LIBRARY G THE CYCLOPAEDIA OP ANATOMY AND PHYSIOLOGY VOL. I. A -DEA 1835-1836 THE CYCLOPAEDIA OF ANATOMY AND PHYSIOLOGY. EDITED BY ROBERT B. TODD, M.D. F.R.S. \\ FELLOW OF THE ROYAL COLLEGE OF PHYSICIANS; PHYSICIAN TO KING'S COLLEGE HOSPITAL ; AND FORMERLY PROFESSOR OF PHYSIOLOGY AND OF GENERAL AND MORBID ANATOMY IN KING'S COLLEGE, LONDON, ETC. ETC. VOL. I. A DBA 18351836 LONDON LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS. QL7 PREFACE. To collect a series of Essays on all the various subjects of Anatomy and Phy- siology, by the co-operation of several Authors, who, as far as possible, should be selected in consequence of their special attention to, or interest in, the subject-matter of the articles which each would undertake to furnish, was the object of the Editor in projecting the "Cyclopaedia of Anatomy and Physiology." The successful inauguration of a similar work on Practical Medicine, which had advanced some way prior to the commencement of this Cyclopedia, afforded great encouragement to the Publishers and to the Editor to prosecute their design. The first part was published in 1835, twenty-four years ago. It was then calculated that twenty parts would complete the book, arid that not many years would have been sufficient for that purpose, A glance at the Table of classified Contents will show the multipli- city of topics on which it was proposed to treat: Anatomy, both as it regards man and all the tribes of inferior creatures, Anatomy de- scriptive, Anatomy physiological or histological, Comparative Anatomy, Morbid Anatomy, general and special. To these were to be added: Physiology (human and comparative) ; some brief notice of Vegetable Physi- ology ; the Anatomy and Physiology of the different classes of Animals, in- volving, in many instances, much reference to their Zoology ; and lastly Animal Chemistry, including the physiology of the fluids and secretions. VOL. i. a PREFACE. Numerous as were the articles which, according to the first plan of the work, were to have been introduced, it was soon found indispensable not only to add others quite new, but also to enlarge considerably the space allotted to each of those which formed the original catalogue, and to multiply greatly the number of illustrations. All this was rendered necessary by the rapid strides which our know- ledge of many subjects in Anatomy and Physiology began to take at the time when the earlier parts of the Cyclopasdia made their appearance. Perhaps there never was greater activity of research in any branch of science during a given period, than that under which the sciences of Anatomy and Phy- siology advanced during the last quarter of a century. Minute anatomy, which thirty years ago was crude and undigested, now takes very high rank among the various branches of Natural Knowledge. During these years every tissue has been scrutinised ; many obscure points have been cleared up ; much that was wholly unknown has been brought to light. The additions to our knowledge of Anatomy, although there is yet ample room for fresh dis- coveries, have given a totally new phase to Physiology. From being little more than a series of vague and ill-founded hypotheses, scarcely deserving even that name, it has become a well-arranged science, embracing a vast amount of clearly defined facts, which, at once, form a solid basis for a superstructure of sound theory, and throw much light upon the various processes of animal and vegetable life. It was the constant aim of the Editor, where it was possible, to secure the assistance of Contributors who would be likely to make original investiga- tions, and to employ new researches for furnishing the materiel of their articles. Whilst it is thankfully acknowledged, that in many instances the Editor's most sanguine hopes were fully attained, it is not less true that he was sometimes disappointed, and that much delay of publication and apparent breach of faith took place. A few completely failed to fulfil their engagements, without any assignable reason; others were unavoidably prevented from so doing. In several instances the articles were not completed at the stipulated time. For some of these the Editor was content to wait, notwithstanding that by so doing the immediate sale of the book was injured, and the Editor himself exposed (with apparent justice) to charges of violation of promises. But, in the particular cases referred to, the Editor knew that delay in the comple- PREFACE. tion of the articles was caused by an earnest wish on the part of the Authors to do ample justice to their subjects, and a praiseworthy scrupulousness in recording facts which they had not verified by actual observation. To this it must be added, that for a considerable period the continuance of the work was jeopardised, and its publication wholly suspended for two years, by the death, in rapid succession, of the leading partners of the publishing firm under whose auspices the work was conducted, prior to its passing into ihe hands of its present publishers, the Messrs. Longman. Nor will the Editor attempt to shield himself from blame as regards the tardy completion of the Cyclopaedia. He is quite ready to confess that, in other hands than his own, it would have been long since finished. He is con- scious that he has been often dilatory, sometimes vacillating, occasionally appalled by the magnitude of the undertaking, and by the knowledge of the inadequacy of his powers to carry it on to a close. At the same time, in self-defence, he feels bound to plead that, soon after the publication of the first two or three parts of the work, certain onerous duties devolved upon him, which greatly curtailed the amount of leisure available for literary pursuits. In the first place, he was called upon, at short notice, to deliver a lengthened course of Lectures on Anatomy and Physiology of a kind quite new in this country, both as regards extent and nature, which demanded a large amount of study and of personal inquiry and investigation ; soon afterwards was added the responsible office of a Hospital Physician and a Teacher of Clinical Medicine; these were, at no long interval, followed by professional engagements, which, although not more responsible, created more urgent and imperative claims upon his time and attention. With all these demands upon him, it will not excite surprise that literary work often became abandoned or postponed. At length, " per varios casus et tot discrimina rerum," the period of com- pletion has arrived. And the Editor, while he is impressed with a deep sense of gratitude that his own health and life have been spared till the completion of the book, acknowledges, with thankfulness and pride, the invaluable aid which he has obtained from all quarters. He looks back with much of the same feelings which fill the mind of an architect who has projected a large a 2 PREFACE. building requiring for its completion a long series of years. While the original design, as well in its defects as in its merits, is due to himself, he is conscious how little he has had to do in supplying the materials, and completing the details of the building. For these he has trusted, and not in vain, to a body of collaborateurs, among whom he is proud to reckon many of the first scien- tific men both in this country and in Europe. How efficiently this work has been done, it is not for the Editor to say, but he deems himself justified in affirming that, for years to come, this Cyclopaedia will furnish a well-stocked field for reference to the student of Anatomy and Physiology. It is remarkable how few of the members of this little phalanx of contributors have failed to see the completion of the work ! Nevertheless, we have to deplore some serious losses ; and the Editor trusts he may be pardoned for offering a passing tribute to the memory of some of the more distinguished among them. Foremost among these, although but recently removed from amongst us, was the late Dr. MARSHALL HALL, who furnished articles on the (to him) favourite subjects, HYBERNATION, IRRITABILITY. x Although a veteran in science, he had finished his career before he had reached the ordinary limits of human life. To large gifts of natural genius he added an indomitable industry and perse- verance. His name must always occupy a prominent position in the annals of Physiology, by reason of the active and highly successful part which he took in advancing our knowledge of the Physiology of the Nervous System, and in promoting its application to the investigation of Pathology and the diagnosis and treatment of disease ; and the extremely ingenious speculations and hypotheses which he, from time to time, suggested for the explanation of various natural and morbid phenomena. The manner in which his almost latest hours were employed in applying physiological knowledge to the treatment of asphyxia shows how little it could have been said of him, " Superfluous lags the veteran on the stage." Still more recently, another veteran, especially distinguished in anatomical science, has fallen while actually in the ranks. Professor HARRISON, having been during the previous day engaged in the duties of his chair, rapidly suc- cumbed, in the course of a night, under an apoplectic seizure. For forty years and upwards he maintained the highest reputation as a Teacher. At PREFACE. a time of life long subsequent to that at which most men seek repose from such labour, he was as fresh, clear, full, and impressive, in teaching ana- tomy, at once the most elementary and the most important of the studies accessory to medicine, as in his early days. The celebrated discoverer of Endosmose, H. DUTROCIIET, lived to the ripe age of seventy-one. The article on that subject in this work was the contribution of his own pen. It contains a summary of his views up to the time of its publication. Dutrochet's discovery has the most interesting and important bearing upon the application of physical laws to the illustration of various processes of living organisms. It gave the clue to the elucidation of many obscure points in the physiology of animals and plants, and took a lead in directing the minds of Physiologists away from abstract and fruitless speculations concerning the nature of Life, into the true path of inquiry as to the dependence of vital phenomena on chemical and physical laws. The value of this discovery is enhanced by the recent researches of Mr. GRAHAM, which have developed the laws of Osmose (to use his more concise and comprehensive designation), and have shown the intimate con- nexion of osmotic with chemical action. Further experiments on the osmotic phenomena of living animals and plants, assisted by the additional light ob- tained from Mr. Graham's researches, can scarcely fail to lead to important, practical results, both in Physiology and Pathology. The loss of NEWPORT was a heavy blow to Physiology. A man of his skill as a dissector and observer of that large and most interesting tribe, the Insects, could ill be spared. The combination of such manual dexterity and of so much acuteness of observation as Newport displayed is rarely met with. His investigations embraced at once the most delicate anatomical analyses and the deepest questions of physiology. The article INSECTA, contributed by him to this work, is perhaps the most comprehensive account extant of the anatomy and physiology of this class of invertebrate animals. Newport was cut down in the prime of life, when, after many struggles and difficulties his merits were becoming recognised, and the value of his researches appre- ciated. There can be no doubt, had health and life been given him, he would have largely extended our knowledge of this branch of Comparative Anatomy and Physiology. PREFACE. Of not less promise, in a still wider field of research, was JOHN REID, who for a few years before his early removal under a painful and tedious disease, filled the chair of Medicine at the University of St. Andrew's, a position in which his great powers had but a limited scope. Reid was one of those men who are content to take nothing for granted which it was at all in their power to examine for themselves. His admirable investigation of the Anatomy and Physiology of the Eighth Pair of Nerves is a model of anatomical and physiological research, scarcely equalled and not surpassed by any similar essay of recent or remoter times. His articles, HEART and RESPIRATION, in this Cyclopaedia, bear ample testimony to his scientific character, and well sustain the high reputation he had acquired even at a very early age. The late venerable Dr. BOSTOCK, who died at an advanced age, belonged to a different school of Physiologists from those already referred to. No man was more remarkable for the patience and depth of his literary researches. Conscientious almost to a fault, he has left a scrupulously faithful record of all that was done in Physiology up to the time at which he wrote, affording to those who take an interest in that branch of inquiry an impartial historical review of the progress of science. From the great erudition and sound judgment of this excellent man, the Editor derived many valuable hints in the first stages of the Cyclopedia, in the plan and early progress of which he was pleased to take a lively interest. Born a British subject, the late W. F. EDWARDS (also a veteran in science although he had by no means attained a great age) had spent most of his life in France and followed his Physiological pursuits there. His principal re- searches were directed to the observation of the influence of various physical agents upon the phenomena of Life, and the investigation of the chemical changes which occur in some of the most important and recondite vital pro- cesses. Many of his Essays, which were at first published as detached Papers, were afterwards collected, and formed his well-known work on the " Influence of Physical Agents upon Life."* Dr. Edwards's researches, whilst they determined many new and highly interesting facts, were especially valu- able as promoting more philosophical views of life than those which referred all vital phenomena to the influence of a hypothetical entity. * Translated into English by Drs, Hodgkin and Fisher, an. 1832. PREFACE An important article on Animal Chemistry in this Cyclopedia (PROTEINE) was contributed by a young and rising chemist, JOHN E. BOWMAN, whose brief career sufficed to impress his friends with a strong sense of the serious loss which society and science experienced by his early removal. His acute and well-cultivated intellect would have done much for chemistry had his life been prolonged, or had he even enjoyed, during its short span, an ordinary amount of health. But his last few years were greatly marred in their use- fulness by a singular chronic malady, which slowly undermined his vital powers, and greatly limited his ability for active exertion, whether bodily or mental. Nevertheless, he has left two works which, although of small size, are of considerable practical utility to the chemical student ; the one devoted to practical chemistry, the other to chemistry in its application to practical medicine. The Editor takes this opportunity of acknowledging his obligations to gentlemen who, at different periods, rendered him the most efficient assistance in superintending the passing of the work through the press, and in other matters connected with his province. Dr. ROBERT WILLIS, formerly of London, now extensively engaged in medical practice at Barnes in Surrey, for many years took an active part in the superintendence of the printing of the work, and contributed largely to the Bibliography appended to most of the articles, as he was so well qualified to do by his extensive knowledge of books. Dr. Willis also con- tributed the article ANIMAL. Upon his retirement, the Editor derived similar valuable assistance from his friend and former pupil, Mr. S. ROOD PITTARD, who also contributed several articles. And, subsequently, Dr, HYDE SALTER, now well-known, and of deservedly high reputation as a Physiologist and Physician, kindly afforded his aid in the same way, as well as by his valuable contributions of the articles PANCREAS and TONGUE. This seems the fitting place to state that it has been found necessary, in a few instances, to depart from the strict alphabetical arrangement, either by placing articles under names not commonly used, or by clubbing together two or more subjects, to which it would appear, at first, more natural to have de- voted separate articles. The necessity for such modifications arose out of PREFACE. contingencies to which all works are liable, when they are published in Parts, and dependent for regularity of publication on the punctual contribution of the various articles. Where such punctuality could not be obtained, and where it was found absolutely necessary to curtail delay, the changes above alluded to were adopted as a matter of necessity rather than of choice. Thus, Ear is referred to HEARING, ORGAN OF; Kidney to REN. The union of certain articles together under one heading was sometimes found both convenient for treating the subjects, and economical of space. Thus, the Anatomy of the Brain was conveniently associated with that of the Spinal Cord, and will be found under NERVOUS CENTRES ; that of the Intestinal Canal under STOMACH AND INTESTINAL CANAL (Dr. Brinton) ; and that of the Ovary in the elaborate article of Dr. Farre, UTERUS AND ITS APPENDAGES. SEROUS AND SYNOVIAL MEMBRANES have been treated of under one heading, from the close analogy of their structure ; and Hairs, Nails, Skin, &c., are described under the general title TEGUMENTARY ORGANS. It was found absolutely necessary, owing to difficulties which otherwise must have completely prevented the completion of the work, to place several articles in a supplementary volume, regardless of strict alphabetical arrange- ment. But it is hoped that for this, as well as the other departures from the strict Encyclopaedic form, compensation will be found in the various Indices, and in the Table of Classified Contents. 26 Brook Street, Grosvenor Square, London, Jan. 1859. CLASSIFIED CONTENTS THE CYCLOPEDIA OF ANATOMY AND PHYSIOLOGY. HUMAN ANATOMY, DESCKIPTIVE. Abdomen Dr. Todd Ankle-joint Dr. Brenan Aorta Dr. Hart Vol. Page i. 1 i. 151 i. 187 Arm, Muscles of' the Dr. Hart i. 219 Articulation ......... Dr. Todd ............ Axillary Artery ... Dr. Hart ............ Azygos ............... Dr. Harrison ...... Bladder ............... Dr. Harrison ...... Brachial Artery ... Dr. Hart ............ Brain. See Nervous Centres. Carotid Artery ...... Dr. Hart ............ Cranium ............ J. Malyn, Esq. ... Diaphragm ......... Dr. Benson ......... Ear. See Hearing, Organ of. Eighth Pair of Nerves. See Glosso- pharyngeal ; Par Vagum ; Spinal Accessory. Elbow-joint ......... Dr. Hart ............ Extremity ......... Dr. Todd ......... Eye .................. Dr. Jacob ......... Femoral Artery ... Dr. Alcock ......... Fibular Artery ...... Dr. Todd ......... Fifth Pair of Nerves Dr. Alcock ......... Foetus ............... Dr. Montgomery... Foot, Bones and 1 ) _ l f Dr. Todd ......... Joints of the J Fourth Pair ofi } Dr. Alcock ......... Nerves J Generation, Or- -^ T. Rymer Jones, -\ gans of J Esq. J Glosso-pharyngeal , T Nerve Dr. Reid Hand, Bones and Joints of the VOL. i. Dr. Todd. i. 246 i. 363 i. 364 i. 376 i. 465 i. 482 i. 724 ii. 1 ii. 65 ii. 154 ii. 171 ii. 235 ii. 267 ii. 268 ii. 316 ii. 338 ii. 370 ii. 406 ii. 494 ii. 505 Hand, Muscles of "i Bishop MacDou- the J gall Hearing, Organ of T. W. Jones, Esq. Heart Dr. Reid Heart, Arrange- - ment of the Fi- \H. Searle, Esq. ... bres of the J Hip-joint H. Hancock, Esq. Iliac Arteries Dr. Alcock Innominata Arteria H. Hancock, Esq. Kidney. See Ren. Knee-joint A. Higginson, Esq. Lachrymal Organs T. W. Jones, Esq. Larynx J. Bishop, Esq. ... Leg, Muscles of. A.T.S. Dodd, Esq. Liver E. Wilson, Esq. ... Mammary Glands S. Solly, Esq Mucous Membrane W. Bowman, Esq. Nervous Centres ... Dr. Todd Ninth Pair of-| Nerve, }*****..- Nose J. Paget, Esq (Esophagus Dr. G. Johnson ... Optic Nerves Dr. Mayne Orbit Dr. G. Johnson ... Pacinian Bodies ... W. Bowman, Esq. Pancreas Dr. Hyde Salter ... Par Vagum Dr. J. Reid Pelvis John Wood, Esq. Penis E. Wilson, Esq. ... Perineum Dr. Mayne Peritoneum S. R. Pittard, Esq. Pharynx W. Trew, Esq. ... Pleura S. R. Pittard, Esq. Prostate J. Adams, Esq. ... Vol. Page [ ii. 519 ii. 529 ii. 577 ii. 619 ii. 776 ii. 827 ii. 850 iii. 44 iii. 78 iii. 100 iii. 137 iii. 160 iii. 245 iii. 484 iii. 712 iii. 721 iii. 723 iii. 758 iii. 762 iii. 782 iii. 876 *. 81 iii. 881 s. 114 iii. 909 iii. 919 iii. 935 iii. 945 iv. 1 iv. 146 CLASSIFIED CONTENTS. . Thos. Williams s. 258 Vol. Page Radial Artery Dr. Brinton iv. 221 Radio-ulnar Arti-T _ \Dr. Brinton iv. 228 culation J Ren Dr. Johnson iv. 231 Respiration, Or- gans of Salivary Glands ... N. Ward, Esq. ... iv. 422 Scrotum Dr. Brinton iv. 438 Serous and Syno-1 ^ ^ J \Dr. Brinton iv. 511 vial Membranes J Sesamoid Bones ... S. R. Pittard, Esq. iv. 541 Seventh Pair ^T n 7? / Nerves J Shoulder-joint Dr. M ( Dowel iv. 571 Sixth Pair of Nerves Dr. Brinton iv. 621 Spinal Accessory^ > Dr. John Reid iv. 745 Nerve J Spinal Nerves N. Ward, Esq. ... iv. 750 Spleen Professor Kolliker i v. 771 Stomach and In- testinal Canal \Dr.Bri Brinton s. 293 Subclavian Arteries Dr. M l Dowel Supra-renal Cap-~i _ \ Prof. Heinrich Frey sules J Sympathetic Nerve Dr. Drummond ... Temporo-Maxil- - lary Articula- I S. R. Pittard, Esq. tions J Testicle T. B. Curling, Esq. Thorax Dr. Hutchinson ... Thymus Gland Dr. Handheld Jones Thyroid Gland ... Dr.Handfield Jones Tibio-fibular Ar- ticulations Tongue Dr. Hyde Salter ... Urethra John Adams, Esq. Uterus and its Ap- 1 _ " \ Dr. Arthur Farre pendages J Venous System . . . Dr. M' Dowel Vesicula Prostatica Prof. Leuckhardt Vesiculse Seminales S. R. Pittard, Esq. Wrist-joint Dr. M' Dowel Dr. M'Dowel Vol. Page iv. 814 iv. 827 s. 423 iv. 937 iv. 976 iv. 1016 iv. 1087 iv. 1102 iv. 1118 iv. 1120 iv. 1244 s. 545 iv. 1403 iv. 1415 iv. 1429 iv. 1505 HUMAN ANATOMY, SURGICAL OR TOPOGRAPHICAL. 