r THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID SYSTEM OF ANATOMY FOR THE USE OF STUDENTS OF MEDICINE. BY CASPAR WISTAR, M.D., LATE PROFESSOR OF ANATOMY IN THE UNIVERSITY OF PENNSYLVANIA. WITH NOTES AND ADDITIONS, BY WILLIAM E. HORNER, M. D., PROFESSOR OF ANATOMY IN THE UNIVERSITY OF PENNSYLVANIA. NINTH EDITION, ENTIRELY REMODELED, AND ILLUSTRATED BY MORE THAN TWO HUNDRED ENGRAVINGS. BY J. PANCOAST, M. D., PROFESSOR OF GENERAL DESCRIPTIVE AND SURGICAL ANATOMY IN JEFFERSON MEDICAL COLLEGE OF PHILADELPHIA, LECTURER ON CLINICAL SURGERY, FELLOW OF THE PHILADELPHIA COLLEGE OF PHYSICIANS, ETC., ETC. IN TWO VOLUMES. VOL. I. PHILADELPHIA: THOMAS, COWPERTHWAIT & CO. 1846. ENTERED, according to the Act of Congress, in the year 1842, by THOMAS, COWPERTHWAIT & CO., In the Clerk's Office of the District Court of the Eastern District of Pennsylvania. GREENFIELD, MASS. MERRIAM AND MIRICK, PRINTERS. ADVERTISEMENT TO THE NINTH EDITION OF WISTAR'S ANATOMY. THE increasing estimation in which this favorite Work on Anatomy is held by the Medical Profession of this country, having already caused the last unusually large edition to be exhausted, the publishers in passing the ninth edition through the press, have been desirous of rendering it wWthy of the continuance of such gratifying support, by having such additions and improve- ments made as the progress of the science required. With this object the text introduced by the editor, has been subject to revision ; much new matter has also been added, with a care however, not so to extend the work as to impair its character for clearness, brevity, and simplicity, which has made it so great a favorite with the Medical Student. Several wood cuts have been added, and the copperplate illustrations of the Arteries by Sir C. Bell, which were formerly sold separate, at a cost greater than the whole of this work, have been renewed by a skillful engraver, so as to serve not only as an ornament to the book, but an aid of the greatest importance to the Student. JOSEPH PANCOAST. Philadelphia, 1846. ADVERTISEMENT TO THE EIGHTH EDITION. THE publishers of " Wistar's Anatomy for the use of Students of Medicine," gratified with the favorable reception, which their attempt to enlarge and illus- trate this well known work has met with, have resolved in preparing another edition for the press, to render it as far as is in their power, deserving of a continu- ation of the patronage it has received. For this purpose it has been carefully re- vised and enlarged so as to include such important additions and investigations of interest as have been recently made in the science. By comparing the present with the former editions, the reader will discover that these have been both numerous and important in each division of the subject. This the publishers have been enabled to do without much increasing the size of the volumes, by substituting, for the old copperplate prints, a very large number of engravings on wood, of the finest description. These which are intercalated with the text and explained by foot notes, cannot fail to render the work more convenient and valuable as a text-book, in the various schools in which it has been adopted, and at the same time make it serve as a most useful guide to the student in the study of practical anatomy. The additional illustrations have been taken mainly from Wilson's Anatomist's Vade Mecum, (London, 1842,) and partly from the English edition of Cruvielhier's Anatomy, (London, 1842,) and from the recent splendid work on General Anatomy, by F. Gerber. The present edition of Wistar, contains eight colored copperplate engravings of the blood- vessels, and upwards of two hundred and twenty engravings on wood, rendering it in this respect more richly and amply illustrated than any other book of the kind that has yet been offered to the American student. The same plan has been pursued as mentioned in the preface to the seventh edition, of distinguishing the new matter that has been added, from the original text of Dr. Wistar. JOSEPH PANCOAST. Philadelphia, 1842. DR. HOMER'S PREFACE. THE value of the present work having been sufficiently tested by its very diffused use in the profession, and by a third edition being now called for, the editor has been induced to superintend the latter, with a hope that its utility and the public conviction in its favor have been in no wise diminished. The close- ness of the connexion between himself and its lamented author, furnished, also, another and a very powerful reason, why he should endeavor by such means as he commanded, to contribute to perpetuate the memory of a man whose literary and professional career had been so conducive to the reputation of his country, and whose philanthropy and suavity of manners had established him so firmly in the affections and confidence of all who knew him. Several amendments have been introduced by the way of corrections, altera- tions and additions. The latter, for the most part, appear between brackets, and in the form of notes, but there are many which could not be marked in such a manner without giving the text a garbled appearance, they therefore appear as portions of the original work. The whole mass of matter introduced as amendments is greater, indeed, than a superficial perusal of the work would intimate ; and the only way for the reader to arrive at it, will be by a careful comparison of the last with the pre- sent edition. The editor, however, has been careful not to allow the spirit of change or improvement to affect the work in any points except such as seemed to him absolutely to require it, and where he was fully warranted by the best authorities in Descriptive Anatomy. It would have been sufficiently easy for him to have extended the work considerably beyond its present dimensions ; but from its having been originally designed as a text-book of the course of Lectures on Anatomy in the University of Pennsylvania, and for the benefit of practitioners, who are always most assisted by condensed views on this subject, he was apprehensive of perverting or of frustrating its objects by such exten- sion. In consequence of which he has principally confined himself to adding where additions were called for by recent discoveries in Anatomy, and by the omission of older ones. Philadelphia, Oct. 10th, 1823. PREFACE TO THE SEVENTH EDITION/ THE publication of the first edition of his " System of Anatomy for the use of Medical Students/' was completed by Dr. Caspar Wistar in 1814. Simple in its construction, concise, but yet clear, and at the same time representing faithfully and fully, the science of Anatomy as it then existed, the book was exactly in keeping with the well known character of its distinguished author. The general approval with which it was received in this country, was manifest- ed by the rapidity of its sale. The second edition which was called for in 1817, was further improved by the author, by the addition of such new anatomical facts as had come to his knowledge, and such further physiological observations as served to give life and interest, to the otherwise dry details of his science. In 1818. before his work had reached the third edition, the author himself died, regretted by all who loved virtue, honored science, or knew how to estimate a kindness of soul, and uniform urbanity of manner, which is yet vivid in the recollection of his friends. The superintendence of the third edition was assumed by Professor Homer, a personal friend of Dr. Wistar, who enriched it, by the addition of much valu* able matter, which the science in its onward progress had at that time develop- ed. The value of these additions, may be inferred, from the increasing favor which the medical public has continued to extend towards the work; four editions having been completely exhausted since that period. Though fifteen years only have elapsed, since its former revision, the zealous and persevering inquiries of modern anatomists, which have scarcely their par- allel in any other department, have in that time added much to the science. The present publishers have therefore been desirous, that the work should be so extended and remodeled, as to be brought up as near as may be, to the existing state of the science, without impairing its value as a manual by too much in- creasing its bulk. The reader will discover how far the attempt has been suc- cessful, by comparing this with former editions. Within the period alluded to, the department of general, more than that of special anatomy, has yielded the richest harvest to the anatomist, and has been advantageously cultivated with particular reference to physiology and thera- peutics. From general, then, more than from special anatomy, have the pre- sent additions been derived; the editor believing that in mere special descrip- tion, that which is most concise and yet so comprehensive as not to omit any I* VI PREFACE. thing of real importance, is the best. He has not, therefore, added a great deal to the individual description of the bones, ligaments, muscles, blood-vessels, and nerves. But in the department of General Anatomy, and especially in Splanchnology the viscera being so important in a medical point of view the student will find the additions to have been both numerous and extensive. The department of Neurology, which has been the fashionable anatomical study, for years past, and upon which hangs so much that is important in physiology and medicine, has appeared to him more deficient than any other portion of the original work, as the brain and spinal marrow have been describ- ed by Dr. Wistar, only from above downwards ; a method which was, however, the most approved and general in his day. The editor has therefore added two entire chapters on that subject, one on the General Anatomy of the Nervous vSystem, and one on the special description of the Spinal Marrow and Brain from below upwards, in the order of its development and the direction of its functions, retaining, nevertheless, here as in other parts, all the original text. It has also been thought advisable, to transpose several portions of the work, when by so doing, parts belonging to the same general tissue could be placed in more natural connexion, and made to correspond with the mode in which they are usually described. Thus, the account of the brain, the eye and the ear, has been transferred from the first volume to the second, and placed in continuity with that of the other parts of the general nervous system. To facilitate the student in the aquisition of this difficult science, all the plates of the former edition, which were sufficiently accurate to be useful, have been retained, and several other copperplate engrav- ings of the blood-vessels added, with upwards of a hundred wood cuts, some of which are original, but the greater part collected with considerable care and labor from the newest and most approved sources. The amount of the new matter added to this edition is nearly equal to a fourth part of the whole. The student, will, however, be enabled to distinguish readily the original text of Dr. Wistar, from the additions which have been made either by Dr. Horner, which are all included in brackets [], or from those of the present editor, which are separated from the other parts of the work by their commencing and terminating with a dash . Various synonyms introduc- ed throughout the work, and some more trifling emendations of the text, it has not been thought necessary to designate. JOSEPH PANCOAST. Philadelphia, Dec. 1, 1838. CONTENTS OF VOL. I. PART I. OSTEOLOGY. CHAPTER I. GENERAL ANATOMY OF THE OSSEOUS SYSTEM. CLASSIFICATION and Structure of Bones, - - - - 13 Of the Periosteum, - - - 33 Medullary Membrane or Internal Periosteum, - 33 Cartilages and their Structure, - 36 Accidental development of Cartilages, - - 39 Of the Formation of Bone, 40 Formation of Callus, - -48 Terms used in the Description of Bones and Joints, 51 CHAPTER II. OF THE SKELETON AND ITS DIFFERENT PARTS. Of the Head, - - . - 54 Sutures, - 57 Os Frontis, - 61 Ossa Parietalia, - - 64 Ossa Temporum, 66 Qs Occipitis, ... 73 Os Ethmoides, - - - 75 Os Sphenoides, - - - - 80 Foramina of the Sphenoidal Bone, - ... 84 Of the Face, - ... 85 Ossa Maxillaria Superiora, - - - 86 Ossa Nasi, ... 89 Ossa Lacrymalia seu Unguis, - - - 90 Ossa Malarum, - - - - 91 Ossa Palati, - .... 93 Ossa Spongiosa, or Turbinata Inferiora, - - - 95 Vill CONTENTS. OftheVomer, - 95 Maxilla Inferior, - 96 Teeth, - 99 Composition of the Teeth, 100 Development of the Teeth, - - 1 10 Of the Enamel, - 112 Permanent Teeth, - - 113 Aberrations of Dentition, - 117 OsHyoides, * - 118 Regions of the Skull, ' - 119 Orbit of the Eye, - - 120 Cavities of the Nose, - 122 Cavity of the Cranium and Internal Basis of the Skull, - 125 External Basis of the Skull, - 128 Side of the Head, - - 131 Form of the Cranium, - 132 Head of the Foetus, - - 135 Trunk, - 137 Spine, ... 137 True Vertebra, - 138 False Vertebra?, - 151 Vertebral Cavity for containing the Spinal Marrow, 154 Thorax, ( - 155 Ribs, 155 Sternum, - - 160 Movement of the Ribs and Sternum in Respiration, 163 Pelvis, - 163 Os Ilium, - 164 Os Ischium, - - 166 Os Pubis, - 167 Trunk of the Foetus, - - 173 Superior Extremities, - 174 Clavicle, - 175 Scapula, - 177 OsHumeri, - - 181 Forearm, - 185 Ulna, - - 186 Radius, - 188 Hand, - 190 Carpus, - 191 Metacarpus, - - - - - - -196 Thumb and Fingers, 199 Inferior Extremities, - - 201 CONTENTS. ]X Of the Thigh, - - 201 Tibia, - - - 205 Fibula, ---- - 207 Patella, - 209 Foot, - . - 211 Tarsus, - - - 211 Metatarsus, 217 Toes, - 219 General Structure of the Foot, - 219 PART II. SYNDESMOLOGY. CHAPTER III. GENERAL ANATOMY OF THE LIGAMENTOUS, FIBROUS, OR DESMOID TISSUE. 223 Ligaments of the Joints, - - 226 Of the Yellow Elastic Ligamentous Tissue, - 229 Fibro Cartilaginous Tissue, - - 230 CHAPTER IV. A GENERAL ACCOUNT OF ARTICULATIONS, AND OF BURS.E MUCOS^. 232 CHAPTER V. OF PARTICULAR ARTICULATIONS. The Connexion of the Head with the Vertebrae, - - 239 Articulations of the Vertebrae with each other, -- 241 Articulation of the Lower Jaw, - - 244 Articulations of the Clavicle and Scapula, 245 Articulation of the Os Humeri and Scapula, - 246 . Elbow, 248 Wrist, - - 250 Carpal and Metacarpal Bones, - 254 Fingers, - - 255 Ribs, - 255 The Hip Joint, - 257 Articulation of the Knee, - 259 Tibia and Fibula, - 263 Leg, Foot, and Ankle Joint, 264 Tarsus and Metatarsus, - - - - 266 CONTENTS. CHAPTER VI. OF PARTICULAR LIGAMENTS AND THE SITUATION OF THE INDIVIDUAL BURS-E MUCOS.&. Ligaments proper to the Scapula, - - 268 Interosseous Ligament of the Forearm, - - 268 Ligaments retaining the Tendons of the Head and Fingers in their position, - 269 Ligaments on the Anterior part of ike Thorax, - 270 of the Pelvis, - - 270 retaining the Tendons of the Foot, - 274 Enumeration of the most important Bursas, - 275 PART III. MYOLOGY. CHAPTER VII. GENERAL ANATOMY OF THE MUSCLES. 279 Of the Tendons, and of Muscular Motion, - - 287 CHAPTER VIII. OF THE INDIVIDUAL MUSCLES. 300 Muscles of the Teguments of the Cranium, - 300 Ear, 301 Eyelids, - 302 Eyeball, 303 Nose, - - 306 Mouth and Lips, - 306 Lower Jaw, - - 311 Anterior part of the Neck, 313 between the Lower Jaw and the Os Hyoides, - 314 Os Hyoides and the Trunk, 316 situated about the Fauces, - - 319 on the Anterior part of the Neck close to the Vertebrae, 321 on the Anterior part of the Thorax, - 323 between the Ribs, . _ . 334 on the Abdomen, - - - - _ 335 about the Male Organs of Generation, - 335 of the Anus, ----.. 339 CONTENTS. XI Muscles of the Female Organs of Generation, - 341 within the Cavity of the Abdomen, - 342 on the Posterior part of the Trunk, - 348 of the Superior Extremities, - 359 Inferior Extremities, - - -^/ 375 CHAPTER IX. OBSERVATIONS ON THE MOTIONS OF THE SKELETON. 397 PART IV. OF THE GENERAL INTEGUMENTS, OR OF THE CELLULAR MEMBRANE AND THE SKIN. - CHAPTER X. OP THE CELLULAR MEMBRANE. 403 CHAPTER XL Of the Cutis Vera, 411 Rete Mucosum, - 415 Derma, - 425 Papillary Body, or Neurothelic Apparatus, - - 425 Sudoriferous Apparatus, - - 426 Inhaling Apparatus, ------ 427 Blennogenous Apparatus, ... 428 Chromatogenous Apparatus, - - 429 Cuticle, or Epidermis, - 430 Nails, - 439 Hairs, ------- 441 PART V. OF THE NOSE, THE MOUTH, AND THE THROAT. CHAPTER XII. OF THE EXTERNAL NOSE. 446 Of the Cavities of the Nose, - 449 CHAPTER XIII. I OF THE MOUTH. 458 Of the Tongue, - - - - - - - 462 The Salivary Glands, - - - - - - 469 Xll CONTENTS. CHAPTER XIV. OF THE THROAT. THE ISTHMUS AND FAUCES. Of the Larynx, Muscles of the Larynx, - Thyroid Gland, Pharynx, - 474 476 483 487 490 FAifr vi. OF THE THORAX. THE MAMMAE. 493 CHAPTER XV. OF THE GENERAL CAVITY OF THE THORAX. 497 CHAPTER XVI. OF THE HEART AND PERICARDIUM, AND THE GREAT VESSELS. Of the Pericardium, - - 502 Heart, - 504 Aorta, Pulmonary Artery and Veins, and the Venae Cavse at their commencement, - - 514 CHAPTER XVII. OF THE TRACHEA AND THE LUNGS. Of the Trachea, - 517 Lungs, - - - 520 Thorax of the Foetus, - 526 Thymus Gland, - 526 Heart, - 529 Pulmonary Artery end the Aorta, 531 Lungs of theTcetus, - 532 Cases of Malformation, - 533 , - SYSTEM OF ANATOM>Y. PART I. OSTEOLOGY. CHAPTER I. GENERAL ANATOMY OF THE OSSEOUS SYSTEM. Classification and structure of bones Chemical composition Recent researches on the intimate structure of bone Periosteum Medullary membrane Car- tilages Formation of bone Terms used in describing bones. THE osseous tissue in man and nearly all large animals not inhabiting a dense medium, constitutes that scaffolding or framework, upon which is supported all the soft parts of the body. Hence the bones when seen in connexion in a perfect skeleton, present so perfect an outline of the animal to which they belonged, as to be sufficient as has been shown by Baron Cuvier, to indicate clearly its shape, size, and mode of life as well as the nature of the food upon which it lived.* The bones may be considered* as designed for the fulfilment of two principal objects the formation of cavities for the protection of delicate and important organs, as in the head, thorax, and pelvis and of columns and levers for support and * A skeleton, or a structure. analogous to it in its uses, that of forjpng a foundation upon which the body can be built, and to which the muscles may be attached in order to move it from place to place, is found in the mammiferae, birds, and many fishes, in the interior of the body ; in the Crustacea and teslacea, some fish, reptiles, &c., it is wholly or in part at the exterior. In a great majority of cases it is bony in its structure ; it is, however, cartilaginous in many fishes, and fibrous in nearly all coleopterous insects, of which it forms the external covering. p. 14 CLASSIFICATION OF THE BONES. motion, as in the spinal column and the upper and lower ex- tremities. They perform, however, but a passive or mechanical part in the movements of the body, forming supporting organs, round which the muscles, nerves and vessels are wreathed, and at the same time serve as levers, by which the limbs are lifted. They are necessarily very numerous in the human body, and exist as separate and distinct pieces, which touch one another at their extremities, where they are generally expanded in. size, and their parts so nicely adjusted to each other, as to form the basis of the structure of the joints. At these places of junction, the bones are fastened together, by strong, fibrous, inelastic, inextensible bands, called ligaments. The number of the bones in the human body, varies accord- ingly as we examine them, in infancy, middle life, or in old age. Nearly all the individual bones of the adult, are developed in separate pieces in the infant, the number of which is very great, and their consolidation into single bones, is not general and complete till about the period of puberty : many of these separate bones of the adult, especially of the head and trunk, are found fused together in extreme old age. Anatomists have generally agreed to consider as distinct bones, those of the adult, and to these they have given indi- vidual names. The skeleton is divided into trunk, head, and extremities : Thus there are for the trunk, fifty-three bones ; the twenty- , four true vertebras, the sacrum, the coccyx, twelve ribs on each side, one sternum in three pieces, and two ossa innominata. For the head, fifty-nine bones ; the occipital, sphenoid, ethmoid, frontal, the two parietal, two temporal with the four small bones of the ear, the vomer, the two superior maxillary, two palatine, two molar, two nasal, two lachrymal or unguiform, iwo inferior turbinated, the inferior maxillary, the teeth, and the hyoid bone. For the two upper extremities, seventy-four bones ; there are on each side, the scapula, clavicle, humerus, radius, ulna, eight wrist or carpal bones, five metacarpal, fourteen phalanges, and five sesamoid bones. - ? CLASSIFICATION OF THE BONES. 15 For the two lower extremities, sixty-six bones ; on each side one femur, a tibia, a fibula, patella, seven ankle or tarsal bones, five metatarsal, fourteen phalanges of the toes, and two and some- times three sesamoid. Thus according to the enumeration of Marjolin, there are two hundred and fifty-two bones in the human body. The number of sesamoid bones, however, is very varia- ble ; and some anatomists of high reputation, do not include the teeth in the enumeration of the bones of the body. The bones are all either symmetrical or unsymmetrical. The symmetrical bones are in pairs, and correspond in size and shape very nearly with each other, and are placed upon either side, like those of the extremities and ribs. The unsym- metrical, which consist of some of the bones of the head, the sternum, vertebrae, sacrum, os coccygis and os hyoides, are situated in the middle line of the body. The lateral halves of these bones correspond very closely with each other. From their general form and geometrical dimensions, the bones have been divided into classes ; the long bones, ossa longa, the broad bones, ossa lati, and the thick bones, OSSQ, crassa. The long bones, occupy the centre of the limbs, are the levers used in locomotion, and form a series of "broken columns, articulated together, which increase in number, and diminish in si^e, as they recede from the trunk. They are divided into a middle part, body or diaphysis ; and into extre- mities or epjphyses. The body is cylindrical in some, prismatic and triangular in others, and generally a little curved or twisted. The extremities are expanded and thick. The bodies which are the smallest part, happily correspond with the bellies or largest .part of the muscles the extremities with their narrow tendinous terminations. The broad bones assist in forming a part of the walls of the trunk and head ; they are flattened, more or less concave on their interior, varied in their form, and thicker usually at their margins, than at their centres. The thick bones are assembled in masses, and form parts at once solid and moveable as in the spinal column, the wrist, and the ankle. 16 STRUCTURE OF THE BONES. -- The human bones in a recent adult subject, are of a dull white color : they possess considerable elasticity, but little flexibility, have the greatest specific gravity of any portion of the human body, and ( are liable to be broken by accidents or even by violent muscular efforts. Their texture is varied not only in different parts of the skeleton, but in different parts^of the same bones. Thus in the long bones, the middle portion or diaphysis is compact, or nearly solid, with a cavity in the centre ; the extremities are cellular or spongy, with but a thin coating of the compact matter; and the central cavity, is occu- pied by a long network formed of thin plates and fibres, called the reticulated tissue of the bones. In flat bones the external surfaces are composed of firm plates of compact bone ; but the internal substance is cellular. In some of these bones, the cellular tissue exists in such small quantity, that the external compact layers almost touch, and the bones become then diaphanous or translucent. The thick bones are formed almost entirely of the spongy or cellular substance, which is surrounded by an extremely thin shell of the compact bony matter, and are somewRat darker in color than the long or the flat. The osseous tissue thus presents three modifications of form : the compact, the reticular, and tho cellular ui spungy. The compact, which is the densest and strongest, is placed upon the outer surface of all the bones of the body ; it forms a covering of greater or less thickness to all the flat and thick bones, and adds to their strength, without much increasing their weight. The long bones, which are narrowed down in the shaft, so as to accommodate the muscles without destroying the symmetry of the limbs, and require to be made of the strongest material, have their shafts or bodies formed almost entirely of the com- pact portion. The cellular or spongy is found, in a greater or less degree, in every bone of the body ; in the extremities of the long bones it is continuous, though indirectly, with the reticulated tissue of the central or medullary canal. The reticulated tissue has been considered only a modification of the spongy, being formed of larger cells with a more open and delicate texture. STRUCTURE Q$ THE BONES, 17 [The cellular structure of bones is attended with several important advantages. In the cylindrical bones it gives great additional strength, by increasing their diameter, without adding to their weight ; for by swelling out their articular e/tfemities, it produces much greater security of the joints, by obviating the tendency to dislocation, and rendering their movements more steady. A simple experiment will satisfy any one that the increase of volume in the extremities of the long bones, is not attended with an increase of osseous matter; for in the dried bone, the section of an inch from the centre gill weigh as much as the same length from the extremities, notwithstanding the greater size of the latter. *Dr. Physick has pointed out another very important advantage of the cellular structure of bones, besides those of its making them nearly as strong as if they were solid, and at the same time diminishing what otherwise would have been a weight too oppressive for the muscular powers. He thinks that thereby the concussion of the brain, and of the other viscera is frequently prevented ; and in nearly all cases diminished, in falls and in blows. He illustrates the position by showing, first, the concussion which takes place through a series of ivory balls suspended by threads ; if one be drawn to some distance from the others, and allowed to impel them by falling. The momentum in this case impels the ball at the farther end of the row, almost to the distance from which the first one fell. But if a ball of the same size, composed of the cellular structure of bone, be substituted for one of the ivory balls, and the experiment be repeated, the momentum of the first ball is lost almost entirely in the cellular structure of the substitute ; particularly if the latter be well soaked previously in water, so as to give it a condition in point of moisture allied to the living state. Adopting this experiment as demonstrative of the fact, Dr. Physick asserts, that in falls from an eminence upon the feet, the percussion, by the time it has passed through the cellular structure of the foot, leg, thigh, vertebral column and the condyles of the occiput, is very much diminished in force, and carries much less impulse upon the brain. / Again, in 2* 18 STRUCTURE OF THE BONES. blows on the head, the brain, though much protected from external injury by the arched form of the cranium, has an additional security -from the interposition of the diploe, wKich weakens the force of the blow. In all the bones there are canals, independent of the cellular structure, which penetrate to a greater or less extent between the lamina, and go in various directions, some longitudinal, others oblique and transverse. These canals transmit the blood- vessels, and were first pointed out with exactitude by Clopton Havers, an English anatomist. But he assigned a wrong application to them, as he believed that the marrow ran through them, in order to make the bones supple, and to unite their lamina more strongly. S. B. Albinus corrected the mistake, by demonstrating that they were filled with blood-vessels. These canals in a vertebra are particularly large, and open on the posterior face of its body, by one or two large foramina. In the cranium they are remarkably well seen ; but their discovery is of more modern date. M. Portal says, that in the bones each kind of vessel has a particular canal for itself alone ; those of the arteries are therefore to be readily distinguished from such as belong to the veins and to the nerves ; and this takes place both in the large and in the small canals. Occasionally the vessels dip into a common canal, but if any one will take the trouble to follow them, he will find them ultimately separating from each other.] The canals for the transmission of blood-vessels, which exist in abundance in the compact bony tissue, cannot be well seen in the healthy state, except by the aid of the microscope. With the aid of this instrument they may be seen in great numbers, running in a longitudinal direction, opening in its internal or medullary cavity, so as to maintain a free commu- nication between the vessels on the exterior, and those in the cavity of the bone. When cut in surgical operations, blood issues from the compact substance, which is also susceptible of inflammation and its consequences like other vascular parts. In inflammation, STRUCTURE OF THE BONES. 19 the compact portion, is sometimes seen swelled and expanded, so as to develop in its substance, a cellular arrangement, somewhat like that of the co'mmon spongy tissue. Maceration of a bone in water, after its earthy part has been removed, exhibits the same cellular structure. In fact, the principal difference between these varieties of bony tissue, consists in their difference of density, with some variation in the disposition of their fibres ; the cells being condensed in the compact portion so as to admit of a decrease in the diameter of the bones, without a corresponding diminution of their strength. Hence the amount of substance being the same, in the extremities and shafts of the long bones, sections of equal length must of course be of equal weight. In structure bone is composed of lamellae, which are con- centric in long and parallel in flat bones. Between the lamellae run the vascular canals of the bones, and are lodged the bony corpuscles, which have been lately discovered. See p. 46. In the firmness of their texture and their general aspect, bones resemble inorganic matter, but they are nevertheless highly organized. /c02 For example, if a bone be macerated in certain acid liquors, J the earthy matter will be dissolved, and a membranous orj fj/% cartilaginous substance will remain, resembling the bone inl form and size.* If the bones of a young subject, after being injected, be treated in the same way, this membranous substance will appear to be very vascular when the injection has been successful, it will appear uniformly reddened by the greatest number of vessels which are filled with the matter of injection. These vessels discharge blood when the periosteum is removed from the surface of bones, in the living subject, and they also form granulations upon bony surfaces that have been thus denuded. On the other hand if a recent bone be exposed for a considerable time to the action of a moderate fire, or boiled for * One part of muriatic acid to thirty of water is a good mixture for this purpose, by taking care to keep up the strength of the mixture by additions of the acid from time to time. H. 20 STRUCTURE OF THE BONES. a long period in a Papin's digester, the other element of the bone may be obtained its earthy structure in a separate state, representing the original perfectly, in size and shape. It is then perfectly white, and is so light and brittle as to crumble on the slightest touch. Exposure of bones for a long time to the action of the climate, will cause it to shell off in layers and fall into powder, from the same cause, the destruction of its animal matter. A bone macerated in acid, or well incinerated, may be torn or split in particular directions, more readily than others, and manifests an apparent fibrous arrangement. *"" In regard to the disposition and arrangement of these fibres, anatomists differ, though it has been with them a subject of much research. The length of each fibre is limited, running but a small part of the length of the long bones, but is much greater than its breadth and thickness. The greater part arc- longitudinal, that is, run in the direction of the axis of the bone ; some are transverse and some oblique. From the shortness and varied direction of the fibres, and the cellular appearance of the bone when macerated, Scarpa denied entirely, the existence of a fibrous arrangement in the bones, and considers them composed throughout, exclusively of cellular substance, more or less compacted. Malpighi and Havers, believed the bones made up wholly of concentric lamellae, -formed of fibres and filaments, encrusted with osseous matter, laying over each other like the leaves of a book. Gagliardi believed also, that these lamellae were united together by little pins of the same material : some of which were straight, some oblique, and some he fancied had round heads. De Lasone says that these lamellae are made up of ossi- fied fibres, united by oblique ones, and Reich el, that the lamellae and fibres, form a porous tubulated tissue, continuous with the spongy substance.* According to J. F. Meckel, the proper * The opinions of these different anatomists are interesting mainly as con- nected with the history of the science. The discrepancies existing between them, may now readily be reconciled, since the true composition or structure of bone has been rendered apparent by the use of the microscope. See page 46. p. STRUCTURE OF THE BONES. 21 substance of the bones, is of a fibro-laminated nature, the fibres in some parts being so closely aggregated, as to form a compact bone, and separated and expanded in others, so as to constitute the cells of the spongy portion. The longitudinal fibres are much the most numerous, one leaning against, and ter- minating near the commencement of another, so as to give an imperfect appearance of continuity throughout the bone. These fibres at the extremities of the bones, are lost in the spongy or cellular tissue which they assist to form. The transverse and oblique,* serve to connect the longitudinal fibres together, and are united with them uninterruptedly upon their sides ; in the spongy portions, they appear also, to assist in the formation of the cells. They are both most abundant in early infancy, and as the bones increase in length, are directed more in the axis of the bone, till the oblique seem nearly lost in the longitudinal, and the transverse become more oblique. The fibres of the different layers of the compact bone, are united to one another more intimately upon the sides, than to the layers below, hence a bone exposed to the action of the weather or the fire, shells off in scales, or in certain morbid states during life, as necrosis, exfoliates in layers.f From these investigations the osseous tissue, may be justly considered as formed of an animal or membranous basis, analo- gous to the common cellular tissue and cellular fibre in other parts of the body, and differing from them only in its being imbued or incrusted with inorganic earthy matter, which gives it ^firm- ness and strength, but at the. same time renders it liable to fracture. The cells of the bones, like those of the cellular tissue ^|*. of the soft parts of the body, are all imperfect, having openings by which they communicate with one another, and may be all readily injected, with any fluid sufficiently thin to run ; and if * * These represent the uniting pins of Gagliardi. | Mr. Howship of England, from some recent microscopical observations on the bones, has been led to support the opinion of Scarpa, that the ultimate tissue of all the bones, is reticular or cellular. This is evidently true, in regard to the ultimate analysis of bones, when the course of the fibres has been destroyed by prolonged maceration, or by suppurative inflammation. p. CHEMICAL COMPOSITION OF THE BONES. fluid mercury be used it will make its way through the vascular foramina to the external surface. The existence of absorbent vessels, and even of nerves, in bones, is equally certain with that of the blood-vessels, but they are not easily demonstrated. [The French anatomists have occasionally traced branches of the fifth pair of nerves going along with the nutritious arte- ries into some of the bones ; hut as yet no other nerves have been seen by them. M. Portal speaks in familiar terms of the existence of both nerves and lymphatics in the bones, as if he had often noticed them ; he, however, has omitted to inform us of the source, from which the former come.] fin the sound state bones have no sensibility, but pain is often felt in them when diseased. ) We cannot doubt the existence of the absorbent vessels in bones, since Cruikshank and Scemmering, affirm it from their own observation, and from their own injections. Breschet, has observed it many times, and Bonamy, in making a mercurial injection of the inferior extremities, " was able to follow them for some time in the interior of the osseous tissue." They possess (according to Bichat,) a certain degree of ex- tensibility and retractility, which is developed so slowly as to be almost insensible in its progress. These properties are de- monstrated in the expansion of the bones of the facje, from tumors of the antrum, and in the retraction of the sockets of the teeth, after the loss or removal of the latter. Modern chemistry has ascertained that the earthy matter of 'bones is principally a phosphate of lime; carbonate of lime, in a smaller quantity, is also found in them. These earthy sub- stances compose near one-half of the weight of bones, and a large proportion of the remainder appears to be gelatinous and cartilaginous matter. The chemical composition of bones will be found to vary, in the different ages of life, and in some measure according to the individual bones selected for investigation ; the inner com- pact plate or vitreous table of the cranial bones, and the petrous portion of the temporal, possessing a greater relative amount CHEMICAL COMPOSITION OF THE BONES. 23 of earthy matter than any other bones in the body. From these causes, arises considerable discrepancy in the analysis given by different chemists. In early life the relative propor- tion of earthy matter is at its minimum, the animal at ijs max- imum. In advanced age, the reverse holds good, when the bones are notoriously brittle and liable to fracture. Diseased conditions of the system are known to still further modify these proportions : in childhood the earthy matter may be so much diminished that the bones become plastic and yielding, as in rickets ; and at later periods of life, it preponderates occasion- ally so much over the animal as to render them liable to break at the slightest shock, as in cases of fragilitas ossium ; and in some of the venereal affections, the bones are rendered nearly as solid and heavy as a piece of ebony. The earthy matter of the bones of the higher animals con- sists chiefly of phosphate of lime, with carbonate of lime, and a small quantity of phosphate of magnesia, and fluate of lime. The phosphate of lime of the bones is a subsalt, according to Miiller, in which the base and acid are combined in peculiar proportions, and which is always obtained when biphosphate of lime is precipitated by an excess of ammonia. The phos- phate of lime of the urine is a super-salt, held in solution ; in the disease called mollities ossium, it seems to be excreted in this state in the urine in larger quantity than natural. The following is the result of Berzelius' analysis of the bones in man and the ox : Man. Ox. Cartilage* completely soluble in water 32.17 VI 1 1Q < * 3 " 30 Vessels - ... 1.13 Neutral phosphate of lime - - 51.04 55.45 Carbonate of lime 11.30 3.85 Fluate of lime - 2.00 2.90 Phosphate of magnesia 1.16 2.05 Soda with a small proportion of cloride of } 1 04* sodium - - 100.00 100.00 * i. e. Gelatine. 24 RESEARCHES ON THE INTIMATE STRUCTURE OF BONE. Schreger states that in the bones of a child, the earthy matter constitutes one-half, that, in the bones of an adult it amounts to four-fifths, and in those of an old person to seven- eighths of the whole mass. Fourcroy and Vauquelin, found no fluate of lime in their analysis, but met with some iron, manganese, silex, alumine, and phosphate of ammonia. The luminous appearance of bones at night, when the animal matter is undergoing decom- position, is believed to be owing to the phosphorus liberated from combination ; and in such instances, Bichat has found an oily or unctuous exudation at the luminous points. The observations of M. Gerdy* who has carefully investi- gated the structure of the bones, coincide in a great degree with the microscopical researches of the German anatomists shortly to be noticed. He considers that there are four distinct tissues in bone, which have been confounded together up to this time ; the compact, the canaliculated,j* reticular, and areolar or cellular. The compact tissue has in certain bones a fibrous appearance ; its fibres appear longitudinal in long bones, radiated or irregu- larly divergent in many of the flat. The whole of this fibrous appearance is illusory, as Scarpa asserted, and is owing to the grooves or canals in the compact portion of the bones which lodge vessels, (canals of Havers,) run longitudinally in the compact portion, and have orifices leading into them from the outer surface ; between the canals is found projecting the pro- per structure of the bone, which is necessarily thin, and from the great number of these vessels, presents the appearance of fibres. The vascular openings leading into the grooves, are some perpendicular, and some oblique in regard to the surface of the bones. They all conduct vessels into the compact tissue. The compact tissue, as will be better seen under the head of formation of bone, is primitively a compound of osseous tubes developed around the vessels. These osseous tubes which are longitudinal in the long bones and radiated in the flat, are so * Bulletin de Clinique, 1835-6. f The canaliculated tissue is formed by the canals of Havers, which lodge blood-vessels. GERDY ON THE INTIMATE STRUCTURE OF BONE. 25 numerous, fine, so closely compressed together and so adherent, that their arrangement has escaped the observation of anato- mists. The existence of these vessels in the forming bone is well understood, and they have been injected with mercury by Tiedemann in the parietal bone,* In the adult healthy bone, they are more difficult of detection, in consequence of *the dense nature of the compact substance, in which the vascular chan- nels of the bones and the vascular orifices on the surface are reduced nearly to a microscopical size. But when the bony tissue is diseased or inflamed, as in fractures or after amputa- tions, their existence is no longer doubtful. Blood issues from them when cut, and the vascular orifices on the surface, as well as the canals in the compact tissue are visible to the naked eye, and in some instances are said to have been Fig. l.f as large as a pigeon's quill. Fig. 1, is a view of these canals, as seen in a bone twenty-five days after amputation. When the orifices and canals are thus expanded, the compact tissue appears rarefied, rough on its surface, more light and fragile and corresponds in appearance with the canaliculated tissue of Gerdy. The absence of fibrous appearance on the thick and mixed f bones is dependent upon the direction of the canals, none of which run parallel to the surface, but are all directed towards the articular surfaces of the bones. In the foetus at birth the compact portion of these bones appears sieve-like, from the number of vascular orifices on the surface, which lead perpen- dicularly to the canals that run towards the centre of the bones. Hence, according to Gerdy, the compact layer of these bones, is made up of minute bony rings, surrounding the numerous * See Breschet, plates of the Venous System. p. f Fig. 1. Section of the extremity of the os femoris, twenty-five days after amputation. It appears cribriform from the number of irregular orifices, be- longing to the canals of Havers (canaliculi,) in. the compact portion of the bone. The vessels which occupy these canals, are greatly enlarged by inflammation. Cases of this sort have been confounded by writers, with inflammation of the veins of the bones. p. \ The mixed bones are those which are mixed in their character ; being partly short and partly flat, as, the sacrum, the temporal, maxillary bones, &c. 3 GERDY ON THE INTIMATE STRUCTURE OF BONE. vascular orifices which touch each other at their circumference like the rings round the orifices of a tin colander.* The canaliculated tissue, is developed in all the bones of the body, but is least evident in the flat. It is an assemblage of small canals traversed by vessels, and has heretofore been described as a part of the cellular or spongy. In the long bones it is found on the inner surface of the com- pact tissue, and separated from the reticulated tissue of the medullary canal, by a parchment-like lamin, pierced with holes for the passage of anastomosing vessels. These canaliculi form elongated cavi- ties, which are slightly tor- tuous, nearly parallel with one another, not exactly rounded, and have their pa- rietes pierced with holes to admit of anastomosis be- tween the vessels which line them ; they run in the long bones in the direction of their length, and in the thick bones, from one articular surface to the other. They arise in part 6 Fig. 2.f * This we shall find is the opinion of the microscopists in regard to the struc- ture of all compact bony layers. f Fig. 2. Vertical section of the inferior third of the tibia. 1. 1. Compact tissue of the body of the bone, becoming gradually thinner towards the inferior extremity. 2. 2. Reticulated tissue in the lower part of the medullary cavity occupying the axis of the cylinder of bone. 3. 3. Canaliculated tissue, the vas- cular canals of which deiach themselves successively from the compact walls of the bone, and run nearly parallel with each other towards the extremity of the bone. 4. 4. Cellular tissue of the epiphysis, composed of interrupted canaliculi, and of tubular cells, which terminate nearly perpendicularly upon the articular surface. 6. 6. The articular or sub-cartilaginous compact tissue, extremely thin. GERDY ON THE INTIMATE STRUCTURE OF BONE. 27 from the divisions of the nutritious foramina, which transmit the medullary vessels of the long bones, but chiefly from the vascular (Haversian,) canals of the compact tissue, as seen in a vertical section of the femur and tibia, fig. 2 and fig. >J. where the increase of the canaliculated structure is in inverse propor- tion to the thickness of the compact. These canals unite together, and divide again and again, so that they become increasingly numerous as they approach the spongy extremities, when they separate from each other and spread out so as to form a large part of these extremities. The cellular or areolar tissue of Gerdy, is formed in the thick bones and the extremities of the long bones by the inter- ruptions of the canaliculated tissue, by other canals arising from the surface of the bone which cross them in an angular direc- tion, so as to form quadrilateral cells, see Fig. 3, No. 1, the par- titions of which are pierced, so that there is a free communica- tion between the vessels lining the different cells. The reticulated tissue which was confounded by Bichat with the canaliculated, should be now as it was before his time dis- tinguished from it. So far from being formed of a canaliculated tissue for the purpose of containing vessels, it consists only of a network of bony filaments for the purpose of supporting a delicate cellular membrane called the medullary which is thrown into the form of cells to retain the fat or marrow, and which is very vascular. It is found chiefly in the cavities of the long bones, and terminates short of the extremities in a point, see Fig. 3, 6, while the canaliculated tissue continues to expand. This tissue is beautifully developed in the long bones of the horse, but scarcely exists at all in those of the bullock. - Vessels of the bones. All anatomists admit three kinds of vessels in the bones ; those of the compact tissue, those of the cellular tissue, those of the medullary canal. Those of the compact tissue are very fine and very nume- rous ; they, penetrate it in great numbers, after having divided Very generally it is deficient in places on the articular surface of bones, so as to leave the cells of the spongy tissue and their vascular canals naked when the cartilage is removed. 7. Internal malleolus. p. 28 GERDY ON THE INTIMATE STRUCTURE OF BONE. Fig. 3.* to capillary minuteness in the periosteum. The diameter of these little vessels, where they enter the bone, has been calcu- lated to be about one-twentieth part of a line. The drops of blood which collect when the periosteum is stripped from the * Fig. 3. Vertical section of the os femoris. 1. 1. Tubular cells perpendicular to the articular surface of the bone ; sometimes these cells are chiefly round. 2. Cartilaginous lamin separating the epiphysis from the shaft of the bone. 3. Vertical canal opening by one or more foramina, in the fossa at the top of the trochanter, and anastomosing with the canals of the canaliculated tissue. It lodges one of the vessels of the cellular tissue ; which penetrate by the extremity of the body of the long bone. 4. 4. Vascular canaliculi, which run obliquely upwards and inwards towards the lamen of the epiphysis, where the cartilage begins to be removed, and the consolidation of the epiphysis and shaft has com- menced. 5. 5. Canaliculi of the upper part of the body of the bone, which are directed towards the axis of the bone, and which anastomose with the vascular canal indicated at 3. 6. Conical termination of the reticulated tissue of the medullary canal. p. GERDY ON THE INTIMATE STRUCTURE OF BONE. 29 recent bone, indicate the position of these vessels. Having entered the compact tissue, they spread in its channels (canals of Havers, canaliculi of Gerdy^) which are imperceptible without a microscope in a healthy bone, but beconae, very manifest in disease. Those of the medullary canal enter usually by a single large foramen, give off some branches to the canaliculi in their course, and having reached the medullary or central cavity, divide into two branches, which run in opposite directions towards the extremities of the bone. These branches divide and subdivide very minutely in the medullary membrane, and anastomose very freely with the vessels of the canaliculated tissue upon the side, and in the adult, (after the cartilage which separates the epiphysis from the body of the bone has been removed,) with the cellular tissue of the extremities. Those of the cellular tissue, that is to say the vessels of the extremities of the long bones and the large vessels of the other bones, penetrate from the surface by foramina much larger than those of the compact bone, and occasionally under the form of distinct canals. They are very numerous. I have counted 145 on the lower end of the femor, 25 upon a vertebra, and. 30 on the os calsis. They anastomose intimately with the other two orders of vessels, and are particularly abundant near the articular sur- face of the bones, where they form the tubular cells, and as some suppose, directly or indirectly assist in the formation of the articular cartilages, which many have considered a simple pro- duct of excretion like the nails or hair. All the vessels are sur- rounded in the canals by a cellular tissue, more or less delicate loose and filled up with a fatty or oily matter, which is least abundant in the compact tissue where the canals are very small. No other nerves except those which accompany these vessels are believed to enter the substance of bone. These facts in regard to the structure of bone are supported both by observa- tion and reasoning. The microscope shows us thousands of vessels in the healthy state entering into the substance of the bones. Inflammation attended with vascular congestion develops and renders them so obvious as to be appreciated by the 3* 30 DEUTSCH AND MIESCHER unassisted eye, the slightest irritation with a probe will cause them to bleed freely, and heat applied to a section of a recent bone, will develop the fatty or oily matter even in the compact portion. From the complexity of their organization, and the frequency and importance of their diseases, bones demand from the student, more earnest study, at least in regard to their general anatomy than is usually given. Deutsch,* under the direction of Purkinje, and Miescherf of Berlin whose investigations were made prior to those of Gerdy, have arrived at nearly similar conclusions in regard to the structure of bone. In very thin transverse sections of long bones, which had been macerated in dilute acid, they disco- vered the circular orifices of the longitudinal canals in the com- pact portions of the bone ; and in thin longitudinal sections the canals were seen divided in the direction of their length. (See Figs. 4 and 5.) The canals, according to these observers, com- municate here and there with each other, and constitute the longitudinal and transverse canals of Havers, and which are described by Lewenhceck, as his third and fourth kinds of pores. Fig. 4.J These canals are rilled with yellowish medullary or adipose matter, in which according to Miescher, are seen many minute capillary vessels, when successfully injected after the method of Krause. * De pentiori ossium stractura observations. Vratislavise, 1834. f De ossium genesi, structura et vita. Berolini, 1836. $ Fig. 4. Is a longitudinal section of a long bone, magnified one hundred times, a. One of the longitudinal canals not fully exposed, b. b. Longitudinal canals, c. c. These canals partially cut across, so as to exhibit the concentric lamellae which surround each one. d. d. Transverse canals joining the others. The straight lines near the margins of the cut, are the lamellae divided in the direction of their length, which surround the canals. The spots seen are the bony corpuscles, not sufficiently magnified to render them distinct. ON THE INTIMATE STRUCTURE OF BONE. 31 Fig. 5.* In the transverse section, each of the orifices of the canals, Fig. 5, is seen surrounded by ten or fifteen concentric lines, which on examining the longitudinal section, Fig. 4, are found to be as many lamellae running the whole length of the canal, and each about the ? | 5 th part of an inch in diameter, accord- ing to the microscopical measurement of Deutsch.f The spaces in the transverse section of the bone, not occupied by the lon- gitudinal canals and their concentric lamellae, are filled by other lamellae, which form larger concentric rings round the great medullary cavity. The diameter of the canals of Havers, according to Miescher, varies from ^th to ^ili of an Eng- lish inch. In the flat bones the canals with their lamella, run parallel with the surface of the bone. In the long bones, the longitu- dinal canals are directed obliquely into the central cavity. In the lamellae concentric to the canals, there is an appear- ance of dots or short lines, which do not occupy the whole * Fig. 5. Is a transverse section of one of the flat bones of the cranium, mag- nified one hundred times, a. Compact substance or table of bone, expanding into diploe. b. b. c. c. Vasculo-medullary canals of the compact portion, cut across, d. Transverse communicating canals, between these and the larger canals or cellular cavities of the diploe. e. Diploic cells communicating with others at /. Diploic cells like the canals of the compact portion, are surrounded with concentric striae or lamellae, and are in fact only amplified vasculo-medul- lary canals. The spots upon the surface, are the bony corpuscles. f Some modern observers have made the diameter or thickness of each of these lamellae, much less than that stated by Deutsch. Mr. Wilson states it to be not more than the ^5^ a measurement which appears to me to err much on the minimum side . 32 OF THE PERIOSTEUM. thickness of each lamellae, and which Deutsch, supposed to be extremely minute tubes. Some of these dots or lines, see Fig. 5, appear to transverse more than one lamella, though the majority, as Miescher describes them, are very short, and appear like the separations between the granules of the carti- lage of the bones, from which the calcerous portions had been removed.* The result of the observations of Miescher, is : 1st. That the spongy structure of bones, is nothing but an amplification of the canaliculi, as is shown by Gerdy. 2d. That the medullary canal, as shown by its formation and name, is provided for the purpose of union or anastomosis, between these enlarged canaliculi, and, 3d. That therefore, the canaliculi, girdled with concentric lamellae and containing a medulla, composed of a great body of vessels, is the primary element or form of the osseous tissue, which is subsequently more fully developed. Scarpa is therefore correct in saying that the solid parts of bone, are formed of the cellular structure in a more compacted state. The reticulated tissue, which forms a sort of link between the cellular substance and the medullary cavity, and the osseous filaments which project every where from the parieties of the cavity into the medulla, are the remains of the walls of the cells, the integrity of which is impaired in conse- quence of the enlargement of the orifices by which they com- municate together. Of the Periosteum. Bones are invested with a firm membrane .denominated periosteum, which is of a fibrous texture, and in some places may be separated into different lamina. The external surface of periosteum is connected with the contiguous parts by cel- lular membrane ; the internal surface is connected with the bone by a great number of fibres and blood-vessels. The orifices of these vessels become apparent, when the periosteum is separated from bones in the living subject. * Subsequent microscopical observations, as will be shown further on, have confirmed this supposition of Deutsch. p. MEDULLARY MEMBRANE OR INTERNAL PERIOSTEUM. 33 This membrane covers the whole bony surface, except those parts which are invested by cartilages, and the capsular liga- ments of joints, those which are occupied by the insertion of tendons and ligaments, and the bodies of the teeth. It appears most intimately connected with the surfaces of spongy oones, and the extremities of the long bones. In a sound state it has very little sensibility ; but in some cases of disease it appears to be very sensible ; of course it must be supplied with nerves, although several expert anatomists have declared they could not trace them. It is probable that the principal use of the periosteum is to transmit vessels to the bones for their nourishment ; but death or exfoliation of the surface, does not always take place when the periosteum is removed from a portion of bone.* This membrane presents a polished, pearly white appear- ance, when examined in the recent bone. It has received different names according to the parts which it covers, though its structure is nearly uniform throughout. Thus, when it covers the exterior surface of the bones of the cranium it is called pericranium ; when it covers the cartilages, perichon- drium ; and when it covers the bones with the exception of those of the head, periosteum. In infancy the periosteum is soft, thick, and spongy, and may be readily separated from the bones. In adult life it is more firm and compact, and is often so intimately united to the bones as to be detached with difficulty from them. In old age it is extremely dense, and becomes not unfrequently ossified at its internal surface. Its vascularity, which is at first rather obscure, also gradually increases as life advances, but in old age it again diminishes.f Of the Internal Periosteum or Medullary Membrane. This membrane is particularly well marked in the cavities * Dr. Physick thinks that the periosteum frequently prevents the bones from participating in contiguous disease, as the pleura turns off an abscess inthe parie- tes of the thorax from its cavity, or the peritoneum from the cavity of the abdomen. 11. f Anat. Phys. and Diseases of Bones and Joints. By S. D. Gross, M. D. 34 MEDULLARY MEMBRANE OR INTERNAL PERIOSTEUM. of the long bones, where it forms a thin, delicate, pellucid, vascular membrane, lining the sides of the cavities of the reticu- lated tissue, in which it forms vesicles, that contain the marrow. The lining membrane of the cells in the spongy portion of the bones is still more delicate in its structure, and more difficult of demonstration, and has been supposed by many anatomists to be formed only from the coats of the blood-vessels which anastomose thousands of times with each other in the interior of these bones. Its office, however, is precisely similar to that of the membrane in the cavity of the long bones, to lodge the fatty or medullary matter which is furnished by exhalation. It is very inflammable/ burning with a beautiful blue tinge, and an oily disagreeable odor, fluid during life, but presents itself after death, under the form of brilliant granules of solid fatty matter. When death has taken place from some wasting disease as dropsy or consumption, the fat is removed by absorption, and its place is supplied by a watery fluid which renders the bones less greasy and more valuable as cabinet preparations. This medullary substance as has been before observed is also found with the vessels in the canals of the com- pact portions of bone< At the extremities of the long bones, the formina for the transmission of the blood-vessels and fibres are much larger than they are in the middle ; but there is an oblique canal near the middle of these bones, which transmits vessels to this membrane in the interior of the bones called nutritious or medullary. The surface of the internal cavities and cells of bones it will then be seen, is lined by a membrane more delicate and more vascular than the periosteum, which contains the medullary matter that is always found in their cavities. [This is the* internal periosteum or the medullary membrane of the bones. M. Portal denies that it exists as a distinct membranous sac, but asserts, that it is derived from the envelop of the vessels which is sent in along with them from the periosteum.] It has been said that in some circumstances this membrane has had great sensibility, but the- reverse is the case in com- mon. MEDULLARY MEMBRANE OR INTERNAL PERIOSTEUM. 35 The medullary matter in the large cavities of bones has a strong resemblance to adeps. That which is in the cells, at the ends of the long bones, appears more fluid. In young animals it is slightly tinged with a red color. *s The chemical properties of the adipose or medullary sub- stance of the bones consist according to Berzelius of the fol- lowing ingredients : Pure adeps or marrow 96 Membrane and blood-vessels - 1 Albumen - Gelatine Extractive and peculiar matter Water 100 The character of this substance differs somewhat at the dif- ferent stages of life ; it is of a thin aqueous consistence and of a reddish color in the infant ; of the consistence and presenting after death somewhat the appearance of butter in the central cavities of the bones, and of a red semi-fluid appearance in the spongy tissue of the bones of the adult ; in old age it has some- thing of a rancid smell, and is of a deep yellow color. The adeps of the bones was supposed at one time to contribute to the flexibility, tenacity, and nourishment of the Irenes, but it is now generally believed to be deposited upon the same principles, as fat in other parts of the body, when nutritive matter is super- abundantly elaborated by the digestive organs, and is held in reversion, as an aliment for the future wants of the economy, during temporary inanition from sickness or other causes. The deposit of fat in bones is not universal among animals. In birds the central cavity of the long bones, is filled only with air which is introduced into them from the lungs, and serves ! greatly to diminish their specific gravity, and facilitates their/ evolutions in the atmosphere. It is found in great quantity in the bones of the head of the wwerocep/m/ws, or sperm whale, far out of the pro- 36 CARTILAGES AND THEIR STRUCTURE. portion required, if its object only was that of nourishing the bones. Its purpose in this animal, besides being a deposit of aliment in reserve, is believed to be that of buoying up its head to ena- ble it to respire with greater freedom. Cartilages and their Structure. CARTILAGES are white elastic substances, much softer than bones, in consequence of a smaller quantity of earth entering into their composition. Their structure is not so evidently fibrous as that of bones ; yet by long maceration, or by tearing them asunder, a fibrous disposition is perceptible. In articular cartilages their fibres are parallel to each other, and directed towards the cavities of the respective joints. Their vessels are extremely small, though they can be readily injected in cartilages where bone is beginning to form. The vessels of the cartilages of the joints, however, seem entirely to exclude the red blood ; no anatomist having yet been able to inject them. They have no cancelli, nor internal membranes, for lodging marrow ; no nerves can be traced into them ; nor do they possess any sensibility in the sound state. Upon their surface, there is a thin membrane termed peri- chondrium, which in cartilages supplying the place of bone, as in those of the ribs or at the ends of long bones in children, is a continuation of the periosteum, and serves the same general purposes to cartilage as this does to bone. Upon the surface of articular cartilages, the perichondrium is a reflection of the inner surface of the capsular ligament, and is so very thin, and adheres so closely, as to appear like part of the cartilage itself.* One set of cartilages supplies the place of bone, and by their flexibility admit of a certain degree of motion, while their * The articular cartilages are the only ones not provided with a fibrous peri- chondrium. The synovial membrane which is supposed to cover them by being reflected from the inner face of the capsular ligament, is said to supply the place of perichondrium. p. CARTILAGES AND THEIR STRUCTURE. 37 elasticity recovers their natural position, as in the nose, larynx, cartilages of the ribs, &c. Another set, in children, supplies the place of bone, until bone can be formed, and affords a nidus for the osseous fibres

. \--\X\ 7SX-- 0V. % . . / 38 CARTILAGES AND THEIR STRUCTURE. of them in various parts of the body, though not from the ar- ticular. When a recent cartilage is cut, a whitish juicy fluid is seen to exude from its substance, which must get into it, by imbibition from the surrounding parts, or as has been thought more proba- ble, be carried into it, by white vessels, too small to admit more than the serous portions of the blood. If inflammation take place, which is admitted in many carlilages, though not as yet proven to exist in those of the joints, it differs from ordinary inflam- mation as these vessels are never so dilated, as to admit the red globules, and present a red appearance. No lymphatics have ever been traced into them, though Mascagni was disposed to consider them as formed entirely of these vessels. Nor have nerves been found in them, the very existence of which in these parts, though so necessary to the perfection of other organs, would have unfitted them for their office. Hence we find them smooth, so as to move upon one another without friction, destitute of nerves, so as to bear pressure without sen- sation, and feebly supplied with vessels, so as to be little prone to inflammation, if they be not, as Gerdy has suggested, a mere secretion like the hair and .nails. Hence they are enabled to bear exposure to the air for a considerable time without change, as stated by Velpeau, and to exist unharmed frequently in the midst of gangrene. According to J. Davy, their chemical composition is 55. parts in the hundred of water, 44.5, of albumine, and .5 of phosphate of lime. As in the bones, however, the chemical proportions vary at the different periods of life. They are nearly fluid in the foetus, contain a large amount of fluid in youth, have the proportions given above at puberty, and a much larger amount of earthy matter in old age. In fact, with some few exceptions in the joints, they all have a natural tendency to ossify as life advances. The structure of cartilage is, however, not fully understood ; that they share in some manner in the general circulation of the body, is rendered probable by their being colored yellow in jaundice ; and that they are not reddened like the bones when an animal is HO ....... ---in ACCIDENTAL DEVELOPMENT OF CARTILAGES. 39 fed upon madder, is said by Beclard, to be owing to tbe small quantity of phosphate of lime which they contain, and with which this coloring matter only has affinity. They participate too in the ulcerative process in many parts of the body, as in those of the nose, and as I have many times seen, in tnose of the larynx and trachea. All cartilages are divided into two classes, temporary or ossescent, and permanent, a distinction which though not per- fectly exact, is nevertheless very convenient for the purposes of study. The temporary cartilages, (cartilag. temporaries) are those employed in the development of the bones, those of which the models of the bones are all formed in the foetus, and which gradually as the infant advances in growth give place to bony matter. The substitution of bony matter for the cartilagi- nous, is completed about the period of puberty. The permanent cartilages (cartilag. permanentes) are devel- oped at an early period of life like the former, but have little tendency to undergo ossification, and retain their cartilaginous character for the whole or the greatest part of life. These com- prise, the articular and costal cartilages, those of the larynx, eustachian tube, auditory meatus, etc. Some of these have a stronger tendency than the rest to ossify, as those of the larynx and ribs, which are frequently found after the fortieth year of life, converted into bone. Accidental development of Cartilages. In almost every one of the different tissues of the body, car- tilages have been occasionally met with, but in general only after the middle period of life, when from their having apparently no fixed laws of development, they have been called acci- dental. 1st. They are found in the form of plates of greater or less size, adherent by both surfaces to the membranes between which they are formed ; in the arteries, where these plates are most frequently met with, they are attached on their inner surface to the serous lining membrane, and on their outer to the middle coat of the vessel. 40 FORMATION OF BONE. 2d. They are frequently met with in the form of roundish or irregular masses in the substance of the different organs, as the arteries, lungs and ovaries. 3d. Under the form of smooth flattened concretions, formed originally according to Meckel on the outer side of the synovial membrane of the joints, and which develop themselves towards the centre of the cavity of the joints, till their attachment to the membrane is stretched out, so that it becomes a mere pedicle, which not unfrequently breaks *off. In this way is formed the loose cartilages often met with in the knee joint. All these accidentally developed cartilages have a tendency to be converted into bone, and which are then called accidental ossifications. Of the Formation of Bone. The generality of bones, and particularly those which are long, are originally formed in cartilage ; some, as those of the skull, are formed between membranes, and the teeth in distinct bags. When ossification is about to begin in a particular part of a cartilage, most frequently in the centre, the arteries, which were formerly transparent, become dilated, and receive the red blood from which the osseous matter is secreted. This matter retains, for some time, the form of the vessels which gave it origin, till more arteries being by degrees dilated, and more osseous matter deposited, the bone at length attains its com- plete form. During the progress of ossification, the surrounding cartilage by degrees disappears ; not by being changed into bone, but by an absorption of its parts, the new-formed bone occupying its place. The ossification of broad bones, as those of the head, begins by one or more points, from which the osseous fibres issue in rays, as seen in Fig. 6. The ossification of long bones, as in those of the extremities, begins by central rings, from which the fibres extend towards the ends of the bones. FORMATION OF BONE. 41 The ossification of spheri-formed bones, Fig. 6.* begins by one nucleus, as in the wrist ; and that of irregularly shaped bones by different nuclei, as in the vertebrae. Some bones are completely formed at the time of birth, as the small bones of the ear. The generality of bones are incomplete until the age of puberty, or between the fifteenth and twentieth year, and in some few instances until a later period. In children, many parts of bones, particularly the ends of long bones, are distinct from the bodies ; they are called epiphyses, and can be readily separated from the bodies of bones, by boiling, or by maceration in water. The epiphyses begin to appear after the body of the bone is ossified, and are themselves ossified at seven or eight years of ,' age, though their external surface is still somewhat cartilagi- nous. They are joined to the body of the bone by the cartilages, which are thick in children, but gradually become thinner as ossification advances, till at last, in the adult, the external marks of division are not to be seen, though frequently some mark of distinction may be observed in the cancelli. The development of bones is the final result of several suc- cessive changes. In the foetus the bone is at first represented, by a soft gelatinous mass, continuous throughout as one piece, and in which there is no appearance of joints. The consistence of this matter gradually increases, and presents a cartilaginous appearance, about the second or third months of foetal life. At the same period a separation is manifested at the place of the joints. A third change takes place in the cartilage, which is that of ossification ; this commences in some of the bones, between the second and third months of foetal life, at various * Parietal boss of the infant at birth magnified, showing the central point of ossification. At first sight the vascular canals, resemble radiated lines, but with a little attention, they will be found to be vascular channels, slightly tortuous, and originating near the centre of the boss or protuberance from the foramina in Ihe newly formed bone. p. 4* 42 FORMATION OF BONE. periods in other bones, in many not till long after birth, and is not completed in all the bones of the body till near the period of puberty. """ In the metamorphosis of cartilage to bone, the white and homogeneous cartilagd which forms the mould of the bone, becomes hollowed out so as to present irregular cavities,* which subsequently form canals lined by a vascular membrane and filled with a viscous fluid "which extend to the centre of its structure. One of these canals forms subsequently the nutritious foramen. The cartilage becomes opaque and yellowish round this spot, the vessels convey red blood, numerous red points are formed in the structure, and ossification commences at the centre of the bone ; never upon the surface. In the long bones a bony ring is first formed in the centre, and the vascular canals extend themselves in the direction of the extremities in the flat and thick bones, in radii, attended by a redness in the cartilage, nearest the seat of ossification, and a diffused yellowness beyond it. From these canals the ossific material is deposited, and the central point of ossification grows, till the bone is completed. As the bony portion advances in growth, its redness diminishes, and the vascular canals which are at first la^e, decrease in size, so as to become in the adult bone microscopical. The ossescent or provisional cartilage of the bone, is solid and has in no instance any cavity in its centre. The ring of bone which, as before observed, is the first step of development in the long bones, has a cavity in its centre which is subsequently destined to lodge the medulla. In the flat bones, and especially those of the cranium, ossification commences between the second and third months of foetal life. Those of the cranium are formed between the pericranium and dura mater, and their cartilaginous mould is so thin and soft, that Howship and Beclard have denied its existence. The vascularity commences in them at a central * According to the German anatomists, see page 44, the hollowing of these canals, is produced by an aggregation of the cartilaginous corpuscles into a series of linear ranges, between which the vessels shoot that convey the earthy mate- rial of the bone. p. GROWTH OF BONE. 43 point, and the ossificrays pass off in a straight direction, as seen in Fig. 6, page 41. Many of these bones, as well as of those in other parts of the body, are of such irregular shape, as to be inca]>able of being formed of fibres radiating from a single centre ; they are, therefore, developed from several centres, the rays of which finally meet and inosculate. The development of the thick bones, and the epiphysis of the long bones, take place in accord- ance with the same laws. Growth of Bones. In all the long bones, the extremities or epiphyses, are developed in separate pieces and between them and the ossified shaft there is a cartilaginous lamen, which does not disappear till the bone has attained its full development. The bones increase in length by the continuous deposit of new ossific matter in this lamen of cartilage, which seems retained there as a soft bed for that purpose. As soon as the bone has attained its full length at puberty, the lamen disappears, and the epiphysis and shaft are consolidated, as seen in Fig. 3, where 2 is the layer of the cartilage, beginning to disappear at one point. The long bones increase in diameter, by the successive addition of new bony matter between the periosteum and bone. It is said to be deposited from the periosteum itself: but that opinion is incorrect, for no membrane can form a tissue, so much at variance with its own structure. It is the blood- vessels which merely ramify minutely through the periosteum, that deposit the matter upon the surface of the bone, precisely as they do in the centre. This mode of growth in diameter by concentric circles, has been proved by experiments made with mixing madder at intervals in the food of animals, by Duha- mil,* Hunter, Professors Homer, Mussey, myself, and others. On killing the animals, red rings were found surrounding the bones, alternated with white ones corresponding to the periods of * Duharail who was no anatomist, considered the growth of bones, as analo- gous to the vegetation of plants. He placed a silver ring upon the bone of a young animal, which he afterwards fed interruptedly on madder. The white and red strata alternately covering the ring as he found on killing the animal, he erroneously considered not deposited on the outer surface, but formed by the expansion of the bone bulging over it as takes place in plants. r. 44 OSSEOUS CORPUSCLES. administering or suspending the madder.* At the same time, that there is this increase of matter on the surface, there is a corresponding enlargement in the central or medullary cavity, which is said to be effected by the action of the absorbents. It appears to me, however, to be far more likely due to an interstitial growth, by which the walls of the cavity are in- creased in dimensions and the cavity itself necessarily enlarged. Corpuscles. Purkinje has -recently Fig. 7.f discovered in cartilage generally, and especially in the cartilage of bone, round- ed corpuscles, which are much larger in diameter than the transverse sections of the canals described in p. 30. The existence of these corpuscles, has also been confirmed by the microscopical re- searches of Deutsch, Miescher, Sharpey and others ; according to Miescher they correspond with the brown spots described by Lewenhoeck as his second order of foramina. In bone de- prived of its earthy parts by maceration in acid, their appear- ance is that of small brown spots,{ pellucid in the centre, and surrounded with a distinct opaque line, which by a high magni- fying power, appeared to Miescher to be denticulated. They are situated between their lamellae, the long diameter being ob- * Rutherford, of Edinburgh, first explained this coloring of the bone, without that of the other tissues, by the affinity of the madder for the phosphate of litne, upon which it acted as a mordant. p. f Fig. 7, is a representation from Miescher of the progress of ossification, caused by inflammation in an adult bone, which takes place nearly in the same manner that new bone is formed ; a a, the cartilage, the first stage in the forma- tion of bone, and the small bodies thickly interspersed through it are the carti- lage corpuscles of Purkinje j b b, the first or primary stage of the bony structure, in which the osseous corpuscles arrange themselves somewhat into lines, and the bony fibres shoot in between them, and in the thickness of the corpuscles themselves saline particles are deposited, which renders them opaque ; c c, the new structure completely ossified. $ These as shown p. 46, are now believed to be new bodies, bony corpuscles, which supplant the cartilaginous corpuscles of Purkinje. The above account is retained in order to show progressively the history of the discovery. NEW VIEWS OF THE GROWTH OF BONES. 45 lique in regard to the direction of the lamellae, and when the work of ossification has not commenced, appear to have no fixed arrangement, and are wedge-shaped, oval, oblong, or flattened, see Fig. 8. Of the nature of these corpuscles, little f is posi- tively known. Neither vegetable or mineral acids have any effect upon them, except to render them a little more prominent on the surface of a section of cartilage. Alcohol, ether, or a cold solution of caustic potash does not change them ; but if exposed to a hot caustic solution, or a long time macerated in water they become completely liquified. The size of the corpuscles according to the measurements of Miescher, varied in length from the 0.0048 to the 0.0072 parts of a line, and in breadth from the 0.0017 to the 0.0030.