovor osseous surfaces, and facilitate, at the same time, standing upon the knees. This threefold object has been attained by the patella, a sesamoid bone, which is developed in the substance of the tendon of the extensor muscle of the leg, viz., of the triceps femoris, whose parallelism, at its insertion into the rotula, is destroyed by this bone. Independently of the anterior ligament, the knee-joint exhibits a large aponeurotic surface, formed by the femoral aponeurosis, by an aponeurotic expansion of the. fascia lata, and by another aponeurotic expansion fur- nished by the tendons of the sartorius, gracilis, and semi-tendinosus muscles ; to this latter expansion is joined a fibrous lamina, given off by the tendon of the vastus externus and internus, which is attached to the libia. This large anterior aponeurotic surface exhibits, on a level with the tendon of the triceps, a saltier-shaped in- terlacing, which closely adheres to this tendon, and seems destined to serve it as a bridle ; on a level with the patella it exhibits a thin layer, which is sometimes interrupt- 3, and, so to say, lacerated, in consequence of the sub-cutaneous synovial capsule being present ; and on a level with the ligamentum patelte it exhibits fibres running obliquely from above downward and from without inward. Finally, I shall point out as appendages of the anterior ligament two proper ligaments of the patella, one m temal, the other external, extending from the edges of the patella to the posterior part of each tuberosity these ligaments are broad and thin, and strongly adliere to the synovial capsule. 166 ARTHROLOGY. (ligamentum mucosum, t,figs. 78 and 81). After having furnished this fold, the syno- vial membrane lines the posterior surface of the patella, and becomes continuous with the cul-de-sac behind the extensor tendon. Sometimes the prolongation, known as the adipose ligament, does not exist ; at other times there is more than one. I have seen a fold of the same nature extending from that part of the synovial membrane which lines the extensor tendon to the surface of the femur above the trochlea. No other synovial membrane in the body is provided with so large a number of villous prolongations, which, in some subjects, may be said to give it a shaggy appearance ; they are especially met with around the patella* and the semilunar cartilages. To these prolongations Clopton Havers has given the name of synovial fringes. Some deep fibres of the triceps cruris have been regarded as a special tensor muscle of the synovial capsule. (Vide Trice fs Cruris, Myology.) Sub-synovial Adipose Tissue. — From the abundance of this tissue in the knee-joint, its disposition requires some special notice. It is chiefly met with behind the ligamentum patellae {_e,fig. 81), where it forms a very thick layer, filling up the interval between the patella and the synovial membrane. This adipose mass, which raises the ligamentum patellae in the extension of the knee, and which, during flexion, fills the empty space which the movement of flexion produces between the condyles of the femur and the tibia, is situated to the outside of the joint, between the ligamentum patellae and the synovial capsule, which is raised by the mtiss. This mass, on being examined on the side which is contiguous to the joint, exhibits several prolongations, which are somewhat similar to the fatty appendages of the epiploon. These appendages are all lined by a fold of the synovial capsule ; one of these appendages, supported by a fibrous bundle, is attached to the inter-condyloid space, under the name of ligamentum mucosum patellas, which hg- ament is sometimes multiple, and has no other object except to draw to it the fatty mat- ter between the tibia and the femur during flexion of the knee, and to keep that matter in its place during the movement of extension. A large quantity of fatty matter is also found behind the tendon of the triceps above the condyles, where that matter fills the in- terval between this tendon and the corresponding part of the femur. Bundles of fatty matter are, lastly, foimd all around the condyles, as well as in the inter-condyloid notch, and around the insertions of the crucial ligaments. This fat, which may be observed even in individuals in a state of marasmus, except that, under those circumstances, it is more serous and infiltrated, is nowhere more evidently than in the knee-joint, destined to fill the intervals produced between the articular surfaces by certain attitudes. Mechanism of the Femoro-tibial Articulation. 1 . With regard to Strength. — The strength of articulations is generally in direct pro- portion to the extent of the articular surfaces, and there is no joint more advantageously constructed in this respect than the one we have been examining. The reception of the spine of the tibia into the inter-condyloid fossa also tends greatly to increase the strength of the joint, although it forms but an imperfect kind of dovetailing. A third and last con- dition conducive to strength is, the multiplicity of the ligaments, and of the tendons, sup- plying, in some respects, the deficiencies in the fitting. 2. With regard to Mobility. — The knee, being a hinge-joint, has two principal move- ments, in opposite directions, \iz., flexion and extension; but, as the mutual reception of the surfaces is very imperfect, it is also capable of some slight rotatory motions. In flexion, the surfaces of the tibia, defended by their inter-articular cartilages, glide backward upon the condyles of the femur ; and, from the great extent of the articular surfaces of the last bone in that direction, the movement can be carried so far as to per- mit the leg and thigh to touch. In this movement, the lateral, the posterior, and the cru- cial ligaments are relaxed, except the anterior fibres of the crucial ligament, which are stretched ; the ligamentum patellae is stretched ; the patella is firmly applied to the front of the joint, and can neither be moved to the right nor to the left, as may be done during extension. In the position of flexion, the patella fills up, as it were, the great hiatus then existing at the front of the joint between the femur and the tibia. Luxation is impossible during this movement, which is only limited by the mutual contact of the leg and the thigh. In extension, the tibia and the inter-articular cartilages glide in the opposite direc- tion. The movement is arrested when the leg is in the same line as the thigh, and whatever muscular feffort be then made, the leg never will pass that limit, excepting trom malformation of the parts. A greater amount of extension is rendered impossible, both by the shape of the articular surfaces, and by the stretching of all the ligaments, ex- cepting that of the patella, which is completely relaxed, and permits of a great mobility of that bone in all directions. One circumstance in the shape of the articular surfaces, which appears to be opposed to any extension beyond the straight line, is the small extent of the trochlea in front ; for, could such extension take place, the glenoid cavities of the tibia would then be applied to a portion of the trochlea, much smaller than themselves. The crucial ligaments are especially intended to limit the movement of extension, as the * [Two slight folds of the membrane formed at the sides of the patella have been particularly described inder the very inappropriate name of the alar ligaments.^ PERONEO-TIBIAL ARTICULATIONS. J67 following experiment will at once demonstrate. Divide all the external ligaments of the joint ; the crucial ligaments will then alone remain ; then endeavour to extend the leg beyond the ordinary limits ; this wiU be found impossible until these ligaments are divided. That both the crucial hgaments oppose the extension of the limb beyond a cer- tain limit, is proven by dividing these ligaments separately. So long as one remains, no matter which, the extension is limited. An analogous experiment, in which all the hga- ments of the joint (even including the crucial) are divided, excepting the lateral, proves that these are not only opposed to lateral movements, but also limit extension with much force ; this they are enabled to do from being situated nearer to the back than to the front of the joint. Complete luxation can only be effected after laceration of all the hga- ments which hmit extension. An interesting remark, which has been suggested to me by'M. Martin, is, that the crucial hgaments are not only destined to limit the movement of extension, but also — and this is, perhaps, their principal object — to prevent the articu- lar surfaces from leaving each other in the anterior posterior direction during a forcible extension. Thus, the anterior crucial ligament will prevent, in a movement of exten- sion, both the displacement of the tibia backward, and that of the femur forward, and the posterior crucial ligament will prevent both the displacement of the tibia forward, and that of the femur backward. It is also important to remark, that while standing upon the feet, the ham-strings being stretched, these extensor muscles of the leg, which are situa- ted upon the thigh, the rectus femoris, and the vastus externus and intemus, are entirely inactive, as is prgved both by the extreme mobility of the patella and the relaxed state of these muscles in a standing position, and by the absence of all sensation of lassitude in these muscles after the vertical position upon the feet has been continued for a long time. The extension of the knee, therefore, takes place without any co-operation on the part of the muscles, simply through the articular surfaces being juxtaposed in all their breadth, and by the tension of the lateral and crucial ligaments, which keeps the articular surfaces mechanically upon each other.* In all these motions the patella is fixed ; it is the femoral trochlea which glides upward or downward upon the posterior surface of that bone. This almost invariable position of the patella depends on the inextensibility of its ligament. The existence of the patella has no effect in limiting the movements of extension ; its only uses, as far as the joint is concerned, are to protect it in front, and to prevent painful pressure in the kneeling posture. Its other and chief uses are connected with the functions of the triceps ex- tensor muscle, in the tendon of which it is developed ; it removes the axis of the muscle from the parallel direction of the lever which it is destined to move. It is movable and depressed during extension of the leg, but during flexion it becomes prominent and fixed, t Rotation. — When the leg is semi-flexed upon the thigh, it can be very slightly rotated mward and outward. These movements are performed, not upon the external, but upon the internal condyle as a pivot, so that the external part of the head of the tibia glides forward during rotation inward, and backward during rotation outward. The difference in the part performed by the two condyles in the movement of rotation does not depend upon any peculiarity of structure in the joint, but exclusively upon the arrangement of the acting forces, as we shall see when treating of the muscles. Rotation inward is limited by the mutual contact of the crucial ligaments, whose decussation is increased during this movement. Rotation outward is more extensive, because in this movement the liga- ments are uncrossed, and become parallel. We shall see hereafter that the biceps is the agent of rotation outward, and the popliteus of rotation inward. Peeoneo-tibial Articulations {figs. 79 and 80). Preparation. — 1. Remove carefully the muscles of the anterior and posterior regions of the leg, which will expose the interosseous ligament, and the anterior and posterior ligaments of these joints. 2. In order to see the interior of the articulations, saw through the two bones in the middle, and then separate them. 3. To gain an idea of the interosseous * M. Robert, one of our most distinguished young surgeons, has observed a fact which sustains these ideas, ■which had already been demonstrated by the artificial legs of M. Martin. An individual in whom the patella was fractured, had recovered with a distance of about ten centimeters. The movement of extension by mus- cular contraction was impossible ; but when the limb was extended, it maintained itself in that position with the same force as the limb upon the healthy side. The patient had succeeded, by a sort of artifice, in exe- cuting spontaneously the movement of extension ; he brought the trunk and the pelvis forcibly forward : the femur followed the pelvis, and extension being once effected, this inferior limb, being very strong and immo- vable, assisted in the standing position just as much as the healthy limb. t It is during flexion of the leg, and, consequently, when the patella is most immovable, that this bone may be displaced in consequence of some external violence, and in this case, the displacement always takes place to the outside. However, one should suppose that the external condyle of the femur, being much more prominent than the internal, would be opposed to the luxation outward, and favour the luxation inward, "ut we may remark, that the patella, when displaced inward, cannot remain in this position, in which nothing maintains it, and from which the oblique direction of the triceps tends, on the contrary, to bring it back to its natural place ; whereas, when the patella is displaced outward, the prominence of the extorual condyle op- Tjoses the reduction of the patella, which can only be effected by artificial means. It should be remarked, that ttie obliquity downward and inward of the femoral trochlea gives a tendency to the patella of being continuaUj drawn outward by the tendon of the extensor muscles, which is slightly oblique in the same direction as the trochlea. This is so true, that in white swellings of the knee-joiut, the spontaneous displacement of the pa- tella always takes place outward. 168 ARTHROLOGY. ligament of the inferior articulation, saw perpendicularly through the lower endc of thp bones of the leg, so as to divide them into an anterior and a posterior portion. The tibia and the fibula, which are contiguous at their extremities, are separated iVoir each other along their shafts, the interval being occupied by an aponeurosis, improperly called the interosseous ligament. We have, then, a superior and an inferior peroneo-tibiai articulation, and an interosseous ligament or aponeurosis. 1. Superior Peroneo-tibial Articulation. Tliis articulation is an arthrodia. The articular facette of the tibia, looking downward and outward, is situated behind its external tuberosity. I'he facette of the fibula looks upward and inward ; it occupies the inner part of the upper end of the bone. The means of union are two ligaments : an anterior {g, Jig. 80) and p. posterior {d, Jig. 79). They are composed of parallel fibres, directed obliquely downward and outward from the exter- nal condyle of the tibia to the heaji of the fibula. There is generally a distinct synovial membrane for this joint, but sometimes it is a prolongation from the capsule of the knee. This communication frequently existing between the synovial capsule of the knee and the peroneo-tibial articulation, should condemn, in an amputation of the leg, the practice of extirpating the superior extremity of the fibula. The formidable accidents which might be consequent upon such an extirpation may readily be conceived, and should for- bid the operation, although it has been accomplished without any accident. Its only ob- ject is to prevent the fibula from pressing upon the soft parts. 2. Inferior Peroneo-tibial Articulation. This articulation is an amphi-arthrosis, that is, it is formed between surfaces that are partly contiguous and partly continuous. The former consists of two articular facettes, narrow from above downward, and oblong from before backward ; of these, one is con- vex, and situated upon the internal surface of the lower end of the fibula above the mal- leolus ; the other is concave, and continuous with the inferior or tarsal articular surface of the tibia. They are both covered with cartilage. The continuous surfaces are rough, and much more extensive ; they are triangular in shape, having their bases directed down- ward : the one situated upon the fibula is convex, that upon the tibia is slightly concave. The means of union are, two ligaments external to the joint, and an interosseous liga- ment connecting the two triangular surfaces just mentioned. Of the two external liga- ments, one is anterior (i. Jig. 80) and the other posterior {e, Jig. 79). They are both very strong, and composed of thick, shining, parallel fibres, which pass obliquely downward and outward from the tibia to the fibula. They are almost always divided into two dis- tinct bundles. They are both remarkable from descending beyond the articular surfa- ces, so that they increase the depth of the cavity for the reception of the astragalus. The sijnovial membrane of this articulation is a prolongation from that of the ankle-joint The interosseous ligament consists of fibrous bundles, mixed with adipose tissue, which unite the two triangular surfaces so firmly that the fibula is sometimes fractured in at- tempting to rupture the ligaments. 3. Interosseous Aponeurosis. The name of interosseous ligament is given to an aponeurotic septum {b,figs. 79 and 80) placed between the muscles of the anterior and those of the posterior aspect of the leg ; it should rather be regarded as serving to multiply the points of insertion for fibres of those muscles, than as a means of union between the bones of the leg. It is narrow- er below than above, and is composed of fibres running obliquely downward and outward from the outer edge of the tibia to the longitudinal crest on the inner surface of the fibula. As in the interosseous ligament of the forearm, we find some other fibres cross- ing the former at an acute angle. The septum thus formed is interrupted above and be- low for the passage of the tibial vessels ; the peroneal artery and veins traverse the low- er opening ; the anterior tibial artery and veins pass through the upper. Mechanism of the Peroneo-tibial Articulations. The fibula is only capable of almost imperceptible gliding movements upon the tibia. This arrangement is directly connected with the mechanism of the ankle-joint. Ankle, or Tibio-taksal Joint (Jigs. 79 and 80).* Preparation. — Cut and turn back the tendons that are reflected round the joint, and remove tl\e sheaths of those tendons by which most of the ligaments are covered. The peroneo-calcanean ligament is seen after the tendons of the peroneal muscles have been removed ; the synovial membrane of these tendons only covers it. The peroneo-astra- galian ligament is the most difficult to uncover, on account of its being deeply seated, and separated from the sheath of the muscles of the posterior region by a large quantity of adipose tissue. The internal lateral ligament is seen immediately beneath the sheaths of the tibialis posticus, the common flexor tendon of the toes, and the proper flexor of the * We should remark th&t, in order to study this as well as all the other articulations efficiently, it is a great ijvantage to be provided with two joints, of which one is opened, while the other has its ligaments untouched ARTICULATIONS OF THE ANKLE-JOINT. 169 great toe. In order to see the deep layer of this ligament, the superficial laj ers must be removed one after the other. The tibio-tarsal articulation belongs to the class of angular ginglymt. Articular Surfaces. — Both bones of the leg participate in this joint, their 1 >wer extrem- ities being united to form a transversely oblong socket, of which the tibia constitutes by far the greater part. On this articular surface there is an antero-posterior ridge, corre- sponding to the groove of the trochlea on the astragalus, and separating two shallow cav- ities. The socket is bounded by the malleoli on each side. The internal or tibial mal- leolus corresponds to the internal lateral articular surface of the astragalus ; and the ex- ternal or fibular malleolus, to the external lateral facette of the same bone. The tibio- peroneal cavity is completed forward and backward by the lower part of the anterior and posterior peroneo-tibial ligaments. The superior articular surface of the astragalus is a trochlea ; it is oblong from before backward, thus contrasting with the cavity on the lower extremity of the leg,* which is transversely oblong. This trochlea presents a shallow depression, running from before backward, and having an external and an internal edge, the external being the more elevated of the two. The pulley of the astragalus is continuous with its lateral articular surfaces, of which the external is by far the larger. The means of union are three external lateral ligaments, two internal lateral ligaments, an anterior {r,Jig. 80) and a posterior {s,fig. 79) ligament, and a synovial capsule. The external lateral or. peroneo-tarsal ligaments are three in number; they all proceed from the fibula, either to the astragalus or the os calcis. 1. The external lateral ligament, properly so called (ligamentum fibulae medium vel per- pendiculare, m,.figs. 79 and 80), is situated beneath the sheath of the peroneus longus and brevis. It arises from the summit of the external malleolus, is directed downward and shghtly backward, to be attached to the outside of the os calcis. It is rounded, and composed of parallel fibres. 2. The anterior external lateral ligament (ligamentum fibulae anterius, n, fig. 80) arises from the anterior edge of the externed malleolus, and proceeding downward and forward, is fixed to the astragalus in front of its external malleolar facette. It is very short, and broader below than above : it forms one of the two anterior hgaments described by Bi- chat in this joint. 3. The posterior lateral ligament (ligamentum fibulae posterius, o,fig. 79) is very deeply seated behind ; it extends from the excavation on the inside and behind the external malleolus to the posterior border of the astragalus, immediately above the pulley of this bone. It is directed almost horizontally, or in a slight degree obliquely downward and inward, and is almost parallel to the posterior ligament of the lower peroneo-tibial ar- ticulation. It is composed of very distinct parallel fibres, which are arranged in several layers, the deepest of which are attached to the astragalus behind the facette of the ex- ternal malleolus. The posterior peroneo-astraglagean ligament is very strong. Bichat calls it the posterior ligament of the joint. The interTwl lateral ligament is much stronger than the three external ligaments taken together. It is composed of two very distinct layers : 1. A superficial layer, consistiiig of fibres stretched from the apex and the anterior and posterior borders of the internal mal- leolus to the OS calcis, and the upper edge of the lower calcaneo-scaphoid ligament, which it maintains in a state of constant tension. The fibres are long and slightly divergent, but still sufficiently so to have given origin to its name of the deltoid ligament {p,figs. 79 and 80). The fibres which are most anterior pass directly forward to the neck of the astragalus, and to the scaphoid ; they form a very thin layer, which has been improper- ly called the anterior ligament of the ankle-joint. 2. Below the above is a deep layer of much greater extent, composed of sliort and strong bundles, passing downward and out- ward from the sununit and sides of the internal malleolus, to the inner surface of the as- tragalus, below the articular facette. + Synovial Capsule. — The external surface of this membrane is brought into view in front and behind by removing the tendons and their sheaths ; and if the external and in- ternal lateral ligaments be divided, it will be seen to extend into the inferior peroneo- tibial articulation. It will also be observed that it is tense at the sides, but very loose behind, and more particularly so in front. A great quantity of adipose tissue covers its external surface in these situations. Mechanism of the Ankle-joint. This articulation not only constitutes the point at which the weight of the body is * Hence, the longest diameter of the astraglagean cavity is from before backwaril ; the longest diametei of the tibio-peroneal cavity is transversely. The extent of the movements of flexion and extension ol '"« '9°' depends upon the disproportion between the antero-posterior diameter of the pulley of the astragalus ana me socket of the leg. , „„„._„„, t [The author has omitted, perhaps intentionally, to give a special description of the anterior anu posienor ligaments of the ankle-joint, already alluded to by him. The former extends from the anterior margin oi tne articular surface of the tibia to the corresponding border of the astragalus, a id is called the wno-iarsai itg- ament ; it is very thin, and covered by the tendons of the extensor muscles. The posterior can scarcely De said to exist as a distinct ligament.] 15» ARTHROLOGY. transmitted to the foot, but also performs a very active part in the movements of pro- gression ; it is therefore so constructed as to unite great strength with the capability of tolerably extensive motion. With regard to strength, the following arrangements should be noticed as especially ad- vantageous : 1. The leg being articulated with the foot at a right angle, transmits the weight of the body directly to it, and this transmission being effected in the perpendicular direction, i. c, in a direction in which the articular surfaces mutually oppose each other, has no tendency either to produce fatigue or to rupture the ligaments. The perpendic- ular position of the leg upon the foot during standing is worthy of notice, because of it- self it proves that man was intended for the erect posture, since in this attitude alone does the entire inferior surface of the foot rest upon the ground. It should be also re- marked, that there is no other articulation, excepting that of the head upon the verte- bral column, in which the parts united are habitually perpendicular to each other. 2. The dovetailing effected at this joint, by the reception of the astragalus into the socket, formed by the bones of the leg, is also highly conducive to its strength. This dovetail- ing results both from the pulley-like surface of the astragalus, and from the angular form of the tibio-fibular socket ; and it should be observed, that this latter condition is, as it were, peculiar to the ankle-joint, for in no other do we meet with such abrupt angles. With regard to mobility, the tibio-tarsal articulation admits of flexion and extension. There is no lateral motion, the movements of the foot in this direction being almost ex- clusively performed at the tarsal joints. Inflexion, the astragalus gUdes backward upon the tibia and fibula, and the back part of the pulley projects behind. Luxation, from an excess of this movement, is almost impossible, for it is limited by the meeting of the neck of the astragalus and the anterior edge of the tibio-fibular sockets. In this movement, the posterior extern2d lateral liga- ment, and the middle and posterior fibres of the internal lateral ligament, are put upon the stretch. In extension, on the contrary, the trochlea of the astragalus glides forward upon the corresponding surface ; the synovial membrane is borne upward in front ; the anterior external lateral ligament, and the anterior and middle fibres of the internal lateral liga- ment, are stretched. Luxation is possible during this motion, but is very rare. Lateral Movements. — Although the shape of the joint is opposed to movements of this kind, yet it cannot be doubted that the elasticity of the fibula, by allowing the external malleolus to yield a little, may permit them in a slight degree. Nevertheless, the fibula must be fractured, if any force, exerted by the astragalus against the external malleolus, be carried so far as to thrust it much outward. Articulations of the Tarsus {figs. 80, 82, 83, 84). The intrinsic articulations of the tarsus comprise, L The articulations of the compo-- nent bones of each row. 2. The articulation of the tv/o rows together. Preparation. — 1. Remove the tendons situated upon the dor- sum of the foot, and also the extensor brevis digitorum mus- cle. 2. Remove all the muscles of the plantar region. 3. Rub off, by means of a rough cloth, the adipose tissue covering the ligaments (a subject much infiltrated with serum is best adapted for this purpose). 4. In order to gain a clear comprehension of the articulation of the two rows together, remove the astrag- alus from the sort of box in which it is contained, by divi- ding the interosseous ligament which unites it to the os calcis. 5. For the examination of the interosseous ligaments, it is ne- cessary to separate the bones by laceration or section of those ligaments ; the resistance experienced in doing this, and the portions of the ligaments remaining attached to the bones, will give a good idea of their strength and situation. 6. In order to obtain a correct notion of all the ligaments together, it is necessary, while studying each, at the same time to examine a foot in which all the joints have been opened above, while the bones are still retained in their situations by means of the plantar ligaments. Articulation of the Component Bones of the First Row, or Articula- tion of the Astragalus with the Os Calcis. This is a double arthrodia, in which each of the bones pre- sents two articular facettes, separated by a furrow deeper on the outer than on the inner side. Tlie posterior surface of the astragalus (1, fig. 84) is concave, that of tlie os calcis (2) is convex ; in front (1) the opposite obtains, so that there is a mu- tual reception of parts. The means of union, properly speak ing, consist only of an extremely strong interosseous ligament (a, Fig.SZ. ARTICULATIONS OF THE TARSUS. 171 /Jg'. 84) formed by ligamentous bundles, of which some are vertical, and others oblique , they are mixed with fat, and occupy the considerable interval formed by the grooves of the two bones, and which is larger towards the outer end. To form a complete idea of this ligament, it is necessary to make a vertical section from before backward, through the middle of the astragalus and os calcis (as in^^. 84). A loose synovial membrane lines the posterior articulation, which is strengthened on the inside by the fibrous sheaths of the tendons of the tibialis posticus, the flexor longus digitorum, and the flexor longus poUicis. There are also about this joint two very small fibrous bundles, one of which is posterior {t, fig. 80 ; a, fig. 83), and the other external {Jb, fig. 83) : some anatomists have described them by the names of posterior and external ligaments. The anterior por- tion of this articulation is often double, from the division of the anterior articular sur- faces into two smaller facettes : it forms part of the astragalo-scaphoid articulation, with which it will be described. Articulations of the Component Bones of the Second Row. All these joints are very compact, for the five bones which constitute this row act as one only in the movements perfonned by the foot at its tarsal pig, 93. articulations. They present for the most part angular facettes ; they have also interosseous ligaments, and are true symphyses or amphiarthroses. Articulations of the Cuneiform Bones with each other. Articular Surfaces. — The corresponding surfaces of the first and second cuneiform bones present contiguous as well as con- tinuous portions. The contiguous portions are square, and sit- uated at the upper and back part of each surface. The con- tinuous portions are placed in front of the preceding. The corresponding articular surfaces of the second and third cunei- form bones are smooth and contiguous behind, but rough and irregular in front. Means of Union. — 1. By dorsal ligaments {c c, fig. 83). This name is given to some very compact fibrous bands stretching transversely from one bone to the other. By their upper sur- faces, on which the longest fibres may be seen, they are in re- lation with the extensor brevis digitorum and with the tendons of the other extensor muscles. Their lower surfaces, the fibres of which are shorter, correspond to the articulations, and to the periosteum of the cuneiform bones, with which they in- terlace. 2. By plantar ligaments. This name may be given to some of the fibres of the interosseous ligaments. 3. By in- terosseous ligaments. These, which are very strong, consti- tute the principal means of union of these joints, and occupy all the rough portions of the corresponding facettes. They so closely unite the bones, that, even when the dorsal liga- ments are removed, it is not easy to open the joints. The synovial membrane is merely a portion of the general sjrnovial membrane of the tarsus. Articulations of the Scaphoid vnth the Cuneiform Bones. Articular Surfaces. — The scaphoid presents the only example in the body of a single articular surface being divided into three facettes by well-marked ridges. Each of these facettes is triangular, and corresponds to a surface of the same form on one of the cunei- form bones. The base of the triangular facette for the first cuneiform bone is below ; the bases of the other two are above (3, fig. 80). Means of Union. — 1 . Dorsal ligaments. There are two for the first cuneiform bone, a superior (d, fig. 83), and an internal (c, figs. 83 and 84) ; and only one for each of the oth- ers (//, fig. 83). The dorsal ligaments of the first cuneiform bone pass directly back- ward ; those of the other two are stretched obliquely for^vard and outward. 2. Plantar ligaments. A very strong plantar ligament (a, fig. 82) extends from the tubercle of the scaphoid to the corresponding tubercle of the first cuneiform bone ; it is blended with the tendon of the tibialis posticus, which furnishes a considerable expansion that crosses the direction of the tendon of the peroneus longus, and extends to the third cuneiform, and the corresponding metatarsal bone ; it may be considered as an inferior ligament of the tarsus. The name of plantar ligaments can scarcely be given to some irregular fibres {h,fig. 82) passing from the lower surface of the scaphoid to the second and third cunei- form bones. A synovial membrane, common to the three articulations, is continuous with that of the three cuneiform bones. )J|S ARTHROLOGY. Articulation of the Third Cuneiform Bone with the Cuboid. This articulation resembles in every respect those of the cuneiform bones. The means of union are a dorsal ligament {g, fig. 83), consisting of a very strong transverse bundle ; an interosseous ligament, which occupies the entire non-articular portion of the correspond- ing surfaces ; and an ill-defined plantar ligament, consisting of some irregular transverse fibres. The synovial membrane communicates with that of the cuneo-scaphoid articulations. Articulation of the Scaphoid with the Cuboid. The scaphoid and the cuboid often unite by a small facette. The means of union are an oblique dorsal ligament {i, fig. 83), a very strong interosseous ligament, occupying the whole of the corresponding surfaces of the bones, excepting the small portions which are contiguous ; and a very thick transverse plantar ligament, extending somewhat ob- liquely from the tuberosity of the scaphoid to the cuboid. These ligaments exist even when there are no articular facettes. Articulation between the two Rows of the Tarsal Bones. The articulation between the two rows consists of the articulation of the astragalus with the scaphoid and os calcis, the articulation of the os calcis with the cuboid, and, lastly, the union of the os calcis to the scaphoid by means of several ligaments. 1 . Articulation of the Astragalus with the Scaphoid. The articular surface on the head of the astragalus {.I, fig. 84), elongated from without jPt^. 84. inward, and from above down- ward, is larger than the glenoid cavity of the scaphoid (3), and pro- jects considerably below it, where it articulates with the anterior fa- cette, or the two anterior semi- facettes of the os calcis. The cavity of reception is completed by a ligament called the inferior calcaneo-scaphoid {b), which occu- pies the triangular interval be- tween the small tuberosity of the os calcis and the scaphoid, and y forms by itself the inner side of the cavity of reception. In order to obtain a good view of this ligament, it is advisable to remove the astragalus by cutting and tearing the interosseous ligament that unites it to the OS calcis ; it will then be seen that the ligament we are describing is very strong and triangular, and that it covers not only the lower, but the inner part also of the head of the astragalus. It is often divided into two parts : one being external, narrow, and shaped like a band ; the other internal, much broader and thicker, in relation below with the sesamoid bone of the tendon of the tibialis posticus, and presenting a cartilaginous thickening at the corresponding point. Another ligament, called the superior calcaneo-scaphoid {I, fig. 83), must also be regard ed as contributing to wedge in the astragalus ; it extends from the inside of the anterior extremity of the os calcis to the outside of the scaphoid. It is situated upon the dorsum of the foot, in the deep hollow occupied by fat, on the outer side of the astragalus. These two ligaments (the inferior and superior calcaneo-scaphoid) constitute the means of union between the os calcis and the scaphoid. These bones are in no part contigu- ous ; but occasionally we find the os calcis continued into the scaphoid, through the me dium of an osseous lamina, which replaces the lower calcaneo-scaphoid ligament.* The OS calcis being very securely articulated with the astragalus, and at the same time very firmly connected with the scaphoid, it follows that the articulation between the scaphoid and astragalus possesses great strength, although the ligaments directly uniting them are by no means powerful ; just as the atlas, which is but slightly connected with the occipital bone by means of its own ligaments, is very firmly fixed by the ligaments stretching from the occipital bone to the axis. Nevertheless, the absence of any very strong and direct means of union between these bones renders it possible for the astrag- alus to be forced by externeil violence out of the sort of osseo-fibrous socket in which it is placed. The superior astragalo-scaphoid ligament {s,fig. 80 ; m,figs. 83 and 84) is the only one proper to this joint ; it is semicircular in form, and extends somewhat obliquely forward and outward, from the neck of the astragalus to the margin of the facette on the sca- phoid. It is thin in texture, and consists of parallel fibres ; it is covered by the ex tensor brevis digitorum above, and is lined below by the synovial membrane of the articu- lation between the scaphoid and the astragalus. * I have represented a case of this nature (vide Anat. Pathol, avec Planches, liv. ii., pi. v.). ARTICULATIONS OF THE TARSUS. l73 2. Calcaneo-cuhoid Arliculahon. This articulation is upon the same line as the astragalo-scaphoid ; an anatomical fact which has suggested the ingenious idea of a partial amputation of the foot between the two rows. It belongs to the class we have designated articulations by mutual reception, and of which we have found examples in the sterno-clavicular joint, and the carpo-meta- carpal articulation of the thumb. Articular Surfaces (2, fig. 80). — The facette of the os calcis is concave from above downward, while the surface of the cuboid is concave transversely, that is, in a direc- tion at right angles to that of the former. At the lower part of the facette of the os cal- cis there is a horizontal projection, which sometimes stops the knife during the disartic- ulation of the two rows. The means of union consist of three ligaments : an inferior or plantar, an internal, and a superior. The inferior -plantar, or calcatieo-cuboid ligament (ligamentum longum plantae, c d,figs. 82 and 84), is the strongest of all the tarsal ligaments, forming a broad band of pearly- white fibres, directed from before backward. These fibres constitute a very thick bundle, and extend from all the under surface of the os calcis, excepting the posterior tuberosities, to the posterior margin of the groove of the cuboid. If the fibres of this ligament be removed layer by layer, we soon arrive at a more deeply-seated ligament, separated from the first by some fatty tissue : it extends obliquely inward, from a tuber- osity at the forepart of the under surface of the os calcis, to all that portion of the infe- rior surface of the cuboid, situated behind its groove. There are, therefore, two inferior calcaneo-cuboid ligaments : a deep (c) and a superficial {d). The internal calcaneo-cuhoid ligament {n, fig. 83) is short, narrow, quadrilateral, and very strong ; it is placed at the side of the superior calcaneo-scaphoid ligament, in the deep excavation between the astragalus and the os calcis. These two ligaments are separated in front, but blended together behind, so as to resemble the letter Y. They may be considered as in some measure forming the key of the articulation of the two rows of tarsal bones ; for, during disarticulation, the articular surfaces are easily separ- ated as soon as they are divided. The superior calcaneo-cuboid ligament (o, fig 83) is only a very thin, small band of fibres, extending directly forward, from the os calcis to the cuboid. Mechanism of the Tarsal Articulations. We should examine the mechanism of the tarsal articulations both as regards their strength and their mobility. With regard to Strength. — The tarsus forms the fiindamental part of the foot ; one might, in fact, consider the metatarsus and the toes as superadded structures, for, even when they are removed, the foot fulfils its office as a basis of support very efficiently. Surgeons avail themselves of this fact in performing partial amputations of the foot at the tarsal and tarso-metatarsal articulations. The construction of the tarsus is, in every respect, adapted to ensure strength ; the number of its pieces, the breadth of the articular surfaces, the strength of the interosse- ous ligaments, and even the mobility of its component bones, all conduce to this end. Suppose, for example, that a single bone had occupied the place of the seven bones in the tarsus, how liable would this long and cancellated lever have been to fractures from the violent shocks to which it is constantly exposed, or from the influence of muscular contraction 1 The tarsus is narrow behind, but enlarged before, so as to increase the transverse extent of the supporting base in that direction ; it is articulated with the leg at a right angle, and, therefore, receives directly the weight of the body, and as directly transmits it to the ground. In order to provide the arm of a lever for the power which raises the weight of the body, it pirojects behind the leg ; indeed, the fitness of an indi- vidual for running and leaping may be, in some degree, calculated from the length of his heel, or, what is the same thing, from the prominence of the tendo Achilles. In stand- ing upon the sole of the foot, the weight of the body is transmitted by the tibia to the astragalus, and from thence to the os calcis. Part of the momentum is lost at the artic- ulation between these bones, and it is easy to comprehend why they are super-imposed, and not arranged in mere juxtaposition. But the astragalus is not placed horizontally above the os calcis, for it inclines inward, downward, and forward ; and from this cir- cumstance, even in standing upon the soles of the feet, the weight of the body is distrib- uted between the os calcis and the anterior range of the tarsus, which is itself subdivi- ded into two rows, but only on the inside, because it is there chiefly that the weight of the body is transmitted by the astragalus. In one attitude, this weight is communicated by the astralagus exclusively to the front row, viz., in standing upon the point of the foot ; and it is then that the division of the tarsus into several bones is especially useful in preventing the injurious effects of shocks transmitted from belOw. There is an im- .nense difference, also, as regards their effects on the system, between falls upon the heels and those upon the points of the feet. The mechanism of the tarsal articulations with respect to mobility should be first studi ed in the two ranges separately, and afterward in the articulation of the two rows to- gether. tT4 ARTHROLOGY. 1. The bones of the first range, viz., the astragalus and the os calcis, glide upon each other from before backward and from side to side. The lateral glidings assist in the torsion of the foot, which, however, is chiefly performed at the articulation between the two rows. The antero-posterior glidings take place under the following circumstances : when the weight of the body presses upon the upper part of the astragalus this bone slips a little forward, and the foot has a tendency to become elongated, or flattened from above downward, as Camper has remarked. "WTien the pressure ceases, the astragalus returns to its original position. The truth of the assertion, that the foot is an elastic arch, is chiefly established by reference to the nature of the astragalo-calcanian joint. 2. The bones of the second row are capable of such very slight gliding movements, that they may be considered as forming but a siilgle piece. However, the articulation between the scaphoid and the cuneiform bones is somewhat more movable than those of the cuneiform bones with each other-and with the cuboid. 3. The chief movements of the tarsus take place between the two rows, and the ar- ticular surfaces are there very favourable to mobility ; for there is in one part a head re- ceived into a cavity (at the astragalo-scaphoid articulation), and in another a mutual re- ception (at the calcaneo-cuboid articulation). These movements consist of a sort of tor- sion or rotation, by means of which the sole of the foot is carried either inward or out- ward. Assisted by slight lateral motions of the astragalo-calcanian joint, they consti- tute what is called adduction and abduction of the foot. They are generally attributed to the ankle-joint ; but, as we have seen, that articulation is limited to flexion and exten- sion ; the sprains, therefore, which result from too extensive movements, either outward or inward, take place at the articulation of the two tarsal ranges, and not at the ankle- joint. When the movement of torsion is carried too far, the external malleolus is forced somewhat outward ; slight gliding motions occur at the tibio-fibular articulations ; the elasticity of the fibula is called into play ; and, if the violence be immoderate, the fibula is fractured. Tarso-mktatarbal Articulations {Jigs. 82 to 84). , In the formation of these joints, the wedge-shaped tarsal extremity of each metatarsal bone is opposed to one of the bones of the tarsus, the corresponding surfaces being plane and triangular. The first metatarsal bone articulates with the first cuneiform ; the sec- ond metatarsal with the second, and shghtly with the first and the third cuneiform bones ; the third metatarsal with the third cuneiform ; the fourth and fifth metatarsal with the cuboid. From this there results an angular articular line, commencing on the outside, at the projection formed by the tuberosity of the fifth metatarsal bone. This line is directed obliquely forward and inward ; it forms an angle at the third, and again more particularly at the second metatarsal bone, because the third cuneiform bone projects, and is wedged in between the second and fourth metatarsal bones, while the second metatarsal bone projects into the tarsus between the first and the third cuneiform bones. The articular surfaces are held together by dorsal, plantar, and interosseous ligaments. We shall now study each of these articulations separately. Articulation of the First Metatarsal Bone with the Tarsus. — ^There are two semilunar facettes in this articulation, one belonging to the first metatarsal, the other to the first cuneiform bone ; the long diameter of these surfaces is directed vertically. The strength of the joint is maintained by a very strong plantar {ffigs. 82 and 84), and a thinner dor- sal {p,fig- 83, and e,fig. 84) ligament. Both these consist of bands directed from before backward. There is a distinct synovial membrane for this joint. We may include among the ligaments of this articulation the aponeurotic expansion given off by the pe- roneus longus to the first cuneiform bone, and also that derived from the tibialis anticus, and attached to the first metatarsal bone. The articulation of the second metatarsal hone with the tarsus is effected by the reception of the posterior extremity of that bone within the recess formed by the three cuneiform bones. We met with a similar arrangement, though less perfectly developed, in the carpo-metacarpal articulation of the second metacarpal bone. It is the strongest of all the joints of this kind, and is provided with, 1. Three dorsal ligaments, as in the corre- sponding articulation in the hand ; one median (r, fig. 83), broad, and constantly divided into two bands, which proceed from the second cuneiform bone ; a very strong internal ligament, extending from the first cuneiform bone, the third being external, thin, and at- tached to the third cuneiform bone. 2. With two plantar ligaments, one of which {g, fig. 82) is very strong, extends obliquely from the first cuneiform to the second metatarsal bone, and is prolonged upward, so as to become interosseous ; the other is very small, and proceeds from the sharp edge of the second cuneiform to the second metatarsal bone. 3. With an interosseous or lateral ligament, extending from the external lateral surface of the first cimeiform bone to the internal lateral surface of the second metatarsal bone. The articulation of the third metatarsal hone with the tarsus is maintained by a dorsal liga- ment {s, fig. 82) from the third cuneiform bone. There is no plantar ligament, properly so called, unless an oblique bundle of fibres from the first cuneiform bone be considered as such ; but the fibrous layer, which, after forming the sheath of the tendon of the pe- ARTICULATIONS OP THE METATARSUS. ITII roneus longus, is prolonged to the third metatarsal bone, appears to me to act as a plantar ligament. There is also an external lateral or interosseous ligament, which separates the articulations of the third and fourth metatarsal bones. The fourth and fifth metatarsal bones together present a slightly concave surface, which articulates with the convex surface of the cuboid. The means of union consist of a dorsal ligament (t, fig. 83) for the fourth, and an oblique ligament (u), running outward and forward, for the fifth metatarsal bone : they are both loose, but especially the latter. There is no plantar hgament, excepting the sheath of the tendon of the peroneus longus, and a very strong tendinous expansion of the tibialis posticus. The tendon of the pe- roneus brevis acts as an external lateral ligament ; and, besides this tendon, there ex- ists a very strong fibrous band, derived from the external plantar aponeurosis, which extends from the os caleis to the process of the fifth metatarsal bone ; and, moreover, an expansion of the tendon of the peroneus longus, given off as it passes over the cuboid. The articulation of the fifth metatarsal bone is very loose. There is a very strong in- terossemis ligament, stretched from the external lateral facette of the third cuneiform bone to the internal lateral facette of the fourth, and the external lateral facette of the third metatarsal bones. This ligament is analogous to one that separates the articula- tion of the fourth and fifth metacarpal bones from the other carpo-metacarpal articula- tions, and it fulfils a similar purpose here ; so that there are three distinct articulations between the tarsus and the metatarsus, and, therefore, three separate synovial mem- branes ; one for the fourth and fifth metatarsal bones, one for the second and third, and another for the first. Articulations of the Tarsal Extremities of the Metatarsal Bones. — These are true amphi- arthroses. The corresponding surfaces are partly contiguous and partly continuous. The contiguous part is nearer to the tarsus ; it is flat, and presents on each bone two small secondary facettes. Contrary to what obtains in the metacarpus, the continuous por- tions are larger than the articular surfaces. There are interosseous, dorsal, and plantar ligaments. The interosseous consist of very strong, short, and compact bundles of fibres, which extend between the rough surfaces of two neighbouring metatarsal bones. The dorsal {b, fig. 83) and plantar {i, fig. 82) pass transversely from one metatarsal bone to another, the plantar being much the larger. Articulations of the Digital Extremities of the Metatarsal Bones. — ^Although the digital ends of these bones do not articulate together, yet, as they are in contact and move upon each other, a synovial membrane covers the continuous surfaces and facilitates their movements ; a ligament, also, the transverse ligament of the metatarsus (x, figs. 82 and 83), is stretched transversely in front, and unites them loosely together. This ligament is conamon to the five metatarsal bones ; it is formed by the junction of all the anterior ligaments of the metatarso-phalangal articulations, by means of small bundles passing from one to another. It is exposed by opening the sheaths of the flexor tendons. Mechanism of the Metatarsal Articulations. With regard to Strength. — 1. The five component bones of the metatarsus are so strong- ly united that it is very uncommon for one of them to be broken by itself; the metatar- sus, therefore, can be only fractured by violence sufficient to crush it. 2. The slight ■ mobility of the bones also concurs in increasing the strength of this part of the foot, by permitting it to yield slightly to external impulse. 3. The metatarsus is not uniformly strong throughout ; the first of its bones is the strongest, and upon it a great portion of the weight of the body rests during standing. The mobility possessed by the tarsal and the digital extremities of the metatarsal bones requires to be separately noticed. 1. In the tarsal extremities, the a'ngular arrangement, the mutual wedging of the tar- sus and the metatarsus, as well as the strength and shortness of the external and inter- osseous ligaments, admit of only very obscure gliding movements ; a proof of which ex- ists in the fact, that no example of the luxation of these bones upon the tarsus has, per- haps, ever been recorded. 2. Obscure, however, as these movements may be, they give rise to considerable motions in the digital ends of the bones, where the mobility is fa- voured by the looseness of the transverse metatarsal ligament, and the presence of a sy- novial membrane between the heads of the bones. The first metatarsal bone is not more movable than the others, contrasting remarkably in this respect with the first met acarpal bone. Articulations op the Toes {figs. 82 to 84). Metatarso-phalangal Articulations. These articulations belong to the class condyloid, and offer a nearly perfect similarity to the metacarpo-phalangal joints. Articular Surfaces. — The head of each metatarsal bone is flattened on the sides, and elongated from above downward, so that it forms a condyle. Each i)halanx presents 3 shallow cavity, the greatest diameter of which, contrary to that of the metatarsal surface is transverse. J 76 ARTHROLOGY. Means of Union. — 1. There is an inferior or glenoid ligament (I, Jig. 82), situated on the plantar aspect of the joint ; it is very thick, of the density of cartilage, and consists of interlacing fibres : its edges are continuous, partly with the sheath of the flexor tendons, partly with the transverse metatarsal ligament, but especially with the lateral ligaments of the joint. It is grooved below for the flexor tendons, concave above, to correspond with the convexity of the head of the metatarsal bone, and completes the cavity in which that head is received. Its anterior edge is very firmly fixed to the plantar border of the cavity of the phalanx, of which it seems a continuation ; its posterior edge is free, or, rather, is loosely connected by some ligamentous fibres to the inequalities behind the head of the metatarsal bone, upon the contracted neck of which it is moulded very ex- actly, so that, while protecting the lower part of the joint, it serves also to increase the extent of the surfaces included in the articulation. 2. There are two very strong lateral ligaments (y, figs. 82 and 83), an internal and an external, inserted, not into the depres- sions on each side of the head of the metatarsal bone, but into tubercles situated behind them ; from this origin they proceed very obliquely forward and downward, like flat bands, spreading out as they advance, and terminating partly in the inferior ligament, and partly on the sides of the phalanx. There is no dorsal ligament, properly so called, but the corresponding extensor tendon evidently occupies its place. It is not uncommon to observe a prolongation from the anterior surface of this tendon united to the metatar- sal end of the first phalanx. Synovial Capsule. — ^Under the extensor tendon we find a very loose synovial capsule ; it covers the internal surface of the ligaments as well as the articular cartilages. The metatarso-phalangal articulation of the first metatarsal bone presents some peculiar- ities which merit special description. 1. The articular surfaces are much larger than in the other similar joints. 2. The head of the first metatarsal bone presents two pulleys on its plantar aspect, separated from each other by a prominent ridge directed from be- fore backward. This construction is connected with the presence of two sesamoid bones {g, fig. 84), developed in the substance of the inferior ligament, which is three or four times thicker than in the other joints. The lateral ligaments are almost exclusively fixed into these sesamoid bones. This joint has also a sort of fibrous ring surmounting the border of the glenoid cavity of the phalanx. Articulations of the Phalanges of the Toes. These are perfect angular ginglymi. Each toe has two such joints, with the excep- tion of the great toe, which has only one. Articular Surfaces. — The anterior extremity of the first phalanx, flattened from above downward, presents a trochlea, which is broader, and prolonged farther on the plantar than on the dorsal surface. On the second phalanx there are two small glenoid cavities separated by a ridge, the cavities corresponding to the sm£dl condyles, and the ridge to the groove of the trochlea just described. Ligaments. — 1. As the articular pulley of the first phalanx projects considerably below the second, it is covered in this direction by an inferior or glenoid ligament (m, fig. 82), exactly resembling those of the metatarso-phalangal joints, and perfoming the same functions. 2. The two lateral ligaments (y, figs. 82 and 83) are fixed precisely like the corresponding ligaments of the metatarso-phalangal joints, viz., into the tubercle above the lateral hollow on the anterior extremity of the first phalanx ; and they extend ob- liquely forward to the glenoid ligament and the second phalanx. 3. There is no superior ligament, its place being supplied by the extensor tendon. This tendon is arranged in a particular manner, for it frequently sends off a prolongation (z, fig. 83) from its anterior surface, which is attached to the upper end of the second phalanx. 4. The synovial cap- sule is arranged as in the metatarso-phalangal articulations. There is often a sesamoid bone in the inferior ligament of the phalangal articulation of the great toe. Mechanism of the Metatarso-phalangal Articulations. Like all condyloid joints, these admit of movements in four principal directions, and, therefore, are also capable of circumduction. Extension or flexion backward can be car- ried much farther than in any other similar joints. The lateral movements of abduction and adduction are very hmited. Let us examine what takes place during each of these movements, in which the glenoid cavity of the first phalanx glides upon the head of the corresponding metatarsal bone. Inflexion, the first phalanx glides downward upon the head of the metatarsal bone ; the extensor tendon and the upper part of the synovial capsule are stretched by the projecting head ; the upper fibres of the laterad ligaments are also stretched ; these fibres then limit the motion, which, nevertheless, may be car- ried so far that the phalanx may make a right angle with the metatarsal bones. In extension, the phalanx glides upward upon the head of the corresponding metatarsal bone ; the superior fibres of the lateral ligaments are relaxed, while the inferior are stretched : these latter and the inferior ligament evidently limit the motion. In all sub- jects it maybe carried so far as to make an obtuse angle behind ; in some so as even to form a right angle. The movements of abduction and adduction are limited by the meet- ing of the toes. ODONTOLOGY. 177 Mechanism of the Phdangal Articulations. As the mechanism of these joints is in every respect identical with that of the fingers, we shall refer to what has been said upon that subject, merely remarking that, eithei from original construction, or from the continued confinement of the toes in tight shoes, their movements, which consist exclusively of flexion and extension, are much more limited than those of the fingers. Note on Artkrology. — [It has been considered advisable to include in a single note the following observation* on the general anatomy of the several tissues that enter into the construction of the articulations : Cartilages (p. 111). — The substance of the articular cartilages, in many joints, appears to be arr'mged in masses placed side by side, and perpendicularly to the surface of the bone ; and hence the fibrous character presented by them alter slight maceration: nevertheless, they are composed of pure cartilage, unmixed with fibrous tissue. When viewed under the microscope, cartilage is found to consist of a transparent substance, in which are imbedded numerous corpuscles, either placed singly or aggregated in groups. The interme- diate substance is homogeneous in youth, but becomes more or less laminated as age advances. The corpuscles, which are, in fact, metamorphosed primitive cells, are of irregular forms, contain nuclei and nucleoli, and are somewhat flattened near the surface of the cartilage. Occasionally, several are seen occupying a distinct cavity in the intermediate substance. Their average size is tsVs*^ °^ '"^ '"'^'^ '" length, by^ iAj-jth in breadth. Neither nerves, bloodvessels, nor lymphatics are found in the articular cartilages, which, al- though non-vascular, can scarcely be considered unorganized. Cartilage contains 66 per cent, of water ; its principal solid constituent is an animal matter, resolved by boiling into a peculiar variety of gelatin, called chondrin ; it also contains salts of soda, lime, magnesia, and potash. The inter-articular cartilages having free surfaces (as those of the knee-joint), are composed of true carti- lage interwoven with fibrous tissue, which particularly abounds at their attached margins. The inter-verte- bral substances, and all other interosseous cartilages, have a similar structure, but contain a greater propor- tion of fibrous tissue. From the two anatomical elements of which these structures consist, they are called ftbro-cartilages. The articular borders surrounding the glenoid and cotyloid cavities, generally described with the ligaments, are also composed of fibro-cartilaginous tissue. Ligaments (p. 112). — The articular ligaments consist entirelyof fibrous tissue, the obvious component fibres of which are divisible into parallel microscopic filaments, exactly similar to those of cellular tissue (see note on Aponeurologt, infra). They are supplied with but very few vessels and nerves ; they contain 62 per cent, of water, the remainder being almost entirely converted into gelatin by boiling. The yellow elastic tissue, of which the ligamenta subflava are composed, differs in minute, as well as in ob- vious characters, from the white fibrous tissue of ordinary ligaments, it consists chiefly of peculiar filaments, intermixed with a few of those of cellular tissue. The proper elastic filaments, examined with the micro- scope, are yellowish and transparent, have a bright aspect and dark outline (very unlike the delicate appesir- ance of the cellular filaments), and are usually curved or bent at their torn extremities. The peculiar char- acter of dividing and uniting again, often assigned to them, is thought to be rather apparent than real, and to depend on an imperfect separation of the larger into their component filaments. The elastic is more vascular than the fibrous tissue. It contains less water (only 29 per cent.), and yields much less gelatin when boiled ; the insoluble residua somewhat resembles coagulated albumen. Synovial Membranes (p. 112). — The basis of an articular synovial membrane is cellular tissue, which be- comes more and more condensed towards the free surface of the membrane. The smoothness of this surface is due to a covering of flattened scales (metamorphosed primitive cells) lying upon it, and constituting what is termed an epithelium. The recent discovery of this epithelium upon the surface of the articular cartilages is suflScient to establish the continuity of the synovial membrane over them; a fact which, though doubted by many, is assumed by M. Cruveilhier upon ansilogical grounds. No nerves have been traced into these mem- branes, and the vessels existing in the sub-synovial tissue cease at the margin of the cartilage. The synovia secreted by these membranes is an aqueous solution of albumen and saline matters. It contains more albu- men than the fluid of serous cavities, the lining membranes of which (as we shall hereafter notice) have a similar structure to those just described. Besides the articular synovial membranes, two other kinds are usually mentioned, viz., the bursal, including the various bursae, erroneously called bursae mucosae ; and the vaginal, examples of which are met with in th« sheaths of tendons. These two forms will be again referred to in the note on Aponeurology, infra. Adipose Tissue. — The constant occurrence, especially in the larger articulations, of masses of fat beneath the synovial membranes, affords an opportunity of jdluding in this place to the minute anatomy of the adipose tissue generally. It may be briefly stated to consist of an aggregation of distinct spherical or oval vesicles, containing the adipose substance, and having numerous vessels ramifying on their transparent and homoge neous parietes. They are held together by the branches of those vessels, and by cellular tissue. In man, the adipose substance is liquid during life, but separates, when obtained in any quantity, into an oily fluid caUed •la'ine, and a solid residue, consisting of two fatty substances, stearine and margarine.] ODONTOLOGY. Circumstances in which the Teeth differ from Bones. — Number. — Position. — Exterrud Confot mation. — General Characters. — Classification — Incisor — Canine — Molar. — Structure. — Development. The teeth, the immediate instruments of mastication, are those ossiform concretions which surmount the edges, and are implanted in the substance of both jaws. The teeth are not bones, though, from possessing an apparent analogy to them, they have long been considered as such. They differ from bones in many respects. 1. With regard to position. The teeth are naked and visible at the surface, while the bones, and tliis is one of their most important characters, are covered by periosteum. 2. In anatomical characters. The teeth consist of a bulb or thick papilla, surrounded by a calcareous envelope, composed of two substances, the enamel and the ivory. This calcareous envelope is not traversed by vessels, nor can any trace of cellular tissue be discovered in it. 3. In regard to their mode of development. In the teeth, the formation of the hard or ossiform matter takes place by successive depositions, from the circumference to the cen- Z 178 ODONTOLOGY. Ire ; while bones are developed in a precisely opposite direction. No nutritive changes are carried on in the teeth as in bones. Moreover, the teeth are renewed by means of the second dentition ; but there is no analogous phenomenon in the development of bone. 4. In physiological relations. The teeth do not participate in the diseases of bone, being susceptible only of chemical and physical alterations ; nor is the period of their existence, like that of the bones, of equal duration with the life of the individual. 5. In regard to chemical composition. They contain a much larger proportion of saline matters, and the enamel is entirely destitute of gelatine. All these circumstances prove that the teeth are not bones. We shall now show that they belong to the epidermoid system, and are analogous to the nails and hair. 1. When examined in the lower animals, they are found to present an uninterrupted series, from such as closely resemble horns or nails to such as present the most perfect- ly characteristic appearances of bone. 2. They have a lamellated structure, hke the nails and hair : in some animals this is very manifest, but is rendered obscure in others from the abundance of calcareous deposite. 3. They are developed in the same manner as horns, nails, and hair. 4. Like them, they present no nutritive phenomena ; they are formed layer after layer, and undergo no renewal of their constituent parts ; they are* inorganic bodies, the products of transudation. 5. According to M. Geoffrey St. Hilaire, the beak of birds, which is evidently a horny structure, belongs to the dental system. Number. — In young subjects, at the period of the first dentition, there are twenty teeth, ten in each jaw : in the adult there are thirty-two, sixteen in each jaw. Man, therefore, during the course of his life, has fifty-two teeth, twenty temporary, and thirty-two per- manent. The varieties in the number of the teeth are either the result of a deficiency or an excess. The varieties from deficiency consist, 1 . In the absence of all teeth, examples 6f which have been recorded by Fox and Sabatier ; 2. In the absence of a great number of teeth, as occurred in an individual who had only the four incisors in each jaw. These deficien- cies are chiefly observed to affect the posterior molares, and frequently they are merely apparent in them from the teeth remaining concealed within the alveoli for a much longer period than usual. Besides, Fox remarks, that there is no tooth which has not occa- sionally been observed to be wanting, either alone or in conjunction with others. The varieties /rom excess are observed in the existence of supernumerary teeth, which may or may not range wth the ordinary teeth. The supernumerary teeth either exist in distinct alveoli, or are blended with some other teeth. There are two varieties of this latter condition ; for the supernumerary tooth may either appear to grow upon a primitive or parent tooth {^dens prolifcr of Bartholin), or several teeth may seem as if united into one. Position. — The teeth are arranged in two parabolic curves, constituting the dental arches, and corresponding to the alveolar arches, which support them. Into these arches the teeth are fixed, not by articulation, but by the implantation of their roots into the al- veoli, which are moulded exactly upon them. This arrangement induced those anato- mists who regarded the teeth as true bones to admit a peculiar mode of articulation for them, called gomphosis (yd/z^of, a nail). The teeth are mechanically fixed in their alveoli ; but yet we must consider the gums and the alveolo-dental periosteum as also forming uniting media. The importance of the latter will be acknowledged, if we consider the effects of scurvy in loosening the teeth, and the ease with which they drop out from the skeleton. Each dental arch forms a regular, uninterrupted curve, an aiTangement peculiar to man, for in the lower animals the teeth are of unequal length, and the dental arches have irreg- ular edges ; moreover, instead of their teeth being uninterruptedly contiguous, very con- siderable intervals, at some points at least, are left between them. Each dental arch presents an anterior convex, and a posterior concave surface ; an adherent or alveolar bor- der, which is regularly scalloped ; and a free edge, thin and cutting at the middle, thick and tubercular at the sides ; in the latter situations it has two lips, of which the external is sharper in the upper teeth, and the internal in the lower. The free edge is so arran- ged that all the teeth are upon a level. As the superior dental arch forms a greater curve than the inferior, it necessarily fol- lows that the two arches meet hke the blades of a pair of scissors ; but the mode in which they meet is not the same in the middle region, occupied by the incisor teeth, as on the sides, where the molares are placed. Thus, the upper incisors pass in front of the lower, while the external tubercles of the superior molares pass to the outside of the external tubercles of the inferior molares, so that these latter tubercles are applied to the furrow formed between the two rows of tubercles of the upper molares. The teeth of the upper jaw, with the exception of the great molaies, are larger, in gen- eral, than those of the lower. I should also remark, that no tooth is placed quite per- pendicularly to its fellow in the other jaw ; for the summit of a tooth in one jaw always corresponds to the interval between the summits of two in the other ; so that the two rows of teeth are not simply in contact, but are really locked together. * See note, p. 183. THE INCISOR TEETH. 179 External Conformation. — ^The teeth, considered in reference to their form or configura- tion, present some general characters which distinguish them from all other organs of the body ; and also certain specific characters, by which one tooth may be distinguished from another. General Characters {figs. 85 to 92). — Each tooth is composed of two very distinct parts : a free portion, projecting beyond the alveolus, named the crown or body {a, figs. 85, &c.), and a portion implanted in the bone called the root ox fang (i), the constricted portion between these two constituting the neck (c). The rim of the alveolus or socket does not exactly correspond to the neck of the tooth, but rather to the root, at some dis- tance from the neck, the intervening space being occupied by the gam. The axis of the teeth is vertical. This direction is peculiar to the human species. The projection of the teeth forward gives a disagreeable aspect to the countenance, and is al- most invariably connected with a diminution of the facial angle. The axis of all the teeth is slightly inchned, so as to converge somewhat towards the centre of the alveolar curve. The length of the teeth (that is, of their crowns) is very nearly uniform. The advan- tage of this arrangement, in preventing one tooth from projecting beyond another, is very obvious. Wlien the teeth are not equal in length, mastication is evidently imperfect ; and therefore the principal object, in cases of fracture of the lower jaw, is to prevent the inconvenience that would arise from irregularity of the dental edge, and which is actu- ally observed when the fragments unite in a wrong position. The teeth are only separated from each other by very small triangular intervals, so that they are almost contiguous. When the intervcds are very considerable, mastica- tion is imperfect. The general form of the teeth is that of a sUghtly elongated cone, flattened in opposite directions, the base of which is formed by the crown and turned towards the free edge of the dental arch, while the summit, formed by the simple or compound root, presents an opening that penetrates into the cavity of the tooth. The conical form of the root, and the accuracy with which the alveolus is moulded upon it, have a twofold result, viz., that the effort of mastication is disseminated over all points of the socket, and that no pressure is ever experienced at the extremity which receives the vessels and nerves. The differences presented by the teetfi, more especially in the crown, have led to their arrangement into three classes, viz., incisors, canine, and molars: the latter have been subdivided into the great and small molars. The crown of the incisor teeth {figs. 85, 86) resembles a wedge with the sharp border shaped like a chisel ; as their name implies, they serve the purpose of cutting the food. The crown of a canine tooth {figs. 87, 88) forms a cone with a free pointed apex ; these teeth serve to tear the food, whence their name of laniaires : Hunter called them cu'spi- dati, from their having only one point. The crown of a molar tooth {figs. 89 to 92) is cuboidal, the free extremity being provided with tubercles or points, intended to bruise the food as in a mill. The smjdl molars, which have only two tubercles, are called by Hunter bicuspides {figs. 89 and 90). Man alone, of the entire animal series, is possessed of the three kinds of teeth in an almost equal state of development. The Incisor Teeth {jigs. 85 and 86). These are eight in number, four in either jaw. They occupy the middle of the dental arches, and, consequently, the anterior extremity of the lever of the third order, repre- sented by each half of the jaw. Their position is unfavourable, and, consequently, they are intended only to divide substances that offer but little resistance. This class of teeth attain their utmost development in rodentia ; as in the rabbit, beaver, &c. General Characters. — The crotcn (a) is wedge-shaped ; its anterior surface {fig. 85) is convex, and the posterior concave ; its sides {fi,g. 86) are triangular ; its e-- 85 K 86 base is thick and continuous with the root, and its free edge sharp, some- '^' what broader than the base, and cut obUquely upward and backward in , „r" the upper teeth, and downward and forward in the lower. This obliqui- ty of the surfaces, by which the incisors of the two jaws correspond, is the result of their constant friction upon each other, for they cross like the blades of scissors. The cutting edge of an incisor tooth, before it is worn down, is marked by three small denticulations. The root {b) has the form of a cone flattened on the sides ; the anterior border is thicker than the posterior. A small vertical furrow (see fig. 86) occasionally ex- ists on each side, appearing to indicate an original division ; and some- times the point of the root is bifid. Two curved lines, having their concavities directed downward, and united on the sides of the tooth, separate the root from the crown.* Differential Characters. — The upper incisors are distinguished from the lowor by their nmch greater size, the fonner being almost twice as large as the latter. In the upper jaw, the middle are distinguished from the lateral incisors, also, by their well-marked su- * [It maybe well to observe, that the illustrations arc all taken from teeth of the upper jaw, in which tha general characters of each class are more strongly marked than in those of the lower.! ODONTOLOGY. periority in size. In the lower jaw, on the contrary, the lateral incisors are the larger, though the difference is but shght. The Canine Teeth {fgs. 87, 88). These are four in number, two in each jaw. They are situated on either side exter- nally to the incisors, and therefore are nearer to the fulcrum, so that they can overcome a greater resistance. These teeth are most completely developed in the camivora. The tusks of the boar and of the elephant are also canine teeth. General Characters. — They are the longest of all the teeth, both in the crown and in Fig. 87. Fig. 88. the root ; they therefore project a little beyond the incisors, particu- larly in the upper jaw. Their crown (a) is thick and irregularly conoid ; it is somewhat enlarged immediately above the neck, and terminates in a blunt point cut obliquely at the sides (see^^. 88), and grooved be- hind. The anterior surface (fig. 87) is convex, the posterior concave. The canine teeth have much longer and larger roots (ft) than any oth- er, and their alveoli are remarkably prominent. The root is flattened on the sides, each of which presents a vertical groove traversing its entire length (see^^. 88). Differential Characters. — The superior canine teeth are distinguished from the inferior by their greater length and thickness. The roots cor- respond to the ascending process of the superior maxilla, and in some subjects are prolonged to the base of that process. The length of their root explains the difficulty of extracting them, and the accidents by which this operation is sometimes fol- lowed. There are several preparations in the museum of the Faculty of Medicine, in which the canine teeth are seen developed in the substance of the ascending process, and reversed, so that the crown is turned upward and the root downward. The Molar Teeth {fgs. 89 to 92). The molar teeth are twenty in number, ten in each jaw. They occupy the last five alveoli on either side, and, consequently, are nearer to the fulcrum than all the other teeth : they are, therefore, most advantageously placed for exercising a powerful pressure upon any substances we may desire to break between the teeth. The instinctive motion by which, in order to crush a very hard body, we place it between the molars, is evidently connected with this arrangement. These teeth are most highly developed in herbivora. The general characters which belong to all the molars are the following : 1. The great extent of their grinding surfaces, which far exceed those of the incisors and canine ; 2. The absence of all obliquity at their summit, the anterior and posterior surfaces be- ing parallel, instead of approaching each other, so as to form a cutting or angular bor- der : this character is evidently connected with the preceding one ; 3. The inequalities of their grinding surfaces, which are marked by eminences and depressions ; 4. The round or even cubical form of the crown ; 5. The shortness of the vertical dimneter of the crown ; 6. The multiplicity of roots. The molars are divided into two classes, according to their difference in size, and the number of tubercles upon their grinding surfaces. The smaller are called small molars, or bicuspides ; the larger, great molars, or multicuspides. It should be remarked, that in the first dentition, all the molars, without exception, are multicuspides. The small molars or biscuspides {figs. 89 and 90) are eight in number ; four in each jaw, two on the right, and two on the left side. They are distinguished by the names first, second, &,c. They are situated between the canine teeth and the great molars. The small molars of the upper jaw correspond to the canine fossae. General Characters. — The crown (a) is irregularly cyhndrical, flattened from before Fig. 89. Fig. 90 backward, with its long diameter directed transversely. The anterior and posterior surfaces, which correspond to the two neighbouring teeth, are plain (see fig. 90). The internal and external {fig. 89) sur- faces are convex ; the free or grinding surface is armed with two tu- bercles or points, separated from each other by a furrow. Of the two tubercles the external is the larger. The crown of the small molars has been compared to that of two small canine teeth united. The root (b) is generally simple, but sometimes double or bifid. When simple, it has a deep vertical groove upon each side ; when it is bifid, the sep- aration is never so deep as in the great molars. Differential Characters. — The lower bicuspides are distinguished from the upper by their smaller size, by a slight projection of the crown inward, and by the external tuber- cle being worn down. In the upper bicuspides, the two tubercles are separated by a deep furrow ; in the lower, on the contrary, the furrow is more shallow, and the tuber- cles are sometimes united by a ridge. The second upper bicuspid has generally two roots {figs. 89 and 90), by which it is distinguished from the others. Tlie first lower bicuspid, somewhat smaller than the second, has most commonly but one tubercle, viz the external. This gives it more resemblance to a canine tooth. STRUCTURE OF THE TEETH. 181 The great molars or multicuspides (figs. 91 and 92) are twelve in number ; six in each jaw, three on one side, and three on the other. They are named pig_ gj, pig 93 nmnerically, proceeding from before backward, first, second, and ^ „ <' third. The last is also called de-ns sapicntia, on account of its tardy appearance. They occupy the most remote part of the alveolar border. General Characters. — The crown (a) is pretty regularly cuboid. The anterior and posterior surfaces (see fig. 92), by which these 4 ] teeth correspond, are flat ; the external and internal surfaces (fi,g. 91) are rounded. The grinding surface is armed with four tubercles (dcntes guadricuspides), separated by a crucial furrow, which is occasionally replaced by small depressions. lu some teeth a fifth tubercle may be found. In almost all the tubercles are of unequal size, and cut into facettes. The crown of the great molars resembles two small molars united. The root (b) is always compound ; it is most commonly double or triple, and, in this case, one of the roots has a longitudinal furrow. Sometimes it is divided into four or five parts, variable both in length and direction. The roots are either divergent or parallel ; and occasionally, after separating, they approach each other again, curving like hooks, so as to embrace a more or less considerable portion of the jaw bone. Such teeth (which are called dents harries) it is impossible to extract without pulling away the included portion of the jaw also. Each root of these teeth exactly resembles the single roots of the teeth already descri- bed, with the exception of being smaller. Differential Characters of the Upper compared with the Loicer Molars. — I . Contrary to what was observed with regard to the other teeth, the crowns of the lower great molars are a little larger than those of the upper. 2. They are slightly bent inward, while those of the upper great molars are quite vertical. 3. The lower great molars have only two roots, an anterior and a posterior. These roots are very strong and broad, flattened from before backward, deeply grooved longitudinally, and bifurcated at the points. The upper great molars have at least three roots {figs. 91 and 92), one internal and two external. It is very easy, then, to distinguish between the molar teeth of the two jaws. Individual Characters of the Great Molars. — 1 . The first great molar is distinguished from the other two by its size, in which it generally exceeds them. 2. The third great molar, or wisdom tooth, is distinguished from the first and second by its evidently smaller size ; by its crown having only three tubercles, two external and one internal ; by its shortness ; and by its roots being, in certain cases, more or less completely joined together. However, even where the roots of these teeth are united, we always find the trace of the characters proper to the series of molar teeth to which they belong ; i. e., the vestige of three roots, an internal and two external for the upper wisdom teeth, and of two roots, an interior and a posterior for the lower. No teeth present so many varieties as the last molares, which occasionally even remain buried in the substance of the maxillary tuberosity. Structure of the Teeth. The crown of each tooth contains a cavity {d, figs. 93, 94) corre^onding with it m shape. This cavity is prolonged with contracted dimensions into ^^ gg y. g^_ the centre of the root, and opens by an orifice of variable size at w- • the apex of the simple or compound cone, represented by the fang. The dimensions of this cavity are in an inverse proportion to the age of the tooth ; so that it is largest at the earliest periods, but during the progress of years it becomes entirely obliterated. It contains a soft substance constituting the dental pulp. A tooth, i;|| therefore, is composed of two substances, an external hard or c * Sfie note, p. 183. |S2 ODONTOLOGY. crown, and has been called the enamel (e, figs. 93 and 94), from a comparison with the vitreous layer or glaze of porcelain ; the other, constituting the entire root and the in- terior of the crown, is the ivory (/), improperly designated the bony •portion of the tooth. The enamel is thickest on the grinding surface of the tooth ; it diminishes in thickness as it approaches the neck, at which part it terminates abruptly. The prominence of the curved line, indicating the termination of the enamel, gives rise to the constriction call- ed the neck. By comparing, and, in some degree, contrasting the peculiar characters of the enamel and the ivory, we shall be better able to assign to each their respective properties. 1. The enamel is of a bluish- white, milky colour, and semi-transparent ; the ivory is yellowish-white, and has an appearance like satin. 2. The enamel, examined in fragments of the crown, exhibits fibres perpendicularly implanted upon the ivory, and pressed closely to each other. The ivory, on the contra- ry, is formed of concentric layers,* the fibres of which are generally parallel to the long diameter of the tooth. 3. Both substances are excessively hard ; but in this respect the enamel is superior to the ivory, for it will strike fire with steel, and is much less easily worn down by use ; it can even turn the edge of a file. This excessive hardness, a principal element of im- mutability, explains how the teeth are preserved uninjured as long as the enamel re- mains entire, and, on the other hand, the facility with which they decay when once it has been removed. The great brittleness of the enamel, which is one of its most char- acteristic properties, is also owing to this extreme hardness. 4. In chemical composition, the enamel and ivory present important diflferences, indi- cated in the following tables : Ivory. Enamel. Phosphate of lime ... 61-95 Phosphate of lime ... 85-3 Fluate of lime .... 210 Fluate of lime .... 3-2 Carbonate of lime ... 5.30 Carbonate of lime 8-0 Phosphate of magnesia - - 1-25 Phosphate of magnesia 1-5 Soda and chloride of sodium 1-40 Membranes, soda and water 2-0 Cartilage and water ... 28-00 It follows, therefore, that the principal chemical distinction between these substances depends on the existence of cartilage, that is, of an animal matter in the ivory, and on its absence in the enamel. The presence of cartilage in ivory forms a trace of resem- blance between this substance and bone ; and this is farther strengthened by the result of the action of heat, by which both are similarly aifected. Between the true bones and the ivory there is, however, all that diflference by which a living tissue is distinguished from a solidified product of secretion. I admit, then, a complete want of vitality both in the ivory and the enamel of the tooth ; nevertheless, there are some phenomena which appear to contradict such an opinion. 1. The cortical substance of the tooth affords a much more perfect sensation of such bodies as come in contact with it than either the nails or hair. 3. Weak acids, particularly vegetable acids, cause a peculiar sensation when they are applied to the teeth, rendering the shghtest touch extremely painful ; a sensation gener- ally expressed by saying that the teeth are set on edge. But if, on the other hand, we reflect that the substance of the teeth is never affected by inflammation, that it never becomes the seat of any tumour or diseased product, and that it is worn away by rubbing and by the file, in the same way as an inorganic body, without any attempt at reparation or any evidence of the existence of a nutritive pro- cess, we must be led to admit the absence of vitality in these organs, and to explain the foregoing facts as dependant simply upon transmission. Lastly, the hardness, fragility, and mutability of the enamel and ivoiy vary in differ- ent individuals ; hence the difference in the durability of the teeth, and their liability to change. It must not be imagined that the ivory, when exposed, is susceptible of caries or necrosis ; its changes are entirely of a chemical nature. The contrary opinion pre- vailed only so long as the teeth were considered true bones, and yet it has exercised an influence over the language of surgery which is not yet removed ; thus, we are in the habit of speaking of a carious or necrosed tooth, and to describe them as affected with exostosis, and even with spina ventosa. It follows, from all that has been said, that the human teeth are simple, i. e., formed by one centre of ivory covered with one layer of enamel. Compound teeth exist only in herbivora, in which animals mastication consists of a most extensive grinding move- ment ; nor are they met with except among the molar teeth. The characteristic feature of a compound tooth is the division of the crown into a greater or smaller number of lesser crowns, each of which consists of a centre of ivory covered by a layer of enamel. All these crowns are united into one by a third substance, called the cement or crusta pe- trosa, of which the tartar of the human teeth will afford a sufficiently good idea.t * See not«, infra. t tRecent researches into the structure of the teeth have brought so many interesting facts to light, that It la necessary to notice the result of these discoveries. DEVELOPMENT OF THE TEETH. 183 Development of the Teeth, or Odontogeny. The study of the development of the teeth is one of the most interesting parts ol their history. It embraces the description of the phenomena that precede, accompany, and follow the eruption of the first and second sets of teeth. First, Temporary, or Provisional Teeth. Phenomena which precede their Eruption* — If the jaws of a foetus of two or three months be examined, it will be seen that they are marked by a broad and deep groove, divided by very thin septa into so many distinct sockets for the reception of the dental germs. The alveolar groove is closed at its free border by the membrane of the gum, which is stretched over a sort of thin, and, as it were, indented crest. This crest is formed by a tissue to which some anatomists have given the name of dental cartilage ; it is a pale, very strong fibrous tissue, and does not extend either upon the anterior or posterior surface of the bone, which are only covered by the mucous membrane, the gum being as yet confined to the alveolar border. The gingivjd fibrous tissue sends a pro- longation into each alveolus (alveola-dental periosteum), that forms a fibro-mucous sac upon Three different structures at least enter into the formation of the human teeth, viz., the ivory, the enamel, and the cortical substance. The ivory {a. Jig. 95) consists of a hard, transparent substance, traversed by numerous tubes, about -r^-^th of a hne in diameter, which commence by open orifices at the cavity of the pulp, and extend in an undulating, but nearly parallel direction, towards the surface of the ivory. In this course the tubes fig. 95. present secondary and smaller undulations, undergo a dichotomous division, diminish in size, at first gradually, then rapidly, give off numerous lateral twigs, and, finally, divide into extremely minute ramifications, of which some anastomose together, others commu- nicate with small irregular dilatations called calcigerous cells, situated in the transparent inter-tubular substance, while the remainder appear to be lost at or near the surface of the ivory. The cells and tubes both contain calcareous matter, and seem to be analogous to the corpuscles of bone and the ramified lines radiating from them. In human teeth the cells are very minute ; but in those of many animals they are much more distinct, and present a striking analogfy to the osseous corpuscles. The hard inter-tubular substance is not homogeneous, but, as may be clearly seen in young and growing teeth, is comjxjsed of fibres arranged parallel to the tubes, which ap- pear to have distinct parietes. It consists of animal tissue, combined with a large amount of calcareous salts ; and it is the scat of by far the greater proportion of the earthy matter contained in tlie ivory of the tooth. The enamel {b,fig. 95) is composed of hexagonal and transversely striated fibres, about x^th of aline in diameter, arranged parallel to each other, and applied by their internal extremities to numerous corresponding depressions on the surface of the ivory, a delicate intervening membrane serving to connect the two structures. Near the neck of the tooth, the enamel fibres rest almost perpendicularly, near the apex of the cro\vn, more or less obliquely upon the surface of the ivory ; moreover, they are often slightly waved or curved. Previously to the eruption of the tooth, each fibre contains an appreciable quantity of organic matter, which, at later periods, almost entirely disappears. The cortical substance (c,fig. 95) consists of a thin osseous layer developed on the ex- ternal surface of the fangs, and, as life advances, extending even into their interior, and encroaching upon the cavity of the pulp. It differs in no essential particular from true bone, containing the characteristic corpuscles, and anastomosing tubuli of that tissue. It has been found, also, on the fangs of the teeth of most mammalia, and of a few reptiles and fishes ; in some instances, direct communications have been discovered between the tubes of the ivory and the cells and tubuli of the cortical substance. The cement, or crusta petrosa, existing on the crowns of the compound teeth of the lower animals, also contains corpuscles and tubuli like those of bone, and may, per- haps, be regarded as an analogous deposite to the preceding, differing from it only in situation. From a perusal of the preceding summary, it will be seen that not only has much additional knowledge been acquired regarding the structure of the teeth, but that many of the statements of M. Cruveilhier must now undergo considerable modification. Thus, 1. The crusta petrosa bears no resemblance to the tartar of the teeth, which is merely a deposite from the saliva. 2. Even simple teeth contain a third element in their struc- ture, besides the ivory and enamel. 3. Instead of being inorganic Iwdies, the teeth are possessed of a complex organization, which, we may add, is uniform throughout each species, and often sufficiently characteristic to be of the highest utility to the zoologist, &c. 4. A remarkable affinity has been established between the teeth and bone, as far as regards the structure of the cortical substance and the ivory.] * [The earliest stage in the development of the teeth, described in the text, is that in which the dental pulps are situated at the bottom of closed sacs ; it has long been familiar to anatomists, and is now called the saccu- lar stage. A. condition antecedent to this, in which the future sacs are as yet open follicles, was first described by Arnold, but we are indebted to Mr. Goodsir (Edin. Med. and Surg. Journ., No. cxxxviii.) for the following connected history of the origin of the pulps and sacs of the temporary and permanent teeth : Origin of the Pulps and Sacs of the Temporary Teeth. — In the upper jaw of a foetus, about the sixth week, between the lip and a semicircular lobe constituting the early condition of the palate, is situated a denression of the form of a horseshoe. During the seventh week, this begins to be divided by a ridge (commencing from behind) into two grooves, of which the outer forms the recess between the lip andithe future external alveolar process, while the inner constitutes the primitive dental groove. The mucous membrane along the floor of this groove is then thickened, and from it a single papiUa is developed, and subsequently four others arise from the external lip of the groove, in either half of the jaw. In the mean time, membranous laminie projecting from the external lip, and at first only partially surrounding the papills, unite with similar but smaller processes from the internal lip, so that each papilla (p, 3, Jig. 97) becomes enclosed in a separate follicle {/, S,Jig. 97), com municating with the cavity of the mouth, and lined by its mucous membrane. The papilla now increase in size, and gradually assuming the form of the future temporary teeih, sink within the yet open follicles. At this period, the edges of the latter appear to be developed into opercula (0, 4, Jig- 97), which differ in number and arrangement according to the shape of the crowns of the different teeth, there being two for the incisors, three lur the canine, and four or five for the molars. The formation of the bony alveoli, by the development of an external and internal alveolar process, and of inter-alveolar septa, closely follows the jireceding changes in the soft parts. The order and time of appearance of these ten papil';K in the upper jaw are as follow : F rst, those of the 184 ODONTOLOGY. each follicle, perforated at the bottom of the socket for the passage of the dental vessels and nerves. As these prolongations or sacs are intimately connected to the gingival {Fig. 96, magnified three diameters.) anterior temporary molars during the seventh week ; of the canine teeth at the eighth ; of the central, and then of the lat- eral incisors, about the ninth ; and in the tenth week those of the posterior molars. The formation of the inter- follicular sep- ta, and the other changes in the papillae, follicles, and alveolar borders described above, proceed in the same order, and are completed about the thirteenth week. The condition of the tipper jaw at that period, constituting the end of the follicular stage in the development of the temporary teeth, is seen in Jig. 96, in which the follicles are shown as if held open ; the diagrams 1 to 5 in_^g'. 97, representing perpendicular sections across the jaw, may serve to illustrate the successive changes in the mucous membrane, from the commencement of the groove to the completion of the follicles. During the fourteenth week, a small crescentic depression (c, 5, Jig. 97) is formed immediately behind each of the folli- cles, the mouths of which are now closed by their opercula, but without adhesion ; the lips of the groove, -which at this time is called the secondary dental groove, are now applied to each other (6, fig. 97). With the exception of the ten depressions just mentioned, and a small por- tion situated beyond the posterior temporary molar follicle, adhesion of every part of the groove now takes place, proceeding from before backward. The follicles are thus converted by the fifteenth week into shut sacs is, T,fig. 97), while the enlarged papilla constitute the dental pulps (p, 7). The relation of the parts in this, the saccular, stage in the development of the temporary teeth, is represented at 7, fig. 97. Independently of a few subordinate differences, the changes in the lower jaw are similar, and occur in the same order, each step in the process being somewhat later than the corresponding one in the upper. Origin of the Pulps and Sacs of the Permanent Teeth.— It has been stated above, that during the general adhesion of the dental groove occurring at the fifteenth week, the part posterior to the second temporary molar follicle (in either half of the j-iw) still remains open ; in this situation, a papilla, sunk in an open follicle, ap- pears 'during the sixteenth week. At the twentieth, the fundus of this follicle is converted into a sac, and the papilla into the pulp of the anterior permanent molar tooth, which is thus the earhest to appear of those of the second set, and is farther characterized by being developed (like the papillae of the temporary teeth) from the primitive dental groove, and on the same level with them. At the end of this week the hitherto open portion of the groove is entirely closed by adhesion of its lips, but its walls still remain disunited, and a cavity is thus formed, situated between the sac of the anterior permanent molar and the surface of the gum ; this is the posterior cavity of reserve, from which the pulps and sacs of the second and third molars are subsequently developed. The ten depressions (c, 6) formed behind the follicles of the temporary teeth during the secondary condi- f^W i^ tion of the dental groove (6, fig. 97), in consequence of their escaping the general adhesion of its lips and sides, Fig. 98. Fig. 98.* are converted into as laany c#rities, called the anterior cav- ities of reserve (c, 7), whfch gradually elongate and recede into the substance of the gum. Pulps and folds (analogous to the opercula of the temporary follicles) are developed within them, appearing first in the anterior cavities ; and they eventually become the sacs of the ten anterior perma- nent teeth, assuming a position behind and above those of the miUc teeth in the upper, and behind and below them in the lower jaw (see? to \%fig- 97 ; aXso fig. 98, and a, figs. 101, 102), each occupying corresponding recesses {a, fig- 102) in the alveolar border. At this time, owing to the great relative increase in the size of the dental sans, that of the anterior perma- nent molar (a, i,fig- 98*) is forced backward and upward into the maxillary tuberosity of the upper, and intc the coronoid process of the lower jaw (a 2) ; and the large posterior cavity of reserve (6 2) is drawn in the same direction. At birth, the length of the alveolar border increases relatively, and this sac again sinks to a level with those of the temporary teeth (o 3). The cavity of reserve (6 3), having now resumed its former poaitioc DEVELOPMENT OP THE TEETH. 185 membrane, by pulling gently upon the latter we can raise the follicles from their recep- tacles, and completely lay bare the alveoli. The follicle or dental germ consists essentially of a membraiie, containing a sort of pe- diculated papilla, known as the bulb or dental pulp. 1. The membrane of the follicle, after having clothed the sac just described as lining the alveolus, is reflected upon the vessels and nerves which form the pedicle of the bulb, and appears to be prolonged upon the bulb itself : this, however, has not yet been demon- strated. The membrane of the follicle, therefore, resembles the serous membranes in forming a shut sac, the inner surface of which is free and smooth, and the outer adhe- rent. A transparent viscid fluid occupies the space between the bulb and the alveolar portion of the membrane. The following is the order in which the follicles of the first set of teeth appear. To- wards the middle of the third month of foetal life there are four distinct follicles in each jaw ; at the end of the third month a third follicle appears in each h£ilf of the jaw, and a fourth and a fifth towards the end of the fourth month. 2. Of the dental bulb. In the earliest stages the membrane of the dental follicle only contains a fluid, which is at first reddish, and afterward yellowish-white ; but towards the third month a small body makes its appearance, rising as a papilla from the bottom of the alveolus.* This papilla is abundantly suppUed with vessels and nerves, and pro- gressively increases in firmness and in size. A very thin pedicle, consisting of the den- tal vessels and nerves, affords attachment to it, so that it is suspended like a grape. This papilla, dental bulb, or pulp, gradually acquires the characteristic form of some par- ticular tooth, of which it presents an exact model, constituting the nucleus around which the tooth itself is deposited. The first part developed upon this papilla is the crown of the tooth, on which we already find indications of the various eminences and depressions subsequently exhibited by it. The development of the hard portion commences towards the middle of pregnancy. The production of the ossiform matter upon the surface of the bulb is eflfected by a pro- cess of secretion ;+ it begins by the deposition of some small laminae, or very delicate scales {I, Jig. 99), upon each projection of the pulp : they are at first pUable and elastic, but gradually become more consistent. These laminae or scales constitute so many formative points for the tooth, and have been compared to the points of ossification in bones. The incisor and canine teeth have only one scale ; the bicuspides have two, and the great molares as many as there are tubercles. These small scales so intimate- ly embrace the pulp upon which they are moulded, that it requires some force to detach them ; and yet their inner surface, as well as the outer, is very smooth. It should be remarked, that the pulp has a much more vividly red colour at the points covered by the scales. The scales are visible in the lower jaw at an earlier period than in the upper. The following is the order in which they appear : the middle incisors are visible from the fourth to the fifth month ; they are soon followed, 1 . By the lateral incisors. 2. By the first or anterior molar, which appears from the fifth to the sixth month. 3. At a short and shape, elongates backward, and a pulp is developed in its fundus, -whicli is converted before the fourth year into the sac of the second permanent molar. About the sixth or seventh year, the remaining part of the cavity once more elongates backward, and forms the pulp and sac of the third permanent molar, or wisdom tooth. Each of these sacs undergoes changes in its relative position in the jaws, similar to those experienced by the anterior permanent molar, at first receding backward and upward, and then descending behind, and on a level with the sac immediately anterior to it. From the preceding observations, it follows that the palps and sacs of both the temporary and permanent teeth have a common origin from the gastro-intestinal mucous membrane ; that a papilla is first formed, after- ward surrounded by and sunk into a follicle, which latter is then converted into a closed sac ; and hence the origin of the terms papillary follicular, and saccular, applied to these several conditions. It moreover appears that all the temporary teeth, and also the anterior permanent molar, originate from the primitive dental groove ; and that all the permanent teeth, except the anterior molar, are developed from cav- ities of resen-e commenced during its secondary condition. For an account of the changes occurring in the pulps aud sacs of the two sets of teeth during the saccular and eruptive stages, the reader may now refer to the text, remembering, however, that the term follicle is there applied to the entire dental germ in its saccular condition, consisting of a closed sac and its contained pulp.] * [The papilla of a temporary tooth appears even before the formation of the open follicle, and therefore long prior to its conversion into a shut sac. (See note, p. 183.)] t [The ivory is no longer regarded, by the best authorities, as a secretion from the surface of the dental pulp, nor the enamel as a similar product from the parietal layer of the lining membrane of the sac. A micro- scopic examination of these two structures in their perfect condition is, indeed, alone sufficient to throw con- siderable doubt on the old opinion adopted in the text. The researches of Schwann into their mode of devel- op-oient have again elucidated the subject. It has been observed that the globules in the centre of the dental pulp are primitive nucleated cells, analogous to those found in the early condition of all organic tissues ; that at the surface of the pulp these cells assuro« a cylindrical form and a perpendicular arrangement, but still con- tain nuclei ; that they adhere in places to the ossified scales, and correspond in size (not to the tubuli) but, to the fibres of the inter-tubular substance in a growing tooth. From these facts Schwann concludes that th« formation of the ivory, likethat of all other organized tissues, is effected by a metamorphosis of primitive nu cleated cells ; in other words, that it is developed by a progressive transformation and ossification of the superfi- cial cells of the dental pulp — a theory which recent observations in Great Britain would seem to have confirmed. Similar evidence is advanced by him to prove that the enamel is formed in a similar manner from the pulp^y enamel membrane, occupying the upper portion of the sac. The hexagonal fibres, of which the surface of this membrane consists, are, in fact, prismatic, nucleated cells, resting perpendicularly on a tissue, in which are other cells of a vesicular form. The hexagonal fibres correspond, therefore, both in form and direction, with those of the perfect enamel ; and, moreover, they are found to agree in size with the membranous remains of the enamel fibres of a growing tooth, after the removal of their earthy matter by means of a dilute acid.] Aa 186 ODONTOLOGY. interval from each other, by the canine and the second molar : the scales of all the teeth of the first set have made their appearance by the seventh month, according to the ob- servations of Meckel ; but at the eighth month, according to Blake. As development advances the scales enlarge, and gradually uniting (2, fig. 99), form a sheath or shell of ivory, which, during its growth, encloses the pulp, and, by degrees, ex- tends to the vascular and nervous pedicle at the part where it penetrates the alveolus.* The outermost sheath being formed, a second is deposited within it, then a third within that, and so on. The external surface of the bulb secretes the ivory. The enamel is formed from the parietal or alveolar layer of the follicular membrane : at the commence- ment of its formation it is so soft that, in a foetus at the full time, it can be very easily separated from the ivory. It has been asserted by some that the enamel, as well as the ivory, is the product of a secretion from the bulb, from which it has transuded in a liquid state through the different layers of the ivory, and has then solidified upon its surface ; others affirm that the enamel is a sort of crystalline deposite from the fluid surrounding the tooth ; but the greater number of anatomists admit, with Hunter, that the enamel is a product of secretion from the parietal layer,! as the ivory is from the layer of the fol- licular membrane, reflected upon the bulb. This opinion appears to me the more proba- ble, because, on examining with attention the parietal layer, we find on its inner sur- face, near the crown of the tooth, a sort of pulp, or very evident enlargement, particular- ly in the follicles of the molar teeth. This external pulp becomes atrophied as soon as the enamel is formed ; and hence the fang is not covered with enamel, although, after the eruption of the tooth, that part occupies the former position of the crown. This ex- ternal pulp does not exist in some of the dental follicles of certain animals, and we can- not, therefore, be astonished that such teeth have no enamel. Lastly, when this ex- ternal pulp remains after the eruption of the teeth, the secretion of the enamel also con- tinues, like that of the ivory. This is the case with the incisors of the rabbit and the beaver. In these animals the enamel occupies only the anterior surface of the tooth ; consequently, the edge alw&ys remains sharp, from the unequal wearing of the anterior and posterior surfaces. From what has been said concerning the phenomena of the formation of the pro vision- ary teeth before their eruption, we may draw the following conclusions : 1 . Of the two constituent parts of a tooth, viz., the corticle or hard portion, and the medullary portion or pulp, the latter is first developed ; and of the two distinct elements of the hard por- tion, viz., the ivory and the enamel, the formation of the ivory is first commenced. 2. The deposition of the cortical substance of the tooth begins at the crown ; the roots are not formed until a subsequent period. 3. The bulb being enclosed within the solidified products which it has furnished, diminishes gradually in size as these press upon it. Phenomena which accompany the Eru-ption of the First or Temporary Teeth. — At the time of birth all the teeth are still contained within their alveoli. Exceptions to this rule have been met with in cases where infants have been born with one or two teeth. If the anterior wall of the alveoli be removed at this time, the teeth will already be found considerably, but unequally developed, none having yet reached the bottom of the socket. But after birth, and at periods to be presently indicated, the extremity of the root having reached the bottom of the alveolus, and the farther growth of the tooth in that direction being impossible, it is effected in the direction of the gum, which is compressed, becomes inflamed, and is perforated ; this perforation, however, is not exclusively the result of distension, for the gum is but very slightly stretched when it opens ; and in other cases where it is greatly distended, as by polypi or other tumours, it is not lacerated at all. The tooth gradually rises, and the gum moulds itself successively upon the different portions of the crown, and, lastly, upon the neck of the tooth. The division of the gum is a severe process, but still it cannot altogether explain those serious symptoms which frequently accompany the first dentition. The eruption of the teeth does not take place simultaneously, but in succession, and in a regular order that admits of but few exceptions. 1. The teeth of the same kind ap- pear in pairs, one on the right side, the other on the left ; 2. The teeth of the lower jaw * [The vascular pulp of either a temporary or permanent tooth having more than one fang is, after tho formation of the crown, divided into as many processes by the advancement into it of the gray membrane of the sac. The dental substance still continuing to be produced on every part of the surface of the divided pulp., abridge of ivory is thus formed across the area of the cavity of the tooth between each process (3, 4,jf^. 99), (Ft^. 99.) around which separate fangs are subsequently developed (5, 6, 7), in the same mannpr ns that around the niK divided pulp of an incisor tooth.] ■• See note, p. 184. DEVELOPMENT OF THE 'JEETH. precede those of the upper in their appearance ;* 3. The middle incisors are cut before the lateral, these before the first molars ; after these come the canine, and then the sec- ond molars. The eruption of the first set of teeth commences towards the sixth month after birth, and terminates at the end of the third or the commencement of the fourth year. The middle lower incisors appear from the fourth to the tenth month, and, soon afterward, the upper middle incisors ; the inferior lateral incisors appear from the eighth to the sixteenth month, and then the superior lateral incisors. The first lower molars are cut from the fifteenth to the twenty-fourth month ; the lower canine from the twen- tieth to the thirtieth ; and the upper first molars and canine soon afterward. In some cases the eruption of the canine and the first molar teeth takes place simultaneously ; sometimes even the canine teeth take the precedence. The second great molars appear from the twenty-eighth to the fortieth month, and thus complete the twenty teeth of the first set. Second or Permanent Teeth. Phenomena which precede the Eruption.i — The second dentition consists of the eruption of the teeth called permanent, to distinguish them from the temporary teeth. They are thirty-two in number, so that there are twelve additional teeth in the second set. In this dentition, as in the former, we have to study the phenomena which precede, ac- company, and follow the eruption of the teeth. The follicles or germs of the second set of teeth correspond to the row of teeth already formed, bony septa intervening between them. They have the following relations with the follicles of the provisionary teeth : 1. The follicles of the additional teeth in the sec- ond set, viz., the last three molars, are situated in the same curve as the milk teeth, but they occupy, of necessity, the lateral extremities of these curves {Jig. 100). 2. The fol- licles of those teeth of the second set that replace others of the first are, on the contrary, situated precisely behind the teeth to which they correspond {a, Jigs. 100, 101, 102). These follicles are at first contained in the same alveoli as the temporary teeth ; but. after a certain time, septa are grad- Fig. lOO. ually formed between them, pro- _.^— -—f ceeding from the bottom of each alveolus towards its orifice (Jigs. 101, 102). Nevertheless, for a long time after the formation of these septa, the temporary (a"" a", Jig. 102) and the permanent ("b ^b) alveoli communicate by tolerably large or- ifices (c' c',Jigs. 101, 102), through which proceed the cords (c. Jig. 102) connecting the two teeth. The follicles of the permanent teeth do not sensibly difier in their mode of development from those of the provisionary teeth, only the increase of the vascular system of the former coincides with the progressive atrophy of the vessels of the latter. Phenomena which accompany their Eruption. — As long as the development of the per- manent teeth can be efiected in a direction towards the bottom of their sockets, the tem- porary teeth remain uninjured ; but when the growth of the permanent teeth influences their upper edges, the alveoli of the first set are compressed, and afterward destroyed at the parts corresponding to the crowns of the permanent teeth Fig. 101. (see^^. 101). After this time the alveoli of the first and sec- ond sets form common cavities : the roots of the milk teeth being compressed by the crown of the permanent teeth, under- go a loss of substance, become loosened, and may be detached by the slightest effort, each tooth being retained in its place only by the sort of ring formed by the gum around its neck. The shedding of the milk teeth is not always effected in the way we have described, viz., by a previous destruction of their root. Sometimes, in fact, the permanent tooth does not pen- etrate into the alveolus of the corresponding milk tooth ; but this alveolus is gradually wasted away by the constantly in- creasing development of the neighbouring permanent socket, teeth may fall without destruction of their roots, which, however, are then almost always slender, and, as it were, atrophied. Some compression, either exercised upon the pa- rieties of the temporary sockets, or upon the roots of the milk teeth, is almost indispen- sable for their expulsion. When, in fact, the permanent tooth deviates from its natural direfction, and, consequently, does not press upon the milk tooth, this latter remains, and forms a supernumerary tooth. We cannot, then, doubt the influence of this compression upon the fall of the milk teeth ; but anatomists are not agreed as to the immediate cause of the destruction of the temporary alveoli, and of the roots of the teeth contained within * [Although the papillae, it wiU be rememliered, appear earlier in the upper jaw.] t See note, p. 183, In this case, the milk 188 ODONTOLOGY. them. How does this compression act 1 Does it produce the fall of the milk teeth in a purely mechanical manner, or does it effect this indirectly by the destruction of the den- tal vessels and nerves 1 One author believes the latter to be the principal cause ; but what we have already said regarding the want of vitality in the teeth will abundantly prove that the wearing away of the alveolus and the milk tooth is the result of mechan- ical pressure. At the same time it should be observed, that, since the destruction of the roots of the milk teeth leaves no debris, a process of absorption must, therefore, be performed, the ex- citing cause of which is, undoubtedly, the compression above alluded to. It is not neces- sary, as some authors have believed, to assume the existence of a peculiar absorbent ap- paratus, appropriated to this office. The teeth of the first dentition are shed in the space comprised between the sixth and j^ JQ2 the eighth year, the fall of each tooth taking place in the same order as its ap- Kr'i^N ' ^1^ /\ pearance. Blake was the first to point out the existence of a cord (c. Jig. 102) passing from the follicle of the perma- nent tooth, along a small, long canal (c' c'), behind the alveolus of the milk tooth, and becoming continuous with the gum. It has been supposed that the canal, and the cord placed within it, were intended to direct the tooth during the progress of its eruption. Hence the name of iter dentis given to the canal, and guhernac- ulum dentis applied to the cord, which has been ingeniously compared by M. Serres to the gubernaculum testis. This cord appears to me to be solid,* not hollow ; it is very well marked in the incisor teeth, but forms a mere thread in the molars. Upon the whole, the influence exerted by the iter dentis and gubernaculum upon the direction of the permanent teeth during its erup- tion is by no means constant. Order of Eruption. — The first permanent teeth which appear are the first great molars ; they precede the other permanent teeth by a considerable interval, and immediately suc- ceed the milk teeth, coexisting with them for some time ; they have been, therefore, im- properly classed among the first set of teeth in some anatomical treatises. The first great molars are known by the vulgar name of seven years' teeth. The eruption of the permanent teeth takes place in the same order as that of the milk teeth. Below are sta- ted the periods at which each pair are protruded : Middle lower incisors from Middle upper incisors .... . . " Lateral incisors . •. " First small molar " Canine teeth " Second small molar " Second great molar " Third great molar " The greatest irregularity exists in the eruption of this last molar tooth, which is often wanting, and frequently remains, during the whole of life, either partially or entirely en- closed within the substance of the jaw. The incisor and canine teeth of the second set are much larger than the corresponding milk teeth. The opposite is the case with regard to the first two permanent molars, viz., the small molars, or bicuspides. It was ascertained by the inquiries of Hunter, that, in this way, there is such a compensation, that the twenty teeth of the first set occupy pre- cisely the same space as the twenty corresponding teeth of the second. This is not a purely speculative question, but one of singular interest in relation to the practice of ex- tracting the milk teeth. The truth of Hunter's assertion may be confirmed by measuring with a thread the space occupied by the twenty temporary teeth, and comparing it with the space occupied by the corresponding teeth of the second set. M. Delabarre has done this upon the same individual at the period of the two dentitions. Plienomena which follow the Eruption of the Permanent Teeth. — These relate, 1. To their growth ; 2. To their decadence. 1. Growth of the Teeth. — ^The teeth of man are not, like those of some animals, the ro- dentia in particular, susceptible of unlimited growth. The enamel of the crown wears away without ever being reproduced. All the facts brought forward in support of the idea of its reproduction are either erroneous observations, or may be interpreted in a different manner. Nevertheless, some changes take place in the interior of the tooth which are worthy of notice. New layers of ivory continue to be secreted; &nO the cavity of the * [Arising from the adhesion of the sides of the elongated part of the cavity of resene.l 6 to 8 years 7 " 9 8 " 10 9 " 11 10 " 12 11 " 13 12 " 14 28 " 30 DEVELOPMENT OF THE TEETH. 199 tooth is gradually encroached upon, and finally obliterated. Thus the teeth of the aged have neither pulp nor dental cavity. 2. Decadence of the Teeth. — The fall of the teeth in aged persons is the effect of a con- traction of the alveoli, produced in the following manner : The teeth are dependances of the buccal mucous membrane, and are, as it were, only accidentally placed in the alveo- lar borders, which, from the tonicity or elasticity of their bony tissue, have a constant ten- dency to displace them. In one word, the tooth is to the alveolus like a foreign body, of which it is incessantly tending to free itself This tendency to contract on the part of the alveolus is effectually resisted, so long as the root of the tooth has a tendency to in- crease towards the bottom of the socket ; but it acts with full force when this resistance ceases in consequence of atrophy of the pulp. Then the alveolus, shrinking upon it- self, expels the tooth by a mechanism similar to that by which, during the progress of syphilitic affections, the most healthy-looking teeth are displaced, solely in consequence of the vitality of the pulp being destroyed by the influence of the virus. The fall of the teeth in the aged is regulated by no law, either as regards the time or the order in which it is effected. Differences between the First and Second Sets of Teeth. — The teeth of the first dentition are distinguished from those of the second by the following characters : 1 . Their colour, instead of being white, like ivory, or clear yellow, is of a bluish or azure white hue. 2. The temporary incisor and canine teeth are always distinguished from the corresponding permanent teeth by their smaller size and the shortness of their roots. 3. The two mo- lars of the first set differ from the two small permanent molars or bicuspids which take their place, and approach nearer in character to the great molars ; from these, however, they are distinguished, by the shortness of their crowns, and by the number of tubercles on them, viz., five ; three on the outside, and two on the inside. 4. Comparative chem- ical analyses of the teeth of the two sets have shown that the milk teeth contain some- what less phosphate of lime than the permanent, and to this circumstance their greater susceptibility of change is due. General Observations. — From the description we have given of the teeth, it will be seen that these organs should be looked upon merely as large vascular and nervous papillae, covered by an unorganized calcareous sheath, which is formed by a species of crystalli- zation.* The diseases of the teeth offer nothing incompatible with this theory, for, with the exception of toothache, and the sensation of being set on edge, which are evidently seated in the pulp, the other alterations of which the teeth are susceptible are either me- chanical lesions, such as splitting, cracking, wearing, &c., or chemical changes, as the dry or moist caries, or, lastly, alterations appearing to have their seat in the hard sub- stance of the tooth, but which are really situated elsewhere. Of this nature are the in- crustations with tartar, the product of a vitiated secretion, attributed by several anato- mists, and especially by M. Serres, to some small follicles, the function of which, before the eruption of the teeth, is to produce a fluid to soften the gum preparatory to its perfo- ration by the teeth. Again, exostosis and spina ventosa of the teeth evidently depend upon irregular secretion of the enamel and ivory. The consolidation of fractures of the teeth is explained by the formation of new layers, resembling those which have been seen surrounding bullets in the substance of an elephant's tusk. Lastly, the coloration of the teeth, from the action of madder, is only observed in the layers deposited during its use, and therefore does not prove the existence of any nutritive process in these or- gans, such as takes place in bone. With regard to the evolution of the teeth in two distinct sets, it may be inquired what is the object of such an arrangement. Without entering here into the discussion of final causes, it cannot be denied that the second set of teeth would not accord with the com- paratively small size of the jaws in the foetus. Use. — 1. The teeth are the immediate agents of mastication. The incisors cut, the canine tear, and the molars grind the food, the position of each being regulated by the resistance they have to overcome. 2. The teeth form a kind of elevated border, which prevents the constant escape of saliva from the mouth. 3. They assist in rendering sounds articulate, by affording a fixed point to the tongue in the pronunciation of certain consonants, called by grammarians dental. 4. The teeth furnish important characters for zoological classifications. Indeed, as they bear a necessary relation to the mode of feeding in different animals, a circumstance that exercises so great an influence over their entire organization, it may easily be conceived that the fonn of the teeth is, to a certain extent, one of the characters by which a summary idea is conveyed of the nature of that organization. At the same time, it is necessary to guard against the evidently erroneous conclusions which some philosophers have delighted in deducing from the ar- rangement of the dental apparatus in man with regard to his fitness for a purely animal or exclusively vegetable diet. Above all, it should be remembered that the mechanical mgenuity of mankind must always form an indispensable element in the solution of every problem of this nature. * [It is necessary, in some degree, to modify this definition of the hard portion of the teeth, which, though extra-vascular, and, on that account, probably subject neither to interstitial absorption nor nutrition, cannot be regarded with propriety as unorganized or crystalline bodies. 190 MYOLOGY. MYOLOGY. The Muscles in general. — Nomenclature. — Number. — Volume and Substance. — Figure. — Di- rection. — Relations. — Attachments. — Structure. — Uses. — Preparation. — Order of Descrip- tion. The active organs of locomotion are called muscles.* They are composed of bundles of red or reddish fibres, consisting of fibrin as their basis, and possessing the essential property of contractility, that is, the power of contracting or shortening upon the applica- tion of a stimulus, t JVomenclature of Muscles The names applied to the various muscles have not been founded upon uniform prin- ciple. Before the time of Sylvius the muscles of any region (of the thigh, for example) were designated numerically, first, second, &c., in the order of their super-position or of their uses. Sylvius first gave particular names to the greater number of the muscles ; and he was followed by almost all succeeding anatomists, especially by Riolanus. In this nomenclature, which is still generally adopted, the names of the muscles are deri- ved, 1. From their situation, as radialis, ulnaris, peroneus, &c. ; 2. From their size, as glutaeus maximus, minimus ; palmaris longus, brevis, &c. ; 3. From their direction, £is rectus abdominis, obliqui capitis ; 4. From their shape, which is generally an imperfect representation, either of certain geometric figures, as rhomboideus, pyramidalis, and sca- lenus, or of well-known objects, as deltoideus, lumbrici, and soleus (from solca, the sole fish) ; 5. From their divisions or complications, as digastricus (from having two bellies), triceps (from having three heads), biceps, complexus, &c. ; 6. From their insertions, as stemo-hyoid, stemo-thyroid, &c. ; 7. From their uses, as flexors, abductors, &c. In modem times many attempts have been made to substitute in the place of these vague and generally arbitrary denominations, a uniform nomenclature, derived from the most important consideration, viz., the attachment of the muscles. The nomenclature of Chaussier, however, which is undoubtedly superior to all others, has not been adopt- ed ; first, because a knowledge of the old names cannot be neglected, since they are the only ones employed in a great number of works on medicine and surgery ; and, second- ly, because even the most imperfect denominations, when they have been long in use, are, from this circumstance edone, preferable to any new appellations. JVumber of the Muscles. Upon this point, likewise, authors are but little agreed. According to most, the num- ber of muscles is four hundred. Chaussier reduced it to three hundred. These differ- ences arise partly from the fact that the natural limits of the different muscles are not so well marked as those of the bones, for example, and partly because the grounds of de- marcation between the various muscles have not been sufficiently established. The fol- lowing rules may be adopted with advantage : 1. When a number of fasciculi unite, and form a mass, which is isolated both in its body and at its extremities, and fulfils distinct and determinate uses, such a collection should be considered a separate muscle. 2. A muscle should also be regarded as distinct when it is separated from others at one por- tion only of its body, and at the most movable of its attachments. On the whole, what- ever be the mode of demarcation adopted, it will be seen that the number of the muscles greatly exceeds that of the bones ; the reason of this is, that each bone acts as a lever in a great variety of movements, while each muscle acts only in a very limited number of motions. Volume and Substance of the Muscular System. Of all the systems of organs in the body, the muscular is predominant both in substance and in volume. This great mass of muscular apparatus is a necessary consequence of the unfavourable position of most of the levers represented by the bones. There is very great variety in different individuals, as regards both the volume and substance of the muscular system. Compare, in this respect, the glutaeus maximus of a robust man, and the same muscle in a thin, nervous individual, much emaciated, but yet in perfect health, for still greater differences are produced by disease : size and strength of the muscular system may also be natural or acquired, partial or general. Partial preponderance is most usuEdly acquired, and is commonly the result of exercise. To be convinced of this, it is only necessary to inspect the muscles of certain regions, in individuals whose em- ployment requires the special exercise of those parts. The preponderance of the mus- cles on the right side is produced solely by the habit of using this side more than the other ; it is not, as has been alleged, the result of congenital difference. Lastly, the size of one or the other region of the muscular system, in different anim£ils, * From nvi)V, a muscle, or /itij, a mouse. t It will be seen that, in constructing this definition, the only object has been to distinguish the muscles gen erally from other orgaas, by pointing out their two characteristic properties, viz., their fibrinous comnosition ■ad their contractility. FIGURE AND DIRECTION OF THE MUSCLES. 191 is in relation either with their instinctive propensities, their mode of feeding, or their natural attitude, or with some other important peculiarity in their organization. Hence we find, 1. In the lion, the tiger, and other carnivorous animals that tear their prey in pieces, the muscles connected with the inferior maxiUa, the most highly developed ; 2. In the bear, which is a climbing animal, the muscles of the back ; 3. In the hare, whose mode of progression is by successive leaps, the muscles of the hind limbs ; 4. The mus cles of the wing in birds ; and, 5. Those of the lower extremities and the vertebral grooves in man, to whom the erect position is peculiar Figure of the Muscles. The figure of the muscles is determined upon the foUoviing data : 1. From a compari- son of them with geometric figures or with famihar objects. 2. From the respective ar- rangement of their surfaces, edges, and angles. 3. From their being symmetrical or otherwise. In this latter respect there is a remarkable difference between the osseous and the muscular systems : many bones are symmetrical, or azygos, while almost all the muscles, on the contrary, are asymmetrical, and arranged in pairs. 4. From the relative proportion between their three dimensions ; from this latter consideration, muscles have been divided into three classes, viz., long, broad, and short, concerning each of which we shall make some general remarks. The long muscles are chiefly met with in the limbs. Their length is sometimes con- siderable ; and the longest are always most superficial. Very long muscles generally pass over several articulations, and can therefore assist in moving them all. This great length of certain muscles has also another advantage, viz., that it enables them to obtain a fixed point of attachment upon a less movable part, as the trunk, from which they can then act upon the more mobile parts : such is the case with the muscles that move the thigh or the leg. Long muscles are either simple or divided. Sometimes the division occurs at the more movable attachment ; sometimes at that which is habitually fixed. The broad muscles occupy the pjirietes of cavities ; they are quadrilateral when all their points of attachment are on the trunk, and triangular when they extend from the trunk to the extremities. When several broad muscles are super-imposed, the fibres of one always cross those of another at an angle ; and this arrangement, by forming a sort of interweaving, greatly augments the strength of the parietes which they assist in forming. This is particularly well shown in the broad muscles of the abdomen. The short muscles are generally met with in the same situations as the short bones. It is not the shortness of its fibres, but of its fleshy body that characterizes a short mus- cle. It is important to notice, with regard to these muscles, that a number of them are often arranged in succession, so as to resemble a long muscle. Of this we shall find many examples in the muscles of the vertebral grooves. Direction of the Muscles. The direction of the muscles is one of the most important points in their history, since, without a knowledge of this, it is impossible to appreciate their uses. Each muscle has an axis or middle line, in which the general action of its fibres takes effect. Few mus- cles are altogether rectilinear ; most are angular or curved ; and almost all undergo cer- tain deviations or reflections in passing round the joints : some, indeed, take a direction at right angles to their primitive course, when they pass over pulleys or hook-like pro- cesses. In muscles of this kind the action is in the direction of the reflected portion. The direction of muscles must be studied with reference to the axis of the body, but especially to the axis of the limb or lever, in relation to which they represent the moving power. Many muscles are almost parallel to the axis of the lever upon which they act ; but it should also be remarked that, in certain positions, these same muscles form great- er or smaller angles with their corresponding levers, and may even become perpendicu- lar to them. In this respect the direction of the muscles is not absolute, but is subordi- nate to the position of the levers. Some muscles are constantly perpendicular to the levers upon which they act. The angles of incidence of the muscles upon their points of attachments are very va- riable, but generally they are more nearly parallel than perpendicular to those points. As the axis of a muscle is not the same as that of its component fibres, it is necessary to study, in each muscle, not only the direction of the fleshy beUy, but that of the fibres also. Relations or Connexions of the Muscles. In reference to surgery, the relations or connexions of the muscles are among the most important circumstances in their history. Relations of the Muscles to the Skin. — Those muscles only which are called cutaneous are immediately connected with the skin ; the remainder are separated from it by apo- neuroses of greater or less density, so that the skin does not participate in the move- ments of the m.uscles, and vice versa. Nevertheless, the changes produced in the form and size of the muscles during their contraction are so decided, that those which lie near the surface are more or less defined through the integuments ; but the projections 192 MYOLOGY. corresponding to the bodies of the muscles and the depressions at their attachments are, in a measure, obliterated by adipose tissue, the quantity of which varies in the two sexes and in different individuals. To this latter circumstance are due the differences in the outward characters of the muscular system of the female, as compared with the male ; and of a fat individual, as compared with the one who is emaciated. Relations of the Muscles to the Bancs. — In the limbs where the muscles form several par- allel layers around the bones, the belly or thickest part of the muscle always corresponds with the shaft or most slender portion of the bone ; while the ends of the muscle, where it is thinnest, correspond with the expanded extremities of the bone. The relations of the bones with the muscles vary, according as the latter are deep-seated or superficial. The superficial are only in contact with the bones by their extremities or their tendons the deep-seated muscles alone correspond to the bones by their entire length. Relations of the Muscles to each other. — The muscles are arranged upon each other in successive layers ; each muscle is covered by a sort of fibro-cellular sheath ; and a loose and moist cellular tissue is interposed between the different sheaths, so as to facilitate the gliding movement and independent contraction of each muscle. This isolation of the muscles does not exist throughout their entire length ; several are often blended together in one conunon insertion, from which they proceed as from a centre, afterward separating from each other. This community of attachment is principally observed in those muscles that perform analogous offices, or that, usually at least, act simultaneously. Most muscles are enclosed in a separate fibrous sheath, which isolates them in their actions, and also in their diseases. Of this we shall find remarkable examples in the rectus abdominis and sartorius. With regard to the relations of their edges, the muscles are sometimes contiguous throughout their entire course, and sometimes separated by intervals, generally of a triangular figure ; and principally important in surgical anatomy, because incisions, for the exposure of vessels, are almost always made in such intervals. Relations of Muscles to the Vessels and Nerves. — The muscles serve to protect the ves- sels and nerves, not only in consequence of the thickness of the layers which they form in front of them, but also by the resistance they oppose during their contraction to ex- ternal violence. Near the centre of a limb there is generally a considerable cellular in- terval between the muscular layers, which is intended for the principal vessels and nerves. The existence of such spaces prevents the injury which these vital parts would sustain from compression during the contraction of the muscles. It is also worthy of notice, that whenever a vessel passes through the body of a muscle, we find an aponeurotic arch or ring, which is non-contractile, and in some degree, therefore, obviates the danger of compression during the action of the muscular fibres. I say in some degree, because, in order to render compression of the vessels impossible, the muscular fibres attached to these rings must have proceeded from them as from a centre, diverging in all directions. In this case, the action 5f the muscles would not change the form of the rings, but would tend to increase their diameters in every direction. It is found, however, that they are invariably elongated in one direction and diminished in another, when the fibres of the muscle contract. Bernouilli, indeed, has shown that it is impossible to change the form of a circle, by making one of its diameters greater than the others, without, at the same time, diminishing its capacity ; because, within a given periphery, the most regular fig- ures have the greatest capacity, and the circle is more regular than either the oval or the ellipse. On the whole, however, it must be understood that the contraction of the fibrous rings does not, in any material degree, impede the circulation. It should also be remarked, that a distinct fibrous sheath surrounds the vessels and the nerves, serving to isolate and protect them amid the various muscles by which they are surrounded. Most of the arteries have accompanying muscles, which may be called their respective satellites : thus, the sartorius is the satellite muscle of the femoral artery, the biceps of the brachial, the stemo-mastoid of the carotid, &c. Attachments or Insertions of Muscles. The attachments or insertions of muscles constitute one of the most important points in their history, and one which requires to be studied with the greatest care, because the uses of a muscle can be determined from a knowledge of its insertions alone. These insertions should be considered in two points of view : 1. As to the direct insertion of the muscular fibres into the tendons, aponeuroses, or other structures ; 2. As to the in- sertion of the tendons and aponeuroses into the levers represented by the osseous system. The muscular fibres themselves are attached, 1. To the skin, of which mode there are numerous examples in the muscles of the face ; 2. To other muscular fibres, as in many muscles of the face and of the tongue ; 3. To cartilages, as in several of the muscles of the chest and larynx ; 4. To aponeuroses, of which they act as tensors, and whose power of resistance they thereby increase; lastly, to tendons or aponeuroses,* that are them- selves attached to the bones. The fleshy fibres are inserted into, or become continuous with, the tendons and apo- * [The tendons afford examples of the fascicular form of fibrous tissue, for a notice of which see note, tn/jd.) ATTACHMENTS AND STRUCTURE OF MUSCLES. 193 neuroses in the following manner : Tlie tendon is prolonged under the form of a mem- brane, either upon the surface or in the substance of the muscle. The results of this arrangement are, 1 . An increase of surface for the attachment of the muscular fibres, which the tendon gathers up, as it were, in order to concentrate their efforts upon one point ; 2. An obliquity in the insertion of the fibres, in reference to the axis of the entire muscle, by which the direction of the power is represented. It may easily be conceiv- ed that this obliquity is of the greatest interest as regards the dynamic relations or ac- tive property of the muscles.* One of the most curious circumstances respecting the continuity of a tendon or an aponeurosis with a muscle is the very intimate union between the muscular and fibrous tissues, which is so complete that they are scarcely ever separated by external violence, which, moreover, tends to lacerate the muscle rather than the tendinous fibres. It is a fact worthy of notice, and one which we have already had frequent occasion to remark, that the adhesion of any two organic tissues is stronger than the respective co- hesion of each ; so that the tissues themselves will sooner break than admit of separa- tion from one another. Insertion of the Aponeuroses and Tendons into the Bones. — A tendon or an aponeurosis forms a species of ligament, by means of which the action of a very large muscle is transmitted to the lever intended to be moved, by a fibrous cord or aponeurotic lamina of small size. A great advantage arises from this mode of economizing the extent of bony surface required for muscular attachments ; for, notwithstanding the extent of surface afforded by the expanded ends of the bones, and by the eminences and ridges with which they are covered, it would be evidently insufficient, were the muscular fibres to be directly attached. The existence of tendons and aponeuroses produces also this remarkable result, viz., that the muscular insertions are much stronger than they would otherwise have been. The aponeurotic tissue acts as a transition structure, being in some points of its organi- zation analogous to bone, and in others approaching that of muscle. The analogy be- tween the bony and fibrous tissues is confirmed by the frequent occurrence of ossifica- tion in the latter, even under normal conditions, as may be observed in the formation of the sesamoid bones, and also in the mode by which tendons are attached. It has been observed, in fact, that at the point of junction of the tendons with the bones there is a sort of mutual fusion of the tissues, from which so intimate a connexion results, that the proper substance of the tendons always gives way before they can be separated from the bones, their attachments to which even maceration will scarcely destroy. Of the different bones with which a muscle is connected, some remain immovable du- ring its contraction, while others are put in motion ; hence the distinction between Jixed and movable attachments. But this eminently useful distinction must not be taken in an absolute sense ; it is only rigorously true of a very small number of muscles, which, like some of those found in the face, being connected by one extremity with the skin, and by the other with the bones, can give rise to movements only at their cutaneous at- tachments. In the greater number of muscles, on the contrary, although one of the at- taclunents is most commonly fixed and the other movable, yet their relative condition may be changed, and they may become alternately fixed and movable ; it is therefore necessary, in explaining the action of a muscle, carefully to notice the supposed mobility or fixedness of the different attachments at the time. In comparing such attachments as are habitually fixed with those that are constantly movable, we shall observe that the former are either numerous or spread out by means of aponeuroses, whereas the latter consist of very accurately-circumscribed tendons. The figurative expressions of head and tail, given to the §nds of a muscle, refer to this arrangement. The fixed attachment of a muscle is usually blended with those of several others, while the movable one is distinct.! In order to facilitate our description, we shall invariably designate the fixed attachment of a muscle, its origin, and the movable attachment, its termination or insertion. Structure of Muscles. Muscles are composed of two kinds of fibres : 1. Of red or contractile fibres, wYiich form the muscular tissue properly so called ; 2. Of white, strong, and non-contractile fibres, con- stituting the tendons and aponeuroses. In speaking of the ligaments, we mentioned the general properties of tendons and aponeuroses as belonging to the fibrous tissues ; we shall now make a few remarks on the peculiar characters of muscular tissue. 1. Colour. — Muscular tissue is of a reddish colour, the intensity of which varies in dif- ferent muscles and in different individuals. This colour is not an essential character even in the human subject, for the contractile fibres of the intestinal canal are very * In fact, as the tendon, and the aponeuroses by which it is continued into the muscle, represent the direc- tion of the power, the fleshy fibres must necessarily be attached to it more or les.s obliquely. It is not our in- tention to examine here the great loss of power which this arrangement involves. t [This assertion must be taken with some limitation. We shall find many exceptions to this general rule, (S we proceed in the description of the muscles.] Bb 194 MYOLOGY. pale ;* still less is it so in the lower animals, some of which have the entire muscular system perfectly colourless. The red colour of the muscular fibre is independent of the blood contained within the vessels of the muscle. 2. Consistence. — The consistence of the muscular fibres varies in different subjects . in some it is soft and easily torn ; in others it is firmer and more resisting, and retains for some time after death a degree of rigidity which yields with difficulty to forcible ex- tension. Structure. — The muscles may be divided into bundles or fasciculi of different orders, and these, again, into distinct fibres, which are visible to the naked eye, and rendered more apparent, either by dissection, or by the action of alcohol, of diluted nitric acid, or even of boiling water. They are of a variable shape, resembling prisms of three, four, five, or six surfaces, but are never cylindrical. Their length also varies in different muscles, in but a few of which do they extend parallel to each other tliroughout the en- tire length of the fleshy belly. Each muscle is surrounded by a sheath of cellular tissue, which also penetrates into its substance, and surrounds both the fasciculi and fibres. This cellular tissue permits the free motion of the different fasciculi upon one another, while it serves, at the same time, to isolate each and combine the whole. + The chemical analysis of muscular tissue shows that it is composed of a small quan- tity of free lactic acid (Berzelius) ; gelatin ; some salts ; osmazome in greater or less quantity, according to the more or less advanced age of the individual ; and leucine, a substance extracted from this tissue by the process described by M. Braconnot. {Ann. de Chim. et de Phys., tom. viii.)t In addition to the tendinous and fleshy fibres, vessels, nerves, and cellular tissue also enter into the composition of muscles. We have already described the disposition of the cellular tissue contained in these organs ; the mode of distribution of their vessels and nerves will be more appropriately alluded to in the description of the vascular and ner- vous systems.^ Uses of Muscles. The muscles are the active organs of motion, constituting the source of the power * [The involuntary muscular tissue, of which the above-named fibres afford examples, are, v»ith the excep- tion of the heart, of a much paler colour than the voluntary muscles, to which this division of the present work exclusively refers.] t [In reference to the microscopic structure of the voluntary muscles, or those of animal life, it has been ascertained that the smallest fasciculi (corresponding with the prismatic fibres of our author, and with the secondary fasciculi of Miiller), the size of which varies in different muscles, are divisible into transversely-slri- ated fibres (the primitive fasciculi of Miiller), having a uniform diameter in all muscles in the same species, and being themselves composed of still smaller elementary parts named _/t?amcn<* (the primitive fibres of Miil- ler). All these elements of the muscular tissue extend parallel to each other, from one tendinous attachment to another, never having been seen to bifurcate or coalesce. In man the fibres vary from y^o^th to -g-^Tfth of an inch in diameter ; the transverse striae upon them are parallel, generally straight, but occasionally slightly waved or curved ; they are situated at intervals of from The filaments are varicose or beaded, i. e., alternately enlarged and contracted ; their diameter is from _ ' th to y-f^^nTr''^ °f *" inch. According to the general opinion, they are held together in each fibre by means of a glutinous substance, which latter, according to Skey, constitutes the entire centre of the fibre, the circumference alone being occupied by the filaments. In the larvae of insects, a delicate membranous sheath, sometimes observed projecting beyond the filaments, has been described by Schwann as forming a proper in- vestment of the fibre ; and, by analogy, this is also presumed to exist in man and the other vertebrata. Be this as it may, it is certain that the fibres have no separate sheaths of cellular tissue derived from the common sheath of the muscle, the prolongations of which appear to extend only so far as to enclose the smallest fasciculi. The cause of the striated appearance has, perhaps, not been quite satisfactorily ascertained ; but since the enlargements on the varicose filaments are darker than the constricted portions, and since they are situated at intervals precisely similar to those between the transverse strios of the corresponding fibre, and from some other additional considerations, it has been supposed, with great probability, to result from the enlarged and dark portions of the filaments being arranged side by side. For an account of the microscopic characters of the involuntary or organic muscular fibres, see the notes ot the structure of the several viscera, &c., in which they are found, viz., the alimentary canal, trachea, genito- urinary organs, and iris. We may remark here, that the muscular fibres of the heart and of the upper part of the oesophagus are striated, and approach very closely in character to those of animal life.] X [The following analysis of the muscles of the ox is on the authority of Berzelius ; Water 77-17 Fibrin (with vessels and nerves) 15.8 Cellular tissue convertible into gelatin 1 '9 Albumen and colouring matter 2'2 Alcoholic extract, or ozmazome, with lactic acid and lactates 1 '8 Watery extract, with phosphate of soda 1'05 Phosphate of lime -08 100- The inadvertent omission, on the part of M. Cruveilhier, oi fibrin as one of the proximate principles of mus- cle, will serve to impress on the mind of the reader its importance as a constituent of that tissue, in which it exists in greater abundance than in any other. The substance called leucine, mentioned in the text, is a product resulting from the action of concentrated sulphuric acid on muscular fibre, and therefore must not be regarded as previously existing in it.] ^ As it is our intention to introduce, after Myology, an account of the Aponeuroses, we shall be content at present with the general ideas that have been already stated regarding this important division of the fibrous tissues. USES OF MUSCLES. 195 that is applied to the various levers represented by the component parts of the skeleton. The movements produced are the result of that peculiar property possessed by the mus- cles of shortening themselves, which is called muscular contractihiy {myotiliti). The shortening of a muscle is termed its contraction, and the opposite state its relaxation. Phenomena of Muscular Contraction. — During contraction the muscular fibres become folded in a zigzag manner throughout their entire length ; the muscle itself becomes hardened, and broader and thicker in proportion to the amount of shortening. There is no oscillation in a muscular fibre during a normal contraction.* The aponeuroses and the tendons take no part in the contraction ; they are entirely passive. The degree of shortening of which the muscular fibre is susceptible cannot be precisely determined ; as far as we know, the shortening, and, consequently, the ex- tent of the resulting movement, is proportional to the length of the fibre. A distinction should be drawn between the force and the velocity or rapidity of muscular contraction. Again, the velocity is very different from the extent of motion : the latter depends upon the length of the fibres ; the former has no connexion with it, but varies according to the constitution of the individual, and is probably dependant on a more or less rapid influx of nervous influence. The muscular force is composed of a great number of elements. According to Borel- li, an intrinsic and an effective farce may be distinguished in each muscle. The in- trinsic force is that power which the muscular fibres would exert if they were in the most favourable position for contraction : the effective force is measured by the result. The estimation of the force of a muscle presupposes a knowledge, 1 . Of the number of its fibres. 2. Of ther quality or constitution. 3. Of the nature of the lever upon which it acts. 4. Of the angle of incidence of the muscle upon that lever ; and, 5. Of the angle of incidence of the fibres with respect to the imaginary axis of the muscle. 1. Each muscular fibre, being distinct from those around it, may be considered as a small power ; it may, therefore, be eeisily conceived that the greater the number of fibres in any muscle, the more energetic will be its contraction. 2. The quality and constitution of the fibre, and the intensity of the stimulus, have no less an influence upon the contractile force of a muscle than the number of its fibres. To be convinced of this, it is sufficient to compare the energy of movement in an individual excited by anger with that in one who is C2ilm. 3. The determination of the kind of levert represented by the bone upon which the muscle acts, is a fundeimental point in studying muscular action. It is a law in mechan- ics, that the power acts with greater effect in proportion as its arm of the lever exceeds in length that of the resistance. The most common lever in the human body is that of the third order, in which the power, being applied between the fulcrum and the weight, is therefore most disadvantageously situated for action. 4. As far as regards energy of movement, the lever to which the power is applied is as unfavourable as possible, because the muscles are generally inserted near the fulcrum. * The observations of Rogerus tend to show that rapid contractions and relaxations are cotutantly takiiig place in muscles, especially during their contraction. — (TV.) " Be Peri)etua Fibrarum Muscularium Palpitatione," 1760. Fig. 103. t A lever, in mechanics, signifies an inflexible rod capable of turning round a point. The point upon which the lever turns is called the /ui- crum if, figs- 103, 104, 105) ; the cause of motion is called the power (p) ; and the obstacle to be surmounted is the resistance (r) ; the space be- tween the fulcrum and the power is the power-arm of the lever ; the space between the fulcrum and the weight is the resistance-arm of the lever. There are three kinds of levers, distinguished by the respective arrange- ment of the three parts : 1. A lever of the first order {fig. 103) has the ful- crum between the power and the resistance. 2. A lever of the second or- der (fig. 104) has the resistance between the fulcrum and the power. 3. A lever of tlte third order {fig. 105) has the power between the resistance and the fulcrum Fig.lOi. 196 MiULoGV, But, as a sort of compensation, an advantage peculiar to animal mechanics, the motions gain in velocity and extent what they lose in force, which, however, may still be obtain- ed by an increase in the number of muscles, and of the fleshy fibres of each muscle. Nevertheless, levers of the most favourable construction, and of the most advantageous position, are met with in situations where considerable force is required ; as in the ar- ticulation of the foot with the leg, presenting an example of a lever of the second order ; and in the articulation of the head with the vertebral column, forming a lever of the first order. The angle of incidence most favourable to the power is the right angle ; but in the hu- man body, as the muscles are arranged in layers upon the bones which they are intend- ed to move, they are for the most part inserted at very acute angles. Their incidence would be still more unfavourable were it not for the enlargement of the articular ex- tremities of the bones, which disturb the parallelism of the muscles. Besides, in certain cases, the angle of incidence more or less approaches, or even attains to a right angle, and is combined with an extremely advantageous lever, when such an arrangement is required : a& in the articulation of the foot with the leg. It is of importance to notice, in determining the action of a muscle, that its incidence upon the bone varies at different periods during its action ; so that a muscle which is eilmost parallel to the lever when it begins to contract, becomes perpendicular to it at a given moment during that process. It maybe said that the momentum of a muscle occurs at that period of its action when its perpendicular incidence gives it the utmost energy of which it is capable : thus, the momentum of the action of the biceps femoris takes place when the leg forms a right angle with the thigh. In a certain number of muscles the momentum coincides with the commencement of action, such as the gastrocnemii and the solei. In some muscles the angle of incidence remains the same throughout the whole time of their action, and, consequently, they have no momentum : this is the case with the deltoid. The angle of incidence of the muscular fibres, with regard to the imaginary axis of the muscle or the terminating tendon, involves a loss of power proportional to the amount of the angle. In some muscles the aponeuroses form a continuation of the fleshy fibres ; in others, the angle of incidence of the muscular fibre is so acute that it may be left out of consideration. Estimation of the Action or Uses of the Muscles. — Since the contraction of a muscle con- sists in its shortening, it follows that its action may be determined, a priori, from a knowledge merely of its attachments and direction. It may also be ascertained experi- mentally, by placing a limb in such a position that the muscfe in question shall be per- fectly relaxed. As the same muscle generally performs several uses, it is necessary to place the limb in several different positions, so as to determine those in which the mus- cle becomes relaxed. Let us take, for example, the glutaeus maximus. If we desire to relax this muscle completely, it is necessary, 1. To extend the thigh upon the pelvis. 2. To abduct it. 3. To rotate it outward : hence it follows that the glutaeus maximus is at once an extensor, an abductor, and a rotator outward of the thigh. As a counter- proof, the limb must be placed in such a condition that the muscle becomes completely stretched. The successive positions in which a muscle becomes stretched will be the very reverse of those which the limb assumes during the contraction of the muscle. Thus, the glutaeus maximus is slightly stretched by rotation inward, more so by adduc- tion, and most completly by flexion of the thigh upon the pelvis. In determining the action of a muscle that is reflected over any angle of a bone, it is necessary to put out of consideration all that portion of the muscle intervening between its origin and its angle of reflection, and to suppose the power to operate directly from the latter points. The action of sphincter muscles is to close the orifices around which they are placed. A curvilinear muscle assumes a rectilinear direction at the very commencement of its action. The insertions of a muscle are neither equally fixed nor equally movable. The fixed • point of a muscle is that extremity which remains immovable during contraction ; but, in certain cases, the fixed may become the movable point : this must be taken into consider- ation in determining the action of a muscle. The fixed point is most commonly that which is nearest to the trunk. But, with few exceptions, it is never completely station- ary ; and since a muscle would lose much of its power when acting between a movable and an imperfectly fixed point, it is necessary that the latter should be kept as immova- ble as possible by the contraction of other muscles. These consecutive contractions are often very extensive, and should be familiar both to the physician and the physiologist. When a muscle passes over several articulations, it moves them all in succession, commencing with the one nearest to the movable insertion. Those muscles which concur in producing the same motion are called congenerous ; those which execute opposite movements are termed antagonists : thus all the flexor muscles of any region are congenerous, and they are antagonists to the extensors. Two muscles may be congenerous at one time, and act as antagonists at another : when they contract simultaneously, their individual and opposite effects are destroyed. PREPARATION, ETC., OP MUSCLES. 197 and a common and intermediate effect results ; thus, when the flexor carpi ulnaris, which is both an adductor and a flexor, acts in conjunction with the extensor carpi ulnaris, which is an adductor and extensor, the hand is neither flexed nor extended, but is mere- ly adducted. We shall constantly have occasion to notice this arrangement, which ap- pears to me calculated to give much greater precision of motion than if two perfectly congenerous muscles had been employed. There are also certain compound motions, which are, as it were, the results of two different movements ; thus, when the flexors and the adductors of the thigh act simul- taneously, the femur passes in the intermediate direction. It is from this kind of com- bination that the movement of circumduction is produced by the action of the four orders of muscles situated at the extremities of the antero-posterior and transverse diameters of the joint. These four orders of muscles are known by the names oijlexors, extensors, adductors, and abductors. Lastly, muscles may contract without producing any motions, as when antagonist muscles act with equal energy. The result of such a simultaneous contraction is an active immobility or tonic movement, as the older WTiters termed it, which is of very great importance. Preparation of Muscles. Dissection. — The end to be attained in the dissection of a muscle is to isolate it accu- rately from all the surrounding parts, leaving only those connexions which are compat- ible with that object. Since, however, it is sometimes impossible to preserve the rela- tions, and at the same time isolate the muscle, it then becomes necessary to be provided with two preparations for the demonstration or study of the same muscle. In order to isolate a muscle, the surrounding cellular tissue, which often forms a very adherent sheath, must be removed ; and to do this completely, 1. Make a section of the skin parallel to the fibres of the muscle, deep enough to reach the muscle through the sheath; 2. As soon as the flap of skin can be grasped by the hand, stretch and separ- ate it from the muscle by cutting with the scalpel in the angle formed by these two parts ; 3. When the superficial surface is exposed, proceed to separate the deep surface, preserving as much as possible all its important relations ; 4. Then dissect the extrem- ities, marking out their limits with the greatest care. In the study of the muscular system, great importance should be attached to the choice of subjects. Robust and tolerably fat subjects are best adapted for this purpose. Preservation of Muscles in Liquids. — Alcohol, oil of turpentine, a mixture of equal parts of these, or solutions of the bichloride of mercury, or persulphate of iron, may be em- ployed for the preservation of muscles, though they alter many of their properties, such as their colour, consistence, &.c. Preparations by Desiccation. — As this kind of preparation requires a peculiar method, we refer to the special treatises upon anatomical preparations for an account of them. (Vide the works of MM. Marjolin arid Louth.) Order of Description of the Muscles. Before passing to the description of the particular muscles, it is necessary to deter- mine in what order they shall be studied. Galen divided the body for this purpose into regions, and described the muscles of each in their order of super-imposition. In place of this arrangement, which is purely topographical, Vesalius substituted a physiological one, founded upon a consideration of the uses of the muscles. This order was adopted by Winslow, who named the different muscular regions in the following manner : 3fus- cles which move the shoulder upon the trunk ; muscles which move the arm upon the scapula, &c. Albinus revived the method pursued by Galen, and divided the muscles into forty- eight regions in the male and forty-six in the female. He was followed by Sabatier, and by Vicq-d'Azyr, who brought the arrangement to perfection by establishing some sub- divisions in the groups formed by Albinus. Thus modified, it has been adopted by most modem anatomists. It is evidently preferable in many respects, since it is essentially anatomical, and is best calculated to exhibit the relations of the different muscles and regions. In regard, also, to economy of subjects and facility of dissection, it has many advantages over the physiological order, with which, however, in many regions it may be made to coincide. We shall, therefore, adopt this arrangement, modifying it so far as to permit all the muscles to be dissected upon one subject ; and, aft;er having descri- bed all the muscles according to their topographical relations, we shall give a table in which they will be grouped in a physiological order. 198 MYOLOGY. MUSCLES OF THE POSTERIOR REGION OF THE TRUNK. TTie Trapezius. — Latissimus Dorsi and Teres Major. — Rhomboideus. — Levator AnguR Scapula. — Serrati Postici. — Splenius. — Posterior Spinal Muscles. — Complexus. — Iriter- spinalis Colli. — Recti Capitis Postici, Major et Minor. — Obliqui Capitis, Major et Minor, — General View and Action of the Posterior Spinal Muscles. The muscles situated on the posterior region of the trunk form several layers, which, proceeding from the skin to the bones, consist, on either side, of the trapezius, the latis- simus dorsi and teres major, the rhomboideus and levator anguli scapulae, the serrati postici, superior and inferior, the splenius, the long muscles of the back, viz., the sacro- lumbalis and longissimus dorsi ; the transversalis colli and the complexus (which I re- gard as two series of accessory fasciculi to the longissimus dorsi) ; the complexus ma- jor, the inter-spinales colli, the recti capitis postici, major et minor, and the obliqui .capitis, major et minor.* The Trapezius. Dissection. — 1. Render the muscle tense by placing a block under the chest ; 2. Make an incision through the skin from the occipital protuberance to the twelfth dorsal verte- bra, and another horizontally from the seventh cervical vertebra to the external end of the clavicle ; 3. Reflect the two flaps, together with the cellular membrane adhering in- timately to the muscle ; 4. Dissect very carefully the insertions into the occipital bone, which consist of a very thin aponeurosis closely united to the skin. The trapezius (cucuUaris, Alhinus, a, figs. 106, 113), the most superficial muscle on the Fig. 106. posterior region of the trunk, covers the nape of the neck and the back. It is a broad triangular, rather than trapezoid muscle, thick in the mid- dle, thin and elongated at its supe- rior and inferior angles. Attachments. — It arises from the spinous processes of all the dorsal and the seventh cervical vertebrae, from the corresponding supra-spi- nous ligaments, from the posterior cervical ligament (ligamentum nu- chae;, and from the internal third of the superior occipital line, and is in- serted into the entire length of the spine of the scapula, into the poste- rior border of the acromion, and into the external third of the posterior border of the clavicle. The fixed attachments or origins of this mus- cle present, 1. A broad, semi-ellipti- cal aponeurosis, which, when united to the one on the opposite side, forms an ellipse, occupying the space be- tween the sixth cervical and the third dorsal vertebrae ; 2. A very thin fibrous lamina, not having the ordi- nary shining appearance of an apo- neurosis, which is firmly adherent to the skin, and forms the truncated occipital angle of the muscle ; 3. A great number of tendinous fibres, constituting all those attachments to the vertebrae that are independ- ent of the two preceding aponeuro- ses. From these origins all the fleshy fibres proceed outward, the inferior fibres from below upward, the superior from above downward, and from behind forward, and the middle ones horizontally. They terminate in the following manner : the lower or ascending fibres are collected together, and at- tached to a triangular aponeurosis, which, gliding over the small facette at the internal extremity of the spine of the scapula, is inserted into the tubercle immediately connect- ed with it ; the middle or horizontal fibres terminate at the posterior border of the spine of the scapula, by tendinous fibres which are very distinct, especially towards the acro- * [The transverso-spinalis muscle includes the semi-spinalis colli, the semi-spinalis tlorsi, and the multifidiu iminse of Alhinus.] THE LATISSIMUS DORSI AND TERES MAJOR. 189 mion ; the upper or descending fibres are inserted into the convex portion of the posterior border of the clavicle, many of them being also attached to the upper surface of that bone. Relations. — The trapezius is covered by the skin, from which it is separated by an aponeurotic lamina, except at the upper part, where the muscle and integuments are intimately adherent. It covers the complexus, splenius, rhomboideus, and levator an- guli scapulae, in the neck ; and the serratus posticus superior, the supra-spinatus, the pos- terior spinal muscles, and the latissimus dorsi, in the back. The most important rela- tions of this muscle are those of its superior and external or occipito-clavicular margin : tms forms the posterior boundary of the supra-clavicular triangle, which is limited in front by the stemo-mastoid muscle, and below by the clavicle. It should be observed in reference to the indications regarding the supra-clavicular space, furnished by this margin of the trapezius, that it sometimes advances as far as the middle of the clavicle, and has even been observed to become blended with the posterior edge of the stemo-mastoid. Action. — 1. The upper or descending portion elevates the clavicle, and, consequently, the apex of the shoulder ; but if the shoulder be fixed, this portion of the muscle inclines the head to one side and extends it, and, moreover, rotates it, so that the face is turned to the opposite side. 2. The middle or horizontal portion carries the shoulder back- ward, but, from the obliquity of the spine of the scapula, it also rotates that bone, so that the apex of the shoulder is carried upward. 3. The lower or ascending portion draws the posterior costa of the scapula inward and downward ; and, by a species of rotation, which was alluded to when treating of the scapulo-clavicular articulations, also elevates the apex of the shoulder. 4. When the whole of the muscle contracts at once, the scap- ula is drawn inward, and the apex of the shoulder is raised. The Latissimus Dorsi and Teres Major. Dissection. — 1. Render the latissimus dorsi tense by the same means as were employ- ed for the trapezius, and also by withdrawing the arm from the side. 2. Make an incis>- ion in the median line from the tenth dorsal vertebra to the sacrum, and another trans- versely from the same vertebra to the posterior border of the axilla, dividing in the lat- ter incision a fibro-cellular membrane, which adheres very firmly to the fleshy fibres. 3. Dissect the humeral insertion very carefully, and at the same time prepare the teres major, which is very intimately related to this extremity. The Latissimus Dorsi. The latissimus dorsi (b,fig. 106, p,figs. 109, 110) occupies the lumbar and part of the dorsal region, and the posterior border of the axilla. It is the broadest of aU the mus- cles, and shaped like a triangle, having its inferior angle truncated, and its upper and external angles considerably elongated. Attachments. — It arises from the spinous processes of the last six or seven dorsal, of all the lumbar, and of the sacred vertebrae, from the posterior third of the crest of the ilium, and from the last four ribs, and is inserted into the bottom of the bicipital groove of the humerus, not into its posterior border. Its origin from the crest of the ilium and from the vertebrae is effected through the medium of a triangular aponeurosis, narrow and thin above, broad and very strong be low, where it is blended with the aponeuroses of the serratus posticus inferior and ob liquus intemus abdominis, and with the posterior layer of the aponeurosis of the trans- versus abdominis. This aponeurosis assists in forming the sheath of the sacro-lumbalis, longissimus dorsi, and trans verso-spinalis. The costal origins consist of fleshy tongues or digitations, which are interposed between similar processes of the external oblique. From this threefold origin the fleshy fibres proceed in the following manner : the upper pass horizontally, the middle are directed obliquely, and the lower vertically upward ; they all converge, so as to form a thick fasciculus, directed towards the inferior angle of the scapula, from which it often receives some accessory fibres. The muscle is then twisted upon itself, so that the inferior or vertical fibres become first anterior and then superior, while the superior or horizontal fibres become first posterior and then inferior. This torsion may perhaps be intended to prevent displacement of the fibres. They all terminate in a flat quadrilateral tendon, which is inserted into the bottom of the bicip- ital groove, above the insertion of the tendon of the pectoralis major. This tendon fur- nishes a fibrous expansion continuous with the fascia of the arm, and also a band which extends to the lesser tuberosity of the humerus. Relations. — This muscle is covered by the skin (from which it is separated by a close- ly-adherent fibro-cellular sheath), and by the inferior angle of the trapezius. It covers the posterior spinal muscles, the serratus posticus inferior, the external intercostals, the serratus magnus, the lower angle of the scapula, the rhomboideus, and, lastly, the teres major, by which muscle it is itself covered in its turn. Its external margin is in relation with the posterior border of the external oblique, from which it is separated below by a small triangular interval. The upper part of the external margin, together with the teres major, forms the posterior border of the axilla ; and from the same margin a muscular fasci- culus occasionally extends beneath the axilla to the lower edge of the pectoralis major. mtfO MYOLOGY. The Teres Major. This muscle (c c,Jig. 106), which, both in its uses and its anatomical arrangements, should be considered an accessory to the latissimus dorsi, is situated behind the shoulder. Attachments.— It arises from the quadrilateral surface, situated at the inferior angle of the scapula, to the outer side of the infra-spinous fossa, and is inserted into the josterior border of the bicipital groove. The scapular attachment consists of short tendinous fibres, some of which are fixed directly to the bone, and some into the fasciae, which separate this muscle from those of the infra-spinous and subscapular fossae. The fleshy fibres arising from these different attachments form a thick fasciculus, flattened from be- fore backward, not cylindrical, and about two or three fingers in bieadth, which is direct- ed outward and upward, and becomes slightly twisted, so as to be inserted by a broad and flat tendon into the posterior border of the bicipital groove. Relations. — The latissimus dorsi at first covers its scapular extremity, and then, turn- ing round its lower edge, becomes anterior to it. The tendon of the latissimus dorsi is, therefore, applied to the anterior surface of the tendon of the teres major ; but since the former is attached to the bottom, and sometimes even to the anterior border of the bi- cipital groove, and the latter to the posterior border of the same groove, they are separ- ated at their insertions by an interval, in which there is almost always a synovial mem- brane, and which forms a true cul-de-sac below, for the lower margins of the two tendons are blended together. The posterior surface of the teres major is covered by the skin, from which it is sep arated on the inside by the latissimus dorsi, and externally by the long head of the tri- ceps. Its anterior surface is in relation with the subscapularis, the coraco-brachialis, the short head of the biceps, the brachial plexus, the axillary vessels, and the cellular tissue of the axilla. Its upper margin is at first in contact with the teres minor, from which it is separated above by the long head of the triceps ; its lower margin forms, in conjunction with the latissimus dorsi, the posterior border of the axilla. Action of the Latissimus Dorsi and Teres Major. — The latissimus dorsi adducts the arm, rotates it inward, and at the same time draws it backward (hence its name, ant scalptor). When only the upper or horizontal fibres contract, the arm is carried inward and backward ; when the lower fibres act alone, it is carried downward. The uses of the teres major are precisely similar to those of the latissimus dorsi, to which it is congenerous and accessory, and with which it is always associated in ac- tion, drawing the humerus inward, backward, and downward. When the humerus is the fixed point, the latissimus dorsi raises the trunk, and with the greater facility, be- cause it is attached to the ribs, the spine, and the pelvis. In consequence of its costal attachments, the latissimus dorsi is a muscle of inspiration ; and it should be observed, that the direction of its fibres, which is almost perpendicular to the ribs, enables it to act with great power. The Rhomboideus. Dissection. — Divide the trapezius by an incision extending from the third dorsal ver- tebra to the lower angle of the scapula ; dissect back the flaps, taking care to remove a fibro-cellular layer which adheres closely to the trapezius. The rhomboideus {d d, fig. 106), situated in the dorsal region, on the posterior aspect of the trunk, approaches closely to the form of a rhomboid or lozenge ; it is broad and thin, but thicker below than above, and is almost always divided into two parts. Attachments. — It arises from the bottom of the ligamentum nuchae, from the spinous processes of the seventh cervical and five superior dorsal vertebrae, and from the corre- sponding interspinous ligaments, and is inserted into all that part of the posterior costa of the scapula situated below its spine. The spinal or internal attachments consist of tendinous fibres, the most inferior of which are the longest. From these points the fleshy fibres proceed, parallel to each other, downward and outward, to a very thin ten- don, which runs along the posterior costa of the scapula, but only adheres to it above and below : the greater number of fibres are inserted into the lower angle of the scapula by a very strong tendon, which forms the principal attachment of the muscle, and to wliich the tendon mentioned above is merely subordinate. The upper part of this mus- cle {e,fig. 103), which arises from the hgamentum nuchae and the seventh cervical ver- tebra, is inserted by itself opposite the spine of the scapula. It is distinct from the re- mainder of the muscle, and from this fact Vesalius, Albinus, and Scemmering gave it the name of rhomboideus minor or superior. Relations. — This muscle is covered by the trapezius, the latissimus dorsi, and the skin. It covers the serratus posticus superior, part of the posterior spinal muscles, the ribs, and the intercostal muscles. Action. — ^The rhomboid raises the scapula and draws it inward. As it acts principal- ly upon the lower angle of that bone, it rotates it in such a manner that the anterior angle, and, consequently, the apex of the shoulder, is depressed. It assists the trape- zius in carrying the entire shoulder inward, and is also associated with the upper fibres THE SERRATI POSTICI. 201 of the same muscle in raising that part ; hut, on the other hand, it antagonizes the tra- pezius by depressing the apex of the shoulder. The Levator Anguli Scapulcs. Dissection. — Detach the trapezius from the spine of the scapula with care ; divide the upper part of the sterno-mastoid, so as to expose the transverse processes of the three or four superior cervical vertebrae. The levator anguli scapula (levator scapulae, Alhinus, f,figs. 106, 110, 113, 114), situ- ated at the posterior and lateral part of the neck, is an elongated bundle, having its up- per portion flattened from without inward, and divided into three or four fasciculi, while the lower part is flattened from behind forward. Attachments. — It arises from the posterior tubercles of the transverse processes of the three or four superior cervical vertebrae, externally to the splenius, and behind the sca- lenus posticus ; it is inserted into the superior angle of the scapula (whence its name), and into all that portion of its internal costa situated above the spine. The cervical attachments of this muscle consist of four tendons, to which succeed an equal number of fleshy fasciculi, at first distinct, but afterward united into one bundle, which proceeds downward, backward, and outward, and spreads out to be inserted into the scapula by short aponeurotic fibres. Relations. — It is covered by the trapezius, the sterno-mastoid, and the skin ; and it lies superficially to the splenius, the sacro-lumbalis, the transversalis colli, and the ser- ratis posticus superior. Action. — When its upper attachment is fixed, this muscle carries the posterior angle of the scapula upward and forward, and, consequently, rotates that bone, so as to depress the apex of the shoulder. It conspires with the rhomboid and the trapezius in elevating the entire shoulder, and with the rhomboid in depressing its apex, in this respect acting as an antagonist to the trapezius. When the fixed point is below, which must be very rarely, it inclines the neck backward and to its own side. The Serrati Postici. These are two in number, a superior and an inferior. Dissection. — 1. To expose the superior muscle, divide and reflect the trapezius and the rhomboid, and draw the scapula forward ; 2. To display the inferior, raise the latissimus dorsi with great care, as its deep aponeurosis is blended with that of the serratus posticus inferior ; 3. Preserve the thin aponeurosis extending between the two serrati muscles.* 1. The serratus posticus superior is situated at the upper and back part of the thorax, and is of an irregularly-quadrilateral figure. Attachments. — It arises from the ligamentum nuchae and the spinous processes of the seventh cervical and of the two or three upper dorsal vertebrae, and is inserted into the upper borders of the second, third, fourth, and fifth ribs. The vertebral attachment con- sists of a very thin aponeurosis, the fibres of which are parallel, and inclined downward and outward. From this aponeurosis, which constitutes at least the inner half of the muscle, the fleshy fibres proceed in the same direction, and almost immediately divide into four digitations, which are inserted into the ribs by means of short tendinous fibres. The superior digitation is attached near the angle of the corresponding rib, and each of the others at successively greater distances from it. 2. The serratus posticus inferior (lumbo-costalis, Chaussier, g, fig. 106) is also of an ir- regularly-quadrilateral form, and is situated at the lower part of the back and the upper part of the loins. It arises from the spinous processes of the two lower dorsal and three upper lumbar vertebrae, and is inserted into the inferior borders of the last four ribs. The vertebral or internal attachment consists of an aponeurosis similar to that of the prece- ding muscle, but its fibres have an inverse direction, i. e., obliquely outward and upward. From this aponeurosis, which forms the internal half of the muscle, the fleshy fibres pro- ceed in the same direction, and divide into four flat digitations, progressively decreasing in size from above downward, which are inserted into the ribs by means of tendinous laminae, the superior digitation near the angle of its corresponding rib, and the others, successively, farther beyond it. Relations. — These two muscles have certain relations in common, and there am some peculiar to each. They both cover the longissimus dorsi, the sacro-lumbalis, the trans- verso-spinalis, the ribs, and the corresponding intercostal muscles. The superior is cov- ered by the rhomboideus, the trapezius, and the serratus magnus, and covers the splenius and transversalis colli. The inferior is covered by the latissimus dorsi, with the apo- neurosis of which muscle its own aponeurotic lamina is so closely united that it is impos- sible to separate them completely ; and it covers the posterior layer of the aponeurosis of the transversalis. Action. — Besides certain common uses, each muscle has its own peculiar action. One * [This exceedingly thia and semi-transparent lamella has received the name of the vertebral aponewrotit Sep A.P0NEUK0I.0OY.] Cc 202 MYOLOGY. impoitant common use is, to retain in the vertebral groove those muscles of the back which, from their extreme length, are the most liable to displacement. This effect is produced by their fleshy portions rendering tense their aponeurotic expansions. With regard to the actions proper to each, 1. The superior elevates those ribs into which it is inserted, and is, consequently, a muscle of inspiration ; 2. The inferior, on the other hand, is a depressor of the ribs, and, therefore, a muscle of expiration. The Splenius. Dissection. — Merely remove the trapezius, the rhomboid, and the serratus posticus su- perior. The splenius {i,Jigs. 106, 113, 114), so named because it has been compared to the spleen {a■!T^v), is situated at the posterior part of the neck and upper part of the back. It is a broad muscle, terminating in a point below, and dividing into two portions above. Attachments. — It arises from the spinous processes of the four or five superior dorsal and the seventh cervical vertebra, from the corresponding supra-spinous ligaments, and also from the ligamentum nuchae, between the seventh and the third cervical vertebrae ; it is inserted, 1. Into the transverse processes of the first, second, and often the third cer- vical vertebrae ; 2. Into the external surface and posterior border of the mastoid process, and the external third of the rough space beneath the superior semicircular line of the occipital bone. The spinal attachments consist of tendinous fibres, the most inferior of which are the longest. From these the fleshy fibres proceed obliquely upward and out- ward, the lower being longer and more vertical, and form a broad, flat muscle, which is much thicker externSly, and soon becomes divided into two portions : one smaller, infe- rior and external ; the other much larger, superior and internal. The former is called the splenius colli ; it is sometimes distinct, even from its origin, and soon subdivides into two or three fasciculi, which terminate in as many tendinous processes, that are in- serted into the atlas, the axis, and often into the third cervical vertebra. The fascicu- lus proceeding to the atlas is usually the largest. The second, or the upper and internal portion of the muscle, is connected with the head, and is called the splenius capitis. Relations. — The splenius is covered by the trapezius (the rhomboid and the serratus posticus superior intervening below), by the sterno-mastoid, and by the levator anguli scapulae. It covers the complexus, the longissimus dorsi, the transversalis colli, and the trachelo-mastoid. The levator anguli scapulae is in contact with its outer border, and rests upon it above, the cervical insertions of the two muscles being blended togeth- er ; below they are separated by the transversalis colli and sacro-lurabalis. The inter- nal edge is very thin, and separated from the muscle of the opposite side by a triangu- lar interval, in which the complexi are visible. Actions. — The splenius extends the head, inclines it to its own side, and rotates it so that the face is turned to the same*ide. This action of the splenius depends on its at- tachments to the occipital bone, the mastoid process, and the atlas. By its insertions into the second and third cervical vertebrae it tends to rotate these in the same direction. When the two muscles act together, the head is drawn directly backward. The splenius is therefore an extensor and rotator of the head and of the neck ; it assists in supporting the head in the erect position, and prevents it from inclining forward in obedience to the force of gravity. The Posterior Spinal Muscles. As these muscles are arranged in a peculiar manner, we shall adopt a method of de- scription in some measure different from that which we have elsewhere employed. The posterior spinal, or long muscles of the back (see Jig. 107), are three in number, viz., the sacro-lumbalis, the longissimus dorsi, and the transverso-spinalis muscle. These three muscles, which extend the entire length of the spine, form a very large muscular mass, completely filling up the corresponding vertebral groove. This mass is small at the lower part of the sacral groove, becomes much enlarged in the loins, then diminishes in the back, and again acquires a considerable size in the neck. Chaussier has given a description of them under the collective name of the sacrospinal muscle ; and they have also been denominated the erector spina. I shall describe the three muscles together ; but, in order to adopt some arrangement in a matter so complicated, I shall divide them into three portions, viz., a lumbro-sacral, a thoracic, and a cervical. Ltimhro-sacral Portion of the Posterior Spinal Muscles. Dissection. — 1. Render this portion of the muscle tense, by placing a block under the abdomen. 2. Divide by a vertical incision the trapezius, splenius, rhomboideus, latis- simus dorsi, and serrati postici ; reflect the divided portions inward and outward. A young subject, from ten to twelve years of age, is best adapted for the study of these muscles, from the facility with which the different fasciculi may be separated. For the same reason, one that is much infiltrated with serum is preferable to one in which the parts are dry. i - THE POSTERIOE SPINAL MUSCLES. 203 The lumbo-sacral portion is usually called the common m/iss of the sacro-lumbalis and longissimus dorsi. It forms the fleshy part of the loins, and is called the fdlet in the low- er animals : it is the most highly developed in man, in whom it exerts a constant and powerful action during the erect posture : it appears to be the coimnon origin of the pos- terior spinal muscles, whence the name of common mass : it fills up entirely the lumbo- sacral groove, and even projects backward and laterally in robust subjects. It is of small size in the sacral region, is much enlarged at the middle of the lumbar region, at the upper part of which it again diminishes, so as to resemble two cones uni- ted by their bases. Attachments. — The common mass arises from the whole extent of the sacro-iliac groove, and from the anterior surface and external border of an extremely strong apo- neurosis, formed of parallel vertical fibres, and strengthened by a superficial layer direct- ed obliquely. This aponeurosis of origin for the posterior spinal muscles {d,fig. 107) is in- serted on the inside to the sacral ridge, to the summits of the spinous processes of the lumbar and three lower dorsal vertebrae, and to the corresponding supra-spinous liga- ments : on the outside, to the series of eminences representing the transverse processes of the sacral vertebrae, and to the back part of the crest of the ilium : it gives attach- ment to many of the fibres of the glutaeus maximus. It is short on the outside, and very long on the inside, reaching in the latter direction to the middle of the dorsal region, un- der the form of parallel and regular bands {d,fig. 107). Arising from these different origins, the coiimion mass appears at first extremely sim pie in its composition, consisting of fibres passing vertically upward. But if the aponeu- rosis be detached from its spinal insertions, and turned outward, it will be seen that the common mass is essentially composed of two portions : one internal and anterior, the lumbosacral portion of the transverso-spinalis ; and the other external and posterior, the lumio sacral portion of the sacro-lumbalis and longissimus dorsi. 1. The lumbosacral portion of the transverso-spinalis* occupies all the sacral groove, and that part of the lumbar groove situated within the articular processes. It is perfectly distinct in the loins, being separated from the common mass by loose cellular tissue trav- ersed by vessels and nerves. It arises from the articular processes of the lumbar verte- brae by flat tendons, directed obliquely inward and upward, and terminating upon the pos- terior surface of the muscle : by the imion of their contiguous edges an aponeurosis is formed, which is itself blended along one of its borders with the deep surface of the com- mon aponeurosis of origin. From these tendons the fleshy fibres arise, and having united into bundles, terminate by other tendons at the spinous processes of the vertebrae above. In the sacral region this portion of the transverso-spinaUs is less distinct, but it may be easily seen that it occupies the whole of the sacral groove, and that the corresponding por- tion of the aponeurosis of origin affords attachments fo it alone. 2. The external and posterior portion of the com- mon mass, or lumbosacral portion of the sacro-lumbalis and longissimus dorsi, is entirely without the sacral groove, but occupies that part of the lumbar groove situated on the outer side of the articular processes. It arises, 1. From all the lumbar portion of the com- mon aponeurosis. 2. From an extremely strong ten- don, which is attached to the posterior superior spi- nous process of the ilium. 3. From the posterior s~ fourth of the crest of the ilium, internally by tendi- nous, and externally by muscular fibres. The thick fleshy mass proceeding from these different origins is disposed of in the following manner : the greater part of the fibres pass directly upward to the dorsal region, forming the proper commencement of the sacro-lumbalis (a a, fig. 107). The remaining fibres are directed forward, and are arranged into two sets of bundles, one of which is inserted into the summits of the transverse processes, forming the external or transverse fasciculi ; and the other into the tubercles of the articular processes, forming the internal or ar- ticular fasciculi. These two sets of fibres constitute the proper origin of the longissimus dorsi (d d, fig. 107). Relations. — The common mass is covered behind Fiff. 107. [This corresponds to the inferior or lumbo-sacral fasciculi of the multifidus spinte,] 204 MYOLOGY. by the united aponeuroses of the latissimus dorsi and serratus posticus inferior, and by the posterior layer of the aponeurosis of the transversalis ; in front, it corresponds to the lumbar groove, the inter-transversales muscles of the loins, and the middle layer of the aponeurosis of the transversalis, which separates it from the quadratus lumborum ; on the inside, it corresponds to the spinous processes ; and on the outside, to the angle of union between the posterior and middle layers of the aponeurosis of the transversalis. In this way it is completely enclosed in an osteo-fibrous sheath. Thoracic Portion of the Posterior Spinal Muscles. The transverso-spinalis muscle may be completely isolated from the others in this region. We have seen the distinction between the sacro-lumbalis and longissimus dorsi commenced at the upper part of the lumbar region ; in the back they are completely sep- arated by some loose cellular tissue and the posterior branches of the dorsal nerves and vessels. The thoracic portion of the sacro-lurnbalis (6 V, fig. 107) consists of a continuation of the vertical or external fibres of the common mass ; as it proceeds upward it becomes more and more slender, and is divided into a series of fasciculi, which are inserted succes.sive- iy into the angles of the ribs, by means of tendinous prolongations, that extend for a considerable distance upon the posterior surface of the muscle. It was the existence of these aponeurotic processes, the contiguous edges of which are often united, that in- duced Winslow to compare the muscle to a palm leaf In this manner the muscular fasciculi are soon expended, terminating at about the sixth rib, but the muscle itself is continued into the neck by means of accessory fibres, which may be exposed by turning the muscle outward, sifter separating it from the longissimus dorsi (as at h') : twelve long, thin tendons will then be seen to arise from the upper portion of the angles of the twelve ribs, and to pass outward and upward : to these succeed fleshy fasciculi, which terminate in aponeurotic processes, situated on their posterior surfaces, and having pre- cisely the opposite direction. These accessory bundles (c c',Jig. 107; i,fig. 108) have been very well described by Diemerbroek under the name ofcervicales descendens, and by Steno under that of musculus accessorius ad sacro-lumbalem ; the four or five superior bun- dles form the transversaire grele of Winslow, and the cervicalis descendens of Albinus. The thoracic portion of the longissimus dorsi (e e', fig. 107) is larger than the preceding muscle, to the inner side of which it is situated : it diminishes much less rapidly, because the common aponeurosis {d) is extended in the form of bands upon its posterior aspect, which afford attachment to additional fleshy fibres. This muscle is a continuation of the internal or articular, and the external or transverse fasciculi, described as existing in the lumbar region, and is itself divided into three orders of fasciculi, one external and two internal. 1. The external or costal fasciculi form the continuation of the transverse bun- dles of the lumbar portion of the muscle, and are inserted by very thin tendons into the space between the angles of the ribs and the summits of the dorsal transverse processes (e',fig. 107). 2. The first set of internal, or the spinous fasciculi, are inserted into the spi- nous processes of the five or six superior dorsal vertebrae ; and as they arise from tendi- nous bands attached to the summits of the spinous processes of the lower dorsal vertebrae, and of that of the first lumbar vertebra, Winslow considered them as forming a separate muscle, which he called le long epineux du dos (spinalis dorsi, /,^o'. 107). 3. The second set of internal, or the transverse fasciculi, are a continuation of the articular fasciculi of the lumbar region ; they constituie the principal termination of the longissimus dorsi, and are attached by very long and thin tendons to the transverse processes of the dorsal vertebrae. The thoracic portion of the transverso-spinalis* (partly seen in^^. 108) is reduced to a very narrow band, concealed by the longissimus dorsi : it arises by very long and delicate tendons from the lower dors^ transverse processes, and is inserted by others equally sinailar, long and slender, into the summits of the superior dorsal spinous processes, some pale fleshy fibres connecting the two series of tendons. Connexions. — The dorsal portion of the posterior spinal muscles entirely fills the dor- sal groove, limited on the outer side of the angles of the ribs. They are covered by several muscular layers, the nearest of which is formed by the two serrati postici and their connecting aponeurosis, which completes the sheath enclosing the long muscles of the back : they are, moreover, separated from the skin by the rhomboid, trapezius, and latfssimus dorsi. The Cervical Portion of the Posterior Spinal Muscles, the Transversalis Colli, and the Trachelo-mastoidcus. Cervical portion of the sacro-lumbalis, or cervicalis descendens. The sacro-lumbalis, whose original fibres are found to terminate at and upon the sixth rib, is continued, by means of its accessory fasciculi (c c',fig. 107), up to the transverse processes of the four or five inferior cervical vertebrae (i,fig. 108), into the summits of which it is inserted by very slender tendons. The number of these terminating fasciculi varies in a remarkable * [This corresponds to the semi-spinalis do.rs-, and to the dorsal portion of the multifidus spinsn of Albinus ■• THE POSTERIOR SPINAL AND COMPI.EXUS MUSCLES. 205 manner. Indeed, the splenius, the transverscdis colli, the sacro-lumbalis, and even the levator anguli scapulas, are so closely connected, that, upon examining their cervical in- sertions only, these might all be ascribed to a single muscle. The cervical portion of the sacro-lumbalis is covered by the levator anguli scapulae, and can only be exposed by turning this muscle outward. The cervical portion of the longissimus dorsi, or the transverscdis colli, and the tra- chelo-mastoid. The extent of the longissimus dorsi is limited to the back ; its highest internal or spinous fasciculus seldom reaches the spinous process of the first dorsal ver- tebra : its highest external or costal fasciculus is attached to the second, sometimes even to the fourth rib, and its highest transverse fasciculus is inserted into the transverse process of the first dorsal vertebra. In some very rare cases, a few internal fasciculi reach the cervical vertebrae : I have seen one of them terminate by becoming attached both to the transverse process of the third cervical vertebra and to the complexus. The longissimus dorsi is, however, prolonged by accessory fasciculi as far as the third cervi- cal vertebra. These fasciculi can only be identified by their direction (for they can never be completely separated from this muscle) : they form a distinct muscle, known as the transverscdis colli (transversalis cervicis, Albinus, g g,fig. 107). By reflecting outward the upper part of the longissimus dorsi, they may be exposed, varying in number, and arising from the summits of the transverse processes of the third, fourth, fifth, sixth, and sometimes seventh and eighth dorsal vertebrae, by long, thin ten- dons, and inserted by other tendons into the posterior tubercles of the transverse pro- cesses of the five inferior cervical vertebras {I, fig. 108) : the transversalis colli is covered by the longissimus dorsi, the splenius, and levator anguli scapulae, and rests upon the trachelo-mastoid and complexus. The trachelo-vtastoideus (complexus minor, i i, fig. 107) may be regarded as another accessory muscle to the longissimus dorsi, which it continues up to the head. In order to expose its origin, the transversalis colli must be reflected outward (as in fig. 107). It arises from the angles between the transverse and articular processes of the four in- ferior cervical vertebrae, by four small tendons, or sometimes by a continuous aponeu- rotic plane. From thence the fibres proceed upward, and form a small muscle, which is inserted into the mastoid process, in a small furrow to the inside of the digastric groove. This small muscle is almost always interrupted by a tendinous intersection near its mastoid insertion. The cervical portion of the transverso-spinalis.* While the preceding muscles present only a few fasciculi in the neck, the transverso-spinalist undergoes an enlargement in this region, so as to occupy the entire cervical groove (a and b,fig. 108). In camivora, this portion of the muscle is enormously developed (much more so than in man), in con- sequence of those animals using the head and neck in seizing or struggling with prey. In mammalia, as in man, the dorsal portion of the transverso-spinalis is, as it were, but a rudiment in the lumbo-sacral region ; the muscle is larger in man than in other animals, on account of his erect posture. Albinus described the enlarged cervical portion as a separate muscle, viz., the spinalis cervicis. In the neck, as in the other regions, the transverso-spinalis is a collection of super- imposed fasciculi, which arise from the transverse processes of the five or six upper dorsal, and from the articular processes of the five lower cervical vertebrae, and are in- serted into the spinous processes of the six lower cervical vertebrae : the highest and the largest fasciculus is attached to the axis. This muscle, which would have been much better named articvio-spinalis, is composed of several layers of fasciculi, placed one above the other, and extending from the whole length of the articular processes and laminae of the vertebrae below to the whole length of the spinous processes and laminae of the vertebrae above. The length of these layers diminishes progressively from the more superficial {a, fig. 108) to the deep-seated ones (6) ; the latter extend only from one ver- tebral lamina to another, and might be considered as proper muscles of the laminae, and not as a part of the transverso-spinalis muscle. The most superficial layer is composed of radiating fasciculi, diverging from one articular process to the summits of several of the spinous processes. The Complexus. Dissection. — ^Divide the splenius perpendicularly to the direction of its fibres, and re- flect the two parts upward and downward ; turn outward the upper portions of the lon- gissimus dorsi, the transversalis colli, and the trachelo-mastoid {see fig. 107). The complexus {I, fig. 107) is situated beneath the splenius at the posterior part of the neck and upper part of the back. It is a flat muscle, broad above, but terminating in a point below. Attachments. — It arises, 1. From the transverse processes of the five or six superior * If we were to follow the order of super-imposition rigorously, the complexus should be described before this muscle, which cannot be brought into view until the former is removed. t [This portion of the transverso-spinalis corresponds to the semi-spinalis colli (a, fig. 108), and the cervj cal fasciculi (6) of the niultifidus spins of Albinus. 1 206 MYOLOGY. dorsal vertebrae ; 2. From the articular tubercles and the angular depression formed be- tween them and the transverse processes of the four inferior cervical vertebrae ; 3. Some- times from the spinous processes of the seventh cervical and two upper dorsal vertebrae : it is inserted upon the side of the external occipitd crest into the inner half of the rough space comprised between the two semicircular lines. The origins of this muscle con- sist of tendons, from which the inferior fleshy fibres pass vertically upward, the superior ones obliquely inward and upward, becoming graduaUy shorter and more nearly horizon- tal. The muscular fibres are interrupted by some very remarkable tendinous intersec- tions. Thus, on the inside, the fleshy fasciculus arising from the sixth, fifth, and fourth dorsal vertebrae, gives origin to a tendon, which proceeds along the inner edge of the muscle, and, at the distance of an inch and a half or two inches, becomes the origin of another fleshy fasciculus, which is attached to the side of the occipital crest ; hence the name of biventer cervicis, given by Eustachius to the whole complexus, and by Albinus to this inner portion only (m, fig. 107). More externally, there is another flat tendon ex- tending along the posterior surface of the muscle, from the outer edge of which an apo- neurotic intersection passes in a zigzag course obliquely outward and upward. It is not uncommon to find another small digastric fasciculus with a separate tendon, on the an- terior surface of the muscle. Relations. — The complexus is covered by the trapezius, splenius, longissimus dorsi, transversalis colli, and trachelo-mastoid, and covers the transverso-spinalis and the recti and obliqui capitis. Its inner edge is separated from the muscle of the opposite side by a considerable quantity of adipose tissue, and by a prolongation of the ligamentum nuchae. The Inter-spinales Colli. The inter-spinales muscles are distinct in the neck oidy. It is generally admitted that there are five pairs, the first of which extends between the axis and the third cervical vertebra, and the last between the seventh cervical and first dorsal vertebras. They are small quadilateral muscles, extending from one of the borders of the groove in the spinous process below to the corresponding lip of the next process above. Externally, they are in relation with the transverso-spinalis, and are separated from each other internally by cellular tissue and an aponeurotic lamina. Fig. 108. The Recti Capitis Posticiy Major and Minor. The rectus capitis posticus major {e,fi^. 108) may be regarded as an axoido-occipital, and the rectus minor (d) as an atloido-occipital inter-spi- ndis muscle. They both arise tendinous, the smaller from the tubercle on the posterior arch of the atlas, and the greater from the superior tubercle of the spinous process of the axis (2) ; and, increasing in size, they both pass obliquely upward and outward. The rectus major, ^h which is much the larger and more oblique, is inserted to the outer side of the inequalities situated below the inferior semicircular line of the occipital bone ; the rectus minor is inserted to their inner side. The name of recti is not, therefore, very appropriate, for both of them (but more especially the larger one) are directed obliquely ; but they are so called in contradistinction to two neighbouring muscles which are much more oblique. The obliquity of these muscles (by increas- ing their length) allows of more extended movements, and, at the same time, enables them to assist in rotating the head. Tht Ohliquus Capitis Major or Inferior^ and Obliquus Minor or Superior. The ohliquus major or inferior (/, fig. 108), as far as its insertions are concerned, may be called the axoido-atloid spino-transversalis ; it resembles, in fact, a thick fasciculus of the longissimus dorsi. The obliquus minor or superior {g) may, for the same reason, be called the atloido-occipital transverso-spinalis, resembling a thick fasciculus of that mus- cle. The ohliquus major arises from the apex of the spinous process of the axis, on the outer side of the rectus major (c), and above the transverso-spinalis (i. c, the semi-spi- nalis colli and multifidus spinas conjoined, a and h) ; it forms a thick, cyhndriccd bundle, passes almost horizontally outward, and is inserted behind and below the transverse process of the atlas, which is excavated for this purpose. It is the axoido-atloideus of Chaussier. The ohliquus minor (atloido-sub-mastoideus) arises by some very long tendi- nous fibres from the upper part of the transverse process of the atlas, proceeds at an angle of about 45° towards the occipital bone, into which it is inserted not far from the mastoid process, by some tendinous fibres, less distinctly marked than those of its origin. From this difference of direction, it follows that the rectus major and the two obliqui form on each side an equilateral triangle ; in the interval between the two triangles a considerable part of the recti minores is seen. Relations. — The recti and obliqui capitis are covered behind by the complexus, from which they are separated by a very strong aponeurotic lamina and much cellular tissue ; THE POSTERIOR SPINAL MUSCLES. 20T they cover tlie posterior arch of the atlas, with the posterior ligaments of the atloido-oc- cipital and atloido-axoid articulations. General View of the Posterior Spinal Muscles. After the preceding description, it will now be easy to comprehend the general guiding principles in the arrangement of the innumerable, and, at first sight, inextricable fasci- cuh which constitute the fleshy mass known by the general name of the posterior spinal muscles. We shall first recall to mind, that the levers to which all these muscles are ultimately attached are, 1. The row of spinous processes ; 2. The row of articular pro- cesses ; and, 3. The row formed by the transverse processes and the ribs, which, for many reasons, may be regarded as extensions of those processes. We shall suppose these three series of levers, and therefore the several points of in- sertion, to be represented by three vertical lines. We must remember, also, that the dorsal transverse processes are upon the same line as the lumbar and cervical articular processes, and that the ribs are upon the same line as the lumbar transverse processes and the anterior roots of the cervical transverse pro- cesses. (See Osteology, p. 5.) These data being admitted, we can now reduce all the posterior spinal muscles into the four following orders of fasciculi, two being vertical and two oblique. 1. The internal vertical or spinous muscles, comprising the spinalis dorsi (i. e., the in- ternal and superficial portion of the longissimus dorsi), the inter-spinalis of the neck, and the recti postici of the head. 2. The external vertical lateral, or transverse muscles, con- nected with the transverse or costiform processes. They comprise the sacro-lumbalis and the inter-transversales, among which the quadratus lumborum may be included. 3. The spino-transverse and spino-articular* oblique muscles, including the longissimus dorsi, with its accessories, the transversalis colli and trachelo-mastoid, the splenius and th6 obliquus major. 4. The transverso-spinous and articulo- spinous* oblique muscles, viz., the transverso-spinalis, the complexus, and the obliquus capitis minor. Action of the Posterior Spinal Muscles. Having once established the general principles according to which the posterior spinal muscles are arranged, it is very easy to determine the mode of action of each, and to re- duce to very simple elements a mechanism to all appearance so complicated. 1. The long and short spinous fasciculi being vertical, directly extend the vertebrcil column ; such is the action of the spinalis dorsi and inter-spinalis colli ; the recti capitis, at the same time that they extend the head, rotate it also to the side on which the mus- cles are acting. When the recti muscles of both sides act simultaneously, the head is drawn directly backward. 2. The fasciculi of the sacro-lumbalis being vertical and lateral, erect the vertebral column, and incline it to one side, when only one set of muscles acts ; when both sets act together, they extend it directly backward. 3. As the fasciculi of the longissimus dorsi, belonging to the spino-transverse and spi- no-articular group, have their fulcra upon the spine, and are inserted into the articular and the transverse processes or ribs, they conspire in erecting the vertebral column, and keeping it in that position. But, from their obUquity, they produce a slight movement of rotation, those fibres which are attached to the articular processes having less effect than those connected with the transverse processes. In this movement, the front of the body is turned to the side on which the muscles are situated. When the muscles of both sides act together, the spine is extended directly backward. The splenius, which is the representative of the longissimus dorsi for the neck and head, acts in the same way, but with greater effect. Thus, by the contraction of the left splenius, the face is turned to the left side, and the head is drawn backward and to the right side. The obliquus infe- rior jilso acts in the sEune direction. When the two splenii and the two inferior oblique act together, the head is inclined directly backward. 4. The fixed insertions of the transverso-spinalis being at the articular or transverse processes, and their movable points at the spinous processes, besides the common effect of erecting the vertebral column, they are also able to rotate it, so that the anterior re- gion of the trunk is turned to the opposite side. From its obliquity, this muscle is the principal rotator of the vertebral column. The complexus, which is its representative in the neck, acts upon the head in the same manner, but in a more remarkable degree. Thus, by the contraction of the complexus of the left side, the face is turned to the right side, and the head is inclined backward upon the left side, so that, in rotation, it acts in a precisely opposite direction to the splenius. When all these muscles act together, the trunk is simply drawn erect. The superior oblique assists the complexus in the move- ments of the head. Lastly, we may now understand the successive actions which take place along the * [The terms spino-transverse and spino-articular are applied to fasciculi passing upward from the spinous to the transverse and articular processes ; transverso-spinous and articulo-spiuous, to such as proceed upward from the transverse and articular to the spinous processes.] 208 MYOLOGY. whole extent of the posterior spinal muscles. The sacrum and the iliac bones furnish a fulcrum for the fasciculi which move the lumbar region : this latter being fixed, then be- comes the fulcrum for those that move the dorsal region, and so on to the head, which alone has independent muscles. It is impossible to extend backward the dorsal region, and the lower part of the cervical, without at the same time erecting the lumbar region; but the head may be moved at will, independently of the vertebral column. The posterior spinal muscles maintain in equilibrium the weight of the whole trunk ; hence the lassitude experienced in the back, but especially in the loins, by long-contin- ued standing, walking, or even sitting without a support to the back ; and hence the re- lief afforded by the recumbent posture. Rotation, we have seen, scarcely exists in the loins, the back, or the lower part of the neck ; but at the upper part of the neck it is very extensive, and here the rotator mus- cles are proportionally strong, and directed very obliquely. MUSCLES OF THE ANTERIOR ABDOMINAL REGION. The Obliquus Externus Abdominis. — Obliquus Internus and Cremaster. — Transversalis Ab- dominis . — Rectus Abdominis. — Pyramidalis . The muscles of the anterior abdominal region are, the external oblique, the internal oblique, the transversalis, the rectus, and, occasionally, the pyramidalis ; being ten in the whole, five on each side. The Obliquus Externus Abdominis. Dissection. — 1. Make an incision through the skin of the abdomen extending from the cartilage of the eighth rib obliquely downward and inward, dividing, at the same time, the very firm layer of cellular tissue which immediately covers the muscle. 2. During the preparation of this, as well as 2ill the other abdominal muscles, place a block under the loins, and in the dissection follow exactly the direction of the muscular fibres. The great or external oblique muscle of the abdomen {o,fig. 106, and a, fig. 109), so call- ed from the direction of its fibres (ob- liquus descendens), forms the most su- perficial muscular layer of the abdom- inal parietes, on the sides and front of which it is situated : it is very broad, quadrilateral, and curved upon itself. Attachments. — It arises from the ex- ternal surfaces and lower borders of the seven or eight inferior ribs, and is inserted into the anterior half of the ex- ternal lip of the crest of the ilium, into the external edge of the anterior ab- dominal aponeurosis, and by it into the linea alba. The upper or costal attach- ments consist of seven or eight angu- lar tongues, or digitations, fleshy and tendinous in their structure, and arran- ged in an oblique line, running down- ward and backward. These digitations increase in size from above downward, as far as the eighth rib, and then diminish to the twelfth. The four or five superior di- gitations are interposed, like the fingers of the two hands (whence the name), between similar prolongations of the serratus magnus. The three or foui lower digitations between those of the latissimus dorsi, by which they are covered. This series of costal attach- ments constituting the upper edge of the muscle, represents a serrated curv- ed line, the convexity of which is di- rected upward and backward. The first digitation is attached close to the cartilage of the corresponding rib, the succeeding ones are farther and farther removed from the first, and the last is inserted into the apex of the cartilage of the last rib. THE OBLiaUUS INTEENUS. 20d From these attachments the fleshy fibres proceed in different directions : the poste- rior pass nearly vertically downward, the middle obliquely downward and inward, and the upper almost horizontally inward ; the posterior terminate by short tendinous fibres at the crest of the ilium ; the anterior at the external concave edge of a broad aponeu- rosis, which forms the superficial layer of the anterior abdominal aponeurosis, and, by interlacing with the corresponding structure of the opposite side, concurs in forming the linea alba, and is folded upon itself below, to form the crural arch, or Poupart's ligament. (See Aponeurolggy.) It should be remarked, that the fibres of the external oblique follow exactly the me direction as those of the external intercostal muscles. Relations. — The external oblique is covered by the skin, a considerable quantity o* adipose tissue, and behind by a small portion of the latissimus dorsi. It covers the in- ternal oblique, the anterior extremities, and the cartilages of the seven or eight inferior rib's, together with the corresponding external intercostal muscles. The most remark- able relation is that of its posterior border with the outer edge of the latissimus dorsi. Most commonly this border is covered by the latissimus dorsi ; but sometimes a trian- gular space exists between them, which has been much noticed since Petit described a hernial protrusion in it, which he called lumbar hernia. Action. — The external oblique performs a threefold action: 1. It compresses the ab- dominal viscera during any exertion, or in expulsion of the faeces, in labour, &c. ; 2. It depresses the ribs, and thus indirectly flexes the vertebral column ; 3. From its obliquity, it rotates the vertebral column, through the medium of the ribs, so that the fore part of the trunk is turned to the opposite side. When the two muscles act together, the tho- rax is inclined directly forward. Hitherto we have supposed that the movable point of the muscle is at the ribs ; if, on the contrary, the thorax be fixed, it then draws the pel- vis upward, and rotates the vertebral column, so that the fore part of the pelvis is turn- ed to the same side as the contracting muscle. The Obliquus Internus, and the Cremaster. Dissection. — Divide the external oblique across the direction of its fibres, i. e., down- ward and backward. The small or internal oblique of the abdomen (obliquus ascendens, p,Jig: 106, and a, Jig. 110) is a broad, irregularly-quadrilateral mus- Fig.llO. cle, much broader in front than behind, and smaller and thinner than the preceding. It occupies the anterior, lateral, and posterior parts of the abdomen. Attachments. — It arises from the spinous processes of the lumbar vertebrae, from the anterior three fourths of the interval between the borders of the iliac crest, and from the crural arch (Poupart's ligaments). It is in- serted into the lower edges of the cartilages of the ninth, tenth, eleventh, and twelfth ribs, and into the linea alba by means of the mid- dle layer of the anterior abdominal aponeu- rosis. The spinal fibres take their origin through the medium of the posterior abdomi- nal aponeurosis : they are few in nmnber. The iliac portion of them arise by very short tendinous fibres, and those which proceed from the crural arch arise from the sort of groove situated on its upper surface. From this threefold origin the fibres proceed in dif- ferent directions : the posterior almost verti- cally upward ; those which arise from the crest of the ilium obliquely upward and in- ward, becoming longer and more oblique an- teriorly ; those which proceed from near the anterior superior spinous process of the ilium are horizontal ; and, lastly, those which arise from the crural arch pass obliquely downward and inward. The posterior fibres terminate at the lower edge of the cartilages of the four inferior ribs, and are continuous with the in- ternal intercostal muscles, in the intervals between the tenth and eleventh and eleventh and twelfth ribs, indicating the analogy between these muscles. I have often observed the insertion into the last rib to be wanting. The middle fibres, which are the most numerous, terminate at the external Dd 210 MYOLOGY. edge of the middle layer of the anterior abdominal aponeurosis. The fibres arising from the crural arch are few in number, pale, and fasciculated ; some terminate at the pubes, passing behind the inguinal or external abdominal ring ; others proceeding from the ring, in the male, form the cremaster muscle. Relations. — It is covered by the external oblique, and behind by a small portion of the latissimus dorsi ; and it lies superficially to the transversalis. The most important re- lations are those of its inferior edge with the inguinal ring of the external oblique, which it partly closes on the inner side, as Scarpa and Bichat have well pointed out, and with the spermatic cord, which passes beneath it, and, during the descent of the testicle, draws with it some of the lower fibres of the muscles ; and hence the looped arrange- ment they assume. The cremaster. The loops so well described by M. Jules Cloquet are very variable, and do not always appear to me to constitute the entire muscle. According to this anatomist, the cremaster is nothing more than the lower fibres of the internal oblique, that had been entangled with the testicle during its descent, forming loops in front of the cord, the concavity of which is directed upward, and which may be traced to the bottom of the scrotum. But I have often been convinced, from the examination of subjects in which the cremaster was much developed, that this muscle {b, Jigs. 109, 137) consists principally of a longitudinal fasciculus, partly derived, it is true, from the lower fibres of the internal oblique, but consisting partly, also, of proper fibres arising from the crural arch, near the external pillar of the ring ; and that this fasciculus is lost upon the proper sheath of the cord, to which it is intimately united. The oflSce of this muscle is to raise the entire testicle. The slow vermicular motion observed in the scrotum during the venereal orgasm, or from the action of cold, is not at all connected with it. The actions of the internal oblique are, 1. Compression of the abdominal viscera; 2. Depression of the ribs, and, consequently, flexion of the trunk ; 3. Rotation of the trunk, so that the fore part of the body is turned to the same side. The right internal oblique, therefore, co-operates with the left external oblique ; when it acts with its fellow, the thorax is drawn directly towards the pelvis ; but if the chest is fijced, they move the pel- vis upon the loins. The Transversalis Abdominis. Dissection. — 1. Make a horizontal section of the internal oblique ; 2. Dissect with care the two flaps of this nmscle, following the direction of the fibres of the transversalis ; 3. In order to obtain a good view of the costal attachments, open the abdomen and exam- ine them on the inner surface of the ribs ; this may be omitted until the diaphragm is to be inspected. The transversalis abdominis, so named from the direction of its fibres, is situated more deeply than the two preceding muscles, and, like them, is irregularly quadrilateral (b, fig. 110). Attachments. — It arises from the six lower ribs, from the anterior three fourths of the internal lip of the crest of the ilium, and from the spinous and transverse processes of the lumbar vertebrae. It is inserted into the linea alba by means of the deep layer of the anterior abdominal aponeurosis. The costal attachments consist of fleshy digita- tions interposed between those of the diaphragm, the two muscles being actually contin- uous at the two inferior intercostal spaces ; the vertebral attachments are efiected by means of the posterior abdominal aponeurosis ; and from the ilium it arises by very short tendinous fibres internally to the small obliqije. From these three origins the fleshy fibres proceed parallel to each other and horizontally inward ; the lower ones alone are slightly inclined downward and inward ; the middle fibres are the longest. They are all inserted into the external convex edge of a tendinous expansion, which constitutes the posterior layer of the anterior abdominal aponeurosis. Relations. — The transversalis is covered by the internal oblique, and rests upon the peritoneum, from which it is separated by a fibrous lamina, which is very distinct in front, where it is named the fascia transversalis. Actions. — 1. It acts more powerfully upon the abdominal viscera than any of the pre- ceding muscles, compressing them strongly, like a girth, against the vertebral column, and assisting greatly in the process of defecation. 2. It draws inward the rib to which it is attached, and thus materially assists in expiration. The Rectus Abdominis. Dissection. — 1. The subject being laid upon its back, place a block under the loins ; 2. After having removed the skin, make a vertical incision through the strong aponeurosis, at about two fingers' breadth from the linea alba ; 3. Dissect off the two flaps inward and : outward. The adhesions between this aponeurosis and the muscle are, however, so in- 'timate at many points, that it is impossible to separate them. The rectus abdominis (c, fig. 110) is situated at the anterior and middle part of the ab- domen on each side of the linea alba, and occupies the sp.^ce between the pubes and the . cartilage of the fifth rib. It is flattened like a riband in front and behind ; it is about THE RECTUS ABDOMINIS. three or four fingers' breadth wide above, and only two below. Its breadth is generally in an inverse proportion to its thickness. Attdchmcnts. — It arises from the upper edge of the os pubis, in the space between the spine and the symphysis ; and is inserted in front of and below the cartilage of the sev- enth rib and costo-xiphoid ligament, to the cartilages of the fifth and sixth ribs, and sometimes to the bone also. The pubic attachment is a flat tendon, consisting of two very distinct portions, of which the external is the larger. This tendon is continuous by its external border Avith the fascia transversalis. It is separated from its fellow of the opposite side by a very narrow and thick fibrous septum, which forms the lower part of the linea alba. Some- times the internal tendinous fibres intersect with those of the opposite side in front of the symphysis pubes ; and some fleshy fibres often arise from the sides of the linea alba. The presence or absence of the pyramidalis affects the size of the lower part of this muscle. From this tendinous origin the fleshy fibres proceed vertically upward (whence the name oi rectus). At the upper part, where they are prolonged in an expanded form upon the thorax, they are slightly oblique from within outv^ard, and divided into three unequal portions : the internal, the smallest, is attached to the cartilage of the seventh rib and to the costo-xiphoid ligament ; the middle, which is larger, is fixed to the carti- lage of the sixth rib ; and the external, by far the largest, to the cartilage of the fifth rib. Very often a small portion of the muscle is insertad into the base and edges of the xi- phoid cartilage, thus justifying the name of stemo-puhien given to it by Chaussier. It is not uncommon to find this muscle give off a fourth bundle to the fourth rib, and even an aponeurotic expansion to the sterno-cleido-mastoid. The rectus is interrupted by two, three, four, or five tendinous intersections, which pass transversely or obUquely across the muscle in a flexuous or zigzag course, seldom occupying either the entire thickness or width of the muscle, which they divide into so many smaller muscles. There are always more intersections above than below the umbilicus. Relations. — This muscle is contained in a very strong tendinous sheath, which is form- ed by the anterior abdominal aponeurosis, is thicker in front than behind, much stronger below than above, and completely isolates the muscle. Below and behind, this sheath is deficient, in which situation the muscle (passing through the openings. Jig. 1 10, in the aponeurosis of the transversalis) rests directly upon the peritoneum ; the upper and pos- terior part of the sheath is also wanting, so that the muscle is in immediate contact with the cartilages of the fifth, sixth, seventh, eighth, and ninth ribs, and with the cor- responding intercostal muscles. The linea alba occupies the interval between the two muscles, which is much larger above than below the umbilicus ; but the most important of all the relations of the rectus is that of its posterior surface with the epigastric artery, which we shall hereafter notice. Actions. — This muscle, having its fixed point below, and its movable attachments di- vided between the fifth, sixth, and seventh ribs, depresses the whole thorax, and, con- sequently, the vertebral column. Few muscles are so favourably situated as the rectus, which both acts upon a very long lever, and is inserted at right angles to the part to be moved. As the rectus forms a curve, the convexity of which is directed forward, and cannot contract without becoming rectilinear, it follows that the first effect of its contraction is the compression of the abdominal viscera; hence it assists in expelling the contents of the bladder, rectum, and uterus ; it aids in expiration, by depressing the ribs, and, by keeping them fixed when the thorax is dilated, it assists in the performance of any ef- fort. \\Tien the fixed point is above, the rectus becomes a flexor of the pelvis. What are the uses of the intersections 1 It is generally stated that their effect is to increase the number of fibres, and thereby augment the force of the muscle ; and in sup- port of this a principle is adduced, which is incontestable in itself, viz., that the power of a muscle is in a direct ratio to the number of its fibres ; for if each fibre represent one partial power, the more of these the greater must be the total power. But it has been overlooked, that this law only applies to fibres arranged side by side, not to those which are placed end to end. In fact, it may be experimentally shown that, when two equal forces are applied to a lever, parallel to each other, they produce double the effect either would have done separately ; but if one be made continuous with the other, and both are then applied to the same lever, they only produce an effect equal to that of either per se. These intersections, therefore, do not increase the power of the muscle ; nor do they diminish the extent of motion, for the sum of the contractions of the small muscles into which they divide the recti is equal to that of an undivided muscle. What, then, are the uses of these intersections 1 Can it be intended, as Bertin has said, to associate the obUque muscles with the recti by means of the intimate adhesions existing between .them and the aponeuroses 1* * Benin considers these adhesions as true points of attachment tor the muscles of the aiitlomeii, so that when the rectus contracts, it acts :iot only upon tho pubes, but also upon the crests of tlie ilia, through the medium of the abdominal aponeuroses. Professor Berard, who Irmgs forward this forgotten opinion of Ber- tin iRipert. Gentr. dcs Sc. Med., art. Abdomen), correctly observes, that tho obliquus internus only adheres to tho rectus. In the same aficle M. Biirard declares he is not satisfied that the intersections increMe the , I \ver of the recti muscles. SICI^ MYOLOGY. ;, v'-.r; wV^jtU-TSia The Pyramidalis. •:^^^^>^.^At.::< The pyramidalis {d, fig. 1 10), a small triangular muscle which is often deficient, occu- pies the lower part of the abdomen on each side of the linea alba. It arises from the pubis and the anterior ligament of the symphysis by tendinous fibres, from which the fleshy portion proceeds upward, the internal fibres vertically, the external obliquely up- ward and inward, and terminates by a pointed extremity, which is attached to the hnea alba, and forms the apex of the muscle, the base being at the os pubis. It is covered by the aponeuroses of the obliqui and transversalis muscles, and rests upon the rectus. The lower part of the rectus and the pyramidalis are united together. When the latter is wanting, the lower end of the rectus is proportionally increased in size, and vice versa- There are sometimes two pyramidales on one side, and one on the other ; sometimes the two are of unequal size. In a negro I found them extending beyond the middle of the space between the pubis and the umbilicus. Action. — It is a tensor of the linea alba. DIAPHRAGMATIC REGION. T^e Diaphragm. Dissection. — Description. — Attachments. — Relations. — Action. Dissection. — In order to expose this muscle, it is necessary to open the abdomen and remove all the abdominal viscera, taking great care in detaching the liver, stomach, and Kidneys. Tie the oesophagus and vena cava where they pass through the diaphragm, and cut them below the ligature. Raise the peritoneum with the fingers or forceps, and tear it gently away ; thus exposing the lower surface of the muscle without using the scalpel. All the insertions of the diaphragm are well seen on this surface. In order to study the convex surface of the muscle, another subject should be provided, and the tho- rax opened before the abdomen. This is the only method by which a good idea of it can be obtained ; for when the abdomen has been previously opened, the muscle becomes relaxed as soon as the thorax is cut into, and affords no idea of its naturally vaulted form. The diaphragm (septum transversum, a a, fig. Ill), which exists in mammalia only p^ jlj is, according to the expression of Haller, with the exception of the heart, the most important muscle. I in '\ f f \U\ of the body. It is a muscular septum, sitotticd ob- liquely at the junction of the upper with the two lower thirds of the trunk. It separates the thorax -a from the abdomen, constituting the floor of the for- mer and the roof of the latter. All other muscles ,^ are placed on the outside of, or around, the levers which they are intended to move ; but the diaphragm alone is situated within those levers, like the mus- cles of animals having an external skeleton. The diaphragm divides the body into two unequal parts : an upper, or supra-diaphragjnatic ; and a lower, or infra-diaphragmatic. It is placed on the median line, but is not symmetrical. It is elliptical in form, its longest diameter being from side to side, thin and flattened, and resembles an arch, or, rather, a fan, the broad and circular portion of which is horizon- tal, while the narrow part is vertical, and at right angles to the former. The older anatomists, there- fore, divided it into two portions : the upper, or great muscle of the diaphragm ; and the lower, or small m)is cle of the diaphragm. Attachments. — It arises partly from the lumbar re gion of the vertebra, column, in front of the bodies and intervertebral substances of the second, third, and fourth lumbar vertebra? ; partly from the posterior surface of the ster- num and the base of the ensiform cartilage ; and partly from the posterior surface and upper edge of the cartilages and contiguous bony portions of the seventh, eighth, ninth, tenth, eleventh, and twelfth ribs. Sometimes it is attached also to the sixth rib. The vertebral origin consists of two tendons, formed by several smaller vertical ten- dons, situated in front of each other, which are blended with the anterior common liga- ment of the spine. To these tendons two thick, fleshy bundles succeed, which pass ver- tically upward, become gradually thicker and broader, give off" a fasciculus to each other, • and are inserted into the posterior notch in the aponeurosis, having the form of a trefoil leaf, which forms the centre of the muscle, and is therefore called the central aponeurosis of the diaphragm {b, fig. 1 1 1), or cordiform tendon. These two fleshy bundles and their ten- dons (c c) are named the pillars, crura, or appendices of the diaphragm. The right crus THE DIAPHRAGM. 213 IS anterior, larger, and descends lower down than the left. Each pillar is occasionally divided into two very distinct secondary pillars, and the trace of this division is always visible in the opening which gives passage to the great splanchnic nerve. The two pil- lars of the diaphragm leave between them an interval, divided into two portions or rings by the fleshy fasciculi which they mutually give to each other. The communicating fas- ciculus from the right pillar is anterior, and larger than that from the left. Of the two openings (ir rings between the pillars of the diaphragm, the loxcer or aortic {d) is parabolic, and gives passage to the aorta, the vena azygos, the thoracic duct, and sometimes, also. to the left great sympathetic nerve. Like all orifices through which arteries pass, it is aponeurotic in its structure, being formed by the tendons of the pillars of the diaphragm at the sides, and above by a fibrous prolongation of those tendons, which arches over and completes the ring : the upper or (Esophageal opening (e) gives passage to the oesoph- agus and the pneumo-gastric nerves; it is elliptical, and altogether muscular. In one subject, however, I found the upper part tendinous ; and in another, a small muscular fasciculus proceeded from the edge of the orifice, and was lost upon the coats of the oesophagus. Haller has twice observed the same peculiarity. A fibrous prolongation proceeds outward from the tendon of each crus, and is fixed to the base of the corresponding transverse process of the first lumbar vertebra, so as to form an arch on each side (fig. Ill), under which the upper end of the psoas muscle pass- es (ligamentum arcuatum proprium). Another aponeurotic arch, which has been improp- erly called ligamentum arcuatum {ligament cintre du diaphragme), for it is nothing more than the upper edge of the anterior layer of the aponeurosis of the transversalis muscle folded upon itself, extends from the outer extremity of the preceding arch to the lower border and apex of the last rib ; under it passes the superior portion of the quadratus lumborum muscle {fig. 111). From both these arches muscular fibres pass forward, and are inserted into the corresponding part of the cordiform tendon. Indeed, the five ten- dinous arches which we have just described, viz., the aortic in the middle, and the two on each side for the psoas and quadratus lumborum muscles, give origin to all the fleshy fibres which terminate at the posterior notch of the central tendon of the diaphragm The existence of these arches led Haller and Scemmering to reckon three or four crura on each side. The cordiform tendon in which the preceding muscular fibres are insert- ed serves, in its turn, as the origin of other fibres, which constitute the vault of the dia phragm. This central aponeurosis (i), to which so much importance was attached by the ancients, under the name of the phrenic centre, and which some modern anatomists regard as the central point of the entire aponeurotic system of the human body, occupies the middle of the vault of the diaphragm, immediately below the pericardium, with which its circiunference is blended in adults, but from which it may be easily separated in young subjects : it is a sort of aponeurotic island, surrounded on all sides by muscular fibres, and converting the diaphragm into a true digastric muscle. In form, it resembles a tre- foil leaf, with a notch in the situation of the pedicle ; each division is called a wing or leaflet ; the middle leaflet is the largest, the right the next, and the left the smallest. Be- tween the right and the middle le^et is an opening (/), sometimes converted into a ca- nal for the inferior vena cava. This orifice is entirely tendinous, and of a quadrangular shape when the vena cava is removed. It is bounded by four tendinous fasciculi, which meet at right angles. The cordiform tendon is itself composed of several planes of fibres ; the principal of which consists of a diverging series, running forward, and uniting into ir- regular, straight, or curved bundles, which intersect each other at various angles ; an arrangement that gives great strength to the tendon. The fleshy fibres are attached to all points of the circumference of this tendon, and radiate from it in all directions. The anterior, very short, and sometimes aponeurotic, proceed to the base of the ensiform car- tilage, describing a slight curve, with the concavity directed downward. A triangular interval, or else several small spaces, are often left between these fibres, establishing a communication between the cellular tissue of the thorax and that of the abdomen. Hence, diaphragmatic hernias occasionally occur ; and pus, formed in the neck or medi- astinum, may ultimately point at the epigastrium. It is not uncommon to find the ster- nal attachment of the diaphragm partially or entirely deficient. ^ The lateral muscular fibres, which are much longer than the anterior, describe very well-marked curves, and form an arch, with the concavity downward, but more convex and projecting on the right than the left side. They then divide into six or seven digi- tations on each side, which are attached to the ribs, intersecting with the costal inser- tions of the transversalis abdominis. It is not uncommon to find considerable intervals between the digitations of this muscle, opposite which the pleura and peritoneum are in contact ; this more especially occurs between the eleventh and twelfth ribs. The fas- ciculus for the twelfth rib is sometimes deficient, its place being occupied by a tendon. The direction of the fibres of the diaphragm is then radiated and curvilinear in the hori- zontal portion, but radiated and rectilinear in the vertical portion. Relations. — 1. The inferior or abdominal surface, concave in the middle, and much more concave on the right side, where it corresponds to the convex upper surface of the liver, than on the left, where it is in contact with the spleen and the large extremity of the 214 MYOLOGY. Stomach, is covered by the peritoneum throughout the greater part of its exteiit, except- ing at the situation of the coronary ligament of the liver, and also behind, where it is in relation with the third portion of the duodenum, the pancreas, the kidneys, the supra- renal capsules, and the solar plexus. 2. Thoracic, or upper surface. The middle portion is convex, and covered by the pleu- ra and pericardium ; it is flat, and serves as a floor to support the heart, the inferior sur- face of which rests upon it ; hence the pulsations of the heart felt in the epigastrium. The lateral portions are convex, and contiguous to the lungs. The convexity is greater on the right than on the left side : the highest point to which the right side reaches, in the natural condition, is the level of the fourth rib ; the highest point which the left side attains is opposite the fifth rib. Hence the surgical rule of operating for empyema high- er on the right than on the left side.* The height to which the diaphragm is raised varies remarkably ; it reaches very much higher in the foetus than in the adult. Should the muscle be only slightly vaulted, it is considered by medical jurists as one of the presumptive proofs that the infant has respired. 3. Circumference. — ^With the exception of the crura, the diaphragm is connected by its circumference only with one muscle, viz., the transversalis, which presents exactly cor- responding attachments, so that, indeed, these two muscles may be considered as form- ing one contractile sac, interrupted by the costal insertions. Action. — The diaphragm forms an active septum between the thorax and abdomen, which affects the viscera of both cavities. The two pillars act like the long muscles ; the body of the diaphragm after the manner of the hollow muscles. When the pillars contract, they take their fixed point upon the lumbar vertebrae, and their movable point upon the notch at the back of the cordiforra tendon, which is carried backward and down- ward. This aponeurosis, in its turn, becomes a fixed point for all the other curved ra- diated fibres that are attached to the ribs. The first effect of the contraction of a curved fibre is its becoming straight ; and, in this process, the highest part of the curve is drawn down towards a level with its extremities : the vertical diameter of the thorax is, there- fore, increased, and that of the abdomen proportionally diminished ; but, during contrac- tion, the fibres act equally upon both their points of insertion, and, as the cordiform ten- don is fixed, and the costal attachments are movable, the ribs are drawn inward, and the transverse diameter of the thoracico-abdominal cavity thereby diminished. The antero- posterior diameter would be equally diminished, were it not for the inclination of the di- aphragm downward and backward, in consequence of which the abdominal viscera are pressed downward and forward. Some experimentalists, among whom we may men- tion Haller and Fontana, have asserted that the diaphragm may become convex below during a forced contraction, but I beheve this can only take place when air has been ad- mitted into the cavity of the pleura. We shall now consider the effects of the contraction of the diaphragm upon the open- ings by which it is perforated. The elliptical, or, rather, oval opening for the oesophagus, being entirely muscular, is contracted during the action of the diaphragm, in the same manner as the mouth by that of the orbicularis muscle : hence the oesophagus is compressed. From this it has been concluded that vomiting cannot take place during inspiration, but experience proves the contrary, vomiting being favoured by this compression. It is generally said that the orifice for the vena cava is not affected by the contraction of the diaphragm ; but if we draw upon the muscular fibres in the neighbourhood of this opening, we see at once that it is diminished in size ; HaUer has even witnessed this in a living animal during inspiration. The arch, or, rather, the parabolic canal, which gives passage to the aorta, is also contracted, and the vessel slightly compressed ; hence, doubtless, arises the frequency of aneurisms of tliis artery, where it passes through the pillars of the diaphragm. LUMBAR REGION. The Psoas and Illiacus. — Psoas Parvus. —Quadratus iMmborum. The lumbar region includes the psoas and iliacus, the psoas parvus (when it exists), and the quadratus lumborum. 7'he Psoas and Iliacus. I consider that, since the psoas and iliacus muscles have a common insertion, they should be described as a single muscle, having a double origin, which we shall term the psoas-iliac muscle. Dissection. — Having opened the abdomen, tear away with the fingers the peritoneum covering the iliac fossae and the lumbar regions. Remove, at the same time, the intes- * This rule should be disregarded : the object of it is to open the thorax at the lowest part, so as to give a more easy exit to the liquid ; but the lowest portion would be behind, in the deep groove formed by the dia- phragm with the parietes of the thorax. It is of little importance to find the most depending part ; it is suf- ficient to establish an outlet ; the fluid will always flow to it. THE PSOAS ANDi,ILIACUS. 215 tines, the stomach, the pancreas, the kidney, the liver, and the spleen ; detach the iliac fascia. In order to see the femoral insertion of this muscle, divide the crural arch through the middle. Dissect with care the muscles at the anterior and superior part of the thigh, especially the pectineus, with which this muscle is in immediate relation Remove the adipose cellular tissue which surrounds the crural vessels and nerves. The psoas-iliac muscle is deep-seated, and extends from the sides of the vertebral column and front of the iliac fossa to the lesser trochanter of the femur. It arises above by two very distinct muscular masses ; an internal, long, or lumbar portion '[lumbaris, sive psoas, Riolanus), the great psoas of authors ; and an external, broad, or iliac portion, constituting the iliacus (iliacus intemus, Albinus). 1, The lumbar portion (psoas magnus, from tpdai, the loins, g g, Jig. Ill) arises from the sides of the bodies of the five lumbar and last dorsal vertebrae, and of the correspond- ing inter- vertebral substances, and from the base of the transverse processes, by means of aponeurotic fibres, united by tendinous arches, which correspond to the grooves on the bodies of the lumbar vertebrae, so that the muscle is, in reality, only attached to the upper and lower borders of the bodies of the vertebra, and to the inter-vertebral sub- stances. From this double origin the fleshy fibres proceed in the form of a conoid bun- dle, compressed on the sides, and directed obliquely downward and outward ; the sum- mit of the cone is flattened, and embraced by the ligamentum arcuatum ; the body is thicker and rounded, and diminishes in size inferiorly, as its constituent fibres are grad- ually attached to a tendon, which, though at first concealed in its centre, afterward ad- vances towards the anterior and external surface, receives the fibres of the iliacus, and is inserted into the lesser trochanter of the femur. The great psoas, therefore, resem- bles a double cone or spindle. Its component fibres are not fasciculated, but are united by a very delicate cellular tissue. The complete absence of fibrous tissue explains the weakness of this muscle, which may be torn with the greatest facility, and perhaps, also, the frequency of its dis- eases. Its tenderness in the ox causes it to be a favourite joint for the table, under the name of short ribs (aloyau) : perhaps this delicacy of texture is connected with the pres- ence of a large plexus of nerves in the substance of the muscle. 2. The iliac portion (iliacus muscle ; iliacus intemus, Alb., i i,fig. Ill) fills the internal Uiac fossa. It arises from the whole of this fossa, from the crest of the ilium, the ilio- lumbar ligament, and the base of the sacnun, and from the anterior superior iliac spine, the notch below, the anterior inferior iliac spine, and even the capsular ligament of the hip-joint. The fleshy fibres converge, and are immediately attached to the external edge of the common tendon, which we have described as originating in the substance of the psoas. This tendon, which receives on its inner side all the fibres of the psoas, and even those fibres of the iliacus which arise from the brim of the pelvis, runs along the side of the brim, diminishing its transverse diameter, and emerges from the pelvis under the crur£d arch, passing through a remarkable groove between the anterior inferior spi- nous process of the ilimn, and the eminentia ilio-pectinea. In this situation all the fibres of the psoas terminate ; those that remain of the iliacus are successively attached to the outside of the tendon, like the barbs of a feather to the shaft, and form a triangular fleshy bundle, which inmiediately changes its direction, passes backward, inward, and downward among the muscles of the thigh, turns slightly round, so that its anterior sur- face looks somewhat inward, and its posterior surface outward, and is inserted into the lesser trochanter, which it embraces on every side, even to its base. It is not uncom- mon to find the fasciculus which comes from the anterior inferior spinous process of the iUum and the capsular ligament forming a very distinct muscle, which has been often described separately, under the name of the ilio-capsulo-trochantericus ; it is inserted separately below the lesser trochanter into the oblique line which extends from this pro- cess to the linea aspera. Relations. — 1. The lumbar portion (psoas magnus) is in relation anteriorly with the diaphragm, the kidney, the ascending colon on the right side, the descending colon on the left, the peritoneum, and the psoas parvus, when it exists. The external Uiac artery and vein run along the anterior surface. On the inside it corresponds to the bodies of the lumbar vertebrae and the lumbar vessels ; behind, to the transverse processes of the lumbar vertebrae and the quadratus lumborum. The lumbar plexus is situated posterior- ly in the substance of the psoas magnus ; this explains the violent pain in the loins ex- perienced during repeated contractions of this muscle, and, during pregnancy, from the pressure of the gravid uterus. 2. The iliac portion lines the iliac fossa ; it is covered by the peritoneum, the caecum, and the end of the small intestines on the right side, and by the sigmoid flexure of the colon on the left. These two muscles form a projection on the inside, which reduces the transverse diameter of the brim of the pelvis from five inches to four and a half 3. The psoas and iliacus exactly fill that portion of the crural arch in which they are placed, so that hernias never take place in this situation. 4. In the thigh, the common tendon is separated anteriorly from the cellular tissue of the groin by the deep femoral fascia ; it is in relation with the crural nerve, which passes out of the pelvis in the same sheath as, but below, the psoas, in a groove between the iJ16 MYOLOGY. latter and the iliacus, between which parts it forms the only separation. Behind, it is in contact with the anterior border of the os coxae and the hip-joint, a large bursa inter- vening, which often communicates with the synovial capsule of the joint, by an opening of variable size.* The inner edge of the psoas-iliac muscle is in relation with the outer edge of the pectineus, and with the femoral artery, which it sometimes covers. The external edge is at first in relation with the sartorius, and afterward with the rectus femoris. The psoas-iliac is also covered by the lumbo-iliac fascia {fascia iliaca), which will be described hereafter. (Vide Aponeurology.) Actions. — The psoas-iliac muscle flexes the thigh upon the pelvis ; this action is the more energetic from the fact of the fixed points of insertion being both on the vertebral column, and on the iliac fossa. The two portions of the muscle do not act in the same direction ; but when they contract simultaneously, the opposite forces are destroyed, and the traction upon the common tendon becomes direct. This muscle affords a remark- able example of the reflection of a muscle over a pulley, which greatly increases the power, by changing the direction of insertion nearly to the perpendicular. The action of this muscle, therefore, must only be calculated from the point of reflection, i. e., the anterior edge of the ilium. It is in semiflexion that the muscle becomes perpendicular to the femur, and acts with the greatest power ; and, therefore, the Tnomentum of the muscle occurs at that period. The psoas-iliac is at the same time a rotator outward of the femur, on account of the obliquity of its insertion at the inner and back part of that bone. When the femur is fixed, as in standing, it draws the lumbar portion of the spine and the pelvis forward ; and its iliac portion rotates the pelvis so as to turn the front to the opposite side. When the muscles of each side act together, the trunk is inclined directly forward. The Psoas Parvus. This muscle (Z I, fig. Ill) lies in front of the preceding ; it arises from the twelfth dor- sal vertebra, the first and sometimes the second lumbar vertebrae, and the corresponding inter-vertebral substances. It forms a small, flat bundle, at first appearing to be a de- pendance of the psoas magnus, but soon becoming isolated ; it terminates in a broad, shining tendon, which crosses the psoas magnus at a very acute angle, and is inserted into the upper part of the ilio-pectineal eminence, and the corresponding portion of the brim of the pelvis. This small muscle receives the lumbo-iliac aponeurosis (fascia ili- aca) on its outer edge. It is often absent ; we have sometimes seen it double. Its use is evidently to render the iliac fascia tense, and to tie down and prevent displacement of the lumbar portion of the psoas magnus. It may assist in flexing the pelvis upon the thorax, as in climbing ; in the recumbent and supine position, if one muscle acts alone, it inclines the pelvis to its own side ; but if its fixed point be below, it inclines the trunk to the same side. The Quadratus Lumborum. Dissection. — Expose the posterior surface, by carefully detaching the common mass Oi the posterior spinal muscles ; and to view the anterior, open the abdomen and remove the viscera. This muscle is enclosed in a sheath formed by the anterior and middle lay- ers of the posterior aponeurosis of the transversalis abdominis ; divide this sheath, and the muscle will be completely laid bare. The quadratus lumborum (m m, fig. Ill) is quadrilateral in shape, and broader below than above ; it is situated in the lumbar region, on the sides of the vertebral column, be- tween the crest of the ilium and the last rib. Attachments and Direction. — It arises from the ilio-lumbar ligament, and from about two inches of the adjacent part of the iliac crest, by aponeurotic fibres, which, on the outer side especially, are very long. These fibres are bound down by others, crossing them at right angles, and give origin to the fleshy part of the muscles, which proceeds upward and a little inward, in the following manner : 1 . Some of the fibres pass verti cally upward, and are inserted into the last rib, to an extent wliich varies in different in dividuals. 2. Others are directed very obliquely inward, and divide into four fleshy bun- dles, inserted, by means of a similar number of tendons, into the summits of the transverse processes of the four superior lumbar vertebrae. 3. There is most commonly a third plane, anterior to the preceding, and consisting of fibres, which arise from the summits of the transverse processes of the third, fourth, and fifth lumbar vertebrse, and are in- serted into the lower edge of the last rib. Connexions. — The quadratus lumborum somewhat resembles the rectus abdominis, in being enclosed and bound down in a very strong tendinous sheath ; it has, therefore, no direct relations. In front are the kidney, the colon, the psoas, and the diaphragm ; be- hind is the common mass of the spinal muscles, beyond which its outer border some- what projects, especially below. Its most important relations are with the kidney and the colon. It is the guide for the necessary incisions in operations performed in this re- gion, particularly in nephrotomy. * See note. p. 296. INTEK-TRANSVERSALES, RECTUS CAPITIS LATERALIS, AND 8CALENI. 217 Action. — ^With its fixed point at the crest of the ilium, this muscle depresses the last rib, by means of its costal insertions, thus acting as a muscle of expiration ; and it in- clines the spine to its own side, through the medium of its vertebral attachment. With its fixed point above, it inclines the pelvis to its ow^n side. LATERAL VERTEBRAL REGION. The Inter-traTisversales and Rectus Capitis Lateralis. — Scaleni. The lateral muscles of the vertebral column are the inter-transversales of the neck and loins, the rectus capitis lateralis, and the scaleni. The quadratus lumborum, already described, belongs also to this region. The Inter-transversales and Rectus Capitis Lateralis. The inter-transversales muscles exist only in the neck and the loins ; in the back they are represented by the intercostals, an additional proof of the analogy between the ribs and the cervical and lumbar transverse processes. Many celebrated anatomists, how- ever, admit the existence of inter-transverse muscles in the back, but they are nothing more than deep-seated fasciculi of the transverso-spinalis. 1. Inter-transversales of the Neck {a to a, fig. 112). — There are two of these muscles in each inter-transverse space, an interior and a posterior. They are small quadrilateral muscles, one arising from the anterior, the other from the posterior margin of the groove on the transverse process below : from these origins the fibres proceed vertically upward, and are inserted into the transverse process of the vertebra above. They are separated from each other by the anterior branches of the cervical nerves and by the vertebral artery, the canal for which they serve to complete. Behind, they are in relation Avith the posterior spinal muscles, the splenius, the levator anguli scapulas, the transversdis colli, and the cervicalis descendens ; and in part with the rectus capitis anticus major. 2. Rectus Capitis Lateralis {h,fig. 112). — This muscle may be regarded as the first posterior inter-transversalis of the neck, and the rectus capitis anticus minor, which we shall presently de- scribe as the first anterior inter-transversalis. The comparative size of the rectus lateralis is not opposed to this view, for it is connected with the increased development of the corresponding cranial vertebra. It arises from the transverse process of the atlas, and proceeds directly upward, to be inserted into the jugu- lar surface of the occipital bone, immediately behind the fossa of that name. This mus- cle separates the jugular vein, with which it is in contact in front, from the vertebral artery, to which it is contiguous behind. 3. Inter-transversalis of the Loins. — The absence of any groove upon the lumbar trans- verse processes would lead us at once to infer that in this region there must be only one muscle in each inter-transverse space. There are, therefore, five on each side. The first extends from the transverse process of the last dorsal to that of the first lumbar ver- tebra ; and the last from the transverse process of the fourth to that of the fifth lumbar vertebra. Action. — These little muscles, by drawing the transverse processes towards each oth- er, incline that portion of the vertebral column with which they are connected towards their own side ; that is, the cervical muscles with the rectus lateralis incline the head and neck, and those of the lumbar region act upon the loins. The Scaleni. Dissection. — These muscles are, in a great measure, displayed in the ordinary dissec- tion of the anterior and posterior cervical regions. In order specially to expose them upon an entire subject, it is sufficient to dissect off the skin on the sides of the neck, and to remove the omo-hyoid, the nerves, the cellular tissue, and the sub-clavicular lymphat- ic glands. But in order to demonstrate the inferior attachments of these muscles, the upper limb must be scarified by disarticulating the clavicle at its sternal end, or, still bet- ter, by sawing the clavicle through the middle, dividing the great and small pectoral mus- cles, raising the stemo-cleido-mastoid, detaching the serratus magnus, and drawing the apex of the shoulder forcibly backward. The scaleni occupy the sides and lower part of the neck, extending from the two up- per ribs to the six lower cervical vertebrae, sometimes to the atlas also. They are, there- fore, fasciculated like all the other vertebral muscles. Anatomists are not agreed con- cerning their number. Albinus enumerated five on each side ; Sabatier reduced these to three •, but we agree with M. Boyer, and modern anatomists, in admitting the exist- ence of two only, an anterior and a posterior. M. Chaussier has followed the example of ♦ Riolanus, in describing only one, which he calls costo-trachelien. E E •gJ8 MYOLOGY. 1. The scalenus anticus {c,figs. 112, 113, and 114) might be termed the anterior lorig in- ter-transversalis colli. Its name sufficiently indicates its triangular shape, though it rathei resembles a cone with the base below and the apex above. Aitachments and Direction. — It arises from the inner margin and upper surface of the first rib, near its middle, the point of attachment being indicated by a tubercle, with which it is highly important that we should be acquainted, because it serves as a guide in pla- cing a ligature upon the subclavian artery, which passes over the upper surface of the first rib. It arises by means of a tendon that expands into an aponeurotic cone, from the interior of which the fleshy fibres take their origin. These unite, form the body of the muscle, and proceed upward and inward, to be inserted by so many separate tendons into the anterior tubercles of the transverse processes of the sixth, fifth, fourth, and third cer- vical vertebrae, and more especially into the notches between the two tubercles at the ex- tremities of these processes. It is not unconmfion to find one or two fasciculi inserted into the posterior tubercles. Relations. — In front and on the outside, this muscle is in relation with the clavicle, from which it is separated by the subclavian muscle and vein ; higher up, with the stemo- mastoid, the omo-hyoid, the phrenic nerve, and the transverse and ascending cervical arteries. Behind, it is separated from the posterior scalenus by a triangular space, which is wide below to receive the subclavian artery, and narrow above, where it corresponds to the brachial plexus of nerves, by the first two branches of which the muscle is some- times perforated. On the inside, it is separated from the vertebral artery by the longus colli. The relations of the scalenus anticus to the subclavian vein and artery are of the highest importance to the surgeon, and, in order to impress them upon the memory, I propose to designate it the muscle of the subclavian artery. I have seen both the artery and vein placed in front of this muscle. The scalenus posticus {d,figs. 112, 113, and 114) may be termed the posterior long inter- transversalis colli. It is situated behind the preceding muscle, is of the same shape, but somewhat larger. Attachments and Direction. — It has two perfectly distinct origins : one, anterior and larger, from all that part of the first rib intervening between the depression for the sub- clavian artery and the tubercle ; and another, posterior, from the upper edge of the sec- ond rib. The latter attachment is sometimes wanting. Proceeding from this double origin, the fleshy fibres form two small muscular bodies, which either remain distinct, or become blended together, and pass upward and inward, to be inserted by six separate tendons into the posterior tubercles of the transverse processes of the six inferior cer- vical vertebrae. It is not uncommon to find a fasciculus extending from the second rib to the atlas. Relations. — It is separated from the anterior scalenus by the subclavian artery and brachial plexus ; and is in relation, behind, with the cervicaJis descendens, transversalis colli, splenius, and levator anguli scapulae : on the outside, with the serratus magnus, the transverse cervical artery, and the stemo-mastoideus : on the inside, with the first intercostal, the first rib, the inter-transversales of the neck, and the cervical vertebrae. Action. — The scaleni are powerful flexors of the neck, when their fixed points are be- low ; but when their upper attachments are fixed, they tend to elevate the first rib, and in a slight degree the second also. DEEP ANTERIOR CERVICAL, OR PREVERTEBRAL REGION. The Recti Capitis Antici, Major et Minor. — Longus Colli. — Action of these Muscles. This region includes three pairs of muscles placed immediately in front of the cervical and three superior dorsal vertebrae, viz., the rectus capitis anticus major, the rectus capi- tis anticus minor, and the longus colli. Their arrangement is extremely complicated and very difficult of elucidation, unless we consider them in the same general manner al- ready adopted with regard to the disposition of the posterior spinal muscles. Let us suppose, then, that there exists in the median line of the basilar process of the occipital bone and the anterior surface of the bodies of the cervical vertebrae a series of spinous processes (a supposition which is realized in some animals) ; then the rectus capitis an- ticus major would be a transverso-spinalis, the rectus minor an anterior inter-transversalis between the occipital bone and the atlas, and the longus colli would be a compound mus- cle, its lower fibres forming a spino-transversalis, its upper fibres a transverso-spinalis, and its internal fibres a spinalis. All this wiU be rendered apparent from the following description. Dissection. — Remove the face and all the parts which cover the cervical portion of the spine by the vertical section, called the section of the pharynx, because it is also employed in demonstrating that part. In order to separate the face from the cranium, remove the roof of the scull by a horizontal section, and then make a vertical cut either from above or from below ; if we cut from above, we may adopt the usual plan of directing the saw transversely, so as to emerge immediately in front of the auditorj' meatus : in doing this, THE RECTUS CAPITIS ANTICUS MAJOR, ETC. "!?t1) however, we are in danger of injuring the superior attachments of the recti, or of cutting into the pharynx. We prefer, therefore, the following method : make two sections with the saw obliquely forward and inward in the course of the occipito-mastoid and petro- occipital sutures, and having arrived at the basilar process, cut it across with a chisel, a little in front of the anterior condyloid foramina. In separating the face from the cra- nium from below upward, a great number of muscles must be scarified : the preceding section is therefore preferable, although it is somewhat more difficult. The Rectus Capitis Anticus Major. This muscle {e,figs. 112 and 114), the transverso-spinalis anterior (rectus capitis in- temus major, Alb.), is the most external of those in the prevertebral region. Attachments and Direction. — It arises from the anterior tubercles of the transverse pro- cesses of the sixth, fifth, fourth, and third cervical vertebrae, by small tendons, to which as many fleshy fasciculi succeed ; these pass obliquely upward and inward, overlying and blending with each other, and terminate on the posterior surface and edges of a shi- ning aponeurosis, that occupies almost entirely the anterior aspect of the muscle. This aponeurosis itself becomes a surface of origin, dividing into two lamina;, from the bor- ders of and interval between which a fleshy bundle ascends, to be inserted into the basi- lar process in front of the foramen magnum. The fasciculus arising from the third cer- vical vertebra does not join the common insertion, but is attached directly, and in a very distinct manner, to the basilar process within and behind the common fasciculus. The muscle must be turned outward in order to display this structure. Relations. — It is covered by the pharynx, the internal carotid artery and jugular vein, the superior cervical ganglion and trunk of the great sympathetic nerve, and the par va- gum, being separated from all these parts by some loose cellular tissue and the preverte- bral aponeurosis. It covers the corresponding vertebrae, the articulation of the occipital bone with the atlas, and that of the atlas with the axis, a portion of the longus colli, and also of the rectus minor. The Rectus Capitis Anticus Minor. This muscle {f,fig- 112), the inter-transversalis anterior (re^ctus capitis internus mi- nor, Alh.), extends from the base of the transverse process and from the adjacent part of the lateral mass of the atlas, to the basilar process of the occipital bone. It is partial- ly covered by the rectus major, which is nearer the mesial plane : the superior cervical ganglion of the sympathetic rests upon it, and it covers the atloido-occipital articulation. It may be regarded as an anterior inter-transversalis between the occipitcd bone and the atlas, the rectus laterahs constituting the posterior inter-transversalis. The Longus Colli. Attachments, Direction, and Relations. — The longus coUi {g,g,figs. 112 and 114), as be- fore stated, is composed of three very distinct sets of fasciculi : 1. The transverso-spina- lis, which, arising by flat tendons from the anterior tubercles of the transverse processes of the fifth, fourth, and third cervical vertebra;, unite so as to form a considerable fleshy bundle directed upward and inward, occupy the hollow on each side of the median line of the axis, and are inserted into the anterior tubercle of the atlas, which may be regard- ed as the representative of an anterior spinous process : 2. The anterior spino-transver- salis, the least numerous of all, arise from the bodies of the three superior dorsal verte- brae by very slight tendinous expansions, proceed upward and outward, and are inserted into the anterior tubercles of the transverse processes of the fourth and third cervical vertebrae : 3. The spinalis which arise, to the inner side of the preceding fasciculi, from the bodies of the three upper dorsal and four lower cervical vertebrae, and from the in- termediate ligaments, and having described a slight curve, are inserted into the crest of the axis and into the third cervical vertebra. The longus colli is elongated and fusiform in shape ; it supports the pharynx, the oesophagus, the internal carotid artery, the inter- nal jugular vein, and the pneumogastric and great sympathetic nerves : it covers the vertebrae to which it is attached. Action of the Muscles of the deep Anterior Cervical Region. When the head is thrown back, these muscles restore it to its original position. The rectus anticus major tends to flex the head, and from its obliquity to rotate it, so as to turn the face to its own side. The rectus minor inclines the head to its own side. The longus colli flexes the atlas upon the axis, and rotates it so as to turn the face to its own Bide. '^I'he same muscle also rotates the lower part of the neck, so as to turn the face to the opposite side • and, lastly, it is a direct flexor of the cervical region. MYOLOGY. THORACIC REGION The Pectoralis Major. — Pectoralis Minor. — Subclavius. — Serratus Magnus. — Intcrcostales — Supra-costales. — Infra-costales. — Triangularis Sterni. The Pectoralis Major. Dissection. — Separate the arm from the side. Make a horizontal incision from the top of the sternum to the front of the arm on a level with the lower border of the axilla, in- cluding in this incision a fascia which adheres closely to the fleshy fibres. Reflect one of the flaps upward and the other downward, by dissecting parallel to the fibres, i. e., transversely to the axis of the body. The ■pectoralis major (c c, fig. 109) is a broad, thick, triangular muscle, situated at the upper and fore part of the thorax and axilla. It arises from the anterior border of the clavicle and anterior surface of the sternum, from the cartilages of the second, third, fourth, and more particularly those of the fifth and sixth ribs, from the osseous portion of the last-mentioned rib, and from the abdominal aponeurosis : it \s inserted into the an- terior margin of the bicipital groove of the humerus. The clavicular origin consists of short tendinous fibres attached to the entire breadth of the anterior border of the clavicle, for about the inferior third, or half of its extent. The sternal attachment consists of aponeurotic fibres, which, intersecting with those of the opposite muscle, form, in front of the sternum, a very thick fibrous layer, sometimes ahnost completely covered by the muscular fibres, which, in certain individuals, advance nearly to the median line. The costal origins consist of very thin tendinous laminae, and the attachment to the abdominal aponeurosis is blended with that of the rectus abdominis. From these different origins the fleshy fibres proceed outward in different directions ; the upper fibres obliquely downward, the middle transversely, and the lower fibres oblique- ly. These last are folded backward, so as to form a sort of groove, which embraces the lower border of the pectoralis minor. It appears, then, that the pectoralis major is com- posed of three very distinct portions, which are sometimes separated by a greater or less quantity of cellular tissue. These three portions, in converging, are so disposed that the upper overlaps the middle, and this, again, the lower portion, the fibres of which are twisted upon themselves, so that the lowest in front become the highest behind, and vice versa.* They are all inserted into the anterior lip of the bicipital groove by means of a flat tendon, about fifteen lines in breadth, which is continuous with the anterior edge of the tendon of the deltoid. The structure of this tendon commands particular attention, and can only be examined after having divided the muscle across, and turned the exter- nal half outward. It will then be seen that it is composed of two laminae, placed one be- fore the other, sometimes blended together, but generally distinct, or united only by their lower edges, so that they form a groove opening upward. The anterior lamina is the thicker, and receives the clavicular and middle portions of the muscle ; the deep lay- er affords attachment to the lower portion. It is not uncommon to find the two laminae separated by the tendon of the long head of the biceps, the groove for which they then contribute to form. The entire tendon is broader and thicker below than above, and gives off, both forward and backward, an aponeurotic expansion, constituting one of the chief origins of the fascia of the arm.t Relations. — It is covered by the platysma myoides, the mammary gland, and the skin. Its deep relations are of the greatest importance. On the thorax it covers the sternum, the ribs and their cartilages, the pectoralis minor, the subclavius nauscle, the serratus m£ignus, and the intercostals. It forms the anterior wall of the axilla, and is in relation with the brachial plexus and axillary vessels, and with the cellular tissue and lymphatic glands of that region. Its external border is nearly parallel to the anterior edge of the deltoid, being separated from the latter by a linear or triangular cellular interval, in which are situated the cephalic vein and acromial artery. Its lower border is thin towards the median line, thick and tendinous externally ; it forms the anterior border of the ax- illa, and gives rise to a projection under the skin, proportionate to the development of the muscle. Its inner border intersects in the median line with the muscle of the opposite side, and is continuous below with the linea alba. Uses. — The pectoralis major is essentially an addTictor of the arm ; at the same time it rotates it inward, and draws it forward. It is by the action of this muscle that the fore- arms are crossed, and that one hand is placed on the opposite shoulder. Its upper or clavicular portion conspires with the anterior fibres of the deltoid and with the coraco- brachialis in elevating the humerus, and carrying it forward. * I believe that this overlapping and folding of the muscular fibres tend, reciprocally, to prevent the dis- placement of any individual portion of the muscle. t I have once observed a very slender muscular fasciculus, arising' from the abdominal aponeurosis, proceed along the inferior border of the pectoralis major, from which it was perfectly distinct, and terminate in a small tendon opposite the humeral insertion of that muscle. This tendon was continued along- the inner side of the arm, adhered to the aponeurotic inter-muscular septum, from which it received a small fleshy fasciculus, and was ultimately inserted into the epitrochlea IHB FECTORALIS MINOR, SUBCLAVIUS, AND SERRATUS MAGNUS. 2l2t If the arm be at a moderate distance from the side and its lower extremity be fixed, as is the case in falling on the elbow when the arm is directed outward, this muscle acts upon the humerus as upon a lever of the third order, of which the fulcrum is below, the pow- er in the middle, and the resistance above ; and it then tends to dislocate the bead of the humerus •with great force, because in this position its insertion is perpendicular to the lever. When the humerus is fixed, the pectoralis major acts upon the ribs, the sternum, and the clavicle, and raises the trunk upon the arm. It is, therefore, one of the chief agents in climbing. Its action upon the ribs renders it an important auxiliary in cases of la- borious inspiration. Hence the attitude of an asthmatic patient, who always nlaces him- self so as to keep the humeri fixed. The Pectoralis Minor. Dissection. — Detach the clavicular insertion of the pectoralis major, and divide that muscle in the middle by a verticle incision ; reflect the two flaps, taking care to remove, at the same time, the loose cellular tissue which invests its deep surface. The pectoralis minor {t,fi.g. 110) is a thin, flat, triangular muscle, having its internal edge serrated (serratus anticus, Albinus), and occupying the anterior and upper part of the thorax and shoulder. It arises from the third, fourth, and fifth ribs, by three delicate, shining, tendinous prolongations, lying superficially to the intercostal muscles ; to these succeed three fleshy fasciculi, which unite and converge, so as to be inserted by a flat tendon into the anterior margin of the coracoid process, near its summit. Relations. — It is covered by the pectoralis major, from which it is separated by the tho- racic vessels and nerves : its posterior surface is in relation with the ribs, the intercos- tal muscles, the serratus magnus, the cavity of the axilla, and, therefore, with the axillary vessels and nerves. This last relation is of great importance, and sometimes renders the section of this muscle necessary for the ligature of the axillary artery. Attention should also be directed, 1 . To its upper border, which is separated from the clavicle by a triangular interval, broad on the inside and narrow on the outside, in which the same artery may be tied ; and, 2. The lower border of the muscle extends downward beyond the pectoralis major. Action. — Most commonly it acts upon the scapula (musculus qui scapulam antrorsum agit, Vesalius). With its fixed point at the ribs, it evidently draws the scapula forward and downward, and forcibly depresses the apex of the shoulder. As a depressor of the shoulder, it acts in conjunction with the levator anguli scapulae and rhomboideus, but an- tagonizes those muscles considered as elevators of the entire scapula : it is also opposed to the rhomboideus when moving the scapula forward. With its fixed point at the scapu- la, this muscle elevates the ribs to which it is attached. The Subclavius. Dissection. — Raise the clavicle by carrying the apex of the shoulder upward ; divide the pectoralis minor, and remove the fibrous membrane, descending from the clavicle, and immeidiately investing the muscle. In order to expose its external or clavicular in- sertion, saw through the clavicle in the middle, divide the muscle at the same point, and reflect the external half with the corresponding portion of the clavicle. The subclavius (g,fig. 110) is a long, thin, fusiform muscle, applied to the lower sur- face of the clavicle, by which it is concealed (musculus qui sub clavicula occultatur, Fa- bricius Hildanus). It arises from the cartilage of the first rib, and is inserted into the in- ferior and external surface of the clavicle. Its costal attachment consists of a cervical tendon, from which the fleshy fibres proceed outward, backward, and upward, and are in- serted into the clavicle by short, tendinous fibres. Relations. — It is covered above by the clavicle, which is grooved beneath for its recep- tion ; it is in relation below with the first rib, being separated from it by the axillary ves- sels and the brachial flexus ; in front, it is enveloped by a very strong aponeurosis, com- pleting the osteo-fibrous canal in which it is included. Its relation with the brachial plexus and axillary vessels prevents the direct compression to which these parts would have been otherwise exposed between the clavicle and the first rib. Action. — ^When its fixed point is at the first rib, it depresses the clavicle, and is, there- fore, a depressor of the shoulder ; it tends also to press the inner end of the clavicle for- cibly against the sternum ; so, also, in fracture of the clavicle, it occasions the external fragment to ride upon the internal. When its fixed point is at the clavicle, it assists in elevating the first rib, and is, therefore, arranged among the muscles that act in impeded inspiration. The Serratus Magnus. Dissection. — Having removed the two pectorals, saw through the clavicle at its mid- dle ; press the scapula backward, directing its axillary edge outward ; remove with care the cellular tissue occupying the axilla, especially that against the axillary vessels and nerves, and near the intercostal attachments of the muscle itself, in order to see the in- ternal surface of which the subject must be turned, and the vertebral eosta of the scap- ula drawn outward. 222 XM.i* - MYOLOGY. The serratus magnus [u,fig. 106, d, 109, and I, 110), very broad, quadrilateral, and ser- rated along one of its borders, occupies the side of the thorax, and extends, hke a mus- cular girth, from the ten upper ribs to the vertebral costa of the scapula. Its costal at- tachments consist of nine or ten digitations arranged in a curve, having its concavity di- rected backward. The first digitation, which is very large, arises both from the first and second ribs, and from an aponeurotic arch between them ; from thence tlie fibres proceed upward, outward, and backward, and are inserted into the inner surface of the posterior and superior angle of the scapula, near the levator anguli. This digitation is the narrowest part of the muscle ; it differs in direction from the remainder, and is sep- arated from them by a cellular interval ; hence it has been termed the superior portion of the serratus magnus. The second, third, and fourth digitations arise in an oblique line, running downward and forward from the second, third, and fourth ribs. These are the largest and the thinnest of all the digitations ; they proceed horizontally backward, and are inserted separately, by short tendinous fibres, into the entire length of the verte- bral costa of the scapula, anterior to the rhomboid ; they are distinguished from the re- maining digitations both by their direction and by an intervening cellular space ; they form the middle portion of the serratus magnus. The fifth, sixth, seventh, eighth, ninth, and tenth digitations arise from the outer sur- face of the corresponding ribs along oblique lines, resembling the fingers crossed, and are interposed between corresponding prolongations of the external oblique. These di- gitations are at first tendinous ; they soon become fleshy, and, converging towards each other, form a radiated fasciculus, which passes upward, outward, and backward, to be inserted into the internal surface of the inferior angle of the scapula. This is the infe- rior portion of the serratus magnus. Relations. — The serratus rnagnus is partially covered by the two pectorals before, by the subscapularis behind, and above by the axillary vessels and nerves ; its deep surface rests upon the ribs and the intercostal spaces, all these parts being united by a quantity of loose cellular tissue. A considerable portion of the lower part of the muscle is sub- cutaneous, and, therefore, the inferior digitations are important studies for the painter and the sculptor, and sometimes even for the surgeon, as indications of the arrangement of the corresponding ribs. Action. — From the disposition of its different fasciculi, the serratus magnus occasions a compound movement of the scapula, which it will be well to analyze. The upper por- tion depresses and brings forward the apex of the shoulder ; the middle portion draws the entire scapula directly forward ; while the lower portion depresses it, and, more- over, rotates it, so that the apex of the shoulder is carried upward. As the lower part of the muscle is composed of six or seven of the converging fasciculi, which act with greater energy than the others, it follows that their action predominates even when the whole muscle contracts. The serratus magnus is, then, a depressor of the entire shoulder, and an elevator of its apex. It is more especially concerned than any other muscle in supporting a burden upon the shoulder. In order that the action of the serratus may be directed upon the scapula, its costal attachments must be fixed : this requires the simultaneous contraction of the oblique muscles of the abdomen to maintain the ribs in a depressed position, and of the dia- phragm and transversalis to prevent their projection outward. This simultaneous con- traction occurs during all great efforts. When the fixed point of the serratus magnus is at the scapula, its upper portion be comes a muscle of inspiration, its middle one of expiration, and its lower one of inspira tion. The greater power of the latter has been the cause of the antagonizing action of the middle portion being overlooked ; and the serratus magnus is, with great justice, re garded as the most powerful accessory muscle of inspiration : hence the various atti- tudes of asthmatic persons, who instinctively take a position which fixes the scapula, either by seizing a cord suspended from the top of the bed, or by bending forward, anc" leaning on their elbows and forearms, or by resting their upper extremities on two lat eral supports. The Inter-costales, Externi and Interni ; the Supra-costdles and the Infra costales. Dissection. — In order to examine the extemeil intercostals and the supra-costales (le vatores costarum), the scapula and all the muscles which cover the thorax must be re moved ; to expose the internal inter-costales and the infra-costales, it is necessary to saw through the middle of the dorsal vertebrae and the sternum in a vertical direction, and to tear off the pleura from one side of the thorax, which may be very easily accom plished by the fingers. The intercostal muscles, as their name implies, occupy the intervals between the ribs there are two in each intercostal space, and, therefore, as many pairs as there are spaces. They are divided into external and internal. They represent two very tliin muscular layers, of exactly the same width as the spaces to which they belong ; taken together. THE INTER-COSTALES, SUPRA-COSTALES, AND INFRA-COSTALES. 223 they also occupy the entire length of those spaces, but not separately, for the external intercostals extend only from the costo-vertebral articulations to the commencement of the cartilages of the ribs, while the internal intercostals commence at the angles of the ribs behind, and extend forward to the sternum. A very thin aponeurosis is prolonged from the free margin of the one forward and of the other backward to the end of the in- tercostal space. The external muscles, which I have generally found thicker than the internal, arise from the lip of the groove on the lower border of one rib, and the internal from the inner hp of the same groove, as well as from the corresponding costal carti- leige ; they are both inserted into the upper border of the rib below. The superior at tachments consist of fleshy and tendinous fibres and lamellae, all of which proceed down- ward to the rib below ; those of the external layer obliquely forward, and those of the internal layer much l6ss obliquely backward. The inferior attachments are similar in structure. The tendinous fibres of the intercostal muscles are very long, and much more numerous than the fleshy fibres : hence the intercostal spaces possess consider- able strength, to which the crossing of the two layers also contributes. Relations. — The external intercostals are covered by the two pectorals, the serratus magnus, the serrati postici, the latissimus dorsi, the sacro-lumbalis, and the external ob- lique ; they are superficial to the internal intercostals, and are separated from them by the intercostal vessels and nerves, and by a very thin fibrous layer. The internal intercostala are covered by the external and by the aponeurotic layer continuous with them anterior- ly. Internally they are in relation with the pleura, which, from the angles to the tuber- osities of the ribs, is in apposition with the external muscles. The infracostal muscles of Verheyen consist of small muscular and aponeurotic tongues, variable in number and length, which extend from the inner surface of one rib to the in- ner surface of the next, and sometimes, also, to the second or third rib below. They are sometimes vertical, but often oblique, like the internal intercostals, of which they may be regarded as portions. Supra-costales (levatores breviores costarum of Alhinus, o to o,fig. 107). These are small triangular muscles, situated at the back part of the intercostal spaces. They are accessories of the external intercostals, resemble them in being half tendinous and half fleshy, and appear to form a continuation of them. There are twelve on either side. Each arises from the summit of the transverse process of a vertebra, and proceeds in a radiated manner downward, to be inserted into the back part of the upper border and ex- ternal surface of the rib below. The fibres of these muscles have the same direction as those of the external intercos- tals, but they are more obhque, especially on the outside. The first arises from the trans- verse process of the seventh cervical vertebra, the last from that of the eleventh dorseil. Some of these muscles have two digitations, one disposed in the ordinary manner, the other attached to the next rib below. The latter, called the long supra-costals (levatores longiores, Albinus and Haller), form a transition between the levatores breviores and the serrati. Morgagni met with all the levatores united together, so as to form a very reg- ular serrated muscle. They are covered by the longissimus dorsi and sacro-lumbaUs, and they cover the external intercostals. Action. — The contraction of the intercostal muscles tends to approximate the ribs ; and, according as the upper or the lower ribs are fixed, they act as muscles of inspira- tion or of expiration. It has never been denied that the external intercostals are mus- cles of inspiration, but the crossing of the tAvo muscidar layers has given rise to the opin- ion that they oppose each other in action ; and hence arose the celebrated dispute be- tween Bamberger and Haller. It is easy to understand that the slight difference exist- ing between their attachments, with regard to their distance from the fulcrum, could not counterbalance the effect of a difference in the relative fixedness of the ribs, and that the intercrossing of these muscles has no other object than to increase the strength of the parietes of the thorax. As the first rib is much more fixed than the last, it follows that it must serve as a fixed point for the first intercostal muscle, which will consequently raise the second rib ; this will then become the fixed point for the third rib, and so on. The scaleni off^en take their fixed point upon the vertebrae, and then assist in elevating the first rib. The quadratus lumborum depresses the last rib, which may then serve as a fixed point for the others during expiration. The levatores act very effectually in raising the ribs ; for, being attached so near to the fulcrum, the slightest movement produced in the posterior extremity of the rib be- comes very sensible at the other end. I agree with Borelli {De Motu Animal., torn, ii-, p. 158), that the intercostals act even during the most easy respiration. This can be observed upon our own persons, and also in individuals in deep sleep. The ribs will be seen distinctly carried outward, and the sternum raised. The Triangularis Sterni, or small Jlnterior Serratus. Dissection. — Divide the ribs vertically at their junction with the cartilages, and tear off" the plenra with the fingers. 224 .i/.(K. :v -'^X- ^" MYOLOGY. '""^ The triangularis sterni represents the levatores costarum in front, or, rather, the ser- rati postici, with this difference, that it occupies the internal instead of the external sur- face of the thorax. Like them, it is sen-ated. It arises from the sides of the posterior surface of the sternum, from the ensiform cartilage and the inner ends of the cartilages ■ of the ribs. From this origin the fleshy fibres proceed, dividing into three, four, five, and sometimes six digitations, which are inserted by tendinous fibres into the posterior sur- face and borders of the sixth, fifth, fourth, third, sometimes of the second, and even of the first costal cartilages. The lower fibres pass horizontally and parallel to the upper fibres of the transvcrsalis, with which they are continuous. The succeeding fibres are directed upward and outward, proceeding more and more obliquely upward : hence the triangular shape of the muscle, to which its name refers. Relations. — It is covered by the sternum, the internal intercostal muscles, and the cos- tal cartilages, from which it is separated by the manunary vessels and some lymphatic glands ; it is lined internally by the pleura, and rests upon the diaphragm below. Its use is evidently to depress the costal cartilages, into which it is inserted, or to op- pose their elevation. Remarks concerning the Intercostal Muscles. — The muscles we have just described, viz., the intercostals and" their accessories, are essential elements in the construction of the chest ; they are found in all animals possessed of a thorax. Their use is to dilate and contract this cavity in its antero-posterior and transverse diameters. The first rib, be- ing Itxed by the contraction of the scaleni, serves as a fulcrum for the agents of inspira- tion ; and the last rib, when fixed by the quadratus lumborum, serves the same purpose for those of expiration ; so that these muscles, whose most common action is to incline to one side the neck and the loins, do not, on that account, act the less u^jon the ribs. I cannot, by any means, agree with Winslow, who denies that the scaleni have any ac- tion upon the ribs, and maintains that the articulation of the first rib with the first dor- sal vertebra is intended for the movement of the vertebra on the rib, not for that of the rib on the vertebra. (Winslow, Expos. Anat., t. ii., p. 360.) SUPERFICIAL ANTERIOR CERVICAL REGION. TAe Platysma Myoides. — Sterno-cleido-mastoideus. The Platysma Myoides. Dissection. — Stretch the muscle by inclining the head backward and placing a block under the shoulders of the subject ; make a horizontal incision through the skin from the angle of the jaw to the symphysis menti, another from the symphysis to the inner end of the clavicle, and a third along the clavicle. These incisions should be very super- ficial, scarcely dividing the entire thickness of the skin. The muscle must be very cau- tiously dissected by taking care to commence at its upper part, to turn the edge of the scalpel towards the skin, and to follow exactly the direction of the fleshy fibres which pass obliquely downward and outward. The platysma myoides (e, fig. 109), called le pcaucier by Winslow, latissimus colli by AI- binus, is a broad, very thin, and irregularly-quadrilateral muscle lining the skin at the fore part of the neck, and adhering to it like the cutaneous muscles of the lower animals. It extends from the skin covering the anterior and upper part of the thorax to the side ' of the face, where it terminates thus : at the base of the lower jaw, at the commissure of the lips, upon the masseter muscle, and at the skin of the face. From its lower at- tachment, which is almost always prolonged as far as the shoulder, and loses itself in the subcutaneous cellular tissue, the fibres proceed obliquely upward and inward ; the pale muscular fasciculi which they form are separated from each other, and sometimes strengthened by additional fasciculi to the posterior border of the muscle : they terminate in the following manner above : the posterior fibres are lost under the skin of the face near the masseter muscle, the lower end of which they cover ; those next in front are partly continuous with the triangularis oris, and partly with the quadratus menti ; the anterior fibres terminate at the external oblique line of the lower jaw, and the most in- ternal intersect with those of the opposite side. The posterior fibres, which are lost upon the skin of the face, are the rudiments of a remarkable fasciculus, an accessory of the platysma found in some subjects. It is directed obliquely downward, from the re- gion of the parotid gland to the angle of the lips. Santorini described it under the name ofrisorius novus. Relations. — These two muscles occupy the whole anterior region of the neck, except- ing the median line, where they leave a triangular interval, having its base below, and occupied by a very dense fibrous tissue, forming a species of raph(5, which is found in the median line throughout the body. This is the linea alba of the neck, from which the dif- ferent component layers of the cervical fascia take their origin. The platysma is intimately connected with the skin, but it does not adhere equally throughout ; it is united closely below, but much more loosely above, where the inter THE STERNO-CLEIDO-MASTOIDEUS. 225 ▼enmg cellular tissue is always adipose, and capable of containing a large quantity of fat, as we find in individuals who have what is called a double chin. There are no lym- phatic glands between this muscle and the skin ; they are all situated beneath the mus- cle. The relations of the deep surface of the platysma are very numerous. It covers the supra and sub-hyoid, and the supra-clavicular regions, being separated from all the structures beneath it by the cervical fascia, to which it is united by loose cellular tissue, seldom containing any fat. If we examine these relations in detail, we find, proceeding from below upward, that it covers, 1. The clavicle, the pectoralis major, and the deltoid ; 2. In the neck, the external jugular vein, and also the anterior jugulars where they ex- ist, the superficial cervical plexus, the sterno-mastoid, the omo-hyoid, the sterno or cle- ido hyoid, the digrastic, and the mylo-hyoid muscles, the sub-maxillary gland, and the lymphatic glands at the base of the jaw. In front of the sterno-mastoid, it covers the common carotid artery, the internal jugular vein, and the pneumogastric nerve ; behind the sterno-mastoid, it covers the scaleni muscles, the nerves of the brachial plexus, and some of the lower nerves of the cervical plexus. 3. In the face, it covers the external maxillary or facial artery, the masseter and buccinator muscles, the parotid gland, &c. Action. — The platysma is the most distinctly marked vestige in the human body of the panniculus carnosus of animals ; and it can produce slight wrinkles in the skin of the neck. Its anterior border, especially at its insertion near the symphysis menti, is the thickest part of the muscle, and therefore projects slightly during its contraction. It is one of the depressors of the lower jaw ; it also depresses the lower lip, and, slightly, the commissure of the lips. It therefore assists in the expression of melancholy feelings, but it is antagonized by the accessory portion, which draws the angle of the lips upward and a little outward, and thus concurs in the expression of pleasurable emotions ; hence its name, risorius. The Sterno-cleido-mastoideus. Dissection. — Divide the skin and the platysma from the mastoid process to thewtop of the sternum, in an oblique line, running downward and forward ; reflect the two flaps, one forward and the other backward, taking care to remove at the same time the strong fascia which covers the muscle. In order to obtain a good view of the superior attach- ments, make a horizontal incision along the superior semicircular line of the occipital bone. The sterno-cleido-Tnastoid {b, Jig. 113) occupies the anterior and lateral regions of the neck. It is a thick muscle, bifid below, and narrower in the middle than at either end. It arises, by two very distinct masses, from the inner end of the clavicle, and from the top of the sternum in front of the fourchette, and is inserted into the mastoid process and the superior semicircular line of the occipital bone. The sternal origin consists of a tendon prolonged for a considerable distance in front of the fleshy fibres. The clavic- ular origin consists of very distinct parallel ten- pig. 113. dinous fibres, attached to the^ inner side of the anterior edge and upper surface of the clavicle, to a very variable extent, an important fact in surgical anatomy. There is often a considerable cellular interval between these two origins ; sometimes this interval scarcely exists, but, in all cases, the two portions of the muscle can be readily separated. From this double origin the fleshy fibres proceed, forming two large bundles, which rfimain distinct for some time. Many anatomists, therefore, Albinus in particular, have considered it as consisting of two separate mus- cles, which they describe as the sterno-mastoid and the cleido-mastoid ; a division that is sanc- tioned by the comparative anatomy of this mus- cle. The sternal portion of the muscle is the larger, and passes upward and outward ; the cla- vicular portion proceeds almost vertically upward, behind the other, and is entirely concealed by it at the middle of the neck ; the two portions still remain separate, although approximated ; ulti- mately they become united, and are inserted into the apex and anterior surface of the mastoid pro- cess by a very strong tendon, which runs for some distance along the anterior border of the muscle, and also into the two external thirds of he superior semicircular line of the occipital bone, by a thin aponeurosis. The direction- or axis of the sterno-mastoid passes obliquely upward, backward, and outward. The relations of this muscle are very important. Its superficial or external surface is covered bv the skin and platysma, from which it is separated by the external jugulai' Fy 226 MYOLOGY. vein, and the branches of nerves, constituting what is improperly termed the superficial cervical plexus. Its deep or internal surface covers, 1. The sterno-clavicular articulation ; 2. All the muscles of the sub-hyoid region, and also the splenius, the levator anguli scap- ulae, the digastricus, and the scaleni ; 3. The accessory nerve of Willis, which crosses beneath its superior third, the pneumo-gastric nerve, the great sympathetic, the loop of the hypoglossal nerve, and the cervical nerves ; 4. The internal jugular vein ; 5. The lower portion of the common carotid artery. Its anterior border produces a ridge under the skin, which it is important to study, because the first incisions for hgature of the common carotid, and for oesophagotomy, should be made along it. The parotid gland rests upon the upper part of this border, which is separated from the corresponding bor- der of the muscle of the opposite side by a triangular interval, of which the apex is be- low and the base above. Its posterior border forms the anterior limits of the lateral tri- angle of the neck, which is bounded behind by the external margin of the trapezius, and below by the clavicle. Action. — When the sterno-cleido-mastoid of one side acts alone, it flexes the head, in- clines it to its own side, and rotates it so that the face is turned to the opposite side. It is, therefore, both a flexor and a rotator of the head. When both muscles act together, they flex the head directly upon the neck, and the neck upon the chest. Their action is particularly manifested in an attempt to raise the head while lying upon the back. Still, there is a position in which this muscle may become an extensor of the head, viz., when it is thrown very far backward ; and this effect is owing to the nature of the upper inser- tion, which is situated somewhat behind the fulcrum of the lever represented by the head. This muscle affords one of the most remarkable examples of the co-operation or si- multaneous action of several muscles, in order to give effect to the action of one. Thus, in order that the sterno-cleido-mastoid may act most advantageously upon the head, it becomes necessary that the sternum, being the fixed point, should be maintained as im- movable as possible, and this can only be effected by the contraction of the recti muscles of the abdomen. These latter, in their turn, require a fixed point at the pelvis, and this renders necessary the contraction of the glutaei, the semi-tendinosus, the semi-mem- branosus, and biceps femoris on either side ; and, lastly, for the action of these, the legs require to be fixed by means of their extensor muscles. This remarkable simultaneous contraction of so many muscles, necessary for the ac- tion of but one, has been extremely well illustrated by Winslow. It has many impor- tant results both in physiology and in pathology. MUSCLES OF THE INFRA-HYOID REGION. The Stcrno-hyoideus. — Scapula- or Omo-hyoideus. — Sterno-thyroideus. — Thyro-hyoideus. The muscles of the infra-hyoid region are four in number«on each side, viz., the sterno, or, rather, cleido-hyoid, the omo-hyoid, and the sterno-thyroid, which is continuous above witli the fourth muscle, viz., the thyro-hyoid. The Sterno-hyoideus. Dissection. — This is extremely easy, and is the same for all the muscles of this region. Tlie only caution necessary is, that the clavicular and sternal attachments of these mus- cles should be studied from their posterior aspect only, and that the trapezius must be removed in order to expose the scapular attachments of the omo-hyoid. The sterno-hyoid [I, figs. 113 and 114) is a flat, thin, riband-like muscle, which is some- times double on each side. It arises from the inner end of the clavicle, and is inserted into the os hyoides. Its inferior attachment is liable to some variations ; most conmion- ly it is connected with the back part of the inner extremity of the clavicle and with the inter-articular cartilage ; sometimes with the outer side of that extremity ; and sometimes with the circumference of the clavicular surface of the sternum. From this origin the fleshy fibres proceed parallel to each other, upward and inward, to be inserted by short tendinous fibres into the lower edge of the body of the os hyoides on the side of the median line, and to the inside of the omo-hyoid, with which it is often blended. Imme- diately above the clavicle this muscle is often divided by an aponeurotic intersection, which is united to that of the opposite side, and forms, as it were, a transverse bridle. Relations. — It is covered by the platysma, the stemo-mastoid, and the cervical fascia. It covers the deep-seated muscles, the thyroid body, the crico-thyroid and thjTO-hyoid membranes, from which it is often separated by a bursa mucosa, the crico-thyroid mus- cle, and the superior thyroid artery. The inner edges of the two sterno-hyoid muscles are generally separated by a fibrous raphe, but they are sometimes blended together, and thus render the operation of tracheotomy more difficult. This impediment may, how- ever, be overcome by keeping accurately in the median line. The Scapulo- or Omo-hyoideua. This muscle (coraco-hyoideus, Albinus, m m, figs. 113 and 114) is longer and more THE STERNO-THYROIDEUS AND THYRO-HYOIDEUS. 227 slender than the preceding ; it is a digastric reflected muscle, composed of two small fleshy bellies, united by an intermediate tendon. It arises from the superior border of the scapula behind the coracoid notch, over an extent varying from a few lines to an inch, and is inserted into the lower part of the body of the os hyoides, externally to the sterno-hyoid. From its origin, which is sometimes tendinous, it proceeds for a variable distance behind and parallel to the clavicle, and is then reflected upward and inward, at an obtuse angle. At the point of reflection it becomes entirely or partially tendinous, and gives origin to another fleshy bundle larger than the former, which is inserted into the OS hyoides. The angular direction of this muscle is maintained by means of an aponeurosis, first described by Soemmering, which extends between the inner borders of the two muscles, and is fixed to the clavicle : it is one of the layers of the cervical fascia, an important structure, to be again alluded to hereafter, and of which the omo-hyoid muscles are ten- sors. These muscles eire occasionally wanting ; sometimes they are double. In one case of this kind the accessory muscle was larger than the normal one, and arose from the upper and internal angle of the scapula. Relations. — This small muscle, before reaching the sub-hyoid region, traverses two others, the supra-clavicular and the stemo-mastoid. It is covered by the trapezius, the subclavius, the clavicle, the platysma, the stemo-mastoid, and the skin ; it covers the scaleni, the brachial plexus, the internal jugular vein, and the common carotid artery, and it is in contact with the outer border of the sterno-hyoid muscle. The Sterno-thyroideus. The sterno-thyroid (w. Jig. 1 14) closely corresponds with the sterno-hyoid, from which it differs only in being shorter and broader. It extends from the posterior surface of the sternum to the thyroid cartilage. It arises from the sternum opposite the first rib ; it is often blended with its fellow, so that their origins form a line reaching the entire breadth of the sternum, and often to the edges and posterior surface of the cartilage of the first rib. From this origin the fleshy fibres proceed directly upward parallel to each other, and are inserted into the thyroid cartilage by a tendinous arch running obliquely downward and inward, which embraces the thyro-hyoid muscle, and is attached by its extremities to two very prominent tubercles on the external surface of the cartilage. It is some- times continued as far as the os hyoides by a small lateral prolongation, and at other times it is continuous with the thyro-hyoid. The sterno-thyroid is interrupted by a ten- dinous intersection analogous to those of the rectus abdominis. It is not uncommon to find the two sterno-thyroid muscles united together by an intervening aponeurosis shaped like the letter V, opening upward, and corresponding to the fourchette of the sternum. Relations. — It is covered by the sterno-hyoid and omo-hyoid muscles, and it covers the trachea, the lower part of the subclavian and internal jugular veins, the common carotid artery, and the arteria innominata on the right side, the thyroid body and the thyroid vessels. The middle thyroid vein runs along its inner border, an important relation in regard to the operation of tracheotomy. The Thyro-hyoideus. This is a small quadrilateral muscle (hyo-thyroideus, Albinus), which may be consider- ed a continuation of the stemo-thjToid (^o,figs. 113 and 114). It arises from the oblique line, and the tubercles of the thyroid cartilage, where it is embraced by the tendinous arch of the preceding muscle, passes vertically upward, and is inserted into the posterioi surface of the body and part of the great cornu of the os hyoides. Relations. — It is covered by the two muscles of the superficial layer, and covers the thyroid cartilage, and the th3TO-hyoid membrane. Action of the Muscles of the Sub-hyoid Region. — These muscles are the most simple, both in structure and in action : they all concur in depressing the lower jaw ; but if the lower jaw is ficxed, they produce flexion of the head. The fixed points of all are below, viz., at the sternum on the inside, at the clavicle in the middle, and at the scapula on the outside. This arrangement not only bestows particular uses upon each, but renders the common action of all more certain. Thus, the omo-hyoid, at the same time that it de- presses the 03 hyoides, carries it backward and towards its own side. Wliere the two omo-hyoid muscles act together, the os hyoides is directly depressed, and forced back- ward against the vertebral column. The sterno-hyoid and the sterno-thyroid, prolonged by the thyro-hyoid, draw the os hyoides directly downward. The principal use of the thyro- hyoid is, to move the os hyoides upon the thyroid cartilage, in which movements the upper part of the cartilage is carried behind the os hyoides, the curve described by which is al- ways greater than that formed by the cartilage. The muscles of the sub-hyoid region nev- er eissume as their movable point 3 either their sternal, clavicular, or scapular attachments ^'P^^^IP^'^F*^ 228 MYOLOGY. MUSCLES OF THE SUPRA-HYOID REGION. The Digastricus. — Stylo-hyoideus. — Mylo-hyoideus. — Genio-hyoideus. — Their Action. The muscles of this region, taken in the order of super-imposition, are the digastric, the stylo-hyoid, the mylo-hyoid, and the genio-hyoid. The Digastricus. Distection. Remove the platysma, reflect the mastoid insertion of the stemo-mastoid ; Pig^ 114. detach and raise the sub-maxillary and the lower extremity of the pa- rotid gland. The digastric muscle (biventer mjixillae inferioris, Albinus,p p,figs. 113 and 114), so named because it consists of two fleshy bellies, united by an intermediate tendon, reaches the whole extent of the supra-hyoid region, from behind forward. It is, in some respects, the type of digas- tric muscles. It is curved upon it- self, forming the arc of a circle, with the concavity directed upward. It arises from the digastric groove in the mastoid process, and from the anterior edge of that process, in front of the sterno-mastoid ; it it inserted into the side of the symphysis menti, below the sub-mental tubercles, into the whole extent of the digastric fos- sa. It is also attached to the os hy- oides by means of an aponeurotic ex- pansion. Its origin from the mastoid pro- cess is partly fleshy and partly ten- dinous, the tendon being prolonged for some distance upon the upper border of the muscle. The fusiform fleshy belly pro- duced in this manner passes forward, inward, and downward, into the interior of a sort of fibrous cone, forming the commencement of the intermediate tendon. This tendon, which is about two inches in length, follows at first the direction of the muscle, almost always perforates the stylo-hyoid muscle, and is then received into a fibrous ring attach- ed to the OS hyoides, and lined by a synovial capsule. This fibrous ring is often wanting. A broad aponeurotic expansion proceeds from the intermediate tendon, and is fixed to the OS hyoides. When this is united to the corresponding structure on the opposite side, they form a very strong, triangular aponeurosis, called the supra-hyoid aponeurosis, which occupies the interval between the two muscles, and serves as a kind of floor for the other muscles of the supra-hyoid region. After having passed through the fibrous ring, the ten- don changes its direction, and is reflected at an obtuse angle upward and forward, to ter- minate in another tendinous cone. From the interior of this cone the fleshy fibres of the anterior belly take their origin. This belly is not so strong as the posterior, and is insert- ed by separate tendons, sometimes intersecting those of the opposite side, into the whole extent of the digastric fossa, below the sub-mental tubercles. Some fibres are often blended with those of the mylo-hyoid. It is not uncommon to see a small fasciculus arising from the os hyoides, and strengthening the anterior belly. The two anterior bel- lies are sometimes united by a raphe, and by a small transverse fibrous bundle. Relations. — It is covered by the platysma and sterno-mastoid, the parotid and the sub- maxillary glands, the latter of which it embraces by the concavity of its upper border : it covers the muscles which arise from the styloid process, the mylo-hyoid muscle, the in- ternal jugular vein, the external carotid artery, and its labial and lingual branches, the mternal carotid, and the hypo-glossal nerve, which lies parallel with, and beneath the intermediate tendon of the muscle. Its action is very complicated : when the posterior belly contracts alone, the os hyoides is carried backward and upward ; the anterior belly carries it forward, and also upward. When the two bodies of the muscle contract at the same time, these opposite effects are destroyed, and the os hyoides is carried directly upward. In all these motions, the low- er jaw must be fixed. If the os hyoides is fixed, the posterior belly becomes a depressoi of the jaw, on account of the reflection of the muscle ; the anterior and the posterior bel- lies can incline the head backward, but this inclination of the head backward during mas- tication, and when the jaws are separated, depends on the action of the posterior exten- THE STYLO, MYLO, AND GENIO HYOIDES. 229 BOr muscles of the neck ; leistly, the anterior belly of the digastric is the tensor of the supra-hyoid fascia. The Stylo-hyoideus. Dissection. — Detach the posterior belly of the digastric. This is a small and very thin muscle {q,fig. 114 ; ^ q,fig^- ^^'^ ^^^ ^^'^), like all those which are attached to the sty- loid process. It arises from the back of the styloid process, at a short distance from the apex, and oppo- site the insertion of the stylo-maxillary ligament. This origin consists of a small tendon, which terminates in a fibrous cone, from the interior of which the fleshy fibres commence. These proceed downward, forward, and inward, and form a bundle, which is almost al- ways perforated by the tendon of the digastric. Occasionally the fibres pass only in front of that tendon. They are iiiserted into the body of the os hyoides, at a short distance from the median line. Sometimes the tendon of insertion is reflected upon itself, and forms the pulley for the digastric. Relations. — It is covered by the posterior belly of the digastric, and has the same re- lations as that muscle. It is not uncommon to find a second stylo-hyoid muscle, ex- tending from the styloid process to the little cornu of the os hyoides. This muscle takes the place of the stylo-maxillary ligament ; it was described by Santorini under the name of the stylo-hyoideus iwvus, and was noticed also by Albinus.* The Mylo-hyoideus. Dissection. — Detach the anterior belly of the digastric at its maxillary insertion ; dis- sect the sub-maxillary gland, and turn it outward. This muscle {r, figs. 113 and 114), situated immediately below, i. e., deeper (as re- gards the surface) than the anterior belly of the digastric, is thin and quadrilateral. It arises from the whole extent of the mylo-hyoid line, from opposite the last molar to the symphysis menti, by short aponeurotic fibres. The fleshy fibres arising from these pass in different directions : the internal (or anterior), very short, proceed inward to a median fibrous raphe, which traverses the whole supra-hyoid region ; the external (or posterior) pass much less obliquely to the upper part of the body of the os hyoides. The median raphe is sometimes wanting, and the muscular fibres of the opposite sides are continuous with each other. Some of the fibres are often lost in the digastric, and are even contin- uous with the sterno-hyoid. The two mylo-hyoid muscles may, with great propriety, be regarded as a single muscle, divided by a tendinous intersection in the median line. Relations. — It is covered by the anterior belly of the digastric, the supra-hyoid fascia, the platysma, and the sub-maxillary gland ; and it covers the genio-hyoid, the hyo-glos- sus, and stylo-glossus muscles, the lingual and hypo-glossal nerves, the Whartonian duct, the sublingual gland, and the buccal mucous membrane. The Genio-hyoideus. This muscle {s,fig. 114, 143, 147) is situated below, i. e., deeper than the preceding, which must be divided very carefully, in order to avoid raising the two together. It is a small, round, fleshy bundle, described by anatomists as consisting of two very minute muscles, separated from each other by an extremely delicate cellular tissue. Sometimes it is impossible to separate them; at other times the two bundles are very distinct They arise from the inferior sub-mental tubercle, and proceed downward and backward, to be inserted into the upper part of the os hyoides. Relations. — ^They are covered by the mylo-hyoids, and cover the hyo-glossal muscles. Actions of the Muscles of the Supra-hyoid Region. These are of two kinds, relating to the depression of the lower jaw, and to the eleva- tion of the OS hyoides. The OS hyoides being fixed by the muscles of the sub-hyoid region, all the supra-hyoid muscles, with the exception of the stylo-hyoids, depress the lower jaw ; and it should be observed that they are situated in the most favourable manner for this purpose ; for, on the one hand, they are almost perpendicular to the lever, and, on the other, they are attached as far as possible from the fulcrum. The obliquity of their direction has also this advantage, that the lower jaw is carried backward as well as depressed, and thus the orifice of the mouth is greatly increased in size. But the most important action of these muscles relates to the elevation of the os hy- oides. This elevation is an indispensable element in the act of deglutition, and also in the protrusion of the tongue. Thus, the os hyoides is carried upward and backward by the stylo-hyoid muscles and by the posterior belly of the digastric, upward and forward by the anterior belly of the digastric and by the mylo- and genio-hyoids, and directly up- ward by the combined action of all these muscles. The base of the tongue, of which the os hyoides constitutes, in some degree, the framework, is associated with it in all * Albinus termed it stylo-hyoideus alter. MYOLOGY. these movements, which take place at different periods of deglutition : thus, the move- ment upward and forward is effected during the period when the alimentary mass is driven from the cavity of the mouth into the pharynx, which enlarges for its reception. The direct elevation takes place when the mass is passing, and the movement upward and backward occurs after it has passed, so as to prevent its return into the mouth. When the lower jaw is fixed against the upper, and the os hyoides is also fixed by the sub-hyoid muscles, the muscles of the supra-hyoid region assist in flexing the head. Lastly, the os hyoides is elevated during the production of acute, and depressed during that of grave, vocal tones. MUSCLES OF THE CRANIAL REGION. Occipito-froTttalis . — A uricular Muscles . The muscles of the cranial region are the occipito-frontalis and the auricular muscles. The Occipito-frontalis. Dissection. — Shave the head, and make a horizontal incision above the superciliary arch ; make a second incision in a vertical direction from before backward, and reaching from the former to the superior semicircular line of the occipital bone ; be very careful not to dissect away the epicranial aponeurosis, nor the fibres of the muscle ; commence the dissection at the fleshy fibres, which adhere less intimately to the skin than the aponeurosis. The occipito-frontalis (epicranius, Albinus, a' a', jig. 113) is sometimes regarded as one muscle with two bellies ; sometimes as a combination of two separate muscles, the oc- cipital and the frontal. It covers the roof of the scull. We shall describe the occipital and frontal portions only ; the aponeurosis will be elsewhere noticed. (Vide Aponeurology.) 1. The occipital portion, or occipital muscle, covers a great part of the occipital bone, and is situated over the superior occipital protuberance. It is thin and quadrilateral. It arises from the two external thirds of the superior semicircular line, and from the neighbouring part of the mastoid process of the temporal bone, and is inserted into the posterior border of the cranial aponeurosis, of which it may be regarded as the tensor. The occipital attachment is composed of tendinous fibres, the fleshy fibres proceeding from which pass upward in a parallel direction, and, after a short course, terminate in the aponeurosis. 