147 Fore-arm, Muscles, 173 and Regions of / 216 Gluteeal Region ... A. T. S. Dodd,Esq. ii. 358 Groin, Region of the Dr. Todd ii. 367 Hand. Regions ofl _ ,. _. .. [ Bishop Mac Dougall u. 746 Leg, Regions of the A. T. S. Dodd, Esq. iii. Neck, Muscles and i _ }J. Simon, Esq. ... in. 62 Regions of the J 207 Parotid Region ... Dr. G.Johnson... iii. Popliteal Region ... W. Trew, Esq. ... iv. Scapular Region ... Dr. M' Dowel iv. Ankle, Region of the Dr. Brenan i. Anus R. Harrison, Esq. i. Arm Dr. Hart i. Axilla Dr. Benson i. Back Dr. Benson i. Cranium, Regions -j and Muscles oflz>r. Todd i. the Elbow, Region of the Dr. Hart. ii. Face R. Partridge, Esq. ii. Foot, Regions arid Muscles of \A.T.S.Dodd,Esq. ii. 350 361 500 503 523 126 561 902 60 433 ANATOMY, GENERAL OR PHYSIOLOGICAL. Adipose Tissue Dr. Craigie i. 56 Artery Dr. Hart i. 220 Bone Dr. Benson i. 430 Bursas Mucosae Dr. Brenan i. 467 Cartilage Dr. Benson i. 495 Cavity Dr. Todd i. 500 Cellular Tissue R.D.Grainger,Esq. i. 509 Cilia Dr. Sharpey i. 606 Erectile Tissue Dr. Hart ii. 144 Excretion Dr. Alison ii. 147 Fascia Dr. Todd ii. 229 Fibro-cartilage. Dr. Todd ii. 260 Fibrous Tissue ... R.D. Grainger, Esq. ii. 263' Ganglion R.D.Grainger,Esq. ii. 371 Gland R.D. Grainger,Esq. ii. 480 Lymphatic S. Lane, Esq iii. 205 Membrane Dr. Todd iii. 331 Meninges Dr. Todd iii. 331 Muscle W. Bowman, Esq. iii. 506 Nerve Dr. Todd iii. 591 Nervous System ... Dr. Todd iii. 585 Osseous Tissue ... J. Tomes, Esq. ... iii. 847 Skeleton Jos. Maclise, Esq. iv. 622 Vein 5. J. A. Salter, Ef S. Lane, Esq. Lacteal System J Muscular System... Prof. It. Jones ... iii. Nervous System ... J. Anderson, Esq. iii. 600 27 iii. 205 530 601 Osseous System ... Prof. R. Jones Shell Dr. Carpenter... Teeth Professor Owen Tegumentary Or- "1 gans (Hair, Nails, I T. Huxley, Esq. Feathers, &c.) J in. iv. iv. 820 556 864 *. 473 ZOOLOGICAL ANATOMY AND PHYSIOLOGY. Acalephse Dr. Coldstream Acrita jR. Owen, Esq. Amphibia T. Bell, Esq Animal Kingdom Professor Grant Annelida Dr. Milne Edwards Arachnida Dr. Audouin Articulata Professor Owen Aves R. Owen, Esq. Carnivora T. Bell, Esq. Cephalopoda JR. Owen, Esq, Cetacea M. F. Cuvier Cheiroptera T. Bell, Esq. Cirrhopoda Dr. Coldstream Conchifera M. Deshayes Crustacea Dr. Milne Edwards Echinodermata Dr. Sharpey Edentata T. Bell, Esq. Entozoa Professor Owen Gasteropoda T. R. J Insecta G. Newport, Esq. n ... i. 35 . ... i. 47 i. 90 nt i. 107 >ards i. 164 i. 198 n ... i. 244 . ... i. 265 i. 470 . ... i. 517 i. 562 i. 594 IM ... i. 683 i. 694 wards i. 750 ii. 30 ii. 46 n ... ii. 111 Esq. ii. 377 Esq. ii. 853 Insectivora T. Bell, Esq ii. 994 Mammalia Professor Owen ... iii. 234 Marsupialia Professor Owen ... iii. 257 Mollusca Professor Owen ... iii. 363 Monotremata Professor Owen ... iii. 366 Myriapoda Prof. R. Jones ... iii. 545 Pachydermata Prof. JR. Jones ...iii. 858 Pisces Prof. R. Jones ...iii. 955 Polygastria Prof. R. Jones ... iv. 2 Polypifera Prof. R. Jones ... iv. 18 Porifera Prof. R. Jones ... iv. 64 Pteropoda Prof. R. Jones ... iv. 170 Quadrumana Professor Vrolik iv. 194 Eeptilia Prof . R. Jones ... iv. 264 Rodentia Prof. R. Jones iv. 368 Rotifera Dr. Lankester iv. 396 rDr. T. Spencer -| Ruminantia <^ } *. 506 I Cobbold J Solipeda Prof. R. Jones ... iv. 713 Tunicata Prof. R. Jones iv. 1185 CLASSIFIED CONTENTS. PHYSIOLOGY. Absorption ... Dr Bostock Vol. i Page 20 Dr. Symonds i. 64 Albino ... Dr. Bostock i. 83 Dr. Willis i 118 i. 257 Dr. Allen Thomson i. 638 Contractility Dr. Alison ......... i 716 Dr. Symonds i. 791 Dr. Bostock ii. 6 Elasticity Dr Brenan , ii 55 Electricity, Animal Endosmosis Dr. Coldstream ... Dr. Dutrochet ... ii. ii 81 98 Dr. Allen Thomson ii. 424 Hearing Heat Animal ... Dr. Todd Dr W F Edwards ii. ii 564 648 Dr. Marshall Hall ii. 764 iii. 1 Dr. Marshall Hall iii. 29 Life Dr. Carpenter iii. 141 Luminousness, T Animal J Motion, Animal, - including Loco- i- motion J Dr. Coldstream ... J. Bishop, Esq. ... iii. iii. 197 407 Dr. J. B. derson San- Muscular Motion... W. Bowman, Esq. Nervous System ... Dr. Todd ............ Nutrition ............ Dr. Carpenter ...... Ovum ............... Dr. Allen Thomson Parturition ......... Dr. Rigby ......... Pulse .................. Dr. Guy ............ Reproduction. Ve- ' getable (Vege- I table Ovum) J Respiration ......... Dr. John Eeid ... Secretion ............ Dr. Carpenter ...... Sensation ............ Dr. Todd ............ Sensibility ............ Dr. Todd ............ Sleep .................. Dr. Carpenter ...... Smell ............... Dr. Carpenter ...... Symmetry ..... . ...... S. R. Pittard, Esq. Sympathy ............ Dr. Todd ............ Taste .................. Dr. Carpenter ...... Temperament ...... Dr. Todd ......... Touch ............... Dr. Carpenter ..... Varieties of Man- Vol. Page iii. 519 iii. 720o. iii. 741 s. 1 iii. 904 iv. 181 s. 211 iv. 325 iv. 439 iv. 508 iv. 510 iv. 677 iv. 697 iv. 845 iv. 852 iv. 856 iv. 935 iv. 1163 kind Dr. Carpenter iv. 1294 Vision W.W. Cooper, Esq. iv. 1436 Voice John Bishop, Esq. iv. 1475 ANIMAL CHEMISTRY, PHYSIOLOGY OF THE FLUIDS AND SECRETIONS. Acids, Animal W.T. Brande, Esq. i. W. T. Brande, Esq. i. 47 55 Milk Mucus .. Dr. G. O. Rees ... iii. .. Dr. G. O. Rees ... iii 358 481 Albumen W. T. Brande, Esq. i 88 Organic Analysis. .. Dr. Miller ... iii. 792 Blood 404 Protein . . Prof. J E. Bowman iv 162 Bile W. T. Brande, Esq. i. 374 Saliva .. Dr. Owen Rees .. iv. 415 W.T. Brande, Esq. i. 562 f Drs. Wagner and ~) . Fat W.T. Brande, Esq. ii. 231 1 Leuckhardt J 472 W. T. Brande Esq ii 257 Sweat .. Dr. G. O. Rees ... iv. 841 Gelatin W. T. Brande, Esq. ii 404 Synovia .. Dr. G. O. Rees ... iv. 856 Haematosine Dr. G. O. Rees... ii. 503 Urine .. Dr. G. O. Rees ... iv. 1268 GENERAL SUBJECTS. Medical Statistics .... Dr. Guy iv. 801 | Microscope Dr. Carpenter iii. 331 i Vital Statistics Dr. Guy iv. 1469 CONTENTS OF THE FIRST VOLUME. Abdomen. Dr. Todd Dr. Bostock .... Page 1 20 Bladder, Normal Ana- ) Page Dr. Harrison .... 376 Dr. Coldstream . . 35 Bladder, Abnormal ^ Acids Animal W T.Brande Esq 47 B. Phillips, Esq. . 388 Acrita R Owen ESQ 47 Blood Dr. Milne Edwards 404 B. Phillips, Esq . 49 Blood, Morbid Condi- ) W T Brande Esq 55 Dr. Babington .. 415 Adipose Tissue ...... Dr. Craiffie . 56 Bone NormalAnatomy Dr Benson,.. . .. 430 A-e ., Dr. Siiwonds .... 64 Bone, Pathological ) Dr. Bostock 83 W.H. Porter, Esq. 438 Albumen W. T. Brande Esq 88 Brachial Artery .... Dr. Hart 465 Amphibia T Bell Esq .... 90 Animal Kingdom < . . Dr. Grant 107 Carnivora T. Bell, Esq 470 Animal . Dr. Willis 118 Dr. Hart 482 Ankle Region of the. . 147 Dr. Benson 495 Ankle, Joint of the . . 151 Cavity Dr. Todd 600 Ankle-joint,Abnormal ) Condition of the . . * R. Adams, Esq. . . 154 Cellular Tissue R.D.Grainger,Esq. 509 R. Owen Esq .. 517 Annelida . Dr Milne Edwards 164 W T Brande Eiq 562 R. Harrison Esq 178 Mons. F. Cuvier . . 562 Aorta Dr. Hart Dr. Audoitin. .... Ib7 198 Cheiroptera Chyliferous System . . T. Bell, Esq 594 Dr Grant 600 Arm Dr. Hart 216 A. T. S.Dodd Esq. 602 Arm Muscles of the . Dr Hart.. 219 Cilia Dr. Sharpey .... 606 Artery Dr. Hart 220 Dr. Allen Thomson 638 Artery, Pathological > Dr. Coldstream . . 683 Conditions of . . . . ' Articulate W.n. Porter, Esq. R. Owen, Esq. . . 226 244 Cirronosis Dr. Todd 694 M. Deshayes .... 694 Articulation Dr. Todd 246 Contractility Dr. Alison 716 257 J. Malyn Esq. . . 724 Aves R. Owen, Esq. . . 265 Cranium, Regions and } Dr. Todd 746 Axilla 358 Muscles of the. . . . * Axillary Artery ...... Dr. Hart 363 Dr. Milne Edwards 750 Dr Harrison .... 364 Cvst . . B. Phillips, Esq. . 787 Back 367 Death Dr Symonds .... 791 Bile W.T Brande Esq 374 THE CYCLOPAEDIA ANATOMY AND PHYSIOLOGY a terms synoi ABDOMEN, (in anatomy,) with which the terms venter and alvus are sometimes used synonymously. Gr. ya, upon, over ; yew-rug, the stomach.) The epi- gastrium is bounded superiorly and laterally by the margin of the thorax, and its inferior limit is indicated by the transverse line. The verti- cal lines subdivide it into two lateral regions, each of which is bounded immediately above by the lower margin of the thorax, beneath which these regions extend in a direction up- wards and backwards : they are hence called hypochondria (Wo, under, p^ov^os, cartilage). Between the hypochondria, is the proper epigastric region, which at its superior part and just below the xiphoid cartilage presents the depression already alluded to under the name of scrobiculus cordis (scrobiculus, the diminutive of scrobs, a depression). Immediately below the epigastrium, and separated from it by the superior horizontal line, is the umbilical region, which has its name from the presence of the umbilicus in it. This region is limited above and below by the two horizontal lines, and is subdivided by the intersection of the two vertical lines into three regions : the lateral ones are the lumbar regions, so called from their correspondence with those portions of the posterior abdominal wall which bear the same name ; and the middle one is the proper umbilical region. Between the inferior horizontal line and the margin of the pelvis, is the hypogastrium, (VTTO, beneath, yacrT*!^, the stomach). This region is li- mited below in the centre by the pubis, and on each side it communicates with the upper part of the thigh. It is subdivided into the iliac regions on each side, and the proper hypo- gastric or pubic region in the centre. The two former constitute the upper or abdominal portion of the great region of the groin, which is completed inferiorly by the upper part of the anterior surface of the thigh. These regions afford peculiar interest to the surgical ana- tomist, in consequence of the occurrence in them of k the most common forms of hernia.* (See GROIN, REGION OF THE.) The structures which enter into the com- position of the abdominal parietes, or their elements, (as the term has been lately applied,) are 1. the skin: 2. the subcutaneous tissue or superficial fascia : 3. muscles and their aponeurotic expansions : 4. a particular fibrous expansion, or fascia : 5. a thin and filamea- tous cellular tissue, which separates the fascia just named from the sixth element: 6. the peri- toneum, which, however, is not to be found in the composition of all the walls of the abdomen. * Velpeau applies the term xone to the primary regions included between the horizontal lines. Anat. Chirurg. t. ii. ABDOMEN. *3 In and between these several structures ramify the various arteries, veins, lymphatics, and nerves, which constitute the vascular and ner- vous supply to the abdominal parietes. 1. The skin on the anterior and lateral parts of the abdomen is thin and smooth, and in some parts covered with hairs, as along the middle line, especially below the umbilicus and over the pubic region. Along the median line the cutaneous follicles are largely developed, and during pregnancy an increased secretion of pigmentum is said to take place, producing a brownish colour of the skin in these regions. In women who have borne children, the skin becomes wrinkled to a considerable de- gree, and the epidermis exhibits, as Winslow has remarked, a great number of lozenge- shaped spaces disposed in a reticular manner.* In the epigastric region the skin is much more sensitive during life than in the other parts of the abdomen, and with some persons sympathizes with the stomach in a remarkable degree, so that pressure on it even in the healthy state produces a degree of pain or un- easiness in that organ, or even a tendency to nausea. In the umbilical region we observe a depression, the floor of which is more or less elevated in the centre. This depression is de- nominated the navel or umbilicus, (the dimi- nutive of umbOj a nob or button.) It is produced by the firm adhesion of the skin to the subjacent structures, its true nature being that of a cicatrix, occupying the site of a former perforation through which the umbilical arteries and veins and the urachus passed in maintaining the circulation between the foetus and placenta. In very fat persons, the depth of the depression is often very much increased by reason of the great thickness of the abdomi- nal parietes, and in some instances its form assumes that of a slit, and sometimes, instead of a depression, there is a greater or Jess pro- minence of the integument. In the lumbar region the skin is thicker and firmer than in the others; and we generally find it in a state of congestion after death, in consequence of the position of the body. 2. The subcutaneous cellular tissue on the anterior surface of the abdomen has obtained especial attention from anatomists, particularly that portion of it which is found in the hypo- gastric regions. It is denominated the superficial fascia,^ and is merely an expanse of cellular tissue possessing the same general characters * Winslow's Anatomy, by Douglas, v. ii. p. 160. t The application of the term fascia to the sub- cutaneous cellular investment in various parts of the body has occasioned no small degree of confusion among anatomists. A singular degree of confusion exists in Velpeau's description of this fascia : he observes in one place that the deep layers of the subcutaneous cellular tissue constitute the super- ficial fascia, and in the next page states that " the superficial fascia is nothing else than the cellular tissue condensed, whose laminae strongly applied one against the other, are ultimately reduced to somewhat of the aponeurotic form." I shall adhere to this latter definition, and consider superficial fascia as synonymous with subcutaneous cellular tissue. Velpeau Anat. Chirurg. vol. ii. p. 4 and 5. as that which is found in all other parts of the body ; it is continued upwards over the thorax, laterally into the region of the back, inferiorly along the thighs, and into the scrotum. It varies in thickness according to the quantity of fat which is deposited in its cells ;"* in some in- stances it has been known to possess a thick- ness of three inches. Thin but muscular subjects afford the best examples from which to study the superfical fascia of the abdomen : in such subjects we find it in general of a much denser character than in others, very strong and elastic and easily divisible into laminae, produced, no doubt, by the pressure which it experiences from the weight of the abdominal viscera, and the constant attrition occasioned by the action of the abdominal muscles. In the iliac region, immediately above Poupart's ligament, the density of this fascia is most conspicuous. Here some have regarded it as a nbro-cellular membrane ; but the opaque bands which give it a fibrous appearance are merely the walls of the membranous cells rendered thicker and denser than they are in other parts. I cannot agree with Beclardf that it presents almost all the characters of an aponeurosis, inasmuch as it differs from an aponeurosis in wanting the shining and regular surface, and in possessing a degree of elasticity which never belongs to aponeurotic expansions. The elasticity of the superficial fascia is remarkable, and is by some compared to the elastic expansion over the abdomen of the larger quadrupeds ; J the comparison, however, is inaccurate, inasmuch as they are two distinct tissues, the former being cellular, and the latter the aponeurosis of the oblique muscles, which in some degree parta.kes of the properties of the yellow elastic fibrous tissue (tissu jaune). Inferiorly the superficial fascia moves freely over Poupart's ligament, and is continued over the thigh (see GROIN, REGION OF THE). Along the middle line it is very adherent to the sub- jacent aponeurotic structure (the linea alba) as well as to the skin, a fact which may be remarked of the subcutaneous cellular tissue in other parts of the body, and which was long ago noticed by Bordeu, when he observed that the cellular tissue is constricted (etranglee) in all its median portion, and that its cells (ballons ou pouches) are closed over the axis of the body. When this superficial fascia is dissected off, a very thin layer of cellular membrane, perfectly diaphanous, is found to adhere to the subjacent aponeurotic expansion. This will be found particularly adherent over Poupart's ligament, and is that which is referred to by some ana- tomists (as Manec, Cloquet, &c.,) as a deep process of the superficial fascia which adheres to Poupart's ligament, and so forms a super- ficial septum between the abdomen and thigh. To see this layer the superficial lamina should be raised by commencing the dissection of it * Cloquet says it is, as it were, decomposed by the deposition of fat. Recherches Anat. sur les Hernies de 1'Abdomen, p. 11. t Diet, de Medecine, art. abdomen. j Vid. Blandin, Anat. Topog. B 2 ABDOMEN. below and carrying it upwards ; the expansion will then appear to arise from Poupart's liga- ment, and spread over the subjacent aponeuro- sis. In some subjects it is so thin as to appear to be little more than the proper cellular cover- ing of the muscle and its aponeurosis, but in others it assumes a considerable degree of density. It may be called the deep layer of the superficial fascia; it deserves attention from the fact that the femoral hernia, in its ascent on the abdomen, lies between it and the super- ficial layer. It is to this fascia that Scarpa must allude under the name of " aponeurotic web of the muscle of the fascia lata," and hence some have called it Scarpa's fascia.* The whole of the superficial fascia has been called Camper's fascia, because it was first fully described by that writer.f On the posterior wall of the abdomen, in the lumbar regions, the cellular tissue is more abundant and more lax; here we frequently find it infiltrated with serous fluid, in conse- quence of the usual supine posture of the body after death. It is continuous above with the subcutaneous tissue in the dorsal region, and below with that in the gluUeal regions. It, too, is firmly adherent along the middle line to the lumbar spine anteriorly, and to the skin posteriorly. 3. Muscles and aponeuroses. The abdo- minal parietes owe their thickness chiefly to the muscular lamellae and the aponeurotic ex- pansions, which enter into their composition. In the anterior and lateral walls we find on each side five pairs of muscles, of which four are constantly present. These are, 1, M. obli- quus externus ; 2, obliquus interims ; 3, trans- versalis ; 4, rectus abdominis ; 5, pyramidalis, which last is frequently absent. 