* The researches of this anatomist, of Miiller, and other recent ob- servers, have shown that the formation of cartilage always precedes that of bone,f and that each ossescent or temporary cartilage, is an organic tissue, homogeneous, more or less pel- lucid, elastic, in its first state almost colorless, afterwards assum- ing a bluish cast, and having a great many peculiar minute corpuscles interspersed through its substance, as shown by the microscope. In the conversion of cartilage into bone, the 'change first commences in the cartilage that surrounds the corpuscles. Weber, Beclard and others, believe that the calcareous matter is deposited by the vessels, in the cartilaginous mould of the tyone, as a foreign body, and that the cartilaginous particles are removed in proportion to make room for it ; but this is a mere opinion which has not been proven. Miescher, asserts that he was unable even with the micro- scope to ascertain in what manner, the calcareous particles were * More recent researches seem to prove that the average diameter of these cartilage cells or corpuscles, is about the one twelve hundredth or one fifteen hundredth part of an inch. P. f This which was admitted by Albinus, Haller/ Scarpa; and others, has been denied by Howship and Beclard, in regard to the diaphysis of the long bones, and the bones of the cranium. In the bones of the rabbit, Miescher found a mould of cartilage before a particle of ossific matter had been deposited, and between the pericranium and dura mater, a thin stratum of cartilage. An ex- ception must be made however in regard to certain flat bones of the human skull, as the parietal. p. 46 NEW VIEWS OF THE GROWTH OF BONES. received into the cartilage, the strongest powers of the micro- Fig. 8.* scope exhibiting no cells in which they were placed, nor any calcareous particles of the size of the dispersed corpuscles ; all that appeared positively was that the cartilage seemed by degrees to assume the aspect of bone. The more recent researches of Gerber,f have given* if not a perfectly clear, at least a more satisfactory explanation of the manner in which the ossific cartilage is so modified, as to form bone. The primitive physical formation of all car- tilage is cellular, that is they grow from cell-germs, as is the case with the other tissues of the body. These cell-germs or cartilage corpuscles are seen at A. Fig. 8, magnified 250 diameters. Between these cells and filling up the vacant spaces between them, is an amorphous, hyaline or transparent intercellular substance ; the cells themselves are filled with . a softish granular matter. As the cartilage* increases in growth, new cells are develop- ed in the hyaline substance by which the older ones are pushed farther and farther from each other. The original cells pro- * duce two or more young or secondary cells by the development of their gra- nular nuclei : between these secondary cells is also formed a secondary hya- line substance, and thus the orginal cells form each one a little group of cells enclosed within itself, and to each group the name * Fig. 8. A scheme intended to represent cartilage in the progressive stages of ossification, magnified 250 diameters. A. Cartilage with the regularly dissemi- nated corpuscles of Purkinje cellular cartilage B. The corpuscles when ossi- fication has begun, are forced into groups, between which the hyaline cartilage is transformed into bone cartilage. This bone cartilage has now undergone a change, so as to be chemically different from those cartilages which are to remain f Elements of General and Minute Anatomy by T. Gerber. London, 1842. NEW VIEWS OF THE GROWTH OF BONES. 47 of cartilage corpuscle is still applied. This is the common em- bryonic constitution of cartilage. The fixed character of the cartilage depends upon the after changes which take place in it. If fibre-cartilage be formed, the intercellular or hyatme sub- stance is developed in the form of fibres and the cells disappear altogether. If elastic cartilage, fibres are developed around the cells forming a kind of network. If ossific cartilage, the hya- line substance takes on a stratified arrangement round the car- tilage cells, and in it a new set of corpuscles are developed, called the bone corpuscles, that are the nuclei of the bone cells, see Fig. 9, of which the microscope has shown in reality all bony structure to consist. As this process is commencing, the cluster of cartilage cells called cartilage corpuscles, become compressed together. The secondary hyaline substance becomes dissolved, transudes through the walls of the parent cell, coagulates round it, and in this state of cytoblastema as it is called this basis structure for the growth of other parts it con- stitutes the proper ossific cartilage. In it arise the bone cor- puscles, called cytoblastty or germs, from which are formed the bone cells. These follow the same mode of development, as the embryonic cartilage cells : that is new corpuscles are forming in the cytoblastema, while those recently produced are growing ; the cartilage corpuscles ever more closely com- pressed together disappear ; radiated points, nutrient vessels, etc. make their appearance, the nuclei of the bone cells, (corpuscles,) and the cells themselves when completely formed receive depos- its of calcareous salts, and the formation of bone is achieved. flexible during life. It does not on boiling yield gelatine like them, but a sub- stance called chondrin, which differs from gelatine in not being precipitated by tannic acid, etc. C. The groups of cartilage corpuscles are now seen completely inclosed by bone cartilage. D. The cartilage corpuscles are here rendered less transparent by the process of resolution that is going on ; the bone corpuscles are at the same time making their appearance in the bone cartilage. E. The cartilage corpuscles are dissolved and partially removed. F. The cartilage cor- puscles have disappeared ; have been absorbed. G. In spongy bones, the spaces occupied by the cartilage corpuscles remain as cells filled with globules of fat. In compact bones the cells are reduced to minute canals, by the growth of bony matter, or they disappear entirely. In Fig. 9, there is a representation of bone in its perfectly formed state, magnified 450 diameters, and representing the bone cells or corpuscles, with iheir calcareous canals. 48 FORMATION OF CALLUS. Fig. 9.* It is according to this from a peculiar sub- stance, not ordinary cartilage, that bone is pro- duced, and we now know that the effused fluid of which the callus in fractures is formed, is in some respects different from the cartilagi- nous mould of bone, and that in fact bone is developed in many parts of the body, as in the human .skull for instance, without the. existence of any previous cartilaginous basis. Formation of Callus. The most ancient opinion entertained in regard to the mode of union between broken bones, was, that it was owing to the con- cretion of a viscous fluid, or imaginary osseous juice poured out between the fragments. This was the opinion of Haller. Du- hamil demonstrated the fallacy of this belief, by numerous experiments, and instituted a theory of his own which is much nearer the truth. According to him the production of callus or new bony matter, is owing to the swelling, elongation, and subsequent adhesion between the periosteum and medullary membrane of one fragment with the corresponding parts of the other; and that from these membranes thus modified, bony matter was deposited in the form of a ring on the exterior of the bone and a plug in its medullary cavity, which held the fragments together by passing across the cavity of fracture, and sometimes by prolongations passing between them through the cavity. John Hunter believed that the re-union of fractured bones took place from the organization of the blood effused around the fracture and between the fragments ; a doctrine which now has few supporters. The credit of giving the most faithful account of the forma- * Fig. 9. Bone corpuscles, a, magnified 450 diameters, which have here been converted into bone cells, b. Branches of the bony cells which by their inoscu- lations form a net work. They are called by Mttller the canaliculi calicophori. It is not yet fully decided whether or not the cells and their branches are filled with calcareous matter, or merely incrusted with it. The diameter of these calcigerous canals (canalic. calicoph.) is reckoned at their largest parts to be between one fourteen thousandth and the one twenty thousandth part of an inch. RESTORATION OF FRACTURED BONES. 49 tion of callus, is due to Dupuytren* and Sanson. According to these, the union of fragments of bone, is effected by the for- mation of two successive stages of callus. One which is pro- visional or temporary, is completed usually in the sp^ce of thirty or forty days, by the union and ossification of the perios- teum, cellular tissue, and even in some cases of the muscles, so as to constitute an external ring and of the medullary mem- brane, so as to constitute an internal plug. The other, which he calls final or permanent, is formed by the re-union of the surfaces of the fracture, with a solidity so much superior ./ /C to that of the bone in other parts, that it will break any where again, rather than at that point, and which is never fully com- pleted, notwithstanding the limb appears earlier than this restored to its proper uses, under eight, ten, or twelve months, by which time all the provisional callus has been removed, and the medul- lary canal is completely re-established. Dupuytren divides the successive organic changes, which attend the formation of callus, into five periods. The first period, extends from the time of the fracture to X the eighth or tenth day, and is characterized by the following phenomena : the medullary membrane, the medulla, the perios- teum, cellular tissue, and sometimes the muscles themselves, are torn at the time the fracture takes place ; blood escapes from the ruptured vessels, surrounds the fragments, spreads in the medullary canal and infiltrates in the surrounding tissue : the hemorrhage stops ; a slight inflammation is developed in all these parts, which is the first step towards the production of the callus. The cellular tissue surrounding the bone, becomes very vascular, is thickened, loses its elasticity, and acquires a great degree of consistence ; it sends irregular processes into the neighboring muscles, transforms them to a greater or less extent into an analogous tissue, and unites them in a common structure with the periosteum, which is also much thickened and very vascular. A nearly similar change takes place in the cavity of the bone in respect to the medulla and its membrane. The calibre of the medullary canal is contracted by the thickening - * Journal Univ. de Med. torn. 20. 5 50 RESTORATION OF FRACTURED BONES. of the membrane, which presents a fleshy appearance, in con- sequence of a sort of gelatinous infiltration. The effused blood becomes absorbed, and a ropy, viscous, gelatinous fluid, is poured out between the ends of the fragments, which is essential to the production of the permanent callus. The second period extends from the tenth or twelfth, to the twentieth or twenty-fifth day. During this period, the engorge- ment of the surrounding parts, diminishes and the muscles are liberated : but the cellular tissue remains condensed and con- centrated round the fracture, presenting grooves or even canals to the tendons of the muscles if any pass in the vicinity of the fracture, in which they are able to play, though with little free- dom, in consequence of some existing induration of the cellular tissue. This constitutes the provisional callus, the external portion of which is thickest at the place of fracture, and insensibly terminates upon the fragments of bone. Its internal portion is formed by the periosteum, which is closely attached to the bone. Its structure is whitish, homogeneous, and of a cartilaginous or fibro-cartilaginous character. The medullary membrane forms a similar plug of provisional cartilaginous matter, which fills up the whole cavity of the bone, above and below the place of fracture. The viscous or gelatinous fluid interposed between the ends of the bones, is now rose-colored or red, presents sometimes a floc- culent appearance, and is adherent by its margins to the external and internal callus. The limb may still be bent at the place of fracture, but no crepitation can be produced. The third period extends from the twentieth or twenty-fifth day, to the thirtieth, fortieth or sixtieth, according to the age and health of the patient. Ossification commences in the centre of the cartilage, and by degrees the whole tumor, internal and external, becomes os- seous. It is very vascular, and Howship* has succeeded in injecting the vessels. If at this period the bone be cut longitu- dinally, the provisional callus will be found presenting all the characters of spongy bone, while the fragments will be found * Microscop. Observ. TERMS USED IN THE DESCRIPTION OF BONES AND JOINTS. 51 movable upon each other, the substance poured out between them, not having apparently undergone much change. The fourth period extends from the fiftieth or sixtieth day, to the fifth or sixth month. During this period the ^callus has been changed from the state of spongy, to that of compact bone. The substance intermediate to the fragments, which present- ed itself under the form of a line or septum between them, becomes more consistent, presents a whiter hue, and is ossified towards the end of this period ; and the permanent callus is now completed. The fifth period extends from the fifth or sixth, to the eighth, tenth or twelfth month, during which time the whole of the provisional callus is entirely removed, the object of its formation having been effected, that of, securely holding the bones together like splints till the fractured surfaces become firmly reunited. The periosteum resumes its usual thickness and polish, and the muscles and tendons their entire freedom of motion. The internal plug of callus having been removed by absorp- tion, the central cavity of the bone, the medullary membrane and the marrow itself, present their usual appearance. i Of the Terms used in the Description of Bones and their Articulations. The study of this subject has been rendered more difficult by the unnecessary introduction of many hard words, but some of these words are so generally used, that they ought to be understood by the student of anatomy. The word process signifies any protuberance or eminence arising from a bone. Particular processes receive names from their supposed resem- blance to certain objects ; and their names are very often com- posed of two Greek words ; thus the term coracoid, which is applied to a well-known process, is derived from the Greek words xo!,, a crow, and eidos*, resemblance. 52 TERMS USED IN THE DESCRIPTION OF BONES AND JOINTS. If a process has a spherical form, it is called a head. If the head is flattened on the sides, it is denominated a condyle. A rough protuberance is called a tuberosity. ,A ridge on the surface of a bone is called a spine. The term apophysis, is nearly synonymous with process. It signifies a protuberance that has grown out of the bone, and is used in opposition to the term epiphysis, which signifies a por- tion of bone growing upon anther, but distinct and separable from it ; as is the case in infancy with the extremities of the long bones. The cavities on the surfaces of bones are named in the same way, as will appear by a reference to the glossary at the end of this work. Words of this kind have been used most profusely in the descriptions of articulations, and here also their utility is doubt- ful. Therefore, for many terms used on this occasion, the reader is referred to the glossary ; but the following are necessary to be understood. SYMPHYSIS does not merely imply the concretion of bones originally separate, as its derivation imports ; but it is under- stood also to mean the connexion of bones by intermediate substances. Thus, there are three species of symphysis, particularly noticed, viz. Synchondrosis, when bones are connected to each other by cartilage ; as the ribs and sternum. Synneurosis, when they are connected by ligaments, as in the movable articulations. Syssarcosis, when they are connected by muscle. The different articulations are of two kinds, viz. Synarthrosis and Diar- throsis. SYNARTHROSIS is the name of that kind of articulation which does not admit of motion. There are three species of synar- throsis, viz. Suture, when the indented edges of the two bones are received into each other, as is the case with the bones of the cra- nium. TERMS USED IN THE DESCRIPTION OF BONES AND JOINTS. 53 Gomphosis, when one bone is fixed in another like a nail in a board, as the teeth in their sockets. Shindyksis, when the thin edge of one bone is received into a narrow furrow of another, as the nasal plate of the efnmoid in the vomer. DIARTHROSIS is the name of that kind of articulation which admits of motion. Of these articulations there are three species, viz. Enarthrosis, when a large head is received in a deep cavity, as the head of the thigh bone in the acetabulum. A.rthrodia, when the head is connected with a superficial cavity. GingKmus, when the extremities of bones apply to each other so as to form a hinge. But most of the important joints have so many peculiarities that they cannot be understood without studying them sepa- rately. It may, therefore, be doubted whether the classification and arrangement of joints is any way necessary. Some of the more common anatomical terms are explained in this place and in the glossary ; but they have now become too numerous, in consequence of the introduction of a multitude of new ones, some of which are of foreign origin, to be sepa- rately defined in this work. A medrcal dictionary will better serve the purposes of the student. That of Prof. Dunglison,* will be found the most comprehensive and useful. * Medical Lexicon A new Diet, of Med. Science. 3d edit, by Robley Dun- glison, M. D. ? Prof. Inst. Med., tec., in Jeff. Med. Coll. Lea & Blanchard. Phil. 1842. 5* 54 OF THE HEAD. CHAPTER II. Of the skeleton and its different parts, and the individual bones of which they are composed. THE bones of an animal arranged and connected to each other in their natural order, separate from the soft parts, compose a skeleton. The skeleton is said to be natural when the bones are connected by their own ligaments, which have been allowed to remain for that purpose. It is called artificial when the bones are connected with wire, or any foreign substance. The artificial skeleton is best calculated for studying the motions of the different bones, because the dry and hard ligaments of the natural skeleton do not allow the bones to move ; but the bones of young animals do not admit of the preparation necessary for an artificial skeleton, as their epiphyses would separate, and they are therefore formed into natural skeletons. The study of the skeleton and its mechanical properties, as a piece of machinery, is absolutely necessary to a perfect under- standing of many motions of the body, and of the action and co-operation of muscles ; but any observations on this subject will be better understood after the individual bones and the muscles have been described. The skeleton is divided into the head, the trunk, the superior and the inferior extremities. Of the Head. The Head comprehends the CRANIUM, and FACE. The cranium consists .of eight distinct bones, which, when placed in their natural order, form a large spheroidal cavity for containing the brain, with many foramina or apertures that communicate with it. OF THE CRANIUM. 55 These bones are of a flattened form. They are composed of two lamina or plates called tables, with a cellular structure between them, called meditullium, or diploe. The external table is more firm and thick than the internal. The letter is comparatively very brittle, whence it is called the vitreous table. [Between the two tables which compose the flat bones of the cranium and running through the diploe are several sinuses, which are occupied by veins in the recent subject. They were discovered by M. Fleury about forty years ago, while he was Prosector at the School of Medicine in Paris, and engaged in some inquiries relative to the structure of the cranium at the instigation of M. Chaussier. The account which M. Chaussier gives of these veins is as follows : they are situated in the middle of the diploe between the two tables of the skull, and like all other veins are intended to return the blood to the heart. They are furnished with small valves, have extremely thin and delicate parietes, and commence by capillary rami6cations coming from the different points of the vascular membrane which lines the cells of the diploe. Their roots are at first extremely fine and numerous, form by their frequent anastomoses a kind of network, and produce by their successive junction, ramuscles, branches, and large trunks, which, becoming still more voluminous, are directed towards the base of the cranium. Some varieties exist in regard to the number, size, and disposition of these trunks, but generally one or two of them are found in each side of the frontal bone, two in the parietal bone, and one in each side of the qccipital bone. Anastomoses exist between these several trunks, by which the veins in the parietal bone are joined to those in the frontal and in the occipital. Branches from the right side of the head also anastomose with some from the left side. Besides the branches already mentioned, one or two smaller than the others are directed towards the top of the head and terminate in the longitudinal sinus. The descending veins of the diploe communicate in their passages with the contiguous superficial veins, and empty into them the blood which they receive from the several points of 56 OF THE CRANIUM. the diploe. These communications are produced through small foramina which penetrate from the surface of the bone to the diploe. The trunks of such diploic veins as are continued to the base of the cranium, open partly into sinuses of the dura mater, and partly into the venous plexus at the base of the pterygoid apophyses, and form there the venous communications called the emissaries of Santorini. Moreover, there are communications sent from the dtploic veins through the porosi- ties of the internal table of the skull to the veins of the dura mater. This fact is rendered very evident by tearing off the skull cap, when the surface of the dura mater will be studded with dots of blood, and the internal face of the bone also, particularly in apoplectic subjects. It appears indeed that the arteries of the cranium are principally distributed on its external surface, and the veins on its internal surface and diploe. In the infant the diploic veins are small, straight, and have but few branches : in the adult they correspond with the description just given ; and in old age they are still more con- siderable, forming nodes and seeming varicose. In children, when the bones are diseased, they partake of the latter character. In order to see them fully, the external table of the skull must be removed with the chisel and mallet, both from its vaults and base.]* The periosteum, which is on their external surface, is called pericranium. Internally the dura mater, or membrane which covers the brain, supplies the place of periosteum. There are eight of these bones, which are thus denominated : Os Frontis, Ossa Parietalia, Ossa Temporum, Os Occipitis, Os Sphenoides, and Os Ethmoides. The two last are called common bones, to denote that they are connected with the bones of the face as well as with those of the cranium. The os frontis forms the whole fore part of the vault of the * The diploe, or meditullium, corresponds exactly in structure and situation with the spongy, or cellular tissue of the other bones of the body, though it has unnecessarily received a distinct name. Neither are the diploic sinuses peculiar to the bones of the skull. They are found presenting exactly the same appear- ance in the bodies of the vertebrae, and appear in fact to be but a development of the canaliculated tissue of the oiher bones. See Fig. 5, page 30. P. THE SUTURES. 57 cranium : the two ossa parietalia form the upper and middle part of it ; the ossa temporum compose the lower part of the sides ; the os occipitis makes the whole hinder part and some of the base; the os ethmoides is placed between the ambits of the eyes, and the sphenoides extends across the base of the cranium. i The Sutures, f- The above bones are joined to each other by five sutures ; the names of which are the Coronal, Lambdoidal,' Sagittal, and two Squamous. The coronal suture is extended over the head, from within about an inch of the external angle of one eye, to the like dis- tance from the other ; which being near the place where the ancients wore their garlands, this suture has hence got its name. Though the indentations of this suture are conspicuous in its upper part, yet an inch or more of its end on each side has none, but is squarnous and smooth. The lambdoidal suture begins some way below, and further back than the vertex or crown of the head, whence its two legs are stretched obliquely downwards, and to each side, in form of the Greek letter A? and are now generally said to extend themselves to the base of the skull ; but formerly, anatomists reckoned the proper lambdoidal suture to terminate at the squamous sutures : and the portion continued from them on each side, where the indentations are less conspicuous than in the upper part of the suture, they called additamentum suturae lambdoidis. This suture is sometimes very irregular, being made up of a great many small sutures, which surround a number of insulated bones, that are generally more conspicuous on the external surface of the skull than internally. These bones are commonly called triquetra or wormiana ; their formation is owing to a greater than ordinary number of points of ossification in the skull, or to the ordinary bones of the cranium not extending their ossification far enough or soon enough ; in which case, the unossified interstice between such bones begins a separate 58 THE SUTURES. ossification, in one or more points ; from which the ossification is extended to form as many distinct bones as there were points which are extended into the large ordinary bones, and into each other.* The sagittal suture is placed longitudinally, in the middle of the upper part of the skull, and commonly terminates at the middle of the coronal and of the lambdoidal sutures ; between which it is said to be.placed, as an arrow is between the string and the bow. This suture is sometimes continued through the middle of the os fronds down to the root of the nose. * The squamous agglutinations, or false sutures, are one on each side, a little above the ear, of a semicircular figure, formed by the overlapping (like one scale upon another) of the upper part of the temporal bones on the lower part of the parietal, where, in both bones, there are a great many small risings, and furrows which are indented into each other : though these inequalities do not appear until the bones are separated. In some skulls, indeed, the indentations here are as conspicuous externally as in other sutures ; and what is commonly called the posterior part of this squamous suture, always has the evident serrated form ; and therefore is reckoned by some a distinct suture, under the name of additamentum posterius suturae squamosae. The squamous suture is not confined to the conjunction of the temporal and parietal bones, but is made use of to join all the edges of the bones on which each temporal muscle is placed ; for the two parts of the.sphenoidal suture, which are continued from the anterior end of the common squamous suture just now described, one of which runs perpendicularly downwards, and the other horizontally forwards ; and also the lower part of the coronal suture already taken notice of, may all be justly said to pertain to the squamous suture. * These ossa triquetra or wormiana are also frequently met with in the sagittal suture, and occasionally in all the different sutures of the cranium. As many as fifteen or twenty have been seen in a single head, though usually their num- ber is much less. Where the cranium is of a globular form, few, and frequently none, are met with. They never begin to ossify till six months or a year after birth. P. THE SUTURES. 59 This structure appears to depend upon the pressure of the temporal muscle externally, and the resistance of the brain within, which makes the bones so thin, that their edges opposed to each other are not sufficiently thick to stop the extetysion of their fibres in length, and thus to cause the common serrated appearances of sutures ; but the narrow edge of the one bone slides over the other. The squamous form is also more con- venient here ; because such thin edges of bones, when accurately applied one to another, have scarce any rough surface to obstruct or hurt the muscle in its contraction ; which is still farther provided for, by the manner of laying these edges on each other ; for, in viewing their outside, we see the temporal bones covering the sphenoidal and parietal, and this last sup- porting the sphenoidal, while both mount on the frontal ; from which disposition it is evident, that while the temporal muscle is contracting, which is the only time it presses strongly in its motion on the bones, its fibres slide easily over the external edges. Another advantage of this structure is, that the whole part is made stronger by the bones thus supporting each other. The indentation of the sutures are not so strongly marked on the inside as on the outside of the cranium ; and sometimes the bones seem to be joined by a straight line : in some skulls, the internal surface is found entire, while the sutures are manifest without. By this mechanism, there is no risk of the sharp points of the bones growing inwards, since the external serrae of each of the conjoined bones rest upon the internal smooth-edged table of the other. The advantages of the sutures are these: 1. The cranium is more easily formed and extended into a spherical figure, than if it had been one continued bone. 2. The bones which are at some distance from each other at birth, may then yield, and allow to the head a change of shape, accommodated to the passage it is engaged in. Whence, in difficult parturition, the bones of the cranium, instead of being only brought into contact, are sometimes made to mount one upon the other. [The sutures which unite the bones of the cranium, are 60 THE SUTURES. generally said to be made by the radii of ossification, from the opposite bones meeting and passing each other, so as to form a serrated edge. This explanation is however insufficient, for the following reasons : we always find the sutures in the same relative situation, and observing the same course in the cranium ; if they, then, depended exclusively on so mechanical a process, as the shooting of the rays of bone across each other when they met, in ossification on one side^rf the head occurring sooner or faster than on the other, we ought to find the sagittal suture to one side of the middle line ; it should also, in many instances, be found crooked. Moreover, in all cases where bones arise from different points of ossification and meet, particularly in the flat bones, the serrated edges ought to be formed ; this, however, is not the case. The os occipitis, which is formed originally from four points of ossification, and has therefore as many bones composing it in early life, never joins these bones together by the serrated edge ; the acromion process of the scapula is never united to its spine by sutures ; the three bones of the sternum never unite by suture, and the same observa- tion holds good in many other instances. Bichat, who rejects this mechanical doctrine, advances an opinion much better founded. The dura mater and the pericranium, before ossifi- cation commences, form one membrane, consisting of two lamina ; it is generally known that the flat bones of the cranium are secreted between these two lamina ; now the out- line of each bone, long before it has reached its utmost limits, is marked off by partitions passing between these two mem- branes. The peculiar shape of the bony junction, or the suture in adult life, will, therefore, depend upon the original shape of the partitions: when the latter are serrated, the points of ossification will fill up these serrae ; but when they are simply oblique, the squamous suture will be formed. This also accounts for cases where the mode of junction is intermediate to the squamous and serrated suture ; for the formation of the ossa triquetra, and why in some skulls they do not exist, whereas in others their extent and number are very considera- ble. The inference will also be drawn from this, that in all ossi- OS FRONTIS. 61 fications from different nuclei, where these original mem- braneous septa do not exist, a suture will not be formed ; but the bones will join each other, as in a case of callus between the broken extremities of bones. When these septa "become weak or thin, either from original tendency, as in the case of the sagittal suture, which in early life is continued to the root of the nose frequently ; or from advanced age, as in the case of nearly all sutures, the bones of the opposite sides amalga- mate, and no appearance of suture is left. It is easy to make a preparation illustrative of these facts, and one now exists in the museum of the University of Pennsylvania, in which, by removing the bone from between the membranes by means of an acid, and afterwards rendering the membranes transparent with oil of turpentine, the septa are seen sufficiently distinctly.] Os Frontis. The os fronds, as its name imports, forms the front part of the cranium, and the upper portion of the orbits of the eyes. Fig. 10.* The external surface of this bone is smooth at its upper convex part ; but several pro- cesses and cavities are ob- servable below ; for at the angles of each orbit, the bone projects to form four processes, two internal, and as many external ; which are denominated angular. Be- tween the internal and exter- nal angular processes on each side, an arched ridge is ex- * The external surface of the os frontis. 1. Frontal protuberance or boss of the right side. 2. The superciliary ridge. 3. Supra-orbital ridge. 4. External angular process. 5. Internal angular process. 6. Supra-orbital notch for the transmission of the supra-orbital nerve and artery ; it is occasionally converted into a foramen. 7. The nasal or superciliary boss ; the swelling around this point denotes the situation of the frontal sinuses. 8. The temporal ridge, com- mencing from the external angular process (4). The depression in which fig. 8 is situated is a part of the temporal fossa. 9. The nasal spine. 6 62 OS FRONTIS. tended, on which the eyebrows are placed. Very little above the internal end of each of these superciliary ridges, a protuber- ance may be remarked in most skulls, called the superciliary or nasal boss, where there are large cavities within the bone, called sinuses. Between the internal angular processes, and in front of the vacuity for the ethmoid bone, the edge of the os frontis is serrated for articulation with the ossa nasi, and the process of the upper maxillary bone ; ad from the centre of this sur- face a small process arises, which is called the nasal spine. From the under part of the superciliary ridges, the frontal bone runs a great way backwards : these parts are called orbitar processes, which, contrary to the rest of this bone, are concave externally, for receiving the globes of the eyes, with their muscles, fat, &c. In each of the orbitar processes, at the upper and outer portion of the orbit, a considerable sinuosity is observed, where the glandula lachrymalis is lodged. Near each internal angular process a small pit may be remarked, where the cartilaginous pulley of the superior oblique muscle of the eye is fixed. Between the two orbitar processes, there is a large vacuity which the cribriform part of the os ethmoides occupies. The frontal bone has frequently little caverns formed in it where it is joined to the ethmoid bone. The foramina, or holes, observable on the external surface of the frontal bone, are'three in each side. On each supra-orbital ridge, 3 fig. 10, at the distance of one- third of its length from the nose, is a foramen, or a notch, through which pass a branch of the ophthalmic artery and a small nerve called the supra-orbital. In the internal edge of each orbitar process are two other foramina denominated anterior and posterior orbitar, or eth- moidal foramina, which lead to the nose : sometimes they are only notches or grooves which join with similar grooves in the bones below, and form foramina. They transmit the anterior and posterior ethmoidal arteries and veins, and the former trans- mits likewise the internal nasal branch of the ophthalmic nerve. The internal surface of the os frontis is concave, except at OS FRONTIS. 63 the orbitar processes, which Fig. 11.* are convex, and support the anterior lobes of the brain. This surface is not so smooth as the external ; for the larger branches of the arteries of the dura mater make some furrows in its sides and back parts, and its lower and fore parts are marked with the convolutions of the anterior lobes of the brain. In the middle of the concave inter- nal surface is a groove, which is small at its commencement, and gradually increases in dia- meter as it proceeds upwards. This is formed by the superior longitudinal sinus ; at its commencement is a ridge to which the beginning of the falciform process of the dura, mater is attached. At the root of this ridge is a small foramen, sometimes formed jointly by this bone and the ethmoid ; it is denominated fora- men ccECum ; in it a small process of the falx is inserted, and here the longitudinal sinus begins. The frontal sinuses are formed by the separation of the two tables of this bone at the part above the nose and the internal extremities of the superciliary ridges. In the formation of these cavities, the external table commonly recedes most from the general direction of the bone. * The internal surface of the frontal bone ; the bone is raised in such a man- ner as to show the orbito-nasal portion, i. The grooved ridge for the lodgment of the superior longitudinal sinus and attachment of the falx. 2. The foramen caecum. 3. The superior or coronal border of the bone ; the figure is situated near that part which is bevelled at the expense of the internal table. 4. The inferior border of the bone. 5. The orbital plate of the left side. 6. The cellu- lar border of the ethmoidal fissure. The foramen ceecum (2) is seen through the ethmoidal fissure. 7. The anterior and posterior ethmoidal foramina ; the anterior is seen leading into its canal. 8. The nasal spine. 9. The depression within the external angular process (12) for the lachrymal gland. 10. The de- pression for the pulley of the superior oblique muscle of the eye ; immediately to the left of this number is the supra-orbital notch, and to its right the internal angular process. 11. The opening leading into the frontal sinuses. 12. The same parts are seen upon the opposite side of the figure. 64 OSSA PARIETALIA. These cavities are divided by a perpendicular bony partition, which is sometimes perforated and admits a communication between them. Their capacities are often very different in different persons, and on the different sides of the same person. In some persons whose foreheads were very flat, they are said to have been wanting. They communicate with the nose by means of a canal in the cellular part of the os ethmoides. The os frontis is composed *)f two tables, and an interme- diate diploe, as the other bones of the cranium are : it is of a mean thickness between the os occipitis and the parietal bones ; and is nearly equally dense throughout, except the orbitar pro- cesses, where, by the action of the eye on one side, and pressure of the lobes of the brain on the other, it is made extremely thin and diaphanous, and the diploe is entirely obliterated. In this place there is so weak a defence for the brain, that fencers esteem a push in the eye mortal. In such skulls as have the frontal bone divided by the sagittal suture, the partition separating these cavities is evidently com- posed of two plates, which easily separate. Each of the frontal sinuses opens into one of the uppermost cells in the' anterior part of the ethmoid bone, and this cell communicates with the middle channel of the nose under the anterior end of the os turbinatum superius. This bone is united with the parietal, ethmoidal and sphe- noidal bones of the head ; and with the nasal, maxillary, ungui- form and malar bones of the face. Ossa Parietalia. Each of the two ossa parietalia is an irregular square ; its upper and front edges being longer than the one behind or below. The inferior edge is concave, the middle part receiving the upper round part of the temporal bone. The angle formed by the under and anterior edges is so extended as to have the appearance of a process. The external surface of each os parietale is convex. Upon it, somewhat below the middle height of the bone, there is a OSSA PARIETALIA. 65 transverse arched ridge, ge- Fig. 12.* nerally of a whiter color than any other part of the bone ; from which, in bones that have strong prints of muscles, we see a great many converging furrows, like so many radii drawn from a circumference towards a cen- tre. From this ridge of each bone the temporal muscle rises : and, by the pressure of its fibres, occasions the furrows just now mentioned. Below these we observe, near the semi- circular edges, a great many risings and depressions, which are joined to like inequalities on the inside of the temporal bone, and form the squamous suture. Near the upper edges of these bones, towards the hind part, is a small hole in each, through which a vein passes from the teguments of the head to the lon- gitudinal sinus.f o On the inner concave surface of the parietal bones we see a great many deep furrows, disposed somewhat like the branches of trees : the furrows are largest and deepest at the lower edge of each os parietale, especially near its anterior angle, where a complete canal is sometimes formed. [These furrows are made by the ramifications of the great middle artery of the dura mater: they have been commonly attributed to the pulsation of the artery causing the absorp- tion of the bone, but it is more probable that the deposition of the bone has been prevented where the artery beats, and thus the bone becomes modelled over the artery in the same way that it is made to conform to the surface of the brain. If it * The external surface of the left parietal bone. 1 . Superior or sagittal border. 2. Inferior or squamous border. 3. Anterior or coronal border. 4. Posterior or lambdoidal border. 5. The temporal ridge. The figure is situated immediately over the parietal protuberance. 6. The parietal foramen, unusually large. 7. The anterior inferior angle. 8. The posterior inferior angle. f It transmits, also, an artery from the integuments to the dura inater, and is called the parietal foramen. p. 6* 66 OSSA TEMPORUM. were exclusively an absorption and not a deposition, we should scarcely find the artery occasionally surrounded perfectly by bone.] Fig. 13.* On the inside of the up- per edge of the ossa parie- talia there is a large sinuos- ity, frequently larger in the bone of one side than of the other, where the upper part of the falx is fastened, and the superior longitudinal sinus is lodged. Part of the late- ral sinuses generally makes a depression near the angle formed by the lower and posterior edges of these bones ; and the pits made by the convolutions of the brain are in no part of the skull more frequent or more conspicuous, than in the internal surface of these bones. The ossa parietalia are the most equal and smooth, and are among the thinnest bones of the cranium ; but they enjoy the general structure of two tables and diploe most perfectly. These bones are joined at their fore side to the os frontis, at their long inferior angles, to the sphenoid bone ; at their lower edge, to the ossa temporum ; behind to the os occipitis, or ossa triquetra ; and above, to one another. Ossa Temporum.^ The ossa temporum are situated at the lateral and inferior * The internal surface of the left parietal bone. 1. The superior, or sagittal border. 2. The inferior, or squamous border. 3. The anterior, or coronal border. 4. The posterior, or larabdoidal border. 5. Part of the groove for the superior longitudinal sinus. 6. The internal termination of the parietal foramen. 7. The anterior inferior angle of the bone, on which is seen the groove for the trunk of the arteria meningea media. 8. The posterior inferior angle, upon which is seen a portion of the groove for the lateral sinus. f This bone has received the name of temporal, because at the region which it covers, the hair usually commences to turn gray, and thus in some measure indicates the different periods of life. p. OSSA TEMPORUM. 67 parts of the cranium ; each of them is divided into three portions, a superior or squamous, a posterior or rnastoid, and a middle or petrous. The squamous portion is nearly semicircular in font!, and very thin ; its edge is sharp, and the inner table appears pared away to form the squamous suture with the corresponding edge of the parietal bone. Its external surface is covered by the temporal muscle. At the lower and anterior part of this surface, the zygomatic process arises, it proceeds forward to join the cheek bone, and form an arch under which the tem- poral muscle passes. At the base of the process is the glenoid cavity for the condyle of the lower jaw. Immediately before this cavity is a tubercle or protuberance, near the commencement of the zygoma and at its lower border, to which the external lateral ligament of the lower jaw is attached ; continued horizontally inwards from the tubercle there is a rounded eminence, called the emi- nentia articularis, which forms part of the articular surface on which the condyle rises when the jaw is opened. In the pos- terior part of the cavity is a fissure called the glenoid in which part of the ligament of this articulation is fixed. In this fissure is an aperture glenoid foramen which communi- cates with the cavity of the tympanum of the ear, and is occu- pied by a small nerve called chorda tympani ; and also by the anterior muscle of the malleus one of the small bones of the ear. The internal surface of the squamous portion is concave ; it is marked by pits and small eminences, which correspond with the convoluted surface of the brain, and also by impressions of the arteries of the dura mater, see 4 fig. 13, as they go towards the parietal bone. The mastoid or occipital portion is the smallest of the three parts of the bone ; it consists of an angular portion, which occupies a vacuity between the occipital and parietal bones ; and of the mastoid process. The mastoid process has some resemblance to the nipple; it is composed internally of cells which communicate with the cavity of the tympanum. On 68 OSSA TEMPORUM. the internal side of its base is a deep groove in which the pos- terior belly of the digastric muscle is inserted. Behind this process is the mastoid hole, which transmits a vein, and some- times a small artery. On the internal surface of this portion is a large groove, which is formed by the lateral sinus. The mastoid hole above mentioned, opens into this groove. The petrous portion, which is * Fig. 14.* situated between the squa- mous and mastoid, resembles a triangular pyramid lying on one of its sides. When in its proper position it projects inward and forward. The two upper sides form a por- tion of the internal surface of the base of the cranium. The angle formed by these sur- faces is very prominent, and divides the fossa for the middle lobes of the brain, or rather the cavities for the cerebrum from those which contain the cerebellum. One of these sides of the petrous portion looks forward and outward, the other backward and inward. Each of them has eminences and depressions to correspond with the convolutions i of the brain. Near the middle of the anterior side is a small j furrow, leading to a foramen denominated Innominatum or i Hiatus Fallopii which transmits the vidian nerve to the aque- i duct of Fallopius. * The external surface of the temporal bone of the left side. 1. The squamous portion. 2. The mastoid portion. 3. The extremity of the petrous portion. 4. The zygoma. 5. Indicates the tubercle of the zygoma, and at the same time its anterior root turning inwards to form the eminenlia articularis. 6. The superior root of the zygoma, forming the posterior part of the temporal ridge. 7. The middle root of the zygoma terminating abruptly at the glenoid fissure. 8. The mastoid foramen. 9. The meatus auditorius externus, surrounded by the processus auditorius. 10. The digastric fossa, situated immediately to the inner side of (2) the mastoid process. 11. The styloid process. 12. The vagi- nal process. 13. The glenoid or Glaserian fissure ; the leading line from this number crosses the rough posterior portion of the glenoid fossa. 14. The open- ing and part of the groove for the Eustachian tube. OSSA TEMPOREM. 69 There is another small oblique foramen immediately beneath this, which transmits the nervous petrosus superjicialis minor, a branch of Jacobson's nerve ; near the apex of the petrous por- tion of the temporal bone there is seen a large forampn, the termination of the carotid canal. On this anterior face of the bone, especially in the young subject, is seen a rising or eminence running from base to apex, which is formed by the projection of the perpendicular semicircular canal. About the middle of the posterior side is the large aperture called meatus auditorius internus. The bottom of this cavity is perforated by several foramina : the largest and uppermost of which is the orifice of a winding canal, called improperly the aqueduct of Fallopius, which transmits the portio dura of the seventh pair of nerves. The other foramina transmit the fibres of the portio mollis of the same nerve. Posterior to the orifice of the meatus internus is an oblong depression, with a foramen in it, covered by a shell of bone, which is the orifice of a proper aqueduct or canal that passes from the vestibule of the ear.* Neither of the so called aqueducts of the vestibule or cochlea, are deserving of the name which has nevertheless been con- tinued to designate them, since we no longer believe with Cotugnius their discoverer, that they are a sort of passages, to admit of the overflow of the lymph, when it was secreted in superabundance in the labyrynth. They are both mere open- ings, for the transmission mainly of blood vessels. The aque- duct of the vestibule transmits a small artery and vein to the vestibule, and lodges a process of the dura mater. The inferior side of the petrous portioh forms a part of the external surface of the basis of the cranium. On the back part of it is the external orifice of the canal, ^hrough which the portio dura passes. It is called foramen stylo mastoideum. Before this foramen is a long and slender styloid process, which varies from one to two inches in length ; it projects * This orifice should not be confounded with one which is nearer to the meatus interims, and situated on the angle made by the two sides of the bone. H. 70 OSSA TEMPORUM. almost perpendicularly from the Fig. 15.* basis of the cranium, and gives origin to a muscle of the tongue, of the os hyoides, and of the pharynx, and also to several ligaments. The base of this process is surrounded by a flat projection of bone, occasionally called the vaginal process. On the inside of this pro- cess, and rather before it, is the jugular fossa, which, when applied to a corresponding part of the occipital bone, makes the posterior foramen lacerum, through which the internal jugular vein, and the eighth pair of nerves pass out. A small spine called the jugular process often projects into this foramen from the temporal bone, and separates the nerve from the vein ; the nerve being anterior. Upon a ridge which is found at the root of this spine, and just behind the margin of the carotid foramen, there is a small opening leading into the canal which transmits Jacobson's tympanic branch of the glosso-pharyngeal nerve, which forms * The left temporal bone, seen from within. 1. The squamous portion. 2. The mastoid portion. The number is placed immediately above the inner opening of the mastoid foramen. 3. The petrous portion. 4. The groove for the posterior branch of the arteria meningea media. 5. The bevelled edge of the squamous border of the bone. 6. The zygoma. 7. The digastric fossa immediately internal to the mastoid process. 8. The occipital groove. 9. The groove for the lateral sinus. 10. The elevation upon the anterior surface of the petrous bone marking the situation of the perpendicular semicircular canal. 11. The opening or termination of the carotid canal. 12. The meatus auditorius internus. 13. A dotted line leads upwards from this number to the narrow fissure which lodges a process of the dura mater. Another line leads down- wards to the sharp edge which conceals the opening of the aquseductus cochleae, while the number itself is situated on the bony lamina which overlies the open- ing of the aquaeductus vestibuli. 14. The styloid process. 15. The stylo-mas- toid foramen. 16. The carotid foramen. 17. The jugular process. The deep excavation to the left of this process forms part of the jugular fossa, and that to the right is the groove for the vein of the cochlea. 18. The notch for the fifth nerve upon the upper border of the petrous bone, near to its apex. 19. The extremity of the petrous bone which gives origin to the levator palati and tensor tympani muscles. OSSA TEMPORUM. 71 an important part of the nervous plexus of the tympanum. Before this spine, or partition, is the orifice of the second aque- duct of the ear, the aqueduct of the cochlea, through which passes a vein from the cochlea to the internal jugular, -6nd in which is lodged a process of the dura mater. This jugular fossa is at the termination of the groove, in the internal surface of the bone, made by the lateral sinus. At a small distance before the jugular fossa is the commencement of the carotid canal, which makes a curve almost semicircular, and then pro- ceeds in a horizontal course to the anterior extremity of the bone : through this winding canal passes the carotid artery, and the filaments from the fifth and sixth pair of nerves, which are the beginning of the intercostal or sympathetic nerve. Between the carotid canal and the cavity for the condyle of the lower jaw, at the junction of the anterior part of the squamous portion with the petrous portion of this bone, is a very rough aperture, the bony margin of which appears broken ; this is the orifice of the bony part of the Eustachian tube, or passage from the throat to the ear. This canal is divided lengthwise by a thin bony plate ; the upper passage contains the internal muscle of the malleus bone of the ear (tensor tympani) ; the lower and largest canal is the bony part of the Eustachian tube. The external passage to the ear, called Meatus Auditorius Externus, is situated between the zygomatic and the mastoid processes. The orifice is large and smooth above, but rough below, and is surrounded by a rough lip called the auditory process. The direction of the canal is obliquely inward and forward. Angles of the bone. The superior angle of the bone which separates the anterior and posterior faces, is sharp and gives attachment to the tentorium cerebelli. It is slightly grooved for the lodgment of the superior petrous sinus, and near its extremity is marked by a smooth notch, upon which rests the fifth or trigeminus nerve. The anterior angle which separates the anterior from the inferior or basilar surface of the bone, is grooved for the Eustachian tube, and forms the posterior OS OCCIPITIS. boundary of the foramen lacerum anterius of the base of the cranium. The posterior angle separating the posterior from the basilar surface of the bone, is grooved for the inferior petrous sinus and excavated for the jugular fossa : it forms the anterior boundary of the foramen lacerum posterius. The temporal is articulated with the parietal, occipital and sphenoidal bones, and by its zygomatic process with the malar bone. Os Occipitis. The occipital bone is situated at the posterior and inferior part of the cranium ; it is of a rhomboidal figure, with convex and concave surfaces. Fig. 16.* The upper part of the external surface is smooth : at a small distance above the middle of the bone is the external occipital protube- rance, with a curved line on each side of it. Near the middle of the bone the tra- pezii muscles are attached to this line, and externally, on each side, the occipito fron- talis, and the sterno mas- toideus. Under this line is a depression, on each side, into which are inserted the complexus and the splenius capitis muscles. Below this is the inferior curved line, and still lower is a * The external surface of the occipital bone. 1. The superior curved line. 2. The external occipital protuberance. 3. The spine or vertical ridge. 4. The inferior curved line. 5. The foramen magnum. 6. The condyls of the right side. 7. The posterior condyloid fossa, in which the posterior condyloid foramen is found. 8. The anterior condyloid foramen, concealed by the margin of the condyle. 9. The jugular eminence or transverse process as it is sometimes called. 10. The notch in front of the jugular eminence, which forms part of the jugular foramen. 11. The basilar process. 12. The rough projections into which the moderator ligaments are inserted. os OCCIPITIS. 73 muscular depression to which the rectus minor posticus is attached on each side near the middle ; and the rectus major posticus, and obliquus superior, near the end. Below the protuberance is a spine which passes do\yn the middle of the bone, and at the lower extremity of this spine is the great occipital foramen, which forms the communication between the cavities of the cranium, and the vertebral column. This great opening transmits the medulla spinalis with its membranes, the accessary nerves of Willis, and the vertebral arteries and veins. It is rather of an oval form, and the occipital condyles are situated anteriorly on its edges. These condyles are of an irregular oval figure ; they are not parallel, but incline towards each other anteriorly. Their articulating surfaces are oblique, looking downward and outward ; they are received into corresponding cavities of the atlas, or first cervical vertebra, and form with them the articulation of the head and neck. From the oblique position of their articulating surfaces, as well as the length of their ligaments and the inclination of their axes towards each other, it results, that their motion is confined to flexion and extension. On the internal sides of these condyles is a rough surface, to which are attached the strong ligaments that come from the processus dentatus of the second vertebra of the neck. Behind each condyle is a depression in which is situated the posterior condyloid foramen, for transmitting the cervical veins ; and at their anterior extremities are two large foramina, (anterior condyloid,) through which pass the ninth pair of nerves. On the internal surface of the os occijfitis is the crucial ridge, to which are attached the falx cerebelli or vertical, and the tentorium or horizontal process of the dura mater. The groove made by the longitudinal sinus continues from the sagittal suture along the upper limb of this cross. Some- times it is on the side of the ridge, and sometimes the ridge is depressed, and it occupies its place ; at the centre of the cross, where is lodged the torcular Herophili, formed by the 7 74 OS OCCIPITIS. common junction of the sinuses, the groove for the longitu- dinal sinus divides into two grooves for the lateral sinuses ; Fig. 17.* these form the horizontal limbs of the cross, and pro- ceed towards the foramen lacerum where the lateral sinuses emerge from the cavity of the cranium. The lower limb of the cross is formed by a spine which pro- ceeds from the centre of the bone to the great occipital fora- men, and supports the falx of the cerebellum. The internal surface of the bone is divided by the cross into four por- tions, each of which is con- siderably depressed so as to form fossae ; the two upper by the posterior lobes of the cerebrum, and the lower by those of the cerebellum. This circumstance occasions great inequality in the thickness of the bone, as the depressed portions are extremely thin, while the ridge adds greatly to the thickness, especially at the centre of the cross, which is opposite to the great external protuber- ance. Before the great occipital foramen is the cuneiform process, which is thick and substantial ; it terminates by a broad truncated extremity, that is articulated with the body of the sphenoid bone. The internal surface of the cuneiform process * The internal surface of the occipital bone. 1. The left cerebral fossa. 2. The left cerebellar fossa. 3. The groove for the posterior part of the superior longitudinal sinus. 4. The spine for the falx cerebelli, and groove for the occipital sinuses. 5. The groove for the left lateral sinus. 6. The internal occipital protuberance which lodges the torcular Herophili. 7. The foramen magnum. 8. The basilar process, grooved for the medulla oblongata. 9. The termination of the groove for the lateral sinus, bounded externally by the jugu- lar eminence. 10. The jugular fossa this fossa is completed by the petrous portion of the temporal bone. 11. The superior border. 12. The inferior border. 13. The border which articulates with the petrous portion of the temporal bone. 14. The anterior condyloid foramen. OS ETHMOIDES. 75 is somewhat excavated, and forms a large superficial groove for the medulla oblongata ; on each side of this groove is a small furrow for the inferior petrous sinuses. The two upper edges of the occipital bone are serrated, to articulate, with those of the parietal, and form the lambdoidal suture. The inferior edges are divided into two portions by a small prominence called the jugular eminence ; the upper and posterior portion is also serrated for articulation with the mastoid portion of the temporal ; the inferior portion, which is not serrated, applies to the petrous portion of the temporal bone, and a notch in it contributes to the formation of the fora- men lacerum. The upper angle of this bone is acute, the lateral angles are obtuse, and the inferior truncated. It is articulated with the parietal, the temporal, and the sphenoidal bones. Os Ethmoides. The 05 ethmoides is truly one of the most curious bones of the human body. It appears almost a cube, not of solid bone, but exceedingly light and spongy, and consisting of many con- voluted plates, which form a network like honey-comb. It is firmly enclosed in the os frontis, betwixt the orbitary processes of that bone. One horizontal plate receives the olfactory nerves, which perforate that plate with such a number of small holes, that it resembles a sieve ; whence the bone is named cribriform, or ethmoid. " Other plates are so arranged that they form a cellular structure, on which the olfactory nerves are expanded by means of a particular membrane ; while an additional plate, appropriated to the nose, descends into that cavity in a perpen- dicular direction, and forms a large proportion of the partition which divides it into two chambers. The cribriform plate is situated in the anterior part of the basis of the cranium. The cellular part occupies most of the space between the orbits of the eyes, and the perpendicular plate is to be found in the septum of the nose. The ethmoid bone, for the purposes of description, may be , divided into three parts, viz. the cribriform plate, the nasal or ( perpendicular lamella, and the cellular portions. , 76 OS ETHMOIDES. The cribriform plate is oblong in shape, and firm in its structure ; in the middle of the anterior extremity the crista galli projects from its upper surface, dividing it into two lateral portions, each of which is rather concave, and occupied by the bulbous extremity of the olfactory nerve ; it is perforated by many foramina, which transmit the fibres of the aforesaid nerve. Near the crista galli, on each side, there is a small fis- sure, through which passes a nCrvous filament derived from the ophthalmic branch of the fifth pair. The crista galli varies in size in different subjects : the beginning of the falciform process of the dura mater is attached to it, and with the opposite part of the os frontis it forms the foramen ca3cum, already mentioned. It is very conspicuous in the basis of the cranium. The nasal plate of the ethmoid bone seems to be continued downwards from the crista galli through the cribriform plate. It is thin, but firm ; it forms the upper portion of the septum of the nose, and, to complete the partition, it unites with the vomer and with a plate of cartilage before. It is very often inclined to one side, so that the nostrils are not of equal size. At a small distance from this perpendicular plate, on each side of it, the cellular portions originate from the lower surface of the cribriform plates ; they extend from before backward, and are as long as the ethmoid bone ; their breadth between the eye and the cavity of the nose varies in different subjects, from half an inch to more ; they extend downwards from the root of the nose or from the cribriform plate, more than half way to the roof of the mouth. Their external surface on each side forms a part of the surface of the orbit of the eye, and is called 05 planum ; their internal surface forms part of the external lateral surface of each nostril. This surface extends the whole depth of the nostril, from before backward ; but in many skeletons it is extremely imperfect, owing to the great brittleness of the bony plates of which it is composed. When the bone is perfect, the uppermost half part of this internal surface is uniformly flat, and rather rough ; but below it, about the middle of the bone, a deep groove begins, which extends downwards and backwards, to the posterior extremity ; this is OS ETHMOIDES. 77 the upper channel or meatus of the nose. The edge of the surface immediately above it projects in a small degree over this channel or groove ; having been described by Morgagni, it bears his name, and may be considered as one of the"~^pongy or turbinated bones ; from its situation, it should be called the first or superior. The groove is very deep, and most of the cells of the posterior part of the ethmoid bone communicate with it, through one or more foramina at its anterior extremity. The part of the surface of the ethmoid which is immediately below this groove, is convex ; that which is before and below it, is rather flat ; the convex part is the middle spongy or turbinated bone, as it has commonly been called ; it projects obliquely into the cavity of the nose, and hangs over the middle channel or meatus, which is immediately below the ethmoid bone. The internal surface of this spongy bone, which is opposite the septum of the nose, is convex and rough or spongy ; the external surface is concave. The anterior cells of the ethmoid, and particularly those which the frontal sinuses on each side communicate with, open into the middle channel or meatus, under the anterior end of this turbinated bone. This middle channel or meatus, is much larger than that above ; it extends from the anterior to the posterior part of the nostrils, and slopes downwards and backwards. The cavity of the upper maxillary bone, or the antrum highmorianum, opens on each side into this meatus, and a thin plate of bone extends from the cellular part of the ethmoid so as to cover a part of it. The cellular portions of the ethmoid are composed of plates thinner than the shell of an egg ; they are entirely hollow, and the cells are very various, in number, size, and shape. Some cells of the uppermost row communicate with those of the os frontis, formed by the separation of the plates of the orbitar process of that bone. From the posterior part of the cribriform plate, where it is in contact with the lesser wings of the sphenoidal bone, thin plates of bone pass down upon the anterior surface of the body of the os sphenoides, one on each side of the azygos process, and often diminish the opening into the sphenoidal cells. These plates are sometimes triangular in form, the basis uniting 7* 78 OS ETHMOIDES. with the cribriform plate. They have been described very differently by different authors, some considering them as belonging to the os ethmoides, and others to the sphenoid bone. To the perfect ethmoid bone there are attached two triangular pyramids, in place of the triangular bones; these pyramids are hollow, the azygos process of the os sphenoides is received between them ; one side of each pyramid applies to each side of the azygos process, another side applies to the anterior surface of the body of the sphenoid bone, in place of the ossa triangularia, and the third side is the upper part of one of the posterior nares.*5 There are two apertures in each of these * This may be considered as an original observation of the lamented "Wistar. The merit of it has been denied to him, more particularly by the anatomists of Paris, under an impression that he had been anticipated in it by Berlin, who has written an excellent and minute treatise on osteology. The extent to which the claims of other anatomists interfere with his, he was fully aware of; and it will be seen by the following communications to the American Philosophical Society, that these are placed in as important a light as they deserve, at the same time that he vindicates his own pretensions, to have first observed the " cornets sphenoidaux " in the form of triangular hollow pyramids, as consti- tuting part of the perfect ethmoid bone. H. Observations on those Processes of the Ethmoid Bone which originally form the Sphe- noid Sinuses. By C. Wistar, M. D., President of the Society, Professor of Anatomy in the University of Pennsylvania. Read, Nov. 4, 1814. It has been long believed that the sinuses, or cavities in the body of the os sphenoides, were exclusively formed by that bone, when Winsl6w suggested that a small portion of the orbitar processes of the ossa palati contributed to their formation.* Many year's after Winslow's publication, Monsieur Berlin described two bones which form the anterior sides of these sinuses, and contain the foramina by which they communicate with the nose.f These bones he denominates "Cornets Sphenoidaux," and states that they are most perfect and distinct between the ages of four years and twenty ; that they are not completely formed before this period, and that after it they appear like a part of the sphenoidal bone. According to his account they are lamina of a triangular form, and are originally in contact with the anterior and inferior surface of the body of the os sphenoides, so that they form a portion of the sur- face of the cavity of the nose. He believed, that as they increase in size, they become convex and concave, and present their concave surfaces to the body of the sphenoidal bone, which also becomes concave, and presents its concavity to those bones; thus forming the sinuses. * In his description of the Ossa Palati, printed in the Memoirs of the Academy of Sciences for 1720. t See Memoirs of the Academy of Sciences for 1774. t Cr f ^/t Vr^^^*^ OS ETHMOIDES. 79 pyramids ; one at the base opening directly into the nose, near the situation of the opening of the sphenoida). sinuses, in the bones of adults ; and the other in each of the sides in contact with the azygos process. './ This account of M. Berlin has been adopted by Sabatier, and also by Boyer, who has improved it by the additional observation, that these triangular bones are sometimes united to the ethmoid, and remain attached to that bone when it is separated from the os sphenoides. Bichat and Fyfe have confirmed the description of Boyer. The specimens of ethmoid and sphenoid bones, herewith exhibited to the society, will demonstrate that in certain subjects, about two years of age, there are continued from the posterior part of the cribriform plate of the ethmoid, two Hollow Triangular Pyramids, which, when in their proper situations, receive be- tween them the azygos process of the os sphenoides. (See Plate X. Figures 1, 2, 3, with the explanation.) The internal side of each of these pyramids applies to the aforesaid azygos process ; the lower side of each forms part of the upper surface of the posterior nares ; the external side at its basis is in contact with the orbit ar process of the os palati. The base of each pyramid forms also a part of the surface of the posterior nares, and contains a foramen which is ultimately the opening into the sphenoidal sinus of that side. In the sphenoidal bones, which belong to such ethmoids as are above described, there are no cells or sinuses ; for the pyramid of the ethmoid bones occupy their places. The azygos process, which is to become the future septum between the sinuses, is remarkably thick, but there are no cavities or sinuses in it. The sides of the pyramids, which are in contact with this process, are ex- tremely thin, and sometimes have irregular foramina in them, as if their osseous substance had been partially absorbed.* That part of the external side of the pyramid which is in contact with the orbitar process of the os palati is also thin, and sometimes has an irregular foramen, which communicates with the cells of the aforesaid orbitar process. Upon comparing these perfect specimens of the ethmoid and sphenoidal bones of the subject about two years of age, with the os sphenoides of a young subject who was more advanced in years, it appears probable that the azygos process and the sides of the pyramid applied to it, are so changed, in their progress of life, that they simply constitute the septum between the sinuses ; that the exter- nal side of the pyramid is also done away, and that the front side and the basis of the pyramid only remain ; constituting the Cornets Sphenoidaux f of M. Berlin. If this be really the case, the origin of the sphenoidal sinuses is very intel- ligible. * * See e, Fig. 3. t " Cornet" is the word applied by several French anatomists to the Ossa Turblnati of the nose ; they seem to have intended to express by it a convoluted lamina or plate of bone. The fine drawing of the Ethmoid Bone, for this plate was done by my friend M. Lesueur, whose talents are so conspicuous in the plates attached to Peron's " Voyage de Descou- vertes aux Terres Australes. 80 OS SPHENOIDES. . Os Sphenoides. The os sphenoides or pterygoideus, resembles a bat with its wings extended. It consists, / 1st. Of a body with two processes arising from it, called the lesser wings, or apophyses of Ingrassias. 2dly. Of two large lateral processes, called the greater wings, or temporal processes ; and, 3dly. Of two vertical portions, denominated pterygoid pro- cesses. The body is situated near the centre of the cranium, and in contact with the cuneiform process of the occipital bone ; the greater wings extend laterally between the frontal and temporal bones as high as the parietal ; while the pterygoid processes pass downwards on each side of the posterior opening of the nose, as low as the roof of the mouth. It is, therefore, in contact with all the other bones of the cranium, and with many bones of the face. The body has a cubic figure ; its upper surface forms a portion of the basis of the cranium ; its lower and anterior surfaces form / Explanation of the Figures in the Plate referred to above. FIG. I. Represents the upper surface, or cribriform plate of the Ethmoid Bone. a. CristaGalli. bbbb. Cribriform plate. c. Surface denominated Os Planum. d d. Hollow Triangular Pyramids. e. Space between the Pyramids for receiving the Azygos Process of the Os Sphenoides. FIG. II. A lateral View of the Bone. a. Crista Galli. c. Os Planum. d. Triangular Pyramid. FIG. III. The Bone Inverted. a. The Nasal Plate of the Ethmoid Bone, which constitutes the upper portion of the Septum of the nose. g g. Those portions of the Ethmoid which are called Superior Turbinated Bones. //. The Cellular Lateral Portions of the Bone. d d. The Triangular Pyramids. e. Space between the Pyramids for the Azygos Process of the Os Sphenoides a foramen on the internal side of one of the Pyramids. s i OS SPHENOIDES. 81 part of the cavity of the nose ; the posterior surface is articu- lated with the cuneiform process of the occipital bone ; and laterally it is extended into the great wings, or temporal processes. On the upper surface of the body, the lesser wings^br the apophyses of Ingrassias,* project from the lateral and anterior parts ; these wings consist of two triangular plates, each of Fig. 18.f which is joined to the other by its base, and to the body of the os sphenoides by its un- der surface near the base, and terminates in a point ; their direc- tion is forwards and outwards, and their flat surfaces are horizontal. Anteriorly they are connected by suture to the ethmoid and frontal bones ; their posterior edge is rounded, and detached from any other bone, forming the upper margin of the foramen lacerum of the orbit of the eye ; this edge is thick and prominent at its internal extremity, and these prominences are called the anterior or clinoid processes ; * A physician of Palermo, who died in 1580, aged 70. H. f The superior or cerebral surface of the sphenoid bone. 1. The processus olivaris. 2. The ethmoidal spine. 3. The lesser wing of the left side. 4. The cerebral surface of the greater wing of the same side. 5. The spinous process. 6. The extremity of the pterygoid process of the same side, projecting down- wards from the under surface of the body of the bone. 7. The foramen opticum. 8. The anterior clinoid process. 9. The groove by the side of the Sella Turcica, for lodging the internal carotid artery, cavernous plexus, cavernous sinus, and orbital nerves. 10. The Sella Turcica. 11. The posterior boundary of the Sella Turcica ; its projecting angles are the posterior clinoid processes. 12. The basilar portion of the bone. 13. Part of the sphenoidal fissure. 14. The foramen rotundum. 15. The foramen ovale. 16. The foramen spinosum. 17. The angular interval which receives the apex of the petrous portion of the temporal bone. The posterior extremity of the Vidian canal terminates at this angle. 18. The spine of the spinous process ; it affords attachment to the internal lateral ligament of the lower jaw. 19. The border of the greater wing and spinous process which articulates with the anterior part of the squamous portion of the temporal bone. 20. The internal border of the spinous process, which assists in the formation of the foramen lacerum basis cranii. 21. That portion of the greater ala which articulates with the anterior inferior angle of the parietal bone. 22. The portion of the greater ala which articulates with the orbital process of the frontal bone. 82 OS SPHENOIDES. immediately before them are the optic foramina, which pass obliquely through the wings into the orbit of the eye, and transmit on each side the optic nerve and a small artery. Behind the optic foramen is a notch and sometimes a foramen, made by the carotid artery. When the notch is converted into a foramen, it is by a small bony pillar being extended from the anterior clinoid process, to the body of the sphenoid. A groove made by the optic nerves, is cften seen extending across the body of the bone, from one of the optic foramina to the other. Behind it is a depression, which occupies the greatest part of this surface of the bone, in which the pituitary gland is lodged ; the back part of this depression is bounded by a transverse emi- nence, called the posterior clinoid process. These three pro- cesses are called clinoid from their supposed resemblance to the supporters of a bed ; and the depression for the pituitary gland is called sella turcica from its resemblance to the saddle used by the Turks. On each side of the posterior clinoid process is a groove in the body of the bone, made by the carotid artery as it passes from the foramen caroticum of the temporal bone. The posterior surface of the body of the sphenoides is rough, for articulation with the truncated end of the cuneiform process of the os occipitis. On the anterior and inferior surfaces is a spine, called the azygos process, or rostrum which is received into the base of the vomer, and extends forward until it meets the nasal plate of the ethmoid bone ; on each side of this spine, in the anterior surface, are the orifices of the sphenoidal cells. Those orifices appear very differently in different bones ; in some very perfect specimens, they are irregularly oval, being closed below and on their external sides, by the processes of the ossa palati, and above by the triangular plates, as they have been called, of the ethmoid bone. The cells or sinuses, to which these orifices lead, occupy the body of the sphenoidal bone ; they are divided by a partition, and each of them has a communication with the cavity of the nose on its respective side, by the orifice above described. The sinuses do not exist during infancy ; they increase in the progress of life, and are very large in old age. OS SPHENOIDES. 83 Laterally, the body of the sphenoides is extended into the portions called the great wings or temporal processes. These great wings compose the largest part of the bone, and their internal surface forms a portion of the middle fossa of the/ base of the cranium. Externally, the surface of each great wing is divided into two portions : one of which is lateral, and unites to the frontal, temporal, and malar bones, forming part of the smooth surface for the temporal muscle ; the other portion forms part of the orbit of the eye, and is very regular and smooth. As the ethmoid bone forms part of the inside, this portion of the great wing forms part of the outside of the orbit, and is termed the orbitary process of the sphenoid bone. The horizontal part of each wing terminates in an acute angle termed spinous process, which penetrates between the petrous portion and the articulating cavity of the temporal bone. In this angle is the foramen for the principal artery of the dura mater ; near the point of the angle is a small process, which projects from the basis of the cranium, and is called styloid. Fig. 19.* The pterygoid pro- cesses pass downwards in a direction almost per- pendicular to the base of the skull. Each of them has two plates, and a middle fossa facing back- wards ; to complete the comparison, they should be likened to the legs of the bat, but are inaccurately named pterygoid, or wing-like processes. The external plates are broadest, and the internal are longest. From each side of * The antero-inferior view of the sphenoid bone. 1. The ethmoid spine. 2. The rostrum. 3. The sphenoidal spongy bone, partly closing the left opening of the sphenoidal cells. 4. The lesser wing. 5. The foramen opticum piercing the base of the lesser wing. 6. The sphenoidal fissure. 