2. The frontal portion, or frontal muscle, is placed at the front of the cranium ; it is thin, and irregularly quadrilateral, like the preceding. It is attached above to the cranial aponeurosis, and terminates below in the following manner : 1. The internal or median fibres are prolonged into a fleshy band, which constitutes the pyramidalis nasi ; 2. The fibres next on the outside are continuous with those of another muscle, viz., the levator labii superioris alaeque nasi — ^to the outside of these fibres, the muscle is attached to the internal orbital process ; 3. The greater number of the fibres are blended with those of the orbicularis palpebrarum. The upper border of the muscle, which is attached to the aponeurosis, forms a semicircular line, that, in many individu^^, causes a projection un- der the skin. Relations. — Tlie occipito-frontalis covers the roof of the scull ; hence the name of epi- cranius (Albinus). It rests upon the pericranium (the periosteum of the cranial bones), being separated from it by a quantity of moist cellular tissue, which admits of a consid- erable degree of mobility of the integuments, and is so elastic that it returns to its origi- nal situation after being displaced by any movements of the hairy scalp. The super- ficial surface of this muscle is covered by the skin, and is united to it by a very dense, almost fibrous cellular tissue, in which are ramified the numerous vessels and nerves of the cranial integuments. Action. — The occipital portion is a tensor of the epicranial aponeurosis, which, when stretched, affords a fixed point for the frontal portion. This latter raises the upper half of the orbicularis palpebrarum, elevates the eyebrows and the skin over the root of the nose, and has a great effect in the expression of emotions of delight. This muscle pro- duces the transverse wrinkles on the forehead, which give to the countenance of indi- viduals who are habitually gay a peculiar expression, that is often imitated by painters. These transverse wrinkles do not extend over the triangular interval, which separates the two fleshy bellies of the muscle in the centre of the forehead. The occipito-frontalis must be regarded as an elevator of the upper eyelids ; it is blend- ed with the orbicularis palpebrarum in the same manner as the labial muscles with the orbicularis oris. In this respect the occipito-frontalis is assisted by the levator palpe- hrse superioris, and antagonized by the corrugator supercilii and orbicularis palpebrarum. Can this muscle erect the hairs on the head 1 It is certain that it can move the entire hairy scalp, for many individuals are able to do this at will ; but it appears to me that the expression, the hairs stand on end, as regards man, is merely figurative, and is de- rived from what occurs in the lower animals, in which this erection of the hair is very THE AURICULAR MUSCLES, ETC. 1281 manifest. Perhaps, however, the skin itself may produce this effect by the same mech- anism as that which gives rise to goose skin. The Auricular Muscles. Dissection. — Be very careful in dissecting the superior and anterior auricular muscles, which are extremely thin, and consist only of a few colourless fibres. To render them as tense and prominent as possible, it is necessary to draw the ear away from the mus- cle to De examined. All these muscles are rudimentary in man, in whom the external ear is almost im- movable. They may all be considered as dilators of the auditory meatus, to which there is no constrictor or sphincter in the human subject : certain animals, however, possess- ing a very delicate sense of hearing, have constrictor muscles, which draw together and move the different pieces forming the cartilaginous portion of this canal. The auricular muscles are three in number : a superior, an anterior, jmd a posterior. The Auricularis Superior. This muscle, which is extremely thin and of a triangular form (b',Jig. 1 13), oocupies the temporal fossa. It arises from the external border of the epicranial aponeurosis, of which it seems to be a dependance , from this origin its fibres converge, and are inserted into the upper part of the concha. It is covered by the skin, and lies upon the temporal fascia. Action. — To raise the ear (attollens auriculam, Albinus). The Auricularis Anterior. This muscle (c'. Jig. 1 13) is still thinner and less marked than the preceding, with which it is continuous. It is also triangular, and arises from the outer edge of the oc- cipito-frontalis and the cellular tissue covering the zygomatic region ; the fibres con- verge from their origin, and are inserted into the front of the helix. It is covered by the skin, and lies upon the temporal fascia, from which it is separated by the temporal artery and vein. Action. — To draw the auricle forward and upward (anterior auriculae, Albinus). The Auricularis Posterior. This muscle {d',fig. 113) is much more decidely marked than the preceding, and is composed of two or three distinct fleshy fasciculi (tres retrahentes auriculam, Albinus), which extend from the base of the mastoid process, and sometimes also from the occipi- tal bone to the lower part of the concha. Action. — To draw the aiu-icle backward. MUSCLES OF THE FACE. All the muscles of the face are arranged in groups around its several openings, and may be classed either as dilators or constrictors. The nostrils alone have no constrictors. The eyelids must be opened and closed entire, without the production of any folds ; the nostrils must remain constantly open, for the skin around these orifices has within it a corresponding lamina of cartilage, which gives it the necessary tension, strength, and elasticity, and into which the muscles are inserted. There is no such arrangement at the orifice of the mouth, the muscles being there inserted into other muscles. From the three openings around which the muscles of the face are grouped, these may be arranged into three distinct regions, viz., the palpebral, the nasal, and the buccal. MCSCLES OF THE PALPEBRAL ReGION. Orbicularis Palpebrarum. — Super ciliaris. — Levator Palpebra Superioris. The muscles of the eyelids are divided into constrictors and dilators. There is one constrictor, viz., the orbicularis palpebrarum, to which the corrugator supercilii is an ac- cessory ; there is also one elevator, viz., the levator palpebrae superioris. The Orbicularis Palpebrarum. Dissection. — ^Make an elliptical incision through the skin round the base of the orbit ; dissect successively the upper and lower half of the muscle, proceeding from the adhe- rent towards the free border of each eyelid. It is of more importance here than in any other situation to dissect the skin parallel to the fleshy fibres. When the external sur- face of the muscle has been studied, detach it carefully from the subjacent parts, and re- flect it inward. The orbicularis palpebrarum {e',fig. 113) forms an elliptical zone of variable size round the eyelids, and also an extremely thin layer upon them. It is a sphincter, and, like all muscles of this kind, is composed of circular fibres ; but, as a special exception, it is also provided with a remarkable tendon of origin, named the straight tendon of the orbicularis ; this is about two hues in length and half a line in breadth, arises from the ascending pro- cess of the superior maxilla, anteriorly to the lachrymal groove, and passes in front of 2JK5 MYOLOGY. the lachrymal sac, where it divides into two unequal parts, an upper and smaller, and a lower more capacious ; sometimes it corresponds entirely to the upper part of the sac. At first it is flattened from before backward, but is then twisted upon itself, so as to pre- sent one surface upward and another downward. Opposite the inner angle of the eye- lids, this tendon, which is also called the palpebral ligament, becomes bifurcated, and each division is attached to the inner end of the corresponding tarsal cartilage ; from the posterior surface of the tendon a very strong aponeurotic lamina is given off, and forms the outer wall of the lachrymal sac : this is the reflected tendon of the orbicularis palpebra- rum. Fleshy fibres proceed from the anterior and posterior surfaces, and from the bor- ders of the straight tendon, and also from the anterior border of the reflected tendon ; but the greater number arise by well-marked tendinous prolongations from the external orbital process of the frontal bone, from the ascending process of the superior maxilla, and from the internal and lower third of the base of the orbit. From these origins the fleshy fibres pass outward, dividing into two halves, an upper, which describes concen- tric curves with the concavity directed downward, and a lower, also describing concen- tric curves, but with the concavity directed upward (duo palpebrarum musculi, Vcsalius). Each of these halves is subdivided into two sets of fibres : an external set, surrounding the base of the orbit ; and an internal or palpebral, belonging to each eyelid : hence the distinction drawn by Riolanus between the orbicularis and the ciliaris or palpebralis mus- cles. The external fibres (forming the orbicular portion) describe a complete ellipse. I have never met with the fibrous intersection at the outer part of the eye, mentioned by some anatomists. The palpebral or ciliary fibres, forming the proper palpebral portion, arise from the bifurcation of the tendon, and describe concentric arcs, which are united on the outside at an acute angle to a cellular raphe. Relations. — The orbicular portion is closely united to the skin by means of a fibrous and adipose tissue, which is very compact over the upper, and loose over the lower por- tion of the muscle ; it is connected with the skin of the eyelids by a serous cellular tis- sue, remarkably susceptible of infiltration. It covers the lachrymal sac, the corrugator supercilii muscle, the orbited arch, the maxillary bone, the temporal muscle, and the su- perior attachments of the zygomaticus major, of the levator labii superioris alaeque nasi, and of the levator labii superioris. It is separated from the conjunctiva by a fibrous membrane and the tarsal cartilages. Its circumference is blended with the pyramidalis nasi on the inside, with the occipito- frontalis and corrugator above, but is free below ; occasionally it gives off a few fibres from its outer border, some of which form the zygomaticus minor, and others of a pailer colour terminate in the skin. Actions. — ^The orbicularis acts in the same manner as £ill other sphincters, that is to say, the circular fibres of which it is composed contract towards the centre ; but, as the fleshy fibres have their fixed point at the straight tendon, and still more at the internal insertions, it follows that, during the contraction of this muscle, it is thrown in some measure inward, and by it the integuments of the forehead, the temple, and the cheek are drawn towards the inner angle of the eye. The intimate adhesion between the skin and the upper half of the muscle explains why, during its contraction, that part is ren- dered more apparent beneath the skin than the lower. The palpebral portion contracts independently of the orbicular, a fact that confirms the distinction made by Riolanus. Nor is this all : the contraction of this palpebral portion, or palpebralis muscle, properly so called, is habitually involuntary, while the contraction of the orbicular portion is subject to the will. The palpebral fibres are pale, and resemble the muscular fibres of the ali- mentary organs ;* the orbicular fibres are red, like those of the muscles of animal life. When the palpebral fibres contract, they do not produce the occlusion of the eye, by a concentric approximation of the fibres, but by bringing together the free edges of the eye- lids, the only method permitted by the tarsal cartilages. The curve described by the rnuscular fibres of the lower being smaller than that formed by those of the upper eye- lid, it follows that the closing of the eyes depends principally upon the latter. The Super ciliaris. Dissection. — Make a vertical incision in the median line between the frontal muscles ; ttim back carefully the frontal and the orbicularis muscles from within outward. The superciliaris (corrugator supercilii, Albinus, a', Jig. 114) is a narrow and tolerably thick fasciculus, generally of a deeper red than the orbicularis, and situated along the superciliary arch, with the direction of which it corresponds. It arises by one, often by two or three portions, from the internal portion of this arch ; proceeds upward and out- ward, describing a slight curve, having its concavity downward, and is blended with the orbicularis palpebrarum at about the middle of the arch of the orbit. From this arrange- ment, Albinus described it as a root of the orbicularis. According to some authors, it terminates in the skin of the eyebrow (cutaneo-surcilier, Dumas) ; but I have always found it attached to the deep layer of the orbicularis muscle. * See note *, p. 238. THE LEVATOR PALPEBE^ SUPERIORIS, ETC. 2SSt Relations. — It is covered by the pjrramidalis nasi, the orbicularis palpebrarum, and the occipito-frontalis, and it covers the os frontis, the supra-orbital and frontal arteries, and the frontal branch of tlie ophthalmic nerve. Action. — This muscle corrugates the eyebrow, and dravrs it downward and inward. It is, therefore, regarded as the principal agent in the expression of grief The repeated contraction of these muscles in irascible individuals gives a character of severity to the countenance, from the constant approximation of the eyebrows, and the permanence of the vertical wrinkles formed between them. The Levator Palpebrce Supreioris. Dissection. — Remove the roof of the orbit by two cuts with a saw, meeting at an acute angle opposite the foramen opticum ; detach the bone with care, so as to leave the peri- osteum untouched ; cut the periosteum from before backward, and separate the frontal nerve which passes above and parallel to the muscle, which may then be separated care- fully from the superior rectus muscle of the eye. The levator palpebro'. superioris (see description of the eyelids) is an elongated, flat, triangular, and very thin muscle, placed in the orbital cavity, directed horizontally from behind forward, and curved at its anterior extremity, sa as to form a concavity directed downward. It arises from the inferior surface of the lesser wing of the sphenoid, im- mediately above the optic foramen, and from the sheath of the optic nerve, and is insert- ed into the upper border of the tarsal cartilage. Its sphenoidal origin consists of a small tendon, and its attachment to the sheath of the optic nerve is a fibrous ring common to aU the muscles of the eye. From these points the fleshy fibres proceed forward, form- ing a broad, thin bundle, increasing in width and diminishing in thickness towards its tarsal insertion, which is effected by means of a broad aponeurosis. Relations. — Covered by the periosteum of the orbit, from which it is separated by the frontal branch of the ophthalmic nerve ; covered, also, by some adipose tissue and by the fibrous membrane of the upper eyelid, it covers the superior rectus of the eye and the conjunctiva. Action. — It raises the upper eyelid. Its reflection over the globe of the eye explains that peculiar motion of the eyelid by which its upper edge is buried below the orbital arch. The relaxation of this muscle suffices for the depression of the upper eyelid in passive closure of the eyes, while the active occlusion depends on the contraction of the orbicularis. There is no analogous muscle for the lower eyelid, which scarcely concurs either in opening or shutting the eyes. NASAL REGION. The Pyramidalis Nasi. — Levator Labii Superioris Alceque Nasi. — Tranaver salts, or Trian- gularis Nasi. — Depressor Ala. Nasi. — Naso-labialis. The muscles of this region are the pyramidalis nasi, the levator labii superioris alae- que nasi, the transversalis or triangularis nasi, the depressor alae nasi, or myrtiformis, and the naso-labialis of Albinus. The Pyramidalis Jfasi. Dissection. — ^Trace doiwn upon the dorsum of the nose the internal fibres of the occip- ito-frontalis, directing the scalpel parallel to these fibres, which have a vertical course. The pyramidalis nasi (/, fig. 113) is a prolongation of the internal fibres of the occipito- frontalis, of which it may be regarded as a prolongation (frontahs pars per dorsum nasi ducta, Eustachius). It lies upon the bridge of the nose on each side of the median line. It is separated from the muscle of the opposite side by a thin layer of cellular tissue. It is narrower at its origin than at its termination, which takes place in the aponeurosis of the transverse muscle of the nose. Relations. — It is covered by the skin, to which it closely adheres, especially below, and it covers the nasal bones and lateral cartilages. Action. — This small muscle has been regarded as an elevator of the ala. and, conse- quently, a dilator of the nose ; but I believe it rather acts in depressing the inner angle of the eyebrow, and the skin between the eyebrows. In this respect it has considerable influence upon the expression of the countenance. The Levator Labii Superioris AlcRque JSTasi. Dissection. — Make a vertical or somewhat oblique incision from the ascending process of the superior maxilla to the upper lip. Reflect outward the inner and lower part of the orbicularis muscle. This muscle (^, fig. 113) is thin, triangular, and divided into two portions below. It extends from the ascending process of the superior maxilla to the ala of the nose and the ^upper lip. It arises by a narrow extremity from the internal orbital process of the frontal bone, immediately below the tendon of the orbicularis palpebrarum, passes obliquely Go 234 T ,? >7, MYOLOGY. downward and outward, becomes much broader, and is inserted partly into the cartilage of the ala of the nose, or, rather, into the very dense skin which covers it, and partly into the orbicularis oris, or, rather, into the skin of the upper lip. The cutaneous portion of this muscle is distinguished by its paleness, compared with the red colour of the rest. Relations. — It is covered by the skin, and a small portion of the orbicularis palpebrarum ; and it covers the ascending process of the superior maxilla, and the transverse muscle of the nose. Action. — It elevates both the ala of the nose and the upper lip. I consider it the most important of all the muscles of the nose, because the elevation of the alae dilates the nos- trils, and thus aids most essentially in cases of impeded respiration. It is a respiratory muscle of the face, and has, also, great influence over the countenance, producing the expression of contempt. Its action upon the upper lip is of much less importance than that upon the nose. The Transversalis, or Triangularis JVasi. Dissection. — Remove with great care the skin covering the ala of the nose, and then fol- low this muscle below the inner edge of the common elevator ; or, what is better, remove all the soft parts covering the ala of the nose, and dissect the muscle from its deep surface. The transversalis vusi (compressor narium, h',figs. 113, 114), which I regard as a de- pendance of the muscle next to be described, is a small and very thin triangular muscle, stretching from the inner part of the canine fossa to the bridge of the nose. It arises by a narrow extremity from the canine fossa, passes forward, enlarging as it proceeds along the ala of the nose, and terminates by a very thin aponeurosis, which is blended in the median line with that of the opposite side, and with the pyramidalis. It is covered by the skin, to which it closely adheres, and by the common elevator ; and it covers the car- tilage of the ala, and a small part of the superior lateral cartilage of the nose. Action. — The action of this small muscle is not yet weU determined. Some have agreed with Riolanus in considering it a dilator (qui alam naris diktat sine elevatione nasi, Riolanus) ; others think, with Spigelius and Albinus, that it is a constrictor of the nose (primi paris constringentium alas, Spigelius ; compressor naris, Albinus). It is prob- able that its action varies according to the shape of the ala : if this be concave outward, it is a dilator ; if convex outward, it is a constrictor. Its action is very slight. The Depressor Alee JVasi, or Myrtiformis. Dissection. — Evert the upper lip, and remove the mucous membrane on each side of the fraenum. The two myrtiformes may then be separated by a vertical incision in the median line. It will be apparent that the myrtiformis and transversalis form only one muscle, which arises from the alveolar border near the lateral incisor, the canine and the anterior bicuspid teeth, and is distributed to the orbicularis oris, the alae, and the septum of the nose. This muscle {if, fig- 114) is short and radiated, and arises by a narrow extremity from the incisive or myrtiform fossa of the superior maxilla, opposite the canine and two in- cisor teeth (incisif moyen, Winslow). Its fibres diverge upward and outward, and are in- serted thus : the lower, or descending, behind and in the substance of the orbicularis oris ; and the upper or ascending, into the ala and septum of the nose. Its upper border is not distinct from the lower border of the transversalis. Chaussier, on account of its termination in the upper lip, regarded it as one of the origins of the orbicularis oris. Relations. — It is covered by the buccal mucous membrane, by the orbicularis oris, and the common elevator, and it lies upon the maxillary bone. It is continuous, without any line of demarcation with the transversalis nasi. The inner border of the muscle of one side is separated from that of the other by an interval, corresponding to the fraenum of the upper lip. Action. — It depresses the ala of the nose, and has also been considered a depressor of the upper lip (depressor labii superioris,* Cowper). I regard it rather as an elevator of that lip. The J^aso-labialis of Albinus. This consists of a fasciculus which it is difficult to demonstrate in many subjects. It arises from the anterior extremity of the septum of the nose, passes horizontally back ward, is then reflected downward, and terminates like the preceding in the orbicularis, of which it may be considered a root. MUSCLES OF THE LABIAL REGION. rhe Orbicularis Oris. — Buccinator. — Levator Labii Superioris. — Caninus. — Zygomatict, Major et Minor. — Triangularis. — Quadratus Menti. — Levator Labii Superioris. — Move- ments of the Lips and those of the Face. No region has so many muscles as the orifice of the mouth : seventeen, nineteen, and * Depressor labii superioris aliBque nasi of other writers. THE ORBICULARIS ORIS AND THE BUCCINATOR. 4)85 often twenty-one muscles, are grouped round it, viz., the orbicularis oris, the common elevators of the alae and lip already described, the proper elevators of the lip, the great zy- gomatics, the canine, the buccinators, the triangulares,the quadrati or the levatores menti ; and often two muscles on each side, viz., the risorius of Santorini, and the small zygomatic. The Orbicularis Oris. Dissection. — Make an elliptical incision round the opening of the mouth, and dissect back the skin with great care, the mouth being previously distended by the introduction of tow between the lips and alveolar borders. The orbicularis oris (J,' I', figs. 113 and 114) is the sphincter of the orifice of the mouth ; it is essentially the constituent muscle of the lips, occupying the entire space betweeii the free edge of the upper lip and the nose, and the free edge of the lower lip and the transverse furrow above the chin. We shall consider, with Winslow, the orbicularis to be composed of two halves, each constituted by a demi-zone, of semi-elliptical concentric fibres, terminating on either side at the commissures of the lips. These fibres, which are all fleshy, do not become con- tinuous opposite the commissures of the lips, but only intersect each other, those of the upper half being continuous with the lower fibres of the buccinator, and those of the low- er half with the upper fibres of the same muscle. The thickness of the two halves varies in different individuals, particularly around the free borders of the lips, where the fasciculi of the muscle are somewhat everted. In the negro this is very remarkable. The thickness of the lips depending upon this cir- cumstance must be distinguished from that which is the effect of a scrofulous habit. Relations. — These muscles are covered by the skin, to which they adhere intimately, and hence the facility of bringing together the entire depth of the surface of wounds in the lips, by retentive applications to the skin only. They cover the mucous membrane but are separated from it by the labial glands, the coronary vessels, and a great number of nervous filaments. Their outer circumference receives all the extrinsic muscles of the lips, which terminate in these as in a conmion centre. Their inner circumference circumscribes the opening of the mouth. The differences in the dimensions of this open- ing occasion the varieties observed in the size of the mouth, but the capacity of the buc- cal cavity is in no way influenced by these variations. Actions. — These are exceedingly various, and may be studied as connected with the closing of the mouth, with the prehension of aliments by suction, with the playing upon wind instruments, and with the expression of the countenance. I shall here only notice the shutting of the mouth. This may be accomplished simply by the approximation of the jaws, which is followed by a corresponding motion of the lips. In active occlusion, or that dependant on the orbicularis, two things may happen : either the lips may be closely drawn against the teeth, and their free edges applied to each other, or they may be pushed forward and puckered ; in the latter case, the buccal opening, which is usually represented by a trans- verse line, resembles a circular, or, rather, a lozenge-shaped orifice. The Buccinator. Dissection. — Distend the cheeks by stuffing the mouth with tow ; make a transverse incision through the skin, from the commissure of the lips to the masseter muscle, and dissect back the flaps': in order to gain a good view of the posterior border of the mus- cle, turn downward the zygomatic arch and the masseter, and then divide with the saw the inferior maxilla in front of the ramus. The buccinator (fig. 113, and b,figs. 114 and 147) is the proper muscle of the cheek; it is broad, thin, and irregularly quadrilateral. It is attached above to the external sur- face of the superior alveolar arch, along the space between the first great molar and the tuberosity of the maxilla ; below, to the external surface of the inferior alveolar arch, or, rather, to that part of the external oblique line of the lower jaw which corresponds with the last two great molars ; and behind, to an aponeurosis existing between this muscle and the superior constrictor of the pharynx (see fig. 147). This aponeurosis, to which the name of buccinato-pharyngeal has been given {ptery go-maxillary ligament), ex- tends from the apex of the internal pterygoid process to the posterior extremity of the internal oblique line of the lower jaw. From these different origins the fleshy fibres proceed forward, the upper somewhat obliquely downward, the lower obliquely upward, and the middle fibres horizontally. In consequence of this arrangement, the fibres inter- sect each other opposite the commissure of the lips, from which points the lower fibres of the muscle proceed to terminate in the upper half of the orbicularis, while the upper fibres end in the lower half of the same muscle. Relations. — It is situated deeply behind, where it is covered by the ramus of the lower jaw, the masseter, and a small part of the temporal muscle ; from all these parts, how- ever, it is separated by a considerable quantity of adipose tissue, and by a mass of fat which exists even in the most emaciated individuals. More anteriorly it is covered by ■-■■'•.■"■~,Trrr"''" " 236 MYOLOGY. the zygomaticus major and the zygomaticus minor, and the risonus jf Santorini, where the two latter exist ; and at the commissure it is covered by the canine muscle {levator angnli oris) and the triangularis. The Stenonian duct runs along this muscle before passing through it ; the buccal nerves and the branches of the transverse facial artery lie parallel to its fibres; the external maxillary (i. e., the facial) artery and vein pass perpenaicularly across it, near the commissure. A peculiar aponeurosis, called the buc- cal fascia, is closely united to it, and intervenes between it and all these parts. It cov- ers the mucous membrane of the cheek, from which it is separated by a dense layer of the buccal mucous glands. Action. — It is the most direct antagonist of the orbicularis. When the cheeks are not distended, its contraction elongates the opening of the mouth transversely, and, conse- quently, renders the hps tense, and produces a vertical fold upon the skin of the cheek. This fold becomes permanent in the aged, and constitutes one of their most prominent wrinkles. When the cheeks are distended by air, or any other substance, the buccinator becomes curved instead of flat, and acquires all the properties of the former class of nmscles. Thus the first effect of its contraction is, that its fibres become straight, or have a ten- dency to become so ; gaseous, liquid, or solid bodies, are then expelled from the mouth, rapidly if the orbicularis offer no obstacle, and gradually should that muscle contract. The buccinator, therefore, fulfils an important ofiice in performances upon wind instru- ments, and hence its name {buccinare, to sound the trumpet). la mastication it is of no less importance, since it pushes the food between the teeth, and expels it from the sort of groove existing between the cheeks and the alveolar arches. The Levator Labii Superioris. Dissection. — Reflect the lower half of the orbicularis palpebrarum upward, and dissect with care the lower extremity of the muscle about to be described, which adheres close- ly to the skin. It can be best studied from the inner surface. This muscle (c', fig. 1 14) is thin and quadrilateral. It is situated upon the same plane as the common elevator, of which it appears to be a continuation, and extends from the base of the orbit to the skin of the upper lip. It arises from the inner half of the lower edge of the base of the orbit, on the outei side of the common elevator : from this origin, which is sometimes bifid, the fibres con- verge dovraward and inward, and are inserted successively into the skin, probably into the bulbs of the hairs, as in animals which have mustaches ; so that this muscle would deserve the name of mustachie, which is given by some anatomists to the naso-labial of Albinus. Relations. — Its two upper thirds are deeply seated ; its lower third adheres closely to the skin. It is worthy of notice, that almost all the muscles of the face are deeply seated at one of their extremities, and terminate by the other in the skin. It is covered by the orbicularis palpebrarum and the skin, and it covers the infra-orbital vessels and nerves, as they escape from the infra-orbital canal. It is also in relation with the ca- nine muscle, from which it is separated by a quantity of adipose tissue, with the trans- versalis nasi, and with the orbicularis oris, being interposed between the latter muscle and the skin. Action. — It raises the upper lip, and draws it a little outward. The Caninus. Dissection. — Merely reflect the levator labii superioris. The canine muscle (levator anguli oris, Albinus, d,fig. 114), so named from its origin, arises from the canine fossa by a broad attachment, from which it proceeds downward and a little outward, diminishing in size, and becoming gradually more superficial, to the commissure of the lips, where it terminates by uniting with the zygomaticus major, and becoming continuous with the triangularis oris. We often find some accessory fibres arising from this muscle, and attached to the skin opposite the commissure. Relations. — Above, it is concealed by the levator labii superioris and the infra-orbitary vessels and nerves ; below, it is quite superficial, being only covered by the skin. It covers the superior maxilla, the buccinator, and the buccal mucous membrane. Action. — It raises the angle of the mouth, and, from its oblique position, draws it inward. The Zygomatici Major et Minor. Dissection. — Make an oblique incision from the malar bone to the commissure of the lip, and remove carefully, from the great zygomatic, the fatty tissue which surrounds it. The Zygomaticus Major. This muscle {m',fig. 113) is a cylindrical, fleshy fasciculus, extending from the malar bone to the conunissure of the hp. It arises, by tendinous fibres, from the entire length of a horizontal furrow, situated above the lower edge of the malar bone. The fleshy fibres approach each other so as to form a fasciculus, which passes obliquely downward THE TRIANGULARIS, ETC. 237 and inward towards the commissure, where it is closely united to the canine muscle, and, like it, is continuous with the triangularis or depressor anguli oris. Relations. — It is covered by the skin, from which it is separated above by the orbicu- laris palpebrarum, and below by a large quantity of adipose tissue ; it covers the malar bone, the masseter and buccinator muscles, a great collection of fat, and the labial vein. Action. — It draws the angle of the mouth upward and outward ; by carrying the com- missure upward, it assists the canine muscle, but in drawing it outward, it antagonizes the same. When the zygomatic and canine contract together, the commissure is drawn di- rectly upward. The Zygomaticus Minor. • This small muscle {n',fig. 113), which is often wanting, maybe regarded as a depend- ance of the proper elevator of the upper lip. It arises from the malar bone, above the great zygomatic, passes downward and inward to the outer border of the levator labii su- perioris, with which it is blended. It is not uncommon to find this muscle enlarged by fasciculi given off from the outer and lower circumference of the orbicularis muscle of the eyelids. It is covered by the skin and the orbicularis palpebrarum ; and it covers the canine muscle and the labial vein. Action. — It assists the common elevator in raising the upper lip and drawing it some- what outward. The Triangularis, or Depressor Anguli Oris. Dissection. — Make a vertical incision of the skin, from the commissure of the lips to the base of the jaw ; then follow the course of the muscidar fibres as they are successively exposed. This muscle {o',fig. 113) is of a triangular shape, as its name implies, and belongs to the inferior maxillary region. It arises, by a broad base within, from the lower border of the inferior maxilla on the side of the median line, and sometimes from the median line itself; and without, from the external oblique line : from these points the fibres pass in different directions, the external almost vertically upward, the internal obliquely upward and outward (the obliquity increasing as we proceed inward), and describing a curve with the concavity looking inward. All these fibres are concentrated into a narrow and thick fasciculus, which terminates at the commissure, on a plane anterior to the fibres of the buccinator and the orbicular oris, being evidently continuous with the canine and the great zygomatic. Relations. — It is covered by the skin, beneath which it is clearly discernible, and it cov- ers the quadratus menti, the platysma, and the buccinator. Some colourless fibres, which intersect those of the quadratus at a right angle, and, moreover, follow the same direc- tion as those of the triangularis, may be regarded as a dependance of that muscle, to the inside of which they are situated. They terminate in the skin, like those of the quadratus. Action. — It depresses the angle of the mouth, thus antagonizing the canine muscle and the great zygomatic, with which it is continuous. The continuity of these muscles is so manifest, that they may be regarded as constituting a single muscle, broad and triangu- lar below ; bifid above, to form the canine and zygomatic ; and narrow in the middle, where it corresponds to the commissure. The internal fibres of the triangularis, from their oblique direction, are directly opposed to those of the canine muscle ; but its exter- nal fibres have not a similar relation to those of the zygomaticus major. The Quadratus Menti, or Depressor Labii Inferioris. Dissection. — Dissect back the skin covering this muscle, cutting obliquely downward and outward. The quadratus menti {-p'tfig. 113 ; q',fig. 114), situated to the inside of the preceding, is of a square, or, rather, lozenge shape. It arises from the external oblique line of the low- er jaw, and is in a great measure continuous with the platysma, the fibres of wliich pass behind, and sometimes through the triangularis. From this origin it proceeds obliquely upward and inward, therefore in an opposite direction to the triangularis, and is inserted into the skin of the lower lip, on a plane anterior to the corresponding half of the orbicu- laris oris. It is closely united to the skin, and covers the lower jaw, the mental nerve and vessels, the lower half of the orbicularis oris, and the muscle next to be described, with which it is intimately connected. It is separated from the muscle of the opposite side by the prominence of the chin below, but is blended with it above. Action. — It depresses the lower lip : from the obliquity of this muscle, it also draws out- ward and downward each half of the lower lip, which is therefore stretched transversely. The Levator Labii Inferioris. Dissection. — Evert the lower lip ; divide the mucous membrane at its reflection upon the lip from the lower jaw, so as to expose the origin of the muscle. In order to show its cutaneous insertion, carefully dissect off the skin covering the chin. As the muscles of each side are blended in the median line, it is necessary to make a vertical incision from before backward, opposite the symphysis, in order to separate them. 2^ MYOLOGY. This muscle (levator menti, Alb., r',Jig. 114) is a small conoid fasciculus, which forma, in a great measure, the prominence of the chin. It arises from the facette on the side of the symphysis menti, opposite the incisor teeth, whence the name incisif inferieur, Wins- low, which is also given to this muscle. From this point the fibres expand like a tuft, downward and forward, to be inserted into the skin. It is red and fasciculated at its or- igin above, but pale, intermixed with fat, and not fasciculated below, where it is blended on the inside with the opposite muscle, and on the outside with the quadratus menti. Its upper fibres form a concavity above, which partially embraces the great circumfer- ence of the lower half of the orbicularis oris. Action. — It raises and wrinktes the skin of the chin, and, consequently, raises the low- er lip, and projects it forward. It appears somewhat singular at first that an elevator of the lip should be situated below it. General Considerations regai-ding the Movements of the Lips, and those of the Face in general. If we take a general view of the muscles of the face, we shall observe, 1. That no re- gion is provided with so great a number of muscles ; 2. That all these muscles are at- tached to a bone by one extremity, while the other is implanted into the skin, or into other muscles ; 3. That the cutaneous portion of these muscles is colourless and non- fjisciculated, presenting all the characteristics of involuntary muscles ;* 4. That those portions which are attached either to the bone or to other muscles have, on the contrary, aH the characters of the voluntary muscles. All these muscles are arranged around the several openings of the face, and, conse- quently, they are either constrictors or dilators ; the orifice of the mouth, however, is peculiar! in having the greater number of the muscles of the face specially intended for it. Indeed, the orbicularis oris, or sphincter of the mouth, is antagonized by the bucci- nators or transverse dilators ; by the proper elevators of the upper lip, and the common elevators of that and the alae of the nose ; by the depressors of the lower lip, or quadrati ; by the elevators of the angle of the mouth, viz., the canine muscles, the zygomatici ma- jores, and, where they exist, the zygomatici minores, and the two risorii of Santorini ; and, lEistly, by the depressors of the commissure, or triangulares oris. The lips fulfil a great number of uses, all requiring a considerable degree of mobility. • They serve for the prehension of aliments, for suction, and for the articulation of soundsj *' whence the name labial given to consonants specially produced by the action of the lips, ' as b, p, m : they modify the state of the expired air so as to produce in it vibrations of a peculiar character, constituting the act of whistling ; and, in this respect, they illustrate the mechanism of the glottis : they assist in mastication, by retaining the food and con- stantly forcing it between the teeth : they are also employed, during performances upon wind instruments, in regulating the volume of the column of air which strikes upon the body to be thrown into vibrations. The mechanism of their action varies according to the kind of instrument : sometimes, for example, they assist in graduating the rapidity of the column of air, by influencing the orifice through which it issues, as occurs in play- ing upon the flute ; and sometimes they represent vibrating cords situated at the mouth of an instrument, and determining the different tones by their various degrees of ten- sion. In this case, the lips themselves become the vibrating bodies, and propagate their oscillations to other bodies with which they are in contact, independently of the effect produced in the instrument from the passage of a column of air. Examples of this are observed in playing on the horn, trumpet, &c. If we examine the muscles of the face in connexion with their influence in producing emotional expressions, we shall find that they are often almost completely removed from the influence of the will, as, for example, where those emotions are not simulated ; but that sometimes, on the contrary, their contraction is altogether voluntary, as in those individuals who, either by profession or habit, are accustomed to imitate feelings which they do not really experience. Nevertheless, it should be remarked that, although the outward expression of every passion may be produced at will upon the face, yet there is always a great difference between the natural emotion and the fictitious representation. On the whole, the general expressions of the countenance may be regarded as varie- ties of two great types, viz., those of the cheerful and those of the melancholy emotions. * This similarity is limited, however, to the colour and general aspect of the two kinds of muscles ; for even the palest muscular fasciculi of the face are found to consist of striated fibres, precisely similar to those of the other voluntary muscles ; but the fasciculi into which they are collected are neither so evident nor so large.- t Man greatly exceeds all animals in the number of muscles attached to his lips. The ape, which is ni'"^ markable for the great mobility of its physiognomy, has, properly speaking, only one muscle for the entire face, which is a dependance of the platysma (or cutaneous muscle) ; therefore, the play of its countenance is con- fined to a grimace, which is always the same, only differing in intensity, and which does not permit it to ex press different and even opposite passions, such as are often depicted upon the human countenance.* * £The platysma myoides in monkeys is certainly extended, as a single muscle, over the entire cheek, and forms a muscular layer, covering the lateral pouches appended to the mouth in some of that tribe of animals. In addition to this, however, monkeys have precisely the same number of muscles attached to their lips as in the human subject : they possess, indeed, all the facial muscles found in man ; and, like him, they appear to be capal)le of expressing, by changes in their features, a variety of internal emotions.] THE MASSETER. 239 The cheerful emotions are expressed by the expansion of the features, i. e., their retrac- tion from the median line, a movement that is due to the occipito-frontalis, the levatores palpebrarum, and especially to the great zygomatic muscles. The melancholy passions, on the contrary, are expressed by the approach or concentration of the features towards the median line, which is chiefly effected on either side of the face by the corrugator supercilii, the depressor anguli oris, the common and proper elevators of the upper lip, the levator labii inferioris, and the quadratus menti. On account of the intimate connexion between the skin of the face and the facial mus- cles, which, from the nature of their insertions, are in some measure identified with it, the frequently-repeated contraction of one or more of these muscles occasions folds oi wrinkles of the skin that remain during the intervals of those contractions, and aftei they have entirely ceased. And thus the continual experience of grave or cheerful emo- tions, with their characteristic expressions of countenance, at length impresses a pecu- liar and permanent stamp upon the features, so that those who are in the habit of close ly observing such circumstances may in some degree judge of the disposition of an indi vidual from an examination of his physiognomy. This is the only foundation of the sys tern of Lavater. MUSCLES OF THE TEMPORO-MAXILLARY REGION. The Masseter and Temporalis. The muscles of this region are four in niunber ; two on each side, viz., the massetei and the temporal. The Masseter. Dissection. — ^Make a horizontal incision along the zygoma, and a vertical one from the middle of this to the base of the jaw ; dissect back the flaps, taking care not to divide the Stenonian duct, which passes over the muscle. In order to see the deep surface, saw through the zygoma in two places, and turn it outward. The masseter {s,Jig. 113) is a short and very thick muscle, of an irregularly-quadrilat- eral form, situated upon the side of the face. Attachments. — It arises from the lower edge of the zygoma, and is inserted into the outer surface of the angle and ramus of the lower jaw. Its origin from the zygoma consists of a very thick aponeurosis, which embraces the anterior borders of the mus- cles, and is composed of several planes of super-imposed fibres, which are prolonged upon its surface and in its substance for a considerable distance. Tlie fleshy fibres pro- ceed from the inferior surface and the borders of this aponeurosis, obliquely downward and backward, and are inserted into the angle of the jaw either directly or by means of very strong tendinous fibres. Not unfrequently a small triangular fasciculus is detached forward to the inferior border of the body of the bone. The fleshy fibres arising from the posterior portion of the zygoma constitute a short, small, and almost entirely fleshy bundle, which passes vertically downward, and is inserted behind the preceding into the external surface of the ramus of the jaw. Lastly, the zygomatic arch being reversed, we see a still smaller fleshy fasciculus, arising directly from its internal surface, and T^assmg forward, to be inserted into the outer surface of the coronoid process, and into the tendon of the temporal muscle. Relations. — It is covered by the skin, from which it is separated by a small fascia, and sometimes by a prolongation of the platysma ; behind, it is covered by the parotid gland, and by the orbicularis palpebrarum and zygomaticus major above. It is crossed at right angles by the divisions of the facial nerve, the transverse artery of the face, and the Stenonian duct. It covers the ramus of the jaw, the temporal and the buccinator mus- cles, from the latter of which it is separated by a collection of fat. Its anterior edge, which is prominent beneath the skin, has an important relation below to the facial ar- tery, which may be compressed against the bone immediately in front of it. The parot- id gland embraces its posterior border. Action. — The action of this muscle is very powerful. Its strength in different animals may be in some degree measured by the size of the zygomatic arclu and by the promi- nence of tiie lines and projections on the angle of the jaw. Its momentum, i. e., its period of most powerful action, occurs when the jaws are slightly separated, because its angle of incidence with regard to the lever is then nearly perpendicular. The general direction of the fibres of the masseter muscles, obliquely downward and backward, is highly advantageous as regards the trituration of the food, for during the contraction of the two muscles the lower jaw is moved upward and for- ward. This same obliquity explains the action of the muscle in producing luxation of the jaw ; for as its insertion is farther back than it would have been had the fibres been vertical, it follows that, however slightly the jaws may be separated, the condyle is placed in front of the axis, to which all the fibres of the masseter may be referred ; and when this muscle contracts, it increases the peculiar movement performed by the con- dyle in becoming dislocated forward. 240 MYOIiOGY. The Temporalis. Dissection. — Having sawn through and turned back the zygoma, remove the fascia covering the temporal region, and the fat surrounding the insertion of the muscle into the coronoid process. In order to gain a view of the deep surface, detach the muscle, either from above downward, by scraping the periosteum from the temporal fossa, or from below upward, after having sawn through the base of the coronoid process. The temporal muscle {e', fig. 114), or crotaphyte, so named because it occupies the whole of the temporal fossa {Kporacjioc, the temple), is a broad, radiated muscle, resem- bling a triangle with the base turned upward. Attachments. — It arises from the whole extent of the temporal fossa, and from the in- ner surface of the superficial temporal fascia, and is inserted into the edges and summit of the coronoid process. The fleshy fibres all arise directly, either from the temporal fossa, or from the inner surface of the fascia, which, being attached above to the entire length of the temporal semicircular line, and below to the upper edge of the zygomatic arch, is very tense, and thus affords a solid and very strong surface of origin. From these two parts the fleshy fibres converge, and proceeding downward, the anterior ob- liquely backward, the posterior obliquely forward, and the middle vertically, form a fleshy mass, which gradually increases in thickness until its fibres are attached, partly to the external, but chiefly to the internal surface and borders of the terminal aponeurosis. The fibres of this aponeurosis, which are very strong, and radiated at its comm'ince - ment, are collected into the form of a very thick tendon, inserted into the coronoid pro- cess, and called the coronoid tendon. The temporal muscle, in its course from the tem- poral fossa to the coronoid process, undergoes a sort of reflection over the groove at the base of the zygoma. I have often seen a very strong muscular fasciculus arising from the lower part of the temporal fossa and the ridge bounding it below, and inserted by a separate tendon into the internal border of the anterior surface of the ramus of the jaw. Relations. — It is covered by the skin, the aponeurosis of the occipito-frontalis, the an- terior and superior auricular muscles, the superficial temporal arteries, veins, and nerves, and more immediately by the superficial temporal aponeurosis, the zygomatic arch, and the masseter. It covers the temporal fossa, the external pterygoid muscle, a small part of the buccinator, the internal maxillary artery, and the deep temporal vessels. Its thickness is in proportion to the depth of the temporal fossa and the strength of the coronoid process. Action. — The strength of the temporal muscle, therefore, may be in some degree measured by the depth of the temporal fossa and the size of the coronoid process. This fact may be demonstrated by an examination of these regions in the skeletons of carniv- orous animals, in which the elevators of the lower jaw are most highly developed. The use of the temporal muscle, like that of the masseter, is to elevate the lower jaw, but the mechanism of its action is diflerent. In fact, the masseter raises the jaw by a direct action ; the temporal muscle, on the contrary, raises it by a sort of swing motion, acting principally upon the back part of the coronoid process. In a word, the temporal muscle acts upon the vertical arm of the bent lever represented by the maxillary bone, while the masseter, on the contrary, acts upon its horizontal arm, the movement depending on the action of the temporal muscle : the lower jaw resembles the curved lever represent- ed by the hammer of a beU. THE PTERYGO-MAXILLARY REGION. The Pterygoideus Internus. — The Plerygoideus Externus. The muscles of this region are the external and the internal pterygoids. Fig. 115 The Pterygoideus Internus vel Magnus Dissection. — Separate the face and that part of the cranium which is situated anterior to the ver- tebral column from the remainder of the scull, and divide the face into two lateral halves by an antero-posterior section. ' This muscle may also be dissected in the fol- lowing manner : saw through the lower jaw ver- tically at the junction of the body and ramus ; re- move the zygomatic arch ; cut through the base of the coronoid process and the neck of the con- dyle, and then disarticulate the latter. The internal pterygoid {a, fig. 115) is deeply seated m the zygomatic fossa, along the inner surface of the ramus of the jaw(tertius nmsculus qui in ore latitat, Vesalius). It is thick and quad- THE PTERYGOIDEttS EXTERNUS, ETC. iilateral, and in its form, structure, and direction, bears a remarkable reselrtBlarice to the masseter ; hence Winslow called it the internal masseter. Attachments. — It arises from the pterygoid fossa, from the hamular process, at the apex of the internal pterygoid plate, and from the lower surface of the pyramidal process of the palate bone ; and is inserted into the inner surface of the angle of the lower jaw Its origin consists of a tendon resembling that of the msisseter, prolonged upon the in- ternal surface, and into the substance of the muscle. From this the fleshy fibres pro- ceed downward, outward, and backward, to be inserted, by very strong tendinous laminae, into the lower jaw. Relations. — On the inside it is in relation with the external peristaphyhne muscle {tensor palcti), and with the pharynx, a triangular interval existing between it and the latter, occupied by a considerable quantity of cellular tissue, vessels, nerves, and the sub-maxillary gland : on the outside it corresponds with the ramus of the lower jaw, from which it is separated above by the dental and lingual nerves, the inferior dental vessels, and the so-called internal lateral ligament of the temporo-maxillary articulation. Action. — As this muscle is inserted almost perpendicularly into the lever upon which it acts, it has very great power. Most of the remarks already made concerning the mas- setor apply to this muscle, which is a true internal masseter. It has only this peculiar- ity, that as its origin is nearer the median line than that of the external masseter, it assists in producing a slight lateral movement of the jaw, which is very useful in bruis- ing the food. The Pierygoideus Externus vet Parvus. Dissection. — This, like the preceding muscle, may be exposed by two opposite methods. The external pterygoid {b,fig. 115) is very short, thick, and conoid, smaller than the preceding, and situated in the zygomatic fossa, extending horizontally from the outer surface of the external pterygoid plate to the neck of the condyle of the lower jaw. It arises from the whole outer surface of the external plate of the pterygoid process, and from the facette of the palatine process, at which it terminates below, from the ridge separating the temporal and zygomatic fossae, and from a spinous process at the extrem- ity of this ridge, which appears to me worthy of notice. It is inserted into the fossa in front of the neck of the condyle of the lower jaw, and into the border of the interarticu- lar cartilage. Its origin consists of a strong tendon, prolonged into the substance of the muscle. From this the fleshy fibres proceed horizontally outward and backward, forming, at first, two distinct portions, between which the internal maxillary artery often pjisses : these two portions then converge, are blended together, and terminate by some small tendinous fibres, which form the truncated summit of the cone represented by the muscle, and are attached to the neck of the condyle and to the inter-articular cartilage. Relations. — This muscle is deeply situated, and is in relation on the outside with the ramus of the lower jaw, the temporal muscle, and the internal mcixillary artery ; on the inside with the internal pterygoid, and above with the upper wall of the zygomatic fossa. Action. — The axis of the external pterygoid being directed outward and backward, and its origin being at the pterygoid process, it may be readily imagined that its con- traction will produce a horizontal motion in two directions, viz., forward and to the op- posite side from that on which the muscle is acting. When the two external pterygoids act together, the jaw is carried directly forward. From the insertion of this muscle into the inter-articular cartilage, the latter is never separated from the condyle during these several movements. It is principally this muscle which causes displacement of the con- dyle in cases of fracture of the neck of the bone, and it is also the chief agent in bruis ing the food. MUSCLES OF THE UPPER EXTREMITIES The muscles of the upper extremities may be divided into those of the shoulder, oi the ann, of the forearm, and of the hand. MUSCLES OF THE SHOULDER The Deltoidexis. — Supra-spinatus. — Infraspinatus and Teres Minor. — Subscapularis. The muscles of the shoulder are the deltoid, the supra-spinatus, the infra-spinatus and teres minor (which I regard as only one muscle), and the subscapularis. The teres major, generally arranged among the muscles of this region, has already been described with the latissimus dorsi, of which it may be regarded as an accessory. The Deltoideus. Dissection. — Make a horizontal incision through the skin, round the summit of the •houlder, extending from the external third of the clavicle to the most distant point of the spine of the scapula : from the middle of this incision let another be made, descend- Hh 242 MYOLOGY. mg vertically half way down the humerus ; dissect back the two flaps, taking care tc raise at the same time a very thin aponeurosis, which is closely applied to the fibres. The deltoid {I, figs. 106, 109), so named from its resemblance to the Greek delta, A, re- versed, is a thick, radiated, triangular muscle, bent in such a way as to embrace the scapulo-humeral articulation before, on the outer side and behind. It is the muscle of the top of the shoulder. Attachments. — It arises from the entire length of the posterior border of the spine of the scapula, from the external border of the acromion, and from the external third, i. e., from the concave part of the anterior border of the clavicle : it is inserted into the del- toid impression on the humerus. The scapulo-clavicular origin of the deltoid corre- sponds exactly to the inferior attachment or the insertion of the trapezius, so that these two muscles, although separate and distinct in man, appear to form a single muscle di- vided by an intersection : a view that is perfectly confirmed by a reference to compara- tive anatomy. The origin consists of tendinous fibres ; of these the posterior are the longest, and are blended with the infra-spinous aponeurosis, which also gives origin to some of the fibres of the deltoid. Three or four principal tendinous laminae, attached at regular intervals to the clavicle and the acromion, penetrate into the substance of the muscle, and give origin to a great number of fleshy fibres. The largest of these laminae extends from the summit of the acromion, and its situation is sometimes indicated by a prominence of the skin, particularly during contraction of the muscle. From this very extensive origin the fleshy fibres proceed downward, the middle vertically, the anterior backward, and the posterior forward : they form a thick, broad mass, moulded over the top of the shoulder, and, gradually converging, are at length inserted into the deltoid impression of the humerus by three evry distinct tendons, the two principal of which, the anterior and posterior, are attached to the bifurcations of that V-shaped impression. Not unfrequently some fibres of the pectoralis major are connected with the front of this tendon. Relations. — It is covered by the skin, the platysma intervening between them, by some supra-acromial nerves, and by a thin fascia extending from the infra-spinous apo- neurosis, the spine of the scapula and the clavicle, and becoming continuous with the fascia of the arm. It covers the shoulder-joint, from which it is separated by a tendi- nous layer continued from the infra-spinous and coraco-acromial ligaments, and which terminates on the sheaths of the coraco-brachialis and biceps muscles. Between this lamina and the greater tuberosity of the humerus there is a quantity of filamentous cel- lular tissue, and frequently a synovial bursa. The deltoid, therefore, is enclosed in a proper fibrous sheath, and glides over the articulation. It also covers the upper third of the humerus, the coracoid process, the tendons of the pectorales, coraco-brachialis, biceps, supra-spinatus, infra-spinatus and teres minor, teres major, and biceps muscles, also the circumflex vessels and nerves. The anterior border of the deltoid, directed ob- liquely downward and outward, is separated from the external margin of the pectoralis major by a cellular interval, but is frequently in contact with it. The cephalic vein and a small artery define the limits of the two muscles. The posterior border is thin above, where it is applied to the infra-spinatus muscle, and becomes thick and free below. The inferior angle of the deltoid is embraced by the brachialis anticus. Issues are generally established over this situation. Remark. — The structure of this muscle has been patiently investigated by some anat- omists, who have counted the exact number of its component fasciculi. Tliese are sep- arated by fibro-cellular prolongations, like the fasciculi of the glutaeus maximus ; some- times, even, the muscle is divided into three distinct portions above, viz., a clavicular, an acromial, and a spinal. Eighteen or twenty small penniform fasciculi, the bases of which are generally turned upward, are collected into a small space by mutually over- lapping each other, and are united by their terminating tendons. Albinus admits ten of these bundles, which he has described separately. Action. — The deltoid elevates the shoulder (elevator, attollens humerum). From the threefold direction of its fibres, it has a different action, according to the particular set of fibres employed. The middle fibres raise the humerus directly, the anterior raise and carry it forward, the posterior raise and carry it backward. When the arm is raised, Bichat states that the anterior and posterior fibres can depress it ; but I do not think this possible. There has been no example recorded of luxation from the over-action of this muscle. When the arm is fixed, as in the act of climbing, the aJioulder is moved upon the head of the humerus. The trapezius must be regarded as the most powerful antagonist of the deltoid, since the scapulo-clavicular attachments of both muscles are the same. Thus, we have seen that the diaphragm and the transversalis abdominis are separated only by their costal insertions. The most complete antagonism follows from such an arrangement, for then one fibre is, as it were, opposed to another, having ex- actly an opposite direction. The action of the deltoid is, however, less powerfnl than might have been supposed from its size ; it is, in fact, parallel to the lever on which it acts. While almost all other muscles have a mmnentum, occurring at the period when their fibres are inserted at the THE SUPRA AND INFRA S>ilJiATUS AND TERES MINOR. S48 most favourable angle, the deltoid, pioperly speaking, has none ; it is parallel to the lever during the entire period of its action. This is the reason vthy the elevation of the arm is so feeble a movement, and why contraction of the deltoid is always accompanied by considerable fatigue. The Supra-spinatus. Dissectimi. — Take off the trapezius, and, in order to see the whole extent of the mus- cle, remove the clavicle, and saw through the base of the acromion. The supra-spinatus {r,fig. 106) is a thick, triangular muscle, broad on the inside, nar- row without, occupying the supra-spinous fossa, and retained therein by a strong apo- neurosis, which completes the osteo-fibrous sheath in which the muscle is enclosed. Attachments. — It arises from the internal two thirds of the supra-spinous fossa, and is inserted into the highest of the three facettes on the greater tuberosity of the humerus Its origin from the supra-spinous fossa is partly tendinous and partly fleshy, and sora„ fibres arise from its aponeurotic investments. From these points the fleshy fibres con- verge to a tendon, which is found among them where the muscle reaches the upper part of the joint, and which is slightly reflected over the head of the humerus before reaching its insertion. This has not the shining appearance of other tendons, but has the dull aspect of many ligaments ; it is blended with the fibrous articular capsule, from which it cannot be separated near its insertion. It may even be regarded as forming the upper part of the capsular ligament. Relations. — It is covered by the trapezius, the clavicle, the coraco-acromion ligament, and the deltoid ; and it covers the supra-spinous fossa, the supra-scapular vessels and nerves,* and the upper part of the shoulder-joint. Its tendon is often blended with that of the. infra-spinatus, and is separated from that of the sub-scapularis by the long head of the biceps, and the accessory ligament of the capsule. Action. — It raises the humerus, and therefore assists the deltoid. Notwithstanding the nmnber of its fibres, and its perpendicular insertion into its lever, it has very little power, on account of the proximity of that insertion to the fulcrum. Its principal action appears to me to have reference to the joint, affording a support to it above, and forming a sort of active arch, the resisting power of which is in proportion to the force tending to thrust the humerus upward against the osteo-fibrous arch, composed of the acromion and coracoid processes and their connecting ligament. There is no muscle, then, to which the name of articular can be more correctly applied. The use of the deep fibres in preventing the folding of the fibrous and synovial capsules, and their compression be- tween the two articular surfaces, though much insisted on by Winslow, appears to me very problematical. The Infra-spinatus and Teres Minor. Dissection. — ^Detach the scapular origin of the deltoid, and saw through the base of the acromion. The infraspinatus (s) and teres minor {t, Jig. 106) constitute a single, thick, triangular aiuscle, broad on the inside and narrow externally, and occupying the infra-spinous fossa, in •rt'hich it is retained by an aponeurosis, exactly resembling that of the supra-spinatus uiuscle. It aiises from the internal two thirds of the infra-spinous fossa, from a very strong fascia interposed between it and the teres major and long head of the triceps, and by a 'ew fibres from the infra-spinous aponeurosis : it is inserted into the middle and inferior 'acettes on the greater tuberosity of the humerus, below the insertion of the supra-spi- natus. It arises from the infra-spinous fossa, directly by fleshy fibres, and also by means uf tendinous fibres attached along the ridges of that fossa. One of these laminae is con- stantly found attached to the ridge situated on the outer side of the infra-spinous groove : ihis has doubtless given rise to the division of the muscle into two parts, called the in- fra-spinatus and the teres minor. From these origins the fleshy fibres proceed, the su- perior horizontally, the next obliquely, and the inferior almost vertically outward : they form a thick, triangular, fleshy body, and become attached to the anterior surface and margins of a flat tendon, which glides upon the concave humeral border of the spine of th,3 scapula, to be inserted into the humerus. Not unfrequently we find the lower fibres of the portion called the teres minor, arising from the posterior surface of the tendon of the triceps, becoming applied to the imder part of the capsular ligament, and inserted into the humerus immediately below the great tuberosity. Relations. — These two united muscles are covered by the deltoid, the trapezius, the. Jatissimus dorsi, and the skin ; and they cover the infra-spinous fossa, from which they are separated by the supra- scapular nerves and vessels ; they also cover the capsular ligament of the joint, and a small portion of the long head of the triceps. Their lower or external border corresponds internally or inferiorly with the teres major, an aponett- rotic septum intervening between them, and externally or superiorly with the long head jf the triceps. * The supra-scapular nerve generally passes through the coracoid notch by itself, and the supra-scapulat lery above the ligament. 244 • ?:'.»,«r^ ' MYOLOGY Action. — This muscle rotates the humerus t,atward and a little backward. When the arm is raised, it assists in keeping it in this position, and carries it backward. But an important use of this muscle is that of retainmg the head of the humerus in its place, pre- venting its displacement backward, and protecting the posterior part of the articulation. The Sub-scapularis. Dissection. — Detach the upper extremity, including the shoulder, from the trunk of the body ; remove from the inner surface of the muscle the cellular tissue, the lymphatic glands, the brachial plexus, the axillary vessels, and the serratus magnus ; and dissect off, with care, the thin fascia which invests it. The sub-scapularis (a, figs. 110, 116) is a thick triangular muscle, occupying the whole of the sub-scapular fossa, beneath the axillary border of which it passes : by itself it rep- resents the supra and infra spinatus and teres minor, upon the posterior scapular region. We not unfrequently meet with tendinous laminae dividing it into three parts, which cor- respond to those three muscles. Attachments. — It arises from the internal two thirds of the sub-scapular fossa, by ten- dinous laminae attached to the oblique ridges already described as existing on that part of the scapula ; also from the anterior lip of the axillary border of the scapula by an apo- neurosis, which separates this muscle from the teres major and the long head of the tri- ceps. Very frequently the lowest fibres arise from the anterior surface of this head of the triceps, just as we have seen that the lower fibres of the teres minor take their ori- gin from the posterior surface of the same head of that muscle. From these different origins the fleshy fibres all proceed outward, the upper horizontally, and the lower ob- liquely, gradually approaching more and more to the vertical direction. The muscle, therefore, becomes progressively narrower and thicker, until its fibres are attached to the two surfaces and borders of a tendon which is inserted into the entire surface of the lesser tuberosity of the humerus. Some of the muscular fibres are inserted below the tuberosity ; and I have seen the inferior fibres of the muscle attached for a certain extent to a fibrous prolongation that completes the bicipital groove behind. Relations. — The posterior surface of this muscle lines the sub-scapular fossa, which it entirely fills, and from which it is separated at the outer third by some cellular tissue and the sub-scapular vessels and nerves ; more externally, it covers the upper and anterior part of the capsular ligament of the shoulder-joint, turning around it, and becoming iden- tified with it at its insertion. Its anterior surface is in relation with the serratus magnus, the sub-scapular fascia, and some very loose cellular tissue intervening between them ; also with the axillary vessels and nerves, and with the coraco-brachialis and deltoid muscles. The upper border of its tendon glides in the hollow of the coracoid process, which serves as a pulley, and forms with the coraco-brachialis and the short head of the biceps a sort of ring, partly bony and partly muscular, in which the tendon is retained. Between this tendon and the coracoid process there is also a synovial bursa, which some- times extends over the tendons of the biceps and coraco-brachialis, and always commu- nicates with the synovial capsule of the shoulder-joint.* Action. — It is essentially a rotator inward of the humerus. In proof of this, we find that the muscie is stretched when the arm is rotated outward, and relaxed when it is ro- tated inward. The movement of rotation is much more considerable than the length of the neck of the humerus would lead us to imagine, and this arises from the muscle turn- ing round the head of the bone. As a rotator muscle, then, it is congenerous with the latissimus dorsi. When the humerus is raised, the sub-scapularis tends to draw it down- ward. And farther, this muscle, as well as the supra-spinatus, infra-spinatus, and teres minor, is essentially an articular muscle, and is sometimes completely identified with the anterior part of the fibrous capsule : in all cases it offers an active resistance to displace- ment forward, and is, therefore, always torn in this kind of dislocation. MUSCLES OF THE ARM. The Biceps. — Brachialis Anticus. — Coraco-brachialis. — Triceps Extensor Cubiti. The muscles of the arm have been divided into those of the anterior region, viz., the biceps, the coraco-brachialis, and the brachialis-anticus ; and those of the posterior region, which constitute the single muscle called the triceps. Anterior Brachial Region. The Biceps. Dissection. — Make a vertical incision through the skin from the middle of the clavicle to the middle of the bend of the elbow ; dissect back the flaps, and divide longitudinally the brachial fascia, which is united to the biceps by very loose cellular tissue ; preserve the vessels and nerves which lie along the inner border of the muscle. Expose the up- per part of the muscle by detaching the pectoralis major and deltoid from their clavicu- * See note, p. 22. THE BICEPS. Fig. 116. tax origins, and turning them inward and outward. In order to trace the whole extent of the long head of the biceps, open the capsular ligament above ; and to see the radial insertion of the muscle, flex the forearm to a right angle upon the arm, and supinate it forcibly ; it is better, however, to wait until the muscles of the anterior region of the fore- arm are dissected. The biceps flexor cubiti (a, flg. 116) is along muscle forming the superficial layer of the anterior region of the arm ; it is divided above into a short and long head ;* and hence its name biceps. Attachmcjits. — It arises by its short head from the apex of the coracoid process, and by its long head from the top of the glenoid cavity ; and is inserted into the bicipital tuberosity of the radius. The origin of the short or coracoid head {b,fig. 116) consists of a flat and very thick tendon, common to it and the coraco- brachialis, and terminating in front of this part of the muscle in an aponeurosis, from which is given off a tendinous septum, be- tween the biceps and the coraco-brachialis. The long, glenoid, or reflected head arises by a tendon apparently forming a contin- uation of the glenoid articular border, which penetrates into the interior of the joint, turns over the head of the humerus, upon which it is reflected, and thus reaches the bicipital groove. It is retained in this groove by a sort of fibrous bridge or canal, traverses the whole of its extent, and ends in a sort of tendinous cone open behind, from the interior of which the fleshy fibres take their origin. These fibres are collected into a rounded belly, which, about the middle of the arm, is applied to the muscular belly of the short portion, equally rounded and of variable size, and ultimately becomes identified with it. The single muscle (fl, fig. 116) thus formed is very thick, flattened from before backward, and directed vertically like the two original fasciculi. Its fibres are attached to the surfaces and edges of an aponeuro- sis, which gradually becomes narrower and thicker, until it emerges in the form of a free tendon opposite the lower end of the humerus, a little nearer to the outer than the inner side. This flattened tendon sinks downward and backward into the triangular space be- tween the supinator longus and the pronator teres, and is then so folded and twisted upon itself that its anterior surface becomes posterior, its internal margin becomes anterior, and its external margin at first posterior and then superior. This folding and torsion are of extreme utility in preventing displacement of the muscle, which thus fastens down it- self The tendon of insertion having given off from its anterior surface and external margin a broad aponeurosis, constituting the principal origin of the fascia of the fore- arm, glides over the bicipital tuberosity of the radius, from which it is separated by a bursa, and is inserted into the posterior part of that process. Relations. — The upper third of the two heads of the biceps, as well as the coraco-brach- ialis, and the axillary vessels and nerves, are contained in the cavity of the axilla, be tween the pectoralis major and the deltoid in front, and the latissimus dorsi and teres major behind. In this part of its course, the short head of the biceps is in relation Witt the coraco-brachialis on the inside, and behind with the sub-scapularis, which separates it from the shoulder-joint ; a bursa intervenes between these two muscles. The tendon of the long head is in contact with the head of the humerus, and surrounded by the sy- novial membrane, which isolates it from the cavity of the joint, and accompanies it, for a greater or less distance, along the bicipital groove. Below the axilla the biceps is sub- cutaneous in front, the brachial fascia intervening between it and the skin, through which it is very clearly defined ; behind, it is in relation with the musculo-cutaneous nerve, and the coraco-brachialis and brachialis anticus muscles ; on the inside, with the brachial ar- tery and its accompanying veins, and with the median nerve, all of which lie along its in- ternal border, by the projection of which they are protected. The tendon is embraced at its insertion by the supinator brevis, and it is separated from that of the brachialis anti- cus by a bursa. Great attention should be paid to the relation of this muscle to the brach- ial artery. I am accustomed, when speaking of the surgical anatomy of these parts, to call the biceps the satellite muscle of the brachial artery. It is worthy of remark, that the relative positions of the long and the short head are altered as the humerus is rota- ted inward or outward ; in rotation inward, the long head is placed behind the other, or even crosses to the inner side of it ; but in rotation outward, the interval between the two heads is considerably increased. Action. — The biceps flexes the forearm upon the arm, and at the same time supinates it. This last effect results from the insertion of the muscle into the inner and back part of the bicipital tubercle of the radius. The momentum of the biceps occurs during seini- * Not unfrequently the biceps is trifid above. The supernumerary head is internal, and arises from the in- ner border of the humerus, below the coraco-brachialis, which may be regarded as the continuation of this head, for they correspond in size. This supernumerary portion is attached to the inner edge and posterior surface of the lower tendon of the biceps. 1 have twice seen this disposition of parts. 246 MYOLOGY. flexion of the forearm • its insertion being at that period perpendicular to tiie lever, the disadvantage arising from its proximity to the fulcrum is then counteracted. The length of Its fibres explains the extent of the movement of flexion. By means of its scapular attachments, the biceps acts upon the arm, either secondarily, after bending the forearm, or primarily, when the forearm is extended. By means of both its heads, it carries the arm forward, and thus co-operates with the anterior fibres of the deltoid and coraco-brach- ialis. The two heads also assist in strengthening the shoulder-joint. The long head forms a sort of fibrous arch, which supports the head of the humerus, and retains it in the glenoid cavity. The short head, together with the coraco-brachialis, forms a continuation of the hook of the coracoid process, and protects the anterior and inner part of the joint. The biceps is, as Winslow first showed, one of the principal supinators of the forearm ; and it is in this movement that the tendon glides over the bicipital tuberosity of the ra- dius by means of the intervening bursa. This tuberosity is almost entirely intended for the tendon to glide over ; it is, therefore, incrusted with cartilage. Dense and reddish granulations, as pointed out by Haller, are found upon the synovial bursa of the tendon. When the forearm is fixed, as in climbing, the biceps flexes the arm upon the fore- arm, and the scapula upon the arm. Lastly, it is a tensor of the fascia of the forearm, upon which the internal fibres of the muscle often terminate. The Brachialis Anticus. Dissection. — Cut the biceps across, opposite the insertion of the deltoid, and turn down the lower part upon the forearm. The brachialis anticus (brachialis internus, Alb., d d,fig. 116; d,fig. 117) is a thick, prismatic, and triangular muscle, situated behind the preceding. It arises from the hu- merus, below the insertion of the deltoid, which it embraces by a well-marked bifurca- tion ; and since the point of insertion of the deltoid is not always the same, it follows that this origin of the brachialis anticus is eilso variable ; it also arises from the internal and external surfaces, and from the three borders of the humerus, and from the external and internal inter-muscular septa. It is inserted into the rough surface on the fore part of the coronoid process of the ulna. The different origins from the humerus are fleshy, the fibres being of very various lengths, and proceeding in different directions ; the middle pass vertically downward, the external somewhat obliquely inward, and the internal out- ward ; they all terminate on the posterior surface of an aponeurosis, which is broad and thin above, and thick below, especially on the outer side, where it turns round so as to embrace the outer border of the muscle, and forms a deep aponeurotic lamina. The fleshy fibres, therefore, are received into a semi-cone of tendinous substance, open on Che inside, the fibres of which are collected together, and finally inserted into an oblique line, running downward and outward, below the coronoid process of the ulna. Relations. — The anterior surface of the brachialis anticus is in relation with the biceps, the musculo-cutaneous nerve, the brachial fascia, the brachial artery and veins, and the median nerve ; its internal surface, with the pronator teres muscle, the ulnar nerve, and the triceps, from which it is only separated by the internal inter-muscular septum ; its external surface, with the supinator longus and the extensor carpi radialis longior, which are received into a sort of groove presented by it, the radial nerve establishing the limit between these two muscles and the brachialis anticus. The posterior surface embraces the internal and external surfaces of the humerus, to which it is attached ; below, it em- braces, and effectually protects the front of the elbow-joint, into the anterior ligament of which many of its fibres are inserted. Action. — The brachialis anticus flexes the forearm upon the arm, and, reciprocally, the arm upon the forearm. Its momentum takes place, like that of the biceps, during semi- flexion. It is worthy of remark, that this muscle acts with greater precision than the bi- ceps upon the forearm, because it arises from the humerus only, and, besides that, it be- longs more especially than that muscle to the elbow-joint. I have already said that it may be regarded as the active anterior ligament of this articulation. In fact, it so com- pletely hmits the movement of extension, that we cannot imagine the possibility of lux- ation of the forearm backward without rupture of this muscle. From the insertion of the biceps into the radius, and of the brachialis anticus into the ulna, it follows that the flexor muscles of the forearm are divided between the two bones, in the same manner as those of the leg are distributed to the tibia and fibula Thus, the contraction of the brachialis anticus has a tendency to carry the forearm outward as well as to flex it, while that of the biceps tends to draw it inward. When the two muscles contract si- multaneously, direct flexion is the result. The Coraco-brachialis. Dissection. — The upper part is exposed as soon as the deltoid is detached ; the middle is situated between the pectoralis major and the latissimus dorsi ; and the lower part is seen upon the mner surface of the humerus, near the tendon of the deltoid. The coraco-brachialis {e,figs. 116, 117) is the smallest muscle of the arm. It is situa- ted at the inner and upper part of the arm, and was confounded by most of the oldei THE TRICEPS EXTENSOR CUBITI. «4T anatomists with the short head of the biceps, with which, indeed, it is intimately united at its upper part. Attachments. — It arises from the apex of the coracoid process, and is inserted towards the middle of the internal surface and border of the humerus. It arises from between two tendinous layers, the most superficial of which is common to it and the short head of the biceps, and also from the septum between these two muscles. From this origin the fleshy fibres proceed, forming an elongated, thin, and flat bundle, the size of which is always in an inverse ratio to that of the short head of the biceps ; this bundle passes downward, backward, and a little outward, to be inserted into the humerus, between the brachialis anticus and the triceps. Its insertion is effected by means of a flat tendon, which receives the fleshy fibres successively upon its edges and external surface, and is accompanied by them even to its attachment to the bone. The precise situation of the attachment varies like that of the deltoid, and hence the different statements of authors regarding this point. According to Winslow, the coraco-brachialis is inserted at the up- per part of the middle third of the humerus ; according to M. Boyer, in the middle of the bone ; and according to Bichat, a little above its middle. I have found it inserted at the junction of the lower with the two upper thirds. Relations. — It is covered by the deltoid, the pectoralis major, and the biceps, and it covers the sub-scapularis, the latissimus dorsi, and the teres major. Its relations to the axillary and brachial arteries, and the median and musculo-cutaneous nerves, are the most important. Above, it covers these parts, and then it is in relation with the outer side of the brachial artery and median nerve, so that its tendon alone separates the ves- sel from the bone. The musculo-cutaneous nerve passes through it ; hence the name of -perf mains Casserii has been given to this muscle. It is also very frequently perfora- ted by one of the branches of origin or roots of the median nerve. Action. — It cames the arm forward and inward, and, at the same time, elevates it It co-operates with the anterior fibres of the deltoid, and the superior fibres of the pecto- ralis major. If the arm be fixed, it depresses the top of the shoulder ; when the arm is carried backward and turned inward, it draws it forward again, and rotates it outward.* Posterior Brachial Region. The Triceps Extensor Cubiti. Dissection. — It is exposed by simply removing the skin and the fascia from the back of the arm, by removing the deltoid, or turning it upward, and by tracing the long head of the muscle between the teres major and minor to the axillary border of the scapula. In order to render it tense, and thus facilitate the dissection, the forearm must be flexed and the humerus abducted. The triceps extensor cubiti {ifg,fig. 117) is a very large muscle, divided above into three portions, named the external, internal, and middle, or long heads. It constitutes by itself the entire muscular apparatus of the posterior region of the arm. Attachments. — It arises, 1. By its long head, from the low- er part of the glenoid cavity of the scapula, and from a rough, triangular depression existing on the contiguous portion of its axillary border ; 2. By its external head (vastus extemus), from all that portion of the posterior surface of the humerus which is above the groove for the radial nerve, from the external border of that bone, and from the external inter-muscular septum ; 3. By its inter- nal head (vastus intemus), from the whole of the poste- rior surface of the humerus below the groove for the ra- dial nerve, from the internal border of the bone, and from the internal inter-muscular septum. It is inserted into the back of the olecranon. The origin of the middle or long head (which we shall find to be analogous to the rectus cruris)t consists of a tendon that is blended with the glenoid ligament, nearly in the same manner as the long tendon of the biceps. This tendon is flattened from before backward, and soon splits into two layers, united by their outer edges, the posterior of which is thin and short, while the anterior is very thick, especially at its outer edge, and prolonged to the middle of the muscle. The head of the humerus, therefore, is bound by the long head of the triceps below, in the same manner as by the long tendon of the biceps * I have seen a small supernumerary coraco-brachialis extending from the base of the corait't ."v**.^ below the lesser tuberosity of the humerus, immediately beneath the insertion of the sub-scapularis : the same arrangement existed on both sides. This small muscle described a curve in front of the sub-soapularis. t The older anatomists regarded this long portion as a separate muscle : longus [Riolanus Albirms), cubitum Rxtendentium primus (Yesalius), le grand ancone (Winslow). 248 a!Y'):,'|(;y. above. The fleshy fibres arise from between the two layers above mea^.o.icu, and form a bundle flattened in front and behind, which irnmediately turns upon itself, so that its anterior surface becomes posterior, and vice versa. From this sort of torsion the strong- est layer of the tendon, which was originally in front, eventually occupies the posterior surface of the muscle. The fleshy fibres arising from between the two layers, and es- pecially from the anterior surface and borders of the now posterior tendon, pass down- ward and a little outward, to be inserted, some into the anterior, but the greater number into the posterior surface of an aponeurotic expaosion, the external border of which is continuous with a similar structure belonging to the external division of the muscle. The aponeurotic fibres are collected together into a very thick tendon, which is folded into a semi-cone, within which the fleshy fibres terminate ; the tendon itself is inserted by a thick mass into the inner and back part of the olecranon, on the outer side of the internal portion of the muscle, and closely united with the posterior aponeurosis of the external portion. A synovial capsule intervenes between this tendon and the olecranon. The origins of the external and internal portions from the humerus divide between themselves, so to speak, the posterior surface of that bone, to which the long head has no attachments. The external head {f,figs. 116, 117), which is larger than the internal, and, from analo- gy, may be termed the vastus externus of the triceps brachii (cubitum extendentium secun- dus, Vesalius ; ancon6 externe, Winslow), arises partly by fleshy and partly by tendinous fibres. They are bounded above by a rough line, which is very well marked in powerful individuals, extending obliquely from the lower part of the head of the humerus to its external border. From these different origins the fleshy fibres proceed dovnward and inward, become partly blended with the internal head, and are almost all attached to the anterior surface of the terminal aponeurosis of the long head, and to the anterior sur- face and external edge of a very broad and strong tendon, which occupies the posterior aspect of the muscle. This latter tendon is united internally with the tendon of the long head, is folded upon itself, and receives the fleshy fibres as far as its insertion into the olecranon, on the outside of the long head. The inferior fleshy fibres of this portion of the muscle are very short and horizontal, and seem to be continued by the anconeus. The internal head of the triceps (tertius cubitum extendentium, Vesalius ; ancone in- terne, Winslow, g, figs. 116, 117), which we denominate the vastus internus of the triceps brachii, might be called the deep and internal portion of this muscle, for, as we find with regard to the vastus internus of the thigh, it is almost entirely covered by the other two portions. Its origins are partly fleshy and partly tendinous. The fibres pass in differ- ent directions, the external downward and inward, a few to the anterior surface of the aponeurosis of the external head, by which they are concealed, but the greater number directly to the olecranon, in front of the insertion of the other portions. The internal pass downward and outward, and terminate, some upon the inner edge and anterior sur- face of the tendon of the long head, but the greater number directly upon the olecranon, to the inside of that tendon. The lowest of these fibres are almost horizontal. Somt of the deepest fasciculi are generally given off from the body of the muscle, to be insert- ed into the synovial capsule of the elbow-joint. Relations. — It is covered through nearly its whole extent by the brachial fascia, and separated by it from the skin, through which it is distinctly defined ; it covers the poste- rior surface of the humerus, the back of the elbow-joint, the radial nerve, and the deep humeral artery. It is separated from the muscles of the anterior region of the arm by the external and internal inter-muscular septa. Its long or scapular portion is in relation with the deltoid and the teres minor behind, and with the sub-scapularis, the teres major, and the latissimus dorsi in front. Action. — The triceps extends the forearm upon the arm, but in order that its long head may act with effect, the scapula must be fixed by other muscles. The power of this muscle is not so great as its size and the number of its fibres would indicate, on account of its disadvantageous insertion near the fulcrum. It is true that here, as in the case of the triceps femoris, nature has, as much as possible, counterbalanced this disadvan- tage by inserting the muscle, not into the apex, but into the back part of the olecranon. We even find, as we have said, a synovial bursa between the tendon and that part of the olecranon with which it is in contact. It would appear, at first sight, that the momentum of this muscle would occur during semi-flexion, but a little consideration would show that, like the triceps femoris, it has, properly speaking, no momentum ; and that the ole- cranon, which may be regarded as the ossified tendon of the muscle, always has the same relation to the ulna, whatever be the position of the forearm. It should also be observ- ed, that this muscle has not nearly so much power during semi-flexion as during exten- sion, because, in the former case, it is opposed by the flexor muscles, which, in that po- sition, act with the greatest possible effect ; while in the latter, when the arm and fore- arm form an obtuse angle, the extensor muscle has the advantage. Lastly, the predom- inance of the extensor over the flexors is less marked in the arm than in the thigh ; and even supposing the extensor to possess more intrinsic power, it has less active force, in consequence of the insertions of the flexors being much more favourable, both as THE PRONATOR TERES. 349 legards their distance from the fulcrum, and their nearer approach to a perpendicular direction. Thus flexion evidently predominates at the elbow, and extension at the knee. This, indeed, ought to be the case, for in the upper extremities the flexion of the elbow is the movement of attraction and prehension ; while in the lower extremities, the ex- tension of the knee is an essential position in standing, walking, running, and leaping. We might suppose the possibility of rupture of the olecranon at its junction with the coronoid process, during violent extension o{ the forearm, an accident that would be anal- ogous to fracture of the patella, or rupture of its ligament. The long head of the tricepa assists in drawing the humerus backward, and slightly adducts the arm. By means oi its tendon of origin from the scapula, and especially by the outer edge of that tendon, which is thick, and, £is it were, arched, so as to fit the head of the humerus, the long head also forms a cord which supports the bone during abduction, and tends to prevent its displacement ; but, as the glenoid cavity is directed forward, and as its inferior ex- tremity is situated almost at the junction of the two anterior thirds with the posterior third of the cavity, it follows that this tendon is well calculated to prevent dislocation backward, but offers no resistance to displacement forward. Sometimes the lower ex tremity of the triceps becomes its fixed point, and then it extends the arm upon the fore- arm, and the shoulder upon the arm. MUSCLES OF THE FOREARM. Fig 118. The Pronator Teres. — Flexor Carpi Radialis. — Palmaris Longus. — Flexor Carpi Ulnaris. — Flexor Sublimis Digitorum. — Flexor Profundus Digitorum. — Lumbricalcs. — Flexor Longus Poinds. — Pronator Quadratus. — Supinator Longus. — Extensores Carpi Radia- lis, Longior et Brevior. — Supinator Brevis. — Extensor Communis Digitorum. — Extensor Digiti Minimi. — Extensor Carpi Ulnaris. — Anconeus. — Abductor Longus Pollicis. — Ex- tensor Brevis Pollicis. — Extensor Proprius Indicis. The muscles of the forearm are divided into those of the anterior, the external, and the posterior regions. Muscles of the Anteeior Region. These muscles form four very distinct layers. The first consists of the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor carpi ulnaris ; the second is formed by the flexor sublimis digitorum ; the third by the flexor profundus digitorum and the flexor longus pollicis ; and the fourth by the pronator quadratus. The Pronator Teres. Dissection. — This muscle is exposed when the inner and anterior part of the fascia of the forearm is removed. Its origin should be carefully studied. The pronator teres, or rotundus {a, fig. 118), the most superficial mus- cle on the anterior and inner aspect of the forearm, forms an oblique ridge under the skin, upon the inner side of the bend of the elbow. It is attached above to the inner condyle of the humerus, or epitroch- lea (a, fig. 1 19), and is inserted below into the middle of the radius (a')- It arises from the lower part of the inner border of the humerus, from the inner condyle, from a large inter-muscular septum, separating it from the flexor carpi radialis and the flexor sublimis, and from the coronoid process of the ulna on the inner side of the brachialis anti- cus, by means of a tendinous and fleshy bundle, which is separated from the rest of the muscle by the median nerve. From these ori- gins the fleshy fibres proceed obliquely downward and outward (pro- nateur oblique, Winsl.), surrounding a flat tendon, which appears first on the anterior surface of the muscle, and then turns over the ante- rior and external surfaces of the radius, to be inserted at the middle of that bone. The muscle, therefore, turns spirally around the radius, but not so completely as the supinator brevis. Its insertion may take place opposite any point in the middle third of the bone. Relations. — It is covered by the fascia of the forearm, by the su- pinator longus and extensor carpi radialis, and by the radial artery and musculo-spiral nerve : it covers the brachialis anticus and flexor sublimis, the median nerve by which it is first perforated, and the ulnar artery. Action. — The greater the amount of supination of the forearm, the more effectual is the action of this muscle as a pronator, because then it is much more completely rolled around the radius. I may remark that, on account of its obliquity, it is inserted into the radius at an angle of 45" ; and that, consequently, the direction in which it operates is rather favourable. It acts with greater advantage in pro- portion as it is mserted nearer to the upper end of the radius ; and, for this reason, it» Ii 250 MYOLOGY. power must vary considerably in different individuals. When pronation is carried asj as possible, the muscle then becomes a flexor of the forearm. After the preceding i amination of this muscle, we need no longer be surprised at the great energy of the mo^ ment of pronation, which is much more powerful than that of supination ; nor yet that is the most natural position of the forearm, for the pronator teres can more than coui teract the two supinators taken together. In fracture of the bones of the forearm, tb. muscle tends to obliterate the interosseous space. The Flexor Carpi Radialis. Dissection. — It is sufficient to divide and dissect off the anterior part of the fsiscia o! the forearm, in order to expose this muscle, which may be recognised by the followinj description : The flexor carpi radialis (radialis intemus, Albinus, I, fig. 118) is situated immediatelj within the pronator teres, occupying the superficial layer of the anterior aspect of tht forearm, and being, as far as its tendon is concerned, the most superficial of all these muscles. It arises from the lower part of the internal border and from the inner con- dyle of the humerus {b,fig. 119), and is inserted {h') into the second metacarpal bone. Its origin consists of a tendon common to it and to the pronator quadratus, palmaris longus, flexor sublimis, and flexor carpi ulnaris. The fleshy fibres immediately arise from within a sort of pyramidal aponeurosis given off by this common tendon, and from the body of the muscle, at first slender, then increasing in size, and again tapering to- wards its attachment to the two surfaces and edges of a tendon, which forms the lower two thirds of the muscle, and passes obliquely outward and downward to the level of the OS scaphoides ; it there penetrates into a groove formed by the scaphoid and the trape zium, is reflected inward along this oblique groove, and terminates upon the second met- acarpal bone, spreading out so as to embrace its upper extremity ; it also gives off a ten- dinous expansion to the trapezium, and sometimes one to the third metacarpal bone. Relations. — It is covered by the fascia and the skin, through which it is very clearly de- fined : it is in relation behind with the flexor sublimis ; on the outside, with the tendon of the flexor pollicis, over which it passes at an acute angle, so as to bind it down ; and lower down, with the wrist-joint. A very strong tendinous sheath, concealed by the ab- ductor brevis and opponens pollicis, completes the groove formed by the scaphoid and trapezium for its tendon, the movements of which are facilitated by a well-marked sy- novial membrane.* Its most important relation is that of the external border of its ten- don with the radial artery. The superficial position of the tendon prevents our feeling the artery when the muscle is contracted. Action. — It flexes the second row of the carpus upon the first, and this, again, upon the forearm. Moreover, on account of its reflection, it is a pronator, and, according to Winslow, it is a more powerful supinator than the supinator longus. Its obliquity down- ward and outward explains why it inclines the hand to the radial border of the forearm, and thus acts as an abductor. The Palmaris Longus. Although this small muscle is rather a tensor of the palmar fascia than a flexor of the hand, I have yet judged it proper to describe it in this place, in connexion with the flexor carpi radialis, which, in contradistinction to this muscle {le petit palmaire), has also been called le grand palmaire {Bichat). It is a small fusiform, slender, fleshy bundle {c,fig. 118), of about four inches in length, arising {c,fig. 119) from the inner condyle of the humerus to the inner side of the preceding muscle, and from a small tendinous cone, which isolates it from that muscle, the flexor sublimis, and the flexor carpi ulnaris. The fleshy fibres terminate around a flat tendon, which constitutes the lower two thirds of the muscle (whence the name palmaris longus), proceeds vertically downward and a little outward, and terminates by expanding in front of the anterior annular ligament {g, figs. 118, 119) of the wrist, and becoming continuous with the middle palmar fascia (c', fig. 118). This muscle is subject to a great many varieties, and is often wanting ; its fleshy belly is sometimes very long, and occasionally occupies the middle of the muscle. Relations. — The same as those of the preceding muscle {flexor carpi radialis) ; its ten- don is very superficial. It is separated from the neighbouring muscles by a very strong sheath. Action. — It is a tensor of the palmar fascia. When this effect has been produced, it flexes the hand upon the forearm. According to Winslow, it would assist the flexor carpi radialis in pronation. The Flexor Carpi Ulnaris. Dissection — Remove the superficial layer of the fascia covering the inside of the 'ire- arm, taking care, in dissecting this as well as the other muscles of the forearm, to stop at the points where that fascia adheres intimately to the fleshy fibres. * See note, p. 296. THE FLEXOR SUBLIMIS DIGITORUM. 251 This is the most deep-seated of all the muscles of the superficial layer of the forearm (ulnaris internus, Alhinus ; cubital interne, Winslow, d,figs. 118, 119, 121, 122). It arises from the inner condyle of the humerus and from the inner edge of the ole- cranon, these two origins forming an arch under which the ulnar nerve passes. It also arises sometimes, though slightly, from the coronoid process of the ulna, from the upper half of the posterior border of the ulna, through the medium of the fascia of the forearm, and from the septum between itself and the flexor sublimis. It is inserted into the pisi- form bone. The origin from the ridge on the ulna is remarkable ; it consists, indeed, of the fascia of the forearm, which becomes thickened and divided into two layers, one deep and very thin, the other superficial and very thick ; in the interval between these the fleshy fibres arise. These fibres are attached to the surfaces and edges of a very strong tendon, which then appears upon the anterior border of the muscle, and continues to re- ceive the fleshy fibres on its posterior edge until its insertion into the pisiform bone. This takes place upon the anterior surface of the bone, like those of the triceps muscles of the arm and thigh into the olecranon and pateUa. The tendon then becomes continu- ous with the inferior vertical ligament of the articulation between the pisiform and cunei- form bones, so that the muscle may, in fact, be regarded as inserted into the fifth meta- carpal bone. Relations. — It is covered by the fascia, and is intimately united with it for a consider- able extent : it covers the ulnar artery and nerve, the flexor sublimis, the flexor profun- dus, and the pronator quadratus. The most important of all its relations is that with the ulnar artery, which is at first under it, and then lies along the external edge of its ten- don, which protects the artery, and serves as a guide in the application of a ligature to it. I have, therefore, been in the habit of calling this muscle the satellite of the ulnar artery. Action. — This muscle acts as if it were inserted into the upper extremity of the fifth metacarpal bone. Were it not for the peculiar mode of its attachment to the pisiform bone, it would have been inserted parallel to its lever ; whereas it is really inserted at an angle of about 45°. It flexes the second row of the carpus upon the first, and this upon the forearm ; at the same time it inchnes the hand towards its ulnar side. Its vio- mentum, as well as that of the preceding muscle, occurs during semi-flexion of the hand upon the forearm. The Flexor Sublimis Digitorum. Dissection. — ^The portion of this muscle, situated in the forearm, is exposed by cutting across the middle, and turning aside the pronator teres, the flexor carpi radialis, and the pahnaris longus, which form a superficial layer in front of it. With a little care, the ori- gin of this muscle may be separated as far as the inner condyle of the humerus. In re- moving the pronator teres, it is necessary to be extremely careful to avoid dividing the radial origin of the flexor sublimis, which forms a very thin prolongation under the pro- nator. The dissection of the palmar and digital portions of the mus- cle is the same as that of the flexor profundus. Divide the anterior annular ligament of the carpus vertically, and remove the palmar fascia ; examine the disposition of this structure opposite the heads of the metacarpal bones, and also the relations of the tendons of the flexor sublimis and flexor profundus in the palm of the hand ; then dissect the digital sheaths, which must be divided in order to display the singular manner in which the ten- dons of the flexor sublimis bifurcate and turn round, so as to em- brace the corresponding tendons of the flexor profundus. The flexor superficialis, sublimis, ox perforatus (e e,fig. 118 ; e,jig. 119), is a broad, flat, thick muscle, divided into four portions below. It arises from the internal condyle or epitrochlea of the humerus, and from the ulnar and radius, and is inserted into the second pha- langes of the fingers. It arises from the epitrochlea by the common tendon, from a rough surface on the fore part of the inner side of the coronoid process of the ulna, and also from about two inches of the radius. This latter origin consists of tendinous fibres attach- ed to that obUque portion of the anterior border of the bone which extends inward towards the bicipital tuberosity, and from which arise the supinator brevis above, the flexor longus pollicis below, and the muscle we are now describing in the middle. A great number of fibres also arise from the broad aponeurotic septa which divide this muscle from the flexor carpi ulnaris, and from the other muscles of the superficial layer, viz., the pronator teres, the flexor carpi radialis, and the palmaris longus. From these diflferent origins the fleshy fibres proceed vertically downward, forming a broad and thick belly, which is almost imme- diately divided into four portions. These at first are in juxtaposi- tion, but soon become arranged in two layers, like the tendons of Fig. 119. 252 MYOLOGY. the extensor communis, viz., one anterior and larger, consisting of the divisions for the median and ring fingers (the latter not being so strong as the former), and another pos- terior, formed by the divisions for the index and little finger. Each division is, indeed, a small muscle, having its own particular tendon, around which the fleshy fibres are ar- ranged, at first regularly, and afterward on one side only : they are thus semi-penniform muscles. The two posterior divisions are not so distinct as the anterior, and have a pe- culiar arrangement : they generally constitute two small digastric muscles ; that is to say, a fleshy belly terminates upon a flat tendon, which, becoming enlarged, gives origin, in its turn, to a new fleshy belly. The four tendons, after emerging from the fleshy fibres, pass together under the annular ligament {g) of the carpus, in conjunction with the me- dian nerve, which lies on their outer side, and is often mistaken for a tendon, and with the tendons of the flexor profundus digitorum and the flexor longus pollicis. This thick bundle of tendons having reached the palm of the hand, is then distributed in a manner to be noticed after the description of the flexor profundus, with the tendons of which those of the flexor sublimis are intimately connected. Relations. — It is covered by the pronator teres, the flexor carpi radialis, the palmaris longus, the flexor carpi ulnaris, and the fascia of the forearm ; and it covers the flexor profundus digitorum, from which it is separated by the ulnar vessels and nerves ; it also covers the median nerve and the flexor longus pollicis, to- which it generally sends a tendinous and fleshy prolongation. The Flexor Profundus Digitorum. Dissection. — This muscle is exposed by cutting across the flexor sublimis and the flex- or carpi ulnaris. The flexor profundus or perforans (i, fl.gs. 119, 120) is situated under the superficial flex- Fig. 120. °^' which it exceeds in size, but resembles it in being divided below into four portions. Attachments. — It arises from the upper three fourths of the internal and anterior surfaces of the ulna, from a well-marked cavity situated on the inner side of the coronoid process behind the rough eminence which gives attachment to the internal lateral ligament of the elbow, from the inner two thirds of the interosseous ligament, from that part of the fascia of the forearm which covers the inner surface of the ulna, and, lastly, by a few fibres, from within and below the bicipital tuber- osity of the radius. It is inserted into the front of the bases of the last phalanges of the fingers ii,figs. 119, 120). The fleshy fibres arise directly from these numerous origins, and proceed vertically downward, the internal fibres alone being directed somewhat obliquely forward and outward. The belly of the muscle thus formed continues to increase in size, and is then divided into four unequal portions, each constituting a semi-penniform muscle. These four small muscles are in juxtaposition, and terminate in as many flat tendons, which occupy the lower two thirds of the anterior surface of the entire muscle, and are remarkable for being divided into very reg- ular and closely-united parallel bands of a nearly white colour. The four tendons emerging from the fleshy fibres at various heights, but always above the anterior annular ligament of the carpus, pass under this ligament conjointly with the tendons of the flexor sublimis, the flexor pollicis longus, and the median nerve. In this situation they are placed behind the tendons of the flexor sublimis, which are ar- ranged in two layers, as we have already seen. The tendons of the flexor profundus are always in juxtaposition, and, moreover, are united together by means of dense cellular tissue and tendinous bands pass- ing from one to the other : the fasciculus for the index finger alone remains distinct ; and, therefore, the flexion of this finger is almost as independent of that of the others as its extension, for which latter movement it receives a special muscle. Immediately below the annular ligament the tendons separate from each other ; the two anterior tendons of the flexor sublimis no longer cover the two posterior, but all four become situated in front of the corresponding tendons of the flexor profundus, and arrive together at the metacarpo-phalangal articulations : here they are received, at first, into a very strong fibrous sheath, resulting from the division of the palmar fascia, and afterward into an- other sheath {s,figs. 118, 119), which converts the groove in front of the phalanges into a canal. If we divide any of these digital sheaths, we find the tendon of the superficial flexor becoming flattened and hollowed underneath, as it were, into a groove, which is exactly moulded upon the tendon of the deep flexor. About the middle of the first pha- lanx the tendon of the sublimis ie,fl.g. 119) bifurcates, and gives passage to that of the profundus, which it embraces by turning round it like the thread of a screw, and be- coming posterior instead of anterior, as it was before. The two halves of the tendon then reunite to form a groove having its concavity directed forward, and again separate THE LUMBEICALES AND THE FLEXOR LONGUS POLLICIS. '253 to be inserted into the rough edge of the groove on the second phalanx. The tendon of the flexor profundus (i' i', figs. 119, 120), on the contrary, passes directly through the sheath formed by that of the flexor sublimis, and is inserted into the third phalanx. The tendons of the flexor profundus, moreover, present in their whole course very slightly apparent traces of division. From the relation of the tendons of the two flexors to each other, the superficial muscle has been called the perforatus, and the deep one the perforans. Relations. — These should be examined in the forearm, in the palm of the hand, and along the fingers. In the forearm the flexor profundus is covered by the flexor sublimis, from which it is separated by an incomplete tendinous septum, and by the median nerve. It covers the ulna, the interosseous ligament, and the pronator quadratus ; it corresponds within to the flexor carpi ulnaris, and without to the flexor longus pollicis. The ulnar vessels and nerves are at first situated between this muscle and the flexor sublimis, and after- ward separate it from the flexor carpi ulnaris. In the palm its tendons are subjacent to those of the flexor sublimis, and cov^r the interosseous muscles and the adductor pollicis. The lumbricales muscles take their origin from them. Along the fingers its tendons are in relation behind with the grooves of the phalanges, and with the metacarpo-phalangal and phalangal articulations, and in front with the tendons of the sublimis and the fibrous sheaths of the fingers. < Action of the two Flexors. — These muscles flex the third phalanx upon the second, the second on the first, this, again, upon the corresponding metacarpal bone, and, lastly, the hand upon the forearm. The flexor sublimis has no action upon the third phalanges. Its origin from the internal condyle of the humerus enables it to act upon the forearm, and to assist in flexing it upon the arm. It is scarcely necessary to say that the bifur- cation of the tendons of the flexor sublimis is intended to afford a sheath to, and bind down, those of the flexor profundus. The flexor profundus flexes the third phalanx upon the second, the second upon the first, the first upon the corresponding metacarpal bone, and, lastly, the hand upon the forearm. The Lumbricales. The lumbricales (x,figs. 119, 120) are small fleshy tongues, which may be regarded as accessories of the flexor profundus. They are four in number, distinguished as the first, second, &c., counting from without inward. They extend from the tendons of the flexor profundus to the first phalanges of three or four fingers. They arise from the tendons after these have passed through the annular ligament : the first and the second in front of the tendons for the index and middle fingers, the third in the interval between those for the middle and ring fingers, and the fourth in the interval between those for the ring and little fingers. From these origins they proceed, those near the median hue verti- cally, and those at either side obliquely downward to the outer side of the metacarpo- phalangal articulations of the corresponding fingers, where they terminate by a broad tendinous expansion inserted into the edges of the extensor tendons, and completing the sheath which those tendons form on the back of the first phalanges. The tendon of the third lumbricalis appears to me to be almost always inserted, not into the outer side of the ring finger, but into the inner side of the middle finger : an arrangement that cannot well be accounted for. It is not uncommon to find this third lumbricalis bifurcated, and attached, not only to the inner side of the middle, but to the outer side of the ring finger. Relations. — They are placed between and upon the tendons of the flexor profundus, and have, therefore, the same relations as those tendons in the palm of the hand ; they are also in relation with the sides of the metacarpo-phalangal articulations, and the ten- dons of the interosseous muscles. Action. — It is difficult to determine their actions precisely. Vesalius has described them as adductors, and Spigelius as flexors. I agree with Riolanus in regarding them as specially intended to keep the extensor tendons closely applied to the phalanges, and to serve instead of a proper sheath. They are of use also in binding together the ex- tensor and flexor tendons, and preventing the displacement of either. The Flexor Longus Pollicis. Dissection. — ^The same as that of the flexor profundus. The flexor longus pollicis {I, figs. 119, 120) is situated upon the same plane as the flex or profundus digitorum, of which it may be considered a division ; it is thick, elongated, and penniform. Attachments. — It arises from the upper three fourths of the radius, from the contiguous portion of the interosseous ligament, from the anterior border of the radius, and not un- frequently by a prolongation, tendinous at its extremities and fleshy in the middle, from the flexor sublimis digitorum. It is inserted into the upper end of the second phalanx of the thumb. The fleshy fibres arise directly from these origins, pass vertically down- ward, and are attached to the posterior surface of a flat tendon, which forms a continu- ation of the series of tendons of the flexor profundus on the outside, and, like them, is 254 MYOLOGY. divided into bands. The fleshy fibres accompany the tendon as far as the anterior an- nular hgament of the carpus ; it then passes beneath this ligament, is reflected over the inside of the trapezium, and proceeds obhquely outward along the first metacarpal bone. When it reaches the metacarpo-phalangal articulation of the thumb, it is received in an osteo-fibrous sheath, resembling in every respect that of the tendons of the other fingers, and, like them, is inserted in front of the upper extremity of the ungual phalanx of its corresponding finger (Z, ^g-. 120). Relations. — It is covered by the flexor sublimis, the flexor carpi radialis, the supinator longus, and the radial artery ; it covers the radius and the interosseous ligament, from which it is separated above by the interosseous vessels and nerves, and below by the pronator quadratus. Its tendon is the most external of those which pass under the an- terior annular ligament of the carpus, after leaving which it is received into a deep mus- cular groove formed by the muscles of the ball of the thumb, and is ultimately enclosed in its own osteo-fibrous sheath. Action. — It flexes the last phalanx of the thumb upon the first, this upon the first met- acarpal bone, and then the hand upon the forearm. In order to understand its action precisely, we must suppose the muscular force to be concentrated upon the upper end of the reflected portion ; it is then easy to see that it draws the phalanges inward, while flexing them. It is, therefore, an opponens muscle. The Pronator Quadratus. Dissection. — Cut across all the tendons occupying the lower part of the anterior region of the forearm, and this muscle will be exposed. This small muscle (le petit pronateur, Bichat, m,figs. 119, 120) is situated at the low- er part of the anterior region of the forearm, and forms the deepest layer of this region. It is regularly quadrilateral, and thicker than at first sight it appears to be. Attachments. — It arises firom the lower fourth of the internal border of the ulna, which is directed so decidedly backward inferiorly, that the muscle is rolled round the bone ; also, from an aponeurotic layer much thicker below than above, directed obliquely up- ward and outward, and occupying the inner third of the muscle, upon which it terminates in a number of elegant intersections ; lastly, from all that portion of the anterior surface of the ulna upon which it lies. From these origins the fibres proceed horizontally out- ward (le pronateur transverse, Winslow), becoming longer as they are more superficial, to the lower fourth of the external border, anterior surface, and internal border of the radius. Relations. — It is covered by the flexor profundus digitorum, the flexor longus poUicis, the flexor carpi radialis, and the radial and ulnar arteries, and it partially covers the two bones of the forearm and the interosseous ligament. Action. — ^The pronator quadratus tends to approximate the two bones of the forearm ; but as it is rolled around the ulna, which is immovable, it causes the radius to turn upon that bone, and is therefore a pronator. Its action is much more energetic than would at first sight appear : this depends on the number of its fleshy fibres, which are arranged in several layers, the most superficial being the longest. The Muscles of the External Region of the Forearm. The muscles of this region are, the supinator longus, the extensores carpi radiales, longior and brevior, and the supinator brevis. The Supinator Longus. Dissection. — The brachial portion of this muscle is exposed in the dissection of the brachialis anticus and the triceps, and the portion situated in the forearm, by removing the fascia from the outer and anterior aspect of the muscles of this region. The 'supinator longus (/, Jigs. 118, 121), which is the most superficial muscle of the ex- ternal and anterior aspect of the forearm, belongs both to the arm and the forearm (bra- chio-radialis, Soemmering), and constitutes, in a great measure, the oblique ridge forming the external boundary of the bend of the elbow. It is a long, flat muscle, fleshy in its upper two thirds, and tendinous in its lower third. Attachments. — It arises from the outer border of the humerus, and from the external inter-muscular septum of the arm ; the extent of its humeral attachment varies from the lower fourth to the lower third of that bone, and is limited above by the groove for the musculo-spiral nerve. It is inserted into the base of the styloid process of the radius. The fleshy fibres proceed from their origins downward, forward, and a little inward, to form a fleshy belly, which is flattened from without inward, and is applied to the brachi- alis anticus. After reaching the lower end of the humerus, the fleshy belly becomes flattened from before backward, and passes vertically downward. At first it is thick, but, during its progress, it expands, and becomes thin, until its fibres terminate successively upon the anterior surface of an aponeurosis, which becomes entirely free from fleshy fibres above the middle of the forearm, and is gradually contracted into a flat tendon, that is inserted into the styloid process of the radius. Relations. — It is covered bv the fascise of the arm and forearm : in the arm it is en- THE EXTENSORES CARPI EADIALES, LONGIOR ET BREVIOR. 255 closed in the same sheath with the brachialis anticus, from which it is separated by the radial or musculo-spiral nerve ; in the forearm it has a sheath proper to itself: it is in relation with the brachialis anticus, which is at first within, and afterward behind it ; then with the extensor carpi radialis longior, the tendon of the biceps, the supinator bre- vis, the pronator teres, the flexor carpi radialis, the flexor digitorum sublimis, the flexor longus pollicis, the radial artery and veins, and the radial nerve. Its inner border limits the bend of the elbow on the outside : the radial artery emerges from beneath this bor- der, and then lies parallel to it. Its outer border is separated from the extensor carpi radialis longior by cellular tissue, and, inferiorly, is in contact with the dorsal branch of the radial nerve, which, at first, was situated beneath it. The most important of all these relations is that with the radial artery, of which the long supinator may be consid- ered the satellite muscle, and might be designated the muscle of the radial artery. Action. — It might be asked, Why does the supinator longus form an exception to the general rule, in being inserted into the lower end of the lever which it is intended to move 1 for, while the forearm is in a state of supination, the axis of the muscle is verti- cal, and its action appears limited to that of flexing the forearm ; but if the limb be pro- nated, the direction of the muscle becomes oblique from without inward, and, therefore, supination is the result of its contraction. After this effect has been produced, if the muscle still continues to act, the forearm is flexed upon the arm. It is needless to state that the distance of its insertion from the fulcrum gives the muscle great power, not- withstanding its disadvantageous angle of incidence. The Extensor Carpi Radialis Longior. Dissection. — This muscle, as well as the succeeding one, will be exposed at the same time as the supinator longus, beneath which it is placed. The lower end of its tendon occupies the dorsum of the wrist, and should also be exposed. The extensor carpi radialis longior (le premier ou long radial exteme ; radiahs externus longior, Albinus, n,figs. 119, 121) is situated on the external and posterior aspect of the forearm, below the supinator longus, of which it seems to be a continuation at its origin from the humerus : like that muscle, it is flattened from within outward in the arm, and from before backward in the forearm : it is fleshy in its upper third, and tendinous in its lower two thirds. Attachments. — It arises from the rough triangular impression terminating the external border of the humerus, from the external inter-muscular septum, and from the anterior surface of the common tendon. It is inserted into the back of the upper end of the sec- ond metacarpal bone. The fleshy fibres arising directly from the parts mentioned con- stitute a bundle, at first flattened on the sides, and forming a continuation of the supina- tor longus, from which it is often difficult to separate it : it afterward becomes flattened from before backward. The fibres pass vertically downward, and are attached to the anterior surface of a tendon, a little beyond the upper third of the forearm. The tendon then becomes narrower and thicker, proceeds along the outer border of the radius, pass- es under the tendons of the abductor longus and extensor brevis pollicis, which cross it obliquely, and turns a little outward, and then backward, to arrive at a groove common to it and the extensor carpi radialis brevier ; it is then crossed at an acute angle by the tendon of the extensor longus pollicis, and is finally inserted, by an expanded termina- tion, into the second metacarpal bone {n',fig. 121). Relations. — It is covered by the supinator longus and the fascia of the forearm ; on the outside of the forearm, it is covered and crossed obliquely by the abductor longus and ex- tensor brevis pollicis. and in the wrist by the tendon of the extensor longus pollicis. It covers the elbow-joint, the extensor carpi radialis brevier, and the back of the wrist-joint. The Extensor Carpi Radialis Brevior, The extensor carpi radialis brevior (le second ou court radial exteme ; radialis externus brevior, Albinus, o,figs. 119, 121, 122) is thicker, but shorter, than the preceding, below which it is placed. It arises from the external condyle or epicondyle of the humerus, by a tendon common to it and the extensor muscles of the fingers ; also, from a very strong aponeurosis, situated upon its posterior surface ; and from another tendinous septum, which divides it from the extensor communis digitorum. It is inserted into the back part of the upper end of the third metacarpal bone. The fleshy fibres, thus arising from the external condyle by means of an aponeurotic pyramid, are attached to the posterior sur- face of a tendon, which becomes gradually narrower and thicker as it receives them. The fibres themselves terminate about the middle of the forearm, and then the flat ten- don passes backward into the same groove on the radius as that of the last-named mus- cle, the two tendons being retained in it by the same fibrous sheath, and lubricated by tne same synovial membranes, but separated from each other by a small vertical ridge of bone. After leaving the common sheath, the tendon of the short separates from that of the long radial extensor, passes still more posteriorly, and is inserted into the third metacarpal bone (o', Tf^s. 121, 122). RelatioDis. — It is covered by the preceding muscle, and, like it, is crossed obliquely on 256 MYOLOGY. the outside by the long abductor, the short, and then the long extensor muscles of the thumb : it covers the external surface of the radius, from which it is separated by the supinator brevis above, and the pronator teres in the middle. Its tendon covers and protects the back of the wrist. In consequence of the different length of their fleshy fibres, the supinator longus and the two radial extensors of the carpus are arranged one above the other, the highest being the supinator longus, and the lowest the extensor carpi radialis brevior. Action of the two Radial Extensors. — These two muscles, which, from their insertions might be called the posterior radials, extend the second row of the carpus upon the firs and this upon the forearm ; they are also abductors of the hand, for they incline it to- wards the radial side of the forearm. The extensor carpi radialis longior being attach- ed to the humerus, can assist in flexing the forearm. The Supinator Brevis. Dissection. — Pronate the forearm forcibly. In order to expose this muscle completely, divide the two radial extensors of the carpus, and even some of the muscles of the su- perficial layer, on the back of the forearm. The supinator brevis (p,figs. 119, 120, 122) is a broad muscle curved into the form of a hollow cylinder, and rolled round the upper third of the radius : it forms by itself the deep layer of the external region of the forearm. Attachments. — It arises from the external lateral Ugament of the elbow, with which it is blended, and by this means from the external condyle ; from the annular ligament of the radius ; from the external border of the ulna, which is provided with a projecting ridge for this purpose ; from a deep triangular excavation, in front of this ridge, arid below the lesser sigmoid cavity of the ulna ; and, lastly, from the deep surface of an expansion of its tendon of origin and the external lateral ligament, which covers the greater part of the muscle. From these different origins {fig. 122) the fleshy fibres pass round the ra- dius, into the posterior, external, and anterior surfaces of which bone they are inserted, embracing in front the bicipital tubercle and the tendon of the biceps {figs. 119, 120). I have seen a fleshy prolongation of this muscle, covering the anterior half of the annular ligament of the radius, of which it might be regarded an extensor. Relations. — The supinator brevis is covered by the radial extensors, the supinator lon- gus, the pronator teres, the extensor communis digitorum, the extensor digiti minimi, the extensor carpi ulnaris, the anconeus, and the radial artery and vein : it covers the upper third of the radius, and also its annular ligament, the elbow-joint, and the inter- osseous ligament. It is perforated by the deep branch of the radial nerve, which is dis- tributed to all the muscles on the back of the forearm. Action. — No muscle in the body is so completely rolled around the lever that it is in- tended to move, for it forms five sixths of a cylinder ; it is, therefore, the chief agent in supination, and the supinator longus can only be regarded as an accessory. Muscles of the Posterior Region of the Forearm. The muscles of the posterior region of the forearm constitute two very distinct layers : one superficial, comprising the extensor communis digitorum, the extensor digiti minimi, and the extensor carpi ulnaris ; the other deep, comprising the abductor pollicis longus, the extensor brevis and extensor longus pollicis, and the extensor indicis Muscles of the Superficial Layer. One mode of dissection is common to all these muscles. Make a circular mcision through the skin at the lower part of the arm ; pronate the arm, arifl make a perpendic- ular incision from the external condyle of the humerus to the third metacarpal bone, entirely dividing the sub-cutaneous cellular tissue down to the fascia ; remove this fascia by careful dissection, except where it is very adherent. Trace the tendons of the ex- tensor muscles along the back of the fingers. The Extensor Communis Digitorum. The extensor communis digitorum {b,fig. 121), situated at the back of the forearm, sim- ple above and divided into four portions below, arises from the external condyle of the humerus, and is inserted into the second and third phalanges of the four fingers. Its ori- gin consists of a tendon common to it, and to the extensor carpi radialis brevior, exten- sor digiti minimi, and extensor carpi ulnaris. This tendon consists of a four-sided pjrra- raid, and is formed by the fascia of the forearm, by a lamina separating this muscle from the extensor carpi radialis longior, by another lamina separating it from the extensor digiti minimi and the extensor carpi ulnaris, and, lastly, by another situated between it and the supinator brevis. The fleshy fibres arising from the interior of this pyramid form at first a thin, but afterward a much larger muscle, which becomes flattened from before backward, and soon divides into four fasciculi. The two middle fasciculi, intended for the middle and the ring fingers, are stronger than those destined for the index and little fingers, i. e., the two extreme fasciculi, which, lower down, become placed in front of THE EXTENSOR DIGITI MINIMI. 257 the middle fasciculi. In this manner they all pass under the dor- Fig. 191. sal ligament (r,fig. 121) of the carpus in a proper sheath. After leaving this sheath, in which they are provided with a synovial capsule,* extending both above and below the dorsal ligament, the four tendons become situated on the same plane, and diverge from each other ; the two middle tendons proceed along the backs of the corresponding metacarpal bones ; the external and internal ten- dons {b' h',Jig. 121) correspond to the interosseous spaces, which they cross obliquely, in order to assume a position behind the heads of the metacarpal bones, to which they belong. Having reached the metacarpo-phalangal articulations, the tendons become nar- rower and thickened, and give oif on each side a fibrous expansion, attached to the sides of the joint ; they then enlarge again so as to cover the dorsal surface of the first phalanges, receive and are re- enforced by the tendons of the lumbricales, and opposite the ar- ticulation of the first with the second phalanx, they divide into three portions, one median, which is implanted upon the upper end of the second phalanx, and two lateral, which pass 2dong the sides of the second phalanx, approach each other at the lower half of the dorsal surface of the second phalanx, unite by their neighbouring edges, and are inserted into the upper end of the third phalanx. Opposite the metacarpal bones they sometimes split into two or three small juxtaposed tendons, and at the lower end of these bones the tendons for the little, ring, and middle fingers commu- nicate with each other by expansions of variable size, and some- times by a true bifurcation (see fig. 121). The tendon for the in- dex finger is alone free. The communication of the tendon of the little with that of the ring finger takes place opposite the metacar- po-phalangal articulation, by means of a transverse band, which forms a projection under the skin. Lastly, we not unconmionly see a tendinous prolongation arising from the anterior surface of these tendons, and in- serted into the upper end of the first phalanx. Relations. — The extensor communis digitorum is covered by the fascia of the forearm, from which a great number of its fibres arise superiorly, by the dorsal ligament of the carpus and the dorsal fascia of the metacarpus, which separate it from the skin : it cov- ers the supinator brevis, the three long muscles of the thumb, the extensor proprius in- dicis, the lower radio-cubital articulation, the carpus, the metacarpus, and the fingers. Action. — ^This muscle extends the third phalanx upon the second, the second upon the first, the first upon the corresponding metcarpal bone, then the carpus, and, lastly, the radio-cubital articulation. It is necessary for me to mention the independence of the muscular fasciculi proceeding to each finger : this is peculiar to man, and is much more remarkable in some individuals than in others. By continual exercise, the faculty of extending one finger without the others may be acquired. The tendon for the index is generally the only one not united to the others, and therefore the movements of this finger are by far the most independent. The Extensor Digiti Minimi. This is a very slender muscle (extensor proprius auricularis, Albinus, c, fig. 121) placed on the inner side of the common extensor, to which it appears to be an appendix. It is difficult to trace its origin as far as the common tendon, with which it is connected only by an aponeurotic prolongation. Its fleshy fibres arise from this prolongation, and from a fibrous pyramid which separates it from the muscles of the deep layer, from the exten- sor communis digitorum externally, and internally from the extensor carpi ulnaris, and is completed superficially by the fascia of the forearm. The fibres constitute a small, fusiform, fleshy belly, which accompanies the tendon (at least on one side) as far as the head of the ulna ; there the tendon enters a special fibrous sheath formed behind the head of that bone ; it is then reflected inward to the fifth metacarpal bone, behind which it is retained in a thinner sheath, which, like the preceding, is lined by a synovial mem- brane. t The tendon then spUts into two bands, of which the external (or radial) re- ceives the inner bifurcation of the extensor communis. The three tendinous prolonga- tions becoming united, envelop, as in a sheath, the dorsal aspect of the first phalanx of this finger ; having reached the articulation of the first with the second phalanx, they divide into three portions, which are attached precisely in the same manner as the ten- dons of the extensor communis. Action. — As its name indicates, this muscle extends the little finger. It might at first sight be imagined that this finger might be moved independently, since it receives a sep- arate muscle ; but the connexion of its tendon with that of the extensor communis ren- See note, p. 296. Kk t See note, p. 296. t,58 MYOLOGY. ders any such independent action as difficult as in the other fingers, and much more so than in the index finger. The Extensor Carpi Ulnaris. The extensor carpi ulnaris (c, fig. 121), the most superficial and the most internal* of the muscles on the back of the forearm, arises from the external tuberosity of the humerus ; from the posterior surface of the ulna, which is a little excavated for this purpose ; from the middle third of the posterior border of that bone ; and from the anterior surface of an aponeurosis covering the muscle behind. It is inserted behind the upper end of the fifth metacarpal bone. Its origin is effected by means of a fibrous pyramid, the apex of which is attached to the outer tuberosity of the humerus. From the interior of this pyr- amid, and from the other origins above mentioned, the fleshy fibres proceed to a tendon, which, by a very uncommon arrangement, extends through the substance of the muscle, even from its superior attachment, without commencing in the form of an aponeurosis. At the lower third of the forearm, this tendon appears on the posterior border of the then semi-penniform muscle, and continues to receive fleshy fibres on its anterior edge until it enters the groove intended for it on the ulna. This oblique groove is continued as far Fig. 182. as the insertion of the tendon into the metacarpal bone, by means of a long, fibrous sheath, and is lined throughout by a synovial membrane. Relations. — The extensor carpi ulnaris is covered by the fascia of the forearm : it covers the ulna, the supinator brevis, and the mus- cles of the deep layer. Action. — It extends the second row of the carpus upon the first, and this upon the forearm. It is, at the same time, an adductor of the _g hand, which it inclines towards the ulnar border of the forearm. The Anconeus. The anconeus (brevis anconeus, Eustachius ; le petit ancone, Wins- low, ff, figs. 121, 122) is a short, triangular muscle, so named from its situation {uyKuv, the prominence of the elbow). It appears to be a continuation of the external portion of the triceps, from which it is only separated by a very slight cellular interval. Attachments. — It arises from the back part of the outer tuberosity of the humerus, and is inserted into the outer side of the olecranon, and a triangular surface bounded internally by the posterior border of the ulna. Its origin from the condyle consists of a tendon quite dis- tinct from that common to the muscles on the back part of the fore- arm. This tendon splits into two diverging bands. The fleshy fibres arising from these proceed inward, the upper horizontally, the lower obliquely downward, and are inserted directly into the outer side of the olecranon, so as to be continuous with the triceps, and into the surface of the ulna. Relations. — It is covered by a prolongation from the fascia of the triceps, and it covers the radio-humeral articulation, the annular lig- ament of the radius, the ulna, and a small portion of the supinator brevis. Action. — ^It extends the forearm upon the arm, and vice versa ; from its oblique direc- tion, it can also rotate it inward. Muscles of the Deep Layer. Dissection. — This is the same for all the muscles of the deep layer of the forearm, and consists in removing the muscles of the superficial layer, especially the extensor com- munis digitorum and the extensor digiti minimi. The Mductor Longus Pollicis. The abductor longus pollicis (extensor ossis metacarpi pollicis, i,figs. 121, 122) is the broadest, thickest, and most external muscle of the deep layer (le grand abducteur, Bichat). Attachments. — It arises from the ulna below the origin of the supinator brevis, from the interosseous hgament, from the radius, and from a tendinous septum between it and the extensor longus pollicis. It is inserted into the upper end of the first metacarpal bone. From the above-mentioned origins the fleshy fibres proceed obUquely downward and outward, constitute a flattened fusiform belly, and are successively attached to the posterior surface of an aponeurosis, which becomes condensed into a flat tendon ; this tendon turns round the radius, crossing over the radial extensors of the carpus, and, at the same time, ceasing to receive any fleshy fibres ; it is then received into the outer groove on the lower end of the radius, conjointly with the tendon of the extensor brevis * It is needless to remark that this internal situation presupposes the supination of the forearm. In prona- tion, this muscle may be correctly termed ulnaris externus, and le cubital externe, according to Albinus and Witulow. THE EXTENSOR BREVIS POLMCIS, ETC. 254 pollicis, a small fibrous septum intervening between them, and, finally, is inserted into the first metacarpal bone. This tendon is almost always divided longitudinally into two equal parts, and not unfrequently the division extends up to the fleshy portion. Of these two divisions, one is inserted into the first metacarpal bone, the other furnishes attach- ments to the abductor brevis pollicis. Relations. — It is covered by the extensor communis digitorum and extensor digiti min- imi : it lies immediately under the fascia, from the outer side of the radius to its termi- nation. It covers the interosseous ligament, the radius, the tendons of the radial exten- sors of the carpus, and the outer side of the wrist-joint, where it may be easily distin- guished under the skin. Action. — It extends and abducts the first metacarpal bone : for a long time it was called the extensor of the thumb ; but its chief use is, as Albinus first remarked, in ab- duction. Winslow observes that, from its obliquity, it can act as a supinator ; lastly, it assists in extending the hand. The Extensor Brevis Pollicis. This muscle (extensor primi intemodii pollicis, I, figs. 121, 122) is situated internally to the preceding, which it exactly resembles- in figure and direction, and with which it was for a long time confounded (partie du premier extenseur du pouce, Winslow). It is, however, shorter and mpre slender (petit extenseur du pouce, Bichat). It arises from the radius, occasionally from the ulna, and from the interosseous liga- ment ; and is inserted into the upper end of the first phalanx of the thumb. Its origin consists of short, tendinous fibres, the fleshy fibres proceeding from which constitute a slender fasciculus, having a similar arrangement to that of the preceding muscle ; its tendon is received into the same fibrous sheath, but is divided from the other by a small septum, and passes on, to be inserted into the first phalanx. Relations. — The same as those of the abductor longus. Action. — It extends the first phalanx upon the first metacarpzil bone, and then becomes an abductor and extensor of the metacarpal bone of the thumb. The Extensor Longus Pollicis. This muscle (extensor secundi internodii pollicis, m,figs. 121, 122) is much larger than the extensor brevis, within and parallel to which it is situated. It arises from a consid- erable extent of the ulna, from the interosseous ligament, and from the tendinous septa, dividing it from the extensor carpi ulnaris, and the extensor proprius indicis : it is insert- ed into the upper end of the second phalanx of the thumb. The fleshy fibres form a flat fusiform bundle, directed obliquely like the preceding muscle ; they terminate in succes- sion around a tendon, which emerges from them at the carpal extremity of the ulna, en- ters a special osteo-fibrous sheath, and crosses obliquely over the tendons of the two ra- dial extensors, being separated from the tendons of the abductor longus and extensor brevis pollicis by an intervjil which may be readily distinguished through the integu- ments, and gives rise to the hollow on the outer side of the wrist, commonly called the salt-cellar. The tendon next crosses obliquely over the first interosseous space, gains the inner edge of the first metacarpal bone, and then that of the first phalanx, upon which it is expanded, and proceeds to be inserted into the second or ungual phalanx of the thumb. Relations. — Its general relations are the same as those of the preceding muscle. Action. — Its uses are also the same ; but it acts in a special manner upon the second phalanx of the thumb, which it extends upon the first before exerting any influence upon this last-mentioned bone. It has less power in abduction than the preceding muscles. The Extensor Proprius Indicis. This is an elongated fusiform muscle (indicator, Albinus, r, fig. 122) like the preceding, below and parallel to which it is situated. It arises from the ulna, the interosseous liga ment, and a septum intervening between it and the extensor longus pollicis : it is insert- ed into the last two phalanges of the index finger. The fleshy fibres proceed obliquely from their origins and terminate around a tendon, which they accompany as far as the sheath of the extensor communis digitorum : into this sheath the tendOn enters, and. having escaped from it, crosses obliquely over the carpus and the second interosseous space, becomes situated on the inside of the tendon given off to the index finger by the extensor conununis, unites intimately with that tendon opposite the lower end of the metacarpus, and terminates with it in the manner already indicated. Its relations are the same as those of the preceding muscles. Action. — It enables the index finger to be extended independently of the others, and hence, without doubt, arises the particular use of that finger. I should add, that the union of its tendon with the one furnished by the common extensor is so intimate, that its in- dependence of action would have been much less, had not the fleshy fasciculus of the common extensor destined for it been itself almost isolated. 260 MYOLOGY. MUSCLES OF THE HAND. Tlie AbdiMor Brevis Pollicis. — Opponejis Pollicis. — Flexor Brevis Pollicis. — Adductor Pol- lids. — Palmaris Brevis. — Abductor Digiti Minimi. — Flexor Brevis Digiti Minimi. — Op- ponens Digiti Minimi. — The Interosseous Muscles, Dorsal and Palmar. The muscles of the hand occupy the entire palmar region. They are divided into those situated on the outer side, viz., the muscles of the thenar eminence, or ball of the thumb ; those on the inner side, viz., the muscles of the hypothenar eminence, or of the little finger ; and those which occupy the interosseous spaces. All the muscles of the thenar eminence belong to the thumb ; they are, in the order of their superposition, the abductor brevis, the opponens, the flexor brevis, and the ad- ductor pollicis. Those of the hypothenar eminence all belong to the little finger, and are the abductor, the flexor brevis, and the opponens. The palmaris brevis may be in- cluded in this region. The interosseous muscles are seven in number — four dorsal and three palmar. The lumbricales, vi^hich belong to this region, have been already described with the tendons of the flexors of the fingers. Muscles of the Thenar Eminence, or Muscles belonging to the Thumb I divide these into three muscles inserted into the outer side of the first phalanx of the thumb, or into the first metacarpal bone, and a single muscle inserted into the inner side. The former are the abductor brevis, the opponens, and the flexor brevis ; the lat- ter consists of the adductor, in which I include a part of the flexor brevis of authors generally. Muscles inserted into the Outer Side of the First Phalanx of the Thumb, or into the First Metacarpal Bone. Dissection. — Make an oblique incision from the middle of the annular ligament of the carpus to the outer side of the first phalanx of the thumb, and a circular incision round the wrist ; detach the flaps, raise the external and middle palmar fasciae, and then cau- tiously separate the muscles of this region, which are recognised by the following char- acters. The Abductor Brevis Pollicis. This is the most superficial of the muscles constituting the ball of the thumb {q, fig. 119). It arises by tendinous and fleshy fibres from the os scaphoides, from the upper, anterior, and external part of the anterior annular ligament of the carpus, and almost always from an expansion of the tendon of the abductor longus pollicis. It is a small, •hin, flat muscle, passing outward and downward, and inserted by a flat tendon into the outer side of the first phalanx of the thumb. A very narrow cellular line separates it on the inside from the flexor brevis, which is situated on the same plane. It is covered by the external palmar fascia, and it covers the opponens muscle, from which it is distin- guished by the direction of its fibres, and by a thin intervening aponeurosis. Action. — It draws the thumb forward and inward, and therefore might be termed the superficial opponens. From its attachments, it might be called scaphoido-phalangal. The Opponens Pollicis. The opponens pollicis (r, figs. 119, 120), a small triangular muscle, arises from the trape- zium, and the anterior and external part of the anterior annular ligament of the carpus, in front of the sheath of the flexor carpi radialis. From these origins, which are partly fleshy and partly tendinous, the fleshy fibres radiate downward and outward, the highest being the shortest and the most horizontal. They are inserted into the entire length of the outer border of the first metacarpal bone. This muscle is covered by the abductor brevis, which projects a little beyond it on the outside, and from which it is separated by a more or less distinct aponeurosis. It cov- ers the first metacarpal bone, and its articulation with the trapezium. Action. — It draws the first metacarpal bone inward and forward, thus opposing it to the others, as its name indicates. From its attachments, it may be called trapezio-metacarpal. The Flexor Brevis Pollicis. It is difficult to point out the limits of this muscle, or, rather, they have hitherto been quite arbitrary. Its inferior attachment has been usually divided between the external and the internal sesamoid bones (Boyer, Traitl d' Anatomic, torn, ii., p. 307 ; Bichat, Ana- tomic Descriptive, torn, ii., p. 272) ; but we shall consider that portion only whioli is at- tached to the external sesamoid bone as belonging to this muscle, referring tlie entire fleshy mass that is inserted into the internal sesamoid bone to the adductor pollicis.* ' The arrangement I have adopted is founded upon the inferior attachments of the musr les, for at their origins they are so blended that their division is more or less arbitrary. I divide the muscular fasciculi con- nected witu the thumb, therefore, into two sets, viz., those proceeding from the carpus to tlie first metacan>al THE ADDUCTOR P0LLICI8, ETC. 26^1 This division is, moreover, established by the tendon (I, fig. 120) of the flexor longns pollicis. Proceeding then from below upward, in the dissection of the flexor brevis {t. iigs. 119, 120), we shall see that it is triangular, much larger than the preceding two muscles, bifid above, and channelled in front. It arises by tendinous and fleshy fibres from a process on the trapezium, from the lower edge of the annular ligament, from all the reflected portion of that ligament forming the sheath of the flexor carpi radialis, and extending as far as the os magnum, and from the os magnum itself by a portion which is usually distinct. From these different origins the fleshy fibres proceed downward and outward, the intem£d being the most oblique ; and, converging so as to form a thick fas- ciculus, are inserted, through the medium of the external sesamoid bone, into the first phalanx. Relations. — It is covered by the external pahnar fascia, which is prolonged in front of it : it covers the tendon of the flexor longus pollicis, and more internally those of the common flexor. It also covers a small portion of the outer border of the adductor pollicis, and the tendon of the flexor carpi radialis. Its outer border, or, rather, side, is in relation with the short abductor, from which it is easily separated, and with the opponens, some- times being continuous with it. Its inner border is distinct from the adductor below, but is confounded with it at its origin. Its tendon of insertion into the phalanx is cov- ered by that of the short abductor, which lies externally to it. From its attachments, it might be called trapezio-phalangal, and, from its uses and position, the opponens internus. Action. — It is evidently not a flexor pollicis, but, like the preceding muscles, it draws the thumb forward and inward, and it acts more decidedly in producing the latter effect. because it is inserted in a more favourable manner than the other muscles. This, there- fore, is also an opponens muscle. Muscle inserted into the Inner Side of the First Phalanx of the Thumb. The Adductor Pollicis. This is the largest of all the muscles of the thumb (m, figs. 119, 120) ; it is very ir- regularly triangular, and arises from the entire extent of the anterior border of the third metacarpal bone, from the anterior surface of the os magnum, from the anterior and up- per part of the trapezoides, from the anterior part of the trapezium by a tendinous and fleshy fasciculus, and from the palmar interosseous fascia, near the third metacarpal bone. From these different origins the fleshy fibres proceed, the lower horizontally, the rest more and more obliquely outward ; they all converge to form a thick fleshy bundle, which is inserted through the medium of the internal sesamoid bone into the first pha- lanx of the thumb. Relations. — Its inner two thirds are deeply situated, and covered by the tendons of the flexor profundus digitorum, by the lumhricales, and by an aponeurosis, which, becoming continuous with the deep interosseous fascia, constitutes the sheath of the muscle. It is sub-cutaneous near its lower border. It covers the first two interosseous spaces, from which it is separated by a very strong aponeurosis. It is again sub-cutaneous behind, also along its lower border, which may be easily felt under the fold of skin, extending from the thimib to the index finger. Action. — It is an adductor ; it draws the thumb towards the median line or axis of tho hand, represented by the third metacarpal bone. Muscles of the Hypothenar Eminence, or Muscles belonging to the Little Finger. These muscles correspond exactly to those of the thumb : the reason that three only are described is, that the one which represents the adductor of the thumb is situated in the fourth interosseous space, and is, therefore, classed with the interosseous muscles, to be hereafter described. All the muscles of the hypothenar eminence are inserted into the inner side of the first phalairx of the little finger, or into the third metacarpal bone We find also a cutaneous muscle in this region, viz., the palmaris brevis. The Palmaris Brevis. This is a very thin square muscle (caro quaedam quadrata, J, fig. 1 18), situated in the adipose tissue covering the hypothenar eminence. It arises from the anterior annular ligament of the carpus, and the inner edge of the middle palmar fascia, by very distinct tendinous fasciculi, succeeded by equally distinct fleshy bundles, which pass horizontally inward, and terminate in the skin. Relations. — It is covered by the skin, to which it adheres intimately, especially by its inner extremity (le pahnaire cutane, Winslow ) ; it covers the muscles of the hypothenar bone and to the outer side of the first phalanx of the thumb, and those extending from the carpus to the inner side of the same phalanx. The first set, which might be regarded as a single muscle, comprises the abductor brevis, the opponens, and the flexor brevis ; the other constitutes the abductor pollicis, which I regard as the first palmar interosseous muscle. The action of the first set is common, viz., to carry the thumb forward and inward ; they are, therefore, all muscles of opposition (perhaps no muscles are so badly named as those of the thenar eminence) ; the muscle formeJ !jy the second set is really an adductor, as its name implies, and so are all the palmar interossci. ;im0Qg .., a :i it ^l (Uld be included. 262 MYOLOGY. eminence and the ulnar artery and nerve, from all of which it is separated by the inter- nal palmar fascia. Action. — It corrugates the skin over the hypothenar eminence. The Abductor Digiti Minimi. It arises from the pisiform bone, and from an expansion of the flexor carpi ulnans, by tendinous fibres ; these are succeeded by a fusiform fleshy belly {v,fig. 119), which passes vertically along the internal (or ulnar) surface of the fifth metacarpal bone, and is inserted by a flat tendon into the inner side of the first phalanx of the little finger. Relations. — It is covered by the external palmar fascia, and covers the opponens digiti minimi. Action. — As it name denotes, it abducts the little finger from the axis of the hand. The Flexor Brevis Digiti Minimi. This muscle {w,fig. 119) is situated on the outer or radial border of the precedmg, from which it is distinguished by arising from the unciform bone. ■ The two muscles are separated by the ulnar vessels and nerves, which pass between them, in order to penetrate into the deep palmar region. In other respects, as in direction, insertions, and relations, the muscles resemble each other ; they have accordingly been described by Chaussier as a single muscle, under the name of Ze carpo-phalangien du petit doigt. This muscle is often wanting, but the fleshy fibres which usuaUy constitute it are then always found in some measure blended with the other muscles. Action. — It produces slight flexion of the little finger. The Opponens Digiti Minimi. This muscle {y,fig. 119) is generally distinct from the preceding, and is the represent- ative of the opponens pollicis. It arises from the hooklike process of the unciform bone, and from the contiguous part of the annular ligament : from these points the fibres pro- ceed downward and inward (i. e., towards the ulnar border of the hand), the highest be- ing the shortest and the most horizontal : they are i-nserted into the whole length of the inner or ulnar margin of the fifth metacarpal bone. Relations. — It is covered by the preceding muscles and by the internal palmar fascia : it covers the fifth metacarpal bone, the corresponding interosseous muscle, and the ten- don of the superficial flexor proceeding to the little finger. Action. — It opposes the little finger to the thumb by drawing it forward and outward. The Interosseous Muscles. Dissection. — Remove the tendons of the extensor muscles behind, and those of the flexor muscles in front, together with the lumbricales, preserving, at the same time, the digital inseiiions of these small muscles. Dissect and study the deep palmar fascia, a fibrous layer covering the interosseous muscles in the palm of the hand, which sends prolonga- tions between the two kinds of these muscles, and is inserted into the anterior borders of the metacarpal bones, enclosing each interosseous muscle in a proper sheath. After having studied the palmar and dorsal fascia, separate the bones of the metacarpus by tearing their connecting ligaments, and the interossei will then be completely exposed. The interossei, so named from their position, and distmguished from each other by the numerical appellations first, second, third, &c., are divided into palmar (p p p, Jig. 123) and dorsal {ddd d), according as they are situated nearer to the palm or to the back of the hand. They are also distinguished into adductors and abductors of the fingers. There are two in each interosseous space, one occupying its dorsal, the other its pal- mar aspect ; and, as there are four interosseous spaces, it would seem that there should be eight interosseous muscles ; nevertheless, seven only are admitted by modern anat- omists, in consequence of the first palmar interosseous muscle, which belongs to the thumb, being separately described as the adductor pollicis. This separation is founded upon the peculiar arrangement presented by that muscle, which is not attached from the first to the second, but extends from the first to the third metacarpal bone ; an importjuit fact, that explains the great extent to which the thumb can be adducted. A minute description of the interosseous muscles would be both useless and tedious. I shall content myself with pointing out their genereil conformation, and the law which regulates their arrangement. In taking a general view of the interosseous muscles, they must be considered with regard to the adduction or abduction of the fingers ; but these terms must not be under- stood in reference to the axis of the skeleton, but to the axis of the hand, which is rep- resented by a line passing through the third metacarpal bone and the middle finger. This being admitted, all the dorsal interossei will be found to be abductors, and all the palmar interossei adductors. Thus, the first dorsal interosseous muscle proceeds from the first and second meta- carpal bones to the outer or radial side of the first phalanx of the index finger : it is there- fore an abductor of that finger. The second extends ft-om the second and third meta- THE DORSAL INTEROSSEI. 263 carpal bones to the outer or radial side of the first phalanx of the middle finger, and is an abductor of that finger. The third extends from the third and fourth metacarpal bones to the inner or ulnar side of the phalanx of the middle fingers, and is also an abductor of the same, because it separates it firom the supposed axis of the hand. The fourth extends from the fourth and fifth metacarpal bones to the inner or ulnar side of the first phalanx of the fourth finger, and it again is an abductor of that finger from the axis of the hand, although, as well as the preceding muscle, it is an adductor as regards the axis of the body. In order to render this view more intelligible, I have been accustomed to rep- resent the five fingers by five lines (see diagram d), to prolong the middle line for the axis of the hand, and then to draw other lines (the four fine lines) representing the axes of the muscles ; the demonstration is thus rendered complete. In the same manner, all the palmar interossei are adductors as regards the axis of the hand. Thus the first, which is represented by the adductor pollicis, and extends from the third metacarpal bone to the inner or ulnar side of the first phalanx of the thumb, is an adductor as regards the axis of the hand as well as that of the body ; the second, ex- tending from the second metacarpal bone to the inner or ulnar side of the first phalanx of the index finger, is an adductor both as regards the axis of the hand and that of the body ; the third, extending from the fourth metacarpal bone to the outer or radial side of the first phalanx of the ring finger, is an adductor as regards the axis of the hand ; and, lastly, the fourth, extending from the fifth metacarpal bone to the outer or radial side of the first phalanx of the little finger, is an adductor as regards the axis of the hand, but an abductor in reference to the axis of the body. A similarly-constructed figure, as that employed for the dorsal interossei, wiU always keep this arrangement in the memory (see diagram p ; the four fine lines represent the axes of the pahnar muscles). The gen- eral disposition of the interossei may be summed up in the following very simple law : All the dorsal interossei have their fixed attachments farther from the axis of the hand than their movable one ; all the palmar interossei have their fixed attaclmients nearer to the axis of the hand than their movable one. We may now consider the general arrangement of these little muscles. The Dorsal Interossei. These are short, prismatic, and triangular muscles (d to d. Jig. 123), extending from the two metacarpal bones, between which they are placed, to fHg. 123. the first phalanx and the extensor tendon of one of the corre- spending fingers. They arise by a double origin, between which the perforating arteries pass. But while one of these origins is limited to the back part of the lateral surface of one of the metacarpal bones, the other occupies the whole length of the corresponding lateral surface of the other metacarpEd bone. From this double origin the fleshy fibres pass obliquely forward round a tendon, which only emerges from them near the metacarpo-phalangal articulation ; it then expands, and is inserted partly to the upper end of the first phalanx and partly to the outer edge of the corresponding extensor tendon. Relations. — The dorsal interossei correspond behind with the dorsal surface of the hand and the extensor tendons, from which they are separated by a very thin aponeurosis ; in front, they are visible in the palm of the hand by the sides of the palmar interossei, and, like the latter, are covered by the muscles and tendons of the palmar region, being separated from those parts by the deep pahnar fascia. A distinct cellular line, or, rather, an aponeurotic septum, intervenes between one of their lateral surfaces and the corresponding palmar interosseous muscle ; the other lateral surface is in relation, through its entire length, with the metacarpal bone on which it is implanted. Action. — These muscles are evidently abductors of the first phalanges of the fingers, the axis of the hand being taken as the point of departure. Their insertion into the ex- tensor tendons explains why previous extension of the fingers is necessary to the move- ment of abduction. The first dorsal interosseous muscle merits a special description. It is larger than the others, on account of the greater size of the space occupied by it ; it is flat and triangu- lar, and arises by two origins, separated, not by a perforating branch, but by the radial artery itself A fibrous arch completes the half ring formed by the interval between the first two metacarpal bones for the passage of this artery. The external head of the muscle arises from the upper half of the inner border of the first metacarpal bone ; the internal from the entire length of the external surface of the second metacarpal bone, and from the hgaments which unite it to the trapezium. From these points the fleshy fibres proceed, forming two thick bundles, which are perfectly distinct above, and con- verge to a tendon that is attached to the outer side of the first phalanx of the index finger. 264 BIYOLOGY. Relations. — It is covered behind by the skin ; it corresponds in front to the adductoi and flexor brevis pollicis, excepting below, where it is sub-cutaneous. Its lower edge, directed obliquely downward and inward, is immediately sub-cutaneous, and crosses the corresponding edge of the adductor pollicis at a very acute angle. The Palmar Interossei. These, like the preceding, are short, prismatic, triangular, and penniform muscles. They are three in number (p p p, fig. 123) according to most authors, but four if we in- clude the adductor pollicis. They all occupy the palm of the hand, as their name indi- cates, and extend from the entire length of one of the metacarpal bones bounding the interosseous space in which they are situated to the first phalanx of one of the corre- sponding fingers, and to its extensor tendon. They arise from about the anterior two thirds of the lateral surface of only one meta- carpal bone ; they are, therefore, covered behind by the dorsal interossei, wliich, being attached to the entire lateral surface of the other metacarpal bone, project equally into the palm. Lastly, their insertions into the phalanges and their extensor tendons corre- spond precisely with those of the dorsal interossei. Relations. — They are covered by the flexor tendons and by the muscles of the palmar region : each is in relation behind with a dorsal interosseous muscle ; on one side with the dorsal muscle of the corresponding finger, and on the other with the metacarpal bone from which it arises. Action. — They are evidently adductors, as regards the axis of the hand, and, like the dorsal interossei, they bind down the extensor tendons ; they can only act effectuall) when the fingers have been previously extended. MUSCLES OF THE LOWER EXTREMITIES. The muscles of the lower extremities may be arranged in four groups, viz., those ol the pelvis, of the thigh, of the leg, and of the foot. MUSCLES OF THE PELVIS. The Glutcei, Maximus, Medius, et Minimus. — Pyriformis. — Obturator Internus. — Gcmelb, Superior et Inferior. — Quadratus Femoris. — Obturator Externus. — Action of these Muscles fig, 1S4, The muscles of the pelvis are divided into those occupy ing the posterior and those occupying the anterior region. The former are very numerous, consisting of the three glutaei, maximus, medius, and minimus, the pyriformis, the obturatoi internus, the gemelli, the quadratus femoris, and the obtura- tor externus. The iliacus, which may with propriety be considered as be- longing to the pelvis, and as forming its anterior vregion, hsis been already described, together with the psoas, under the name of the psoas-iliac muscle. The GlutcBUs Maximus. Dissection. — Having placed the subject on its face, raise the pelvis by a block, flex the leg forcibly, and rotate it inward ; then make an oblique incision along the middle of the but- tock, from the sacrum towards the great trochanter, dividing both the skin and fascia covering the muscle : dissect up the tw(( "aps, one from below upward, the other from above down- wani, following the direction of the muscular fibres. The idutaus maximus {a, fig. 124) is the most superficial of the muscles on the posterior aspect of the pelvis ; it is broad, thick, and pretty regidarly quadrilateral ; it is the largest mus- cle of the human body, in this respect coinciding with the great size of the pelvis and femur in man ; it causes the prom- inence of the buttocks. Its great size is one of the most dis- tinctive characters of the muscular system of man, and has reference to his biped position. Attachments (see a, fig. 125). — It arises from the posterior semicircular line of the ilium, and the portion of the bone be- hind that line ; from the vertical sacro-iliac ligament, and the outer margin of the common aponeurosis of the posterior spi- nal muscles ; from the crest of the sacrum, sometimes only from the tubercles which form a continuation of the trans- verse processes of the vertebrae on the outside of the posteiior THE GLUTiEUS MEDIUS. 265 sacral foramina ; from the edges of the coccyx, and the notch terminating the crest of the sacrum below, this origin being often effected by means of a tendinous arch, under which the last posterior sacral nerves pass ; from the posterior surface of the great sacro-sci- atic ligament ; and, lastly, from the posterior surface of the aponeurosis of the glutseus medius. It is inserted {a, fig. 125) into the rough line leading from the great trochanter to the linea aspera of the femur. The fleshy fibres arise either directly or by short tendinous fibres, and proceeding par- allel to each other outward, and a little downward, unite into large distinct fasciculi, ca- pable of being separated through their entire length, and constituting an extremely thick, quadrilateral, and very regular muscle, which, having reached the outside of the thigh, terminates by tendinous fibres. These are received between two layers of the fascia lata, which is here very thick ; in passing downward they converge, escape from the fascia lata, curve round the base of the great trochanter, or, rather, the tendon of the vas- tus externus, from which they are separated by a synovial bursa, and are successively inserted by so many large fasciculi into the series of tubercles and depressions, extend- ing from the great trochanter to the linea aspera, and from the external bifurcation of that line. The lower fleshy fibres are attached directly to the linea aspera, and a cer- tain number are inserted merely into the fascia lata. In order to obtain a good view of the femoral insertions of this muscle, its tendon must be separated from the fascia lata. Relations. — It is covered by a large quantity of fat, being separated from it by an ex- pansion from the aponeurosis of the glutaeus medius, from which are given off the cellu- lar prolongations that divide the muscle into thick, parallel, and easily separable fasciculi. It covers the glutaeus medius, the pyriformis, the gemelli, the obturator internus, the quadratus femoris, the great sciatic notch, and the tuberosity of the ischium, together with the muscles attached to it, viz., the semi-tendinosus, the semi-membranosus, and the long head of the biceps. It covers also the great trochanter, the adductor magnus, and the triceps femoris, the glutaeal, ischiatic, and internal pudic vessels and nerves, and the great sciatic nerves. Its upper border is very thin, and rests upon the glutaeus me- dius ; its lower border forms a very marked prominence beneath the skin, that affords the surgeon very precise indications, both in the diagnosis of many diseases of the hip- joint ; in operations performed for the purpose of reaching the tuberosity of the ischium, when it is either carious or necrosed ; in those for the relief of sciatic hernia ; or, lastly, in searching for the sciatic nerve, whenever it becomes necessary to operate upon it. Several bursae mucosae, which have been well described by Monro, separate the glutaeus maximus from the eminences which are covered by it. One of these separates it from the great trochanter, and is almost always multi-locular : I have seen it filled with a san- guineous synovia. A second exists over the tuberosity of the ischium, but is often want- ing ; and a third between the tendon of this muscle and the vastus externus.* Action. — The glutaeus maximus is an extensor, an abductor, and a rotator of the thigh outward. When the femur is fixed, as in standing, it acts upon the pelvis, which it draws backward and to its own side, and rotates so that the anterior surface of the trunk is turned to the opposite side. Besides this, it is easy to see that the lower fibres can act as adductors. By its connexions with the fascia lata, it is one of the principal tensors of this structure ; by its attachment to the coccyx, it tends to prevent that bone from being thrown backward, forward, or to one side. The Glut (BUS Medius. Dissection. — Make a vertical incision through the middle of the glutaeus maximus, or detach that muscle from the pelvis ; remove the adipose tissue from the sub-cutaneous portion of the muscle, and also the fascia lata ; dissect the tensor vaginae femoris, which covers the anterior fibres of this muscle. The glutaus medius (b,figs. 124 to 127) is intermediate to the other two glutaei, both as regards size and position ; it is a broad, thick, radiated muscle, situated more deeply than the preceding, beyond which it projects upward and forward (^fig. 124). The glu- taeus maximus is attached to a small portion only of the iliac fossa : the glutaei medius and minimus share almost the whole of it between them. Attachments. — It arises from the whole extent of the curved triangular surface included between the superior semicircular line behind, the anterior three fourths of the crest of the ilium above, and the inferior semicircular line below ; from the anterior superior spine of the ilium and the notch immediately below it ; from the deep surface of a dense aponeurosis, which is inserted into the outer lip of the crest of the ilium, covers all the upper portion of the muscle, and becomes continuous with the fascia lata : opposite the junction of the anterior with the middle third of the crest of the ilium, at which point a large tubercle exists upon the bone, this aponeurosis is so dense as to resemble a tendon. The muscle also arises from a deep aponeurosis, extending from the anterior part of the inferior semicircular line, and giving attachment, on its external surface, to a great num her of fleshy fibres ; and, lastly, from the fascia lata internally to the tensor vaginae femo ris. It is inserted into the external surface of the great trochanter {figs. 125, 127) * See note, p. 296. L L k 266 MYOLOGY. From these numerous origins the fleshy fibres proceed in different directions ; the pos- terior forward, the middle vertically, and the anterior backward, becoming more and more horizontal in front. They all terminate upon the two surfaces and edges of a radiated aponeurosis, the fibres of which are gradually concentrated, and folded upon themselves, so as to form a flat tendon, inserted, not into the upper border, as it is generally said, but into the external surface of the great trochanter, along an oblique line running downward and forward, so that the anterior fibres of the muscle are inserted into the anterior ex- tremity of the lower border of the great trochanter, and the posterior fibres into the back part of the upper border ; at this latter point a well-marked projection sometimes exists, the size of which generjdly indicates the power of the glutaeus medius. A synovial bursa intervenes between the tendon and that part of the great trochanter over which it passes.* Relations. — It is covered by the glutaeus maximus, the tensor vaginas femoris, and the skin : it covers the glutaeus minimus, with which its outer border is blended, and the glutaeal vessels and nerves. Its lower border is parallel with the pyriformis {fig. 125). Action. — The glutaeus medius is both an extensor and an abductor of the thigh. More- over, the anterior fibres rotate the femur inward, and the posterior outward ; but the for • mer have the greater power, for they are more numerous, the muscle being twice or thrice as thick in front as behind ; it is, therefore, an extensor, an abductor, and a rotator inward of the thigh. Winslow denies that it is an extensor, and considers it only as an abductor ; this is only true in the position of standing upon both feet. In the sitting pos- ture, again, this muscle in some degree loses its power as an extensor and abductor, and acts merely as a rotator. When the femur is fixed, as in standing, the glutaeus medius extends the pelvis, draws it to its own side, and rotates it> so that the front of the trunk is turned towards the same side. It co-operates with the glutaeus maxunus in the first two motions, but antagonizes it in the last. Finally, its anterior fibres appear to me calculated to flex the thigh upon the pelvis, especiaUy when the flexion has been already contmienced by other muscles. The Glutce.us Minimus. The glutaus minimus (c,fig. 127) is exposed by simply cutting across the preceding muscle, beneath which it lies ; it is thinner, and more regularly radiated. It arises from the anterior part of the crest of the ilium, below the glutaeus medius, from the outside of the sciatic notch, and from all that part of the external iliac fossa situated below the in- ferior semicircular line : from these points the fibres converge, the middle passing ver- tically, the posterior forward, and the anterior backward, to the deep surface of a radia- ted aponeurosis, the fibres of which are collected together into bands, that are inserted separately into the anterior border and anterior half of the upper border of the great tro- chanter. Most commonly the posterior band is intimately attached to the tendon of the pyriformis. Relations. — It is covered by the glutaeus medius, with which its anterior fibres are blended ; it covers the external iliac fossa, the reflected tendon of the rectus femoris, and the upper part of the hip-joint, from which it is separated by some fatty cellular tissue. Action. — It is much more directly an abductor than the preceding muscles. Its ante- rior half rotates the thigh inward, and its posterior half outward. If the femur be fixed, it extends the pelvis, inclines it to its own side, and turns the anterior aspect of the trunk to the same side ; by its anterior fibres it assists slightly in producing flexion. General Remarks upon the Action of the Glutcei. — The three muscles we have just ex- amined generally have their fixed points upon the pelvis ; and, in this point of view, are of the greatest importance in the standing posture. By their means the pelvis, firmly held down from behind, is enabled to resist the effects of the weight of the trunk, which tends to throw it forward : hence the enormous development of these muscles in man, evidently proving his destination for the erect position. These same muscles are the principal agents in the position of standing upon one foot, inclining the pelvis to their own side, and balancing the entire weight of the opposite side of the trunk. They also rotate the trunk when the individual is standing upon one foot. They are all extensors and abductors ; the glutaeus maximus is a rotator outward ; the other two are rotators inward. Hence we may understand how the thigh can be so powerfully rotated inward, although there are no direct muscles for that purpose ; while a great number are spe- cially intended to produce rotation outward, which movement, indeed, is performed much more energetically than rotation inward. The Pyriformis. Dissection. — Detach the glutaeus maximus, and separate the pyriformis from the lowei border of the glutaeus medius, to which it is parallel. In order to see the sacral attach- ments of the muscle, make an antero-posterior section of the pelvis. The pyriformis or pyramidalis {d, fig. 125) is sometimes double : it is a flat muscle, of a p5Tifonn, or, rather, pyramidal shape, lying almost horizontally along the lower margin of the glutaeus medius, with which it seems to be continuous, and is sometimes intimately * See note, p. 296. THE OBTURATOR INTERNUS. 267 united : it is partly situated in the cavity of the pelvis, and assists in filling up the sciat- ic notch. Attachments. — It arises from the anterior surface of the sacrum (p,^. Ill), in the in- tervals between the grooves forming the continuations of the anterior sacral foramina, and also opposite those grooves, by three or four digitations, which are sometimes trav- ersed by the great sciatic nerve : these origins are sometimes concentrated into a small space around the second and third anterior sacral foramina. It also arises from the an- terior surface of the great sacro-sciatic ligament, and from the upper part of the sciatic notch. It is inserted into the back part of the upper edge of the great trochanter. The fleshy fibres pass irom their origins almost horizontally outward and a little backward, and form a muscle which fills up the upper part of the great sciatic notch, and, becoming much narrower immediately after emerging from the pelvis, from the convergence of its fibres, terminates on the posterior surface and edges of an aponeurosis, which is after- ward converted into a round tendon, and is fixed to the upper border of the great tro- chanter, behind the glutaeus minimus, and above the gemelU and obturator internus, with which it is almost always intimately connected. Relations. — Its anterior surface is in relation with the rectum, the sciatic plexus, and the hypogastric vessels within the pelvis, and with the hip-joint outside that cavity ; its posterior surface, with the sacrum and the glutaeus maximus ; its upper margin, with the glutaeal vessels and nerves, which separate it from the glutaeus medius ; its lower mar- gin, with the ischiatic vessels, and with the great and small sciatic nerves. Sciatic her- niae take place between the upper margin of this muscle and the sciatic notch. Some- times the muscle reaches the summit of the notch ; occasionally, a considerable interval exists between them ; in such cases, there is a predisposition to this species of hemiae. The Obturator Internus. The oUurator internus {e,fig. 125) is a triangular reflected muscle, extending from the inner surface of the margin of the obturator foramen to the digital cavity of the great trochanter. Its course and direction are alike remarkable. Attachments. — It arises from the posterior surface of the obturator ligament, from the pelvic fascia lining the inner surface of this muscle, and from the tendinous arch which converts the sub-jmbic groove into a canal ; also, from the entire circumference of the ob- turator foramen, viz., from the internal surface of the descending ramus of the pubes and the ascending ramus of the ischium, and from the whole extent of the quadrilateral sur- face situated between the obturator foramen and the sciatic notch ; and, lastly, by a few fibres from the brim of the pelvis. It is inserted into the digital cavity of the great tro- chanter. The fleshy fibres arise directly from this extensive surface, and, converging downward and outward, pass out of the pelvis through a triangular opening formed by the spine of the ischium and lesser sacro-sciatic ligament above, by the great sacro-sciatic ligament on the inside, and by the body of the ischium on the outside. At its exit from the pelvis the muscle becomes much narrower, is reflected at a right angle over the body of the ischium as over a pulley, is next received into a groove formed for it by the gemelli, and proceeds horizontally outward, to be inserted into the digital cavity of the great tro- chanter below the pyriformis. In order to obtain a good view of the structure of this muscle, it must be detached from its insertion and turned inward. We shall then per- ceive that the tendon divides into four or five diverging portions upon the deep surface of the muscle, which are lost in its interior. A well-marked synovial membrane* inter- venes between the tendon and the trochlear surface on the body of the ischium, which is covered with cartilage that is streaked, as it were, in the direction of the movements. Cowper and Douglas alluded to the presence of this bursa when they named the muscle marsupialis vel bursalis. Relations. — In the pelvis the obturator internus is in relation with the obturator liga- ment and the circumference of the obturator foramen, by its anterior surface ; and with the pelvic fascia and levator ani muscle, which separates it from the bladder, by its pos- terior surface. During its passage through the orifice I have described, it is in relation with the internal pudic vessels and nerves ; externally to the pelvis, it is covered by the great sciatic nerve and the glutaeus maximus, and it covers the hip-joint. From the great extent of the pelvic origins of this muscle, almost the whole of the an- terior and lateral parietes of the pelvis are covered internally by a layer of muscular tis- sue ; the posterior wall is also in a great measure covered by the pyriformis. The origin' of the muscular fibres from the tendinous arch of the obturator ligament are so arranged, that the contraction of the muscle can have no effect in diminishing the size of the sub-pubic foramen intended for the passage of vessels and nerves. There are sometimes two small tendinous arches ; one for the nerve, the other for the artery and vein. The Gemelli, Superior et Inferior. The gemelli (gemini, Albinus ; les petits jumeaux, Winslaw, f and g, Jig. 135), two small 1 See note, p. 295. 268 MYOLOGY. fleshy fasciculi, accessories to the obturator intemus, are generally distinguished by anat- omists into the superior (/) and the inferior (g) ; they are separated from each other by the tendon of the obturator intemus, for the reception of which they form a groove. Above and below this groove they take their origin ; the superior from the spine of the ischium, and the inferior, which is the larger, from the tuberosity of that bone, immedi- ately above the attachment of the great sacro-sciatic ligament, and even slightly from the ligament itself They both pass horizontally outward, are sometimes united either behind or in front of the tendon of the obturator intemus, which they then completely embrace, and with which they are entirely or partially blended, being inserted with it into the digital cavity of the great trochanter. Their relations are the same as those of the reflected portion of the obturator intemus. The gemellus superior is often wanting, and the inferior is frequently double. I have several times seen the superior terminate in the tendon of the pyriformis, and the in- ferior in the tendon of the obturator intemus. Actimi. — They rotate the thigh outward. Their relations with the synovial capsule of the obturator intemus led to their being designated marsupiales by Cowper, and by Portal, le muscle capsulaire de la capsule du tendon de I'obturateur interne. The Quadratus Femoris. This muscle (i, fig. 125), shaped like a parallelogram, is situated immediately below the gemellus inferior. It arises from the external border of the tuberosity of the ischium, in front of the semi-membranosus, from which it is separated by adipose tissue. From this point the fibres proceed horizontally outward, parallel to each other, and are inserted into " an oblong ridge* projecting partly from the back of the root of the great trochan- ter, and partly from the femur immediately below it ;" but above the attachment of the adductor magnus, with which, at first, it appears to be continuous, but from which it is always separated by the internal circumflex vessels. This muscle is sometimes wanting ; but very frequently its pelvic attachments are pro- longed as far as the ascending ramus of the ischium ; in which cases it is twisted inferi- orly upon itself, so as to oppose a surface, not a border, to the adductor magnus. Its re- lations behind are the same as those of the preceding muscles ; in front, it covers the obturator externus and the lesser trochanter, from which it is often separated by a sy- novial capsule. The Obturator Externus. Dissection. — The lower or horizontal portion of the obturator externus is exposed, by dividing the quadratus femoris into two equal parts by a vertical incision. In order to see the upper or pelvic portion, it is necessary to detach the gracilis, pectineus, psoas, ili- acus, and adductor brevis. This is a triangular, flat muscle (e, fig. 127), of the same shape, but thinner and smallei than the obturator intemus, and, like it, reflected, though at an obtuse angle. It arises from the circumference of the obturator foramen, from the obturator ligament, and from the tendinous arch which completes the sub-pubic canal for the vessels and nerve. It is inserted into the deepest and lowest part of the digital cavity of the great trochanter. The fleshy fibres arise directly, the lower ones proceed horizontally outward, and the upper obliquely downward, backward, and outward ; thus converging, they form a fleshy belly, which turns round the neck of the femur, and terminates in a tendon that passes horizontally outward, to be inserted into the digital cavity, below the gemelli and the ob- turator intemus. Relations. — Its outer and anterior surface is in relation with the pectineus, the adduc- tors, the psoas and iliacus muscles, and more externally with the neck of the femur and the lower part of the capsular ligament of the hip-joint. Its inner and posterior surface is in contact with the obturator foramen and the quadratus muscle. Action of the preceding Muscles. The last six muscles are evidently rotators of the thigh outward. The pyriformis, the gemelli, and the obturator internus, which are almost always united at their insertions, would deserve the name of quadri-gemini, given by the older anatomists to the gemeUi, the pyriformis, and the quadratus. When they take their fixed point upon the femur, as, for example, in standing upon one foot, they become rotators of the pelvis, and turn the anterior surface of the trunk to the opposite side. They are only rotators when tlie limb is extended ; in the sitting posture, they become abductors. Winslow, who first demon- strated their use in abduction in the semiflexed position, attached great importance to the connexion of so many of these muscles with the capsular ligament, which he believed prevented pinching of the capsule during the different movements of the joint. The insertion of these muscles is exceedingly favourable. Moreover, we shall find, that besides the glutaeus maximus and the posterior fibres of the glutaeus medius and * [M. Cruveilhier states the insertion of the quadratus femoris to be into the inter-trochanteric line. Tba description in the text, copied from Albinus, gives a more accurate idea of the insertion of this muscle.] THE BICEPS CRURIS. minimus, they have many other muscles as accessories in rotation. The effects pro- duced by the contraction of the two obturators can be easily understood, if we bear in mind that the action of a reflected muscle is to be calculated from the point of reflection, leaving the rest of the muscle out of consideration. Thus, with regard to the obturator internus, the sciatic notch acts as a pulley, and may be regarded as the fixed point. MUSCLES OF THE THIGH. The Biceps Cruris. — Semi-tendinosus. — Semi-memhranosus. — Tensor Vagina. Femoris. — Sartorius. — Triceps Extensor Cruris. — Gracilis. — Adductor Muscles of the Thigh. The muscles of the thigh are divided into those of the posterior region, viz., the biceps, the semi-tendinosus, and the semi-membranosus ; those of the external region, viz., the tensor vaginae femoris and the vastus externus ; those of the anterior region, viz., the sartorius, the rectus, and the triceps extensor cruris of authors ; and, lastly, those of the internal region, viz., the gracilis, the pectineus, and the three adductors. Posterior Region. The Biceps Cruris. Dissection. — This is the same for the biceps, the semi-tendinosus, and the semi-mem- branosus. Place the subject upon its face, with a block under the pelvis, and allow the leg to hang over one side of the table. Make an incision from the middle of the space between the tuberosity of the ischium and the great trochanter to the interval between the two condyles of the femur. Both the skin and the fascia of the thigh must be di- vided in this incision. Cautiously remove the cellular and adipose tissue surrounding the subjacent muscles, the relations of which with the popliteal vessels and nerves must be carefully studied. In preparing the superior attachments of these muscles, the glu iaeus maxiraus must be divided in the middle, perpendicularly to its fibres. The biceps femoris (biceps cruris, Albinus, I, figs. 124, 125), so named because it con- sists of two fleshy bodies or heads above, is a long, large muscle, situated on the poste- rior and external aspect of the thigh. Attachments. — It arises from the tuberosity of the ischium and the linea aspera of the femur, and is inserted into the head of the fibula, and slightly jp^. 125. into the external tuberosity of the tibia. Its origin from the ischium {I, fig. 125) is common to it and the semi-tendinosus ; -;; ■; ^^f ; it takes place, not from the tuberosity properly so called, but from the highest and most external part of the tuberosity, above and behind the adductor magnus, and immediately be- low the gemellus inferior. It arises by a tendon which is sel- dom completely free from muscular fibres. This tendon, at first very thick, and separated from the tuberosity of the ischium by a synovial bursa, expands into an aponeurosis, which gives origin to the fleshy fibres of the biceps by its ex- ternal edge and posterior surface, and to those of the semi- tendinosus by its internal surface. Up to this point the biceps and semi-tendinosus are blended together so as to form a single fleshy belly, which, after extending from two to four inches, is divided into two portions : one posterior and external, consti- tuting the long head, or ischiatic portion of the biceps ; the other anterior, forming the origin of the semi-tendinosus, which we shall next describe. Arising thus in succession, the fleshy fibres of the long head of the biceps form a fusiform belly passing obliquely downward and a little outward, and termina- ting on the anterior surface of an aponeurosis, which extends for a considerable distance on the posterior surface of the muscle, and which gradually becomes contracted, so as to form the terminal tendon. Just where these fleshy fibres are about to terminate {l,Jig. 125), the aponeurosis receives upon its anterior surface and external edge the fleshy fibres of the short head, or femoral porticm of the biceps. This portion of the muscle {I', fig. 125) arises from the greater part of the in- terval between the two margins of the linea aspera, and the posterior surface of the external inter-muscular septum of the thigh ; it passes downward, inward, and backward, to be at- '.ached to the common tendon, almost as far as its insertion. This insertion is not confined to the head of the fibula, but extends also to the external tuberosity of the tibia by means of a strong division of the tendon, which, at the same time, gives ofF^n expansion to the fascia of the leg. The insertion into the fibula is ef- 2^0 MYOLOGY. fected on the outer side, in front of and behind the extemzd lateral ligament of the knee- joint, which ligament it embraces in a bifurcation. Relations. — The biceps is covered by the glutaeus maximus and the femoral fascia. It covers the semi-tendinosus, semi-membranosus, and vastus externus. It is in relation, also, with the great sciatic nerve, which is placed at first externally, then in front, and, lastly, on the inside of the muscle ; finally, its short head is in relation with the popliteal vessels. The biceps forms the external border of the popliteal space ; near its termination it is in relation with the outer head of the gastrocnemius and with the plantaris longus muscle. Action. — The biceps flexes the leg upon the thigh. When this movement is com- pleted, its long portion extends the thigh upon the pelvis. From its obliquity downward and outward, it rotates the leg outward during semi-flexion ; but this rotation is impos- sible when the leg is extended, in consequence of the tension of the crucial ligaments. The fixed point of this muscle is as often below as above, and it then performs an im- portant part in the mechanism of standing ; for it tends to prevent the individual from ialhng forward, because it holds back the pelvis. When the pelvis is thrown quite back- ward, this muscle can then flex the thigh upon the leg. The Semi-tendinosus. The semi-tendinosus {m,figs. 124, 125), so named on account of the great lengta of its tendon, is situated on the posterior and internal aspect of the thigh. AttcLchments. — It arises from the tuberosity of the ischium, and is inserted into the an- terior tuberosity of the tibia. Its origin (m, fig. 125) consists of a tendon common to it and the long head of the biceps, which is prolonged in the form of an aponeurosis, upon the external (or popliteal) border of the muscle. Some of the fleshy fibres are attached directly to the tuberosity of the ischium. Having arisen in this manner, it enlarges and constitutes a fusiform bundle, which passes at first vertically downward, and then ob- liquely inward. About four or five fingers' breadth above the knee-joint it terminates in a long, thin tendon, which turns round the internal tuberosity of the tibia, describing a curve having its concavity directed forward, and is then reflected horizontally forward, to be inserted into the anterior teberosity of that bone, behind the tendon of the sarto- rius, and parallel with the lower edge of that of the gracilis, to which it is united. The union of these three tendons constitutes the patte d'oie (goose's foot). The length of its tendon of insertion is the most characteristic feature of the muscle ; and hence its name, semi-nervosus (Spigelius), and le demi-nerveux ( Winslow), for which the term semi-tendinous has now been substituted. The structure oi this muscle is re- markable. The fleshy fibres are interrupted across the middle by a tendinous intersec- tion, analogous to that of the great complexus, which gives origin to new fleshy fibres. Relations. — It is covered by the glutaeus maximus and the femoral fascia, and it cov- ers the semi-membranosus and part of the upper portion of the adductor magnus. Its tendon is first placed behind the semi-membranosus, and then, before it turns round the internal tuberosity of the tibia, between the tendon of that muscle and the inner head of the gastrocnemius. Action. — ^The same as that of the biceps. It is a very powerful flexor, on account of the reflection of its tendon. Its oblique direction enables it to rotate the tibia inward du ring semi-flexion of the leg. It is, therefore, a congener of the popliteus. The Semi-membranosus. The semi-membranosus {n,figs. 124, 125) is situated upon the posterior aspect of the thigh, thin and aponeurotic above, thick and fleshy below. Attachments. — It arises from the upper and outermost part of the tuberosity of the is- chium, in front of the biceps and semi-tendinosus ; and is inserted into the internal tuber osity of the tibia, and also, by an expansion of its tendon, into the femur. It arises by means of a very thick tendon, which becomes wider immediately after its origin. From its inner border is given off" an aponeurotic lamina, that splits into two layers, from the in- terval between which the superior fleshy fibres arise. Lower down, the muscular fibres proceed directly from the tendon itself, which runs along the outer (or popliteal) border of the muscle, as far as the lower fourth of the thigh, but is afterward buried in its sub- stance. The union of all these fibres constitutes a very thick, four-sided, fleshy belly, which is received into a tendinous semi-cone, open on its outer side, and soon becoming converted into a thick tendon, which, after a passage of a few lines, separates into three divisions, terminating in the following manner : the posterior division passes inward and upward, forms the chief part of the posterior ligament of the knee-joint, and is inserted into the femur ; the middle division is attached to the back of the internal tuberosity of the tibia, below the articular surface ; the third is horizontal, and turns round the inter- nal tuberosity of that bone in the horizontal furrow existing there, and is inserted on the inner side of the tuberosity. A synovial bursa intervenes between it and the bone. Relations. — The semi-membranosus is covered by the glutaeus maximus, the semi-ten- THE TENSOR VAGINA FEMORIS. THE SARTORIUS. 271 dinosus, the biceps, and the femoral fascia : it covers the quadratus femoris, the adduc- tor niagnus, and the inner head of the gastrocnemius. A synovial membrane separates it from the knee-joint. It also covers the popliteal artery and vein, which soon come into relation with its outer or popliteal border. The sciatic nerve lies parallel with its outer border through the whole of its extent ; the gracilis is in contact with its inner border. I shall remark here, that the biceps on the outside, and the semi-membranosus and semi-tendinosus on the inside, constitute the lateral boundaries of a cellular interval which extends along the whole of the back of the thigh, and is continuous with the pop- liteal space. This large cellular interval communicates above with the cellular tissue of the pelvis at the sciatic notch, and below with the fossa of the ham. It is in this di- rection that purulent matter so readily escapes from the pelvis. The greater part of this interval is destined for the great sciatic nerve, which, however, is soon accompani- ed by the popliteal vessels. Action. — Precisely similar in nature to that of the preceding muscle, but much more powerful. The momentum of all these flexor muscles occurs, on the one hand, during semi-flexion of the leg upon the thigh ; and, on the other (i. e., when their lower attach- ments are fixed), during semi-flexion of the thigh upon the pelvis. External Region. The Tensor Vagince Femoris. Dissection. — In order to expose this muscle, it is sufficient to make a vertical incision through the thick, tendinous layer given off from the anterior portion of the crest of the ilimn, and to dissect back the two flaps of that aponeurosis. The tensor vagina femoris (le muscle du fascia lata, o,fig. 126) is the largest of all the extensor muscles of aponeuroses : it is a short, flat, quadrilateral muscle, contained within the substance of the fascia lata, and occupying the upper third of the external region of the thigh. It arises from the anterior part of the outer margin of the crest of the ilium, and from the outer border of the anterior superior spinous process of the ilium, between the sartorius and the glutasus medius, by means of a tendon, which also furnishes some points of attachment to the anterior fibres of the last-named muscle. From these points the fleshy fibres proceed downward and a little backward, and, at about the upper fourth or third of the thigh, terminate in a series of small tendinous bundles, the anterior of which become continuous with the fascia lata, while the posterior cross obliquely over the vertical fibres of the fascia, with which they are very soon blended. Relations. — It lies between two layers of the fascia lata, the external layer being much thicker than the internal. It is covered by the skin, and it covers the glutaeus medius, the rectus, and the vastus extemus. Its anterior border is in contact with the outer edge of the sartorius, but is soon separated from it by a triangular space, in which the rectus femoris may be seen. ' Action. — It is a tensor, not only of the entire femoral fascia, but particularly of the very dense portion or band of the fascia lata, which, being continuous with it, may be regard- ed as an aponeurotic tendon to this muscle (muscle aponeurotique de la bande large, Winslow), and which is inserted into the outer tubercle of the anterior tuberosity of the tibia, and into the adjacent part of its external tuberosity. When the tensor vaginae is in action, this band compresses the vastus extemus, which has so great a tendency to displacement ; by means of this band, also, the muscle acts upon and extends the leg. Lastly, on account of its slight obliquity downward and backward, it may be regarded as a rotator of the thigh inward ; it is but little concerned, however, in the production of this movement, which, as I have already said, is chiefly effected by the anterior fibres of the glutaei medius and minimus. Anterior Region. The Sartorius. Dissection. — This is common to all the muscles of the anterior and inner regions ol the thigh. Make a horizontal incision along the fem.oral arch, and another perpendicu- larly from the middle of that to the anterior tuberosity of the tibia. Dissect the fascia of the thigh with care. As all the muscles of the anterior and inner region are separa- ted from each other by distinct sheaths, their dissection consists simply in opening these sheaths successively, and removing the cellular tissue that fills up the inter-muscular spa- ces. It is necessary to preserve the vessels, in order to obtain a good view of their rela- tions : avoid opening the vena saphena, as it generally contains a large quantity of blood, the escape of which will impede the dissection. If the vein should be opened, it must be tied above and below the orifice, and then cut across. When the superficial muscles have been studied, they must be divided in the middle, in Order to expose the muscles of the deep layers. The sartorius {p, fig. 126), so named on account of its uses, crosses diagonally over the anterior, and then the inner part of the thigh, to the top of the leg. It is the longest mus- cle in the body, both as regards its total length, and more especially in reference to the «72 MYOLOGY. Fig- 126. length of its fibres ; whence the name of longus, given to it by Riolanus. This is the case even although it be nneasured by a line stretched directly between its two extremities. Attachments. — It arises from the anterior superior spinous pro- cess of the ilium, from the upper half of the notch below that pro- cess, and from a tendinous septum between the muscle and the fascia lata. It is inserted into the inner margin of the crest of the tibia, situated beneath the ligamentum patellae. Its origin con- sists of some tendinous fibres, which are more marked beb md and on the outer side than in front and within. The fleshy fibres commence almost immediately, and form a flat, riband-like mus- cle (fascialis, Spigelius), which in reality is prismatic and trian- gular, as well as the tendinous sheath in which it is enclosed. The muscle increases in breadth as far as the lower third of the thigh, and passes obliquely downward, inward, and a little back- ward ; it becomes internal and vertical at the lower third (p, Jigs. 124, 125), and reaches the back part of the inner condyle of the femur, to turn round the knee-joint, tendinous fibres having al- ready conmienced on the anterior edge of the muscle. The fleshy fibres terminate precisely where the muscle changes its direction to pass forward. The flat tendon by which they are succeeded is at first narrow, but becomes considerably expanded, to be inserted into the crest of the tibia, in front of the tendons of the semi-ten- dinosus and gracilis muscles, with which it is united, so as to form what is called the patte d'oie (goose's foot). A synovial membrane separates it from the tendons of these muscles. A considerable tendinous expansion is given off from its lower edge, and contributes to form the inner part of the fascia of the leg. Relations. — ^The sartorius is the most superficial muscle in the anterior aspect of the thigh ; it lies beneath the femoral fascia, and covers the psoas and iliacus, the rectus, the vastus internus, the adductor longus, the gracilis, the adductor magnus, and the internal lateral ligament of the knee-joint. The borders of this muscle deserve particular attention, because incisions for ligature of the femoral artery must be made along them. Its most important relation, indeed, is with the femoral artery and vein ; it is the satellite muscle of the femoral artery. Thus, in the upper third of the thigh, it forms, with the adductor longus and femoral arch, an isosceles triangle, having its base turned upward, and the femoral artery represents a perpendicular drawn from the apex to the base of the triangle. In the middle third of the thigh, the artery is in relation, first, with the inner border, then with the posterior surface, and, lastly, with the outer border of the muscle. In the lower third, the sarto- rius occupies a deep groove, formed by the gracilis and vastus internus ; from the latter muscle it is separated below by an interval containing adipose tissue, of which circum- stance advantage may be taken in the application of issues. It also covers the saphenus nerve (a deep branch of the anterior crured), which emerges from beneath its anterior bor- der, opposite the lowermost point of insertion of the adductor magnus. Near the knee- joint, the saphena vein is in relation with the posterior border of the muscle. The structure of the sartorius is very simple. The fleshy and tendinous fibres are all parallel, and the former correspond exactly with the length of the muscle. Action. — The sartorius flexes the leg upon the thigh, which it draws inward, so as to cross one leg over the other. When this movement is produced, it flexes the thigh upon the pelvis. If the fixed point of the muscle be at the leg, it then flexes the pelvis upon the thigh, and rotates it, so that the anterior surface of the trunk is directed to the op- posite side. The Rectus Femoris and Triceps Extensor Cruris, or the Triceps Femoralis. I have included under the name triceps femoralis the two muscles, or, rather, the two parts of the same muscle, which are described separately in most anatomical works. The reasons for this arrangement will be understood after the following description of the muscle : I shall consider the triceps femoralis as composed of three portions, viz., a middle or long portion, the rectus femoris of authors ; an external and an internal portion, which constitute together the triceps cruris of authors ; for these I shall retain the names of vastus internus and externus, including in the former the middle portion or crureus, prop- erly so called, of most anatomists. The long portion of the triceps femoralis, or the rectus femoris (r, fig. 126), is situated in the anterior region of the thigh, extending from the anterior inferior spinous process of the ilium to the patella : it is vertical in its direction, thick and broad in the middle, and narrowei at its extremities in..-;-r THE RECTUS FEMORIS AND TRICEPS EXTENSOR CRURIS. 273 It arises by a very strong tendon (r, fig. 127), which embraces the anterior inferior spinous process of the ihum, and is proportioned to the power of the muscle. This ten- don receives on its outer side another flat tendon, arising from a groove upon the rim of the cotyloid cavity, and following its curvature ; this is the rejected tendon, which is blended with and strengthens the straight tendon. It then expands into a broad aponeu- rosis, the outer portion of which is very thin and prolonged over the anterior surface of the muscle as far as the middle, while the inner portion is very thick, and penetrates into its substance nearly as far as its insertion. The fleshy fibres arise from the poste- rior surface and edges, and also from the anterior surface of the inner portion of this aponeurosis ; they all pass downward and backward, the internal inward and the exter- nal outward, and form a fleshy belly, which increases as it proceeds downward, and then terminates on the anterior surface of a broad, thick, and shining aponeurosis, occupying the lower two thirds of the posterior surface of the muscle, and soon becoming contract- ed into a flat tendon, which receives upon its inner edge the superficial fibres of the vastus intemus, again expands, and is finally blended with the common tendon of the two vasti. Triceps Femoris of Authors, or Vastus Internus and, Externus. — This is a voluminous mass of muscular tissue, situated behind the preceding muscle, and extending from the three surfaces of the shaft of the femur to the patella and tibia. It is commonly but er- roneously considered to be divided above into three heads, which are described under the names of vastus internus, vastus externus, and crureus. I have searched in vain for the middle portion, but have never been able to find more than two separate parts : one external, very large and superficial, viz., the vastus externus; the other internal, anteri- or, and even external, viz., the vastus internus ; it is much smaller than the vastus ex- ternus, and is partly covered by it and by the rectus. The external portion, or vastus externus {s, figs. 124 to 127). This is the largest portion of the triceps femoralis. It arises from a projecting border or horizontal crest, situated at the base of the great trochanter, and from a vertical edge in front of that trochanter, which forms a continuation of its anterior border, and sometimes presents a very prom- inent tubercle : in the angle formed by these two attachments is situated tlie tendon of the glutseus medius. It also arises along a line running from the great trochanter to the linea aspera, and from the whole extent of the external lip of the linea aspera itself All the preceding origins are effected by means of a broad aponeurosis which covers the superior three fourths of the muscle, and from the deep surface of which almost all the fleshy fibres proceed. Lastly, some of these arise from the tendon of the gluta?us max- imus, and from the tendinous septum intervening between the vastus externus and the short head of the biceps. From these origins the fleshy fibres proceed, some vertically downward, the others somewhat obliquely downward and forward, the lowest being the shortest and the most oblique ; they form a large bundle, which partially covers the an- terior portion of the vastus intemus, but is separated from it by vessels, nerves, and cel- lular tissue. After a course of variable length, some of the fleshy fibres are attached to the deep, but the greater number to the superficial surface of another equally strong apo- neurosis : this becomes thickened and contracted into a flat tendon, which is sometimes divided into thick parallel bands, emerges from the fleshy fibres at the external margin of the rectus, and is inserted into the outer half of the upper border of the patella, being blended on the inner side with the rectus and the vastus intemus. The lower fleshy fibres which arise from the inter-muscular septum are attached directly to the outer bor- der of the patella.* The internal or anterior portion, vastus internus {t and u,fig. 127), is much smaller than the external, and surrounds the femur. Its inner portion lies immediately under the fas- cia, and is the only part which is generally described as the vastus internus {t,figs. 126, 127). Its anterior portion is covered by the rectus, or long portion, and is usually called the crureus (cmralis, Alb., u,fig. 127). Its outer portion is covered by the vastus externus, with which many of its fibres are blended ; but they may always be separated by cutting along the outer margin' of the middle aponeurosis. Thus defined, the vastus internus arises from a rough oblique line, extending from the front of the neck of the femur to the linea aspera, and from the internal lip of the linea aspera itself, in front of the adductor muscles : both of these origins are effected by means of an aponeurosis, which is weaker and smaller than that of the vastus externus, and is blended with that of the adductors, concurring w ith it in the formation of a canal for the femoral artery. It also arises from almost the whole of the internal, anterior, and external surfaces, and from the two ante- rior borders of the femur ; lastly, the lower fibres arise from the internal inter-muscular septum. From these different origins the fleshy fibres pass in various directions ; the external inward, the middle vertically, and the internal, which are the most numerous, downward, forward, and outward ; they thus form a fleshy belly, thicker below and with- in than above and without, and are successively attached to both surfaces, and espe- cially to the posterior surface of a broad aponeurosis, which is covered by the tendon of * Tke anterior border of this tendon is free, and perfectly distinct from the tendon of the rectus, which is lined by it ; and also from the expanded tendon of the vastus internus. Mm 2T4 MYOLOGY. the vastus externus, but can be easily separated from it. The uiner fibres are attached to the anterior surface of the aponeurosis, and terminate very regularly opposite a verti- cal line, running parallel to the inner margin of the rectus femoris. The aponeurosis extends over the anterior surface of the middle portion of the mus- cle, which lies behind the rectus : this fact has, doubtless, given rise to its division into two parts, viz., a middle, or the crureus, and an internal, called the vastus internus. The superficial layer of the interna! fleshy fibres is attached below to the inner margin of the rectus, or long portion of the triceps femoralis : the lowest of these fibres, which arise from the inner and inferior bifurcation of the linea aspera, and from the corresponding inter-muscular septum, are almost horizontal, and accompany the tendon as far as its in- sertion into the inner border of the patella. Lastly, the terminating aponeurosis is pro- longed inward to the internal tuberosity of the tibia, below which it is inserted, being covered by the tendons of the semi-tendinosus, semi-membranosus, and gracilis muscles, on the inner side of the internal lateral ligament of the knee. This very strong aponeu- rotic insertion represents the fascia lata on this aspect of the limb, and forms an acces- sory internal lateral ligament. From the above description, it follows that the triceps femoralis is composed of three muscles and three tendons, super-imposed upon each other, viz., the rectus femoris, the vastus externus, and the vastus internus. Relations. — The long portion of the triceps, or the rectus femoris, is covered by the fascia lata in its lower three fourths. Its upper part is covered by the sartorius, by the anterior fibres of the glutajus medius, and by the psoas and iliacus. It covers the hip- joint, the anterior circumflex vessels, and the two vasti muscles. The vasti surround the femur as in a muscular sheath, and have relations with all the muscles of the thigh. They are superficial in a great part of their extent : in front, they are in relation with the psoas and iliacus, the rectus femoris, and the sartorius, and they lie immediately under the fascia, in the triangular spaces left between these muscles : behind, they are in relation with the biceps and semi-membranosus ; on the inside, with the adductors, with the femoral artery, the sheath of which the vastus internus contributes to form, and with the sartorius ; on the outside, with the glutaeus maximus, which glides over the upper end of the vastus externus, and is separated from it by a synovial bursa ; and, lastly, with the tensor vaginae femoris, and the fascia lata. It is necessary to allude here to a small fleshy bundle, formed by the deepest and lowest fibres of the vastus in- ternus, which is always distinct from the rest of the muscle, and is inserted into the up- per part of the synovial membrane of the knee. This bundle has been regarded by Wins- low as an articular muscle, intended to prevent the synovial membrane from being pinched between the surfaces of the joint. Action. — This muscle extends the leg upon the thigh ; its action is facilitated by the existence of the patella, which serves to increase the angle of insertion, and which we have described as a sesamoid bone, developed in the substance of the tendon. We must, therefore, regard the triceps as inserted into the anterior tuberosity of the tibia, or, rath- er, into tiie lower part of that tuberosity. It should be observed, that the tendon is in- serted into the patella, in front of its base, and not into the base itself, in the same man- ner as the ligameutum patellae is attached to the anterior surface of that bone, and not to the rough mark on its posterior surface : this important arrangement increases the angle at which the moving power operates. The triceps femoralis is the most powerful muscle in the body, no other having such large surfaces of origin, and, consequently, so great a number of fibres. By itself it supports, in a state of equilibrium, tlie entire weight of the body in standing, and may be adduced as a striking example of the pre- dominance of the extensors over the flexors ; it is also this muscle which raises the whole trunk in progression and in the act of leaping. We cannot, therefore, be astonish- ed at rupture of the patella, of its ligament, or of the common tendon, during a violent contraction of this muscle, notwithstanding its disadvantageous insertion so near to the fulcrum. The rectus necessarily acts with the two vasti, but it can also flex the thigh upon the pelvis. The somewhat oblique direction of the tendon of the triceps down- ward and iawar^, and of the ligameutum patelljff downward and outward, so that Siey form an obtuse angle, open to the outside {see Jig. 126), and more especially Jliejjjfedom- inance of the vastus externus over the vastus internus, sufficiently account for the oc- currence of luxation of the patella>Qulw.aj:d,taiid (dr the impossibility of its beiifig dislo- cated inward. When the patella is forced inward by external violence, the contraction of the vastus externus draws it back into its original position : on the other hand, the action of this muscle has a tendency to displace it outward ; and when this is accomplished, the same muscle keeps it in its abnormal position. Luxations of the patella, therefore, if not al- together irreducible, can only be temporarily replaced ; whenever the hand ceases to re- tain tlie bone in its proper place, the contraction of this muscle again dislocates it. Pro- fessor Ant. Dubois has informed me of an individual whose knees were bent very much inward, who could not contract the triceps femoralis with any force without dislocating the patella outward. THK GRACILIS, ETC. iM Internal Region of the Thigh. The muscles of the internal region of the thigh are the gracilis and the adductors, among which I include the pectineus. The Gracilis. The gracilis (le grele interne, ou droit interne, Winslow, v,figs. 124, 125, 126) is a long, straight, and slender muscle, and the most superficial of those situated on the inside of .he thigh. Attachments. — It arises from the symphysis pubis, between the pubic spine and the ascending ramus of the ischium, and is inserted into the spine of the tibia. It arises by some long, shining, and parallel tendinous fibres, which bind down a perpendicular fibrous bundle that lies on the inner side of the line of attachment. The fleshy fibres succeed- ing to these are at first parallel, and "form a broad, thin bundle ; they then converge to- wards each other, so that the entire muscle resembles a much elongated isosceles tri- angle. It is rounded below, and terminates in a long, thin tendon, which runs for a con- siderable distance upon its posterior border, and receives all the fleshy fibres in succes- sion. This tendon becomes free immediately above the knee-joint, is then situated be- hind the internal condyle of the femur, turns round this process and the corresponding tuberosity of the tibia, and is inserted into the spine of the last-mentioned bone, behind the tendon of the sartorius, and above that of the semi-tendinosus, with both of which it is united so as to form the trifid aponeurotic interlacement, denominated la patte d'aie (goose's foot). Relations. — The gracilis is covered by the femoral fascia, and slightly by the sartorius at its lower part : it covers the three adductors, the inside of the knee-joint, and the in- ternal lateral ligament, from which it is separated by a synovial bursa common to it and the semi-tendinosus : the vena saphena interna crosses the inner surface of this muscle obliquely, near its lower extremity. Action. — It flexes the leg, and carries it slightly inward, at the same time, by means of its reflection round the knee ; in this part of its action it assists the sartorius ; it also ad- ducts the thigh. In the position of standing, its movable point is at the pelvis. The Mductor Muscles of the Thigh. There are three muscles on the inner aspect of the thigh which are called adductors ; with these the older anatomists were acquainted under the collective name of the triceps adductor. Modern viTiters, however, describe them either in the order of their super- imposition, as the fo-st, seco7id, and third (Boyer) ; or in the order of their size, as the mid- dle, small, and great adductors (Bichat). These vague denominations are the source of much confusion, for the one which occupies the middle place as regards size is the first as regards its position. I have therefore thought it right to modify these names, and have, at the same time, included the pectineus among the adductor muscles. I consider, therefore, that there are four adductors, which I shall divide into superficial and deep ; the two superficial are the pectineus and the first or long adductor ; these I shall term the first and second. Superficial Adductors. — The two deep are the short and the great adductors, which I shall denominate the small deep adductor and the great deep adductor. Strictly speaking, we could only admit the existence of two adductors, one superficial, the other deep ; and this mode of division would perhaps be preferable. Dissection. — This is common to all the adductors. Abduct the thigh so as to render these muscles tense. Make an incision through the integuments from the middle of the femoral arch to the patella, and a semicircular incision at either end of this ; preserve the vessels and nerves, in order to examine their relations ; tie and cut across the vena sephena where it enters the femoral vein ; divide the fascia lata, and dissect the mus- cles, which will then be brought into view. The First Superficial Adductor, or Pectineus. Tiie pectineus {pecten, the pubes) is a square muscle {w, fig. 126) situated at the upper anterior and inner aspect of the thigh, on the inner side of the psoas and iliacus (c). Attachments. — It arises (w, fig. 127) from the spine and crest of the pubes, from the trian- gular surface in front of this crest, and from the lower surface of a very strong tendinous and arched prolongation of Gimbernat's ligament, which is attached to the crest of the pu- bes, and is continuous with the fascia covering the muscle. It is inserted (w, fig- 127) below the lesser trochanter, into the ridge extending from that process to the linea as- pera. With the exception of the spine of the pubes, where there are always some well- marked tendinous attachments, the fleshy fibres commence directly from the several ori- gins : they proceed downward, backward, and outward, and constitute a bundle, which is at first flattened from before backward, and afterward from without inward .- the fibres of this after a short course converge, and are inserted into the internal bifurcation of the linea aspera, in part directly, and partly through the medium of an aponeurosis which oc- cupies the anterior surface of the muscle. MYOLOGY. Tig. 127. Relations. — The pectineus is covered by the deep layer of the femoral fascia, and by the femoral vessels. It covers the capsular ligament of the joint, the small deep adductor, and the obturator externus, from which it is separated by the ob- turator vessels and nerves. Its outer border is parallel with the inner border of the conjoined portions of the psoas and iliacus, and is separated from them by a cellular interval, over which the femoral artery passes ; so that, were it not for the projection of this outer border, this vessel would be in imme- diate contact with the bone. Its inner border is in relation with the second superficial adductor, and is sometimes blend- ed with it, except below, where it is separated by an interval in which the small deep adductor may be seen. It has an im- portant relation with the anterior orifice of the sub-pubic canal, which corresponds with the posterior surface of the muscle. When hernial protrusions, therefore, take place at the fora- men ovale, the displaced parts are always covered by the pec- tineus muscle. The Second Superficial Adductor^ or Mductor Longus. The adductor longus of Albinus (le premier adducteur, Ba- yer; le moyen adducteur, Bichat, x,fig. 126) is a flat, triangu- lar muscle, situated on the same plane as the pectineus, of which it seems to be a continuation, and with which it is often blended above. For this reason, Vesalius made of these two muscles his eighth pair of muscles of the thigh, under the name of pars octava femur moventium. It is certain that there is a sort of consolidation between these two muscles, and that a small pectineus is always observed in conjunction with a large adductor longus. Attachments. — It arises {x, Jig. 127) from the spine of the pubes, and is inserted {x) into the middle third of the linea as- pera of the femur. Its origin consists of a narrow, flat ten- don, which expands anteriorly, and gives origin to a thick and broad fleshy belly ; this passes downward, backward, and out- ward, and is inserted into the middle third of the linea aspera of the femur, between the triceps femoralis in front, and the great deep adductor behind : with the latter of these muscles it becomes blended at its insertions. It is attached to the bone by means of two tendinous layers, between which the fleshy fibres are receiv- ed. A number of foramina, intended for the perforating arteries, are observed in the neigh- bourhood of this attachment. Relations. — Its upper part lies immediately under the fascia, and it becomes gradually deeper as it passes downward. It is in relation with the sartorius, from which it is sep- arated by the femoral artery and veins. This relation is one of great importance, as I shall hereafter have occasion to point out. The Small Deep Adductor, or Adductor Brevis. The adductor brevis o{ Albinus (le seconde of Boyer ; le petit of Bichat, y,fig. 127) is of the same form as the preceding muscle, and is the second in the order of super-im- position, but the smallest in size. It arises below the spine of the pubes on the outer side of the gracilis and the inner side of the obturator externus, from a variable extent of surface. The fibres proceed outward, downward, and a little backward, and form a thick bundle, at first flattened from within outward, and then from before backward, which increases in breadth, and terminates at the middle of the linea aspera of the femur, in front of the great deep adductor, and behind the two superficial adductors, with which it is blended at its insertion. Relations. — It is covered by the superficial adductors, and it covers the great deep ad- ductor, or adductor magnus. Its outer border has a relation with the obturator externus, and the conjoined psoas and iliacus muscles ; its inner border is at first in contact with the gracilis, and is then applied to the adductor magnus, from which it is sometimes difficult to separate it. The Great Deep Adductor, or Adductor Magnus. Dissection. — In order to obtain a good view of this muscle, it is not suflicient to study its anterior surface only, which is exposed after the preceding muscles have been divi- ded ; its posterior surface must also be examined ; and for this purpose it is necessary to remove the three muscles of the posterior region of the thigh, viz., the biceps, the semi-tendinosus, and the semi-membranosus. THE ADDUCTOR MAGNUS, ETC. 277 The adductor magnus of Alhimis (le troisi^me of Boyer ; le grand of Bir.hat, z, z', figs. 124 to 127) is a very large, triangular muscle, extremely thick internally, where it con- stitutes almost the entire substance of the inside of the thigh {fig. 127). It arises from the whole extent of the ascending ramus of the ischium, from a small part of the de- scending ramus of the pubes, and from the apex, i. c, the lowest portion, of the tuberos- ity of the ischium. It is inserted into the whole extent of the interval between the two lips of the linea aspera, and into a very prominent tubercle upon the inner condyle of the femur, above the depression for the insertion of the tendon of the inner head of the gas- trocnemius. Its origins, especially those from the ischium, which are the principal, can only be seen on the posterior surface of the muscle (see fig. 125). They consist of ten- dinous bundles, giving origin immediately to fleshy fibres, which form an extremely thick mass, directed downward and outward, and presenting coarse bundles, almost as large and as easily separable as those of the glutasus maximus. The muscle soon divides into two portions, or, rather, into two distinct muscles, an internal and an external. The internal portion {z,figs. 125, 127) forms the inner border of the adductor magnus, the original course of which it follows. About the lower third of the thigh, its fibres are received into a tendinous semi-cone, open on the outside, and terminating in a shi- ning tendon, which is inserted into a well-marked tubercle on the upper and back part of the internal condyle of the femur. Throughout its whole course, this tendon lies close to the aponeurosis of the vastus internus. The external portion (z',^^. 125), abandoning the primitive direction of the muscle, is directed outward, and separates into thick bundles, which are inserted into the whole extent of the interval between the lips of the linea aspera by means of a very large aponeurosis, which is intimately united to the tendons of the other adductors, and forms a series of arches (see fig. 125) for the passage of the perforating arteries. These two divisions of the adductor magnus are separated below by the femoral ar- tery and veins and their sheath, and are generally distinct for a considerable extent, and sometimes entirely so. I have met with a case of this kind. That portion of the mus- cle which was inserted into the internal condyle arose entirely from the apex of the tu- berosity of the ischium ; while the origin of that portion which was attached to the linea aspera took place from a prominence situated on the external side of that tuberosity, and projecting outward from it, and also from the ascending ramus of the ischium, and the descending ramus of the pubes, externally to the gracilis muscle. The superior fibres {fig. 125) are horizontal, and, forming a distinct, and, as it were, a radiated bundle, turn in front of the succeeding fibres, and are inserted into the line leading from the great trochanter to the linea aspera, internally to the glutaeus maximus. Relations. — The adductor magnus is covered by the superficial adductors and by the small deep adductor : it covers the semi-tendinosus, the biceps, the semi-membranosus, and the glutaeus maximus. Its inner border is bounded by the gracilis above, and by the sartorius below: its upper border is in contact with the obturator externus ie,fig. 127) on the inside, and with the quadratus femoris (i, fig. 125) more externally. Its most important relation is that with the femoral artery and vein, which pass through it before reaching the popliteal space. At the place where this periforation occurs we observe a tendinous arch, or, rather, canal, into which the fleshy fibres are inserted ; and so, also, where the perforating arteries pass through this muscle. Action of the Adductor Muscles. — ^The muscles we have just described are both flexors and rotators outward ; but their principal office, as their name indicates, is to perform adduction, a very energetic movement, as might be anticipated from the strength of the muscles concerned in its production. We have seen, indeed, that the line of origin ex- tends from the ilio-pectineal eminence as far as and including the tuberosity of the ischi- um, and that the insertions occupy the entire length of the linea aspera, the two branch- es of its superior bifurcation, and the inner condyle of the femur. These muscles are powerfully exerted during equestrian exercise ; it is by their means that the horse is firmly grasped between the knees. The two superficial adductors and the adductor bre- vis are also flexors, because their insertions are posterior to their origins. All the ad- ductors are, as it were, rolled around the femur during rotation inward. MUSCLES OF THE LEG. The Tibialis Anticus. — Extensor Communis Digitorum. — Extensor Proprius Pollicis. — Pe- roneus Longus and Brevis. — Gastrocnemius, Plantarus, and Soleus. — Popliteus. — Titia- lis Posticus. — Flexor Longus Pollicis. The muscles of the leg may be divided into those of the anterior, those of the exter- nal, and those of the posterior regions. Muscles of the Anterior Region of the Leg. The muscles of the anterior region of the leg are the tibialis, the extensor communis digitorum. and the extensor proprius pollicis pedis. The anterior peroneus, or peroneus ms MYOLOGY. tertius, wlien it exists, is nothing more than an accessory fasciculus of the extensor communis. The Tibialis Anticus. Dissection. — ^Make a vertical incision through the skin from the anterior tuberosity of Fig.l^ the tibia to the middle of the inner border of the foot ; dissect back the two flaps of skin, and expose the fascia of the leg ; di- vide this fascia vertically, commencing from the middle of the leg, and terminating at the lower end of the tibia, taking care to preserve the annular ligament ; prolong the dissection and sep- aration of the fascia as far upward as possible ; lastly, remove the fascia on the dorsum of the foot, which covers inferiorly the tendon of the tibialis anticus. The tibialis anticus {a, fig. 128) is a long, thick, prismatic, and triangular muscle, placed superficially along the outer side of the tibia. Attachments. — It arises from the crest which bounds the ante- rior tuberosity of the tibia on the outside, and from the tubercle terminating this crest above ; from the external tuberosity of the tibia, and the superior two thirds of its external surface, which presents a depression proportioned to the strength of the muscle ; from all that portion of the interosseous ligament situated to the inner side of the anterior tibial vessels and nerves ; from the deep surface of the fascia of the leg ; and, lastly, from a tendi- nous septum intervening between this muscle and the extensor communis digitorum. It is inserted into the tubercle on the first or internal cuneiform bone, and sends oflT a tendinous expansion to the first metatarsal bone. It arises from the internal surface of an osteo-fibrous quadran- gular pyramid formed by the tibia, the fascia of the leg, the inter- osseous ligament, and the inter-muscular septum ; from these points the fleshy fibres proceed vertically downward, and termi- nate around a tendon which commences in the substance of the muscle above its middle third ; the anterior fibres cease at the lower third of the muscle, the posterior accompany the tendon to the point where it passes under the dorsal ligament of tlie in- step (seen in fig. 128). As soon as the tendon appears on the anterior border of the muscle, it is deflected forward in a similar manner to the external surface of the tibia, and follows the same oblique course, after having left the common sheath of all the muscles of the anterior region of the leg. Another sheath, which is nothing more than the condensed dorsal fascia of the foot, re- ceives the tendon at the point where it passes vertically downward, to be inserted into the tubercle of the first cuneiform bone. Relations. — The tibialis anticus is covered by the fascia of the leg asad the dorsal fascia of the foot ; on the inside it is in relation with the external surface of the tibia ; on the outside, at first with the extensor communis digitorum, and then with the extensor pro- prius pollicis, from which it is separated behind by the anterior tibial vessels and nerves. Action. — It flexes the foot upon the leg ; and, from tlie obliquity of its tendon, it raises the internal border of the foot, and, consequently, produces that sort of rotation inward at the articulation of the two rows of the tarsus which we have already alluded to. It tends, also, to adduct the ankle-joint, and is, consequently, opposed to dislocation out- ward. The absence of a proper sheath for this muscle explains the considerable pro- jection formed by its tendon during contraction, which may serve as a guide to the pre- liminary incisions in ligature of the dorsal artery of the foot. Spigelius called this mus- cle the musculus catencE, because fetters applied around the ankles of criminals press chiefly upon the projection formed by its tendon. The Extensor Longus Digitorum Pedis, and the Peroneus Tertius vel Anticus. Dissection. — Remove the fascia of the leg and the dorsal fascia of the foot. This is an elongated, semi-penniforra, and reflected muscle {b c, fig. 128), flattened from within outward, single above, and divided into four or five tendons below. Attachments. — It arises from the external tuberosity of the tibia, on the outer side of the tibialis anticus ; from the whole of the internal surface of the fibula in front of the interosseous ligament, and slightly from that ligament ; from the upper part of the fascia of the leg, and from the tendinous septa interposed between this muscle and the tibialis anticus within, and the peroneus longus and brevis without. It is inserted into the sec- ond and third phalanges of the last four toes. From these numerous origins the fleshy fibres proceed in different directions ; the su- THE EXTENSOR PEOPRIUS POLLICIS. "^9 perior vertically downward, the rest obliquely downward and forward, the lowest being the most oblique ; they all terminate around a tendon, which appears upon the anterior border of the muscle below the upper third of the leg. This tendon soon divides into two portions : one internal, and itself subdivided into three tendons for the second, third, and fourth toes ; the other external, and generally split into two tendons, one of which is intended for the fifth toe, while the other is fixed to the posterior extremity of the cor- responding metatarsal bone. This last subdivision is often wanting : it is but imperfect- ly separated from the fasciculus belonging to the fifth toe, to which it almost edways sends off an accessory tendon : it has been generally described as a separate muscle, under the name of the peroneus tertius or anticus {c,Jig. 128). I have thought it right, however, to connect this muscle with the extensor longus digitorum (i), from which it can be so imperfectly separated that it has been designated by Cowper, pars extensoris digitorum pedis longi ; and by Morgagni, quintus tendo extensoris longi digitormn pedis. The extensor communis is directed vertically as far as the ankle-joint, where it enters a sheath conmion to it and the flexor proprius poUicis, is next reflected under this sheath, becomes horizontal, passes obliquely inward and opposite the tarsus, is received into a much stronger proper sheath, after leaving which the five tendons separate so as to cov- er the dorsd surface of the metatarsal bone of the toes, to which they correspond. In this course they cross the extensor brevis digitorum at a very acute angle, reach the dorsal surface of the metatarsal phalangal articulations, apply themselves to the inner edges of the corresponding tendons of the extensor brevis, receive some expansions from the interossei and lumbricales, and are arranged in precisely the same manner as the ex- tensor tendons of the fingers, forming a fibrous sheath on the dorsal surface of the first phalanx of the toes ; and like these, having arrived at the articulations of the first with the second phalanges, each divides into three portions : one median, attached to the pos- terior extremity of the second phalanx ; and two lateral, which unite upon the dorsal sur- face of the second phalanx, to be inserted into the posterior extremity of the third. Relations. — Internally this muscle is in relation with the tibialis anticus, from which it is soon separated by the extensor proprius pollicis, and externally with the peroneus longus and brevis. It is covered by the fascia of the leg and foot, and it covers the fibula, the interosseous ligament, the ankle-joint, the extensor brevis digitorum, which separ- ates it from the tarsus and metatarsus ; lastly, it covers the toes. Action. — As in all reflected muscles, we must suppose the power to be exerted imrne- diately after its reflection, and in the direction of the reflected portion : in this way, it will be seen that it extends the third phalanges upon the second, and the second upon the first ; and having produced this effect, it flexes the foot upon the leg. From its obliqui- ty, it also draws the toes outward, and turns the sole of the foot inward. The Extensor Proprius Pollicis. The extensor proprius pollicis {d,fig. 128) is an elongated, thin, flat muscle, placed in front of the leg, betwisen the extensor longus digitorum and the tibialis anticus. Attachments. — It arises from the interned surface of the fibula, and slightly from the adjacent part of the interosseous ligament, within and behind the extensor communis This origin is situated at variable heights, but commonly not above the middle third of the leg. It is inserted into the posterior extremity of the second phalanx of the great toe. The fleshy fibres arise directly from the fibula and the interosseous ligeiment, and proceed at first vertically around, and then obliquely behind a tendon, which occupies the anterior border of the muscle, and to which the fleshy fibres are all attached in a sloping manner, like the barbs of a feather, as far down as below the proper sheath formed for it at the tarsus. From thence the tendon is reflected at a right angle, proceeds oblique- ly and horizontally forward and inward upon the dorsum of the foot, passes along the dorsal surface of the first metatarsal bone and first phalanx of the great toe, to the latter of which it gives off a prolongation on each side, and is then inserted into the second phalanx. Relations. — Internally, it is in relation with the tibialis anticus, from which it is sep arated behind by the anterior tibial nerve and vessels ; and externally, with the extensor longus digitorum. Its anterior border, at first concealed between the preceding muscles, is soon situated immediately beneath the fascia, and during its contraction forms a pro- jection, which it is important to know, because it serves as a guide in searching for the dorsal artery of the foot, which will always be found on the outer margin of the tendon : it may be called the muscle of the arteria dorsalis pedis. In the foot it crosses superfi- cially to the extensor brevis digitorum. Action. — It extends the second phalanx of the great toe upon the first, and that upon the metatarsus ; when this is accomplished, it flexes the foot upon the leg. In conse- quence of its obliquity, it tends, like the preceding muscle, to turn the toes outward, and slightly to elevate the inner border of the foot. External Region of the Leg. In this region are found the peroneus longus and peroneus brevis muscles. 9^ MYOLOGY. The Peroneus Longus. «k-«.'i Dissection. — This is common to both muscles. Remove the skin on the outer side of the leg ; make a vertical incision through the fascia ; reflect the two flaps, in order to ar- rive at the tendinous septa dividing the peronei from the muscles of both the anterior and posterior regions of the leg. To expose these muscles in the foot, remove the outer portion of its dorsal fascia, and divide obliquely inward and forward all the muscles of the pkntar region, from the groove of the cuboid to the posterior extremity of the first metatarsal bone. The peroneus longus {e,figs. 128 to 130) is a long, thick muscle, prismatic and trian- gular at its upper part, and superficially situated on the outer side of the leg (peroneus primus, Spigelius). Attachments. — It arises externally from the outer and anterior part of the head of the fibula ; from a small portion of the contiguous part of the external tuberosity of the tibia ; from the upper third of the external surface of the fibula ; and from the anterior and pos- terior borders of that bone, by means of very strong tendinous septa, interposed between it and the anterior and posterior muscles of the leg ; lastly, from the fascia of the leg superiorly. It is imerted into the posterior extremity of the first metatarsal bone, on the outer side of which a process exists for this purpose. From these very numerous origins, the fleshy fibres proceed vertically and form a bun- dle {e,fig. 130), thick above, thin and flat below, and terminating in a tendon which is at first concealed in the substance of the muscle, but appears in the form of a band on its outer side, a little above the middle of the fibula, and becomes narrower and thicker as it proceeds. Tlie tendon soon leaves the fleshy fibres, and accompanies the external sur- face of the fibula as it turns backward (peroneus posticus, Riol), then passes behind the external malleolus in a groove common to it and to the peroneus brevis, and is reflected forward and downward to the outer side of the os calcis, upon which it is held by a sep- arate sheath. Having reached the outer side of the cuboid bone, it is again reflected, enters a groove running obliquely inward and forward upon the lower surface of that bone {e,figs. 132, 133), where it is retained by a very strong and compact sheath, and continues its oblique course, without any deviation, along the lower surface of the tarsal bones ; as far as the posterior extremity of the first metatarsal bone. In this way the tendon of the peroneus longus undergoes a double reflection : first, behind the external malleolus, in which situation a thickening or knot is often seen ; and, secondly, at the cuboid bone, opposite which a sesamoid bone almost always exists. There are also three? fibrous sheaths, and three synovial membranes belonging to this tendon, one be- hind the external malleolus, one upon the outside of the os calcis, and a third under the cuboid bone. Relatioiis. — In the leg, the peroneus longus is covered by the skin and the fascia of the leg : it covers the peroneus brevis. In front, a tendinous septum intervenes between it and the extensor longus digitorum : behind, another inter-muscular septum exists between it and the soleus above, and the flexor proprius below. On the outside of the foot, its tendon corresponds to the skin externally, and to the os calcis internally. In the plantar region, it is covered below by the entire thickness of the soft parts, and corresponds above to the inferior tarsal ligaments. Action. — As we have already so frequently observed, a reflected muscle acts as if the power were applied at the point of reflection. In this way, by transferring the power to the outer end of the groove on the cuboid bone, we shall find that the foot is abducted, or, rather, rotated outward by this muscle ; by next supposing the power to act from the other point of reflection, i. e., from behind the external malleolus, we may observe that the foot is extended upon the leg, and its outer border turned upward. In this move- ment, the lower end of the external articular surface of the astragalus tends to carry the external malleolus outward, and to increase the curvature of the fibula, which is some- times fractured in consequence. It may be easily conceived that if the fibula be frac- tured, the contraction of this muscle will no longer be counteracted, and accordingly will turn the sole of the foot outward, and may luxate the astragalus inward. This is the mechanism of luxation of the foot occurring after fracture of the fibula, the only species of lateral dislocation of this part which has ever been observed.* The Peroneus Brevis. The peroneus brevis o{ Albinus (peroneus secundus, Spigel ; le petit peronier, Wins- tmB,f,figs. 129, 130) is a flat, penniform, and reflected muscle, smaller and shorter than the preceding, beneath which it lies. Attachments. — It arises from the lower half, sometimes from the lower two thirds of the external surface of the fibula, which is more or less excavated for this purpose ; from the anterior and posterior borders of the same bone, and from the tendinous septa exist- ing between this muscle and those of the anterior and posterior regions of the leg. It is inserted into the posterior extremity of the fifth metatarsal bone, and sometimes * See the admirable memoir by M. Dupuytren, on fracture of the fibula. THE GASTROCNEMIUS. 2B1 CYcn, by a tendinous expansion, into the fourth metatarsal bone ; it often gives off a pro- longation to the extensor tendon of the httle toe. The fleshy fibres proceed successively from their different origins to the internal sur- face and edges of a tendon, situated upon the outer surface of the muscle ; the bundle which they form gradually increases in size, and then diminishes, is at first penniform, and afterward semi-penniform, and accompanies the tendon as far as the fibrous sheath behind the external malleolus : after leaving the sheath, the tendon enters another, prop- er to itself, upon the outer side of the os calcis, above that for the tendon of the peroneus longus, and passes somewhat obliquely downward and forward, to be inserted into the base of the fifth metatarsal bone. Relations. — It is covered by the peroneus longus, and covers the fibula and the outer side of the os calcis. It is, therefore, only in comparison with the peroneus longus that Riolanus and others have called this muscle the anterior peroneus. Action. — The same as that of the peroneus longus, with the exception of that of its subtarsal portion. Thus, supposing the power to be applied at the external malleolus, we have extension of the fifth metatarsal bone upon the cuboid ; extension and rotation inward of the second row of the tarsus upon the first ; rotation of the calcaneum upon the astragalus ; extension, and a tendency to abduction of the entire foot, which is therefore considerably everted when the fibula is fractured. PosTEKioK Region. There are two layers in this region : one superficial, formed by the gastrocnemius and soleus (or triceps suralis) and the plantaris ; the other deep, consisting of the popliteus, the tibialis posticus, the flexor longus digitorum, and the flexor longus pollicis. The Gastrocnemius and Soleus, or Triceps Suralis, and the Plantaris. Dissection. — Make a vertical incision from the upper part of the popliteal space to the heel ; at right angles to this, above, make another horizontal and semicircular incision, embracing the back part of the thigh ; divide and dissect the fascia of the leg. The gas- trocnemii will then be exposed, and must be dissected very carefully at their origins. In order to study the structure and attachments of these muscles properly, they must be cut transversely in the middle, and the superior half turned upward. In dividing the outer head of the gastrocnemius, be careful not to cut the plantaris, which seems to be merely a small fasciculus detached from that muscle. The soleus is exposed by simply removing the gastrocnemius ; but, in order to study its structure and attachments, it must be divided vertically from behind forward at the side of a median tendinous raph^, and the fibres which conceal this median aponeurotic lamina of the muscle must be scraped away. From this division we have a fibular and a tibial portion of the soleus. The gastrocnemius (g g) and the soleus (i i',Jig. 129) together constitute a very powerful triceps muscle (musculus surae. Seem.), which, by itself, forms the fleshy part of the leg, commonly called the calf The great development of these muscles is one of the most marked characteristics of the muscular apparatus of the human sub- ject, and is connected with his destination for the erect position. The three portions of the triceps suralis are united together below in a common tendinous insertion, constituting the tendo Achillis {t, Jig. 129), but are divided above into two very distinct planes : one, anterior or deep, formed by the soleus ; the other, posterior or su- perficial, consisting of the two heads of the gastrocnemius. We shall describe these in succession. Gastrocnemius. The gastrocnemius, from yaarrip, a belly, and Kv^firj, the leg (ge- mellus, Albinus ; primus pedem moventium, cum secundo, Vcsalt- us), is the most superficial muscle on the back of the leg : it con- sists of two heads above {g g',fig. 129), but forms a single fleshy belly, which is thick and flattened from before backward. It arises from the condyle of the femur by two perfectly distinct but similar heads, viz., an outer or smaller, called the gemellus ex- ternus {g), and an inner or larger, named the gemellus internus (g-')- They take their origin from the bone, by two very strong and flat tendons, which are attached on the outer side, and behind the con- dyle of the femur, to two well-marked digital impressions, that for the outer head being situated above a much deeper impression foi the popliteus muscle, and that for the inner head inmiediately be hind the tubercle into which the adductor magnus is inserted, so that the inner head is situated upon a plane a little posterior to that of the outer head. They also arise, by tendinous fasciculi, from Nn Fig. 139. S82 MYOLOGY. the rough triangular surfaces surrounding the digital impression, and terminating at the inferior bifurcation of the linea aspera. Each tendon of origin (that for the inner being much larger than that for the outer head) expands into an aponeurosis upon the posteri- or surface of that portion of the muscle to which it belongs. The aponeurotic expansion of the inner head is, moreover, thicker and longer than the other, and embraces the inner border of that part of the muscle, like a tendinous semi-cone. The fleshy fibres arise from the anterior surface of these tendinous expansions, and are disposed in the follow- ing manner : those in the middle, which are few in number, are strengthened by fleshy fibres proceeding from the rough projections of the bifurcation of the linea aspera, pass inward and downward, and are united together like the limbs of the letter V opening up- ward, upon a median raphe, which consists either of a simple thickening of the termina- ting aponeurosis, or of a small tendinous septum : the other fibres, constituting almost the entire muscle, arise from the anterior surface of the tendons of origin, and from the aponeurosis in which they terminate, and proceed vertically downward to the back of an- other very dense aponeurotic expansion, which covers the whole anterior surface of the muscle. This last aponeurosis commences above by two very distinct portions ; at first it is of equal breadth with the muscle, then becomes narrower and thickened, and, finally, closely united with the terminal tendon of the soleus. At the lower part of the calf the fleshy fibres terminate suddenly upon the posterior surface of this aponeurosis, forming a V opening downward. Although the two portions of the gastrocnemius become inti- mately united shortly after their origin, they are not confounded together, and the inter- nal portion forms on the inside of the tibia the greatest part of the fleshy mass called the calf of the leg. Relations. — The gastrocnemius is covered by the fascia of the leg, and it covers and adheres intimately to the capsular ligament, which envelops the back part of the con- dyles of the femur. It is also in relation with the popliteus and the soleus. The tendon of the inner head corresponds to the posterior surface of the internal con- dyle ; that of the outer head to the outer side of the external condyle. We often find at the upper part of the tendon of each head, but most commonly in the substance of that of the outer head, a sesamoid bone, that glides upon the back of the condyle, and belongs to the sort of fibrous capsule or hood by which the back of each condyle is cov- ered. (Vide Syndesmology, Articulation of the Knee.) The Plantaris. This little muscle (le plantaire grele, 1 1', Jig. 129) should be regarded as an accessory of the outer head of the gastrocnemius, or, rather, as a rudimentary muscle in the hu- man subject. Its small fusiform, fleshy belly, varying much in size, is found beneath the outer head of the gastrocnemius. It arises {I) from the fibrous capsule covering the external condyle, and sometimes from the lower part of the external bifurcation of the linea aspera. From these points, it pass- es obUquely downward and inward, and after a course of from two inches and a half to three inches, ends in a long, flat, and slender tendon, which is at first situated between the gastrocnemius and soleus, and afterward (/') lies parallel with the inner edge of the tendo Achillis, and is inserted into the os calcis, either at the side, or in front of that ten- don. Sometimes, however, it is lost in the sub-cutaneous adipose tissue. This muscle, which is often wanting, is occasionally double.* The Soleus. The soleus (partly seen at i i',fig. 129) is so called because it has been compared to the fish called a sole, or to the sole of a shoe. Attachments. — It arises from the fibula and tibia, and is inserted into the os calcis. Its fibular origins (i) consist, first, of a tendon attached behind, and on the inner side of the head of that bone ; this tendon is extremely strong, especially on the inside, opposite a process existing on the fibula for its attachment ; it is prolonged within the substance, Snd along the anterior surface of the muscle : and, secondly, of some tendinous fibres attached to the upper half of the external border of the fibula, and the upper third of the posterior surface of the same bone. The tibial origins {i') take place from the oblique line on the posterior surface of the tibia below the popliteus, and from the contiguous portion of the aponeurotic expansion of that muscle ; from an aponeurosis which arises from the middle third of the inner border of the tibia, and is prolonged upon the anterior surface, within the substance of the muscle ; and, lastly, by a few fleshy fibres from a tendinous arch extending between the head of the fibula and the oblique line on the posterior surface of the tibia. From these diflferent origins, the fleshy fibres pass in different directions to the anterior sur- face and edge of an aponeurosis, which covers the posterior surface of the muscle, be- comes narrower and thickened as it proceeds downward, unites with the terminal ten- don of the gastrocnemius about the middle third of the leg, and is soon blended with it to form the tendo Achiljis. * Fourcroy, in his sixth memoir upon the liursce mucosa;, states that the plantaris, whose tendon, according to Albinus, is received into a groove along^ the inner border of the tendo Achillis, is the tensor muscle of the synovial capsule of that tendon. This is an error. THE POPHTEUS. In order to study accurately the structure of the soleus, divide it longitudinally at the aide of tlie raphes or tendinous septum existing in the middle of the lower half of this muscle, and then, by scraping off some of the fleshy fibres, it will be seen that a dense, fibrous septum given off by the terminal aponeurosis, separates the muscle into two equal halves, and forms with that aponeurosis two tendinous semi-cones, in the interior of which the fleshy fibres are received. It will now be understood why Douglas, who had designated the gastrocnemius the two external and superficial heads of the great extensor of the tarsus, should call the soleus the two internal and deep heads of the same muscle There are, in fact, two principal aponeuroses of origin, and two hollow tendons of insei- tion ; each aponeurosis of origin covers almost the entire anterior surface of tlie corre- sponding half of the muscle. Relations. — It is covered by the gastrocnemius, which projects beyond it on both sides, but especially on the inner side, and from which it is separated by the plantaris. It is thickest immediately below the largest part or belly of the inner portion of the gastroc- nemius, and, consequently, it prolongs the swelling of the calf downward. It covers the muscles of the deep layer, viz., the flexor communis digitorum, the flexor proprius polli- cis, and the tibialis posticus ; it also covers the posterior tibial and the fibular vessels and nerves. The Tendo Achillis. — ^The tendo Achillis {I, figs. 129, 130) results from the union of the tendons of the gastrocnemius, plantaris, and soleus. It is formed in the following man- ner : the terminal aponeurosis of the gastrocnemius, shortly after leaving the Ik fy seeiii to ciime off from the linea alba like abdominal ribs. THE ANTERIOR ABDOMINAL APONEUROSIS. 301 sels. In these foramina, round masses of fat are developed, which dilate them, and draw down the peritoneum into them, or are absorbed in consequence of emaciation, and thus open an easy way for the production of hernia of the linea alba. Of all these orifices, the most remarkable is the umbikcal ring, which gives passage to the umbilical vessels in the foetus, but becomes cicatrized after birth, at least in the majority of subjects.* The situation of the umbilicus varies at different ages. The middle point of the length of the body is situated above the umbilicus before the sixth month of foetal existence, and corresponds with it after that period. In the adult it is situated below the umbil- icus. Its situation with regard to the abdomen varies in different individuals. Thus, the umbilical cicatrix, which is generally a little below the middle of the abdomen, is sometimes exactly in the middle. I have even seen it at the/ point of junction of the lower with the upper two thirds. This cicatrix, moreover, is much stronger than the neighbouring parts. Thus, an umbilical hernia, which, in a new-born infant, always occupies the navel itself, in an adult is almost invariably situated a little above the umbilicus. Still it occasionally yields, either in cases of dropsy or of hernia ; and I have records of several instances of hernia in the adult, that have occurred through the umbilical ring. The linea alba is in relation, in front, with the skin, which adheres more closely to it than to the neighbouring parts, especially opposite the umbilicus. In the, male, it is sep- arated from the skin below by th,e suspensory ligament of the penis, which sometimes extends as far as the middle of the space between the pubes and the umbilicus : behind, it is in relation with the peritoneum, separated from it, however, by the remains of the urachus, and by the bladder itself, when that viscus is distended. It is, then, through the linea alba that the bladder is punctured in cases of retention of urine, and that the incision is made in the high operation of lithotomy. The peritoneum does not adhere more closely to the umbilicus than to the other parts of the abdomen, and therefore um- bilical hemiae, like all others, are invariably provided with a proper sac. The upper extremity of the linea alba is attached to the ensiform appendix, a flexible, elastic, cartilaginous body, constituting, as it were, a transitional structure between the sternum and the part we are now describing. The lower extremity corresponds to the symphysis pubis. If we examine the structure of the linea alba, we shall see that it is formed by the in- tersection of the layers of the anterior abdominal aponeuroses. One remarkable circum- stance is, that the intersecting fibres do not stop at the median line, but pass from one side to the other ; so that the tendinous fibres of the external oblique of the right side become the tendinous fibres of the internal oblique of the left ; and, again, that the inter- section occurs not only from side to side, but also from before backward. Below the umbilicus the point of intersection is elevated by some longitudinal fibres, constituting a small and very distinct cord, which appears to form a septum between the recti mus- cles ; it increases in thickness as it proceeds downward from the umbilicus to the sym- physis, and may be easily felt under the skin in emaciated individuals. We may add, that the fibres of the linea alba have no resemblance to the yellow elastic tissue ; they are neither extensible nor elastic, at least in the human subject. Its uses entirely re- fer to its capability of offering resistance. The pyramidales are its tensor muscles. The Four Layers of the Anterior Abdominal Aponeurosis. From each side of the linea alba {a, Jig. 134, a diagram representing a horizontal sec- tion of the abdominal parietes) two fibrous layers proceed Fig. 134. out'vard, one anteriorly, the other posteriorly, to the rec- tus muscle (r). The anterior layer (b), having arrived near the outer bor- der of the muscle, subdivides into two other layers : one superficial, constituting the aponeurosis of the external ob- lique (d) ; the other deep, forming the anterior layer of the aponeurosis of the internal oblique (e). The posterior lay- er (c) is also simple as far as the outer border of the rec- tus, and then separates likewise into two layers : one an- terior, which becomes united with the aponeurosis of the internal oblique (e), and is regarded as the posterior layer of that aponeurosis ; the other posterior, which continues its course outward from the rectus, and forms the aponeu- rosis of the transversaUs muscle (/). We shall describe these different parts in succession. The Aponeurosis of the External Oblique. — This is the most superficial layer, and is )f a quadrilateral figure {a, fig. 109) ; it is broad below, where it corresponds to the in- * Some cases are on record of the persistence of the umbilical vein, and, consequently, of the umbilical ring. I have nariated a case where a sub-cutaneous abdominal vein, prodigiously developed, became continuous with the vena cava, which was also very large. — {Anat. Path., 1. xvi., pi. 6.) APONEUROLOGY. terval between the anterior superior spinous process of the ilium and the linea alba, be- comes narrower immediately above, and again expands at the upper part, but to a less extent than below. It is covered by the skin and the superficial fascia, and it covers the aponeurosis and the anterior portion of the fleshy fibres of the internal oblique. It adheres intimately to the aponeurosis of the internal oblique, as far as the vicinity of the outer border of the rectus, excepting below, where the two fasciae are perfectly distinct, and can be easily separated throughout their entire extent. Its external margin, slightly concave and denticulated, presents irregular prolongations, with which the fleshy fibres become continuous. A line extending from the anterior superior spinous process of the ilium to the extremity of the cartilage of the eighth rib, will indicate with tolerable accuracy the direction of this margin, which appears to be divided into two layers, one superficial, very thin, and continuous with the proper cel- lulo-fibrous sheath of the muscle ; the other deep, and giving origin to fleshy fibres. Its upper margin is narrow, and cannot be exactly defined ; it often gives attachment to some fibres of the pectoralis major. Its lower margin consists of two very distinct portions : one, extending from the ante- rior superior spinous process of the ilium to the spine of the os pubis, is called the fem- oral arch (p p',figs. 136, 137) ; the other, stretching between the spine and the symphy- sis pubis, offers for consideration the pillars and the cutaneous orifice of the inguinal canal (m, figs. 109, 136, 137). The aponeurosis of the external oblique is composed of tendinous fasciculi, directed obliquely downward and inward, like the fleshy fibres with which they are continuous. It is also perforated, especially in the neighbourhood of the linea alba, by a considerable number of bloodvessels and nerves. Not unfrequently the component fasciculi have between them, especially near the femoral arch, linear or triangular spaces of variable size, through which the fibres of the internal oblique are visible. The component fas- ciculi are also intersected at right angles, and, as it were, bound down by other tendi- nous fibres, which are more or less developed in different individuals, and are most usu- ally situated in the neighbourhood of the femoral arch. Having made these preliminary observations, we shall now describe in detail, 1. The lower margin of the aponeurosis of the external oblique, or the femoral arch; and, 2. The inguinal ring and canal. Th& Femoral or Crural Arch. — ^When the aponeurosis of the external oblique has ar- Fig. 136. rived opposite a line extending from the anterior superior spinous pro- cess of the ilium to the spine of the pubes, it suddenly terminates, be- comes thickened, and is reflected (a a', fig. 137) from before back- ward upon itself The reflected border {pp',figs. 136, 137) has been variously denominated the femoral or crural arch, the reflected margin of the teiidon of the external oblique, PouparVs ligament, and the ligament of Fallopius. , This arch, which is stretched like a cord, corresponds to the fold of the groin, and defines the limits of the abdomen and the lower extremity : it forms the ar terior border of a considerable tri- angular space, which is completed by the ilium (I, fig. 136) on the out- side, and by the os pubis (2) behind. This space establishes a communi- cation between the lower extremi- ty and the abdomen, and is occupied (proceeding from without inward) by the psoas and aiacus muscle (» to i), the crural nerve (n), the femoral artery (a) and vein {v), and the pectineus muscle.* The crural arch is directed somewhat obliquely downward and inward ; and as its out- er third is more oblique than the inner two thirds, it describes externally a slight curve, having its concavity directed upward. Its lower or reflected border is continuous with the fascia of the thigh. This adhesion occasions the tension of the arch, as may be shown by cutting the femoral fascia at the point of its junction with the arch : hence the precept of Scarpa, who recommended incisions to be made in this situation, in order to relieve the constriction in femoral hernise. The free margin of the reflected portion of the aponeurosis, of which the femoral arch * This is not represented in the woodcut. ^^ THE CRURAL ARCH. 303 consists, is continued backward into the iliac fascia («') externally ; and internally, into the fascia transversalis (t). Externally near the psoas and iliacus (beyond a', fig. 137), the posterior or reflected portion of the arch is closely blended with its anterior or direct portion, as well as with the iliac fascia and the fascia of the thigh, so that, in this situation, there is a thickening rather than an actual reflection of the aponeurosis. Internally to the psoas and iliacus, however (at a), the direct and reflected portions are perfectly distinct, and form a groove with its concavity upward, which we shall find to assist in the formation of the inguinal canal. These two separate portions of the inner part of the femoral arch require a spe- cial description. The direct portion (part of which is shown turned downward at d, fig. 137) passes on to be attached to the spine of the pubes (p,figs. 136, 137), becoming more and more prominent, so that it can be easily felt under the skin, especially when the thigh is ex- tended upon the pelvis. The reflected portion, externally, is narrow, and, as it were, folded ; but internally it becomes expanded, from its fibres slightly changing their direc- tion, and diverging, so as to be inserted into the spine of the pubes behind the direct portion, and also into the pecten or crest of the pubes. This reflected and expanded portion, described even in the oldest anatomical works, has become celebrated in recent times under the improper name of Gimbernat's ligament {g,fig. 136), from a Spanish surgeon, who pointed out its importance as the seat of stric- ture in femoral hernia. It is triangular in shape ; its anterior margin corresponds to the crural arch ; its posterior margin to the crest of the pubes ; its outer margin is free, con- cave, tense, and sharp, and forms the inner part of the circumference of the crural ring (r). This concavity, against which the protruded intestine becomes strangulated, has obtained for the ligament the name of the falciform ligament or fold.* Its strength is very considerable ; but, occasionally, intervfds are left between its fibres, through which hernial protrusions may take placet From the lower surface of Gimbernat's ligament a fibrous prolongation is given off, which sometimes represents a second arch below the femoral arch, and assists in form- ing the superficial layer of the fascia lata of the thigh. This tendinous expansion has a great effect in rendering the arch tense. We may add, that there is considerable vari- ation in different subjects, both in the strength and development of Gimbernat's liga- ment ; varieties that must have great influence on the position of crural herniae, and on the seat of strangulation in that disease. Behind the femoral arch, on the outer side of Gimbernat's Ugament, is an opening (a to r,fig. 136) or rkig, intended to give passage to the femoral artery (a) and vein (v), and to a great number of lymphatic vessels and glands : this is the crurcU ring.X The sub-peritoneal cellular tissue sometimes acquires great strength opposite this ring, and constitutes what is called the crural septum (situated at r). The form of the crural ring is that of an isosceles triangle, the base of which is very long, and formed by the cniral arch, the inner border by the pectineus, and the outer by the psoas and iliacus muscles. Of the three angles, the internal is rounded, and corre- sponds to the concave margin of Gimbernat's ligament ; the external angle, opposite which the epigastric artery is situated, is very acute, and corresponds to the point at which the femoral arch separates from the iliac fascia ; the posterior angle is very ob- tuse, and corresponds to the ilio-pectineal eminence {d). The femoral vein is in relation with the inner or pectineal border of this triangular space ; the femoral artery with the ilio-pectineal eminence and the outer border. The crural nerve («) lies behind and externally to the artery, being separated from it only by the iliac fascia («')• Crural herniae descend through the inner portion of the crural ring.^ The femoral arch is formed by proper fibres, arising from the anterior superior spinous process of the ilium ; and also by those fibres of the aponeurosis of the external oblique, which, after having arrived at the arch, change their direction, become reflected inward, and are collected together, so as to form a strong and tense cord. The Inguinal Ring and Canal. — On the inner side of the spine of the os pubis, between the spine and the symphysis, the aponeurosis of the external oblique divides into two almost parallel, or at least very slightly diverging, bands, which leave between them an opening for the passage of the spermatic cord in the male, and of the round ligament in the female. This opening is the inguinal ring {m,figs. 109, 136, 137), and the bands which form its limits are called the pillars (o p, figs. 136, 137). The inguinal ring is oval or triangular ; its greatest diameter has the same direction as the fibres of the external obUque, viz., obliquely downward and inward. Its base corresponds to the interval be- * tTnis term is now generally applied (after Bums) to the external margin of the saphenous opening {n,Jig. 137) in the fascia lata.] t M. Laugier has lately recorded a case of hernia through the fibres of Gimbernat's ligament. I have since had an opportunity of seeing, in an old woman at the Salptr^iere, two hernial sacs near each other, one of which protruded through the crural ring, and the other internally to the ring; the necks of these sacs wer« separated by a fibrous band, which appeared to me to be formed by the external fibres of Gimbernat's ligament. X [The term " crural ring," it must be remembered, is limited by British anatomists and surgeons to the small space (r), bounded internally by the free margin of Gimbernat's ligament, and externally by the femora] vein. It is through this space, and therefore through the internal portion only of the " crural ring" of M CrUTcilhier, that crural hemiEB descend.] I) See note, supa. 304 APONEUftOLOGY. Fig. IS". tween the spine and symphysis pubis. Its apex is not always well defined, and is generally truncated by fibres which pass at right angles to its pillars. From the up- per part of the margin of the ring a tendi- nous prolongation is given off, which ac- companies the sper- matic cord in the male, and the round ligament in the fe- male. Of the pillars, one is external or inferior, the other internal or superior. The external pillar (p) is attached, not to the spine of the OS pubis, but into the fore part of the symphysis : this pillar is nothing more than the in- ternal extremity of the direct portion of the femoral arch. Moreover, some anatomists consider Gimbemat's ligament as the reflected portion of the external pillar. The internal pillar (o) is broader than the external, and intersects the corresponding structure of the opposite side in front of the symphysis, not unfrequently some fibres of the right internal pillar intersecting those of the left external pillar. Inguinal Canal or Passage. — The inguinal ring^ {m) is the anterior or cutaneous orifice of an oblique passage, formed in the substance of the lower edge of the inferior parietes of the abdomen opposite the crural arch, and destined to transmit the cord (s) of the spermatic vessels in the male, and the round ligament of the uterus in the female. This passage, which modern writers only have correctly described, has been styled by them the inguinal canal (i c wi). Its length varies from an inch and a half to two inches and a half; it is directed obliquely downward, forward, and inward. The inguinal canal is formed, in reality, by the groove resulting from the reflection backward of the aponeurosis of the external oblique (at a), the posterior border of which groove is continuous with the fascia transversalis, and its anterior border with the apo- neurosis of the external oblique itself We may, then, consider this passage as having an inferior concave wall (at a) formed by the groove of reflection ; an anterior wall, formed by the aponeurosis of the external oblique (shown turned downward at d) ; and a posterior wall, formed by the fascia transversalis (c). There is no superior wall, or, rather, it is sup- plied by the lower margins of the internal oblique (c) and transversalis (/) muscles, which occupy the groove of the crural arch, and receive from it externally numerous points of attachment. Internally the margins of these muscles are separated from the groove by the spermatic cord, or the round ligament. It has been supposed that this canal is lined by a funnel-shaped prolongation of the fascia transversalis. The peritoneal or interrml orifice (t, figs. 110, 137) of the inguinal canal is much less accurately defined than the external, or, rather, its inner border alone is well defined, consisting of a concave fibrous edge fonned by the fascia transversalis, and somewhat analogous to the concave edge of Gimbemat's ligament. The strangulation of the intestine in inguinal hernia sometimes occurs against this edge. The peritoneal orifice of the inguinal canal is closed by the peritoneum, and the epigastric artery runs aloug its inner border. The testicle, which is originally situated within the abdomen, descends through the inguinal canal ; so, also, do those herniae, commonly called oblique inguinal hemis, in order to distinguish them from the direct or internal inguinal herniae. The Anterior Aponeurosis of the Obliquus Internus and Transversalis. — The aponeurosis of the internal oblique commences at the linea alba, and immediately divides in its upper three fourths into two layers, one of which passes in front, and the other behind the rectus (r, fig. 1 34). The lower fourth passes entirely in front of the same muscle without division (as shown in^^. 135). The anterior layer is very closely united with the aponeurosis of the external oblique (at b), from which it can be distinguished only by the direction of its fibres. In some parts there is even a true interlacement between the tendinous fibres of these two muscles ; the lower or undivided portion of the aponeurosis of the internal oblique may, on the contrary, be easily separated from that of the external oblique. The posterior layer of the aponeurosis of the internal oblique is no less intimately blended with that of the transversalis (at c), from which, also, it is to be distinguished by the direction of its fibres only. At the outer border of the rectus muscle the anterior layer of the apo- THE FASCIA TRANSVERSALIS, ETC. 305 aeuroFis of the internal oblique separates from that of the external oblique, and the pos- terior .ayer from that of the transversalis, and then immediately unite together, and give origin to the fleshy fibres. The outer margin, therefore, of the aponeurosis of the internal oblique exactly corresponds to the outer border of the rectus, and is directed vertically. The aponeurosis of the transversalis (/, Jigs. 134, 135) is the deepest layer of the an- terior abdominal aponeurosis : it is very narrow above, increases in breadth as far down as opposite the crest of the ilium, and then progressively diminishes towards its lower portion. It commences at the linea alba, and is divided into two portions : one inferior (below s,Jig. 110), consisting only of the lower fourth of the aponeuroses, and passing in front of the rectus (as in Jig. 135) ; the other superior (above s, Jig. 110), which passes behind the rectus (as in^^. 134), and is formed by the upper three fourths of the apo- neurosis. Its external margin is convex, and gives origin to the fleshy fibres of the muscle. Its anterior surface is closely united to the aponeurosis of the internal oblique, beyond which it passes on the outside : its posterior surface is loosely connected with the peritoneum, excepting in its lower fourth, which, as already stated, passes in front of the rectus muscle. The tendinous fibres of the transversalis, which have the same direction as its fleshy fibres, are occasionally found not to terminate abruptly behind the lower part of the rectus ; but the aponeurosis merely becomes thinner, and its fasciculi separated from each other. The Fascia Transversalis and Sub-peritoneal Aponeurosis, In order to complete the description of t"he anterior abdominal aponeurosis, it only re mains for me to describe the fascia transversalis, which I regard as a thickened portion of the sub-peritoneal fascia. The fascia transversalis (seen at a' and c,Jig. 137) was first pointed out by Sir Astley Cooper, but has been more correctly described by Lawrence and J. Cloquet : it com- mences below at the reflected border (a a') of the crural arch, so that it may be regard- ed as a thin prolongation of the reflected portion of the tendon of the external oblique. It also frequently arises from the brim of the pelvis, as well as from the crural arch. From these points it passes upward, becoming more and more attenuated as it approach es the umbilicus, at which point it cannot be distinguished from the sub-peritoneal apo- neurosis. The fascia transversalis is situated between the abdominal muscles and the peri- toneum. Its internal margin is continuous with the outer border of the rectus muscle ; and its external margin, which gradually becomes thinner, is blended with the sub-peri- toneal aponeurosis. The only part deserving a special description is that portion which lies between the outer border of the rectus muscle and the abdominal opening of the in- guinal canal. In this situation it assists in strengthening the parietes of the abdomen, which are here remarkably weak ; and it is to the existence of this fascia that we may attribute the extreme rarity of direct inguinal hemiae*, which, in fact, can only result from a congenital weakness, or a relaxation of this fascia. A very interesting portion of the fascia transversalis is an infundibuliform prolonga- tion, given off from it to the spermatic cord. It is impossible, indeed, to conceive the descent of the testicle to occur without its pushing before it a portion of the fascia, which then constitutes the immediate investment of the cord upon which the cremaster muscle {b,Jig. 137) is spread out. The peritoneal orifice of the inguinal canal is, there- fore, the superior opening of the infundibuliform process, furnished by the fascia trans- versalis to the testicle and its cord. The Sub-peritoneal Aponeurosis. The peritoneum, throughout the whole extent of the abdominal parietes, is strength- ened on its outer surface by a very thin tendinous layer, the existence of which may serve to explain why abscesses, formed in the parietes of the abdomen, so seldom open into the cavity of the peritoneimi ; and, on the other hand, why collections within the peritoneal cavity so seldom open externally. The Posterior Abdominal Aponeurosis. The posterior abdominal aponeurosis is much smaller and of less importance than the anterior : it consists of three layers, one anterior (Ji, in diagram,/^. 134), and very thin, which commences at the base of the transverse processes of the lumbar vertebrae, and passes in front of the quadratus lumborum {q) ; another, middle («), and much stronger, commencing at the summits of the same transverse processes, and passing behind the quadratus lumborum ; and a third, posterior (k), which arises from the summits of the lumbar spinous processes, and passes behind the sacro-lumbalis, longissimus dorsi, and transverso-spinalis muscles («). This last-mentioned layer is connected both with the internal oblique (e) and with the transversalis muscle (/), and is blended with the apo- neuroses of the serratus posticus inferior, and of the latissimus dorsi (/). The two an- * [/. e., herniiE occurring directty downward and forward throagh the inguinal ring {.rn,jig. J 37), and not descending along the inguinal canal.l Qq 306 APONEUROLOGY. terior layers are connected with the transversalis only. The posterior abdominal apo- neurosis has, therefore, nearly the same relation to the quadratus lumborum and the common mass of the sacro-lumbalis, longissimus dorsi, and transverso-spinalis muscles, that the anterior aponeurosis has to the rectus muscle. The Lumho-iliac Aponeurosis. The lumbo-iliac aponeurosis, or fascia iliaca of modem authors, forms the tendinous sheaths of the abdominal portion of the psoas and ihacus muscles, and is, therefore, bi- furcated at its upper part. That portion which invests the psoas commences at the ten dinous arch of the diaphragm, already described as embracing the upper end of this mus- cle. The iliac portion arises from the whole extent of the inner border of the crest of the ilium. The circumflex ilii artery is situated in the substance of this iliac portion, at its origin. The internal margin of the fascia iliaca is attached to the sides of the lumbar vertebrae, and, lower down, to the brim of the pelvis ; it is arranged in arches, which give passage to the lumbar vessels and to the nervous cords, establishing a communica- tion between the lumbar plexus and the lumbar ganglia of the sympathetic nerve. The centre of each arch is opposite to the groove on one of the bodies of the lumbar verte- brae, the intervals between the arches corresponding with the intervertebral substance. The largest arch extends from the last lumbar vertebra to the brim of the pelvis, and is opposite to the base of the sacrum. The obturator and lumbo-sacral nerves pass under it. Opposite the femoral arch, the fascia iliaca adheres intimately to the outer part of Poupart's ligament ; but towards the median line it separates from that ligament, passes behind the femoral vessels, and forms the posterior half {s,Jig. 136) of the crural ring. Below the femoral arch, the fascia is prolonged upon the thigh ; on the outside («') it completes the sheath of the psoas and iliacus, accompanies them as far as the lessei trochanter, and becomes continuous with the iliac portion {g, fig. 137) of the femoral fascia ; on the inside, it forms the posterior wall (s, fig. 136) of the canal for the femoral vessels, and forms the deep layer or pubic portion {h,fig. 137) of the femoral fascia. Relations. — It lies beneath the peritoneum, to which it is united by a very loose cellu- lar tissue ; it covers the psoas and iliacus, but is not adherent to them, in consequence of the interposition of some equally delicate cellular tissue. All the nerves from the lumbar plexus are subjacent to this fascia, excepting one very small cord, which perfo- rates it at the side of the sacrum, and becomes situated in the sub-peritoneal cellulai tissue. The femoral vessels are situated on the inner side of the fascia, and are separ- ated by it from the crural nerve, which lies on its outer side, and underneath it. Structure. — The upper part of the fascia is extremely thin, but it increases in thick- ness as it approaches the femoral arch. It is formed of well-marked transverse fasci- culi, intersected perpendicularly by the tendon of the psoas parvus, when that muscle exists. This tendon is blended with the fascia, and is distinguished from it only by the different direction of its fibres ; it is inserted by spreading out, at the side of the pelvic brim, into a tendinous arch which lines this brim, and with which the psoas parvus and the iliac fascia are continuous above, and the pelvic fascia below. Few aponeuroses are more deserving the attention of anatomists than this, on account of the practical consequences resulting from its arrangement. In fact, notwithstanding its tenuity, it forms a boundary between the sub-peritoneal and sub-aponeurotic cellular tissue, which is very rarely passed by inflammatory action. When inflammation termi- nates in suppuration, the pus, whether it be beneath the peritoneum or beneath this fas- cia, descends towards the femoral arch ; but if the inflammation be sub-peritoneal, the femoral vessels lie behind the purulent collection ; and should it be sub-aponeurotic, the vessels will be in front of it. The latter is especially the case in abscesses following caries of the vertebrae. The Aponeuroses of the Pelvis. The aponeuroses of the pelvis should be distinguished into the pelvic, properly so called, and the perineal : the former constitute essential parts of the pelvis, and are deeply seat- ed. The others belong to that part of the floor of the pelvis which is called the perineum. I shall commence with the description of the latter. The Aponeuroses of the Perineum. These are two in number ; one superficial, the other deep. The Superficial Perineal Fascia.* Dissection. — Remove tne sub-cutaneous adipose tissue very cautiously, layer by layer, commencing the dissection along the edges of the pubic arch. This aponeurosis (which is very distinct from the fibrous laminae, intercepting spaces filled by fat, and forming what is called the fascia superficialis) is of a triangular shape, and consists of well-marked transverse fibres. The outer margin of each half of the fas- cia is attached to the descending ramus of the os pubis and the ascending ramus of the ischium : its inner margin is lost at the raphe, along the median line : its posterior maX' * M Bouvier, in his thesis, and M. Blandin, in his Traiie d'Anaiomie Chirurgicale, first described this fascia THE DEEP PERINEAL APONEUROSIS. 807 Fig. 138. ^a IS bounded by a line extending from the tuberosity of the ischium to the anus ; it cor- responds with the posterior edge of the transversus perinei muscle, and appears to be reflected behind it, so as to line the corresponding perineal or ischio-rectal fossa.* Relations. — It is covered by a prolongation of the dartos, to a greater extent in the me- dian line than on each side ; also by the sub-cutaneous adipose tissue, which is thicker behind than in front, and by the sphincter ani, above which it terminates in the median line : it covers the transversus, the bulbo-cavernosus, and the ischio-cavernosus mus- cles, the fibrous sheaths of which may even be regarded a^ a prolongation of this aponeu- rosis. It also covers the superficial perineal vessels and nerves, which are sometimes lodged within its substance. The existence of this membrane explains why, in cases of perforation of the urethra, the urine is infiltrated forward, and very rarely backward. The Deep Perineal Aponeurosis. Dissection. — Remove with great care the ischio- and bulbo-cavernosus and the trans- versus perinei muscles. This aponeurosis, which was well described by M. Carcassone under the name ofpe. rineal ligament, and called by modern writers the middle pe- rineal fascia, appears to me perfectly distinct from the aponeuroses of the pelvis. It is an extremely strong trian- gular layer {b a, fig. 138t), oc- cupying the pubic arch, and apparently forming a continu- ation of the sub-pubic ligament (jb). It is vertical near the arch, as far as the ball of the urethra, below which it be- comes horizontal, or, rather, oblique, from before back- ward. Its lateral margins are attached to the descending ra- mi of the ossa pubis, and the ascending rami of the ischia {d, d), above the attachment of the ischio-cavernosi muscles. Its posterior margin becomes blended with the posterior margin of the superficial perineal fascia, behind the transversi muscles, in front of the perineal fossse, of which it forms the anterior boundary. Relations. — Its lower surface is in relation with the ischio- and bulbo-cavernosus mus- cles, and gives off, in the median line, a fibrous septum, which passes between these muscles, and affords them points of attachment. Its upper surface is in relation with the artery or arteries (e e) of the bulb, which are sometimes contained within its sub- stance : it is also in contact with a very remarkable plexus of large veins, with which it is very closely united, so that, when divided, they remain open : these veins are also fre- quently enclosed within its substance. It is also in relation with the levator ani. There constantly exists another transverse muscle, very distinct from the transversus perinei generally described, which is situated farther behind. This muscle (transversus perinei alter. Alb.) is applied to the lower surface of the perineal fascia, and passes trans- versely inward to the bulbous portion of the urethra. The deep fascia of the perineum is perforated (at c) by the posterior part of the bulb of the urethra, or, rather, by the point of union (c, fig. 181) between its bulbous and membranous portions : it gives off prolongations upon the sides of the bulb, and serves to support the membranous portion of the urethra : whence the name, triangular liga- ment of the urethra, given to it by CoUes. It is also perforated, beneath the arch of the pubes, by a great number of veins, and by some arteries. Uses. — This remarkable aponeurosis evidently supports the canal of the urethra. It has been correctly regarded as an obstacle to the introduction of the catheter, the point of which strikes against it, however slightly it may deviate from the direction of the ca- nal. The prostate gland is situated above it. The Pelvic Jlponeuroses. From the sides of the pelvis, and from the entire circumference of the brim (which, as * Sec note, p. 309. t [The triangular liganfient consists of two layers, which approach each other more ne.irly above tliati below . m^g- 138, the anterior layer has been removed. Between the two layers are situated the sub-pubic ligamoa (A), perforated by the vena dorsales penis, the pudic arteries (//), the arteries of the bulb (e e), the g^eat part of the membranous portion of the urethra, with its comjjressor muscle, to be described hertaftiir, an. lastly, Cowper's glands (g g). In the female, the triingular ligament is perforated by the vagina, as wel bv the urethra.] 308 APONEUROLOGY. we have seen, is covered and rendered smooth by a thick layer of fibrous tissue, that forms a hmit to the lumbo-iliac aponeurosis), a tendinous lamina is given off, which pass- es into and lines the pelvis, and is soon divided into two distinct layers : one external, the lateral pelvic or obturator fascia, which continues to line the sides of the pelvis, and covers the obturator intemus muscle ; the other internal, or superior, which passes in- ward upon the side of the prostate gland, bladder, and rectum, in the male, and of the bladder, vagina, and rectum, in the female, in order to form the floor of the pelvis. This IS the superior pelvic aponeurosis, with the description of which we shall commence. The Superior Pelvic Aponeurosis, or Recto-vesical Fascia. Dissection. — This aponeurosis must be studied both from the cavity of the pelvis and from the perineum. It is exposed in the pelvis by removing the peritoneum, and the loose cellular tissue beneath that membrane : this should be done without any cutting instiument. To view this fascia from the perineum, it is necessary to take away the adipose tissue that occupies the perineal fossae, and also the levator ani muscle. The superior pelvic aponeurosis forms a complete floor for the pelvis. Anteriorly it is remarkable for its strength and shortness ; in fact, it does not reach the inlet in this sit- uation, but arises on each side from the symphysis pubis, presenting the appearance of bands or columns, which are more or less separated from each other, and become at- tached to the front of the neck of the bladder, whence the name of anterior ligament of the bladder, which the older anatomists gave to this part of the aponeurosis. More exter- nally, it forms a strong arch (the sub-pubic arch), which completes the posterior orifice of the obturator or sub-pubic canal (i, fig. 48). This arch is not unfrequently double, and then one of the foramina gives passage to vessels, and the other to nerves. Still more externally, it is attached to the brim of the pelvis, in the manner I have al- ready pointed out. Posteriorly it is extremely thin, passes in front of the sciatic plexus, and is lost upon the sacrum. Sometimes it appears to be divided into two lamina, the posterior of which passes in front of the sciatic plexus, and the anterior in front of the internal ihac vessels, to which it would seem to furnish sheaths. Relations. — Its upper surface is concave, and connected with the peritoneum by loose cellular tissue, containing more or less fat. Its lower surface is convex, and covered by the levator ani : it forms part of the great perineal excavation, and is in relation with the pjTiformis and obturator intemus mucles, with the sacral plexus, &c. This aponeurosis is perforated by a great number of openings : in the male it is pierced by the prostate {i,fiff. 181) and the bladder (h), on the sides of which it is prolonged, and reflected on to the rectum, whence the name of the recto-vesical aponeurosis, given to it by M. Carcassone. In the female it is also perforated by the vagina. On each side of the bladder and prostate it is strengthened by two tendinous bands, which run from before backward. These are sometimes very strong ; they extend from the symphysis pubis (6) to the spine of the ischium (e), pass along the bladder and the prostate, and are re- flected upon their sides. In front, it has some openings for the vesical and prostatic vessels. Behind it presents a considerable opening, which corresponds to the outlet of the pel- vis, and gives passage to the lumbo-sacral nerve and the gluteal vessels. The extrem- ity of the arch formed by it corresponds to the anterior border of the sciatic notch. It is through this opening that sciatic herniae protrude. We not uncommonly find larger or smaller openings in this fascia, of an oblong or cir- cular shape, leading into conical culs-de-sac, which are filled with fat. Lastly, it is per- forated behind by the ischiatic and internal pudic vessels. It does not appear to be in- tended for the passage of the vessels which are distributed in the interior of the pelvis, for it seems to invest these in fibrous sheaths. Uses. — The superior pelvic aponeurosis forms the floor of the pelvis ; it is pushed downward by the action of the diaphragm and abdominal muscles, and tends to prevent the occurrence of perineal herniae, which otherwise would be extremely common : it forms a boundary between the sub-peritoneal and the perineal cellular tissue, and also limits the progress of inflammation and infiltrations. Infiltration of urine above the fas- cia can only be caused by rupture of the bladder itself The prostate {i,fig. 181) is al- most entirely below the fascia, and therefore, in the lateral operation for stone, in which this gland is the principal structure to be divided, inflammation and infiltration of the cellular tissue are extremely rare. When they do occur, the section or laceration must have been prolonged into the body of the bladder. The Lateral Pelvic Aponeurosis, or Fascia of the Obturator Muscle. Dissection. — ^This aponeurosis is more advantageously studied, at least in its most impor- tant part, from the perineum, than from the cavity of the pelvis : it is exposed on either side by removing the adipose tissue, which fills up the perineal fossa. This aponeurosis, which is quite distinct from the obturator ligament, commences at the upper part of the circumference of the obturator foramen, and at the brim of the pelvis, in connexion with THE FEMORAL APONEUROSIS. 30P the superior pelvic aponeurosis, which it soon leaves, and is applied to the obturator in- temus muscle : it then unites below with the reflected portion of the great sacro-sciatic ligament, and is prolonged upon that portion of the anterior surface of the glutaeus max- imus which projects beyond the ligament, and also upon the coccygeus muscle. Relations. — On the inner side and above, it is only separated from the superior pelvic aponeurosis by the levator ani, which is applied to that aponeurosis ; lower down, the two aponeuroses are separated by a considerable interval, which is occupied by fat : this interval forms the perineal fossa. On the outside it is in contact with the obturator in- ternus, and lower down with the internal pudic vessels and nerves. Uses. — It binds down the obturator internus muscle, and protects the internal pudic vessels and nerves, which are, therefore, rarely cut in operations in the perineum. It forms the external boundary of the perineal fossa. TTie Perineal Fosscb. — Situated between the superior pelvic aponeurosis (which is lined below by the levator ani) and the lateral pelvic aponeurosis, there is found on each side of the anus a conical space, the base of which is directed downward, and corresponds to the skin : it is formed behind by the lower border of the glutaeus maximus ; in front, by the transversus perinei muscle ; on the inside, by the levator ani and the superior pel- vic aponeurosis ; and on the outside, by the tuberosity of the ischium.* Each of these fossae is filled by a large quantity of fat, and traversed by fibrous laminae, some of which extend vertically from the apex to the base, and divide the contained adipose ceUular tissue into several distinct portions. When an abscess occurs in either of these fossae, it may be easily conceived how difficult it is for the inner surface of its parietes to come into opposition : hence the pathology of fistulae, and the modes of cure which are adopted. The Aponeuroses of the Lower Extremity. The aponeuroses of the lower extremity comprise the femoral fascia ; the fascia of the leg ; the annular ligaments, which bind down the tendons of the muscles of the leg, as they are passing upon the dorsal or plantar surface of the foot ; the plantar and dorsal fascia of the foot ; and, lastly, the fibrous sheaths, which maintain the tendons in con- tact with the phalanges of the toes. We shall describe these in succession. The Femoral Aponeurosis, or Fascia Lata. After the remarks which we have already made upon the aponeuroses generally, it may be easily conceived that the muscles of the thigh, which are so numerous, of such great length, and so loOsely united together, and almost all of which are reflected to a greater or less amount over the knee, require to be kept in close contact with each oth- er and with the bones ; hence the necessity for the femoral' aponeurosis, consisting of a large fibrous sheath, that confines without compressing the muscles, and the strength of which is directly proportioned to the force of the muscles, and their tendency to dis- placement. Its superficial or sub-cutaneous surface {g h,fig. 137) is separated from the skin by a very thin fibrous layer, the fascia superficialis (not shown in fig. 137), which can be more easily demonstrated immediately below the femoral arch, and along the sa- phenous vein. Between the femoral aponeurosis or fascia lata and this superficial fas- cia, which results from the union of the fibrous prolongations given off by the deep sur- face of the skin, the sub-cutaneous vessels and nerves take their course, and communi- cate with the deep vessels and nerves, either by simple openings or by fibrous canals, of variable length. Under this fascia, also, are situated the superficial lymphatic vessels and glands of the groin. A great number of the superficial nerves of the thigh have special sheaths, which are hollowed out, as it were, in the substance of this aponeurosis. The femoral aponeurosis is perforated with a great number of foramina opposite the femoral vessels, from Poupart's ligament to the entrance of the vena saphena {x) into the femoral vein (y). These foramina, which occupy a triangular space, of which the base is above and the apex below, are intended for the ' passage of a great number of lymphatic vessels, which pass through it to join the deep set. This has been called the sieve-like portion of the fascia lata, or the fascia cribriformis (v) : it has been said by some, that the aponeurosis is altogether wanting in this situation.! We not unfrequently find a lymphatic gland occupying one of the foramina. * [These spaces are the ischio-recial fossie of Velpeau ; they are described by him as if lined by an aponeu- rosis (the ischio-rectal) composed of two layers, one external or ischiatic, corresponding to the lateral pelvic aponeurosis of M. Cruveilhier, and another internal or rectal, which covers the lower surface of the levator ani from the coccyx to the posterior border of the transversus perinei, and unites with the other layer before, above, and behind. This latter layer is very thin, and continuous with the united margins of the superficial perineal fascia and the triangular ligament, behind the transverse muscle, and is alluded to by M. Cruveilhier (p. 307) as a reflection of the superficial fascia. 1 t [And then the cribriform fascia is regarded, not as belonging to the fascia lata, but as formed by a deep layer of the superficial fascia, situated beneath the sub-cutaneous vessels, adherent to the borders of the saphe- nous opening in the fascia lata, and perforated by those vessels. The saphenous opening is, according to this view, not the foramen (t) through which that vein passes, but the aperture (n) left between the iliac (g) and pubic (A) portions of the fascia lata, and is bounded externally by the crescentic margin of the iliac portion or the falciform process of Bums (see the left side of Jiff. 137, where the cribriform fascia has been enlirelj removed).] 310 APONEUROLOGY. The most remarkable of all these openings is undoubtedly that (i) for the vena saphena interna, where that vessel enters the femoral vein, at the upper part of the thigh, eight or ten lines below Poupart's ligament. The margin of this opening, which has been improperly called the inferior orifice of the crural canal, can only be demonstrated in its low- er half, on account of the almost complete absence of the aponeurosis above it : this is the reason of the semilunar form of the portion of the fascia over which the vein passes. The deep surface of the fascia lata gives off a great number of prolongations, which pass between the muscles, and form their proper investments or sheaths. The largest of these prolongations form two lateral septa, called the inter-muscular sep- ta, which extend from the fascia to the linea aspera ; each has the form of a triangle, having its base directed downward and its apex upward ; they are extremely thick, es- pecially below. The Inter-muscular Septa of the Femoral Aponeurosis. Of these there are two, one internal and the other external. The Internal Inter-muscular Septum. — This serves at once as a septum, an aponeurosis of insertion, and a sheath for the vastus intemus : it extends from the anterior inter- trochanteric line to the inner condyle of the femur. Its anterior surface affords attachments to the vastus intemus throughout its whole extent : its posterior surface is in opposition with the adductors, and is intimately uni- ted to their aponeuroses. Its outer margin is attached to the Unea aspera : its inner margin is very thick, and prominent below, where it is strengthened by the inferior ten- don of the adductor magnus, and may be felt under the skin like a cord. It appears to become continuous below with the internal later£il ligament of the knee. It is composed of very strong vertical fasciculi, passing somewhat obliquely down- ward and inward. These fasciculi are bound together above the inner condyle by oth- ers passing transversely, and are crossed almost at right angles by the tendinous fibres of the adductors. Lastly, the internal septimi is perforated, near the linea aspera, by a number of orifices destined for the passage of vessels, and forming communications between the anterior and the internal sheath of the muscles of the thigh. The External Inter-muscular Septum. — This serves as a septum, an aponeurosis of in sertion, and as a sheath for the vastus extemus. It extends from the great trochanter to the external condyle, above which it forms a projecting cord : it affords attachments to the vastus extemus in front, and to the short head of the biceps behind. . Its inner margin is attached to the linea aspera : its outer margin forms a prominent cord, especially below. It consists of fibres directed vertically, or somewhat obliquely outward, and strength- ened by transverse fibres above the condyle. Like the internal septum, it is perforated, especially above and below : above, for the passage of the circumflex vessels ; below, for the passage of the articular vessels of the knee. We shall now examine the different sheaths fiirnished by the femoral aponeurosis. One of the most important of these is, as it were, hollowed out of the sides of the others, and belongs to the femoral vessels. The Sheath of the Femoral Vessels. The femoral artery (z,fig. 137) and vein (y) are enclosed in a prismatic and triangular tendinous canal, which protects them in their course amid the muscles of the thigh. The portion of the canal (laid open in fig. 137) included between the femoral arch and the point where the vena saphena opens into the femoral vein, has received the name of the crural canal, a term to which I have always objected, since it was first introduced into anatomical nomenclature, because it establishes a false analogy between the ingui- nal canal and this upper portion of the sheath of the femoral vessels ; for, while an oblique inguinal hernia traverses the entire length of the inguinal canal, crural herniae, as far, at least, as my own observation extends, never protrude through the saphenous opening, but escape inunediately below the femoral arch, and lift up the cribriform por- tion of the fascia lata.* The anterior wall of the sheath of the femoral vessels is formed above by the cribri- form portion of the femoral fascia (g',fig. 137), then by the fascia itself, and, lastly, by the posterior layer of the sheath of the sartorius, in which place it is thin and transparent. Tlie internal wall is formed above by the very strong layer covering the pectineus ; be- low, by the weaker layer investing the adductors. The external wall consists of the very strong sheath {s',fig: 136) of the psoas and ilia- cus : externally to this wall is situated the crural nerve, a branch of which perforates * [The tenn "crural ring" is, in this country, commonly limited to the space (r,fig. 136) situated internal- ly to the femoral vein. By the term " crural canal" is generally understood that portion only of the canal de- scribed by M. Cruveilhier as the " craral canal," which is situated on the inner side of the femoral vein, and is occupied by cellular tissue, lymphatic vessels, and sometimes by a lymphatic gland. If the term crural ca- nal be thus defined, if the cribriform fascia be regarded as a part of the superficial fascia, and the saphenous aperture as the space between the iliac and pubic portions of the fascia lata (see note, p. 309), the analogy be- tween the crural and inguinal canals will not be so very remote.] THE FEMORAL APONEUROSIS. 81 J the sheath and joins the vessels. Lower down, the external wall is formed by the apo neurosis of the vastus internus. The three great Muscular Sheaths of the Femoral Aponeurosis. By means of the internal and external inter-muscular septa, the muscles of the ante- rior region of the thigh are separated from those of the posterior and internal regions ; a weaker septum than the preceding intervenes between the muscles of the internal and posterior regions. It foUows, then, that the femoral aponeurosis presents three great tendinous sheaths : an anterior, an internal, and a posterior. The great posterior sheath is undivided : it is common to the biceps, the semi-tendino- sus, and the semi-membranosus. The great anterior and internal sheaths are subdivided into a number of secondary uheaths, in most cases corresponding with the number of the muscles. The great Anterior Sheath. — The sartorius has a proper sheath, remarkable for its pris- matic and triangular form. The rectus femoris, or long head of the triceps, is separated from the two vasti by a tendinous layer, very thin below, but strong above, and com- posed of vertical fibres. The tensor vaginae femoris is contained in the strongest sheath in the human body, for it is formed by the fascia lata itself The deep layer of this sheath is much thinner than the superficial ; it commences at the anterior inferior spinous process of the ilium, below the rectus, and may be regarded eis the deep origin of the ^road band in which the tensor vaginae femoris terminates : it is composed of verticed fibres, prolonged be- tween the rectus and the vastus externus. Lastly, above and on the outside, we find the sheath of the psoas and iliacus {s',fig. 136), which forms a continuation of the lum- bo-iliac aponeurosis, or fascia iliaca. The great internal sheath furnishes a number of tendinous lamellae, which separate the different muscles of this region. Thus, there is a proper sheath for the gracilis, a com- mon one for the pectineus and the adductor longus, one for the adductor brevis, and an- other for the adductor magnus. The sheath of the obturator externus is continuous with that of the adductor brevis ; it commences by a very strong fibrous lamina or arch, which arises from the anterior edge of the pubes, and is directed obhquely outward to the fibrous capsule of the hip-joint. This arch conceals the anterior orifice of the obtu- rator canal, and protects the obturator vessels and nerves. Lastly, the two vasti, which extend into all the regions of the thigh, have sheaths formed by the femoral fascia, where they are superficial, and by the internal and exter- nal inter-muscular septa, and the posterior laminae of the other sheaths in their more deeply-situated portions. In the midst of the sheaths of the anterior and internal regions we find the sheath of the femoral vessels already described. The Superior Circumference of the Femxiral Aponeurosis. In front the femoral aponeurosis arises from the femoral arch, with which it is so pei- fectly continuous as to render the arch tense : hence the plan, already mentioned as proposed by Scarpa, of endeavouring to remove the constriction in cases of strangulated crural hernia, by puncturing the femoral aponeurosis. But the mode of origin and continuity of this fascia with the femoral arch is not the same on the inner and outer sides. On the outside, the iliac portion of the femoral apo neurosis (g, fig. 137) arises by a single very thick layer ; more internally, in the situation of the femoral vessels, it arises by two layers, one superficial, thin, and perforated by foramina (the cribriform portion, v) ; the other deep, called its pubic portion (A), which is continuous with the fascia iUaca (s,fig. 136), covers the pectineus, and sends off a pro- longation between that muscle and the psoas. This deep layer forms the posterior wall of the canal of the femoral vessels. On the inside of the thigh, the femoral aponeurosis arises from the body of the os pu- bis and the ascending ramus of the ischium. On the outside and behind, it arises from the crest of the ilium by very numerous ver- tical fibres, which are strengthened, especially behind, by other horizontal fibres. Be- tween the posterior superior spine of the ilium and the crest of the sacrum there is a tendinous arch, which is common to the femoral fascia and the aponeurosis of the long muscles of the back. The Glutceal Aponeurosis. The glutaeal aponeurosis forms the upper and back part of the femoral fascia. It cov- ers the glutaeus medius, in which situation it is extremely thick, and is continuous with the broad band of the tensor vaginae femoris. Having reached the upper border of the glutaeus maximus, it is divided into two layers : one superficial and very thin, which covers the outer surface of the gluta;us maximus, becomes thinner below, and continu- ous with the femoral fascia ; the other deep and thicker, especially above and behind, where it affords attachment to the glutaeus maximus, and is blended with the great sa- cro-sciatic ligament. It becomes ver}' thin whe: e it separates the gluta3us maxirau? 312 APONEUROLOGY. from the deep-seated muscles. A synovial capsule intervenes between this fascia and the great trochanter, and another between it and the tuberosity of the ischium. It presents a very remarkable opening called the glutaal arch, for the passage of the glutseal vessels and nerves. Lastly, over that portion of the glutaeus maximus which enters into the formation of the corresponding perineal fossa, it acquires a great degree of thickness, and, at the lower border of the muscle, is blended with the superficial layer of the gluteal fascia. The Inferior Circumference of the Femoral Aponeurosis. The femoral aponeurosis terminates below, around the knee-joint, where it becomes continuous, partly with the fascia of the leg, and partly with the fibrous structures cov- ering this articulation. Concerning the arrangement of these fibrous laminae we shall offer a few remarks. Behind, the femoral aponeurosis passes over the popliteal space, and is continuous with the fascia of the leg. In front, it is prolonged over the patella, from which it is separated by a synovial bur- sa; it is very thin, and is continued in front of the ligament of the patella, upon which it forms a thin layer of transverse fibres. 071 the inside, it is at first blended with the sheath of the sartorius, and then with the horizontal portion of the tendon of this muscle ; it crosses the fibres of that portion per- pendicularly, and becomes continuous with the fascia of the leg. Under this layer of fibrous tissue we find, on the inside of the knee, another very dense layer, formed by vertical tendinous fibres derived from the vastus internus, and inserted into the upper part of the inner surface of the tibia, beneath the tendon of the sartorius. This fibrous layer, which may be regarded as the lower or tibial insertion of the vastus extemus, occupies the interval between the internal lateral ligament of the knee-joint and the patella. Its vertical fibres are crossed by others at right angles, extending from tne internal tuberosity of the femur to the corresponding margin of the patella. Lastly, under this we find another very thin layer, belonging to the synovial capsule. On the outside, the femoral aponeurosis is blended with the broad band of the tensor vaginae femoris, from which it can be distinguished only by the horizontal direction of its fibres. Beneath this very thick layer we find a thin one, composed of fibres stretching from the external tuberosity of the femur to the patella ; and, lastly, another thin layer be- longing to the synovial membrane. Structure of the Femoral Aponeurosis. It is thin behind and on the inside, thicker in front, and extremely thick on the out- side of the thigh, where, indeed, it may be said to exceed all other fibrous membranes in thickness and in strength. This thickened portion is bounded in front by a line extend- ing vertically downward from the anterior superior spinous process of the ilium. Its lim- its behind are no less distinctly defined ; hence the name given to it of the broad hand {fascia lata). This great density is owing to some very strong vertical fibres, arising from the front of the crest of the ilium. It is connected with the great force and tendency to displace- ment of the vastus externus. We may add, that the femoral aponeurosis is composed of horizontal fibres, sometimes regularly parallel, as in its thinnest portions, and sometimes intersecting each other. These horizontal fibres are even seen opposite the broad band on the outer side, from which they are distinguished by their direction. There is a very beautiful preparation of this aponeurosis in the Museum of the Facul- ty of Medicine : similar preparations should be made by those who wish to obtain a good idea of the tendinous sheaths, and the shape of the muscles of the thigh. It is to be made by removing all the muscles from their sheaths by means of longitudinal incisions, and substituting for them a quantity of tow, which must be taken out when the aponeu- roses are completely dried. The form of the sheaths exactly represents that of the cor- responding muscles. A tolerably accurate idea of these sheaths may also be obtained by cutting across each sheath and the muscle which it contains, in a fresh subject. The circumference of the section of the portion of the sheath that becomes visible after the retraction of the muscle will give an excellent idea of the figure of the different sheaths, which are all angular and polyhedral like the muscles, but never rounded : during health they are completely filled by the muscles, which in emaciated persons, on the contrary, do not occupy more than a half, a third, or a sixth of the area of their sheaths. Such is the femoral fascia. Its tensor muscles consist of the tensor vaginae femoris and the glutaeus maximus, the tendon of which is received between two layers of this fascia. Aponeuroses of the Leg and Foot. Aponeurosis of the Leg. The aponeurosis of the leg forms a strong general investment for the whole leg, except- ANNULAR LIGAMENTS OF THE TARSUS. 313 mg the internal surface of the tibia, which is covered by it only at its lower part, a little above the malleoli. Its external surface is separated from the skin by the superficial vessels and nerves, several of which perforate it, either directly, or after having run for a short distance in its substance. The external saphenous vein and nerve receive from it a complete sheath. Its internal surface covers all the muscles of the leg, and does not adhere to them ex- cepting above and in front, where it gives attachment to the tibialis anticus and the ex- tensor communis digitorum. From the internal surface there proceeds on the outer side of the leg two principal tendinous septa, one situated between the muscles of the ante- rior tibial region and the peronei, the otlier between the peronei and the muscles of the posterior region of the leg. There are, therefore, three principal sheaths in the leg, an anterior, an internal, and a posterior. The latter is subdivided into two other sheaths by a very strong transverse lamina, becoming still stronger below, which separates the muscles of the deep posterior layer and the posterior tibial and peroneal vessels and nerves from the superficial layer of muscles, or the triceps suralis. Lastly, some tendi- nous laminae, more or less complete, are interposed between the different muscles of each region. Thus, a tendinous layer separates the tibialis anticus, at first from the ex- tensor communis digitorum, and then from the extensor proprius pollicis : this layer dis- appears in the middle of the leg. Another very strong tendinous lamina separates the tibialis posticus from the flexor longus digitorum on the one hand, and from the flexor longus pollicis on the other. Superior Circumference. — If we now examine the manner in which the aponeurosis of the leg becomes continuous with that of the thigh, we shall find that, posteriorly, the femoral fascia is prolonged directly upon the leg, in order to form the posterior part of its aponeurosis, which, in this situation, also receives an expansion from the ten- dons of the biceps, sartorius, gracilis, and semi-tendinosus, and from the broad band of the fascia of the thigh. Anteriorly the fascia of the leg is continous with that of the thigh over the patella, and appears also to arise directly from the outer edge of the ante- rior tuberosity of the tibia, from the head of the fibula, and from the tendon of the biceps, which, as we have already seen, gives off an aponeurotic expansion backward. By its lower circumference this fascia is continuous with the annular ligaments of the ankle, which we shall presently describe. Structure. — On examining the direction of the fibres and the thickness of the fascia of the leg, it is found that it is much thicker in front than on the outer side of the leg, and still more so than behind ; that, in the first situation, in the ujpper three fourths of its ex- tent, it is composed of obliquely interlaced fibres, some of which descend from the spine of the tibia, and others from the anterior angular surface of the fibula ; and that in the lower fourth of the anterior region of the leg, and in the whole extent of the posterior re- gion, it is composed of circular fibres. At the point where the muscles of the leg become tendinous, and are reflected over the ankle, they require very strong sheaths to keep them in contact with the joint ; the fascia of the leg, therefore, forms, opposite this part, the anterior, internal, and external annular ligaments. The Annular Ligaments of the Tarsus. The annular ligaments of the tarsus are three in number : an anterior or dorsal, an in- ternal, and an external. The dorsal annular ligament of the tarsus. The aponeurosis of the leg is thicker at the lower and anterior part of the leg, and binds down the corresponding portion of the mus- cles in that region. But there is, in addition to this, a dorsal annular ligament of the tarsus (see fig. 128), which arises, by a narrow but thick extremity, in front of the as- tragalo-calcanean fossa, becomes broader as it extends inward, and is divided into two bands. The superior band passes upward and inward above the internal malleolus, and is split into two layers, in such a way as to form two complete sheaths : one internal, for the tibialis anticus ; the other external, for the extensor longus digitorum and the peroneus tertius. Between these two complete sheaths, which are separated from the synovial capsule of the joint by a layer of cellular tissue, we find an incomplete sheath (for the annular ligament is not split into two layers in this situation), intended for the extensor proprius pollicis and the anterior tibial vessels and nerves : the internal sheath is the higher, and situated opposite the lower extremity of the tibia ; the external sheath is lower, and corresponds to the ankle-joint. The inferior band, or the lower bifurcation of the annular ligament, passes forward and inward to the front of the tarsus, and be- comes continuous with the internal plantar aponeurosis. This lower band forms a sec- ond annular ligament, which furnishes to each of the three preceding muscles, upon the dorsum of the foot, a less powerful sheath than that afforded by the upper band : it keeps the tendons closely applied to the bones. The external and internal annular ligaments of the tarsus are two fibrous bands, contin- uous with the fascia of the leg on the one hand, and with the plantar aponeurosis on the other. Rr i 314 APONEUROLOGY. The internal annular ugament arises from the borders and summit of the internal mal- leolus, and proceeds in a radiating manner to the inner side of the os calcis, and the in- ner margin of the internal plantar aponeurosis. Beneath this sheath, which is thick- er below than above, and closes in the concavity on the inner surface of the os cal- cis, proceed the posterior tibial vessels and nerves, and also the tendons of the tibialis posticus, the flexor longus digitorum, and the flexor longus poUicis. For these several parts there are four very distinct sheaths : the most superficial is that for the vessels and the nerves ; two sheaths, placed one over the other (see Jig. 130), and behind the internal malleolus, belong, the anterior to the tibialis posticus (w), and the posterior or more superficial to the flexor longus digitorum (o). These two sheaths soon separate as the two tendons diverge from each other towards their insertions : as the sheath of the tibialis posticus is continued as far as the insertion of that muscle, the sheath of the flexor longus digitorum accompanies it to where it gets beneath {i. e., deeper from the surface than) the plantar fascia. The sheath of the flexor longus pollicis {p) is lower than the preceding, and extends obliquely along the astragalus and os calcis, to be cov- ered by the internal plantar fascia. The external annular ligament forms a common sheath for the two peronei, longus et brevis : it extends from the border of the external malleolus to the os calcis, and is completed on the inside by the external lateral ligaments. It is at first single, but soon becomes subdivided into two other sheaths, one of which is destined for the tendon of the peroneus brevis, and the other for that of the peroneus longus. The Aponeuroses of the Foot. These are divided into the dorsal and plantar. The Dorsal Aponeuroses of the Foot. These comprise the dorsal aponeurosis, properly so called, the pedal aponeurosis (Vapo- neurose pidieuse), and the dorsal interosseous aponeuroses. Dorsal Aponeurosis of the Foot. — While the upper margin of the annular ligament is blended with the fascia of the leg, which appears to be inserted upon it, the anterior margin of the same ligament becomes continuous with the dorsal aponeurosis of the foot. This dorsal aponeurosis is a thin layer, which forms a general sheath for all the tendons situated upon the dorsum of the foot : it gradually disappears in front, opposite the an- terior extremities of the metatarsal bones, and is attached at the sides to the borders of the foot, becoming continuous with the plantar fascia. These tendons, again, are sep- arated from the extensor brevis digitorum by another and still thinner layer, which in- vests that muscle : this is the pedal aponeurosis ; lastly, upon the same surface of the foot we find the four dorsal interosseous aponeuroses, viz., one for each interosseous space. The Plantar Aponeuroses. The plantar aponeuroses or fasciae are three in number : one middle, the other two lateral. The middle plantar aponeurosis is very strong, is attached to the inner of the posterior tubercles of the calcaneum, becomes suddenly contracted, and afterward gradually ex- pands without diminishing perceptibly in thickness. Opposite the anterior extremities of the metatarsal bones, it divides into four bands, which are themselves bifurcated al- most immediately, so as to embrace the flexor tendons of the four outer toes. Becom- ing moulded on the sides of these tendons, they furnish those of each toe with an almost complete sheath, which is attached to the upper and lateral borders of the anterior gle- noid ligament of the corresponding metatarso-phalangal articulation, and becomes con- tinuous with the tendinous sheath of the corresponding toe. These four sheaths are separated by three arched openings, through which proceed the lumbricales and interos- seous muscles, and the plantar vessels and nerves. There is a perfect analogy between the middle plantar and the middle palmar aponeurosis ; but the former is by far the stronger. It constitutes, indeed, a true ligament for the foot, offers a powerful resist- ance to the forced extension of the phalanges upon the bones of the metatarsus, and sup- ports the antero-posterior arch of the sole of the foot. I have known exceedingly vio- lent pain to be produced by distension, and, probably, laceration of some of the fibres of this aponeurosis. The margins of the middle plantar aponeurosis are curved upward, so as to embrace the flexor brevis digitorum on each side ; they become continuous with the external and internal plantar aponeuroses, and form septa between the muscles of the middle and those of the external and internal plantar regions : in front these septa are complete, but only partial behind. The upper surface of this fascia gives attach- ment, posteriorly, to the short flexor of the toes : the proper tendinous expansion of this muscle appears to be given otf from the upper surface of the plantar aponeurosis. Some transverse fibres strengthen this fascia in front, and I shall also notice some other transverse fibres, perfectly distinct from the preceding, which form a true trans- verse ligament for the four outer toes : it is situated opposite the middle of the lower surface of the first phalanges, and is admirably adapted for opposing their dislocation. The External and Internal Plantar Aponeuroses. — The external plantar aponeurosis, very THE APONEUROSES OF THE SHOULDER. 