1. Obliquus externus. (Obliquus descen- dens ; c&sto-abdominal ; ilio-pubi-costo-abdo- minal.) When the superficial fascia covering the an- terior and lateral surfaces of the abdomen has been dissected away, this muscle is brought into view. It consists of a flat muscular portion, situated superiorly and posteriorly, and of a tendinous or aponeurotic lamella anteriorly and inferiorly, but which is largest and strongest in the latter situation. The muscular portion of the external oblique is attached by separate fasciculi to the external surfaces of the eight inferior ribs, from the fifth to the twelfth inclusive. These fasciculi indigitate at their attachment with similar ones, of the serratus magnus, from the fifth to the ninth inclusive, and of the latissimus dorsi from the tenth to the twelfth. -From these points of attachment, described by most English anatomists as the origin of the muscle, the fibres pass obliquely downwards and forwards, with different degrees of ob- liquity, the middle fibres being the most ob- * Vid. Scarpa on Hernia, by Wishart, p. 22 ; also Todd on Hernia, Dub. Hosp. Reports, vol. i. S246 ; and Flood's plates of Inguinal and Femoral ernia. | Camper, Icones Herniarum, p. 11. lique, the superior taking a direction nearly horizontally inwards, and the posterior ones passing nearly vertically downwards. The an- terior and middle fibres are inserted into the outer convex border of the aponeurotic lamella of the muscle, but the posterior are inserted into the outer lip of the two anterior thirds of the crista of the ilium by short tendinous fibres. The fibres of this muscle vary considerably in length, those which are highest up being the shortest, the middle ones the longest, and next in length the posterior fibres. The aponeurotic lamella of the external oblique muscle is found on the anterior part of the abdomen, both su- periorly and inferiorly. In the former situa- tion the aponeurosis is extremely thin and weak ; it is transparent, so that the upper extremity of the rectus muscle which it covers is visible through it. This, too, is the narrow- est portion of the aponeurosis, which increases in breadth, strength, and thickness as it de- scends. The aponeurosis, like the muscular portion, consists of a series of fibres, for the most part inclined obliquely downwards and inwards, excepting the superior ones, whose direction is horizontal. At several places these fibres are separated from each other so as to allow the subjacent muscle to be seen through the interval. At various parts the tendon is perforated by vascular apertures, which are oc- casionally so enlarged as to admit little peri- toneal prolongations to pass through them. Along the middle line, from the ensiform car- tilage to the symphysis pubis, the aponeurosis forms an interlacement with its fellow of the opposite side, and this interlacement with that of the subjacent aponeuroses constitutes the tendinous line called linea alba, which, as Velpeau observes, may be regarded as the centre in which all the fibrous elements of the abdomen terminate. Just above the symphysis pubis, the decussating fibres are not inter- mixed in the same manner as in other parts of the linea alba : there the bundle of one side crosses anteriorly or posteriorly to that of the other, without any union of fibres, to be in- serted into the pubis of the side opposite to that from which it came. A little above and external to the pubis, a separation of the fibres of the tendon of the obliquus externus takes place, leaving an opening which is denominated the external abdominal ring, through which the rounded bundle composed of the spermatic vessels and duct (the spermatic cord) passes in the male, and the round ligament of the uterus in the female. The aponeurotic fibres which form the immediate boundaries of this opening are termed the pillars of the ring, of which one is superior, internal, and anterior, the other is in- ferior, external, and posterior, and passes behind the cord. External and inferior to this opening, we observe that the aponeurosis of the external oblique muscle is extended from the pubis to the anterior superior spine of the ilium. On the pubic side, the fibres, which are the same that form the inferior pillar of the ring, are in- serted into the spine of the pubis, and being ABDOMEN. reflected backwards, outwards, and a little upwards, they are likewise inserted into the linea ilio-pectinea, which commences at the spine of the pubis. The lower margin of the tendon is thus folded back a little as it arches over the excavation between the pubis and ilium, so as to present towards the abdomen a slight channel-like excavation, which affords origin to the muscular fibres of the internal oblique as well as to those of the transver- salis, whilst it has the appearance of a rounded ligamentous cord towards the thigh. In this manner is formed Poupart's ligament, which, contrary to what its usual name denotes, is not a distinct ligamentous cord, but the in- ferior margin of the external oblique stretched from pubis to ilium, and folded a little upon itself. By its superior margin it is continuous with the fibres of the tendon of the external oblique, which fall obliquely upon it ; by its in- ferior margin it is intimately connected with the fascia lata of the thigh ; externally it is inserted into the anterior superior spine of the ilium ; and by its pubic extremity it has three attachments, 1. to the body of the pubis; 2. to the spine of the same; and 3. to the linea ilio-pectinea, constituting what has been called GimbernaCs ligament, which has a sharp slightly crescentic margin directed backwards and outwards to- wards the femoral vessels.* (See GROIN, REGION OF THE.) The external abdominal ring is a triangular opening, situated obliquely ; the superior angle being directed upwards and outwards, and its base, represented by a line uniting the pubic insertions of the two pillars, resting upon the pubis. The superior angle is formed evidently by the separation of the fibres of the aponeu- rosis, the primitive direction of which is the same as that of a perpendicular from the apex to the base of the triangle, viz. downwards and in- wards, (sacrad and pubad.) This separation, however, is strengthened, and the angle round- ed by some tendinous fibres which inter- sect the oblique ones nearly at a right angle, arising as a cord of variable thickness from Poupart's ligament, and passing upwards and inwards over the apex of the ring, gradually separating into several tendinous fibres. These fibres are sometimes very strong, at other times very feeble and scarcely perceptible ; but it rarely, if ever, happens that they are completely absent ; they have been termed intercolumnal bands. I have seen them so strong that they could be distinctly dissected off the external oblique aponeurosis, like a separate tendinous expansion; but most fre- quently they are so united to the aponeurosis as to render it impossible to remove them without injury to it. These fibres are evi- dently intended, as Scarpa expresses it, " to fix the limits of the inguinal ring, and to oppose the further divergence of the tendi- nous pillars towards the side." They are * The terms crural arch, and ligament of Fallopius, are also used synonymously with Poupart's liga- ment. Velpeau calls it bandelette ilio-pubieune du grand oblique. equally met with, although not nearly so much developed, in women and children as in men ; and Mr. Lawrence asserts that in old herniae they are particularly strong. I cannot confirm this remark from my own observation, as in my dissections of old herniae, I have not found them particularly developed; nor is it con- sistent with the general result of pressure from within on tendinous fibres to believe that such pressure would produce an increase of deve- lopment in them. The size of the external abdominal ring is greatest in the male subject, but here it varies considerably, sometimes closely embracing the cord as it passes through it, and at others appearing much too large for it. In the male the parts which pass through it are the sper- matic cord, enveloped in its proper tunic, and in one of condensed cellular membrane pro- longed from the fascia transversalis, a branch of the genito-crural nerve, the cremaster mus- cle, the cremasteric artery, and the spermaticus superficialis nerve. In the female, we find the round ligament of the uterus, covered and accompanied by similar parts, excepting (he cremaster. From the margin of the external abdominal ring, a cellular expansion or fascia is carried over the cord or round ligament, and has been denominated fascia spermatica. This fascia consequently forms a covering of any hernia that may be protruded through the external ring; and, accordingly, in old herniae we find it greatly thickened. Its formation is simply in accordance with what we find oc- curring in all parts of the body, viz. that when any part passes through an opening in a fibrous membrane, it carries with it a cellular expan- sion from the margin of that opening. This we observe in the passage of the vena cava through the diaphragm, of the urethra through the triangular ligament or deep perineal fascia. This view confirms the opinion of Sir A. Cooper, that this fascia is a production from the margin of the ring itself. The external oblique muscle is covered in all its extent by the superficial fascia ; its costal margin is related to the serratus magnus,and to the latissimus dorsi, with which muscle it is also in close relation by its posterior margin, being sometimes slightly overlapped by the anterior margin of the latissimus, but at others separated from that muscle by a triangular interval through which the fibres of the obliquus inter- nus appear: interiorly the fascia lata of the thigh is related to the margin of the external oblique muscle, both as it covers the glutaei,and as it lies in front of the thigh. Along the middle line the aponeuroses of opposite sides meet at the linea alba, and superiorly the mus- cular fibres are related to and sometimes con- nected by a fleshy slip with those of the pecto- ralis major, and the aponeurosis is continuous with that of the same muscle.* When the ex- * " By its position, the direction of its fibres, and the short distance to which its fleshy portion extends forwards, the external oblique corresponds so much to the external intercostals, that one is led to say that it represents them in the abdomen," Mechel. ABDOMEN. ternal oblique is removed from its osseous at- tachments, and raised inwards, it is found to cover the internal oblique, with part of the ten- don of which it is ultimately united as the two tendons approach the linea alba. 2. Obliquus internus (obliquus ascendens, ilio-abdominal, ilio-lumbo-costi-abdominal) is smaller than the preceding muscle, which it resembles in shape and general characters. The direction of its fibres, however, is opposite, inasmuch as the fibres of the two muscles decussate with each other, thus adding con- siderably to the strength of the abdominal wall, and forming a great protection against visceral protrusions. The external attachments (or, as systematic writers call it, the origin of the mus- cle) is 1. by short fleshy fibres to the tendinous expansion covering the lumbar mass of muscles, called fascia lumborum, which is formed by the posterior lamina of the tendon of the trans- versalis abdominis : 2. to the two anterior thirds of the middle portion of the crista ilii, between the external oblique and the transver- salis as far forwards as the anterior superior spine : 3. to the groove in the upper or abdo- minal surface of Poupart's ligament for about its external third. The superior fibres pass upwards and inwards, and are inserted by fleshy slips into the cartilages of the twelfth, ele- venth, and tenth ribs, in the intervals between which they are either separated from the inter- costal muscles by a fibrous intersection, or con- founded with them, and by a tendinous aponeu- rosis into the cartilages of the ninth, eighth, and seventh ribs as well as into the xiphoid cartilage. Lower down, the fibres which arise from the crista ilii, as well as those from Poupart's liga- ment, pass inwards, the superior obliquely upwards and inwards, the inferior more hori- zontally, and the lowest fibres inclining a little downwards, and are all inserted, like those of the obliquus externus into the outer convex margin of an aponeurotic expansion,, which goes to be inserted along the middle line. This ten- don passes inwards for a short distance, nearly as far as the outer margin of the rectus muscle, as a single lamina. Along this margin, and as low down as the inferior fourth of the rectus muscle, the tendon divides into two laminae, of which the anterior adheres to the posterior surface of the tendon of the external oblique, and the posterior to the subjacent tendon of the transversalis, both laminae going to be inserted into the ensiform cartilage and linea alba, the one in front, the other behind, the rectus muscle. (Seej%. 4, a. ) For a distance, however, corres- ponding to the inferior fourth of the rectus muscle, the tendon of the obliquus internus re- mains undivided, and does not adhere to that of the obliquus externus. It, however, is united, although not inseparably, to the tendon of the transversalis, and both go in front of the rectus to be inserted into the linea alba and pubis : these tendons are here called by some the con- joined tendons. Along the line at which the tendon of the obliquus internus divides into two laminae., the aponeurosis of the obliquus externus and that of the trausversalis adhere to it more closely than they do externally to that line, and thus a thickened portion of the abdominal aponeurosis is formed, taking the course of the outer margin of the rectus muscle : this line is called the Linea semilunaris, and is that in which the operation of paracentesis abdominis used formerly to be practised. The inferior margin of the obliquus internus is deserving of particular attention. The in- ferior fibres attached to the external third of Poupart's ligament in the groove formed in it pass transversely inwards and parallel to the ligament, crossing over the spermatic cord, to be inserted into the pubis. Here the muscle is confounded with the inferior fibres of the sub- jacent one, the transversalis ; so that it is not only difficult to say which muscle passes low- est down, but it is difficult, and often impossible, to separate the two muscles. Hence the lower margins of the fleshy fibres as well as of the apo- neuroses of these two muscles are constantly spoken of conjointly ; however, I have several times succeeded in separating them distinctly, and I am decidedly of opinion that the apo- neurosis of the obliquus internus seldom or never descends so low down as that of the trans- versalis. The lowest of the fibres of the obliquus internus are sometimes observed to separate a little from the others, so as, instead of a directly transverse, to assume a course slightly curved with the concavity upwards and a little outwards, lying in front of the cord ; in some cases fibres of this kind are observed to lie in front of th^ spermatic cord, and to descend much lower down, taking of course a much more curved direction, still attached on the outside to Pou- part's ligament, and on the inside to the pubis, so that a series of curved fibres are thus found to adhere to the anterior surface of the cord and of the tunica vaginalis, exhibiting an equal num- ber of reversed arches. But this disposition is rarely seen in its most highly developed state, excepting where some tumour has been con- nected with the cord or testicle, as hernia, hydrocele, &c. This arched arrangement of muscular fibres in connection with the spermatic cord and tunica vaginalis testis constitutes the Cremas- ter muscle (K^^atu, suspendo,} the great tenuity of which in the natural state of the parts has ren- dered it difficult to determine its precise attach- ments, and consequently has given rise to the great discrepancy which is observable between the descriptions of different writers. When this muscle is examined in a case of old hernia or hydrocele, it is found, as Scarpa originally described it, to consist of two bundles ; the first, external to the cord which arises from Poupart's ligament along with the internal oblique, follows the course of the spermatic cord, which it ac- companies through the external abdominal ring, sending at intervals fibres arching in front of the cord to join a similar bundle on the inner side, as may be seen in the accompanying en- graving from a plate in Sir A. Cooper's work on the testis (fig. 3 ). Inferiorly, this bundle, a ABDOMEN. Fig. 3. c, the internal oblique ; e, the descending fibres ; /, point, of insertion into the pubis ; h, one of the re- versed arches ; d, conjoined tendons ; a, rectus muscle. good deal diminished in size, crosses over the inferior and anterior portion of the tunica vagi- nalis testis, and begins to ascend along the inner side of the testicle and cord, keeping more pos- teriorly : this constitutes the second bundle ; it gradually increases in size as it ascends by re- ceiving the transverse fibres from the bundle of the opposite side, and it is inserted, sometimes by a distinct tendon, into the pubis near its spine. In some cases I have totally failed, even after the most careful dissection, in detecting a conti- nuity by muscular fibre between these two bun- dles, insomuch as to lead me to imagine that they may be connected by a very condensed cel- lular tissue or thin aponeuro^c lamella after the manner of the digastric musaj^s. . In general the external bundle is largej^han the internal, but Cloquethas seen the re^K three times ; and on referring to my notes, I mjd I have seen two instances in which the internal bundle exceeded the external in size. V Many anatomists have notic^ed only the ex- ternal bundle of the cremaster? and altogether overlooked its reversed arches, which is not to be wondered at when we remember that even where the lateral bundles are strong and well developed, the arched fibres are sometimes pale and thin. However, the description now given is pretty generally admitted as the true one, and is sanctioned by such observers as Scarpa, Cloquet, Cooper, Velpeau, and I may add that I have seen this arrangement in cases where both testicle and cord were healthy. It would appear that its formation is effected by the testicle in its descent, for before that takes place the muscle does not exist ; at least such is the result of Cloquet's observations on a con- siderable number of foetuses before, during, and after the descent of this organ. Before the de- scent the gubernaculum testis occupies the inguinal canal, and is covered by the fibres of the internal oblique, which adhere to it : when the gubernaculum is drawn down, these fibres descend with it, forming a series of reversed arches. In some female subjects we see an arrange- ment of the inferior fibres of the internal oblique as they cross over the round ligament, which resemble a rudimentary state of the cremaster muscle. A thin layer of cellular tissue, sometimes containing a small quantity of fat, is interposed between the anterior surface of the obliquus internus and the obliquus externus. At the infe- rior edge of the obliquus internus the spermatic cord is seen emerging from the abdomen and passing obliquely inwards and a little down- wards to the external abdominal ring. Here it lies in a groove or channel, called the inguinal canal, which extends from the point at which the spermatic cord emerges from the abdomen, (the opening in the fascia transversalis called in- ternal abdominal ring) to the external abdo- minal ring. This canal is bounded or covered anteriorly by the tendon of the obliquus externus; posteriorly by the fascia trans- versalis and some fibres of the tendon of the transversalis muscle towards the inner side ; superiorly by the margin of the obliquus in- ternus and transversalis muscles ; and inferiorly by the groove of Poupart's ligament.* (A full description of this canal will be found in the article GROIN, REGION OF THE.) 3. Transversalis ( lumbo-abdominal, lumbo- ili-abdominal). This muscle is immediately under cover of the obliquus internus ; its name is derived from the transverse direction of its fibres. In its general character it resembles the obliqui, being like them a muscular lamella, inserted into a tendinous expansion, which again is inserted into the linea alba. Supe- riorly the fleshy fibres of this muscle are attach- ed by distinct bundles to the internal surface of the cartilages of the ribs forming the lower margin of the thorax, where these bundles in- digitate with those of the diaphragm : 2dly, in the interval between the last rib and the crista Fig. 4. * " The obliquus internus corresponds to the in- ternal intercostals by the direction of its fibres, by its being situated under cover of the obliquus externus, and because its fleshy fibres extend much further forwards than those of the last-named mus- cle. " ABDOMEN. ilii, the fibres arise from a tendinous lamella, which itself is trifoliate in its origin. This ten- don is found as an undivided lamella between the outer margin of the quadratus lamborum and the commencement of the fleshy fibres of the muscle, extending vertically from the last rib to the crista ilii. ( Fig. 4, 1.) The three laminae of which this tendon is composed arise from different portions of the vertebrae in the lumbar region of the spine; the posterior, which is thick and strong, and is commonly called fascia lumborum, arises from the extremities of the spinous processes, and covers the lum- bar mass of muscles. (Fig. 4, g.) The mid- dle, which is weak, is attached to the apices of the transverse processes ; it lies in front of the lumbar mass and behind the quadratus lumbo- rum (Jig. 4, h); and the anterior arises from the pedicles which connect the transverse processes to the bodies of the vertebrae, and covers the quadratus lumborum muscle in front (Jig. 4, f). Inferiorly, the transversalis muscle at- taches itself to the inner lip of the crista ilii for its three anterior fourths, and to the ex- ternal third or half of Poupart's ligament, cor- responding to the attachments of the obliquus internus. The fleshy fibres of the muscle pass from these several points of attachment trans- versely inwards, the middle being the longest, and the superior the shortest, and are in- serted into the outer convex margin* of a tendinous aponeurosis, which extends to the linea alba. This aponeurosis is intimately connected with the posterior division of that of the obliquus internus for an extent corre- sponding to the three superior fourths of the rectus muscle, behind which both pass to be inserted into the ensiform cartilage and linea alba, (Jig. 4, a,) forming the posterior wall of the sheath of the rectus. Inferiorly, as we have already remarked, these conjoined tendons go together in front of the rectus, and are inserted into the inferior fourth of the linea alba and into the pubis. At the inner extre- mity of the inguinal canal, it will be seen by carefully raising up the spermatic cord, that this union of the tendons of these two muscles ceases, and we can trace the fibres of the trans- versalis tendon passing down in a curved direc- tion, more curved as they are more external, and insinuating themselves behind the cord to be inserted into Gimbernat's and Poupart's ligament for about its ^xternal third or fourth. This mode of insertion of the transversalis ten- don was first described by Sir Astley Cooper, f and these fibres were by him called thejblded fibres of the transversalis. They adhere to the subjacent fascia, (fascia transversalis,) and add to the strength of the inner portion of the pos- terior wall of the inguinal canal. They cor- respond, in a great measure, to the external abdominal ring, and may be counted as one of the obstacles provided against the direct descent of a hernia. Such is unquestionably the usual mode of * This margin forms the linea semilunaris of Spigelius. t Cooper on the Testicle, p. 35. insertion of the tendon of the transversalis muscle ; but Mr. Guthrie has lately called the attention of anatomists to a variety which it is important to know, although it cannot be of frequent occurrence. In this variety the spermatic cord appears to pass through a slit in the inferior margin of the transversalis muscle, so that a bundle of muscle passes behind as well as before the cord ; the posterior one end- ing in tendinous fibres, which, like the folded fibres above described, are inserted into Pou- part's ligament.