7. The foramen rotun- dum. 8. The orbital surface of the greater wing. 9. Its temporal surface. 10. The pterygoid ridge. 11. The pterygo-palatine canal. 12. The foramen of entrance to the Vindian canal. 13. The internal pterygoid plate. 14. The hamular process. 15. The external pterygoid plate. 16. The foramen spino- sum. 17. The foramen ovale. 18. The extpemity of the spinous process of the sphenoid. 84 FORAMINA OF THE SPHENOIDAL BONE. the external plates the pterygoid muscles take their rise. At the root of each internal plate, a small hollow may be remarked, where the musculus circumflexus palati rises, and part of the cartilaginous end of the Eustachian tube rests. At the lower end of the plate is a hook-like process (hamulus) round which the tendon of the last named muscle plays, as on a pulley. The ossa palati, on each side, rest upon these internal plates ; and, therefore, the pterygoid processes seem to support the whole face. Foramina of the Sphenoidal Bone. Before these foramina are described, it is necessary to state, that the nerves of the brain are named numerically, beginning with the olfactory, which is foremost. It should also be observed, that each nerve of the fifth pair is divided, before it passes from the cavity of the cranium, into three large branches. The first foramina are the optic, which have been already described; they transmit the optic, or second pair of nerves, and a small artery, to the ball of the eye. The second foramen, on each side, is the foramen lacerum. It commences largely at the sella turcica, and extends laterally a considerable distance, until it is a mere fissure. The upper margin of this foramen is formed by the anterior clinoid processes, and the edges of the smaller wings of the sphenoid bone. This foramen transmits the third, fourth, and sixth pair of nerves, and the first branch of the fifth pair, to the muscles, and the other parts, subservient to the eye. The foramen rotundum, or third hole, is round ; as its name imports. It is situated immediately under the foramen lacerum, on each side, and transmits the second branch of the fifth pair of nerves to the upper maxillary bone. The foramen ovale is the fourth hole. It is larger than the foramen rotundum, and half an inch behind it. It transmits the third branch of the fifth pair of nerves to the lower jaw. The fifth hole is the foramen spinale. It is small and round, and placed in the point of the spinous process, behind the fora- men ovale, to transmit the principal artery of the dura mater, which makes its impression upon the parietal bone. THE fACE. 85 The sixth foramen is under the basis of each pterygoid process, and is therefore called the pterygoid, or the Vidian* foramen. It is almost hidden by the point of the petrous portion of the temporal bone, and must be examined m the separated bone. It is nearly equal in size to the spinous hole. This foramen transmits a nerve that does not go out from the cavity of the skull, but returns into it. The second branch of the fifth pair, after passing out of the cranium, sends back, through this foramen, a branch called the Vidian, which upon its arrival in the cavity of the cranium, enters the temporal bone by the foramen innominatum. Of the Face. The face is the irregular pile of bones composing the front and under part of the head, and is divided into the upper and lower maxillae, or jaws. The upper jaw consists of six bones on each side, of one single bone placed in the middle, and of sixteen teeth. The thirteen bones are, two ossa maxillaria superiora, two ossa nasi, two ossa unguis, two ossa malarum, two ossa palati, two ossa spongiosa inferiora, and the vomer. The ossa maxillaria superiora form the principal part of the cavity of the nose, with the whole lower and forepart of the upper jaw, and a large proportion of the roof of the mouth. The ossa nasi are placed at the upper and front part of the nose. The ossa unguis are at the internal angles of the orbits of the eyes. The ossrt palati in the back part of the palate, extending upwards to the orbits of the eyes. The ossa spongiosa in the lower part of the cavity of the nose ; and The vomer in the partition which separates the two nostrils. * From its reputed discoverer, Vidius, a professor at Paris, 8 86 OSSA MAXILLARIA SUPERIORA. Ossa Maocillaria Superiora. The ossa maxillaria superiora, or upper jaw bones, may be considered as the basis or foundation of the face ; as they form a large part of the mouth, the nose, and the orbit of the eye. The central part of each bone, which may be considered as its body, is hollow, and capable of containing, in the adult, near half an ounce of fluid. . The plate which covers this cavity is the bottom of the orbit of the eye. The sockets of the large teeth are below it. The roof of the mouth projects laterally from the inside of it. A process for supporting the cheek bone is on the outside ; and another process goes up before it, which forms the side of the nose. Fig. 20.* In each upper maxillary bone the fol- lowing parts are to be examined : The nasal process ; the orbitar plate ; the malar process ; the alveolar process ; the palatine process ; the anterior and posterior surfaces ; the great cavity ; the internal or nasal surface ; and the three foramina. The nasal process, which extends upwards to form the side of the nose, is rather convex outwards, to give the nostril shape. Its sides above support the nasal bone ; and a cartilage of the alae nasi is fixed to its edge below. The margin of the orbit of the eye is marked by a sharp ridge on the external surface of this process ; and the part * The superior maxillary bone of the right side, as seen from the lateral aspect. 1. The external, or facial surface ; the depression in which the figure is placed is the canine fossa. 2. The posterior, or zygomatic surface. 3. The superior, or orbital plate or surface. 4. The infra-orbital foramen : it is situated immediately below the number. 5. The infra-orbital canal, leading to the infra- orbital foramen. 6. The inferior border of the orbit. 7. The malar process. 8. The nasal process. 9. The concavity forming the lateral boundary of the anterior nares. 10. The nasal spine. 11. The incisive, or myrtiform fossa. 12. The alveolar process. 13. The internal border of the orbital surface, which articulates with the ethmoid and palate bones. 14. The concavity which articu- lates with the lachrymal bone, and forms the commencement of the nasal duct. 15. The palate process, t. The two incisor teeth, c. The canine, b. The two bicuspidati. m. The three molares. OSSA MAXILLARIA SUPERIORA. 87 posterior to this ridge is concave to accommodate the lachrymal sac. The orbitar plate, which covers the great cavity, and forms the bottom of the orbit, is rather triangular in form, arid con- cave. In the posterior part is a groove or canal, which pene- trates the substance of the bone, as it advances forward, and terminates in the infra-orbitary foramen, below the orbit. At the place where this plate joins the nasal process above men- tioned, viz. at the inner angle of the orbit, is the commencement of the bony canal, which transmits the lachrymal duct into the cavity of the nose. The malar process projects from the external and anterior corner of the orbitar plate ; it supports the malar bone, and is rough for the purpose of articulating with it. The alveolar processes compose the inferior and external margins of the upper maxillary bones. When these bones are applied to each other, they form more than a semicircle : their cavities contain the roots of the teeth, and correspond with them in size and form. They do not exist long before the formation of the teeth commences ; they grow with the teeth ; and when these bodies are removed, the alveoli dis- appear. The palate process is a plate of bone, which divides the nose from the mouth, constituting the roof of the palate, and the floor or bottom of the nostrils. It is thick where it first comes off from the alveolar process ; it is thin in its middle ; and it is again thick where it meets its fellow of the opposite side. At the place where the two upper jaw bones meet, the palate plate is turned upwards, so that the two bones are opposed to each other in the middle of the palate, by a broad flat surface, which cannot be seen but by separating the bones. This surface is so very rough, that the middle palate suture almost resembles the sutures of the skull ; and the maxillary bones are neither easily separated, nor easily joined again. The meeting of the palate plates by a broad surface, makes a rising, or sharp ridge, towards the nostrils ; so that the breadth of the surface by which these bones meet, serves a double purpose ; it joins the 88 OSSA MAXILLARIA SUPERIORA. bones securely, and it forms a small ridge upon which the edge of the vomer, or partition of the nose, is planted. Thus we find the palate plates of the maxillary bones conjoined, forming almost the whole of the palate ; while what properly belongs to the palate bones forms a very small share of the back part only, As these thinner bones of the face have no medulla, they are nourished by their periosteum only, and are of course perforated with many small holes. The anterior, external or facial surface of the upper maxil- lary bone is concave ; the margin formed by the lower edge of the orbit, by the malar process, and by the alveolar processes, being more elevated than the central part, which consists of a depression called \\\Q fossa canina, which gives attachment to two muscles, the compressor nasi, and levator anguli oris. At a small distance below the orbit is the infra-orbitary foramen for transmitting a branch of the superior maxillary nerve. When these two bones are applied to each other, and the ossa nasi are in their places, they form the anterior orifice of the nasal cavity, which has a small resemblance to the inverted figure of the heart on cards. The concave border of the open- ing of the nostrils, is projected forwards at its lower surface into a sharp process, forming with a similar process at the oppo- site side the nasal spine. Beneath the nasal spine, and above the two superior incisor teeth, is a slight depression called the incisive or myrtiform fossa, which gives origin to the depressor labii superioris alaeque nasi muscle . The posterior zygomatic surface has been called a process or tuber. The tuberosity is pierced by a number of small foramina, giving passage to the posterior dental nerves, and branches of the superior dental artery. It expands to a con- siderable size, and is united internally and posteriorly to the ossa palati. The great cavity extends from the bottom of the orbit of the eye to the roof of the mouth, and from the anterior to the posterior surface of the bone ; it opens in the cavity of the nose, and is called antrum maxillare, or Highmorianum.* There is but a small portion of bone between this cavity * After an anatomist who described it. OSSA NASI. 89 and the sockets of the teeth, particularly those of the second molar tooth ; occasionally the fangs of the tooth enter the cavity. The internal or nasal surface of this bone forms a large part of the cavity of the nose, and is concave. At the roof of the nasal process is a ridge, for supporting the anterior end of the lower turbinated bone. The nasal process seems continued into the cavity of the nose, and forms a portion of the orifice of the canal for the lachrymal duct, which is on the external side of this cavity, near its anterior opening, and under the lower furbinated bone. The orifice in this bone by which the antrum maxillare communicates with the nose, is very large ; but it is reduced to a small size, by a plate from the ethmoid bone, by a portion of the os palati, and of the lower spongy bone, each of which covers a part of it. The three foramina are, 1st. The infra-orbitary foramen already described. 2d. The foramen incisivum or anterior palatine hole, which passes through the palatine process, from the nose to the mouth. In the nose it forms generally two foramina, which unite and form but one in the mouth, imme- diately behind the middle incisor teeth. This foramen is closed by the soft parts during life, and transmits a branch of the spheno-palatine nerve from each side, which runs on the septum narium, and joining at the lower part of the canal with its fellow, they unite, and, according to M. Cloquet,* form a ganglion. 3d. The posterior palatine foramen, which is formed by this bone, and by the os palati, on each side, is situated in the suture which joins them to each other, and transmits to the palate a branch of the upper maxillary nerve. This bone is united to the frontal, nasal, unguiform, ethmoid and malar bones, above ; to the ossa palati behind ; to the cor- responding bone, on the opposite side ; and to the inferior spongy bone, in the cavity of the nose. Ossa Nasi. The ossa nasi are so named from their prominent situation * This ganglion, though it varies in size, is readily found. I always exhibit it in the course of my lectures. p. 8* 90 OSSA UNGUIS. at the root of the nose. They are each of an irregular oblong figure, being broadest at their lower end, narrowest near the middle, and larger again at the top, where the edge is rough and thick, and their connexion with the os frontis is conse- quently very strong. They are convex externally, and concave within. The lower edges of these bones are thin and irregular. Their anterior edges are thick, and their connection with each other, by means of their edges, is firm ; the suture between them, extending down the middle of the nose, forms a promi- nent line on the internal surface, by which they are united to the septum narium. The uppermost half of their posterior edges is covered by the edges of the nasal processes of the upper maxillary bones ; the lower half laps over the edges of these bones ; and by this structure they are enabled to resist pressure. [On the posterior surface of the os nasi is a groove occupied in the recent subject by a branch of the ophthalmic nerve called the nasal, which enters the nose through the fora- men orbitare internum anterius.] They are joined above to the os frontis ; before, to each other ; behind, to the upper maxillary bones ; below, to the cartilages ; and internally, to the septum of the nose. Ossa Unguis, or Ossa Lachrymalia. The ossa unguis are so named from their resemblance to a nail of the finger. They are situated on the internal side of the orbit of the eye, between the os planum of the ethmoid, and the nasal process of the upper maxillary bone. Their external surface is divided into two portions, by a middle ridge ; the posterior portion forms part of the orbit ; and the anterior, which is very concave, forms part of the fossa and canal, for contain- ing the lachrymal sac and duct. This portion is perforated by many small foramina ; and the whole, being extremely thin and brittle, is therefore often destroyed by the preparation of the subject. The internal surface of this bone is generally in contact with the cells of the ethmoid ; a small portion of the anterior parts is in the general cavity of the nose. Each os unguis is joined OSSA MALARUM. 91 above to the frontal bone ; behind to the os planum ; before and below to the maxillary bone. It sometimes is extended into the nose, as low as the upper edge of the inferior spongy bone. Ossa Malarum. The ossa malarum are the prominent square bones which form the cheek, on each side. Before, their surface is convex and smooth ; backward, it is unequal and concave, for lodging part of the temporal muscles. The four angles of each of these bones have been reckoned as processes. The one at the external canthus of the orbit called the superior orbitar process, is the longest and thickest, The second terminates near the middle of the lower edge of the orbit in a sharp point, and is named the inferior orbitar process. The third, placed near the lower part of the cheek, and thence called maxillary, is the shortest and nearest to a right angle. The fourth, which is called zygomatic, because it is extended backwards to the zygoma of the temporal bone, ends in a point, and, has one side straight and the other sloping. Between the two orbitar angles there is a concave arch, which makes about a third of the external circumference of the orbit, from which a fifth process is extended backwards within the orbit, to form near one-sixth of that cavity ; and hence it may be called the internal orbitar process. From the lower edge of each of the ossa malarum, which is between the maxillary and zygomatic processes, the masseter muscle takes its origin. On the external surface of each cheek bone, one or more small holes are commonly found for the transmission of small nerves or blood-vessels from, and sometimes, into the orbit. On the internal surface are the holes for the passage of the nutritious vessels of these bones. A notch, on the outside of the internal orbitar process of each of these bones, assists to form the great slit common to this bone, and to the sphenoid, maxillary, and palate bones. The substance of these bones is, in proportion to their bulk, thick, hard, and solid, with some cancelli. 92 OSSA PALATI. Each of the ossa malarum is joined, by its superior and internal orbitar processes, to the os frontis, and the orbitar process of the sphenoid bone; by the edge between the internal and inferior orbitar processes, to the maxillary bone ; by the side between the maxillary and inferior orbitar process, again to the maxillary bone ; and by the zygomatic process to the os temporis. Ossa Palati. The ossa palati form the back part of the roof of the mouth, and extends from it along the external sides of the posterior openings of the nose, into the orbits of the eyes. Each bone may therefore be divided into four parts, the palate square bone, or palatine, or horizontal process, the pterygoid process or tuberosity, the nasal lamella or perpendicular plate, and the orbitar process. The square bone is irregularly concave, for enlarging both the mouth and cavity of the nose. The upper part of its internal edge rises in a spine, after the same manner as the palate plate of the maxillary bone does, to be joined with the vomer. Its anterior edge is unequally ragged, for its firmer connexion with the palate process of the os maxillare. The internal edge is thicker than the rest, and of an equal surface. for its conjunction with its fellow of the other side. Behind, this bone is somewhat in form of a crescent, and thick, for the firm connexion of the velum pendulum palati ; the internal point being extended backwards, to afford origin to the palato- staphylinus or azygos muscle. This square bone is well dis- tinguished from the pterygoid process by a perpendicular fossa, which, applied to a similar one in the maxillary bone, forms a passage (ptery go-maxillary) for the palatine branch of the fifth pair of nerves ; and by another small hole behind this, through which a twig of the same nerve passes. The pterygoid process is somewhat triangular, having a broad base, and ending smaller above. The back part of this process has three fossae formed in it ; the two lateral receive the ends of the two pterygoid plates of the sphenoid bone ; the OSSA PALATI. 93 Fig. 20.* middle fossa, which is very superficial, makes up a part of what is commonly called the fossa pterygoidca. The foreside of this pterygoid process is rotf^h and irregular where it joins the back part of the great tuberosity of the maxillary bone. Frequently several small holes may be observed in this triangular process, par- ticularly one near the middle of its base, which a little above communicates with the common and proper holes of this bone already mentioned. The nasal lamella of this bone is extremely thin and brittle, and rises upwards from the upper side of the external edge of the square bone, and from the narrow extremity of the ptery- goid process ; it is so weak, and, at the same time, so firmly fixed to the maxillary bone, as to be very liable to be broken in separating the bones. From the part where the plate rises, it runs up broad on the inside of the tuberosity of the maxillary bone, to form a considerable share of the sides of the maxillary sinus, and to close up the space between the sphenoid and the great bulge of the maxillary bone, where there would other- wise be a large slit opening into the nostrils. On the middle of the internal side of this thin plate, there is a transverse ridge, continued from one which is similar to it in the maxillary bone * A posterior view of the palate bone in its natural position ; it is slightly turned to one side to obtain a view of the internal surface of the perpendicular plate (2). 1. The horizontal plate of the bone; its upper or nasal surface. 2. The perpendicular plate or nasal lamella, seen on its internal or nasal surface. 3, 10, 11. The pterygoid process or tuberosity. 4. The broad internal border of the horizontal or palatine process, which articulates with the similar process of the bone of the other side. 5. The ridge which with a similar elevation of the opposite bone forms the palate spine. 6. The horizontal ridge which gives attachment to the inferior turbinated bone ; the concavity below this ridge forms a part of the inferior meatus of the nose, and the concavity (2) above the ridge forms a part of the middle and superior meatus. 7. The spheno-palatine fora- men. 8. The orbital process of the bone. 10. The middle facet of the ptery- goid process or tuberosity which forms the middle of the pterygoid fossa. The fossae 11 and 3, articulate with the two pterygoid plates of the sphenoid bone: 11 with the internal, and 3 with the external. 94 OSSA PALATI. for supporting the back part of the os spongiosum inferius. Along the outside of this plate, the perpendicular fossa made by the posterior palatine nerve is observable. At the upper and posterior edge of this nasal plate is a notch, which when applied to the sphenoid bone, forms the spheno- palatine foramen, through which a nerve, artery, and vein pass to the nostril ; this notch forms two processes on the posterior part of the bone, the inferior of which is in contact with the internal plate of the pterygoid process of the sphenoidal bone, and has, therefore, been called by some French anatomists, the pterygoid apophysisofthe ospalati. The superior and anterior portion is the proper orbitar process of this bone, which is Fig. 21.* situated at the posterior part of the lower surface of the orbit, and forms a portion of it. This process of the os palati is hollow ; and its cavity generally com- municates with the contiguous cell of the os ethmoides. It has several surfaces, one of which is to be found in the orbit, and another in the zygomatic fossa. The palate square part of the palate bone, and its pterygoid process, are firm and strong, with some cancelli ; but the nasal plate, and orbitar processes, are very thin and brittle. The palate bones are joined to the maxillary, by the fore edges of the palate square bones ; by their thin nasal plates, and part of their orbitary processes, to the same bones ; by their pterygoid processes, and back part of the nasal plates, to * The perpendicular plate of the palate bone seen upon its external or spheno- maxillary surface. 1. The rough surface of this plate, which articulates with the superior maxillary bone. 2. The posterior palatine canal, completed by the tuberosity of the superior maxillary bone. The rough surface to the left of the canal (2) articulates with the internal pterygoid plate. 3. The spheno-palatine or lateral nasal foramen. 4, 5, 6. The orbital portion of the perpendicular plate. 4. The pterygoid apophysis or spheno-maxillary facet of this portion. 5. Its orbital facet or process. 6. Its maxillary facet, to articulate with the superior maxillary bone. 7. The sphenoidal portion of the perpendicular plate. 8. The pterygoid process or tuberosity of the bone. OSSA SPONGIOSA INFERIORA. THE VOMER. 95 the pterygoid processes of the os sphenoides ; by the transverse ridges of their nasal lamellae to the ossa turbinata inferiora, and by the spines of the square bones to the vomer. *j j/n The Ossa Spongiosa, or Turbinata Inferiora. The ossa spongiosa, or turbinata inferiora, are so named to distinguish them from the upper spongy bones, which belong to the os ethmoides ; but these lower spongy bones are quite distinct, and connected in a very slight way with the upper jaw bones. They are rolled or convoluted, very spongy, and exceedingly light. Each of them is attached to the os maxil- lare superius, near the transverse ridge, by a hook-like process, and covers a part of the opening of the maxillary sinus. One end is turned towards the anterior opening of the nose, and covers the end of the lachrymal duct ; the other end of the same bone points backwards towards the throat. The curling plate hangs down into the cavity of the nostril, with its convex side towards the septum. This spongy bone differs from the spongy processes of the ethmoid bone, in being less turbinated or complex, and in having no cells connected with it. The Vomer. The vomer is a thin flat bone, which forms the back part of the septum of the nose. Its posterior edge extends downwards from the body of the os sphenoides to the palatine processes of the ossa palati, separating the posterior nares from each other. The figure of this bone is an irregular rhomboid. Its sides are smooth ; and its posterior edge appears in an oblique direction at the back part of the nostrils. The upper edge is firmly united to the base of the sphenoid bone, and to the nasal plate of the ethmoid. It is hollow for receiving the processus azygos of the sphenoid, and where it is articulated to the nasal plate of the ethmoid, it is composed of two lamina which receive this plate between them. The anterior edge has a long furrow in it, where the middle cartilage of the nose enters. The lower edge is firmly united to the nasal spines of the .-, 96 MAXILLA INFERIOR. maxillary and palate bone. These edges of the bone are much thicker than its middle, which is as thin as paper ; in conse- quence of which, and of the firm union or connexion this bone has above and below, it can very seldom be separated entire in adults ; but in a child it is much more easily separated entire, and its structure is more distinctly seen. Its situation is not always perpendicular, but often inclined and bent to one side, as well as the nasal plate of the ethmoid bone. It is united above to the os sphenoides and the nasal plate of the ethmoid bone ; before to the middle cartilage of the nose ; and below, to the ossa palati and ossa maxillaria supe- riora. Maxilla Inferior, or Lower Jaw. The form and situation of this bone are so generally known, that they do not require description. To acquire an accurate idea of the lower jaw, it is, however, necessary to examine attentively its different parts : viz. the chin, or mental protuber- ance, the sides, the angles, and the processes. In subjects where the bones are strongly marked, there is a prominent vertical ridge in the middle and most inferior part of the chin which becomes broad below so as to form a triangle, and on each side of this triangular prominence are transverse ridges ; from these eminences the muscles of the lower lip originate. On each side of the jaw, commonly under the second of the bicuspides, or small molar teeth, is the anterior maxillary or mental foramen, through which pass out branches of the inferior maxillary nerve and blood-vessels.^ This foramen, has a direction upward and backward. At a ?mall distance behind these foramina, on each side, is the commencement of a ridge which continues backward until it forms the edge of the anterior or coronoid process. The alveolar processes, which form the upper edge of the jaw, are on the inside of this ridge ; the alveoli or sockets corresponding with the roots of the teeth, in number and form. The lower edge of the jaw, which is 7^ : MAXILLA INFERIOR. 97 denominated the base, is round and firm, except at the angles, where it is thin. The angle is formed at the posterior extremity of the base : in children it is obtuse ; but in adults whose teeth are perfect, it is nearly rectangular. The masseter muscle is inserted into the lower jaw, at the angle ; and there are several inequalities on the surface made by this muscle. Fig. 22.* The anterior or coronoid process, is rather higher than the posterior, and forms an obtuse point : into this process the temporal muscle is inserted. The anterior edge of the coro- noid process is sharp, and con- tinued into the rid^e above O mentioned ; from this edge the buccinator muscle arises. As the alveoli are on the inside of this edge and ridge, the jaw is very thick at this place. There is a semicircular or sigmoid notch between this coronoid process and the posterior or condyloid ; and here the bone is very thin. The condyles are oblong, and are placed obliquely ; so that their longest axes, if extended until they intersect each other, would form an angle of more than one hundred and forty degrees. The neck of the process, or the part immediately below the condyle, is concave on the anterior, arid convex on the posterior surface. On the inside of the jaw, in the middle of the chin, is a small protuberance, sometimes divided by a vertical fissure ; to this are attached the fraenum lingua, and some muscles of the tongue and os hyoides. Farther back is a ridge called the mylo-hyoid, which extends backwards and upwards, until it * The lower jaw. 1. The body. 2. The ramus. 3. Thesymphysis. 4. The fossa for the depressor labii inferioris muscle. 5. The mental foramen. 6. The external oblique ridge. 7. The groove for the facial artery. 8. The angle. 9. The extremity of the mylo-hyoidean ridge. 10. The coronoid process. 11. The condyle. 12. The sigmoid notch. 13. The inferior dental foramen. 14. The mylo-hyoidean groove. 15. The alveolar process. . The middle and lateral incisor tooth of one side. c. The canine tooth, b. The two bicuspides. m. The three molares. 9 98 MAXILLA INFERIOR. approaches the alveoli of the last molar teeth ; where it termi- nates in an oblong protuberance. To the anterior part of this line the mylo-hyoidei muscles are attached ; and to the posterior extremity, the superior constrictor of the pharynx. The surface of the bone above this ridge is smooth, and covered with the gums and lining membrane of the mouth. The surface below the posterior part of the line is rather concave, to accommodate the submaxillary gland. At a small distance behind the alveoli, and nearly on a line with them, midway between the roots of the two processes, is a large foramen, called the inferior dental, for transmitting the third, or inferior maxillary branch of the fifth pair of nerves, and the blood-vessels which accompany it ; the canal, which commences here, terminates at the anterior foramen, already described.* The surface of this canal is perforated by many foramina, through which blood-vessels and nerves pass to the different teeth, and to the cancelli of the bone. On the anterior side of the foramen is a sharp-pointed process, from which a ligament passes to the temporal bone. The nerve and vessels, before they enter into this foramen, make an impression on the bone ; and there is generally a small superficial groove called the mylo-Jiyoid, which proceeds downwards from it, being made by a small nerve which supplies some of the parts under the tongue. At the angle of the jaw, on the inside, is a remarkable rough- ness, where the internal pterygoid muscle is inserted. The lower jaw moves like a hinge upon its condyles in the glenoid cavity, when the mouth opens and shuts in the ordinary way. When the mouth is opened very wide, the condyles move forward upon the tubercles before the cavities : if the effort to open the mouth is continued, the lower jaw is fixed in that situation, and the whole head is thrown back, which separates the upper jaw still farther from the lower. The lower jaw can be projected forward without opening the mouth, by the movement of both condyles, at the same time, on the tubercles. This bone can also rotate upon one condyle, as a centre, while * A branch of this canal is continued forwards to the symphysis by which the front teeth are supplied with vessels and nerves. p. THE TEETH. 99 the other moves out of the glenoid cavity, upon the tubercle : but these important motions can be better understood, after the muscles, and the articulation with the temporal bone, in its recent state, have been described. Fig. 23. Of the Teeth. In the adult, when the teeth are perfect, there are sixteen in each jaw, and those in corresponding situations, on the opposite sides, resemble each other exactly. They are of four kinds, viz. incisores, or the fore teeth ; cuspi- dati, or the canine ; bicuspides, or the small grinders ; and molares, or the large grinders. On each side of the jaw, supposing it divided in the middle there are two incisores, one cuspidatus, two bicuspides, and three molares. They occur in the order in which they have been named, beginning at the middle of the jaw, as in the above figure. Each tooth is divided into two parts, viz. the body, or that portion which is bare, and projects beyond the alveoli and gums ; and the root, which is lodged in the socket. The boundary between these parts, which is embraced by the gums, is called the neck of the tooth. The body and roots consist of a peculiar kind of bone (dentine) which is more firm and hard than the substance of the other bones ; but all the surface of the body, which projects beyond 100 COMPOSITION OF THE TEETH. the gums, is covered with enamel, a substance very different from common bone. Every tooth in its natural condition has a cavity in it, which commences at the extremity of each root, and extends from it to the body of the tooth, where it enlarges considerably. This cavity is lined by a membrane, and contains a nerve, with an artery and vein, which originally entered the tooth, by a foramen near the point of the root, as is evidenf during the growth of the teeth. These vessels, and the nerve, have been traced into the teeth ; although in many subjects the foramina appear to be closed up. A third substance has lately been discovered by Prof. Ret- zius of Stockholm as entering into the..co'nGfyoit]6n*of the teeth of man, called the cortical substance or cementum. It com- mences at the lower edge of the enamel and surrounds com- pletely the fang. In many of the lower animals it is found also? on the faces of the compound teeth, filling up the spaces between the vertical ridges of enamel. Composition of the Teeth. The bone or ivory of the teeth, now called Dentine, (see Fig. 24,) constitutes the whole of the root, and a greater part of the body and neck. The cavity in the centre, for the lodg- ment of the pulp, (cavitas pulpi) in whichever of the teeth it is examined, presents an exact similarity of shape to the bodies and fangs of the teeth, as though the latter had been moulded upon the pulp. The ivory is of a polished pearly whiteness, like that of a piece of white satin. It is composed chemically both of animal and earthy matter, but in different propor- tions from ordinary bone. If exposed for a considerable Fig. 24. time to the action of a weak acid solu- tion, the earthy matter is dissolved, and there is left a flexible, tenacious, dense, and homogeneous mass, much resembling cartilage, but more dense. If, on the contrary, it is exposed to the action of fire, the animal matter is first blackened, then consumed, and there is left a white, hard, friable residue of calcareous matter. COMPOSITION OF THE TEETH. 101 When examined with the microscope, the bone or ivory appears to consist of minute branching fibres, which begin at the pulp and run toward the periphery of the tooth, and aje im- pacted in some homogenous bony tissue lodged between them. These fibres have been shown by Mr. Nasmyth to be nothing more than little opaque bodies, the nuclei of the bone or ivory cells arranged in a linear series. The enamel or vitreous substance, (see Fig. 24,) so named from its resemblance to vitrified minerals, has been with greater propriety called by Blake, the cortex striatum, from the lines which it presents upon its sides. It forms a covering nearly a line in thickness upon the crown of the teeth, and is thinned down at its termination upon the neck. It is composed of minute hexagonal crystalline fibres, consisting like those of the ivory of minute cells filled with calcareous substance piled one upon another, perpendicularly to the bony part, and so closely compressed together, as to leave no obvious interval between them. All the wear of the teeth takes place, therefore, at the end of these fibres and not upon their sides ; and the enamel is rendered by this arrangement much less liable to frac- ture. No vessels have been traced to this substance, nor has it ever been seen like the bony portion, colored by madder in young animals fed on this substance during the development of the teeth. But Mascagni, infatuated with his discoveries in the absorbent system, absurdly regarded this substance as entirely formed of absorbent vessels.* It is exceedingly hard and strikes fire, on collision with steel. While covering the bone, it presents a milky white appearance ; removed from it, it is semi-transparent and opaline. The enamel is thickest on those parts of the teeth most exposed to friction, as on the horizontal surfaces of the grinders, the edges of the incisors, and the points of the cuspi- dati. The position of the enamel and its arrangement into fibres is well seen in Fig. 24. * Vide Prodrome. 9* 102 PURKINJE AND MULLER ON THE TEETH. The enamel and ivory of the teeth are the most indestructible after death of all parts of the body. In opening tumuli or other ancient places of sepulchre, they are frequently found to have undergone scarcely any decomposition. The cortical substance or cementum, see Fig. 24, consists of a thin osseous layer developed on the external part of the fangs, down to the orifices which lead to the cavity of the tooth. It is essentially of the same structure as true bone, containing the characteristic corpuscles, and calcigerous branching tubuli of that tissue. It is supposed to be formed by ossification of the capsule in contact with the fang, and is certainly the seat of the exostosis often met with on the roots of the teeth. In old age it makes its appearance in the cavity of the tooth, and is formed from the membrane of the pulp the pulp shrinking and retiring in proportion as the cement accumulates. The chemical composition of the two substances of the hu- man teeth, consists, according to Berzelius, in the hundred parts, of Enamel. Bone. Animal matter, - 20.0 Phosphate of lime, with fluate of lime, 88.5 - 64.3 Carbonate of lime, 8.0 - 5.3 Phosphate of magnesia, - 1.5-1.0 Soda, with some chloride of soda, - 1.4 Free alkali and animal matter, 2.0 100.0 100.0 Purkinje and Miiller, have recently, with the aid of the microscope, investigated very minutely, the structure of the teeth, and their discoveries have been confirmed by many other observers of high reputation. They describe the bony part of the tooth as consisting of fibres running parallel to each other from the external to the internal surface of the tooth, between which is placed a semi-transparent, homogeneous por- tion. These fibres they believed to be really tubular; for on PURKINJE AND MULLER ON THE TEETH. 103 bringing ink into contact with them, it was drawn into them, as if by capillary attraction. These tubes Miiller believed to be filled, at least partially, with calcareous matter, which was the cause of the whiteness and opacity of the toofh. In the more transparent part of carious teeth, the white sub- stance in these tubes presented more of a granular, and less of a compact appearance, under the microscope, than in a sound tooth. The white color and opacity of these tubes were removed by the application of acids. On breaking a thin lamella of a tooth transversely in regard to the fibres, and examining the edge of the fracture, he perceived the tubes, stiff, straight, and inflexible, projecting here and there from the surfaces. If the lamella had previously been acted on by acid, the tubes were flexible, transparent, and often very long. Hence Miiller inferred that the walls of the tubes have a basis of animal tissue, and that besides containing calcareous matter in their cavity, they have this tissue in the natural state impregnated with calcareous salts. The greater part of the earthy matter of the tooth is, however, contained in the transparent homogeneous portion between the fibres, in which it can be rendered visible in a granular state by boiling thin lamina of teeth in a ley of potash. Purkinje, by the aid of high magnifying powers, discovered the corpuscles that characterize true bone, in layers taken from the external and internal surface of the root ; he considers the great mass of the tooth, however, as destitute of organization. These fibres which have been still more fully proved by Retzius* to be true canals, having their own walls, are differ- ently arranged in the separate substances of the tooth, but are every where exceedingly minute. In the ivory they are about g^th of a line in diameter: they commence by open orifices at the cavity of the pulp, and extend in an undulating but nearly parallel direction to the surface, dividing and branching * Mikroskopiska Undersokningar ofver Tandernes sardeles Tandbenets, struktur : Stockholm, 1837. 104 OF THE ALVEOLI. in their course ; the branches anastomosing together, and com- municating occasionally with very minute calcigerous cells, lodged in the transparent intertubular structure, which may be compared to the corpuscles of ordinary bone. The fibres or filled tubes of the enamel are about 5 th of a line in diameter, and are hexagonal. They are striated, arranged parallel to each other, and are applied by their internal extremities to corresponding depressions on the surface of the ivory. The ordinary bony tubuli of the cement or cortical substance communicate here and there with the branching tubes of the ivory. These minute but interesting details in regard to the structure of the teeth, which are found to vary in the different classes of animals, are important, not only as furnishing one of the best methods of their classification, but in exhibiting the striking analogy that exists, as to their structure, between teeth and bone. The tubes or canals of common bone are occupied by blood-vessels, the calcareous matters being lodged in the bony corpuscles and their reticular tubuli ; while those of the teeth are vascular in the growing state, and become nearly all filled up as well as their corpuscles with earthy matter, to give that great degree of solidity requisite in biting and masti- cation. The alveoli or sockets of the teeth, are formed upon the edge of the jaw : the bone, of which they consist, is less firm than any other part of the jaws: they correspond exactly with the roots of the teeth ; and are lined with a vascular membrane, which serves as a periosteum to the roots, and assists in fixing them firmly. They are developed pari passu, with the teeth, and solely for the purpose of giving them a lodgment ; hence when the teeth are removed from the jaw, in the living subject, the sockets subsequently disappear by absorption, as being of no further use. There are two sets of alveoli, one for the deci- duous teeth of the child, and one for the permanent teeth of the adult. Their walls are formed of one plate on the external THE ALVEOLI. 105 side of the jaw, and one on the internal, with transverse bony laminae passing between them. On the side of the cavity which they form, their substance is loose and cellular ; on their outer side, like other bones, they are smooth and compact: The transverse processes, are rather more prominent than the lateral part of the parietes, corresponding in this respect inversely with the line of enamel on the teeth. The enamel terminates on the neck of the teeth a little above the level of the sockets, leaving a small space on the bony part of the neck round which the gum is attached. The alveoli, terminate in as many hollow processes, as there are fangs to the teeth which they lodge : and at the bottom of each of these processes there are one or more minute foramina, for the transmission of vessels and nerves to the internal mem- brane and pulp of the teeth. The mode of articulation of the teeth in the sockets is called gomphosis ; even in their perfect state, the teeth are slightly movable in the socket, of which dental surgeons, occasionally take advantage, in altering the direction of the teeth, by mechanical means. The firmness of the articulation, depends upon the adaptation in size and shape of the sockets to the fangs, on the gum which surrounds the neck, of the periosteum of the sockets which is continuous with that of the fangs, and of the vessels and nerves which enter into the foramina of the fangs. The teeth of different kinds differ greatly from each other, in form and size. The body of the incisores is broad, with two flat surfaces, one anterior and the other posterior ; the anterior surface is rather convex and the posterior concave ; they meet in a sharp cutting edge. At this edge the tooth is thinnest and broadest; it gradually becomes thicker and narrower, as it is nearer the neck. The enamel continues farther down on the anterior and posterior surfaces than on the sides. The incisores of the upper jaw are broader than those of the lower ; especially the two internal incisores. The cuspidati are longer than any other teeth, and are thicker 106 PERMANENT TEETH. than the incisors. Their edges are not broad, as those of the incisors, but pointed ; this point is much worn away in the pro- gress of life. The enamel covers more of the lateral part of these teeth than of the incisors. The bicuspides are next to the cuspidati, two on each side. They resemble each other strongly ; but the first is smaller than the other, although it generally* has a longer root. The bodies are flattened laterally, but incline to a roundish form. On the middle of the grinding surface are depressions which make the edges prominent. On the external edge there is generally one distinct point in each of the bicuspides. The internal edge is lower than the external in the first bicuspis, which gives it a resemblance to the cuspidatus. In the second bicuspis, the internal edge is more elevated, although the point is not so distinct as it is on the external edge. The bicuspides have generally but one root, which is often indented lengthwise, so as to resemble two roots united. The three molares or large grinders are placed behind the bicuspides, on each side. The first and second strongly resem- ble each other, but the third has several peculiarities. The body of the large grinders is rather square ; the grinding surface has often five points, and three of these are on the external side. In the upper jaw these teeth have three roots, two situated externally, and one internally, which is very oblique in its direction ; they are all conical in their form. It seems probable that the roots of these teeth are arranged in this way to avoid the antrum maxillare. The molares of the lower jaw have but two roots, which are flat, and are placed one anterior and the other posterior ; in each of these broad roots there are two canals, leading to the central cavity ; whereas, in each root of the upper molares there is but one. The third grinder is called dens sapientia^ from its late appearance. It is shorter and smaller than the others ; its body is rather rounder, and its roots are not so regular and distinct ; for they are sometimes com- pressed together, and sometimes there appears to have been but one root originally, when the whole tooth has a conical DECIDUOUS TEETH. - 107 appearance. In some cases the denies sapientiae take an irregular direction, and shoot against the adjoining teeth. Infants have a set of deciduous teeth, which differ in several respects from those of adults. They are but twenty in ntfmber ; the five on each side of each jaw, consist of two incisores, one cuspidatus, and two molares or large grinders. The first of them generally protrudes through the gums between the fourth and eighth months of age ; the last about the end of the second year. They commonly appear in pairs,* which succeed each other at irregular intervals. Those of the lower jaw are, in most cases, the first. The order of their appearance is this : the central incisors appear first, then the external incisors on each side ; after these the first molaris, then the cuspidatus, and finally the last molaris on each side. There are many deviations from this order of succession, but it takes place in a majority of cases. These deciduous teeth become loose, and are succeeded by those which are more permanent, nearly in the same order in which they appeared, but with a progress much more slow. The incisores generally become loose between the sixth and seventh year ; the first molares about the ninth, the cuspidati and the second molares not until the tenth or twelfth, or even fourteenth year. The bicuspides take the places of the infant molares. The three permanent molares appear in the following order : the first of them protrudes a short time before the front teeth are shed ; it is the first of the permanent teeth which appears, and is seen between the sixth and seventh year. The second molaris appears soon after the cuspidati and the second bicus- pides are seen. There is then a long interval ; for the last molaris or dens sapientise is seldom seen before the twentieth year, and sometimes not until the twenty-fifth. The teeth are formed upon pulpy substances, which are situated in the alveoli, and are contained in capsules. A shell of bone is first formed upon the surface of the pulp, which * The two teeth of a pair do not appear at the same precise time, but very near to each other. 108 DEVELOPMENT OF THE TEETH. gradually increases, and the pulp diminishes within it. The body of the tooth is produced first, and the root is formed gradually afterwards ; during its formation the root has a large opening at the extremity, which is gradually diminished to the small orifice before described. The roots, as well as the body, are formed upon the pulpy substance, which gradually diminishes, as they increase. After the external surface of the body of the tooth is formed* the enamel begins to appear upon it, and gradually increases, until it is completely invested. It is probable that the enamel is deposited upon the body of the tooth by the membranous capsule which contains it. This substance, which appears to be formed of radiated fibres, is harder and less destructible than bone. Like the substance of bone, it is composed of phosphate, with a small propor- tion of the carbonate of lime; but it is destitute of the cartila- ginous or membraneous structure which is demonstrable in bone. The pulpy substances, or rudiments of teeth, may be seen in the foetus, when about four months old. At six months, ossification can be seen to have commenced on the pulps of the incisores. At the time of birth, the bodies of the infant teeth are distinctly formed. The alveoli, at first, have the appearance of grooves in the jaw, which afterwards are divided by transverse partitions ; they enlarge, in conformity to the growth of the teeth, and appear to be altogether influenced by them. The permanent teeth are formed very early : the rudiments of the first permanent grinder on each side have commenced their ossification at birth. At the same time, the rudiments of the permanent incisors are to be perceived ; and their bodies will be found nearly ossified, by the time the infant incisors are protruded completely through the gums. About the age of six years, if none of the infant teeth are shed, there will be forty-eight teeth in the two jaws, viz : the twenty infantile, and twenty-eight permanent teeth, more or less completely formed. From their mode of development, apparent structure, and .c *&f* DEVELOPMENT OF THE TEETH. 109 connexions with the rest of the economy, the teeth were prior to the microscopical researches above detailed considered analogous to the hair, nails, and feathers of mammiferae and birds, and to the shells of molluscae. It cannot be said that the teeih are absolutely inorganized, that they are mere concretions of an effused fluid, since there is no part appertaining to living beings, entirely destitute of life ; but in the hard structure of the teeth, no anatomist has yet demonstrated either vessels or nerves, though there are practical dentists, who assert that they have seen blood issu from the bony part of the teeth, in some of their operations.* * Hunter denies positively the existence of any vessels passing between the. pulp and bone of the teeth, as he was not able to render them manifest by injec- tion, as the coloring matter does not pass into them when animals are fed upon madder, except in the forming state, and as they do not share in the general soft- ening of the bones, in rickets and malacosteum. Blake believed that these vessels did exist, but were difficult to demonstrate, like those that we know to pass in the eye from the capsule of the crystalline lens, to the lens itself; Beclard, that there were no vessels in the bone of the teeth, continuous with those of the pulp, but that the former received continually from the latter a nourishing liquid which penetrated it by imbibition, and that it was situated in regard to the pulp, as the hair and nails to the vascular part of the skin. But the morbid altera- tions which take place in the body of the teeth, the softening and exostosis seen frequently at their roots, and the fusion of the latter occasionally to the bottom of the alveoli, render their vascularity highly probable. The fang of a perfectly developed tooth, is covered closely by a membrane, called its periosteum, which is continuous with the periosteum of the socket, and is on all hands admitted to be vascular ; the internal cavity is also lined by a highly nervous and vascular membrane. Both of these are intimately con- nected with the bony structure of the tooth, and require a little force to separate them. This connection Mr. T. Bell believes to be made by vessels and probably nerves, which pass between them and the bone. Though no artificial injection? has been made of the teeth, this writer has seen them tinged with a bright yel- low in a young woman who died of jaundice ; and where death has taken place from hanging or drowning, when there is usually a congestion of the capillary system, " he has found the osseous part colored with a dull deep red which could not possibly take place if they were devoid of a vascular system ; in both instances the enamel remained wholly free from discoloration." I have observed the same thing in the teeth of subjects who have died of cholera. The existence of nerves in the bony part of the teeth Bell considers manifested by the facts common'y observed by dentists ; in filing the teeth no pain whatever is produced till the. enamel is removed ; but the instant the file begins to act upon the bone, the sensation is exceedingly acute : and when the gums, alveoli and periosteal lining membrane, have receded from the teeth so as to leave the bony part bare, it is exquisitely sensitive when touched with any hard instrument. He admits likewise the existence of absorbents in the bony part of the teeth, for in a tooth in which inflammation had existed for a considerable time, he 10 110 DEVELOPMENT OF THE TEETH. If the pulp which produces them be destroyed from any cause, they lose the little vitality that they may possess, become foreign bodies mechanically retained in the living parts, and sooner or later are thrown off. The teeth are distinguished from the common bony tissue, by the absence of any demonstrable cellular or vascular parenchyma in their composition, by their being in part exposed to the contact of the atmosphere, whiah no bone can be without losing its vitality, by the enamel which covers them externally, by their successive evolution and renovation at certain periods of life, and lastly by their wearing out, and being lost in old age, whilst the vital actions are still going on in the rest of the economy. In many of the lower animals the teeth are evidently a production of the skin or dermoid tissue, which is reflected in at the commencement of the digestive passages, and many modern anatomists have for the reasons above mentioned, con- nected them with the description of the digestive organs. They have, however, again been restored for purposes of convenience to the student, to their proper connexion with the bones in which they are developed. Development of the Teeth. The teeth, as we have before observed, are developed on a principle different from that of other parts of the body, by germs or gemmules. If the jaws of a foetus are examined with care, even at the period of two months* after conception, an extremely soft, jelly-like substance is seen lying in a groove along the edge of each maxillary arch. At the third month it is more consistent, and two plates of bone have sprung up at its sides, which are the rudiments of the external and internal alveo- lar plates. Shortly after this period, the pulpy substance sepa- rates into distinct portions, and rudiments of the transverse plates of the alveoli are seen shooting across, from side to side. These distinct portions of the pulpy substance, have a papillary form and are the germs or rudiments from which the teeth are devel- found after its extraction an abscess in the very centre of the bony structure, communicating with the natural cavity and filled with pus. p. * T. Bell. Beclard. DEVELOPMENT OF THE TEETH. Ill oped ; each is partially enclosed in a sac, and receives branches from the vessels and nerves which run along the bottom of the groove. At the fourth month, the enveloping sac is thick in its texture, and consists of two layers, which are easily separated after a short maceration. Both of these layers, Fox and T. Bell have proved, by their injections, to be vascular:* laying loosely within this double sac is the gelatinous vascular pulp itself, covered by an extremely thin, delicate vascular membrane, (to which it is closely united by vessels,) which secretes the bony part of the tooth, and is a sort of internal periosteum.f The pulp and its membrane receive their vascular and nervous fila- ments from the proper dental vessels and nerves, which run along the groove in the jaw. The double saccular membrane receives its vessels and nerves solely from the gums ; and the only attachment between this and the membrane of the pulp, is near the base of the latter, where the dental vessels enter it. The sac is closely united to the gum, hence if we tear away the gum that covers the jaws, we necessarily bring with it the entire structure of the germ. If at this period, the fourth month, we open the germ, w,e find the pulp presenting exactly the size and shape of the body of the teeth first cut, (incisors) and that its membrane has already commenced the deposit of the bony tip. At birth, ossification will be found to have commenced on all the pulps of the temporary teeth, (the body of the incisors being nearly completed,) and on each of those of the anterior permanent grinders. The commencement of ossification is by three points in the incisors, which form their serrated edges as seen on their first development, by a single point for the canine, two for the bicuspide, and three, four, or five on the * Hunter declared, that the external is soft and spongy, without any vessels; the other much firmer, " and extremely vascular." Blake on the contrary asserts, that the external is spongy and full of vessels, the internal one is more tender and delicate, and seems to contain no vessels capable of containing red blood. f This membrane is called by Bell the proper membrane of the pulp, and was conjectured by Blake, with much probability, to be a "propagation of the peri- osteum of the jaw." Blake on the Teeth, p. 8. 112 THE ENAMEL. large molar, according to the number of processes which they present. Continuous deposition of the bony matter from the membrane of the pulp, unites these points together, and by degrees at different epochs, all the bodies are formed ; the pulp retiring as it were, as the deposition of bone goes on and encroaches upon its cavity, and elongates itself downward, into the shape of the fang. This is finally formed in the same manner as the bodies, and the pulp is completely enclosed in the bony case of the tooth, except at the foramina where the vessels and nerves enter. Where more than one fang exists to a tooth, the lower part of the pulp, is previously divided into an equal number of processes, by little bony partitions which shoot across from the sides of the alveoli. Of the Enamel. When the development of the bony shell has fairly begun, the inner layer of the sac becomes thickened and more vascular, receives a greater amount of blood, becomes closely attached to the neck, and forms a loose capsule over the body. From the internal face of this membrane,* is poured out a thickened whitish granular fluid, called by Mr. Goodin the enamel organ which Berzelius considers of the nature of lactic acid ; this is speedily consolidated into a dark chalky substance, deposited first upon the tips of bone, and gradually extending down in layers till it covers the whole crown of the teeth. This is the enamel. It becomes gradually whiter and harder, as though by a more perfect crystallization, but ^near (o the period at which the teeth are cut,) it is still so soft, as to be frequently cut with the gum lancet. * Blake believed that in man, the enamel was formed solely by the inner membrane of the sac. The external contributing nothing to the structure of the teeth. But in graminivorous animals, where the flinty covering of the food they feed on requires a more perfect grinding apparatus, he thought the external membrane performed an important part, in adding another element to the struc- ture of the molar teeth, called by him, crusta petrosa. The cutting teeth are constructed as those of man. In these animals the enamel of the grinders does not form a continuous smooth layer as in man, but passes a little way into the body of the teeth, and is arranged in the form of vertical layers, between which THE PERMANENT TEETH. 1 13 Of the three membranes of the germ or follicle, one only may be considered as permanent, that of the pulp or internal, which secretes the bone of the tooth. The two outer, or those of the sac, cover the crown -of the tooth ; and as this is pushed forwards by successive depositions of bony matter from within, they are pressed upon and wasted away by absorption, like the gum, in direct proportion with the advancement of the tooth, so that in perfectly natural den- tition, there is little tension or pressure felt. This is called cutting the teeth, a name which expresses the fact, sufficiently well, but literally conveys a wrong idea. In cases of difficult dentition, the membranes of the sac re- tain their density and vascularity, and are probably thickened by inflammation, and the bony layers formed from the pulp, resisted in their advancement by these membranes, make compression upon the pulp and dental nerves ; this, like continued pressure made in other parts of the body, becomes exquisitely painful, and gives rise to distressing sympathetic disturbances. The relief procured by cutting the gums and sac, will be more or less immediate, according to the degree of compression and inflammation of the pulp. The periosteum covering the fangs of the tooth, is a reflected continuation of the periosteum lining the socket, and this again is continuous with that lining the jaw. Of the Permanent Teeth. The adult or permanent teeth, are developed in a manner almost exactly analogous to the deciduous or infantile. The germs of many of them are distinctly perceptible in the gums of the infant at birth. They are placed at first deep in the jaw after the inner membrane of the sac has been removed by absorption, the outer one, according to Bell, deposits the pars petrosa, and fills up the intervening space. This is a substance harder than the bone, but softer than the enamel ; and the advantage derived from it is, that it is worn oft' by trituration more readily than the enamel, so that the latter is constantly maintained in sharp prominent lines upon the surface of the teeth. The same object is here insen- sibly attained, as a natural consequence of the difference in density of these parts, which the miller effects with much labor with his pick-hammer, on the burr-stones of his mill. P. 10* 114 THE PERMANENT TEETff. at the inner side of those of the deciduous teeth, to the sac of which they are attached at top by a neck-like process, as seen in Fig. 25. As the infantile teeth rise up and make their way Fig. 25. through the gum, this process becomes connected with the gum, and forms what is called by Hunter the gubernaculum^. dentis, from its influence in giving the permanent teeth their proper vertical direction, and preventing their making their way at random through the sides, as they do occasionally in cases where the gubernaculum has been destroyed. Delabarre has given the gubernaculum the name of iter dentis, from an erroneous belief that it was tubular, like the duct of a sebaceous follicle, and gradually opened as the tooth progressed. At the fifth month of foetal life, according to Bell, and the eighth and ninth, according to Blake and Fox, the germs of the first permanent molars, may be seen at the outside of the in- fantile row, and those of the permanent incisors behind the deciduous. Fig. 25 1, 2, shows the attachment of the incisor and molar germs of the two sets, just prior to the eruption of the first. The permanent germ is at first placed in the socket of the deciduous tooth, of which it appears, on first view, to be an offshot or gemmiperous production. Its vessels and nerves are believed to be mere branches of those of the deci- duous set. By degrees a distinct socket is formed for it be- hind the latter, and its process or gubernaculum is elongated, as seen in Fig. 25 3. When the deciduous teeth have cut the gum, the two sockets are completely distinct, as seen in Fig. 26, and the gubernaculum is attached to the gum. Ossification first commences in the permanent set on the anterior molares, and may be seen at birth ; at the age of DEVELOPMENT OF THE TEETH. 115 Fig. 26. twelve months, it has progressed to a considerable extent upon these as well as upon the incisors and the lower cuspi- data. At the sixth or seventh year of age the whole of the permanent teeth are more or less ossified, and the incisors are so far completed as to be nearly ready to make their appearance through the gum. At this period there are no less than forty-eight teeth in the two jaws, the twenty deciduous and the twenty-eight permanent, which are in different degrees of development. The last molars do not begin to ossify till the ninth year, and are the last of all to make their appearance through the gum, whence they have received the name of denies sapientm or wisdom teeth. The permanent teeth, which are more in number and individually of larger size and form a larger arch than the temporary, are developed at successive intervals, so as to correspond exactly, with the increasing size of the jaws from the infantile to the adult state. Hence they cannot correspond in position with the deciduous teeth ; the outer permanent incisor will rise up near the cuspidatus, and the permanent cuspidatus near the first molar of the deciduous set. Exactly in proportion as the bodies of the permanent teeth are completed and approach the gum, the roots of the decidu- ous are removed by absorption, till finally the bodies of the latter only are left fixed mechanically in the gum, and are tumbled off at the slightest effort. The process of the removal of the fangs is not perfectly understood ; it is not as was once supposed produced by the pressure of the subjacent tooth, for very frequently the commencement of absorption is at the neck, and not at the root of the tooth, where no pressure can come, and occasionally takes place even where the germ of the permanent tooth has been destroyed. It is more probably owing to the enlarged vessels of the growing permanent teeth, which come from the same branch with those of the deciduous, carrying off all its blood by derivation, which leads to the 116 DEVELOPMENT OF THE TEETH. wasting of the latter set, a process of which we find the analogue in the development of many parts of the foetus. Below is a tabular view of the appearance of the temporary- teeth, and also of the periods at which they are changed for the permanent. It is to be taken, however, as a general rule liable to continual exceptions, not only in regard to the time, but also as to the regular order of appearance. As a general rule, the teeth of the lower jaw appear first, then the corresponding teeth of the upper. Deciduous Teeth. From 5 to 8 months, the four central incisors, " 7 " 10 " four lateral incisors, " 12 " 16 " four anterior rnolares, "14 " 20 " four cuspidati, " 18 " 36 " four posterior molares. Permanent Teeth. The first permanent molares usually pierce the gum before the fall of the central incisors, and their appearance indicates the approaching change. The following are about the medium periods at which they are cut, but there is a great degree of variation in this respect. Those of the lower are here indicated, and they most commonly precede the upper by about two or three months. About 6| years, the anterior molares, " 7 " central incisors, " 8 " lateral incisors, " 9 " anterior bicuspides, " 10 " posterior bicuspides, 11 to 12 " cuspidati, 12 " 13 " second molares, 17 " 19 " third molares or denies sapientice. Fig. 8 *is a side view of a beautiful s of the permanent teeth of both jaws, fitted in their socke' showing the exact manner in which the surfaces of ea^i set are adjusted to each ABERRATIONS OP DENTITION. 117 other, and the smaller dimensions of the fangs of the wisdom teeth, owing to the contracted space in which they are developed. These teeth decay early, are comparatively of little utility, and probably from the same cause ; for in cases, where prior to their development one of the molares in front of them have been removed, they take a more forward position, are developed with larger fangs, and become much more serviceable. When the first teeth have made their appearance through the gum, they are not yet completed ; the process of thickening the body by~ layers from within, and of lengthening the root below, is for a time still continued by the pulp. After their completion, the only physiological changes they undergo, is the wearing down of the bodies by friction, and the filling up of the top of their cavity within by the pulp, with a yellowish bony matter in old age, (cementum,) which prevents the exposure of the cavity, and protects the vasculo-nervous pulp, which is so exquisitely sensitive, as to be considered by some in the light of a nervous ganglion. This latter process unhap- pily is not universal, and is especially defective when the teeth decay early in life, apparently before the period nature has assigned them. * Aberrations of Dentition. Occasionally at birth teeth have been found developed on the surface of the gum, as in the cases of Louis XIV. of France and Richard III. of England : in such cases they are generally mere shells, and are quickly shed, and below exist the double series of germs, which are developed in the regular order. In some rare cases, from the non-existence or disease of the germs, no teeth have ever been developed.* Borelli mentions a case of this sort occurring in a woman then seventy-two years old. Sometimes the temporary teeth only exist, which fall at the regular period and ?s never replaced. Occasionally the set * Oudet. Consid. sur la Nature des Dents et leur Alterations ; Journal Univ. Des Sciences Med. torn. 43, 1826. 113 OS HYOIDES. of permanent teeth have consisted of double or molar teeth all round. Sometimes the appearance of the temporary teeth has been protracted to the sixth or seventh year, and even then followed at regular intervals by the permanent set. The number of the permanent teeth are sometimes less than usual, in consequence of the non-development of the wisdom teeth, which remain locked up in the jaw, and occasionally produce pain, and even abscesses in the 1 bony structure. Sometimes there are supernumerary teeth. Haller has seen in an infant of fourteen years^seventy-two teeth, thirty-six in each jaw, which appeared to depend upon a greater number than usual of the dental germs. Some, fond of the marvelous, have described the eruption of a third set of teeth analogous to the two first: but according to Hudson and others, this appearance has probably been owing to the tardy removal of the deciduous set, and the late supplial of their place by the permanent teeth. "Sometimes the direction of the teeth is vicious, leading into the ramus of the jaw, or upon the outer or inner surface of the gums ; or upon the roof of the mouth. Accidental develop- ments of teeth have likewise been met with in the orbit, the tongue, pharynx, stomach, and not unfrequently in the ovaries and uterus. Os Hyoides. The 05 hyoides is a small insulated bone, supported between the lower jaw and the larynx, by muscles and ligaments, which proceed from the neighboring parts in various directions. The figure of this bone, as its name imports, resembles the Greek letter v. In its natural situation, the central and convex part is anterior, and the lateral portions extend backwards. The central part is called the body, and the lateral portions the cornua. The body is broad and its upper edge bent inwards, so that the external surface is convex, vertically, as well as horizon- tally. On this surface is a horizontal ridge: the muscles which proceed from the lower jaw are generally inserted REGIONS OF THE SKULL. 119 above this ridge, and the muscles from the sternum and scapula below it. The internal or posterior surface of the body is very concave. The cornua, in young subjects, are distinct from the 7 body of the bone, and joined to it by cartilages : near the body of the os hyoides they are flat ; but their figure soon changes, and they terminate on each side in a small tubercle. Fig. .21.* On the upper edge of the bone, where the cornua unite to the body, is a process, equal in size to a small grain of wheat, which has a direction upwards and backwards ; this is called the appendix, or lesser cornu of the os hyoides : from it proceeds a ligament which is attached to the styloid process of the temporal bone, and is sometimes ossified. The basis of the tongue is attached to the os hyoides, and the motions of the bone have a particular reference to those of that organ ; but they will be better understood when the parts with which it is connected have been described. Regions of the Skull. The skull considered as a whole may be divided for the occasional purpose of defining the seats of injuries into four regions. The superior region or vertex, is bounded anteriorly by the frontal eminences ; on each side by the temporal ridges and parietal eminences, and behind by the superior curved line of the occipital bone and occipital protuberance. The anterior region or face as seen in Fig. 28, is somewhat oval in contour, irregular in surface and excavated for the reception of two principal organs of sense, the eye and the nose. It is formed in part by the frontal bones and by the bones of the face. It is bounded above by the frontal protuberances, below by the * The os hyoides seen from before. 1. The anterior convex side of the body. 2. The great cornu of the left side. 3. The lesser cornu of the same side. The cornua were ossified to the body of the bone in the specimen from which the figure was drawn. 120 ORBIT OF THE EYE, chin, and on the sides by the malar bones. If a per- Fig. 28.* pendicular line be drawn down the face from the inner third of the supra-orbital ridge to the inner third of the body of the lower jaw, it will intersect three fora- mina, the supra-orbital, infra- orbital, and mental, each giving passage to one of the facial branches of the fifth nerve, the common seats of facial neu- ralgia. The lateral region or side of the head, comprises the tem- poral and zygomatic fossae and the mastoid portion of the tem- poral bone. The inferior region or base of the skull, is very irregular and presents an internal or cerebral and an external or basilar surface. From the importance of the vessels and nerves which traverse it, this region requires to be particularly studied. An acquaintance with the individual bones which compose the head is princi- pally useful, as it leads to a perfect understanding of the whole structure, of which each bone is but a small part. This structure comprises the cavities which contain the brain and the most important organs of sense, as well as the foramina subservient to them, which are of so much importance in the practice of medicine and surgery, and also in physiology, that the following descriptions are subjoined. Orbit of the Eye. The figure of this cavity is that of a quadrangular pyramid with its angles rounded ; so it resembles a cone, the bottom being the apex and the orifice the base. * A front view of the skull. 1. The anterior portion of the frontal bone. 2. The nasal protuberance. 3. The supra-orbital ridge. 4. The optic foramen. 5. The sphenoidal fissure. 6. The spheno-maxillary fissure. 7. The lachrymal fossa in the lachrymal bones, the commencement of the nasal duct. The figures 4, 5, 6, 7. are within the orbit. 8. The opening of the anterior nares, divided into two parts bythevomer: the number is placed upon the latter. 9. The infra-orbital foramen. 10. The malar bone. 11. The symphysis of the lower ORBIT OF THE EYE. 121 The diameter of the cavity passes obliquely outward from the apex behind. As the figure is irregular, the side next the nose does not partake of this general obliquity, but extends in a straight direction from behind forwards. The orbit is somewhat contracted at its orifice, and enlarged immediately within. The form of the orifice is rather oval, as the transverse diameter is longer than the vertical. Seven bones are concerned in the formation of this cavity ; the os frontis and a portion of the lesser wing of the sphenoid bone above, the os planum of the ethmoid, the os unguis, and the nasal process of the upper maxillary bone, and the os palati below ; the osmalae, and orbitar plate of the sphenoid bone, on the outside. On the upper surface is the depression for the lachrymal gland ; and at the orifice is the notch or foramen for the supra- orbitary vessels, See., which have already been mentioned. On the inner surface are two longitudinal sutures, which connect the os planum and the os unguis to the os frontis above, and the os maxillare below. In the upper suture are the two internal orbitary foramina mentioned in the description of the os frontis, the anterior of which transmits a fibre of the ophthal- mic nerve, with an artery and vein ; the posterior transmits only an artery and vein. There are also two smaller vertical sutures on each side of the os unguis. On the anterior part of this inner surface is the ridge of the os unguis, and the grooves for accommodating the lachrymal sac, which passes into the canal of the same immediately below. On the lower surface is the aforesaid canal, formed by the nasal and orbitar process of the upper maxillary bone, and that part of the os unguis which is anterior to the ridge. On the posterior part of this surface is a groove which proceeds for- wards, and penetrating into the bone, becomes a canal that terminates in the infra-orbitar foramen ; this groove in the bone is made a canal by the periosteum. The thin plate which forms this jaw. 12. The mental foramen. 13. The ramus of the lower jaw. 14. The parietal bone. 15. The coronal suture. 16. The temporal bone. 17. The squa- mous suture. 18. The upper part of the great ala of the sphenoid bone. 19. The commencement of the temporal ridge. 20. The zygoma of the temporal bone, assisting to form the zygomatic arch. 21. The mastoid process. 11 122 CAVITIES OF THE NOSE. surface is the partition between the antrum maxillare and the orbit of the eye, and is more or less absorbed in those cases where polypi of the antrum maxillare occasion a protrusion of the eye. The external surface, formed by the malar bone and the orbitar plate of the sphenoid, is almost flat. In the posterior part of the orbit it is bounded by two large fissures, which are now to be described. In the posterior part of the orbit are three apertures. The optic foramen, the sphenoidal fissure, and the spheno-maxillary fissure. The optic foramen opens almost at the bottom of the orbit on the inside ; its direction is forwards and outwards. The sphenoidal fissure, formed principally by the lesser and greater wings of the sphenoidal bone, begins at the bottom of the orbit, and extends forward, upward, and outward. It is broad at the commencement, and gradually diminishes to a fissure. This fissure opens directly into the cavity of the cranium, and admits the passage of the third, fourth, sixth, and one branch of the fifth pair of nerves, and an artery, and a vein. The spheno-maxillary fissure commences also at the bottom of the orbit, and extends forward, outward, and downward, between the maxillary bone and the orbitar plate of the sphe- noid, from the body of the sphenoid to the malar bone. This fissure opens from the orbit directly into the zygomatic fossa. In the recent subject it is closed, and only transmits the infra-orbi- tary nerve and vessels, and a small branch of the superior maxillary nerve. The Cavities of the Nose. These cavities, which are separated from each other by the septum narium, are contained between the cribriform plate of the ethmoid and the palatine process of the upper maxillary and palate bones, and between the anterior and posterior nares. They are, therefore, of considerable extent in these directions ; but the distance from the septum to the opposite side of the nose is so small, that each cavity is very narrow. The upper surface of each cavity consists of that portion of the cribriform plate of the ethmoid which is between the septum and the cellular portions. Anterior to this, each cavity is CAVITIES OF THE NOSE. 123 bounded by the internal surface of the os nan of its respective side ; and posterior to it, by the anterior surface of the body of the sphenoid bone. These anterior and posterior surfaces form obtuse angles with the upper surface of the nose, and^are im- mediately above the openings called anterior and posterior nares. The anterior surface partakes of the figure of the os nasi ; the upper surface has the perforations of the cribriform plate ; the posterior surface has an opening, equal in diameter to a small quill, that leads into the sphenoid cell, and is also broader than the anterior or superior surface. The internal surface, formed by the septum of the nose, which is composed of the vomer, the nasal plate of the ethmoid, and the cartilaginous plate, is flat, but rather inclined to one side or the other, so as to make a difference in the size of the nasal cavities. Fig. 29.