315 thick behind and thin in front, gives attachment by its upper surface to the abductor muscle of the Httle toe, and is bifurcated at the posterior extremity of the fifth metatar- sal bone. The external division of this bifurcation is very strong, is inserted into the enlarged posterior extremity of the fifth metatarsfd bone, and may be regarded as a pow- erful medium of connexion between that bone and the cuboid. The internal plantar apo- neurosis is thin in comparison with the external ; it commences behind by an arch, ex- tending from the inner malleolus to the os calcis ; its inner margin is attached to the corresponding border of the tarsus, and is continuous with the dorsal annular ligament and with the dorsal fascia of the foot ; its outer margin is blended with the middle plan- tar fascia, or, rather, is reflected upward, to complete the sheath for the internal mus- cles of the foot. These three plantar fasciae just described form three sheaths, which are quite distinct in their anterior five sixths, but communicate with each other behind. The internal plantar sheath includes the abductor and the short flexor* of the great toe, which are separated from each other by a layer of fibrous tissue ; it also contains the internal plantar artery and nerves. The external plantar sheath includes the abductor and the flexor of the little toe, Avhich are also separated by a tendinous layer. Lastly, the middle plantar sheath includes the short flexor of the toes, the tendon of the flexor longus digitorum, the flexor accesso- rius, the lumbricales, the tendon of the flexor longus poUicis, the oblique adductor,! the transversus pedis, and the external plantar vessels and nerves. The sheath of the flexor brevis digitorum is completed above by an aponeurotic layer, which separates it from the tendons of the long flexor and from the accessorius. A prope\' sheath exists for the oblique adductor,+ and a subdivision of the same sheath for the transverse ad- ductor. It is formed above by the interosseous aponeuroses, and below by a thin layer attached to the circumference of the deep hollow in which the adductors are lodged. Lastly, the inferior interosseous aponeurosis is remarkable for its thickness, and for the septa which it gives off between the interosseous muscles. The sheaths into which the flexor tendons of the toes are received opposite the pha- langes resemble so exactly those of the fingers, that I shaU not anticipate what will be said hereafter regarding the latter. We find the same system of synovial membranes, and the same loose, membranous, and extensible cellular tissue for the flexor tendons of the toes as for those of the fingers. In all sheaths that are partly osseous and partly tendinous, we find a synovial membrane ;t but, on the other hand, there is nothing more than a loose cellular tissue in situations where a tendon or muscle ghdes in the interior of a confining aponeurosis. The Aponeuroses of the Upper Extremity. Tliese comprise the aponeuroses of the shoulder ; the brachial aponeurosis ; the apo- neurosis of the forearm ; the dorsal and anterior annular ligaments of the carpus ; the palmar aponeurosis ; and, lastly, the sheaths for the tendons of the flexor muscles of the fingers. The Aponeuroses of the Shoulder. These are the supraspinous, the infror spinous, the sub-scapular, and the deltoid aponeu- roses. The supraspinous aponeurosis is a thick layer of fibrous tissue, attached to the entire circumference of the supra-spinous fossa, and converting it into a sort of osteo-fibrous case, that serves as a sheath for the supra-spinatus muscle, to which it also affords sev- eral points of attachment. This tendinous layer is gradually lost, externally, under the acromio-coracoid arch. The infra-spinous aponeurosis is an equally dense and strong fibrous lamina, attached to the entire margin of the infra-spinous fossa, and completing the osteo-fibrous sheath of the infra-spinatus muscle : it is continuous on the outside with the brachial fascia, and gives off from its anterior surface a thick septum intervening between the scapular at- tachments of the teres major and those of the teres minor, and also some thinner septa interposed between the teres minor and the infra-spinatus, and between the different portions of the infra-spinatus muscle itself The deltoid aponeurosis. The infra-spinous aponeurosis having reached the posterior border of the deltoid muscle, splits into two layers : of these, the superficial layer invests the deltoid, and terminates in the brachial aponeurosis ; the deep layer continues to cover the tendon of the infra-spinatus, and becomes attached to the tendon of the short head of the biceps. Some very loose cellular tissue, or even a synovial bursa, separates this aponeurosis from the head of the humerus, and the tendons inserted around it. The subscapular apo7icurosis is a very thin membrane, which completes the sheath of the sub-scapularis, and gives the muscle some points of attachment. It is fixed to the entire margin of the sub-scapular fossa. * [/. e., the inner half of the flexor brevis pollicis of anatomists generally.] t [Including the outer portion of the flexor brevis pollicis of most anatomists.] t See note on ApoNE urology, p. 296. I APONEUROLOGY. The Brachial Aponeurosis. The brachial aponeurosis commences above at the clavicle, the acromion, and the spine of the scapula, and is continuous with the infra-spinous aponeurosis : on the inner side it arises from the tendons of the pectoralis major and the latissimus dorsi ; and, in the interval between them, from the cellular tissue of the axilla ; it envelops the arm as far down as the elbow, where it becomes continuous with the fascia of the forearm, and is attached to the different bony projections presented by the surface of that joint. Its su- ■perficiaJ, surface is separated from the skin by vessels and nerves, to which it furnishes sheaths of greater or less extent. We may admit the existence of a superficial fascia between the vessels and the skin. Its deep surface presents various septa, dividing its interior into a certain number of thin sheaths for the several muscles. It is composed almost entirely of circular fibres, some of which have a somewhat spiral direction : these fibres are intersected at right angles by others passing vertically downward to the fascia of the forearm. The brachial aponeurosis is so loose as to permit the free exercise of the muscles con- tained within it, yet sufficiently tense to prevent their displacement. It is slightly thickened on either side, along the outer and inner borders of the humerus, and gives off in those situations two very strong inter-muscular septa : one external, the other internal. These septa are in every respect analogous to those of the femoral fascia, and divide the brachial sheath into two great compartments : an interior, contain- ing the muscles on the anterior aspect of the arm, viz., the biceps, the brachialis anti- cus, and the coraco-brachialis, also the upper or brachial portion of the supinator longus, and the extensor carpi radialis longior ; the posterior compartment belongs to the triceps. The external inter-muscular septum arises from the anterior border of the bicipital groove, by a narrow and very thick extremity, blended with the posterior margin of the tendon of the deltoid ; it reaches the outer border of the humerus, expands and becomes somewhat thinner, and separates the anterior from the posterior muscles, more espe- cially the triceps from the brachialis anticus, affording attachments to them both. It is perforated very obliquely by the musculo-spiral or radial nerve, and the superior profunda artery, which at first lie behind, but are afterward in front of it. The sheath of this nerve and artery establish a free communication between the anterior and posterior com- partments already alluded to. The internal inter-muscular septum, broader and thicker than the preceding, but, like it, of a triangular form, arises from the posterior border of the bicipital groove, below the teres major, is continuous with the tendon of the coraco-brachialis, crossing it at a very acute angle, and becoming partially united to and blended with it, proceeds along and adheres closely to the inner border of the humerus, and terminates at the inner condyle or epitrochlea of that bone. Both of these septa are formed by bands and fibres given off in succession from the corresponding borders of the humerus, and they both afford attachments to the brachialis anticus in front, and to the triceps behind. The ulnar nerve is anterior to the internal septum in the upper part of the arm, but perforates it, and remains in contact with its posterior surface, passing between the attachments ot the triceps. From these two great sheaths the proper sheaths of the muscles proceed. First, the deltoid has its proper sheath : another thin aponeurotic layer, gradually becoming thicke? from above downward, consisting almost entirely of vertical fibres, and forming one of the origins of the aponeurosis of the forearm, separates the biceps from the brachialis anticus ; again, the brachial vessels and the median nerve have a special sheath, which also receives at its upper part the basilic vein, and the ulnar and internal cutaneou* nerves ; this is the brachial canal, the counterpart of the femoral canal ; it establishes a communication between the cellular tissue of the axilla, and that in the bend of the elbow ; lastly, a tendinous layer separates the upper half of the long head of the triceps from the other portions of that muscle : the sheath of the coraco-brachialis is given ofl from the inner edge of the biceps. We must consider as dependances of the common brachial investment the several sheaths furnished by it to the cephalic, basilic, and median veins, to the branches of the internal cutaneous nerve, and to the superficial ramifications of the musculo-cutaneous nerve. When an artery or a vein previously situated under an aponeurosis becomes sub-cutaneous, the perforation in the aponeurosis is almost always of an arched form. The brachial aponeurosis has no muscle analogous to the tensor vaginae femoris ; the pectoralis major and the latissimus dorsi are sufficient to effect its tension. The Aponeurosis of the Fokeakm and Hand. The Aponeurosis of the Forearm. Dissection. — ^Make a circular incision through the skin, immediately above the elbow, and from this let two vertical incisions be carried downward to the wrist, one in front and the other behind ; let the incisions extend through to the fascia, without dividing it ; then cautiously remove the skin, being careful to take Math it the sub-cutaneous adipose THE APONEUROSIS OF THE FOREARM. 31*3 tissue ; the superficial veins and nerves may be preserved. The external surface of the fascia may be studied first, and its several sheaths afterward opened in succession. The aponeurosis, or fascia of the forearm, ■^orms a general sheath, entirely surrounding or embracing that portion of the upper extremity, with the exception of the posterior border of the ulna. It is semi-transparent, and hence can be seen to be traversed by white lines, generally vertical in their direction, which indicate a corresponding number of thickenings of the sheath, and inter-muscular septa given off from them. It is separated from the skin by the superficial veins and nerves ; by its upper part it gives numerous attachments to the subjacent muscles, and this renders the dissection very difficult. By making a vertical incision, however, along the separate sheath which it furnishes to each of the muscles, and then carefully removing the latter, a good idea may be formed of the numerous angular compartments into which the common cavity of the fascia is subdivided. In the first place, it will be seen that this fascia, like all other investing aponeuroses, is composed of proper and superadded fibres ; that the proper fibres are nearly or quite circular, are more or less oblique, and more or less in- terlaced, but the superadded fibres are vertical. It will be found that it is twice as thick upon the dorsal as upon the palmar surface of the forearm ; that its thickness and its strength increase from above dowTiward ; and that it is strengthened by a great number of superadded fasciculi, consisting of aponeurotic expansions from the tendons of the adjacent muscles. Thus, the brachialis anticus on the outside, the biceps on the inside and in front, and the triceps behind, give off tendinous expansions to this aponeurosis : of these the most remarkable is, without doubt, that given off from the biceps, which muscle may be regarded, indeed, as the tensor of the anterior portion of the fascia. This expansion constitutes, in fact, one of the terminations of the biceps, with the ex- ternal fasciculi of which it is continuous, and, moreover, arises from the outer edge and the anterior surface of its tendon. This expansion, so important in consequence of its relations with the brachial artery, passes obliquely inward and downward, and, as it ex- pands, intersects at right angles the vertical fasciculi proceeding from the epithrochlea and epicondyle of the humerus. These last-mentioned fasciculi also appear to me to be supplementary ; they are continuous with the common tendons of origin of the external and internal muscles of the forearm, and constitute the anterior walls of those two mul- tilocular pyramids, of which one is on the inner, the other on the outer side of the fore- arm, or of that series of trumpet-shaped cavities (cornets), as M. Gerdy calls them, from each of which the muscles of these regions take their origin. I must not omit to men- tion the thick tendinous band, which arises from the entire length of the posterior border of the ulna, divides into two layers to give origin to the flexor carpi ulnaris, and by its internal or deep surface affords attachment to the flexor sublimis. In the fascia of the forearm there are numerous foramina for the passage of vessels and nerves, but I shall direct attention to one very large orifice existing in front, at the bend of the elbow, and bounded on the inside by the outer margin of the tendinous ex- pansion of the biceps. This opening establishes a free communication between the sub- cutaneous and the sub-aponeurotic cellular tissue at the bend of the elbow, and leads into a sort of fossa, in which are found the tendon of the biceps, the brachial artery, the commencement of the radial artery, and the median nerve. This fossa is lined by apo- neurotic laminae : on the outside, by the layer which covers the inner surface of the supi- nator longus, the radial extensors, and the flexor sublimis ; on the inside, by the layer which completes the sheath of the pronator teres : it communicates above with the canal of the brachial artery, and below with the canals through which the radial, ulnar, and interosseous arteries and the median nerve proceed downward to the forearm. From the internal surface of this fascia a number of laminaj are given off, to form the following muscular sheaths : In the anterior region of the forearm, a transverse septum, thicker below than above, divides the superficial layer of muscles from the middle layer, consisting of the flexor sublimis, and also from the deep layer, composed of the flexor profundus digitorum and the flexor longus pollicis. Other septa, passing from before backward, divide the mus- cles of the superficial layer from each other. Lower down the sheaths of the flexor carpi radialis and palmaris longus, which are perfectly distinct from each other, are situated in front of the remainder of the fascia ; and this has led to the statement of some anat- omists, that the fascia is perforated by the tendons of these muscles, especially by that of the palmaris longus. The radial artery has a special sheath throughout its whole ex- tent ; the ulnar artery and nerve have a proper sheath only in the lower part of the forearm. In the posterior region of the forearm, the fascia is much stronger than in the anterior. A transverse layer separates the muscles of the superficial from those of the deep layer; and septa, passing from behind forward, subdivide these common sheaths into several smaller ones, corresponding in number to that of the muscles. Thus, we find a sheath for the extensor communis digitorum, a second for the extensor digiti minimi, a third for the extensor carpi ulnaris, and a fourth for the anconeus. The supinator longus and the two radial extensors of the wrist appear to be in the same sheath ; but a more or less distinct membrane surrounds the first of these muscles : the supinator brevis has 318 APONEUROLOGY. also a proper sheath. We find a common sheath for the extensor longus poUicis and the extensor proprius indicis. The abductor longus and the extensor brevis poUicis, which, properly speaking, constitute but one muscle, have also a common sheath accompanying them as far as the dorsal annular ligament of the wrist. The Dorsal Annular Ligament of the Wrist, and the Dorsal Aponeurosis of the Metacarpus. The dorsal annular ligament of the wrist (r, Jig. 121) may be considered as a depend- ence of the fascia of the forearm, which in this situation is strengthened by a great number of fibres. It is a band of six or eight lines in width, passing obhquely inward and downward over the extensor tendons of the hand, perforated by a number of open- ings for the passage of vessels, and distinguishable from the fascia of the forearm only by its somewhat greater thickness and by the parallel arrangement of its fascicuU. It arises internally from the pisiform bone and the palmar fascia, passes first over the ulnar side, and then the posterior surface of the carpus, is interrupted by the outer mar- gin of the groove for the two radi2d extensor muscles, takes a fresh origin from that mar- gin, covers the radial side of the wrist, and is inserted partly into the radius, and partly into the fascia of the forearm. From the anterior surface of this thick fibrous band arise several small prolongations, which are interposed between the numerous tendons passing over the dorsal and radial aspects of the carpus, and convert the grooves upon the lower extremities of the radius and ulna into canals. Thus, proceeding from with- out inward, and from before backward, we find, 1 . A sheath for the united tendons of the abductor longus and extensor brevis pollicis ; 2 and 3. Two distinct sheaths opposite the radius : one for the two radial extensors of the carpus, the other for the extensor longus pollicis, which sheaths become blended together lower down into a single com- pletely fibrous sheath ; 4. A fourth sheath, stronger than the preceding, for the extensor communis digitorum and the extensor proprius indicis ; 5. An entirely fibrous sheath for the extensor digiti minimi ; 6. A very strong sheath for the extensor carpi ulnaris, which is prolonged below the ulna, and accompanies the tendon as far as the fifth meta- carpal bone. All these sheaths are lined by synovial membranes,* which extend some distance above the dorsal annular ligament, and, on the other hand, accompany the ten- dons very far down, sometimes even to their insertions. The dorsal aponeurosis of the metacarpus is a continuation of the dorsal annular liga- ment : it is composed of a very thin layer of transverse fibres, and separates the exten- sor tendons from the sub-cutaneous vessels and nerves. A very loose, extensible, and elastic cellular tissue takes the place of the synovial membranes over these tendons, and greatly facilitates their movements. The Anterior Annular Ligament of the Carpus. The deep groove upon the anterior surface of the carpus is converted into a canal by a very thick fibrous band, viz., the anterior ligament of the carpus {g,fig. 118). It com- mences internally by two well-marked origins, separated from each other by the ulnar nerve, one being from the pisiform bone and the tendon of the flexor carpi ulnaris, the other from the unciform bone. The first bundle passes downward, the second trans- versely, and their united fibres, some of which are transverse and others interlaced, ter- minate at the trapezium and the scaphoid, giving off an expansion to the fascia cover- ing the ball of the thumb, with which they are continuous. This ligament is continuous above with the fascia of the forearm, which is much thickened in this situation : it re- ceives in front the expanded tendon of the palmaris longus, and terminates below in the palmar fascia. Its anterior surface gives attachment to most of the muscles of the the- nar and hypothenar eminences. A small portion only of this ligament is generally seen and described, viz., the free portion. If it is wished to obtain a perfect conception of it, the muscles attached to its anterior surface should be carefully removed ; it will then be seen that, on the outside, it describes a curve having its concavity, directed inward, in order to be attached to the scaphoid and the trapezium, and that the sheath of the flexor carpi radiahs is contained in its substance : this sheath is entirely fibrous above, and partly fibrous and partly osseous below, where it converts into a canal the groove on the trapezium. While there are almost as many synovial membranes as there are sheaths under the dorsal ligaments of the carpus, on the palmar aspect nine tendons with the median nerve form but a single bundle, which is lubricated by one or two synovial membranes. This synovial membrane* presents a curious arrangement, subject, moreover, to numerous varieties. It lines the posterior surface of the anterior annular ligament of the carpus is prolonged above and below that ligament, and is reflected (without passing between the different tendons) upon the anterior surface of the bundle formed by them and by the median nerve, which is to their outer side. In order to obtain an accurate idea of the termination of this synovial membrane, cut across the tendons at the lower part of the forearm, and turn them forward upon the palm of the hand : it will then be seen that the * See note, p. 296. THE PALMAR APONEUROSIS, ETC. 319 synovial membrane is reflected upon the ulnar border of the bundle of tendons ; that it lines the posterior surface of this bundle, passing more or less between the tendons, and separating them from each other in a rather irregular manner ; that it is reflected upon the groove of the carpus, prolonged upward and downward much farther than it was in front, and divided below into four small prolongations corresponding to the flexor ten- dons of each finger. Nor is this all, for there is a special synovial membrane for the flexor longus poUicis. In order to expose this, the synovial membrane must be cut through where it is reflected, on its radial side, from the annular ligament on to the me- dian nerve and the anterior surface of the bundle of tendons : a special and very exten- sive synovial membrane will then be seen to pass high up along the tendon of the flexor longus pollicis, and to be prolonged downward as far as the last phalanx of the thumb. The Palmar Aponeurosis. The palmar fascia (,c,fig. 118) forms a common sheath for all the muscles of the palm of the hand, and is divided into three portions, a middle and two lateral. The middle portion. This is the only part generally described as the palmar fascia ; it is triangular and strong, but of variable thickness : it binds down the numerous sub- jacent tendons. It arises from the anterior surface and lower margin of the anterior annular Ugament of the carpus, and from the tendon of the palmaris longus, which may be regarded as its tensor muscle. Between these two origins the ulnar artery pene- trates into the palm of the hand. Not unfrequently the expanded tendon of the palma- ris longus forms a fibrous layer in front of the proper palmar fascia. This fascia is nar- row and thick at its origin, but expands as it proceeds from above downward, and, op- posite the heads of the metacarpal bones, divides into eight prolongations for the four inner fingers. At the seat of this division we find very strong transverse fibres binding the prolongations together, and preventing disjunction of the fingers and laceration of the fascia. By this arrangement four arches are formed, under which the tendons of the flexor muscles pass : between these four arches there are three smaller ones, giving passage to the collater£il vessels and nerves of the fingers, and to the lumbricales, so that al- together there are seven arches. These arches are true fibrous canals. In order perfect- ly to understand their structure, make a vertical incision through the palmar fascia ; it will then be seen that, opposite the arches, tendinous prolongations or tongues are detached from the deep surface of the fascia : these prolongations turn round the sides of the ten- dons so as to embrace them, and become continuous with the anterior or glenoid liga- ment of the metacarpo-phalangal articulations : the same arrangement obtains with re- gard to the three small arches for the vessels and nerves situated between the four prin- cipal tendinous arches. The palmar fascia is, moreover, intimately united to the skin by very numerous prolongations : its deep surface covers the superficial palmar arch of the arteries of the hand, the median and ulnar nerves, and the flexor tendons ; a very loose and extensible cellular tissue separates it from these parts, and facilitates the move- ments of the tendons. From its inner margin is given off a very strong layer, which becomes continuous with the interosseous aponeurosis, and separates the middle from the internal palmar region ; a thinner layer proceeds from its outer margin, and passes down between the muscles of the thenar eminence and the first lumbricalis muscle. This small muscle, called the palmaris brevis (Jb,fig. 118), arises from the inner margin of the middle palmar fascia, and is merely a cutaneous muscle. The external and internal palmar fascia, or the thenar and hypothenar aponeuroses. These consist of two rather thin fibrous layers, forming the sheaths of the muscles of the ball of the thumb and those of the little finger : they are both continuous with the middle palmar fascia : the external appears to consist, in a great measure, of an expan- sion from the tendon of the abductor longus pollicis ; and the internal, of an expansion from that of the flexor carpi ulnaris. At the limits between these aponeuroses and the middle fascia are formed two septa, passing from before backward, and dividing the palm of the hand into three distinct sheaths : one median, completed by the interosseous apo- neurosis, and intended for all the flexor tendons and the principal vessels and nerves of the hand ; the other two placed on either side, and binding down the muscles of the the nar and hypothenar eminences. The Sheaths of the Flexor Tendons of the Fingers, and their Synovial Mem- branes. After leaving the arches, or, rather, the curious sheaths, formed by the palmar fascia immediately above the corresponding metacarpo-phalangal articulation, each pair of flex or tendons is received into a special sheath, by which they are accompanied down to the last phalanx. It will be remembered that the anterior surfaces of the first and sec- ond phalanges are marked by a longitudinal groove ; to the two borders of this groove is attached a very regular semi-canal of fibrous tissue, which is exactly large enough to contain the two flexor tendons. This very strong sheath preserves its shape when the tendons have been removed ; and a correct idea of its importance may be obtained by observing the effects of contraction of the flexor muscles after it has been divided. This 320 SPLANCHNOLOGY. sheath is formed of parallel semicircular laminae, placed one above the other, densely ag- gregated over the bodies of the phalanges, and, for the most part, forming a continuous sheath, but becoming more and more separated, and sometimes even completely disap- pearing opposite the articulations and the articulating extremities of the bones. It ap- pears to me that, in the movements of flexion, these articular rings are pushed into each other. The sheath ceases altogether above the articulation of the second with the ter- minal phalanx. A very remarkable synovial membrane,* which is prolonged upward beyond the arch- es formed by the palmar fascia, lines the whole lenth of each osteo-fibrous sheath on the one hand, and on the other is reflected upon the two flexor tendons, affording each of them a sheath, and forms two, often three or four triangular folds, having their bases directed upward, and being perfectly analogous to the so-called adipose ligament of the knee- joint. Of these folds, the superior is situated opposite the upper extremity of the first phalanx, and extends from the tendon of the flexor sublimus to that of the flexor pro- fundus ; the inferior fold passes from the bifurcation of the superficial tendon to the deep tendon ; the others are intermediate, and proceed from the phalanx to the two tendons. These synovial folds can be very well seen by raising and separating the flexor tendons from the phalanges. Not unfrequently the synovial membrane forms a hernia between two of these tendinous rings, either opposite the body of a phalanx, or, still more com- monly, over one of the articulations. We may add, that these synovial folds are proba- bly intended to support the nutritious vessels of the tendons, and not to connect these tendons together. SPLANCHNOLOGY. General Observations on the Viscera. — External Conformation. — Structure. — Development. — Functions. — Dissection. Splanchnology (from crcTMyxvov, viscus) is that division of anatomy which treats of organs more or less compound in their structure. Some of these are contained within the three great visceral cavities (_the viscera), while others are situated without these cavities {organs, properly so called), t The brain, the spinal cord, the heart, and the organs of the senses, are generally in- cluded in this division. I have thought it advisable, however, to confine myself here to the description of the digestive, respiratory, and genito-urinary apparatus. The organs of the senses, the brain, and the spinal cord will be studied more advantageously in con- nexion with the rest of the nervous system, and the heart with the other organs of the circulation. As the organs we are about to examine have few relations with each other, they do not admit of such extended and important general remarks as those which preceded the osteological and myological divisions. I shall content myself with explaining briefly the method in which the description of each organ should be pursued. Every organ presents for consideration its external conformation, its internal confor- mation or its structure, its development, and its functions. The External Conformation of Organs. The description of the external conformation of organs includes that of their nomen- clature, number, situation, direction, size, shape, and relations. Nomenclature. — The nomenclature of organs has not been subjected to so many chan- ges as that of the bones and muscles : the names adopted by the oldest authors have been retained in modern science, and are even used in common language. The names of organs are derived, 1. From their uses, as the asophagus (from olu, I convey, and (^ayo), I eat) ; also, the lachrymal and the salivary glands. 2. From their length, as the duodenum. 3. From their direction, as the rectum. 4. From their shape, as the amygdala (the tonsils). 5. From their structure, as the ovaries. 6. From the name of the authors who have best described them, as the Schneiderian membrane, the FaUopian tubes. Lastly, they are conventional words ; for example,the tongue, the liver, &c. Number. — Some organs are single ; others exist in pairs. Varieties in number are very common, both by excess and by defect. Thus, three kidneys have been found in the same individual, and there is often only one. Examples have been recorded of in- dividuals having three testicles ; one is uncommon. Lastly, varieties by excess almost always result from the division, and those by defect, from the union or fusion of organs. Situation. — This must be considered with regard to the region of the body occupied by an organ, i. e., its general or absolute situation; and also with regard to its relations with neighbouring organs, i. e., its relative situation. Thus, when it is stated that the stom- * See note, p. 298. t All the viscera are organs, but all the organs are not viscera. The word viscus is probably derived from veacor, I eat, because a great number of the viscera are eng:aged in the functions of nutritioi . STRUCTURE AND DEVELOPMENT OF ORGANS. 321 ach occupies the left hypochondrium and the epigastrium, its absolute or general situa- tion is indicated ; but when it is added that this viscus is situated between the oesopha- gus and duodenum, below the diaphragm, and above the transverse mesocolon, its relative situation is implied. Many of the organs are subject to varieties of position ; and this constitutes an im- portant point in their history. These varieties of position depend upon congenital oi upon accidental displacement, either affecting the particular organ only, or consequent upon displacement of the neighbouring organs ; or they may result from a change in the size of the organ itself Size. — The absolute size of an organ is determined by linear measurements, by the quantity of water which it displaces, and by its weight ; its relative size, by comparison with bodies of a known size, or with other organs. The size of organs is subject to a great number of varieties. These depend either on age, as in the liver, testicles, and thymus gland ; on sex, temperament, or on individual peculiarities ; also on the state in which an organ is found : for example, the uterus, pe- nis, and spleen. Lastly, there are some pathological variations, which shoxild not be omitted in a treatise upon descriptive anatomy. Figure. — The figure of the organs treated of in splanchnology appears to follow these rules. The double organs do not exactly resemble each other on the right and left sides of the body. The single organs, occupying the median line, are symmetrical ; but most of those which are removed from that line are not symmetrical. Nevertheless, symme- try is not so completely wanting in the viscera belonging to nutritive life, as stated by Bi- chat, for the stomach and the small and great intestines may be divided into two equal halves. In regard to their forms, organs are compared, in general, either with familiar objects, or with geometric figures. Thus, a kidney is said to resemble a kidney-bean, and either lung, a cone. In very irregular organs, we merely describe the surfaces and the borders. We shall not find in the viscera the same constancy of form as exists in the organs of relation. Direction. — The direction of an organ is determined in the same manner as that of the bones and muscles, viz., by its relations with the imaginary planes surrounding the body, or with the mesial plane. Relations. — The figure of an organ being determined, its surface is then divided into regions, the relations of which are accurately ascertained. These regions are generally termed surfaces and borders. As the situation of many organs is subject to great varie- ties, their relations must also vary. Too much cannot be said of the value of an accu- rate knowledge of these relations, from which a number of the most important practical inferences may be derived. The Internal Conformation &r Structure of Organs. The surface of an organ being well understood, we next proceed to the study of its structure, comprising its colour, its consistence, and its anatomical elements. Colour. — The colour both of the surface and the substance of an organ requires to be studied. All variations of colour should be very carefully noted. Age and disease have much influence over it ; and it is often difficult to distinguish positively between its physiological and pathological condition. Consistence. — The consistence, density, and fragility of organs are connected with their structure. The specific gravity or density of a single organ only, the lung, has been ac- curately studied, and that in a medico-legal pomt of view. In estimating the con^^isience and fragility of organs, we can only approximate the truth. It is desirable that some more methodical and accurate means should be devised for the estimation of these qualities. Anatomical Elements. — The determination of the immediate anatomical elements, or tissues, which enter into the composition of an organ, together with their proportions and their arrangement, constitutes the knowledge of its structure. Every organ has either a cellular, fibrous, cartilaginous, or bony framework. Some organs are provided with muscular fibres, or even with distinct muscles ; they all contain the several kinds of vessels, viz., arteries, veins, and lymphatics ; and they edl possess nerves. The glan- dular organs have excretory ducts. In explaining the structure of organs, we shall, generally, confine ourselves to a brief enumemtion of their constituent parts, referring to works on the anatomy of textures for details which would be misplaced in an elementary treatise. Tkt Devdopment of Organs. The study of the development of organs, and the changes which they undergo at the different periods of intra- and extra-uterine life, is of the greatest interest, at least as re- gards some among them. The formation of the soft parts, however, is not nearly so weL understood as that of the hard tissues, because the most important phenomena of devel- opment occur during the first weeks after conception. The remarks upon this subject will, therefore, generally point out some hiatus to be filled up. Ss 822 SPLANCHNOLOGY. The Functions of Organs. The functions or uses of organs flow so naturally from their anatomical description, that we shall follow the example of the greater number of anatomists, in adding to such description a short account of the functions of an organ. We shall only notice particu- larly those uses of organs which depend immediately upon their structure, referring to physiological works for the details and discussions of yet disputed points in the science of functions. No part of anatomy excites so much curiosity and interest as splanchnol- ogy, in consequence of the importance of the organs of which it treats. Without a knowledge of this department of anatomy, it is impossible to understand the mechanism of functions the most indispensable to life ; and as the organs themselves are the seat of the greater part of the lesions which are assigned to the physician, as well as of many of those which fall under the care of the surgeon, most of the fundamental questions of the heeding art require a profound knowledge of these organs. The Dissection of the Viscera. The dissection of organs does not consist in merely isolating them from surrounding parts, which, as far as regards those contained in the visceral cavities, is done by sim- ply laying open the latter, but in the separation of their anatomical elements or tissues. For this purpose, injections of the most delicate kind, maceration, boiling, preservation in alcohol, desiccation, the action of acids, in short, aS\. the resources of his art, are em- ployed by the anatomist. Having made these preliminary observations, we shall now describe in succession the organs of digestion, the organs of respiration, and the genito-urinary apparatus. THE ORGANS OF DIGESTION AND THEIR APPENDAGES, ALIMENTARY OR DIGESTIVE CANAL. General Observations. — Division. — Mouth and its Appendages. — Lips. — Cheeks. — Hard and Soft Palate. — Tonsils. — Tongue. — Salivary Glands. — Buccal Mucous Membrane. — Pha- rynx. — (Esophagus. — Stomach. — Small Intestine. — Large Intestine. — Muscles of the Pe- rineum. — Development of the Intestinal Canal. The organs of digestion form a long canal, the alimentary or digestive canal, extending from the mouth to the anus, which receives alimentary substances, induces in them a series of changes, by which they are rendered fit to repair the losses incurred by the body, and, moreover, presents a vast absorbent surface for the action of the lacteal ves- sels. The entire series of these organs constitutes the digestive apparatus. Tlie existence of an alimentary canal is one of the essential characters of an animal. In consequence of possessing it, animals may be detached from the soil, so as to move from place to place. In the lowest species, the entire animal is nothing more than an alimentary sac, having a single opening, and formed by a reflection of the skin ; so that, according to the beautiful observation of Trembley, when polypes are turned inside out, the digestive process is performed as well by their external as by their internal surface. Ascending in the scale of animals, the canal soon presents two openings, acquires larger dimensions, becomes more or less convoluted, and is distinct from other systems of or- gans. A skeleton clothed by muscles is interposed between it and the skin. It becomes more and more voluminous, in proportion as the nutritive materials and the textures of the body differ more widely in their chemical composition. What a difference there is, in this respect, between certain fishes, in which the alimentary canal is not nearly so long as the animal, and some herbivora ; the ram, for example, in which it is twenty- seven times the length of the body. Carnivorous animals, again, have a short and nar- row alimentary canal. Man, being destined to live both upon animal and vegetable sub- stances, occupies, as it were, a middle station between the herbivora and carnivora. General Situation. — The digestive canal is situated in front of the vertebral column, with the direction of which the straight portion of the canal accurately corresponds, while its tortuous part is distant from, though invariably connected with it by means of membranous attachments. It commences at the lower part of the face, traverses the neck and the thorax, penetrates into the abdominal cavity, which is almost exclusively intended for it, and the dimensions and mechanism of which bear strict relation to the functions of the alimentary canal ; and it terminates at the outlet of the pelvis, anterior to the coccyx, by the anal orifice. Its upper part is in immediate relation with the or gans of respiration ; its lower, with the genito-urinary apparatus. Dimensions. — The length of the digestive canal has been calculated to be seven oi eight times that of the body of the individual. Its diameter is not equal through its whole extent ; and its alternate expansions and contractions establish very distinct lim- its between its several portions. The largest portion is, undoubtedly, that which re- ceives the name of the stomach ; the narrowest parts are the cervical portion of the oesophagus, the pyloric opening of the stomac-h, and the ileo-caecal orifice. It is impor- GENERAL REMARKS. tant to remark, that the transverse dimensions of an alimentary canal have, to a certain extent, an inverse ratio to its length. Thus, a very wide intestinal canal is generally less remarkable for length. This remark is illustrated by comparative anatomy in the fact that, in the horse, an herbivorous animal, the intestinal canal is shorter, but, at the same time, of a much greater calibre than in the ruminantia, which are also herbivorous. Direction. — The upper or supra-diaphragmatic portion of the alimentary canal, through which the food merely passes, is straight ; the sub-diaphrjigmatic portion is very much convoluted upon itself, but again becomes straight before its termination. General Form. — The digestive apparatus forms a cylindrical continuous canal, in which we have to consider an external and generally free serous surface, and an internal mu- cous surface. Struclure. — The digestive canal is composed of four membranes or tunics : 1 . The most external is the serous or peritoneal coat, also named the common tunic, because it is conunon to almost all the organs in the abdominal cavity. This membrane, which may be regarded as an accessory tunic, is often incomplete, and even entirely wanting through- out the supra-diaphragmatic portion of the digestive canal. At the same time that it constitutes the external covering of this canal, it separates it from the neighbouring parts, facilitates its movements, and forms certain bands, which maintain the several portions of the canal more or less fixedly in their proper situations. The serous membranes, of which this external tunic is only a dependance, are shut sacs, which, on the one hand, line the walls of the cavities to which they belong, and, on the other, are reflected upon the organs contained therein,* without, however, including them within their ovm prop- er cavity. A serous membrane may be compared to a balloon, or, rather, to a double nightcap ; its internal surface is free, smooth, always moistened with serosity, and its parietal and visceral portions are in contact with each other : its external surface is adherent, t 2. Beneath the serous coat is situated the muscular coat, consisting of two layers : one su- perficial, composed of longitudineil fibres ; the other deep, and composed of circular fibres. These fibres are colourless, like almost all the muscles of nutritive or organic life. J 3. The fibrous coat, interposed between the muscular and mucous coats, may be regard- ed as constituting the framework of the alimentary canal. It consists of dense areolar cellular tissue.^ 4. The mucous coat or membrane forms the internal lining of the digestive canal. Ev- ery cavity having a communication with the exterior is hned by a mucous membrane, so called on account of the mucus with which it is constantly lubricated. In mucous membranes generally, we find, 1. A dermis or chorion, 2. Papilla or villosi- ties, which give them a velvety appearance ; hence the designation papillary, villous, or velvety membrane frequently given to them. 3. On the outer surface of the dermis we find a very dense network of capillary vessels, which may be completely injected from the veins, but less easily and less completely from the arteries. 4. Either follicles or small closed sacs are seen here and there in the substance of mucous membranes ; but they are not essential, as the name follicular, given to these membranes by Chaussier and some other anatomists, would seem to indicate. * [Hence the terms parietal and visceral, applied to these two portions of a serous membrane (see Jig, of the testis, letters p and v). In consequence of the existence of an aperture in the free extremity of each Fallopian tube, the peritoneal cavity in the female is an exception to the general rule, that serous membranes form shut sacs, not communi- cating with the external medium.] t [Serous membranes are transparent, colourless, extremely thin, and highly distensible and elastic. They are composed of a basis of cellular tissue, loose and connected to the adjacent tissues externally, more or less condensed towards the inner and free surface of the membrane, and covered with an extra- vascular epithelium, consisting of a single layer of nucleated cells, Ilattened into the form of scales, and arranged parallel to that surface. Cilia have been detected on many serous membranes, as on the peritoneum and pericardium of the frog ; on the same parts, and also on the pleura and lining membrane of the ventricles of the brain in certain mammalia ; and in the latter situation in man. Bloodvessels ramify in the sub-serous cellular tissue, but do not penetrate far towards the free surface, where they are entirely wanting. Lymphatics also exist in the sub-serous tissues, but have not been found in the membranes themselves ; nor have nerves been traced into them. The fluid secretion found in serous cavities appears to be of an albuminous nature.] t [The involuntary muscular fibres of the alimentary canal (according to Dr. VV. Baly) consist of bands, va- rying from o^j'g-jjth to , A ^ th of an inch in diameter, apparently formed of flattened tubes, in the parietes of which are seen, at irregular intervals, numerous transparent oval or linear bodies, sometimes very difiicult of detection : they are believed to be the nuclei of the primitive cells, from which the fibre itself is developed. These fibres contain no varicose filaments, nor do they present any transverse striK, like those of animal life (see p. 194). Moreover, although they have a parallel arrangement in the fasciculi into which they are col- lected, the fasciculi themselves are irregularly interlaced, at the same time that they all pursue a common direction. The muscular coat of nearly the entire alimentary canal consists essentially of these involuntary or organic muscular fibres ; but at the commencement and termination of the canal, where the muscular systems of ani- mal and organic life come into relation with each other, this tunic appears also to consist of fibres resembling those of the voluntary muscles. Thus, at the upper part of the (Esophagus, fibres containing varicose filaments, and possessing the cross stri b) be- tween the crests of the iliac bones. The superior zone is called the epigastric ; the middle, the umbilical ; and the inferior, the hypogastric. These three zones are then subdivided by two vertical parallel lines drawn from the cartilages of the eighth rib down to the centre of Poupart's ligament. The epigastric zone is thus divided into two hypochondriac (1 Ij^and a middle epigastric region (2) ; the umbilical into two lumbar (3 3), and a middle umbilical region (4) ; and the hypogastric into two iliac (5 5), and a middle hypogastric region (6).] * It is impossible to insist too strongly upon the influence of too tight stays on the situation, and even the form, of the viscera occupying the base of the thorax. Thus, changes in the situation and direction of the stomach are much more frequent in females than in males. Soemmering observed, but without stating the cause, that the stomach is more rounded in the male, and more oblong in the female. t It may, strictly speaking, be stated that ruminants have only one stomach, the rennet or obomasum; and that the iirst three, viz., the paunch, the reticulum, and the manypHes or omasum, are nothing more than dila- tations of the oesophagus, in which the food undergoes a preparatory elaboration. The same observation ap- plies to birds, in which the crop and the gizzard are not organs of chymification, the first being merely an or- ?ar of insalivation, the second one of trituration. Yy 364 SPLANCHNOLOGY. when the abdominal parietes are entire ; in which case the distended stomach passes in the direction of the least resistance, i. e., forward and downward, and its anterior sur- face cannot then be completely turned up. This surface is in relation with the diaphragm, and is separated by it from the heart ; with the liver, which is prolonged upon it to a greater or less extent ;* with the last six ribs, being separated from them by the diaphragm ; and with the abdominal parietes in the epigastrium : hence the name given to that region. It is not uncommon to find the great omentum turned upward between the stomach and the liver. When distended, the stomach has much more extensive relations with the epigastrium, or, rather, with the abdominal parietes, both in a vertical and transverse direction. All these relations are of the greatest importance ; and, with the exception of those which concern the epigastrium, they are constant. In fact, it rarely happens that the stomach precisely corresponds to the sub-sternal or xiphoid depression, which has been called the pit of the stomach, or the scrobiculus cordis, but which belongs neither to the heart nor the stomach. In exploring this depression, it is almost always the liver wliich is felt ; the stomach lies lower down, and is generally below the ensiform appendix. The posterior surface {inferior surface of some anatomists, seen turned up at s,fig. 154) is directed downward and backwjurd, and is seen in the sac of the omentum, of which it forms the anterior wall. It has relations with the transverse mesocolon, which serves as a floor for it, and sep- arates it from the convolutions of the small intestines ; with the third portion of the duo- denum (e' to b), by some of the older anatomists called the pillow of the stomach {ven- triculi pulvinar) ; and, lastly, with the pancreas (o). The duodenum, the pancreas, the aorta (a), and the pillars of the diaphragm {d d), separate it from the vertebral column, upon which it rests obUquely. These relations are modified by the emptiness or fulness of the stomach. The great curvature (the inferior or anterior border of some anatomists, cad, fig. 149) Fig. 149. is convex, and directed almost vertically downward in the empty condition of the organ, and almost di- rectly forward when it is full ; it gives attachment to the two anterior layers of the great omentum. It is in relation with the abdominal parietes and the cartilages of the lower ribs, and lies along the trans- 1^ verse arch of the colon (,t,Jlg. 155), in front of which it advances when considerably distended ; hence it was termed the colic border by Chaussier. In the distended state its relations with the abdominal pa- rietes become much more extensive ; but even then I can scarcely believe the assertions of some, that the pulsations of the gastro-epiploic arteries can be felt by the finger in emaciated individuals. The lesser curvature (the superior or posterior border of some anatomists, o b p, fig. 149) is concave, and extends from the oesophageal orifice to the pylorus ; it gives attachment to the small or gastro-hepatic omentum ; it is directed upward when the viscus is empty, upward and backward when it is full ; and it then embraces the vertebral column in its curvature, being separated from it by the aorta and the pillars of the diaphragm (see^^. 154) ; it also embraces the small lobe of the liver or the lobulus Spigehi, the coeliac axis (f), and the solar plexus of nerves. The great extremity or great cul-de-sac of the stomach (the bottom or great tuberosity, from c to the dotted line, fig. 149) comprises all that portion which is to the left of the car- diac or cEsophageal opening ; it is a sort of semi-spheroid, applied to the base of the cone formed by the rest of the stomach ; it is the highest and the largest portion of that or- gan ; it is almost entirely absent in carnivora ; it is very large in herbivora, and of a medium size in man. There are also many individual varieties in the size of this por- tion of the stomach ; I have met with some instances in which it W2is not larger than it is in carnivora. It is in contact with the spleen {k, fig. 154) (hence it is called the splenic extremity by Chaussier), with which it is connected by a fold of the peritoneum, called the gastro- splenic omentum, and by the vasa brevia. When the stomach is distended it comes into close contact with, and is, as it were, moulded upon, the spleen (see fig. 161). From this relation a great number of physiological inferences may be deduced. t The great cul- de-sac occupies the left hypochondrium, and corresponds also, in the greater part of its * The relations of the anterior surface of the stomach with the liver are very variable in extent ; it some- times reaches even to the gall-bladder. I have seen a case in vphich the gall-bladder adhered to the anterior surface of the stomach, and, therefore, to the left of the pylorus, and communicated with it by an orifice, through ■which bile and biliary calculi were discharged. t The great end of the stomach is so closely connected with the spleen, that it necessarily follows all dis- placements of that organ. I have met with a case in which the spleen, three or four times its natural size, ■was situated in the umbilical region, and had dragged down the great end of the stomach with it. The left extremity of the transverse colon, and the upper part of the descending colon, occupied the place of the great extremity of the stomach. The patient had long suffered from indigestion, which had been attributed to chron- ic gastritis. THE STOMACH. 355 extent, to the left half of the diaphragm, which is in accurate contact with it, and separ- ates it from the lungs above and from the last six ribs in front. It is more or less ele- vated, according to the degree of distension of the stomach ; and from this we can easi- ly understand that difficult respiration may be caused by too large a meal. Lastly, it may be stated that the great extremity of the stomach has relations behind with the pancreas, and with the left kidney and supra-renal capsule. The (Esophageal extremity (o, Jig. 149). The oesophagus opens into the stomach at different angles, according to the emptiness or fulness of that organ. The situation of this opening, which is improperly denominated the cardia {cor, heart), is at the left ex- tremity of the lesser curvature, to the right of the great cul-de-sac, and opposite the (Esophageal opening in the diaphragm. It is embraced (c. Jig. 154) in front by the left extremity of the liver, which sometimes forms a half circle round it, and behind by the lobulus Spigelii. It is surrounded by a circle of vessels and some nerves. Examined externally, the lower end of the oesophagus is continuous with the stomach, without any other line of demarcation than that depending upon a difference in size and direction. The peritoneum is directly reflected from the diaphragm upon the oesophagus and the stomach, and forms the gastro-diaphragmatic fold (ligamentum phrenico-gastricum. ScBJnmerifig).* The pyloric extremity {pylorus, from ttCIt], a gate, and o^pof, a keeper, p,figs. 149, &c.) iS situated at the right extremity of the stomach. It forms the apex of the cone, and presents a circular constriction or strangulation, which exactly defines the limits between the stomach and duodenum. About an inch from this constriction the stomach is much curved, so as to form a decided bend, and presents a dilatation, on the side of the great curvature corresponding to an internal excavation, called by Willis the antrum pylori, and by others the srnall cul-de-sac of the stomach (from d to the dotted line e). Not uncom- monly we find a second dilatation near the first, and a third, still smaller, on the side of the lesser curvature, resulting from the bend formed by the stomach. The pyloric ex- tremity of the stomach is directed to the right side, backward and upward, and some- times even a little to the left, when the stomach is much distended. The relations of the pyloric extremity with the abdominal parietes are very variable, for the changes in the situation of the stomach chiefly affect this extremity. It corresponds to the liaiit between the epigastrium and the right hypochondrium ; sometimes it is in relation with the gall-bladder, and hence may become stained ; in some cases it passes to the right of the gall-bladder, to the extent of an inch or an inch and a half. I have seen it occupying the horizontal fissure of the hver, the edges of which were separated for its reception. Very commonly we find the pylorus in the umbilical region. I have seen it in the hypogastrium in a female who was affected vdth schirrus of the pylorus, and I have also found it in the right iliac fossa. It is, therefore, extremely difficult to determine the seat of an organic lesion of the pylorus from external examination. The relations of the pylorus with the abdominal viscera are more constant : above, it corresponds to the liver and the lesser omentum ; below, to the great omentum ; in front, to the abdominal parietes ; and behind, to the pancreas. It is not uncommon to find it adhering to the gall-bladder. # The Internal Surface. — This presents the same regions as the external surface ; all its peculiarities may be referred to the raucous membrane, which will be noticed when the structure of the stomach is described. Besides these, however, we observe here the two orifices of the stomach. The oesophageal orifice (cardiac, left, or superior orifice, ostium iiitroitus, o, Jig. 150) is remarkable for its radiated folds (ad steUae similitudi- pj UO nem. Holler), which are effaced by distension ; for the ^, irregularly fringed border and the change in colour ^ ,• , ? \ which mark the limits between the mucous membrane of the oesophagus and of the stomach ; for its size and its capabihty of dilatation ; and, lastly, for the total ab- sence of any valve or sphincter. The duodenal or pyloric orifice (right or anterior ori- fice, janitor, sphinctor, ostium, exitus, p) is remarkable for an internal rim, or circular valve, which in a distend- ed and dried stomach forms a sort of diaphragm (in speciem diaphragmatis, quedia sunt in tubis telescopicis, Morgagni) ; for the narrowness of the passage, which, with difficulty, admits the little finger in most subjects ; for its slight dilatability ; and, lastly, for the existence of a muscular ring, which may be regarded as a true sphincter. It is of importance to remark, that this orifice, independently of ajiy disease, presents a great number of varieties in its dimensions, and it is probable that these congenital or acquired variations may have some influence upon its diseases. The relative position of these two orifices is an important anatomical point. Upon this we should observe, 1. That they are but little apart from each other, considering * [Hence this extremity is comparatively fixed.] 356 SPLANCHNOLOGY. the size of the stomach, and that the interval between them does not increase in propor- tion to that size ; 2. That the oesophageal orifice is directed upward, the pyloric open- ing backward and a little upward ; 3. That the two openings are not upon the same plane, the oesophageal being higher and more posterior than the pyloric. The Structure of the Stomach. — In order to study the structure of the stomach, it is necessary, in the first place, to distend it. Two stomachs are indispensable for this pur- pose, one to be dissected from without inward, and the other from within outward. One of the stomachs should be everted, and then inflated. The parietes of the stomach are formed by the super-position of four membranes or coats, differing in texture and properties. These, proceeding from without inward, are the serous, the muscular, the fibrous, and the mucous coats. We must also examine the vessels, nerves, and cellular tissue, which enter into the composition of these parietes. 1. The serous or ■peritoneal coat. Like almost all the movable viscera of the abdomen, the stomach receives a complete covering from the 'peritoneum {membrana communis of the ancients ; la membrane capsulaire, Chauss.). It is formed in the following manner : Two layers of the''peritoneum, in contact with each other, pass from the transverse fis- sure of the liver to the lesser curvature of the stomach : there they separate, so as to leave between them a triangular space, the base of which corresponds to the lesser curva- ture ; the anterior layer then passes over the anterior surface of the stomach, and the pos- terior covers it behind ; they again approach each other at the great curvature, along which they form another triangular space, exactly resembling that which we have already de- scribed as existing at the lesser curvature, and then unite so as to form the two ante- rior layers of the great omentum (see description of Peritoneum). The same airange- ment takes place at the great extremity of the stomach. Bloodvessels pass round the stomach, along the line where the two layers of the peritoneum are applied to each oth- er at its two curvatures. The peritoneum, therefore, forms a complete covering for the stomach, excepting at the curvatures, where we find triangular spaces, into which the stomach is forced during its distension. I doubt whether these triangular spaces can afibrd sufficient space for the stomach when greatly distended, and I believe that, in such cases, the two anterior layers of the great omentum separate, and are applied upon that organ. It is evident, besides, that distension of the stomach chiefly affects its great curvature. The peritoneal coat does not adhere firmly to the subjacent tissues of the stomach, in the neighbourhood of either curvature ; but it is closely united to them at the middle points of both surfaces. The imperfect extensibility of the peritoneal coat requires such an ar- rangement as exists along the curvatures. I have observed some small fibrous bands in the sub-serous cellular tissue along the lesser curvature, which must be intended to maintain the shape of that part. The uses of the peritoneal coat, in reference to the stomach itself, are merely mechanical ; it strengthens, preserves the shape, and facili- tates the movements of this organ. The Muscular Coat. — This coat has engaged much of the attention of anatomists since the time of Fallopius, who was the first to give a correct description of it ; and to whom Morgagni {Advers. Anat., iii., p. 6) has^ttributed the honour of discovering it, in opposi- tion to the claims of Willis. Helvetius made it the subject of a special work {Hist. Acad. Roy. des Sciences, 1719). We shall describe, in accordance with Haller (Elem. Phys., tom. vi., lib. xix., sect, i., Fig. 161. p. 126), and the majority of anatomists, three layers of muscu- lar fibres. The superficial or longitudinal layer (1, fig: 151) is formed by a continuation of the longitudinal fibres of the oesophagus, whioh spread out in a radiated manner from the cardiac orifice of the stomach. They are scattered thinly over its surfaces, the great curvature, and the great extremity, but are collected into a band along the lesser curvature, the shape of which they assist in preserving. On account of this arrangement, they have re- ceived the name of cravatc de Suisse. These fibres form a continuous plane of considerable thick- ness over the contracted portion of the stomach, near the pylo- rus. In this situation they are stronger, and fasciculated, and appear partly to terminate in the pyloric constriction, and part- ly to be continued upon the duodenum. The second or circular layer (2, fig. 151) is composed of fibres which cross the axis of the stomach at right angles, so as to form a succession of rings from the oesophagus to the pylorus. They are few in number at the great extremity of the stomach, but become much more numerous towards the pylorus, through- out all the contracted portion of the stomach. At the pylorus itself they form a thick ring, which forms a sort of rim, project- ing in the interior. I have always found this more developed THE STOMACH. 357 in old age than at any other period of life. It is a true sphincter, which, by its contrac- tion, effectually opposes the passage of food and gas from the stomach into the duode- num. It is not uncommon to find the whole of this ring, or a half, or two thirds of it, in- creased to the thickness of three or four lines, independently of any organic lesion. The older anatomists admitted also an oesophageal ring (or (esophageal sphincter), simi- lar to that at the pylorus, and having the power of closing the oesophageal orifice. This, however, does not exist ; the last circular fibres of the oesophagus do not form a thicker layer than the others. Lastly, the different rings formed by the circular fibres of the stomach intersect each other obliquely at very acute angles. The spired arrangement admitted by Santorini cannot be demonstrated. The third muscular layer (3, fig. 151), which I have only been able to see distinctly upon hypertrophied stomachs, is composed of looped or parabolic fibres, the middle portions of which embrace the great end of the stomach, extending from the left side of the cardiac orifice obliquely downward towards the great curvature, while their anterior and posterior extremities are situated upon the corresponding surfaces of this viscus. The superior loops reach the lesser curvature, the inferior the great curvature, and the intermediate loops seem to be lost upon either surface, or, rather, to become blended with the circu- lar fibres. This layer of fibres appears intended to compress the great extremity of the stomach, and to push the food into the body of the organ, towards the pylorus. From what has been stated, it follows that, excepting in the vicinity of the pylorus, the muscular layers of the stomach do not form a continuous plane, but have an areolar disposition : the areolae, or spaces between the different fibres, are of considerable size ; hence the necessity for a strong membrane, like the fibrous coat, which, as we shall find, constitutes the framework of the stomach. The muscular fibres of the several layers are much paler than those of the oesopha- gus.* They have a pearly appearance when seen through the peritoneal coat, which has led to the supposition that they are tendinous. Hence the error of Helvetius, Wins- low, and others, who regarded the two white lines running along the two surfaces of the stomach, between the curvatures, as ligaments of the pylorus ; they are nothing more than longitudinal muscular fibres. Other authors have merely admitted some tendinous intersections of these fibres. The muscular coat is not uniformly thick at all points. It is very thin at the great cul-de-sac, and becomes much thicker towards the pylorus. It also presents many va- rieties in different subjects ; it is but slightly developed in large stomachs, and much more so when this organ is contracted. There is a physiological as well as a pathological hy- pertrophy of the muscular coat. In the latter it has been found seven or eight lines thick. The Fibrous Coat. — This coat, the existence of which has been alternately admitted and denied, is situated between the muscular and the mucous coats, and is quite distinct from both. It was known by the ancients as the membrana nervosa ,•+ it constitutes, properly speaking, the frcmiework of the organ. In order to demonstrate this coat, it is sufficient to remove the peritoneal and muscular tunics, and then to evert the stomach and remove the mucous membrane. This experiment will also very clearly show the great strength of the fibrous coat, which, even thus unsupported, can bear considerable distension ; while, on the other hand, when this coat has been divided, the remaining membrane or membranes burst through the opening thus made. This coat should not be confounded with the dermis of the mucous membrane, for it adheres much more strongly to the muscular coat, into which it sends numerous pro- longations, than to the mucous membrane, with which it is connected only by loose cel- lular tissue. The fibres of this coat have not a parallel arrangement like those of aponeuroses and fibrous sheaths, but they form a very dense network, the filaments or lamellae of which can be separated by inflation or infiltration. It is concerned in a very important man- ner in chronic diseases of the stomach ; it is very liable to hypertrophy ; and, in certain cases, acquires a thickness of several lines. The Mticous Membrane. — The history of this membrane is curious. It was for a long time confounded with the mucus by which it is covered, being regarded as merely a dried layer of that secretion.J It was pointed out by Fallopius, who applied to it the very ap- propriate appellation of the velvet-like tunic ; but it was first described as a separate mem- brane by Willis, under the title of the glandular tunic. The discovery was confirmed by the beautiful injections of Ruysch, who gave it the name of epithelium ; to which term, however, he did not attach the same meaning as modern authors. It was afterward re- garded as an epidermic membrane, analogous to the epidermis of the skin,^ and capable * [Thejr are principally of the involuntary class, but have a few striated fibres among- them (see note, p. 3 JJ t [So called from its white appearance.] X Riolanus states positively {Anthropol, 1. ii., c. xii., p. 171) that the stomach, like the intestines, is com- posed of three coats, viz., a common external membrane, a nervous, and a muscular coat; and that a closely adherent mucus, consisting of the thickest part of the chyle, lines it on the inside. t) Such was the opinion of Ilaller, lib. xix. p. 132. 358 SPLANCHNOLOGY. of being thrown off and renewed. In recent times it has been supposed to be concerned tanquam omnium lerna malorum, and has become in the present day the object of a great number of most interesting researches. The mucous membrane of the stomach presents an adherent and a free surface. The adherent surface is united to the fibrous coat by cellular tissue, so loose as to permit very free motions. The free surface has the following characters : When the stomach is strongly contracted, it forms a number of folds (see^^. 150), the principal of which are longitudinal ; these folds disappear when the organ is distended, as may be shown in an everted stomach. Their only use is to allow of the rapid distension of this organ, a con- dition that could not have been attained in any other mode, in consequence of the slight elasticity of the mucous coat. These longitudinal and temporary folds, which are perfectly distinct from the perma- nent folds observed in other parts of the alimentary canal, are most strongly marked near the pyloris ; they are extremely regular, sometimes straight and sometimes flexu- ous ; and they proceed parallel to each other from the cardiac towards the pyloric orifice They are intersected more or less obliquely by other winding folds of different degrees, which often give an areolar appearance to the internal surface of the stomach. From this arrangement, it follows that dilatation of the stomach occurs principally in a direction across its long axis ; the resources for dilatation in the direction of its axis are much less numerous. Of all the folds of the mucous membrane, the most important is undoubtedly that called the pyloric valve, which is often nothing more than a mere elevation of the membrane by the sphincter muscle.* This cellular fold is equally op- posed to the regurgitation of food from the duodenum into the stomach, and to its passage from the stomach into the duodenum ; it is completely effaced by distension, and it belongs as much to the duodenum as to the stomach. Its upper half has the characters of the gastric ; the lower half offers those of the duodenal mucous membrane. Diseases are sometimes observed to stop at the line of separation. We may add, that the folds upon the internal surface of the stomach are formed by the mucous membrane alone ; the fibrous coat does not enter into them. Besides these folds, the mucous membrane presents numerous slight and tortuous furrows, dividing it into small spaces or compartments, which are either lozenge-shaped, hexagonal, polygonal, circular, oblong, or irregular. Examined by the naked eye, the mucous membrane has a soft, spongy, tomentose, or velvety appearance ; hence the name of villous or velvet-like membrane, by which it is still generally known. It is covered by a layer of mucus of variable thickness, which may be detached by friction with a coarse cloth. In order to avoid the inconveniences arising from this method, which is more or less injurious to the texture of the membrane, I have been accustomed to use a gentle stream of water, which, at the same time that it com- pletely washes away the mucus, clearly displays the papillary structure of the surface of the membrane. There are some stomachs which might be called granular or glandjtlar, because the mucous membrane has a granular appearance, so that at first sight it might be imagined that some small glandular bodies (like the salivary glands) were scattered over the in- ternal surface of the stomach ; but this glandular aspect is merely apparent, depending upon the circular or semicircular direction of the furrows in the mucous membrane, which give a spheroidal character to the kind of islets that are intercepted between them. This gi'anular appearance is seldom observed over the entire stomach ; it rarely exists at the great extremity. I have found it limited to the great curvature ; most frequently it occurs in the vicinity of the pylorus ; sometimes it is observed over all that part of the stomach which is to the right of the oesophagus. These granulations are particularly developed in the stomach of the pig. There is one remark upon which too much importance cannot be placed ; and that is, the difference in the appearance of the mucous membrane of the great extremity of the stomach, and of the part situated to the right of the oesophagus. Sometimes the line of separation forms a perfect circle ; and this is a very remarkable fact, because in man, who has a single stomach, it may be considered as a rudiment of the division into the compound stomachs found in the lower animals ; for a multiple stomach results rather from some difference in the structure of the mucous membrane, than from the existence of different compartments or distinct cavities. It will not be uninteresting to connect this remark with what has been already stated regarding bilocular stomachs. We shall now examine the characters of the mucous membrane in the oesophageal and in the pyloric portion of the stomach. In the oesophageal portion it is thinner, softer, and more vascular, and can only be separated in flakes from the subjacent parts. When the stomach contains any liquid after death, this part is converted into a sort of pulp, which becomes of a blackish colour, from the action of the acids in the gastric fluid upon the blood contained in the vessels of the stomach. This is the pultaceous softening, which I regard as a post-mortem change, * [It usually consists of the mucous membraue, the cellular coat, and the circular muscular fibres.] THE STOMACH. 359 but which has been erroneously confounded with the gelatiniform softening. I'his second portion of the mucous membrane, i. e., the part situated to the right of the oesophagus, is thicker, stronger, and whiter, and may be separated entire from the other coats. Dis- eases often observe the line of separation between the right and the left portions of the stomach. Modern pathologists having attached great importance to the condition of the gastric mucous membrane, it has become highly interesting to determine its characters in the healthy state ; these characters relate to its colour, its consistence, and its thickness. Colour. — It is extremely difficult to determine what is the natural colour of this mucous membrane. The opinion generally maintained by the best authorities, that it is either primarily or secondarily affected in the majority of diseases, compels us to reject all ob- servations made upon persons who have died from acute or chronic diseases, or even from wounds or injuries of long standing. We are, therefore, obliged to have recourse to cases of accidental death in persons previously in health. In such cases, for example, in criminals who are executed while the stomach is empty, the mucous membrane is found of a grayish-white colour, with a slight tint of yellow and pink.* When death has occurred during digestion, the mucous membrane is found to vary from a delicate pink to the most vivid red. After putrefaction has made some little progress, we find a red or port wine colour, or a brownish black tint prevailing over the great extremity of the stomach, and at the free edges of the folds or wrinkles to which the vessels correspond ; again, it is often found marked with blackish patches, or marbled ; but these discolora- tions are the result of post-mortem transudation. In the pultaceous and blackish softening of the mucous membrane, the colour is owing to the action of the acids in the gastric juice. Wlien the stomach contains bile, the mu- cous membrane is tinged with yellow or green, and the stain sometimes remains after the longest maceration. If the mucous membrane be rubbed with a rough cloth, so long as the vessels contain blood, we may produce a red punctuated appearance, which has been often mistaken for a sign of inflammation. Lastly, in the aged we not unfrequently observe a slate gray colour, either in points or in patches, or diffused over the surface. This colour occupies the papillae, and may afford proof of some former irritation, but is certainly not due to any diseased action during the later periods of life. These different discolorations of the stomach must not be confounded with the alterations in its colour resulting from disease. Thickness. — It is difficult to estimate the exact thickness of the gastric mucous mem- brane. Like the muscular coat, it varies in different individuals ; in chronic inflamma- tion it is twice or three times its natural thickness. In determining the thickness of this membrane, it is important to bear in mind the difference in this particular between the oesophageal and pyloric portions ; the former being extremely thin, and the latter twice or three times as thick as that. Consistence. — The same remarks apply to its consistence, for there are many individ- ual varieties in this respect. The oesophageal portion may be torn with great ease ; but the pyloric portion is so dense, that the back, and even the edge of a scalpel, may be drawn over it with considerable force without wounding it. If there has been any liquid, or even food in the stomach, in however small quantity, the mucous membrane of the oesophageal portion, when macerated, is converted into a pulp ; moderate distension will then rupture the weills of the stomach, which may be broken through by the point of the finger. From want of sufficient reflection upon this subject, men of great merit have commit- ted serious errors in the appreciation of morbid lesions. In the gelatiniform softening, the gastric mucous membrane, as well as the other coats of the stomach, become dis- solved, and resemble a solution of gelatine. In many old people, and in some adults, I have found the mucous membrane so thick and so strong, that it could be dissected off entire, and removed in one piece. This condition coexisted with the slate colour, either accompanied or not with chronic inflammation. The PapillcB. — If we examine the mucous membrane of the stomach, placed under wa- ter, and exposed to the direct rays of the sun by the aid of a powerful lens, we shall find that its surface is very irregular, mammillated. Fig. 152. Fig. 153. and furrowed, so as to present an appearance very like the convolutions of the small intestine. The eminences, which are much more distinct to- wards the pylorus than near the oesophagus, are studded with holes, or, rather, with small pits resembling the cells of a honeycomb (figs. 152, 153). These alveolar depressions are well de- scribed by Home, who states that they exist only r-i m -tj^an— « in the great cul-de-sac, while the viUi occupy the ""'il^fi J32 a.aB.rt^!' ^^S^S^toT * In a great number of individuals who have died from acute or chronic diseases, the gastric mucous mem- brane is found in the same state as in those who have died accidentally ; it is, therefore, not always affectedi either primarily or secondarily, in disease 360 SPLANCHNOLOGY. rest of the stomach. The truth is, that a precisely similar stmcture is observed ovei the whole stomach. The alveoli, or pits, are separated from each other by small pro- jections, or papilla {fig. 153), of vi^hich the papillae of the tongue convey an excellent idea.* Should these papillae be distinguished from other projections that have been termed villi, by Ruysch, for example, who called the entire membrane villoso-papillaris ? Aftei the most minute examination, I have only detected one order of eminences,! viz., the papilla, the existence of which I regard as the essential character of all tegumentary membranes, whether mucous or cutaneous, which might all, therefore, be designated papillary membranes. We shall return again to the structure of the papillse. If we examine with a lens or simple microscope a perpendicular or oblique section of the mucous membrane of the stomach, we shall perceive that it consists essentially of a strong membrane, the mucous dermis, from which arise an immense number of small eminences closely pressed together, and of unequal lengths, like the pile of velvet. These eminences are the papillae ; they are liable to great enlargement in cases of hy- pertrophy, and then the structure just described becomes very apparent. The Follicles. — The follicles of the stomach can be very easily demonstrated in the pigt and in the horse. In the last-mentioned animal, entozoa are frequently found in the centre of these follicles, which then become developed into hard, and sometimes very large tumours. It is so difficult to demonstrate them in the human subject, that, with most anatomists, I, for a long time, doubted their existence. Haller only saw them once or twice ;^ but in some individuals they are very distinct. I found them well marked in a great number of cholera patients. II They are not situated in the sub-mucous cellular tissue, as is generally stated, but in the substance of the membrane itself, so as to form a projection on the inside of the stomach, but not on the outer surface. They are rounded, flattened, and perforated by a central foramen, which is usually visible to the naked eye. I have observed them upon all points of the mucous membrane, but they appear to be most numerous near the oesophageal orifice, and along the lesser curvature. IT The Vessels and Nerves of the Stomach. — The arteries are very large and numerous in proportion to the size of the stomach ; they must, therefore, assist in the performance of some function besides the mere nutrition of the organ ; this function is the secretion of the gastric juice. They all arise from the cceliac axis, and are the coronary, the su- perior pyloric and right gastro-epiploic branches of the hepatic, and the left gastro-epi- ploic and vasa brevia, which are branches of the splenic artery. These arteries anas- tomose, so as to form around the stomach a vascular zone, which is in close contact with that organ during distension, but at some distance from it when empty. From this arterial circle branches are given off, which at first lie between the peritoneal and the muscular coats, but, after a certain number of divisions and anastomoses, perforate the muscular and fibrous coats, and again subdivide and anastomose a great number of times in the loose sub-mucous cellular tissue, until, having become capillary, they penetrate the mucous membrane. The veins bear the same name, and follow the same direction as the arteries ; they contribute to form the vena portae. Schmiedel (Variet. Vasorum, No. xix., p. 26) has seen the coronary vein of the stomach anastomose with the renal vein, the pyloric with the vena azygos, and one of the venae breves with the phrenic vein. The lymphatic vessels are very numerous, and terminate in the lymphatic glands, situ- ated along the two curvatures of the stomach. The peculiar ducts, said to proceed from the spleen to the stomach, and supposed by the ancients to be passages for the atra bilis, are purely imaginary. The nerves are of two kinds, some being derived from the eighth pair, and others from the solar plexus. The nerves of the eighth pair form a plexus around the cardiac orifice, the left nerve being distributed upon the anterior, and the right upon the posterior surface of the stom- * [The alveoli are from t^tt'^ '■° oTo*^ °^ ^^ inch, and, near the pylorus, y^n^th of an inch in diameter. At the bottom of each alveolus is seen a group of minute apertures (fig. 152), which are the open mouths of small tubes placed perpendicularly to the surface of the membrane, and closed at the other end. In a vertical section of the membrane, these tubes, which average about -jijyth of an inch in diameter, are seen to rest upon the sub-mucous tissue by their closed extremities. In the cardiac portion of the stomach they are short and stiuight ; near the pyloric end they are longer, and convoluted, or irregularly dilated, and are sometimes bifur- cated. Bloodvessels pass up between these tubes, and form a capillary network round the borders of the al- veoli. The membranous projections sometimes found between the alveoli {fig. 153) form irregular fringes, broader than the lingual papillae, and seem rather to be imperfectly developed villi (see note, p. 361), and are usually so called. The epithelium covering the entire mucous membrane of the stomach consists of a single layer of minute columnar cells ; it is very delicate, and invisible, except by a high magnifying power ; hence its existence was formerly denied.] t Upon this subject see the Memoir of Helvetius.— (/Tj'ii. Acad. Roy. des Sciences, 1720.) t [In the pig these follicles appear to be nothing more than prolongations of the mucous membrane, or small diverticula; so that, after having detached the mucous membrane, they may, by slight pressure, be turned inside out.] t> " Neque rejici debent, etsi non semper possint ostendi." — (Haller, 1. vi., lib. xix., p. 140.) II Vide Anat. Path, avec planches, liv. xiv., pi. 1. IT [In the neighbourhood of the (esophageal orifice there are also several small cgmpound glands, analogous to Brunner's glands in the duodenum. — (W. S.)] THE INTESTINES. 36] ach. They may be followed as far as the muscular coat, where they seem to be lost , division of them paralyzes this coat. By means of the nerves of the eighth pair, the stomach is connected with the oesophagus, the lungs, the pharynx, the larynx, and' the heart. Through the nerves derived from the central epigastric plexus, and named after the arteries that support them, the stomach is connected with the ganglionic system and is brought into relation with the numerous viscera of the abdomen. Lastly, a very delicate serous cellular tissue unites the different coats of the stomach. There are three layers of this tissue, viz., one between the peritoneal and the muscular coats, another between the muscular and the fibrous, and a third between the fibrous and the mucous coats. The last of these is the most distinct ; it is liable to both serous and sanguineous effusions, and may become the seat of diffuse inflammation. I have lately seen it infiltrated with pus to a considerable extent, the mucous and the fibrous coats being both perfectly healthy. Develcypment of the Stomach. — The stomach of the foetus is remarkable on account of its vertical position, which is due to the great development of the liver, especially of its left lobe. An unnatural development of that lobe will also occasion a similar position of the stomach in the adult. The relative smallness of the stomach, and the slight de- velopment of its tuberosity, are also characteristic of its foetal condition.* Nevertheless, from the first moment of its appearance, it is distinguished from the rest of the aliment- ary canal by its greater size. The changes which the adult stomach undergoes, and the variations in size which it presents, are, perhaps, less dependant upon congenital differences than upon particular habits. The differences in the two sexes are manifest- ly due to the pressure to which the stomach of the female is subject, either from the use of stays or from the gravid uterus. I may here advert to the development of the mus- cular ring of the pylorus, and of the neighbouring part of the stomach in aged persons. Function. — The stomach is the organ of chymification, or of that process by which the food is converted into a homogeneous gray pulp, called chyme. For that purpose it is evidently necessary that the food should remain for some time in this organ, and the elasticity of the muscular coat of the oesophagus and of the ring at the pylorus are suffi- cient to prevent its regurgitation into the gullet, or its passage into the duodenum. When the process is completed, however, the peristaltic contraction of the muscular fibres of the stomach overcomes the resistance of the pylorus ; in eructation, regurgita- tion, and vomiting, the same peristaltic movements are assisted by the contraction of the diaphragm and the abdominal muscles. Chymification is a chemical, or, at least, a molecular action, and is effected by means of the gastric juice, mixed with the salivary and oesophageal secretions. These fluids are acid.t The influence of the nerves upon digestion has been ascertained by ingenious experi- ments, the results of which, however, have been interpreted in various ways. The Intestines in general. The term intestine, in its widest signification, is applied to the whole alimentary ca- nal ; but, in a more limited sense, it means that long and frequently-convoluted tube, extending from the pylorus to the anus, and occupying almost the whole of the abdomi- nal cavity. The intestines have been divided, according to their calibre, into the small {b to d,Jig. 139) and the large (c to i) ; this distinction, which is applicable to most ani- mals, is anatomically established in man by a difference in size, by the sacculated char- acter of the large intestine, by a difference in direction, by the presence of a valve, by the existence of a caecum and of a vermiform appendix, and, lastly, by a difference in structure, especially in the muscular and mucous coats. Tlie same distinction is recog nised in physiology, and upon equally good grounds, for the small intestine is essentid- ly concerned in the formation and absorption of the chyle, while the large intestine is the organ of defsecation.J These differences will be rendered more apparent from the de scription of these two important parts of the alimentary canal. The Small Intestine. The small intestine includes all that part which is situated between the stomach and the large intestine (i to d,fig. 139). According to Haller, Bichat, and their followers, the upper portion, called the duodenum (b to c), should be abstracted from the small in- testine, which, according to them, would commence at the termination of the duodenum. It appears to me that the former definition should be adhered to, on account both of the * [At early periods of foetal life, villi are found on the mucous membrane of the stomach g-enerally, after- ward on the pyloric portion only ; and, subsequently to birth, the only traces of these are the irregular frmgcB observed here and there between the alveoli.] t [The saliva, though sometimes acid, is usually alkaline.] i The division into a small and large intestine exists among all vertebrated animals ; but no animals, ex- cepting the ourangs and the wombat, have both a ciecum and an appendix vermiformis. In some we find one caecum, or several caeca ; in others, one or more vermiform appendices ; others have neither csecum nor appen- dix, but a valvular fola arit a well-marked change in diameter indicate the limit between the small ana larf« intestines. In some, again, the only difference consists in a change of diameter. Zz 9m SPLANCHNOLOGY. absence of any real line of separation between the duodenum and the rest of the small intestine, and of their similarity in structure and function. The small intestine is divided into three parts, the duodenum, the jejunum, and the ileum. The division between the duodenum and the rest of the small intestine is defi- nite, but that between the jejunum and the ileum is altogether arbitrary ; so that we shall follow the example of Haller, Scemmering, and others, in describing the jejunum and ileum together (c to d), under the name of the small intestine, properly so called. The Duodenum. Dissection. — ^When the abdomen is opened, the first portion only of this intestine is visible ; the second is hid by the ascending colon ; the third is seen in the cavity of the omentum. The second is brought into view by turning aside the colon. The third por- tion, which is the most difficult to demonstrate, may be exposed in two ways : either by cutting through the inferior layer of the transverse mesocolon, or by turning the stomach upward, after having divided the lavers of the grest omentum, which are attached along its greater curvature. Fig- 154. The duodenum {dudsKa 6uKTvXov, p b, Jig. 154), so called by Herophilus (Ga- len, Administr. Ariat., lib. vi., c. 9) on account of its being about equal in length to the breadth of twelve fin- gers, commences at the py- lorus, and terminates, with- out any precise line of de- marcation, to the left of the second lumbar vertebra, at the point where the small intestine enters into the mesentery, or, rather, op- posite the superior mesen- teric artery (m) and vein, which pass in front of it. Its fixed position, its struc- ture, and its curvatures, have led to its being de- scribed separately.* It is difficult to determine its precise situation with regard to the abdominal parietes. It is not exclusively confined to any one region, but occupies in succession the adjacent borders of the right hypochondrium and the epigastrium, of the right lumbar and the um- bilical regions, and of the epigastric and umbilical regions. The duodenum is found more deeply situated in proportion as we recede from the py- lorus, and hence the difficulty of exploring it through the parietes of the abdomen. It is fixed firmly in its place by the peritoneum, by the mesenteric vessels and nerves, which bind it down, and by the pancreas. This fixedness is one of its principal peculi- arities, and is indispensable in consequence of its relations with the ductus communis choledochus ; for had it been movable like the rest of the small intestine, incessant ob- structions to the flow of the bile would have occurred. It follows, also, that the duode- num can never form part of a hernia ; its first portion may, indeed, be displaced, for it is less firmly fixed than the remainder, and is sometimes dragged out of its proper situ- ation by the pyloric extremity of the stomach. Dimensions. — It is eight or nine inches in length ; its calibre is somewhat greater than that of the rest of the small intestine, but the difference is not so decided as to war- rant the names of second stomach, or ventriculus sUccenturiatus, which have been given to it. I have even met with subjects in whom the duodenum, when moderately distended, was five inches, while the succeeding portion of small intestine was six inches in cir- cumference. It has been supposed that this part is more dilatable than the rest of the small intestine ; this has been attributed to the absence of the peritoneum. The fact and the explanation are equally without foundation. It is the fibrous membrane, and not the peritoneal coat, which is opposed to dilatation of the intestines. Direction. — This is very remarkable. Commencing at the pylorus, the duodenum passes upward to the right side and backward ; having reached the neck of the gall- bladder, it suddenly changes its direction, and becomes vertical, forming an acute angle ■with the former portion ; this is its first curvature (e) : then, after proceeding vertically through a variable space, it passes transversely from the right to the left side, and be- comes continuous with the rest of the small intestine. This change in its direction takes place at a right angle, and is, therefore, less abrupt than the former ; the point at which it occurs is called the second curvatare (e'). * Glisson considered the insertion of the ductus communis chnlfidochm! "■••'"' ".-er limit of the duodtJiiuni. THE INTESTINES. 363 It follows, then, that the duodenum describes a double curve, or, rather, one single curve, of which the concavity is directed towards the left, and the convexity to the right side. Haller has ingeniously- compared the course of the duodenum to two parallel lines, intersected by a perpendicular. This double change in the direction of the duode- num, which is probably intended to retard the passage of the food, enables us to consider it as composed of three portions, distinguished as the first (p e), second (e e'), and third (e' d). Relations. — These should be studied in each of the three portions. Relations of the First Portion. — Above, with the liver (/', fig. 154*) and the gall-bladder (g), to the neck of which it is united by a fold of the peritoneum. It is not uncommon to see the gall-bladder and the duodenum closely adherent to each other, and to find an opening through which biliary calculi have passed into the gut. Li front, with the gas- tro-colic omentum and the abdominal parietes. Behind, with the hepatic vessels, and the gastro-hepatic omentum. This portion of the duodenum, which may be denomi- nated the hepatic, is about two inches in length. Relations of the Second Portion. — In front, with the right extremity of the arch of the colon (t,fig. 161, e being the duodenum), which crosses it at a right angle. Behind, with the concave border of the right kidney, along which it descends to a greater or less dis- tance, together with the vena cava inferior and the ductus communis choledochus. Some- times this portion is not in relation with the kidney, but rather with the vertebral col- umn. The ductus communis choledochus {c,fig. 169) and the pancreatic duct (m) enter the intestine at the posterior and inner surface, and below the middle of this portion of the duodenum. The relations of the duodenum behind are direct, i. c., without the in- tervention of the peritoneum. On the right, this portion of the duodenum is in relation with the ascending colon {a, fig. 161). On the left, with the pancreas {o,fig. 154), which is closely united to it, and embraces it in a sort of half groove. This second portion is two or three inches in length ; it may be called the renal portion. Relations of the Third Portion. — The third portion is situated in the substance of the adherent border of the transverse mesocolon. Below, it rests upon the lower border of that fold. Above, it is bounded by the pancreas, which adheres closely to it. In front, it corresponds to the stomach, from which it is separated by the layer of peritoneum which lines the sac of the great omentum. Behind, it corresponds to the vertebral col- lunn, from which it is separated by the aorta (a), the vena cava, and the pillars of the diaphragm {d d).i As the internal surface and the structure of the duodenum are very analogous to those of the jejunum and ileum, I shall postpone the description until I have noticed the exter- nal conformation of the rest of the small intestine. Fig. 155. The Small Intestine, or the Jejunnm and Ileum. The small intestine, properly so call- ed (c d,fig. 139 ; i i i,fig. 155), or the jejunum and ileum, consists of that por- tion of the alimentary canal which fills almost the whole of the abdomen, oc- cupies the mnbilical, hypogastric, iliac, and lumbar regions, and is surround- ed, as it were, more or less complete- ly, by the large intestine {efgh, fig. 139 ; a t d, fig. 155). Its upper ex- tremity (/ fig. 161) is continuous, without any hne of separation, with the duodenum. The distinction be- tween the two parts is established by the angle which the mesentery forms with the mesocolon, or, rather, by the point where the superior mesenteric vessels cross over the small intestine. Its lower extremity {d,fig. 139 ; i,fig. 161) enters at a right angle into the large intestine. The old division of the small intestine into the jejunum and ileum should be banished with oth- er anatomical niceties, for it is found- ed only upon trivial distinctions ; and although the upper part of this intes- tine differs in many respects from the * In which figure the liver and stomach are turned upward. t In one subject I found a fourth portion which passed upward, and was ahmit one inch ir len!?th, so that the duodenum described a third curve, with its conc.avitv directed to the right. 364 SPLANCHNOLOGY. lower, still the alteration takes place by imperceptible gradations.* So that Winslow, unable to find any real difference, established a purely conventional distinction, by pro- posing to call the upper two fifths the jejunum, and the lower three fifths the ileum. No portion of the alimentary canal is so movable as the small intestine, properly so called. It is exceedingly loosely attached, or, as it were, suspended from the vertebral column, by a large fold of the peritoneum, called the mesentery (the attached portion of which is seen at m,fig. 161), which, being broader in the middle than at either extrem- ity, gives an unequal mobility to the different parts supported by it. The small intes- tine is displaced with great facility. The circular boundary described around it by the large intestine is only exact above, where the mesocolon and the arch of the colon («, fig. 155) completely separate it from the stomach («), the liver (Z), the spleen (k), and the duodenum. But below, between the caecum {c,fig- 161) and the sigmoid flexure of the colon (/), it descends into the pelvis, and, extending laterally, passes in front of the colon in both the right and left lumbar re- gions. This excessive mobility is one of the most characteristic and important facts regarding the small intestine, which, in some measure, floats in the abdominal cavity, yielding to the slightest impulse or concussion. Of all the viscera, it is the most frequently involv- ed in hernia. It is liable to invagination, i. e., one portion may be received, as into a sheath, into that immediately succeeding it. When any organ in the abdomen becomes enlarged, the small intestine yields, and passes in the direction where there is least re- sistance. It appears to partake of the mobility of fluids. It collects together, or spreads out ; it moulds itself upon the adjacent parts, and fills up every space, so as to elude aU causes of compression ; and, by means of this admirable contrivance, the abdomen ac- commodates itself without inconvenience to the occasional enormous development, either natural or diseased, of the organs contained within it. Direction. — We have seen that the upper or supra-diaphragmatic portion of the diges- tive canal is straight. The stomach presents one slight curve. The duodenum has two decided curves, and the rest of the small intestine pursues a not less flexuous course. The following is the direction of this intestine: commencing at the duodenum {j,fig- 161), it passes forward and to the left side ; it is then folded a great number of times upon itself, and, at its lower part, it passes transversely from the left to the right side, and a little upward, in order to enter at a right angle (i) into the great intestine. The numerous foldings or turnings (gyri) of the small intestine upon itself have re- ceived the name of convolutions ; they are moulded upon each other, without intermixing or becoming entangled, so as to form a mass, which so closely resembles the surface of the brain, that the term convolutions has also been applied to the winding eminences of that organ. Each convolution represents an almost complete circle. In the complexity presented by the numerous windings of the small intestine, it appears to be very difficult to assign to it any general direction ; nevertheless, if we consider that the small intestine com- mences to the left of the second lumbar vertebra, and terminates in the right iliac fossa, it will be seen that its general direction coincides with that of the membranous fold (m, Jig. 161) which supports it ; that is, it may be expressed by an oblique line ruiming downward from the left to the right side. If, however, we examine the particular di- rection of the convolutions, we shall find that they all present a concavity towards the mesentery, and a convexity towards the parietes of the abdomen, so that each resem- bles the half of the figure 8. In consequence of this arrangement, the intestine may be- come folded without much change in its position, either in advance or otherwise ; and hence the great number of folds which can be placed between two points so near each other as the left side of the second lumbar vertebra and the right iliac fossa, the distance between which is not more than four inches. Dimensions. — The determination of the length of the small intestine, properly so called, has at all times been a subject of interest. Meckel says that it varies from thirteen to twenty-seven feet, including the duodenum. According to my observations, it varies from ten to twenty-five feet in the adult, t The length of the small intestine, compared to that of the large intestine, is generally as five to one. The different results which have been obtained by various authors may be explained partly by individual varieties and partly by the mode in which the measurements were made. Thus, a more or less perfect separation of the gut from the membranous folds which support it would lead to different results. But another, and less understood cause of difference, is the influence of the caliber of the intestine upon its length. The caliber and the length have always an inverse ratio to each other. Of this we may be easily convinced, by strongly infla- ting a portion of gut which has been previously measured. I have often been struck * The upper part of the intestine is caWed jejunum, because it is generally found empty ; the second, ileum, either because it has been supposed chiefly to occupy the iliac regions, or on account of its convoluted disposi- tion, which, however, is common to it with the other (tiXtti', to turn, to twist). t The average length of the small intestine, including the duodenum, is 20 feet. I have lately measured several : in a female affected with chronic peritonitis, it was only 7 feet long ; in another, 14 ; in a third, 18 ; in a fourth, 20 ; and in a fifth, 22. THE INTESTINES. 365 with the shortness of the small intestine in cases of hernia, accompanied with retention of the contents of the gut above the strangulation. Some authors have attempted to establish a relation between the length of the intes- tine and the stature of the individual ; and it has been affirmed that the former is four or five times the height of the body. But differences in stature have not a uniform rela- tion to the length of the alimentary canal. Lastly, individual varieties in the length of the small intestine do not appear to h8T6 any influence upon the activity of the digestive process. Caliber. — The cahber of the small intestine, properly so called, is not the same through- out. It is greater at the commencement than at the termination of the intestine. When moderately distended by inflation, I have found it six inches and four hnes in circum- ference at its commencement, four inches and two lines at the middle, and three inches and a half a little above its entrance into the large intestine ; but at the point of entrance itself it is dilated to about four inches and a half The small intestine, therefore, is funnel-shaped, a form which must facilitate the rapid passage of its contents, by causing them to proceed from a wider into a narrower space. Lastly, the caliber of the small intestine presents many varieties. When any obstruc- tion occurs to the passage of its contents, it may attain the caliber of the large intestine. In certain cases of marasmus, when it contains no gases, it becomes so contracted that the tube is completely obliterated. Figure and Relations. — The smaU intestine is cylindrical ; a section of it is almost cir- cular. Its posterior harder, to which the mesentery is attached, is concave ; it is thrown into shght folds, as every straight cylinder must be when it is bent into a curve. Its anterior border is convex, free, and corresponds to the abdominal parietes, being separa- ted from them by the great omentum,* which seems intended to contain the whole mass of the intestinal convolutions. When the omentum is wanting, as in the foetus, or in cases of displacement from its being rolled up into a cord, the small intestine is in im- mediate contact with the parietes of the abdomen. The lateral surfaces of the different convolutions of the small intestine are in contact with each other. As these surfaces are convex, they intercept triangular spaces before and after them, in which either effused blood, or serum, or pus, or false membranes, are sometimes collected. The small intestine corresponds to all the regions of the abdomen, excepting those of the upper zone. Not uncommonly, we find it escaped from under the omentum, and sit- uated between the hver and the abdominal parietes, or reaching into the left hypochon- drium. It is immediately forced, as it were, in any direction in which there may be an opening, t More or less of the small intestine is always found in the pelvis ; in the male, between the bladder and the rectum ; in the female, between the bladder and the uterus, and be- tween the uterus and the rectum. In several persons who were emaciated from chronic diseases, and in whom the vertebral column could be plainly felt through the parietes of the abdomen, I have found almost the whole, and, in some cases, even the whole, of the small intestine within the pelvis, contracted, and almost entirely void of air. When one portion only of the small intestine is in the pelvis, it is invariably the lower part. WTien any large mass is developed in the abdomen, as in pregnancy, or in encysted dropsy of the ovarium, the small intestine passes upward and laterally, becomes diffu- sed, fills up every space, and almost always escapes compression in the most remarka- ble manner. It is not uncommon to find, in the small intestine, appendices or diverticula, like the fingers of a glove, which are sometimes two or three inches in length, and have been found in the sacs of herniae. These diverticula are usually much nearer the lower than the upper part of the small intestine. They are formed by all the coats of the bowel, and are very different from mere protrusion of the mucous membrane through the mus- cular coat, of which I have seen one example in the duodenum, and which I have often met with in other parts of the small intestine. In a subject which I recently examined, the small intestine presented about fifty spheroidal tumours of unequal size, all situated along the mesenteric side of the gut, and formed by protrusions of the mucous membrane through the muscular fibres. Structure of the Small Iritesttne. Dissection. — This structure must be studied upon a distended and moist portion of in- testine, upon a distended and dried specimen, and also upon one inverted and distended. It is also of importance to study the mucous membrane under water, with the assistance of a strong lens. Injections thrown in first by the veins, and then by the arteries, are also useful in developing its structure. t * [Injig. 155, the great omentum has been removed.] . . t The small intestine is found in diaphragmatic hernicc ; it constitutes perineal hernia ; and it is this por ion of the bowels which escapes from the pelvis when the lower wall of that cavity is divided. t The internal surface of the small intestine will be noticed with the mucous membrane. 1 i 366 SPLANCHNOLOGY. The small intestine, as well as the stomach, is formed of four coats or membranes, which, proceeding from without inward, are the serous, muscular, fibrous, and mucous coats. The Serous Coat. — The arrangement of this coat upon the duodenum differs from that upon the rest of the small intestine. The peritoneum is apphed to the first portion of the duodenum in the same way as upon the stomach, i. e., it covers it entirely, excepting in front and behind, where there is a triangular space devoid of this coat. Like the stomach, this first portion gives at- tachment to the great omentum in front, and to the small omentum behind. The fold of peritoneum which passes from the liver to the duodenum has been improperly called the hepatic ligament of the duodenum. The peritoneum merely passes over the front of the second and third portions of the duodenum, so that the posterior surface of the in- testine is in immediate contact with the parts with which it is in relation, and is very perfectly fixed. The peritoneum forms a complete sheath for the small intestine, properly so called, ex- cepting along its concave border, where the two layers which constitute the mesentery separate from each other, so as to include the bowel. In this situation we find a trian- gular cellular space, exactly resembling those which we have already described along the curvatures of the stomach, and performing a similar office, viz., that of remedying the slight extensibility of the peritoneum, and permitting the intestine to undergo sudden dilatation to a great extent. We should have a very incorrect notion of the dilatability of the intestine if we imagined that it is limited by the triangular space along its con cavity, for when the bowel is much distended, the mesentery itself becomes separatee into its two layers to allow of such distension. Of this I am convinced from having measured the antero-posterior diameter of the mesentery both before and after inflation of the bowels. The cellular tissue which unites the peritoneal to the muscular coat is extremely del- icate, and its adhesion to the latter coat increases in proceeding from the concave to the convex border of the intestine. Although the peritoneal coat is very thin, and so trans- parent that the muscular fibres may be seen through it, yet it has considerable strength. The muscular coat is composed of two layers of involuntary muscular fibres, one su- perficial, the other deep. The superficial layer is the thinner ; it consists of longitudinal fibres placed around the bowel in a very regular manner, and forming a continuous plane. I have never found these fibres more numerous at the mesenteric than at the convex border. This layer of fibres is almost always removed with the peritoneal coat, to which it adheres very intimately. From their white colour and shining appearance under the serous membrane, they have been supposed to be of a tendinous nature. It is difficult, though by no means important, to determine exactly whether the same fibres reach the whole length of the intestine, or whether they are interrupted at inter- vals. It is generally admitted that they are interrupted, and that their extremities are received in the spaces between other fibres. The deep layer of muscular fibres is thicker than the preceding, and consists of circu- lar fibres, either parallel or crossing each other at very acute angles. They appear to me to describe complete circles, and to have their ends united. They have no tendinous intersections. The fibrous coat is intermediate between the muscular and mucous tunics, and presents the same characters as in the stomach. The Mucous or Papillary Membrane. — Its external surface adheres to the fibrous membrane by a loose cellular tissue, which is liable to serous, sanguineous, and purulent infiltra- tion. The emphysematous or cedematous condition may be imitated in the dead body, by everting a portion of bowel and distending it either with air or water. The tenuity of the mucous membrane displayed in these experiments has led to the opinion that this coat is nothing more than an epithelium, a continuation of the epidermis of the skin, and that the fibrous coat represents the cutaneous dermis. Its internal surface is free, and is covered with more or less mucus ; it is remarkable for its duphcatures or valves, call- ed valvules conniventes ; for its highly-developed papillee, and for the arrangement of its follicles. The ValvulcB Conniventes {Valvulce Intestinales). Dissection. — Evert the small intestine, so that its external surface becomes internal, and then plunge it in water ; or, what is better, lay open the bowel, and examine its internal surface under water. Also study a portion of intestine inflated and dried. Hitherto the mucous membrane of the alimentary canal has only presented to our no tice certain folds which are intended to facilitate the dilatation of that canal, as in the cesophagus and stomach, and which are completely effaced by distension. The folds of the mucous membrane of the small intestine fulfil another purpose ; and although they must, undoubtedly, in some measure assist in the elongation and dilatation of the bowel, yet they are never entirely effaced, however far this extension in length or width maj be carried. These folds deserve a special description. They are called valvulce conni- ventes or the valves of Kerkringius, although Fallopius had given a complete description THE INTESTINES. 367 of them before that anatomist. Kerkringius gave them the name of conniventes {con niveo, to close partially). They commence in the duodenmn (see fig. 169), an inch, oi sometimes two inches, from the pylorus ; and it is not unconunon to find them preceded by some vertical folds. They are few and small at first, but become very numerous and very large towards the end of the duodenum and the commencement of the small intestine, properly so called. From the upper two fifths of that intestine they gradually diminish in number, and become less regular and less marked towards the lower part of the small intestine ; sometimes they are altogether wanting in the last two or three feet of the bowel. In some rare cases, I have seen valvulae conniventes as far down as the ileo- caecal valve ; in no part are they sufficiently numerous to have a true imbricated arrange- ment. These valves are placed perpendicularly to the axis of the intestine, and describe one half, two thirds, or three fourths of a circle ; but they seldom form a complete ring. They are broader in the middle, being from two or three lines in width, than at their ex- tremities, which are slender. In order to ascertain their dimensions, they must be placed under water, or studied upon a fresh portion of intestine. They are generally parallel, incline towards each other by their extremities, bifurcate, and send off smdj verticular oblique prolongations. Sometimes we find small valves placed between the larger ones. Some of them are suddenly interrupted, so that they might be supposed, at first sight, to have undergone some loss of substance. Several of them are alternate, and seem to be disposed in a spiral manner ; but there is no general rule in this respect ; their free edge is sometimes directed towards the pylorus, and sometimes towards the ileo-cffical valve. Their direction is very irregular ; they yield to any impulse that may be conamunicated to them, and their free edge passes either upward or downward, ac- cording to circumstances. When examined upon a dried specimen, they resemble very much the diaphragms in optical instruments. The valvulae conniventes are formed by folds of mucous membrane, within which we find some loose cellular tissue, different kinds of vessels and nerves. Inflation, by rais- ing the mucous membrane, completely effaces them. The fibrous coat presents a slight thickening opposite the bases of these valves. The valves, notwithstanding the ease with which they are moved, must in some manner retard the passage of the food, with- out offering any decided resistance to it, for that would become a cause of obstruction, and give rise to serious accidents. Their chief use, perhaps, is to increase the extent of surface ; according to Fabricius, they double the surface of the intestine ; Fallopius says they increase it three times, and Kew six times. Soemmering has given the some- what conjectural opinion, that the surface of the intestinal mucous membrane is greater than that of the entire skin (Corpor. Hum. Fabrica, t. vi., p. 295). Although not peculiar to the human species, they are much more developed in man than in the lower animals. Besides the valvulag conniventes, the mucous membrane of the small intestine presents some irregular folds, which are effaced by distension. The PapilloR, or Villi. Preparation. — 1. Place the opened intestine in water, exposing it to a strong light, and agitate the fluid. A stream of water previously received upon the membrane will re- move the mucus, which sometimes forms a tenacious sheath around each papilla.* 2. Roll up a portion of the detached mucous membrane, taking care to turn the adherent surface inward. 3. Evert a loop of intestine, so that the peritoneal coat may be on the inside : stretch it upon a cylinder, and then agitate it in a cylindrical vessel, so as to float out the valves. The papilla, or villi, are much more developed in the small intestine than in any other part of the alimentary canal, with the exception of the tongue. Fallopius has the honour of having discovered them. They were T,vell described by Helvetius, Hewson, and Lie- berkuhn, but still more accurately of late by Albert Meckel. When examined by the naked eye and under the microscope, the internal surface of the intestine appears to be roughened by an inunense number of prominences or vilh {figs. 157, 159), resembling very close, short grass, or a very hairy caterpillar. In some animals, as in the dog, and especially in the bear, the villi are so numerous and so long, that they in some degree resemble the filzmientous roots of plants. They are found through the whole length of the small intestine, and cover the valvulae conniventes, as well as the intervals between them. They vary in length : according to Lieberkuhn, they are one fifth of a line ; their maximum length appears to be about four fifths of a line : and I have even found some in the duodenum, which, when extended, were a line in length ; their number is very con- siderable, and attempts havQ been made to determine it. Lieberkuhn computed them at 500,000. Several Germans have taken up the subject ; allowing 4000 to every square inch, by a calculation, the exactness of which I have not verified, there would be a mill- ion altogether. I have not observed any well-marked difference as regards the number of the vilh, between the commencement and the termination of the small intestine. It * A. Meckel recommends that the mucus should be removed by plunging the intestine first in an arsenical solution, and then in water impregnated with sulphuretted hydrogen ; but the continued action of a stream of water is far preferable. 368 SPLANCHNOLOGY. appears to me that the number and length of the villi are much greater in carnivora than in herbivora. The otter has been said to have the largest vilU of any animal. Their form varies much. In the majority of animals which I have examined, as the dog, cat, calf, and bear, they are fUiform. In the human subject they are all lamellar or foliaceous, but with many varieties. In the duodenum they are curved upon themselves, presenting the appearance of a calyx or corolla, and sometimes adhering to each other by their ex- tremities. In the small intestine, properly so called {figs. 157, 159), they are rectilinear, floating, cylindrical, conical, clubbed at the end, constricted, and sometimes bent in the middle. In the neighbourhood of ulcerations, they are, as it were, cut oiF close or trun- cated, without presenting any alteration in their structure. Structure. — Brunner calls them membranous tubes ; Leeuwenhoek regarded them as muscular organs ; Helvetius and Hewson considered them to be small valves, an idea which has been revived and carried out more lately by Albert Meckel. This anatomist, who has given representations of the villi in a great number of animals {Journ. Comple- ment, t. vii., p. 209), regards them as formed of small Icunellae, sometimes twisted upon their axes, like the first leaf of a germinating grain of wheat, and sometimes folded into a semi-canal or groove ; but he considers that all these varieties m^y be referred to that of a lamella, broad at the base and narrow at the apex ; a fundamental form, which may always be demonstrated with the aid of a needle.* Lieberkuhn states, that at the base of each villus there is an ampulla, which opens upon the summit of the villus by a single orifice ; and he considers that both the ampul- la and the orifice belong to the commencement of the lacteal vessels ; arteries and veins ramify round the ampuUa ; and each villus has an afferent artery and an efferent vein. According to Mascagni, the villi are composed of an interlacement of bloodvessels and smEill lymphatics, and are covered by an extremely thin membrane, composed of lym- phatics. The following are the results of my own observations : Having had occasion to examine a subject in which the lymphatic vessels were filled with tubercular matter, I was able to trace a lymphatic trunk into each villus (vide Anat. Path, avec planches, liv. 2), which traversed its entire length. This perfectly agrees with Lieberkuhn's ac- count. In another subject I injected mercury into one of the mesenteric veins, and then above the mercury I forced in a coarse black injection. The mercury and a part of the black injection passed into the cavity of the intestine, and a globule of mercury appear- ed upon the summits of the villi, which were blackened from the injection. From this I have concluded that the villi are perforated at their summits. I shall return to this subject again. t The Duodenal Glands and Follicles. Preparation. — Some intestines are not well adapt- ed for the study of the follicles, which, indeed, seem to be entirely wanting in them. Others, again, are very favourable for that purpose. The folhcles are rendered more apparent by plunging the intestine into acidulated water. They must be examined from the internal surface of the mucous membrane, and also from its external surface, by re- moving the serous, muscular, and fibrous coats by which they are covered. In the study of the duodenal glands, this last method of investigation is absolutely necessary. The follicles are generally divided into two kinds, the simple or solitary, and the ag- minated ; to these we shall add the duodenal glands. The Duodenal Glands. — These, properly speaking, are the glands of Brunner. This anat- omist, who had already made some curious experiments upon the pancreas, says that, having partially boiled the duodenum, he observed upon its internal membrane some granular bodies, which he has had figured, resembling the solitary follicles in the neigh- bouring portion of intestine. To this collection of granules he gave the name of the sec- ond pancreas. Farther observations have shown, that in the upper half, or upper two * [Many of the villi are certainly cylindrical, and, therefore, not referrible to the fundamental form described by Albert Meckel. In the fostus and young subject they are comparatively broader and flatter, and are con- nected at their bases so as to form folds having irregular margins. In this stage of their development they re- semble the rugiB in the intestines of birds and reptiles.] t [The villi contain all the elements of the intestinal mucous membrane ; no nerves, however, have been ao- toally demonstrated in them. Fig. 156. The bloodvessels are numerous, and form a very Deautiful capillary network in each \';llu8 (3, Jig. 156). Great differences of opinion have existed, and still exist, as to the mode of origin of the lacteals in the in- testinal villi ; the best authorities, however, agree in stating that they do not commence by open orifices. Rudolphi and A. Meckel considered that they arose by a closed network. Dr. Ilenle found a single dilated but closed lacteal in each viUosity ; and more recent- ly, Krause observed that in each villus the lacteal arose by several branches, some of which ended in free but closed extremities, while others anastomosed together (i,fig. 156). The villi, and, it may be ob- served here, every portion of the intestinal mucous membrane, are covered by a transparent, columnar epithelium, consisting of elongated prismatic nucleated cor- puscules. The perpendicular arrangement of these upon the surface of a villus is shown in the diagram (1, %. 156).] THE INTESTINES. thirds of the duodenum, there is a layer of flattened granular bodies, perfectly distinct from each other, however close they may be. This layer must not be confounded with the glanduliform arrangement of the duodenal villi ; it can only be well seen after hav- ing removed the three outer coats. These granular bodies are nothing more than small (compound) glands, which, when examined with a powerful lens, present all the charac ters of the salivary glands. These glands do not cease abruptly, but become few and scattered towards the lower end of the duodenum ; so that it is by no means inconsist- ent to admit that the solitary folhcles of the rest of the intestinal canal may be of a simi- lar nature.* The solitary follicles, or glandula solitaries, are generally known in the present day ao the glands of Brunner {Disput. de Gland Duoden., Heidelberg, 1687, 1715), although that anatomist only described the glands or follicles of the duodenum, which he said dimin- ished in number below that portion of the intestine, and disappeared adtogether in the je- junum. It is, therefore, by an extension of the author's meaning that we speak of the glands of Brunner as occupying the termination of the small intestine, the stomach, and even the large intestine. The glandulae solitariae present the appearance of small rounded granulations, like mil- let seeds, projecting upon the internal surface of the mucous membrane, without any distinct orifice, and covered with villi (fig. 157) ; they are found upon the valvulae con- niventes, as well as in the spaces between them. Their number is very considerable ; so that in certain diseases, where they become more prominent than usual, they might be mistaken for a confluent eruption. It is a mistake to say that they diminish in num- ber from the upper towards the lower part of the small intestine, the contrary being nearer to the truth. When examined with the simple microscope, they have appeared to me to be hollow, and filled with mucus. t The agminated follicles, or glandular plexuses, are more generally knov^n as the glands of Peyer, although both the solitary and agminated glands were described by that anato- mist. Pechlin noticed them under the name of vesicularum agmina. Willis, Glisson, Malpighi, Duvemey, and Wepfer have given more or less complete descriptions of them: but Peyer (De Glandulis Intestinorum, J. C. Peyer, 1667, 1673), when still a young man, and without any knowledge of the work of Pechlin, described and figured them under the title oi glandula agminatce so accurately as to leave nothing to be desired. These agminated glands are arranged in elliptical patches {fig. 158), the long diameter of which corresponds with the direction of the intestine : —g.. 153. they are pierced with holes, or small depressions, so that they have a honeycombed appearance ; and hence has arisen the name of plaques gaufries, under which I believe I was the first to describe them : they are all situated on the border opposite to that by which the mesentery is at- tached to the intestine ; that is, along the convex border of the intestine, and never along the concave border, nor even upon either side. They are chiefly found towards the end of the small intestine ; they become more and more scattered as we approach the duodenum, in which, how- ever, Peyer once met with a single patch. Their nuniber varies considerably, twenty, thirty, and even more having been counted. Are they ever entirely wanting 1 The dif- ficulty of detecting them in some subjects has led to their being rejected altogether, or considered as the results of a pathological condition ; but this opinion is clearly at va- riance with observation. Again, these patches are not constant either in situation, form, or dimensions. Some- times they assume the appearance of bands two or three inches in length {fig. 158), and sometimes they form cir- cular or irregular clusters. The largest are found near the ileo-cffical valve. It is not rare to find the termina- tion of the small intestine surrounded by a circular patch ; in other cases, the patches termi- nate some inches above the ileo- ■f!3cal valve, and their place is sup- jjlied by simple follicles. * [According to Dr. Boehra (He Gland. Intestm. Struct, penitiori), this is not tte case, the compound glands of Brunner not existing below the commencement of the jejunum.] t iFig. 157 is a solitary gland magnified ; it is represented, after Boehm, as a closed vesicle, filled with whitish matter, which contains granules smaller than those of mucus. Villi are seen upon the free surface of its capsule, and it is sur- rounded by the crypts of Lieberkuhn (the mouths of which are indicated by the ^aj^e' spots), which have no communication with the vesicle itself (see also note, p 370J.1 A A A Fig. 157. 370 SPLANCHNOLOGY. These patches are generally contained in the substance of the mucous membrane, to _p. j.g which they give a much greater density, so that, in _ ■ ■ these situations, it will bear to be scraped. In some f- < ^ ftases they appear to be imbedded in the fibrous coat. pi; V,. They should be examined both from the external and f' : rwmMfi m internal surfaces of the mucous membrane.* When y '.^millll they are filled with their secreted fluid, and are exam- ined by transmitted light, they may be compared to the vesicles in the skin of an orange : this observation may be easily made in the day. They evidently consist of collections of glands, exactly resembhng the solitary glands {fig. 159). Each depression appears to be the orifice of one of the follicles, which are quite independ- ent of each other ; so that we sometimes find two or three altered in the middle of a patch, which is other- wise perfectly healthy. Lastly, viUi are found upon the patches of the glandulse agminatae : they occupy the in- tervals between the depressions.! The Follicles or Corjruscules of Lieberkuhn. — Lieberkuhn speaks, also, of innumerable, rounded, whitish foUicles, which are seen between the villi, and of corpuscules which are visible between these follicles. He calculates that there are eighty follicles for eighteen villi, and eight corpuscules for each follicle. I am disposed to think that these follicles and corpuscules, which have never been seen excepting by the microscope, should be refer- red to those globules which are reveededin all the tissues by the aid of a magnifying power. | The Vessels and Nerves. — ^All the arteries of the small intestine, properly so called, are branches of the superior mesenteric. They are very numerous. Those of the duodenum arise from the hepatic. The branches from the superior mesenteric are remarkable for the numerous anastomotic loops which they form before reaching the intestine, for their flexuous course within its coats, and for the series of vascular layers formed by them between the peritoneal and muscular, the muscular and fibrous, and the fibrous and mu- cous coats. The last layer forms a very complicated network, from which the vessels of the mucous membrane are derived. The veins are much larger than the arteries, and present a similar arrangement, except in regard to the flexuous course, which is peculiar to the arteries ; they constitute the superior mesenteric vein, which is one of the prin- cipal branches that contribute to form the vena portae. The lymphatic vessels are of two kinds, viz., lacteals and lymphatics, properly so called ; they both enter the numerous lymphatic glands, situated in the mesentery ; those which belong to the duodenum enter the glands above the pancreas. The nerves are derived from the solar plexus. The development of the small intestine will be noticed in conjunction with that of the large intestine. Uses. — Chylification, i. e., the transformation of the chyme into chyle, is effected in the duodenal portion of the small intestine. The essential agents of this process are the bile and the pancreatic fluid. In the remainder of the small intestine (the jejunum and ileum), the absorption of the chyle takes place. The numerous convolutions, the valvu- lae conniventes, and the villi, all tend to increase the extent of the absorbing surface. The products of exhalation and of follicular secretion serve to complete the digestive process. The contents of the bowels are forced along by the shortening of the longitu- dinal, and the contraction of the circular fibres, the latter producing the vermicular mo- tion of the intestines. The Large Intestine. The large intestine is that part of the alimentary canal which extends from the end oi the small intestine {d,fig. 139) to the anus (i). It commences in the right iliac region {c,fig. 161), and passes upward (a) as far as the right hypochondrium ; then, having reached the liver, it makes a sharp flexure (the right or hepatic flexure), and proceeds * [Their contents are sometimes transparent, and tliey are then very difficult of detection.] filn fig. 169, representing part of a patch of Peyer's glands magnified, are seen some of the elevated white bodies described by Boehra as resembling the solitary glands, except in not generally having any villi situated directly upon them. Each is surrounded by a zone of dark points, the elongated openings of the crypts of Lieberkuhn. Many of these crypts are also seen scattered irregularly between the numerous villi ; none of them communicate vpith the interior of the whitish bodies, in which, whether solitary or agminated, Boehm could discover no opening, at least, not in a healthy human intestine. He considers them, therefore, to be closed vesicles, not follicles. More recently, however, Krause has observed that, in the pig's intestine, they are occasionally open, independ- ently of disease ; and Dr. Allen Thomson has lately made a similar obsen'ation in reference both to the pig and to the human subject.] i [The follicles or crypts of Lieberkuhn are tubes placed more or less perpendicularly to the surface of the mucous membrane, like those in the stomach, but situated more widely apart ; their open mouths are seen scattered over the whole surface of the membrane, or collected around the solitary and agminated glands (figt 157, 159). The corpuscules {corpora albicantia), described by the same observer as being situated in the bot- tom of the crypts, are probably collections of desquamated epithelium within them.] THE INTESTINES. 371 iransTersely (t) from the right to the left side {transverse arch of the colon) ; in the left h3T)Ochondrium, below the spleen, it again makes a sharp bend and becomes vertical (d), (left or splenic flexure). In the left iliac region (/) it is twice bent upon itself, hke the Ro- man letter S {iliac or sigmoid flexure), and it then dips into the pelvis (r), and terminates at the anus. The large intestine, therefore, describes within the abdomen a nearly complete circle, which surrounds the mass of convolutions of the small intestine ; and it occupies the right and left iliac regions, the right and left lumbar, the base of each hypochondriac, and the adjacent borders of the epigastric and umbilical regions. Although it is much more firmly fixed in its place than the small intestine, and is, therefore, less liable to displacement, yet it presents some varieties in length and curvature which have a con- siderable influence over its position. The large intestine is more deeply situated than the small in one part of its extent, but in another is at least quite as superficial. From its long course, and from the different relations piesented by its diflferent parts, it has been divided into the ccecum, the colon, which is itself subdivided into several parts, and the rectum. Dimensions. — The IcTigth of the large intestine is four or five feet, and, compared with the small intestine, is as one to four ; but it varies considerably, rather, it would seem to me, from the eflfects of repeated distension, than from any original conformation ; for it may be easUy imagined that the bowel cannot be distended transversely without lo- sing somewhat in length, and that, on returning to its former diameter, it must be elon- gated in proportion to the distension it had previously undergone. The large intestine has also generally appeared to me longer in persons advanced in age than in adults. Its caliber or diameter usually exceeds that of the small intestine, but may become so reduced that the gut resembles a hard cord, about the size of the little finger. In other cases it is so large that it occupies the greatest part of the abdominal cavity : this is ob- served in tympanitic distension of the large intestine. It is not of uniform caliber throughout, as the following measurements will show. The circumference of the caecum, moderately distended, and taken immediately below the ileo-caecal valve, was found to be eleven inches and three lines in one subject, and nine inches and a half in another ; the right colon in the loins and the right half of the arch were eight inches and nine lines in the first, and five inches some lines in the second subject. The circumference of the left half of the arch of the colon, and of the left lumbar colon, was six inches in the first and five inches and a half in the second. The circumference of the sigmoid flexure was five inches and a quarter ; that of the rectum was three inches until near its termination, where it presented a dilatation four inches in circumference in one, and five inches in the other subject. It follows, therefore, that the large intestine, like the small, has an infiindibuliform shape ; it resembles, indeed, two ftmnels, the base of the one corresponding to the caecum, and its apex to the sigmoid flexure, while the base of the other is at the dilated portion of the rectum, and its apex is apphed to that of the first. It is probable that this infundibuliform arrangement has some reference to the passage of the faecal matters. It also follows that there is no uniform relation between the diameters of the different portions of the large intestine : thus, a very large caecum and ascending colon may co- exist with a small descending colon In some cases we find in the large intestine con- siderable dilatations, separated from each other by such constrictions that the caliber of the corresponding part of the gut is obliterated. These strangulations from a con- traction of the circular fibres are very different from those produced by organic diseases : they probably take place during life, and may account for the affection known as the windy colic. In some chronic diseases, accompanied with diarrhcea, the large intestine, contracted and containing no gases, is not as large as the small intestine. The CcEcum. — The caecum (e, fig. 139), so named because it resembles a cul-de-sac, is the first part of the large intestine The existence of a caecum is one of the numerous indications of the line of separation between the large and the small intestine. Its up- per boundary is altogether arbitrary ; it is determined by a horizontal plane intersecting it immediately above the insertion of the small intestine. It is single in the human sub- ject, but is double in some species of animals. It is situated {c,fig. 161) in the right iliac fossa, and occupies it almost entirely. It is one of the most fixed portions of the ali- mentary canal, for the peritonemn merely passes in front of it, and binds it down into the iliac fossa. It is not, however, so firmly fixed in all subjects ; it is often enveloped by the peritoneum on all sides, and floats, as it were, in the region which it occupies, its capability of motion depending on the looseness of the right lumbar mesocolon. This arrangement of the peritoneum is not necessary, however, to explain the great amoun of displacement which the caecum undergoes in certain cases. It is not uncommon to find it in the cavity of the pelvis : it occasionally enters into the formation of herniae and, what is somewhat remarkable, it has been at least as frequently found in hernia upon the left as upon the right side. Its direction, which is in general the same as that of the ascending colon, is not alway vertical a.s may be seen by examining a moderately-distended intestine, but it pass* 379" SPLANCHNOLOGY. obliquely upward and to the right side, so that it forms with the colon an obtuse angle projecting on the right side ; and I have even seen it form a right angle with the colon. This arrangement, connected with the obliquity of the plane of the iliac fossa, explains why, when its attachments are relaxed, it has less tendency to be displaced towards the right inguinal ring and femoral arch than to the same parts on the left side. In some subjects, the caecum and its vermiform appendix are applied to the lower part of the small intestine, so that the caecum and the neighbouring part of the colon describe a curve, the concavity of which embraces the lower end of the ileum. In size it is generally larger than the portion of the intestine which succeeds it : this, perliaps, depends less upon its primitive conformation than upon the accumulation of faecal matters resulting from the inclined position of this intestine, and from the direc- tion in which its contents are moved. It may be said, as a general rule, that, next to the stomach, the caecum is the largest part of the alimentary canal. There are many individual varieties in the length and capacity of this intestine, in which the faecal mat- ters are liable to be retained. These accumulations occasion great pain ; they have been much studied lately, and have been often mistaken for inflammations. The caecum is very shghtly developed in carnivora, but, on the other hand, it is very large in her- bivora. Figure. — ^The caecimi is a sort of rounded ampulla, all the diameters of which arc nearly equal ; it is also sacculated like the rest of the large intestine. Upon it we ob- serve the conamencement of the three longitudinal bands, which I have already noticed : of these, the anterior is, in the caecum, twice as broad as either of the two posterior ; some folds of peritoneum, loaded with fat, which are called fatty appendages {appendices epiploica) ; and, lastly, some protuberances, separated by parallel depressions, an ar- rangement which exists in the colon also, and is produced by the longitudinal bands. Relations. — In front, the caecum is in relation with the abdominal parietes, through which it can be felt when it is distended with gases or faecal matters. When the cae- cum is collapsed, the small intestine is often interposed between it and the parietes of the abdomen. Behind, it rests upon the iliacus muscle, from which it is separated by the lumbo-iliac fascia. The cellular tissue uniting it to this aponeurosis is extremely loose, and, there- fore, offers no opposition to displacement of the intestine. When the peritoneum forms a complete covering for the caecum, that intestine is, of course, in indirect relation with the iliacus. The vermiform appendix is often turned back behind the caecum. On the inside, the caecum receives the small intestine ; the angle at which they unite (the ileo- csecal angle) varies much. Sometimes the small intestine is inserted at a right angle ; most commonly the angle of incidence is obtuse above and acute below {fig. 160). Some- times the ileum, instead of passing upward, is directed downward, and then the angle of incidence is changed. A circular depression indicates the limit between the two in- testines. Below, upon the free extremity or cul-de-sac of the caecum, is seen the \^r- miform appendix {v), situated behind and on the left side, a few lines below the ileo- caecal angle. The arrangement of the internal or mucous surface of the caecum is in accordance with that of its external surface : thus, three projecting ridges correspond with the three lon- gitudinal bands ; some cavities or pouches with the protuberances ; and some transverse projecting folds, forming incomplete septa, which are easily seen in a dried specimen, correspond with the parallel depressions. Upon this surface, to the left and a little be- hind, we also find the ileo-caecal valve (a b,fig. 160), and the orifice (o) of the vermiform appendix (»). The Ileo-caecal Valve. — This is also called the valve of Bauhin, from the name of the anat- omist to whom its discovery is attributed, although it had been described before his time. To obtain a perfect knowledge of it, it should be examined upon a fresh specimen under water, and also upon an inflated and dried intestine. In a fresh specimen, when viewed from the caecum, it presents the appearance of a projecting cushion, oblong from before backward, and fissured in the same direction. It is a membranous and movable cushion, and was incorrectly compared by Riolanus to the pyloric ring. It has two lips and two commissures ; the two lips are in contact, except during the passage of the contents of the bowels. Two folds, proceeding from the two commissures, one of which is anterior and the other posterior, are lost upon the corre- sponding surfaces of the intestine. The posterior fold is much longer than the anterior ; Morgagni called them ihefrana of the valve. When viewed from the ileum, it presents the appearance of a funnel-shaped cavity, directed upward and to the right side. In a dried intestine, the ileo-caecal valve is seen to consist of two prominent valvular segments, projecting into the caecum, so as to form an angular ridge. The upper, or ileo- colic segment {b,fig. 160), is horizontal ; the lower, or ilco-ccecal (a), forms an inclined plane of about 45°, and both are parabolic. The upper segment is fixe J by its adherent convex border to the semicircular line, along which the upper part of the tube of the ileum is united with the colon ; the adherent border of the lower segment, \^ hich is also convex, is continuous with the semicircular hue of junction between the lower half of the ileum THE INTESTINES. 373 and the caecum. The free borders of the segments are directed to- wards the right side, and are semilunar ; they are united at their ex- tremities, but in the middle leave between them (between a and h) an opening like a buttonhole, which becomes narrower as the intes- tine is more distended. The diameter of this opening is in proportion to that of the small intestine. The free border of the lower segment is more concave than that of the upper. When examined from the ileum, the valve presents an angular excavation exactly correspond- ing to the projecting edge found in the cavity of the large intestine. The lower surface of the upper valvular segment is slightly concave ; the corresponding surface of the lower segment is slightly convex. This double ileo-caecal valve differs widely from the ring of the py- lorus ; it offers no obstruction to the passage of the contents of the small into the large intestine ; but in ordinary cases, it will not per- " mit their regurgitation from the latter into the former. The lower or ileo-caecal segment is elevated so as to prevent reflux from the caecum, and the ileo-colic segment becomes depressed, and opposes any return of the contents of the colon. Still, from a great num- ber of experiments which I have performed on this subject, I am satisfied that both wa- ter and air injected into the large intestine most frequently overcome the resistance offer- ed by this valve, though with different degrees of facility in different subjects. This re- gurgitation, however, only takes place with gaseous or liquid matters ; such as have a greater degree of consistence cannot pass back, and therefore the reflux of faecal matter is impossible.* Structure. — ^The structure of the ileo-caecal valve was perfectly demonstrated by Albi- nus. If we follow his example, and remove the peritoneal coat from a distended intes- tine, at the point where the ileum enters the large bowel, we shall at once perceive most distinctly that the small intestine seems to sink in there ; and if, by means of careful and gradual force, we attempt to disengage it from the large intestine, it may be drawn out, as it were, from the colon to the length of an inch or an inch and a half; and then, on inspecting the inside of the large intestine, we shall find that the valve has altogether disappeared, and that the ileum communicates with the caecum and colon by a large ap- erture. The precise structure of the valve is as follows : it is composed of the circular muscu- lar fibres of the ileum, which are prolonged as far as its free edge ;t of the fibrous coat, and of the mucous membrane. A similar fact has been observed regarding this mucous membrane to one we have already several times noticed in describing the alimentary ca- nal, viz., a sudden change in its character opposite the free margin of the valve. That portion of the membrane which lines the surface turned towards the large intestine has all the characters of the mucous membrane of that bowel, while that lining the surface directed towards the ileum has those of the mucous membrane of the small intestine. The limit between them is generally observed in diseases. The Appendix Vermiformis. — The appendix vermiformis {v,figs. 139, 160, 161), so na- med from its resemblance to an earth-worm, commences at the posterior lower and left portion of the caecum, of which it may be considered an appendage {the cacal appendix) ; it resembles a small, hollow, and very narrow cord {duodecies jiascente colo angustior, says Haller). In length and in direction, it presents much variation : its length is from one to six inches. It is somewhat wider at its point of junction with the cascum than in any other part, and is in general about the diameter of a goose-quill. Its direction is sometimes vertically downward, sometimes upward, and often tortuous. I have found it spiral, and at other times contained in the substance of the mesentery, parallel to the ileum, and only free at its extremity. In some subjects it is funnel-sha- ped, widening out to become continuous with the caecum, which, in such cases, is very narrow. Its situation and relations are equally variable. Thus, most conmionly, it oc- cupies the right iliac fossa, near the brim of the pelvis : it is attached to the caecum and to the iliac fossa by a triangular or falciform fold of the peritoneum, which extends only to one half of its length, and allows it a greater or less capability of movement. It is still more movable when it is entirely surrounded by the peritoneum, and has no mesentery. From this it may be conceived that it may enter into the formation of herniae, and may be twisted around a knuckle of the small intestine, so as to cause strangulation. It is * Nevertheless, if we consider that the large intestine must always be very much distended in order to pro- duce a reflux of gases and liquids, it may be questioned whether the passage of gaseous or liquid matters from the large to the small intestine can take place during life. I have been able to determine the mechani.sm of the resistance oflfered by the valve from the effects of distension. The two segments are turned back, the lower one upward, and the upper one downward ; their corresponding surfaces become convex, and they are pressed together the more and more forcibly in proportion to the amount of distension. In some subjects dis- tension may be carried so far as to rupture the longitudinal bands, and yet not overcome the obstacle. In most cases, the free edge of the lower segment glides from right to left under the upper one, which remaina immovable ; and the gas and liquids escape with more or less facility according to the degree of disturbance in the parts. t I The longitudinal muscular fibres and the peritoneal coat pass directly from the small to the large intes- tine, without entering into the formation of the valve.] 374 SPLANCHNOLOGY. often turned back behind the ascending colon between that intestine and the kidney : in one case of this kind, I found the free extremity of the appendix in contact with the lower surface of the liver. I have also once seen it turned up behind the lower end of the -amall intestine, and, at another time, embracing that bowel in front. None of these dif- * ferences, however, depend on the situation of its point of attachment to the csecum, which is always on the left side, below and behind the cul-de-sac, at a short distance from the ileo-caecal valve. When divided lengthwise, the cavity within it is seen to be so narrow that the walls are always in contact. A small quantity of mucus is found in it, and it often contains small scybala ; cherry-stones and shot have also been found in it. The whole of its internal surface has a honeycomb appearance, like that at the lower end of the small intestine.* A valve of different size in different subjects, but never sufficiently large to cover the orifice entirely, is found at the point (o. Jig. 160) where the appendix commu- nicates with the caecum. The cavity of the appendix, like the caecum, terminates be- low in a cul-de-sac ; and in this, which is extremely narrow, foreign bodies may be lodged, and may then sometimes become the cause of those spontaneous perforations which are occasionedly seen. The uses of this appendix are edtogether unknown ; in the human subject, it is merely a vestige of an important part in many animals. Haller says that he has twice seen the vermiform appendix obliterated, i. e., without any cavity. I presume that this was the effect of morbid adhesion. Lastly, I once found this appendix as large as the index finger, and two inches in length ; its cavity contained some thick, transparent mucus. The orifice by which it should have conununicated with the caecum was obliterated. The Colon. — The colon {kuXvu, to impede, dfg h,fig. 139) constitutes almost the whole of the large intestine. It extends from the caecum to the rectum, and, as we have al- ready seen, there is no line of demarcation between these different parts. In the first part of its course it ascends vertically, then becomes transverse, next descends vertical- ly, and is then curved like the Roman letter S, and becomes continuous with the rectum. From this long course, and also from its direction and numerous relations, the colon has been divided into four portions, viz., the ascending or right lumbar colon, the transverse colon, or arch of the colon, the descending or left lumbar colon, and the iliac colon, or sigmoid flexure. Each of these parts requires a separate description, at least with regard to its relations. Let us first point out the general form of the colon. The colon presents a sacculated appearance throughout, which gives it some resem- blance to a chemical apparatus, consisting of a long series of aludels. The sacculi of the colon are arranged in three longitudinal rows, separated by three muscular bands. Each of these rows presents a succession of enlargements and constrictions, or deep grooves, placed across the length of the intestine. These enlargements and grooves are produced by the longitudinal bands, which, bemg much shorter than the intestine, cause it to be folded inward upon itself at intervals. It follows, therefore, that division of these bands by means of a bistoury, or, rather, their rupture, from great distension of the gut, should de- stroy this sacculated appearance, and such, indeed, is the result of the exper- iment ; at the same time, the large in- testine becomes twice or three times as long as it was before, and forms a regular cylinder, hke the small intes- tine. An incontestable proof of the relation between the cells of the colon and the muscular bands, is the con- current absence of both in a great num- ber of animals. Lastly, the three rows of sacculi vary much in different sub- jects, and also in different parts of the great intestine. The descending colon and the sigmoid flexure have only two rows of sacculi, and, consequently, two intermediate bands. The sacculi al- most entirely disappear in the sigmoid flexure. The Ascending or Right Lumbar Colon (a, figs. 135, 161). — This portion of the colon is bounded below by the caecmn, * [Nevertheless, the structure of the mucouf membrane in the two situations is very different (see notes, p. 3T0, 379).] .THE INTESTINES. 375 and above by the transverse arch, with which it forms a right angle, near the gall-blad- der. It is more or less firmly held in its place by the peritoneum, which in some sub- jects merely passes in front of it, and in others forms a fold or lumbar mesocolon. The ascending and descending colon may be included among the most fixed portions of the alimentary canal. In front of it are the parietes of the abdomen, from which, excepting when greatly distended, it is separated by the convolutions of the small intestine. Be- hind, it is in immediate relation with the quadratus lumborum and the right kidney, no layer of peritoneum intervening. It is united to these parts externally by loose cellular tissue. This relation accounts for the bursting of abscesses of the kidney into the colon, and explains the possibility of reaching the colon in the lumbar region without wound- ing the peritoneum. On the left side, advantage has been taken of this fact in attempt- ing to form an artificial anus. On the inside and on the outside it is in relation with the convolutions of the small intes- tine ; and on the inside also with the psoas muscle, and with the second portion of the duodenum. The Transverse Colon, or Arch of the Colon. — This (<) is the longest portion of the large intestine ; it extends from the ascending to the descending colon, from the right to the left hypochondrium, and generally occupies the adjacent borders of the epigastric and umbilical regions. It is not unfrequently found opposite the umbilicus, and even in the hypogastrimn. Its right extremity corresponds to the gall-bladder {g), its left is below the spleen {k). It describes a curve having its convexity directed forward, and its con- cavity backward ; hence the name, arch of the colon. In some subjects it is two or three times its ordinary length, and hence it presents various inflections. I have seen its middle portion descending as low eis the umbilical or hypogastric region, and even reach- ing the brim of the pelvis ; in other cases it descends parallel to, and on the inner side of, the ascending colon, and then passes upward again, or it describes curves of different extent. The arch of the colon is supported by a very remarkable fold of peritoneum, called the transverse mesocolon, which forms a horizontal septum between the small in- testine below, and the stomach, the liver, and the spleen above. The extent of this fold, which is one of the largest of all those formed by the peritoneum, explains the great freedom of the movements of the transverse colon, which, next to the small intestine, is the part of the alimentary canal most frequently found in hernia. Relations. — Above, it has relations with the liver (Z), which generally presents a shght depression, corresponding to the angle formed by the ascending and transverse colon ; with the gall-bladder (£), whence the discoloration of the right extremity of the arch from the bile ; it is not rare to find the gall-bladder opening into the colon ; with the stomach («), which projects in front of it when distended, but is separated from it by a considerable interval when empty ; and, lastly, with the lower extremity of the spleen {k). The two anterior layers of the great omentum, which proceed from the greater curvature of the stomach, pass over the arch of the colon without adhering to it. I have seen a large loop of the arch of the colon interposed between the liver and the diaphragm. Below, the arch of the colon corresponds to the convolutions of the small intestine {fig. 155). In front, it corresponds to the parietes of the abdomen, beneath which it may sometimes be felt when distended with gas. It is separated from them by the two an- terior layers of the great omentum. The two posterior layers of the great omentum are given off from the middle of its anterior border. Behind, it gives attachment to the transverse mesocolon. The Descending or Left Lumbar Colon. — The descending colon {d,figs. 155, 161) so close- ly resembles the ascending portion, both in situation and relations, that we can only re- fer to what has been already stated. We must observe, however, that it is more deeply situated above than the ascending colon, and that it is of less size. Advantage has been taken of its immediate relations behind, with the quadratus lumborum, in the operation for artificial anus in cases of imperforate rectum. It is preferred, for this purpose, to the ascending colon, simply from its proximity to the anus. The Iliac Portion, or Sigmoid Flexure, of the Colon. — The sigmoid flexure of the co- lon {f,Jlgs. 155, 161) is situated in the left iliac fossa, and is continuous below with the rectum. The line of demarcation between it and the descending colon is determined by the commencement of a fold of peritoneum, called the iliac mesocolon, or, rather, by the change in the direction of the large intestine, as it appears to detach itself from the pa- rietes of the abdomen, opposite the crest of the ilium. It is continuous with the rectum at the point where it dips into the pelvis, opposite the left sacro-iliac symphysis. But, as it often happens that the lower portion, or even the whole of the sigmoid flexure, is con- tained in the cavity of the pelvis, it may be understood that such a definition is not precise. It is retained in its place by a very loose fold of peritoneum, called the iliac mesocolon, and therefore, in some measure, partakes of the mobility of the small intestine. It has been found in almost all the regions of the abdomen, but especially in the sub-umbilical zone. It has been seen in the umbilical region, its first curvature reaching even to the liver. I have met with a case in which the sigmoid flexure extended upward, and the arch of the colon downward to the umbilicus, so that they came in contact with each oth. 376 SPLANCHNOLOGY. er ; the large intestine, therefore, corresponded with the whole anterior region of the abdomen, the sigmoid flexure alone occupying the umbilical, the hypogastric, and the left iliac region. Should the following disposition, which I have met with several times, be regarded as accidental or congenital 1 Commencing from the descending colon, the sigmoid flexure passed transversely from the left to the right side, on a level with the brim of the pelvis as far as the right iliac fossa, below the caecum, which it turned upward in one case, and pushed in front of itself in another ; the sigmoid flexure then described its two curves either in the right iliac fossa or in the pelvis. These cases, in which the sigmoid flex- ure of the colon alone is transposed, must be carefully distinguished from general trans- position of the viscera. The most peculiar character of the sigmoid flexure is its direction. It passes at first upward, in an opposite direction to the descending colon, then descends vertically, and then, curving again, passes to the right or to the left, forward or backward, and becomes continuous with the rectum (r), (the iliac flexure). These several flexures, however, vai7 exceedingly : I have seen them very shght ; but then the upper or free portion of the rectum was found decidedly flexuous ; and, indeed, it is difficult to ascertain whether such flexures belong to the rectum or to the displaced sigmoid flexure. • There can be no doubt that this double curve of the colon is connected with its uses as a receptacle for fajcal matters. The size of the sigmoid flexure varies considerably. In a case of imperforate anus in an infant, which lived twenty days, it became enormously distended. Retention of the faeces in the adult seldom causes so proportionally great an accumulation in the sigmoid flexure : the rectum is almost entirely the seat of the accumulation. Relations. — The sigmoid flexure corresponds to the abdominal parietes in front. When empty, its relations with the latter are indirect, in consequence of the interposition of some convolutions of the small intestine ; when it is distended, they are inmiediate ; and hence we are recommended to make an artificial anus in the sigmoid flexure of the colon, in cases where the rectum is imperforate. It is in contact behind with the iliac fossa, to which it is fiLxed by the mesocolon : hence it can be easily compressed and ex- plored by the fingers, for the purpose of detecting hardened masses of faeces. In the rest of its circumference it is in relation with the convolutions of the small intestine. The Internal Surface of the Colon. — On the internal surface of the colon are seen three longitudinal ridges, corresponding to the three muscular bands on its external surface ; three intermediate rows of sacculi, the concavities of which agree exactly with the pro- tuberances on the external surface ; and, lastly, numerous ridges or incomplete septa, dividing the cells of each row from one another, and improperly called valves ; they cor- respond to the grooves or depressions on the external surface. In order to comprehend the arrangement of the cells and the intervening septa, we must examine the large in- testine when moderately distended and dried. If the muscular bands have been previ- ously divided, the cells and septa disappear. The internal sacculi, as well as the external protuberances, vary much in different in- dividuals, and even in diflerent parts of the same colon. Thus, there are generally only two rows in the descending colon and the sigmoid flexure, because there are only two muscular bands in those parts. Sometimes, indeed, there are no cells in the sigmoid flexure. Lastly, the internal surface of the large intestine presents some irregular folds, which are completely effaced by distension. The Rectum. — The rectum (A i,fig. 139), so called from its direction, which is gener- ally less flexuous than that of the rest of the intestinal canal, is the last portion of the large intestine, and, consequently, of the digestive tube. It commences at the base of the sacrum, and terminates at the anus. It is situated, in the true pelvis, in front of the sacrum and coccyx {r,fig. 161 ; a o',fig. 181). We see, then, that the alimentary canal, after having abandoned the vertebral column in order to describe its numerous convolutions, is situated at its termination in front of the lower part of that column, just as, at its commencement, it is applied to the upper part of the same. It is firmly fixed, especially below, where it. is surrounded on all sides by cellular tissue, and is also bound down by the superior pelvic fascia. This part of it cannot, therefore, suffer such displacements as occur in hernia ; but, from its functions as an organ of expulsion, the whole effort of the abdominal inusoles is concentrated upon it, and it is, therefore, liable to displacements of a different kind, viz., to invagination and eversion. Its situation, which is in some degree constant, within a bony cavity, having unyield- ing walls, and its relations with the pelvic fascia, place it in conditions altogether pecu- liar to itself; for while the bladder and the uterus, which are also contained in the same cavity, ascend into the abdomen when they are distended, the rectum, in which the fajces are accumulated, dilates entirely within the pelvis, and undi^rfoes no change of position. From this fixed condition of the rectum along the miildle of the pelvic cavity, it also follows that, in cases where the gut is denuded by destmrtion of the surrounding cellu- lar tissue, it remains separate from the walls of the pelvis : such is the nature of fistu- f THE INTESTINES. 377 lae ; and hence the necessity of cutting the rectum, in order to bring it in contact with the walls of the pelvis. Direction. — Particular attention should be paid to the direction of this bowel, as an anatomical fact from which practicEd inductions of the greatest interest may be derived. It is not straight, but is curved both in the antero-posterior and lateral directions. In the antero-posterior direction it follows the curve of the sacrum and coccyx, to which it is closely applied ; it is, therefore, concave in front and convex behind {see fig. 181). Opposite the apex of the coccyx it bends slightly backward, so as to terminate about an inch in front of that bone. By this very remarkable inflection, it is separated from the ragina in the female, and from the urethra in the male. T?ie Lateral Inclination. — On the left side of the base of the sacrum, and opposite the sacro-iliac symphysis, the rectum passes downward, and to the right side, until it reaches the median line opposite the third piece of the sacrum. It then passes forward, still in the median line, and forms a slight curve with the preceding portion. It has been fre- quently said that the lower part of the rectum does not occupy exactly the median hne, but deviates a little to the right : this is not unfrequently the case at the lower part of the sacrum, but it always regains its original position before its termination. There are, however, some important varieties in the curvature described by the rec- tum. Thus, it is not uncommon to see the upper part of the gut twisted like an italic j'> -A ■ ■ . . The Livee. The liver {I I', figs. 155, 161) is a glandular organ, intended for the secretion of bile. Moreover, it is to this organ that the blood of the abdominal venous system is carried in the adult, and that of two systems of veins in the foetus. It is situated near the duodenum, i. e., the portion of the intestinal canal into which the bile is poured ; it occupies the whole of the right hjT)ochondrium, advances into the epi- gastrium, and even slightly into the left hypochondrium. It is protected by the seven or eight lower ribs on the right side, which defend it from external violence ; and it is separ- ated from the thoracic organs by the diaphragm. It is supported by folds of the peri- toneum connecting it with the diaphragm, and regarded as suspensory ligaments ; by the stomach and intestines, which form a sort of elastic cushion for it ; and by the vena cava, which is intimately adherent to it. These me^ns of support and attachment allow of slight movements to and fro, and even of certain changes of position, not amounting to displacement. Thus, it is depressed during inspiration, and projects a little below the edges of the costdi cartilages ; it is raised during expiration ; it sinks slightly downward during the erect posture, and backward, or in the direction in which its own weight would drag it, according to the way in which the body lies during the horizontal posi- tion ; it is pushed upward by tumours in the abdomen, and dovraward by effusions in the chest. The disturbed sleep to which many individuals are subject when lying upon the left side, is attributed to the pressure of the liver upon the stomach ; and to the dragging of the liver upon the diaphragm has been eiscribed the sensation of hunger, as well as the relief of that feeling produced by tying something tight around the abdomen. These notions are, however, purely hypothetical ; and generally, in solving such questions, the exact state of fulness of the abdomen, and of the mutual action and reaction of the ab- dominal parietes and viscera, has not been sufficiently taken into account. True dis- Dlacements of the liver are very rare, and hepatocele (hernia of the liver) is the result of an imperfect development of the walls of the abdomen. Size. — The liver is the largest and heaviest of all the organs of the body ; and, indeed, in the human subject, it exceeds in weight and in size all the other glands together. It is not true, as the ancients declared, that the liver is larger in man than in any other animal. But the opinion maintained by many naturalists, that there is, in the animal series, an inverse ratio between the size of the liver and the development of the respira- tory organs, so that this organ is much larger in reptiles and fishes, whose respiration is slight, than in birds and mammalia, which respire vigorously, is not altogether devoid of loundation. The liver weighs from three to four pounds, thus forming one thirty-sixth of the whole weight of the body according to Bartholin, and one twenty-fifth according to others. Its longest diameter, the transverse, is from ten to twelve inches ; its antero-posterior di- ameter is from six to seven inches ; and its vertical diameter in the thickest part, from four to five. These dimensions are extremely variable, but are always inversely pro- portional to each other. In a great many livers the transverse diameter is the shorter, and the vertical the longer. Few organs present a greater variation in size and form in different individuals than the liver. I am certain that the relative proportion between different livers may be as much as one to three, in the absence of all disease. It is pretty generally believed that a large liver occasions such modifications in the whole system as will give rise to a par- ticular temperament. But it may be doubted whether there is any proof that the bilious and melancholic temperaments are specially accompanied by a large liver, or that hypo- chondriasis in particular is the result of a predominance of that organ.* AnatomicEil evidence affords but little support to such ideas, which are rather the result of precon- ceived notions respecting the functions of the liver and the influence of the bile, than the fruit of positive observations. It varies much in size according to the state of its circulation ; when its vessels, and especially the ramifications of the vena portae, are empty, the tissue of the liver shrinks, and its surface becomes, as it were, wrinkled. When, on the other hand, the hepatic vessels are injected, the organ is in a state of turgescence. I have often been struck with the increase in the size of the liver produced by an injection pushed forcibly and continuously into the vena portffi. The size of the liver, as influenced by age and disease, deserves particular attention. I shall point out the influence of age under the head of development. We shall then see that the liver is largest during intra-uterine life, and that it is proportionally larger at periods nearer to that of conception : hence it arises that the greatest relative size of the liver is coincident with the least amount of biliary secretion ; and we may there- fore conclude that this organ has some other use besides that of secreting bile. When diseased, the liver has been found to weigh from thirty to forty pounds ; but the enormous size in these cases is almost invariably owing to the development of acci- * Hippocrates sometimes gave the name of hypochondria to the liver, and hence, no doubt, the term hypo- chondriac. Ccc 386 SPLANCHNOLOGY. dental tissues. Some cases, however, have been recorded of simple hypertrophe of the liver without any organic disease, in which the size acquired was prodigious. In oppo- sition to this, we must notice the state of atrophy* in which the liver is shrivelled, and not more than a third, fourth, or even a sixth of the natural size. In one subject, in which the umbihcal vein remained pervious, and the sub-cutaneous abdominal veins were dilated and varicose, the liver weighed only about half a pound. The specific gravity of the liver is, to that of water, as fifteen to ten Figure. — The liver is a single and asymmetrictd organ, of such an irregular form as to defy description. We shall compare it, with Glisson, to a segment of an ovoid, cut ob- liquely lengthwise, thick at its right extremity, and progressively diminishing towards the left, which terminates in a tongue. Its shape is represented by the sort of mould formed by the right half of the diaphragm, and bounded below by an oblique plane di- rected upward and to the left side {fig. 161). No organ is more exactly moulded upon the surrounding parts, nor undergoes changes in form with greater impunity, either from external pressure or from that exercised upon it by other viscera ; it may even be said to be, as it were, ductile or malleable under the influence of a slowly-exerted pressure. The injurious effects of very tight lacing are chiefly experienced by the liver. A circular constriction and a fibrous thickening of this organ opposite the base of the thorax sometimes afford evidence of this compression ; its transverse and antero-posterior diameters become diminished, and its vertical diam- eter is increased ; it projects more or less below the base of the thorax, descends as low down as the right iliac fossa, and may even touch the brim of the pelvis without any structural lesion. In these cases, its upper surface becomes anterior, and its lower sur- face posterior. There are but few female subjects without some deformity of the liver, and, therefore, the type of the organ must be sought for in the male.t No practical conclusions, then, can be derived from the shape of the liver ; and I am almost inclined to agree with Ve- salius, in saying that it has no determinate form, but accommodates itself to the sur- rounding parts. In a few rare exceptions, we find the human liver divided into lobules by deep fissures, as it is in a great number of animals. The errors which have for a long time existed upon this subject, even since the time of Vesalius, arise from a blind respect for the assertions of older anatomists, who, having dissected few human sub- jects, were accustomed to confound, in their descriptions, the structure found in animals with that observed in man. ^ The liver presents for consideration a superior or convex surface, an inferior or plane surface, an anterior and a posterior border, a base, and a summit. The superior surface (pars gibba) is convex and smooth, and in contact with the dia- phragm, which is moulded exactly upon it : this convexity is not regular, but much greater on the right than on the left side, where the surface is almost flat {fig. 161). This surface is divided into two unequal parts {I I') by a falciform fold of peritoneum (1 to 2), called the falciform or suspensory ligament of the liver, which seems to be principal- ly intended to protect the umbilical vein, and which is never put upon the stretch during the natural state of fulness of the abdomen. One or more fissures are not unfrequently found running from before backward upon the upper surface of the liver ; and I am sure that these fissures, in explanation of which Glisson and Fernel have advanced some very singular opinions, are due, at least in some cases, to the pressure of projecting folds of the diaphragm. The falciform ligament forms the line of separation between the right {I') and the left (/) lobes, a purely nominal distinction, which results from the old habit of admitting several lobes in the liver, and is retained here only for the sake of conformity to custom. The portion of the liver situated to the left of the suspensory ligament is always smaller than that upon the right. The convex surface of the liver is bounded behind by the reflection of the peritoneum upon it from the diaphragm. It is separated by the diaphragm from the heait, the ribs, and the base of the right lung. Its relations with the base of the right lung are very ex- tensive : the base of the lung and the convexity of the liver are exactly fitted to each other ; this may be shown by making a vertical section from before backward, upon the right side of the trunk, when the liver will be seen to be received, as it were, into a deep excavation in the base of the lung. This relation explains why abscesses and cysts of the liver may burst into the lung, and why abscesses of the lung point towards the liver ; why the liver may increase in size in the direction of the thorax, and push up the lung as far as the third or even the second rib ; and why effusions into the pleura may force the liver downward in the abdomen ; and also why peritonitis, confined to the region of the liver, is sometimes mistaken for pleurisy at the base of the thorax. The relations of the liver with the seven or eight inferior ribs account for the impressions which are often seen upon its surface ; and also explain the facts, that violent blows upon the ribs may bruise this viscus ; that pointed instruments thrust into the intercos- * We cannot admit the proposition of Soemmering, " Quo sanior homo, eo minus ejus hepar est." + Soemmering, without giving any reason, says, " In sexH masculo magit, minus in femineo coatis istit ter. . turn latet."—(Corpor. Hum. Fabric, t. vi., p. 163.) m THE LIVER. ^ spaces on the right side may wound it ; and that abscesses of the liver point and open between the ribs. The relations of the convex surface of the liver Avith the abdominal parietes, which are so extensive in the new-bom infant, and stiU more so in the foetus, are generally confined in the adult to a variable extent of the epigastrium, and to a small space below the edges of the ribs on the right side {fig. 155). In certain conformations of the liver (almost always acquired), and in such diseases as are attended with an increased size of the organ, these relations become much more extended; and, even in the absence of any disease, the liver is not unfrequently found to extend into the neighbourhood of the umbihcus, or even into the right iliac region. In the erect posture, the liver has a ten- dency to project below the ribs ; and, therefore, the sitting posture, with the upper part of the body inclining forward, and resting upon some object, is the most favourable one for exploring this organ.* It is by no means rare to meet with accidental adhesions between the liver and the diaphragm, consisting either of cellular filaments in the form of bands, or of cellular tissue of a greater or less density. The inferior or plane surface {pars sima, 1 1, fig. 154 and fig. 164). This is much more complfeated than the upper surface, and upon it the hepatic vessels enter and make their exit from the liver. Certain eminences and depressions, or fissures of variable depth, are met with here, which have led to the division of the liver into several lobes ; but that kind of division, which in animals appears to enable the organ to adapt itself to the form of the viscera of the abdomen, and has probably some relation with the conforma- tion of the heart, cannot be said to exist in man.t This lower surface is directed down- ward and backward, and sometimes directly backward : it presents for our consideration, in the first place, an antero-posterior fissure, or fissure of the umbilical vein, called also the Fig. 16i. longitudinal or horizontal fissure (uh,fig. 164), which extends from the anterior to the posterior bor- der of the liver, and is divided by the transverse fissure {dp), meet- ing it at a right angle, into two halves, one anterior, the other posterior. The anterior half lodg- es the umbilical vein in the foe- tus,t or the fibrous cord {u), to which it is reduced in the adult : the posterior half lodges the duc- tus venosus in the fcetus, or the fibrous band {v), by which it is re- placed after birth. The anterior half of the longitudinal fissure is much deeper than the posterior, and is often converted into a com- plete canal by a sort of bridge formed by a prolongation of the substance of the liver : when incomplete, this bridge is always situated near the transverse fissure : it often consists of a band of fibrous tissue. Even when quite complete, it invariably presents a notch near the anterior border of the liver. ^ The posterior half of the longitudinal fissure inclines more or less obliquely to the left of the lobulus Spigelii (3), gives attachment, like the transverse fissure, to the gas- tro-hepatic omentum, and communicates with the fissure for the vena cava superior (c), behind the lobulus Spigelii. The existence of this fissure has been the chief cause of the division of the liver into the right or great lobe (1), and the left lobe (2), also termed the middle-sized lobe by those anatomists who admit as a third lobe the small lobe, the lobule or the lobulus Spigelii (3). This division of the liver into two lobes is also marked on the upper surface, as we have already seen, by the suspensory ligament. Of these lobes, the right is much larger than the left ; the former occupies the right hypochondrium, the latter the epigastrium and left hypochondrium {fig. 161). The proportion between the right and the left lobe can- not be precisely determined. The left lobe is sometimes reduced to a thin tongue, while, at other times, it is almost half the size of the right lobe. Generally, the relative pro- portion between them is as six to one. This, however, is of but little consequence ; for as the distinction between the two lobes is quite imaginary, the substance of the left * In an old woman, whose liver was deformed but healthy, and projected below the ribs, I was able to diag- nosticate, by mediate percussion, the existence of a knuckle of intestine between the liver and the parietei of the abdomen. Very lately I found a large loop of the transverse arch of the colon between the right lobe and the abdominal parietes, and a loop of the small intestine between the left lobe and those parietes. t The ancients admitted four lobes in the liver, which they distinguished by the singular names of mensa, porta, gladius, and unguis. t [The term umbilictil fissure is often restricted to this part of the longitudinal fissure ; the posterior half it then called the fossa of the ductus venosus.] [This bridge was purposely divided in the liver from which Jig. 164 was drawn.] SPLANCHNOLOGY. may, without any inconvenience, be included in the right, and vice versa. TKe transverie fissure, or fissure of the vena ■porta {d p), is the true hilus of the liver, for through it the hepatic vessels enter and pass out. It is a very broad, transverse fissure, from fifteen to eighteen lines in length, occupying ahnost the middle of the lower surface of the liver, a little nearer to the posterior than to the anterior border, and to the left than to the right extremity. It is bounded on the left by the longitudinal fissure, with which it commu- nicates ; to the right of the gall-bladder {g), it is prolonged obliquely forward by a deep and narrow cleft. In the transverse fissure we find the vena portae, or the sinus (p) of the vena portae, the hepatic artery (a), the roots of the hepatic duct (d), a great number of lymphatic vessels and nerves, and a considerable quantity of cellular tissue. The gastro-hepatic omentum is given off from this fissure. The transverse fissure is situa- ted between two eminences, called by the ancients the pillars of the gate {portal eminen- ces). All the peculiarities of the inferior surface of the liver may be referred to these two fissures. Thus, to the left of the longitudinal fissure we observe the inferior surface of the left lobe, slightly concave behind, where it is applied to the lobulus Spigelii, from which it is separated by the gastro-hepatic omentum ; concave in front, so as to be adapted to the convexity of the stomach, upon which it is prolonged to a greater or less extent. This relation of the liver with the stomach is of the utmost importance. Thus, when the stomach is distended, it pushes the liver upward and backward in such a manner that its lower surface is directed somewhat forward. In cases of chronic ulceration of the stomach, the tissue of the liver is not unfrequently found supplying the place of the de- stroyed coats of the stomach, and this to a considerable extent. The lower surface of the left lobe is often in relation with the spleen, which it occasionally covers like a helmet. To the right of the longitudinal fissure, and in front of the transverse fissure, we find, upon the lower surface o'f the right lobe, the fossa for the gall-bladder, which is more or less deep, oblong, and directed from before backward, upward, and to the left side, like the gall-bladder (g) itself, for the reception of which it is intended. This fossa is not al- ways prolonged as far as the anterior border of the liver. Between the fossa of the gall- bladder and the longitudinal fissure is a square surface, the lobulus quadratus, anterior portal eminence, or anterior lobule (4). This surface sometimes terminates behind in a dis- tinct rounded prominence, which justifies the name of eminence applied to it ; at other times, on the contrary, this portion of the liver is flattened. Behind the transverse fissure we find the posterior portal eminence, or small lobe (pos- terior lobule or lobule), also called the lobulus Spigelii (3), from the name of the anatomist to whom its discovery has been attributed, although it was described, and even figured before his time by Vesalius, Sylvius, and Eustachius. It varies much, both in size and shape, and is situated between the transverse fissure and the posterior border of the liver, and between the fissure of the ductus venosus (») on the left, and the fissure of the vena cava inferior (c) on the right. It is situated to the right of the oesophageal orifice of the stomach, opposite its lesser curvature, by which it is embraced ; its form is that of a flattened semilunar tongue, convex upon its lower and free surface, which corresponds to the upper border of the pancreas, and has a projection in the centre, surrounded by an arterial circle, formed by the coronary artery of the stomach with the splenic and hepatic arteries. This projection (above 3) is called by Haller major colliculus in magna papilla similitudinem; and by Winslovv, r eminence triangulaire. From its posterior ex- tremity a prolongation is given off opposite the posterior border of the liver, which con- verts the fissure for the vena cava inferior into a canal that is sometimes complete.* A prolongation or ridge (5) {the right prolongaiion of the lobule) passes from its anterior ex- tremity to the right of the transverse fissure, and, proceeding obliquely forward, separ- ates the renal (r) from the colic (o) depression. This prolongation was minutely descri- bed by the older anatomists, and has been termed by Haller the colliculus caudatus.j At its junction with the lobule, this prolongation is marked in front by a groove (the groove of the vena porta), sufficiently deep to lodge the vena portae (p) and the hepatic artery (a) ; and it is still more deeply excavated behind for the vena cava inferior (c) {the groove of the vena cava inferior). Sometimes the right margin of the first-mentioned groove has a papilla similar to that of the lobulus Spigelii ; and in this case it might be Sciid that there are two lobes of Spigelius ; opposite this groove, the vena portae is separated from the vena cava only by a very thin lamina. The lobulus Spigelii presents much variety in its size ; but not such as to enable it to be felt through the abdominal parietes, unless the enlargement is the consequence of disease. Physicians who pretend to recognis.e by the touch obstruction or adhesion of the lobulus Spigelii,t are certainly not anatomists. To the right of the longitudinal fissure, the lower surface of the liver presents, behind, * [This prolong-ation did not exist in the liver represented in fig. 1G4.] + [Now termed the lobulus caudatus.] ; Meckel and others consider that there is a right antero-posterior, or longitudinal fissure, formed by the tossa for the gall-bladder and the groove of the vena cava inferior ; the latter groove being partly hollowed t ut af the loCulus Spigelii, and partly out of the continguous portion of the right lobe, and then prolonged upon the lower surface of the liver THE LIVER. au excavation of variable depth and extent in different subjects ; this is the renal im- pression (r) : it corresponds to the kidney, upon which it is exactly moulded, and with which it is loosely united, and also, though more loosely, with the supra-renal capsule. Sometimes the impression for the capsule is distinct from that for the kidney. It may be conceived that this impression must vary according as the liver corresponds to the uj^er third, to the upper half, or to the whole of the right kidney. This impression is always directed backward. In front of the renal impression is a slight one, termed the colic depression (o), which corresponds with the angle formed by the ascending and transverse colon with part of the transverse colon itself, and sometimes, also, with the first portion of the duodenum. Behind is the groove for the vena cava inferior (c), which advances slightly upon the lower surface of the liver, on the inner side of the renal and capsular impression. The accidental fissures sometimes observed upon the lower surface of the liver are traces of the divisions which exist in a great number of mammalia. To recapitulate the numerous objects seen upon the lower surface of the liver, we find as follows : the antero-posterior or longitudinal fissure, intersected at right angles by the transverse fissure ; on the left of the antero-posterior fissure is the lower surface of the left lobe, presenting the depression for the lobulus Spigelii, the gastric impression, and sometimes the splenic ; on the right and in front of the transverse fissure, are the fossa of the gall-bladder, and the anterior portal eminence, or lobulus quadratus ; behind the transverse fissure is the posterior portal eminence, or lobulus Spigelii, with its right prolongation or lobulus caudatus, and the groove for the vena portae ; and still more to the right are the renal and colic impressions, and the groove for the inferior vena cava. The Circumference of the Liver. — The anterior border of the liver presents a very thin, and, as it were, sharp edge, which is directed obliquely upward and to the *ft side, cor- responding to the base of the thorax on the right side, and projecting below it, opposite the sub-sternal notch (Jig. 155). Upon this edge there is invariably found a deep notch (below 2, Jig. 161) for the umbilical vein ; and more to the right another notch, which is often larger than the preceding, and corresponds to the base (g) of the gall-bladder. Sometimes there is merely a trace of this notch, and sometimes it is altogether wanting. In some subjects there is only one great notch, common to the gall-bladder and the um- bilical vein, and the borders of it are sinuous, or cut into small notches. It is almost always possible, when the parietes of the abdomen are relaxed, to insinuate the fingers between the ribs and the liver. The posterior border of the liver is very thick in all that part which corresponds to the right side, and becomes gradually thinner as it approaches the left extremity. This border, which is short, rounded, and curved, so as to fit the convexity of the vertebral column, adheres intimately to the diaphragm by rather dense cellular tissue. The peri- toneum is reflected, both above and below this border, from the diaphragm to the liver, to form what is called the coronary ligament. The cellular interved between these two layers of peritoneum is of irregular form, and taries in size. This border is divided into two parts by a deep notch, which forms two thirds or three fourths of a canal for the re- ception of the inferior vena cava {c,Jig. 164). This notch is converted into a complete canal, sometimes by a sort of fibrous bridge, and sometimes by a prolongation fi-om the posterior extremity of the lobulus Spigelii. In order to comprehend the arrangement of the liver opposite this notch for the vena cava, that vein should be slit open, and we then see at the bottom of a deep notch a large cavity, into which all the hepatic veins (Ji h) open. We observe, also, that the antero-posterior fissure is continuous with the fissure of the vena cava, behind the lobulus Spigelii. This lobule, viewed from behind, appears like a tongue detached from the rest of the liver, by circumscribing fissures and grooves. On the right side, the liver terminates in a thick, smooth extremity, forming the base of the pyramid, to which this organ has been compared. A triangular fold of peritone- um, caUed the right triangular ligament (/), is stretched from the middle of this thick ex- tremity to the diaphragm. On the left side, the liver terminates in an angular or obtuse tongue, more or less elon gated, and sometimes reaching as far as the spleen, to which I have seen it adherent This prolongation, which is attached to the diaphragm byatriangular fold of peritoneum, called the left triangular ligament (3, fig. 161 ; I, fig. 164), is slightly notched behind for the lower end of the oesophagus, which is bordered by it upon the left side. In one sub- ject I saw this tongue completely separated from the rest of the liver, with the excep- tion of a veiscular pedicle about four lines in length. This peculiarity was probably ow- ing to traction exercised by the spleen, to which the prolongation from the Uver was in- timately adherent. Colour. — The liver is of a reddish-brown colour, the depth of which varies in different individuals. Its surface, and also sections of it, resemble in appearance a granite com- posed of two kinds of grains, the one deep brown, the other yellowish ; and hence has arisen the distinction between the two substances of the Uver. In no tissue in the body is there greater variety in colour than in that of the liver. Independently of the differ- ent shades, which it is imoossible to describe, the liver is sometimes of a yellowish or 390 SPLANCHNOLOGY. canary-yellow, or a chamois-yellow (hence the name cirrhosis given to a particular dis- .ease of the liver) ; or it may be of a more or less deep olive-green hue, or of a slate colour. These differences in colour, which have not, perhaps, been sufficiently investi- gated, are connected with more or less decided alterations of texture. The chamois- yellow colour almost always indicates the existence of fatty degeneration. Fragility. — ^The fragility of the liver is one of the most important particulars in its de- scription. It is compact and fragile, and cannot, therefore, be forcibly compressed with- out suffering laceration ; hence the danger of contusions in the region of the liver, and the rules laid down by accoucheurs for avoiding all compression of the abdomen of the feet us during the manipulations required in protracted labours. The fragility and the weight of the liver explain the occurrence of injuries of that organ by contre-coup, after falls from an elevated height. In fatty degeneration of this organ, the liver retains the impression of the finger, and its fragility is in a great measure lost. Olive-green and slate-coloured livers are dense, their molecules are much more closely united, and they are lacerated with difficulty. Texture. — Before the admirable works of Glisson and Malpighi, anatomists were in the habit of saying, with Erasistratus, that the liver, like all other organs of a complicated structure, was a parenchyma ; a vague term, intended to imply the effusion of a particular juice around a series of vessels. Malpighi showed, in opposition to the assertion of Warthen, that the liver is a conglomerate gland : he examined the glandular granules (the lobules of Kiernan), which Ruysch subsequently, by means of his beautiful injec- tions, appeared to convert into vessels. Anatomists are still divided between the opin- ions of these two eminent observers concerning the intimate structure of the liver, as well as of all other glands, some believing it to be granular, others that it is vascular. We have to' consider the coverings, and then the proper tissue of the liver. The Coverings of the Liver. — These are two in number, viz., a peritoneal coat, and a proper fibrous membrane. The peritoneal coat forms an almost complete covering for the liver ; the posterior bor- der, the transverse fissure, the groove for the vena cava, and the fossa for the gall-blad- der, are the only parts that are destitute of this coat. The peritoneum, from being re- flected upon the liver from the diaphragm, constitutes the several folds called the falci- form, coronary, and triangular ligaments, of which we have already spoken. By means of this membrane, which is always moist, the liver is enabled to glide upon the adjacent parts without friction. We frequently find cellular adhesions between the liver and sur- rounding structures, which do not positively impair its functions. The peritoneal coat adheres intimately to the proper membrane. The proper or fibrous membrane is very well seen over such portions of the liver as are not covered by the peritoneum, and from these points it can be easily traced over the whole of the remainder of the organ. It constitutes the immediate investment of the liver ; its outer surface is adherent to the peritoneal coat, and its inner surface is connected with the tissue of the liver by means of fibrous prolongations interposed between the granules (lobules), affording to each a distinct covering. It passes into and lines the transverse fissure, and is prolonged around the correspond- ing divisions of the vena portae, the hepatic artery, and the biUary ducts, so as to form cylindrical sheaths for those groups of vessels, and for all their farther divisions and sub- divisions. These sheaths constitute the capsule of Glisson, which we must therefore re- gard as a dependance of the proper fibrous coat. The internal surface of these sheaths is united to the vessels only by a very loose cellular tissue. Their external surface ad- heres intimately to the tissue of the liver by fibrous prolongations, which interlace in every direction, and form distinct coverings for the deep-seated granules, analogous to those which we have already stated are produced from the proper coat. The liver, therefore, is traversed in all directions by very delicate fibro-cellular prolongations, form- ing a vast network, in which the granules are contained. This proper coat, moreover, is fibrous,* not muscular, as Glisson believed. It may be said, with truth, to constitute the skeleton or framework of the liver, for it affords a general covering for the organ ; it is prolonged around the vena portae, the he- patic artery, and the biliary ducts, and it furnishes a fibrous or cellular covering for each of the granules composing the proper tissue of the liver. The fibrous cells thus fonned become very distinct in certain cases of hepatic disease. In fact, this fibrous tissue not unfrequently becomes so much hypertrophied, that some of the glandular granules are compressed and atrophied ; and then larger or smaller portions of the liver appear to be converted into a reticulated fibrous tissue. The arrangement of the fibrous tissue is also very manifest in cases of softening of the granules, which may then be easily scraped out of their cells, and the surface of the section thus treated presents the appearance of the cells in a honeycomb. The Proper Tissue of the Liver. — The first thing that strikes an observer in examining the structure of the liver, is the smoothness of its external surface, which does not pre- sent any of the lobulated appearance of most other glands. If we attentively examine * [It is composed of dense cellular or fibro-cellular tissue : for its use, see note, p. 393.1 THE LIVER. 391 this surface, either before or after the removal of its coverings, we find that it is most distinctly composed of granules (lobules, Kieman) : the same is also rendered evident by making sections of the organ, or by tearing it : the granular arrangement has, it is true, been supposed to be the result of laceration. From the mottled appearance of the liver (like granite), already noticed, anatomists have admitted the existence of two substances, or, rather, two kinds of granules in this organ, viz., reddish brown and yellow granules. This distinction was first made by Fer- rein (Hist. Acad, des Sciences, 1735) ; it is now generally recognised, and has even served as the basis of several more or less ingenious explanations. This anatomist called the brown substance medullary, and the yellow cortical, names evidently derived from a rude analogy between them and the medullary and cortical substances of the brain. Others have reversed the meaning of these two words ; but that is of little consequence. " These two substances," says Meckel, " are not arranged as in the brain, one exter- nal and the other internal ; but alternately throughout the whole liver, the yellow sub- stance forming the mass of the organ, and the brown substance occupying the intervals." This distinction into two substances does not appear to me to be well founded. The error has arisen from assuming as constant the existence of two colours, which, how- ever, are far from being distinguishable in all subjects. The two colours, yellow and brown, when they do exist, do not belong to two distinct granules, but rather to the same granule, which is yellow in the centre, where the bile is found, and reddish brown at the circumference, where the blood is collected.* The granules of the human liver are so small, that, excepting when they become con- siderably enlarged, it is not well adapted for examination. The liver of the pig, in which the granules are naturally very large, appears to me the best suited for this purpose. I have been accustomed to divide the liver in different directions, to slit up and remove the veins which have been cut across, and afterward to examine the granules in the semi-canals {g g,fig. 165 ; c c,fig. 166) which they then form. The granules (/ 1 1) may thus be separated with the greatest facility ; they are small, ovoid, elliptical, or, rather, polyhedral bodies, having five or six surfaces, and shaped so as to be moulded upon the surface of the adjacent granules, without leaving any interval. It is evident, therefore, that there is only one order of granules ; that these granules are not arranged in lobules, as stated by Malpighi,+ but are merely in juxtaposition ; and that each has its proper cap- sule, formed by prolongations of the fibrous coat. And as these granules can be isolated, and detached from the capsules in which they are merely lodged, without adhering to them, except at the points by which they receive and emit their vessels, it follows that they are independent of each other, and that the most complete alteration of one or more of them may take place, without the adjacent or intermediate granules being in any way affected, or, at least, that such alteration would not be propagated by continuity of tissue. The size of the granules varies much in different individuals, and is quite independent of the size of the liver itself Physicians who have paid much attention to pathological anatomy have often mentioned their increased development, by the name of hepar aci- nosum. This disease is characterized by the simultaneous occurrence of atrophy of the entire organ, which is reduced to one half or one third its original size, and of hyper- trophy of the granules themselves. In what is called cirrhosis, the greater number of the granules are atrophied, t The investigation of the structure of the liver is, then, reduced to the determination of the arrangement of the granules with respect to each other, of the mode in which the vessels are arranged, and of the structure of each granule. 1. The arrangement of the granules, with regard to each other, is revealed by the fol- lowing fact : In the disease of the liver called ramollisement {Diet, de Med. et Chir. Pratiq., art. Maladies du Foie), in which that organ is reduced to a sort of pulp, as soon as the investing membranes are torn, the tissue of the liver escapes like a brownish-yellow pulp, which, as it is not fetid, cannot be supposed to be the result of gangrene. If this pulp be placed in water, myriads of small and very distinct yellow granules will be seen, resembling small raisin stones, and appended to the ramifications of the different kinds of vessels by vascular pedicles. This fact, which I have several times observed, is confirmed by the observations of Harvey, who, in his work upon the generation of animals, says, that the tissue of the liver is formed along the umbilical vessels like a grape on its footstalk, a bud on the end of a twig, or an ear of corn springing from its stalk ; and also by reference to compara- * See note, p. 395. t [This statement illustrates the confusion that has prevailed from the terms lobule and acinus having' been employed by anatomical writers in different senses to those attached to them by Malpighi ; the lobule of Mal- pighi is, in fact, equivalent to the granule of M. Cruveilhier, and was described by him as consisting of a col- lection of acini {see note, p. 395).] t The ingenious explanation which has been given of cirrhosis is, then, destitute of foundation. In cirrhosis, as I have shown in another place, there is neither atrophy of the red substance, nor hypertrophy of the yellow, but rather atrophy of the greater number of granules, with hypertrophy and yellow discoloration of the re- mainder. 392 SPLANCHNOLOGY, tive anatomy, for M. Blainville has informed me that, in certain species of animals, the liver is formed by rows of glandular granules attached aJong the vessels.* 2. The Vessels of the Liver. — The study of the vessels of the liver is one of the most important points in the history of that organ. Besides the arteries and veins correspond- ing to those of other parts of the body, the liver receives also a special system of veins, viz., the system of the vena porta, which is distributed in its interior like an artery. It presents also, in the adult, the remains of a venous system peculiar to the foetus, the sys- tem of the umbilical vein ; and, lastly, it contains canals intended for the conveyance of the bile, named the biliary ducts. The special venous system of the liver, or the system of the vena porta, will be described more particularly in another place. I shall only now observe, that the branches of ori- gin of this system commence in all the abdominal organs concerned in the function of digestion ; that the ventral venaportae, resulting from the union of these branches, reaches the transverse fissure of the liver, and divides there into a right and left branch, which constitute the hepatic vena portae {p, fig. 164) ; and that these branches subdivide and spread into all parts of the liver, some forward and others backward, but all following a transverse direction. The capsule of Glisson, as we have seen, is developed around this vein ; so that, in sections of the liver, the branches of the vena portae can always be rec- ognised by these two characters : a transverse direction, and the presence of the capsule. Remmtis of the Umbilical Vein. — We can easily conceive the arrangement of these re- Fig. 164.t mains, if we consider that, in the foetus, the umbilical vein (m, fig. 164t), proceeds from the placenta to the longitudinal fissure of the liver ; and at the point where this is intersected by the transverse fissure, divides into two branches, one of which, under the name of the duc- tus venosus (d), passes directly to the vena cava (c), at the point where it traverses the posterior border of the liver ; while the other is continuous with the hepatic vena portae (jf), which, as we have seen, occupies the transverse fissure. The portion common to the umbil- ical and portal veins remains pervious in the adult ; but it then belongs exclusively to the vena portae. The ductus venosus then becomes a mere fibrous cord {v, fig. 164t), as well as the trunk of the umbilical vein itself (m). It is not rare to find the trunk of the umbilical vein persistent in the adult, from an abnormal com- munication between it and the veins of the abdominal parietes. (See Anat. Path, avec planches, liv. xvii., pi. 6.) No example has been recorded of a persistent ductus venosus. Arteries. — The hepatic artery is a branch of the coeliac axis {t,fig. 154), which also furnishes branches to the spleen and the stomach ; and although a difference in the ori- gin of an artery dose not occasion any difference in the blood within it, yet this com- munity of origin is not the less remarkable, for it seems to denote a community, a coinci- dence, or a connexion of function. Moreover, as the nervous plexuses are supported upon the arteries, it follows that the nerves of the spleen, stomach, and liver, are de- rived from a common plexus, the cceMac. We frequently find a second hepatic artery arising from the superior mesenteric. I must not omit to mention the smaUness of the hepatic artery in comparison with the size and mass of the liver. In this respect few organs present so great a disproportion : compare, for example, the kidney and the renal artery, look at the muscles, and I may almost say at the bones. The small caliber of the hepatic artery enables us to determine d priori, that it cannot serve both for the nutrition of the organ and for the secretion of the bile. Lastly, it exactly follows the r2unifications of the vena portae and the biliary ducts, and the capsule of Glisson is common to it and to those two sets of vessels. The Hepatic Veins. — The hepatic veins, the efferent vessels of the liver, are not pro portion al to the size of the hepatic artery, but to that of the vena portae. Proceeding from all points of the liver, and converging towards the fissure of the vena cava, the hepatic veins {h h',fig. 164) empty themselves into that vein (c), especially near the pos- terior border of the liver. It follows, therefore, that the direction of the hepatic veins and of their divisions is from before backward, while that of the divisions of the vena portae is transverse. t This direction, and the absence of the capsule of Glisson, on ac- * Arrangement of the ioiuZe^.— [According to M. Kieman, from whose paper in the Phil Trans, for 1833 this and the succeeding notes on the structure of the liver are derived, the lobules (g^ranules, Cruveilhier) of the human liver are many sided bodies, flattened on one surface, called the base, and forming- processes in every other direction ; hence, in a longitudinal section they present a foliated, and in a transverse section a polyhedral form. The bases of all the lobules (c c,fig. 166) rest on certain branches of the hepatic vein, call- ed «u4-lobular veins (A h) ; while their other surfaces, surrounded by the capsular investments, are either in contact with those of the adjacent lobules, or appear on the outer surface of the liver, or in the portal canals ^g gifig- '65). which contain the \4ka. portae, hepatic artery, and hep.atic duct, or in those fur the lars^er trunks (h,fig. 166) of the hepatic vein. The intervals between the sides of the lobules are the inter-l(>bular/«s«r««, and the points at which two or more of ihese meet are the inter-lobular spaces. The superficial lobules are imperfect, or more or less flattened on their exposed side.] t At least in the principal t'orVs ; for there are a great number of ramifications of the hepatic veins which pass transversely. THE LIVEE. 393 count of which the walls of these veins are directly adherent to the tissue of the liver, so that the veins themselves remain patent, while the sections of the vena portae collapse, are the two characters by which the divisions of the hepatic veins may be distinguished from those of the vena portae, on simply inspecting a section of the liver. Do these anatomical differences between the two kinds of veins produce any difference in the mechanism of the circulation through them ] And is the want of immediate connexion of the divisions of the vena portae to the tissue of the liver intended to permit them to contract so as to propel the blood ] If we consider that the blood of the vena portae pro- ceeds from the trunk towards the branches, as in the arteries, we may conceive the ad- vantages which must result from an anatomical arrangement that would allow these vessels to exert a direct pressure upon the blood. Another point of difference between the branches of the hepatic vein and of the vena portae is, that the walls of the former are perforated by a multitude of extremely small openings or pores, which are the orifices of very small veins. The Lymphatic Vessels. — The lymphatics of the liver are so numerous that these ves- sels were first discovered in that organ ; indeed, it was for a long time regarded as the origin of the lymphatic system, just as it had been originally considered the origin of the veins. The lymphatics of the liver form a superjicicd and a deej> set. The superficial lymphatics are arranged in an extremely close network under the peritoneal coat. Tlie deep set, which are very large and numerous, pass out of the transverse fissure of the liver, and terminate partly in lymphatic glands situated along the hepatic vessels, and partly in the lumbar glands. They communicate directly and freely with the thoracic duct, so that one of the best methods of injecting this duct consists in throwing the in- jection into the lymphatics of the liver. The Nerves. — These are very small, considering the size of the liver. They are deri- ved from two sources, the cerebro-spinal and the ganglionic gystems. The former are branches of the pneumogastric nerves ; the latter constitute the hepatic plexus, which is an offset from the solar plexus. They are interlaced around the hepatic artery : some of these nerves, however, by a special exception, accompany the vena portae. It is gen- eredly admitted that a few filaments of the phrenic nerve are given to the liver. The Biliary Ducts. — Wiiatever may be the origin of the biliary ducts, their radicles, however small they may be, are always found in the capsule of Glisson, together with the corresponding branches of the vena portae and hepatic artery. These radicles are united like veins into smaller, and these into larger branches, which, at length, consti- tute the hepatic duct (d,fig. 164). They can be readily distinguished from the other vas- cular canals of the liver by their yellowish colour, by the fluid which they contain, and by the appearance of their parietes.* * Vessels. — [The first divisions ef the vena portae, hepatic artery, and hepat- ic duct, are situated in the portal canals, which are tubular passages formed in the tissue of the liver, commencing at the transverse fissure, and branching through the Substance of the organ. The smallest divisions of the portal ca- nals contain one principal branch of each of these vessels (P a d,fig. 165) : from these proceed smaller branches, called vaginal, from their situation with- in the capsule of Glisson. jf In the larger canals, the vaginal veins (p" form a plexus in the substance ■p of the capsule, and then give off the tn(er-lobular veins (p p), which pass be- tween the lobules opposite the inter-lobular spaces, ramify in the inter-lobular fissures (p p,fig. 167), and, after freely anastomosing upon the capsular surfa- ces of the lobules, divide into branches, which penetrate the lobules them- selves. In the smaller portal canals, the vaginal venous plexuses are less ap- parent, for many of the inter-lobular veins (i) arise at once from the principal branch of the vena portae : where Fig. 166^ this occurs, the capsule of Glis- son is very thin ; and, indeed, the chief use of this structure, in oth- er situations, appears to be to form a web, on which the vessels may ramify, so as to enter the liver at a great number of points, a use analogous to that of the pia mater and periosteum, in refer- ence to the brain and bones. The hepatic artery also forms vaginal plexuses in the portal canals, wiiich give off inter-lobular hranches ; from these vessels the proper capsule of the liver, the capsule of Glisson, the cap- sules of the lobules, and the coats of the different vessels, derive their nutrier.'. aT*«ries, which terminate in veins that enter the vena portse. But few arterial branches enter the lobules them- selves. The hepatic duct, also, has its vaginal branches, but it is doubt- ful whether they anastomose ; they are formed by the union of the inter-lobular branches (d d,fig. 168), which do appear to anas- tomose, and are derived from the biliary ducts, which pass out at the surface of the lobules. The several divisions of the hepatic veins are termed the he- patic venous trunks, the su6-lobular veins, and the infra-lobular veins. The inira-lobular veins (i,fig. 166 ; h,fig. 167), of which , but one, independent of the rest, emerges from the centre of the * base of each lobule, open into the sub-lobular veins (A A), through - . •/ ■< r v the thin walls of which can be seen the polyhedral bases of the lobules, and the central orifices (t t ) of Ul0 D n D 394 SPLANCHNOLOGY. 3. What is the structure of the gramdcs ? In examining a section of the liver of a pig with the simple microscope, I have seen most distinctly that each granule has a porous and spongy appearance, like the pith of the rush or elder, so that the proper tissue of the liver resembles a sort of filter. This appearance was much more distinct in livers which I had injected with walnut oil, either pure or coloured blue. The colouring matter thrown into the vena portae was, as it were, infiltrated into the spongy tissue of the liver. If we endeavour to ascertain the structure of the liver by means of injections, we shall see what was observed by Soemmering, that whichever vessel be injected, whether the hepatic artery, the duct, the vena portae, or the hepatic vein (provided only the injection be thin, as, for example, coloured glue, size, or spirits of turpentine, or, better still, a strong aqueous solution of gamboge), there will not be a single granule into which the injection will not have penetrated ; and, moreover, that the liquid throvra into one ves- sel will pass either into one, two, or all three of the others ; and the facility with which this takes place proves that the different orders of vessels communicate with each other directly, and not through the medium of cells or small cavities.* In a foetus, or an infant that has died immediately after birth, an injection through the umbilical vein gives similar results. I have never been able to force the liquid into the l)Tnphatic vessels, at least without rupturing the tissue of the liver. Air driven into the vessels penetrates more easily than liquids into the lymphatics, no doubt on account of its greater subtilty. It follows, then, that in each granule there is an arterial radicle, a radicle of the vena portae, one of the hepatic vein, and one of the duct, probably some lymphatic vessels, and a nervous filament. The aggregate has been represented by Soemmering as having some resemblance to the arrangement of a Damask rose.f All the different vessels communicate freely with each other.t The manner in which these different vessels are arranged in each granule can only be discovered by injecting them simultaneously, or, rather, successively, for it is nearly impossible to inject all the vessels of the liver at the same time. I have accordingly in- jected the vessels in the following order : the vena cava, and, consequently, the hepatic veins, with wax coloured with Prussian blue — a certain quantity of walnut oil, also con- taining Prussian blue, had been previously thrown into the same vein ; the vena portee with a red injection ; the hepatic artery with the same ; and then the hepatic duct with a yellow injection. These injections were made in the liver of a pig, the liver being placed in warm water, and the injections pushed in with a gradually-increasing force. During the injection of the vena cava and vena portae, the wrinkles of the liver disap- peared, and the central depressions of the superficial granules became, on the contrary, slightly prominent. It was therefore evident that each granule was hollow, and that the space had been filled by the injected matter. The liver thus injected and submitted to different chemical agents gave the following results : The blue injection, or that which had been thrown into the vena cava, had pen- etrated into the central part of each granule, which is generally called the yellow suh stance of the liver. In the middle of the central part was the yellow injection from the hepatic duct. Around tl\^ blue injection was found that coloured red, which had been forced into the vena port* and the hepatic artery, and which occupied all the so-called red substance of the liver. It follows, therefore, that each granule had a vascular appa- ratus thus arranged : in the centre, a biliary duct ; farther removed from the centre, a vascular circle formed by the ramifications of the hepatic vein ; and external to this another vascular circle, formed by ramifications of the vena portae and hepatic artery. As to the manner in which the vena portae and hepatic artery are arranged in relation to each other, we shall find, if we trace them into the substance of the liver, that the ram- ifications of the hepatic artery correspond exactly to those of the vena portae and biliary duct, which, as we have already said, are all contained in the same sheath ; and that they ramify and are lost upon the parietes of the vein and duct, almost in the same manner as the bronchial arteries are distributed upon the divisions of the air tubes. I must, therefore, conclude that the hepatic artery furnishes for the liver the nutritious vessels (vasa vasorum) of the vena portae and hepatic ducts ; and this will explain the disproportion between its cahber and the size of the Uver. The subdivisions of the hepatic veins, which follow a separate course, present a sim ^ilar peculiarity to that observed in the splenic vein, viz., a multitude of pores or holes inter-lobular veins. This appearance is peculiar to the sub-lobular veins, the canals for vehich alone are form- ed by the bases (c c) of the lobules. The portal canals (g,fig- 165) are formed by their capsular surfaces, and the openings (d), seen in the interior of the small divisions of the vena portae, correspond to the inter-lobular spaces, not to the centres of the lobules. The sub-lobular veins anastomose with each other (this the divis- ions of the vena portae never do), and unite to form the hepatic venous trunks (H,fig. 166), into which no in- tra-lobular veins open, nor do tlie bases of any lobules rest upon them.] * [From this statement the ducts must be excepted ; they do not communicate with the bloodvessels. — (See note, p. 395.)] « t " Quilibet acinus hepatis e glomeroso constat, vel e particulis arteriE, venae portarum, venie hepaticae, duc- tus biliferi et vasorum absorbentium, cujus formam rosie sic dictie Damascenae imaginem pingere nobis licet," —(Corp. Hum. Fab., t. vi., p. 180.) t See note, p. 395. THE LIVER. g§5 by which very small veins open directly into them. Their ramifications are much less numerous than those of the vena portae. The result of the injections described above also explains the difference in colour be- tween the centre and the circumference of each granule ; it shows, moreover, that one part of the granule is impermeable to injections ; and its spongy nature, resembhng that of the pith of the rush or elder, is apparent even to the naked eye, in a section of a liver thus injected, when viewed by a strong light. To resume, then, it may be said that the liver is composed of ovoid, elliptical, or, rath- er, polyhedral granules, moulded closely upon each other. Each granule has its proper fibrous capsule ; and all the capsules are united together by prolongations, which also connect them with the general cellular investment of the liver, and with that extension of it called the capsule of GUsson. The granules are independent of each other. Each of them consists of a spongy tissue, impermeable to injections ; of a biliary duct proceed- ing from its centre ; of a venous network foimed by the hepatic veins ; of another ve- nous network belonging to the vena portae ; and of a very delicate arterial network deri- ved from the hepatic artery, which is ramified upon the parietes of the vena portae and biliary ducts. Such is the structure of the hver.* It remains for me now to examine its excretory apparatus. The Excretory Apparatus of the Liver. The excretory apparatus of the liver consists of the hepatic duct, of the cystic duct, of the gall-bladder, and of the ductus communis choledochus. The hepato-cystic canals, t admitted by some authors as constant or occasional in man, can be easily shown in the lower animals, but do not exist in the human species. TTie Hepatic Duct. — The hepatic duct arises in the granules of the liver by hepatic radr KleSjt which, by uniting successively like veins, constitute small and then larger branch- es. These latter all converge towards the transverse fissure of the liver, where they terminate ultimately in two trunks of almost equal size, which join each other at a very obtuse angle, and form the hepatic duct {d,fig. 164). The condition of the branches of the hepatic duct in the transverse fissure is extremely variable : thus, sometimes the trunk of the right side is larger than that of the left, and sometimes the opposite is the case. Frequently several branches join the trunks late in the transverse fissure ; but, whatever be the nature of these variations, the right trunk never corresponds exactly to the right lobe of the liver, nor the left to the left lobe. All the divisions and subdivisions of the hepatic duct^ are contained in the capsule of Glisson, together with the ramifications of the vena portaj and hepatic artery, to which * Structure of the Lobules. — [It appears from the preceding note, that while several branches of the vena portae and hepatic artery enter, and several of those of the hepatic duct pass out at the capsular surface of each lobule, only a single branch of the hepatic vein emerges from its base ; within the lobules, the following is the arrangement of these vessels : The branches from the inter-lobular (portal) veins Cp p p,Jig. 167) form in the outer portion of each lobule a venous plexus {I I), consisting of branches radiating towards the centre, rv jg~ connected by others passing transversely ; these veins become capillary, e • ' • ramify upon the biliary ducts, and terminating in the branches of the intra- lobular (hepatic) vein (h), which correspond in number with the processes on the surface of the lobule, ultimately unite to form the central vein that «:;>^^^Ji^^^/^}^^'^i^'^ passes out at its base. The lobular arteries are few in number, and, according to Kieman, end in branches of the vena portse, and not directly in those of the hepatic vein. Miiller inclines to the more commonly received opinion, that the three kinds of bloodvessels communicate with each other. No communication, how- ever, exists, as stated by M. Cruveilhier, between the bloodvessels and the biliary ducts, which, like the ducts of other glands, are an independent system of vessels. According to Mr. Kieman, the ducts form a reticulated plexus, occupying principally the outer portion of each lobule (as shown at 6 b, jig. 168, which is a diagram copied from Mr. Kieman's paper). MUUer expresses doubts as to the anastomosis of the ducts, and thinks it probable, from analogical observation, that they terminate in tufts of tubes having blind extremities. The islets formed between the radiating and transverse branches of the lobular (portal) veins (I, fig. 167) correspond to the acini of Malpighi, and contain the biliary ducts with their capillary bloodvessels, and also a pecu- liar tissue, which occupies all the intervals between the several kinds of vessels, and consists, according to Krause, of hexagonal, nucleated cells, having several bright points in them, like globules of oily matter. The appearance of two substances in the liver can now be explained ; it does not depend on the biliary ducts being situated in the centre, and the '' ' ' veins nearer to the circumference of each lobule (sec p. 391, 394), but in a partial congestion of either the portal or hepatic system of veins. In portal congestion, the margins of the lobules are dark, and their centres pale ; it is very rare, and has been seen only in children. Of hepatic venous congestion there are two stages : in the first, the centre of each lobule is dark, and the margin pale (fig. 166) ; it constitutes passive congestion, and is the common state of the liver after death : in the second, the congestion extends to the portal veins in the iuter-lobular_/isiures, but not to those in the inter- lobular spaces, or points at which those fissures meet, which spaces are then seen to occupy the centre of each pale isolated spot : this is active congestion of the liver ; it occurs in diseases of the heart, and in acute dis- eases of the lungs and pleura.] + [/. c, canals passing directly from the liver into the gall-bladder.] t See note, suprA <) [Excepting those within the" lobules.] 396 SPLANCHNOLOGY. they are connected by loose cellular tissue. The trunks of the hepatic duct lie at the bottom of the transverse fissure, and are hid by the trunk of the vena portse and the branches of the hepatic artery. The hepatic duct {t, fig. 169), thus formed by the union of the two trunks which occupy the transverse fissure, passes downward and to the right side for about an inch and a half, and then unites at a very acute angle with the cystic duct (s), to form the ductus communis choledochus (c ; and x, fig. 154). In this course the duct is contained in the gastro-hepatic omentum, together with the vena portas, which is behind it, and the right branch of the hepatic artery, which is in front of it. A great quantity of loose cellular tissue unites the duct to these vessels. The Gail-Bladder. Dissection. — ^A gall-bladder filled with bile may be studied without any preparation : if it is empty it must be distended, either with a fluid or vpith air. A beautiful preparation of the gall-bladder may be made for preservation by drying it after inflation, or by filling it with fat, which is afterward removed by oil of turpentine. The gall-bladder {cystis fellea, g,fig. 164) is the reservoir of the bile. It is situated at the lower surface of the right lobe of the liver, occupying a particular fossa (the fossa of the gall-bladder) on the right of the longitudinal fissure, from which it is separated by the lobulus quadratus. It is held in this place by the peritoneum, which, in the majority of instances, merely passes below it, but, in others, almost entirely invests it, and thus at- taches it to the liver by a sort of mesentery. In this latter case it is at some distance from the liver, as in certain animals. Its fcrrm. is that of a pear, or of a cone with a rounded base ; it is directed obliquely, so that its great extremity (g,figs. 155, 161) looks forward, downward, and to the right ; and its small extremity, backward, upward, and to the left side. Size. — The small size of the gall-bladder corresponds with that of the rest of the ex- cretory apparatus of the bile, and is strongly contrasted with the great bulk of the liver. This difference becomes still more striking if we compare, on the one hand, the kidney with the liver, and, on the other, the urinary bladder with the gall-bladder. It is true, however, that all the urine must pass through the former, while a part only of the bile is deposited in the latter. The size of the gall-bladder, however, is subject to considerable variety ; it sometimes acquires three, four, or even ten times its usual size from retention of the bile, in conse- quence of obstruction in the ductus choledochus.* Cases have been recorded in which it contained six, eight, or ten pounds of bile, but this I can scarcely credit. On the oth- er hand, it is sometimes closely contracted round a small calculus, while the cystic duct is completely obliterated, and reduced to a fibrous cord. It must undoubtedly have been such cases as these that have been regarded as examples of congenital absence of the gall-bladder. Relations. — In order to facilitate our description, we shall consider the gall-bladder as consisting of a body, a fundus, and a neck. The body is conical, and has the following relations : below, where it is covered by the peritoneum, it is in relation with the first portion of the duodenum, and the right extrem- ity of the arch of the colon. It is not unfrequently found in contact with the pylorus, or even with the pyloric end of the stomach. Sometimes it is united by accidental or nor- mal adhesions to the duodenum and arch of the colon. These relations account for the yellow or green discoloration which always takes place after death in those parts of the alimentary canal that are in contact with the gall-bladder ; and also for the passage of biliary calculi into the duodenum, the colon, and the stomach. It is not very rai-e to find the gall-bladder applied by its whole length to the right kidney : this relation can only occur after descent of the duodenum and transverse colon. Above, the body of the gall- bladder adheres to the cystic fossa by a more or less loose cellular tissue,! and by ar- teries and veins, but never in the human subject by biliary, i. e., hepato-cystic, ducts. The fundus of the gall-bladder {g,fig. 161), entirely covered by the peritoneum, gen- erally projects beyond the anterior margin of the liver, and comes into relation with the abdominal parietes, opposite the outer border of the right rectus muscle, immediately below the costal cartilages near the anterior extremity of the tenth rib. When distend- ed with bile or calculi, the fundus of the gall-bladder becomes prominent, so as to raise the abdominal parietes, through which it has been felt in emaciated individuals. It has even been stated that the noise made by the calculi may be heard on percussion. This relation explains the possibility of the occurrence of abdominal biliary fistulae, and why calculi may escape through such openings : on it, also, is founded the scheme for ex- tracting the calculi by an operation analogous to that performed for stone in the urinary b adder, and which I should not have mentioned had it not been proposed by J. L. Petit. The relations, as well as the size of the fundus of the gaU-bladder, present many vari- * Anrf.her cause of enlargement of the gall-bladder is the obstruction of its neck by a calculus : but, in- stead of bile, it then contains a limpid serum, and, in fact, is converted into a serous cyst. The tumour thus formed may t)e compared to the lachrymal tumour in cases of obstruction of the lachrymal puncta or canals. t This cellular tissue may become inflamed, and, if pus be formed, it may pass into the gall-bladder, while the bile escapes into the cellular tissue, and hence death may ensue. I have observed, in a very short space of time, three examples of this lesion, which, perhaps, has not been thoroughly examined ; and several cases have been shown me under the name of gangrene of the gall-bladder. THE LIVER. 3g7 eties. The fundus, or that part which projects beyond the Uver, is sometimes as large as the body. I have seen this part of the gall-bladder turned back at a right angle upon its body, and reaching the umbilicus. It may be conceived, that the differences in the form and situation of the liver must greatly influence the situation of the fundus of the gall-bladder, which I have found in the hypogastrium and in the right iliac fossa, either with or without adhesion to the neighbouring parts. The neck or apex of the gall-bladder is twice bent suddenly upon itself, like an italic S, having its three portions in contact. It would appear, in some cases, that these two curves resemble the thread of a screw. This double curvature may be easily elTaced by removing the peritoneum with the subjacent cellular tissue. The limits between the neck and the body of the gall-bladder on the one hand, and between the neck and the cystic duct on the other, are marked externally by a constriction. The internal surface of the gall-bladder is tinged either green or yellow, according to the colour of the bile ; but this staining is the effect of transudation after death ; its nat- ural colour is a whitish gray. Moreover, the internal surface is irregular, like shagreen, and has some crests or prominences arranged upon it in polygons, and again subdivided by smaller crests, like the reticulum in the stomach of ruminantia ; so that, when ex- amined by a strong lens, it appears divided into a number of small and very distinct al- veoli : some highly-developed papillae or villi, of a very irregular shape, are also found upon it. As to the object of either the crests or the papillae, or whether they favour ab- sorption by multiplying the surface, we are altogether unable to decide. Opposite each of the two curves of the S, described by the neck of the gall-bladder,, we find a very large valve. The two valves, which are in opposite directions, as well as the curves, result from the alternate inflection of the neck itself, and are efl^aced by straightening that part. The portion of the neck between the two valves is not unfre- quently dilated into an ampulla. A calculus is often formed in this intermediate portion, where it remains, as it were, encysted, and intercepts the course of the bile ; and that the more easily, because the valves greatly contract the openings from the neck into the body of the bladder, and into the cystic duct. Moreover, these valves are opposed nei- ther to the entrance of the bile into, nor to its exit from, the bladder. Structure. — Proceeding from without inward, we find that the gall-bladder is composed of, 1. A peritoneal coat, which is reflected from the lower surface of the liver upon the bladder, completely invests its fundus, forms a more or less incomplete covering for its body and neck, and is continuous with the anterior layer of the gastro-hepatic omentum. 2. An areolar fibrous coat, which forms, as it were, the framework of the bladder, and pre- vents its sudden distension, though it will yield to a long-continued distending force ; but I have not been able to see the muscular fibres admitted by some authors, and which can be so easily detaonstrated in the larger animals, the ox in particular. 3. An interned mucous membrane, the principal characters of which I have noticed when speaking of the internal surface of the gall-bladder : it presents some folds, which may be easily distin- guished from the borders of the alveoh, because they are readily effaced by distension. Af- ter the most attentive examination, I have been unable to recognise any crypts or follicles. The gall-bladder receives one very considerable artery, the cystic branch of the hepatic. The cystic vein terminates in the vena portae. The lymphatic vessels are very numerous, and easily demonstrated ; they are sometimes tinged by the colouring matter of the bile. Its nerves are derived from the hepatic plexus. The Cystic Duct. — The cystic duct {,s,fig. 169), or excretory duct for the bile, is the smallest of all the biliary canals : it is not unconunon, however, to find it of an equal or even larger size than the others, in which case there has always been some obstacle to the flow of the bile through the ductus communis choledochus (c). It conm[iences at the neck of the gall-bladder, passes downward and to the left side for about an inch, and unites at a very acute angle with the hepatic duct (t). It is not straight, but inflected, and, as it were, sinuous. Relatio-ns. — It is situated in the substance of the gastro-hepatic omentum, in front of the vena cava, the cystic artery being on its left side. Its internal surface is remarkable for its valves, which are indefinite in number ; according to Soemmering, there are from nine to twenty, but this appears to me to be an exaggeration : I have counted from five to twelve. These valves are concave at their free margins, irregular, alternate, oblique, transverse, sometimes even vertical, and united together by small oblique valves. In order to understand their structure, a cystic duct must be examined under water, or, rath- er, an inflated and dried specimen. This alternate arrangement of the valves some- times gives a spiral appearance to the inner surface of the cystic duct.* These valves, which only exist in man, perhaps on account of the erect position peculiar to him, are not effaced, like the valves in the neck of the gall-bladder, by such dissection as will al- low of straightening of the duct. Small calculi are occasionally met with in the inter- vals between the valves, giving to the cystic duct a nodulated appearance, and intercept- ing the flow of the bile. Moreover, the valves of the cystic duct are not more opposed to the descent than to the ascent of the bile. It is even probable that they facilitate the * " Quae possint aliquam spiralis fabricse imagincm ferre." — {Holler, torn, vi., liv. xxiii., p. 530.) 398 SPLANCHNOLOGY. ascent of the bile into the gall-bladder by supporting the column of liquid, like the valves of the veins. Perhaps they are also intended to retard the course of the bile from the gall-bladder towards the ductus choledochus. From their appearing sometimes to have a spiral arrangement, M. Amussat has advanced a very ingenious opinion : that the as- cent of the bile is effected by a contrivance like an Archimedes' screw. But an Archi- medes' screw only causes the ascent of a liquid when a rotatory movement is communi- cated to it, and how can such a movement be performed by the cystic duct 1* The Ductus Communis Choledochus. — The ductus communis choledochus ( xo^, bile, doxo^, containing ; c, c. Jig. 169), the last excretory canal of the bile, seems to be formed Fig. 169. by the union of the hepatic (0 and the cystic ducts («). Another, and, perhaps, more simple manner of viewing the excretory cansils of the liver, would be to consider the hepatic duct as giving off to the right, after a certain course, the cystic duct, which, after passing backward, di- lates into an oval ampulla to form the gall-blad- der ; and the ductus choledochus as nothing more than the continuation of the hepatic duct. The direction of the ductus choledochus is, in fact, the same as that of the hepatic duct, i. e., obliquely downward, a little to the right, and backward : there is no line of demarcation be- tween these two ducts : in the natural state there is no marked difference in their diame- ters : the ductus choledochus, when collapsed, is about as large as a moderately-sized goosequill. 't The same causes give rise to dilatation of the ductus choledochus and of the hepatic duct. I have seen the former as large as the duo- denum. {Anat. Pathol, avec planches.) Its length is from two to two inches and a half Relations. — In the first part of its course, before it reaches the duodenum, the ductus choledechus is included in the gastro-hepatic omentum, in front of the vena portae, and below the hepatic artery, having the right gastro-epiploic artery along its left side, and surrounded by loose cellular tissue, a great number of lymphatic vessels, and several lymphatic glands. Having reached the duodenum, opposite the first flexure of that in- testine, it passes behind and to the inner side of its second portion, and is there received into a groove, or, more commonly, into a complete canal, formed for it by the pancreas. Lastly, it penetrates very obliquely into the substance of the duodenum, about the mid- dle of its second or vertical portion, perforates the muscular coat, passes between that and the fibrous coat, then between the fibrous coat and the mucous membrane, elevating the latter when distended with bile or by a probe, and after a course of about seven or eight lines between the coats, opens into the duodenum, about the lower part of the sec- ond portion, at the summit of a nipple-like eminence (above c), which is more or less prominent in different subjects. In this third portion of its course the ductus choledochus is in relation with the pan- creatic duct (m), which is situated on its left. Opposite the base of the eminence above- mentioned, the two ducts unite, or, rather, the pancreatic duct opens into the ductus choledochus ; so that, at its termination, the latter may be regarded as a canal having a triple origin, viz., an hepatic, a cystic, and a pancreatict Internal Surface of the Ductus Hepaticus and Ductus Choledochus. — ^The internal surface of both the hepatic duct and the ductus choledochus is characterized by the absence of valves, though traces of valves are occasionally met with in the ductus choledochus ; by the absence of the alveolar structure observed in the gall-bladder ; and by having a niultitude of openings or well-marked pores, which are considered as belonging to mu- ciparous follicles, and are apparently formed by an interlacement of fasciculi, having a fibrous character, and intersecting each other at very acute angles. The ductus chole- dochus and the hepatic duct are of uniform caliber throughout their whole length. The ductus choledochus is contracted a little in its third or duodenal portion ; it dilates into an olive-shaped ampulla, opposite the base of the papilla in the duodenum, and opens by an extremely small orifice or mouth : hence the reason why biliary calculi are so fre- quently arrested in the ampulla of the ductus choledochus. From the narrowness of the duodenal orifice of the ductus choledochus, from the mo- * Another opinion, founded upon the existence of the valves, is that of Bachius, who, believing that he had shown that the valves prevent the ascent of the bile from the hepatic duct into the gaU-i)ladder, has advanced very singular views concerning the formation and uses of the bile. The bile, according to him, is formed in the gall-bladder, and carried l)y the cystic duct into the hepatic duct and the ductus choledochus. By his theory, the bile which reaches the liver through the hepatic duct assists greatly in sanguification. This opin- ion, altogether erroneous as it is, has perhaps exercised a great influence in science, by contributing to eradi- cate the idea of the bile being an acrid, corrosive, and essentially injurious excrementitial fluid. t Hence the definition of SoDminering : " Ductus choledochus, id est, ductus hepaticus, cysticus, et pancreatir cus, in unum conflati," — ICorpor. Hum. Fabric, tom.\i., p. 186.) THE LIVER. ▼able or yielding nature of the eminence upon which it opens, and from the oblique course of the duct through the substance of the walls of the duodenum, it follows that the bile and the pancreatic fluid may pass freely from the ductus choledochus into the duodenum, but cannot regurgitate from the duodenum into the duct. On this subject I have made several experiments. I have forcibly injected both water and air into the duodenum, included between two ligatures, but nothing entered into the biliary canals : on the other hand, I have injected the same fluids from the gall-bladder into the duodenum, which I was thus able to distend at pleasure. But then, on compressing the bowel thus distend- ed with great force, I have never been able to cause the slightest reflux into the biliary caneils.* At the union of the cystic and hepatic ducts there is a very long spur-shaped process, formed by the hning membrane reflected upon itself At the junction of the ductus cho- ledochus and the pancreatic duct there is also a similar process, which I have seen ex- tending down to the duodenal orifice. In neither situation do these processes prevent the fluid of one canal from passing into the other. Thus, the cystic bile might flow back into the hepatic duct, the pancreatic fluid might regurgitate into the ductus choledochus, and, on the other hand, the bile might enter the pancreatic duct, if these canals were not habitually full. Moreover, the spur-shaped process between the ductus choledochus and the pancreatic canal cannot arrest the flow, either of the bile or the pancreatic fluid, by being applied to the orifice of the one or other duct. Structure of the Biliary Ducts. — ^AU the biliary ducts have a similar structure : they have an internal mucous membrane, continuous on the one hand with the lining mem- brane of the gall-bladder, and on the other with that of the duodenum ; it is thin, and provided with slightly-developed papillae ;t a. proper membrane, composed of a dense are- olar tissue, generally regarded as fibrous, but which appears to me analogous to the tis- sue of the dartos condensed ; a cellular layer connecting these canals to the surrounding parts ; and, lastly, the peritoneimi, which forms a very incomplete accessory tunic for them. Thus constituted, the biliary ducts have very thin walls, so that they collapse like veins, and are extremely dilatable. In certain cases of retention of the bile we find the ductus choledochus and the hepatic duct as large as the duodenum, the divisions of the hepatic duct dilated in proportion, and the tissue of the liver more or less atrophied by the compression to which it has been subjected. Development of the Liver. — The development of the liver is one of the most important subjects in its history. Under this head we have several points to consider : 1. The time of its appearance is anterior to that of any other organ :t in the first days of intra-uterine life it may be distinguished by its colour in the midst of the ceUular mass which represents the foetus. 2. In size the liver is relatively larger as it is examined at an earlier period of devel- opment. Thus, according to Walter, in the embryo of three weeks it forms one half the weight of the whole body. This enormous proportion is maintained during the first half of intra-uterine life. After this period its growth is slower, while that of the other or- gans is proportionally increased, so that at birth the weight of the liver is one eighteenth that of the whole body.ij After birth the liver undergoes an absolute diminution ; some authors have even affirmed that a comparison of the weight of the liver in new-bom in- fants and in children of nine or ten months old, gives a difference of one fourth in favour of the former. It is generally said that the difference in size affects the left rather than the right lobe ; but this has not appeared evident to me. Towards the age of puberty the liver has the same relative bulk as at later periods. Attempts have been made to ascertain the proportion between the weight of this organ and that of the body, and it has been said that it forms one thirty-sixth part of the whole body. But what relation can be established between two terms, one of which, viz., the weight of the body, is subject to continual variations 1 In old age the liver is smaller than in the Eidult, a dim- inution apparently in unison with that which occurs in all the other organs. 3. The differences in the situation of the liver are connected with its variations in size : thus, in the first half of intra-uterine life, the liver occupies the greatest part of the ab- domen, and is in relation with certain regions in which it is not found at more advanced stages. In the earUest periods it descends as low as the crest of the ilium, and when the abdomen is opened it presents the appearance of a red mass, beneath which are * How can this fact be reconciled with another no less incontestable, viz., the passage of lumbrici into the biliary ducts 1 The reason is, that the lumbricus is a foreign body, which has a power of selection, and is able to overcome an obstaCie, to seek for the orifice of the ductus choledochus, and to introduce itself within it. t [Numerous follicles are found in the ductus communis and in the hepatic duct, and all its subdivisions ; according to Mr. Kiernan, even in the smallest that can be examined. In the larger branches they are ar- ranged irregularly; in the smaller ones, in two longitudinal rows, along opposite sides of the duct.] t [In the embryo of the bird the liver is developed by a conical protrusion of the walls of the intestinal ca- nal into a granular mass or blastema. — (See Milller^s Phys. by Baly, p. 448.) The rudiments of the cerebro- gpinal axis, of the heart, and of the intestinal canal, appear previously to the liver.] f) I have had occasion to notice, at the Matemite, the very great differences in the size of the liver in in- fants at birth, for which I have been unable to find any sufficient reason. There ai'.' some well-formed in fauts in whom the liver at birth is not relatively larger than that of adults 400 SPLANCHNOLOGY. placed the other abdominal viscera. During the second half of intra-uterine life, and at birth, it occupies only a part of the abdomen ; but it still corresponds to a considerable extent of the abdominal parietes : hence the ease with which it is ruptured by pressure upon the abdomen of a new-born infant. One fact on record seemed to me to prove, that in a first labour, where the feet presented, the pressure of the genital organs of the mother was S'ufficient to produce this result. — (Vide Proces-verbal de la Distribution des Prix de la Maternite, 1832.) In the eariiest periods the falciform ligament of the liver corresponds to the median line of the body ; at birth it is a little to the right of that line, and is afterward removed still farther in the same direction. 4. The great size of the liver during intra-uterine life is connected with the existence of the umbilical vein, by which the foetus receives the blood returned from the placenta, that is to say, all the blood necessary for its nutrition. The rapid diminution of the liver after birth is probably owing to the obliteration of this vein. It is a very remark- able fact, that the persistence of this vein in the adult is not accompanied by an unusu- ally large liver. In one particular case of persistence of the umbilical vein the liver was of a very small size. — {Anat. Path, avec planches, liv. xvii.) 5. The tissue of the liver of the foetus is of a pale red colour in the early periods, and of a deep brown near the full term of pregnancy ; its colour becomes lighter after birth. The liver contains a greater quantity of blood before than after birth. Its tissue is the less consistent the earlier the stage of development at which we examine it, and its soft- ness is accompanied with great fragility. 6. The distinction between what are called the two substances of the liver is not ap- preciable during intra-uterine life. It only becomes apparent after birth. Functions. — The liver is the secreting organ of the bile. The bile is secreted in the glandular granules by an unknown process. Doubts are stiU entertained as to whether the materials from which the secretion is formed are conveyed by the hepatic artery or the vena portae.* The opinion advanced by some modern authors, that the yellow sub- stance of the liver is the only part concerned in the secretion of the bile, and that the brown substance has other uses, is a purely gratuitous hypothesis. The bile traverses the several ramifications of the hepatic duct, and, having arrived in the principal duct, it may either enter directly into the duodenum by the ductus chole- dochus, or it may pass into the gall-bladder by the cystic duct. This retrograde move- ment towards the gall-bladder has much occupied the attention of physiologists : perhaps it may be explained by the narrowness of the duodenal orifice of the ductus choledochus, by the elasticity of that canal, and especially by the pressure exercised on its duodenal portion by the circular fibres of the duodenum. The gall-bladder and the cystic duct are not indispensable to the elimination of the bile. Nothing is more common than to find the excretory apparatus of the liver in old subjects reduced to the hepatic duct and the ductus choledochus. Has the liver any other function besides that of secreting bile 1 The disproportion ex- isting between the size of that organ and of its excretory apparatus, and also the enor- mous bulk of the liver during foetal life, i. e., at a time when the secretion of bile is at its minimum of activity, are both in favour of the opinion that the liver has some addi- tional function ; and if, again, we consider that, in the adult, a very important system of veins is distributed to the liver, and that in the foetus it receives the blood from the veins of the foetal portion of the placenta, we shall be led to presmne that the unknown func- tions of this organ are in some way connected with the process of sanguification. The Pancreas. Dissection. — The pancreas may be seen through the gastro-hepatic omentum, after drawing down the stomach, without any dissection. In order to expose it, turn the stomach upward (see fig. 154) after having divided the two layers of peritoneum which proceed from its greater curvature to form the great omentum. It may also be ex- posed by turning the arch of the colon upward, and dividing the inferior layer of the transverse mesocolon. The excretory duct is situated in the interior of the organ. In order to dissect it, the glandular substance which covers it must be very carefully re- moved towards tlie middle and the right extremity of the gland. It may be injected from the ductus choledochus, after the vertical portion of the duodenum has been included be- tween two ligatures : when the duodenum is filled with the injection, the pancreatic duct becomes filled in its turn. It may also be injected from the ductus choledochus after hav- ing passed a ligature round the projection or ampulla which is common to the two ducts. The -pancreas {Trdv-Kpeag, all flesh) is a glandular organ annexed to the duodenum, with which it has immediate relations : it is situated transversely and deeply behind the stom- ach, and in front of the lumbar vertebrae. * [From the researches of Mr. Kiernan (see note p. 395), it would appear that the blood of the vena ports is directly concerned in the secretion of the l)ile, while that of the hepatic artery is only indirectly concerned, i. e., after it has afforded nutrition to the tissue and vessels of the liver, and has entered the branches of the ■'•ena portae, and thus become portal blood.] THE PANCREAS. 401 Form and Size. — In form, the pancreas resembles no other gland ; it is transversely oblong, flattened from before backward, large at its right extremity, where it presents a sort of angular expansion like a hammer, and gradually tapering towards its left extrem- ity : hence the division of this organ into a head, body, and tail. Its long or transverse diameter is measured by the interval between the concavity of the duodenmn (e e) and the spleen (A). The size and weight of the pancreas present many varieties. Its weight is generally from two to two and a half ounces, but may reach six ounces. The pan- creas is sometimes found atrophied, and in one case of this kind it did not exceed an ounce in weight. Relations. — Its anterior surface, convex and covered by the peritoneum, is in relation with the stomach, which moves freely upon it. In certain cases of disease, adhesion between the pancreas and the stomach takes place, so that in chronic ulceration of the latter we find the pancreas supplying the place of large portions of the walls of the stom- ach which had been destroyed. When the stomach is situated lower down than usual, the pancreas has relations either with the liver or with the anterior walls of the abdo- men, from which it is separated only by the gastro-hepatic omentum, so that it may be felt with the greatest ease through the abdominal parietes.* In such cases, even expe- rienced practitioners have not unfrequently been led to infer the presence of scirrhus of the pylorus. The pancreas is also in relation, in front, with the first portion of the duo- denum, and with the angle formed by the ascending and transverse colon. Its posterior surface is concave, and corresponds to the vertebral column, opposite the first lumbar vertebra ; it is separated from the spine, however, by the splenic and the superior mesenteric veins, and by the commencement of the vena portae. The two last- mentioned veins are lodged in a deep groove, or, rather, almost complete canal, formed in the pancreas, which also includes the superior mesenteric artery and its surrounding plexus of nerves. A great number of lymphatic vessels and glands, the pillars of the diaphragm (d d), the vena cava on the right side, and the aorta on the left, also separate the pancreas from the vertebral column. To the left of the spine it is in relation vrith the left supra-renal capsule and kidney, and the corresponding renal vessels. The rela- tion of the pancreas to the aorta is important ; it is through the pancreas that the pulsa- tions of that vessel are felt in the epigastrium in emaciated individuals, and it is here that the vessel may be compressed. Its upper border is thick, and is grooved for the reception of the splenic artery, which often runs in a sort of hollow canal formed in the substance of the gland through its en- tire length. It also has relations with the first portion of the duodenum (e), with the lobulus Spigelii, and with the coeUac axis (<). The thickness of this border has led some anatomists to say that the pancreas is prismatic and triangular. Its lower border is much tliinner than the upper, and is bounded by the third portion of the duodenum, from which it is separated on the left by the superior mesenteric vessels {rOf the artery). Its right, or duodenal, or great extremity is in contact with the duodenum and the duc- tus choledochus. This extremity presents a very remarkable arrangement ; it is curv- ed upon itself from above downward, like the duodenum, by the concavity of which it is circumscribed ; then, having reached the third portion of the bowel, it passes transverse- ly to the left, behind the superior mesenteric vessels, and forms the posterior wall of the canal in which they are situated. This reflected portion, arranged in the form of a whorl, is sometimes detached from the rest of the gland, on which account it has been called the lesser pancreas. By its great extremity the pancreas is, as it were, attached to the duodenum, beyond which it projects in front, but especially behind : it accompa- nies this intestine in all its displacements, so that when the duodenum is situated lower down than usual, which happens in displacements of the stomach downward, the head of the pancreas is always removed in the same direction. Its left, or splenic, or small extremity is narrow, and touches the spleen, upon which it is flattened and blunted, and sometimes slightly enlarged. It is seen, then, that in its relations to other parts, the pancreas has a great analogy with the salivary glands. Thus, large vessels are situated near and penetrate this gland, which forms a sort of covered passage for them, and is moved by their pulsations. The diaphragm, the duodenum, and the stomach, also tend to disturb and press upon the pancreas. Structure. — The analogies in structure between the pancreas and the salivary glands are no less numerous, and fully justify the name of abdominal salivary gland given to it by Siebold : it has the same whitish colour, the same density, t and the same arrange- ment into lobes, which are themselves divisible into lobules. The identity is such that it would be impossible to distinguish a portion of the pancreas from a part of a salivary * This condition may be foretold : it occurs whenever the vertebral column can be felt immediately behind the parietes of the abdomen. I have never met with it excepting in emaciated individuals, where a great part of the small intestine occupied the cavity of the pelvis. It is probably the traction exercised by the small intestine contained in the pelvis that occasions the low position of the stomach. t The pancreas sometimes assumes an extreme density, strongly resembling that of scirrhus. In such a case it is necessary to make sections of it, to be assured of the perfect soundness of the glandular tissue. This stony hardness generally occurs along with atrophy of the organ Ee E ii402 Sl'LANCHNOLOCfY. gland. Wlicn boiled, they both have the same aspect and the same taste. There is no fibrous capsule, properly so called, but some fibrous lamellae, which separate the lobes and lobules. Cellular tissue is tolerably abundant. Fat is not uncommonly met with, either on the surface or in tlie substance of the pancreas ; I have even seen cases of atro- phy of the gland, in which fat appeared to have been substituted for the glandular substance. The determination of the structure of the pancreas, like that of all glands, involves two considerations, viz., the texture of each lobule, and the arrangement of the vessels and nerves in the substance of the gland. With regard to the first point, I shall merely re- fer to what has been already stated respecting the salivary glands.* The arrangement of the vessels is perfectly well known. As in the salivary glands, the arteries enter the pancreas at a great number of points. They are very numerous and very large, considering the small size of the organ : they arise from the hepatic, the splenic, and the superior mesenteric. The principal arterj" is called the pancreatico-duodenalis. The veins terminate in the superior mesenteric and the splenic. The lymphatic vessels are not well known ; it is probable that they enter the numerous glands which are in the neighbourhood. The nerves of the pancreas are derived from the solar plexus. The excretory duct {u,fig. 169) is called the canal of Wirsung, from the name of its dis- coverer, a young anatomist, who was too soon lost to science. By an arrangement, of which we have no other example in the body, this excretory duct is contained entirely in the substance, we might even say, in the centre of the gland ; so that, in order to ex- pose it, the superficial portion of the organ must be carefully divided. It is generally single, but sometimes double, and then there is a principal duct belonging to the body of the pancreas, and a small duct for the reflected portion, or lesser pancreas. The pan- creatic duct measures the entire length of the gland ; it is narrow at the splenic extrem- ity, which may be regarded as its origin, and gradually increases in size as it approach- es the duodenal extremity ; there it bends downward, to reach the ductus choledochus, to the left of which it is placed ; it runs along the side of that duct, then perforates it ob- liquely, and opens, as I have already described when speaking of the liver, in the olive- shaped ampulla immediately preceding the duodenal orifice of the ductus choledochus. It follows, therefore, that the pancreatic duct and the ductus choledochus open by a com- mon orifice in the human subject. This arrangement is constant, and, when we find a pancreatic duct perforating the duodenum separately, we may be certain that there is another duct presenting the regular arrangement ; at least, I have never observed to the contrary. As to the precise situation of the separate opening of the supernumerary pan- creatic duct, it may be either in front of, behind, below, or above, the orifice of the duc- tus choledochus. Tiedemann, who has collected all the known cases of double pancre- atic duct, and all the varieties of insertion found in the human subject, has arrived at the curious result, that these varieties have their analogies in the different species of animals. The mode in which the divisions of the pancreatic duct are inserted into the principal trunk deserves to be noticed. The ultimate ducts of the pancreas do not, in fact, unite into larger and larger branches, like the veins, but the small branches coming from each lobule cpen directly, and in succession, into the general duct : an arrangement which gives to the excretory apparatus of the pancreas the appearance of those insects called centipedes. As to the structure of the pancreatic duct, its walls are very thin ; it is collapsed, and of a milk-white colour, very distinct from the grayish- white hue of the proper tissue of the gland. Its internal surface is extremely smooth, like a serous membrane ; t its thin- ness renders the determination of its texture very difficult ; it is very extensible. Development. — The development of the pancreas presents no peculiarities excepting such as relate to its size, which is relatively greater in the foetus and the new-born in- fant than in the adult. Examples have occurred of disease of the pancreas during intra- uterine life ; and I have found a scirrhous pancreas in a foetus at the full term. Function. — The pancreas is the secreting organ of a particular fluid called the pancre- atic fluid, the physical and chemical characters of which have not been well known until very lately. I have met with two cases of retention of the pancreatic fluid. The dila- ted canal resembled a transparent serous cyst ; the contained liquid was extremely vis- cid and transparent, but of a whitish hue, like a solution of gum-arabic ; it had a slight- ly saline taste ; the collateral ducts were extremely dilated. There were some white patches, resembling plaster, in the centre of many of the lobules. This substance was more abundant in some of the lobules, and, when removed, presented the appearance of small lumps of plaster or chalk. The pancreatic fluid submitted to chemical analysis by M. Barruel proved to be an extremely pure mucus. M. Barruel even stated to me that it was the purest mucus he had ever examined. It possesses in the highest degree the * [The only obsen'able difference between the lobules of the pancreas and salivary glands is, that the closed tenninatiou of the ducts are cylindrical in the former, and slightly dilated in the latter (see note, p. 341).] t lit is a mucous membrane, continuous with that of the duodenum, and covered with epithelium. In some subjects, Mr. Kiernan found mucous follicles in it, similar to those in tlie biliary ducts ; in others, no traces of them could be discovered. None were seen in the salivary ducts.] THE SPLEEN. 460 property of rendering water viscyi, either by dissolving, or by being diffused in it. This mucus contains free soda, a trace of chloride of sodium, and a very slight trace of phos- phate of lime. There is, therefore, an analogy belvi^een the pancreatic and salivary fluids, as the anatomical investigation of these glands had previously led us to suppose.* The Spleen. The spleen {aizTiriv, lien ; k,fig. 154) is a spongy and vascular organ, the functions of which, though little known, appear to be connected with those of the abdominal venous system. It is deeply situated {k,figs. 155, 161) in the left hypochondrium, behind and to the left of the great end of the stomach, to which it is united by a fold of peritoneum, called the gastro-splenic omentum. It is also retained in its place by the peritoneum, which is reflected upon it from the diaphragm,! and by the vessels which enter and pass out from it. Being suspended rather than fixed to certain movable parts, the spleen necessarily participates in their movements ; and the contraction or relaxation of the diaphragm, as well as the alternate distension and collapse of the stomach, exert an undoubted influ- ence upon it ; but these slight and temporary changes of position do not constitute a true displacement. It may even be said that displacements of the spleen, which are very rare, are almost always congenital. Thus, Haller has seen this organ situated at the left side of the bladder, in an infant one year old ; Desault has found it in the right cavity of the thorax in a foetus at the full time. I do not here allude to cases of complete transposition of the viscera, nor to cases where the change of situation depends on enlargement of the spleen, or on displacement of the stomach, t I have mentioned elsewhere that I have found the spleen in the umbilical region. Accidental adhesions of the spleen are so frequent that they deserve to be mentioned. They are sometimes filamentous, and sometimes cellular, and they render painful the slightest changes of position in this organ, from violent contractions of the diaphragm, or from great distension of the stomach : these adhesions are almost always the sequelae of intermittent fevers. Number. — ^The spleen is single in the human subject. The supernumerary spleens oc- casionally met with near it are nothing more than small ovoid or spheroidal fragments of the spleen, which at first sight might be taken for lymphatic glands. I have never seen more than two supernumerary spleens in man. It is said that they are more fre- quent in the fcetus than in the adult : this opinion is erroneous. § It has been said that ten, twelve, and even twenty-three supernumerary spleens have been observed. With- out denying the possibility of the fact, I am inclined to doubt its occurrence. As the spleen is always multiple in a great number of animals, supernumerary spleens in man may be regarded as the last trace of such an arrangement. With regard to the examples of congenital or accidental absence of the spleen men- tioned by some authors, it should be remarked, that they were accompanied with se- rious diseases of the abdomen, and that small adherent spleens, lost in some measure among the surrounding organs, may easily have escaped notice in a not very close ex- amination. Size and Weight. — There is no organ which varies more than the spleen in regard to size and weight. These differences may be referred to the following heads : Individual Differences. — It is in vain to attempt to establish a relation between the size of the spleen and that of the liver, or between the size of the spleen and the stature, weight, constitution, and habits of the individual.il Differences from Physiological Conditions. — The spleen is often found small, wrinkled, shrunk, or, as it were, withered and collapsed ; a state that certainly supposes the op- posite condition of distension. In other cases the spleen is large, and looks as if it were stretched. Ought we, then, to admit, with Lieutaud,1F that the pressure from the * [According to the best analyses, the pancreatic fluid differs from saliva in containinsr a greater amount of solid matter, and also in the character of its constituents : saliva is usually alkaline, and, besides other sub- stances, contains salivine, mucus, and sidpho-cyanate of potassa ; the pancreatic fluid contains albumen, ca- sein, but little salivine and mucus, and no sulpho-cyanate ; in other respects the two fluids agree.] t [This reflection is called the ligamentum phrenico-lienale. The spleen is also connected by the peritic Ileum to the arch of the colon.] i The great end of the stomach is the most fixed part of that viscus, on account of its connexion with the CBSophagus. Changes of position in this organ affect partly the portion between the pylorus and the cardia, and partly the pylorus itself. () It is true that a greater number of cases of supernumerary spleens in the fcetus have been recorded than in adults; but the fact is easily explained, if we consider that in the fcetus supernumerary spleens cannot escape notice, while they are often diflicult to be seen in the adult, on account of the fat with whicli the omenta are loaded. II The spleen is proportionally larger in man than in the lower animals. It has been said, as if it were pos- sible to establish a relation between two such variable terms as the weight of the spleen and the body, that the former is i^^ th of the latter. % Lieutaudasserts that he has constantly found the spleen larger when death has occurred while digestion was going on in the stomach than when it has happened after that process had been completed ; but the spleen varies so much in size that we cannot compare the spleen of one subject with that of another. An in- genious experiment has been made, the re.sult of which is opposed to Lieutaud's opinion : out of four newly- 404 SPLANCHNOLOGY. distended state of the stomach during digestion diminishes the size of the spleen, which, on the other hand, becomes the seat of an afflux of blood in the intervals between the occurrence of that process. This idea is, perhaps, erroneous as far as regards the pe- riods of collapse and turgescence ; but it is correct as to the principal fact, viz., the al- ternation of those two opposite conditions. Differences from Age. — The spleen is proportionally smaller in the foetus than in the adult, and in the adult than in the aged. Differetices from Disease. — The morbid differences in the size of the spleen suggest most important considerations. In a great number of patients suffering with intermit tent fevers, more especially when this organ is already enlarged from previous attacks, it is manifestly swollen during each access. Hypertrophy of the spleen may proceed to an extraordinary extent ; so that this organ, which, in the natural condition, is with- drawn so deeply into the left hypochondrium as not to be seen on opening the abdomen, in certain cases fills almost the whole of the abdominal cavity ; while its weight, which varies from two to eight ounces in the healthy condition, may be as much as ten, twen- ty, or thirty pounds ; one case, indeed, has been recorded where the spleen weighed forty-three pounds. Atrophy of the spleen is very rare. I have seen it reduced to the weight of two drachms. The specific gravity of the spleen is, to that of water, as 1160 to 1000. The spleen, both upon the surface and in the interior, most commonly resembles in colour the dark lees of wine. This colour, however, presents many varieties from a deep-brown red to a pale gray. When the surface has been some time exposed to the air, it becomes bright red, like the surface of venous blood soon after its abstraction. Age, the kind of death, and diseases, have much effect on the colour of this organ, the different parts of which are not always of a uniform tint. I have seen a spleen of a deep chestnut-brown hue. Consistence. — One character of the tissue of the spleen is its extreme friability. In general it may be lacerated by the pressure of the finger, to which it communicates a feeling of crepitation, and emits a sound like the crackling produced by bending tin. The spleen may be regarded as the most friable of all organs excepting the brain. Thus, examples have been recorded of its laceration from blows, or falls upon the abdomen, and even from a general concussion, or from the contraction of the diaphragm and ab- dominal muscles during violent exertion, &c. The consistence of the spleen also varies much in different individuals, and in dis- eases ; indeed, the most important alterations of this organ may be referred to either increased or diminished consistence. In induration, which is generally accompanied with hypertrophy, the tissue of the spleen is compact, brittle, and dry, and breaks like a piece of compact resin. In softening, carried to its highest degree, the spleen is con- verted into an inorganic pulp, exactly resembling a healthy spleen broken down by the fingers, and containing a greater quantity of fluid than natural. This state is often ob- served after malignant fevers,* and when the membranes are torn, the substance of the spleen escapes spontaneously. Figure. — The spleen has a crescentic form ; its long diameter is vertical, its concavity directed to the right, and its convexity to the left side. It may be compared, as was done by Haller, to a segment of an ellipse cut longitudinally. It presents for consideration an external and an internal surface, and a circumference. The external or costal surface is convex, smooth, and in relation with the diaphragm, which separates it from the ninth, tenth, and eleventh ribs ;t hence arises the influence of contractions of the diaphragm upon the spleen, and the possibility of its being rup- tured during a violent effort. This relation also accounts for tlie pain felt in the region of the spleen after quick running, and the difficulty and pain attendant on a strong inspi- ration made while running by persons in whom the spleen is hypertrophied. We frequently find a prolongation of the liver almost completely covering the external surface of the spleen. The internal or gastric surface is concave in all directions, and presents, at the junc- tion of the two anterior thirds with the posterior, a somewhat irregular series of open- ings, which are themselves irregular in form and number, are situated at greater or less intervals, and arranged longitudinally. This row of openings is called XYve fissure, or hi- lus {h,fig. 154) of the spleen. The gastro-splenic omentum is attached near this fissure. Some varieties are observed in the arrangement of the internal surface of the spleen. Thus, it sometimes presents a uniform concavity, and sometimes there is a sort of projecting ridge opposite the hilus, which divides it into two unequal parts, one anterior bom puppies, belonging to the same litter, two were kept witbout food, while to the other two milk was given ; on killing them, their spleens were all found of the same size. * Vide Anat. Path, avec Planches, liv. ii., art. Maladies de la Rate. I have been able to collect tho splenic fluid in a medicine vial, and to submit it to different experiments. t It is said that the ribs produce marks upon the spleen from the pressure exercised by them upon it during life. 1 have never observed this appearance, and can only conceive it to exist in cases of hypertrophy of the spleen. THE SPLEEN. 405 and larger, the other posterior and smaller : in the latter case, which is common, the spleen is of a prismatic and triangular form. The following are the relations of the internal surface : the part situated in front of the hilus has relations with the great cul-de-sac of the stomach, and, on the right and behind this cul-de-sac, with the gastro-splenic omentum and the vasa brevia situated within it : the left extremity of the liver, which, as we have seen occasionally, covers the external surface of the spleen, is more frequently in relation with the internal sur- face of that organ. Behind the hilus the spleen corresponds with the left kidney, supra renal capsule, and pillar of the diaphragm, which separate it from the spine, and with the small extremity of the pancreas. The circumferenc is elliptical ; its posterior border is thicker above than below, and is in relation with the kidney, which it sometimes covers through its entire length ; its an- terior border is thinner, and is applied to the stomach ; its upper extremity is thick, often bent upon itself, and in contact with the diaphragm, from which, however, it is occasion- ally separated by the liver ; its inferior extremity is pointed, and rests upon the angle formed by the transverse and descending colon, or upon the portion of transverse meso- colon which supports that angle. The circumference of the spleen is notched, and sometimes marked more or less deeply by fissures, which are prolonged upon both its surfaces, particularly upon the external surface, and which divide it into a greater or less number of distinct lobules. This lobular arrangement is the last indication of the mul- tiple spleens, of which we have already spoken. The description of the relations just given applies when the stomach is empty ; when that viscus is distended, they are some- what different. The spleen, which before was separated from the stomach by the gas- tro-splenic omentum, is then applied directly to it, and is moulded upon it, so, as it were, to cover its walls. It has no longer any relations with the kidney and the vertebral column, but is situated below and behind the great cul-de-sac of the stomach, and not to the left of it ; and it becomes horizontal instead of being vertical, as when the stomach is empty. Structure. — Besides two investing membranes, one serous, the other fibrous,* the spleen consists of cells having fibrous parietes, and filled with a grumous fluid,t of the colour of port wine dregs, of certain corpuscules not very distinct in the hirnian subject, of a very large artery and still larger vein, and of lymphatic vessels and nerves. The serous or peritoneal coat invests the whole spleen, with the exception of the hilus, which corresponds to the gastro-splenic omentum. It gives a smooth appearance to the spleen, lubricates its surface, and, at the same time, fixes it to the neighbouring parts by the bands which it forms. Its internal surface adheres closely to the fibrous membrane. The proper coat of the spleen forms a sort of fibrous shell, which is strong, notwith- standing its tenuity and transparency. This membrane is the seat of those cartilaginous plates which are so often found upon its surface, and which conceal its true colour. It is intimately united to the peritoneal membrane by its outer surface, and adheres still more closely by its inner surface to the tissue of the spleen by means of exceedingly nu- merous and dense fibrous prolongations, which penetrate it in all directions, and inter- lace in every way, so as to form areolae or cells, the arrangement of which \fre shall here- after examine. Farther, the proper coat is not perforated at the hilus for the passage of the vessels, but by an arrangement similar to that already noticed in the liver, it is re- flected around the vessels opposite the hilus, like the capsule of Glisson, and is prolong- ed upon both the arteries and veins, forming sheaths which divide and subdivide like the vessels themselves, and receive the prolongations given off" from the inner surface of the proper coat. This arrangement has been very well described by Delasonne {Mim. Acad, des Scien- ces, 1754), and especially by Dupuytren (Thise de M. Assolant). It follows, therefore, that the basis of the spleen is composed of a fibrous structure, consisting of an investing fibrous membrane, of fibrous sheaths which accompany the vessels in their divisions and subdivisions, even to their terminations, and of prolongations arising from the inner sur- face of the membrane, interlacing in all directions, and attached to the outer surface of the sheaths.J The internal framework of the spleen is therefore an areolar tissue, which may be very well displayed by washing away the pulpy matter of this viscus by means of a stream of water ; there will then remain a whitish areolar and spongy tissue. This is also very clearly shown by injecting it either with mercury or some coloured liquid, or even by in- flating it with air blown through a puncture. The coats are then raised in different pla- ces, and after desiccation, the areolar structure becomes evident. This experiment also shows that the spleen is divided into a number of compartments, for, without rupture, only a small portion of the organ can be injected in this way. It appears, then, that the proper tissue of the spleen is composed of an areolar fibrous * See note, infra. t See Bote, p. 406. t [This basis or framework is more or less developed in the different species of animals : it is much stronger in the horse than in the ox. The proper coat of the spleen, together with the sheaths for the vessels, and the prolongations or trabcculae given off from it, are highly elastic, and are generally »tated to consist of yellow elastic tissue, not of ordinary fibrous tissue.] ^6 SPLAI^dHNOLOGY. network, and of a pultaeeous matter, gf the colour of port wine lees — ^the splenic juice or matter, regarded by the anciepts as one of the fundamental humours of the body, called atra bills, and which modern Aemists have not yet sufficiently examined. We have now to determine the arrangement of the cells, and the relation between these cells and the arteries, veins, and nerves. The Splenic Artery. — No organ of so small a size receives so large an artery. The splenic artery is, in fact, the largest branch of the cceliac axis, and, on this account, rup- tures or wounds of the spleen are almost always followed by fatal hemorrhage. It is also remarkable for its tortuous course ; when reduced to half its original size, from hav- ing given off several branches, it enters the spleen by four or five branches at greater or less distances from each other. These branches divide in the usual manner in the sub- stance of the organ, and preserve their tortuous character even to their terminations. One peculiarity well worthy of attention is, that the arteries constantly divide in a ra- diating manner, so that air, or water, or tallow, thrown into one arterial division, does not pass into the branches of the others. This mode of division is observed not only in the larger, but also in the smaller arteries,* so that the spleen may be considered as an aggregate of a considerable number of small spleens, united together by a common in- vestment ; and accordingly, if in a living animal one division of the splenic artery be tied, the portion of the spleen to which it is distributed becomes blighted, while the rest re- mains in the natural state. This arrangement of the arteries may be shown in a very striking manner by injecting their several divisions with differently-coloured substances. The injected matters will not mix, and the line of demarcation between the lobes will become evident. This structure explains how multiple spleens may occur in man and the lower animals, and why there are so many varieties in this respect in the animal series. Some branches from the splenic, lumbar, and spermatic arteries enter the spleen through the folds of the peritoneum. The splenic vein is four or five times larger than the artery : it forms one of the prin- cipal roots of the vena portae, and is almost equal to the other root formed by the supe- rior mesenteric vein. The venous communication between the spleen and the liver has, in a great measure, given rise to the opinion that they are connected in function. The spleen is filled by the numberless and large divisions of this vein ; it might even be said that the texture of the spleen is essentially venous, that it is composed of a venous plexus or an erectile tissue, and that it bears the same relation to the veins that the lymphatic glands do to the lymphatic vessels. All the splenic cells communicate with the veins, or, rather, they are nothing more than these veins themselves, supported by the fibrous columns and sheaths already described : this is shown by the following consider- ations and experiments : 1. If, according to the example of Delasonne,t we examine the spleen of the ox by lay- ing open the splenic veins and their divisions by means of a grooved director, we shall find that these veins are almost immediately reduced to their lining membrane, and per- forated with very distinctly formed foramina, through which the dark reddish-brown sple- nic matter is visible. These foramina soon become so numerous, that the veins are con- verted into cavities or cells, the walls of which are perforated with openings of various sizes, filled with the splenic pulp. This arrangement, which is most manifest under water, proves that the tissue of the spleen is composed of venous cells,t like the corpo- ra cavernosa of the penis. In man, the horse, and the dog, the great veins are not per- forated with foramina, but the cellular and areolar arrangement of the splenic v^ins, at a certain depth, is not less manifest. 2. If we inject the splenic artery, the spleen will become very slightly increased in bulk at first, i. c, as long as the injected matter does not pass into the venous system ; but as soon as this occurs, and it does so readily, the increase in size becomes rapid : it follows, therefore, that the communication between the artery and the splenic cells is indirect."^ On the other hand, if we inject the vein, the cells are immediately dilated, and the spleen becomes prodigiously increased in bulk : it is easy to perceive that the communication is direct, and that the venous system, in some measure, forms the basis of this organ. We can very seldom meet with a human spleen sufl5ciently healthy for the following experiment. It will succeed perfectly with the spleen of a horse, which is of a much denser structure. The spleen ought, in the first place, to be freed from the liquid which it contains ; this must be accomplished by forcing water into the splenic artery. The * [The minute arteries ramify in tufts orpenicilli.] t Delasonne has described the structure of the spleen in the ox as belonging to the human subject. t [According to Mr. Kiernan, these venous cells are lateral dilatations, which communicate with the venous trunk by small branches. They contain only blood, however, for the red pulpy matter of the spleen is said by Miiller to be external to, and not within them. This red substance consists principally of red granules, about the size of the blood-globules, but spherical, not flattened.] ■ t) It has been erroneously asserted that the communication between the artery and vein is more direct in the .spleen than in any other organ. The great anastamoses, visible to the naked eye, between the splenic artery and vein, admitted by Spigelius, Diemerbroeck, Bartholin, and others, are purely imaginary. The pre- cise mode of communication is still unknown. THE SPLEEN. 407 water will return by the veins, at first turbid, then merely tinged, and at last limpid and pure.* I have in vain attempted to force the injection from the veins into the arteries. After the water, air should be blown into the artery, so as to empty the spleen as much as possible of any liquid which it may contain. If we examine a spleen thus freed of its contained matter, we observe that it is wrin- kled, and, as it were, shrivelled on the surface, and remarkably diminished in bulk ; and, on making a section of it, we find a white, spongy tissue, composed of laminae or fibres, interlacing in every direction. The following preparationt exhibits this structure most fully : The spleen of a horse, prepared in the way I have indicated above, and weighing one pound, could receive ten pounds of tallow. Tlie injection was thrown in by the veins : at each stroke of the pis- ton, the spleen swelled up readily, an evident proof that the splenic cells communicate directly with the veins ; while, in order to obtain the same effect by injecting through the arteries, very considerable force was required. The injection of the spleen by the veins did not take place in a uniform manner, but successively ; in one injection, the upper part was injected before the lower, and the anterior border before the posterior. The independence of different portions of the spleen on each other exists in regard to their veins as well as their arteries. I have been enabled to observe the resistance of- fered by the tissue of the spleen to the distending power ; a resistance which caused the injection to flow back whenever the impelhng force was discontinued. The cells are extensible to a certain degree, beyond which they resist very powerfully ; it does not appear that they possess any elasticity.J After some days, when desiccation was complete, the spleen thus injected was divided into several portions, which were then immersed in spirits of turpentine moderately heat- ed. The tallow, by which all the cells were distended, and which had taken the place of their contents, having been dissolved out, the sections presented a spongy, areolar structure, like that of erectile tissue, as found in the corpora cavernosa, or the substance of the placenta : and this cannot be considered, as Meckel would have it, as the artificial result of the insufflation and injection, which lacerate, as he believes, a part of the ves- sels and fibrous tissue. — (Manuel d' Anatomic, t. iii., p. 479.) This spongy cellular struc- ture explains why the spleen, as well as the corpora cavernosa, is susceptible of such great variations in bulk ; and why it is sometimes found collapsed and wrinkled, and sometimes distended, and, as it were, swollen. Are the splenic cells lined by the inter- nal membrane of the veins T if so, the membrane is so thin as to be incapable of dem- onstration. Corpuscles of the Spleen. — Malpighi described, as existing in the spleen, certain cor- puscles, regarded by him as the principal elements in this organ, and believed by him to effect some important changes in the splenic bloodt These corpuscles, which Ruysch considered to be essentially vascular, have been again brought into notice by Dela- sonne, who demonstrated them by maceration. Haller denied their glandular nature, because, as he said, there can be no glands where there is no secretion and no ex- cretory ducts. The question is not, however, whether these corpuscles are glands or not, but rather whether they exist at all. It is certain that, in many animals, in the dog and the cat, for example, a great number of granules may be seen scattered through the spleen, and which, according to a calculation, the accuracy of which I do not guarantee, would seem to form two fifths of the weight of the organ. These corpuscles are soft, whitish or reddish, and vary in diameter from a fourth of a line to a line. They do not appear to me to exist in man.^ The lymphatic vessels of t^e spleen are divided into the superficial and deep. The su- perficial only are well known ; a certain number pass from the spleen to the stomach ; they all terminate in lymphatic glands situated opposite the hilus, within the layers of the gastro-splenic omentum. * This injection, which requires considerable force, continued without interruption for a long time, occa- sions an exudation of a perfectly transparent fluid upon the surface of the spleen, even when water returned by the vein is stiU turbid. Here we have an imitation of an exhalant process. And, as this transudation takes place without Tupture, it is evident that there are a set of vessels by which it is effected.* Instead of making an injection, which is always troublesome, we may attach the splenic artery to a tube, which is itself adapted to another tube, running from the bottom of a cistern ; the column of water will overcome the resistance offered to its passage from the arteries into the veins, and in twenty-four hours it will pass through perfectly limpid. t This mode of preparation was suggested to me by the plan adopted with the corpora cavernosa by Bogros, prosector to the Faculty, who died a victim to his zeal for science. t [The lining membrane of these venous cells is not veiy eitensible, but the trabecuUe, between which they lie, are highly extensible and elastic also.] ^ [The corpuscles here described are not those discovered by Malpighi, but large, soft, grayish bodies, rare- ly found in the human spleen, and the nature of which is not understood. The Malpighian corpuscles are much smaller ; they are very evident in the ox, sheep, and pig ; they lie in the red pulpy matter externally to the venous cells, and are attached by short pedicles, or without pedicles, to the minute arteries, which, however, have not otherwise any special relation to them ; they contain grayish granules, similar in size and form to those of the red pulpy matter. In the human spleen they are very difficult to distinguish. The extremities of the divided trabeculse may be mistaken for white corpuscles.] *■ [This transudation evidently depends on the porosity or permeability of animal tissues, and not on the ex- istence of any special vessels.] 408 SPLANCHNOLOGY. Nerves. — The nerves are derived from the solar plexus, and are termed the splenic plexus. It has been stated that some terminal divisions of the pneumogastric have been seen distributed upon the spleen. Several of the nerves are remarkable for their size, which enables us to examine in them the peculiar structure of the ganglionic nerves, and also to trace the splenic nerves themselves deeply into the substance of the organ.* We are completely ignorant of their mode of termination. As to the proper ducts of the spleen, said to pass directly from that organ to the great cul-de-sac of the stomach, or even to the duodenum, and to pour into these parts a pecu- liar liquid, it may be confidently stated that they are purely imaginary. And again, the three kinds of vascular conununication between the spleen and the stomach cannot in any way explain the afflux of liquids from the spleen to the stomach ; in fact, the arte- rial vasa brevia of the stomach are given off from the splenic artery before it reaches the spleen ; nor do the venous vasa brevia enter the splenic vein until after it has left the hilus of the spleen ; the lymphatic vessels alone pass directly from the spleen to the stomach, but they are superficial, and have no connexion with the splenic cells. There is no cellular tissue, properly so called, in the spleen, which, nevertheless, is liable to inflammation. Development. — In opposition to the liver, the spleen is smaller in proportion as it is ex- amined nearer the period of conception. It appears late ; it begins to be distinguisha- ble towards the end of the second month, and it then resembles a clot of blood. I hav^e never seen it developed from separate lobules, which were afterward to be united by a common investment. At birth, its proportions are almost the same as at subsequent pe- riods. The spleen is hard, and, as it were, tense, in most infants who die during birth : this is probably owing to impeded circulation. The changes which the spleen undergoes during growth, both in density and in size, are partly physiological, which are not very remarkable, and partly pathological ; these are very considerable, but they are foreign to my subject. In the aged, the spleen decreases, like all other organs ; and atrophy of this organ, which may proceed so far that it only weighs a few drachms, is often accompanied by the development of a cartilaginous shell. Functions. — The functions of the spleen appear to me to be referrible to its structure and its vascular connexions. The quantity of blood which passes through it, its entire- ly vascular structure, and the physical qualities of the splenic pulp prove, on the one hand, that the blood sent to the spleen serves other purposes besides that of nutrition ; and, on the other, that it undergoes some important changes, of which we are complete- ly ignorant, because the means of analysis are wanting ; but, whatever they may be, they have undoubtedly some connexion with the functions of the liver, t for in all animals possessing a spleen, even though its arterial blood does not come to it from the same trunk as the hepatic artery, the veins of the spleen terminate in the venous system of the liver. It is, therefore, extremely probable that the spleen performs an important office in the abdominal venous system ; but what this office is we do not know ; and what tends to confound all our calculations is, that extirpation of this organ in animals does not seem to have any marked effect upon their health, that the most complete atro- phy of the spleen is consistent with the most regular performance of all the functions, and that hypertrophy, even to such a degree that the organ occupies almost the whole of the abdomen, merely produces a discoloration of the skin, diminished nutrition, and, in young subjects, an arrest of growth. The spongy and vascular texture of the spleen, and the absence of valves, which al- lows the venous blood to regurgitate into the spleen when there is any obstacle to the circulation, has led to the opinion that the spleen is nothing more than a diverticulum intended to restore the equilibrium of the abdominal venous system whenever it is de- ranged ; and this opinion, which we owe to Haller, is pretty generally admitted.^ A modification of this opinion is, that the spleen fulfils, with regard to the circulation in general, and especially to the abdominal circulation, the office of the safety-tube of Wolf in chemical apparatus. It is certain that compression of the splenic vein in a living an- imal causes tumefaction of the spleen, which gives place to a quick collapse, as if by elastic contraction, when the pressure on the vein is removed : it is certain that the whole structure of the spleen indicates that this organ may undergo alterations of ex- pansion and turgescence, and of collapse and flaccidity ; and it is known that, during in- termittent fever, the spleen may be felt below the false ribs, &c. But all this leads to presumptions, and not to certainty. From the preceding considerations, it would follow that the spleen is only an accesso- ry organ. * The sensibility of the spleen is very important. In a living animal it may be cat or torn without an> apparent signs of pain. Dogs have been seen devouring their own spleens, which had been drawn out of the abdomen'. What a diiference, in this respect, between the spleen and the intestine! and yet they derive their nerves from the same source. t We cannot state, with Malpighi, that the spleen is the preparatory organ of the bile, because we have seen that it is extremely probable that the liver is concerned in the process of sanguification. t May we not quote, in support of tliis view, the pain felt in the region of the spleen after violent running, which can only be referred to extreme di&teusiou of this organ ' THE LUNGS. 40& THE ORGANS OF RESPIRATION. General Observations. — The Lungs and Pleura. — The Trachea and Bronchi. — Development of the Lungs. — The Larynx — its Structure, Development, and Functions. — The Thyroid Gland. After describing the digestive apparatus, the object of which is to elaborate soHd and liquid materials for the reparation of the waste that occurs in the body, and, at the same time, to present a vast surface for the absorption of those materials, we naturally turn to the consideration of the apparatus of respiration, the object of which is to renew the Tital properties of the blood by the action of atmospheric air in the lungs. This latter apparatus, whicli is much less complex than the former, is composed, 1. Of the lungs, the essential organs of respiration ; 2. Of the thorax, a cavity forming a sort of bellows, and having walls capable of alternately expanding and contracting ; 3. Of a tubular apparatus, by which the lungs communicate with the external air, and which consists of the bronchi, trachea, larynx, pharynx, and nasal fossce; for it is only accidental- ly, so to speak, and in order to render respiration more certain, that air is allowed to pass through the mouth. The thorax has been already described (see Osteologt and Myology), and also the pharynx, which is common to both the respiratory and digestive passages. The nasal fossae, situated at the entrance of the respiratory passages, form the natu- ral passages for the introduction of the air, and, at the same time, serve for the reception of the organ of smell, by which sense we may consider the qualities of the air are exam- ined. Their bony framework has been already described under osteology. The pitui- tary membrane which covers the irregular surfaces of these fossae will be described in the article devoted to the organs of the senses ; we shall only consider, in this place, the lungs, the trachea, and the larynx. The Lungs. The lungs (pulmoncs ; mevfiuv, from Trviu, to breathe, p p,figs. 155, 170, 171) are the essential organs of respiration. While the presence of an alimentary canal is the attri- bute of all animals, that of lungs is limited to those vertebrata which live in the air, dif- ferent modes of respiration prevailing in the other classes. Number. — The lungs are two in number ; but, as the air which penetrates them is re- ceived from one tube, and the blood circulating through them is derived from one vascu- lar trunk, they must be regarded as separated parts of a single organ ; by this arrange- ment, respiration is rendered certain, and its unity maintained. Situation. — The lungs are situated {p p, fig. 155) in the thoracic cavity, which is, in a great measure, occupied by them, and effectually protects them from the action of exter- nal agents ; they are placed on each side of the heart {h,figs. 155, 170, 171), with which, physiologically, they are so directly connected ; they are separated from each other by the mediastinum (m) ; hence the independence of the two cavities in which they are contained. Being separated by the diaphragm from the stomach, the liver, and all the other abdominal organs, they are so enclosed in all directions as not to be liable to dis- placements, or, rather, such displacements are only partial, and due to a loss of substance in the walls of the cavity in which they are placed. Size. — The size of the lungs necessarily corresponds exactly with the capacity of the thorax, and therefore, like it, is subject to variations ; and as, on the one hand, the size of the lung is generally a measure of the energy of respiration, and, on the other, the en ergy of respiration is a measure of the muscular strength, one cannot be astonished that a capacious chest, coinciding with broad shoulders, should be the characteristic of a san- guine temperament and athletic constitution. In the natural state there is neither air nor watery fluid between the parietes of the thorsix and the surface of the lung. The absence of air or other fluid may be shown af ter death as well as upon a Uving animal, by raising the inter-costal muscle from the costal pleura, so as to preserve the latter,* or by removing the muscular fibres of the dia- phragm. It is then seen that the lung is always in contact with the parietes of the chest ; in some subjects it even appears as if ready to escape ; but scarcely is the thorax opened when the lungs instantaneously collapse, in consequence of the expulsion of the air from their interior. It is very common to find a small quantity of serum in the cavity of the pleura, but it is probable that this fluid did not exist during life. There is no space to be filled up here as in the cranium. The differences in the size of the lungs depend, 1. On the state of inspiration or expi- ration. Attempts have been made to determine the difference from this cause by esti- mating the volume of air inspired or expired ; it is about thirty cubic inches, and may be increased to forty in forced inspiration or expiration. 2. On age ; thus, in the foetus, the lungs are relatively much smaller than after birth. 3. On some morbid condition. The * In order to demonstrate the absence of air, we may also repeat another experiment performed by Haller, ■which consists in opening the thorax of a dead body under water. F F F 410 SPLANCHNOLOGY. lungs diminish in size when the abdominal viscera encroach upon the thorax, either m ascites, in pregnancy, or in diseases of the liver, vv'hich organ has been found in some cases to become enlarged entirely by encroaching on the chest, and to extend as high up as the second rib. They diminish, also, when the heart is enlarged in aneurism, or when a large quantity of fluid is accumulated in the pericardium. In effusions into the thorax, the fluid takes the place of the lung ; the latter gradually wastes, and is reduced to such a thin lamina, or to so small a mass, that it has sometimes been overlooked in a superficial examination ; but if, in such cases, air be blown into the trachea, the organ appears of its full size, and gradually fills the remainder of the cavity. This extreme diminution of the lung, without any alteration of its substance, proves that the size of the organ is essentially dependant upon the air within it. Attempts have been made to cal- culate exactly the quantity of air contained in the cavity of the lungs, or, in other words, the capacity of these organs : according to one estimate, which can only be regarded as an approximation to the truth, it would seem to be about 1 10 cubic inches after expira- tion, and 140 inches after an ordinary inspiration. When an effusion in the thorax has been very slowly absorbed, the lung of the affect- ed side remains atrophied, and the thoracic cavity contracted, while the other lung ac- quires a very considerable size, so that the mediastinum is pushed to one side, and the healthy lung passes beyond the median line.* In certain cases of acute pneumonia, and in rickets affecting the thorax, we often see one of the lungs reduced to very small di- mensions, whUe the other is very much enlarged.! The size of the two lungs is not absolutely the same. In consequence of the heart projecting into the left cavity of the thorax, the transverse diameter of the left lung is not equal to that of the right ; and on account of the projection of the liver into the right cavity, the vertical diameter of the right lung is less than that of the left. After edlow- ing for these facts, the difference is in favour of the right lung. In determining the size of the lungs, we must bear in mind, that the lung eis well as the thoracic cavity gains in one direction what it loses in another : elongated lungs, which are regarded as particu- larly liable to phthisis, have not seemed to me to be smaller than the lungs of a person of similar stature, but having a broad chest. The weight of the lungs must be examined with reference to their specific gravity and to their absolute weight. The specific gravity of the lungs is less than that of any other organ, and even much less than that of water. Their lightness depends on the great quantity of air which penetrates them in every direction, so that the lungs rise to the surface of the fluid in which they are immersed. The specific gravity of the lungs pre- sents some important differences depending on age. Thus, before birth, and in an in- fant that has died during birth, without having respired, the lungs sink in water ; on the contrary, they swim when the infant has breathed ; not because any change has taken place in the intrinsic nature of the organ, but because the air has insinuated itself into the cells. The estimation of the specific weight of the lungs constitutes what is called in legal medicine the hydrostatic test. In the adult, the lung always floats, notwithstand- ing any efforts which may be made to expel the air contained in the pulmonary cells ; it seems as if the air enters in some way into the composition of the lung, and even in vacuo it cannot be completely extracted. The specific gravity of the lungs varies also from disease. Thus, lungs infiltrated with serum, or indurated by inflammation, being completely or partially deprived of air, on the presence of which their lightness depends, assume, in a greater or less degree, the appearance of compact organs, such as the liver or the spleen. The absolute weight of the lung varies from similar causes. From age : thus, although the specific gravity of the foetal lung is much greater than that of the adult, yet its abso- lute weight is considerably less. In infants that have not breathed, the weight of the body is to that of the lungs as 60 to 1, on an average, while in those that have breathed the proportion is as 30 to 1, so that the changes in the lungs resulting from respiration are such as to double their weight. We may easily conceive the great importance of this fact in legal medicine. This method of estimating the weight of the lungs is known by the name of the static test. The absolute weight of the lungs varies much in disease. Healthy lungs are very light ; diseased lungs may become eight or ten times heavier than natural, without in- creasing in size. The lungs ahnost always becoming engorged at their posterior bor- der during the last moments of life, their weight must not be estimated from an ordinary corpse. It must undoubtedly have been from the examination of engorged lungs that authors have stated their average weight to be four pounds. Colour. — The colour of the lungs varies according to age and disease. In the fcetus they are reddish-brown ; after birth, rosy-white ; in the adult and in the aged they are * In a case of chronic induration of the left lung, the deviation of the mediastinum was so great, that the nght lung was in relation with the left costal cartilages. t The lungs become less increased in size from inflammation than most other organs ; and this peculiarity is explained by the vesicular structure of the lung, the increase in size being effected at the exp«ase of the cavity of the air-vesicles. ♦ffiE LUNGS. 411 gra>\sh-blue, and almost always marked by black spots, forming points, lines, or patches, and describing polygons more or less regular in figure. These black patches, which be- come much more numerous in advanced age, coexist with the black deposites in the bronchial glands, and probably depend upon the same cause ; they lie below the serous covering of the lungs, and are very superficial, excepting in disease. The posterior part of the lung is usually of a reddish-brown colour, because it is distended with blood and serum. It has not been shown that this is altogether a post mortem condition, and the necessary consequence of the position of the corpse upon its back ; many facts woidd, on the contrary, induce us to admit that it occurs antecedently to death. Density, Crepitation, and Cohesion. — The lung, a spongy or aerial organ, so to speak, is the least dense of all the organs in the body ; it yields to the pressure of the hand, and, if no cause prevents the escape of the air, it loses very much of its original size. I have remarked, when speaking of the spleen, that, under pressure, that organ emitted a peculiar noise, or, rather, gave rise to a sensation which might be compared to the crackling of tin, and that this sound was the result of rupture of the fibrous prolongations which traverse its tissue. Pressure of the lung causes a sensation and a sound some- what analogous to the preceding ; this sound is called crepitation. It may, in fact, be compared to the sound produced by the decrepitation of salt or the rattling of paper. This crepitation is only observed under a moderate pressure, and if the sensation com- municated be strictly noted, we shall find that it is the feeling of a resistance overcome. On careful examination of the portion of the lung which has thus crepitated, bubbles of air are found under the pleura ; in fact, emphysema is produced. Notwithstanding its slight density, the tissue of the lungs possesses tolerable strength ; it resists laceration to a certain point ; and all its parts are pretty firmly bound together. Resistance to Distension. — The lung, though it yields to the finger without recovering itself at all, or only very imperfectly, is yet possessed of great elasticity, but such an elasticity as is in harmony with its functions. It also offers powerful resistance to any distending force. Thus, if a stopcock be adapted to the trachea of a dead body, and the lungs be inflated by means of bellows having double valves, the pulmonary tissue becomes extremely tense and hard ; the effort necessary to rupture some of the air-cells, and pro- duce emphysema, is surprising. In opposition to those authors who speak of the dan- gers of artificial insufflation of the lungs of asphyxiated persons, I have in vain endeav- oured, with aU the force I could employ in expiration, to produce a laceration of some of the pulmonary cells : and how, it may be asked, without great means of opposing every attempt to dilate them beyond measure, could the lungs resist the force to which they are subjected during violent exertions 1 Elasticity. — The lungs are very elastic, i. e., they have a constant tendency to tol- lapse, and to free themselves of part of the air contained in their cells. It is this elasti- city which maintains the vaulted form of the diaphragm after the abdomen has been opened, and occasions the lung to collapse suddenly, when an opening is made in the parietes of the thorax : before the chest is opened, the atmospheric pressure, opera- ting through the trachea, prevents the elasticity of the lungs from being brought into ac- tion. * This elasticity is also shown by the quick collapse of inflated lungs. I have been accustomed to demonstrate, in my lectures, perfectly healthy lungs, preserved in alco- hol. After having shown how far the inflation of the lungs may be carried, I open the stopcock used in the experiment, and the lungs instantly collapse, driving out the air with considerable force. Shape and Relations. — The lungs are shaped like an irregular cone, deeply excavated on the inner side, with the base below and the apex above ; they present for consideration an external and an internal surface, an anterior and a posterior border, a base, and an apex. Outer or Costal Surface. — This surface is irregularly convex, corresponding to the con- cavity of the thoracic parietes, with which it is in contact, and on which it is exactly moulded ; it is in relation with the costal pleura, which separates it from the ribs and the intercostal muscles. It presents a deep fissure, the inter-lobular fissure, which pen- etrates the entire thickness of the lung as far as the root. This fissure conunences be- low the apex of the lung {v',Jig. 171), passes downward and forward {v',fig. 170) as fair as the anterior part of the base, upon which it encroaches a little at its termination. It is simple in the left lung («'), but is bifurcated in front in the right ; the lower division of this bifurcation continues in the original direction ; the upper division (ic) passes up- ward and forward. The left lung, therefore, is divided into two portions or lobes, dis- tinguished as the superior («') and the inferior {u') ; while the right is divided into three lohes, the superior (s), the inferior (m), and the middle {t). Of these lobes, the inferior, comprising the base of the lung, is larger than the superior, which forms the apex ; the middle lobe is the smallest. Tlie contiguous surfaces of these lobes are plane, and cov- ered by the pleura : they are often Eidherent, and sometimes purulent matter collects be- * [The longs Jo not collapse nntil the chest is opened, because the atmospheric pressure is exerted only on the inner surface of the lungs, their outer surface being- protected from it by the unyielding parietes of the thorax. When this protection is removed, the pressure on both surfaces is equal, and the elasticity of the pulmonary tissue is tlien enabled to act.] 412 SPLANCHNOLOGY. Fig. 170. tween them, and, being sm- rounded on all sides by adhe- sions, it hollows out, as it were, a cavity for itself, at the expense of the corresponding surfaces of the lobes, and thus simulates an abscess of the lung. There are many varieties in the arrangement of these lobes. Thus, sometimes, the fissures, and more especially those which bound the middle lobe, do not reach as far as the root of the lungs, but are only slightly indicated. Three lobes are not unfrequently found in the left lung, or four in the right ; there were four lobes in the lung of a negro lately presented to the ana- tomical society. Examples are on record of lungs with five, six, and even seven lobes, but in general this multiplicity of lobes is only rudimentary, and represents the normal condition in the majority of animals. The dog, the sheep, and the ox have seven lobes in their lungs Inner or Mediastinal Surface. — This corresponds to the mediastinum (p p). On it we observe the root (r) of the lungs, that is, the part at which they communicate with the trachea, through the bronchi, and receive and emit their bloodvessels. This root oc- cupies a very limited space upon the inner surface, one inch in height, and half an inch in breadth ; it is situated at the junction of the posterior with the two anterior thirds of this surface, at an almost equal distance from the apex and the base. That part of the inner surface of the Jung which is behind the root corresponds to the vertebral column and the posterior mediastinum, in which are found, on the left side, the descending aorta and the upper part of the thoracic duct ; and on the right side, the vena azygos, the oesophagus, and the lower part of tlie thoracic duct. All that portion of the inner surface which is in front of the root corresponds with the anterior mediastinum, and is excavated to receive the heart (l) ; and as the heart projects more to the left than to the right side, it follows that the left lung, which cor- responds to the left border and apex of the heart, and higher up to the arch of the aorta ig), is more deeply excavated than the right lung, which corresponds to the right auricle (m) and the vena cava superior {see Jig. 170). We can obtain an accurate idea of the manner in which the lungs are excavated for the reception of the heart only by ex- amining them when inflated ; we are then struck with the propriety of the expression of Avicenna, who called the lung the bed of the heart. We can also understand how diseases accompanied with enlargement of the heart may directly influence the respiration, by reducing the size of the lungs. These organs, it may be remarked, are here in apposi- tion with the heart through the medium of the pericardium and the pleura. I should not omit to mention their relation with the phrenic nerve, which is affixed closely to the pericardium by the pleura. In the foetus, the lungs are in relation anteriorly with the thjTnus gland, which presses them backward. The anterior border is thin and sinuous, presenting on the left side two notches, one inferior and very large, corresponding to the apex of the heart ; the other superior and small, for the subclavian artery. On the right side there are also two notches, but smaller than those on the left ; an inferior for the right auricle, and a superior for the vena cava superior. The posterior border (fig. 171) is the thickest part of the lung. It fills the deep costo- vertebral groove situated at each side of the dorsal portion of the spine. The base is concave, and exactly moulded upon the convexity of the diaphragm (x, fig. 170); it is, therefore, a little more excavated on the right than on the left side. Its circumference is very thin, and slightly sinuous. Like the diaphragm, the base of the lung forms an inclined plane from before backward and downward ; and it occupies the deep angular groove formed behind, between the diaphragm and the parietes of the thorax. On account of this obliquity of its base, the vertical diameter of the lung is much THE LUNGS. 