* It is very generally believed that the inferior fibres of this muscle contribute, as well as those of the obliquus internus, to form the cremaster. The two muscles are so closely connected externally by their inferior margins, that it is natural to suppose that both do send fibres to the cremaster. Sir Astley Cooper expresses the relation of the cremaster to these two muscles in the clearest way, when he says that it arises from Poupart's ligament within the inguinal canal, and there blends with some of the fibres of both these muscles.f A thin layer of cellular tissue covers the transversalis muscle, and separates it from the obliquus internus. At its superior margin it is intimately related to the diaphragm, and some of its fibres seem to be continuous with it : posteriorly, by the triple partition of its tendon, it ensheaths the lumbar muscles, and it lies upon the fascia transversalis, which, with a layer of cellular tissue, separates it from the peritoneum. | 4. Rectus abdominis (ster no-pub ien). After the superficial fascia has been removed so as to expose the aponeurosis of the external ob- lique, the recti muscles are seen on either side of the middle line covered by this aponeurosis, which it is necessary to slit up in order to ex- pose the muscles. The rectus owes its name to the perpendicular course of its fibres, which pass from the pubis to the thorax, nearly parallel to the middle line. It is long and narrow ; however, its breadth increases as it advances upwards, and as it increases in breadth it diminishes in thickness. At the pubis the muscle has its most fixed point of attachment, whence it is generally said to have its origin there: it arises by a short tendon from the symphysis of the pubis; this tendon is very narrow at its origin, but soon expands, and unites with the muscular fibres, which pass vertically upwards to the lower margin of the thorax, where the muscle is considerably increased in breadth, and divides into three portions; the first or internal one is inserted into the costoxiphoid ligament and cartilage of the seventh rib ; the middle, larger than the preceding, into the cartilage of the sixth rib at its inferior edge and anterior surface; * Guthrie on Inguinal and Femoral Hernia, pp. 11, 12, 13, 4to. Lond. 1833. t Op. cit. p. 38. t " The transversalis corresponds, by the direction of its fibres, to the ' triangularis sterni ;' also, by its situation, by the attachment of its external edge to the internal surface of the ribs, and by that of its internal edge to the sternum and linea alba." Mechel. ABDOMEN. and the external, the largest of the three, into the inferior edge of the cartilage of the fifth rib. This muscle is remarkable for its tendinous intersections, which cut the fibres at right angles, and are called linear transverse. ;* they vary in number from three to five, and are always more numerous above than below the umbilicus. In general there is one on a level with the umbilicus; the superior one being about an inch below the superior attachment of the muscle, and a third midway between these two : when a fourth and a fifth exist, they are below the umbilicus. They adhere to the an- terior wall of the sheath closely, and but very slightly or not at all to the posterior. Some- times the intersection does not go completely through the thickness of the muscle so as to appear on its posterior surface, and thus the posterior fibres are longer than the anterior; but as Bichat remarks, it never happens that any of the muscular fibres pass from one extre- mity of the muscle to the other without uniting at least one of these intersections. Sometimes, too, the intersection does not go through the breadth of the muscle, and this is generally the case with that below the umbili- cus. The effect of these intersections is to convert the muscle into so many distinct bellies, each of which has its proper action, and is, as Beclard asserts, provided with a separate nerve.f The rectus muscle is enveloped in a fibrous sheath, the mode of formation of which the reader must have collected from the description of the oblique muscles. The anterior wall of this sheath is formed by the aponeurosis of the external oblique alone over the chest, and by the same aponeurosis and the anterior layer of that of the internal oblique, from the xiphoid cartilage to the inferior fourth of the muscle ; (both which aponeuroses over the internal half of the muscle are so adherent to each other as to form but one lamina;) and in its inferior fourth by the conjoined aponeuroses of the two obliqui and transversalis. The posterior wall of the sheath is deficient superiorly where the muscle covers the carti- lages of the ribs with which it is' in contact, and inferiorly for a space corresponding to the inferior fourth of the muscle. So much of it as exists is formed by the tendon of the transver- salis and the posterior lamina of that of the internal oblique, so that the rectus appears to have passed at its inferior extremity through a transverse slit in these conjoined tendons, so as to get between them and the peritoneum. The rectus muscle covers, at its superior ex- tremity, the cartilages of the two last true ribs and a part of those of the two first false, and also the xiphoid appendix. The internal mam- mary and epigastric arteries are found behind it in the sheath. Between the recti muscles is the fibrous cord called linea alba, produced by the interlace- * Also called enervations. Window. They are, says Meckel, incontestahly incomplete repetitions of the ribs in the walls of the abdomen. t Hence Meckel classes it among the polygastric muscles. ment of the aponeuroses of the opposite sides, noted in surgery as being in its inferior half the seat of the operations of paracentesis abdominis, paracentesis vesicse supra pubem, the supra- pubic lithotomy, and the Caesarean operation. This cord extends from the xiphoid cartilage to the symphysis pubis, with the anterior liga- ment of which articulation it is identified. It does not present the same breadth in its whole course, being broader in the umbilical region than elsewhere. In this region we find in the linea alba the perforation which gave passage to the umbilical vessels in the foetus and the urachus, and through which the fibrous remains of those vessels pass to be inserted into the skin, whereby is formed the cutaneous depres- sion which marks the situation of this opening. In the adult the umbilicus may be considered as a point of considerable strength ; in the esti- mation of some it is the strongest point in the abdominal parietes : in dissecting away the skin at this point, we find subjacent to it a very con- densed cellular tissue, to which and to the skin the fibrous cords into which the umbilical vessels have degenerated adhere closely ; these cords, too, adhere not only to the skin, but likewise to the margin of the. fibrous ring through which they pass. " The umbilical opening, therefore," says Scarpa, " in the infant two months after birth, and still more in the adult, is not only like the other natural openings of the abdomen, strength- ened internally by the application of the peri- toneum and of the cellular substance, and on the outside by the common integuments, but it is likewise plugged up in the centre by the three umbilical ligaments and by the urachus; these ligaments form a triangle, the apex of which is fixed in the cicatrix of the in teguments of the umbilicus, the base in the liver, in the two ilio-lumbar regions, and in the fundus of the urinary bladder ; by this triangle is formed a strong and elastic bridle, capable of itself alone of opposing a powerful resistance to the viscera attempting to open a passage through the aponeurotic ring of the umbilicus, which apparatus does not exist at the inguinal ring or femoral arch."* In the foetus the ring of the umbilicus is proportionally larger than at any period after birth when the cicatrix is fully formed : it is, however, at the full term, or even at the seventh or eighth month, and in the healthy state of the parts, equally filled up by the umbilical vessels and urachus, and we would say is equally capable of resisting intestinal protusion as at any subsequent period. Hence it may be in- ferred that congenital umbilical ruptures are always of very early date, being attributable to the persistence of the opening at the umbilicus, and the continuance in it of the intestinal pro- longation which exists there naturally at a very early period. It may likewise be inferred that the rupture in the adult can much more easily occur in the vicinity of, than through the umbi- lical ring; and experience confirms this deduc- tion from the anatomy of the parts. * Scarpa on Hernia, p. 373. 10 ABDOMEN. Above the umbilicus the linea alba is from two to four lines broad in the greater part of its extent; and below the umbilicus it gradually tapers down to the pubis, at the same time in- creasing in thickness.* 5. Pyramidalis ( pubio-sub-umbilical ) . At the inferior extremity of the recti, and separa- ting their origin, are two small muscles of a pyramidal form; their bases are inferior, and attached to the symphysis and body of the pubis, and uniting ligaments, and their apices superior and inserted into the linea alba by small tendons, from two to three inches above the symphysis pubis. Each muscle is enve- loped in a distinct sheath, and lies a little more prominently than the origin of the rectus of the same side. These muscles are not unfrequently absent. Sometimes, on the contrary, there have been two on one side and one on the other, or even two on each side.f The muscles which enter into the composi- tion of the posterior wall of the abdomen are chiefly those which occupy the lumbar region of the back, filling up that empty space which in the skeleton is observed on each side of the spinal column between the crista ilii and the last rib. In dissecting from behind forwards in this region, having removed the skin and lax cellular tissue already described, we come upon the strong fibrous expansion, the fascia lumbo- rum. This has extensive osseous attachments, and thus firmly binds down the subjacent mus- cles. When it is removed, the lumbar portions of the sacrolumbalis and longissimus dorsi, and a little of the spinalis dorsi, are brought into view, the two former of which are described by some as a single muscle the sacrospinalis. The external of these muscles is the sacrolum- balis, and its outer margin may be said to con- stitute the limit of the posterior wall of the abdomen in that direction. In this situation the posterior and middle layers of the tendon of the transversal is separate from each other to ensheath these muscles, the posterior layer forming the fascia lumborum. We must refer to the article BACK for a particular description of these muscles. When the lumbar mass of muscles (as the three preceding have been called) has been re- moved, the next part brought into view is the anterior layer of their fibrous sheath formed by the middle lamina of the transversalis tendon, which is inserted into the apices of the trans- verse processes. This lamina is thin and semi- transparent, so that the fibres of the muscle * " The linea alba performs the same office in the abdomen as the sternum does in the thorax, with this only difference, that it is not formed of bone. The anterior tendons of the broad muscles are at- tached to it, in the same way that the cartilages of the ribs are articulated with the sternum, and the difference of tissue which exists between it and the sternum is attributable to the general difference of structure between the abdominal and pectoral cavi- ties, the latter being formed almost entirely of osseous parts, whilst the walls of the former are fleshy and tendinous/' Meckel. t Meckel says that this muscle rarely presents anomalies ; in this he must be mistaken, as its ab- sence is ceitainly not a rare occurrence. which lies immediately before it, are seen through it. This muscle is the Quadratus lumborum (ilio-costal, ilio-lumbi- costal). The term quadratus is applied to this muscle, more from its quadrilateral form than from any nearer resemblance to a square, in- asmuch as all its sides are unequal. The most fixed attachment of this muscle is its inferior, where it is inserted by tendinous fibres into the iliolumbar ligament and into the inner lip of the crista ilii for about an inch to the outer side of the insertion of that ligament. From these points the fibres proceed vertically upwards, the ex- ternal ones going to be inserted into the inferior margin of the last rib for nearly its entire length, and the internal fibres, those in parti- cular which are attached to the ligament, ter- minating by four aponeurotic tongue-like bun- dles, which are inserted into the anterior surface of the transverse processes of the four superior lumbar vertebrae near their bases. The several bundles which end in these tongue-like pro- cesses vary in length ; those which are external being the longest, as going to higher vertebrae. This muscle is covered on its anterior or abdo- minal surface by the anterior lamina of the tendon of the transversalis muscle, by which it is separated from the diaphragm as well as from the psoas magnus.* The last dorsal nerve and the first two branches of the lumbar plexus, pass between the quadratus and the aponeurotic lamina which covers it. Psoas magnus, (-]/oa, lumbus) (prelombo, trochanterien, lumbaris.) The greatest por- tion of this muscle belongs to the abdominal region ; it lies along the side of, not only the lumbar but also of a small portion of the dorsal region of the spine, lodged in the angle between the transverse processes and bodies. It passes as high up as the twelfth dorsal vertebra, to the body of which as well as to those of the four suc- ceeding lumbar vertebrae, and to their interven- ing fibro-cartilages, the muscle is attached : it likewise is attached to the bases of the corres- ponding transverse processes, so that the inter- vals between the portions that are attached to the bodies, and those to the transverse processes, correspond to the intervertebral foramina or points of exit of the lumbar nerves, the an- terior branches of which plunge at once into the substance of the psoas muscle to form the lumbar plexus. The several bundles which thus take their origin from the vertebrae form a thick rounded muscle, which passes nearly vertically downwards, inclining a little out- wards, over the brim of the true pelvis, so as often to appear to encroach upon the circum- ference of the upper outlet of that cavity. A little way above Poupart's ligament the mus- cular fibres are inserted around a strong thick tendon. This tendon, which had commenced high up by distinct portions in the interior of the muscle, passes under Poupart's ligament over the horizontal ram us of the pubis. It descends over the capsular ligament of the hip- * See Jig. 4,y; see also fig. 5, where on one side the muscle has been removed from between the laminae of the transversalis tendon. ABDOMEN. 11 joint (from which as well as from the ramus of the pubis it is separated by a bursa) over the head and along the inner side of the neck of the femur, and is inserted into the posterior part of the trochanter minor at its base, being separated by a small bursa from the surface of that process. As the tendon is passing over the ramus of the pubis, it receives by its outer margin a series of fibres from the iliacus in- ternus muscle. At its superior portion the psoas muscle is covered by a thin fibrous ex- pansion, which is attached on the one hand to the apices of the transverse processes, and on the other to the bodies of the upper lumbar vertebrae ; this expansion, the arcus interior of Senac and Haller,* also called ligamentum arcitatum, separates the psoas from the dia- phragm. Below this the psoas muscle is covered with a lax, and in some degree fatty cellular tissue, which separates the muscle from the kidney externally, and from the peritoneum and ureter within, excepting where the psoas parvus covers it, and on the right side where the vena cava lies upon it. Along its internal margin are the lumbar portion of the sympathetic, the crura of the diaphragm, more especially on the left side, and on this side too the aorta ap- proaches a little its internal margin. The common and external iliac arteries and veins lie along the internal margin of the pelvic portion of the muscle, which is covered by the fascia iliaca. The several branches of the lumbar plexus issue from this muscle at its external margin, and the genito-crural nerve descends in front of it inferiorly. We refer to the article on the muscles of the thigh for a further account of this muscle, its relations in the upper part of the thigh, and its actions. Psoas parvus, (prelombo-pubien). This muscle is similar to the psoas magnus in course and position. It is very much elongated, its fleshy portion being small and tapering. Su- periorly it is attached to the body of the first lumbar vertebra, and to the intervertebral sub- stance between it and the last dorsal, and sometimes to the body of the last dorsal ver- tebra. The fleshy belly soon ends in a flattened tendon, which descends obliquely downwards and outwards over the anterior surface of the psoas magnus, and at its inferior extremity ex- pands considerably, and is inserted along the linea ilio-pectinea near the junction of the ilium and pubis. An expansion from the margins of this tendon becomes united on the outside to the fascia iliaca, and on the inside to the internal portion of the same fascia which covers the great psoas, and passes beneath the iliac vessels to become united at the brim of the pelvis to the pelvic fascia. We must not omit to state that the crura of the diaphragm, as they descend over the bodies of the lumbar vertebrae, (see DIAPHRAGM,) may be regarded as entering into the formation of the posterior wall of the abdomen. The inferior wall of the abdomen is not devoid of muscle, although those muscles can exercise very little, if * Vid. Haller Icon. Scpti Transversi. Op. Minora, torn. 1. any influence upon the contents of the cavity. The iliac fossa affords a large surface for the attachment of one of the principal muscles connecting the thigh with the trunk. This muscle is named Iliacus internus, (iliaco-trochanterien.) This muscle fills up the iliac fossa, to the whole of whose concavity as well as to its margin, and the two anterior spinous processes of the ilium and the interval between them, its fibres are attached. From these several points of origin the fibres converge to form a thick and broad belly, which passes over the upper part of the acetabulum and horizontal ramus of the pubis, filling up the external portion of the upace between that bone and Poupart's ligament ; and it is inserted, as we have already observed, into the outer margin of the tendon of the psoas magnus, which is for thgt reason gene- rally described as the common tendon of the psoas and iliacus. The anterior surface of this muscle is traversed by two of the external branches of the lumbar plexus (inguino-cuta- neous), and the anterior crural nerve passes between its internal margin and the psoas magnus. The superior wall of the abdomen is entirely formed by the muscular vault of the diaphragm, which by its contraction and relaxation exer- cises a considerable influence on the abdominal contents, and causes very obvious changes in the form of the cavity. The concavity of this vault is towards the abdomen, and is greater on the right side than on the left, in consequence, as it is said, of the presence of the liver on that side. It is through the several openings in this wall that a communication is established be- tween the thorax and abdomen. The largest of these openings are, that on the right side, which is completely tendinous, for the passage of the vena cava; the opening for the reso- phagus; and that for the aorta; in addition to these there is a small one behind the centre of the xiphoid appendix formed by a divarication of the anterior fibres of the dia- phragm, through which the cellular tissue of the anterior mediastinum communicates with the abdominal subserous tissue. There are, moreover, openings for the transmission of the splanchnic nerves, and the continued trunks of the sympathetics, as well as of branches of the phrenic arteries and nerves, and the abdominal branches of the internal mammary. The par- ticular description of this muscle will be given under the article DIAPHRAGM. 