* The external surface is very irregular; it is formed by the cellular portions of the ethmoid; by a small portion of the os unguis ; by the upper maxillary bone ; the os turbinatum infe- rius ; the os palati ; and the internal pterygoid process of the 05 sphenoides. The upper part of this surface is formed by the internal surface of the cellular portions of the ethmoid, * Fig. 29. A longitudinal section of the nasal fossa (taken from Wilson) made to the right side of the vomer, and the bony septum removed in order to exhibit the external wall of the left nasal fossa. 1. Os frontis 2. Os nasi. 3. The cristagalli process of the ethmoid. The groove between fig. 1 &c 3, is the lateral boundary of the foramen caecum. 4. The cribriform plate of the ethmoid. 5. Part of the sphenoidal cells. 6. The basilar portion of the sphenoid bone. Bones 2, 4, & 5. form the superior boundary of the nasal fossa. 7, 7. The articulating surface of the palatine process of the superior maxillary bone. The groove between 7, 7. is the lateral half of the incisive canal, and the dark aperture in the groove the inferior termination of the left naso palatine canal. 8. The nasal spine. 9. The palatine process of the palate bone. a. The superior turbinated bone marked by grooves and apertures for filaments of the olfactory nerve, b. The superior meatus. c. A probe passed into the posterior ethmoidal cells, d. The opening of the sphenoidal cells into the superior meatus. e. The spheno-palatine foramen. /. The middle turbinated bone, g, g. The middle meatus. h. A probe passed into the infundibular canal, leading from the frontal 124 CAVITIES OF THE NOSE. which have been described at page 76. It extends from the sphe- noid bone, very near to theossanasi ; and is uniformly flat and rough. About the middle of it begins a deep groove, which penetrates into the cellular structure of the ethmoides, and passes obliquely downwards and backwards. At the upper end of this groove is the foramen by which the posterior ethmoidal cells communicate with the nasal cavity. This is the upper channel &r meatus of the nose. At the posterior end of it is a large foramen formed by the nasal plate of the os palati and the pterygoid process of the os sphenoides, and therefore called pterygo or spheno-palatine foramen. It opens externally, and transmits a nerve and an artery to the nose. Below the meatus is the upper spongy bone, which presents a convex surface ; its lower edge is rolled up and not connected with the parts about it. This spongy bone covers a foramen in the ethmoid bone, by wbich its anterior cells and the frontal sinuses communicate with the nose. Below this spongy bone is the middle channel, or meatus of 'the nose. The channel extends from the anterior to the poste- rior part of the cavity. It is very deep, as it penetrates to the maxillary bone. The cells of the ethmoid are above it; the inferior turbinated bone below it ; and the upper spongy bone projects over it. In this channel is the opening of the great cavity of the upper maxillary bone. At the anterior extremity of it is a small portion of the os unguis, which intervenes between the nasal process of the upper maxillary bone and the cells of ihe ethmoid, and continues down to the lower spongy bone. The lower spongy bone is nearly horizontal, and very conspi- sinuses and anterior ethmoid cells ; the triangular aperture immediately above the letter is the opening of the maxillary sinus, i. The inferior turbinated bone. Jc, k. The inferior meatus. I, L A probe passing up the nasal duct, showing the direction of that canal. The anterior letters g, /;, are placed on the superio? maxillary bone, the posterior on the palate bone. m. The internal pterygoid plate, n. The hamular process. 0. The external pterygoid plate, p. The situa- tion of the opening of the Eustachian tube. q. The posterior palatine foramina, the letter is placed on the hard palate, r. The roof of the left orbit. 5. The optic foramen, t. The groove for the last turn of the internal carotid artery converted into a foramen by the development of an osseus communication be- tween the anterior and middle clinoid processes, v. The sella turcica. z. The posterior clinoid process. THE CAVITY OF THE CRANIUM. 125 cuous. It extends almost from one opening of the nose to the other. Under this bone is the third and largest channel or infe- rior meatus of the nose. It is made large by an excavation of the upper maxillary bone, particularly at the anterior part. It affords a direct and very easy passage to the posterior opening of the nose and the throat. Near the anterior extremity of this meatus is the lower orifice of the lachrymal duct, which is so situated that a probe properly curved can be readily passed into it through the nostril. There are, then, four foramina on each side, which form com- munications between the cavities of the nose and the adjacent cells, viz. One in the upper meatus, which leads to the posterior ethmoid cells. A second in the middle meatus, which leads to the anterior ethmoid cells and the frontal sinuses. A third in the same meatus, which opens into the maxillary sinus. A fourth in the anterior surface of the body of the sphenoidal bone, which opens into the sphenoidal sinus. To these must be added the opening of the lachrymal canal. It will be moat useful to the student of anatomy, after placing three or four of the uppermost cervical vertebrae in their natural situation, to take a view of The Cavity between the spine and the posterior Nares, which is bounded above, by the cuneiform process, passing obliquely upward and forward ; laterally, by soft parts not yet described ; behind, by the bodies of the cervical vertebrae ; and before, by the posterior nares, each of which is oblong in form, rounded above, flat below, and separated from the other by a thin parti- tion, the vomer. The Cavity of the Cranium. The upper concave surface of this cavity corresponds with the figure of the cranium. The ridge in it for supporting the fal- ciform process of the dura mater, the groove made by the longi- tudinal sinus, the impressions of the arteries, and the pits made by the convolutions of the brain, are particularly to be noticed. 11* 126 THE INTERNAL BASIS OF THE CRANIUM. The Internal Basis of the Cranium Is much more important. It is divided into three fossae on each side ; the anterior of these are most superficial, and the posterior the deepest. The bottoms of the anterior foss& are formed by the orbitar processes of the osfrontis, and consequently are con- vex ; between them is the cribriform plate of the ethmoid, which is commonly sunk below the adjoining surface. The crista galli is very conspicuous ; and the foramen caecum can almost always be seen. The crista galli is evidently the beginning of the pro- minent ridge, which continues on the os frontis, and supports the falx of the dura rnater. The posterior margins of these fossae are formed by the lesser wings of the sphenoid bone. The middle fossa are formed by the great wings of the sphenoidal bone, and by the squamous and petrous portions of the temporal bone. They are lower than the anterior, and higher than the posterior fossae. The projection of the Fig. 30.* margin of the anterior fossae into these cavities, corresponds with the separation between the anterior and middle lobes of the brain. The suture be- tween the sphenoidal and tem- poral bones is evident in these fossae. The upper surface of the body of the sphenoid bone, or the sella turcica is between them ; and all the peculiarities of its surface are very conspi- cuous. The first five foramina of the sphenoidal bone can IK- easily ascertained, and also, the anterior foramen lacerurn and * The cerebral surface of the base of the skull. 1. One side of the anterior fossa j the number is placed on the roof of the orbit, formed by the orbital plate of the frontal bone. 2. The lesser wing of the sphenoid. 3. The crista galli. 4. The foramen caecum. 5. The cribriform lamella of the ethmoid. 6. The processus olivaris. 7. The foramen opticum. 8. The anterior clinoid process. 9. The carotid groove upon the side of the sella Turcica, for the internal carotid artery and cavernous sinus. 10, 11, 12. The middle fossa of the base of the skull. 10. Marks the great ala of the sphenoid. 11. The squamous portion of THE INTERNAL BASIS OF THE CRANIUM. 127 termination of the foramen caroticum, with the impressions made by the carotid arteries on the sides of the sella turcica. The petrous portions of the temporal bones are the posterior boundaries of the middle fossae. Their oblique direction, inwards and forwards, is particularly remarkable; being formed like triangular pyramids. Two of their sides are in the cavity of the cranium ; one, which is anterior, forms a portion of the middle fossa ; and the other forms a part of the posterior fossa. The edge between them is very prominent, and has the tento- rium or horizontal process of the dura mater attached to it. On the anterior surface, in the middle fossa, may be traced the groove, and the foramen for the Vidian nerve. The posterior fossae are larger as well as deeper than the other two. Their boundaries are well defined by the edges of the petrous bones above mentioned, and by the grooves of the horizontal parts of the lateral sinuses. These fossae are nearly separated from the general cavity by the tentorium, which is attached to the edge of the petrous bone and also to the edge of the horizontal part of the groove for the lateral sinuses. On the tentorium lie the posterior lobes of the cerebrum ; and under it, in these fossae, is the cerebellum. These fossae may be considered as one great cavity, which is circular behind, and somewhat angular before. The angular surfaces are formed by the posterior sides of the petrous portions. Between them, is the oblique surface of the cuneiform process of the occipital bone, which descend to the great foramen. On the surface of each petrous bone is the meatus auditorius internus, and the orifice of the aqueduct of the vestibule. Behind the petrous" portion, the groove for the lateral sinus is very conspicu- ous ; it terminates in the posterior foramen lacerum, which is evidently formed by the temporal and the occipital bones. At the temporal bone. 12. The petrous portion of the temporal. 13. The sella Turcica. 14. The basilar portion of the sphenoid bone, surmounted by the pos- terior clinoid processes. 15. The foramen rotundum. 16. 'the foramen ovale. 17. The foramen spinosum ; the small irregular opening between 17 and 12 is the hiatus Fallopii. 18. The posterior fossa of the base of the skull. 19, 19. The groove for the lateral sinus. 20. The ridge upon the occipital bone, which gives attachment to the falx cerebelli. 21. The foramen magnum. 22. The meatus auditorius internus, 23. The jugular foramen. 128 EXTERNAL BASIS OF THE SKULL. the anterior part of this foramen is most commonly a small bony process, which separates the eighth pair of nerves from the internal jugular vein, as they pass out here. The anterior condyloid foramen for the passage of the ninth pair of nerves, appears in the surface of the great occipital hole, immediately below the foramen lacerum. From the back part of this hole the spine, which forms the lower limb of the cross, passes up; and on each side of it are the great depressions which accommodate the two lobes of the cerebellum. External Basis of the Skull. t The external surface of the base of the skull is very irre- gular. When the head is inverted, we see the external protu- berances of the as occipitis, formerly described. The mastoid processes of the ossa temporum are on the same transverse line with the great foramen of the os occipitis ; but the foramen being larger extends farther forward. On the inside of the mastoid process, the fissure for the digastric muscle is very con- spicuous, and also the suture between the mastoid process and the occipital bone. Fig. 31.* The oblique direction of the occipital condyles and the slanting position of their articulating surfaces are particularly striking. The posterior condyloid foramina for the cervical veins, and the anterior for the ninth pair of nerves, are also in view. The position of the cuneiform process of the os occipitis is by no means horizontal, but extends forwards and upwards. The petrous or pyramidal portion of the temporal bone commence? * The external or basilar surface of the base of the skull. 1,1. The hard palate. The figures are placed upon the palate processes of the superior maxil- BASIS OF THE SKULL. 129 between the mastoid process and the condyle of the lower jaw, and extends obliquely forwards and inwards, having the occipital bone behind it, and the glenoid cavity or fossae and the os sphenoides before it. At the commencement, the surface of the petrous portion is not horizontal, but oblique, sloping into the glenoid cavity with a sharp edge downwards. This edge in some cases is curved so as to surround the basis of the styloid process, which arises in contact with it, and projects downwards, on each side of the vertebrae. Between the mastoid and styloid process, is the foramen stylo-mastoi- deum. On the inside of the styloid process, and rather anterior to it, is the foramen lacerum posterius, for the internal jugular vein, the eighth pair of nerves, &tc. This foramen passes obliquely backwards and upwards, and is bounded behind by the jugular process of the os occipitis, which bone seems to contribute most to its formation. Very near to this hole on the inside is the anterior condyloid foramen ; and rather anterior to it is the opening of the carotid canal, which forms a curve in the bone as it passes upwards, inwards, and forwards. From the foramen lacerum posterius, the suture between the cuneiform process of the occipital and the petrous portion of the temporal bone, extends to the foramen lacerum anterius of the base of the cranium ; which is closed by cartilage in the recent subject, but is of an irregular and rather triangular form in the macerated head ; this hole is formed by the occipital, sphenoidal, and petrous bones. The suture or connexion between the petrous bone and the os sphenoides, is lary bones. 2. The incisive, or anterior palatine foramen. 3. The palate pro- cess of the palate hone. The large opening near the figure is the posterior palatine foramen. 4. The palate spine ; the curved line upon which the num- ber rests, is the transverse ridge. 5. The vomer dividing the openings of the posterior nares. 6. The internal pterygoid process. 7. The scaphoid fossa. 8. The external pterygoid plate. The interval between 6 and 8 (left side of the figure), is the pterygoid process. 9. The zygomatic fossa. 10. The basilar process of the occipital bone. 11. The foramen magnum. 12. The foramen ovale. 13. The foramen spinale. 14. the glenoid fossa. 15. The meatus audi- torius externus. 16. The foramen lacerum basis cranii. 17. The carotid fora- men of the left side. 18. The foramen lacerum posterius, or jugular foramen. 19. The styloid process. 20. The stylo-mastoid foramen. 21. The mastoid process. 22. One of the condyles of the occipital bone. 23. The posterior condyloid foramen. 130 BASIS OF THE SKULL. continued on the anterior side of the petrous bone, from the fissure of the glenoid cavity to the anterior foramen lacerum. The styloid process of the os sphenoides, which is seldom more than four lines in length, appears at the edge of this suture. On the inside of the glenoid cavity, and on the inside of this process, in the suture formed between the petrous and sphenoid bones, is the bony orifice of the Eustachian tube. The foramen spinale, for" the middle artery of the dura mater, is at a very small distance from the Eustachian tube, immediately anterior to it ; and at a small distance on the inside and front of this foramen is the foramen ovale, for the inferior maxillary nerve, or the third branch of the fifth pair. Proceeding from before backwards the base of the skull apper- taining to the face is seen to be formed by the palate processes of the superior maxillary and palate bones ; by the vomer ; the pterygoid spinous processes, and part of the body of the sphenoid. The roof of the mouth as seen at 1, 3, Fig. 31, is constituted by the palatine processes of the superior maxillary and palate bones. The transverse suture which separates them is well seen on the left side of the cut. In the longitudinal suture and directly behind the front incisor teeth, 2, is the incisive or anterior palatine foramen, the inferior opening of the naso- palatine canal, which lodges the ganglion of Cloquet (naso- palatine) and transmits the anterior palatine nerves. The posterior palatine foramina, are placed near the posterior angles of the hard palate, for the purpose of transmitting to the palate the blood-vessels and nerves of that name. The opening of the larger foramen is seen near 3, Fig. 31. On the innetf side of this foramen is seen the transverse ridge upon which is inserted the expanded tendon of the tensor palati muscle. The rounded crescentic border, which terminates posteriorly each half of the hard palate, gives attachment to the velum pendu- lum palati ; and in the middle line 4, is seen the palate spine from which is hung the azygos uvuloe muscle. The posterior nares is seen immediately above divided by the vorner, 5, and bounded externally by the internal pterygoid processes, 6. By the side of the shelving base of the vomer and partly formed by it are the pterygo-palatine canals, which transmit the SIDE OF THE HEAD. 131 ptery go-palatine arteries. The external pterygoid process is seen at 8, and between the two processes, is the pterygoid fossa, which is occupied by the internal pterygoid muscle. On the outer side of the external pterygoid process i^ the zygomatic fossa. The internal pterygoid process is long and narrow, having at its apex the hamulus, and at its base the scaphoid fossa from which arises the circumflexus or tensor palati muscle. Side of the Head. Those portions of the side of the head which are formed by the frontal, parietal and occipital bones, and by the squamous part of the temporal, require no explanation here ; but the region which is behind the malar and upper maxillary bone, and within the zygomatic processes of the temporal and malar bones, which comprises part of the temporal and zygomatic fossae of some anatomists, is both important and obscure. To obtain a view of this, the lower jaw should be removed, and the zygoma sawed away, in one preparation ; and in another, the upper maxillary and palate bones of one side should be applied in their natural position, to the os sphenoides, without any of the other bones. The upper part of this region, formed by the sphenoidal, frontal and malar bones, is made concave by the form of the external angular part of the os frontis and of the os malse ; which projects backwards so as to cover a large portion of it. The lower part is formed principally by the external surface of the pterygoid process of the sphenoid bone, and by the posterior surface of the upper maxillary. Between the lower end of the pterygoid process and the upper maxillary bone, a small portion of the os palati intervenes ; but in many adult subjects it is not to be distinguished from the other bones. At this place, the pterygoid process and these bones appear to be in close contact ; but as they pass upwards they recede from each other so as to form a considerable aperture, which continues the whole length of the pterygoid process. This fissure, which may be called pterygo-palatine or pterygo- maxillary, would open into the posterior part of the cavity of 132 THE FORM OF THE CRANIUM. the nose, if the nasal plate of the os palati did not intervene ; this plate forms a partition, which separates the nose from this fissure : and the spheno-palatine foramen, formed principally by it, transmits a nerve and blood-vessels to the nose. The fissure is vertical : at the back of the orbit, it unites with the spheno-maxillary fissure of the orbit, which is almost horizontal, and at the place of their junction, the sphenoidal, or upper fissure of the orbit, opeffs also. The foramen rotundum, which transmits the second branch of the fifth pair, or the upper maxillary nerve, is likewise situated near this place ; and when the upper maxillary, the sphenoidal, and the palate bones are in their natural situation, the distribution of the branches of this important nerve can be easily understood : for the same view presents the course of its various branches ; viz. to the nose, by the spheno-palatine fora- men ; to the cavity of the cranium, by the pterygoid foramen ; to the orbit, and the inferior obitary canal, by the spheno-max- illary fissure ; and to the roof of the mouth, by the palato-max- illary canal. The Form of the Cranium. The form of the cranium is that of an irregular oval. The greatest length of its cavity is between a part of the os frontis above the crista galli, and of the os occipitis above the centre of the crucial ridge. The greatest breadth is at about two-thirds of the distance from the first to the last of these positions. This tranverse diameter touches the sides of the cranium near the posterior part of the basis of the petrous portion of the temporal bone. The difference between these longitudinal and transverse diameters varies greatly in different persons, as their craniums approach to the oval or round figures. The greatest depth of the cavity is between the posterior part of the cuneiform process of the occipital bone, and a part of the cranium which is nearly over it about the middle of the sagittal suture. The figure of the cranium is somewhat varied in different THE FORM OF THE CRANIUM. 133 races of men ; and it has been much changed by the particular management of several savage nations. In North America, the Choctaw tribe of Indians were for- merly accustomed to x make their foreheads perfectly flat, and sloping obliquely backwards. They have latterly disused this practice ; but one of their nation, whose head had this form, was in Philadelphia about the year 1796. At this time a tribe who inhabit a district of country near the sources of the Missouri river, are in the practice of flattening both the frontal and occipital regions of the head ; so that a small part only, of the middle of it, remains of the natural form, between these flattened sloping surfaces. J^ In the case of the Choctaw man above-mentioned, it did not appear that his health, or his intellectual ^operations, were any way affected by this form of his head. During infancy, the cranium sometimes increases to a preter- natural size, as disproportionate to the face as if it were affected by hydrocephalus. In many of these instances, that disease ultimately shows itself; but in other cases, the preter- natural increase of the cranium finally stops without the occur- rence of disease ; and the disproportion is lessened by the increase of the face in the ordinary progress of growth. In many cases where men have deviated from the ordinary stature, the head has preserved the common size. It is therefore said to be small in giants, and large in dwarfs. Many efforts have been made to determine rigorously the dimensions of the cavity of the cranium. This may be done with considerable accuracy from the exterior of the skull, by making allowances for the various degrees of development in which the frontal sinuses are found in different individuals. The thickness of the diploe seldom varies in different skulls more than one or two lines in thickness. I have, however, several negro skulls in my possession the walls of which are nearly three-quarters of an inch in thickness, and so com- pact in their composition as to present very little of the diploic or cellular structure. When measured from the interior, a skull of ordinary capacity will be found in its '" ' '; : < / * rr *^' / ^ ~ *- ' 134 FACIAL AND OCCIPITAL ANGLES. longitudinal diameter, (between the frontal spine and longitudi- nal sulcus,) five inches and a half; in its transverse, (between the bases of the petrous portions of the temporal bones,) four and a half; between the parietal fossae five inches, and between the lesser wings of the sphenoid bones, three inches and three- quarters ; in the vertical, from the foramen magnum to the sagit- tal suture, four inches and a half. Several plans have also bean adopted, by the cranioscopists, to determine the relative development of the cranium (which is filled with the brain) and that of the face. The best known of these are those of Camper, Daubenton and Cuvier. The facial angle of Camper, is taken by extending a horizontal line from the external auditory meatus, on a line with the floor of the nostril, so as to follow nearly in the direction of the base of the cranium, and by dropping upon this a second from the most prominent part of the forehead to the extremity of the upper jaw. The area between them is the facial angle, and will be the more acute, in direct proportion as the face is devel- oped in front, and the forehead is sloped backwards. This angle is of course larger in man than in any other animal, and varies in size in the different races of men. In a well formed white or Caucasian, it is usually about 80; in the Mongolian about 75 ; in Negroes about 70 ; in the different species of monkeys it varies from 65 to 30. As a test of the intellectual capacity of individuals, it is but little to be relied on. The occipital angle of Daubenton, is formed by drawing two lines, one from the inferior border of the orbit, to the anterior margin of the occipital foramen, the other drawn from the anterior to the posterior border of the occipital foramen, and extended forwards. The angle between the two, is the occipital. As the direction of the occipital foramen depends upon the manner in which the head is articulated with the vertebral column, it will be the larger, the less favorably the animal is constructed for the upright posture. In a well-formed Caucasian skull, it is about 3. In the ox it is about 70. Daubenton has thus done for the posterior part of the head what Camper has done for the anterior. HEAD OF THE FffiTUS. 135 Cuvier's method consists in dividing the skull vertically, and establishing a comparison between the area of the cranium and that of the face. In a well-formed Caucasian he finds the area of the cranium, quadruple that of the face. In the Mongolian variety, he found the area of the face had increased over this proportion one-tenth, in the Negro, one-fifth ; in monkeys, one- half. Tiedemann has adopted a plan of measuring the capacities of different crania, by filling them with seeds from the occipital foramen, and subsequently measuring their contents. This method as well as some others, has been employed for the same purpose by Prof. S. G. Morton of this city, in the preparation of his elegant and interesting work on Crania Americana, and the results have been so carefully detailed by him, as to leave hence- forth little to be wished upon a subject which has excited much attention among physiologists. The whole capacity of the cranium is found on an average, greater in the Caucasian variety of the human race, than in any other. The Head of the Foetus. In the foetus, those bones, which form the vault of the cra- nium, originally consist of one plate only ; which is compose^ of radiant fibres. At birth, the os frontis consists of two pieces, which join each other in the middle of the forehead. The parietal bones are each in a single piece ; but they are incomplete at their edges and their angles. The temporal bones have no appearance of mastoid or styloid processes. Instead of a meatus auditorius externus, there is a bony ring in which the membrana tympani is fixed. The squamous and petrous portions, and this ring, are originally formed separate ; but at the period of birth they often adhere to each other. The os occipitis is composed of four pieces : the first and largest, extends from the beginning or angle of the lambdoidal suture to the upper edge of the great occipital foramen. Each side of the foramen, and the condyle on it, is formed by a distinct piece. The front part is formed by the cuneiforrc 136 HEAD OF THE FOETUS. process, which is separate from the other parts and forms the fourth piece. The sphenoidal bone may be separated by maceration into three pieces. The body and the little wings form one piece. Each of the great wings, with the pterygoid processes united to it, forms also a piece. The body of the bone is entirely solid. A large part of the ethmoid 9 is in a cartilaginous state. It is divided into two portions by a partition of cartilage, which occupies the place of the nasal plate and the crista galli. In consequence of the imperfect formation of the bones which compose the vault of the cranium, there are several deficiencies in it. Thus the superior anterior angles of the parietal bones being incomplete, and also the upper angles of the pieces which compose the os frontis, a vacuity with four sides is occasioned, which is termed the Anterior fontanel. This opening may be distinguished by its form, as well as its greater size, from another vacuity which is produced in a similar way at the other end of the sagittal suture, and called the Posterior fontanel: but as there are only three bones con- ce*rned in its formation, viz. the two parietal and the occipital, this vacuity is triangular. Besides these, there are two other vacuities or fontanels on each side, at the two lower corners of each parietal bone : these, however, are much less than those first described. The smaller fontanels do not continue open long ; but the anterior fontanel is seldom completely closed before the end of the third year. It is very obvious upon an examination of the cranium, that the centre of the base is better calculated to resist pressure than any other part; as the cuneiform process of the occipital bone, the petrous portion of the temporal, and the body of the sphe- noidal bone, which compose a large part of it, are very firm and substantial. The face of the fcetus differs very essentially from that of the adult. Although the orbits of the eyes are very large when THE SPINE. 137 compared with the size of the head, that portion of the face which is below them is very small, and has little depth. The upper maxillary bones have no sinuses in them ; and their orbitar plates are not much elevated above the cavities for con- taining the posterior teeth ; in consequence, the depth of the face is very small, and its whole aspect is affected. The nose of the fwtus differs greatly from that of the adult in respect to its sinuses ; for not only are the maxillary cavities wanting, but those of the frontal and sphenoidal bones also. The lower jaw is formed in two pieces, which unite at the middle ; and hence the term symphysis is used in describing the chin. The bone is not only less broad in proportion than that of the adult, but the Angles are more obtuse, and the pro- cesses which arise from them are more sloping. The head of the foetus is much larger in proportion to the body than that of the adult. Of the Trunk. The Trunk consists of the SPINE, THORAX, and PELVIS. The Spine. The spine is the long pile of bones extending from the condyles of the occiput to the end of the os coccygis. It some- what resembles two unequal pyramids joined in a common base. It is not, however, straight; for its upper part being drawn backwards by strong muscles, it gradually advances forwards to support the oesophagus, vessels of the head,.&c. Then it turns backwards, to make room for the heart and lungs. It is next bent forwards to support the viscera of the abdomen. It afterwards turns backwards for the enlargement of the pelvis. ( And, lastly, it is reflected forwards, for sustaining the lowest ' great intestines. The spine is commonly divided into true and false vertebra ; the former constituting the long upper pyramid, which has its base below ; while the false vertebrae make the shorter lower pyramid, whose base is above. 138 Fig. 32. THE VERTEBRAE. True Vertebra. The true vertebra are the twenty-four upper bones of the spine, on which the seve- ral motions of the trunk of our bodies are per- formed. Their name is derived from the Latin verb verier e. Each of these vertebrae is composed of its body and processes. The body is the thick spongy forepart, which is convex before, concave backwards, horizontal and flat in most of them above and below. Numerous small holes, especially on the fore and back part of their surface, giving passage to their vessels, and allow the ligaments to enter their substance. The edges of the body of each vertebra? are covered, especially at the forepart, with a ring of bone firmer and more solid than the substance of the body any where else. These rings seem to be joined to the vertebrae in the form of epiphysis. They are of great use in pre- venting the spongy bodies from being broken in the motions of the trunk. Between the bodies of each two adjoining vertebrae, a substance between the nature of ligament and cartilage is interposed ; which seems to consist of concentrical curved fibres, when it is cut horizontally ; but when it is divided perpendicularly, the fibres appear * The vertebral column consisting of twenty-four true vertebrae ; and two false, the sacrum and os coccygisj each made up by the consolidation of four bones which are separate in the young subject. It extends the whole length of the trunk. It may be divided into four regions the cervical comprising the seven vertebrae from a to b. The dorsal, the twelve vertebrae from b to c. The lumbar, the five vertebrae from c to d. The pelvic, or sacro-coccygeal portion comprising the false vertebrae, the sacrum and coccyx from d to /. From e to /. are the four small bones forming the os coccygis. THE VERTEBRJE. 139 oblique and decussating. The outer part of these intervertebral ligaments is the most solid and hard; and they gradually become softer till they are almost in the form of a glairy liquor in the centre. The external fibrous part of each is capafcle of being greatly extended, and of being compressed into a smaller space, while the middle fluid part is incompressible, or nearly so. The middle point is therefore a fulcrum or pivot, on which the motion of a ball and socket may be made, with such a gradual yielding of the substance of the ligament, in whatever direction our spines are moved, as saves the body from violent shocks, and their dangerous consequences. This ligamento- cartilaginous substance is firmly fixed to the horizontal surfaces of the bodies of the vertebrae, to Connect them ; in which it is assisted by a strong membranous ligament, which lines all their concave surface, and by a still stronger ligament that covers all their anterior convex surface. The elastic substance seems to be in a state of compression by the exterior ligament and the bones ; for, if a section be made through a portion of the vertebrae and the intervertebral substance, this substance will expand, so that its surface will be much higher than that of the vertebrae, h is s_o elastic, and so much confined, in some subjects, that a sharp knife, if plunged into it will be gradually ejected when the hand is with- drawn. The bodies of the vertebrae are, with some exceptions, smaller and more solid above, but more spongy as they descend. The cartilages between them are thick, and the surrounding ligaments are strong in proportion to the size of the vertebrae. By this disposition, the greatest weight is supported on the broadest, best secured base, and the middle of the body is allowed a large and secure motion. From each side of the body of each vertebrae, a bony bridge or pedicle is produced backwards, and to one side ; from the posterior end of which one slanting process rises, and another descends. The smooth, and generally the flattest side of each of these four processes is covered with a smooth cartilage ; and the two lower processes of each upper vertebrae are fitted to 140 THE VERTEBRA. and articulated with the -two upper processes of the vertebrae below, having their articular ligaments fixed into the rough line round their edges. These processes are termed the oblique or articulating. *" From between the oblique processes of each side, another pro- cess extends laterally, which is called the transverse. From the back part of the roots of the two oblique processes, and of the transverse process of* each side, a broad oblique bony plate called the lamella is extended backwards : where these meet, the seventh process of the vertebra takes its rise, and stands out backwards. This being generally sharp-pointed and narrow-edged, it has therefore been called spinous process ; from which this whole chain of bones has got its name. Besides the common ligament which lines all the internal sur- face of the spinous processes as well as of the bodies, particular ligaments connect the bony bridges and processes of the contig- uous vertebrae together. The substance of the processes is considerably stronger and firmer, and has a thicker external plate than the bodies of the vertebrae themselves. The seven processes form a concavity at their forepart, which, joined to the one at the back part of the bodies, make a great hole ; and when the vertebra are placed upon each other in their natural order, these holes form a long tube for containing the spinal marrow. In the upper and lower edge of each lateral bridge or pedicle, there is a notch. These are so adapted to each other in the contiguous vertebras, as to form a round hole in each side, be- tween each two vertebrae, through which the nerves proceed from the spinal marrow, and its blood-vessels pass. The articulations of each two vertebrae are consequently double ; for their bodies are joined by the intervening cartilage above described ; and their oblique processes, being tipped with cartilages, are connected together by ligaments so as to al- low a small degree of motion on every side. Hence, it is evident that their centre of motion is altered in different positions of CERVICAL VERTEBRJE. 141 the trunk : for, when we bow forwards, the weight bears entirely on the bodies of the vertebrae ; if we bend back, the oblique processes support it ; if we recline to one side, we rest upon the oblique processes of that side and part of the boclies ; if we stand erect all the bodies and oblique processes have their share in our support. The true vertebrce are divided into three classes, which agree with each other in their general structure, but are distinguished by several peculiarities. These classes are named Cervical, Dorsal, and Lumbar. The CERVICAL are the seven uppermost vertebrae ; which are distinguished from the rest by these marks : their bodies are smaller and more solid than any others ; and are flattened on the front surface. They are also flat behind, where small processes rise, to which the internal ligaments are fixed. The upper surface of the body of each vertebras is made hollow, by a slanting thin process which is raised on each side. The lower surface is also hollowed, but in a different manner; for here the posterior edge is raised a little, and the anterior one is considerably extended. Hence, the cartilages between these vertebrae are firmly connected, and their articulations are secure. Fig. 33.* These cartilages are thick, especially at their forepart; which is one rea- son why the vertebrae project for- ward as they descend, and have the larger motion. Their oblique processes more justly deserve that name than those of any other vertebrae. They are situated slanting ; the upper ones having their smooth and almost flat surfaces facing obliquely backwards * A central cervical vertebra, seen upon its upper surface. 1. The body concave in its middle, and rising on each side into a slanting thin process or ridge. 2. The lamina or lamella. 3. The pedicle rendered concave by the superior intervertebral notch. 4. The bifid spinous process. 5. The bifid or notched transverse process. 6. The vertebral foramen. 7. The superior oblique or articular process. 8. The inferior oblique or articular process. 142 CERVICAL VERTEBRAE. and upwards ; while the inferior oblique processes have these surfaces facing obliquely forwards and downwards. The transverse processes of these vertebrae are formed in a different manner from those of any other bones of the spine ; for, besides the common transverse process rising from between the oblique processes of each side, there is a second one that comes out from the side of the body of each vertebras ; and these two processes, after leavmg a circular hole for the passage of the vertebral artery and vein, unite and form a groove on their upper surface to protect the nerves that pass in it. They terminate obtusely on each side, for the insertion of the muscles. The spinous processes project backwards almost horizontally. They are shorter than those of any other vertebrae, and are forked or double at their ends ; they therefore allow a more con- venient insertion to muscles. The thick cartilages between the bodies of these cervical vertebrae, the obliquity of their oblique processes, and the shortness and horizontal situation of their spinous processes, all conspire to allow them large motion. The holes between the bony cross bridges, for the passage of the nerves from the spinal marrow, have their largest share formed in the lowest of the two vertebrae, to which they are common. So far most of the cervical vertebrae agree ; but they have some particular differences, which require a separate conside- ration. The first, from its use in supporting the head, has the name of atlas. \ Contrary to all the other vertebrae of the spine, it has no body ; but, instead of it, there is a bony arch. In the convex forepart of this arch a small rising appears ; and on each side of this protuberance, a small cavity may be observed. The upper and lower parts of the arch are rough and unequal, where the ligaments that connect this vertebrae to the os occi- pitis, and to the second vertebra, are fixed. The back part of the arch is concave, smooth, and covered with a cartilage, in a recent subject, to receive the tooth-like process of the second CERVICAL VERTEBRAE. 143 vertebra. On each side of it a small rough sinuosity may be remarked, where the ligaments going to the sides of the tooth- like process of the following vertebra are fastened ; and on each side a small rough protuberance and a depression is observable, where the transverse ligament, which secures the tooth-like process in the sinuosity, is fixed, and hinders that process from injuring the medulla spinalis in the flexions of the head. The atlas has as little spinous process as body; but, instead of it, there is a large bony arch, that the muscles which pass over this vertebra at that place might not be hurt in extending the head. On the posterior and upper part of this arch, there are two depressions, where the recti postici minores muscles take their rise ; and at the lower part are two other sinuosities, into which the ligaments that connect this bone to the following one are fixed. The superior oblique processes, of the atlas are large, and more horizontal than those of any other vertebra. They form an oblong concave surface which has an internal aspect, and corresponds exactly with the articulating surface on the external side of each condyle of the os occipitis. Under the external edge of the posterior part of each of these cavities is the fossa, or deep open channel, in which the vertebral arteries make the circular turn, as they are about to enter the great foramen of the occipital bone, and where the tenth pair of nerves go out. In some subjects, this fossa is covered with bone. The inferior oblique processes, extending from within outwards and down- wards, are large, circular, and slightly concave. So that this vertebra, contrary to the other six, receives the bones with which it is articulated, both above and below. \ The transverse processes of this vertebra are not much hol- lowed or forked ; but are longer and larger than those of any other vertebrae of the neck, for the origin and insertion of several muscles ; and, therefore, those muscles which move this vertebra on the second, have a considerable lever to act with, because of the distance of their insertion from the axis of revolution. The hole for the medulla spinalis is larger in the atlas than 144 CERVICAL VERTEBRA. in any other vertebra, not only on account of the medulla being largest here, but also to prevent its being hurt by the motions of this vertebra on the second. This large hole, and the long transverse processes, make this the brqadest vertebra of the neck. The condyles of the os occipitis move forwards and backwards in the superior oblique processes of this vertebra ; but from the figure of the bones forming these articulations, it is evident that very little motion can here be" allowed to either side ; and there must be still less circular motion. The second vertebra of the neck is called dentata. It is somewhat of a pyramidal figure, being large, and extended down- wards, especially in front, to enter into a hollow of the vertebra below ; while the upper part has a long process, with its extre- mity formed into an obtuse point. This process, from its sup- posed resemblance to a tooth, has given name to the vertebra. The side of it, on which the concave surface of the anterior arch of the first vertebra plays, is convex, smooth, and covered with a cartilage ; and it is of the same form behind, to accom- modate the ligament which is extended transversely from one rough protuberance of the first vertebra to the other, and is cartilaginous in the middle. A ligament likewise goes out in an oblique transverse direction, from each side of the processus dentatus, to be fixed at its other end to the first vertebra, and Fig. 34.* to the occipital bone ; and another liga- ment rises up from near the point of the process to the os occipitis. The superior oblique processes of the vertebra dentata are large, circular, very nearly in a horizontal position, and slightly convex, to be adapted to the inferior oblique processes of the first * A lateral view of the axis or vertebra dentata. 1. The body. 2. The dentated or odontoid process. 3. The smooth surface on the anterior face of the tooth-like or dentated process, which articulates with the posterior face of the anterior arch of the atlas. 4. The lamina. 5. The spinous process. 6. The transverse pro- cess pierced obliquely by the foramen for the vertebral artery. 7. The superior oblique or articular process. 8. The inferior articular process. - CERVICAL' VERTEBRJE. 145 vertebra. The inferior oblique processes of this vertebra answer exactly to the description given of those common to all the cervical vertebrae. The transverse processes of the vertebra dentata are short, very little hollowed at their upper part, and not forked at their ends ; and the canals through which the vertebral arteries pass, are reflected outwards about the middle of each process, so that the course of these vessels may be directed towards the trans- verse processes of the first vertebra. Had this curvature of the arteries been made in a part so movable as the neck is, while they were not defended by a bone and placed in the cavity of that bone, scarce a motion could have been performed without the utmost hazard of compression. This is the third instance, of similar mechanism in cases of sudden curvature of arte- ries. The first is the passage of the carotids through the temporal bones ; and the second is that lately described, where the vertebral arteries turn round the oblique processes of the first vertebra, to come at the great hole of the occipital bone. The spinous process of this vertebra is thick, strong, and short, to give sufficient origin to the musculi recti majores and obliqui inferiores, and to prevent the contusion of the^se and other muscles in pulling the head back. The four cervical vertebras which are next in order have nothing particular in their structure, but agree with the general description. The seventh vertebra approaches the form of those of the back, having the upper and lower surfaces less excavated than the others. The oblique processes are more perpendicular ; and the spinous as well as transverse processes are without bifurcation. After an examination of the condyles of the os occipitis, and of the whole structure of the atlas and vertebra dentata, it will be evident, that the flexion and extension of the head, or its motion backwards and forwards, is effected by the movements of the condyles of the occipital bone on the atlas ; and that in the rotation of the head, the atlas revolves to a certain degree round the processus dentatus of the second vertebra : the head necessarily moving with it. 13 146 DORSAL VERTEBRJE. The TWELVE DORSAL may be distinguished from the other vertebra of the spine by the following marks. Their bodies are of a middle size, between those of the neck and loins. They are more convex before than either of the other two sorts ; and are flattened laterally by the pressure of the ribs, which are inserted into small cavities formed in their sides. This flatness of their sides, which makes the figure of these vertebrae almost a ^ialf oval, is of great use ; as it affords a firm articulation to the ribs, allows the tracheal tube to divide at a small angle, and the other large vessels to run secure from the action of the vital organs. Their bodies are more concave behind than any of the other two classes. The upper and lower surfaces are horizontal. The cartilages interposed between the bodies of these verte- brae are thinner than in any other of the true vertebrae ; and contribute to the concavity of the spine in the thorax, by being thinnest in their forepart. The oblique processes are placed almost perpendicularly : the upper ones slanting but a little forwards, and the lower ones slanting as much backwards. The convexity or concavity is not so remarkable as to require particular notice. Between the oblique processes of opposite sides several sharp processes stand out from the upper and lower parts of the plates which join to form the spinous processes : into these sharp processes strong ligaments are fixed for connecting the vertebrae. The transverse processes of the dorsal vertebrae are long, thicker at their ends than in the middle, and turned obliquely backwards, which may be owing to the pressure of the ribs ; the tubercles of which are inserted into a depression near the end of these processes. The spinous processes are long, small-pointed, and sloping downwards and backwards. From their upper and back part a ridge rises, which is received by a small channel in the forepart of the spinous process immediately above, which is here connected to it by a ligament. The canal for the spinal marrow is here more circular, but corresponding to the size of that chord, is smaller than in any DORSAL VEKTEBRJE. 147 of the other vertebrae; and a larger share of the holes in the Fig. 35.* bony bridges for the transmission of the nerves, is formed in the vertebra above than in the one below. The connexion of the dorsal vertebrae to the ribs, the thinness of their cartilages, the erect situa- tion of the oblique processes, the length, sloping, and connexion of the spinous processes, all contribu- ting to restrain these vertebrae from much motion, which might disturb the actions of the heart and lungs ; and in consequence of the little motion allowed here, the intervertebral cartilages sooner shrivel, by becoming more solid ; and therefore the first remarkable curvature of the spine observed, as people advance to old age, is in the least stretched vertebrae of the back ; or old people first become round-shoul- dered. The bodies of the four uppermost dorsal vertebrae deviate from the rule, that the vertebrae become larger as they descend ; for the first of the four is the largest, and the other three below gradually become smaller, to allow the trachea and large ves- sels to divide at smaller angles. The two uppermost vertebras of the back, instead of being very prominent forwards, are flattened by the action of the musculi longi colli and recti majores. The proportional size of the two little depressions in the body of each vertebra for receiving the heads of the ribs seems to vary in the following manner : the depression on the upper edge of each vertebra decreases as far down as the fourth, and, after that, increases. * A lateral view of a dorsal vertebra. 1. The body. 2. 2. Articular facets for the head of the ribs. 3. The pedicle. 4. The superior intervertebral notch. 5. The inferior intervertebral notch. 6. The spinous process. 7. The extremity of the transverse process marked by an articular surface for the tubercle of the rib. 8. The two superior oblique processes looking backwards. 9. The two inferior oblique processes looking forwards. 148 LUMBAR VERTEBRAE. The transverse processes are longer in each lower vertebra to the seventh or eighth, with their smooth surfaces, for the tubercles of the ribs, facing gradually more downwards ; but afterwards, as they descend, they become shorter, and the smooth surfaces are directed more upwards. The spinous processes of the vertebrse of the back become gradually longer and more slanting from the first, as far down as the eighth or ninth vertet5ra ; from which they manifestly turn shorter and more erect. The first vertebra, besides an oblong hollow in its lower edge that assists in forming the cavity wherein the second rib is received, has the whole cavity for the head of the first rib formed in it. The eleventh often has the whole cavity for the eleventh rib in its body, and wants the smooth surface on each transverse process. The twelfth always receives the whole head of the last rib, and has no smooth surface on its transverse processes, which are very short. The smooth surfaces of its inferior oblique processes face outwards as the lumbar do. In general the upper vertebra of the back lose gradually their resemblance to x those of the neck, and the lower ones approach gradually to the figure of the lurnbar. Fig. 36.* The LUMBAR VERTEBRA are five bones, that may be distin- guished from any others by these marks: 1. Their bodies, though of a circular form at their fore- part, are somewhat oblong from one side to the other. The epiphysis on their edges are larger ; and therefore the upper and lower surfaces of their bodies are more concave than in the vertebrse of the back. * A lateral view of the lumbar vertebra. 1. The body. 2. The pedicle. 3. The superior intervertebral notch. 4. The inferior intervertebral notch. 5. The spinous process. 6. The transverse process. 7. The superior articular processes. 8. The inferior articular processes. I LUMBAR VERTEBRA. 149 The pedicles are very strong, the lamella or laminae, see page 139, are thick and narrow. 2. The cartilages between these vertebra are very thick, and render the spine convex within the abdomen, by their great thickness anteriorly. 3. The oblique processes are strong and deep ; the superior, which are concave, facing inwards, and the convex inferior ones facing outwards ; and therefore each of these vertebrae receives the one above it, and it is received by the one below, which is not so evident in the other two classes already described. 4. Their transverse processes are small, long, and almost horizontal, for allowing large motion to each bone, and sufficient insertion to muscles, and for supporting and defending the internal parts. 5. Between the roots of the superior oblique and transverse processes, a small protuberance may be observed, where some of the muscles that raise the trunk of the body are inserted. 6. Their spinous processes are strong, straight, and horizontal, with broad flat sides, and a narrow edge above and below; this last being depressed on each side, by muscles ; and, at the root of these edges, we see rough surfaces for fixing the ligaments. 7. The medullary canal is larger in these bones than in the dorsal vertebrae. 8. The holes for the passage of the nerves are more equally formed out of both the contiguous vertebrae than in the other classes ; the upper one furnishes, however, the larger share of each hole. The thick cartilages between these lumbar vertebrae, their deep oblique processes, and their erect spinous processes, are all fit for allowing large motion, though it is not so great as what is performed in the neck ; which appears from comparing the arches that the head describes when moving on the neck or the loins only. The lumbar vertebrae, as they descend, have their oblique processes at a great distance from each other, and facing more backward and forwards. The transverse and spinal processes of the first and last lumbar vertebrae are shorter than those in the middle. The epiphyses round the edges of the bodies of the lumbar vertebrae are most raised in the two lowest; which conse- 150 LUMBAR VERTEBRJE. quently make them appear hollower in the middle than the others are. The body of the fifth vertebrae is rather thinner "than that of the fourth. The spinous process of this fifth is smaller, and the oblique processes face more backwards and forwards, than those of any other lumbar vertebrae. In consequence of this particular construction, the spine is capable of flexion, principally in an interior and lateral direc- tion, and also of extension. It ought to be remarked, that during flexion it forms a curve, and not an angle ; for, in the last case, the spinal marrow would be more or less com- pressed. The cervical vertebrae have most motion, and the dorsal the least. This circumstance is fully explained by the form of the different parts of these vertebrae, and the difference in the thick- ness of the intervertebral substance. The necessity of fixing the dorsal vertebrae is very evident: as their motion would greatly interfere with the motion of the ribs in respiration. The lumbar vertebrae have more motion than is commonly supposed ; for, in addition to a certain degree of flexion, they perform a species of rotation or twisting, which is very observa- ble in persons who are diseased in one of their hip joints ; such persons move their whole pelvis, by a rotation of the lumbar vertebrae, to avoid moving the diseased joint. The first cause, the predisposing cause of spinal curvatures is the relative feebleness of the spinal column, compared to the forces exercised upon it, at the same time that the bones, by a premature increase, or by a lesion of nutrition as yet little known, do not acquire the degree of solidity necessary to resist the action of the muscles, and especially the weight of the vis- cera contained in the head and chest. There results from this necessarily a curvature in some direction at one of the points of the lever. The direction of the curvature will be determined by the inequality of the forces brought into play around it. For with- out this inequality, the curvature would be direct ; that is, straight. It has place ordinarily to the left, because FALSE VERTEBRA. 151 the muscles of the right side, stronger than those of the left, draw the vertebra in that direction, as Ludvvig first pointed out. False Vertebra. The lower pyramid or under part of the spine, consists of one large triangular bone, called the os sacrum, and of some small bones, denominated the os coccygis. These bones are called the false vertebrae, because the sacrum in young subjects is composed of five distinct bones, each of which has some resemblance to a vertebra ; but they are com- pletely united in the adult, and form but one bone, which is supposed to have been denominated sacrum, because it was offered in sacrifice by the ancients. The os sacrum is of a triangular form, with its base upwards. It is concave anteriorly, and convex posteriorly. The middle of the bone, when viewed anteriorly, appears to be composed of the bodies of five vertebrae, united to each other, and their union is marked by four transverse lines. At the two extremities of; each of these lines, are large round holes, which communicate \ with the vertebral cavity of the bone. On the exterior sides of these holes the surface is free from any marks of the original separation. The middle of the upper surface, or base of the bone, is formed for articulating with the last lumbar vertebra, and has two oblique t - processes, with a groove in each side, which forms part of the foramen for transmitting the twenty-fourth pair of nerves. The back part of the os sacrum is rough and convex ; in the middle there are commonly three processes similar to the spinous processes of the lumbar vertebrae, and a fourth, which is much smaller. Below this, there is a deficiency of the bony spine, and the vertebral cavity is consequently open behind, but the sides of the canal continue lower down. On each side of the spinous processes are four smaller holes, which are opposite to the larger holes on the anterior surface. Between the spinous processes and the anterior part, which , 152 OS COCCYGIS. Fig. 37.* resembles the bodies of vertebrae, is the continuation of the vertebral cavity which contains the spinal marrow. From the cauda equina, contained in this cavity, the great nerves of the lower extremities pass off} through the large holes on the antwior surface, and some small nerves through the posterior holes. In some bones the spinous pro- cesses are" entirely deficient, and the cavity above mentioned is completely open behind ; but the contained parts are defended by strong membranes. The anterior part of each lateral surface is covered by a plate of cartilage, and articulated to the os ilium. The poste- rior part is rough, and perforated by the fibres of the strong ligaments, which are inserted into it. On the posterior surface of the sacrum, the sides of the open part of the vertebral canal terminate, so as to form a notch through which passes the twenty-ninth pair of nerves. The os sacrum is very spongy, and is lighter in proportion to its bulk than any bone in the body: it is defended by the muscles that cover it, and the ligaments which adhere to it. It is articulated, above, to the last lumbar vertebrae ; below, to the os coccygis by its apex and two cornua ; and on the sides, to the ossa ilia. That triangular chain of bones depending from the os sacrum, in which each bone becomes smaller as it descends, till the last ends in a small tubercle, is called os coccygis. It is convex behind, and concave before ; from which crooked * The sacrum seen upon its anterior surface. 1, 1. The transverse lines marking the original constitution of the bone of four pieces. 2, 2. The anterior sacral foramina. 3. The promontory of the sacrum. 4. The ear-shaped surface which articulates with the ilium. 5. The sharp edge to whjch the sacro-ischiatic ligaments are attached. 6. The vertebral 'articular surface. 7. The broad tri- angular surface which supports the psoas muscle and lumbosacral nerve. 8. The articular process of the right side. 9. The inferior extremity, or apex of the sacrum. 10. One of the sacral cornua. 11. The notch which is converted into a foramen by the coccyx. OS COCCYGIS. 153 pyramidal figure, which was thought to resemble a cuckoo's beak, the name is derived. There are four pieces in people of middle age. In children, they are almost wholly cartilaginous. In old subjects, all the bones are united, and become frequently one continued bone with the os sacrum. The highest of the four bones is the largest, with shoulders extended farther to each side than the end of the os sacrum ; which enlargement may serve as a distinguishing mark to fix the limits of either bone. The upper surface of this bone is a little hollow. From the back of that bulbous part called its shoulders, a process often rises up on each side, to join with the os sacrum. Sometimes these shoulders are joined to the sides of the open end of the vertebral canal, to form the hole in each side common to these two bones, for the passage of the twenty-ninth pair of spinal nerves. Immediately below the shoulders of the os coccygis, a notch may be remarked on each side, where the thirtieth pair of the spinal nerves passes. The lower end of this bone is formed into a small head, which very often is hollow in the middle. The three lower bones gradually become smaller, and are spongy,, but are strengthened by a strong ligament, which covers and connects them. Their ends, by which they are articulated, are formed in the same manner as those of the first bone. Between each of these four bones of young subjects a carti- lage is interposed ; therefore their articulation is analogous to that of the bodies of the vertebrae of the neck ; for the lower end of the os sacrum, and of each of the three superior bones of the os coccygis, has a small depression in the middle ; and the upper part of all the bones of the os coccygis, is a little concave, and, consequently, the interposed cartilages are thick- est in the middle, to fill up both cavities ; by which they connect the bones more firmly. When the cartilages ossify, the upper end of. each bone is formed into a cavity, exactly adapted to the protuberant lower end of the bone immediately above. From this sort of articulation, it is evident that, unless 154 VERTEBRAL CAVITY. when these bones grow together, all of them are capable of motion ; of which the first and second enjoy the largest share. The lower end of the fourth bone terminates in a rough point, to which a cartilage is appended. To the sides of these bones of the os coccygis, the coccygaei muscles, and part of the levatores ani, and of the glutaei maximi, are fixed. The connexions of thes% bones hinder them from being moved to either side ; and their motion backwards and for- wards is much confined : yet, as their ligaments can be stretched by a considerable force, it is of great advantage in the excretion of the faeces alvinae, and much more in child-bearing, that these bones should remain movable ; and the right management of them, in delivering women, is very important. The mobility of the os coccygis diminishing as people advance in age, especially when its ligaments and cartilages have not been kept flexible by being stretched, is, probably, one reason why women, who are advanced in years before they marry, have gen- erally difficult parturition. These bones serve to sustain the intestinum rectum ; and, therefore, are curved forwards ; by which they are preserved, as well as the muscles and teguments, from any injury when sitting with the body inclined back. The Vertebral Cavity for containing the Spinal Marrow. The canal, formed by the foramina of the different vertebrae, when these bones are placed in their natural order, extends from the great occipital foramen to the end of the sacrum. Its direction varies with the different curvatures of the spine, and its figure and diameter are also very different in different places. In the cervical vertebrae, it is largest, and nearly triangular in form ; in the dorsal, it is much smaller and almost cylin- drical ; in the lumbar, it is somewhat enlarged, and approaches again to the triangular figure ; in the sacrum, it is broad, but flat, and diminishes gradually, so as to assume the form of a long triangle. THE RIBS. 155 It has a ligamentous lining, which will be described, when an account is given of the fresh bones and their ligaments. The Thorax. The thorax resembles a flattened cone, cut away obliquely at its basis ; and regularly truncated at its apex. It is formed by the dorsal vertebrae behind, the ribs on the sides, and the sternum before. The Ribs Are long crooked bones, placed in an oblique direction downwards as respects the back-bone. - Their number is gene- rally twelve on each side ; though sometimes eleven or thirteen have been found. They are convex externally, and concave internally. They are made smooth by the action of the contained parts, which, on this account, are in no danger of being hurt by them. The ribs approach towards a round form at their extremities, near the vertebrae. Farther forwards they are flat and broad, and have an upper and lower edge ; each of which is made rough by the action of the intercostal muscles inserted into them. These muscles being all of nearly equal force, and equally stretched in the interstices of the ribs, prevent the broken ends of these bones, in a fracture, from being removed far out of their natural place, to interrupt the motion of the vital organs. The upper edge of the ribs is more obtuse, and rounder than the lower, which is deepened on its internal side by a long fossa, for lodging the intercostal vessels and nerves : on each side of which there is a ridge, to which the intercostal muscles are fixed. The fossa is not observable at the ends of the ribs ; for, at the posterior, or root, the vessels have not yet reached the bones ; and, at .the fore end, they are split away into branches, to serve the parts between the ribs. From this situation of the blood-vessels, has originated the rule adopted by surgeons, that the incision, in cases of empyema, &c., should be made midway between the spine and sternum, and that the lower edge of the upper rib should be avoided. * ' ~ ^ /?' ^/ 156 THE RIBS. Fig. 38.* At the posterior end of each rib, a little head is formed, which is divided by a middle ridge into two flat or hollow surfaces ; the lowest of which is ge- nerally the broadest and deepest. The two surfaces are joined to the bodies of two different vertebrae, and the ridge forces itself into the intervening carti- lages. A little way from this head, we find, on the external surface, a small cavity, where mucilagi- nous glands are lodged ; and round the head, the bone appears spongy, where the capsular ligament of the articulation is fixed. Immediately beyond this, a flattened tubercle rises, with a small cavity at its root, which is surrounded by a roughness, for the articula- tion of the rib with the transverse process of the lowest of the two vertebrae, with which the head of the rib is joined. Advancing farther on this external surface, another smaller tubercle may be observed in most cases, into which ligaments connecting the ribs to each other, and to the transverse pro- cesses of the vertebrae and portions of the longissimus dorsi, are inserted. Beyond this, these bones are made flat by the sacro-lumbalis muscle, which is inserted into the part of this flat surface farthest from the spine, where each rib makes a considerable curve, called by some its angle. Then the rib * An anterior view of the thorax. J . The superior piece of the sternum. 2. The middle piece. 3. The inferior piece, or ensiform cartilage. 4. The first dorsal vertebra. 5. The last dorsal vertebra. 6. The first rib. 7. Its head. 8. Its neck, resting against the transverse process of the first dorsal vertebra. 9. Its tuberosity. 10. The seventh or last true rib. 11. The costal cartilages of the true ribs. 12. The two last false ribs the floating ribs. 13. The groove along the lower border of the rib for the lodgment of the intercostal vessels and nerve. THE RIBS. 157 begins to turn broad, and continues so to its anterior end, which is hollow and spongy, for the reception of, and firm coalition with, the cartilage that runs thence to be inserted into the^ter- num, or to be joined with some other cartilage. In adults, the cavity at this end of the ribs is generally smooth. The substance of the ribs is spongy, cellular, and only covered with a very thin external lamellated surface, which increases in thickness and strength as it approaches the vertebrae. To the fore end of each rib a long, broad, and strong cartilage is fixed, which reaches the sternum, or is joined to the cartilage of the next rib. This course, however, is not in a straight line with the rib : for the cartilages generally make a considerable flexure, the concave part of which is upwards; therefore, at their insertion into the sternum, they make an obtuse angle above, and an acute one below. These cartilages are of such a length as never to allow the ribs to come to a right angle with the spine ; but they keep them situated so obliquely as to make the angle very considerably obtuse above, till a force exceeding the elasticity of the cartilage is applied. These cartilages, as all others, are firmer and harder internally than they are on their external surface ; and, sometimes, in old people, all their middle substance becomes bony, while a thin cartilaginous lamella appears externally. The ossification, however, begins frequently at the external surface. The greatest alternate motions of the cartilages being made at their great curvature, that part remains frequently cartilaginous after all the rest is ossified. The ribs then are articulated at each end, and that behind is doubly joined to the vertebrae ; for the head is received into the cavities of two bodies of the vertebra?, and a larger tubercle is received into the depression in the transverse process of the lower vertebrae. When we examine the double articulation, we must immediately see, that no other motion can here be allowed than upwards and downwards. Since the transverse process hinders the ribs to be thrusted back, the resistance of the sternum on the other side prevents the ribs coming forward ; and each of the two joints, with the other parts attached, oppose its 14 158 THE RIBS. turning round. But then it is likewise as evident, that even the motion upwards and downwards can be but small in any one rib at the articulation itself. But as the ribs advance forwards, the distance from their centre of motion increasing, the motion must be larger ; and it would be very conspicuous at their anterior ends, were they not resisted there by the car- tilages which yield so little, that the principal motion is per- formed by the middle part of the ribs, which turns outwards and upwards, and occasions the twist remarkable in the long ribs at the place near their fore end where they are more resisted. The ribs differ from each other in the following respects : The upper rib is the most crooked ; and as they descend they become straighter. Their obliquity, with respect to the spine, increases as they descend, so that though their distances from each other are nearly equal at their back part, yet at their fore ends the distances between the lower ribs must increase. In consequence of this increased obliquity of the lower ribs, each of their cartilages makes a greater curve in its progress from the rib towards the sternum ; and the tubercles that are articulated to the transverse processes of the vertebrae, have their smooth surfaces gradually facing more upwards. The ribs becoming thus more oblique, while the sternum advances forwards in its descent, makes the distance between the sternum and the anterior end of the lower ribs greater than between the sternum and the ribs above ; consequently, the cartilages of those ribs that are joined to the breast bone are longer in the lower than in the higher ones. These cartilages are placed nearer to each other as the ribs descend, which occasions their curvature to be greater. The length of their ribs increases fromthe first and upper- most rib, as far down as the seventh ; and from that to the twelfth, it gradually diminishes. The superior of the two surfaces, by which the ribs are articulated to the bodies of the vertebras, gradually increases from the first to the fourth rib, and is diminished after that in each lower rib. The distance of their angles from the heads always increases as they THE RIBS. 159 descend to the ninth, because of the greater breadth of the sacro- lumbalis muscle. The ribs are commonly divided into true and false. The true ribs are the seven uppermost of each side. Their cartilages are all gradually longer as they descend, and are joined to the breast bone : so that, being pressed constantly between two bones, they are flattened at both ends ; and are thicker, harder, and more liable to ossify than the other cartilages that are not subject to so much pressure. These bones include the heart and lungs ; and therefore are called true ribs. The five inferior ribs of each side are the false, whose carti- lages do not reach to the sternum ; but on this account having less pressure, their substance is softer. To these five ribs the circular edge of the diaphragm is connected. The first rib of each side is so situated, that the flat sides are above and below, while one edge is placed inwards, and the other outwards, or nearly so ; therefore sufficient space is left above it for the subclavian vessels and the muscles ; and the broad concave surface is opposed to the lungs. But in conse- quence of this situation, the channel for the intercostal vessels is not to be found. The head of this rib is not divided into two plane surfaces by a middle ridge, because it is only articulated with the first vertebra of the thorax. Its cartilage is frequently ossified in adults, and is united to the sternum at right angles. This first rib frequently has a ridge rising near the middle of its posterior edge, where one of the heads of the scalenii muscles rises. Farther forward it is flattened, or sometimes depressed by the clavicle. The position of the second rib is such that its two broad surfaces have oblique aspects, inward and downwards, outwards, and upwards, so as to make the surface of the thorax uniform : and it may be observed of all the ribs, that the aspect of their surfaces is varied upon this principle, according to their situation in the thorax. The sixth, seventh, and eighth ribs have their cartilages nearly contiguous. They are frequently joined to each other by cross cartilages ; and frequently the cartilages of the eighth, 160 THE STERNUM. ninth, and tenth, are connected to the former, and to each other by firm ligaments. The eleventh, and sometimes the tenth rib, has no tubercle for its articulation with the transverse process of the vertebra, to which it is only loosely fixed by ligaments. The fossa, in its lower edge, is not so deep as in the upper ribs ; because the vessels run more towards the interstice between the ribs. Its front end is smaller than its Ibody ; and its short small cartilage is but loosely connected to the cartilage of the rib above. The twelfth rib is the shortest and straightest. Its head is only articulated with the last vertebra of the thorax ; and therefore is not divided into two surfaces. This rib is not joined to the transverse process of the vertebra, and therefore has no tubercle, being often pulled necessarily inwards by the diaphragm, which an articulation with the transverse process would not have allowed. The fossa is not found at its upper edge, because the vessels run below it. The forepart of this rib is smaller than its middle, and has only a very small pointed cartilage fixed to it. To its whole internal side the diaphragm is connected. The Sternum Is the broad flat bone, in the front part of the thorax. In adults it is composed of three pieces, which easily separate after the cartilages connecting them are destroyed. . The two lower pieces are frequently found intimately united ; and very often, in old people, the sternum is a continued bony substance from one end to the other ; though we still observe two, some- times three, transverse lines on its surface ; which are marks of the former divisions. The sternum, considered as one bone, is broadest and thickest above, and smaller as it descends. The internal surface of this bone is somewhat concave for enlarging the thorax : but the convexity on the external surface is not so conspicuous, because the sides are pressed outwards by the true ribs ; the round heads of whose cartilages are received into seven smooth pits, formed in each side of the sternum, and are kept firm there by THE STERNUM. 161 strong ligaments, which, on the external surface, have a par- ticular radiated texture. The pits, at the upper part of the sternum, are at the greatest distance one from another, and as they descend, are nearer ; so that the two lowest are con- tiguous. The substance of the breast bone is cellular, with a very thin external plate, especially on its internal surface, where we may frequently observe a cartilaginous crust spread over it. On both surfaces, however, a strong ligamentous membrane is closely braced ; and the cells of this bone are so small, that a considerable quantity of osseous fibres must be employed in the composition of it. Whence, with the defence which the muscles give it, and the movable support it has from the cartilages, it is sufficiently secured from being broken : for it is strong by its quantity of bone ; its parts are kept together by ligaments ; and it yields enough to elude considerably any violence offered. The three pieces which compose this bone are very different from each other. The first piece resembles a triangle, with the corners cut off. The upper edge of it is thick, and has a regular depression in the middle, to accommodate the trachea. On each side of this depression is a superficial cavity, which, on viewing it trans- versely, from before backwards, appears a little convex. Into these cavities the ends of the clavicles are received. Imme- diately below them, the sides of this bone become thinner ; and in each a superficial cavity, or a rough surface is to be seen, where the first ribs are received or joined to the sternum. In the side of the under end of this first bone, the half of the pit for the second rib on each side is formed. The upper part of the surface behind is covered with a strong ligament, which secures the clavicles ; and is afterwards to be more particularly taken notice of. The second, or middle division of this bone, is much longer, narrower, and thinner, than the first; but, excepting that it is a little narrower above than below, it is nearly uniform in its 14* 162 THE STERNUM. dimensions of breadth or thickness. In the sides of it are com- plete pits for the third, fourth, fifth, and sixth ribs, and one half of the pits for the second and seventh ; the lines, which are marks of the former division of this bone, being extended from the middle of the pits of one side, to the middle of the corresponding pits of the other side. Near its middle an un- ossified part of the bone has sometimes been found ; which, freed of the ligamentous membrane or cartilage that fills it, is described as a hole. When the cartilage between this and the first bone is not ossified, a manifest motion of this upon the first may be observed in respiration ; or in raising the sternum, by pulling the ribs upwards ; or distending the lungs with air, in a recent subject. The third bone is much less than the other two, and has only one half of the pit for the seventh rib formed in it ; where- fore it might be reckoned only an appendix of the sternum. In young subjects it is always cartilaginous, and is better known by the name of cartilago-xiphoides or ensiformis, than any other. This third bone is seldom of the same figure, mag- nitude, or situation, in any two subjects ; for, sometimes, it is triangular ; with one of the angles below, and perpendicular to the middle of the upper side, by which it is connected to the second bone. In other persons, the point is turned to one side ; or obliquely forwards or backwards. Frequently it is nearly of an equal breadth, and often it is bifurcated ; some- times, also, it is unossified in the middle. In the greatest number of adults, it is ossified, and tipped with a cartilage ; in some, one half of it is cartilaginous ; and in others, it is all in a car- tilaginous state. The sternum is joined by cartilages to the seven upper ribs, except when the first coalesce with it. It is also articulated with the clavicles. It contributes to the formation of the cavity of the thorax, and supports the mediastinum. As a movable fulcrum for the ribs, it assists in respiration ; and it affords origin and insertion to several muscles. THE PELVIS. 