413 greater behind than in front ; and as the posteiior border is the largest part of the organ, it may be conceived that an examination of the lung should be directed chiefly to this part. It is of importance to form a correct idea of the manner in which the base of the right lung and the convexity of the hver are arranged with regard to each other. The liver is, as it were, received into the concavity of the base of the lung so completely, that the posterior part of this base is almost on a level with the lower surface of the liver. The relation of the hver with the base of the lung, which is only separated from it by the diaphragm, explains how abscesses and cysts of the liver may Jjurst into the lung. The apex is obtuse, and projects above the first rib, a very strongly-marked impression of which is found on its anterior surface. I have observed that the height of the portion which passes above the first rib varies in different subjects. In severed I found it from an inch to an inch and a half In an aged female, in whom the base of the thorax was extremely constricted, the apex of the lung (i. e., the part bounded below by the depres- sion corresponding to the first rib) was two inches in height. May not the mechanical pressure of the inner edge of the first rib upon the apex of the lung exercise some influ- ence in the very frequent development of tubercles in that region 1 In order to form a correct idea of the apex of the lung, that organ must be previously inflated. The whole surface of the lung is free, smooth, and moistened with serum ; it is con- nected with the rest of the body only by its root, which attaches it to the bronchi and the heart, and by a fold of the pleura. It is very rare to meet with lungs free from adhe- sions upon their surface, so that the older anatomists regarded these adhesions, whether filamentous or otherwise, as natural formations. Structure of the Lungs. On examining the structure of the lungs, we find in each an investing membrane oi serous sac, formed by the pleura, and a proper tissue. We shall conmxence with the pleiira. The Pleura. Dissection. — In order to obtain a view of the costal pleura, saw through the six or seven upper ribs behind, near their angles ; cut through the cartilages of the same ribs, at a distance of some lines from their sternal articulations ; remove the intermediate portions of ribs and intercostal muscles with great care, so as to leave the costal pleura imtouched. The cavity of the pleura may be inflated. In order to see the mediastinal and pulmonary portions, the costal pleura must be opened, and its continuity traced. The -pleura {nXevpu, the side) is a serous membrane, and, therefore, a shut sac, which is extended partly over the parietes of the thorax, and partly over the lungs. There are two pleurae, one for the right and the other for the left lung. The following is their gen- eral arrangement : The pleura lines the parietes of the thorax, the ribs, and the diaphragm, forming the pleura costalis (p p,fig. 151) and pleura diaphragmatica ; it invests the entire surface of the lung, constituting a sort of integument for it, and forming the pleura pulmonalis ; lastly, it is applied to the pleura of the opposite side, so as to form a septum between the two lungs ; this part is the mediastinal pleura. In order to facilitate the description of the pleura, we shall suppose it to commence at a certain point ; and then, following its course without interruption, shaU trace it back to the point from which we started. If we thus commence at the sternum, we shall find that it lines the internal surface of the thorax, being apphed to the ribs and the intercostal muscles, and covering the mammary vessels and lymphatic glands in front, the intercostal vessels and nerves behind, and the ganglia of the great sympa- thetic opposite the heads of the ribs : below, it is reflected upon the diaphragm, and covers the whole of its upper surface : above, it is reflected beneath the first rib, and terminates in a cul-de-sao, intended for the reception of the apex of the lung, and pro- jecting more or less above that rib. Having reached the sides of the vertebral column, the two pleurae are reflected for- ward as far as the root of the corresponding lung, and form, by their approximation, a septum, which is called the posterior mediastinum. This septum contains within it the aorta, the oesophagus, the pneumogastric nerves, the thoracic duct, the vena azygos, a considerable quantity of cellular tissue, a great number of lymphatic glands, and the trachea. We see, then, that the two pleurae are by no means in immediate contact. Arrested, as it were, by the root of the lungs, the pleura is reflected outward behind that pedicle, passes over a small portion of the pericardium, covers all that part of the inner surface of the lungs which is behind its root, and also its posterior border and its outer surface, dips into the inter-lobular fissure, so as completely to invest the contigu- ous surfaces of the lobes, is reflected over their anterior margin upon their inner surface, reaches the root of the lung, and covers its anterior surface, is then reflected forward upon the side of the oericardium, in front of which it is applied to the pleura of the op- 414 SPLANCHNOLOGY. posite side, and at length arrives at the border of the sternum, from which we had sup- posed it to commence.* The antero-posterior septum formed by the two plurae, between the sternum and the root of the lung, is called the anterior mediastinum {m,fig. 155).t This septum is not vertical nor median, Uke the posterior mediastinum, but is directed downward and to the left side, an arrangement that is connected with the oblique position of the heart, which encroaches more upon the left than the right cavity of the thorax. It follows, from this, that the uppej part of the anterior mediastinum {p p,fig. 170) is behind the sternum, while its lower portion is behind the left costal cartilages, and hence the in- terior of this mediastinum may be reached without opening the cavity of the pleura, by Introducing an instrument close to the left border of the sternum, opposite the fifth rib. The anterior mediastinum is narrow in the middle, and expanded above and below, Uke an hour-glass. The upper cone or expansion is very much developed in the fcetus, and Is occupied by the thymus gland, which is afterward replaced by cellular tissue : the lower cone or expansion is much larger, and contains the heart and pericardium, the phrenic nerves, and in front of the heart a large quantity of cellular tissue. This latter, which is so abundant in the anterior mediastinum, communicates freely above with the cellular tissue in front of the neck, and below with that of the abdominal parietes, through a triangular interval existing in the diaphragm behind the sternum. This double communication explams how the pus of an abscess formed in the neck or in the mediastinum may reach the surface in the epigastric region. The pleura has two surfaces, one an external, the other internal. External or Adherent Surface. — ^This does not adhere with equal firmness to all the parts which it covers. The pleura costalis is but slightly adherent, and may be separa- ted from the ribs and the intercostal muscles with the greatest ease. It is sometimes raised in the situation of these muscles by subjacent adipose tissue. It is strengthened by a layer of fibrous tissue, which, notwithstanding its tenuity, performs an important part in diseases of the chest ; it explains why abscesses formed in the parietes of the thorax so seldom open into the cavity of the pleura, and why effusions into the pleura are so rarely discharged externally. The diaphragmatic pleura is more adherent than the costal. We sometimes find here, especially round the pericardium, some large fat- ty appendages, resembling the appendices epiploicae of the great intestine. The pleura is extremely thin upon the lungs {pleura pulmonalis), where it is not strengthened by any fibrous tissue ; and although it is more adherent here than the parietal pleura, still it can be easily demonstrated. The mediastinal pleura is united to the parts contained within the mediastinum by very loose cellular tissue, but it adheres more firmly to the Bides of the pericardium, to which the phrenic nerves are closely applied. The internal or free surface is smooth,t moistened with serum, and in contact with itself throughout its entire extent, as is the case in all serous membranes. The adhe- sions so commonly met with here are altogether accidental. The structure of the pleura is cellular.^ It is doubtful whether it receives any arteries and veins. The vascular network, which is sometimes so highly developed after pleurisy, does not belong to it, but is situated upon its external surface. No nerves have been traced into this mem- brane. Uses. — Each pleura forms an investment for the corresponding lung, separates it from the parietes of the thorax and from the other viscera, and, at the same time, facilitates its movements upon the walls of the thoracic cavity by means of the serosity, which is constantly exhaled and absorbed at its internal surface. The Proper Tissue of the Lungs. The pulmonary tissue appears like a spongy or vesicular texture, the cells of which are filled with air. This is rendered apparent by the most simple inspection of the sur- face of an inflated lung, either with the naked eye or with a lens. A microscopical ex- amination of sections of a dried lung shows the existence of this cellular or vesicular tex- ture in the most evident manner throughout the entire organ. The different shapes of the cells and their unequal size may also be distinguished. But what are the relations of the cells with each other 1 Do they communicate throughout the whole extent of the lung, or only within a determinate space, or are they independent of each other 1 In order to resolve these questions, it is necessary to ex- amine the lung of a large animal, of the ox, for example, the structure of which is simi- lar to that of the human lung, on which the same observations may be subsequently re- * [A fold of the pleura reaching' from the lower edge of the root of the lung downward to the diaphragm, is called the ligamentum latum pulmonis. It is triangular ; its base is attached to the diaphragm, one side to the lung, and the other to the mediastinum.] t According to Meckel, the anterior mediastinum is the portion of the septum situated in front of the heart, just as the posterior mediastinum is the part situated behind that organ. X [It is covered with a squamous epithelium, and cilia have been observed upon it in some of the mam- malia.] ^ [Beneath the pleura another cellular layer may be demonstrated ; and in the lung of the seal and leopard an elastic coat is said to exist. 1 THE LUN38. 415 peated. We then observe that the surface of the lung is traversed by lines, dividing it into lozenge-shaped compartments ; and if the lung be previously inflated, it will be seen that the surface is slightly depressed opposite these lines, but that it bulges out between them. If, by means of a dehcate tube, air be blown under the pleura, or if the lung be forcibly inflated through the trachea, so as to rupture some of the vesicles and produce emphysema, we then perceive that the lines bounding the lozenge-shaped intervals cor- respond to thin layers of very delicate, but tolerably loose cellular tissue, which divide the lung into a large number of groups or cells, which may be completely separated from each other by dissection, until at last we arrive at the pedicles by which they are united into a common mass. These groups of cells are the lobules of the lung; the cellular tissue uniting them is the interlobular cellular tissue, which is extremely delicate, never loaded with fat, but oft,en infiltrated with serosity, and is subject to emphysema. A great number of lymphatic vessels traverse this cellular tissue : they are often visible to the naked eye, and are always easily injected ; they pass deeply into the substance of the lung. The pulmonary lobules do not communicate with each other, but each is perfectly in- dependent of the rest. This fact is shown by inflation ; it is most distinctly proved by dissection ; and an examination of the lungs of the foetus will remove all doubts con- cerning it. The pleura and the interlobular cellular tissue having but little strength in the fcEtus, the lobules become separated without dissection, resemble grapes attached to their footstalks, and hang from a common stem, formed by the divisions of the bronchi and the pulmonary vessels. This independence of the lobules is also proved by pathological anatomy : thus, we con- tinually find one lobule infiltrated with serum, with pus, or with tubercular matter, in the midst of perfectly healthy lobules. Each lobule, then, is a small lung, and may act independently of those by which it is surrounded. I have satisfied myself, by a great number of experiments, that the lobules are not all equally permeable to the air, and that a moderate inflation of the lungs, made as much as possible within the limits of an ordinary inspiration, does not, perhaps, dilate one third of the pulmonary lobules. I have observed, and this fact appears to me of great importance, that the most permeable lobules are those of the apex of the lung ; and this, perhaps, will explain the greater frequency of tubercles in that situation.* There are some lobules in the lung which are kept, as it were, in reserve, and only act in forced inspirations.! The puhnonary lobules vary much in shape ; all the superficial ones resemble a pyra- mid, the base of which is at the surface of the lung ; the deep lobules lie along the bron- chial tubes, have numerous facettes, and are exactly fitted to each other, like the frag- ments of mosaic work ; but they are so irregular in form, that it would be equally diffi- cult and useless to give a description of them. The lung, then, is a collection of an immense number of lobules, placed along the bron- chial tubes and pulmonary vessels, which serve as a support and framework for them, and to which they are appended by pedicles ; they are united to each other by serous cellu- lar tissue, and are all covered by one great cell formed by the pleura, which merely unites together this great number of parts. The problem of the texture of the lungs reduces itself, therefore, to the determination of the structure of a single lobule ; but the difficulty is rather postponed than got rid of, for each lobule is a little lung, receiving an air-tube and an artery, and giving out several veins and lymphatics. Before describing the arrangement of the air-tube, and the vessels in each lobule, we shall say a few words upon the structure of the lobule itself Each lobule is an agglomeration of cells and of vesicles, all of which communicate with each other.J These cells are always full of air. Their size is not always the same. M. Magendie has already shown that the pulmonary cells are smaller in the infant than in the adult, and smaller in the adult than in the aged.§ Nor is the size of the different cells in the saime lobule constantly uniform. All the cells of the same lobule communi- cate, but they are not all equally permeable. t Thus, in a given degree of inspiration, some cells only are distended, while others require a greater degree of dilatation. The septa between the cells of a lobule are incomplete,^ and consist of filaments or lamellae ; and the reticulated arrangement of the cells, which is so evident to the naked eye in the lung of the frog, seems to me to represent with tolerable accuracy the appearance of the human lung under the simple microscope. * It is rather too much to say that pneumonia almost always attacks the base of the lungs ; this disease has no special locality ; it perhaps as often affects the apex as the base. t In ordinary respiration, perhaps not more than one third of the lung is in action ; exercise and yawning are probably required, from the necessity for bringing the whole lung into action. Thus, a great number of tu- bercles may exist in the lung without manifesting their presence by impeding ordinary respiration. It is in Tiolent inajnration, in exercise, in efforts of the voice, and in all movements during which the whole of the lungs is called into play, that we detect the existence of a lesion in the central organ of respiration. { See note, p. 419. ^ Diseases have a remarkable influence upon their size ; in chronic catarrh, and in some varieties of asthma, we find the pulmonary cells excessively dilated. Laennechas called this dilatation pulmonary emiihysemo. 416 SPLANCHNOLOGY. With regard to the structure of the cells,* we cannot admit the existence of muscular fibres round them ; the anatomist is unable to demonstrate them, and physiology rejects them. Tlie most probable opinion is, that they are formed of dense cellular tissue, or of an elastic fibrous tissue, and that the bloodvessels are ranrified upon their parietes. The Air-tubes. The air-tubes of the lungs consist of the trachea, the bronchi, and their divisioris. The Trachea. The trachea (from rpaxvg, rough), or aspcria arteria ib,fiffs. 170, 171), is the common trunk of the air-tubes of the lungs ; it is situated between the larynx {a,Jig. 171), of which it is a continuation, and the bronchi (p p'), which are nothing more than its bifurcation in front of the vertebral column, extending from the fifth cervical to the third dorsal verte- bra, t In this situation, however, it is movable, and may easily be pushed to the right or left side. This mobility has occasioned serious accidents in tracheotomy, and has led to the invention of an instrument for fixing the trachea.^ Its direction is vertical ; it occupies the median line above, but appears to be slightly deflected to the right side be- low. I have often seen it somewhat flexuous, but these slight deviations only existed when the neck was bent upon the thorax ; they disappeared during extension. Dimensions. — The length of the trachea equals that of the space between the fifth cer- vical and the third dorsal vertebrae, and is, therefore, from four to five inches ; but it varies according as the larynx is raised or depressed, and as the neck is flexed or ex- tended. The difference produced in its length, by the utmost elongation and shortening, may be about half its entire length, i. e., from two inches to two inches and a half; its shortening is limited by the contact of its cartilaginous rings. ^ The diameter of the trachea is determined by that of the cricoid cartilage of the larynx ; it is much wider in the male than in the female, and after than before puberty. Indi- viduals who have been many years labouring under chronic catarrh have the air-passages remarkably large, especially the trachea. The mean diameter of the trachea is from ten to twelve lines in the male, and from nine to ten in the female. The trachea is not of equal diameter throughout ; it is almost always dilated at its lower extremity, Avhere it bifurcates. In some subjects it gradually increases in size from above downward, and resembles a sort of truncated cone, with the base below. External Surface, Form, and Relations. — In front and on the sides the trachea is cylin- drical {fig. 170), but is flattened behind {fig. 171), so that it resembles a cylinder, the posterior fourth or third of which has been removed. The external surface is rough, and, as it were, interrupted by circular ridges, which correspond to the cartilaginous rings. The relations of its external surface must be examined in the neck and in the thorax. Relations of the Cervical Portion (x,fig. 140). — In front the trachea is in relation with the thyroid body, the isthmus of which being sometimes very narrow and sometimes very largely developed, covers a greater or less number of the rings of the trachea. In general, the first ring of the trachea is above the isthmus of the thyroid. Below the thyroid body the trachea is in relation with the stemo-thyroid muscles, the edges of which are separated only by the linea alba of the neck ; also with the cerviced fascia, the thyroid plexus of veins, a considerable quantity of cellular tissue, the thyroid artery of Neubauer, when it exists, and the brachio-cephalic artery, which always passes a little above the supra-sternal notch. All these relations are of the greatest importance in ref- erence to the operation of tracheotomy. On the sides the trachea is embraced by the lateral portions of the thyroid body, and, therefore, in diseases of that organ, the corre- sponding part of the trachea is deformed, flattened on the sides, and elliptical, or even triangular. The compression of this canal may be carried so far as to produce suffoca- tion. The common carotid artery and the pneumo-gastric nerve are in contact with it on either side ; and hence the possibility of wounding that artery in the operation of tracheotomy. A great number of lymphatic glands are situated upon the sides of the trachea, and may become so large as to prevent the passage of the air. Lastly, all the relations of the trachea, excepting those with the thyroid body, take place through the medium of a very loose cellular tissue in which this canal is imbedded. Behind, the trachea is flat and membranous, and is in relation with the oesophagus, which projects a little beyond it on the left side, and separates it from the vertebral col- * See note, p. 419. t The terai trachea is derived from the roughness produced by the projection of the cartilages of the wind- pipe. The application of the term arteria, by the ancients, to the vessels which carry red blood, arose from a serious anatomical mistake. These vessels being habitually empty in the dead body, it was supposed that they contained air during life ; and hence the name artery, which tliey still retain. t By a surgeon of the name of Buchot. The mobility of the trachea is an obstacle to its puncture in the operation of tracheotomy. ^ The elongation and shortening of the trachea is much more limited in man than in birds, in which the rings of the trachea are moved by longitudinal muscles, and can be drawn within each other ; in the greatest possible degree of shortening three rings overlap each other, so as to equal only one in height ; and, therefore, the trachea of a bird may be diminished by two thirds. These peculiarities of structure are connected with the different uses of the parts ; the trachea in man and other mammalia merely conveying the air (unporte-verU), while tlie trachea of birds conveys the voice (vn porte-voix). THE LUNGS. 417 omn. The left recurrent nenre is situated in the groove formed between the trachea and the oesophagus in this direction ; the right recurrent nerve lies behind the trachea. The inunediate relation of the trachea with the oesophagus explains why foreign bodies arrested in the gullet may produce suffocation, and require the perfonnance of trache- otomy. The softness and flexibility of the trachea opposite the oesophagus have appeared to some physiologists to be intended merely to facilitate the dilatation of the latter during the passing of the food ; but we shall see that the air-tubes continue to be membranous behind, even where they have no relation with the oesophagus, and comparative anatomy, which shows the trachea to be cylindrical in the bird, and angular behind in the ox, the sheep, &c., most completely refutes this opinion. Rdaiions of the Thoracic Portion of the Trachea. — In the thorax, the trachea occupies the posterior mediastinum. It corresponds in. front, proceeding from above downward, with the sternum and the sterno-thyroid muscles ; with the left brachio-cephalic vein (c, fig. 170) ; with the brachio-cephalic artery (A), an aneurism of which may open into the trachea ; its left side is, as it were, embraced between the brachio-cephalic artery (A) and the left common carotid (;) ; with the back part of the arch of the aorta {g), which rests immediately upon it, and hence the dyspnoea which so generfdly accompanies aneu- rism of the aorta, and the frequency of its bursting into the windpipe ; and, lastly, lower down, with the bifurcation of the pulmonary artery, which corresponds with that of the trachea. The trachea is in relation behind with the oesophagus, which separates it from the spinal column ; and on the sides with those portions of the pleurae which form the mediastinum, with the pneumogastric nerves, and with the upper part of the recurrent nerves. In all its thoracic portion the trachea is surrounded by numerous lymphatic vessels and glands, and by a loose and very abundant cullular tissue, which communicates with that of the cervical region. These lymphatic vessels and glands with the loose cellular tissue are the parts immediately adjoining the trachea ; and it may readily be conceived that enlargement of the glands may be productive of serious consequences. Internal Sarface. — The internal surface of the trachea is of a rosy colour, and presents the same circular ridges as the external surface, but they are more distinct. It is also remarkable in its membranous portion for the projection of certain vertical fasciculi, to which we shall again refer when speaking of the structure of these parts. The Bronchi. The bronchi {(JpSyxoc, gutter, p p,Jig. 171) are the two branches formed by the bifiirca- tion of the trachea, which Ft^. 171. spread out from each other at a right or a slightly obtuse angle ; one {p) is intended for the right, the other for the left (p') lung. A tolerably strong triangular ligament exists at the angle of the bi- furcation, and seems intend- ed to prevent too great sep- aration of the bronchi. The bronchi differ from each other in many respects ; first, in width. The right bronchus is much wider than the left, and its diameter is not much less than that of the trachea. In a female whose trachea w£is ten lines in diameter, the right bron- chus was eight, and the left five. This difference in width corresponds with the differ- ence in the size of the two lungs, and may afford a toler- ably correct measure of that size ; they differ also in length, the right bronchus being one inch in length, the left two ; also in direction, the right bronchus passing less obhquely than the left, probably because it enters the correspond- ing lung sooner than the latter ; and, lastly, in their relations. Thus, the right bronchus is embraced by the vena azygos, which forms a loop immediately above it, in order to terminate in the vena cava superior. The left bronchus is embraced above by the arch of the aorta {g), and has an important relation with the oesophagus behind, which it Ggg 4ih SPLANCHNOLOGY. crosses obliquely. Both are connected with the pulmonary plexus of nerves ; both are surrounded with lymphatic glands, remarkable for their black colour, and for being fre- quently diseased, and which in some measure fill up the angle formed by the bifurcation of the trachea ; and, lastly, both have the following relations with the pulmonary artery and veins. Each pulmonary artery {k k') is situated in front of the corresponding bron- chus, then passes above, and finally behind it. The two puhnonary veins on each side {I I, mm) are situated upon the same vertical plane as the corresponding artery ; they pass up- ward in front ofthe artery and the bronchus, which is, therefore, behind the bloodvessels.* The shape of the bronchi exactly resembles that of the trachea, i. e, they represent cylinders, the posterior fourth of which has been removed, and which are formed by par- allel rings. The area of the two bronchi is greater than that of the trachea, in the same way as the area of the bronchial ramifications is greater than that of the bronchi them- selves, so that the velocity of the expired air increases as it approaches the exterior. At the root of the lungs the bronchi divide into two equal branches, but in a some- what different manner. The upper branch of the bifurcation of the right bronchus is the smaller, and is intended for the upper lobe of the lung, in order to reach which it is bent slightly upward. The lower branch, which is larger, follows the original direction, and after passing about an inch, divides into two unequal branches, a small one for the mid- dle lobe, and a larger one for the lower lobe. I have once seen a small bronchus pro- ceeding from the lower part of the trachea directly to the apex of the right lung ; the vena azygos passed between it and the regular bronchus.t The secondary divisions are precisely the same in the two lungs ; each branch of a bifurcation becomes bifurcated in its turn. All these ramifications pursue a diverging course, some ascending, others descending, and, after proceeding for a variable distance, they again bifurcate ; so that, by separating a small portion of the pulmonary substance, we can see that several diverging series of tubes proceed in succession from a bronchial trunk, and pass outward into the tissue of the lung. The prevailing mode of division of the air-tubes in the lungs is that called dichotomous, viz., a division into two equal branch- es, which we shall afterward find to be the most favourable to the rapid transmission of the contents of any vessel. (See Aeteries.) The two branches of a bifurcation sep- arate at an acute angle, and a spur-shaped process, situated within the tube at the an- gle of division, cuts and divides the column of air. However, some small bronchial tubes are not unfrequently found arising directly from a principal division, to be distrib- uted to the nearest pulmonary lobules. The number of subdivisions, which always cor- responds with that of the pulmonary veins, is not so great as might at first be supposed ; there are not many more than fifteen. The form of the bronchial ramifications (bronchia) differs essentially from that of the bronchi themselves and of the trachea. They represent, indeed, a complete cylinder, which is not truncated behind ; and the cartilages, instead of forming rings, have another arrangement, which I shall point out when speaking of their structure. Relations. — The first divisions ofthe bronchi are surrounded, even in the substance of the lung, by very numerous and dark-coloured bronchial lymphatic glands, enlargement of which is a very frequent result of chronic bronchitis, and may cause suffocation. The bronchial ramifications, as I have said, support the pulmonary lobules, which are applied to and moulded upon them, and are united to them by very loose cellular tissue. The following are their relations with the branches of the pulmonary artery and veins : the artery always accompanies the bronchial ramification, and is situated behind it ; the vein is often separated from it ; the artery and vein are not unfrequently found interla- ced around the corresponding bronchial tube. Relations of the Bronchial Ramifications with the Pulmonary Lobules. — ^Each pulmonary lobule has its bronchial tube. This tube is cylindrical, of uniform diameter throughout, and entirely membranous ; having entered the lobule, it dilates into a small ampulla, and disappears. There can be little doubt that these small ampullae have deceived Malpighi, Reisseisen, and others, who have stated that the bronchial tubes terminate in culs-de- sac ; so that, according to these authors, each pulmonary cell is the termination of a par- ticular bronchicd tube. But it is evident that such cannot be the case, for, on the one hand, the bronchial tubes are not sufficiently numerous, and, on the other, it can be shown that only a single bronchial tube enters into each group of cells or each lobule. If we inject with tallow a lung which has previously been deprived of air, either by an effu- sion in the chest during life, or by an artificial one after death, it wiU be seen that the injection is divided into small globules or rounded tubercles, which correspond to so many pulmonary ceUs, and that these globules are all connected with a common pedicle, corresponding to the bronchial tube. Reisseisen, who has made this injection, thinks that the granular appearance of the injected matter represents the culs-de-sac, into which it had penetrated.^ * [In consequence of the oblique direction of the left bronchus towards the root of the lung, the correspond- ing pulmonary artery is placed somewhat above it, and the pulmonary veins below it ; on the right side, the pulmonary artery is in the middle, the bronchus above, and the veins below.] t This appears to be the natural arrangement iu the sheep and the ox. t [According to Reisseisen, each small bronchial tube, on entering its corresponding lobule, divides and sub- THE LUNGS. 419 * ^ Structure of the Trachea, Bronchi, and Bronchial Ramijicattons. Structure of the Trachea. — The trachea is composed of a series of imperfect cartilagi- nous rings, separated by an equal number of fibrous rings, and hence it has a knotted ap- pearance ; these cartilages keep the canal permanently open. Had the trachea been en- tirely membranous, it would have collapsed during inspiration, which tends to produce a vacuum in the thorax, and this collapse would have prevented the entrance of the air. The number of the cartilaginous rings varies from fifteen to twenty. They are more prominent on the internal than on the external surface of the trachea. In some subjects they form two thirds, in others three fourths or four fifths of a circle. Each ring has two surfaces, one anterior and convex, the other posterior and concave ; an upper and a lower edge, both of which are thin, and give attachment to the fibrous rings ; and two extremities, which terminate abruptly, without being inflected or thickened. In general, there is but little regularity in the arrangement of these rings ; they are not exactly par- allel, nor are they of equal depth, which varies from a line to a line and a half, two, or even two lines and a half; and the same ring is often of unequal depth at different pakits. Two rings are often united for a certain extent, and sometimes a ring is found birarca- ted ; indeed, it is probable that differences in the number of the rings depend upon their thus uniting or dividing. They are sufliciently thin to £illow of being compressed, so that the opposite surfaces may touch without breaking. Their eljisticity enables them to recover their original position immediately, and thus permit free access to the air. They can only be broken when ossified, which is frequently the case in the aged. The first ring and the two lower rings present some peculiarities. The first is broad- er than any of the others, especially in the middle line, and it is often continuous with the cricoid cartilage.* The last ring of the trachea, which forms the. transition between it and the bronchi, has the following characters : the middle part is prolonged considerably dowmward, and curved backward, forming a very acute angle, and is developed into a spur-shaped pro- jection within the trachea, which separates the two bronchi. The two half rings result- ing from this arrangement/ constitute the two first rings of the bronchi. The last ring but one of the trachea presents an angular inflection in the middle, less marked, howev- er, than that observed in the lowest ring. The Fibrous Tissue of the Trachea. — This is arranged in the following manner : a fibrous cylinder commences at the lower edge of the cricoid cartilage ; the cartilaginous rings are situated within the substance of this cylinder in such a manner, that the thick- er layer of fibrous tissue lies on their exterior, so that, at first sight, their internal sur- faces would appear to be in immediate contact with the mucous membrane. In the pos- terior part of the trachea, where the cartilaginous rings are wanting, the fibrous tissue alone forms its basis or framework. The Muscular Fibres of the Trachea. — If we carefully remove the fibrous tissue from the back of the trachea, opposite its membranous portion, we arrive at certain transverse muscular fibres, extending from one end of each ring to the other, and also occupying the intervals between the rings. The existence of these muscular fibres, which I have seen forming a layer half a line tliick in certain cases of chronic catarrh, cannot be doubt- ed. It is evident that their contraction must draw the ends of the rings towards each other, and therefore narrow the trachea, the diminution in the width of which is limited by the contact of the ends of the rings. The Longitudinal Yellow Fasciculi. — In the membranous portion of the trachea, be- divides in a certain uniform order into numerous tv„ i-rn twigs (<,_/r^. 172), which, extending towards tbe °' surface of the lobule, gradually decrease in di- ameter, but increase in number, and at length ter- minate in clusters of short, free, closed and round- ed extremities (c c) ; these are the pulmonary cells, which vary from ij^ to -g^ of an inch in diameter. Not only are the several lobules in- dependent of each other, but the cells of each lobule have no communication with one another except indirectly through the twig or twigs from which they proceed. This view of the minute structure of the lung, which is opposed to the opinion of M. Cruveil- hier, receives support from what is known con- cerning the development of the lungs, and from the analogy between these organs and the com- I)onnd glands. ^___^__ In_^g'. 172, after Reisseisen, a shows the nat- "*^^ici^ h ural size of the portion represented, magnified about nine diameters in 6. The bronchial twigs Minute itmcture of the lung, and pulmonary cells are seen distended with air ; the knots or projections (i) on the sides of some of the ^ga indicate the commencement of other twigs, into which no air has passed.] * I have met with one case in which the thin upper rings of the trachea and the cricoid cartilage were joined together, l)ut only on one side ; the crico-thyroid muscle and the inferior constrictor of the pharynx ev- idently arose from the first ring of the trachea. This continuity of the cricoid cartilage with the trachea manifestly proves that the rings of the latter arc cartilages, and not fihro-cartilag-es. 420 SPLANCHNOLOGY. tween the muscular anS'ttie mucous layer, are situated a great number of parallel, lon- gitudinal, yellow fasciculi, which, at first sight, resemble longitudinal folds, but are not at all effaced by distension ; these fasciculi adhere to, and produce an elevation of, the mucous membrane, and opposite the bifurcation of the trachea they also divide, and are continued into the bronchi. The nature of this tissue is not well known ; it can only belong to the muscular or to the yellow elastic tissue, though I would rather incline to the latter opinion. According to either supposition, its use is to prevent too great an elongation of the trachea and the bronchi ; actively in the one case, and by virtue of its elasticity in the other. Not un- frequently some longitudinal fasciculi are found behind the cartilaginous rings. The Tracheal Glands. — If we carefully examine the posterior surface of the trachea, we find a certain number of ovoid flattened glands (see^^. 171), placed upon the outer surface of the fibrous membrane ; and, by removing this membrane, we see a tolerably thick, but not continuous, layer of similar glands between the fibrous and the muscular coate ; and, moreover, if either the inner or the outer layer of the fibrous tissue, situated between the cartilaginous rings, be removed, a series of much smaller glands will be found between these layers, occupying the intervals between the rings, and even ex- tending behind them. The Mucous Membrane. — This is a continuation of the mucous membrane of the larynx , it is remarkable for its tenuity, which permits the colour of the subjacent parts to be seen through it, and for its intimate adhesion to the structures covered by it. The lon- gitudinal folds of which some authors speak do not exist ; the yellow longitudinal fas- ciculi have been mistaken for them. Lastly, it presents a great number of openings, from which mucus can be expressed. These openings are nothing more than the orii- ces of the excretory ducts of the tracheeil glands.* The Vessels and Nerves. — The arteries Of the trachea are derived from the superior and inferior thyroid. The veins are generally arranged thus : some venous trunks running along the inner surface of the trachea, beneath the mucous membrane, receive on each side, in the same manner as the vena azygos, small veins corresponding to the intervals between the cartilaginous rings, and then terminate in the neighbouring veins. The lymphatic vessels are very numerous ; they enter the surrounding glands, which are of considerable size. The nerves are derived from the pneumogastrics. Structure of the Bronchi. The structure of the bronchi is exactly the same as that of the trachea. The lett bronchus has ten or twelve cartilaginous rings ; the right has five or six. They both possess transverse muscular fibres, longitudinal yellow fasciculi, glands, &c. Their arter- ies generally arise directly from the aorta, and are named bronchial. The veins of the right bronchus enter the vena azygos ; those of the left terminate in the superior intercostal. Structure of the Bronchial Ramifications {Bronchia). — The fibrous cylinder of the trachea and the bronchi is prolonged into the bronchial ramifications. The cartilaginous rings are remarkably modified beyond the first division of the bronchi ; they become divided into segments, which together form a complete ring, so that there is no longer any mem- branous portion, properly so called, and the bronchial tubes become perfectly cylindrical. The segments above mentioned are oblong, curved, terminated by very elongated angles, and so arranged that they can overlap and be mutually received between each other. They are also united together by fibrous tissue. This arrangement of curved and angu- lar segments exists as far as the last bifurcations of the bronchial tubes ; but the size of the segments gradually diminishes, so that they soon form only narrow lines, and ul- timately mere cartilaginous points. The fibrous and membranous constituents of the cylinder preponderate more and more over the cartilaginous laminae, which disappear be- yond the ultimate bifurcations of the bronchial tubes, being found last at the several an- gles of bifurcation : the ultimate bronchial ramifications are altogether membranous. The mucous membrane is prolonged to the very last ramifications, where it becomes extremely thin. The longitudinal elastic fasciculi, which were limited to the membra nous portion of the bronchi, are expanded over the entire surface of the bronchial tubes beyond their first subdivision. The muscular fibres, which are confined to the mem branous portion in the trachea and bronchi, become circular on the inner side of th» bronchial ramifications, and form an uninterrupted but very thin layer, precisely resem bling the circular fibres of the intestinal canal, t When we consider, on the one hand. * structure of the Trachea.— iTtin muscular fibres of the trachea are of the involuntary class (see p. 323), and are attached to the internal surface of the ends of the rings : the longitudinal fibres exist all round tht trachea, but are collected into bundles on its membranous portion only ; they are believed to consist of elastif tissue. The glands of the trachea and bronchi are compound ; its mucous membrane is covered vfith a columnar epithelium, and is provided with cilia, which urge the secretions upward towards the larynx.] t Structure of the Bronchi and their Branches. — [According to Reisseisen, the fibrous cylinder gradually de- generates, in the smallest bronchial tubes, into cellular tissue ; according to the same author, the longitudinal elastic and the circular fibres can be traced as far as the tubes can be opened. The contractility of the pul- monary tissue on the application of galvanism, recently observed by Dr. C. J. B. Williams, establishes the muscularity of the circular fibres of the bronchial tubes. The mucous membrane, as in the trachea, has a co- lumnar and ciliated epithelium ; it of course enters into and lines the pulmonary cells.] THE LUNGS. 421 the arrangement of the cartilaginous segments, which appear, as it were, shaped ex- pressly for the purpose of fitting between each other at their extremities, and of consti- tuting an apparatus capable of being moved, and, on the other, the existence of circular contractile fibres on the inner surface of these segments, we cannot doubt that they are moved upon each other, the extent of such motion being measured by the space they have to traverse in order to come into contact. When this is effected, the canals must be almost completely obliterated.* The Pulmonary Vessels and Nerves. Besides the trachea, the bronchi and the bronchial ramifications, which may be re- garded as forming the framework of the lungs, these organs receive two sets of arteries, viz., the pulmonary and the bronchial, and give out two sets of veins, also called _p? Such is the chief mcxie of distribution of the pulmonary artery and veins ; but both vessels, as indicated be- low, also communicate with the bronchial arteries. The bronchial arteries are the nutrient vessels of the lung ; some of their branches are distributed upon the air-tubes and to their lining membrane, even as far as the air-cells, upon all the pulmonary vessels and nerves, and to the bronchial lymphatic glands ; while others, passing between the lobules, or upon the surface of the lung, anastomose with twigs from the pulmonary artery, and form, with the branches of the pulmonary vein, a vascular network in those situations, but more particularly beneath the pleura. The branches distributed to the lirger bronchia and vessels, and to the lymphatic glands, and also some of the vessels composing the superficial network, terminate in the bronchial veins, which, however, cannot be traced very deeply into the substance of the lung. But by far the greater number of the bronchial arteries end in the pulmonary veins ; for example, those distributed deeply to the smaller air-tubes and pulmonary vessels, and to the air-cells, and nearly all the vessels which enter into the formation of the interlobular and superficial network.] i [This is due to rupture of the pulmonary vessels, which have exceedingly delicate coats, and are, perhaps, less supported by surrounding tissue than the vessels of other organs.] I> [The development of the lungs has been traced by various recent observers in frogs, birds, and mammalia, including man ; according to Rathke and Miiller, it closely resembles, in its early stages, that of the compound glands. In mammaUa, the lungs appear at first as a protuberance upon the anterior part of the (Esophagus, consisting of a soft mass, like the primitive blastema of a gland : within this substance a more opaque portion is formed, from which white lines extend, dividing and subdividing, and terminating in enlarged extremities 422 SPLANCHNOLOGY. The lung is smallest at the earliest period of its development. Its place appears then to be occupied by the thymus, which is the only organ that is seen when the thorax is opened, the lungs being situated behind it, upon each side of the vertebral column. The development of the lung takes place in an inverse ratio to that of the thymus, the lung increasing in proportion as the thymus diminishes. In the last two months of pregnancy the lung is completely developed, and fit for performing respiration. Tlie weight of the lung in the foetus and in the adult presents some differences, which are well worthy of attention. During the whole period of intra-uterine life, the foetal lung is specifically heavier than water ; but as soon as the infant respires, it become? much lighter, and floats in water. Yet the absolute weight of the lung is sensibly increased, because it receives a much greater quantity of blood than it did previously. Before birth, the absolute weight of the lung to that of the whole body is as 1 to 60 ; after birth, it is as 1 to 30. It follows, therefore, that lungs which float in water, and which have acquired a much greater ab- solute weight than they would have had in the foetus, must belong to an infant that has respired. After birth, the lung participates in the development of the rest of the body. At the tmie of puberty it acquires the proportions which it subsequently presents. I have not observed that the lungs are smaller and lighter in the aged than in the adult. The colour of the lungs varies considerably at different periods. In the earlier periods ot development, the lung of the foetus is of a delicate pink colour ; subsequently it be- comes of a deep red, like lees of wine, and remains so until the time of birth. After birth, it again becomes of a pink colour. Still later, from the tenth to the twentieth year, black spots become visible at different points along the lines which form the loz- enge-shaped intervals on its surface. These spots subsequently unite into lines or patches, which give to the grayish surface of the organ a mottled appearance. The de- velopment of the black matter is so clearly the effect of age, that it is very rare not to find small masses of it in the apex or some other part of the lungs in the old subject. It is worthy of notice, that the black matter appears simultaneously on the surface of the lung, and in the lymphatic glands situated at its root and along the bronchi. With regard to structure, it may be observed, that during the four or five earlier months of gestation, the pulmonary lobules are perfectly distinct from each other ; they may be separated by very gentle traction, on account of the weakness of the pleura and cellular tissue which unites them, as compared with the pulmonary tissue itself. The cartila- ginous rings begin to be visible after the third month. Functions. — The lungs are the essential organs of respiration, that process by means of which the blood, though dark and unfit for supporting life before entering these or- gans, becomes red and vivifying. For the accomplishment of this function, the lungs receive, on the one hand, the atmospheric air, and, on the other, the venous blood, the whole of which, in the human subject, passes through the lungs. The air is not drawn in by any power resident in the pulmonary tissue itself, but by the muscular action of the parietes of the thorax ; the blood is propelled into it by the right ventricle of the heart. While the blood undergoes the changes above mentioned, the atmospheric air loses a portion of its oxygen, which is replaced by carbonic acid gas. The manner in which these changes in the blood are effected is not yet weU known. The Larynx.* It is necessary to have several specimens, from subjects of different ages and sexes, so as to be able to examine the genpred relations of the larynx in its natural situation ; its cartilages separated from each other, its ligaments and muscles, its vessels and nerves, and its mucous membrane. The larynx is a sort of box (jnxis cava) or cartilaginous passage, consisting of several movable pieces, which form a complex apparatus intended for the organ of the voice. It is situated {v, fig. 140) in the median line, in the course of the air-passages, opening into the pharynx (3) above, and being continuous with the trachea (x) below : it occu- , pies the anterior and upper part of the neck, below the os hyoides, the movements of which it follows, and in front of the vertebral column, being separated from it by the pharynx : it is covered by the muscles of the sub-hyoid region, which intervene between it and the skin, and it is, therefore, veiy liable to woimds, and may easily be reached by the surgeon. Its mobility allows of its being raised, depressed, and carried forward or backward, all of which movements are concerned both in deglutition and in the produc- tion of different tones of the voice. It may also be carried to the right or left side ; but these lateral displacements are most commonly produced by external violence, or by the growth of tumours. these are accompanied by bloodvessels, and are at first solid, but soon become hollowed ont, into the trachea, bronchi, bronchial tubes, and air-cells.] * The voice belongs essentially to the functions of relation, and, therefore, Bichat describes its organ after the apparatus of locomotion ; but the anatomical connexions between the larynx and ihe respiratory organs are such that all animals provided with lungs have a larynx also, while the larynx disappears where the lungs oease to exist. THE LARYNX. 45J3 Dimensions. — The larynx appears like an expansion of the trachea, and has, therefore, been denominated its head, caput asperez arteria. The exact determination of its dimen- sions, according to age and sex, or in different individuals, and their relations to the various qualities of the voice, would be extremely interesting in a physiological point of view. Its greater size in the male than in the female, and the development it under- goes in both sexes, but especially in the male, at the period of puberty, are among the most remarkable phenomena in the human economy. Form. — It is cyhndrical below, like the trachea, but is expanded above, and becomes prismatic and triangular. It may, therefore, be compared to a three-sided pyramid, the truncated apex of which is directed downward and the base upward ; it is perfectly sym- metrical. As the larynx is a very complicated organ, I shall describe, in succession, the numer- ous parts which enter into its composition. Being intended to admit of the continual passage of the air in the act of r-espiration, it must, therefore, present a constantly per- vious cavity, having strong and elastic wedls ; but as it is also the organ of the voice, it requires to be provided with a movable apparatus, subject to the wiU. We accordingly find in it a cartilaginous skeleton or framework, much stronger than that of the trachea ; certain articulations and ligaments, and a vocal apparatus, composed of four fibrous bands, or vocal cords ; muscles, which move the different pieces of the cartilaginous skeleton, and produce certain changes in the vocal apparatus indispensable for the pro- duction of sounds ; a mucous membrane, lining its inner surface ; glands, which pour out their fluid upon that surface ; and, lastly, certain vessels and nerves. We cannot enter upon a general description of the organ untU we have studied sep- arately its constituent parts. The Cartilages of the Larynx. — ^These are five in number, of which three are median, single, and symmetrical, viz., the cricoid, the thyroid, and the epiglottis ; and two are lat- eral, viz., the arytenoid, of which the cornicula laryngis are merely appendages. The car- tilaginous nodules, described by some authors under the name of the cune^orm cartilages, and situated in the membranous fold extending from the arytenoid cartilages to the epi- glottis, do not exist in the human subject. The Cricoid Cartilage. — The cricoid or annular cartilage (c c', figs. 173 to 177) forms the base of the larynx ; it is much thicker and stronger than any j^^ j73 of the others. Its form is that of a ring, whence its name («pi«of , a ring); it is narrow in front (c,fig. 173), where it resembles a ring of the trachea ; it is three or four times broader or deeper behind (c'and c,fig. 175), where it forms by itself alone the great- er part of the larynx, being there about an inch in height. Li front, its external surface is sub-cutaneous in the median line ; on each side it gives attachment to the crico-thyroid muscle, and presents a smooth process (m, fig. 177) for articulating with the thyroid cartilage. Behind, where it is covered by the mucous membrane of the pharynx, it presents in the median line a verti- cal projection, which gives attachment to some of the longitudi- nal fibres of the oesophagus, and on each side a depression for the posterior crico-arytenoid muscle. Its internal surface is covered by the laryngeal mucous mem- brane. Its lower border is perfectly circular and slightly waved, and is connected by a membrane with the first ring of the trachea ; sometimes it is even united with it, and can only be distinguished by its greater thickness. Its upper border is not exactly circular, but is oblong from before backward, as if the ring had been flattened laterally. It is cut very obUquely forward and downward, or, rather, it is deeply notched in front, where it is concave, and gives attachment to the crico-thyroid membrane in the median line, and laterally by its inner lip to & fibrous membrane, which is continuous veith the inferior vocal cord, and in the rest of its thick- ness with the lateral crico-arytenoid muscle. Behind, and on each side, is an oblong, articular facette, the arytenoid facettes (h h,fig. 173), which are directed outward and upward, and articulate with the arytenoid carti- lages. Between these two facettes, the upper border of the cricoid is horizontal, and very slightly notched, and gives attachment to the arytenoid muscle. The upper bor- der of the cricoid cartilage is, therefore, horizontal behind, oblique at the sides, and hor- izontal and slightly concave in front. The arytenoid facettes are situated upon the ob- lique portion. The Thyroid Cartilage. — The thyroid or scutiform cartilage (t,figs. 173 to 177), so na- med because it has been compared to a shield (i^upcdf, a shield),* occupies the upper and fore part of the larynx. It is formed by two quadrilateral plates (or alee), united at an acute angle in the median line, and embracing the cricoid cartilage behind. Its aia- * The name may also have been derived from its use. 424 SPLANCHNOLOGY. teriar or cutaneous surface presents in the median line an angular projection (below c, fig. 173), more marked and deeply notched above, and completely effaced below; much less distinct in the female, in whom it forms only a rounded surface, than in the male, in whom it has received the special appellation of the pomum Adami. This angular pro- jection does not appear until puberty ; it presents certain individual varieties, but these do not appear to me to have any relation with the qualities of the voice. On each side the surface {t, Jigs. 173, 174) is smooth and quadrilateral, and has two tubercles behind ; one of which is superior (b), and the other inferior {d). The latter, or larger, is prolonged upon the inferior border of the cartilage. The two tubercles are united by an aponeurotic arch, but there is no oblique intermediate line, as has been gen- erally alfirmed. These tubercles, and the imaginary line between them, separate the anterior three fourths of the surface, which are covered by the thyro-hyoid muscle, from the posterior fourth, which is covered by the inferior constrictor of the pharynx and the sterno-thyroid muscle. The tubercles give attachment to these three muscles. The posterior surface {fig. 175) presents, in the median line, a retreating angle, which gives attachment to the thyro-arytenoid ligaments, or vocal cords, and to the thyro-ary- tenoid muscles. This angle is sometimes so acute that the cartilage has the appear- ance of having been subjected to strong lateral pressure. On each side {t t) the posterior surface projects beyond the cricoid cartilage, and forms part of the lateral groove of the larynx. It is lined by the pharyngeal mucous membrane, and corresponds in part to the thyro- and crico-arytenoid muscles. Its upper border is horizontal and sinuous, and gives attachment to the hyo-thyroid membrane in its whole extent. It presents a notch (e, fig. 173) in the median line, which is shallower, but broader and more rounded in the female than in the male. On the sides there is a small prominence, which forms a continuation of the superior tubercle, and is often wanting. More posteriorly, we find on each side a slight notch, bounded by cer- tain processes called the great or superior comua {s, figs. 173, 174) of the thyroid cartilage. The lower border is sinuous, and shorter than the upper, and hence the pyramidal shape of the larynx. It presents a slight median projection, to which the crico-thyroid liga- ment is attached ; in the rest of its extent, it gives insertion to the crico-thyroid muscle, and presents a rough eminence, which forms a continuation of the inferior tubercle ; and more posteriorly, on each side, a slight notch, bounded by the lesser or inferior comua {I, Jigs. 173, 175) of the thyroid cartilage. Its posterior borders (s r, fig. 174) are slightly sinuous, give attachment to the stylo- pharyngei and palato-pharyngei, and rest upon the vertebral column. As the thyroid cartilage projects behind the upper portion of the larynx, it may be regarded as protect- ing the larynx by its posterior borders resting upon the vertebral column. The comua of the thyroid cartilage are four in number, two superior and two inferior, and appear to be prolongations of the posterior borders of the cartilage. They are all round- ed, and are bent inward and backward ; the upper or great comua (s) are generally the larger, and are united by ligaments to the os hyoides ; the lower or lesser comua (J) are usually smaller, and articulate with the cricoid cartilage. The Arytenoid Cartilages. — The arytenoid cartilages {a, figs. 173, 175 to 177) are two in number,* are situated at the upper and back part of the larynx, and have a pyramidal and triangular form ; they are directed vertically, and bent backward like the lip of an ewer, whence their name {dptraiua, a funnel). Their posterior surface (fig. 175) is trian- gular, broad, and concave, and receives the arytenoid muscle ; their internal surface is fined by the mucous membrane of the larynx ; their anterior surface (fig. 173) is convex, narrow, rough, and furrowed, and corresponds to the series of glands called tlie aryte- noid glands, and to the superior vocal cord ; their base is very deeply notched, articulates with the cricoid cartilage, and is terminated by two processes : one posterior and exter- nal (/), which gives attachment to the lateral and posterior crico-arytenoid muscles ; the other is anterior (a), pyramidal, and more or less elongated, has the inferior vocal cord attached to its point, and it forms a fourth, or almost a third, of the antero-posterior di- ameter of the glottis ; their apex is surmounted, or rather formed, by two very small and delicate cartilaginous nodules (g), which are bent inward and backward, and iiicurvated so that they almost touch ; they are called the cornicula. They were very correctly descri- bed by Santorini, under the name of the sixth and seventh cartilages of the larynx. They are now generally known as the tubercles of Santorini, the capitula or cornicula laryngis. They appear to me constantly to exist, sometimes closely united with the arytenoid carti- lages, and not moving at all upon them, and sometimes perfectly distinct and very movable. The Epiglottis. — The epiglottis (em, upon, and yluTrlg, the glottis, i,figs. 174 to 178), or lingula, forming a movable and highly elastic valve, is a fibro-cartilaginous lamina, situated (i, fig. 140) behind the base of the tongue, and in front of the superior opening of the larynx, not upon the glottis, as its name would seem to indicate. * It was for a long time believed that there existed only one arytenoid cartilage, because the larynx was al- ways examined when covered by its membranes ; so that the word arytenoid, in the works of Galen, is always applied to the two united, Galen only admitted three cartilages in the larynx— the thyroid, the cricoid, and the arytenoid, . ^^r THE LARYNX. 42^ Its direction is vertical, excepting at the moment of deglutition, when it becomes hori- zontal, so as to protect the opening of the larynx like a lid {laryngis operculum). Its tri- angular shape has been well compared to that of a leaf of purslaine. It must be separa- ted from the neighbouring parts to be properly studied. It varies much in size in different subjects, but always appears to me to bear some re- lation to the dimensions of the upper orifice of the larynx, beyond which it almost al- ways projects when depressed. Its anterior or lingual surface presents a free and an adherent portion. The free por- tion surmounts the base of the tongue ; it may be felt by the finger, and even seen by strongly depressing the tongue.* Three folds of mucous membrane, one in the middle and one on each side, pass from the epiglottis to the base of the tongue. The adherent portion corresponds in front with the base of the tongue, the os hyoides, and the thyroid cartilage. In order to expose it, it is necessary to have recourse to dis- section. We then find a median glosso-epiglottid ligament, which is very strong, and com- posed of yellow elastic tissue, and which, I beheve, assists in drawing back the depress- ed epiglottis ; its place is occupied by muscular fibres in the larger animals ; also a hyo- epiglottid ligament, extending from the epiglottis to the posterior surface of the os hy- oides ; and, lastly, beneath this ligament, a yellow fatty tissue, improperly called the epiglottid gland, occupying the interval between the epiglottis and the concavity of the thryoid cartilage. Moreover, the anterior surface of the epiglottis, examined in the vertical direction, is concave above, convex in the middle, and again concave below ; it is convex in the trans- verse direction. The posterior or laryngeal surface {figs. 175, 178), the curvatures of which are the reverse of those on the anterior surface, is free in the whole of its extent, and covered by the laryngeal mucous membrane. Circumference. — Its upper margin, or the base of the triangle which it represents, is free, bent forward, slightly notched, and continuous, by two rounded angles, with its lat- eral margins, from each of which proceed two folds, viz., the aryteno-epiglottid {h,fig. 178), extending from the epiglottis to the arytenoid cartilage, and enclosing a ligament (b,fig. 176), and the pharyngeo-epiglottid, situated anterior to the preceding, passing al- most transversely outward, and lost upon the sides of the pharynx. The epiglottis terminates below in a sort of pedicle, which is extremely slender, and is fixed {fig. 176) into the retreating angle of the thyroid cartilage, immediately above the attachment of the vocal cords. This attachment is effected by means of a ligament, called the thyro-epiglottid. The epiglottis is remarkable for the great number of perforations found in it, which give it an appearance very much resembling that of the leaves of several of the lauracece. In these foramina we find small glands, which, for the most part, open on the laryngeal surface of the epiglottis. The so-called epiglottid gland has no relation with these orifices. It is also remarkable for its flexibility and elasticity ; on account of which it is classed by Bichat among the fibro-cartilages, a sort of tissue which we have stated does not ex- ist. Its yellow colour gives it an appearance like the yellow elastic tissue. It is brittle, and may be crushed between the fingers ; this depends partly upon the nature of its tis- sue, and partly upon the numerous foramina with which it is perforated, and which ne- cessarily diminish its strength. The Artictdations and Ligaments of the Larynx. The articulations of the larynx may be divided into the extrinsic and the intrinsic. The Extrinsic Articulations. — The thyro-hyoid articulation consists of three ligaments, which unite the thyroid cartilage to the os hyoides. The middle jy.. 174. thyro-hyoid ligament {n, fig. 174) is a loose yellowish membrane, ex- tending from the upper border of the thyroid cartilage {t) to the os hyoides (m). Its vertical dimensions are much greater at the sides than in the middle ; and, therefore, the comua of the os hyoides can be raised higher than its body, and hence the sides of the tongue can be elevated so as to form a groove, along which the food glides. This membrane is thick in the middle, and thin, and, as it were, cellular on each side. Relations. — It is sub-cutaneous in the middle, but is covered on each side by the thyro-hyoid muscle. It corresponds behind with the epiglottis, from which it is separated by some adipose tissue, and with the mucous membrane covering the posterior surface of the tongue. It is attached to the posterior lip of the upper edge of the OS hyoides, not to the lower edge, as is frequently asserted. It therefore passes behind the os hyoides. The lateral thyro-hyoid ligaments (0) may be considered as the margins of the thyro- hyoid membrane. They are small cords, extending from the great comua of the thyroid * I attach groat importance to inspection of the epiglottis in diseases of the larynx. Hb H ^88 8PLANCHN0L0GT. cartflage to the tubercular extremities of the great comua of the os hyoidea. We often find a cartilaginous or bony nodule in these ligaments. There is a very distinct synovial capsule between the posterior surface of the body of the OS hyoides and the upper part of the thyroid cartilage. Its presence attests the fre- quent movements which take place between these parts, and during which the middle and upper part of the cartilage is placed behind the os hyoides. The Tracheo-cricoid Articulation. — The first ring of the trachea is connected with the lower border of the cricoid cartilage by a fibrous membrane of the same nature as that between the rings of the trachea. A small vertical fibrous cord is added to it in the median line in front. This membrane permits some movements between the cricoid cartilage and the first ring of the trachea, and in these the sides of the ring are buried behind the cricoid cartilage. The intrinsic articulations are the crico-thyroid and the crico-arytenoid. I need merely remind the reader of the articulation between the arytenoid cartilages and the comicula larjTigis. Tlie Crico-thyroid Articulations. — ^These are arthrodial. Each of the lesser comua of the thyroid cartilage terminate in a plane surface, directed downward and inward, which rests upon a similar plane surface {m,fig. 177) on the cricoid cartilage, directed upward and outward. An orbicular or capsular ligament (r,figs. 174, 175), composed of shining, fasciculated, and parallel fibres, surrounds the articulation, which is provided with a synovial membrane. The posterior fasciculus is remarkable for its length and shape, and extends nearly to the crico-arytenoid articulation. In some subjects the orbicular ligament is very loose, in others the articulation is exceedingly close. The movements are limited to simple gliding, combined with a forward and backward movement of the th3Toid cartilage. The direction of the facettes upon the cricoid car- tilage renders them fitted to support the thyroid. The Crico-thyroid Membrane, or Middle Crico-thyroid Ligament. — Besides the preceding articulations, the lower border of the thyroid cartilage is connected with the upper border of the cricoid by a thick triangular membrane, the pyramidal or conoid ligament (v, Jig. 174), which is attached in the median line to the lower border of the thyroid cartilage, and the base of which is fixed to the upper border of the cricoid cartilage. This mem- brane is fibrous, thick, very strong, perforated with foramina for vessels, and is yellow and elastic. The Lateral Crico-thyroid Ligament. — This ligament {d,fig. 176) can be well seen only from the inner surface of the larjoix. It consists of very strong fibres, which arise from the inner lip of the upper border of the cricoid cartilage, in front of the crico-ary- tenoid articulation, and pass horizontally inward to the retreating angle of the thyroid cartilage, below the insertion of the inferior vocal cord (r). This ligament, which is very strong, appears to be continuous above with the inferior vocal cord. It is covered on the inside by the mucous membrane of the larynx, and it corresponds on the outside {d, fig. 177) to the thyro- (e) and crico-arytenoid (/) muscles, which separate it from the thyroid cartilage. The Crico-arytenotd Articulations. — These articulations are effected by mutual reception. The articular swr/ace, upon the cricoid cartilage, is an eUiptical facette {h,fig. 173), di- rected obliquely downward and forward, and oblong and slightly concave in the same di- rection. The base of the arytenoid cartilage presents an oblong articular facette, deeply concave from without inward, i. c, in an opposite direction to the former, which it accu- rately receives. Means of Union. — Properly speaking, there is only one ligsunent, the internal and poste- j^. ,.- rior (e, fig. 175). It arises from the cricoid cartilage, and is insert- ^' ' • ed in a radiated manner into the inner and back part of the base of the arytenoid cartilage, and to the inner side of its anterior process, behind the inferior vocal cord. This ligament is very strong, but yet suiEciently loose to allow of certain extensive movements. There is also a very loose synovial capsule, which can be easily demonstrated. The movements of this articulation, like those of all similar joints, take place in every direction ; but the movements inward and out- ward are much more extensive than those which are performed forward and backward. On account of the mode of insertion of its muscles, the arytenoid cartilage is not moved in a direct line, but undergoes a partial rotatory movement, the centre of which is in the articulation. In the movement, which is oblique, on account of the obliquity of the articular surfaces, the apex of the arytenoid cartilage is carried either outward and backward or inward and for- ward. These motions should be studied with the greater care, because they afford an ex- planation of the changes which take place in the glottis during the production of the voice. The Aryteno-epiglottid Ligament. — This ligament {b, figs. 176, 177) is constituted by some radiated ligamentous fibres contained within the aryteno-epiglottid fold of mucous THE LARYNX. 427 membrane, and which pass from the anterior surface of the arytenoid cartilage to the corresponding margin of the epiglottis. In some animals, this ligament is replaced by muscular fibres. The Thyro-arytenoid Ligaments, or Chorda Vocales. — Although there is no immediate relation between the thyroid and the arytenoid cartilages, they are united by four very important ligaments, named the chorda vocales, which require a special description. The chorda vocales are also called the vocal bands, the ligaments of Ferrein, or the thy- ro-arytenoid ligaments, because tliey have a ligamentous appearance, and extend from the retreating angle of the thyroid cartilage to the arytenoid cartilages. There are two vocal cords on each side, a superior (s, Jigs. 176, 178) and an inferior (r) , the space between them is called the ventricle of the larynx (v), and the interval between the cords of the right and left sides is called the glottis {o,Jig. 178).* I shall speak of these parts again presently. The inferior vocal cord (r, Jig. 176) is much stronger than the superior, and has the form of a rounded fibrous cord, stretched horizontally from the retreating y. j^g angle of the thjToid cartilage to the anterior process of the arytenoid cartilage. It is free in all directions, excepting on the outside, where it is in contact with the thyro-arytenoid muscle. Its free portion is covered by the mucous membrane of the larynx, which adheres inti- mately to it, and is so thin that the white colour of the cord can be seen through it. This vocal cord is thinner than it appears at first sight, the projection which it forms being, in a great measure, due to the thyro-arytenoid muscle. Its structure is entirely ligamentous, and consists of parallel fibres, running from before backward, and not at all elastic, t It is continuous below with the lateral thjrro-cricoid ligament (d). The superior vocal cord (s) is smaller, and situated farther from the axis of the larynx than the inferior one (see Jig. 178), and extends from the middle of the retreating angle of the thyroid cartilage to the middle of the anterior surface of the arytenoid cartilage : like the inferior cord, it has a fasciculated and fibrous appearance ; but the fasciculi are few in number, and are inter- mixed with a series of glandular masses. The superior vocal cord can only be distin- guished from the rest of the parietes of the laiynx from the reflection of the mucous membrane below it, so as to form the ventricle. It is continuous with the aryteno-epi- glottid ligament (Jb, Jig. 176) above, without any line of demarcation. Muscles of the Larynx. These are divided into the extrinsic and the intrinsic : the former, which move the en- tire larynx, have been already described, viz., the sterno-hyoid, omo-hyoid, stemo-th)Toid, and thyro-hyoid ; to which we might add all the muscles of the supra-hyoid region, and those muscles of the pharynx which have attachments to the cricoid and thyroid cartilages. The intrinsic muscles are nine in number, viz., four pairs and one single muscle. Those which exist in pairs are the crico-thyroidei, the crico-arytenoidei postici, the cri- co-arytenoidei laterales, and the thyro-arytenoidei. The single muscle is the arjrtenoideus. The Crico-thyroideus. . Dissection. — This muscle is completely exposed by separating the larynx from the muscles by which it is covered. In order to gain a good view of the deep portion of the muscle, the lower part of the thyroid cartilage must be removed. The crico-thyroideus {a, figs. 147, 170) is a short, thick, triangular muscle, situated on the anterior part of the larynx, on each side of the crico-thyroid membrane, and divided into two distinct bundles. It is attached below to the cricoid cartilage on each side of the median line, to the whole of the anterior surface, and even to part of the lower bor- der of the cartilage. From these points the fleshy fibres radiate in different directions : the internal fibres pass somewhat obliquely upward and outward ; the middle ones very obliquely, and the lower fibres horizontally outward, to the lower border of the thyroid cartilage (excepting to its middle portion), and to the lower margin of the corresponding lesser cornu. The greatest number of fibres are inserted into the posterior surface of the thyroid cartilage ; some of them are continuous with the inferior constrictor of the pharynx (w, Jig. 147). It is covered by the sterno-thyroid muscle and the thyroid gland, and it covers the lat- eral crico-arytenoid and the thyro-arytenoid muscles. The inner borders of the crico- thyroid muscles are separated from each other by a triangular space, broad above and narrow below, in which the crico-thyroid membrane is visible. * [In consequence of the voice being essentially produced opposite the inferior cords, they are termed the true vocal cords ; the superior being- called the false vocal cords.] t [The inferior vocal cords are certainly composed of elastic tissue, so, also, are the thyro-hyoid and crico- thyroid ligaments ; and, according to M. I.auth (M'm. de VAcad. Roy. de Med., 1835), the lateral crico-thyroid membranes, the superior vocal cords, and the aryteno-epiglottid ligaments are also composed of this tissue, which, he says, exists even in the thyro-epiglottid, hyo-epiglottid, and glosso-epiglottid ligaments.] 428 SPLANCHNOLOGY. Their action is not yet well determined. By taking theif'feed'pmnfuponthe' cricoid cartilage, it appears to me that they would move the thyroid cartilage in such a way as to increase the antero-posterior diameter of the glottis, and thus act as tensors of the vocal cords. The Crico-arytenoideus Posticus. Dissection. — This muscle is exposed by removing the mucous membrane from the posterior surface of the larynx. It is a triangular muscle {g,figs. 171, 177), situated at the back of the cricoid carti- lage. Its fibres arise from the lateral depression, which we have described on tlie pos- terior surface of the cartilage, and pass in different directions ; the upper fibres are the shortest, and are almost horizontal ; the middle are oblique, and the lower are nearly vertical ; they £dl converge towards the posterior and external process on the base of the arytenoid cartilage, behind the crico-arytenoideus lateralis. Relations. — It is covered by the mucous membrane of the pharynx, to which it is very loosely united, and it covers the cricoid cartilage. Action. — It is a dilator of the glottis. It carries the base of the arytenoid cartilage backward, outward, and downward, and thus renders the inferior vocal cord tense The Crico-arytenoideus Lateralis. Fig. 177. Dissection. — Remove with care one of the lateral halves of the thyroid cartilage (as in fig. 177). It is impossible to separate this muscle from the thyro-arytenoideus. This is an oblong muscle (/), situated deeply under the thyroid cartilage. Its fibres arise from the side of the upper border of the cricoid cartilage, in front of the crico-arytenoid articulation ; from this point they proceed obliquely upward and backward, to be insert ed into the posterior and external process of the arytenoid cartilage, by a tendon common to them, and to the thyro-arytenoideus. It is covered by the thyroid cartilage and by the crico-thyroid muscle, and it covers the lateral crico-thyroid membrane (d). The Thyro-arytenoideus. Dissection. — The same as for the preceding. This muscle may be dissected from the interior of the larynx, by removing the vocal cords. I describe the thyro-arytenoideus and the crico-arytenoideus lateralis separately, merely in accordance with custom, for in no instance, not even in large animals, such as the ox, have I ever been able to separate them completely. They have the same arytenoid insertion ; their fibres are situated upon the same plane, without any line of demarcation, and they fulfil the same uses. We naight, therefore, imite them under the name of the thyro-crico-arytenoideus. The thyro-arytenoideus (e) is a broad muscle, very thin above and very thick be- low. It arises on each side from about the lower two thirds of the retreating angle of the thyroid cartilage. The greater number of its fibres arise from the lower part of the angle, and form a very thick fasciculus. From these points they pass horizontally back- ward and outward, and terminate in the following manner : The thick fasciculus above mentioned is inserted into the outer surface of the anterior process of the arytenoid car- tilage, and into a depression on the outer side of the base of that cartilage, between the two processes. The upper fibres are attached to the outer border of the arytenoid car- tilage. In the larger animals, the upper fibres of the muscle evidently proceed to the epiglottis, and form the thyro-epiglottideus of some authors. Relations. — On the outside it corresponds with the thyroid cartilage, from which it is separated by loose and sometimes adipose cellular tissue ; on the inside it is in contact with the vocal cords and the ventricle of the larynx. The thickest part of the muscle corresponds with the inferior vocal cord, and is almost the only cause of its projecting into the interior of the larynx. This fasciculus may even be considered as contained within the substance of the inferior vocal cord, and the two structures are so closely adherent that great care is required to separate them. Many anatomists, indeed, have thought that the fibres of the thyro-arytenoideus terminate in the vocal cord, which they therefore regarded as the tendon of the muscle ; but the cord and muscle may always be completely separated. Action. — It carries the arytenoid cartilage forward, and would thus seem to relax the inferior vocal cord, as Haller believed : " Cartilagines guttales (the arytenoid) antrosum ducunt, glottidem dilatant, ligamentorum glottidis tensionem minuunt." {Elemcnta Physiol., t. iii., liv. ix., p. 387.) But if we consider the mechanism of the crico-arytenoid articula- tions, and the mode of insertion of the thyro-arytenoid muscles into the outer side of the bases of the arytenoid cartilages, we shall perceive that, at the same time that these cartilages are carried forward, they undergo a partial rotatory movement, by which their anterior processes are turned inward. The ligaments of the glottis are, therefore, ren- THE LARYNX. 429 dered tense, and approximated towards each other. This movement may be carried to such an extent that the anterior processes may touch, and the antero-posterior diameter of the glottis be diminished accordingly.* The thyro-arytenoideus is, then, both a tensor and a constrictor of the glottis. This, moreover, was the opinion of both Cowper and Albinus, but Hedler attempted to re- fute it.t The sudden action of the thyro-arytenoid muscle, pressing upon the ventricle of the larynx, may expel any mucus collected within it. The Arytenoideus. Dissection. — Remove the mucous membrane and glandular masses which cover it be- hind. Detach it along one of its borders, so as to be enabled to examine its thickness. The arytenoideus {a, fig. 171) is a single, short, thick, trapezoid muscle, situated be- hind the arytenoid cartilages, and filling up the concavity on their posterior surfaces, as well as the interval between them. It arises from the whole length of the outer border of the right arytenoid cartilage, and is inserted into the corresponding part of the left. Some of the fibres arise from the upper border of the cricoid cartilage. The fibres have a triple direction, and form three layers, which have been regarded as so many distinct muscles. The two more superficial layers are oblique, and cross each other, one passing from the base of the right arytenoid cartilage to the apex of the left, and the other following the opposite direction ; they constitute the arytenoideus ohliquus of Albinus : both of these layers are thin. The third and deepest layer is very thick ; it is composed of transverse fibres, and forms the arytenoideus transversus of Albinus. None of the fibres reach the comicula. Under the name of the aryteno-epiglottideus, muscular fibres have been described, extending from the arytenoid muscle to the mar- gins of the epiglottis. Some fibres of the arytenoideus are also said to be continuous with the thyro-arytenoideus. Relations. — Behind, with the mucous membrane and some glandular masses, which ad- here to the muscle by means of loose cellular tissue ; in front it is in relation with the posterior surface of the arytenoid cartilages, and in the interval between them with a thin fibrous membrane, extending from the upper border of the cricoid cartilage to the whole extent of the inner borders of the arytenoid cartilages. Action. — It would appear, at first sight, that this muscle must forcibly approximate the two arytenoid cartilages, and therefore constrict the glottis ;t but if we remember that it is attached to the outer borders of these cartilages, we shall understand that, besides drawing them together, it must produce in them such a movement as will carry their an- terior processes outward, and stretch the vocal cords, but, at the same time, separate them from each other. And if we call to mind that the th3TO-arytenoideus occasions an ex- actly opposite movement, it will be understood that the simultaneous action of the two muscles must produce tension of the cords, and, at the same time, fix the processes. Having thus obtained a knowledge of the cartilages of the larynx, the articulations by which they are united, and the muscles which move them, we shall now proceed to give a general description of this organ. The Larynx in general. The larynx, the general position of which has been already described, presents certain diflferences in its dimensions, depending either upon the individual, upon sex, or upon age. These differences affect both the whole of the larynx and its constituent parts. Thus, the larynx of the female may always be distinguished from that of the male by being smaller, i. e., about two thirds the size of the male larynx ; and by the angles and pro- cesses of its cartilages being less prominent, and their depressions less marked. These differences are connected with the characters of the voice, and affect principally the di- mensions of the glottis. The individual differences in the size of the larynx have not been thoroughly examined. The differences depending on age will be noticed when speaking of its development. The larynx presents for our consideration an external and an internal surface. The External Surface of the Larynx — Anterior Region {fig. 170). — In the median line we observe a vertical ridge, formed by the angle of the thyroid cartilage ; beneath this the crico-thyroid membrane, and still lower the convexity of the cricoid cartilage. On the sides we find the oblique leuninae of the thyroid cartilage, a portion of the cri- coid covered by the crico-thyroid muscle, and the thyro-cricoid articulation. Sub-cutaneous in the median line, where it is only separated from the skin by the linea alba of the neck, the external surface of the larynx is covered on each side by the mus- cles of the sub-hyoid region, the inferior constrictor of the pharynx, and the thyroid gland. * [The effect of this will be, as stated by Haller, to relax the vocal cords, which is considered by the latest observers to be the action of these muscles.] ■t Loc. cit. " Cum magui viri glottidem dixerint ab istis musculis arctari, experimento facto diducere didici. Neque potest ille ad latus cartilaginis arytsenoidse musculus terminari xjuin earn rimam diducat." t [When acting together with the lateral crico-thyroid muscles, this is certainly their action.] 430 SPLANCHNOLOGY. The superficial position of the surface enables us to examine its different parts through the integuments, and renders it liable to wounds. Its still greater proximity to the skin in the median line has suggested the operation of laiyngotomy. Posterior Region {figs. 141, 171). — In the median line we observe a prominence like a small barrel, on either side of which the thyroid cartilage projects. This prominence is formed by the back of the cricoid, and by the arytenoid cartilages, the expanded portion corresponding with the bases of the latter, which are covered by folds of a pale mucous membrane. Under this membrane we find, proceeding from above downward, the ary- tenoideus muscle, the vertical ridge of the cricoid cartilage, the crico-arytenoidei posti- ci, and the crico-arytenoid articulations. On each side of the barrel-shaped prominence is a deep angular groove, formed by the meeting of two flat surfaces, which are separated above, but approximated below ; along these grooves it is supposed that liquids flow during deglutition. The external wall of each groove is formed by the posterior surface of the thyroid cartilage, the os hyoides, and the thyro-hyoid membrane. The internal wall is formed by the upper and lateral part of the barrel-shaped prominence. The grooves are lined by a closely-adherent nmcous membrane ; and it should be observed, that they exist only on a level with the aryte- noid cartilages, and, consequently, in this region alone is the larynx protected by the thyroid cartSage, the posterior borders of which rest upon the vertebral column. The back of the cricoid cartilage is on a level with the posterior borders of the thyroid {fig. 174), and, like them, rests upon the vertebral colunm. The Internal Surface of the Larynx. — The internal surface of the larynx does not cor- respond, either in shape or dimensions, with its outer surface ; and this depends princi- pally on the fact that the retreating angle of the th)T:oid is the only part of that cartilage which enters into the formation of the laryngeal cavity, the lateral laminae being alto- gether unconcerned in it. Cylindrical below, where it is formed by the cricoid cartilage, the cavity of the larynx is prismatic and triangular above, where it is constituted by the epiglottis in front, the arytenoid cartilages and the arjrtenoid muscle behind, and on the sides by the two mu- cous folds which extend from the margins of the epiglottis to the arytenoid cartilages. The dimensions of the lower of these two portions of the laryngeal cavity undergo no change, always remaining the same as those of the cricoid cartilage ; while the upper, on the contrary, which is broadest in front, varies much in size, in consequence of the mobility of the epiglottis and the arytenoid cartilages. Between these two portions, and about the middle of the larynx, a fissure exists, which is narrower than the rest of the cavity, and oblong from before backward ; this is the glottis, or vocal apparatus, properly so called. It can be seen without any dissection by looking down into the larynx {fig. 178), and requires a very particular description. The Glottis, or Vocal Apparatus. — The glottis (yXwrrif, from y^uaaT), the tongue), fre- quently confounded with the superior orifice of the larynx,* is a trian- gular opening or fissure {o,fig. 178) {rima), elongated from before backward, and included between the vocal cords of the right and left sides. It represents two isosceles triangles, placed one above the other, and having perfectly equal borders, the base of each being directed backward, and its apex forward. The lower isosceles tri- angle is formed by the inferior vocal cords (r), and the upper one by the superior vocal cords (s). The inferior vocal cords are situated nearer to the axis of the larynx than the superior, so that a vertical plane let fall from the latter would leave the inferior vocal cords on its inner side. Many authors limit the term glottis to the lower tri- angle. This view is supported by the absence of the superior vo- cal cords in a great number of animals, the ox in particular. Dimensions of the Glottis. — The glottis is the narrowest part of the larynx, and hence the danger from the introduction of a foreign body into it, and from the formation of false membranes in this situation. The only action of the intrinsic muscles of the larynx is to dilate or contract the opening of the glottis. We have seen that, with the exception of the crico-thyroidei, they are all, in some measure, collected round the crico-arytenoid articulation, the movements of which determine the dimensions of the glottis. The individual differences which constitute the tenour, baritone, or bass voices in sing- ing, depend upon the size of the glottis ; to which, also, must be attributed the difference between the male and female voice, and the change produced in its tone at the time of puberty. A deep voice coincides with a large glottis, and a shrill voice with a small one. In the adult male the antero-posterior diameter of the glottis is from ten to eleven lines, in the female it is only eight lines ; in the male, the greatest transverse diameter is from three to four lines ; in the female, from two to three lines. t * This error is, perhaps, to be attributed to the use of the word epiglottis, so much do words influence our ideas. It was committed even in Haller's time, who says, " Etiam hoc (laryngis) ostktm non bene pro glottide sumilur." t Tliese measurements are taken at the level of the inferior vocal cords ; the transverse diameter is rather l(!i:L'er opposite the superior vocal cords THE LARYNX. 431 From these dimensions, it may be understood how a Louis d'or might pass edgewise through the glottis, and thus fall into the trachea. In a case of this kind, most of those ■who were called in consultation rejected the idea of the presence of the coin in the wind- pipe, because, said they, the glottis cannot admit it. The patient died in about a year, and the Louis d'or was found in the trachea. Ventricle of the Larynx. — Between the superior and inferior vocal cords of each siile there is a cavity, called the ventricle or simis of the larynx {v,figs. 176, 178) ; it is oblong from before backward, and of the same length as the cords ; its depth is determined by the interval separating the cords from the thjToid cartilage, or, rather, from the thyro- arytenoid muscle, which forms the bottom of the corresponding ventricle. The opening of the ventricle is somewhat narrower than the bottom, is elliptical in its longest diame- ter, and has admitted the introduction of a foreign body. To each ventricle there is a supplementary cavity, which is accurately described and figured in the works of Mor- gagni.* This cavity resembles in shape a Phrygian cap ; it has a broad base, opening into the ventricle, and a narrow apex ; it is found at the anterior part of the ventricle, and is prolonged on the outer side of the superior vocal cord, between it and the thyroid cartilage, upon the side of the epiglottis. Its dimensions vary much. In one case its ver- tical diameter was six lines, and it was divided into two parts by a transverse band. The Circumferences of the Larynx. — The superior circumference of the larynx {fg. 178) is much wider than the inferior, and presents the following objects : the superior angu- lar border of the thyroid cartilage, and the great cornua, in which it terminates ; behind the thjToid cartilage, the epiglottis (i) ; and between the cartilage and the epiglottis, a small triangular space, filled by a compact fatty mass, which has been incorrectly descri- bed as the epiglottid gland. I have already said that this fatty mass is bounded above by a fibrous membrane, extending from the epiglottis to the posterior surface of the os hyoides. Behind the epiglottis, we find the upper orifice of the larynx, which must not be con- founded with the glottis ; it slopes obliquely from before backward and from above down- ward, having the form of a triangle, with its base directed forward and its apex back- ward, consequently in the opposite direction to the glottis. This orifice is formed in front by the free margin of the epiglottis, which is slightly notched ; on each side, by the upper part of the lateral margin of the epiglottis, and by the free edge of the aryteno- epiglottid fold (b) ; and behind, by the cornicula laryngis, and by the summits of the ary- tenoid cartilages (a), and the deep notch between them. The superior orifice is the widest part of the larynx, and admits foreign bodies which cannot pass through its lower portion. The epiglottis, when depressed, generally cov- ers it completely, and may even overlap it at the sides. The inferior circumference of the larynx is perfectly circular, is formed by the cricoid cartilage, and is continuous with the trachea. The Mucous Membrane and Glands of the Larynx. — The mucous membrane of the la- rynx is a continuation of that of the mouth and pharynx. The larynx presents the only example in the body of an organ, part of whose external surface, namely, the posterior, is covered with mucous membrane ; and this depends upon the circiunstance of its form- ing part of the parietes of the pharynx. The mucous membrane is disposed in the following manner : From the base of the tongue it i& reflected upon the anterior surface of the epiglottis, forming the three glos- so-epiglottid folds already described, one in the middle and one on each side ; it adheres pretty closely to the epiglottis, is reflected over its free margin, covers its posterior s«r- face, and penetrates into the larynx : on each side it passes from the epiglottis to the •arytenoid cartilages, and becomes continuous with the pharyngeal mucous membrane, which covers the back of the larynx. At the superior orifice of the larynx, it is reflect- ed upon itself, to form the aryteno-epiglottid folds, which constitute the sides of the su- pra-glottid region of the larynx ; it then covers the superior vocal cord, and lines the ven- tricle, sending a prolongation into its supplementary cavity. In the ventricle it is re- markable for its slight adhesion to the subjacent parts. It is reflected from the ventri- cle upon the inferior vocal cord ; there, as well as opposite the superior cord, it is so thin that it does not conceal the pearly appearance of the ligament beneath, to which it adheres so closely that it is difficult to separate them. Lastly, it covers the internal sur- face of the cricoid cartilage, and the middle and lateral crico-th)Toid membranes. The laryngeal mucous membrane is characterized by its tenuity, its adhesion to the parts heneath it, and by its pale pink colour.! It is perforated by the openings of a num- ber of mucous glands. Its extreme sensibility, especially at the upper orifice and in the * I first saw this cavity in a patient affected with laryngeal phthisis, in whom it was very much developed. I then examined the larynx in other individuals, and found it to be constant. I did not then know that Mor gagni had pointed it out and figured it (Advers. i., Epist. Anat., viii.). t [The epithelium of the laryngeal mucous membrane is, in the greater part of its extent, columnar and cil iated. The cilia urge the secretion upward ; according to Dr. Henle, they extend higher up in front than on each side and behind ; on the sides, for example, as high as the border of the superior vocal cords, or about two lines above them, and in front upon the posterior surface of the epiglottis, as high as its base or widest por- tion. Above these points the epithelium gradually assumes the laminated form, like that in the mouth and pharynx.] 432 SPLANCHNOLOGY. supra-glottid portion of the larynx, is well known.* The aryteno-epiglottid folds, which include the ligaments of the same name, and some muscular fibres in the larger animals, aie remarkable for the great quantity of very loose cellular tissue which they contain : this fact explains their liability to a serous infiltration, called oedema of the glottis, which proves rapidly fatal. The Glands of the Larynx. — The glands of the larynx are the epiglottid and the aryte- noid. The thyroid gland, or body, cannot be considered as belonging to the larynx ; if it belongs to any organ, it must be to the trachea. The Epiglottid Glands. — The name of epiglottid glands is generally given to the fatty mass already described as being situated between the thyroid cartilage and the epiglot- tis ; and it has even been asserted that it opens by special ducts on the posterior surface of the epiglottis. But there is no other epiglottid gland besides those situated in the sub- stance of the epiglottis, which is perforated with innumerable holes for their reception : these small glands are so numerous, that Morgagni (^Advers., i., 2 ; v., 68) regarded them as forming a single gland ; they all open upon the laryngeal surface of the epiglottis by very distuict orifices, from which a considerable quantity of mucus can be pressed. The Arytenoid Glands. — These were well described by Morgagni, who very properly considered them as forming a single glandular mass, situated in the substance of the ary- teno-epiglottid fold. They are arranged in two lines, united at an angle, like the letter L;t the vertical line runs along the anterior surface of the arytenoid cartilage and its comiculum, and produces a slight prominence, perfectly distinct from that made by the cartilages ; the liorizontal line is less prominent, and is situated in the superior vocal cord. The arytenoid glands open separately upon the internal surface of the larynx. Vessels and Nerves. — The arteries are derived from the superior thyroid, a branch of the external carotid, and from the inferior thyroid, a branch of the subclavian. The veins enter the corresponding venous trunks. The lymphatic vessels, which are little known, terminate principally in the glands of the supra-hyoid region, if we may judge from the frequency of their inflammation in cases of acute laryngitis, &c. The nerves are branches of the pneumogastric, viz., the superior and the inferior, or recurrent laryngeal. The superior laryngeal nerves are not exclusively distributed to the muscles called constrictors of the glottis (thearytenoideus and the crico-thyroidei) ; nor do the inferior laryngeals belong exclusively to those called dilators (the crico-arytenoi- dei postici and laterales, and the thyro-arytenoidei), as a celebrated physiologist has af- firmed. (See Nkukology. ) The peculiar rotatory movement of the arytenoid cartilages somewhat interferes with any classification of these muscles into dilators and constrictors. Development. — The evolution of the larynx is remarkable in this respect, that, after hav- ing attained a certain size, it undergoes no appreciable change until the time of puberty. The ventricles are as yet so slightly developed that their existence has been denied. The prominence of the os hyoides in some measure conceals that of the larynx. M. Rich- erand {Mem. de la Societe Med. d' Emulation, torn, iii.) has proved that there is no very remarkable difference between the larynx of a child at three years of age and of one at twelve. Up to the age of puberty the larynx presents no trace of the sexual differences which afterward become so evident ; and to these anatomical conditions are owing the shrillness and uniformity of the voice in the youth of both sexes. At the period of puberty, at the same time as the genital organs, the larynx increases so rapidly as to attain its full development in the space of one year ; the voice then loses ilj uniformity, and acquires its pecidiar timbre and quality, and then also the sexual dif- ferences in the vocal apparatus become manifest. Is it from an unequal development of the different parts of the larynx, or from want of a certain degree of education, that the voice at this period is so discordant, especial- ly in singing, or breaks, as it is said 1 The simultaneous development of the genital organs and the larynx has led to the opin- ion that they stand to each other in the relation of cause and effect ; and observation has established that the vocal apparatus is in some measure under the influence of the generative organs ; for in eunuchs the larynx remains as small as it is in the female. (M. Dupuytren, Mem de la Soc. Phil., tom. ii.), At the age of puberty the size of the glottis is increased by one third in the female, and is nearly doubled in the male. After puberty, any changes which the larynx may undergo are the result of exercise, not of development, properly so called. Ossification of the cartilages of the larynx is not always the effect of age. I have seen it at the thirtieth year quite independently of disease. Chronic inflammation of the la- rynx induces a premature ossification of the cartilages. The th)Toid has the greatest tendency to this change, then the cricoid, and, lastly, the arytenoid cartilages : I have never observed it in the epiglottis. Functions. — The larynx is the organ of voice. Numerous experiments upon living animals, and many surgical facts, show that the vocal sound is produced exclusively in * It has been observed, in experiments upon animals, and in introducing the canula after the operation of laryngotomy, that the sensibility of the mucous membrane beyond the glottis is much less acute, t " Gnomonis, sed obtusanguli figuram utervis acervns habet." — (Haller.) THE THYROID GLAND. 433 the larynx. The lungs, the bronchi, and the trachea perform, with regard to the voice, the office of an elastic conductor of air capable of contraction and dilatation, of shorten- ing and elongation. The thorax acts like a pair of bellows, by which the air is driven into the larynx with any wished-for degree of force ; and hence the quantity of air pass- ing through the larynx, and the rapidity with which it moves, may vary to a very great extent. What, then, is the mechanism of the voice 1 Is it the same as that of a horn {Dodart), of a stringed instrument {Fcrrein), of a flute ( Cuvier), of a reed instrument {Biot and Mw- gendic), or of a bird-call* (Savart) 1 Is it produced by the vibration of the tense vocal cords, or merely by the vibration of the air while passing through a narrow opening, which is itself incapable of vibrating 1 We shall leave these questions to the decision of physiologists. It is sufficient for our purpose to know that the action of the muscles of the larynx and the arrangement of the vocal apparatus are perfectly fitted to produce either dilatation or contraction of the glottis ; and such is the mechanism of this part, that, from the rotatory movement of the arytenoid cartilages, the vocal cords are always rendered tense, whatever may be the other actions of the muscles. The voice as it issues from the larynx is simple, for the larynx is, with regard to the voice, what the mouth-piece is in the flute, or the reed in the bassoon ; but during its pas- sage througli the vocal tube, composed of the epiglottis, the pharynx, the isthmus of the fauces, the mouth, and the nasal fossae, the voice becomes modified. According to a very ingenious theory of M. Magendie, the epiglottis resembles those soft; and movable valves which M. Grenie places in the pipes of an organ to enable the sound to be increased without modifying the tone. The isthmus of the fauces resembles the superior larynx of birds, which consists of a contractile orifice that can be diminished, and even closed at pleasure ; and it is princi- pally owing to this mechanism that the small glottis of birds can execute such an exten- sive range of notes. We know, in fact, that the tone of a wind instrument is reduced an octave lower by completely closing the lower orifice of the tube, and that, when it is only partially closed, the tone is depressed in proportion. Now the isthmus of the fau- ces acts exactly like the superior larynx of birds. On watching a person who wishes to utter a very low note, we see that he depresses and flexes the head slightly upon the neck, so as to approximate the chin to the thorax : by this means the vertical diameter of the isthmus of the fauces is diminished, the larynx being carried upward, while the velum palati is depressed ; and from this we may judge of the important part performed by the velum in producing modulations of the voice. If to this we add the changes which may be effected in the length and diameter of the pharynx (see Pharynx), and if we remember that, by diminishing by one half the length or diameter of the tube or body of a wind instrument, its tone is raised one octave, we shall be able to understand how the human voice can execute so extensive a scale of notes, although the glottis is so small. The voice is also modified while traversing the buccal and nasal cavities. Do the nasal fosscr. favour the resonance of the voice 1 or does the air, when passing through them, merely give rise to certain sounds denominated nasal 1 The latter opin- ion, which is supported by Mr. Gerdy, appears to me the most consistent with facts. MM. Biot and Magendie had already correctly observed that the voice becomes nasal only when it traverses these passages. The voice becomes articulate in passing through the mouth, i. e., the vocal sound is interrupted, and modified by the more or less rapid percussion of the lips and tongue against the teeth and the palate. Articulate voice is very distinct from speech. Animals which differ much from man in the conformation of their vocal organs, the parrot, for example, may be made to artic- ulate ; but speech is the peculiar attribute of man, because he alone is possessed of in- telligence. The Thyroid Gland. The thyroid gland, or thyroid body, is a glanduliform organ, the uses of wnich are un- known : it is situated like a crescent with its concavity directed upward, in front of the first rings of the trachea, and upon the sides of the larynx. In describing this organ in connexion with the larynx, I follow the usual custom, which has arisen not from any direct relation between their functions, but from their contiguity to each other. The thyroid body varies much in size in different individuals ; there are few organs which present greater varieties in this respect. ^ The sexual differences in the size of this organ, like all those relating to the vocal ap- paratus, are very well marked, but in an inverse manner, that is to say, the thyroid body is larger in the female, in whom it forms a rounded projection, which assists in making the thyroid cartilage in that sex apj)ear still less prominent. * A bird-call is a cavity with elastic walls, perforated upon the two opposite sides. Tlie cavity is repre- ■ented by the ventricles, and the openings by the intervals between the vocal cords. If a tube capable of contracting and dilating be fitted to such an instrument, an infinite variety of sounds may be produced. I I I 484 SPLANCHNOLOGY. Climate, and more especially certain qualities in the water used as drink, have a re- markable influence upon its size, which, in many cases of goitre, is enormous. These differences in size affect either the whole of the gland equally, or only one lobe, or occasionally the middle portion alone. The iveight of the thyroid body, which is about an ounce, may be increased to a pound and a half, or even more. Form. — The thyroid body is generally composed of two lateral lobes or cornua, united by a contracted portion, flattened from before backward, and called the isthmus. Tlie varieties in shape principally affect the isthmus, which may be very narrow, long or short, regular or irregular, or entirely absent, or it may be as thick and as long from above downward as the lobes themselves. I have seen one case in which the thickest part of the thyroid gland was in the middle, and the lobes terminated above in a very narrow point. The opinion of the ancients, and which is also met with in Vesalius, that the human subject has two thyroid glands, no doubt arose from the narrowness or absence of the isthmus, or, rather, from the separation and complete independence of the two lobes in a great number of animals. The surface of the thyroid body is smooth and well defined, and sometimes divided into lobules by superficial furrows. We shall examine in succession the relations of the middle and lateral portions : The middle portion or isthmus is convex in froTit, and is separated from the skin by all the muscles of the sub-hyoid region. Behind, where it is concave, it is in contact with the first rings of the trachea. Moreover, this middle portion descends to a greater or less distance in different subjects, and sometimes so low, that there is not room to per- form tracheotomy between it and the sternum. Each lateral lobe is convex in front, and corresponds with the muscles of the sub-hyoid region : in particular, I ought to mention the sterno-thyroid, by which it is directly cov- ered, and the breadth of which seems to be proportioned to the size of the lobe ; in many cases of goitre I have seen this muscle twice or three times as broad as in the natural state. 0)1 the inside, each lateral lobe is concave, so as to be applied to the side of the trachea and cricoid cartilage, to the lower and latter part of the thyroid cartilage, to the lower part of the pharynx, and to the upper part of the CESophagus. The two lobes, to- gether with the middle portion or isthmus, form a half or sometimes three fourths of a canal, which embraces all those parts ; an extremely important relation, which explains how, in certain goitres, the trachea is flattened on the sides, deglutition is impeded, and true asphyxia by strangulation is the final result. Behind, each lateral lobe corresponds with the vertebral column, from which it is separated, on the outside, by the common carotid artery, the internal jugular vein, and the pneumogastric and great sympathetic nerves, which, according to the size of the gland, are either covered by it, or are merely in relation with its outer surface. The upper extremity of each lateral lobe terminates in a point, and hence the two- homed figure assigned to the thyroid body. It is situated on the inside of the carotid artery, in contact with the lateral and back part of the thyroid cartilage, and sometimes extends nearly to its upper border. Its lower extremity is thick and rounded, descends to a greater or less distance in different individuals, and corresponds to the fifth, sixth, or seventh rings of the trachea : it is situated between the trachea and the common ca- rotid. The inferior thyroid artery enters the gland at its lower extremity. Its upper border is concave and notched in the middle ; the superior thyroid arteries run along it. A prolongation extends from this border, which has been correctly repre- sented by Bidloo, and named the pyramid by Lalouette. It almost always exists ; it passes perpendicularly upward, either on the right or left side of the median line, and presents numerous varieties in several respects. Thus it varies in its origin, sometimes arising from the isthmus, and sometimes from one of the lobes at one side of the isth- mus ; also in its termination, sometimes ending opposite the notch in the upper border of the thyroid cartilage, sometimes opposite the thyro-hyoid membrane, and at other times even on a level with the body of the os hyoides ; but always firmly adherent eithei to the membrane or the bone. It also varies in its structure : sometimes it is a fibrous cord, and sometimes a reddish linear band, which has all the appearances of a muscular fasciculus, and has even been described as a muscle ; it often consists of a series of gremules arranged in a line ; sometimes, again, we find, in the middle, or at one end of the cord, a glanduliform enlargement, exactly resembling the tissue of the thjroid gland ; lastly, it may be double, or bifurcated, or even completely wanting ; in which case, how- ever, there exists a glanduliform mass of a certain height. This prolongation, in which I and many others have in vain attempted to find an excretory duct, is evidently of a compact nature. Is it the remains of a fcetal structure, or the trace of a normal dispo- sition in some animals 1 The lower border of the thyroid body is convex, more or less deeply notched in the cen- tre, and is in contact with the inferior thyroid arteries. Structure. — The proper tissue of the thyroid gland is of a variable colour, sometimes resembling the lees of Port wine, and sometimes of a yellowish hue. It is of tolerably THE UEINARY ORGANS. 435 nrm consistence, and feels granular. This organ presents all the anatomical characters of glands, and, like them, may be separated by dissection into glandular grains ; but with this difference, that these grains communicate with each other, while, in ordinary glands, they are independent. The communication of the glandular grains may be shown in the following manner : if the tube of a mercurial injecting apparatus be inserted into the thyroid gland, the mercury will enter into and distend the cells, and after a certain time all the grains will be injected ; it is easy to satisfy the mind that the mercury is not in- filtrated into the cellular tissue, but is contained in the tissue of the gland itself, in the centre of the granulations. The right and left lobes do not conununicate, but all the granulations of each lobe communicate with each other. The thyroid gland has, therefore, a vesicular structure ; and we have seen that the glandular grains of all glands are spongy and porous, and that the products of their secre- tion may be accumulated in these pores. The glandular nature of the thyroid body is also shown by the viscid, Umpid, yellowish fluid which pervades it in certain subjects, and which may be collected in sufficient quantity for chemical analysis ; and also by the retention of this matter within a greater or less number of the vesicles when their orifices of communication with the neighbour- ing vesicles become obliterated. But, in connexion with this view regarding its glandular nature, we seek in vain for an excretory duct. If we examine the trachea and the larynx, or lay open the oesophagus, and then press the thyroid gland, we shall see that no fluid escapes into those canals. It has been asserted, indeed, that the excretory duct of the thyroid gland terminated in the foramen ccecum of the tongue, in the ventricles of the larynx, or in the trachea opposite its first ring ; but, after the example of Santorini, we are compelled to reject these fancied and too hastily announced discoveries. I may here notice the intimate adhesion of the side of the thyroid gland to the first ring of the trachea. This can be very well shown by detaching the gland from behind for- ward ; it is of a fibrous nature, and I have sometimes thought that I saw a duct in the centre of it, passing through the membrane which connects the trachea with the cricoid cartilage, though I have never been able satisfactorily to demonstrate it. Still, I do not think that the absence of an excretory duct should remove the thyroid from among the glandular organs ; for I believe that there exist in the body glands with- out excretory ducts, as the thymus, the supra-renal capsules, and the thyroid body. The secretion of the gland is entirely absorbed, and fulfils certain unknown uses. Arteries. — The size and the number of the arteries distributed to the thyroid gland in- dicate that something more than a mere nutritive process must be carried on in it. The arteries are sometimes four, sometimes five in number ; two superior arise from the ex- ternal carotid ; two inferior from the subclavian, and the fifth, or the thyroid artery of Neubauer, where it exists, arises from the arch of the aorta. The veiTis are proportionally as large as the arteries, and form so considerable a plexus in front of the trachea, as, in certain cases, to have prevented the completion of the operation of tracheotomy. The lymphatic vessels terminate in the cervical lymphatic glands. The nerves are derived from the pneumogastrics, and the cervical ganglia of the sym- pathetic. A thin cellular membrane envelops the gland, and sends very delicate prolongations into its substance, where we find a very firm cellular tissue, always destitute of fat. Development. — The thyroid gland is developed in two lateral halves, which are after- ward united by a median portion. It is not uninteresting to remark, that this dispo- sition, which is transitory in the foetus, represents the permanent condition of the gland in a great number of animals. During intra-uterine life and infancy it is relatively larger than at subsequent periods. Nevertheless, the changes which it afterward undergoes are not to be compared with those that occur in the thymus ; and we cannot say, as of the latter structure, that the existence of the thyroid body has any peculiar relations with foetal life. Functions. — It is a secreting organ, but the uses of its fluid are not known. THE GENITO-URINARY ORGANS. I HAVE thought it proper to describe the genital and the urinary organs together, because, although their functions are very distinct, yet they have the most intimate anatomical, physiological, and pathological connexions. THE URINARY ORGANS. Division. — The Kidneys and Ureters. — The Bladder. — The Supra-renal Capsules The urinary organs form a very complex secretory apparatus, consisting of two secre- ting organs, the kidneys ; of two provisional reservoirs, the calyces and the pelvis of each kidney ; of two excretory ducts, the ureters ; of a second and final reservoir, the bladder ; 436 SPLANCHNOLOGY. and, lastly, of a second and final excretory canal, which, in the male, is common to both the genital and the urinary organs, viz., the canal of the urethra. The Kidneys. The kidneys {ve^pol) are glandular organs, intended to secrete the urine. They are deeply situated {k k,fig. 199) in the lumbar region, hence called the region of the kidneys, on each side of the vertebral column, externally to the peritoneum, which merely passes in front of them ; they are surrounded by a great quantity of fat, and, as it were, suspended by the vessels which pass into and emerge from them. Fixed firmly in this situation, they are but little liable to displacement. Most of the changes in their position are congenital. The right kidney generally descends a little lower than the left, doubtless on account of the presence of the liver. One of the kid- neys may not uncommonly be found in front of the vertebral column, or even in the. cavity of the pelvis ; and this unusual arrangement may, in certain cases, render diag- nosis very obscure.* I have frequently found the right kidney in the corresponding iliac fossa in females who had been in the habit of wearing very tight stays. This displace- ment happens when the pressure of the stays upon the liver forces the kidney out of the depression in which it is lodged in the lower surface of that organ. Number. — The kidneys are two in number. It is not very uncommon to find only one, which, is almost always formed by the union of the two, by means of a transverse portion crossing in front of the vertebral column, and having its concave border directed upward. Sometimes the two united kidneys are situated in the right or left lumbar region, or ija the cavity of the true pelvis. Cases of union of the two kidneys should be distinguish- ed from those in which one of them is atrophied. Again, Blasius, Fallopius, Gavard, &c., relate examples of individuals having three kidneys ; in some of these cases, two were situated upon the same side, in others the supernumary kidney was placed in front of the vertebral column. Size. — The kidney is not subject to such great variations in size as most other organs. Its ordinary dimensions are from three and a half to four inches in length, two inches in breadth, and one inch in thickness. Its weight is from two to four ounces, t I have found them more than three times their ordinary size in a diabetic patient. When one kidney is atrophied, the other becomes proportionally enlarged, sometimes even to twice the usual dimensions. Atrophy of the kidney may be so extreme as to reduce it to a drachm and a half or two drachms in weight, and make it appear to be lost among the surrounding fat ; but the presence of this fat distinguishes such a case from one of con- genital absence of the kidney.t Density and Colour. — The tissue of the kidney is harder than that of other glands. Its fragility accounts for its laceration by direct violence, or by a concussion produced by a fall from a great height. Its colour is that of the lees of red wine, somewhat analogous to that of the muscular tissue, but offers several different shades. Figure. — The shape of the kidney may be well compared to a bean, with the hilua turned inward. This form enables us to consider its two surfaces and its circumference. Relations. — The anterior surface of the kidney is directed slightly outward ; it is con- vex,^ and is covered by the lumbar colon, but sometimes only by the peritoneum, the gut lying to its inner side ; on the left side it is also in relation with the spleen and the great tuberosity of the stomach, and on the right side with the liver and the second portion of the duodenum. The relations of the right kidney with the liver are more or less extensive ; sometimes it is entirely covered by the liver ; in other instances it is inclined downward, and has no relation with that organ. The gall-bladder sometimes lies upon the anterior surface of the right kidney through the whole of its extent. Lastly, I have seen the kidney in immediate relation with the parietes of the abdomen, through which it could be easily felt. As practical inferences from these relations, we would notice the difficulty of explo- ring the kidneys from the anterior surface of the abdomen, on account of their deep sit- uation ; also, the possibility of an abscess of the kidney opening into the colon. The posterior surface is less convex than the anterior, and is turned inward ; it corre- sponds with the quadratus lumborum, from which it is separated by the anterior layer of the fascia of the transversalis muscle ; with the diaphragm, which separates it from the * 1 latplyhad in my warJs a female labouring under hectic fever, of which I could detect no cause, either in the thorax or the abdomen. Upon opening the body after death, I found the two kidneys united, situated in the true pelvis, behind the rectum, and projecting a little above the brim. They contained a large quantity of pus, which escaped by the rectum. + [According to M. Raver, the average weight of the kidney in the male is 4i ounces, in the female 3^ ounces ; he also states that the left kidney is almost always larger and heavier than the right.] t 1 do not speak here of enlargement of the kidneys from disease. Many examples of extreme enlargement wall be found in my work on Pathological Anatomy, liv. i., xviii. () Not unfrequently the fissure of the kidney is found on the anterior surface of this organ. In one case of this kind, the right kidney occupied the right iliac fossa; it had two arteries, a superior, which proceeded di- rectly to the fissure, and an inferior, arising from the angle of the bifurcation of the aorta, in front of the mid' 1 He sacral artery, and terminating at the lower extremity of the kidney. THE KIDNEYS. 437 (w6 or three lower ribs ; and with the psoas, which intervenes between it and the ver- tebral column. These relations explain the possibility of exploring the kidney in the lumbar region through the quadratus lumborum, account for abscesses of the kidney opening in the lumbar region, and for the escape of renal calculi in the same direction, and form the grounds on which the operation of nephrotomy has been proposed. It is of importance to remark, that the relations of the kidneys with the ribs are variable in extent, and that sometimes they do not pass beyond the last rib. The circumference of the kidney presents an external border, convex, semi-elliptical, and directed backward ; an internal border, directed forward, and deeply notched in the middle, to form ih.e fissure of the kidney (hilus renalis, k,fig. 179). This notch is more marked behind, where it corresponds with the pelvis of the kidney, than in front, where it corresponds with the renal vein ; it is from fifteen to eighteen lines in depth. If we separate the edges of this fissure, we expose a deep cavity containing fat, and called the sinus ; in which are seen the pelvis of the kidney (p), the calices (c c c'), and the divisions of the renal artery and vein. The upper end of the kidney is directed inward, and is more or less completely em- braced by the supra-renal capsule ; it is generally larger than the lower end, which is di- rected slightly outward, and projects beyond the last rib. Structure. — Make a vertical section of the kidney from its convex to its concave bor- der. Detach the proper capsule in the same direction. Inject the arteries, veins, and ureter, in different kidneys, and also in the same kidney. Inject also the uriniferous ducts. The Proper Coat. — The kidney has no peritoneal covering. The remarkable fatty mass in which it is imbedded is called the fatty capsule of the kidney. Besides this, it is pro- vided with a proper fibrous coat, the external surface of which adheres to the fatty tis- sue, by means of fibrous lamellae passing through it ; its internal surface is adherent to the tissue of the kidney, through the medium of a number of small prolongations, which are very easily lacerated. The Tissue of the Kidney. — The kidney differs from other glands, all of which present a homogeneous and granular texture, in being Fig. 179. composed of two substances : one of these is ex- ternal, cortical, or glandular {a a) ; the other inter- nal, medullary, or tubular {b b b). Some anato- mists have described a third substance, the mam- millated ; but the papillas {d d) of which it is com- posed belong to the tubular substance. The following is the respective arrangement of these two substances : The cortical sabstance forms a soft, reddish, sometimes yellow layer, of a granular appear- ance, and about two lines in thickness, which occupies the surface of the kidney, and sends prolongations, in the form of pillars or septa, from one to three lines thick, between the cones of the tubular substance. The tubular or medullary substance is redder, and presents the appearance of striated cones or pyramids (the pyramids of Malpighi), the bases of which adhere to the cortical substance, while their free apices are turned towards the sinus, where they appear like papillae. Bellini, and, before him, Berenger di Carpi, considered the fibres or striae of the medullary substance as so many uriniferous tubes (the tubes of Bel- lini), and hence the term tubular substance. It follows, then, that the kidney is divided into a number of compartments, correspond- ing to the number of cones of tubular substance ; there are from ten to twenty of these compartments, which represent the temporary lobules of the human foetal kidney, and the permanent lobules in the kidneys of the greater number of animals, t The kidney, therefore, is formed by the union of a greater or less number of small kid- neys, applied together, and connected within a common investment. We shall see, pres- ently, that, in reference to the circulation, these small kidneys are entirely independent of each other. Although the distinction between the two substances is well marked, it is easy to see that some of the fibres or striae of the tubular structure penetrate the cor- tical substance in a flexuous course, and reach the surface of the organ. This fact was clearly shown by Ferrein, who considered the stri^ to be the excretory ducts of the gran- ules. These cortical and flexuous portions of the tubes, which become straight as soon as they reach the medullary substance, are termed the cortical ducts, or the convoluted tubes of Ferrein. * This figure is a plan, not an actual representation of the structure of the kidney. + In some animals the kidney resembles a bunch of grapes. SectioDafkidoey.* 438 SPLANCHNOLOGY. Ferrein having examined the tubes of Bellini under the microscope, believed that each of them formed a pyramid analogous to those of the tubular substance, and that each of these secondary pyramids consisted of about a hundred ducts ; hence the tubes of the tubular substance have been named the pyramids of Ferrein,* in contradisl inction to the pyramids of Malpighi. We shall now examine the structure of the tubular and the cortical substance. Structure of the Tubular Substance. — The tubular substance, which, at first sight, looKs like muscular tissue, from its red colour and arrangement in lines, evidently consists of tubes or ducts. In fact, an examination under the simple microscope of a section made perpendicu- Fig. 180. larly to the axis of the tubes, demonstrates the existence 6 \ of a number of small openings, each corresponding to a tube ; and if, while the eye is fixed upon the section, the kidney be compressed, urine will be seen to exude from all points of the cut surface. Direct injection of the ducts, by means of a tube containing mercury, introduced at hazard into the tubular substance, will fill all the tubes, in whatever direction the instrument may be directed. The ingenious experiment performed by Galvani, who tied the ureters of birds, and by this means obtained an injection of the tubes with the white matter of their urine, leaves no doubt of the existence of these tubes. Lastly, the tubes themselves are collected together in the papillae, and open either over their entire surface, or in a small depression which sometimes exists at their summits. Structure of the Cortical Substance. — The cortical sub- stance is tubular and granular. The granules are regularly disposed around the convoluted tubes of Ferrein. t On examining a thin slice of uninjected kidney by the simple microscope, we perceive a great number of oval and spheroidal granules {c",fig. 180), the acini of Malpighi, which may be separated from each other by maceration ; and those granules which have been cut through present that spongy appearance, resembling the pith of the rush, which seems to belong to all glands. When the section is verti- cal, these corpuscles are seen appended to the tubes of Ferrein, like grapes upon their stalk. [The urinifcrous tubes, commencing at their orifices upon the surface of the papillae, pass up into the tu- bular portion of the kidney, dividing and subdividing dichotomously several times {a, fig. 180), so as to consti- tute fasciculi of straight and radiating tubes : these are the pyramids of Ferrein, a considerable number of which are united to form one of the pyramids of Malpighi (b,fig. 179). At the base of the latter the fasciculi spread out, and the straight tubes become the convoluted tubes of the cortical substance (fig. 180). In the human kidney, the tubuli uriniferi are said by Weber to be of a nearly uniform diameter throughout their entire course (averaging ^^ th of an inch) ; and all appeared to him to end in loops (b b), none in free and closed extremities (as at b') : according to Krause, they terminate in both ways. In either case, however, they form a closed system of tubes, independent of the bloodvessels, which merely ramify on their parietes. They are lined with a mucous membrane, continuous with that on the papillae, and having a columnar epi- thelium. The acini of Malpighi, or granules of M. Cruveilhier (c"), are not of a glandular nature ; they consist en- tirely of minute convoluted arteries, which terminate in the veins, but have no direct communication, as wai formerly supposed, with the uriniferous tubes ; they are called the glomeruli.'] Ma^ified sixty timu.t THE KIDNEYS. .^^ artery.* Having filled the artery with red injection, the vein with blue, and the ureter with yellow, I observed the following facts : The renal artery divides into several branches within the sinus, where it is surround- ed with fat ; these branches pass between the calyces, and then between the cones of the tubular substance, proceeding as far as the conunencement of the cortical substance without giving off any smaller branches : at that point, however, they divide and subdi- vide, so as to form a vascular network, the meshes of which are quadrilateral and of different sizes, inscribed within each other. The largest of these meshes embrace the entire base of each pyramid ; the smaller pass in different directions through the sub- stance of the bases. In order to obtain a good view of this arrangement, it is necessary to divide an inject- ed kidney along its convex border, and scrape away the tubular substance, which is so soft as to be easily removed. We shall then perceive that the arterial and venous net- work, corresponding to the base of each cone, is surrounded by a very thick fibrous sheath, apparently prolonged from the fibrous coat, which passes into the hilus. All the tubular substance being thus removed, the remaining cortical portion of the kidney presents the appearance of a series of perfectly distinct alveoli, each of which corresponds to a cone of the tubular substance. A very beautiful preparation may thus be made. It remains for us to inquire how the arteries terminate. A number of vessels pro- ceed from the convexity of the vascular network above described, traverse the cortical substance, become twisted like tendrils of the vine, and appear to terminate in small red masses, regularly arranged along the convoluted tubes of Ferrein. These small red masses are formed by the penetration of the injection into the cavity of each granule, as may be seen by examining a section of the kidney with a lens.f If both the artery and the vein be injected in the same kidney (and it is of importance that the vein should be injected before the artery, in order to prevent a mixture of the two injections), we shall see that the matter injected by the vein circumscribes that injected by the artery. Almost all the vessels are destined for the cortical substance, the tubular substance scarcely receiving any branches :$ the vessels of any one lobule do not communicate with those of the adjacent lobules. Injection thrown into the ureter does not enter the uriniferous ducts, or, at leeist, very incompletely. Development. — The surface of the kidney in the foetus, as in the lower animals, is fur- rowed and lobulated. Each lobule is fonned by the medullary substance, covered by a layer of the cortical substance. After birth the furrows are effaced, and the surface of the kidney becomes plane and smooth. This change takes place during the first three years after birth ; nevertheless, the lo- bular arrangement not unfrequently continues for nine or ten years, and even during the whole periwi of life. When the kidney is the seat of disease, and more particularly when it is distended from an accumulation of urine within the calyces and pelvis, the lob- ular arrangement reappears. Each lobule is then converted into a pouch, which is perfectly distinct from those in contact with it. The kidney is proportionally larger in the foetus than in the adult. Functicms. — The kidneys are the secreting organs of the urine. The urine is secreted by the cortical substance, and, as it were, filtered by the tubular substance ; for perfect- ly-formed urine is found in the former situation. The mechanism of this is not better known than that of other secretions ; its rapidity is explained by the great quantity of blood received by the kidneys. The Calyces, Pelvis, and Ureter. Dissection. — Remove the fat from the sinus, and study the arrangement of the pelvis and calyces externally. Divide the kidney from the convex border towards the hilus. The calyces (c c c', fig. 179) are funnels (infundibula), or, rather, small membranous cylinders, embracing the bases of the papillae by one of their extremities, almost in the same manner as the corolla of a flower embraces the stamina and pistil, and uniting at their other extremity with the adjacent calyces, to form the pelvis of the kidney. They vary in number like the papillae, or even more so, for two or three papillae frequently open into the same calyx. Whatever their number may be, they generally unite into three trunks, a superior, a middle, and an inferior, which correspond to the three groups of lobules, into which the kidney may be divided. These three trunks unite to form the pelvis. The external surface of the calyces is in relation with a great quantity of fat, and with the divisions of the renal artery and vein. The pelvis (p) is a small membranous pouch, situated behind the renal artery and vein, opposite the deep notch in the posterior border of the hilus, so that, when seen from be- hind, it projects completely beyond that fissure. It is elongated from above downward, * [This is the result of rupture.] t See note, suprd. t [The vessels (c,fig. 180) of the tubular portion nm parallel with the tubuli from the cortical substance to the papillae ; they were mistaken by Ruysch fur the tubub themselves, which were, therefore, supposed by him to communicate with the arteries in the glomeruli.] 440 SPLANCHNOLOGY. and flattened from before backward, and may become greatly dilated from retention of the urine, or from renal calculi : almost immediately after its commencement it becomes smaller, and takes the name of the ureter. In certain cases it would appear that there is no pelvis, and that the ureter succeeds immediately to the two or three trunks formed by the union of the calyces. The pelvis is, therefore, nothing more than the expanded or infundibuliform commencement of the ureter. The ureter {ovpov, urine, u, Jigs. 179, 181, 199) is the excretory duct of the kidney, and ex ends obliquely from the pelvis of that organ to the inferior fundus {bos fond) of the bladder. It is generally single on each side, but sometimes double, and that under two very different circumstances : for example, where the two kidneys are united into one, a double ureter is almost invariably found ; and, secondly, when, there being two kidneys, one of them is divided into two very distinct portions. In the latter case the two ureters are often united into one, after a course of a few inches. There is, then, no pelvis properly so called, and the two ureters may be regarded as the prolongation of the two trunks of the calyces, which remain separate longer than usual. The ureter is a cylindrical tube, having whitish, thin, and extensible parietes, and va- rying in size from that of a crow's to that of a goose's quill. The most contracted por- tion of the canal is that situated in the substance of the parietes of the bladder. Occa- sionally it presents, at various parts of its extent, some circumscribed dilatations, which seem to indicate that the course of the urine had been for a time arrested. Tiiis canal is liable to extreme dilatation, when any obstacle occurs to the passage of the urine : I have seen it as large as the small intestine. Each ureter is directed obliquely downward and inward, as far as the side of the base of the sacrum : from this point {fig. 181) it passes downward, forward, and then inward (Uffig. 186), to the lateral part of the inferior fundus (a) of the bladder, where it enters between the muscular and mucous coats, and passes obliquely for about ten lines within the substance of that organ, to one of the posterior angles of the trigone, at which point it opens by an orifice narrower than the canal itself, and having the form of a parabolic curve, with its concavity directed inward. Relations. — In proceeding from the pelvis of the kidney to the base of the sacrum, the ureter passes edong the anterior margin of the psoas, and is covered by the peritoneum and by the spermatic vessels, which cross it very obliquely. The right ureter is in rela- tion with the vena cava inferior, being situated on its outer side. Opposite the base of the sacrum, each ureter crosses the common iliac, and then the external iliac artery and vein of its own side. In the pelvis, the ureter is applied to the parietes of that cavity, is covered by the peritoneum, and crosses in succession the umbilical artery, or the cord by which it is replaced, the obturator vessels, the vas deferens (,t,fig. 181) in the male,* and the upper and lateral part of the vagina in the female. That portion of it which is contained within the substance of the walls of the bladder corresponds indirectly with the neck of the uterus ; and this important relation explains why carcinoma of the neck of the womb is so frequently accompanied with retention of urine. I have also observ- ed that the ureters of all females who have died after delivery, or during the last months of pregnancy, are remarkably dilated. Internal Surface. — The internal surface of the calyces, pelvis, and ureters is white, smooth, and has longitudinal folds, which are effaced by distension. There are no valves, either at the opening of the calyces into the pelvis, or of the pelvis into the ure- ter, or in any part of that canal. Structure. — ^The calyces, the pelvis, and the ureter have all the same structure : they are formed by two membranes ; an internal membrane, continuous with the vesical mu- cous membrane, very thin, and even having the appearance of a serous membrane ; it is reflected from the calyces upon the papillas, and is prolonged into the uriniferous tubes : an external membrane, which is very thick, and supposed to be a continuation of the ex- ternal coat of the kidney, and therefore to be fibrous. Others regard it as muscular ;t I believe that it is formed of a tissue analogous to the dartos. Some arteries and veins, probably, also, some lymphatics and nerves, are distributed upon the calyces, the pelvis, and the ureters, but do not require any special description. The Bladder. The Madder {h,Jig. 181) is a musculo-membranous sack, which serves as a reservoir for the urine. It is situated in the cavity of the pelvis, upon the median line, behind the pubes (6), and is retained in that position by the peritoneum (m), which only partially covers it, and by the urachus, a sort of ligament connecting it with the umbilicus. These means of attachment are in accordance with the great enlargement of which the organ is ca- pable ; but they cannot prevent certain partial displacements, known as hcrnice of the llcdde'' When collapsed, it is completely protected from external injury ; but when * Passing to its outer side. ^ [lu some quadrupeds the ureter distinctly contracts on applying a stimulus.! THE BLADDER. 441 filled, it passes above the osseous girdle in which it is contained, and enters the dilatable cavity of the abdomen, where it can be distended to the utmost without inconvenience. Number. — The bladder Fig. 181. is always single ; the ex- amples of double bladder which have been recorded are cases of protrusion of the mucous membrane through the separated muscular fibres. But, whatever may be the size of these accidental blad- ders (and I have seen them twdce as large as the true bladder to which they were attached), they may always be distinguished by their having no muscu- lar coat. The cases of de- ficiency of the bladder are generally examples of that species of malformation, in which the viscus is open anteriorly, and is everted, 80 as to resemble a fungous mass. Dimensions. — The bladder is the largest of all the reservoirs of secretion ; but its ca- pacity varies, from a number of circumstances : from hahit — in persons who are accus- tomed to retain their urine for a considerable period, the bladder is more capacious than in those who immediately attend to the desire to pass urine ; from sex — thus, in the fe- male the bladder is generally larger than in the male, because she is more influenced by the customs of society ; from age — ^the bladder appears to be relatively larger before than after birth ; from disease — in consequence of which it presents every variety be tween a morbid state of contraction, in which, from the contact of its parietes, it scarce ly permits the accumulation of a spoonful of urine, and an extreme state of dilatation, in which it can hold several pints of that fluid. Direction. — The direction of the bladder is determined by that of the anterior wall of the pelvis, so that its axis is oblique from above downward and backward. On account of this obliquity, a slight inclination of the trunk forward makes the neck of the bladder the most dependent part of the organ. The obliquity becomes still greater when the distended bladder has escaped from the pelvis and entered the cavity of the abdomen : its axis then exactly corresponds with that of the brim of the pelvis, i. c, it is directed from the umbilicus to the lower part of the curvature of the sacrum. It has been said, since the time of Celsus, that the upper part of the bladder is a little inclined to the left side, but I have not observed this. Shape. — The bladder is ovoid, the great end being directed downward and the smaller upward. Its shape differs according to age and sex, and in different individuals. The sexual differences are not congenital ; they seem to result from the pressure to which the female bladder is subjected during pregnancy ; but the transverse enlargement and the vertical shortening of the bladder in a female who has borne children are not so well marked as is generally said. Relations. — In determining these, the bladder is divided into the fundus, which is the highest and the narrowest part ; the body, or middle portion ; and the base, which is the lowest and the broadest portion. It has, moreover, like all hollow organs, an external and an internal surface. The external surface of the bladder is convex, and presents six regions for our con- sideration, the relations of which we shall now study, both in the collapsed and distend- ed condition of the viscus. The anterior region, not covered by the peritoneum, is in relation with the symphysis and bodies of the ossa pubis, and with the internal obtura- tor muscles, with which parts it is connected by a very loose serous cellular tissue, in stout persons more or less loaded with fat. Some fibrous bundles pass from the lower part of this region, and are attached to the sides of the symphysis ; they are called the anterior ligaments of the bladder, and are traversed by numerous veins ; they are a de- pendance of the superior pelvic aponeurosis (q,fig. 181). (Vide Aponeurologv.) In the female, on account of the absence of the prostate, the anterior region of the bladder passes below the symphysis, and advantage may be taken of this circumstance in the extraction of calculi. When the bladder is full, its anterior region corresponds imme- diately with the parietes of the abdomen, and sometimes rises as high as the umbilicus. The practical conclusions to be derived from these relations refer to the examination of the bladder in the hypogastrium, to puncture of this organ in the same situation, to Kkk i 442 SPLANCHNOLdGT. the high operation for stone, to the operation of dividing the symphysis, and, lastly, to ruptures of the bladder in consequence of fracture of the pubes.* The posterior region of the bladder is covered by the peritoneum (u) throughout the whole of its extent ; in the male it corresponds with the rectum (o), and in the female with the uterus. Some convolutions of the small intestine almost always intervene be- tween the bladder and those parts. The lateral regimis are also covered by the peritoneum ; and passing upon each of them are found the umbilical artery in the foetus, and subsequently the hgament by which it is replaced, and also the vas deferens (0 in the male. When the bladder is perfectly contracted, there is some distance between it and that vessel and duct on either side. The relations of the hwer region or base of the bladder, which are all very important, differ in the two sexes. In the male it corresponds to the rectum, from which it is separated on either side in front by the vesicula seminalis («) and the vas deferens {t). The only part in direct re- lation with the rectum is, therefore, the triangular space {fig. 186) comprised between the vesiculae (s s') and the vaisa deferentia (J, I') of the two sides. It is of importance to remark, that the peritoneum, where it is reflected from the rectum upon the posterior region of the bladder, forms a more or less deep cul-de-sac in the middle, and two small folds on the sides, which have been improperly named the posterior ligaments of the blad- der. When the bladder is much contracted, the peritoneum covers the whole of the space between the vesiculae and the vasa deferentia ; so that, properly speaking, there is no immediate relation between that organ and the rectum. On the other hand, when it is distended, it becomes much enlarged posteriorly, and has much more extensive re- lations with the rectum, t It is important, also, to remark, that the peritoneum is very loosely united to the base of the bladder, so that they can be easily separated whenever it is desirable to reach the bladder from the rectum. On each side of the rectum the base of the bladder corresponds with the cellular tissue of the pelvis. The superior pel- vic fascia and the levatores ani are attached to and embrace the sides of the base. In the female, the base of the bladder corresponds not only with the vagina, but with the lower half of the neck of the uterus ; it adheres very intimately to the former, but loosely to the latter. As practical consequences of these relations, I would point out the following : In the male, the occurrence of recto-vesical fistulae, the possibility of exploring the bladder by the rectum, and of operating upon it in the same situation. In the female, the capability of examining the bladder by the vagina, of puncturing it, and of performing lithotomy through the same part ; the occurrence of vesico- vaginal fistulae, and the frequency with which carcinoma of the bladder follows the same affection of the cervix uteri. Summit, or Fundus. — This part of the bladder is directed forward and upward, and is covered by peritoneum. The urachus is a sort of cord, having a muscular appearance, and stretching from the summit of the bladder to the umbilicus, into which it appears to enter. This cord adheres tolerably firmly to the peritoneum,^ which forms a falciform fold over it, and may be drawn down with it when it is displaced. In a case of hyper- trophy of the bladder, I found the cord it^lf hypertrophied, and continuous with the longi- tudinal muscular fibres of the bladder, almost in the same way as the round ligament of the uterus with the fibres of that organ. The urachus is merely the vestige of a canal which ex- ists in the foetus of quadrupeds, and, according to several authors, in the human foetus also. There have been many discussions upon this subject, some stating that the cord is hollow, others that it is solid. I have always found it solid, both in the adult and in the foetus. In one case I found a small concretion in it, which I regret not having submit- ted to chemical analysis. It is very common to find the urachus large at its origin, and becoming narrower after a course of two or three inches, and then blending with the cord, which takes the place of the left umbilical artery ; at other times it expands into cellular tissue, and the filaments resulting from its division proceed, some to the umbili- cus, and others to the cords which represent the obliterated umbihcal arteries. In the erect posture, the weight of the intestines presses on the summit of the bladder, which is thus pushed downward ; and hence the necessity for placing the patient, during certain operations, especially that of lithotrity, in the horizontal position, or even on an inclined plane, so arranged that the pelvis is more elevated than the shoulders. The internal surface of the bladder is covered by a mucous membrane, hke all cavities which conununicate with the exterior ; and is remarkable for certain folds or wrinkles, which are effaced by distension, and for the reticular ridges formed by the fasciculi of its muscular coat ; these are sometimes very highly developed, and, in certain cases, * It has even been proposed to puncture the bladder through the symphysis, by means of a flattened tro- car ; but the difficulty of coming exactly upon the symphysis will probably prereut the execution of this plan. t The varieties in the depth of the cul-de-sac formed by the reflected peritoneum, pointed out by modern •nrgeons, appear to me to be explicable by the difference in size of the bladders examined. The arrange- ment of the peritoneum seems to me to be exactly the same in all subjects. t It would appear, from a fact which I have observed, that the bladder cannot be dragged into either inter- nal abdominal rin^, excepting after the urachus ; this being itself drawn down by the peritoneum, with whick it is closely united. THE BLADDER. 443 are so large, that they form pillars, which project into the interior of the bladder. The mucous membrane not unfrequently becomes insinuated between these columns, so as to form cells, or what is termed sacculated bladder. The base of the bladder presents three openings, viz., the orifices of the two ureters (r r,fig. 182), and the opening into the urethra. These three openings occupy the angles of an equilateral triangle (" coUi- cula ab ureteribus ad urethram producta," Holler), the sur- pig. 182. face of which is smooth and white, and is always devoid of wrinkles or columns. This is the trigone of the bladder, or trigone of Lieutaud, which has been supposed to possess a pecuhar degree of sensibihty. The posterior border (r r) of this trigone is more or less prominent in different individ- uals, and is formed by a line stretching between the orifices of the two ureters ; this prominence is prolonged outward on each side by the portion of the ureter which lies in tl>e parietes of the bladder. It has been stated incorrectly, that the trigone is formed by the projection of the prostate, for it exists in females as well as in males, though it is less prom- inent than in the former. All that part of the base of the bladder which is behind the trigone is generally called the las fond, ot inferior fundus.* Most anatomists follow Lieutaud in describing, under the name of uvula vesica, a tubercle which arises from the low- er part of the orifice of the urethra, and partially fills up that opening ; but it exists only in cases of disease, being the re- sult of hypertrophy of the middle portion of the prostate, de- scribed by Home as the middle lobe. The orifices of the ureters are so constructed as to per- mit the easy passage of the urine into the bladder, but com- pletely to oppose its reflux. Their long oblique course be- neath the mucous membrane before opening into the blad- der explains this arrangement. The raised and reflected portion of the membrane might be called the valve of the ureter. The opening of the urethra, which is also called the neck of the bladder, is habitually closed, and, as it were, corrugated. Some force is required in order to overcome the resistance offered by it ; the crescentic form which has been attributed to it is not very evident. Structure. — The bladder has three coats : a peritoneal, which is incomplete, a muscu- lar, and a mucous coat ; these are connected by layers of cellular tissue : it has also ves- sels and nerves. The peritoneal coat covers the posterior and laterjil regions, and the inferior fundus of the bladder. The anterior region, and that part of the base which is in front of the infe- rior fundus, are not covered by it. It is united to the muscular coat by very loose cellu- lar tissue. The muscular coat is formed of interlacing fibres, the direction of which it is, at first sight, very diiScult to determine. + This coat is very thin, and does not form a continu- ous layer in enlarged bladders ; but in small and contracted bladders it is continuous, and consists of several layers, and may even acquire a thickness of eight or ten lines from hypertrophy. It is, then, very easy to determine the direction of the fleshy fibres, which seem to form a number of layers. The external layer consists of longitudinal fibres, all of which proceed from the neck of the bladder, and expand over the whole sur- face of the organ ; the next layer is formed of circular fibres, some of which are irregu- larly interlaced, while the others are parallel. The regular circular fibres are most nu- merous opposite the inferior fundus of the bladder, and are continuous with the annular fibres of the neck. The irregular circular fibres are most common in the posterior region of the organ. In the situation of the trigone, the muscular layer consists of transverse parallel fibres, pla- ced near each other, and forming a perfectly regular plane. The transverse thick bun- dle stretching between the orifices of the ureters has been regarded by Sir C. Bell as the muscle of the ureters. Its contraction, by enlarging their orifices, will facilitate the entrance of the urine into the bladder. The term sphincter of the bladder is applied to a muscular ring, which is continuous with the circular fibres of the body of the bladder, and is situated at the opening of the urethra. The vagueness and disagreement in the descriptions of this sphincter suffi- ciently prove that no very distinct structure of the kind exists at the neck of the blad- der. Winslow describes some fibres arising from the ossa pubis, and embracing tie * It is not uncommon to find the bladder forming behind the trigone a deep cul-de-sac, which I have seen insinuated between that part and the rectum. _ t [These fibres belong to the involuntary class, the microscopic characters of which are described in the note, p. 32.-?.] 444 SPLANCHNOLOGY. sides of the vesical orifice, as the sphincter muscle, but they evidently belong to the le- vator ani. It is certain, however, that, in the neck of the bladder, there is a thin exter- nal layer of longitudinal muscular fibres, and also a deep and very thick layer formed of circular fibres ; both layers seem to be continued into the prostatic portion of the urethra The mucous coat is extremely thin,* of a whitish colour, and presents some small papil lae. It is so difficult to demonstrate its follicles, that their existence has been denied ; but, with a little attention, they may always be found in the neighbourhood of the neck of the bladder, and upon the trigone. I have seen them in all parts of the bladder, under the form of vesicles, in certain cases of disease. The mucous membrane is moulded upon all the ridges of the muscular coat : it sometimes dips between the muscular bun- dles, and forms cells, in which calculi are often lodged. Bladders of this kind are call- ed sacculated, and, moreover, are almost ,a\vf?iys fasciculated ; i. e., the muscular fibres are so highly developed as to raise up the mucous membrane into ridges. The cellular tissue uniting the muscular and the mucous coats is tolerably loose, serous, and extreme- ly delicate. Vessels and Nerves. — The vesical arteries arise either directly from the hypogastrics, or from their branches. They are variable in number. The veins form a very remarkable plexus around the neck of the bladder, which is prolonged upon the sides of the inferior fundus, and terminates in the hypogastric veins. The lymphatic vessels are, for the most part, situated between the muscular and the peritoneal coats, and terminate in the hypo- gastric lymphatic glands. The nerves are derived from the hypogastric plexus, which is composed both of ganglionic and spinal nerves ; and hence the bladder is partly subject to, and partly beyond the influence of the will. Development. — The bladder of the foetus is remarkable for the predominance of its ver- tical over its transverse diameters, the latter being very short. This fact, added to the imperfect development of the pelvis, explains why the entire bladder projects above the brim of the pelvis at this period of life. The inferior fundus does not exist. The sum- mit is gradually continued into the urachus, which is then much larger than at subse- quent periods, and of which the bladder appears to be merely an expansion. According to some authors, the bladder is relatively larger, and, according to others, smaller before than after birth. In the early periods of infancy, the bladder retains tht characters which it had in the foetus, and many important surgical inferences may, therefore, be drawn from its more extensive relations with the abdominal parietes. In proportion as the pelvis is devel- oped, and also, perhaps, in proportion as the frequently-accumulated urine dilates the bladder in its transverse and antero-posterior diameters, this organ sinks into the pelvic cavity, and, when completely developed, presents the characters already assigned to it. The urachus, which, we have seen, is converted into a muscular cord in the adult, and is sometimes lost before reaching the umbilicus, is much more developed in the foetus : it may then be traced as far as the umbilicus, and even, according to some anatomists, through the whole extent of the umbilical cord. Analogy, and some observations upon the human subject, would seem to show that the urachus is hollow in the foetus. In the lower animals the cavity of the urachus may be traced into a bag called the allantois, which is situated between the membranes of the ovum ; and it is stated by several au- thors, that they have caused mercury injected into the bladder to pass some distance (half an inch, one inch, or one inch and a half) into the urachus, and even for a greater or less extent into the umbilical cord. Moreover, in new-born infants, and even in adults, the urine has been seen to escape through the umbilicus ; but, in these cases, the urethra is always obliterated. I have already said that I have met with a calculous concretion within the substance of the urachus, and I find that Haller and Harder have made a similar observation {arenuliB in uracho visa,). M. Boyer {Traiti d" Anatomic, p. 477, Splanchnoi ogie) says that he has dissected the bladder of a man twenty-six years of age, whose urachus formed a canal an inch and a half long, and contained twelve urinary calculi as large as millet-seeds ; one of them was larger, and resembled a grain of barley. He convinced himself that the canal which contained these calculi was not formed by a prolongation of the internal membrane of the bladder through the other coats. On the other hand, a number of ob- servers (myself among them) have found the urachus solid in the foetus. New facts are, therefore, necessary to settle this anatomical question ; although it is very probable that the urachus of the human subject is of the same nature as that of animals, but becomes obliterated at a much earlier period. Functions. — The bladder is intended as a reservoir for the urine, and is also the prin- cipal agent in its expulsion. The urine constantly trickles, drop by drop, into the blad- der, but cannot flow back by the ureters, on account of the mechanism already described. Wlien the bladder is distended, it occasions a desire to evacuate its contents, and the urine is then expelled by the combined action of the bladder itself and the abdominal muscles. I have said that the bladder is the chief agent in this expulsion, for, in cases * [This and all the other portions of the genito-urinary mucous membrane have A ^ th of an inch in di- ameter, and a long caudal filament : their total length is from ^J^th to j-^-^th of an inch : their organization is yet unknown ; but in the spermatozoa of the bear, Valentin has lately observed evidences of a definite in- ternal structure ; they perform very rapid movements, which continue some hours after evacuation or removal from the body. They are not found before puberty, and then only in the vesicuIiE seminales, vas deferens, and epididymis. The semen of the testis contains, besides the seminal granules, certain vesicles or cysts, in which, as shown by Wagner, the future spermatozoa are developed. i 454 SPLANCHNOLOGY. The structure of the parietes of the vesicles is also precisely the same as that of the deferent vessels, excepting that the external coat is thinner ; in the larger animals this coat is evidently muscular, and it appears to me to be so in the human subject also. I have in vain attempted to find the glands described by Winslovsr in the substance of the walls of the seminal vesicles. Efferent Ducts of the Vesiculcs Seminales. — From the anterior extremity or neck of each vesicle, which we have said is situated in the substance of the prostate, arises a very delicate duct, the efferent duct (c) of the vesicula seminalis : this duct almost immediately unites with the vas deferens, the walls of which are thin and very dilatable in this situa- tion. By the junction of the two, which occurs at a very acute angle, the ejaculatory duct (d) is formed ; this passes through the prostate (which is shown divided in the figure), upward and forward, parallel to and in contact with its fellow of the opposite side, but without communicating with it. The ejaculatory ducts have very thin parietes, but they are tolerably wide, and very dilatable ; closely apphed to each other, they open separately on the enlarged extremity of the verumontanum, one on the right, the other on the left (Jg. 182). The Penis. The penis, the organ of copulation, is situated in front of the symphysis pubis. When collapsed, it is flaccid, and forms a curve with the concavity looking downward ; but du- ring erection, it is large and hard, and forms a curve with its concavity turned upward. It is cylindrical when collapsed, but has a triangular prismatic form, with blunt edges, when in the opposite condition. Two of these edges are lateral, and are formed by the projection of the corpus cavemosum ; the other is anterior, and corresponds with the canal of the urethra. Its posterior extremity is attached to the pubis ; its anterior ex- tremity forms a conical enlargement, called the glans, on which is seen the orifice of the urethra. Structure. — The penis consists essentially of the corpus cavemosum and the canal of the urethra, the expanded extremity of which forms the glans penis. Some proper mus- cles are attached to it ; it receives large vessels and nerves, and it is covered by integu- ment. The Skin of the Penis and Prepuce. — The skin of the penis has several peculiarities : thus, it is very thin, although not so thin as that of the scrotum and the eyehds. In this respect it contrasts remarkably with the thick hairy skin which covers the- cushion of adipose tissue situated over the symphysis ; it is generally of a browner colour than that of the rest of the skin ; it has no hair bulbs visible to the naked eye ; it is extremely movable, being capable of gliding forward upon the corpus cavemosum, of forming a covering for tumours in the scrotvun, and also of folding upon itself when the penis is re- duced to its smallest dimensions. This great mobility of the skin is owing to the loose- ness of the sub-cutaneous cellular tissue, which is continuous with the dartos, and ap- pears to me to be of the same nature ; like that structure, it never contains fat, but may become infiltrated with serum. The Prepuce. — The skin of the penis forms a non-adherent sheath for the glans, upon Avhich it advances, and either projects beyond it or not, according as that part is flaccid or distended. At the free border of this sheath the skin does not terminate abruptly, but is reflected upon itself, assumes the characters of a mucous membrane, and passes back- ward as far as the base of the glans, so as to hne the inner surface of the cutaneous layer. Opposite the constriction or neck surrounding the glans, the mucous membrane or re- flected skin again becomes reflected over the glans, to which it forms a closely adherent covering, and at the margin of the orifice of the urethra becomes continuous with the mucous membrane hning that canal. The non-adherent sheath which covers the glans is called the prepuce.* Sometimes the orifice of this sheath is so narrow as to prevent its being easily drawn backward, especiedly during erection. This constitutes what is called phymosis.i Cir- cumcision, an operation which consists in removing an annular portion of the prepuce, was, as we know, a general custom among the Jews, and is now recognised among the operations of surgery. The length of the prepuce varies in difierent individuals ; in some it is very short, and only covers one half of the posterior third of the glans. The term franum praputii is applied to a triangular fold of mucous membrane, which is reflected from the prepuce upon the furrow on the lower surface of the glans, below the urethral orifice. Sometimes the prolongation of the fraenum as far as the orifice renders erection painful, and requires a slight operation, called section of the fraenum. The cellular tissue, between the cutaneous and mucous layers of the prepuce, par- takes of the characters of the sub-cutaneous cellular tissue of the penis ; its looseness * [Beneath the mncous membrane covering the constriction behind the corona glandis are situated clusters of small sebaceous glands, named glandule Tysoni, or odorifera.'] t When this malformation exists, if the prepuce he drawn back over the base of the glans, it cannot be re turned ; this comlition of the parts, and the sort of strangulation resulting from it, constitutes what is known by the name of para-phymosis. THE PENIS. 456 enables the prepuce to be unfolded, and this takes place more or less completely during erection. The Corpus Cavemosum. — The corpus cavemosmn, so named on account of its struc- ture, forms the greater portion of the penis ; it commences behind by a bifurcated ex- tremity, forming its roots, or crura. Each root arises immediately on the inside, and above the tuberosity of the ischium, by a very slender extremity, and gradually increas- ing in size, passes forward and inward along the ascending ramus of the ischium and the descending ramus of the pubes, to both of which it adheres intimately. At the sjrm- physis the two roots unite. The triangular interval between them is occupied by the canal of the urethra. The corpus cavemosum results, therefore, from the union of two distinct conical roots ; and on this account the older anatomists distinguished two corpora cavernosa ; but the communications existing between its two halves are opposed to any such distinction. The corpus cavemosum is cylindrical, and presents a longitudinal groove above, in which are lodged the dorsal vessels and nerves of the penis, and a broad and deep groove below, in which the urethra is situated. The anterior extremity is obtuse, and is em- braced by the base of the glans, with which it does not appear to have any vascular communication. Structure. — The corpus cavemosum is composed of a very strong fibrous cylinder, filled with a spongy or erectile tissue. The Fibrous Cylinder. — The external coat is of a fibrous nature, and is remarkable for its thickness, which is one or two lines ; for its strength, which is such that the corpus cavemosum will bear the whole weight of the body without breaking, as may be proved experimentally upon the dead body ; and for its extensibility and elasticity, properties which do not belong intrinsically to the tissue itself, but depend upon the areolar disposition of its fibres.* Septum of the Corpus Cavemosum. — The interior of the cavernous body is divided into two lateral halves by an incomplete septum, formed of very strong vertical fibrous col- umns, which are much thicker and more numerous behind than in front. This median septum (septum pectiniforme, h, fig. 187), between the two halves of the corpus caver- nosum, is not complete ; it appears to be intended to prevent too great a distension of this part during erection. - The Spongy or Erectile Tissue. — An areolar tissue (a a), the meshes of which contain a greater or less quantity of blood, occupies the interior of the fibrous cylinder of the corpus cavemosum. This tissue, which is the chief agent in erection, consists of an interlacement of veins, supported by prolongations or trabecule, given off from the inner surface of the fibrous membrane. If air or any fluid be injected into the crura of the corpus cavemosum, the penis will acquire the same size as it has during erection, and the injection will pass readily into the veins ; we may therefore conclude that all the cells of the corpus cavemosum com- municate with each other, and, farther, that they communicate freely with the veins If the corpus cavemosum be distended with tallow, and then, after being allowed to dry, if the injection be dissolved out by hot oil of turpentine, we shall find that the cavernous body presents a spongy stmcture, analogous to that of the spleen. The several grada- tions from tme veins to spongy tissue may be traced in the venous plexus, situated at the root of the penis. At first we find veins communicating with each other laterally, as it were, by perforations ; then the communications become more and more numerous ; and, lastly, in the corpus cavemosum all traces of distinct vessels are lost, and nothing can be detected but a mass of cells, apparently resulting from the anastomoses of veins. The structure of the spongy tissue of the corpus cavemosum is, therefore, essentially venous. A transverse section of the corpus cavemosum (^. 187), after it has been prepared in the manner above indicated, exhibits an appearance of cells, somewhat resembling that seen on a section of the body of a ver- tebra ; these cells are bounded by laminae, which appear to be chiefly derived from the lower wall of the corpus cavemosum, on the inner surface of which is found a convexity, corresponding with the groove for the urethra {d). These laminae radiate, as from a centre, to the entire internal surface of the cyhnder, repre- sented by the corpus cavemosum. Vessels. — The veins of the corpus cavemosum are extremely large, and are divided into the dorsal veins of the penis and the o'/ proper veins of the cavemous body ; they all pass beneath the symphysis, and are received into fibrous canals, through which they are transmitted into the pelvis. These veins are provided with a great number of valves, so that injections thrown into the trunks cannot pass into the branches. * [The outer coat of the corpus cavemosum and the trabecule, in its interior, consist of tendinous fibres, mixed with some elastic tissue. In the penis of the horse there are pale red fibres, differiu? from cellular tendinous, and elastic tissue, but which, according to Miiller, do not possess muscular contractility.] 456 SPLANCHNOLOGY. The arteries arise from the internal pudic, and enter the substance of the corpus ca vemosum. Injection of these arteries does not produce erection until the fluid has pass- ed from them into the veins.* The lymphatic vessels are little known. No nerves have been traced into the interior of the corpus cavemosum.t The Triangular Suspensory Ligament of the Penis. — This ligament is composed of yel- low elastic tissue, and extends in the median hne from the symphysis pubis to the cor- pus cavemosum. Muscular fibres have been described as existing in it ; but it is prob- able some fibres prolonged from the bulbo-cavernosus, and now known as the muscle of Houston, have been regarded as forming part of this ligament. I have seen the sus- pensory ligament reach along the linea alba, half way up to the umbilicus. Muscles of the Penis. These are eight in number, four on each side, viz., the ischio-cavernosus, the bulbo-ca- vernosus, the pubio-urethralis, and the ischio-bulbosus. The Ischio-cavernosus, or the Erector Penis. The ischio-cavernosus {c,Jig. 163) is an elongated muscle, situated upon the corre- sponding root of the corpus cavemosum ; it is curved upon itself, and is aponeurotic in part of its extent. It arise* from the inner lip of the tuberosity of the ischium, below the transversus pe- rinaei, by tendinous and fleshy fibres, and also from the surface of the root of the corpus cavemosum. From these points its fibres pass inward, and are inserted, after a short course, into the edges of the upper surface of a very strong, shining, and fasciculated aponeurosis, having its fibres directed from behind forward, which covers the correspond- ing root of the cavernous body, upon which it is then prolonged. The fleshy fibres, ter- minating at the edges of the aponeurosis, form two bundles ; one internal, and extend- ing upon the inner side of the root, the other extemal, which passes on the outer side of the same, and is prolonged, much farther than the internal fasciculus, upon the cav- ernous body. In order to see the structure of this muscle, it is necessary to make a longitudinal incision into the aponeurosis, which entirely covers its lower surface ; we then observe a muscular layer, which is tolerabjy thick behind, but thin in front, and is formed partly by the original fibres, and pertly by others arising from the root of the corpus cavemosum itself Relations. — Below, with the cellular tissue and the dartos ; above, with the root of the corpus cavemosum, upon which it is closely applied ; on the inside, with the bulbo-cav- ernosus, being separated from it by a triangular space, the base of which is directed backward. Uses. — It acts solely upon the corpus cavemosum, drawing the root of the penis down- ward and backward • instead of compressing the root of the corpus cavemosum by the contraction of its fibres, it tends, on the contrary, to dilate its cavity, by separating the wer from the upper wall, and, in this manner, facilitates erection. The Bulbo-cavernosus, or Accelerator Urince. This muscle {d,fig. 163) is much larger than the preceding ; it is situated in front of the anus, extending along the lower surface of the bulb and the spongy portion of the urethra, upon which it seems to be moulded. It arises in front of the sphincter ani by a median fibrous raphe, which is common to the two muscles of this name, and which appears to arise from the bulb, to which it ad heres closely ; while the exteraed fibres arise from the posterior margin of the triangu- lar ligament, or deep perineal fascia, and frequently from the rami of the ossa pubis, op- posite that margin. From this double origin the fibres pass forward, and terminate in the following manner : the outermost fibres form a thin layer upon the lower surface of the triangular ligament, and are inserted by short, tendinous fibres to the inner side of the root of the corpus cavemosum ; the middle fibres, which are larger, are directed oblique- ly inward, and are inserted by very distinct tendinous fibres immediately in front of the jtoint of junction of the roots of the corpus cavemosum, in the sort of groove between that body and the urethra ; the innermost fibres are the longest ; they pass directly for- * [Miiller has described, besides the nutritious arteries of the corpus cavemosum, which terminate, as usual, ill the veins, a peculiar set of vessels, called the arterite helicina. They are short, curled branches, much larger than capillaries, and ending abruptly in free rounded extremities ; they project either singly, or in tufts arising ii-om one stem, into the venous cells,by the lining membrane of which they are supported and invested. They are found principally in the posterior portions of the cavernous and spongy bodies, and are more marked in man than in animals. In the horse they are very indistinct ; in the elephant they do not exist at all. Miil- ler believes that the blood, during erection, is poured out directly from these vessels into the venous cells ; but no openings through which the blood could escape have been detected, either in their sides o-- at their ex tremities, nor is analogy in favour of their existence. According to Valentin, the so-called helicine arteries are the divided branches of common arteries curled up (after having been injected), in consequence of the retraction of the elastic trabeculie on which they are sup- ported ; to this it is replied, by Miiller, that these vessels may be seen in cells deeper than the surface o; the lection. Valentin farther maintains that the arteries terminate in the veins by wide, funnel-shaped orifices.] t [Numerous nerves enter the corpus cavemosum; they arc derived from the internal pudic and sympatheV ic nerves, and have been carefully traced by Mtiller.l THE URETHRA. 45^ ward, and, at the point where the penis is bent in front of the pubis, are inflected out- ward ie,fig. 163), pass upon the sides of the penis, and terminate on its dorsal surface, becoming continuous with the suspensory ligament. Tlie last-named termination ap- pears to me to constitute the muscle described by Houston, which, according to that anatomist, is intended to compress the dorsal veins of the penis* in man and other ani- mals ; but it is evident, on the one hand, that it cannot compress the veins of the penis ; and, on the other, as M. Lenoir has pointed out, that the dorsal veins of the penis are cutaneous veins, which do not communicate with those of the corpus cavemosum.t Relations. — I3elow, the bulbo-cavernosus corresponds with the dartos, from which it is separated by the superficial perineal fascia by a very thin layer of fat, and by a proper fibrous sheath. Above, it is in relation with the bulb of the urethra, which it embraces, like a contractile sheath, resembling the sheath around the stems of grasses. The inner border is continuous with the muscle of the opposite side ; so that, at first sight, it might be thought that there is but one bulbo-cavernosus. Uses. — Its attachment to the inner side of the corpus cavemosum enables it to separ- ate the lower wall of that body from the upper, and, consequently, to induce the entrance of the blood. It therefore contributes powerfully to erection. On the other hand, by compressing the urethra, it accelerates the expulsion of the urine and semen. The Puhio-urethralis. This muscle, known also as the muscle of Wilson, because it was described by that anat- omist, may be regawied as the continuation of the levator ani. The two nmscles arise from the middle of the sub-pubic arch, and descend first upon the sides and then on the lower surface of the membranous portion of the urethra, which they surround as in a ring. They are situated behind the triangular ligament, or deep perineal fascia.t When spasmodically contracted, it is said that they may arrest the point of a catheter. The Ischio-bulbosus. We may describe under this name a small muscle situated below the deep perineal fascia. It is stronger than the transversus perinaei ; it arises from the ascending ramus of the ischium and the descending ramus of the pubis, and terminates on the sides of the bulb. This muscle, which is of a triangular shape, is separated from the one last de- scribed by the deep perineal" fascia, so that it cannot be regarded as a dependance of the levator ani. <""' rather, with some very strong ligamentous bundles, which extend from the pubes to the blad- der, and are called the ligaments of the bladder. This surface has no immediate rela- tions with the arch of the pubes, behind which it is placed ; it is always some lines dis- tant from it. Nevertheless, by means of a silver catheter or sound, introduced into the bladder, we may draw the prostate under the pubes, and make it project in the perineum. The sides are embraced by the levator ani and the levator prostatae. When the prostate is pushed downward by the catheter, its sides are embraced by the circumference of the arch of the pubes, and they then approach very near the trunk of the internal pudic artery. The base of the prostate embraces the neck of the bladder, and is prolonged a little upon that organ, so as to surround the vas deferens and the neck of the vesiculffi semi- nales. * It was this direction of the canal which suggested to J. L. Petit the idea of making silver bougies, shaped like the letter S, to remain in the passage. t An Improved Method of treating Stricture of the Urethra, 1816. THE URETHRA. 43^ The apex terminates behind the membranous portion of the urethra. Relations of the Prostate vsith the Parts situated in its Interior. — The prostate is perfo- rated by the urethra, by the ejaculatory ducts, and by its own excretory ducts. The relations of the urethra with the prostate vary in different subjects : thus, sometimes its lower three fourths only are surrounded by the gland, which is accordingly wanting above, and is merely grooved, not perforated by a canal ; sometimes the prostate forms a complete hollow cylinder around the urethra. The portion of the prostate situated above the urethra is scarcely ever thicker than the part beneath it. In some cases, however, the urethra has been found occupying the lower part of the prostate, and only separated from the rectum by a very thin layer of glandular substance. When such is the case, the rectum is very liable to be wounded in the different steps of the operation of lithotomy.* In the natural state the prostate does not project into the urethra ; but not unfrequent- ly we find a prominence, of greater or less size, rising from the lower part of the urethra, opposite the base of the prostate, and obstructing more or less completely the com- mencement of that canal : this tubercle was named by Lieutaud la luette visicale {uvula vesica) ; by Sir Everard Home, an enlargement of the middle lobe of the prostate. But, in the first place, this prominence only exists in disease ; and, secondly, there is no middle lobe, unless that term be applied to the slightly-grooved, and, therefore, thinner portion by which the two lateral halves of the prostate are united. Relations of the Ejaculatory Ducts with the Prostate. — The ejaculatory ducts (d,fig. 186), which lie close to each other, are received into a sort of conical canal, formed in the prostate. Some loose cellular tissue separates them from the substance of the gland, of which they are altogether independent ; it was chiefly to the portion of the prostate which is situated above this canal that the name middle lobe was given by Home. Density. — The density of the prostate is considerable, and yet the tissue of this gland is friable, and can be very easily torn after having been once divided. It is of the greatest importance to remember this friability in performing the operation of lithotomy. The prostate, in fact, is the only obstacle to the extraction of the calculus ; and when this gland has been divided in its antero-posterior diameter, the bladder itself may be torn with the greatest facility. Structure. — The structure of the prostate can only be properly studied in the adult. In certain cases of hypertrophy without alteration of tissue, its characters are, as it were, exaggerated. It consists of a collection of glandular lobules, which may be subdi- vided into granules pressed close to each other in the midst of a tissue that appears to me to be muscular, for it is continuous with the muscular coat of the bladder, and bears the most perfect resemblance to it in cases of hypertrophy. From these granules, which are generally of unequal size, small excretory ducts proceed, and unite into an irregular number of prostatic ducts that open, not upon the verumontanwn itself, but upon its sides {see fig. 182), in the whole extent of the lower wall of the prostatic portion of the ure- thra, or prostatic sinus. I have assured myself of the existence of these ducts and their orifices in many cases where I have found them filled with innumerable small calculi, resembling grains of brownish sand. The orifices of the prostatic ducts may be easily detected by pressing the gland, when the fluid secreted by it will be observed to exude at several points. The Membranous Portion. — The membranous portion of the urethra (c,fig. 181) ex- tends from the prostatic portion to the bulb, and passes upward and forward.! It is in relation above and laterally with the arch of the pubes, from which it is separated by some considerable veins, or, rather, by a sort of erectile tissue ; below it corresponds with the rectum, but is separated from it by a triangular space, having its base directed forward and downward, and its apex backward and upward. It is generally in this tri- angular space that the urethra is divided in the operation of lithotomy. Its upper concave surface is about an inch long ; its lower surface is from four to six lines. This difference in length is caused by the bulb projecting backward upon the lower surface of the membranous portion of the urethra. This part of the canal is embraced laterally and below by the two muscular bundles which have been already described as the muscles of Wilson ; and also by the transverse muscular fasciculi described by Santorini and Guthrie. The Spongy Portion. — The spongy portion {I) constitutes the greatest part of the length of the urethra ; it commences opposite the symphysis pubis by a very considerable ex- pansion, called the bulb (below I), and terminates at the extremity of the penis by an- other and still larger expansion, which constitutes the glans penis. * The varieties in the situation of the urethra, in relation to the prostate, were yreU pointed out by M. Senn, in an inaugural dissertation in 1825. According to his observations, the portion of the prostate situ- ated below the canal is seven or eight lines thick in the middle, and ten or eleveu lines when measured down- ward and outward. t [The membranous portion perforates both layers of the triangular ligament, about an inch below the arch of the pubes {see Jig. 138) ; but as the two layers are separated from each other below, the greater part of this portion of the urethra is included between them ; a very small part is situated behind the posterior laver both layers are prolonged over the urethra, one forward and tlie other backward.] 400 ' SPLANCHNOLOGY. The hdb occupies the highest part of the pilbic arch, and fills the interval between the crura of the corpus cavemosum. Its size varies in different individuals, and according to the state of the penis ; it projects several lines below the level of the membranous portion, which is partially covered by it in this direction, and seems to open into its up- per part. As the bulb is directed very obliquely upward and forward, we might be inclined to consider the urethra to be much more curved than it actually is, if we judged of it only by the external appearance of the canal. The bulb is embraced below and upon the sides by the bulbo-cavernosi muscles, which have numerous points of insertion upon it. Between these muscles and the bulb we find Cowper's glands. The bulb terminates insensibly in front, becoming continuous with the spongy portion : the angle of union of the crura of the corpus cavernosum may be assigned as its anterior boundary. The Glands of Cowper. — These are two small, rounded bodies (g g,figs. 168, 181, 182) (so called after the anatomist who has given the best description of them), situated against the bulb, in contact with which they are retained by a tolerably dense layer of fibrous tissue.* From each of these glands, which are of variable dimensions, an excre- tory duct proceeds, and after a course of an inch and a half or two inches, opens into the canal of the urethra upon the sides of the spongy portion (c, fig. 182), passing ob- liquely through its parietes.t In front of the bulb, the spongy portion of the urethra enters the groove on the lower surface of the corpus cavernosum, and is in relation below, in the first part of its course, with the bulbo-cavernosi muscles, which separate it from the cellular tissue of the scro- tum, and more anteriorly with the skin of the penis. The glans, so called from its shape, is the conical enlargement which forms the ex- tremity of the penis. It is covered by the prepuce, which is united to it below by means of the fraenum ; its base projects considerably beyond the end of the corpus cavernosum, and forms what is called the corona glandis. This circular projection is grooved perpen- dicularly throughout its entire extent by some large nervous papillae, which are visible to the naked eye. The base of the glans is cut very obliquely, so that its upper surface is twice as long as its lower. Below, and in the median line, the corona glandis pre- sents a groove, in which the fraenum is received. At the extremity of the glans is situated the orifice of the urethra, meatus urinarius, a vertical fissure, three or four lines in extent, and placed in the same line as the frae- num, from which it is separated by a very short interval. Sometimes this orifice is placed exactly opposite the fraenum, and, like it, is directed downward : this malforma- tion constitutes what is called hypospadias. Internal Surface of the Urethra. — Upon this surface (see fig. 182) we find no trace of the distinction established between the different portions of the urethra, considered from without, except that the prostatic portion of the canal is of a white colour, while all the rest of it is of a more or less deep violet hue. Dimensions. — Opposite the prostate the urethra becomes dilated, sometimes to a con- siderable extent (sinus prostaticus) ; at the commencement of the membranous portion it suddenly contracts, and then continues cylindrical as far as the glans, where it again dilates so as to form the fossa navicularis (o), and terminates by an orifice, which is the narrowest part of the entire canal.J In order to obtain more exact ideas of the comparative dimensions of the different portions of the urethra, M. Amussat inflated this canal, and then carefully removed all the structures superadded to its proper parietes, so as to reduce the latter to the mu- cous membrane only, and thus leave them of almost unifonn thickness, instead of being very unequal. According to this mode of appreciation, which, however, is not free from objection, he has shown that the narrowest part of the canal is the bulbous, not the membranous portion ; that the canal, after being contracted opposite the bulb, again ex- pands at the spongy portion, and then gradually contracts as it proceeds forward. He denies the existence of a dilatation opposite the fossa navicularis ; and attributes the dilated appearance of that part to the fact of the tissue of the glans being very dense, and closely adherent to the mucous membrane of the urethra, so as not to allow it to collapse, like that of the other parts of the canal. However, the extreme dilatability of the walls of the urethra render an exact deter- mination of its dimensions less important than might be imagined. Besides the extensibility of the tissues, there is another anatomical condition which favours the extreme dilatabihty of the urethra, viz., the existence of longitudinal folds on the inner surface of the canal, which are effaced by distension. These folds must * [They are placed between the two layers of the triangular ligament : the transverse musrles of Santorini cover them below, am Jhe arteries of the bulb (e e,Jig. 168) cross above them : they are compound glands.] t I have never seen the gland called, by Litre, the anti-prostatic ; nor have I seen the third gland of Cow- per, which is said to be situated below the arch of the pubes. i [Three dilatations in the urethra are usually described, viz., the prostatic sinus, the sinus of the bulb, and the fossa navicularis. The first and the third of these are described above ; the second is at the commenco ment of the soongy portion, in the inferior wall of the urethra.! THE OVARIES. 461 not be confounded with certain small longitudinal fasciculi which lie beneath the mu- cous membrane throughout the whole extent of the canal, and appear to me to be of a muscular nature. The whole of the inner surface of the urethra presents a nmnber of oblique orifices, which lead into culs-de-sac of variable depths. These sinuses, the ori- fices of which are always directed forward, are sometimes large enough to receive the extremities of bougies ; they were very well described by Morgagni, and, therefore, they are generally called the sinuses of Morgagni. I have seen them more than an inch long. No glands open into them.* The Verumontanum, or Crest of the Urethra. — The lower wall of the membranous por- tion of the urethra presents, in the median line, a crest, which has been named the ve- rumontanum, caput gallinaginis, or urethral crest {a to d). This crest commences in front by a very delicate extremity ; is directed backward along the median line, and termi- nates at the anterior part of the prostatic portion by an enlarged extremity (a), upon which the ejaculatory ducts open by two distinct orifices. From this posterior extrem ity several radiated folds proceed on either side, called the frcena of the verumontanum, which are lost in the opening of the neck of the bladder ; they were carefully described by Langenbeck. The prostatic ducts open at the sides of the verumontanum. Structure of the Urethra. — ^A very fine transparent mucous membrane, of an epidermic character, lines the inner surface of the urethra ; and is continuous, on the one hand, with the mucous membrane of the bladder, and, on the other, with that covering the glans. It is also continued through the ejaculatory ducts, into the vasa deferentia and the vesiculae seminales.f The structure of the urethra, as regards the coats external to the mucous membrane, is not the same in the different portions of the canal. In the prostatic portion, we find the same elements as in the bladder, which seems as if it were continued into the cavity of the prostate. The deepest layer of the muscular coat of the bladder is prolonged between the mucous membrane and the prostate, while the other layers form different planes which penetrate into the substance of the gland. The membranous portion would be more correctly denominated the muscular part of the canal, for it is surrounded by a layer of muscular fibres. A plexus of veins sur- rounds these muscular fibres. The spongy portion Q f,fig. 182; c,fig. 187) has a similar appearance to that of the cavernous body ; it is an erectile structure, composed of a fibrous framework, formed by numerous prolongations interlaced in all directions, so as to resemble areolar tissue. It is probable that the internal coat of the veins lines all the cells, which contain more or less blood, according to the state of the penis. In the tissue of the corpus spongiosum, as well as in that of the corpus cavernosum, are found longitudinal muscular fibres, very evident to the naked eye in the larger ani- mals, and the existence of which appears to be shown by the microscope in the human subject. The structure of the glans (//) is exactly the same as that of the bulb, only its tissue is more dense. The corpus spongiosum urethrae does not communicate with the corpus cavernosum, although at first sight it appears to be nothing more than a con- tinuation of it. The blunt extremity of the corpus cavernosum is evidently embraced by the base of the glans, but no communication exists between the erectile tissue com- posing these two bodies, so that it is possible to inject them separately. THE GENERATIVE ORGANS OF THE FEMALE. The Ovaries. — The Fallopian Tubes. — The Uterus. — The Vagina. — The Urethra. — The Vulva. The genital organs of the female consist of the ovaries, the Fallopian tubes, the uterus, the vagina, and the several parts forming the vulva. With these we may include the mammae, as appendages to the generative apparatus. The Ovaries. The ovaries {ovaria), so called on account of the small vesicular ova which they con- tain, are the representatives of the testicles in the male ; the product secreted by both the one and the other is absolutely indispensable for reproduction. From this analogy between the ovaries and testes the ancients called them testes muliebres (Galen). The ovaries (a a, fig. 188) are two in number, and are situated one on each side of the uterus, in that portion of the broad ligament {d d') termed the posterior ala (J), and be- hind the Fallopion tube. They are retained in this position by the broad ligament, and by a proper ligament called the ligament of the ovary (c). * [One of these sinuses or lacunae, larger than the rest, and situated on the upper surface of the fossa na- vicularis, is called the lacuna magna ; they appear to be mucous crypts.] t [It is prolonged into the ducts of Cowper's glands and the prostate, into the vesiculiE seminales, vasa def- erentia, and tubuh seminiferi, and through the ureters into the uriniferous ducts ; in the female it also linei the vagina, uterus, and Fallopian tubes ; the whole forms the genito-urinary system of mucous membranes ; it is covered throughout with an epithelium, which, in the male generative apparatus, approaches the columnar form.] 462 SPLANCHNOLOGV. Then situation varies at different ages, and also according to the state of the uterus. In the foetus, they are placed in the lumbar regions, like the testicles. During pregnan- cy they are carried up into the abdomen with the uterus, upon the sides of which they are applied. Immediately after delivery, they occupy the iliac fossae, where they some- times remain during the whole period of life, being retained there by accidental adhe- sions. It is extremely common to find them thrown backward,* and adhering to the pos- terior surface of the uterus. The ovary has sometimes been found in inguinal or femoral hernise : by descending into the labia majora, they have simulated the appearance of testicles. The size of the ovaries varies according to age, and according as the uterus is gravid or unimpregnated, healthy or diseased. They are relatively larger in the foetus than in the adult ; they diminish in size after birth, again increase at the period of puberty, and become atrophied in old age. During the latter periods of pregnancy, they sometimes acquire double or triple their ordinary size. The ovaries are of an oval shape, a little flattened from before backward ; they are of a whitish colour ; their surface is rough, and, as it were, cracked, and is often covered with very dark-coloured cicatrices, which have been incorrectly regarded as remains of ruptures in their external coat, to allow of the escape of the fecundated ovum. The ovary is free in front, behind, and above, but is attached by its lower border to the broad hgament, by its outer end to the trumpet-shaped extremity of the Fallopian tube, and by its inner end to the corresponding side of the uterus, some lines below the upper angle of that organ, by means of a ligamentous cord, called the ligament of the ovary (c) ; which was for a long time regarded as a canal {ductus ejaculans), intended to convey an ovarian fluid into the uterus. The tissue of this ligament strongly resembles that of the uterus, and seems to be a prolongation from it. I Structure. — The ovary is composed externally of a dense fibrous coat, covered by the peritoneum, which adheres so closely to it that it cannot be detached ; and, internally, of a spongy and vascular tissue, the areolae of which seem to be formed by very dehcate prolongations from the external coat ; in the midst of this tissue (the stroma, from arpufia, a bed) the Graafian vesicles are deposited. These vesicles vary in number, from three or four to fifty. The structure of the ovary is most evident in the recently-delivered fe- male. At that time its tissue, expanded, and, as it were, spongy, appears to me to re- semble that of the dartos, and is traversed by a great number of vessels. I have also seen, in recently-delivered females, the ovaries from twelve to fifteen times larger than usual, and converted into a sac, having very thin parietes, which were easily torn ; the ovary itself was of a spongy, vascular, and diffluent texture, in the midst of which the vesicles were seen unaltered. The vesicles are nothing more than small cysts of variable size, with very thin trans- parent walls, adhering to the tissue of the ovary, and containing a hmpid serosity, either colourless, or of a citron yellow. According to Von Baer, the most superficial vesicles which approach the expanded extremity of the Fallopian tube, contain a floating body, which was imperfectly seen by Malpighi, and constitutes the germ or ovum. J I have often metvdth ovaries destitute of vesicles ; but then they had undergone some change, that of induration, for excunple. May the absence of these vesicles be regarded as a cause of sterility 1 The corpora lutea, according to the observations of Haller, consist of the remains of vesicles that have been ruptured in consequence of the act of impregnation ; they are brownish-yellow masses, of a tolerably firm consistence, and which I have found as large as a cherry-stone in females recently delivered. These bodies have been ascertained to exist in females who have never borne children, and this anomaly has been explained by supposing that they may be produced in consequence of masturbation. We would re- mark, however, that there is no constant relation between the existence of these bodies and the occurrence of fecundation. In some females who have had many children, no corpora lutea can be detected, and, on the other hand, a corpus luteum has been found in a girl of five years of age. The bloodvessels and veins of the ovary correspond exactly with those of the testicles. * The situation of the ovaries, behind the Fallopian tabes, prevents their displacement forward. t It has even been stated that this so-called efferent duct of the ovary divides into two branches, one of which opens directly into the uterus, while the other runs along its border, and opens near the os uteri. t [The vesicles of De Graaf vary from the size of a pea to that of a pin's head ; they have two tunics, ono external and vascular, the other called the ovi-capsule, which, according to Schwann, is lined internally with epithelium (membrana granulosa, Bair). In each vesicle there is usually but one ovum, which at first occu- pies its centre, but in the mature condition approaches the inner surface of its internal coat, and, sunounded by a granular covering (tunica granulosa, Barry), is held there by retinacula (Barry). The ovum is a perfect- ly spherical body, of uniform size (about y^th of an inch in diameter) ; it consists of a thick but very trans- parent coat (zona pellucida, Valentiri ; chorion, Wagrier), which surrounds the sul)stance of the yolk ; within the yolk is situated the germinal vesicle of Purkinj6 (about yg-jrth of an inch in diameter), and within that the germinal spot of Wagner (about-g-^^th or g-rWth of an inch). The changes incidental to impregnation, according to Dr. Barry, commence in tlie germinal spot and vesicle. For farther information, and for a list of works upon this subject, see Milller''s Physiology, translated by Dr Baly, and Wagner's Physitlogy, trausla- tpd by Dr. Willis.] THE FALLOPIAN TUBES. 463 Uses. — Without precisely determining the part performed by the ovaries in reproduc- tion, it may be said that they are indispensable to that function. Extirpation of these bodies is followed by sterility. And, again, ovarian foetation proves that fecundation may occur within the ovary. The use of the Graafian vesicles in generation is not well known.* The Fallopian Tubes. The tula uterina {ff,fig- 188) are two ducts, situated in the substance of the upper margin of the broad ... ,„ Ugament. They are t^-vsa. also called the tubae rallopianae,+ the Fal- lopian tubes, after Fallopius, who first gave a good descrip- tion of them ; they ex- tend from the upper angle of the uterus to the sides of the cavity of the true pelvis. Situation and Di- rection. — Floating, as it were, in the cavity of the pelvis, between the ovaries behind, and the round ligaments (^ g) in front, they pass transversely out- ward, and at the point where they terminate, bend backward and inward, in order to approach the outer end of the ovary, to which they are attached by a small ligament. Each Fallopian tube is straight in the inner half of its course, but describes certain wind- ings in the remaining outer portion, which are so considerable in certain cases, and especially when the tube has been the seat of chronic inilammation or of dropsy, as to resemble in some degree the windings of the vas deferens. Moreover, accidental adhe- sions of the expanded extremity very frequently give it an entirely different direction from the one it usually takes. The tubes may be drawn down with the ovaries into a hernial sac, as I have several times observed. The length of the Fallopian tube is four or five inches, but it sometimes varies on the two sides. The canal in their interior is very narrow along their inner half, but gradu- ally enlarges as it proceeds outward to their termination, which is expanded and divided into irregular fringes, like the calyces of certain flowers ; this expanded end constitutes the mouth of the trumpet, or the fimbriated extremity (e) of the Fallopian tube. In order to obtain a good view of this structure, it is necessary to place the tube in water, and then a number of fringes or small shreds of unequal length will be seen floating in the liquid, and consisting of folds divided unequally, and sometimes forming two or three concentric circles. It is generally said that one of these fringes, longer than the rest, is attached to the outer end of the ovary ; but this connexion appears to me to be effected by means of a small ligament. All these folded fringes terminate around a circle some- what narrower than the adjoining portion of the tube ; this circle constitutes the free orifi.ce, or ostium abdominale of the tube. The outer portion of the tube will admit the end of a moderate-sized catheter, while the inner portion will scarcely admit a bristle. The diameter of that portion of the tube which traverses the uterine walls is capillary, and it is very difficult to detect with the naked eye its uterine orifice, or ostium uterinum (o o, fig. 189). As the canal of the tube opens into the uterine cavity on the one hand, and into the cavity of the peritoneum on the other, it forms a direct communication between the two ; and hence certain cases of peritonitis have been supposed to depend upon the passage of a fluid from the uterus into the peritoneal sac. Not very unfrequently the fimbriated orifice of the tube is ob- literated ; in this case the tube becomes dilated like a cone, having its base directed out- ward, and it also becomes much more flexuous. When opened longitudinally, and placed under water, the outer or wide portion of the tube presents longitudinal folds of unequal breadth, and touching by their free edges. There is no valve, either in the course or at the orifices of the tube. Its narrow jior- tion is hard to the touch, inextensible, and closely resembles in appearance the vas def- erens ; its wide portion is collapsed, and its walls are thin and extensible. Structure. — The peritonium adheres closely to it, and forms its outer coat ; it is lined by a mucous membrane, which can be easily shown in the whole extent of the broad and folded portion, and appears to form of itself the longitudinal folds already described. This lining membrane is continuous, on the one hand, with the uterine mucous mem- brane, and on the other, with the peritoneum, at the fimbriated extremity of the tube ; it thus presents the only example in the human body of the direct continuity of a serous * See note, p. 462. t [Literally, the Fallopian tnimpeU, from their expanded abdominal extremities.! 464 SPLANCHNOLOGY. and mucous membrane. Between the peritoneal and the mucous coats is found a proper membrane, which appears to be a prolongation of the tissue of the uterus, and is proba- bly muscular.* Uses. — The Fallopian tubes, which represent in the female the vasa deferentia in the male, serve not only to transmit the fecundating principle of the male, but also to con- duct the fecundated ovum into the uterus. These uses are proved by the sterility of females in whom the tubes have been tied ; and by the occurrence of tubal fcEtations, in which the fecundated ovum is arrested in the cavity of the tube, and thei'e passes through the several stages of development. The fimbriated extremity of the tube is intended to embrace the ovary during the act of fecundation, and to apply itself to the spot from which the ovxun is to be detached ; it follows, therefore, that any adhesion of the ovary or of the tube which prevents this, acts as a cause of sterility. The Uterus. The uterus (uter, a leather-bottle), matrix (mater), or womb, is the organ of gestation. It is situated {u,fig. 190) in the cavity of the pelvis, in the median line, between the bladder and the rectum, and is retained in that position by the round and broad ligament on each side, and by the upper end of the vagina below. The looseness and extensibility of its connexions enable it to float, as it were, in the cavity of the pelvis, and to be moved to a greater or less extent. The facility with which it can be drawn towards the vulva in certain surgical operations, and its displace- ment during pregnancy, when it rises into the abdomen, are proofs of its great mobility. Direction. — Its long axis is directed obliquely downward and backward, i. e., it coin- cides with the axis of the brim of the pelvis. Its direction is liable to frequent varia- tions, the history of which belongs to midwifery ; but one of them, viz., the obliquity downward, and from the right to the left side, is so frequent that it has been regarded as natural, and, according to some anatomists, appears to be connected with the posi- tion of the rectum on the left side of the pelvis. In pregnancy, this inclination is almost constant, and has some relation with the most usual position of the child, viz., that in which the occiput is turned towards the left acetabulum of the mother. Number. — The uterus is single in the human species ; it is double in most animals. The cases of double uterus observed in the human subject are nothing more than bifid uteri, or such as are divided by a septum : this state may exist either in the body of the uterus alone, or at the same time in the body and neck, and even in the vagina. Size. — The size of the uterus varies according to age, and certain physiological con- ditions peculiar to this organ. It is very small until puberty, and then acquires the size which it subsequently presents. In females who have borne children it never returns to its original size. It becomes enormously enlarged during pregnancy, or from the de- velopment of certain tumours. In old age it becomes atrophied, and is sometimes as small as it is in newborn infants. The following are the measurements of the uterus after puberty : length, two and a half to three inches ; breadth, at the fundus, sixteen to eighteen lines, at the neck six lines ; antero-posterior diameter, or thickness, six lines.t Weight. — The weight of the uterus is from six to ten drachms at puberty, an ounce and a half or two ounces in females who have had children. I have seen it from one to two drachms in aged females, in whom it had become atrophied. At the end of preg- nancy the weight of the uterus is from a pound and a half to three pounds. Form. — The uterus is shaped like a small gourd, or a pear flattened from before back- ward. It is divided into a body (m), and cervix or neck (A) ; the distinction between these two parts being established by a more or less marked constriction. Relations. — These must be studied in front, behind, on the sides, at the upper border or fundus, and at the lower or vaginal extremity. The anterior surface is covered by the peritoneum in its upper three fourths, and is in- directly in relation with the posterior surface of the bladder, from which it is often sep- arated by some convolutions of the small intestine ; in its lower fourth it is in imme- diate contact with the inferior fundus of the bladder, and is united to it by rather loose cellular tissue. The latter relation explains why cancerous affections of the uterus so often extend to the base of the bladder. The posterior surface is entirely covered by the peritoneum, and is in relation with the anterior surface of the rectum, from which it is often separated by some convolutions of the small intestine. This surface is much more convex than the anterior ; it may be examined from the rectiun. Its sides are slightly concave, and give attachment to the broad ligaments (d d', d d'), which are two quadrilateral folds of peritoneum, extended transversely from the lateral * [Muscular fibres have not yet been demonstrated in the human subject, though in some animals circular and longitudinal contractile fibres have been found. The epithelium of the mucous membrane is columnar and ciliated : by the action of the cilia the contents of the tubes are urged towards the uterus : Dr. Heul6 has found cilia on both surfaces of the fimbrise.] t [The body of the uterus, at its thickest part, viz., immediately below the fundus, is from eight to twelTe lines thick.] THE UTERUS. 465 borders of the uterus to the sides of the pelvis. Their upper margin is divided on each side into three folds or ridges, formed in the following manner : a posterior fold formed by the ovary (a) and its ligament (c), an anterior one by the round ligament (g), and a middle fold by the Fallopian tubes (/). Hence some anatomists have described threr wings {alee vespertilionis) in each of the broad ligaments. The broad ligaments may be regarded as forming across the cavity of the pelvis a transverse septum, within which the uterus and its appendages are contained. This septum divides the cavity into two portions : one anterior, containing the bladder, the other posterior, in which are situated the rectum, and almost always some intestinal convolutions. Besides the broad ligaments, there are also the ligaments of the ovary and the round ligaments, proceeding from the sides of the uterus. The round ligaments {g g) have a fibrous appearance, but are evidently continuous with the tissue of the uterus. They arise from the side of the uterus, below and in front of the Fallopian tubes, pass upward and outward in the anterior fold of the broad ligament to the abdominal orifice of the inguinal canal, into which they enter, being ac- companied by a prolongation of the peritoneum, which forms around them a cylindrical sheath called the canal of Nuck. In females far advanced in life, this sheath may be traced as far as the external orifice of the inguinal canal. Besides the uterine fibres which enter into its composition, the round ligament also contains a great number of veins, which may become varicose, especially near the ex- ternal orifice of the inguinal canal, where they sometimes simulate a hernia. The upper border or fundus (i) of the uterus is convex, and is directed upward and for- ward ; it is covered by convolutions of the small intestine ; when not distended, it never reaches as high as the brim of the pelvis, and cannot, therefore, be felt by the fingers in the hypogastric region. The lower or vaginal extremity of the uterus, called also the os tincce, from its shape, is directed downward and backward ; it is embraced by the vagina, into which it projects, and is divided by a transverse fissure into two lips, one anterior, the other posterior. The OS tinccR is small, and perforated by an almost circular opening {n) in females who have not borne children ; but in those who have been mothers it forms a more consid- erable projection, and its fissure is more marked and longer transversely.* In some females the os tinea; is of considerable length, and, as it were, hypertrophied, although the uterus is healthy. The anterior lip is thicker than the posterior, which is a little longer than the other. It frequently happens that in old females every trace of the lips of the os tincae disap- pears ; the orifice alone remains, and in some cases even that is obliterated. In such a case the vagina terminates in a cul-de-sac, at the bottom of which a round and yielding point may be felt. This disappearance of the two lips is much more common than the elongation of the neck of the uterus, which was pointed out by my venerable colleague, M. Lallemand. Cavity of the Uterus. — The cavity of the uterus is extremely smeill in comparison with the size of the organ ; its figure is that of a curvilinear triangle ; its walls are in con- tact, and are smooth, and covered with a layer of mucus. We shall examine it in the body and neck of the uterus. The cavity of the body of the uterus (w, fig. 189) is of a triangular form, and has an opening at each angle. The inferior opening {ostium internum, k) Fig. 189. establishes a free communication between the cavities of the body and neck ; it is often obliterated in old women, t The other two orifices (o o) are those of the Fallopian tubes ; they are scarcely visible to the naked eye, and are situated at the bottom of two fiuinel-shaped cavities formed at the superior angles of the uterus, and constituting the remains of the division of the body of the ute- rus into two halves or comua. This division, which is normal in many animals, is sometimes met with in the human female. Congenital deficiency of the cavity of the uterus is very rare. My colleague. Profes- sor Rostan, kindly sent me a specimen, in which there was no trace of a cavity in the body of the uterus, although the cavity of the neck remained. The female to whom it belonged had never menstruated. It is unnecessary to say that she was barren. The cavity of the neck {h to n) represents a cyUnder flattened from before backward, and has upon its anterior and posterior walls certain ridges, which form upon each wall along the whole length of the neck a tolerably regular median column, from which pro- ceed, at more or less acute angles, a certain number of smaller columns,^ which pro- ject to a greater or less degree. The whole appearance resembles that of a fern-leaf, * I have seen the os tincse lacerated and fissured in different directions, in consequence of parturition. + This obliteration, which causes retention of mucus and blood, and, consequently, distension and ramol- lisa'inent of the body of the uterus, is so common that M. .Mayer regards it as normal. t These rugae, which vary considerably in their arrangement. havfi-JlBfin described in detail by Haller, Bo- yer, and others. v»^^-«^ N N N # 466 SPLANCHNOLOGY. and has been called the arbor vita. It generally disappears after the tirst latGtlr, at least only traces of it are left. Nevertheless, it is not unfrequently found perfect, even after several accouchements — a circumstance of some importance in legal medicine. The internal surface of the body of the uterus is much more vascular than the neck. This difference is particularly observed in females who have died during a menstrual period, in whom the vessels of the body of the womb are much developed, and that or- gan itself is swollen and softened, while the cervix retains its accustomed whiteness and consistence. Another character of the uterine cavity is the existence of a greater or less number of transparent vesicles, which were mistaken by Naboth for ova {ova of Naboth), but are only muciferous follicles. They exist both in the body and neck of the uterus, but are more numerous in the neck, near the vaginal orifice, and only become apparent when the mucus accumulates in them from obliteration of their orifices. They are sometimes much enlarged, and have then given rise to the opinion that some more serious disease has existed. The orifices of the uterine sinuses, described by the older anatomists at the fundus of the uterus, cannot be detected. They are only to be seen after delivery in the situa- tion where the placenta had been attached. The parietes of the unimpregnated uterus are from four to six lines in thickness. The thinnest part is at the entrance of the Fallopian tubes, where they are not more than two lines thick. The parietes of the cervix are thinner than those of the body. Structure of the Uterus. — The constituent parts of the uterus are, a proper tissue, an external peritoneal coat, an internal mucous membrane, and some vessels and nerves. The proper tissue is of a grayish colour, very dense and strong, and creaks under the knife like cartilage. The body appears less consistent than the neck, but this depends upon the fact of its being more frequently the seat of sanguineous congestion. It is com- posed of fibres, i. e., it has a linear arrangement. It may be asked, with regard to the nature of these fibres. Do they consist of fibrous tissue 1 are they muscular, or are they analogous to tlie yellow tissue of the arteries 1 The following considerations will de- termine this question : The walls of the unimpregnated uterus appear to be composed of a fibrous tissue, trav- ersed by a great number of vessels. During pregnancy, or in consequence of the devel- opment of tumours, or the accumulation of fluid in the cavity of the uterus, its proper tissue acquires all the properties of the muscular tissue, as it exists in the viscera of organic life, and, like it, is endowed with contractility. Can, therefore, the presence of a foetus or a foreign body in the uterus cause a transformation in the tissue of that organ 1* Assuredly not ; but the great influx of blood into the uterus, and the conse- quent distension and development of its fibres, reveals a structure which before was con- cealed by the state of condensation and atrophy kept up by inactivity. This view is fully confirmed by the microscopical observations of Rtederer, and the chemical experiments of Schwilgue ; and also by the results furnished by comparative anatomy, which has shown circular and longitudinal muscular fibres in the uteri of some animals, even when not in a gravid condition, t The nature of the fibres of the uterus being determined, we may now examine their direction. Some anatomists agree with Malpighi and Monro, that they have no regu- larity in their disposition, but are interlaced in an inextricable manner. It must be con- fessed that, in the unimpregnated uterus, such is the case ; but during gestation, the ar- rangement of the greater number of fibres can be traced. J In the body the external thin layer is composed of two median vertical fasciculi, one on each surface of the uterus ; of another fasciculus occupying the fundus, and of some oblique ascending and descending fibres, which converge towards the Fallopian tubes, the round ligaments, and the ligaments of the ovaries, which contain prolongations of these fibres.^ This first, or superficial layer, belongs exclusively to the body of the ute- rus. The deep layer of the body consists of two series of circular fibres ; each series forming a cone, the apex of which corresponds to the Fallopian tube, while the base is directed towards the median hne, and is there blended with that of the opposite side. The neck is composed entirely of circular fibres, which intersect each other at very acute angles. The facts furnished by comparative anatomy perfectly accord with the preceding de- scription Thus, in the uterus of a sow, which had httered, I found that the cervix was composed exclusively of circular fibres ; and that the cornua (aduterum of M. Geoffrey * I conceive that I have proved by facts, that only three tissues, viz., the muscular, the nervous, and the glandular, are never the products of organic transformations. — (Vide Essai sur VAnalomie Pathol., 1816.) t CThe muscular fibres of the gravid uterus have been described by Dr. Baly (translation of MUller's Phys- iology). Like other inorganic muscular fibres, they have no transverse striae ; they arc much broader than those of the alimentary canal, and taper very much at their extremities, which are sometimes split into two or three points : the corpuscles upon them are comparatively small.] X Hunter, Analomia uteri. Rosemberger in Schlegel, ^yllog. Oper. Minor, ad Arlem Obstetric. Lipsis, \om. ii., p. 290. M6moire pnisentt i 1' Academic de M6decine, par Mmc. Boivin. Oct., 1821. ft I. c, in the i,'ravid state. THE UTERUS. 467 St. Hilaire), which represent the body of the uterus of the human female, were formed by two layers of fibres, one external and longitudinal, the other deep and circular. From this arrangement, we may therefore conclude that the human uterus results from the union of two comua, which communicate directly with each other, instead of opening separ- ately into the cavity of the cervix. When examined in the state of pregnancy, the tissue of the uterus is found to be trav ersed by venous canals, or uterine sinuses, which are of very considerable size, especial- ly opposite the attachment of the placenta. This great number of vessels gives to the tissue of the uterus the appearance of an erectile or cavernous structure, having muscu- lar parietes.* The External or Peritoneal Coat. — ^The peritoneum, after covering the posterior surface of the bladder, is reflected upon the anterior surface of the uterus, of which it covers only the upper three fourths, the lower fourth being in immediate contact with the blad- der. At the fundus of the uterus, it passes to the posterior surface, which it covers en- tirely, is prolonged a short distance upon the vagina, and is then reflected upon the rec- tum. The broad ligaments are formed by a transverse duplicature of this coat. Two falciform folds, formed by this membrane between the bladder and the uterus, are called the vesico-uterine ligaments, and two others, between the uterus and the rectum, are na- med the recto-uterine ligaments. The peritoneum adheres very loosely to the borders of the uterus, but much more closely as it approaches the median line. When enlarged during pregnancy, the uterus becomes covered with the peritoneum of the broad ligament, a species of mesentery, the folds of which become separated, and yield to the increasing size of the organ. The Internal or Mucous Membrane. — The existence of a mucous membrane upon the internal surface of the uterus has been denied by those anatomists who have examined it after parturition, especially by Morgagni and Chaussier, and so, also, by those who do not admit the presence of a mucous membrane unless it can be demonstrated over a certain space. But the existence of a mucous membrane on the internal surface of the uterus appears to me incontestably proved by the following considerations : First, every organized cavity which communicates with the exterior is hned by a mu- cous membrane ; why, therefore, should the uterus form an exception to this rule ! Sec ondly, by dissection it is shown that the mucous membrane of the vagina is continued into the neck of the uterus, and then into the body ; but in this latter situation it is des- titute of epithelium.! Notwithstanding the difficulty of dissecting this membrane, on account of its tenuity, and its close adhesion to the tissue of the uterus, its presence is demonstrated by the following observations : Under the microscope, the internal surface of the uterus presents a papillary appearance, but the papillae are very small ; it is pro- vided with follicles or crypts, from which mucus may be expressed by a number of points, and which form small vesicles w^jen distended with mucus, in consequence of obstruction or obliteration of their orifices. Thirdly, it is extremely vascular, and pre- sents a capillary network of the same appearance as that of the other mucous mem- branes ; and, lastly, it is constantly lubricated with mucus. Pathological observations Eilso show that the internal surface of the uterus, like all raucous membranes, is liable to spontaneous hemorrhages from exh2dation, without breach of continuity, to catarrhic secretions, and to those growths which are denominated mucous, vesicular, and fibrous polypi : and it is generally admitted that, where there is an identity of disease, there is also identity of structure. During pregnancy, the elements of the mucous membrane are separated; the vessels become penicillate, and greatly increased in size ; but in proportion as the uterus returns to its original dimensions, the mucous membrane regains its primitive form, and its dis- sociated elements approach each other. It seems as if this membrane was destroyed by a true exfoliation, and then entirely reproduced. The arteries of the uterus are derived from two sources : the principal, called the ute- rine, arise from the hypogastric ; the others proceed from the spermatic or ovarian ar- teries to the borders of the uterus, and are distributed upon it : both sets are very tor- tuous. The veins are remarkable for their enormous size during pregnancy and after parturi- tion. The term uterine sinuses has been given to the large veins which are then found in the substance of the organ ; and this term is not altogether without foundation, for these venous canals are formed by the lining membrane of the veins which adheres to the proper tissue of the uterus, just as, in the sinuses of the dura mater, it adheres to the fibrous tissue of that membrane. The lymphatics, which have been well examined only during pregnancy and after par- * This combination of the erectile and muscular tissues is found in the penis of the horse, and perhaps, also, in that of man. t [The mucous membrane of the uterus contains numerous tubular glands, or crypts, resembling, in form and direction, the tubuli of the stomach, and the crypts of Lieberkuehn, found in the intestinal canal. The epithelium of this mucous membrane is, according to Henl6, columnar, and also ciliated from the fundus to the middle of the cervix uteri ; below that point it passes into the squamous form of epithelium found in the ragina and on the labia.] 4§8 SPLANCHNOLOGY. turition, at which time I have often seen them full of pus, are, like the veins, extremely large (see Anat. Path., avec planches, liv. xiv.) ; they form several layers in the sub- stance of the uterus, ^^e most superficial of which is the most developed. They termi- nate in the pelvic and lumbar lymphatic glands ; some accompany the ovarian veins. The nerves, as seen in the pregnant condition, have been well described and figured by Tiedemann. Some of them are derived from the renal plexus, and surround the ovarian arteries ; others proceed from the hypogastric plexus, and are formed by some of the anterior branches of the sacral nerves, and by branches from the lumbar ganglia of the sympathetic. Development. — It is generally agreed that the body of the uterus is always bifid, or two- horned, in the embryo, up to the end of the third month ; and that, towards the end of the fourth month, the two halves are united to form a single cavity. I have not observed tliis in the earliest periods of intra-uterine life. During fcetal life, the uterus, instead of presenting the same form as it subsequently possesses, is decidedly larger at the neck than in the body : at this period the broadest part of the uterus is its vaginal extremity. After birth, and up to the time of puberty, the development of the uterus is almost stationary ; so that, according to the observations of Roederer, which are confirmed by Professor Duges, it is from twelve to fourteen lines long in the new-born infant, and only an inch and a half at ten years of age. At puberty, the uterus rapidly acquires its full dimensions, and at the same time be- comes the seat of a periodic and sanguineous exhalation, the occurrence of which con- stitutes menstruation. In old age, the uterus becomes atrophied, and altered in shape ; the cervix and body are separated by a much more decided constriction. These two parts of the uterus seem to become more independent of each other. The lips of the os tincae are general- ly effaced in old women. The tissue of the body preserves its softness, while that of the neck acquires an extreme density. The situation of the uterus is very different at different ages. In the foetus it projects beyond the brim of the pelvis, and is in the abdominal cavity ; after birth, and in conse.- quence of the development of the pelvis, it seems gradually to sink into that cavity. At the age of ten years, the fundus of the uterus is on a level with the brim ; afterward it is lower down. In old women it is generally inclined to one side, or reversed upon the, rectum. Functions. — The uterus is the organ of gestation ; the fecundated ovum is deposited in its cavity, and there meets with the most favourable conditions for its development. The uterus is also the principal agent in the expulsion of the foetus. The Vagina. The vagina is a membranous canal, extending from the vulva to the uterus ; it is the female organ of copulation, and also forms the passage for the menstrual blood, and the product of conception. It is situated in the cavity of the pelvis between the bladder and the rectum, and is held in that situation by tolerably close adhesions to the neighbouring parts, but still is so loose that it can be everted like the finger of a glove. Direction. — It is directed obliquely forward and downward, i. e., it coincides with the axis of the outlet of the pelvis ; and as the direction of the uterus corresponds with the axis of the brim, these two parts form an angle or curvature with each other, having its concavity directed forward. Shape and Dimensions. — The vagina is shaped like a cylinder, flattened from before backward, and having its walls in contact, as may be seen upon applying the speculum. It is from four to five inches long ;* sometimes it is much shorter : I have seen it as short as an inch and a half This congenital shortness must be distinguished from the apparent shortness produced by prolapsus uteri. The vagina is not of the same diameter throughout. Its lower orifice is the narrow- est part, while its upper extremity is the widest. In females who have borne children, the bottom of the vagina forms a large ampulla, in which the speculum may be moved about extensively, and in Avhich, also, a considerable quantity of blood may accumulate during hemorrhage. It is, moreover, a dilatable canal, as is proved during parturition ; and is, at the same time, elastic, and contracts after delivery, so as almost to return to its original dimensions. It would appear, also, to be capable of a vermicular contraction. Relations. — In front, where it is slightly concave, it corresponds to the inferior fundus of the bladder, to which it is united by very dense filamentous cellular tissue, resembling the dartos ; it cannot be separated from the urethra, which appears to be hollowed out of the substance of its walls. The close adhesion of the vagina to the bladder and ure- tlua accounts for these latter organs always following the uterus in its displacements. Behind, the vagina corresponds with the rectum, through the medium of the peritoneum in its upper fourth, and immediately in its lower three fourths. It adheres to the rec- * LFrom the nature of the cune formed by the vagina, its anterior wall is shorter than the posterior.] THE VAGINA. 4^ turn by cellular tissue resembling the dartos, and analogous to that existing between it and the bladder, but much looser, so that the rectum does not follow the vagina in its displacement. The sides of the vagina give attachment to the broad ligaments above, and to the superior pelvic fascia and the levatores ani below, and they are in relation with the cellular tissue of the pelvis and with some venous plexuses. Internal Surface. — The internal surface of the vagina is covered with an epithelium, which can be very easily demonstrated, and which is prolonged as far as the os uteri, where it terminates by a sort of indented margin, in the same manner as the epithelium of the oesophagus ceases at the stomach.* This surface presents on both walls, but es- pecially in front and near the orifice of the vulva, some transverse rugae, or, rather, prominences, which very nearly resemble the irregular ridges upon the palate ; they all pass from a median prominent line, which is often prolonged like a median raphd along the whole anterior wall of the vagina ; the raphe on the posterior wall is not so well marked. These two median raphes are called the columns of the vagina. They are the remains of the median septum, which generally coexists with a bifid uterus, but ex- ists sometimes independently of it. The transverse rugae of the vagina are very numerous in the new-bora infant and in virgins ; they are partially effaced after the first labour, at the upper part of the vagina, but always remain at the lower part. These rugae are not folds, and do not appear to assist in the enlargement of the vagina. The upper extremity of the vagina embraces the neck of the uterus, upon which it is prolonged without any line of demarcation, and forms a circular trench around the os tincae, which is deeper behind than in front. The lower extremity, or opening into the vulva, presents a corrugated transverse pro- jection in front, which is exposed by separating the labia and nymphae ; it narrows, and seems even to close the entrance of the vagina. In virgins, the orifice of the vulva is provided with a membrane, concerning the form and existence of which there have been numerous disputes ; it is called the hymen, and is a sort of diaphragm interposed between the internal genitals on the one hand, and the external genitals and urinary passages on the other. This membrane is of a crescentic shape, having its concavity directed forward, and closing up the posterior and lateral parts of the vagina: it sometimes forms a complete circle, perforated in the centre. Its free margin is fringed ; it varies in breadth in different individuals, and thus regulates the dimensions of the vaginal orifice. The hymen sometimes forms a complete mem- brane, constituting what is called imperforate vagina. The hymen is composed of a duplicature of mucous membrane, varying in strength, and containing within it some cellular tissue and vessels. The debris remaining after its laceration constitute the carunculce myrtiformes, which vary in number from two to five. Structure. — The walls of the vagina consist of an erectile spongy tissue interposed be- tween two very strong fibrous layers, of which the external is the thicker. Around this erectile tissue we find a tolerably thick layer resembling the tissue of the dartos con- densed. I cannot agree with sonie anatomists in admitting an identity of structure in the walls of the vagina and uterus, for in no case does the vagina assume a muscular character hke the latter organ. From the presence of the dartoid tissue an obscure ver- micular movement may take place, and assist the elasticity of the walls of the vagina. The posterior wall and the upper part of the anterior wall are thin ; the vagina is veiy much thicker opposite the urethra, which seems to be hollowed out of its substance, and terminates by a rugous enlargement, which forms, at the entrance of the vagina, the pto- jection already mentioned, and which is only a very dense spongy tissue. The mucous membrane of the vagina is remarkable for the thickness of its epitheli- um,t for its close adhesion to the proper membrane, and for its highly developed papillae, especially at the entrance of the passage, where the rugae are nothing more than papillae in an exaggerated form. The mucous follicles can be easily demonstrated. The Bulb of the Vagina. — Besides the spongy expansion at the orifice of the vagina, there is in front and on each side of this orifice an enlargement or cavernous body, occu- pying the interval between the entrance of the vagina and the roots of the clitoris. It is not very thick in the middle, where it is placed between the meatus urinarius and the union of the roots of the clitoris, but gradually enlarges from this point, and terminates below, upon each side of the vagina, by an enlarged extremity. The posterior wall of the vagina is the only part in which it does not exist. In position, as well as shape, it resembles the bulb of the urethra in the male. J The Constrictor Vagina. — ^This consists of two muscles, one on each side of the ori- fice of the vagina, the arrangement of which very nearly resembles that of the bulbo- * tin both of these situations the epithelium does not cease, but is merely changed in its character (see note, p. 467).] t [The epithelium in the vagina, and also in the vulva, is squamous.] t In one subject, on the outer side of this vaginal bulb, I found a smooth sero-fibrous pouch, containing' a transparent mucous fluid. A narrow canal, proceeding from this pouch, passed directly towards the entrance of the vagina. I could not find the orifice of this caual, which was probably obliterated. The same dispoai- tion existed on both sides. 470 SPLANCHNOLOGY. cavernosus in the male. Each muscle commences in front of the rectum, by an inter- lacement of fibres common to it, to its fellow of the opposite side, and to the sphincter ani, passes forward under the fonxi of a flattened band, and terminates upon the sides of the clitoris, a portion being continued above it, and blended with the suspensory liga- ment of that body. Relations. — It is covered on the outside by the skin and the fatty cellular tissue of the labia majora ; it corresponds on the inside with the bulb of the vagina, which it must strongly compress. The proper vaginal arteries arise from the hypogastric. The uterine arteries also send numerous branches to the vagina. The veiiis are very niunerous, form plexuses, and terminate in the hypogastric veins. The turves are derived from the hypogastric plexus. Development. — The rugae of the vagina are not visible until about the end of the fifth month of intra-uterine life ; from the sixth to the eighth they become much more devel- oped than they are subsequently. The transverse rugae are visible in the whole length of the vagina, and are placed closely to each other. The hymen does not make its ap- pearance until about the middle of fcetal life ; it is directed forward, and is rough and jagged. It is always present. The Urethra in. the Female. This canal, which is, as it were, hollowed out of the anterior wall of the vagina, dif- fers considerably from the male urethra, of which it represents the membranous portion only. It is about one inch in length. It is very difficult to determine its diameter, on account of its dilatability ; but it is about three or four lines when quite undilated. Its lower end is somewhat contracted. It is directed obliquely downward and forward, and is slightly concave in front. Relations. — Anteriorly, while behind the symphysis, it is in contact with the cellular' tissue of the pelvis ; opposite the symphysis, it is in relation with the angle of union of the two crura of the clitoris. The pelvic fascia, or, rather, the anterior ligaments of the bladder, form a half sheath for it above, but are separated from it by numerous venous plexuses. Posteriorly, the canal is so closely united to the vagina, that it is impossible to separate them. The vesical orifice of the female urethra is similar to that of the male, only there is no prostate gland. The internal surface is of a deep colour, and is remarkable for certain longitudinal folds or parallel ridges, the majority of which are not effaced by distension ; one of these folds is in the median line of the lower wall of the canal. We also find the orifices of mucous crypts or lacunae, and some parallel longitudinal veins. Structure. — It is muscular and erectile, like the membranous portion of the male ure- thra. It is surrounded by a thick layer of circular muscular fibres, which seem to be continuous with the fibres of the bladder, some of the longitudinal fibres of that organ being prolonged upon the outside of these.* A thin layer of spongy or erectile tissue lies subjacent to the mucous membrane, which is very thin. The Vulva. Under the term vulva we include all the external genitals of the female, viz., the mons Veneris, the labia majora and minora, the clitoris, and the meatus urinarius, to which we may add the orifice of the vagina already described. The mons Veneris is a rounded eminence, more or less prominent in different individ- uals, situated in front of the pubes, and surmounting the vulva ; the prominence of this part is owing partly to the bones, and partly to a collection of fatty tissue beneath the skin ; it is covered with hair at the time of puberty. The labia majora are two prominent cutaneous folds, which form the limits of an an- tero-posterior opening, by most anatomists named the vulva. They are flattened trans- versely, and are thicker in front than behind ; their external surfaces are covered with hairs ; their internal surfaces are moist and smooth, and in contact with each other ; their free borders are convex, and provided with hair ; their anterior extremities are con- tinuous with the mons Veneris ; their posterior extremities unite to form a commissure called the fourchette, which is almost always lacerated in the first labour. The interval between the fourchette and the anus constitutes the perineum, which is generally from * [The female urethra perforates the triangular ligament precisely in the same way as the membranous por- tion of the urethra in the male ; and, moreover, between the two layers of the ligament it is surrounded by mus- cular fibres corresponding exactly with the compressor urethra in the male sex. The vertical fibres, or Wil- son's muscles, were noticed by him (loc. cit.), descending from the symphysis, separating on the urethra, and passing around it ; the transverse fasciculi, which are often very large, form together the depressor urethra Of Santorini, and were described and figured by that author (Obs. Anat.) as arising by a broad tendou from the lower part of the rami of the pubes, above the erectores clitoridis, passing obliquely upward and inward, and uniting with each other dijove the urethra. Mr. Guthrie has shown {loc. cit.) that the relations of the verti- cal and transverse fasciculi to each other, to the urethra, and to the layers of the Uiaugular ligament, are pre- cisely the same as in the male.] ' .,-j4J-i THE VULVA. 471 eight to ten lines long. The interval between the fonrchette and the entrance of the vagina is called the fossa navicularis. The constituent parts of the labia majora are, a cutaneous layer, a mucous layer, both provided with numerous sebaceous follicles.* In fat persons, a great quantity of adipose tissue, a layer of dartoid tissue next the mucous membrane, and some arteries, veins, lymphatics, and nerves. They are therefore very analogous to the scrotum in the male, and, Uke it, are liable to serous infiltration in anasarca. The labia minora, or nymphcB, are seen after separating the labia majora, under the form of two layers of mucous membrane ; they are narrow behind, where they commence upon the inner surface of the labia majora, and they enlarge gradually as they converge towards each other in front. At the chtoris they become slightly contracted, and bifur- cate before their termination. The lower division of the bifiircation is attached to and continuous with the glans of the clitoris ; the upper division unites with that of the op- posite side, and forms a hood-like fold above that body, called the preputium clitoridis. Tlie nymphae are provided with very large crypts, wliich are visible to the naked eye, and secrete an abundance of sebaceous matter. They vary much in size, according to age : thus, in new-bom infants, they project beyond the labia majora, principally on ac- count of the imperfect development of the latter. They also vary in different individ- ujds : in some females being extremely small, and in others always projecting beyond the labia majora ; and, lastly, in different countries ; for in certain African nations, among the Hottentots, for example, they are of a disproportionate length, and constitute what is called in females of that race the apron. The clitoris is an erectile apparatus, forming a miniature representation of the corpus cavernosum of the penis. Its free extremity is seen in the anterior part of the vulva, about six lines behind the anterior commissure of the labia majora, and resembles a tu- bercle situated in the median line, covered, as by a hood, with the upper divisions of the bifurcated nymphae, and continuous with the lower divisions of the same. This tuber- cle, which, though imperforate, has been compared to the glans penis {glans clitoridis), is generally very small. Sometimes, however, it is very long, so as to have excited a sus- picion of the existence of hermaphrodism. In one instance that came under my obser- vation, the free part of the clitoris was two inches long, and extremely slender. Like the corpus cavernosum in the male, the clitoris arises from the ascending rami of the ischia by two roots, which expand and converge until they arrive opposite the symphysis, where they unite and form a single corpus cavernosum, flattened on each side ; this, after passing for some lines in front of the symphysis, separates from it, and forming a curve with the convexity directed forward and upward, and the concavity downward and backward, gradually becomes smaller towards its free extremity. It has a suspensory ligament precisely resembling that of the penis, and ischio-cavei- nosi muscles, similar to, but smaller than those of the male. We have already said that the constrictor vaginae, which represents the bulbo-cavemosi of the penis, has a similar arrangement to those muscles, t. c, it passes upon the sides of the clitoris, and then be- comes continued on to its suspensory ligament. The last circumstance which completes the analogy between the clitoris and the corpus cavernosum of the penis, is the reception of the canal of the urethra into the V-shaped interval formed by the union of the two crura of the clitoris. The corpus cavernosum of the clitoris forms a longitudinal ridge between the labia ma- jora, extending from the anterior commissure to the glans of the clitoris. The Meatus Urinarius. — About an inch below and behind the clitoris, we find in the median line, immediately above the projecting margin of the opening of the vagina, tfce meatus urinarius, or the orifice of the urethra, which constantly appears closed. The Mucous Membrane of the Vulva. — The mucous membrane lining the vulva is con- tinuous, on the one hand, with the skin at the intemad surface of the labia majora, and with the mucous membrane of the vagina on the other ; upon the labia majora and nym- phae it has a great number of sebaceous follicles visible to the naked eye, and yielding a cheesy, odorous secretion ; and also mucous follicles, which are most numerous near the meatus urinarius, and open into culs-de-sac, the orifices of which are visible to the na- ked eye, and are often large enough to admit the blunt extremity of a probe. Development. — In the foetus the labia majora are small, and separated from each other by the nymphae, which are much larger in proportion, and also by the clitoris, which pro- jects beyond them to a greater extent in the earlier periods of development. This pre- dominance of the clitoris is still so decided at birth, that it has occasioned mistakes con- cerning the sex of the infant. THE MAMM^. Number. — Situation. — Size. — Form. — Structure. — Development. The mavima or breasts (jiadrbg, from fidu, to seek eagerly, because the infant seeks^ * It is not rare to see small and very short hairs growing from the sebaceous follicles on the inner surface of the labia majora ; they are analogous to '.hose of the carunculse lachrymales. 472 SPLANCHNOLOGY. them for the milk) are glandular appendages of the generative system, which secrete the milk, and even after birth establish intimate relations betvireen the mother and the infant. The important office performed by the mammje has led zoologists to arrange in the same class, under the term mammalia, all animals having an apparatus for lactation. We may mention here another character peculiar to this class of animals, because it is in- timately connected with the existence of mammae, viz., that all mammalia are vivip- arous that is to say, give birth to their young freed from all their foetal envelopes. The mammsE exist in both sexes, but are rudimentary and atrophied in the male, and belong essentially to the female. Number. — They are two in number in the human species, which is uniparous ; in the lower animals they are generally double the number of the young. Examples of three or four mammae in the human subject are very rare, and the supernumerary mammae are generally nothing more than simple nipples, or, rather, masses of fat. Situation. — They are situated on the anterior and upper part of the chest, the trans- verse enlargement of which in the human subject is so favourable to their development. In the lower animals they occupy the abdominal region. They are situated on each side of the median line, over the interval between the third and the seventh ribs. They are therefore placed at the same height as the arms, and occupy this region, says Plutarch, in order that the mother may be able to embrace and support her infant while she is suckling it. Size. — In the male they are rudimentary during the whole of life ; in the female until the period of puberty only, when they become much enlarged as the generative appara- tus is developed more completely. They again increase in size during pregnancy, and especially after delivery ; they become atrophied in old age. In some females who are still young, the size of the mammas by no means corresponds to their statm-e, strength, and soundness of constitution ; while, on the other hand, it is not uncommon to see thin, phthisical individuals with very large breasts. In judging of the size of the mammae, we must not confound that depending upon the gland itself with that due to fat. The lar- gest breasts are not always those which furnish the most milk, because their extreme size often depends on an accumulation of fat, the gland itself being small. The left mam- ma is almost always a little larger than the right. Form. — The mammae represent a semi-sphere surmounted by a large papilla called the nipple. The skin covering the mamma is remarkably delicate. Surrounding the nipple is an areola or aureola of a pinkish hue in young girls, but of a brownish colour in most females who have borne children ; it has also a rough appearance, owing to a number of sebace- ous glands, which yield a kind of waxy secretion that prevents the irritating action of the saliva of the infant. Morgagni, Winslow, and Meckel state that they have observed milk to escape from them ; but if there was no error in their observations, it must be admitted that, by some unusual anomaly, a lactiferous duct opened at the side of one of these little glands. The mammilla or nipple is of a pinkish or brown colour, rough, and, as it were, crack- ed at the summit, and capable of undergoing a sort of erection ; it varies in form and size in different subjects ; it is either cylindrical or conical, and sometimes so short that the lips of the infant cannot lay hold of it ; in certain cases it is even depressed. In the centre of the nipple we observe one or more depressions, in which the lactiferous ducts open by a variable number of orifices. The papilla is provided also with a great number of sebaceous glands having the ap- pearance of tubercles, and secreting a substance which prevents the nipple from being chapped by the act of sucking and the saliva of the infant.* Structure. — The breasts consist of the mammary glandular tissue and of fat. The Mammary Gland. — ^When freed from the fat by which it is surrounded, the mam- mary gland appears like a mass flattened from before backward, and thicker in the cen- tre than at its circumference, which is irregular, but less so on the inside than on the outside. Its base, which is plane, and even slightly concave, rests upon the pectoralis major, and sometimes beyond it upon the serratus magnus ; a continuation of the fascia superficialis separates it from these muscles, to which it adheres by very loose serous cellular tissue only, and hence it is very movable. The cutaneous surface of the mammary gland is very unequal, and forms alveoli filled by fat, by which means the inequalities are concealed. The proper tissue of the gland is considerably denser than that of most glandular or- gans. It should be examined both during lactation, and when that function is not being performed. In the absence of lactation, the gland has the appearance of a very compact, whitish, * [Sir A. Cooper has described numerous cutaneous papillae upon the nipple and areola ; they are highly *wascular and nervous. He has also shown that the glands found in the areola and at the base of the nipple nave branched ducts, ending in blind extremities : in the female, from one to five open on each tubercle.— (Anatomy of the Breast, 1840.)] THE MAMMiE. 473 fibrous tissue, divided into unequal lobes, which cannot be compared to anything bettei than to certain fibrous tumours of the uterus. The granular structure proper to the tis- sue of glands is not visible during this state. During lactation, the granular structure becomes very evident. The following are the results of my observations respecting it at this period : The glandular granules or lobules are united into small clusters, forming flattened lobes, placed one upon another. From each little lobe proceeds an excretory duct, which may be recognised by its white colour, is easily injected, and is formed by the union of a number of smaller ducts cor- responding to the number of lobules. Having had an opportunity of dissecting the mam- ma of a female recently delivered, in which the cellular tissue between the lobules was infiltrated with serum, the lobules themselves, as it were, dissected, and the lactiferous ducts injected with yellowish coagulated milk, I found that some of the lobules were iso- lated, and, as it were, pediculated, while others were collected into regular or irregular clusters. In one of these clusters the lobules had a circular arrangement, small ducts proceeded from each lobule, and, passing from the circumference towards the centre of the circle like radii, opened into a common efferent duct, which issued from the central point. Another cluster was elongated and swollen at intervals, and in the centre was a duct which received the smaller ducts from the several lobules. Each lobule had a central cavity, from which a worm-shaped mass of coagulated caseous matter could be expressed. When examined by the simple microscope, the parietes of these cavities had a spongy aspect like the pith of the rush, a character which I have already noticed as belonging to all glandular organs.* The Fibrous Tissue of the Mamma. — Besides the lobules, a large quantity of fibrous tis- sue also enters into the structure of the gland, forms a complete investment for it, and then sends more or less loose prolongations into its substance, and unites the lobes to- gether. It is to the great quantity of fibrous tissue that the hardness of the mammary gland is to be ascribed. Sometimes the enlargement of the mamma at the time of pu- berty is confined entirely to the fibrous tissue ; in such a case, the organ may acquire an enormous size, the glandular tissue disappears, and the mamma is transformed into a many-lobed fibrous mass, wliich has been sometimes mistaken for a degenerated lipoma. The Adipose Tissue. — The alveoli on the outer surface of the mamma are filled with masses of fatty tissue, which are separated by fibrous laminae extending from the gland to the skin. The cells in which these masses are contained do not communicate with each other, and hence the frequency of circumscribed abscesses in the mamma. The relative quantities of fat and glandular tissue have an inverse ratio to each other. The great size of the mammae in some men is owing to development of the fatty tissue. Haller says that it is an essential element in the structure of the gland, and that he has several times seen lactiferous ducts arise from it. The Lactiferous Ducts. — If the mamma of a female who has died during lactation be divided, the milk will be seen to exude from a number of points, as from the pores of a sponge ; these points correspond to sections of the thin, whitish, semi-transparent ex- cretory ducts of the mammary glands, which are called lactiferous, or galactophorous ducts. They arise from the lobules, and perhaps, also, from the fatty tissue, as was thought by Haller ;t they unite successively like the veins, converge from the circumference to the centre, traverse the substance of the gland, and at length form a variable number of ducts, which reach the centre of the gland, opposite the areola. In that situatioa they acquire their utmost size, and form considerable ampullae or dilatations, between which scarcely any intervals are left. According to some anatomists, the number of these am- pullae is not less than twenty ; I have never counted more than ten. They are of un- equal size. At the base of the nipple they become contracted, straight, and parallel, and open upon its summit by orifices, which are much narrower than the ducts themselves. Thus, then, although there is no reservoir properly so called in the mammary gland, the ampullae above described may be regarded as such ; with this difference only, that in- stead of one reservoir there are several. The lactiferous ducts, moreover, are surrounded, both in the mammilla and opposite the areola, with a dartoid tissue, the existence of which explains the state of orgasm and erection of the nipple, as well as the expulsion of the milk in a jet when the gland is excited. There is no trace of the cavernous structure described by some anatomists as existing in the nipple. The lactiferous ducts do not communicate with each other in any part of their course ; neither in their terminating canals, nor in their ampullae, nor in their smaller ducts ; this may be proved by mercurial injections, or by filling each duct with a differently-coloured injection. The mammary gland, like most others, is therefore divided into a certain number of distinct compartments, which may perform their functions independently of each other. Injections also show that the lactiferous ducts have no valves. Tlieir structure is little * tThe ultimate structure of the mammary gland consists of the terminations of the lactiferous ducts in clusters of microscopic cells within each lobule ; these cells are round, and have a diameter twenty times as great as that of the capillaries which ramify upon them. + (Our present knowledge of the minute structure of glands has proved the inaccuracy of this supposition ol HaUerJ o 474 SPLANCHNOLOGY. known. It is generally admitted that they consist of an internal membrane continuoQs with the skin, and which must be analogous to the mucous membranes, and of an exter- nal fibrous coat, which I am inclined to regard as analogous to the tissue of the dartos. The arteries of the manuna arise from the thoracic, especially that which is called the external mammary, also from the intercostals and the internal mammary. The veins are very large, and of two kinds, sub-cutaneous and deep ; the latter accom- pany the arteries, the former are visible through the skin. The lymphatics are very numerous, and enter the axillary glands. The older anato- mists admitted a direct communication between the thoracic duct and the glandular tis- sue of the breast ; but this opinion, suggested by the resemblance in colour between the chyle and milk, is altogether erroneous. The nerves are derived from the intercostals and the thoracic branches of the brachial plexus. Development. — The mammae become visible after the third month of intra-uterine life. At birth they are more developed than at a subsequent period, and contain a certain quantity of miUcy viscid fluid. Until puberty the mammae of the two sexes differ only in the nipple being larger, and the gland somewhat larger in the female than in the male. In the female, at puberty, they gradually acquire the size which they subsequently re- tain, their development coinciding with that of the genital organs. Most commonly the change precedes, but sometimes it follows, the appearance of the menses. The mammae of the male also participate in the development of the generative appara- tus at the time of puberty, and in some subjects even a milky secretion is formed.* The manunae become atrophied in old age, and are sometimes replaced by fibrous tis sue ; in several old women I have found the lactiferous ducts distended with a dark, in- spissated mucus, of a gelatinous consistence which has enabled me to trace the ducts even to their most delicate radicles. THE PERITONEUM. The Suh-umhilical Portion. — The Supra-umbilical Portion. — General Description and Structure. The peritoneum (nepl, around, and teIvu, to extend) is a serous membrane, which, on the one hand, lines the abdominal parietes, and, on the other, invests nearly all the vis- cera contained in the cavity of the abdomen. As it enters into the formation of almost all the abdominal viscera, it has been already Fig, 190. partially examined while describing them. It remains for us to demonstrate these parts as a whole, and for this purpose, we shall suppose the membrane to com- mence at one particular point, and shall trace it with- out interruption in a circular course until we again ar- rive at the point from which we started. The peritoneum is the largest and most complica- ted of the serous membranes ; it forms, like all of them, a shut sac, the external surface of which ad- heres to the parts over which it is reflected, while its internal surface is free and smooth. Taking the umbilical region as a point of departure, we shall divide the peritoneum into two portions, a superior, epigastric or supra-umbilical, and an inferior or sub-umbilical portion. The Inferior or Sub-umbilical Portion of the Peritone- um.. — The inferior or sub-umbilical portion, supposed to commence at the umbilicus, lines the whole of the parietes of the abdomen (a, ^^. 190) below that point. In so doing, it is raised up by the urachus and the two umbilical arteries, or, rather, by the ligaments repla- cing those arteries, so as to form three falciform folds, one median and two lateral, which converge towards their termination at the umbilicus, but diverge in the direction of the bladder ; the peritoneum then dips into the pelvis, and covers the fundus, the sides, and the posterior surface of the bladder (J), but to a varia- ble extent, according as that organ is distended oi empty. When the bladder is contracted, the perito- neum descends behind the symphysis ; when, on the * [It has been shown by Sir A. Cooper, that the mammary gland of the male has a system of ducts and cells like those of the fejnals gland, but very much smaller.] THE PERITONEUM. 475 Other hand, it is distended and rises into the abdomen, the peritoneum retires before ii, and the bladder then comes into direct contact with the anterior wall of the abdomen, so that it can be reached by the surgeon without wounding the peritoneum. From the posterior surface of the bladder the peritoneum is reflected upon the other pelvic organs, being arranged differently in the two sexes. In the male it is reflected from the bladder upon the rectum, forming- two lateral semilunar folds, called the pos- terior ligaments of the bladder, and a cul-de-sac between them of variable depth, which sometimes reaches as low as the prostate.* In the female it is reflected from the pos- terior surface of the bladder upon the neck of the uterus (m), forming a cul-do-sac between the two, so that the inferior fundus of the bladder is entirely uncovered by it. It then covers the two surfaces and the superior border of the uterus, and forms two lateral, broad, transverse folds (the ligamenta lata), each of which is subdivided superiorly into three smaller folds, the ala vespertilionis or ala of the broad ligament, the anterior fold corresponding with the round ligament, the middle one to the Fallopian tube, and the posterior fold to the ovary. The peritoneum has no relation with the front of the vagina (b), but it covers the up- per third of that canal behind ; from thence it is reflected upon the rectum (r), and has then the same arrangement in both sexes. Inferiorly it is limited to the anterior sur- face of the gut, but superiorly it entirely surrounds it, excepting behind, where it forms a duplicature known as the mesorectum. After leaving the cavity of the pelvis, the peritoneum continues to ascend, so as to cover the posterior wall of the abdomen ; in this situation we shall examine it in the middle and at the sides. In the middle it passes in front of the sacro- vertebral angle, then in front of the lumbar vertebrae, and having arrived opposite an oblique line, extending from the left side of the second lumbar vertebra to the right iliac fossa, it is reflected forward to constitute the left layer (m) of the mesentery {neaoq, middle, evrepov, an intestine) ; it immediately ex- pands, so as to correspond to the whole length of the small intestine (i), lines the left lateral half, the convex borders, and the right lateral half of that intestine, and then pass- ing from before backward (m'), is applied to the back of the layer just described, and in this manner forms the mesentery (m m'), the largest of all the duplicatures of the peri- toneum, and remarkable for its resemblance to a plaited ruffle. On the left side, the peritoneum, after having formed the mesorectum, then forms the iliac Tnesocolon, a considerable fold, which allows great mobility to the sigmoid flexure of the colon. From the sigmoid flexure it is prolonged upon the left lumbar colon, cover- ing the anterior five sixths of that part of the intestine, and applying it against the kidney, but without forming any duplicature for it ; so that the kidney and the colon are in im- mediate relation. Still, the left lumbar colon is not unfrequently entirely surrounded by the peritoneum, so as to have a duplicature behind it, called the left lunibar mesocolon. Along the whole course of the great intestine, the peritoneum usually forms a number of small folds containing fat, and named the appendices epiploica. On the right side the peritoneum arrives at the caecum, and may be arranged in one of two modes : it either entirely invests that portion of intestine, which is then very mo- vable ; or else, and this is the most common arrangement, it passes iimnediately in front of the cascum, which is thus applied against the right iliac fossa, and is attached there by rather loose cellular tissue. The peritoneum sometimes forms a small mesentery for the vermiform appendix, sometimes fixes it against the posterior surface of the caecum, or against the ileum, or, lastly, against the lower portion of the mesentery. Above the caecum the peritoneum covers the right lumbar colon, and has the same arrange- ments as on the left side. Such is the course of the sub-umbilical portion of the peritoneum. The Superior or Supra-umblical Portion of the Peritoneum. — We shall trace the superior or supra-umbilical portion from the umbilicus to the posterior wall of the abdomen, op- posite to the mesentery and the lumbar mesocolon, to which points we have already traced the lower portion. Commencing at the umbilicus and proceeding upward, the peritoneum (e) lines the an- terior abdominal parietes ; on the right side it meets with the umbilical vein, or the fibrous cord to which that vein is reduced in the adult, covers it, and forms a falciform duplicature, named the suspensory ligament of the liver, or falx of the umbilical vein ; this fold is of a triangular shape, its apex corresponds with the umbdicus, and its base with the upper surface of the liver, which is divided by it into two lateral portions or lobes, t From the umbilicus, then, as from a centre, proceed four peritoneal folds : one superior or ascending, for the umbilical vein ; and three descending, one for the urachus and two for the umbilical arteries. From the anterior wall of the abdomen, the peritoneum is continued upon the Idwer * The peritoneum, forming the cul-de-sac between tlie bladder and the rectum, sometime.s has a fissured ap- pearance, like that seen upon the parietes of the abdomen in women who have had many children. t [Its lower free margin encloses the umbilical vein, and its upper or interior border is attached to the ab- dominal parietes.] 476 SPLANCHNOLOGY. surface of the diaphragm (/), and is arranged differently on the right and left sides and in the middle. The Right or Splenic Portion. — The peritoneum, after having lined the lower surface of the diaphragm as far as the vertebral column, is reflected upon the posterior surface of the vascular pedicle of the spleen, covers the posterior half of the internal surface of that organ, its posterior border, the whole of its external surface, the anterior half of its internal surface, and the anterior surface of its vascular pedicle, from which it is pro- longed upon the great end of the stomach, and becomes continuous with the anterior layer of the great omentum. The two layers which are applied to each other, one in front of and the other behind the vessels of the spleen, constitute the gastro-splenic omen- tum. Below the spleen, the peritoneum forms a horizontal fold, or septum, by which that organ is separated from the viscera below it. The Middle or Gastro-epiploic Portion. — In the middle the peritoneum lines the lower surface of the diaphragm, as far back as the cardiac extremity of the oesophagus, is re- flected over the anterior surface of the stomach (s), and descends into the abdomen in front of the arch of the colon and the convolutions of the small intestine, to form the an- terior layer (w) of the great omentum. After descending towards the lower part of the abdomen for a distance, which varies in different individuals and at different ages, it is folded backward upon itself, and passes upward to form the posterior layer (o) of the great omentum. Having arrived at the con- vex border of the arch of the colon (c), it covers the lower surface of that intestine, and passes horizontally backward (q) to the anterior surface of the vertebral column, in front of which it is again reflected, and becomes continuous with the right layer {m') of the mesentery. The horizontal portion, which extends from the arch of the colon to the vertebral column, forms the inferior layer {q) of the transverse mesocolon. It follows, then, that the portion of the peritoneum which is continuous with that upon the anterior surface of the stomach, forms below that organ a kind of bag, which has a direct or descending layer, and a reflected or ascending layer, in the interval between which are placed the stomach (s), the pancreas (p), the duodenum (d), and the arch of the colon (e). We shall afterward find that each of these layers is lined internally by another layer of peritoneum, so that the great omentum consists of four layers of serous membrane. The Right or Hepatic Portion. — On the right side the peritoneum is reflected from the diaphragm upon the convex surface of the liver (/), and forms the coronary ligament of the liver (at g), being continuous with the suspensory ligament, the direction of which is at right angles to its ovm. From the convex surface of the liver, the peritoneum is reflected over its anterior margin, and then upon its concave surface, investing the gall-bladder, sometimes almost entirely, but generally on its lower surface only. At the transverse fissure it is reflect- ed downward in front of the vessels of the liver, and to the left of those vessels reaches the lesser curvature of the stomach, and is continued upon the anterior surface of that organ. That portion of the peritoneum which extends from the transverse fissure to the lesser curvature of the stomach, constitutes the anterior layer (A) of the gastro-hcpatic or lesser omentum. To the right of the vessels of the liver and to the right of the gall- bladder, the peritoneum covers the lower surface of this viscus, and becomes directly continuous with the portion which covers the right lumbar colon. As the peritoneum is reflected from the diaphragm upon the right and left extremities of the liver, it forms two folds, one on each side, called the triangular ligaments of the liver. The Foramen of Winslow and Sac of the Omentum. — Behind the vessels of the liver, and under the anterior root of the lobulus Spigelii, is an opening which leads into a cav- ity situated behind the stomach and the gastro-hepatic omentum. This opening is the orifice of the omental sac, or the foramen of Winslow (in which a probe is placed in the figure) ; the cavity is called the posterior cavity of the peritoneum, or the sac of the omen- tum (i). The foramen of Winslow is semicircular, sometimes triangular in shape, and about one inch in its longest diameter. It is bounded in front by the vessels of the liver, behind by the vena cava inferior, below by the duodenum, and above by the neck of the gall-bladder, or, rather, by the lobulus caudatus, or anterior root of the lobulus Spigelii, these several parts being covered with peritoneum. Through this opening the perito- neum enters the sort of pouch formed between the two layers of the great omentum. In tracing the course of the reflected portion of the peritoneum, we shall commence at this opening, and shall return without interruption to the same point. The perito- neum is first applied to the posterior surface of the anterior layer of the gastro-hepatic omentum already described, and forms the posterior layer (t) of that omentum ; it then covers the posterior surface of the stomach ; below that organ it is applied (iv) to the descending or anterior layer of the great omentum, behind and parallel to which it passes down ; having arrived at the point where the anterior layer of the great omentum is re- flected, the layer we are now describing is itself reflected (x) in the same manner, and becomes applied to the anterior surface of the posterior layer of that omentum ; con- THE PERITONEUM. 477 tinuing to ascend, it gains the convex border of the transverse colon, covers the upper surface of that intestine, and, farther back, is applied to that layer of the great omentum which is continued over the lower surface of the colon ; it thus forms the upper {y) of the two layers of which the traiisverse mesocolon is composed. Having reached the front of the vertebral column, it leaves the inferior layer of the transverse mesocolon, covers the anterior surface of the third portion of the duodenum (d), the anterior surface of the pancreas (f>), the lobulus Spigelii and the anterior part of the vena cava, and ar- rives at the transverse fissure of the liver, opposite the foramen from which we began to trace it. It follows, therefore, that the great omentum, notwithstanding its thinness and trans- parency, consists of four perfectly distinct layers, two of which, united together in front, and two behind, constitute the parietes of a cavity called the posterior cavity of the peri- toneum, or the sac of the omentum. We may, however, describe the omentum in a different mode, as follows : Two lay- ers of peritoneum applied to each other pass off from the transverse fissure of the liver, separate along the lesser curvature of the stomach, in order to enclose that organ, again unite along its greater curvature, then pass downward, and, opposite the brim of the pelvis, are reflected backward upon themselves, and proceed upward. Having reached the convex border of the colon, they separate to receive that intestine between them, become reunited at its concave border to form the transverse mesocolon, and then sep- arate finally. The inferior layer is reflected downward, to become continuous with the right layer of the mesentery ; the superior is reflected upward, to cover the third portion of the duodenum, the pancreas, and the lobulus Spigelii, and then becomes continuous with the rest of the peritoneum at the foramen of Winslow.* General Description of the Peritoneum. — From the preceding description, it follows that the peritoneum forms a continuous membrane, so that, if it were possible to unfold all its duplicatures, and to detach it entire from the surface of all the organs covered by it, it would form a large membranous sac without an opening. Nevertheless, in the fe- male there is a remarkable interruption at the point corresponding to the free extremity of the Fallopian tube, in which situation we find the only example in the body of a serous and mucous membrane being continuous with each other. The peritoneum has two surfaces, an external and an internal. The internal surface is free, smooth, and moist, and is the seat of an exhalant and absorbent process, which, in the natural condition, exactly counterbalance one another. The external or adherent surface lines the parietes of the abdominal cavity, covers most of the abdominal viscera, of which it forms the external or common coat, and is in con- tact with itself in the different folds formed by the peritoneum. The attachment of this surface is effected by means of cellular tissue, the character of which varies in different situations. We shall examine the external surface of the portion of the peritoneum applied to the abdominal parietes, or the parietal peritoneum ; of that upon the viscera, or the visceral peritoneum ; and also of that forming the different folds. The Parietal Portion of the Peritoneum. — ^Upon the diaphragm it is attached by a very dense cellular tissue ; nevertheless, it may be torn off in dissecting that part. Upon the anterior wall of the abdomen it adheres most strongly opposite the linea alba and the sheath of the rectus muscle, and more loosely opposite the crural arches than in any other part. Still, it is not very difficult to separate the whole of the membrane correspond- ing to the parietes of the abdomen. In the lumbar region the adhesion is extremely loose, and also in the iliac fossae on the front of the vertebral column : the same is the case in the cavity of the pelvis. The cellular tissue on the outside of the peritoneum, which most anatomists have re- garded as forming the external tissue of that membrane, sends prolongations through the numerous openings with which the walls of the abdomen are perforated. These prolongations connect the sub-peritoneal cellular tissue with that of the lower extremi- ties on the one hand, and with the cellular tissue external to the pleura on the other. The peritoneum is supported throughout by a fibrous layer, and this accounts for the dif- ficulty with which abscesses of the abdominal parietes open into the cavity of the peri- toneum. The Visceral Portion of the Peritoneum. — Among the viscera of the abdomen some re- ceive a complete investment from the peritoneum, always excepting the point at which their vessels reach them ; to this class belong the spleen, the stomach, and the small intestines. Others have a less complete covering, so that a portion of their surface is in immediate relation with surrounding parts : of this number are the ascending and de- scending colon and the caecum. Lastly, others have only very slight relations with the peritoneum, which merely pass over them, and do not appear to enter into their forma- * In many subjects the existence of the sac of the omentum may be demonstrated by introducing a large catheter into the foramen of Winslow, and by blowing carefully through it ; the air will enter between the two anterior and the two posterior layers of the great omentum, and form a large and more or less regular 'iladder. For this experiment to succeed, the omentum must be parfectlv uninjured, and free from adhesions. 478 SPLANCHNOLOGY. tion : to this class belong the bladder, the lower part of the rectum, the pancreas, the two lower portions of the duodenum, and the kidneys. To the last-named organs the peritoneum is connected only by very loose cellular tissue. The visceral portion of the peritoneum is not strengthened by the fibrous layer met with in its parietal portion, and, therefore, perforation of the serous coat of the viscera is much more common than perforation of the parietal portion of the serous membrane. The Folds of the Peritoneum. — Among the folds of the peritoneum, most of which have been already described, and which need be only recapitulated here, some bear the name of ligaments, viz., the triangular, coronary, and falciform ligaments of the liver, the pos- terior ligaments of the bladder, and the broad ligaments of the uterus. Others are called mesenteries, viz., the mesentery, properly so called, or the mesentery of the small intestine, the transverse mesocolon, the right and left lumbar mesocolon when they exist, the ihac mesocolon, and the mesorectum. With these we should in- clude the duplicature extending from the transverse fissure of the liver to the lower cur- vature of the stomach, and known as the lesser omentum ; it really constitutes the me- sogastrium. Lastly, there are certain folds, named omenta or epiploa {em, upon, n?Ju, to float), viz., the great, or gastro-colic, small, or gastro-hepatic, gastro-splenic, and colic omenta.* With this class we may connect the appendices epiploicae. It may be well to make a few observations upon the great and lesser omenta. The Great Omentum. — The great or gastro-colic omentum, so called because it is at- tached, on the one hand, to the stomach, and on the other to the colon, scarcely exists in the new-born infant ; it is gradually developed as age advances, and about the period of the termination of growth it reaches to the brim of the pelvis. It has been remarked that it descends a little lower on the left than on the right side. When the stomach and the colon are distended, this omentum is reduced to a more or less narrow border extending along the arch of the colon. It presents also a number of individual varieties : sometimes it is very regularly sus- pended in front of the intestinal convolutions ; sometimes it is folded upon itself, and carried to one side or the other ; occasionally it adheres at some point, becomes stretch- ed hke a cord, and may then give rise to strangulation ; and, lastly, it is not very rare to find it turned upward and backward between the diaphragm above and the stomach and liver below. It is so transparent and thin that it is difficult to conceive it to be formed of four lay- ers. In some individuals it is even perforated with holes like a piece of lace. The great omentum is found, in very fat persons, to be loaded with an immense quantity of adipose tissue, deposited chiefly along the vessels ; so that it may acquire a very con- siderable size, and a weight of several pounds. The great omentum has an anterior and posterior surface, both of which are free, an upper adherent border, a lower border, free, convex, and more or less sinuous, which cor- responds with the crural arches, and the internal openings of the inguinal canals ; it is, therefore, very often found in hernial sacs. The lower border is more liable to adhesions than any other part of the omentum. The lateral borders have nothing remarkable ; they proceed parallel to the ascending and descending portions of the colon, which are sometimes covered by them. The arteries of the great omentum are furnished by the right and left gastro-epiploic arteries ; they descend vertically between its two anterior layers, scarcely diminishing in caliber. At its lower border they turn upward, and ascend between the two posterior layers as far as the arch of the colon, where they communicate with the arteries of that intestine. The veitis follow the same course as the arteries, and assist in forming the vena portee. Some lymphatic glands are found in the great omentum along the curvatures of the stomach and the arch of the colon. Nerves. — Some nervous filaments from the solar plexus can be traced upon the arter- ies of the omentirai ; it is doubtless from them that the epiploon derives its peculiar sen- sibility, and on them that the phenomena of strangulation depend when it is constricted in a hernia. The uses of the omentum are not known. The Lesser Omentum. — The lesser omentum, a true mesentery, the mesogastrium, pre- sents a lower concave border, attached to the lesser curvature of the stomach, and an upper border, attached to the transverse fissure of the liver, to that part of the antero- posterior fissure which is behind the transverse fissure, and also to the oesophagus and the diaphragm ; its right border contains the ducts and vessels of the liver, and behind the border thus formed is seen the foramen of Winslow ; on the left it is bounded by the cesophagus.t ' [The colic omentum consists of two layers of peritoneum, with intermediate vessels and fat, which de- scend, behind the great omentum, from the upper part of the ascending colon.] t [The cellular tissue surrounding the vessels, ducts, and nerves, contained between the layers of this small omentum, has been described as giving origin to Glisson's capsule.] THE HEART. 479 IStruetin-e of the Peritoneum. — ^The peritoneum, like all other serous membranes, has neither arteries, veins, nor nerves. Those which are contained within the omenta and the mesentery do not properly belong to this membrane. The finest capillary injections, either natural or artificieil, form an extremely delicate network below the peritoneum, but never penetrate it.* ANGEIOLOGY. Definition and Objects of Angeiology. Angeiologt {ayyelov, a vessel) is that division of anatomy which treats of the orgauL of the circulation. The circulating system consists of a central organ, the heart, the agent for propelling the blood ; of the arteries, vessels through which the blood is conveyed from the heart to all parts of the body ; of the veins, through which the blood is returned from all parts of the body to the heart again ; and, lastly, of the lymphatic vessels, appendages of the venous system, into which their contents are ultimately poured. THE HEART. General Description. — External and Internal Conformation. — Structure. — Development. — Functions. — The Pericardium. Dissection. — In order to study the external conformation of the heart, inject the cavi- ties of the right side of that organ by the pulmonary artery, or by one of the venae cavae, taking care to tie the other ; the cavities of the left side may be filled from the aorta, or one of the pulmonary veins. Tallow, wax, and glue-size are the most suitable materials for this purpose. The heart {Kapdia), the central part of the circulating apparatus, is a hollow muscular organ, divided into several compartments, and intended for propelling through the arter- ies into all parts of the body the blood which is poured into it from the veins. The heart is one of the most important organs in the body. In a zoological point of view, the presence or absence of a heart, and the complexity or simplicity of its struc- ture, deserve particular attention, because such variations in regard to the central organ of the circulation are accompanied by very great modifications in the entire organism.! Congenital absence of the heart is extremely rare, and is always accompanied with other malformations, more especially with absence of the brain. These deficiencies are incompatible with life. Number. — Man and vertebrated animals have only one heart ; in moUusca it is double, or even triple. This plurality of hearts, instead of being an index of perfection, should be regarded as a subdivision, and less perfect condition of the organ. We shall see that man, as well as mammalia and birds, has, in reality, two hearts united into one. Situation. — The heart is situated at the junction of the upper third with the lower two thirds of the body ; hence the upper parts of the system are more immediately under the influence of this important organ, t The heart (/, fig. 170 ; o,fig. 171) occupies the middle of the thoracic cavity ; it is sit- uated in the mediastinum, in front of the vertebral column, behind the sternum, which forms a kind of shield for it, and beyond which it projects on the left side ; it is placed between the lungs, and above the diaphragm, by which it is separated from the abdom- inal viscera. It is retained in this situation by the pericardium (p p,fig. 170), a fibro-serous cover- ing, which is itself closely adherent to the diaphragm (x) ; by the pleurae {q q), which are reflected on each side of it, to form the parietes of the mediastinum ; and, lastly, by the great vessels which pass out or enter at its base. * [The basis of the peritoneum is cellular tissue ; its smooth surface is covered with a squamous epithelium.] t Vertebrata and mollusca are the only animals which are provided with a heart. Mammalia and birds alone possess a double heart, i. e., a heart with two auricles and two ventricles. Fishes and reptiles have a simple heart, t. e., a heart with only one auricle and one ventricle, this ventricle being pulmonary in fishes, and both systemic and pulmonary in reptiles.* t The distance from the heart to the brain varies in different individuals, according to the length of the tho- rax and the neck. This difference may amount to two inches, and may exercise some influence upon the cere- bral circulation. In consequence of this observation, extreme shortness of the neck has been regarded as a predisposing cause of apoplexy. * [A central pulsating vessel is found in some of the higher radiata, and in the articulata ; in some of the latter it constitutes a strong muscular ventricle, but the addition of a systemic auricle to this ventricle is first observed in the mollusca ; in the invertebrata, generally, the ventricle is entirely systemic : in the higher ce- phalopods there are two branchial hearts. In fishes the heart consists of a systemic auricle and a pulmonary ventricle, and is preceded by a sinus venosus, and followed by a bulbus arteriosus. In the early condition of the batrachia the same conformation exists ; but in their adult state, and also in all reptilia, there are two auricles and one ventricle, the additional auricle being pulmonary, i. e., receiving the blood from the lungs. In the higher reptilia, the single ventricle, which is both systemic and pulmonary, is divided by an imperfect leptura ascending from the apex of the heart. In the crocodilus lucius, as well as in birds and mammalia, this interventricular septum is complete, so that in them the heart is divided into two auricles and two ventri- cles, the cavities of one side being systemic, and of the other pulmonary.] ANGEIOLOGY. These means of attachment are not such as to prevent the heart from undergoing re markable changes of position, depending upon peculiar attitudes, upon shocks acting on the body, or upon diseases of the surrounding organs. Thus, in a case of hydrothorax on the left side, the apex of the heart struck against the right side, and gave rise to the suspicion that the viscera were transposed. Size and Weight. — Neither the size nor the weight of the heart can be estimated with exactness, on account of the numerous individual varieties in both. It is very difficult to determine the limits, in either the one or the other, between a healthy and a morbid con- dition ; and a heart which would be considered normal in one individual would be re- garded as hypertrophied in another. The defects of the method proposed by Laennec for obtaining an approximative esti- mate of the size of the heart, by comparing it with that of the closed hand of the samo subject, afford sufficient evidence of the difficulty of arriving at an accurate result in this matter.* No organ in the body is more subject to enlargement than the heart ; when caused by dilatation of the cavities, it constitutes aneurism of the heart {dilatation) ; when due to thickening of the parietes, it is termed hypertrophy. When enlargement occurs from both these causes, the heart acquires an enormous size, and has been called bullock's heart (hypertrophy with dilatation). The size of the heart may be estimated directly by ascertaining the quantity of water displaced by it, and by admeasurement ; it may also be determined, in an approximate manner, by its weight, which bears a certain relation to the size. In making these estimates, it is necessary to distinguish the size and weight depend- ant upon thickness of the parietes of the heart, from the increase occasioned by blood contained in its cavities. In order to obtain comparative results upon this point, the heart must be weighed and measured both in its empty and its distended state. The average weight of the empty heart is from seven to eight ounces. Some atrophied hearts do not weigh more than two ounces : dilated and hypertrophied hearts, when empty, may weigh twenty-two ounces. The ordinary weight of the heart distended with tal low is twenty-four ounces. I have seen dilated hearts, also, filled with tallow, which weighed three pounds. As to the admeasurement, we shall apply it in succession to the ventricles and to the auricles. Form, Direction, and Divisions. — The heart has the form of a flattened cone, the axis of which is directed obliquely from above downward, from the right to the left side, and from behind forward. This direction, which is peculiar to the human species (for in the lower animals the heart is vertical), appears to have some relation to the erect position. The heart is not symmetrical in reference to the median line of the body, nor yet in re- gard to its own axis. The general relations of the heart will be indicated when we describe the pericardium. I shall here simply state that the heart is in relation with the left lobe of the lungs, which is deeply notched to receive it ; that that portion of the heart which is uncovered in front between the lungs, after the sternum and the ribs have been removed, is extremely vari- able in different subjects ; that independently of the volume of the heart, the adhesions of the lungs exercise a very great influence upon the extent of these direct relations of the heart with the anterior part of the sternum. In an old woman, whose lungs were closely adhering to the walls of the thorax, the anterior face of the heart was almost en- tirely bare behind the sternum and the cartilages of the ribs on the left side.t That the posterior face of the heart deserves the name of vertebral surface just as well as that of diaphragmatic surface ; that this surface occasions a marked impression upon the liv- er ; that the relations of the posterior surface of the heart with the oesophagus are such as will cause the distended oesophagus to raise the corresponding portion of the pericar- dium, and that the posterior surface of the heart is not only separated from the vertebral column by the oesophagus, but also by the aorta, which is situated between the oesopha- gus and the bodies of the dorsal vertebrae. The heart is divided into ventricles and auricles. The ventricles (Jt o,figs. 191, 192) constitute the chief part, in some measure the body of the organ, the conical form of which is determined by them ; the auricles (m n) are a kind of appendices, which can be well seen only when the heart is raised ; they occupy the base of the organ ; the limit between the auricles and the ventricles is indicated by a circular furrow. External Conformation of the Heart. The External Surface of the Ventricles. The external surface of the ventricles, or the ventricular portion of the heart, called also * The large hand of a workman does not imply the existence of a larger heart than the small hand of a fe- male, or of a man exempt from manual labour. t The heart descends as far as the middle portion of the xiphoid appendix. The upper half of this appendix is, therefore, in direct relation with the heart, and the inferior half in direct relation with the liver. Should not this circumstance be of some weight in explaining the acute pains by which a pressure upon this appendix u accompanied ? THE HEART. 48'! by the ancients the arterial portion, because the arteries arise from it, presents for our consideration an anterior and an inferior surface, a right and a left border, a base and an apex. The anterior or sternal surface {Jig. 191) is convex, and is divided into two unequal parts, a larger on the right, and a smaller on the left side, ^^ 191_ by the anterior furrow of the heart (e b), which passes verti- cally from the base towards the apex, is occupied by the an- terior coronary artery, and is often obscured by fat. All that part of the organ which is to the right of the furrow be- longs to the right ventricle (I), all on the left belongs to the left ventricle (o). The furrow itself corresponds to the sep- tum between the ventricles. This surface, or, rather, the pericardium which covers it, is in relation with the sternum, more especiedly in that part which hes to the right of the furrow ; also with the fourth, fifth, and sixth costal cartilages of the left side, and with the lungs, which cover it more or less completely. It should be remarked that, in large hearts, this surface, or its peri- cardium, corresponds immediately to the sternum, while in the natural state it is situated at some distance from that bone. The relations of the heart with the anterior wall of the thorax enable us to examine its condition by means of percussion and auscultation. The inferior or diaphragmatic surface {fig. 192) is plane and horizontal ; it rests upon the diaphragm, which forms a sort of floor for it, and separates it from the hver and the stomach. Like the anterior surface, it is marked by a longitudinal furrow, the posterior furrow of the heart {e i), which is traversed by vessels and concealed by fat. It differs from the anterior furrow in running parallel to the axis of the heart, and dividing its diaphragmatic surface into two nearly equal parts, excepting near the apex. In conse- quence of the relations of this surface, pidsations are observed in the epigastrium, which are sometimes much more distinct than those felt upon the anterior wall of the thorax. Another result of these relations is, that the same meaning is attached to the terms scrobiculus cordis and pit of the stomach, and also to the expressions pain at the heart, pain at the stomach, 4-c. The right or lower border is thin and horizontal, and rests upon the diaphragm ; it is straight near tlft apex, but becomes convex towards the base. The left border (o b, fig. 191) is very thick, convex, and almost vertical; it resembles a surface rather than a border, and corresponds to the left lung, which is deeply notched to receive it. The base of the ventricular portion of the heart is turned upward, backward, and to the right side. From it arises, upon an anterior plane, an artery, which immediately passes from the right to the left ; this is the pulmonary artery {k) ; the portion of the ventricle from which it proceeds forms a prominence on the right side of the anterior furrow of the heart, and is prolonged towards the left, becoming narrower at the same time, so as to form a funnel-shaped projection {infundibulum, conus arteriosus) {a), extending a little beyond the base of the ventricles. Upon a second plane we find the aorta (/), the origin of which, from the left ventricle, is concealed by the funnel-shaped prolongation of which we have just spoken. On a third plane we find a circular furrow (o u, fig. 195), separa- ting the auricles from the ventricles. Its posterior half is occupied by the coronary ar- teries and veins, and the anterior and posterior furrows of the heart terminate in it at right angles. This circular furrow at first sight appears to be superficial, but is very deep in its pos- terior half If we dissect carefiiUy down to the bottom of this furrow, it is found that the base of each ventricle is, as it were, turned inward, so as to be in contact by a broad surface with the base of the auricle. We find, also, that the base of the ventricles is cut obUquely, and hence the anterior surface of the heart is longer than the posterior surface. The difference in length between these two surfaces is about fifteen lines upon the right, and from nine to ten Unes upon the left ventricle. Thus, in a heart of the ordinary size, the length of the ventricles in front was three inches three lines, and behind two inches three lines. In a very large heart the length in front was four inches, and behind only three. The circumference of the base of an injected heart, of the average size, measured ten inches ; that of a large heart was thirteen inches six lines. The apex {h) or point of the heart is slightly curved backward in the majority of sub- jects, and is notched opposite the junction of the two longitudinal furrows. This notch, which is partially concealed by vessels and adipose tissue, divides the apex of the heart into two unequal portions ; a right and a smaller, belonging to the right ventricle, and a left and larger portion, belonging to the left ventricle. The relative size of the two por- tions of the apex of the heart is not constant. In some cases of hypertrophy of the left ventricle, the apex of the heart is entirely formed by it ; in other cases, on the contrary the apex of the heart is nearly equally subdivided. Ppp 482 ANOEIOLOGY. The apex of the heart is directed forward, downward, and to the left, and corresponds to the cartilages of the fifth and sixth ribs of the left side, and therefore to the region of the corresponding mamma ; the left lung is notched opposite the apex of the heart, so that the latter strikes directly against the parietes of the thorax. The External Surface of the Auricles. The attricles (m n,figs. 191, 192), forming the auricular portion of the heart, are saccular cavities in which the veins terminate ; they may, in fact, be regarded as dilatations of those vessels, and hence this portion of the heart is called the venous portion, in contra- distinction to the ventricles. They are situated upon the hindermost portion of the base of the heart (fig. 192). Their size varies in different individuals ; in an injected heart, the average height of the auricular portion is two inches ; its antero-posterior diameter is nearly the same ; and when the auricles are distended, its transverse diameter extends beyond the tcl tricles on each side. The shape of the auricular portion of the heart, which can only be accurately deter mined by means of injection, is irregularly cuboid. It therefore presents several sur faces ; its anterior surface is situated on a plane much farther back than that of the front of the ventricles {fig. 191). It is concave, and describes three fourths of a circle, so as to embrace the aorta and the pulmonary artery, being moulded upon those vessels, and completely concealed by them. The anterior surface of the auricular portion has no anterior furrow along the middle line. The posterior surface (fig. 192) is convex, and is continuous with the inferior surface of the ventricles ; it presents a vertical furrow, which is prolonged upward from the posterior furrow of the ventri- cles, then deviates to the left side, and forms a curve, the concavity of which is directed towards the right ; it corre- sponds to the septum of the auricles. Immediately to the right of this furrow we find the termination of the vena cava inferior (r), and lower down, that of the great coronary vein. The posterior surface of the auricles is turned towards the vertebral column, from which it is separated by the oesopha- gus and the aorta. The superior surface of the auricular portion forms the highest part of the heart, and is directed backward and to- wards the right side. It is divided by a furrow, which is convex on the right side, is continuous with the furrow upon the posterior surface, and, like it, corresponds to the inter- auricular septum. Upon this surface we find the termina- tions of five different veins ; one only of these is to the right of the furrow, viz., that of the vena cava superior (d,fig. 191) ; the other four are on the left of the furrow, and are those of the four pulmonary veins, which are arranged in pairs (c c,fig. 192), two at the extreme left of the auricles belonging to the left pulmona- ry veins, and two immediately in the neighbourhood of the posterior furrow belonging to the right pulmonary veins. This surface corresponds to the bifurcation of the trachea, which, as it were, rides upon it. The extremities of the auricles, or the aurievJee, are free, and somewhat resemble the pendulous portion of a dog's ear ; hence the term auricles. They are indented like a cock's comb ; the right auricula is anterior, the left posterior. The right auricula {c,fig. 191) is broader and shorter than the left ; it is triangular and concave, so as to embrace the aorta, in front of which it projects ; the left auricula (i) is narrower and longer, it is sinuous, and curved twice upon itself like an italic S ; it em- braces the pulmonary artery, and terminates opposite the highest part of the anterior fur- row of the ventricles. The right auricula is continuous with the rest of the corresponding auricle, vdthout any well-marked line of separation ; but the left auricula is very distinct from its auricle ; and upon this latter side, the distinction pointed out by Boerhaave, between the sinuses and the auricles properly so called, may be particularly observed : according to him, the sinus constitutes the body of the auricle, and may be regarded as a dilatation of the veins, while the auricular appendix forms the proper auricle. The Internal Conformation of the Heart. The heart is divided internally into four cavities, which are separated from each oth- er by complete or incomplete septa ; two of these cavities belong to the auricles, and two to the ventricles. There are a right ventricle and auricle, and a left ventricle and auri- cle. The auricle and ventricle of the same side are separated by incomplete septa or valves, and communicate with each other. The cavities of the opposite sides are sep- arated by complete septa, and do not communicate. Tlie heart is therefore, in this lat- ter respect, truly double. The right ventricle and auricle constitute the right heart, also THE HEART. 4^ named the cmur d. sang noir, from the colour of the blood which it contains ; and the pul- monary heart, because it propels the blood into the lungs. The left ventricle and auricle constitute the left heart, called also the caur a sang rouge, or the aortic heart, because it throws the blood into the aorta. The Internal Conformation of the Ventricles. Dissection. — In order to obtain a general idea of the internal conformation of the heart, make a series of sections at right angles to its length, or else make an incision along its borders parallel to its long axis. To obtain a more exact notion of the ventricles, make a V-shaped incision in the right ventricle, letting one branch of the incision extend along the anterior furrow, and tte other along the right border, while the angle at which they meet should correspond to the apex of the ventricle. The best method of opening the left ventricle consists in making a vertical section through the septum ; but in doing this, the right ventricle must be sacrificed. In order to obtain a general view of the appearance of these cavities, they may be pre- pared in the dried state. For this purpose, the heart is to be injected with tallow, and then, after being dried sufficiently, to be opened in the manner above described, and im- mersed in warm turpentine, which will dissolve the tallow,and leave the ventricles dilated. Interior of the Right Ventricle. The right ventricle occupies the right anterior and inferior portion of the heart, and has, therefore, been called the anterior or the inferior Fig. 193. ventricle. Its cavity (Jig. 193) has a three-sided pyrjunidal form. Its inner wall (6) is convex, and is formed by the septum of the ventricles ; in its lower half it has a well-marked reticulated appear- ance, which is almost entirely absent in the upper half (a). The anterior and inferior walls (partly re- moved in^. 193) are both concave, and are re- markable for their thinness, so that they are al- ways collapsed when the ventricle is empty. The base of this ventricle presents two openings, which are separated from each other by a projecting part, and which may be compared to the wide circular end, and the narrow mouthpiece of a huntsman's horn. The opening into the auricle (in which a bristle is placed) corresponds to the wide end of the horn, and the infundibulum (a) to the narrower end. The transverse diameter of the base of this ventricle is nearly equal to its height. The sum- rait (Z) is turned towards the apex of the heart. The walls of the right ventricle are very remark- able for their reticulated or areolar character ; this areolar portion might be termed the corpus cavernosum of the heart, for it presents the spongy structure of the erectile tissues. The fleshy columns which form the areolae are observed not only upon each of the walls of the ventricle, but they also pass across the cavity of the ventricle near its summit, extending from one wall to the other ; in conse- quence of which the capacity of the ventricle is singularly diminished. The cylindrical fleshy columns {columnce carnece, teretes lacerti), which separate the meshes or areolae, are of three kinds. Some (c) are attached to the parietes of the heart by one of their extremities, and are free in the rest of their extent ; they terminate by a kind of simple or double meimmillated projection, from which proceed small tendinous cords {chorda tendinem), that are inserted into the auriculo-ventricular valves (c). They are very few in number, and have been named the muscles of the heart {musculi papillares). The fleshy columns of the second kind are free throughout the whole of their extent, ex- cepting at their extremities, which are attached to the walls of the ventricle. These col- umns, which are the most numerous, are divided and subdivided to form the areolae. The third kind of columnae carneae adhere to the walls of the ventricle by one of their sides ; they are therefore sculptured like pilasters upon the walls of the ventricle. Most of the colmnnae carneae pass from the apex towards the base of the heart. In all their free portion, the columns of the two first kinds are attached to each other or to the walls of the ventricle, by means of small tendinous cords, which are much more deli- cate than those proceeding to the valves. The areolar muscular structure just described is the essential constituent of the walls of the ventricle ; but in addition to it there is a rather thin, compact, and non-reticulated layer of superficial fibres, on which depends the smooth appearance of the external surface of the ventricle. The Orifices of the Right Ventricle. — At the base of the right ventricle there are two orifices, one auricular, which establishes a communication between the ventricle and the ANGEIOLOGY. auricle ; the other arterial, which leads into the pulmonary artery. They are both fur- nished with valves. The right auricular or auriculo-ventricular orifice (through which the bristle is inserted, Fig. 194. fig. 193) is placed at the posterior and right part of the base of the ventricle ; it is elliptical, and is provided with a mem- branous structure, called the tricuspid or triglochin valve (c), which projects into the interior of the ventricle. This valve is of an annular form (annulus valvulosus). Its ventricular sur- face {t 1 1, fig. 194) is directed towards the parietes of the ven- tricle, and receives a great number of small tendinous cords, which, being attached to it at different points, give it an ir- ^ regular aspect. Its auricular surface {t t t,fig. 195), which is turned towards the axis of the ventricle, is smooth. The ad- herent border is fixed to the margin of the auricular orifice. The free border or margin forms a ring, the diameter of which is equal to that of the .gg adherent border : this margin is irregularly divided, so that, in- ''^' ■ stead of the three segments {t 1 1) generally described, and from which the name of the valve has been derived {rpelc, tres, three, and y^uxk, cuspis, a point), some authors admit four, or even six segments. The construction of the tricuspid valve can be understood only by regarding it as composed of two parts, an anterior, cor- responding to the anterior half of the elliptical auriculo-ventric- ular orifice, and a posterior, corresponding to the posterior half of the same. The tricuspid valve is not unfrequently in- terrupted on the left side opposite the junction of these two valves. This valve might, with as much propriety, be termed mitral, as that which is attached to the lefl auriculo-ventricular opening. To the free margin of the valve, upon which some small nodules are occasionally found, are attached a number of tendinous cords of a nacreous aspect, which are ex- tremely strong considering their tenuity. These small cords, or, rather, tendinous fila- ments, always arise in greater or less number from the summits of the columnae car- nese ; diverging from thence, often bifurcating during their course, and sometimes be- coming united together, they terminate, some at the free margin, others at the ventric- ular surface of the valve, and others, again, at its adherent border. All the smalll tendinous cords do not arise from the columnae cameas of the first kind ; many of them proceed directly from the parietes of the heart. We constantly find a fasciculus of diverging cords arising from the septum. These cords are so arranged, that, by drawing upon them, the valve is depressed and stretched. We find, in fact, that both in the anterior and posterior part of the tricuspid valve, those cords which arise from the free margin on one side converge towards those of the opposite side, some even crossing each other in the form of the letter X. The arterial or pulmonary orifice {ostium arteriosum, d,fig. 194) is placed at the anterior Fig. 196. part of the left side of the base of the right ventricle. It is sep- arated from the auricular orifice by a tolerably prominent mus- cular band, which is concave on its lower surface, and divides the right ventricle into two portions, an auricular and a puhno- nary portion or infundibulum. This orifice is circular, and is provided with three very distinct valves, which are named sig- moid or semilunar {f,fig. 195 ; a a a, fig. 196).* Although thin and semi-transparent, they are very strong. They are directed vertically as the blood is passing from the ventricle into the artery, and become horizontal when it tends to flow back from the artery into the ventricle. Of their two surfaces, the ven- tricular corresponds to the .cavity of the ventricle ; the other, or arterial surface, includes between it and the walls of the artery a small cul-de-sac, which has been compared to a pigeon's nest. The adherent border of each valve is convex, and directed to- wards the ventricle ; its free margin presents in the middle a small nodule, by which it is divided into two semilunar halves. When depressed, the valves completely close the vessel, the three nodules filling up the triangular interval left between the approximated free mar- gins. These valves must, therefore, oppose the reflux of the blood into the ventricle ; but the resistance offered by them is easily overcome by an injection thrown into the pulmonary artery. Interior of the Left Ventricle. The left ventricle occupies the left upper and back part of the heart ; it is evidently * It is extremely rare to find any anomaly in the number of these valves, either by an increase or a dinu BUtion of them. THE HEART. 485 constructed upon the same fundamental type as the right ventricle, but difFers from il in many respects, as we shall now proceed to show. Difference in Situation. — The different positions of the two ventricles are sufficient- ly known from what has already been stated ; but it is important to remark, that the left ventricle projects beyond the other at the apex of the heart {fig. 197), while the right is more prominent at the base, in consequence of the existence of the infundibulum. Difference in Shape. — The right ventricle is pyramidal, and becomes collapsed when not distended ; the left is conical and convex, not only on its free surface (6), but even at the septum (a, fig. 194), where it seems to project into the interior of the right ven- tricle. Difference in Size. — It is generally stated, in accordance with Senac, Winslow, and Haller, that the right ventricle is more capacious than the left : this statement is found- ed upon direct observation, which proves that the right ventricle gains more at the base than the left does at the apex ; also upon deductions made by comparing the right auri- cle and the pulmonary artery with the left auricle and the aorta ; and, lastly, upon the results obtained by injecting the cavities of the heart. No two observers agree as to the exact numbers which would represent the capacities of the two ventricles, as the following different estimates will show. The capacity of the left ventricle to that of the right has been stated as 31 to 33, as 10 to 11, as 5 to 6, as 2 to 3, and as 1 to 2. — {Hol- ler, t. i., 1. iv., sect. 3, p. 327 ) Now the discrepancies in these estimates prove either the deficiency of the methods of observation, or the existence of real differences resulting from a greater or less amount of accidental obstruction to the pulmonary circulation occurring shortly before death. In the great majority of subjects, the right ventricle is proved to be more capacious than the left, and this, according to the judicious remark of Sabatier, depends upon the state of the circulation through the heart during the last moments of life, at which time the blood flows back from the lungs into the right ventricle, while the left ventricle, not ex- periencing a similar obstruction, and, moreover, acting with greater vigour, empties it- self, more or less completely, of the blood contained within it. After death by decapita- tion, the right ventricle is as much contracted as the left ; also, in individuals that have died without any agony or exhaustion, the cavity of the left ventricle has been com- pletely contracted.* The condition of the heart, then, in the dead body, in which that organ is found as it was at the moment of death, affords us no means of judging of the relative capacity of its cavities during life. If, by tying the aorta in a living animal, we cause stagnation of the blood in the left ventricle, while the exit of that fluid from the right cavities through the pulmonary artery remains unimpeded, the relative capacity of the two ventricles will be found to be exactly the reverse of what is generally indicated. The gradual injection of the heart with wax or tallow, so as to distend the ventricles without producing laceration, enables us to determine the size and the weight of the mass of injection contained within each cavity of the heart, and also to measure these cavities under similar conditions, that is to say, in a state of distension. From obser- vations which I have made in this way, it appeared that the left ventricle was rather more capacious than the right. Difference in the Appearance of the Cavity and in the Structure of its Parietes. — In the left ventricle we find the three kinds of columnas carneae. Of the columns of the first kind there are only two (i i,fig. 197), which are remarkable for their great size. Their summits are almost always bifurcated, and sometimes they are divided into three parts ; not unfrequently each of these columnae results from the apposition of two or three others, which are united by small fibrous cords or filaments. The fleshy columns of the second kind are smaller in the left than in the right ventricle. The areolar arrangement is less strongly marked, and is observed only in the innermost layer, excepting always at the apex, the whole thickness of which, with the exception of the most superficial layer, pre- sents the cavernous arrangement. Moreover, the areolae are remarkable for their small size, and for the slenderness and jiumber of the columnae by which they are surrounded. These muscular areolae are often completed by fibrous cords. Difference in Thickness. — The walls of the left ventricle are much thicker than those of the right {figs. 193, 194, 197). The proportion of one to two, arrived at by Laennec#is too slight ; it is one to four, or even one to five. It is gener- ally said that the muscular tissue of the heart is more compact on the left than on the right side. * The concentric hypertrophy mentioned by authors appears to apply to ordinary hearts, or to hearts in « state of hypertrophy, with their cavities closed, in conseqaence of the eontraction continuing to the last mo- ment. I, therefore, am opposed to admitting concentric liypertrophy as a pathologioal state. 486 ANGEIOLOGY. Difference in the Orifices. — The left auriculo-ventricular orifice (through which a bristle is inserted, ^o'. 197) exactly resembles the right one, and, like it, is provided with a valve {g) analogous to the tricuspid, and named by Vesalius the mitral valve, from its being regularly divided into two opposite segments {mm, figs. 194, 195). The mitral valve is stronger than the tricuspid, it is thick<|- and longer, and receives stronger and more numerous chordae tendineae. These differences are more particularly observed in the right segment of the mitral valve, which projects, like an incomplete septum, into the cavity of the ventricle, and appears to divide it into an aortic and an auricular por- tion ; the left segment of the valve {g,fig. 196), on the contrary, is applied against the walls of the ventricle. The aortic orifice {e,fig. 194) exactly resembles the pulmonary orifice of the right ven- tricle ; like that opening, it is also provided with three sigmoid valves (e, fig. 195), which differ from those of the pulmonary artery merely in being stronger, and in having larger nodules or globules upon their free borders ; and, as Arantius admitted their existence only in these valves, they are therefore called globuli, noduli or corpora Arantii.* The right auriculo-ventricular and arterial orifices are placed at a" distance from each other, but the corresponding orifices of the left side are contiguous, so that the adherent border of the right half of the mitral valve is continuous with the adherent border of the corresponding sigmoid valve ; and hence it follows, that when these valves are removed, the base of the ventricle presents only one orifice. Interior of the Jiuricles. Dissection of the Right Auricle. — Make a horizontal incision from the auricula to the inferior vena cava, and then a vertical one from the vena cava superior perpendicularly to the first. Of the Left Auricle. — ^Make a vertical incision from before backward, between the right and left pulmonary veins, including the entire posterior wall of the auricle. In or- der to have an accurate idea of the shape of the interior of the auricles, inject a heart with tallow or wax, and then examine the cast thus taken of their cavities. Interior of the Right Auricle. The shape of the right auricle, when distended, may be compared to the segment of an irregular oval, the long diameter of which is directed from before backward. It has three walls : an anterior, which is convex ; an internal, which is slightly concave, and corresponds to the septum ; and a posterior, also concave, which forms the greatest part of the auricle, and is remarkable for the existence upon it of fleshy columns. The right auricle has four orifices. in the adult, and five in the foetus, viz., the auriculo-ventricular orifice, the opening of the vena cava superior, that of the vena cava inferior, that of the coronary vein, and, in the foetus, the foramen ovale (trou de Botal), the situation of which is occupied in the adult by the fossa ovalis. The auriculo-ventricular wifice {see fig. 195), the largest of all, is of an elliptical form, from sixteen to eighteen lines in its longest diameter, which is from before backward, and about twelve lines in its shortest diameter. It is surrounded by a whitish zone (a q), to which is attached the adherent border of the tricuspid valve {t 1 1). The cavity of the auricle presents a sort of constriction opposite the auriculo-ventricular orifice. The orifi.ce {h,fig. 193) of the vena cava superior {d) is circular, and is directed down- ward and a little backward ; it has no valves ; it is bounded on the left by a projecting muscular band, which separates it from the auricle, and on the right by a less prominent band intervening between it and the vena cava inferior. The former of these two bands, which are distinctly marked upon the cast of wax, separates the fasciculated portion of the auricle from the non-fasciculated portion, which seems to be formed by an expansion of the venae cavae. The orifice (?) of the vena cava inferior (r) opens into the auricle, near the septum, not perpendicularly upward, but horizontally, and at right angles to the original direction of the vein, which is vertical. The orifice is circular, and larger than that of the superior cava ; the inferior cava sometimes forms an ampulla or dilatation before it enters the auricle ; us orince, unlike that of the superior cava, is provided with a remarkable semi- lunar valve, the valvula Eustachii (n), which surrounds the anterior half, and sometimes two thirds of this opening. Its free margin is concave, and directed upward ; its adhe- rent border is convex, and directed downward : one of its surfaces is turned forward to- wards ihe auricle, the other backward towards the vessel ; one of its extremities ap- pears to be continuous with the margin of the fossa ovalis (*), and the other is lost upon the margin of the opening of the inferior cava. The valve of Eustachius closes the orifice of that vein very imperfectly. In its upper two thirds it is extremely thin, and resembles the valves of the veins ; its lower third contains a muscular fasciculus. * The three sigmoid valves of the aorta are generally very similar in form ; in one case, however, which I examined, one of these valves had twice the size of the others. I have lately observed, in a man of sixty, who died of a disease of the heart, the rare sight of an aorta provided with only two sigmoid valves ; these two mlves were very large, and ia relation with the diameter of the aortic orifice, which they covered completely THE HEART. 487 The orifice of the coronary vein is placed immediately in front of the preceding, from which it is separated by the Eustachian valve. It is sometimes situated at the bottom of a small cavity or vestibule. It is provided with a very thin semilunar valve {valvula Thebesii, below and behind the bristle), which exactly resembles the valves of the veins, and completely covers the mouth of the vessel. The upper extremity of this valve is continuous with the lower end of the Eustachian valve. The Inter-auricular Orifice. — In the foetus, the inter-auricular septum is perforated be- hind and below by an opening improperly called the foramen of Botal, for it was known to Galen, who described a free communication between the auricles. After birth, we find in the situation of the foramen ovale a fossa {fossa ovalis, vestigium foramims ovalis), or, rather, a plane surface, which is generally smooth, but occasionally uneven, and, as it were, reticulated ; it is bounded in front and above by a semicircular ridge or border (s), which is improperly called the isthmus or annulusVieussenii, and may be regarded as a more or less perfect sphincter. Behind, the fossa ovalis is continuous with the vena cava in- ferior ; the semicircular ridge or border of the fossa ovalis is formed by a curved mus- cular fasciculus, sometimes very thick, the concavity of which is directed backward ; the inferior extremity of the fasciculus is continuous with the Eustachian valve. The fossa ovalis is frequently found to be prolonged beneath the semicircular border or annulus, so as to form a sort of cul-de-sac, the bottom of which is often perforated, and the handle of a scalpel may not unfrequently be introduced through this opening into the left auricle, although no morbid phenomenon may have been observed during life. The Fasciculated and Reticulated Portion of the Auricle. — Upon the internal surface of the auricle, to the right of the vena cava, are observed certain muscular fasciculi or fleshy columns (musculi pectinati auricula,), which are directed vertically from the auric- ula towards the auriculo-ventricular orifice. These fasciculi adhere to the auricle on one side only ; they are intersected by other oblique and smaller bundles, which give a reticulated aspect to the inner surface of the auricle. Cavity of the Auricula. — The auricula, or that portion of the auricle which extends from the vena cava superior to the bottom of the appendix, consists of an areolar or cav- ernous structure, exactly resembling that which has been described in the ventricles. The same cavernous structure is found in other parts of the auricle, and in particulai near the orifice of the coronary vein. I agree with Haller* and Boyer, in denying the existence of the tubercle of Lower, described by that anatomist as situated (at m) between the openings of the venae cavse. It is generally admitted that a certain number of small veins open into the right auri- cle by minute orifices without valves. We find, in fact, some openings resembling vas- cular orifices, and known under the name of the foramina Thebesii ; they are constantly found below the orifice of the vena cava superior, but most of them only lead into small groups of areolae, and injections do not demonstrate the existence of any corresponding vessels. The only true vascular orifices are those for the anterior coronary veins. Interior of the Left Auricle. The cavity of the left auricle (fig. 197) differs from that of the right in the following circumstances : in being less capacious than the right auricle, the proportion between them being four to five ; in its form, which is irregularly cuboid ; in the number of its orifices, of which there are five after birth, and six in the fcetus ; in the character of those orifices : thus the left auriculo-ventricular orifice (see fig. 195) is smaller than the right ; its long diameter, which is transverse, is from thirteen to fourteen lines, its short diameter is from nine to ten lines ; the four other openings belong to the pulmonary veins, two (c) on the right, and two (c c) on the left side, and all are without valves ;t in the structure of its auricula, which is perfectly distinct from the rest of the auricle, and con- tains a central conical cavity, leading into the auricle by a well-defined circular open- ing ; in the left auricle, nothing is seen on the septum corresponding to the fossa ovalis,t at least we perceive neither band nor ring by which it is circumscribed. When the two auricles communicate by an oblique passage, we find a very thin fibrous band, beneath which the scalpel may be introduced into the right auricle. Structure op the Heart. The heart is essentially a muscular organ, and has a framework consisting of certain fibrous rings or zones ; it is covered by a layer of serous membrane ; the left cavities are lined by a membrane continuous with the internal coat of the arteries, and the right * " Id tuberculum cupide receptum est, ut fere fit, ab iis scriptoribug quibus occasio ad propria experimenta nulla est,deinde etiam abiis qui tandem omnin(Jiu corporibus humanis dissecandis se exercuerunt." — (Ualler Elem. Phys., t. i., lib. iv., sect. 2, p. 314.) t It is not uncommon to meet with five openings, three on the right and two on the left side ; in other cases, the two left pulmonary veins open by a common orifice. t [The situation of the foetal opening {a. Jig. 197) is very commonly indicated by a recess of variable depth opening between the left surface of the septum and the (still free) crescentic border ofhbe valve of the fora- men ovale.] 