4. The next element which enters into the formation of the abdominal parietes is a fibro- cellular expansion, which, varying in density in different situations, lines the whole internal surface of the muscular walls. It is strongest and exhibits most of the real fibrous character in the iliac region on the anterior wall, and over the iliac fossa in the inferior. In the former situation it has received the name of fascia transversalis, which was applied to it by ' Sir A. Cooper in consequence of its close con- nexion with the transversalis muscle : in the latter, it is called the fascia iliaca, from its connexion with the iliac fossa and muscle. 12 ABDOMEN. The fascia transversalis is best seen by re- moving the muscles which lie anterior to it : it is then distinctly observed to extend from the outer margin of the rectus muscle internally over the posterior surface of the anterior wall of the abdomen, and gradually to assume the character of a thin but condensed cellular la- mella over the abdominal surface of the lateral wall : it may, however, be traced internally as far as the linea alba behind the rectus muscle, but here it is extremely thin, and has totally lost the fibrous character. Inferiorly this fascia adheres to Gimbernat's ligament and to the reflected margin of Poupart's, from which it is said, by some French anatomists, to originate. Along the line of Poupart's ligament and ex- ternal to it along the crista ilii, this fascia is united with the fascia iliaca, the union be- ing indicated by a white opaque line formed by a thickening of the membrane, taking the course of Poupart's ligament and the crista ilii, except where it is interrupted for the passage of vessels or other parts. Superiorly, the fascia transversalis also degenerates into a cellular lamella, which passes on the transversalis muscle to the diaphragm. It is for a short distance above Poupart's ligament that this fascia demands most attention ; here it forms the posterior wall of the inguinal canal, and at a point a little external and superior to the middle of Poupart's ligament it presents an opening or separation of its fibres, through which the sper- matic vessels and vas deferens united by lax cellular tissue pass into the inguinal canal, carrying around them a funnel-shaped mem- brane which seems to be a prolongation from or continuation of the margins of this opening, but which is in texture merely a condensed cel- lular layer. This prolonged membrane is the first covering which the spermatic cord receives upon its formation, which takes place as its several constituent parts meet at the opening or slit in the fascia transversalis ; it immediately invests the cellular tissue connecting these parts, which is the tunica vaginalis of the cord ; as it proceeds, the cremaster muscle adheres to it from the external oblique and transversalis muscles, and this again receives at its exit through the external abdominal ring another cellular expansion, to which we have already alluded. The opening or slit in the fascia transversalis which we have just described is denominated by anatomists the internal abdominal ring, although, if we speak with reference to the mid- dle line, it is external to the opening in the tendon of the obliquus externus, which is called the external ring. It would certainly be more consistent with the ordinary use of these ad- jectives in anatomy to reverse their application, or if the term anterior were applied to the ex- ternal ring, and posterior to the internal, every purpose would be answered. The direction of the internal abdominal ring is vertical and inclined very slightly outwards. When the fibrous character of the fascia trans- versalis is obvious, we can generally observe two very distinct portions of it, one on each side of the ring. The fibres of the external portion pass upwards and inwards ; those of the internal portion, which are generally stronger and more developed than in the external, pass upwards and outwards so as to decussate with the external fibres at the upper extremity of the ring. The outer margin of this internal portion often presents towards the ring a lunated ap- pearance, over which the vas deferens turns at a sharp angle ; it can be best seen by examining the parts from behind after the peritoneum has been removed.* The fascia transversalis is continued upwards along the posterior and lateral surface of the abdominal muscles and over the diaphragm under the form of a fine lamina of very condensed cellular membrane, which adheres pretty closely to the muscles, but especially to the diaphragm, where it seems to be incorporated with the proper cel- lular covering of that muscle. We refer to the article GROIN, REGION OF THE, for further particulars respecting the fascia transversalis. In the iliac fossa we find a very distinct fibrous expansion covering the whole abdo- minal surface of the iliacus internus muscle. This is tine fascia iliaca. It is seen by raising the peritoneum and the subperitoneal cellular tissue from the fossa. Inferiorly this fascia is connected with the fascia transversalis along the line of Poupart's ligament, except where that connexion is interrupted by the passage of the vessels under the ligament. That space comprises the interval between the inner margin of the tendon of the Psoas and Gimbernat's ligament; and here the fascia lies close to the horizontal ramus of the pubis, and passes be- hind the vessels into the upper part of the thigh, where it adheres to the linea ilio-pectinea, and seems to become continuous with the fascia lata. Externally the fascia iliaca is con- tinuous with the fascia transversalis along the crista ilii, where an opaque line indicates the union, and just internal to which it splits to ensheath the circumflexa ilii artery. On the inner side of the iliac fossa this fascia unites with the pelvic fascia along the brim of the pelvis, this union being likewise indicated by an opaque line similar to that already noticed along the crista ilii. To arrive at this point the fascia, in proceeding from without inwards, passes over the iliacus internus, then over the psoas magnus and parvus, upon which it is thinner than elsewhere ; it then passes behind the iliac artery and vein, and arrives at the pelvic margin. Posteriorly this fascia is con- tinuous with a thin and less fibrous expansion which covers the psoas and quadratus lumborum muscles, adheres to the ligamentum arcuaturn, and is identified superiorly with the cellular expansion on the diaphragm, and externally with the fascia transversalis. It has already been stated that the iliac fascia passes behind the iliac vessels. These vessels have also anterior to them a fibrous or cellulo- fibrous expansion, which is connected on the inner and outer side to the fascia iliaca. Some * This lunated margin is very well delineated by Cloquet in the third figure of the first plate annexed to his work on Hernia, now translated by Mr. A.M. M'YVhinuic. ABDOMEN. 13 consider this as merely a portion of the subperi- toneal cellular tissue, but I cannot help regard- ing it as a process from the iliac fascia itself to envelope the vessels just as that fascia envelopes the circumflexa ilii artery between two lamina at its outer margin. I have never seen an in- stance in which this sheath was not perfectly dis- tinct, in some cases it is of considerable strength, but in the majority weak and transparent. It was this slveath which impeded Mr. Abernethy in one of his earliest operations for applying a ligature to the external iliac artery.* The connexion which the iliac fascia has with the fascia transversalis at the crural arch, and the relation both bear to the iliac vessels at their exit to become femoral, suggested to Mr. Colles a comparison which is constantly referred to by anatomists. " It may be said to resem- ble," he says, " a funnel, the wide part or mouth of which occupies the hollow of the ilium and lower part of the abdominal muscles, and the narrow part or pipe of which passes downwards on the thigh. The mouth of this funnel may be supposed to rise as high as the upper edge of the iliac muscle, and to be turned toward the cavity of the abdomen : the pipe joins the wide part where the external iliac vessels are passing under Poupart's ligament, and it is continued down on the thigh, so low as to reach the insertion of the saphena into the femoral vein."f From the preceding sections it appears that a fibro-cellular expansion lines the whole in- ternal surface of the abdominal parietes. It is so likewise with the pelvis, and also with the thorax. The cavity of the cranium, too, is lined with a fibrous membrane,, although of a different nature, and doubtless performing a dif- ferent office. 5. Between the internal fibrous expan- sion of the abdomen and the peritoneum is a cellular tissue, which presents different cha- racters in each region ; it is the subperitoneal cellular tissue. Along the anterior wall it is thin and fine, except inferiorly opposite the in- ternal abdominal ring, where it becomes more abundant, as well as in the hypogastric region, immediately above the pubis. In the iliac fossa and lumbar region it is lax and abundant, especially in the latter, where there is also a considerable quantity of fat surrounding the kidney. In the iliac fossa this cellular tissue is stretched across the crural ring, and forms what Cloquet describes under the name of septum crurale. On the superior wall it is ex- tremely fine, and in very small quantity. Im- mediately behind the sternum, and in the mid- dle line, this cellular tissue communicates with that of the mediastinum through a separation of the anterior fibres of the diaphragm. This subserous cellular tissue forms the pri- mary covering of all herniae, which push a peritoneal sac before them, and as being the fascia constituting the nearest investment of the sac, it is generally called the fascia propria. * Abernethy's Surgical Works, vol. i. p. 225. t Colics' Surgical Anatomy, pp. 68, 69. Opposite the crural canal this cellular tissue is often so abundant, as, when condensed by the pressure of the hernial tumour, to form an ex- pansion over the sac of considerable thickness. Sometimes it contains fat, and not unfrequently we find a large lymphatic ganglion in it, filling up the crural ring. 6. Peritoneum. A considerable part of the abdominal surface of the walls of the abdomen is lined by a very fine transparent serous mem- brane the peritoneum, which is likewise con- nected, to a greater or less extent, with every viscus within the cavity. In consequence of this double connexion, it happens that in various situations the peritoneum is reflected from the wall of the abdomen upon an adjacent viscus, and thus are produced various folds of this mem- brane, which demand the attention of the ana- tomist. These folds are rendered distinct when such a section of the anterior abdominal wall is made as without dividing them to allow of it being held apart from the viscera. I shall enumerate these folds in describing the relation of the peritoneum to the several walls. The anterior wall of the abdomen is entirely lined by peritoneum, and has in connexion with it four folds, all of which, as it were, radiate from the umbilicus. In the adult these folds are reflected round four ligamentous cords (three of which are the remains of bloodvessels in the foetus), which meet at the umbilicus and diverge, one upwards, backwards, and to the right side (the obliterated umbilical vein), two downwards and outwards towards Pou- part's ligament on each side, so as to pass behind the inguinal canal, nearly midway between the two rings (the obliterated um- bilical arteries), and the fourth nearly ver- tically downwards along the middle line to be inserted into the apex of the bladder (the ura- chus). The four folds are similar in direction to that of the fibrous cords contained within them : the fold which passes upwards towards the liver is falciform, the concavity being di- rected downwards and backwards. From its connexion with the convex surface of the liver it is also called the falciform ligament of the liver, and the fibrous cord contained in its in- ferior margin, the ligamentum teres. The in- ferior and external folds pass each from the umbilicus, downwards and outwards to the iliac fossa, to a point a little on the inner side of the internal abdominal ring, where it dis- appears, being continued externally over the iliac fossa, and internally behind the rectus muscle. This fold, when stretched towards the umbilicus, evidently forms the partition between two pouches, the external and in- ternal inguinal pouches, which correspond re- spectively to the internal and external abdo- minal rings, and indicate the situations at which make their escape those two forms of inguinal hernia, which, from their connexion with these pouches, are called by Hesselbach external and internal inguinal hernias ; the for- mer being that by oblique descent, the latter that by direct descent. The fourth or vertical fold indicates the 14 ABDOMEN. reflection of the peritoneum from the anterior abdominal wall upon the superior fundus and posterior surface of the bladder : when that viscus is empty and contracted, this fold dis- appears totally ; it is more apparent when the bladder is partially filled, and is still more distinct in the foetus in consequence of the greater size of the urachus at that period. Just above the pubis the peritoneum is con- nected to the abdominal wall by a very lax cellular tissue; and accordingly when the blad- der is much distended, the peritoneum is pushed upwards, and stripped off the abdo- minal wall to an extent proportioned to the degree of distension of the bladder, so that its anterior surface is then in immediate contact with the abdominal wall, and may be opened with impunity so far as the peritoneum is con- cerned. The lateral walls of the abdomen are like- wise completely lined by peritoneum, which extends backwards as far as the junction of these walls with the posterior, where it is re- flected from them so as to involve the ascending colon on the right side and the descending on the left, and here it forms on each side the folds respectively termed right and left meso- colon. From the right lateral wall the peri- toneum is continued upwards upon the dia- phragm, and contributes to form the right lateral ligament of the liver ; on the left side it is continued in a similar manner on the diaphragm, and in passing from the spleen to that muscle forms the fold called splenico- phrenic. The concave surface of the diaphragm is in greatest part lined by peritoneum : the an- terior half of the muscle is uninterruptedly covered by peritoneum, which adheres very closely to the central tendon, but is much more easily separated from the muscular portion. On the right side and in the middle, in front of the cesophageal opening, the peritoneum is re- flected from the diaphragm to the liver, forming the right lateral, coronary, and left lateral liga- ments of that organ. The posterior half of this surface is likewise covered by peritoneum, that membrane being deficient for a little way behind the opening for the vena cava and behind and on each side of the cesophageal and aortic openings : the crura of the diaphragm are covered chiefly on the outer side. The peritoneum comes into immediate con- tact with the posterior abdominal wall only in a very small portion of its extent : in tracing it on the right side we find it covering the right colon, then passing inwards over the kidney and suprarenal capsule, the duodenum and vena cava, to the eras of the diaphragm above, and in the middle and below, where it also covers the vena cava, and the renal vessels, to form the right or superior lamina of the mesentery. On the left side it covers in a similar manner the left colon, the left kidney and capsule, and that portion of small intestine which projects just to the left of the superior mesenteric artery, which may be regarded as the commencement of the jejunum ; below this it manifests its continuity with the layer of the opposite side by forming the left or inferior lamina of the mesentery. This lamina commences at the left side of the body of the second lumbar vertebra; as it descends, it gradually crosses more in front of the aorta, so as to terminate at the right sacro-iliac symphysis ; the right lamina is situated quite on the right side of the spine. In the iliac fossae the peritoneum is in con- nexion with the fascia iliaca, except where it is separated by the coecum on the right side (on which side it sometimes forms a fold termed mesoccecum,} and by the sigmoid flexure on the left. Internal to these portions of intestine on each side, the peritoneum covers the ex- ternal iliac artery and vein, from which it is separated by a very loose and sometimes adi- pose cellular tissue, and by a process of the iliac fascia, to which allusion has already been made. From the preceding description of the con- nection of the peritoneum with the parietes of the abdomen, it will appear how few are the situations at which the surgeon could cut through any portion of these walls without risk of wounding the serous membrane. Im- mediately above the pubis this may be done in consequence of the abundance of cellular membrane there which separates the serous membrane from the wall ; but in the con- tracted state of the bladder the operator must proceed with the greatest caution : in the dis- tended state of that viscus, however, the wall of the abdomen is deprived of its lining to an extent proportionate to the height to which the bladder ascends behind the recti muscles; and accordingly it is under such circumstances that the paracentesis vesicae supra pubem, and the high operation for the stone may be per- formed with impunity to the serous membrane. At the posterior wall an instrument may be passed into any part of the posterior surface of the kidney without injury to the peritoneum ; the pelvis of the kidney, or any part of the abdominal course of the ureter, may be opened too, or the vena cava ; and by cutting into the bodies of the vertebrae, and the muscular por- tion of the posterior wall in the dead body, a view of all the parts which lie upon that wall may be obtained without at all injuring the peritoneum.* Further details respecting the anatomy of the peritoneum will be found in the article under that head. Vessels and nerves of the abdominal walls. a. The arteries. The most important arterial ramifications are found in the anterior wall. In the superficial fascia we find the superficial epigastric artery or tegumentary artery, which exists as a trunk in the iliac regions. This artery, arising from the femoral, pierces the fascia lata, and passes over Poupart's ligament upwards and inwards, crossing the anterior * The reader may examine with advantage, Lud- wig, Icones cavitatum thoracis et abdominis a tergo apertarum. Leipzig, 1789. ABDOMEN. wall of the inguinal canal between the two rings ; it is distributed in the integuments and fascia of the iliac and umbilical regions, and anas- tomoses with its fellow of the opposite side, and by deep branches which pierce the aponeuroses, with the deep epigastric artery. In the epigas- trium and hypochondria the superficial fascia and integument are supplied by cutaneous branches from the internal mammary and the inferior intercostals. The deep-seated parts of this region are likewise supplied from the last- named arteries ; the largest and most constant of which is the abdominal branch of the internal mammary, which in the sheath of the rectus supplies that muscle, and establishes an im- portant communication with the epigastric : this anastomosis is said to have been known to Galen, who by it proposed to account for the sympathy which exists between the uterus and the breasts.* Another branch of the mammary supplies the muscles external to the rectus ; it runs between the obliquus internus and trans- versalis, and is lost in anastomosing with the inferior intercostal, the lumbar, and the circum- flexa ilii arteries. Inferiorly, the abdominal wall is supplied by two considerable and very constant arteries, viz. the epigastric, which may be distinguished from the artery that supplies the integuments by the appellation deep, and the circumflexa ilii. The epigastric artery arises in general from the external iliac a little way above Poupart's liga- ment; it at first inclines downwards to that ligament, and then turns upwards, and directs itself forwards and inwards, crossing the iliac vein; it then runs along the posterior surface of the anterior wall of the abdomen, inclosed be- tween the peritoneum and fascia transversalis, at first situated between the external and inter- nal abdominal rings, and on arriving at the rectus muscle, the sheath of which it enters about two inches above the pubis, it gives off branches from either side to the abdominal muscles and peritoneum, and behind the linea alba, establishes a very free inosculation with its fellow of the opposite side. As it lies behind the inguinal canal, the epigastric artery is much nearer to the internal than to the external abdo- minal ring, being to the pubic side of the former ; here the vas deferens, as it passes up from the pelvis to the inguinal canal, hooks over it, and receives one or two small branches from it. In passing to the rectus muscle, this artery lies internal to the linea semilunaris. It enters the sheath of the rectus, and then termi- nates by anastomosing with the internal mam- mary. The course of this artery demands par- ticular attention from the surgical anatomist in reference to the operations for inguinal herniae, and to that for paracentesis abdominis, when the abdomen is perforated in the linea semilu- naris. The trunk of the artery is so distant from the linea alba in its whole course, that it is free from danger in any operation performed in that line, or in the internal half of the rectus muscle, and its security in such operations is increased under the altered state of parts con- * Diet, de Medecine, art. Abdomen. sequent on pregnancy, ascites, or any abdomi- nal tumour pressing similarly on the abdominal wall. In these cases the distance of the artery from the linea alba is increased by the flattening of the rectus muscle, which results from its compression. (See GROIN, REGION OF; HERNIA; ILIAC ARTERY.) The circumflexa ilii artery comes likewise from the external iliac, near to the origin of the epigastric; it passes upwards and outwards to- wards the spine of the ilium, runs along the line of junction of the fascia iliaca with the fascia transversalis, covered by the fascia, and follows the circumference of theiliacus internus muscle to end in anastomosing with the iliolum- bar artery. From that part of the artery which intervenes between its origin and the spine of the ilium, come the principal branches which it supplies to the abdominal muscles. The lateral and posterior walls of the abdo- men are supplied by the inferior intercostals, the lumbar, the iliolumbar, the circumflexa ilii arte- ries; the superior walls by the phrenic branches of the internal mammary and by those of the aorta. It is in cases where the aorta has been obliterated that we can see best the extent of arterial ramification on the abdomen, and can appreciate the benefit of these numerous anas- tomoses, and the connexion which they esta- blish between the upper and lower portions of the aorta.