163 The movement of the Ribs and Sternum in respiration. The ribs and their cartilages are articulated to the spine behind, and the sternum before, in a way which admits of a compound motion. They are drawn from a position which slopes obliquely downwards and forwards, into one which is more horizontal ; and the posterior extremity of each rib, which is the centre of this motion, is moved very little, while the anterior extremity moves much more. At the same time, the ribs perform a rotation outwards, upon their extremities connected with the spine and sternum ; in consequence of which, the middle of each rib is moved out- wards to a considerable extent. It is very obvious, that, by these motions, the thorax must be enlarged from side to side, and from behind forwards. As the ribs are raised from the oblique towards the horizontal position, the sternum is necessarily moved forward by them; and, if this bone does not move upon the first rib, the rib must move to accommodate it : a small motion at the articulation of the rib with the spine, being sufficient to produce considerable motion at the lower end of the sternum. The sternum, there- fore, vibrates forward when the ribs are elevated, and backward when they are depressed. In easy respiration, these motions are not very great, for then the enlargement of the thorax appears to be produced by the increase of its vertical diameter, in consequence of the descent of the diaphragm ; but when the inspirations are very large, and when the descent of the diaphragm is impeded, as in pregnancy, and in a^cites, these motions are very considerable. It ought to be observed, that the first rib has very little motion, except the rotation which favors the motion of the sternum ; and that the lower ribs, having no support at their anterior extremi- ties, have no rotation. The Pelvis. The pelvis is the cavity at the lower part of the trunk, formed by the os sacrum, os coccygis, and ossa innominata. 164 OS ILIUM. The ossa innominata are the two large bones which are con- nected to the sacrum behind, and to each other by the interven- tion of a cartilage in front. Each of the ossa innominata is composed of three portions, in children ; and although these are united in adults, so as to form but one bone,- yet anatomists have generally considered the bone as divided into its original parts, which are denominated os ilium, os ischium, and os pubis. The original separation was at the acetabulurn, or cavity for receiving the head of the os femoris, which is on the outside o{ the os innominatum. The upper and posterior part of this cavity, to the amount of two-fifths, is formed by the os ilium, two-fifths of the inferior portion by the os ischium, and the anterior fifth by the os pubis. The Os Ilium Fig. 39.* Is the largest of the three portions. Its external sur- face has been called its dorsum, and the internal concave surface its costa or venter. The semicircular edge at the upper part of the bone, is named the spine or crest; the external oblique muscle of the abdomen is in- serted into it, and the inter- nal oblique, and the transver- salis arise from it. The ends of the spine are prominent, and therefore are'called pro- * The os innominatura of the right side. 1. The ilium ; its external surface. 2. The ischium. 3. The os pubis. 4. The crest of the ilium. 5. The superior curved line. 6. The inferior curved line. 7. The surface for the glutens maxi- mus. 8. The anterior superior spinous process. 9. The anterior inferior spinous process. 10. The posterior superior spinous process. 11. The posterior inferior spinous process. 12. The spine of the ischium. 13. The great sacro-ischiatic notch. 14. The lesser sacro-ischiatic notch. 15. The tuberosity of the ischiurfij showing its four surfaces. 16. The ramus of the ischium. 17. The body of the os pubis. 18. The ramus of the pubis. OS ILIUM. 165 cesses. In front the crest terminates in the anterior superior spinous process ; below this is another protuberance, called the inferior anterior spinous process ; and the edge of the bone between these two processes is curved. Behind the crest terminates in the posterior superior spinous process ; below this another protuberance is also observable, (post. inf. spin, process) which is applied closely to the os sacrum. Under this is a large notch, which, with the ligaments that pass from the os sacrum to the os ischium, forms a foramen, through which the great sciatic nerve, the pyriform muscle, and some blood-vessels pass. The external surface, or, dorsum, of the os ilium, is greatly undulated by the action of muscles that lie upon it ; the gluteus maximus, on the posterior, and the gluteus medius and minimus, on the anterior parts of it. The lower part of this bone, which contributes to the formation of the acetabulum, is the thickest. The internal surface of the os ilium is concave, and supports some of the intestines. From this concave surface a slight con- cavity is continued obliquely forwards, at the inside of the anterior inferior spinous process, where part of the psoas and iliacus muscles, with the crural vessels and nerves pass. The large concavity is bounded below by a sharp ridge, which runs from behind forwards ; and, being continued with such another ridge of the os pubis, forms a line of partition between the cavities of the abdomen and pelvis. Into this ridge called linea ilia innominata the broad tendon of the psoas parvus is inserted. All the internal surface of the os ilium, behind the continu- ance of this ridge, is very unequal : for the upper part is flat, but spongy, where the sacro-lumbalis and longissimus dorsi rise. Lower down, there is a transverse ridge from which ligaments go out to the os sacrum. Immediately below this ridge, the rough unequal cavities and prominences are placed, which are exactly adapted to those described on the side of the os sacrum. In the same manner, the upper part of this rough surface is porous, for the firmer adhesion of the ligamentous cellular substance ; while the lower part is more solid, and covered with a thin cartilaginous skin, for its immovable arti- 166 OS ISCHIUM. culation with the os sacrum. From all the circumference of this large unequal surface, ligaments are extended to the os sacrum, to secure more firmly the conjunction of these bones. The passages of the medullary vessels are very conspicuous, both in the dorsum and costa of many ossa ilia ; but in others they are inconsiderable. The posterior and lower parts of these bones are thick; but they are generally exceeding!^ thin and compact at their middle, where they are exposed to the actions of the musculi glutaei and iliacus internus, and to the pressure of the bowels contained in the belly. The substance of the ossa ilia is cellu- lar, except a thin external plate. The Os Ischium, Or, hip-bone, is of a middle size, between the two other parts of the os innominatum, and of a very irregular figure. Its extent might be marked by a horizontal line drawn a little below the middle of the acetabulum ; for the upper bulbous part of this bone forms rather less than the lower half of that great cavity, and the small leg of it rises to much the same height on the other side of the great hole common to this bone and the os pubis. From the upper thick part of the os ischium, a sharp process, called by some authors spinousj stands out backwards, from which chiefly the musculus coccygaeus and superior gemellus, and part of the levator ani, rise ; and the anterior, or internal sacro-sciatic ligament is fixed to it. Between the upper part of this ligament and the bones, it was formerly observed, that the pyriform muscle, the posterior crural vessels, and the sciatic nerve, pass out of the pelvis. Immediately below this process, is a depression for the tendon of the obturator internus muscle. In a recent subject, this part of the bone serves as a pulley on which the obturator muscle plays with a ligamentous cartilage. Below the depression of the obturator muscle, is the great knob or tuberosity, covered with cartilage or tendon. The upper part of the tuberosity gives rise to the inferior gemellus os PUBIS. 167 muscle. To a ridge at the inside of this, the external, or pos- terior sacro-sciatic ligament is so fixed, that between it, the internal ligament, and the sinuosity of the os ischium, a passage is left for the internal obturator muscle. The upper thick smooth part of the tnber, called by some its dorsum, has two oblique impressions on it. The inner one gives origin to the long head of the biceps flexor cruris, and semitendinosus muscles ; and the semimembranosus rises from the exterior one, which reaches higher and nearer the acetabulum than the other. The lower, thinner, more scabrous part of the knob, which bends forwards, is also marked with two flat surfaces ; whereof the internal is what we lean upon in sitting, and the external gives rise to the largest head of the triceps adductor femoris. Between the external margin of the tuberosity, and the great hole of the os innominatum, there is frequently an obtuse ridge extended down from the acetabulum, which gives origin to the quadratus femoris. As the tuber advances forwards, it becomes smaller, and is rough for the origin of the musculus transversalis and erector penis. The small leg of it, which mounts upwards to join the os pubis, is rough and prom- inent at its edge, where the two lower heads of the triceps adductor femoris take their rise. The upper and back part of the os ischium is broad and thick ; but its lower and forepart is narrower and thinner. Its substance is of the structure common to broad bones. The os ilium and pubis, of the same sides, are the only bones which are contiguous to the os ischium. The Os Pubis, The least of the three portions of the os innominatum, is placed at the upper and front part of it. The thick, largest part of this bone is employed in forming the acetabulum ; from which, becoming much smaller, it is stretched inwards to its fellow of the other side, where it again grows larger, and forms a surface to be connected with the cartilage of its sym- physis and then sends a small branch downwards to join the 168 os PUBIS. end of the small leg of the os ischium. The upper surface of each os pubis is broad, near its junction with the cartilage of the symphysis ; on the internal edge of this surface begins a ridge, which is continued from it along the os ilium, and forms the division between the cavities of the abdomen and pelvis. This ridge is called crista, and including that on the ilium, forms the linea innominata, or ileo-pectinea. On the anterior and ex- ternal edge of this surface of the pubis, at a small distance from the cartilage, is a prominence or process, called the spine. From this process, another ridge, which is much more obtuse, extends to the acetabulum. The upper surface of the pubis, which is included between these ridges, is concave, for the transmission of the crural vessels and nerve, and the psoas and iliacus internus muscles. Immediately below the lower ridge, and near the acetabu- lum, a winding notch is made, which is comprehended in the great contiguous foramen ; but is formed into a hole in the recent subject by a subtended ligament, for the passage of the posterior crural nerve, and artery, and vein. The internal end of the os pubis is rough and unequal, for the firmer adhesion of the thick ligamentous cartilage that connects it to its fellow of the other side. The process which goes down from that to the os ischium is broad and rough before, where the gracilis and upper heads of the triceps adductor femoris have their origin. The substance of the os pubis is the same as that of other broad bones. Between the os ischium and pubis a very large irregular hole is left, which has been called obturator, thyroid. The whole of this foramen, except the notch for the posterior crural nerve, is filled up, in a recent subject, with a strong ligamentous mem- brane, that adheres very firmly to its circumference. From this membrane chiefly, the two external and internal obturator muscles take their rise. The great design of this hole, besides rendering the bone lighter, is, to allow a strong origin to the obturator muscles, and sufficient space for lodging them ; that there may be no danger of disturbing the functions of the con- ACETABULUM. 169 tained viscera of the pelvis by the actions of the internal ; nor of the external being bruised by the thigh bone, especially by its lesser trochanter, in the motions of the thigh inwards : both which inconveniences must have happened, had the ossa mnom- inata been complete here, and of sufficient thickness and strength, as the fixed point of these muscles. The bowels sometimes make their way through the notch for the vessels at the upper part of this thyroid hole ; and this causes a hernia at this place. The acetabulum is situated near the outside of the great foramen. The margin of this cavity is very high, and is still much more enlarged by the ligamentous cartilage, with which it is tipped in a recent subject; round the base of this margin the bone is rough and unequal, where the capsular ligament of the articulation is fixed. At the upper and back part of the acetabulum the margin is much larger and higher than any where else ; which is very necessary to prevent the head of the femur from slipping out of its cavity at this place, where the whole weight of the body bears upon it, and consequently might otherwise thrust it out. As the margin is extended downwards and forwards, it becomes less ; and, at the internal lower part, is a deficiency in it ; from the one side of which to the other, a ligament is placed in the recent subject, under which a large hole is left. Besides this difference in the height of the margin, the acetabulum is otherwise unequal ; for the lower internal part of it is depressed below the cartilaginous surface of the upper part, and is not covered with cartilage ; into the upper part of this particular depression, where it is deepest, and of a semilunar form, the ligament of the thigh bone, commonly, though improperly called the round one, is inserted : while, in its more superficial lower part, a mass of adipose matter is lodged. The greatest part of this separate depression is formed in the os ischium. The ossa innominati are joined, at their back part, to each side of the os sacrum, by a sort of suture, with a very thin intervening cartilage, which serves to cement these bones together: and strong ligaments go from the circumference of 15 170 CAVITY OF THE PELVIS. this unequal surface to connect them more firmly. They are connected together at their forepart by the ligamentous cartilage interposed between the two ossa pubis, and therefore have no motion in a natural sjate, except what is common to the trunk of the body, or to the os sacrum. Considering the great weight that is supported in our erect posture, by the articulation of the ossa innominati with the os sacrum, there is great reason to think, that, if the conglutinated surfaces of these bones were once separated, (without which the ossa pubis cannot move on each other,) the ligaments would be violently stretched, if not torn. Each os innominatum affords a socket (the acetabulum) for the thigh bones to move in ; and the trunk of the body rolls so much on the heads of the thigh bones as to allow here the most conspicuous motions of the trunk, which are commonly thought to be performed by the bones of the spine. The form of the cavity of the pelvis, at its upper opening, or brim, is somewhat oval ; as a line drawn from one side to the other, is about an inch longer than a line drawn from the back to the front part of it. This margin is well defined by the ridge on the surface of the ossa ilia, and the upper edge of the os pubis ; but the margin of the lower opening is very irregular ; and it ought to be observed, that the dimensions of this opening are made less by the sacro-sciatic ligaments, than they appear upon an examination of the bare bones. In consequence of the oblique position of the sacrum, sloping downwards and backwards, the position of the pelvis is very oblique. A line drawn through the centre of this cavity, perpendicular to the plane of the upper orifice, or brim, would not coincide with the vertical diameter of the cavity of the abdomen, but would pass out of that cavity near the umbilicus. This cavity, and the bones which form it, are different in the two sexes. In women, the brim of the pelvis is wider, and inclines more to the oval form. In men this opening is more circular. CAVITY OF THE PELVIS. 171 The outlet or lower opening of the pelvis is also larger in women. This greater size of the pelvis and its openings, in women, is derived particularly from the following circumstances : The os sacrum is broader, and sometimes straighter than in men. The ossa ilia are flatter, and consequently the ossa ischia are farther apart. The ligamentous cartilage at the symphysis pubis is broader, and shorter. The angle formed by the crura of the ossa pubis with each other, at the symphysis, is much larger. The pelvis, considered as a whole, is very irregular, though symmetrical in its shape. It has the form of a truncated cone, or a funnel with its base upwards, curved from behind forward with its concavity in front, and is bounded both above and below by bony walls of unequal elevation. It is divided by the projection of the base of the sacrum and the two ilio-pectineal lines, into a greater and lesser pelvis, the former of which is above. The dividing line is called the superior strait of the lesser pelvis. The bony walls of the greater pelvis is incom- plete. The boundaries of this cavity, are formed upon the sides by the iliac fossa?, and behind by a notch which is nearly filled up, when the last lumbar vertebrae is left connected with the sacrum ;* and in front by all the wide triangular opening be- tween the anterior superior spine of the ^lium of each side and the symphysis pubis'which is filled up by the lower part of the abdominal muscles. From the flaring direction of the upper part of the ilia, the diameters of the base of this cavity, or that towards the abdomen, is greater than those opposite the ilio- pectineal lines. The lesser pelvis, forms nearly an entire bony canal, and which the student is too apt to consider as constituting the whole pelvis. This cavity is larger at its middle than at its extremities. It is bounded behind by the sacrum and coccyx ; in front by the * The attachment of the lumbar muscles completes this wall behind. j, ,-f? to ^^L^Lr 172 DIMENSIONS OF THE PELVIS. symphysis pubis and a part of the obturator foramen ; and upon the sides, by the bony surface which corresponds to the cotyloid cavity. Its superior margin (superior strait,) is regular and ovoidal in its shape. Its longest diameter is transverse. Its inferior strait is very irregular, though symmetrical in the form of its bony walls ; and in consequence of the posterior walls of this pelvis being of much greater length than the anterior, presents an oblique cut, which faces slightly forwards, so that if its axis was extended downwards, it would cross just above the middle of the thigh. It is bounded behind, by the point of the coccyx ; in front, by the sym- physis pubis ; and on the side, by the tuberosities of the ischium. The sacro-sciatic notches and the arch of the pubis, are filled up by ligaments and soft parts. From the general form of the whole pelvic cavity it will then be obvious, that a body passing through its axis from above downwards, must advance successively in three directions : 1st, as it passes through the greater pelvis, obliquely backwards ; 2d, vertically ; and 3d, as it passes through the inferior strait, obliquely forwards. For obstetrical purposes, it is necessary for the student to have precise notions in regard to the dimensions of the pelvis. To determine this, it is necessary to measure the superior opening of the greater pelvis, and the two straits of the lesser. The pelvis of the male, differs in many respects from that of the female. In the former length predominates, in the latter, breadth. In the female all the diameters of the pelvis are more extensive than those of the male, which is caused by the greater size and outward direction of the iliac fossae, from a less degree of curvature in the iliac crests, and from the roundness of the pubic arch which in the male forms an acute angle. In conse- quence of the wider space which exists between -the cotyloid cavities, the gait of the female is characterized by more lateral rotation or waddling, than that of man. A In a well formed woman, the different measurements are nearly as follows : TRUNK OF THE FOETUS. 173 Greater Pelvis. - In the superior opening of the greater pelvis, we distinguish but two diameters, both transverse. The posterior extended from the middle of one iliac crest to the other, eleven mches. The anterior, between the two anterior superior spinous processes of the ilium, ten inches. From the middle of the iliac crest, to the superior strait, three and a half inches. From the middle of the iliac crest to the tuberosity of the ischium, (whole depth of the pelvis) seven and a half inches nearly.* Lesser Pelvis. Superior Strait, sometimes called ab- Inferior Strait, or perineaL dominal. Inches. Inches. Antero-posUrior diameter, from Antero-posterior diameter, be- the symphysis of the pubis to the tween the symphysis pubis andS promontory of the sacrum, - - 4 front of the coccyx, which may be Transverse, or iliac, which increased near an inch by the mo- crosses the former, at a right bility of the coccyx backwards, 4 angle, ------ 5 Transverse, or ischiatic, from Oblique, from the acetabulum of one tuberosity of the ischium to one side, to the sacro-iliac, articu- the other, ----- 4 Lation of the other, - - - 4.J. Oblique, from the tuberosity of the ischium of one side, to the mid- dle of the great sacro sciatic liga- ment of the other, nearly 4 The height of the posterior wall of the lesser pelvis, formed by the sacrum and coccyx, (of which the latter forms an inch,) is nearly - - 5 inches. Height of the anterior wall formed by the os pubis, 1| " Height of the lateral walls, - - 3J " Thickness of the symphysis pubis, about - \ " Depth or sine of the cavity of the sacrum,f nearly - I " The Trunk of the Fcstus. At birth, each vertebra consists of three pieces, connected by * The depth or length of the pelvis is rather greater in the male than in the female. f Dimensions of the child's head at birth. The long diameter, from the vertex or posterior extremity of the sagittal suture to the chin, 5 1-4 inches ; antero- posterior, from the middle of the frontal bone to the tubercle of the occipital, 4 inches; transverse, from one parietal protuberance to the other, 3 1-2 inches. 15* 174 THE SUPERIOR EXTREMITIES. cartilages, viz. : The body, not perfectly ossified ; and a bone on each side of it, of a form almost rectangular, on which the oblique processes are very distinguishable, and the transverse processes may be ascertained. These bones are so applied to the body, as to include a triangular space for the vertebral cavity. The ends of the longest portions are nearly in contact behind ; but the spinous process is not formed. The atlas is cartilaginous in front, and has only the two late?al portions ossified. The verte- bra dentata consists of four pieces ; for, in addition to the three pieces common to the other vertebrae, the processus dentatus is a distinct portion. The false vertebra, of which the sacrum consists, are each formed of three bones as the true vertebras. The bones of the os coccygis are cartilaginous, except the first, which is partly ossified. The ribs are almost perfect at birth : their heads and tuber- cles covered with cartilage. The necessity of their motion in respiration, immediately after birth, explains this difference be tween them, and most of the other bones of the foetus. The sternum consists of several small bones, surrounded by flat cartilages. Ossification goes on in these cartilages from various points ; and the distinct bones finally unite into the three pieces of which the sternum is finally composed. The ossa innominata, on each side, are formed of three dis- tinct pieces, united at the acetabulum. The spine of the os ilium is cartilaginous ; and the lower part of the bone is not completely ossified. The back part of the os ischium is ossified ; but the portion which forms the acetabulum, the tuber, and the crus, is cartila- ginous. The upper part of the os pubis, and that portion which forms the symphysis, are ossified. The crus, like that of the ischium, is cartilaginous. Of the Superior Extremities. Each superior extremity consists of the SHOULDER, the ARM, the FOREARM, and the HAND. THE CLAVICLE. 175 The shoulder is composed of the clavicle and scapula. It has been supposed by some persons that the two last mentioned bones belong properly to the thorax ; but upon examining the motions of the upper extremity, it will appear that they fdrm an essential part of it : and it is equally evident that they do not contribute to the perfection of the thorax ; they are, therefore, considered as a part of the upper extremity. The Clavicle^ Is the long crooked bone resembling the italic /, which is placed almost horizontally between the upper lateral part of the sternum and the acromion, or most prominent process of the scapula which it keeps off from the trunk of the body. The clavicle, as well as other long bones, is larger at its two ends than in the middle. The end next to the sternum is trian- gular ; the angle behind is considerably protruded, to form a sharp ridge, to which the transverse ligament, extended from one clavicle to the other, is fixed. The side opposite to this is some- what rounded. The middle of this protuberant end is irregularly hollowed, as well as the cavity in the sternum for receiving it : but, in a recent subject, the irregular concavities of both are supplied by a movable cartilage ; which is not only much more closely connected every where, by ligaments, to the circumference of the articulation, than those of the lower jaw are, but it grows to the two bones at both its internal and external end ; its sub- stance at the external end being soft, but very strong, and resembling the intervertebral cartilages. From its internal end, the clavicle, for about two-fifths of its length is bended obliquely forwards. On the upper and front part of this curvature a small ridge is seen, with a plane rough surface before it ; whence the sterno-hyoideus and sterno-mas- toideus muscles have in part their origin. Near the lower angle, a small plane surface is often to be remarked, where the first rib and this bone are contiguous, and are connected by a firm ligament. From this a rough plane surface is extended outwards, where the pectoral muscle has part of its origin. Behind, the bone is made flat and rough by the insertion of the larger 176 THE CLAVICLE. share of the subclavian muscle. The clavicle is then curved backwards, and at first is round ; but it soon after becomes broad and thin ; which shape it retains to its external end. Along the external concavity a rough sinuosity runs ; from which some part of the deltoid muscle takes its rise : opposite to this, on the con- vex edge, a scabrous ridge gives insertion to a share of the trapezius muscle. The upper surface of the clavicle is here flat ; but the lower is hollow, for lodging the beginning of the musculis subclavius ; and towards its back part a tubercle rises ; to which, and to a roughness near it, the strong, short, thick ligament, connecting this bone to the coracoid process of the scapula, is fixed. The external end of this bone is oblong horizontally, smooth, sloping at the posterior side, and tipped in a recent subject with a cartilage, for its articulation with the acromion scapulae. Round this the bone is spongy, for the firmer connexion of the ligaments. The surfaces of contact with this bone, and the scapula are remarkably small, and flat also. The medullary arteries, having their direction obliquely out- wards, enter the clavicles by one or more small passages in the middle of their back part. The substance of this bone is the same as that of the other round long bones. The ligaments which surround the articulation of this bone with the sternum, are so short snd strong, that little motion can be allowed any way ; and the strong ligament that is stretched across the upper forcula of the sternum, from the posterior prominent angle of the one clavicle to the same place of the other clavicle, serves to keep each of these bones more firmly in its place. By the assistance, however, of the movable inter- vening cartilage, the clavicle can move at this articulation, so that the external extremity may be elevated or depressed, and moved backwards and forwards. The whole bone may be moved so as to describe a cone ; of which the end at the sternum is the apex. The movements of the scapula and arm are the objects of THE SCAPULA. 177 these motions of the clavicle ; and the general use of the bone is to regulate the motions of these parts. From the situation, figure, and use of the clavicles, it is evident that they are much exposed to fractures ; that their broken parts must generally pass each other, and that they will be kept in their places with difficulty. The Scapula, Or shoulder-Hade , is the triangular bone situated on the upper and back part of the thorax. The back part of the scapula has Fig. 40.* nothing but the thin ends of the ser/atus anticus major, and sub- scapularis muscles between it and the ribs: but as this bone advances forwards, its distance from the ribs increases. The longest side of this bone is near- est the spine, and has an oblique position as respects it. The up- per or shortest side, called the superior costa of the scapula, is nearly horizontal, and parallel with the second rib. The lower .side, which is named the inferior costa, is extended obliquely from the third to the eighth rib. The situation of this bone, here described, is, as when people are sit- ting or standing, in a state of inactivity, and allowing the mem- bers to remain in the most natural easy posture. The inferior angle of the scapula is very acute ; the upper one is near to a * A posterior view of the scapula. 1. The supra-spinous fossa. 2. The infra- spinous fossa. 3. The superior border. 4. The supra-scapular notch. 5. The anterior or inferior border. 6. The head of the scapula and glenoid cavity. 7. The inferior angle. 8. The neck of the scapula, the ridge opposite the number gives origin to the long head of the triceps. 9. The posterior border or base of the scapula. 10. The spine. 11. The triangular smooth surface, over which the tendon of the trapezius glides. 12. The acromion process. 13. One of the nutritious foramina. 14. The coracoid process. 178 THE SCAPULA. right angle ; and what is called the anterior does not deserve the name, for the two sides do not meet to form an angle. The body of this bone is concave towards the ribs, and convex behind, where it has the name of dorsum. Three processes are generally reckoned to proceed from the scapula. The first is the large spine that rises from its convex surface behind, and divides it unequally. The second process stands out from the forepart of the upper side; and, from its imaginary resemblance to a crow's beak, is named coracoides. The third process is the whole thick bulbous forepart of the bone. Into the oblique space the musculis patientia (levator scapul( At the internal root of this neck is a flat tubercle, into the inner part of which the biceps flexor cubiti is inserted. From this a ridge runs downwards and outwards where thesupinator radii brevis is inserted; and a little below, and behind this ridge, there is a rough scabrous surface, where the pronator radii teres is fixed. The body of the radius is not straight, but curved externally the greater part of its length. Its external surface is rounded ; tne anterior and posterior surfaces are flattened ; and between them is a sharp spine, to which the strong ligament extended between the two bones of the forearm is fixed. On the ante- rior surface, at a distance from its head, nearly equal to one- third the length of the bone, is the orifice of the canal for the medullary vessels, which has a direction obliquely up- wards. Towards the lower end the radius becomes broader and flatter, especially on its forepart, where the pronator quadratus muscle is situated. Its back part, at this end, has a flat strong ridge in the middle, and fossae on each side. In a small groove, ' RADIUS. 189 immediately on the inside of the ridge, the tendon of the extensor of the last joint of the thumb plays. In a large one, inside of this, the tendons of the indicator, and of the common extensor muscles of the fingers pass. On the outside *6f the ridge there is a broad depression, which seems again subdivided, where the two tendons of the extensor carpi radialis are lodged. The external side of this end of the radius is also hollowed by the extensors of the first and second joints of the thumb. The ridges at the sides of the grooves, in which the ten- dons play, have an annular ligament fixed to them, by which the several sheaths for the tendons are formed. The forepart of this end of the radius is also depressed, where the flexors of the fingers and flexor carpi radialis pass. The internal side is formed into a semilunated smooth cavity, lined with a cartilage, for receiving the lower end of the ulna. The lowest part of the radius is formed into an oblong cavity ; in the middle of which is a small transverse rising, gently hollowed, for lodging mucilaginous glands ; while the rising itself is insinuated into the conjunction of the two bones of the wrist that are received into the cavity. The external side of this articulation is defended by a remarkable process of the radius, from which a ligament passes to the wrist ; and this structure resembles that of the styloid process of the ulna with its ligament. The ends of both the- bones of the forearm being thicker than the middle, and the radius being curved, there is a considerable distance between the bodies of these bones ; in the larger part of which a strong, tendinous, but tliin ligament, is extended, to give a sufficient surface for the origin of the numerous fibres of the muscles situated here, that are so much sunk between the bones as to be protected from injuries, to which they would otherwise be exposed. But this ligament is wanting near the upper end ~ of the forearm, where the supinator radii brevis and flexor digi- torum profundus, are immediately connected. As the head of the radius receives the tubercle of the os humeri, it is not only bended and extended along with the ulna, but may be moved almost half round its axis ; and that this 190 THE HAND. motion round its axis may be sufficiently large, the ligament of the articulation is extended farther down than ordinary, on the neck of this bone, before it is connected to it ; and it is very thin at its upper and lower part, but makes a firm ring in the middle. This bone is also joined to the ulna by a double articulation : for above, a tubercle of the radius plays in a socket of the ulna ; whilst below, the radius gives the socket, and the ulna the tubercle. But then the motion performed at the two ends is very different : for, at the upper end, the radius does little more than turn round its axis ; while, at the lower end, it moves nearly half round the cylindrical end of the ulna ; and, as the hand is articulated and firmly connected here with the radius, they must move together. When the palm is turned uppermost, the radius is said to perform supination : when the back of the hand is above, it is said to be prone. But then the quickness and large extent of these two motions are assisted by the ulna, which, as was before observed, can move wilh a kind of small rotation on the sloping sides of the pulley. This rocking motion, though very inconsiderable in the elbow joint itself, is conspicu- ous at the lower end of such a long bone ; and the strong ligament connecting this lower end to the carpus, makes the hand more readily obey these motions. The Hand. The hand comprehends the whole structure, from the end of the radius to the points of the fingers. Its back part is convex, for greater firmness and strength ; and it is concave before, for containing more surely and conveniently such bodies as we take hold of. One half of the hand has an obscure motion in comparison of what the other has ; it serves as a base to the movable half, which can be extended back very little farther than to a straight line with the forearm, but can be considerably bent forwards. The hand consists of the carpus or wrist ; metacarpus, or part adjoining the wrist ; and the fingers, a*mong which the thumb is reckoned. CARPUS. 191 Carpus. No part of the skeleton is more complex than the carpus. The following descrip- tion will, therefore, be of little use to a young student, unless the bones are before him when he is reading it. Great advantage will be derived from examining two sets of carpal bones: each set belonging to the same side. In one of these sets the bones should be connected by their natural ligaments ; but the two rows separated from each other. The bones of the other set should be accurately cleaned; so that their forms and surfaces may be examined. The carpus is composed of eight small bones, arranged in two rows ; one of which rows is attached to the bones of the fore- arm, and the other to the body of the hand. <@ These bones are named from their figure and shall be mentioned in the order in which they occur, beginning with the row next to the forearm ; and with the external bone in each row. They are, Os Scaphoides, Lunare, Cuneiforme, Pisiforme, forming the upper row ; Os Trapezium, Trapezoides, Magnum, and Unciforme, forming the lower row. First Row. Os scaphoides is the largest of the eight, excepting one. It is convex above, concave and oblong below ; from which small resemblance to a boat, it has got its name. Its smooth convex surface is divided by a rough middle fossa, which runs obliquely across it. The upper largest division is articulated with the radius. The common ligament of the joint of the wrist is fixed into the fossa ; and the lower division is joined to the trapezium and trapezoides. The concavity receives more than half of the round head of the os magnum. The internal side of this hollow is formed into a semilunar plane to be articulated with the following bone. The external, posterior, and anterior edges are rough, for fixing the ligaments that connect it to the surrounding bones. Os lunare has a smooth convex upper surface, by which it is articulated with the radius. The external side, which gives the name to the bone, is in the form of a crescent, nad is joined with the scaphoid : the lower surface is hollow, for receiving part of the head of the os magnum. On the inside 192 CARPUS. Fig. 43.* of this cavity is another smooth, but narrow, oblong sinuosity, for receiving the upper end of the unciforme : and on the inside of this a small convexity is found, for its connexion with the os cuneiforme. Between the great convexity above, and * the first deep inferior cavity, there is a rough fossa, in which the circular ligament of the joint of the wrist is fixed. Os cuneiforme is broader above and towards the back of the hand, than it is below and forwards ; which gives it the resem- blance of a wedge. The superior slightly convex surface is included in the joint of the wrist, being opposed to the lower end of the ulna. Below this the cuneiforme bone has a rough fossa, wherein the ligament of the articulation of the wrist is fixed. On the external side of this bone, where it is contiguous to the os lunare, it is smooth, and slightly concave. Its lower surface, where" it is contiguous to the os unciforme, is oblong, somewhat spiral, and concave. Near the middle of its anterior surface, a circular plane appears, where the os pisiforme is sustained. Os pisiforme is almost spherical, except one circular plane, or slightly hollowed surface, which is covered with cartilage for its motion on the cuneiforme bone, from which its whole * A diagram showing the dorsal surface of the bones of the carpus, with their articulations. The right hand. R. The lower end of the radius. U. The lower extremity of the ulna. F. The inter-articular fibro- cartilage attached to the styloid process of the ulna, and to the margin of the articular surface of the radius. S. The scaphoid bone : the numeral (5) indicates the number of bones with which it articulates. L. The semilunare articulating with five bones. C. The cuneiforme, articulating with three bones. P. The pisiforme, articulating with the cuneiforme only. T. The first bone of the second row the trapezium, articulating with four bones. T. The second bone the trapezoides, articulating also with four bones. M. The os magnum, articulating with seven. U. The unciforme, articulating with five. The numerals, 1, 3, 1,2, 1, on the metacarpal bones, refer to the number of their articulations with the carpal bones. CARPUS. 193 rough body is prominent forwards into the palm ; having the tendon of the flexor carpi ulnaris, and a ligament from the styloid process of the ulna fixed to its tipper part ; the trans- verse ligament of the wrist is connected to its externaFside : ligaments extended to the unciforme bone, and to the os metacarpi of the little finger, are attached to its lower part ; the abductor minimi digiti has its origin from its forepart ; and, at the external side of it, a small depression is formed for the psssage of the ulnar nerve. Second Row. Os Trapezium has four unequal sides and angles in its back part, from which it has got its name. Above, its surface is smooth, slightly hollowed, and semicircular, for its conjunction with the os scaphoides. Its internal side is an oblong concave square, for receiving the following bone. The inferior surface is formed into a pulley, which faces obliquely outwards and downwards when the palm presents forward. On this pulley the first bone of , the thumb is moved. At the internal side of the pulley, a small oblong smooth surface is formed by the os metacarpi indicis. The forepart of the trapezium is prominent in the palm, and near to the in- ternal side has a sinuosity in it, where the tendon of the flexor carpi radialis is lodged, on the ligamentous sheath of which the tendon of the flexor longus pollicis manus plays : near this the bone is scabrous, where the transverse ligament of the wrist is connected, the abductor and the flexor brevis pollicis have their origin, and ligaments go out to the first of the thumb. Os trapezoides, so called from the irregular quadrangular figure of its back part, is the smallest bone of the wrist, except the pisiforme. The figure of it is an irregular cube. It has a small hollow surface above, by which it joins the scaphoides ; a long convex one externally, where it is contiguous to the trapezium ; a small internal concavity, for its conjunction with the os magnum ; and an inferior convex surface, the edges of which are, however, so raised before and behind, that 17 194 CARPUS. a sort of pulley is formed, where it sustains the os metacarpi indicis. Os magnum, so called because it is the largest bone of the carpus, is oblong, having four quadrangular sides, with a round upper end, and a triangular plane one below. The round head is divided by a small rising, opposite to the connexion of the os scaphoides and lunare, which together form the cavity for receiving it. On the outside a short plane surface joins the os magnum to the trapezoides. On the inside is a long narrow concave surface where it is contiguous to the os unciforme. The lower end, which sustains the metacarpal bone of the middle finger, is triangular, slightly hollowed, and farther advanced on the external side than on the internal, having a considerable oblong depression made on the advanced outside by the metacarpal bone of the fore-finger ; and generally there is a small mark of the os metacarpi digiti annularis on its inter- nal side. Os unciforme has got its name from a thin broad process that stands out from it forwards into the palr% and is hollow, for affording passage to the tendons of the flexors of the fingers. To this process, also, the transverse ligament is fixed that binds down, and defends these tendons ; and. the flexor and abductor muscles of the little finger have part of their origin from it. The upper plane surface is small, convex, and joined with the os lunare : the external side is long and slightly convex, adapted to the contiguous os magnum. The internal surface is oblique, and irregularly convex, to be articulated with the cuneiforme bone. The lower end is divided into two concave surfaces; the internal is joined with the metacarpal bone of the little finger; and the external one is fitted to the metacarpal bone of the ring finger. The nature of the carpus will be best understood by studying the bones placed together, in their natural order, in the two rows. When thus placed, they compose a structure of an oblong form, whose greatest length extends across the wrist, and forms a concavity in front, while it is convex posteriorly. CARPUS. 195 Fig. 44.* Two bones of the first row, viz., the scaphoides and lunare, form an oblong convex surface, which has a transverse position with respect to the arm, and applies to the concave surface at the end of the radius. These surfaces are particularly calculated for flexion and extension, and also for a considerable motion to each side ; and by a suc- cession of these flexures, in different directions, the hand performs a cir- cular motion, although it cannot perform at this joint a rotation, or revolution, on the axis of the car- pus. The under surface of the bones has a deep concavity, which is composed by the scaphoides, lunare and cuneiforme, and receives a prominence of the second row. It also presents a convex surface, formed by the scaphoides, which is received by the second row. The upper surface of the second row, which is concerned in this articulation, is very irregular ; it has a head formed by the magnum and unciforme, which penetrates deeply into the cavity of the first row. On the outside of this head the tra- pezium and trapezoides form a surface, which receives the projecting part of the scaphoides ; so that the first row receives, and is received by the second, and the two surfaces are well calculated for moving, to a certain extent, in the way of flexion and extension, upon each other. I The lower surface of the second row, which is connected to * The hand viewed upon its anterior or palmer aspect. 1. The scaphoid bone. 2. The semilunare. 3. The cuneiforme. 4. The pisiforme. 5. The trapezium. 6. The groove in the trapezium that lodges the tendon of the flexor carpi radialis. 7. The trapezoides. 8. The os magnum. 9. The unciforme. 10, 10. The five metacarpal bones. 11, 11. The first row of phalanges. 12, 12. The second row. 13, 13. The third row, or ungual phalanges. 14. The first phalanx & the thumb. 15. The second and last phalanx of the thumb. 196 THE METACARPUS. the metacarpal bones, appears like the side of an arch, which is partly induced by the wedge-like form of the two bones in the centre ; viz., the trapezoides, and the magnum. When the hand hangs by the side, and the palm is forward, all of this surface presents downwards, except that portion of it which is formed by the trapezium. This bone is placed obliquely between the two rows, and its gurface for supporting the thumb presents obliquely downwards and outwards. The trapezoides supports the fore-finger, the magnum the middle finger. The scaphoides and the trapezium are very prominent at the external side of the anterior concave surface of the car- pus ; and the unciforme process, and the os pisiforme on the internal. The Metacarpus, Consists of four bones, which sustain the finger. Each bone is long and round, with its ends larger than its body. The upper end, which some call the base, is flat and oblong, in- clining somewhat to the wedge-like form, without any con- siderable head or cavity ; but it is, however, somewhat hollowed for the articulation with the carpus. It is made flat and smooth on the sides where these bones are contiguous to each other. Their bodies are flattened on the back part, particularly below the middle, by tendons of the extensors of the fingers. The anterior surface of these bodies is a little convex, especially in their middle ; along which a sharp ridge stands out, separating the musculi interossei placed on each side of these bones, which are there made flat and plain by these muscles. Their lower ends are raised into large oblong smooth heads, whose greatest extent is forwards from the axis of the bone. At the forepart of each side of the root of these heads, one or two tubercles stand out, for fixing the ligaments that go from one metacarpal bone to another, to preserve them from being drawn asunder. Around the heads a rough ring may be THE METACARPUS, 197 remarked, for the capsular ligaments of the first joints of the fingers to be fixed to ; and both sides of these heads are flat, by pressing on each other. s The substance of the metacarpal bones is the same with that of all long bones. The metacarpal bones are joined above to the bones of the carpus, and to each other by surfaces almost flat. These con- nexions do not admit of much motion. The articulation of the round heads, at their lower ends, with the cavities of the first bones of the fingers, will soon be described. The concavity on the forepart of the metacarpal bones, and the position of their basis on the arched carpus, cause them to form a hollow in the palm of the hand, which is often useful to us. The spaces between them lodge muscles, and their small motion makes them fit supporters for the fingers to play on. Though the ossa metacarpi so far agree, yet they may be dis- tinguished from each other by the following marks : The metacarpal bone of the fore-finger is generally the longest. Its base, which is articulated with the os trapezoides, is hollow in the middle. The small ridge on the external side of this oblong cavity is smaller than the one opposite to it, and is made flat on the side by the trapezium. The internal ridge is also smooth, and flat on its ulnar side, for its conjunction with the os magnum ; immediately below which, a semicircular smooth flat surface shows the articulation of this to the second metacarpal bone. The back part of this base is flattened where the long head of the extensor carpi radialis is inserted, and its forepart is prominent where the tendon of the flexor carpi radialis is fixed. The tubercle at the internal root of its head is larger than the external. Its base is so firmly fixed to the bone it is connected with, that it has no motion. The metacarpal bone of the middle finger is generally the second in length ; but often it is as long as the former : some- times it is longer ; and it frequently appears only to equal the first by the os magnum being farther projected downwards than any other bone of the wrist. Its base is a broad super- 17* 198 THE METACARPUS. ficial cavity, slanting inwards ; the external posterior angle of which is so prominent, as to have the appearance of a process. The external side of this base is made plane in the same way as the external side of the former bone, while its internal side has two hollow circular surfaces, for joining the third metacarpal bone ; and between these surfaces there is a rough fossa, for the adhesion of a ligament, and lodging mucilaginous glands. The extensor carpi radialis brevior is inserted into the back part of this base. The two sides of this bone are almost equally flat- tened ; but the ridge on the forepart of the body inclines inwards. The tubercles at the forepart of the root of the head are equal. The motion of this bone is very little more than that of the former ; and therefore these two firmly resist bodies pressed against them by the thumb or fingers, or both. The metacarpal bone of the ring finger is shorter than the second metacarpal bone. Its base is semicircular and convex, for its conjunction with the os unciforme. On its external side are two smooth convexities, and a middle fossa, adapted to the second metacarpal bone. The internal side has a triangular smooth concave surface to join it with the fourth one. The anterior ridge of its body is situated more to the inside than to the outside. The tubercles near the head are equal. The mo- tion of this third metacarpal bone is greater than the motion of the second. The metacarpal bone of the little finger is the smallest and sharpest. Its base is irregularly convex, and rises slanting inwards. Its external side is exactly adapted to the third meta- carpal bone. The internal has no smooth surface, because it is not contiguous to any other bone ; but it is prorninent where the extensor carpi ulnaris is inserted. As this metacarpal bone is furnished with a proper moving muscle, has the plainest articu- lation, is most loosely connected and least confined, it not only enjoys a much larger motion than any of the rest, but draws the third bone with it, when the palm of the hand is to be made hollow by its advancement forwards, and by the prominence of the thumb opposite to it. THUMB AND FINGERS. 199 Thumb and Fingers. The thumb and fore-fingers are each composed o three bones. The THUMB is situated obliquely in respect to the fingers ; neither opposite directly to them, nor in the same plane with them. All its bones are much thicker and stronger in proportion to their length, than the bones of the fingers are ; which is extremely necessary, as the thumb counteracts all the fingers. The first bone of the thumb has its base adapted to the pecu- liar articulating surface of the trapezium : for, in viewing it from one side to the other, it appears convex in the middle ; but, when viewed from behind forwards, it is concave there. The edge at the forepart of this base is extended farther than any other part ; and round the back part of the base a rough fossa may be seen, for the connexion of the ligaments of this joint. The body and head of this bone are of the same shape as the ossa metacarpi ; only that the body is shorter, the head flatter, and tubercles at the forepart of its root larger. The articulation of the upper end of this bone is remarkable ; for, though it has protuberances and depressions adapted to the double pulley of the trapezium, yet it enjoys a circular motion, as the joints do where a round head of the one plays in the orbicular socket of another ; it is, however, more confined, and less expeditious, but stronger and more secure than such joints generally are. The second bone of the thumb has a large base formed into an oblong cavity, whose greatest length is from one side to the other. Round it several tubercles may be remarked, for the insertion of ligaments. Its body is convex, or half round behind ; but flat before, for lodging the tendon of the long flexor, of the thumb, which is tied down by ligamentous sheaths, that are fixed on each side to the angle at the edge of this flat surface. The lower end of this second bone has two lateral round protu- berances, and a middle cavity, whose greatest extent of smooth surface is forwards and backwards. 200 FINGERS. The articulation of the upper end of this second bone would seem calculated for motion in all directions ; yet, on account of the strength of its lateral ligaments, the oblong figure of the joint itself, and mobility of the first joint, it only allows flexion and extension ; and these are generally much confined. The third bone of the thumb is the smallest, with a larse base, / O * whose greatest extent is from oj?e side to the other. This base is formed into two cavities and a middle protuberance, to be adapted to the pulley of the former bone. This bone becomes gradually smaller, till near the lower end, where it is a little enlarged, and has an oval scabrous edge. Its body is rounded behind, but is flatter than in the former bone, for sustaining the nail. It is flat and rough before, by the insertion of the flexor longus pollicis. The motion of this third bone is confined to flexion and extension. The regular arrangement of the bones of the FINGERS in three rows, has obtained for them the name of the three phalanges. All of them have half round convex surfaces, covered with an aponeurosis, formed by the tendons of the extensors, lumbri- cales, and interossei, and placed directly backwards, for their greater strength ; and their flat concave part is forwards, for taking hold more surely, and for lodging the tendons of the flexor muscles. The ligaments for keeping down these tendons are fixed to the angles that are between the convex and concave sides. The bones of the first phalanx of the fingers answer to the description of the second bone of the thumb ; only that the cavity in their base is not so oblong ; nor is their motion on the metacarpal bones so much confined ; for they can move laterally or circularly, the fore-finger in particular, but have no rotation, or a very small degree of it, round their axis. The second bone of the fingers has its base formed into two lateral cavities, and a middle protuberance : while the lower end has two lateral protuberances, and a middle cavity : there- fore, it is joined at both ends in the same manner ; which none of the bones of the thumb are. THE THIGH. 201 The third bone differs in nothing from the description of the third bone of the thumb, except in the general distinguishing marks ; and, therefore, the second and third phalanx -6f the fingers enjoy only flexion and extension. All the difference of the phalanges of the several fingers consists in their magnitude. The bones of the middle finger being the longest ancf largest ; those of the fore-finger come next to these in thickness, but not in length, for those of the ring finger are a little longer. The little finger has the smallest bones. This disposition is the best contrivance for holding the largest bodies ; because the longest fingers are applied to the middle largest periphery of such substances as are of a spherical figure. The Inferior Extremities. The inferior extremities consist of the THIGH, LEG, and FOOT. The Thigh Consists of one bone only ; the os femoriSj which is very strong, and larger than any other in the skeleton. It is nearly cylindrical in the middle, and slightly curved. The upper extremity is a spherical head, connected to the body of the bone by a neck. The lower extremity is much larger than the body, and is formed into two condyles. The upper end of this bone is not continued in a straight line with the body of it, but the axis of it inclines obliquely inwards and upwards, whereby the distance between these two bones, at their upper part, is considerably increased. The head is the greater portion of a sphere. Towards its lower internal part, a round, rough spongy pit is observable, where the strong ligament, commonly, but inaccurately, called the round one, is fixed, to be extended from thence to the lower internal part of the receiving cavity, where it is considerably broader than near to the head of the thigh bone. The neck of the os femoris has a great many large holes, into which the fibres of the strong 202 THE THIGH. ligament, continued from the capsular, enter, and are thereby firmly united to it ; and round the root of the neck, where it rises from the bone, a rough ridge is found, where the capsular Fig. 45.* ligament of the articulation itself is con- nected. Below this root, a large unequal protuberance, called trochanter major, stands out ;. the external convex part of which is distinguished into three different surfaces; whereof the one on the upper and front part is scabrous and rough, for the insertion of the glutaeus minimus ; the supe- rior one is smooth, and has the glutaeus medius inserted into it ; and the one behind is made flat and smooth, by the tendon of the glutaeus maximus passing over it. The upper edge of this process is sharp and pointed at its back part, where the glutaeus medius is fixed ; but forwards it is more obtuse, and under it is a depression, into which some of the muscles, which rotate the thigh outwards, are fixed. From the posterior prominent part of this great tro- chanter, a rough ridge runs backwards and downwards, into which the quadratus is inserted. In the deep hollow, at the inter- nal upper side of this ridge, the obturator externus is implanted. More internally, a conical process, called trochanter minor, rises, for the insertion of the musculus psoas and iliacus internus ; and the pectineus is implanted into a rough hollow, below its internal root. The muscles inserted into these processes being the principal instruments of the * The right femor, seen upon the anterior aspect. I. The shaft. 2. The head. 3. The neck. 4. The great trochanter. 5. The anterior intertrochanteric line. 6. The lesser trochanter. 7. The external condyle. 8. The internal condyle. 9. The tuberosity for the attachment of the external lateral ligaments. 10. The groove for the tendon of origin of the popliteus muscle. 11. The tuberosity for the attachment of the internal lateral ligament. OS FEMORIS. 203 y rotary motion of the thigh, have occasioned the name of trochan- ters to be given to these processes. The body of the os femoris is convex on the forepart and concave behind, which enables us to sit without leaning too much on the posterior muscles. On the posterior concave surface is a broad rough ridge called lima aspera, which commences near the great trochanter, and continues downwards, more than two-thirds of the length of the bone, when it divides into two ridges, which descend towards each condyle. The internal of these ridges is the most smooth, and the space between them is nearly flat. Near the end of each of these ridges, a small, smooth-protuberance may often be remarked, where the two heads of the external gastroc- nemius muscles take their rise ; and from the forepart of the internal tubercle, a strong ligament is extended to the inside of the tibia. The lower end of the os femoris is larger than any other part of it, and is formed into two great protuberances, one on each side, which are called its condyles : between them a considerable cavity is found, especially at the back part, in which the crural vessels and nerves lie. The internal condyle is longer than the external, which must happen from the oblique position of this bone, to give less obliquity to the leg. These processes are of an oblong form, and are placed obliquely with respect to each other ; being in contact before and separated to a considerable distance behind. They form in front a smooth pulley-like surface, the external side of which is highest, on which the patella moves. Below, they are flat ; and posteriorly, they are regularly convex. Between these convex portions is a rough cavity, from which the crucial ligament arises, to be attached to the tibia. Round the lower end of the thigh bone, large holes are found, into which the ligaments for the security of the joint are fixed, and blood-vessels pass to the internal substance of the bone. The thigh bone being articulated above with the acetabulum of the os innominatum, which affords its round head a secure and extensive play, can be moved to every side : but it is 204 THE LEG. restrained in its motion outwards by the high brims of the cavity, and by the round ligament ; for otherwise the head of the bone would have been frequently thrust out at the breach of the brims on the inside, which allows the thigh to move consider- ably inwards. The body of this bone enjoys little or no rotary motion, though the head most commonly moves round its own axis ; because the oblique direction of the neck and head from the bone, is such, that the rotary motion of the head can only bring the body of .the bone forwards and backwards. Nor is the head, as in the arm, ever capable of being brought to a straight direction with its body ; so far, however, as the head can move within the cavity backwards and forwards, the rest of the bone may have a partial rotation. From the oblique position of these bones it results, that there is a considerable distance between them above, while the knees are almost contiguous. Sufficient space is thereby left for the external parts of generation, for the two great outlets of urine and faeces, and for the large thick muscles that move the thigh inwards. At the same lime this situation of the thigh bone renders our progression quicker, surer, straighter, and in less room : for, had the knees been at a greater distance from each other, we must have been obliged to describe some part of a circle with the trunk of our body in making a long step ; and when one leg was raised from the ground, our centre of gravity would have been too far from the base of the other, and we should consequently have been in danger of falling ; so that our steps would neither have been straight nor firm, nor would it have been possible to walk in a narrow path, had our thigh bones been otherwise placed. In consequence, however, of the weight of the body bearing so obliquely on the joint of the knee by this situation of the thigh bones, weak rickety children become knock-kneed. The Leg Is composed of the two bones, the TIBIA and FIBULA. The patella being evidently appropriated to the knee-joint, may be regarded as common both to the thigh and leg. THE TIBIA. 205 Fig. 46, The Tibia Is the long thick triangular bone, situated at the internal part of the leg, and continued in almost a straight line from the thigh bone. The name is derived from i'ts resem- blance to the ancient musical instrument. The upper end of the tibia is large, bul- bous, and spongy. It has a horizontal sur- face, divided into two cavities, by a rough, irregular protuberance, which is hollow at its most prominent part, as well as before and behind. The anterior of the two ligaments that compose the great crucial is inserted into the middle cavity ; and the depression behind receives the posterior ligament. The two broad cavities at the sides of this pro- tuberance are not equal ; for the internal is oblong and deep, to receive the internal condyle of the thigh bone ; while the exter- nal is more superficial and round, for the external condyle. In each of these two cavities of a recent subject, a semilunar cartilage is placed, which is thick at its convex edge, and becomes gradually thinner towards the con- cave or interior edge. The thick convex edge of each cartilage is connected to the capsular and other ligaments of the articu- lation ; but so near to their rise from the tibia, that the cartilages are not allowed to change their places; while their narrow ends are fixed at the insertion of the strong cross ligament into the tibia, and seem to have their substance united with it ; there- fore a circular hole is left between each cartilage and the ligament, in which the most prominent convex part of each * The tibia and fibula of the right leg, articulated and seen from the front. 1. The shaft of the tibia. 2. The inner tuberosity. 3. The outer tnberosity. 4. The spinous process. 5. The tubercle. 6. The internal or subcutaneous surface of the shaft. 7. The lower extremity of the tibia. 8. The internal malleolus. 9. The shaft of the fibula. 10. Its upper extremity. 11. Its lower extremity, the external malleolus. 18 206 TIBIA. condyle of the thigh bone moves. The circumference of these cavities is rough and unequal, for the firm connexion of the ligaments of the joint. Immediately below the edge, at its back part, two rough flattened protuberances stand out ; into the internal, the tendon of the semimembranosus muscle is inserted ; and a part of the cross ligament is fixed to the exter- nal. On the outside of this last tubercle, a smooth slightly hollowed surface is formed by the action of the popliteus muscle. Before the forepart of the upper end of the tibia, a large rough protuberance rises, to which the strong tendinous liga- ment of the patella is fixed. On the internal side of this, there is a broad scabrous slightly hollowed surface, to which the internal long ligament of the joint, the aponeurosis of the vastus internus, and the tendons of the semitendinous, gracilis, and sartorius, are fixed. Below the external edge of the upper end of the tibia, there is a flat circular surface, covered in a recent subject with cartilage, for the articulation of the fibula. The body of the tibia is triangular. The anterior angle is very sharp, and is commonly called the spine or shin. This ridge is not straight ; but turns first inwards, then outwards, and lastly inwards again. The plane internal side is smooth and equal, being little subjected to the actions of muscle ; but the external side is hollowed above by the tibialis anticus, and below by the extensor digitorum longus and extensor pollicis longus. The two angles behind these sides are rounded by the action of the muscles ; the posterior side comprehended between them is not so broad as those already mentioned, but is more oblique and flattened by the action of the tibialis posticus and flexor digitorum longus. A little above the middle of the bone, the internal angle terminates, and the bone is made round by the pressure of the musculus soleus. Near to this, the passage of the medullary vessels is seen slanting obliquely downwards. The lower end of the tibia is hollowed, with a small protu- berance in the middle. The internal side of this cavity, which is smooth, and in a recent subject is covered with cartilage, is FIBULA. 207 extended into a considerable process, commonly named malleolus internus ; the point of which is divided by a notch, and from it ligaments are sent out to the foot. The externafVide of this end of the tibia has a rough irregular cavity formed in it, for receiving the lower end of the fibula. The posterior side has two lateral grooves, and a small middle protuberance. In the internal depression, the tendons of the musculus tibialis posticis and flexor digitorum longus are lodged ; and in the external, the tendon of the flexor longus pollicis plays. From the middle protuberance, ligamentous sheaths go out, for tying down these tendons. The Fibula Is the small bone, placed on the outside of the leg, opposite to the external angle of the tibia ; the shape of it is irregular. The head of the fibula has a circular surface formed on its inside, which, in a recent subject is covered with a cartilage ; and it is so closely connected to the tibia by ligaments, as to allow only a very small motion backwards and forwards. This head is protuberant and rough on its outside, where a strong round ligament and the musculus biceps are inserted, and, below the back part of its internal side, a tubercle may be re- marked, that gives rise to the strong tendinous part of the soleus muscle. The body of this bone is a little crooked inwards and back- wards : which figure is owing to the actions of the muscles. The sharpest angle of the fibula is forwards ; on each side of which the bone is considerably, but unequally, depressed by the bellies of the several muscles that rise from or act upon it. The external surface of the fibula is depressed obliquely from above downwards and backwards, by the two peronaei. Its internal surface is unequally divided into two narrow longitudinal planes, by an oblique ridge extended from the upper part of the anterior angle. To this ridge the ligament stretched between the two bones of the leg is connected. The anterior of the two planes is very narrow above, where the extensor longus digitorum and extensor longus pollicis arise from it : but is 208 FIBULA. broader below, where it has the print of the peroneus tertius. The posterior plane is broad and hollow, giving origin to the larger share of the tibialis posticus. The internal angle of this bone has a tendinous membrane fixed to it, from which some fibres of the flexor digitorum longus take their rise. The posterior surface of the fibula is the plainest and smoothest ; but is made flat above by the splaeus, and is hollowed below by the flexor pollicis longus. In the middle of this surface, the canal for the medullary vessels may be seen slanting downwards. The lower end of the fibula is extended into a spongy oblong head : on the inside of which is a convex, irregular, and frequently a scabrous surface, that is received by the external hollow of the tibia, and so firmly joined to it by a very thin intermediate cartilage and strong ligaments, that it scarce can move. Below this the fibula is stretched out into a smooth coronoid process, covered with cartilage on its internal side, and is there contiguous to the outside of the first bone of the foot, the astragalus, to secure the articulation. This process, named malleolus externus, being situated farther back than is the internal malleolus, and in an oblique direction, obliges us, naturally, to turn the forepart of the foot outwards. At the lower internal part of this process, a spongy cavity for mucilaginous glands may be remarked ; from its point, ligaments are extended to the bones of the foot, viz. the astragalus, os calcis, and os naviculare ; and from its inside, short strong ones go out to the astragalus. On the back part of it a sinuosity is made by the tendons of the peronei muscles. When the ligament, extended over these tendons from the one side of the depression to the other, is broken, stretched too much, or made weak by the sprain, the tendons frequently start forwards to the outside of the fibula. The conjunction of the upper end of the fibula with the tibia is by plain surfaces tipped with cartilage ; and at its lower end the cartilage seems to glue the two bones together; not, however, so firmly in young people, but that the motion at the other end is very observable. In old subjects, the two bones THE PATELLA OR ROTDLA. 209 of the leg are sometimes united by anchylosis at their lower ends. The principal use of this bone is to afford origin arvd inser- tion to muscles ; and to give a particular direction to their tendons. It likewise assists to make the articulation of the foot more secure and firm, and to complete the hinge-like joint at the ankle. The ends of the tibia and fibula being larger than their middle, a space is here left, which is filled up with a ligament similar to that which is extended between the bones of the forearm ; and which is also discontinued at its upper part, where the tibialis anticus immediately adheres to the solaeus and tibialis posticus j but every where else k gives origin to muscular fibres. The Patella or Rotula Is a small flat bone situated at the forepart of the joint of the knee. Its shape resembles the common figure of the heart with its point downwards. The anterior convex surface of the rotula is pierced by a great number of holes, into which are inserted the fibres of the strong ligament that is spread over it. Its posterior surface is smooth, covered with a cartilage, and divided by a middle convex ridge into two cavities, of which the external is the largest ; and both are exactly adapted to the pulley of the os femoris, on which they are placed in the most ordinary unstraining postures of the legs : but, when the leg is much bent, the patella descends far down on the condyles ; and when the leg is fully extended, the patella rises higher in its upper part than the pulley of the thigh bone. The plane smooth surface is surrounded by a rough prominent edge, to which the capsular ligament adheres. Below, the point of the bone is scabrous, where the strong tendinous ligament from the tubercle of the tibia is fixed. The upper horizontal part of this bone is flattened and unequal where the tendons of the exten- sors of the leg are inserted. The substance of the patella is cellular, with very thin firm external plates ; but then these cells are so small and such a quantity of bone is employed in their formation, that scarce 18* 210 PATELLA. any bone of its bulk is so strong. But, notwithstanding this strength, it is sometimes broken by the violent straining effort of the muscles. The principal motions of the knee joint are flexion and extension. In the former of these, the leg may be brought to a very acute angle with the thigh, by the condyles of the thigh bones being round, and made smooth far backwards. In performing this, the patella is pulled down by the tibia. When the leg is to be extended, the patella is drawn upwards, conse- quently, the tibia forwards, by the extensor muscles; which, by means of the protuberant joint, and of this thick bone wkh its ligament, have the chord, with which they act, fixed to the tibia at a considerable angle, and act, on that account, with advantage ; but they are restrained from pulling the leg farther than to a straight line with the thigh, by the posterior part of the cross ligament, that the body might be supported by a firm perpendicular column : for, at this time, the thigh and leg are as little movable in a rotary way, or to either side, as if they were one continued bone. But, when the joint is a little bent, the rotula is not tightly braced, and the posterior ligament is relaxed ; therefore, this bone may be moved a little to either side, or with a small rotation in the superficial cavities of the tibia ; which is done by the motion of the external cavity backwards and forwards, the internal serving as a sort of axis. Seeing, then, one part of the cross ligament is situated perpen- dicularly, and the posterior part is stretched obliquely from the internal condyle of the thigh outwards, that posterior part of the cross ligament prevents the leg from being turned much inwards ; but it could not hinder it from turning outwards almost round, were not that motion confined by the lateral ligaments of this joint, which can yield little. This rotation of the leg outwards is of great advantage to us in crossing our legs, and turning our feet outwards, on several necessary occasions ; though it is necessary that this motion should not be very large, to prevent frequent luxations here. While all these motions are performing, the part of the tibia that moves immediately on the condyles is that which is within THE FOOT. TARSUS. 211 the cartilaginous rings, which, by the thickness on their out- sides, make the cavities of the tibia more horizontal, by raising their external side where the surface of the tibia/ slants downwards. By these means the motions of this joint are more equal and steady than otherwise they would have been. The cartilages being capable of changing a little their situation, contribute to the different motions and postures of the limb, and, likewise, make the motions larger and quicker. The Foot. The foot is divided into the tarsus, metatarsus, and toes. The sole of the foot is necessarily described as the inferior part, and the side of the great toe as the internal. Fig. 47, Tarsus. The tarsus consists of seven spongy bones ; to wit, the astragalus, os cakis, naviculare, cuboides, cuneiforme externum, cuneiforme medium and cuneiforme inter- num. The astragalus is the uppermost of these bones. The os calcis is below the astragalus, and forms the heel. The os naviculare is in the middle of the internal sides of the tarsus. The os cuboides is the most external of the row of four bones, at its forepart. The os cuneiforme externum is placed at the inside of the cuboid. The cuneiforme medium is between the external and internal cuneiforme bones ; and the internal cuneiforme is at the internal side of the foot. The upper part of the astragalus is formed * The dorsal surface of the left foot. i. The astragalus j its superior quadri- lateral articular surface. 2. The anterior extremity of the astragalus, which articulates with (4.) the scaphoid bone. 3. The os calcis. 4. The scaphoid bone. 5. The internal cuneiform bone. 6. The middle cuneiform bone. 7. The exter- nal cuneiform bone. 8. The cuboid bone. 9. The metatarsal bones of the first and second toes. 10. The first phalanx of the great toe. 11. The second pha- lanx of th3 great toe. 12. The first phalanx of the second toe. 13. Its second phalanx. 14. Its third phalanx. 212 ASTRAGALUS. into a large smooth head, which is slightly hollowed in the middle ; and therefore resembles a superficial pulley, by which it is fitted to the lower end of the tibia. The internal side of this head is flat and smooth, to play on the inter- nal malleolus. The external side has also such a surface, but larger, for its articulation with the external malleolus. Round the base of this head there is a rough fossa ; and immediately before the head, as also below its internal smooth surface, we find a considerable rough cavity. The lower surface of the astragalus is divided by an irregular deep rough fossa, which, at its internal end, is narrow, but gradually widens as it stretches obliquely outwards and forwards. The smooth surface, covered with cartilage, behind this fossa, is large, oblong, extended in the same oblique situa- tion with the fossa, and concave for its conjunction with the os calcis. The posterior edge of this cavity is formed by two sharp-pointed rough processes, between which is a depression made by the tendon of the flexor pollicis longus. The lower surface before the fossa is convex, and composed of three distinct smooth planes. The long one behind, and the exterior or shortest, are articulated with the heel bone ; while the internal, which is the most convex of the three, rests and moves upon a cartilaginous ligament, that is continued from the os calcis to the os naviculare, without which ligament the astra- galus could not be sustained, but would be pressed out of its place by the great weight it supports; and the other bones of the tarsus would be separated. Nor would a bone be fit here, because it must have been thicker than could conveniently be allowed ; otherwise it would break, and would not prove such an easy bending base, to lessen the shock which is given to the body, in leaping, running, &c. The forepart of this bone is formed into a convex oblong smooth head, which is received by the os naviculare, and is placed obliquely ; its longest axis inclining downwards and inwards. Round the root of this head, especially on the upper surface, a rough fossa may be remarked. The astragalus is articulated above to the tibia and fibula, which together form one cavity. In this articulation, flexion OS CALCIS. 