488 ANGEIOLOGY. cavities by one continuous with the lining membrane of the veins.* Some nerves, prop- er vessels, and cellular tissue, also enter into its structure. The Framework of the Heart. This term may be applied to foxxx fibrous zones (the tendinous circles of Lower), which may be regarded as affording both origin and insertion to all the muscular fibres of the heart. These zones are situated at the four orifices of the ventricles, viz., the two au- riculo-ventricular and the two arterial orifices. Dissection. — Remove with care the adipose tissue, and the vessels which occupy the furrows of the heart. Examine the fibrous zones from the internal surface of the heart In order to study the relations of the orifices with each other, remove the auricles, the aorta, and the pulmonary artery, a little above those orifices. The Auriculo-ventricular Zones. — Each auriculo-ventricular zone is a tolerably regular fibrous circle, which surrounds the opening between the auricle and ventricle, and de- termines its form and dimensions. These fibrous circles give off expansions of a sim- ilar nature, which enter into the formation of the tricuspid and mitral valves, and thus add to their strength. The chordae tendineae of the heart also terminate in these zones, either directly or through the medium of the valves. The left auriculo-ventricular zone is stronger than the right. The Arterial Zones. — These are two circular rings, the diameter of each of which is somewhat less than that of its corresponding artery, so that there are some very distinct folds or wrinkles produced. These two zones are exactly alike in form, but differ some- what in strength, the aortic being stronger than the pulmonary. From these zones are given off three very thin but very strong prolongations, which occupy the angular inter- vals formed by the indented border by which the aorta and pulmonary artery commence ; and three other prolongations extend into the substance of the sigmoid valves. These prolongations form very distinct fibrous bundles in the sigmoid valve of the aorta.t Relative Position of t'he Orifices of the Ventricles (see fig. 195). — The two auriculo-ven- tricular orifices are situated upon the same plane, posterior to the other orifices, and ap- proach each other at their middle. The long diameters of these two orifices are at right angles to each other : thus, the long diameter of the right auriculo-ventricular orifice is directed from before backward, while that of the left orifice is directed transversely. In the angular interval left between these two orifices in front, the aortic opening (f) is closely united to them both ; so that the posterior half of the circumference of the aor- tic zone is blended with both auriculo-ventricular zones. At the point of junction be- tween them, we find a cartilaginous, and in the larger animals a bony, arch, which was described by the ancients under the name of the bone of the heart : in this situation, also, we frequently find the ossiform concretions of the orifices. Lastly, upon a plane in front and on the left of the aortic opening, and about five or six lines above it, is situated the orifice (/) of the pulmonary artery. The orifice of the aorta is directed towards the right side, that of the pulmonary ai- tery towards the left, so that these two vessels cross each other, so as to represent the letter X. It follows, therefore, that the pulmonary orifice is separated from the right auriculo-ventricular opening by the orifice of the aor a. In examining these openings, we observe that the plane of the auriculo-ventricular or- ifices is directed obliquely backward and downward : this explains the difference in the heights of the ventricles before and behind. We also notice the reflection or turning in- ward of the base of each ventricle (q a, p b) upon itself, so as to form a circular groove or trench on the inner surface of its cavity, running entirely round the margin of the cor- responding auriculo-ventricular orifice. The Muscular Fibres of the Heart. The Muscular Fibres of the Ventricles. Dissection. — The muscular fibres of the heart may sometimes be traced without any preparation ; but, generally speaking, either commencing putrefaction, maceration in vinegar, or, still better, hardening and separation of the fibres by means of alcohol, and especially by boiling, are necessary for this purpose. This being done, remove first the * [The muscular fibres of the heart, though involuntary, very closely resemble in structure those of the voluntary muscles (see note, p. 194), but the transverse striae upon them are less distinct. The lining membranes of the two sides of the heart are covered by epithelium, and form what is termed the endocardium.'] , t I for a long time believed that the sigmoid valves, both the aortic and the pulmonary, were formed by two prolongations of the internal membrane of the heart reflected upon itself ; but I have from pathological facts lately the positive demonstration that each sigmoid valve was formed, 1st, by a prolongation of the in- ternal membrane of the aorta ; 2d, by a prolongation of the internal membrane of the ventricle ; 3d, by an in- termediate lamella occupying only the half of the height of the valve on the side of its adhering borde.i ; this lamella is fibrous, and comes from the arterial zone. The half of the valve which is near the free border is not furnished with this intermediate lamella. Now the arterial lamella may be affected independently of the ventricular, and both Ijie arterial and ventricular lamellis may be injured independently of the intermediate fibrous lamella which constitutes the foundation of these valves, since it gives them chiefly their power of re- sistance. THE HEART. 489 oater membrane, and then the different muscular layers one by one, taking care to fol- low the fibres from their origin to their termination. The most general formula which can be given respecting the structure of the ventri- cles is, that this portion of the heart is composed of two muscular sacs, co7itained within a third, which is commjon to both ventricles. We should add, that, when the superficial or common fibres arrive at the apex of the heart, they turn up so as to pass into the interi- or of the ventricles at that point, and form the deep fibres of these two cavities, so that the proper fibres of each ventricle are situated between the direct and the reflected por- tion of the common fibres. We shall now enter into some details regarding these fibres. All the muscular fibres arise from the fibrous zones, and they all terminate upon them, as was clearly pointed out by Lower.* They do not consist of short fibres placed end to end, but are of considerable length, descending in one part of their course, and as- cending in the other. The muscular fibres are ranged in successive layers, which pass, as it were, into each other. The muscular fasciculi of each layer are not distinct from one another, but they mutually send off fibres, by which they are bound together like the pillars of the diaphragm ; or it may be said that they intersect each other at very acute angles ; it is, therefore, impossible to calculate the number of layers, which, according to Wolff, are about three in the right ventricle and six in the left. All that we are able to determine is, the different sets of fibres which enter into the formation of the heart, and of these we find that there are two sets, one common, the other _pro^er fibres. The Superficial Common Fibres. — All the superficial fibres are common to the two ven- tncles, and all are oblique and curved ; they commence at the base of the heart, and pass obliquely, in a spiral manner, towards the apex. All the superficial fibres of the an- terior region of the heart pass from the right to the left side ; all those of the posterior region from the left to the right side. There are neither vertical nor horizontal fibres in the heart, as some authors have stated. The arrangement of the fibres at the apex of the heart forms, as it were, a key to the stnicture of the entire organ. The anterior and the posterior superficial common fibres both converge towards that point. Each of these sets of fibres forms a very distinct fasciculus or band, and the two bands mutually turn round each other in a semi-spiral direction, so that the anterior band is embraced on the left side by the posterior, which is, in its turn, embraced by the anterior band on the right side ; from the apex of the heart the fibres change their course, and instead of descending, they ascend ; and instead of being superficial, they become deep-seated. Having entered the heart at its apex, they continue to be reflected upward, and present an arrangement which I shall describe after having explained the course of the proper fibres. The Proper Fibres. — ^These are situated between the superficial or descending, and the deep or ascending portion of the common fibres. They form in each ventricle a sort of small barrel or truncated cone, which is applied to that of the opposite ventricle ; the su- perior openings of these cones correspond to the auriculo- ventricular orifices ; while the inferior, which are smaller, leave opposite the apex of the heart two considerable inter- vals, which are filled up by the common fibres. Do these proper fibres turn round and round without end, hke an uninterrupted spiral, as Senac was inclined to believe 1 It appears to me that their extremities are attached to the auriculo-ventricular zones, and that they describe more or less complete circles, which intersect each other at very acute angles. The Reflected or Deep Common Fibres. — The superficial common fibres are reflected at the apex of the heart, and penetrate into its interior through the lower orifices of the small barrels or cones, formed by the proper fibres. In this situation the anterior and posterior bands, by being reflected upward, and mutually turned round each other, form, at the apex of the heart, a sort of star with curved rays. Nothing can be more evident than the reflection or turning up of the fibres ; it was pointed out, thougn vaguely, by Vesalius, but has been most explicitly described by Ste- no, who stated expressly that the external fibres enter the heart at the apex, and, assu- ming an opposite direction to their former one, become the innermost layers, and who compared the apex of the heart to a star. It was also described by Lower, who has ac- curately figured a radiated structure at the summit of each ventricle ; by Winslow, who says that the superficial fibres enter the heart at its apex ; and by Wolff and Gerdy, who state that the fibres of the heart are twisted into a whorl or vortex. From the turning back and the lateral twisting of the anterior and posterior bands, it follows that, by removing the serous membrane which covers the apex of the heart, we may, without injuring the fibres, penetrate into its interior at two points, one to the right, and the other to the left of the anterior band. The deep reflected fibres having thus reached the interior of the ventricles, pass on the inner side of the proper fibres, and are arranged in three perfectly different modes : thus, some form simple loops with the superficial portion ; others are arranged like the thread of a screw, or the figure 8. and others constitute the columnae carneae. * The same arTangement occurs in regard to the fibres of the auricles ; it follows, therefore, that the nxii» cular fibres of the ventricles are not directly continuous with those of the auricles. Qqq 490 ANGEIOLOGY. The looped fibres, noticed by Winslow under the name of the bent or arched fibres, and so well described by Gerdy, form, by their superficial and their deep portions, the opposite walls of the ventricle : thus, the anterior superficial fibres constitute by their reflection the deep layer of the posterior wall, while the posterior superficial fibres, after being re- flected, form the deep layer of the anterior waU. The fibres, arranged like the thread of a screw, or like the figure 8, with its lower ring ex- tremely narrow, have been accurately described and even figured by Lower, and were improperly rejected by Winslow, Senac, and others. The superficial portion of these fibres exactly resembles that of the looped fibres, and are always twisted after their re- flection, so that their deep portion belongs to the same wall as their superficial. Thus, those fibres whose superficial portion belongs to the anterior wall of the ventricle, assist in forming the same wall by their deep portion. The columnce, carnea of the heart are formed by a certain number of fibres reflected in loops, or like the figure 8. Such is the arrangement of the muscular fibres of the ventricles.* The Muscular Fibres of the Auricles. The auricles, like the ventricles, have common and proper muscular fibres. There is only one fasciculus of common fibres ; it occupies the anterior surface of both auricles, and extends transversely from the right to the left auricula. The proper fibres constitute a very thia muscular layer for each auricle ; they all commence and terminate at the cor- responding ventricular zone. The Proper Fibres of the Left Auricle. — The muscular layer in this auricle is continuous and uniform, and not areolar. It consists of circular fibres, which occupy the neighbour- hood of the auriculo- ventricular orifice, and all the anterior region of the auricle ; and of oblique fibres, also arising from the auriculo-ventricular orifice, and divided into several very distinct loops. One circular loop passes between the auricula and the left pulmo- nary veins ; a second forms a vertical zone, interposed between the right and left pulmo- nary veins ; it is very broad, and occupies the entire interval between the veins of the right and left side ; a third and a fourth, very small, are interposed between the two pul- monary veins of each side. These fasciculi, by changes in their direction, become adapt- ed to the circular form of the orifices, and constitute true sphincters. It would appear that, besides these bundles, there are some proper circular fibres around each orifice. The Proper Fibres of the Right Auricle. — In the right auricle the fleshy fibres do not form a continuous layer. This auricle may be regarded as consisting, in the first place, of a non-muscular portion, which may be called the confluence of the vence cavce {sinus ve- nosus) ; in it there is only one small muscular bundle, situated immediately to the right of the orifice of the vena cava superior ; and, secondly, of a muscular portion, which re- sembles a sort of grating, and is comprised between two fasciculi, one a circular bun- dle, surrounding the auriculo-ventricular orifice ; the other a very prominent semilunar bundle, interposed between the vena cava inferior and the auricula, and forming a ver- tical, or, rather, an oblique arch, which terminates to the right of the inferior cava. Muscular Fibres of the Auricula. — The walls of the left auricula present a cavernous or areolar structure, in the middle of which we see a central canal, which opens into the anterior of the auricle by a distinct orifice. There is not, in general, any central canal in the right auricula, but only an areolar or cavernous structure. The muscular fibres of the inter-auricular septum form a muscular ring for the border of the fossa ovalis (so incorrectly termed the isthmus or annulus of Vieussens), which must be regarded as a true sphincter, consisting of two thirds, three fourths, or even an entire circle. The fibres of which it is formed arise from the auriculo-ventricular ori- fice, near the septum. Some muscular fibres are often found in the substance of the floor of the fossa ovalis. The other muscular fibres of the septum are continuous with the circular fibres of the auricles. Separation of the Two Hearts. Dissection. — Divide the anterior fibres of the ventricles carefully, layer by layer, paral- lel to the anterior furrow. Then separate the two ventricles, by means of the finger or the handle of the scalpel. In order to separate the auricles, carry the scalpel along the posterior inter-auricular furrow, being particularly careful upon arriving at the fossa ova- lis. It is often possible to separate the auricles completely without opening either of them. The division of the heart into the right and the left heart is not merely imaginary or theoretical, but is capable of actual demonstration. After making the beautiful prepara- tion described above, we find that the left convex ventricle is received into a correspond- ing concavity in the right ventricle ; the two are therefore adapted to each other, and * The arrangement described above is common to both ventricles. In the ri^ht ventricle almost all the re- flected fibres enter into the columnve cameae. There is no interlacing, or indigitation of the fleshy fibres along the anterior and posterior furrows, as has been stated ; still less do we find a raph6 in the situation of these furrows. The splitting and separation of the muscular fibres, caused by the entrance of the bloodvessels oppo- site the furrows, and the condensation of the fibres between the openings for the vessels, have occasioned thes« •rroneous views. THE HEART. 4#1 their mutual reception is rendered complete by means of the infiindibuliform prolonga- tion of the right ventricle. On the other hand, the right auricle is convex, and is received into a corresponding concavity in the left auricle. By placing the two halves of the heart together, we see clearly the position of the aor- tic opening behind and to the right side of the pulmonary, the crossing of the aorta and the pulmonary artery in the form of the letter X ; the relation of the aorta with the base of the right ventricle, and its situation between the right auriculo-ventricular orifice, which is behind, and the infundibuliform prolongation of the right ventricle, which is in front of it. This last relation explains how a communication may take place between the aorta and the right ventricle. The separation of the two sides of the heart also enables us to judge accurately of the shape and the relative size of the two ventricles, the regular conical form of the left ventricle, and the prismatic and triangular form of the right ventricle, the left wall of which is, as it were, pushed inward by the corresponding projection of the left ventricle. We can also ascertain the shape and relative size of the two auricles. Vessels, JVerves, and Cellular Tissue. Arteries. — The heart receives certain proper arteries, called cardiac or coronary, from their being arranged in the form of a circle or crown. They are two in number, and are the first branches given off by the aorta. They form two arterial circles placed at right angles to each other ; that is to say, one circle follows the auriculo-ventricular furrow, and the other occupies the inter- ventricular furrow. Veins. — Corresponding to these two arteries there is one vein, named the great car- diac or coronary vein, and a few small ones, called the anterior coronary veins. I do not think that the existence of those accessory veins described by Thebesius as terminating directly in the right auricle and the other cavities of the heart has been clearly demon- strated. I have already said that the common openings of several groups of areolae have been often mistaken for the orifices of veins. There is always an opening resembling the orifice of a vein below the vena cava superior, but injection does not show any ves- sel there. Lymphatics. — These terminate in the numerous lymphatic glands which surround the bronchi and the lower part of the trachea. Nerves. — The cardiac nerves are small when compared with the nerves received by other muscular organs, with those of the tongue, for example, and especially with those of the muscles of the orbit. Some are derived from the cervical ganglia of the sympa- thetic nerves, the others from the cerebro-spinal system, viz., the cardiac branches of the pneumogastric. These nerves, which are placed near the arteries, follow them at first, but soon sep- arate from them, and are lost in the muscular substance. We cannot, therefore, admit the opinion of Behrends, who attempted to prove that the nerves are intended only for the vessels of the heart, and not for its proper tissue. Cellular Tissue. — The serous cellular tissue which unites the muscular fasciculi of the heart is so delicate, that it is extremely difficult to demonstrate it. In certain cases of disease it may become loaded with fat. • We always find a greater or less amount of fat upon the surface of the heart beneath the serous membrane ; it abounds in the circular furrow between the auricles and ven- tricles, in the furrow of the ventricles, at the apex and right border of the heart, in the furrow between the pulmonary artery and the aorta, and between the small digital ap- pendages upon the top of the left auricle. ' Development. In Size. — The heart is larger in proportion to the rest of the body in the earlier stages of its development. In the foetus, at the full term and after birth, the weight of the heart is to that of the body as 1 to 120 ; before the end of the third month of intra-uterine life it is as 1 to 50. It should be renoembered that, at the fourth or fifth week, the heart of the foetus occu- pies the entire cavity of the thorax. In old age, the heart does not undergo atrophy like most of the other organs ; and, in many subjects far advanced in years, it is even hyper- trophied. In Direction. — During the first three months the heart of the foetus is directed verti- cally, as in other mammalia ; it does not begin to deviate to the left side and forward, as in the adult, until the fourth month. In Shape.* — The heart, at an early period, forms a rounded and symmetrical mass, of which the auricles constitute the greatest part ; the ventricles appear at this time to be only appendages of the heart, and the right auricle alone is equal in size to all the rest of the organ. The ventricles are gradually enlarged, while the auricles diminish, and towards the fifth month the due proportion between the auricles and ventricles is estab- ■ "^ ^ * See note, p. 492. 4^ ANGEIOLOGY. lished ; the left ventricle is, at this period, more capacious than the right. The walls of the heart are thicker than they are afterward, and the heart is firmer, and does not col- lapse when empty. The thickness of the parietes of both ventricles is almost the same. In Interned Conformation. — It is in reference to its internal structure that the principal changes occur during the development of the heart. The right and left sides of the heart communicate freely during the whole period of intra-uterine existence. The in- ter-auricular septum does not exist, or, at least, only in a rudimentary state, during the earlier months of foetal life. Is there any period of fcetal existence during which the inter- ventricular septum is entirely wanting 1 and does the development of the human heart, which would then re- semble the heart of reptiles, coincide with the general law by which the organs of man, before acquiring their perfect form, pass successively through the several conditions rep- resented by the corresponding organs in the lower animals'! The observations of Meck- el, which extend as far back as the fourth week, prove that the inter-ventricular septum always exists at that period, but that it is imperfect at the upper part, where it is perfo rated or notched.* Cases of malformation, in which the septum of the ventricles is absent, cannot be quo ted in support of the opinion that the septum is wanting in the early periods of life ; foi it would be necessary to prove that such a malformation is an arrest of development. The opening between the two auricles becomes contracted, and forms the foramen ovale (or foramen ofBotal), which is found at the posterior and inferior part of the septum. The valve of Eustachius is sufficiently broad to separate the orifice of the vena cava inferior from the cavity of the right auricle, so that the blood of that vein is carried di- rectly into the left auricle. Towards the end of the third month, the valve of the foramen ovale, which afterward forms the bottom of the fossa ovalis, begins to appear ; it arises from the posterior half of the opening of the vena cava inferior. About the same period the Eustachian valve decreases in size, and from this time the development of these two valves proceeds in- versely, that is to say, the Eustachian valve diminishes, while that of the foramen ovale becomes larger. In consequence of this change, the vena cava inferior no longer opens into the left auricle, but into the right. At the fifth month the foramen ovale is almost entirely closed by the valve which grows from below upward, and from behind forward ; at a later period it projects into the left auricle, beyond the margin of the foramen ovale, so that there is an oblique pas- sage from one auricle to the other. After birth, adhesion takes place between these parts ; but even when this does not occur, the obliquity of the passage is such, that the want of adhesion does not necessarily allow of any admixture of the blood of the two auricles. Function. The heart is the agent by which the blood is impelled tlirough the vessels. The ve- nous blood is poured into the auricles, which then contract ; part of the blood flows back into the veins, but the greater portion passes into the ventricles, which contract in their turn. The auriculo- ventricular valves meet, and prevent the reflux of the blood into the auricles, and it is, therefore, propelled intg the arteries. The sigmoid valves at first lie in contact with the walls of the arteries, so as to permit the blood to pass from the ven- tricles ; they then fall down at the moment when the distended arteries react upon their contents, and thus prevent the reflux of the blood into the ventricles. The contraction and dilatation of the heart have been termed its systole and its diastole. The two auricles contract simultaneously ; so also do the two ventricles. The dila- tation of the auricles occurs during the contraction of the ventricles, and vice versa. Dilatation is not an active phenomenon, for the fibres of the heart are so arranged that they can produce shortening and contraction of this organ, but can neither elongate nor dilate it. The spiral direction of the fibres of the heart induced the ancients to conjecture that the contractions of the ventricles took place in a spiral fashion ; and, in the first edition of this work, looking only at the anatomical arrangement, I said that this view of the subject was not so devoid of foundation as at first sight it might be imagined. But, * [The researches of modern emhryologists have shown that the heart, in its simplest condition, consists of a straight tube, which is placed vertically in the body, receives the veins at its inferior extremity, and gives off the arteries from its superior extremity. The lower or venous end soon turns upward, so that the tube be- comes bent into a loop, which for a time projects through a cleft on the anterior aspect of the body. The tube then becomes divided into an auricular and a ventricular portion, and into a bulbus arteriosus, all enclosed in a pericardium; and in this state the heart of the human ftstus corresponds with the permanent condition of this organ in fishes. Each of these three portions becomes again subdivided : the auricular portion by a de- scending septum into the two auricles, the ventricular by an ascending septum into the two ventricles, and the bulbus arteriosus into the aorta and pulmonary artery. For a certain period, the right and left auricles and the right and left ventricles communicate with each other. When the septum between the ventricles ii yet imperfect (a condition which is permanent in reptiles generally), the common ventricular cavity gives ori- gin to both the aorta and the pulmonary artery. Before the middle of fcetal life this septum is completed, and then the two vessels arise each separately from its proper ventricle. The septum between the auricles re- mains imperfect until after birth, when the foramen ovale at length becomes closed.] THE HEART. from the opportunities I have lately had of observing the movements of the heart in a new-born child, full of life and vigour, whose heart, deprived of the pericardium, had passed entirely outside of the chest, through a circular perforation in the upper part of the sternum, I have been enabled to establish the following facts in reference to this in- teresting subject (see Gazette de Paris, August 7th, 1841) : First, the contraction of the right ventricle and the contraction of the left ventricle are simultaneous, or synchronous ; this is also the case with the contraction of the au- ricles. Second, the contraction of the ventricles coincides with the dilatation of the auricles and the projection of the blood into the arteries. The dilatation of the ventricles coin- cides with the contraction of the auricles and that of the arteries. Third, there are but two conditions in the movements of the heart : those of its con- tractions and those of its dilatations ; the state of rest which is spoken of by authors is completely wanting. Dilatation is immediately followed by contraction, and contraction by dilatation. Fourth, in observing the heart in the case referred to, the question about the order of succession in the movements of the heart, viz., whether the contraction of the auricles precedes that of the ventricles, as most observers assert, or whether the contraction of the ventricles precedes that of the auricles, is found to have no foundation to rest on : it seems that the contraction and the dilatation of the ventricles and that of the auricles result from two opposite forces, continually active, which alternately, and, as it were, necessarily conquer each other in an invariable order, in the fashion of the two alternate movements of a pendulum, or a perfectly-balanced balance-pole. Fifth, the duration of the contraction of the ventricles continues twice as long as that of their dilatation. On dividing into three equal periods the whole duration of the sys- tole and diastole of the ventricles, we will have two for the contraction and one for the dilatation. The period of repose mentioned by authors has been taken from the first period of the contraction. In regard to the auricles, on dividing into three equal parts the whole duration of their contraction and dilatation, we wiU have two for dilatation and one for contraction. Sixth, during the time of their contraction or systole, the ventricles grow pale, their surface becomes rugged, strongly folded, and, as it were, shrivelled. The superficial veins swell ; the columnse carneae of the ventricles are marked off; the twisted fibres of the summit of the left ventricle, which of itself constitutes the apex of the heart, be- come more manifest. Seventh, during their contraction the ventricles contract in all their diameters ; and if the phenomenon of their shortening is the most sensible, this is attributable to the greater dimension of the vertical diameter. During the systole of the ventricles, the summit of the left ventricle, or, what is the same, the summit of the heart, describes a spiral movement from right to left and from behind forward. Eighth, it is this spiral contraction, which is slow, gradual, and successive, as it were, which produces the movement forward of the summit of the heart, and, conse- quently, the striking of the apex against the walls of the thorax. The systole of the ventricles is not accompanied, as I had before beheved, with a movement of projection of the heart forward : it is the spiral contraction which determines exclusively the ap- proximation to, and even the striking of the apex of the heart against the walls of the thorax. Ninth, the dilatation or diastole of the ventricles takes place in a sudden, instanta- neous manner : at first sight one would say that it constituted the active movement of the heart, it is so rapid and energetic. No one can have any idea, without having ex- perienced it, of the force with which the dilatation overcomes pressure made upon this organ. The hand which firmly grasps the heart is forcibly opened by its diastole. Tenth, the dilatation or diastole of the ventricles is accompanied with a movement of projection of the heart downward. This movement of projection was carried to its maximum when the child was placed in the vertical position ; it was so marked, that at first I was induced to believe that it was during the diastole of the ventricles that the percussion of the heart against the walls of the thorax took place. This idea I still en- tertained, rom an experiment which I had made at a former period upon the hearts of frogs ; but a more accurate examination of the phenomenon has shown me that it was, indeed, during the systole of the ventricles, and towards the end of this systole, that the percussion of the apex of the heart against the walls of the thorax took place. Eleventh, the dilatation of the auricles takes place as suddenly as the dilatation of the ventricles, but it lasts as long as the systole of the ventricles : the contraction of the auri- cles, on the contrary, lasts no longer than the diastole of the ventricles. Twelfth, during its dilatation, the right auricle seems on the point of bursting, so great is its distension and so thin are its walls. The left auricle, which is narrower, more elongated, and thicker, does not exhibit the same phenomenon, at least not in the same degree. I have not been able to judge of what takes place in the auricular pro- cesses except from the movements of the auricles. 494 ANGEIOLOGY. In regard to the sounds of the heart, it results, from the experiments which I have made upon the heart of this child {Medical Gazette, loco citato), that the two sounds of the heart have their seat at the origin of the pulmonary and aortic arteries, and that they originate in the clashing of the sigmoid valves ; that the first sound, which coin- cides with the systole of the ventricles and the dilatation of the arteries, results from the rising of the sigmoid valves, which were previously lowered ; that the second sound, which coincides with the diastole of the ventricles and with the contraction of the ar- teries, results from the lowering of the sigmoid valves pressed down again by the gush of the returning blood. The simplicity of this theory, the easy and natureil explanation which it affords of all the facts that have come to my knowledge, may, perhaps, be con- sidered as a proof of its truth. THE PERICARDIUM. The pericardium {pp,fig- 170) is a fibro-serous sac, which surrounds and protects the heart. Congenital absence of the pericardium is extremely rare ; complete adhesion of the pericardium to the heart, or cellular transformation of this membrane, have been most commonly mistaken for such malformation. Nevertheless, I have seen the heart of an adult to which there was no pericardium : this anomaly has been figured by M. Breschet. The heart was free from any adhesion, and occupied the cavity of the left pleura. The older anatomists, and particularly Senac, attempted to determine exactly how much larger the cavity of the pericardium is than the heart. Having injected water into the pericardium in different subjects, this observer found that the quantity of liquid con- tained between the heart and its covering varied from six to twenty-four ounces. I have satisfied myself that in the healthy state, the capacity of the pericardium exactly corre- sponds to the size of the heart when that organ is dilated to the utmost. In certain cases of hydrops pericardii, this sac becomes enormously enlarged ; on the other hand, its inextensibility explains the syncope which immediately follows rupture of the heart,* and which is produced by the accumulation of a small quantity of blood in the pericar- dium. The syncope which accompanies the effusion from acute pericarditis probably depends upon a similar cause. Form. — The pericardium is shaped like a cone, with its base downward and its apex upward. It has an external and an internal surface. External Surface. — The pericardium is situated in the mediastinum, and has the fol- lowing relations : In front it corresponds to the sternum and the cartilages of the fifth, sixth, and seventh ribs on the left side, from which it is separated by the pleura and the lungs ; in the mid- dle it is separated from the sternum by some cellular tissue only. The pericardium is in more or less immediate relation with the sternum, according to the size of the heart, or the quantity of fluid in the pericardium. Behind, it corresponds to the vertebral col- umn, from which it is separated by the posterior mediastinum and the organs contained in it, viz., the oesophagus, the aorta, the thoracic duct, &c. On the sides, it is in imme- diate relation with the pleurae, and indirectly with the lungs. The phrenic nerves and the superior phrenic arteries are applied along the sides of the pericardium. The base corresponds to the cordiform tendon of the diaphragm, and to the muscular fibres on the left side of it. It adheres closely to the diaphragm only in the anterior half of its cir- cumference ; in every other part the base of the pericardium may be easily detached. The apex is prolonged upon the great vessels which enter and pass out at the base of the heart. The pericardium is covered by the pleurae in the greatest part of its extent, and is united to them by cellular tissue, which is tolerably dense at the sides, and very abun- dant in front and behind. The cellular tissue of the anterior mediastinum is often load- ed with fat, as well as that which surrounds the base of the pericardium, where it sometimes forms prolongations resembling the appendices epiploicas upon the large in- testine. The internal surface of the pericardiimi is free and lubricated by serosity, like the inner surface of allfserous cavities. t Structure. — The pericardium is a fibro-serous membrane analogous to the dura mater, and, like it, is composed of two very distinct layers, one externd and fibrous, the other internal and serous. The fibrous layer consists of fasciculi mterlacing in all directions. It is extremely thin, and from its adhesions to the cordiform tendon of the diaphragm, it has been re- garded as a prolongation of that structure, but it adheres closely to the diaphragm only * Death from rupture of the heart is not produced by hemorrhag'e, for often we do not find more than seven or eight ounces of blood escaped ; but it is caused by compression of the heart, in consequence of the inexten- sibility of the pericardium. t On opening the thorax of dead bodies, the internal surface of the pericardium is, as it were, dried up ; this drying up is owing to the air contained in the lungs. THE ARTERIES. 495 in front, and much less intimately in the foetus and the new-bom infant. In conse- quence of this adhesion, the pericardium follows all the motions of the diaphragm. The fibrous layer is prolonged upon the surface of the great vessels which open into the cavities of the heart, and furnishes for each of them an indistinct sheath, which is soon lost upon them. The scratis layer of the pericardium, like the serous membranes generally, forms a shut sac, adherent by its outer surface, but free and smooth internally.* After having lined the fibrous layer, it is reflected upon the great vessels at the base of the heart, and then covers the heart itself, of which it forms the external membrane. We shall consider it as consisting of a parietal, and a visceral or reflected portion. The Parietal Portion. — The fibrous and the serous layer of the pericardium are so closely adherent, that it is very difficult to separate them. We shall find the same to be the case with the dura mater. The Reflected w Visceral Portion. — The existence of this portion of the serous mem- brane can be shown most readily at the points where it is reflected from the fibrous mem- brane upon the great vessels. It forms one complete sheath, which is coirunon to the aorta and pulmonary artery ; some fat is often found in the furrow between these two vessels ; it also forms two semi-sheaths for the venae cavae and the four pulmonary veins, which are thereby rendered smooth only in the anterior half of their circumference. The heart is entirely covered by the serous membrane, which is here extremely thin. In fat hearts it is raised from the muscular fibres by some flakes of adipose tissue, like the ap- pendices epiploicae of the great intestine. Vessels and Nerves. — The arteries of the pericardium are very small ; they are derived from the surrounding arterial branches, viz., the superior phrenic, the anterior mediasti- nal, and the bronchial. The veins accompany the arteries, and open into the brachio- cephalic veins. Several of them are also said to terminate in the coronary veins. The lymphatic vessels enter the lymphatic glands, which surround the vena cava superior. No nerves have yet been demonstrated in the pericardium, though possibly they may exist. THE ARTERIES. Definition. — Nomenclature. — Origin. — Varieties. — Course. — Anastomoses. — Form and Re- lation. — Termination. — Structure. — Preparation. The term arteriesf is applied to the vessels which arise from the ventricles of the heart, and to their several divisions. There are two systems of arteries, one of which commences at the right ventricle, while the other commences at the left. The primitive trunk of the first is the pulmona- ry artery, that of the second is the aorta. These two arterial systems are perfectly distinct in the adult, but communicate fi-eely, and form only one system in the foetus. The following general remarks apply more particularly to the aorta and its divisions : The arteries form an uninterrupted succession of decreasing canals, all arising from a common trunk. In this respect we may compare the entire arterial system to a tree, the trunk of which is the aorta, while the larger and smaller branches and the twigs are rep- re^sented by the divisions which arise in succession from that vessel, as from their com- mon origin. Again, since the total area or capacity of all the arterial divisions greatly exceeds that of the aorta, we may also regard the arterial system as a cone, the base of which is sit- uated in the entire body, and the apex at the aorta.t The study of the arteries includes that of their nomenclature, origin, course, direction, relations, anastomoses, termination, and structure. Nomenclature. The nomenclature of the arteries leaves little to be desired in regard to precision ; the names of these vessels are derived either from those of the parts to which they are dis- tributed, as the thyroid, lingual, and pharyngeal arteries, &c. ; or from their situation, as the femoral and radial arteries ; or from their direction, as the circumflex and coronary arteries. ' The limits by which one artery is distinguished from another immediately succeeding to it, may be either natural or artificial. We may regard as natural limits the point of origin on the one hand, the point of divis- ion on the other, as in the common iliac and conmion carotid arteries. * Its inner surface is covered with epithelium. t From anp, air, and Trjpclv, to keep. The etymology of this term affords us evidence of the error of the ancients, who, because they always found these vessels empty and patent after death, imagined that they con- tained air during life. X Haller has collected all the comparative estimates that have been made between the area of the priacipa] trunks and that of their respective divisions collectively. — {Elem. Phys., t. i., p. 151-163.) 406 ANGEIOLOGY. The object oi artificial limits is to enable us to establish certain divisions of the same arterial trunk, by which means we can describe its relations with greater accuracy. Thus we shall find successive portions of the artery of the upper extremity named the subclavian, the axillary, and the brachial artery. Origin of the Arteries. The common origin* of the arterial system is the aorta, which arises from the left ven- tricle of the heart in the manner already indicated (see The Heart) ;t but the origins of the other arteries take place according to certain very general laws : thus, two arteries of equal size may arise from the extremity of a larger artery, and appear to result from the bifurcation of that vessel ; arteries arising in this manner might be called terminal arteries. Other arteries arise from some point in the circumference of a larger vessel ; these may be termed collateral arteries. The terminal arteries almost always arise so as to form a bifurcation at an acute an- gle ; the dichotomous division or bifurcation is the most common mode of division. The acute angle is evidently favourable to the passage of the blood, which, in the first place, maintains nearly the primitive direction in which it was impelled, and, secondly, is easi- ly divided into two columns by the projecting crest at the angle of division. The collateral arteries very often arise at an acute angle, but sometimes at a right, or even at an obtuse angle. The two latter modes, especially the last, are unfavourable to the flow of the blood. It must, however, be remarked, that many of the arteries which follow a retrograde course in reference to the trunk from which they are derived, never- theless arise at an acute angle. The caliber of the terminal arteries is very nearly pro- portional to that of the artery from which they are given oft", but the collateral arteries bear no proportion to the caliber of their trunks. We shall see a remarkable example of this in the spermatic arteries, as compared with the aorta from which they arise. It should also be observed, that the caliber of a principal trunk does not diminish in proportion to the branches which it supplies : in proof of this, observe the aorta as it en- ters the abdomen, and just before its division into the common iliac. Anatomical Varieties of the Arteries. No system of organs is more subject to anatomical varieties than the arteries. These varieties sometimes affect their origin only, sometimes their course, but hardly ever their termination.^ The study of these varieties is of great importance in surgery, both in reference to the ligature of arteries, and also to operations performed in their vicinity.^ Course of the Arteries. The principal arteries generally follow the direction of the axis of the limbs. The sec- ondary, tertiary, and farther divisions pursue the most varied courses, subject to no par- ticular rule. The principal arteries are usually straight ; but they present slight curves, which ren- der the artery longer than the corresponding limb, and hence tend to prevent laceration during the movement of extension, when the curves merely become obliterated and the vessel undergoes no injurious stretching. The use of these curves in the arteries may be proved by comparing the opposite conditions of the vessels during extension and flex- ion of the upper and lower extremities. A great number of the arteries pursue a very distinctly tortuous course, which, as Haller remarks, is preserved by the surrounding cellular tissue, and which is connected with certain particular conditions of the organs to which they are distributed. Thus, we meet with very tortuous arteries in parts which are alternately subject to considera- ble dilatation and contraction ; as, for example, the coronary arteries of the heart and of the lips. Again, the serpentine course of an artery, by increasing its length in a given space, adds to the extent of surface from which collateral branches may arise. The curvatures of the internal maxillary and of the ophthalmic arteries evidently have this advantage ; and it is highly probable that the arch of the aorta may serve a similar purpose. The arteries are tortuous in certain parts also, in which this arrangement would seem to diminish the force and rapidity of the current of blood ; it cannot fail to be perceived * The word origin must not be taken here in its exactly literal sense, for it has by no means been shown that the arteries are developed from the heart towards the extremities. A very ingenious theory tends, on the con- trary, to prove that development proceeds from the extremities towards the heart. t I should add that the proper tissue of the aorta only touches the fibrous arterial zone opposite the angle, or at the summit of the three festoons which the origin of the aorta exhibits. The arterial zone may be con- sidered as the tangent of the three festoons. t While the origin of the nerves exercises a great influence on their functions, the place from whence the arteries originate appears to be of but little consequence, and is, at all events, very secondary. We cannot agree in the opinion of Walther, that the origin of the arteries of an organ are intimately connected with the mode of its existence, and with the functions which it performs. ^ [For special information on the varieties in the distribution of the arteries, the reader is referred to Hal- ler, Icones Anatomicce, 1756; Murray, Descriptio Arteriarum, &c., 1783-98; Barclay, Description of the Ar- teries, a Fig. 208. deep fossa seen on the base of the brain at the inner end of the fissure of Sylvius, and immediately divides into three branches, which spread out from each other. Of these three branches, the anterior is called the anterior cerebral, or artery of the corpus callosum ; the external is named the middle cerebral, or artery of the fissure of Sylvius ; and the third, or posterior, is the posterior communicating artery. Not unfrequently the carotid gives origin to the pos- terior cerebral artery, from which, in that case, the posterior communicating artery is then given off, and immediately joins the anterior extremity of the basi- |^/ lar artery. The Anterior Cerebral Artery. Dissection. — The study of these arteries requires no preparation ; it is sufficient to overturn the brain in a manner which will bring its base into view. Each artery will be recognised by the following description : This vessel {d d, fig. 208), also called the artery of the corpus cal- losum, passes, immediately after its origin, forward and inward, towards the median line, and thus reaches the longitudinal fissure between the right and left anterior lobes of the brain. There it approaches its fellow of the op- posite side, and communicates with it by a transverse branch, which passes at right an- gles between them. This anastomotic branch (a), so remarkable for its size, shortness. and direction, is called the anterior communicating artery ; instead of one, there are some- times two smaller branches ; sometimes it is so short that the two anterior cerebral ar- teries may be said to be applied to each other, and blended together at this point : most commonly it is from one to two lines in length, and it then gives off some small twigs. which penetrate into the third ventricle. ^Lfter communicating in this manner, the anterior cerebral arteries become parallel, run from behind forward, turn upward in front of the anterior extremity of the corpus callosum, and then run backward upon its upper surface, as far as its posterior extremity, describing a curve, which exactly corresponds with that of the corpus callosum itself Before turning over the anterior border of the corpus callosum, the anterior cere bral arteries give off some ramuscuh to the optic and olfactory nerves, to the third ven- tricle, and the adjacent part of the anterior lobe of the brain,"and also a series of large branches, which are distributed to the inferior surface of the samr lobe. At the poin* X X X 530 ANGEIOLOGY. where the arteries are reflected, and also along the upper surface of the corpus callosum, large branches arise from the convexity of the curve described by these vessels, and ramify upon the inner surface of the two hemispheres : the anterior branches run from behind forward, and the others from before backward, and from below upward ; most of them reach the convex surface of the brain. Some capillary twigs proceed from the con- cavity of the curve, and penetrate the substance of the corpus callosum. We may regard as the termination of each anterior cerebral artery a very small branch which continues in the same course, reaches the posterior extremity of the corpus callo- sum, is there reflected downward, and terminates in the adjacent convolutions of the brain. The Middle Cerebral Artery. — This is larger than the preceding vessel ; it passes (/, Jig. 208) outward and backward to enter the hssure of Sylvius, having previously given off a great number of rather large branches, which run perpendicularly upward into the very thin layer of cerebral substance situated at the junction of the longitudinal fissure of the brain with the fissure of Sylvius.* As soon as the middle cerebral artery has entered the fissure of Sylvius, it divides into three branches : an anterior, which is applied to the anterior lobe ; a posterior, which lies upon the middle lobe ; and a median branch, which corresponds to the small lobe that is concealed within the fissure : they all follow the direction of this fissure, and are concealed within it, but soon emerge so as to ramify upon the convolutions and anfrac- tuosities of the brain, anastomosing with each other, and with the branches of the ante- rior and posterior cerebral arteries. It is of importance to remark, and this observation applies to all the cerebral arteries, that the arterial ramifications destined for the surface of the brain are extremely tortuous, that they dip into the anfractuosities, and cover the free borders and the two surfaces of the convolutions, between which they are situated ; that they ramify very freely, and run a very extensive course ; and that they do not divide gradually into smaller and smaller branches, but that bundles of very fine capillary vessels arise from every part of the cir- cumference of vessels of a certain size, and immediately penetrate the cerebral substance. The Posterior Communicating Artery, or Communicating Artery of Willis. — This artery varies exceedingly in size, being generally small, but sometimes forming the largest di- vision of the internal carotid. It arises from the back of the carotid, runs from before backward (?), and terminates in the posterior cerebral branch of the basilar artery. In certain cases, the communicating artery of Willis may be regarded as the chief origin of the posterior cerebral, which then seems to result from the union of this communica- ting artery with the anterior bifurcation of the basilar. The Choroid Artery. — A very small but constant branch (s) arises from the back of the internal carotid, on the outer side of the communicating artery of Willis. This is the artery of the choroid plexus, which passes backward and outward, along the optic tract, and, consequently, along the eras cerebri, to both of which it sends branches, and then en- ters the lateral ventricle at the anterior extremity of the great transverse fissure of the brain, gives twigs to the hippocampus major and corpus fimbriatum, and terminates in the choroid plexus, t Summary of the Distribution of the Common Carotid Arteries. The common carotids are distributed to the head, and to the organs which occupy the front of the neck. The internal carotid belongs exclusively to the brain, and to the organs of vision ; and hence, doubtless, at least in part, arises that intimate relation between the condition of the brain and of the eye, which is expressed by the common saying, that the eye is the mirror of the soul. Although the size of the internal carotid is almost always in proportion to that of the brain, yet this artery is not the only one by which that organ is supplied with blood. The vertebral artery, a large branch of the subclavian, completes the arterial system of the brain ; and the fact of an artery, principally destined for the upper extremity, also send- ing a branch to the brain, proves that there is nothing peculiar in the quality of the blood transmitted to the encephalon. We have already seen that the ophthalmic artery communicates by its nasal branch with the facial artery, and by its inferior palpebral branch with the infra-orbital branch of the internal maxilleury. But the internal carotid has no direct communication with the external, unless when it gives origin to the ascending pharyngeal and the occipital arter- ies. I may remark, however, that some meningeal branches are given off by the inter- nal carotid within the cavernous sinus. The external carotid differs from the internal, in giving origin to a very great number of branches, which are distributed to the face, to the parietes of the cranium, to the or- gans of respiration, and, lastly, to the organs of digestion. The facial branches may be divided into the superficial and the deep-seated. * We shall see hereafter that this region of the brain belongs to the corpus striatum. .- ^ f See vertebral artery (p. 533), for the completion of the arterial system of the enceohalon. ARTERY OF THE UPPER EXTREEITY. 531 The superficial arteries of the face are derived from many sources. The principal one is furnished by the facial or external maxillary ; the others are the transverse artery, or transverse arteries of the face, coming from the temporal ; the nasal, a descending branch of the ophthalmic ; the buccal, masseteric, infra-orbital, and mental— all derived from the internal maxillary. The arteries of the right side communicate very freely and fully with those of the left ; and on each side, branches from the different sources communi cate as freely with each other ; so that, in hemorrhage from any of them, the injured vessel must be tied on both sides of the wound. I may call attention to the abundance of arterial vessels in the face, and to the number and size of the muscular and cutaneous branches ; this is evidently connected with the extreme susceptibility of the skin of tliis region, the existence of the hair-bulbs, and the action of the muscles in giving expression to the features. The deep arteries of the face are principally derived from the internal maxillary. Thus, the spheno-palatine supplies the nasal fossae : some branches of the infra-orbital enter the orbit. We shall afterward allude to the branches which are furnished to the buccal cavity and the zygomatic and spheno-maxillary fossae. Lastly, the superficial and deep arteries of the face are united by numerous anastomoses. The first set of cranial branches, derived from the external carotid, are the arteries of the hairy scalp, viz., the occipital, temporal, posterior auricular, supra-orbital, and frontal. With regard to these arteries, it is important to notice their large size, which is connect- ed with the great vitality of the skin of the head, and with the existence of the bulbs of the hair ; also, that they are extremely tortuous, which appears to me to be in corre- spondence with the great number of branches which they give off; and, lastly, that they are situated in the dense cellular tissue which connects the skin with the muscles and the epicranial aponeurosis. Besides these, small branches are found upon the pericranium, under the muscles and epicranial aponeurosis : they are seen on the forehead, where they arise from the fron- tal and infra-orbital arteries, and also in the temporal region, where they axe C2illed the deep temporals ; these branches are both periosteal and muscidar. The second set of branches to the cranial parietes are arteries of the interior of the cra- nium, viz., the meningeal, the chief of which is the middle meningeal, a branch of the in- ternal maxillary : the others, or small meningeals, enter through most of the foramina at the base of the cranium. Among these latter we would mention the meningeal branches of the ascending pharyngeal artery, and meningeal branches from the ethmoidal arteries, to which may be added some small twigs given off from the internal carotid, while enclosed in the cavernous sinus. We may also refer the arteries of the organ of hearing to those of the cranial pirietes. They are the posterior auricular and the anterior auricular, which are distributed to the pinna and to the external meatus ; the tympanic, which passes through the fissure of Glasserus, and a small branch of the middle meningeal, which enters through the hiatus Fallopii. The branches of the external carotid distributed to the orguns of digestion belong to the following parts : To the organs of mastication, viz., the alveolar, the infra-orbital, and the inferior den- tal arteries, which go to the teeth and the jaws ; the superior palatine, which supplies the roof of the palate ; and, lastly, the deep temporal, the masseteric, and the pterygoid, which are distributed to the muscles of mastication. To the salivary organs : thus, the parotid receives its branches from the external carotid and the temporal ; the sub-max- illary gland from the facial ; and the sub-lingual gland from the sub-lingual branch of the lingual artery. To the velum pdati and the tonsils we find the ascending or inferior palatine branch of the facial artery, the superior palatine branch of the internal maxillary, and the ascending pharyngeal. To the pharynx, the pharyngeal twigs from the superior thyroid, the ascending pharyngeal, the pterygo-palatine or superior pharyngeal, and the vidian from the internal maxillary, and the inferior palatine branch of the facial. To the oesophagus there are the descending oesophageal branches of the superior thjToid. The branches given by the external carotid to the air-passages are the superior and infe- rior laryngeal, from the superior thyroid artery, which is essentially distributed to the thyroid gland. Aeteet of the Uppee Extremity. A aiagle arterial trunk, called the brachial trunk ( Chaussier), is destmed for the upper extremity. On the left side it arises directly from the arch of the aorta, and on the right side from the innominate artery ; it emerges from the thorax, between the first rib and the clavicle, traverses the axilla, runs along the inner side of the arm, passes in front of the elbow-joint, and divides into two branches, which supply the forearm and the hand. As the brachial trunk has some highly important relations during its course, and, moreover, furnishes a very great number of branches, it has been artificially divided, in order to facilitate its study : each of the divisions has received a particular name, ac- cording to the region through which it passes : thus, the arterv of the upper extremity 532 ANGEIOLOGY. is called successively the sub-clavian, the axillary, and the hwneral artery , and its termi- nal divisions are named the radial and ulnar arteries. The Brachio-cephalic Artery. The brachio-cephalic or innominate artery {arteria anonyma of many authors, e,fig. 198) is the common trunk of the right sub-clavian and right common carotid arteries, and has in turns been regarded as a portion of the carotid, and as a part of the sub-clavian. It arises from the aorta, at the point where that vessel changes its direction from vertical to horizontal. It is situated in front and to the right of the other arteries given off from the arch of the aorta. It is from one inch to fifteen lines in length. It is directed ob- liquely upward and outward. Relations- — In front of the mnommate artery is the sternum, beyond the upper end of which the artery almost always projects, and from which it is separated by the left brachio-cephalic vein, by the remains of the thymus, and by the sternal attachments of the stemo-hyoid and sterno-thyroid muscles. Behind, it is in relation with the trachea, which it crosses obliquely ; on the outer side, with the pleura and mediastinum, which separate it from the lungs ; on its inner side is the left common carotid, from which it is separated by a triangular interval, in which the trachea is seen. From a knowledge of these relations, modem surgeons have succeeded in applying a ligature to the innominate artery. Its relations, however, vary in different individuals. In some cases almost the whole length of the vessel projects beyond the sternum ; and it is then extremely accessible, either to accidental wounds, or to the surgeon in the ap plication of a ligature. It has been thought that the presence of the innominate artery explains the predominance of the right over the left upper extremity ; but this opinion is entirely unfounded. The arteria innominata gives off no collateral branch, except in those cases in which it affords origin to the thyroid artery of Neubauer, so named from the anatomist who called attention to this anatomical variety.* The same anatomist has seen the right in- ternal mammary artery arise from the brachio-cephahc trunk The Right and Left Sub-clavian Arteries. The right sub-clavian artery {g, fig. 198 ; f,fig. 204) arises from the innominate (c) ; the left sub-clavian {g"), from the arch of the aorta. Varieties of Origin. — One very common variety is that in which the right sub-clavian arises below the left, from the posterior and inferior part of the arch of the aorta, from which it passes upward and to the right side, generally behind the trachea and oesopha- gus, sometimes between the two, and rarely in front of the trachea, t The precise termination of this artery is not well defined. By some authors it is said to end, and the vessel to take the name of axillary artery as it passes between the sca- leni.t It appears to me more convenient to take the clavicle as indicating the respect- ive limits of the two vessels. All above the clavicle, then, belongs to the sub-clavian, and all below it to the axillary artery.^ From the difference, as to origin, between the right and left sub-clavians, they diffei from each other remarkably in length, direction, and relations. Differences in Length. — The right sub-clavian is shorter than the left by the length of the innominate artery ; and we should, moreover, bear in mind the slight difference in the height between the origin of the innominate and the left sub-clavian. The difference in the size of the two sub-clavian arteries requires no special notice. Differences in Direction. — The right sub-clavian passes at first obliquely outward and a little upward, and then bends over the apex of the lung, describing a curve with the con- cavity looking downward. The left sub-clavian passes vertically upward before curving over the apex of the lung, opposite which it changes its direction abruptly, and becomes horizontal. Differences in Relations. — In describing these, we shall divide the sub-clavian artery into three portions : the^rs^, extending from the origin of the artery to the scaleni mus- cles ; the second, situated between the scaleni ; and the third, extending from the scale- ni to the clavicle. The relations of the right and left sub-clavians differ from each other only in the first of these portions. The first portion {I, fig- 204) of the right sub-clavian is in relation in front with the inner end of the clavicle, the sterno-clavicular articulation, the platysma, and the clavicular attachment of the sterno-mastoid muscle, with the stemo-hyoid and sterno-thyroid mus- cles, with the termination of the internal jugular and vertebral veins in the sub-clavian * This inferior thyroidean artery arises, perhaps, more frequently from the arch of the aorta, between the brachio-cephalic trunk and the left primitive carotid. t [It rarely passes between the trachea and o;sophagTis ; and it appears there is no record of its having been actually seen in front of the trachea (see Quain on the Arteries).'^ X According to some authoi-s, the artery changes its name as it emerges from between the scaleni ; accord- ing to others, while it is yet between those muscles. ^ We are in the habit of dividing this artery into three portions : a cardiac, a middle, and an axillary por- lion. The first, that part between its origin and the scaleni ; the second, the portion embraced between tho Bcaloni ; and the third, the remaining part of the artery. — Ed. THE VERTEBRAL ARTERY. 533 Tein, and with the right pneumogastric and phrenic nerves ; behind, with the recurrent laryngeal nerve and the transverse process of the seventh cervical vertebra ; on the out- er side, with the mediastinal pleura, which separates it from the lung. On the inner side, it is separated from the conmion carotid by a triangular interval.* It is surround- ed by loose cellular tissue, a great number of lymphatic glands, and nervous loops formed by the great sympathetic. The first portion of the left sub-clavian is in relation with the same parts, though to a somewhat different extent : thus, its relations with the left mediastinal pleura and lung are much more extensive. The sub-clavian vein crosses it at right angles, instead of being parallel to it ; but the left pneumogastric and phrenic nerves run parallel to, in- stead of crossing it. It is parallel to the left common carotid, instead of forming an an- gle with it ; and, instead of being near the clavicle, the left sub-clavian is close to the vertebral column, and rests on the longus colli, the inferior cervical ganglion of the sym- pathetic nerve, and the thoracic duct, which is there to its inner side. The second portion of both the right and left sub-clavian arteries, situated between the scaleni, is in close relation below with the middle of the upper surface of the first rib, on which there is a corresponding depression behind the tubercle for the attachment of the anterior scalenus ; above, with the two scaleni, which are in contact with each other above the vessel ; behind, with the brachial plexus ; in front, with the scalenus anticus, which separates the subclavian artery from the sub-clavian vein. This separation of the artery from the vein is one of the most important points in its history. + The third portion of the sub-clavian, or that extending from the scaleni to the clavicle, corresponds to a triangular space, bounded in front by the stemo-mastoid and anterior scalenus, above by the omo-hyoid, and below by the clavicle : this space is named the lower or clavicular portion of the posterior triangle of the neck, which is bounded in front by the stemo-mastoid, behind by the trapezius, below by the clavicle. In front of, but somewhat lower than the artery, is the clavicle, that bone being separated from the ves- sel by the sub-clavian vein, which is here below and in contact with the artery, and by the sub-clavius muscle ; behind and to the outside of the artery is the brachial plexus of nerves, which surrounds the vessel in the axilla ; it is covered by the deep cervical fascia, the platysma, the superficial fascia, and the skin, and is crossed by the descend- ing cutaneous branches of the cervical plexus, and obliquely by the supra-scapular ar- tery and vein ; below, it rests upon the first rib. In consequence of these relations, the sub-clavian artery may be compressed, and the circulation of the upper extremity stopped by forcible depression of the clavicle ; the sub-clavian may be easily felt, compressed, and tied above the clavicle ; and, lastly, it follows that the sharp fragments of a broken clavicle can wound the coats of the artery only after having transfixed the sub-clavius muscle and the sub-clavian vein. This artery, moreover, presents individual varieties both in regard to its direction and relations ; it usually rises slightly above the clavicle, but in persons with short necks and high shoulders it is situated deeply under the clavicle, while in those who have long necks and low shoulders it may even slightly raise up the platysma and the skin. But the most important variety is that in which the relations of the sub-clavian with the sca- leni muscles are changed. It is not uncommont to see the sub-clavian artery situated in front of the scalenus anticus, forming immediate relations with the sub-clavian ▼ein.ij Collateral Branches. — The sub-clavian artery gives off certain collateral branches, which may be divided into the superior, inferior, and external. The superior are the rer- tebral and the inferior thyroid ; the inferior are the internal mammary and the superior in- tercostal ; the external are the supror scapular, the posterior scapular or transversalis colli, and the deep cervical. Besides these, the sub-clavian arteries sometimes give off, near their origin, pericar- diac, thymic, and oesophageal branches ; not unfrequently the left sub-clavian gives ori- gin to the bronchial artery of that side. The Vertebral Artery. TTie vertebral artery, destined for the cerebro-spinal nervous centre, supplies more particularly the spinal cord, the pons Varolii, the cerebellum, and the posterior portion of the cerebrum. It is the first and largest branch of the sub-clavian, and in some subjects is about equal in size to the continuation of that vessel. A very great inequal- ity in the size of the two vertebrals is rather frequently met with. Morgagni states * [It has been observed by Professor R. Quain (Joe. cit.) that the origin of the right sub-clavian is sometimes partially or completely covered by the right carotid, a process of the cervical fascia separating the two vessels.] t [Professor Quain has seen, in a few cases, the artery perforating the anterior scalenus ; and it has even been found, by himself and others, anterior to that muscle, and therefore in contact with the vein.] t According to our observation, this is a most rare variety. — Ed. ♦ In a case of this kind, which has been communicated to me by M. Demeaux, adjunct of anatomy to the Faculty, there was no brachio-cephalic trunk, but a bi-carotid trunk : the right sub-clavian arose from the de- scending aorta, and went behind the trachea and the oesophagus. (This preparation has been deposited in the museum of the Faculty.) h^ ANGEIOLOGT that he has seen the right vertebral four times as large as the left ; I have seen the left vertebral represented by a very small twig. The vertebral artery arises (2, fig. 204) from the upper and back part of the sub-clavi- an, at the point where it curves over the apex of the lung ; the left vertebral often ari- ses directly from the arch of the aorta, between the common carotid and sub-clavian of the same side. The right vertebral has been found arising from the point at which the innominate divides into the right common carotid and right sub-clavian. It has also been seen arising by two trunks, both of which sometimes come from the sub-clavian ; and at others, one proceeds from that artery, and the other from the arch of the aorta.* Immediately after leaving the sub-clavian, the vertebral artery passes vertically up- ward and a little backward, enters between the transverse processes of the sixth and seventh cervical vertebrae, in order to reach the foramen in the base of the transverse process of the sixth, ascends through the foramina in the transverse processes of the succeeding cervical vertebrae, describing some slight curves in passing from one to an- other. In order to gain the foramen in the axis, it forms a considerable vertical curve between the atlas and that bone ; it then forms a second horizontal curve between the atlas and the occipital bone.t perforates the posterior occipito-atloid ligament and dura mater, and enters the cranium by the foramen magnum. The right and left vertebral arteries turn round the sides of the medulla oblongata, between the hypoglossal and sub- occipital nerves, converge {i i, fig. 208) in front of the medulla, and near the furrow which separates it from the pons Varolii, unite at an acute angle to form the basilar ar- tery {b). The two remarkable curves described by the vertebral artery before it enters the cranium are in accordance with those formed by the internal carotid within the ca- rotid canal and cavernous sinus. I have seen the vertebral very tortuous at the lower part of the neck, before it entered the covered way formed for it by the cervical trans- verse processes. Not unfrequently the vertebral artery enters the canal of the transverse processes at the fifth cervical vertebra ; it has occasionally been seen to enter at the fourth, third, and even at the second. It very rarely enters the foramen of the seventh cervical vertebra. Relations. — Before entering the foramen of the sixth cervical vertebra, the vertebral artery is situated deeply upon the spine, between the longus colli and the anterior scale- nus, and behind the inferior thyroid artery. The thoracic duct is at first on the inner side, and then in front of the left vertebral artery. From the sixth cervical vertebra to the atlas, it is protected by the canal formed by the series of foramina in the transverse processes, and in the intervals between them by the inter-transversales muscles ; it lies in front of the cervical nerves, but the sub-occipital nerve lies between it and the groove in the atlas. In the intervals between the axis and atlas, and between the atlas and oc- cipital bone, it is in relation with the complexus and trachelo-mastoideus, and with the rectus capitis posticus major and obliquus superior. In those cases where the vertebral artery does not enter the vertebral foramina until it has passed up to the third or second cervical vertebra, it goes upward along the side of the internal carotid artery. In the cranium, it is situated between the basilar surface of ti^e occipital bone and the anterior surface of the medulla oblongata. Collateral Branches. — In its course along the canal of the transverse processes, the ver- tebral artery gives off spinal branches, which enter the vertebral canal through the in- ter-vertebral foramina, and are distributed in the same manner as the spinal branches of the intercostal and lumbar arteries. Several of these branches, however, are derived from the ascending cervical artery, and from the praevertebral branches of the ascending pharyngeal. From the two curves formed by the vertebral artery arise a great number of small muscular branches, which are distributed to the deep muscles of the cervical re- gion, and anastomose with branches of the occipital and deep cervical arteries. Among these there is one, sometimes two, which enters the cranium through the foramen mag- num, and is distributed to the dura mater lining the inferior occipital fossa:, and to the falx cerebelli : it is the posterior meningeal artery (rami meninges posteriores, Holler). Soemmering has pointed out a small meningeal branch, which enters the cranium with the first cervical or sub-occipital nerve, and which appears to me to be constant. In the cranium, before uniting to form the basilar, the vertebral arteries give off the posterior and anterior spinal arteries, and the inferior cerebellar. Spinal Arteries. — These are small branches, remarkable for being extremely slender, and for arising at an obtuse angle, so that they descend in a precisely opposite direction * One of the most remarkable varieties of origin of the vertebral artery is the followring, which has been communicated to me by Professor Dubreuil : In a woman of forty- five years, the left vertebral arteries arose neither on the right nor on the left side from the corresponding sub-clavian arteries. The left Tertebral took its origin directly from the arch of the aorta, be- tween the left sub-clavian and the left primitive carotid. The right vertebral arose from the right primitive carotid, at the distance of four millimeters from its origin. Both arteries passed upward, in parallel lines, along the vertebral column, as far as the third cervical vertebra, when they entered the vertebral foramina of the transverse processes of this vertebra, having previously given off several small supplementary branches of the ascending cervical arteries. The sub-clavian artery gave here origin only to five collateral branches. t Have the curvatures of the vertebral artery any relation to the motions of the head upon the vertebnkl (tolumn ? THE VERTEBRAL ARTERY. 635 to the vertebral arteries, which ascend vertically ; they are distinguished into the anterior and the posterior spinal artery. It is incorrect to regard them as continued down to the lower part of the spinal cord : they are so slender, that they can only supply a very small portion of the cord ; in reality, they are nothing more than the commencement of the spi- nal arteries, which are continued through the whole extent of the cord by means of branches given off from the cervical, dorsal, and lumbar arteries. The posterior spinal artery arises from the vertebral while that vessel lies upon the side of the medulla oblongata, and sometimes from the inferior cerebellar artery ; it pass- es in a tortuous manner inward, and divides into an ascending branch, which terminates upon the sides of the fourth ventricle, and a descending tortuous branch, which winds along the sides of the posterior surface of the cord, and divides into two twigs, a small one situated before, and a larger one placed behind the posterior roots of the spinal nerves ; around each of these roots they form a network, and, by means of transverse branches, which are twisted on themselves and much interlaced, they communicate with the corresponding branches of the opposite side. Chaussier was therefore incorrect in giving the name of the posterior median artery of the spine to the two posterior spinal ar- teries. Tliese small branches of the vertebral are soon exhausted ; they are continued on each side by branches of the cervical, dorsal, and lumbar spinal arteries, which run upward along the posterior roots of the nerves, and having reached the sides of the cord, divide into ascending and descending branches, which anastomose witli the neighbour- ing vessels, form a network around each pair of nerves, and communicate by tortuous transverse branches with the arteries of the opposite side. The anterior spinal artery (m, Jig. 208), which is somewhat larger than the posterior, arises from the vertebral near the basilar, sometimes even from the basilar itself, or from the inferior cerebellar, passes almost vertically inward and downward, in front of the medulla oblongata, and anastomoses in the same manner as the vertebral with its fellow of the opposite side, so as to constitute a median trunk, which is correctly named the anterior median artery of the spine ; it is situated beneath the pearly fibrous band found along the anterior median furrow, and is continued by branches from the cervical, dorsal, and lumbar arteries. The anterior, or median spinal artery, therefore, results from the anastomoses of the two anterior spinal branches of the vertebral. In one case there was no artery on the left side, but the right was twice as large as usual. The vessel is of considerable size, until it has passed below the cervical enlargement of the cord, from which point down nearly to the dorsal enlargement it becomes exceedingly delicate ; a little above the last- named enlargement it suddenly increases in size, again gradually diminishes as it ap- proaches the lower end of the spinal cord, and becoming capillary, is prolonged down to the sacrum, together with the fibrous string in which the spinal cord tenninates. During its course, this artery receives lateral branches from the ascending cervical and the vertebral in the neck, and from the spinal branches of the intercostal and lum- bar arteries in the back and loins. These branches penetrate the fibrous canal formed by the dura mater around each of the spinal nerves ; become applied to the nervous ganglia, to which they supply branches ; get intermixed with, and follow the course of, the corresponding nerves ; send small twigs backward to the posterior spinal arteries, and terminate in the anterior spinal trunk, at variable angles, similar to those at which the nerves are attached to the spinal cord. The re-enforcing spinal branches are not nearly so numerous as the nerves. If the con- dition which I have observed in three subjects be constant, there are three in the cervi- cal region, one or two in the contracted portion of the cord, and one only at the inferior enlargement. This last, which in one case was as large as the ophthalmic artery, reach- ed the cord at a very acute angle ; opposite the median line, it divided into two branch- es, one ascending and very small, the other descending, of considerable size, and form- ing the true continuation of the trunk. From the anterior spinal arteries there proceed a great number of twigs, which pass backward into the anterior median furrow, and from thence into the substance of each half of the corresponding portion of the cord ; also some lateral branches, which ramify on the sides of the cord in the pia mater. The Inferior and Posterior Cerebellar Arteries. — These (A h) arise from the outer side of the vertebral, and sometimes from the basilar ; they are of considerable size, and often differ in this respect on the two sides. Each of them soon turns round the medulla ob- longata, pursuing a tortuous course, passes between the filaments of origin of the hypo- glossal nerve, runs in front of the roots of the pneiunogastric and glosso-pharyngeal nerves, crosses the restiform body, and reaches the back of the medulla oblongata on one side of the opening of the fourth ventricle ; it then passes backward, between the inferior ver- miform process and lateral lobe of the cerebellum, and divides into two branches : one internal, which continues along the furrow between the vermiform process and lateral lobe, supplies the former, and turns upward into the notch in the posterior margin of the cerebellum ; the other branch is external, and passes outward upon the lower surface of the cerebellum, and divides into a great number of twigs, which may be traced as far as 536 ANGEIOLOGY. the circumference of the cerebellum, and which anastomose with those of the superior cerebellar artery. The Basilar Trunk. — The basilar trunk (^>) results from the junction or confluence of the two vertebral arteries. It is larger than either of them singly, but its area is not equal to the sum of their areas ; so that, by this arrangement, the passage of the blood is accelerated. It commences opposite the furrow between the medulla oblongata and the pons Varolii, and terminates by bifurcating in front of the anterior border of the pons ; its length, therefore, corresponds to the antero-posterior diameter of the pons, on the median furrow of which it is situated. When the vertebral arteries are displaced to- wards the right side (a very common condition), the basilar trunk passes horizontally or obliquely to the left, so as to reach the median furrow. It gives off no branch from its lower surface, which rests upon the basilar groove of the occipital bone. A great number of capillary twigs are detached from its upper sur- face, and enter the pons Varolii. From its sides proceed the anterior inferior cerebellar and the superior cerebellar. The anterior and inferior cerebellar arteries {I I) vary much in size in different subjects, and are rarely equal in this respect on the right and left sides : each of them arises from about the middle of the basilar, and occasionally from the vertebral itself, passes out- ward and backward, sometimes behind, and sometimes in front of the sixth nerve, l^lns along the cms crebelli, passes in front of the facial and auditory nerves, and terminates upon the anterior portion of the hemisphere of the cerebellum. The superior cerebellar arteries (t t) arise one from each side of the basilar, immedi- ately before it divides into its two terminal branches ; they might, therefore, also be re- garded as terminal branches of that artery, which would thus end by dividing into four branches. Having arisen at a right angle behind the third, or motor oculi nerve, each superior cerebellar artery, accompanied by the fourth or trochlear nerve, turns round the crus cerebri in the groove between it and the pons Varolii, and, having reached the up- per surface of the corresponding crus cerebelli, divides into two branches : one external, which passes outward on the upper surface of the cerebellum, along the anterior half of its circumference ; the other internal, which is directed inward upon the sides of the su- perior vermiform process, or median lobule of the cerebellum, and then subdivides into an antero-posterior branch, which passes from before backward upon the sides of the vemiiform process, as far as the circumference of the cerebellum, upon which it ramifies ; and a transverse branch, which continues the original course of the vessel towards the median line, running between the superior vermiform process and the valve of Vieussens, and being distributed to both. The terminal branches of the basilar trunk are the posterior cerebral arteries (n n) ; they arise at variable angles, are directed forward and outward, and then curve backward, so as to turn round the crus cerebri, parallel to the superior cerebellar arteries, from which they are separated by the third or motor oculi nerve. They follow the concave bordei of tiie great transverse fissure of the brain, and, having reached the posterior extrem- ity of the corpus callosum, leave this fissure to pass backward upon the lower surface of the posterior lobe of the cerebrum, where they may be traced as far as the occipital region. Each of the posterior cerebral arteries gives off, immediately after its origin, an immense number of small parallel twigs, which enter the substance of the brain between the anterior crura, whence the name of perforated spot given to that portion of the brain. Just as each posterior cerebral artery curves backward, it receives the communicating artery of Willis (r), which is sometimes very large, and at other times very small. When large, it evidently assists in the formation of the posterior cerebral, which, after its junc- tion with the communicating artery, sometimes becomes doubled or trebled in size. The part performed by the internal carotid in the formation of the posterior cerebral is, there- fore, subject to variety. In certain cases, as I have already stated,, the posterior cere- bral is exclusively derived from it. The posterior choroid artery arises from the back part of the posterior cerebral, imme- diately after the junction of that vessel with the communicating artery ; it turns round the crus cerebri, passes above and supplies the tubercula quadrigemina, and terminates in the velum interpositum and choroid plexus. As the posterior cerebral artery quits the crus cerebri, it gives off a branch which passes outward and backward, crosses obliquely the long convolution which forms the lateral boundary of the great fissure of the brain, and ramifies upon the lower surface of the cerebrum. Lastly, the posterior cerebral gives off a small constant branch, which may be called the artery of the fascia dentata, to which it is distributed. Remarks on the Arteries of the Brain, Cerebellum, and MeduU-a Oblongata. The arteries of the encephalon, i. e., of the brain, cerebellum, and medulla, are deri ved from four principal trunks, tw^o anterior, viz., the internal carotids, which arise from the common carotids, and two posterior, viz., the vertebrals, which are branches of the sub-clavian arteries. There are several circumstances to be remarked concerning these vessels, viz., their great size, which is dependant on that of the brain ; their depth from THE INFERIOR THYROID ARTERY. 637 the surface before they enter the cranium ; the numerous curves formed by them as they are entering the cranial cavity, the use of vphich is evidently to retard the course of the blood ; the absence of any large collateral branches, the only exception being the oph- thalmic branch of the internal carotid, by the existence of which the circulation in the eye is connected with that in the brain. Another remarkable point concerning these vessels is their anastomoses at the base of the cranium, viz., the anastomosis, or, rath- er, the confluence of the right and left vertebral so as to form the basilar artery ; the anastomosis of the right and left internal carotids by means of the anterior communica- ting artery, which unites the anterior cerebrals, and the anastomosis of the internal ca- rotids with the vertebrals by the communicating arteries of Willis. By these anasto- moses an arterial hexagon (the circle of Willis) is formed, the anterior margins of which correspond with the anterior cerebral arteries, the posterior with the posterior cerebrals, ' and the lateral with the communicating arteries of Willis.* From this hexagon, as from a centre, proceed all the arteries of the brain, viz., from the anterior angle, the anterior cerebral arteries ; from the posterior angle, the basilar artery ; from the anterior lateral angle on each side, the middle cerebral ; and from the posterior lateral angle on each side, the posterior cerebral artery Owing to the existence of these large anastomotic communications, any one of the four arterial trunks would be sufficient to carry on the circulation in the brain, if the other three were wanting or obliterated The situation of this arterial hexagon between the bones of the cranium and the brain is remarkable, because it explains the alternate movements of elevation and depression seen in the brain when that organ is exposed during life It should also be observed, that the arteries of the cerebellum, pons Varolii, and me- dulla oblongata, are derived from the same sources as those of the brain. Lastly, as to the mode of distribution of these vessels, it may be remarked, that the arteries of the brain pass over the free surface of one or more convolutions, dip into the sulci between the convolutions, are reflected from one side of them to the other, give off a great number of very small branches, emerge from a given sulcus to regain the surface of the adjacent convolutions, and so on until they are exhausted. The princi- pal arteries of the cerebellum run upon its surface without passing into the sulci, be- tween the laminae, into which they send only very small branches. With some excep- tions, the arteries are reduced to capillary dimensions before they enter the nervous substance. The Inferior Thyroid Artery. Dissection. — Dissect the muscles of the sub-hyoid region ; follow the branches of the thyroid ; trace the divisions of the ascending cervical artery into the grooves upon the transverse processes of the cervical vertebrae, and into the vertebral canal. The inferior thyroid artery. (3, fig. 204) arises from the front of the sub-clavian on a plane anterior to the vertebral, which often comes off exactly opposite to it. It varies remarkably in size and origin, as well as in the branches which it furnishes. It fre- quently arises from the common carotid ; sometimes from the arch of the aorta, between the brachio-cephalic and the left common carotid ; at other times from the brachio-ce phalic itself Lastly, it is occasionally replaced by the thyroid of Neubauer. It often commences by a common trunk with the supra-scapular, less frequently with the posterior scapular, and rarely with the internal mammary. Its size bears an inverse proportion to that of the superior thyroid of the same side and depends, also, on the presence or absence of a third thyroid. It is larger in infancy than at any other period. In certain cases of goitre it becomes prodigiously developed. Sometimes there is merely a trace of its existence, or it is even altogether wanting. Immediately after its origin it passes vertically upward, then descends so as to de- scribe a curve with its concavity directed downward, and again forms another curve with its concavity turned upward, to reach the lower end of the lateral lobe of the thy roid gland, in the interior of which it ramifies. Relations. — Behind, it is in relation with the trachea, the oesophagus, and the verte- bral column, being separated from the latter by the praevertebral muscles and the ver- tebral artery. Its relation with the oesophagus is more marked on the left than on the right side, and it is important to bear this fact in mind in performing thq operation of oesophogotomy. In front, its first curve embraces the common carotid, the internal jugular vein, the pneiuntiogeistric, and the great sympathetic nerves. The middle cervi- cal ganglion, when it exists, rests upon it. The second curve embraces the recurrent laryngeal nerve, and is also in relation with the muscles of the sub-hyoid region. It may be remarked, that there is one point in the neck where three arteries come into contact, viz., the common carotid, the inferior thyroid, and the vertebral. Collateral Branches. — The inferior thyroid gives off, downward, an oesophageal branch, " In a person who died ol apoplexy, Morgagni found a want of communication between the vertebrals and carotids ; and he attributed the apoplexy partly to this circumstance, and partly to the fact that the left ver- tebral arose directly from the arcli of the aorta. Yyy ^4|P ANGEIOLO&Y. some tracheal branches, and a small brojichial twig. I have seen the right bronchial ar- tery derived from it. It also gives off several muscular branches to the scalenus anti- cus and the praevertebral muscles. The most remarkable of all these is the ascending cervical artery (4), which is of variable size, and is sometimes so large that it may be regarded as resulting from the bifurcation of the inferior thyroid. It passes vertically upward, in front of the scalenus anticus, then in the groove between it and the rectus capitis anticus major, to both of which, as well as to the attachments of the levator an- guli scapulae, it gives some small branches. The most remarkable of its branches, call- ed the cervicorspitial, enter the grooves by which the cervical nerves emerge, run in front of these nerves, and anastomose with the branches of the vertebral artery. I have seen these branches divide into two ramusculi : the one anterior, very small, which passed in front of the vertebral artery, and emerged upon the sides of the body of the vertebra ; the other posterior, which passed between the corresponding nerve and the artery, entered the spinal canal through the intervertebral foramen, and was distributed to the vertebrae, and to the spinal cord and its membranes, in the same manner as the dorsal and lumbar spinal arteries. The praevertebral branch of the ascending pharyn- geal artery sometimes supphes the cervico-spinal branch of the first two intervertebrcd spaces in the cervical region. Terminal Branches. — Opposite the lower extremity of the lateral lobe of the thyroid gland, the inferior thyroid artery divides into three branches : of these, one follows the lower border of the gland, another passes to the posterior surface of its lateral lobe, while the third dips between the gland and the trachea, runs along the lower border of the cricoid cartilage, sometimes becomes superficial opposite the isthmus of the thyroid body, and forms an anastomotic arch with its feUow of the opposite side, along the upper margin of that isthmus. The Supra-scapular Artery. The superior or supra-scapular artery {transversus humeri, 5, fig. 204), destined for the supra- and infra-spinous fossae, and which might also be denominated the cleido-supra- scapular from its course, arises from the front of the sub-clavian below the inferior thy- roid, and often by a common tmnk, either with the posterior scapular, or with the in- ferior thyroid and posterior scapular united, forming what is then called the thyroid axis. It is at first directed vertically downward, then bends horizontally outward, to run along behind the clavicle and gain the upper border of the scapula, where it passes over, very rarely under, the ligament, which converts the coracoid or supra-scapular notch into a foramen, and, being reflected over that ligament, dips into the supra-spinous fossa, and crossing the concave border of the spine of the scapula, enters the infra-spinous fossa, in which situation it terminates {5', fig. 209). Relations. — It is concealed at its origin by the stemo-mastoid muscle, and is then sit- uated along the base of the supra-clavicular triangle ; it is in relation in front with the clavicle, following the direction of that bone ; behind, with the sub-clavian artery and the brachial plexus of nerves, which it crosses at right angles ; above, with the deep fascia and the platysma myoides, which separate it from the skin ; and below, with the sub-clavian vein : more externally, it dips under the trapezius, and comes in contact with the supra-scapular nerve, is separated from it at the coracoid notch, and again be- comes applied to it in the supra- and infra-spinous fossae, where it is situated between the muscles of the bone. Collateral Branches. — Among a great number of unnamed muscular and cutaneous branches, I would particularly notice, 1. A small thoracic branch, which passes verti- cally downward behind the clavicle, perforates the sub-clavius, and anastomoses with the thoracic arteries. 2. A branch for the trapezius, which is so large that it appears to result from the bifurcation of the artery. It generally arises at the point where the ves- sel dips into the supra-spinous fossa ; at other times it comes off very near the origin of the artery, passes from before backward, turns round the scaleni muscles parallel with the posterior scapular artery, with which one might confound it, and ramifies in the tra- pezius and the supra-spinatus muscles, entering the former at its under, and the latter at its upper surface : some of the branches are distributed to the periosteum of the acromion and to the corresponding integuments. Again, in the supra- and infra-spinous fossae it gives off a great number of periosteal, osseous, muscular, and articular branches. In the infra-spinous fossa (5, fig. 209), it forms a free arched anastomosis with the sub-scapular artery, and gives off a branch which runs along the axillary border of the scapula, and anastomoses with the posterior scapular artery at the lower angle of that bone. The Posterior Scapular Artery. The posterior scapular {transversus cervicis, transvcrsalis colli, 6, fig. 204, 209) is larger than the preceding, and extends from the sub-clavian to the vertebral border of the scap- ula ; it arises from the front of the sub-clavian, sometimes to the inner side of the sea- THE INTERNAL MAMMARY ARTERY. 639 leni, sometimes between them, but most commonly on the outer side of those muscles ;* in the first case it often comes off by a common trunk with the inferior thyroid, and in the two other cases by a common trunk with the supra-scapular. It passes transversely and in a slightly tortuous manner outward, through the nerves of the brachial plexus, and sometimes through the scalenus posticus, and curves backward towards the poste- rior superior angle of the scapula. Then, opposite the levator anguli scapulae, it divides into an ascending and a descending- branch. The ascending or cervical branch, the super- Jicial cervical artery of authors, passes beneath the trapezius, and divides into a great number of twigs, which ramify in that muscle, in the levator anguli scapulae, and in the splenius. The descending branch forms the posterior scapular artery, properly so called (a. Jig. 209), and may be regarded as the continuation of the vessel ; it turns round the posterior superior angle of the scapula, beneath the levator Fig. 209. anguli,. passes vertically downward along the vertebral bor- ^ der of that bone, and terminates at the inferior angle by an- , ^\ astomosing with the sub-scapular artery, a branch of the ax- , ^A illary, and with the supra-scapular, already described. '^^^jS^^»— ^.^^ Relations. — It is superficial in the first part of its course, ••',:^^^^^^~^^^ during which it traverses the supra-clavicular triangle hor- -V>^^^^^^^ izontally, being merely covered by the cervical fascia, the '^^^^ib^W^tk platysma myoides, and the omo-hyoid ; and hence, doubt- ^^^-■C/Wt^^^>\ less, the name superficial cervical, which has been given to -' v~T^^^^^^\ it by some authors. + It is but rarely that the posterior ' /-^•^^'P^^^^^w scapular turns round the posterior scalenus and the brach- , ' / -s5^y^;J^W^w//^ ial plexus, without passing between the nerves of the plex- .^j!^yj/^ fms^mWli^w us, which it traverses at variable heights. As it proceeds \ ' v^ it0^i^MJMj]r' backward, it is protected by the trapezius ; and, lastly, ^- it'^^^^^^^oi-.JssJ along the vertebral border of the scapula, it lies between the rhomboideus and the serra- tus magnus Its collateral branches are destined for the following muscles : the trapezius, sc£ilenus posticus, levator anguU scapulae, splenius, supra- and infra-spinati, sub-scapularis, rhom- boideus, and serratus magnus. The Internal Mammary Artery. The internal mammary, or internal thoracic artery, not so remarkable for its size, which is less than that of the vertebral, as for its length and the number of its branches, arises (7, fig. 204) from the sub-clavian opposite the inferior thyroid, and behind the supra- scapular. Few arteries are less variable in their origin. The only varieties which have been observed are those in which it arises from the brachio-cephalic, from the arch of the aorta, or from a common trunk with the inferior thyroid. Immediately after its ori- gin, it passes vertically doAvnward behind the inner end of the clavicle, enters the thorax, crosses obliquely behind the cartilage of the first rib, and bends a little inward to run along the first portion of the sternum, below which it resumes its vertical direction, par- allel to the border of that bone, as low down as the sixth rib, where it divides into an internal and an external branch. Relations. — It is situated in front of the scalenus anticus, and is covered at its origin by the phrenic nerve, which crosses it very obliquely, in order to reach its inner side ; it corresponds to the inner end of the clavicle, from which it ie separated by the brachio- cephalic vein ; it is then placed behind the costal cartilages and the intercostal muscles, in front of the pleura, from which it is separated by the triangularis sterni. It is situa- ted about two lines to the outer side of the margin of the sternum, so that a cutting in- strument may be carried into the thorax along that bone without injuring the internal mammary ; the name sub-sternal is, therefore, not at all appUcable to this artery, which would be better named sub-chondro-costal. Collateral Branches. — These are very numerous ; they may be divided into the poste- rior, anterior, and external. The posterior branches are, the thymic or anterior mediastinals, and, lower down, the superior phrenic, an extremely small artery, which runs along the phrenic nerve, is situated, like it, between the pericardium and the corresponding layer of the mediastinum, and reaches and is ramified in the diaphragm. Bichat has seen the superior phrenic artery as large as the internal mammary itself. The external branches are the anterior intercostals. Their number corresponds with that of the intercostal spaces : they are small in the first two, and gradually increase or diminish according to the length of the corresponding spaces. I have seen the common trunk for the third intercostal space so large, that it appeared like a bifurcation of the mammary. There are generally two branches for each intercostal space : one, which runs along the lower margin of the rib above, and the other along the upper margin of the rib below. These two branches sometimes arise separately from the mammary, * In the last case, those authors who describe the sub-clavian as terminating between the scaleni, say that the posterior scapular arises from the axillary artery, t [It is the ascending- or cervical branch only that is named superficial cervical.] 540 ANGEIOLOGY. sometimes by a common trunk ; as they arise above the level of the space for which they are intended, it follows that they pass obliquely behind the costal cartilages. The anterior intercostals inosculate with the aortic or posterior intercostals, so that it is sometimes impossible to determine the limits between these two sets of vessels. In some subjects they form a communicating arch of uniform caliber, extending between the internal mammary and the thoracic aorta. The anterior branches are superficial, and correspond in number to the intercostal spa- ces ; they arise from the internal mammary, pass directly from behind forward, through the corresponding intercostal space, and divide into cutaneous and muscular branches, both of which sets curve outward, the muscular branches beneath the pectoralis major, in which they ramify, and the cutaneous branches beneath the skin. Tlie anterior branches of the first three spaces are distributed to the mammary gland. In females re- cently delivered, and in nurses, these branches become extremely large, especially the second, which I have seen as large as the radial artery, and very tortuous. Before per- forating the intercostal muscles, the anterior branches send some periosteal twigs be- hind the sternum, some of which penetrate the bone directly, while others ramify on the periosteum. Terminal Branches. — Of the two terminal branches, the internal, and smaller, contin- ues the original course of the artery, passes behind the rectus abdominis muscle, enters its sheath, and then divides into a great number of branches ; some of these are lost in this muscle by anastomosing with the capillary divisions of the epigastric, while the oth- ers emerge from the sheath of the rectus by special openings, and are distributed to the broad muscles of the abdomen, and to the integuments. Before leaving the cartilage of the seventh rib, it gives off a small twig, which passes inward upon the side of the en- siform cartilage, and forms an anastomotic arch with its fellow of the opposite side, in front of that cartilage. The anastomosis of this artery with the epigastric, which has been known from the very earliest periods, and afforded the ancients an explanation of the intimate physiological connexions between the genital organs and mammary glands, is accomplished in the usual manner of capillary communication. The external terminal branch, as far as distribution is concerned, is the continuation of the internal mammary. It is directed downward and outward, behind the cartilages of the seventh, eighth, ninth, tenth, and eleventh ribs, which it crosses obhquely, and ter- minates opposite the last intercostal space. During its course, it gives off the anterior intercostals of the corresponding spaces, two for each space, sometimes only one, which immediately subdivides. These intercostals diminish gradually in size as the spaces decrease in length, and are distributed precisely as the anterior intercostal branches of the internal mammary itself The external terminal branch, and also the internal, while passing through the diaphragm near its costal attachments, give off a great number of branches to that muscle, and hence the name musculo-phrenic, given by Haller to the external division, which, indeed, furnishes many more branches to the diaphragm than the internal. The Deep Cervical Artery. Dissection. — Seek at first for the artery behind the scalenus anticus, between the transverse process of the seventh cervical vertebra and the first rib ; trace it, both to its termination, between the complexus and semi-spinalis colli, and towards its origin, with- in the scaleni. The posterior, or deep cervical, comes off deeply from the upper and back part of the sub-clavian, on the same plane as the vertebral, to the outside of which it is situated. Very often it arises by a common trunk with the first intercostal. It passes at first up- ward and backward, then bends outward behind the scalenus anticus to dip between the transverse process of the seventh cervical vertebra and the first rib. I have never seen it pass between the transverse processes of the sixth and seventh cervical vertebrae, though for this purpose I have examined forty subjects.* After leaving the inter-transverse space, the deep cervical artery divides into two branches : one descending, which I have been able to trace as far as the middle of the dorsal region, between the long muscles of the back ; the other ascending, which passes up between the complexus and the semi-spinalis colli, in which it terminates, and anas- tomoses with the occipital and vertebral arteries. The Superior Intercostal Arteries. Dissection. — This artery can only be dissected from the internal surface of the thorax. For this purpose it is necessary to saw through the thorax vertically. The artery must be exposed by removing the pleura from the two upper ribs and intercostal muscles. * This relation is so constant, that, even in cases where there is a supernumerary cervical rib, the deep cervical artery passes betwreen this supernumerary rib and the first dorsal rib. Some students having called me to examine a subject in which this artery was wanting, I sought in vain for it between the first rib and the transverse process of the last cervical vertebra, and then perceived that there was a cervical rib, between which and the first dorsal rib the artery was found. [In 264 observations, Professor Quain met with this variety in the course of the artery four times, and also other peculiarities.] THE AXILLABY ARTERY. The superior intercostal artery, intended for the two or three superior intercostal spa- ces, sometimes only for the first, varies in size according to the extent of its distribu- tion. It comes off from the lower and back part of the sub-clavian, near the deep cer- vical, and sometimes by a common trunK with it. It descends, m a tortuous manner, m front of the neck of the first, and then of t'ne second rib, on the outside of the first dorsal ganglion of the sympathetic nerve, and terminates in the second intercostal space, like an aortic intercostal artery ; sometimes it anastomoses freely with the first of the aortic intercostals. It gives off in each space a dorso-spirud branch, and an intercostal branch, properly so called. It is not rare to find the intercostal branch wanting in the first space : in all cases it is extremely small. The Axillaky Artery. Dissection. — In order to prepare the axillary, as well as all the other arteries of the upper extremity, it is sufficient to dissect the muscles carefully, at the same time preserving aU the branches which are met with, and tracing them to their origin. The axillary artery {a a', fig. 210) is that part of the artery of the upper extremity which intervenes be- tween the sub-clavian and the brachial. Its limits, which are entirely artificial, are the clavicle,* on the onp hand, and the lower border of the pectoralis major on the other. It traverses the axilla diagonally, and bends opposite the neck of the humerus, so as to be- come continuous with the brachial artery. Its upper part rests upon the thorax, and its lower upon the hu- merus ; it is not very tortuous, so that in forcible ab- duction of the arm it may be stretched even to lacera- tion. Its direction corresponds pretty nearly with the cellular interval so generally existing between the sternal and the clavicular portions of the pectoralis major, or, rather, with an imaginary line, extending from the junction of the outer with the two inner thirds of the clavicle to the inner side of the neck of the hu- merus. Relations. — From the importance necessarily attach- ed to an accurate knowledge of the relations of this ar- tery, we shall consider them in the four aspects of the vessel. In front, the axillary artery is in relation from above downward with the sub-clavius muscle, a process of the deep cervical fascia intervening between them ; then with the costo-coracoid ligament and the pecto- ralis major ; next with the pectoralis minor ; below this muscle, with the pectoralis major again ; and, last- ly, with the coraco-brachialis. In a subject where the pectoralis major had no clavicular insertions, that por- tion of the axillary artery which is intermediate be- tween the clavicle and the superior border of the pec- toralis minor, was separated from the skin only by the platysma myoides. Behind, it is in relation with the cellular interval between the sub-scapularis and serra- tus magnus ; lower down, with the teres major and latissimus dorsi. On the inside, it rests at first upon the first rib and the first intercostal space ; it next leaves the thorax, from which it is separated by the hollow of the armpit, and its inner side is then in re- lation with the skin which forms the outer wall of the armpit, and with the subjacent fascia. On the outside, it is at first embraced by the concave surface of the coracoid process, and it is then placed opposite the head of the humerus, from which it is separated by the sub-scapularis muscle Relations with the Axillary Vein and Nerves. — Immediately below the clavicle, tne axdlary vein is situated on the inner side of, and at some distance from, the artery ; lower down, the vein lies upon the artery. The cephahc and acromial veins pass in front of the artery. Immediately below the clavicle, the entire brachial plexus is situated on the outer side * Those authors who consider the sub-clavian as terminating between the scaleni, describe the axillary aa commencing at the same point [The axillary artery is commonly said, in this country, to commence at the lower border of the first rib (a), and to terminate at the lower border of the conjoined tendons (a') of the latissimus dorsi and teres major muscles.] 542 ' ^ ANGEIOLOGY. of the artery, only one thoracic nerve crossing in front of it. Under the pectoralis minor the artery is surrounded by the plexus ; it is at first embraced by the external and inter- nal roots of the median nerve, which meet in the form of a V opening upward ; lower down, it is placed between the external cutaneous nerve on the outer side, the median in front, the internal cutaneous and the ulnar on its inner side, and the radial, or muscu- lo-spiral, and the circumflex behind. In order to expose the artery in the axilla, the ves- sel may be sought for between the median and ulnar nerves. In consequence of these relations, wounds of the axilla may be very serious ; com- pression may be applied to the axillary artery, either by forcibly depressing the clavicle against the first intercostal space and second rib, or by placing the finger upon the ves- sel in the axilla, and pressing it against the head of the humerus ; a ligature may be ap- plied to this artery, either under the clavicle above the pectoralis minor, or in the axilla ; lastly, the artery may be torn from extreme violence in attempting to reduce a dislocation.* Collateral Branches. — The axillary gives off five branches, viz., the acromio-thoracic, alpove the pectoralis minor ; the inferior thoracic, or external mammary, below the pecto- ralis minor ; the inferior scapular, and the anterior and posterior circumflex arteries, op- posite the neck of the humerus. The Acromial and Superior Thoracic Arteries. Under the name of acromio-thoracic I include two arteries, the acromial and the supe- rior thoracic, which almost always arise by a common trunk, which is detached at right angles from the inner side of the axillary artery immediately above the pectoralis minor, then crosses the upper border of that muscle at right angles, and immediately divides into the two above-named branches. The thoracic branch passes downward and inward, and subdivides {b b) between the two pectoral muscles, both of which it supplies, but especially the lesser. Some branches perforate the pectoralis major, and are distributed to the skin and the mamma. The acromial branch subdivides into two others : a descending or deltoid branch (c), which enters the cellular interval between the pectoralis major and the deltoid, traverses it throughout, and is distributed to these two muscles, but especially to the deltoid ; it is accompanied by the cephalic vein : the second is a transverse or acromial branch {d), which runs horizontally outward, passes over the apex, and sometimes over the base of the coracoid process, then upon the coraco-acromial ligament, and runs along the outer third of the anterior border of the clavicle. It is covered in the whole of its course by the deltoid, to which it is in a great measure distributed. Some twigs terminate in the skin over the acromion. This acromial branch terminates near the acromio-claviculax articulation : sometimes one of its divisions closely follows the anterior border of the clavicle. The Inferior or Long Thoracic Artery. The inferior thoracic, long thoracic, or external mammary artery (e, fig. 210), is much lar- ger than the acromial thoracic, and sometimes arises by a common trunk with it or with the sub-scapular ; it is given off from the axillary below the pectoralis minor, passes downward and forward upon the side of the thorax, between the pectoralis major and serratus magnus, then between the serratus and the skin, and terminates at about the sixth intercostal space. During this course it gives off a great number of branchest to the lymphatic glands in the axilla, to the sub-scapularis, pectoralis major, and serratus magnus muscles, to the second, third, fourth, fifth, and sixth 'intercostal spaces, to the mamma, and to the skin. Not unfrequently the inferior thoracic partially supplies the place of the sub-scapular artery, in which case it is as large as that vessel. The Sub-scapular Artery. The inferior, common, or sub-scapular artery (/), the largest branch of the axillary, arises near the lower part of the head of the humerus opposite the lower border of the sub-scapular muscle, sometimes by itself, sometimes by a common trunk with the poste- rior circumflex, the long thoracic, or the deep humeral artery ; in the last case it is as large as, perhaps even larger than, the brachial. At its origin, which is from the outer aspect of the axillary, it has the musculo-spiral nerve to its inner side, and the principal orig;in of the median on its outer side ; it passes in a tortuous manner downward and out- ward along the lower border of the sub-scapularis muscle, parallel with the teres major, and beneath the head of the humerus,^ furnishes large branches to all these muscles, and having arrived below the insertion of the sub-scapularis, divides into two branches, a descending or thoracic, and a scapular, properly so called. * I hare seen two cases of rupture of the axillary artery from attempts to reduce old dislocations. t [These branches represent the alar thoracic artery, and sometimes arise directly from the axillary, behind the pectoralis minor, or from the sub-scapular.] t The relation of the sub-scapular artery to the head of the humerus appears to me to be important. In abduction thi« artery is much stretched, and I am surprised that it has not been torn in same cases of luxation ; on the contrary, the circumflex artery, and, therefore, the circumflex nerve, appear to me to be much less lia ble to be stretched during abduction. Nevertheless, it is certain that the circumflex nerve has been lacerated in some dislocations of the humerus, because they have been followed by paralysis of the deltoid muscle. THE BRACHIAL ARTERY. 543 The descending or thoracic branch (g), which is often given off by the inferior or long thoracic, passes downward and forward near the axillary border of the scapula, parallel with and behind the long thoracic, and divides into a great number of large branches, some of which enter the latissimus dorsi, several penetrate the serratus magnuseven as far as the lowest portion of that muscle, while others turn round the lower angle of the scapula, and anastomose with the following or scapular branch, and with the posterior scapular derived from the sub-clavian. The scapular branch (i), properly so called, proceeds along the lower border of the sub- scapularis muscle, in front of the long head of the triceps, and having reached below the scapular attachment of the triceps, divides into three branches : an anterior or sub-scapu- lar branch, which dips into the sub-scapular fossa below the muscle, and expands into a great number of branches, the highest of which are distributed to the capsule of the shoulder-joint ; an infra-spinous branch (Jb,fig. 209), which turns round the axillary border of the scapula, runs between the muscle and the infra-spinous fossa, and anastomoses, by a considerable branch, with the termination of the supra-scapular artery ; a median branch (c,fig. 209), which continues in the original course of the vessel, runs along the axillary border of the scapula, between the teres major and minor, then becomes poste- rior, and terminates by anastomosing again upon the lower angle of the scapula with the thoracic branch of this artery, and with the infra-spinous branches of the supra-scapular. The Posterior Circumflex Artery. The posterior circumflex artery (Z, fig. 210) arises from the back of the axillary opposite the sub-scapular, which it sometimes equals in size. It passes horizontally backward, between the sub-scapularis above and the teres major below, turns inward round the surgical neck of the humerus, passing first between the internal head of the triceps and the teres minor, then between the long head of the triceps and the bone, and finally (Jl,fig. 209) under the deltoid, to the deep surface of which it is applied ; it always turns round so as to describe three fourths of a circle, and thus reaches the anterior and outer aspect of the humerus, and is lost in the deltoid by anastomosing with the deltoid branches of the acromio-thoracic artery. In the whole of its course it is accompanied by the cir- cumflex vein and the circumflex nerve. As it turns round the bone, the posterior cir- cumflex gives off some articular and periosteal branches, which pass to the capsular lig- ament of the shoulder-joint, and to the periosteum of the humerus. The Anterior Circumjlex Artery. The anterior circumflex, a small artery {n,fig. 210), sometimes represented by several branches, arises from the axillary in front of the posterior circumflex, and often by a common trunk with it. It passes horizontally outward above the conjoined tendons of the latissimus dorsi and teres major, covered by the coraco-brachialis and the short head of the biceps, runs beneath the tendon of the long head of the biceps, turns round the neck of the humerus, crosses the bicipital groove at right angles, being held down by the synovial membrane, and divides into an ascending and a descending branch. The Jatter presents nothing remarkable ; but the ascending branch, having reached the up- per part of the groove, anastomoses with the osseous branch of the acromial artery, and is lost in the head of the humerus, which it penetrates at one or more points. The anterior circumflex is, therefore, intended for the humerus, its periosteum, and the syno- vial membrane of the groove. Sometimes there are several anterior circumflex arteries, which enter the substance of the deltoid muscle. The Brachial Akteky. The brachial or humeral artery (a' h,fig. 210) is that portion of the artery of the upper extremity which extends from the lower border of the axilla to the point of its bifurca- tion at the upper part of the forearm. It passes downward, and a little forward and outward, so that it is situated on the inner side of the humerus above, and in front of it below. The absence of any bendings in this artery explains the possibility of its being torn from extreme extension of the forearm in dislocations of the elbow, &c.* The relations of the brachial artery require to be examined separately along the arm, and in front of the elbow-joint. Along the arm, the artery is in relation, in front, with the coraco-brachialis and the in- ner margin of the biceps, which may be regarded as the satellite muscle of the artery : in emaciated subjects the biceps does not cover the artery, which is then situated im- mediately under the fascia ; behind, it is in relation with the triceps, and then with the brachialis anticus ; on the inner side, with the fascia of the arm, which separates it from the skin ; on the outer side, with the coraco-brachialis, then with the inner side of the hu- merus, from which it is separated by the tendon of the coraco-brachialis, and in the rest of its extent with the cellular interval between the biceps and the brachialis anticus. The brachial artery is enclosed in a fibrous sheath, which is common to it and the me- * In old subjects, the humeral artery is almost always tortuous, and sometimes these windings are so re- markable that the artery is sub-aponeurotic during a portion of its course. 6)44 ANGEIOLOGY. dian nerve. The following are its relations with the veins and nerves : the principal brachial vein is situated on its inner side ; another smaller vein is on its outer side : both are in contact with the artery, which they separate from the nerves, and they are connected by several transverse branches, which embrace the artery. The median nerve is situated in front of the artery, excepting above, where it is on its outer side, and below, near the elbow, where it passes to its inner side ; the median nerve sometimes crosses behind the artery.* The ulnar nerve is placed on the inner side of the artery above, then passes behind it, and is lodged in a separate sheath. The musculo-spiral nerve is situated, together with the deep humeral artery, at first behind the brachial, but soon leaves it to turn round the humerus ; lastly, the internal cutane- ous follows the same course as the vessel, crossing it slightly from before backward. From these relations, it follows that the vessel may be most eificaciously compressed from within outward, against the inner surface of the humerus, and also that it may be tied in any part of its course. At the bend of the elbow, the brachial artery occupies the middle of the articulation ; it is superficial in front, where it is only separated from the skin by the fascia and tendi- nous expansion of the biceps, and by the median basilic vein, which crosses it at a very acute angle ; behind, it rests upon the brachialis anticus, by which it is separated from the elbow-joint ; on its inner side is the median nerve and pronator teres muscle, and, on its outside, the tendon of the biceps, over which it soon crosses, and, farther outward, the supinator longus. In consequence of the superficial position of the brachial artery at the bend of the el- bow, and from its relations with the median basilic vein and the elbow-joint, it follows that this artery may be easily compressed, may be wounded in the operation of vene- section, and may be lacerated in dislocations of the joint, t Collateral Branches. — These may be divided into the external and anterior, and the inter- nal and posterior. The external and anterior are very numerous, and are intended for the coraco-brachia- lis and biceps, which they penetrate at different heights, and also for the brachialis an- ticus. A very remarkable branch, which appears to me to be constant, viz., the deltoid, passes transversely in front of the humerus, beneath the coraco-brachialis and the biceps, and terminates partly in the deltoid at its humeral insertion, and partly in the brachialis anticus. The internal and posterior branches are small, excepting those which enter the brachialis anticus directly : I have seen them all arise from the axillary by a large branch given off from a common trunk with the sub-scapular and the posterior circumflex arteries. Whatever may be their mode of origin, four of these collateral branches are remark- able for their regular distribution, viz., the deep humeral, the internal collateral, the super- ficial branch for the internal portion of the triceps, and the superficial branch for the brachi- alis anticus. The two former only have received particular names. The deep humeral artery {profunda superior, k, fig. 210), called aJso the external collateral, from its terminating on the outer side of the articulation of the elbow, arises from the brachial, opposite the lower border of the teres major. It occasionally comes off by a common trunk with the posterior circumflex, which, in that case, arises from the brachial instead of the axillary artery. It passes downward and backward, gains the groove for the musculo-spiral nerve, and traverses the whole extent of that groove to- gether with the nerve. In this part of its course it is situated between the triceps mus- cle and the humerus, as it turns round the posterior surface of that bone ; below the in- sertion of the deltoid it emerges from the groove, between the brachialis anticus and the triceps, and divides into a deep branch, which continues with the nerve, and a superficial branch. The former is distributed essentially to the triceps muscle, and sometimes comes off directly from the brachied ; it passes vertically downward in the substance of the triceps, supplies its internal and external portions, and terminates in them by anastomosing freely with the collateral branches situated around the elbow-joint. The superficial branch perforates the external head of the triceps, and the external inter-mus- cular septum, along which it descends vertically to the back of the epicondyle, or external condyle of the humerus, where it anastomoses with the interosseous recurrent artery. The internal or ulnar collateral artery {profunda inferior, m, figs. 210, 211) is much smaller than the external collateral, from which it is sometimes derived ; it is often double. It usually arises at a variable height from the lower part of the brachial, some- times passes transversely inward, and sometimes proceeds in a tortuous manner down- ward before becoming transverse, and then divides into two branches : one anterior, which is distributed to the brachialis anticus, the muscles attached to the epitrochlea or internal condyle of the humerus, and the periosteum upon that process ; the other posterior, which perforates the internal intermuscular septum, and divides into muscular branches for the * Dubreuil has seen that arrangement in three cases ; and M. Chassignac has met with it twice last winter. t I have seen this artery lacerated in a case of luxation forward of the humerus on the forearm, in conse- quence of a fall from a horse upon the wrist. The lower extremity of the humerus had torn the brachialis anticus, the artery and the skin through which it had passed. A hemorrhage, followed by syncope, took place at the moment of the accident. The patient having been carried to her residence in this swoon, the reduction was accomjdished, the hemorrhage did not return, and the cure was as perfect as possible. THE BRACHIAL AATEEY. 545 triceps ; into periosteal and osseous branches, which pass transversely in front of the triceps, and anastomose with the interosseous recurrent ; and into a descending branch, which accompanies the ulnar nerve, and anastomoses with the posterior ulnar recurrent. The superficial branch for the internal portion of the triceps is remarkable for its size and length ; it arises from the brachial, inunediately below the profunda superior, from which also it is rather frequently derived, and passes vertically downward applied to the idnar nerve. It is at first situated in front of the internal intermuscular septum, then perfo- rates it, accompanied by the idnar nerve, and, passing backward between the epitrochlea and the olecranon, aneistomoses with the posterior ulnar recurrent. The superficial branch for the braehialis anticus arises from the brachial artery at the same height as the preceding, runs along the inner side of the braehialis anticus, grad- ually diminishing in size down to the lower part of the arm, where it anastomoses with the internal collateral artery.* The terminal branches of the brachial are the radial (jp,figs. 210, 211) and ulnar (g) ar- teries. The bifurcation of the brachial artery into the radial and ulnar usually takes place below the bend of the elbow, sometimes on a level with it, but rather frequently above the articular line ; in the latter case, the bifurcation has been observed to occur sometimes at the lower third or at the middle of the arm, sometimes at the junction of the upper with the two lower thirds, and sometimes in the axilla itself, the radial and ulnar arteries immediately succeeding to the axillary. In these cases, one division of the artery, generally the radial, is sub-cutaneous, while the ulnar assumes the ordinary relations of the brachial ; but the reverse of this may take place ; and, lastly, the radial and the ulnar have both been found sub-cutaneous. Not unfrequently, the radial artery, at its origin, is the inner branch of the bifurcation, and then crosses the ulnar at a very acute angle, in order to reach the radius. Besides these anomalies resulting from va- rieties in the point of bifurcation, there is yet another, in which a premature division takes place into two branches, one of which forms the interosseous artery, and the other the brachial, which has its usual arrangements ; at other times, instead of a bifurcation, only a very slender branch is given off, and terminates in the ulnar, which in that case arises by two roots. The frequency of high divisions of the humeral artery require that the practical con- siderations to which these give rise should be taught. If, therefore, a hemorrhage by the arteries of the forearm should not yield to a ligature of the humeral artery, we should, with M. Danyau, suspect the high division of the humeral artery, and search for the other branch. Here follows the minute description of three rare varieties which I have exhibited at the Anatomical Society. From the inferior part of the axillary artery arose a slender ar- tery, which first coursed all along the humeral artery, on the inside of which it was situ- ated ; it then crossed this vessel by passing before it at the union of the two superior with the inferior third of the arm, and finally joined the radial artery opposite the bicipital tu- berosity of the radius. At the bend of the elbow, this artery, which might be considered as a slender branch of origin of the radial artery, occupied the same relations as the humeral artery, and was situated below the aponeurotic expansion of the biceps, while the trunk of the hu- meral artery was not placed under this expansion, but below the tendon of the biceps. It was behind this tendon, a little above its insertion into the radius, that the humeral artery was divided into radial and ulnar ; the radial, instead of coursing directly down- ward, described a curve with the concavity inward ; and it was with the lower part of this curve that the long and feeble branch coming from the axillary artery united. I have met, again, a similar anomaly, with this difference, that the long and slender arterial branch, instead of going to the radial, anastomosed with the ulnar. This variety may be considered as a mode of anastomosis between the upper and the lower part of an arterial trunk, a mode of anastomosis by a collateral canal, unusual in the arterial, but very frequent in the venous system. In a case where one of the branches of the high division was the interosseous artery, and the other the common trunk of the radial and ulnar arteries, the respective relations of these vessels were as follows : The humeral dichotomic division took place below the hollow of the axilla. One of the branches was the common trunk of the interosseous arteries, which first followed the usual course of the humeral artery, then crossed, at a very acute angle, the other branch by passing behind it, coursed obliquely downward and outward, and finally reach- ed the external border of the tendon of the biceps. Having been sub-aponeurotic so far, it now dipped under the pronator teres, gave off the radial and ulnar recurrent branches. iQd terminated as the interosseous arteries terminate. ITie other branch constituted the common trunk of the radial and cubital arteries ; * [These two superficial braaches are frequently represented in their distributioo by a sing-le branch, nailed the anastomotic artery (u,figs. 210, 211), which arises from the brachial, about two inches above the elbow. The nutritious artery of the humerus is small, but constant : it as-ises from the outer side of the brachial, or one of its collateral branches, passes downward, perforates the insertion of the coraco-lwachialis muscle, and enters the oblique foramen in the inner side of the humerus, to ramify in the aicduilary c«nal of that bone 1 Z 2 Z 546 AN6EI0L06T. sub- aponeurotic, like the preceding, it reached the anterior side of the epitrochlea, and divided into two secondary branches : one internal, which was the ulnar, a little tortu- ous, coursed downward as far as the annular carpal ligament ; the other external, which was the radial, passed obliquely downward and outward as far as the radial insertion of the pronator teres, when it became vertical. During their whole course, the radial and ulnar arteries were sub-aponeurotic. I have been on the point of opening the radial artery at the bend of the arm, in a case where it lay over the superficial tendon of the biceps.* A knowledge of these anomahes, both in reference to the point of bifurcation and to the new relations of the parts, is extremely important to the surgeon. The Radial Artery and its Branches. Dissection. — The radial artery in the forearm is completely exposed by dissecting the supinator longus ; the carpal portion of the artery by dissecting the tendons of the thumb opposite the vnrist ; the palmar portion by dividing all the flexor tendons in the palm. It is, therefore, advisable to postpone the examination of the palmar portion of the artery until the ulnar has been studied. The raAial artery (j),figs. 210, 211), the outer of the two branches into which the brach ial divides, is more superficial and smaller than the ulnar ; it extends from the point of bifurcation of the brachial down to the peilm of the hand. Sometimes the radial turns backward, after having reached the lower third of the forearm, and remains sub-cutane- ous until it dips between the first and second metacarpal bones ; its place in front of the lower part of the radius is then supplied by the radio-palmar artery or superficialis volaj, which is extremely small. It is very common to find the radial artery of one arm larger than that of the other ; in one case I found both radials wanting in front of the lower part of the radius. Tlie radial artery is at first directed downward, and somewhat obliquely outward, like the brachial, with the direction of which it corresponds ; it then descends vertically as far as the lower end of the radius, turns round the anterior surface and apex of the sty- loid process, to gain the outer side of the carpus, and passes obliquely downward and backward, to reach the upper part of the first interosseous space ; there it turns abrupt- ly forward, between the upper extremities of the first and second metacarpal bones, passing between the two origins of the first dorsal interosseous muscle, enters the palm of the hand, and runs almost transversely inward, to form the deep palmar arch {b, Jig. 211). The radial artery is frequently tortuous at the lower part of the forearm. From the long course and the direction of the radied, it may be divided into three portions, corresponding to the forearm, the wrist, and the palm of the hand. The first jiortion of the radial artery, viz., that situated in the forearm, has the following re- lations : In front, with the inner border of the supinator longus, which overlaps it, especial- ly above ; in the rest of its extent it lies beneath the fascia. In emaciated subjects the su- pinator longus is narrow, and this part of the artery is sub-aponeurotic in its whole extent. Behind, it corresponds to the anterior surface of the radius, from which it is separated above by the supinator brevis ; lower down by the pronator teres, and by the radial ori- gins of the flexor sublimis and flexor longus poUicis ; still lower by the pronator quadra- tus, below which it rests directly upon the inferior portion of the radius. The superficial position of the radial artery, and the support afforded it by the bone, are the reasons why it is chosen for examining the pulse. On the inner side, it is in relation with the pronator teres, then with the tendon of the flexor carpi radialis, along which it runs, and which is on a plane anterior to it ; so that the contraction of this muscle, by causing its tendon to project, renders the pulsations of the vessel more difficult to be felt. On the outer side, it is in relation with the supinator longus, and in the middle part of its course with the radial nerve (the continuation of the musculo-spiral), which is situ- ated at some distance from it, both above and below, and has a separate fibrous sheath. Of the collateral branches of the radial artery in the forearm, only three require a special description, viz., the anterior radial recurrent, the anterior carpal branch, and the radio- palmar artery. The anterior radial recurrent artery {r,figs. 210, 211) is given off from the back part, and immediately below the origin of the radial. It is very large in some subjects, in- deed as large as the radial itself : it descends a little, and then turning upward, so as to describe a curve with its convexity directed downward, it ascends between the supina- tor longus and the brachialis anticus, in order to anastomose with that part of the pro- * The editor, engaged as he has been, for thirty years, in teaching anatomy, has had very extensive oppor- tunities of observing varieties in the origins of the radial and ulnar arteries ; and as the result of these, he would state as a general rule, liable to very few exceptions, 1st. When the radial arises prematurely, it pass- es, like the humeral, under the aponeurotic expansion of the biceps muscle. 2d. When the ulnar arises above the elbow, it passes superficially above this aponeurosis, being placed sub- cutaneous in connexion with th« veins. The editor believes, that in the majority of cases where an artery is wounded in performing the operation of jloodletting at the bend of the arm, the vessel injured is the ulnar, which has arisen prematurely. In several cases where he has been called on to operate for aneurism produced by this accident, he has found this to he the case. THE RADIAL ARTERY. 549 fimda superior which forms the external collateral branch of the elbow. I have seen this recurrent artery arise from the ulnar. From the convexity of the arch described by the radial recurrent, a great number of branches proceed obliquely downward and outward, and are distributed to all the raus cles on the external aspect of the forearm, viz., the long and short supinators, and the two radial extensors. One of these branches passes transversely between the long supi- nator and the long radial extensor, to anastomose on the outer condyle with the profun- da artery ; others pass between the radius and the muscles attached to it, ramifying in the extensor muscles of the forearm, and anastomose with the posterior interosseous artery derived from the ulnar. The anterior carpal branch of the radial artery is a small branch {a, fig. 211) which passes transversely inward at the lower margin of the pronator quadratus muscle, and anastomoses with a similar branch from the ulnar artery. The radio-palmar or superficial palmar artery {superficialis voIcf,, s, fig. 210) arises at an acute angle from the inner side of the radial, at the point where that vessel turns out- ward to pass over the carpus. Sometimes its origin is situated at the junction of the lower with the two upper thirds of the forearm. It varies much in its size and distribu- tion ; most commonly it passes vertically downward, on a level with the anterior liga- ment of the carpus, perforates the origin of the short abductor of the thumb, and anasto- moses with the extremity of the superficial palmar arch {t) of the ulnar (g). Several branches arise from its convexity, and are distributed to the muscles and integuments of the ball of the thumb. The radio-palmar branch is frequently very small, is entirely lost in those muscles, and does not assist in the formation of the superficial palmar arch. On the contrary, it is often so large that it may be regarded as formed by the bifurcation of the radial, and then assists as much as the ulnar in forming the superficial palmar arch. In some cases in which the superficial palmar arch did not exist, I have seen the radio-palmar give origin to the internal collateral artery of the thumb, both collateral ar- teries of the index, and the external collateral of the middle finger, the ulnar artery fur- nishing the collaterals of the other fingers. In one case, a transverse branch, resembling the anterior communicating artery of the brain, formed the anastomosis between the ra- dio-palmar and the ulnar arteries. The second or carpal portion of the radial artery extends from the styloid process of the radius to the upper part of the first interosseous space. Closely applied to the ligaments and bones of the carpus, it passes at first obliquely downward and inward, and then be- comes vertical as it dips into the interosseous space, to pass between the two heads of the first dorsal interosseous muscle. It is well protected on the outer side of the carpus by the projecting tendons of the two extensors and the long abductor of the thumb, edl of which cross it obliquely, and separate it from the skin ; but between the tendons of the long abductor of the thumb and the long radial extensor it becomes sub-aponeurotic, and therefore very superficial. In this short course it gives off several branches. The dorsal carpal branch of the radial artery, more remarkable for its constancy and the mode of its distribution than for its size, which is inconsiderable, arises opposite the articulation of the two rows of carpal bones, passes transversely inward, and terminates either by being lost in the adjacent parts, or by anastomosing with the corresponding branch of the ulnar artery. From the arch thus formed proceed certain ascending branch- es, which anastomose with twigs from the anterior interosseous artery, sometimes ap- pearing to form the termination of that vessel, which, as we shall presently describe, be- comes posterior at the lower part of the forearm ; and also some descending branches, of very variable size, which, having reached the upper part of the third and fourth interos- seous spaces in peirticular, anastomose with the perforating branches of the deep palmar arch, and form ope of the origins of the small twigs, which are named the dorsal interos- seous arteries of those spaces. The dorsal interosseous branch for the second space, known also as the dorsal metacarpal branch of the radial artery, is sometimes so large that it seems to be a continuation of the radial, and at other times very small, and, as it were, a mere vestige. It often ari- ses by a common trunk with the dorsal carpal branch just described ; it runs along the dorsal surface of the second interosseous space, and, having reached the lower part of it, gives superficial dorsal arteries to the index and middle fingers, and then bends for ward between the heads of the second and third metacarpal bones, to anastomose witli that digital branch of the superficial palmar arch which gives off the internal collateral artery of the index, and the external collateral artery of the middle finger.* The interosseous artery of the first space is so large that it is described as formed by the bifurcation of the radial : it arises from that artery between the first and second meta- carpal bonesj and sometimes runs along the dorsal aspect of the first interosseous space, and at others between the first dorsal interosseous muscle and the adductor poUicis ; in * [Three small branches, two of which usually arise by a common trunk, are given off from the radial ar- tery near the dorsal aspect of the head of the first metacarpal bone ; two of them form the superficial dorsal arteries of the two sides of the thumb {dorsales pollids), while the other is the dorsal artery of the radial side •f the indtx finger {dorsahs indicis).'i $4^ AN6ET0LO6Y. «ther case, when it reaches the lower part of the space, it divides into two branches, which may arise separately from the carpal portion of the radial artery, as in^^. 211, and which constitute the internal collateral artery of the thumb and the external collateral artery of the index finger (x). The external collateral artery of the thumb, sometimes deri- ved from the preceding, or even from the extremity of the superficial palmar arch, cross- es the muscles of the ball of the thumb obliquely, to reach the outer side of its metacar- po-phalangal articulation (v,fig. 210), and runs along the outer border of the thumb.* The Deep Palmar Arch. The third or 'palmar portion of the radial artery constitutes the dee'p palmar arch (i, fig. 211), which is completed by inosculating with a branch of the ulnar, in the same man- ner as we have seen the superficial palmar arch of the ulnar artery completed by a branch of the radial. This arch is situated deeply across the front of the metacarpal bones, im- mediately below their upper extremities ; it rests immediately upon them and the inter- osseous muscles, and is therefore subjacent to all the nerves, tendons, and muscles (ex- cept the interosseous) in the palm of the hand. The deep palmar arch describes a slight curve, the convexity of which is directed downward. I have seen the palmar arch form- ed by the dorsal artery of the second interosseous space, which then dipped between the upper ends of the second and third metacarpal bones. The deep palmar arch gives off very short superior or ascending branches {recurrentes), which are lost in front of the carpus, anastomosing with the anterior carpal branches of the radial and ulnar arteries ; also some descending or palmar interosseous arteries (d d, interosseae volares, Holler), three or four in number, which descend vertically along the interosseous spaces, and anastomose with the descending digital branches (cut across in fig. 211) of the superficial palmar arch, either opposite or above their bifurcation into the collateral arteries of the fingers. The size of the palmar interosseous arteries is ex- tremely variable, as well as that of the deep palmar arch itself; it bears an inverse pro- portion to that of the superficial palmar arch and its branches. The relative size of the difierent palmar interosseous arteries, also, varies much ; most generally the first is the largest, at other times the second, and occasionally the third. The deep palmar arch also gives off the posterior or perforating branches (c c). These are three in number, and form for the second, third, and fourth interosseous spaces what the radial itself is for the first, with this difference, that the radial perforates the first space from behind forward, while these perforating branches traverse the corresponding spaces from before backward. They arise from behind the deep palmar arch, and imme- diately perforate the upper part of the interosseous spaces in a straight line, and having reached the dorsal aspect of the hand, generally anastomose with the corresponding dor- sal interosseous arteries, which, in a great number of cases, are formed entirely by these perforating branches. In some subjects, the dorsal interosseous arteries result from the anastomoses of the perforating arteries with the interosseous arteries derived from the dorsal carpal arch formed by the dorsal carpal branches of the radial and ulnar arteries ; they pass vertically downward on the dorsal surface of the interosseous spaces, and hav- ing reached their lower parts, anastomose with the descending digital branches of the superficial palmar arch, and thus assist in the formation of the collateral arteries of thp fingers. The Ulnar Artery and its Branches. The ulnar artery {g,figs. 210, 211), which is larger than the radial, leaves that vessel at a very acute angle, passes at first downward, inward, and backward, in front of the ulna, describing a slight curve, the convexity of which is directed upward and inward, and then descends vertically. Having arrived at the wrist, it is placed on the outer or radi- al side of the pisiform bone, in front of the annular ligament of the carpus, and then enters the pahn of the hand,'where it describes beneath the palmar fascia an arch, which has its convexity turned downward, and is named the superficial palmar arch {t,fig. 210 ; removed in^^. 211). The relations of the ulnar artery must be separately examined in the forearm and in the hand. In the forearm, it is at first covered by the thick bundle of muscles which are attached to the inner condyle of the humerus, and also by the median nerve, from which it is sep- arated by that part of the pronator teres which arises from the coronoid process ; it is then covered by the flexor sublimis, and finally by the fascia and skin ; the tendon of the flexor carpi ulnaris is upon its inner side, and that of the flexor sublimis on its outer : these two tendons, by their projection, occasion an interval between the artery and the skin. It is in relation behind with the brachialis anticus, the flexor profundus digitorum, and the pronator quadratus. The ulnar nerve is applied to the inner side of the artery * [The two collateral arteries of the thumb, and the external collateral of the index finger, frequently arise in a different manner from that described above : thus, the two arteries for the thumb may take origin from a common trunk, which is then named the great or principal artery of the thumb (magna vel princeps pollicis) , while the artery for the index finger arises separately, and is named the radial collateral artery of the index Unger (radialis indicis).1 THE ULNAR ARTERY. mi I!^. 211. at the point where the vessel becomes vertical, and accompanies it as far as the hand. The median nerve is situated on its inner side at the bend of the elbow, but afterward becomes anterior, and then external to it. In some cases of high division of the humeral artery, the ulnar has been found immediately under the fascia in its whole length. In the hand, it is at first situated on the outer or radial side of the pisiform bone, and then in front of the hook-like process of the unci- form bone ; finally, where it forms the superficial palmar arch, it is entirely sub-aponeurotic. In the forearm, the ulnar artery gives off a great number of un- named collateral branches, which are divided into internal, external, anterior, and posterior, and are distributed to the muscles and integ- uments. Four branches, however, require special notice, viz., in the forearm, the common trunk of the ulnar recurrents, the interosseous artery, the branch for the median nerve, and the anterior artery of the carpus; in the palm of the hand, the ulnar artery gives off the collet- erai arteries of the fingers. The anterior arid posterior ulnar recurrent arteries generally arise by a common trunk, which is given off from the back of the highest portion of the ulnar artery, passes transversely inward, and divides into two branches — an anterior and a posterior. The former, or an- terior ulnar recurrent artery {e,fig. 211), passes between the brachialis anticus and pronator teres, gives branches to all the muscles attach- ed to the inner condyle, and anastomoses with the internal collateral branch from the brachial. The other branch, the posterior ulnar re- current, is larger than the anterior, runs behind the muscles arising from the inner condyle, is then situated between that condyle and the olecranon, passes between the two origins of the flexor carpi ulnaris in front of the ulnar nerve, anastomoses freely with the in- ternal collateral branch of the brachial artery and with the interosseous recurrent, and contributes to form an arterial network upon the back of the elbow-joint. The branch given off by the posterior ulnar recurrent to the ulnar nerve deserves to be pointed out ; it may be traced from below upward, along that nerve, and anastomoses with the other branches given off to the same nerve from the brachial artery. The interosseous artery is so large that it appears to be the result of a bifurcation of the ulnar, and is described as such by many anatomists ; it comes off from the back of the ulnar, immediately below the trunk of the recurrents, on a level with the bicipital tuber- osity of the radius ; it not unfrequently arises from the radial. Lastly, in several cases of high division, either of the brachial or of the axillary artery, the interosseous has been found to constitute one of the branches of the bifurcation, the other branch being the common trunk of the radial and ulnar arteries. Immediately after its origin, the interosseous passes directly backward, and divides into two branches of almost equal size, which are named, from their distribution, the an- terior and posterior interosseous. The anterior interosseous if fig- 211) descends vertically in front of the interosseous ligament, and is held down to it by a layer of fibrous tissue ;* it is placed behind the flexor profundus digitorum and the flexor longus pollicis, in the cellular interval between these muscles. Having reached the upper borders of the pronator quadratus, it passes between that muscle and the interosseous ligament, rests upon the latter, and perforates it towards its lower part ; having thus reached the back of the forearm, the anterior in- terosseous descends upon the dorsal surface of the carpus, and terminates by anastomo- sing with the dorsal carpal branches of the radial and ulnar. While perforating the in- terosseous ligament behind the pronator quadratus, the artery almost always gives off a small twig, which descends perpendicularly to join the arch formed by the anterior ar- teries of the carpus. In one case where the radial artery was exceedingly small, indeed in a rudimentary state, its place was supplied by the anterior interosseous ; which, after having passed behind the pronator quadratus, escaped forward under the lower border of that muscle, and passed transversely outward, to anastomose with the rudimentary radial artery, which, thus re-enforced, immediately assumed its usual size. During its course, the interosseous artery only gives off some small branches to the front of the forearm, among which the artery of the median nerve deserves special notice ; but several large branches are detached in succession from its posterior aspect, and im- mediately perforate the interosseous ligament : they are called the perforating arteries of the forearm, and are distributed to the deep layer of muscles on the back of the forearna. I have seen one of these run along the posterior surface of the interosseous ligament, in the same manner as the anterior interosseous artery. * After amputation of the forearm, the interosseous artery becomes retracted between thi« fibrous layer and the interosseous ligament ; and it is hence so difficult in some cases to place a ligature upon it, that it haa been recommended to divide the inte"-=«^"~ '■ -•nent for a short distance. ANGEIOLOGY. The artery of the median nerve is remarkable for its constancy and its length ; it comes , off from the front of the anterior interosseous artery, reaches the posterior surface of the median nerve, penetrates it, and then runs downward along its inner side. I have seen the artery of the median nerve very large, and anast9mosing with the superficial pahnar ar<3h. It has also been found continuous with the brachial artery, and supplying the place of both the radial and ulnar, which were in a rudimentary state. The posterior interosseous artery is generally smaller than the anterior ; it perforates the interosseous ligament opposite the lower border of the supinator brevis, and imme- diately gives off an ascending branch, the interosseous recurrent ; it then descends be- tween the deep and superficial layer of muscles on the back of the forearm, and divides into a number of branches, which are distributed to those muscles, but especially to the superficial layer.* The interosseous recurrent is a branch of the posterior interosseous, of such size that it may be regarded as resulting from the bifurcation of that artery : it passes vertically up- ward, having the anconeous and the extensor carpi ulnaris behind it, and the supinator brevis in front of it ; it runs behind the inner condyle, and anastomoses on the outer side of the elbow-joint with the cutaneous, muscular, and periosteal divisions of the superior profunda artery, the external collateral branch of the brachial The anterior carpal branch of the ulnar artery is a small twig, which arises opposite the lower borders of the pronator quadratus, passes between the tendon of the flexor carpi ulnaris and the ulna, and anastomoses with a similar branch from the radial, to form the anterior carpal arch, from which several branches descend to reach the interosseous muscles, and those of the ball of the thumb - The Superficial Palmar Arch. Opposite the articulation between the two rows of carpal bones, and before it forms the superficial palmar arch, the ulnar artery gives off a deep branch backward, called the radio-cubital, or communicating artery {y,fig- 210), which dips between the short abduc- tor and short flexor of the little finger, then passes outward between the short flexor and opponens, to anastomose with and complete the deep palmar arch. This artery is some- times so large that it may be regarded as formed by the bifurcation of the ulnar The superficial palmar arch (t,fig. 210), which constitutes the termination of the ulnar, gives off no important branch from its upper or concave side. Four or five diverging digi- tal branches pass from its lower or convex side, and constitute the collateral arteries ol the fingers. The digital branches (w u u) are distinguished as the first, second, third, and fourth, proceeding from within outward. The first reaches the inner or ulnar border of the lit- tle finger, and constitutes its internal collateral artery ; the second runs along the fourth interosseous space, and divides into the external collateral artery of the little finger, and the internal collateral artery of the ring finger ; the third runs along the third interosseous space, and supplies the external collateral artery of the ring finger and the internal collateral artery of the middle finger ; the fourth runs in the second interosseous space, and gives the ex- ternal collateral artery of the middle finger and the internal collateral artery of the index fin- ger. It is very rare to find the external collateral artery of the index finger (x), and the internal collateral of the thumb derived from the superficial palmar arch ; and still more rare to see the external collateral artery of the thumb (r) given off by that arch. Whatever varieties there may be in the arteries of the palm of the hand,J in reference to the share which the radial and ulnar respectively take in the formation of the collat- eral arteries of the fingers, the following general facts are apparent in their distribution : The size of the superficial and deep palmar arches respectively are always inversely pro- portioned to each other ; the communication between the two arches takes place not only directly between the arches themselves, but also indirectly in a great number of points by their branches ; all the descending branches of the deep palmar arch anasto- mose with the angle of bifurcation of the descending branches of the superficial palmar arch : those from the deep arch are sometimes smaller, sometimes larger than those * Some branches may oe traced as far aa the carpus. t [There are usually two other branches given from the ulnar in the vrrist : the first is a dorsal metacarpal branch, which arises above the anterior carpal, runs under the tendon of the flexor ulnaris, turns round the ulna to reach the back of the carpus, anastomoses with the dorsal metacarpal branch of the radial, and sends a twig along the fifth metacarpal bone, to form the superficial dorsal artery of the little finger. The second branch of the ulnar in this situation may arise with the one just described ; it is a posterior or dorsal carpal branch, which passes backward, and anastomoses beneath the extensor tendons with the dorsal carpal branch of the radial artery.] i In one case the superficial palmar arch was formed in the most regular manner by the radial and the ul- nar arteries, which concurred in its formation by two perfectly equal trunks, and gave off the collateral branch- es to all the fingers except the external collateral of the thumb, the internal collateral of the index, and the external collateral of the middle finger. The deep palmar arch, very small in comparison with the superficial palmar arch, which was very consider- able, was formed as usual. It gave off the external collateral of the thumb and the common trunk of the in- ternal collateral of the index, and the external collateral of the middle finger. This common trunk was the continuation of the non-flexed portion of the radial artery. The radial artery in this case was much larger than the ulnar. REMARKS ON THE ARTERIES OF THE UPPER EXTREMITY. 551 trom the superficial arch ; they are rarely of the same size, but always bear an inverse ratio to them ; the bifurcation of each digital branch of the superficial pahnar arch takes place two or three lines below the metacarpo-phalangal articulation, opposite the junc- tion of the body with the upper end of the first phalanx ; the collateral arteries of the fingers are situated upon the anterior aspect of the phalanges, on each side of the sheath of the flexor tendons ; they give off dorsal and palmar branches, and anastomose with each other in front of the body of the phalanges by small transverse branches ; having reached the middle of the last phalanx, they anastomose in an arch, from the convexity of which a great number of anterior branches pass to the skin, over the last phalanx, and some dorsal branches to the matrix of the nail ; one of these branches runs along the curved adherent border of the nail. The termination of the superficial palmar arch is subject to variety: thus, it terminates either by anastomosing with the radio-palmar or superficialis volae, of the same size as itself, or by receiving a very small radio-palmar branch, and being prolonged so as to con- stitute the common trunk of the internal collateral artery of the thumb, and the external collateral artery of the index finger ; or else it terminates in the external collateral of that finger ; or, lastly, after having given off the internal collateral of the thumb and the external collateral of the fore-finger, it ends in the external collateral of the thumb. At other times, again, there is no superficial palmar arch properly so called, and the ulnar artery terminates by furnishing the collaterals of the little and ring fingers, and the in- ternal collateral of the middle finger, the other collaterals being derived from the radio- palmar, which is then very large. In certain cases, a very small transverse branch forms the communication between the radial and the ulnar arteries. General Remarks on the Arteries of the Upper Extremity. A single trunk, which may be called the brachial trunk, supplies the whole of the up- per extremity ; it forms, in succession, the sub-clavian, the axillary, and the brachial ar- tery, which latter bifurcates near the bend of the elbow into the radial and ulnar arteries : these form the palmar arteries, from which the arteries of the fingers take their origin. The difference in the origin of the right and left brachial trunks has been considered to account for the difference in strength between the two arms ; and the different size of the two vessels has also been supposed to be connected with the same fact, which, however, in reality, depends upon the more frequent exercise of the right than of the left arm. The brachial trunk is not exclusively distributed to the upper extremity, but supplies the most dissimilar parts ; a fact which shows that the conditions of origin, which have so great an influence in regard to nerves, are altogether without importance in reference to the arteries. Thus, the brachial trunk sends branches to the following parts : the ver- tebral artery to the brain, the cerebellum, the pons varolii, the medulla oblongata, and the spinal cord ; the inferior thyroid artery, to the thyroid gland, the larynx, the trachea, the oesophagus, and sometimes the bronchi ; the internal mammary and thoracic arteries, to the corresponding manrnia ; and the same arteries, together with the superior inter- costal, to the parietes of the thorax and abdomen ; the ascending cervical, to the praever- tebral muscles and the spine ; and, lastly, the deep cervical, sub-scapular, and posterior scapular arteries, to the superficial and deep muscles of the back of the neck. Setting aside those branches which do not belong to the upper extremity properly so c^ed, we find that, during its course along the limb, the artery always occupies the as- pect of flexion, which is at the same time the position where it can be best protected ; and that, for this purpose, it is directed from the axilla to the bend of the elbow : we find, also, that it gives off a great number of anastomotic branches around the articula- tions, and thus establishes a collateral circulation, through which the blood can pass when the principal artery is obliterated. This anastomosis, and, consequently, the col- lateral circulation, is effected by the cutaneous, muscular, and periosteal branches, and even by those distributed to the nerves. Thus, along the clavicle, we find the acromio- thoracic in front, and the supra-scapular or transversus humeri behind ; around the scap- ula there are the supra-scapular on the upper border, the posterior scapular on the ver- tebral border, and the sub-scapular on the axillary border ; so that that bone is complete- ly surrounded by an anastomotictriangle. Around the elbow-joint are the external and internal collateral branches of the brach- ial artery, and the radial, ulnar, and interosseous recurrents. Around the wrist we find the anterior and posterior carpal arteries, and also anasto- motic arches around the metacarpo-phalangal and phalangal articulations. On comparing the size and number of the arteries of the arm and forearm with the size and number of the arteries of the hand, it will be seen that the latter has greatly the advantage : indeed, in this part of the body, there is an unusual distribution of the arterial system into a deep and a superficial set of vessels, precisely as is the case with the veins. Why is this \ Is it not extremely probable that, as the deep veins are in- tended to supply the place of the superficial, when the circulation in the latter is for a time impeded, so in the hand the arteries are arranged in a similar manner, because the bS2 ANGEIOLOGY. superficial circulation is liable to be interrupted by pressure from grasping hard bodies firmly in the hand for a longer or shorter period 1 and is it not for the same reason that the superficial system derived from the ulnar artery has so many communications with the deep system given off from the radial 1 It is virorthy of remark that the radial, which is the superficial eirtery of the forearm, becomes deep-seated in the hand ; and that the ulnar, which is deep-seated in the fore- arm, becomes superficial in the hand. The great quantity of blood circulated through the hand is connected with the active use of that part, in the ahnost constant exercise of the sense of touch, and in prehension ARTERIES ARISING FROM THE TERMINATION OF THE AORTA Enumeration. — The Middle Sacral. — The Common Iliacs. — The Internal Iliac, or Hypogas- tric — the Umbilical — the Vesical — the Middle Hemorrhoidal — the Uterine — the Vaginal — the Obturator — the Uio-lumbar — the Lateral Sacral — the Glutceal — the Sciatic — the Inter- nal Pudic. — Summary of the Distribution of the Internal Iliac. — Artery of the Lower Ex- tremity. — The External Iliac — the Epigastric — the Circumflex Iliac. — The Femoral — the Superficial Epigastric — the External Pudic — the Muscular — the Deep Femoral, its Cir- cumflex and Perforating Branches. — The Popliteal and its Collateral Branches. — The An- terior Tibial and the Dorsal Artery of the Foot. — The Tibio-peroneal — Peroneal — Poste- rior Tibial, and the Internal and External Plantar. — Comparison between the Arteries of the Upper and Lower Extremities. The arteries arising from the termination of the aorta are the middle sacral and the two common iliac arteries. The Middle Sacral Artery. The middle or anterior sacral artery {n,fig. 199), the small median artery of the sacrum, arises from the lower and back part of the aorta, a little above its termination. Like the aorta, it is a single vessel, and seems to be the continuation of it, as far as direction is concerned ; which, indeed, is really the case in such animals as are provided with a tail. Sometimes, but rarely, it arises from the left common iliac, or the last lumbar ar- tery. I have seen it arise by a common trunk with the two lower lumbar arteries.* It passes vertically downward in front of the fifth lumbar vertebra, the sacrum and the coccyx being closely applied to them all. It is situated in the median line at its origin, but sometimes deviates to one side or the other. In size it is scarcely equal to one of the lumbar arteries, and it gradually diminishes from its origin to the first bone of the coccyx, towards the apex of which it terminates in a very variable manner. The size of the middle sacral is generally inversely proportioned to that of the lowest lumbar arteries. When the aorta divides higher than ordinarily, and the last lumbar is given off from the middle sacral, the last-named artery is of course unusually large. During its course, the middle sacral gives off, opposite the fifth lumbar and each of the sacral vertebrae, a right and left lateral branch, which correspond with the series of intercostal and lumbar arteries. The two lumbar branches are generally small, but are very large when the fifth lumbar arteries are neither furnished by the aorta, nor by the fourth lumbar, nor by the ilio-lumbar. The lateral branches given off upon the sacrum pass transversely outward, supply twigs to the periosteum and bone, and anastomose with the lateral sacral, the place of which they sometimes supply within the interior of the sacral canal. The middle sacral having become very slender near the base of the coccyx, bifurcates in order to form an anastomotic arch with the right and left lateral sacral arteries. I have seen its lower end divided into three branches, of which the median was prolonged as far as the tip of the coccyx, while the lateral branches anastomosed with the lateral sacral arteries. The Common Iliac Aeteeies. The primitive or common iliac arteries (i i, figs. 199, 212), the two branches into which the aorta subdivides, commence opposite the lower margin of the fourth lumbar vertebra, and terminate by bifurcating opposite the base of the sacrum ; they separate from each other at an acute angle, pass obliquely downward and outward, and form the two sides of an isosceles triangle, the base of which corresponds with the transverse diameter of the fifth lumbar vertebra. These arteries are generally straight, but not unfrequently they are tortuous in aged persons. In the adult they are about two inches long, the right being rather longer than the left, from the position of the aorta ; but they are often much shorter, on account of their bifurcating higher than usual. Meckel has remarked that this premature bifurcation is more common on the left than on the right side. In a specimen deposited in the museum of the Ecole de Medecine, the right common iliac * 1 have geen the middle sacral artery arise from the renal artery. In this case, the renal artery came frtau the angle of bifurcation of tke aorta. THE INTERNAL ILIAC ARTERY. 553 is entirely wanting ; the aorta dividing into three branches, two on the right, viz., the in- ternal and external iliacs, and one on the left, viz., the common iliac, which is distributed in the usual manner. In this case the descending aorta resembled, to a certain extent, the ascending aorta, and, like it, gave off three trunks Relations. — They are covered by, and loosely connected with, the peritoneum ; they are crossed by the ureters and the spermatic vessels, besides which, the left common il- iac is crossed by the inferior mesenteric artery ; they are surrounded by a great number of lymphatic glands, and rest above upon the vertebral column, and on the outside and below upon the inner side of the psoas muscle. It is of great importance to comprehend their relations with the common iliac veins. The veins are situated behind the arteries ; but as the right and left vein unite on the right side of the vertebral column, the left common iliac vein comes into relation with both common iliac arteries. The common iliac artery gives off no collateral branch ; it merely supplies some twigs to the cellular tissue, the lymphatic glands, and the coats of the common iliac veins. It occasionally gives off one of the renal arteries ; and it has been seen to supply the sper- matic and the ilio-lumbar arteries. Terminal Branches. — The common iliac artery terminates by dividing into two branch- es, which remain in contact with each other for a short distance : the internal branch dips into the pelvis, and is called the internal iliac or hypogastric artery ; tlie external branch continues in the original course of the common iliac, and is termed the external iliac artery. Thk Internal Iliac or Hypogastric Artery. The internal iliac or hypogastric artery {t,figs. 199, 212) is distributed to all the organs contained in the cavity of the pelvis ; to the muscles pig, 212. which line it within and cover it without ; to the exter- nal and internal organs of generation, and to the integ- uments. It passes at first obliquely downward and forward, and, as it were, in contact with the external iliac ; it then dips vertically into the pelvis in front of the sacro- iliac synchondrosis, describing a short curve ; and, after a course of about one inch or one inch and a half in length, divides opposite the upper part of the sacro-sciatic notch into a greater or less number of branches, which do not always arise in the same way from the principal trunk, but whose ultimate distribution is constant. It is cov- ered by peritoneum, and is crossed by the ureter ; it rests behind on the lumbo-sacral nerve and pyriformis muscle*; and the internal iliac vein is behind and to its outer side. Its branches, all of which sometimes arise from two principal trunks, one anterior and the other posterior, may be divided into an antenar set, consisting of the umbilical, vesical, obturator, middle hemorrhoidal, uterine, vaginal, aei- atic, and internal pudic arteries ; and a posterior set, including the ilio-lumbar, lateral, *a- cral, and gluteal arteries. Altogether, there are nine in the male and eleven in the female. The Umbilical Artery. The umbilical artery, which is so large in the foetus, is converted into an impermeable cord {xt;fig. 212) in the adult, excepting near its origin {a), where it gives off some ves- ical branches : the examination of the umbilical arteries belongs, therefore, more espe- cially to the anatomy of the foetus. They are intended to convey the blood of the foetus to the placenta, and are then the continuations of the common iliac arteries. The ex- ternal and internal iliacs, being very small at that period, in correspondence with the small size of the abdominal extremities, appear to be nothing more than divisions of the umbilical. The umbilical arteries pass downward, forward, and outward, and, having arrived at the sides of the bladder, run along them, in order to reach the umbilical ring, through which they emerge from the abdomen, and, having traversed the whole length of the umbilical cord in a spiral and tortuous manner, are at length distributed to the placenta.* The vesical, middle hemorrhoil.il, uterine, vaginal, and obturator arteries are given off in succession from the apparently ligamentous cord formed by the umbilical artery near its origin. The Vesical Arteries. These are variable in number : the principal of them on each side are given off from * It is curious to study the variable manner in which the umbilical arteries are converted, after Ijirth, into a fibrous tissue. Sometimes these arteries are converted into two regular cords, which converge towards the umbilicus. At other times each of these cords is subdivided into irregular bundles which it is difficult to trace to their true origin. 4A 654 ANGEIOLOGY. the umbilical artery (a), which seems to be converted into a ligamentous cord (u) at the place where the vesical arteries arise, but which is in reality pervious. This ligament- ous appearance of the umbilical arteries depends upon the narrowness of their canal, as compared with the thickness of their coats. Other vesical branches arise from the mid- dle hemorrhoidal and obturator arteries, and in the female from the uterine and vaginal. We shall divide the vesical arteries into the posterior, the anterior, and the inferior. The posterier vesical artery {b,fig. 212) frequently arises, in the female, by a common trunk with the uterine. It reaches the base of the bladder, on the outer side of the ure- ter, passes inward and upward upon the posterior surface, as far even as the summit of that viscus. I have seen the right posterior vesical artery, of large size, running along the posterior surface of the bladder in the median line, and prolonged upon the urachus ; the left posterior vesical was very small, and, in fact, rudimentary. The anterior vesical (c) arises from the umbilical, from the obturator, and sometimes from the internal pudic artery. When it arises from the umbilical, it is given off from that artery opposite the sides of the bladder, and passes downward and inward along its anterior surface. I have seen it given off near the summit of that organ. When it ari- ses from the obturator or the internal pudic, it traverses the anterior lig2iment of the blad- der, and passes upward upon the front of that organ. I have seen a very large vesical artery given off from the obturator, which, in that case, arose from the epigastric, and farther the vesical artery arose by a common trunk with the artery of the corpus cavernosum. The inferior vesical {d), which often arises direct from the internal iliac, reaches the inferior fundus of the bladder, and ramifies abundantly upon it and the commencement of the urethra : in the male it also supplies the corresponding vesicula seminalis and vas deferens, the branch to which is called the deferential artery, and the prostatic portion of the urethra. I have seen the dorsal artery of the penis arise from the inferior vesical. The Middle Hemorrhoidal Artery. This is a small artery (e), which is sometimes wanting, its place being then supplied by branches from different sources, but especially from the sciatic or the internal pudic ; it passes upon the sides of the anterior surface of the rectum, where it terminates by anastomosing with the superior and inferior hemorrhoidal arteries. The Uterine Artery. The uterine artery {n n,jig. 198) arises from the umbilica., near the posterior vesical, and frequently by a common trunk with it ; passes transversely inward to the corre- sponding lateral border of the uterus, a little above the os tincae ; is reflected upward along the uterus, and terminates by expanding into several ascending branches, of which the anterior reach the front, the posterior the back, and the middle the upper border of the viscus, and inosculate either with their fellows of the opposite side, or with the uter- ine branches of the ovarian artery. The uterine arteries are remarkable for the great size which they acquire during pregnancy, and also for their tortuous and spiral course, even to their smallest branches : a disposition which no other artery presents in the same degree. These tortuosities, instead of diminishing, appear to increase during pregnancy : a fact which seems opposed to the view generally adopted regarding the use of arterial flexuosities in organs liable to variations in their size. Collateral Branches. — At the point of its reflection, each uterine artery gives off one or more descending branches between the vagina and the bladder to supply both parts ; in their course along the borders of the uterus, they furnish a series of anterior and poste- rior ascending branches, which are distributed in the same way as the terminal ascending branches ; they all anastomose in the median line with their fellows of the opposite side. Relations. — The trunks of the uterine arteries are beneath the peritoneum ; the prin- cipal branches are situated under a thin layer of the substance of the uterus, and the ul- timate divisions and subdivisions enter its tissue. The Vaginal Artery. The vaginal artery arises from the umbilical, sometimes before, sometimes after the origin of the uterine, which is sometimes given off from a conunon trunk with it. It is as large as the uterine in young subjects, but is smaller than it after puberty. It de- scends directly upon the sides of the vagina, to which it gives off a numerous series of branches, supplies a considerable branch to the neck of the bladder and the urethra, gives an equally large one to the bulb of the vagina, and then passes backward between the orifice of the vagina and the rectum, and anastomoses with its fellow of the oppo- site side. The Obturator Artery. The obturator artery {f,fig. 212) is remarkable for the varieties of its origin, and for the important consequences which result from those varieties, in reference to the oper- ation for femoral hernia. THE ILIO-LUMBAR ARTERY. SS5 It generally arises from the internal iliac by the side of the umbilical, but sometimes above the gluteal ; it is almost as frequently given off from the external iliac, either di- rectly,* which is rare, or by a common trunk with the epigastric. Lastly, and much - more rarely, it arises from the femoral artery. The course of the obturator artery is modified by these differences of origin, which, notwithstanding the assertion of some anatomists, are as common in the male as the fe- male, and which may occur on one side only, or on both sides of the same subject. Thus, when the obturator comes from the femoral, it passes upward on the inner side of the femoral vein, enters the pelvis through the crural ring, is reflected upon the upper surface of the body of the os pubis, then passes behind it and gains the internal opening of the sub-pubic canal. When it arises by a common trunk with the epigastric, it dips vertically behind the os pubis to the same opening. In its ordinary mode of origin, it passes horizontally forward upon the sides of the brim of the pelvis, being bound down by the peritoneum, runs parallel with the obturator nerve (n), which is placed above i gains with it the internal orifice of the sub-pubic canal, and, having traversed this pas- sage, divides into an internal and an external terminal branch. Collateral Branches. — Near its origin, the obturator artery gives off a tolerably large branch, the iliac, which perforates the iliac fascia, dips between the iliacus muscle and the ihac fossa, and anastomoses with a branch of the circumflex iliac artery, t As it enters the sub-pubic canal it gives off a small branch, which passes transversely behind the body of the pubis, and ramifies upon the side of the symphysis, anastomo- sing with its fellow of the opposite side ; also a small ascending branch (s), which anas- tomoses with the epigastric artery, and which may be regarded, according to Meckel, as one of the origins of the obturator ; so that the variety in which the obturator arises from the epigastric is often nothing more than an unusual development of this commu- nicating branch. In support of this view, we may quote the very rare case, in which the obturator arises by two roots of almost equal size, one coming from the epigastric, and the other from the interned iliac. Terminal Branches. — The interned branch passes between the obturator extemus mus- cle and the conjoined rami of the pubes and ischium, so as to describe a semicircle around the inner half of the obturator foramen, gives branches to the periosteum of the OS pubis, muscular branches to the two obturator and to the adductor muscles, some genital branches to the coverings of the testis in the male and to the labia majora in the female, and, lastly, some very important anastomotic branches, which join those of the internal circumflex. The external branch runs along the outer half of the obturator foramen ; it is placed, like the preceding, between the two obturator muscles, and terminates between the neck of the femur and the quadratus femoris muscle by anastomosing with the sciatic artery. This anastomosis is very remarkable. During its course, the external branch supplies the obturator muscles and the hip-joint ; the articular branch enters by the notch of the cotyloid cavity, and is lost in the reddish, fatty tissue situated at the bottom of it. The distribution of the obturator artery is much more limited than that of the ob- turator nerve. The Ilio-lumbar Artery. The ilio-lumbar artery (A) arises from the back of the internal iliac, and, tolerably fre- quently, from the gluteal. There are often two ilio-lumbar arteries. This vessel bears the same relation to the lumbar arteries that the superior intercostal does to the aortic intercostals ; its size and distribution vary according to the presence or absence of the fifth lumbar artery. It has a retrograde course, running upward and backward in front of the lumbo-sacral nerve, and behind the psoas muscle, and soon divides into two branches : an ascending or lumbar, and a transverse or iliac. The ascending or lumbar branch passes vertically upward along the bodies of the lumbar vertebrae, hidden by the psoas, and subdivides into a muscular branch, which corresponds to the abdominal branches of the lumbar ar- teries, and is distributed to the psoas and to the quadratus lumborum ; and a spinal branch, which enters the vertebral canal by the foramen between the fifth lumbar verte- bra and the sacrum, and is distributed in the same manner £is the other spinal arteries. * The cases where th*' obturator artery arises separately from the external iliac are not unfrequeut. The following description may serve as an example. In one case, the obturator artery arose separately from the external iliac artery, at the distance of one inch above the femoral arch, and above the origin of the epigastric artery ; it went downward and inward to reach the lateral wall of the pelvis, crossed the obturator nerve, and entered the sub-pubic canal. In this subject, the obturator vein joined also the external iliac vein. The same disposition existed on both sides. t The obturator artery sometimes gives off the artery to the bulb of the urethra. In a preparation which was exhibited by M. Dcnonvilliers, now chef des travaux anatomiques, at the concours for the office of prosec- tor, I have seen a voluminous branch whicli had arisen from the obturator artery, extending all along the in- ternal part of the obturator foramen, cross perpendicularly the posterior surface of the descending branch of the pubis, reach the bulb transversely by crossing the internal pudic artery, above which it was placed. This was on the left side. On the right side the arrangement was normal. This arrangement is not as rare as might be believed : it is evident that the ligature of ihe internal pudic artery would be useless in a case of this kind, in arresting a hemorrhage consequent upon nii operation for the stone. ANGEIOLOGT. The transverse or iliac branch passes horizontally outward, opposite the brim of the pelvis, and divides into a superficial branch, which passes under the iliac fascia, ramifies upon the iliacus muscle, and anastomoses with the circumflex iliac artery ; and into a deep and much larger branch, which passes between the ihacus muscle and the ihac fossa, and divides into muscular and periosteal twigs. The principal nutritious artery of the ilium is derived from this branch. When there are two ilio-lumbar arteries, the superior represents the lumbar branch, and the inferior the iliac branch : in such a case the latter branch always arises from the gluteal artery. The Lateral Sacral Arteries. Most'commonly there are two lateral sacral arteries on each side ; they belong rather to the interior of the sacral canal than to the cavity of the pelvis, and form a continuation of the spinal branches of the lumbar arteries ; they almost as frequently arise from the gluteal as from the internal iliac ; sometimes they are derived from the sciatic or the Sio-lumbar arteries. The superior lateral sacral is generally of considerable size. It passes almost horizon- tally inward, and after having given off some small transverse branches, which anasto- mose with the middle sacral, enters the first anterior sacral foramen, and divides into two branches : one intended for the nerves and their coverings, and another which emer- ges from the sacral canal by the corresponding posterior sacral foramen, and is distribu- ted to the spinal muscles and to the skin. The inferior lateral sacral (Ji,fig. 212) is situated at first under the digitations of the pyriformis muscle, afterward passes in front of that muscle, and is directed inward and downward on the inner side of the sacral foramina, and along the borders of the coccyx, where it anastomoses with the middle sacral. In this course it gives off a series of very small internal branches, which correspond to the several sacral vertebrae, and anastomose with the middle sacral ; also some posterior or spinal branches, each of which enters the sacral canal through the corresponding sacral foramen, and subdivides into two small branches : one intended for the nerves and their coverings, while the other emerges from the sacral canal by the corresponding posterior sacral foramen, and is distributed to the muscles and the skin. "When the superior lateral sacral is small, the posterior or spinal branch of the inferior lateral sacral is very large. The inferior lateral sacral artery often terminates by a spinal branch, which enters at the lowest anterior sacral foramen. The Gluteal Artery. The gluteal artery (rn,fig. 212), called also the posterior iliac, is the largest branch of the internal iliac, of which it might be considered the continuation. It might be called superior gluteal, in contradistinction to the sciatic, which is, in reality, an inferior gluteal. It passes downward and backward between the lumbosacral nerve and the first sacral nerve, escapes from the pelvis at the upper part of the great sacro-sciatic notch, above the pyriformis muscle {m,fig. 45), is reflected upon the border of that notch, and divides into a superficial and a deep branch. The superficial branch (a) passes horizontally for- ward, between the glutaeus maximus and medius, and is almost entirely distributed to the upper part of the first-named muscle and to the adjacent part of the skin ; the deep branch {b) passes between the glutaeus medius and minimus, and subdivides into two branches ; the lower of these runs horizontally, and may be traced as far as the anterior border of the glutaeus medius, while the other very nearly follows the curve described by the origin of the glutaeus minimus. This branch gives off some muscular arteries, several nutri- tious arteries to the bone, and severtd articular branches. One circumstance regarding the gluteal artery worthy of remark is the fact that, in common with all arteries of a certain size, it is liable to aneurism, and that for the cure of this aneurism (which has always been the result of external violence), the common iliac artery has in two cases been tied in America, and the gluteal artery itself recently by an English surgeon. The Sciatic Artery. The sciatic artery (o, fig. 212), from its distribution, might be called the inferior gluteal. It often arises by a common trunk, either with the gluteal or with the internal pudic, be- hind and internal to which it is situated ; it descends in front of the sacral plexus and the pyriformis muscle, traverses the sacral plexus, emerges from the pelvis (o, fig. 215) be- tween the pyriformis and the lesser sacro-sciatic ligament, accompanied on its inner side by the great sciatic nerve, and behind by the internal pudic artery (p). Outside the pel- vis, the sciatic artery gives off iniernal or transverse branches, some of which pass trans- versely inward between the gluteus maximus and the great sacro-sciatic ligament, while others (c) perforate that ligament, and ramify in the internal attachments of the glutaeus maximus. Several of these branches ramify upon the skin of the coccygeal region ; its other branches are descending, the largest of which {d) gains the deep surface of the glutaeus maximus, and enters that muscle by numerous branches, which become cuta- INTERNAL PUDIC ARTERY. 657 Fig. 213. neous at their termination ; one and often two or three branches (c) of the sciatic artery attach themselves to the deep surface of the great sciatic nerve, and accompany it to the lower part of the thigh. A great number of twigs are given off from the several branches of the sciatic artery, which are distributed to the small rotator muscles, or to the origins of the muscles attached to the tuberosity of the ischium, while others anastomose with the circumflex (/) and perforating arteries («) derived from the femoral. Among these anastomoses, I would point out one very considerable anastomotic loop, formed behind the neck of the femur by the sciatic and internal circumflex arteries, and constituting one of the principal communications between the internal iliac and femoral arteries. The hitemal Pudic Artery. The internal pudic (jp,fig. 212), the terminal branch of the internal iliac, is, practically speaking, the most important of all the pelvic arteries. It is smaller than the sciatic, from which it is sometimes given off, either shortly after the origin of that vessel, or as it is passing out from the pelvis. The internal pudic runs in a tortuous manner down- ward, in front of the sacral plexus and the pyriformis muscle, parallel to the sciatic ar- tery (o), which is behind it ; escapes from the pelvis, together with that vessel {p, o,fig. 215), between the pyriformis muscle and the spine of the ischium ; is reflected upon that process, turning round it from behind forward, so as to embrace in succession its posterior, its external, and its anterior surfaces, and then enters the pelvis again between the two sacro-sciatic ligaments. The artery, af- ter descending a short distance, then becomes as- cending, and is situated in the ischio-rectal fossa {a, Jig. 213), and is applied to the internal surface of the tuberosity of the ischium, or, rather, of the obturator internus muscle, with which it is kept in contact by a layer of fascia : it is separated from the levator ani by a considerable quantity of fat, and having reached the posterior border of ^ the transversus perinei muscle, it divides into an inferior, superficial, or perineal branch (c), and a stiperior or deep branch (e), w^hich is distributed to the penis in the male and to the clitoris in the fe- male. An important variety in the course of this artery has been pointed out by Bums, who, in a male subject, saw the trunk of the internal pudic, instead of passing out of the pelvis, run upon the sides of the inferior fundus of the bladder, perforate the upper part of the pros- tate, and then terminate in the usual manner. Collateral Branches. — During its course within the pelvis, the internal pudic supplies branches to the bladder, rectum, vesiculae seminales, and prostate in the male, and to the vagina in the female ; it also rather frequently gives off the middle hemorrhoidal. As it turns round the spine of the ischium, it gives some branches to the rotator mus- cles of the thigh. Opposite the internal surface of the tuberosity of the ischium, it gives origin to one or more branches, named the external or inferior hemorrhoidal (b,jig. 213), which run inward to be distributed to the lower end of the rectum, to the sphincter, the levator ani, and the skin ; also some branches which proceed outward, some to sup- ply the periosteum of the tuberosity, while others ramify in the muscles attached to that process ; lastly, a very important communicating branch passes between the tuberosity of the ischium and the great trochanter, and anastomoses with the sciatic and internal circumflex arteries. Terminal branches. — These differ in the two sexes. We shall first describe them in the male : The inferior branch, the superficial artery of the perineum, or the perineal artery (c), is smaller than the superior branch : it passes forward and inward, in the cellular interval between the ischio-cavernosus and the bulbo-cavernosus ; above, i. e., deeper than the superficial fascia of the perineum, which separates it from the skin ; and below, i. e., superficial to the transversus perinei muscle, it thus reaches the dartos at the side of the median line, where it is named the artery of the septum, and is distributed to the scrotum and the skin of the penis. During its course the superficial perineal artery gives internal and external branches. Some of the internal branches run along the posterior border of the transversus perinei muscle, and are sometimes so large as to bleed very profusely when they are divided in the operation of lithotomy ; from its situation, one of them is named the transverse ar- tery of the perineum (d). The deep superior or deep branch (e), or the artery of the penis (in the male), is the con- tinuation of the trunk of the internal pudic, both in regard to size and direction : it runs along the ascending ramus of the ischium, between the layers of the triangular ligament ; above, i. e., deeper than the transverse muscle, which it sometimes perforates, also above the ischio-cavernosus and the corresponding crus of the corpus cavernosum ; and oppo- ANGEIOLOGY. site the point at which the two crura unite, it subdivides into two branches, viz., the dorsal artery of the penis (g) and the artery of the corpus cavernosum Qi). During its course, the artery of the penis gives off a very important collateral branch, named the artery of the bulb (/), which is as large as the superficial perineal artery, is sometimes double, and generally arises near the bulb, passes transversely inward, above the middle perineal fascia or triangular ligament, or, rather, in the substance of that ligament, and is distributed to the bulb of the urethra and to the spongy portion of this canal.* The dorsal artery of the penis (g) is sometimes the only terminal branch of the internal pudic, and then a very delicate twig supplies the place of the artery of the corpus cav- ernosum, which, in this case, is supplied from another source. This artery reaches the dorsal surface of the penis by passing between the symphysis pubis and the crura of the corpus cavernosum, and perforating the suspensory ligament of the penis, and then runs in a very tortuous manner along, beneath the skin, upon the dorsal aspect of that organ, on one side of the median line, being retained in its position by a layer of fibrous mem- brane : it terminates by ramifying in the prepuce and in the glans, around the base of which it forms a corona. I have seen the dorsal artery of the penis given off by one of the external pubic arteries, from which it arose immediately above the entrance of the saphenous vein into the femoral ; it then formed a curve in the groin, with its concav- ity directed downward, and passed upon the sides of the dorsal surface of the penis ; in another instance, the dorsal artery of the penis was derived from the obturator, or, rath- er, it had two roots : a very small one, which had the usual origin, and a large one, which arose from the obturator and passed under the symphysis. The right and left dorsal arteries of the penis sometimes anastomose by a transverse branch, like the an- terior cerebral arteries. The artery of the corpus cavernosum (h) is also sometimes the only terminal branch of the internal pudic artery, the dorsal artery of the penis, in such cases, being derived from some other source. I have seen the cavernous artery arise from the obturator. In all cases it enters the corpus cavernosum by the corresponding crus, runs along its median septum, and ramifies in its areolar structure. I have seen the dorsal arteries of the penis and the cavernous artery arise by a com- mon trunk from the hypogastric ; this trunk passed directly from behind forward to be divided immediately. The same disposition existed on both sides. The internal pudic artery gave off a small cavernous artery. In the female, the terminal branches of the internal pudic are arranged as follows : the inferior or superficial perineal branch is larger than the superior, and might be named the artery of the labia majora, to which it is distributed ; the superior or deep branch, or the artery of the clitoris, runs along in contact with the tuberosity of the ischium, and then with its ascending ramus, and having given off a branch, which runs inward to the bulb of the vagina, terminates in the dorsal artery and cavernous artery of the clitoris, these ves- sels being very small in consequence of the diminutive size of that organ. Summary of the Distribution of the Internal Iliac Jlrtery. The internal iliac artery, which is so deeply situated as to be inaccessible to the sur- geon, sends branches to all the organs contained in the cavity of the pelvis ; to the bony parietes of the pelvis and the sacral canal ; to the muscles which line the pelvis within and cover it without ; and to the skin and the external genital organs. Its several branches may be divided into parietal and visceral. The visceral branches are the vesical, middle hemorrhoidal, vaginal, and uterine arteries, and the deep branch of the internal pudic. The sympathy existing between all the organs to which the above- named vessels are distributed, depends less upon those vessels having a common source than upon the community of origin of the several nerves which those vessels serve to support. The parietal branches are the ilio-lumbar and lateral sacral arteries, which, with the^ middle sacral, continue the series of intercostal and lumbar arteries into the sacral re-* gion, and supply the sacrum, the spinal nerves and their coverings, and also the muscles of the vertebral grooves and the skin of the sacral region ; the glutaeal and the sciatic ar- teries intended for the muscles of the glutaeal region ; the superficial branch of the internal pudic artery, which supplies the perineum ; and, lastly, the obturator artery, which forms an arterial circle around the obturator foramen, and supplies the obturator muscles. Several branches of the internal iliac artery establish anastomoses between that ves- sel and the femoral artery ; these are more especially the sciatic, the internal pudic, the gluteal, and the obturator arteries. Artery of the Lower Extremity, or Crural Trunk. The arterial trunk of the lower extremity, or the crural trunk (Chaussier), corresponds * The artery of the bulb, after having traversed the bulb, is directed from behind forward in the substance of the spongy portion of the urethra, and may be followed up to about its middle part. When the artery of ths bulb comes from the obturator artery, the inferior pudic sends a rudimentary branch to the bulb. It is the pudic artery which supplies Cowper's glands. THE EXTERNAL ILIAC ARTERY. 559 With the brachial trunk of the upper extremity. This vessel, which is the direct con- tinuation of the common iliac artery, passes downward and outward, emerges from the pelvis beneath the crural arch, and thus reaches the anterior region of the thigh. Op- posite the junction of the two upper thirds with the lower third of the femur, it traverses the fibrous canal formed for it by the tendon of the great adductor muscle, and thus gains the popliteal space, at the lower part of which it terminates by dividing into two branches. The numerous and important relations of this vessel, and the great number of branches arising from it, have led to its division by anatomists into three portions, which are named the external iliac artery, the femoral or crural artery, and the popliteal ar- tery. The two terminal branches are the anterior tibial, which, in the foot, is termed the dorsal artery of the foot, and the tibio-peroneal trunk, which divides into the peroneal and posterior tibial arteries, the latter of which terminates in the sole of the foot by subdivi- ding into the internal and external plantar arteries. The External Iliac Arteky. The external iliac artery (r, figs. 199, 212), the outer of the two branches into which the common iliac divides, is analogous to the subclavian artery in the upper extremity. It extends from the highest part of the sacro-iliac symphysis to the lower border of the fem- oral arch or Poupart's ligament, below which it takes the name of femoral artery. It is directed obliquely downward and outward, in a line extending from the sacro-iliac sym- physis to the crural ring, and is almost always straight, but sometimes tortuous. It has the following relations : in front and on the inner side, it is covered by the peritoneum, which is very loosely attached to it : an important fact, which enables the surgeon to separate that membrane from it in applying a ligature to the vessel ; on the outer side, it rests against the psoas muscle, from which it is separated by the iUac fascia ; behind, the artery of the right side is in relation with the corresponding external iliac vein, which is placed to its inner side below ; on the left side the vein is below, and on the inner side of the artery ; lastly, the genito-crural nerve, just as it is about to enter the inguinal ca- nal, crosses in front of this artery, and so also do the spermatic vessels ; the circumflex iliac vein crosses it at right angles behind the femoral arch, in order to terminate in the external iliac vein ; besides this, it is covered immediately behind the arch by several lymphatic glands ; higher up, the ureter crosses obliquely in front of it, and the artery of the right side is covered by the termination of the ileum, and that of the left side by the sigmoid flexure of the colon. Collateral Branches. — The external iliac artery furnishes no branches, excepting at its lower part, near the femoral arch, where it gives off the epigastric and circumflex iliac arteries. The Epigastric Artery. The epigastric artery is, practically speaking, one of the most important to be well un- derstood, on account of its relations with the crural ring and inguinal canal, that is to say, with the parts through which the viscera generally descend in herniae. This artery (v,figs. 199, 212) arises from the inner side of the external iliac, two or three lines above the femoral arch. Its origin, however, is subject to some varieties : sometimes it takes place half an inch, one, or even two inches above the crural arch : an important fact in reference to the application of a ligature to the external iliac. Hessel- bach and several others state that they have seen the epigastric arise from the obtura- tor artery ; but their descriptions appear to me to prove nothing more than that the epi- gastric and obturator arteries may arise by a common trunk. It is worthy of remark that the obturator is often observed to arise from the epigastric, while there is, perhaps, no example of the epigastric being derived from the obturator. The obturator so fre- quently arises by a common trunk with the epigastric,* that many anatomists have thought that the obturator is derived from the epigastric more frequently than from the internal iUac artery. In 250 subjects examined for this purpose by M. Jules Cloquet, the obturator arose 150 times from the epigastric on both sides, 28 times on one side only, and 6 times from the femoral artery. Althoug:h it is a very common occurrence to have the obturator artery arising from the epigastric, it is very rare to find the epigas- tric taking its origin from the obturator. This anatomical variety has only been report- ed as having occurred in two cases. One can easily understand how dangerous it would be to operate for the relief of a strangulated hernia in such a case. The epigastric artery, whether it gives off the obturator or not, passes transversely or obliquely inward, and, having arrived below the spermatic cord in the male, and the round ligament in the female, is reflected upward, so as to describe a curve having its concavity directed upward, and corresponding to the loop formed by the spermatic cord o' round ligament, the concavity of which is directed downward. When the cbturator arises by a common trunk with the epigastric, it is given oflf at the point where the lat- ter is reflected upward, and from the convexity of the curve. After being reflected, the * It would be very difficult to explain why the epigastric and the obturator arteries are so intimately cott nected at their origins. 9Bfk ANGEI0L06Y. epigastric artery ascends obliquely inward, soon reaches the outer border, and next the posterior surface of the rectus abdominis muscle, and then passes vertically upward. Having reached the umbilicus, it penetrates into the substance of the rectus, and termi- nates by anastomosing with the internal mammary artery. Relations. — The relations of the transverse, oblique, and vertical portions of the epi- gastric artery should be examined separately. The transverse portion varies in length in different subjects ; sometimes it is almost entirely wanting, the artery running im- mediately upward ; at other times it is an inch and a half in length. This difference in length, which is of no consequence when the obturator artery arises from the internal iliac, becomes highly important when that vessel is given off from the epigastric* This transverse portion of the artery is directed obliquely downward, when the ej - gastric arises at a certain distance above the ring. The oblique portion of the epigastric artery forms the outer side of a triangle, the in- ner side of which is formed by the outer border of the rectus abdominis muscle, and the base by the crural arch : the epigastric constitutes the true boundary between the inter- nal inguinal fossa, which comprises all the triangular space situated on the inner side of the vessel, and the external inguinal fossa, which comprises the space upon its outer side. The abdominal orifice of the inguinal canal is situated in the external inguinal fossa, and, consequently, to the outer side of the epigastric artery. Those inguinal her- nise which pass through the internal fossa are called internal or direct inguinal herniae ; those which take place on the outer side of the artery are called external or oblique in- guinal. In its horizontal and oblique portions, the epigastric artery is placed between the per- itoneum and the fascia transversalis. I should observe that the spermatic cord in the male, and the round ligament in the female, do not cross the epigastric artery precisely in the situation of the loop which this vessel describes, but a little above it. The axis of the inguinal canal being directed obliquely downward and inward, intersects at right angles the oblique portion of the artery, which slopes in the opposite direction. In its vertical portion, the epigastric artery is situated between the rectus and the pos- terior wall of the sheath of that muscle until near the umbilicus, where it dips into the fleshy fibres. Collateral Branches. — Near its origin, or, rather, opposite the bend which it takes, the epigastric artery sometimes gives off the internal circumflex, which, as we shall here- after see, generally arises from the deep femoral. It always gives off the following branches : a cremasteric branch {I, Jig- 214), which enters the inguinal canal, runs along the fibrous sheath of the cord in the male, and the round ligament in the female, and passes in the one to the coverings of the testicles, and in the other to the labia majora ; a second branch, which runs along the inner portion of the femoral arch, and anasto- moses with its fellow of the opposite side behind the symphysis ; and, lastly, a branch which crosses the horizontal ramus of the pubes at right angles, and anastomoses with the obturator. I have already stated that this small branch may be regarded as forming the trunk of the obturator when that artery arises from the epigastric. In its oblique and vertical portions, the epigastric gives off a number of internal and external ascending branches, which pass very obliquely through the rectus abdominis, partially supply that muscle, and then pierce the anterior wall of its sheath, the internal branches near the linea alba, and the external branches near the outer border of the sheath, to ramify upon the skin. These branches anastomose with the internal mammary and with the lumbar arteries. The anastomosis of the epigastric with the internal mammary takes place only in the substance of the rectus, and by very small vessels. The Circumflex Iliac Artery. The circumflex or posterior iliac artery {x, figs. 199, 212), smaller than the epigastric, arises from the outer part of the external iliac, either opposite the epigastric or a little below it. It sometimes arises from the upper part of the femoral artery : it is generally single, but occasionally double, which may be regarded as resulting from a premature division of the vessel. It passes obUquely upward and outward, behind the crural arch, with which it is held in contact by a fibrous layer interposed between it and the peritoneum. Opposite the anterior superior spinous process of the ihum it divides into two branches : one is an ascending or abdominal branch, which passes upward, in the substance of the abdominal parietes, between the transversalis and obUquus intemus muscles, parallel with the ep- igastric artery, and terminates by anastomosing with the inferior intercostal and the lumbar arteries ; the other is the circumflex ihac artery properly so called, which is the * [If the obturator arises high up from the epigastric, it describes, before it euters the pelvis, a semicircle extending along the upper, and then the inner border of the crural ring ; and, consequently, has such rela- tions with the neck of the sac in femoral hernia, that render it almost impossible to avoid wounding the ar- tery in dividing the stricture upward and inward. But if, as is much more frequently the case, it arises from near the commencement of the epigastric, or by a common trunk with it, it then descends at once into the pel vis obliquely along the outer border of the crural ring, and will have the same relation with a femoral henua.J THE FEMORAL ARTERY. 56« continuation of the vessel in direction and sometimes in size ; it runs along the crest of the ilium, is at first sub-aponeurotic, or, rather, is contained between two layers of fascia in the cellular interval separating the transversalis from the obliquus internus, and terminates by anastomosing with the fourth lumbar artery upon the crest of the ilium. During its course, the circumflex iliac artery gives off ascending branches, which ram- ify in the muscles and integuments of the abdominal parietes ; and descending branches, which ramify in the iliac fossa, and anastomose with the iliac branches of the obturator artery. The Femoral Artery. The femoral or crurcu artery (a a', fig. 214) is that portion of the artery of the Icn'er ex- tremity which intervenes between the external iliac and pop- Fig. 214. liteal arteries ; it is bounded above by the crural arch, and below by the junction of the two upper thirds with the lower third of the thigh, or, rather, by the place where the artery passes through the tendinous ring formed by the adductor magnus. It has been proposed to take as the lower boundary of the femoral artery the origin of the deep femoral or profunda ar- tery, which has been correctly regarded as a terminal branch resulting from the bifurcation of the femoral artery, rather than as a collateral branch. According to this view, which has not been generally adopted, the femoral would not be more than from an inch and a half to two inches in length, and would divide into a superficial and deep femoral. The femoral artery is directed vertically, and somewhat obliquely backward, so that it forms a slight angle with the external iliac, on account of the oblique inclination forward of that vessel ; and, farther, although it is in front of the fe- mur above, it is placed on the inner side of it below, prepara- tory to becoming posterior to it in the popliteal space. A line drawn from the middle of the space between the anterior su- perior spinous process of the ilium and the symphysis pubis, down to the inner side of the femur, below the middle of that bone, would exactly represent its direction. The direction of the femoral artery, in respect to the femur, is such, that immediately below the femoral arch it is situated over the point of junction of the inner with the two outer thirds of the head of that bone, while lower down it is in relation with the inner aspect of the bone ; the artery, therefore, forms an acute angle, opening upward, with the shaft of the femur, and there is an interval of an inch to eighteen lines between the vessel and the upper part of the bone, into which instruments may be passed without wounding the artery. Advantage is taken of this fact in disarticulating the head of the femur in amputation at the hip-joint. The femoral artery, which is slightly tortuous when the thigh is flexed upon the pelvis, becomes straight when the limb is extended, and it is much stretched during forcible ex- tension. Relations. — In front, the femoral artery lies beneath the fascia in the triangular space which is bounded on the inside by the inner border of the adductor longus ; on the out- side, by the sartorius ; and above, by the femoral arch. Lower down, the sartorius is placed between the fascia and the artery, which is in relation, first, with the inner bor- der, then with the posterior surface, lastly, with the outer border of that muscle : besides the fascia, a number of lymphatic glands lie between the upper part of the artery and the skin. Enlargement of one or more of these glands has been mistaken for an aneu- rism, and an aneurism for an enlarged gland. From these relations of the front of the femoral artery, it foUoivs that its anterior aspect may be exposed in the whole of its ex- tent, but that it is more superficial in the neighbourhood of the crural arch. Behind, the femoral artery rests, first, upon the body of the pubes, or the ilio-pectineal eminence, with which it is in immediate contact in emaciated subjects, but from which it is generally separated by the contiguous borders of the psoas-iliac and the pectineus muscles. The iliac fascia separates it from the psoas-iliac muscle, so that, in cases of simple psoas abscess, or congestive abscess from caries of the lumbar vertebrae, the fem- oral artery is situated in front of the sac of the abscess. The femoral artery is also in relation, behind, with the head of the femur ; lower down, with the pectineus, and then with the adductor longus. It follows, therefore, that the femoral artery may be very eflfectually compressed at its upper part, since it is superficially situated, and rests upon hard parts. On Ike outer «ie, it is in relation, first, with the psoas-iliac, then with the inner border 4B 562 ANGEIOLOGY. of the sartorius, and, lastly, with the vastus internus, which separates it from the inner surface of the femur. In consequence of this relation to the bone, and also of the slight thickness of the sar- torius, which separates it from the skin, the femoral artery may be compressed against the femur from within outward in the middle third of the thigh. On its inner side, it is in relation with the pectineus, the adductor longus, and afterward with the outer border of the sartorius. Relations of the Artery with the Vein and Nerves. — The femoral vein is situated on the inner side of the artery above, but it soon passes behind it, and, still lower down, is on its outer side. The crural nerve lies on the outer side of tlie artery, from which it is separated by a fibrous layer belonging to the sheath of the psoas and iliaeus. The artery and nerve, therefore, have no immediate relation with each other ; but the internal or long saphenous nerve soon runs upon the sheath of the femoral vessels, and is situated on the outside of the artery ; but as the vessel is passing through the tendon of the ad- ductor magnus, the nerve leaves it, and, lower down, escapes from under the tendon of the sartorius. The short saphenous nerve, or nerve of the internal vastus, is in relation with the outer side of the artery for a short distance, and the vessel is also crossed by another small nerve. The Sheath of the Femoral Vessels. — ^The femoral artery and vein are enclosed in a proper fibrous sheath, which is constructed, as it were, in the midst of the muscles of the thigh (see Aponeurology). It is, therefore, necessary to open this sheath, and not that of any of the surrounding muscles, in order to expose the artery. Anatomical Varieties. — Independently of the very frequent and remarkable anatomical varieties in the origin of the deep femoral artery, which is often given off opposite, and sometimes above the femoral arch — varieties to which I shall immediately refer in speak- ing of the deep femoral artery — ^the common femoral artery itself offers some varieties which are not less interesting. The most important is the following, found in a prep- aration deposited by M. Manec in the museum of Clamard : In this preparation, the fem- oral artery presents behind the Fallopian ligament a caliber which is not larger than that of the radial artery, and is lost in the anterior muscles of the thigh. The ischiatic ar- tery, which is a branch of the hypogastric, presents, on the contrary, the caliber of the femoral artery, descends backward along the great sciatic nerve, and is continuous with the popliteal artery. During its course along the thigh, the ischiatic artery gives off the muscular branches which generally come from the deep femoral artery. Collateral Branches. — The collateral branches of the femoral are, the superficial epigas- tric artery, the two external pudic arteries, a great number of muscular branches, and the deep femoral artery. The Superficial Epigastric Artery. The superficial epigastric or sub-cutaneous abdominal artery (cut across at b,fig. 214) is a very small, but remarkably constant branch, which arises from the front of the femoral, and sometimes from the external pudic, immediately below the crural arch, passes vertically upward, between the integuments and the superficial fascia, gives some branches to the inguinal lymphatic glands, and terminates in the skin, near the umbili- cus (arteria ad cutem abdominis, Haller). The External Pudic Arteries. The external pudic or genital arteries, also named scrotal in the male, and vulvar in the female, arise from the inner side of the femoral : they are two in number (c c, fig. 214), and are named the superior or sub-cutaneous, and the inferior or sub-aponeurotic. The superior or sub-cutaneous arises immediately below the crural arch, passes trans versely inward in the sub-cutaneous cellular tissue, and divides into two branches : a superior, which passes to the pubic eminence, and an inferior, which is distributed to the skin of the penis and scrotum in the male, and to the corresponding external labium in the female. I have seen the dorsal artery of the penis arise from this vessel. The inferior or sub-aponeurotic branch arises a little below the preceding, and some- times even from the deep femoral ; it passes transversely inward, crosses the femoral vein at right angles immediately below the point where it is joined by the saphenous vein, so that this artery is generally received in the loop described by the upper end of the saphenous vein : it soon perforates the fascia and becomes sub-cutaneous, and then ramifies in the scrotum in the male, and in the external labium in the female. The anastomoses of the superior and inferior external pudics, both with each other and with those of the opposite side, are so free and large, that when one of them is cut across, it becomes necessary to tie both of the cut ends of the vessel. These arteries are re- Tnarkable on account of their relations with hernial tumours. The Muscular Arteries. The femoral gives off a great number of muscular and cutaneous branches, which have received no particulai names. One, however, is usually described as the superficial m THE DEEP FEMORAL ARTERY. 563 greax muscular artery, which frequently arises from the deep femoral ; it passes trans- versely between the sartorius and the rectus femoris, and immediately divides into as- cending branches, which proceed to the iliacus, sartorius, and tensor vaginee femoris, and into very large descending bra?iches, some of which are distributed to the rectus fem- oris, passing in at its posterior surface, while others penetrate the vastus internus and vastus externus. The last-mentioned branches can be traced as far as the lower part of the triceps muscle ; and, indeed, the great muscular artery might be named the mus- cular artery of the triceps extensor femoris, which ig,fig. 214) may arise from the deep femoral artery. The Deep Femoral Artery. The deep femoral artery {profunda femoris ; d d', fig. 214.) is intended to supply the muscles and integuments of the internal and posterior regions of the thigh.* It arises from the back of the femoral, generally about one and a half or two inches below the crural arch, about half way between the pubes and the lesser trochanter, very rarely below this point, but more commonly above it. Thus the femoral often divides, either about six lines below the crural arch, or immediately beneath and on a level with it, into two equal and parallel branches, of which the external is the deep femoral, and the internal the femoral properly so called. I have seen this subdivision, which bears a rather close analogy to the bifurcation of the humeral artery into the radial and ulnar in the axilla, take place above the crural arch, that is to say, in the external iliac artery. Immediately after its origin, the deep femoral passes backward and outward, and then vertically downward, gradually approaching the femur ; it is situated deeply behind the femoral artery, but is separated from it by the femoral and deep femoral veins ; it runs parallel to th'fe femoral artery, in front of the pectineus, and on the outer side of the vastus internus ; having reached the upper border of the long adductor, it passes behind that muscle to arrive between it and the short and great adductors, perforates the latter mus- cle a little below the tendinous opening for the proper femoral artery, and terminates by ramifying in the biceps and semi-membranosus. Sometimes the deep femoral perforates the adductor magnus almost immediately, and at once becomes posterior to it. Varieties of Origin. — In the history of the deep femoral artery, the varieties in its origin are most important, considered in a surgical point of view. The common femoral artery is very often divided prematurely into two equal and parallel branches, the external of which is the deep femoral, and the internal the true or superficial femoral artery, t This premature division may take place at a distance of six lines below the crural arch, opposite this arch, or even beneath it. I have seen this division, which bears a resemblance to the high division of the humeral artery into the radial and ulnar arteries in the hollow of the axilla, to take place above the femoral arch, consequently at the expense of the external iliac artery. Bums has seen this division taking place in the pelvis three times ; Tiedemann, who has observed it on both sides, thinks that it is only met with in small-sized individuals. In a case which Professor Dubreuil has communicated to me, where the right femoral artery was divided higher than usual, the epigastric artery, instead of being given off by the external iliac, came from the deep femoral, and the anterior circumflex iliac artery came from the superficial femoral artery. In another case which has been furnished to me by the same observer, the external iliac or femoral artery, in its passage below the crural arch, was divided into three branch- es : the external branch was the superficial muscular, the internal branch was the deep muscular, which, immediately after its origin, dipped between the muscles ; the middle branch, which was of a larger size than the two others, was the true femoral artery. The only anomalies in this case were in the origin of the branches ; in their distribution they were as usual. During its course, the deep femoral gives off a great number of collateral branches, which are soon expended in the adjacent muscles, and most of which are unnamed. Those that are named are the internal and external circumflex, and the several f erf orating arteries. The internal circumflex artery (e) is larger than the external, and is the first branch given off from the deep femoral ; not unfrequently it arises from the femoral. I have observed, however, that this only takes place when the deep femoral artery arose a lit- tle lower down than usual. In a case of this kind, the origin of the deep artery took place * It is the proper artery of the thigh, while the femoral itself may be regarded as the artery of the leg and foot. t This relation is the one which always exists when the deep femoral artery arises opposite or above the femoral arch ; the deep femoral passes down close by the external side of the superficial femoral ; this latter covers the vein : if, in a case of this kind, the femoral artery were to be tied, and the ligature were applied only to one vessel, it would be to the deep artery, which holds the relations that generally belong to the trunk of the femoral artery itself. Tn a case exhibited at the Anatomical Society by M. Mercier, the deep femoral, which arose from the ante- rior side of the common femoral six lines below the arch, descended downward before the feiii ral vein, which it crossed opposite the opening for the scaphena vein, turned round this vessel to become the c<;f\i artery, and coursed along as usual. In this case, the deep femoral gave off the external pudic iirteries 564 ANGEIOLOGY. more than two inches below the femoral arch. Sometimes the internal circamflex comes from the external iliac artery. Whatever may be its origin, it almost immediately dips backward, between the pectineus and the neck of the femur, round which it turns in the same manner as the posterior humeral circumflex artery, so that it may be ruptured in luxation of the femur inward : it escapes backward beneath the quadratus femoris, and terminates by dividing into ascending branches, and into internal and external descend- ing branches. Opposite the pectineus, it gives off the following collateral branches : cae very re- markable articular branch ascends along the capsular ligament, enters the hip-joint, passes under the ligament which converts the cotyloid notch into a canal, and is distributed to the synovial membrane, the adipose tissue, and the fibrous capsule of the joint : one or more anastomotic branches communicate freely with the ramifications of the obturator artery ; lastly, a great number of muscular branches, some of which are very small, and pass in front of, while others, which are larger, run behind, the pectineus, and are distrib- uted to the obturator externus, the pectineus, and the adductors : the largest is intended for the adductor magnus. The terminal branches are as follows : Ascending muscular branches, some of which are external, and ramify in the glutaeus maximus, while others are internal, and are dis- tributed to the ischiatic attachments of the biceps, semi-tendinosus, and semi-membra- nosus muscles ; descending muscular branches, which ramify upon the anterior surface of the biceps, semi-tendinosus, and semi-membranosus, upon the great sciatic nerve, and also in the small muscles situated between the pelvis and the trochanter major ; periosteal branches, of which some ramify upon the periosteum of the trochanter, other& upon the posterior surface of the neck of the femur ; and, lastly, anastomotic branches, which pass upon the obturator, gemelli, and pyriformis muscles, and anastomose freely with the sciatic, glutaeal, internal pudic, and obturator arteries, but especially with the sciatic and the obturator. It follows, then, that the internal circumflex is an important means of communication between the internal Uiac, and, consequently, the common iliac and the femoral ; for, independently of the direct anastomoses above mentioned, there are a great number of indirect communications in the substance of the muscles and upon the periosteum. The external or anterior circumflex (/), smaller than the internal, sometimes arises di- rectly from the femoral ; it is often given off from the profunda by a common trunk with the great muscular artery of the triceps, and it may then be regarded as fonned by the bifurcation of the profunda : it passes horizontally behind the rectus femoris, crossing in front of the psoas and iliacus, to which it gives a rather large vessel, and then divides into two branches : an ascending muscular, Avliich is distributed to the glutaeus minimus and to the tensor vaginse femoris ; and a circumflex branch, properly so called, which turns round the base of the great trochanter {f,flg. 215), dips into the substance of the triceps, and expands into a great number of ascending branches, which anastomose w ith the internal circumflex upon the outer surface of the great trochanter. Not unfrequent- ly, an anastomosis is formed in front by a transverse branch between the internal and ex- ternal circumflex arteries, by which the arterial circle of the hip-joint is completed. The perforating arteries (r r,fig. 214) are both muscular and cutaneous, and are intend- ed for the posterior region of the thigh : they vary in number from one to four, and are all distributed in a similar manner. They perforate the tendinous attachments of the adductor muscles to the femur, and, having reached the back of the thigh, they turn horizontally round the bone, and divide into ascending and descending branches, which form a series of loops or anastomotic arches in the substance of the muscles ; these loops acquire a great size in cases where the femoral has been tied after Hunter's meth- od, i. e., in the middle third of the thigh. The first perforating artery {r,fig. 215), which is the largest, and sometimes repre- sents two, or even the whole of the perforating arteries, passes through the great ad- ductor about one inch below the lesser trochanter, between the horizontal and oblique fibres of the muscle ; its ascending branch («) turns round the great trochanter, and anas- tomoses with the internal circumflex and sciatic in the substance of the glutaeus maxi- mus ; its descending branch (Z) is distributed to the vastus externus, the semi-tendinosus, semi-membranosus, biceps, and adductor magnus muscles. Some branches ramify upon the great sciatic nerve.* I have seen an inferior perforating artery arise from the femoral, just where it passed through the tendon of the adductor magnus. The terminal branch (d',flg. 214) of the deep femoral constitutes the last perforating artery, which is distributed in the same manner as the other arteries of that name. The Popliteal Arteky. When the femoral artery has perforated the tendinous portion of the adductor magnus, it takes the name of the popliteal artery, which extends down to its division into the an- terior tibial and tibio-peroneal arteries. * The principal nutritious artery of the femur arises from the first or second perforating artery. THE POPLITEAL ARTERY. ffe The popliteal artery {o,figs. 215, 217) is the artery of the ham or popliteal space ; it Fig. 215. is bounded above (p,fig- 215) by the tendinous ring formed in the adductor niagnus, and below (p, fig. 217) by the low- er border of the popliteus muscle, at which place it is sit- uated opposite the lower end of the upper fourth of the leg.* Its length in an adult subject is about seven inches. It passes vertically, or somewhat obliquely outward and downward, the direction of the artery being represented by a line extending from the inner surface of the femur to the space between its two condyles. It is tortuous when the leg is flexed upon the thigh, but it becomes straight when the leg is extended, and may be ruptured by very forcible extension. It has been proved by experiment, that extension may be carried as far as to cause lacera- tion of the ligaments of the joint, without rupturing the ar- tery, t Relations. — It is situated deeply in the whole of its course, and it is in relation, behind, with the semi-mem- branosus above ; lower down, with the popliteal fascia, from which it is separated by a layer of fat of greater or less thickness, according to the prominence of the ham- string muscles ; below this, with the gastrocnemius and plantaris muscles ; and still lower, with the soleus. The popliteal vein lies behind and slightly to the outer side of the artery, and then behind it, adhering rather firmly to it. The internal popliteal nerve also lies upon it behind, but is separated from it by a very thick layer of fat. The veins and nerves both cross the artery beneath the gas- trocnemius, so as to get to the inner side of the lower portion of the vessel. From these relations, it follows that the popliteal artery may be exposed from behind in the whole of its extent, but that it is deeper seated below than above. hi front, it is in relation, from above downward, with the adductor magnus ; with the internal surface of the fe- mur, which appears to be expanded and become posterior, so as to support the vessel ; with the knee-joint, with which it is in direct contact ; and, lastly, with the popli- teus muscle. The direct relation of the popliteal artery with the joint explains the fa- cihty with which it may be lacerated when its tissue has been rendered fragile from or- ganic change, and accounts for the frequency of aneurism in this region. On the inner side, this artery is in relation with the semi-membranosus, the inner con- dyle of the femur, and the inner head of the gastrocnemius. On its outer side, it has the biceps, the outer condyle, the outer head of the gastroc- nemius, and also the plantaris and soleus muscles. Collateral Branches. — The popliteal artery gives off- from its posterior aspect several small branches, which pass into the muscles of the ham ; most of them are not named ; but there are some which are distinguished as the sural arteries : in front it gives sev- eral arteries, named articular, because they surround the knee, like the collateral arter- ies of the elbow-joint. The articular arteries are divided into superior, middle, and in- ferior ; the superior and inferior would have been better named the collateral arteries of the knee. The sural arteries {g g,fig*- 215, 217) are two in number: one internal, for the innei head of the gastrocnemius, and the other external, for the outer head of the same muscle. Arising from the back of the popliteal artery, they pass downward and backward, are separated from each other by the internal popliteal nerve, enter the anterior and inter- nal surface of each head of the gastrocnemius a little before the two heads meet, and may be traced down to the lower part of the fleshy belly of that muscle. Generally one of their branches accompanies the external saphenous nerve from the popliteal space to the upper part of the tendo Achillis. The superior articular or collateral arteries of the knee are divided into internal and external. The internal superior articular arteries are sometimes three, but most commonly two in number, one of which arises higher than the other ; their origin is subject to variety, * The divisioa of the popliteal artery takes place sowetiraes higher, sometimes lower than usual. In a case ■where its bifurcation was premature, the anterior tibial has been seen passing between the popliteus muscle and the posterior face of the til)ia. t I have had an opportunity of observing a case of luxation of the knee, with complete laceration of the crucial ligaments, where the popliteal artery was left entire. 566 ANGEIOLOGY. but they are constant in their distribution. We sheill distinguish them as the first and second. The first internal superior articular artery, usually called the great anastomotic artery of the knee, is the largest of the whole : it arises opposite the point where the femoral becomes the popliteal artery, and sometimes even from the lower part of the femoral it- self; it perforates the adductor magnus from behind forward, and immediately divides into four descending branches: the first is a muscular branch {i,fig. 214), which enters the substance of the vastus internus, passes inward and downward to reach the inner border of the tendon of the triceps, and, opposite the base or upper border of the patella, perforates the fibres of the muscle, becomes superficial, and runs transversely outward along the base of the patella, and forms an anastomotic arch with the external superior articular artery. The second and third branches are periosteal ; one of them passes be- tween the triceps and the femur, with which it is in contact, and terminates above the trochlea of that bone by anastomosing (at s) with the external superior and the second internal superior articular arteries ; while the other runs along the adductor magnus, being held down against it by a layer of fibrous tissue, and anastomoses with tlie second internal superior articular artery, supplying its place when that vessel is only in a rudi- mentary state. The fourth branch (A) accompanies and supplies branches to the inter- nal saphenous nerve : it appears to be constant ; it is placed under the sartorius, along which it runs, together with the internal saphenous nerve, continuing with it below that muscle. The second internal superior articular artery {h,figs. 215, 217) arises immediately above the inner condyle of the femur, turns round it horizontally, and divides into condyloid branches, which cover the condyles with their ramifications, and communicate partly with the first internal superior articular artery, and partly with the external superior ar- ticular artery coming from the opposite side. It also gives off a patellar branch, which runs upon the borders of that bone, supplies the skin and the synovial membrane of the knee-joint, and anastomoses with the internal inferior articular artery. The external superior articular artery {i,figs. 215, 217) arises opposite the second in- ternal superior, turns horizontally round the outer condyle of the femur, gives off some ascending muscular branches, which ramify in the vastus externus, and then terminates in three periosteal branches. One, which is superior and transverse, turns round the lower end of the femur, and anastomoses with the corresponding branch of the second internal superior articular ; another and inferior branch ramifies upon the inner condyle, and anastomoses freely by a great number of branches with the external inferior articu- lar ; the third is a more superficial branch for the patella, on the side of which bone it runs, and near its upper border gives off a transverse twig, which anastomoses on the upper border of the patella with a similar one from the internal superior articular arter- ies, and a descending twig, which runs along the outer border of the bone, and anasto- moses with the external inferior articular artery. The inferior articular or collateral arteries of the knee are also divided into the internal and the external. They both arise from the front of the popliteal artery, opposite the middle of the knee-joint. The internal inferior articular artery {c,fig. 217) runs downward and inward, and, hav- ing reached the internal tuberosity of the tibia, turns horizontally forward, passes be- neath the tendons of the semi-teHdinosus, semi-membranosus, and gracilis muscles, and also beneath the internal lateral ligament of the knee, turns upward upon the inner side of the anterior tuberosity of the tibia and ligamentum patellaj, describing a curve with its concavity directed upward, and anastomoses either with the superior articular arter- ies or with the anterior tibial recurrent. During its course it gives off ascending and descending periosteal and osseous branches.* The external inferior articular artery {b,fig. 217) arises opposite the internal vessel, turns horizontally forward, not upon the external tuberosity of the tibia (for this is pre- vented by the tibio-fibular articulation), but upon the convex borders of the external semilunar cartilage, passes beneath the tendon of the biceps and the external lateral ligament of the knee-joint, and terminates by dividing into an ascending branch, which runs upward along the outer border of the patella, a descending branch, which anasto- moses with the anterior tibial recurrent, and a transverse branch, which passes behind the ligamentum patellae below the patella, and anastomoses with a similar branch from the internal inferior articular. The inferior articular arteries complete the arterial circle which surrounds the patella, and from which numerous branches are given off, some covering the patella by their anastomoses, and others entering the bone directly through the numerous foramina which exist upon its surface. The middle articular arteries (*, fig. 215) consist of several small branches, which arise directly from the front of the popliteal artery, or from the external inferior articular, run from behind forward into the interior of the knee-joint, and are distributed in the inter- condyloid notch to the crucial ligaments, the adipose tissue, the synovial membrane, and * By osseous branches I mean those which enter the bone directly through the foramina, on the internal and external tuberosities of the tibia. THE ANTERIOR TIBIAL ARTERY. 567 especiaDy to the lower extremity of the femur, which they penetrate through the large foramina on the adjacent surface of each condyle. The middle articular artery or arter- ies belong, therefore, to the knee-joint exclusively, and do not assist in the restoration of an impeded circulation : in this respect they differ entirely from the other articular arteries, which acquire a very considerable size when the principal trunk has been tied. The Anterior Tibial Artery. Opposite the lower border of the popliteus muscle, the pophteal artery divides into two branches : an anterior, named the anterior tibial {a, Jig. 217) ; and a posterior, which forms the continuation of the popliteal, and may be denominated the tibio-peraneal trunk (/). This trunk soon subdivides into the posterior tibial (t) and the peroneal {k) arteries. The anterior tibial artery {a, Jigs. 216, 217), the anterior branch of the bifurcation of the popliteal, terminates opposite the dorsal annular ligament of the Fig. 216. tarsus (J), Jig. 216), below which the vessel is named the dorsal artery oj the foot (/). Immedidtely after its origin, it passes horizontally forward, perforates the upper part of the interosseous ligament, is re- flected over it, and descends vertically in front of it ; having reached the lower fourth of the leg, it is directed somewhat obliquely inward, following the direction of the external surface of the tibia, and then passes under the annular ligament, at the lower border of which, as stated, it terminates. A line stretched from that process of the tibia, which has been de- scribed as the tubercle of the tibialis anticus (Osteology, p. 278), to the middle of the tibio-tarsal articulation, will indicate its direction and course. Relations. — The anterior tibial artery is situated very deeply, and yet it can be exposed at any point ; it is in relation, behind, with the | f interosseous ligament in its three upper fourths, and with the tibia in its lower fourth ; it lies in contact with the interosseous ligament, and is retained in its place by a layer of fibrous tissue, so that, after amputation of the leg, it retracts between these two fibrous layers, and is sometimes seized and tied with difficulty. In front, it is covered successively by the tibialis anticus, the ex- tensor longus digitorum, and the extensor proprius poUicis, the ten- don of which crosses over it ; it is placed exactly along the cellular interval between the tibijdis anticus and the extensor muscles ; and the incision should, therefore, be made along the line corresponding to that interval, in order to expose the artery when it is to be tied ; lower down it is only separated from the skin by the fascia of the leg and the projecting tendon of the extensor proprius pollicis, and hence it may be compressed in this situation. UiPS?iiif ANGEIOLOGY. of the facial vem/wRicIi^lie calls the internal and anterior maxillary: it corresponds to all the branches given off from the internal maxillary artery behind the neck of the condyle, in the zygomato-maxillary fossa ; while the alveolar vein, the deep branch of the facial, corresponds to all the branches given off by the internal maxillary artery upon the tuber- osity of the superior maxilla and in the pterygo-maxillary fossa. Thus it is joined by the middle meningeal veins. The venae comites of the middle me- ningeal artery, the existence of which has been erroneously denied, are two in number, and are situated, one in front, the other behind the artery. These veins often receive some inferior and anterior cerebral veins, which enter them near the foramen spinosum of the sphenoid ; they always receive veins from the bones of the cranium and from the dura mater, and communicate with the superior longitudinal sinus ; they are sometimes so large, especially the anterior branch, that they have deep grooves formed for them upon the sphenoidal fossa, reaching from the foramen spinosum to the point of the great ala of the sphenoid bone. Lastly, the distribution of the middle meningeal veins is sim- ilar to that of the corresponding artery. The internal meixillary vein is also joined by the inferior dental, by the deep temporal, by the pterygoid, and by the posterior masseteric veins. All of these veins communicate with a very large and important venous plexus, the pterygoid plexus, situated between the temporal and external pterygoid muscles, and between the two pterygoid muscles. In this plexus, which communicates freely with the alveolar plexus, so freely, indeed, that they may be regarded as forming but a single plexus, the internal maxillary vein commences and joins the temporal vein, behind the neck of the condyle of the lower jaw. The temporo-maxillary trunk, thus formed by the junction of the temporal with the internal maxillary vein, is much larger than the former vein, and continues its course through the substance of the parotid gland ; it is joined directly by some parotid veins, by the posterior and anterior auricular veins, and, lastly, by the transverse veins of the face. The last-named veins form, between the parotid gland and the masseter muscle (j, fig. 219), between that muscle and the ramus of the lower jaw, and around the temporo-max- illary articulation, a very large plexus, named the masseteric plexus, which communicates freely with the pterygoid plexus through the sigmoid notch. Termination of the Temporo-maxillary Trunk. — Most commonly the temporo-maxillary vein or trunk terminates directly in the external jugular vein (h) ; at other times it enters the internal jugular, and then there is merely a trace of the external jugular, which is formed principally by the superficial branches of the occipital vein, and by some commu- nicating branches from the anterior jugular. In some cases, the temporo-maxillary vein is almost equally divided between the internal and external jugulars ; lastly, it is some- times united to the lingual and the facial vein : when it ends in the external jugular, it sends to the internal jugular a large conmiunicating branch which passes above the di- gastric muscle. The Posterior Auricular Vein. The posterior auricular vein follows the distribution of the artery of that name ; it re- ceives the stylo-mastoid vein, and enters the external jugular, or, rather, the temporo- maxillary vein, which does not take the name of external jugular until after it is joined by this vein. The Occipital Vein. The occipital vein is distributed in the same manner as the occipital artery ; it com- mences at the back of the cranium, passes beneath the splenius muscle, and is joined opposite the mastoid process by one or more large mastoid veins, which come from the corresponding lateral sinus, establishing a direct and free communication between the venous circulation in the interior and exterior of the cranium. It was this that led Mor- gagni to prefer the occipital veins for the purpose of bloodletting in apoplexy. The oc- cipital vein ends in the internal, and sometimes in the external jugular. The Lingual Veins. The lingual veins, being intended for a contractile organ, the circulation in which is on that account liable to be much interfered with, are divided, hke the veins of the limbs, into the superficial or suh-mucous, and the deep veins. The superficial veins of the dorsum of the tongue, which are generally named the lingual veins, occupy the dorsal region of the tongue, ramifying in a remarkable manner between the mucous membrane and the muscular fibres of that organ : all these veins open into a dorsal or superior lingual plexus, which is situated at the base of the tongue, and is joined by a great number of veins from the tonsils and epiglottis. The satellite vein of the lingual nerve emanates from this plexus, accompanies the lin- gual nerve, receives some branches from the sub-lingual glands and the tissue of the tongue, and enters the facial or the pharyngeal vein, or terminates directly in the exter- nal jugular, communicating freely with the ranine veins. The ranine veins are the superficial veins of the lower surface of the tongue. They THE PHARYNGEAL VEIN, ETC. 991 are seen one upon each side of the fraenum, where they form a ridge beneath the mucous membrane. Each of them accompanies the corresponding hypoglossal nerve, between the genio-hyoglossus and hyoglossus muscles, and terminates either in the common trunk of the lingual and facial veins, or directly in the facial vein. The ranine veins communicate upon the sides of the tongue with a very large plexus, the vessels composing which are sometimes provided with valves, so that it is impossi- ble to inject it in a direction from the heart towards the extremities of the veins, which, in other cases, may be done with the greatest facility. Lastly, the lingual veins, properly so called, are extremely small; they are two in number, and accompany the lingual artery throughout the whole of its course. Not un- frequently the veins of the tongue terminate directly in the internal jugular : I have seen them open into the anterior jugular. The Pharyngeal Vein and Pharyngeal Plexus. The Pharyngeal Plexus. — In making the section already described for examining the pharynx, we observe round the back of that organ a considerable venous plexus, which forms loops or rings for embracing the pharynx ; several meningeal branches, and some derived from the vidian and spheno-palatine veins, open into this plexus ; from which a variable number of pharyngeal branches arise, and terminate by a common trunk, or by several distinct branches, in the lingual vein, sometimes in the facial or the inferior thy- roid, and frequently in the internal jugular. Besides this plexus, which may be called the superficial pharjTigeal plexus, an ex- tremely dense network is found beneath the mucous membrane, from which branches proceed to join with those that arise from the superficial plexus just described The Superior and the Middle Thyroid Veins. The superior thyroid, or thyro-laryngeal vein, commences upon the thyroid gland by branches corresponding to the thyroid arteries, and upon the larynx by branches corre- sponding to the ramifications of the superior laryngeal artery. The thyroid and laryn- geal branches unite and end in the internal jugular vein, opposite the upper part of the larynx ; they perhaps end more frequently in the common trunk of the facial and lingual veins. It is not uncommon to find the superior laryngeal branch terminating directly either in one or the other of these veins, or in the anterior jugular. The middle thyroid vein arises from the lower part of the lateral lobe of the thyroid gland, and is joined by some branches from the larynx and the trachea. By their union they form a trunk, which ends in the lower part of the internal jugular vein. The con- stant existence of this vein explains in some degree a rather frequent variety in the ar- teries of the thyroid gland, viz., the existence of a middle thyroid artery given off by the common carotid. Not unfrequently there are two middle thyroid veins on each side These, as well as all the other thyroid veins, are much enlarged in goitre The Veins of the Diplo'e. To complete the description of the vessels of the head, it only remains for me to no- tice the diploic veins, or the proper veins of the bones of the cranium. They were first described by M. Dupuytren, in his inaugural thesis, under the name of venous canals of the bones : they were afterward figured by M. Chaussier (Traite de V Encephale), and, to- gether with their principal varieties, they have lately been represented with uncommon accuracy by M. Breschet, in his admirable work upon the veins. In the substance of the cranial bones there are found ramified venous canals, which are occupied by veins, having only their internal membrane, the bony canals themselves serving for an external coat. These venous canals are not exclusively confined to the bones of the cranium : they exist in all spongy bones, and even in compact bones ; but, while the canals are found in the entire substance of spongy bones, in the compact part of the long bones they are situated near the medullary canal. The venous canals of the bones of the cranium vary much in their size, and in the extent to which they are distributed : they are independent of each other as long as the cranial bones remain distinct and separable ; but they almost always communicate when, in the progress of age, those bones become united together. They get larger and larger as life advances, and their size is indirectly proportioned to the number of their ramifi- cations : they sometimes present ampullae or dilatations, and at other times are suddenly interrupted, and terminate in culs-de-sac, reappearing again farther on, or ceasing alto- gether : these peculiarities depend upon the venous canal opening at different points into the middle meningeal veins. Moreover, these venous canals communicate by a number of orifices of different sizes, either in the interior of the cranium with the me- ningeal veins, and with the sinuses of the dura mater, or on the exterior with the veins which lie in contact with the bones of the scull. In some heads of old subjects, these canals are found blended with the furrows for the branches of the meningeal arteries ; those furrows- themselves present some large foramina, which open into the cranium in various nlaces. 69^ ANGEIOLOGY. In new-born infants there are no venous canals, properly so called ; but the whole substance of the bones is traversed by a venous network, which may be seen when its constituent veins are naturally injected with blood, or when they have been filled with mercury, by which as delicate a network of vessels can be shown in the diploe as in in- jections of the soft parts. At this period all the cells of the bones are filled with venous blood. On the roof of the cranium the canals of the diploe are divided into the frontal, tempo- ral, parietal, and occipital. The frontal diploic canals are two in number, one on the right, the other on the left side : they commence by numerous ramifications upon the upper part of the frontal bones, increase in size as they approach the lower part of the roof of the scull, commu- nicate with each other by transverse branches, and also with the periosteal or the me- ningeal veins, open externally by vascular foramina, and then enter the supra-orbital and frontal veins. The temporo-parietal diploic canals are divided into anterior and posterior : they corre- spond to the furrows which contain the ramifications of the meningeal artery, and open into those furrows by a great number of foramina, which become very distinct in advanced life : they also communicate with the deep temporal veins on the exterior of the scull. The occipital diploic canals, two in number, a right and a left, communicnte with each other by a great number of branches, and open below into the occipital veins. Summary of the Distribution of the Veins of the Head. Circulation in the Brain. — Corresponding to two of the arterial trunks, the common carotids, which convey blood to the head and neck, there are six veins, to return it back to the heart from the same parts, viz., the two internal, the two external, and the two anterior jugulars. This arrangement tends to prevent interruption of the venous circu- lation in the head, which, from so many causes, is liable to be disturbed. The external and anterior jugular veins belong to the sub-cutaneous venous system, and may be re- garded as supplementary veins which have no corresponding arteries, and which would be sufficient of themselves to carry on the venous circulation ; and as the veins of the right and left sides communicate very freely with each other, it follows that one of them would suffice to return the blood from the head. It will be seen hereafter, when de- scribing the veins of the spine, that the obliteration of all the six jugular veins would not of necessity be followed by interruption of the venous circulation in the cranium. Lastly, it is important to observe, that the external and anterior jugulars open into the sub-clavian vein, while the internal jugular joins the inner end of the sub-clavian, to form the brachio-cephalic vein. We have seen that the lower part of the internal jugular vein represents the common carotid, and the upper part of it the internal carotid ; and that the external carotid is represented by all the veins of the face and neck, which open into the internal jugular either by a common trunk, or by several distinct branches. The cerebral venous system is remarkable for the extreme thinness of the parietes of the veins upon the brain, and for the existence of the sinuses, which take the place of the venous trunks, and differ so much in their distribution from the arteries. The cerebral veins are divided into the ventricular veins, which go to form the venae Galeni, and the superficial veins of the brain. All of them run towards the sinuses, in which they terminate in succession like the barbs of a feather upon the common shaft, but do not acquire a great size. From the absence of valves at their orifices into the sinuses, the blood may regurgitate into them. The presence of the spongy areolar tissue at the or- ifices of these veins, together with their oblique course through the walls of the sinus, must diminish this regurgitation : the communication of the cerebral veins with each other, and the continuity of the several sinuses, explain the varied means contrived for carrying on the cerebral circulation, which can only be interrupted by obliteration of the lateral sinuses. Lastly, the position of the principal sinuses opposite the fissures between the great di- visions of the encephalon, and the resisting nature of the walls of the sinuses themselves, prevent the fatal effects which might otherwise ensue from compression produced by obstruction of the venous circulation. Circulation in the Parietes of the Cranium. — In the parietes of the cranium we find the veins of the dura mater, the veins of the diploe, the periosteal veins, and the veins of the hairy scalp. The numerous communications existing between these four systems of veins, and the direct communications established between the sinuses of the dura mater and the veins on the exterior of the scull, are worthy of particular attention. I would observe that the principal veins of the scalp, like the arteries of the same part, are situated between the skin and the epicranial aponeurosis. I have ascertained the existence of free and frequent anastomoses among these veins. As at the back of the cranium there is a very free communication between the occipital vein and the lateral sinus by means of a large vein, so, also, along the superior longitudinal groove, and op posite the sutures upon the base of the scull (through most of the foramina found in that THE DEEP VEINS OP THE UPPER EXTKEMITY. 593 ntoation), an uninterrupted communication is established between the veins within and ^ose outside the cranium. Venous Circulation of the Face. — ^All the veins of the face and of the parietes of the cranium end in two principal trunks, the facial and the temporal. The facial vein cor« responds to a part of the internal maxillary artery, to a part of the ophthalmic artery, and to the facial artery properly so called. One of the most remarkable circumstances connected with the distribution of the facial vein is the communication between it and the cavernous sinus, established at the inner angle of the orbit by means of the ophthal- mic vein, so that the veins on the inside and on the outside of the cranium are most in timately connected.* The temporal vein represents the temporal artery, a part of the internal maxillary ar- tery, and the upper part of the external carotid, and returns the blood from the entire side of the head. With regard to the veins of the tongue, we should remark the existence of two sub- mucous veins, corresponding to the sub-cutaneous veins in the limbs, and intended to return the blood, instead of the deep veins of the tongue, during the contractions of that organ. The size of the superior middle thyroid veins, their number, which exceeds that of the arteries, and their free anastomoses with the inferior thyroid veins, render them an important medium of circulation when the passage of the blood from the head is obstruct ed, and, at the same time, a diverticulum in great impediments to the circulation. The irregularity which exists in the relative size of the internal, external, and ante- rior jugular veins, and also in the distribution of the veins of the head between these three trunks, proves that, in the venous as well as in the arterial system, the origin or termination of the vessels is of little importance, and that, after the venous system of any part is once formed, it matters but little with which of the great vascular trunks it is connected. Lastly, the free communications which exist between all the preceding veins afford sufficient evidence that but little interest need be attached to their termination in one or another of the principal venous trunks. The Deep Veins of the Upper Extremity. The veiTts of the upper extremity are divided into the deep and the superficial or sub- cutaneous. The Palmar^ Radial, Ulnar, Brachial, and Axillary Veins. The deep veins of the upper extremity exactly follow the course of the arteries, form their venae comites, and take the same names : there are almost always two to each ar- tery. The large venous trunks alone form exceptions to this rule. Thus, there are two superficial and two deep palmar veins ; two deep radial and two deep ulriar veins ; we also find two brachial veins ; but there is only one axillary and one suh-clavian vein. All these venae comites receive branches formed by the union of still smaller ones, which are them- selves the vense comites of the ramifications of the arteries, there being two veins with each small artery. The sub-clavian vein, however, is an exception to this, for it does not receive all the veins which correspond to the branches of the sub-clavian artery ; while, on the other hand, it receives other veins that are totally unconnected with the distribution of that artery. I ought to allude, in this place, to a mode of termination of the collateral veins, which is frequently observed, especially in the brachial vein. The circumflex veins, for example, instead of entering the brachial vein directly, terminate in a collateral branch, which runs parallel to the brachial vein, like a canal running along- side a river, and communicates with that vein above and below. Several large veins have these collateral caneils, which establish a communication between different points of their length. Thus, I have seen a venous trunk proceed from the external jugular, de- scend through the brachial plexus of nerves, and enter the lower part of the axillary vein. The deep veins, moreover, communicate freely and frequently with the superficial veins. They are also provided with valves, like the superficial veins, and, it appears, even with a greater number : an injection thrown from the heart towards the extrem- ities will not enter more readily into one than into the other set. We always find two valves at the mouth of a small vein where it opens into the larger trunk ; and it is a re- markable fact that, while the valves situated in the course of the veins are sometimes passed by the injection, those which are placed at the mouths of the small veins are scarcely ever overcome. The Sub-clavian Vein. The term suh-clavian is generally given to all that portion of the brachial venous trunk * The study of these anastomoses ought to lead us again to have recourse to those local venesections which have fallen into disuse since the discovery of the circulation ; and it will enable us to determine, on anatomi- cal grounds, the proper places at which they should be performed. Thus, it appears to me that we might ad- vantageously introduce into jiractice bleeding from the angular vein in diseases of the eye ; from over the mas- toid region, and the point wl'.ch corresponds to the junction of the longitudinal with the lambdoidal suture, in cerebral affections; and bleeding from the ranine vein in diseases of the pharynx. 4 F 694 ANGEIOLOGY. which extends from the vena cava superior to the scaleni muscles ; but this vein may be described more naturally, as being limited internally by the brachio-cephalic vein, or, rather, by the junction of the internal jugular vein with the venous trunk of the upper extremity, and externally by the clavicle, or, rather, by the costo-coracoid, or sub-cla- vian aponeurosis. If the sub-clavian veins be thus defined, they will be of equal length on both sides ; and the left vein, and even the right vein also, will be shorter than the corresponding artery. The direction of the sub-clavian veins differs much from that of the arteries : we have Seen that the sub-clavian arteries describe a curve over the apex of the lung, with its concavity turned downward ; the sub-clavian veins, on the contrary, proceed directly outward as far as the first rib, over which they bend, so that they resemble the cord of the arc described by the sub-clavian artery. We have seen, also, that the inferior thy- roid vein, the internal mammary, the vertebral, the supra-scapular, the posterior scapu- lar, the deep cervical, and the left superior intercostal veins, enter not into the sub-cla- vian, but either into the superior vena cava, or into the brachio-cephalic vein. The right superior intercostal vein, when it exists, that is to say, when the branches which should form it do not terminate separately in the vena azygos, is the only one of the veins cor- responding to the branches of the sub-clavian artery which opens into the sub-clavian vein The external jugular, the anterior jugular, and a small branch from the cephalic vein of the arm, also terminate in the sub-clavian vein. It would therefore, in some respects, be proper to describe the external and anterior jugulars in connexion with the sub-cla- vian vein, instead of with the internal jugular. I would remark, that the external and anterior jugulars frequently terminate, not in the sub-clavian vein, but at the point where it ends in the brachio-cephaUc vein, in front of the internal jugular. Relations. — In front of the sub-clavian vein is situated the clavicle, which is separated from the vein only by the sub-clavian muscle, so that this vessel may be wounded in fractures of the clavicle : a very dense fibrous sheath binds it down to the sub-clavius muscle ; and it perforates the costo-coracoid or sub-clavian aponeurosis, which adheres to it, and keeps it open when cut across ; behind the vein is the sub-clavian artery, from which it is separated, towards the inner part, by the scalenus anticus ; below, it is in re- lation with the pleura and with the first rib, on which there is a corresponding but slight depression ; above, it is covered by the cervical fascia, which separates it from the skin : a considerable swelling is often seen in this region when the venous circulation is ob- structed. The Superficial or Sub-cutaneous Veins of the Upper Extremity. The sub-cutaneous veins of the upper extremity belong essentially to the skin and to the subjacent adipose tissue, since all the branches from the muscles enter the deep veins. The superficial are larger than the deep veins, with which they communicate freely at a great number of points ; and it may be remarked, that the size of the one set of vessels is always inversely proportioned to that of the other set. We proceed to describe them in succession in the hand, the forearm, and the arm. The Superficial Veins of the Hand. All the largest veins of the hand are situated upon its dorsal aspect ; and it is worthy of notice, that the largest arteries, on the contrary, occupy the palm of the hand. If the superficial veins had existed on the palmar aspect, the venous circulation would have been impeded whenever the hand was used in prehension. Entering into the large sub- cutaneous network of veins situated upon the back of the hand are several branches, which constitute the superficial, external, and internal collateral veins of each fingei , they occupy the outer and inner borders of the dorsal surface of the fingers, and comnmni- cate frequently on the dorsal surface of each phalanx and around the phalangeal artic- xilations, but not upon the articulations themselves. Opposite the lower part of each interosseous space, these collateral veins unite at an acute angle, just as the digital arteries bifurcate at the same point. All the superficial digital veins ascend vertically between the metacarpo-phalangeal articulations, which they seem to avoid, and then enter into the convexity of a very irregular venous arch, ■which is formed by a series of loops, at each of the junctions of which one of the digital veins is seen to terminate. From the concavity of this irregular arch, which is turned upward, are given off a /greater or less number of ascending branches, which are sometimes formed directly by ■ the junction of the digital veins, without the intervention of an arch. Among these branches, we should especially notice the external branch, which is situated nearest to the first metacarpal bone, and is called the cephalic vein of the thumb; also the innermost branch, which corresponds to the fifth metacarpal bone, and, for some reason not very '.well known, has been named the vena salvatella. The Superficial Veins of the Forearm. "The superficial veins are much more numerous on the anterior than on the posterior THE SUPERFICIAL VEINS AT THE ELBOW, ETC. 595 aspect of the foreann. We find there the radial vein or veins, the ulnar vein, and the median vein. The superficial radial vein (r, in the representation of the superficial nerves of the arm) is the continuation of the cephalic vein of the thumb ; it is situated along the outer side of the carpus and of the radius, and it soon unites with some branches from the vena salvatella, or vi^ith the salvatella itself The superficial radial vein often divides into several branches, which are joined by others from the venous arch at the back of the hand. There are sometimes two superficial radial veins. The vein or veins having reached the middle of the forearm, turn forward upon the outer border of the radius, and then continue to ascend vertically along the outer side of the anterior surface of the fore- arm, up to the bend of the elbow. The ulnar vein {u) commences partly from the vena salvatella, and another vein on the dorsal region of the forearm, and partly from some branches which arise from the lower part of the back of the forearm, and even from some small veins proceeding from the thenar and hypothenar eminences. The branches which arise from the vena salvatella and the back of the wrist pass for- ward ; the other branches run backward ; the common trunk or trunks resulting from their union are directed at first vertically upward, parallel with the superficial radial vein, then somewhat obliquely forward, to anastomose with the median basilic vein, above the bend of the elbow. When there is a second or posterior ulnar vein, it ends in the basilic higher up, or else it anastomoses with the anterior ulnar vein. Between the anterior radial and ulnar veins we find the common median or median vein (m), formed by the anterior veins of the carpus and forearm. There may be more than one median vein, and it is not unfrequently wanting, in which case its place is supplied by a venous network, the branches from which enter separately into the radial and ulnar veins. In some cases its place is supplied by an additional radial vein, and at other times by the deep veins. The Stiperficial Veins at the Elbow. At the elbow all the veins are on the anterior aspect. The most common arrangement is the following : on the outer side we find the upper portion of the radial vein or veins ; on the inner sMe, the upper portion of the ulnar vein or veins, which pass in front of the internal condyle of the humerus ; between the radial and ulnar veins is the median, which divides into two branches : one external (a), which unites with the radial to form the cephalic vein (c), and is called the median cephalic ; the other internal (e), generally smaller, but more superficied than the preceding, which unites with the ulnar to form the basilic vein {b), and is called the median basilic. Several varieties are observed in the arrangement of the veins of the elbow ; some- times the common median vein is wanting ; but then its cephalic and basilic branches are given off by the radial, and the cephalic vein is almost always very small. In other cases we only find two veins at the bend of the elbow, viz., the radial and the ulnar, which are directly continuous with the cephalic and basilic. I once saw the common median vein replaced by the anterior radial, and by a branch from one of the deep ulnar veins. The Superficial Veins in the Arm. In the arm there are only two superficial veins, an external, named the cephalic vein, and an internal or basilic. The cephalic vein (c) is formed by the junction of the radial with the median cephalic vein, which junction may occur at very different heights. It ascends vertically along the outer border of the biceps ; then, running a Uttle inward, it gains the furrow be- tween the deltoid and pectoralis major, passes over the summit of the coracoid process, above or in front of which it curves backward, so as to enter the axillary vein immedi- ately below the clavicle. From this curve the cephalic vein gives off a branch, which passes in front of the clavicle, crosses at right angles over the middle of that bone, and enters the sub-clavian vein. Not unfrequently the cephalic vein is replaced by a very small branch. The internal vein of the arm, which is called the basilic vein (i), is generally larger than the cephalic. It is formed by the junction of the ulnar with the median basilic vein, passes at first obliquely backward, and then vertically upward, in front of the internal intermuscular septum, and enters either the brachial or the axillary vein. General Remarks upon the Superficial Veins of the Upper Extremity. From the preceding description, it follows that the cephalic vein forms the continua- tion of the radial, which is itself the continuation of the cephalic vein of the thumb, and that the basilic is a prolongation of the ulnar, which is a continuation of the vena salva- tella. The median vein, placed as it is between the radial and ulnar veins, bifurcates so as to tei-minate equally in the two latter veins, and estabhshes a free anastomosis be- tween them. • , 998 ANGEIOLOGY. The anastomoses of the several sub-cutaneous veins together are very numeroois, and enable them mutually to supply the place of each other. The anastomoses betvireen the sub-cutaneous and deep veins are not less numerous. Thus, the superficial collateral veins of the fingers communicate with the deep collat- eral veins : communications exist between the superficial and deep veins of the carpus ; very large communications exist between the two sets of vessels at the bend of the el- bow, so that, in fact, they are continuous with each other ; thus, the superficial radial vein is sometimes continuous with one of the deep radials, and the median, as it divides into the median basilic and median cephalic, occasionally sends a very large branch to the brachial. In one case, where the median vein was wanting, I found that the ulnar, the deep interosseous, and the deep radial veins, formed a plexus, which gave oflT two branches, an external to the cephalic, and an internal, which formed the deep brachial vein. The superficial ulnar veins often communicate freely with the deep ulnar, beneath the muscles attached to the internal condyle. Along the arm, the basilic vein communicates with one of the brachial veins by several transverse branches. Not unfrequently the basilic vein communicates with the brachial by a very delicate branch, which forms a lateral canal. Valves. — ^The valves are more numerous in the deep than in the superficial veins ; they increase in number as we approach the upper part of the arm, and are much more numerous in the basilic than in the cephalic vein. There are three in that part of the cephalic which corresponds to the furrow between the deltoid and the pectoralis major. There is one at the opening of the cephalic into the axillary ; another at the opening of the basilic into the brachial ; all the small veins which enter the cephalic and basilic, as well as those which terminate in the deep veins, are also provided at their openings with valves, which prevent the regurgitation of the blood during life, and the passage of an injection from the heart towards the extremities. General Relations. — The sub-cutaneous veins are separated from the skin by the super- ficial fascia, and by the layer of fat above it. The median basilic is the only exception, for it is in contact with the skin, at least in the majority of subjects. The sub-cutaneous veins must be carefully distinguished from the cutaneous veins, prop- erly so called, which are in contact with the true skin, or even ramify in its substance, and which are sometimes of considerable size, especially in the neighbourhood of certain tumours. From the relation of the median basilic vein with the brachial artery, over which it crosses at a very acute angle, and from which it is separated only by the fibrous expan- sion from the tendon of the biceps, it follows, that in emaciated persons the vein is al- most in contact with the artery ; so that, in bleeding from the median basilic, if the vein be perforated quite through, the artery may be wounded. The practical rules to be de- rived from this anatomical fact are, in the first place, to avoid bleeding in the median basilic as much as possible, and whenever it must be chosen, to open it either below or above the point where it crosses over the artery. In the description of the lymphatics and nerves of the arm, I shall point out their re- lations with the superficial veins. I may now state, however, that the musculo-cutane- ous nerve passes behind the median cephalic vein, and that the internal cutaneous di- vides into several branches, some of which pass in front, and others behind the median basilic vein. THE INFERIOR OR ASCENDING VENA CAVA AND ITS BRANCHES. The Inferior Vena Cava — the Lumbar or Vertebro-lumbar Veins — the Renal — the Middle Supra-renal — the Spermatic and Ovarian — the Inferior Phrenic. — TVie Portal System of Veins — the Branches of Origin of the Vena Porta — the Vena Porta — the Hepatic Veins. — The Common Iliacs — the Internal Iliac — the Hemorrhoidal VeiTis and Plexuses — the Pelvic Veins and Plexuses in the Male and in the Female. — The Deep Veins of the Lower Extremity — the Plantar, Posterior, Tibial, Peroneal, Dorsal, Anterior Tibial, and Pop- liteal — the Femoral — the External Iliac. — The Superficial Veins of the Lower Extremity — the Internal Saphenous — the External Saphenous. The vcTia cava inferior or ascendens, or the abdominal vena cava {I, fig. 222), is the large venous trunk which returns the blood from all the parts below the diaphragm to the heart. It is formed below by the junction of the two common iliac veins (n n), opposite the mtervertebral substance between the fourth and fifth lumbar vertebras ; it passes verti- cally upward, and, having reached the lower surface of the liver, inclines a little towards the right side, to gain the groove formed for it in the posterior border of that organ. At the upper end of that groove the vena cava inferior perforates the tendinous opening in the diaphragm, and also the fibrous layer of the pericardium, which is, as it were, blend ed with the cordiform tendon at this point ; the vein then curves suddenly to the left, and opens (r, fig. 192) horizontally into the posterior inferior part of the right auricle. THE VERTEBRO-liUMBAU VEINS, ETC. 597 It is larger than the vena cava superior, but is not of uniform caliber throughout ; for example, it increases in size in a marked degree immediately above the renal veins. The vena cava inferior presents also a second still larger dilatation opposite the liver, vphere it is joined by the hepatic veins ; in comparison w^ith its diameter at that point, the vena cava inferior appears to be slightly contracted as it passes through the dia- phragm. Relations. — The inferior cava is in contact with the anterior surface of the vertebral column, and runs throughout the whole of its extent along the right side of the aorta ; it inclines somewhat obliquely to the right as it is about to pass into the groove on the liver. In front it is covered by the peritoneum, the third portion of the duodenum, the pancreas, the vena portse, which crosses it at a very acute angle, and at its upper part by the liver, which forms a semi-canal, or a complete canal for it. It adheres closely to the margins of the tendinous opening in the diaphragm, and to the fibrous layer of the pericardium, as if its outer coat were blended with those struc- tures. The serous layer of the pericardium covers the vein, but the fibrous layer does not form a sheath for it. The relations of the inferior cava with the liver account for the erroneous notion of some old anatomists, that this organ was the centre from which all the veins of the body proceeded. There is no valve in the inferior cava ; but at its termination we find the Eustachian valve, which has been already described with the heart. Branches of Origin. — We have stated that the junction of the common iliac veins con- stitutes the origin of the inferior cava. It is very rare to find these veins uniting above the intervertebral disc between the fourth and fifth lumbar vertebrae ; but in some few cases the junction has been observed to take place opposite the renal veins. Collateral Branches. — The vena cava inferior receives all the veins corresponding to the branches of the abdominal aorta, excepting the veins from the alimentary canal and its appendages, of which it only receives those from the liver, viz., the hepatic veins. All the abdominal veins which do not open directly into the inferior cava unite to form a large venous trunk, called the vena porta. Thus, the vena cava inferior receives the renal, the spermatic or ovarian, the lumbar, the supra-renal, and the inferior phrenic veins ; while the superior and inferior mesenteric, the splenic, the pancreatic, and the gastric veins open into the vena portae. It may still be said, however, that the vena cava inferior receives all the abdominal veins ; for, in fact, the veins of the portal sys- tem terminate in the vena cava through the medium of the hepatic veins. The portal system is, therefore, an appendage to the inferior cava. For this reason, and also for the sake of economizing subjects, I shall not describe the vena portae and its branches until I have noticed the collateral veins of the vena cava inferior. The Lumbar or Vertebro-lumbar Veins. The vertebro-lumbar veins are three or four on each side, and correspond to the arteries of the same name ; they have two branches of origin : an external or abdominal branch, which represents the intercostal veins, and a posterior or dorso-spinal branch, which is itself formed by the union of two other branches ; one muscular or cutaneous, which com- mences in the muscles and integuments, and the other a proper spinal branch, which forms part of the rachidiau venous system, to be hereafter described. By the junction of these two branches a lumbar vein is formed, which runs forward and inward in the groove on the body of the corresponding lumbar vertebra, and enters the vena cava at a right angle. The left lumbar veins are longer than the right, in con- sequence of the vena cava being situated towards the right side of the vertebral column • they pass under the aorta. The Renal Veins. The renal veins are remarkable for their size, and occasion a great increase in the diameter of the inferior cava, above the point where they open into it ; they are of un- equal size on the two sides, and are unequal in length, on account of the vena cava be- ing placed towards the right side of the vertebral column, and, therefore, nearer the right than the left kidney : they also run more obliquely on the right side, on account of the right kidney being generally situated lower down than the left. These veins commence in the substance of the kidney by a number of minute divisions, which unite into small, and then into larger branches, gain the surface of the organ, and are collected into a single trunk, either in the hilus or at some distance from it. The trunk of each renal vein is always placed in front of the corresponding artery. The left renal vein passes in front of the aorta. We sometimes find one division of the left renal vein in front of the aorta, and another behind it. Plurality of the renal vein appears to me less common than an excess in the number of the arteries. The renal veins receive the inferior supra-renal and several veins from the surrounding 598 ANGEIOLOGY. adipose tissue. The left renal vein is almost always joined by the spermatic or ovarian vein of that side. In some cases we find several communicating branches between the left renal vein and the superior mesenteric, which is one of the branches of the portal system. The Middle Supra-renal Veins. The middle supra-renal or capsular veins, which are often numerous and very large, are found on the surface of the supra-renal capsules, while the arteries enter into their sub- stance from every point. The venous trunks run in the grooves seen upon the surface of the organ. The left middle supra-renal vein almost always enters the renal vein of the same side ; the right vein generally opens into the vena cava inferior. The Spermatic or Ovarian Veins. The spermatic veins commence in the interior of the testicle, where they form a great number of those filaments which traverse the proper substance of the gland : they aU terminate in branches, which are applied to the inner surface of the tunica albuginea, and are bound down to it by a thin layer of fibrous tissue, a disposition somewhat resembling that of the sinuses of the dura mater. The spermatic veins perforate the tunica albu- ginea on the inner side of the epididymis, not opposite that body. They are soon joined by the veins of the epididymis, so as to form a plexus, which communicates with the dor- sal veins of the penis, and with the external and internal pudic veins. The spermatic veins soon unite into five or six trunks, which pass upward in front of the vas deferens, and, together with that caneil and the spermatic artery, enter into the formation of the spermatic cord. These veins are tortuous ; they divide, and anastomose so as to form the spermatic venous plexus, which is often tlie seat of varicose dilatations. The veins ascend through the inguinal ring and canal, and having reached the interior of the pel- vis, they leave the vas deferens, accompany the corresponding spermatic artery along the psoas muscle, and terminate either in the renal vein, or in the inferior vena cava of their own side. In some cases the right spermatic vein opens both into the renal vein and the inferior cava. When there are two veins on one side, they communicate with each other by a great number of transverse branches, and, before terminating, unite into a single trunk. The name plexus pampiniformis is given to a plexus generally formed by the spermatic veins before their termination : this plexus is more frequently found on the left than on the right side, according to the observations of Meckel. The spermatic veins sometimes communicate with some branches of the portal system. The left spermatic vein passes under the sigmoid flexure of the colon, which may per- haps account for the greater frequency of varicocele on the left side. The ovarian veins accompany the arteries of the same name : they commence by sev- eral sets of branches, viz., uterine branches, which communicate very freely with the uterine sinuses ; ovarian branches, properly so called ; branches from the round ligaments ; and, lastly, some from the Fallopian tubes. All these unite within the substance of the broad ligaments, and pass vertically upward, without being at all tortuous : in some ca- ses they form a plexus pampiniformis. The ovarian veins, like the uterine veins, become much enlarged during pregnancy. The Inferior Phrenic Veins. These exactly follow the course of the inferior phrenic arteries, to each of which there are two veins. The hepatic veins do not in any way correspond to the artery of that name ; they form a separate system, or, rather, they are connected with the portal venous system, of which they may be regarded as an appendage. The Poktal Ststem of Veins. The system of the vena porta {vena portarum), or the portal system, constitutes a spe- cial venous apparatus, appended to the general venous system, and representing by it- self a complete circulatory tree, having its roots, trunk, and branches. The first, or ve- nous portion of this system of veins, is arranged like the veins of the other parts of the body, and has its roots of origin in the spleen and pancreas, and in the sub-diaphragmatic portion of the alimentary canal ; while the second, or arterial portion, sends its branches, like those of an artery, into the interior of the liver. The hepatic veins, which perform the functions of ordinary veins in reference to the second or arterial portion of the vena portae, connect the system of the vena portae with the general venous system. The Branches of Origin of the Vena PortcB. The branches of origin of the vena portae {i, fig. 222) consist of all the veins which return the blood from the sub-diaphragmatic portion of the alimentary canal, and also from the spleen and pancreas. They correspond to the branches of the coeliac axis, THE VENA PORTiE. M9 with the exception of the hepatic artery ; they unite FigL a». ' into three trunks, the great mesenteric (a), small mes- enteric (b), and splenic (c) veins. These veins are arranged like venae coraites to the corresponding arteries. The Great and Small Mesenteric Veins. — The intes- tinal or mesenteric veins commence just as the ar- teries terminate, by two layers of vessels, viz., a sub-serous layer, the vessels of which ramify be- neath the peritoneum, and a deep layer, formed by the vessels of the coats of the intestinal canal. These small vessels unite into anastomotic meshes, which always lie subjacent to the arterial network, and which terminate in larger branches, and thus con- stitute a series of veins corresponding to the arter- ies of the intestine. The right colic veins {d d) and the veins of the small intestine (shown cut short at e) terminate, the one in the right and the other in the left side of the superior mesenteric or great mes- araic vein (a) : this vein, in the early periods of in- tra-uterine life, receives the omphalo-mesenteric vein, a branch which corresponds to the omphalo-mesen- teric artery, and commences upon the vesicula um- i bilicalis ; the artery and the vein disappear about the third month of utero-gestation, but the vesicle remains for a longer period. On the other hand, the left colic veins (/) enter the inferior mesenteric or small mesaraic vein (J) : this vessel forms the continuation of the superior hemorrhoidal veins {g), which commu- nicate very freely with the middle and inferior hemorrhoidal branches of the internal iliac vein. The splenic vein (c), which is proportionally larger than the artery, arises in the cells of the spleen by a great number of roots, which gradually unite in the hilus of that organ, and form the same number of branches as there are arteries, each coming from a dis- tinct compartment of the organ. All these branches soon unite into a single trunk, which passes across to the right side behind the pancreas, and, therefore, behind the splenic artery, which it accompanies without being tortuous : it is one of the branches immediately concerned in forming the trunk of the vena portae. During its course, the splenic vein receives the venous vasa brevia {h h) from the stomach. The inferior mesenteric vein opens into the splenic ; so that there are only two venous trunks, the union of which constitutes the vena portae, viz., the splenic and the great or superior mesenteric. The Vena Portce. The trunk of the vena porta (i) is formed by the union of the splenic and superior mes- enteric veins at an acute angle, behind the right extremity of the pancreas, in front of the Tertebral column, and to the left of the vena cava inferior. The vena portae is larger than either of its two branches of origin, but is smaller than the two taken together. It passes obliquely upward and to the right side ; and, after running for about four inches, reaches the left extremity of the transverse fissure of the liver, where it terminates by bifurcating. The following are its relations during its course : anteriorly it is covered by the head of the pancreas, the second portion of the duodenum, the hepatic artery, the biliary ducts, and the lymphatics of the liver, and also by some branches from the hepatic plexus of nerves ; posteriorly it is covered by that portion of peritoneum which dips be- hind the vessels of the liver into the foramen of Winslow, to line the sac of the great omentum. By this foramen it is separated from the inferior vena cava, the direction of which it crosses at a very acute angle. The two branches into which the vena porta? divides in the transverse fissure of the liver separate so widely from each other, that they seem to form a trunk, at right angles to which the vena portae itself is attached. Some anatomists apply the term sinus of the vena porta to that portion of the vein which is situated in the transverse fissure ; that part of the vein which adheres to the liver is more commonly called the hepatic portion of the vena portae, to distinguish it from the free and floating part, which is named the abdom- inal portion. The two divisions of the vena portae pass horizontally each towards the correspond- ing lobe of the hver ; they soon divide and subdivide into diverging branches, which sup- ply all the granules or lobules of the liver. The branches of the vena portae are accom- panied by the ramifications of the hepatic artery and biliary ducts. The capsule of Glis- son, or the fibrous coat of the liver, is reflected upon them, and forms a common sheath for them. (See Liver.) Before birth, the hepatic portion {p, fig. 164) of the vena portae receives, besides the v|690 ANGEIOLOGY. abdominal portion of the same vein, the umbilical vein (u), which is obliterated soon after birth. Nevertheless, I once found it perfectly permeable in an adult.* Before birth the ductus venosus (d) extends from the hepatic portion of the portal vein to the vena cava inferior, between which and the vena portae it establishes a direct com- munication. This hepatic portion might> therefore, be named the confluence of the veins of the liver. The Hepatic Veins. The capillary radicles of the hepatic or supra-hepatic veins commence in the capillary divisions of the vena portae, and, gradually uniting into larger and larger branches, con- verge towards the posterior border of the liver, or, rather, towards the fissure for the vena cava inferior, at which point they terminate by an indefinite number of small branches, named the small hepatic veins, which open all along the fissure ; and also by two principal trunks, the great hepatic veins, which end in the vena cava immediately before It passes into the opening in the diaphragm. One of these great hepatic veins comes from the right lobe, and the other from the left lobe of the liver. The vein of the left side often receives a great number of branches from the right lobe of the liver, and is larger than the vein of the right side. The vena cava inferior is always dilated into a large ampulla opposite the openings of the hepatic veins. It follows, from the previous description, that, in the liver, the branches of the hepatic veins and those of the vena portae run directly across each other, since the latter diverge from the centre of the organ towards its right and left extremities, while the former con- verge from the anterior towards the posterior border. Moreover, the branches of the hepatic veins are unaccompanied by other vessels, and are in direct contact with the tissue of the liver ; while those of the vena porta; are sep- arated from it by the capsule of Glisson, and are accompanied by the ramifications of the artery, the nerves, and the hepatic ducts. I shall farther remark, that although the hepatic veins gradually unite, like other veins, into branches, which decrease in number, but increase in size, they most of them receive besides, during their course, a multitude of capillary vessels, the inter-lobular hepatic veins, from the neighbouring lobules ; so that their internal surface is perforated with in- numerable foramina. The cribriform structure of their internal surface is therefore a peculiar characteristic of all the hepatic veins [except the very large ones], and enables us always to distinguish them from the branches of the vena portae. Lastly, the capillary communication between the extremities of the vena portse and hepatic veins is extremely free, as may be shown even by very coarse injections. AH the veins of the portal system are without valves,t and they can therefore be in- jected with the greatest ease from the trunks towards the extremities. An injection thrown in towards the intestine penetrates very readily into the interior of the alimentary canal, so that the minute branches of the vena portae appear to open at the apex of each villus. This can be made evident by throwing mercury into the vena portae, and then forcing it on by an ordinary injection ; drops of the mercury will then be seen in the open mouth of each villus.J The system of the vena portas is not so completely isolated from the general venous system as is commonly stated. It always communicates with branches of the iirtemal iliac veins by means of the middle hemorrhoidal veins, and communicating branches with the renal veins have also been noticed ; and hence injections of the vena cava in- ferior always enter in a greater or less degree into the veins of the portal system. The Common Iliac Veins. The common iliac veins (n n, fig. 222) correspond exactly to the arteries of the same name ; they commence opposite the sacro-vertebral articulation by the junction of the internal and external iliac veins, and terminate by uniting at an acute angle to form the vena cava inferior or ascendens, the point of union being opposite the articulation of the fourth and fifth lumbar vertebrae, to the right side of, and a little below, the bifurcation of the aorta. The common iliac veins hare the same relation to the lower extremities that the brachio-cephalic veins bear to the upper ; and as the right brachio-cephalic vein is shorter and more vertical than the left, so also is the right common iliac vein shorter and mere vertical than the left. The relations of the common iliac veins with the corresponding arteries are remarkable, inasmuch as they are placed between these vessels and the vertebral column. The right common iliac vein is situated to the outer side of and behind the corresponding ar- * Anat. Pathol., livraison 17. t M. Bauer says that he has seen valves in the venous vasa brevia of the stomach ; I have never been able to discover them. t [The escape of the mercury is due to rupture of the bloodvessels. In tlie villi, the minute branches of the vena portae commence la t!',t ciijiillary network described and figured at page 36!).] THE INTERNAL ILIAC VEIN, ETC. %9i leiy, and is parallel to it ; while the left common iliac is situated on the inner side, and behind the corresponding artery, and is covered by its lower part. At the point where the left common iliac vein joins the vena cava inferior, it is also crossed obliquely by ihe right common iliac artery. It follows, therefore, that the left common illiac vein is covered, and may be compressed by both common iliac arteries, while the right common iliac vein cannot be compressed by either of them, and probably this is partly the reason why anasarca of the left lower extremity is more common than in the right extremity m atonic diseases. The right common iliac vein receives no collateral branch ; the left common iliac (n, fig. 223) is joined by the middle sacral vein (h). The middle sacrai vein is situated in the median line, and its size depends upon that of the artery of the same name ; it belongs to the rachidian veins, with which it will be described The Internal Iliac Vein. The internal iliac or hypogastric vein exactly represents the internal iliac artery, on the inner side of which it is situated, separated from it, however, by a very thin fibrous layer, which holds it down against the walls of the pelvis. The internal iliac vein receives the venae comites of the branches of the internal iliac artery, the umbilical arteries in the foetus alone being excepted ; for their satellite vein, the umbihcal vein, which is £dso peculiar to the foetus, terminates in the hepatic portion of the vena portae, as we have already seen. The internal iliac vein, therefore, receives the blood returned from the parietes of the pelvis, from the organs contained within the cavity of the pelvis, and from the external genitals. There are always two veins for each artery ; but the two unite into a single vein at their point of termination in the principal trunk. The veins belonging to the parietes of the pelvis, viz., the gluteal, obturator, and sciatic veins, are arranged precisely like the corresponding arteries. The ilio-lumbar and lateral sacral veins {i,fig. 223) form part of the rachidian system, which will be specially described. The veins belonging to the genito-urinary organs present a plexiform arrangement both in their trunks and in their roots, which deserves particular attention. Some of the venous plexuses of the pelvis are found both in the male and female, as the hemorrhoidal, while some are peculiar to one or the other sex, as the vesico-prostatic and the plexuses of the penis to the male, and the vaginal and uterine plexuses to the female. The Hemorrhoidal Veins and Plexuses. The hemorrhoidal veins and plexus form a venous network, surrounding the lower end of the rectum. They are formed by the superior hemorrhoidal veins, which form the com- mencement of the inferior mesenteric, and by the middle and inferior hemorrhoidal veins, which are branches of the internal iUac. We ought to notice in particular the sub-mu- cous venous network near the anus. The plexus formed by it is analogous to that found in all other mucous membranes ; its vessels are liable to become varicose, a condition which constitutes the greater number of hemorrhoidal tumours. The Pelvic Veins and Plexuses in the Male. Preparation. — Introduce one injection-pipe into the corpus cavernosum, and another into the glans penis, and then push an injection simultaneously into both of them, and also into the crural vein. The superficial scrotal veins tenninate partly in the superficial veins of the perinseum, and partly in the external pudic branches of the femoral vein ; they communicate with the superficial veins of the under surface of the penis. The Vesical Veins, or Vesico-prostatic Plexus. — The prostate gland and the neck ol the bladder are covered by a very complicated plexus of veins, which become exceedingly developed in chronic inflammation of the bladder ; it receives the superficial veins of the penis, and gives off the vesical veins. This plexus, which communicates with the hemorrhoidal plexus behind, is supported by a very thick fibrous layer, which is continuous with the pelvic fascia, and which lim- its the degree of dilatation of the veins of the plexus in the same way as the dura mater limits the dilatation of the sinuses contained between its layers. The Veins and Plexuses of the Penis. — The veins of the penis are divided into a superfir cial and deep set, the former representing the sub-cutaneous veins of the limbs. They commence in the skin of the prepuce, and run backward along the upper and lower sur- faces of that organ. The superior are called the dorsal veins of the penis ; they commu- nicate freely with each other by large branches ; most of them run beneath the arch of the pubes, between it and the corpus cavernosum, passing through some openings or fibrous canals in the sub-pudic ligament, which have the effect of keeping the veins al- ways open ; they end by assisting in the formation of the prostatic plexus. These veins communicate freely with the deep veins, especially opposite the junction of the two crura 4 G 602 ANGEIOLOGY. of tHfe corpus cavemosum : this communication is proved by the fact that the superficial vessels are always filled when the injection is thrown into the deep veins. The areolar tissue of the corpus cavemosum and that of the corpus spongiosum may be regarded as composed of a venous network or plexus at its maximum of development. Branches proceed from this plexus, which correspond to the divisions of the internal pudic artery, and follow the same course. These veins, and the vesico-prostatic plexuses, are liable to become varicose ; hard earthy concretions, called phlebolites, are also frequently found in them. The Pelvic Veins and Plexuses in the Female. The vesical, or vesico-urethral plexus of the female, is less developed than that of the male, on account of the absence of veins corresponding to the superficial veins of the pe- nis, which are represented by a few branches from the labia majora. This plexus commu- nicates with the veins of the clitoris, and also very freely with the vaginal plexus behind The vaginal plexus is a vascular network, extremely well developed, especially oppo- site the orifice of the vulva, which is entirely surrounded by it with several series of cir cular anastomosing veins : it communicates with the vesical plexus in front, and with the hemorrhoidal plexus behind ; so that all the plexuses in the pelvis are involved in the state of turgescence, which a.ccompanies the phenomenon of erection in the female. The radicles of this vaginal plexus commence in the mucous membrane of the vagina, and especially in the erectile tissue surrounding the orifice of that canal ; some large veins arise, in particular, from the bulb of the vagina, forming a true erectile apparatus, which we have already described. (See Splanchnology, p. 320.) The Uterine Plexus. — The veins contained in the substance of the walls of the uterus do not present any trace of the tortuous arrangement of the corresponding arteries. In order to obtain a satisfactory idea of them, they should be studied in a gravid uterus. The uterine veins, like the uterine arteries, are then found along the sides and upper an- gles of the organ ; opening into these veins are found larger venous canals, which run from side to side through the substance of the uterus, and anastomose frequently with each other. These venous canals are called the uterine sinuses, on account of their great size during gestation, and from the dilatations presented by them at the confluence of sev- eral secondary veins : they are also entitled to be so named from their structure, which has some analogy with that of the sinuses of the dura mater, inasmuch as only the lining membrane of the veins is prolonged into them ; their outer coat is formed by the proper tissue of the uterus, and hence the walls of these veins are contractile. I have stated elsewhere that, in reference to its veins, we may consider the uterus as consisting of an erectile tissue with muscular walls ; it is scarcely necessary to add, that these sinuses are unequally developed in different parts of the uterus, and that the point to which the placenta has been attached may be recognised by the greater size of the adjacent ute- rine sinuses. The veins contained within the substance of the walls of the uterus do not open into the uterine veins alone ; several of them terminate in the ovarian veins, which commu- nicate freely with the uterine, and may, if necessary, supply their place. The great size acquired by the uterine veins, both in the substance and on the surface of the uterus, proves that the venous apparatus plays an important part in the intersti- tial development of this organ. Moreover, the size of the veins and venous plexuses belonging to all the genito-urinary organs, and the essentially venous structure of such organs as are capable of being erect- ed, prove that the venous system performs an essential part in the truly active phenom- ena of erection. It is partly upon these anatomical and physiological arguments that I have endeavoured to show the active part performed by the veins in all the great phe- nomena of the economy, such as nutrition, secretion, inflammation, &c. The pelvic veins are provided with a great number of valves, which prevent injections from passing from the heart towards their extremities ; it ought to be remembered, that the venous plexuses of the pelvis establish a very important and verv free communica- tion between the veins of the right and left sides of the body. The Deep Veins of the Lower Extremity. The veins of the lower extremities, like those of the upper, are divided into the deep veins or venae comites of the arteries, and the superficial veins. The Plantar, Posterior Tibial, Peroneal, Dorsal, interior Tibial, and Pop liteal Veins. The external and internal plantar veins unite to form the posterior tibial, which accom- panies the artery of that name, and soon joins the peroneal vein, to constitute the tibio- peroneal vein : again, the anterior tibial vein, which commences by the vena dorsalis pedis, perforates the upper part of the interosseous ligament, joins the tibio-peroneal vein, and in this way forms the popliteal vein Up to this point there are two venae comites for each artery, one of the veins being placed on each side of the artery, across which thev THE FEMORAL VEIN, ETC. 608 very frequently send communicating branches. The peroneal veins are generally larger than the posterior tibial, and receive all the muscular veins from the posterior and out«»- tegions of the leg. Commencing with the popliteal, there is only one vein for the main artery of the limb ; but the arteries of the second and third order always have two veins. The popliteal vein is situated in the popliteal space, behind and in contact with the ar- tery. Its coats are remarkably thick, so that when cut across it remains open, and in the dead body has been sometimes mistaken for the artery. Below, and opposite the articulation of the knee, the vein is situated immediately behind the artery ; above the joint it is behind, and a little to the outer side. The popUteal vein receives the large bundles of veins, the sural veins, from the gas trocnemius muscle : they are remarkable ft)r the number of their valves ; also the articu- lar veins, and generally the external saphenous vein. I have seen a small vein having very numerous valves, and being analogous to the collateral venous canals of which I have already spoken, extend from the upper part of the anterior tibial to the middle of the popliteal vein. The Femoral Vein. The femoral vein, like the artery of that name, is bounded below by the ring in the tendon of the adductor magnus, and above by the crural arch ; it has different relations with the femoral artery in various parts of its course : thus, below, it is on the outer side of the artery ; higher up, it is situated behind that vessel ; lastly, from the entrance of the vena saphena interna to the crural arch, it is placed to the inner side of the artery, and is in close contact with the posterior part of the opening for the femoral vessels ; so that femoral hemiae descend in front of the vein, but not of the artery. The femoral vein is single, like the artery ; nevertheless, there are one or two collateral venous canals, which run parallel with the lower half, or lower two thirds of that vein ; some commu- nicating branches from the internal saphenous vein, and some muscular branches, open into these venous cauEds, which are always abundantly supplied with valves. The femoral vein receives all the branches corresponding to the divisions of the fem oral artery, excepting the external pudic veins and the cutaneous veins of the abdomen, which terminate in the internal saphenous vein. The great deep vein (profunda) opens into the femoral about ten or twelve lines be- low the crural arch. The External Iliac Vein. The external iliac vein is bounded below by the femoral arch, and terminates at the up- per part of the sacro-iliac symphysis by uniting with the internal iliac vein ; it has the same relations as the artery, and is placed behind and to the inner side of that vessel, excepting over the os pubis, where it is exactly to the inner side of the artery. In one case I found the left common iliac receiving the right internal iliac, so that the right ex- ternal iliac was prolonged into the vena cava. The external iliac receives the epigastric and the circumflex iliac veins. These two veins are double, but each pair unites into a single trunk, as it is on the point of open- ing into the external iliac vein. All the deep veins of the lower extremity, excepting the external iliac, are provided with valves. There are four in the deep femoral, the same number in the popliteal, and many more in the tibial and peroneal veins ; the mouths of all the small veins which open into them are provided with a pair of valves. The Superficial Veins of the Lower Extremity. The superficial veins of the lower extremity are much less numerous than those of the upper, and all terminate in two trunks, viz., the internal saphenous vein and the exter- nal saphenous vein. As in the hand, they are all situated upon the dorsal region of the foot. All the col- lateral veins of the toes enter the convexity of a venous arch, which is more regular and constant than that in the hand, and which is placed on the fore part of the metatarsus. From the inner end of this arch is given off a large branch, named the internal dorsal veir of the foot, which is the origin of the internal saphenous vein ; the outer extremity also gives off a somewhat smaller branch, called the external dorsal vein of the foot, which forms the commencement of the external saphenous vein. The Internal Saphenous Vein. The internal or great saphenous vein (saphena interna, s, in the representation of the superficial nerves of the leg) is a collateral vein gf the femoral venous trunk, and is con- tinuous with the internal dorsal vein of the foot. The last-mentioned vein commences at the inner extremity of the dorsal venous arch of the foot, into which the collateral veins of the great toe open ; it runs along the dorsal surface of the first metatarsal bone and the corresponding part of the tarsus, and receives, during its course, a deep branch from the internal plantar vein and all the superficial veins of the internal olantar region, 604 ANGEIOLOGY. and particularly the internal calcaneal vein, which is sometimes large, and which, in cer- tain cases, does not terminate in the saphenous vein until it has reached above the in- ternal malleolus, around the posterior border of which it turns. The internal saphe- nous vein succeeds to the one just described ; it is reflected upward in front of the internal malleolus, and continues to ascend upon the inner surface, then along the pos- terior border of the tibia, and upon the back of the internal tuberosity of that bone and the internal condyle of the femur. In this place it is situated on the inner side of the tendons of the semi-tendinosus, gracilis, and sartorius ; it then inclines forward, descri- bing a slight curve, with its concavity directed forward ; ascends along the anterior bor- der of tfie sartorius, and crosses obliquely over the adductor longus ; having arrived at the saphenous opening in the fascia lata, about eight or ten inches below Poupart's lig- ament, it immediately curves backward, passes through that opening, and enters into the femoral vein, just as the vena azygos enters into the superior vena cava, that is to say, it describes a loop having its convexity directed downward. Several lymphatic glands are found near this curve. Relations. — The internal saphenous vein is separated from the skin by a very thin fibrous layer, the superficial fascia, and is in relation with the internal malleolus, the tibia, the tibial origin of the soleus, the tendons of the semi-tendinosus, gracilis, and sar- torius, with the last-named muscle itself, and with the adductor longus. It is accompa- nied by the internal saphenous nerve, from the knee down to the internal malleolus. During its course it receives all the sub-cutaneous veins of the thigh, most of the sub- cutaneous veins of the leg, the sub-cutaneous veins of the abdomen, the external pudic veins, and several communicating branches from the deep veins. The sub-cutaneous femoral veins of the back of the thigh sometimes unite into one rath- er large trunk, which appears like a second internal saphenous vein ; it runs parallel with the regular vein, and enters it at a greater or less distance from its termination. I have met with an anterior superficial vein which commenced around the patella, ascended vertically along the anterior region of the thigh, and might be regarded as a third.saphe- nous vein. In one case of this kind, these three saphenous veins, viz., the anterior, posterior, and internal, entered separately into the femoral vein, or, rather, into a dilata- tion in which the internal saphenous vein terminated. The internal saphenous vein often presents the following arrangement : opposite the lower part of the leg, or at the lower end of the thigh, it divides into two equal branches which pass upward, communicate with each other by transverse branches, and unite af- ter running a variable distance ; in these cases the two branches represent a very elon- gated ellipse. I have even seen this arrangement in both the thigh and leg of the same subject, that is to say, the saphenous vein divided into two branches in the leg, which united opposite the internal tuberosity of the tibia, and again divided in the thigh. It is not uncommon to find a venous network supplying the place of the internal saphe- nous vein in the thigh. The sub-cutaneous abdominal veins should be arranged among the superficial and sup- plementary veins, although there is a small artery, the superficial epigastric, which cor- responds to them. There are three or four of these veins, which are joined by one from the gluteal region ; they open sometimes by a common trunk, sometimes by three or four distinct trunks, into the internal saphenous, just as that vein is passing through the fascia lata. In a case of obliteration of the vena cava I found these veins very large, and prolonged over the thorax into the axilla, where they anastomosed with the cuta- neous branches of the intercostal and thoracic veins. In a case in which the umbilical vein was persistent, the right and left internal saphenous veins were tortuous, and as large as the little finger.* The internal saphenous also receives the external pudic veins ; and I have seen it joined by the obturator vein, which commenced by a common trunk with the epigastric. The communicating branches of the internal saphenous with the deep veins are very nu- merous, and should be studied in the foot, the leg, and the thigh. The origin of the in- ternal saphenous vein gives off a branch, which communicates with the internal plan- tar vein. Along the leg several other branches exist, which establish a communication between the internal saphenous and the posterior tibial veins ; these branches perforate the tib- ial origins of the soleus muscle. There is a very remarkable communication between the anterior tibial and internal saphenous veins in the middle third of the leg, by means of a branch which proceeds from the anterior tibial vein in front of the fibula, becomes sub-cutaneous, is reflected inward and upward between the fascia of the leg and the skin, and terminates in the in- ternal saphenous. Again, an inferior, internal, articular vein enters the internal saphenous. Lastly, the anastomoses in the thigh, between the deep and the superficial veins, aiu less numerous than those in the leg ; at most we only find two such describing loops, with the concavity directed upward. * Anat. Path., liv. xviii. 