* b. The veins. The veins of the abdominal parietes are much more numerous than the arteries ; each artery has its accompanying vein or veins, but those which are especially de- serving of attention are the tegumentary veins which accompany the superficial epigastric artery, and those which ramify along with the deep epigastric and mammary. The subcuta- neous veins demand attention in consequence of the considerable size which they sometimes attain ; this enlargement is commonly attendant on ascites and on pregnancy, and is occasionally, to a remarkable extent, a consequence of some irregularity, obstructionf or retardation of the circulation, in the deep-seated veins of the ab- domen, more especially the inferior vena cava. The veins which accompany the superficial epigastric artery empty themselves by one or more trunks into the vena saphena at the upper part of the thigh. Two veins generally accompany the deep epigastric artery, which empty themselves into the external iliac vein. These veins are equally subject to enlargement with the preceding, and from similar causes, and they are often found in a varicose condition in women who have borne many children. Some curious anomalies have been observed in the venous circulation of the anterior abdo- minal wall, which, as being calculated to in- terfere with the operator, the practitioner would * See the interesting case of obliterated aorta re- corded by Messrs. Crampton and Goodissen. Dub. Hosp. Reports, vol. ii. t As in the case of obliteration of the infeiior vena cava from the pressure of an aneurismal tumour observed by Reynaud. Journal Hebdom. de Med. vol. ii. p. 110. 16 ABDOMEN. do well to note. M. Meniere* has described a case in which a very large vein, arising from the external iliac, passed up along the linea alba to the umbilicus, was continued along the obliterated umbilical vein, and opened into the vena portae. In another case, recorded by Manec, the vein originated in the same manner by two roots, reached the umbilicus, taking a course parallel to the umbilical artery, formed an arch outside the navel, and having re-entered the abdomen, opened into the vena portae. In another instance which occurred to Cruveilhier the superficial veins in the hypogastric region were enormously enlarged, at the umbilicus they ended in a trunk as large as a finger, which communicated with the vena cava as it passed under the liver.f Berard proposes to explain, by the supposition of the existence of such anomalies as those above described, the occurrence of fatal hemorrhages from wounds inflicted at the umbilicus, which have been attributed to the persistence of the um- bilical vein.J c. The lymphatics. Those on the anterior wall communicate above with the axillary glands, and below with those of the groin : the deep-seated lymphatics of the posterior wall communicate with the glands which lie along the lateral and anterior surfaces of the lumbar spine. d. The nerves. The nerves of the abdo- minal parietes are derived from the inferior intercostals and from branches of the lumbar plexus. The seventh, eighth, ninth, tenth, eleventh, and twelfth intercostal nerves termi- nate in supplying the transverse and oblique muscles and the recti ; the twelfth lies in front of the quadratus lumborum muscle, and gives several filaments to that muscle. The ilio- scrotal and inguino-cutaneous nerves are the branches of the lumbar plexus which mainly supply the inferior part of the oblique and transverse muscles. One branch of the genito- crural, which is found in the inguinal canal, also sends some twigs to these muscles. The posterior wall is supplied by the sub- divisions of the posterior branches of the lumbar nerves. Physiological action of the abdominal parietes and muscles. We have already alluded to the peculiarity which distinguishes the abdominal cavity when compared with the other great cavities, namely, that its walls are in greatest part composed of contractile tissue. At first view the muscular apparatus of the abdomen would appear to be a great constrictor muscle destined principally to exert its influence on the cavity and its contents ; but when we take into account the attachments of those muscles * Archives Gen. de Med. t. x. p. 381. The vascular distribution which existed in this subject presents, as Meniere has remarked, a striking simi- larity to that which is naturally found in the Saurian, Ophidian, and Batrachian reptiles, viz. a division of the general venous system which communicates with the hepatic vena portae. t Velpeau, Anat. Chir. ed. 2. vol. ii. p. 32, and Mauec, Dissertation inaugurale. Paris, 1826. $ Diet, de Med. art. Abdomen. to the ribs, the vertebrae, and the pelvis, it becomes evident that they must likewise be destined to act upon the thoracic and pelvic cavities, as well as upon the vertebral column. In the constitution of the abdominal parietes we observe, as Berard* remarks, the most happy adaptation of structure to uses. A completely osseous covering would have greatly interfered with the functions of the abdominal organs, which are liable to experience changes both extensive and often very rapid, either by reason of the introduction of alimentary matter, whether solids or fluids, or by the disengage- ment of gases within the digestive tube, or by the progressive development of the impregnated uterus. We may moreover add that an exact repetition of the structure of the walls of the thorax would not have been well adapted to the abdomen for the same reason, namely, the too great resistance which it would afford to compression from within, thereby interfering with the distensibility of the enclosed viscera. The resistance, too, which a wall so constituted would afford to impulses from without could not have been so easily adapted to the impetus of the forces likely to act upon them as a purely muscular wall whose contractions and the intensity of them are obedient to the will. The consideration of the action and uses of the abdominal muscles naturally comes under two heads : 1 . their action upon the abdo- minal cavity and its contents ; 2. their influ- ence on the trunk generally, or parts of it. It is the muscles that enter into the compo- sition of the anterior and lateral walls of the abdomen which act chiefly on the cavity and its contained viscera. The solidity of a con- siderable portion of the posterior wall, and the great strength of the lumbar muscles, give to that wall such a power of resistance as enables it to receive the compressed viscera without at all yielding. A reference simply to the attach- ments of the muscles of the anterior and lateral walls is sufficient to shew that these muscles when contracted must diminish the capacity of the abdomen, both in the lateral and antero- posterior directions ; and as the posterior wall is but little influenced, the viscera will be pushed partly upwards against the diaphragm, and partly downwards into the cavity of the pelvis, where their further descent is opposed by the levator ani. Hence it appears that a degree of antagonism exists between the diaphragm and the abdominal muscles, as well as also between those muscles and the levator ani. It is extremely difficult to maintain the abdominal muscles and the diaphragm at the same moment in a state of contrac- tion; in general they alternately yield the one to the other : and when it does happen that they are simultaneously contracted, the abdominal viscera must suffer an unusual de- gree of compression ; and it is not improbable that vomiting is sometimes produced by such a cause, and defecation, no doubt, is likewise aided by it. The danger of the protrusion of some of the hollow viscera between the fibres * Loc. cit. ABDOMEN. 17 of the muscles is provided against by the variation of direction in the fibres of the several layers; thus the fibres of the obliqui are in the directions of two intersecting diagonals, and those of the transversalis are different from both. By this arrangement a sort of network is formed, with meshes so small as to render a protrusion perfectly impossible in the healthy condition of the muscle. In the compression of the viscera the abdominal muscles are most completely congeneres, although the trans- versalis seems to be the best adapted to this action, and probably, for that reason, forms the layer which is placed nearest the peri- toneum. The recti muscles are powerful auxiliaries in affording a fixed point of attach- ment in front for the aponeuroses of the broad muscles, and the pyramidales assist in a similar manner by rendering tense the linea alba. Is this constant action of the abdominal parietes on the viscera necessary or favourable to the due performance of the functions of those organs, or to the continuance of the abdominal circulation? There certainly does not appear to be any evidence for the necessity of them for this purpose : that they are favour- able to it may be inferred from the fact that they do bear their present relation to them. We know from numerous experiments on animals, that both the transmission of the intestinal contents, and the abdominal circulation may go on when the abdominal muscles have been freely opened or removed. Hence we may answer this question with perfect justice in the words of Bichat : " The walls of the ab- domen favour these functions by their motions; but these motions are by no means essential to them." It is in consequence of the power which the abdominal muscles thus appear to exert in compressing the viscera, that some physiolo- gists have attributed the act of vomiting to their action united with that of the diaphragm; and Magendie, reviving the opinions of Bayle, Chi- rac, and Shwartz,* went so far as to deny to the muscular coat of the stomach any partici- pation in this act, and to ascribe it wholly to the influence of the abdominal muscles. But Beclard, to whom the question was referred by the Academy of Medicine of Paris, proved satisfactorily that the abdominal muscles are active in producing vomiting when the sto- mach is distended in a certain degree, and that the muscular coat of the stomach is also active in emptying the contents of that viscus. This conclusion Haller had arrived at long ago, and clearly expresses it in the following passage : " Evidentissimum ergo videtur, vomitus qui- dem causam esse in ventriculo eumque in con- tractionem niti propriis vinbus atque aliquando vomitum perficere. Plerumque tamen irrita- tionem in ventriculo natam et sensum summse anxietatis, quse vomitum praecedunt, facere ut ad levandam aegrimoniam vires diaphragmatis 2t musculorum abdominis excitatae atque mo- lestiam de homine amoliturae, vomitum per- * Vide Haller, Elementa Physiologiae, t. vi. sect. iv. xiv. VOL. I. ficiant. Unde neque a sola voluntate in pie- risque certe mortalibus vomitus cieri potest ncque a .sola absque voluntate natura Quare recte conjunctas vires ventriculi et or^anorum respirationis Cl. Viri fecerunt. Et videtur dia- phragmaet abdomen plusvirium habere,quando ventriculus aut cibis repletus est, aut clausis ostiis distentus : tune enim magis ad perpen- diculum proximum ventriculum comprimunt et tota contingunt."* If it be admitted that the abdominal muscles are active in producing vomiting, and in defe- cation and micturition, it will follow likewise that they must assist in parturition. While these pages were preparing for press, the fol- lowing passage presented itself to me, in an able arid interesting review of M. Velpeau's Treatise on Midwifery. It so fully illustrates the part which the abdominal muscles take in promoting parturition, that I venture to tran- scribe it, " It is certain," says the reviewer, " that a woman who ' bears down ' as it is termed, with all her force, who makes the most of her pains, however feeble they may be, will thus accelerate her delivery ; and that another may more or less delay delivery by voluntarily opposing muscular action as much as she can. For example; a woman was admitted for de- livery at M. Baudelocque's theatre ; labour went on regularly, and the pupils assembled. The dilatation of the cervix now slackened, and no progress was made during the whole night. The ileves were fatigued and retired ; the pains immediately returned, and dilatation again went on. The young men again entered ; the phenomena of labour again ceased. Baude- locque, suspecting the cause, gave a hint to the students to retire, but to be at hand and enter upon a given signal. The patient now began to * bear down,' and the head of the child was quickly at the vulva The spectators were once more brought to the scene of action, and the labour was speedily terminated; for it had now advanced too far to be suspended by any voluntary effort or moral alarm of the woman. "f The fixedness of the inferior attachment of the abdominal muscles to the pelvis, and the mobility of the ribs, to which they are attached superiorly, evidently indicate that these muscles are destined to act upon the thoracic cavity. The transversalis does not, from the direction of its fibres, admit of this action to any extent; that office, therefore, devolves chiefly on the obliqui and recti. When these last-named muscles act together, they must compress the inferior opening of the thorax, draw its inferior margin downwards and backwards, and, by the compression thus exerted on the abdominal vis- cera, push them upwards against the diaphragm, which muscle is thus made to ascend into the thorax, and that cavity is thereby diminished in its vertical and antero-posterior diameters, and also, though not so obviously, in its trans- verse. Hence the lungs become so compressed as to be adapted to the altered capacity of the * Haller, ubi supra. See, also, Richerand, Physi- ologic par Berard, art. Digestion, $ xxiv. t Medical Quarterly Review for April, 1835. p. 100. Itf ABDOMEN. thorax, and thus these muscles must be con- sidered as very important agents in the act of expiration. It must be observed, however, that in order that they may act on the chest with their full force, it is necessary that that cavity should have been previously in a state of full dilatation, for under such circumstances the fibres of the obliqui and recti are con- siderably stretched and their levers elongated.* It is in the excited states of expiration, cough- ing, sneezing, &c., that this action of these muscles is most obvious. But it is in the motions of the trunk that the abdominal muscles are called most into play. In all the inflexions of the trunk, whe- ther the body be horizontal or erect, these muscles are main agents. When the body is recumbent on a horizontal plane, the recti are thrown into action when the individual attempts to raise up the thorax, the spine being thereby brought into the state of flexion. If the thorax be fixed, while the body is still supine, the action of the recti will draw the pelvis upwards and forwards, causing slight flexion of the spine, and slightly approximating the upper margin of the pelvis to the lower margin of the thorax. Although the recti muscles are the principal agents in thus flexing the spine, the obliqui co- operate with them very powerfully, and are especially useful in maintaining the due propor- tion between the middle and lateral regions of the abdomen. When the two obliqui of the same side act together, the direction of their force is, as with all oblique muscles whose fibres decussate, in the diagonal between their fibres; and, therefore, when the obliqui of op- posite sides act in unison, they very powerfully aid the recti in flexion of the spine, approx- imating the thorax and pelvis anteriorly. When the obliqui of one side act, they produce a lateral inflexion of the trunk to that side, the middle and opposite region of the abdomen being in this position rendered prominent by the viscera pushed over from the side of the contracted muscles. In what have been called the rotatory motions of the trunk, the obliqui muscles of the same side antagonize each other; thus in that movement by which the anterior surface of the trunk is made to look to the left side, the obliquus externus of the right side will co-operate with the obliquus internus of the left, but the obliquus internus of the right will antagonize the external muscle of the same side. " These muscles," (obliqui externi et in- terni,) says Dr. Barclay, " from occupying the whole of the lateral aspects extending be- tween the ilia and ribs, and from acting at the greatest lateral distance from the centre of motion, must always be muscles principally concerned in producing inflexions dextrad and sinistrad on the lumbar vertebrae, principal di- rectors in all the inflexions sternad and dorsad ; and, from the assistance which they give to the recti, principal librators also of the trunk, whe- ther we be sitting, standing, or walking." The reciprocal action of the recti and ob- liqui on each other is one of the most beauti- * Barclay on Muscular Motion, p. 522. ful parts of the mechanism of the abdominal muscles. This is mainly to be attributed to the close connection which subsists between these muscles in consequence of the formation of the sheaths of the recti by their aponeuroses, and the adhesion of the anterior wall of those sheaths to the tendinous intersections of the recti. When the recti contract, the antero-pos- terior diameter of the abdomen is diminished, and consequently the viscera are pushed to- wards the sides ; when, on the other hand, the obliqui contract, they diminish the transverse diameter of the abdomen, and push the viscera forward in the middle line. In the one case, then, it will be evident that the obliqui act as moderators to the recti, and in the other the resistance of the recti moderates the action of obliqui, the former muscles being, as Cru- veilhier remarks, as it were, two active pillars compressing forcibly the viscera against the an- terior surface of the spine. It is probably to enable the recti to act more completely as moderators upon the several segments of the obliqui that they are intersected by tendinous lines, with which theaponeurosesof those muscles are connected. Another use has been assigned to these intersections by Berlin, viz., to multi- ply the points of attachment of the obliqui muscles, and to associate them, in many ac- tions, with the recti muscles. This is explained by a reference to the action of the recti in flex- ing the pelvis: were these muscles uncon- nected with the obliqui, they would act only on the pelvis, into which they are inserted ; but in consequence of the insertion of the internal oblique into the intersections of the recti, and the attachment of that muscle also to the crista ilii, the force of contraction of the recti is com- municated not only to the pubis, but also through the fibres of the obliquus internus to the rest of the pelvic margin.