213 and extension are the most considerable motions ; the other motions being restrained by the malleoli, and by the strong ligaments which go out from the points of these processes, to the astragalus and os calcis. When the root is bent, as it commonly is when we stand, no lateral or rotary motion is allowed in this joint ; for then the head of the astragalus is sunk deep between the malleoli, and the ligaments are tense : but when the foot is extended, the astragalus can move a little to either side, and with a small rotation. By this contrivance, the foot is firm, when the weight of the body is to be supported on it ; and, when a foot is raised, we are at liberty to direct it more exactly to the place we intend next to step upon. The astragalus is joined below to the os calcis ; and before to the os naviculare, in the manner to be explained when these bones are described. The 05 calcis is the largest bone of the seven. Behind, it is formed into a large knob, commonly called the heel, the poste- rior surface of which is rough below for the insertion of what is called the tendo-achillis, and oblique above to allow the heel to be depressed without pressing against the tendon. On the upper surface of the os calcis, there is an irregular oblong smooth convexity, adapted to the concavity at the back part of the astragalus ; and beyond this a narrow fossa is seen, which divides it from two small concave smooth surfaces, that are joined to the forepart of the astragalus. The posterior of these smooth surfaces, which is the largest, is the upper surface of a process which projects inwards : and under it is a small sinuosity for the tendon of the flexor digitorum longus. The external side of this bone is flat, with a superficial fossa running horizontally, in which the tendon of the musculus peroneus longus is lodged. The internal side of the heel bone is hollowed, for lodging the origin of the massa carnea, and for the safe passage of tendons, nerves, and arteries. Under the side of the internal smooth concavity, a particular groove is made by the tendon of the flexor pollicis longus ; and from the thin protuberance of this internal side a cartilaginous ligament that supports the astragalus, goes out to the os naviculare ; on 214 OS NAV1CULARE. which ligament, and on the edge of this bone to which it is fixed, the groove is formed for the tendon of the flexor digito- rum profundus. The lower surface of this bone is flat at the back part, and immediately before this plane, there are two tubercles, from the internal of which the musculus abductor pollicis, flexor digitorum sublimis, as also p^rt of the aponeurosis plantaris, and of the abductor minimi digiti, have their origin ; and the other part of the abductor minimi digiti and aponeurosis plan- taris rises from the external. Before these protuberances, this bone is concave, for lodging the flexor muscles; and, at its forepart, we may observe a rough depression, from which, and a tubercle behind it, the ligament goes out that prevents this bone from being separated from the os cuboides. The forepart of the os calcis is formed into an oblong pulley- like smooth surface, which is circular at its upper external end, but is pointed below. The smooth surface is fitted to the os cuboides. Though the surfaces by which the astragalus and os calcis are articulated, seem fit enough for motion, yet the very strong ligaments, by which these bones are connected, prevent much motion, and give firmness to this principal part of our base, which rests on the ground. Os naviculare^'is somewhat oval. It is formed into an oblong concavity behind, for receiving the anterior head of the astragalus. The upper surface is convex. Below, the surface is very unequal and rough ; but hollow for the safety of the muscles. Its internal extremity is very prominent. The abductor pollicis takes in part its origin from it, the tendon of the tibialis posticus is inserted into it, and to it two remarkable ligaments are fixed ; the first is the strong one, formerly men- tioned, which supports the astragalus ; the second is stretched from this bone obliquely across the foot, to the metatarsal bones of the middle toe, and of the toe next to the little one. On the outside of the os naviculare there is a semicircular smooth surface, where it is joined to the os cuboides. The forepart of this bone is covered with cartilage, and divided into three smooth planes, fitted to the three ossa cuneiformia. i& ivyti ^j LO^> OS CUBOIDES. OS CUNEIFORMS EXTERNUM. 215 The os naviculare and astragalus are joined as a ball and socket ; and the naviculare moves in several directions in turn- ing the toes inwards, or in raising or depressing either ^ide of the foot, though the motions are greatly restrained by the liga- ments which connect this to the other bones of the tarsus. Os Cuboides is an irregular cube. Behind, it is formed into an oblong unequal cavity, adapted to the forepart of the os calcis. On its internal side, there is a small semicircular smooth cavity, to join the os naviculare. Immediately before which, an oblong smooth plane is made by the os cuneiforme exter- num ; below this the bone is hollow and rough. On the internal side of the lower surface, a round protuberance and fossa are found, where the musculus abductor pollicis has its origin. On the external side of this surface, there is a broad ridge running forwards and inwards, covered with cartilage ; immediately before which a smooth fossa may be observed, in which the tendon of the peroneus primus runs obliquely across the foot. Before, the surface of the os cuboides is flat, smooth, and slightly divided into two planes, for sustaining the os metatarsi of the little toe, and of the toe next to it. The form of the back part of the os cuboides, and the liga- ments connecting the joint with the os calcis, both concur in allowing little motion in this part. Os cuneiforme externum is shaped like a wedge, being broad and flat above, with long sides running obliquely down- wards, and terminating in an edge. The upper surface of this bone is an oblong square. The one behind is nearly a triangle, but not complete at the inferior angle, and is joined to the os naviculare. The external side is an oblong square divided as it were by a diagonal ; the upper half of it is smooth, for its conjunction with the os cuboides : the other is a scabrous hol- low, with a small smooth impression made by the os metatarsi of the toe next to the little one. The internal side of this bone is flattened before by the metatarsal bone of the toe next to the great one, and the back part is also flat and smooth where the os cuneiforme medium is contiguous to it. The forepart of this bone is triangular, for sustaining the os metatarsi of the middle toe. 216 OS CUNEIFORMS. Os cuneiforme, or minimum, is still more exactly the shape of a wedge than the former. Its upper part is square ; its in- ternal side has a flat smooth surface for its connexion with the adjoining bone; the external side is smooth and a little hol- lowed, where it is contiguous to the last described bone. Be- hind, this bone is triangular, where it is articulated with the os naviculare ; and it is also triangular at its forepart, where it is contiguous to the os metatarsi of the toe next to the great one. The broad thick part of the os cuneiforme maximum, or in- ternum, is placed below, and the small thinner edge is above. The surface of the os cuneiforme behind, where it is joined to the os naviculare, is hollow, smooth, and of a circular figure below, but pointed above. The external side consists of two smooth and flat surfaces. With the posterior, that runs ob- liquely forwards and outwards, the os cuneiforme minimum is joined ; and with the anterior, whose direction is longitudinal, the os metatarsi of the toe next to the great one is connected. The forepart of this bone is flat and smooth, for sustaining the os metatarsi of the great toe. The internal side is scabrous, with two remarkable tubercles below, from which the muscu- lus abductor pollicis rises, and the tibialis anticus is inserted into its upper part. The three cuneiforme bones are all so secured by ligaments, that very little motion is allowed in any of them. These seven bones of the tarsus, when joined, are convex above, and leave a concavity below, for lodging safely the several muscles, tendons, vessels, and nerves, that lie in the sole of the foot. In the recent subject, their upper and lower surfaces are covered with strong ligaments, which adhere firmly to* them ; and all the bones are so tightly connected by these and the other ligaments, which are fixed to the rough ridges and fossae, that notwithstanding the many surfaces covered with cartilage, some of which are of the form of the very movable articulations, no more motion is here allowed, than is necessary to prevent too great a shock of the fabric of the body in walking, leaping, &c., by falling on too solid a base. If the tarsus was one continued bone, it would likewise be METATARSUS. 217 much more liable to be broken, a-nd the foot could not accom- modate itself to the surfaces we tread on by becoming more or less hollow, or by raising or depressing either of its sid^s. Metatarsus. The Metatarsus is composed of five bones, which agree, in their general characters, with the metacarpal bones ; but may be distinguished from them by the following marks : 1. They are longer, thicker, and stronger. 2. Their anterior round ends are not so broad, and are less in proportion to their basis. 3. Their bodies are sharper above and flatter on their sides, with their inferior ridge inclined more to the outside. 4. The tubercles at the lower part of the round head are larger. Fig. 48.* The first or internal metatarsal bone is easily distinguished from the rest by its thickness. The one next to it is the longest, and with its sharp edge almost perpendicular. The others are shorter and more oblique, as their situation is more external. Which general remarks, with the description now to be given of each, may teach us to distinguish them from each other. Os metatarsi potticis is by far the. thickest and strongest, as having much the greatest weight to sustain. Its base is oblong, irregularly concave, and of a semilunar figure, to be adapted to the os cuneiforme maximum. The inferior edge of this base is a little prominent and rough, * The sole of the left foot. 1. The inner tuberosity of the os calcis. 2. The outer tuberosity. 3. The groove for the tendon of the flexor longus digitorum. 4. The rounded head of the astragalus. 5. The scaphoid bone. 6. Its tuberosity. 7. The internal cuneiform bone ; its broad extremity. 8. The middle cuneiform bone. 9. The external cuneiform bone. 10, 11. The cuboid bone. 11. Refers to the groove for the tendon of the peroneus longus. 12, 12. The metatarsal bones. 13, 13. The first phalanges. 14, 14. The second phalanges of the four lesser toes. 15, 15. The third, or uugual phalanges of the four lesser toes. 16 The last phalanx of the great toe. 19 218 METATARSUS. where the tendon of the peroneus primus muscle is inserted. On its outside, an oblique circular depression is made by the second metatarsal bone. Its round head has generally on its forepart a middle ridge, and two oblong cavities, for the ossa sesamoidea ; and, on the external side, a depression is made by the following bone. Os metatarsi of the second tof is the longest of the five, with a triangular base supported by the os cuneiforme medium, and the external side produced into a process ; the end of which is an oblique smooth plane, joined to the os cuneiforme externum. Near the internal edge of the base, this bone has two small depressions, made by the os cuneiforme maximum, between which is a rough cavity. Farther forwards we may observe a smooth protuberance, which is joined to a foregoing bone. On the outside of the base are two oblong smooth surfaces for its articulation with the following bone ; the superior smooth surface being extended longitudinally, and the inferior perpendic- ularly, between which there is a rough fossa. Os metatarsi of the middle toe is the second in length. Its base, supported by the os cuneiforme externum, is triangular, but slanting outwards, where it ends in a sharp-pointed little process, and the angle below it is not completed. The internal side of this base is best adapted to the preceding bone ; and the external side has also two smooth surfaces covered with cartilage, but of a different figure ; for the upper one is concave, and being round behind, turns smaller as it advances forwards; and the lower surface is a little smooth, convex, and very near the edge of the base. Os metatarsi of the fourth toe is nearly as long as the former, with a triangular slanting base joined to the os cuboides, and made round at its external angle ; having one hollow smooth surface on the outside, where it is pressed upon by the following bone ; and two on the internal side, corresponding to the former bone, behind which is a long narrow surface impressed by the os cuneiforme externum. Os metatarsi of the little toe is the shortest, situated with its two flat sides above and below, and with the ridges laterally STRUCTURE OF THE FOOT. 219 The base of it, part of which rests on the os cuboides, is very large, tuberous, and produced into a long-pointed process externally, where part of the abductor minimi digiti infixed; and into its upper part the peroneus secundus is inserted. Its inside has a flat conoidal surface, where it is contiguous to the preceding bone. When we stand, the fore ends of these metatarsal bones, and the os calcis, are our only supporters, and, therefore, it is necessary that they should be strong, and should have a confined motion. The Toes. The bones of the toes are nearly similar to those of the thumb and fingers ; particularly the two of the great toe, which are precisely formed as the two last of the thumb ; but their position, as respects the other toes, is not oblique ; and they are proportionally much stronger, because they are sub- jected to a greater force ; for they sustain the impulse by which our bodies are pushed forwards by the foot behind at every step we make, and on them principally the weight of the body is supported, when we are raised on our tip-toes. The three bones in each of the other four toes, compared with those of the fingers, differ from them in these particulars. They are less, and smaller in proportion to their lengths. Their basis are much larger than their anterior ends. The first pha- lanx is proportionally much longer than the bones of the second and third, which are very short. The toe next to the great one has the largest bones in all dimensions, and the bones of the other toes diminish according to the order of their position ; those of the exterior being least. The General Structure of the Foot. The foot may be considered as an arch, of which the back part of the heel, and the anterior extremities of the metatarsal bones and the toes, are the abutments. The heel, or posterior abutment is not so broad as the anterior, and is placed on the outside and not in the middle of the extremity of the arch. The 220 STRUCTURE OF THE FOOT. process on the inside of the os calcis, which supports the astragalus, increases the breadth of the arch ; and the os naviculare completes it. The arch, thus constructed, does not appear very firm, and this apparent want of strength seems increased by the position of the anterior portion of the astra- galus, a part of which is between the os calcis and os naviculare, and not supported by either. These bones, however, are firmly connected by ligaments, and one which passes from the os calcis to the os naviculare, under the forepart of the astra- galus, gives effectual support to that bone. The outside of the foot, formed by the os calcis, os cuboides, and the lesser metatarsal bone, does not partake much of the nature of an arch ; for it is almost flat. As the internal side forms a considerable arch, the foot is to be considered as possessing a double convexity, viz. transversely, as well as longitudinally. 2f The great toe, from its internal situation, is the principal anterior abutment of the arch on the internal side of the foot ; hence its great importance. The astragalus, which is the basis of the tibia, and of course pressed by half of the weight of the body when we stand, appears to be in a situation which is very oblique, and imper- fectly supported ; and accordingly it has been completely forced from its position, by accidents in which the leg has been twisted or turned inward, and the foot prevented from turning with it. It is probable that this misfortune would often take place if the fibula did not previously yield, as in some of the cases of fracture of that bone near the external ankle. One great object of this peculiar structure is, that the foot may yield in cases of violent and sudden pressure, as when we jump or fall upon the feet. The safety of the foot, and the facility of its ordinary movement, are not the only objects of its peculiar structure, but concussion of the whole body, and particularly of the brain, is thereby avoided to a certain de- gree. ^his may be inferred from the fact that many persons suffer * \=^ C-' / 2fc+* ** /, &r SESAMOID BONES. EXTREMITIES OF THE FffiTUS. 221 violent concussions, in consequence of falling upon other parts of the body, who are free from these effects when they fall upon the feet. The Sesamoid Bones Are seldom larger than half a pea. They are most commonly found at the second joint of the thumb, and of the great toe ; and are placed in pairs, especially at the great toe, between the tendons of the flexor muscles and the bones.* In these situa- tions they are convex externally, and on their internal surfaces they are concave and covered with cartilage. They are also sometimes found between the heads of the gastrocnemius muscle and the condyles of the os femoris. In the joints of the thumb and toe they appear to be very analogous to the patella. Besides the four pair of sesamoid bones above described as belonging to the skeleton, viz. two upon the metacarpo-pha- langeal articulation of each thumb, and two upon the corres- ponding joint of each great toe, there is often found in addition, one upon the metacarpo-phalangeal joint of the little finger, and upon the corresponding joint in the foot. There is one also often met with in the tendon of the peroneus longus muscle, where it glides through the groove in the cuboid bone. Some- times they are found in the tendons that wind round the inner and outer malleolus and in the psoas and iliacus where they glide over the body of the os pubis. The Extremities of the Foetus. In the upper extremity the clavicle is almost perfect at birth ; but the acromion and coronoid processes of the scapula, as well as the head, are in a cartilaginous state. Both ends of the os humeri are cartilaginous. They after- wards ossify in the form of epiphyses, and are united to the body of the bone. The two bones of the forearm are in the same situation. * They are properly speaking developed in the tendons of these muscles, like the patella in the tendon of the extensor muscles of the thigh. The patella itself may be considered a specimen of a sesamoid, considering its mode of development. p. 19* 222 EXTREMITIES OF THE FffiTUS. There are no bones of the carpus ; but in their situation is an equal number of cartilages, which resemble them exactly. These cartilages are separated from each other, by synovia membranes, as the bones afterwards are. Each of them ossifies from a single point, except the unciforme. The metacarpal bones, and the first bone of the thumb have cartilages at each extremity, which afterwards become epiphysis. The bones of the phalanges are likewise cartilaginous at each extremity. The extremities next to the hand are epiphyses ; but it is probable that the other extremities ossify gradually from their centres.* In the lower extremity, the head and neck, and two tro- chanters of the os femoris are cartilaginous and form three epiphyses. The other end of this bone is also cartilaginous, and consti- tutes but one epiphysis, notwithstanding its size ; the ossification commencing in the centre. At birth, the body of the os femoris is less curved than it becomes afterwards ; and the angle formed by the neck of the bone is less obtuse than in the adult. The patella is entirely cartilaginous at birth. The two extremities of the tibia and fibula are also cartilag- inous, and become epiphyses. The astragalus and os calcis are somewhat ossified within, and have a large portion of cartilage exteriorly. In place of the other bones of the tarsus there are cartilages of their precise shape, which are as distinct from each other as the future bones are. The state of the metatarsal bones, and the phalanges of the toes, resembles that of the bones of the hand.f * See Nesbit's Osteology, page 126. f Volehn Koyter, a disciple of Fallopius, has given to the profession one of the best accounts of Osteogeny, according to Lassus. H. PART II. SYNDESMOLOGY. CHAPTER III. GENERAL ANATOMY OF THE LIGAMENTOUS, FIBROUS, OR DESMOID TISSUE. Of the ligaments aud membranes which connect the different parts of the body to each other Of the articular cartilage Fibro-cartilages Synovial cap- sules, and particular articulations. THE tendons and the strong membranes connected with them called aponeuroses, the fascia which bind down some of the muscles and afford an origin to many of their fibres, and the membranes which confine the tendons, appear to be composed of the same substance. Notwithstanding some slight shades of difference which exist in the physical and chemical composition of these different parts, they are all now included with the periosteum, perichon- drium, dura mater, sclerotic coat of the eye, &c., under the general head of ligamentous, fibrous, or desmoid tissue.* This tissue is sometimes called, from the whiteness of its appearance, the albugineous tissue. It is spread very gene- rally throughout the body, and is found wherever extraordinary strength and resistance is required, without elasticity or muscu- lar contraction. It has been called ligamentous or desmoid, from its fastening together the bones and cartilages, as in the ligaments proper, and from binding down the muscles so as to preserve the symmetry of the limbs, in the form of fascia and * The term ligament is frequently, though not with exact propriety applied to the duplicatures of serous membranes, which are attached to and assist in sup- porting different viscera, as the liver, bladder, uterus, &c., since these do not belong to the fibrous or desmoid tissue. p. 2'24 FIBROUS TISSUE. aponeurosis, and from fastening the tendons in their grooves in the form of their theca's or sheaths. The term fibrous was applied to it by Bichat, (though its elements are dissimilar to muscular fibre,) in consequence of its performing the office of bands or chords, and being composed essentially of firm in- elastic threads, or albuminous fibres. These fibres crossing each other in various directions and woven densely together, with some intervening cellular tissue, form the aponeuroses, fascia?, sheaths, articular capsules, periosteum, dura mater, and tunica albuginea ; arranged longitudinally, they form the tendons of the muscles and the straight ligaments of the joints. The tendons, by a little dissection, may be spread out into a membrane, and in some parts of the body we see them naturally unfolding themselves to form an aponeurosis. Between all these different parts there is more or less con- nexion. The tendons are inserted upon the bones only through the intermedium of the periosteum, by which the bones are covered. The aponeuroses are connected with the periosteum by the fasciae which they send down between the muscles. The ligaments and periosteum are directly continuous, and the dura mater, as it sends out processes around the nerves, becomes continuous with the periosteum that lines the foramina of the bones, through which the nerves pass. Bichat, con- sidered the periosteum the source and centre of this system ; Bonn, of Amsterdam, as well as Clarus, believed the aponeu- roses investing the limbs to be the centre ; an opinion more venerable than either of these, that of the Arabian anatomists, fixed it in the dura mater. But, in truth there is no proper centre. In many parts, there is a fibrous tissue isolated from the rest, as the investing coat of the spleen and kidneys, and the fibrous portion of the pericardium. The fibrous tissue in all parts of the body is continuous, at its surfaces and margins, with the common cellular tissue, and in many parts we find it, especially in the aponeuroses and fasciae, degenerating insensibly into it. There appears in fact to be a close relationship between these two tissues ; in its development in the foetus, it first appears as a soft, flexible, FIBROUS TISSUE. 225 i extensible, homogeneous tissue, resembling much the cellular, and presents no appearance of fibres, till near the period of birth. As life advances it becomes more hard, soliti*^ and yellow, and in extreme old age presents much rigidity, and is occasionally even converted into bone. When macerated in water, or imbued with fluids, as in scrofulous inflammation of the joints, it presents a pulpy, spongy appearance, in the cells of which the fluid is contained. If the maceration is carried only to a limited extent, the fibres will separate into filaments, as delicate as those of the silk worm ; but by prolonged mace- ration these filaments themselves disappear in the cellular mass. Mascagni, believed these fibres were lymphatics en- closed in a vascular web. Beclard, that they were nothing but condensed cellular tissue. Isenflam, that it was cellular tissue, with the walls imbued and the cells filled with gluten and albumen, and more or less in the advance of life with earthy matter; an opinion which seems to accord with the different phases which the tissue presents. Chaussier and Bichat, con- sidered the fibre as primitive and peculiar, and that maceration only brought into view the cellular tissue which connected the fibres together. However this may be, and it is a question not yet decided, in the form in which it presents itself to study, it differs in many respects from cellular tissue. It is not elastic or yielding to the application of sudden force as the latter ; the fibres will break or tear up at their bony attachment, but cannot be stretched or strained in the proper sense of the word. But when the force is gradually applied, as by the accumulation of a fluid in a joint, they yield to receive it, by a sort of interstitial expansion or growth, and retract in the same gradual manner, when the distending power is removed. Fibrous tissue contains but little adipose matter, and is affected only to a slight extent in anasarca. The labors of the microscopists have recently confirmed the opinion of Chaussier and Bichat. They have shown fibrous tissue to consist of fine transparent undulating cylindrical filaments, about i^ 00 part of an inch in 226 FIBROUS TISSUE. diameter. They are generally collected in minute fasciculi, from 5 ^ 00 to T0 ^g and these again into larger fasciculi ^ to ^ of an inch wide, the filaments of which are held together, by a firm structureless amorphous substance, which has received the name of cytoblastema. Under the microscope, the elementary struct- ure of the cellular, fibrous and fibro-cellular tissues, appear to be the same. Their anatomical ^differences depending on the mode in which their elementary fibres are put together. In fibrous tissue the undulating primitive filaments are arranged side by side into fasciculi, which differ from those of cellular tissue in being much larger, more dense and more opaque and in being straight instead of flexuous. Their whiteness and strength, depend upon the compact parallel disposition of the compound fila- ments ; and their slight amount of elasticity is owing to the absence* of sinuosity in the arrangement of the compound fasciculi. According to the manner in which these fasciculi or fibres are arranged and combined, we have either the mem- branous or fascicular form of fibrous tissue as has been above explained. Cellular membrane in a more or less condensed state, is found in general intermixed to a greater or less extent, with the fibrous fasciculi. The Ligaments of the Joints, Are all divided into the capsular or bag-like, and into funicu- lar, or cords. The capsular, or fibrous bags, of greater or less thickness, open at both ends, into which the heads of the bones forming the respective joints are thrust, and round the necks of which it is closely inserted, where they are continuous with the peri- osteum of the bones. In very many of the joints the capsules are imperfect in some part of their periphery, and in others are represented only by a few scattered fibres. The hip and shoulder joint furnish the best specimen of a perfect capsule. The funicular ligaments are cords, flat, round, or oval, intended to give a side support to the joints, and constitute the lateral ligaments. These are placed, some within, some- FIBROUS TISSUE. 227 without, and some in the very thickness of the capsular liga- ment. They consist of fibres which are flexible but extrefnely strong, and in general have but little elasticity ; their surfaces are smooth and polished ; their color is whitish and silver- like. The vessels which enter into their composition do not com- monly carry red blood ; and although it seems certain that they must have nerves, many very expert anatomists have declar- ed that no nerves could be traced into them. A branch of the fourth cranial nerve, has however been found distributed in the dura mater. Blood vessels abound in the periosteum, but they merely divide in that membrane, so as to enter the bone at a great number of points, as has been before observed. In a healthy state, they are entirely void of sensibility, and ^ can be cut and punctured, or corroded with caustic appli- cations, without pain. When inflamed they are extremely painful. The ligaments which connect the different bones to each other, have a very strong resemblance to these tendinous parts, not only in their structure but in their qualities also. Many of them appear rather more firm in their texture and more vascular. Their vessels are also larger: their color sometimes inclines to a dull white, and when examined chemically, they appear to differ, in some respects, from tendons. t They agree, however, with the tendinous parts as to their insensibility in a sound state, and the extreme pain which occurs when they are inflamed. No nerves have been traced into their structure. Notwithstanding the ordinary insensibility of these parts, it was asserted by M. Bichat that several animals who seem to suffer no pain from cutting, puncturing, or corroding the liga- \ ments of their joints, appeared to be in great agony when these parts were violently stretched or twisted ; and he de- clared this to be the case when all the nerves which passed over the ligaments, and could have been affected by the 228 FIBROUS TISSUE. process, were cut away. He explained by this the pain which sometimes occurs instantaneously in sprains, in the reduction of luxations, and in other analogous processes. The ultimate structure of these parts is, perhaps, not perfectly understood. An anatomist of the highest authority, Haller, appears to have considered them as fqrmed of membrane, while a late writer, who has paid great attention to the subject, and is also of high authority, M. Bichat, has satisfied himself that their structure is essentially fibrous. If a tendon, or portion of tendinous membrane, be spread out, or forcibly extended, in a direction which is transverse with respect to its fibres, it will seem to be converted into a fine membrane, and the fibres will disappear to the naked eye. The same circumstances will occur when a ligament is treated in a similar way ; but much more force is required. Thus constructed, these parts are perfectly passive portions of the animal fabric, and have no more power of motion than the bones with which many of them are connected. But notwithstanding their ordinary insensibility, they often induce a general violent affection of the system when they are diseased. A high degree of fever, as well as severe pain, attends their acute inflammations ; and hectical symptoms, in their greatest extent, are often induced by their suppurations. There is another circumstance in their history which is very difficult to reconcile with their ordinary insensibility. They are the most common seats of gouty painful affections. In these cases, pain does not seem to be the simple effect of inflammation : it often occurs as the first symptom of the dis- ease ; it frequently exists with great violence for a short time and goes off without inflammation, and it is frequently vicarious with affections of the most sensible and irritable parts, -v Parts of a tendinous and ligamentous structure do not appear retentive of life, but lose their animation very readily, in conse- quence of the inflammation and other circumstances which attend wounds. When thus deprived of life, they retain their usual appear- - %#^, ^^ v", ***? *) ts*J**rjL.&^ ft>Cs&^ +-*<, ~^f' \. sfi&^-^tf jffif^ ' &* "*^&j fT jtffa, ev^^V YELLOW ELASTIC LIGAMENTOUS TISSUE. 229 ance and their texture a long time. The dead parts separate from the living in large portions, in a way which has a con- siderable analogy with the exfoliation of bones. The tendons and their expansions, and the various fasciae, have the same chemical composition. If boiled a long time, they dissolve completely, and form the substance called by chemists gelatine, or pure glue. The ligaments differ from them in some respects. When boiled they yield a portion of gelatine, and do not dissolve entirely ; but are said to retain their form and even their strength, after a very long boiling. The composition of the part so insoluble in water, has not yet been ascertained. Of the Yellow Elastic Ligamentous Tissue. Fig. 49.* This is a modification of the common ligamentous tis- sue,*which though not usual- ly treated apart, differs from it in many essential particu- lars. It contains, according to the younger Girard, some fibrine in its composition ; it is eminently elastic, and is placed to give resistance and support to parts, where in other animals, we meet with muscular fibres, for which it is in some sort a substitute. In some situations it is of a deep yellow color, and rarely presents the silvery aspect of the common tissue. It forms the middle coat of the arteries, the ligaments between the bridges of the verte- brae, the ligamentum nucha3 in quadrupeds with heavy pen- dant heads, the elastic involucrum oj the corpus cavernosum and spongiosum penis in the male, of the clitoris in the female, * Reticulate elastic tissue from the ligamentum nuchae of the horse magnified to 200 diameters (from Gerber). a. Loosened elastic tissue with the meshes opened, b. Elastic tissue in its natural condition, the meshes close j the fibres being disposed in lines and layers, parallel to one another. 20 230 FIBRO-LIGAMENTOUS TISSUE. / and the elastic covering of the spleen ; it is found in the rami- fications of the bronchia, in various parts of the eye ball, and in the ligaments of the larynx and os hyoides including the vocal chords ; we might also add, the elastic membrane of the nose and ear, which are more allied to it, than to cartilage, though they are called membraniform cartilage. This yellow elastic tissue, (tissue jaune) unlike otfcer ligamentous tissue, yields no gelatine on boiling. It resists decomposition for a very long time, either by maceration, putrefaction, or digestion ; it becomes brown and transparent on drying, but not brittle like cartilage. Fig. 50.* When examined with the mi- croscope, it is found to bear in the arrangement of its fibres a strong resemblance to a net work of capillary vessels. Its fibres are rigid, prismatic in form and about the ^ g part of a line in diameter, highly elastic and interlaced with each other at all angles ; its embryonic cells are elon- gated and mixed with the fibres. If injured it is very imperfectly reproduced ; a dense fibrous tissue being substi- tuted in its place. It is very sparingly supplied with blood- vessels. Of the Fibro-cartilaginous or Ligamento-cartilaginous Tissue. There is another variety of the desmoid tissue, which holds a middle station between ligament and cartilage, partakes partly of the nature of both, and has been treated of by Bichat as a distinct tissue under this compound name. Vesalius and * Elastic tissue from the middle fibrous coat of the aorta of the ox magnified 300 diameters. The intertangled fibres, and elongated cells are well shown (from Gerber). These fibres, according to Henle, are contractile, and resemble .somewhat the muscular fibres of the stomach. FIBRO-LIGAMENTOUS TISSUE. . 231 Morgagni, called them cartilaginous ligaments ; Haase, mixed ligaments. Like ligaments, they present a well marked fibrous appearance, and are strong and resisting. Like cartilages, they are white, very dense and elastic. Beclard divides them into the temporary and permanent.* The temporary, are those which pass regularly and at determined periods to the state of ossification, and are developed in the midst of the ligaments and tendons, as the patella and sesamoid bones. The permanent are of several kinds. 1. Those which are free at both these surfaces, and are lined by the synovial mem- brane. These constitute the interarticular or meniscous carti- lages, (menisci,) and are attached at their outer surface to the inner face of the capsular ligament. They are found in the knee, maxillary, clavicular, and lower ulnar articulations. 2. Those which are adherent by one of their surfaces ; these are found whenever the fibrous tissue is subjected to habitual friction by the tendons, as in the different grooves, through which they play, or upon the sides of the ligaments or carti- lages, against which they rub ; the periosteum, or whatever fibrous membrane it may be, first becomes thickened and then converted into a semicartilage. It also exists in the fibrous rings, placed at the margin of the glenoid and cotyloid cavities for the purpose of deepening their sockets. 3. Those adherent by both surfaces. These are found between the bodies of the vertebrae and the pubic bones. The accidental production of this tissue is by no means uncommon ; it is found occasionally in the cavities of fractures forming false joints, in the tubercular cavities of the lungs, in the uterus, ovaries, etc. * Bichat considered the elastic cartilaginous membranes of the nose, ear, and trachea, as belonging to this division of the tissues, but they certainly have a closer affinity to the yellow elastic fibrous tissue. p. 232 OF ARTICULATIONS. CHAPTER IV. A GENERAL ACCOUNT OF ARTICULATIONS, AND OF Of Articulations. THOSE surfaces of bones which form the movable articula- tions are covered with cartilaginous matter which has been already described.* In many of the immovable articulations, as the sacro-iliac symphysis for instance, a thin lamen of cartilaginous matter, with all the other appurtenances of joints, are likewise met with. The connexion between the articular cartilage and the bones is strong, but its nature is not well known. None of the vessels of the bone pass into the cartilage, but terminate in its immediate neighborhood. Gerdy, (page 29) considers it a secretion from these vessels, and that its formation is like that of the cuticle, from the vessels of the skin. This, however, is but a mere opinion, unsustained by proof. It presents the appearance of a couch of white wax spread over the end of the bones, though it is composed of vertical fibres like the frill of velvet, so crowded together as to leave no sensible interval between them, and presenting a free extremity to the cavity of the joint. The cartilages terminate insensibly at their circum- ference on the surface of the bone. On the heads of the bones they are thicker at the central part, than at their circumference ; in the corresponding socket, the cartilaginous coating is thickest at the margin, and sometimes spreads out into a sort of carti- laginous rim. On the formation of the epiphysis of the long bones, and its covering cartilage. In the foetus and young subject, there is no distinction between the cartilage that is to become the bone of the epiphysis and that which is to remain as articular carti- * See page 36. FORMATION OF THE EPIPHYSIS OF LONG BONE. 233 lage. In my preparations alluded to, page 236, a careful dis- section shows branches running from the zone of vessels across the head of the bone isolating the articular cartilage froni the epiphysal. These branches have beds of bone formed round them, communicate freely with the vessels of the epiphysis, but appear to send no branches towards the free surface of the articular cartilage. The portion of the articular cartilage immediately overlaying them, is , however , more tough and periosteal in its character, than that on the free surface of the cartilage, and has been, though not with exact propriety, described by Mr. Listen, as cellular tissue connecting the carti- lage and epiphysis. It is well known that in young subjects, the articular cartilage is thick, and fhe compact layer of the epi- physis below it thin and fragile ; while in old persons the com- pact layer of the epiphysis is thick and strong, and the cartilage covering is thin, rigid, and so firmly united to the bone below, as to be with difficulty removed from it by the ordinary process of cleaning. It would seem from this, that .while the cartilage gets its nutritive fluids by imbibition from the epiphysal vessels and the marginal zone, some change is effected by their passage into its structure during the progress of life, by which the inner portions of the articular cartilage is converted into bone. Though in the healthy state no vessels can be injected in carti- lage, in some diseases of the joints blood-vessels and granula- tions may shoot up from the bone below into the place of the cartilage. It has been most probably in cases of this de- scription, that the appearance of vascularity in the cartilages has been observed; that of Mr. Liston, detailed in a late num- ber of the medico-chirurgical transactions was from a diseased The bones are retained in their relative situations by liga- ments, such as have been lately mentioned, which are exterior to the cavities of the articulations, and placed in such situa- tions that they permit the motions the joints are calculated to perform, while they keep the respective bones in their proper places. 20* 234 SYNOVFAL CAPSULES. Of the Synovial Capsules. < The synovial capsules are formed of an extremely thin transparent, double reflected tissue, the vessels of which circu- late in the healthy state only the serous portions of the blood, and which, though erected into a distinct tissue or system by Bichat, under the name of synovial, is now generally considered as forming only a part of th general serous tissue, which it closely resembles in structure, and with which it intimately sympathizes in disease. They are of three kinds : 1st. Those which line the inner surface of the ligaments of the joints, and are reflected over the surfaces of the articular cartilages. These are called the articular synovial cartilages. 2d. Those which are placed between the tendons of the muscles, and the bones and cartilages against which the tendons rub. These are called burscE mucoscs. 3d. Those which are placed between the* skin and the bones, tendons, or other hard parts, over which it per- forms frequent and extensive movements. These are called the subcutaneous synovial capsules. Of the Articular Synovial Capsules. They are invested in a particular manner by a thin delicate membrane, which in some joints, as those of the hip and shoulder, seems to be the internal lamina of a stronger liga- ment called the capsular ; and, in other joints, the knee, for example, appears to be independent of any other structure. In each case, this synovial membrane, as it has lately been called, forms a complete sac or bag which covers the articular surface of one bone, and is reflected from it to the correspond- ing surface of the other ; adhering firmly to each of the articulating surfaces, and extending loosely from the margin of one surface to that of the other. In the distribution it supplies the place of perichondrium to the cartilages, and of periosteum to those surfaces of bone with which it is connected. It seems greatly to resemble the membranes which line the - ' ;4&**v. -U^2 See page 346, 347. 2. lliacus Internus. ) 376 MUSCLES or THE os FEMORIS. 3. Pectinalis, Arises, broad and fleshy, from the upper and anterior part of the os pubis or pectinis, immediately above the foramen thy- roideum. Inserted into the anterior and upper part of the linea aspera of the os femoris, a little belo^v the trochanter minor, by a flat and short tendon. Use. To bring the thigh upwards and inwards, and to give it a degree of rotation outwards. 4. Triceps Adductor Femoris, Under this appellation are comprehended three distinct muscles : a. Adductor Longus Femoris, Arises, by a strong roundish tendon, from the upper and anterior part of the os pubis, and from the symphysis pubis, on the inner side of the pectinalis. Inserted, tendinous, near the middle of the posterior part of the linea aspera, being continued for some way down. b. Adductor Brevis Femoris, Arises, tendinous, from the os pubis near its joining with the opposite os pubis, below and behind the former. Inserted, tendinous and fleshy, into the inner and upper part of the linea aspera, from a little below the trochanter minor, to the beginning of the insertion of the adductor longus. c. Adductor Magnus Femoris, Arises, a little lower down than the former, near the symphysis of the os pubis, tendinous and fleshy from the tuberosity of the os ischium ; the fibres run outwards and downwards. Inserted into almost the whole length of the linea aspera ; into a ridge above the internal condyle of the os femoris ; and, by a roundish long tendon, into the upper part of that condyle, MUSCLES OF THE OS FEMORIS. 377 a little above which, the femoral artery takes a spiral turn towards the ham, passing between this muscle and the boiy?. Use of these three rrfuscles, or triceps. To bring the thigh inwards and upwards, according to the different directions of their fibres ; and, in some degree, to roll the thigh outwards. 5. Obturator Externus, Arises, fleshy, from the lower part of the os pubis, and fore- part of the inner crus of the ischium ; surrounds the foramen thyroideum ; a number of its fibres, arising from the membrane which fills up that foramen, are collected like rays towards a centre, and pass outwards around the root of the back part of the cervix of the os femoris. Inserted, by a strong tendon, into the cavity at the inner and back part of the root of the trochanter major, adhering in its course to the capsular ligament of the thigh bone. Use. To roll the thigh bone obliquely outwards, and to pre- vent the capsular ligament from being pinched. Behind are, First layer, Glutens Maximus, Arises, fleshy, from the posterior part of the spine of the os ilium, a little higher up than the joining of the ilium with the os sacrum, from the whole external side of the os sacrum, be- low the posterior spinous process of the os ilium ; from the posterior sacro-ischiatic ligament, over which part of the in- ferior edge of this muscle hangs in a folded manner, and from the os coccygis. All the fleshy fibres run obliquely forwards, and a little downwards, to form a thick broad muscle, which is divided into a number of strong fasciculi. The upper part of it covers almost the whole of the trochanter major, between which and the tendon of this muscle there is a lar^e bursa mu- O cosa, and where it is inseparably joined to the broad tendon of the tensor vagina femoris. Inserted, by a strong, thick, and broad tendon, into the upper and outer part of the linea aspera, which is continued from the 32* 378 MUSCLES OF THE OS FEMORIS. troclianter major, for some way downwards, as far as the origin of the short head of the biceps flexor cruris and also into the fascia femoris. Use. To extend the thigh, by pulling it directly backwards, and a little outwards. Second layer, Glutens Medius, Arises, fleshy, from the anterior superior spinous process of the os ilium, and from all the outer edge of the spine of the ilium ; except its posterior part, where it arises from the dorsum of that bone. Inserted, by a broad tendon, into the outer and upper mar- gin of the trochanter major. Use. To draw the thigh bone outwards, and a little back- wards ; to roll the thigh bone outwards, especially when it is bended. N. B. The anterior and upper part of this muscle is covered by a tendinous membrane, from which a number of its fleshy fibres arise, and which joins with the broad tendons of the glutens rnaximus, tensor vagina femoris, and latissimus dorsi. Third layer consists of four muscles. 1. Glutens Minimus. Arises, fleshy, from a ridge that is continued from the superior anterior spinous process of the os ilium, and from the middle of the dorsum of that bone, as far back as its great niche. Inserted, by a strong tendon, into the fore and upper part of the trochanter major. Use. To assist the former in pulling the thigh outwards and backwards, and in rolling it. i 2. Pyriformis. Arises, within the pelvis, by three tendinous and fleshy ori- gins, from the second, third, and fourth pieces of the os sacrum ; from thence growing gradually narrower, it passes out of the MUSCLES OF THE OS FEMORIS. 379 pelvis along with the posterior crural nerve, below the niche in the posterior part of the os ilium, where it receives a few fleshy fibres. Inserted, by a roundish tendon, into the upper part of the Fig. 99.* cavity, at the inner side of the root of the trochanter major. Use. To move the thigh a lit- tle upwards, and roll it outwards. 3. Gemetti, Arise, by two distinct origins ; the superior from the spinous process, and the inferior from the tuberosity of the os ischium ; also, from the posterior sacro- ischiatic ligament. They are both united by a tendinous fleshy membrane, and form a purse for the tendon of the obturator in- ternus muscle, which was for- merly described. Inserted, tendinous and fleshy, into the cavity at the inner side of the root of the trochanter major, on each side of the tendon of the obturator internus, to which they firmly adhere. Use. To roll the thigh outwards, and to preserve the tendon of the obturator internus from being hurt by the hardness of that part of the os ischium over which it passes ; also, to hinder it from starting out of its place, while the muscle is in action. * The deep muscles of the gluteal region. 1. The external surface of the ilium. 2. The posterior surface of the sacrum. 3. The posterior sacro-iliac ligaments. 4. The tuberosity of the ischium. 5. The great or posterior sacro- ischiatic ligament. 6. The lessor or anterior sacro-ischiatic ligament. 7. The trochanter major. 8. The gluteus minimus. 9. The pyriformis. 10. The gemellus superior. 11. The obturator internus muscle, passing out of the lesser sacro-ischiatic foramen. 12. The gemellus inferior. 13. The quadratus femoris. 14. The tipper part of the adductor magnus. lo. The vastns exfer- nus. 16. The biceps. 17. The gracilis. 18. The semi-tendinosus. 380 MUSCLES OF THE THIGH. 4. Quadratus Femoris, Arises, tendinous and fleshy, from the outside of the tuberosity of the os ischium; and, running transversely, is Inserted, fleshy, into a rough ridge, continued from the root of the large trochanter to the root of the small one. Use. To roll the thigh outwards. Muscles situated on the Thigh. These are called muscles of the leg ; and consist of one, on the outside; two on the inside; four, before; and four, behind. Previous to the description of the muscles that are situated on the thigh and leg, it is necessary to take notice of a broad tendinous fascia or sheath, (aponeurosis of the lower extremi- ties^) which is sent off from the back and from the tendon of the glutei and adjacent muscles. It is a strong thick membrane on the outside of the thigh and leg ; but, towards the inside of both, it gradually turns thinner, and has rather the appearance of cellular substance than a tendinous membrane. A little below the trochanter major, it is firmly fixed to the linea aspera ; and, farther down, to that part of the head of the tibia that is next the fibula ; where it sends off the tendinous expansion along the outside of the leg. It serves to strengthen the action of the muscles, by keeping them firm in their proper places while in action, particularly the tendons that pass over the joints where this membrane is thickest, and it gives origin to a number of. the fleshy fibres of the muscles. On the outside is, Tensor Vagina Femoris, Arises, by a narrow, tendinous, and fleshy beginning, from the external part of the anterior superior spinous process of the os ilium. Inserted, a little below the trochanter major, into the inner side of the membranous fascia which covers the outside of the thigh. MUSCLES OF THE THIGH. 381 Fig. 100.* Use. To stretch the membranous fascia, to assist in the adduction of the thigh, and somewhat in its rota- tion inwards. On the inside are, 1 . Sartorius, Arises, tendinous, from the anterior superior spinous process of the os ilium, soon grows fleshy, runs down for some space upon the rectus, and going oblique- ly inwards, it passes over the vastus in- ternus, and, about the middle of the os femoris, over part of the triceps ; it runs down farther between the tendon of the adductor magnus and that of the gracilis muscles. Inserted, by a broad and thin ten- don, into the inner side of the tibia, near the inferior part of its tubercle. Use. To bend the leg obliquely in- wards, or to bring one leg across the other. 2. Gracilis, Arises, by a thin tendon, from the os pubis, near the symphy- sis of these two bones, soon grows fleshy, and, descending by the inside of the thigh, is Inserted, tendinous, into the tibia under the sartorius. Use. To assist the sartorius. Before are, * The muscles of the anterior femoral region. 1. The crest of the ilium. 2. Its anterior superior spinous process. 3. The gluteus medius. 4. The ten- sor vaginoe femoris ; its insertion into the fascia lata is shown inferiorly. 5, The sartorius. 6. The rectus. 7. The vastus externus. 8. The vastus inter- nus. 9. The patella. 10. The iliacus internus. 11. The psoas magnus. 12. The pectineus. 13. The adductor longus. 14. Part of the adductor mag- nus. 15. The gracilis. 382 MUSCLES OF THE THIGH. 1. Rectus, Arises, fleshy, from the inferior anterior spinous process of the os ilium, and tendinous from the dorsum of the ilium, a little above the acetabulum ; runs down over the anterior part of the cervix of the os femoris ; the fibres not being straight, but running down like the plumage of a feather obliquely outwards and inwards, from a tendon in* the middle. Inserted, tendinous, into the upper part of the patella, from which a thin tendon runs down, on the forepart of this bone, to terminate in a thick strong ligament, which is sent off from the inferior part of the patella^ and inserted into the tubercle of the tibia. Use. To extend the leg, and, in a powerful manner, by the intervention of the patella, like a pulley. 2. Vastus ExternuSj Arises, broad, tendinous and fleshy, from the root of the trochanter major, and upper part of the linea aspera ; its origin being continued from near the insertion of the gluteus minimus, the whole length of the linea aspera, by fleshy fibres which run obliquely forwards to a middle tendon, where they terminate. Inserted into a large share of the upper part of the patella ; and part of it ends in an aponeurosis, which is continued down to the leg, and in its passage is firmly fixed to the head of the tibia. Use. To extend the leg. 3. Vastus Interims, Arises, tendinous and fleshy, from between the forepart of the os femoris and root of the trochanter minor, and from almost all the inside of the linea aspera, by fibres running obliquely forwards and downwards. Inserted, tendinous, into the upper and inside of the patella, continuing fleshy lower than the vastus externus. Part of it likewise ends in an aponeurosis continued down to the leg, and fixed in its passage to the upper part of the tibia. Use. To extend the leg. MUSCLES OF THE THIGH, 383 Fig. 101.* 4. Cruralis, Arises, fleshy, from between the two trochanters of the os femoris, but nearer the lesser trochanter, and firmly adhering to most of the forepart of the os femoris, and connected to both vasti muscles. Inserted, tendinous, into the upper part of the patella, behind the rectus. Use. To assist in the extension of the leg. N. B. These four muscles before, being inserted into the patella, have the same effect upon the leg as if they were immediately inserted into it by means of the strong tendon, or rather ligament which is sent oft* from the inferior part of the patella to the tibia. Behind are, 1 . Semitendinosus, Arises, tendinous and fleshy, in com- mon with the long head of the biceps, from the posterior part of the tubero- sity of the os ischium ; and sending down a long roundish tendon, which ends flat, is Inserted, into the inside of the ridge of the tibia, a little below its tubercle. Use. To bend the leg backwards and a little inwards. * The muscles of the posterior femoral and gluteal region. 1. The gluteus medius. 2. The gluteus maximus. 3. The vastus externus covered in by fascia lata. 4. The long head of the biceps. 5. Its short head. 6. The semi- tendinosus. 7. The semi-membranosus. 8. The gracilis. 9. A part of the inner border of the adductor magnus. 10. The edge of the sartorius. 11. The popliteal space. 12. The gastrocnemius muscle: its two heads. The tendon of the biceps forms the outer hamstring ; and the sartorius with the tendons of the gracilis, semi-tendinosus, and semi-membranosus, the inner hamstring 384 MUSCLES OF THE THIGH. 2. Semimembranosus, Arises, tendinous, from the upper and posterior part of the tuberosity of the os ischium ; sends down a broad flat tendon, which ends in a fleshy belly, and, in its descent, runs at first on the forepart of the biceps, and lower, between it and the semitendinosus. Inserted, tendinous, into the inner and back part of the head of the tibia. Use. To bend the leg, and bring it directly backward. N. B. The two last form what is called the inner hamstring. 3. Biceps Flexor Cruris, Arises by two distinct heads. The first, called longus, arises, in common with the semitendinosus, from the upper and pos- terior part of the tuberosity of the os ischium. The second, called brevis, arises from the linea aspera, a little below the termination of the gluteus maxirnus, by a fleshy acute begin- ning, which soon grows broader as it descends to join with the first head, a little above the external condyle of the os femoris. Inserted, by a strong tendon, into the upper part of the head of the fibula. Use. To bend the leg. JV. B. This muscle forms what is called the outer ham- string ; and between it and the inner, the nervus popliteus, the arteria and vena poplitea, are situated. 4. Popliteus, Arises, by a round tendon, from the lower and back part of the external condyle of the os femoris, then runs over the liga- ment that involves the joint; firmly adhering to it, and part of the semilunar cartilage. As it runs over the joint, it becomes fleshy, and the fibres run obliquely inwards, being covered with a thin tendinous membrane. Inserted, broad, thin and fleshy, into a ridge at the upper and internal edge of the tibia, a little below its head. Use. To assist in bending the leg, and to prevent the cap- x I MUSCLES ON THE FRONT OF THE LEG. 385 sular ligament from being pinched. After the leg is bent, this muscle serves to roll it inwards. Muscles situated on the Leg. These muscles may be arranged in the two general classes of flexors and ex- tensors of the foot, and flexors and extensors of the toes ; but several of them, viz. the tibialis and the peronei, produce effects which are different from flexion or extension. For the accommodation of the student of anatomy, they may be studied in the order of their position as they lie on the front, on the outside, and on the back of the leg. Muscles on the Front of the Leg. 1. Tibialis Anticus. Arises, tendinous and fleshy, from the middle of that process of the tibia, to which the fibula is connected above ; then it runs down fleshy on the outside of the tibia ; from which, and the upper part of the interosseous ligament, it receives a num- ber of distinct fleshy fibres ; near the extremity of the tibia, it sends off a strong round tendon, which passes under part of the ligamentum tarsi annulare near the malleolus internus. Inserted, tendinous, into the inside of the os cuneiforme internum, and posterior end of the metatarsal bone that sustains the great toe. Use. To bend the foot, by drawing it upwards, and, at the same time, to turn the toes inwards. 2. Extensor Proprius Pollicis Pedis, Arises, by an acute, tendinous, and fleshy beginning, some way below the head and anterior part of the fibula, along which it runs to near its lower extremity, connected to it by a number of fleshy fibres, which descend obliquely towards a tendon. Inserted, tendinous, into the posterior part of the first and last joint of the great toe. Use. To extend the great toe. 33 386 MUSCLES ON THE FRONT OF THE LEG. 3. Extensor Longus Digitorum Pedis, Arises, tendinous and fleshy, from the upper and outer part of the head of the tibia, and from the head of the fibula where Fig. 102.* it joins with the tibia, and from the interosseous ligament; also from the tendinous fascia, which covers the up- per and outside of the leg by a number of fleshy fibres ; and tendinous and fleshy from the anterior spine of the fibula, almost its whole length, where it is inseparable from the peroneus tertius. It splits into four round tendons, under the ligamentum tarsi annulare. Inserted, by a flat tendon, into the root of the first joint of each of the four small toes ; and is expanded over the upper side of the toes, as far as the root of the last joint. Use. To extend all the joints of the four small toes. N. B. A portion of this muscle, which is called 4. Peroneus Tertius, Arises, from the middle of the fibula, continues down to near its inferior ex- tremity, and sends its fleshy fibres forwards to a tendon, which passes under the annular ligament, and is * The muscles of the anterior tibial region. 1. The extensor muscles inserted into the patella. 2. The subcutaneous surface of the tibia. 3. The tibialis anticus. 4. The extensor communis digitorum. 5. The extensor proprius pollicis. 6. The peroneus tertius. 7. The peroneus longus. 8. The peroneus brevis. 9, 9. The borders of the soleus muscle. 10. A part of the inner belly of the gastrocnemius. 11. The extensor brevis digitorura ; the tendon in front of this number is that of the peroneus tertius ; and that behind it, the tendon of the peroneus brevis. MUSCLES ON THE LEG. 387 Inserted, into the root of the metatarsal bone that sustains the little toe. Use. To assist in bending the foot. Muscles on the outside of the Leg. 1. Peroneus Longus. Arises, tendinous and fleshy, from the forepart of the head of the peroneus, or fibula, the fibres running straight down ; also from the upper and external part of the fibula, where it begins to rise into a round edge ; as, also, from the hollow between that and its anterior edge, as far down as to reach within a hand's breadth of the ankle, by a number of fleshy fibres, which run outwards towards a tendon, that subsequently becomes long and round, and passes through a channel at the outer ankle, in the back part of the inferior extremity of the fibula ; then being reflected to the sinuosity of the os calcis, it runs along a groove in the os cuboides, above the muscles in the sole of the^ foot. Inserted, tendinous, into the outside of the root of the meta- tarsal bone that sustains the great toe, and bysome tendinous fibres into the os cuneiforme internum. Use. To turn the foot outwards, and to extend it a little. 2. Peroneus Brevis, Arises, by an acute fleshy beginning, from above the middle of the external part of the fibula ; from the outer side of the anterior spine of this bone ; as also from its round edge externally, the fibres running obliquely outwards towards a tendon on its external side : it sends off a round tendon which passes through the groove at the outer ankle, being there included under the , same ligament with that of the preceding muscle ; and a little farther, it runs through a particular one of its own. Inserted, tendinous, into the root and external part of the metatarsal bone that sustains the little toe. Use. To assist the former in pulling the foot outwards, and extending it a little. MUSCLES ON THE LEG. Muscles on the Back of the Leg. 1. Gastrocnemius Externus, seu Gemellus, Arises, by two distinct heads. The first head arises from the Fig. 103.* upper and back part of the internal condyle of the os femoris, and from that bone, a little above its condyle, by two distinct tendinous origins. The second head arises tendinous from the upper and back part of the exter- nal condyle of the os femoris. A little be- low the joint, their fleshy bellies unite in a middle tendon ; and, below the middle of the tibia, it sends off a broad thin tendon, which joins a little above the extremity of the tibia with the tendon of the following. 2. Soleus, seu Gastrocnemius Internus, Arises by two origins. The first is from the upper and back part of the head of the fibula, continuing to receive many of its fleshy fibres from the posterior part of that bone for some space below its head. The other origin begins from the posterior and upper part of the middle of the tibia ; and runs inwards along the inferior edge of the popliteus towards the inner part of the tibia, from which it receives fleshy fibres for some way down. The flesh of this muscle, covered by the tendon of the gemellus, runs down nearly as far as the extremity of the tibia ; a little above which the tendons of * The superficial muscles on the posterior surface of the leg. 1. Biceps flexor cruris muscle, forming the outer hamstring. 2. The tendons forming the inner hamstring, consisting of the tendons of the semitendinosus, semi- membranosus, gracilis and sartorius. 3. The popliteal space. 4. The gastroc- nemius muscle. 5, 5. The soleus muscle. 6. Tendo Achillis. 7. The posterior tuberosity of the os calcis. 8. The tendons of the peroneus longus and brevis muscles, passing behind the outer ankle. 9. The tendons of the deep layer of muscles passing into the foot behind the inner ankle. MUSCLES ON THE LEG. 389 both gastrocnemii unite, and form a strong round cord, which is called tendo-Achillis. Inserted into the upper and posterior part of the os caleis, by Fig. 104.* the projection of which the tendo-Achillis is placed at a considerable distance from the tibia. Use. To extend the foot, by bringing it backwards and downwards. 3. Plantaris. Arises, thin and fleshy, from the upper and back part of the root of the external condyle of the os femoris, near the interior extremity of that bone, adhering to the liga- . ment that involves the joint in its descent. It passes along the second origin of the soleus and under the gemellus, where it sends off a long, slender, thin tendon, which comes from between the great extensors, where they join tendons ; then runs down by the inside of the tendo-Achillis. Inserted, into the inside of the posterior part of the os caleis, below the tendo- Achillis. Use. To assist the former, and to pull the capsular ligament of the knee from between the bones. It seems likewise to assist in rolling the foot forwards, * The deep layer of muscles of the posterior libial region. 1. The lower extremity of the femur. 2. The ligamentum posticum Winslowii. 3. The tendon of the semi-membranosus muscle dividing into its three slips. 4. The internal lateral ligament of the knee-joint. 5. The external lateral ligament. 0. The popliteus muscle. 7. The flexor longus digitorum. 8. The tibialis posticus. 9. The flexor longus pollicis. 10. The peroneus longus muscle. 11. The peroneus brevis. 12. The tendo-Achillis divided at its insertion into the os caleis. 13. The tendons of the tibialis posticus and flexor longus digito- rum muscles, just as they are about to pass beneath the internal annular liga- ment of the ankle ; the interval between the latter tendon and the tendon of the flexor longus pollicis is occupied by the posterior tibial vessels and nerves. 33* 390 MUSCLES ON THE LEG. 4. Flexor Longus Digitorum Pcdis, Profundus, Perforans, Arises, by an acute tendon, which soon becomes fleshy from the back part of the tibia, some way below its head, near the entry of the medullary artery ; which beginning, is continued down the inner edge of this bone by short fleshy fibres, ending in its tendon ; also by tendinous and fleshy fibres, from the outer edge of the tibia, and between this double order of fibres, the tibialis posticus muscle lies enclosed. Having passed under two annular ligaments, it then passes through a sinuosity at the inside of the os calcis ; and about the middle of the sole of the foot, divides into four tendons, which passes through the slit? of the perforatus ; and just before its division it receives a con- siderable tendon from that of the flexor pollicis longus. Inserted into the extremity of the last joint of the four lesser toes. Use. To bend the last joint of the toes. 5. Tibialis Posticus, Arises, by a narrow fleshy beginning, from the fore and upper- part of the tibia, just under the process which joins it to the fibula ; then passing through a perforation in the upper part of the interosseous ligament, it continues its origin from the back part of the fibula next the tibia, and from near one half of the upper part of the last named bone ; as also, from the interos- seous ligament, the fibres running towards a middle tendon, which sends off a round one that passes in a groove behind the malleolus internus. Inserted, tendinous, into the upper and inner part of the os naviculare, being farther continued to the os cuneiforme inter- num and medium ; besides it gives some tendinous filaments to the os calcis, os cuboides, and to the root of the metatarsal bone that sustains the middle toe. Use. To extend the foot, and to turn the toes inwards. 6. Flexor Longus Pollicis Pedis, Arises, by an acute, tendinous, and fleshy beginning, from the posterior part of the fibula, some way below its head, being MUSCLES ON THE SOLE OF THE FOOT. 391 continued down the same bone, almost to its inferior extremity, by a double order of oblique fleshy fibres ; its tendon passes under an annular ligament at the inner ankle. Inserted, into the last joint of the great toe, and, generally, sends a small tendon to the os calcis. Use. To bend the last joint of this toe. On the upper surface of the foot there is one muscle, viz. Extensor Brevis Digitorum Pedis, Arises, fleshy and tendinous, from the fore and upper part of the os calcis ; and soon forms a fleshy belly, divisible into four portions, which send off an equal number of tendons that pass over the upper part of the foot, under the tendons of the for- mer. Inserted, by four slender tendons, into the tendinous expan- sion from the extensor longus which covers the small toes, ex- cept the little one ; also into the tendinous expansion from the extensor pollicis, that covers the upper part of the great toe. Use. To extend the toes. Muscles on the Sole of the Foot. On the sole of the foot there is a strong tendinous membrane called Aponturosis Plantaris, which originates from the tuberosity of the os calcis, and proceeds forward to the toes, increasing gradually in breadth. It is divided into three portions. That in the middle is the largest ; it protects and covers the short flexor muscles, and the tendons in the middle of the foot. That on the outside, which covers the adductor and flexor of the little toe, it> next in size. The internal portion, which covers the adductor of the great toe, is the smallest. The edges of these portions dip down so as to separate the muscles they cover from each other. They are divided into five processes, corresponding with the heads of the metatarsal bones ; each of these portions is divided into two bands, which are inserted into each side of the head of each metatarsal bone, and the tendons, nerves, and arteries pass between them. Immediately under the middle portion of this aponeurosis are the common short flexors of the toes, viz. 1. Flexor Brevis Digitorum Pedis Sublimis Perforatus, Arises, by a narrow fleshy beginning, from the inferior and posterior part of the protuberance of the os calcis, between the adductors of the great and little toes, soon forms a thick 392 MUSCLES ON THE SOLE OF THE FOOT. Fig. 105.* fleshy belly, which sends off four tendons that split for the pas- sage of the flexor longus. Inserted into the second phalanx of the four lesser toes. The tendon of the little toe is often wanting. Use. To bend the second joint of the toes, 2. Flexor Digitorum Accessorim, seu, Massa Carnea Jacobii Sylvii, Arises, by a thin fleshy origin, from most part of the sinuosity at the in- side of the os calcis, which is continued forwards, for some space on the same bone ; also, by a thin tendinous begin- ning, from before the tnberosity of the os calcis, externally, and, soon becom- ing all fleshy, is Inserted into the tendon of the flexor longus, just at its division into four tendons. Use. To assist the flexor longus. 3. Lumbricales Pcdis, Arises, by four tendinous and fleshy beginnings, from the tendon of the flexor profundus, just before its division, near the insertion of the massa carnea. Inserted, by four slender tendons, into the inside of the first joint of the four lesser toes, and are lost in the tendinous ex- pansion that is sent from the extensors to cover the upper part of the toes. * The first layer of muscles in the sole of the foot : this layer is exposed by the removal of the plantar fascia. 1. The os calcis. 2. The posterior part of the plantar fascia divided transversely. 3. The abductor pollicis. 4. The ab- ductor minimi digiti. 5. The flexor brevis digitorum. 6. The tendon of the flexor longus pollicis muscle. 7, 7. The lumbricales. On the second and third toes, the tendons of the flexor longus digitorum are seen passing through the bifurcation of the tendons of the flexor brevis digitorum. MUSCLES ON THE SOLE OF THE FOOT. 393 Use. To increase the flexion of the toes, and to draw them inwards. On the inside of the foot, and under the common flexors, are the muscles which are considered as exclusively appropriated to the great toe, viz. 1. Abductor Pollicis Arises, from the internal side of the tuberosity of the os calcis, and from a ligament which extends from this tuberosity to the sheath of the tendon of the tibialis posticus muscle, and also from the internal and inferior side of the os navicu- lare and cuneiforme internurn. It likewise arises from that portion of the aponeurosis plantaris, which separates it from the short flexor of the toes, and many of its fibres appear to be connected with the ligaments which pass from the posterior to the anterior bones of the foot : as it passes under the cuneiform bone, a portion of its lower surface is tendinous. It is inseparably connected to the flexor of the great toe, and is inserted into the internal sesamoid bone, and the inferior and internal part of the root of the first bones of the great toe. This muscle not only separates the great toe from the other toes, but it must increase the curvature, or arched form of the foot. 2. Flexor Brevis Pollicis Pedis, Arises , tendinous, from the under and forepart of the os calcis, where it joins with the os cuboides, from the os cunei- forme externum, and is inseparably united with the abductor and adductor pollicis. Inserted, into the internal and external sesamoid bones, along with the abductor and adductor pollicis, and into the root of the first joint of the great toe. Use. To bend the first joint. 3. Adductor Pollicis Pedis, Arises, by a long thin tendon, from the os calcis, from the os cuboides, from the os cuneiforme externum, and from the root of the metatarsal bone of the second toe. 394 MUSCLES ON THE SOLE OF THE FOOT. Fig. 106.* Inserted into the external os sesa- moideum, and root of the inetatarsal bone of the great toe. Use. To bring this toe nearer the rest. Near the outer edge of the foot, under the second portion of the aponeu- rosis plantaris, are the muscles pecu- liar to the little toe, viz. 1. Adductor Minimi Digiti Pedis. Arises, tendinous and fleshy, from the semicircular edge of a cavity on the inferior part of the protuberance of the os calcis, and from the root of the metatarsal bone of the little toe. Inserted into the root of the first joint of the little toe externally. Use. To draw the liyle toe outwards from the rest, and assist in preserving the arched form of the foot. 2. Flexor Brevis Minimi Digiti Pedis, Arises, tendinous, from the os cuboides, near the sulcus or furrow for lodging the tendon of the peroneus longus ; fleshy from the outside of the metatarsal bone that sustains the little toe, below its protuberant part. Inserted, into the anterior extremity of the metatarsal bone, and root of the first joint of this toe. Use. To bend this toe. * The third and a part of the second layer of muscles of the sole of the foot. 1. The divided edge of the plantar fascia. 2. The musculus accessorius. 3. The tendon of the flexor longus digitorum, previously to its division. 4. The ten- don of the flexor longus pollicis. 5. The flexor brevis pollicis. 6. The ad- ductor pollicis. 7. The flexor brevis minimi digiti. 8. The transversus pedis. 9. Interossei muscles, plantar and dorsal. 10. A convex ridge formed by the tendon of the peroneus longus muscle in its oblique course across the foot. INTEROSSEOUS MUSCLES. 395 Between the metatarsal bones are four external and three internal interossei : and one muscle which is common to all the metatarsal bones. Interossei Pedis Externi, Bicipites. 1. Abductor Indicis Pedis , Arises, tendinous and fleshy, by two origins, from the root of the inside of the metatarsal bone of the fore toe, from the outside of the root of the metatarsal bone of the great toe, and from the os cuneiforme internum. Inserted, tendinous, into the inside of the root of the first joint of the fore toe. Use. To pull the fore toe inwards from the rest of the small toes. 2. Adductor Indicis Pedis, Arises, tendinous and fleshy, from the roots of the metatarsal bones of the fore and second toe. Inserted, tendinous, into the outside of the root of the first joint of the fore toe. Use. To pull the fore toe outwards towards the rest. 3. Adductor Medii Digiti Pedis, Arises, tendinous and fleshy, from the roots of the metatarsal bones of the second and third toes. Inserted, tendinous, into the outside of the root of the first joint of the second toe. Use. To pull the second toe outwards. 4. Adductor Tertii Digiti Pedis, Arises, tendinous and fleshy, from the roots of the metatarsal bones of the third and little toe. Inserted, tendinous, into the outside of the root of the first joint of the third toe. Use. To pull the third toe outwards. 396 INTEROSSEOUS MUSCLES. Interossei Pedis Interni, 1. Abductor Medii Digiti Pedis, Arises, tendinous and fleshy, from the inside of the root of the metatarsal bone of the middle toe internally. Inserted, tendinous, into the inside of the root of the first joint of the middle toe. Use. To pull the middle toe inwards. 2. Abductor Tertii Digiti Pedis, Arises, tendinous and fleshy, from the inside and inferior part of the root of the metatarsal bone of the third toe. Inserted, tendinous, into the inside of the root of the first joint of the third toe. Usl. To pull the third toe inwards. 3. Abductor Minimi Digiti Pedis, Arises, tendinous and fleshy, from the inside of the root of the metatarsal bone of the little toe. Inserted, tendinous, into the inside of the root of the first joint of the little toe. Use. To pull the little toe inwards. The common muscle, Transversalis Pedis, Arises, tendinous, from the under part of the anterior extremity of the metatarsal bone of the great toe, and from the internal os sesamoideum of the first joint, adhering to the adductor pollicis. Inserted, tendinous, into the under and outer part of the anterior extremity of the metatarsal bone of the little toe, and ligament of the next toe. Use, to contract the foot, by bringing the great toe and the two outermost toes nearer each other. MOTIONS OF THE SKELETON. 397 CHAPTER IX. OBSERVATIONS ON THE MOTIONS OF THE SKELETON. THE falling down of the body during life, when muscular action is suspended, as well as the examination of the artificial skeleton, evince that this machine is not constructed to preserve the erect position of itself; but that, when unsupported, it bends at the joints, and invariably falls forward. It is retained in the erect position by the action of muscles : and that the muscles should produce this effect, it is necessary that they should have a fixed basis to act from. This basis is the feet, and they are fixed to the ground by the weight of the body. To keep the body from falling, it is necessary that the centre of gravity should be immediately over the centre of the common basis. All our movements, both in walking, standing, and rising from our seats, are regulated by this principle ; and whenever we move our body, so that the centre of gravity is changed, we must change the position of the feet, that the centre of the basis may be directly under it. If this proposition were not almost self-evident, it might be illustrated by several very easy experiments. If a person stand against a wall with his heels and the back parts of his legs and thighs in contact with it, and, in this situa- tion, attempts to stoop forward, he will fall upon his face ; there is no power in his muscles, or in any other part of the body, when thus circumstanced, to prevent it ; but a small movement forward of one foot, will enable him to stoop with ease by altering the basis of the body. When we sit in such a position that we cannot bring the centre of gravity over the feet, the lower limbs are divested of 34 398 ADJUSTMENT OF THE CENTRE OF GRAVITY. all power of elevating the body : this is always the case when we sit with the thighs and legs at right angles with each other. Bend the knees to an acute angle, so that the feet are placed under the body, and we rise with ease. When we wish to stoop forward without advancing one of our feet, we acquire the power in a small degree, by placing our hands behind us, to preserve the equilibrium. Some old persons, whose spines curve forwards in conse- quence of age, bend their lower limbs, so that the pelvis may be projected backwards beyond the centre of the base of the body, and form a counterpoise to the upper part of the trunk. Bending the knees alone, without projecting the pelvis back- wards, will not produce this effect ; for a person who stands with his back to a wall will bend his knees without obtaining this advantage, while the heels and back part of the pelvis are in contact with the wall. When we stand with the toes pointing directly forwards, the base of the body is a square ; of which the feet are two of the sides. As the positions of the feet are changed, the figure of the base and its centre necessarily change also. When the feet are placed one immediately before the other, the centre is be- tween the toes of the one and the heel of the other. When the position of the feet is such, that the toes point directly out- wards, and the heels are opposite to each other, the centre of the base is between the heels. In these cases, when the situation of .the centre of the base is changed, we immediately change the centre of gravity. Thus, as we turn the toes outwards, the centre of the base moves backwards, we, therefore, immediately make the body more erect ; and by that means keep the centre of gravity over the centre of the base. We move the centre of gravity laterally, as well as back- wards and forwards, in conformity to this principle. Thus, when we raise one foot from the ground, the body inclines so much in the opposite direction, that the centre of gravity is directly over the other. If the spine is diseased in one spot, and assumes a lateral curvature, placing the centre of ADJUSTMENT OF THE CENTRE OF GRAVITY. 