1 THE VEINS OF THE SPINE. #11$ Valves. — The number of the valves appears to me variable : I have counted six along the internal saphenous, but at other times I have not found more than two or four. There is a greater number of valves in this vein in the thigh than in the leg. The External or Posterior Saphenous Vein. The external saphenous vein (la peroneo-malleolaire, Chauss. ; see figure of nerves ot .eg), smaller and much shorter than the internal saphenous, is a branch of the popliteal vein ; it forms a continuation of the external dorsal vein of the foot, vi'hich commences from the outer extremity of the dorsal venous arch ; it passes behind the peroneo-tibial articulation, crossing it from before backward ; it receives, as it runs outward, a grea< number of branches, the chief of which come from the external plantar region ; also an external calcaneal vein, which is sometimes of considerable size, and comes from thr outer side of the os calcis ; the vein then runs along the outer border of the tendo Achil- lis, and crosses it at a very acute angle, to reach the middle line of the posterior aspect of the leg : conmiencing at this point, it passes directly upward, crosses the internal popliteal nerve, and terminates in the popliteal vein between the internal and external popliteal nerves, between the two heads of the gastrocnemius, and by the side of the in- ternal inferior articular vein. In some subjects the external saphenous, at the moment when it bends to dip into the pophteal space, gives off an ascending vein, which runs along the posterior border of the semi-membranosus muscle, as high as the upper third of the thigh, where it then turns forward to open into the internal saphenous, or one of the branches of that vein, immediately below its opening into the femoral. Relations. — The external saphenous vein is covered by the superficial fascia, which separates it from the skin, and it covers the externeil saphenous nerve, from which it is separated by a layer of fascia ; it crosses this nerve twice, being at first situated to the inner side, then to the outer side, and again on the inner side of the nerve. The external saphenous vein communicates with the deep veins only, behind the ex- ternal malleolus, and upon the dorsum of the foot. This vein has only two valves, one of which is situated immediately before its open- ing into the popliteal vein. Such are the veins of the lower extremity. The analogy which exists between the in- ternal dorsal branch of the foot and the cephalic vein of the thumb ; between the exter- n£il dorsal branch and the vena salvatella ; between the external saphenous and the ra- dial and cephalic veins ; between the internal saphenous and the ulnar and basilic veins, cannot be doubted. There is no branch in the lower extremity analogous to the median vein. THE VEINS OF THE SPINE. General Remarks. — The Superficial Veins of the Spine. — The Anterior Superficial Spinal Veins, viz., the Cheater Azygos — the Lesser Azygos — the Left Superior Vertehro-costals — the Right Vertebro-costals — the Vertebro-lumbar — the Ilio-lumbar, and Middle and Lat- eral Sacral — the Anterior Superficial Spinal Veins in the Neck. — The Posterior Superfi- cial Spinal Veins. — The Deep Spinal or Intraspinal Veins — the Anterior Longitudinal, and the Transverse Veins or Plexuses, and the Vein^ of the Vertebra — the Posterior and the Posterior and Lateral Transverse Veins or Plexuses — the Medullary Veins. — General Remarks on the Veins of the Spine. The spinal or rachidian veins constitute a very important part of the venous system, which has only recently been specially studied. These veins differ, in many respects, from the spinal arteries, so that the description of the one does not afford much assistance in the study of the other ; nevertheless, I shall frequently have occasion to point out some remarkable analogies between these two sets of vessels. The spinal veins are arranged most distinctly as venae comites and supplementary veins. We shall divide them into the veins exterior to the spine or the superficial veins, and the wms in the interior of the spinal canal, or the deep veins. The Superficial Veins of the Spine. The superficial veins of the spine may be subdivided into the anterior and posterior. The Anterior Superficial Rachidian Veins. The anterior superficial rachidian or spinal veins (see fig. 223) comprise the vena azy- gos major, the vena azygos minor, the common trunk of the right superior intercostals, that of the left superior intercostals, the vertebro-lumbar and ilio-lumbar veins, and the lateral and middle sacral veins ; in the neck, the ascending cervical and the vertebral veins. The Greater Azygos Vein. The vena azygos major (a «',^^.223) is a large single vein (dC^rof' without a rellow), 606 ANGEIOLOGY. Fig. 223. situated along the vertebral column ; it commences {a') in the lumbar region, and termi- nates at the upper part of the thorax by opening into the vena cava superior. Its origin is subject to much variety. It very rarely arises from the trunk of the inle rior vena cava itself, with which, however, it almost always communicates by small branches. It generally forms the continuation of a series of anastomoses, which sur- round the bases of the right transverse processes of the lumbar vertebrae, and which may be called after some authors the ascending lumbar vein {b, on the right side) ; sometimes it arises from the trunk of the last vertebro-costal, or the first vertebro-lumbar vein : we rarely find a branch of origin from the renal or supra-renal veins. It often has two ori- gins, one from the ascending lumbar, and the other from the first vertebro-lumbar, or last vertebro-costal vein. The vena azygos, almost immediately after its origin, passes from the abdominal into the thoracic cavity, through the aortic opening in the diaphragm, ascends upon the right side of the bodies of the thoracic vertebrae, as high as the third intercostal space, i. e., between the third and fourth ribs, where it curves forward, forming, like the aorta, an arch, which passes over and embraces the right bronchus, and opens into the back of the vena cava superior, as that vein is enter- ing the pericardium. During its course the vena azygos is in contact with the vertebred column, and is situated in the posterior mediasti- num, on the right side of the aorta and of the thoracic duct {t t), which runs parallel to it ; it lies in front of the right in- tercostal arteries, and crosses them at right angles. It va- ries in size, according to the number of branches which it re- ceives, but gradually increases from below upward. The question of the existence of valves in the vena azy gos has given rise to much discussion. It appears to me to be settled in the negative. The vena azygos is joined in front by the right bronchial vein and some oesophageal and mediastinal veins ; on the right side by the eight inferior vertebro-costal veins (c c) of that side ; and on the left by the lesser azygos (d) and the common trunk (e) of the left superior intercostal veins. Before opening into the superior vena cava, opposite the third intercostal space, the azygos vein receives at its curve, either by a common trunk, or by two or three separate branch- es, the three superior right vertebro-costal veins, which some- times enter the right brachio-cephalic vein, and sometimes the vena cava superior, above where it is joined by the vena azygos. In the last case they pass vertically upward ; in the second they are directed almost vertically downward. The Semi-azygos, or Lesser Jlzygos Vein. The lesser azygos vein {d d,' azygos minor, semi-azygos) may be regarded as the common trunk of the three, four, or five inferior vertebro-costal veins (c' c') of the left side : it opens into the great azygos vein. It commences below {d') in as many different ways as the great azygos vein, but it communicates with the renal vein much more frequently. It runs upward upon the left of the vertebral coliunn, approaches the median line, and opens into the great azygos at a different height in different subjects. It joins the great azygos either at right angles or obliquely, passing behind the thoracic duct. The lesser azygos vein may be regarded as the left branch of origin of the greater azy- gos : sometimes it is extremely large ; in that case the great- er azygos is directly continuous with it, and the right branch is very small. The lesser azygos vein is joined by the four or five inferior vertebro-costal veins (c' c') of the left side. It also frequent- ly receives the common trunk of the superior vertebro-costal veins, which might be said to form a superior lesser azygos vein. The Left Superior Vertebro-costal Veins The common trunk (e) of the left superior intercostal veins (//) might be called the left superior lesser azygos, for it has the same relation to these veins that the lesser azy- gos has to the inferior intercostals of the same side. It runs downward upon the left of the vertebral column, increasing in size as it approaches its termination, which is THE INTERCOSTAL VEINS, ETC. 60T either near the end of the lesser azygos, or in the greater azygos. Not unfrequently the common trunk of the left superior intercostals bifurcates and opens both into the lesser azygos and into the left brachio-cephaUc vein. In some cases it terminates entirely in the left brachio-cephalic vein : I have myself met with this disposition. I have seen the left superior phrenic and the mediastinal veins enter the trunk of the lesser vena azygos immediately before its termination. The number of the left vertebro-costal veins which unite to form the lesser azygos vein varies from three to seven ; when only three or four of the highest of these verte- bro-costal veins end in it, the two or three lower ones enter directly into the greater azygos vein. General Remarks on the Vena Azygos Major. — This vein returns the blood of the right and left vertebro-costal vems to the heart ; its presence is rendered necessary, first, in con- sequence of the inferior vena cava not being able to receive any veins from the point where it enters the groove in the liver to its termination in the right auricle ; and, sec- ondly, because the superior vena cava is also unable to receive any veins while it is within the pericardium. The greater azygos is, therefore, a supplementary vein, a true collateral canal which supplies the place of the venae cavae, and receives all the veins corresponding to the branches given off" by the aorta during this long course. These ob- servations are, for the most part, applicable to all the azygos veins. Anatomical Varieties of the Azygos Veins. — It would be both useless and tedious to no- tice here all the varieties that have been observed in the distribution of the azygos veins. M. Breschet has described six, but there are many more. The following is a very cu- rious variety : the greater azygos occupies the median line of the dorsal portion of the vertebral column, and is divided below into two equal branches, a right and a left, each of which receives the three inferior vertebro-costal veins of its own sides ; all the other vertebro-costal veins end directly in the greater azygos. Another not less curious variety is the following : there are two equal and parallel azygos veins, a right, which receives all the right intercostal veins, and a left, which re- ceives till the left intercostals : the two main trunks communicate with each other oppo- site the seventh or eighth dorsal vertebra by a very large transverse branch. The Intercostal or Vertebro-costal Veins. The intercostal or vertebro-costal veins of both sides (c c, c' c',ff) correspond to the in- tercostal or vertebro-costal arteries, the distribution of which it is important to caU to mind. We have seen that each of these arteries divides into two branches : an intercos- tal branch, properly so called, intended for the intercostal spaces ; and a spinal branch, the dorsal division of which terminates in the spinal muscles and the skin, while its ver- tebral, or intra-spinal division, is distributed to the vertebrae, to the spinal cord, and to its coverings. In like manner, the vertebro-costal vebis are formed by the junction of the spinal branch, to which we shall presently return, and the intercostal branch. These two sets of branches unite into a common trunk, the vertebro-costal vein, which passes transversely along the groove on the body of each vertebra, receives some veins from the bone in that situation, and enters at a right angle into the corresponding axygos vein. The Lumbar or Vertebro-lumbar Veins. In the lumbar region there are no azygos veins, and each vertebro-lumbar vein en- ters separately, or by a common trunk, with its fellow of the opposite side, into the back of the vena cava inferior. Not unfrequently two of the vertebro-lumbar veins of the same side open by a common trunk ; and it is not rare to find the left superior vertebro- lumbar vein enter the renal vein. The vertebro-lumbar veins {g) are distributed very differently from the corresponding arteries. Opposite the bases of the transverse processes there are a series of anasto- motic arches, wliich together constitute, on each side, an ascending branch, called the ascending lumbar vein {b b), which communicates above with the corresponding azygos vein, and below with the ilio-lumbar veins, and which might be regarded as a lumbar azygos vein. The trunks of the vertebro-lumbar veins proceed from this series of arches to the vena cava ; and all the intra-spinal and dorsi-spinal veins terminate in it. The Ilio-lumbar, Middle Sacral, and Lateral Sacral Veins. The ilio-lumbar vein, which opens into the common iliac, is distributed like the artery of that name ; it sometimes receives the last vertebro-lumbar vein : it is joined by the great veins which emerge from the lower inter- vertebral foramina of the lumbar verte- brae ; by the branch which is continuous in front of the fifth lumbar vertebra, with the series of arches forming what may be called the lumbar azygos ; and, lastly, by a com- municating branch from the lateral sacral veins. The middle sacral and lateral sacral veins represent the azygos veins in the sacral re- gion ; they are joined by all the dorsi-spinal branches passing out from the inter-vertebral foramina, and end in the common iliac veins. The middle sacral vein (A) often conmiences below by three branches, a median in ANGEIOLOGY. front of the coccyx, and two lateral and anterior branches. One of these joins the ves- ical plexus, while the other communicates with the hemorrhoidal veins, and establishes a remarkable communication between the general venous system and the system of the vena portae. The middle sacral vein passes vertically upward, somewhere near the middle line, and opens into the left common iliac vein {71) at a greater or less distance from its junction with the right common iliac. I have seen it bifurcate above to enter both common iliacs. During its course it is joined opposite each vertebra by some transverse, plexiform branches, which establish a free communication between it and the lateral sacral veins, and which receive some large branches from the bodies of the sacral vertebrae. These transverse branches represent the vertebro-costal and vejrtebro-lumbar veins, which also receive the veins which issue from the bodies of the vertebrae, through the foramina, upon the inner surface of those bones. The lateral sacral veins (i), of which there are always more than one on each side, are continuous with the dorsi-spinal veins, which emerge from the anterior sacral foramina ; there are generally two, a superior, which enters the common iliac vein, and an inferior, which forms a very remarkable plexus, opposite the great sciatic notch, and ends in the internal iliac vein, or in its gluteal and sciatic branches. The Jlnterior Superficial Spinal Veins in the J^eck. In the anterior cervical region we lind transverse plexiform branches (A) opposite each vertebra, more particularly opposite the first and second ; these plexuses open partly into the ascending cervical vein, which corresponds to the ascending cervical artery, but principally into the vertebral vein, which is contained within the canal formed by the series of foramina at the base of the transverse processes of the cervical vertebrae. These plexiform branches, which cover the sides of the bodies of all the vertebrae, are joined by the veins from the praevertebral muscles, by the articular veins, and by the anterior osseous veins from the bodies of the corresponding vertebrae. The vertebral veins and the ascending cervical veins may therefore be said to repre- sent the azygos veins in the cervical region. The Posterior Superficial Spinal Veins. The posterior superficial spinal veins commence in the skin, and in the muscles of the vertebral grooves : some of them closely accompany the arteries ; for example, those that pass between the muscles of the vertebral grooves ; the others have a peculiar dis- tribution, and require a special description. These veins, which are called dorsi-spinales by MM. Dupuytren and Breschet, form an exceedingly complicated network, the meshes of which surround the spinous process- es and laminae, and the transverse and articular processes of all the vertebrae : these meshes are more numerous in proportion as the injection is more perfect. After a successful injection, we sometimes find along the summits of the spinous pro- cesses, especially in the dorsal and cervical regions, certain median longitudinal veins, from which the interosseous branches proceed. These latter run forward, on each side of, and in contact with, the inter-spinous ligaments. Having reached the base of the corresponding spinous process, they pass outward, opposite the intervals between the laminae of the vertebrae, as far as the bases of the transverse processes, and then divide into two branches : one of these ascends, and anastomoses with the descending branch from the vein above ; while the other branch descends, and anastomoses with the as- cending branch of the vein below. It follows, therefore, that around the transverse pro- cesses and the laminae of the vertebrae there is a series of venous circles, which com- municate, opposite each inter- vertebral foramen, with the veins contained in the interior of the spine. The posterior superficial spinal veins in the neck have a much more complicated ar- rangement, and, indeed, form a plexus. Moreover, we generally find, between the com- plexus and the semi-spinalis colli, two longitudinal veins, which appear to me to deserve a jiarticular description, under the name of the posterior jugular veins. The posterior jugular veins commence between the occipital bone and the atlas, pass tortuously out from the interval between these bones, run downward and inward, and, opposite the spinous process of the axis, the veins of the two sides anastomose by a transverse branch. They then change their direction, pass downward and outward, and having reached the lower part of the neck, turn forward, between the seventh cervical vertebra and the first rib, and open into the back of the brachio-cephalic vein behind the vertebral vein. The two posterior jugular veins are therefore arranged in the form of the letter X. The posterior jugular vein, which does not always exist, for its branches of origin sometimes remain separate, seems to be inversely proportioned to the vertebral vein, with which it communicates opposite each inter-transverse space. It has appeared to me to communicate above with the deep occipital and the mastoid veins, with the veins situated in the spinal caned, and with the interned jugular vein. Throughout the whole THE INTRA-SPINAL VEINS. OOII 01 Its course, it communicates freely, opposite each inter-vertebral foramen, with the veins contained in the interior of the spinal canal, and with the vertebral vein. The Deep Spinal or Intra-spinal Veins. The veins in the interior of the spine comprise the proper veins of the spinal cord, and the veins situated between the bones and the dura mater, which are subdivided into the anterior and the posterior longitudinal veins or plexuses, and the transverse veins or plexus- es ; the latter establishing a free communication between all four of the longitudinal veins or plexuses, opposite each vertebra. Before describing the veins situated between the bones and the dura mater, I must state, in a few words, what is the arrangement of the proper arteries of the vertebras. The spinal branches which are given off on each side of the body by the vertebral ar- tery in the neck, by the intercostal arteries in the back, by the lumbar arteries in the loins, and by the lateral sacral arteries in the pelvis, enter the spinal canal through the several inter- vertebral foramina, and then each of them divides into an ascending and a descending branch ; the ascending branch runs upward upon the lateral part of the body of the vertebra above, and anastomoses with the descending branch of the spinal artery above it, while the descending branch anastomoses with the ascending branch of the artery below. Each of the anastomotic arches thus formed has its concavity directed outward ; so that there is a series of arterial arches, united at their extremities, situ- ated upon each side of the posterior surface of the bodies of all the vertebra. From the convexity of each arch two transverse branches are given off, one running above and the other below the small foramina upon the posterior surface of the body of the corre- sponding vertebra. The cribriform portion of the bone is thus surrounded by the arte- rial arches with their transverse branches ; and from all points of the polygon which they form small arteries are given off, which penetrate into the substance of each ver- tebra, and anastomose with the arterial twigs that enter the anterior surface of the body of the vertebra. The arrangement of these arteries gives a perfect idea of that of the veins known as the anterior longitudiruU veins or plexuses, and of the transverse plexuses, which pass from one to the other. The ^Interior Longitudinal Intra-spinal Veins or Plexuses, the Transverse PlexuseSy and the Proper Veins of the Bodies of the Vertebra. Dissection. — Remove the arches of the vertebrae, and the spinal cord and its coverings. The plexus may also be viewed from the front, by carefully sawing through the pedicles and then removing the bodies of the vertebrae. The anterior longitudinal plexuses, described by Chaussier, but still more correctly by Breschet, form two venous trunks, named the great anterior longitudinal veins, extending from the foramen magnum to the base of the coccyx, one on each side of the posterior common vertebral ligament, and therefore upon the sides of the posterior surface of the bodies of the vertebrae, and on the inner side of their pedicles. These veins, improperly called vertebral sinuses, communicate together opposite each vertebra by a transverse plexus, situated between the body of the vertebra and the posterior common ligament. These longitudinal plexuses are less developed in the cervical and sacral regions. It is probable that in the neck their place is supplied by the vertebral veins. It would be in vain to consider these plexuses as having a distinct origin, course, and termination ; the description given above of the distribution of the arteries is applicable to the veins in every respect : thus, the venous plexuses are formed by a series of plex- iform arches, which embrace the pedicles of each vertebra, have their concavity directed outward and their convexity inward, and the extremities of which anastomose together opposite the inter- vertebral foramina, where they communicate with the branches on the outside of the spine, and assist in the formation of the vertebro-lumbar and vertebro- costal veins, and, consequently, of the azygos veins. From the convexity of each arch proceeds a transverse plexus, which goes to join with its fellow of the opposite side ; and, just as we have seen that the transverse arteries extending from one arterial arch to another give off branches to the bodies of the vertebrae, so, in like manner, the trans- verse venous plexuses receive the veins which emerge from the body of each vertebra. The arrangement of the veins or plexuses just described explains the alternate en- largements and contractions observed in different parts of the anterior longitudinal plex- uses. The rare interruptions described by M. Bresche( I believe to depend upon im- perfect injections, which succeed so differently in different subjects. The anterior longitudinal veins or plexuses cannot be regarded as sinuses, for they are not contained in a fibrous sheath, like the veins of the dura mater, nor are they reduced* merely to the lining membrane of the veins. Notwithstanding their extreme tenuity, we can recognise an external coat, and the posterior common ligament does not covet them behind. Nor is the term sinus more applicable to the transverse plexuses, although they are situated between the bodies of the vertebrae and the posterior common ligament,. for the ligament merely covers them without forming a sheath for them. 4H 610 ANGEIOLOGY. The Proper Veins of the Bodies of the Vertebra. — The foramina upon the posterior sux- face of the body of each vertebra, which are generally proportioned to the size of the ver- tebra, are principally intended for the proper veins of the bodies of their bones : the ar- teries are much smaller, and though they enter by the same openings, they occupy but a small part of their areas. These veins belong to that system of venous canals found in the substance of bones, which we have already noticed as existing in the bones of the cranium. Their chief varieties have been correctly described and delineated by M. Bres- chet. These venous canals, which are more developed in the old than in young sub- jects, occupy the centre of the body of the vertebra, and always run parallel to the up- per and lower surfaces of the bone : they arise from all parts of the circumference of the vertebra, communicating with the veins which enter by the foramina on its anterior sur- face, and converge towards the principal foramen, or foramina, upon its posterior eis- pect. They frequently enter a semicircular canal, which has its convexity directed for- ward, and gives off from its concavity a venous canal, which opens directly into the transverse plexus : the lateral veins of the body of the vertebra open into the extremities of this semicircular canal ; while within the venous canals of the vertebrae, the veins are reduced to their lining membrane, like the veins in the canals of the cranial bones. The transverse plexuses, therefore, collect the blood from the bodies of the vertebra), and transmit it to the anterior longitudinal plexuses. The Posterior IntrU'Spinal Veins or Plexuses, and the Posterior and Lateral Transverse Plexuses. The posterior intraspinal plexuses, much smaller than the anterior, are situated one on each side between the vertebral laminae and ligamenta subflava behind, and the dura mater in front. These veins are rarely injected along the whole length of the spine, and hence they sometimes appear to exist only in the dorsal region. They communicate op- posite each vertebra, by means of posterior transverse plexuses, or by transverse veins. They communicate with the anterior longitudinal plexuses by small lateral transverse plexuses, which pass from behind forward. It follows, therefore, that the veins within the spine, but external to the coverings of the cord, consist of four longitudinal plexuses, all of which are connected by a transverse circular plexus opposite each vertebra. A strict analogy may be said to exist between the sinuses of the cranium and the intra-spi- nal plexuses ; an analogy which did not escape the notice of the ancients, as the com- mon application of the term sinus by them to the veins of the cranium and to those of the spine would seem to indicate. Thus, in the cranium we find certain longitudinal sinus- es, that is, those which run from before backward, viz., the superior longitudinal sinus, the straight sinus, and the posterior occipital sinuses ; also, the superior and inferior pe- trosal sinuses, the cavernous sinuses, and the right and left lateral sinuses. The former set represent the posterior intra-spinal plexuses ; the latter correspond to the anterior in- tra-spinal plexuses. In the cranium we also find certain transverse sinuses, viz., the basilar or transverse occipital sinuses and canals, and the coronary sinus, which exactly correspond to the transverse plexuses, extending from one anterior intra-spinal plexus to the other. We sometimes find two or three transverse venous plexuses in the basilar groove of the oc- cipital bone. Lastly, may we not compare the veins on the outer surfaces of the spine to the occipital, frontal, and temporal veins ; and do not the veins passing through the posterior lacerated foramen and the sphenoidal fissure, which we have regarded as representing the inter- vertebral foramina (see Osteology), establish a communication between the veins on the inside and those on the outside of the cranium, just as the veins which escape through the inter-vertebral foramina connect together the superficial and the intra-spinal veins 1 The anterior and posterior deep spinal veins communicate with the superficial veins of the spine at the inter-vertebral foramina so freely, that the circulation would not be interfered with even if a considerable amount of obstruction existed. I have already stated (see VERTEBRiE) that the diameter of the inter-vertebral foramina is in relation, not with the size of the nervous ganglia, but rather with that of the veins, which estab- lish a communication between the superficial and intra-spinal venous systems. The Proper Veins of the Spinal Cord, or the Medullary Veins. If we examine the pia mater of the spinal cord, even without having injected it, in the body of a person who has died suddenly, as in that of a new-born infant after death from asphyxia or apoplexy, the surface of the pia mater will be found covered by very tortu- ous veins, which emerge from the posterior median furrow of the spinal cord. This ve- nous network, which is spread over the whole surface of the cord, gives off opposite the roots of each nerve a small vein, which runs directly between those roots, enters the corresponding inter-vertebral foramen, is enclosed with the nerve in the sheath formed by the dura mater, and having emerged from that sheath, opens into the large vein sit- uated in the inter-vertebral foramen. There is, therefore, this difference between the proper veins and arteries of the spinal THE LYMPHATIC SYSTEM. 811 cord, that the number of veins is equal to that of the nerves ; while the arteries are less numerous, and enter the fibrous sheaths of the nerves only at intervals, and in propor- tion as the preceding arteries are exhausted. Moreover, the anterior and posterior spi- nal veins, like their corresponding arteries, may be regarded as belonging only to the up- per part of the cord, and not as being intended to traverse its whole length. General Remarks on the Veins of the Spine. The veins of the spine maybe regarded, in reference to the general circulation, as es- tablishing an unbroken communication between the veins of all parts of the trunk ; so that we can suppose one of the venae cavae to be obliterated, without the venous circu- lation being interrupted. The greater azygos itself, which is generally regarded as the principal means of communication between the two venae cavae, is not, however, neces- sary, when we consider the arrangement of the anterior and posterior spinal plexuses. Thus, I have sometimes seen the inferior, and sometimes the superior vena cava oblit- erated without any apparent increase in the diameter of the vena azygos, and, what will perhaps be thought surprising, without oedema, either of the upper or lower extremities. Supposing the vena cava ascendens to be obstructed from the entrance of the hepatic veins down to the renal veins, the blood would then flow back by the vertebro-lumbar veins into the plexuses contained within the spinal canal ; through these plexuses, it would ascend to the vertebro-costal veins, from thence to the azygos veins, and through them into the superior vena cava. If all the jugular veins were obliterated, the venous circulation in the head would still continue, and would be carried on through the spinal veins. I have tied the two exter- nal jugular veins in a dog. The animal showed no sign of cerebral congestion : after opening the body, I did not find any increase of size in the small veins which accom- pany the carotid arteries, and which in those animals are naturally very smalL In this case, the circulation was evidently carried on by means of the spinal veins. THE LYMPHATIC SYSTEM. Definition, History, and general View of the Lymphatic System. — Origin. — Course. — Tcrim- nation and Structure of the Lymphatic Vessels. — The Lymphatic Glands. — Preparation oj the Lymphatic Vessels and Glands. The term lymphatic vessels is applied to certain transparent tubes provided with valves, and conveying either lymph or chyle, which pass through small, rounded, glanduliform bodies called lymphatic glands, and in all cases empty themselves into the venous sys- tem, to which, indeed, they may be said to form an appendage. From their tenuity and transparence, these vessels for a long time escaped the notice of anatomists. The thoracic duct was discovered by Eustachius in 1565. The lac- teals were discovered in 1622 by Gaspard Asellius, who, by a lucky chance, while seek- ing quite another object, discovered certain vessels filled with chyle. In 1641, Pecquet discovered the receptaculum chyli, and showed that the lacteals entered the thoracic duct, and not the liver, as Asellius and all his contemporaries believed. Rudbeck, Thomas Bartholin, and JolyfF dispute the honour of having discovered the l)Tnphatic vessels, properly so called, in contradistinction to the lacteals or chyliferous vessels. Mascagni devoted a great part of his life to the study of the lymphatic system ; and his work, ornamented by magnificent plates, is a monument of science, which should be taken for a model by all who are engaged in anatomical inquiries. Lastly, within the last few years, MM. Fohmann, Lauth, Lippi, Panizza, and Rossi have thrown light upon some most important points in the anatomy of this system. In describing this system of vessels, the lacteals, or the Ijntnphatics containing chyle, have commonly been separated from the lymphatics, properly so called, or the vessels containing lymph. This distinction, however, is not warranted by anatomy, for the two sets of vessels are perfectly identical in structure. The IjTnphatic system offers many analogies with the venous system ; but there ar also no less remarkable differences between the two. Like the venous system, it consists, as a whole, of afferent or converging vessels which arise from all parts of the body, and run from the periphery towards the centre. Like the veins, the lymphatics are divided into two sets : a srib-cutaneous set, which, in general, accompanies the superficial veins of the limbs ; and a deep set, which follows the course of the deep arteries and veins ; and, lastly, the lymphatics resemble the veins in being provided with valves. The lymphatics differ from the veins in passing through certain bodies improperly called glands, which, at intervals, intercept their course. They differ from the veins, also, in their arrangement ; for they do not successively unite into larger and larger branches, and these into trunks, but they scarcely increase in size from their origin to their termination ; and, though they communicate with each other by numerous anasto- 6t$ ANGEIOLOGY. moses, each of them follows, as it were, an independent course : lastly, the blood which circulates in the veins is still, though indirectly, under the influence of the heart's ac- tion, while the onward movement of the lymph is exclusively dependant upon the pari- etes of the vessels. Before proceeding to the special description of the lymphatics, we shall make some general remarks upon the origin, course, and termination of these vessels. Origin of the Lymphatics. Tlie origin of the lymphatics, hke every point connected with the minute structure of the tissues, is yet a new subject for inquiry.* It has been said that the Ijmnphatics are continuous with the arteries, so that, accord- ing to this hypothesis, the arteries are continuous with two kinds of vessels, viz., with the lymphatics, which carry off the serum, and with the veins, which transmit the col- oured part of the blood. The continuity of the arteries with the lymphatics has been admitted, in consequence of its having been observed that injections thrown into the arteries passed into the lymphatics. I have frequently seen this in injecting the spleen and the liver ; but it was only when the injection was pushed in with great and contin- ued force : so that it is possible, as thought by Hunter, Monro, and Meckel, that, in these cases, some of the vessels had been ruptured, and the injection extravasated ; or, what is still more probable, there may have been transudation through the pores of the tis- sues. Microscopical observations show most distinctly that the arteries are continuous with the veins ; but there is no fact to demonstrate the continuity of the arteries with the lymphatics. The origin of the lymphatics can be actually shovra only upon free surfaces, such as the mucous membranes, the skin, the serous and synovial membranes, and the lining membranes of arteries and veins ; so that, in the actual state of our knowledge, it might be maintained that the lymphatic vessels arise exclusively from all the free surfaces. All the lymphatics arise by a network of such tenuity that, when .injected with mer- cury, the whole surface appears changed into a metallic layer. About eight years since, having introduced at random a tube filled with mercury for injecting the lymphatics into the pituitary membrane in a calf, I was astonished to find the surface covered by a metallic pellicle : I repeated the experiment frequently, and constantly found that the pellicle was not caused by extravasation, for the mercury ran in determinate lines, forming plexuses of different kinds ; also that, to succeed in this experiment, it was necessary to puncture the membrane very superficially, or the mer- cury would run into the subjacent plexus of veins; and, lastly, that there was no com- munication between that plexus of veins and the more superficial network, which I sus- pected to consist of lymphatic vessels, for it exactly resembled the network of those vessels in the peritoneum covering the liver. I ascertained that the same structure ex- isted in the skin ; in the lingual, buccal, and vaginal mucous membranes ; in the con- junctiva ; and, lastly, in the uterine mucous membrane of a sow which had lately lit- tered. I showed this lymphatic network of the pituitary membrane in several of my lectures ; and lately, having again examined the subject for the purposes of the present work, I have ascertained that this network exists upon all the free surfaces, that it com- municates with the lymphatics, and that it is possible to inject those vessels and the lymphatic glands by introducing the pipe very superficially into the surfaces of these membranes.! I may be permitted to observe, that it is only a few months since I be- came acquainted with the splendid work of M. Panizza, of Pavia, upon the lymphatic ves- sels of the testicles {Osservazioni Antropo-zootomico Fisiologiche, 1830) ; and with M. Foh- mann's last very important memoir {Mimoire sur les Vaisseaux Lymphatiques de la Peau, des Membranes Muqueuses, Sereuses, du Tissu Nerveux, ct des Muscles, 1833). Origin of the Lymphatics from the Mucous Membranes. — The villi found upon the mu- cous membrane of the small intestines contain, in their centre, a cavity, named the am- pulla of lAeberkuhn, which I have seen in one instance filled with tuberculous matter. {Anat. Pathol, \w. ii.) Still, I have never been able to discover any open orifice on the summit of that villus.J Independently of these cavities within the villi, which are proper to the system of lacteal vessels, the thin pellicle of the mucous membranes which can- not be injected from the arteries or veins {vide p. 370), when carefully and very super- ficially punctured by the pipe of a mercurial injecting apparatus, is covered by a metallic pellicle. Panizza and Fohmann have proved that the membrane which covers the glans penis has two sets of lymphatics : a superficial and a deep. M. Fohmann has figured, in some very beautiful plates, the lymphatic network of the mucous membranes of the glans penis, bladder, urethra, trachea, bronchi, oesophagus, stomach, ileum, and colon. This network is so superficial, that the mercury appears almost uncovered ; it does not com- * Do lymphatics commence in all parts of the body ? It is true that absorption is carried on in every part, for absorption is one element of the process of nutrition ; but, as it can be effected by other vessels besides the lymphatics, its occurrence in any part does not necessarily involve the presence of this peculiar class of vessels. T These preparations were made by M. Bonami, my prosector, under my direction, with extreme skill, and a zeal above all praise. ', [For what is known conceming^ the structure of the villi, see note, p. 369] ORIGIN OF THE LYMPHATICS. 613 municate either with the arteries or the veins, but communicates freely with the lym- phatic vessels. It was correctly delineated by Mascagni : according to that anatomist, it covers all the intestinal villi, as with a sheath, and does not appear to have any open- ings on the exterior. Origin of the Lymphatics from the Skin. — Are the openings or pores so evident upon the skin when viewed through a lens, and from which drops of sweat maybe seen to exude, intended to serve the purpose both of exudation and absorption 1 or are there rather two distinct kinds of orifices for these two functions 1 or, lastly, are these orifices altogether unconnected with the absorbent vessels 1* If we puncture the skin very superficially, so that the injecting pipe may enter imme- diately below the epidermis, the mercury will be seen to run with great rapidity into some very small vessels, and to form a metallic network, precisely like that already de- scribed as existing in the mucous membranes ; from this layer proceed sub-cutaneous lymphatics, which may be traced filled with mercury as far as the adjacent lymphatic glands, or even beyond them. In order that this experiment may succeed, it is neces- sary that the skin to be injected should be plunged into hot water. I made the following experiment in order to detect, if possible, in the lymphatics of the skin, the mercury absorbed during mercurial frictions. I caused two dogs to be rubbed with mercurial ointment night and morning ; and, that the absorption might be more complete, I enveloped their bodies in a frock made of skin. These animals died in about eight days with gangrene of the gums ; but I could not find in any part the slight- est trace of mercury, although the frictions were continued up to the period of their death. Origin of the Lymphatics from the Serous and Synovial Membranes. — The same results as those above stated are obtained by injecting the serous and synovial membranes. The portion of peritoneum covering the liver is generally chosen for injecting the l>Tn- phatic network of serous membranes, because the tension and adhesion of the perito- neum over the liver renders it more easy to inject. The same results may be obtained by injecting the costal or pulmonary pleura, the tunica vaginalis, or the parietal and vis- ceral portions of the arachnoid. The synovial membranes may be injected with the greatest facility, either near the cartilages, where they are more tense than in other parts, or upon the ligaments, to which they adhere. Origin of the Lymphatics from the Lining Membrane of the Veins and, Arteries. — ^The lymphatic plexuses upon the lining membrane of veins and arteries have hitherto been only partially displayed, but the analogy between these and serous membranes is so close, that I have no doubt of their identity in this respect. I have, moreover, found the lymphatic vessels of the aorta filled with blood in several cases of degeneration of the coats of that vessel. Origin of the Lymphatics in the Free Cellular Tissue. — In order to exhibit the origin of the lymphatics in this situation, I injected coloured liquids, such as ink, into the sub- cutaneous and inter-muscular cellular tissue in several animals, and I found the lym- phatic vessels and the corresponding lymphatic glands of a jet-black colour. I made a great number of experiments to induce absorption of mercury, by injecting it either into the cellular tissue, or into a serous cavity ; but the metallic mercury always acted like a foreign body, the mechanical effect of which produced more or less inflanunation, but it was never absorbed. I have found pus in both the superficial and deep lymphatics, and in the lymphatic glands of the groin, after phlegmonous erysipelas and acute abscesses of the leg ; but it is not proved that the presence of this pus was the result of absorption. It is more probable that it had been produced by inflammation of the lymphatics themselves. Although it is impossible to demonstrate, anatomically, the presence of lymphatics in the free cellular tissue, it is most probable that that tissue, as well as the serous mem- branes, with which it heis so many anedogies, is formed by this kind of vessels. Mas- cagni stated that all the white tissues consist of lymphatic vessels, and that the lym- phatic system forms the basis of the whole body. From the preceding observations, it may be stated that, with the exception of the lacteals which open upon the summits of the villi, + all the lymphatic vessels of free sur- faces arise by an exceedingly delicate network ; M. Fohmann believes that all the lym- phatics commence by a network of closed vessels.t I have never been able to discover the l)Tnphatic networks, either in the nervous sub- stance, in muscles, glands, or in the fibrous, cartilaginous, and osseous tissues. * [These pores are the orifices of the ducts of the sudoriferous glands, which are imbedded in the true skin, or the sub-cutaneous cellular membrane, and have no direct connexion with the lymphatics.] + [Whether the lacteals commence in each villus by a network, or by free closed extremities, is not yet de- termined ; but they form no exception to the rule that the absorbent vessels arise by closed extremities, and not by open mouths. See p. 370.] t [These networks are arranged in layers, the most superficial of which is formed by the finest vessels, and has the smallest meshes.] m4 ANGEIOLOGY. Course of the Lymphatics. From the networks above described, the lymphatics themselves arise, and, in aD the organs, are divided into a deep and a superficial set. The former set accompany the deep vessels of the organ, while the others follow the superficial veins in such parts of the body as are provided with them. In those organs which are covered with a serous coat, they appear to be contained within the substance of that membrane. The lymphatics run parallel with each other, and communicate pretty frequently by bifurcating, and then joining the neighbouring vessels ; but they do not converge towards each other, nor do they, like the veins, unite successively into a smaller and smaller number of larger and larger branches ; thus, their increase in size is not progressive ; and it might even be said that, throughout their whole course, they undergo no decided increase nor dimi- nution. Their direction is slightly tortuous. (In^^. 224 are shown short portions of lymphat- ics of different sizes.) Anastomoses. — ^We do not find in the lymphatics those numerous and important anas- tomoses which form such characteristic points in the history of the arteries and veins. These vessels present only one kind of anastomosis, which is accomplished in the fol- lowing manner : A Ijonphatic, after a certain course, divides into two equal branches, which diverge at a very acute angle ; these two branches anastomose with two other lymphatics, each of which communicates either by bifurcation or directly with the neigh- bouring lymphatic vessel. This explains how, by injecting a single lymphatic, a certain group of these vessels may be filled. Not unfrequently, a lymphatic divides into two branches, which, after a certain distance, again unite. During their course, the lymphatic vessels meet certain small giandulifm-m ladies, the conglobate glands of the ancients, but which are also called lymphatic ganglia, on account of the analogy pointed out by Soemmerring between them and the ganglia of nerves ; the lymphatic glands form centres, to which a number of lymphatic vessels proceed, and are lost in them for a time, but from which they afterward emerge. The name of afferent lymphatics (vasa afferentia, a a a, fig. 225) is applied to those which enter a gland, and those which emerge from it are called efferent lymphatics (vasa efferentia, b h). Do all the lymphatics necessarily traverse one or more of these glands t Mascagni has successfully maintained the affirmative in opposition to Hewson and others, who as- sert that they have seen lymphatics entering directly into the thoracic duct. Mascagni states that he invariably found that these vessels passed through one or more glands. As to the argument derived from the absence of dropsy in oases of obstruction in the lymphatic glands, Mascagni explains this by the frequent anastomoses of the lymphatic vessels, the result of which is, that they communicate with several series of glands, some of which are situated at very great distances. The most numerous anastomoses of the lymphatics take place within the lymphatic glands ; thus, if we inject the afferent vessels of a lymphatic gland, the mercury escapes by its efferent vessels. In injecting a gland, it frequently happens that the mercury passes not only into the efferent, but also into some of the afferent vessels. Size of the Lymphatics. — The lymphatics are generally so small as to escape the no- tice of the observer ; but they may become enlarged to a remarkable degree. Thus, I have seen the lymphatics of the groin and of the uterus as large as the thumb. An attempt has been made to draw some comparison between the toted capacities of the lymphatic, venous, and arterial systems ; but all that has been said respecting this is founded upon no positive data. I would, moreover, observe, that in all probability we are acquainted with but a portion of the lymphatic system. Termination of the Lymphatics. According to the most generally received opinion, all the lymphatics terminate in two trunks, the thoracic duct and the great right lymphatic duct; the latter vessel receives the lymph from the right upper extremity, and from the right half of the head, neck, and tho- rax ; the lymphatic vessels of all the other parts of the body end in the thoracic duct ; the lymphatic vessels enter successively into these two trunks, as the plumes of a feath- er are attached to its shaft. The two trunks themselves end as follows ; the thoracic duct enters the left sub-clavian vein, at the junction of that vein with the internal jugu- lar ; the great right lymphatic duct terminates in the right sub-clavian vein ; hence it is that the lymphatic system may be regarded as an appendage of the venous system. Are the thoracic and the great right lymphatic ducts, notwithstanding their small size, the only terminations of the lymphatic system] With this question may be connected another : Are the lymphatics the exclusive agents of absorption, or do they share this function with the veins 1 Mascagni appeared to have established, beyond dispute, that absorption was performed by the lymphatics to the exclusion of the veins ; when Magendie* and Delille in France, * It is established, says M. Magendie, that the lacteals absorb the chyle, and that the intestinal veins ab- TERMINATION OF THE LYMPHATICS. 615 Tiedemann and Gmelin in Germany, and Flandrin and Emmert in England, relying upon some ingenious experiments, again attributed a power of absorption to the veins, and hence led other anatomists to undertake still farther researches. The inquiry was soon entered upon by M. Fohmann in 1820 and 1821, by M. Lauth in 1824, and by M. Lippi in 1825, all of whom again referred the phenomena of absorption exclusively to the lymphatics, and supported that opinion both by arguments and facts. MM. Fohmann and Lauth admit two other modes of termination of the lymphatic sys- tem in the veins besides the one already indicated : first, a direct termination of the lymphatic radicles in the radicles of the veins, which is supposed to occur in the sub- stance of organs ; and, secondly, a communication between the lymphatics and veins within the lymphatic glands. This opinion, which seems reconcilable with the fact that the area of the thoracic and right Ijonphatic ducts is very small as compared with that of all the IjTnphatic vessels, appears, k priori, to be exceedingly probable. But an anatomical fact must be shown anatomically before it can be admitted. Now there is no proof of the communication of the lymphatic and venous radicles. M. Foh- mann relies upon certain more or less ingenious inductions, but not upon direct ana- tomical facts. I am, therefore, still compelled to doubt the existence of these commu- nications, and to class them with the vasa serosa, or serous veins of Haller. Again, a communication between the lymphatics and the veins in the substance of the lymphatic glands had been conjectured by many anatomists ; the elder Meckel had seen mercury, when thrown into the lumbar lymphatics, pass into the abdominal veins ; but this fact was attributed to rupture in the interior of the glands. — {Hewson, Cruickskank.) This apparent communication had also frequently been observed by Mascagni, and was attributed by him to rupture. M. Fohmann urges in reply, that this communication takes place under too slight a pressure to be referred to rupture, that actual extravasations may be easily recognised, and that the mercury is then infiltrated into the cellular tissue with much greater facility than it can enter the veins. " Why," he asks, " supposing the existence of rupture, does the mercury never pass from the lymphatics into the arteries 1" He also adduces in support of his opinion a considerable number of facts, which show that injections thrown into the lymphatic glands sometimes escape by the lymphatics alone, sometimes by the veins alone, and sometimes by both the lymphatics and the veins. He states that, having emptied the veins passing out from a mesenteric gland in a horse which had been killed while digestion was going on, and having replaced the intestines in the ab- domen, he found some streaks of chyle in the veins. Lastly, he has seen, in birds, the renal lymphatic vessels, which represent the l)Tmphatic glands in those animals, opening directly into the renal and sacral veins. M. Lauth has repeated these experiments, and obtained the same results. But, however imposing the authority of the authors just ci- ted may be, I must confess that I am far from being convinced, and that the facts stated by them do not appear to me to be conclusive. I have made a great number of injec- tions of lymphatics, and in by far the greater number of cases the mercury passed from the afferent into the efferent lymphatic vessels, and not at all into the veins. In some cases, it passed from the glands into the veins ; but it appeared to me that the glands had then undergone a change in their texture, more particularly a red softening. It does not seem to me, then, to be shown that there is any direct conununication be- tween the lymphatics and the veins within the substance of the lymphatic glands. Lippi (of Florence) denies the communication of the lymphatics with the veins within the lymphatic glands ; but believes that, besides the terminations of the lymphatics in the venous system through the thoracic duct and the great right lymphatic trunk, there are a great number of direct communications between the lymphatics and the vena por- tae, the internal pudic and the renal veins, and the vena cava ascendens and vena azygos. Several anatomists, indeed, had already met with lymphatic vessels opening directly into the venous system ; among whom were Walceus, Wepfer, Abraham Kaw, Heben- streit, the elder Meckel, Galdani, and Vrolyk ; but the isolated facts recorded by them were regarded by Haller, Mascagni, and Soemmering as anomalies, or as the results of rupture. The memoir published by Lippi excited new investigations on all sides. I was the more inclined to subscribe to the opinions of that observer, because, in 1825, I had most distinctly seen a large lymphatic trunk opening directly into the external iliac vein ; be- cause it appeared to me rational to admit that the communications between the lymphatic and venous systems would not be restricted to the internal jugular and sub-clavian veins ; because the communications supposed to exist by Fohmann and Lauth had not been de- monstrated ; because ligature of the thoracic duct does not prove fatal to all anunals subjected to that experiment, even when the duct is single ; and, lastly, because the thoracic duct has been found obliterated in many individuals. There seemed, besides, a difliculty in admitting that the thoracic and right lymphatic ducts formed the termination Borb other substances. It is shown that the veins are the absorbing- agents in other parts of the body, but tt is not shown that the lymphatics absorb. Some authors have stated that the veins absorb only when the lym- phatic; system is diseased. 616 ANOEIOIiOGT. of the whole of the lymphatic vessels. It appeared, moreover, at variance with the gen- eral laws of the animal economy to suppose that two sets of organs should be devoted to the same functions ; fbr, if the veins absorb, the lymphatic system would seem to have no special use. Nevertheless, truth compels me to state that, after the most minute and frequent re- searches which I have been able to make, I have not obtained a single result confirma- tory of the statements of M. Lippi ; and that, with his plates before me, I have searched for the communications in all the points which he has indicated, and have never found any. I am, therefore, obliged to conclude, with MM. Rossi, Fohmann, and others, that the vessels which M. Lippi has described as lymphatics opening into different parts of the venous system are nothing more than veins. Structure of the Lymphatics. The lymphatics, as well as the veins, have two coats. This structure can be readUy shown in the thoracic duct of the human subject, and still better in that of the horse : the existence of these two coats may also be shown by a method suggested by Cruickshank, which consists in turning the thoracic duct inside out, and forcibly introducing a tube into it ; the lining membrane, which is then on the outside, being less extensible than the external coat, becomes lacerated. The external coat is considered to be fibrous by some, and muscular by others. Shel- don says that he has distinctly seen muscular fibres arranged circularly around the tho- racic duct of the horse. It appears to me that this external coat resembles the dartoid tissue, like the outer coat of the veins. It is not uninteresting to remark, that the outer surface of the lymphatics is often covered by a thin layer of fat, which has deceived sev- eral anatomists. The internal coat of the lymphatic vessels appears to be of a serous nature, like that of the veins. Some arterial and venous twigs ramify in their parietes ; but no nerves have yet been traced into them. Minute lymphatics probably arise from the coats of the larger ones. Mascagni believes that their lining membrane is entirely lymphatic. Notwithstanding their excessive tenuity, the lymphatics are tolerably strong ; less so, however, than is generally stated, for they are often lacerated by the weight of a small column of mercury. They do not appear to me to be stronger than the veins. They are much less extensible. When the thoracic duct, or any other lymphatic vessel, is punc- tured, it immediately collapses, and forces out its fluid contents sometimes in a jet. Some admit the existence of muscular contractility in them. The vemiicular motion caused by contraction of their external coat is sufficient to explain the above-named fact.* The lymphatics are much more abundantly supplied with valves than the veins. The Fig. 224. valves {a a, Jig. 224) are parabolic, and are arranged in pairs ; they have an adherent border turned towards the commencement, and a free border towards the termination of the vessel ; they are generally sit- uated at very short intervals apart, as is shown by the knotted ap- pearance of the vessels (see fig. 224), and occasionally they present a circular or annular arrangement, from which they have been re- garded as true sphincters. In general, these valves are strong enough to prevent the retrograde course of the lymph, and, consequently, of injections also. Never- theless, Hunter inflated all the lacteals from the thoracic duct ; Hal- ler filled all the lymphatics of the lung from the upper part of the same canal, and Marchettis says that he has injected the whole of the lym- phatics from the reservoir of Pecquet. The valves are extremely numerous in the lymphatics ; they have sometimes appeared to me to be wanting in the thoracic duct. Like those of the veins, the valves of the lymphatic vessels appear to be formed by a fold of the internal membrane. The Lymphatic Glands. Sylvius was the first to distinguish the lymphatic glands under the term conglobate glands, from the glands properly so called, which he named conglomerate. Chaussier called these little bodies lymphatic ganglia, following Soemmering, who first pointed out the analogy between them and the venous ganglia. The lymphatic glands are situated along the course of the lymphatic vessels, in refer- ence to which they may be regarded as centres in which a certain number of the ves- sels open ; those of the extremities are chiefly found at the upper part of the limbs on the aspect of flexion ; those of the thorax, the abdomen, the head, and the neck are pla- ced along the vertebral column and the great vessels ; they are found also in tlie sub- stance of the mesentery, in the mediastina, at the roots of the lungs, &c. * [The lacteal vessels have been seen to underijo a slow contractility on exposure to air. or to the action of any other stimulus ; but there is no evidence of the muscularity of any part of the lymphatic system of mam malia. In certain reptilia and amphibia there are pulsating muscular sacs connected with the lymphatic syi tern, v?hich are called lymphatic hearts.'^ PREPARATION OF THE LYMPHATIC VESSELS AND GLANDS. 617 Their size varies from that of a millet seed to that of a large filbert. The smallest are situated in the epiploon, the largest at the roots of the lungs. They are often greatly enlarged by disease. They are generally of a reddish-gray colour, excepting at the root of the lungs, when they are black. Their form is irregularly spheroidal ; and they have been distinctly shown by Malpighi to have a cellular structure.* If we examine with a lens a lymphatic gland distended with fluid, we observe that it contains cells ; the same fact is clearly demonstrated by injecting it with mercury, which shows, moreover, that the cells communicate freely with each other. It is, nevertheless, doubtful whether all the cells communicate. The researches which I have made upon this subject appear to show that each lymphatic vessel is connected with a distinct portion of the lymphatic gland ; and diseases of the glands establish the same fact, by attacking one part only of a gland, the rest continuing unaffected. Several l)rmphat?ic vessels enter each gland, and several emerge from it. Each affer- ent vessel (a a a, fig. 225), as it reaches the circumference of the pig. 225. gland, divides into a considerable number of branches, which diverge and run for a short distance upon the surface of the gland, and then dip into its substance.! The efferent lymphatics (i b) commence in precisely the same manner as the afferent vessels terminate. The study of these vessels in the larger animals appears calcula- ted to clear up all doubts as to the structure of the lymphatic glands. Abernethy having injected the mesenteric arteries and veins of a whale, saw the fluid run into pouches about the size of an orange ; he then injected mercury into the lacteals, and found that it flowed into the same cavities ; he therefore concluded that the arteries, veins, and lacteals all opened into the same cavities. This fact ap- pears to confirm the observations quoted by MM. Fohmann and Lauth, relative to the communications of the lymphatics with the veins within the substance of the glands ; but the objections already urged against those observations will apply to this one also. The lymphatic glands are enclosed in a fibrous membrane ; I have in vain attempted to find the fleshy coat described by Malpighi, and which he imagined sent prolongations into the substance of these glands. The lymphatic glands are supplied with very large arteries for their size, and they give off still larger veins : a proper tissue {d) appears to enter into their composition. The lymphatic glands may be said to consist essentially of an inextricable interlace- ment of lymphatic vessels, their structure having some analogy to that of the corpus cavernosum penis, and to that of the spleen. This opinion is confirmed by reference to the anatomy of birds, in which lymphatic glands exist only in the neck, their place being supplied by plexuses in all other parts. Preparation of the Lymphatic Vessels and Glands. I have already said, that in order to inject the network of lymphatics, the pipe should be very superficially introduced into the free cutaneous, serous, or mucous surfaces. When the injection is successful, the mercury passes from this network into the vessels which emerge from it, reaches as far as the l3anphatic glands, and even penetrates through several series of them. The great number and peculiar arrangement of the valves prevents the injection of the lymphatics from the centre towards the extremities ; I have attempted to do this several times, without success, by introducing the tube into the thoracic duct. From the small caliber of the lymphatics, it is necessary to use a capillary tube for these injections. Mercury, notwithstanding the inconvenience of its fluidity, and in- capability of being made solid, is the most convenient material for the purpose ; the weight of a column of mercury about fifteen or eighteen inches in height aflJbrds suffi- cient power for the injection. Anel's syringe is well adapted for injecting the thoracic duct, which may be filled with a solution of isinglass, or, still better, with milk, which be- comes coagulated by the alcohol. The best apparatus for injecting the lymphatics is a glass cylinder, to the lower end of which is adapted a flexible tube, which is terminated by a metal pipe, provided with a stopcock, and supporting a capillary tube of glass, which is better than one made of steel or platinum, like those generally used in Germany. A ring is attached to the upper end of the glass tube, by means of which the apparatus may be suspended : this greatly facilitates the employment of the apparatus. In order to inject the lymphatics, one of these vessels should be exposed at a greater or less distance from the centre ; for example, in the lower extremity, upon either the internal or external malleolus, or, what is still better, over the metatarso-phalangal artic- ulations, in the way practised by Mascagni ; the vessel must then be punctured, and the tube introduced into its interior ; the stopcock is then opened, and the mercury run? * See note, infra. t [Within the gland the lymphatics form a dense network (c) ; when the vessels of which this network ia composed are distended, they give the cellular appearance to a section of the g-land noticed by Malpighi. Cruickshank, <&c.] 41 'IBI'8 ANGEIOLOGY. as far as the gland into which the vessels opens, and at the same time enters all the vessels which anastomose either directly or indirectly with the one into which the tube IS introduced. The vasa efferentia are also soon injected, and if the experiment be con- tinued long enough, the mercury will, in all probability, reach the thoracic duct if no rupture should occur. The internal jugular, sub-clavian, and brachio-cephalic veins of both sides of the body may be previously injected, in order to prevent the mercury enter- ing these vessels by the thoracic duct and its supplemental canals. We may also have recourse to the following method, on account of its greater facility . Puncture a lymphatic gland with a capillary tube ; all the efferent vessels which com- municate with the cells thus punctured, and all the other portions of the lymphatic sys- tem which communicate with those vessels, will thus be injected. But this method is manifestly defective. With regard to the choice of subjects, it may be remarked that the lymphatics are much more easily seen when the cellular tissue is moderately infiltrated than when there is extreme emaciation. Fat subjects are the worst of all : adults are preferable to chil- dren and old subjects. In describing the lymphatics, I shall follow the same arrangement as Mascagni, with some slight modifications. Thus, after having described the thoracic duct and the great right lymphatic trunk, I shall notice in succession all the lymphatic vessels which enter it, beginning with those of the lower extremities. I shall not describe the vessels and glands separately, but I shall group the vessels around the glands, as around central points towards which they all converge. DESCRIPTION OF THE LYMPHATIC SYSTEM. The Thoracic Duct — the Right Thoracic Duct. — The Lymphatic System of the Lower Ex- tremity — of the Pelvic and, Lumbar Regions — of the Liver — of the Stomach, Spleen, and Pancreas — of the Intestines — of the Thorax — of the Head — of the Cervical Regions — of the Upper Extremity and Upper Part of the Trunk. The Thohacic Duct. Dissection. — The thoracic duct may be examined, when distended with chyle, in an animal killed during the process of digestion. If it is to be injected in the human sub- ject, turn the intestines to the left and the liver to the right ; seek for the reservoir of Pecquet (receptaculum chyli) between the aorta and the right crus of the diaphragm ; fol- low one of the lymphatic trunks leading from this reservoir to the lumbar glands, and puncture it with the injecting tube. Care must be taken to tie the left sub-clavian vein both on the inside and on the outside of the termination of the internal jugular vein ; or, still better, first fill the sub-clavian and internal jugular veins with a solid injection. If we wish to make a preparation to be preserved, it is much better to inject the thoracic duct with isinglass size by an Anel's syringe than to use mercury. The thoracic duct {s 1 1 u, fig. 223), so called from its situation, is the common trunk of all the lymphatics of the human body, excepting those of the right side of the head, neck, and thorax, and of the right upper extremity. It commences opposite the second lumbar vertebra, by the junction of a variable num- ber of branches : Meckel says there are three, but I have generally found five or six. These vessels, which are usually of large size, pass out from the abdominal lymphatic glands ; they all converge towards a dilatation or ampulla of a triangular shape, which is called the reservoir or cistern of Pecquet (cisterna, receptaculum chyli, s, fig. 223), after the anatomist who showed that the lacteals did not pass to the liver, as was generally be- lieved, in accordance with the opinion of Aselli, but that they entered the thoracic duct. This ampulla, which is often nothing more than the point at which the lymphatic ves- sels meet, and presents no dilatation, is situated to the right of and behind the aorta, immediately below the aortic opening in the diaphragm, and by the side of the right eras of that muscle. Having commenced thus, the thoracic duct passes verticaUy upward, enters the tho- rax through the aortic opening in the diaphragm, and becomes situated in the posterior mediastinum {t t), in front of the vertebral coliunn, a little to the right of the median Jine, and has the vena azygos (a a') on its right side, and the aorta on its left. Having reached the front of the fourth dorsal vertebra, it inclines towards the left, still continu- ing to ascend, passes behind the aorta, gains the left side of the oesophagus, runs along oehind and on the inner side of the left sub-clavian artery, and escapes through the su- perior opening of the thorax ; having arrived behind the left internal jugular vein, and in front of the seventh cervical vertebra, it immediately bends forward, so as to form an arch (m) like that of the aorta, and finally opens into the angle formed by the junction of the left internal jugular and sub-clavian veins, or sometimes into the sub-clavian vein externally to that angle. The direction of the thoracic duct is not straight, but flexu- ous : its windings are sometimes very mmierous. From the relations of the thoracic duct while within the posterior mediastinum, it fol- THE RIGHT THORACIC DUCT, ETC. ^'Wfe lows that, in order to expose its lower portion, it must be sought for on the right side of that cavity, and that we must look for its upper portion on the left side, and must di- vide the left layer of the mediastinum in order to expose it. The thoracic duct terminates in many different ways : thus, it not unfrequently opens by several trunks into the left internal jugular and sub-clavian veins. A still more fre- quent method of termination, and one which it is extremely important to know, is that in which the duct, at its upper part, is divided into two branches, the left one of which (m) is distributed in the usual manner, while the right (indicated by a smaller letter «) opens into the right sub-clavian vein in connexion with the great lymphatic duct of the right side. The caliber of the thoracic duct is not at all proportioned to the number and size of the lymphatics which terminate in it. Sometimes, in fact, lymphatics are found which, when distended, are as large as a goose-quill. Still less is it proportioned to all the lymphatics of the body, of which it is regarded as the common trunk. Its caliber is even smaller than that acquired by some lymphatics under many circumstances ; for exam- ple, by those of the uterus during pregnancy : this is a powerful argument in favour of those who regard the thoracic duct as by no means corresponding to all the lymphatics of the human body. The thoracic duct is not of uniform caliber in its entire length. It commences by a dilatation of two or three lines in diameter ; in the middle of the thorax it becomes con- tracted to less than two lines in diameter, and it is again dilated a little at the arch which it forms before its termination. The thoracic duct not unfrequently divides, during its course, into several branches, which form a sort of network ; it often subdivides into two branches of unequal size, which unite again after a variable distance. The thoracic duct receives, while in the thorax, a very large trunk, which is derived from the liver, and perforates the diaphragm through a special opening. I have seen this trunk cross and continue in front of the thoracic duct, being equal to it in size, and at last enter it opposite the fifth dorsal vertebra. The thoracic duct has been observed to end on the right side, and then the lymphat- ics of the left side of the head, left upper extremity, left lung, and left side of the heart, entered separately into the sub-clavian vein of the corresponding side. Meckel has cor- rectly observed, that such a disposition is a first trace of the lateral transposition of the viscera. Valves. — Of all parts of the lymphatic system, the thoracic duct has the fewest and the smallest valves. The most remarkable are those situated at its termination in the sub-clavian vein ; their free borders are turned towards the vein, so that they oppose any influx of the venous blood into the thoracic duct. The free borders of the other valves, when they exist, are turned upward, their convex borders being directed down- ward : the course of the fluid within the duct is, therefore, from below upward. The Right Thoracic Duct. The great right lymphaiic duct, or right thoracic duct, is a large vessel, the common trunk of all the lymphatics derived from the right half of the head and neck, the right upper extremity, the right lung, the right side of the heart, and often, also, of those from the right half of the diaphragm and of the liver. This trunk (v, fig. 223), which is not more than an inch long, resembles the curved portion of the thoracic duct ; it opens at the angle formed by the junction of the right internal jugular and sub-clavian veins. Sometimes this common trunk does not exist, and then the lymphatics, by the junc- tion of which it is usually formed, enter the veins separately. Anastomoses always ex- ist, moreover, between the left and right thoracic ducts. The Lymphatic System of the Lower Extremity. The Lymphatic Glands of the Lower Extremity. Tlie lymphatic glands of the lower extremity are the anterior tibial gland, the popliteal gland, and the inguinal glands. The anterior tibial gland is situated at a variable height in front of the interosseous ligament, generally at its upper part. Hewson has seen it below the middle : Meckel has found two glands here ; but the existence even of one gland is not constant. The popliteal glands are four in number ; one of them is situated immediately beneath the fascia ; the other three are placed deeply at variable heights along the vessels of the popliteal space : they are rather small. The inguinal glands are the most numerous and important ; they are situated in the fold of the groin, below Poupart's ligament, and are generally grouped around the en- trance of the internal saphenous into the femoral vein, in a sort of depression formed between the adductor longus and pectineus on the inside, and the psoas and iliacus on the outside. They are not unfrequently continued along the internal saphenous vein as low down as the middle of the thigh. They are divided into superficial and deep. The latter are very variable in size and number, and are often wanting : they are sometimes 620 ANGEIOLOGY. continuous with the superficial, through the saphenous opening in the fascia lata. Thff number of the superficial glands also varies much : it is nearly always inversely propor- tioned to the size of the glands, which is also subject to great variety in diflferent indi- viduals and at different ages. There can be no doubt that these differences in number and in size depend, ceteris paribus, no less upon actual differences than upon the subdivis- ion of one gland into several, or, rather, upon the union of a certain number of glands into one. Sometimes we find a large circular gland situated around the termination of the saphenous vein. The inguinal glands, moreover, are placed at different depths in the substance of the fibrous layers which constitute the superficial fascia. Several of these glands are frequently united to each other, not only by lymphatic vessels, but also by prolongations of their proper substance. The Lymphatic Vessels which enter the Lymphatic Glands of the Lower Ex- tremity. Preparation. — Introduce the pipe into some of the lymphatic vessels between the toes, over the metatarso-phalangal articulations. Mascagni employed this method, which is as easy as introducing the pipe into the vessels which run between the internal malleo- lus and the skin. A still better method of injection, when it proves successful, is to fill the lymphatic network in the skin by introducing the pipe into the dermis at any point beneath the cuticle. But the limb requires to be warmed for this injection to succeed. I have made a very beautiful preparation by injecting the cutaneous network of lymphat- ics upon the sole of the foot in a new-born infant. The mercury ran as far as the glands situated along the iliac vessels. If the pipe be inserted into the skin upon the scrotum, or into the mucous membrane covering the glans penis in the male, or into the skin of the labia majora in the female, the mercury will reach the lymphatic glands of the groin. The lymphatics which ramify in the gluteal region, and those situated in the sub-cu- taneous cellular tissue of the abdominal parietes, may be injected in the same manner. The deep lymphatics of the leg open into the anterior tibial gland and popliteal glands. All the superficial lymphatics of the lower extremity, and also those of the gluteal re- gion, perineum, external genital organs, and sub-umbilical portion of the parietes of the abdomen, terminate in the inguinal glands. Lymphatics of the Lower Extremities. — The lymphatics of the lower extremities, like the veins, are divided into superficial and deep. The deep-seated lymphatics are fewer in number and less accurately known than the superficial ; they accompany the deep-seated bloodvessels. It is probable that every ar- terial and venous branch has its corresponding lymphatics ; but those only which ac- company the great vessels have been as yet discovered. They are divided into the pe- roneal, the anterior and posterior tibial, and the femoral. Of the anterior tibial lymphatics, two only have been demonstrated, although their num ber must certainly be greater. One of these accompanies the plantar arch, the dorsal artery and vein of the foot, and the anterior tibial vessels ; it communicates with the posterior tibial and the peroneal lymphatics, opposite the upper part of the interosseous ligament, and enters the anterior tibial gland, or more frequently perforates the interos- seous ligament, and enters the popliteal glands. The other anterior tibial lymphatic arises deeply from the outer side of the foot, and joins the preceding. The posterior tibial lymphatics, two or three in number, and likewise the peroneal lymphat- ics, sometimes unite into a single trunk, and enter the popliteal glands. The branches which emerge from the popliteal glands, five or six in number, traverse the opening in the adductor muscle, ascend along the femoral vein, and open into the deep inguinal glands. The superficial lymphatics, which can be very easily shown to arise from a network in the skin, run upward and inward, to reach the inner side of the leg, and then pass be- hind the internal condyle of the femur : those which arise from the outer side of the foot and leg, after ascending vertically in front of the muscles of the anterior region of the leg, cross over the upper part of the tibia obliquely from without inward, so that all the superficial lymphatics at last gain the inner and back part of the internal condyle of the femur : from this point they incline forward like the sartorius, upon which they are pla- ced, and then pass vertically upward, and are distributed to the different lymphatic glands of the groin. A certain number of lymphatic vessels which commence upon the outer border of the foot (there are not more than two or three) pass over the external malleolus tc reach the external saphenous vein, become sub-aponeurotic like that vein, and enter the most superficial of the popliteal glands. These lymphatics, which accompany the exter- nal saphenous vein, are regarded by some authors as forming part of the deep set o* vessels. Superficial Lymphatics of the External Genital Organs, Gluteal Region, Perineum, and THE PELVIC AND LUMBAR LYMPHATIC GLARDS. 621 Lower Part of the Abdomen. — The superficial lymphatic vessels from these parts also en- ter the inguinal glands. The superficial lymphatics of the external genital organs of the male are divided into those of the scrotum and those of the penis. If the skin of the scrotum be injected, several 8ub-cutaneous branches will be seen to pass from the network beneath the epidermis upward along the sides of the penis, and then, after describing a curve with the concav- ity directed downward, to open into the inguinal glands, generally into those which are nearest the middle line, but I have seen them pass to the glands surrounding the saphe- nous opening. If we inject the skin of the penis, and more especially the membrane covering the glans, the mercury penetrates into the dorsal lymphatics of the penis, and reaches the innermost and highest of the inguinal glands. The injection from the skin of the penis enters the superficial lymphatics ; the injection from the membrane cover- ing the glans enters only those superficial lymphatics which accompany the dorsal blood- vessels of the penis. In the female, injections of the skin of the labia majora, and of the mucous membrane of the labia majora, labia minora, and clitoris, yield similar results as the injection of the scrotum and penis in the male. We know that diseases of the labia, nymphai, and clitoris, like those of the prepuce, penis, and scrotum, occasion enlargement of the in- guinal lymphatic glands. The lymphatics of the perineum unite with the preceding, and with the lymphatics of the lower extremities. The superficial lymphatics of the gluteal region turn horizontally round the glutaeus max- imus and medius, and enter the external and middle lymphatic glands of the groin. This is the reason why furunculi or other diseases of the skin upon the nates may give rise to enlargement of the inguinal glands. The superficial lumbar lymphatics, as well as those of the sub-umiilical portion of the abdominal parietes, have a descending course : those of the loins run forward and down- ward, those of the abdomen vertically downward ; they both terminate in the outermost and highest of the inguinal glands ; and hence diseases of the skin covering the lumbar and sub-umbilical regions may occasion swelling of the inguinal glands. The lymphatic vessels which accompany the epigastric and circumflex iliac veins also enter the glands of the groin. The Lymphatic System of the Pelvic and Lumbar Regions. The Pelvic and Lumbar Lymphatic Glands. The lymphatic glands of the pelvis are divided into the external iliac, the internal iliac, and the sacral. The external iliac lymphatic glands, irregular in number, are situated along the artery of that name. Three of them require to be particularly noticed ; they are situated im- mediately behind the femoral arch, one of them on the outer side, another in front, and the third on the inner side of the external iliac vessels. It is important, in reference to the ligature of the external iliac artery, to know that these lymphatic glands are subject to enlargement. The internal iliac lymphatic glands occupy the space between the external and internal iliac vessels. The bladder has proper lymphatic glands situated upon its posterior sur- face, and near its summit. In the female, some of the pelvic lymphatic glands may be regarded as belonging to the vagina and uterus. One tolerably large gland, which may be said to be constant, occupies the internal orifice of the obturator canal, and I have often found it inflamed or indurated in diseases of the uterus. The sacral lymphatic glands occupy the sides of the anterior surface of the sacrum : several of them are situated within the folds of the meso-rectum, and belong to the rec- tum itself The lumbar or aortic lymphatic glands are very numerous, and form a continuous chain with the pelvic glands ; they occupy the angular interval between the conunon iliac ar- teries, being placed along those arteries themselves, and also surround the aorta and the ascending vena cava, but more particularly the aorta. It is important to note the rela- tion of these lymphatic glands with the aorta, for that vessel is sometimes found much compressed and narrowed from enlargements of these glands by tubercular or cancerous deposite. There is also a lymphatic gland in each intef-transverse space on both sides of the lumbar region ; so that the lumbar lymphatic glands may be divided into the median and the lateral. The Lymphatic Vessels which enter the Pelvic and Lumbar Lymphatic Glands. The different lymphatic vessels which proceed from the inguinal glands enter the pel- vis behind the femoral arch, and near the femoral vein. The foramina through which they pass are so numerous, that the fascia which is perforated by them is named the cribriform fascia. Having arrived beneath the peritoneum, they are divided into two 633' ANGEIOLOGY. sets, one of which descends into the cavity of the pelvis, and tenninates in the several internal iliac lymphatic glands ; while the other enters the external iliac glands, and more particularly those situated behind the femoral arch. These external iliac glands, moreover, are joined by the epigastric lymphatics, some of which enter the inguinal glands, and by the ilio-lumbar lymphatics. The lymphatic glands of the pelvis also receive the deep lymphatics of the nates, which accompany the gluteal and sciatic arteries ; the lymphatics corresponding with the ob- turator vessels ; the lymphatics of the bladder and lower end of the rectum, those of the prostate and vesiculse seminales, and the deep lymphatics of the penis in the male, and those of the vagina, clitoris, and neck of the uterus, in the female. The lymphatics of the bladder, before entering the pelvic glands, traverse the glands proper to itself : the greater number of the lymphatics of the bladder run beneath the peritoneum upon its posterior surface. I have seen the vesical lymphatics filled with pus. Some other lymphatics emerging from the internal iliac glands accompany the external and internal iliac arteries and veins, ascend in front of the sacrum, pass through other lymphatic glands, and arrive at the brim of the pelvis. At this point, the lymphatics of the right and left sides unite together. These vessels pass through one or several series of lumbar lymphatic glands, and at last open into the thoracic duct. This collection of lymphatic vessels and glands forms the internal and external iliac lymphatic plexuses. The inter- nal iliac lymphatic plexus is placed in the cavity of the pelvis, and surrounds the inter- nal iliac vessels : the external iliac lymphatic plexus is situated along the vessels of that name. All the lymphatics of the lower extremities, after having passed through a greater oj less number of glands, open at last into these lumbar glands, so that the vessels and glands together may be said to form an uninterrupted chain. Thus, passing from plex- us to plexus, and from gland to gland, the lymphatics of even the most distant parts ar- rive, at length, at the thoracic duct. The lateral lumbar lymphatic glands, viz., those which occupy the spaces between the transverse processes of the lumbar vertebrae, receive the lumbar lymphatics, properly so called, which correspond to the bloodvessels of that name. From these glands, commu- nicating vessels pass to the aortic lumbar glands. The collection of lymphatic vessels and glands occupying the lumbar region is called the lumbar lymphatic plexus. The following lymphatic vessels also enter directly into the lumbar glands : the lymphatics of the testicles in the male ; the lymphatics of the ovaries and Fallopion tubes, and also of the body and upper part of the neck of the uterus, in the female ; and the lymphatics of the kidneys in both sexes. The Lymphatics of the Testicle. — It has been already stated that the lymphatics of the covering of the testicle enter the superficial inguinal glands ; those which belong to the gland itself are divided into the superficial and deep. The superficial lymphatics may be injected with the greatest facility by puncturing the serous membrane covering the tu- nica albuginea ; the tunica vaginalis will then appear as if covered with a coat of silver. (See the beautiful plates of Panizza.) These superficial vessels have numerous commu- nications with the deep-seated lymphatics, so that both sets are injected at the same time. All the lymphatics from the epididymus and the body of the testicle, which are very numerous and large, ascend with and assist in forming the spermatic cord, pass through the inguinal canal, follow the course of the spermatic vessels, and enter the lumbar lymphatic glands. The Lymphatics of the Uterus. — Having, in diseases of the uterus incidental to the pu- erperal state, frequently detected pus in the lymphatics of the uterus (vide Anat. Path., liv. xiii., pi. 1, 2, 3), I have been able to trace the exact distribution of these vessels, and would divide them into superficial and deep. The superficial lymphatics are situated im- mediately under the peritoneum ; the deep lymphatics form several successive layers, which occupy different planes within the substance of the uterus. The IjTnphatics near the neck of this organ enter the pelvic and sacral lymphatic glands. A certain number of the uterine lymphatics enter a lymphatic gland situated at the internal orifice of the obturator canal. All the uterine IjTnphatics, excepting those near the neck of that organ, pass towards the sides and upper border of the uterus ; some run within the substance of the broad lig- aments, and they all reach the upper or tubal angles of the viscus. They are joined by the lymphatics of the ovaries, broad ligaments, and Fallopian tubes, and then ascend in front of the corresponding ovarian artery and veins. Having arrived in front of the lower part of the kidneys, they incline towards the middle line, and enter the glands which are situated in front of the vena cava and aorta. Without having witnessed it, it is impos- sible to form any idea of the enormous size which the uterine lymphatics may acquire during pregnancy : several of these vessels, when filled with pus, become so dilated that one would at first sight believe that an abscess had been formed. The Lymphatics of the Kidneys and Supra-renal Capsules. — These are divided into super- ficial and deep. The superficial lymphatics have never been injected directly ; but if a fine injection be thrown into the renal arteries and veins, the injection, freed from col- THE LYMPHATICS Of THE LIVER. 623 ouring matter, passes into the lymphatics. This was the only way in which Mascagni could inject the superficial lymphatics of the kidney, which he has represented in his beautiful plates. The deep lymphatics, which are very numerous, pass out of the fissure of the kidney, and enter the glands in front of and behind the aorta and vena cava. The lymphatics of the supra-renal capsules are remarkable for their size and number ; they unite with those of the kidneys, and terminate in the same manner. The Lymphatic System of the Liver. Preparation. — Of all the lymphatic vessels, those of the liver are the most easily de- monstrated. Before they are injected, they may be rendered more apparent, and even be filled, by throwing water either into the hepatic arteries, the vena ports, the hepatic veins, or the hepatic ducts. In order to inject them, it is sufficient to make a superfi- cial puncture in any part of the peritoneum covering the liver ; but it is most convenient to operate upon one of the lymphatic trunks which run upon the surface of that organ. It is of importance that the tube should be introduced between the peritoneal covering and the fibrous coat, without perforating the latter. It is sufficient to inject from a sin- gle vessel in order to fill all the others. The mercury generally runs as far as the near- est lymphatic gland, the resistance in which causes the fluid to flow back into the sur- rounding branches, even as far as their most delicate ramifications, so that, in successful injections, the whole surface of the liver has a silvery aspect ; the possibility of injecting the lymphatics of the liver, from the trunks towards the branches, must lead us to sup- pose that there are fewer valves in them than in the lymphatics of other pjirts of the body. The Lymphatic Glands of the Liver. These are situated along the hepatic vessels, behind the pylorus, and are continuous with the cceliac lymphatic glands. I have seen them of a jet-black colour ; a liquid may be expressed from them, resembling that contained in the bronchial lymphatic glands. The Lymphatic Vessels of the Liver. The lymphatics of the liver may be divided into the superficial and the deep. The Superficial Lymphatics. — These are subdivided into those of the convex and those of the concave surface. The lymphatics of the convex surface of the liver consist of a certain number of trunks, some of which belong to the right and the others to the left lobe. Some of them run from behind forward, others from before backward, towards the posterior border of the organ. The first set, or those which run from behind forward, reach the suspensory ligament of the liver, and unite into several trunks, some of which perforate the diaphragm, enter the anterior mediastinum, behind the xiphoid cartilage, and tenninate in the mediastinal lymphatic glands ; while others are reflected over the anterior margin of the liver, to gain the longitudinal fissure, along which they run as far as the gastro-hepatic omentum, by which they are conducted to the lymphatic glands placed round the pylorus, to tbose around the cardiac orifice of the stomach, and to those which lie along the lesser curva- ture of that organ, and near the lobulus Spigelii. The second set of the lymphatics of the convex surface of the liver, or those which run from before backward, having reached the posterior border of the liver, divide into three distinct groups of vessels : those on the left enter the substance of the left triangu- lar ligament of the liver ; those on the right pass into the right triangular ligament ; while the remainder, which occupy the middle, enter the substance of the coronary ligament. Those lymphatics of the second set that do not perforate the diaphragm enter the lymphatic glands along the vena cava, and from thence reach the thoracic duct. Some of them run along the lower border of the twelfth rib, and open into the glands situated near its posterior extremity, and into another gland which rests upon the twelfth dorsal vertebra. Those lymphatics of the second set which do perforate the diaphragm pass through its crura, and proceed, some to the intercostal lymphatic glands, or into those which lie along the vena azygos and the aorta, and thence into the thoracic duct ; while others enter that duct directly. I have seen a veiy large lymphatic trunk open directly into the thoracic duct, opposite the fifth dorsal vertebra. Mascagni pointed out some lym- phatic vessels which, after having perforated the fleshy fibres of the diaphragm, ran be- tween the pleura and that muscle, re-entered the abdomen through the aortic opening in the diaphragm, and then passed into the glands surrounding the aorta and vena cava, or entered the thoracic duct at no great distance from the reservoir of Pecquet, without passing through any lymphatic glands. The lymphatics of the concave surface of the liver consist of several tninks, which are all directed from before backward, and are divided into three sets : those which are situ- ated to the right side of the gall-bladder ; those which surround it ; and those which are situated to its left side. ANGEIOLOGY. Those situated on the right of the gall-bladder partly enter the lumbar glands, and partly terminate in the glands around the vena cava and aorta. Those which surround the gall-bladder lorm a remarkable plexus, vphich accompanies the hepatic vessels, and terminates in the lymphatic glands which lie along those ves- sels, and in the glands situated in the substance of the gastro-hepatic omentum. Among this set of lymphatics I would point out one considerable trunk, which runs in the cellu- lar tissue connecting the gall-bladder to the liver. The lymphatic trunks on the left of the gall-bladder end in the oesophageal lymphatic glands, and in those which occupy the lesser curvature of the stomach. The Deep-seated, Lymphatics of the Liver. — These vessels accompany the hepatic ducts and the vena portae, and are contained with them in the capsule of Glisson ; they emerge from the transverse fissure of the liver, penetrate the substance of the gastro-hepatic omentum, and enter the lymphatic glands situated along the lesser curvature of the stomach and behind the pancreas. Those lymphatics of the liver which accompany the hepatic artery and duct and the vena ports are extremely large, and are often filled with yellow lymph : they are some- times found distended with gas in cases of commencing putrefaction. They were known long before the lacteals ; indeed, they were the first lymphatic vessels that were dis- covered. The Lymphatic System of the Stomach, Spleen, and Pancreas. The Lymphatic Glands of the Stomach,, Spleen,, and Pancreas. Those of the stomach accompany the coronary vessels along the great and lesser cur- vatures of the stomach ; some of them are situated within the gastro-splenic omentum, and a great number surround the pyloric and cardiac orifices. The lymphatic glands of the spleen occupy the hilus of that organ. The pancreatic lymphatic glands are ranged along the splenic artery, and, consequently, along the upper border of the pancreas ; several of them are grouped around the coeliac axis. They receive a very great number of lymphatic vessels. The Lymphatic Vessels of the Stomach, Spleen, and Pancreas. The lymphatic vessels of the stomach are divided into the superficial and deep. The sxiperficial lymphatics form a network beneath the peritoneum ; the deep lyni phatics arise from an equally complex network situated in the mucous membrane. They follow difl'erent directions : a great number of them pass to the great curvature, and enter the glands situated there ; others proceed to the lesser curvature, and pass through the glands in that situation. Several run towards the spleen, and enter the splenic lymphat- ic glands ; and, lastly, others go to the lymphatic glands around the pylorus. It has been stated that the lymphatics of the stomach have been seen filled with chyle : this is at least doubtful. The Lymphatics of the Spleen. — The superficial lymphatics of this organ cannot be seen unless the splenic bloodvessels have been previously injected with size injection : the size freed from the colouring matter will pass into them. I have seen tallow, thrown into either the arteries or veins of the spleen, pass into the superficial lymphatics. It is true that the injection was made forcibly, and kept up for some time. The deep lym- phatics of the spleen are not known. The proper lymphatics of the pancreas are little known. The Lymphatic System of the Intestines. The Lymphatic Glands of the Intestines. The lymphatic glands of the small intestine, or the mesenteric glands, are extremely nu- merous. Several anatomists, who have had the patience to count them, have arrived at very different results, partly on account of individual varieties, and partly because sev- eral, having chosen tuberculated subjects for the purpose, have mistaken the tubercles for Ijnnphatic glands. The mesenteric glands are situated between the folds of the mesentery, in the meshes of the network formed by the arteries and veins. Those which are nearest to the intestine are found in the intervals observed between the vessels of the mesentery close to the in- testine. Those which are most distant from the intestine are situated near the adherent border of the mesentery, along the trunk of the superior mesenteric artery. The largest of these glands are found near the origin and termination of that artery. Thus we find, below, a group of large lymphatic glands, the ileo-colic, opposite the termination of the il- eum in the colon. Another cluster, named the duodenal, is situated above, in front of the du- odenum : they are extremely large. We generally find one larger than the rest ; it is repre- sented in the oldest works on anatomy, and has been sometimes mistaken for the pancreas. The group of ileo-colic lymphatic glands is remarkable for frequently becoming inflamed in follicular enteritis. The lymphatic glands of the great intestine, or m^so-colic glands, much less numerous than those of the mesentery, generally lie along the vascular arches formed by the colic art(iries and veins : several of them are situated near the posterior border of the intes- THE LYMPHATICS OF THE INTESTINES, ETC. -fHI tine ; and some are even found upon the intestine, accompanying those bloodvessels which run for a short distance beneath the peritoneal coat, and then penetrate the mus- cular coat. The meso-colic lymphatic glands are not nearly so numerous along the transverse colon as along either the ascending or descending colon. Those situated in the transverse meso-colon form an uninterrupted chain with the mesenteric glands. The. Lymphcaic Vessels of the Intestines. The Lymphatics of the Small Intestine.— These vessels are divided into two sets, the lymphatics, properly so called, and the lacteals. The lymphatics, properly so called, like those of the stomach and great intestine, arise from two sets of networks ; one in the serous, the other in the mucous coats. The ves- sels which pass out from these networks have a remarkable character, which was well described by Mascagni ; instead of passing directly into the mesentery, they first proceed for a short distance along the intestine, and then curve and enter the mesenteric glands. The lacteals, or lacteal vessels of the small intestine, can be easily seen in an animal that has been killed while the absorption of chyle is going on in the intestine ; and they have occasionally been observed in the human subject, in cases of accidental death. They then appear as white, nodulated, and slightly flexuous lines, which communicate occa- sionally with each other, pass from one mesenteric gland to another, enter the lymphat- ic glands situated in front of the aorta and vena cava, and terminate in the thoracic duct by a variable number of trunks : the lymphatic plexuses of the left side pass behind the aorta. The lacteals commence, according to Lieberkuhn, upon the summit of each of the villi «)f the small intestines, run down to its base, and then enter at right angles mto the sub- mucous lacteal vessels, which invariably perforate the other coats of the intestine, on its concave border. This arrangement was very evident in a case in which the lacteals were filled with tuberculous matter. — {Anath. Pathol., liv. ii., pi. 2.)* The Lymphatics of the Great Intestine. — We may, with Mascagni, divide these l)Tnphatics into two sets, according to the glands in which they terminate, viz., those of the coecum and of the ascending and transverse colon, which pass through the meso-colic lymphatic glands, and then terminate in the mesenteric glands ; and those of the descending colon and rectum, which enter the lumbar lymphatic glands together with the lymphatics of the genital organs, and of the lower extremities. The Lymphatic System of the Thorax. The Lymphatic Glands of the Thorax. The thoracic lymphatic glands are divided into those of the parietes of the thorax, those of the mediastinum, and the bronchial or pulmonary glands. The lymphatic glands of the parietes of the thorax are very small, and are thus arranged : t>ie intercostal glands are situated on each side of the spine near the costo- vertebral ar- ticulations ; some are placed between the two layers of the intercostal muscles : they are very smaU, and irregular in number. The sub-sternal or mammary glands are found at the anterior extremity of the intercostal spaces near the internal mammary vessels, and applied along the borders of the sternum ; there is one for each intercostal space. The mediastinal lymphatic glands are divided into those of the posterior mediastinum, which are arranged along the cEsophagus and aorta, and form a continuation of the intercostal glands : they have been known to become enlarged and press upon the oesophagus, so as to cause dysphagia ; and into those of the anterior mediastinum, the principal of which lie upon the diaphragm in front of the pericardium, and around the great vessels connected with the base of the heart. The bronchial or pulmonary glands were noticed by the oldest anatomists, and espe- cially by Vesalius, whence the name of glandula Vcsdiance, by which they are still known : they are remarkable for their situation, number, size, and colour. They are situated along the bronchi and their first divisions. The largest are generally placed opposite the bifurcation of the trachea. The smallest lie within the substance of the lungs, around the first divisions of the bronchi ; some of them are seen in the inter-lobular fissures. Their number is very considerable. In disease, they may acquire such a size as to compress and narrow the bronchi, and thus prevent the passage of the air through those tubes. In infancy they do not differ in colour from the other lymphatic glands, but they are black in the adult, and especially in the aged. They are also liable to become the seat of depositions of phosphate of lime. Senac considers them to be secreting glands quite distinct from the lymphatic glands. Portal divided them into true glands and lymphatic glands ; but no one has been able to demonstrate the excretory ducts, which, according to Portal, proceed from the lymphat- ic glands upon the trachea. The communications between these and the trachea, ob- served in some cases of disease, are altogether accidental. * See also note, p. 368. 4K ANGEIOLOGY. - The Lymphatic Vessels of the Thorax, The lymphatic vessels of the thorax are divided into those of the parietes and those of the organs contained in the thoracic cavity. The Lymphatics of the Thoracic Parietes. — We shall here merely notice the deep-seat- ed lymphatics. They are divided into the intercostal, the sub-sternal or internal mam- mary, and the diaphragmatic. The intercostal lymphatics accompany the arteries and veins of that name ; they re- ceive the lymphatic vessels of the intercostal muscles and costal pleura, run along the grooves of the ribs, pass through the intercostal lymphatic glands, reach the sides of the vertebrae, unite with other lymphatics from the back of the thorax and from the spinal canal, enter the lymphatic glands on the sides of the vertebral column, and are for the most part directed downward to terminate in the thoracic duct. The sub-sternal or internal mammary lymphatics arise from the supra-umbilical portion of the anterior walls of the abdomen : they pass into the thorax, behind the ensiform cartilage, and form two bundles, which run upon the sides of the sternum, unite with the anterior intercostal and external mammary lymphatics, and enter the internal mammary lymphatic glands. From the lowest of these glands other lymphatics proceed, and as- cend in succession from one gland to another up to the inferior cervical lymphatic glands ; on the left side they enter the thoracic duct, and on the right, the great lym- phatic trunk. Sometimes, but rarely, the mjimmary lymphatics open directly into the internal jugular and sub-clavian veins. The lymphatics of the diaphragm for the most part unite with the intercostal and he- patic lymphatics ; the others run forward between the pleura and the fleshy fibres of the diaphragm ; some of them enter the inferior mediastinal glands, and the others, the in- ternal mammary lymphatic glands. The Lymphatics of the Thoracic Viscera. — The lymphatics of the lungs are divided into superficial and deep : the superficial lymphatics may be injected in the same manner as those of the liver ; they form an extremely close network beneath the pleura pulmonalis, and frequently present a number of, as it were, varicose enlargements : these were no- ticed and figured by Mascagni ; and the frequency of their occurrence led him to inquire whether such was not the natural structure of lymphatics. Some of the vessels which proceed from this network run in the inter-lobular fissures, and enter the lymphatic glands situated at the bottom of these fissures ; while the others reach the internal surface of the lung, and terminate in the bronchial glands. These superficial lymphatics also communicate with the deep lym^phatics in the cel- lular intervals between the lobules of the lung. The deep lymphatics of the lung are very numerous : the manner in which they com- mence in the lobules is not well known : they run in the inter-lobular cellular tissue, and all proceed towards the root of the lung, in order to terminate in the glands situated around the bronchi, and in several which lie along the oesophagus. It is doubtful wheth- er a single pulmonary lymphatic vessel enters directly into another lymphatic gland without first going through a bronchial gland. Other lymphatics proceed from these bronchial glands ; some of which pass in front of the trachea to enter the tracheal lymphatic glands, while the others proceed to the lymphatic glands upon the oesophagus. On the left side both sets enter the thoracic duct, at a short distance before its termination ; these are more numerous than those on the right side, which enter the right lymphatic duct. Some of them terminate in the thoracic duct, before it emerges from the thorax ; severeil of these vessels are sdso seen to enter the internal jugular and sub-clavian veins. I should observe that, in consequence of the above-mentioned anatomical fact, the cervical lymphatic glands sometimes become enlarged in diseases of the lungs. The Lymphatics of the Heart, Pericardium, and Thymus. — The lymphatics of the heart are divided into superficial and deep ; the superficial vessels commence by a sub-serous network, and, for the most part, run along the right border of that organ ; the deep lym- phatics arise from the internal membrane of the heart, in which I have never been able to inject a perfect network : they all accompany the coronary vessels, and all pass out of the pericardium ; some of them unite with the lymphatics of the lung ; the others en- ter the glands in front of the arch of the aorta and puhnonary artery, and from thence pass to the thoracic duct. The lymphatics of the pericardium and thymus enter the internal mammary, anterior mediastinal, and bronchial lymphatic glands. The Lymphatic System of the Head. The Lymphatic Glands of the Head. There are more lymphatic glands in the face than in the cranium. All the lymphatic glands of the cranium are found upon its posterior region : some of ■"them are situated behind the ear, along the attachments of the occipito-frontalis ; several .are placed beneath the upper end of the sterno-mastoid ; they are very small, and often THt; I.YvIPHATICS OF THE HEAD, ETC. 627 escape notice in a hasty dissection : they become veiy distinct in diseases of the scalp. Are there any deep lymphatics of the cranium ? The pituitary body, the pineal gland, and the white bodies known as the glandulae Pacchioni, have been regarded as belong- ing to the lymphatic system. Some authors have even considered the tubercles, so frequently found in the brains of infants, and which are evidently accidental formations, to be of the same nature. Certain bodies found in the carotid canal, and which are evidently enlargements of the ganglionic nerves, have also been described as lymphatic glands ; but this opinion is now completely rejected. Of the lymphatic glands of the face, the largest occupy the base of the lower jaw, and are called the sub-maxillary l5Tnphatic glands : several of them are situated upon the outer surface of the maxillary bone, along the facial vessels, in front of the masseter muscle. We find, also, in the face, the parotid lymphatic glands, some of which are superficial and others deep, the latter being situated in the substance of the gland : we find some, also, between this gland and the masseter : lastly, there are the zygomatic glands, situ- ated imder the zygoma, and the buccinator lymphatic glands. TJie Lymphatic Vessels of the Head. These belong either to the cranium or to the face. The Lymphatics of the Cranium. — The superficial or sub-cutaneous cranial lymphatics are divided into two sets : the temporal lymphatics, which run along the superficial tem- poral artery, and pass through the parotid lymphatic glands, from which vessels proceed to the glands in the anterior region of the neck ; and the occipital lymphatics, which fol- low the occipital artery, and terminate in the mastoid and the occipital lymphatic glands. The deep lymphatics of the cranium, the lymphatics of the dura mater, or the meningeal lymphatics, accompany the meningeal vessels, escape through the foramen spinale of the sphenoid bone, and enter the jugular lymphatic glands. Ruysch appears to have been the first who noticed lymphatics in the brain ; he has named them vasa pseudo-lymphatica. Mascagni could only show the presence of the su- perficial lymphatics of the brain by injecting coloured size into the carotid arteries. The size freed from the colouring material passed into the lymphatics. The lymphatics of the brain are but little known. M. Fohmann has described and figured a lymphatic plexus situated between the arachnoid and pia mater, and precisely resembling those found in other parts of the body. This network dips into the sulci, and appears to be continued into the substance of the brain, where it is no longer possi- ble to follow it. From this network some small lymphatic trunks proceed, and accom- pany the arteries and veins as far as the foramina, in the base of the cranium, beyond which M. Fohmann was never able to trace them ; so that he inquires whether these vessels do not form an exception to the general rule from their want of connexion with the absorbent system generally, and whether they do not enter directly with the veins upon which they are- placed. On the other hand, Mascagni has figured some lymphatics around the internal carotid, within the carotid canal, and also around the vertebral ar- teries and internal jugular vein. The existence of these trunks leads us to suppose that there must be cerebral lymphatics. M. Fohmann has also found lymphatics in the choroid plexuses of the lateral ventri- cles of the brain : these vessels were remarkably dilated, so as to present ampullae. The Lymphatic Vessels of the Face. — These are divided into the superficial and deep. The superficial lymphatics are much more numerous than those of the cranium. They commence upon all parts of the face ; those from the frontal region accompany the frontal vessels : the others accompany the adjacent bloodvessels ; several of them pass through the buccinator glands, and they all finally enter the sub-maxillary lymphatic glands. The lymphatics of the face are to be injected by introducing the pipe into the plexus contained in the skin. The deep lymphatics of the face accompany the bloodvessels. They are divided into those of the temporal fossae, those of the zygomatic and pterygo-maxillary fossae, and those of the nasal fossae. The lymphatics of the pharynx, velum palati, mouth, tongue, and larynx, enter the deep parotid and the cervical lymphatic glands. The lymphatic plexuses of the pituitary membrane, and of the lingual, buccal, and pharyngeal mucous membranes, may be perfectly injected. Indeed, it is only in that way that we can demonstrate the lymphatic vessels which emerge from these diflTerent parts The Lymphatic System of the Cervical Regions. The Cervical Lymphatic Glands. The lymphatic glands of the neck are concentrated in the anterior region of the neck. They are divided into the superficial and deep. The superficial lymphatic glands of the neck are found principally along the external jugular vein ; they are therefore situated between the platysma and the stemo-mastoid ; and in the supra-clavicular triangle, that is to say, in the triangulfr interval between the 6!^ ANGEIOLOGY. «>- clavicle, the sterno-mastoid, and the trapezius. We also find several very small supei- ficial glands between the os hyoides and the thyroid cartilage, and upon the sides of the larynx. The deep lymphatic glands of the neck are very numerous, and form an uninterrupted chain around the internal jugular vein and the carotid artery, from the mastoid process to the superior opening of the thorax, in front of the vertebral column, and upon the sides of the pharynx and oesophagus. The tracheal lymphatic glands are also continuous with the deep cervical glands. The cervical glands form a continued series with the facial and sub-maxillary lym- phatic glands on the one hand, and with the lymphatic glands of the thorax and axilla on the other. The Cervical Lymphatic Vessels. The cervical lymphatics consist of those which have passed through the sub-maxillary and facial lymphatic glands, and which afterward traverse the chain of glands along the jugular veins. They are joined by those of the pharynx, oesophagus, larynx, trachea, and thyroid gland. They then proceed from one lymphatic gland to another, and from one plexus to another, down to the lower part of the neck, where they are joined by some lymphatics from the lung, which also pass through some of the cervical glands : they terminate on the left side in the thoracic duct, and on the right side in the right lymphatic duct. The Lymphatic System of the Upper Extremity. The Lymphatic Glands of the Upper Extremity and of the Upper Part of the Trunk. There are generally no lymphatic glands in the hand or forearm, but Meckel found several very small ones along the ulnar and radial bloodvessels. There are two or three which are sub-cutaneous in the front of the bend of the elbow, and one or two above the internal condyle of the humerus, behind the basilic vein ; in the arm we also find a se ries of small lymphatic glands, which are never numerous, along the inner side of the humeral artery. The axillary lymphatic glands are situated deeply in the axilla, and are very numerous , some lie along the great vessels, others are scattered through the axilla : they are often of a very large size. The following may be regarded as appendages of the axillary glands : a small sub-cla- vicular gland, situated deeply beneath the costo-coracoid membrane, opposite the trian- gular interval between the pectoralis major and the deltoid, and two or three small glands situated along the attachments of the pectoralis major, as far as the mammary gland. Mascagni has figured a small lymphatic gland near the umbilicus. The Lymphatic Vessels of the Upper Extremity and of the Upper Half of the Trunk. The Lymphatics of the Upper Extremity. — The superficial set of these vessels arise from the skin of the hand, and run parallel to the fingers : they are, for the most part, sit- uated upon the back of the hand ; they cross obliquely over the metacarpal bones, pass over the carpus, and thus reach the forearm. In the /orcarm they are distributed almost equally upon its anterior and posterior aspects. The anterior lymphatics are collected upon the inner and outer sides of the forearm ; having reached the elbow, some pass in front of the epitrochlea and its muscles ; others in front of the epicondyle. In this place they are re-enforced by the lymphatics from the posterior aspect of the forearm, which are also collected into an outer and innei' group. Not unfrequently a certain number of the posterior lymphatics, which arise from the outer side of the hand and forearm, after ascending almost vertically for some dis- tance, pass obliquely, or cross transversely inward, above and below the olecranon, and unite with the inner group. In the arm some of the inner group of lymphatics pass to the lymphatic glands above the epitrochlea ; the others run along the inner border of the biceps muscle and basilic vein, and then pass backward and upward to reach the axillary glands. The external lymphatics cross very obliquely over the anterior aspect of the arm, to terminate, like the preceding, in the axillary glands. One of them has a remarkable course ; it runs along the cephalic vein, gains the cellular interval between the pectoral- is major and the deltoid, dips down over the upper edge of the pectorahs minor and be- low the costo-coracoid membrane, and describes a curve so as to enter the sub-clavicu- lar lymphatic ganglion. The deep lymphatics of the upper extremity exactly follow the course of the bloodves- sels ; they often communicate with the superficial lymphatics, and terminate in the ax- illary glands. I have seen some of the deep lymphatics of the forearm communicate at the bend of the elbow with the superficial lymphatics on the outer part of the back of the arm, and enter the glands above the epitrochlea. THE SKIN. 010111^ The Lymphatic Vessels of the Upper Half of the Trunk. — We have seen that all the lym- phatics of the sub-umbilical portion of the trunk enter the inguinal glands ; and so all the lymphatic vessels of the supra-umbilical portion terminate in the axilla. The anterior and lateral lymphatics pass upward upon the pectoralis major and the ser- ratus magnus, to gain the axilla. The posterior lymphatics are divided into those of the neck and those of the back ; the posterior cervical lymphatics descend upon the trapezius and the deltoid, and are reflected over the posterior border of the leist-named muscle, in order to reach the cavity of the axilla ; the posterior dorsal lymphatics run in different directions ; some horizontally, the others from below upward, to be reflected into the axilla below the tendons of the la- tissimus dorsi and teres major. NEUROLOGY. Neuroloot is that part of anatomy which treats of the apparatus of sensation and in- nervation : this apparatus consists of the organs of the senses, of the cerebrospinal axis, or central portion of the nervous system, and of the nerves, or peripheral portion of that system. THE ORGANS OF THE SENSES. The Skin — its External Characters, Structure, and Appendages. — The Tongue considered as the Organ of Taste. — The Organ of Smell — the Nose — the Pituitary Membrane. — The Or- gan of Sight — the Eyebrows — the Eyelids — the Muscles of the Orbit — the Lachrymal Ap- paratus — the Globe of the Eye, its Membranes and Humours — the Vessels and Nerves of the Eye. — The Organ of Hearing — the External Ear — the Middle Ear or Tympanum — the Internal Ear or Labyrinth — the Nerves and Vessels of the Ear. The organs of the senses are certain parts of our bodies which are intended, by means or surface of the tongue. t It has already been stated that the perforated eminences found at the base of the tongue are not papillae, but glands ; and the true papillae have been divided into the large or cahciform papillae, which are arranged in the shape of the lettov V at the base of the tongue, and the small papillae ; which may be again subdivided iiiro the conical, the filiform, and the lenticular or fungiform, according to their respect- iv shapes. i>ery special sense, by which term is understood ail such as receive sensations dif- ftrent from that of touch, properly so called, presents for our consideration a special ap- *■ rThe root of some hairs is larger than the shaft, and is named the bulb ; this, however, does not depend (.u thu hair being covered by the epidermis, a thin layer of which (d d,fig. 230) lines the follicles, and is be- liiivdd to terminate at the root of the hair. Into each hair-foUicle one or more sebaceous glands (i i,fig' 227) ;i.n;r tlieir secretion.] t Lllairs, like the nails, consist, according to recent researches, of nucleated corpuscles, which differ in U.xm, density, and arrangement, in different parts of the hair. At the root, upon the surface of the papilla, »h: re they are first developed, they are soft and vesicular ; in the central medullary part of the shaft they are b:inkr, compressed, and polyhedral ; in the cortical part they form an immense number of very long and fine liiirrs, and, on the outside of these, a layer of short, hard scales. The hairs consist principally of keratin and an oily matter ; besides which, they yield sulphur, phosphorus, iron, salts of lime, and traces of manganese, silica, and magnesia.] X [The mucous membrane on the under surface of the tongue, and that covering the buccal surface of the soft palate and the immediately adjacent parts of the fauces, also possess the sense of taste.] 649 NEUROLOGY. paratus, on which the impressions act, and a special nerve or nerves, adapted to receive those impressions and transmit them to the brain. The nmscular structure of the tongue, which at first sight appears to be useful only in mastication, deglutition, and the articulation of sounds, is intimately connected with the sense of taste, which would have been exceedingly imperfect, had not the gustatory membrane been capable of being moved over the bodies to be tasted. The gustatory apparatus of the tongue consists, then, of a papillary membrane stretched over a muscu- lar surface, and united so closely to it that it is impossible to separate one from the oth- er. Moreover, this membrane is constantly kept in a state of humidity, and occupies the first cavity presented by the digestive apparatus. The Gustatory Papillary Membrane. — All the elements of the skin are found in the gus- tatory membrane. The chorion is as dense as the densest part of the chorion of the skin : a very great number of muscular fibres are inserted into it, so that the gustatory membrane can be moved not only as a whole, but each part of it has its own separate movements. The papilla, by which the surface of the tongue is rendered so rough, may be said to represent the papillary body of the skin in a very highly-developed state.* The lingual papilla are supplied with nerves, which can be more easily shown than those in the cutaneous papillee. Haller has traced them into the papilla; ; and I have suc- ceeded in doing the same, but without being able to ascertain their mode of termination. The papillae also receive bloodvessels, which are so abundant that, in successful injec- tions, the papillary body appears to be altogether vascular. The Lymphatic Network. — By making a superficial puncture into any part of the mem- brane which covers the dorsum or the borders of the tongue, we may inject a lymphatic network upon it, precisely similar to that found in the skin. The mucous body, or rete mucosum, does not exist as a distinct membrane upon the tongue any more than in the skin. I have already stated that it was while examining the boiled tongue of the ox that Malpighi discovered a glutinous stratum situated be- tween the epidermis and the papillae, and perforated by a number of openings, corre- sponding to that of the papillae themselves ; hence the name of reticulum which he gave it ;t but it is as impossible to demonstrate it upon the tongue as in the skin. The Pigmentum. — There is never any black colouring matter in the tongue of the hu- man subject ; but it is distinct upon the tongue of some animals, as the ox, and can be easily demonstrated between the papillae and the epithelium.t The Epithelium. — Each papilla is covered with a sort of epidermic sheath, which, ac- cording to Haller, was discovered by Mery and Cowper, and which has been perfectly described by Albinus under the name of the periglottis. This epidermis, or epithelium, so easy of demonstration in the lower animals, in which it has the consistence of horn, may be also readily shown in the human subject, although, in accordance with the great- er perfection of the sense of taste in man, the epithelium is comparatively thin. If the upper surface of the tongue be examined with a lens, especially after maceration, the lingual epithelium will be seen to be arranged in precisely the same manner as the epi- dermis of the skin, and to form a protecting sheath for each papilla. In persons who have sunk after long abstinence, the epithelial covering forms several imbricated layers, which can be rubbed off; the fur which adheres to the tongue is in a great measure formed by this debris of the epithelium somewhat dried. The epithelium of the tongue can be removed by friction ; and, in certain inflammatory diseases, the tongue is denuded of it. When one of the lingual papillae is thus exposed, it becomes excessively painful. The Nerves of the Tongue. — No other organ, perhaps, of equal size, receives so many nerves as the tongue : one pair, the ninth or hypoglossal, is exclusively appropriated to it ; and it also receives, on each side, the glosso-pharyngeal branch of the eighth, and the lingual branch of the fifth of the cerebral nerves. Which of these nerves must be regarded as the nerve of taste in the tongue 1 Evidently the one that is distributed to the papillae. On this account, since the time of Galen, the lingual branch of the fifth pair, or the lingual nerve, as it is called, has been regarded as the gustatory nerve ; though it would seem more natural to admit, with Boerhaave, that the hypoglossal nerve, which is distributed exclusively to the tongue, should, as it were, preside over the spe- cial sense situated in this organ. But the lingual nerve is found to enter the tongue at its corresponding border, and to spread out into branches which pass vertically upward, and are exclusively distributed to the papillary membrane of the anterior, or free portion of the tongue. The ninth or hypoglossal nerve of each side runs from behind forward, between the ge- nio-glossus and stylo-glossus muscles, and communicates with the lingual nerve, so as to form the lingual plexus. It is not certain that some of the filaments of the hypoglos- * If the epidennic tubes, which are so remarkably distinct on the foot of the bear, be removed from the pa- pillae, the latter, when exposed, exactly resemble those of the tongue.] t " Hanc fabricam a Malpighio inventam, et a Bellino libenter acceptam, scriptores anatomicorum, et phys- iologicorum operum iconibus etiam pictis expresserunt." — {Haller, t. v., lib. xiii., p. 107.) t [The pigment in these cases, and the lingual rete mucosum also, are the lowermost layers of the ectra vascular squamous epithelium.] THE NOSE» 641 sal nerve do not reach the papillae ; but there is no doubt but that almost all of them are lost in the intrinsic muscles of the tongue. The right and left glosso-pharyngeal nerves supply the base of the tongue, and are ex- clusively distributed to the mucous membrane covering that part. No filament of the glosso-pharyngeal nerve is intended for the muscular fibres ; and it is a remarkable fact, that in one case in which the facial nerve sent a branch to the tongue supplementary to the glosso-pharyngejd, that branch was distributed precisely in the same manner as the glosso-pharyngeal itself; that is, it was exclusively distributed to the mucous membrane at the base of the tongue. From what is stated above, then, it is anatomically shown that the lingual branch of the fifth nerve and the glosso-pharyngeal nerve are the specijil nerves of the tongue.* The following case is no less demonstrative of the same fact ; Anf individual had com- plete paralysis of the right half of the tongue. That side of the tongue became atrophied, and had scarcely one third of its natural thickness. Both its tactile and gustative sen- sibiUty were equally acute on the two sides of the organ. After the death of the person thus afflicted, an acephalo-cyst was found in the right posterior condyloid foramen, which had caused a complete atrophy of the right hypoglossal nerve. The corresponding half of the tongue had undergone the fatty degeneration. The Organ of Smell. The organ of smell is situated in a cavity formed within the bones of the face, as, in- deed, are most of the other senses ; it is placed at the entrance of the respiratory pas- sages, and above the organ of taste, with which it has many points of relation. Although situated in the median line, it is a double organ. It consists of an external apparatus, which serves to protect the organ, to keep it in the necessary state of moisture for the proper exercise of its functions, and to direct the air towards that part of it which is en- dowed with the greatest olfactory sensibility : this is the nose, properly so called. And, secondly, of two complicated and winding cavities, the nasal fossa, lined by a mucous membrane, cedled the pituitary membrane, which is the essential seat of the sense of smell. The J^ose. The nose resembles in form a three-sided pyramid, directed vertically, and projecting from the middle of the face, so that the olfactory organ is the most anterior of all the or- gans of the special senses. Its numerous varieties in shape and size fall under the consideration of painters rather than anatomists ; for these varieties have greater effect upon the physiognomy than upon the exercise of its functions. On each side of the nose, at its lower part, is observed a semicircular furrow, having its concavity directed downward, and forming the upper border of the alse nasi ; from this furrow, on either side, the naso-labial furrow of the semeiologists commences. The lateral surfaces of the nose form, by their union, the dorsum, which is either straight, convex, or concave, according to the subject ; differences which, in a great measure, determine the national or individual forms of this part of the face. The term lobe of the nose is applied to the rounded eminence in which the dorsum nasi terminates below. The summit, or root of the nose, is separated from the nasal protuberance by a trans- verse furrow. The base of the nose presents two elliptical or semilunar orifices, called the nostrils (jiares) : the long diameters of these two orifices are directed horizontally backward and outward, and they are separated from each other by an antero-posterior septum ; they are provided with stiff" hairs, or vibrissce, which serve to arrest any small particles floating in the air.t The direction of the nostrils is a proof that the erect position is natural to man ; for, if he were to assume the attitude of a quadruped, only the dorsum of the nose would be directed towards odoriferous bodies. The situation of the nostrils above the orifice of the mouth explains how no ^llimentary substance can be introduced into that cavity without having been previously examined by the sense of smell. The nose consists of a skeleton or basis, and of certain muscles ; it is covered by the skin externally, and by a mucous membrane internally ; and it receives both vessels and nerves. The Structure of the Nose. The basis or framework of the nose is composed of bone, cartilage, and fibrous tissue. * [The result of the vast number of experiments and observations made upon this subject, by persons of op- posite opinions, would appear to be, that the lingual nerve (a branch of the fifth), and the lingual portion of the glosso-pharyngeal nerves, are both of them gustatory nerves, and also nerves of ordinary sensibility to the tongue. The portion of the palate and fauces endowed with the sense of taste derives its power from the pal- atine nerves, which are given off from a gangUon (Meckel's) connected with the second division of the fifth nerve.] t This use of the vibrissse becomes very evident in serious diseases ; when, in consequence of the humed respiration, dry particles floating in the air become attached like a fine powder to these hairs. The coUectioo of particles of dust around the nostrils often warns the practitioner of the serious nature of a disease 4M 642 NEUROLOGY. The osseous portion occupies the upper part of the organ, and consists of the proper nasal bones, and of the ciscending processes of the superior maxillary bones. The cartilaginous part consists of the two lateral cartilages of the nose, to which we may add the cartilage of the septum, although it rather forms part of the nasal fossae than of the nose properly so called ; and, secondly, of the two alar cartilages, or cartilages of the nostrils, making five in all. To this we must add certain cartilaginous nod^iles, situated between the lower part of the cartilages of the alae and that of the septum. Santorini described eleven cartilages in the nose, doubtless because he reckoned certain cartila- ginous nodules, which are sometimes accidentally developed in the substance of the fibrous tissue.* The fibrous portion of the nose consists of a fibrous layer, which occupies the interval between the lateral 'cartilages of the nose and the cartilages of the alae. From this structure, it follows that the nose is inflexible above, flexible in the middle, and extremely movable below. This arrangement has the threefold advantage of pro- viding against fractures of the most prominent part of the nose, of permitting the dilata- tion of the nostrils, and, lastly, in consequence of the solidity of the highest and narrow- est part of the n2isal fossae, of ensuring a free passage to the air. The lateral cartilages of the nose (a a, fig. 231) are of a triangular form ; and they are Fig. 231. united together along their anterior margins, which are thick above, so as to form a sharp ridge, which constitutes the dorsum of the nose. Along the line of union there is a sort of furrow or groove, which can be felt even through the skin. By their upper and posterior margins, they are articulated with the nasal bones ; I say articulated, because there is no continuity of substance, but the parts are connected by fibrous tissue, which allows a considerable degree of motion. Their lower margins are convex, and correspond in front to the cartilages of the alae of the nose, and behind to the fibrous tissue which occupies the intervals between the cartilages. The lateral cartilages are intimately united with the cartilage of the septum, along the dorsum of the nose ; so that we might regard these three pieces as forming a single cartilage. The thickest part of each lateral cartilage is above and in front. The cartilages of the nostrils are generally called, after Bichat, the filro-cartilages of the alcR of the nose ; but we have already seen that some of the fibro-cartilages of Bichat are thin layers of ordinary cartilage, while others consist merely of condensed fibrous tissue. The so-called fibro-cartilages of the nostrils belong to the former kind. There is but a single cartilage on each side {b b,fig. 231) for the ala nasi, the lobe, and the in- ferior portion of the septum ; it consists of an irregular lamina folded upon itself into a semi-ellipse or parabola, opening behind. We shall examine its external and internal portions. The external portion (b) is extremely thin, and corresponds to the ala of the nose ; it is not situated in the substance of the ala, but is placed above it, so that its lower margin corresponds to the curved furrow which forms the upper boundary of the ala.t The internal portion (b,fig. 232) is thicker than the external, and is situated upon a lower plane than it : it corresponds, on the inside, to the internal portion of the cartilage of the opposite side, from which it is separated above by the cartilage of the septum. The internal portions of the two alar cartilages are separated from each other by some rather loose cellular tissue, which allows them to move upon each other, and also per- mits the cartilage of the septum to extend between them, without interfering with them at all. The internal portions of the cartilages of the alae do not reach the anterior nasal spine, but terminate abruptly at a certain distance from it, by forming a projection, which is very distinct, especially in some individuals, and which sensibly elevates the mucous membrane at the entrance of the nostrils. At the point of union between the internal and external portions of each alar cartilage, that is to say, at the summit of the parabola, the cartilage itself becomes wider and excavated behind, and assists in forming the lobe of the nose. The margins of these cartilages are irregularly notched or scolloped. The upper margins are united to the other cartilages by means of a fibrous tissue, which al- lows them to move frgely, both upon the cartilage of the septum and upon the lateral cartilages of the nose. A small cartilaginous nodule is found on either side, between the lobe of the nose and the cartilage of the septum ; the only use of these nodules is to facilitate the movements of the lobe upon the septum. The cartilage of the septum nasi (c,fig. 232) occupies the triangular interval between the perpendicular plate of the ethmoid bone and the vomer. It consists of two parts : one, wide and free, which is that generally described ; the other, which is narrow, and may be called the caudal prolongation of the cartilage, is received into the bony portion • of the septum, between the two lamellae of the vomer * See note, infra. t [Two or three cartilaginous nodules (e e,fig. 231) are generally found appended in a curved line to the posterior extremity of this portion of the cartilage of the ala.l THE PITUITARY MEMBRANE. 643 The fret portion of the cartilage is thick and triangular ; it has the same direction as the bony septum, and presents two lateral surfaces, covered by the pituitary membrane ; an anterior margin, of which the upper half (c, fg. 231) is blended with the lateral cartilages along the dorsum of the nose, while its lower half is free, convex, directed downward, and received between the two cartilages of the nostrils ; a superior and posterir margin, which is extremely thick and rough, and is intimately united to the corre- sponding margin of the perpendicular plate of the ethmoid bone (e, Jig. 232) : the mode in which this union is effected is not by articulation, but by a continuity of tissue, like that between the costal cartilages and the ribs ; lastly, an inferior margin, which is received between the two plates of the vomer (»). The groove into which it is received is very deep ; and as the two plates of the vomer become more and more separated in extending forward, so does the corre- sponding margin of the cartileige increase in thickness ; hence the lower extremity of the septum frequently projects considerably into one or other of the nostrils. The caudal prolongation of the cartilage of the septum may be seen by carefully exani ining the retreating angle formed by the perpendicular plate of the ethmoid and the vo- mer ; in which situation the cartilage of the septum gives off a considerable prolonga- tion, in the form of a band, which occupies the interval between the two plates of the vomer, and is attached to the rostrum of the sphenoid bone. This cartilaginous band is contained entirely within the substance of the middle portion of the bony septum : its upper margin is thin, and, as it were, toothed ; the lower margin is thick and rounded. The two naso-palatine nerves are situated in the same canal as the cartilage, and are placed one on each side of it. The muscles of the nose are the pyTamid2ilis nasi, the levator labii superioris alaeque nasi, and the transversalis nasi, or compressor narium, which we have described as a dependance of the depressor alae nasi, or rayrtiformis : an accurate description of these muscles is still to be desired. The skin covering the nasal bones and the lateral cartilages of the nose has no par- ticular character : it is thin and movable. That which covers the alae and the lobe of the nose is very thick and extremely dense ; it crepitates under the knife, to such a de- gree, that cartilages have been supposed to exist in the substance of the alae. We have seen, however, that the cartilages of the nostrils are not prolonged into the alae, which are composed essentially of the dense integument just described, and which is reflected inward upon itself around the margins of the nostrils. I should remark, that the antero-posterior diameter of the opening of each nostril is much less than that of the corresponding cartilage ; this depends upon the fact that the skin is prolonged anteriorly, and is reflected for some lines below and behind the lower margin of the cartilage. The skin of the nose is remarkable for the great development of its sebaceous follicles. The orifices of these follicles are shown in many individuals by certain black points, which are nothing more than the sebaceous matter discoloured. When forced out of the follicles by lateral pressure, the masses of sebaceous matter resemble in form small worms. The skin, which is reflected upon itself around the margins of the nostrils, preserves the character of integument as far as where it is provided with hairs, and then suddenly assumes the characters of mucous membranes. The Pituitary Membrane. The pituitary or Schneiderian* membrane, the immediate seat of smell, is a fibro-mucous membrane, which lines the whole extent of the nasal fossae, and is prolonged, with some modifications of texture, into the different cells and sinuses which open into those fossae. When covered with this membrane, the nasal fossae present a configuration differing in many respects from that which they have in the skeleton. Many of the foramina and canals are closed, and several are contracted in their dimensions. The irregularities of the surface of the turbinated bones are, in some measure, concealed. Besides this, the mucous membrane, where it is reflected upon itself, forms a number of folds, some of which prolong the turns of the turbinated bones ; while others, more or less, contract the orifices of communication between the various cells and sinuses and the nasal fossae. The pituitary membrane, originating, then, on the one hand, from the skin, which is reflected at the margins of the nares, and provided with hairs {h,Jig. 233), is, on the other hand, continuous, without any line of demarcation, with the mucous membranes of the pharynx and velum palati (at t s), of the Eustachian tubes (at m), and of the nasal ducts (at r). In the roof of each nasal fossa {u v) it closes the foramina of the cribriform plate * Conrad Victor Schneider (de Caiarrho) gave his name to this membrane, because he was the first to refute •nccessfuUy the erroneous notion of the ancients, that the secretion of the nasal fossae descended from llie ven tricles of the brain ; the common term cold in the head still remains as a vestig-e of this error 644 NEUROLOGY. Fig. 233. of the ethmoid bone, and those of the nasal bones, so that all the vessels and nerves which pass through these foramina enter the mucous membrane by its external surface ; before it enters into the sphenoidal sinus, it forms a fold around the orifice of that sinus, by which the opening is narrowed, so as to have the form of a vertical fissure (see the bristle marked d). Upon the external wall of each nasal fossa (see Jig. 233)* it covers a great number of parts, counting from below upward, viz., the inferior meatus, at the upper and anterior part of which it meets with the lower orifice of the nasal duct {r,figs. 233, 234) ; around this opening it forms a semilunar valvular fold, the free margin of which is directed down- ward, and which prolongs the canal of the ducts to a greater or less distance in differ- ent subjects ; in passing a probe into the na- sal duct from the inferior meatus, this valve must, almost of necessity, be torn. From the inferior meatus the pituitary ttiembrane is reflected upon the inferior tux' hinated bone (c c,figs. 233, 234), which appears longer in the recent state, in consequence of a fold of the mucous membrane being con- tkiued in front, and another still more marked behind the bone : this is the thickest part of the nasal mucous membrane. In the middle meatus (t) the pituitary membrane covers the infundibulum, at tlie lower extremity of which is an ampulla or dilatation, where the orifice of the maxillary sinus is generally found. This orifice (see bristle a, fig. 234) has a very different appearance from that which it presents in the dried scull : it is extremely narrow, scarcely admit- ting the blunt end of a common probe. It sometimes appears as if it were wanting ; but it will then be found opposite the middle of the infundibulum ; in this case, the max- illary sinus might be said to communicate directly with the frontal sinus. Not unfre- quently the maxillary sinus opens both into the middle meatus and the infundibulum The pituitary membrane is prolonged from the infundibulum into the anterior ethmoidal cells (c e, fig. 234), and into the frontal and maxillary (m m) sinuses. If we remove the middle turbinated bone, we find a considerable projection, which bounds the infundibu- lum above (n, fig. 233), and corresponds to a large ethmoidal cell. Upon, the back part of this projection, on which the middle turbinated bone is moulded, an opening (see bris- tle) is often found leading into this great cell, and on its fore part (at e), one or more or- ifices leading into the anterior and superior ethmoidal cells. From the middle turbinated bone {b, figs. 233, 234), which is continued backward hy a fold of the membrane, the pituitary membrane passes into the superior meatus, where I have fre- quently met with four or five openings leading into as many of the posterior ethmoidal cells, which, in this case, did not communicate with each other : I have even seen the orifice of an ethmoidal cell upon the superior turbinated bone (a). The pituitary membrane dips into all the etlimoid- al cells, and into the frontal sinuses, either directly or indirectly, but it does not enter the spheno-pala- tine foramen, which, on the contrary, is completely closed by it. Upon the septum the pituitary membrane is remark- able for its thickness, being exceeded in this respect only by the membrane covering the inferior turbinated bone. We do not find in man that prolongation or cul-de-sac, which is so very distinct in some animals, in front of the lower border of the septum ; but at this point the pituitary membrane closes the two superior orifices of the anterior palatine canal. Structure. — The pituitary membrane is a mucous membrane, and its peculiarity con- sists in its being extended over osseous and cartilaginous surfaces. Its free surface is smooth, red, and scattered over with foramina, from which a great quantity of mucus maybe expressed. + Its adherent surface is intimately united to the periosteum and perichondrium of the bones and cartilages of the nasal fossee, so that it is classed among the fibro-mucous membranes. * [In this figure, portions of the middle and inferior conchse are represented as cut away, to show the parts m the middle and inferior meatuses.] t [In the nasal fossa; the epithelium of the pituitary membrane is columnar and ciliated ; in the sinuses it approaches the squamous in character, but yet it is provided with cilia, the movements of which have been obserTed in the lower animals to produce currents towards the openings of the respective sinuses.] Fig. 234. THE ORGANS OF SIGHT. 645 The pituitary membrane is generally thicker than the other mucous membranes, so that it is very easy to determine the highly vascular and truly erectile structure of this membrane. If it be punctured, and the tube of a mercurial injecting apparatus intro- duced, the mercury w^ill immediately enter the cells of the erectile tissue, and from thence pass into the veins arising from those cells. If a more superficial puncture be made, a lymphatic network will be injected, situated so superficially, that the mercury exhibits all its metallic lustre. This lymphatic network has no communication with the venous cells just mentioned.* This lymphatic network, which is common to all the mucous membranes, gives to the non-vascular layer by which they are covered the appearance of a serous membrane. The pituitary membrane receives a great number of arteries, which penetrate it by sev- eral points, and which are almost all derived from the same source, viz., the internal maxillary artery ; as, for example, the spheno-palatine, the infra-orbital, the superior al- veolar, the palatine, and the pterygo-palatine. Some arise from the ophthalmic arterj', viz., the supra-orbital and the ethmoidal ; and others from the facial artery, viz., the dor- salis nasi, the artery of the alae, and the artery of the septum. The capillary veins are so numerous, that they in a great measure form the basis of the pituitary membrane ; the larger veins which proceed from them follow the course of the arteries, and enter, by very large trunks, into the internal maxillary, the facial, and the ophthalmic veins. There are numerous communications between these last-named veins and those of the ethmoidal region of the base of the cranium. The spongy character of the internal surface of the nasal fossae, and more particularly of the surface of the turbinated bones, is due to certain grooves and foramina intended for the reception and transmission of bloodvessels. I am only acquainted with the superficial lymphatic network already noticed. In order to inject it, it is necessary to scratch the membrane with the injecting pipe. Are there any glands or follicles in the pituitary membrane 1 Steno has described cer- tain glands which I have not been able to find. The follicles in this membrane are rather difficult to be shown. Like all the organs of the special senses, the pituitary membrane is provided vdth a special nerve, called the olfactory, the nerves of the two sides constituting the first pair of cerebral nerves. Comparative anatomy shows that the development of the olfactory nerves is in relation with the development of the sense of smell, and thus establishes, in a most positive manner, the generally-received opinion regarding the function of this pair of nerves. Without entering here into the description of the olfactory nerves, which will be given hereafter, I would observe, that they pass through the foramina and canals of the cribriform plate of the ethmoid bone, at the same time becoming enveloped in fibrous sheaths ; that they enter the pituitary membrane by its external surface ; and that they expand into a plexus in its substance. The branches of these nerves cannot be traced lovi-er than the middle turbinated bones on the one hand, and the middle of the septum on the other. Thus, while the upper and extremely narrow part of each nasal fossa {s,fig. 234) is the essential seat of the sense of smell, the lower and much wider part only gives passage to the air during the act of respiration. Besides the special nerve of smell, the pituitary membrane receives other nervous fil- aments, all of which are derived from branches of the fifth nerve, viz., from the internal nasal and the frontal branches of the ophthalmic division of that nerve, and from the spheno-palatine, the great palatine, the vidian, and the anterior dental branches of its second or superior maxillary division. The experiments of modern physiologists have shown that the integrity of these different branches of the fifth pair is necessary for the perfect possession of the olfactory sense. This, however, is very different from saying that the seat of that sense is in the branches of the fifth pair. The membrane which lines the several sinuses, although it is continuous with the pi- tuitary membrane, does not resemble it in character ; it is exceedingly thin and trans- parent, and appears like a serous rather than a mucous membrane ; that it is a mucous membrane, is satisfactorily established only by certain pathological f3,cts. The mucous membrane of the sinuses has a very close resemblance to the conjunctiva.t The Organs of Sight. . The eyes, or the organs of sight, are situated at the highest part of the face, so that they are enabled to explore objects at a distance. They are two in number ; but they co-operate in their function so as to act like a sin- gle organ. The result of this is, that vision is rendered more certain, and its field of operation more extensive, at the same time that, from the unity of action of both eyes, it is single. The eyes are protected by the orbital cavities in which they are contained ; they are covered by the eyelids, and these are surmounted by the eyebrows. They are surround- ed by six muscles, by which they can be moved in all directions ; they are divided into * It was in the pituitary membrane of the calf that, about ei jht vears ago, I first accidentally injected th*- tuperficial lymphatic network. ' " t See note, p. 648. 646 NEUROLOGY. the straight and the oblique muscles. There is also a secreting a{5paratus,tKeapparafti# of the lachrymal passages, the secretion from which lubricates the anterior surface of the ball of the eye, and facilitates the exercise of its functions. The study of the organ of sight, therefore, is not limited to that of the eyes alone, but includes that of the means of protection, viz., the orbital cavities (see Osteology), the eyelids, and the eyebrows ; that of the muscles, or moving organs ; and that of the lachrymal passages, or lubricating apparatus. These accessory parts, or appendages of the organ of vision, have been collectively named by Haller the tutamina oculi. We shall commence our description with them. The Eyebrows. The eyebrmjos are two arched ridges, which are covered with short stiff hairs, that are directed from within outward, and overlap each other ; the eyebrows are situated at the lower part of the forehead, and form the boundary of the upper eyelid. Their direc- tion corresponds precisely with that of the orbital arch. The hairs upon them are more numerous, and longer at the inner extremity, which is called the head, than at the outer, which is denominated the tail of the eyebrow. The heads of the two eyebrows are sep- arated from each other by an interval which corresponds to the root of the nose ; some- times, however, they are blended together. Structure. — The skin in which the hairs of the eyebrow are implanted is thick, and very closely united beneath to a muscular layer formed by the frontalis, the orbicularis palpebrarum, and the corrugator supercilii, the last-named muscle being situated beneath the other two. The orbital and superciliary arches serve as a basis to support the eye- brows ; the nerves of these parts are very numerous, and are derived from the facial and the fifth nerves ; their vessels arise from the ophthalmic and temporal arteries. Uses. — The eyebrows, which give a peculiar character to the human countenance, pro- tect the eye, and, when depressed in front of it, intercept a great number of the rays of light ; they assist in a remarkable degree in giving expression to the face. The Eyelids. The eyelids are two movable and protecting curtains, placed in front of the ball of each eye, which they conceal or leave uncovered, according as they are in a state of approx- imation or separation. The eyelids are two in number — a superior and an inferior. In a great number of ani- mals there is a third eyelid, of which merely a trace exists in man. The eyelids are large enough to close the base of the orbit completely, and to intercept entirely the pas- sage of light. Each of the eyelids presents for our consideration a cutaneous surface, which is con- vex, and marked with concentric semilunar folds that become effaced when the lids are closed ; an ocular surface {fig. 235), which is concave, is accurately moulded upon the ball of the eye, and presents a series of yellowish vertical lines, formed, as we shall see, by the Meibomian glands ; an adherent border, which is indicated by the orbital arch in the upper eyelid, but is less clearly defined in the lower lid, in which it is continuous with the cheek ; lastly, a free border, or margin, which, in both eyelids, is straight when the lids are closed, and curved when they are open : in the latter position they enclose an elliptical space {rima palpebrarum), the dimensions of which vary in different persons, and hence give rise to the expressions large eyes and small eyes, which have no refer- ence to the actual size of the globe of the eye, but merely to the size of that part which is exposed to view. The free margins of the eyelids are not cut obliquely from before backward, so as to intercept, when they are closed, a three-sided interval or channel, which is completed behind by the globe of the eye, and which is supposed to become larger from without inward, in order to conduct the tears towards the larchrymal punc- ta. On the contrary, these margins are cut horizontally from before backward (see sec- tion,^^. 240) ; and when approximated, they leave a narrow fissure between them, which may serve as a channel for the tears during sleep, quite as well as the three-sided canal which is generally supposed to exist. The margins of the eyelids, moreover, are tolerably thick, and are ftirnished at their anterior hp with three or four rows of hard, stiff, and curved hairs, which are more nu- merous and longer on the upper than on the lower eyelid, and at the middle than at either end of each : these are the eyelashes. Their direction is worthy of notice : in the upper eyelid they are at first directed downward, and are then curved upward, so as to de- scribe an arc having its concavity turned upward ; the eyelashes of the lower lid have just the opposite arrangement. From this it follows, that the convexities of the eye- lashes of the two lids are turned towards each other ; and thus, when the eye is shut, they touch each other without being able to interlace. Serious inconvenience is pro- duced when the eyelashes deviate from their proper course, and are turned inward ; When the eyelashes are wanting, the free margins of the lids are attacked with chronic inflammation. Along the posterior lip of the free margin of each eyelid, or, rather, along the angular ridge formed by the union of that margin with the posterior surface of the THE EYELIDS. Q47 lid, are placed a very regular series of foramina {figs. 235, 236), from which the sebace ous matter secreted by the Meibomian glands may be expressed in masses having the form of small worms. At the junction of the external five sixths with the internal sixth of the free margins of the two eyelids are found two very remarkable tubercles, the lachrymal papillcB or tu- bercles {a,fi^. 239 ; also seen in/^«. 235, 236), each of which is perforated by an open- ing, visible to the naked eye ; these openings are the puncta lachrymalia, the orifices of the corresponding lachrymal canals. That part of the free margin of each eyelid which is on the inner side of the corresponding lachrymal papilla is straight, rounded, and destitute of hairs or follicular orifices : in the space enclosed between this part of the eyelids, and called lacv^ lachrytnalis, is situated the caruncula lachrymalis (*, fig. 239). The upper eyelid, moreover, is twice as deep as the lower ; so that, when depressed, it descends below the transverse diameter, or equator of the eye, to use an expression invented by Haller. • The terms angles of the eye, or commissures of the eyelids, are applied to the angles formed by the junction of the extremities of the free margins of the eyelids. The ex- ternal angle, external or temporal commissure (b, fig. 239), is also named the little angle (canthus minor).* The internal angle, internal or nasal commissure (e), improperly cedled the great angle of the eye {canthus major), corresponds to the posterior border of the ascending process ol the superior maxillary bone. Structure of the Eyelids. — ^The constituent parts of the eyelids are, the tarsal cartilages, a fibrous membrane, a muscular layer, two integumentary layers, one mucous and the other cutaneous, and certain follicles, with vessels, nerves, and cellular tissue. The tarsal cartilages, which resemble in their use the cylinders of wood attached to the bottom of a map or diagram, to prevent it from hanging in folds, are two in number, one for each eyelid ; they are cartilaginous plates, situated within the free margin and the contiguous portion of the lids. The tarsal cartilage of the upper eyelid (a, figs. 235, 236) is semilunar ; that of the lower eyelid {h) has the form of a small, narrow band ; neither of them occupies the entire length of the corresponding lid. Their anterior sur- face is convex, and is covered by the fibres of the orbicularis palpebrarum muscle. Their posterior surface {fig. 235) corresponds to the conjunctiva, and is closely adherent to it. The Meibomian glands are situated between the conjunctiva and the cartilage, or, rath- er, in the substance of the cartilage. The adherent border of each tarsal cartilage is thin, and affords attachment to the fibrous membrane of the lids ; the adherent border of the cartilage of the upper eyelid, which is convex, also gives attachment to the levator palpebrae superioris muscle. The free margins of these cartilages are their thickest parts, and occasion the thickness of the free margins of the eyelids, t The cutaneous layer is remarkable for its excessive tenuity and semi-transparency : the eyelashes are appendages of this part of the integument. The cellular layer is no less remarkable for the absence of fat than for its extreme delicacy : it is the type, indeed, of serous cellular tissue, and is frequently the seat of serous infiltrations. The muscular layer is formed by the palpebral portion of the, orbicularis muscle, the pale colour of which, as I have already noticed, contrasts with the dark-red hue of the orbital portion of the same muscle. Besides this, the upper eyelid has an extrinsic mus- cle, the levator palpebrce superioris {a, fig. 237), the tendon of which, however, is alone concerned in the formation of that eyelid, by being attached to the upper border of the corresponding tarsal cartilage. The fibrous layer consists of a fibrous membrane, which arises from the margin of the orbit, and is attached to the corresponding borders of the tarsal cartilages. This mem- brane is very strong and unyielding in the outer half of the base of the orbit, but dimin- ishes in thickness towards the inner half of that base, especially on the inner portion of the upper eyelid, where it degenerates into cellular tissue. The term ligament of the external canthus might be applied to a fibrous raphe, which extends horizontally from that angle to the base of the orbit. This raphe bifurcates op- posite the outer canthus, so as to become attached to the outer end of each tarsal car- tilage, and it exactly corresponds to the tendon of the orbicularis palpebrarum, which is situated at the inner canthus, and which is also bifurcated, to join the inner ends of the same cartilages. (hi cutting through this raphe, some very strong fibrous bundles are exposed, which arise from the external wall of the orbit, and spread out into the substance of the upper eyelid. * The external commissure does not correspond to the outer extremity of the transverse diameter of th* base of the orbit, but is situated about three lines nearer to the nose ; hence the necessity of dividing this commissure in extirpation of the eye. t [The substance of the tarsal cartilages differs from that of ordinary cartilage in being more opaque, and also in having a few microscopic filaments scattered through it ; in this respect approaching in character to fibro-cartilage.] 648 NEUROLOGY. The expanded tendon of the levator palpebrae superioris, which is subjacent to the fibrous layer, completes the fibrous structure of the upper eyelid. The tarsal cartilages and the fibrous layer are situated upon the same plane. The mucous layer, or palpebral conjunctiva, consists of a membrane which lines the posterior surface {fig. 235) of the eyelids, and is, moreover, extended over the globe of tig. 235. the eye. This membrane is called the conjunctiva, or tunica adnata, because it connects the eyelids with the ball of the eye. In order to facilitate our description, we shall suppose it to commence at the free margin of the upper eyelid (a', fig. 240), where it is continuous with the skin : having covered the whole thickness of this margin, it then lines the posterior surface of the tarsal cartilage (c'), to which it is intimately adherent, and continues in the same direction as far as beneath the orbital arch. At this point it is refldfcted upon the anterior surface of the globe of the eye, so as to form a cul-de-sac between that organ and the eyelid : upon the eyeball, where it is called the ocular conjunctiva, it adheres to the sclerotic coat by means of cellular tissue, which is at first loose, but gradually becomes closer and closer as it approaches the transparent cornea. Upon the cornea (d') its adhesion is so intimate that some anatomists have denied its existence in that situation. In fact, it can only be anatomically demonstrated in the healthy state upon the margin of the cornea, but its ex- istence over the whole of that part of the eye is shown in some diseases. After having covered the anterior and inferior part of the sclerotic (c"), the conjunctiva is reflected upon the posterior surface of the lower eyelid (b'), lines its tarsal cartilage, covers its free margin, and then becomes continuous with the skin. On the inner side of the ball of the eye the conjunctiva forms a small semilunar fold, the plica semilunaris (e, figs. 235, 239), which has its concavity turned outward, and which may be regarded as the vestige of the third eyelid found in animals : it is misnamed the membrana nictitans (la membrane clignotante). On the outer side, the conjunctiva dips between the eyelids and the ball of the eye, and forms a deep cul-de-sac. Opposite the lachrymal papillae the conjunctiva passes into the puncta, and Hues the lachrymal passages. From what has been stated above, it will be seen that the conjunctiva would form a shut sac, like the serous membranes, if the eyelids were supposed to be united. Like the serous membranes, it covers two surfaces that rub one upon the other. Its tenuity, its transparency, and the filamentous adhesions which are sometimes observed between its contiguous surfaces, have induced some anatomists to place this membrane among the serous rather than the mucous membranes ; but its continuity with the skin, its ex- treme vascularity, and its uses, which require it to be in contact with the air, prove that it should be retained among the latter class of membranes.* The glands found in the eyelids consist of an appendage of the lachrymal gland, which will be described with it, of the Meibomian glands, and of the caruncula lachrymalis. The Meibomian glands (m m, fig. 236) are situated upon the posterior surface of both Fig. 236. eyelids, opposite the tarsal cartilages ; they resemble yellowish vertical and parallel lines, sometimes straight and sometimes curved ; their length is proportioned to the depth of the cartilages, and they never project upon the inner surface of the eyelids. Each of these lines, of which there are from thirty to forty in each eye- lid, consists of a tortuous canal, folded upon itself a great number of times, and having a considerable number of small follicles open- ing into it on each side. All these canals open very regularly upon the posterior lip of the free margin of the lid by a row of orifices arranged in a single line. I have never seen two rows of openings, as Zinn states he has observed. If the eyelids be compressed over the tarsal cartilages by a pair of pin- cers, masses of a waxy substance exude from these orifices, having the form of small worms twisted frequently upon themselves. Sometimes these small linear canals com- municate with each other opposite the adherent border of the tarsal cartilage ; at other times they bifurcate. It is the waxy sercetion from the Meibomian glands which pre- vents the tears from trickling in front of the eyehds. These glands are lodged in the deep grooves in the tarsal cartilages ; they are, therefore, as visible upon the external as the internal surface of the cartilages. The Meibomian glands belong to the class of sebaceous follicles, and form a transition, as it were, from follicles to glands. The caruncula lachrymalis {c,fig. 235,* fig. 239) consists of a small, oblong group of follicles, situated at the inner angle of the eyelids, and on the inner side of that semilu- nar fold of the conjunctiva, which we have spoken of as the trace of a third eyelid. It is about the size of a grain of wheat. It is interposed between the free margins of * The absence of villi has been stated as characteristic of the conjunctiva ; but villi or papillae are found ■pon that portion which lines the superior tarsal cartilage. [The epithelium of the conjunctiva is squamous, and consists of several layers : according to Henl6, it i* ciliated upon the inner surface of the eyelid ; but cilia have not been observed upon the eyeball.] THE MUSCLES OF THE EYE. 6^ tiie eyelids, in that part of those margins which extends between the lachrymal tuber- cles and the internal commissure ; but it is upon a plane posterior to these margins, so that it does not prevent their mutual contact. It is covered by a fold of the conjunctiva, which gives it a reddish aspect ; it presents a great number of openings, through which a waxy secretion exudes, and projecting from it are several small hairs, which may be- come so long as to produce ophthalmia. The caruncula lachrymalis is composed of se- baceous follicular glands, of the same nature as the Meibomian glands. It was for a long time considered to be a second lachrymal gland. In order to obtain a good view of the orifices, and of the light-coloured and sometimes very numerous hairs of the carun- cula lachrymalis, that body should be covered with ink or a solution of carmine, and then examined with a lens. Vessels and. Nerves of the Eyelids. — The arteries are the internal and external palpe- bral branches of the ophthalmic, and the palpebral branches of the temporal, infra-orbital, and facial arteries. I have already said that the palpebral arteries form two arches, one for each eyelid. The veins have the same name, follow the same direction, and open into the corre- sponding venous trunks. The nerves are derived from two sources, viz., the facial and the fifth nerve. Uses. — The eyelids protect the eye from the action of light and air, and of any parti- cles floating in the latter ; by a sweeping movement, they clean the surface of the or- gan, over which they also spread the lachrymal fluid, which serves as a protection to the eyeball against the action of the air. The eyelids, from their capability of being inter- posed between the eye and external objects, place the exercise of vision under the con- trol of the will. The Muscles of the Eye, and the Levator Palpebrce Superioris. The muscles of the eye are six in number, and are distinguished into the straight and the oblique. There are four straight and two oblique muscles. With these we shall also describe the levator palpebrae superioris. Dissection. — Remove the roof of the orbit by two cuts with the saw, meeting each oth- er at an acute angle opposite the optic foramen ; be careful that the inner cut does not injure the cartilaginous pulley of the superior oblique muscle. Dissect the origins of these several muscles from the deepest part of the orbit with the greatest care. They are arranged completely round the optic nerve (o, figs. 237, 238) and the motor oculi nerves. Those which arise above the optic nerve are attached to the dura mater and periosteum, but not to the bone ; but those which arise below the nerve adhere more closely to the bone. The inferior or small oblique muscle is the only one which does not arise from the bottom of the orbital cavity. The Levator Palpehra Superioris. The levator paipebra superioris (a, figs. 237, 238), much thinner and narrower than the rectus superior, which is subjacent to it, arises from ^^ 237. the bottom of the orbit, at the upper part of the mar- gin of the optic foramen, or, rather, from the fibrous sheath given oflT from the dura mater around the op- tic nerve. It arises by short and radiated tendinous fibres, to which the fleshy fibres succeed, in the form of a thin, flat muscle, that passes outward in a line parallel with the axis of the orbit, is reflected upon the globe of the eye, and ends in an aponeirrotic ex- pansion, which is inserted in the upper border of the tarsal cartilage of the upper eyelid Relations. — It is covered by the periosteum of the roof of the orbit, it is covered obliquely at its origin by the ophthalmic nerve, and it covers the superior rectus muscle. Action. — ^This muscle raises the upper eyelid, and draws it backward, so that the up- per border of the eyelid is concealed under the orbital arch. The Rectus Superior, or Levator Oculi. The superior rectus (5) has two very distinct origins. The first resembles that of the levator palpebrae superioris in being from the upper part of the fibrous sheath of the optic nerve, but it is on a lower plane than that muscle ; the second is from the inner margin of the sphenoidal fissure, i. e., between that fissure and the optic foramen. The latter origin, which is continuous with those of the external rectus, appears to take place from the sheath furnished by the dura mater to the third cranial or motor oculi nerve. The fleshy fibres arising from this radiated tendon form a flat bundle, which passes for- ward and outward in the direction of the axis of the orbit, and is reflected upon the eye- ball, where it becomes converted into a broad and thin aponeurosis, and is inserted into the sclerotic coat, at a short distance from the cornea. This muscle, like all the other recti, is in relation with the periosteum of the orbit, 4N «iv 650 NEUROLOGY. from which it is separated towards the inner side by the levator palpebrae superioris ; it covers the optic nerve and the eyeball. The Rectus Inferior, or Depressor Oculi. The inferior rectus (c) arises, together with the internal and external recti, by a common tendon, called the tendon or ligament of Zinn, which is attached to the lower half of the optic foramen, and more particularly to a depression which is seen to the inner side of the sphenoidal fissure. Almost immediately after its commencement this tendon divides into three branches, from the middle one of which the inferior rectus muscle arises, and then passing horizontally forward and outward, is reflected upon the globe of the eye, and terminates in a similar manner to the preceding muscle. The Rectus Internus, or Adductor Oculi. The internal rectus {d) has two very distinct origins : one from the tendon of Zinn, the other from the inner side of the fibrous sheath of the optic nerve ; the latter origin is contmuous with those of the superior rectus. From these points it passes forward along the internal wall of the orbit, is reflected upon the globe of the eye, and terminates like the preceding muscles. The Rectus Externus, or Abductor Oculi. The external rectus (e) also has a double origin : one inferior, derived from the liga- ment of Zinn ; the other superior, from the fibrous sheath of the sixth cranial or abdu- cens oculi nerve, and continuous with the external origin of the superior rectus. A fibrous arch, under which certain veins pass, unites these two origins, and also serves as a point of attachment to the muscular fibres. From these points the muscle passes obhquely forward and outward along the external wall of the orbit, is reflected upon the eyebaU, and terminates like the other recti muscles. General Description and Action of the Recti Muscles. The four straight muscles of the eye arise from the bottom of the orbit, and terminate upon the eyeball, a few lines from the cornea. They all have the same form, viz., that of a long isosceles triangle, having its base turned forward and its apex backward. Their relations are also similar : tlius, they cor- respond, on the one hand, to the periosteum of the orbit, and on the other to the optic nerve and the globe of the eye, from which they are separated by some fat and vessels. In consequence of their being inserted in front of the transverse diameter of the eye, they are all reflected upon the eyeball ; this fact is rendered much more evident when the eye is drawn in an opposite direction to that in which the particular muscle under examination would act. Their tendons are surrounded with a whitish, and, as it were., elastic cellular tissue, by which the movements of these muscles are facilitated.* The recti differ from each other, both in length and thickness. Thus, the internal rectus is the shortest and thickest, the external rectus is the longest, and the superior rectus is the smallest. Action. — If these muscles were not reflected upon the globe of the eye, their action would be simply to draw it forcibly backward towards the bottom of the orbit ; but, in consequence of this reflection, they can give it a rotatory motion. Thus, the superior and inferior recti rotate the eyeball upon its transverse axis, while the internal and ex- ternal recti rotate it upon its vertical axis. After either of these effects is produced, the eye is then drawn backward. The direct movement backward is produced by the si- multaneous contraction of the four muscles. When any two adjacent recti act together, the eye is moved in the diagonal of the two forces exerted by those muscles ; and hence the eye, and therefore the pupil, can pass over all the radii of the circle represented by the base of the orbit ; this arrangement is not only highly favourable to the exploratory power of the eye, but also assists in placing the function of vision under the control of the will, since it enables us to turn away the eyes from any offensive object. The straight muscles of the eye, as well as the oblique muscles, also aid in expressing the passions ; and hence the following names have been given to them by the ancients. The superior rectus is called superbus (mirator, Haller) ; the inferior rectus, humilis ; the external rectus, indignatorius ; the internal rectus, amor torius seu bibitorius. Lastly, it has been supposed that the muscles of the eye, by compressing that organ, can alter the distance between the retina and the crystalline lens ; and a theory to ex- plain the power we possess of adapting the eye for distinct vision at different distances has even been constructed on the supposed possibility of this compression. The necessarily simultaneous and co-ordinate action sometimes of the same muscle, and sometimes of different muscles in the two eyes, is a remarkable physiological fact. Thus, the contraction of the superior rectus of the right eye is of necessity accompanied by contraction of the corresponding muscle of the left eye ; while the contraction of the external rectus of one eye is accompanied by contraction of the internal rectus of the * [Small synovial bursa have been described as existing between tbese tendons and the globe of the eye.] THE OBLiaUE MUSCLES OF THE EYE. 651 other eye, and vice versa : the will can neither prevent nor disarrange these co-ordinate contractions. However, even without much practice, it is possible to overcome them, so far as to squint by endeavouring to look at the nose. It is not uninteresting to remark, that the sixth cranial nerve, or the abducens oculi, is destined exclusively for the external rectus muscle ; and that the third cranial nerve, or motor oculi, supplies the three other recti, the levator palpebrae superioris, and the obliquus minor. No other muscles in the body receive such large nerves in proportion to their size as those of the eye. Tke Oblique Muscles of the Eye. These are two in number, the superior or great oblique, and the inferior or lesser oblique. The Obliquus Superior. Tke superior or great oblique muscle of the eye (/, fig. 238) is a long filiform muscle, which is reflected over a pulley or trochlea, and hence has been jv^. 238. termed the trocklearis muscle ; it arises from the fibrous sheath of the optic nerve, between the superior and internal recti, in the same manner and upon the same plane as those muscles ; from this point it passes forward along the i^ngle formed by the junction of the roof with the inner wall of the orbi, and forms a rounded muscular fas- ciculus, which ends in a rounded tendon near the cartilaginous pulley intended for its reception ; the tendon passes through this pulley, is i| reflected upon itself at an acute angle, so as to be directed down- " ward, outward, and somewhat backward ; gets beneath the superior rectus, where it spreads out, and is then inserted into the sclerotic coat on a level with the longest transverse diameter of the eyebsil], and, consequently, farther back than the insertion of the recti. The superior oblique is the longest muscle of the eye The trochlea, or pulley of the superior oblique, is a small cartilage, which forms five sixths of a short cylinder or ring ; the edges of this imperfect cylinder are attached to the slight bony ridges which bound a depression upon the superior wall of the orbit. Its attach- ment is effected by means of loose ligamentous fibres, so that the pulley itself has a certain degree of mobility. The gliding of the parts is facilitated by a synovial membrane, which is reflected from the tendon upon the pulley, and is prolonged in front of and behind the latter. Beyond the pulley, a whitish filamentous tissue takes the place of the synovial membrane. The relations of the superior oblique are similar to those of the superior rectus. Action. — Like aU reflected muscles, the superior oblique must act from the point of its reflection. It follows, therefore, that this muscle rotates the eye upon itself from with- out inward, that is, around its antero-posterior axis. From the oblique direction of its t^don from before backward, after it is reflected, it can draw the eye forward, and tends to bring it out beyond the orbit. This muscle is believed to assist in the expres- sion of the tender passions (jnusculus patheticus). The fourth cranial nerve, also called the trochlear or pathetic nerve, is destined exclusively for this muscle. The Obliquus Inferior. The inferior or lesser oblique (g, fig. 237, 238) is the shortest muscle of the eye, and the only one which does not arise from the bottom of the orbit ; it arises from the inner and anterior part of the floor of that cavity, and, therefore, from the orbital surface of the superior maxillary bone, immediately behind the margin of the orbit, and often even from the lachrjnnal sac. From this origin it passes backward, in the form of a flat bun- dle, which turns round the lower surface of the globe of the eye, situated at first between the eyeball and the inferior rectus, then between it and the external rectus, and at length ends in an aponeurotic expansion, which is blended with the sclerotic, near the outer border of the superior rectus. Its insertion into the sclerotic is farther back than that of the superior oblique, and, therefore, much farther back than those of the recti. Action. — It rotates the eye in the opposite direction to the superior oblique. Its turn- ing round the lower surface of the eyeball renders its action extremely effective. From its oblique course from before backward, it can draw the eye slightly forward. The Lachrymal Passages. The term lachrymal passages includes both the apparatus for secreting and that for con- veying away the tears, consisting of a secreting organ, named the lachrymal gland ; of excretory ducts, which pour out the tears upon the conjunctiva ; and of a second set of ducts, intended to absorb the tears and convey them into the nasal fossae, comprising the puncta lachrymalia, the lachrymal canals, the lachrymal sac, and the nasal ducts. Such is the order in which we shall describe this apparatus. 6S2 NEUROLOGY. The Lachrymal Gland. . , ^ The lachrymal gland (glandula innominata of the ancients) consists of two very distinct parts : an orbital portion, situated in the fossa on the roof of the orbit ; and a. palpebral por- tion, which is enclosed in the substance of the upper eyehd. The first or orbital portion (I, fig. 207), the only part generally described, is of an irreg- ular semi-ovoid form, having its long diameter placed transversely. It varies in size in different subjects, but is generally about as large as a filbert.* Its upper surface is con- vex, and corresponds to the fossa in the frontal bone, to which it adheres, especially in front, by very distinct fibrous bands : its interior surface is concave, and is in relation with the external rectus, and with a small part of the superior rectus. Its anterior bor- der corresponds to the orbital arch, or, rather, to the fibrous membrane of the eyelid, im- mediately behind which it is situated ; hence it maybe exposed by an incision along this arch. By its posterior edge it receives its vessels and nerves. The second or palpebral portion, though continuous with the first, is separated from it by several fibrous bands. It forms a thin granular layer, which is covered and concealed by a very dense lamina of fibrous tissue that appears to be prolonged into its interior. This palpebral portion occupies the outer portion of the upper eyelid, and extends almost as far as the upper border of the tarsal cartilage. The Excretory Ducts of the Lachrymal Gland. — Before the discovery of these excretory ducts, it was only by inference that the so-called glandula in7iominata was regarded as the secreting organ of the tears. In 1661 Steno discovered these ducts in the sheep, m which animal they are large enough to admit bristles. He described thirteen or fourteen ducts. The difficulty of detecting these ducts in the human subject is sufficiently proved by the fact that neither Morgagni, Zinn, nor Haller could ever find them ; the second Monro, however, succeeded in filling them with mercury, and described them accurate- ly. They are from ten to twelve in number ; they run parallel to each other beneath the palpebral conjunctiva, and open upon the inner surface of the eyelid by a corresponding number of orifices {d,fig. 235), placed very regularly about a line from the tarsal cartilage, along its outer half. MM. Chaussier and Ribes have succeeded in filling them with mer- cury, by injecting them from the gland towards the eyelids. Having sought in vain, both with the naked eye and with a lens, for the orifices of the excretory ducts of the lachrymal gland in the human subject, I thought of dipping the eye and eyelids in a so- lution of carmine or slightly-diluted ink ; and I then saw distinctly a dozen openings ar- ranged in a line along the point of reflection of the palpebral conjunctiva upon the eye- ball, and occupying the outer half of the eyelid, t The Lachrymal Puncta and Canals. The puncta lachrymalia {a, fig. 239), two in number, one for each eyelid, are those small Fig 239. orifices or foramina which are visible to the naked eye in the centre of the lachrjonal papillae : they are perfectly circular, are always open, and are directed backward, the upper one being turned do*n- ward, and the lower one upward. These openings, which are ia^t apart from each other by the caruncula lachrymalis, are the cjq)il- lary orifices of two small canals, called the lachrymal canals. The lachrymal canals {I I) are small tubes, extending from the puncta lachrymalia to the lachrymal sac. They are two in num- ber, a superior and an inferior, each being somewhat larger than the corresponding lachrymal punctum. Their angular course is very remarkable. They pass at first vertically, the superior duct upward, and the inferior duct downward, and after a short course they bend abruptly at right angles, run inward, and open by separate orifices, never together, into the anterior and external part of the lachrymal sac. The direction of the second portion of each of the lachrymal canals varies according as the eyelids are closed or open : the duct of the lower eyelid is directed somewhat obliquely upward, that of the upper eyelid downward, even when the lids are completely closed ; but they are both very oblique when the eyelids are separated ; and as this separation is principally due to the elevation of the upper eyelid, it follows that the obliquity of the upper lachrjrmal canal must be very well marked. The coats of the lachrymal canals are dense and elastic, so that they do not collapse when empty, and must, therefore, act as capillary tubes. We do not find any sphincter, either at their palpebral or their nasal orifice ; they appear to be formed in the sub- stance of the free margin of each eyelid ; they are lined by a prolongation of the con- junctiva, and are covered by the fibres of the orbicularis palpebrarum muscle. Behind them are found some muscular fibres, forming a dependance of a small fasciculus, called the muscle of Horner, or the lachrymal muscle, which was believed by that anatomist to serve in drawing the lachrymal ducts inward. * [It has all the anatomical characters of a compound gland.] t T find in Haller that it was in a human eye which had been macerated for some time in water tinged with blood, that Monro (Secundus) discovered these orifices. After they have been discovered, it is easy to intro- duce the end of the rasrcurial injecting pipe into them. THE LACHRYMAL PASSAGES. 658 The Muscle of Homer. Dissection. — ^Turn the eyelids inward, and carefully remove a fibrous layer which cov- ers this muscle upon the lachrymal sac. This small muscle arises from the vertical ridge of the os unguis, which forms the pos- terior border of the lachrymal groove ; from this point it passes transversely outward along the posterior tendon of the orbicularis palpebrarum, and divides into two tongues, a superior and an inferior, which correspond to the lachrymal canals, and terminate at the respective lachrymal puncta. I regard these fibres as a dependance of the orbicularis palpebrarum. The Lachrymal Sac and Nasal Duct, or Lachrymo-nasal Canal. The lachrymal sac and nasal duct constitute a single canal, which extends from the up- per part of the lachrymal groove to the inferior meatus of the corresponding nasal fossa. The lachrymal sac (wi), that portion of the lachrymo-nasal canal which occupies the lachrymal groove, represents the half of a cylinder terminating above in a cul-de-sac. It is buried, so to speak, in the substance of the inner wall of the orbit, immediately be- hind the margin of that cavity, and is in relation with the inner angle of the eyelids, the caruncula lachrymalis, the adipose tissue of the orbit, and the tendon of the orbicularis muscle. The last-named relation is one of the most important points in the anatomy of the lachrymal sac. If a circular incision be made through the eyelids from their outer aigle along their adherent borders, and the lids be then turned inward, by then careful- ly dissecting the tendon of the orbicularis, it will be found that that tendon divides into three branches ; that the anterior branch, called the straight tendon, is inserted in front of the ascending process of the superior maxillary bone ; that the posterior branch, which is of equal size with the anterior, is inserted into the ridge upon the os unguis, behind the lachrymal groove ; that the middle branch ascends to be attached to the upper part of the lachrymal groove ; and, lastly, that the lower part of the tendon gives off a fibrous expansion, which forms the outer side of the lachrymal sac, and which may be regard- ed as a fourth tendinous expansion. The muscle of Homer lies upon the posterior of these tendons, and must be regarded as a portion of the orbicularis itself The tendon of the orbicularis palpebrarum corresponds to the upper part of the lachry- mal sac, only its cul-de-sac projecting above the tendon. The greatest part of the sac is, therefore, situated below it. The internal surface of the lachrymal sac presents the ordinary appearance of all ca- nals lined by mucous membrane : a considerable quantity of mucus is often found in it. At the anterior part of its external wall, and at about an equal distance from the top and bottom, are the two orifices of the lachrymal canals ; above, is the narrow cul-de-sac, in hich it terminates in that direction ; and below, it becomes continuous with the nasal duct : in this place there is rather frequently found a semilunar, sometimes even a cir- cular valve ; this is the kind of diaphragm spoken of by Zinn, but the existence of which w^denied by Morgagni. Haller says that he only met with it once. lachrymal sac consists of a partly bony and partly fibrous canal, lined by a mu- embrane. The bony portion of this canal is formed by the groove upon the as- ing process of the superior maxillary bone, and upon the os unguis ; the last-men- led bone, which is thin and pierced with foramina, may be easily perforated ; and hence the facility of making an artificial passage for the tears. The lachrymal sac is opposite to the middle meatus of the corresponding nasal fossa. The fibrous portion forms the external flattened wall of this canal ; it is very strong and unyielding, unless to long-continued extension. The slight muscular layer, described as the muscle of Horner, may be regarded as be- longing to the lachrymal sac : this muscle is itself covered by a layer of fibrous tissue. The lining mucous membrane of the lachrymal sac is reddish, and, as it were, pulpy, and closely resembles the pituitary membrane ;* from its close attachment to the peri- osteum of the walls of the canal, it might be called afibro-mucous membrane. The nasal duct (n), which may be said to be formed in the outer wall of the corre- sponding nasal fossa, extends from the lachrjTnal sac to the anterior part of the inferior meatus of the nose. It is of a cylindrical shape, slightly flattened on the sides, and rath- er narrower at the middle than at its extremities. It is directed vertically, but forms a slight curve, having its concavity turned forward and outward. It may be also readily conceived that the relative breadth of the root of the nose must affect the direction of this canal. It corresponds, on the inner side, to the middle meatus of the nose, and the inferior tur- binated bone ; on the outer side, to the maxillary sinus, from which it is separated by a very thin lamina of bone. This latter relation has doubtless led one anatomist to state that the nasal canal opens both into the maxiUary sinus and the nasal fossa. The nasal canal consists of a bony canal lined by a fibro-mucous membrane ; the bony canal is complete, and is formed by the superior maxillary bone, the os unguis, and the inferior turbinated bone. It is very strong in the part formed by the superior maxillary * See note, p. 654. 654 NEUROLOGY. bone, excepting opposite to the sinus in that bone, but it is very thin and fragile where it is formed by the os unguis and inferior turbinated bone. Its lining membrane is of a fibro-mucous structure ; it adheres very slightly to the walls of the canal, and is contin- uous, on the one hand, with the mucous membrane of the lachrymal sac, and, on the other, with the pituitary membrane.* This lining membrane is often prolonged for sev- eral lines beyond the nasal duct, so as to form a valvular fold (o). Where this fold ex- ists, the inferior orifice of the nasal duct (see r,fig. 233) is always closed, and, there- fore, difficult to be detected, even when the inferior turbinated bone has been taken away or displaced, so that, in order to discover it, it becomes necessary to introduce a probe through the lachrymal passages from above. In catheterism of thelift|J duct from below upward, according to the method practised by Laforest, this fold ^Btocous membrane must of necessity be torn. ^fe It has been stated by some authors, that the lower orifice of the nasal duct isp^e- ded by an ampulla, or infundibuliform dilatation. I have met with this disposition, but regarded it as morbid. I am convinced that a great many lachrymal tumours depend upon contraction or obliteration of the lower orifice of this canal. « The Globe of the Eye. The globe of the eye {v,fig. 240) is situated in the fore part of the orbital cavity ; it is retain- Fig. 240. ed in this situation by the optic nerve (o), the straight and oblique muscles {beg), the vessels, the conjunctifa (d), and the eyelids ; these parts, however, do not con- fine it in a fixed position, but allow it great mobility. In fact, the eye can be rotated around all its axes, and can even be drawn forward and backward (see Mus- cles of the Eye). The eyes are small in comparison to the orbital cavities ; and they present some slight dif- ferences as to size in different persons, which have not yet been properly estimated. The common terms. large and small eyes apply less to the eyeball than to the opening between the eyelids. The eye is propor- tionally larger in the foetus and new-born infant than'in the adult and aged. Inform, the globe of the eye resembles a regular spheroid, to- the front of which r? at- tached a segment of a smaller sphere {see fig. 241) : by this arrangement, the anjfero- posterior diameter of the organ is increased to the length of eleven lines, whil^it^l^h- er diameters are only ten lines. It is said that the form of the eyeball can ' by the contraction of its muscles, but, in consequence of the great tension of tj the alteration produced is so slight tj^at it scarcely deserves to be mentioned. The general relations of the eyeball are the following : in front, it is covere conjunctiva and the eyelids, which defend it from light and from dust, rather external violence. It results, also, from the obliquity of the margin of the orbit,' the outer side, the eye projects considerably beyond the bones. In every other pi its surface the eye rests upon an elastic cushion of fat (//), which separates it' the muscles and nerves, fills up all intervals, and facilitates the movements of the or^ The absorption of this fat in emaciated individuals causes the depression of the eyej the orbital cavity. A membranous cellular tissue, or, rather, a rudimentary sync membrane, exists between the eye and this fat. ., Structure. — Like all the other organs of the senses, the eye consists essentially of a membrane provided with a special nerve, and of a particular apparatus, placed in relation with the external agent by which the organ is to be acted upon. In the organ of vision, the sentient membrane is the retina, which is the immediate seat of the sense of sight ; the other parts of the eyeball form nothing more than a very comphcated dioptric instru- ment, a dark chamber, in which the rays of light are refracted, and concentrated so as to form a vivid image, and which is, moreover, provided with a movable diaphragm to regulate the number of rays to be admitted. In an anatomical point of view, the eye is said to consist of certain membranes and humours. The membranes, counting from without inward, are the sclerotic coat and cor- nea, the choroid coat and iris, and the retina. The humours are, the vitreous body and its hyaloid membrane, the crystalline lens and its capsule, and the aqueous humour. The Sclerotic. Dissection. — Clean the globe of the eye, leaving the attachments of the muscles to the sclerotic coat ; with a pair of strong scissors divide this coat circularly into an anterior and posterior portion, taking care to avoid the choroid coat ; turn the one portion for- ward and the other backward. It is easier to make this section, without injuring the choroid, upon a slightly flaccid eye than upon one which is perfectly fresh. The sclerotic {aK%T]pdg, hard), or the opaque cornea {b,fig. 241), is the outermost of the * [The epithelium of the mucous membrane of all the lachrymal passages is columnar, and, according to Henle, is provided with cilia, although Perkinj6 and Valentin failed to discover them in these situations.] THE CORNEA. 655 coats of the eye, and forms, as it were, the shell of that organ ; it is of a pearly- white colour, and very stroag,;. it is perforated behind to give passage to the optic nerve (o), and presents a circular opening in front (from a to a), into which the cornea is fitted. Its external surface forms the outer surface of the eyeball, and therefore has the same relations. Thus, it is covered in front by the conjunctiva, which adheres to it by means of very loose cellular tissue, that is liable to infiltration. The straight and oblique mus- cles of the eye are implanted into it. An imperfect or rudimentary synovial capsule separates it from the cushion of fat, and gives it a smooth aspect. Its internal surface has a dull, rough appearance, very different from that of its exter- nal surface : it is, moreover, of a deep-brown colour, from the choroid pigment ; it cor- responds to the choroid coat (c), and is united to it by a very delicate cellular tissue, and by the ciliary vessels.* The ciliary nerves run from behind forward between the scle- rotic and the choroid, occupying slight grooves upon the internal surface of the former. Both the ciliary vessels and nerves perforate the sclerotic coat very obliquely. Structure. — ^The sclerotic is one of the thickest and strongest fibrous membranes in the body^ it is not of uniform thickness throughout ; it is thickest behind, at the entrance of the optic nerve, and thinnest in front, near the cornea. Like all the fibrous mem- branes, it is unyielding ; and on this depends the firmness and tense condition of the globe of the eye : it is also the cause of the intense pain produced by inflammation of the interior of the eye and by certain cases of hydrophthalmia. The older anatomists considered the sclerotic to be composed of two layers, the inner of which was, according to Zinn, a prolongation of the pia mater, and, according to Meckel, of the arachnoid. But, independently of the fact that the division of the sclerot- ic into two layers is purely artificial, it may be stated that neither the pia mater nor the arachnoid is prolonged upon the optic nerve. Lastly, the sclerotic has been regarded as a continuation of the dura mater, through the medium of the neurilemma of the optic nerve ; and this view is supported by dissection, which shows clearly that the sheath furnished by the dura mater to the optic nerve is prolonged upon the sclerotic. It has, moreover, been stated, but incorrectly, that the anterior part of the sclerotic has an ad- ditional layer, formed by the union of the tendons of the recti muscles. The sclerotic is composed of fibrous bundles which interlace in all directions. Its use is especially to protect the globe of the eye, of which it forms the covering and determines the shape. .;- The Cornea. ^' The transparent cornea {a a, fig. 241) completes the external shell of the eye in front : in reference to the sclerotic coat, it represents a segment of a smaller sphere superadded to a larger sphere ; its circumference is circular, or, rather, slightly elliptical, for its transverse diameter is half a line longer than its vertical diameter. Its anterior surface is convex, and projects forward beyond the sclerotic ; it is covered by^he conjunctiva, which adheres to it so closely, that the existence of that membrane v^^fm it has Been denied by some anatomists.! ■"Ij^o great a convexity of the cornea, by increasing the refracting power of the eye, ^jgftasions myopia, or short-sightedness. ■ its posterior surface is concave, and forms the anterior wall of the anterior chamber of the eye. A thin membrane (m) covers this surface, and is called the membrane of the aqueous humour. The circumference of the cornea, which is fitted into the opening in the front of the scle- rotic, is cut obliquely, so that its external surface is smaller than its internal surface ; the oblique edge of the sclerotic, to which it corresponds, is sloped in the opposite direction. The cornea and sclerotic adhere so closely that they were for a long time regarded as forming but one coat ; but, independently of their difference in appearance and texture, they may be separated by boiling or by long-continued maceration. Structure. — The cornea is thicker than the sclerotic : it may be separated into a great number of lamellas, united by very thin layers of cellular tissue ; but this separation is purely artificial, so that the number of lamellae is indefinite. The thinnest layer of fluid interposed between the lamella; is sufficient to impair the transparency of the cornea; maceration, accordingly, gives it a milky appearance. The opacity of the cornea, which occurs in some cases of ophthalmia, depends upon the infiltration between the lamellae of a certain quantity of fluid, after the absorption of which the cornea recovers its ori- ginal transparency. No vessels can be shown in the cornea, even by the aid of the finest injections of the arteries and veins of the eye : its superfi^cial layer, which is continuous with the con- junctiva, contains a network of lymphatics communicating with those of the conjunc- tiva, and capable of being demonstrated by puncturing any part of the superficial layer of * See note, p. 656. t A careful dissection, especially after prolonged maceration, shows the continuity of the most superficial layer of the cornea with the conjunctiva. A malformation sometimes occurs iu which oni^ part of the cornea is covered by a prolongation of the conjunctiva. 656 NEUROLOGY. the cornea. It is useless to introduce the tube deeper, for the lymphatic network is en- tirely superficial. Uses. — The transparent cornea is the first medium through which the rays of light have to pass ; in consequence of its density and its convexity, it refracts the rays of light, and causes them to converge. The density of the cornea is the same in different per- sons ; but its convexity is subject to variations, upon which depend, in a great measure, the states of myopia (short sight), presbyopia (long sight), and natural vision. The Choroid Coat, and the Ciliary Circle and Processes. The choroid (indicated by the thick black hue, c,Jlg. 241), so called from its extreme vascularity,* is the second membrane of the eye, proceeding from without inward ; it is a vascular membrane, covered with a thick layer of pigment : it exactly lines the sclerotic, and terminates, like it, at the circumference of the cornea. Its external surface (c, jigs. 242, 244) adheres to the schlerotic by means of the ciliary vessels and nerves, and by a thin and very delicate cellular tissue, which is easUy lacer- ated, and when raised appears like a spider's web.+ This surface, when magnified, has a fiocculent appearance. Its internal surface is in relation with, but does not adhere to, the retina (r, fig. 241), by which it is lined nearly throughout its whole extent. Both surfaces of the choroid are covered with a pigment, which resembles the pigment of the skin of negroes ; this pigment is much more abundant on the internal than on the external surface, and less so behind than in front, where it forms a thick layer, in the form of a zone surrounding the corona ciliaris. Upon both surfaces are found innumerable longitudinal and contorted lines, which correspond to the vessels of the choroid. In a great number of animals, in the ox, for example, the pigment on the interned sur- face of the choroid at the back of the eye is replaced by a brilliant metallic-looking sub- stance called the tapetum. When deprived of its pigment, the internal surface of the choroid presents a smooth aspect, and is not fiocculent like the external surface. It is of a grayish- white colour, and anteriorly, where it is covered by a thick layer of pigment, it becomes white and shining when the pigment is removed. Behind, the choroid is pierced by a circular opening for the passage of the optic nerve ; in front, it terminates in the ciliary circle and ciliary processes, which must be regarded as appendages to it. T'he Ciliary Circle. — The ciliary circle, ring, or ligament («, fig, 241 ; b, figs. 242, fin. ail, 244), IS a circular zone, from a line to a J j_ line and a half in breadth, of a grayish col- our, and soft consistence, which bounds the choroid coat (c c) in front. It is of con- siderable thickness. Its external surface corresponds to the sclerotic, to which it is slightly adherent. Its internal surface Qpr- responds to the ciliary processes (e, fig. 241) ; by its outer or larger border, which is distinguished from the choroid by a slight ridge, it receives the ciliary nerves (a a, fig. 242), which bifurcate, and appear to anastomose with each other before they enter the substance of the ciliary circle : by its lesser or inner border, wliich corre- sponds to the iris (i), it adheres intimately to the circumference of the cornea, exactly where that membrane is continuous with the sclerotic (at a a, fig. 241). The older anatomists called this structure the ciliary liga- merU. From the great number of the nerves which enter the ciliary circle, from its gray- ish colour, and its pulpy aspect, modern anatomists have regarded it as a nervous gan- glion (annulus gangliformis, or annular ganglion, Sammering). Fig. 242. Some anatomists describe, under the name of the ciliary canal, or the canal of Fontana, a very small and extremely narrow cir- cular space (u V, fig. 241), which is formed between the ciliary circle, the cornea, and the sclerotic. This space can be filled with injection, and it is not certain that it is not the cavity of a bloodvessel. The Ciliary Processes and the Ciliary Body. — If the back part of the sclerotic, choroid, and retina be cut away, or even if the fc globe of the eye be merely divided into an anterior and posterior * Choroid is synonymous with vascular. t [A serous cavity is said by some to exist betvreen the sclerotic and choroid ; the lining membrane of this supposed cavity is named the arachnoid membrane of the eve.] THE IRIS. ^7 half by a circular incision, on looking into the anterior half a perfectly regular radiated disc {d, Jig. 241 ; a b, fig. 243) will be seen around the crystalline lens. This disc, which has been very correctly compared to a radiated flower, is called the ciliary body, or cormia ciliaris ; each of the rays is called a ciliary process or ray (rayon sous-irien, Chaussier). If, after a correct idea of the arrangement of this radiated disc has been obtained, the choroid coat be separated from the humours of the eye, it will be found that there are two perfectly distinct discs : one of these remains attached to the choroid coat, and constitutes the ciliary disc or ciliary body of the choroid (a b, fig. 243) ; the other remains attached to the vitreous body and to the crystalline lens, and is the ciliary zone of pig, 243. Zinn, which may be termed, after M. Ribes, the ciliary processes of the vitreous body (a b,fig. 248). We shall now describe the cil- iary processes of the choroid coat only, leaving the ciliary pro- cesses of the vitreous body to be described together with that part of the eye. The ciliary processes of the choroid coat, so well described by Zinn, who enumerates sixty of them, are regarded as so many folds of the internal layer of the choroid. They may be divided into great and small, the latter occupying the intervals between the former. They all increase in size (from b to a, fig. 243) as Pcterior or imemJ view. they approach the outer border of the iris, behind which they are prolonged without adhe- ring to it, and are then bent forward upon themselves, to be attached to that border. These ciliary processes, the sides of which are turned towards each other, have, therefore, a posterior adherent or choroid portion (b), and an anterior free or iridian portion (a). The free portion (c e, fi^. 241 ; a, fig. 244) floats among the humours of the eye like a fringe ; ,the slightest agitation of the vessel or of the liquid in which the ciliary processes are contained is immediately communicated to this free portion of the corona ciliaris. The ciliary body or disc, which is formed by the union of all the ciliary processes or rays, is in relation behind with the vitreous body {v in the centre, ^^. 241), and advances (e,fig. 241 ; a, fig. 244, in which the iris is removed) over the circumference of the crystalline lens. It is not simply in contact with the vitreous body, but is rather firmly adherent to it ; and we shall afterward see that they are dovetailed together, that is, the ciliary processes of the vitreous body are fitted into the intervals between the ciliary pro- Anterior view-im removed cesses of the choroid, and vice versa. If the thick layer of pigment with which they are covered be removed, the ciliary processes of the choroid, when examined through a lens under water, have a white colour. In their substance are seen irregular cells which are filled with the brown pigment, and which give them a spongy, and, as it were, jagged appearance. They are evidently con- tinuous with the choroid, which irxmiediately around them presents a zone of a whiter colour than the rest of the inner surface of that membrane. Structure of the Choroid Coat and its Ciliary Processes. — The structure of these parts is essenticdly vascular. Fine injections thrown into the carotid artery and internal jugular vein, in young subjects, fill a beautiful network of vessels in this membrane. The vor- ticose arrangement {v, fig. 244) of some of these vessels is then clearly displayed ; and, indeed, this is very well indicated, without the aid of an injection, by the striae already described as visible upon the surfaces of the choroid. The short ciliary arteries belong exclusively to the choroid coat. From a great number of experiments made by M. Ribes, it would appear that injections pushed into the arteries do not enter the vdli and fringes of the ciliary body, but that their vessels may be filled from the veins ; so that, accord- ing to this, the structure of the free and fringed portion of the ciliary processes is alto gether venous, like the cavernous or erectile tissues.* From the different appearance of the external and internal surfaces of the choroid, anatomists have regarded this coat as being composed of two layers, of which the in- ternal is called the membrana Ruyschiana, after Ruysch, who has given the best descrip- tion of it. According to one view, which is not altogether unsupported, the internal layer alone concurs in the formation of the ciliary processes, while the external layer corresponds to the ciliary ring. The Iris. The iris {i, figs. 242, 243), so called on account of the varied colours which it presents, is a membranous vertical septum, perforated in the centre, like the diaphragm of an op- tical instrument. By means of this septum (i, fig. 241), the space {p) between the cornea (m) and the crystalline lens (f) is divided into two parts or chambers, an anterior and a posterior. The iris is circular, and perforated in its centre by an opening which consti- tutes the pupil {p, fig. 242), vulgarly, the apple of the eye, and which is surrounded by the lesser or inner border of the iris ; the pupil is circular in the human subject, and oblong, * [In successful injections, arterial as well as venous ramifications are demonstrated in the ciliary processes. 1 40 658 NEUROLOGY. either transversely or vertically, in the lower animals ; the number of luminous rays suf- fered to impinge upon the retina are regulated by variations in the size of this opening. We constantly find in several kinds of animals, and occasionally in the human subject, small fringes attached to the lesser border of the iris, which float in the aqueous humour. The outer or greater border of the iris is, as it were, fitted in between the ciliary liga- ment, which projects beyond it slightly in front, and the ciliary processes, which encroach upon it behind {see Jig. 241). The manner in which it adheres to these parts is not well understood. There is a true continuity of tissue, and yet they may be separated by a slight degree of force ; on this is founded the operation for artificial pupil by detaching the iris. The outer border of the iris is not continuous with the circumference of the cornea. The anterior surface of the iris {i, fig. 242), with its different shades of colour, is the part which is seen through the transparent cornea ; it is plane, not convex. The inter- val between it and the cornea constitutes the anterior chamber of the eye {fig. 241). The form and size of this interval can be correctly estimated in a frozen eye ; it is filled with the aqueous humour ; its longest diameter from before backward is about one line. When examined with a lens, the anterior surface of the iris has a flocculent appear- ance, more distinct than, but similar to, that of the external surface of the choroid. It appears as if it were fissured here and there, and in the human subject presents some very well-marked radiated bands. When the pupil is contracted these radiated banda are straight, but during its dilatation they become flexuons. They appear to interlace, and thus to become blended with each other near the pupil. It is generally admitted that the membrane of the aqueous humour covers the anterior surface of the iris ; but it cannot be demonstrated in that situation. The colour of this surface differs in different individuals, and it has generally some relation to that of the hair ; upon these differences depend the colour of the eyes, whether blue, black, gray, &c. Whatever may be the colour of the iris, two shades of different intensity may be distinguished in it, and occa- sion the appearance of two concentric coloured zones in this membrane ; the smaller and deeper-coloured zone is situated near the pupil ; the larger and lighter-coloured one in- cludes the two outer thirds of the membrane. It is not always easy to distinguish these two zones. The posterior surface {i, fig. 243) of the iris corresponds to the crystalline lens, from which it is separated by an interval filled with the aqueous humour, and called the pos- terior chamber of the eye {fig. 241). The two chambers of the eye, therefore, communicate at the pupil {p). The posterior surface of the iris is covered by a thick layer of pigment, which is con- tinuous with the pigment of the choroid ; near its outer border it is also overlaid by the free or iridian portion (c e) of the ciliary processes of the choroid, which can be easily turned back so as to expose the entire posterior surface. It presents extremely well- marked radiated bands, which can be well seen, even before the choroid pigment is re- moved. The aspect of the posterior surface of the iris differs essentially from that of the an- terior surface ; it is white and smooth, and resembles in many respects the internal sur- face of the choroid. Some anatomists are of opinion that the posterior surface of the iris is covered by the membrane of the aqueous humour. If such be the case, it is difll- cult to comprehend how that membrane is arranged with reference to the pigment. Structure. — The iris is three or four times as thick as the choroid ; it diminishes in thickness from its outer to its inner border. Its real structure is but little understood. The old opinion of its muscularity, which was refuted by Weitbrecht and Demours, has been revived by M. Maunoir, who admits two sets of muscular fibres, viz., radiated fibres, which correspond to the external coloured ring, and circular fibres, which correspond to the internal coloured ring, and form a sort of sphincter around the pupil ; but no circular fibres can be distinguished around the pupil. An appearance as if such were the case, is occasioned by a peculiar arrangement of the radiated fibres, which seem to bifurcate opposite the internal coloured ring, to interlace with each other, and then terminate ab- ruptly around the pupil ; so that the inner border of the iris, or the pupil, appears to be formed by the blunt extremities of these radiated fibres. In the ox and the sheep, the iris has two very distinct sets of fibres : an anterior and circular layer, which occupies the whole of the anterior surface ; and a posterior and radiated set of fibres, which converge from the outer to the inner border. The anterior set of fibres does not exist in the human subject. Another and much more plausible opinion regarding the structure of the iris is, that it consists of a vascular or erectile texture.* If we examine an oblique section of the iris under a lens, we find, indeed, that it has an areolar spongy structure ; and the extreme vascularity of this part also supports the same view. * A case is related of a young man who could produce contraction of the pupils by holding his breath. [The muscularity of the fibres of the iris i.s now established beyond a doubt ; the fibres of the iris of the pig are described by Schwann as being very minute, cylindrical, and not beaded ; thev therefore resemble the muscular fibres of organic life.] THE MEMBBANA PUPILLARIS, ETC. 659 Arteries of the Iris. — The arteries of the iris are principally derived from the two long ciliary arteries, which bifurcate and anastomose after they have reached the ciliary liga- ment, and form a vascular circle, which gives off radiated vessels that converge from the outer border of the iris towards the pupil. There are also some anastomotic arches near the pupil. Veins of the Iris. — The veins of the iris are much more numerous than the arteries ; they terminate in the venae comites of the long ciliary arteries, and in the vasa vorticosa. Nerves. — The nerves of the iris, or ciliary nerves {a a, fig. 242), are very large ; as we have stated, they gain the ciliary circle, and then pass through it in great numbers, to enter the iris, and be distributed in its substance. Most of these nerves are given off from the ophthalmic ganglion : some of them are derived directly from the nasal nerve, which is a branch of the fifth cranial nerve. The older anatomists distinguished two layers in the iris : one anterior, which they called the membrane of the iris ; the other posterior, covered with pigment, which they called membrana uvea. By examining an oblique section of the iris with a lens, two layers may, in fact, be seen, separated by the spongy tissue of which I have spoken The Memhrana Pupillaris. Dissection. — By opening the eye of the foetus from behind, this vascular membrane may be easily seen through the vitreous body and the crystalline lens. In the foetus, the opening of the pupil is closed by a membane, called the membrana pupillaris, which was discovered and very well described by Wachendorf, but more per- fectly so by Haller and Soemmering, and recently by M. Jules Cioquet. It may be seen about the third month of intra-uterine life, and generally disappears towards the seventh month. When persistent, it may occasion congenital blindness. Wachendorf and Soemmering have demonstrated the vessels of this membrane, which are continuous with those of the iris. During the existence of the membrana pupillaris, the membrane of the aqueous humour forms a shut sac. From the researches of M. Jules Cioquet con- cerning the pupillary membrane, it appears that it consists of two thin layers, between which the bloodvessels are arranged in loops ; that the convexities of these loops are turned towards each other, but that the loops which approach each other from opposite sides do not anastomose together ; that between these loops, and towards the centre of the pupil, there is a small irregular portion of the membrane which is destitute of ves- sels, and is, therefore, weaker than any other part ; that the formation of the pupil is effected by the rupture of this membrane, and that this rupture is occasioned by the re- traction of the vascular loops, which ultimately occupy the lesser border of the iris. Uses of the Iris. — The iris regulates the quantity of light that is admitted into the in- terior of the eye. The contraction of the pupil is an active movement, and its dilatation is passive ; facts which are opposed to the doctrine of its muscularity, but support the idea of its being a vascular and erectile structure. It has been stated that the movements of the iris are intended to enable us to judge of the distance and size of objects, or, rather, to enable us to see objects at different dis- tances : this is erroneous, for the pupil remains of the same size, under the action of a similar quantity of light, whether the object looked at be near or distant.* The effect of narcotics, and especially of belladonna, either applied topically, or taken internally, in producing dilatation of the pupil, is one of the most curious facts concerning the iris. The direct action of the rays of light upon the iris has no influence upon the size of the pupil, the dimensions of which are altered either by the action of light upon the retina, or in consequence of a peculiar condition of the optic nerve of the brain The Pigment of the Eye. It has been stated that the external surface of the choroid and the internal surface of the sclerotic are coloured by a very thin layer of pigment ; and also that the internal sur- face of the choroid is covered with a thicker layer, which is itself thickest on the fore part of that surface, near the ciliary body, between the greater ciliary processes, and be- hind the iris. By means of this pigment the interior of the eye is converted into a true dark chamber. StUl, it may be asked why the pigment is less abundant behind than in front. The choroid pigment is not black, but of a very dark-brown colour, like bistre ; in this respect resembhng the pigment of the skin of the negro ; it consists of molecules or globules insoluble in water. The pigment of the choroid of the iris is wanting in albinoes. as well as the cutaneous pigment. Both have the same chemical composition, t * [The pupil certainly dilates in looking at distant objects, and contracts under the opposite circumstances ; but it is by no means certain that the adjustment of the eye to objects at different distances depends on these alterations in the condition of the iris.] t [The pigment of the eye consists of nucleated cells containing the pigment granules ; on the inner surface of the choroid these cells are flattened and hexagonal, and their sides fit accurately together, so as to present an appearance like mosaic work ; on the back of the iris the cells are irregularly rounded. In albinoes the cells contain no coloured granules.] mi NEUROLOGY. In some animals the pigment of the eye has a metallic lustre, and an iridescent aspect in a great part of its extent. The Retina. The retina (r,figs. 241, 245), counting from without inward, is the third membrane ol the eye ; it is the immediate seat of vision, and is an essentially nervous membrane, sit- uated within the choroid and the sclerotic. Its external surface (jr,fi.g. 245) corresponds to the choroid, from which it is separated by the pigment, which, in eyes that have un- dergone slight decomposition, forms an irregular layer upon it, like a web. Dr. Jacob (Philosoph. Trans., 1819) has described a serous membrane between the retina and the choroid, in the cavity of which a dropsical effusion may occur, and constitute what is called ;)os. 247. It is certain that * [From recent researches, especially those of Valentin and Hanover, the following appears to be the mi- nute structure of the retina: 1. The membrane of Jacob consists of minute cylindrical or prismatic bodies, placed closely together, and perpendicularly to the surface of the membrane ; among these are somewhat lar- ger bodies, "coni gemini," which might be compared in shape to two cylinders applied to each other length- wise. Both kinds of bodies are attached by one extremity to the inner surface of the choroid, being received into exceedingly minute sheaths, which rise from the surface of the pigment cells. 2. The filaments of the optic nerve spread out on the inner surface of this structure, and, according to Valentin, have a plexiform ar- rangement, but their mode of termination seems doubtful. This nen-ous expansion is covered on its outer and also on its inner surface by a layer of ganglionic globules.] t [The vitreous humour, according to Ilerzelius, contains 98'4 per cent, of water ; its solid matter consists of albumen, extractive matter, and chloride of sodium.] 662 NEUROLOGY. a circular layer, having the form of a radiated crown, is given off from the anterior part of the hyaloid membrane ; this circular radiated disk w^as described by Petit and Cam- per, but it is called the corona ciliaris, or the zonula Zinni : it corresponds accurately to the ciliary processes and ciliary body of the choroid coat. The ciliary zone of Zinn (a, Jig. 245, b, figs. 247, 248), or the ciliary processes of the vit- Fig.m. reous body, can be seen through that transparent body {d,fig. 241) when the several coats are removed from the back part of the globe of the eye : it is completely exposed to view when the cho- roid coat and the iris are separated from the vitreous body {fig. 248). It is this structure which constitutes the beautiful radiated crown situated in front of the vitreous body around the crystalline lens, and which extends considerably beyond the ciliary body of the choroid ; it consists of alternate black and transparent rays, and is generally regarded as a reverse impression of the ciliary processes of the choroid. The ciliary processes of the vitreous body correspond to the black lines, and the intervals between the processes to the transparent rays. The ciliary processes of the vitreous body are not so thick as those of the choroid ; but the folds of which they consist commence farther back than the ciliary processes of the choroid, so that the radiated disc formed by them is larger than that formed by the processes of the choroid. These folds of the vitreous body have the same spongy and jagged appearance as those of the choroid : they have no free portion, or, rather, that part of the zone of Zinn (a, fig. 248) which corresponds to the free portion of the ciliary processes of the choroid is applied to the crystalline lens. The cihary processes of the choroid and those of the vitreous body are so arranged that those of the one are received in the intervals between those of the other. It ap- pears to me difficult to determine whether they are simply applied to each other, or whether their structure is continuous. However, on examining these parts through a lens while they are being separated, it has appeared to me that a sort of cellular struc- ture was lacerated, and that the black pigment, which had been hitherto confined, es- caped together with a little fluid. M. Ribes believes that, during this separation, some shreds of the hyaloid membrane are drawn away with the ciliary processes of the choroid. The inner border (a) of the cihary zone of Zinn is in contact with the margin of the crystalline lens (/), and adheres rather firmly to it. Around the outer border, which ex- tends beyond the ciliary body of the choroid, are found the origins of certain radiated folds (i), which form, as it were, the commencement of the ciliary processes. This bor- der adheres to the anterior margin of the retina {m, fig. 245), which appears to me to be thickened and shghtly uneven in this situation, and not to be continuous with the hya- loid membrane. From what has been stated, it follows that the canal of Petit is formed between the hyaloid membrane and the zone of Zinn, and that the crystalline lens is fixed by this zone to the anterior margin of the vitreous body ; that the anterior surface of the crys- talline lens is not covered by a prolongation of the hyaloid membrane, besides its own capsule ; and that the retina does not reach as far as the margin of the crystalline lens. M. Jules Cloquet has described, under the name of the hyaloid canal, a cylindrical pas- sage, which is formed by the reflection of the hyaloid membrane into the interior of the vitreous body around the nutritious artery of the lens, and which, like that artery, trav- erses the vitreous body from behind forward. I have never been able to see this canal. No vessels have been demonstrated in the hyaloid membrane ; it does not receive any from the retina, and yet we cannot doubt that it is provided with them. Although the structure of the ciliary processes of the vitreous body is little known, yet, as it is probable that it is similar to that of the ciliary processes of the choroid, and, therefore, essentially vascular, it may be, as stated by M. Ribes, that the materials for the forma- tion and nutrition of the lens and of the ciliary processes of the vitreous body are con- veyed to both of these parts through the vascular ciliary processes of the choroid. The Crystalline Lens and its Capsule. The crystalline lens {I, figs. 241, 244, 245, 248) is a transparent body, having the form of a lens, as its name implies ; it is situated at the junction of the posterior three fourths with the anterior fourth of the globe of the eye, and is placed between the vitreous body, which is behind, and the aqueous humour, which is in front {see fig. 241). Its axis corresponds to the centre of the pupil. It is shaped like a double convex lens, the posterior surface of which is more convex than the anterior. From some very exact and minute investigations which have been made upon this point by Fran5ois Petit and others, it appears that both the relative and the absolute convexity of the two surfaces of the crystalline lens are subject to great varieties in different individuals ; that, in general, the posterior convexity forms part of a circle from four to five lines in diameter, while the anterior forms part of one from six to nine lines in diameter. In some subjects the degree of curvature of the two surfaces THE CRYSTALLINE LENS AND ITS CAPSULE. 668" of the crystaDine lens is almost equal. In the foetus the crystalline lens approaches the spheroidal form, which is that which it has in fishes. The anterior surface of the crystalline lens corresponds to 'the iris, from which it is separated by the aqueous humour. It has been incorrectly stated by Winslow that the crystalline lens pushes the iris forward : there is a space between the crystalline lens and the iris which constitutes the posterior chamber of the eye. The anterior surface of the lens may be seen through the pupil, so that slight shades of difference in the col- our of the lens may be detected. When the pupil is very much dilated, the anterior sur- face of the lens is entirely exposed. Its posterior surface is in relation with the vitreous body, which is depressed so as to receive it. This surface does not adhere to the hyaloid membrane. When dissecting a subject of twenty-seven years of age who had suffered with hydrophthalmia in both eyes, M. Ribes found about six grains of a limpid fluid between the hyaloid membrane and the crystalline lens ; so that the space occupied by tliis fluid might have been taken for a third chamber. The margin of the lens {I, fig. 248) is set (like the stone of a brooch) in the ciliary pro- cesses (a) of the vitreous body, which cover and adhere to the fore part of that margin, so that the lens is kept firmly in its place. Its margin is surrounded by the canal of Petit {fig. 247). The crystalhne lens presents different shades of colour at different periods of life. It is reddish in the foetus, but is perfectly transparent after birth ; in the adult, it becomes slightly opaline at the centre ; in the aged, it acquires a yellowish opacity, which ap- proaches somewhat to the colour of amber or topaz. Morbid opacity of the lens consti- tutes lenticular cataract. The crystalline lens consists of a capsule, and of a proper substance enclosed within it. The Substance of the Crystalline Lens. — When stripped of its capsule, the crystalhne lens is found to have three degrees of consistence, at different parts : thus, at its sur- face, it is almost of a liquid softness ; below this, it is soft and gelatinous, and may be crushed by the finger — this is the cortical layer ; and, lastly, it is hard in the centre, which is called the nucleus, and closely resembles a mass of gum-arabic. The most superficial and fluid layers constitute the liquor Morgagni. The substance of the crystalline lens consists of concentric layers {b c, Jig. 249), which can be very easily demonstrated, even without any previous preparation, but are rendered most distinct by boiling, or immersion in a diluted acid. The crystalline lens then separates into su- perimposed laminae or scales, like the bulb of the onion. The different degrees of consistence observed in the substance of the lens do not depend upon differences in na- ture, but upon mere modifications. When hardened by an acid, the structure of the lens is exactly the same throughout : even the liquor Morgagni appears to become laminated. Each of these concentric lamina; is itself composed of radiated fibres (a. Jig. 249), which can be readily seen without dissection, by placing one of them upon a black sur- face, and examining it through a lens, or even by a strong Ught. Lastly, the crystalline lens, when boiled, or submitted to the action of an acid, splits into three, four, or even a greater number of triangular segments (ab), all of which unite by their summits at the centre of the lens, so that its anterior and posterior surfaces have a stellate appearance.* Pathologists have successfully applied this anatomical fact to the explanation of the stellate forms of cataract, in which the opacity branches out in three or more directions. What is the nature of the crystalline lens 1 Is it the product of a secretion 1 or is it an organized structure 1 M. Duges has recently supported by his authority and by ad- ditional facts the opinion of Dr. Young, who believed that the crystalline lens is not only an active organized structure, supplied with vessels and veins, but that it is even mus- cular and possessed of contractility, so as to be able of itself to increase or diminish its curvatures and its density, thus endowing the eye with the power of adjusting itself to the different distances %f the objects to be seen. The substance of the lamina; of the crystalline lens has, indeed, a linear structure ; but it does not at all resemble muscular tissue, either in its consistence or in its regularly stratified character. I conceive, therefore, that I am warranted in regarding the superimposed layers of the crystalline lens as the solidified product of a secretion formed by its capsule, t * See note, infrd. t [The lines indicating- the divisions between the triangular segments of the lens (a, Jig- 249) are called sep- ta; the septa of the anterior surface are placed opposite the intervals between the septa of the posterior sur- face. The fibres of which the laminie are composed have a linear arrangement, and, as discovered by Sir D. Brewster, are fitted into each other by indented margins {Jig. 250). Schwann has shown that those fibres are developed from rounded, nucleated cells, which become elongated into fibres, the margins of which sub- The capsule of the crystalline lens (jt,fig- 241) is accurately fitted to the lens itself; iff the healthy state it is transparent, but may become opaque, and thus constitute a mem- branous or capsular cataract. Its external surface is free in front, where it is bathed by the aqueous humour : it is merely in contact with the hyaloid membrane behind, but its circumference adheres in- timately to that membrane, or, rather, to the ciliary zone of Zinn. Its internal surface does not appear in the slightest degree adherent to the lens. If an incision be made into this capsule in the living subject, the lens is forced out merely by the tonicity of the coats of the eye. The anterior segment of the capsule is twice as thick as the posterior : it might be compared to a layer of the cornea,* It receives bloodvessels derived from the arteria centralis retinae. t These vessels, according to Meckel, are distributed only upon the posterior half of the capsule ; those which belong to the anterior half arise from the vessels of the ciliary processes. Some anatomists believe that these vessels send ramifications between the different concentric laminae of the crystalline lens for its nutrition ; but I am not aware that they have ever been demonstrated. No nerves have been discovered in the crystalline lens. M. Duges believes that the retina gives off some net vous filaments which reach as far as the lens, and spread out upon its capsule ; but, after the most careful examination, I am convinced that such is not the case. The Aqueous Humour and, its Membrane. The term aqueous humour is applied to a perfectly limpid and transparent fluid, which occupies the two chambers of the eye. These two chambers, which have been correctly understood only since the discovery of the true seat of cataract in the crystalline lens, correspond to that small portion of the cavity of the eye which is situated between the cornea and the lens {see fig. 241). The space between these two parts is divided un- equally by the iris (i) into two chambers : an anterior and larger, which is called the an- terior chamber; and a posterior and smaller, named the -posterior chamber. These two chambers communicate through the pupil (jpi). The existence of the posterior chamber was long disputed, but it may easily be proved by freezing the eye ; and by the same experiment we may obtain an approximation to the relative capacity of the two cham- bers, which will be found as 3 to 1, the anterior being decidedly the larger. The total quantity of the aqueous humour is about five grains ; 100 parts of it are found to contain 981 of water, with traces of albumen and chloride of sodium. The Membrane of the Aqueous Humour. — It is now generally admitted that the aqueous humour is secreted by a special membrane, called the membrane of the aqueous humour, or membrane of Demours, although it had been previously described by Zinn and Descemet. This membrane, according to Demours, hues the posterior surface of the cornea {m,fig. 241), and is reflected upon the front of the iris. At this point, according to most anat- omists, it is lost, and cannot be traced to the pupil ; but, according to others, it proceeds as far as the pupil, and there terminates ; and, lastly, some believe that it is reflected through the pupil, in order to cover the posterior surface of the iris, where it retains the pigment in its situation. It is easy to detach a tolerably thick and strong layer, of a cartilaginous aspect, from the posterior surface of the cornea, either after long-continued maceration, or after slight boiling ; but it is not shown that this is anything more than the posterior layer of the cornea, which it resembles in appearance. It is only from analogy that the existence of the membrane of the aqueous humour can be admitted. We cannot demonstrate anatomically its reflection upon the outer border of the iris ; and, moreover, it is certain that it does not exist upon either surface of that membrane. According to M. Ribes, the aqueous humour is supplied by the vitreous body, and is poured into the posterior chamber by the canals said by him to exist in the substance of the ciliary processes of the vitreous body. This opinion is founded, 1. Upon an exper- iment which consists in carefully removing the cornea, and suspending the eye by the optic nerve, when the vitreous humour will exude from the wound of the cornea, so that, in less than twenty-four hours, two thirds of that body will have escaped ; and, 2. Upon the observation of cases of imperfect iris, in which, according to M. Ribes, the aqueous Fig. 250. • — - sequently become dentated ; the lens, therefore, resembles some other non-vascular parts (as the horny tissues) in its mode of growth. It consists, according to Berzelius, of 58"0 per cent, of water, 3'7 of extractive and salts, 2'4 of membrane, and 35"9 of a peculiar Bubstanee, which, except in its colour, resembles the colouring matter of the blood. * According to M. Ribes, whom I always have pleasure in quoting, btcause his re- searches are worthy of every confidence, " by examining the internal surface of the crys- talUne capsule in a good light, and with a good lens, a series of transverse fissures are observed around its entire circumference, where the anterior and posterior segments of the capsule unite. I could never satisfy myself whether these fissures corresponded to the ciliary processes of the vitreous body, or to the villous fringes of the ciliary processes of the choroid." T Vide fig. v., pi. 6, of Soemmering's Icones Oculi Humani. THE ORGAN OP HEARING. Bnrhdur is contained entirely in the posterior chamber. He believes that the free por- tion of the vitreous ciliary body has the power of absorbing this liquid. M. Duges adopts the following modification of this opinion : the canal of Petit, accord- ing to him, is divided into as many compartments as there are ciliary processes. It re- sembles, therefore, a collection of short canals directed from before backward, rather than a single circular canal ; these short canals communicate behind with the vitreous body, and open in front by certain slits or perforations existing in the Zone of Zinn, which enable the aqueous humour secreted by the vitreous body to escape in front of the crys- talline lens. Haller has stated all the opinions which have been entertained regarding the produc- tion of the aqueous humour, which has been said to be secreted by the vitreous body, as believed by MM. Ribes and Duges, by the ciliary processes, by the choroid, by the iris, and, lastly, by certain special ducts proceeding from without the eye, and perfora- ting the sclerotic at its junction with the cornea. The Vessels and JVerves of the Eye. The arteries of the eye are the following : a considerable number of short posterior cil- iary arteries, which surround the optic nerve, perforate the sclerotic near it, and ramify in the choroid, m the ciliary processes, and in the iris ; the anterior short ciliary, which perforate the anterior part of the sclerotic, and are distributed to the iris ; the long cilia- ry arteries, two in number, which run between the sclerotic and the choroid, as far as the outer border of the iris, and then, bifurcating and curving inward, anastomose with each other around that border. From the vascular circle thus formed most of the ves- sels of the iris are given off. The central artery of the retina {arleria centralis retina) en- ters the globe of the eye through the centre of the optic nerve (at the porus opticus, b, fig. 246), and, sending off a branch to the crystalline lens, which traverses the vitreous body from behind forward, covers the internal surface of the retina with its other rami- fications. The veins correspond to the arteries, but are much more numerous. The posterior, or short ciliary veins, form vortices or whorls in the choroid, and are hence called vasa vorticosa (v, fig. 244). All the veins of the globe of the eye open into the ophthalmic and angular veins. The nerves of the eye consist of a special nerve called the optic nerve, the origin, course, and structure of which will be described hereafter (see Cranial Nerves) ; and, second- ly, of the ciliary nerves, which are derived from the fifth nerve, either directly from its nasal branch, or indirectly from the ophthalmic ganglion. These nerves (a a, fig. 242) are distributed to the ciliary ligament, and to the iris. The Organ of Hearing Hearing is that sense by which we perceive the vibrations of the air, which produce tound. The organ of hearing is not situated in the face, like those of the other senses, but is contained in the substance of the base of the cranium, in the petrous portion of the tem- poral bone, its deep situation preserving it from external violence : it is composed essen- tially of a membranous and nervous apparatus contained in an extremely complicated osseous cavity, named the labyrinth or internal ear. The labyrinth if, fig. 251) communicates with the exterior by means of an acoustic trumpet formed by the auricle, or pinna (a), and external audita- p^g 251. ry meatus (b), and named the external ear, which may be regard- ed as an apparatus for collecting sonorous undulations. The term middle ear, or tympanum, is applied to a cavity (d) which is placed between the labyrinth and the external ear, and may be considered as an apparatus for modifying sounds, the intensity of which is increased or diminished by it, according as they happen to be weak or loud.* It follows, therefore, that the ear is formed by a succession of cayities, which, proceed- ing from without inward, are, the external ear, consisting of the auricle and external auditory meatus, of the middle ear, or tympanum, and of the internal ear, or labyrinth. I shall de- scribe the ear in this order, and shall thus proceed from the less to the more complica- ted parts of this organ. The External Ear. The exiexnal ear resembles a funnel or ear-trumpet, the expanded part of which rep- resents the auricle, while the contracted portion corresponds to the external auditory meatus. + * M. Richerand (Elemens de Physiologie, first edit.) has drawn an excellent comparison lictween the uses of the tympanum in hearing-, and those of the iris in vision. 1 The external ear, properly speaking, only exists in mammalia- and eren among- mammalia, those -which do not hve constantly in the air are not proirjded with it. 4P NEUROLOGY The Auricle. The auricle of the ear {auricula, 'pimia), commonly called the ear, is placed at the side of the head, behind the articulation of the lower jaw, and in front of the mastoid process ; it is an oval elastic lamina, folded in various ways upon itself, and having an undulated surface. The auricle or pinna is free above, behind, and below, but is so firmly attached in front and on the inner side, that the two ears can support the weight of the entire body. The individual varieties in the shape, direction, prominence, and size of the auricle are generally known. Of these varieties, some are congenital, and others acquired. Among the latter should be noticed the effects produced by the habit of confining the entire ear more or less closely by the head-dress. The direction or prominence of the auricle is not without some influence upon hearing, the perfection of which sense, ac- cording to Mr. Buchanan, depends on the kind of angle formed by the auricle with the side of the face, and which should be from 25° to 30°. The internal or mastoid surface of the auricle presents certain eminences and depres- sions, which correspond inversely with those on its external surface. The external surface is remarkable for the alternate ridges and depressions observed Fig. 252. upon it : at its centre, but somewhat nearer to the lower than the up- per part, we find the concha (a, fig. 252), a funnel-shaped excavation, the form and expansion of which are familiar to all, and at the fore part of the bottom of which is found the orifice of the external audito- ry meatus. The concha is bounded in front by the tragus {h ), a triangular pro- cess, the adherent base of which is turned forward and inward, while iM^n~JljiS^ its free apex is directed backward and outward : it advances like a lid over the orifice of the external auditory meatus, which is com- pletely closed by its depression. The posterior surface of the tragus, which forms part of the concha, is covered with stiff hairs, especially in old subjects ; whence its name of tragus, from rpdyog, a goat. The use of these hairs is to arrest any small particles that are floating in the air. Behind and below, that is, opposite the tragus, the concha is bounded by the anti-tra- gus (c), a triangular tongue, which is smaller than the tragus, and is separated from it by a wide, deep, and rounded notch, named the notch of the concha (incisura tragica). Behind and above, the concha is bounded by the anti-helix (e), a curved fold, which commences above the anti-tragus, being separated from that part by a slight depression, passes upward and forward, bifurcates, and then ends in the groove of the helix. The superior branch of the bifurcation of the anti-helix is broad and smooth, while the inferi- or is sharp ; between them is situated a slight depression, called the scaphoid, or navicv^ lar fossa, but which would be more correctly named Vae fossa of the anti-helix (/). The term helix {ili^, a roll, from kTiiacu, to roll around) is applied to a curved fold {g g), which forms the external border of the auricle : it commences in the cavity of the concha, which it divides into two unequal parts, one superior and narrow, the other in- ferior and broader ; gradually increasing in size, it then passes upward and forward above the external meatus, then above the tragus, from which it is separated by a very distinct furrow : it next runs directly upward, curves backward, descends to form the posterior margin of the auricle, and terminates by becoming continuous with the anti-helix in front, and with the lobule {I) behind. The groove or furrow of the helix is the groove (i) which surrounds the helix, and sep- arates it from the anti-helix. The lobule occupies the lower or small extremity of the auricle, from the rest of which it is distinguished by its softness ; it is surmounted by the tragus in front, by the anti- tragus behind, and by the notch of the concha in the middle. The lobule of the ear va- ries exceedingly in size in different individuals, and is the part to which ear-rings are generally appended. The Structure of the Auricle. — The cartilage of the ear {figs. 253, 253*) constitutes the Fig. 253. Fig. 253.* framework of the auricle, in a great measure deter- mines its shape, and is the cause of its phability and elasticity. When the skin is removed from it, this cartilage, therefore, presents certain eminences and depressions, corresponding, with some exceptions, to those already described as existing upon the surface of the auricle. The cartilage of the ear has no part corresponding with the lobule : again, the cartilaginous fold which consti- tutes the helix terminates at the middle of the concha, from whence it is continued by a fold of skin, which, moreover, covers it throughout, and increases its prominence. Upon the cartilage of the auricle we also observe the following parts : 1. A mammillated eminence {a, fig. 253V THE AURICLE. 667 called the p-ocess of the helix : it is of considerable size, is very dense, and arises from the anterior margin of the helix, above the tragus. This process gives attachment to a ligament. 2. A tail-shaped tongue of .cartilage (5), separated from that of the anti-tragus and concha by a very long fissure, which is occupied by ligamentous fibres. This tongue is formed by the united ends of the helix and anti-helix, and is very thick and dense : it may be called the caudal extremity of the helix and anti-helix ; it supports the base of the lobule. 3. A well-marked thickening, situated opposite the concha, and characterized by a dead white colour. This thickening occupies a vertically elongated portion of the mas- toid surface of the concha, and terminates at the lower part of the auricular cartilage : it seems to be intended to preserve the form of the concha, which cannot be flattened unless this thickened portion of the cartilage is first divided. Several fissures or notch- es are also found in the cartilage of the ear, which is thus imperfectly divided into sev- eral pieces that are movable upon each other, and united together by ligaments. The principal fissure, independently of that already described as existing between the anti- tragus and the caudal extremity of the helix and anti-helix, are, a small vertical fissure upon the anterior margin of the heUx ; another vertical fissure upon the tragus ; several irregular notches in the helix ; and, lastly, a much more important fissure, to which I shall have to allude in describing the external auditory meatus. It is situated between the helix and the tragus, and is prolonged upon the outer half of the orifice of that meatus. The skin of the auricle is remarkable for its thinness and transparency : hence the sub-cutaneous vascular network can be seen through it without dissection ; it is no less remarkable for its tension, and its close adhesion to the cartilage, upon which it is mould- ed, so as accurately to reveal its form. The portion of skin which covers the concha is especially remarkable for its great tenuity and intimate adhesion to the cartilage. The skin upon the free border of the auricle adheres but slightly to, and projects be- yond the helix ; the same fold of skin, when doubled upon itself and prolonged below the helix, constitutes the lobule, which, together with the adjacent part of the free border of the auricle, is nothing more than a duplicature of the skin, containing some soft fat. A small quantity of fat is formed around the entire circumference of the auricle, but none exists in other situations. The skin of the ear is provided with sebaceous folhcles, which can be easily shown by maceration, after the method employed by Soemmering, and which are most numerous in the concha and the scaphoid fossa. The ligaments of the auricle are divided into the intrinsic and the extrinsic ligaments. The extrinsic ligaments are, the posterior ligament, which is a thick, tendinous layer, ex- tending from the concha to the mastoid process ; the anterior ligament, which is a triangu- lar, very broad, and very strong hgament, arising from the process of the helix and the ad- jacent part of the border of the helix, and terminating at the zygomatic arch, where it is blended with the superficial temporal fascia ; and, lastly, the ligament of the tragus, which is very strong, and extends from the tragus to the adjacent part of the zygomatic arch. The intrinsic ligaments, the object of which is to keep the cartilage of the auricle fold- ed upon itself, are, the ligament which keeps the caudal extremity of the helix applied to the concha ; the very strong ligament which extends from the tragus to the helix, and . unites the outer half of the auditory meatus to the cartilage of the auricle ; some very strong bundles, which are situated upon the mastoid surface of the auricle, and are in- tended to preserve its convolutions, for when they are divided the auricle may be un- folded ; lastly, those most remarkable ligamentous bundles, which occupy the fold pre- sented by the inferior branch of the bifurcation of the anti-helix. The three extrinsic muscles of the ear, which exist in a rudimentary condition in the human subject, but are so highly developed in timid animals, are intended to move the auricle as a whole (see Myology). The intrinsic muscles move the different parts of the auricular cartilage upon each oth- er. Like the extrinsic, they are quite rudimentary. There is no difference in their size in savage and civilized races. They are five in number, four of them being situated on the concave, and one only on the convex, or mastoid surface of the auricle. The great muscle of the helix (helicis major, c, fig. 253) is situated vertically upon the anterior part of the helix, near the tragus ; it is a narrow, oblong tongue, fleshy in the middle, and tendinous at its extremities ; its fibres are vertical. The small muscle of the helix (helicis minor, d), the smallest of the intrinsic muscles of the ear, lies upon that portion of the helix which divides the concha into two parts. The muscle of the tragus (tragicus, e) is a broad band, lying upon the external surface of the tragus ; its fibres are directed vertically. The muscle of the anti-tragus (anti-tragicus,/) is a tongue-like bundle, which covers the external surface of the anti-tragus, and is inserted by a tendon to the upper part of the caudal extremity of the helix. Its use may be to move this caudal extremity upon the anti-tragus. The fifth is the transverse muscle (transversus auriculae, a, fig. 353*), which is situated 4 NEUROLOGY. on the mastoid surface of the auricle. According to Soemmering, it consists of a trans- verse layer of fibres of unequal length, which spread out in a semicircular form from the convexity of the concha to the ridge, corresponding to the groove of the helix. I doubt the muscularity of these fibres, which I am inclined to regard as constituting an intrin- sic ligament intended to preserve the fold of that portion of the anti-helix by which the concha is bounded behind and above. The arteries of the auricle are the posterior auricular, a remarkable branch of which passes through the cartilage, between the caudal extremity of the helix and the concha, so as to ramify in the cavity of the concha. All the branches of the posterior auricular arteries turn over the free border of the helix, so as to reach the concave surface of the auricle. The anterior auricular arteries arise from the external carotid and the tempo- ral, and divide into inferior branches or arteries of the lobule and ascending branches. The vei7is have the same names and follow the same course as the arteries. The nerves of the auricle are derived from the auricular branch of the cervical plexus ; three or four of them ramify upon the internal surface of the auricle. A remarkable branch perforates the cartilage between the anti-tragus and the caudal extremity of the helix, and is distributed to the skin which lines the concha.* The External Auditory Meatus. The external auditory meatus {b,fig. 251) is a partly cartilaginous and partly osseous canal, extending from the concha (a) to the membrane of the tympanum (c). It fonns the narrow portion of the ear-trumpet represented by the external ear. It is about an inch in length. Its section represents an ellipse, of which the longest diameter is vertical. Its direction is transverse, and it describes a very slight curve, having its convexity turned upward. Moreover, near its external orifice it is bent at an angle which projects upward, and hence it is necessary to draw the auricle upward and backward, if we wish to examine the bottom of the external auditory meatus. The external meatus is in relation with the temporo-maxillary articulation in front, with the mastoid process behind, and with the parotid gland below. Its external orifice, which is vertically oblong, more or less widened out in different in- dividuals, and covered with hairs in old age, occupies the anterior and inferior part of the concha behind the tragus, which serves as a lid for it. It is bounded behind by a sort of semilunar ridge, which projects more or less forward in different individuals, so as to contract its orifice to a greater or less extent. In front of the auditory meatus there is an excavation or fossa concealed by the tragus, and named the tragic fossa of the co7icha ; it forms, as it were, the vestibule of the meatus. The internal orifice of the auditory meatus is circular : it is directed very obliquely downward and inward, and is closed by the membrana tympani. Structure. — The auditory meatus consists of an osseous portion, and of a cartilaginous and fibrous part. The osseous portion has been already described with the temporal bone, as the external auditory meatus. It is wanting in the foetus, and in the new-born infant, in whicli its place is supplied by the tympanic ring or circle. We have stated that, in the adult, this ring forms an osseous lamina distinct from the rest of the temporal bone, that it rests behind upon the mastoid and styloid processes, for the latter of which it forms the vagi- nal process, and that it is separated in front from the auricular portion of the glenoid cavity by the fissure of Glasserius ; this lamina forms both the anterior and inferior walls of the auditory meatus and cavity of the tympanum. The cartilaginous and fibrous portion forms the outer half of the external auditory mea- tus, and may be separated from the cartilage of the auricle by a careful dissection. If an incision be made over the similunar ridge which constitutes the outer border of the orifice of the auditory meatus, it will be seen that this ridge is formed by the juxtaposi- tion of two cartilaginous borders, one of which belongs to the concha, and the other to the auricle, and which are united by fibrous tissue. If the dissection be continued be- tween the tragus and the corresponding part of the helix, the auricle may be separated from the auditory meatus, exceping below, where their continuity is established by means of a tongue or isthmus of cartilage. The tragus belongs essentially to the auditory meatus, the cartilage of that canal being merely a prolongation of the tragus folded upon itself (see b,fig. 253*), so as to form- the lower two thirds or three fourths of a cylinder. The inner end of this imperfect cylin- der is attached to the rough external rim oi the osseous portion of the meatus by means of a fibrous tissue, which extends farther above and behind than below and in front, and which gives the cartilage a great degree of mobility ; there is a thick prolongation or process at the lower and anterior part of the inner end of the cartilage of the meatus. The fibrous portion of the auditory meatus forms the upper third or fourth of that canal, and also fills up the large notch in the inner end of the cartilaginous portion. * [The auricle also receives twigs from the posterior auricular branch of the facial nerve, from the auriculo- temporal branch of the inferior maxillary division of the fifth nerve, and from a small branch of the pneumo- fastric nerve. See description of those nerves.] THE TYMPANOM. Near the tragus there are two or three fissures or divisions in this cartilage, named the fissures of Santorini, which give it some resemblance to the rings of the trachea : these fissures are at right angles to the length of the canal, and are filled up with a fibrous tissue, which some anatomists have conceived to be mixed with muscular fibres, or to consist entirely of muscular fibres intended to move the small and partially separa- ted portions of the cartilage. It is evident that the mode in which the partly cartila- ginous and partly fibrous portion is united with the osseous portion of the canal, and also the existence of the fissures just described, have reference to the mobility of the entire canal. The internal surface of the auditory meatus is lined by a prolongation of the shin, which is remarkable for its extreme thinness. It becomes thinner and thinner in ad- vancing from the orifice to the bottom of the meatus ; and the fineness and extreme del- icacy of that portion of the skin which corresponds to the osseous part of the meatus deserves special attention. The skin of the meatus is also characterized by being cov- ered in all parts with fine downy hairs ; a fact which proves that it is of a cutaneous structure, and not a mucous membrane. In old subjects, there are some tolerably long hairs at the commencement of the auditory meatus, as well as upon the internal surface of the tragus ; they prevent the entrance of dust and insects, which, moreover, get in- volved in the ceruminous secretion. The skin of the meatus is farther characterized by the presence of a number of se- baceous follicles, or glands, called the ceruminous glands,* the orifices of which are vis- ible to the naked eye, and give the skin an areolar appearance. These small glands oc- cupy the entire inner surface of the cartilaginous and fibrous portions of the auditory meatus : from their yellowish-brown colour, they can be readily seen in oblique sections of the skin. They secrete a rather thick unctuous substance, resembling wax, whence it is called cerumen {cera, wax). It is very bitter, and is partially soluble in water, with which it forms an emulsion which leaves a greasy stain upon paper ; it sometimes be- comes exceedingly hard from remaining long in the passage, and then acts as a mechan- ical cause of deafness. By analysis, this substance, according to Berzelius, yields a fatty oil, an albuminous substance, and a colouring matter, and, according to Rudolphi, a bitter principle like that of the bile. Nature intended, says Soemmering, that there should be a sufficient quantity of cerumen, not only to keep out insects, but also to di- minish the intensity of sonorous vibrations. It is, therefore, a bad habit to remove it artificially, unless there be an abnormal accumulation of this substance. The Middle Ear, or Tympanum. Dissection. — The cavity of the tympanum may be laid open, either from its external wall, by removing the membrana tympani, or from its upper wjdl, by cutting away the anterior part of the base of the petrous portion of the temporal bone with a strong scal- pel ; the situation in which this may be done is indicated by a fissure, or, rather, a su- ture, which exists between the petrous and squamous portions ; lastly, the tympanum may be opened from its lower M^all, by breaking down the osseous plate of the auditory meatus. In order to show all the parts contained in the cavity of the tjTnpanum, several speci- mens should be prepared in different ways. It is of importance, moreover, to study the ear in the temporal bones of the adult subject and the fcetus, as well in macerated speci- mens as in such as have been dried without previous maceration. The tympanum, tympanic cavity, or drum of the ear {tympanum, a drum, d, fig. 251), is a cavity situated between the external auditory meatus (b) and the labyrinth or interned ear (/) ; it communicates with the pharynx, and, consequently, with the air-passages, by means of the Eustachian tube (e, fig. 255) ; it is prolonged into the mastoid process, by means of the mastoid cells (c), and it is traversed by a chain of small bones (1, 2, 3), neuned the ossicula audittis. The tympanum is placed in the anterior part of the base of the petrous portion of the temporal bone, above the osseous lamina of the external meatus, and in firont of the mastoid process ; it is directly continuous with the osseous portion of the Eustachian tube, of which it seems only to be a dilatation. From its form, which is otherwise irregular, or, rather, from the two dry membranes formed upon its opposite walls, it has been compared to a military drum ; it is flattened from without inward, so that its transverse diameter is the shortest. It presents for our consideration an internal and an external wall, and a circumference. The External Wall of the Tympanum. — This wall is formed by the membrana tympani, and by that portion of the temporal bone in which the membrane is fitted. This portion of the temporal bone is a compact lamina, which is flat in the human subject, but ex tremely prominent in some animals. The membrana tympani {c,fig. 251) is a nearly circular, semi-transparent membranous septum, dry-looking like parchment, and vibratile ; it is situated between the external * [The ceruminous glands consist of a long- conToluted tube, closed at one end, and opening by the other upon the internal surface of the meatus.] NEUROLOGY. auditory meatus, at the bottom of which it may be seen in the living subject, and the cavity of the tympanum. It is directed very obliquely downward and inward ; so that, instead of passing perpendicularly across the auditory meatus, it is continuous, at a very slight angle, with the upper wall of that canal. In consequence of this obliquity, the membrana tympani unites with the lower waU of the meatus at an angle of about 45°, and the meatus itself terminates in such a manner that its lower wall is much longer than the upper. The external surface of the membrana t)mipani is free, and is directed downward and outward ; the internal surface is turned upward and inward, and adheres very firmly to the handle of the bone of the ear, called the malleus, by which it is drawn inward, so that its centre presents a funnel-shaped depression, which is concave externally and convex within. The circumference of the membrane is fitted, like a watch-glass, into a circular furrow formed at the inner end of the external meatus in the adult, and into the tympanic ring in the foetus. Above and behind, near its insertion into its bony frame, the membrana tympani is elevated by a small process (the short process) of the malleus. Immediately on the inner side of the insertion of the membrana tympani, opposite the posterior extremity of a line drawn across its middle, is situated a small foramen, the orifice of a canal which transmits the chorda tympani nerve. Is the membrana tympani perforated 1 Some anatomists have asserted that there is an aperture between the membrane and the bone, at one point of its circumference ; and others have believed that an oblique slit traverses the membrane. But these perfora- tions do not exist in the natural state ; so that the membrana tympani forms a complete septum between the tympanum and the external auditory meatus. Notwithstanding its tenuity and transparency, the membrana tympani consists of three very distinct layers. The external or epidermic layer is a prolongation of the epidermic portion only of the skin which lines the external meatus. The internal or mucous layer is a prolongation of the extremely thin mucous mem- brane which lines the tympanum. The handle of the malleus is situated between this and the middle layer. The middle or proper layer, on which the strength of the membrane depends, appears to be of a fibrous nature. According to Sir Everard Home, it is muscular ; he states that he distinctly saw muscular fibres radiating from the centre to the circumference, first in the elephant, and afterward in the ox, and in the human subject.* By fine injections some very delicate vessels are demonstrated in the membrane. The network represented by Scemmering, who only injected the arteries, is not nearly so dense as that which may be displayed by filling the veins. If a blue injection be thrown into the jugular vein of the foetus, the whole membrane will become of that col- our, and will present an exceedingly fine vascular network under a lens. In a new-born infant, which had died with inflammation of the tympanum, the membrane was found quite red. The bloodvessels appear to be situated entirely in the internal layer ; they run from the circumference towards the centre of the membrane ; and this arrangement has probably led to the supposition of the existence of radiated muscular fibres. The use of the membrana tympani is to transmit the sonorous vibrations received through the external auditory meatus to the air contained within the tympanum, and to the ossicula of the ear. Its obliquity, besides increasing the dimensions of this vibratile membrane, has certainly some use in the reflection of sonorous vibrations. As it ad- heres to one of the chains of small bones of the ear, it is influenced by their movements ; and in this way it maybe either stretched or relaxed. The Internal Wall of the Tympanum. — The inter- nal wall of the tympanum {figs. 254, 255), which is perfectly exposed when that cavity is opened from its external wall, presents a great number of objects for our consideration. At its upper part is situated the fenestra ovalis if, fig. 254), the long diameter of which is directed transversely, but rather obliquely down- ward and forward ; the upper border of this fenestra if, fig. 258) is semi-elliptical, while the lower border is straight, or, rather, it projects somewhat into the opening. The fenestra ovalis, called also the vestib- ular orifice of the tympanum, would establish a free communication between the tympanum and the ves- tibule if it were not closed by the base of the stapes {d,fig. 255 ; n,fig. 257), which is accurately fitted to it. The fenestra ovalis is placed at the bottom of a depression, which is named the fossette of the fe- nestra, and the depth of which depends upon the de- * Philosopliical Transactions, p. 23, 1823. To his paper are annexed three plates, representing the membrana tympani in the elephant, the ox, and man. tig. 254. Natural size. (Section of the tympanam.) THE TYMPANUM. 671 gree of projection of the aqueduct of Fallopius, which bounds it in front, by that of the promontory, which is below, and by an osseous tongue which passes up to the pyramid behind. Below the fenestra ovalis is the promontory (r, figs. 254, 255), an eminence which corresponds to the first turn of the cochlea, and has three grooves upon its surface, that diverge above and converge below, where they terminate in a common canal, which opens upon the lower surface of the petrous portion of the temporal bone, be- tween the carotid canal and the groove for the internal jugular vein. This canal (ca- nalis tympanicus, Arnold) may be called the canal ofJacobson, because it contains Jacob- son's nerve, a branch given off from the glosso-pharyngeal, which establishes a very re- markable anastomosis between the glosso-pharyngeal and the nervi molles derived from the vidian and great sympathetic nerves.* The furrows upon the promontory are in- tended to lodge this anastomosis. They are often formed into complete canals. Behind the fenestra ovalis, and opposite its transverse diameter, is a small projection of variable size, called the pyramid {t,figs. 254, 255). There is an opening upon it which is distinctly visible to the naked eye, and makes the p)Tamid appear tubular. From thia opening emerges a small cord (o, fig. 255), the nature of which is not known, but which is called the stapedius muscle. A bristle passed into this opening enters the canal of the pyramid, which canal is generally described as ending in a cul-de-sac, but this is not the case. M. Huguier, prosector of the faculty, has clearly demonstrated, in a series of preparations, that the canal of the pyramid is a long passage, which passes backward and downward below the aqueduct of Fallopius, becomes vertical like the aqueduct, is separated from it only by a thin lamina of bone, communicates with it by a small open- ing, and at length abandons it below, to open upon the inferior surface of the petrous bone, on the inner side of the stylo-mastoid foramen, at a variable distance from it. Sometimes this canal bifurcates below ; so that two bristles introduced into the small openings near the stylo-mastoid foramen will both enter the canal of the pyramid. A small, very short, and horizontal passage, which terminates in the diploe of the tem- poral bone, may be regarded as a diverticulum of this canal. I have already stated that a fibrous-looking cord, named the stapedius muscle, emerges from the canal of the pyramid. It is not yet known what structures are transmitted through the divisions of this canal. Below the fenestra ovalis, and behind the promontory, is situated the fenestra rotunda (*, figs. 254, 255) ; it is placed at the bottom of a funnel-shaped depression, which was well described by M. Ribes as the fossa of the fenestra rotunda, at the bottom of which is found a partly membranous and partly osseous lamina, which is the commencement of the spiral septum of the cochlea. In a dry bone, which has been previously macerated, the membranous part being destroyed, the fossa of the fenestra rotunda communicates with the vestibule. Below this compound lamina, i. e., at the lower part of the fossa just described, is found the fenestra rotunda (*, fig. 257) properly so called, which leads into the tympanic scala of the cochlea (l) ; whence the term cochlear orifice of the tym- panum is applied to the fenestra rotunda, in contradistinction to the term vestibular orifice, which is given to the fenestra ovalis. The fenestra rotunda is closed, in the fresh state, by a membrane called the secondary membrana tympani, which is said to be composed of three layers — a middle layer, an external or tympanic, and an internal or cochlear layer. The two last named are mucous membranes.} Under the pyramid, and behind the fenestra rotun- da, is seen a deep fossa, the sub-pyramidal fossa {v,fig, 254), remarkable for its constancy, and pierced by several foramina at the bottom. Upon the internal wall of the tympanum, in front of the fenestra ovalis, somewhat above the trans- verse diameter of that opening, and under the prom- inence of the aqueduct of Fallopius, is the internal orifice (n, figs. 254, 255) of the canal (m) for the internal "\ muscle of the malleus, or tensor tympani muscle. This orifice is wide and cup-shaped, and is supported by a hollow eminence (z, jQ. 254), which is itself sustain- ed by several ridges ; so that there is the greatest analogy between it and the hollow projection consti- tuting the pyramid. Both of them transmit a tendon. One is situated in front, and the other behind the fe- nestra ovalis. M. Huguier, who has paid much at- tention to this subject, has shown that the cochleari- * This can be clearly seen in some preparations in the museum of the Faculty at Paris. + [The internal or cochlear layer is merely apart of the common lining membrane of the labyrinth, and is, most probably, a. fibre- Natural size. lerous membrane, see p. 681.] (Section of the tympanum.) Fig. 255. NEURO1.0GY. form, process of anatomists (n, fig. 255) is nothing more than the remnant of the hollow projection (x, fig. 254) just described, one half of which is very thin and fragile, and is sometimes destroyed by long-continued maceration. The so-called cochleariform pro- cess, therefore, is merely the reflected canal for the internal muscle of the malleus. The Circumference of the Tympanum. — We shall examine this circumference above, be- low, in front, and behind. Above, the tympanum corresponds to the projection formed on the anterior part of the base of the petrous portion of the temporal bone. In it there is formed a recess, which may be named the recess of the tympanum, and which is intended for the reception of the head of the malleus {\,fig. 255), and the body and posterior ramus of the incus (2). It is thin and spongy, and is separated from the squamous portion of the temporal bone by a suture, which persists even to the most advanced age. This suture is traversed by a great number of canals, through which communicating vessels pass from those of the dura mater to those of the tympanum. Below, the tympanum is very narrow, and has the form of a trench, in which there is nothing particular to notice. The wall of the tympanum is here formed by the osseous lamina of the external meatus. At the upper and back part of the circumference of the tympanum is situated a large opening which leads into the mastoid cells (c c, figs. 254, 255). These cells are extremely numerous, and of very unequal size ; they occupy the whole of the mastoid portion, and the adjacent parts of the petrous portion of the temporal bone, and are prolonged even above the external meatus. We may therefore regard the mastoid portion of the temporal bone as an appendage to the tympanum. The mas- toid cells have a very regular arrangement in the ox and horse, in which animals they are disposed in a series radiating from the surface of the mastoid process towards the tympanum ; their arrangement is much more irregular in the human subject. Two large cells are almost always found, one near the apex, and the other at the posterior border of the mastoid process. In one case I found the whole mastoid process forming a single large cell, having extremely thin parietes. The mastoid cells are lined with a very delicate fibro-mucous membrane, which is con- tinuous with the mucous membrane of the tympanum. They contain air, and it is only in some cases of disease that any quantity of mucus is found in them. The mastoid cells represent, in the auditory apparatus, the cells and sinuses which are connected with the organ of smell. It may be easily conceived that the intensity of sounds may be increased by being reverberated from so considerable a surface. In the foetus there are no mastoid cells ; but there exists instead, in the base of the petrous portion of the temporal bone, a cavity prolonged from the recess already de- scribed in the upper wall of the tympanum, for the ossicula of the ear. In front, the tympanum is contracted like a funnel, to become continuous with the Eustachian tube (c, fig. 255) ; it might even be said that the tympanum and the Eustachian tube form together a single funnel-shaped cavity, the expanded portion of which is con- stituted by the tympanum, and the contracted portion by the tube of Eustachius. The canal for the internal muscle of the malleus is formed in the upper wall of the Eu- stachian tube ; it is a narrow tubular canal (m), which, having reached the anterior part of the tympanum, becomes applied to the internal wall of that cavity ; it passes horizon- tally backward, forming a projection upon this wall, and is then reflected outward, at a right angle, to form the hollow eminence already described. This canal is separated only by a very thin osseous lamina from the Eustachian tube ; so that the two passages, placed one above the other, have some resemblance to a double-barrelled gun. The Eustachian Tube. The Eustachian tube (more correctly called the Eustachian trumpet, from tuba, a trumpet, e,fig. 255), or the guttural meatus of the ear, is a straight, funnel-shaped canal, flattened upon its outer side, and about two inches in length ; it extends from the tym- panum to the upper and lateral part of the pharynx, where it terminates by a free, ex- panded extremity (wi, fig. 234), directed inward and downward, named the guttural orifice, or the mouth of the Eustachian tube. This orifice is wide and dilatable, of an oval shape, the larger end of the ovoid being turned upward, and being exceedingly dilatable ; but beyond its mouth the tube almost immediately contracts, and will scarcely admit an or- dinary probe. It continues narrow as far as its tympanic orifice, where it again becomes sensibly dUated. It is directed obliquely inward, forward, and downward ; hence the facility with which the mucus of the tympanum flows into the back of the throat. The Eustachian tube consists of an osseous portion and of a cartilaginous and fibrous portion. The osseous portion, which is about seven or eight lines in length, is situated at the re- treating angle formed between the squamous and petrous portions of the temporal bone A triangular cartilaginous plate, formed into a groove, constitutes the inner half of the tube ; a fibrous layer, which is at first applied against the circumfiexus palati muscle, and is then lodged in the groove between the petrous portion of the temporal bone and the THE OSSICULJlf^OP THE EAR. 673 posterior border of the sphenoid, forms the external wall of the canal, which is habitu- ally collapsed. The base of the triangular cartilage, which forms the guttural orifice of the tube, is notched in the middle, and terminates in two thickened elongated angles ; of these, the posterior one, which is more distinct, is movable, and may be pushed upward and backward. The anterior angle is firmly fixed to the posterior margin of the ptery- goid process. As catheterism and injection of the Eustachian tube have become com- mon operations in treating diseases of the ear, it is of importance to define the exact position of its guttural orifice ; it is situated (m, fig. 234) upon the side of the pharynx, immediately behind, and a little above the inferior turbinated bone. The mucous membrane •w\imY\. lines the Eustachian tube is thin, but at the mouth of the tube it assumes the characters of the mucous membrane of the pharynx and of the pitui tary membrane, with both of which it is continuous ; it is also continuous with the mu- cous membrane of the tympanum ; hence the close sympathy which exists between the lining membrane of these several parts.* The use of the Eustachian tube is to renew the air contained within the tympanum , but it also gives exit to the mucous secretion of that cavity, t Besides the orifice of the Eustachian tube, and that of the canal for the internal mus- cle of the malleus, the anterior funnel-shaped part of the circumference of the tympanum presents two orifices placed one above the other : the uppermost of these is the internal orifice of the canal for the chorda tympani nerve ; the lower one is an oblique fissure, which transmits a fibrous cord called the anterior muscle of the malleus. M. Huguier has shown me a number of preparations in which the chorda tympani nerve does not escape through the fissure of Glasserius, but runs in a very narrow special canal, about five or six lines in length, which is situated on the inner side of the Glasserian fissure, and opens at the base of the scull in the retreating angle formed between the squamous and petrous portions of the temporal bone, upon the outer side of the Eustachian tube, be- hind the spinous process of the sphenoid, and sometimes upon that bone itself The fissure of Glasserius, then, merely transmits a fibrous bundle, named the anterior muscle of the malleus, and some small arteries and veins. We may now describe the course of the chorda tympani nerve. In its course this nerve passes through two canals, entering the tympanum by one, and escaping from it by the other. The canal by which it enters commences at the vertical portion of the aqueduct of Fallopius, in which the facial nerve is situated, passes upward and forward, and opens immediately on the inner side of the posterior margin of the membrana tympani, on a level with the horizontal diameter of that membrane, and al- most in the groove into which it is inserted. Having entered the tympanum through this canal, the chorda tympani describes a curve, having its concavity directed down- ward, passfes between the handle of the malleus and the long ramus of the incus, enters its proper canal upon the inner side of the fissure of Glasserius, and emerges at the point already mentioned. The Ossicula of the Ear. The tympanum is traversed from without inwaM by an osseous chain, which describes several angles, and consists of four bones articulated with each other, and extended from the membrana tympani to the fenestra ovalis. These little bones, forming the links of the chain, are named, from their respective shapes, the malleus, or Fig. 256. hammer {I, fig. 256) ; the incus, or anvil (2) ; the os orbicular e, or ^ a ^ round bone (4) ; and the stapes, or stirrup bone (3) : the os orbicu- lare, however, appears to be merely a tubercle belonging to the incus. The Malleus. — The malleus {I, fig. 256) is the most anterior of the bones of the ear; it is divided into a head, a neck, and a handle, and it has also two processes. The head of the malleus (a, fig. 257) is situated in the recess of the tympanum, ir front of the incus, and above the membrana tympani. It is ovoid, and smooth, excepting behind and below, where it is concave, in order to be articulated with the incus. Soemmering has figured a small fibrous cord, which he calls the proper ligament of the malleus, extending from the head of this bone to the upper part of the recess of the tympanum. The head is supported by a constricted neck (b), which is slightly twisted and flattened, and serves also as a support for the two processes. The handle (manubrium, c) is directed vertically, and, Magnified three diameters. * [According to Dr. Henl6, the mucous membrane of the Eustachian tube, like that of the upper part of the pharynx, is covered with a columnar ciliated epithelium ; but in the tympanum and mastoid cells the epithelium is squamous, and not ciliated.] t [The Eustachian tube, by establishing; a communication between the tympanum and the external air, en- sures an equal atmospheric pressure on the two surfaces of the membrana tympani, so that the necessary con- dition of that membrane, and of the ossicula auditOs, as conductors of vibrations, is not interfered with.] 4Q 674 NEUROLOGY. with the head and neck, forms a very obtuse angle, which retreats on the inner side ; it is in contact with, and adheres firmly to the internal surface of the membrana tyrn- pani, opposite the centre of which its rounded extremity is placed ; it therefore forms a radius to the circle represented by the membrana tympani. The lower part of the handle of the malleus is distinctly curved, having its concave side turned outward ; this ex- plains the funnel-shaped depression upon the external surface of the centre of the mem- brana tympani. The processes of the malleus are two in number : the external, or short process {d), is directed slightly outward, and rests against the upper part of the margin of the mem- brana tympani, so as to make it project outward ; the other, or lo7ig process, is very slender (processus gracilis of Raw, e), and is shaped like a thorn (processus spinosus) : rt arises from the anterior part of the neck, enters the Glasserian fissure, and affords at- tachment to a muscular or fibrous cord. I have several times found a simple ligament- ous cord instead of this process. The Incus. — This bone (2, Jig. 256) has been well compared to a bicuspid tooth, the body of which would be represented by the body of the incus, and the fangs by its two processes. The body (f,fig. 257) is contained in the recess of the tympanum, behind the malleus, with which it is articulated by a very concave surface, directed forward and somewhat upward ; so that the articulation between the head of the malleus and the body of the incus is effected by mutual reception. Of its two rami, the superior or short one (g) is thick, conoid, and directed horizontally backward : it is situated upon the S£une plane as the body, and, like it, is contained in the recess of the tympanum, in which it terminates ; its extremity does not appear to me to be free. The inferior, or long ramus (h), is longer and thinner than the superior one ; it passes vertically downward, parallel to the handle of the malleus, on a plane internal and some- what posterior to it. Its lower portion is bent into a hook, the concavity of which is turned inward ; and at its point is formed a sort of lenticular and distinctly defined tu- bercle (4, fg. 256 ; i, Jig. 257), which has been regarded as a separate bone, and named the OS orbiculare, or os lenticulare ; it appears to me to be merely a dependance of the in- cus, with which I have always found it united, even in the foBtus. The Stapes. — ^The stapes (3, fig. 356), which is shaped like a stirrup, extends horizon- tally from the extremity of the long process of the incus to the fenestra ovalis (see Jig. 257), and is situated upon a lower plane than the rest of the small bones of the ear. Its head presents a small articular cavity, for the reception of the orbicular tubercle of the incus. Its base (n) is directed inward, and consists of a thin plate exactly corre- sponding to the fenestra ovalis, which is rather accurately fiUed up by it, and to draw it away from which a slight force is necessary, so that it has a greater tendency to fall into the vestibule than into the cavity of the tjTnpanum. The slight obliquity of the long diameter of the fenestra ovalis causes an inclination of the stapes in the same di- rection. Of its two crura, or branches (fig. 256), the anterior is the shorter and straight- er. Upon those surfaces of the crura which are turned towards each other there is found a groove, which appears to indicate the existence of a membrane stretched be- tween the crura. I have found the stapes very small, and, as it were, atrophied. In one case, the two crura of the stapes were united together. Muscles belonging to the Ossicula of the Ear. Most modem anatomists agree with Soemmering in admitting four muscles for the ossicula of the ear, viz., three belonging to the malleus, and one to the stapes. The incus has no proper muscle, because it is merely an intermediate bone between the malleus and the stapes. It is certain, however, that only one of these muscles has been actually demonstrated, viz., the internal muscle of the malleus; but it is so easy to fall into error when examining such minute objects, that I feel bound to suspend my judg- ment as to the existence or non-existence of the other muscles. The internal muscle of the malleus, or tensor membrancB tympani of Soemmering (e, fig. 251), is an elongated, fusiform muscle, contained within the bony canal formed in the retreating angle of the temporal bone, above the Eustachian tube, with which it exactly corresponds in direction. It arises from the cartilaginous portion of the tube, from the adjacent part of the sphenoid bone, behind the spinous foramen, and from the bony canal which forms its sheath. The fleshy fibres converge around a tendon, which appears from among them, before it passes out from the bony canal. This tendon is reflected at a right angle, like the canal in which it is contained, and then passes directly outward, to be inserted into the anterior and superior part of the handle of the malleus, below the processus gracilis of Raw. The muscularity of the band or cord named the anterior muscle or ligament of the mal- leus, or the great external muscle of Meckel, is doubted by a great number both of pres- ent and former anatomists.* I have never seen anything more than a fibrous cord, which " Fu^re autem et dudum et nuper clari viri qui de veris hujus musculi fibris carneis dubitarunt, cum THE OSSEOUS LABYRINTH. 61^ cwmmehced at the tip of tTie processus gracilis of the malleus, traversed the glenoid fis- sure, was re-enforced by other fibres arising from that fissure, and became continuous with a fibrous layer arising from the spinous process of the sphenoid bone, and generally regarded as the internal lateral ligament of the temporo-maxillary articulation. The same remarks will also apply to the small external muscle of the malleus, or small muscle of the malleus of Casserius. This muscle is figured by Soemmering, who says that he found it exceedingly developed in one subject. All that I have clearly seen is a cylindrical cord, extending from the upper part of the frame of the membrana tympani to the short process of the malleus, or, rather, below it, according to the observations of Scemmering {ad manubrium mallei, infra brevem ejus processum). This small muscle would relax the membrana t3TTipani ; hence it has been named by Soemmering the lax- ater membrance tympani. The muscle of the stapes, or stapedius muscle (o, fig. 255), which is the smallest in the body, has, since the time of Varolius, by whom it was discovered, been regarded as a ligament by some anatomists ; nevertheless, it is more generally admitted to be muscu- lar than that last described. It arises from some part of the interior of the pyramid, and, escaping from that process, passes forward, and terminates at the back of the neck, or constricted part of the head of the stapes, behind its articulation with the incus. Soem- mering has not only represented its fleshy belly and its tendon, but also (see fig. 20, tab. 11) a filament of the facial nerve terminating in it. It is difficult to conceive that such a serious mistake should have been committed by this great anatomist. I have exam- ined this cord under a lens, and have never been able to discover any muscular fibres in it. We do not conceive how a muscle should exist in so delicate a cord. Supposing, however, that it does exist, it must move the stapes in such a way that the posterior ex- tremity of the base of that bone would be pushed into the fenestra ovalis, while the an- terior extremity would be carried outward. Movements of the Ossicula. — The chain of small bones in the ear is so arranged, that any movement of one of its extremities is communicated to the entire chain. Their mo- tion is precisely similar to that of a bell-crank. M. Huguier is incUned to believe that the processus gracilis of Raw serves as a fulcrum, around which the malleus performs a rotatory movement, the effects of which are transmitted to the stapes through the in- cus. The contraction of the internal muscle of the malleus, or tensor membranae tym- pani, must draw the handle of the malleus inward and its head outward ; the incus, from its firm connexion with the head of the malleus, follows that bone, and as it swings upon its short horizontal process, its vertical process is carried inward, and therefore presses the stapes into the fenestra ovalis. The Lining Membrane of the Tympanum. The tympanum is lined by a very thin membrane, which not only covers the walls of this cavity, but also forms a very evident investment for the ossicula, and is, moreover, prolonged into the mastoid cells, lining them throughout, and forming small duplicatures around the vessels by which some of the cells are traversed. This membrane is con- tinuous with the mucQus membrane of the Eustachian tube, and therefore indirectly with that of the pharynx.* It serves at once as an internal lining for the tympanum, and a periosteum for the os- seous walls of that cavity, and should therefore be regarded as a fibro-mucous membrane. It secretes a mucus, which in the natural state simply moistens its surface, but in some cases of disease occupies the whole cavity. The catarrhal character of the products ol suppuration in the tympanum, the continuity of this lining membrane with the mucous membrane of the pharynx, and its extreme vascularity, leave no doubt of its being a mu cous membrane. The Internal Ear, or Labyrinth. The internal ear, or labyrinth (f,fig. 251), the deep-rooted and essential portion of the organ of hearing, is situated on the inner side of the tympanum, in the substance of the petrous portion of the temporal bone. It consists of the osseous labyrinth, which forms a receptacle for the membranmis labyrinth, which is the immediate seat of the sense of hearing. No part of the body has a more conlplex and delicate structure. The labyr inth is composed of three very distinct compartments, which have been named the ves tibule, the semicircular canals, and the cochlea. The Osseous Labyrinth. Preparation. — This is justly regarded as one of the most difficult dissections, even when the parts are previously known. The dissection should be made upon temporal bones from subjects of different ages, upon bones that have been macerated, upon oth- ers that have been dried without maceration, and also upon bones in the fresh state. inultam quidem membranam a periosteo propa^atam, sulcuin maxillje repleri viderent, et processui longissimo circumnasci, esEterum in eo carneam naturam non deprehenderent. Neque mea erperimenta remexpediunt Musculum quoties volui, ostendi, num veras fibras viderem, plerumqiie dub^us hxsi."— (Holier, torn, v , lib TV., p. 218.) ■ ■ * See note, p. 673. 676 NEUROLOGY. Commence with a foetal temporal bone, in which the labyrinth can very easily be isola- ted, in consequence of its being surrounded only by a spongy texture, readily yielding to the knife. In the adult, the labyrinth is, in proportion, much less developed than in the foetus, and is surrounded with so compact a tissue, that, in order to cut it, it is necessa- ry to use a chisel, a file, or a very strong scalpel. It is important to have a great num- ber of temporal bones, so as to be able to make several different sections. Preparation of the Vestibule. — Open the vestibule through its upper wall, which corre- sponds to the upper surface of the petrous portion of the temporal bone, opposite the fe- nestra ovalis, between the superior vertical semicircular canal and the internal auditory meatus. Preparation of the Semicircular Canals. — In the foetus, one of the semicircular canals projects upon the base of the petrous portion of the temporal bone ; it is easy to isolate it, as well as the other canals, by removing, with a strong scalpel, the spongy tissue in which they are imbedded. It is useful to have two preparations of the semicircular ca- nals ; one in which the canals remain entire, and another in which they have been opened. Preparation of the Cochlea. — Remove layer by layer that part of the petrous portion of the temporal bone which corresponds to the bottom of the internal auditory meatus. A layer of very thin spongy tissue shows, in the foetus, that we have arrived at the coch- lea ; remove this spongy tissue with care, and expose the cochlea, both on its upper and lower surfaces. In one preparation, the cochlea should be merely isolated ; in another, it should be carefully opened, and for this purpose it is sufficient to make a simple cut into each of its turns : it is of importance not to remove the summit of the cochlea. The Vestibule. If a probe be passed from the tympanum through the fenestra ovalis {f,fig. 258), it P^ 25g enters an ovoid cavity (a b t, fig. 259) called the vestibule. The vestible is the centre of the internal ear, and forms an intermediate cavity or passage (fo- rum fodinaj metallicas, Vesalius) between the semicircular canals {op q,fig. 258), which are on its outer side, and the cochlea (Z), which is to its inner side. It is situated in a line with the axis P^ of the internal auditory meatus. It is remark- able for having a great number of both large and small openings into it. The large openings are seven in number: the first is the fenestra ovalis {ffigs. 258, 261), which would establish a free communication between the vestibule of the tympa- num if it were not for the base of the stapes, which closes it hermetically, as we may be convinced by examining it from the vestibule, when the stapes remains in its plac ♦ There are five openings (o' p' q',fig. 259 ; o' a', fig. 261) for the three semicircular canals ; yi„. 259. and the seventh is the orifice (/) of the vestibular scala of the cochlea. In macerated bones we find, besides, an eighth opening, situated below the fenestra ovalis, having an oblong shape, and leading into the highest part of the fenestra ro- tunda. Of the small openings, the first is the orifice (r, fig. 259) of the aqueduct of the vestibule, which opens upon the posterior wall of this cavity to the inner side of the common opening for the two „ , ^. .V ..V w. ,, vertical semicircular canals (i. e., in the recessus ^XgJ^^'Co-iumeTer,"'" sulciformis). The aqueduct of the vestibule turns a short distance around that common opening, and then, bending at a right angle, ter- minates upon the posterior surface of the petrous portion of the temporal bone by an orifice already described (see Osteology). The other small openmgs m the vestibule are foramina for the passage of vessels and nerves ; they form the macula cribrosa, which corresponds with the bottom of the internal auditory meatus. The character of the vestibule is irregularly ovoid, and is divided by a cn»ta into two fossae : one inferior and hemispherical, named the fovea hemispherica {a, fig. 259) ; the other, superior and semi-elliptical, called the fovea semi-elliptica (h). Morgagni has de- scribed a third groove-like fossa {recessus sulciformis), situated at the mouth of the com- mon orifice of the two superior semicircular canals. The Semicircular Canals. The semicircular canals, three in number, represent three cylinders or tubes (tubaeformes canales, Simmering), of equal diameters, and curved very regularly, so as to describe * CThe base of the stapes is retained in its situation, and the complete closure of the fenestra ovalis is ef- fected, by the reflection of the lining membrane of the tympanum on the one hand, and by that of the bning membrane of the labyrinth on the other.] THE COCHLEA. 677 portions of circles ; they are situated within the substance of the base of the petrous portion of the temporal bone, behind the vestibule, into which they open by the five ori- fices already described. They have been named the great, the middle, and the small semicircular canals ; terms which have caused much confusion, because the differences between them, in regard to length, are not alone sufficient to distinguish them from each other. Their direction forms a much better ground of distinction between them. Two are vertical, and one is horizontal : there is an anterior and superior vertical, and a posterior and inferior vertical canal ; the horizontal canal is external, and is situated between the two others. , . ^ Tlie superior vertical canal (p, figs. 258, 260), which describes two thirds of a circle, is placed at the highest part of the labyrinth, immediately to the outer side of the vestibule. A plane passing through the two branches of this canal would cut the base of the petrous portion almost at a right angle. The convexity of this canal is turned upward, and its concavity downward. In the foetus, its concavity is free, so that it can be seen without any dissection ; but in the adult it is filled up with osseous tissue. The anterior and outer extremity {f,figs. 258, 259) of this canal is dilated into an ampulla, and opens separately at the upper and outer part of the vestibule. The poste- rior and inner extremity unites with the corresponding extremity of the inferior vertical canal to form a common canal (a, fig. 260), which opens without any dilatation into the upper and inner part of the vestibule {a', fig. 261). Fig. 260 The inferior vertical canal {q, figs. 258, 260) is placed at right angles to the preceding, and par- allel with the posterior surface of the petrous portion. It commences at the inner and upper part of the vestibule, by the common canal (a, fig. 260) already described, passes almost di- rectly outward, curves at first downward, and then forward, and becomes dilated into an am- pulla {q', fig. 258) near the vestibule, into which cavity it opens {q', fig. 259), about the distance of a line from the point at which it commences. This canal, therefore, describes nearly a com- plete circle ; and hence the term canalis major et longior, still given to it by Soemmering, in contradistinction to the superior vertical semi- circular canal, which he calls minor et brevior. The horizontal canal (o, figs. 258, 260), canalis minimus, brevissimus, sive exterior of Soemmer- fc;*^ji_ ing, commences in the vestibule {o',figs. 258, 259) between the fenestra ovalis, which is be- low, and the ampullar opening of the superior vertical canal, which is ahove ; it becomes dilated into an ampulla, describes a horizontal curve having its convexity turned out- ward, and opens {o',fig. 261) upon the inner wall of the vestibule, between the common opening (a') of the two vertical canals and the proper opening ({'') of the inferior vertical canal. It appears, then, that each of the three semicircular canals has one of its extremities dilated into an ampulla, and the other not dilated ; that the two vertical canals unite by their non-dilated extremities ; that of the five openings belonging to the semicircular canals, two occupy the outer, and three the inner wall of the vestibule, and that the three last consist of the common canal formed by the two vertical canals, by the ampullar ex- tremity of the posterior vertical canal, and by the non-ampuUar extremity of the horizon- t£il canal. The Cochlea. The cochlea {I, fig. 258), or snail, so called from its resemblance to the shell of that molluscous animal, may be said to consist of a conoid tube, which is subdivided into two cavities, called scales, by a septum extending from its base to its apex, and is coiled upon itself into a spiral containing two turns and a half The cochlea is the most anterior part of the internal ear ; it is situated on the inner side, and in front of the tympanum ; its base {d, fig. 260) rests upon the bottom of the internal auditory meatus.* Its external surface is blended, in the adult, with the substance of the petrous portion of the temporal bone, so that it requires much skill to carve it out vnthout breaking into its cavity : in the foetus, on the contrary, such a dissection is extremely easy, on ac- count of the thin layer of spongy osseous tissue by which it is separated from the rest of the bone. * [The summit of the cochlea is directed forward, downward, and outward. The gyri of the cochlea are soiled in a direction from below upward, a"' ''""ti without inward.] C78 NEUROLOGY. The following parts of the cochlea are separately described : the tube of the cochlea or lamina gyrorum, the lamina spiralis, the axis or columella, the two scala, and the aqueduct. The Tube of the Cochlea. — The tube of the cochlea {canalis spiralis cochlce, or lamina gy- rorum) is the compact lamina (l, figs. 258, 262) which forms the external walls of the cochlea. If we imagine a hollow osseous cone, coiled spirally, cicut circa fulcrum convol- vulus {Holler), or like a winding staircase ; and farther, that the lowest turn of the spire embraces the turn above it, and that the walls of the different turns are blended with each other, we shall have a correct idea of the tube of the cochlea : as before stated, the spire thus formed describes two turns and a half The Spiral Lamina of the Cochlea. — The spiral canal, or tube of the cochlea, is subdi- vided lengthwise into two secondary cavities (c e, c e, figs. 263, 264), called scala. {scala, a staircase), by a septum (a), which is named the spiral lamina of the cochlea {lamina spi- ralis cochlea). Commencing at the base of the cochlea {t, fig. 259 ; also fig. 263), and at the fenestra rotunda, where it can be very easily seen, the spiral lamina winds edgewise around the axis or columella {b b, fig. 262), and is continued without any interruption to the summit or cupola (/) of the cochlea, the several turns of which it exactly follows. Its internal border is applied against the axis of the cochlea, and adheres intimately to it, excepting above, where it is free for a short distance, and leaves a communication {n, fig. 263) be- tween the two scalae. Mar go liber lamina spiralis quo fit ut utriusque scala. sit communica- tio {Sammering). Its external border adheres to the inner surface of the lamina gyrorum, or tube of the cochlea. In consequence of the conical form of this tube, the lamina spi- ralis would, if unrolled, represent an isosceles triangle, the base of which had corre- sponded to the fenestra rotunda, and the apex to the summit of the cochlea. The spiral lamina consists of two portions — an internal osseous and an external mem- branous portion.* The osseous portion {lamina spiralis ossea, d, figs. 259, 261, 262, 264) predominates in the first turn, diminishes gradually in the second, and ceases at the commencement of the third, where it termi- nates in a kind of hook or beak {hamulus vel rostrum, e,fig. 262). This bony portion is thick, and consists of two la- mellae, between which are found a great number of very delicate canals, through which the nerves of the cochlea v pass. These two lamellae form two distinct furrows upon 1^' the columella. The membranous portion {lamina spiralis membranacea, a a, figs. 263 to 265) completes the septum, forming its Cochlea (dry) magnified four times. ^y^gj. ^^^ J^ jg narrow in the first tum of the cochlea, becomes broader in the second, and constitutes the entire septum in the third Fig. 263. Cochlea ( The bony and membranous portions of the spiral lamina, therefore, represent two isosceles triangles, so arranged that the base of the one corresponds to the apex of the other, and vice versa. Moreover, as Comparetti remarks, three zones can be distinguished in the membranous portion of the spiral lam- ina, the consistence of which diminishes progressively ■/ from the margin of the osseous lamina towards the inter- nal surface of the tube of the cochlea. The Axis or Columella of the Cochlea. — From the bottom, or, rather, from the posterior part {d, fig. 260) of the bottom of the internal auditory meatus, arises a bony process, which is directed almost horizontally outward ; it occupies the centre or axis of the cochlea, and around it both the tube and spiral lamina describe their several turns. This bony process is called the axis of the cochlea, columella, modiolus, or nucleus {b, figs. 262, 264). It extends from the base to the summit of the cochlea, but undergoes certain changes during its course. Opposite the first turn it is extremely thick, but becomes much thinner in the first half of the second tum. In the second half of the second turn, and in the last half turn, it is replaced by a cup-shaped lamella, called the infundibulum (scyphus, Vieussens, c, fig. 262), the expand- ed portion of which is turned towards the cupola (/) of the cochlea. The modiolus or axis of the cochlea, then, has three perfectly distinct parts. The base of the modiolus, which is seen at the bottom of the auditory meatus, is marked by a very distinct spiral tract {d, fig. 260), perforated with foramina, through which the filaments of the auditory nerve are transmitted. It is the tractus spiralis foraminulentus of Cotugno. The apex of the modiolus, when examined in a cochlea which has been opened from the under surface of the petrous portion of the temporal bone, presents a decidedly in- fundibuliform figure. But in a cochlea which has been opened from its upper surface * [In the dried cochlea [fig. 262), the two seals communicate along their whole course.] THE COCHLEA. 679 ifig. 264), on the contrary, it has the appearance of a very slender stalk, continuous with the rest of the modiolus, and proceeding directly to the cupola of the cochlea. This two- fold structure depends upon the fact that the terminal lamella of the modiolus forms only half a funnel, which half is turned towards the lower half of the cochlea. , This terminal lamella of the modiolus, which has been very well described by Huguier, is of a triangular form, extends through half a turn of a spiral, and adheres to the inner surface of the tube of the cochlea by its external convex border. Its internal border or margin is straight and free, and is the only part of this lamella which is seen when the cochlea is opened from above, while its convex border and its surfaces are distinctly seen when the coch- lea is opened from below. The hamulus (e, fig. 262) of the osseous portion of the lamina spirahs terminates opposite the middle of this free border or margin. The surface of the modiolus is marked like a screw by two furrows correspondmg to the two lamellae of the osseous part of the spiral lamina ; this surface is pierced with foramina for the branches of the auditory nerve. If the modiolus be divided longitudinally (fig. 264), it wDl be seen that its centre is traversed by a number of canals, for the passage of the branches pig. 264. of the auditory nerve. These canals open by the foramina on its surface. In the centre of the half funnel formed by the ter- milial lamella of the modiolus is an opening, through which the terminal filament of the cochlear branch of the auditory nerve passes out ; it is the orifice of the tubulus centralis modioli. The Scarce of the Cochlea. — The spiral lamina {d d, fig. 264) di- vides the cavity of the tube of tne cochlea into two secondary cavities (c e, c e), called the scala of the cochlea. They are dis- tinguished as the external, superior, or vestibular scaia (scala ves- tibuli, c c, figs. 263, 264), and the internal, inferior, or tympanic scala (scala tympani, e e). The first (c c, fig. 265) communicates ^ directly with the vestibule (between t and s) ; the second, which Coehiea magnified. commences at the fenestra rotunda (s, fig. 258), would communicate with the tympanum if that fenestra were not closed by a membrane ; hence the term scala clausa. The tympanic scala is decidedly larger than the vestibular. The section of either of the scalae, at right angles to its axis, is semicircular. The two scalae conununicate near the summit of the cochlea (at n, figs. 263, 265). Both the situation and nature of this communication can be easily eiscertained, and have been well described by Soenomering, and more recently by MM. Breschet and Huguier. The lamina spirahs, which, we have seen, adheres closely to the modiolus, continues to wind spirally around the half-funnel-shaped termination of the modiolus, but when it arrives opposite the concavity of this half funnel, it ceases to be attached to that con- cavity, its internal border becomes free, and is then continued on to the inner surface of the summit of the cochlea. It follows, therefore, that the free concave border of the lamina spiralis is opposite to the concavity of the infundibulum ; and hence there is an interruption in the septum, in the form of a circular opening, the canalis scalarum commu- nis of Cassebohm, the helicotrema of Breschet {n,figs. 263, 265), which establishes a com- munication between the two scalae : moreover, this opening is not situated precisely at the summit of the scalae, but a little below that point ; nor is the opening of communica- tion (between t and s, fig. 265) between the vestibular scala and the vestibule situated at the lowest part of that scala. The Aqueduct of the Cochlea. — The aqueduct of the cochlea opens at one end {n,fig. 259) into the tympanic scala of the cochlea, near the fenestra rotunda ; and at the other, by an expanded extremity, upon the lower border of the petrous portion of the temporal bone, near the jugular fossa. It does not appear to have any such use as was attributed to it by Cotugno. Like the aqueduct of the vestibule, it is merely a canal for a vessel, and as such was denominated by Wildberg canalis vcnosus cochlea. The liquor Cotunnii could not pass through this canal, for it is closed by the dura mater. Ilg has taken a very ingenious view of the structure of the modiolus and cochlea. According to that author, the modiolus is not an osseous centre independent of the lamina gyrorum, but rather the internal wall of the spiral tube of the cochlea, which, in describing its first turn, intercepts a considerable cylindrical space of about two lines and a half in diam- eter, and then a smaller, but still cylindrical space, of about half a line in diameter, in its second turn ; while in the third turn there is no space, and therefore the axis or modiolus is wanting, but it is replaced by the internal wall of the spiral tube of the cochlea itself The terminal lamella of the modiolus would therefore be formed by the internal wall of the spiral tube. This view is supported by the structure of the bottom of the internal auditory meatus, on which is found a turn and a half of a spiral groove, precisely corresponding to the spire of the cochlea, and by sections of the cochlea made after Scemmering's plan, from the apex to the base. {Vide figs. 11, 12, 13, 14, 15, of Scemmering's fourth plate.) The Membranous Labyrinth. The membranous labyrinth, discovered by Conipannti and .Scarpa, ha.s been correctly NEUROLOGY. described and figured by Soemmering. M. Breschet has recently enriched our knowl- edge of this intricate anatomical subject with many most interesting facts. {Etudes anatomiques et physiologiques sur Vorgane de Vouie et sur V audition dans Vhomme et Us ani- maux vertebres, 1833.) It is useless to attempt the examination of the membranous labyrinth in the human subject without some previous preparation. If the labyrinth be opened, it is found to contain a fluid ; the eye can detect nothing else. By previously macerating it in diluted nitric acid, the twofold advantage is gained of softening the bones, so that they can be cut with a scalpel, and of hardening and rendering opaque the nervous tissues. Before studying the membranous labyrinth in the human subject, it should first be examined in the large cartilaginous fishes, such as the ray and the turbot, in which it is most highly developed. It is then seen that the semicircular canals and the vestibule contain, be- sides a fluid, certain semi-transparent membranous tubes and sacs, the aspect of which closely resembles that of the retina. The membranous labyrinth (fig. 265) is not so extensive as the osseous labyrinth : thus, it does not enter the cochlea, and its diameter is much less than that of the bony labyrinth. It scarcely occupies one half the cavity of the latter. The space between the bony and membranous lab- yrinths is filled with a limpid fluid, named, after Co- tugno, the liquor Cotunnii, although it had been no- ticed by several anatomists before that author. (De aqua ductibus auris humane ischi- ade nervosa commcntarium), but the fact was neglected by anatomists, and the fluid re- garded by some as the result of cadaveric exudation, and by others as that of a morbid action. The existence of this fluid has been again confirmed by M. Magendie, who, moreover, has clearly proved that it is seated in the sub-arachnoid tissue. In order to prove the existence of the sub-arachnoid fluid, or cephi o-iaunoian nuid * [The existence of the canal of Bichat is admitted by Arnold, a recent authority. Perhaps the opposite statements of anatomists concerning this canal may depend on the fact that the canal itself, though originally present, is sometimes closed subsequently, and at other times remains open.] t [The spinal sub-arachnoid space is divided behind by a thin, and, in some parts, cribriform longitudinal septum, which extends from the loose arachnoid to the posterior median fissure of the cord. This space is probably4i>ied throughout by a serous membrane, which contains the rachidian fluid, and which might be named the internal arachnoid. The septum just mentioned may be supposed to consist of two layers of thJB membrane reflected from the loose arachnoid to the cord, and having the same relation to it as the mesentery has to the intestine ; and the membrane itself may be conceived to.be prolonged through the foramen described by Magendie at the Ijottom of the fourth ventricle (see p. 718), so as to form the lining membrane of the fourth, third, and lateral ventricles ; and, farther, in case of the existence of the foramen of Bichat, to become con- tinuous with the external or true arachnoid through that foramen.] THE SUB- ARACHNOID FLUID. 691 of Magendie, it is necessary to open the lumbar region of the spinal canal in a certain number of subjects. If an incision be very carefully made through the dura mater, it will be seen that the serous fluid raises the visceral layer of the arachnoid, so as to make it protrude like a hernia through the incision : if this layer of arachnoid be then divided, the liquid will escape. Cotunni, who performed this experiment upon tw^enty subjects, collected from four to five ounces of fluid in each case. To the objection that this fluid is found after death, but does not necessarily exist in the living subject, we may answer thus : There is a space between the spinal cord and the dura mater, and the brain itself does not exactly fill the cranial cavity. Now in no part of the animal body does there exist any vacuum ; the spaces between the solids are always filled either with liquids or gaseous fluids. But if it be said that in this situation the space is filled by a serous vapour, the elasticity of which might establish an equilib- rium with the external air, it may be replied, that this vapour would not be sufficient to produce so large a quantity of fluid as is found in the spinal canal. Moreover, all these objections, and also the supposition that the brain and spinal cord may be smaller after death than during life, are overthrown by the following experiment. If the posterior cervical muscles be divided in a living dog, at their occipital attachments, the posterior occipito-atlantoid ligament will be exposed. The parts being weU cleansed from blood, the ligament must be cut away, layer by layer, with a scalpel held flat against it. The ligaments will scarcely be cut through before a small hernial protrusion, con- taining a fluid, will be seen ; this consists of the visceral arachnoid raised by the rush of fluid. If a crucial incision be then made in the occipito-atlantoid ligament, by the aid of a director,* a fluid as limpid as distilled water will be seen beneath the visceral layer of the arachnoid, which fluid is agitated by two kinds of motion, one of which is isochro- nous with the pulse, and the other with the respiratory movements. If the arachnoid be next punctured, the fluid will immediately escape in jets, and its quantity may be as- certained. The difficulty of not wounding the visceral layer of the arachnoid explains why, until recently, it was thought that the spined fluid was contained within the arachnoid cavity {c,jig. 266), i. e., between the two layers of the arachnoid membrane, although most ob- servers had noticed that the serous fluid in the cranium occupied the sub-arachnoid cel- lular tissue. It follows, therefore, that besides the fluid which is exhaled from the free surface, i. e., into the cavity of the arachnoid, a certain quantity of a similar fluid fills up the areolar tissue of the sub-arachnoid space : in this respect the arachnoid differs es- sentially from other serous membranes, all of which pour their secretions into their cav- ities, and not into the subjacent cellular tissue. This peculiarity depends simply upon the non-adhesion of the arachnoid to the spinal cord ; it may be stated as a law, that serous membranes exhale almost indifferently from either their internal or their external surface, when the latter surface is not adhe- rent. The arachnoid exhales a fluid from both surfaces ; a certain quantity of fluid is rather frequently found between its two layers ; and although, in acute inflammations, the deposite of purulent matter or of false membranes most generally takes place in the sub-arachnoid cellular tissue, yet these morbid products are not unfrequently found in the cavity of the spinal arachnoid itself The sub-arachnoid fluid exists not only in the vertebral canal, but also within the cra- nium, in which it fills up all the spaces between the brain and the dura mater. Now these spaces are subject to much variety in size in different individuals, or from age or from disease : thus, in atrophy of the brain and spinal cord, from old age or dis- ease, the interval between the dura mater and the cerebro-spinal axis is augmented, and the quantity of fluid increases in the same proportion. The quantity of the sub-arachnoid fluid is in a direct ratio with the progress of age ; in aged lunatics, in whom the convolutions of the brain are much atrophied, the quanti- ty of this fluid contained within the cavity of the cranium is very great, t The sub-arachnoid fluid in the cranium is not distributed equally around the brain, but is chiefly seated at its base. In order to show this fluid, it is merely necessary to raise up the brain carefully from before backward, when it will be seen distending all the fun- nel-shaped prolongations formed by the arachnoid around the nerves, and it will escape as soon as the membrane is divided. As regards quantity, the sub-arachnoid fluid at the base of the brain and the fluid of the ventricles are always directly proportioned to each other, but are inversely propor- tioned to the sub-arachnoid fluid upon the convex surface of the brain. Upon opening the head of infants who have died from acute ventricular hydrocephalus, we sometimes * It is highly important to make the transverse incision very short, in order to avoid injuring- the very large vertebral veins ; for if these vessels be cut, the hemorrhage will be so abundant as to prevent the continuation of the experiment. t None of these facts escaped the notice of Cotugno : " Nee tantnm 'axe aqua complens ab occipite ad usque imum os sacrum, tubum dun-e matris . . . sed et u ipso redundat calcarise cavo omniaque complet intervalla quae inter cerebrum et durse matris ambitum )nven> antur .... quantum autem magnitudinis cerebrum in his perdit, tantum a contactu subtrahitur durs matns et quidquid loci decrescendo reliquit, aquosus vapor coUectus lotum adimplet." — (Op. cit., p. 11. 12.) 692 NEUROLOGY. find the convex surface of the brain dry, and, as it were, adhesive. It is of importance to determine whether the cavities containing the cephalic and the spinal fluids commu- nicate with each other. There can be no doubt that the sub-arachnoid spaces of the brain communicate with the sub-arachnoid space around the spinal cord ; but do the cavities of the ventricles communicate with the sub-arachnoid space 1 Haller admitted that the fluid could flow from the ventricles into the spinal canal, and he believed that this was effected by a communication between the ventricles and the cavity of the arachnoid itself* Cotugno expresses the same opinion still more distinct- ly. Both Haller and Cotugnot thought that this communication occurred at the bottom of the fourth ventricle, but they neither indicated the exact situation, nor the mode in which it is effected. M. Magendie has pointed out that it occurs at this very spot, near the point of the calamus scriptorius. Bichat stated that the communication between the ventricles and the arachnoid cavity was at the so-called canal of Bichat. The mode in which the fourth ventricle communicates with the sub-arachnoid space will be much better understood if stated in our description of that ventricle, t Uses of the Arachnoid and of the Sub-arachnoid Fluid. Uses of the Arachnoid. — Like all serous membranes, the essential use of the arachnoid is to lubricate the surface of the brain and spinal cord, and thus facilitate their move- ments. No other membrane more completely fulfils such a use, for the arachnoid is moistened in both its external and internal surfaces. It would, in fact, be an error to suppose that the serous secretion is poured out solely by that surface of the arachnoid which is turned towards the pia mater : the fluid is exhaled upon its internal surface also, as in all other serous membranes, so that we sometimes find serum, pus, and false membranes in the cavity of the arachnoid itself Uses of the Sub-arachnoid Fluid. — The sub-arachnoid fluid forms a sort of bath around the spinal cord, which effectually protects it during the various motions of the vertebral column. It might be said that the spinal cord, being, in reference to its delicacy, in con- ditions somewhat analogous to those of the foetus in utero, requires a similar method of protection ; and in this point of view the sub-arachnoid fluid exactly represents the liquor of the amnios. As to the other uses which have been attributed to it, they are all more or less hypo- thetical. If we open the spinal canal of a dog, between the atlas and the occipital bone, some fluid will immediately gush out ; air is drawn in, which is forced out in bubbles during expiration, and again enters during inspiration. If the animal be then left to himself, he will stagger like a drunken man ; he will crouch into a comer, and remain in a drowsy state for some hours. On the next day he will walk about again perfectly well. I have repeated this operation several times upon the same dog, until at last he became accus- tomed to it, at least as far as regards the physiological effects resulting from the remo- val of the fluid, by which means the slight pressure usually exercised upon the spinal cord was removed. The Pia Mater. The pia mater is the innermost of the three membranes of the encephalon and spinal cord. It consists of an extremely delicate membrane, or, rather, of a vascular network, which inunediately invests the nervous axis, and which may be regarded as the nutri- tious membrane of the parts that are covered by it. In fact, the arterial vessels divide into an infinite number of branches within this membrane before they enter the nervous substance, and so, also, the veins which pass out from the brain and spinal cord unite into small, and then into larger vessels, which form part of this same network. These vessels are supported by a very delicate serous cellular tissue : to this is added, in some regions, a certain amount of fibrous tissue, which converts the membrane into a very strong fibrous structure, having all the characters of the neurilemma, or proper invest- ment of the nerves. The characters of the spinal portion of the pia mater are so distinct from those of the cranial portion, that it will be better to postpone the description of the former until we are treating of the spinal cord, of which it constitutes the proper covering. The Cranial Portion of the Pia Mater. This portion, or the cerebral pia mater, does not merely enclose the brain like the arach- noid, but dips into the sulci or anfractuosities on its external surface, and penetrates into the interior of the ventricles. That portion of the pia mater which invests the brain is * " Qua prodit de ventriculo aqua, facili in medullse spinalis circumjectum spatium etiam parat ; earn aquam enim difficulter omnino in tertium ventriculum et ad infundibulum redderet, quoad perpendiculum oportet a»- cendere (Haller, torn, iv., sect. 3, p. 77) . . . Non dubito quin coUecta ex ventriculis cerebri aqua eo descen- dere possit." — (Ibid., sect. 3, p. 87.) t " His spinae aquis eas etiam subinde commisceri, quas, sive a majoribos cerebri ventriculis per lacunar et Sylvii aqueductum, sive a propriis exhalantibus arteriis, cerebelli ventriculus accipiat ; cujus positio perpen- diculata et via ad spine cavum satis patens defluxum liumoris in spinam manifest! persuadent." — {Cotugno, p. 18, 19.) t See note, p. 960. THE EXTERNAL CEREBRAL PIA MATER, ETC. 693 called the external pia mater, and that which is continued into the ventricles is denomi- nated the internal pia mater. The internal pia mater cannot be satisfactorily studied until the internal conformation of the brain is understood, and it will therefore be described together with the ventricles. The External Cerebral Pia Mater. Dissection. — At the base of the brain, the pia mater is naturally separated from the arachnoid by a considerable space, which is occupied by the sub-arachnoid fluid ; but it is easy to separate these two membranes everywhere by introducing air or water be- tween them. The arachnoid may be easily distinguished from the pia mater in cases of serous or purulent infiltration into the sub-arachnoid cellular tissue. The external pia mater is subjacent to the arachnoid, and is connected with it by a very delicate serous cellular tissue ; it not only covers the free surface of each convolution, but also dips into the adjacent sulci ; it passes down on one side of a sulcus, and then, being reflected upon the other, is continued over the free surface of the next convolu- tion, and so on. It follows, therefore, that this part of the pia mater is in contact with itself to a great extent ; and also that its superficies is much larger than that of the arachnoid, so that if the brain could be unfolded, as Gall supposed, its surface would be entirely covered by the pia mater. These remarks apply equally to the pia mater of the cerebellum, for every one of the numerous leuninae of that organ is covered on each side by a fold of the pia mater. The internal surface of the pia mater is in contact with the brain, and is united to it by innumerable vessels, which penetrate into the substance of that organ. This adhe- sion, however, is such, that the pia mater can generally be detached without injuring the surface of the brain. I do not think, however, with some pathologists, that the adhesion of this membrane to such a degree that it cannot be removed without injuring the substance of the brain is any evidence of disease.* For displaying the vessels which pass into the substance of the brain from the pia mater, an asphyxiated subject is very well adapted. But an injected condition of these vessels may be produced by allowing the head of the subject to hang down for some hours. The pia mater will then be not only black from its congested state, but it will be infiltrated with serum ; and if it be detached slowly, an immense number of vascular filaments, looking like hairs, will be seen emerging from the substance of the brain, re- markable for their extreme tenuity and length, and for having no anastomoses. Some drops of blood will indicate the points upon the surface of the brain from which the ves- sels escape, and which, when examined through a lens, prove to be foramina. The use of the pia mater is connected solely with the circulation of blood through the brain. This membrane affords to the vessels a very large surface, on which the arteries divide into their capillary branches, and the veins unite into their larger and larger trunks. According to my observations, five sixths of the vessels of the pia mater belong to the venous system. The pia mater is the nutritious membrane of the brain, and may thus be regarded as its neurilemma. It will afterward be seen that the internal pia mater is connected with the arteries and veins of the walls of the ventricles, ^ust as the external pia mater is with the ex ternal vessels. THE SPINAL CORD AND THE MEDULLA OBLONGATA. General View of the Cord — its Limits and Situation — the Ligamentum Denticulafum. — Size of the Spinal Cord — Form, Directions, and Relations — the Cord in its proper Membrane — the proper Membrane, or Neurilemma of the Cord — the Cord deprived of its proper Mem- brane. — Internal Structure of the Cord — Sections — Examination by Means of Water — and when hardened in Alcohol — the Cavities or Ventricles of the Cord. — The Medulla Oblonga- ta — Situation — External Conformation — Anterior Surface, the Anterior Pyramids, and the Olivary Bodies — the Posterior Surface — the Lateral Surfaces — the Internal Structure — Sections — Examination by Dissection, and under Water. — Development of the Spinal Cord. — Development of the Medulla Oblongata. — Comparative Anatomy of the Spinal Cord. — Comparative Anatomy of the Medulla Oblongata. The spinal cord (fzvelog jidxiTTig, medulla spinalis, a b c, fig. 268)'is that white, round- ish, symmetrical, nervous trunk, which occupies the spinal canal ; it is continuous with the encephalon, of which it has been alternately considered the origin and the termina- tion. It is called the medulla, in consequence of a rude analogy between it and the mar- row of the long bones, in regard to its situation and consistence. Chaussier has sub- * In some cases the membranes are so dry that the pia mater cannot be removed without tearing the sub itance of the brain, even when that organ is perfectly healthy. 094 NEUKOLOGY. stituted for this term the title of racfddian prolongation, but the generally received name of spinal marrow, which can give rise to no error, might be retained.