* The action of the pyramidales seems to be chiefly on the linea alba, which they render, tense ; thus limiting the separation of the recti, and opposing the tendency to visceral protru- sion. Fallopius supposed that they acted on the bladder, especially when it was in a dis- tended state ; and Parsons conjectured that they might depress the suspensory ligament of the bladder (the urachus), and thus facilitate the contraction of that organ. The other muscles which are from situation abdominal muscles in consequence of their connexion with the posterior wall of the abdo- men, are chiefly agents in the extension of the vertebral column : in their contracted state, however, they form a tense and resisting sur- face, against which the viscera are compressed by the contraction of the anterior muscles. II. Of the Abdominal Cavity. The annexed engraving (Jig. 5.) exhibits a view of the abdo- minal cavity, the anterior and part of the lateral walls having been cut away and the viscera removed. The subject is so bent backwards as to render the bodies of the vertebras very * Berard, loc. cit., et Berlin, sur 1'usage de enervations des muscles droits du bas-ventre, in . de 1'Acad. des Sciences de Paris. ABDOMEN. (Fig. 5.) prominent anteriorly, and the continuity of the abdominal and pelvic cavities is thus clearly shewn. It is useful to examine the relations of the axes of these two cavities ; that of the pelvis passes forwards and upwards towards the umbilicus, while the axis of the abdomen passes from above downwards and forwards so as to terminate a little above the pubis, the two axes accordingly would intersect each other a little below the umbilicus at an obtuse angle. This angle may be obliterated by bringing the pelvis very much forward and producing a full flexion of the spine, and hence in all efforts for expulsion that attitude is almost instinctively assumed which shall identify the axes of the two cavities, and thus direct the efforts in the most favourable manner. The ordinary form of the cavity in the adult male is oval, but it presents some slight differences in the female and in the fetus ; and these differ- ences are dependent on the great or incomplete development of the pelvis. In the female the abdomen is generally more capacious than in the male ; and this greater size is more remark- able at the inferior part of it in the hypogastric region. In fact in the male it would seem that the great extremity of the oval is toward the thorax, and its smaller one towards the pelvis ; but in the female it is just the reverse, the larger extremity being toward the pelvis. It should be observed, however, that the modern fashion of tightly compressing the lower part of the thorax has a material effect on the external characters of the female abdomen, otherwise there is no reason that the superior part of it should be proportionally less than in the male. In the foetus the abdomen is proportionally larger than at any other period of life : this is to be attributed to the imperfect development of the pelvis, and likewise to the great size which some of the abdominal viscera possess ; and as some time must elapse before the pelvis reaches its full dimensions, or the viscera lose their superfluous parts, the abdomen continues of this large size for a long period after birth. The subdivision of the abdomen into regions is especially useful in reference to the contents of the abdominal cavity, which it is highly de- sirable the student should examine, so as to be able to assign to each compartment its appro- priate contents. The abdominal viscera may be subdivided into the membranous and the parenchymatous ; the former being such as the stomach and intestinal canal, the latter, such as the liver, spleen, pancreas, &c. The viscera have likewise been distinguished in reference to their position with respect to the peritoneum, by the names intra-peritoneal and extra-peri- toneal ; but it is sufficient to know that no serous membrane contains any organ within it (i. e. within its sac) to see the error of such a distinction. But we cannot adopt a better di- vision of the abdominal viscera than that which has reference to the functions of those organs, and which Beclard has adopted : viz. 1 . the organs of digestion the stomach, the intes- tinal canal, the liver and its appendages, the spleen, and the pancreas : 2. the urinary organs the kidneys and the ureters, to which may be added from their close relation to the kid- neys, the suprarenal capsules : 3. the organs of generation in the male the vasa deferentia, and in the male foetus at the sixth or seventh month of intra-uterine life, the testicles ; none of the organs of generation can strictly be said to be abdominal organs in the female. In both male and female the other internal generative organs are pelvic viscera. If we add to the above enumeration of parts the abdominal por- tion of the aorta, its primary subdivision into the common iliacs ; the anterior subdivision of these arteries under the name of external iliacs ; the branches of the aorta which are distributed to the viscera as well as to the walls of the abdomen ; the common and external iliac veins; the vena cava ascendens ; the system of the vena portae ; the abdominal portion of the sympa- thetic system of nerves, both that which follows the arterial ramifications, and that which is the continuation of the chain of ganglia that lies along the spine, the termination of the par vagum ; the mesenteric glands, and the lacteals ; the lymphatics and their ganglia which lie along the spine; the origin of the thoracic duct, a portion of the course of that duct ; these wil I complete the list of parts contained in the abdo- minal cavity. The full particulars of the relative positions of the contents of the abdomen, and the abnormal c 2 20 ABSORPTION. states of that cavity, both congenital and mor- bid, including also the abnormal states of its parietes, we prefer to bring together in a sepa- rate article under the head CAVITY ABDO- MINAL, to which we beg to refer the reader. The special anatomy, both natural and ab- normal, of the several abdominal viscera is distributed among the articles INTESTINAL CANAL, KIDNEY, LIVER, PANCREAS, SPLEEN, SUPRARENAL CAPSULE. BIBLIOGRAPHY. The several systematic writers, as Winslow, Boyer, Portal, Bichat, Meckel, Cloquet, Marjolin, Hildebrandt, &c. for the titles of whose respective works seethe Bibliography of ANATOMY, (Introduction, ) Velpeau, Anat. Chirurgicale. Paris, 1833. t. ii. Blandin, Anat. Topographique. Cru- veilhier, Dictionnaire de Med. et Chirurg. art. Abdo- men. Beclard et Berard, Diet, de Medecine. Ed. 2d. art. Abdomen. Pierer Anatomisch- Physiologisches Realworterbuch. herausgegeben von J. F. Pierer. Leipzig, 1816. art. Abdominal- muskeln. Gerdy, Anat. des formes exterieures. Paris, 1829. p. 122 and 199. Cloquet, Recherches Anat. sur les Hernies de 1'Abdomen, or the trans- lation by McWhinnie. Lond. 1835. Scarpa, on Hernia, by Wishart. Lawrence on ditto. Todd, on ditto. Dub. Hosp. Reports, vol. i. Flood's plates of Inguinal and Femoral Hernia. Lond. 1834. Cam- per, Icones Herniarum. Guthrie, on Inguinal and Femoral Hernia. A. Cooper, on ditto, and on the Testicle. Munec, Dissertation Inaugurale sur 1'Her- nie.1826. Colles's Surgical Anatomy. Dublin, 1811. Barclay on Muscular Motion, p. 337 et sqq. ( R. B. Todd.) ABSORPTION in physiology (from ab- sorbeo : Lat. absorptio, Fr. absorption, Ger. die einsaugung, Ital. assorbimento.} The term absorption is employed in physiology to de- signate a vital organic function, the primary or immediate object of which is to furnish the system with a due supply of matter for its growth and subsistence. It is proposed, in the following article, first, to give an account of the organs by which the function is performed ; this will lead us, 2dly, to consider the question of venous absorption ; in the third place, we shall inquire into the mode in which the ab- sorbents act ; and, lastly, we shall offer some remarks upon the specific uses of the different parts of the absorbent system, and upon the re- lation which it bears to the other vital functions. . 1 . Description of the Absorbent System. We propose, in the first instance, to restrict the term absorbent system to those organs, which are supposed to be exclusively appropriated to the function of absorption ; these may be in- cluded under the two heads of vessels and glands, the vessels being again subdivided into the lacteals and the lymphatics. Although the absorbents are distributed to al- most every part of the body, and perform so im- portant an office in the animal economy, they were among the organs which were the latest in being discovered by anatomists. There are, indeed, some passages in the writings of Galen,* which would lead us to suppose that certain * De Anat. Admin, lib. 7, sub finem ; De usu partium, lib. 4. cap. 19 ; An sanguis in arteriis &c. cap. 5. parts of the absorbents had been seen by Erasistratus and Herophilus, as well as by himself; but it appears that they were, all of them, unacquainted with the relation which these vessels bore to the other organs, and were entirely ignorant of their office and destination. These scanty observations of the ancients seem to have been entirely neglected, or even for- gotten, until the study of anatomy was revived, together with that of the other medical sciences, in the sixteenth century. In the course of the researches which were then made into the structure of the animal body, various parts of the absorbent system appear to have been brought into view, and are noticed, among other writers, by Fallopio,* who discovered the lym- phatics, connected with some of the abdominal viscera, and by Eustachio,f who detected the thoracic duct. But although their descriptions, especially that of Eustachio, are sufficiently correct to enable us to identify them, as forming a part of the absorbent vessels, yet they were unacquainted with their specific nature and office, and with their relation to the sangui- ferous system. It is generally admitted that the merit of the discovery of the lacteals is due to Aselli ; this discovery he made in the year 1622. While he was examining the abdominal viscera of a dog, he observed a series of vessels attached to the mesentery, which appeared to have no direct connexion with the arteries or veins, and which, from the circumstance of their con- taining a white opake fluid, he denominated Lacteals.]: He regarded them as a distinct set of vessels, exercising a specific function, distinct from that of the sanguiferous system, and he as- certained that they took their origin from the surface of the intestines, and proceeded to- wards the more central parts of the body, but it was not until the year 1651, that their ter- mination in the thoracic duct was discovered by Pecquet. The discovery of the other species of ab- sorbent vessels, styled, from the appearance * " Observ. de Venis," lib. 3., in Op. p. 532; first published in 1561. We may add the names of Fabricio, Piso, and Gassendi, who appear to have seen certain parts of the lymphatics, although they were not aware of their specific nature. See Bar- tholin, de Lact. Thor. c. 2 ; and Mascagni, Vas. Lymph. Hist. Proleg. sub init. t De Vena sine pari, Antig. 13, sub finem, in Opusc. Anat. ; first published in 1564. See Haller, Bibl. Anat., p. 224 ; also Douglas, Bibliog. Anat., p. 99. $ Dissertatio de Lactibus ; first published in 1627. See Bartholin, de Lact. Thor., c. 4 ; Sheldon on the Absorbent Syst., p. 20, 1. Aselli's work is ac- companied by plates of very rude execution, but sufficiently expressive of the object. Exper. nova anat. ; first published in 1651 ; Bartholin, c. 5. In 1652, Van Home published the first plate of the thoracic duct. There is some reason to suppose that Vesling had an imperfect view of it previous to Pecquet ; he published his Syntagma Anat. in 1647. In describing the pancreas he speaks of the venae lacteae, lately discovered by Aselli, which convey the chyle to the liver, and figures them in tab. 4. fig. 3. ABSORPTION. -21 of the fluid which they contain, the lymphatics, was posterior to that of the lacteals. The trans- parency of their contents rendered them less conspicuous and less easy of detection, so that, although certain parts of them appear to have been seen by Fallopio, and afterwards by Aselli and others, yet it was not until the year 1650, that they were distinctly recognized, and their connexions ascertained. The discovery of the lymphatic system was the subject of a warm controversy between Bartholin and Rud- bek, on the merits of which we are, after so long an interval, scarcely able to decide. It appears, however, to have been the opinion of Haller, and the most distinguished anatomists of the last century, that the lymphatics were detected, in the first instance, by Rudbek ; that Bartholin had some intimation of the dis- covery, that he then took up the subject, and pursued it much farther than it had been done by Rudbek.* There is a third individual, on whose behalf a claim of priority has been made, which pos- sesses at least considerable plausibility. We are informed by Glisson, that an English ana- tomist of the name of JolifTe distinctly re- cognized and exhibited the lymphatics of many of the abdominal viscera, previously to the alledged discovery of either Rudbek or Bar- tholin.f But even if we allow Joliflfe the full merit both of discovering these vessels, and being aware of their specific nature, it does not appear that he published his discovery, so that it will scarcely affect the rival claims of the former anatomists. The discovery of the ab- sorbent or conglobate glands, as they have been termed, was made, for the most part, at the same time with that of the vessels, as a ne- cessary consequence of the intimate connexion which subsists between them. After the existence of the lacteals had been clearly announced by Aselli, and of the lym- phatics by Rudbek and Bartholin, the atten- tion of anatomists was very generally directed to these organs, and discoveries were suc- cessively made, by various individuals, of the presence of the latter in almost every part of the body, and in connexion with almost every one of its organs. The labours of William and John Hunter, of Monro sec , arid of Hewson, were among the most important in their re- sults, while we are indebted to Cruikshank, and still more to Mascagni, for their minute descriptions and accurate representations of the absorbent system, in all its parts, and with its various relations and connexions.]: * El. Phys., ii. 3. 1; BiV.l. Anat., t. i. .378 and 415; and Not. 4. ad . 121. Boer. Prsel. Bartholin's statement of his claim is contained in his " Anat. Reform." p. 621, 2 ; see also his trea- tise, " Vas. Lymph. Hist. Nov." and Rudbek's *' Nova Exerc. Anat." For the historical part of the subject we may refer to Mascagni, Prolegomena, and to Meckel, Manuel d'Anat. par Jourdan et Breschet, t. i. ch. 2. p. 179 . . 202. t Anat. Hepat. c. 31. See Haller, Bibl. Anat., t. i. p. 452 ; also Mascagni, Prolegomena. t For the most original and correct desciiption of the lacteals, the reader is referred to Haller, El. Phys. xxv. 1. 4 . . 8 j Mascagni, Vas. Lymph. Corp. With respect to the minute anatomy of the lacteals, we are informed that they originate from certain small projecting bodies, termed villi, which are attached to the interior surface of the intestines, styled from this circumstance the villous coat. These villi are described as consisting of a number of capillary tubes, which terminate with open mouths, and that by the union of these tubes the branches of the lacteals are composed, which are suffi- ciently large to be visible to the eye. We must remark, however, that although these villi, as constituting the mouths of the lacteals, have been minutely described, and even figures given of the appearance which they exhibit in the microscope, yet that considerable doubt is still entertained of their existence, and that they are even entirely discredited by some anatomists of the first eminence.* Upon the whole we may conclude that the opinion, which has been generally adopted, respecting the capillary termination of the lacteals, is somewhat theo- retical, rather derived from the supposed ne- cessity of such a formation to cany on the functions of the vessels, than from any actual observations that have been made upon them. When the lacteals have acquired sufficient magnitude to become visible to the eye, they are seen to proceed along the mesentery, the small vessels running together to form large branches, and these again forming others that are still larger, until the whole of them unite into a few main trunks, which terminate in the receptacle at the lower extremity of the thoracic duct. During their progress, the small vessels Hist., p. 1. $. 7. art. 8. tab. 1. fig. 7; Sheldon,~on the Absorb. Syst. ch. 2. pi. 3, 4, 5 ; Santorini, Tabulae, No. 13. fig. 3 ; Magendie, Physiol. t. ii. p. 158 . . 0. The translation of Mascagni 's work, with copious notes by Bellini, may be advantageously consulted ; it is not accompanied by plates. For the lymphatics we may refer to Haller, ii. 3. 2 ; Meckel, Diss. Epist. de Vasis Lymphaticis ; Hew- son, Enq., ch. 3. pi. 3, 6 ; Mascagni, ps. 1. sect. 7. tab. 4 et seq. ; Cruikshank, on the Absorb., p. 148 et seq. ; Soemmering, Corp. Hum. Fabr. t. v. p. 388 et seq. ; many of Mascagni's plates are transferred into Cloquet's valuable " Manuel." Art. " Inhalation," par Rullier, in Diet, des Sc. Med. t. xxv. 3. Art. " Lymphatique," par Chaussier et Adelon, ibid, t. xxix. p. 249, 260 ; Meckel, Manuel, sect. 6. ch. 2; Quain's Elem. of Anat. p. 560 . . 574. In Elliotson's Physiol. ch. 9. p. 140 . . 2, we have a " short account of the first discovery of the absorbent system." Scemmer- ing's treatise, De Morbis Vasorum Absorb, con- tains a most ample and learned catalogue of the various works on absorption, from the earliest period to the date of its publication in 1795. * See Lieberkuhn, Diss. de Fabr. Vill. Intest. passim, cum tab. 1, 2; Hewson's Enq., c. 12, pt. 2 ; Cruikshank's letter to Clare, p. 32 . . 4 ; Shel- don on the Absor. Sys., p. 32 . . 8, tab. 1, 2 ; Hedwig, Disq. Ampull. In opposition to these and other authorities, on the affirmative side of the question, we have the strong negative evidence of Mascagni, whose plates do not sanction the description of Lieberkuhn, tab. 1. fig. 1. 3 ; and tab. 3. fig. 1,2,3, 5; and the decided opinion of Magendie, Journ. de Physiol. t. i. p. 3 et alibi. On this sub- ject see the remarks of Haller, not. 9. ad . 91. Boerhaave, Prael. et not. 4. ad . 103. The ob- servations of Du Vernoi, Mem. Petrop. t. i. p. 262 ec seq., seem scarcely to have been confirmed. 22 ABSORPTION. frequently anastomose with each other, so as, in many instances, to form a complete network or plexus, in which respect their course differs from that of the veins, where the small branches unite to form the larger ones, without the lateral communications. The lacteals are furnished with numerous valves, which are disposed in pairs, and have their convex surface turned towards the intes- tine,* so that, in the ord.nary and healthy con- dition of the vessels, their contents are pre- vented from retrograding, and necessarily pro- ceed from the small branches to the larger trunks. The coats of the lacteals are thin and transparent, and hence it is that these vessels, except when they are filled with chyle, are so difficult of detection. They seem, however, notwithstanding the apparent delicacy of their texture, to be possessed of considerable strength, and to bear being distended far be- yond their ordinary dimensions without being ruptured. When they are completely filled with chyle, and still more, when they are for- cibly distended by injections, the number of valves which they possess gives them a jointed or knotted appearance, and it seems to have been this circumstance, together with the white colour of their contents, which first attracted the notice of anatomists, and led to their dis- covery. With respect to their structure, besides the peritoneal covering which they possess in common with all the abdominal viscera, they seem to be composed of two distinct parts, an internal membrane, which by its duplicature forms the valves, and an external membrane, which constitutes the main substance of the vessel. To these two obvious component parts many authors have added a muscular coat, and some anatomists of great respectability assert that they have actually detected transverse fibres, in which their contractile power is supposed to reside. Other anatomists, however, of equal authority, deny the existence of this muscular coat, and, it must be acknowledged, that the weight of the negative evidence seems to pre- ponderate. But we may remark, on the other hand, that although these transverse fibres, constituting the muscular coat, in consequence of their transparency, or from some other cause, have hitherto eluded our observation, so that we have no positive proof of their existence, the lacteals certainly exhibit what appears to be very decided marks of contracti- lity, and as they are not immediately con- nected with any organ equivalent to the heart, there seems to be no means, except their own contractility, by which their contents can be propelled-! See CHYLIFEROUS SYSTEM; LAC- * These were very minutely examined by Ruysch, Dilucid. Valvul., op. t. i, p. 1 . . 13 ; they are ac- curately described by Sheldon, p. 28. t Mascagni, ps. i. sect. 4. p, 26, informs us that he could not detect the fibres; Cruikshank, on the contrary, conceives that he has seen them in the thoracic duct, p. 61 et alibi ; and Sheldon speaks of the muscular coat as sufficiently obvious, p. 26. Meckel, Manuel, (. i. p. 185, does not admit their sxistence ; and this is the case with Chaussier and The anatomical structure of the lymphatics seems to be essentially similar to that of the lacteals ; they are composed of a firm elastic membranous substance, capable of consider- able distention without being ruptured, and furnished with numerous valves ; like the lac- teals they form very frequent anastomoses. We have the same evidence of their contracti- lity as of that of the lacteals, although we are perhaps still less able to demonstrate the actual existence of their muscular fibres. We presume that they are likewise analogous to the lacteals in the nature of their office, and in their desti- nation, although they differ from them with respect to their situation, or the parts of the body to which they are attached ; the lacteals being confined to the membranes connected with the intestines, while the lymphatics are found in almost every part of the body, and connected with nearly all its various textures.