399 gravity on one side of the natural centre of the base ; another curve is formed by a muscular action, in a sound part of the spine, to counteract the first, and keep the centre of gravity in its natural position. The perception of a tendency to fall, when the centre of grav- ity is in a wrong situation, first induces us to make efforts to resist this tendency ; we learn by experience what these efforts ought to be : and by habit we at length make them without consciousness. As the natural tendency of the skeleton, when we stand, is to bend at the articulations, and, therefore, to fall forwards; the muscles which have the principal effort in keeping the body erect, must be the extensors. Thus, the muscles on the back of the leg, and particularly the soleus, keep the tibia erect : while the muscles on the front of the thigh, the vasti and crureus, produce the same effect upon the os femoris : the bones being kept steady by the occa- sional counteraction of the antagonist muscles. The whole lower limb is thus made erect by an exertion which begins at the foot, while the foot is fixed to the ground by the weight and pressure of the body above it. The trunk of the body has a strong tendency to bend for- ward at the articulations of the thigh bones and the ossa innominata. This tendency is resisted by the muscles which lie on the back part of the ossa femoris, and extend the trunk on those bones, viz. the glutei maximi. The muscles which arise from the tuberosity of the ischium, and are inserted into the leg, the semitendinosus, semimembra- nosus, and the long head of the biceps flexor cruris, have also this effect. The flexure of the thoracic and lumbar portions of the spine is counteracted by the sacro-lumbalis, and longissimus dorsi, which act from the sacrum and back parts of the pelvis. The yellow ligaments, which are elastic, must also co-operate to this effect : so that with regard to the spine, there is an additional agent distinct from the muscular power. Indeed, respecting the vertebral articulations in general, it 400 MUSCLES WHICH KEEP THE BODY ERECT. may be observed, that the connexion of the bodies of the vertebrae, by the intervertebral cartilaginous matter, and of the plates behind, by the elastic ligament, renders these articulations perfectly anomalous ; and very different in their principles from the articulations in general. In no part of the skeleton is this tendency to bend forward more strongly perceived thac in the head. When we are awake, and the muscles in a healthy situation, it is effectually restrained, and the head kept erect, by the splenius and corn- plexus, and other muscles, which act from the spine below, upon the back part of the head and the vertebrae of the neck. When we stand on one foot, some very different muscles are called into action ; the tendency of the body is to fall sideways, towards the foot which is raised from the ground. To coun- teract this tendency the two larger peronei muscles, which are situated on the outside of the leg, act from the foot, to keep the leg erect. The vastus externus acts upon the same principle from the leg upon the os femoris. The gluteus medius and minimus, and the muscle of the fascia, act from the os femoris upon the pelvis and trunk ; while the quadratus lumborum, and those abdominal muscles which draw the spine to that side, continue the operation : and so do likewise the muscles which act on the same side of the neck and head. In rising from a seat, the tibialis anticus acts very powerfully, to keep the tibia erect, and prevent it from inclining backwards. The two vasti, and the cruraeus, raise up the os femoris, while the gluteus maximus, the sernitendinosus, and semimembra- nosus, and the long head of the biceps, extend the trunk of the body. There are several modes of walking, which are different from each other, in a small degree. We may walk, for example, with the knee of the hind limb straight or bent, as we bring it forward. This circumstance is merely a matter of accommodation. But there are two essential processes in walking, viz. 1. Projecting one foot forward, and placing it on the ground while thus projected : and 2. Moving the body over that foot. MUSCLES EMPLOYED IN RISING FROM A SEAT. 401 The mode of projecting the foot requires no explanation; but the manner of bringing it to the ground, when thus ad- vanced ought to be noticed. If, after standing with both feet on the same line, we move one foot forwards, suppose the right foot, it cannot be applied flat to the ground, unless we either incline the body forward or move the pelvis on the left thigh, so that the right side may present obliquely forward ; or lower the right side of the pelvis, so that it may be nearer the ground. When we incline the body forward, and thus bring the right foot to the ground, we perform the second essential process in walking, along with the first : for we move the body over the fore foot. The muscles on the front part of the hind leg, and particularly the tibialis anticus, seem to produce this effect, by bending, or inclining forward, the tibia on the foot. When the foot is brought to the ground by a rotation of the pelvis, it is likewise the tibialis anticus, and the muscles on the front of the hind leg, that move the body over it, or that begin the motion. The gastrocnemius and soleus, and the flexors of the toes, particularly that of the great toe, occasionally co-operate with great effect. By raising the heel, and thus lengthening the hind limb, they push the body forward, and continue its motion in that direction after the effect of the tibialis anticus ceases. The length of the step appears, therefore, to require this elevation of the heel, and depression of the toes ; but it should be observed, that when we take long steps, we also turn the pelvis partly round, presenting the side obliquely forward ; and in this manner increase the anterior projection of the front leg. Although the action of the gastrocnemius, &c., seems neces- sary to walking with long steps, we can walk without their operation. This is proved incontestably by the act of walking on the heel : when the gastrocnemii and the flexors are so far from acting, that they are in a state of extension. In this ope- ration, the principal effort seems to be made by the tibialis anticus, and the muscles on the front of the leg ; and the exten- sor muscles on the front of the thigh. 34* 402 MOTIONS NECESSARY IN WALKING. Notwithstanding these facts, the action of the gastrocnemius and soleus is essential whenever we raise the heel from the ground, while the weight of the body presses on the front part of the foot ; and it then acts with a force which equals, if it does not exceed, the weight of the body. Jumping, at the first view of it, appears an extraordinary operation ; but if a man whcj/m, color, and yewau, to create. p. f The coloring matter as is very obvious in the black, is now found to be deposited in delicate hexahgedral cells which are called pigmentary cells. In the choroid coat of the eye the cells are arranged in several layers over each other, so as to form a pigmentary membrane, the surface appearing perfectly black. 430 OF THE CUTICLE. coverings of the papillae, and which are thus secreted and moulded around these organs. The whole of the corneous tissue of the skin, (included usually under the terms of rete mucosum and epidermis,) is formed according to these anatomists of the mingled products of these mucous and coloring glands.* The Cuticula or Epidermis, has been examined with the greatest care by several of the most successful anatomists ; but notwithstanding their labors, the structure of this substance is by no means understood. It appears to have some resemblance to the matter of the nails, and of horn : but is rather more flexible, even after allowing for the difference in thickness. In those parts where it is thinnest it is semitransparent. It is insensible, and no vessels can be seen in it.f * In investigating this obscure and difficult part of anatomy, it has been usual with observers to select the skin of the palms of the hands and soles of the feet, as a type of the whole cutaneous system. There is, however, a difference to be observed. In the palms and soles resides pre-eminently the sense of touch. These parts are likewise destitute of hair, and the papillae which are there very numerous and visible to the naked eye. are very sparsely distributed and appear rudimental in other parts of the body. Much of the discrepancy among anatomists in regard to the structure of the skin, appears to be owing to whether they have made their researches mainly upon the palms and soles, or upon the skin of other parts of the body. Chevalier* and Wallace,! have described especially in the skin of the face, arms, and legs, a system of epidermoid glands, seated in the rete mucosum, and so minute that the latter counted one hundred of them in the one-twenty-fourth part of a square inch, and which gave issue to the sweat. These appear to me, to correspond with the diapnogenous apparatus of Breschet, as he represents them in the palms and soles. The opinion of Bichat, is therefore erroneous, that the sense of touch is only more perfect in the hands than other portions, in consequence of the shape of the parts, and the facility with which they may be applied round objects, and that the skin of the abdomen substituted for that of the fingers, would have constituted organs of touch. p. f In the early part of the last century, an anatomist by the name of St. Andre, exhibited a preparation of the cuticle which appeared to be injected with mercury. Ruysh declared the thing impossible, and invited him to an investigation of the subject. This invitation was not accepted, and the affair has been generally considered as a mistake or an imposition. H. * Lectures on the general structure of the human body, and on the anatomy and functions of the skin, by J. Chevalier. t Lectures on the structure of the skin, by W. Wallace, London Lancet, 1837. OF THE CUTICLE. 431 It extends over the whole external surface of the body, except the parts covered by the nails, and is accommodated to the surface of the skin, by forming ridges or furrows, cotfes- ponding to it. It adheres most closely to the cutis ; and when abraded by mechanical violence, the surface of the skin appears moistened by effusion. It is not certain that its mode of union with the skin is perfectly understood ; the adhesion of these membranes to each other is as uniform as that of two smooth surfaces glued together, but it is generally said that the cuticle is attached to the cutis by very numerous and fine filaments. It has often been asserted that these filaments are the exhaling and absorbing vessels, which pass through the cuticle, to and from the skin. This sentiment appears very reasonable, but no vessels that pass in this way can be injected. There are innumerable processes which pass from the cuticle to the skin. Many of these are the linings of the cavities which contain the roots of the hairs ; but they are reported by micro- scopical observers to be like the fingers of a glove, closed at their extremities. There are also many processes which contain a sebaceous substance that may be pressed out of them in the form of worms ; these are the ducts of sebaceous glands. Besides these, there is an immense number of whitish fila- ments, which are as fine as the most delicate thread of a spider's web. These filaments can be best seen while the cuticle is separating from the skin of the sole of the foot, as suggested by Dr. William Hunter.* They are supposed to be vascular, but they have never been injected. When the cuticle is in its natural situation, in union with the skin, there appears to be three species of foramina or pores, on its external surface: viz. 1. Those formed by the passage of the hairs ; and 2. Those which are the orifices of the ducts of the sebaceous glands ; each of which has been already men- * See the London Medical Observations and Inquiries, vol. ii, n. 432 OF THE CUTICLE. tioned. And 3. Such pores as exist on the ends of the fingers and the inside of the hands. It is said that these last are very visible, when magnified to twice or thrice their original bulk, and drawings of them have accordingly been made by Dr. Grew* and by Mr. Cruikshank.f Small specks of fluid can be seen with the naked eye, in the same situations, in warm weather, or when the ends of the fingers are made turgid by a ligature. It is probable that they are formed by the accumulation of fluid at these orifices. The above described pores are situated on the ridges at the ends of the fingers and not in the furrows ; and it is probable that similar pores are distributed over the surface of the body. , Notwithstanding the appearance of these foramina, when the cuticle is in its natural situation, several of the most suc- cessful investigators of the subject have declared that they could not discover any pores or foramina in the cuticle, when it was separated from the cutis. The late Professor Meckel of Berlin, who was one of this number, was induced to believe that the matter of exhalation, and of absorption, soaked through the cuticle, as the vapor of warm water passes through leather.f In support of this doctrine he states that perspiration goes on through the cuticle on the palms of the hands and soles of the feet when it is very thick ; and observes, that if it were trans- mitted by delicate vessels, the vessels in the feet must be torn by the weight of the body, in persons who walk ; and those in the hands would experience the same fate, in laborers, who work with heavy hammers, &tc. On the other hand, Mr. Cruikshank, who could likewise find no pores in the separated cuticle, contends strenuously for their existence notwithstanding ; and explains their non-appearance by the following facts, among others ; viz. that no foramen will appear in the separated cuticle, although it has been punctured by a needle ; and that when the cuticle has been peeled off, * In the Philosophical Transactions, vol. iii. Lowthrop's Abridgement. f See his Experiments on Insensible Perspiration. $ See Memoirs of the Royal Academy of Sciences of Berlin, vol. xiii. for 1757 . CAUSES WHICH PRODUCE VESICATION. 433 from portions of the cutis on which were hairs which must necessarily have perforated it, no foramina have appeared in it. M. Bichat took very different ground : he asserted that the pores of the separated cuticle were to be seen distinctly, in large numbers, by looking through it towards the light ; he also believed that the course of the exhalent vessels, through the cuticle, might be seen in the same manner; and that they passed obliquely. That the cuticle is pervious, is proved incontestably by the functions of perspiration and sweating, as well as of absorption ; but there are good reasons for believing that the perforations of the cuticle have a peculiar structure ; and are not simple foramina. Thus, when a vesicle is formed by the operation of cantharides or any other process, if the cuticle is not lacerated, it will confine the effused fluid for a considerable time, without any appearance of its escape through these pores. This fact, which is strongly opposed to the hypothesis of Meckel, is explained by Cruikshpnk upon the supposition that the pores of the skin are lined by processes of the cuticle, and that when the cuticle is separated from the cutis, these pro- cesses go with it, and act like valves in confining the fluid. Bichat supposes the oblique vessels to produce the same effect upon analogous principles ; and compares their situation to that of the ureters, which pass obliquely between the coats of the bladder. This peculiar quality of the cuticle, in admitting of perspira- tion and sweat, and also absorption, while it prevents evapo- ration from the parts which it encloses, is of immense impor- tance. If a portion of skin be deprived of cuticle a short time before death, by a blister for example, this portion will, in a few days, become perfectly dry and hard, like horn ; while the other parts of the skin of the subject, covered by the cuticle, retain their moisture and flexibility. It may, therefore, be admitted, that the use of the cuticle is to keep the -skin soft and flexible, by confining its moisture, as 37 434 SEPARATION OF THE CUTICLE. well as to defend it.* And it is probable tbat the sebaceous matter is secreted for the purpose of preserving the cuticle in a state of flexibility. As the cuticle is capable of confining fluid, and resisting the action of chemical agents, it is surprising that epispastics and rubefacients should act through it, upon the skin, with so much certainty as we find they do; and that cantharides should pro- duce vesications, when applied dry. The thickness of the cuticle on every part of the body is much increased by long continued pressure, forming corns and excrescences of its own nature. By this cause also it is ren- dered very thick on the palms of the hands and soles of the feet ; although it is originally thicker there than in other parts. It is said that, after long boiling, these thick portions of cuti- cle may be separated into distinct lamina. In the living subject, the cuticle, when immersed in warm water, seems to absorb some of that fluid ; as is evinced by the hands when they have been long in that situation ; and also by those parts of the skin to which poultices have been applied. Notwithstanding the uniform adhesion of the cuticle to the cutis, it is observed, in the living subject, to be separated, and formed into vesicles, by a variety of causes, viz. 1. Pinching of the skin, or violent mechanical irritation ; such as laboring with hard instruments. 2. By the application of cantharides, and certain other sub- stances which produce vesications. Sometimes these sub- stances appear to inflame the skin ; but on other occasions the vesication is produced while the skin appears unchanged in color, and free from inflammation. The process appears dif- ferent from that of simple inflammation ; for certain rubefa- cients often inflame the skin considerably without vesicating or blistering it. 3. Boiling heat will, very generally, produce vesication. 4. Certain diseased processes seem to occasion vesication in * This property of the cuticle is rendered very apparent in attempting to dry anatomical preparations with the skin on, in which the student will fail, unless the cuticle is previously removed by maceration. p. CHEMICAL, QUALITIES OF THE CUTICLE. 435 a manner which is not well understood, viz. erysipelas, zona, or shingles, pemphigus, and some other eruptions which have no name. In erysipelas there is an obvious inflammation of the skin ; but in some of the other diseases the vesication takes place without the appearance of inflammation. 5. Vesications often appear when there is a tendency to gangrene. 6. They also occur in some cases of simple fracture, where there is considerable injury. In these cases the fluid effused is often tinged with blood. After death the cuticle is separated from the cutis : 1. By putrefaction; in which case large vesicles are some- times formed. 2. By long continued maceration, 3. By boiling, and 4. By violent dry heat. The cuticle appears to be least deranged when it is separated by putrefaction and maceration : in these cases the internal surface corresponds to the surface of the skin ; and the pro- cesses which contain the hairs, as well as those which are the ducts of the sebaceous glands, are particularly obvious. The external surface of the cuticle varies in different places, according to the surface of the skin. In some places it appears scaly at times, and has therefore been supposed to consist entirely of scales ; but in other parts, when examined atten- tively, it appears like a half transparent concreted substance, with a rough surface. When the skin has continued dry for a long time, bran-like scales can be rubbed off from it. These are probably com- posed of the residuum of the secretion deposited on the skin, and of a portion of the external surface of the cuticle. The same substance appears upon the first washing of the skin, after that process has been discontinued for any length of time. Many speculations have arisen respecting the manner in which the cuticle is originally formed, and reproduced ; but none of these are perfectly satisfactory. It is also a question whether the cuticle is endued with vitality, 436 CHEMICAL DUALITIES OF THE CUTICLE. or is merely an inanimate unorganized concrete. No decisive argument have been adduced in favor of its vitality ; and it has already been stated, that neither nerves nor vessels can be demonstrated in it. It appears particularly calculated for protecting the skin which it covers ; for it is insoluble in water, and resists the action of several powerful Chemical agents. Thus, it is not affected by immersion for a considerable time m the sulphuric and muriatic acids ; although the nitric acid acts upon it. It resists for a short time, but is at length dissolved, by the pure fixed alkalies, and by lime. It is supposed by the chemists to consist of albumen, in a peculiar state of modification. Malpighi, was the first to discover, by the use of the microscope, an intervening substance between the cuticular covering, and the cutis vera, which he called the rete mucosum or corpus reticulare. This he considered the seat of coloration in the negro, and asserted the cuticle to be alike in all varieties of the human race that is, colorless. For a long period his researches formed the basis of all the systematic treatises upon the skin, and it is only within a recent period, as has before been observed, that the study of the subject has been resumed. The cuticle of the black is now generally admitted to be of an ashy color.* And Flourensf has shown, that the reticular appearance of the rete mucosum is entirely an adventitious circumstance. Malpighi first discovered his rete mucosum on * Breschet has asserted that the color of the skin in different animals is dependent upon the form of the scales of the epidermis, by which the light is reflected. Fig. 115. The larger cut represents, after this observer, the scales of the epidermic or corneous matter of a white man, diluted with water, and highly magni- fied, in which are seen fragments of the sudoriferous canals and inhalent vessels. The scales all have a trapezoidal or lozenge shape. The smaller cut, represents a single scale from the skin of a whale, highly magnified. It is black at its summit, and whitish at its pedicle of insertion. The skin of the whale is black, and these writers assert, that in all animals with black skins, including negroes, the scales of the epidermis, appear under the microscope of this shape or spatulate. P. f Annales des sciences naturelles, 1837. CHEMICAL QUALITIES OF THE CUTICLE. 437 the tongue of the ox, and subsequently under the epidermis of the human hand, from which he drew his description. By ebullition he softened the outer covering of the cutis vera,>6nd then tearing off the epidermis, he saw a layer of soft substance with holes in it like the meshes of a net. This was owing to a laceration of the mucous layer: the part covering the apices of the villi going off with the cuticle, while that between the villi and the bases of the papillae adhered to the cutis vera. By maceration in water, which is the surest and most success- ful method of effecting a dissection in delicate parts, FJourens, found in the same organs the cuticle to come off, leaving the whole of the mucous body attached, which then presented none of the reticular appearance. The cuticle arid mucous body were both continuous layers, covering the papillae and forming their sheaths. The sheaths formed by the latter body were broken in Malpighi's preparation. The cuticular sheaths in the ox, were thin and delicate over the fungiform or smaller papillae, but formed thick horny layers over the larger which assist in the action of mastication. Albinus, repeating the experiments of Malpighi, corrected his error, and in the beautiful designs of Ladmiral, has repre- sented the mucous body as a continuous layer. Since then by Bichat and others, the use of the term rete mucosum, has been continued, not exactly in the original signification of Malpighi, but under the belief that it contained a net-work of vessels. Its foliated structure has been well established by Cruikshank, Gaultier, and Flourens. It thus appears that the whole of the anatomy of the skin, requires to be constructed anew. Several of the German and French anatomists have applied themselves to the task, among whom may especially be men- tioned Weber* of Leipzig, and Breschet of Paris.f The views of the latter, on account of his having treated the subject more extensively than the rest, as well as from his high situation in the school of Paris, have already been given. The physiology * Arch, fur die Physiologic. f Nouvelles Recherches sur la Structure de la Peau, par G. W. Breschet et Roussel de Vauzeme. Paris, 1835. 37* 438 CHEMICAL DUALITIES OF THE CUTICLE. of cuticle has received an entirely new aspect, from recent observations, and especially from those of Henle.* He has shown that with very few exceptions, all the free surfaces of the body not only the skin which has its cuticular covering but those of the serous cavities, the mucous passages,! the blood-vessels, and the ducts of the glands, are invested by a membrane, composed of one, or more layers of primary cells, forming a delicate cuticle or epithelium. The epidermis, cuticle, or external covering of the skin, when examined with a powerful microscope, is seen to be composed of several layers of cells, which 'are the consequence of an uninterrupted process of exudation which has place upon the corion or true skin. This exudation, though unorganized, retains some vital proper- ties, and is a cytablastema ; that is, a basis structure, or soil/ from which new growths or developments take place. These new growths are cytoblasts, or cell germs ; that is, cells or vesicles, at first globular, afterwards lenticular and opaque, (each one surrounding a central nucleus), which possess within themselves the inherent principles of growth.^ The more recently produced cells, which of course are those in contact with the corion, are like all young cells, spherical in their figure ; they become flattened as they develop themselves and approach the surface ; so that when examined on a sec- tion, they are found to have undergone changes of form from that of a globular cell, provided with a nucleus, to that of a flat scale, in which no trace of a nucleus appears, and which lay, one over another, like so many layers of tiles or pavement. The innermost layers are soft and cellular; the outer ones become dried on the surface from exposure to the air, and fall off in squamae or scales. * Allgera. Anat., p. 260. f Vide Gen. Anat. of Serous and Mucous Membr. Vol. 2. f The cell germs, here and in other parts of the body, bear a general rela- tion to the size of the blood globules of the same individual. This is a remarka- ble fact, and somewhat in favor of the views of Dr. Barry, who states that it is the blood disks that are transformed into these cell germs. Phil. Trans. Part 11. 1840. Henle, makes three varieties of epithelium or cuticle, 1st. The pavement- ed sqnamous or tesselated epithelium, above described, found on the skin, serous THE NAILS. 439 The Nails. The roots of the nails appear to originate in a fold of the cutis vera, from the epidermis which lines the fold ; but "ihe bodies of the nails adhere firmly to the cutis on which they lie, and appear to cover it, in the place of the cuticle. The papillae of those parts of the cutis which are covered by the nails are very conspicuous when the nails are removed. It has been supposed that there was no rete mucosum between the nails and cutis ; but this opinion is probably erroneous, as the black pig- ment is perceptible under the nails of some negroes. The nails can be separated from the cutis by all those pro- cesses which separate the cuticle from it. When this is effected, they remain connected with the cuticle, which appears to be continued into them ; and on this account, as well as their insensibility, and their resemblance to the horny excrescences of the cuticle, they are considered as appendages of it. The root is opaque, and appears white. The body is trans- parent, and in health shows the florid color of the cutis which it covers ; but the color of this portion of the cutis depends upon the state of the circulation ; and becomes livid when the blood is disoxygenated, or when the circulation ceases there ; and this color also appears through the nails. The nails are unquestionably organized, although their ultimate structure is not known. They appear to be composed of lamellae, and these lamellae of fibres. They grow rapidly, and when they are not pared or worn away, they sometimes acquire an immense size. As a remarkable instance of this, it is related, that a nail of the great toe was sent from Turin to the Academy of Sciences at Paris, which measured four inches and a half in length. The growth seems to take place altogether at the roots. The nails, when chemically examined, appear to consist of membranes, the lining membrane of the mouth, pharynx, oesophagus, and the vagina and cervix uteri. 2d. The cylinder epithelium, found in the remainder of the alimentary canal, the ducts of the glands, and a great part of the genito- urinary apparatus of the male. 3. The ciloary epithelium, found in the respira- tory organs, the lachrymal passages, Eustachian and Fallopian tubes, etc. Vide the account of these organs, 440 THE NAILS. a modification of albumen ; and thus resemble cuticle and horn in their composition. The growth of the nails, forwards, is entirely from a fold of the cutis vera, at its root, called, though not with exact pro- priety, the matrix of the nail, as seen iri fig. 116. It grows also in thickness %>m the upper surface of the skin, upon which the nail rests. In the formation of a new nail the la- men which starts from the matrix, receives successive layers from be- neath, as it approaches the extremity, the deepest seated of which is the shortest. In this way the nail gets its thickness and strength, and occasionally, where the deposition of new matter, goes on more rapidly under the body of the nail than at the matrix, the body is thrown up into unsightly rugosities. Its development is exactly similar to that of the horns and hoofs of animals. The striated appearances of the nail, is said to be owing to the papillary prominences below, being arranged in con- centric plicae. The white semicircular line at the root, is called the lunula. The nails are not exactly analogous in structure to the cuticle, in the ordinary acceptation of the term to that part which is raised up under a blister. The proper cuticle is that thin coating which is scraped away and worn off near the root, and which otherwise would cover the surface. . The nails consist of the proper cuticle, and tunica albuginea superficialis and the gem- mules of Gaultier leaving interposed between them and the cutis vera, the tunica albuginea profunda which is insensible, and explains why it is that a splinter, or the blade of a small pair of scissors, in the operation for onychia, may be run along close on the under surface of the nail, without the production of much pain. According to Breschet, the nail is formed like the other parts of the horny coat exterior to the cutis vera, by the glands for the secretion of the mucous and coloring matter ; the products of which would be mixed up together, coloring the substance of the nail, as we know is the case in regard to the horns and hoofs of animals. THE HAIRS. 441 The Hairs Originate from bulbs which are situated at the bottom of pores or cavities in the skin. These pores appear to be Imed by a production of the cuticle, and the extremities of the bulbs project beyond them into the cellular membrape. In some cases, where the cuticle is separated after putrefaction, it seems that these lining processes of the cuticle come away completely, and bring the hairs and roots with them ; but in other cases, the cuticle separates from the cutis, and leaves the hairs in their natural situation.* When viewed in a microscope, the bulb appears half trans- parent, and whitish ; and of a softer consistence than the hair itself. The extremity of it is remarkably flexible, and some- times much darker than the rest of the bulb. The hair does not appear to extend completely to the end of the bulb. Neither blood-vessels nor nerves have been traced to these bulbs, although it is probable they extend there ; for the operation of extracting hair by the roots is generally very painful ; and blood sometimes appears in the pore from which the hair is extracted. The body of the hair appears to be composed of smaller fibres, enclosed in a membrane which often is imperfect at the extremity ; in consequence of which the fibres often separate from each other, or split. Within the hair is diffused the substance upon which its color depends : this does not appear to be essential to the structure, as in the advance of life the hair is so generally without it, while its structure continues unchanged, although it becomes less flexible. The color of the hair appears to have some connexion with * Dr. Dom. Nardo, of Padua, asserts that he has succeeded frequently upon himself, in transplanting a hair with its bulb, from one of the pores of the head into one of the pores of the chest ; which is done by enlarging the latter pore with a needle, introducing the bulb into it with exactness, and exciting a slight inflammation around it by friction. The planted hair takes root, grows, arid in process of time, undergoes the usual changes, becomes gray, and is shed. Giorn delV ltd. 442 BULBS OF THE HAIRS. the color of the rete mucosum, as it is so generally black when the rete mucosum is dark colored. The sudden change of color in consequence of fright or grief, is a very rare occurrence indeed ; but Bichat relates an instance which came under his observation, in which the hair became perfectly white in one night, in consequence of grief. The substance of the hair is of a corneous nature like the epidermis. Each hair consists of two parts, a bulb or follicle, and a stalk or hair proper. The follicle is ovoidal, and consists of two membranes. The exterior is white, firm, and continuous with the cutis vera ; the interior, which is thin, soft and reddish, appears to be continuous with the corneous layers. The cavity of the follicle is filled up at the bottom with a conical papilla, into which, according to Beclard, the nerves and blood-vessels may be seen running below. Rudolphi and Andral, have traced nerves into the whiskers of the seal ; Shaw has done the same, and discovered that they were branches of the fifth pair. The root of the hair possesses a coni- cal cavity, in which is lodged the point of the papilla which appears to secrete the matter of the hair, and cause its growth, by the continuous deposition of new matter at its root, as takes place in regard to the nails of man, and the horns of animals ; this deposit of new matter in the fluid state, has been seen between the hair and papilla. It is sometimes secreted in pro- fusion, especially in the head ; and has appeared to me, by over- flowing from the follicles, and drying in the form of scales, to be the source of the dandriff. The epidermis is reflected from the mouth of the follicle, and lost upon the surface of the hair. The hair, when examined with the microscope, appears to be covered externally with small scales, and to be hollow inter- nally. The latter, however, is as regards the human hair, an optical illusion, as it is merely loose and porous or pith-like in its central part. The stalks of hairs have neither vessels nor nerves in their structure, and anatomists no longer admit STRUCTURE OF THE HAIRS. 443 a fluid in their interior described by Bichat and others as the marrow.* Around the orifices of the follicle, and in the substance o/its neck according to Gaultier, we find a number of minute sebaceous glands, that secrete an unctuous fluid, which imbues the hair and preserves its softness and pliability. The hairs are hygrometrical, and increase in length and thickness when exposed to humidity ; and are shortened again by dry heat. From the changes which take place in regard to the color of the hair, there is reason to believe, that it is traversed by some fluid. This passes along the hair by imbibition, from the root upwards, in consequence of its hygrometrical nature, passing up through the spongy or cellular tissue of which the body of the hair appears to be formed. This fluid is derived from the surface of the skin forming the papilla, and is analogous to the fluid of the rete mucosum, and corresponds more or less in color with that of the skin and iris. The hairs vary much in size, but appear all to be constructed on the same plan. They have different names in different parts of the body, as beard, whiskers, eyelashes, &c. The minute hairs generally spread over the body, are called down or duvette, and those which cover the scalp, in man, have particu- larly appropriated to them the term of hair. In the white or Caucasian variety of the human race, the hairs of the head are very numerous, fine, long, and vary in color from white to black : in the Mongolian they are straight, black and short : in the Negro, black, fine, thick and crisped : in the Indian, black, straight, fine and thick: and in the Malay, thick and frizzled. Their size and number vary in regard to their color. Withoff, has calculated that in a quarter of an inch square of skin there are one hundred and forty-seven black hairs, one hundred and sixty-two chestnut, and one hundred and eighty- two, blond. The hairs are composed chemically, agreeably to Vauquelin, 4 * Note to Bichat, 4th edit. Paris. 444 CHEMICAL COMPOSITION OF THE HAIRS. chiefly of animal matter, of some concrete white, and some black oily matter; iron, oxide of manganese, phosphate and carbonate of lime, silex and sulphur. The change of color to gray, is said to be owing to a preponderance in the formation of the white oily substance, and the development of some phosphate of magnesia.* The shape of the hairs vary in differ- ent parts. From the large size of the nerves which enter the papilla?, to which the hairs are attached, they become in many animals delicate instruments of touch. The formation of the hair depends upon the follicle ; while this remains healthy, though the hair should be removed by its roots, it will again be repro- duced. Boucheron in a recent work on the hair, says that in baldness the bulbs are often only partially atrophied, a circumstance which does not render hopeless the idea of their recovering their original functions, and re-secreting the horny matter which forms the hair, under the influence of certain stimuli. Round the bulbs of the larger hairs, are found some smaller ones, which, as seen in extraction of the former in some cases of tinea capitis, are sometimes developed to an unusual extent. It has also been frequently observed, that in many women the almost imperceptible down of the face presents, after the fortieth or fiftieth year of age, a great increase of development. The bulbs of the hairs are obliquely and confusedly implanted in the dermis hence when one straggling white hair is extracted from the head, the neighboring ones speedily whiten in their turn from the disturbance and injury which their bulbs have suffered. There are many hairs, which are developed so feebly that they do not pass the epidermis, but roll and curve themselves under it. From accidental circumstances the energy of the bulbs of these hairs is sometimes so increased, that skin which had been previously smooth, becomes hairy. Boucheron, attri- butes the color of the hair to a peculiar animal oil, secreted * C. P. Ollivier. CHEMICAL COMPOSITION OF THE HAIRS. 445 by the bulbs, and varying consequently in its properties in different individuals. It is to a change in the color of this oily matter, arising from a variety of causes, which enfeeble' the general system, as grief, intense study, &c., that is attributed the whitening of the hair. The SKIN, constructed as above described, answers a fourfold purpose in the animal economy. It is the organ of touch. It covers and protects the whole structure. It is the outlet for a large proportion of the insensible perspira- tion, and it performs to a certain extent absorption. Many facts have been noticed by practitioners of medicine, which proves that it has a connexion with the lungs and stomach, which is not yet explained by anatomy. As one of these, an effect of the urticaria or nettle-rash may be mentioned. This eruption sometimes relieves completely the spasmodic croup; and in other cases, nausea and vomiting. Some children, when affected with this species of croup, are relieved by rubbing the skin with harsh woolen cloth. In some places, the urticaria and the affection of respiration are so much regarded as symptoms of the same disease, that the term hives is used as the name for each of them. 38 PART V. OF THE NOSE, THE MOUTH, AND THE THROAT. CHAPTER XII. OF THE NOSE. THE prominent part of the face, to which the word nose is exclusively applied in ordinary language, is the anterior covering of two cavities which contain the organ of smelling. These cavities are formed principally by the upper maxillary and palate bones ; and, therefore, to acquire a complete idea of them, it is necessary to study these bones, as well as the os ethmoides, the vomer, and the ossa spongiosa inferiora, which are likewise concerned in their formation. In addition to the description of these bones, in the account of the bones of the head, it will be useful to study the descrip- tion of the cavities of the nose which follows it, (see page 122.) After thus acquiring a knowledge of the bony structure, the student will be prepared for a description of the softer parts. Of the External Nose. The superior part of the nose is formed by the ossa nasi, and the nasal processes of the upper maxillary bones, which have been already described, (see pages 86-89) ; but the inferior part, which is composed principally of cartilages, is much more complex in its structure. The orifice, formed by the upper maxillary and nasal bones, is divided by a cartilaginous plate, which is the anterior and inferior part of the septum, or partition between the two cavi- ties of the nose. The anterior edge of this plate projects beyond the orifice in the bones, and continues in the direction of the OF THE NOSE. 447 suture between the ossa nasi. This edge forms an angle with the lower edge of the same cartilage, which continues from it in a horizontal direction, until it reaches the lower part df the orifice of the nose, at the junction of the palatine processes of the upper maxillary bones ; where a bony prominence is formed, to which it is firmly united. The upper part of the anterior edge of this cartilage, which is in contact with the ossa nasi, is flat, and, is continued into two lateral portions that are extended from it one on each side, and form a part of the nose : these lateral portions are sometimes spoken of as distinct carti- lages, (superior lateral?) but they are really continuations of the middle portion or septum. Below the lower edge of these late- ral portions are situated the fibro carti- lages which form the orifices of the nose, or the nostrils. Of these, there is one of considerable size, (inferior late- ral,) and several small fragments, on each side of the septum. Each of the larger cartilages forms a portion of an oval ring, which is placed obliquely on the -side of the septum : so that the extremity of the oval points downward and forward, while the middle part of the oval is directed upwards and back- wards. The sides of this cartilage are flat, and unequal irf breadth. The narrowest side is internal, and projects lower down than the cartilaginous septum ; so that it is applied to its fellow of the other nostril. The external side is broader, and continues backward and upward to a con- siderable distance. * a, b, Ossa nasi, which show above, the serrated surface by which they are united to the os fronds, c, d, Superior lateral cartilage, e, Vertical carti- laginous septum of the nose. /, /, Sesamoid cartilages, filling up part of the vacuity here. g t I, Oval or inferior lateral cartilages, or cartilages of the alse nasi ; below they are thin and curved so as to form the arch of the anterior nares. h, i, k, Small square cartilages appended to the alae nasi and circum- scribing the outer and back part of the nostrils, m, n, o, Same parts of the right side. 448 OF THE NOSE. The upper and posterior part of this oval ring is deficient ; but the remainder of the nostril consists of several small pieces of cartilage, (cartilages carres,) which are fixed in a ligamen- tous membrane that is connected by each of its extremities to the oval cartilage, and thus completes the orifice. The anterior parts of the oval cartilage form the point of the nose ; and the ligamentous portions, the alae or lateral parts of the nostrils. When the external integuments and muscles are removed from the lower portion of the nose, so that the internal mem- brane and these cartilages only remain, the internal membrane will be found attached to the whole bony margin of each orifice, and to each side of the whole anterior edge of the middle cartilage, which projects beyond the bones. This membrane is afterwards continued so as to line the oval cartilages and the elastic membrane of the ala nasi, to the margin of the orifice of the nostril. The internal portions of the oval cartilages being situated without the septum, and applied to each other, they form the external edge of the partition between the nostrils, or the columna nasi ; which is very movable upon the edge of the middle cartilage. The orifices of the nostrils, thus constructed, are dilated by that portion of the muscle, called Levator Labii Superioris Alceque Nasi, which is inserted into the alae nasi. They are drawn down by the depressor labii superioris alsque nasi. They are pressed against the septum and the nose by the muscle called Compressor Naris y which has however an opposite effect when its upper extremity is drawn upwards by those fibres of the occipito frontalis, which descend upon the nose, and are in contact with it. The end of the nose is also occasionally drawn down, by some muscular fibres which descend from it, on the septum of the nose, to the orbicularis oris : they are considered as a por- tion of this muscle by many anatomists, but were described by Albinus as a separate muscle, and called Nasalis Labii OF THE CAVITIES OF THE NOSE. 449 When inspiration takes place with great force, the alae nasi would be pressed against the septum, if they were not drawn out and dilated by some of the muscles above mentioned. Of the Cavities of the Nose. To the description of the osseous parts of the nasal cavities in page 89, it ought now to be added, that the vacuity in the anterior part of the osseous septum is filled up by a cartilaginous plate, connected with the nasal lamella of the ethmoid bone above, and with the vomer below. This plate sends off those lateral portions already described, which form the cartilaginous part of the bridge of the nose. It should also be observed that at the back parts of these cavities are two orifices called the Posterior Nares, (see fig. 118, p. 454,) which are formed by the palate bones, the vomer, and the body of the sphenoidal bone, and are somewhat oval. The nasal cavities, thus constructed, are lined by a peculiar membrane, which is called pituitary from its secretion of mucus, or Schneiderian after the anatomist who described it with ac- curacy.* This membrane is very thick and strong, and abounds with so many blood-vessels, that in the living subject it is of a red color. It adheres to the bones and septum of the nose like the periosteum, but separates from them more easily. The surface which adheres to the bones has some resemblance to periosteum, while the other surface is soft, spongy, and rather villous. Bichat seems to have considered this membrane as formed of two lamina, viz. periosteum, and the proper mucous membrane ; but he adds, that it is almost impossible to separate them. It has been supposed that many distinct glandular bodies were to be seen in the structure of this membrane by examin- ing the surface next to the bones ;f but this opinion is adopted * Conrad Schneider, a German professor, in a large work, "De Catarrhis," published about 1660. f See Winslow, Section X. No. 337. 38* 450 SCHNEIDERIAN MEMBRANE. by very few of the anatomists of the present day. The texture of the membrane appears to be uniform; and on its surface are a great number of follicles of various sizes, from which flows the mucus of the nose. These follicles appear like pits, made by pushing a pin ob- liquely into a surface which retains the form of the impression. They can be seen very distinctly with a common magnifying glass when the membrane is immersed in water, both on the septum and on the opposite surface. They are scattered over the membrane without order or regularity, except that in a few places they occur so as to form lines of various lengths, from half an inch to an inch. The largest of them are in the lower parts of the cavities. The surface of this membrane when examined with the mi- croscope, is found to be furnished with the ciliary epithelium, consisting of minute projections or columns, thickly set with fine cilia or fringes, which have a peculiar vibratile motion of their own for carrying on fluids, not well understood. It may be presumed that the secretion of mucus is effected here by vessels which are mere continuations of arteries spread upon a surface analogous to the exhalents, and not convoluted in circumscribed masses, as in the case of ordinary glands. The arteries of this membrane are derived from various sources : the most important of them is the nasal branch of the internal maxillary, which passes into the nose through the spheno-palatine foramen, and is therefore called the Spheno- palatine Artery. It divides into several twigs, which are spent upon the different parts of the surface of the nasal cavities. Two of them are generally found on the septum of the nose : one, which is small, passes forwards near the middle ; the other, which is much larger, is near the lower part of it. Two small arteries, called the anterior and posterior eth- moidals, which are branches of the ophthalmic, enter the nose by foramina of .the cribriform plate of the ethmoidal bone. These arteries pass from the orbit to the cavity of the cranium, and then through the cribriform plate to the nose. In addition to these, there are some small arteries derived from the infra- OLFACTORY NERVES. 451 orbital, the alveolar and the palatine, which extend to the Schneiderian membrane; but they are not of much importance. The veins of the nose correspond with the arteries. Tliose which accompany the ethmoidal arteries open into the ocular vein of the orbit, which terminates in the cavernous sinuses of the head. The other veins ultimately terminate in the external jugulars. The nerves of the nose form an important part of the struc- ture ; they are derived from several sources ; but the most important branches are those of the olfactory. The olfactory nerves form oblong bulbs, which lie on each side of the crista gilli, on the depressed portions of the cribri- form plate of the ethmoid bone, within the dura mater. These bulbs are of a soft consistence, and resemble the cortical part of the brain mixed with streaks of medullary matter. They send off numerous filaments, which pass through the foramina of the ethmoid bone, and receive a coat from the dura mater as they pass through it. These filaments are so arranged that they form two rows, one running near to the septum, and the other to the surface of the cellular part of the ethmoid bone, and the os turbinatum : and in addition to these are some intermediate filaments. When the Schneiderian membrane is peeled from the bones to which it is attached, these nervous filaments are seen passing from the foramina of the ethmoid bone to the attached surfaces : one row passing upon that which covered the septum, and the other to that of the opposite side ; while the intermediate fila- ments take an anterior direction, but unite to the membrane as soon as they come in contact with it.\^~ All of these can be traced downwards on the aforesaid surfaces of the membrane for a considerable distance, when they grad- ually sink into the substance of the membrane, and most pro- bably terminate on the internal villous surface ; but they have not been traced to their ultimate termination. They ramify so that the branches form very acute angles with each other. On the septum the different branches are arranged so as to form 452 SPHENO-PALATINE AND OTHER NERVES OF THE NOSE. brushes, which lie in contact with each other. On the opposite sides, the different ramifications unite, so as to form a plexus. Dr. Soemmering has published some very elegant engravings of the nose, representing one of his dissections, which appears to have been uncommonly minute and successful.* These represent the ramifications as becoming more expanded and delicate in the progress towards their terminations, and as observing a tortuous course, with very short meandering flexures. It is to be observed that the ramifications of the olfactory nerve, thus arranged, do not extend to the bottom of the cavity. On the external side, they are not traced lower than the lower edge of the etbmoid, or of the superior spongy bone: and on the septum, they do not extend to the bottom, although they are lower than the opposite side. On the parts of the mem- brane not occupied by the branches of the olfactory nerves, several other nerves can be traced. The nasal twig of the ophthalmic branch of the fifth pair, after passing from the orbit into the cavity of the cranium, proceeds to the nasal cavity on each side by a foramen of the cribriform plate ; and after send- ing off some fibrillae, descends upon the anterior part of the septum to the point of the nose. The spheno-palatine nerve, which is derived from the second branch of the fifth pair, and enters the nose by the spheno-palatine foramen, is spread upon the lower part of the septum and of the opposite side of the nose also, and transmits a branch through a canal in the fora- men incisivum to the mouth. Several small branches also pass to the nose from the palatine and other nerves; but those already mentioned are the most important. A question has been proposed, whether the olfactory nerve is exclusively concerned in the function of smelling, or whether the other nerves above mentioned are also concerned in it. It seems probable that this function is exclusively performed by the olfactory nerve, and that the other nerves are like the ophthalmic branch of the fifth pair, with respect to the optic * They are entitled, Icones Organorum Humanorum Olfactus. EXTENT OF THE SCHNE1DER1AN MEMBRANE. 453 nerve. In proof of this, it is asserted that the sense of smelling has entirely ceased in some cases, where the sensibility to mechanical irritation of every kind has remained unchanged. If the olfactory nerve alone is concerned in the function of smelling it follows, that this function must be confined to the O' ' upper parts of the nasal cavities ; but it ought to be remem- bered, that the structure of the Schneiderian membrane, in the lower parts of these cavities, appears exactly like that which is above. The surface of the nasal cavities and their septum, when covered with the Schneiderian membrane, correspond with the osseous surface formerly described. The membrane covers the bones and cartilage of the septum, so as to make one uniform regular surface. From the upper part of the septum, it is con- tinued to the under side of the cribriform plate of the ethmoid, and lines it ; the filaments of the olfactory nerve passing through the foramina of that bone into the fibrous surface of the mem- brane. It is continued from the septum, and from the cribri- form plate, to the internal surface of the external nose, and lines it. It is also continued backwards to the anterior surface of the body of the sphenoidal bone ; and, passing through the foramina or openings of the sphenoidal cells, it lines these cavities completely ; but in these, as well as the other cavities, its structure appears somewhat changed ; it becomes thinner and less vascular. At the above mentioned foramina, in some subjects, it forms a plate or fold, which diminishes the aperture considerably. From the upper surface of the nasal cavities, the membrane is continued downwards over the surface opposite to the sep- tum. On the upper flat surfaces of the cellular portions of the ethmoid, it forms a smooth uniform surface. After passing over the first turbinated bone, or that called after Morgagni, it is reflected into the groove, or upper meatus immediately within and under it ; the fold formed by the membrane, as it is reflect- ed into the meatus, is rather larger than the bone : and the edge of the fold therefore extends lower down than the edge of the bone, and partly covers the meatus like a flap, consisting 454 EXTENT OF THE SCHNEIDERIAN MEMBRANE. only of the double membrane. This fold generally continues backwards as far as the spheno-maxillary foramen, which it closes ; the periosteum, exterior to the foramen, passing through H, and blending itself with the fibrous surface of the Schneide- Fig. 118.* * Fig. 118 is a vertical section, exhibiting a profile view from the inside of the cavities of the nostrils, mouth, and pharynx, a, The nose, b, Upper lip, situated in front of the palatine arch, which runs horizontally backwards, and divides the cavity of the mouth from the nasal fossae, c, The tongue, the base of which is attached to the os hyoides d. e, The larynx, suspended from the os hyoides, by the thyreo-hoid ligaments which are seen intervening ; it opens backwards towards the pharynx. /, Trachea, g, Cuneiform process of the occipital bone, united to the body of the sphenoid, and to which is chiefly suspended the pharynx h, which is laid open (in order to show its shape and position) by the removal of its right half, and is seen terminating below opposite the cricoid cartilage in the ossophagus. i, Commencement of the resophagus. 7;, Section of the velum pendulum palatae, the lower point of which constitutes the uvula; above this is seen the opening of the posterior nares, 7, into the top part of the cavity of the pharynx ; below this are seen the two half arches of the palate, o, Posterior half arch, r, Anterior half arch, the space or cavity between these occupied by the tonsil gland or amygdala p. 7, Sublingual DISTRIBUTION OF THE SCHNEIDERIAN MEMBRANE. 455 nan membrane within. Here the spheno-palatine nerves and arteries join the membrane. Below this meatus, it extends over the middle, (formerly called the upper,) turbinated bope, and is reflected or folded inwards on the under side of this bone, and continued into the middle meatus below it. In the middle meatus, which is partly covered by the last mentioned turbina- ted bone, there are two foramina ; one communicating with the maxillary sinus, and the other with the anterior cells of the ethmoid and the frontal sinuses. The aperture into the maxil- lary sinuses is much less in the recent head, in which the Schneiderian membrane lines the nose, than it is in the bare bones. A portion of the aperture in the bones is closed by the Schneiderian membrane, which is extended over it : the re- mainder of the aperture is unclosed ; and through this foramen, the membrane is reflected so as to line the whole cavity. As a portion of the foramen is covered by the 'membrane, and this portion, as well as the other parts of the cavity, is lined by the membrane, it is obvious that at the place where the membrane is extended over the foramen in the bone, it must be doubled ; or, in other words, a part of the aperture of the maxillary sinus is closed by a fold of the Schneiderian membrane.* This aperture varies in size in different subjects, and is often equal in diameter to a common quill. It is situated in the gland, placed under the tongue, and communicating with the mouth by a small duct, (ductus Bartholinus :) many small ducts from this gland, open into the duct of the gland below, m, Sub- maxillary gland, situated below and behind the preceding gland, n, Thyroid gland, s, Vertical section of the border of the cervical vertebrae, to which the pharynx is attached by cellular tissue. tj Spinal canal, u, Section of spinous processes and muscles of the neck. v, Left nostril. TV, Bony palate, z, Trumpet-shaped orifice of the Eustachian tube, y, Inferior turbinated bone, covered by the Schneiderian membrane. z, Middle turbinated bone. 1, Superior turbinated bone, both covered with the same membrane. 2, Superior meatus. 3, Middle meatus. 4, Inferior meatus. 5, Place of opening of the ductus ad nasum. 6, Frontal sinuses. 7, The posterior nares. 8, Sphenoidal cell in the body of the sphenoid bone, showing the orifice below, by which it communicates with the top of the pharynx ; above is seen the sella turcica of the sphenoid bone. * In the mucous membrane lining the cavities of the maxillary, sphenoid and ethmoid bones, no one has yet detected any mucous follicles. The pouch formed by the reflection of the membrane, seems itself to constitute a large follicle, from which mucus is abundantly secreted. r. 456 OBSERVATIONS RESPECTING THE NOSE. middle of the meatus, and is covered by the middle turbinatedv bone immediately above it, a prominence of the cellular structure of the ethmoid bone, which has a curved or semicir- cular figure. Near this prominence, in the same meatus, a groove terminates, which leads from the anterior ethmoid cells and the frontal sinuses. From the middle meati^s, the membrane proceeds over, the inferior turbinated bone, and is reflected round and under it into the lower meatus. It appears rather larger than the bone which it covers ; and therefore the lower edge of the bone does not extend so low as the lower edge of the membrane, which of course is like a fold or plait. The membrane then continues and lines the lower meatus : here it appears less full than it is in the turbinated bone. In this meatus, near to its anterior end, is the lower orifice of the lachrymal duct ; this is simply lined by the Schneiderian membrane, which is continued into it, and forms no plaits or folds that effect the orifice. Orifice of the Eustachian Tube. Immediately behind each of the nasal cavities, on the exter- nal side, is the orifice of the Eustachian Tube. It has an oval form, and is large enough to admit a very large quill. Its posi- tion is oblique: the upper extremity being anterior to the other parts of the aperture, and on a^ line with the middle meatus, while the centre is benind the inferior turbinated bone. The lower part of the oval is deficient. This tube is formed poste- riorly by a cartilaginous plate. It is lined by the membrane continued from the nose. The cavities of the nose answer a twofold purpose in the animal economy ; they afford a surface for the expansion of the olfactory nerves, and a passage for the external air to the windpipe, in respiration. The function of smelling appears to be dependent, to a certain degree, upon respiration. It has been asserted that unless the air passes in a stream through the nose, as in respiration, the perception of odor does not take place ; that in persons who breathe through wounds and apertures in the windpipe, the function of smelling is not performed. It is rather in confir- mation of this proposition, that most persons, when they wish to have an accurate perception of any odor, draw in air rapidly through the nose. Although the ultimate termination of the olfactory nerves cannot be demon- strated like those of the optic and auditory nerves, it is probable, from the USES OF THE SINUSES OF THE NOSE. 457 appearance of the fibres, while they are distinguishable, that they are finally arranged with great delicacy. It is certain that the impressions from whence we derive the perceptions of many odors, must be very slight, as some odorous bodies will impregnate the air of a large chamber for a great length of time, without losing any sensible weight. With respect to delicacy of structure and sensibility, it is probable that the nose holds a middle rank between the eye or ear, and the tongue : and on this account the mucus is necessary as a covering and defence of its surface. It has been ascertained, by the investigations of chemists, that this mucus con- tains the same ingredients as the tears already described, namely, animal mucus and water ; and muriate of soda, and soda uncombined j phosphate of lime, and phosphate of soda. The animal mucus, which is a most important ingredient in the composition, resembles the mucilage formed by some of the vegetable gums in several particulars ; and differs from them in others. The mucus of the nose, if it remain there long after it is secreted, becomes much more viscid in consistence, and changes from a whitish color to one which partakes more or less of the yellow. It is probable that an incipient putrefaction may occasion these changes in it. The use of the frontal, maxillary and other sinuses, communicating with the nose, has been the subject of some inquiry. As there can be no stream of air through them, and as the membrane lining them is neither so thick, villous nor flexible as that lining the nose, it may be concluded, a priori, that they are not concerned in the function of smelling. This opinion is strengthened by the fact, that very young children, in whom these sinuses scarcely exist, enjoy the sense of smelling in perfection. The following fact is also in sup- port of it. The celebrated Desault attended a patient, in whom one of the frontal sinuses was laid open by the destruction of the bone which covered it anteriorly. This patient was able to breathe a short time through the sinus when the mouth and nose were closed : at the request of Desault he breathed in this manner when a cup of some aromatic liquor was held near the open- ing of the sinus, and had not the least perception of odor. This experiment was repeated several times. Many physiologists believe that these sinuses have an effect in modulating the 39 458 OF THE MOUTH. CHAPTER XIII. OF THE MOUTH. THE general cavity of the mouth is formed anteriorly and laterally by the connexion of the lips and cheeks to the upper and lower jaws ; so that the teeth and the alveoli of both jaws may be considered as within the cavity. Above, it is bounded principally by the palatine processes of the upper maxillary and palate bones, and the soft palate, which continues back- ward from them in the same direction. Below, the cavity is completed by several muscles, which proceed from almost the whole internal circumference of the lower jaw, and, by their connexions with each other, with the tongue and the os hyoides, form a floor or bottom to it. The tongue is particularly connected to this surface, and may be considered as resting upon and supported by it. To acquire an idea of the parietes of this cavity, after studying the upper and lower maxillary bones, the orbicularis oris and the muscles connected with it, especially the buccina- tor, ought to be examined ; and also the diagastricus, the mylo-hyoideus, genio-hyoideus, and genio-hyoglossus. By this it will appear that the lips and cheeks, and the basis or floor of the mouth, are formed in a great measure by muscles. Upon the internal surface of these muscles, a portion of cellular and adipose substance is arranged, as well as glandular bodies of different sizes ; and to these is attached the membrane which lines the inside of the mouth. This membrane passes from the skin of the face to the lips, and the inside of the mouth ; and, although it is really a con- tinuation of the skin, there is so great a change of structure that it ought to be considered as a different membrane. At the orifice of the lips it is extremely thin, and so vascular, that it INTERNAL SURFACE OF THE MOUTH. GUMS. 459 produces the fine florid color which appears there in health. It is covered by a cuticle, called by some anatomists, Epithe- lium, which has a proportionate degree of delicacy, and carf be separated like the cuticle in other parts. When this cuticle is separated, the lips and the membrane of the mouth appear to be covered with very fine villi, which are particularly apparent in some preparations of the lips after injection and maceration.* Under this membrane are many small glandular bodies of a roundish form, called glandulae labiales, whose excretory ducts pass through it to the inner surface of the mouth, for the pur- pose of lubrifying it with their secretion, which is mingled with the saliva. The membrane which lines the inside of the lips and cheeks, is somewhat different from that which forms the surface of the orifice of the mouth : it is not so florid ; the blood-vessels in its texture are larger, and not so numerous. This change, however, takes place very gradually, in the progress of the membrane, from the orifice of the lips to the back part of the cheeks. Glandular bodies, like those of the lips, are situated immediately exterior to this membrane of the cheeks, between it and the muscles : their ducts open on its surface. These glands are called Buccales. This lining membrane is continued from the internal surface of the lips and cheeks to the alveolar portions of the upper and lower jaws, which are in the cavity of the mouth, and covers them, adhering firmly to the periosteum. The teeth appear to have passed through apertures in this membrane, and are surrounded by it closely at their respective necks. The portion of membrane, which thus invests the jaws, con- stitutes the gums ; which have now acquired a texture very different from that of the membrane from which they were continued. They are extremely firm and dense, and very vascular. It is probable that their ultimate structure is not perfectly understood. * Ruysch had a fine preparation of this structure. See Thesaurus VII. Tab. III. Fig. 5. 460 MEMBRANE LINING THE HARD OR BONY PALATE. In the disease called scurvy, they tumefy and lose the firm- ness of their texture : they acquire a livid color, and are much disposed to hemorrhage. From the alveoli of the upper jaw, the lining membrane is continued upon the palatine processes of the upper maxillary and palate bones, or the roof of the mouth. The membrane of the palate is not quite so firm as" that of the gums, and is also less florid : it adheres firmly to the peri- osteum, and thus is closely fixed to the bones. There is gene- rally a ridge on its surface, immediately under the suture be- tween the two upper maxillary bones ; and some transverse ridges are also to be seen upon it. On the internal surface of this membrane, are small glandular bodies, whose ducts open on the surface of the palate. It is asserted, that this membrane has a limited degree of that sensibility which is essential to the functions of tasting ; and that if certain sapid substances are carefully applied to it, their respective tastes will be perceived, although they have not been in contact with the tongue. The membrane is continued from the bones above mentioned to the soft palate, or velum pendulum palati, which is situated immediately behind them. This soft palate may be considered as a continuation of the partition between the nose and mouth ; it is attached to the posterior edge of the palatine processes of the ossa palati, and to the pterygoid processes of the sphenoidal bone. Its interior structure is muscular. The upper surface is covered by the membrane of the nose, the lower surface by the membrane which lines the mouth. The muscles, which contribute to the composition of this structure, are the circumflexi and the levatores palatii above, and the constrictores isthmi faucium and palato-pharyngei below. (See pages 318, 319.) Thus composed, the soft palate con- stitutes the back part of the partition between the nose and mouth. When viewed from before, with the mouth open, it presents towards the tongue an arched surface, which continues downwards on each side, until it comes nearly in contact with the edges of that organ. On each of the lateral parts of this SOFT PALATE. UVULA. 461 arch, are two pillars, or rather prominent ridges, which project into the mouth. These ridges are at some distance from each other below, and approach much nearer above, so that *hey include a triangular space. They are called the lateral half arches of the palate, (see fig. 118, p. 455.) Each of them is formed by a plate or fold of the lining membrane of the mouth, and contains one of the two last mentioned muscles ; the anterior, the constrictor isthmii faucium ; the posterior, the palato- pharyngeus. These muscles, of course, draw the palate down toward the tongue when they contract. From the centre of the arch, near its posterior edge, is sus- pended the uvula, a conical body, which varies in length from less than half an inch, to rather more than one inch. It is connected by its basis to the palate; but its apex is loose and pendulous. This body is covered by the lining membrane of the mouth. It contains many small glands, and a muscle also, the azygos uvulae, which arises from the posterior edge of the ossa palati, at the suture which connects them to each other, and, passing posteriorly upon the soft palate, extends from the basis to the apex of the uvula, into which it is inserted. By the action of this muscle, the length of the uvula can be very much diminished : and when its contraction ceases, that body is elongated.* The pendulous part of the uvula can also be moved, in certain cases, to either side. It is commonly supposed, that the principal use of this little organ is to modulate the voice ; but there are good reasons for believing, that it has another object. It was remarked by Fallopius, (and the observation has been confirmed by many surgeons since his time,) that the uvula may be removed com- pletely without occasioning any alteration of the voice, or any difficulty of deglutition, if the soft palate be left entire. The soft palate is so flexible, that it yields to the actions of the levatores palati, which draw it up so as to close the posterior nares completely. * A careful dissection, shows two of these muscles. p. 39* 462 THE TONGUE. It also yields to the circumflexi or tensores, which stretch it so as to do away its arched appearance. It is therefore very properly called the Palatum Molle, or soft palate. It is also frequently called the Velum Pendulum Palati, from the position which it assumes. The Tongue, which is a very important part of this structure, is retained in its position and connected with the parts adjoining it, by the following arrangements. The os hyoides, which, as its name imports, resembles the Greek letter v, or half an oval, is situated rather below the angles of the lower jaw, in the middle of the upper part of the neck. It is retained in its position by the sterno-hyoidei muscles, which connect it to the upper part of the sternum, by the coraco, or omo-hyoidei, which pass to it obliquely from the scapula ; by the thyro-hyoidei, which pass to it directly upward from the thyroid cartilage, all of which connect it to parts below. To these should be added the stylo-hyoidei, which pass to it obliquely from behind and rather from above : the mylo-hyoidei, which come rather anteriorly from the lateral parts of the lower jaw; and the genio-hyoidei, which arises from a situation directly anterior and superior to the chin. When these muscles are at rest, the situation of the os hyoides is, as above described, below the angles of the lower jaw : when those, in one particular direction act, while the others are passive, the bone may be moved upwards or downwards, backwards or forwards, or to either side. This bone may be considered as the basis of the tongue ; for the posterior extrem- ity of that organ is attached to it, and of course the move- ments of the bone must have an immediate effect upon those of the tongue. The tongue is a flat body of an oval figure, but subject to considerable changes of form. The posterior extremity, connected to the os hyoides, is com- monly called its base ; the anterior extremity, which, when the tongue is quiescent, is rather more acute, is called its apex. The lower surface of the tongue is connected with a number STRUCTURE OF THE TONGUE. 463 of muscles, which are continued into its substance. This con- nexion is such, that the edges of the tongue are perfectly free and unconnected ; and so is the anterior extremity for a con- siderable distance from the apex towards the base. The substance of the tongue consists principally- of muscu- lar fibres intermixed with a delicate adipose substance. It is connected to the os hyoides by the hyo-glossus muscle, and also by some other muscular fibres, as well as by a dense mem- branous substance, which appears to perform the part of a ligament. This connexion is also strengthened by the con- tinuance of the integuments from the tongue to the epiglottis cartilage, to be hereafter described ; for that cartilage is attached by ligaments to the os hyoides. The tongue is thin at its commencement at the os hyoides ; but it soon increases in thickness. The muscular fibres in its composition have been considered as intrinsic, or belonging wholly to its internal structure ; and extrinsic, or existing in part outside of this structure. The lingualis muscles are intrinsic (see page 316) : they are situated near the under sur- face of the tongue, one on each side, separated from each other by the genio-hyo-glossi muscles, and extending from the basis of the tongue to its apex. These muscles can be easily traced as above described : but there are also many fibres in the structure of the tongue, which seem to pass in every direction, and of course are different from those of the linguales muscles. To these two sets of fibres are owing many of the immensely varied motions of the different parts of the tongue. According to Gerdy, (whose researches on this subject have been approved by Ribes and Breschet,) the structure of the tongue consists of the mucous membrane forming its outer coat, of a peculiar yellow lingual tissue ' which forms the liga- ment by which it is attached to the os hyoides and is extended along the middle line of the tongue to form a sort of raphe for the attachment of the transverse muscular fibres, and of the intrinsic and extrinsic muscles ; it is mixed up with some delicate cellular and adipose tissue. The intrinsic muscles consist, 1st, of a superficial lingual muscle ; 2d, of two deep-seated, all of 464 STRUCTURE OF THE TONGUE. which are longitudinal ; 3d, of transverse muscular fibres, reunited at the raphe, in the middle line of the tongue ; 4th, of some vertical fibres which are inserted on the lower surface of the mucous membrane. The ligament from the os hyoides extended along the middle line of the tongue, Blandin calls the lingual cartilage. The evidence in favor of its cartilaginous nature, is not very satisfactory in man. The epidermis of the tongue, which is much thicker than that of other portions of the mouth, forms, according to Blandin, a sheath open at top, round the sensitive papilla, which protects them when the tongue acts as an instrument of mastication, and through which the papillae protrude, to come fully in contact with the sapid sub- stance when tumefied or erected by the gustatory excitement. In addition to these, are the extrinsic muscles, which origi- nate from the neighboring parts, and are inserted and continued into the substance of the tongue. See fig. 122. Among the most important of the muscles, are those which proceed from the chin, or the genio-hyo-glossi. They are in contact with each other ; their fibres radiate from a central point on the inside of the chin, and are inserted into the middle of the lower surface of the tongue : the insertion commencing at a short distance from its apex, and continuing to its base. As the genio-hyo-glossi muscles have a considerable degree of thickness, they add much to the bulk of the tongue in the middle of the posterior parts of it. The hyo-glossi and the stylo-glossi, being continued into the posterior and lateral parts, contribute also to the bulk of these parts. The tongue, thus composed and connected, lies, when at rest, on the mylo-hyoidei muscles ; and the space between it and these muscles is divided into two lateral parts by the above described genio-hyo-glossi. In the space above mentioned, is a small salivary gland, of an irregular oval form ; the greatest diameter of which extends from before backwards, and its dges present outwards and inwards. It has several excretory ducts, the orifices of which form a line on each side of the tongue. This gland is very prominent under the tongue ; and PAPILLAE OF THE TONGUE. 