* The Extent and Situation of the Spinal Cord. Authors are not agreed as to the superior limit of the spinal cord. The natural limit is evidently at the groove, between the medulla oblongata (a. Jig. 268) and the pons Varolii (e), which groove, on account of the great size of the pons in man, is much more distinctly marked in him than in those vertebrated animals in which the pons is also found. The spinal cord is situated in the median line, at the back part of the trunk ; it is be- hind the organs of digestion, circulation, and respiration, t The vertebral column, the dura mater, the arachnoid, and the pia mater form a fourfold sheath for the spinal cord ; the first being osseous ; the second, fibrous ; the third, serous ; and the fourth, or proper sheath, both fibrous and vascular ; this last-named membrane is accurately adapted to the cord, so as to support it, and gently compress it on all sides. The spinal cord is not suspended freely in the vertebral canal, but is attached on each side by a ligament called the ligamentum denticulatum. The Ligamentum Denticulatum. The ligamentum denticulatum (c c, fig. 267), so called from the toothlike prolongations Fig. 267. which proceed from its outer border, is an extremely slen- der, fibrous band, which runs along the side of the spinal cord, and adheres to the proper sheath of the cord by its inner border, which is very thin. The outer edge is free, thicker than the inner portion, and gives off certain tooth- like prolongations, which are attached to the dura mater in the intervals between the canals formed by that membrane for the spinal nerves : the first denticulation of this liga- ment, which may be regarded as its origin, is very long, and is found opposite the margin of the foramen magnum, be- tween the vertebral artery and the hypoglossal nerve ; the last, which is the twentieth or twenty-first, forms the ter- mination of the ligament, and corresponds very nearly to "^3 the lower extremity of the spinal cord. The form, thin- ness, and length of these toothlike processes are subject to much variety. The ligamentum denticulatum is evidently fibrous, and cannot be regarded, as Bonn imagined, as a prolongation of the arachnoid.^ The ligamentum denticulatum appears to answer the twofold use of assisting in fixing the spinal cord, and of separating the anterior (a) from the posterior {b) roots of the spi- nal nerves. The Dimensions of the Spinal Cord. Tlie length of the spinal cord in the adult is from fifteen to eighteen inches. Its cir- cumference is twelve lines at the thinnest part and eighteen at the thickest. But it is of much less importance to determine the actual dimensions of the spina] cord than to estimate its relative size as compared with that of the brain, or in reference to the ca- pacity of the vertebral canal, or than to examine the differences in size which it pre- sents at different parts of its extent. If the size of the spinal cord be compared with that of the whole body, throughout the series of vertebrated animals, we shall perceive that it always bears a direct ratio to the vital activity of the animal. Thus considered, the spined cord is small in fishes and rep- tiles, and large in birds and the mammalia. Size and Weight of the Spinal Cord compared with the Size and Weight of the Brain. — It was while studying the spinal cord and the brain in serpents and fishes that Praxagoras, as quoted by Galen, originated the idea that the brain was a production of the spinal cord. All the old anatonusts, on the other hand, who studied the brain and cord in man, in mammalia, and in birds, regarded the medulla spinalis as a prolongation or appendix of the brain (tanquam cerebri effusionem, Rufus) ; indeed, it was for a long time consid- * The first description of the spinal cord which is worthy of notice was given by Huber (J. Huber, De Me- duUd Spinali, Goeltingae, 1741) ; it served as the basis for the works of Haller {Elem. Physiol., torn, iv., sect. 1) ; of Mayer, who published a l)eaTitiful plate of it in 1779; and perhaps of Alexander Monro, Secundus (06- servations on the Structure and Functions of the Nervous System, 1783). Scsmmering-, Reil, and Gall, who so successfully studied the other parts of the nervous system, have noticed the spinal cord in a superficial man- ner. Chaussier (De V Encephale en general et en particulier) ; Keuffel, in his inaugural dissertation {De Me- dulld Spinali, 1810, dedicated to Reil, his preceptor) ; and Rolando {Richerche Anatomiche sulla Strutlura dei Midollo Spinale, Torino, 1824), have supplied many of the deficiencies in our knowledge of this part. There is a good description of the medulla in M. OUivier's work upon the diseases to which it is subject. t The position of the nervous axis behind the alimentary canal constitutes one of the great differences whicli exist between the nervous system of the vertebrated and the invertebrated animals ; in the latter, the nervous system lies below, i. «., in front of the alimentary canal. t It is idle to inquire whether it should be considered a prolongation of the dura mater, or an eztension at the neurilemma, or a proper ligament. DIMENSIONS OP THE SPINAL OORD. 695 ered that the medulla was the principal nerve in the body, summus in corpote humano tier- vus. In the present day, anatomists have returned to the opinion of Praxagoras, and the spinal marrow is generally regarded (Reil, Gall, Tiedemann) as the fundamental part of the nervous system, and that the brain is merely a production, an appendage, or an expansion of the cord. I shall not here enter into these purely speculative questions of production or emanation, origin, and relative importance, for the spinal cord no more produces the brain than the brain produces it. Soemmering has shovni that, in man, the spinal cord is smaller in proportion to the size of the encephalon than in the lower animals ; and of this there can be no doubt ; but it does not follow that the lower animals have a larger spinal cord than man in propor- tion to the size of their bodies : on the contrary, from actual observation, I should say thiit, if we except birds, man has a relatively larger spinal cord than any other animal. Compare, indeed, the medulla of the horse, or of the ox, with that of man, and it will at once be found that the last is the largest and heaviest in proportion to the rest of the body. According to Chaussier, the weight of the spinal cord in the adult is from the nine- teenth to the twenty-fifth part of that of the brain, and in the newborn infant about the fortieth part. According to Meckel, this last is also the proportion in the adult. It must be remembered, however, that Meckel examined the cord when deprived of its proper membrane, and, therefore, after the roots of the nerves were detached from it. Size of the Spinal Cord compared with the Capacity of the Spinal Canal. — The spinal cord does not, by a great deal, fill up the vertebral canal, and a considerable interval oc- cupied by fluids exists between it and the sides of the canal. What is the object of this disproportion 1 and why is there any interval 1 We have already stated (see Osteol- ogy) that the dimensions of the canal are in relation, not only with the size of the cord, but also with the extent of motion of the vertebral column. The opinion of Vieussens, that this space is intended to allow of certain movements of elevation and depression in the spinal cord analogous to those which have been observed in the brain, is sufficiently refuted by the fact that, although the latter organ is affected by movements synchronous with the respiration and with the pulse, it still fills the cavity of the cranium. * The length of the spinal cord does not correspond with that of the vertebral canal, for the cord terminates near the first lumbar vertebra (between 20 and 21, fig. 268), while the canal is prolonged into the sacrum. The position of the lower end of the spinal cord has not been determined with the pre- cision which so important a question demands. According to Winslow, it terminates opposite the first lumbar vertebra ; Morgagni has seen it reach down to the second ; Keuffel has observed it to descend as low as the third lumbar vertebra in one subject, and to terminate opposite the eleventh dorsal vertebra in another. The discrepancy be- tween various authors upon this subject depends upon individual varieties in the point of termination of the cord, and upon the different acceptation of the term lower extremity of the spinal cord ; some regarding the thick swollen part as the end of the cord, while others include in it the tapering portion also. From some experiments which I made upon this subject by thrusting a scalpel horizontally from before backward through the inter-vertebral substance between the first and second lumbar vertebrae, I ascertained that there are varieties in different subjects in regard to the point of termination of the spinal cord, and that it was influenced by the position of the body, and by the state of flexion or extension of the head and spine, but that, in general, the widest part or base of the cone in which the cord ends corresponds to the first lumbar vertebra, and the apex of the cone to the second. During the early periods of foetal life, the cord descends as low as the sacrum ; but in foetuses at the full time, I have never found so marked a difference as has been descri bed by some modem anatomists. + Differences in the Size of the Spinal Cord at different Points of its Extent.— The spinal cord is not of uniform dimensions throughout its whole extent : it is much enlarged at * From several experiments which I have made upon this subject, it appeared that the spinal fluid seen (con- fined in its membranes) in the cervical region, between the occipital bone and the axis, was agitated by move- ments synchronous with the pulse and the respiration ; but that, when this fluid had been evacuated, the spi- nal cord did not move at all. I have examined with the greatest care the tumours existing in the lumbar re- gion in infants afilicted with spina bifida ; I could never detect in them any movement corresponding with the pulse, but the movement of respiration exerted a manifest influence upon them ; thus, when the sac was emp- tied by compression, the cries of the infant, excited by pain, were almost instantly followed by extreme ten- sion of the sac. As the spinal cord is not affected by the great arteries at the base of the brain, it cannot par- ticipate in the slightest degree in those movements which are observed in the spinal fluid at every puise of the heart, and which are communicated to that fluid by the cerebral arteries. t The spinal cord is capable of elongation and retraction ; it is elongated during flexion, and returns to its original condition during extension of the vertebral column; the difference between the two states appears to mo to be from an inch to fifteen lines. In the body of an infant at the full time, which was affected with spina bifida in the sacral region, and died a short time after birth, the spinal marrow descended as low as the sacrum, and there was no cauda equina Malacarne had already observed a similar fact ; this peculiarity depends not upon an arrest of development in the cord, but upon adhesions contracted by it at an early period of foetal life. — (See Auat. Pathol., liv. xvii., art Spina Bifida.) vi., NEUROLOGY. its upper part, opposite the basilar groove, where it constitutes the superior or occipital rachidian bulb, or the medulla oblongata (a) ; it becomes narrowed immediately after hav- ing emerged from the foramen magnum. This constriction, which is named the neck of the rachidian bulb, is regarded by many anatomists as the commencement of the spinal cord. Another oblong enlargement, extending over a much greater length than the prece- ding, and named the middle, cervical, or brachial rachidian bulb, or cervical enlargement (6), commences opposite the third cervical, and terminates opposite the third dorsal vertebra. The spinal cord again becomes considerably contracted from the first to the eleventh dorsal vertebra, and then presents a third enlargement of less extent than either of the other two, constituting the inferior lumbar or crural rachidian bulb, or lumbar enlargement (c) ; it then immediately tapers like a spindle, and terminates in an exceedingly slender semi-transparent cord, which has a fibrous, filiform aspect, is concealed among the nerves of the cauda equina {d), and is always accompanied by a vein. This cord may be distinguished from the surrounding nerves by its being situated in the median line, and by its thinness, its fibrous character, and its termination. It may be traced as far as the base of the sacrum, when it terminates in the dura mater. In some cases the narrow portion of the inferior rachidian bulb is bifurcated, but the two branches of the bifurcation terminate in a single fibrous cord. Huber, Haller, and Stemmering describe the spinal cord as terminating below by two small globular enlarge- ments, of which the superior is oval, and the inferior conical. They have evidently mis- taken an exception for the rule. These three enlargements of the spinal cord constitute a totally different structure from that admitted by Gall, who, comparing with Haller the spinal cord of man, and the vertebrata generally, to the double series of ganglia in annelida and insects, maintained that there are as many enlargements of the cord as there are pairs of nerves. A strict examination into facts is completely at variance with this opinion, for even in the foetus, the temporary conditions of which so frequently resemble the permanent state of the lower animals, we find no trace of this series of enlargements. An erroneous inference, together with the aspect of the cord when surrounded by its nerves, have misled this celebrated physiologist, who should have sought for the representatives of the ganglia of insects, not in the spinal cord itself, but in the series of ganglia on the spinal nerves.* The existence of the three enlargements of the spinal cord above described is in ac- cordance with two general laws relating to the nervous system, viz., 1. That the size of the spinal cord is in proportion to the size and number of the nerves which arise from and terminate in it, and to the functional activity of the organs to which those nerves are distributed ; and, 2. That the exercise of sensibility is connected with larger nerves than that of muscular contractility. Now the most numerous and the most important nervous communications take place opposite those three enlargements. The nerves of the lower extremities correspond with the inferior or lumbar enlargements ; those of the upper extremities, with the mid- dle one ; and the nerves of respiration, the nerves of the tongue, and a part, or perhaps the whole of the nerves of the face, with the superior enlargement. The cervical enlargement, which corresponds to the upper extremities, is certainly larger than the lumbar one, but this is because the upper extremities possess a greater degree of muscular activity than the lower, and also because they are the organs of touch. This explanation is completely justified by comparative anatomy, and is applicable also to the differences in the length of the spinal cord .- thus, it is found that in the dif- ferent species of animals, the length of the spinal cord depends, not upon that of the vertebral canal, nor upon the presence or absence of a tail, but is proportionate to the muscular energy, and to the degree of sensibility. Desmoulins, a young anatomist, too soon lost to science, hsis established this fact by incontrovertible evidence.! The Form, Direction, and Relations of the Spinal Cord. The spinal cord has the form of a cylinder flattened in front and behind (D, fig. 269). * These supposed enlargements are not to be found even in the spinal cord of the calf, which Gall too* as offering the type of this structure. The committee of the institute likewise failed to discover them in the dog, the pig, the deer, the roe-buck, the ox, and the horse, in which Gall asserted that he had found them. The beautiful researches of Tiedemann into the development of the spinal cord have completely overthrown Gall's opinion, which rested merely upon unsubstantiated analogies. [It may be remarked, that though Gall's anatomical statement is not correct, his view as to the analogy is more in accordance with received doctrines than that of the author.] t The spinal cord of birds furnishes a striking pioof of the law which presides over the development of this part of the nervous system. There are no movements performed by animals which require greater force and agility than those observed in the act of flying. It is therefore not astonishing to find that the spinal cord is enlarged opposite the nerves which go to the muscles of the wings. It would be supposed that the portion of the cord which corresponds to the lower extremities should be much smaller than that corresponding to the upper, but yet the inferior enlargement is equal to the one for the wings, because, according to a more inge- nious than probable idea, the lower extremities are the organs of touch in birds. The spinal cord of the tortoise most clearly confirms the law which we have adopted from Desmoulins. The sort of calcareous and homy case in which the trunk of that animal is enclosed is destitute of all power of motion or sensation ; and it is found, the enlarged part of the spinal cord which corresponds to the upper ex tremities is united to that which corresponds to the lower by an extremely slender portion. NEURILEMMA OP THE SPINAL CORD. 697 It exactly corresponds in direction with the vertebral column, every deviation of which it closely follows ; and it is an interesting fact, that it escapes compression, even in an- gular curvatures of the spine. ' The right and left halves of the spinal cord are perfectly symmetrical. There is less symmetry between the anterior and posterior halves, and still less between the upper and lower halves of the cord. The spinal cord is divided by anatomists into a body and extremities. The body of the cord requires to be examined, both when covered by its proper sheath, and after the re- moval of that membrane. The Body of the Spinal Cord enveloped in its Proper Membrane. The surface of the cord everywhere presents certain transverse folds, united by oth- ers running obliquely, so as to form zigzag folds, which were compared by Huber to the rings of a silkworm, and regarded by Monro as so many small articulations ; these folds are situated in the sheath of the cord, and are precisely analogous to those which have been noticed in the tendons during relaxation of the muscles, and those which we shall hereafter have to describe as appearing in relaxed nerves ; they are effaced by exten- sion of the spinal cord, and are reproduced when it resumes its original length. The existence of these folds prevents that stretching of the cord which would other- wise occur in the different movements of the vertebral column. They endow the cord with a certain degree of elasticity. The spinal marrow presents for consideration an anterior, posterior, and two lateral surfaces. The anterior surface presents in the median line a fibrous band, which runs along the entire length of the medulla, and conceals the anterior median groove. The posterior surface, at first sight, presents no trace of a median groove. Many anatomists, therefore, and especially Huber, have denied its existence ; but with a little care we may detect a very delicate line which indicates the situation of the posterior median groove, to which we shall presently advert. On each side of the median line, both on the anterior and posterior surfaces of the cord, are seen the roots of the spinal nerves (1 to 31, fig. 268), which are arranged in four regular lines down the cord, and are divided on either side into the anterior {a, fig. 267) and the posterior {b) roots. The dif- ferences which we shall hereafter describe as existing between these two sets of roots, both in their number, size, and mode of attachment, enable us, at first sight, to distin- guish between the anterior and posterior surfaces of the cord. If these roots be detached, it will be seen that their place of insertion is marked by a series of depressed points, which together constitute two furrows both upon the front and back of the cord, accurately described by Chaussier under the name of the collateral fur- rows of the spinal cord. We cannot deny the existence of the posterior collateral fur- rows, but I do not think that the anterior collateral furrows should be admitted. The sides of the spinal cord are rounded, and narrower than either tlie anterior or the posterior surface : there is no furrow upon these sides, as described by some authors. The two ligamenta denticulata are attached to them. "We must next examine the proper membrane of the cord, or the rachidian pia mater, which we shall name the neurilemma of the cord, from its analogy to the neurilemma of the nerves ; we shall then describe the cord itself J^eurilemma of the Spinal Cord, or Rachidian Pia Mater. Dissection. — It is difficult to separate the rachidian pia mater from the cord, in the greater number of subjects, on account of the softness of the cord itself, and of the rapid changes which it undergoes after death. In order to succeed in doing so, it is advisable to select the body of a person who has died from an acute disease or from an accident. The spinal cord of new-born infants is more fitted for this purpose than that of adults, not only from its relatively greater density at that period of life, but also from its adhesion to the neurilemma being less firm. In the bodies of infants, after making a circular incision through the neurilemma op- posite the medulla oblongata, the sheath may be drawn downward, in the same manner as an eel is skinned, or a stocking drawn off by turning it inside out. When the sheath is more adherent to the cord, it must be very carefully divided along each side of the median furrows, and then detached by breaking down, with the handle of a scalpel, the cellular and vascular prolongations which connect it with the cord. Although the proper covering of the brain, or cerebral pia mater, consists essentially of an interlacement of vessels, the proper sheath of the spinal cord, or rachidian pia mater, is a fibrous, and, therefore, a strong membrane, which supports and protects that part of the cerebro-spinal axis, as the neurilemma does the nerves. The external surface of this membrane is surrounded with a network of remarkably tortuous bloodvessels ; and vessels are also found in its substance. The spinal cord is visible through this semi-transparent membrane, which is naturally of a pearly-white 4T 698 NEUROLOGY. colour, but IS sometimes dull, yellowish, blackish, or even covered with black spots, es- pecially in the cervical region.* This surface of the rachidian neurilemma is also rough, being covered with small cel- lular and fibrous filaments which float under water, and are the remains of small fibrous cords, which extended from the neurilemma to the arachnoid. The internal surface of the neurilemma adheres to the spinal cord by a great number of cellular and vascular prolongations, which form areolae or meshes in its interior, and which have been well described and figured by Keuffel. Along the anterior median furrow, the neurilemma sends off a prolongation, which, en- tering that furrow, lines one of its walls, and is then reflected at its bottom, so as to hne the other waU ; within the substance of the duplicature thus formed, the bloodvessels penetrate. A simple prolongation of the neurilemma, of extreme tensity, also enters into the posterior median furrows, and forms a line of separation between the two pos- terior halves of the spinal cord. The neurilemma is prolonged below the lower extremity of the spinal cord as a fibrous filament, very well described by Huber, which is inserted into the base of the coccyx. This filament the older anatomists regarded as a nerve, and named it the nervus impar ; it is very strong considering its thinness ; it is always tense, and appears to be intended to fix the lower end of the spinal cord ; in this respect serving a similar purpose with the ligamentum denticulatum. Its upper part is hollow, and is filled with a gray and ex- tremely soft substance. The ligamentum denticulatum, which has been considered as a prolongation of the prop- er membrane of the cord, is attached to the external surface of this membrane ; and the proper neurilemma of each nervous filament is also given off from this surface. Monro has stated that a soft layer of gray substance covers the white substance of the spinal cord, and separates it from its neurilemma, but such a layer does not exist. t While the other membranes of the spinal cord are much larger than the part which they have to invest, the neurilemma of the cord is exactly moulded upon it, and even exerts a certain degree of pressure upon it, as is evident from the manner in which the substance of the cord protrudes when this covering is punctured ; this compression oc- casions the apparent consistence of the cord when it is enveloped in its sheath ; a con- dition which contrasts so strongly with its softness when that sheath has been removed. This compression, as well as the absolute inextensibility of the neurilemma, accounts for the rarity of effusions in the cord, and also for the fatal effects of even the slightest effusions within its substance when they do occur. Structure. — The proper membrane of the cord is essentially fibrous ; nor has it any claim to be termed a vascular membrane (tunica vasculosa, Soemmering). Its component fibres interlace in every direction, but the majority of them are longitudinal. It is quite evident that the vessels which ramify upon its surface, and afterward penetrate it, do not belong to the membrane itself. Uses. — The neurilemma is essentially a protecting structure ; it constitutes the frame- work of the spinal cord, and serves, at the same time, as a support for the nutritious ves- sels of that organ ; in this latter respect it has been compared to the pi a mater of the brain. The transition from the spinal into the cerebral portion of the pia mater takes place gradually. The fibrous character of this tunic diminishes upon the medulla oblon- gata and tuber annulare, and is entirely lost opposite the peduncles of the brain ; while its vascular character, on the contrary, becomes gradually more and more marked as it passes from the cord towards the brain. It has been stated that the neurilemma is the secreting organ of the spinal cord ; one might as well say that the testicle is secreted by the tunica albuginea, and the heart by the pericardium. The Body of the Spinal Cord deprived of its J^eurilemma. When the neurilemma of the cord is removed, the spinal nerves are also taken away. We shall hereafter have to inquire whether this fact should lead us to conclude that the nerves do not enter into the substance of the cord, but merely come into contact with it. We would observe, however, in this place, that the posterior roots of the spinal nerves arise in a perfectly regular line, while the anterior roots come off irregularly from differ- ent points of the corresponding medullary column, t The Anterior Median Grocwe and the Commissure. — The anterior median groove, or fissure * These different shades of colour are much more common in certain animals, in the sheep, for example, than in man ; they result from the deposition of a colouring matter, and are in no way connected with any recent or previous morbid action. t In several subjects, I have most distinctly seen a very thin yellowish layer over the medulla oblongata, which dipped between the pyramidal bodies, and filled up the shallow groove which separates the olivary from the pvramidal bodies. X This mode of origin of the anterior roots is perfectly distinct in the spinal cord of the futus or new-bom infant ; up to this period, the tract from which the anterior roots arise is still formed of gray substance. Th« roots, which are white, emerge fmm this gray tract, and when the neurilemma is removed, their small, white, ruptured ends which remain may be traced into the substance of the cord. THE SPINAL CORD DEPRIVED OF ITS NEURILEMMA. Fig. 268. (Jig. 26R ; f, fig. 269, D), penetrates to about one third of the thickness of the cord. At the bottom of the groove, which is occupied by a prolongation of the neurilenuna and a great number of vessels, is seen an extremely thin white layer, perforated with foramina, which is named the anterior com- missure (commissure longitudinale, Chaussier). The foramina in this structure are intended for the trans- mission of tufts of vessels, which enter the sub- stance of the cord. The alternate arrangement of these foramina greatly increases the difficulty of drawing out the vessels, and gives to the commis- sure the appearance of being formed by interlacing fibres ; and, in fact, several anatomists have not only admitted such an interlacement, but have ex- pressly stated that it was produced by the spinal nerves themselves.* According to Gall and Spurzheim, the bundles of which this commissure consists are directed trans- versely, and are fitted into each other like the mo- lar teeth ; but I repeat, that the most careful ex- amination demonstrates nothing in the commissure, besides a white lamella, perforated for the transmis- sion of bloodvessels. The Posterior Median Groove. — The posterior me- dian groove or fissure (a) not only exists, but is much deeper than the anterior one. Its narrow- ness, and the tenuity of the membranous prolon- gation which enters it, have alone concealed it from the observation of anatomists ; there is no white band analogous to that of the anterior median fis- sure at the bottom of this fissure, but the gray sub- stance of the commissure is all that is seen. As there are two median furrows, it follows that there are really two distinct spinal cords, connected together by an extremely thin band or commissure. The Furrows opposite the Posterior Roots of the Nerves, or the Posterior Lateral Furrows. — Immedi- ately to the outer side of the line of origin of the posterior roots of the spinal nerves, there is a gray- ish line or furrow (i), which extends the whole length of the cord. If a stream of water be allowed to fall upon this line, the continuity of the cord is soon destroyed, and the water penetrates to the centre of the organ. But there are no true fissures in these situations analogous to the anterior and posterior median fur- rows. The separation is effected by the destruc- tion of the gray substance, a prolongation of which reaches to the surface of the cord opposite these points. We shall, nevertheless, suppose these fur- rows to exist in accordance with the views of Soem- mering and Rolando, who divided each half of the spinal cord into two columns : a posterior column, consisting of that portion (e) which is comprised be- tween the posterior median furrow (a) and the posterior roots (i) ; and an antcro-lateral column, including all that portion (rf) which is situated between the anterior median fur- row (/) and the supposed posterior lateral furrow (r). We must also admit, with Haller, Chaussier, Gall, and Rolando, a third column on each side ; these may be called the pos- terior median columns, and are continuous with the projecting bundles which form the borders of the calamus scriptorius, and which are each limited externally by a slight groove. These small and exceedingly narrow columns, the existence of which is admit- ted by most anatomists in the cervical region only, are prolonged through the whole ex- tent of the spinal cord. Is there an anterior lateral furrow ? If the line on the outer side of the attachment of the anterior roots of the spinal nerves be closely examined, the appearance of a furrow is seen along the whole of the cord. But if water be allowed to fall upon that line, it is * There is uo physiological or pathological fact which demonstrates the crossing nal cord. eiTect of lesions of the spi 700 NEUROLOGY. found that there is no fissure or furrow properly so called, and that the jet of water has no more effect upon this line than on the adjoining parts ; we are therefore led to reject, with Rolando, both these anterior lateral furrows and the lateral tracts described by Chaussier, which would be bounded in front by the furrow of the anterior roots, and be- hind by that of the posterior roots ; these lateral tracts have, nevertheless, become cele- brated, since so much importance has been attached to them by Sir C. Bell and Bellin- geri as the lateral columns of the spinal cord. From what has been stated above, it follows that each half of the cord is composed of two columns, a posterior and an antero-lateral, and as an appendage to the posterior column, of a small column, which forms the border of the posterior median furrows. Internal Structure of the Spinal Cord. The following results regarding the structure of the cord have been obtained by va- rious modes of investigation : by making sections of it ; by acting upon it with a stream of water ; by hardening it in alcohol and dissecting it ; by studying its development ; and, lastly, by a reference to its comparative anatomy, which appears to be necessary to complete the knowledge acquired by the other means of investigation. Sections of the Cord. ' It appears, from an examination of the external structure of the spinal cord, that it consists of two white, juxtaposed cylinders ; that the surfaces by which these cylinders correspond are flat, closely in contact, and united together by a median commissure ; and that each of them may be divided into two columns, the one posterior and smaller, of which the posterior median column is only an appendage; the other, antero-lateral, which forms two thirds of the circumference of the cylinder. Horizontal Sections. — If various horizontal sections be made through different parts of Fig. 269. t^^ spinal cord, we see that each half consists of a cylinder of white substance, containing gray substance in its interior (see Jig. 269, D) ; that the median commissure is composed of a white layer {white commis- sure) and a gray layer (gray commissure) ; and that in each section the gray matter has a tolerably close resemblance in form to the letter x, the two halves or curves of which are joined in the middle by a horizontal line, while the extremities of the curves are directed towards the ori- gins of the anterior and posterior roots of the nerves. The posterior I B extremities reach much nearer to the surface than the anterior. We perceive, also, in these different sections, that the circumference of the cord is not perfectly regular, but is somewhat sinuous, as we shall pres- ently mention. The size of the central gray mass in each half of the spinal cord, the length and thickness of the prolongations or points, which it sends off towards the anterior and posterior roots, and, lastly, the thickness of the gray commissure, present many varieties, according to the place of section ;* and hence there is a discrepancy between different authors as to the appearances of this section. Thus, Huber compared the sec- tion of the gray matter to an os hyoides ; Monro, to a cross ; Keuffel, to four rays converging towards a central point. Rolando has given figures of sections of the cord at every part of its length. From sections of the cord the general fact is established, that the white substance en- closes the gray matter. The thin layer of gray matter on the surface of the cord ad- mitted by Monro has been justly rejected by all anatomists. The relative situation of the two substances in the cord, which is the reverse of what is observed in the brain, has attracted the attention of anatomists, and various explanations, of greater or less ingenuity, but all hypothetical, have been given of this fact. According to Rolando, there are two kinds of gray matter in the cord, one occupying the anterior, and the other the posterior half of the cylinder ; and these two halves are fitted into each other by a series of indentations, like the bones of the cranium. I have never been able to convince myself of the existence of these two kinds of gray matter, but I have distinctly observed the denticulated appearance of the circumference of the gray matter, which indicates that the gray and white matter mutually penetrate into each other. The colour of the gray substance varies considerably. In some subjects it is whitish, and can only be distinguished from the white matter by its softness, its vascularity, and its not having a fibrous structure. The younger the individual, the more marked is the difference in colour between the two substances. The two substances appear also to differ in their relative proportions in different in- dividuals. Keuffel has ascertained that the gray matter is more abundant in man than * I would recommend five sections of the cord, which appear to rae to give a very accurate notion of its in- ternal structure : the first should be immediately below the decussation of the pyramids ; the second through the middle of the brachial enlargement ; the third through the dorsal constricted part ; the fourth through the middle of the lumbar enlargement ; and the fifth near the apex of the cone formed by the lumbar enlargement. INTERNAL STRUCTURE OP THE SPINAL CORD. ^'Wl in the lower animals ; and this fact would account for the pre-eminent sensibility of the human subject, in accordance with the view of BeUingeri, who considers that the gray matter is the seat of sensation. These horizontal sections enable us not only to determine the relative position and proportions of the white and gray substances, but also to distinguish the superficial fur- rows from those which really enter into the cord ; the existence of these columns in the spinal cord, which have already been described, is in this way fully established. Vertical Sections. — The most important of these is one made from before backward in the median line, so as to separate the two halves of the cord. Each of these halves may then be unfolded like a riband, on the inner surface of which the gray matter forms a thin layer. A transverse vertical section, through the centre of the cord, displays the mode of origin of the anterior and posterior roots of the nerves. Examination of the Spinal Cord under a Stream of Water. The different sections above mentioned expose the general internal arrangements of the cord rather than its actual structure. Until lately, authors had regarded the spinal cord as consisting of a semi-fluid pulp, which oozed out when the neurilemma was divided. Several had said, incidentally, and without distinguishing between the white and the gray substance, that the cord had a fibrous structure, and that its fibres were directed longitudinally. Gall supposed the cord to consist of a series of ganglia, arranged one upon the other ; but it is now gener- ally admitted that the white matter is fibrous, and that its fibres have a linear arrange- ment ; and this is clearly shown by examining this organ by means of a stream of water, the force and size of which may be varied at will. When directed upon the surface of a vertical section, made from before backward down the middle line, the stream of water penetrates the substance of the cord through the gray commissure, breaks down the central gray matter, and spreads the cord out like a riband, from which it is very difficult to wash off all the gray matter. When treated in this way, each half of the cord is almost immediately subdivided into two col- umns, and if the stream of water be now directed upon the internal surface of the col- umns themselves, they may be separated into a great number of wedge-shaped vertical lamellae, directed from the circumference to the centre, the thick external backs of which are turned towards the surface, and the thin internal edges towards the centre of the cord. Now, as all these lamellae are not of equal depth from back to edge, their internal edges reach to different distances from the centre ; hence the denticulated appearance of the circumference of the gray matter in a section ; and hence, also, the mistake of Rolando, in describing the white matter as formed by a medullary layer, folded a very great many times upon itself* According to my observations, each lamella is completely independent of the adjacent ones ; and pathological anatomy fully confirms this observation, by showing that one only may be altered or atrophied, while the others remain unaffected. If the action of the stream of water be continued, these medullary lamellae are decom- posed into very delicate juxtaposed filaments, which extend along the entire length of the cord ; they are all independent of each other, and are merely connected by cellular tissue and some vessels. The structure of the spinal cord is therefore filamentous or fasciculated ; its filaments are almost perfectly identical with those which constitute the proper substance of the nerves. Each filament in the cord traverses its entire length, as each nervous filiiment extends along the whole nerve. The very important inference to be drawn from these facts is the independence, not only of each lamella, but, I may venture to say, of each filament, t * Rolando has even counted these folds : he numbers fifty in the spinal cord of the ox, opposite the origin of the sixth pair of sacral nerves, and about thirty opposite the third pair of sacral nerves ; both of these ob- servations refer to the anterior columns only, for in the two figures which he gives of them the posterior col- umns appear to have no folds. Rolando made his observations upon spinal cords which had been macerated eil'jcr in pure water or in salt and water. t [The microscopic structure of the white and gray substances of the brain and spinal cord has been inves- tigated by Fontana, Ehrenberg, Weber, Remak, Valentin, and others. The fibres of the white matter consist of coherent threads of a soft, semi-transparent, tenacious substance, enclosed in an extremely delicate homo- geneous or structureless sheath, which is very difficult of detection : these fibres are smaller than those of the nerves ; they differ much in size, but each of them is of uniform diameter throughout ; when submitted to the slightest pressure during examination, they have a remarkable tendency to become varicose or beaded, a property which is peculiar to them and to the fibres of the olfactory, optic, and auditory nerves, which also re- semble the fibres of the brain in other respects. The gray matter of the brain and spinal cord consists of large reddish gray globules, containing a nucleus and one or more nucleoli, and having spots of pigment upon them, in situations where the gray matter is dark- er than usual. Surrounding and attached to these globules there are minute jointed fibres, which are marked at intervals with granules (nuclei) ; by Ehrenberg these jointed fibres were considered to be of the same na- ture as the fibres of the white matter, differing from them only in size ; by Miiller and Schwann they are re- garded as organic nervous fibres, resembling those found in such abundance in the sympathetic nerves and ganglia ; while by Valentin and others they are supposed, not only in the brain, but also in the ganglia and nerves, to be the filaments of a delicate cellular tissue. The mode in which the white fibres of the brain and spinal cord end in the gray substance is not well made I9|tt NEUROLOGY. Examination of the Spinal Cord hardened in Alcohol. When deprived of its humidity by alcohol, the spinal marrow becomes very firm, ex- tensible, and elastic. Its filamentous texture becomes very apparent, and the filaments themselves, which, from the contraction of the cord, are flexuous, may be separated from each other, either by the handle of the scalpel, or by slight traction. I have not seen that interlacement of the fibres of the cord which is figured in the beautiful plates of Herbert Mayo, and which, in my opinion, is only apparent, and is produced by drawing the parts under examination in different directions. The Cavities or Ventricles of the Spinal Cord. Several anatomists are of opinion that there is a canal in each half of the spinal cord.* Morgagni has slightly alluded to its existence, which he had not leisure to trace for a greater extent than about five fingers' breadth, t Gall relates that, in examining the body of an infant 8iffected with spina bifida, he cut transversely through the cord, and found that it contained two canals, which he traced into the substance of the medulla oblongata and tuber annulare, beneath the tubercula quadrigemina, and as far as the optic thalami, where they terminated in a pouch as large as an almond.t It is certain that, up to the fourth month of foetal life, each half of the spinal cord con- tains a canal precisely similar to that which exists in fishes ; but after this time the gray matter takes the place of the gelatiniform fluid which had occupied the canal. However, in one case I found the canal persisting after birth. The Medulla Oblongata. Situation. — The medulla oblongata, the rachidian bulb, or cranial enlargement, is that conoid enlargement (a, fig. 268) which forms the upper part of the spinal cord, crowning it like the capitsil of a column : it is situated upon the basilar groove of the occipital bone, and connects the spinal cord with the cerebrum and cerebellum. It was named medulla oblongata by Haller ; but it has also been called the cauda or tail of the medulla oblongata, this term being derived from a comparison of the pons Varolii, the four pe- duncles, and the medulla oblongata to an animal, the body of which was represented by the tuber, the arms by the anterior peduncles, the legs by the posterior peduncles, and the tail by the rachidian bulb. External Conformation of the Medulla Oblongata. The medulla oblongata is received into the deep groove on the fore part of the cir- cumference of the cerebellum (see fig. 276), so that its anterior part only is exposed. In man and the mammalia the medulla oblongata is bounded above and in front by the tuber annulare or pons Varolii {a, fig. 270) ; but above and behind its limits are quite arti- ficial, for it is prolonged upward beyond the pons, cis we shall presently see. Its limits below are altogether arbitrary : the medulla oblongata, in fact, does not contract abrupt- ly, as the term neck of the bulb, applied to its lower extremity, would seem to imply, but it is very gradually narrowed, so as to become continuous with the spinal cord. A plane, which is a tangent of the lower surface of the condyles of the occipital bone, would correspond with the lower boundary of the medulla oblongata. ^ I think, however, that it is more rational to fix this boundary according to the precise point where the me dulla undergoes some decided modifications ; and this point is immediately below the decussation of the pyramids. The medulla oblongata is from fourteen to fifteen lines in length, nine lines in out ; according to Valentin, they separate to admit the gray globules between them, and then unite with one another so as to form loops. The substance of the brain and spinal cord, according to Vauquelin, contains 80 per cent, of water ; its solid constituents consist of albumen, stearine and elaine, phosphorus (1-5 per cent.), osmazome, some acids and salts, and sulphur.] * It is unnecessary to say, that the existence of the single central canal admitted by some authors, is quite irreconcilable with the real structure of the cord. t Adversaria Anat. ,\ol. i., p. 17. Morgagni relates that, having separated the medulla oblongata from the rest of the spinal cord by a horizontal section, he saw in the substance of the cord, and for the space of about five fingers' breadth (etfortasse etiam hngius siquis tunc otium habuisset ulteriorum meduUam e vertebris exi- mendi), a cavity which admitted the end of the finger ; everything appeared to be in a natural state, except- ing this cavity. He adds, that he had never met with so large a cavity ; which seems to imply that he had seen cavities of this kind before. — Negue enim alias tantam out qua: huic accederet vidi. t Spina bifida and hydrocephalus have no direct relation with the persistence of the canals of the spinal cord ; and on this point, I can remove all the doubts expressed by Keuffel (De Medulld Spinali, 62) concerning Morgagni's observation. " Forsan nos quoque," says Keuffel, "earn (scilicet medulla; spinalis caveam) inve- nissemus, si medullam spinalem ex homine hydrocephalico aut spinJl l)ifid^ laborante, inquirere potuissemus. Utinam hujusmodi opportunitas, si occurreret, a nemine negligatur, ut tandem de hJlc re certiores fiamus." In five infants affected with spina bifida, and two who died of chronic hydrocephalus, which I examined for this purpose, the spinal marrow was perfectly normal. Tiedemann regards the canals described by Gall as produced by insufflation. t) I have made experiments upon several subjects, which show that the relations of the medulla oblongata to the foramen magnum vary according as the head is directly vertical, flexed, or extended ; an instrument thrust horizontally between the atlas and occipital bone divides the medulla oblongata at different part* n these various positions of the head. THE MEDULLA OBLONGATA, ETC. 708 breadth, and six in thickness ; it is therefore much broader and thicker than the spinal cord. The medulla oblongata is directed obliquely, like the inclined plane of the basilar groove, so that it forms with the spinal cord a very obtuse angle, which projects back- ward. In shape it resembles a cone flattened in front and behind, and having its base turned upward and its apex downward ; it has, therefore, four surfaces, viz., an anterior, a pos- terior, and two lateral. Anterior Surface of the Medulla Oblongata. This surface (fig. 270) is directed downward, and is therefore named inferior by some anatomists ; it is convex, and is lodged in the basilar groove of the occipital bone ; it can be properly examined only after its '^' _' neurilemma has been dissected off, which is easily done, because its substance is denser than the spinal cord. On this surface we observe a median furrow (/), into which numerous vessels enter : this furrow, which is not nearly so deep as the anterior median furrow of the spinal cord, with which it is continuous, is interrupted by a decussation of fibres about ten si^ lines below the pons Varolii (below n), and terminates above in a tolerably deep fossa (le trou borgne, or foramen cacum, of Vicq d'Azyr), at the point where the furrow meets the pons. Not un- frequently some transverse fibres occupy the place of this median furrow, in which case the anterior surface of the medulla ob- longata resembles the pons Varolii ; sometimes these transverse fibres are found upon only a part of the medulla oblongata. On each side of this median furrow are seen two eminences, which seem as if mould ed in relief upon the part, and which form two planes, succeeding one another like steps from within outward. The two internal eminences are called the anterior pyramids ; the two external are named, from their shape, the olivary bodies. The interior Pyramids. The anterior pyramids ( Vieussens, b b), situated on each side of the median line, and to the inner side of the olivary bodies, are two white pyramidal bundles (bandes medul- laires, Maiacarne), which extend through the entire length of the medulla oblongata ; they project in relief upon the body of the medulla, and seem to emerge or originate near its narrow portion or neck, where they separate from each other the anterior col- umns of the spinal cord, from which columns they are quite distinct : at their point of emergence they are closely approximated and narrow, being about a line and a half in width ; they pass somewhat obliquely upward and outward, become more prominent, and about three lines wide ; having reached the pons Varolii, they become rounded and cylindrical, and are constricted before they enter the substance of the pons, in which we shall afterward trace them. Wniien the two pyramids are gently held apart, it is said that some transverse fibres are seen passing from one to the other, along the bottom of the median furrow ; and it is even stated that there is a decussation of their fibres : this, however, is only apparent, and I cannot here too particularly caution the student against those illusive appearances, which depend either upon the existence of foramina for the passage of vessels, or may be produced by pulling about the scattered fibres in drawing the parts asunder. It wiU soon be shown that there are no transverse fibres fiere, and that there is no decussation of fibres at an acute angle along the whole length of the anterior pyramids, as was ad- laitted by Petit, Winslow, Santorini, and others. The two halves of the medulla oblongata are, in fact, merely applied to each other, and agglutinated together. There is no decussation excepting at the point where the pyramids emerge. The Olivary Bodies. Upon the anterior surface of the medulla oblongata, to the outer side of the anterior pyramids, and upon a plane somewhat posterior to them, are found two white ovoid bodies (corpora ovata), sometimes projecting in relief; these are peculiar to the human subject, and are more prominent in the foetus and new-born infant than in the adult. They were first described by Eustachius, and afterward more accurately by Vieussens, who, on account of their shape, gave them the name of olivary bodies (corpora olivaria, c c) ; they are much shorter than the anterior pyramids, being not more than six lines in length ; they are directed obliquely downward and inward. The upper extremity of the olivary body does not reach the pons Varolii, but is separated from it by a deep furrow ; the lower extremity, which is less prominent than the upper, is bound down by a bundle of arched fibres, the concave borders of which are directed upward (processus arciformes,e). The outer border of the anterior pyramids and the series of nervous filaments which unite to form the hypoglossal nerve (9, fig. 276) constitute the internal boundary of each 704 'NEUROLOGY. olivary body ; and a deep furrow, directed vertically, separates them on the outer side from the inferior peduncles of the cerebellum or the restiform bodies.* It is of importance to observe, that that portion of the olivary body which projects on the outer side of the pyramid is only the external half of the olivary body, its interned half being imbedded in the substance of the medulla oblongata, so as to reach behind the anterior pyramid, t The Posterior SurfcLce of the Medulla Oblongata. This surface is partly concealed by the cerebellum, being received into a groove on Fig. 271. its under surface, and cannot be completely exposed unless the medulla oblongata be forcibly bent forward, or the middle part of the cerebellum be divided vertically. It is then seen that the cord appears to open out {t,fig. 271) opposite the upper part of this surface, and to be turned inside out, so that the gray sub- stance is exposed. In consequence of this separation of the posterior columns of the cord, there is left between them a shal- low, triangular, or V-shaped depression (;?), the bottom of which is smooth, and forms the anterior wall of the fourth ventricle ; Herophilus named this depression, from its appearance, the cal- amus scriptorius. A vertical median groove corresponds to the shaft of the quill ; while its barbs are represented by certain white medullary lines, which vary exceedingly in number, and are not symmetrical ; some of these lines are lost upon the walls of the ventricle, and others turn round the lateral surface of the medulla oblongata, and constitute, in part, the origin of the auditory nerves. The point of the pen is represented by the very acute inferior angle lormed by the sides of the depression, which terminates below in a cul-de-sac, the fos- settc of the fourth ventricle, also called the ventricle of Arantius. According to some au- thors, at the point of the calamus is situated the upper orifice of a canal, which runs through the whole length of the spinal cord ; such a canal, however, does not exist, but is, in fact, produced by the means employed to demonstrate it, for example, by insuffla tion, by the introduction of a probe, or by the weight of a column of mercury. A slight V shaped deposite of corneous matter is constantly found inserted within the corresponding- ly-shaped bifurcation of the columns of the cord : between the branches of the V is found the prolongation of gray substance, which is continuous with the gray matter of the cord. The medullary columns which immediately bound the calamus on each side, and which result from the separation of the elements of the cord, are formed by the posterior me- dian columns {e,fig. 269, B C, and _^^. 271), already described, which become slightly enlarged where they separate from each other, so as to form a mammillary projection, and then terminate insensibly upon the back of the restiform bodies : we shall call the upper part of these columns the mammillary enlargements of the posterior median columns^ and not '■^posterior pyramids. ''''% On the outer side of these mammillary enlargements are found the restiform bodies (d, fig. 269, C ; fig. 271), which, as we shall afterward describe, pass to the cerebellum, and may be said to form its root ; they are also called the inferior peduncles of the cerebellum, or processus a cerebello ad medullam ohlongatam. Ridley named them the restiform bodies, or cord-like processes ; and others, again, call them the posterior pyramids. Fig. 272. TheJjateral Surface of the Medulla Oblongata. These present {fig. 272), in front, the olivary bodies (c), which we have already seen upon the anterior surface. Behind them are the restiform bodies (d) ; and, lastly, about three lines below the lower extremity of each olivary body, is found an oblong projection, the colour of which is intermediate between that of the white and that of the gray substance : this projection is continuous with the gray matter of the furrow, from which the posterior roots of the spinal nerves arise ; and Rolando, who first directed attention to it, has named it the ash-coloured tubercle (tuberculo cinereo). The arched fibres, or processus arciformes {e,fig. 270), pointed out by Santorini, and still better described by Rolando, are principally found upon the lateral surfaces of the medulla oblongata ; they con- sist of filaments of medullary substance, which vary exceedingly in * I do not say, with some authors, that the filaments of origin of the glosso-pharyngeal and pneumogastric nerves (8, fig. 270) bound the olivary bodies behind, for these filaments arise from the inferior peduncles of the cerebellum, or the restiform bodies, not from the furrow between those peduncles and the olivary bodies t In the body of a female who died at the Maternity, the left pyramidal and olivary bodies were not more than half their usual width. It might have been supposed that they were atrophied ; but the patient had ex- hibited no symptom indicative of so serious and uncommon a lesion. With a little attention, I could easily see that the pyramid was divided into two portions, the anterior of which occupied the usual position, while the posterior covered the posterior half of tlie olivary body. I [The term posterior pyramids is, nevertheless, applied to these bodies by many modern anatomists.] INTERNAI? STRUCTURE OP THE MEDULLA OBLONGATA. 705 number and arrangement ; they appear to arise from the anterior median furrow of the medulla oblongata, to turn like a girdle around the pyramidal and olivary bodies, and, having reached the restiform bodies, to pass obliquely upward and outward to terminate upon the sides of the restiform bodies. These arched fibres sometimes seem to be en- tirely wanting ; at other times they are collected on each side into two bundles : one superior, which turns round the anterior pyramid, as that body is about to enter the pons ; the other inferior, which covers and circumscribes the lower extremity of the olivary body. Lastly, the pyramidal and olivary bodies are not unfrequently found to be completely and regularly covered by a thin layer of circular fibres : it will be presently shown that these fibres dip into the anterior median furrow of the medulla oblongata, and reach as far as the posterior median furrow.* Internal Structure of the Medulla Oblongata. The internal structure of the medulla oblongata should be examined by means of sec tions, by the ordinary method of dissection, by separating its elements by means of a jet of water, and by dissecting it after it has been hardened in alcohol or boiled in oil. Sections. Horizontal Sections. — Following the example of Rolando, we shall examine four sec- tions of the medulla oblongata. The first should be made immediately below the decussation of the pyramids ; the second, opposite the middle of the decussation ; the third, through the middle of the oli- vary bodies ; and the fourth, immediately below the pons. The first section presents exactly the same appearances as a section of the spinal cord. The second presents a very different arrangemeirt : the decussating bundles of the pyramids are of very considerable size, and occupy the anterior two thirds of the sub- stance of the medulla : their section represents a triangle having its base turned for- ward, and its truncated apex backward. The gray matter is not circumscribed, as in the first section, but appears to penetrate irregularly into the white substance of which the remaining part of the medulla consists. The white substance itself has not the pure whiteness of medullary substance ; nor does the gray matter resemble that of the rest of the spmal cord, but it is of a yellowish-gray colour, and is much denser. The third section through the middle of the olivary bodies {fig. 269, C) presents, be- sides the triangular section of the pyramidal bodies (i), the serrated section of the corpus dentatum (c') of the olivary bodies (c) ; it enables us to form an accurate idea of the shape and size of these bodies, which extend to each side of the median line ; it shows that they are directed obliquely inward and backward, and that they consist of successive layers, viz., of an external white layer, of an interrupted yellowish layer, and of a sec- ond white layer, which lines the inner surface of the yellowish one. It is seen that the corpora dentata of the olivary bodies are interrupted, or, rather, open on the inner side towards the median line, so as to admit the white fibres with which their interior is filled. The waving gray line seen on these sections depends upon the yellow layer be- ing frequently folded inward and outward upon itself; and from this appearance the terms corpwi dentatum, or corps festonne, have been applied to the gray substance of the olivary bodies. The remaining part (<£) of the medulla oblongata consists of a substance which is of the colour of coffee mixed with milk, and which offers more resistance to the knife than other parts of the medulla, and consists neither wholly of white matter nor wholly of gray, but of a mixture of both. The fourth section, made immediately below the pons {fig. 369, B), presents a trian- gular surface, on which we remark, at each of the posterior angles, a thick white bun- dle, almost as large as the posterior pyramidal body, and which will be hereafter shown to constitute one of the roots of the fifth nerve : these bundles are also seen upon the third section made through the olivary bodies, but they are much smaller than in this section. The section of the two anterior pyramids {b) is circular at this point. The centre of this section of the medulla consists entirely of a grayish- white or coffee-col- oured substance {d c'), covered by a white layer. The grayish-white substance belongs specially to the medulla oblongata ; the surrounding white layer is the continuation of the columns of the spinal cord, t The oblique sections display appearances corresponding with those of the horizontal section. Vertical Section. — A very interesting section of the medulla oblongata is a vertical one, extending from before backward through the median line. I prefer the plan of forcibly separating the two halves of the medulla to that of dividing it with a scalpel. By this means it may be shown that there are in the median line of the medulla some an- * Ought we to regard as a part of this system of arched fibres a small, slender cord which surrounds the upper part of the anterior pyramids, and which in other respects has a similar arrangement to the arched fibres generally % t The medulla oblongata of a child seven or eight years old is much better adapted for the examination of these sections than that of an adult or old subject, because the two substances are blended in the latter ; a stream of water directed upon the sections will greatly assist the examination, by makiug the colours more iistinct 4 U 706 NEUROLOGY. • tero-posterior fibres, which appear to me to vary in number in different subjects : fhesc fibres (o, Jig. 274) run from behind forward through the whole antero-posterior diameter of the medulla ; having reached the anterior median furrow, they pass horizontally out- ward to cover the pyramids and olivary bodies, and form the arched fibres already de- scribed. These antero-posterior fibres are limited below by the decussating fibres of the pyramids. Examination of the Medulla Oblongata by Dissection under a Jet of Water, and when hardened in Alcohol. The anterior pyramids may be separated by ordinary dissection, and a tolerably accu- rate view obtained of their decussations ; and, moreover, the medulla oblongata may be divided into two lateral halves, and its principal parts may then be isolated. The ex- amination of the medulla when hardened in alcohol, or boiled in oil, or in a solution of salt, leads to important results, by enabling us to dissect it fibre by fibre, and to trace these fibres above and below their points of decussation. Together with these different modes of investigation I have employed another, viz., that of acting upon the medulla and its parts by a jet of water, the force and size of which is to be varied at pleasure, and the drops of which insinuate themselves between the fibres and separate them from each other.* If a stream of water be directed upon the anterior pyramids, the fasciculated ar- rangement of their component fibres, all of which are parallel, will be clearly demonstra- ted ; and it will also be seen that these two bodies are not mere medullary bands, but are two three-sided bundles occupying an angular groove between and in front of the two ohvary bodies {fig. 269, C). The decussation of the anterior pyramids demands attention, as one of the most impor- tant points in the anatomy of the cerebro-spinal axis. On examining the anterior median groove of the medulla oblongata (see^^*. 270, 276), it will be found that, at a distance from the pons Varolii of about ten lines (Gall says an inch and some lines), the anterior pyramids divide into three or four bundles, which al- ternately interlace in a regular manner (below n), so as to form a plaited structure of from two to four lines in length. Is this decussation only apparent 1 and if so, does the ap- pearance result, as has been said, from the traction of parallel fibres in opposite direc- tions 1 or do the pyramids commence by alternate bundles arising from each side of the middle line, and does this alternate arrangement occasion the appearance of a decussa- tion 1 or, lastly, do the right and left pyramids actually cross like the limbs of the letter X 1 On consulting the various authorities on this subject, it is found that the decussation of the pyramids, first pointed out by Aretaeus, renoticed by Fabricius Hildanus, and de- monstrated by Mistichellit and Pourfour Dupetit,t has been admitted by Santorini, Wins- low, Lieutaud, Duverney, Scarpa, and Soemmering ; and that the opposite opinion has been maintained by Morgagni, Haller, Vic d'Azyr, Sabatier, Boyer, Cuvier, Chaussier, and Rolando.iJ As to Gall and Spurzheim, they do not seem to have had a decided opinion upon this point ; for, after having appeared to admit the decussation in some passages of their work, they say elsewhere that the small cords of the pyramids do not form a true decussation, but merely intersect and pass over each other obliquely. In order to settle the question of decussation, I submitted the medulla oblongata to the action of a jet of water upon both its anterior and posterior surfaces ; and by then examining it from behind forward, I was able to ascertain that the right and left p)Tam- idal bundles do most evidently decussate (a, fig. 273) ; that this decussation is effect- ed, not only from side to side, but also from before backward (i, fig. 274) ; that the left pyramidal bundle (i) passes downward to the right side and backward (w), traverses the gray matter of the cord, and becomes continuous with the right lateral column of the cord, and vice versa ; and, lastly, that the anterior pyramids are not in the slightest de- gree continuous with the anterior columns of the spinal cord. The Olivary Bodies. — ^When the anterior pyramids are removed, it is seen that the olivary bodies {d, figs. 273, 274) do not consist merely of the prominent masses which project beyond and on the outer side of the anterior pyramids, but that they extend in- ward to the median hne behind the pyramids, which are received in a slight concavity formed by the anterior surfaces of the olivary bodies {fig. 269, C). This arrangement is very evident, without any preparation, in anencephalous infants, or in such as are born * If we employ a stream of water in the eiamination of a fresh medulla oblongata, it may easily be con- ceived that the results will be much more conclusive than if we had thus examined one which had already > been subjected to different modes of preparation that may have altered its structure. t Trattato dell' Apoplessia, 1709. t Letters d'un Med6cin des Hdpitaux, 1710. os- terior in camivora — in the dog, for example. INTERNAL 8TRUCTUEK OP THE ISTHMUS OP THE ENCEPHALON. 713 sponding posterior tubercle or testis. The anterior tubercles or nates are continuous with the optic thalami (a, fig. 271), being separated from them by a slight depression. Some white fibres proceed from the anterior extremity of these tubercles, and, as we shall afterward see, form a thin layer above the corresponding corpus geniculatum ex- ternum (;'), and assist in the formation of the optic nerves. These white bands are gen- erally proportioned to the size of the nates.* The Internal Structure of the Isthmus of the Encephalon. Dissection. — By antero-posterior and transverse sections of the isthmus. The parts to be examined by laceration, by submitting them to the action of a stream of water, and also after they have been hardened in alcohol, or by being boiled in oil, or a solution of salt. The internal structure of the isthmus presents three very distinct strata placed one upon the other : an inferior, formed by the pons, the middle peduncles of the cerebellum, and the fasciculated portion of the peduncles of the cerebrum ; a middle stratum, form- ed by the prolongation of the bundles of re-enforcement of the medulla oblongata ; and a superior stratum, which consists of the triangular lateral bundles of the isthmus, the su- perior peduncles of the cerebellum, the valve of Vieussens, and the tubercula quadri- gemina. iTiternal Structure of the Pons and the Peduncles of the Cerebellum. It has been stated that the lower surface of the pons presents some white transverse fibres (see left side, fig. 273), which twist g^ ^^^ upon each other to form the middle pedun- '^ ^^/ cles of the cerebellum. On making a very superficial incision into the pons, we find, beneath the external layer of white matter, which is very thin behind, and a little thick- er in front, a grayish-yellow substance, which is traversed by the transverse fibres of the pons, so that the part (m, fig. 274) has a striated appearance. If the handle of the scalpel be passed be- neath the anterior border of the pons, so as to remove all that part which projects be- yond the level of the peduncles of the cere- brum, it will be seen that the pons is trav- ersed longitudinally by certain white bun- dles of fibres {b', figs. 273, 274) ; and if, moreover, the handle of the scalpel be insinuated beneath the posterior border of the pons, and all that part be removed which projects be- yond the pyramidal bodies of the medulla oblongata, these white longitudinal bundles which traverse the pons are found to be the prolongation of the pyramids (i), and are themselves continuous with the peduncles of the cerebrum {n,fig. 282). By thus separ- ating the pons into very thin horizontal layers, it will be found that the longitudinal {b') and transverse (m) fibres form several alternate layers, above which we arrive at the middle stratum of the isthmus. The peduncles of the cerebrum are continuous with the longitudinal fibres of the pons, and the middle cerebellar peduncles with the transverse fibres of the same part ; the gray matter of the pons extends into the substance of%he latter, and gives them a stria- ted appearance. At the boundary between the pons and the middle peduncles of the cerebellum there is on each side a very considerable longitudinal bundle, which forms the origin of the fifth nerve, and which, therefore, does not belong to the anterior pyram- idal bodies.! m The absolute continuity of the anterior pyramids with the peduncles of the cerebrum, through the pons, may be regarded as a type of the structure of the nervous centre. The two sets of fibres are intermixed in the pons, so as to intersect each other at right an- gles, but they maintain their individuality, t The pons presents neither a raphe nor a septum in the median line : the fibres of the right half are continuous with those of the left. The white fasciculated fibres {b') of the * They are very large in the sheep ; it appears that it was chiefly from the anatomy of the brain in this an- imal that Gall founded his opinions as to the optic nerves, which he regards as arising from the tubercula quadrigemina. This opinion is very doubtful as far as concerns the human subject. t The most anterior and the most posterior transverse fibres of the pons have a very peculiar arrangement the anterior are inflected {o,fig. 282) between the peduncles of the cerebrum, and completely occupy the in- terval between them ; so that each of these peduncles is embraced by a distinct ring, formed by the fibres of the pons ; and, again, the most posterior fibres of the pons dip between the anterior pyramids, each of which is also embraced by a distinct ring. t The continuity of the pyramids with the peduncles of the cerebrum, through the inferior portion of the pons, was accurately described and figured by Varolius (Dc Nervis Opticis nonnulksque aliis, 1573), by Vieus- sens {NeuTographia Universalis, tab. 16), by Morgagni {Adversaria Anatomica, v.), and by Vicq d'Azyr. Vieus lens showed this continuity by lacerating the pons. Vicq d'Azyr showed it by successively removing the thin layers of the pons by means of a cutting instrument. The plates given by Gall surpass those of his predeces- sors in execution, but not in a scieatific point of view. 4X '714 NEUROLOGY. peduncles of the cerebrum, which are continuous with the anterior pyramids (A), form part of the inferior stratum of the isthmus ; these fasciculated fibres are parallel and per- fectly white, without any intermixture of gray matter. Internal Structure of the Middle Stratum of the Isthmus. When the pons, or, in other words, the successive layers of the inferior portion or etratmn of the isthmus, have been removed, the middle stratum is exposed. This may Fiff. 274. be very easily displayed in a brain that has been well hardened in alcohol. It is then seen that this middle stratum is formed by a prolongation of the fasciculi of re-enforcement \faisceauxinnominis) of the medulla oblongata, which becomes enlarged in passing above the pons, and still more so opposite the peduncles of the cerebrum, above which we shall trace them presently. This prolongation {I, fig. 274) then passes through the pons at right an- gles. It was doubtless to illustrate this arrange- ment that Varolius described the medulla, when viewed from below, as passing beneath the pons like the water of a canal under a bridge. This re-enforcing bundle, pointed out by Ro- lando {Recherches sur la Moelle Alongee, 1822) under the appellation of the middle fasci- culus, has been correctly represented by Mr. Herbert Mayo. Those portions (c, fig. 269, A) of the bundles of re-enforcement which correspond to the peduncles of the cerebrum are separated from the superficial part of the peduncles themselves (a) by a layer of black or blackish matter (5) : opposite the peduncles, these two bundles are intimately united,* but they soon diverge to enter the optic thalami. Are they simply in juxtaposition, or do they interlace at the point in which they appear to be blended 1 I am inclined to believe that they do interlace ; but I have not yet been able to demonstrate this clearly, because they do not consist of very distinct bundles. The Internal Structure of the Upper Stratum of the Isthmus. The superior peduncles of the cerebellum are fasciculated : their lower extremities {r,jig. 274) assist in forming the central nucleus of the cerebellum ; their upper extremities (r') expand into a great number of fibres, some of which terminate upon the anterior wall of the fourth ventricle, on each side of the median line, while others form a loop below the tubercula quadrigemina. Structure of the Tubercula Quadrigemina. — Reil, who first examined the structure of the tubercula quadrigemina, considers them as consisting of four rounded masses of gray matter, placed upon the radiated fibres of a white bundle, which spreads out beneath them. This white bundle (forming part of the bundle h, fig. 274), which he calls the ^Z- let or loop, is derived (c), according to him, partly from the anterior pyramidal, and part- ly from the olivary body (^d). It appears to me to be nothing more than the above-men- tioned loop formed by the superior peduncles of the cerebellum, below the tubercula quadrigemina. The tubercula quadrigemina themselves seem to me to be rather of a laminated than of a fasciculated structure. Mayo represents them as having a fasciculated texture. The triangular lateral fasciculus of the isthmus (A, fig. 272) passes in one direction be tween the upper and middle strata of the isthmus, and in another it may be traced (form- ing the other part of the bundle h, fig. 274) downward as far a^s the olivary body. The anterior fibres extend from the testis {g) to the corpus geniculatum internum (»), pass beneath that body, and penetrate into the interior of the optic thalamus. This triangu- lar fasciculus forms a layer upon the superior peduncle of the cerebellum, from which it is perfectly distinct. Sections of the Isthmus of the EncephaJon. A vertical section made from before backward through the median line of the istnmus will give an excellent view of its three portions or strata : the section should include the medulla oblongata (see fig. 274). Upon it are seen the white and gray striated mass (m b' m) which constitutes the pons, the re-enforcing fasciculus (/) of the medulla oblon- gata becoming much thicker opposite the peduncles of the cerebrum than in the pons. Transverse vertical sections will display the arrangement of the pyramidal bodies and the re-enforcing fasciculi as they pass from the medulla oblongata into the isthmus. In these sections a thick bundle belonging to the fifth nerve is always seen. Sections of the tubercula quadrigemina show that they are neither distinct from each other, nor from the external and internal corpora geniculata, nor from the re-enforcing fasciculi of the medulla oblongata ; but that these latter fasciculi and the tubercula qua- drigemina form a single system, surmounted by masses of nervous matter, which are the tubercles themselves. * IThey here constitute the so-called integumentum (c,fig. 269, A) : the black snbstance is called the locut tiger (6), and the suj^rficial part of the peduncle is named the crust or basis (o).] THE CEREBELLUM. 715 Development of the Isthmus Encephah. The development of the pons and of the peduncles of the cerebellum is in relation with that of the cerebellum ; and the development of the cerebral peduncles with that of the cerebrum. In the embryo of two months, the tubercula quadrigemina consist merely of two lam- inae, which curve upward and outward, and become united at the end of the third month. At this period the tubercula quadrigemina of the human subject are in the same con- dition as those of the lower animals. They are as yet, indeed, only two in number, one on each side of the middle line ; and they are hollow, as in birds. At first they are com- pletely exposed, but are gradually covered by the hemispheres of the cerebrum, as those parts are prolonged backward. The transverse groove which divides the hitherto single pair of tubercles into an an terior and a posterior tubercle on each side does not appear until about the sixth month, at which time the cavity in their interior has been obliterated by the thickening of their ■parietes.* Comparative Anatomy of the Isthmus. The pons Varolii and middle peduncles of the cerebellum exist only in the human subject and in mammalia generally ; these structures, which may be regarded as forming the com- missure of the cerebellum, are developed exactly in proportion to the size of the lateral lobes of that orgem ; so that they attain their utmost development in the human subject, and are smallest in rodentia. The pons and cerebellar peduncles do not exist in the re- maining three classes of vertebrata (birds, reptiles, and fishes), because those animals have no lateral lobes of the cerebellum. The tubercula quadrigemina are less developed in man than in the lower animals. It may even be said that the development of these tubercles is inversely in proportion to that of the lateral lobes of the cerebellum and the hemispheres of the cerebrum. The anterior tubercles are a little larger than the posterior in the human subject : in the ruminants, solipeds, and rodentia, on the contrary, the anterior tubercles are twice or three times as large as the posterior. In the carnivora the posterior are somewhat larger than the anterior. They are covered by the cerebrum in the human subject and the highest orders of manomalia, but are in a great measure exposed in the rodentia and cheiroptera. In birds, reptiles, and fishes, the tubercles are only two in number (the tubercula bige- mina), and attain their maximum development : sometimes they are even larger than the cerebral hemispheres ; they are hollow, and form true lobes, which are called the optic lobes, because, in fact, the optic nerves arise exclusively from them. In birds, the optic lobes are situated at each side of the base of the cerebrum. The optic lobes of birds are not the thalami optici, as was at first believed : in this class of animals the optic thalami are thrown forward. In reptiles, the tubercula quadrigemina consist, as in birds, of two large, ovoid, and contiguous lobes. In fishes, it is extremely difficult to determine what are the tubercula quadrigemina ; so much so, indeed, that the lobes of which they are composed have been taken some- times for the cerebral hemispheres, and sometimes for the optic thalami. M. Arsaky (De Piscium Cerebro) has successfully refuted both of these errors. THE CEREBELLUM. General Description. — External Characters and Conformation — Furrows, Lobules," Lamina, and Lamellce. — Internal Conformation — the Fourth Ventricle, its Fibrous Layers, its In- ferior Orifice, and its Choroid Plexus. — Sections of the Cerebellum, Vertical and Horizon- tal. — Examination by Means of Water, and of the Hardened Cerebellum. — General View of the Organ. — Development. — Comparative Anatomy. The cerebellum {TrapEyKealic, Aristotle, 1 1, fig. 276 ; h h, fig. 280), or little brain, is that part of the encephalon which occupies the right and left inferior occipital fossae. It exists in all animals which have a cerebrum and spinal cord, and, therefore, in all the vertebrata. Cases of congenital absence of the cerebellum are extremely rare.t Though for a long time neglected, the anatomical examination of the cerebellum was commenced with considerable talent by Petit, of Namur {Lcttre d'un Medecin des Hopi- tava du Roi, Namur, 1710), and Malacarne {Encephalotomia nuova Universale, Torino, 1780). Vicq d'Azyr and Chaussier have described its external conformation with ex- traordinary accuracy ; and Reil, Gall, and Rolando, have more particularly investigated its structure. * In a fetus of seven months, I found the tubercula qnadrig-emina not yet divided into the nates and testes, t Vide Anat. Pathol., avec fi^., for a case of absence of the cerebellum. #f§ NEUROLOGY. The External Characters and Conformation of the Cerebellutn. Situation. — The cerebellum is enclosed between the inferior occipital fossae and the process of the dura mater, called the tentorium cerebelli. It is placed {see fig. 282) at the top of and behind the spinal cord, and the isthmus of the encephalon. It is covered by the cerebrum in the human subject only, whence the name cerebrum inferius. It is posterior to the brain in the lower animals, and is therefore called cerebrum posterius. The dura mater, the arachnoid, and the pia mater form a threefold investment around it, the arrangement of which has been already described. Size and Weight. — The cerebellum is larger in man than in any other species. It has been stated by Cuvier, that its size in the human subject is so exactly proportioned to that of the brain, that correct tables may be formed of their relative weights ; but it ap- pears to me that facts are opposed to this view. The mean weight of the cerebellum, including the pons Varolii and medulla oblongata, is from four to five ounces ; the proportion between the cerebrum and cerebellum may be estimated approximately to be as 7 to I.* According to Gall and Cuvier, the cerebellum of the female is proportionally larger than that of the male. Gall believes that its size is in a direct ratio with the energy of the generative function, and that this is indicated externally by the relative size of the inferior occipital protuberances.! The cerebellum is proportionally much smaller in the infant than in the adult ; the relation between the cerebrum and cerebellum in the infant is as 20 to 1. Density. — The consistence of the cerebellum has been much studied by anatomists, who are far from being agreed upon this subject. The great difficulty depends upon the ■want of accurate means of estimating its consistence. In fact, it may be readily con- ceived that the conversion of its substance into a pulp, by letting weights fall upon it from a determinate height, is at once a most inconclusive and almost inapplicable meth- od of ascertaining the point. Another source of difficulty consists in the fact that the cerebellum is not homogeneous ; so that results obtained in reference to the gray matter do not apply to the white substance. Out of fifty cerebella which Malacarne compared •with the corresponding brains, twenty-three were softer than the brains in both the me- dullary and cortical substances ; in thirteen the cortical substance was equally firm, but the medullary substance more consistent and elastic than that of the brain ; ten were more dense in texture, and the remaining five were much harder than the corresponding brains. In some cerebella one of the hemispheres was much more firm than the other. The results of my observations are, that the medullary centre of the cerebellum is of a firmer consistence than that of the cerebrum ; that the gray substance of the cerebel- lum is softer than that of the cerebrum; and that the gray substance of the former be- comes softened in the dead body with such extreme rapidity, that it is difficult to meet with a cerebellum in which this substance is in the normal state. Form. — The general outline of the cerebellum is that of an ellipsoid flattened from above downward ; its long diameter is transverse, and measures from three and a half to four inches ; its antero-posterior diameter is from two to two and a half inches, and its vertical diameter two inches in the thickest part, and about six lines in the thinnest part, that is, at its circumference. The figure of the cerebellum may also be compared to that of a heart on playing cards, the notch of which is directed backward, and the truncated apex forward ; or, rather, as was done by the old anatomists, to two flattened spheroids, united together at their points of contact. The cerebellum is perfectly symmetrical, but yet a marked difference between the right and left half of this organ is not unfrequently observed.} The cerebellum presents for our consideration an upper and a lower surface, and a circumference. The upper surface {h h, fig. 280) presents along the median line an antero-posterior em- inence (d), which is rather prominent in front, but gradually disappears as it extends backward : it is named the superior vermiform process {vermis superior). This eminence, which covers the valve of Vieussens and the tubercula quadrigemina, should be regard- ed, as Malacarne states, as the upper part of the median lobe of the cerebellum. On each side {h h) the upper surface of the cerebellum forms an inclined plane. This surface is separated from the posterior lobe of the cerebrum by the tentorium cerebelli. * Chaassier says, " In a considerable number of comparative experiments, we sometimes found that the adult cerebellum was -^th or ^th, and at other times, but rarely, -pn th or -ryth the weight of the cerebrum. In the infant, at birth, we found it to be yV*-^' tV*^' PT*''' "^V^'' ^'^i ""''' '" °"® '^*'^» *^®" 3 S*^ '^^ ^"^'^^ weight of the brain." — {De VEncephale,^.71.) + In my opinion, this idea can only be regarded as an ingenious hypothesis. The aptitude for the generative act is not dependant upon the cerebellum, for all invertebrate animals are destitute of this organ ; and in cer- tain vertebrata, where the generative orgasm is quite remarkable, the cerebellum is extremely small. Some observations, however, are quoted, which appear to show that diminution of the occipital protuberance ha» followed extirpation of the corresponding testicle : but it must first be proved that these observations are cor red ; for example, that the inequality of the occipital protuberances did not exist previously to the castration, t In four cases which have come under my own observation, atrophy of the right hemisphere of the cerebrum coexisted with atrophy of the left hemisphere of the cerebellum ; I am, therefore, led to conclude that there ve certain intimate relations between the opposite hemispheres of these two portions of the encephalon. THE FURROWS, LOBULES, ETC., OF THE CEREBELLUM. 717 The lower surface of the cerebellum {figs. 275, 276) is received into the concavity oi the occipital fossae, to which it is exactly fitted: it is divided into. two rounded, lateral halves {h, fig. 275), the lobes of the cerebellum, by an antero-posterior fissure (a to n), the great median fissure of the cerebellum (vallecula, Haller). The back part of the cerebellum is completely subdivided by this fissure {see fig. 282), which receives the falx cerebelli ; in front, the fissure opens into a wide furrow, into which the medulla oblongata is received {see fig. 276) ; in the middle of the fissure is a lozenge-shaped interval, at the bottom of which is seen the base of a pyramidal emi- nence {a h c, fig. 275), divided transversely pig. 275. into rings like a silkworm, and n£imed, ac- cordingly, by the older anatomists, the in- ferior vermiform process {vermis inferior, 'pyr- amid, of Malacarne). This eminence is de- veloped into four prolongations or branch- es, arranged in the form of a cross ; the posterior prolongation (c) is tapering, an(: occupies the back part of the great median fissure ; the two lateral processes dip (on each side of h) into the adjacent portion of the fourth ventricle ; and the anterior (i) tapers from behind forward, and terminates in a mammillary enlargement (a), which is free, and projects into the fourth ventricle. It has been unnecessarily distinguished from the rest of the inferior vermiform process by Malacarne and Chaussier, under the name of the laminated tubercle of the fourth ventricle {tubercle lamineux du quatrieme ventricule).* The inferior vermiform process is merely the lower part of the median lobe of the cere- bellum, of which the superior vermis constitutes the upper part. The superior vermis is continuous, without any line of demarcation, with the two hemispheres of the cerebel- lum, so that the upper part of that organ appears undivided. The inferior vermis, which seems at first sight to be intended to separate the two hemispheres, nevertheless forms the means of connexion between them, as may be easily seen by drawing them apart from each other. The circumference of the cerebellum is somewhat elliptical, or, rather, resembles the heart upon playing cards ; behind and in the middle line it presents a notch (n), between the convex margins of which a triangular interval is left, into which the falx cerebelli and the internal occipital crest are received. At the bottom of this notch the surface of the cerebellum is transversely grooved ; this part unites the superior to the inferior vermiform process, and belongs to the median lobe of the cerebellum. The rounded margins of the 7iotch are continuous with the circumference of the cere- bellum. In front, the circumference of the cerebellum appears to be formed by the pons Varolii {d,fig. 276) and middle cerebellar peduncles (m), which are in relation with the posterior surface of the petrous portion of the temporal bones, and are therefore straight, and form a truncated angle, which projects forward, and corresponds to the pons Varolii. All the bundles of fibres which connect the cerebellum with the cerebrum and spinsd cord enter at the anterior part of its circumference : thus, besides the middle peduncles of the cerebellum, we find in this situation its superior peduncles (r, fig. 272), or pro- cessus ad testes, and its inferior peduncles (cut at n), or processus ad medullam oblongatam, to which we shall presently return. The Furrows, Lobules, Laminae, and Lamellce of the Cerebellum. The whole surface of the cerebellum is traversed by curved lines or furrows, which are, for the most part, concentric and horizontal, but not very regular. These furrows are not parallel, but are inflected towards each other, and intersect at very acute angles. They may be divided into four sets, according to their depth. The first set of furrows are the deepest : they reach as far as the central nucleus, and divide the cerebellum into segments or lobules {g, h, I, fig. 275). omj These segments are divided into secondary segments by the second set of furrows. The secondary segments are again subdivided into lamiruB or folia, and these lamina into lamella, by two sets of yet smaller furrows. Pourfour du Petit, Malacarne, and Chaussier have studied the sepnents, laminae, and lamellae of the cerebellum with great care, and have even counted them. The differen- ces in their results! are not so much a proof of varieties in the structure of the organ as of the want of some uniform method of enumeration. * [The inferior vermiform process is usually described as consisting of three portions : the pyramid (.c,fig. 275), the uvula (6), and the nodulus (o).] t Winslow admitted 3 lobules, Collins 6, Ponrfour du Petit 15, Malacarne 11, and Chaussier 16. Chaus- sier counted 60 laminae, and from 600 to 700 lamellae ; Malacarne had previously counted from 700 to 800 la- mellae. It is a very curious fact that Malacarne only found 324 lamells in an individual labouring under mental alienation 718 NEUROLOOV The segments which occupy the circumference of the organ are the largest : they rep- resent segments of an ellipsoid, and are very broad in the middle, and narrowed at each extremity. The segments of the upper surface are concentric, and their curvature cor- responds to that of the entire cerebellum. The segments of the lower surface are also concentric in each half or lobe of the cerebellum, but the curves of one side are inde- pendent of those of the other. The laminae or folia of the cerebellum are applied to each other like the leaves of a book ; they are separated from each other in their whole length, and are attached to the rest of the cerebellum by their adherent borders only. The lamellae, however, are ar- ranged in a different manner, for they pass from one lamina to another, and even from segment to segment. In fact, if the segments of the cerebellum be drawn asunder, the furrows between them are seen to be traversed obliquely by a great number of lamellae, which extend from one segment to another. The arrangement of the segments, laminae, and lamellae in the median line deserves particular attention. Opposite the superior vermiform process, they are not interrupted, but are merely bent slightly, so that the middle portion of each of the anterior segments is, as it were, drawn forward, so as to describe a curve, having its concavity turned backward. Upon this surface some slight peculiarities are observed in the arrangement of the parts. Along the median line there seems, indeed, to be an interchange of lam- inae and lamellae, some of each of which become thin, and end in points, from which oth- ers appear to originate. Opposite the inferior vermiform process the two hemispheres of the cerebellum are connected together by means of the latercd prolongations of that process. But in front, i. c, opposite the medulla oblongata, the two hemispheres of the cerebellum are perfect- ly distinct from each other (see Jig. 275). From these facts we may estimate to what extent the comparison is correct which was drawn by HaUer between the superior ver- miform process and the corpus callosum. At the back part of the cerebellum, opposite the notch in that situation, the two hem- ispheres are connected by means of certain small transverse rings, of which we have already spoken. The superior and inferior vermiform processes and the portion situated at the bottom of the notch constitute together the middle lobe of the cerebellum, which Gall and Spurz- heim named the primitive or fundamental part of the cerebellum, because it exists in all vertebrata, and because, in a great number of them (as in birds, reptiles, and fishes), where the lateral lobes of this organ are altogether wanting, it constitutes the entire cerebellum. It is well to add, that the lateral lobes are relatively larger, and the medi- an lobe smaller in man than in other mammalia. A rudimentary median lobe, and very large lateral lobes, are the characteristics of the human cerebellum, while a very large median lobe, and rudimentary lateral lobes, form the characters of the cerebellum of the lower animals. All the segments of the cerebellum, of which there are from ten to twelve, might with propriety be distinguished by particular names. The following segments, however, re- quire special mention : the segment or lobule of the circumference {I, fig. 275), which is the largest ; the lobules of the medulla oblongata (lobuli medullae oblongatae), which are situa- ted behind that part (see fig. 276), are concave on their internal surface, which is accu- rately adapted to the medulla, and convex on their external and posterior surface, which dips slightly into the foramen magnum. These lobules (removed from f,fig. 275), which have been noticed by all qnatomists, are separated from one another by the inferior vermi- form process (the uvula, b), and each of them terminates in front and on the inner side by a mammillated extremity (called the amygdala or tonsil), which partially fills up the fourth ventricle. The other inferior segments of each lobe of the cerebellum describe concen- tric curves around this segment. The lobule of the pneumogastric nerve (rf) is a sort of prominent tuft (flocculus), situated (w, fig. 276) behind the pneumogastric nerve (8), and below the facial and auditory nerves (7). The Internal Structure of the Cerebellum. It is convenient to include under this head the description of the fourth ventricle, as well as that of the substance of the cerebellum. The Fourth Ventricle. Dissection. — Divide the median lobe of the cerebellum vertically ; make a vertical section of the pons along the median line ; draw asunder the medulla oblongata from the cerebellum. By means of the first section the anterior wall of the fourth ventricle is exposed, and by the second its posterior wall ; by drawing apart the medulla oblongata and cerebellum, the ventricle is reached by its inferior extremity, and its whole depth can be seen. It is important to examine the fourth ventricle in all its aspects. The fourth ventricle {c to y, fig. 282) is that rhomboidal cavity situated between the medulla oblongata and isthmus of the encephalon (? n), which forms its anterior wall, and the cerebellum (w), which constitutes its posterior wall. The old anatomists follow- THE FOURTH VENTRICLE. 719 ea Galen m calling it the ventricle of the cerehellum. Tiedemann speaks of it as the first ventricle, because it is developed before the other ventricles, and is constant in all mam- malia. The fourth ventricle terminates in a point below, expands considerably in the middle, and is again contracted at its upper part, where it becomes continuous with the third ventricle. . We shall consider separately its anterior and posterior walls. The anterior or inferior wall is formed by the posterior surface of the medulla oblonga- gata (see^. 271) and that part of the upper surface of the isthmus of the encephalon which corresponds to the pons. In shape it resembles a lozenge or diamond, truncated at its upper point ; the upper borders of the lozenge being represented by the superior peduncles of the cerebellum (r to g), and the lower by the restiform bodies (e) : the poste- rior surface of the re-enforcing fasciculi {faisceaux innomines) of the medulla oblongata constitutes this anterior wall, which is lined by a dense and easily separable membrane. The 'posterior or superior wall represents a vaulted roof, which is formed above by the superior peduncles of the cerebellum (r to g) and the valve of Vieussens {l, fig. 271 ; I, fig, 275 ; g w, fig. 282), lower down by the cerebellum (w), and below by a fibrous mem- brane, continuous with the neurilemma of the spinal cord. Opposite the middle, i. e., the broadest part of this posterior wall (see_^. 275), are sit- uated three mammillary projections — one median and two lateral : the first (b, the uatu- la) is the anterior segment of the median lobe of the cerebellum ; the other two (the amygdcdae) are formed by the innermost laminae of the lobule of the medulla oblongata (cut away at/). These latter are not bathed in the fluid of the ventricle, but are sep- arated from it by the fibrous membrane lining that cavity. The median mammillary projection (6), named by Malacarne and Chaussier the lami- nated tubercle of the fourth ventricle, resembles a movable valve. It is attached to the cerebellum by two white pedicles, which pass outward and backward upon the lateral processes of the crucial eminence formed by the inferior vermis. Connected to its an- terior extremity (the nodulus, a) are seen two broad folds {semilunar folds, e), which arise from it, one on each side, and become continuous with the roots of the corresponding sub-peduncular lobules or flocculi {d). These folds, which are quite distinct from the valvulse Tarini, are extremely thin and semi-transparent ; their convex borders adhere to the back part of the fourth ventricle ; the concave margins and their two surfaces are free.* The two semilunar folds and the intermediate projection, or the nodule, may be compared to the soft palate, the mam- millary projection representing the uvula, t Opposite the upper angle of its rhomboidal cavity, the fourth ventricle {v, fig. 282) be- comes continuous with the third (Z), through a canal, named iter a tertio ad quartum ven- triculum, or the aqueduct of Sylvius, which, however, had been described by Galen : this aqueduct is formed beneath the tubercula quadrigemina {f g) and the valve of.Vieus- sens {g w). The lateral angles of the fourth ventricle are much elongated, and reach as far as op- posite the inner extremity of the corpus dentatum of the cerebellum. At the inferior angle (y) of the fourth ventricle is situated a fibrous layer, which con- stitutes its floor, and also an orifice of communication between the ventricle and the sub-arachnoid space. The Fibrous Layers of the Fourth Ventricle. Floor of the Fourth Ventricle. — On carefully drawing the medulla oblongata away from the cerebellum, a fibrous layer is seen extending from one to the other, and forming, as it were, the floor of the fourth ventricle. This layer, which is continuous with the neu- rilemma of the medulla oblongata, consists of three very distinct parts : of a median portion, shaped like a triangular tongue, which passes horizontally backward, and is ap- pUed to the anterior extremity of the inferior vermis, to which it adheres ; and of two triangular lateral portions, which form the sides of the orifice of the fourth ventricle, and which were described by Tarin as the valves of the base of the fourth ventricle. Besides this fibrous layer, there is another on each side, situated behind the roots of the pneumogastric nerve : these layers adhere to those roots, and we shall therefore name them the fibrous layers of the pneumogastric nerves ; they close the fourth ventricle upon the sides of the medulla oblongata, and when they are removed the ventricle is quite open. They extend from the restiform bodies to the lobules of the pneumogastric nerves, and are prolonged upward upon the auditory nerves. The Inferior Orifice of the Fourth Ventricle. If the medulla oblongata and cerebellum be drawn apart, there is seen in the median * [These two folds constitute the posterior medullary velum of the cerebellum, the valve of Vieussens form- ing the anterior velum.] t [The terms uvv.la and amygdalie, or tonsils, have, as already noticed, been applied to another series ot three bodies which are arranged behind the nodule, the flocculi and the posterior vela, and consist of the lam- inated tubercle of the fourth ventricle, and of the inner portions of the lobes of the medulla oblongata (see p. 718).] • s{ vj' »»i»<»««>n»^-"iTiv r- - -■ 71^ NEUROLOGY. line, between the inferior cerebellar arteries, a lozenge-shaped opening (at y, fig. 282), bounded, in front, by the base of the calamus scriptorius ; behind, by the anterior pro- longation of the inferior vermiform process, which is covered by the median tongue of the fibrous layer ; and upon the sides, in front, by the ragged edges of the lateral por- tions of the fibrous layer, and by the internal surfaces of the lobules of the medulla ob- longata. This opening was pointed out by M. Magendie as establishing a communication be- tween the general ventricular cavity and the sub-arachnoid space. It has been asked, Is it a natural opening, or is it produced accidentally by the very means employed in its demonstration 1 The following are the arguments on both sides of the question : In opposition to the existence of an opening in this situation, it is urged that the mar- gin of the orifice has none of the characters of that of a natural opening, the edges of which are generally smooth and rounded ; but in this orifice they are lacerated, and there is almost always some membranous shreds at the point of the calamus scriptorius. If the median triangular tongue of the fibrous layer, which is applied to the inferior vermis, be detached, it is seen to be merely a flap of that membrane, the size of which exactly corresponds to that of the opening, so as to close it completely. This point may be ren- dered still more evident by tracing the membrane from before backward, after having di- vided the pons and medulla oblongata. Again, the fibrous layer, which forms the floor of the fourth ventricle, is entire in the dog and sheep ; I have found it in the same condition five or six times in the human subject ; and if it be objected that, in this case, there might have been an accidental ob- literation of the opening, I could answer that there was no trace of disease, either in the cerebro-spinal axis, or in the membranes. I may also mention that, in several cases of chronic hydrocephalus, several pounds ol fluid were found in the ventricles, and none whatever in the sub-arachnoid space. Lastly, in the brains of several infants, who had died with all the symptoms of acute ventricular hydrocephalus, I have found the lateral ventricles very large, but empty ; and in these cases, it has occurred to me that the fibrous layer might have been perforated opposite the inferior angle of the fourth ventricle, and have thus allowed the fluid to escape, which, in the greater number of cases, is retained by this layer within the ven- tricular cavity. Such are the facts which appear to me to militate against the idea of the existence of an opening in the floor of the fourth ventricle ; but, on the other hand, if we consider that, in an immense majority of instances, whatever care may be taken in removing the brain from the cranium, we always find this opening both in the foetus and in the adult ; that in apoplectic effusions into the ventricles, we always find some bloody serum in the sub-arachnoid space ; and that if a coloured fluid be injected into the ventricles of the cerebrum, or into the sub-arachnoid space around the cord, it will in either case pass freely /rom one into the other, we shall be led to conclude that there is a regular com- munication between the cavity of the ventricles and the sub-arachnoid space, and that the orifice just described is the channel of communication between them.* The Choroid Plexuses of the Fourth Ventricle. The choroid ■plexuses of the fourth ventricle are two in number ; they commence one on each side, by a very slender extremity, upon the anterior surface of the sort of fibrous tongue which is attached to the inferior vermis ; from this point they pass in a diver- ging course upward, are then inclined outward, turn round the sides of the median emi- nence of the fourth ventricle, pass horizontally outward behind the restiform bodies, and then behind the fibrous layer of the corresponding pneumogastric nerve, where they be- come considerably enlarged, and at length terminate upon the sub-peduncular lobes. The inner surface of the fourth ventricle is smooth, in consequence of being lined by a membrane resembling a serous membrane, which is much stronger over the posterior surface of the medulla oblongata than at any other point. Sections of the Cerebellum. On cutting through the cerebellum, it is found to be composed (see figs. 273, 274) of two substances, an external cortical or gray substance, and a central or medullary substance, which is white ; the gray substance is soft, and is almost always torn off with the mem- branes, however slightly the cerebellum may be altered by decomposition. The white substance is compact, and resists a tolerably firm pressure.! Between the gray and white substances there is seen, upon a section of the cerebellum, a narrow yellowish band or streak, which depends on the existence of a layer of a yellow substance, of much greater firmness than the gray matter, and strongly adherent to the white substance. By laceration the gray matter is destroyed, and this yellow layer is exposed. There are, therefore, three substances in the cerebellum : the gray, the yellow, ' See note on the sub- arachnoid space (p. 690). t For an account of the minute structure of these substances, see note, p. 701. SECTIONS OF THE CEREBELLUM. 781 and the white. I would compare the yellow layer of the cerebellum to the yellow folded membrane of the olivary bodies.* A question liere arises, What is the proportion between the gray and the white mat- ter ? The most superficial examination of the cerebellum will show that the gray mat- ter predominates ; and this can be clearly demonstrated by macerating the cerebellum for several days. The gray matter, which is more easily decomposed, becomes con- verted into a pulp, and the remaining nucleus of white substance scarcely represents a third, eitlier of the weight or bulk of the cerebellum. We shall now proceed to describe the appearance of vertical and horizontal sections of the cerebellum. Vertical Sections. Upon longitudinal vertical sections of the cerebellum, the gray and white substances present a very elegant arrangement, known by the picturesque name of the arbor vita ; a title derived either from the importance which has been attached to this structure, or from its resemblance in figure to the foliage of the tree so called. Upon a section maule through the median line, the arbor vita of the middle lobe {w, fig. 282) is seen ; and upon one made on either side, the arhor vita of the lateral lobes. The arbor vita of the median lobe consists of a central nucleus of white substance, of a triangular form, from which two principal branches proceed : one inferior, which is dis- tributed to the whole of the inferior vermis and the back part of the median lobe ; the ' other superior, which passes into the whole of the superior vermis. These two branches subdivide into six others, which vary in direction, length, and thickness, and are them- selves subdivided into still smaller branches, and these, again, into the smallest ramifica- tions. A slight enlargement of the white substance is always observed opposite the points of division. A very thin yellowish layer, and outside this a layer of gray matter, about a line in thickness, covers each of the ramifications of the white substance, and thus forms the lamellie, laminae, and segments of the median lobe. This section enables us to prove the existence of the middle lobe of the cerebellum and the continuity of the superior and inferior vermis ; it also shows the general form of the middle lobe, which is rotate or wheel-shaped (the anterior extremity of the in- ferior vermis, i. e., the nodule, comes into contact with the valve of Vieussens) ; the number and arrangement of the segments, laminae, and lamellae of the cerebellum; and, lastly, the nature of the valve of Vieussens, which is nothing more than the uppermost subdivision of the central nucleus, and may be regarded as one half of a lamella of the cerebellum. The Arbor Vita of the Lateral Lobes. — A vertical section from the middle peduncles of the cerebellum towards the circumference displays the arbor vitae of the lateral lobes. In the centre of each lobe is seen a white central nucleus, from which fifteen or six- teen principal branches are given off, to form the nuclei of a corresponding number of the segments. These branches are subdivided into secondary branches, and those into the ultimate ramifications. A yellowish layer covers each of these successive divisions, and upon that a gray layer, about a line in thickness, is accurately moulded. Upon sections of this kind it is easily seen that the segments of the cerebellum are very unequal in size, in direction, and in their manner of division ; that the superior segments are the smallest, the segments of the circumference the largest,! and the in- ferior segments of an intermediate size ; that there is no vacant space between the seg- ments, but that both laminae and lamellae occupy the intervals ; and, lastly, that all of these segments curve forward upon themselves, so as to form a series of horizontal wheels or circles, the plane of which is at right angles to that of the wheel-shaped mass of the middle lobe. In the centre of the white nucleus of each half of the cerebellum is the corpus rhom- boideum, or corpus dentalum :% these bodies are of an ovoid form ; their yellowish invest- ing layer is dense, and folded backward and forward upon itself, and exactly resembles that of the olivary bodies ; and I have been accustomed to speak of these bodies as the olivary bodies of the cerebellum. Gall and Spurzheim regarded them as ganglions of re-enforcement, and called them tlie ganglions of the cerebellum. Their shortest or verti- cal diameter is about one third of their long or horizontal diameter ; in one case, where the latter was fifteen lines, the former was five lines : moreover, the size of the corpora dentata of the cerebellum varies in different subjects, and is in proportion to the size of * Rolando ( Ossemazioni suV Cervetetto, p. 187, 1823) appears to me to have been the first to establish the fact of the existence of three substances : the medoHare, the cinereo rossigna, and the cinerea esterna e corticate. t The segment of the circumference, which is the largest of all, immediately divides into two smaller seg- ments ; it has liecu iucorrecUy stated that there is a horizontal fissure along the circumference of the cere- bellum, extending from one of the middle peduncles to the other. t In order to divide the corpus dentatum, the section must be made opposite the corresponding inferior pe- duncle (if the cerebellum. I would recommend that one section be made to extend through the corpus denta- lum of the cerebellum, and also through the olivary body, so that some idea may be formed of the analogy be- tween these two |>arts. 4Y NEUROLOGY. the lateral lobes of that organ : they are, therefore, much less developed in the lower animals than in man. The peduncles of the cerebellum are six in number, three on each side, namely, a supe- rior, a middle, and an inferior ; they all originate, or, it may be said, terminate in the cen- tral nucleus. The superior peduncles of the cerebellum are generally known as the processus cerebelli ad testes ; ttiey are seen (r, fg. 280) in front of the superior vermiform process, and seem to pass up to the tubercula quadrigemina. We shall afterward see that this is only ap- parent. The inferior peduncles (processus cerebelli ad medullam oblongatam) are, in fact, the resti- form bodies ; they establish a direct and intimate communication between the cerebel- lirni and the spinal cord. Lastly, the middle peduncles {m, fig. 276), which are anterior to the two preceding sets, occupy the fore part of the circumference of the cerebellum, and are continued into the pons Varolii without any line of demarcation. They are called also the cerebellar pedun- dea {processus cerebelli ad potitem), and the crura or legs of the medulla oblongata. Horizontal Sections. Horizontal sections of the cerebellum have been studied with very great care, and have been well figured by Vicq d'Azyr ; they show that the dimensions of the central nucleus are much greater in the horizontal than in the vertical direction.* Upon these sections, which should be made parallel to the upper surface of the cere- bellum, is seen the relative disposition of the laminae, which are sometimes parallel and sometimes oblique in reference to each other, and which either extend around the entire circumference of the organ, or terminate in tapering extremities and again commence, and pass from one segment to another. Lastly, these horizontal sections show the continuity of the right and left lobes of the cerebellum by means of the middle lobe. In this middle lobe the lamellae are more ir- regular than in the lateral lobes ; they intersect each other at various angles, and be- come again united into new combinations, so that several anatomists have admitted the existence of a true decussation in this middle portion of the cerebellum. The middle lobe also has its medullary centre, which connects the lateral medullary centre in such a manner that, by a successful section, a sort of cerebellar centrum ovale is obtained, analogous to the centrum ovale of Vieussens in the cerebrum. Examination of the Cerebellum by means of a Stream of Water, and Dissec- tion of the Hardened Cerebellum. A stream of water directed upon vertical sections of the cerebellum decomposes the white nucleus of each lateral lobe into a great number of extremely thin leaves, which constitute the different laminae or lamellae of the cerebellum. All these laminae and la- mellae terminate in the central nucleus of the corresponding lobe. Each lamella is fan- shaped, its adherent border being very narrow, concave, and applied io the central nu- cleus, with which it is evidently continuous, while its convex margin corresponds to the surface of the cerebellum. The arrangement of these lamellae is very beautiful and cu- rious : some of them ascend to form the segments, lamina, and lamellae of the upper surface of the cerebellum ; others descend to form the corresponding parts of the lower surface, and the intermediate ones pass horizontally to the circumference, and are dis- posed in a similar manner. Opposite each point of subdivision there seems to be an en- largement of the white substance, but this depends not upon an actual increase of that substance, but upon the divergence of the lamellae. The structure of the cerebellum, therefore, considered generally, is laminated. From the central white nucleus proceed innumerable lamina;, which, though in juxtaposition, are never blended together, and which form groups, that are themselves subdivided again and again, like the branches of a tree, the ultimate lamella always containing at least two leaflets. Can anatomy teach us anything beyond this laminated arrangement 1 In each lamella certain radiated striae are seen ; and it may be asked. Whether these prove the existence of a linear or fibrous structure 1 It is certainly true that the lamellae may be divided in the direction of these striae, but it is far from being evident that they con- sist of linear fibres. In the central nucleus, the laminae, being more firmly pressed together, are separated by the stream of water with greater difiiculty than the laminae near the surface : the corpora dentata of the cerebellum are peculiarly firm. The stream of water insinuates itself into these bodies opposite their internal extremity, which appears to be naturally open, and divides them into two halves, a superior and an inferior. It is then seen that the dentated appearance of their section results from the reduplication of the dense yel- lowish layer in which they are enclosed ; also, that the white substance penetrates into the interior of these bodies at their internal surface, accompanied by a great number of * In each lobe of the cerebellum there is a medullary centre, that is, a spot in which the section of the whit* substance is larger than at other points. GENERAL VIEW OF THE CEREBELLUM. 723 vessels ; and that this white substance is arranged in lamellae, which terminate at three different points of the yellowish layer, so that each of the corpora dentata resembles a small cerebellum. Examination of the Hardened Cerebellum. — The examination of the cerebellum, when hardened by alcohol, or by boiling in oil, or salt and water, or by maceration in a solu- tion of salt and bichloride of mercury, of the strength recommended by Rolando, confirms all the results which have been obtained by the preceding method of investigation. These modes of preparation, moreover, enable us to examine more completely than in any other way the relations of the central nuclei of the lobes to the peduncles of the cere- bellum. It is seen most distinctly that these peduncles (m n. Jig. 273 ; n r, fig. 274) emerge from or terminate in the central nuclei ( p p), but it is very difficult to ascertain their precise arrangement within the nuclei. All that we know is the fact that, as soon as they emerge from the central nuclei, they assume a fasciculated character, and that all the lamellae and laminae of the cerebellum seem to terminate in the fibres of the mid- dle peduncles. General View of the Cerebellum. From the preceding statements we may draw the following conclusions : The cerebel- lum consists of two lateral lobes and a middle lobe ; the lobes are formed by a consider- able number of segments, which are subdivided into smaller segments, and these into laminae and lamellae ; each lobe contains a central medullary nucleus, upon which all the segments rest, and which constitutes the termination or the origin of the several pedun- cles ; the substance of these peduncles is fibrous or fasciculated, and that of the central nucleus has a similar character, but not so well marked ; the medullary substance of each segment is formed by laminae applied to each other, but not actually continuous ; each of these laminae is fan-shaped, and those which constitute the central nucleus of each segment become separated from each other to form the secondary segments, the laminae, and the lamellae ; the ultimate lamellae of the cerebellum consist of two leaflets of white matter covered externally by a very thin yellowish layer, which is itself cover- ed by a rather thick layer of gray matter ;* the corpora dentata, or olivary bodies of the cerebellum, consist of fibres or laminae of medullary substance, which are spread out so as to terminate at different points upon the inner surface of the dense yellow membra- nous layer which constitutes their external investment. A very ingenious explanation of the structure of the cerebellum has been proposed by Gall, and is now rather generally adopted. The opposite directions of the inferior and middle peduncles of the cerebellum sug- gested to him the idea of diverging and converging fasciculi, and to this he has added his theory regarding the ganglia, which he considered as apparatuses of re-enforcement, that is to say, as points of origin for new fasciculi. According to Gall, then, the inferior peduncles of the cerebellum or the restiform bod- ies (n,fig. 274), which he calls the primitive fasciculi of the cerebellum, are the roots, or fasciculi of origin of the cerebellum. After they have penetrated a few lines into the substance of the organ, they meet with and join the corpus dentatum, which Gall regards as a true ganglion, or apparatus of origin and re-enforccment for a great part of the nervous mass of the cerebellum. According to him, a principal nervous fasciculus corresponds to each of the folds of the corpus dentatum, from which ganglion arise all those prolonga- tions of medullary substance which, together with the gray matter upon them, consti- tute the middle and lateral lobes of the cerebellum. Besides the preceding fasciculi, which are named by Gall the diverging fasciculi, and are said by him to constitute the formative system of fibres, there are certain converging fasciculi, which constitute the uniting system of fibres, or the commissures of the cerebellum. These are supposed to have no direct connexion either with the primitive fasciculi or the corpus dentatum, but to emanate from the gray matter upon the surface of the cere- bellum, and to pass in different directions (p q, fig. 273) between the diverging fasciculi, so as to enter into and constitute the middle peduncles of the cerebellum (m) and the pons Varolii, which Gall regarded as forming together the commissure of the cerebellum. The superior peduncles of the cerebellum (?•', fig. 274) he considered as fasciculi o*" communication between the middle median lobe of the cerebellum and the corpora quad rigemina, and the valve of Vieussens as the commissure of these peduncles. We can only regard Gall's view concerning the structure of the cerebellum as an in- genious speculation. Why should the inferior fasciculi be the roots or primitive bundles of the cerebellum rather than the superior 1 Who has seen the re-enforcement of these primitive fasciculi in the corpus dentatum 1 Why should the corpus dentatum be regard- ed as a ganglion 1 Whence is this distinction between converging and diverging fasci- culi 1 1 and, finally. Why are figure and metaphor employed in reference to strictly ana- tomical questions 1 * [The white substance of the laminae is said to consist of two sets of fibres — one coming from the central mass, and passing up the centre of the laminie, and the other set lying; upon the first, and passing from one lamina to another.] * " These converging fibres," says Tiedemann (French translation by Jourdan, p. 169j, " are merely chimer- 724 NEUROLOGY. Another theory regarding the structure of the cerebellum has been offered by Rolan- do, who, by combining the results derived from an examination of the human cerebellum, when hardened in a strong saline solution, with those furnished by the anatomy of the brain of the shark, and those obtained by studying the development of the brain of the fowl, was led to regard the human cerebellum as formed by the folding and refolding upon themselves of the parietes of a large bladder or vesicle, so as to give rise to innumera- ble laminae.* The facts we have already stated sufficiently refute this hypothesis. It is quite cer- tain that the cerebellum is formed by the union of one middle and two lateral lobes : the lobes themselves are composed of a considerable number of segments, which are subdi- vided into smaller segments, laminae, and lamellae. The general structure of the cere- bellum is laminated, and these laminae are striated ; each lamella contains two leaflets of white substance covered with gray matter. The cerebellum is connected with the medulla oblongata by the inferior peduncles, and with the brain by the superior pedun- cles ; the middle peduncles and the transverse fibres pf the pons establish an intimate connexion between the two lobes of the cerebellum, t Development of the Cerebellum. The cerebellum does not appear until some time after the spinal cord : it consists, at first, of two laminae and plates prolonged from the cord, which approach each other to- wards the median line ; these are the inferior peduncles of the cerebellum, or the resti- form bodies. The human cerebellum in this condition has a close resemblance to the same organ in fishes and reptiles. At the fourth month, the cerebellum forms a sort of uniform girdle, four lines in width, around the tubercula quadrigemina and the medulla oblongata ; the pons Varolii is already visible ; there is a rudiment of the corpus denta- tum, and the surface of the cerebellum is entirely devoid of fissures. At the fifth month there are four transverse fissures : a vertical section of the cerebellum presents five branches ; but there are as yet neither laminae nor lamellae, nor is there any distinction between the middle and lateral parts. At the sixth month, the cerebellum is divided by the posterior notch, the different orders of fissures are visible, and the corpus dentatum has acquired considerable size. During the last three months of intra-uterine existence, the lateral lobes generally acquire that predominance over the middle lobe which is found to hold after birth. As the development of the spinal cord precedes that of the cerebellum, and as the cer- ebellum appears to be formed by a prolongation of the posterior fasciculi of the cord, does it follow that that organ is a production or an expansion of the cord 1 Certainly not ; all that we can conclude is, that they are developed in succession. Reil and Tiefdemann have advanced the opinion that the cerebellum is secreted by the pia mater, and that the gray matter is deposited the last ; but this is only an assertion without demonstration. The cortical substance is formed at the same time as the medullary, and neither of them can be considered as the product of the other. Comparative Anatomy of the Cerebellum. In fishes the cerebellum is generally small, but in the ray and shark it is large, subdi- vided into convolutions, and prolonged above the optic lobes in front, and above the lobe of the eighth pair of nerves behind. In the silures, as Weber has observed, the cere- bellum is relatively as large as the human cerebrum ; for it covers the posterior half of the cerebral lobes, as the cerebrum in man covers the cerebellum. In all fishes the cer- ebellum contains a considerable cavity. In some of Ihis class of animals it is subdivi- ded into segments, laminae, and lamellae.J Reptiles. — There is no cerebellum in the batrachia (as in the frog, toad) and ophidia (serpents) ; most anatomists, however, admit its existence in a rudimentary state. It is very small, and shaped like a roof, or vaulted, in the chelonians (tortoise) ; it is very long in the saurians (lizard, crocodile). Birds. — The cerebellum is very large, and represents an ellipsoid, having its long di- ameter directed vertically. It is deeply and regularly traversed by horizontal fissures, which are curved downward on the upper half, and upward on the lower half of the or- ical ; for the pons Varolii, and the meilallary fibres of which it consists, are found in the foetus at the fourth month, that is, at a period when there are no laminae nor lamells, nor even any leaflets covered with gray mat- ter. Gall, therefore, assumes these converging- fibres to originate from parts which do not appear until after those fibres themselves." The refutation of Tiedemami appears to me to be itself founded on an assumption, for there is no proof that the gray matter is formed after the white. " Osservazioni sul' Cerveletto, p. 187. In the shark, the cerebellum consists of a gray and a white layer united together and folded a great number of times upon themselves. t It is not yet ascertained whether the lateral halves of the cerebellum act upon the same or opposite sides of the body ; some cases, in which atrophy of one hemisphere of the cerebrum coexisted with atrophy of the op posite hemisphere of the cerebellum, would appear to show that the action of the latter is not crossed. The laminated structure of the cerebellum and its twofold composition suggested to Rolando the idea of comparing it to a voltaic pile, or electro-motive apparatus. t [It is divided into segments by deep transverse furrows in some cartilaginous fwhe.^.1 THE CEREBRUM. 725 gan. They all tenninate opposite two small tubercles or appendages, situated one at each extremity of the transverse diameter. Upon a section of the cerebellum of birds is seen an arbor vitae, composed of white substance covered with gray matter. Mammalia. — In the three classes already examined, the cerebellum has merely a mid- dle lobe : in all mammalia there are also lateral lobes. They are at lirst small, like ap- pendages, as in the rodentia, in which the cerebellum differs but little from that of birds ; they gradually increase in size as we proceed upward in the scale, until they reach their highest state of perfection in man, the development of whose cerebrum and cerebellum exceeds that of the same parts in all the lower animals. In mammalia the size of the lateral lobes of the cerebellum is directly proportioned to that of the oUvary bodies, the existence of which in this class Vicq d'Azyr has erroneously denied. THE CEREBRUM, OR BRAIN PROPER. Definition — Situation — Size and Weight — General Form. — The Superior or Convex Surface. — The Inferior Surface or Base — its Median Region, containing the Inter-peduncular Space, the Corpora Albicantia, the Optic Tracts and Commissure, the Tuber Cinereum, Infundibu- lum, and Pituitary Body, the Anterior Part of the Floor of the Third Ventricle, the reflected Part of the Corpus Callosum, the Anterior Part of the Longitudinal Fissure, the Posterior Part of the Longitudinal Fissure, the Posterior Extremity of the Corpus Callosum 'and Me- dian Portion of the Transverse Fissure, and the Transverse Fissure. — The Lateral Regions, including the Fissure of Sylvius and the Lobes of the Brain. — The Convolutions and Anfrac- tuosities of the Brain, upon its Inner Surface, its Base, and its Convex Surface — Uses of the Convolutions and Anfractuosities . — The Internal Structure of the Brain — Examination by Sections — Horizontal Sections showing the Corpus Callosum, the Septum Lucidum, the For- nix and Corpus Fimbriatum, the Velum Interpositum, the Middle or Third Ventricle, the Aqueduct of Sylvius, the Pineal Gland, the Lateral Ventricles, their Superior and Inferior Portions, the Choroid Plexus, and the Lining Membrane and the Fluid of the Ventricles — Median Vertical Section — Transverse Vertical Sections — Section of Willis. — General Re- marks on this Method of Examining the Brain. — Methods of Varolius, Vieussens, and Gall. — Gall and Spurzheim's Views on the Structure of the Brain. — General Idea of the Brain. — Development. — Comparative Anatomy. The cerebrum or brain, strictly so called, is that portion of the encephalon which occu- pies the whole of the cavity of the cranium, except the inferior occipital fossae. It forms, as it were, the crown or summit of the spinal axis, surmounting it {cerebrum superius), and, at the same time, lying in front of (cerebrum aiiterius) the spinal cord, as the origin and termination of which it has been alternately regarded. By the pons Varolii and the anterior or cerebral peduncles it is intimately connected with the cerebellum and the spinal cord. The tentorium cerebelli completes the cavity in which it is enclosed, and separates it from the cerebellum, wljich is situated below its posterior lobes. The cra- oiiim, the dura mater, the arachnoid, and the pia mater form a fourfold investment for it. Size and Weight of the Cerebrum. The great size of the cerebrum is undoubtedly one of the most characteristic points in the structure of man : in several animals, the entire encephalon is relatively as large, and even larger {ex., the canary bird, the sapajou, the dolphin) ; but in reference to the size of the brain properly so called, i. e., of the cerebral hemispheres, even the most fa- voured animals are much inferior to man.* In the adult, the weight of the cerebrum, detached from the cerebellum and the pons by a section through its peduncles, varies from two to three pounds. t I believe it to be impossible to construct a table of the comparative size and weight of the brain and of the body. Is it not evident, indeed, that one element in the comparison, namely, the weight of the body, is subject to great variety 1 Haller has recorded the results of all the cal- culations which have been made upon this subject, and the diversity of those results is the best comment that can be made upon this mode of comparison. These remarks do not apply to the relative proportions between the cerebrum and • The weight of the cerebrum of the horse and the oi is scarcely half that of the human cerebrum. t [From the statements given by Tiedemanu (Htm des Negers, . 772 NEUROLOGY. this difference, which is much greater than is observed in any other region, obtains not only in reference to the filaments taken altogether, but also to each particular filament. The cervical nerves increase rapidly in size from the first to the fifth, and then main- tain the same size to the eighth. The first cervical nerve, so well described by Asch, has some peculiarities : its pos- terior filaments of origin are much less numerous than the anterior, the spinal accessory of Willis appearing to supply this deficiency ; it is also frequently without a ganglion.* Proper Characters of the Dorsal Nerves. — Excepting the first, which has all the charac- ters of the cervical nerves, the roots of the dorsal pairs of nerves (9 to 20) present the following peculiarities : A small number of filaments or roots ; so that, with the exception of the sacral, the dorsal are the smallest of all the spinal nerves. Uniformity in the number of the filaments, i e., in the size of their roots. The dorsal nerves are almost of equal size, the twelfth nerve alone being somewhat longer than the rest. A considerable interval between their roots, and a want of regularity in this interval. Frequently a portion of the spinal cord, from eight to ten lines in length, gives origin to only a small pair of nerves. A more marked slenderness of the filaments of origin than in any other region. The slight disproportion between their anterior and posterior roots when compared filament for filament. The direction of their roots, which remain in contact with the cord for some distance, and then leave it ; this circumstance is calculated to give rise to errors concerning the precise situation of their origin. The length of their course within the spinal canal ; this length is equal to the height of at least two vertebrae. Proper Characters of the Lumbar and Sacral Nerves. — The roots of these nerves form the Cauda equina ; their characters are, the great number of their filaments of origin, which exceeds those of the dorsal, and even those of the cervical nerves. The extreme closeness of these filaments, which form an uninterrupted series. The proportion between the filaments of the anterior and those of the posterior roots, which is as 2 to 1. The uniformity in point of size between the two sets of filaments, the anterior fila- ments, taken individually, being as large as the posterior. The continuance of the origin of the posterior roots to take place at the groove, while the anterior approach nearer and nearer to the median line towards the lower part of the cord, and almost touch those of the opposite side. The concurrence of both the anterior and posterior roots in the formation of the spi- nal ganglia. The almost vertical direction of the roots, a character common to both the lumbar and sacral pairs of nerves. The singular length of their course before they emerge from the spinal canal.t The Real Origins of the Spinal Jferves. The apparent central extremity or origin of the spinal nerves is very different from their real central extremity or real origin. On examining the spinal cord of an adult, for the purpose of determining this important point, one is inclined to admit that the point of contact between any nerve and the cord is the real origin of the nerve, so readily can the latter be separated from the cord without leaving any trace of the separation. It has even been stated by some that the nerves arise from the neurilemma of the spinal cord. Chaussier believed that the two series of roots arose from two lateral furrows, one anterior and the other posterior ; but Gall has with reason regarded these furrows as formed by pulhng off the roots. Others agree with the older anatomists in regarding the spinal cord as a large nerve formed by the junction of all the nervous filaments which are given off from it. But this idea is refuted by the fact that the cord does not progressively diminish in size from above downward, as it must have done if fonned by the junction of the roots of the spi- nal nerves. The ingenious and correct observation made by Vicq d'Azyr, that the gray matter is always found in large quantity at those parts from which a great number of nerves ori- ginate, and that it bears a proportion to the number of these nerves, and the confirma- tory observations of Gall and Spurzheim, seem to prove that the nerves originate from the gray matter. This presumption is also strengthened by the consideration, that the * According to the principles of classification which I have already stated, I should range the spinal acces- sory nerve among the cervical nerves, because it originates from the cervical portion of the spin;il cord : iu classing it among the cranial nerves, 1 yield to general usage. t [Lastly, the situation of the ganglia of the sacral nerves within the sacral canal, and of the lowest of them within the cavity of the dura mater.l POSTERIOR BRANCHES OP THE CERVICAL NERVES 773 central gray substance of the cord is more abundant opposite the posterior roots, which are the larger, than opposite the anterior roots, which are the smaller. On examining the spinal cord of an adult by means of a stream of water, it is seen that, after tearing away the filaments of the nerves, a small conical depression remains where each fila- ment had been attached, and that the real origin of the filaments is not in this depression, but is much more deeply seated. This is all that can be discovered from an examina- tion of the spinal cord of the adult ; but in the foetus, at the seventh or eighth month, a considerable part of the cord is semi-transparent, so that the already white filaments by which the nerves arise can be traced into its interior. On making a vertical section transversely through the spinal cord of the foetus, just level with the commissure, and then directing a strong light on the surface of the section, it will be seen that the great number of very delicate filaments of which the anterior and posterior roots of the spinal nerves are composed traverse the central gray matter, are arranged like the teeth of a comb, and may be traced into the posterior median columns ; these small filaments, are, moreover, all parallel. The white coimnissure might ahnost be regarded as the com- missure of these nerves. This view is very different from that of Bellingeri, who, entertaining certain physio- logical ideas, supposes that the anterior as well as the posterior roots of the spinal nerves consist of three sets of filaments, some of which come from the surface of the cord, others from the interior of the white matter, while the third set traverse the white matter, so as to reach the extremities of the cornua of the gray substance. Lastly, some anatomists agree with Santorini in believing that the nerves decussate at their origin ; but they have not attempted to demonstrate this. The Posterior Branches of the Spinal Nerves. Dissection. — Divide the integuments from the external occipital protuberance down to the coccyx. Dissect off the skin over the spinous processes with great care, especially opposite the trapezius. Be particularly cautious opposite the cellular interval between the sjicro-lumbaJis and the longissimus dorsi. Common Character's. The posterior branches of the spinal nerves, which are generally smaller than tne anit- rior branches, emanate from the plexiform cords which form the continuation of the cor- responding spinal ganglia, are directed backward, and immediately pass through tlic fora- mina, which I may regard as posterior inter-vertebral foramina.* These branches sub- divide into several twigs, which enter the great cellular intervals between the long mus- cles of the back, and are distributed to the muscles of the integuments. The greatest uniformity prevails among such of these nerves as are distributed to the same kinds of organs, and their differences depend on peculiarities in the parts to which they belong. We shall now study in succession the posterior branches of the cervical, dorsal, and Iimibar spinal nerves. The Posterior Branches of the Cervical Serves. Common Characters. All the posterior branches of the cervical nerves (« to o', fig. 300) pass transversely inward between the complexus and the semi-spinalis colli, haviiig first given off some very small twigs : having reached the sides of the posterior cervical ligament, thoy per- forate the aponeurotic attachments of the trapezius from before backward, lie close be- neath the skin, and are directed transversely outward. The course of these branches, therefore, is at first inward, and then outward. The posterior branch of the first cervi- cal nerve is the only one which presents any exception to these general characters. Proper Characters. The Posterior Branch of the First Cervical Nerve. The posterior branch of the first cervical or sub-occipital nerve, larger than the anterior branch, escapes between the occipital bone and the posterior arch of the atlas, on the inner side of the vertebral artery, with which it is in contact, below the rectus capitis posticus major, and in the area of the equilateral triang'e formed by that with tlie two oblique muscles ; in this situation (i, fig. 300) it is concealed by a large quantity of fatty tissue, which renders it rather difficult of dissection ; and it immediately divides into several branches, which may be arranged into the internal, which go to the great and small recti muscles ; extertud, which supply the great and small oblique muscles ; and inferior or anastomotic, which, by uniting with the second cervical nerve, assist in the formation of the posterior cervical plexxts. The branch to the rectus minor passes at first between the rectus major and the com- plexus, and then reaches the rectus minor. * Vide Osteology (vertebral column in general). Tiies-- n.ra .j. ;. are situated between the transverse processes, and in the dorsal region are cumpliti^d on ihu .uiTs.ue ii. . MsnKrior costo-transverse ligament. 774 NEUROLOGY. The principal branch for the inferior oblique, before ramifying in that muscle, forms an arch or loop, which has been well described by Bichat. It follows, therefore, that both of the recti and both of the oblique muscles are supplied by the first cervical nerve, which gives no filament to the complexus,* and none to the skin. The Posterior Branch of the Second Cervical Nerve. This is the largest of all the posterior branches of the cervical nerves, and is three or four times larger than the anterior branch of the same nerve ; it emerges («■, fig. 300) from the spine, between the posterior arch of the atlas and the corresponding lamina of the axis, in the same line as the posterior branch of the first nerve, immediately below the lower border of the obliquus major, and is reflected upward between the hairy scalp on the one hand, and the occipitalis muscle and epicranial aponeurosis on the other ; it passes horizontally inward between the obliquus major and the complexus, perforates this last muscle in the outer side of its digastric portion (the biventer cervicis), then changes its direction, and turns outward between the complexus and the trapezius, through which latter it passes to become sub-cutaneous and accompany the occipital ar- tery ; it is here called the great occipital nerve (occipitalis major, a, fig. 285). Hither- to cylindrical, this nerve, on becoming sub-cutaneous, is flattened, and increased in width, and then, passing upward, spreads out into a considerable number of diverging branches, internal, middle, and external, which cover the occipital region with their ramifications, and may be traced even to the parietal region : the internal branches are the shortest, and are successively lost in the skin of the occipital region. It supplies several branches, as follows : Some anastomotic branches to the first and third cervical nerves. Opposite the lower border of the obliquus major, it gives off a considerable muscular branch (w, fig. 300), which is distributed to that muscle, to the complexus, and especial- ly to the splenius (w, fig. 298) ; the branches to the splenius are of great size, and spread upon its deep surface into diverging twigs, which anastomose both with each other and with branches derived from the third cervical nerve. During its passage between the obliquus major and the complexus, and between the last-named muscle and the trapezius, the posterior branch of the second cervical nerve supplies these different muscles with a rather large number of nervous twigs. Its sub-cutaneous portion is distributed exclusively to the hairy scalp. The occipi- talis muscle, upon which it ramifies, does not receive any branch from it : as we shall elsewhere show, this muscle is supplied by the auricular branch of the facial nerve. The subdivisions of the sub-cutaneous portion of the second cervical nerve may be tra- ced into the hair follicles, and several of its external branches anastomose with the mas- toid branch of the anterior cervical plexus. The Posterior Branch of the Third Cervical Nerve. The posterior branch of the third cervical nerve, smaller than that of the second, but much larger than that of the fourth nerve, and partially intended for the occipital region, emerges between the transverse process of the atlas and that of the third cervical ver- tebra, and, consequently, farther outward than the posterior branches of the first and sec- ond nerves ; it is immediately curved, and passes transversely inward (t, fig. 300) be- tween the complexus and the semi-spinalis colli. Having reached the inner border of the complexus, it divides into two cutaneous branches : an ascending or occipital, which perforates the innermost fibres of the complexus, passes vertically upward upon one side of the median line, applied to the under surface of the skin, and ramifies upon the occip- ital region, near the median line, and to the inner side of the branch from the second cervical nerve ; and a horizontal or cervical branch, which perforates the aponeurosis of the trapezius between the complexus and the posterior cervical ligament, and passes horizontally outward beneath the skin, to which it adheres, and in the substance of which it terminates As the posterior branch of the third cervical nerve emerges from the posterior inter- vertebral foramen, it gives off an ascending branch, which forms an anastomotic arch with the descending branch of the second nerve : the succession of arches formed by the anastomoses of the first, second, and third nerves, and the very numerous branches which arise from their convexities, constitute a plexus, which may be called the posterior cervical plexus : it is situated beneath the complexus, near its external attachments, and it supplies both that muscle and the splenius. The direct anastomoses between the pos- terior branches of the three superior cervical nerves appear to me to be sometimes want- ing ; but then the branches given off from them still exist, and form a plexus between the splenius and the complexus. The Posterior Branches of the Fourth, Fifth, Sixth, Seventh, and Eighth Cervical Nerves. The posterior branches of the fourth, fifth, sixth, seventh, and eighth cervical nerves are much smaller than the preceding, and diminish in size successively from the fourth to the * [Asch saw and has described a twig {m,fig. 300) proceeding from the posterior branch of the first cenri- «al nerve to the complexus muscle ; Swan and Arnold Iso observed it.] POSTERIOR BRANCHES OF THE DORSAL NERVES. TT6 seventh. Immediately after their exit from the posterior inter- vertebral foramina, they are reflected inward and downward in the following manner : the fourth and fifth (o') in- cline downward upon the semi-spinalis colli, between it and the complexus ; the sixth, seventh, and eighth descend ahnost vertically beneath the lowest fasciculi of the semi- spinalis colli, supply that muscle and the raultifidus spinae, and having reached the side of the median line, perforate the aponeuroses of the splenius and trapezius, become ap- plied to the skin, and ramify in it. The Posterior Branches of the Dorsal, Lumbar, and Sacral JVerve. The Posterior Branches of the Dorsal Nerves. — These are intended for the dorsal region of the trunk, and resemble each other closely in their distribution, presenting only a few dif- ferences connected with the arrangement of the particular muscular layers of each region. The posterior branch of the first dorsal nerve has the same muscular and cutaneous re- lations as the corresponding branches of the lower cervical nerves ; it is of the same size, and is distributed in precisely the same manner. The posterior branches of the second, third, fourth, fifth, sixth, seventh, and ei^A^A dorsal nerves are destined for the thorax, properly so called, and present the greatest uniformity in their size and distribution. They all emerge from the posterior inter-vertebral foramina, immediately on the outer side of the semi-spinalis dorsi and multifidus spinae, and divide into two branches. The external or muscular branch is directed towards the cellular interval between the sacro- lumbalis and longissiraus dorsi, and subdivides into a great number of twigs, which are distributed to these two muscles [and to the levatores costarum]. The internal or mus- culo-cutaneous branch has a very remarkable course. It is reflected inward over the semi- spinalis dorsi, embracing the outer border of that muscle, and supplying it with nervous twigs ; having reached the side of the spinous process, it is reflected backward along that process, perforates the spinal attachments of the latissimus dorsi, and thus gains the under surface of the trapezius ; in this situation it is reflected outward between the latissimus dorsi and the trapezius, perforates the latter muscle very obliquely, and be- comes sub-cutaneous ; it then passes horizontally outward in the fonn of a small nervous riband, the distinct fibres of which do not disunite and spread out in the substance of the skin until they have arrived at the scapular region. The cutaneous branch, which belongs to the second dorsal nerve, always corresponds to the triangular surface on the spine of the scapula, over which the aponeurosis of the trapezius glides. In one subject which I examined, the musculo-cutaneous divisions of the posterior branches of the third, fourth, and fifth dorsal nerves presented two ganglia at the point where they bifurcated into their muscular and cutaneous branches ; in another, the ganglia were situated upon the cutaneous branches belonging to the first and third dor- sal nerves. All these cutaneous branches are horizontal, parallel, and separated from each other by an interval corresponding to the height of one vertebra. Such of the pos- terior branches of the dorsal nerves as are in relation with the trapezius always present the preceding arrangement. But the branches lower down than that muscle are dis- tributed in the following manner : The posterior branches of the ninth, tenth, eleventh, and twelfth dorsal nerves are distribu- ted in precisely the same way as the posterior branches of the lumbar nerves, and, like them, are intended for the abdominal parietes. There is no longer any internal or musculo-cutaneous branch, the external branch representing both the muscular and the cutaneous branch.* Immediately after emerging from the inter-vertebral foramina, these posterior branches pass very obliquely downward and outward, gain the cellular interval between the sacro- iumbalis and the longissimus dorsi, or, rather, pass very obliquely through the common mass formed by the union of the sacro-lumbalis and longissimus dorsi, and almost al- ways communicate with each other during their long course through the fleshy fibres ; having arrived opposite the outer border of the latissimus dorsi, or of the common mass, these branches, diminished fully one third in consequence of having supplied the poste- rior spinal muscles, perforate very obliquely the aponeurotic layer formed by the union of the aponeuroses of the latissimus dorsi and serratus posticus inferior, with those from the internal, oblique, and transverse muscles of the abdomen, and become sub-cutaneous ; they then divide into some very small internal cutaneous filaments, whicli are directed inward upon the side of the spinous processes, and some large external cutaneous fila- ments, which descend to terminate in the skin of the gluteal region. I would especially notice several large nerves, which, either joined together, or only in contact, descend vertically, cross perpendicularly over the crest of the ilium in front of the outer border of the common mass of the lumbar muscles, and become applied to the integuments of the gluteal region, upon which they may be traced as far as the great trochanter. * iThe internal branches of the four lower nerve.s are not absent, but are much reduced in size, do not reach the surface, and are distributed principally to the multifidus spinae: the external branches give the cutaneous twigs. (Demonstrations of Anatomij, by G. V. Ellis, of whose labours in reference to the anatomy of the nerves, free use has been made in this and many of the succeeding notes.)] 776 NEUROLOGT. The Posterior Branches of the Lumbar Nerves. — These resemble in their distribution the corresponding branches of the four lower dorsal nerves ; they gradually diminish in size from above downward ; the fifth is extremely small, and is entirely expended in the common mass of the lumbar muscles. The Posterior Branches of the Sacral Nerves. — These branches emerge from the poste- rior sacral inter-vertebral foramina. It is difficult to dissect them, because they are extremely small, and penetrate immediately into the muscular mass which occupies the sacral groove ; they moreover decrease in size from above downward, and are uniformly arranged in the following manner : immediately after their exit from the posterior inter- vertebral foramina, they form anastomotic arches with each other, from which muscular and cutaneous filaments are given off. The former are distributed to the common mass and the glutaeus maxiraus, and the latter are intended for the skin of the sacral region.* The Anterior Branches of the Spinal Nerves. The anterior branches of the spinal nerves, which are generally larger than the posterior, are the true continuations of these nerves, and supply the lateral and anterior parts of the trunk, and also the upper and lower extremities. Such of these branches as are intended for the trunk of the body have an extremely uniform and very simple mode of distribution ; to this class belong the intercostal nerves : those, on the other hand, which are intended for the upper and lower extremi- ties, present, in their distribution, a degree of complexity which depends on that of the parts which they supply. To this class belong the anterior cervical, anterior lumbar, and anterior sacral branches. The three last-named sets of branches, almost immediately after their exit from the spinal canal, communicate with each other, so as to form interlacements or plexuses, from which are given off the nerves, that ultimately ramify in all parts of the body. There are four great plexuses : two for the region of the neck and the upper extrem- ity, viz., the cervical plexus (x,fig. 268) and the brachial plexus (h), which might be re- garded as a single plexus, the cervico-brachial ; and two for the lumbar region and the low- er extremity, viz., the lumbar (/) and the sacral or crural plexus (s), which also might be regarded as one, the lumbosacral plexus. After these preliminary observations, I shall now describe, in succession, the anterior branches of the cervical, dorsal, lumbar, and sacral nerves. THE ANTERIOR BRANCHES OF THE CERVICAL NERVES. Dissection. — Anterior Branch of the First, Second, Third, and Fourth Cervical Nerves. — The Cervical Plexus — Its Anterior Branch, the Superficial Cervical — Its Ascending Branches, the Great Auricular and the External or Lesser Occipital — Its Superficial De- scending Branches, the Supra-clavicular — Its Deep Descending Branches, the Nerve to the Descendins Noni and the Phrenic — Its Deep Posterior Branches. — The Anterior Branches of the Fifth, Sixth, Seventh, and Eighth Cervical, and First Dorsal Nerves. — The Brach- ial Plexus. — Its Collateral Branches above the Clavicle — Its Muscular Branches, Poste- rior Thoracic, Supra-scapular, opposite to the Clavicle, the Thoracic, below the Clavicle, the Circumflex — Its Terminal Branches, the Internal Cutaneous and its Accessory, the Mus- culo-cutaneous, the Median, the Ulnar, the Musculo-spiral or Radial. — Summary of the Distribution of the Branches of the Brachial Plexus. Dissection. — It is convenient to dissect the sub-cutaneous branches which emerge from the cervical plexus before examining the anterior branches of the cervical nerves : one side of the neck may be reserved for the superficial, and the other for the deep branches. The Anterior Branches of the First, Second, Third, and Fourth Cervical Nerves. The Anterior Branch of the First Cervical Nerve. — This branch {u. Jig. 300) emerges from between the occipital bone and the posterior arch of the atlas in the groove for the vertebral artery, and beneath that vessel ; opposite the foramen in the transverse pro- cess of the atlas, it leaves the artery, passes in front of the base of that process, is re- flected downward, and descends to form an anastomotic arch with the anterior branch of the second nerve. As all the branches belonging to the first nerve come off from this anastomotic arch, they will be described with the second nerve. The Anterior Branch of the Second Cervical Nerve. — This is much smaller than the pos- terior branch of the same nerve ; it passes horizontally forward between the transverse processes of the atlas and axis, is reflected in front of the axis, and divides into an as- cending and a descending branch. * Among the cutaneous filaments which proceed from the arch formed by the jposterior branches of the first and second sacral nerves, there i* one wliich passes below the posterior and inferior spinous process of the ilium, is directed vertically downward between the glutieus m:i.\iraQs and the lesser sacro-sciatic ligament, oerforates the gluUeus muxiiuus, and is then reflected outward in noutact with the skin. THE CERVICAL PLEXUS. 777 The ascending branch curves upward in front of the transverse process of the atlas, and j^j^astomoses in an arch with the anterior branch of the first nerve. ., The descending branch {z, fig. 298) subdivides into two others of almost equal size : the .'one internal (see also fig. 300), which constitutes the internal descending cervical nerve (before s, fig. 298) ; the other external (behind s), which anastomoses with the third nerve ^.^above s), to form the superficial cervical nerve {k) and the great auricular nerve (q). Several large filaments for the rectus capitis anticus major are given off from the angle .of bifurcation of the ascending and descending branches. ** The anastomotic arch formed by the anterior branches of the first and second cervi- cal nerves gives off three or four very large grayish branches and several small white filaments, which go to the superior cervical ganglion of the sympathetic ; above these it gives a short gray filament, which almost immediately swells into a ganglion, from which a long, slender, descending filament proceeds to join the internal descending nerve ; lastly, it furnishes two ascending filaments, the lower one of which joins the pneumogastric nerve, and the upper one the hypoglossal or ninth nerve. The Anterior Branch of the Third Cervical Nerve. — This (above s, fig. 298) is twice as * large as the preceding ; it at first passes forward to emerge from the inter-transverse space, then downward and outward, and having gained the under surface of the stemo- mastoid muscle, it expands into a great number of branches, which constitute the cervi- cal plexus properly so called, and may be divided into a superior and an inferior portion. The superior division passes outward and backward beneath the sterno-mastoid mus- '■■«de, and bifurcates upon its posterior borders. One of the branches of the bifurcation as- cends, and is called the mastoid nerve (y) ; the other, which is reflected over the posterior border of the muscle, anastomoses by one or two filaments with the anterior branch of the second cervical nerve, and subdivides into the superficial cervical nerve {k) and the auricular nerve (q) : both of the branches of the bifurcation anastomose with the second cervical nerve. This superior division, moreover, gives off a small nerve, which as- cends between the auricular and mastoid nerves ; also a communicating branch to the superior cervical ganglion ; and, lastly, a series of branches («), which anastomose with the spinal accessory nerve of Willis (<), some immediately, and others while v/ithin the substance of the sterno-mastoid muscle. This superior division of the third nerve some- times joins the lowest branch of the second nerve. The inferior or descending portion passes vertically downward in front of the scalenus anticus, gives off a long slender filament to the internal desccndi7ig cervical nerve, and ter- minates partly by anastomosing with the fourth cervical nerve (below s), and partly by becoming continuous with the clavicular nerves (w). A considerable branch which enters the levator anguli scapulas may be regarded as be- longing to this inferior portion. This branch for the angularis sometimes arises at the point of bifurcation of the anterior branch of the third nerve. The Anterior Branch of the Fourth Cervical Nerve. — This branch (below s) is of the same size as the preceding ; it gives off the phrenic nerve (J), which sometimes arises in the inter-transverse space ; it then passes downward and outward in contact with the scalenus anticus for about ten lines, and divides into two terminal branches, the one in- ternal, the other external, which soon subdivide and cover the supra-clavicular triangle with their diverging ramifications : these branches constitute the supra-clavicular and acromial nerves (m). Just opposite its division the anterior branch of the fourth cervi- cal ner\'e receives a branch from the third, which appears to be shared between its two terminal divisions. The fourth cervical generally sends off a small communicating branch to the fifth cer- vical nerve. The Cervical Plexus. The term cervical plexus is applied to the series of anastomoses (z s) formed by the an terior branches of the first, second, third, and fourth cervical nerves. Some anatomists call it the deep cervical plexus, in contradistinction to the superficial branches given off from it, which, according to this view, constitute the superficial cervi cal plexus. This plexus, which occupies the anterior and lateral aspect of the four superior cer- vical vertebrae, is situated beneath the posterior border of the sterno-cleido-mastoid mus- cle, to the outer side of the internal jugular vein, between the rectus capitis anticus ma- jor and the cervical attachments of the splenius and levator anguli scapulae : it is con- cealed by a considerable quantity of fat, and by a great number of lymphatic glands : it is also covered by an aponeurotic lamina, which adheres to it intimately, and is prolong- ed upon the nerves which emanate from it. After the example of Bichat, this plexus may be regarded as a centre in which the anterior branches of the four superior cervical nerves terminate, and from which a great number of branches proceed. This plexus is by no means inextricable ; it is always easy to determine the origin of the branches which come from it. These branches consist of one anterior branch, the superficial cervical {k) ; of ascending 5 F 778 NEUROLOGY. branches, viz., the great mastoid (y), the small mastoid, and the great auricular (q) ; and of descending branches, subdivided into the deep and the superficial ; the deep ones consisting of the itUerjial descending branch (before s), the •phrenic nerve (/), and the branch- es for the trapezius, levator anguli scapula, and rhomboideus ; the superficial descending branches are the supra-clavicular and the acromial (m). According to their distribution, they may also be divided into muscular and cutaneous branches ; the muscular consist of the internal descending, the phrenic, the branches for the trapezius, the levator anguli, and the rhomboideus ; all the others are cutaneous, and are flattened like ribands. The Ajiterior Branch. The Superficial Cervical JVerve. The superficial cervical nerve (superficialis colli, s, fig. 285), which is often double, Pig. 285. in consequence of dividing earlier than usual, is des- tined exclusively for the skin of the neck and lower part of the face (sous-mentonniere, Chauss.), and is formed by the anastomoses of the second and third cervical nerves ; it emerges from the plexus opposite the middle of the neck, beneath the posterior border of the sterno-mastoid, around which it turns in the form of a loop, and then passes horizontally forward between that muscle and the platysma, runs at right angles beneath the external jugular vein, and divides into two branches — one ascending and larger, the oth- er descending ; these two branches often form two distinct nerves. The descendijig branch passes downward and in- ward between the sterno-mastoid and the platysma, is reflected upward so as to form a loop, having its con- cavity turned upward, perforates the platysma, and then lies in contact with the skin, beneath which it may be traced as far as opposite the os hyoides. One of its twigs, which appears to me to be constant, having reached the side of the median line, is reflected upward in front of the anterior jugular vein, ascends vertical- ly, and may be traced into the skin of the supra-hyoid region. The ascending branch, which sometimes arises by a common trunk with the auricular nerve, immediately divides into four or five very slender and slightly waving filaments, which, situated at first between the sterno-mastoid and the platysma, generally perfo- rate the last-named muscle, to become sub-cutaneous ; two of these diverging filaments, which remain subjacent to the platysma, are very slender, and run along the external jugular vein, one in front of and the other behind that vessel. Ail the other filaments pass upward and inward in contact with the skin, and subdi- vide into a great number of filaments, which may be traced as far as the skin of the chin and lower part of the cheek ; I have seen two of these filaments anastomose with the facial nerve. It is important to observe, that the cervical filaments of the facial nerve occupy a deeper plane than those of the superficial cervical nerve, and are separated from these latter in front by the platysma. The Ascending Branches. The Auricular J^erve. The auricular nerve (auricularis magnus, d, fig. 285), the ascending anterior branch of the cervical plexus, arises from the second and third cervical nerves by a trunk which is common to it and to the superficial cervical ; it emanates from the plexus immediate- ly above the last-named nerve, hke which it embraces the posterior border of the sterno- mastoid so as to form a loop with the convexity turned backward, and then passes up- ward and a little forward between the platysma and the sterno-mastoid, and reaches the anterior border of that muscle opposite the angle of the lower jaw. In this situation it gives off" several facial or parotid filaments, and terminates by dividing into a superficial and a deep branch. The facial or parotid branches are very slender ; some of them pass between the parot- id and the skin, with which they are in contact ; the others pass through the parotid gland from behind forward, and from below upward, to be distributed to the skin of the cheek ; I have traced them as far as the skin which covers the malar bone ; it has not been shown that some of them terminate in the substance of the parotid, as has been stated.* The superficial auricular branch ascends vertically, in the substance of the very dense * I have seen two of these parotid filaments terminate in a small abnormal ganglioii, from which other fil aments were given off and distributed in the manner above described THE SUPRA-CLAVICULAR NERVES. 779 fibrous tissue which connects the parotid to the skin ; it gains the lower part of the concha opposite to the anti-tragus, and then divides into several filaments, the distribu- tion of which is remarkable : the largest passes above the lobule in the fissure between the concha and the caudal extremity of the helix, and is distributed to the skin on the concave surface of the auricle, and especially to the skin of the concha ; another fila- ment turns round the margin of the auricle, and gains the groove of the helix, which it follows even to its upper part. The deep auricular branch, which may be called the antenor mastoid, perforates the substance of the parotid gland, and gains the front of the mastoid process ; here it crosses at an acute angle over the auricular branch of the facial nerve, which is more deep- ly seated, and with which it anastomoses by a rather large branch ; it then passes be- hind the posterior auricular muscle, and divides into two secondary branches : a poste- rior, which passes upward and backward, and may be traced as far as the outer border of the occipitalis muscle, where it anastomoses with a very delicate filament of the ex- ternal occipital nerve ; and an anterior, which runs upon the upper part of the cranial surface of the auricle. The superior filaments are reflected over the upper margin of the auricle, and are distributed to the skin which covers its external or concave surface. From what has been just stated, it follows that the auricularis magnus gives off no . muscular filament. The posterior auricular and occipitalis muscles are supplied entire- " ly from the auricular branch (c) of the facial nerve. The Mastoid or External Occipital Kerve. The mastoid or external occipital nerve (occipitalis minor, b), the posterior ascending branch of the cervical plexus, rises from the second cervical nerve ; it comes off from the plexus above the preceding nerve, describes a loop with the convexity turned up- ward upon the posterior border of the sterno-mastoid, ascends almost vertically, parallel to the great occipital nerve and to the posterior border of the sterno-mastoid, crosses the posterior occipital attachments of that muscle, continues to ascend upon the occipi- fe'tal region, and then upon the parietal region, and may be traced as far as opposite the t anterior border of the parietal bone. During this course it is situated between the sple- jiius and occipitalis muscles and epicranial aponeurosis on the one hand, and the skin on "the other. This nerve gives off in the occipital region some external branches, which are distrib- uted to the skin, and anastomose with a filament of the auricular nerve, but none of them pass to the auricle. The term occipito-auricular (Chauss.) is, therefore, not applicable to it ; it should rather be called the external occipital (occipitalis minor, b),* to distinguish . it from the internal occipital (occipitalis major, a), given off by the posterior branch of the second cervical nerve. It also supplies some internal branches, which anastomose several times with the in- ternal occipital nerve, and are distributed to the skin. It gives no filament to the occipitalis muscle, nor does it anastomose with the facial nerve. The mastoid or external occipital nerve is essentially a cutaneous nerve. We sometimes find a small supplementary branch between the great auricular and .external occipital nerves, which runs parallel to them, and may be called the small mas- .. jtoid nerve (c). The Superficial Descending Branches. The Supra-clavicular JVerves. The Supra-clavicular Nerves {e,fig. 285 ; u,fig. 298). — The terminating branches of the cervical plexus are two in number : one internal, or the supra-clavicular nerve, properly so called ; the other external, or the acromial nerve ; they come off from the plexus at the posterior border of the sterno mastoid, descend perpendicularly towards the clavicle, and divide into several branches, which again subdivide before reaching that bone, so that they cover the supra-clavicular triangle with their diverging filaments. All these branches cross over the clavicle at almost regular intervals, and are lost upon the upper and anterior part of the thorax. The innermost or sternal branches cross very obliquely over the external jugular vein, then over the clavicular and sternal attachments of the sterno-mastoid, and ramify in the skin, where they may be traced as far as the median line. The external or acromial branches pass obliquely over the external surface of the tra- pezius, cross the outer end of the clavicle, and are distributed to the skin over the acro- mion and the spine of the scapula. I have followed some filaments over the top of the shoulder as far as the lower borders of the pectoralis major. The intermediate or clavicular branches cross the clavicle at right angles, are in con- tact with the skin upon the upper part of the thorax, and maybe traced to within a short distance of the nipple, t * The name mastoid branch is bad, for this branch has no relation with the mastoid process, t Not unfrequcntly the supra-clavicular nerve passes through a foramen in the clavicle, at the junction of the external third with the internal two thirds of that bone ; sometimes, instead of a bony canal, there is A t80 NEUROLOGY. All these branches lie at first beneath the platysma, and then become sub- cutaneous. A layer of fascia and the omo-hyoid muscle are interposed between them and the scaleni muscles and brachial plexus. Some loose cellular tissue separates them from the clav- icle, upon which they glide with the greatest freedom. The Deep Descending Branches. The Internal Descending Cervical J^erve. The internal descending cervical nerve (before s, fig. 298), which is destined exclusively for the muscles of the sub-hyoid region, may be considered as the inferior branch of the bifurcation of the second cervical nerve, although the first and third nerves each give to it a small re-enforcing filament. It passes vertically downward, on the outer side of the internal jugular vein, along which it runs, is joined on its inner side by a filament from the first cervical nerve, and having reached a little below the middle of the neck, is reflected inward in front of the internal jugular vein, and forms an anastomotic loop, which is sometimes plexiform, with the descending branch (descendens noni, h) of the hypoglossal nerve ; this is a remark- able anastomosis, and presents many varieties in its arrangement. The convexity of this loop is turned downward, and from it arises a branch, which sometimes scarcely ex- ceeds in size either of the formative branches of the loop, and which expands into sev- eral filaments {g). One of these ascends and supplies the superior attachments of the sterno-hyoid and omo-hyoid ; a transverse filament proceeds to the bodies of the sterno- hyoid and sterno-thyroid muscles. Several filaments can be traced as far as the lower part of the latter muscle, that is to say, down to opposite the second rib. The inferior fleshy belly of the omo-hyoid is supplied by some twigs derived from the filaments which enter its superior belly. The Phretdc or Diaphragmatic Jferve. The phrenic nerve {I, figs. 298, 302) is a branch derived from the fourth cervical nerve, sometimes re-enforced by a very small filament from the third nerve, and almost al- ways by a larger branch from the fifth.* Not unfrequently one of the formative branch- es of the loop of the hypoglossal nerve just described joins the phrenic nerve. The right and left phrenics are rarely of the same size. After its origin, the phrenic nerve descends vertically in front of the inner border of the scalenus anticus, with which it is held in contact by a fascia. It is round at first, but becomes flattened as it passes between the sub-clavian vein and artery (I have seen it pass in front of the vein), and is then inclined slightly inward, to enter the superior orifice of the thorax. In the thorax (Z, fig. 302) it continues its vertical direction, runs along the brachio-cephalic vein on the left side, and along the vena cava superior on the right side, is then applied against the pericardium, to which it is bound down by the pleura, and, having reached the diaphragm, ramifies in that muscle. It is accompanied by the superior phrenic artery, which is a branch of the internal mammary, and the su- perior phrenic vein. The phrenic nerve gives off no branches in the thorax : at a short distance from its origin, it anastomoses with the great sympathetic by a transverse branch : at the lower part of the neck, it sometimes gives off a filament, which forms an anastomotic arch with a branch derived from the fifth and sixth cervical nerves. I have never seen it com- municate with the inferior cervical ganglion. The distribution of this nerve in the diaphragm is curious. Some of its expanded, di- verging, and generally very long filaments, run between the pleura and the diaphragm, and enter the muscle from its upper surface ; others pass through the diaphragm, run between it and the peritoneum, and enter the fleshy fibres from below ; they may be traced as far as the costal attachments of the muscle. The right phrenic nerve termi- nates by a transverse branch which passes behind the vena cava, and anastomoses with certain transverse branches of the left phrenic, before it enters the pillars of the dia- phragm, in which it terminates. I have never seen any filament of the phrenic nerv6 pass either to the oesophagus or to the solar plexus. The Posterior Deep Cervical Branches. These are, an anastomotic branch iv,fig. 298) from the cervical plexus to the spinal ac- cessory nerve of Willis (t) ; it is of considerable size ; it comes off from the second nerve at the same point as the external occipital nerve, and an2istomoses at an acute angle tendinous arch upon the posterior border of the bone. In this case the clavicular branches are not scattered, but closely aggregated together : the internal branches then pass horizontally inward between the clavicle and the skin as far as the sternum ; and I have even seen a small twig enter the attachments of the pectoralis ma jor. The external branches proceed horizontally outward upon the anterior border of the clavicle as far as the acromion. * The communication between the phrenic nerve and the fifth cervical nerve occurs in many different modeg. Sometimes the phrenic supplies the communicating filament, instead of receiving it ; most commonly the phrenic branch of the fifth arises by a common trunk with the nerve for the sub-clavius muscle, crosses in front of the subclavian vein, between it and the cartilage of the first rib, with which it is in contact, and •Mscs behind the internal mammary artery, to join the phrenic nerve at a very acute angle. THE BRACHIAL PLEXUS. 781 with the spinal accessory, between the cervical fasciculi of the splenius and the sterno- mastoid. Also, a ira.ncM.jor the trapezius, which arises from the third nerve, passes obliquely downward and backward to the deep surface of the muscle, and anastomoses with the spinal accessory of Willis, which it re-enforces, and with which it may be traced as far as the lower angle of the muscle. Lastly, the branches for the levator anguli scapulce and the rhomboideus ; these are rath- er small branches, which arise from the back part of the third and fourth cervical nerves, as they emerge from between the transverse processes of the vertebrae, pass obliquely downward and backward, turn round the scalenus posticus in contact with it, and are distributed to the levator anguli scapulsD and the upper part of the rhomboideus. The same branches appear to supply both muscles. The Anterior Branches of the Fifth, Sixth, Seventh, and Eighth Cervical AND First Dorsal Nerves. These branches are remarkable for their size, in which respect they surpass the pre- ceding, and are almost all equal. On emerging from the inter-vertebral foramina, they come into relation with the two scaleni muscles, which are separated from each other, and sometimes are perforated by them ; they give off some very slender filaments to these muscles, and, converging, anastomose together so as to form the brachial plexus, from which all the nerves of the upper extremity are derived. The Brachial Plexus. The brachial plexus {h,jig. 268) extends obliquely from the lateral and inferior part ol the neck to the cavity of the axilla, or, rather, to the inner side of the head of the hume- rus, where it terminates by dividing into the nerves of the upper extremity ; it is formed in the following manner : The fifth and sixth cervical nerves (5, 6, fig. 286) unite at a short distance from the scaleni, and the cord thus formed passes very obliquely downward and outward, and then bifurcates. Again, the eighth cervical (8) and the first dorsal (1) nerves unite immediately after converging from the scaleni, and sometimes even between those muscles ; and the com- mon cord passes almost horizontally outward, and bifurcates near the head of the humerus. Between these two anastomotic cords is the seventh cervical nerve (7), which pur- sues a much longer course than the others, and bifurcates on a level with the clavicle ; the upper branch of its bifurcation joins the lower branch of the bifurcation of the first- named cord, and its lower branch unites with the upper branch of the second-named cord. From these several bifurcations and subsequent anastomoses, all of which take place at very acute angles, results the interlacement known as the brachial plexus. The brachial plexus is broad at its upper part, contracted in the middle, and broad again at its lower part, on account of the divergence of its terminating branches ; it com- municates with the cervical plexus by a considerable branch, which it receives from the fourth cervical nerve, and also by the filament which it gives to the phrenic nerve ; it is not so complicated but that the origins of the branches which emanate from it may be traced ; I shall take care to do this for each nerve. Relations. — At its origin it is situated between the scaleni, which cover it for a great- er extent below than above. A very strong aponeurosis, which extends over it and the scaleni also, completely isolates it from the surrounding parts. Lower down, it is situated between the clavicle and sub-clavius muscle on the one hand, and the first rib and upper part of the serratus magnus on the other. Still lower, it is contained in the cavity of the axilla, separated from the pectoral- is major in front by the costo-clavicular aponeurosis, and resting upon the scapulo-hu- meral articulation behind, from which it is separated by the tendon of the sub-scapularis. The following are its relations with the axillary artery : Between the scaleni and be- low them, the artery is situated upon the same plane as the brachial plexus, and lies be- tween the plexus and the first rib. Lower down it is placed on the anterior part of the plexus ; at the lower extremity of the plexus it passes under the angle of union of the two roots of the median nerve, by which it is embraced ; the axillary vein always lies in front of the artery, and therefore has less direct rela- tions with the plexus. The branches of the brachial plexus may be divided into the collateral and the terminal. The terminal branches are five in nimiber, namely, the internal cutaneous {g, fig. 286) and its accessory, the mus- culo-cutaneous {b), the median (c), the radial or musculo- spiral (/), and the ulnar {d) nerves.* The collateral branches may be divided into those giv- * I think it right to class the circumflex nerve among the collateral branches, and not, like most authors, among the terminal branches of the plexus. ^^2 NEUROLOGY. en off above the clavicle, namely, the nerve for the suh-clavius, those for t^eJevator angu li scapula and rhomboidcus, the posterior thoracic or nerve for the serratus magnus, the su- pra-scapular nerve (a) or nerve for the supra- and infra-spinati muscles, and the superior sub- scapular nerve ; those given off opposite the clavicle, namely, the thoracic branches ; and those given off in the axilla, namely, the circumflex nerve (e) and the sub-scapular branches^ which comprehend the nerve for the latissimus dorsi, the nerve for the teres major, and the inferior scapular nerve. One hranch only, namely, the nerve for the sub-clavius muscle, arises from the front part of the brachial plexus : all the other collateral branches are given off from the back of the plexus. The Collateral Branches of the Brachial Plexus. The Branches given off below the Clavicle. The Nerve for the Sub-clavius Muscle. — This is a small but constant branch, which comes off from the fifth cervical nerve, immediately before its junction with the sixth, passes vertically downward in front of the sub-clavian artery, and then enters perpendic- ularly into the middle of the sub-clavius muscle. This small nerve, before reaciiing the sub-clavius, always gives off a phrenic branch, which passes obliquely inward in front of the sub-clavian vein, and anastomoses with the phrenic nerve. The Nerve for the Levator Anguli Scapula. — This branch arises as frequently from the cervical as from the brachial plexus ; in the former case, it arises from the fourth cervi- cal nerve, in the latter from the fifth. It arises from the nerve immediately after its exit from the canal of the transverse processes, turns round the scalenus posticus to gain the deep surface 'oi the levator anguli scapulae, enters the muscle, supplies it with a great number of filaments, and perforates it to reach the rhomboideus, under which it passes. One of its terminating filaments anastomoses with a filament from the proper nerve for the rhomboideus. The Nerve for the Rhomboideus. — ^This arises from the fifth cervical nerve, immediately below the preceding ; I have seen it arise by a common trunk with the superior branch^, of origin of the nerve for the serratus magnus ; it passes downward and backward be- ^ tween the scalenus posticus and the levator anguli scapulae, and then beneath the last- * mentioned muscle, nearly as far as its scapular attachments, in order to get between the rhomboideus and the ribs ; it may be traced as far as the lower part of that muscle. One of its filaments perforates the rhomboideus, and anastomoses in the trapezius with the posterior spinal nerves. The Nerve for the Serratus Magnus {Posterior Thoracic Nerve of authors ; External Res- piratory Nerve, Sir C. Bell). — This branch, which is very remarkable for the length of its course, is derived from the fifth and sixth cervical nerves, immediately after their exit from the canal of the transverse processes ; it arises by two roots, which are sometimes equal and sometimes unequal in size ; it passes vertically downward behind the brachial plexus and the axillary vessels, in front of the scalenus posticus, reaches the side of the thorax (e', fig. 287), between the sub-scapularis and the serratus magnus, runs the whole length of the last-named muscle, and ramifies in its lower portion. During this course, it gives off a great number of filaments to the muscle : the lowest of these may be traced as far as the lowest digitation. The branch which it gives to the . upper part of the muscle is remarkable for its size. I have seen a branch from the seventh cervical nerve join the external thoracic nerve ; upon the upper part of the serratus magnus, so that this nerve would then be derived from the fifth, sixth, and seventh cervical nerves. The Supra-scapular Nerve, or Nerve for the Supra- and Infra-spinati Muscles. — This j branch (a, fig. 286) is given off from the back part of the fifth cervical nerve at its junc- tion with the sixth ; it passes obliquely backward, outward, and downward, dips beneath ,, the trapezius, and then under the omo-hyoid, the direction of which it nearly follows, and gradually increases in size as it approaches the coracoid notch of the scapula, and passes by itself under the ligament which converts this notch into a foramen ; the supra- scapular artery and vein, which had hitherto been in contact with the nerve, leave it op- posite this notch to pass above the ligament, and then join it again in the supra-spinous fossa. The nerve then runs from before backward in the supra-spinous fossa, protected by a .^ thick fibrous lamella, reaches the free concave border of the spine of the scapula, against" which it is held by a fibrous band, is then reflected inward and downward over this con- ,j cave border to gain the infra-spinous fossa, and immediately divides into two branches, ,.^ one of which spreads out in the upper part, and the other in the lower part of the infra- ,^ spinatus muscle. During its course through the supra-spinous fossa, the supra-scapular nerve gives off two supra-spinous branches, one of which is detached opposite the coracoid notch, and the other upon the spine of the scapula. They both enter the supra-spinatus muscle. » BRANCHES BELOW THE CLAVICLE. 783 The supra-scapular nerve is exclusively destined for the supra- and infra-spinati mus- cles. It gives no filament to the sub-scapularis. The Superior Sub-scapular Nerve. — This is a very small branch which arises imme- diately above the clavicle, and passes downward and forward to reach the upper border of the sub-scapularis, and then enters that muscle. The Branches given off opposite to the Clavicle. These, which are named the thoracic branches,* are generally two in number, one an- terior, the other ;?os^mor : they arise from the anterior part -of the brachial plexus, oppo- site the sub-clavius muscle. The anterior branch, or nerve for the pectoralis major, which is the larger, passes downward and forward between the sub-clavius muscle and the sub- clavian vein, and divides into two branches : an external, or anastomotic, which some- times arises directly from the brachiad plexus, and forms a loop around the axillary ar- tery, by anastomosing with the posterior thoracic branch ; and an internal, which runs along the deep surface of the pectoralis major, and expands into a great number of re- markably long and slender filaments, which enter the muscle very obliquely, and may be traced as far as its sternal attachments. A very slender filciment is constantly foimd running along the clavicle. The posterior thoracic branch, or nerve for the pectoralis miner, passes behind the axillary artery, below which it curves forward, to form, with the external branch of the anterior thoracic, the anastomotic loop of which I have already spoken. From this loop or arch, in forming which the nervous filaments are separated from each other, two sets of branches proceed : the one set runs between the pectoralis major and minor, closely applied to the former muscle, which they then enter, diverging to its lowest part ; the others pass beneath the pectoralis minor, and penetrate its deep surface ; some of them pass obliquely through this muscle and join the anterior thoracic branches in the pecto- ralis major. The Branches given off below the Clavicle. The Axillary or Circumflex Nerve. — This is no less remarkable for its great size, which has led some anatomists to regard it as a terminal branch of the brachial plexus, than for its reflected course : it comes off from the back of the plexus, behind the musculo- spiral nerve, or, rather, the circumflex and musculo-spiral nerves (e and f, fig. 286) ap- pear to be the two divisions of a trunk formed by filaments from the five branches of the brachial plexus. Immediately after its origin, the circumflex nerve passes downward and outward (g, fig. 288) in front of the sub-scapularis, which separates it from the shoulder-joint, turns obliquely round the lower border of that muscle, round the back part of the articulation, and, lastly, round the surgical neck of the humerus, is then reflected upward, so as to de- scribe a curve with the concavity turned in the same direction, and terminates by ram- ifying in the deltoid. During this curved course, the circumflex nerve, accompanied by the posterior cir- cumflex vessels, passes at first between the sub-scapularis and the teres major, then be- low the teres minor, on the outer side of the long head of the triceps (i. e., next to the bone), and then lies in contact with the deep surface of the deltoid, against which it is held by a very dense layer of fascia. The relation of the circumflex nerve to the articulation explains the possible occur- rence of laceration of this nerve in luxations of the humerus downward. The collateral branches of the circumflex nerve are three in number. One branch almost always goes to the sub-scapularis. I have already said that the sub-scapular nerves might be regarded as branches of the circumflex. As it turns round the lower border of the sub-scapularis, the circumflex gives off a branch for the teres minor and the cutaneous branch of the shoulder. The nerce for the teres minor enters that muscle by its lower border ; it almost always arises by a common trunk with a deltoid branch, which runs upward and backward to supply the back part of the deltoid muscle. The cutaneous nerve of the shoulder frequently arises by a common trunk with the two preceding, and, in this case, the circumflex nerve appears to bifurcate ; it passes under the posterior border of the deltoid, then lies in contact with the skin covering the back part of the top of the shoulder, and divides into diverging branches, some ascending, oth- ers descending, and others running horizontally. A second, and sometimes a third cu- taneous branch perforates the fleshy fibres of the deltoid, and is distributed to the corre- sponding skin. The terminal or deltoid branches of the circumflex nerve are given off as that nerve is turn ■ ing round the neck of the humerus, in which situation it divides into several diverging branches, the superior of which ascends, and appears like the continuation of the nerve, while the others descend, and may be traced as far as the insertion of the muscle into the humerus. * The anterior thoracic nerves of those who name the nerve for the serratus magnus the posterior thoracic 784 NEUROLOGY. Tlie Sub-scapular Nerves. — The nerve for the latissimns dor si is the largest of the nerves generally described as the sub-scapular ; it comes off at an acute angle from the inside of the circumflex nerve, and descends vertically in the midst of the cellular tissue of the axilla, between the sub-scapularis and serratus magnus, parallel to the external thoracic nerve, which it greatly resembles in size and direction as well as in its length ; it then passes in front of the latissimus dorsi, reaches its outer border, and may be traced down to the lower part of that muscle. The nerve for the teres major arises at a very acute angle from the preceding nerve, to the inner side of which it runs ; it passes to the sub-scapularis, turns round its outer bor- der, and enters the anterior surface of the teres major by a great number of filaments. The inferior sub-scapular nerve {I, Jig- 288) is sometimes multiple, and presents many varieties in its origin and number. Thus, it sometimes curves directly from the brachial plexus ; sometimes from a common tnmk with the circumflex nerve. Again, it often arises by a common trunk with the nerve for the teres major. Whatever be its origin, and whether it be single or multiple, it enters immediately into the sub-scapularis, and terminates there. We have seen that a small branch given off from the brachial plexus above the clavi- cle, the superior sub-scapular nerve, enters the same muscle at its upper border. The Terminal Branches op the Brachial Plexus. The Internal Cutaneous Jferve and its Accessory. ^- 287. The internal cutaneous nerve (g, fig. 286), the most internal and the smallest of the terminal branches of the brachial plex- us, arises by a common trunk with the ulnar nerve (i-;'*'I. The musculo-spiral or radial nerve, which is the largest of the terminal divisions of the brachial plexus, is intended for the triceps extensor cubiti, for the muscles of the pos- terior and external region of the forearm, and for the skin of the arm, the forearm, and dorsal region of the hand. It arises {f,Jig. 286) from all the five nerves of which the brachial plexus is composed, by a trunk which is common to it and to the circumflex nerve, and it issues from the plexus behind the ulnar nerve, to which it is closely applied. Immediately after its ori- gin, it passes downward, backward, and outward (b, fig. 288), in front of the conjoined tendons of the latissimus dorsi and teres major, to gain the groove of torsion or spiral groove of the humerus, into which it enters, passing between the long head of the tri- ceps and the bone, then between the external head and the bone ; it traverses the whole extent of this groove, and is in relation with the profunda humeri artery and vein. Leaving this groove, opposite the junction of the two upper thirds with the lower third of the humerus, it lies on the external and anterior aspect of the arm, descends vertical- ly between the supinator longus and brachialis anticus, and next between the brachialis anticus and extensor carpi radialis longior, crosses the elbow-joint (at b), passing in front of the outer condyle of the humerus and the upper extremity of the radius, and then di- vides into two terminal branches. Collateral Branches of the Musculo-spiral Nerve. During its winding and spiral course along the arm, this nerve gives off a great num- ber of collateral branches in the following order : Branches given off by the Musculo-spiral Nerve before it enters the Spiral Groove. — The first is the internal cutaneous branch (/', fig. 287) of the musculo-spiral, which is sub- aponeurotic at its commencement, but perforates the fascia, becomes applied to the skin, and divides into two filjiments, which pass obliquely backward, and may be traced as far as the olecranon.* There are several considerable branches to the long head of the triceps ; the highest of which is recurrent, and may be traced as far as the scapular attachments of the muscle. A very large descending branch may be traced to the olecranon. There is a branch for the internal head of the triceps, one division of which is rather large, and runs along the inner border of the humerus in front of the muscle, which it does not enter until it approaches the elbow. Branches given off by the Musculo-spiral after leaving the Spiral Groove. — These are the external cutaneous branch of the musculo-spiral, a very large branch which perforates the muscular fibres of the triceps and the brachial aponeurosis, then lies in immediate con- tact with the skin of the external region of the arm, passes obliquely backward, and di- vides into a great number of filaments, which supply the skin of the posterior region of the forearm, and may be traced down to the carpus. The branch for the external head of the triceps and for the anconeus, which is remarkable for its length, descends vertically between the external and long heads of the triceps, supplies the former of these, enters the anconeus, and may be traced as far as the lower part of that muscle. All these branches are remarkable for being given off at nearly the same height ; that is to say, near the shoulder-joint, and for accompanying the trunk of the musculo-spiral nerve. Branches given off by the Musculo-spiral Nerve in the Forearm. — These are the branches for the supinator longus, and those for the extensor carpi radialis longior, which enter the inner surface of the upper part of those muscles. Terminal Branches of the Musculo-spiral Nerve. Reduced to one half, or less, of its original size, by the successive emission of the pre- ceding branches, the musculo-spiral or radial nerve divides in front of the elbow (b, fig. 388) into two unequal branches, the one deep or muscular, the other superficial or digital. The deep or muscular division of the musculo-spiral nerve, or the posterior interosseous, is larger than the superficial division ; it immediately gives off a branch which passes vertically in front of the extensor carpi radialis brevier, and soon dips into that muscle ; the nerve then becomes flattened, perforates the supinator brevis, and pursues a very oblique and spiral course around the radius and within that muscle, to which it gives branches {branches for the supinator brevis) : it then emerges from the posterior aspect of this muscle, and immediately divides into a great number of diverging branches, some of which are intended for the superficial, and the others for the deep layer of muscles on the posterior region of the forearm. The branches given to the superficial layer are, those for the extensor communis digt- torum, which are very numerous and diverging, the superior being also recurrent; the branch for the extensor proprius digiti minimi ; and the branch for the extensor carpi lU- * [Anastomosing with the accessory of the internal cutaneous.) 792 NEUROLOGY. naris : all these branches arise by a common trunk, and enter the deep surface of the muscles. The branches for the deep layer also arise by a common trunk (i, Jig. 289), whicli may be Fig. 289. regarded as the continuation of the muscular division of the mus- culo-spiral, considerably diminished in size. This common trunk passes vertically downward between the superficial and deep lay- ers of muscles, gives off a branch, which enters the superficial as- pect of the extensor longus ■pollicis, then passes between the adduc- tor longus and extensor brevis pollicis on the one hand, and the extensor longus pollicis on the other, runs in contact with the inter- im/, osseous ligament, and gives off a first branch to the extensor lon- gus pollicis, a second which enters the deep surface of the same muscle, and a small branch which enters the outer border of the entensor proprius indicis. Reduced at length to a very small branch, the muscular division of the musculo-spiral nerve enters the groove (at s) for the tendons of the extensor communis digitorum, lying beneath them, in con- tact with the periosteum ; it runs over the carpus, and expands into a number of articular fdaments, which enter the radio-carpal, carpal, and carpo-metacarpal articulations ; in this latter portion of its course, the nerve is of a grayish colour, swollen, and, as it were, knotted ; a condition which is observed in all articular nerves. The superficial, cutaneous, or digital division of the musculo-spiral nerve, or the radial nerve properly so called, forms the external dor sal nerve of the hand, and is about half the size of the muscular di- vision. It passes vertically downward, between the supinator lon- gus and the extensor carpi radialis longior, along the outer side of the radial artery : having reached the middle of the forearm, it es- capes from beneath the tendon of the supinator longus, and runs along the outer border of that tendon. Situated at first beneath the fascia, it soon perforates it, becomes sub-cutaneous, runs vertically downward, and, about an inch and a half above the styloid process of the radius, divides into an external and an internal branch. The external branch (o, figs. 288, 289), which is the smaller, runs along the outer side of the styloid process of the radius, and then along the outer border of the carpus,* of the first metacarpal bone, and of the first and second phalanges of the thumb, and termi- nates in the skin beneath the nail ; it is the external dorsal collateral branch of the thumb. The internal branch (e, fig. 289), which is much larger, passes obliquely behind the ra- dius, crosses the tendons of the adductor longus and extensor brevis pollicis, and divides into three secondary branches, namely, counting from without inward, the internal dor- sal collateral nerve of the thumb, and the external and internal dorsal collateral nerves of thf index finger, t Summary. — The musculo-spiral nerve gives off, in the arm., two cutaneous branches, one internal, the other external, the latter of which is much the larger, and may be tra- ced as far as the carpus ; and also muscular branches to the three portions of the triceps and to the anconeus : to the forearm, it supplies muscular branches to all the muscles of the deep and superficial layers of the posterior and external regions ; and to the hand, certain cutaneous branches, namely, the dorsal collateral nerves of the thumb and index finger. General Summary of the Distribution of the Jferves of the Brachial Plexus. The preceding description shows that the brachial plexus supplies the skin, the mus- cles, and the articulations of the upper extremity, including the shoulder. We shall briefly recapitulate, first the muscular and then the cutaneous branches. The Muscular Branches. — By its collateral branches, the brachial plexus supplies the scaleni and all the muscles which move the shoulder, excepting the trapezius, which receives its nerves from the brachial plexus and from the spinal accessory nerve of Wil- lis ; by its terminal branches it supplies all the muscles of the arm, the forearm, and the hand. Each of the muscles which move the shoulder receive a special nerve ; thus, besides the nervous filaments for the scaleni, there is the nerve for the sub-clavius ; the nerve for the levator anguU scapulae ; the nerves for the rhomboideus ; the nerve for the serratua magnus, which is better known as the external thoracic nerve ; the nerve for the latis- simus dorsi, which is generally described as a branch of the sub-scapular ; and the nerves for the pectoralis major and minor. The muscles which move the arm upon the shoulder also receive their nerves from the * [NVhere it sends an anastomotic filament to the palmar cutaneous branch of the median. J t [It also supplies the external dorsal collateral of the middle finger, and often unites with tlie ulnar cuta- oeius, to form the dorsal collaterals for the contiguous sides of the middle and ring fingers.] THE NERVES OF THE BRACHIAL PLEXUS. 793 brachial plexus ; sometimes there is a separate nerve for each muscle, sometimes the same nerve supplies two muscles. The nerve for the deltoid, or the circumflex nerve, also supplies the teres minor. The supra-spinatus and infra-spinatus receive their fila- ments from the same branch, viz., the supra-scapulum nerve. The teres major receives a branch from the sub-scapular nerve.* Of the muscles which move the forearm upon the arm. Those of the anterior region, oi the flexors, viz., the biceps, coraco-brachialis, and brachialis anticus, receive their fila- ments from the musculo-cutaneous nerve ; the muscle of the posterior region, the tri- ceps, is supplied entii ely by the musculo-spiral nerve. The ulnar nerve gives no branch in the arm. The muscles which move the radius upon the ulna, and those which move the hand and the fingers, are thus supplied. The interosseous division of the musculo-spiral nerve sup- plies the muscles of the posterior region of the forearm, viz., in the superficial layer, the common extensor, the extensor proprius digiti minimi, and the extensor carpi ulnaris ; in the deep layer, the supinator brevis, the adductor longus, extensor brevis, and extensor longus pollicis, and the extensor proprius indicis. The muscles of the exterior region of the forearm, namely, the two supinators, and the two radial extensors of the carpus, also receive their branches from the musculo-spiral nerve. The muscles of the anterior region of the forearm receive their filaments from the median nerve, excepting the flexor carpi ulnaris and the internal half of the flexor profundus, which are supplied by the ulnar nerve. The flexor profundus, then, by a peculiarity which not unfrequently occurs in regard to compound muscles, receives its nerves from two different sources. The intrinsic muscles of the hand are supplied in the following manner : Those of the ball of the thumb by the median nerve ; those of the ball of the little finger by the ulnar nerve ; the two external lumbricales by the median nerve ; the two internal lumbricales by the ulnar nerve ; all the interossei, including the adductor pollicis, by the ulnar nerve. The Cutaneous Branches A — The skin which covers the shoulder on the outer side re- ceives its nerves from the cervical plexus. The skin of the external surface of the arm receives its nerves from the cutaneoiis branches of the circumflex nerve, and from the external cutaneous branch of the mus- culo-spiral. The skin of the anterior and internal regions of the arm receives its nerves from the internal cutaneous branch of the musculo-spiral, from the accessory nerve of the internal cutaneous, which anastomoses with the second intercostal, from a small branch of the internal cutaneous, and from the humeral branch of the third intercostal. The skin of the forearm receives its filaments from the internal cutaneous, which anastomoses with the cutaneous filaments of the musculo-spiral, ulnar, and musculo-cu- taneous nerves. The skin of the dorsal region of the hand and of the fingers receives its filaments from the dorsal branches of the radial nerve, in the two external thirds of that region, and from the dorsal branch of the ulnar nerve in the internal third. The skin of the palmar region of the hand and fingers receives its filaments from the median nerve in the two external thirds, and from the ulnar in the internal third, or, to speak more precisely, the median nerve supplies the external and internal collateral branches of the thumb, the index, and the middle fingers, and the external collateral nerve of the ring finger ; the ulnar nerve supplies the external and internal collateral nerves of the little finger, and the internal collateral branch of the ring finger. Some of the terminal branches of the median nerve, and the terminal divisions of the internal cutaneous and musculo-cutaneous, are lost in the skin of the upper part of the palm of the hand. The palmar collateral nerves of the fingers offer the following peculiarities : the branches which they give to the skin are placed either opposite to each other, or alter- nately ; each of these branches tenninates separately in a pencil of filaments ; the twigs from the internal branches do not anastomose with those from the external ; lastly, the terminal extremities of the external and internal collateral branches do not anastomose with each other in the pulp of the finger, but expand separately, and are distributed to the skin of the pulp and to the skin under the nail. The branches which supply the palmar aspect of the fingers present a very remark- able condition,t consisting in the presence of small, grayish, gangliform bodies, always of a crescentic form. These bodies are very numerous ; they are sometimes separate, * The teres minor and the infra-spinatus are, therefore, supplied by two different branches, which would induce us to describe these muscles separately, did we not see that compound, and sometimes even simpla muscles receivo-two or more distinct nerves.- t A beautiful preparation of the cutaneous nerves of the upper extremity may be made by removing Ihs skin, either by turning it inside out, in the same way as an eel is skinned, or by making a longitudinal incision along the outer side of the limb. In both cases the fascia should be removed with the skin. In the first meth- od, by which a very fine preparation may be made, the everted skin represents a kind of glove, the inner sui- face of which is formed by tlie epidermis, and the outer by the deep surface of the skin X This was pointed out in one of the last concours of tlie assistants (aides) of the Faculty, by M.M. AndjaJ, ramus, and Lacroix, who had to dissect the cutaneous nerves of the hand. 5 H 704 NEUROLOGY. and sometimes arranged in groups ; they do not essentially belong to the nerves, but are applied to them, and may be separated from them by slight force. They are, therefore, not ganglia. If we consider that these gangliform bodies occupy the palmar region only, and are never found in the dorsal region, that they exist in the sole of the foot as well as in the palm of the hand, that they have been found upon the nerves which surround the artic- ulations, and, consequently, upon nerves which are subject to constant pressure, that I have even found them upon an intercostal nerve which was reflected over the side of the sternum, and, lastly, that they do not exist in the infant at birth, and are more numer- ous in proportion as the palm of the hand is more callous we shall be warranted in con- cluding that they are the result of external pressure. THE ANTERIOR BRANCHES OF THE DORSAL NERVES, OR THE INTER- COSTAL NERVES. Dissection. — Enumeration. — Common Characters. — Characters proper to each. Dissection. — Search carefully for the cutaneous branches, some of which are to be found opposite the sides of the sternum, and others about the middle of the intercostal spaces. Saw through the sternum in the median line, and open the abdomen through the linea alba. Sacrifice one half of the thorax, or, rather, break the ribs through the middle, so as to trace the nerves from within outward. The anterior branches of the dorsal nerves, twelve in number, are intended for the parietes of the thorax and abdomen.* These branches offer at once a great uniformity, and a great simplicity in their distri- bution. I shall first explain their common characters, and shall then notice the pecu- liarities Dresented by each. Common Characters. The anterior branches of the dorsal nerves, or the intercostal nerves, separated from the posterior branches by the superior costo-transverse ligament, appear like flattened cords, which pass to the middle of the corresponding intercostal space (see^lf^. 268) ; there they are situated between the pleura and the aponeurosis, which is continuous with the in- ternal intercostal muscle. After proceeding for a certain distance, they pass between the external and internal intercostal muscles, and approach the groove of the rib above, but they are not lodged in it, for they always lie below the intercostal vessels. At about the same situation in each space, that is to say, about half way between the vertebral column and the sternum, the intercostal nerves divide into two branches, the one intercostal, and the other perforating or cutaneous. The intercostal branch is the continuation of the trunk of the nerve, and is distinguish- ed from it only by its smaller size. It runs along the lower border of the rib above, and then that of the corresponding costal cartilage ; it is sometimes situated on the internal surface of the cartilage, and having reached the forepart of the intercostal space, it per- forates this space from behind forward, runs along the sternum, is inclined somewhat inward over that bone, and is then reflected outward, between the pectoralis major and the skin, to which latter it is distributed. These small filaments may be called the an- terior perforating filaments. During its course, the intercostal nerve and its continua- tion give off a great number of nervous filaments. Not unfrequently the intercostal nerve gives off, in the back part of the space, a small branch, which reaches the upper border of the rib below. When this branch does not exist, its place is supplied by sev- eral twigs which have a similar distribution, some of which even pass to the intercostal space below, crossing obliquely over the internal surface of the rib. In like manner, we sometimes find some small twigs proceeding from the upper side of the nerve over the internal surface of the rib above, and reaching the next intercostal space. Lastly, from the lower side of the intercostal nerve and its continuation a series of twigs are given off, which divide into filaments that curve towards each other so as to form arches or loops, from which the terminal filaments proceed. In no part of the body are there found longer or more delicate nervous filaments ; some of them run through half the length of an intercostal space without diminishing in size, and several evidently belong to the periosteum. The perforating or cutaneous branches are often larger than the intercostal branches ; they pass very obliquely through the external intercostal muscles, and after running for a certain distance between those muscles and the serratus magnus, each of them divides into two smaller branches, the one anterior, and the other posterior or reflected : the an- terior branches run horizontally forward, become sub-cutaneous by escaping between the digitations of the serratus magnus in the eight superior intercostal spaces, and between the digitations of the obliquus externus abdominis in the four lower spaces, and then, * Haller only admits eleven dorsal nerves, because he considers, and not without reason, the twelfth as a Inmbar nerve. " ANTERIOR BRANCHES OF THE DORSAL NERVES. 795 becoming applied to the skin, spread into a number of filaments, which almost always anastomose with the adjacent filaments of the nerves above and below. The posterior or reflected branches immediately perforate the serratus magnus and the obliquus externus abdominis, are reflected upon themselves, pass backward between the latissimus dorsi and the skin, and after running horizontally for a distance of one .or two inches, are again reflected forward, and are then lost in the skin. Proper Characters of each of the Anterior Branches of the Dorsal J^erves. The First Dorsal Nerve. — This nerve belongs to the brachial plexus, into which it en- ters immediately after its escape from the inter-vertebral foramen, crossing over the neck of the first rib at an acute angle. P'rom its size, it resembles the lower cervical nerves, and diflfers widely from the remaining dorsal nerves. It becomes intercostal only by giving off a small intercostal twig at its exit from the inter- vertebral foramen. This in- tercostal branch is applied to the under surface of the first rib, which it crosses obliquely from behind forward, so that it does not reach the first intercostal space until opposite the junction of the rib with its cartilage ; it gains the middle of this space near the ster- num, at which point it passes forward through the space, like the other intercostal nerves, and ramifies in the muscles and the skin. The Second Dorsal Nene. — This nerve crosses obliquely over the second rib, on the outer side of its neck, to reach the first intercostal space, and then recrosses the same rib, about its middle, to gain the second intercostal space, where it divides into two branches : the intercostal, which follows the lower border of the second rib, and presents nothing remarkable ; and the -perforating or cutaneous branch, which requires a special description. The perforating or cutaneous branch, which is destined exclusively for the skin of the arm, is much larger than the other branches of the same kind. It emerges from the thorax at the middle of the second intercostal space, immediately below the second rib, passes directly through that space, is reflected at right angles over an aponeurotic arch, runs outward, and immediately subdivides into two branches of equal size, the one ex- ternal and the other internal. The external or intercosto-humeral branch (to the left of d, fig. 287) traverses the axilla, receives an anastomotic twig from the accessory nerve (c) of the internal cutaneous of the ann, reaches and crosses over the outer border of the latissimus dorsi, and divides into two cutaneous filaments, one of which is distributed to the skin of the posterior re- gion of the arm, while the other lies in contact with the skin of the internal region of the arm, runs parallel to the accessory nerve of the internal cutaneous, and may be traced as low down as the elbow. The internal branch crosses the outer border of the latissimus dorsi, lower down than the preceding branch, becomes applied to the skin, and divides into internal and posterior filaments, which are lost in the skin of the arm. The perforating branch, therefore, of the second dorsal nerve completes the system of cutaneous nerves of the arm. The third dorsal nerve is precisely similar to the others, excepting in its perforating, cutaneous, or intercosto-humeral branch, which is distributed to the integuments both of the thorax and arm. It is much smaller than the preceding ; it emerges (d,fig. 287) from between the digitations of the serratus magnus, is reflected backward upon itself, gives a small branch to the mamma, crosses the outer border of the latissimus dorsi, below the perforating branch of the preceding nerve, and having reached the upper part of the shoulder, is reflected upon itself, describing a curve with the concavity turned upward, and terminates in the skin of the inner and upper part of the arm. The fourth, fifth, sixth, and seventh dorsal nerves agree exactly with the general descrip- tion. The intercostal muscles, the triangularis stemi, the serratus magnus, the obli- quus externus abdominis, the upper part of the recti abdominis, and the integuments of the thorax, are supplied with nerves from these branches, in the order and manner al- ready pointed out. I would direct attention to the considerable number of filaments dis- tributed to the skin of the mamma in the female. The perforating branches of the fourth and fifth dorsal nerves each give a branch to the mamma, and a posterior branch, which crosses the latissimus dorsi, and is distributed to the skin over the scapula ; the skin of the mamma receives nerves from the third, fourth, and fifth dorsal nerves. The eighth, ninth, tenth, and eleventh dorsal nerves belong to the intercostal spaces form- ed by the false ribs : they leave those spaces at the point where the costal cartilages change their direction to bend upward ; they perforate the costal attachments of the di- aphragm, without giving that muscle any filaments, continue their oblique course in the substance of the parietes of the abdomen, for which they are destined, and are distribu- ted to these parts, in the same way as the nerves in the intercostal spaces, with some slight modifications. Thus, the perforating branches perforate the external intercostals and the obliquus externus abdominis in the same line as the perforating branches of the preceding nerves ; the intercostal branches, properly so called, having thus become ab- dormnal, run between the external and internal oblique muscles, just as, in the upper spa- fBi NEUROLOGY. ces, they ran between the external and internal intercostals. Having reached the rec- tus abdominis, they give off a cutanemis or perforating branch, and then enter the sheath of that muscle, through certain openings at its outer border, and proceed between the muscle and the posterior layer of the sheath : at the junction of the two external thirds with the internal third of the rectus, these branches pass through it very obliquely to- wards the middle line, and divide into muscular filaments, which are lost in the muscle, and the lowest of wliich pass vertically downward, and cutaneous filaments, which per- forate the anterior layer of the sheath of the rectus, on each side of the linea alba, but not always at the same distance from it, and are reflected horizontally outward in the sub-cutaneous cellular tissue lying immediately in contact with the skin. The twelfth dorsal nerve {d, fig. 290) might, according to the opinion of Haller, be re- garded as the first lumbar nerve. It is larger than the other dorsal nerves ; it emerges from the vertebral canal between the last rib and the first lumbar vertebra, passes in front of the costal attachments of the quadratus lumborum, runs along the lower border of the twelfth rib, proceeds very obliquely downward, like that rib, perforates the apo- neurosis of the transversalis muscle, and, like the preceding nerves, divides almost im- mediately into two branches. The abdominal branch, which corresponds to the inter- costal branch of the other nerves, passes horizontally forward between the transversalis and obUquus internus, supplying those muscles, and almost always gives off, below, an anastomotic branch to the abdominal or ilio-inguinal branch of the lumbar plexus, and then penetrates the sheath of the rectus, where it is arranged like the preceding nerves. The perforating or cutaneous branch is remarkable for being larger than the abdominal branch, and for its distribution ; it perforates very obliquely, and at the same time gives branches to the external and internal oblique muscles, becomes sub-cutaneous, passes vertically downward, crosses at right angles over the crest of the ilium, and divides into anterior, posterior, and middle branches, which are distributed to the skin of the gluteal region. Not unfrequently this gluteal cutaneous branch is given off by the first lumbar nerve, and then the cutaneous branch of the twelfth dorsal nerve is arranged like those of the preceding nerves, and ramifies in the skin between the last rib and the crest of the ili- um. There is a mutual relationship between the twelfth dorsal and the first lumbar nerves, so that they are often inversely developed ; they always communicate with each other by a branch called the dorsi-lumbar, but the mode and place of communicati»n are subject to many varieties : thus, it is sometimes effected by a winding branch which runs along the outer border of the quadratus lumborum, at other times it takes place in the substance of the abdominal muscles.* Summary of the Dorsal or Intercostal JVerves, These nerves are distributed to the parietes both of the thorax and the abdomen, which in all respects 'may be regarded as constituting a single cavity, the thoracico-abdominal. The muscular and cutaneous thoracic branches from the brachial plexus, some small branches derived from the lumbar plexus, and the posterior spinal branches of the dorsal nerves, complete the nervous system of the thoracic and abdominal parietes. The dorsal nerves are divided into muscular nerves, for the muscles of the thoracico- abdominal parietes, and for the muscles which lie upon them, and into cutaneous nerves. To obtain a good idea of the latter, they should all be displayed in the same preparation. Several rows of parallel cutaneous filaments will then be seen, in the following order, proceeding from before backward. The anterior perforating or cutaneous nerves, which are extremely small, emerge at the sides of the sternum and of the linea alba, and are reflected forward. The perforating or cutaneous nerves, which might be called middle, divide into orie set of branches, which run parallel to each other forward, towards the sternum, and another set, also parallel, which run backward, towards the vertebral column. We have elsewhere stated that other posterior cutaneous branches are gren off from the posterior branches of the dorsal nerves. They are parallel, and run outward, and may be traced as far as on a level with the axilla. THE ANTERIOR BRANCHES OF THE LUMBAR NERVES. Enumeration. — The Lumbar Plexus — Collateral Branches, Abdominal and Inguinal. — Ter- minal Branches — the Obturator Nerve — the Crural Nerve and its Branches, viz., the Mus- culo- c^ttaneous — the Accessory of the Internal Saphenous — the Branch to the Sheath of the Vessels — the Muscular Branches — the Internal Saphenous. Dissection. — In order to see these nerves at their exit from the inter-vertebral forami- na, and also to obtain a view of the lumbar plexus, it is necessary carefully to divide the * In a subject which had a thirteenth or lumbar rib, there was a tTiirteenth dorsal nerve, of large size, which crossed the supernumerary rib, and which corresponded in its distribution with both the twelfth dorsal and the first lumbar nerves ; it only communicated with the first lumbar nerve by a very small filament ; it gave off a deep perforating or cutaneous branch to the gluteal region, and also an ilio-scrolal branch. In thia •abject there were only four lumbar nerves. THE LUMBAR PLEXUS. 797 psoas muscle, m which they are situated ; the branches which emerge from the plexus must be dissected with the greatest care as they are passing under the femoral arch, and then to their final distribution. The anterior branches of the lumbar nerves (21 to 25, fig. 268) are five in number, and are distinguished as the first, second, third, fourth, and fifth : they gradually increase in size from the first to the fifth, and form a continuation of the series of anterior branches of the dorsal nerves : after having given off one or two branches to the lumbar ganglia (tt) of the sympathetic, and some branches to the psoas muscle, they end by anastomo- sing so as to form the lumbar plexus (Z). The anterior branch of the first lumbar nerve (1 I, fig- 290) is the smallest of all, and ia almost equal in size to the anterior branch of the Fig-. 290. twelfth dorsal nerve ; immediately after emerging from the inter-vertebral foramen, it divides into three unequal branches ; two of these (a and above b) are external and oblique, and constitute the ab- dmninal branches {ilio-scrotal nerves of some authors) ; the third is internal, vertical, and often very small ; it is the anastomotic branch which joins the second nerve. The anterior branch of the second lumbar nerve is at least twice as large as the preceding ; it passes al- most vertically downward, and gives off an anterior branch, the internal inguinal (genito-crural of Bichat, b), and an external branch, the external inguinal {in- guino-cutaneous of Chaussier, c). It is scarcely di- minished in size by giving oif these nerves, but be- comes flattened, plexiform, and riband-shaped, fur- nishes some large branches to the psoas, and anas- tomoses with the third nerve. The anterior branch of the third lumbar nerve is twice as large as the preceding, passes obliquely downward and outward, and is joined by the branch from the second nerve, which greatly increases its size. The large trunk thus formed, after a short course divides into two unequal branch- es, which diverge at a very acute angle, and anastomose with two branches derived from the fourth nerve, to constitute the crural (g) and the obturator (A) nerves. The anterior branch of the fourth lumbar nerve is a little larger than the third ; it divides after a short course into three branches : an external, which unites with the external bifurcation of the third to form the crural nerve ; a middle, which unites with the internal bifurcation of the same nerve to form the obturator nerve ; and an internal, vertical, an- astomotic branch, which joins the fifth nerve. The anterior branch of the fifth lumbar nerve (5 1) is somewhat larger than the fourth ; it receives the internal branch of that nerve, and with it forms a large trunk, which enters the sacral plexus, and was named by Bichat the lumbosacral nerve (i). The Lumbar Plkxus. The lumbar plexus (fig. 290) (lumbo-abdominal, Bichat) is a rather complicated inter- lacement, formed by the anastomoses of the anterior branches of the lumbar nerves. It is narrow above, where it consists of the sometimes slender communicating cord be- tween the first and second lumbar nerves, and it becomes wider towards its lower part, so as to have a triangular form ; it is situated upon the sides of the lumbar vertebrae, be- tween the transverse processes and the fasciculi of the psoas muscle. The branches which emanate from the lumbar plexus are divided into terminal branch- es, namely, the crural (g), obturator (A), and lumbosacral nerves (i) ; and collateral branches, improperly named musculo-cutaneous ; these are four in number ; they run between the psoas and iliacus and the peritoneum, and reach the femoral arch. I shall divide these collateral branches into two sets : an abdominal set, subdivided into the great (a) and small (above b) ; and an inguinal set, subdivided into the internal (i) and external (c).* Of these collateral branches, the abdominal only run in the sub-peritoneal adipose tis- sue, the inguinal branches being covered by a layer of fascia, which keeps them in con- tact with the psoas iliac muscle. Collateral Branches of the Lumbar Plexus. Jlbdominal Branches. The abdominal branches of the lumbar plexus are intended for the parietes of the abdo- * A change in the nomenclature of the collateral branches of the lumbar plexus appeared to me to be ne- cessary. Bichat, who first distinguished them by special names, divides them into external or musculo-cuta- neous branches, and an internal or genito-crural branch. Of the three external branches, Chaussier named the external the ilio-sr'o'al. and the internal the inguino-culaneous ; the intermediate one, to which he gave no particular name, - ■ ~ its old appellation of the midd/e JrancA. ■.- • 798 NEUROLOGY. men, and form a continuous series with the dorsal nerves, to which they are very anal- ogous as regards their distribution.* The great ahdominal nerve {a, fig. 270) is the most external, or, rather, the highest of the branches which come from the lumbar plexus (it is the superior musculo-cutaneous nerve of Bichat) ; the terms ilio-inguinal and ilio-scrotal, which are generally applied to it, are derived from the fact of its giving a small cutaneous branch to the pubic region. + It arises from the first lumbar nerve, of which it may be regarded as a continuation ; it immediately perforates the psoas, becomes sub-peritoneal, runs in front of the quad- r.itus lumborum obliquely downward and outward, through the sub-peritoneal adipose tissue, parallel to the twelfth dorsal nerve, and thus reaches the crest of the ilium to the outer side of the quadratus lumborum. It next passes obliquely through the aponeu- rotic attachments of the transversalis, runs along the crest of the ilium between that muscle and the obliquus internus, and divides into two branches, the abdominal branch, properly so called, and the pubic branch. The abdominal branch, properly so called, runs inward between the transversalis and the internal oblique, parallel to the abdominal branch of the twelfth dorsal nerve, with which it almost always anastomoses, and soon divides, like the lower intercostal nerves, into two filaments, one of which perforates the rectus, while the other, after having en- tered the sheath of that muscle, perforates it and ramifies upon the skin. The pubic branch (a, fig. 292) continues in the original course of the nerve : opposite the anterior superior spinous process of the ilium, and often much beyond that point, it receives an anastomotic twig from the small abdominal nerve {¥), and sometimes even the whole of that nerve, runs parallel to the femoral arch, at a variable distance above it, meets with the spermatic cord in the male, and the round ligament in the female, emerges from the anterior orifice of the inguinal canal {a, fig. 291), is reflected outward upon the superior angle of that orifice, and then expands into internal or pubic filaments, which are distributed to the skin of the pubes, and external filaments, which supply the skin of the fold of the groin ; this pubic branch sometimes divides behind the femoral arch into two filaments, which escape separately from the inguinal ring. At the point where the great abdominal nerve reaches the crest of the ilium, it very frequently divides into two branches, a gluteal cutaneous, which crosses obliquely over the crest of the ilium, and an abdominal, properly so called, which is distributed in the manner just described ; in this case, the great abdominal nerve has an analogous distri- bution to that of the dorsal nerves. The small abdominal or small musculo-cutaneous nerve (above b. Jig. 290), the second branch derived from the lumbar plexus, counting from without inward (the middle muscu- lo-cutaneous of Bichat), is merely an accessory of the great abdominal nerve, sometimes arising from it, often applied to it, and always anastomosing with it. It crosses oblique- ly over the anterior surface of the quadratus lumborum, and then over the iliacus, and is sometimes directed obliquely outward towards the anterior superior spine of the ilium, to join the pubic branch of the great abdominal nerve, with which it is blended ; it some- times runs alone between the transversalis and internal oblique : having reached the middle of the femoral arch, it anastomoses {b',fig. 291) by a single twig with the pubic branch of the great abdominal nerve, runs along the femoral arch below and parallel to that branch, and terminates in the same manner, that is to say, in the skin of the pubes and groin. I have seen it give off a small branch to the lower part of the rectus ab- dominis. The small abdominal nerve deserves the name of ilio-scrotal as much as the great abdominal. If this denomination is to be preserved, it might be called the small ilio-scrotal. The Inguinal Branches. The external inguinal, or external cutaneous nerve (c, fig. 290), the third branch of the lumbar plexus, counting from without inward (inguino-cutaneoiis, Chauss. ; inferior mus- culo-cutaneous, Bichat), is intended exclusively for the integuments of the external and posterior regions of the thigh. It generally comes off from the second lumbar nerve : I have seen it arise by a common trunk from the second and third lumbar nerves, and I have also seen it come off from the outer side of the crural nerve. It arises by one and often by two cords, which unite as they emerge from the psoas, or within the substance of that muscle. In either case, the nerve passes obliquely through the back part of the psoas, crosses the iliacus, being bound down by a layer of fascia, and then gains the an- terior superior spinous process of the ilium, below which it emerges {cfig. 291) from the abdomen, passing behind the femoral arch, and apparently increasing in size during its passage. Below the femoral arch the nerve is sub-aponeurotic, or, rather, is situated in a sheath * The varieties ^¥hich they prpsent as to their number, origin, and divisions, render their description diffi- cult ; I shall point out the most important varieties as we proceed. t I have frequently found the great abdominal branch divided into two distinct branches, which anastomosed upon the crest of the ilium, and then had a common distribution. I have seen the uppermost division lying »o close to the twelfth dorsal nerve that it might have been taken for a branch of that nervo. THE INGUINAL BRANCHES, ETC. 799 formed by the deepest layers of the fascia lata, and divides into two cutaneous branches (c c,fig. 292), a posterior or gluteal,* and an anterior or femoral. The posterior or gluteal branch turns very obliquely outward, downward, and backward, crosses the tensor vaginae femoris, and is distributed to the skin of the posterior region of the thigh. It is sometimes derived from the internal inguinal nerve, and then emerges from the abdomen on the outer side of the external inguinal nerve, crossing obliquely in front of it. When the great abdominal nerve (ilio-scrotal of authors) gives off a cuta- neous gluteal branch, there is only a trace of this posterior branch of the external ingui- nal nerve. The anterior or cutaneous branch divides into two others, which diverge at an acute angle : one is external, the other hiternal ; the external branch gives off a series of fila- ments, which pass backward and downward, forming loops with their concavities turned upward, and is then lost towards the lower third of the thigh ; its place is then supplied by the internal branch, which had at first descended vertically, but now turns outward and backward, and is distributed over the outer and fore part of the knee. These several divisions of the external inguinal nerve lie in contact with the femoral fascia, and their ultimate filaments are applied to the skin. The internal inguinal nerve (branche genito-crurale, Bichat ; rameau sous-pubien, Chauss., b. Jig. 290) arises from the second lumbar nerve, passes directly forward through the psoas, from which it emerges at the side of the bodies of the lumbar verte- brae, runs vertically downward upon the anterior surface of the muscle covered by a very thin layer of fascia, and having arrived within a greater or less distance from the femo- ral arch, divides into two branches, an internal or scrotal, and an external ot femoral cuta- neous branch (e). Not unfrequently this division takes place as the nerve emerges from the psoas. Sometimes, indeed, the genito-crural nerve is double, but this arises merely from its early subdivision. During its course, the internal inguinal nerve is crossed by the ureter and covered by the spermatic vessels. + The internal or scrotal branch (e, fig. 290) crosses over the front of the femoral artery, gains the internal orifice of the inguinal canal, crosses the epigastric artery, and, before entering the inguinal canal, gives off several filaments, which are reflected upward, and dip into the substance of the internal oblique and transversalis ; the scrotal branch is placed below the spermatic cord, from which it is perfectly distinct, runs with it through the whole length of the inguinal canal {b,fig. 291), rests upon the reflected portion of the femoral arch or Gimbernat's ligament, and emerges from the external orifice of the in- guinal canal, opposite the lower end of the external pillar : at this point it is reflected, passes vertically downward behind the cord, and ramifies in the skin of the scrotum of the male, and of the labia majora in the female. The femoral cutaneous branch gains the crural ring ; but before entering the ring, it gives off a great number of very delicate filaments, which are reflected upward behind the arch, to be distributed to the lower part of the psoas-iliac and transverse muscles : it then passes through the crural ring, in contact with its outer angle, and crosses the circumflex ilii artery at its origin, just as we have shown that the scrotal nerve crosses the epigastric artery ; after leaving the crural ring (e, figs. 291, 292), it lies beneath the fascia, but soon becomes sub-cutaneous, anastomoses with a cutaneous branch of the crural nerve, and may be traced beyond the middle of the thigh, t I have already stated, in describing the external inguinal nerve, that the posterior or gluteal cutaneous branch of the external inguinal nerve is often given off by the internal inguinal nerve. In that case, this branch runs outward, crosses the external nerve at a very acute angle under the femoral arch, and escapes from below the arch on the outer side of that nerve to turn round the tensor vaginae femoris. Not unfrequently the fila- ments for the lower part of the internal oblique and transverse muscles arise by one or more distinct branches. , The Terminal Branches of the Lumbar Plexus. These are three in number, viz., the obturator nerve, the crural nerve, and the great communicating branch between the lumbar and sacral plexus, called the lumbosacral trunk or nerve, which I regard as a dependance of the sacral plexus. The Obturator JVerve. The obturator nerve (A, fig. 290), which is distributed exclusively to the external obtu- * Not unfrequently the external inguinal nerve gives off a third and very small internal branch, which lies immediately in contact with the skin of the anterior region of the thigh, and may be traced as far as the lower third of that region. This branch always anastomoses with a cutaneous branch of the crural nerve. t Sometimes a small filament comes off from the genito-crural nerve while it is still within the substance of the psoas, descends vertically on the inner side of this nerve, gives off a filament which is lost upon the ex- ternal iliac artery, and then again becomes united with the nerve from which it had been given off. t In order to assist the memory, by connecting these nerves with important parts, I am in the habit of call- ing the femoral cutaneous branch of the internal inguinal nerve the branch of the crural ring, and the scrotal branch, the branch of the inguinal canal. The scrotal branch may be cut, in relieving the stricture in inguinal hernia, by the division of Gimbernat's ligament ; and the femoral cutaneous branch may be wounded when the external angle of the crural ring is divided for the relief of femoral hernia. 800 NEUROLOGY. rator muscle, to the three adductors of the thigh, and to the gracihs, is the smallest of Fig. 291. I'^'N- \ m the terminal branches of the lumbar plexus ; it arises from the third and fourth lumbar nerves by two equal branches, which unite at an acute angle ; it perforates the psoas, passes under the angle of bifurcation of the common iliac artery and vein, runs along the inner surface of the psoas, crosses very obliquely over the sides of the brim of the pelvis, and is then placed below the external iliac vessels, with which it forms an acute angle, and above the obturator artery : throughout the whole of this course, it is enveloped in the sub-peritoneal cellular tissue of that region, and, thus flattened and enlarged, reaches the internal ori- fice of the obturator or sub-pubic canal, on emerging from which it expands into diverging branches (A, fig. 291) for the adductors and the gracilis muscle of the thigh. Collateral Branch. — The obturator nerve gives off no branch in the pelvis : during its passage through the obturator or sub-pubic canal, it gives two filaments to the obturator cxternus ; one of these penetrates the upper border of the muscle, and the other enters at its anterior surface.* The obturator intemus receives no fila- ment from the obturator nerve. Terminal Branches. — These are four in number ;t three of them, constituting a superficial set, pass under the pectineus, and are dis- tributed as follows : the internal to the gracilis, the external to the adductor longus, and the middle to the adductor brevis ; the fourth, which is more deeply seated, belongs to the adductor magnus. The branch for the gracilis expands, as it enters the muscle, into several filaments, the largest of which (r,fig. 291) runs for some distance upon the internal surface of the muscle before termi- nating in it. The branch for the adductor longus enters the upper border and deep surface of the muscle : a rather large division (q) of this branch, taking a different course, passes sometimes in front of and sometimes behind the muscle, which is crossed by the nerve in the first case, and perforated by it in the second ; the nerve then divides into several filaments, some of which anastomose with the accessory branch (at m) of the internal saphenous nerve, while another anastomoses with the saphenous nerve itself, and a third terminates in the synovial membrane of the knee-joint : this is an articular nerve ; it may unite with the articular branch of the nerve for the vastus internus. The anastomotic division of the branch for the adductor longus is sometimes as large as the musculfu: branch itself t The branch for the adductor brevis crosses the upper border of that muscle, expands upon it, but does not enter it until it reaches the middle ; there is almost always an anastomotic twig, which joins the internal saphenous branch of the crural nerve.r,i- The Crural J^erve. . ^♦.rr**^;r:;. ' - The crural nerve {g,]ig. 290) is the external terminal hraiu^'.i ol' the lumbar plexus; the third and fourth lumbar nerves arc almost entirely devoted to the formation of thja large branch, which supplies all the muscles of the anterior region of the thigh, and the integuments of the anterior regions of the thigh, leg, and foot. After emerging from the psoas, the crural nerve is lodged in the groove betw^een the psoas and iliacus ; it escapes from the pelvis with this muscle, in the sheath of which it is contained : having arrived below the femoral arch (^, jig. 291), it turns slightly out- ward, becomes flattened and widened, and immediately divides into a great number of diverging branches. The nerve sometimes bifurcates, and then gives off these different branches. Relations. — In the iliac fossa, the crural nerve is covered by the iliac fascia, and is separated by the psoas from the external iliac artery and vein. Opposite the femoral arch it always occupies the groove between the psoas and iliacus, and is situated on the outer side of the femoral artery, being separated from the vessel by the psoas, which is very narrow at that point. It is of importance to remark, that the crural nerve is not contained in the sheath of the femoral vessels, but is separated from them by the iliac fascia (see ^^. 136). Collateral Branches. — ^In the pelvis, the crural nerve gives off from its outer side a great number of small branches {iliac branches), which enter separately into the iliacus muscle, after having run for some distance obliquely downward and outward upon the surface of that muscle. Only one branch enters the psoas. One of the branches for the iliacus is very long, and descends vertically in front of that muscle, into which it enters, after having turned round its outer border. I have already said that the external ingui- nal nerve {ingiiino-cutaneous of authors) not unfrequently arises from the crural nerve. Of the terminal branches of the crural nerve there are two which arise in front of the others : these are, the musculo-cutaneous nerve, and the small nerve for the sheath of the femoral vessels.* The Other branches are, proceeding from without inward, the branch for the rectus, the branches for the vastus externus, the branches for the vastus internus, and the cutaneous branch, called the internal saphenous nerve. The Musculo-cutaneous Crural Nerve. This nerve passes obliquely downward and outward between the sartorius and the psoas and iliacus, and immediately expands into muscular branches, distributed exclu- sively to the sartorius, and cutaneous branches. The muscular branches may be divided into the short, which enter the upper part of the sartorius, and the long, which run for some distance upon the deep surface of that mus- cle, before passing into it. The cutaneous branches are three in number ; two of them perforate the sartorius at different points, and may be called •perforating branches. I shall call the third the acces- sory branch of the internal saphenous nerve. The superior perforating cutaneous or middle cutaneous nerve {f,fig. 291) passes, very obliquely, through the upper part of the sartorius, and often, as it emerges from that muscle, anastomoses with a branch from the internal inguinal (genito-crural) nerve ; it then passes vertically downward, parallel to and on the inner side of the external ingui- nal (external cutaneous) nerve ; it Hes in contact with the femoral fascia (/, Jig. 292), or, rather, is contained in a proper fibrous sheath. During its course, the superior per- forating cutaneous nerve gives off internal and external cutaneous filaments, and bifur- cates, opposite the middle of the thigh, into two branches of equal size, which run par- allel to each other, gradually diminishing in size, and may be traced down to the skin over the patella. io the anastomotic division of the branch for the adductor longus, gives off cutaneous branches (q,fig. 292), which perforate the fascia to the inner side of the sartorius muscle, and supply the skin on the inner part of the thigh ; it also gives anastomotic branches to the plexus (m, Jig. 291 ) formed in the middle of the thigh, and sometimes an articular filament to the knee {these anastomotic and articular branches are described in the text, p. 800) ; it then ends in a descending cutaneous branch, which perforates the fascia near the knee (r,fig. 292), communicates with the intern.al cutaneous and internal saphenous nerves, and is distributed to the skin on the inner and back part of the two upper thirds of the leg. The deep branch of the obturator gives off within the upper part of the adductor magnus an articular filament destined for the knee-joint ; this filament descends in the substance of the adductor near the linea aspera, and enters the popliteal space, either by per- forating the tendinous insertion of the muscle about its lower third, or by coming forward on the front of that insertion, and then passing backward through the opening for the femoral artery : having reached the popli teal space, it surrounds the artery with small filaments, and enters the back part of the knee-joint. The cutaneous branches just stated to be given off by the superficial part of the obturator to the thigh and leg, and the articular filament given by the deep branch of the obturator to the knee-joint, correspond, in their dittnbulion, with the three collateral branches described by M. Cruveilhier {p. 803) as arising from the in- ternal saphenous nerve after it has received a remarkable branch of origin from the obturator nerve, opposite to the commencement of the profunda artery : these collateral branches of the internal saphenous were never met with in Mr. Ellis's dissections. In some cases, then, it seems that part of the obturator joins the internal saphenous, which afterward gives off cutaneous branches to the thigh and leg, and an articular filament to the knee ; in other c:»ses, again, the obturator does not join the internal saphenous, the above-mentioned branches arise directly from the obturator, and the internal saphenous gives no collateral branches.] ' LThe crural nerve also gives some small branches (s,_^^. 292), which pass inward behind the femoral vessels, enter the pectineus muscle, and sometimes the psoas also.1 51 802 NEUROLOGY. Tlie inferior perforating cutaneous or internal cutaneous nerve {I, fig. 291) run along the inner border of the sartorius, enclosed in its sheath, passes obliquely through the muscle at the middle of the thigh, but perforates the femoral fascia much lower down {I, Jig. 292) ; it descends vertically, in contact with that fiiscia, and having arrived opposite the internal condyle of the femur, is reflected forward upon itself, describing a loop with the concavity turned upward ; it thus gains the patella, runs between the skin and the sub-cutaneous bursa, and expands into a number of diverging filaments, which anasto- mose with the reflected branch (/ 1) of the internal saphenous nerve on the inner side of the patella. A small filament often remains in the sheath of the sartorius, anastomoses upon that muscle with a branch from the accessory of the internal saphenous nerve, per- forates the sheath of the sartorius opposite the knee, and anastomoses, on the inner side of the joint, with the reflected branch of the internal saphenous. The accessory cutaneous branch of the internal saphenous nerve arises from the mus:. Ulo- cutaneous nerve on the inner side of the perforating branches, descends vertically, and divides into two branches. The smaller of these is superficial (n, fig. 291) ; it enters the sheath of the sartorius, runs along the inner border of the muscle, escapes from the sheath below the middle of the thigh, crosses the adductor and the gracilis, and is in contact with the internal saphenous vein until it reaches the inner side of the knee, where it anastomoses with the internal saphenous nerve. The other branch, the satel- lite nerve of the femoral artery, crosses obliquely over the nerve for the vastus internu* and the internal saphenous nerve, and is situated in front of the latter, runs along the femoral artery, covering the lower fourth of that vessel, and crosses very obliquely over it, then passes over the tendon of the adductor magnus, and, having reached the fibrous ring through which the femoral artery passes, it expands into a great number of fila- ments, of which one anastomoses with the preceding branch (w), another joins the obtu- rator nerve (at m), and a third unites with the internal saphenous nerve ; a sort of plex- us is thus formed which gives origin to several nerves that cross obliquely over the gra- cilis, to be distributed to the skin upon the posterior region of the leg. The Small Nerve for the Sheath of the Femoral Vessels. This branch, which often comes oflT separately from the lumbar plexus, is situated, like the musculo-cutaneous, in front of the other branches of the crural nerve ; it then expands into a great number of very slender filaments, which surround the femoral ar- tery and vein. Two of these filaments, of which one passes in front of and the other behind the femoral artery, unite to form a small nerve {p,fig3. 291, 292), that escapes by the opening (p) for the internal saphenous vein, and accompanies the vein for a great part of its course. Not unfrequently, the filaments which have passed between the ar- tery and vein perforate a lymphatic ganglion. Two other filaments are distributed to the adductor brevis and adductor longus ; several of them turn round the deep femoral artery and vein, to become sub-cutaneous, and anastomose with other accompanying branches of the femoral vessels, and more particularly with the internal saphenous nerve. This small branch presents many varieties. I have seen it arise separately from the fourth lumbar nerve, and it then runs along the anterior surface of the crural nerve. The Nerve for the Rectus Femoris. The nerve for the rectus femoris arises on the inner side of the preceding, enters the upper part of the deep surface of the muscle, and divides into a superior or short branch, which passes horizontally outward in the substance of the muscle, and an inferior or long branch, which lies in contact with its inner border, and enters the muscle at the middle of the thigh. The Nerve for the Vastus Externus. The nerve for the vastus externus sometimes arises by a common trunk with the pre-' ceding, passes obliquely downward and outward beneath the rectus, to which it gives &., filament, and then divides into two branches : one of these immediately enters the upper part of the vastus externus, and gives off, before penetrating it, a cutaneous branch, which perforates the fascia lata and lies in contact with the skin of the external region of the thigh : the other is longer, dips between the vastus externus and internus, and enters the middle of the former muscle. This last branch almost always gives off a sm8dl twig to the vastus internus. The Nerves for the Vastus Internus.* These are two in number ; the one is external, and descending vertically, enters that portion of the vastus internus which corresponds to the anterior surface of the femur (the crureus of authors), and may be traced as far as the lower part of the muscle : this nerve furnishes several periosteal and articular filaments ; the other is internal, and much larger ; it often arises by a common trunk with the internal saphenous nerve, runs ver- tically downward in front of the vastus internus, parallel to and on the outer side of the * It will be remembered that, according to my views, the portion of the triceps which is called the crurau is not distinct from the vastus internus (see Mvojlooy). THE INTERNAL SAPHENOUS NERVE. m femoral artery, being in contact with that vessel above, but separated from it below, where it enters the vastus intemus. Before penetrating it, it gives off a very remark- able articular and periosteal branch, which runs along the surface of the muscle, to the aponeurosis of which it is applied :* opposite to the knee-joint it is reflected forward, perforates the thick fibrous layer which invests the inner side of the joint, and divides into two filaments, of which one, the articular, is lost behind the ligamentum patellae in the quantity of adipose tissue which is found there ; while the other, or the periosteal, gains the anterior surface of the patella, and is lost in the periosteum. This last filament is re-enforced upon the inner border of the patella by another which passes out from the substance of the vastus intemus. The Internal Saphenous Nerve. ^- 292. The internal saptienous nerve {t t',fig. 291), the satellite nerve .; of the femoral artery in the thigh, and of the internal saphenous vein in the leg, is at first situated on the outer side of the ar- tery, but soon passes in front of that vessel, and is contained in the same fibrous sheath ; when the artery passes through the tendon of the adductor magnus to enter the popliteal space, the nerve continues its vertical course in front of that tendon, and crossing it very obliquely from before backward, gains the back of the internal condyle of the femur, situated in front of the ten- don of the gracilis, and separated from the skin by the sartorius ; it then divides into two terminal branches (m, t',figs. 291, 292). This division often takes place £is the nerve is crossing the ten- don of the adductor magnus. Collateral Branches. — At its upper part, the internal saphenous nerve receives from the obturator nerve a remarkable branch of origin, which passes from behind forward in the angle formed by the femoral artery and the profunda.! It then gives off from its inner side, at the middle of the thigh, a cutaneous femoral branch, which passes between the sartorius and the gracilis, runs back- ward and downward, and is distributed to the skin of the poste- rior and internal region of the thigh. Several filaments continue their course to the inner and back part of the knee, anastomose with some branches given off from the saphenous nerve in the leg, and are distributed to the skin of the internal and posterior region of the leg. At the point where the femoral artery perforates the adduc- tor magnus, the internal saphenous nerve gives off a second or tibial cutaneous branch, which passes between the sartorius and gracilis, turns round the inner border of the latter muscle, pass- es vertically downward parallel to the saphenous nerve, and di- vides into several filaments, some of which anastomose with that nerve, while the others are distributed to the skin upon the internal and posterior region of the leg. In the sheath of the adductor magnus the saphenous nerve gives off an articular filament, which passes vertically downward in the substance of the internal inter-muscular septum, gains the knee-joint, perforates the fibrous layer, and may be traced into the synovial adipose tissue. t Terminal Branches. — The anterior, reflected, or patellar branch (u, figs. 291, 292) perforates the sartorius^ opposite to the back of the internal condyle, is reflected forward and downward in a flattened form upon the inner side of the knee-joint, parallel to and above the tendon of the sartorius, and expands widely into ascending filaments, which pass in front of the ligamentum patellae, and turn round the lower and then the outer borders of the patella ; into descending filaments, which cross obliquely over the crest of the tibia, and ramify in the skin which covers the external region of the leg ; and into middle filaments, which oc- cupy the space between the two preceding sets ; they are all dis- tributed to the skin, and several of them anastomose with the cu- taneous filaments upon the external region of the patella. * [In this situation it sometimes receives the articular filament of the anasto- motic or long cutaneous branch of the obturator nerve.] t [This junction of part of the obturator with the internal saphenous nerve was never seen in the dissec- tions of Mr. Ellis, nor did the saphenous give any collateral branch in the thigh ; but branches correspond- ing in their distriliution to the three collateral branches described in the text arose from the obturator itself (see also note, p. 800.)] % See note, p. 800. ^ The sartorius is, therefore, perforated in succession by three cutaneous branches, namely, two pprf.ii.i- ting branches from the musculo-cutaneous nerve, and one from the internal st' •nous. 804 NEUROLOGY. The posterior or straight branch {t') is larger than the preceding, and continues in the original course of the nerve ; it almost always receives an anastomotic branch from the obturator nerve, passes in front of the tendon of the gracilis, then between the sartorius and that tendon, which it crosses very obliquely, to meet the internal saphenous vein («), whose direction it then follows : having arrived opposite the junction of the three upper fourths with the lower fourth of the leg, it divides into two branches ; the one, posterior and smaller, passes vertically downward in front of the internal malleolus, upon which it ramifies, some of the filaments reaching as far as the skin upon the inner side of the sole of the foot ; the other branch, which is anterior and larger, runs along the internal saphenous vein, like it, is situated in front of the internal surface of the tibia, then in front of the internal malleolus, and expands into articular branches, which enter the tib- io-tarsal articulation, and into cutaneous filaments, which ramify in the skin upon the inner side of the tarsus. The following are the relations of the saphenous nerve with the internal saphenous vein : the nerve is at first placed in front of the vein, then crosses obliquely under it to get behind it, and, lastly, it again returns to its position in front of the vessel. During its course along the leg, the posterior branch of the saphenous nerve gives off some internal and some external branches : the internal branches are very small ; the up- per ones anastomose with the tibial cutaneous branch of the trunk of the internal saphenous nerve, and concur with it in supplying filaments to the skin of the back of the leg. The external branches, three or four in number, are large, and, in this respect, diminish from above downward ; their direction is obliquely downward and outward, in front of the tibia, which they cross ; their course is a long one, and they are distributed extensively to dif- ferent portions of the skin of the leg. All these divisions are parallel to each other, and to the anterior reflected or patellar branch of the saphenous nerve. THE ANTERIOR BRANCHES OF THE SACRAL NERVE. Dissection. — Enumeration. — The Sacral Plexus. — Collateral Branches, viz., the Visceral Nerves — the Muscular Nerves — the Inferior Hemorrhoidal — the Internal Pudic and its Branches — the Superior Gluteal Nerve — the Inferior Gluteal, or Lesser Sciatic Nerve — the Nerves for the Pyramidalis, Quadratus Femoris, and Gemelli. — Terminal Branch of the Sacral Plexus, or the Great Sciatic Nerve. — The External Popliteal and its Branches — the Peroneal Saphenous, Cutaneous, and Muscular Branches — the Musculo-cutaneous — the Anterior Tibial. — The Internal Popliteal and its Branches — the Tibial or External Saphenous — Muscular and Articular Branches — the Internal Plantar — the External Plan- tar. — Summary of the Nerves of the Lower Extremity. — Comparison of the Nerves of the. Upper with those of the Lower Extremity. Dissection. — Make an antero-posterior section of the pelvis, as in dissecting the inter- nal iliac artery. The anterior branches of the sacral nerves (26 to 3\,fig. 268), which are six in number, communicate with the sacral ganglia of the sympathetic, after they have emerged from the sacral foramina, and present the following arrangement : The first nerve (I, fig- 290), which is very large, passes obliquely downward and out- ward, in front of the pyriformis, and is joined at a very acute angle by the lumbo-sacral nerve (i), to assist in the formation of the sacral plexus. The second nerve, which is as large as the preceding, passes much more obliquely downward and outward, and immediately enters the sacral plexus. The third nerve (3), which is scarcely one fourth as large as the second, passes more horizontally outward to enter the sacral plexus. A considerable interval, in which is a large part of the pyriformis, separates it from the second nerve. A filament stretched in front of this muscle passes from the second to the third sacral nerve. The fourth nerve (4), which is only one third the size of the third, is divided and dis- tributed in the following manner : One of its divisions assists in forming the sacral plexus ; it gives off several viscer^d branches, which enter the hypogastric plexus ; it communicates with the fifth sacral nerve by another division ; it gives off one or two branches to the coccygeus muscle ; and, lastly, it gives a cutaneous coccygeal branch, which runs along the border of the sacrum, penetrates the great sacro-sciatic ligament, crosses that ligament very obliquely, and turns round its lower edge, perforates the coc- cygeal attachments of the glutseus maximus, passes very obliquely through the muscle, gives branches to it, and then ends in the integuments. The fifth and sixth nerves, which have no connexion with the sacral plexus, are ex- tremely small ; the fifth is not more than half the size of the fourth ; the sixth is so very slender a filament, that it has often escaped the notice of anatomists, and hence the in- correct but prevalent opinion that there frequently exist only five sacral nerves. The fifth nerve, at its exit from the anterior sacral foramen, divides into an ascending branch, which comnaunicates with the fourth, and a descending branch, which passes di- COLLATERAL BRANCHES OF THE SACRAL PLEXUS. 805 recfty downward to anastomose with the sixth, of which it appears to form the ascend- ing branch. The sixlh nerve consists of a mere filament, which divides, while still contained within the sacral foramen, into an ascending or anastomotic branch, which is merely the de- scending branch of the fifth ; a descending or inferior coccygeal branch, which passes ver- tically downward along the coccyx in the substance of the sacro-sciatic ligament, and is distributed to the skin ; and certain external branches, which perforate the sacro-sciatic ligament, and terminate in the glutaeus maximus. The Sacral Plexus. The sacral plexus {Jig. 290) is formed by the four upper sacral nerves (1 to 4) and the lumbo-sacral nerve (i) from the lumbar plexus ; the three superior sacred nerves pass entirely into this plexus ; the fourth nerve only sends one of its divisions to it. The lumbo-sacral trunk or nerve, which emanates from the lumbar plexus, is formed by the whole of the fifth lumbar nerve add0 to a branch from the fourth. This great nervous trunk establishes a free connexion between the lumbar and sacral plexuses, which, in fact, constitute only one plexus, which may be called the lumbo-sacral. I would here recall to mind that there is a precisely similar arrangement with regard to the cervical and brachial plexuses, to which the lumbar and sacral plexuses have an undoubted an- alogy. The sacral plexus is distinguished by its simplicity from most other plexuses, which are always more or less complicated. It is formed by the convergence of five cords to- wards the sciatic notch. As the lumbo-sacral cord is vertical, and the third and fourth sacral nerves are horizontal, it follows that the form of the sacral plexus resembles a triangle, the base of which measures the entire length of the sacrum, while its apex corresponds to that portion of the sciatic notch which is situated above the spine of the ischium. The great sciatic nerve («) is the continuation of this plexus, which, as Bichat judiciously remarked, is merely the sciatic nerve itself flattened from before backward, the intricacy of arrangement so evident in the plexus representing that which exists in all nervous cords. The following are the relations of the sacral plexus : It rests behind upon the pyri- formis, and it corresponds in front to the internal iliac vessels, from which it is separa- ted by a layer of fascia : these vessels also separate the plexus from the rectum and peritoneum. Of the collateral branches, some are anterior, namely, the visceral nerves, which enter the hypogastric plexus ; the nerve for the levator ani ; the nerve for the obturator inter- nus ; the internal pudic nerve : the other collateral branches are posterior, namely, the superior gluteal nerve ; the inferior gluteal or lesser sciatic nerve ; the nerve for the pyriformis ; the nerve for the geraelli ; and the nerve for the quadratus femoris. The great sciatic nerve is the only terminal branch of the sacral plexus. The Collateral Branches of the Sacral Plexus. The Visceral Jferves. Dissection. — After having made a section of the pelvis at one side of the symphysis, turn the bladder and the rectum over to the same side ; carefully detach the peritoneum, which is reflected from the pelvis upon these viscera ; lacerate the cellular tissue to reach the branches given off" from the fourth nerve ; and then trace the rectal and vis- ceral nerves, following the annexed description. It is advantageous to empty the large veins of the pelvis, and to soak it in water for some time previously to dissecting these nerves. The visceral nerves do not, properly speaking, come from the sacral plexus, but rather directly from the fourth and fifth sacral nerves ; they are three or four in number, and pass upward upon the sides of the rectum and bladder in the male, and of the rectum, vagina, and bladder in the female ; some of them are distributed directly to those organs, but the greater number (y, fig. 302) enter the hypogastric plexus (m), which will be de- scribed with the sympathetic system. The JSTervesfor the Levator Ani. Besides several rectal and vesical filaments which go to the levator ani, this muscle receives two filaments directly from the fourth sacral nerve (4, fig. 290) : the larger of these filaments enters the middle of the muscle ; the other, which is smaller, passes upon the sides of the prostate in the male, and of the vagina in the female, and termi- nates in the anterior portion of the muscle. The Nerve for the Obturator Internus. It arises from the anterior part of the sacral plexus, and more particularly from that portion which belongs to the lumbo-sacral cord and the first sacral nerve ; it passes im- mediately behind the spine of the ischium, is reflected forward through the small sciatic 806 NEUROLOGY. notch, and expands into three diverging branches, which are distributed within the mus- cle. In order to expose this nerve, the lesser sacro-sciatic ligament may be divided. The Inferior Hemorrhoidal J^erve. This nerve, which is intended for the sphincter ani and the adjacent skin, arises (from 4, Jig. 290) on the inner side of the internal pudic nerve, of which it is sometimes a branch, passes, like that nerve, behind the spine of the ischium, and then between the two sacro-sciatic ligaments, reaches the front of that portion of the glutaeus maxiraus which projects below the great sacro-sciatic ligament, communicates with the superfi- cial nerve of the perineum, gains the side of the rectum, and opposite the upper border of the sphincter expands into a great number of branches ; of these, some are anterior, and often anastomose with one of the divisions of the superficial perineal nerve ; others are median, and pass upon the sides of the sphincter ani as far as the skin, in which they terminate ; lastly, others are posterior, and proceed to the back part of the sphincter. The hemorrhoidal or anal nerve is sometimes di^pbuted exclusively to the skin round the anus ; it may then be named the anal cutaneoits nerve. The Internal Pudic JVerve. Dissection. — It is convenient to commence the dissection of this nerve from within outward, by dividing the lesser sacro-sciatic ligament, and separating the obturator fas- cia from the obturator internus muscle. The superior branch of the nerve upon the dor- siun of the penis may then be traced without taking it away. The perineal branches must then be very carefully dissected, and the continuity of these branches with those already dissected within the pelvis should be made out. The internal pudic nerve (d. Jig: 293) arises from the lower border of the flattened band formed by the nerves of the sacral plexus opposite to their junction ; it passes be- hind the spine of the ischium, and then enters the ischio-rectal fossa through the lesser sciatic notch, that is, between the two sacro sciatic ligaments, on the inner side of the internal pudic artery, and divides into two branches (/, Jig. 290), the injcrior branch, or 'perineal nerve, and the superior or deep branch, or the dorsal nerve oj the penis. The Perineal Nerve. The inferior branch or perineal nerve corresponds to the trunk of the internal pudic ar- tery, and to all its divisions, excepting the dorsal artery of the penis. It is the true con- tinuation of the nerve, and accompanies the trunk of the internal pudic arterj", being sit- uated below that vessel ; it runs forward and then upward between the obturator inter- nus and the obturator fascia, describes a curve having its concavity directed upward, and placed on the inner side of the tuberosity of the ischium, perforates the obturator fascia, opposite to the junction of the tuberosity with the ascending ramus of the ischium, and immediately divides into two branches : an inferior or anterior superficial perineal, which corresponds to the superficial artery of the perineum ; and a superior, which corresponds to the artery of the bulb, but which has a much more extensive distribution ; I shaU call it the bulbo-urethral nerve. The Collateral Branches of the Perineal Nerve. — During its course, the perineal nerve gives off a branch which might l>e called the external perineal ( posterior superficial perin eal) ; this branch perforates the great sacro-sciatic ligament, passes by the internal sur face of the tuberosity of the ischium, turns inward and downward, and then beneath the tuberosity, runs along the crus of the corpus cavernosum, and is lost in the dartos and scrotum in the male, and in the substance of the labia majora in the female. I have seen this nerve give a branch to the coccygeus, and two branches to the sphincter. This external perineal branch, moreover, presents many varieties. In some cases it terminates by anastomosing with the superficial branch of the perineum. In one case, in which the external perineal branch was very small, it was re-enforced by a branch from the inferior gluteal or lesser sciatic nerve, which crossed the outer side of the tuberosity of the ischium, and united, in front of that tuberosity, with the external perineal branch. The Terminal Branches of the Perineal Nerve. — The superjicial {anterior superjicial) pe- rineal nerve follows the superficial artery of the perineum, passes, like it, obUquely in- ward and forward, through the cellular interval between the ischio-cavernosus, and bulbo-cavernosus, receives a rather large filament from the external perineal branch, and almost always divides into several remarkably long filaments, which pass through the dartos, some reaching the bottom of the scrotum, while others, running along the lower surface of Uie penis, are distributed to the skin of that organ, and may be traced as far as the prepuce. The bulbo-urethral nerve, the second terminal branch of the perineal nerve, passes above and sometimes through the fibres of the transversus perinei muscle, supplies some small branches to the anterior part of the compressor urethrae and the posterior part of the bulbo-cavernosus, furnishes a bulbar branch which dips into the substance of the bulb, and then expands into very delicate filaments on the corpus spongiosum. DEEP BRANCH OF THE INTERNAL PUDIC, ETC. "gOV The Deep Branch of the Internal Pudic, or the Dorsal Nerve of the Perns. This is the highest of the terminal divisions of the internal pudic nerve, and corre- sponds to the deep branch of the internal pudic artery. It is at first applied, together with that vessel, against the internal surface of the tuberosity of the ischium, and pass- ing upward between the levator ani and obturator internus, gains the arch of the pubes ; it then runs forward among the sub-pubic veins through the several ligamentous struc- tures below the arch, and reaches the dorsum of the penis, where it is situated at the side of the suspensory ligament. Having now become the dorsal nerve of the penis, it runs along that organ in the median line, like the dorsal artery, but superficially to that vessel, and divides into an internal and an external branch. The internal branch, or branch for the glans penis, continues in the original course of the nerve upon one side of the median line, becomes more deeply seated as it runs for- ward, but without entering the corpus cavernosum, and thus arrives at the corona glan- dis ; at this point it expands and passes deeply between the base of the glans and the corpus cavernosum, gives no filament to the latter, but is entirely distributed to the glans, penetrating that part by extremely delicate filaments, which traverse the spongy tissue, and may be traced, at least in a great measure, to the papillae on the surface of the glans. The external or cutaneous branch, which is more superficial, comes off from the prece- ding at a very acute angle, passes obliquely upon the sides of the penis, and expands into a number of very long and slender filaments, some of which lie in contact with the corpus cavernosum, and supply it with very slender filaments, "while others run into the sub-cutaneous cellular tissue, and are distributed to the skin of the penis ; a considera- ble number terminate in the prepuce. The external branch of the dorsal nerve of the penis supplies the skin upon the three upper fourths of the circumference of the penis. The perineal branches supply that of the lower fourth. I have not found any branch of the internal pudic nerve corresponding to the artery of the corpus cavernosum. In the female, when this nerve reaches the clitoris, it becomes very small ; it passes under the arch of the pubes, between it and the cms of the clitoris ; it runs along that crus, becomes curved like the clitoris itself, upon the side of which it expands into fila- ments, and then ramifies in the substance of that organ ; several of the filaments run forward to the skin of the anterior part of the labia majora. The superficial perineal branch passes between the constrictor muscle and the bulb of the vagina, and then terminates in these parts. , The internal pudic nerve in the female does not appear to me to be half the size of the internal pudic nerve of the male. In one case I found that it consisted only of the branch for the clitoris, the superficial branch being supplied by the inferior gluteal nerve. The Superior Gluteal JSTerve. The superior gluteal nerve, which is intended for the glutaeus medius and minimus, and the tensor vaginae femoris, arises from the back of the lumbo-sacral trunk, before its junction with the first sacral nerve. I have seen it arising by two roots, of which one came from the lumbo-sacral nerve and the other from the posterior surface of the plex- us : it emerges from the pelvis (a, fig. 293) by the upper and fore part of the great sci- atic notch, in front of the pyriformis, is reflected upon this notch to pass between the glutaeus medius and minimus, and divides into two branches ; the one ascending, which en- circles the origin of the glutaeus minimus, like the corresponding branch of the gluteal ar- tery ; and the other descending, which passes obliquely downward and outward, between, the glutaeus medius and minimus, to which it gives off numerous filaments, and thus, grad- ually diminished in size, it embraces, as it were, the posterior surface of the glutaeus min- imus, and having reached the external border of that muscle, it passes downward, and enters the sheath of the tensor vaginae femoris, in which it terminates. Before entering the sheath of the tensor vaginae it gives off a remarkable branch, which turns round the anterior border of the glutaeus minimus, and ramifies in that muscle. The JVervefor the Pyriformis. This little nerve arises separately from the posterior surface of the sacral plexus, and more particularly from the third sacral nerve ; it divides into two branches, which im- mediately enter the anterior surface of the muscle. The Inferior Gluteal JVerve. > The inferior gluteal nerve (Bichat), or the lesser sciatic nerve {Boyer), is intended for the glutaeus maximus, the integuments of the posterior region of the thigh, and for a part of the skin of the leg. It arises from the back of the sacral plexus, sometimes by one cord, sometimes by several very distinct cords. It emerges from the pelvis (near c,fig. 293), below the pyriformis, together with and on the inner side of the great sciatic nerve, to which it may be regarded as an accessory ; it passes behind that nerve, and divides into two sets of branches, viz., muscular and cutaneous. The muscular branches (c) are numerous, although exclusively intended for the glutaeus maximus ; they divide into ascending and external branches, which run along the ante- 808 NEUROLOGY. rior surface of the muscle, spread out upon it, and may be traced as far as its upper oor- der, and descending and internal branches, which pass between the tuberosity of the is- chium and the muscle, and then enter the latter. The cutaneous branch (b) continues in the original course of the nerve, behind the great sciatic, and in front of the glutajus maximus ; it crosses obliquely, downward and in- ward, over the tuberosity of the ischium and the origins of the biceps and senii-tendi- nosus muscles ; considerably reduced in size, from having given off several branches, it assumes the name of lesser sciatic (/), runs vertically downward, becoming smaller and smaller, and may be traced down to the posterior region of the leg. The cutaneous branch, as it emerges from the glutaeus maximus, gives off a consid- erable recurrent branch (e), which might be regarded as a terminal branch of the nerve. This branch is reflected upward so as to describe a curve having its concavity turned upward, and subdivides into two secondary branches, an internal and an external : the external branch is the larger, and ramifies in the skin of the gluteal region ; the internal or scrotal branch (pudendalis longus inferior, Sammering) is a very remarkable one ; it is reflected forward upon the under surface of the tuberosity of the ischium, runs along at some distance from the ascending ramus of the ischium and the descending ramus ot the OS pubis, anastomoses with the superficial perineal nerve, reaches the scrotum above the testis, and divides into two branches — an external, which passes on the outer side, and an internal, which runs on the inner side of the testis ; having embraced this organ, they are distributed to the skin of the anterior part of the scrotum and the lower part oi the penis. In the female, this branch belongs to the labia majora. All along the thigh, the cutaneous branch of the inferior gluteal nerve gives off some very small external branches, and some larger internal branches, which are reflected forward, describing curves having the concavity turned upward, and supply the skin of the internal region of the thigh. In the pophteal space, the cutaneous branch divides into two filaments, one sub-cuta- neous, which may be traced, notwithstanding its extreme tenuity, as far as the middle of the posterior region of the leg ; and the other sub-aponeurotic, which perforates the fas- cia of the leg, runs along the external saphenous vein, and anostomoses with the exter- nal saphenous nerve. The Jferves for the Quadratus Femoris and the Gemelli. The superior gemellus receives a special nerve from the anterior part of the sacral plexus. The nerve for the inferior gemellus is a branch of the nerve for the quadratus femoris. The nerve for the quadratus femoris is remarkable. It arises from the front of the sa- cral plexus, or, rather, from the limit between this plexus and the great sciatic nerve, passes vertically downward in front of the gemelli and obturator internus, by which it is separated from the great sciatic nerve, and it is placed in contact with the os innomi- natum, to the outer side of the tuberosity of the ischium. It gives off some external pe- riosteal and osseous branches, which enter the foramina in the tuberosity of the ischium ; some internal or articular branches, which perforate the fibrous capsule of the hip-joint ; a branch for the inferior gemellus ; and then terminates in the quadratus femoris, which it enters by its anterior surface. The Terminal Branch of the Sacral Plexus, or the Great Sciatic Nerve. The great sciatic nerve (grand femoro-poplite, Chauss.) is intended for the muscles of the posterior region of the thigh, and for the muscles and integuments of the leg and foot : it is the termination (s, fig. 290) of the sacral plexus, or, rather, it is the sacral plexus itself condensed into a nervous cord. The fifth lumbar nerve, a branch of the fourth lumbar, the three superior sacral nerves, and a branch from the fourth, form the origins of this great nerve, which is the largest in the body. It emerges from the pelvis, through the great sciatic notch, below the pyriformis im- mediately above the spine of the ischium, passes vertically downward (s, fig. 293) be- tween the tuberosity of the ischium and the great trochanter, both of which project so as to separate it from the skin, or, more exactly, it runs along the outer side of the tu- berosity of the ischium, in a very deep groove between that process and the margin of the cotyloid cavity. At its exit from the pelvis, it is a flat, riband-shaped nerve, six lines in breadth, but it soon becomes rounded, runs vertically downward along the back of the thigh, sloping, however, a little outward ; having arrived about three or four fin- gers' breadth above the knee-joint, it divides into two branches, which are called the external popliteal sciatic or the peroneal nerve (i), and the internal popliteal sciatic or tibial nerve (A). The sciatic nerve sometimes divides at its exit from the pelvis, but it may do so at any other point between that and the popliteal space. This premature division is of no importance ; in fact, it always exists ; for when there is apparently only one trunk, the two branches of the bifurcation are perfectly distinct through the whole length of ihe thigh, and are merely in contact with each other.* * When the great sciatic nerve divides within the pelvis, the upper division perforates the pyriformis, while 'He lower emerges from below that muscle. THE GREAT SCIATIC NERVE, ETC. 809 Relations. — Behind., the great sciatic nerve is covered by the Fig. 293. glutaeus maximus, and then by the long head of the biceps and the semi-tendinosus ; lower down it occupies the cellular inter- val between these two last-named muscles, and when they sep- arate from each other to form the borders of the popliteal space, it becomes sub-aponeurotic. In front, it corresponds to the gemelli and obturator internus, by which it is separated from the os coxffi, to the quadratus femo- ris and the adductor magnus. During its course it is surround- ed by a large quantity of adipose cellular tissue, but has no ac- companying vessel.* Collateral Branches of the Cheat Sciatic. — The great sciatic nerve gives off in the thigh five muscular and three articular branches ; they sometimes arise separately, sometimes by a common trunk. They are the following : The nerve for the long head of the biceps, which divides into two ascending branches for the origin of that muscle from the ischium, and descending branches, which run for a long time in front of the muscle, and then enter it by a series of filaments. The nerve for the semi-tendinosus, which runs upon the anterior surface of the muscle, and does not enter it until it reaches the lower third of the thigh. The nerves for the semi-membranosus are two in number ; they almost always anastomose and enter the internal surface of the muscle at two different points. A nerve for the adductor magnus, which runs forward and then inward, and enters near the inner border of the muscle. We have seen that the adductor magnus receives most of its nerves from the obturator nerve. All the preceding branches arise from the upper part of the sciatic nerve, opposite to the quadratus femo- ris, and often by a common trunk. A nerve for the short head of the biceps sometimes arises at the same height as the preceding, but is most commonly given off from the sciatic nerve at the middle of the thigh. When the sci- atic nerve divides prematurely, the branch we are now descri- bing comes from the external popliteal. This nerve enters the upper extremity of the muscle, expanding into diverging fila- ments. An articular nerve of the knee, which often arises by a common trunk with the preceding, and is not unfrequently given off from the external popliteal ; it passes vertically downward in front of the great sciatic nerve, through some adipose tissue, to gain the outer side of the joint ; having arrived above the external con- dyle, it turns and divides into several filaments, which perforate the fibrous tissue of the joint, and are distributed to the articular adipose tissue, where they are scattered, some above, others be- low, and others on the outer side of the patella, t The External Popliteal Sciatic or Peroneal J^erve. The external popliteal sciatic, external popliteal, or peroneal nerve {i,fig. 293), the external terminal branch of the great sciatic, is intended for all the muscles of the anterior and external region of the leg, and for the skin on the leg and on the dorsum of the foot. It is scarcely half the size of the internal popliteal ; it runs obliquely downward and out- ward, behind the external condyle of the femur through the popliteal space, and is pla- ced nearer to the surface than the internal popliteal nerve, which is lodged in the inter- condyloid fossa ; it then crosses obliquely over the origin of the outer head of the gas- trocnemius, passes behind the head of the fibula, from which it is separated by the ori- gin of the soleus, turns horizontally upon the neck of that bone (at v), between it and the peroneus longus, and expands into four branches, two superior or recurrent, for the tib- ialis anticus, and two inferior and larger, which form the true terminations of the nerve. Collateral Branches. During this course, the external popliteal nerve gives off two superficial collateral * In three instances I have found the great sciatic accompanied by a large vein, which was continuous with the popliteal vein, and perforated the upper part of the adductor magnus, like the profunda artery. In two of these cases the sciati* nerve divided at its exit from the pelvis. I did not note the arrangement of the nerve in the third case. It was a remarkable circumstance that there was another popliteal vein accompanying the artery : in one of the cases the vein was in front instead of behind the artery. t See note, p. 812. 5K 810 NEUROLOGY. nerves : a saphenous nerve, which we shall call the peroneal saphenous^ to distinguish it from the tibial saphenous, and the peroneal cutaneous branch. The Peroneal Saphenous Nerve. The peroneal saphenous nerve {n) presents many varieties in different subjects, both in regard to its size and origin. It is generally smaller than the tibial saphenous (/), of which it may be regarded as an accessory ; it arises in the popliteal space, descends vertically beneath the fascia, between the external and internal popliteal nerves, perfo- rates the fascia opposite the middle of the leg, to join the external saphenous vein, with which it runs along the tendo Achillis, and terminates upon the outer side of the OS calcis. During this course, it gives off" several cutaneous filaments and a communi- cating branch to the tibial saphenous nerve : this branch is of considerable size, and comes off" while the nerve is still beneath the fascia. Having become very slender after giving these branches, the peroneal saphenous nerve subdivides opposite the lower part of the tendo Achillis, and upon the outer side of the os calcis, into several calcaneal branches, one of which turns obliquely round the posterior surface of the os calcis, while the others descend vertically, are reflected upon the under surface of that bo^e, and are distributed to the skin of the heel. Not unfrequently the peroneal saphenous nerve gives off a malleolar branch, which passes between the external malleolus and the skin, and anastomoses in front of the ankle-joint {y,fig. 291) with a twig from the muscuJo-cuta- neous nerve. This malleolar branch, which often comes from the last-mentioned nerve, is, moreover, remarkable, like all nerves which are subjected to strong pressure, for its thickness, its grayish colour, and, lastly, for its knotted, and, as it were, ganglionated appearance. The peroneal saphenous nerve is often very small, and is lost in the skin upon the middle of the leg : its place is then supplied in the lower two thirds of the leg by the tib- ial saphenous nerve, the size of which is always in an inverse ratio to that of the pero- neal saphenous. No nerve presents more varieties than the peroneal saphenous ; they relate to its size and to the point at which it anastomoses with the tibial saphenous. One of the most remarkable varieties is that in which the peroneal and tibial saphenous nerves, those call- ed communicating saphenous branches {communicans fibula, n; communicans tibia, I) unite in the popliteal space into a single trunk, the external saphenous {p), the distribution of which corresponds to the ordinary distribution of the two nerves. The Peroneal Cutaneous Branch. This comes off from the external popliteal nerve, behind the outer condyle of the fe- mur, passes vertically downward along the fibula, in contact with the skin, and divides into ascending and descending branches, the latter of which may be traced as far as the lower part of the leg. The Terminal Branches of the External Popliteal J^erve. The Branches for the Tibialis Anticus. The two superior or recurrent branches, resulting from the subdivision of the external popliteal, pass horizontally inward, behind the extensor communis digitorum, and are distributed to the tibialis anticus ; one of these branches supplies the peroneo-tibial ar- ticulation. The Musculo-cutaneous Branch, or External Peroneal Nerve The musculo-cutaneous branch {x,fig. 291), the lowest of the terminal branches of the external popliteal, is intended for the muscles of the externail region of the leg, and for the skin upon the dorsum of the foot (pretibio-digital, Chauss. ; peroneus externus, Saemm.). It passes at first obliquely, then vertically downward in the substance of the peroneus longus, turns forward to enter between the extensor longus digitorum and the peroneus longus and brevis, and perforates the fascia of the leg, above the ankle-joint : having thus become sub-cutaneous, it passes obliquely downward and inward, following the di- rection of the extensor longus digitorum, becomes flattened and widened, and divides a little below the tibio-tarsal articulation into an internal and an external branch ; the lat- ter subdivides into three other branches, so that there are in all four terminal branches, which form the dorsal collateral nerves of the toes. Not unfrequently the musculo-cutaneous nerve bifurcates as it escapes from beneath the fascia of the leg, and its two branches reunite opposite to the tibio-tarsal articula- tion, so as to describe an elongated ellipse. Collateral Branches. — There are two branches for the peroneus longus, of which one comes off from the nerve immediately after its origin, while the other arises lower down, and runs a very long course in the substance of the muscle ; there is also a branch for the peroneus brevis,' which often arises by a common trunk with the preceding. In its sub-cutaneous portion, the musculo-cutaneous nerve supplies several filaments to the skin, among which we should distinguish an external malleolar filament, which passes between the external malleolus and the skin, increases considerably in size, and becomes THE ANTERIOR TIBIAL NERVE, ETC. 811 grayish and knotted, like all nerves subjected to pressure. This filament often anastomo- ses with the malleolar branch of the peroneal saphenous nerve, and sometimes supphes the place of that malleolar branch. Terminal Branches. — There are four terminal branches of the musculo-cutaneous nerve, distinguished numerically as the first, second, third, and fourth (see^^. 291). The^r«( or internal branch passes very obliquely forward and inward, to form the internal dorsal collateral nerve of the great toe ; this nerve, like all nerves subjected to pressure, increas- es in size and becomes grayish, and, as it were, knotted opposite the metatarso-phalan- gal articulation. The second branch, which often arises by a common trunk with the first, supplies the external dorsal collateral nerve of the great toe, and the internal collateral nerve of the second toe. The third branch supplies the external collateral nerve of the sec- ond, and the internal collateral nerve of the third toe. These two large branches are often replaced by one (») from the anterior tibial nerve, with which they anastomose. The fourth terminal branch or internal branch supplies the external dorsal collateral nerve of the third, and the internal dorsal collateral nerve of the fourth toe. All the filaments from these branches are distributed to the skin upon the dorsal re- gion of the foot and digital phalanges. In a great number of subjects, the tibial or external saphenous nerve supplies the in- ternal collateral nerve of the little toe, and the external collateral nerve of the fourth toe ; but in others, these nerves are furnished by an additional terminal branch of the mosculo-cutaneous nerve ; in all cases the nerves anastomose with each other. The Anterior Tibial, or Interosseous Nerve. The anterior tibial or interosseous nerve (v v,fig. 291), intended for the muscles on the anterior region of the leg, for the extensor brevis digitorum, and for the interosseous muscles in the foot, is as large as the musculo-cutaneous nerve just described ; it runs to the inner side of that nerve, beneath the extensor communis digitorum, and passes along the interosseous ligament, together with the anterior tibial artery lying in front of that vessel. It is placed, like the artery, between the tibialis anticus and the extensor communis digitorum, from which it is separated below by the extensor proprius pollicis pedis ; it supplies a great number of filaments to all these muscles, passes with the ar- tery under the annular ligament of the tarsus, in the sheath of the extensor proprius pol- licis, and divides into two branches : The internal deep branch of the dorsum of the foot (v), which is the true continuation of the nerve, passes horizontally forward, under the arteria dorsalis pedis, over the first in- terosseous space, gives off a small twig to the muscles of that space, and divides into two branches, which form the deep external dorsal collateral nerve of the great toe, and the internal dorsal collateral nerve of the second toe. These branches communicate with the superficial dorsal branches of the musculo-cutaneous nerve, and sometimes supply their place. The external and deep nerve of the dorsum of the foot runs outward between the tarsus and the extensor brevis digitorum, in which it terminates ; it gives off in front, opposite the interosseous spaces, a series of very delicate filaments, which enter the posterior extremities of those spaces. The filaments for the fourth and fifth spaces often arise by a common trunk. They are extremely delicate, and are closely applied to the tarsus. The Internal Popliteal Sciatic^ or Tibial JVerve. The internal popliteal sciatic, internal popliteal, or tibial nerve (h, fig. 293), is intended for all the muscles of the back of the leg, and for the skin of the sole of the foot ; both in direction and size it appears to be the continuation of the great sciatic nerve. It pass- es vertically downward in the inter-condyloid fossa of the femur ; it is at first placed be- tween the heads of the gastrocnemius, it then passes under that muscle and under the arch formed by the soleus, descends, under the name of the posterior tibial nerve {k), be- tween the soleus and the deep layer of muscles, inchnes a little inward, and, having reached the termination of the fleshy belly of the soleus, gains the inner side of the ten- do Achillis ; lower down, it passes behind the internal malleolus, against which it is flat- tened and widened, and divides into the internal and external plantar nerves (a, b, and c, /«■• 294). In the popliteal space it is sub-aponeurotic, in the fleshy portion of the leg it is sep- arated from the fascia by the double layer formed by the gastrocnemius and the soleus, and it again becomes sub-aponeiirotic along the tendo Achillis. It is in relation, in front, with the popliteal and posterior tibial vessels, which separate it, above, from the knee-joint and popliteus muscle, and lower down, from the deep layer of muscles in the leg.* Behind the internal malleolus, and under the groove upon the os calcis, it is en- closed in a common fibrous sheath with the posterior tibial vessels, which are placed in front of it ; this sheath is behind that for the tendons of the tibiahs posticus and flexor communis digitorum. * [The nerve is at first at a short distance to the outer sid« of the artery ; lower down it lies immediately behind the vessel, and still lower croises to the imier side of the artery, and is separated from it by the vein.] NEXJEOLOGY. Its coilaieral 'IfrancMs are very numerous. I shall div'de them info Itliose ^ven'ra^dp- posite the knee-joint, and those supplied along the leg. The Collateral Branches of the Internal Popliteal Jferve, behind the Knee- Joint. These are six in number, namcl}', two anterior, which are very small, one for the plantaris longus, and one for the knee-joint ; two internal, namely, the tibial saphenous nerve, and the nerve for the inner head of the gastrocnemius ; two external, namely, the nerve for the outer head of the gastrocnemius, and the nerve for the soleus. The Tibial Saphenous Nerve. This is generally known as the external saphenous. It is much larger than the pero- neal saphenous, which always anastomoses with it. I have already said that the mode and situation of this anastomosis present many varieties. The tibial saphenous nerve {communicant tibia, I, Jig. 293) arises in the popliteal space, passes vertically downward between the two heads of the gastrocnemius, and then upon their posterior surface, along their fibrous septum, between them ; it is here situated in a small fibrous canal common to it and to a small artery and vein ; it receives, at a variable height in the leg, a more or less considerable filament from the peroneal saphenous nerve (or communicans fibulce, n) ; it then becomes sub-cutaneous, forming the external saphenous nerve (p), runs along the outer side of the tendo Achillis, just as the posterior tibial runs along its inner side ; it now accompanies the external saphenous vein, which is accompanied above this point by the peroneal saphenous nerve ; it is reflected behind the external malleolus, in the same manner as the tibial nerve is reflected upon the internal malleolus, then runs forward and downward {y,fig. 291) upon the outer side of the os calcis, where it gives off several very large external calcaneal nerves, and terminates difTerently in va- rious subjects. In some it terminates by forming the dorsal collateral nerve of the fifth • toe ; in others it is larger, and divides into two branches, of which the external forms the external collateral nerve of the fifth toe, while the internal, which receives an anasto- motic branch from the musculo-cutaneous nerve (z), passes horizontally forward, crosses the extensor brevis digitorum, and the tendons of the long extensors, and divides into two secondary branches, of which one constitutes the internal dorsal collateral nerve of the little toe, and the other the external dorsal collateral nerve of the fourth toe. I may point out the thickening, the gray colour, and the knotted, and, as it were, ganglionated structure of the external collateral nerve of the little toe opposite to the articulations. The cxtertMl calcaneal nerves, which may be regarded as forming the termination of the tibial saphenous, are very remarkable ; they pass vertically along the outer side of the OS calcis, expand into several filaments, which are reflected upon the ridge which separates the external from the inferior surface of that bone, and are distributed to the skin upon the heel. During its course along the leg, the tibial saphenous gives off scarcely a single fila- ment, but along the outer border of the foot it supplies a great number, which run down- ward and forward, and terminate in the skin covering the external plantar region. The size of the tibial saphenous nerve is inversely proportioned to that of the pero- neal saphenous and musculo-cutaneous nerves. Thus, when the peroneal saphenous nerve is large, it furnishes most of the external calcaneal branches ; and when the mus- culo-cutaneous nerve is large, it supplies, besides the external calcaneal, the internal dorsal collateral nerve of the little toe, and the external dorsal collateral nerve of the fourth toe. The Nerves for the two Heads of the Gastrocnemius and for the Soleus. The nerve for the inner head of the gastrocnemius often arises by a common trunk with the tibial saphenous ; again, the nerves for the outer head of the gastrocneniius and for the soleus often arise by a common trunk : the nerves for the gastrocnemius en- ter the anterior surface of the head of that muscle, and immediately ramify. The nerve for the soleus is the largest, and enters the muscle at its upper arch ; all these nerves ramify as soon as they enter the muscles which they supply. The Articular Nerve and Nerve for the Plantaris Longus. The posterior articular nerve of the knee runs forward to enter the posterior ligament of the articulation : one of its filaments follows the direction of the internal articular ar- tery, and is lost in the popliteus.* * [From the dissections of Mr. EUjs, it appears that there is an articular nerve to the knee-joint with each articular artery. The superior external articular nerve is the one described at p. 809 ; it most commonly arises from the extertial popliteal. The inferior external articular also arises from the external popliteal, and sometimes from the ioiatic nerve ; it is a long branch which descends towards the external condyle, passes be- low it on the outer side of the joint, and perforates the capsule. The superior internal articular is very small, and is not constant ; it arises from the internal popliteal nerve, and passes on the outer side, and then in front of (t. e., deeper than) the popliteal vessels, and reaches with its artery the inner side of the joint. The infe- rior internal articular is the largest of all : it arises from the internal jiopliteal above the joint, descends on the outer side, and then in front of the popliteal vessels, is applied to the corresponding artery upon the popliteus muscle, passes beneath the mternal lateral ligament, and enters the inner side of tlie joint. The posterior ar- ticular, or azygos, is given off opposite the joint from the internal popliteal, or from the inferior internal ar- ticular ; it perforates the postferior ligament. — {Ellis's Demonstrations of Anatomy, p. 675, 67(1.)] THE INTERNAL PLANTAR NERVE. 813 Tlie nerve for the ■plantaris longus always arises separately from the posterior tibial nerve, and immediately dips into the substance of the muscle. Collateral Branches of the Internal Popliteal Jferve in the Leg. There are three sets of collateral branches given off by the posterior tibial nerve in the leg: namely, the nerve for the popliteus ; the nerves for the deep layer of muscles ; the internal calcaneal nerve. Lastly, several very small filaments come off from the nerve, run along the posterior tibial artery, and, after a course of variable length, perfo- rate the aponeurosis and ramify in the skin. The nerve for the popliteus arises opposite the knee-joint, runs forward on the outer side of the popliteal vessels to gain the lower border of the muscle, around which it # turns ; before entering the muscle, the nerve expands into several branches, all of which pass horizontally forward opposite to the interosseous ligament, which they ap- pear to perforate. But with a little care it is seen that almost all of these filaments are lost in the muscle. I have, however, seen one of them perforate the interosseous liga- ment together with the anterior tibial artery, and then, leaving that vessel, return through the substance of the ligament, and terminate in the tibialis posticus ; several filaments of the popliteal nerve are also evidently distributed to the peroneo-tibial artic- ulation, and to the periosteum of the tibia and fibula. The nerves for the deep layer of muscles of the leg consist of two sets. The nerve for the tibialis posticus almost always arises by a coimnon trunk with the preceding, runs down- ward and forward, is applied to the posterior surface of the muscle, to which it gives a series of filaments from its anterior aspect ; the continuation of the nerve enters the muscle about its middle, and maybe traced in it as far as its lower part. The nerves for the flexor longus pollicis and for the flexor communis arise by a common trunk a little be- low the preceding ; the nerve for the flexor longus pollicis, which is larger than those for the flexor communis and tibialis posticus, accompanies the peroneal artery as far as the lower part of the leg. The Internal Calcaneal Nerve. — ^This is a large branch which comes off from the inner side of the posterior tibial nerve, and which, in cases of premature bifurcation of that nerve into the internal and external plantar, comes from the externeil plantar ; it passes vertically downward, on the inner side of the os calcis, and divides into two diverging branches, which are applied to the inner side of the bone, are reflected upon its lower surface, and are distributed to the skin of the heel, one in front, and the other behind. The Terminal Branches of the Internal Popliteal Jferve. The Internal Plantar Nerve. The internal plantar nerve, which is intended for the muscles and skin of the sole ol the foot, is larger than the external plantar ; at its origin it is situated behind the inter- nal malleolus, in front of the posterior tibial vessels, which cross it at an acute angle, and occupies a groove which is common to it and to those vessels, and which is quite distinct from and lies behind the groove for the tendons. It is reflected beneath the in- ternal malleolus, becomes horizontal, reaches the calcaneal groove, perforates the pos- terior extremity of the flexor brevis digitorum, and during this passage through the groove is protected by a fibrous canal, which is subjacent to the grooves for the tendons. At its exit from this fibrous canal, the internal plantar nerve is situated upon the boundary, between the internal and middle plantar regions, between the flexor brevis pollicis on the inside, and the flexor brevis digi- torum on the outside ; having given off a considerable branch (a, fig. 294), which becomes the internal plantar collateral nerve of the great toe, it perforates the aponeurosis of the flexor brevis digitorum to enter the same sheath as that muscle, and runs (J) along its in- ner border. Having reached the posterior extremity of the meta- tarsal bones, it divides into three branches, which form the collateral nerves of the toes. Sometimes there is a fourth branch (d), which passes outward, to anastomose with the external plantar nerve. The collateral branches are very numerous. Some of them are cutaneous, and perforate the plantar fascia to ramify in the skin. The most remarkable are, a small calcaneal cutaneous nerve, which crosses the posterior tibial vessels, to supply the skin upon the in- ner side of the os calcis ; and s. plantar cutaneous nerve, which emerges between the flexor brevis pollicis and the flexor brevis digitorum, and divides into two small cutaneous branches, one of which pro- ceeds forward, while the other runs backward, like a recurrent nerve. There are cilso some muscular collateral branches, namely, far the flexor brevis pollicis, the abductor pollicis, and the flexor brevis digitorum. Lastly, the internal plantar collateral nerve of the great toe {a), which is so large that it might be regarded as a terminal branch of the internal plantar nerve ; it comes off from the last- Fig. 294. I 814 NEUROLOGY. named nerve, at its exit from the covered canal formed for it by the flexor brevis poUicis, passes forward along the outer side of the tendon of the flexor longus poUicis, below, i. e., superficial to the inner portion of the adductor poUicis (oblique adducteur, Crnveilhier), and gains the inner and under surface of the metatarso-phalangal articulation of the great toe ; in this place it is situated in the furrow between the internal and external sesamoid bones of that articulation ; it runs forward below the inner border of the former, and then of the second phalanx of the great toe, and, having arrived below that bone, it divides, like the collateral nerves of the fingers, into two branches, the one dorsal or un- gual, and the other plantar. The terminal branches of the internal plantar nerve are three in number, and are distin- guished as the first, second, and third, counting from within outward. i The first terminal branch, which is the largest, runs along the outer side of the tendon of the flexor longus poUicis, gives filaments to that muscle, passes between the meta- tarso-phalangal articulations of the first and second toes, under an arch which is com- mon to it and the corresponding vessels, and divides into two secondary branches, which form, the external collateral nerve of the great toe, and the internal collateral nerve of the second toe. Not unfrequently this branch gives an anastomotic filament to the internal coUateral nerve of the great toe, which passes beneath the metatarso-phalangal articu- lation of that toe. The first terminal branch of the internal plantar nerve gives off the filament for the first lumbricalis ; it then supplies several articular twigs to the metatarso-phalangal artic- ulation of the great toe, and a very numerous series of cutaneous filaments. The second terminal branch, much smaller than the preceding, passes somewhat out- ward, crossing below, i. e., superficial to the flexor tendon of the second toe, and then forward, and bifurcates opposite the metatarso-phalangal articulations, to constitute the external plantar collateral nerve of the second toe, and the internal plantar collateral nerve of the third. During its course, this branch supplies filaments to the second lumbricalis, to the meta- tarso-phalangal articulation of the second toe, and also to the integuments. The third terminal branch passes very obliquely outward, crosses below the flexor tendon of the third toe, and bifurcates to form the external collateral nerve of the third and the internal collateral nerve of the fourth toe. This branch supplies the metatarso-phalangal articulations of the third and fourth toes, and the corresponding integuments. Summary. — The internal plantar nerve, therefore, supplies branches to the skin on the inner part of the sole of the foot, also the plantar collateral nerves of the first, second, and third toes, and the internal collateral nerve of the fourth toe, aU of which are cu- taneous branches. It gives muscular branches to the flexor brevis poUicis, the abductor poUicis, the flexor brevis digitorum, and to the two internal lumbricales. Lastly, it gives off a great number oi articular filaments to the tarsal, tarso-metatarsal, metatarso-phalangal, and phalangal articulations. The External Plantar Nerve. The external plantar nerve (c, fig. 294), which is smaller than the internal, is placed with it in the groove of the os calcis, and perforates the flexor brevis, under an arch dis- tinct from that for the internal plantar, and which is common to it and the external plantar vessels ; it then runs downward and outward, between the flexor brevis and flexor accessorius, is reflected forward, and divides into two branches, a superficial and a deep. Collateral Branches. — During its course, the external plantar nerve gives off, immedi- ately after its origin, one large branch, which runs horizontally outward, in front of the tuberosities of the os calcis, passes under the flexor accessorius, and is reflected for- ward to enter the abductor minimi digiti. At the point of its reflection, it gives off a transverse branch, which is lost in the posterior attachment of the muscle. The exter- nal plantar also supplies the nerve or nerves for the flexor accessorius. Terminal Branches. — The superficial terminal branch (c, fig. 294), which is the continu- ation of the trunk of the nerve, divides into two others, one external, the other internal. The external branch passes very obliquely outward, below the flexor brevis digiti min- imi, crosses the tendon of the abductor brevis obliquely, then runs along the outer side of the fifth metatarso-phalangal articulation, and forms the external collateral nerve of the little toe. It supplies a great number of cutaneous nerves, also the nerves for the_^ea;or brevis digiti minimi, those for the interosseous muscles of the fourth space, and, lastly, some articular filaments. The internal branch passes forward, below the flexor tendon, foUowing the original di- rection of the superficial branch of the external plantar, and, after a rather long course, bifurcates to form the internal collateral nerve of the little toe, and the external collateral nerve of the fourth toe ; hke the external branch, it also gives off some cutaneous and ar- ticular nerves. The deep terminal branch of the external plantar passes above, i. e., deeper than the THE EXTERlPrAt PLA>rTAR NERVE. 81§ flexor accessorius, changes its direction, so as to describfe an arch, having its concavity turned inward and backward, and the convexity outward and forward, enters, together with the external plantar artery, above which it is situated, between the adductor polli cis and the interossei, and is lost in the former muscle. Before reaching the adductor pollicis it gives off some articular filaments to the meta tarsal and tarso-metatarsal articulations, and also a filament for the fourth lumbricalis. Beyond the adductor pollicis the nerve gives off the ^amcw^ /or the third lumbricalis ; this filament, which is remarkable for the length of its course, passes horizontally forward, opposite to the third interosseous space, and passes through the fibres of the transversus pedis, to reach its destination ; it then gives off the filaments for the transversus, and those for the interosseous muscles of the third, second, and first spaces. Summary of the External Plantar Nerve. — The external plantar nerve, therefore, sup plies cutaneous filaments to the outer side of the sole of the foot, to the fifth toe, of which it forms both collateral nerves, and to the fourth toe, of which it forms the external col- lateral nerve. It also gives off muscular nerves to the flexor accessorius, the flexor bre- vis, and abductor digiti minimi, to the adductor pollicis, and transversus pedis, to all the interossei, and to the two external lumbricales. Lastly, it furnishes some articular filaments. Summary of the Nerves of the Lower Extremity. — The lower extremity is supplied with nerves from the lumbar and sacral plexuses. The Lumbar Plexus. — The lumbar plexus gives almost all its branches to the lower extremity, viz., the external and internal inguinal nerves, the obturator nerve, and the crural nerve ; the lumbo-sacral cord is also distributed to the lower extremity through the medium of the sacral plexus. The external and internal inguinal nerves are the principal cutaneous nerves of the anterior and external regions of the thigh ; the obturator nerve is a muscular nerve in- tended for the obturator externus, the three adductors, and the gracilis.* The crural nerve is a musculo-cutaneous nerve which supplies the following parts : its cutaneous portion is distributed to the skin upon the anterior region of the thigh, upon the internal region of the leg, and internal dorsal region of the foot ; its muscular portion supplies all the muscles of the anterior region of the thigh ;t it also gives several articular nerves to the hip and knee joints. The Sacral Plexus. — The sacral plexus is entirely distributed to the lower extremity, excepting the internal pudic nerve and certain rectal and vesico-prostatic branches in the male, and rectal, vaginal, and uterine branches in the female. The obturator internus, the pyriformis, the gemelli, and the quadratus femoris, are each provided with a special nerve from the sacral plexus ; the glutaeus medius and min- imus, and the tensor vaginae femoris, are especially supplied by the superior gluteal nerve, and the glutaeus maximus by the inferior gluteal or lesser sciatic nerve. The last-named nerve also furnishes the cutaneous nerves of the posterior region of the thigh. The great sciatic is the nerve of the posterior region of the thigh, and of the entire leg and foot. It supplies all the muscles of the posterior region of the thigh ; thus, its external popliteal or peroneal division supplies the muscles of the external region of the leg by its musculo-cutaneous branch, and the muscles of the anterior region by its in- terosseous branch ; it also supplies the external region of the leg, and the dorsal region of the foot. Its internal popliteal or tibial division supplies all the muscles of the posterior region of the l6g, the skin upon the internal and external calcaneal regions, and that upon the external dorsal region of the foot. Of its terminal branches, the internal plantar nerve is distributed to the muscles of the internal plantar region of the foot, to the flexor .brevis digitorum, to the two internal lumbricales, and to the skin of the internal plantar region ; lastly, it gives off the col- lateral branches of the toes, excepting the two for the fifth toe, and the external collat- eral branch of the fourth. The external plantar nerve is distributed to the muscles of the external plantar region, to the flexor accessorius, to all the interossei, to the two external lumbricales, to the adductor pollicis and transversus pedis, and to the skin of the external plantar region : it also gives the internal and external collateral nerves of the fifth toe, and the external collateral nerve of the fourth. Comparison of the Nerves of the Upper and Lower Extremities. The lumbo-sacral plexus, which supplies the whole of the lower extremity, precisely corresponds to the cervico-brachial, which supplies the- upper extremity. The lumbar corresponds to the cervical, and the sacral to the brachial plexus. The connexion, or sort of fusion of the cervical with the brachial plexus, and of the lumbar with the sacral plexus, explains why it is found, on comparing the nerves of the upper and lower extrem- * [The obturator also supplies part of the pectineus, and sometimes gives cutaneous branches to the thigh ,»nd leg, and an articular filament to the knee (see note II, p. 800).] fAnd also a few filaments to the iliaciu, psoas, and pectineus.] 816 NEUROLOGY. ity, that several of the nerves arising from the brachial plexus are represented by nerves from the sacral plexus, and that several of those from the cervical plexus have their representatives in nerves derived from the lumbar plexus. It will be seen, moreover, that this analogy ought not to be carried too far, and that it is necessary, in making the comparison, to exclude all nerves which belong to peculiar organs in both regions. Thus, the phrenic, occipital, and auricular nerves, branches of the cervical plexus, have no representatives in the lower extremity, nor is there any nerve in the upper extremity corresponding to the internal pudic. On the other hand, there is no objection to admitting that the external and internal inguinal nerves in the lower extremity are represented by the clavicular nerves in the upper extremity. The crural nerve, a branch of the lumbar plexus, has no corresponding branch in those of the cervical plexus, but its muscular branches are represented by the brachial portion of the musculo-spiral nerve, and its cutaneous branches by the internal brachial cutane- ous. The crural nerve, in fact, supplies the muscles which extend the leg upon the thigh, in the same way that the musculo-spiral nerve supplies the muscles which ex- tend the forearm upon the arm ; the internal saphenous nerve supplies the skin of the leg, just as the internal brachial cutaneous is distributed to the skin of the forearm. The obturator nerve, which supplies the adductors of the thigh, is represented by the thoracic nerves and the nerve for the latissimus dorsi, which supply the pectoralis ma» jor and latissimus dorsi, the adductor muscles of the arm. The gluteal nerves are analogous to the supra-scapular and circumflex nerves. The superior gluteal, which is distributed to the glutaeus medius and minimus, corresponds to the supra-scapular, which belongs to the supra- and infra-spinatus ; and the inferior gluteal or lesser sciatic nerve, which supplies the glutaeus raaximus and the skin of the thigh, corresponds to the circumflex nerve, which is distributed to the deltoid, and the skin of the arm. The trunk of the great sciatic nerve represents by itself the musculo-cutaneous, the ulnar, and the median nerves, and the musculo-spiral in the forearm. The muscles of the anterior region of the arm, that is to say, the muscles that flex the forearm upon the arm, receive their branches from the musculo-cutaneous nerve, just as the muscles of the posterior region of the thigh, or the flexors of the leg upon the thigh,, receive theirs from the great sciatic. The external popliteal nerve represents the musculo-spiral in the forearm : the former, supplies the muscles of the anterior and external regions of the leg, while the latter is distributed to the muscles of the posterior and external regions of the forearm ; the for- mer gives off the dorsal cutaneous nerves of the foot, and the latter furnishes the dorsal cutaneous nerves of the hand. The internal popliteal nerve represents the median and ulnar nerves together. The muscles of the posterior region of the leg are supplied by the internal popliteal, as the muscles of the anterior region of the forearm are supplied by the median and the ulnar. The internal popliteal nerve completes the series of dorsal cutaneous nerves of the> foot, just as the ulnar nerve completes the dorsal nerves of the hand. Lastly, the internal plantar nerve gives off all the plantar collateral nerves of the toes,; excepting those for the little toe, and the external plantar collateral of the fourth toe ; it therefore represents the palmar portion of the median nerve ; and so the external plan- tar represents the palmar portion of the ulnar nerve, and completes the series of plantar collateral nerves. .; THE CRANIAL NERVES. Definition and Classifi/:ation. — The Central Extremities of the Cranial Nerves — viz., of. the Olfactory — of the Optic — of the Common Motor Oculi — of the Pathetic — of the Tn-^ geminal — of the External Motor Oculi — of the Portio Dura and Portio Mollis of the Sev- enth — of the Glosso-pharyngeal, Pneumo-gastric, and Spinal Accessory Divisions of the Eighth — and of the Ninth Nerves. The cranial nerves are those which pass through the foramina in the base of the cra- nium, not those which arise from the brain, as the rather generally adopted terms cere- bral nerves and encephalic nerves would seem to indicate. We shall follow Willis and the majority of anatomists in admitting nine pairs of cra- nial nerves, which are almost indifferently named, either numerically, from the order of their origin, counting from before backward, or they are named from their distribution and uses. The following exhibits their nomenclature upon both principles : First pair, or olfactory nerves. Second pair, or optic nerves. Third pair, or common motor nerves of the eyes. Fourth pair, or pathetic nerves, nervi trochleares. Fifth pair, or trifacial nerves, nervi trigemini CENTRAL EXTREMITY OP THE OLFACTORY NERVE. 817 Sixth pair, or external motor nerves of the eyes, nervi abducentes. c. »u • J -J J • * ( portio mollis, or auditory nerve, Seventh pair, divided mto { ^^-^ ^^^^^ ^^ f^^i^, ^^^^ I pneumogastric nerve, or par vagum. Eighth pair, divided into < glosso-pharyngeal nerve, ( spinal accessory nerve of Willis. Ninth pair, or hypoglossal nerve. Scemmering has introduced the following modification of this nomenclature. He has divided the seventh pair into two, viz., the facial nerves, which form his seventh pair, and the auditory nerves, which he calls the eighth ; and then he has divided the eighth pair into three others, namely, a ninth pair formed by the glosso-pharyngeal nerves, a tenth formed by the pneumogastric nerves, an eleventh by the spinal accessory nerves ; the hypoglossal nerves, therefore, constitute his twelfth pair. This modification is founded on the separation of nerves so completely distinct as the fiicial and the auditory, which have only been described together because they enter the same canal in the base of the cranium, namely, the internal auditory meatus. Still, this modification is a useless one, and it has the greater inconvenience of render- ing the language employed obscure, from giving a double acceptation to the same terms. It would be more philosophical to name and describe the cranial nerves from behind forward, so that the hypoglossal nerves would constitute the first pair, and the olfactory the last. The indisputable analogy which exists between the posterior cranial and the spinal nerves, and, moreover, the example of J. F. Meckel, would fully warrant this innovation Nevertheless, I think it right to retain the old usage, and to proceed from before back- ward, in the enumeration as well as in the description of the nerves. As the origins or central extremities of all the cranial nerves and their course within the cranium can be studied upon the same brain, I have thought it right to describe, in one article, all these origins or central extremities, which will mutually illustrate each other by their differences and their anadogies ; the experience of the dissecting-room proves, moreover, that, from want of a sufficient number of brains to study the origin of each nerve in particular, this part of anatomy is generally neglected. The Central Extremities of the Cranial Nerves. Dissection. — Two preparations are required, namely, a brain removed from the crani- um, together with the origins of the nerves perfectly preserved ; and the base of a crani- um, together with those parts of the brain which are near the origin of the nerves. The first will serve for the examination of the central extremities of the nerves ; and the sec- ond for tracing their course within the cranium. While the origin of all the spinal nerves is uniform and regular, that of the cranial nerves appears to be subject to no rule ; so that the cranial nerves diflfer as much from each other in regard to their origin as they differ collectively from the spinal nerves in the same particular. We shall see presently, however, that the origins of all but the special nerves of the head may, to a certain extent, be referred to the same law of double roots (one of which is ganglionic) which presides over the origin of the spinal nerves. The Central Extremity of the Olfactory JVerve. The olfactory nerves, or the first pair of cranial nerves (nerfs ethmoidaux, Chauss., 1, fig. 276) are two bands, composed of white and gray substance, which arise from the hindermost convolution of the anterior lobe of the brain, run forward in the anfractuosity already described as the anfractuosity of the olfactory nerves, and expand in the ethmoidal groove into a sort of ganglion or bulb, from which filaments are given off to be distribu- ted to the pituitary membrane. In regard to their central extremity and their course within the cavity of the cranium, the olfactory nerves are singular, and their peculiarities justify the uncertainty which has for a long time prevailed, and still prevails, concerning their true character. The old anatomists did not regard them as nerves, but as prolongations of the brain, named by them caruncula: or processus maxillares, and believed to be intended to drain off the mucosity of that organ : it was Massa, according to Sprengel, and Zerbi, according to Haller, who first connected them with the other cranial nerves as the first pair. Com- parative anatomy, which probably suggested to the older anatomists the opinion which, they held concerning these nerves, has now caused some doubts as to the propriety of considering them as nerves, and has given rise to the opinion that they are the repre- sentatives of the olfactory lobes of the lower animals.* Without entering here into dis? cussions which belong to philosophical anatomy, let us examine the most remarkable- circumstances connected with the origin and cranial course of this nerve. Apparent Origin. — The olfactory nerves arise from the cerebrum, and this is a char- * When speaking of the comparative anatomy of the brain, it was mentioned that in a great number of anK mals there existed, in front of the cerebral lobes or hemispheres, a pair of lobes (olfactory lobes), which were- ^.ontinuous with the nerves distributed to the pituitary membrane, and the development of which oorresponde
  • rfhead. S30 NECROLOGY. with the filaments of the facial nerve, which accompany the angular vein ; ani frontal twigs, which anastomose with those of the internal frontal nerve.* The Internal Nasal or Ethmoidal Nerve (u, fig. 296). — The course of this nerve is very remarkable. It enters the anterior internal orbital canal, which conducts it into the eth- moidal groove, on the internal surface of the basis cranii ;t it is then reflected forward upon the side of llie crista gaili, passes through the ethmoidal fissure into the corre- sponding nasal fossa, becomes sensibly increased in size, and divides into two filaments, in internal, or nerve for the septum, and an external, or naso-lobar nerve. The internal filament, or anterior nerve of the teptum nasi {a, fig. 297), enters the fibro- mucous membrane upon the anterior part of the septum, and divides into several very slender filaments, which may be traced below the middle of the septum. The external filament, or nerve of the external wall of the nasal fossa (u, fig. 299), runs along the anterior border of the septum, and divides into two terminal filaments, one of which passes upon the fore part of the external wall of the nasal fossa, and ramifies upon the turbinated bones ; while the other and larger filament (e, naso-lobaire, Chauss.) fol- lows the original course of the nerve, and passes behind the nasal bone, which is mark- ed with a groove, and frequently even by a canal for the reception of the nerve ; from this latter filament several twigs proceed, which perforate the nasal bone more or less obliquely, and are distributed to the skin of the nose ; having reached the lower border of the nasal bone, it passes forward, increasing in size, through the fibrous tissue which unites the bone to the lateral cartilage of the nose, and then ramifies in the skin cover- ing the ala and lobe of the nose, where I have seen it anastomose with the facial nerve. While within the cavity of the cranium, the internal nasal nerve lies beneath the dura mater, and is perfectly distinct from the olfactory nerve, with which it never anastomoses. The Ophthalmic Ganglion and its Branchcs.X Dissection. — The ophthalmic ganglion may be exposed in several ways : for example, ♦jither in dissecting the branch given by the common motor nerve to the inferior oblique anuscle, or directly by removing the adipose tissue between the external rectus and the »ptic nerve. The long branch from the nasal nerve to the ophthalmic ganglion and the ;iliary nerves can also be exposed with the greatest ease. The ophthalmic or ciliary ganglion (behind i,fig. 298) is a small, grayish, and flattened enlargement, of a lenticular form (the lenticular ganglion), applied to the outer side of the optic nerve, and situated about two or three lines from the optic foramen, in the midst of a great quantity of adipose tissue, which renders its dissection difficult. It varies much in size, and sometimes consists of a simple miliary enlargement, which forms a point of origin and termination for a certain number of nerves. For the convenience of description, this ganglion is said to have four angles, two posterior and two anterior ; by its posterior and superior angle it receives a long slender branch {its long root), given off from the nasal nerve while still contained within the cavernous sinus. Not unfre- quently a second long, but extremely slender root, is furnished by the nasal nerve to the ophthalmic ganglion. By its posterior and inferior angle it receives a short, thick branch, which comes from the inferior division of the common motor nerve {its short root). From its two anterior angles it gives off two small bundles of nerves, named the ciliary nervet {i, fig. 298 ; x, fig. 301). Lastly, the ophthalmic ganglion has a ganglionic or soft root, or, rather, a communicating filament, between this ganglion and the superior cervical gan- glion of the sympathetic ; this soft root arises frohi the cavernous plexus, and passes .■sometimes to the long or nasal root of the ophthalmic ganglion, and sometimes to the ophthalmic ganglion itself The ciliary nerves are remarkable for their tortuous course, in which respect they re- semble the ciliary arteries ; and also for being collected into two bundles, the one supe- rior, which is generally composed of four filaments, and the other inferior, composed of five or six. The ciliary nerves do not anastomose before they reach the globe of the eye, with the exception, however, of the ciliary nerve, which is derived directly from the nasal nerve, and which anastomoses with an inferior ciliary nerve from the ophthal- mic ganglion. Having reached the sclerotic, the ciliary nerves perforate the coat more or less obliquely, around the entrance of the optic nerve, excepting two or three, which enter the globe of the eye near the attachment of the muscle ; after having perforated the sclerotic, they become flattened or riband-shaped, and run forward {a, fig. 242) par- allel to each other, between the sclerotic and the choroid coats, slightly adhering to the former of these membranes, on which grooves exist for their reception ; on approaching the ciliary circle or ligament (h), they bifurcate, and divide into filaments, which anasto- mose with the neighbouring filaments, and appear to be lost in the ciliary circle, which * [It also supplies branches to the lachrymal sac and caruncula, and to the parts of tha inner canthns.] t Not unfrequently the internal nasal nerve, while within the ethmoidal groove, gives off a recurrent net* vous twig, which enters the orbit by a small canal, in front of the anterior internal orbital canal, and anasto- moses with the external nasal or infra-trochlear nerve. I have seen this small nerve anastomose with the tronto-nasal branch, which I have already described (note, p. 828) as an unusual branch of the frontal nerve. t The connexions of the ophthalmic ganglion with the nasal nerve, as well as with the common motor nerve, have induced me to describe it here. SUPERIOR MAXILLARY DIVISION OP THE FIFTH NERVE. 831 has been, and not without some reason, considered by modern anatomists as a nervous ganglion, ganglion annulare (annulus gangliformis seu ganglion annulare, Sammering). I have seen some of these ciliary nerves pass through the ciliary circle and enter the iris ; they are not distinctly seen to enter the ciliary processes.* The Superior Maxillary Division of the Fifth Merve. Dissection. — Saw through the zygomatic arch, turn down the masseteric muscle, and remove the roof of the orbit ; first dissect the lachrymal, malar, and temporal twigs of the orbital branch of the nerve ; then clean out the orbital cavity, remove the upper wall of the zygomatic fossa to reach the spheno-maxillary fossa by means of two cuts joined at an acute angle in the foramen rotundum. Detach the origins of the pterygoid mus- cles ; lastly, trace the nerve into the infra-orbital canal and on the face. The superior maxillary nerve Q),figs. 298, 300, 301), the second or middle division of the fifth nerve, both in position and size, runs forward to enter, after a very short course, the foramen rotundum, by which it is conducted into the spheno-maxillary fossa ; from thence it passes into and traverses the whole length of the infra-orbital canal, where it is named the infra-orbital nerve (/) ; having reached the fore part of that canal, it bends downward, and ramifies in the cheek. It is plexiform at its origin and in the foramen rotundum, but is fasciculated throughout the rest of its course. Its collateral branches, taken in the order of their origin, are the orbital nerve ; certain nerves which are given off from the enlargement called Meckel's ganglion, namely, the palatine, spheno-palatine, and vidian or pterygoid nerves ; the posterior dental nerves, and the anterior dental nerve ; lastly, several small filaments come off either from the ganglion of Meckel or from the superior maxillary nerve itself, and, surrounding the in- ternal maxillary artery, assist in the formation of its plexus. The Orbital Nerve. This branch [t, jig. 300) comes off immediately in front of the foramen rotundum, from the upper side of the superior maxillary nerve, passes through the spheno-maxillary fis- sure, along which it proceeds to enter the orbit ; it then runs along the floor of tl>e orbit, and divides into two branches : the one ascending, the lachrymal branch of the orbital nerve, which enters the lower surface of the lachrymal gland, anastomoses with the lachrymal branch (s) of the ophthalmic nerve (a), and sends off some branches to the upper eyelid, near its external angle ; the other branch is the temporo-malar, which pass- es horizontally forward, enters a small canal in the malar bone, and subdivides into a malar filament, which perforates the bone, and is distributed to the skin upon the malar region,! and a temporal filament, which perforates the orbital portion of the malar bone, and dips into the anterior part of the temporal muscle, in which it anastomoses with the anterior deep temporal nerve, a branch of the inferior maxillary. I have sometimes seen two temporal filaments pass through the malar bone at two different points.^ The Spheno-palatine Ganglion and its Branches. After having given off the orbital nerve, and while it is still contained in the spheno- maxillary fossa, the superior maxillary nerve gives off from its lower side a thick branch, frequently two, and occasionally several branches, from which a great number of diver- ging nerves immediately proceed ; these are the three palatine nerves, the spheno-pala- tine nerves, and the vidian nerve ; at the point where these nerves diverge is found an enlargement which the elder Meckel,^ whose name is connected with the description of the fifth pair, regarded as a ganghon, and which is, therefore, called Meckel's ganglion, or the spheno-folatine ganglion (situated before s,fig. 299 ; below b,fig. 301). In a certain number of cases, I have sought in vain for the ganglionic structure in this enlargement, i. e., for gray matter with white filaments scattered through it. It appear- ed then to be nothing more than the common trunk or starting-point of a great number of nerves ; in the majority of cases, however, a quantity of gray matter certainly exists, but is so arranged that the nerves may generally be traced quite through the enlarge- ment, so that they clearly are not given off from the ganglion itself, but come directly from the superior maxillary nerve. II * Tiedemann, from the results of observations in comparative anatomy, believes that the arteries vv'hich ram- ify in the retina are accompanied by very delicate nervous filaments, derived from the ophthalmic ganglion and the ciliary nerves : he has seen a nervous filament penetrate the optic nerve with the arteria centralis retinje ; and he states that the ciliary arteries are accompanied by very delicate nervous filaments, which he has tra- ced into the retina as far as the zone of Zinn. Tiedemann also says that he has seen, only once, it is true, a rather large nervous filament proceed from Meckel's ganglion, and join the thick and short branch which is pveu oflFfrom the third pair to assist in the formation of the ophthalmic ganglion. t It is said that this twig anastomoses with the facial nerve in the malar region ; I have never been fortu- nate enough to discover this anastomosis. X [Both of these temporal filaments maybe joined by communicating twigs from the lachrymal nerve withia the orbit ; one of them anastomoses with the anterior deep temporal nerve, as above mentioned ; the other, having entered the temporal fossa through the malar bone, ascends on the temporal surface of that bone, turns outward, perforates the temporal fascia about an inch above the zygoma, anastomoses with filaments of the facial nerve, and of the auriculo-temporal branch of the inferior maxillary nerve, and is lost in the skin on the temple.] t) Mem. de I'Acad. de Berlin, 1749 II In one case the ganglion of Meckel was in contact with the internal surface of the superior maxillary nerve In the same case a filament proceeded from the upper part of the ganglion, and joined the branch .flB NEUROLOGY. I shall now describe, in succession, the branches which proceed from Meckel's ganglion. The Palatine Nerves. These nBrves {gg,fig- 299; g,Jig. 301) are three in number: an anterior palatine, which is the largest, a posterior palatine [the middle of some authors], which is the next in size, and an intermediate nerve [the posterior of some authors], which is the smallest ; these nerves are continuous with Meckel's ganghon ; it is most evident that, in the greater number of cases, they arise directly from the lower part of the superior maxil- lary nerve. The anterior or great palatine nerve immediately enters the posterior palatine canal, through the whole length of which it passes, and, having reached the lower orifice of that canal, is reflected forward, and terminates by bifurcating on the hard palate. During its course, it gives off an inferior nasal branch (lower f, Jig. 299), which is dis- Fig. 299. tributed over the middle meatus and the middle and inferior turbinated bones : the twig for the inferior turbinated bone may be traced to the fore part of that bone ; it also gives off the anterior palatine, and several small twigs, which perfo- rate the inner wall of the maxillary sinus, and are distributed to the last molar teeth ; lastly, at its exit from the posterior palatine canal, and even sometimes while yet within that canal, it sends off a staphyline branch, which spreads into several filaments, all of which run backward in the soft pal- ate, and divide into superior filaments distributed to the mu cous membrane on the nasal surface ; and inferior, which run beneath the mucous mem- brane on the buccal surface of the soft palate. Of the two terminal branches of the an- terior palatine nerve, both of which occupy the hard palate, the external runs near the alveolar border, and the internal near the median line ; they enter into the midst of the glandular layer of the palate, and are ultimately distributed to the glands, to the mucous membrane of the hard palate, and to the gums. The posterior [middle] palatine nerve, the next in size, enters a special canal : on es- caping from which it passes backward, beneath the mucous membrane of the nasal sur- face of the soft palate, to which it is distributed. The same is the case with the intermediate [posterior] or small palatine nerve, which is extremely slender. I have seen a palatine nerve enter the maxillary sinus, run beneath its lining mem- brane, pass vertically through the maxillary tuberosity behind the last molar tooth, and ramify upon the hard palate. The Spheno-palatine or Posterior Nasal Nerves. Dissection. — ^Make a vertical section of a head, previously macerated in dilute nitric acid, strip off the pituitary membrane lying upon the septum and the turbinated bones, and examine the nerves from the internal or deep surface of that membrane. The spheno-palatine nerves are very slender ; they enter the corresponding nasal fossae through the spheno-palatine foramen, and have been traced by Scarpa with his customary exactness. They are all situated in the pituitary membrane, or, rather, be- tween the periosteum and the mucous membrane, and cannot be readily seen until this fibro-mucous membrane has been removed from the bones which it covers ; the nervous filaments are then seen through the semi-transparent fibrous layer. For this purpose, preparations macerated in diluted nitric acid are indispensable. The spheno-palatine nerves are distributed to the septum nasi and the external wall of the corresponding na- sal fossa ; they are divided into internal and external. There is only one internal spheno-palatine nerve, viz., the nerve of the septum nasi, or ine naso-palatine of Scarpa {b,fig. 297) ; it passes inward, in front of the sphenoidal si- nus, and below the orifice of that sinus, to gain the septum nasi ; it is then directed at first almost vertically downward, but afterward almost horizontally forward, as far as the superior orifice of the anterior palatine canal, which it enters, and then passes into a special canal, quite distinct from the anterior palatine canal, and parallel to the one for the naso-palatine nerve of the opposite side. According to M. Hippolyte Cloquet, the two naso-palatine nerves terminate in the upper part of a ganglion, which he calls the naso-palatine, and do not reach the mouth ; but in some researches which I have made on the subject, I have failed in detecting this ganglion. t The nerves can be distinctly seen to enter the mucous membrane of the hard palate behind the incisor teeth, and upon that prominence of the mucous membrane against which the point of the tongue is so often applied. I have never seen any anastomoses either between the two naso-palatine nerves, or between these and the anterior palatine nerves. given by the external motor nerve to the sympathetic. I have not been able to discover the filaments which are said to establish a communication between Meckel's ganglion and the optic nerve. t I find that it is stated by Arnold, whom I have so often quoted, because his works are above all praise fijr their rigorous accuracy, that the spheno-palatine ganglion docs not exist ; and he observes, with reason, that the subjoined description of M. Hippolyte Cloquet is very imperfect. " It consists of a small , reddish, fungous mass, rather hard, as if fibro-cartilaginous, and surrounded by adipose cellular tissue " THE PTERYGOID NERVE, ETC. 833 Anatomists are not agreed as to whether the naso-palatine nerve gives off any fila- ments upon the septum. I have failed in detecting any ramification of the nerve in a great number of preparations, in which tlie pituitary membrane had been rendered trans- parent by long maceration in diluted nitric acid. Rather frequently a filament was given off from the upper part of the nerve, and then joined it again. Three times only did I observe a twig running upward from the anterior part of the nerve. The external spheno-palatine, or superior nasal nerves (upper /, fig. 299), so called to distinguish them from thfe inferior nasal branch of the anterior palatine nerve, are three or four in number ; they are directed vertically along the back part of the outer wall of the corresponding nasal fossa, and spread out into filaments, which extend over the tur- binated bones and the meatus ; these filaments can only be seen from the deep surface of the pituitary membrane.* I have never been able to find the anastomoses between the internal and external spheno-palatine nerves and the divisions of the olfactory nerve, which are admitted by some anatomists. The Vidian or Pterygoid Nerve. The vidian nerve {v,figs. 300, 301) arises from the back part of Meckel's ganglion, and enters the vidian or pterygoid canal, after emerging from which it perforates the carti- laginous plate of the foramen lacerum anticus, and divides into a superior cranial branch, the great superficial petrosal nerve, and an inferior, deep, or carotid branch. The subdivis- ion of the pterygoid nerve often occurs at its origin from Meckel's ganglion. The inferior or carotid branch, which is much larger than the superior, forms the con- tinuation of the nerve : it enters the carotid canal, and is applied to the outer side of the carotid artery, where it anastomoses with the nerves which establish a communica- tion between the superior cervical ganglion and the external motor nerve of the eye, and assists in the formation of the carotid plexus ; a flattened gangliform enlargement is seen at the point of anastomosis. I have sometimes seen two carotid branches, one of which was very small. The superior or cranial branch, the great superficial petrosal nerve, enters the cranium between the temporal and sphenoid bones, runs backward and outward {v, fig. 296) be- neath the dura mater, in a groove on the upper surface of the petrous portion of the temporal bone, passes through the hiatus Fallopii into the aqueductus Fallopii or canal for the facial nerve (part of 7), and anastomoses with that nerve. t I say that it anasto- moses, because there is a sort of fusion of the two nerves, and not a simple juxtaposi- tion. The branch called the chorda tympani, which comes off from the facial nerve at some distance from the point of fusion, should not be regarded as a prolongation of the superficial petrosal nerve, supposed in that case to be merely applied to the facial nerve.t The Posterior Dental Nerves. Dissection. — These nerves can be readily seen without any dissection through the bone, when this is rendered transparent by nitric acid. They must be examined both from the external surface of the bone, and from the interior of the sinus. The posterior dental or alveolo-dental nerves (e,figs. 298, 300, 301) are two in number, a superior and an inferior ; sometimes there are three ; they arise from the superior maxillary nerve, sometimes by a common trunk, sometimes separately, just as that nerve is about to enter the infra-orbital canal : they run forward and downward, at first in contact with the maxillary tuberosity, and give off some filaments to the buccinator muscle, and to the gums, and some which are distinctly distributed to the mass of fat in the cheek ; they then enter certain canals in the substance of the maxillary tuberosity, and become flattened or riband-shaped. The posterior and superior dental nerve passes from behind forward, through the base * Bock, and Arnold after him, have described, under the name of the pharyngeal branch, a rather large branch, which may be regarded as belonging to the external spheno-palatine nerves ; it enters into the ptery- go-palatine canal, formed between the under surface of the sphenoid and the sphenoidal process of the palate bone, passes backward and inward, and divides into several filaments, which are distributed to the upper part of the pharynx. [Some of these superior nasal branches are said to supply the lining membrane of the pQS<.e- rior ethmoidal and the sphenoidal sinuses.] t I have seen the superior branch of the vidian formed by three very distinct filaments: anatomists are still undecided as to whether the inferior or carotid branch is derived from the ganglion of Meckel, or from tlie su perior cervical ganglion. According to Arnold, it resembles the organic system of nerves in its colour, soft- ness, and structure. I cannot coincide in this opinion, for it appears to me that the cranial and carotid branch, es of the vidian are analogous in every respect. t Arnold, who regards this opinion of Hippolyte Cloquet, which is adopted by Hirsel, as erroneous, states that, at the junction of the cranial branch of the vidian with the facial nerve, there is a gangliform swelling, in which he finds some analogy to the inter- vertebral ganglia, and which he considers to be a transition be- tween a gangliform stalk and a true ganglion. According to Arnold, the superficial or cranial branch, and the deep or carotid branch of the vidian, do not come from a common trunk, but are merely juxtaposed, and are distinct throughout their entire extent. The carotid branch is soft and reddish, presents all the characteristics of the ganglionic nerves, and is intended to establish a communication between the superior cervical and the spheno-palatine ganglion. The cranial or sui perficial petrosal branch, on the contrary, presents all the characters of the cerebro-spinal nerves ; it i«of t white colour and firm consistence. 5N 834 NEUROLOGY. of the malar eminence of the superior maxillary bone, and anastomoses on a level with the canine fossa with a filament from the anterior dental nerve. The posterior and, inferior dental nerve, which is larger than the preceding, runs in a curved direction below the malar eminence, the concavity of the curve being directed upward, and anastomoses with the posterior and superior dental nerve, on a level with the canine fossa. No filament is given off from the upper side of these nerves, but they give off a great number of filaments downward, which anastomose, and form a series of very remarkable meshes or areolae ; these meshes, and the 'dental nerve which come from them, are situated within the substance of the bone, but are much nearer to the sinus than to the outer surface of the bone. It is from these meshes that the extremely delicate filaments arise which form the dental nerves of the molars and bicuspids ; their number corresponds to that of the fangs of these teeth.* Some filaments evidently terminate in the substance of the superior maxillary bone ; no other bone in the body has so large a number of proper filaments. The Anterior Dental Nerve. The anterior dental or alveolo-dental nerve {j,fig. 298) is the only branch given off by the superior maxillary nerve while within the infra-orbital canal ;t it arises about five or six lines from the anterior orifice of that passage. It is so large that it may be regarded as resulting from the bifurcation of the infra-orbital nerve. It soon enters a special ca- nal formed for it in the superior maxillary bone, gives off on the outer side a small branch which anastomoses with the posterior and superior dental nerve, passes at first horizontally inward, and then vertically downward, turning round the margin of the an- terior opening of the corresponding nasal fossa, and is reflected upon the floor of that fossa ; during the whole of this course, it is situated within the substance of the superior maxillary bone ; its horizontal portion is superficial, and its vertical portion is deep- seated, having merely a thin bony lamella between it and the pituitary membrane. Having arrived on a level with the floor of the nasal fossa, about two lines from its an- terior opening, it expands into a great number of ascending and descending filaments ; the aseending filaments are reflected upward within the anterior nasal spine, where they ter- minate. They appear to me to send off a small ramification to the pituitary membrane. The descending filaments terminate by supplying the dental nerves for the incisor, canine, and first bicuspid teeth. A great number of filaments are also lost in the substance of the bone. I have never seen any filaments from the dental nerves entering the membrane of the maxillary sinus. The Terminal Branches of the Superior Maxillary Nerve. Having reached the anterior orifice of the infra-orbital canal, the superior maxillary nerve, the component bundles of which had been merely in juxtaposition, immediately expands {i,fig. 301) into a pencil of diverging filaments beneath the levator labii supe- rioris. These filaments {i,fig- 285) may be divided into ascending or palpebral, which pass upward and outward beneath the orbicularis palpebrarum, and are distributed to the skin and conjunctiva of the lower eyelid ; a great number of internal or nasal filaments, which run upon the side of the nose, and are distributed to the skin of that organ ; one of them runs along beneath the septum ; and, lastly, into descending or labial filaments, which are the most numerous, and which enter the substance of the upper lip, and are distributed to the skin and the mucous membrane : all these filaments, and especially the labial, interlace and anastomose with the facial nerve, so as to form a plexus, named the infra-orbital, to which we shall return in describing the facial nerve. I have seen the nasal and the palpebral filaments arise together from the superior max- illary nerve, before it had given off the anterior dental, enter a special canal situated on the inner side of the infra-orbital canal, emerge opposite the line of demarcation between the cheek and the nose, and then expand into their nasal and palpebral divisions ; while the labial filaments had their usual arrangement. The Inferior Maxillary Division of the Fifth J^erve. Dissection. — As this nerve must be examined both upon its internal and its external aspect, it must be dissected in both directions. An antero-posterior section of the head in the median line will enable us to see, on the internal surface of the nerve, the chorda tympani, the otic ganglion, and the origins of all the other branches which come from the inner side of the inferior maxillary nerve, viz., the nerve of the internal pterygoid, the lingual nerve, and the dental nerve. In order to see the distribution of the deep temporal, the masseteric, the buccal, the internal pterygoid, and the auriculo-temporal nerves, the inferior maxillary nerve must be exposed from its outer side, by breaking down the zygomatic arch, reflecting down the masseter, which is to be detached as far * In those molar teeth which have two or three roots, the nervous filaments snbdiii'ide and anastomose with each other in the substance of the dental pulp. t Sometimes, however, I have seen the posterior and superior dental nerve arise within the infra-orbital 'lanal. THE DEEP TEMPORAL NERVE, ETC. 835 back as the sigmoid notch, by sawing through the base of the coronoid process, and turning the temporal muscle upward, and then by carefully dividing the external ptery- goid muscle, through which the buccal nerve passes. The inferior maxillary nerve (c, figs. 296, &c.), the most posterior and the largest di- vision of the fifth nerve, passes outward and a little forward, and, after a very short course within the cranium, escapes through the foramen ovale into the zygomatic fossa, where it divides successively into seven branches. The non-ganglionic root (i, fig. 299) of the fifth nerve is connected exclusively with the inferior maxUlary division (c) of its other root, beneath which it lies, from which it can be distinguished by not having a plexiform structure, with which it is not blended until it emerges from the foramen ovale. Of the seven branches of the inferior maxillary nerve, three are external, namely, the an- terior and posterior deep temporal, the masseteric, and the buccal ; one is posterior, name- ly, the auriculo-temporal ; one is internal, the internal pterygoid ; and two are inferior, the lingual or gustatory, and the inferior dental. These nerves may also be divided into col- lateral branches, including the first five, and the terminal branches, namely, the lingual and the inferior dental ; the otic ganglion, described by Arnold, is connected vidth this nerve.* The Collateral Branches of the Inferior Maxillary Nerve. The Deep Temporal Nerve. The first external branch, or the deep temporal -nerve, arises from the outer side of the inferior maxillary nerve, passes horizontally outward and forward between the roof of the zygomatic fossa, with which it is in contact, and the eternal pterygoid muscle. Having arrived at the ridge which separates the temporal from the zygomatic fossa, it anasto- moses with several temporal branches derived from the buccal and masseteric nerves, and forms a sort of plexus with them. The branches which emerge from this plexus ascend vertically in the deep layers of the temporal muscle, in which most of them ter- minate. Some twigs anastomose with the temporal filaments derived from the lachrymal branch of the ophthalmic nerve, and from the orbital branch of the superior maxillary nerve. t One and sometimes two filaments perforate the temporal fascia, about a finger's breadth above the zygomatic arch, and then ascend beneath the skin, to anastomose with the auriculo-temporal and the facial nerves.t The Masseteric Nerve. The second external branch, or the masseteric nerve, arises from the same point as the last nerve, and greatly exceeds it in size ; it comes off at an acute angle, passes horizon- tally backward and outward in contact with the roof of the zygomatic fossa, between it and the external pterygoid muscle ; it is then reflected downward over the upper part of that muscle to gain the sigmoid notch of the lower jaw, upon which it is again reflected, and then descends vertically, between the rcimus of the jaw and the masseter, or, rather, in the substance of the deep layers of that muscle, down to the insertion of which it may be traced. During its course along the upper wall of the zygomatic fossa, the masse- teric nerve gives off a small, deep temporal branch, which runs along the periosteum, passes into the temporal fossa, and sends off an articular branch to the temporo-max- illary articulation. The Buccal or Bucco-lahial Nerve. The third external branch {g, fig. 300), the buccal, or, rather, the bucco-lahial nerve (Chauss.), is very remarkable on account of its size and the extent of its distribution, which gives it some resemblance to the corresponding portion of the facial nerve. It arises from the outer side of the inferior maxillary nerve, by one, two, and sometimes three roots, which perforate the external pterygoid, and join together as they emerge from that muscle ; from thence it runs downward between the coronoid process of the lower jaw and the tuberosity of the upper jaw, gives several twigs to the external pterygoid muscle, and also some branches to the temporal muscle, of which one ascends and an- astomoses with the deep temporal nerve, whUe another descends and is distributed to the same muscle, near its insertion into the coronoid process ; the buccal nerve itself sometimes perforates the lowest part of the insertion of the temporal muscle, and having reached the back part of the buccinator, it expands into a great number of diverging branches, like the facial nerve. The ascending branches are distributed to the skin of the malar and buccal regions j one of them forms an anastomic arch with the facial nerve behind the duct of Steno. This anastomosis is very remarkable. The middle branches pass horizontally forward on a level with the commissure of the lips, and terminate in the skin ; several of them form a sort of plexus around the inferior coronary artery of the lip. The lowest of the descending branches pass vertically downward, and even a little backward, upon the outer surface of the buccinator, also beneath the deep surface and upon the outei" surface of * We sometimes find a communicating filament between the superior and inferior maxillary nerves imme- diately before they enter their respective foramina. + [There is hence a communication between the branches of the three divisions of the fifth nerve.] i [This cutaneous filament is one of the temporal filaments of the orbital branch of the superior maxillary Qerve. — lEllis's VemonstraUons ; see note, p. 8.31.)] «36 NEUROLOGY. the triangularis oris, and are entirely lost either in the skin or in the mucous membrane It is doubtful whether the buccal nerve partially terminates in the orbicularis oris, the triangularis oris, and the zygomaticus major. AH the filaments which enter these mus- cles, and which appear at first sight to terminate in their substance, pass through them to supply the mucous membrane ; their branches anastomose with the mental nerve be- neath the triangularis oris ; several filaments are lost in the buccinator. The Internal Pterygoid Nerve. The internal collateral branch (<, fig- 299), or nerve for the internal pterygoid muscle, which is very slender, comes off from the inner side of the inferior maxillary nerve in contact with a grayish body, named the otic ganglion, runs downward and inward along the inner surface of the internal pterygoid muscle, and ramifies in it. The Auricula-temporal Nerve. The posterior collateral branch, or the auricula-temporal nerve (the auricular or superfi- cial temporal nerve of authors), is very large, flattened, and plexiform at its origin (be- hind c, fig. 298 ; r, fig. 299) ; it sometimes arises by a great number of distinct roots ; it passes backward and a little downward behind the neck of the condyle of the lower jaw, and divides into two branches, a superior or ascending, and an inferior or descending branch. The superior or ascending branch, the superficial temporal nerve, turns round the back of the neck of the condyle, and ascends vertically between the articulation and the ex- ternal auditory meatus ; having become sub-cutaneous, it divides into several filaments (r, fig 285), which may be traced up to the highest part of the temporal fassa. During its course this nerve gives off a very remarkable anastomotic branch, which arises behind the neck of the condyle, and is reflected upon it so as to run forward be- neath the facial nerve, with which it is blended opposite to the posterior border of the masseter. This anastomotic branch is sometimes double. It may be regarded as one of the origins of the facial nerve, which increases considerably in size after having re- ceived it. This branch is one of the principal communications between the facial nerve and the fifth nerve, and modern physiologists have justly attached great importance to it. The ascending branch also gives off some plexiform branches to the temporo-max- illary articulation, and several filaments to the auditory meatus and the auricle. In the temporal region it anastomoses with a very small filament, which is derived from the deep temporal nerve, and which perforates the temporal fascia.* It accompanies the temporal artery, for which it forms a sort of plexus, and then di- vides into cutaneous filaments, which reach the crown of the head. The inferior, descending, or auricular branch is as large as the preceding ; it forms a plexus around the internal maxillary artery, behind the condyle, and sometimes presents small ganglia ; it divides into several branches, some of which pass through the parotid gland and are distributed to the lobe of the ear, while the others anastomose with some filaments of the auricularis magnus nerve derived from the cervical plexus. One of these branches joins the dental nerve, before that nerve enters the dental canal ; an- other branch terminates in the temporo- maxillary articulation. The Terminal Branches of the Inferior Maxillary Nerve. The Lingual Nerve. The lingual or gustatory nerve {n,figs. 298, 300; n n',fig. 301) passes downward and Fig. 300. forward : it is at first situated between the exter- nal pterygoid muscle and the pharynx, but it soon passes between the two pterygoids {fig. 300), then between the internal pterygoid and the ramus of the lower jaw {fig. 298), and then runs forward along the upper border of the sub-maxillary gland, between it and the buccal mucous membrane, and above the mylo-hyoid muscle ; it then passes be- neath the sub-lingual gland, which it crosses, to pass to its inner side, and, accompanied by the Warthonian duct, which lies to its inner side and crosses it at a very acute angle, it gains the corre- sponding border of the tongue, and ramifies in the substance of that organ. During its passage between the two pterygoids the lingual nerve is joined by that branch of the fa- cial nerve which is known as the chorda tympani {x, fig. 298), and which unites to it behind, forming a very acute angle opening upward ; this branch of the facial, which may be regarded as one of the roots * tThis perforating cutaneous fUament is one of the temporal filaments of the orbital branch of the superior maxillary nerve (see notes, p. 831, 835J.1 THE INFERIOR DENTAL NERVE, ETC. 837 of the lingual, remains in contact with that nerve for some time, and is at last blended with it. The lingual nerve also receives, sometimes before, and sometimes after being joined by the chorda tympani, a very considerable anastomotic branch from the inferior dental : this branch is rarely wanting. After receiving these two branches, the lingual nerve becomes considerably increased in size, and during its course gives off several filaments to the tonsils, the mucous mem- brane of the cheeks and the gums. Opposite the sub-maxillary gland, the lingual nerve presents a very remarkable gan- glion, generally described as the sub-maxillary ganglion {aitVLdtei behind X, fig. 300); the trunk of the nerve does not enter into its formation, but it appears to be formed only by its inferior filaments. It has been gratuitously supposed that this ganglion is formed exclusively by the chorda tympani, which, according to such a view, after running in mere contact with the lingual nerve, becomes detached from it (opposite n) to enter the ganglion (x) : we have stated that there was equally little reason to suppose that the chorda tympani was the continuation of the cranial branch of the vidian. The sub-max- illary ganglion, the size of which is very variable, gives off a great number of filaments, most of which are distributed to the sub-maxillary gland ; one of these filaments accom- panies the Warthonian duct. Having reached the sub-lingual gland, the lingual nerve supplies that gland with a great number of filaments, which dip into it and form a plexus of very delicate meshes. In the tongue, the lingual nerve is situated at the lateral border of that organ, and on a plane above that of the hypoglossal nerve, with which it communicates by an anasto- motic branch, forming a loop. It becomes gradually diminished in size by giving off a very numerous series of filaments {n',fig. 301), which turn round the border of the tongue, pass forward and upward, perforate the muscles of that organ, and spread out into pen- cils, the filaments of which may be traced into the papillae of the mucous membrane. The nerve, reduced to a single filament, terminates at the point of the tongue The Inferior Dental Nerve. The inferior dental nerve {m,fig. 298), larger* than the lingual, descends with it, at first between the two pterygoid muscles, and then between the internal pterygoid and the ra- mus of the lower jaw : in this situation it is kept in contact with the bone by a layer of fibrous tissue, which is improperly called the internal ligament of the temporo-maxillary articulation, and which separates the nerve from the lingual nerve and the internal pter- ygoid muscle ; it soon enters the dental canal, which it traverses (m) throughout its entire extent, accompanied by the inferior dental artery, and protected by a fibrous ca- nal ; during its course it supplies the molar and the bicuspid teeth, giving a twig to each prong, and having reached the mental foramen, divides into a mental and an incisor branch. The Myloid Branch. — As it enters the inferior dental canal, the nerve gives off a small branch, the myloid branch {z, fig. 300), which arises from its posterior border, opposite the corresponding artery, is received into a furrow upon the inner surface of the ramus of the jaw, against which it is retained by a layer of fibrous tissue, and then, emerging from this furrow, passes upon the upper surface of the mylo-hyoid muscle, in which it ramifies. A great number of filaments from the myloid nerve enter the anterior belly of the digastric muscle. t The mental branch {t,fig. 285), the continuation of the inferior dental nerve, as far as size is concerned, passes through the mental foramen, and expands into diverging fila- ments, which are distributed, in reference to the lower lip, in the same way as the infra- orbital branch is to the upper lip. These filaments interlace with the facial nerve, and form with it a sort of mental plexus ; they are intended for the skin and the mucous membrane of the lower lip : most of them pass to the free border of that lip. The inrisor dental branch, which is extremely small, continues in the original course of the inferior dental nerve, and subdivides to supply the canine and two corresponding incisor teeth. The inferior dental nerve represents in the lower jaw the infra-orbital portion of the superior maxillary nerve in the upper jaw. The Otic Ganglion. I cannot terminate the description of the inferior maxillary nerve without noticing a ganglion recently described by Arnold, under the name of the olic ganglion, which he compares to the ophthalmic ganglion, and which has served him as the basis of an inge- nious theory respecting the nerves of the head. The following is the position of the ganglion, as indicated by Arnold : "The otic ganglion is situated (behind I, fig. 299) im- mediately below the foramen ovale, on the inner side of the third or inferior maxillary * I have observed that thi.s nerve was much smaller in old than in young- subjects. t [Filaments are also given to the sub-maxillary gland ; according to Ellis, some branches pass through the mylo-hyoid muscle and enter the genio-hyoid ; and it is stated bv Alcock that a branch reaches the de- pzecsor labii inferioris.] 888 NEUROLOGY. division (c) of the fifth nerve, a little above the origin of the superficial temporal or au- ricular nerve (auriculo-temporal), at the spot where the inferior maxillary nerve gives off from its external surface the deep temporal and buccal nerves, and where the small root of the fifth unites intimately with the large root. On the inner side, this ganglion is covered by the cartilaginous portion of the Eustachian tube, and by the origin of the ex- ternal peristaphyline {circumflexus palati) muscle ; behind, it is in contact with the mid- dle meningeal artery. Its external surface rests upon the inner side of the inferior max- illary nerve." There can be no doubt that in the situation indicated by Arnold, there is a thin and not very well-defined layer of reddish, pulpy tissue, placed upon the inner side of the in- ternal pterygoid nerve, and which presents the chief characters of ganglionic tissue ; for it is traversed by nervous filaments, which proceed from it as from a centre, and run in various directions. Its connexions with the inferior maxillary nerve are effected by its direct adhesion to that nerve, which adhesion, according to Arnold, takes place by means of several very short, nervous filaments {short root), which appear to come from the small root of the fifth pair, and also by its adhesion to the internal pterygoid nerve ; so that, at first sight, the ganglion would appear to originate from that nerve, or the nerve from the ganglion. The otic ganglion is also connected with the glosso-pharyngeal by means of a filament, which Arnold describes under the name of the small superficial petrosal nerve, to distin- guish it from the great superficial petrosal, or cranial branch of the vidian. This fila- ment, which proceeds from the nerve of Jacobson, or tympanic branch of the glosso-pha- ryngeal, is compared by Arnold to the Imig root of the ophthalmic ganglion : it passes out of the cavity of the tympanum by a special canal, in front of the hiatus Fallopii, runs forward and outward (from 7 towards c, fig. 296), emerges from the cranium through a special foramen, between the petrous portion of the temporal bone and the spinous pro- cess of the sphenoid, and proceeds (above I, Jig. 300) to enter the otic ganglion.* Ar- nold admits a third root for the otic ganglion, namely, a soft root, which he traces from the nervous plexus that surrounds the middle meningeal artery, and is derived from the great sympathetic. The preceding filaments may be regarded as the filaments of origin of the otic gan- glion.t The Branches which proceed from the Otic Ganglion. — The principal filament from the otic ganglion runs backward and upward towards the canal which contains the internal muscle of the malleus, and is lost in that muscle. This twig must be carefully distin- guished from the small superficial petrosal nerve, which is placed above it. Some other filaments join the auriculo-temporal nerve, which generally arises by two roots. Lastly, the otic ganglion sends off a twig to the circumflexus palati muscle. The Sixth Pair, or External Motor Nerves of the Eyes. The very simple distribution of the external motor nerve of the eye, or sixth crania} nerve, contrasts strongly with that of the fifth nerve ; it arises from the furrow between the pons Varolii and the medulla oblongata, immediately forms two fasciculi or roots, a large and a small, which unite in the cavernous sinus ; they pass vertically upward, per- forate the dura mater {b, fig. 296) at the side of the basilar groove by one or two open- ings, to the inner side of and below the fifth nerve, gain the apex of the petrous portion of the temporal bone, over which they turn, and then pass horizontally forward to enter the cavernous sinus. During the course of the nerve through that sinus, it rests upon its lower wall, crosses (above 6, fig. 301) on the outer side of the vertical portion of the internal carotid artery, around which it turns, and then runs along its horizontal portion. The sixth nerve forms a most important anastomosis, on account of which it was for a long time regarded as the origin of the great sympathetic. As it crosses the internal carotid in the cavernous sinus, it communicates by one or two filaments with the supe- rior cervical ganglion. It also communicates, at the same point, with the ophthalmic division of the fifth nerve. Lastly, it enters the orbit through the widest part of the sphenoidal fissure, passes through the fibrous ring which is common to it and to the inferior division of the com- mon motor nerve, crosses, at an acute angle, beneath the ophthalmic nerve, and gains the inner surface of the external rectus, and penetrates that muscle, after having ex- panded into a pencil of very delicate filaments. We shall again advert to the communication between this nerve and the superior cer-'» vical ganglion. * This small superficial petrosal nerve is very distinct from the great superficial petrosal nerve, being situ ated in front of and parallel to that nerve. In a subject which I dissected in J826, I found this small nerve presenting the following peculiarity : it had a well-marked nodule or ganglion, which gave off a filament to the middle meningeal artery, and some small twigs, which appeared to me to be lost in the substance of the sphenoid bone ; but I did not discover the connexions of this nerve. t Arnold admits an indirect communication between the otic gan!>;lion and the acoustic nerve through the intervention of the facial nerve. The existence of this communication appears to me very doubtful, as well as the communication of the otic ganglion with the great sympathetic, by means of the twigs on the middle meningeal artery THE FACIAL NERVE. 839 The Seventh Pair of Nerves The Portio Dura, or the Facial JVerve. We have already traced the facial nerve, or the portio dura of the seventh, from its on gin to the internal auditory meatus, which it enters together with the auditory nerve (7, Jig. 296), which nerve lies below and behind the facial, and forms a groove for its recep- tion. Having reached the bottom of the internal auditory meatus, this nerve follows the long course of the facial canal,* or aqueduct of Fallopius, a winding passage which is formed in the petrous portion of the temporal bone, and which opens by one end into the internal auditory meatus, and, by the other, upon the lower surface of the pars petrosa at the stylo-mastoid foramen. The facial nerve traverses this canal, which is exclusively appropriated to it ; it is at first directed outward (n, fig. 296), and, after proceeding for about a line, bends sudden- ly, and runs backward, in the substance of the internal wall of the cavity of the tympa- num, above the fenestra ovalis. Having reached the back of the tympanum, it forms another bend, and passes vertically downward (o, figs. 298, 300) to the stylo-mastoid fo- ramen. It follows, therefore, that the facial nerve describes two curves, like the aque- duct of Fallopius, and is horizontal in its first two portions and vertical in the third. On emerging from the stylo-mastoid foramen, the facial nerve runs forward in the substance of the parotid gland, and, after a course of about five or six hues, divides into two terminal branches, the temporo-facial (g, fig. 285) and the cervico-facial (/), which expand into a great number of diverging filaments, and cover the temples, the whole of the face, and the upper part of the neck, with their radiations and anastomoses. The facial nerve gives off and receives certain collateral branches before and others after its exit from the stylo-mastoid foramen. The Collateral Branches of the Facial Nerve, before its Exit from the Stylo-mastoid Foramen. In the internal auditory meatus the facial nerve receives some twigs from the auditory, a remarkable anastomosis, which deserves the attention of physiologists. Opposite to the hiatus Fallopii, i. e., at the first bend formed by the Fallopian aque- duct, the facial nerve is joined by the cranial branch of the vidian, or the great super- ficial petrosal nerve (c> figs. 296, 300). According to MM. Ribes, Hippolyte Cloquet, and Hirzel, this branch is applied to the facial nerve, but does not anastomose with it, and is detached from it lower down to constitute the chorda tympani nerve ; and as the cranial branch of the vidian arises from the spheno-palatine ganglion, and the chorda tympani is supposed to enter the sub-maxillary ganglion, it is seen that, according to this view, the cranial branch of the vidian and the chorda tympani, which is regarded as its prolongation, would establish a communication between the spheno-palatine and sub-maxillary ganglia. It is by no means proved, however, that the chorda tympani en- ters the sub-maxiUary ganglion ; and, again, the supposed connexion between the cra- nial branch of the vidian and the chorda tympani is opposed to facts. The cranial branch of the vidian and the facial nerves, indeed, are not in mere juxtaposition, but anastomose and are blended with each other, and the chorda tympani has no sort of re- lation to the former of these nerves. This independence of the branch of the vidian nerve and the chorda tympani can be most clearly seen when the parts have been ma- cerated in diluted nitric acid.t If an explanation must be given of this remarkable anastomosis between the vidian and facial nerves, I would say that the cranial branch of the vidian may be regarded as a remote origin or a re-enforcing branch of the facial nerve. The facial nerve, according to Soemmering and those who have followed him, gives off a twig to the internal muscle of the malleus, and another to the small muscle of the stapes ; but, in the first place, the existence of a stapedius muscle is doubtful, and, con- sequently, the existence of a corresponding nervous twig must also be so, and, in the second place, the internal muscle of the malleus is not supplied from the facial nerve, but from the inferior maxillary division of the fifth nerve, and more especially from that pulpy, reddish tissue, named by Arnold the otic ganglion. Before leaving the aqueduct of Fallopius, the facial nerve (n,fig. 296) gives a remark- able filament, named the chorda tympa7ii, which pursues a recurrent course (y) from be- low upward in a peculiar canal, parallel to the aqueduct of Fallopius, enters the cavity of the tympanum through an opening to the inner side of and behind the attachment of the membrana tympani, passes downward and forward through the cavity of the tym- * For what purpose is this long- course within the petrous portion of the temporal bone ? Those physiolo- gists who believe the facial nerve to be of a mixed nature, that is, both sensory and motor, have laid great stress upon this point, which they conceive to be favourable to their views ; but there is not the slightest shadow of a proof that the facial nene possesses these two properties. t Arnold has pointed out, at the junction of the cranial branch of the vidian with the facial nerve, a gangli- form swelling, which he regards as a transition between a gangliform enlargement and a true ganglion ; from this swelling, which he compares to the ganglia of the posterior roots of the spinal nerves, he says a filament is given off to anastomose with the auditory nerve at the bottom of the internal .auditory meatus. I have not been fortunate enough to discover this filament ; nor have I ever seen any gangliform appearance at the junc- tion of the vidian and facial nerves. 840 NEUKOLOGY. panum, between the handle of the malleus and the vertical ramus of the incus, and emerging from that cavity {x,fig. 298), not through the Glasserian fissure, but through a special opening already described (see Organ of Hearing — Cavity of the Tympanum), is applied to the lingual nerve («), of which it may be regarded as a late origin, or re-enfor- cing branch. The facial branch also receives, in the aqueduct of Fallopius, opposite to where it gives off the chorda tympani, a very remarkable branch from the pneumogastric nerve, which Arnold has named the auricular branch of the pneumogastric. The Collateral Branches of the Facial Nerve, after its Exit from the Stylo-mastoid Foramen. Before its terminal division, the facial nerve gives off two branches, the posterior auricular and the styloid. I have never seen any parotid branch, properly so called. The posterior auricular, which would be better named the auriculo-occipital, comes ofl from the nerve within the stylo-mastoid foramen, and is immediately applied against the mastoid process, turning round over its anterior and then its outer surface ;* as it lies in front of the mastoid process, it anastomoses with a remarkable twig from the deep auric- ular branch of the auricularis magnus from the cervical plexus ;t after this, it divides into two branches : an ascending or auricular branch {m, fig. 299), properly so called, which, having first supplied, then perforates the posterior auricular muscle, turns round the auricle, and terminates in the superior auricular muscle ; and a horizontal or occipital branch («, fig. 285), which is larger, and forms the continuation of the nerve ; it passes immediately beneath the posterior auricular muscle, to which it gives some filaments, then runs exactly along the superior semicircular line of the occipital bone, and termi- nates by giving off from its upper side a series of small filaments, which are lost in the occipital portion of the occipito-frontalis : they can be traced as far as the median line, but none of them are distributed to the skin. The styloid branch arises from the back of the facial nerve, at its exit from the stylo- mastoid foramen, and enters the stylo-hyoid muscle, after having run along its upper border. The posterior mastoid or digastric branch often arises by a common trunk with the pre- ceding, enters the posterior belly of the digastric muscle, and sends off an anastomotic twig to the glosso-pharyngeal nerve. The Terminal Branches of the Facial Nerve. The Temporo-facial Nerve. The temporo-facial nerve {g, fig. 285) passes upward and forward in the substance of the parotid, forming, with the trunk of the facial nerve, an arch having its concavity turned upward ; it crosses the neck of the condyle of the lower jaw, and receives in this situation, by its deep surface, one, or sometimes two branches from the auriculo-tempo- ral nerve, a branch of the inferior maxillary. This anastomotic branch establishes a very important connexion between the fifth and facial nerves. The temporo-facial nerve, which is flattened and plexiform where it is joined by the branch from the fifth, afterward expands into a number of filaments, which anastomose with each other, so as to form arches, from the convexity of which a number of diverging filaments of unequal size proceed like rays, and cover the whole space comprised be- tween a vertical line drawn in front of the ear, and a horizontal line corresponding to the base of the nose. All these branches, which anastomose several times with each other, and form a suc- cession of arches somewhat resembling those of the mesenteric arteries, may be divided into the temporal, the orbital, and the infra-orbital or buccal branches. The temporal branches ascend, cross over the zygomatic arch at right angles, and cov- er with their ramifications the whole of the temporal and frontal regions, anastomosing with filaments from the frontal branch of the first [from the orbital branch of the second], and from the auriculo-temporal branch of the third division of the fifth nerve. All these branches lie between the skin and the temporal aponeuroses ; some of them supply the skin, but* the majority are distributed to the frontal portion of the occipito- frontalis muscle, below which they are situated, and may be traced as far as the median line. The orbital branches may be divided into the superior palpebral, which are remarkably long, and pass beneath the orbicularis palpebrarum, to ramify in that muscle and the corrugator supercilii. Several of these anastomose with twigs from the supra-orbital nerve : the middle palpebral branches. Which gain the outer angle of the eyelids, and are distributed between the upper and lower eyelids, and the superior palpebral branches, which are generally named the malar branches ; they pass horizontally forward, opposite to the lower part of the orbicularis palpebrarum, and are reflected upward, to enter the * This little nerve is lodged in the furrow between the mastoid and vaginal processes (see Osteology, p. 43). t [It is also joined, according to Arnold, by a filament from the auricular branch of the pneumogastric (sea note, p. 844). THK CERVICO- FACIAL NERVE. 841 substance of the lower eyelid, between the palpebral aponeurosis and the palpebral por- tion of the orbicularis, in which they terminate. They may be traced as far as the free border of the tarsal cartilage, where they anas- tomose with each other. The infra-orbital or buccal branches of the temporo-facial are given off from one or two large branches which accompany the Stenonian duct ; they expand into a great number of filanients, which may be divided into a superficial and a deep set : the superficial branch- es ran beneath the skin, and above the orbicularis oris, the two zygomatic, and the le- vator labii superioris, all of which they supply ; there can be no doubt that they also give cutaneous filaments ; these are very small, and very long, and may be followed as far as the hair follicles in the upper lip ; some of these superficial branches reach the lower eyelid, several accompany the facial and angular veins, anastomose with twigs from the infra-trochlear branch of the nasal nerve, and ascend as far as the pyramidalis nasi, in which they terminate. The deep branches pass beneath the levator labii superioris, send off numerous fila- ments to that and the levator anguli oris, and form, together with the terminal divisions of the infra-orbital branch of the superior maxillary, a very remarkable plexus, which may be called the infra-orbital. This plexus is formed by the interlacement of the radiating branches of the facial nerve with those of the infra-orbital branch of the superior maxillary division of the fifth nerve. Now, as the facial nerve radiates from without inward, and the infra-orbital from above downward, it follows that the branches of these two nerves meet each other at right angles. This arrangement can be rendered more evident by pulling the two sets of nerves in the direction of their length. Most of these branches interlace with- out anastomosing, and proceed directly to their destination. The destination of the facial nerve is evidently rather to the muscles than to the skin ; that of the infra-orbital branch of the fifth nerve is rather to the skin and mucous membrane than to the mus- cles ; nevertheless, it cannot be doubted that the facial nerve supplies some cutaneous filaments, and that the fifth nerve gives some twigs to the muscles. Besides, there are some undoubted anastomoses between these two nerves. The facial also communicates very freely with the buccal nerve, a branch of the inferior maxillary. The infra-orbital branches of the temporo-facial nerve supply the two zygomatics, the levator labii superioris, the levator labii superioris alaeque nasi, the depressor alae nasi, the transversalis nasi, the levator anguli oris, and the orbicularis oris. I would also point out a very remarkable branch, which enters the substance of the ala of the nose, and appears to be intended for that sort of sphincter muscle found in the cutaneous fold of the alae. This branch anastomoses with the naso-lobar branch of the internal nasal nerve. The infra-orbital branches of the fifth nerve are distinguished from the infra-orbital branches of the facial nerve, by their direction ; by being more deeply seated ; by being much larger ; and by being arranged in successive layers, which are three in number : a sub-cutaneous, a sub-mucous, and a muscular ; this last set perforates the orbicularis oris, in which some filaments appear to terminate. Among the infra-orbital branches of the fifth nerve, there is one which may be called the nerve of the sub-septum, which runs on the side of the median line, as far as the tip of the nose, where it terminates. Lastly, the infra-orbital branches of the fifth give a dorsal branch for the nose, and two ascending palpebral branches, which can be easily distinguished from the palpebral branches of the facial nerve. The Ccrvico-facial Nerve. The ccrvico-facial nerve (/, fig. 285), which is smaller than the temporo-facial, follows the original course of the facial nerve, and, like it, runs downward and forward in the parotid gland ; opposite to the angle of the lower jaw it divides into three or four branch- es, which subdivide into secondary branches, which may be arranged into the buccal, men- tal, and cervical sets. The buccal branches run horizontally forward in front of the masseter, to which they give off" some small filaments, and then anastomose with each other and with the infra- orbital branches of the temporo-facial nerve. A very beautiful anastomosis is found be- tween the buccal branch of the inferior maxillary and one of these buccal branches of the cervico-facial nerve : we have already pointed out a similar anastomosis between an infra-orbital branch of the temporo-facial and this same buccal branch of the inferior maxillary. The mental branches are intended for the lower lip. They are reflected upward, so as to describe an arch having its concavity directed upward ; they are at first situated be- neath the platysma myoides, then pass beneath the triangularis oris, and form, with the mental branch of the inferior maxillary division of the fifth nerve, an interlacement or mental plexus, which has a close analogy with the interlacement of the infra-orbital branches of the facial with those of the superior maxillary division of the fifth nerve, but is less comnlicated. 50 842 NEUROLOGY. Thus, the mental branches of the facial nerve are more superficial than those of the fifth, and their filaments are smaller ; the radiating branches of the facial nerve run at first forward and then upward, while those of the fifth nerve run directly upward. The mental brandies of the facial nerve perforate the quadratus rnenti and the orbicularis oris, to which muscles they are almost entirely distributed ; they also send several long and slender filaments to the point of the chin, some of which are cutaneous. The men- tal branches of the fifth nerve are chiefly situated between the muscles and the mucous membrane, to w hich latter they are distributed, more especially to the free borders of the lower lip. The cervical branches of the cervico-facial run forward in the supra-hyoid region, be- neath the platysma, and, describing arches with their concavities turned upward, they pass upward and forward to terminate near the chin. Among these branches, there is one which passes vertically downward to anastomose with the superficial cervical nerve of the cervical plexus. The cervical branches of the facial nerve are separated from the cervical branches of the cervical plexus by the platysma, and they are all distributed to that muscle and the levator labii superioris. Summary. — The facial nerve supplies all the cutaneous muscles of the cranium and of the face, and, therefore, section and compression of this nerve cause complete paral- ysis of these muscles : it is the nerve of expression, or the respiratory nerve of the face {Bell) ; it also evidently gives off some cutaneous filaments, especially near the commissure of the lips, and this may explain the numbness which I have known to oc- cur in individuals affected with hemiplegia of the face ; lastly, it furnishes a great num- ber of anastomotic filaments (whence it has been called the small sympathetic) ; these are given to the branches of the cervical plexus, to the auditoiy nerve, to the pneumo- gastric, and more especially to the fifth nerve. The anastomoses of the facial with the fifth nerve merit special notice ; they are ef- fected with the frontal and nasal nerves of the ophthalmic or first division of the fifth ; with the superior maxillary or second division by means of the infra-orbital nerves and the cranial branch of the vidian, which latter I even regard as one of the origins of the facial nerve ; and with the inferior maxillary or third division of the fifth by means of the mental nerve, the buccal nerve, and more especially the auriculo-temporal nerve. The branch given by the auriculo-temporal to the facial nerve may be regarded as one of the origins of the last-mentioned nerve. Notwithstanding these numerous anastomoses, the facial nerve and the fifth nerve cannot supply the place of each other. Anatomy shows no difference in the structure of these nerves, but a great difference in their distribution ; the facial nerve being in- tended for the muscles, while the fifth is distributed to the integuments and the organs of the senses. Function. — The facial is a nerve of motion. This fact may be deduced from its ana- tomical description no less than from physiological experiments and the effects of disease. The Portio Mollis, or the Auditory J^erve. The auditory nerve (7, figs. 296, 301), which we have already traced as far as the in- ternal auditory meatus, enters that canal with the facial nerve, for which it forms a groove, and divides into two cords, which remain distinct throughout the whole extent of the passage, but continue in contact with each other, and at length pass through the foramina in the cribriform plate already described as existing at the bottom of the meatus (see Osteology). In order to understand the farther distribution of the auditory nerve, the cribriform plate of the auditory meatus must be examined with the same attention as was devoted by Scarpa to the cribriform plate of the ethmoid, with which it has so many analogies. As the cribriform plate of the ethmoid presents a particular fissure for the passage of the ethmoidal branch of the ophthahnic nerve, so the cribriform plate of the internal auditory meatus presents a special opening for the passage of the facial nerve ; and again, the auditory, like the olfactory nerve, seems as if it were pressed through the foramina of the cribriform plate to enter the internal ear. Of the two terminal branches of the auditory nerve, the anterior is intended for the cochlea, the posterior for the vestibule and semicircular canals. The cochlear branch turns spirally, like that part of the bottom of the auditory meatus to which it belongs, and which is called the tractus spiralis. It then turns upon itself, as observed by Valsalva, and presents somewhat of a ganglionic appearance. From this sort of enlargement the cochlear filaments proceed ; those which belong to the first turn of the cochlea run along the surface of the modiolus ; the others enter the canals of the modiolus, and are distributed on the second, and the succeeding half turn at the summit of the cochlea. I have already described the very regular manner in which these fila- ments spread upon the spiral septum, the subdivision of each of them into two or three filaments, which anastomose with each other lite the ciliary nerves, and the gradual dim- inution in the length of these filaments from the base to the apex of the cochlea ; so that, THE GLOSSO-PHARYNGEAL NERVE. it we suppose the spiral septum spread out, it might be compared to a harpsichord, the longest strings of which would be represented by the filaments at the base of the trian- gle formed by the septum, and the shortest by those at its apex (see Internal Eae, p. 681). The vestibular branch divides into three parts, the largest of which enters the utricle and the ampullce of the superior vertical and horizontal membranous canals, the middle, sized branch passes to the sacculus, and the smallest branch to the ampulla of the pos- terior or inferior vertical semicircular canal. Function. — The auditory nerve is exclusively the nerve of hearing. The Eighth Pair op Nerves. The First Portion, or Glosso-Pharyngeal JVerve. Dissection. — Remove, by a triangular section, the posterior half of the border of the foramen lacerum posterius ; carefully detach the jugular vein, in front of which the nerves are situated, examine the connexions of the glosso-pharyngeal with the pneumo- gastric and spinal accessory nerves. The glosso-pharyngeal nerve {pharyngo-glossal), the anterior portion of the eighth nerve (8, Jigs. 296, 301), the ninth nerve of some authors, is intended for the pharynx and the tongue. Having arisen from the restiform body, above and on a line with the pneumogastric,* by a series of roots which are continuous with the roots of that nerve, the glosso-pharyn- geal emerges from the foramen lacerum posterius through a fibrous canal which is prop- er to it, and which is situated in front of the canal that is common to the pneumogastric and spinal accessory nerves ; it is placed to the inner side of the internal jugular vein, from which it is separated by a cartilaginous and sometimes osseous lamina. During its passage through this canal it presents a ganglionic enlargement, which was described by Andersh under the name of ganglion petrosum, and is now more generally known as the ganglion of Andersh. This ganglion is situated in a depression on the petrous portion of the temporal bone {receptaculum ganglii petrosi) ; from it the nerve pro- Pig. 301. ceeds as a rounded cord, which descends vertically (I, fig. 301) behind the styloid muscle in front of the internal carotid, then between the stylo-pharyngeus and the stylo-glossus, and passing forward so as to describe a curve with its concavity turned upward, runs in front of the posterior pillar of the fauces and behind the tonsil, and then passing beneath the hyo- glossus muscle (2), ramifies, to enter the base of the tongue and supply the mucous membrane. During this course it gives off the nerve of Jacob- son, and an anastomotic twig to the facial nerve ; it communicates with the spinal accessory and the pneumogastric ; it gives off a muscular branch to the digastricus and stylo-pharyngeus, and it supplies some carotid filaments, and some pharyngeal and tonsillar branches. The Nerve of Jacobson. — In order to facilitate the study of the course of this nerve, I shall first de- scribe the canals through which it passes : Upon the ridge which separates the jugular fossa from the carotid canal, to the outer side of the aqueduct of the cochlea, is found an open- ing, which is the inferior orifice of the canal of Jacobson. This canal runs backward and upward into the substance of the internal wall of the cavity of the tympanum, in front of the fenestra rotunda ; there it branches into three canals : one descending, which opens into the carotid canal ; and two ascending canals, an anterior, which runs forward and upward, and opens into the groove for the great superficial petrosal or cranial branch of the vidian nerve, and a posterior, which at first ascends vertically behind the fenestra ovalis, then curves suddenly and becomes horizontal, and opens upon the upper surface of the pars petrosa in a groove parallel to and on the outer side of the groove for the cranial branch of the vidian nerve. The nerve of Jacobson, which comes off from the petrosal ganglion, or ganglion of An- dersh, enters this canal. In one subject I found it to consist of two filaments, one from the pneumogastric, and the other from the glosso-pharyngeal. t This nerve soon divides into three filaments corresponding to the three branches of the * Several modern physiologists, believing the glosso-pharyngeal to be a mixed nerve, sensory in its lingual portion, and motor in its pharyngeal, have, therefore, supposed it to have tviro distinct roots : a larger, which is near the par vagum, and a smaller, v^hich lies near the facial nerve ; and, from analogy, they regard the former as the sensory, and the latter as the motor root. t In another subject it was formed by the anastomoses of a twig from the auricular branch of the pneumo- gastric with a twig from the glosso-pharyngeal. 844 ■.i''.i:.: il/ NEUROLOGY. canal ; the descending filament joins the carotid plexus ; of the two ascending lilaments, one anastomoses with the cranial branch of the vidian, or the great superficial petrosal nerve {v, Jig. 300), while the other constitutes the small superficial petrosal nerve, which reaches the upper surface of the pars petrosa in front of the preceding, and terminates in the reddish tissue known as the otic ganglion.* It follows, therefore, that the nerve of Jacobson connects the glosso-pharyngeal nerve with the superior maxillary division of the fifth nerve (especially with the spheno-pal- atine ganglion through the intervention of the vidian nerve), with the otic ganglion of the inferior maxillary division, and with the superior cervical ganglion of the sympathetic. The anastomotic branch to the facial nerve arises from the ganglion of Andersh imme- diately below the nerve of Jacobson ; it runs downward and outward behind the styloid process, is then reflected upward, so as to describe a loop with its concavity turned up- ward, and anastomoses with the facial immediately after the exit of that nerve from the stylo-mastoid foramen. This branch appears to me to be the remaining trace of a con- siderable branch of the facial nerve, which I have seen partially supplying the place of the glosso-pharyngeal (see the Tongue, p. 646). The Anastomosis of the Glosso-pharyngeal with the Spinal Accessory and Pneumogastric Nerves. — Most commonly the glosso-pharyngeal runs along the pneumogastric, or, more correctly, along the anastomotic branch of the spinal accessory. Sometimes it is com- pletely separated from these nerves, and merely communicates with them by means of its pharyngeal branches. The Branch for the Bigastricus and Stylc-hyoideus. — This branch comes off from the outer side of the nerve, and bifurcates ; one of its divisions enters the posterior belly of the digas- tricus, and the other supplies the stylo-pharyngeus and stylo-hyoideus. It has already been stated that this branch anastomoses with the facial nerve in the digastric muscle. The Carotid Filaments. — These are very numerous ; they descend along the internal carotid artery, and, having reached the point of bifurcation of the common carotid, anas- tomose with the carotid filaments of the superior cervical ganglion, and assist in form- ing the arterial plexus. I have not been able to trace them below the bifurcation of the common carotid. Some of these filaments are described as joining the cardiac nerves. The Pharyngeal Branches. — These are two or three in number ; they anastomose with the pharyngeal branches of the pneumogastric, to constitute the pharyngeal plexus. These branches evidently supply the middle and superior constrictors. The filaments for the latter muscles are reflected upward upon the posterior surface of the pharynx. The tonsillar branches are very numerous, and form a sort of plexus. The Lingual Branches. — After having given off the different branches above mentioned, the glosso-pharyngeal, reduced to half its original size, enters the base of the tongue, and then r-amifies ; some of its lingual branches lie close beneath the mucous membrane ; others traverse the upper layers of the muscular substance of the tongue to proceed to the mucous membrane in front of the preceding branches ; they are all intended for the mucous membrane ; the internal branches proceed from without inward at the side of the median line, while the external runs along the border of the tongue ; I have never seen any filament terminating in the muscular fibres. Function. — From its distribution, this nerve must be regarded as a motor nerve for the pharynx, and a sensory nerve for the base of the tongue. The Second Portion of the Eighth J^erve, or the Pneumogastric Jferve. Dissection. — Lay open the back part of the foramen lacerum posterius, and afterward examine the nerve in the different parts of its course successively. The pneumogastric nerve, called also the vagus nerve, the par vagum, and the tenth era/- niaX nerve of some modern authors, is the principal branch of the eighth nerve (8, fig. 301), and is one of the most remarkable nerves in the body, both on account of the extent of its distribution, and of the importance of the organs supplied by it. It supplies branches, on the one hand, to the larynx, the lungs, and the heart ; and, on the other, to the pharynx, the oesophagus, the stomach, and the solar "plexus. It has already been stated that this nerve arises from the upper part of the medulla ob- longata, upon the restiform bodies, and in a line with the posterior roots of the spinal nerves ; that its filaments of origin converge, and then unite at first into seven or eight fasciculi, and then into a single cord, which passes towards the foramen lacerum poste- rius, through which it emerges from the cranium. The pneumogastric nerve then mns vertically {p,fig. 301) in the neck along the vertebral column, enters the thorax, runs along the oesophagus, with which it passes through the diaphragm, and terminates on the stomach and in the solar plexus. We shall now proceed to examine this nerve while it is within the foramen lacerum * Arnold admits six filaments for the nerve of Jacobson, and, consequently, six small ducts as branches of the canal of Jacol)son ; these six filaments consist of the three described in the text above, and of a twig for the fenestra rotunda, one for the fenestra ovalis, and one for the Eustachian tube. I have distinctly seen the twig for the fenestra ovalis, that is to say, a twig which reaches the margin of the fenestra ovalis, but cannot be traced any farther. I have also seen the twig which passes to the Eustachian tube ; but I have not yet been able to find the twig for the fenestra rotunda. THE PNEUMOGASTEIC NERVE. 845 posterius ; as it is emerging from that foramen ; and as it descends in the neck, in the thorax, and in the abdomen. The Pneumogastric Nerve witfdn th£ Foramen Lacerum Posterius. At the foramen lacerum posterius, the pneumogastric nerve passes through the same opening as the spinal accessory, which lies in contact with it ; a fibrous, cartilaginous, or bony septum separates it from the glosso-pharyngeal, which lies in front of it ; and an- other cartilaginous and often bony septum separates it from the internal jugular vein. As it is passing through the foramen it presents a well-marked ganghonic structure ; I would say, rather, a gray substance containing white nervous filaments, but without any observable swelling : hence most anatomists have denied the existence of a ganglion at this spot. To this ganglion, the ganglion of the pneumogastric, which may be compared to the Gasserian ganglion and to the inter-vertebral ganglia, the spinal accessory nerve is ap- phed, and is connected with it by several very delicate filaments. I have already sta- ted that, not unfrequently, the highest roots of the spinal accessory nerve join the pneu- mogastric directly. This ganglion gives off an anastomotic twig, which enters the petrosal ganglion of the glosso-pharyngeal : I have not always found this filament ; it also gives an anastomotic branch to the facial nerve, viz., the auricular branch of the pneumogastric of Arnold. This branch might be called, the branch of the jugular fossa ; it can be very well seen through the coats of the jugular vein when that vessel is laid open. It runs along the anterior part of the jugular fossa, between it and the internal jugular vein, gives off an anasto- motic twig to the nerve of Jacobson, enters the temporal bone through an opening in the jugular fossa, near the styloid process, and traverses a very short canal, which conducts it directly into the Fallopian aqueduct, in which it anastomoses with the facial nerve.* The Pneumogastric Nerve, at its Exit from the Foramen Lacerum Posterius. At its exit from the foramen lacerum posterius, the pneumogastric nerve presents the appearance of a plexiform cord, which is often accompanied by the gray matter of the ganglion for the space of about six lines or an inch. This plexiform cord has certain important connexions with the spinal accessory, the ninth or hypo-glossal nerve, the glos- so-pharyngeal nerve, and the superior cervical ganglion. It is joined by one of the branches of bifurcation of the spinal accessory, which we shall name the internal or anastomotic branch ol the spinal accessory nerve ; it becomes applied to the pneumogastric nerve, and may be distinguished from it for a considerable distance. It also anastomoses with the hypo-glossal, at the point where it is crossed by that nerve, and at other times above that point. This anastomosis, moreover, is subject to great variety ; sometimes it takes place by a very small filament, at other times by two or three twigs, which form a sort of plexus. It also anastomoses with the glosso-pharyngeal. The examination of this anastomo- sis, after the parts had been macerated in diluted nitric acid, enabled me to see that it is not, properly speaking, effected with the pneumogastric nerve, but with the anasto- motic branch of the spinal accessory. Nothing can be more variable than these anasto- moses, which are sometimes wanting on one side, and which are rather frequently ef- fected through the intervention of the pharyngeal branches. Lastly, the pneumogastric nerve commu)iicates with the great sympathetic by one or two branches in man and some mammalia ;t in the- other classes of animals the con- nexion is so intimate that it is altogether impossible to separate the pneumogastric from the superior cervical ganghon. The connexions of the pneumogastric with the spinal accessory and superior cervical ganghon are two very important points in its anatomy, t The Pneumogastric Nerve in the Neck. In the cervical region, the pnemnogastric nerve {p,figs. 298, 300, 301) is situated in front of the vertebral column, the praevertebral muscles intervening between them, upon the side of the pharynx and oesophagus, and between the internal and then the common carotid, which are on its inner side, and the jugular vein, which is on its outer side ; it is placed behind these vessels. It is closely applied to the carotid artery, being in the same * I have seen this branch, immediately after its origin, enter the sheath of the glosso-pharyngeal nerve, run along its ganglion, and then curve backward to enter the jugular fossa. Arnold, who first described this anas- tomotic branch, represents it as divided into three filaments : an ascending, which anastomoses with the trunk of the facial nerve ; a descending, which anastomoses with the posterior auricular branch of the same nerve ; and a middle {u,fig. 299), which ramifies upon the external auditory meatus. t I have seen the pneumogastric nerve communicate with the great sympathetic, by filaments which come off at different heights from the cervical ganglion ; two proceeded from tlie upper part of the superior cervical ganglion, and then ascended ; and two came from the lower part of the ganglion, and descended to unite with the pneumogastric. I have met with a case in which the superior cervical ganglion was applied in its whole extent so closely to the pneumogastric that it was impossible to separate them. t [The pneumogastric also receives a filament from the anastomotic loop of the first and second cervical iif rvcs (see p. 777). J 846 NEUROLOGY. sheath : it is separated from the cervical portion of the great sympathetic (i), which lies behind and to the outer side of it, by a great quantity of cellular tissue. During this course it supplies the pharyngeal branch, the superior laryngeal nerve, and the cardiac filaments. The Pharyngeal Branch, or Small Pharyngeal Nerve. — This is often double, and is then distinguishable into a superior and an inferior ; it comes off at a little distance from the foramen lacerum posterius, but its real origin is variable. In some cases it arises ex- clusively from the pneumogastric ; at other times exclusively from the anastomotic branch of the spinal accessory, which, as already stated, does not become immediately blended with the pneumogastric ; and it often arises both from the pneumogastric and the spinal accessory : lastly, the glosso-pharyngeal sometimes gives it a filament. It passes behind the internal carotid, gives off" some carotid filaments, which join the more numerous twigs from the glosso-pharyngeal, and then anastomoses with the ramifica- tions of the glosso-pharyngeal, and with several large branches from the superior cervi- cal ganglion, to form the pharyngeal plexus, which is one of the most remarkable plex- uses in the body, and to which the varied and frequent nervous phenomena observed in that region must be referred. I shall recur to this plexus when describing the great sympathetic. The Superior Laryngeal Nerve {x',fig. 301). — This is larger than the pharyngeal branch ; it comes off" from the inner side of the pneumogastric* as a rounded cord, which may be traced as high as the ganglion of the nerve ; it passes downward and inward upon the side of the pharynx, behind the internal and external carotid arteries, which it crosses obliquely : it then turns forward and inward to gain the thyro-hyoid membrane, passing above the upper margin of the inferior constrictor of the pharynx ; it runs for some time between the thyro-hyoid muscle and the thyro-hyoid membrane, perforates the lat- ter at the side of the median line, and then enters the substance of the ar)rteno-epiglot- tid fold of mucous membrane, where it terminates by dividing into a great number of fil- aments. During its course, it gives off a branch which is called the external laryngeal (y), and which I have seen arise directly from the pneumogastric itself; this branch communi- cates with the superior cervical ganglion by one or two filaments, and passes inward and downward upon the side of the larynx. It gives off one or two filaments, which anasto- mose with the superior cardiac nerve, behind the common carotid ; Haller calls this communication between the external laryngeal and the great sympathetic the laryn- geal plexus. \ The external laryngeal nerve also gives off several branches to the infe- rior constrictor of the pharynx, some to join the pharyngeal plexus, and some twigs to the thyroid gland ; it then passes downward and forward between the inferior constric- tor and the thyroid cartilage, and terminates by ramifying in the crico-thyroid muscle. The terminal expansion of the superior laryngeal nerve is remarkable for its radiated arrangement ; it is preceded by a flattening and thickening of the nerve. These ex- panded branches are all sub-mucous, and may be arranged into the anterior or epiglottid, and the posterior. The anterior or epiglottid branches are numerous and small ; they run upon the margin, and on the fore part of the epiglottis ; some of them reach its free extremity, others run between the fibro-cartilage of the epiglottis and the adipose tissue, called the epiglottid gland ; some of them perforate the epiglottis, and ramify upon its posterior surface. Among these anterior terminal filaments of the superior laryngeal nerve there is at least one which runs forward under the mucous membrane covering the base of the tongue, and may be traced as far as the two rows of glands, which are arranged like the letter V. These filaments of the superior laryngeal nerve to the tongue are placed be- tween the lingual branches of the right and left glosso-pharyngeal nerves, with which they have probably been confounded. The posterior or laryngeal filaments contained in the aryteno-epiglottid fold are more numerous than the anterior branches ; they are divided into the mucous filaments, the arytenoid filament, and the anastomotic or descending filameiit. The mucous filaments are very numerous, and run upward in the aryteno-epiglottid fold ; some of them lie beneath the external, and others beneath the internal layer of mucous membrane of this fold. They are intended for these two layers, and they ter- minate, for the most part, at the superior orifice of the larynx : their number explains the exquisite sensibility of this opening. Some of these mucous filaments may be traced into the substance of the arytenoid glands. The filatnent for the arytenoid muscle is very liable to be confounded with the mucous * It arises, therefore, on the opposite side to the anastomotic branch of the spinal accessory, which has not appeared to me to assist in its formation. I have seen the superior laryngeal arise by two roots, the larger of which came from the pneumogastric, while the other, which was very small, came from the glosso-pharyn- geal. It appears to me that M. BischofTs remarks concerning the origin of the superior laryngeal nerve on a level with tlie spinal accessory, would apply to the pharyngeal branch of the pneumogastric. t The superior laryngeal nerve (x',Jig. 301) forms a loop behind the carotids, like tliat formed by the hypo- glossal (d) in front of them, but lower down in the neck ; that portion of the nerve which runs between the thyro-hyoid membrane and the thyro-hyoid muscle is exceedingly tortuous in some positions of the larynx. THE PNEUMOGASTRIC NERVE IN THE THORAX, ETC. 847 filaments ; it perforates the muscle from behind forward, and is partly distributed to it and partly to the lining membrane of the larynx. The descending or anastomotic filament, which is small, but of variable size, descends vertically, between the mucous membrane on the one hand, and the thyro- and crico- arytenoid muscles on the other, gains the posterior surface of the cricoid cartilage, and anastomoses upon it with the recurrent laryngeal nerve. This remarkable anastomosis was known to Galen.* Thus, the superior laryngeal nerve chiefly belongs to the mucous membrane of the larynx ; but it gives branches to the arytenoid and crico-thyroid muscles : the branch for the latter comes from the external laryngeal division of this nerve. The Cardiac Branches of the Pneumogastric Nerve of the Neck. — These vary both in number and size in different subjects, and even upon the two sides of the same body : they come off at different heights from the trunk of the pneumogastric ; some of them, after a course of variable extent, join the superior cardiac nerves, either in the neck or in the thorax ; the others pass directly to the cardiac plexus. The most remarkable of the cervical cardiac branches of the pneumogastric is that which comes off at the lower part of the neck, a little above the first rib ; on the right side, it descends in front of the common carotid, and then in front of the brachio-cephalic artery, below which it anasto- moses with the superior cardiac nerve. On the left side, it passes in front of the arch of the aorta, and anastomoses below that vessel with the superior cardiac nerve of that side. This branch sometimes goes directly to the cardiac plexus : it is sometimes double. The Pneumogastric Nerve in the Thorax. The thoracic portion of the pneumogastric nerve presents this peculiarity, that it differs remarkably on the right and left sides. On the right side, the nerve {p,fig- 302) enters the thorax between the sub-claviaa vein and artery : lower down, it passes behind the brachio-cephalic vein and the supe- rior cava, and behind the phrenic nerve, at the side of the trachea, or, rather, in the groove between the trachea and oesophagus : it then passes behind the root of the lung, where it becomes flattened and enlarged, gives off a great number of branches, and ap- pears to expand, in order to unite in a different arrangement. Below the root of the lung the right pneumogastric is always divided into two flattened branches, which run along the right side of the cesophagus, join together at a short distance from the dia- phragm, and pass behind the cesophagus, with which canal the common trunk enters the abdomen. On the left side, the pneumogastric enters the thorax between the common carotid and the sub-clavian artery, in the triangular interval between those vessels, internal to and then behind the phrenic nerve, behind the brachio-cephalic vein, and to the left of the arch of the aorta ;t it then passes behind the left bronchus, upon which it ramifies, and unites again into one or two branches, which pass in front of the oesophagus, and enter the abdomen with it. In the thorax the pneumogastric gives off the recurrent or inferior laryngeal nerve, a cardiac branch, some tracheal and oesophageal branches, and branches to the anterior and posterior pulmonary plexuses. The Recurrent or Inferior Laryngeal Nerve.t This nerve (r, fig. 302), so called on account of its reflected course, arises in front of the arch of the aorta on the left side, and of the sub-clavian artery on the right side : it is sometimes so large that it may be regarded as resulting from the bifurcation of the pneumogastric : it is reflected below and then behind the arch of the aorta on the left side, and the sub-clavian artery on the right, so as to form a loop or arch, which has its concavity turned upward, and which embraces the corresponding vessel. Having thus changed its course from a descending to an ascending one, the recurrent nerve enters the groove {q,fig. 301) between the trachea and the oesophagus, and continues to ascend as high as the lower border of the inferior constrictor muscle of the pharynx ; it then passes beneath that muscle, gives some filaments to it, runs behind the lesser cornu of the thyroid cartilage and the crico-thyroid articulation, along the outer border of the posterior crico-arytenoid muscle, and terminates by ramifying in the muscles of the larynx. During its course, the recurrent nerve gives off the following collateral branches : at the point of its reflection, it gives several cardiac filaments, which unite with the cardiac branches of the pneumogastric and great sympathetic. It is important to remark the intimate connexion which exists between the recurrent and the cardiac nerves : some very considerable anastomoses are almost always found between the superior and infe- * See note, p. 848. t The relation of the pneumogastric with the arch of the aorta explains the stretching and atrophy of this nerve in aneurisms of that portion of the vessel. 1 Those anatomists who regard the superior laryngeal nerve as a dependance of the spinal accessory be- lieve that the inferior or recurrent laryngeal has a similar origin. I may repeat, and with still more reason, in reference to this nerve, what I have already stated in regard to the superior laryngeal, that it is impossible to '«monstrate this continuity by dissection. 848 NEUROLOGY. rior cardiac nerves and the recurrent nerve : sometimes, indeed, the recurrent nerve forms the point at which the superior and middle cardiac nerves meet, and from which the inferior cardiac nerve is given off; the anastomoses between the recurrent and car- diac nerves sometimes form a true plexus. The recurrent also gives oesophageal branches, which are much more numerous on the left than on the right side, so that the left recurrent nerve is much smaller in the larynx than the right nerve. It also gives tracheal branches, which chiefly supply the posterior or membranous por- tion of that canal. And, lastly, some pharyngeal filaments, all of which are destined for the inferior con- strictor. Excepting an anastomotic branch* for the superior laryngeal nerve, all of the terminal branches of the recurrent nerve are intended for the muscles of the larynx, and are thus distributed : The branch for the posterior crico-arytenoid simply enters that muscle. The branch for the arytenoid, runs between the cricoid cartilage and the posterior crico- arytenoid muscle, and then ramifies in the arytenoid. It has already been stated that the last-named muscle is also supplied by the superior laryngeal nerve. The branch for the lateral crico-arytenoid and thyro-arytenoid muscles is the true termina- tion of the nerve ; it passes on the outer side of these two muscular bundles, which, as formerly stated, constitute a single muscle in the human subject, and then enters them by very delicate filaments. I have distinctly seen a very delicate filament entering the crico-th)Toid articulation. After the pneumogastric has given off the recurrent nerve, and often before doing so, it furnishes certain cardiac branches (thoracic cardial) ; these are subdivided into the pericardial, which run upon the outer surface of the pericardium, and are lost in it and in the cellular tissue which replaces the thymus ; and into the cardiac branches, properly so called, which assist in the formation of the cardiac plexus. The pneumogastric also gives off certain anterior pulmonary branches, which run in front of the bronchus and of the pulmonary arteries and veins, cross obliquely over them, and then enter the substance of the lung, following the ramifications of the air-tubes and bloodvessels ; these pulmonary branches form what is called the anterior pulmonary plex- us. I have seen several of them extend some considerable distance beneath the serous membrane, covering the inner surface of the lungs, before they entered the substance of those organs. Behind the bronchus, and along the oesophagus, the pneumogastric nerve gives off posterior branches, consisting of a great number of esophageal branches ; of some tracheal branches, which principally supply the back or membranous portion of the trachea ; and, lastly, of posterior pulmonary or bronchial branches, which form the posterior pulmonary plexus. The posterior pulmonary plexus is one of the most remarkable in the body ; in it the pneumogastric nerve appears to be decomposed and expanded ; there is a right and a left pulmonary plexus. The left is much larger than the right. The two plexuses are not independent of each other, but are connected by free anastomoses : this remarkable disposition establishes a community of function between the two nerves, and explain* how one of them may supply the place of the other. The pulmonary plexuses, which are completed by filaments from the great sympathetic, are situated behind the root of each lung, or, to speak more exactly, behind the bronchi (whence the name of bronchial plexuses). A few of the twigs emerging from them follow the pulmonary arteries, and appear to be lost in their coats ; the others accompany the bronchi, some of them passing behind these canals, and others, being reflected forward in the angles formed by their bifurcation, run along their anterior aspect, and terminate in their parietes. They may be traced as far as the ultimate ramifications of the aii- tubes. In large animals they can be easily seen entering the circular muscular fibres which surround the bronchial tubes, t Below the pulmonary plexus, the pneumogastric merely gives off certain cesophagcal branches, which surround the oesophagus in very great numbers. The right and left pneumogastric nerves anastomose with each other ; but the communicating arches do not constitute those circular anastomoses, which have been so decidedly said to explain the pain caused by swallowing too large a morsel of food. The Pneumogastric Nerve in the Abdomxn. The two pneumogastrics enter the abdomen with the oesophagus, the left nerve being in front and the right nerve behind that canal, and are distributed in the following manner : * [This anastomotic branch is superficial, and joins the descending filament from the superior laryngeal nerve, beneath the mucous membrane on the back of the larynx, and sometimes sends filaments into the ary- tenoid muscle ; there is, generally, a second anastomosis between the superior and inferior laryngeal nerves on the side of the larynx, between the thyroid cartilage and the thyro-arytenoid muscle.] t I have seen a nerve from the pulmonary plexus pass through some of the fibres of the oesophagus and ram- ify iu the aorta. SPJNAL ACCESSORY NERVE OF WILLIS. 849 The left nerve {q,fig. 302), which is situated in front of the cardia, expands into a very- great number ot diverging filaments, some of which extend over the great cul-de-sac, and others over the anterior surface of the stomach ; but the greater number gain the lesser curvature, and divide into two sets or groups ; one of these leaves the lesser cur- vature, enters the gastro-hepatic omentum, is conducted by it to the transverse fissure of the liver, and enters that gland. The other group continues in the lesser curvature, and may be traced as far as the duodenum. The right pneumogastric (p'), situated behind the cardia, gives a much smaller number of branches to the stomach than the left, and joins the solar plexus (z), of which it may be regarded as one of the principal origins. Summary of the Distrilmtion of the Pneumogastric Nerve. — This nerve, it wiU be seen, has an extremely complicated distribution. Within the foramen lacerum posterius, it anastomoses with the spinal accessory ; with the facial nerve by means of the auricular branch of Arnold, or the branch of the jugular fossa ; and with the nerve of Jacobson, and, therefore, with the glosso-pharyngeal nerve, by a twig from the same auricular branch. At its exit from the foramen lacerum posterius, it anastomoses with a Isirge branch of the spinal accessory ; with the hypo-glossal ; with the glosso-phyrangeal ; and with the su- perior cervical ganglion. In the neck, it gives off the pharyngeal branch or small pharyngeal nerve, the superior laryngeal nerve, and the superior cardiac branches of the pneumogastric. In the thorax, it gives off the recurrent or inferior laryngeal nerve, which supplies some cardiac, oesophageal, pharyngeal, tracheal, and laryngeal branches ; the inferior cardiac branches ; and the pulmonary or bronchial branches. In regard to its structure, the pneumogastric differs essentially from the other cerebro- spinal nerves, by the tenuity of its filaments and by their plexiform arrangement ; and in both of these particulars, as well as in its distribution, it rather resembles the nerves of organic than those of animal life. In the description of the sympathetic it will be seen how intimate are its relations with the pneumogastric nerve. Functions of the Pneumogastric. — From the manner in which the pneumogastric is dis- tributed, it follows that it is a nerve both of sensation and ot motion ; for it supplies both the lining membrane of the respiratory and digestive passages, and the muscles and muscular coats of the same canals. Anatomy does not confirm the ingenious idea of Bischoff, that the pneumogastric is essentially a nerve of sensation, and that the por- tion which appears to be motor really belongs to the spinal accessory. Physiologists have studied the influence of the pneumogastric upon the larynx, the lungs, the heart, and the stomach in an infinite variety of ways ; it appears, from some experiments which I made upon this subject, that animals in which both pneumogastrics are simul- taneously cut die almost immediately, when they are permitted to eat as much as they please ; for, the contractility of the stomach and oesophagus being destroyed, the food, after having filled the stomach, distends the oesophagus, and passes from it into the larynx. The Third Portion of the Eighth Jferve, or the Spinal Accessory JN'&rve oj Willis. We have already described the very remarkable origin of the spmal accessory nerve at the side of the cervical portion of the spinal cord, between the anterior and posterior roots of the spinal nerves, or, rather, immediately in front of the posterior roots, of which it appears to be a dependance : we particularly alluded to the arrangement of its highest filaments of origin, which come from the restiform bodies, and are continuous above with the roots of the pneumogastric, so that they sometimes even join that nerve, and below with the posterior roots of the spinal nerves. Lastly, we have pointed out the varieties of its origin, its connexions with the first pair of cervical nerves, of which it almost always forms the posterior roots, its ascend- ing course to the foramen magnum, through which it enters the cranium, and its exit from the scull by the foramen lacerum posterius. It emerges from the foramen lacerum posterius by an opening quite distinct from that for the glosso-pharyngeal, but common to itself and the pneumogastric nerve, behind which it is situated {9, fig. 301). While passing through the foramen lacerum poste- rius, it lies in contact with the ganglionic enlargement of the pneumogastric, and is con- nected with the ganglion by very delicate filaments, but it neither assists in the forma- tion of that enlargement, nor is blended with it : at its exit from the foramen it divides into two branches of equal size ; an internal or anastomotic, which remains in contact with the pneumogastric, and is distributed with it, and a muscular branch* (cut off in %. 301). The Anastomotic Branch. — So intimately are the spinal accessory and pneumogastric nerves connected, or, as it -were, fused together, that, up to the time of Willis, they were " It is well to observe, that as they are passing through the foramen lacerum posterius, the pneumogastric and spinal accessory nerves adhere to the dura mater, in the iame manner as the Gasserian ganglion. 5 P 850 NEUROLOGY. regarded as a single nerve. Willis first described the former, perhaps erroneou§^^, as a separate nerve, under the name of nervus accessorius ad par vagum, sive nerviis spinalis. In an excellent thesis, published in 1822,* M. Bischoff endeavoured to prove that the pneumogastric or par vagum and spinal accessory form but a single nerve, analogous to the spinal nerves in every respect ; the spihal accessory being the nerve of motion, and the par vagum the nerve of sensation : " Nervus accessorius Willisii est nervus moto- rius, atque eandem habet rationera ad nervum vagum quam antica radix nervi spinalis ad posticam. Omnis motio cui vagus praeesse videtur, ab ilia portione accessorii quae ad vagum accidit, efEcitur. Itaque vox quoque, sive musculorum laryngis et glottidis motus, ab accessorio pendet, et eo nomine accessorius nervus vocalis vocari potest." To this view there are serious objections : in the first place, it is opposed to the law that the anterior roots preside over motion and the posterior over sensation ; for the filaments of origin of the spinal accessory evidently form part of the posterior roots. Again, how can it be supposed that two nerves, which, like the spinal accessory and pneumogastric, arise so distinctly from the same line, that it is often difficult to separate them, can have such opposite functions ! Must we suppose that the law which regulates the anterior and posterior roots of the spinal nerves ceases to operate at the medulla oblongata 1 or must we admit, with Ar- nold, that there is not only a decussation of fibres from side to side in the medulla ob- longata, but also from before backward, so that the posterior columns of the medulla ob- longata become the motor and the anterior the sensory 1 Still, even with this hypothe- sis, it must be remembered that the spinal accessory arises in part below the point where this antero-posterior decussation is supposed to exist. There evidently is an antero- posterior decussation opposite to the two anterior pyramids, as I have elsewhere stated (see Medulla Oblongata), but the other columns of the spinal cord are not concerned in it. However this may be, the anastomotic branch of the spinal accessory may be traced, after maceration in dilute nitric acid, along the outer side of the pneumogastric. In a great number of cases, it evidently gives off the small pharyngeal nerve, which sometimes arises exclusively from the pneumogastric, and sometimes from both the pneumogastric and the spinal accessory. Scarpa declares the last arrangement to be constant and normal, and has represented it in several figures. In some subjects, the spinal accessory appears to have no share in the pharyngeal nerve, but then its anastomotic branch be- comes applied to the pneumogastric below the origin of the pharyngeal nerve. The anastomotic branch appears to me to have no share in the formation of the supe- rior laryngeal nerve ; and the same is the case with regard to the recurrent nerve. It appears to me anatomically impossible to prove the continuity of the spinal accessory and the superior and recurrent laryngeal nerves ; I cannot, therefore, admit that the spi- nal accessory supplies the intrinsic muscles of the larynx. The spinal accessory generally gives off a number of twigs, which unite in front of the reddish, and, as it were, ganglionic trunk of the pneumogastric nerve, to form a small plexus, which adheres to that nerve, and ends in the hypo-glossal nerve. Lastly, there are so many varieties in the mode of communication between the pneu- mogastric and spinal accessory nerves, that it is extremely difficult to refer them to any general law. The Muscular Branch. — This nerve descends vertically between the internal jugular vein and the occipital artery, beneath the digastric and stylo-hyoid muscles ; it runs back- ward and outward {t, figs. 285, 298), beneath the sterno-mastoid, generally perforating that muscle, but sometimes merely running along its deep surface, passes obliquely across the supra-clavicular triangle, and terminates in the deep surface of the trapezius. While perforating the sterno-mastoid, the spinal accessory nerve gives several branches to that muscle, which anastomose with others from the third cervicd nerve, and form a sort of plexus within the muscle. On emerging, somewhat reduced in size, from the sterno-mastoid, it receives a branch {v, fig. 298) from the anastomosis, between the second and third cervical nerves, by which its size is greatly increased : it assists in the formation of the cervical plexus, and some- times of the posterior auricular nerve. Having reached the anterior surface of the trapezius, it receives two considerable branches, derived from the third, fourth, and fifth cervical nerves, which appear to me to re-enforce it. It gives off ascending filaments to the occipital portion of the muscle ; and descending filaments, which continue in the original course of the nerve in front of the muscle, approach its scapular attachments, and may be traced down to its inferior angle. The muscular branch of the spinal accessory belongs exclusively to the sterno- mastoid and trapezius muscles. It has been incorrectly stated that it supplies other mus- ■des, such as the rhomboidei, the levator anguli scapulae, the complexus, the splenius, and the sub-scapularis, and that it is also distributed to the skin. In front of, or, rather, in the substance of the trapezius, the spinal accessory anasto- fjoaoses with the posterior branches of the spined nerves. * Ne-vi Accessorii Willisii Anatomia etPhysiologia. Bischoff. Darmstadii. THE HYPO-GLOSSAL NERVE. 851 Summary. — ^The spinal accessory gives branches to the stemo-mastoid, the trapezius, and the phar)Ttx ; it is believed also to send some to the larynx by means of its anasto- motic branch with the pneumogastric. It communicates with the second, third, fourth, and fifth cervical nerves. Function. — In reference to its muscular branch, Sir C. Bell has classed the spinal ac- cessory among the respiratory nerves, under the name of the superior respiratory nerve of the trunk ; for, according to that anatomist, it arises from the lateral column of the cord, between the anterior and posterior columns. With regard to the anastomotic branch of this nerve, which becomes blended with the par vagum, M. BischofT lays down the following proposition (page 95) : " Nervum acces- sorium nimirum nervum motorium esse, ideoque in partes vagi adscisci, ut motus, qui- bus hie qui sensificus tantummodo nervus est, praeesse videatur, ipse perficiat : eundem ergo praeesse motibus quoque musculorum laryngis, indeque nerviun esse vocalem.". This idea, which was suggested to him by theory, he endeavoured to confirm by experi- ment. The section of all the roots of the spinal accessory proved to be very difficult ; but, after many fruitless attempts, he at length succeeded in dividing them on both sides. The hoarseness produced by section of all the roots of the right side gradually increased as he divided those of the left side, and when all had been cut, the natural voice of the animal was changed to a very hoarse sound, which could not be called the voice. I have already said that anatomy affords no proof that the laryngeal nerves are derived from the spinal accessory ; nor does it show that the muscular fibres of the bronchi, oesophagus, and stomach, receive their filaments from it. The Ninth Pair, ok Hypo-glossal Nerves. The hypo-glossal, or great hypo-glossal nerve, the ninth cranial, or the twelfth nerve of some modem authors, arises on each side from the furrow between the olivary and pyramidal bodies, by a row of filaments collected into two very distinct fasciculi, which proceed to the anterior condyloid foramen (q, fig. 296), perforate the dura mater separ- ately, and join together so as to emerge from the canal in the form of a rounded cord.* After leaving the anterior condyloid canal, the hypo-glossal nerve (d, fig. 301) descends vertically between the internal carotid, which is on its inner side, and the internal jugu- lar on its outer side. At first it lies behind the pneumogastric (8 to p) ; it then crosses very obliquely over the outer side, and lower down it gets in front of that nerve, around which, therefore, it describes a semi-spiral. Having arrived below the posterior belly of the digastric muscle, the hypo-glossal changes its direction and runs forward and downward {d, fig. 300), crossing in front of the internal and external carotids [and hooking beneath the occipital artery] ; it is then reflected upward to reach the under surface of the tongue {d, near x), and thus describes a loop having the concavity turned upward, parallel to and below the digastricus, and almost ten lines above the os hyoides. Relations. — It is situated deeply in its vertical portion, where it runs along the verte- bral column, becomes superficial in its middle portion (d, fig. 298), where it is merely separated from the skin by the platysma and the prominence of the sterno-mastoid, and again becomes deep-seated anteriorly, where it rests on the hyo-glossus muscle, and is covered by the anterior belly of the digastricus and by the stylo-hyoideus, and then by the sub-maxillary gland and the mylo-hyoideus, after which it enters the genio-glossus, and is lost in the substance of the tongue. The relations of the hypo-glossal nerve and the lingual artery are worthy of remark. The nerve is at first parallel to and above the artery, is soon separated from it by the hyo-glossus, and then rejoins it in front of that muscle. In the substance of the tongue, the artery lies to the outer side of the genio-glossus, while the nerve runs forward through the fibres of the muscle. The Collateral Branches of the Hypo-glossal Nerve. Some of these are anastomotic. Thus, as it crosses the three divisions of the eighth nerve, the hypo-glossal lies in contact with the pneumogastric nerve, with which it sometimes communicates by very delicate filaments. Most commonly the anastomosis between these two nerves forms a true plexus, t This communication is sometimes eftected with the anastomotic branch of the spinal accessory, sometimes with the pneu- mogastric itself The hypo-glossal is also connected by a very small anastomotic twig to the superior cervical ganglion. It also receives three filaments from the nervous loop formed by the union of the first and second cervical nerves, namely, two from the first nerve and one from the second. The superior filament from the first nerve ascends, an arrangement which it is difficult to understand, for it passes in a direction towards the roots of the hypo-glossal ; if it be * The vertebral artery is situated in front nf the filaments of the hypo-glossal. t [In connexion with this fact, it may be observed that the descendens noni (a branch of the hypo-|floaaal ttBr\-ol sometimes arises in part or entirely from the pneumogastric, lower down in the neck.] 85S NEUROLOGY. supposed that this filament is derived from the hypo-glossal, then it is directed towards the roots of the first cervical nerve. Opposite to the anterior border of the hyo-glossus it gives off a very remarkable anas- tomotic branch, which forms an arch with the lingual nerve. The other collateral branches which it gives off are the descending branch ; a small muscular infra-hyoid branch ; and the branches for the hyo-glossvs and stylo- glossus. The descending branch {ramus descendens noni, h,figs. 298, 300, 301). This is the most remarkable branch of the hypo-glossal nerve.* It comes off at the point where the nerve changes its direction, descends vertically in front of the internal carotid and then of the common carotid, curves outward, and anastomoses upon the internal jugular vein with the descending branch of the cervical plexus {z,fig. 298), so as to form a loop, hav- ing its concavity turned upward. From the convexity of this loop two branches proceed, .of which one is distributed to the omo-hyoid, while the other (5^) divides into two twigs, one of which enters the outer border of the stemo-hyoid, while the other penetrates the deep surface of the sterno-thyroid muscle. I have seen one of these branches come di- rectly from the hypo-glossal. t It is equally important to study both the mode of origin and anastomosis of the de- scending branch of the ninth ner^'e.t The origin of this branch is, in fact, almost en- tirely from the anastomotic branches of the first and second cervical nerves, which, after having been in contact with the hypo-glossal, are given off from it to constitute the de- scending branch. This arrangement is especially evident in preparations that have been macerated in diluted nitric acid. I should state, however, that it is not equally evident in all subjects ; and that some filaments, derived from the hypo-glossal itself, always join those from the cervical nerves. It has appeared to me that the most internal of the fila- ments derived from the hypo-glossal nerve itself followed a retrograde course ; that is to say, that it ran from below upward, as if it arose at the terminal extremity of the hyi^o- glossal, and then left that nerve to join the descendens noni at the point where that branch is given off. The branches from the first and second cervical nerves to the hypo-glossal should be regarded as late origins of that nerve, which is sensibly increased in size after being joined by them. I have seen the third and even the fourth cervical nerve assist in the formation of the descendens noni ; the branch from the fourth nerve arose partly from the phrenic. The mode of anastomosis of the descendens noni with the descending branch of the cervical plexus, or, rather, of the third cranial nerve, is subject to much variety. The following is the most frequent arrangement : All the filaments composing these two descending branches unite together, with the exception of the uppermost filament, which describes a loop having its concavity turned upward, and resembhng a vascular anastomosis : so that, if we suppose it to be derived from the loop of the Kypo-glossal, it would be directed towards the origin of the cervical nerves ; and if, on the contrary, we suppose it to arise from the cervical nerves, it would be directed towards the origin of the hypo-glossal. This arrangement, which I have had the opportunity of observing in many parts of the nervous system, appears to me to con- stitute a mode of anastomosis well worthy the attention of physiologists. I am induced to regard it as intended to establish connexions between the different points of the spinal cord.^ * See note, last page. t [Another branch is described and figured by Arnold as descending in front of tlie vessels, and joining the cardiac nerves in the thorax.] X There are certain cases in which the descendens noni is analyzed by nature ; namely, when the branch from the second cervical nerve is not applied to the hypo-glossal, but remains at a distance from it. In this case, the filaments derived from the hypo-glossal join themselves to this branch ; one of them ascends towards the origin of the second cervical nerve, and the others proceed towards its termination. In one case, the hypo- glossal gave a very small twig to the first cervical nerve, before receiving its accustomed branch from that nerve ; the descending branch from the cervical plexus was replaced by tEree branches derived from the first, second, third, and fourth cervical nerves, which formed, together with the descendens noni and its branches, a succession of loops, in front of the external and common carotids. In another case, the three superior cervical nerves assisted in forming the descendens noni. The following is a detailed description of that case, which throws considerable light upon the connexions between the hypo-glossal and cervical nerves. One large branib proceeded from the anastomotic arch of the first and second cervical nerves ; this large branch, as soon as 't reached the hypo-glossal nerve, divided into three filaments of unequal size : an ascending, which was directed towards the origin of the hypo-glossal nerve ; a middle, which became blended with that nerve ; and a descend- ing, which was the largest, and which merely ran along in contact with the same nerve. At the point where this last-named filament left the hypo-glossal to form the descendens noni, it evidently received a twig from the hypo-glossal itself, which came from the lower part of that nerve, and was reflected upon the descendens noni in a retrograde manner, so that this twig, derived from the hypo-glossal, had one end at the terminal ex- tremity of that nerve, i. e., in the muscles of the tongue, and the other end in the muscles of the infra-hyoid region. In this same case, the descending branch of the second cervical nerve divided into three filaments, one of which joined the hypo-glossal nerve, another formed an anastomotic arch with the third cervical nerve, while the third filament passed downward to assist m forming the descending branch of the cervical plexus. Lastly, the third cervical nerve in this case gave off an ascending branch, which anastomosed with the seo(md, and a descending branch, which assisted in forming the descending branch of the cenical plexus ; there were therefore two loops or arches, one internal and the other external ; they were situated opposite to the bifurca- tion of the common carotid artery. i, This mode of anastomosis may, perhaps, have some relation to that reflex action of the spinal cord, which GENERAL VIEW QF THE CRANIAL NERVES, 853 The Small Muscular Branch of the Infra-hyoid Region. — This nerve comes off at the posterior border of the hyo-glossus, and ramifies in the upper part of the muscles of the infra-hyoid region ; a small transverse filament runs along the hyoid attachments of these muscles. This small nerve may be regarded as an accessory to the descendens noni. 'The Branches for the Hyo-glossus and Stylo-glossus. — As the hypo-glossal nerve comes into contact with the hyo-glossus, it becomes flattened and widened, and gives off sev- eral ascending branches, most of which ramify in the hyo-glossus, though several end in the stylo-glossus. The Terminal Branches of the Hypo-glossal Nerve. Opposite to the anterior border of the hyo-glossus the hypo-glossal nerve gives off some twigs to the under surface of the genio-hyoideus ; it then enters the genio-hyo- glossus, and expands (d, near x, fig. 300) into a great number of filaments, which run for- ward, perforate that muscle at successive points, and are lost in the substance of the tongue. It is impossible to follow these filaments to the papillary membrane of the tongue. Some of them anastomose with the lingual («) nerve, a branch of the inferior maxillary division of the fifth ; several accompany the lingual artery. The relations of the lingual portions of the hypo-glossal nerve with the lingual of the fifth are worthy of attention. The lingual nerve occupies the under part of the border of the tongue, runs along the stylo-glossus, and may be traced as far as the apex of the organ : it is sub-mucous in the whole of its extent. The hypo-glossal nerve is situated on a much lower plane, and occupies the under surface of the tongue, on each side of the median Une. Function. — The hypo-glossal is a muscular nerve : it regulates the movements of the tongue, while the lingual of the fifth and the glosso-pharyngeal confer sensibility upon it. This fact is most clearly established by anatomical, physiological, and pathological ob- servations. Like all nerves having a simple distribution, the hypo-glossal has not a plexiform structure. General View of the Cranial Nerves. All the spinal nerves present the greatest regularity in arising from two series of roots, in having a ganglionic enlargement on their posterior roots, and even in their course and termination, the differences or modifications of which depend on the different struc- ture of the parts to which they are distributed ; but the greatest irregularity appears to prevail in reference to the origin, the course, and the termination of the cranial nerves. From the comparison which has been made between the scull and the vertebrae, and from the possibility of resolving the bones of the cranium into a certain number of cra- nial vertebrae, anatomists have entertained the idea of drawing a parallel between the cranial and the spinal nerves. It has been conceived that the number of cranial nerves ought to be regulated by the number of cranial vertebras admitted by different anato- mists ; and, moreover, that in order to draw a fair comparison between these two sets of nerves, the special nerves of the face, namely, the olfactory, the optic, and the auditory nerves, should be entirely disregarded. Now we have already shown (see Osteology) that there are three cranial vertebrae, between which there are two inter- vertebral foramina ; that the anterior inter-vertebral foramen is represented by the sphenoidal fissure, to which we must annex the foramen rotundum and the foramen ovale ; and that the posterior inter- vertebral foramen is rep- resented by the foramen lacerum posterius, together with the anterior condyloid foramen. This being premised, we shall admit two pairs of cranial nerves, an anterior and a posterior. The posterior cranial pair consists on each side of the eighth and ninth nerves, namely, of the pneumogastric, glosso-pharyngeal, spinal accessory, and hypo-glossal nerves. The pneumogastric and the glosso-pharyngeal, each of which has a ganglion analogous to the inter- vertebral ganglia, represent the posterior roots of a spinal nerve, while the spi- nal accessory and the hypo-glossal, which have no ganglion, represent the anterior root. The two last-named nerves are exclusively motor, while the pneumogastric and the glosso-pharyngeal appear to me to be mixed nerves, that is, both sensory and motor. The anterior cranial pair is composed on each side of the fifth nerve, the ganglion of which is quite analogous to the inter- vertebral ganglia, and the large portion of the root of which accurately represents the posterior root of a spinal nerve ; and of the third or conmion motor nerve of the eye, of the fourth or pathetic nerve, of the sixth or exter • nal motor nerve of the eye, of the portio dura of the seventh, and, lastly, of the non- ganglionic portion of the fifth. All these last-named nerves are the nerves of motion ; while the ganglionic portion of the fifth is the nerve of sensation. Moreover, as the spinal nerves communicate with the ganglia of the great s3Tnpa- thetic, it is of importance, for the completion of our comparison, to determine the com- munications of the two cranial pairs of nerves with the same system of ganglia. Now Dr. Marshall Hall believes to be the cause of certain instinctive motions. (" On the Reflex Functions of the .Medulla Oblongata and MeduUa Spinalis."— PAtZ. Trans.. 1833.) 854 NEUROLOGY. I regard the superior cervical ganglion of the great sympathetic as common to the ivm supposed cranial pairs and to the three superior cervical pairs ; in fact, the superior cer vical ganglion communicates with all the branches of the posterior cranial pair, except- ing the spinal accessory, viz., with the pneumogastric, the glosso-pharyngeal, and the hypo-glossal ; and it also communicates with the anterior cranial pair, and more partic- ularly with the fifth and sixth nerves. As to the ophthalmic, spheno-palatine, otic, and sub-maxillary ganglia, which Arnold regards as annexed to the organs of the senses, viz., the ophthalmic to the eye, the spheno-palatine to the nose, the otic to the ear, and the sub-maxillary to the organ of taste, and which Bichat described as the cephalic portion of the great sympathetic, [ am of opinion that they are mere local ganglia, which do not form part of the general sym- pathetic system : besides, the ophthalmic and the otic ganglion only can be shown to be connected with the organs of any sense : it is impossible to show that the spheno-pala- tine ganglion, the very existence of which as a ganglion is often doubtful, has any con- nexions with the organ of smell, or that the sub-maxillary ganglion, which is much more closely connected with the sub-lingual gland, has any relations with the organ of taste. THE SYMPATHETIC SYSTEM OF NERVES. General Remarks. — The Cervical Portion of the Sympathetic. — The Superior Cervical Gan- glion — its Superior Branch, Carotid Plexus, and Cavernous Plexus — its Anterior, Exter- nal, Inferior, and Internal Branches. — The Middle Cervical Ganglion. — The Inferior Cer- vical Ganglion. — The Vertebral Plexus. — The Cardiac Nerves : Right, Superior, Middle, and Inferior, Left. — The Cardiac Ganglion and Plexuses. — The Thoracic Portion of the Sympathetic. — The External and Internal Branches. — The Splanchnic Nerves, Great and Small. — The Visceral Ganglia and Plexuses in the Abdomen, viz., the Solar Plexus and Semilunar Ganglia. — The Diaphragmatic and Supra-renal ; the Coeliac, the Superior Mesenteric, the Inferior Mesenteric, and the Renal, Spermatic, and Ovarian Plexuses. — The Lumbar Portion of the Sympathetic. — The Communicating, External, and Internal Branches. — The Lumbar Splanchnic Nerves and Visceral Plexuses in the Pelvis. — The Sacral Portion of the Sympathetic. — General View of the Sympathetic System. We have seen that the nerves arising from the cerebro-spinal axis are distributed to the organs of the senses, to the skin, to the muscles, in short, to all the organs of ani- mal life. The pneumogastric nerve alone is distributed to the organs of respiration, and the upper part of the alimentary canal, viz., the pharynx, the oesophagus, and the stom- ach. We shall now see that all the internal organs, which are beyond tlie influence of volition and consciousness, are provided with a special nervous apparatus, which is call- ed the great sympathetic, the sympathetic system, the ganglionic system, or the nervous sys- tem of organic or nutritive life. The sympathetic system consists of two long, knotted cords (/to v,fig. 268, in which figure these cords are represented as if drawn outward away from their natural position) extended one on each side of the vertebral column, from the first cervical to the last sacral vertebra ; these cords are enlarged opposite each vertebra, to form a series of ganglia, which communicate with all the spinal and cranial nerves on the one hand, and give off all the visceral branches on the other. The sympathetic system consists es- sentially of two distinct parts : of a central portion, formed by the two cords ; and of a visceral, median, or prevertebral portion, consisting of certain plexuses and ganglia, which communicate with the central cords, surround the arteries as if in sheaths, penetrate the viscera with them, and establish a communication between the sympathetic cords of the right and left sides. We cannot pay too much attention to the connexion be- tween the ganglionic nerves and the arteries, which always serve as a support for these nerves, and for which, according to some anatomists, the nerves are exclusively des- tined. Each half of the sympathetic system may be described in two ways : either as a con- tinuous cord, having ganglia at intervals upon it, or as a series of ganglia or centres, which may first be examined independently of each other, and around which all the fila- ments that enter or emerge from them may then be arranged. The first method, which is the more natural one, was adopted by the older anato- mists, who described the sympathetic in the same way as other nerves ; according to the second method, which is the one adopted by Bichat, all the ganglia, whatever situa- tion they may occupy, are included in the sympathetic system ; the ophthalmic, the spheno-palatine, and other cranial ganglia would, according to this view, be comprised in the sympathetic system. I believe that the better mode of description is one which associates the idea of a centre with that of a cord. In fact, as the sympathetic system consists of a double line, it is natural to describe it as a nervous cord, having two extremities, one cephalic, the other pelvic ; and as each ganglion forms the point of termination or of origin to a great THE SUPERIOR CERVICAL GANGLION. 856 number of nervous filaments, these bodies may very properly be regarded as central points. The visceral portion of the sympathetic nerves will be described with the gan- glia to which they are connected. * I shall describe in succession the cervical, the thoracic, the abdominal, and the pelvic portion of the s}aTipathetic. I have already said that I do not recognise any proper ce- phalic portion of this system of nerves, for the ophthalmic and the other cranial ganglia seem to me to belong to a totally different class The Cervical PortioiWf the Sympathetic System. The cerw:a„ portion of the sympathetic {ft, fig- 302) has this peculiarity, that, instead of being composed of as many ganglia as there are j?i^. 302. vertebrae, it has only two or three. This may be explained by supposing that the superior cervical ganglion represents by itself the ganglia which are wanting. It will hereafter be seen that the lumbar ganglia are rather frequently fused in a similar man- ner. The cervical portion of the sympathetic is situated on the anterior region of the vertebral col- umn, behind the internal and common carotid ar- teries, the internal jugular vein, and the pneumo- gastric nerve (p). It is connected to all these parts, and to the praevertebral muscles, by some very loose cellular tissue, a layer of fascia intervening between them ; it commences by a large fusiform ganglion, the superior cervical ganglion (/) ; this is succeeded by a nervous cord of variable size, which terminates in the middle cervical ganglion (a) when that exists, but when it is absent in the inferior cer- vical ganglion (t), which is continuous with the first thoracic ganglion, either directly or through the medium of two or three very remarkable nervous loops, or frequently by both methods of connexion. We shall proceed to examine the three cervical ganglia. The Superior Cervical Ganglion. Dissection. — Remove the corresponding ramus of the lower jaw ; separate the ganglion very careful- ly from the pneuraogastric, glosso-pharyngeal, and hypo-glossal nerves, behind which it is placed. In order to trace the superior or carotid branch, make an antero-posterior median section of the head ; open the foramen lacerum posterius from behind, in the manner indicated for exposing the pneumo- gastric, and then examine the ganglion and its su- perior branch from the inner side. The superior cervical ganglion (/) is olive-shaped or fusiform : it is situated in front of the second and third cervical vertebrae, from which it is sep- arated by the rectus capitis anticus ; it is behind the internal carotid artery, and the glosso-pharyn- geal, pneumogastric, and hypo-glossal nerves ; its upper extremity is about ten or twelve lines distant from the lower orifice of the carotid canal ; it is said to have been found two inches from it. It is larger than the other cervical ganglia {gan- glion cervicale magnum), but it varies much both in its length and its other dimensions ; thus, its low- er extremity has been seen to reach the fourth, fifth, and even the sixth cervical vertebra. Its col- our is grayish, and its surface smooth : not unfre- quently it is bifurcated at its lower extremity ; it is rather often double. Lobstein has figured a case of this kind ; and there were also two superior cervical ganglia, one placed above the other, in a case of hypertrophy of these ganglia, examined and represented by myself — (Anat. Path., liv. i., pi. 3.) These cases of a double superior cervical ganglion evidently depend on subdivision ol the single ganglion usually existing. The branches which end in or emerge from the superior cervical ganglion may be di- ' vided into superior, inferior, external, internal, and anterior. I shall divide them into those 856 NEUROLOGY. which communicate with the cranial and cervical nerves, those which communicate with the other cervical ganglia, and into arterial and visceral branches. The superior cervical ganglioR also gives off several twigs to the muscles of the prevertebral region. The superior cervical ganghon communicates with the cranial nerves by means of its superior or carotid branch and its anterior branches. It communicates with the cervical nerves by its external branches. It communicates with the other cervical ganglia by its inferior branch. Its visceral and arterial Ranches are the pharyngeal, the cardiac, and the branches for the external carotid, ^j^ The Superior or Carotid Branch from the Inferior Cervical Ganglion. The superior or carotid branch, or the branch of communication with the nerves which constitute the anterior cranial pair, has been for a long time regarded as the origin of the sympathetic nerve ; and as, previously to the time of Meckel, the anastomosis of this carotid branch with the sixth cranial nerve, or external motor of the eye, was the only one known, it was supposed that the sympathetic arose from the sixth nerve ; the discovery of the vidian nerve by the elder Meckel has led to the admission of two ori- gins or roots of the sympathetic, namely, one from the fifth and another from the sixth cranial nerve. Since the researches of modern anatomists, the study of the superior or carotid branch of the superior cervical ganglion has become one of the most complicated points in the anatomy of the nervous system. This carotid branch appears to be a prolongation of the superior cervical ganglion ; it tapers as it approaches the carotid canal, into which it enters, after having divided into two branches, one of which runs on the inner side and the other on the outer side of the artery. These branches communicate with each other, subdivide, and unite to form the carotid plexus, and having reached the cavernous sinus, form a plexus, named the cavernous plexus, which gives off the communicating branches to the sixth and fifth nerves, and also the small plexuses which surround the internal carotid and its branches.* Laumonier, and after him Lobstein and several others, described a ganghon, named the carotid ganglion, in the first turn of the carotid canal ; but it is in vain to search for it, unless some slight enlargements on the external and internal branches, wherevei they give off or receive twigs, are to be regarded as ganglionic. + During their course in the carotid canal, the external and internal divisions of the ca- rotid portion of the sympathetic give off the following branches : An Anastomotic Twig to the Nerve of Jacobson. — This comes off from the external branch, and is very small ; it perforates the external wall of the carotid canal, enters the cavity of the tympanum, and anastomoses with the nerve of Jacobson, a branch of the glosso-pharyngeal. An Anastomotic Twig to the Spheno-palatine, or McekeVs Ganglion. — This, like the pre- ceding, comes from the external division of the carotid branch of the sympathetic, and passes to the vidian or pterygoid branch of the superior maxillary nerve. We have al- ready spoken of this twig, under the name of the carotid or deep branch of the vidian nerve. Anatomists differ as to whether it should be regarded as passing from the fifth nerve to the superior cervical ganglion, or from the superior cervical ganglion to the fifth nerve. Arnold, on account of its grayish colour and slight consistence, regards it as coming from the superior cervical ganglion, while he believes the great superficial petrosal nerve, i. e., the cranial branch of the vidian, also from its colour and consist- ence, to belong to the cerebro-spinal system of nerves, and to be a branch of the fifth nerve. I have already said that I have never found sufficient difference between the superior petrosal and carotid branches of the vidian to warrant this distinction. These two nerves are, moreover, perfectly distinct from each other as far as the spheno-pala- tine ganglion, in which they terminate. It is important to observe that the two branches of the vidian nerve terminate in the enlargement called the spheno-palatine, or Meckel's ganglion : the connexion of this ganglion with the superior cervical ganglion has not been overlooked by those anato- mists who regard the spheno-palatine enlargement as a ganglion, and who consider the cranial ganglia as forming part of the sympathetic system. Anastomotic Branches to the Sixth Nerve. — Several branches, generally three, turn round the convex side of the second curve of the internal carotid, reach the outer side of that artery, and anastomose, either separately, or, after having united together, with the sixth or external motor oculi nerve. The nerves join at an acute angle opening backward, within the cavernous sinus, and at the point where the sixth nerve crosses the carotid ; as this nerve becomes flattened and widened opposite to the artery, it has been imagined that it was really enlarged, and that this augmentation was due to the addition of fila- ments from the sympathetic nerve ; but the enlargement is only apparent, and, notwith- standing the difference in colour, I should be inclined to admit that the communicating * The carotid branch is sometimes single, and turns spirally around the artery, being: placed at first behind, then on the outer side, next on the inner, and a^ain on the outer side of the vessel. t Arnold, whose authority upon such a subject is of great weight, has never seen this ganglion ; he very properly remarks, that even those anatomists vho admit the existence of it aro not agreed as to its situation THE CAVERNOUS PLEXUS, ETC. filaments between the sixth nerve and the carotid branches of the sympathetic are fur- nished by the sixth nerve, and have a reflected course. I have seen the three commu- nicating filaments between the upper part of the sympathetic and the sixth nerve form a ganglifonn enlargement as they were about to join the latter ; and it was this gangli- form enlargement which gave origin to the plexus surroimding the internal carotid ar- tery and its branches. The Cavernous Plexus. The cavernous plexus, in which the two divisions of the carotid branch of the superior cervical ganglion at length terminate, is situated on the inner side of the carotid artery, at the point where that vessel enters the cavernous sinus. From this grayish plexus, which is intermixed with small vessels (plexus nervoso-arteriosus, Walter), a consider- able number of filaments proceed, some of which establish a communication between it and the fifth nerve, while others surround the internal carotid, and accompany all its ramifications. The following very numerous branches emerge from the cavernous plexus : Some communicating Filaments to the Third Nerve or External Motor Oculi, before the Di- vision of that Nerve. — These filaments pass above the sixth nerve, to which they appear to be applied.* A Filament of Communication with the Ophthalmic Ganglion. — This arises from the an- terior part of the cavernous plexus, enters the orbit between the third nerve and the oph- thalmic division of the fifth, and unites sometimes with the long root of the ophthalmic ganglion, which we have stated to be derived from the nasal branch of the ophthalmic, and sometimes with the ophthalmic ganglion itself This root had been described and figured by Lecat, before Bock, Ribes, and Arnold recalled the attention of anatomists to it. It follows, from the arrangement just described, that the ophthalmic ganglion has three roots, two cerebro-spinal and one ganglionic. Communicating Filaments of the Fifth Nerve. — Some of these pass to the Gasserian gan- glion, and others to the ophthalmic division of the fifth.t The Filaments which accompany the Internal Carotid Artery and its Branches. — These are extremely delicate, but they are beautifully distinct in some subjects. They may be followed even upon the branches of the internal carotid. Anatomists admit the existence of a plexus for the ophthalmic artery, and for each of its subdivisions. It is even supposed that there is one for the arteria centralis retinae. t Several authors have described a certain number of filaments proceeding from the cavernous plexus to the pituitary body (filets sus-sphenoidaux, Chaussier). I have nev- er been fortunate enough to discover them, nor yet the ganglion (the ganghon of Ribes) which is said to exist upon the anterior communicating artery of the brain, and which is found at the point of junction of the right and left trunks of the sympathetic. It follows, from what has been stated, that the superior cervical ganglion, by means of its upper or carotid branch, communicates with most of the nerves of the anterior cra- nial pair ; namely, with the fifth nerve, by means of the Gasserian ganglion, of the oph- thalmic division of the fifth, and of the ophthalmic ganglion, either directly or indirectly ; also by means of the superior maxillary division of this nerve, through the intervention of the spheno-palatine ganglion ; secondly, with the third nerve ; and, lastly, with the sixth. The Anterior Branches from the Superior Cervical Ganglion. The anterior branches of the superior cervical ganglion establish a communication with the different nerves of the posterior cranial pair, excepting the spinal accessory nerve, which does not appear to have any direct communication with it. The glosso-pharyngeal and pneumogastric nerves communicate with the superioi cervical ganglion at two different points, viz., at their ganglia, and by their branches. The communication of the superior cervical ganglion with the ganglia of the glosso-pha ryngeal and pneumogastric nerves has been pointed out by Arnold ; it is difficult to dem onstrate it through the dense tissue which surrounds these ganglia. On the contrary, it is extremely easy to demonstrate the communications of the glos- so-pharyngeal nerve and the plexiform cord of the pneumogastric with the superior cer- vical ganglion. I have already said (see Pneumogastric Nerve) that in one case I found the pneumogastric so closely applied to the whole length of the superior cervical gangli- on, that it was impossible to separate them. The communication of the superior cervi- cal ganglion with the hypo-glossal is quite as evident as the preceding. The filaments of communication with the nerves forming the posterior cranial pair do not always proceed from the superior cervical ganglion itself, but sometimes from its ca. rotid branch. * I have never seen the communication between the superior cervical ganglion and the facial nerve noticed by some anatomists. t I may here again notice, that in two subjects I have seen a twig from the spheno-palatine ganglion join the communicating branches between the sixth nen-e and the sympathetic. t M. Ribes, Miimoires de la Societfi Medicale d'EmuIatiun, t. vii. .5Q NEUROLOGY. The External Branch from the Superior Cervical Ganglion The external branches of the superior cervical ganglion establish a communicatton be- tween it and the first, second, and third cervical nerves ; they are large, have a gray colour, and a ganglionic structure ; we may regard them as true prolongations of the superior cervical ganglion ; the principal of them enter the angle of bifurcation of the second cer vical nerve, into its ascending and descending branches ; the others, which are very small, join the first cervical nerve. They constitute a true ganglionic plexus, and often form two distinct groups. Frequently the superior cervical ganglion communicates only with the first and sec- ond cervical nerves. At other times it also communicates with the third and fourth nerves by means of a long and very oblique branch. In one case it communicated di- rectly with the phrenic nerve. The Inferior Branch from the Superior Cervical Ganglion. The inferior branch from the superior cervical ganglion, or the branch of communica tion with the middle cervical ganglion, is a white cord, resembling a spinal nerve, ex- cepting in a few cases, in which it appears to be a prolongation of the tissue of the ganglion itself: when the lower extremity of the superior cervical ganglion is divided into two parts, its inferior branch arises from the external division. It varies much in size in different subjects : it descends vertically in front of the spinal column, behind the com- mon carotid, the internal jugular vein, and the pnemnogastric nerve, to which it is uni- ted by a very loose cellular tissue. Having reached the inferior thyroid artery, the cord of the sympathetic passes behind that vessel, and enters the middle cervical ganglion, when that exists ; but when it is ab- sent, the cord continues on to join the inferior cervical ganglion. As it descends, it most commonly receives some twigs from the third and fourth cervical nerves, which twigs we have already said occasionally enter the superior cervical ganglion. At its origin, it gives off on the inner side two filaments, which join the superior cardiac nerve, and in- crease its size ; and an anastomotic twig to the external laryngeal nerve, a branch of the superior laryngeal. Not unfrequently the superior cardiac nerve arises entirely from the communicating branch between the superior and middle cervical ganglia, that branch appearing to bifurcate. The communication between the superior and middle cervical ganglia is subject to much variety. I have seen a small ganglion upon it opposite to the inferior thyroid ar- tery ; from this ganglion, which rested upon the artery, and which might be regarded as the vestige of a middle cervical ganglion; two cords proceeded, an anterior, which join- ed the cardiac nerve, and a posterior, which ended in the inferior cervical ganglion : both of these had a gangliform structure. The cord of the sympathetic is not uncom- monly found enlarged at intervals into ganglionic nodules. The Internal Branches, or Carotid and Visceral Branches. The internal branches from the superior cervical ganglion are divided into those which accompany the external carotid and its ramifications, and those which are distributed to the viscera. The Carotid Branches. — It has been stated that from the upper extremity of the supe- rior cervical ganglion certain branches are given off, which surround the internal carot- id, and are prolonged upon its ramifications. From the inner border of the same ganglion other branches proceed, which embrace the external carotid and the ramifications of that vessel. These nerves are of a gray colour (subruji), of a soft texture (nervi molles et pene mu- cosi, Scarpa), and of a knotted and gangliform structure (rami gangliformes, Neubauer) ; they come off from the ganglion opposite to the origin of the facial artery ; they pass in- ward behind the external and internal carotids, and form a sort of gray plexus, which ex- tends as far as the origin of the internal and external carotid ;* they turn like a loop around the former of these vessels, and anastomose with the carotid filaments from the glosso-phaiyngeal, and from the pharyngeal and superior laryngeal branches of the pneu- mogastric. None of the branches from this plexus are prolonged upon the conmuon ca- rotid ; they all pass upon the external carotid and its different ramifications, forming as many plexuses as there are vessels, and are distributed with those vessels to the neck and the face. Thus, there is a thyroid plexus, which surrounds the superior thyroid ar- tery, and may be traced into the thjToid body ; a lingual plexus, which enters the sub- stance of the tongue, and is supposed to anastomose with the lingual branch of the infe- rior maxillary division of the fifth, and even with the hypo-glossal nerve ; and & facial plexus, which is supposed to anastomose with the facial nerve. Anatomists have par- ticularly directed their attention to the branches which enter the sub-maxillary gland ; some imagining, and others regarding it as certain, that these branches communicate with the sub-maxillaiy ganglion. I have never been fortunate enough to discover this communication. * At this division there is frequently a gangliform enlargement, which Arnold proposes to call the inter-ca- rotid ganglion. THE MIDDLE AND INFERIOR CERVICAL GANGLIA. 8S9 There is, moreover, a pharyngeal plexus, an occipital plexus, and an auricular plexus : the elder Meckel* has even described an anastomosis between the facial nerve and the sympathetic filament which accompanies the posterior auricular artery. Lastly, the temporal artery, and the internal maxillary artery and its divisions, are also surrounded (hederae ad modum, Scarpa) by small nervous plexuses ; these plexuses are sometimes so well developed, that the elder Meckel states that the arteries of the face have larger nervous plexuses than any others in the body. These plexuses appear to me to be pe- culiarly remarkable for containing a mixture of white fibres and nervi molles, which proves their double origin. All these plexuses present gangliform enlargements at various points, as is shown in the splendid plate in Scarpa's work.t This author has figured, after Andersh, a gangli- on which he believes to be constant at the division of the external carotid and temporal arteries. A twig from the facial nerve terminates in this ganghon.f The Visceral Branches. — All these come off from the inner side of the ganglion, and divide into pharyngeal, laryngeal, and cardiac branches. The pharyngeal branches are certain thick ganglionic cords which arise from the upper and inner part of the superior cervical ganglion, pass transversely inward, and combine with the pharyngeal branches of the glosso-pharyngeal and pneumogastric nerves to form one of the most remarkable plexuses in the body, which is distributed to the pha- rynx. To this plexus must be relterred all those highly important nervous phenomena which are manifested in connexion with the pharynx, more particularly the sensation of thirst. • The laryngeal branches unite with the superior laryngeal nerve and its divisions. In a case in which the external laryngeal nerve arose separately from the pneumogastric and not from the superior laryngeal, it had as many filaments of origin from the superior cervical ganglion as from the pneumogastric itself The cardiac branches form the superior cardiac nerve, to which I shall recur after hav ing described the middle and inferior cervical ganglia. The Middle Cervical Ganglion. The middle cervical ganglion {a, Jig. 302) is wanting in a great number of subjects, and then the branches usually given off from and received by it are given off and received by the cords which connect the superior and inferior cervical ganglia, or by the inferior cervical ganglion itself The middle cervical ganglion is sometimes double ; at othe'' times it is in quite a rudimentary state. It is situated on a level with the fifth or sixth cervical vertebra, in front of the inferior thyroid artery, opposite to the first curve of that vessel, and sometimes behind it ; its relation to this artery, which is very nearly constant, induced Haller to name it the thy- roid ganglion : however, I have frequently seen it eight lines above that artery. Its form and size are extremely variable, not only in different subjects, but even upon oppo- site sides of the same subject.' Sometimes it is a simple gangliform enlargement. Scarpa has figured a middle cervical ganglion almost as large as the superior, and, like it, olive-shaped. I have never seen it as large as this.^ The middle cervical ganglion, when it exists, receives, Above, the cord which communicates with the superior cervical ganglion ; below, the cord of communication, often multiple, with the inferior cervical ganglion ; on the out side, three branches, derived from the third, fourth, and fifth cervical nerves : not un- frequently the communicating branch from the fourth cervical nerve belongs to the phrenic ; on the inside, the middle cardiac nerve, or great cardiac of Scarpa, which I shall presently describe. The size of the middle cervical ganglion has always appeared to me to be proportioned to that of its filaments of communication with the cervical nerves. The Inferior Cervical Ganglion. Neubauer has given an excellent description of the inferior cervical ganglion, under the name of the first thoracic ganglion, rather an appropriate title for it, because it is fre- quently continuous with the first thoracic ganglion (as at i, fig. 302) ; and, secondly, be- cause it is situated in front of the transverse process of the seventh cervical vertebra and of the head of the first rib. This ganglion is constant ; it is deeply seated behind the origin of the vertebral artery, by which it is completely concealed. Ii * M6moires de I'Acad. de Berlin, 1752. t Tabulae Neurologicae, tab. iii., 1794. T Arnold has described and figured a twig from the plexus which surrounds the middle meningeal or spheno- spinous artery, and which, according to this laborious inquirer, terminates in the otic ganglion ; he also de scribes some nervous twigs passing from the plexus of the ascending palatine artery to the sub-maxillary ganglion. In this way he establishes a connexion between the sympathetic system and these two cranial gan- glia. I have devoted great care to this subject, but have never been able to make out these communicating filaments, even though all the difficult dissections have been made upon specimens previously macerated in diluted nitric acid. 1) I believe that it is incorrect to regard as a middle cervical ganglion those ganglionic nodules, without either afferent or efferent filaments, which are rather frequently found at various points on the trunk of the sympathetic. H It is not rare to see the inferior cervical ganglion describe around the vertebral artery a half ring, which is completed in front by a gray cord extended from one end of the ganglion to the other. 860 NEUROLOGY. It is of a semilunar shape, its concave border being turned upward and its convex one downward ; at its internal extremity it receives the trunk of the sympathetic ; at its ex- ternal extremity it receives a large nerve which accompanies the vertebral artery, and which may be called the vertebral nerve ; at the same extremity it also receives some communicating branches from the fifth, sixth, and seventh cervical nerves, and often from the first dorsal. Several branches proceed from its convex border, which is turned downward ; some pass in front of and others behind the sub-clavian artery, which they embrace like loops. Most of these inferior branches are the communicating branches between the inferior cervical and the superior thoracic ganglion, and they exist even when the two ganglia are directly continuous with each other. One of the branches sometimes joins the recurrent laryngeal branch of the pneumogastric ; the most remark- able of the inferior branches constitutes the inferior cardiac nerve, which is rather fre- quently derived from the superior thoracic ganglion. To complete the description of the cervical portion of the sympathetic, we have now only to speak of the vertebral nerve and of the cardiac nerves. The Vertebral Plexus. The vertebral plexus or vertebral nerve occupies the canal which is formed for the verte- bral artery in the transverse processes. It is generally said that this nerve arises from the inferior cervical ganglion ; that it traverses the entire length of the canal formed for the vertebral artery, enters the cranium with that vessel, and then unites with its fel- low of the opposite side to form the basilar plexus, which divides and subdivides around the terminal ramifications of the basilar artery, like the plexuses which are formed around the internal carotid ; but such is not a correct description of the nerve. It ap- pears to me to be formed by the junction of filaments derived from the third, fourth, and fifth cervical nerves, gradually to increase in size from above downward as it receives new filaments, then to pass behind the artery, to emerge from the canal also behind the vessel, and, finally, to enter the inferior cervical ganglion. I conceive that this branch is intended to establish a communication between the third, fourth, and fifth cervical nerves and the inferior cervical ganglion. I have never found upon these branches the swellings or gangli which, according to M. Blainville's ingenious idea, might be intend- ed to supply the place of the cervical sympathetic ganglia, and to destroy the appear- ance of irregularity which exists in the cervical region in this respect. The Cardiac Jferves. Dissection. — This comprises the dissection of the cardiac nerves, from their origin to the point where the aorta and pulmonary artery cross each other ; and from that point to the extreme divisions of the nerves. For this purpose, after having previously ex- posed the cervical ganglia and the cardiac nerves, the preparation should be macerated in diluted nitric acid ; all the internal nerves which proceed from the ganglion should then be carefully dissected, so as to preserve their relations with the cardiac branches of the pneumogastric and recurrent nerves ; we must then examine the nerves which pass in front of the aorta, those which run between that vessel and the pulmonary ar- tery and trachea, and, lastly, those which pass behind the pulmonary artery ; we should study, at the same time, their relations with the anterior and posterior cardiac plexuses. The cardiac nerves, or nerves of the heart, which are distinguished into the right and the left,* arise essentially from the cervical ganglia. These ganglionic nerves are then joined by several branches from the pneumogastric ; they all converge upon the origin of the aorta and pulmonary artery to form the cardiac plexuses, which give off the right and left coronari/ plexuses ; these latter plexuses surround the coronary arteries, and their branches are scattered over the surface of the heart, but do not enter its substance un- til they have advanced a considerable distance beneath the serous membrane by which the heart is covered. Such is the most general idea that can be given of the cardiac nerves and plexuses, which afford one example of the most remarkable of the median anastomoses. Scarpa first described and figured them correctly in his plates, which will always be models for anatomical drawings. No nerves present so many varieties, in number, size, and ori- gin, as the cardiac nerves ; and on this subject especially, the want of a work upon ana- tomical varieties is especicilly felt. For my part, I declare that I have never found the cardiac nerves in my dissections as they are represented in Scarpa's magnificent plates, * The history of flie nerves of the heart is singular. The ancient philosophers, with Aristotle, influenced by certain preconceiited ideas, staled that the heart was the source of all the nerves in the body. Galen re- futed this opinion, and J^dmitted that the heart had but one very small nerve, which descended from the brain. Vesalius considered that this slender nerve came from the recurrent, and represented it in a figure. Fallo pius first described the nerves of the heart, and says that he showed his audience " insignem nervorum plexum » quo ahundans copia nervosa materia totam cordis basim complexatur, pergue ipsam plures propagines parvo- rum nervorum dispergit." Behrends, in 1792, defended a thesis in which he endeavoured to demonstrate that the heart has no nerves, cornervis carere. Such was the amount of knowledge on this subject when, in 1794, Scarpa published his splendid work, and settled the state of science on this point. — (.Tabulae Neurohgicee ad Illustrandam Anatomiam Cardiacorum Nervorum, Noni Nervorum Cerebri, Glosso-pharyngax et Pharynga:i ex Octavo Cerebri.) THE RIGHT CARDIAC NERVES. Wfl which have served as the type for all descriptions. I have minutely described the cardiac nerves in eight different subjects ; these eight descriptions present very great differen- ces, at least, until one arrives at the account of the cardiac plexuses ; the ultimate dis- tribution of the nerves of the heart appeared to be the same in all these subjects. All the cardiac nerves are gray, but they are not all soft, as declared by Scarpa, who called them nervi molles. Sometimes the right, and sometimes the left cardiac nerves, are the larger ; the nerves of the two sides are inversely proportioned to each other in this respect, and there is evidently a mutual dependance between them. In one case, in which tlie middle and inferior cardiac nerves of the right side were wanting, and the superior cardiac nerve very small, their places were supplied by some large branches from the right recurrent nerve, and by the left cardiac nerves, which were largely de- veloped. Anatomists follow Scarpa in describing three cardiac nerves on each side : a superior, named by him the superficial cardiac nerve, which is derived from the superior cervical ganglion ; a middle, called by him the great or deep cardiac nerve, which arises from the middle cervical ganglion ; and an inferior, or small cardiac nerve, proceeding from the inferior cervical ganglion. Although this is the usual arrangement, it is often impossible to distinguish three nerves, in consequence of the anatomical varieties which I have al- ready mentioned. There is frequently no middle cardiac nerve properly so called ; at other times there is no inferior cardiac nerve, or, rather, they are both in a rudimentary state ; lastly, the superior cardiac nerve, if not entirely wanting, may be extremely small, and may join the middle cardiac nerve. Sometimes all the cardiac nerves of one side unite into a single trunk, or else into a plexus situated behind the sub-clavian artery, upon the side of the trachea ; the recurrent nerve assists in forming this plexus, from which three, four, or more branches are given off to be distributed to the heart in the usual manner. One of the most important points in the history of the cardiac nerves is their sort of fusion with the pneumogastric, which is so intimate that the cardiac branch- es of the pneumogastric, and those which come from the ganglia, form a single system. There is a similar fusion between the superior, middle, and inferior cardiac nerVes of each side, and between the nerves of the two sides. The recurrent nerve, in particular, appears sometimae to be distributed equally to the larynx and the heart, so large and numerous are the cardiac branches given off from it ; it will hereafter be seen that there is an equally intimate connexion between the pneu- mogastric nerve and the solar plexus. I shall first describe in detail the right cardiac nerves, and shall then briefly point out the differences between them and the left cardiac nerves. The Right Cardiac Nerves. The Superior Cardiac Nerve. — Its origin is very variable. Most commonly, it arises from the internal division of the bifurcated lower extremity of the superior cervical gan- glion, the cord of communication between the superior and the next cervical ganglion forming the external division. At other times it arises from the communicating cord. In a great number of cases it has several origins, being formed by two or three very small filaments, which come from the inner side of the superior cervical ganglion ; by a branch, often a large one, from the cord of communication ; and by two filaments from the pneumogastric nerve. In one of these latter cases the cardiac branch from the cord of conmiunication presented a very distinct ganglion. Whatever may be its origin, the superior cardiac nerve passes obliquely doTvnward and inward, behind the common carotid, from which it is separated by a very thin layer of fascia, so that it is almost impossible to include it in applying a ligature to that artery ; it runs along the trachea, very often receives a branch from the trunk of the sympathet- ic, and crosses in front of the inferior thyroid artery, or sometimes divides into two branch- es, one of which, the anterior, passes in front of the artery, while the posterior joins the recurrent nerve.* At the lower part of the neck the superior cardiac nerve runs along the recurrent laryngeal nerve, with which it may be confounded ; it enters the thorax, passing behind and sometimes in front of the sub-clavian artery,t runs along the brachio- cephalic trunk, gains the back of the arch of the aorta, gives off a certain number of fila- ments, which pass in front of that part of the vessel, then runs obliquely downward and to the lelt between the arch of the aorta and the trachea, anastomoses very fi-equently with the middle and inferior cardiac nerves and with the branches of the recurrent, and divides into two sets of filaments ; some of these pass between the aorta and the pul- monary artery, and others between the right puhnonary trunk and the trachea ; they both * The trunk of the sympathetic, havin? reached the inferior thyroid artery, sometimes divides into two branches, one of which passes in front of that artery, to join the superior cardiac nerve, while the other passes behind it to the inferior cervical ganglion ; not nnfrequently the superior OM-diac nerve presents a ganglionic enlargement, which occupies the whole or a part of the thickness of the nerve. t The superior cardiac nerve often bifurcates so as to embrace the sub-clavian artery in a complete ring. At other times the superior cardiac nerve passes liehind the sub-clavian artery, and the cardiac branch of the pneumogastric in front of it, so as to form beneath the sub-clavian an anastomotic loop, which lies to the inner side of the one formed by the recurrent nerve. Most commonly the cardiac branch of the pneumogastric anas tomoses with the superior cardiac nerve, between the arch of the aorta and the trachea. 862 NEUROLOGY. anastomose with the left cardiac nerves, and are arranged as we shall soon describe. In some rare cases, the right superior cardiac nerve goes directly to the cardiac plexus, without anastomosing with the middle and inferior cardiac nerves. During its course along the neck, the right superior cardiac nerve receives the small superior cardiac branches of the pneumogastric, and gives off several filaments, some to the pharynx, others to the trachea and the thyroid body, while several assist in forming the plexus of the inferior thyroid artery ; it often gives off three or four branches which anastomose with the recurrent nerve. In the thorax, the superior cardiac nerve is joined by the cardiac branch given off by the pneumogastric in the lower part of the neck, and which is sometimes of very consid- erable size, and evidently re-enforces the cardiac nerve ; this branch of the pneumogas- tric sometimes terminates directly in the cardiac plexus. The Middle Cardiac Nerve. — This nerve arises from the middle cervical ganglion, or, when that is absent, from the trunk of the sympathetic, at a variable distance from the inferior cervical ganglion. It is rather frequently the largest of the cardiac nerves, and has, therefore, been called by Scarpa the great cardiac nerve {magnus, jirofundus). At other times it is in a rudimentary state, and is replaced either by the superior or the in- ferior cardiac nerve, or by branches from the recurrent : it frequently divides into sev- eral twigs, between which the sub-clavian passes ; it almost always anastomoses with the superior and inferior cardiac nerves of the same side, runs along the recurrent nerve, for which it might be mistaken, and with which it is always connected, and then terminates in the cardiac plexus. The Inferior Cardiac Nerve. — This is generally smaller {cardiacus minor) than the pre- ceding nerve, though it is sometimes larger ; it usually arises from the inferior cervical ganglion, but rather fequently from the first thoracic ; it accompanies the middle cardi- ac nerve, anastomoses with that nerve, and, like it, descends vertically in front of the trachea, and terminates in the cardiac plexus. The connexion of the middle and inferior cardiac nerves with the recurrent nerve de- mands especial attention. Sometimes the recurrent sends off certain large branches which join the cardiac nerves, and form their principal origin. I have seen the middle and inferior cardiac nerves united together, crossing over the recurrent nerve at right angles, and adhering intimately to it without presenting that admixture of filaments which constitutes an anastomosis.* The Left Cardiac Nerves. The peculiarities of the left cardiac nerves maybe stated in a few words :t in the neck, they are situated in front of the oesophagus, on account of the position of that canal. The connexions between the cardiac nerves and the recurrent on the left side appear to me more numerous than those on the right. In one case, the superior and inferior car- diac nerves gave off a series of four rather large filaments, which ran along the recur- rent, left that nerve opposite to its point of reflection, and then terminated in the usual manner. I ascertained that, in this case, the two nerves were merely in contact, and did not anastomose. In the thorax, the superior and middle cardiac nerves of the left side descend between the carotid and sub-clavian, and then run upon the concavity of the arch of the aorta ; the inferior cardiac nerve, which is the largest of all the cardiac nerves in a subject which I have now before me, passes to the left of the trunk of the pulmonary artery, turns round its back part, and embraces it in a loop, so as to enter that portion of the cardiac plexus which is situated between the aorta and the right division of the pulmo- nary artery. Lastly, on the left side, more commonly than on the right, the anterior pulmonary plexus sends off some filaments to this same part of the cardiac plexus. The Cardiac Ganglion and Plexuses. We have seen that the cardiac nerves of the same side anastomose with eacn other on the sides or in front of the trachea. Besides this, the right cardiac nerves anasto- mose with the left upon the concavity of the arch of the aorta ; also in front of the tra- chea, above the right pulmonary artery ; and, lastly, in the anterior and posterior coro- nary plexuses. Wrisberg was the first to describe a ganglion in the situation of the first-named anas- tomosis, that is to say, upon the concavity of the arch of the aorta, between that vessel and the pulmonary artery, to the right of the remains of the ductus arteriosus. This ganglion, which is by no means constant, is named the cardiac ganglion ; it is joined [so as to form the superficial cardiac plexus] by the superior cardiac nerve of the right side, * It is especially in these anastomoses between the cardiac and recurrent nerves that I have been able, from the different aspect of the iiljuaents of each, to ascertain that the anastomoses of nerves are often mere- ly apparent, and consist of a simple^uxtaposition of two nerves without any communication of their component fasciculi, which can be traced uninterruptedly from their entrance to their emergence. The same observa- tion applies also to some of the anastomoses between nerves of the same kind. t In one subject, three filaments arose from the left superior cervical ganglion, and united in a small gan- glionic nodule, which also received a twig from the laryngeal nerve. This ganglionic nodule gave off several pharyngeal twigs, and also the superior cardiac nerve THORACIC PORTION OP THE SYMPATHETIC SYSTEM. 863 by the same nerve of the left side, and sometimes also by the right and left cardiac branches given off from the pneumogastric nerves in the lower part of the neck. The second anastomosis, or that which takes place in front of the trachea, above the right pulmonary artery, and behind the arch of the aorta, has been known, since the time of Haller, as thJB great cardiac plexus (magnus, profundus plexus cardiacus, Scarpa). A ganglionic enlargement is not unfrequently found at the junction of the principal branch- es. This great cardiac plexus is chiefly formed by the middle and inferior cardiac nerves of both sides : [it also receives part of the right superficial nerves.] Lastly, all the car- diac nerves end in the third set of anastomoses, namely, those upon the anterior and posterior coronary arteries around the root of the aorta. Great as the variety may be in the course and size of the cardiac nerves up to the origin of the great vessels from the heart, there is as constant a uniformity in their ar- rangement around those vessels, and in their ultimate distribution to the heart. Upon the origin of the great vessels, the cardiac nerves are arranged in three layers or sets. The superficial layer of nerves is the smallest ; it occupies the anterior surface of the arch of the aorta, and especially its right side ; the nerves are visible without any dis- section through the transparent pericardium ; they all pass {v) to the anterior coronary artery, to the right side of the infundibulum of the right ventricle. In this superficial layer, the superficial cardiac plexus, may be included the ganglion of Wrisberg, when it exists, and its several branches, which in a great measure assist in forming the anterior coronary plexus. The middle layer of nerves is composed of two very distinct parts, viz., of the great or deep cardiac plexus of Haller, which is situated between the trachea and the arch of the aorta, above the right pulmonary artery ; and of a much smaller part, situated below the great cardiac plexus, from which it is derived, and between the right pulmonary artery and the arch of the aorta. In order to obtain a good view of this layer, the arch of the aorta must be cut through. The deep layer of nerves is situated between the right pulmonary artery and the bifur- cation of the trachea. The trunk of the pulmonary artery must be divided in order to expose it. The Anterior and Posterior Coronary Plexuses. — ^The whole of the superficial cardiac plexus or superficial layer of nerves ends in the anterior coronary plexus (») which sur- rounds the right coronary artery. The middle and posterior layers unite below the right pulmonary artery, in front of the auricles, to form a plexus, which might more properly be named the great or deep cardiac plexus than the interlacement so called by Haller. From this plexus, into which the left inferior cardiac nerve enters directly, the follow- ing branches proceed : anterior auricular branches, which are very numerous ; certain branches which pass between the aorta and the pulmonary artery to gain the right side of the infundibulum, and join the anterior coronary plexus, which, as we have seen al- ready, is derived from the superficial cardiac plexus ; lastly, the branches for the poste- rior coronary plexus, which surrounds the origin of the left coronary artery, and divides, like that vessel, into two secondary plexuses, one of which runs round the left auriculo- ventricular furrow, while the other (»') enters the anterior ventricular furrow. The nervous filaments from these plexuses soon leave the ramifications of the arter- ies ; they proceed separately ; they are all equally small, and can be seen without any dissection, like white lines, extending from the base towards the apex of the heart. They all belong to the ventricular portion of the heart ; a few of them, however, ascend on the posterior surface of the auricles, which are much more abundantly supplied upon their anterior surface. The cardiac nerves are not entirely distributed to the heart ; several of them are lost in the coats of the aorta, some join the anterior pulmonary plexus, and some ramify in the pericardium. The Thoracic Portion of the Sympathetic System. In the thorax, the trunk of the sympathetic (i t, fig. 302) consists, on each side, of a grayish cord, having as many nodules or ganglia upon it as there are vertebrae. This cord is situated, not in front of the dorsal vertebrae, but in front of the heads of the ribs, to which the gangUa for the most part correspond : the two superior thoracic ganglia are the largest, and are almost always united ; the succeeding ganglia are almost of equal size, the twelfth being next in size to the first and second. The ganglionic struc- ture is observed throughout the whole extent of this part of the sympathetic, so that the cords of communication between the ganglia may be said to be merely prolongations of the ganglia. In some subjects the ganglia cannot be distinguished from the portions of the sympathetic trunk above and below them, except by the branches which enter and converge from those points ; it would, therefore, be a serious anatomical error to regard the portions of the trunk between the ganglia as mere filaments of communica- tion. In some subjects the cords between the ganglia are divided into two or three fila- ments. The varieties observed in the number of the thoracic ganglia are rather appa- 864 NEUROLOGY. rent than real : tliey depend, some upon fusion of the first thoracic ganglion with the inferior cervical ganglion, or of the first and second thoracic ganglia ; others upon fusion of two central ganglia, or upon that, which is more common, of the last thoracic with the first lumbar ganglion ; upon a transposition of the last thoracic ganglion, which is then found upon the first lumbar vertebra ; and, lastly, upon the two inferior thoracic ganglia being situated in the last intercostal space. Besides this, the three lowest tho- -acic ganglia are subject to much variety, both in situation and in shape ; and the same may be said of the mode of connexion between the twelfth thoracic and the first lumbar ganglion. The thoracic portion of the sympathetic lies beneath the pleura and the very thin fibrous layer by which that membrane is strengthened. It can be distinctly seen with- out any dissection, in consequence of the transparency of these layers. The intercos- tal arteries and veins pass behind it ; on the right side, the vena azygos runs along it. The thoracic portion of the sympathetic gives off external branches, or branches of communication with the dorsal nerves ; and the internal branches, which are intended for the aorta and the abdominal viscera. The External or Spinal Branches. There are at least two spinal branches from each ganglion, one superficial and larger, which is connected to the outer angle of the ganglion ; the other deep and smaller, which is attached to its posterior surface : there is sometimes a third filament of com- munication. Not unfrequently these branches unite into a single trunk, before reaching the ganglion. I regard these anastomotic branches (e e), between the spinal nerves and the ganglia of the sympathetic, not as branches furnished by the ganglia to the spinal nerves, nor simply as means of communication between one and the other, but rather as branches of origin of the sympathetic : this, indeed, is clearly demonstrated by the arrangement of these spinal branches of the sympathetic, which are always proportioned to the size of the ganglia from which they arise. In general, each ganglion communicates only with the corresponding spinal nerve ; not unfrequently, however, a ganglion receives a twig from the intercostal nerve immediately below it.* The branches of conununication from the dorsal nerves to the thoracic ganglia of the sympathetic are horizontal, or, rather, they are inclined obliquely downward and inward, excepting those which ascend to the first thoracic ganglion, and those which descend to join the last thoracic ganglion. These branches are white, like the nerves of the cere- bro-spinal system, and not gray, like the ganglionic nerves. On examining their ulti- mate distribution in the sympathetic ganglia, and their connexions with the dorsal and intercostal nerves, after the parts have been macerated, first in diluted nitric acid and then in water, it is seen that these branches are evidently reflected funiculi of the spi- nal nerves ; and that the nerves, immediately after having given off these branches, are proportionally diminished in size ; that, having reached the ganglia, the communicating branches divide into filaments, of which some ascend, and may be traced upon the trunk of the sympathetic above the ganglion, and appear to be continuous with the descending filaments derived from the spinal nerve above, while the others descend to pass upon the portion of the sympathetic trunk below the ganglion ; and, lastly, that these white fila- ments run upon the surface of the sympathetic, and contrast with the gray colour of the central portion of that nerve. The Internal, or Aortic and Splanchnic Branches. The internal branches of the first five or six thoracic ganglia are exclusively intended fo~ the aorta ; some of them appear to enter the pulmonary plexus. Some of the internal branches of the last six thoracic ganglia are intended for the aorta, and the remainder, which are the principal, unite to form the splanchnic nerves or nerves of the abdominal viscera. I have never seen any of them pass to the oesophagus. The Aortic Branches. — The aortic branches consist of very small filaments, of which two or three proceed from each ganglion. They accompany the intercostal arteries, around which they form small plexuses. These filaments are much longer on the right than on the left side, on account of the position of the aorta ; they pass, some in front and others behind that vessel, upon which it soon becomes impossible to follow them. The aortic branch from the fourth thoracic ganglion is the only one of any considerable size ; it appears to be shared between the aorta and the pulmonary plexus. A number of these aortic filaments sometimes converge towards certain small knots or ganglia, which are arranged in front or along the sides of the aorta, and give off a number of fil- aments. The first thoraci© ganglion sends some twigs to the cardiac plexuses ; and not unfre- * In one subject I found a yery remarkable disposition of the branches for the four inferior thoracic gang-lia. Some small twigs from these four ganglia terminated in a minute gangliform structure, which gave off the branches to the spinal nerves. It will be seen that the same arrangement frequently occurs in the lumbal region. THE SPLANCHNIC NERVES. ISIJJJ quently the inferior cardiac nerve proceeds from this ganglion. Some filaments from the same ganglion are distributed to the lower part of the longus colli muscle. Lobstein (De Nerco Magna Sympathetica, p. 19) describes a very delicate filament from this ganglion, which perforates the anterior common vertebral ligament, and enters the substance of one of the vertebrae. A similar filament appears to me to be given off by all the cervical, thoracic, lumbar, and sacral s)Tnpathetic ganglia. The vertebrae like the other bones, are provided with nerves, which are overlooked in a hasty examination from their excessive tenuity. The Splanchnic Branches. — ^These constitute the splanchnic nerves, which require a separate description. The Splanchnic Jferves. The splanchnic nerves are divided into the great splanchnic and the small splanchnic or renal * The Great Splanchnic Nerve. — ^The great splanchnic is a white nerve, and has no re- semblance to the ganglionic nerves. It is formed in the following manner : a thick branch derived from the sixth and seventh thoracic ganglia, sometimes also from the fifth, and even from the fourth ganglion (see fig. 302), passes downward and inward upon the side of the dorsal vertebrae : this branch is joined by a series of three or four smaller branches given off not only from the succeeding thoracic ganglia, but also from the com- municating cords between them ; these branches {g g) are parallel to each other, and pass obliquely downward and inward. The eleventh and twelfth thoracic ganglia never assist in the formation of the great splanchnic nerve. The branches just mentioned unite on each side to constitute the great splanchnic nerves, which have the same relation to the thoracic ganglia that the cardiac nerves have to the cervical ganglia : it is important to remark that the ganglionic nerves of the thoracic viscera are derived from the cervical ganglia of the sympathetic, and that the ganglionic nerves of the abdominal viscera are given off from the thoracic ganglia. In general, the great splanchnic nerve arises by four roots ; but not unfrequently it arises only by two, which then represent the four origins. If, after having macerated the parts in diluted nitric acid, an attempt be made to de- termine exactly the highest point from which the great splanchnic nerve originates, it will be seen that the white filaments of which this nerve is composed are already dis- tinct opposite the third thoracic ganglion, and, moreover, that they are merely in contact with the trunk of the sympathetic and with the ganglia, and are continuous with the coomiunicating branches from the spinal nerves. Anatomy, therefore, most clearly proves that the splanchnic nerve is continuous with the spinal nerves. Thus formed and completed opposite to the eleventh rib, the great splanchnic nerve passes downward and inward in front of the vertebral column ; it becomes flattened and' widened, perforates the diaphragm, the fibres of which separate to allow it to pass through, and immediately terminates in the semilunar ganglion {x). An oUve-shaped ganglion is not unfrequently found upon the great splanchnic, at a short distance before the nerve passes through the diaphragm.* The Small Splanchnic, or Renal Nerves.-^ think it proper to include in the same de- scription the lesser splanchnic nerve of authors, and the posterior renal nerves of Walter, the distinction between these nerves appearing to me to be quite arbitrary. They are two, ani sometimes three in number. The highest is named the small splanchnic (h) ; it arises from the eleventh thoracic ganglion, and sometimes from both the tenth and the eleventh. The lowest, which is the renal nerve of authors, is larger than the preceding, and is derived from the twelfth thoracic ganglion (f) : it often gives off a small fileunent to the first lumbar ganglion, and in a great number of cases this is the only means of communication between the thoracic and the lumbar ganglia of the sympathetic. In such a case, the series of ganglia is said to be interrupted ; but a complete interruption never exists. The small splanchnic or renal nerves exactly resemble the separate or single origins of the great splanchnic, with which they form a continuous series. They arise in the same manner, from the two or three inferior thoracic ganglia. They pass inward and downward, parallel to and on the outer side of the great splanchnic, perforate the crus of the diaphragm either to the outer side of or at the same point as the great nerve, and enter the renal and aortic plexuses ; they are often shared between these two plexuses and the great splanchnic nerve. The highest of the small splanchnic nerves rather fre- quently anastomoses with the great splanchnic, or even becomes entirely blended with it.t * Lobstein has recorded a case (p. 2) mwhich this unusual ganglion on the great splanchnic was of a semi- lunar shape, and gave off, from its convex side, seven or eight slender filaments, which accompanied the aorta and were all lost in the diaphragm ; he has also mentioned another case, in which three filaments arose from this ganglion, two going to the solar plexus, and the third to the mesenteric plexus. t Among the numerous varieties which I have observed in the formation of the small splanchnic nerves, I would especially notice the following: a twig from the eleventh thoracic ganglion, and one from the great splanchnic nerve, terminated in a small ganglion ; from this ganglion were given oflf several filaments that were lost ni)on the aorta, and also a small cord which joined with a twig from the twelfth thoracic ganglion, and was di.itributed in the ordinary manner. 5R 866 NEUROLOGY. The Visceral Ganglia and Plexuses in the Abdomen. As the semilunar ganglia and the visceral plexuses in the abdomen form the continuation of the splanchnic nerves, it is not only theoretically, but practically convenient to enter upon their description now. The central point of all these ganglia and plexuses is situated at the epigastrium, and is formed by a ganglionic plexus, named the solar or epigastric plexus. The Solar or Epigastric Plexus. The solar plexus (opposite x,fig. 302) is formed by an uninterrupted series of ganglia, extending from the great splanchnic nerve of the one side to its fellow of the opposite side. From this point as from a centre proceed a great number of branches, which have been compared to the rays of the sun, and hence the term solar plexus. This solar plexus, which is regarded by physiologists as the centre of the nervous sys- tem of nutritive life, is deeply seated in the epigastric region, and might therefore be called the epigastric nervous centre ; it is situated in the median line, in front of the aorta, around the coeliac axis, and above the pancreas ; it is bounded on each side by the supra- renal capsules, and is of too irregular a shape to be clearly defined. The ganglia of which it is composed, the solar ganglia, are as irregular and variable as the plexus it- self They consist of thick and swollen cords, or ganglionic arches or circles, arranged in a network, in the meshes of which are found some lymphatic glands easily distin- guishable from the nervous ganglia and cords. Anatomists, in general, describe only the two extreme ganglia of the solar plexus, in which the great splanchnic nerves terminate ; these are the semilunar ganglia (x), so called from their shape, but which are subject to much variety both in form and size. Their convex border, which is turned downward, is divided into several teeth, from each of which a pencil of nerves is given off; a great number of filaments are also given off from their concave border, which is directed up- ward. These ganglia are situated close to the supra-renal capsules ; they are often without any regular form, and, as it were, divided into fragments. A single glance at the solar plexus will suffice to convince us of the impossibility of extirpating it, as some experimenters pretend to have done, in living animals. The great splanchnic nerve of each side (g), a part of the small splanchnic nerves (A), and the right pneumogastric nerve (j)'), end in the solar plexus. I have also seen the right phrenic enter this plexus. From it, as from a centre, plexuses are given off for all the arteries arising from the fore part of the aorta, and also for the renal and spermatic arteries. The plexuses for the renal arteries and the inferior mesenteric artery are completed by the visceral nerves derived directly from the lumbar ganglia. There are two diaphragmatic plexuses, a coeliac plexus, a superior and an inferior mesenteric plexus, renal plexuses, spermatic or ova- rian plexuses, and supra-renal plexuses. All the nerves given off from the solar ganglia are gray, and very small ; they are al- ways plexiform, and are generally strong on account of the thickness of their neurilemma. The Diaphragmatic and Supra-renal Plexuses. The diaphragmatic or phrenic plexuses are small ; they are given off from the upper part of the solar plexus, and reach the phrenic arteries, with which they enter the diaphragm ; they at first lie beneath the peritoneum, but afterward dip into the substance of the fleshy fibres of the muscle, and do not exactly follow the course of the vessels. In some cases I have been able to ascertain that they anastomose with the filaments of the phrenic nerve : they always run in nearly the same direction. The diaphragmatic plexus of the right side is larger than that of the left. I have seen two ganglia, upon the right cms of the diaphragm, which formed the origin of the right diaphragmatic plexus and of some hepatic nerves. I arrange the plexuses of the supra-renal bodies with the preceding, because they have so many relations with them. They arise directly from the semilunar ganglia, by two very delicate pencils of nerves, which reach the back of the supra-renal arteries, and are lost in the substance of the supra-renal bodies. Several filaments from the diaphrag- matic plexuses join them, passing in front of the arteries. The supra-renal plexuses are large in proportion to the size of the organs they supply. The Cceliac Plexus. The coeliac plexus is one of the principal divisions of the solar plexus, of which it is • the immediate prolongation, so that it is almost impossible to distinguish one from the ■ other ; it surrounds the coeliac axis, and immediately divides, like it, into three plexuses, .the coronary of the stomach, the hepatic, and the splenic. The Coronary Plexus of the Stomach. — This is given off from the upper part of the solar t plexus ; it receives some filaments from the right pneumogastric, before that nerve joins ;. the solar plexus ; of these filaments, some ramify upon the cardia, while the remainder follow the coronary artery along the lesser curvature of the stomach, and anastomose ■jwith the pyloric filaments of the hepatic plexus. It follows, therefore, that the stomach THE SUPERIOR MESENTERIC PLEXUS. 867 is principally supplied by the pneuraogastric nerve. The filaments from the coronary plexus of the stomach, as well as those of the pneumogastric nerve, after having run for some distance beneath the peritoneum, perforate the muscular coat of the stomach, and appear to be partly lost in it and partly in the mucous membrane. The hepatic plexus is of very considerable size, and might be divided, after the example of Lobstein, into an anterior and a posterior plexus. The anterior accompanies the hepat ic artery, and is formed by some twigs from the right pneumogastric, and by seven or eight large gray, cylindrical filaments from the left semilunar ganglion, which are joined by two or three branches from the right semilunar ganglion. The posterior hepatic plexus accompanies the vena portae, and is derived almost entirely from the right semilunar ganglion ; it is also composed of grayish, thick, cylindrical cords. I would especially notice one cord, which is remarkable both from its size and its course ; it arises directly from the solar ganglion of the right side, passes in a horizontal and curved direction to reach the gastro-hepatic omentum, and continues horizontally be- tween the layers of that omentum, in front of the lobulus Spigelii ; it then ascends to the transverse fissure of the liver, becomes situated beneath the vena portae, and may be traced along that vein into the interior of the liver. I have seen this great he- patic branch come directly from two ganglia situated upon the right crus of the dia- phragm. Before reaching the liver, the hepatic plexus gives off a secondary plexus of consider- able size, around the right gastro-epiploic artery, the right gastro-epiploic plexus ; it is considerably augmented by filaments which are derived immediately from the solar plexus, and perforate the pancreas. The hepatic plexus also furnishes branches to the pylorus and the lesser curvature of the stomach, to the pancreas, to the great curvature of the stomach, and to the great omentum. The pylorus, therefore, and the great curvature of the stomach, are supplied almost exclusively by the hepatic plexus.* The hepatic plexus likewise gives off a small cystic plexus, which is easily seen beneath the peritoneum, surrounding the cystic artery as far as the gall-bladder. Diminished in size, from having given off a series of branches and plexuses, the he- patic plexus gains the transverse fissure of the liver, divides like the hepatic artery and vena portae, and may be traced for some distance in the capsule of Glisson. All the nerves of the liver are gray, but very strong. The Splenic and Pancreatic Plexuses. — The splenic plexus is not so remarkable for the number as for the size of the filaments of which it is composed ; it surrounds the splenic artery, furnishes some twigs to the pancreas, and it also gives off the left gastro-epiploic plexus, which is smaller than the right, is situated upon the great curvature of the stom- ach, and supplies that organ and the great omentum. The splenic plexus also gives off nervous filaments to the great cul-de-sac of the stomach, and being thus very much di- minished in size, reaches the hilus of the spleen, within which organ it can be easily tra- ced in man, and still more easily in the larger animals, along the ramifications of the bloodvessels. These nerves are gray, and very strong. The numerous filaments which pass to the pancreas, and form a plexus around its arteries, constitute the pancreatic plexus, which may be regarded as a dependance of the splenic plexus. The Superior Mesenteric Plexus. The superior mesenteric plexus, which may be regarded as the lower division of the bi- furcation of the epigastric plexus, is the largest of all the abdominal plexuses ; it sur- rounds the superior mesenteric artery, forming an extremely thick plexiform sheath for it ; it passes below the pancreas, enters the substance of the mesentery {w) with the artery, and divides, like that vessel, into a great number of secondary plexuses, which are distributed to all the parts supplied by the artery, namely, to the whole of the small intestine, excepting the duodenum, and to the right portion of the great intestine. Without entering into tedious and useless details, I shall content myself with a few remarks upon the general distribution of these nerves. The mesenteric nerves are remarkable for their length, their number, and their strength. I am certain that their neurilemmatic sheath is proportionally much thicker than that of other nerves. They are placed at variable distances from the vessels, and proceed in a straight line in the substance of the mesentery towards the intestine, with- out giving off any filaments : at a short distance from the concave border of the intes- tine, they either pass directly to the bowel, or else they anastomose at an angle or in an arch ; from the convexity of these anastomotic arches the filaments for the intestine are given off. There is never more than one series of anastomotic nervous arches in the mesentery, whatever may be the number of rows of vascular arches ; the single nervous arch al- * The cardia and the lesser curvature of the stomach are the parts which are the most abundantly provided with nerves. The pylorus, to which we attribute such great .".ensibility, has incomparably fewer. NEUROLOGY. ways cdiTesponds fb the vascular arch nearest to the intestine : the filaments ■which proceed from it are exceefl'ngly minute.* The nervous filaments pt netrate the intestine by its adherent border, run for some time between the serous ai .d muscular coats, perforate the latter, to which they give some twigs, then spread out lO the fibrous coat, and finally terminate in the mucous mem- brane The Inferior Mesenteric Plexus. The inferior mesenterf pit ms (n) is formed by some twigs from the epigastric plexus, :r, rather, from the sup( ric; mesenteric plexus, with which it is continuous on the front lif the abdominal aorta ; ai l, secondly, by some branches from the lumbar sympathetic 4;anglia, which, as hereai'^tr stated, constitute the lumbo-aortic plexus. The meshes of ..he inferior mesenteric plexus are by no means so close as those of the superior mesen- teric plexus. The inferior mesenteric plexus, like the artery by which it is supported, supplies the Left half of the transverse arch of the colon, the descending colon, the sigmoid flexure, and the rectum : of its filaments, those which accompany the left colic arteries are re- markable for their tenuity, their length, and for giving no branches in their course to the intestine. I would particularly notice the twig which accompanies the left superior colic artery. It is not uninteresting to remark, that these nerves are more numerous in the iliac meso-colon, which supports the sigmoid flexure, than at any other point. The inferior mesenteric plexus, thus diminished by having given off other smaller plexuses, terminates, like the inferior mesenteric artery, by bifurcating ; the two divis- ions of this bifurcation are called the hemorrhoidal plexuses ; they surround the two divis- ions of the artery, viz., the superior hemorrhoidal arteries, and terminate partly in the hypo-gastric plexus and partly in the rectum. The Renal and Spermatic, or Ovarian Plexuses. The renal plexuses are extremely complicated : they are formed by branches from the solar plexus, and by the two or three small splanchnic or renal nerves, and terminate almost exclusively by surrounding the renal artery. The two spermatic plexuses in the male, and ovarian plexuses in the female, are derived principally from the renal plexuses. The spermatic plexuses are destined exclusively for the testicles ; the ovarian plexuses, like the arteries of the same name, are distributed both to the ovaries and the uterus. The intimate connexions between the nerves of the kidneys and testicles in the male, and those of the kidneys, ovaries, and uterus in the female, deserve the most particular attention of anatomists. The Lumbar Portion of the Sympathetic System. The lumhar portion of the trunk of the sympathetic {II, fig- 302) is situated in front of the vertebral column, along the inner border of the psoas muscle. The ganglia of this re- gion are therefore nearer the median line than the thoracic ganglia ; but the inferior lum- bar ganglia not unfrequently deviate from their ordinary position, and approach the lum- bar nerves as these emerge from the spinal canal : in this case, they are concealed by the psoas muscle. The lumbar ganglia of the sympathetic vary much in size ; some of them are so small that they would escape notice, if their grayish colour did not distinguish them from the rest of the trunk of the sympathetic. The number of these ganglia is also variable ; there are rarely more than four. Two or three ganglia are often blended into a gangliform cord ; this fusion may be easily recognised by the arrangement of the communicating filaments between it and the lum- bar spinal nerves. In one subject, the twelfth thoracic ganglion on the right side was blended with the first lumbar ganglion : a small filament, corresponding in length to the thickness of two vertebrae, established a communication between this ganglion aiid a large gangliform cord, which represented by itself the four inferior lumbar ganglia. On the left side, the second and third lumbar ganglia were united, and the fifth was blended with the first sacral. This fusion of the lumbar ganglia almost constantly exists, and it establishes a close analogy between the lumbar portion of the sympathetic and the cervical portion, which, as we have already seen, has only three, and frequently only two ganglia. It proves that the superior cervical ganglion may be regarded as representing five superior cervical ganglia and the ganglia corresponding to the two sets of cranial nerves, and that the inferior cervical ganglion may be viewed as the representative of two lower cer- vical ganglia, when the middle ganglion is wanting. Moreover, the trunk of the sympathetic is not unfrequently interrupted either between the twelfth thoracic and the first lumbar ganglion, or between the last lumbar and the ' In one case I found a very remarkable anastomosis. Four filaments, proceeding from four opposite points, converged towards a common centre ; but, as they were about to cross, they diverged from one another so as to intercept a lozenge-shaped space. Two of these might lie regarded as filaments of origin, and the other two ;i5 terminating filaments LUMBAR PORTION OF THE SYMPATHETIC SYSTEM. 869 first sacral ganglion : this interruption is, however, more apparent than real, for. as I have already stated, the continuity between the twelfth thoracic and the first lumbar ganglion is always established by means of a small twig from the renal nerve. The branches of the lumbar ganglia may be divided into the branches of communi- cation between the ganglia ; the external branches, and the internal branches : besides these, there are some small and very delicate filaments, which enter the bodies of the yertebrse. The Communicating Branches between the Ganglia. These communicating branches consist of one or more white cords extending between every two ganglia ; they scarcely ever have the gray appearance and ganglionic struc- ture usually found in similar branches of conununication : the communicating filament between the fourth and fifth lumbar ganglion is often wanting. The External Branches. These are the branches (at d) which communicate with the lumbar nerves. I c6n- ceive that they are furnished by the lumbar spinal nerves to the lumbar ganglia of the sympathetic. There are generally two, but sometimes three for each ganglion ; they arise from the anterior branches of the several lumbar nerves, as they emerge from the inter- vertebral foramina ;* they accompany the lumbar arteries, along the grooves upon the bodies of the lumbar vertebrae, and terminate in the corresponding ganglia ; they are usually directed obliquely downward. In general, each ganglion receives branches not only from the corresponding lumbar nerve, but also from the nerve next above it. Thus, two branches end in the second lumbar ganglion, one from the first, and another from the second lumbar nerve ; the third ganglion receives filaments from the second and third lumbar nerves ; when one ganglion is wanting, its place is supplied by the next, which receives its own proper branches, and also those belonging to the absent ganglion. One ganglion not unfrequent ly communicates with three lumbar nerves. When several ganglia are united into one, it is easy to conceive that this single gan- glion must receive aU the filaments corresponding to those ganglia. It is also easy to understand that these filaments must be directed more or less obliquely either upward or downward, and that they will correspond in length to the distance between the lum- bar nerves and the single ganglion, the superior filaments being directed downward, and the inferior filaments upward. A very remarkable condition of the branches of communication between the lumbar nerves and the sympathetic ganglia consists in the existence of certain ganglia or swell- ings upon them ; and the ahnost indefinite anomalies observed in this particular are no less remarkable. I have found as many as three ganglionic nodules upon the same communicating branch: sometimes, when the two or three communicating branches reach the side of a vertebra, they unite in a ganglion, from which two or three other branches are given off to the proper sympathetic ganglion, t Moreover, these ganglia, like all the irregular ganglia, rarely present that peculiar character which is common to the regular ganglia, namely, that of forming a centre in which a certain number of filaments end, and from which others are given off. The Internal, or Aortic and Splanchnic Branches. The internal branches from the lumbar ganglia are the aortic and the lumbar splanchnic branches, and form a continuous and uninterrupted series with the aortic and splanchnic branches from the thoracic ganglia ; so that the internal branches from the first (/) and sometimes from the second lumbar ganglion join the branches from the eleventh and twelfth thoracic ganglia, to form a small splanchnic nerve, which is shared between the solar and the renal plexus. Some small gangliform nodules are occasionally found upon the course of these branches, among which are some very delicate filaments, which evi- dently pass into the bodies of the lumbar vertebrae. All these internal branches assist in the formation of the lumbar splanchnic, or pelvic visceral nerves. The Lumbar Splanchnic Serves and the Visceral Plexuses in the Pelvis. The lumbar splanchnic nerves (at k) pass inward in front of the aorta, below the su- perior mesenteric artery, and anastomose with each other and with those of the opposite side to form a very complicated plexus, which is completed by a very considerable pro- longation from the superior mesenteric plexus. This plexus (n), which may be called the lumbo-aortic plexus, surrounds all that por- tion of the aorta which is included between the superior and inferior mesenteric arteries ; in the intervals between the nervous filaments are found lymphatic glands, which should be carefully distinguished from some nervous ganglia which form part of the plexus. The lumbo-aortic plexus is bifurcated below ; one portion of it passes upon the infe- * These communicating branches frequently arise in the substance of the psoas muscle from twigs derived from the lumbar plexus. f This dispositiou is well seen in the beautiful plate of the sympathetic published by M. Manec. NEUROLOGY. rior mesenteric artery to constitute the greater part of the inferior mesenteric plexiis (below n) ; while the other portion descends upon the aorta, and even a little below the bifurcation of that vessel, and ends between the common iliac arteries, in front of the sacro-vertebral angle, from which it is separated by the common iliac veins. Some fila- ments are prolonged around the common iliac and the external and internal iliac arter- ies and their branches. The aortic portion of the lumbo-aortic plexus bifurcates below into two secondary plex if arm cords, one right and the other left, which pass downward upon the sides of the rec turn and bladder, and enter the right and left hypogastric plexuses, which are almost entirely formed by these cords. The Hypogastric Plexuses. The hypogastric plexuses (m) are among the great plexuses of the body ; they supply the rectum and the bladder in both sexes, and also the prostate and testicle in the male, and the vagina, uterus, and Fallopian tubes in the female. There are two hypogastric plexuses, one on the right, the other on the left side. They are situated upon the lateral and inferior surfaces of the rectum and bladder in the male, and of the rectum, vagina, and bladder in the female ; they are distinct from each other, and are connected not by median anastomoses, which I have never been able to detect, but through the lumbo-aortic plexus, by the bifurcation and spreading out of which they may be said to be formed. The hypogastric plexuses, from the enlargement and areolar disposition of their component cords, very closely resemble the solar plexus. Each plexus is formed essentially by one of the two divisions of the lumbo-aortic plexus ; it is also joined by some filaments from the inferior mesenteric plexus, by some very small twigs from, the sacral ganglia, among which those derived from the third sa- cral ganglion are especially remarkable ; and, lastly, by some twigs from the anterior branches of the sacral nerves (see Sacral Nervks). Formed by a combination of filaments from these different sources, each hypogastric plexus gives off a hemorrhoidal, a vescical, a vaginal, a uterine, and a spermatic or ova- rian plexus ; all of these plexuses, like the hypogastric plexus itself, are found on each side of the body. The inferior hemorrhoidal plexuses are blended with the superior hemorrhoidal plex- uses, which, as already stated, are the terminations of the inferior mesenteric plexus ; they pass behind and in front of the rectum. The filaments belonging to the anterior branches of the sacral nerves may be distinguished from those belonging to the sympa- thetic system by the difference in the colour of the two kinds of nerves. The vesical plexuses are composed of a great number of exceedingly small filaments. They are situated upon the sides of the posterior fundus (bas-fond) of the bladder, on the outer side of the ureters, and are divided into two sets, viz., ascending vesical nerves, which pass upward upon the sides of the bladder, embrace the outer and inner surfaces of the ureters, and ramify upon the anterior and posterior surfaces of the bladder ; and horizontal vesical nerves, which run forward upon the sides of the fundus of the bladder, externally to the large plexus of veins found in that situation, and spread out into ex- tremely delicate filaments, of which some enter the substance of the bladder, especially at its neck, while the others, in considerable numbers, turn round the prostate gland, and are distributed within it ; one of the prostatic filaments may be traced into the mem- branous portion of the urethra. The Plexuses for the Vesictila Seminales, and Vasa Deferentia, and Testicles. — Some of the filaments situated on the inner side of the ureters surround the vesiculae seminales, and are lost in them ; these are very small ; two or three remarkably large filaments run upward along each vas deferens ; having reached the inguinal ring, they unite with the corresponding spermatic plexus, which is a production of the renal plexus, and descend to the testicle. The branches for the prostate, vesiculae seminales, vasa deferentia, and testicles, are represented in the female by the utero-vaginal, ovarian, and tubal nerves. The Uterine Nerves. — Notwithstanding the figures of the sympathetic published by Walter, in which the nerves of the uterus are well represented, and notwithstanding the still more explicit description given of them by Hunter, most anatomists continue to en- tertain doubts regarding the existence of the uterine nerves. Lobstein, in his work on the Sympathetic, published in 1822, even denied them altogether ; but Tiedemann, in the same year, published two beautiful figures, representing the nerves of the gravid uterus.* The uterine nerves are derived from several sources. I have already stated that the plexuses surrounding the ovarian arteries, which are productions of the renal plexuses, are distributed, like the vessels by which they are supported, both to the uterus and the ovaries. It appears to me that the ovarian nerves and vessels have a similar arrangement, that is to say, that the uterine branches derived from the ovarian plexuses are larger than the ovarian nerves properly so called. * Tabula Nervorum Uteri, Heidelberg, 1822, folio. GENERAL VIEW OF THE SYMPATHETIC SYSTEM. 8H The tubal nerves are also derived from the ovarian plexuses. The uterine nerves derived from the hypogastric plexuses are divided into ascending branches, which run upward along the lateral borders of the uterus, pass forward and backward upon the surfaces of that organ, and terminate in its substance ; and into de- scending branches, which run along the sides of the vagina, and terminate in it. These vaginal nerves appear to be inseparably blended with the vesical and hemorrhoidal nerves.* Such are the divisions of the hypogastric plexuses ; analogy, rather than direct obser- vation, has led to the admission of the existence of gluteal, ischiatic, and internal pudic plexuses ; in fact, of plexuses around all the branches of the internal iliac arteries. The Sacral Poetion of the Sympathetic System. The sacral portion of the sympathetic (s s, fig. 302) is formed on each side by a cord en- larged at intervals, and situated on the inner side of, and along the anterior sacral fo- ramina. It forms a continuation of the lumbar portion of the sjnnnpathetic ; but sometimes there appears to be an interruption in the ganglionic chain, between the fifth lumbar ganglion and the first sacral. This interruption is merely apparent ; it is never complete. The sacral trunks of the sympathetic of the right and left sides gradually approach each other as they descend, corresponding in this respecf to the anterior sacral foramina. The sacral ganglia, which are rarely five, more commonly four, and sometimes three in number, are occasionedly collected into a small gangliform enlargement, situated be- tween the first and second anterior sacral foramen ; the first sacral ganglion is some times double, and at other times it rather resembles a gangliform cord than a true gan- glion. The mode of connexion between the first sacral and the last lumbar ganglion is sub- ject to much variety. + The manner in which the sacral portion of the sympathetic terr- minates is also somewhat variable. The following is the arrangement most generally admitted : a filament proceeds from the last sacral ganglion, which is usually the fourth, and forms an anastomotic arch with its fellow of the opposite side, in front of the base of the cocc)rx. At their point of junction is often found a small ganglion (ganglion inp- par, c), from which certain terminal filaments are given off. Sometimes there is neither a coccygeal ganglion nor any anastomosis, properly so called, but the terminal filaments are distributed in the usual way. I have not been able to trace these filaments beyond the periosteum of the coccyx and the sacro- sciatic ligaments. Like the other ganglia of the sympathetic, the sacral ganglia present communicating branches with each other ; rather large external branches derived from the corresponding sacral nerves ; internal branches, which anastomose with those of the opposite side, in front of the sacrum, and surround the middle sacral artery. Some of these filaments I have distinctly seen entering the substance of the sacrum ; and^ lastly, very small ante- rior branches (y), some of which join the hypogastric plexuses, while the others termi nate directly upon the rectum. General View of the Sympathetic System. The following dissection is necessary, in order to present a correct general idea of the S)mapathetic system. Take a spinal column which has been macerated in diluted nitric acid, remove the bodies of the vertebrae, leaving, if it be wished, the inter- vertebral substances ; be very careful to preserve the branches of communication between the sympathetic and the cra- nial and spinal nerves. It is then clearly seen that the two gangliated trunks of the S3rmpathetic are connect- ed with the cerebro-spinal axis by as many roots, or small groups of roots,t as there are cranial and spinal nerves ; it is, moreover, no less evident that the communicating branches between the ganglionic chain and the spinal nerves do not proceed from the ganglia, but from the spinal nerves ; so that it may be stated as a demonstrated ana- tomical fact, that the sympathetic system has its origin in the cerebro-spinal system <) * [Dr. Lee has recently examined minutely the distribution of the nerves of the unimpregnated and fravid uterus. He has described (Anatomy of the Nerves of the Uterus, with plates, 1841, and Proceedings of the Royal Society, No. 49) several large uterine plexuses ; also, several " large ganglia on the uterine nerves, and on those of the vagina and bladder ;" and, farther, '' two great ganglia situated on the sides of the neck of the uterus."] 1 • • J u t In one case, the continuation of the lumbar portion of the sympathetic deviated outward, and joined the fifth lumbar nerve ; a very small filament only formed the communication between the last lumbar ganglion and the first sacral. In another case, these two filaments proceeded from the last lumbar ganglion of the right side, t'ae inner of which joined the first sacral ganglion of the opposite side, crossing over the sacro-vertebral t It must be remembered that there are always two, and sometimes three communicating branches between the sympathetic and each of the spinal nerves. 4 These facts in human anatomy are in perfect accordance with the observations in comparative aiiatomr made by Meckel and Weber, namely, that the development of the sympathetic system is in direct ratio with that of the cerebro-spinal system ; tliat the former is more developed in man than in any other animal, and 19 proportionally larger in the fietus than in the adult. 872 NEUROLOGY. The sympathetic trunks of the right and left side generally anastomose below in front of the coccyx ; it has been somewhat hastily affirmed that they anastomose above, either upon the pituitary body, or upon the anterior communicating artery of the brain ; the true anastomoses of the two halves of the sympathetic system are in the central and median plexuses. If, after having acquired this general idea of the trunks of the sympathetic, its neuri- lemma be removed by continued maceration in water, the connexions of the branches given from the spinal nerves to the ganglia, with the branches given from the ganglia to the viscera, may then be ascertained : it then becomes evident, that the greater number of the branches from the spinal nerves do not penetrate to the centre of the ganglia, but expand, as it were, upon their surface, and divide into two sets of filaments ; of these, some are applied to the surface of a ganglion, and proceed directly to form the internal or visceral branches ;* while the others assist in forming the cords of communication between one ganglion and another, and divide into ascending and descending filaments, of which the latter are the more numerous. They all run along the outer side of the cords of communication, and afterward become visceral branches themselves ; it is doubtful whether any filament arises in the interior of a ganglion ; the continuity of them all can be traced completely through these bodies. It follows, therefore, that it is anatomically shown that the visceral nerves given off from the sympathetic are connected or belong to a very great nimiber of spinal nerves at once, and always to spinal nerves much higher than that portion of the sympathetic from which the visceral branches are immediately given off; and again, that the vis- ceral or splanchnic nerves, the actual origins of which we have seen to be so complica- ted and so remote from their apparent origins, always run a very long course before reaching their destination. Thus, the splanchnic nerves of the thorax or the cardiac nerves are derived from the cervical ganglia ; the splanchnic nerves of the abdomen are given off, for the most part, by the thoracic ganglia ; and most of the splanchnic nerves of the pelvis proceed from the lumbar ganglia. Nevertheless, the proper ganglia of each splanchnic cavity complete the visceral nerves belonging to that cavity. Thus, the first thoracic ganglion assists in the formation of the cardiac nerves ; the superior lumbar ganglia in that of the visceral nerves of the abdomen ; and the sacral ganglia in that of the pelvic nerves. The visceral nerves sometimes pass directly to the viscera from the ganglia of the sympathetic, and sometimes indirectly, after being mingled and combined in plexuses. There is no relation between the branches which enter and those which pass out of the several visceral plexuses, so that the branches which proceed from the ganglia and trunk of the sympathetic to those plexuses must be regarded, not as branches of forma- tion, but as branches of communication. The visceral plexuses are also formed in a very peculiar manner, not only by inter- laced nerves, but by nerves and ganglia, and these nerves themselves present a gangli- onic structure altogether different from the fasciculated and plexiform structure of other nerves. There are four great visceral plexuses : the pharyngeal plexus, the cardiac plexus, the solar plexus, and the hypogastric plexus ; the largest of all these is the solar plexus, which, both in an anatomical and in a physiological point of view, deserves the title of the abdominal brain, which was given to it by Wrisberg. These four great plexuses may also be very properly regarded as nervous centres, to which all the physiological and pathological phenomena of the nutritive system are singly or collectively referred. These visceral plexuses differ as much from the ganglionic chain formed by the two trunks of the sympathetic as these trunks differ from the spinal cord itself : in these plexuses a sort of fusion is effected between the cerebro-spinal and the sympathetic sys- tems, and also between the trunks of the sympathetic belonging to the two sides of the body. The pneumogastrie assists in the formation of three of these jdexuses ; namely, the pharyngeal, the cardiac, and the solar plexus. In man there is a tendency to fusion of the pneumogastrie with the sympathetic, and in the lower animals this fusion is still more complete ; it is in those animals in which the sympathetic is the least developed that the par vagum acquires its greatest development, and supplies the place of the for- mer in reference to the intestinal canal. The glosso-pharyngeal nerve also assists in the formation of the pharyngeal plexus, and the sacral nerves contribute to that of the hypogastric plexus. The visceral plexuses differ essentially from those formed by the cerebro-spinal nerves. In the latter, the branches which emerge from the plexus are precisely the same branch- es that entered it, only combined in a different manner. However inextricable they may be, the plexuses of the spinal nerves are merely points in which a number of affe- rent branches converge and combine together. In the visceral plexuses, on the contra- ry, there is no relation, either in size or structure, between the afferent branches and the plexuses themselves. * Some filaments from the spinal nerves are seen to croFS at right angles over the anterior surface of the gang^iia, and then to join the visceral nerves ilirectlv. GENERAL VIEW OF THE SYMPATHETIC SYSTEM. 873 The nerves derived from the sympathetic system differ eilso in their mode of distribu- tion from the nerves of the cerebro-spinal system. In general, they form a plexiform sheath around the vessels, and enter with them into the substance of organs. This ar- rangement has induced some anatomists to believe that the sjrmpathetic nerves belong essentially and exclusively to the vascular system, and are lost upon the coats of the arteries ; others hold an opposite opinion, and deny altogether that the sympathetic nerves enter the coats of those vessels. From some researches which I have made on this subject, I believe that there are proper filaments for the coats of the vessels, but that these are very few in number, and that by far the larger number of the nervous fila- ments are intended for the several organs. It is not uninteresting to remark, that the s)Tnpathetic nerves always accompany the arteries, and never the veins ; the trunk of the vena portae forming the only exception to this rule. A gray colour and a soft texture are not, as is generally stated, the peculiar character- istics of the nerves of the sympathetic system ; the gray colour is observed only in a portion of this system ; and the softness, which only very rarely accompanies the gray colour, is confined to a very minute portion of it indeed. There are gray cords, which are nothing more than prolonged ganglia, and are not nerves, properly so called ; when examined they present no nervous structure, that is to say, they contain no white funiculi which can be decomposed into primitive filaments as fine as the silk fibre. Almost all the sympathetic nerves are of a white colour, which is sometimes conceeiled by an unusually thick neurilemma. The structure of the white nerves of the sympathetic system does not differ from that of the cerebro-spinal nerves ; except that the funicidi of the former are smaller, and their arrangement is more deci- dedly plexiform.* Lastly, there are some mixed nerves, partly gray and partly white, which partake of the structural characters of both the gray and the white nerves, t * See note, p. 840. + I am much indebted to M. C.Bonamy, my private prosector, for the zeal and ability with which he ha» assisted me in the numerous dissections required for the compilation of this work. SOURCES FROM WHICH THE ILLUSTRATIVE ENGRAVINGS HAVE BEEN TAKEN. Figs. 1 to 7, 8t, 9 to 20, 24, 25, 28 to 30, 33, 34, 36, 38, 41 to 45, 47, 48t, 49 to 53, 57 (Sue). Figs. 21 to 23, 37 (Gordon). Figs. 26, 27, 35, 58t to 60t, 61 to 70, 71t, 72 to 84, 106 to 110, lilt, 112, 113, 114t, 115, 116t to 123t, 124 to 126, 127t, 128 to 133, 141t, 147t, 155, 161, 163t, 169t, 170, 171t, 191t, 192, 194, 195 (Bourgery). Figs. 39, 40, 46t, 54 to 56 (Ckeselden). Figs. 85 to 94 (Hunter). Fig. 95 (d.) (Retzius). Fig. 97 (d.) (Goodsir). Fig. 98 (Serres). Figs. 99, 101, 102 (Blake). Fig. lOO (T. Bell). Figs. 103 (d.) to 105 (d.), 286 (Cloquet). Figs. 136t, 138, 181 (Morion). Fig. UOf (Watts). Figs. 142, 173 to 175, 178, 231, 233, 234, 257 (Sam- mrring). Figs. 145, 160, 182, 187, 189,220,221,223t(We6er). Figs. 152, 153 (Boyd). Figs. 154t, 198 to 206, 208 to 218 (Tiedemann). Fig. 156 (No. 2) (Krause). Fig. 156 (No. 3) (Dallinger). Figs. 157 to 159, 162 (Boehm). Fig. 172 (Reisseissen). Fig. 180 (d.) (Wagner). Fig. 183 (A. Cooper). Fig. 185 (Holier). Figs. 207, 232t, 235 to 240, 242 to 246, 248, 249, 251t, 252 to 256, 258 to 265, 266, 269 to 275, 284, 285, 296tto301t (Arnold). Fig. 219t (Walter). Fig. 222t (Caldani). Fig. 226 (Harvey). Figs. 227, 228 (Gurlt) Fig. 250 (Brewster). Fig. 268 (Cruveilhier). Figs. 281t, 283, 295 (Mayo). Figs. 289t, 290t (Saan). Fig. 302t (Manec). Figs. 143 (d.), 144 (d.), 164* (d.), 179 (d.), 193+, 197, 241 (d.), 276 to 280, 282 (Models, Castt, and Di agrams in the Museum of Anatomy, University College). Figs. 31, 32, 96, 98* (d.), 134 (d.), 135 (d.), 137 (d.), 139 (d.), 146 (d.), 148 (d.), 149 (d.) to 151 (d.), 156 (No. 1, d.), 164, 176 (d.) to 178 (d.), 184 (d.), 186 (d.), 190 (d.),196 (d.),218* (d.),224 (d.),225 (d.),229 (d.), 230 (d.), 247 (d.), 267 (d.), 287 (d.), 288 (d.), 291 (d.) to 293 (d.) (Original). Figs. 165 to 168 (Kieman). The mark (t), affixed to the number of a figure, indicates that such figure differs in some respects from the (aiginal. The letter (d.), similarly aflixed, signifies that the figure is intended as a diagram or plan. Th« asterisk (*), used occasionally, serves to distinguish between two figures bearing the same number 5S ««#***'<' '*ll^- INDEX. Abdomen, aponeurosis of, anterior, 300. posterior, 305. superficial, 297. regions of, 352. Abducens, nerve. See Nerve, Motor Ocul. Abductor muscles. See Muscles. Accessory ligaments. See Ligaments. nerves. See Nerves. Acetabulum, 88. Acini of glands. See those glands. Acromion process, 76. Adductor muscles. See Muscles. Adipose tissue, 175. Alee of sphenoid bone, lesser, 37. greater, 37. vespertilionis, 475. Alimentary canal, 322. appendages of, 384. coats of, 322. direction and situation of, 323. divisions of, 322. —————— dimensions of, 323. form of, 323. • membranes of, 323. ' muscular fibres of, 323. structure of, 323. Alveoli, 53, 58. Amphiarthroses, 113. ■ characters, ligaments, and motions, 113 Ampulla of semicircular canals, 677. Amygdala, 333. See Tonsils. Amygdaloid fossa, 331. Anastomoses of arteries, 496. lymphatics, 614. nerves, 762. veins, 574. Anastomotic artery, brachial, 544. femoral, 565. ATUitomy, objects and divisions of, 1, 2. descriptive, 1. general, 1, 2. Anfractuosities. See Cerebrum. Angeiology, 479, Angle, sacro-vertebral, 26. of the femur, 93. facial, of Camper, 45. occipital, of Daubenton, 45. of the jaw, 58. changes daring growth, 59. of the pubes, 89. Angles of bones, 9. AtucIc joint, 168. ligaments of, 169. Ankle. See Tarsus. Annular ligaments. See Ligament!. Anti-helix, and its fossa, 666. tragus, 666. Antrum Highmori, 52. pylori, 355. Anus, 380. muscles of, 380. structure of, 380 Aorta. See Arteries. Aponeurology, 294. Aponeuroses in general, 294. classification of, 294. containing, 294. definition of, 294. functions of, 296. insertion of, 294. structure of, 296. ■ tensor muscles of, 295. Aponeuroses in particular, 297. ————— abdominal anterior, 300. layers of, 301. Aponeuroses, cervical, superficial, 299. cephalo-pharyngeal, 346. costo-clavicular, 137. of the cranium, 299. cremasteric, 302. cribriform, 309. deltoid, 315. dorsal of the foot, 314. metacarpus, 318 interosseous, of foot, 314. hand, 318. ■ epicranial, 298. ■ external oblique, 301 ■ of the eyehds, 647. face, 299. ■ femoral, 309. septa of, 310. sheath for vessels, 310. ' muscles, 311. posterior, 305. superficial, 297. brachial, 316. buccinator, 298. buccinato-pharyngeal, 235. cervical, deep, 299. - of the fore-arm, 316. -gluteal, 311. - hypothenar, 319. • iliac, 306. • infra-spinous, 315. • intercostal, 360. ■ inter-muscular of thigh, 310. • of internal oblique, 304. ■of the leg, 312. lower extremity, 309. superficial, 297. ■ lumbar, or posterior abdominal, 30i6. • lumbo-iliac, 306. - masseteric, 298. - of the neck, 299. - obturator, 309. - occipito-frontal, 298. - occipito-pharyngeal, 346. -palmar, 319. -parotid, 298. ■ pedal, 314. ■ pelvic lateral, 308. superior, 308. ■ of the pelvis, 306. proper, 307. • perineal, deep, 307. superficial, 306. ■ petro-pharyngeal, 346. ■ of the pharynx, 346. ' plantar, external, 314. internal, 314. ■ interosseous, 315. middle, 314. — prasvertebral, 299. — of the quadratus lumborum, 306. — recto-vesical, 308. — of the serratus posticus, 300. shoulder, 315. • spermatic cord, 304. sub-peritoneal, 305. sub-scapular, 315. superficial, 2i97. of abdomen, 297. supra-clavicular, 299. supra-spinous, 315. temporal, 298. thenar, 319. of the thorax, 300. of transversalis, 305. of the upper extremity, 316. superficial, 297. ■ of velum palati, 346. - vertebral, 205. ■ vesical, 309. Aponeurotic sheaths for muscles, 296. tendons, 296. vessels, 296. Apparatus, hyoid, 109. Apparatttses of human body, general view of, 3, 4. Appendices epiploicse, 372. Appendix, ensiform, or xiphoid, 65. vermiformis, 373 876 INDEX. Appendix, vermiformis, development of, 384. structure of, 373. Aqueductus Fallopii, 43, 839. vestibuli, 44. cochlea;, 44. Sylvii, 719, 742 Aqueous humour, 65.5. membrane of, 655. Arachnoid, 687. canal (of Bichat), 687. cranial portion of, ©7. internal, 691. loose, 690. membrane of eye, 656 (note). spinal portion of, 690. uses of, 692. Arbor vitas uterina, 465. Arch, aortic, 502. of colon, 374. crural, 302. femoral, 302. gluteal, 3U. orbital, 36. palatine, 329. pubic, 89. sub-pubic, 307. ■ zygomatic, 61. Arches, alveolar, 174. dental, 174. zygomatic, 61. Arm, bone of, 78. compared -with thi^h bone, 107. Arteries in general, 496. anastomoses of, 496. branches of, 497. coat of, external or cellular, 498. internal, 498. . middle, proper, or elastic, 498. — ..— - — course or direction of, 496. definition of, 496 division of, 496. form of, 496. nerves of, 497. nomenclature of, 495. origin of, 496. preparation of, 497. relations with other parts, 497. retia mirabilia of, 496. satellite muscles of, 497. sheaths for, 499. structure of, 499. termination of, 498. varieties of, 496. vasa vasorum of, 499. venae comites of, 497. vessels of, 499. Artery or Arteries in particular, 497. of particular organs or tissues. gans, Sec. acromial, descending, 542. supra-scapular, 538. transverse, 542. acromio-thoracic, 542. of ala nasi, 518. alar thoracic, 542. alveolar, 524. anastomotic, brachial, 544. - great, of thigh, 564. See those or- angular, of face, 517, 529 aorta, 501. abdominal, 503. arch of, 502. ascending, 503. branches of, 503 descending, 503. sinuses of, 501. thoracic, 503. valves of, 486. arising from abdominal aorta, 606. '■ — arch of aorta, 513. varieties of, 513. origin of aorta, 504. termination of aorta, 552. thoracic aorta, 505. articular, of hip, 564. knee, inferior, 565. middle, or azyg»s, 565. superior, 565. - ascending cervical, 538 pharyngeal, 520. Arteri; auricalar, anterior, 521. posterior, 519. aiiliary, 531, 542. axis, coeliac, 507. thyroid, 535. azygos, or middle articular of knee 565. basilar, 534. brachial, 543. brachio-cephalic, 531. bronchial, 505. ' distribution of, 421. buccal, 524. of bulb, 558. calcaneal, external, 570. inferior, 571 capsular, inferior, 513. middle, 513. superior, 513. cardiac, 503. carotid, common, left and right, 514. general distribution of, 530. ■ external or facial, 515. - internal, 525. • superficial, 515. carpal, radial, anterior, 546. posterior dorsal, 546. ulnar, anterior, 549. posterior dorsal, 549. central of retina, 597, 665. cerebellar, inferior, anterior, 534. posterior, 534. ■ superior, 635. cerebral, anterior. 529. ■ communicating anterior, 529. • posterior, 529. middle, 530. posterior, 537. cervical, ascending, 538. deep, 540. princeps, 519, superficial, 539. cervico-spinal, 538. choroid, anterior, 530. posterior, 536. ciliary, anterior, 527. middle, or long, 528. posterior, or short, 528, 665. circle of Willis, 536 circumflex, femoral, external, 564. internal, 563. iliac, 560. humeral, anterior, 543. posterior, 543. of clitoris, 558. coccygeal, 552. coeliac (axis), 507. colic, left, 511. right, 510. collateral, of fingers, radial, 547. ulnar, 549. humeral, external, 543. internal, 543. of knee. See Articular. of toes, from external plantar, 57 internal plantar, 572 comites. See Satellite. communicating, cerebral, anterior, 529. posterior, 529, 535 palmar, 548. plantar, 572. of Willis, 529. coronary of heart, left or anterior, 504. right or posterior, 504. • lips, inferior, 5l7. superior, 518. • stomach, 507. of corpus callosum, 529. cavemosum, 558. cremasteric, 560. crural, 560. cystic, 508. deep, brachial or humeral, 544. cervical, 540. femoral, 563. temporal, 522. deferential, 452. dental, anterior, 524. inferior, 523. superior, 524. ■ diaphragmatic, inferior, 506. INDEX. 877 Artery, diaphragmatic, superior, 539. digital, collateral, radial, 547 ulnar, 549. of foot, 572. dorsal, carpal, radial, 547. ulnar, 549. ■ of foot, 568. — index finger, 548. metacarpal, radial, 547. ulnar, 549. • metatarsal, 569. • of nose, 529. — penis, 558. — scapula, 538. — tarsus, 572. — thumb, 548. — toe, great, 572. tongue, 518. - dorsi-spinal, of inferior intercostals, 507. superior intercostals, 540 - emulgent, 512. ■ epigastric, 559. Superficial, 562. ■ epiploic, 510. ■ ethmoidal, anterior, 528. posterior, 528. • ■ facial, 517. • femoral, 559. deep, 563. Artery, magna pollicis, of hand, 547. malar cutaneous, 521. malleolar, externa], 567. internal, 567. mammary, external, 542. internal, 539. ■ masseteric, 521, 523. ' mastoid, 520. posterior, 519. maxillary, external, 517. internal, 522. general distribution of, 525. of median nerve, 549. mediastinal, 540. medullary, 506. meningeal, anterior, 528. middle or great, 522. of ascending pharyngeal, 620. posterior, 519, 514. small, 523. - of fissure of Sylvius, 529. -of fraenum lingua;, 519. - frontal, 529. of temporal, 520. • gastric, inferior, 509. superior, 509. ■ gastro-duodenal, 508. epiploic, left, 509. right, 508. hepatic, 508. • gluteal, inferior, 556. superior, 556. • hemorrhoidal, 557. inferior, 557. middle, 554. -superior, 511. - helicine, 456. ■ hepatic, 508. — in the liver, 391, 392. ■ humeral, 543. deep, inferior, 544. deep, superior, 544. ■hyoid, of lingual, 518. superior thyroid, 515 (note). • hjrpogastric, 553. • iliac, common, 552. external, 559. internal, 553. general distribution of, 558. — mental, 523. -- mesenteric, inferior, 511. • superior, 510. metacarpal, radial, 546. ■ ulnar, 549. • metatarsal, 569. ■ muscular, of orbit, 528. thigh, 562. • musculo-phrenic, 540. for mylo-hyoideus, 523. nasal, 528. • dorsal, 529. -- lateral, 518. — of pterygo-palatine, 524. of septum, 518. nutritious, of femur, 542. fibula, 570. humerus, 545. tibia, 569. ■ obturator, 554. • occipital, 519. • (Esophageal, 505. • omphalo-mesenteric, 511. ophthalmic, 525. ' orbital, of temporal, 521. ovarian, 512. palatine, inferior, 517. — superior, 524. ■ ileo-colic, 511. ■ ilio-lumbar, 555. ■ incisory, inferior, 523. superior, 524. • infra-orbital, 524. or sub-scapular, 542. spinous, 542. ' innominate, 531. ■ intercostals, anterior, 540. aortic or inferior, 505. superior, 540. • interlobular, of liver, 391. • interosseous, dorsal, of foot, 569. — hand, 547. of forearm, anterior, 548. posterior, 549. palmar, 547 ■ plantar, 572. recurrent, of forearm, 549. ■ of the intestines, great, 511. ■ small, 510. intra-spinal, 534. ischiatic, 556. of labia pudendi, 558. labial, inferior, 517. superior, 517. lachrymal, 526. laryngeal, inferior, 516. superior, 516. lingual, 518. lumbar, 506. magna pollicis, of foot, 572. ■ palmar, deep, 546. ' palmar, interosseous, 548. superficial, 547. ■ recurrent, 547. • palpebral, inferior, 528. superior, 528. • pancreatic, great (from splenic), 509. small (from mesenteric), 510, • pancreatico-duodenal, 508. ■ parietal, 519, 521. ■ parotid, 520. • of penis, 558. dorsal, 558. ' perforating, of forearm, 549 palmar, 548. peroneal, 570. plantar, anterior and posterior, 569. 572. • of thigh, 564. • pericardiac, 495. perinaeal, superficial, 557. transverse, 557. peroneal, 570. anterior, 570. • perforating, 570. ■ pharyngeal, ascending or inferior, 520. ■ pharyngo-meningeal, 520. • phrenic, inferior, 507. ■ superior, 539. ■ for phrenic nerve, 539. ■ plantar, external, 571. ' internal, 571. ■ popliteal, 564 • prevertebral, 520. • princeps cervicis, 519. — pollicis, 547. profunda cervicis, 549. femoris, 563. humeri, inferior, 545. superior, 544. pterygoid, of facial, 517. internal maxillary, 523. INDEX. Artery, pterygo- palatine, 524. "^tffl^ pudic, external inferior; 562.'' superior, 56?. internal, 557. — in the female, 558. pulmonary, 500. '~ left branch of, 501. right branch of, 501. ' distribution of, 431. pyloric, inferior, 508. superior, 508. radial, 546. ■ collateral of fingers, 547. recurrent, 540. radialis indicis, 548. radio-cubital, 549. palmar, 547. ranine, 518. of receptaculum, 525. — recurrent interosseous, of forearm, 549. palmar, 547. radial, 546. tibial, anterior, 668. internal, 569. ' ulnar, anterior, 549. ' posterior, 549. ■ renal, 512. distribution of, 439. ■ of retina, central, 527. ■ sacral, lateral inferior, 556. superior, 556. middle or anterior, 552. satellite of median nerve, 549. phrenic, 540. sciatic, 556. ulnar, 548. • scapular, inferior, 542. posterior, 538. ■ superior, 538. — sciatic, 556. — for sciatic nerve, 556. scrotal, 557. — of septum of nose, 518. ' ventricles of heart, 504. — short, of stomach, 511. — sigmoid, 511. spermatic, 511. — spheno-palatine, 524. spinous, 522. — spinal, 534, 609. anterior, 534. ■ general distribution of, 609. Artery, thoracic htuneral, or deltoid, of acromio-tbora cic, 542. inferior, 542. long, 542. - thymic, 540. - thyroid axis, 537. inferior, 537. middle, 515. of Neubauer, 537. superior, 516. • tibial, anterior, 567. posterior, 570. recurrent, 567. • tibio-peroneal, 569. ' tonsillar, 521. ■ transverse, of perineum, 556. neck, 539. face, 521. • shoulder, 538. ■ tympanic, 522. • ulnar, 548. collateral, 543. of fingers, 649. recurrent, anterior, 549. posterior, 549. ' umbilical, 553. • uterine, 554. ■ vaginal, 554. • of liver, 392. ■ vasa brevia, of stomach, 609. • for vertebrae, 504. • vertebral, 533. • vesical, 553. ■ vidian, 524. Arthrodia, 114. characters, ligaments, and motions, 115 Arthrology, 111. Articular surfaces, in general, 111. - of particular articulations, those articulations. Se« posterior, 534. re-enforcing, cervical, 534. lumbar, 504. thoracic, 504. of spinal cord, 504, 634. — ^ — splenic, 509. in spleen, 405. for sterno-mastoid, 516, 519. stylo-mastoid, 519. sub-clavian, left and right, 531. sub-diaphragmatic, 504. sub-lingual, 518. ■ for sub- maxillary gland, 517. —— — sub-mental, 517. — — — sub-scapular, 542. superciliary, 527. superficial, of neck, 546. palm, 547. perineum, 556. superficialis voIk, 547. supra-orbital, 527. renal, inferior, 512. middle, 512. ■ superior, 512. . sural, 565. scapular, 538. ' spinous, 538. tarsal, dorsal, or external, 568. internal, 568. temporal, 521. ■ deep anterior, 524 middle, 521. • posterior, 523. superficial, 521. testicular, 511. ■ distribution of, 536. thoracic acromial, 542. alar, 542 (note). • borders, 112, structure of, 177. ■ cartilages. 111. structure of, 177. ■ cavities, 10. supplementary, 128. processes, or eminences, 10. of Tertebrse, 20, 22. — union of, 116. Articular arteries. See Arteries. nerves. See Nerves. Articulations in general, 111-116. ■ amphiarthroses, 113. arthrodia, 1 14. classification of, 113. condylarthrosis, 114. definition of. 111. diarthroses, 113. enarthrosis, 114. ginglymus, 114. gomphosis, 114. harmonia, 114. — ■ immovable, 113. — - meningoses, 113 mixed, 113. movable, 113. movements of, 113. — by mutual reception, 113. schindylesis, 114. — sutures, 114. — symphyses, 114. — synarthroses, 114. — synchondroses, 113. — syneuroses, 113. — syssarcoses, 113. — trochlear, 114. • trochoid, 114. Articulations in particular, 113. acromio-clavicular, 135. mechanism of, 136. ' of ankle. See Tibio-tarsal, ■ astragalo-scaphoid, 171. ' of astragalus with os calcis, 170. ■ movements of, 153. atlanto-axoid, 117. ' mechanism of, 124. 'odontoid, 117. ' of atlas and axis, 117. articular processes of, 118 INDEX. 879 Arttculations, calcaneo-cuboid, 173. carpal, in general, 147. . — mechanism of, 148. of each row, 147. of two rows together, 147. ■ pisiform and cuneiform, 147. ■ carpo- metacarpal, in general, 149 mechanism of, 150. first, 149. mechanism of, 150. fifth, 150. mechanism of, 150. second, third, & fourth, 150. • carpo-metacarpal, of the thumb, 150. ■ mechanism of, 150. ■ chondro-costal, 132. • sternal, in general, 131. in particular, 131. movements of, 133. ■ coccygeal, 120. ■ condyloid, of occiput and atlas, 116. • coraco-clavicular, 135. • mechanism of, 136. ' of the costal cartilages, 132. • movements of, 132. ■ costo-clavicular, 138. mechanism of, 138. ■ costo-transverse, 131. vertebral, 131, in general, 131. in particular, 131. movements of, 131. proper, 131. of first rib, 131. of eleventh and twelfth ribs, 131. • coxo-femoral, 159. movements of, 161. • cranial, 124. ■ mechanism of, 125. — cranio-vertebral, 120. mechanism of, 123. — crico-arytenoid, 426. thyroid 426. — of the elbow, 143. — of the extremities, upper, 135. lower, 153. — of the face, 126. — of the fingers, in general, 151. — of the head, with vertebral column. Cranio-vertebral. — of the hip. See Coxo-femoral. — humero-cubital, 141. • movements of, 142. ■ of jaw, lower. See Temporo-maxillary, 128. upper, 126. with cranium, 126. • of the knee, 162. mechanism of, 166. • of larynx, 425. ■ of metacarpal bones, carpal ends of, 148. digital ends of, 149. with carpus, 149. • metacarpo-phalangal, 151. movements of, 152. • of metacarpus in general, 148. ■ of metatarsal bones, tarsal ends of, 175. digital ends of, 175. ' mechanism of, 175. ■ metatarso-phalangal, 175. movements of, 177. ■ occipito-atlantoid, 116. • mechanism of, 122. axoid, 117. ■ peroneo-tibial, inferior, 167. middle, 168. superior, 168. mechanism of, 168. ■ of the pelvis, 154. mechanism of, 156. ' phalangal, of fingers, 153. movements of, 153, toes, 177 movements of, 177. Articulations, radio-cubital, mechanism of, 144. inferior, 142, movements of, 144. — middle, 143. movements of, 143. — — superior, 142. • movements of, 144. • sacro-coccygeal, 120. iliac, 154. sciatic, 155. vertebral, 120, • scapulo-humeral, 138. -—- movements of, 139. • of the shoulder, 135. ■ sterno-clavicular, 136. mechanism of, 137. ■ syndesmo-odontoid, 117. ' tarsal, in general, 170. • mechanism of, 173 of first row, 171. of second row, 171. movements of, 173. of two rows together, 172. movements of, 173. -- tarso-metatarsal, in general, 174. movements of, 173. in particular, 173. — temporo-maxillary, 128. • mechanism of, 129, • of the thorax, 130. ' mechanism of, 132. ■ movements of, 134. ■ thyro-hyoid, 425. tibio-tarsal, 168. mechanism of, 169, 170. tracheo-cricoid, 426, of the vertebral column, 115. mechanism 121-123. movements 122. of, ■ of the vertebris with each other, 115. bodies of, 115. articular processes of, 116. laminae of, 116. spinous processes of, 116. -^— ^— — — peculiar, 1 16. ■ of the wrist, 145. See Radio-carpal Astragalus, 100, Atlas, 23, Auditory process, 44. meatus, internal, 44. external, 44, nerve. See Nerve, portio molHt. Auricle or auricula of ear, 666. See Ear. Auricles of heart. See Heart. Auricular surface of os coxse, 91. Axis (vertebra), 24, Basilar process, 34, groove, 35. Bicipital groove, 78, tuberosity, 81, Bi-parietal suture, 46, Biventer cervicis, 205, maxiOae inferioris, 245, Bladder, 440. bas-fond of, 442. coats of, 442. development of, 443. functions of, 444. fundus, inferior, 442, superior, or summit. 443. — ligaments of, anterior, 441, ■ posterior, 441. sacculated and fasciculated, 444. sphincter of, 443. structure of, 443. trigone of, 443. uvula of, 443. ■ vessels and nerves, 444, •j)ubic, 155, ■ radio-carpal, 145, • movements of, 145 - cubital, 142. Bones in general, 5-18. - arteries of, three kinds, 14, 15. - asymmetrical, 8. - broad or flat, 9. diploe of, 13. ossification of, 17. structure, internal, 13. tables of, 13. vitreousi 35. 880 INDEX. flonei, eavities of, 9, 10. '■ articular, 10. alveolar, 10. cotyloid, 10. glenoid, 10. trochleae, 10 non-articular, 10. canals or conduits, iO. fosse, 10. furrows, grooves, or chan- nels, 10. notches, 10. sinuses or cells, 10. Bones, coronal, 35, costae. See Ribs. of cranium, 33. cubital, 79. cuboid, 101. cuneiform, carpal, 83. tarsal, external, 102. internal, 102. middle, 103. ossification of, 17. — changes in, after maturity, 18. — chemical composition of, 14. -- description of, mode of, 11. — development of, 15. cartilaginous stage, 15. — mucous stage, 15. osseous stage, 16. symmetry of, 17. ■ direction of, absolute and relative, 7. • eminences of, 9. articular, 9. condyles, 9 ■ heads and necks, 9. -non-articular, 9 apophyses, 9. epiphyses, 9. - marginal, 18, -ossification of, 16. • lines and crests, 9, ■ mammillary process- es, 9. ■ processes, 10. ■ prominences, 9, • spines or spinous pro- cesses, 9. • tuberosities, 9. — foramina of, 11. ~ growth, mode of, 18. -- long, 8. extremities and shafts of, 9. marrow or medulla of, 10. medullary canal of, 10. membrane of, 13. -structure of, internal, 10. •ossification of, 16. ~ nerves of, 14. nomenclature of, 6. number of, 6. • nutrition of, 18. ossific points of, 16. ossification of, 16, 17. eminences and cavities of, 17. ■ three kinds of, 17. regions of, 9. shape and symmetry of, 8. short, 9. ossification of, 18. structure, internal, of, IS. situation of, general, 6. size, weight, and density of, 7. structure of, internal, 13. -microscopic, 11. — of ear, 673. — epactal, 50. — ethmoid, 40. development of, 41. — efface, 51. — femur, 93. development of, 95 — fibula, 98. development of, 99. — of fingers. See Phalanges. — of foot, 99. — of forearm, 79, 80. — frontal, 35. development of, 36. •of hand, 82. ■ of haunch, 89. ■ humerus, 78. development of, 79. ■ hyoid, 109. development of, 111. ■ ilium, 89. • incus, 674. ■ ischium, 89. ■ of jaw, lower, 57. upper, 61. jugal, 54. lachrymal, 56. development of, 56. • of leg, 96. • lenticular, 674. • malar, 54. - development of, 55. malleus, 673. maxillary, inferior, 57. development of, 58 superior, 51. • development of, 53. substance of, areolar, 11. cancellated, or spongy, 11. ■ compact, 11. reticulated, 11, 13. surfaces, angles, and bordeni of, 8, symmetrical, 8. torsion of, 99. veins and lymphatics of, 14. Bones in particular, 18-111. of arm, 78. astragalus, 100. atlas, 23. development of, 31. axis, 24. - development of, 31. — calcaneum, 100. — of carpus or wrist, 82. development of, 84. first row of, 83. second row of, 83. — clavicle, 74. development of, 75. coccyx, 20. development oi, 31. ■ of metacarpus, 84. development of, 85. : first, 85. second, third, and fourth, 85. fifth, 85. ■ of metatarsus, 103. development of, 104. first, 103. second, third, and fourth, 103 ■ fifth, 103. • nasal, 55. development of, 56. • navicular, of carpus, 83. > tarsus, 101. • occipital, 33. development of, 34. • orbicular, 674. • OS calcis, 100. carinse, 33. hyoides, 110. iimominatum, I • development of, 90. - magnum, 83. • planum, 40. • prorae, and os puppis, 33. quadratum, 53 ■ unguis, 55 - ossa triquetra, or Wormiana, 50 - ossicula auditfis, 673. • palate, 63. development of, 54. ■ parietal, 41. development of, 42. ' patella, 95. development of, 96. • of pelvis, 87. • perone. See Fibula. ■ phalanges of fingers, 86. • development of, 87 ■ pisiform, 83. ■ of pubes, 90. ■ radius. 81. ■ toes, 104. - development of, 104 JXBBX 881 BoHtM, radius, development of, 89. ribs, 67. — ^-^— ^ development of, 68. false and true, 67. rotula, 95. sacrum, 26. - development of^ SS. scaphoid of carpus, 83. tarsus, 101. ' scapula, 75. ' development of, 75. - semilunar, 83. sesamoid, 96. of foot, 176. of gastrocnemius, 165. of hand, 153. ' of knee or patella, 06. of shoulder, 73. sphenoid, 36. development of^ 38. - spheno-occipital, 36. - spongy. See Turbinaitd. - sternum, 64. development of, 65. - styloid, 43. - of tarsus, 99. development of, 103. first row of, 100. second row of, 101. temporal, 42. development of, 44. mastoid portion of, 43. petrous portion of, 43. squamous portion of, 43. Condi, for anterior muscle of malleus, 679. — arachnoid, of Bichat, 978. — carotid, 43. — for chorda tympani, 67S. — crural, 310. — dental, inferior, 50 — of Fontana, 656. — godronn6, 661. — hyaloid, 661. — incisive, 52. — infra-orbital, 51. — inguinal, 306. — for internal muscle of malleus, 43, 679. — of Jacobson, 671. — maxillary, superior, 51. inferior, 60. — medullary of long bones, 13. — nasal, 653. — of Nuck, 465. — palatine, anterior, 53. posterior, M. • of thigh, 93. • of thorax, 64. ' tibia, 96. development of, 98 ' of toes. See Phalanges. ■ trapezium, 63. ■ trapezoid, 83. ' turbinated, ethmoidal, 41. inferior, 56. ' development of, 56. middle, 41. sphenoidal, 37. superior, 41. tympanic, 45. ulna, 79. development of, 81. unciform, 83. of vertebral column. See Vertebra, Vertebra, and Vertebral Column. vomer or ploughshare, 57. — ' development of, S7. Wormian, 50. zygomatic, 54. Borsa appiattita, 706. Brain. See Cerebrum, Cerebellum, IsthmtU, and Me- dulla Oblongata. Bronchi, 417. structure of, 420. Bronchia or bronchial tubes, 418. relations of, with lobules, 418. structure of, 420. Bronchial arteries, 420. ultimate distribution, 490 glands (lymphatic), 430. tubes, 418. veins, 420. ultimate distribution, 430 mucous membrane, 342. characters of, 343. fiucco-labial furrow, 326 Bulbs of fornix, or corpora albicantia, 728. Bulbus arteriosus, 494. Bursa synovial of tendo Achillis, 283. of ligamentum patella, 164. over patella, 311. Bursa mucosse (so called), 175. synovial, 175. around eyeball, 649. near shoulder joint, 143. " hip joint, 161. knee joint, 164. • sub-cutaneous, 630. Calamus scripforius, 703. Calcaneum, 100. Calcar, 736. Canal, alimentary See Alimentary Canal. of Petit, 661. pterygo- palatine, 38. pterygoid, 38. sacral, 27. for tensor tympani muscle, 43, 87L tympanic, 673. vertebral, 30. vidian, 38. of Wirsung, 401. zygomatic, 55. Canals of bones, 12. dental, superior, 51. lachrymal, 652. palatine, accessory, 54. semicircular, 576. See Semicireuha- Cmak. Canine fossa, 51. Canthi of eyelids, 647. Capitula laryngis, 426. Capitulum costae, 68. ligaments. See Ligament Capsule of GUsson, 478. lens, 663. Capsules, synovial, 1 14. of particular joints. See those joints. supra-renal, 445. See Supra-renal Capsule*. atrabiliary, 445. Caput coecum coli, 37l gallinaginis, 464< Cardia, 442. nerves Carotid arteries. -— nerves. See Nerves. See Arteries. See Nerves. See Arteries. Carpal arteries. Carpus, bones of, 82. bones of first row of, 83. compared with first t of tarsus, 108. second row of, 83. compared with second! of tarsus, 108. ■ compared with tarsus, 107. ' sheaths for tendons on, 316. Cartilage, chemical composition of, 174. cricoid, 423. of ear, 666. ensiform, 65. structure of, 174. thyroid, 433. xiphoid, 65. Cartilages, articular, 111. characters of, 111. structure of, 174. — chemical composition of, 174. ■ arytenoid, 424. - costal, 69. articulations of, 133. ■ falciform, of knee, 162. ' inter-articular, 1 12. structure of, 174. temporo-maiillary, 128. -^-— ~^>— .-.- acromio-clavicular, 136 stemo-clavicular, 137. of wrist, 143. of knee joint, 168. ' inter-osseous, 113. • structure of, 174. 5T ■ of larynx, 423. ossification of, 435. of nose. See Nose. 882 INDEX. Cartilages, semilunar, of knee, 163. tarsal, of eyelids, 647. Caruncula lachrymalis, 647. Carunculx myrtiformes, 468. Cauda equina, 770. Caudal extremity of helix and antihelix, 667. Cavernous body. See Corpus Cavemosum. Cavity, coronoid, 80. cotyloid, 88. digital or ancyroid, 947. glenoid, of scapula, 76. temporal bone, 43. olecranoid, 80. of omentum, 478. sigmoid, great and lesser, 81. supplementary, of temporo-maxiUary articula- tion, 128. ' of shoulder joint, 139. • trochanteric, 95. Cavities, articular, 10. supplementary, 128. orbital, 62. glenoid, of tibia, 97. • nou-articular, 11. Cells of bones, 11. ethmoidal, 42. frontal, 36. sphenoidal, 39. Cellular tissue, 298. lymphatics of, 613. Central foramen of retina, 661. Centrum ovale minus, 736. of Vieussens, 736, 752. semicirculare geminum, 746. Cerebellar arteries. See Arteries. veins. See Veins. Cerebellum, 715. arbor vitie, lateral and median, 721. commissures of, 723. comparative anatomy, 724. corpus callosum of, 711. dentatum or rhomboideum, 721. development of, 724. falx of, 684. fasciculi, converging and diverging, 724. fibres of, formative and uniting, 724. fissure of, median, 717. furrovrs of, 717. Gall's views of, 724. ganglia of, 721. general view of, 724. internal structure of, 718. examined by hardening, 722. • ■ sections, 721. water, 722. Cerebrum, anfractuosities, uses of, 735. arbor vitae of, 750. base of, 727. lateral regions, 731. median excavation of, 727. region, 727. commissures, 753. See Commissur* comparative anatomy of, 757. convolutions or gyri, 732. of digital cavity, 733. inferior surface, 733. superior surface, 734. internal surface, 733. ■ structure of, 755. • uses of, 734. Gall's views of, 754 • crura of, 723. • development of, 756. • falx of, 684. - fibres of, formative or diverging, 752. radiating, 754. uniting or converging, 752. general idea of, 754. - fissure, longitudinal, 726. Sylvian, 727. transverse, great, 727. ' ganglia of, 752. hemispheres of, 726. • nuclens of, 749 • internal structure of, 735. examined by hardening, 75ff. sections of, 736. ■— water, 750 laminae and lamellae of, 717. structure of, 722 (note). lobe, sub-peduncular, 718. lobes, lateral and median, 717. lobule of circumference, 718. medulla oblongata, 718. pneumogastric nerve, 718. lobules or segments, 717. medullary centre of, 722. peduncles of inferior, 704, 722. middle, 710, 722. superior, 711, 722. sections of, 720. — horizontal, 722. vertical, 721. size and weight of, 716. substances, gray, white, and yellow, 721. surface, upper, 716. lower, 717. - tentorium pf, 684. ventricle of. See Ventricle, fourth. Cerebr jI axteries. See Arteries. — —- nerves. See Nerves, cranial. peduncles, substance, &c. See Cerehrvm. veins. See Veins. Cereiro-spinal axis, 681. . • divisions of, 682. membranes of, 682. See Arachnoid, Dura Mater, and Pia Mater. Cerebrum, 725. anfractuosities or sulci, 732. of digital cavity, 733. inferior surface, 733. internal surface, 734. superior surface, 734. Foville's views of, 755. Gall's views of, 751. general idea of, 753. Mayo's views of, 754 Rolando's views of, 759. ■ lobes of, 731 (note), 735. • medullary centres of, 737. • peduncles of, 710. transverse fibres of, 711. course of, in brain, 753. ■ structure of, 713. ■ section, vertical median, 748. -Willis's, 750. • sections of horizontal, 736. vertical, transverse, 750. general remarks on, 751 ■ size and weight, 725. compared to that of ceio bellum, 725. • substance, gray or cortical, 702 (note). • white or medullary, 702 (note^ ■ surface, inferior, or base, 727. ■ superior, or convex, 727. unfolding of, by Gall, 753. ventricles of, 753. See Ventricle. Cervical arteries. See Arteries. ■ ganglia. See Ganglion. ■ nerves. See Nerves. ■ plexuses. See Plexuses. vertebrce. See Vertebra and Vertebra Cervix uteri, 465. Cheeks, 328. development of, 328. muscles of, 328. structure of, 328. vessels of, 328. Chemical composition of tissues, &c. See thoM t» sues, &c. Chiasma, optic, 728, 819. Chorda tympani nerve, 836. - canal for, 672. Chorda tendineae, 483. vocales, 426. inferior or true, 427. superior or false, 427. Chorion, 631. Choroid coat of eye, 657. structure of, 657. • pigment, 659. ■ plexuses, 747. See Plexuses. ■ veins of brain, 586. eye, 657. Ciliary body, crown, or disc, 656. canal, 656. circle, ligament, or ring, 656. processes of the choroid coat, 656 zone of Zinn, 657. INDEX. 883 OfrcteofWilliB, 727. Circular sinus of Ridley, 587. Circumflex arteries. See Artenei, veins. See Veins. Clavicle, 74. Clitoris, 471. artery of, 558. crura, glans and prepuce of, 471. ligaments and muscles of, 471. — nerve of. 807. Cochlea, 677. aqueduct of, 679. axis, columella, or modiolus of, 678. lamina gyrorum, or tube of, 678. • spiralis of, membranous and osseous, 678 nerves of, 681. ■ scalae of, tympanic and vestibular, 677. Cochleariform process, 44. Coccygeal vertebrse, 18, 27. Coccyx, 27. Ccecal appendix, 373. Cacum, 371. appendix vermiformig of, 373. development of, 383. • internal surface, 373. structure, 378. Collateral arteries. See Arteries. nerves. See Nerves. Colon, 373. arch of, 374. ascending, 374. — — - descending, 374. — — development of, 384. ' flexures of, iliac and sigmoid, 371. — — internal surface of, 376. longitudinal bands of, 374. lumbar, left and right, 374. structure of, 378. transverse, 375. Columella of cochlea, 708. valve of Vieussens, 712. Columnce cameae, 483. of rectum, 377. Columns, fronto-nasal, 127. zygomato-jugal, 127. jugal, 127. pterygoid, 127. • of face, 127. of vagina, 469. • of spinal cord. See Spinal Cord. Comites, arteriae. See Arteries, satellite. nervi. See Nerves, satellite. venae, 572. Commissura mollis, 740. Commissure, anterior, of brain, 741. antero-posterior, 753. external and internal, of eyelids, 647. ■ great transverse, of brain, 735. of lips, 326. longitudinal, of brain, or fornix, 737. optic, 729. ' of pineal body, 742. posterior, of brain, 742. soft or gray, 741. of spinal cord, anterior, 698. gray and white, 699. at Sylvian fissure, 746. Commissures of brain, 742. See Commissure. Common mass of posterior spinal muscles, 201. Communicating arteries. See Arteries. nerves. See Nerves. Comparison of arm-bone with thigh-bone, 105. ■ arteries of upper and lower extremities, 572. bones of upper and lower extremities, 105. carpus and tarsus, 107. development of upper and lower extrem- ities, 109. enamel and ivory of teeth, 183. first rows of carpus and tarsus, 108. hand and foot, 107. ■ leg with forearm, 105. lower parts of radius and tibia, 107. metacarpus and metatarsus, 108. ■ nerves of upper and lower extremities, 815. permanent and temporary teeth, 187. phalanges of fingers and toes, 109. Comparison of second rows of caipus and tarsus, 108. shoulder with pelvis, 105. ■ teeth and bones, 177. epidermoid appendages, 177 upper and lower molar teeth, 181 upper parts of ulna and tibia, 107, Compressor muscles. See Muscles. Conarium, 742. Concha of ear, I ■ tragic fossa of, I ■ nose, inferior, 56. middle, 41. ■ superior, 41. Concha, ethmoidal, 41. Condylarthrosis, characters, &c., 114. Condyle, 10. humeral, 78. Condyles, occipital, 34. of lower jaw, 58. femur, 95. tibia, 97 Condyloid foramen, anterior, 34. — posterior, 34. fossa, 34. Confluences of the sinuses, 588. Coni vasculosi testis, 452. Conjunctiva, 648. Constrictor muscles. See Muscles. Conus arteriosus, 481. Convolutions of brain. See Cerebrum. small intestines, 364. Coracoid process, 76. Cordiform tendon of diaphragm, 213. Cornea, opaque, 655. transparent, 655. Comicula laryngis, 424. Comu Ammonis, 745. Cornua of hyoid boue, 109. lateral ventricle. See Ventrieh styloid, 109. thyroid cartilage, 424. Corona ciliaris, 656. radians of Reil, 755. of glans penis, 461. Coronal bone, 35. Coronary arteries. See Arteries. ligaments. See Ligaments. veins. See Veins. Coronoid cavity, 80. process of lower jaw, 58. ulna, 80. Corpora albicantia, 728. structure of, 738. Arantii, 486. bigemina, 712. lutea, 462. mammillaria, 728. olivaria, or ovata, 706. quadrigemina, 712. restiformia, 707. Corpus bulbosum, 461. artery of, 558. nerve of, 806. — callosum, artery of, 529. ■ — bourrelet or cushion of, 731 of cerebellum, 711. extremity, anterior, 737. posterior, 731. ■ genu or knee, 737. - peduncles of, 730. ■ reflected portion, anterior, 730. ■ rostrum or beak, 737. • convolution of, 733. ■ ventricle of, 737. ■ longitudinal tracts of, 737 ■ fibres of, 753. — cavernosiun penis, 455. 1 crura of, 455. nerves, 456. structure, 455. ■ vessels, 456. ■ dentatum cerebeUi, 721. meduUae, 705. fimbriatum, 739. — uteri, 464. geniculatum externum, 728. internum, 712. Highmori, 450. luteum, 462. • mucosuiD of skin, 635- INDEX. Corpus papillare of skin, 689. psalloides, 738. . reticulare of skin, 635. I spongiosum urethrse, 460. striatum, 744. fibres of, 753. lobule of, 731. rein of, 745. Costal cartilages, 69. Costa, 67. See Ribs. of scapula, 76. Cotyloid cavity, 88. cavities in general, 11. Crania, national, 44. Cianial nerves, in general. See Nerves. in particular. See Nerves. — — ganglia. See Ganglia. arachnoid. See Arachnoid. dura mater. See Dura Mater. Cranium, aponeuroses of, 299. area of, 45. articulations of, 125. — base of, exterior of, 45. interior of, 46. ——— bones of, 34. circulation of, arterial, 531. — venous, 562. - development of, 50. - external surface o.'', 45. ■ lymphatic system of, 627. - in general, 45. - internal surface of, 46. - mechanism of, 126. ■ regions of, 45. ■ sutures of, in general, 154. particular. See Sutures. -varieties of, 45. - vault of, 45. Crest of ilium, 89. pubes, 89. tibia, 97. urethra, 459. Crests, occipital, 35. Cribriform plate of ethmoid bone, 40. Crijtta gaUi, 40. ilii, 89. vestibuli, 676. Crura of clitoris, 471. corpus cavemosum, 455. diaphragm, 212. cerebri, 711. Crural arch, 309. ring, 310. septum, 310. Crust of cerebral peduncles, 713 (note). Crusta petrosa, 182. Crypts of Lieberkuhn, 369. Cuneiform bone of carpus, 83. Cutaneous nerves. See Nerves. Cuticle, 633. Cutis, or cutis vera, 631. anserina, 630. Cystic duct, 397. Cijslis fellea, 396. Uo'tns, 446. tissue of, 446 (note). Deltoid impression, 78. Wfrt/a; arteries. See Arteries. — — canal, inferior, 57. canals, superior, 31. nerves. See Nerves, veins. See Veins. Dentata (vertebra), 24. Denies. See Teeth. Depressor muscles. See Muscles. Development of particular bones, organs, or parts body. See those bones, organs, &c. Diaphragm, 218. Diarthroses, 114. Digastric fossa, 43. groove, 43. Digestive apparatus, general view of, 3. D^tal arteries. See Arteries. nerves. See Nerves. Diploe, 14. Diploic canals. 591. veins, 585, 591. Dissection of different parts. See those parts. Oorsal arteries. See Arteries. Dorsal ligaments. See Ligament*. nerves. See Nerves. veins. See Veins. vertebrae. See Vertebra and Ve rt tirtt . Dorsum ilii, or external iliac fossa, 88. lingua;, 337. manus, 82. nasi, 64l. ——pedis, 99. Duct, common biliary, 398. ' internal surface, 399. structure, 399. • cystic, 397. structure, 399. ' ejaculatory, 452. ' hepatic, 395. internal surface, 3W. structure, 399. — lymphatic, right, 619. — nasal, 653. — pancreatic, 402. — parotid, 341. — Stenonian, 341. — thoracic, 618. ■ right, 619. Warthonian, 342. Ducts, biliary, 398. lactiferous or galactophorona, 473. prostatic, 458. of Rivinus, 342. Ductus arteriosus, 500. communis choledochus, 398. ejaculatorius, 452. venosus, 600. Duodenum, 361. curvatures of, 362. ~ glands of, 370. — lymphatic glands of, 625. • structure of. See Smalt Intestine. Dura mater, 682. cranial portion of, 683. cranial nerves of, 686. sinuses of, 584. structure of, 685. uses of, 686. vessels of, ( dissection of, 682. spinal portiou of, 686. vessels of, 687. Ear, auricle of, 666. cartilage of, 666. ligaments of, 667. muscles of, extrinsic. See MtudUf auricular. intrinsic, 668. skin of, 668. vessels and nerves, 668. • drum of. See Tympanum. external. See auricle and meatus of. general view of, 666. internal, or labyrinth of See Labyrinth. meatus of external, 668. cartilaginous and fibrous portion of, 688. — glands of, 669. osseous portion of, 44. — skin of, 6. — internal, 44. . bottom of, 680. middle. See Tympanum. ossicula of, 673. movements of, 674. muscles belonging to, 674. tympanum of. See T)/mpanum. vessels of, 680. Eighth cranial nerve. See Nerves, glosso-pharyngsal, pneumogastric, and spinal accessory. J^aeulatory duct, 452. Elastic tissue, structure of, 174. chemical composition of, 174. ligaments, general characters of. 112. ■ of vertebrsB, 115. Elbow-joint, 143. Eminence, jugular, 34. nasal, 35. frontal, 35. ilio-pectineal, 89. hypothenar, 261. thenar, 260. unciform of lateral ventricle, 730 INOB2. 88$ Eminenlia collateralis, 746. EminentitB natiformes, 712. testiformes, 712. Enamel of teeth. See Teeth. Enarlhroses, 114. Encephalic nerves. See Nerves, craniai. Encephalon, arteries of, in general, 535. isthmus of. See Isthmus. £mio-cardium, 488. lymph, 680. Ensiform process, cartilage or appendix, 65. Epactal bones, 50. Epicondyle, 79. Epidermis, 633. Epididymis, 451. globus major, 451. — minor, 451. - structure, 451. Epigastric region, 352. Epiglottis, 425. Epiploon, i78. See Omentum. Epithelium ciliated, 323. columnar, 323. squamous, 323. of particular membranes. See those mem- branes. Epitrochlea, 80. Erectores muscles. See Mutdt*. Ergot, 736. Ethmoid bone, 40. Ethmoidal bulb, 818. cells or sinuses, 40. — fossa, 48. groove, 40. labyrinth, 40. EustacJaaa tube, or trumpet, 672. cartilaginous and fibrous portion, 672. mucous membrane, 673 (note}. osseous portion, 44, 672. Extensores muscles. See Muscles. Extremities, lower, aponeuroses of, 306. articulations of, 153. arteries of, 557. 7 bones of, 87. development of, 104. lymphatic system of, 619. nerves of, 797. veins of, 603. upper, aponeuroses of, 315. arteries of, 531. ■ articulations of, 135. bones of, 74. ——— development of, 87. ■ lymphatic system of, 628. nerves of, 781. •^— ^— veins of, 593. upper and lower, arteries of, compared, 572. bones of, compared, 105. — — ^— — developmont of, compa- red, 109. aeires of, oMnpared, 815. Eye, 645. appendages of, 646. — — brows, 646. — — chamber of, anterior, 658. ■ posterior, 658. globe of, 654. humours of, aqueous, 664. crystalline, 662. ■ vitreous, 66l. ■ lashes, 646. ' Uds. 646. cartilages of, 647. commissures or canthi, 647. glands, 648. mucous membrane, 647. muscles of, 647. uses of, 647. vessels and nerves, 648. ■ membranes of, 654. of aqueous humour, 655. arachnoid of, 656 (note). • capsule of lens, 662. choroid coat, 656. cornea, 655. hyaloid, 661. ■ — iris, 657. Jacob's, 661. pupillary, 659. retina, 660. Eye, membrane, Raysch's, 659. sclerotic coat, 654. of vitreous humour, 661. muscles of, oblique, 651. recti, or straight, 651. action of, 651 nerve of. See Nerve, optic. pigment of, 660. vessels of, 665. Face, area of, 46. bones of, 51. cavities of, 62. circulation of, arterial, 530. venous, 593. ' development of, general, 63. regions of, 63, 64. in general, 60. lymphatic system of, 626. movements of, 238. muscles of, 231. regions of, 60. Facial angle of Camper, 45. nerve. See Nerve, portio dura. Fallopian aqueduct, 43. hiatus, 44. ligament, 302. tubes, 463. fimbriae of, 463. structure and uses of, 463. Fascia. Fall of umbilical vein, 475. cerebelli, 684. cerebri, 684. See Aponeurosis. — cervical, 209. — cremasteric, 302. — cribriform, 309, 621. — dentata, 476. — iliac, 302. — infundibuliform, of cord, 302. — intercolumnar, of inguinal ring, 301. — lata, 309. iliac portion, 310. pubic portion, 311. structure, 311. obturator, 308. propria (sub-peritoneal fascia), 803-30$ recto-vesical, 308. spermatic, 304, superficial, 297, 630. tensor muscles of, 294. transversalis, 305. Fasciculi, muscular, 193. of medulla. See MeduUa. Fauces, arches of, 330. isthmus of, 330. pillars of, 330. Femur, 93. Fenestra ovalis, 670. rotunda, and its fossa, 671 Fibres, muscular, involuntary, 324. voluntary, 193. nervous, 767. Fibrous tissue, 298. fV6ro-cartilage of epiglottis, 425. cartilages, 177. of particular joints. See those joiata FOula, 98. Fifth cranial nerve. See Nerve, trifacial Filaments, muscular, 193. nervous, 767. FiOet, 712. FinU>ri- and toes, phalanges of, compared, 130. First cranial nerve. See Nerve, olfactory. Fissure, Glasserian, 43. glenoidal, 43. incisive, 53. orbital, 63. pterygo-maxillary, 55. spheno-maxiUary, 39, 52, 55. - sphenoidal, 39. Sylvian, 730. Fissures of brain, liver, etc. See tbose oigani* Flexor muscles. See Muscles. Flocculus, 718. Fluid, ventricular, 744. of Scarpa, 680. 886 INDEX. Fluid, sub-arachnoid, 144. Folds, aryteno-epiglottid, 433. glosso-epiglottid, 336. pharyngeo-epiglottid, 426. Follicles, dental, 184. of Goodsir, 183. intestinal. See Intestines. Lieberkuhn's, 379. sebaceous, 635. — solitary, 370. of stomach, 360. tubular, 360. uterine, 471. Fontanelles of scull, 49. Foot, bones of, 99. compared with hand, 106. Foramen, of Bichat, 688. ofBotal, 486. centrale of retina, 660. caecum of frontal bone, 36. Morgagni {in tongue), 333. ' medulla oblongata, 703- condyloid, anterior, 34. posterior, 34. infra-orbitary, 59. lacerum superius, 39. posterius, 44, 47, 49. anterius, 47. magnum, 34. mastoid, 43. mental, 57. of Monro, 740. nutritious of humerus, 78. ulna, 79. radius, 81. femur, 93. tibia, 96. fibula, 99. obturator, 88. occipital, 34. optic, 37. orbital, internal anterior, 36. posterior, 36. ovale of heart, 487. ■ sphenoid bone, 38. parietal, 42. rotundum, 38. spheno-palatine, 54. spheno-spinosum or spinosun, 38. Etylo-mastoid, 43. superciliary, 36. supra-orbitary, 36. vertebral, 20, 21. of Winslow, 476. Foramina Thebesii, 488. malar, 54. of bones, 11. inter-vertebral, 20, 30. posterior, 775 (note). sacral, 27. Forearm, bones of, 79. compared vdth leg, 105. Fornix, 739. • bulbs of, 740. pillars of anterior, 739. — posterior, 740. Fossa, amygdaloid, 331. canine, 51. digastric, 43. ethmoidal, 48. iliac, external, 88. internal, 88. infra-spinous, 76. ischio-rectal, 309. jugular, 43. lachrymal, 36. mental, 58. myrtiform, 49. navicularis of urethra, 461. vulva, 470. ear, 670. ■ ovalis of heart, 488. ■ parietal, 43. ■ perineal, 309. ■ pituitary, 37, 48. • pterygoid, 38. ■ scaphoid. See Navicularis. ■ spheno-maxillary, 60. • sub-lingual, 57, 60. ■ sub-maxillary, 57, 60. Fossa, ffub-pynmidal, 671. sub-scapular, 75. supra-sphenoidal, 37. supra-spinous, 76. temporal, 47. zygomatic, 60. Fossa of bones, II. - condyloid, 34. - frontal, 36. - internal iliac, 91. - nasal, 63. - middle lateral, or spheno-temporal, 48 - occipital, 35. Fourchette of sternum, 65. vulva, 470. Fourth cranial nerve. See Nerve, pathette. Fovea hemispherica, 676. - semi-elliptica, 676. Frcenum labii, 324. lingus, 336. prsputii, 455. Frontal bone, 35. cells or sinuses, 37. eminence, 35. fosss, 36. Fronto-JMgaH suture, 48. maxillary suture, 59. nasal suture, 59. — columns, 127. parietal suture, 45, 47. sphenoidal suture, 48. Fundus of stomach, bladder, Ac. See those organ*. Furrow, mylo-hyoidean, 57. mento-labial, 326. bucco-labial, 326. Furrows of heart and spinal cord. See those organa. Galactophorous ducts, 473. Galea capitis, 208. Gai2-bladder, 396. structure of, 397. use of, 400. Ganglia, lymphatic. See Lymphatic Glands. Ganglia, nervous, in general. See Nerves, ganglia oj Ganglia, nervous, in particular, 765. abdominal, 865. of brain, 753. cervical, sympathetic. See Ganglion. cranial, 765. • sympathetic, 854. - intercosttj, 765. ■ lumbar, sympathetic, 868. external and intemtl branches of, 860. - spinal or rachidian, 765. - splanchnic, 765. - sympathetic, 765. — — connexions of, 766. structure of, 768. -thoracic, 864. external branches, 864. ' internal branches, 804. -vertebral, 761. Ganglion of Andersh, 843. annulare (of eye), 831. cardiac, 862. carotid, 856. of cerebellum, 722. cervical, inferior, 859. middle, 859. superior, 855. ^ — branches of, anterior, 857. . external, 858. inferior, 858. — internal, 858. —— superior, 856. ■ ciliary, 830. — Gasserian, 827. — of glosso-pharyngeal, 843. — impar, 871. — inter-carotid, 858. — lenticular, 830. — Meckel's, 831. — naso-palatine, 831. — ophthalmic, and branches, 830. — otic, and branches, 837. — petrosal, 843. — of pneumogastric, 845. — of Bibes, 857. — of root of hypoglossal, 823 (note). INDEX. 887 (hmglioH of root of spinal accessory, 823. semilunar abdominal, 866. of fifth nenre, 827. solar, 866. ' spheno-palatine, and branches, 831. sub-maxillary, 837. thoracic, first, 859. thyroid, 859. Gasserian ganglion, 827. Genial processes, 58. Ginglymus, angular and lateral, 114. Glabella, 35. *iland, accessory, of parotid, 341. epiglottid (so called), 430. lachrymal, 652. • parotid, 340. See Parotid Gland. pineal. See Pineal Gland. pituitary, 729. prostate, 459. • structure, 459. sub-lingiial. See Sub-lingual Glana. sub-maxillary, 342. See Sub-maxillary Gland. thymus, 415. • thyroid, 433. Glands, agminated, 370. arytenoid, 433. Brunner's, 370. buccal, 329. ceruminous, 669. conglobate (lymphatic), 614. Cowper's, 460. duodenal, 370. epiglottid, 430. of Havers, 113. — in knee, 163. intestinal. See Intestines. labial, 328. laryngeal, 432. lingual, 337. lymphatic, in general, 616. particular. Glands. Groove, superior petrosal, 44. of torsion, of humertu, 78. Grooves of bones, 12. calcaneal, 100. carotid, 37. cavernous, 37. for lateral sinuses, 34. on back of radius, 81. sacral, 92. of spinal cord. See Spinal Cori, vertebral, 29. Gubemaculum dentis, 189. testis, 44«. Gula, 344. Gulf of the internal jugular, 583, Gums, 329. HabentB of pineal body, 742. Hamular process of sphenoid bone, 37. cochlea, 678. Hand, bones of, 82. compared with foot, 107. Hairs, description of, general, 638. follicles of, 638. structure and growth, 638 (note). Harmonia, 114. Harmonic sutures, 114. Haunch bone, 89. Heads of bones, 9. particular. See those bonoa. See Lymphatic mammary, 472. Meibomian, 648. molar, 329. odoriferous, of prepuce, 453. oesophageal, 352. of Pacchioni, 585, 685. palatine, 329. Peyer's, 370. salivary, 340. See Salivary Glands. solitary, 370. sudoriferous, 633. synovial (so called], 113. of trachea, 416. tubular, 360, 370. Tyson's, 454. of uterus, 467. of Vesalius (bronchial), 625. Glandula socia parotidis, 341. Glans clitoridis, 471. penis, 460. corona of, 460. — - structure of, 461. Glasserian fissure, 43. Globuli Arantii, 486. Globus major, 451. minor, 451. Glomeruli, 437. GJoMo-epiglottid folds or ligaments, 430. pharyngeal nerve. See Nerve. Glenoid cavities in general, 11. ligaments. See Ligaments. Glottis, 430. differences in size of, 435, Gomphosis, 114. Groove, basilar, 34. bicipital, 78. cuboid, 100. dental primitive, 184. ■ secondary, 184. ■ digastric, 43, 47. - ethmoidal, 40. - inferior petrosal, 49. - lachrymo-nasal, 51. ■ longitudinal, of cranium, 47 ■ mylo-hyoidean, 50. • obturator, 88. - optic, 37. ■ sub-pubic, 88. Heart, 479. auricles of, external surface, 482. interior of, 486. muscular fibres of, 490L musculi pectinati, 404. orifices of, 484. ' auriculae of, 482. — interior of, 487. • bone in, 489. ■ cellular tissue, 493. ■ chordae tendineee, 483. - columnae cameae, 483. ■ conformation of, external, 480. internal, 482. ■ development of, 492. ■ fibrous framework of, 488. ' foramen of Botal, 486. ovale, 486. ' remains of, 486. ■ foramina Thebesii, 487. - fossa ovalis, 486. - function, 492. - furrow, auriculo-ventricular, 481. inter-auricalar, 482. ventricular, anterior and port*- nor, 481. . muscular fibres of, 488. structure of, 488. ■ nerves of, 492. • separation of, into right and left hearts, 490. ■ septum, inter-auricular, 482. ventricular, 481. • serous coat, external, 487. internal, 487. sounds of, 493. • structure of, 487. ■ tubercle of Lower, 486, • valve, Eustachian, 486. mitral, 484, of Thebesius, 486, tricuspid or Iriglochin, 484, ■ valves of, auriculo-ventricular left, 484, right, 485, — ^ semilunar. See Sigmoid. ■ sigmoid, aortic, 484. pulmonary, 484. ventricles of, external surface, 480, interior of, 483. muscular fibres of, 488. . musculi papillares, 484. orifices of, 483. vessels of, 491. zones, fibrous, of, 488. Heel, bone of, 100. Helicotrema, 679. Helix, and its furrow or groove, 666. cartilaginous process of, 667. Hemorrhoidal arteries. See Arteries. nerves. See Nerves. Hepatic artery, in the liver, 394, 395. 888 INDEX. Hepatic duct, 395. in the liver, 394, 395. Hiatus Fallopii, 44. Hilus of spleen, )i|N^- solitary, 369. «^ ' functions of, 370, glands of, 366. ■ lymphatic glands of, 624. lymphatics of, 624. papillae of, 367. • properly so called, 363. structure of, 365. tubuli of, 370. valves of, 366. vessels and nerves of, 370. villi of, 367. Intestines in general, 361. development of, 383. JnZra-lobular veins of liver, 395 (note). spinal veins. See Veins. Iris, 657. layers of, 659. muscular fibres of, 658 (note). structure, 658.- uses of, 659. vessels and nerves of, 659. Ischiadic notch, 89. Ischio rectal fossas, 308. Ischium, 89, Island of Reil, 745. Isthmus faucium, 325. ovalis (heart), 486. of the encephalon, 710. comparative anatomy, 715. ■ development of, 715. divisions of, 710. fasciculus of, triangular, 710-711. furrow, lateral, of, 710. internal structure of, 713. lower stratum, 713, -- middle stratum, 713. upper stratum, 713. sections of, 713, Iter dentis, 188, Ivory of teeth. See Teeth. Jacob's membrane, 660, structure of, 661. Jaw, lower, 57. articulations of, 128, upper, bones of, 51, — articulations of, 126, Jejunum, 362. — ; structure of. See Small Intestme. Joints. See Articulations. Jugal columns, 127. bone, 54. Jugular eminence, 34. fossa, 43. veins. See Veins. internal, sinus of, 583. Kidneys, 436, - acini, 438, -- adipose capsule of, 437 - calyces of, 439, - coat of, 437. - cortical substance of, 438. - development of, 440. - functions of, 440. - glomeruli, 437. - hilus or fissure, 436. - papillae, 437. ■- pelvis of, 440. - pyramids of, Ferreim'a, 437, Malpighi's, 437. ■ tubes of, convoluted, 437, ' straight, 437. tubular portion, 438. — structure of, 438, • vessels and nerves, 438, See thoM Knee-joint, arteries, ligaments, and nerves, parts. Labia pudendi, 470. Labyrinth, ethmoidal, 40, fluids of, 679. lining membrane of, 680. membranous, 679. osseous, 675. See Cochlea, Semi-ciraikm Canals, and Vestibule. Lacerated, foramen anterior, 47. posterior, 44. IKDEX. Lacerated, foramen superior, 39. Lacerti teretes of heart, 483. Lachrifmal bone, 56. canals, 651. caruncula, 647. gland, 651. groove, or fossa, 36, 651. papills, or tubercles, 645. passages, 651. mucous coat of, 654. ■ puncta, 652. sac, 653. Lachrymo-aasal groove, 51. canal, 652. Lacteals, 611. of intestines, 612. Lactiferous ducts, 473. Lacuna magna, 460 (note). Lacuna of urethra, 460. Lacus lachrymalis, 647. Lambdoidal suture, 46. Lamina cinerea, 730. of cornea, 745. cribrosa of ethmoid, 40. of internal auditory meatus, 678, 680. gyrorum, 677. papyracea, 41. spiralis, membranous and osseous, 677. Laryngeal nerves. See Nerves. Larynx, 422. articulations of, 426. cartilages of, 423. ossification of, 435. Ligaments of auricle, intrinsic, 667. of bladder, anterior, 308, 440. ■ posterior, 440, 475. broad, of liver, 386. uterus, 465. ' calcaneo-cuboid, inferior, 173. internal, 173. superior. 172. • scaphoid, inferior, 172. superior, 172. of canthus, external, 647. capsular, acromin-clavicular, 135. atlanto-axoid, 119. carpo- metacarpal of thumb, 150. ■of little finger, ISO. hip-joint, 160. knee-joint, 166. occipito-atlautoid, 118. axoid, 119. - development of, 435 • functions of, 435. • glottis, 430. • m general, 429. • ligaments of, 425. • mucous membrane and glands of, 475. • muscles of, 427. ' sinus of, 434. ' surface, external, 429. internal, 430. ■ ventricle of, 427. ' vessels and nerves, 435. Leg, articulations of, 168. bones of, 96. compared with forearm, 105. fascia of, 311. Lemniscus, 711. Lens. See Crystalline Lens. Levator muscles. See Muscles. Levers, three orders of, in body, 199. Ligamenta-lsXs. of uterus, 475. subflava, general characters, 112. of vertebral column, 115. Ligaments in general, 1 13. articular, 112. capsular, 1 12. interosseous, 112. membranous, 112. structure of, 174. yellow or elastic, 112. Idgaments in particular, 113. accessory, of shoulder-joint, 139. hip-joint, 160. knee-joint, 165. • Weitbrecht, 144. ' alar, of axis (or odontoid), 119. of knee, 165. ' of ankle-joint, lateral, anterior external, 1 69. external proper, 169. internal, 169. posterior, 169. annular, of radius, 142, atlas, 117. carpus, anterior, 318, dorsal, 318. tarsus, dorsal and lateral, 313. arjrteno-epiglottid, 426. astragalo-calcaneal, interosseous, 171. • external, 171. posterior, 171. scaphoid, superior, 172. atlanto-axoid, anterior, 117. ■ posterior, 117. capsular, 117. odontoid, transverse or annular, 117, crucial, 117. scapulo-humeral, 137. sterno-clavicular, 136. ■ of each row of carpal bones, 147. - two rows of carpal bones, 147. carpo-metacarpal, dorsal, 150. palmar, 150. interosseous, with os mag num, 150. of little finger, 150. thumb, 150. cervical, posterior, of quadrupeds, 117. check, of axis (or odontoid), 119. chondro-sterual, anterior, 131. interosseous, 131. posterior, 131. ■ superior and inferior, 131 ' xiphoid, 131. ciliary, 656. conoid, 135. coraco-acromial. 140. clavicular, anterior, or trape7oid, 136 posterior, or conoid. 136 coraco-humeral, 139. — coracoid, 139. — costo-clavicular, 138. coracoid, 1 39. ■ transverse, interosseous, 131 posterior, 131. — superior, 131. ■vertebral, anterior, 131. inferior, 131. interosseous, 131. stellate, 131. superior, 131. cotyloid, of hip-joint, 159. crico-arytenoid, 426. thyroid, middle and lateral, 436 crucial, of atlas, 117. knee-joint, 164. of cuneiform bones of tarsus, 170. and scaphoid, 171 third and cuboid, l7l deltoid, 169. dorsal, annular, of carpus, 318. ■ tarsus, 313. carpo-metacarpal, 149. • of carpus, 149. — metacarpus, 149. — metatarsus, 175. ■ tarso-metatarsal, 175. • of tarsus, 171. elbow-joint, external lateral, 141. internal lateral, 141. anterior, 141. ■ posterior, 142. falciform, 303 Fallopius's, 302 of Ferr^in, 427. Gimbernat's, 303. glenoid, carpal anterior, 148. ■ posterior, 148 metacarpo-phalangal, 152. metatarso-phalangal, 175. phalangal, of fingers, 153. toes, 176. scapulo-humeral, 138. of auricle, anterior and posterior, 667. 5U glosso-epiglottid, 425. of hip-joint, anterior superior, 160. — accessory. 160. cotyloid, 160. iuter-articular, 161. 890 Ligaments of hip-joint, round, 161. capsular, 160. — I of humero-cubital, 141. hyo-epiglottid, 425. ilio-lurabar, 156. inter-articular, acroinio-claTicular, 135. of hip-joint, 160. of shoulder-joint, 137. sterno-clavicular, 136. temporo-maxillary, 128. of wrist, 143. osseous, astragalo-calcaneal, 171. of carpal bones, 147. carpo-metacarpal, 149. costo- transverse, 131. vertebral, 131. of forearm, 144. — knee-joint, 164. — leg, 169. — OS magnum and metacar- pus, 149. ■ metacarpal, 149. ■ metatarsal, 175. peroneo-tibial, 168. pubic, 156. radio-cubital, 143. sacro-iliac, 155. tarsal, of first row, 171. ■ second row, 171. tarso-metatarsal, 175. vertebral, 115. clavicular, 137. spinous, 116. vertebral, 115. of knee-joint, 163. accessory, 166. adipose (so called), 166. alar, 166. anterior, 163. capsular, 163. crucial anterior, 164. • posterior, 163. ■ inter-articular, 163. osseous, 164. lateral, external, 163. internal, 163. ■ mucous (so called), 166. • posterior, 163. transverse, 163. of laryni, 425. — malleus, 673. metacarpo-phalangal, glenoid, 152. lateral, 152. ■of thumb, 152. of metacarpus, 148. metatarso-phalangal, glenoid, 176. — lateral, 176. of metatarsus, 175. occipito-atlantal anterior, superficial, 116. deep, 116. capsular, 117. lateral, 117. posterior, 116. ' axoid, lateral, 120. middle, 120. odontoid, lateral, 120. middle, 120. orbicular, of acromio-clavicular articula- tion, 137. ■ of hip-joint, 158. scapulo-humeral, 139. sterno-clavicular, 137. palmar of carpo-metacarpal joints, 149. carpus, 147. - metacarpus, 148. of patella, 164. perineal, 307. peroneo-tarsal, anterior external, 170. external, 170. posterior, 170. — of peroneo-tibial articulations, 167, 168. — perpendicular, 170. — phalangal of fingers, glenoid, 153. ■ lateral, 153. toes, glenoid, 177. lateral, 177. of pisiform and cuneiform bones, 147. plantar inferior, 174. of metatarsus, 176. tarso-metatarsal, 176. Ligaments, plantar of tarsus, 172 Poupart's, 302. proper, of scapula, anterior, 140. posterior, 140. - pterygo-maxillary, 235. - pubic anterior, 155. inferior, 155. interosseous, 155. posterior, 155. superior, 155. triangular, 155. ■ radiated chondro-sternal, 133. ■ of radio-carpal articulation, 145. cubital articulations, 144. ■ recto-uterine, 467. ■ round, of forearm, 144. hip-joint, 161. ■ uterus, 466. ■ sacro-coccygeal, anterior, 120. posterior, 120. ■ iliac, anterior, 154. interosseous, 154. posterior vertical, 155. superior, 154. sciatic, great, 155. small, 155. vertebral, 120. — scaphoid and cuboid, 172. — of shoulder-joint, 136. — spheno-maxillary, 129. — stellate, costo-vertebral, 130. ' or radiated, chondro-stemal, 13L • stylo-maxillary, 129. mylo-hyoid, 129. ■ sub-pubic, or inferior pubic, 156. • supra-spinous, 119. ■ suspensory of clitoris, 471. ' penis, 456. — liver, 386, 475. — of first row of tarsal bones, 171 . second row of tarsal bones, 171. — tarso-metatarsal, dorsal, 174. interosseous, 174. oblique of fifth toe, 175. plantar, 174. — of temporo-maxillary articulation, lateral external, 128. — internal, 129. — thyro-arytenoid, or chords vocales, 427. epig:lottid, 425. hyoid, middle and lateral, 425. — tibio-tarsal, anterior, 169. internal, 169. posterior, 169. ■ of tragus, 667. • transverse of atlas, 117. knee, 163. metacarpus, 149. • trapezoid, 136. ■ triangular of perinaeum, 307. penis, 455. symphysis pubis, 156. urethra, 307. wrist, 143. ■ of two rows of tarsal bones, 171. ■ vertebral, anterior common, 116. interosseous, 116. • posterior, 116. — yellow elastic, 117. - vesico-uterine, 467. - of Weitbrecht, 144. — Winslow, 164. — wrist-joint, external anterior, 146. — internal anterior, 146. middle anterior, 146. ■ external lateral, 146. . internal lateral, 146. posterior, 146. of Zinn, 650. Ligamentum arcuatum of diaphragm, 213 denticulatum, 694. fibulae anterius, 170. medium, 170. perpendiculare, 170. posterius, 170. gastro-phrenicum, 354. latum pulmonis, 413. longum plantae, 173. mucosum of knee-joint, 164. nnchffi, 202. INDEX. 891 Ligamentum-piteXIs, 164. phrenico-lienale, 403. proprium anterius scapuls, 140. posterius scapula, 140. teres of forearm, 144. ■ '■ hip-joint, 161. lambs. See Extremities. Limbus luteus, 660. Line, inter-trochanteric, 94. mylo-hyoidean, 57. naso-labial, 327. Lines, semicircular of occipital bone, S3> -— ^— — ^— OS cuxse, 88. Litua alba, 301. cervical, 300. aspera, 94. Ups, 325. — — development of, 326. movemeuts of, 238 muscles of, 326. structure of, 326. uses of, 327. vessels of, 327. Liquor Cotunni, 680. • Morgagni, 663. of Scarpa, 680. Liver, 385. acini of, 390. circumference of, 389. • coats of, 390. colour and fragility, 389. development of, 399. ducts of, 391 (notes). excretory apparatus of, 395. figure, 386. fissures, 387. functions, 400. groove for vena cava, 389 hilusof, 388. ligament, broad or suspensory, 386. coronary, 390. falciform, 386. triangular, left and right, 390 lobes, 387. lobules or granules, 388. arrangement of, 391. ' structure of, 394 (note). - lymphatics of, 393. -nerves of, 393. -porta of, 388. - proper tissue, 390 (note). ■ situation, 385. ■ size, 385. -structure of, 390. - surface, inferior or plane, 386. • superior, 386. Lungs, vessels and nerves of, 421. weight of, absolute and specific, 410. Lymphatic duct, right, 619. - glands in general, 616. preparation of, 617. structure of, 617. in particular, 619. axillary, 628. bronchial, 625. cervical, deep, 628. superficial, 627. ■ of cranium, 626. • duodenal, 624. ■ of face, 626. ■ ileo-colic, 624. • iliac, external, 622. internal, 622. ■inguinal, 619. ■ intercostal, 625. ■ of intestine, great, 624. — small, 624. of liver, 623. of lower extremity, 620. lumbar, 621. mammary, 625. mediastinal, 625. mesenteric, 625. meso-colic, 624. of pancreas, 624. parotid, 627. of pelvis, 621. popliteal, 619. pulmonary, 625. sacral, 621. of spleen, 624. of stomach, 624. .sub-maxillary, 627. sub-sternal, 625. tibial anterior, 619. tracheal, 627. of upper extremity, 628. ■ part of trunk, 628. ■ hearts of lovfcr animals, 617. ' networks, superficial and deep, 613. ■ plexuses, 612. system, 611. vessels of, 392. arrangement of, 393. Lobes and lobules of organs. See thorn organs. Lobule of ear, 666. Lobulus caudatus, 389. quadratus, 389. SpigeUi, 389. Locus niger, 751. perforatus anterior, 731. middle or posterior, 727. Longissimus dorsi. See Muscles. Longitudinal fissures of liver, &c. See those organs. vein of spine. See Vein*. Luette of bladder, 459. Lumbar nerves. See Nerves. region of abdomen, 352. veins. See Veins. vertebne. See Vertebra and Vertebra. Lungs, 409. air-ceUs of, 415. air-tubos of, 416. cellular tissue of, inter-lobular, 415. development of, 421. external conformation of, 411. ^, fissures of, inter-lobular, 411. foetal, 421. functions, 422. lobes of, 411. lobules of, 415. structure of, 419. lymphatic system of, 421. root of, 412. size of, 409. ■ structure of, 413. vessels in general, 611. aflferent, 614. ' anastomoses of, 614. branches of, 614. coat of external, 616. ' internal, 616. course and direction, 614. ' deep and superficial sets of, 618. ■ efferent, 614. origin of, in different tissues, 612. • preparation of, 617. structure of, 616. terminations of, 614. valves of, 617. vessels of, 616. in particular, 618. of bones, 16. of brain, 628. of cellular tissue, 613. cervical, 628. ' posterior, 639. of cranium, 637. dorsal, 629. of dura mater, 627. epigastric, 622. of external genitals, male and &• male, 620. of face, 627. gluteal, 620. of heart, 626. ilio-lumbar, 622. intercostal, 626. of intestines, great, 625. ■ small, 625. of kidneys, 622. of lining membrane of bloodvessels, 613. of liver, deep, 623. superficial, 623. ' of lower extremity, deep and super* ficial, 619. lumbar, lateral, 622. ■ superficial, 620. of lungs, deep and superficial, 626. 892 INSEJX. Lymphatic vessels, mammary, internal, 626. meningeal, 627. of mucous membranes, 612. occipital, 627. of pelvis, 621. pericardiac, 626. periuaeal, 620. peroneal, 620. of serous and sysovial tissues, 613, of skin, 613. of spleen, 624. of stomach, 624. sub-sternal, 626 supra-renal, 622, temporal, 626. of testicles, 622. thorax, 625. thymic, 626. thyroid, 627. tibial, anterior and posterior, 620. of upper extremity, 628. • part of trunk, 628. uterine 628. Lyra, 738. Macula cribrosa, 676l Malar foramina, 54. process, 51. bone, 54. Malleolus, external, 97. internal, 98. Malleus, and ligament of, 673. muscles of, 673. Mamma, 471. adipose tissue of, 473. development of, 474. fibrous tissue of, 473. glandular tissue of, 473. lactiferous ducts of, 473. ■ of the male, 473. vessels and nerves of, 474. Mammary gland. See Mamma. Mammillm. See Nipples. Mammillary enlargements of posterior median colunms of spinal cord, 704. of inferior vermis, 716, 718. tubercles, 426. Manubrium of malleus, 673. of sternum, 65. Marrow of bones, 12. Massa camea Jacobi Sylvij, 291. Mastoid foramen, 43. portion of temporal bone, 43. process, 43. Maxillary arteries. See Arteries. bone, inferior, 57. superior, 51. canal, superior, 51. inferior, 58. nerves. See Nervet. tuberosity, 51. Jlfar^o-dentatus, 660. MeeUus of nose, inferior, 54. middle, 41. • superior, 41. auditorius externus, 44. iutemus, 44. urinarius, female, 471. male, 461. See Bar. See Ear. Mechanism of particular joints. Mediastinum, anterior, 414. posterior, 413. See those joints. Medulla oblongata, 702. comparative anatomy of, 709. development of, 708. external conformation of, 702. anterior surface, 703. lateral surfaces, 704. — posterior surface, 704. ' faisccaux innomines of, 706. at base of brain, 706. • in isthmus, 715. fasciculi graciles, 708 (note). olivary, 708 (note). re-enforcing, 708. teretes, 708 (note). • pyramidal, 702, 704, ' fibres of, antero-posterior, 707. arched, 704. decussation of, 706. MeduUa oblongata, foramen caecum of, 703. furrow of median, anterior, 703. posterior, 704. ■ internal structure of, 706. — neck of, 702. sections of, 705. of long bones, 12. spinalis. See Spinal Cord. examined by hardening, 706. sections, 705. water, 706. Medullary canal of long bones, 13. membrane, 14. Meibomian glands, 648. Membrana nictitans, 648. pupillaris, 659. Ruyschiana, 657. sacciformis, 143. tympani, 669. secundaria, 670. uvea, 659. Membrane, hyaloid, 661. obturator, or sub-pubic, 155. Membranes of cerebro-spinal axis. See ATodmotd, Dura Mater, and Pia Mater. of eye. See Eye. fibro-mucous See Tibro-mucous Mem- branes. — fibro-serous. See Fibro-serous Membranes — — — ^ mucous. See Mucous Membranes. — ^^^— serous. See Serous Membranes. ^— — ^— synovial. See Synovial Membranes. Membranous labyrinth, 679, part of urethra, 458. Meningeal arteries. See Arteries. Meninges, 681. Meningoses, 113. Meniscus, 113. Mental fossa, 57. foramen, 57. process, 56. Mesentery, 364, 477. left layer, 475. right layer, 475. Meso-cxcxim, 471. ■ colon, iliac, 475. left and right, 475. transverse, 375. layer, inferior, 476. — superior, 477 ' ■ - ga-strium, 478. — — rectum, 475. Metacarpus, bones of, 84. ■ differential characters, 89. general characters, 85. ■ compared with metatarsus, 109. Metatarsus, bones of, 103. characters, general, 103. differential, 102. compared with metacarpus, 109. Milk teeth. See Teeth. Modiolus of cochlea, 678. Mom Veneris, 470. Morsus diaboli, and fimbriie of Fallopian tube, 463. Motores oculi nerves. See Nerves. Mouth, component parts of, 422. situation, dimensions, &c., 422. Movements of joints. See Articulations. in general, 148. lips and face, 238. Mucous bursae (so called), 175. membranes, in general, 421. chemical composition, 42L epithelium, 421. ■ of particular organs. See thoa organs. — structure, 421. Mucro, 65. MultifiduM spinae. See Muscles- Muscles in general, 190. action of, 194. angle of incidence on bones, 195. antagonist, 196. aponeuroses of, 193. arrangement, physiological, of, 291. attachments of, 192. — fixed, 191 movable, 193. broad, 190. conge.nen 789. - hand, 790. - for ulnar artery, 790. - uterine, 870. - vaginal, 870. - for vasti femoris, 802. - vertebral (sympathetic), 860. ■ vesical, 870. ■ vestibular, 843. ■ vidian, 833. ■ visceral, abdominal, 866. cervical, 845. pelvic, 869 ■ sacral, 805 Nervi moUes, 845. Nervous system, central portion, 681. peripheral portion, 769.1 Nervut impar, 698. Neurilemma of nerves, 766. spinal cord, 697. Neurology, 629. Ninth nerve. See Nerve, hypoglossal. Nipples, 472. glands and papillte of, 473. Noduli Arantii, 479. Nodulus of cerebellum, 716 (note). Nodus encephali (Soemmering), 844- Ncsud de I'encephale, 844. Nost, general description, 641. bones of, 55, 641. cartilages of, 641. mucous membrane of« MStt ' muscles of, 643. septum of, 56, 642. skin of, 643. Nostrils, 641. cartilages of, 641. Notch, inter-cocSyloid, 91. ischiatic, 89. -—^— sacro-sciatic, 89. great, 15S. small, 156. sciatic, 89. ' sigmoid, 57. Notches, vertebral, 20, 31. Nutritious arteries. See Arteries. foramina of bones. See Fontmen. Nympha, 471. ■Obligue muscles. See Musclet. 'Obturator foramen and groove, 88. nerve. See Nerves. ' Occipital angle of DaubentOB, 45. bone, 33. condyles, 33< crests, 34. foramen, 34. fossae, 34. ' nerves. See iVerM*. Occipital protuberances, 34. veins. See Veins. Occt7>ito-atlantoid articulations, 118 ligaments, 118. ' axoid articulations, 119. ' ligaments, l20. parietal suture, 46, OcuZo-muscular nerves. See Nenitt, Motwr Oaii tad Pathetic. Odontoid process, 26. Odontogeny, 184. Odontology, 177. (Esophagus, 350. • glands of, 352. ihooous membrane, 352. muscular coat, 351. structure of, 351. uses, 352. vessels and nerves, 3S3, OUcranoid cavity, 80, Olecranon process, 80. Olfactory nerve. See Nervtt ■ lobes, 758. Olivary process, 37, bodies, 703. corpus dent&taiB of, 704. sections of, 704. structure of, 706. fasciculi, 705. Omentum, colic, 478 (note). - gastro-colic, 478. hepatic, 476. — splenic, 408. ■ great, 476. layers of, anterior, 476. -posterior, 476. «ac of, 477. vessels and nerves of, 478. lesser, 476. layer of, anterior, 476. posterior, 476. Operculum laryngis, 426, Ophthalmic nerve, 828. Optic thalami, 727, 745. fibres of, 746, tracts, 820. Orbicular ligaments of joints.- See Ligaments. Orbital arch, 36. cavities, 6 fissure, 53. foramina, internal, 36. process of palate bone, 6S. processes of frontal bone, 36. plate, 36. Orbits, 62. Organ of hearing, 665. See Ekir. sight, 645, See Eye. smell, 641, See Nose, &aA Pituitary Mttnbrcoi*. taste, 639. See Tongue. touch, 629. See Skin. the voice, 422. See Larynx. Organs, anatomical elements of, 320. colour and consistence of, 321. development of, 321, of digestion, 322, direction and relations of, 3S1. dissection of, 322, functions of, 322, of generation, female, 46], male, 446. genito-urinary, 435, nomenclature, 320, number, 320. of respiration, 409. of the senses, 629. situation, 320. size and figure, 321. structure of, 321. urinary, 435. Os, bone. See Bone, oi. tincsE, 465. uteri, 465. Ossa pisiformia, or lingualia. 111. triquetra, or Wormiana, 50. Ossicula auditOs, 669. movements of, 675. muscles belonging to, 674. Ossification of bones. See those bones Osteology, 5. Osteogeny, 16. INDEX. 899 Ottia of Fallopian tube, 463. Ottium internum of uterus, 465. Otoconia and otolithes, 843. Ova of Naboth, 466. Ovarian vesicles, 463. Ovaries, 461. • ligaments of, 461. - structure, 463. Ovum, 462 Palate, bone, 53. hard, 330. development, 330. structure, 330. uses, 330. soft, 330. - aponeurosis of, 331. ————— development of, 333. glands of, 333. — — — — mucous membrane of, SSS. muscles of, 331, pillars of, 331. ■ structure of, 331 — uses of, 331. — vessels, &c., of, 333. Palatine aponeurosis, 331. arch, 329. canals, 52, 54. accessory, 53, 54. glands, 330. • process, 52. Palm of hand, 83. Palmar arteries. See Arteries. ligaments. See Ligament*. nerves. See Nerve*. Pancreas, 400. development of, 409. duct of, 402. function of, 402. lesser, 402. structure of, 401. 1 vessels and nerves of, 408. Panniculus adiposus, 629. camosus, 629. Papula, conjunctival, 648. dental, 181. (Goodsir), 183. of kidney, 437. — — — lachrymal, 646. of skin, 630. ~ of small intestine, 367. of stomach, 361. of tongue, 333. Par vagum. See Nerve, pneumogoitric Parietal bone, 41. foramen, 41. ■- fossa, 41. protuberance, 41. Parotid dnct, 341. gland, 340. development of, 340 (note). structure of, 340. Pars mastoidea of temporal bone, 43. petrosa of temporal bone, 43. squamosa of temporal bone, 43. Patella, 95. ligament of, 97. Pathetic nerve. See Nerve*. Patte d'oie, 270, 271. Peduncles of cerebellum and cerebram. gans. Pelvis, aponeuroses of, 306. articulations of, 154. •^—^ axes of, 90. • circumferences of, 92. • compared with shoulder, lOS. . development of, general, 93. ' in general, 90, ■ great or false, 90. of the kidney, 439. : structure of, 439. little or true, 90. brim of, 92. strait, superior, 92, ■ inferior, 92. See those or- mechanism of, 158-159. regions of, 90. ' varieties of, sexual, 90. excavation or cavity of, 12S. outlet of, 92. Penis, 454. corpus cavemosum of, 455. glans of, 461. ligament, suspensory or triangular, 45A muscles of, 457. Perforated spot, anterior, 734. ■ posterior, 730. Perforating arteries. See Arteries. nerves. See Nerve*. Pert-cardium, 494. structure, 494. vessels, 495. Peritoneum, 474. folds of, 478. general description of, 478. portion of, parietal, 478. sub-umbilical, 474. supra-umbili(^, 474 visceral, 477. structure of, 479. Permanent teeth. See Teeth. Perone, 98. Peroneal arteries. See Arteries. See Nerve*. Pes accessorius, 746. hippocampi, 745. Petrosal nerves. See Nerves. ^ Petrous portion of temporal bone, 4S. process, 43. ' glottis, 640. • lymph, 679. ' osteum, 296. ' alveolo-dental, 338. Pharyngeal nerves. See Nerve*. Pharynx, 344. aponeuroses of, 346. development of, 349. mucous membrane of, 319. muscles of, 346. extrinsic, 346. intrinsic, 346. supernumerary, 346. uses, 349. vessels and nerves, 349. Pia mater, 692. cerebral, 692. spinal, or rachidian, 697. Pigmentum of skin, 632 (note) eye, 659, Pillar of valve of Vieussens, 712. Pillars of diaphragm, 212. - fauces, or palate, 331. fornix, 740. Pineal gland or body, 742. - commissure and peduncles of, 743. - concretions, 743. function of, 744. Pisiform bone, 83. Pt ' bronchial, 848. • cardiac, deep, 860. great, 863. ' carotid, 856. ■ superficial, 862. — cavernous, 856. — cervical, 777. deep, 777. 900 INDEX. Plexuses, cervical, posterior, 774. superficial, 777. — ■^-— cervico-brachial, 77(i coeliac, 866. coronary, of heart, anterior and posterior, 863, of stomach, 866. ' diaphragmatic, I ' epigastric, 866. ' facial (sympathetic), 858. ' gastro-epiploic, left, 868. • right, 867. — hemorrhoidal, inferior, 890. snporior, 868. ■ hepatic, 867. • hypogastric, 870. ■ infra-orbital, 841. • laryngeal, 846. ' lingual, 858. ' lymphatic, 612, . lumbar, 797. ' lumbo-aortic, 868, 869. sacral, 776. ' mental, 837. ' mesenteric, inferior, 868. superior, 867. ■ nervous, 762. ■ occipital, 859. ■ ovarian, 868. • pharyngeal, 846, 859. • phrenic, 866. ■ pulmonary, anterior and poBtraior, 848. • renal, 868. ■ sacral, 805. • solar, 866. ■ spermatic, 868. ■ splenic, 867. ' supra-renal, 866. • thyroid, 858. • tympanic, 843. • uterine, 870. ' vertebral, 860. vesical, 870. visceral of abdomen, 866. pelvis, 805, 869 ■ of veins, 575, et infrd. alveolar, 589. choroid, of brain, 747. fourth ventricle, 730. ■ third ventricle, 741. - reflected portion of, 746. ■ hemorrhoidal, 601. ■ intra-spinal, 609. • lingual, 590. ■ masseteric, 590. • pampiniform, 598. ' pharyngeal, 591. • pterygoid, 590. ■ spermatic, 598. ' spinal, deep, 609. ■ longitudinal, 609. - transverse, 609. ' tonsillar, 333. ' uterine, 602. ' vaginal, 60S. ■ vesico-prostatic, 601. urethral, 602. Plica semilunaris, 648. Pneumo-gastric nerve. See Nene. Pomum Adami, 424. Pons Varolii, or cerebelli, 710. internal structure rf, 718. Porta, 388. Portia dura nerve. See Nerve. mollis nerve. See Nerve. Prepuce, 454. of clitoris, 471. frcenum of, 454. Process, acromion, 76. auditory, 44. basilar, 34. cochleariform, 44, 673. - coracoid, 76. — — — coronoid, of lower jaw, 58. of ulna, 80. ensiform, 65. of fifth metatarsal bone, 104. ' genial, 58. — gracilis of Raw, 673. — hamular, of sphenoid bone, 37. of cochlea. 678. Process, of helix, 667. ■ malar, 51. ■ mastoid, 43. ■ mental, 58. ■ nasal, 51. ■ odontoid, 26. ' olecranon, 80. — olivarv, 37. — orbital, external, 36. ■ internal, 36. — of palate bone, M. palatine, 52. ' petrous, 43. ' pyramidal, 54. ' scaphoid, 101. ' styloid, of temporal bone, 4S. ulna, 80. ■ radius, 81. fibula, 99. ' vaginal, of temporal bone, 44. — vermiform, inferior, 716. ■ superior, 716. ' zygomatic, of temporal bone, 43. of malar bone, 55. Processes of bones, 9. ciliary, of choroid coat, 656. vitreous humour, 661 calcaneal, 101. clinoid, 37. pterygoid, 37. spinous, of ilium, 89. spinous, of vertebne, 21. Processus a cerebello ad meduUam, 704. pontem, 721. testes, 711. ' a cerebro ad meduUam, 710. • arciformes, 703. — gracilis of Raw, 673. Profunda artery. See Arteries. vein. See Veins. Promontory of sacrum, 26, 92. tympanum, 671. Pronator muscles. See Musclet, Protuberances, occipital, 34. parietal, 42. Psalterium, 738. Pterygoid canal, 37. columns, 126. fossa, 37. processes, 37. P/ery^o-maxillary fissure, 52. palatine canal, 38, 52. Pubes, 90. Pubic arch, 89. Pudic arteries. See Arteries. Pulmonary arteries. See Arteries. veins. See Veins. Puncta lachrymalia, 647. Pupil of eye, 657. Pupillary membrane, 659. Pyloric valve, 355. Pylorus, 354. antrum of, 354. Pyramid of cerebellum, or of Malacame, 717. of tympanum, and its canal, 671. Pyramids, anterior, 703. decussation of, 706. sections of, 706. ■ of kidney, 437. posterior, 704. sections of, 706. Quadrati muscles. See Muscles. Rachis. See Vertebral Column. Rachidian bulb, proper. See Medulla Oblongata. bulbs, 697. veins. See Veins, spinal. Radial nerve. See Nerve. Radiating crown of Reil, 744. Radius, 81. ^ and tibia, lower parts of, compared, 107. Ra/ni of lower jaw, 57. Ramus of pubes, 90. ischium, 91. Receptaculi arteriie, 525. Receptaculum chyli, 618. ganglii petrosi, 843. Recess of tympanum, 672. Recessvs sulciformis, 676. INDEX. 901 Recti muscles. See Muteltt, Rectum, 376. columns of, 377. curves of, 377. ■ internal surface, 378. muscular coat of, 377. structure of, 377. Recurrent arteries. See Arteriet. nerves. See Nerves. Renes. See Kidneys. succenturiati. See Supra-renal Capsules. Respiratory apparatus, 409. nerves, in particular. See Nerves. Restiform bodies, 704. Rete of Malpigbi, 640. mucosum, 640. of tongue, 646. yasculosum testis, 451. Reiia mirabilia, 496. Retina, 660. artery of, 660. folds of, 660. foramen centrale, and limbnt Inteua of, 660. • margo dentatus, 660. structure of, 660 (note). termination of, 660 (note). Ribs, angles of, 68. characters of, general, 67. — special, 68. false, 67. movements of, 134. supernumerary, 32. true, 67. torsion of, 67. tubercle of, 68. Rima glottidis, 434. palpebrarum, 646L Ring, crural, 310. inguinal, 310. umbilical, 308. Rostrum of cochlea, 676. of corpus callosum, 787. Rotula, 95. Rugee, vaginal, 468. Sac, lachrymal, 652. Sacculus vestibuli, 680. or sinus laryngis, 434. Sacral arteries. See Arteries. canal, 27. foramina, 27. nerves. See Nerves. vertebne. See Vertebra and Vertebra.. Socro-coccygeal vertebne, 26. sciatic notch, 92. vertebral angle, or promontory, 90. Sacrum, 26. promontory of, 26. — — — small comua of, 27. Saliva, 396. Salivary glands, 340. Saphenous nerves. See Nerves, Satellite arteries. See Arteries. • — nerves. See Nerves. Scaphoid bone of carpus, 83. of tarsus, 101. ' process, 101. Scapula, 75. Scapular arteries. See Arteries. Schindylesis, 114. Sciatic notch, 89. spine, 89. Scrobiculis cordis, 354, 482. Scrotum, 447. Second cranial nenre. See Nerve, optic. Sella turcica, 37. Semen, 453. Semi-circular canals, and their ampulle, 677. membranous, 680. lines of occipital bone, 33. lunar bone, 83. ■ ganglion, of fifth nerve, 843. Seminiferous tubes, 454. Septa, inter-muscular, 294. — ^— — ^-^— — ^— — of arm, 315. of thigh, 306. Septum crarale, 303. of dartos, 446. inter-auricular, 482. Seytum, inter-ventricular (of brain), 518. (of heart), 481 • lucidum, 738. layers of, 738. ventricle of, 738. nasal, artery of, 518. cartilaginous, 642. osseous, 56, 62. pectiniforme, 454, Serrati muscles. See Muscles. Sesamoid bones, 96. of hand, 153. of foot, 177. of gastrocnemius, 164. Seventh cranial nerve. See Nerve, Portio Dura, aiui Portio Mollis. Sheath of brachial vessels, 316. - femoral vessels, 310. - for muscles, 296. of arm, 316. thigh, 311. ■ synovial, 178. ■ for tendons, 397. around carpus, 319. - - tarsus, 314. • for vessels, 396. ' structure of, 397. Shoulder, aponeuroses of, 315. bones of, 73. compared -with pelvis, 105. development of, general, 77. in general, 77. Sigmoid cavities, great and small, 80. - flexure, 371. - notch, 57. - valves, 484. Sinus, or sinuses, aortic, 498. basilar, 587. of bones, 1 1 . of bulb of urethra, 459. cavernous, 587. circular, of Ridley, 588. common, of vestibule, 680. confluences of, 588. ■ coronary, of heart, 577. of Ridley, 587. of dura mater, 583. ethmoidal, 43. frontal, 36. of internal jugular, 583 lateral, or transverse, 584. of larynx, or sinus of Morgagui, 584- longitudinal, inferior, 586. superior, 584. — maxillary, 52. -^ of Morgagni, 461. — occipital, anterior, 587. posterior, 587. ' ophthalmic, 587. ' petrosal, inferior, 586. superior, 566. — prostatic, 459. — sphenoidal, 40. — straight, 585. — transverse, or lateral, 984. — of urethra, 459. — uterine, 602. >- of Valsalva, 498. — of veins, 575. — of vena ports, 599. — venosus (heart), 492. Sixth cranial nerve. See Nerve. Skeleton, general view of, 5. natural, 5. artificial, 5. Skin, 629. appendages of, 635. characters, external, 629. Spine, cutis or dermis of, 630. epidermis of, 632 (note). follicles, sebaceous, 627. functions of, 627. glands, sudoriferous, 632. lymphatics of, 631. papilla of, 639. pigmentum of, 631, 632 (note). pores of, 632. rete mucosum, 633 (note). structure of, 630-634. true, 630. ^P^2 Skull, 33 See Cranium and Face. Socio parotidis, 341. Sole of foot, 102. Solitary glands. See Glands. Space, inter-peduncular, 711, 728. Spaces, inter-costal, 71. osseous, hand, 84. foot, 106. INDEX. ' sub-arachnoid, 688. Sphenoidal cells, or sinuses, 39. fissure, 39. Sphenoid bone, 37. S;)Aeno-frontal suture, 47. jugal suture, 47. maxillary fissure, 39, 5S. ' fossa, 60. ■ occipital bone, 36. ~ suture, 47. palatine foramen, 54. parietal suture, 47. spinous foramen, 39. temporal fossae, 48. suture, 47. Sphincter muscles. See Muscles. Spinal accessory nerre. See Nerve, accessory. arteries. See Arteries. cord, 693. — ■ arachnoid of, 690. enlargements of, cervical, lumbar, and oc- cipital, 697. ■ enveloped in its proper membrane, 697. extent and situation of, 694. form, direction, and relations of, 696. furrows or grooves, 698. — ^— — ^— membrane proper, or neurilemma of, 697. pia mater of, 697. ■ sections of, 700. structure of, internal, 700. examined by hardening, 702. ■ sections, 700. water, 701. substance, gray and white, 702. • minute structure, 702 (note). • ventricles of, 702. See Vertebral Column. muscles, posterior. See Muscles. nerves. See Nerves. veins and plexuses. See Veirts. Spine, nasal, anterior, 52. posterior, 54« of ischium, 89. of pubes, 89. of scapula, 75. sciatic, 89. or spinal column, 18. of tibia, 97. Spinous foramen of sphenoid, 39. processes of ilium, 89. of vertebrsE, 19, 31. Splanchnic nerves. See Nerves. Splanchnology, 320. Spleen, 403. cells of, 405. coats of, 405. • corpuscules of, 407. development of, 407. • fissure, or hilus, 405. functions, 408. lymphatics of, 407. size of, differences in, 403. ■ structure of, 405. vessels and nerves, 405, 408. Spleens, supernumerary, 403. Splenic artery, 406. omentum, 405. veins, 406. Spongy bones. See Bone*. Stapes, 674. Stenonian duct, 341. Sternum, 64. Stomach, 352. alveoli of, 361. coat of, cellular or fibrous, 357. mucous, 356. muscular, 356. nervous (so called), 356, - serous, or peritoneal, 357. culs-de-sac of, 354. curvatures of, 354. development of, 361. extremities of, 354. Stomach, follicles of, 360. function, 361. glands of, 360. granular appearance of, 397. ' lymphatic system of, 360. ' orifices of, 355. ' papillse or villi, 359. ■ structure of, 356. ' surface of, external, 353. ' internal, 355. tuberosity of, 355. tubnli of, 360. vessels and nerves of, 360. Structure of tissues and organs. See those organs and tissues. Styloid bone, 43. process of temporal bone, 43. fibula, 99. radius, 81. ulna, 80. Sui-arachnoid fluid, 690. uses of, 692. ■ space, cranial, anterior, 688. ' posterior, 686. spinal, 689 (note). lingual fossa, 58. gland, 343. ducts of, 343. maxillary fossa, 58. gland, 342. duct of, 342. synovial adipose tissue, 113. Sulci. See Cerebrum, anfractuositiet of. Super-ciliary foramen, 36. ridge, 35. Superficial petrosal nerves. See Nerves. Supplementary cavity of shoulder-joint, 139. of temporo-maxillary joint, 138. Supro-orbitary foramen, 36, 59. renal capsules, development of, 445. structure, 446. sphenoidal fossa, 37. spinous fossa, 76. Sustentaculum tali, 101. Suture, coronal, or fronto-parietal, 45, 47. ethmoido-frontal, 48. ethmo-sphenoidal, 48. fronto-jugal, 48, 59. maxillary, 59. nasal, 59. sphenoidal, 48. lambdoidal, or occipito-paxiet^, 40. maxiUary, 59. palatine, 60. petro-occipital, 47. sphenoidal, 48. ■ sagfittal or bi-parietal, 46. ■ spheno-frontal, 47. jugal, 47. parietal, 47. temporal, 48. ■ squamous, 47. ■ temporo-parietal, 47. ■ transverse or spheno-occipital, 46, 49. Sutures, 114. indented, squamous, and harmonic, 114. cranial, in general, 154. Sympathetic ganglia in particular. See Ganglia^ nerves. See Nerves. plexuses, in particular. See Plexuset, system, in particular. See Ganglia and Nerves. Symphyses, characters of, 114. Sympftysis menti, 57. pubis, 89, 155. sacro-iliac, 155. Synarthroses, 114. characters, ligaments, and motioni, llSk Synchondroses, 113. Syndesmology, 111. Syneuroses, li3. Synovia, 112. Synovial bnrsae, 178. capsules, 113. of particular joints. See thov joints ' fringes, 112. ■ in the knee, 164. ■ glands (so-called), 112. membranes, articular, general characters of, 112. INDXX. 903 Synovial membranes, bursal, 178, 298. ■ minute structure of, 178. vaginal, 178, 299. sheaths for tendons, 178, 298. Syssarcostf, 114. Taenia hippocsunpi, 746. semicircularis, 740, 745. Tarsus, bones of, 99. • first row of, 100. • ^_^____ compared with first row of carpus, 107. -^————— second row of, 101. ' compared with second row of carpus, 107. ■ compared with carpus, 108, sheaths for tendons on, 313. Teeth, 177. arteries of, 182. bicuspid, 179. bulbs of, 181. canine, 180. cement of, 182. changes in, after eruption, 190. ■ characters of, general, 179. — differential, 179. classification of, 178. compared with bones, 183 (note). epidermoid appendage*, 177. - compound, 182. - conformation of, external, 179. — internal, 181. - cortical portion of, 181. substance of, proper, 182. ■ crowns of, 179. - crusta petrosa of, 182, and note. ■ cuspid, 179. - development of, 183. different stages of, 184. ■ distinguished from bones, 177. ■ enamel of, 182. chemical composition of, 183. development of, 186. structure of, 183 (note). ■ fangs of, 178. ■ formation of, 186. Teeth, wisdom, 181. uses of, 189. two sets of, 189. Tela choroidea, 731. Temporal arteries. See Arteriei. bone, 42. fossa, 47. nerves. See Nerves. Temporo-pditietaX suture, 47. Tendo AchiUis, 283. Tendon of Zinn, 650. straight of orbicularis palpebranun, 053 Tendons of muscles, 193. structure of, 299. Tensor muscles. See Muscles. Tentorium cerebelU, 684. Testes (of brain), 712. Testicles, 446. coverings of, 446. excretory duct of, 452. proper coat of, 449. structure of, 449. tubuli of, 450. tunica albuginea, 449. erythroides, 447. propria, 449. vaginalis, 447, - vessels and nerves of, iSl. Testis, coni vasculosi of, 452. mediastinum, 450. rete vasculosum, 451. tubuli, 450. Testicular artery, 451. Thalami optic, 742. structure of, 744. TAt^Abone 93. compared with arm bone, lOS. nird cranial nerve. See Nerve. Thoracic arteries. See Arteries. Thorax, aponeuroses of, 300. - articulations of, 130. - bones of, 64. development of, geikersl, 73. - follicles of, 185. (Goodsir). 183 (note). - general idea of, 190. - incisor, 179 - ivory of, 183. ~ chemical compomtion of, 182. development of, 165. structure of, 183 (note). -milk. See Temporary. ' molar, 180. great and small, 180. upper and lower compared, 181. ■ multi-cuspid, 181. ■ nerves of, 181. • number of, 177. ■ permanent, 177. decadence of, 190. development of, 190. differences of, from temporary, 190. eruption of", 189. — ■ follicular stage of, 184. origin of pulps and sac* of, 164. papillary stage of, 184. — saccular stage of, 185. ■ provisional. See Temporary. ■ pulps of, 181. • origin of, 184. ■ quadri-cuspid, 181. - sacs of, 186. origin of, 184. - simple, 183. ■ structure, general, 181. — minute, 183. ■ supernumerary, 187. tartar of, 183. • temporary, 177. development of, 183. differences of, from permanent, 190. ■ eruption of, 183. follicular stage of, 180. origin of pulps and sacs of, 184. papillary stage of, 184. saccular stage of, 184. shedding of, 188. - general description of, 70. - mechanism of, 132. - movements of, in general, 134. one rib of, 132. 7%yro-arytenoid ligaments. See Chords Yoctiei Thyroid arteries. See Arteries. • — — veins. See Veins. Tibia, ' and ulna, upper parts of, compared, 107. radius, lower parts of, compared, 107. Tibial arteries. See Arteries, nerves. See Nerves. Tissue, adipose, 175. bony, 12, 13. cartilaginous, 174. ceUular, 298. elastic, 174. fibro-cartilaginoni, 17i. cellular, 298. fibrous, 298. ligmmentous, 174. muscular, 198. nervous, 757. tendinous, 289. Toes, articulations of, 174. bones of, 104. phalanges of, 104. Tongue, 332. bone of, 333. development of, 336. dorsum of, 332. frsnum of, 333. lymphatics of, 646. median cartilage of, 333. mucous membrane of, 646. muscles of, 333. extrinsic, 334. intrinsic, 334. — nerves of, 646. — papills of, 333. — rete mucosum of, 646. — structure of, 334. — uses of, 339. ■ vessels, 339. Ton-tils, 333. of cerebellum, 718. Torcular lIeroi)hili, 5S8. INDEX. TrabecuJa of corpus cavernosum, 455. ————— spleen, 405. Trachea, 416. cervical portion, 416. glands of, 416. structure of, 416. thoracic portion, 416. - vessels and nerves, 416. Tractus spiralis foraminulentus, 678. Tragic fossa, 668. Tragus, 666. ■ - ligament of, 666. Transversahs muscles. See Muscles. Transverse arteries. See Arteries. muscles. See Muscles. suture, 46, 47. veins. See Veins. 7V«njti«rjo-spinalis muscle. See MuseU. Trapezium, 83. Trapezoid bone, 83. ligament, 136. Triangulares muscles. See Muscles. Triceps muscles. See Muscles. Trifacial, or trigeminal nerve. See Nerve. Trochanteric cavity, or fossa, 95. Trochanters of femur, 95. of humerus, 79. ' Trochlea, femoral, 95. humeral, 79. of orbit, 651. Trochlear articulations, characters of, &c., 114. nerve. See Nerve, pathetic. Trochoid articulations, characters of, &c., 114. Tube, Eustachian. See Eustachian Tube. Fallopian, 463. T^ber annulare. See Pons Varolii. cinereuni, 729. Tubercle, ash-coloured, of Rolando, 703. lachrymal, 645. laminated, 717. of Lower, 488. Tidtercles of Santorini, in larynx, 424. in nose, 640. Tuberrula quadrigemina, or bigemina, 712, structure of, 714. T\iberosities, calcaneal, 102. of femur, 95. of humerus, 79. ■ of tibia, 97. Tuberositi/, bicipital, 81. of ischium, 89. maxillary, 51. Tubes of Bellini, 437. TViu/t of intestine. See Intestine. recti, of kidney, 437. of testicle, 452. seminiferi, 452. ' of stomach, 361. ' uriniferi, convoluted, 437. straight, 437. T\ibulus centralis modioli, 679. Ttmica adnata, 648. albuginea testis, 449. conjunctiva, 648. erythroides, 448. propria testis, 449. Ruyschiana, 657. sclerotica, 654. vaginalis testis, 448. vasculosa testis, 449 (note). Tunics of eye. See Eye. Turbinated bone, inferior, 56. - middle, 41, superior, or ethmoidal, 41. ' sphenoidal, 38. Ti/mpanic bone, circle, or ring, 45 T)/mpanum, bones in, 674. circumference of, 672. lining membrane of, 670. membrane of, 675. secondary, 671. • orifice of, cochlear, 671. vestibular, 670. — recess of, 672. — wall of, external, 669. internal, 670. Ulna, 79. and tibia, upper parts of, compared, 107, Vmbilicus, 308. Unciform bone, 83. eminence, 730. Unguis, 730. Urachus, 443. Ureter, 440. structure of, 441. orifices of, 444. muscles of, 445. valve of, 444. Urethra, female, 469, muscles of, 470, male, 457. bulb of, 459. dilatations, or sinuses, 459. internal surface, 459. lacunee, 460. membranous portion, 459. muscles of, 457. prostatic portion of, 457. spongy portion of, 459. structure of, 460. Urinary apparatus, 435, Uterine veins, 467. Uterus, 464. cavity and mouth of, 465, cervix or neck of, 465, coat, mucous, 467, - serous, 467, • development, 468. ■ follicles of, 466. • functions of, 468. ■ fundus of, 466. • glands, tubular, of, 468 (note). ■ gravid, fibres of, 467. sinuses of, 467. - vessels and nerves of, 464. ■ ligaments of, broad, 466. round, 466. • nerves of, 468. • structure of, 466. vessels of, 468. Utriculus vestibuli, 681. Uvea, 670. Uvula, 332. vesicae, 459. cerebelli, 715 (note). Vagina, 468. bulb of, 469. — columns and rugse of, 468. — development of, 469. — mucous membrane of, 469. — muscles of, 469. structure of, 468. Vaginal process of temporal bone, 44. Valve of Bauhin, 372. • Eustachian, 486. • ileo-ccecal, 372. colic, 372, ■ mitral, 484, ■ pyloric, 352, ■ of Thebesius, 486. ■ tricuspid, 484. ■ of Vieussens, 711. ' columella of, 71S. Valves of Kerkringius, 365. of heart. See Heart. of intestines. See Intestine of lymphatics, 617. semilunar, or sigmoid, 464. of Tarin, 720. of veins, 575. Valvula conniventes, 365. Vas aberrans, 452. deferens, 452. structure, 452. Vasa afferentia, lymphatic, 614. brevia, arterial, 509. venous, 599. ■ efferentia of epididymis, 451. • lymphatic, 614, ' sudatoria, 634. • vasorum of arteries, 520, of veins, 576, — vorticosa, 587. 665. Veins, in general, 573, — anastomoses of, 574, branches of, 575. — coats of, 576. — course of, 574. INDEX. 905 Veins, deep, 574. method of description of, 577. nerves of, 576. ^^— origin of, 574. plexuses of, 574. preparation of, 576. relations of, with arteriei, 575. satellite, 574. sinuses of, 575. structure of, 576. sub-cutaneous, 574. superficial, 574. termination of, 575. valves of, 575. varieties of, 575. vasa vasorum of, 575. vessels of, 575. in particular, 577. abdominal sub-cutaneoiu, 604. of ala of nose, 588. alveolar, 589. angular, 588. of the arm, superficial, 594. articular, of knee, 603. ascending cervical, 580. lumbar, 606. auricular anterior, 590. posterior, 590. axillary, 593. azygos, general remarks on, 60) great, 605. lesser, 606. lumbar, 607. ■ basilic, 595. ■ brachial, 597. • brachio-cephalic, left and right, *; * ■ bronchial, left, 420. right, 420, 606. - distribution of, 421. ' buccal, 589. ■ calcaneal, internal, 604. ■ capsular, inferior and middle, 591 ■ cardiac, great, 578. small, 578. cava, ascending or inferior, 596. descending or superior, 51H cephalic, 595. ■ of thumb, 594. • cerebral, inferior, anterior, 587. lateral, 584. ' median, 586. internal, 585. superior, 585. ■ median, SSC ■ cerebellar, anterior lateral, 58* inferior lateral, 5Sa ' cervical, ascending, 580. deep, 580. ■ choroid, 586. of eye, 658. • ciliary, 587. ' circumflex, brachial, 598. femoral, 603. • iliac, 603. ' colic, left and right, 599. ■ coronary of the heart, anterior, 578. great, 578. lips, inferior, 589. — superior, 589. stomach, 362. • of the corpus cavemosum, 601. striatum. 586. deep cervical, 580. — femoral, 603. • dental, anterior, 589 inferior, 590. superior, 589 ■ diaphragmatic, 601. ' diploic, 585, 591. • dorsal of the foot, deep, 602. external, 603. internal, 603. ' nose, 588. - penis, 601. ' dorsi-spinal, 608. ■ of the dura mater, 583. ■ at the elbow, 595. • emulgent, 598. ■ epigastric, deep, 603. superficial, 60S Veins, facial, 588. posterior, 589, of the falx cerebri, 586. • femoral, 603. deep, 603. • frontal, 587. ■ of Galen in brain, 584. ■ heart, 577. • gastro-epiploic, 361. ■ gluteal, 601. • of hand, superficial, 594. • hemorrhoidal, inferior, 601. ' middle, 601. --superior, 601. — head, general remarks on, 592. — hepatic, 600. in the liver, 391, 398. — hypo-gastric, 601. — iliac, common, 600. eriemal, 603. internal, 601. — ilio-lumbar, 607. — infra-orbital, 589. — innominate of Meckel, 579. ■ of Vieussens, 578. ■ inter-costal, 607. superior, left, 606. right, 606. lobular, of liver, 391 (note). — of intestines, 599. — intra-lobular, of liver, 393 (note). spinal, 609. anterior, longitudinal, 609. ■ transverse, 609. - lateral, 610. — posterior, longitudinal, 610. • transverse, 610. ■jugular, 581. anterior, 582. external, 581. compared with cranial, 610. — internal, or deep, 583. posterior, 607. • laryngeal, inferior, 580. — superior, 582. ' lingual, 590. ' longitudinal of scull, inferior, 586. spine. See Intraspinal. ■ of lower extremity, deep, 602. superficial, 603. lumbar, or vertebro-lumbar, 5'17. ascending, 606. azygos, 607. ' mammary, internal, 580. masseteric, anterior, 589. • posterior, 590. ' mastoid, 584, 590. ■ maxillary, external, 588. ' intornal, 589. — median of the fom, 595. basilic, 595. cephalic, 595. — mediastinal, 580, 60C. — medullary, 610. — meningeal, 591. ■ middle, 590. ■ mesaraic, 599. ' mesenteric, inferior or smaL, &(*^ superior or gre. t, 59^ ' nasal, 588. • obturator, 601. ■ occipital, deep, 590. superficial, 589. ■ (esophageal, 606. ■ omphalo-mesenteric, 599. ■ ophthalmic, 587. ■ orbital, external, 589. ■ ovarian, 598. • palatine, inferior, 589. su-perior, 589. palmar, 593. ' palpebral, external, 589. ' inferior, 588. • pancreatic, 402. • parotid, 590. • of particular organs or tissues. gans or tissues. • of pelvis, in female, 602. male, 601. of penis, 601. 5Y 906 INDEX. Veins, pericardiac, 580. peroneal, 602. pharyngeal, 591. phrenic, inferior, 598. . superior, 580. plantar, 602. popliteal, 602. portal, or vena porta, 597, 599. branches of origin of, 598. in the liver, 390. ■ sinus of, 599. profunda cervicis, 580. femoris, 603. — pterygoid, 590. — pudic, external, 604. internal, 601. — pulmonary, 577. ' distribution of, 421. ■ rachidian. See Spinal. ■ radial cutaneous, 595. deep, 594. • ranine, 590. ■ renal, 597. ' sacral, lateral, 607. middle, 607. ' salvatella, 594. ' of Santorini, 585. ' saphenous, external, 605. ' internal, 603. ' second, 604. ' satellite, of lingual nerve, 590. ■ scapular, superior, 582. posterior, 582. ^— sciatic, 601. scrotal, 601. semi-azygos, 606. short, of stomach, 599. spermatic, left and right, 598. spheno-palatine, 589, 591. spinal, 605. '— deep. See Intraspinal. general remarks on, 611. posterior, deep. See Inira^spinal. ■ superficial, 608. ■ superficial, 60S. in neck, 608. — posterior, 608. ■ of spinal cord, 610. • splenic, 599. ■ distribution of, 406. ■ stylo-mastoid, 590. sub-clavian, left and right, 593. mental, 589. supra-orbital, 588. renal, inferior and middle, 598 scapular, 581. sural, 603. temporal, 589. deep, 590. middle, 589. • superficial, 589. • temporo-maxillary, 589. ■ofThebesius, 578. • thymic, 580. • thyroid, inferior, 580. middle, 591. superior, 591. • tibial, anterior, 602. -posterior, 602. tibio-peroneal, 602. tonsillar, 333. transverse, cervical, 582. facial, 590. humeral, 582. ■ ulnar cutaneous, anterior, 595. — posterior, 595. ■ deep, 592. • umbilical, 600. ■ of upper extremity, deep, 592. superficial, 593. • uterine, 467, 601, 602. ■ vaginal, 602. • vasa brevia, 599. vorticosa, 587. ■ ventricular, cerebral, 586. ■ of vertebra, 610. ■ vertebral, 581. • vertebro-costal, inferior, 606. superior, left, 606. — i right, 605 Veins, vertebro-lumbar, 607. vesical, female, 602. male, 601. vidian, 589. Velum interpositum, 731, 740. meduUare, anterior, 713. posterior, 718 (note). palati, 331. See Palate, soft. pendulum palati, 331. Vena cava inferior, or ascending, 596. superior, or descending, 578. Venm comites, 572, minimse, 508. Venous plexuses. See Plexuses. system generally, 572. Venter ilii, or internal iliac fossa, 88. Ventricle of Arautius, 704. of corpus callosum, 737. fifth, 738. fourth, 718. choroid plexuses of, 720. — fibrous layers of, 719. -- fossette of, 704. ■ laminated tubercle of, 717 • orifice, inferior, 719. ■ semilunar fold of, 719. valves of base of, 719. ■ of larynx, 424. ■ lateral, 744. body of, 744. comu anterior, 744. descending, 744. posterior, 744. ■ of septum lucidum, 738. •third, 729, 741. choroid plexuses of, 741. commissure of, anterior, 742. posterior, 742. - soft or gray, 729, 741. ■ floor of, anterior part of, 729. middle and posterior part of, 729. • openings of, 742. Ventricles, cerebral, fluid of, 744. lining membrane of, 747. Gall's views regarding, 750. — — of heart. See Heart. of spinal cord, 701. Ventriculus, 352. succenturiatus, 362. Vermiform appendix, 373. process, inferior, 716. superior, 716, Vertebra, cervical, first, 23. second, 24. seventh, 25. dentata, 24. dorsal, first, 25. eleventh and twelfth, 85. general description of, 19. lumbar, fifth, 26. prominens, 25. Vertebra, articular processes of, in different regiou, S8» articulations of. See Articulatiom. bodies of, in different regions, 20. cervical, 19. • characters of, general, 19. distinctive, 20. proper, 22. — coccygeal, 19. — development of, 31. — dorsal, 19. — false, 19. — foramen of, in different regions, 19. — internal structure of, 31. — laminse of, in different regions, 20. — ligaments of. See Ligaments. — lumbar, 19. — notches of, in different regions, 80. -- number of, 19, — sacral, 19, -► sacro-coccygeal, 26. union of, 32. spinous processes of, in different regions, SS, transverse processes of, in diflferent region*, 23. ■true, 19. Vertebral canal, 30. column, 19. articulations of, 115-123. INDEX. 90*2 Vertebral column, curvatuiea of, 28. deTelopment of, 32. ' dimensions of, 28. figure and aspects of, 29. ' moTements of entire, 121-123. grooves, 20. ligaments. See Ligaments. See Veins. Vertebro-costaX veins. Yerumontanum, 461. Vesica fellea, 394. urinaria, 440. Vesicles, Graafian, 461. Vesicula seminales, 453. efferent duct of, 454. structure, 454. Vestibule of ear, 676. aqueduct of, 676. calcareous matter of, 681. crista of, 676. ■ fovea and recessus sulcifonnis, 676. membranous, 680. openings into, 676. sacculus of, 680. — ; sinus, common, or utricle of, 680. Visceral nerves. See iferves. Vitreous table of cranial bones, 35. Vocal cords, 426. Vomer, 57. Vulva, 470. development of, 471. fourchette, 470. mucous membrane, 471. parts of, 470. Wings of sphenoid bone, lesser, 37. great, 38. Ingrassius, 37 Womb. See Uterus. Wormian bones, 50. Wrist. See Carpus. Xiphoid cartilage, or appendix, 65. Zinn, zone of, 655. Zonula Zinni, 655. Zygoma, 61. Zygomatic arch, 61. bone, 54. canal, 55. - fossa, 61. - process of temporal bone, 42. malar bone, 55. THE END. THE LIBRARY UNIVERSITY OF CALIFORNIA San Francisco Medical Center THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW Books not returned on time are subject to fines according to the Library Lending Code. Books not in demand may be renewed if application is made before expiration of loan period. 30m-10,'61 (0394184)4128