465 when the tongue is raised it is particularly conspicuous : it is called the Sublingual. The lining membrane of the mouth continues from the inside of the alveoli of the lower jaw, which it covers, over the sublin- gual glands to the lower surface of the tongue. In this situa- tion it is remarkably thin ; but, as it proceeds to the upper surface of the tongue, its texture changes considerably, and on this surface it constitutes the organ of taste. The upper surface of the tongue, although it is continued from the thin membrane above described, is formed by a rough integument which consists, like the skin, of three lamina. The cuticle is very thin ; and under it, the rete mucosum* is thicker and softer than in other places. The true skin here abounds with eminences of various sizes and forms, all of which are denominated Papilla. The largest of these are situated on the posterior part of the tongue, and are so arranged that they form an angle rather acute, with its point backwards. They are commonly nine in number : they resemble an inverted cone, or are larger at their head than their basis. They are situated in pits or depressions, to the bottoms of which they are connected. In many of them there are follicles, or perforations, which have occasioned them to be regarded as glands. They are called Papilla Maxima, or Capitata. The papillae, next in size, are denominated fungiform by some anatomists, and Media or Semilenticulares by others. They are nearly cylindrical in form, with their upper extremi- ties regularly rounded. They are scattered over the upper surface of the tongue, in almost every part of it, at irregular distances from each other. The third class are called conoidal or villous. They are very numerous, and occupy the greatest part of the surface of the tongue. Although they are called conoidal, there is a great * M. Bichat appears to have had doubts whether the real rete mucosum existed here. He says that he could only perceive a decussation of vessels in the intervals of the papillae, which, as he supposes, occasioned the florid color of the tongue. -466 PAPILLA OF THE TONGUE. difference in their form ; many of them being irregularly angular and serrated as well as conical. Soemmering and other German anatomists consider the smallest papillae as a fourth class, which they call the filiform: these lie between the others. It is probable that these papillae are essential parts of the organ of taste ; and their structure is of course an interesting object of inquiry. The nerves of the tongue have been traced to the papillae, and have been compared by some anatomists to the stalk of the apple, while the papillae resembled the fruit ; but their ultimate termination does not appear to have been ascer- tained.* The papillae maximae or capitatae, are supplied, accor- ding to Cloquet, by filaments from the glosso-pharyngeal nerve, the fungiformes by filaments from the fifth. The papillae maximae appear to consist only of a collection of mucous follicles, which differ only from those of the soft palate and lips, by standing out more in relief. The follicles of each papilla open occasionally upon the side; several open by a common orifice at the top of the papilla, which is often very visible to the naked eye, as a little reddish point. Weber succeeded in injecting this orifice with mercury, and found it led to a central cavity irregularly divided by septae into cells, visible to the naked eye, having some resemblance to, but much larger than those of the parotid. Other mucous follicles of a simpler kind are spread over the whole surface of the tongue between the smaller papillae. Some are mere small pouches, opening by simple orifices, without canals. Others are more complicated, and according to Weber, who filled them with mercury, have ducts three or four lines in length, which run down between the muscular fibres of the * In the explanation of the plates, referred to in the following sentence, Soemmering observes, that when the fibrillaB of the lingual nerve of the fifth pair are traced to the papillae of the second class, they swell out into a conical form ; and these nervous cones are in such close contact with each other, that the point of the finest needle could not be insinuated into the papillae without touching a nerve. BLOOD-VESSELS OF THE TONGUE. 467 tongue, to terminate in little flattened sacs divided into several cells, and having sometimes, a diameter of three lines. From all these follicles, comes that profusion of muoous secretion, which we see covering the tongue in diseases. He describes the sebaceous glands of the skin as being analogous in structure to these follicles, as well as those of the trachea and of the inside of the lips and cheeks. Soemmering has lately published some elegant engraved copies of drawings of these papillae, when they were magnified twenty-five times ; from which it appears that a very large number of vessels, particularly of arteries, exist in them. These vessels are arranged in a serpentine direction, and are prominent on the surface ; but they appear doubled, and the most prominent part is the doubled end. This arrangement of vessels is perceptible on the sides of the tongue, as well as on the papillae. Behind the large papillae is a foramen, first described by Morgagni, and called by him Foramen Cwcum. It is the orifice of a cavity which is not deep ; the excretory ducts of several mucous glands open into it. On the upper surface of the tongue, a groove is often to be seen, which is called the linea mediana, and divides it into two equal lateral parts.* Below, the lining membrane of the mouth, as it is continued from the lower jaw to the tongue, forms a plait, which acts as a ligament, and is called the frcenum lingua. It is attached to the middle of the tongue, % at some distance behind the apex. t The tongue is well supplied with blood-vessels, which are derived Irom the lingual branch of the external carotid on each side. This artery passes from the external carotid, upwards, inwards, and forwards, to the body of the tongue. In this course it sends off several small arteries to the contig- uous parts, and one which is spent about the epiglottis and the adjoining parts, called the Dorsalis Lingua. About the anterior edge of the hyo-glossus muscle, it divides into two * This groove indicates the position of the middle raphe of Gerdy. 468 BLOOD-VESSELS OF THE TONGUE. large branches: one of which, called the Sublingual^ passes under the tongue between the genio-hyo-glossus and the sub- lingual gland, and extends near to the symphysis of the upper jaw ; sending branches to the sublingual gland, to the muscles under the tongue, to the skin, and the lower lip. The other is in the substance of the tongue, on the under side near the sur- face, and extends to the apex. The veins of this organ are not so regular as the arteries : they communicate with the external jugular, and some of them are always very conspicuous under the tongue : these are called ranular. It is to be observed, that the vessels on each side have but little connexion with each other ; for those of one side may be injected while the others continue empty. The tongue is also well supplied with nerves, and derives them from three different sources on each side, namely, from the fifth, the eighth, and ninth pairs of the head. The lingual portion of the third branch of the fifth pair pass- ing under the tongue, enters its substance about the middle, and forms many minute branches, which pass to the papillae of the forepart of the tongue. The glosso-pharyngeal portion of the eighth pair, sending off several branches in its course, passes to the tongue near its basis, and divides into many small branches, which are spent upon the sides and middle of the root of the tongue, and also upon the large papillae. The ninth pair of nerves are principally appropriated to the tongue. They pass on each side to the most fleshy part of it, and after sending one branch to the mylo-hyoideus, and another to communicate with the lingual branch of the fifth pair, they are spent principally upon the genio-glossi, and linguales muscles. The tongue answers a threefold purpose. It is the princi- pal organ of taste. It is a very important agent in the articu- lation of words, and it assists in those operations upon our food, which are performed in the mouth. PAROTID GLAND. 469 The Salivary Glands. The salivary glands have such an intimate connexion with the mouth that they may be described with it.* There are three principal glands on each side : the Parotid, Submaxillary, and the SublinguaL They are of a whitish or pale flesh color, and are composed of many small united masses or lobuli, each of which sends a small excretory duct to join similar ducts from the other lobuli, and thereby form the great duct of the gland. The Parotid is much larger than the other glands. It occupies a large portion of the' vacuity between the mastoid process and the posterior parts of the lower jaw. It extends from the ear and the mastoid process over a portion of the masseter muscle, and from the zygoma to the basis of the lower jaw. Its name is supposed to be derived from two Greek words which signify contiguity to the ear. It is of a firm con- sistence. It receives branches from the external carotid artery and from its facial branch. From the anterior edge of this gland, rather above the middle, the great duct proceeds anteriorly across the masseter muscle ; and, after it has passed over, it bends inward through the adipose matter of the cheek to the buccinator muscle, which it perforates obliquely, and opens on the inside of the cheek opposite to the interval between the second and third molar teeth of the upper jaw. The aperture of the duct is rather less than the general diameter of it, and this circumstance has the effect of a valve. When the duct leaves the parotid, several small glandular bodies called sociae parotidis, are often attached to it, and their ducts communicate with it. The main duct is sometimes called ductus stenoMyinus, after Steno, who first described it. When the mouth is opened wide, as in gaping, there is often a jet of saliva from it into the mouth. The parotid gland furnishes the largest proportion of saliva. It covers the nerve called Portio Dura, after it has emerged from the foramen stylo-mastoideum. * For a further account of glands, see General Anatomy of Glandular System. 40 470 ULTIMATUM STRUCTURE OF THE SALIVARY GLANDS. . . This nerve after being covered a short distance by the gland, enters its substance, and forms there the plexus called pas anserinus, so as to leave a portion of the gland on the inner face of the nerve. The external carotid artery likewise traverses the gland and is situated rather more exteriorly than the nerve, so as to leave about one-third of the gland on its inner face. Branches from the artery* are sent off in various directions as it traverses the gland, to the face, and to the structure of the gland itself. The duct of Steno, is very feebly attached to the surrounding parts, and is accompanied by many branches of the middle division of the facial nerves, and some small arteries which supply its walls ; it is covered only by the skin, some adipose tissue, by some fibres of the platysma myoides, and the zygomaticus major which crosses it obliquely. Its general diameter is about a line ; and it is very distensible. It will be found, according to the rule laid down by Dr. Physick, under a line drawn from the lobe of the ear, to the tip of the nose. 119. The duct is composed of two coats, one, external, white, fibrous, and resisting; the other, internal, is a mucous membrane, con- tinuous with the lining membrane of the mouth, and appears to differ from it only in being paler. Fig. 119, is a microscopical representation of the structure of a portion of the parotid gland of a young infant, after it had been minutely injected with mercury from the duct of Steno, by E. H. Weber, of Leipzic. The small figure, to the right, is the natural size of the piece magnified, in which the salivary ducts were filled with the fluid to their very terminations. A branch of the salivary duct, is seen on the right margin of this figure, ramifying like the branch of a tree. These ramifications never anastomose together, and are of much greater size than the capillary blood-vessels. Each ramification, at its termination, resolves itself into cells densely compacted together, like a THE SUBMAXILLARY GLAND. 471 bunch of grapes upon its stem, a, a, a. Some of the cells open by a minute excretory tube directly into the salivary duct. In other instances some of the ducts of the cells uffite into a common tube, before entering the salivary duct. The cells are not round, and vary among themselves in regard to size. The- average diameter of these cells, measured by a micro- meter, were found by Weber, to be the ^gth part of an inch, which he finds to be three times greater than that of the most delicate sanguineous vessels. The cellular structure of the parotid, seems therefore to be very analogous to the cellular structure of the lungs discovered by Soemmering and Reisseis- sen, the cells of the lungs, however, being five or six times larger than those of the parotid. The elaborate researches of Weber and Muller, have shown also that this is the common mode of termination of the excretory ducts in the different glands of the body ; viz. that they terminate in closed cells, upon which ramify the delicate secretory capillary vessels. The second gland is called the Submaxillary. It is much smaller than the parotid, and rather round in form. It is situated immediately within the angle of the lower jaw, between it on the outside, and the tendon of the digastric muscle and the ninth pair of nerves internally. Its posterior extremity is connected by cellular membrane to the parotid gland ; its anterior portion lies over a part of the mylo-hyoideus muscle ; and from it proceeds the excretory duct, which is of considerable length, and passes between the mylo-hyoideus and genio-glossus muscles along the under and inner edge of the sublingual gland. In this course the duct is sometimes surrounded with small glandular bodies, which seem to be appendices to the sublingual gland. It terminates under the tongue, on the side of the fraenum linguae, by a small orifice which sometimes forms a papilla.* (See fig. 118, p. 454.) * Lassus informs us that Oribases, afterwards all the Arabians, and subse- quently Guy De Chauliac, Lanfranc, Achillini, Berenger De Carpi, Charles Etienne, Casserius and several others have given the description of these salivary ducts ; notwithstanding which, Wharton, a physician of London, attributed to himself the discovery of them on the bullock, in 1656. u. 472 SUBLINGUAL GLAND. The orifice is often smaller than the duct ; in consequence of which, obstruction frequently occurs here, and produces the disease called ranula. The Sublingual gland, which has already been mentioned, lies so that, when the tongue is turned up, it can be seen pro- truding into the cavity of the mouth, and covered by the lining membrane, which seems to keep it fixed in its place. It lies upon the mylo-hyoideus, by the side of the genio-hyoideus ; and is rather oval in form, and flat. Its greatest length is from before backwards ; its position is rather oblique, one edge being placed obliquely inwards and upwards, and the other outwards and downwards. It has many short excretory ducts, which open by orifices arranged in a line on each side : they are discovered with difficulty on account of their small size, and sometimes amount to eighteen or twenty in number. In some few instances, this gland sends off a single duct, which com- municates with the duct of the submaxillary gland. The duct of the Submaxillary gland is called the duct of Wharton, (ductus Whartonionus) from an English anato- mist who first described it. It is accompanied in nearly the whole of its course by the lingual branch of the fifth pair of nerves. The usual arrangement of the ducts of the sublingual gland is as follows : six or eight run from the upper part of the gland, to open by the side of the fraenum linguae. Five or six others proceed from its sides to open separately in the mucous membrane above the gland. Several open into the duct of Wharton which runs by the side of the gland ; these most frequently unite to form a single duct, called the duct of Bar- tholinus, or duct of Rivinus. This I have frequently succeeded in distending with mercury from the duct of Wharton. The structure and office of these salivary glands appear the same, and not unfrequently a slight continuation of structure is observed at the two extremities of the submaxillary gland. The salivary fluid secreted by these glands is inodorous, insipid, and limpid, like water ; but much more viscid, and of greater specific gravity. Water constitutes at least four-fifths OBSERVATIONS ON THE TONGUE. 473 of its bulk ; and animal mucus one half of its solid contents. It also contains some albumen ; and several saline substances ; as the muriate of soda, and the phosphates of lime, of soda, and of ammonia. It is probable that this fluid possesses a solvent power with respect to the articles of food. There are small glandular bodies, situated between the masseter and buccinator muscles, opposite to the last molar tooth of the upper jaw, whose nature is not well understood : they are called Glandula molares. They are believed to be mere mucous glands. The motions of the tongue are very intelligible to a person who has a prepara- tion of the lower jaw before him, with the tongue in its natural situation, and the muscles which influence it, properly dissected. Its complicated move- ments will appear the necessary result of the action of those muscles upon it, and the os hyoides ; and also upon the larynx, with which the os hyoides is connected. The muscular fibres of the tongue itself are also to be taken into this view, as they act a very important part. Although the tongue appears very necessary, in a mechanical point of view, to the articulation of many words, yet there are cases where it has been entirely deficient, in which the parties thus affected, have been able to speak very well in general, as well as to distinguish different tastes.* The tongue is also a very delicate organ of touch. We can perceive the form of the teeth, and the state of the surface of the mouth, more accurately by the application of the tongue than of the fingers. On the three nerves which go to the tongue, it is generally supposed that the lingual portion of the third branch of the fifth pair is most immediatety con- cerned in the function of tasting, as it passes to the front part of the surface of the tongue. The glosso-pharyngeal are probably concerned in the same function on the posterior part, while the ninth pair of nerves seems principally spent upon the muscular parts of the organ. It is obvious that the tongue is most copiously supplied with nerves. This probably accounts for the great facility of its motions, and the power of con- tinuing them. * There is a very interesting paper on this subject, in the Memoirs of the Academy of Sciences for the year 1718, by Jussieu ; in which he describes the case of a female fifteen years old, examined by himself, who was born without a tongue. In this paper he refers to another case, described by Rolland, a surgeon of Saumur, of a boy nine years old, whose tongue was destroyed by gangrene. In each of these cases the subject was able to articulate very well, with the exception of a few letters ; and also enjoyed the sense of taste. 40* 474 OF THE THROAT. CHAPTER XIV. OF THE THROAT. To avoid circumlocution, the word throat is used as a general term to comprehend^ the structure which occurs behind the nose and mouth, and above the ossophagus and trachea. This structure consists, 1st. Of the parts immediately behind the mouth, which con- stitutes the Isthmus of the Fauces : 2d. Of the parts which form the orifice of the windpipe, or the Larynx ; and 3d. Of the muscular bag, which forms the cavity behind the nose and mouth, that terminates in the oesophagus or the Pharynx. Of the Isthmus oj the Fauces. In the back part of the mouth, on each side, are to be seen the two ridges or half arches, passing from the soft palate to the root of the tongue, (see fig. 118, p. 454,) formed by plaits of the mucous membrane, containing muscular fibres. The anterior plait, which contains the muscle called Constrictor Isthmi Faucium, passes directly from the side of the root of the tongue to the palate, and terminates near the commence- ment of the uvula. The posterior plait runs from the palate obliquely downwards and backwards, as it contains the palato- pharyngeus muscle, which passes from the palate to the upper and posterior part of the thyroid cartilage. In the triangular space between these ridges is situated a glandular body, called the Tonsil or Amygdala.* This gland * It is named amygdala, from its resemblance in form and appearance to an almond covered by its shell. The exterior or adhering surface of the tonsil gland is connected by the means of cellular tissue to the superior constrictor muscle of the pharynx. The internal carotid artery is situated behind and to the outer side of the tonsil, and separated from it only by the constrictor muscle, and cellular tissue. It has been wounded in opening abscesses of the tonsils, when the cutting instrument has been inclined too much outwards and backwards. r. TONSILS. EPIGLOTTIS. 475 has an oval form, its longest diameter extending from above downwards. * Its surface is rather convex, its natural color is a pale red. On its surface are the large orifices of many cells of considerable size, which exist throughout the gland. These cells often communicate with each other, so that a probe can be passed in at one orifice and out at the other. Into these cells open many mucous ducts, which discharge in part the mucus of the throat, for the purpose of lubricating the surface, and facilitating the transmission of food. In its healthy state, the free surface of the tonsil glands, are a little below the level of the two half arches of each side. But when their cells are distended by inflammation, or effaced by granulations, as in tonsillitis, they sometimes project beyond the half arches so as nearly or quite to meet in the middle line. The epiglottis, or fifth cartilage of the larynx, is situated at the root of the tongue, in the middle, between the tonsils. The part which is in sight is partly oval in form, and of a whitish color. Its position, as respects the tongue, is nearly perpen- dicular, and its anterior surface rather convex. The mucous membrane continued from the tongue over the epiglottis is so arranged that it forms a plait, which extends from the middle of the root of the tongue along the middle of the anterior surface of the epiglottis, from its base upwards. On each side of this plate or fraenum, at the junction of the surfaces of the tongue and of the epiglottis there is often a de- pression, in which small portions of food sometimes remain ; and a small fraenum, similar to that above described, is sometimes seen on the outside of each of these cavities. The epiglottis is situated immediately before the opening into the larynx. The above described parts can be well ascertained in the living subject, by a person who has a general knowledge of the structure. Thus, looking into the mouth, with the tongue de- pressed, the uvula and soft palate are in full view above, and the epiglottis is very perceptible below ; while the two ridges 476 THE LARYNX. or lateral half arches can be seen on each side, with the tonsil between them. Of the Larynx. f The larynx is situated immediately below the os hyoides, and is continuous at its inferior part with the trachea, to which it is attached, like a capital upon a column. It serves a double purpose ; that of a tube for the introduction of air into the lungs ; and that of a very complicated apparatus for the pro- duction of the voice. It is composed of cartilages which form its frame-work, liga- ments and synovial capsules which unite the cartilages together, muscles to put them into motion, and an exquisitely sensitive mucous membrane, that lines the whole of its interior. It is larger and much more prominent in males than females, and undergoes a rapid and remarkable degree of development, both in regard to size and energy of function at the period of puberty. In this structure are five cartilages, upon which its form and strength depends, namely, the Cricoid, the Thyroid, the two Arytenoid, and the Epiglottis. These cartilages are articulated to each other, and are supplied with muscles by which certain limited motions are effected. The basis of the structure is a cartilaginous ring, called the cricoid cartilage, and which may be considered as the com- mencement of the windpipe. It may be described as an irregular section of a tube : its lower edge connected with the windpipe, being nearly hori- zontal when the body is erect ; and the upper edge very oblique, sloping from before, backwards and upwards ; in consequence of this, it has but little depth, before, but is eight or nine lines deep behind. In front, and upon each side of the middle line there is a depression, in which arises the two crico-thyroid muscles. Upon each side, and near its upper and outer surface, there is a smooth convex facet, upon which is articulated, the corres- CRICOID CARTILAGE. THYROID CARTILAGE. 477 ponding facet of the inferior cornua of the thyroid cartilage. Posteriorly are two slight vertical depressions, to which are attached the crico-arytenoidei postici muscles. Its internal fcrce is covered by mucous membrane. Its superior border gives attachment in front to the crico-thyroid membrane, on the sides to the lateral crico-arytenoid muscles, and posteriorly presents a little notch, limited by two convex facets upon which are articulated the arytenoid cartilages. The Thyroid cartilage is a single plate, bent in such manner that it forms an acute angle with two similar broad surfaces on each side of it. It is so applied to the cricoid cartilage, that the lower edge of the angular part is at a small distance above the front part of that cartilage, and connected to it by ligamen- tous membrane ; while its broad sides are applied to it later- ally, and thus partially enclose it. The upper edge of the angular part of the thyroid cartilage forms a notch ; and the natural position of the cartilage is such, that this part is very prominent in the neck ; it is called the Pomum Adami. Both the upper and lower edges of the thyroid cartilage terminate posteriorly in processes, which are called Cornua. The two uppermost are longest : they are joined by ligaments to the extremities of the os hyoides. The lower and shorter processes are fixed to the cricoid cartilage. The thyroid car- tilage, therefore, partly rests upon the cricoid cartilage below, and is attached to the os hyoides above. It is influenced by the muscles which act upon the os hyoides, and also by some mus- cles which are inserted into itself. It is moved obliquely downwards and forwards in a slight degree upon the cricoid cartilage, by a small muscle, the crico-thyroideus, which arises from that cartilage and is inserted into it. The external lateral surface of the thyroid cartilage is slightly concave, and across it, passes a small ridge obliquely from above downwards, and from behind forwards, which gives attachment above to the thyro-hyoid and below to the sterno-hyoid muscles. The posterior or inside face of the Pomum Adami presents an entering angle, where the two 478 ARYTENOID CARTILAGES. symmetrical sides of the cartilage meet, and in which is attached the thyro-arytenoid muscles, the pedicle of the epi- glottis and one end of the vocal ligaments. The upper margin of the cartilage presents a curved appearance like that of the italic long /; a similar curvature is also observable on its pos- terior margin. Fig. 120.* The ^Arytenoid cartilages are two small bodies of a triangular or pyramidal form anc ^ slightty curved backward. They are placed upon the upper and posterior edge of the cricoid cartilage, near to each other ; their upper ends, taken together, resem- ble the mouth of a pitcher or ewer ; from _ which circumstance their name is derived. Their bases are broad ; and on their lower surfaces is a cavity, which corresponds with the convex edge of the cricoid carti- lage, to which they are applied. At these places, a regular movable articulation is formed, by a capsular ligament between each of these cartilages and the cricoid, in consequence of which they can be inclined backward or forward, inward or outward. From the anterior part of each of these cartilages, near the base, a tendinous cord passes forward, in a direction which is horizontal when the body is erect, to the internal surface of the angle of the thyroid. These ligaments are not perfectly parallel to each other ; they are nearer before than behind. The aperture between them is from two to five lines wide when the muscles are not in action ; and this aperturef is the orifice of the windpipe : for the exterior space, between these ligaments and the circumference of the thyroid, is closed up by mem- * Vertical section of the larynx, h, Os hyoides. t, Thyroid cartilages, c c, Cricoid cartilage, a, Arytenoid cartilage, v, Ventricle of the larynx, bounded below by the ligamenta vocales, and above by the superior ligaments of the glottis, e, Epiglottis cartilage, g, Ligamentous attachment of the tongue to the os hyoides. b, Trachea cut off at the third ring. The lining membrane is left out in this section. f It forms also the rima glottidis of the larynx. EPIGLOTTIS. 479 brane and muscle. At a small distance above these ligaments are two others, which also pass from the arytenoid to the thyroid cartilages. They are not so tendinous aud distinct as -the first mentioned, and cannot be drawn so tense by the muscles of the arytenoid cartilages. They are also situated at a greater distance from each other, and thus form a large aperture. On the external side of the upper extremity of each of the arytenoid cartilages, and nearly in contact with it, is a small cartilaginous body, not so large as a grain of wheat, and nearly oval in form. These are connected firmly to the aryte- noid cartilages, and are called their Appendices.* Being in the margin of the aperture of the larynx, they have an effect upon its form. The arytenoid cartilages are the posterior parts of the larynx. The Epiglottis, which has already been mentioned is the anterior. When this cartilage is divested of its membrane, it is oval in its upper extremity, and rather angular below, terminating in a long narrow process, which is like the stalk of a leaf. It is firmly attached to the internal surface of the angular part of the thyroid by this lower process ; and, being placed in a perpendicular position, one of its broad surfaces is anterior towards the tongue, and the other posterior towards the opening of the windpipe. It is attached to the os hyoides by dense cellular texture or ligament, and to the tongue by those plaits of the membrane of the mouth which have been already described. It is elastic, but more flexible than the other cartilages ; being somewhat different in its structure. Its surface is perforated by the orifices of many mucous ducts. There is a small space between the lower part of this carti- lage, and the upper part of the thyroid and the ligamentous membrane passing from it to the os hyoides. In this is a sub- stance, which appears to consist of glandular and of adipose * They are also called Cornicula Laryngis, Tubercles of Santorini. p. 480 VENTRICLE OF GALEN OR MORGAGNI. matter, (see fig. 120.) It is supposed that some of the orifices on the lower part of the epiglottis communicate with this substance. This substance is a collection of mucous glands, called glandules epiglottidtz ; the ducts which arise from them are twenty or thirty in number, and perforate the, epiglottis to throw their mucus on the side of^the larynx. In the erect position of the body, the epiglottis is situated rather higher up than the arytenoid cartilages, and at the dis- tance of ten or twelve lines from them. The mucous membrane which covers the epiglottis, is reflected backwards from the base of the tongue, and is extended from each side of it to the arytenoid cartilages, and being continued into the cavity of the larynx, as well as upon the general surface of the throat, it is necessarily doubled : this doubling forms the lateral margins of the orifice of the cavity of the larynx. In these folds of the membrane are seen some very delicate muscular fibres, forming the Aryteno-epi- glottideus muscle. The epiglottis maintains its vertical position, partly from its own elasticity of structure, and partly from the folds of mucous membrane, reflected to it from the tongue, which contain some yellow elastic ligarnentous fibres. The membrane continues down the cavity of the larynx, and, covering the upper ligaments, penetrates into the vacuity between them and the lower ligaments, so as to form a cavity on each side of the larynx, opening between the two ligaments, which is called the Ventricle of MorgagnL The shape of each cavity is oblong. Its greatest length extends from behind forward, on each side of the opening into the windpipe formed by the two lower or principal ligaments ; so that when the larynx is removed from the subject, upon looking into it from above, you perceive three apertures : one in the middle, formed by the two lower ligaments ; and one on each side of it, between the lower and upper ligament, which is the orifice of the ventricle of Morgagn^. If a probe be passed* into this ventricle of the larynx, or ven- VENTRICLE OF GALEN OR MORGAGNI RIMA GLOTTIDIS. 481 tricle of Morgagni, it will be found to pass much above the supe- rior thyro-arytenoid ligament, into a prolongation of the cavity of Fig. 121.* the ventricle, which extends as high as^the upper margin of the thyroid cartilage, and which has been called by Mr. Hilton, the Sacculus Laryngis. It was pointed out by Morgagni, and has been compared by M. Cruvielhier, from its shape, to a Phry- gian casque. It is apt to escape observation in the healthy state. When death has taken place, from pulmonary emphysema, or lar- yngeal phthisis, I have, on several occasions, found the sac so large as to project considerably above the thyroid cartilage. The ventricle and its sac, appear to be intended for the supply of a lubricating secretion to the vocal chords, which are kept in such constant action, during respiration and phonation. The sur- face of the cavity, is studded with sixty or seventy small follicu- lar glands, which are seated in the submucous tissjue, and give to the mucous membrane, when dissected out, a rough appear- ance. The greater part of these follicles is placed in the sac, and the fluid which they form, is directed upon the rima glottidis, by two small folds of mucous membrane, at the entrance of the sacculus. The aperture between the two lower ligaments is called the Rima Glottidis, or Chink of the Glottis; the upper aperture, formed by 4 the fold of the membrane and extending from the epiglottis to the arytenoid cartilages, may be termed Glottis. The folds of the membrane forming the upper margin of the glottis is loose and distensible, and is liable in laryngeal inflammation to become oedematous and bag out so as to im- pede respiration to a great extent, and even produce suffoca- tion. If the windpipe is divided near the larynx, and the larynx inverted, so that the rima glottidis may be examined from below, the structure appears still more simple: it resembles a * Front view of the larynx ; plan of its interior cavity, represented by the lines a c, b b. /s, Superior ligaments of the glottis. U, Inferior ligaments. 41 482 GLOTTIS. septum fixed abruptly in the windpipe, with an aperture in it of the figure of the rima glottidis. The anterior surface of the two arytenoid cartilages is con- cave. This concavity is occupied in each by a glandular substance, which lies between the cartilage and the lining membrane ; and extends itself horizontally, covered by the upper ligament of the glottis. The nature of these bodies is not perfectly understood ; but they are supposed to secrete mucus.* The membrane which lines the cavity of the glottis being continued from the mouth and throat, resembles the membranes which invest those parts. In some places, where it is in close contact with the cartilages, it appears united with the perichon- drium, and acquires more firmness and density. The general motions of the larynx are very intelligible to those who are acquainted with the muscles which are con- nected with the thyroid cartilage, and which move the os hy- oides. They take place particularly in deglutition, and in some modifications of the voice ; and also in vomiting.f The motions of the particular cartilages on each other can also be well understood, by attending to the origin and inser- tion of the various small muscles connected with them. The most important of these muscles are the crico-arytenoidei pos- tici and laterales, the thyreo-arytenoidei, the arytenoidei obli- qui, and the arytenoideus transversus. The effects of their actions appear to be the dilating or contracting the rima glotti- dis, and relaxing or extending the ligaments which form it. The arteries of the larynx are derived from two sources, namely, the superior thyroid, or laryngeal branch of the external carotid, and the thyroid branch of the subclavian. The nerves of the larynx also come to it in two very differ- ent directions on each side. It receives two branches from the par vagum ; one which leaves that nerve high up in the neck, and is called the Superior Laryngeal branch ; and another * They constitute the glandulce arytenoidea. p. j- For an excellent exposition of the uses of the larynx, see Dunglison's Physiology, 5th edition. VESSELS AND NERVES OF THE LARYNX. 483 which proceeds from it after it has passed into the cavity of the thorax, and is called from its direction the Recurrent. According to M. Blandin, who has rather recently m#de some research upon this subject, the superior laryngeal nerve, is distributed chiefly to the mucous membrane and cryptae of the larynx ; it likewise sends some filaments to the arytenoid and crico-thyroid muscles, and others which anastomose with the branches of the recurrent. The recurrent supplies all the muscles of the larynx, with the exception of the crico-thyroid. There is still among anatomists some difference of opinion in regard to the distribution of these nerves. Muscles of the Larynx. These are divided into extrinsic and intrinsic. The extrinsic muscles, which are attached by but one extre- mity to the larynx, have been already described. They consist of the sterno-hyoid, omo-hyoid, sterno-thyroid, and thyreo- hyoid ; to which might indeed be added, all the muscles of the supra-hyoid region, and those of the pharynx, which are attached to the cricoid and thyroid cartilages. These, when they act upon the organ, move the entire larynx. The intrinsic muscles, are attached by both extremities to different parts of the larynx, and produce various movements in the different pieces of which it is composed. There are ten, viz., five pairs, and one single muscle which are called the muscles of the chorda vocales, and rima glottidis. Those which exist in pairs are the crico-thyroid, the crico-arytenoidei postici, the crico-arytenoidei lateralis, the thyro-arytenoidei and the arytenoidei obliqui. The single muscle is the aryte- noideus transversus. The oblique and the transverse arytenoid muscles consist, but of a few thin fibres with difficulty distin- guished from each other and are spoken of by many anato- mists, as a common muscle, called simply the arytenoid. There are three other minute muscles, which are called the muscles of the epiglottis, viz. the thyro-epiglottideus, the aryteno-epiglottideus superior, and another muscle lately observed by Mr. Hilton, called aryteno-epiglottideus inferior. 484 MUSCLES OF THE LARYNX. 1 . Crico- Thyroideus, Arises from the side and forepart of the cricoid car- tilage, running obliquely up- wards. Inserted by two portions: the first, into the lower part of the thyroid cartilage ; the se- cond, into its inferior cornu. Use. To pull forwards and depress the thyroid, or to ele- vate and draw backwards the cricoid cartilage. 2. Crico- Arytanoideus Pos- Arises, fleshy, from the back part of the cricoid cartilage ; and is Inserted into the posterior part of the base of the arytenoid cartilage. Use. To open the rima glottidis a little, and, by pulling back the arytenoid cartilage, to stretch the ligament so as to make it tense. 3. Crico- Arytanoideus Later alis, Arises, fleshy, from the cricoid cartilage, laterally, where it is covered by part of the thyroid, and is * The styloid muscles and the muscles of the tongue. 1. A portion of the temporal bone of the left side of the skull, including the styloid and mastoid processes, and the meatus auditorius externus. 2, 2. The right side of the lower jaw, divided at its symphysis ; the left side having been removed. 3. The tongue. 4. The genio-hyoideus muscle. 5. The genio-hyo-glossus. 6. The hyo-glossus muscle ; well seen at the base of the tongue. 7. Its portion con- nected with the os hyoides. 8. The anterior fibres of the lingualis issuing from between the hyo-glossus and genio-hyo-glossus. 9. The stylo-glossus muscle, with a small portion of the stylo-maxillary ligament. 10. The stylo-hyoid. 11. The stylo-pharyngeus muscle. 12. The os hyoides. 13. The thyro-hyoi- dean membrane. 14. The thyroid cartilage. 15. The thyro-hyoideus muscle arising from the oblique line on the thyroid cartilage. 16. The cricoid cartilage. 17. The crico-thyroidean membrane, through which the operation of laryngo- tomy is performed. 18. The trachea. 19. The commencement of the oesopha- gus. MUSCLES OF THE LARYNX. 485 Inserted into the side of the base of the arytenoid cartilage near the former. Use. To open the rima glottidis, by pulling the ligaments from each other. Fig. 123.* 4. Thyreo-Arytanoideus, Arises from the under and back part of the middle of the thyroid cartilage ; and, running backwards and a little upwards, alo.ig the side of the glottis, is Inserted into the arytenoid cartilage, higher up and farther forwards than the crico-arytaenoideus lateralis. Use. To pull the arytenoid cartilage forwards nearer the middle of the thyroid, and consequently to shorten and relax the ligament of the larynx or glottis vera. 5. Arytanoideus Obliquus, Arises from the base of one arytenoid cartilage ; and crossing its fellow, is Inserted near the tip of the other arytenoid cartilage. Use. When both act they pull the arytenoid cartilages towards each other. N. B. One of these is very often wanting. The single muscle is, the Arytanoideus Transversus, Arises from the side of one arytenoid cartilage, from near its articulation with the cricoid to near its tip. The fibres run straight across, and are Inserted, in the same manner, into the other arytenoid car- tilage. * A posterior view of the larynx. 1. The thyroid cartilage. 2. One of its ascending cornua. 3. One of the descending cornua. 4. 7. The cricoid carti- lage. 5, 5. The arytenoid cartilages. 6. The arytenoideus muscle, consisting of oblique and transverse fasciculi. 7. The crico-arytenoidei postici muscles. 8. The epiglottis. 41* 486 MUSCLES OF THE LARYNX. Use. To shut the rima glottidis, by bringing these two carti- lages, with the ligaments, nearer one another. Fig. 124.* Besides these, there are a few separate muscular fibres on each side ; which, from their general direction, are named 1. Thyro-Epiglottideus, Arises, *by a few pale separated fibres, from the thyroid cartilage : and is Inserted into the epiglottis laterally. Use. To draw the epiglottis obliquely downwards, or, when both act, directly downwards ; and at the same time, it expands that soft cartilage. 2. Aryt&no-Epiglottideus, superior. Arises, by a number of small fibres, from the lateral and upper part of the arytenoid cartilage ; and, running along the outer side of the external rima, is Inserted into the epiglottis along with the former. Use. To pull that side of the epiglottis towards the external rima ; or, when both act, to pull it close upon the glottis. It is counteracted by the elasticity of the epiglottis. 3. Aryteno-Epiglottideus, inferior. This muscle may be exposed by raising the mucous mem- brane immediately above the ventricle of the larynx. It arises by a narrow and fibrous origin from the arytenoid cartilage, just above the attachment of the chorda vocalis and passing forwards and a little upwards, expands over the upper half or two-thirds of the sacculus laryngis, and is inserted by a broad attachment into the side of the epiglottis. Its action according * A side view of the larynx, one ala of the thyroid cartilage has been removed. 1. The remaining ala of the thyroid cartilage. 2. One of the arytenoid cartilages. 3. One of the cornicula laryngis. 4. The crycoid carti- lage. 5. The crico-arytenoideus posticus muscle. 6. The crico-arytenoideus lateralis. 7. The thyro-arytenoideus. 8. The crico-thyroidean membrane. 9. One half of the epiglottis. 10. The upper part of the trachea. THE THYROID GLAND. 487 to Mr. Hilton, is to approximate the epiglottis and arytenoid cartilage, to compress the subjacent glands which open into the pouch of the larynx, to diminish the capacity of that cavity and to change its form. The extreme irritability of the glottis is unequivocally demonstrated by the cough, which is excited when a drop of water, or any other mild liquid, or a crumb of bread enters it. Notwithstanding this, a flexible tube, or catheter, has several times been passed into the windpipe through the rima glottidis, and been endured by the patient a considerable time. The cough, which occurs when these parts are irritated, does not appear to arise exclusively from the irritation of the membrane within the glottis; for, if it were so, mucilaginous substances, when swallowed slowly, could not suspend it. Their effect in relieving cough is universally known ; and as they are only applied to the surface exterior to the glottis, it is evident that the irrita- tion of this surface must also produce coughing. Several curious experiments have been made to determine the effect of dividing the different nerves which go to the larynx ; by which it appears that the recurrent branches supply parts which are essentially necessary to the forma- tion of the voice ; whilst the laryngeal branches supply parts which merely influence its modulation, or tone. See Mr. Haigton's Essay on this subject: Memoirs of the Medical Society of London, vol. iii. The Thyroid Gland, (see fig. 118, p. 454,) May be described here, although a part of it is situated below the larynx. This body consists of two lobes, which are united at their lower extremities by a portion which extends across the anterior part of the windpipe. Each lobe generally rises upwards and backwards from the second cartilaginous ring of the windpipe over the cricoid cartilage and a portion of the thyroid. It lies behind the sterno-hyoidei, and sterno-thyroidei muscles. It is of a reddish-brown color, and appears to consist of a granular substance ; but its ultimate structure is not understood. It is plentifully supplied with blood, and receives two arteries on each side : one from the laryngeal branch* of the external carotid : and the other from the thyroid branch of the subclavian. Notwithstanding this large supply of blood, there is no * The main branch from the external carotid, is now more commonly called superior thyroid. r. 488 THE THYROID GLAND. proof that it performs any secretion : for although several respectable anatomists haVe supposed that they discovered excretory ducts passing to the windpipe, larynx, or tongue, it is now generally agreed that such excretory ducts are not to be found. Several instances, have, however, occurred, in which air has been forced, by violent straining, from the windpipe into the substance of this gland. [There are two membranous expansions in the neck which should be noticed in its dissection. The first, called Fascia Superficialis, lies immediately beneath the skin, may be considered as a continuation of the fascia superficialis abdomi- nis, and is strongly connected to the base of the lower jaw, being also spread over the parotid gland. It is not very distinct in all subjects. The second is called the Fascia Pro- funda Cervicis ; it extends from the larynx and thyroid gland to the upper part of the sternum and first ribs ; the great ves- sels, &,c. of the superior mediastinum are placed immediately below it.] The thyroid gland, gets a thin capsular investment, from two layers of the deep-seated cervical fascicf, (fascia profunda cer- mcis) as seen in fig. 125. The same fascia likewise gives off layers, that form cellular investments or tunics to the trachea, oesophagus, and to the blood-vessels of the neck. Other processes pass off from it which supply sheaths to the sterno-cleido mastoid and other muscles of the neck. Between the sheaths of the different muscles of the neck, dense processes of cellular tissue are con- tinued, so as to give them all the appearance of being formed as it were, from a common fascia. At the posterior part of the neck they are thus indirectly connected with the ligamentum nuchce. Though this for practical purposes is not considered the best way for studying the fascia of the neck, it serves to give an idea of the continuity of the cellular investments, which is so common throughout the body. The accompanying cut and explanation is taken from Wilson. The two lobes of the thyroid gland, when extended and measured from side to side are together about three inches in THE THYROID GLAND. 489 diameter. The lobes extend upwards on the sides of the larynx and downwards on the oesophagus, and lie upon the inner face of, and partly covering the primitive carotid artery and internal jugular vein. That part of the gland which unites the lobes Fig. together, and is stretched across the trachea, covering the two or three usually and sometimes the seven upper rings of the trachea, is called the isthmus of the gland. From the upper surface of the isthmus a process of the gland is usually seen * A transverse section of the neck, showing the deep cervical fascia and its numerous prolongations, forming sheaths for the different muscles of the neck, the thyroid gland trachea, O3sophagus and blood-vessels. As the figure is symmetrical, the figures of reference are placed only on one side. I. The platysma myoides. 2. The trapezius. 3. The ligamentum nuchae, from which the fascia may be traced forwards beneath the trapezius, enclosing the other muscles of the neck. 4. The point at which the fascia divides, to form a sheath for the sterno-mastoid muscle (5). 6. The point of reunion of the two layers of the sterno-mastoid sheath. 7. The^point^of union of the deep cervical fascia of opposite sides of the neck. 8. Section of the sterno-hyoid. 9. Omo-hyoid 10. Sterno-thyroid. 11. The lateral lobe of the thyroid gland. 12. The trachea. 13. The oasophagus. 14. The sheath containing the common carotid artery, internal jugular vein, and pneumogastric nerve. 15. The longus colli. The nerve in front of the sheath of this muscle is the sympathetic. 16. The rectus anticus major. 17. Scalenus anticus. 18. Scalenus posticus. 19. The splenius capitis. 20. Splenius colli. 21. Levator anguli scapulae. 22. Corn- plexus. 23. Trachelo-mastoid. 24. Transversalis colli. 25. Cervicalis ascen- dens. 26. The semi-spinalis colli. 27. The multifidus spinoe. 28. A vertical vertebra. The transverse processes are seen to be traversed by the vertebral artery and vein. 490 THE PHARYNX. extending upwards, on the left side over the front surface of the larynx, to be attached by ligamentous fibres to the os hyoides. A small muscle called the levator glandule thyroideae, has been described by Duverney, Soemmering and others, run- ning down from the os hyoides in front of the larynx to the upper part of the isthmus of the gland. According to Professor Homer, its existence is verv. rare, with which opinion my own more limited observation coincides. The lobes of the gland are composed of smaller lobules, and the spongy structure of the latter, is filled with a yellowish and somewhat oily fluid. Of the uses of this gland nothing positively is known. Its importance in the system of the adult cannot be great, as its removal by extirpation, which has been many times practised, has not appeared to leave any functional lesion in the economy. Of the Pharynx. The pharynx is a large muscular bag, which forms the great cavity behind the nose and mouth that terminates in the oesophagus. It has been compared to a funnel, of which the oesophagus is the pipe ; but it differs from a funnel in this respect, that it is incomplete in front, at the part occupied by the nose and mouth and larynx. It is connected above, to the cuneiform process of the occipital bone, to the pterygoid processes of the sphenoidal, and to both the upper and lower maxillary bones. It is in contact with the cervical vertebrae behind ; and, opposite to the cricoid cartilage, it terminates in the oesophagus. If the pharynx and oesophagus be carefully dissected and detached from the vertebrae, preserving the connexion of the pharynx with the head, and the head then be separated from the body, by dividing the articulation of the atlas and the os occipitis, and cutting through the soft parts below the larynx, the resemblance to a funnel will be very obvious. In this situation, if an incision be made from above down- wards through the whole extent of the posterior part of the STRUCTURE OF THE PHARYNX. 491 pharynx, the communication of the nose, mouth, and windpipe, with this cavity, will be seen from behind at one view. The openings into the nose, or the posterior nares, appear uppermost. Their figure is irregularly oval, or oblong ; they are separated from each other by a thin partition, the vomer. Immediately behind, on the external side of each of these orifices, is the Eustachian tube. (See fig. 118, p. 454.) The soft palate will appear extending from the lower boundary of the posterior nares, obliquely backwards and downwards, so as nearly to close the passage into the mouth. The uvula hangs from it ; and, on each side of the uvula, the edge of the palate is regularly concave. Below the palate, in the isthmus of the fauces, are the ridges or half arches, and the tonsils between them. The half arch which presents first, in this view, runs obliquely downward and backward, and not parallel to the other. Close to the root of the tongue is the epiglottis erect ; and immediately adjoining it, is an aperture large enough to admit the end of a middle-sized finger. This aperture is widest at the extremity next to the epiglottis, and rather narrower at the other extremity : it is the glottis or opening of the windpipe. When the larynx is elevated, the epiglottis can be readily depressed so as to cover it completely. The extremities of the arytenoid cartilages, and their appendices, may be recognized at the posterior edge of the glottis. At a short distance below this edge, the oesophagus begins. The Pharynx is composed of the membrane continued from the nose and mouth internally, and of a stratum of muscular fibres externally. The internal membrane is very soft and flexible and perforated by many muciferous ducts. The surface which it forms is rather rough, owing to the mucous glands which it covers. It has a red color, but not so deep as that of some other parts. It is connected to the muscular stratum by a loose cellular membrane. The muscular coat consists of three different portions, which are considered as so many distinct muscles. They are called 492 CONSTRICTOR MUSCLES OF THE PHARYNX. the superior, middle, and inferior constrictor muscles of the pharynx. The fibres of each of these muscles originate on 'each side, and run in an oblique direction to meet in the middle, thus forming the posterior external surface of the dissected pharynx. The fibres of the upper muscles originate from the cuneiform processes of the occipital bane, from the pterygoid processes of the os sphenoides, and from the upper and lower jaws, near the last dentes molares, on each side. They unite in a middle line in the back of the pharynx. The fibres of the middle muscles originate principally from the lateral parts of the os hyoides, and from the ligaments which connect that bone to the thyroid cartilage. The supe- rior fibres run obliquely upwards, so as to cover a part of the first mentioned muscle, and terminate in the cuneiform process of the occipital bone ; while the other fibres unite with those of the opposite side in the middle line. The fibres of the lower muscles arise from the thyroid and the cricoid cartilages, and terminate also in the middle line : those which are superior, running obliquely upwards ; the inferior, nearly in a transverse direction. It is obvious, from the origin and insertion of these fibres, that the pharynx must have the power of contracting its dimensions in every respect ; and, particularly, that its diameter may be lessened at any place, and that the whole may be drawn upwards. PART VI. OF THE THORAX. BEFORE the thorax is described, it will be in order to con- sider the Mamma ; Or those glandular bodies situated on the anterior part of it, which, in females, are destined to the secretion of milk. These glands lie between the skin and the pectoral muscles, and are attached to the surfaces of those muscles by cellular membrane. They are of a circular form ; and consist of a whitish firm substance, divisible into small masses or lobes, which are com- posed of smaller portions or lobuli. Between these glandular portions, a great deal of adipose matter is so diffused, that it constitutes a considerable part of the bulk of the mammae. The gland, however, varies greatly in thickness in the same person at different periods of life. The mammae become much enlarged about the age of pu- berty. They are also very large during pregnancy and lacta- tion ; but after the period of child-bearing they diminish con- siderably. They are supplied with blood by the external and internal mammary arteries, the branches of which enter them irregularly in several different places. The veins correspond with the arteries. From the small glandular portions that compose the mamma, fine excretory tubes arise, which unite together and form the great lactiferous ducts of the gland. These ducts proceed in a 42 494 MAMM2E. radiated manner from the circumference to the centre, and terminate on the surface of the nipple.* They are commonly about fifteen in number, and vary con- siderably in size : the largest of them being more than one-sixth of an inch in diameter.f Fig. 126.J They can be very readily injected by the orifices of the nip- ple from a pipe filled with mercury, in subjects who have died during lactation or pregnancy ; but they are very small in sub- jects of a different description. It has been asserted by respectable anatomists, that these ducts communicate freely with each other; but they do not appear to do so ; each duct seems to be connected with its pro- per branches only.<$> * Described in the 10th century, by Charles Etienne, Vesalius and Posthius, but their uses were unknown. H. f These ducts vary in number in different individuals, from fifteen to twenty. p. $ Fig. 126, is a vertical section of the mammary gland of a young female who died during lactation. The ducts were injected with wax, and two dissected out their full length to their origin in the lobules of the gland. 2, 2, Base of the nipple. 3, 3, 3, Lactiferous ducts cut off at the base of the nipple. 4, 4, The top of the ducts exhibited their whole length. 5, 5, Sinuses formed by these ducts at the base of the nipple. 6, 6, 6, 6, Branches of these ducts running to the lobules. 7, 7, 7, 7, 7, The lobules separated from each other. 8, 8, The orifices of these ducts on the top of the nipple. See Edinburgh Medical Commentaries, vol. i. p. 31. A paper by Meckel. LACTIFEROUS DUCTS. 495 Haller appears to have entertained the remarkable senti- ment, that some of the ducts originate in the adipose matter about the gland, as well as in the glandular substance.* > The papilla, or nipple, in which these ducts terminate, is in the centre of the mamma : it consists of a firm elastic substance, and is nearly cylindrical in form. It is rendered tumid by irritation, and by certain emotions. This power of erectibility of the nipple is due to the presence of some contractile tissue in its composition analogous to the dartus structure of the scrotum. There is now believed to be no erectile tissue in its composition. The lactiferous ducts terminate upon its extremity. When it is elongated they can freely discharge their contents ; but when it contracts, this discharge is impeded. The skin imme- diately around the nipple is of a bright red color in virgins of mature age. In pregnant women it is sometimes almost black ; and in women who have borne children it is often brownish. It abounds with sebaceous glands, which form small eminences on its surface. During gestation these follicles or glands are much increased in size, so as to become in consequence of this enlargement, one of the most certain signs of pregnancy. During suckling they are still farther enlarged, so as to appear like small pimples projecting from the skin, and serve by the increased secretion they throw out, to defend the nipple and areola, from the excoriating action of the saliva of the child. This gland exists in males, although it is very small. In boys, soon after birth, it has often been known to tumefy, and become very painful, in consequence of the secretion and accu- mulation of a whitish fluid, which can be discharged by pres- sure. It also sometimes swells and is painful, in males at the age of puberty. * Elementa Physiologiae, Tom. 7, Pars II. page 7. In the adipose matter about the gland, the lactiferous tubes (ducti gdlactophori) appear to communi- cate with the absorbent vessels. In injecting the gland with mercury, I have frequently found the metal to pass off from the ducts along the absorbent vessels. p. 496 LACTIFEROUS DUCTS. There have been some instances in which it has secreted milk in adult males ; and a few instances also in which it has been affected with cancer, in the same sex. The mamma is plentifully supplied with absorbent vessels, which pass from it to the lymphatic glands in the axilla. Its nerves are principally derived from the great plexus formed by the nerves of the, arm. The skin covering the mammary gland, is exceedingly thin, delicate and vascular, and that of the nipple and areola, more delicate and sensitive than any other portion. Each lactiferous duct by its branching and convolutions, forms a distinct lobule of the gland, and terminates in a series of vascular granules* the ultimate caecal termination of the ducts about the size of a millet seed, which are readily distinguished from each other in individuals who have died during lactation. The lobules of the gland vary in size, which, in subjects where the subcutaneous matter is not abundant, gives a feeling of un- evenness or roughness to the gland. There are no valves in the lactiferous tubes. * Histoire de la Generation, par Grimaud de Caux et Martin Saint- Ange, 4to. Paris, 1837. p. CAVITY OF THE THORAX. 497 CHAPTER XV. OF THE GENERAL CAVITY OF THE THORAX. Of the Form of the Cavity of the Thorax. THE osseous structure of the thorax is described in page 155. The cavity is completed by the intercostal muscles, which close the vacuities between the ribs ; and by the diaphragm, which fill up the whole space included within its lower margin. If we except the apertures of the diaphragm, which are completely occupied by the aorta, the vena cava, and the oeso- phagus, &c., the only outlet of this cavity is above : it is formed by the upper ribs, the first dorsal vertebra, and the sternum. The figure of this aperture is between that of the circle and the oval ; but it is made irregular by the vertebrae, and by the upper edge of the sternum. When the superior extremities and the muscles appropriated to them are removed, the external figure of the thorax is coni- cal ; but the cavity formed by it is considerably influenced by the spine, which protrudes into it ; while the ribs, as they pro- ceed from the spine, curve backwards, and thus increase the prominency of the cavity. The diaphragm has a great effect upon the figure of the cavity of the thorax. It protrudes into it from below, with a convexity of such form that it has been compared to an inver- ted bowl ; so that although it arises from the lower margin of the thorax, the central parts of it are nearly as high as the fourth rib. The position of the diaphragm is also oblique. The anterior portion of its margin, being'connected to the seventh and eighth ribs, is much higher than the posterior portion, which is.attached to the eleventh and twelfth. In consequence of the figure and position of the diaphragm, 42* 498 PLEURJE. the form of the cavity of the thorax resembles that of the hoof of the ox when its posterior part is presented forwards. Of the Arrangement of the Pleura. The thorax contains the two lungs and the heart, as well as several very important parts of smaller size. The lungs occupy the greatest part of the cavity ; ana to each of them is appointed a complete sac, called Pleura, which is so arranged that it covers the surface of the lungs, and is continued from it to the contiguous surface of the thorax, which it lines. After covering the lung, it is extended from it to the spine posteriorly : so that in tracing the pleura in a circular direction, if you begin at the sternum, it proceeds on the inside of the ribs, to the spine ; at the spine it leaves the surface of the thorax, and proceeds directly forwards towards the sternum. In its course from the spine to the sternum, it soon meets with the great branch of the windpipe and blood-vessels, which go to the lung : it continues on these vessels and round the lung until it arrives at the anterior side of the vessels, when it again proceeds forwards until it arrives at the sternum. Each sac being arranged in the same way, there is a part of each extended from the spine to the sternum. These two laminae form the great vertical septum of the thorax, called Medias- tinum. They are situated at some distance from each other; and the heart, with its investing membrane or pericardium, is placed between them. The pericardium is also a complete sac or bladder, which, after covering perfectly the surface of the heart, is extended from it so as to form a sac, which lies loose about it, and appears to contain it. This loose portion adheres to those parts of the laminae of the mediastinum, with which it is contiguous ; and thus three chambers are formed within the cavity of the thorax: one for each lung, and one for the heart. The two laminae of the pleura, which constitute the mediasti- num, are at different distances from each other, in different places. At the upper part of the thorax, they approach each other from the internal edges of the first ribs ; and as these MEDIASTINUM. 499 include a space which is nearly circular, the vacuity between these laminae is necessarily of that form, at its commencement above. Here, therefore, is a space between them above, (Superior Mediastinum) which is occupied by the transverse vein that carries the blood of the left subclavian and the left internal jugular to the superior cava ; by the trachea ; by the oesopha- gus ; and by the subclavian and carotid arteries, as they rise from the curve of the aorta. This space is bounded below by the above mentioned curve of the aorta. The heart and pericardium are so placed that there is a small distance between them and the sternum : in this space the two laminae of the mediastinum are very near to each other ; and cellular substance intervenes between them. This portion of the mediastinum is called the Anterior Medias- tinum.* Posteriorly, the heart and pericardium are also at a small distance from the spine ; and here the lamina of the mediasti- num are at a greater distance from each other, and form a long narrow cavity which extends down the thorax in front of the vertebrae : this is called the Posterior Mediastinum. It contains a considerable portion of the aorta as it descends from its curve, the oesophagus, the thoracic duct, and the vena azygos. The aorta is in contact with the left lamen, and can often be seen, through it when the left lung is lifted up. The posterior and anterior mediastina are separated from each other by the pericardium which encloses the heart. But as the serous layers of the anterior, are reflected one on each side of the pericardium, to meet the posterior mediastinum, it appears to -me to render the study of this part more easy, to * This mediastinum, being placed in front of the longitudinal diameter of the pericardium is found at its lower part inclined to the left of the middle line. The cellular tissue between its layers, communicates indirectly with the cellular tissue on the outer side of the peritoneum, in the notch formed by the origin of the greater muscle of the diaphragm, under the xiphoid appendix of the sternum. By this channel, abscesses of the anterior mediastinum, may make their way externally upon the abdomen. p. 500 PREPARATION OF THE THORAX. consider that embracing the pericardium as a middle medias- tinum. The oesophagus is in contact with the right lamen ; in its progress downwards, it inclines to the left side and is advanced before the aorta. The vena azygos appears posterior to the oesophagus ; it proceeds upwards until it is as high as the right branch of the windpipe : here it bends forward, round that branch, and opens into the superior cava, laefore that vein opens into the right auricle. The thoracic duct proceeds upwards from below, lying in the space between the aorta and the vena azygos, until the begin- ning of the curve of the aorta, when it inclines to the left, pro- ceeding towards the place of its termination. The anterior and posterior mediastina are formed as is shown above, by the layers of the pleura, between the sternum and pericardium, and between the pericardium and spine. But the pericardium does not extend the whole length of the thoracic cavity ; it terminates about two inches short of the top of the sternum, and at this part, there being nothing interposed to divide the layers into an anterior and posterior portion, they pass directly from the vertebrae to the sternum, and constitute what is called the Superior Mediastinum. The two layers con- stituting this, continuous below with the anterior and superior mediastina, and each lining the upper margin of the first rib, so as to form a conical pouch projecting a slight distance above the middle of the clavicle, constitute a triangular cavity, the base of which is upwards, and corresponds to the root of the neck. This cavity contains the thymus gland, the arteria innominata, the primitive carotid and subclavian of the left side, the superior vena cava, the trachea, oesophagus, and par vagum nerves. The sympathetic nerve is not contained in this mediastinum ; it passes a little to the "outside of the posterior external angle of it. The formation of the mediastinum, and the arrangement of the pleura, as well as the connexion of these membranes with the parts contained in the thorax, PREPARATION OF THE THORAX. 501 may be studied advantageously, after the subject has been prepared in the manner now to be described. Take away, from each side, the five ribs which are situated between the first and last true ribs, by separating their cartilages from the sternum, alfd their heads from the spine ; so that the great cavities of the thorax majf be laid open. The precise course of the mediastinum is thus rendered obvious; and the sternum may now be divided with a saw throughout its whole length in the same direction j so that the division of the bone may correspond with the space between the lamina of the mediastinum. Separate the portion of the sternum cautiously, so as to avoid lacerating the lamina of mediastinum ; and to keep them separate, while the trachea is dissected from the neck into the cavity of the thorax ; the great transverse vein and the descending cava are dissected to the pericardium ; and the left carotid artery, with the right subclavian and carotid, are dissected to the curve of the aorta, taking care not to destroy the lamina of the mediastinum. After this preparation the upper space between the lamina of the mediastinum can be examined, and the relative situation of the trachea and the great vessels in it can be understood. The anterior mediastinum can also be studied : the root of each lung, or its connexion with the mediastinum, may be seen perfectly ; and the precise situation of the lung, in its proper cavity, may be well conceived. After this, while the portions of the sternum are separated, the pericardium may be opened, and the heart brought into view : the attachment of the pericardium, and to the mediastinum, and to the diaphragm, may be seen with advantage in this situation. The portions of the sternum may now be detached from the ribs, with which they remain connected ; and further dis- section may be performed to examine the posterior mediastinum and Us con- tents, and the parts which constitute the roots of the lungs. 502 THE PERICARDIUM. CHAPTER XVI. - OF THE HEART AND PERICARDIUM, AND THE GREAT VESSELS CONNECTED WITH THE HEART. Of the Pericardium. THE heart is enclosed by a membranous sac, which, upon a superficial view, seems only connected with its great vessels. The whole of the organ lays unattached in the cavity of the sac, except, by the arteries and veins connected with its base. The sac is in fact composed of two layers, one external and fibrous, and one internal and serous ; the latter of these not only lines the inner face of the outer membrane, but is reflected like other serous membranes, over the roots of the vessels placed in the pericardium, and over the whole of the outer sur- face of the heart itself. This internal serous lining is very thin and delicate, and can only be raised in small shreds, either rom the outer layer of the pericardium, or from the heart ; except at the base of the latter organ, where, in females, it is usually, and in males, frequently, separated from the muscular tissue, by some sub-serous fatty matter. If it were dissected from the heart, without laceration or wounding, it would be an entire sac. The pericardium, thus arranged, is placed between the two lamina of the mediastinum, and adheres firmly to them where they are contiguous to it ; it also adheres firmly to the dia- phragm below, and thus preserves the heart in its proper position. The figure of the pericardium, when it is distended, is some- what conical ; the base being on the diaphragm. The cavity formed by it is larger than the heart after death, but it is probable, that the heart nearly fills it during life ; for when this THE PERICARDIUM. 503 organ is distended by injection, it often occupies the whole cavity of the pericardium. The attachment of the pericardium to the diaphragm, is exactly over the cordiform tendon of the latter. The French anatomists have erroneously considered the fibrous layer of the pericardium, as a mere reflection of the tendon upwards. By separating them with a knife, we find, they are united by a short cellular tissue, which is densest and strongest at the peri- phery of their junction. The sides of the pericardium are covered in part by the pleura, which gives the sac the appear- ance of being formed by three tunics. Underneath the pleural lining, is found the phrenic nerve, and in fat subjects, a good deal of adipose matter. The pericardium is composed of two lamina, the internal of which covers the heart, as has been already described ; while the external merely extends over the loose portion of the other, and blends itself with the mediastinum, where that membrane invests the great vessels. Its principal attachment or termination above, is upon the arteries and veins entering the heart, (with the exception of the vena cava inferior,) over which it sends tubular prolongations, which gradually blend with their external coats. Between these prolongations on the inside of the sac, hollow pouches are necessarily left, which are called the cornua of the pericardium. The fibrous layer of the pericardium resembles in structure and appearance, the dura mater of the brain. The arteries of the pericardium are very small ; they are de- rived from the phrenic, bronchial, cesophageal, internal mam- mary arteries, and from the aorta itself. Its veins terminate in the vena azygos. Its nerves are few and small, and originate from the cardiac plexus. - The internal surface of the pericardium is very smooth and polished ; and in the living subject is constantly moistened with a fluid which is probably effused from the exhalent vessels on its surface. The quantity of this fluid does not commonly exceed two drachms ; but in cases of disease it sometimes amounts to 504 THE HEART. many ounces.* It is naturally transparent, but slightly tinged with red in children, and yellow in old persons. It is often slightly tinged with red in persons who have died by violence. Of the Heart. The great organ of the circulation consists of muscular fibres, which are so arranged that they give it a conical form, and compose four distinct cavities within it. Two of these cavities, which are called Auricles, receive the contents of the veins ; the other two communicate with the arteries, and are called Ventricles. The auricles form the basis of the cone ; the ventricles the body and apex. The structure of the auricles is much less firm than that of the ventricles, and consists of a smaller proportion of muscular fibres. They appear like appendages of the heart, while the ventricles compose the body of the viscus. The ventricles are very thick, and are composed of muscular fibres closely compacted. The figure of the heart is not regularly conical ; for a portion of it, extending from the apex to the base, is flattened ; and in its natural position, this flat part of the surface is down- wards. It is placed obliquely in the body ; so that its base presents backward and to the right, and its apex forward and to the left. Notwithstanding this obliquity, the terms right and left are applied to the different sides of the heart, and to the different auricles and ventricles ; although they might, with equal pro- priety, be called anterior and posterior. / The two great veins called Vena Cavce, which bring the blood from every part of the body, open into the right auricle \ from above and below ; the right auricle opens into the right * The pericardium has been so distended, by effusion in dropsy, that it has formed a tumour, protruding on the neck from under the sternum. This tumour had a strong pulsating motion. It disappeared completely when the other hydropic symptoms were relieved. RIGHT AURICLE. 505 ventricle; and from this ventricle arises the artery denomi- nated Pulmonary, which passes to the lungs. The Pulmonary veins, which bring back the bloody from the lungs, open into the left auricle ; this auricle opens into the left ventricle ; and from this ventricle proceeds the Aorta, or great artery, which carries blood to every part of the body. The heart is preserved in its position, 1st, by the venae cavae which are connected to all the parts with which they are con- tiguous in their course ; 2d, by the vessels which pass between it and the lungs, which are retained in a particular position by the mediastinum ; 3d, by the aorta, which is attached to the mediastinum in its course downwards, after making its great curve ; and 4th, by the pericardium, which is attached to the great vessels and to the mediastinum. By these different modes the basis of the heart is fixed, while its body and apex are perfectly free from attachment, and only contiguous to the pericardium. The external surface of the heart, being formed by the serous layer of the pericardium, is very smooth : under this surface a large quantity of fat is often found. The two auricles are contigu- ous to each other at the base, and are separated by a partition which is common to both. The Right Auricle originates from the junction of the two venae cavae. These veins are U united at some distance behind Fig. * Longitudinal section of the heart, showing its cavities. *, Right ventri- cle, c, Septum ventriculorum. d, Right auricle, e, Left auricle. /, Section of the mitral valves, g, Section of tricuspid valves, h, Arch of aorta. A, Descending aorta, i, i, Vena cava superior and inferior, k, k, Right and left branches of the pulmonary artery. I, I, Pulmonary veins. 43 506 RIGHT AURICLE. the right* ventricle, and are dilated anteriorly into a sac or pouch, which is called the Sinus, and extends to the right ven- tricle, to which it is united.f The upper part of this pouch, or sinus, forms a point with indented edges, which is detached from the ventricle, but lies loose on the right side of the aorta. This point has some resemblance to the ear of a. dog, from which circumstance the whole cavity has been called auricle ; but by many persons the cavity is considered as consisting of two portions : the Auricle, strictly speaking ; and the Sinus Venosus, above described : they however form but one cavity. This portion of the heart, or Right Auricle, is of an irregular oblong figure. In its posterior surface, it is indented ; for the direction of the two cavae, at their junction, is not precisely the same; but they form an angle, which causes this indentation. The anterior portion of the auricle, or that which appears like a pouch between the ventricle and the veins, is different in its structure from the posterior part, which is strictly a portion of the veins. It consists simply of muscular fibres, which are arranged in fasciculi that cover the whole internal surface : this is also the case with the point, or that part which is strictly called auricle. These fasciculi are denominated Musculi Pectinati, from their resemblance to the teeth of a comb. That part of the internal surface, which is formed by the septum is smooth, and the whole is covered by a delicate mem- brane. On the surface of the septum, below the middle, is an oval depression, which has a thick edge or margin: this is called the Fossa Ovalis.^ In the foetal heart, it was the Foramen Ovale, or aperture which forms the communication between the two auricles. * In this description the heart is supposed to be in its natural position. } At the place of junction of these veins there is a projection, indistinctly seen in man, but very manifest in some of the larger mammalia, called tuber- culum Loweri. P. : The thick edge or margin is spoken of as the annulus ovalis. P. RIGHT AURICLE. 507 Near this fossa is a large semilunar plait, or valve, with its points and concave edge uppermost, and convex edge down- wards. It was described by Eustachius, and therefore, is called the Valve of Eustachius. It commences at the lower surface of the opening of the inferior vena cava, and runs forwards to terminate below the fossa ovalis. It served in the foetus to obstruct the passage of the venous blood from the right auricle into the right ven- tricle, and to direct it in a great measure through the foramen ovale. Anterior to this valve, and near the union of the auricle and ventricle, is the orifice of the proper vein of the heart, or the coronary vein. This orifice is covered by another semilunar valve, which is sometimes reticulated.* The aperture, which forms the communication between the right auricle and right ventricle, is about an inch in diameter, and is called ostium venosum. From its whole margin arises a valvular ring, or duplicature of the membrane lining the surface : this circular valve is divided into three angular por- tions, which are called Valvula Tricuspides. From their margins proceed a great number of fine tendinous threads, which are connected to a number of distinct portions of mus- cular substance, which arise from the ventricle. The Right Ventricle, when examined separately from the other parts of the heart, is rather triangular in its figure, It is composed entirely of muscular fibres closely compacted ; and is much thicker than the auricle, although not so thick as the other ventricle. Its internal surface is composed of bundles or columns of fleshy fibres, which are of various thickness and length. Some of these columns (columna carne