* They differ also in the nature of the fluid which they contain, for while that of the lac- teals, as has been stated above, is white and opaque, the fluid found in the lymphatics is transparent and colourless, so as to resemble water, from which they have derived their spe- cific denomination. It is very difficult, if not impossible, to trace the actual commencement of the lymphatics ; but partly from anatomical researches, and partly from physiological considerations, we are led to conclude that they originate from the various surfaces of the body, of all de- scriptions, both internal and external. They resemble the lacteals, in passing from larger to smaller branches, which, after numerous anastomoses, unite in a few large trunks, the greatest part of which terminate in the thoracic duct. The great trunks of the lymphatics are, for the most part, arranged into two distinct series, one considerably more superficial than the other; it is observed that they generally follow the course of the great veins, but it may be doubted whether any direct communication Adelon, " Lymphatique,"Dict. des Sc. Med. t.xxix. p. 256. Breschet, art. " Lymphatique Systeme," Diet, de Med. t. xiii. p. 389, considers it doubtful. Some curious observations were made by Desge- nettes, on the action of the absorbents after the apparent death of the system, Journ. Med. t. Ixxxiv. p. 499 et seq. Similar observations were after- wards made by Valentin, t. Ixxxvi. p. 231, et seq. ; this action was not, however, supposed to depend on contractility. Wrisberg informs us that he has frequently seen spasmodic contractions in the large vessels a'nd in the thoracic duct, Observ. Anat. Med. de Vas. Abs. Morb. in Comment. Soc. Reg. Gotting. v. ix. 19. p. 149. * For the extent of the lymphatic system, see Haller, El. Phys. ii. 3. 4, and the later account of M. Magendie, Physiol. t. ii. p. 174, and Jour, t. i. p. 3, who conceives that absorbent vessels have not been detected in the brain, the spine, and the organs of sense. Dr. Alison likewise conceives that they have not been detected in the cranium or ner- vous system, Outlines of Physiol. p. 76. Mas- cagni, however, appears to have detected a few small lymphatics in the brain, tab. 27. fig. 1. Monro secundus argues in favour of their existence, but it does not appear that he actually detected them in any part of the nervous system ; on the Nervous System, ch. v. sect 1. and Three Treatises, ch. 4, 5. ABSORPTION. 23 exists between them during their course, and we are not aware of any physiological cause of this arrangement. With respect to the mouths or origin of the lymphatics there is even more uncertainty than with respect to that of the lacteals ; no anato- mical investigation has hitherto been able to detect them, and although numerous facts of constant occurrence would seem to prove that their capillary extremities are distributed over all the surfaces of the body, it is from various pathological observations and from the analogy of the lacteals that we arrive at this conclu- sion.* The thoracic duct is a vessel of considerable size, which is situated near the spine, and which extends from about the middle of the dorsal vertebrae to a short distance above the left subclavian vein ; here it assumes an arched form, and is bent down until it enters the vessel near its junction with the jugular vein of the same side.f The duct, in its passage along the spine, is deflected in various ways, and proceeds in a somewhat irregular or tortuous course. For the most part it consists of a single trunk, but occasionally there are two trunks, either of the same or of different sizes, and we have not unfrequently partial appen- dages, which are added to the main trunk in different parts of its course.]: Besides what is properly considered as the thoracic duct, in which all the lacteals and the greatest part of the lymphatics terminate, a portion of these latter, especially those which proceed from the upper part of the body and from the superior extremity of the right side, are generally col- lected into a separate trunk, named the great right lymphatic vessel, or right thoracic duct, which is connected with the right subclaviau vein. These irregularities in the disposition and form of the thoracic duct may be consi- dered as in no respect affecting its physiological uses, and to be no more than an anatomical variation of structure, probably depending * See Magcndie, Physiol. t. ii. p. 175 Watson, however, conceived that he had detected their open mouths on the surface of the bladder, Phil. Trans, for 1769, pi. 16. Monro, in speaking of the lym- phatics of fishes, remarks that there is " no doubt that they begin by open mouths," p. 30. t For descriptions and plates of the thoracic duct the following works may be referred to; Haller, Prim. Lin. c. xxv. 565; Op. Min. t. i. p. 586 et seq. tab. 11, 12 ; and El. Phys. xxv. 1. 10 . . 3 : Albinus, Tab. Vas. Chylif. ; Holius and Saltzmann, in Haller, Disp. Anat. t. i. ; Cheselden, Anat. pi. 26; Portal, Mem. Acad. pour 1770; Sabatier, ibid, pour 1786 ; Haase, De Vas. Cut. et Intest. Abs. tab. 2. and tab. 3. fig. I ; Mascagni, ps. i. sect. 7. art. 8. tab. 13, 15, 19; Sheldon, pi. 5; Cruikshank, p. 166. . 176 ; Magendie, Physiol. t. ii. p. 160; Meckel, Manuel, 1698. J In Mascagni, tab. 15, we have an example of this irregularity. This is said to have been discovered by Stenon in 1664 ; Meckel, Manuel, 1703. See Haller, Prim. Lin. $ 766 and Hewson's Enq. pt. 2. p. 61 . . 3, pi. 4. Cruikshank, p. 176, 7, conceives that Hew- son was the first who described the lymphatics of the right side as being collected into one trunk. For the figure of this part, see Mascagni, tab. 19. nos. 185, 187. upon some mechanical cause. It is, however, a circumstance of considerable importance in respect to the pathological conclusions that have been sometimes drawn from the obstruc- tions of this organ, as well as from the experi- ments that have been performed upon it.* The structure and properties of the thoracic duct appear to be similar to those of the large trunks of the lacteals and lymphatics; its coats are comparatively thin and transparent, yet it is possessed of considerable strength, and is ca- pable of being distended much beyond its ordinary bulk ; it is furnished with numerous valves, and exhibits a great degree of con- tractility. The lymphatic or conglobate glandsf com- pose a very important part of the absorbent system, if we may judge from their number and their general diffusion over every part of the body. They are of various sizes, and are grouped together in various ways; occasionally they are single, but more frequently connected together in masses of considerable extent. They are found in almost every part of the body, always connected with the lacteals and lympha- tics, and it is asserted that each one of these ves- sels, in some part of its course, passes through or is connected with one or more of these glands.}; There are certain parts of the body in which they are more numerous, and are connected in larger masses ; the lacteals are furnished with numerous glands in their passage along the mesentery, while the glands that belong to the lymphatics are found in the greatest number and largest masses in the groin, the axilla, and the neck. It is necessary to remark that this account of the distribution of the lymphatic glands applies only to the animals which belong to the class of the mammalia; in birds they are much more rare, and still more so in fish, while among the lower animals, where we have suffi- cient evidence of the existence of an absorbent system, the glands have not yet been satisfac- torily demonstrated . With respect to the structure of these glands, as well as that of glands of other descriptions, a controversy has long existed among anato- mists, whether they consist of a series of cells or follicles, as they have been termed, or whe- ther they are composed simply of a congeries of vessels. The question may be regarded as still at issue ; but it may be remarked that whereas the older anatomists generally leaned to the opinion of the follicular structure of the * See on this subject Sir A. Cooper, in Med. Rec. and Res. p. 86 ct seq., and Magendie, Journ. t. i. p. 21. t Some ot the late French physiologists prefer the term lymphatic ganglions, upon the principle that the term gland more properly belongs to an organ of secretion. $ Mascagni, ps. 1. sect. 4. p. 25 : but this h<* been doubted by some anatomists; see Hewson, pt.2. p. 44. 5. $ See Fleming's Zool. t. i. p. 338 ; Blumenbarh's Coimp. Anat. by Lawrence, ch. xiii. p. 256 ; Diet, des Sc. Med. art. < Lymphatique," par Chnussier et Adelon, p. 249; Breschct, art. " Lymph. Syst.," Diet, de Mod. t. xiii. p. 397. Hewson in- forms us that birds have lymphatic glands in the 24 ABSORPTION. glands,* the moderns have more frequently adopted the hypothesis of their vascular texture, so that we may consider this doctrine as sup- ported by the most recent and elaborate re- searches, f See LYMPHATIC; GLAND. 2. The guest ion of venous absorption con- sidered. We have now been describing those organs, which are more specifically or appro- priately termed the absorbent system, as being those parts the office of which is confined to this operation. But a very important and in- teresting question must now be discussed, whether the function of absorption is exclusive- ly performed by the lacteals and the lymphatics. The ancient anatomists and physiologists being unacquainted with the existence of the lacteals and the lymphatics, yet observing the evident effect of the operation of absorption, ascribed these effects to the action of the veins; and among the moderns, for some time after the discovery of what were more appropriately termed the absorbent vessels, it was still sup- posed that the veins co-operated with them, and in some cases were even the principal agents. This was the universal doctrine until the middle of the last century, and was one of the points which was decidedly maintained by Haller and his disciples.^ The arguments by which the hypothesis of venous absorption was supported may be re- duced to two classes, partly of a physiological and pathological, and partly of an anatomical nature; the first consisting of the results of experiments performed for the express purpose of investigating the subject, and of considera- tions derived from the morbid conditions of the system ; the second depending more exclu- sively upon anatomical considerations. The neck, but that they are not found connected with the absorbents of the abdomen, and that they are en- tirely wanting in fish and in the amphibia ; Phil. Trans, for 1768, p. 217 et seq., and Enquiries, pt. ii. ch. 4, 5, 6. We have the same statement made by Monro. with respect to fish, p. 31. An- tommarchi, on the contrary, asserts that birds, fish, reptiles, and amphibia have " pochissime glan- dule ;" Prod, delle grande anat. di Mascagni, p. 8^ but the statement is made in a general way, and without reference to any particular observations. It would appear that no specific apparatus for ab- sorption has been discovered in any of the inverte- brated animals. * We have the authority of Nuck, in favour of the cellular structure, Adenologia, c. ii. p. 30 et seq., fig. 9 . . 12 ; also of Cruikshank, c. 14 ; and of Abernethy, Phil. Trans, for 1776, p. 27 et seq. t See Hewson, v. iii. c. 2. pi. 2; Werner and Feller, Vas. Lact. and Lymph. Descript. tab. 2; their figures, however, appear to be exaggerated ; Beclard, add. a Bichat, p. 231 ; Monro tert., Elem. v. i. p. 558. On the lymphatic glands generally see Haller, El. Phys. ii. 3. 16. .27 ; Beyer, Anat. t. iii. p. 243 . . 257 ; Mascagni, ps. i. sect. 5. p. 31 ; Rnliier, ubi supra, p. 120 et seq. ; Breschet, ubi supra, p. 394. For plates of the glands, see Mas- ca?, discerno,) a pri- mary division of the animal kingdom founded by Virey, and so called by Macleay,|| composed of the lowest classes of the radiate animals of Cuvier, and characterised by an indistinct, dif- fused, or molecular condition of the nervous system. The necessity for a dismemberment of the Radiata of Cuvier, which RudolphiH justly calls a chaotic group, has been felt, and directly or indirectly expressed, by most naturalists and comparative anatomists.** It is impossible, in- deed, to predicate a community of structure in either the locomotive, excretive, digestive, sensitive, or generative systems, with respect to this division, as it now stands in the " Regne Animal." As in the animal organization the nervous * First obtained by Dr. Prout from the pure lithic acid, of which the excrements of the boa constrictor consist. t Procured from the expressed liquor of ants. t Supposed by Vauquelin to exist in the liquor amnii of tbe cow. Extracted by Chaussier from the silk-worm, but its existence is very problematical. || Horae Entomologicae, vol. i. pt. ii. p. 202. f Synopsis Entoxoorum, p. 572. * Lamarck observes, " Les animaux apathlque* (as he terms the Acrita) furent tres-improprement appeles zoophytes: ils ne tiennent rien de la nature vegctale, et tous generalemeut sont completement des animaux. La denomination d'animaux ra- yonnes ne leur convient pas plus que la prece- dente ; car elle ne 'peut s'appliquer , qu'a une partie d'entr'eux , et il s'en trouve beaucoup parmi eux qui n'ont absolunnnt rien de la forme rayonnante." Anim. sans Vertebres i. p. 390. system is that which is subject to the fewest varieties, and as its relative perfection is the surest indication of the relative perfection of the entire animal, the modifications of this system necessarily indicate the highest or pri- mary divisions of the animal kingdom, and form their distinguishing characters. Taking, then, the nervous system as a guide, the radiata of Cuvier will be found to re- solve themselves into two natural groups, of which the first, composed of the Polyastric In- J'usoria of Ehrenberg, the Polypi of Cuvier, the Entozoa parenchyniatosa, Cuv. or Sterel- mintlia, and the Acalepha?, differs in the absence or obscure traces of nervous filaments from the second division, including the Echinoderma, the Entozoa cavitaria or Cceldm'mtha, the epi- zoa, and the Roti/'era, Ehr., in which nervous filaments are always distinctly traceable, either radiating from an oral ring, or distributed, in a parallel longitudinal direction, according to the form of the body. These different conditions of the nervous system are accompanied with corresponding modifications of the muscular, digestive, and vascular systems, and a negative character, ap- plicable to the higher division of Cuvier's Radiata, may be derived from the generative system. With respect to the muscular system, we find that although all the Acrita possess the loco- motive faculty at some period of their exist- ence, and many never become fixed, yet that distinct muscular fasciculi are not necessarily developed. In the fresh-water polype, for ex- ample, the whole of the homogeneous paren- chyma of which it consists is equally con- tractile ; and even in the medusa, which ranks among the highest of the Acrita, no distinct muscular organs for effecting the contractions of the gelatinous disc have yet been detected. In the higher division of radiata, on the other hand, which from the filamentous condition of the nervous system may be termed Nemato- neura, the muscular system is always distinctly eliminated. The difference in the condition of the diges- tive system between the Acrite and Nemato- neurous classes is still more striking: in the former the alimentary canal is excavated in the parenchyma of the body, and is devoid of dis- tinct parietes : in the Nematoneura it is pro- vided with a proper muscular tunic, and floats in an abdominal cavity. A corresponding difference is presented by these two divisions of the invertebrate animals, in the condition of the vascular system. Where traces of sanguiferous organs are met with in the Acrita, they are equally with the digestive organ devoid of proper parietes, but consist of reticulate canals in the substance of the body, generally situated near the surface, and in which a cyclosis of the nutrient fluids is observed analogous to that of plants, but not a true circulation. This structure obtains in the Acrita as low down in the scale as the poly- gastrica, in which class Ehrenberg has deter- mined the existence of a superficial network of vessels containing an opaline fluid. In those 48 ACRITA. genera of sterelraintha or parenchymatous in- testinal worms which manifest traces of the circulating system, the fluids undulate in canals of a similar structure, as is displayed in the planariae, and parasitic trematoda, and also in the echinorhynchi, in some species of which genus the cutaneous canals form a rich net- work.* In the acalephae the condition of the vascular system is equally simple with that of the lowest Acrita, as is exemplified in the mar- ginal reticulate canals in the disk of the rhizos- toma. In the Nematoneura, on the contrary, those classes which manifest a circulating sys- tem distinct from the digestive tube, as the echinoderma and rotifera, possess vessels with proper parietes, distinguishable into arteries and veins. No Nematoneurous class presents an example of generation by spontaneous fision or gem- mation, but these modes of reproduction are common in the Acrite division. The planariae among the sterelmintha are capable of indefinite multiplication by simple division; and the medusae are stated to pro- duce, not ova, but ciliated locomotive gem- mules or internal buds. The various examples of these plant-like modes of generation which the polypi and polygastrica present are fa- miliar to most persons, and will be especially treated of under their respective articles. The fissiparous and gemmiparous modes of reproduction are not, however, the exclusive modes by which the Acrite classes are perpetu- ated. Most of the sterelmintha are propagated by means of ova : in the cystica and cestoi- dea, the generative organs consist of ovaries alone, or are cryptandrous ; in the tremato da, a fecundating gland is superadded to the ovary; while in the acanthocephala the sexes are separate, so that thus early in the animal kingdom, we find typified all the different modes of generation by which the race is con- tinued in the higher classes of animals. The different conditions of the important organic systems which are thus seen to obtain in the great group of animals called Radiata and Zoophyta fully justify a partition of the group corresponding with those differ- ences. For the lower organized division we retain the name proposed by Macleay, but ex- tend its application to the acalephae ; and thus constituted it may be characterized as follows. Sub-kingdom ACRITA. Gelatinous polymor- phous animals, without distinct nervous fibre, or visceral cavities. Alimentary canal excavated in the parenchyma of the body, generally without an anus. SanguiJ'erous system composed of reticulate canals without proper tunics. Generation in most fissiparous or gemmi- parous ; in some oviparous.-^ The Acrita have been termed Protozoa, as * Rudolph! terms one species echinorhynchus vasculosus, from this circumstance. Synopsis Ento- zoonun, p. 581. t The definition of the Acrita given by Macleay is confessedly a negative one as referred to animals j it is as follows : being on the first step of animal organization. They are analogous to the ova or germs of the higher classes, and have, therefore, been termed by Carus Oozoa ; and as the changes of the embryo succeed each other with a rapidity proportionate to the proximity of the ovum to the commencement of its development, so also we find that in each class of Acrita there are genera which advance into close approximation with some one or other of the classes belong- ing to the higher divisions of the animal king- dom. It results, therefore, from this tendency to ascend in the scale of organization that there is greater difficulty in assigning constant or gene- ral organic characters to the Acrita than to any of the higher divisions of animals. Even in the nervous system, we find as we are led step by step from the hydra to the actinia in the class Polypi, that the nervous globules begin to manifest the filamentary arrangement about the oral orifice in the last named genus. That, again, in tracing the successive complica- tion of the sterelmintha from the hydatid to the echinorhynchus we also come to perceive traces of longitudinal nervous filaments in the latter highly organized genus of parenchymatous worms. In the acalephae the examples of the ag- gregate form of the nervous system would seem to be more numerous and distinct. Ehrenberg has detected what he considers as a nervous sys- tem in a gelatinous medusa; and Dr. Grant has recently described a nervous collar giving off simple filaments in the more highly or- ganized beroe, which, in its distinct intestine and anal outlet, recedes too far from the medu- sidae to be placed in a natural arrangement in the same class. Many of the polygastrica are endowed with simple visual organs or ocelli, in the form of red or yellow spots; similar organs of a dark colour are exhibited by the planariae, and Nordmann also describes them in some internal parasitic trematoda. Ehren- berg has recently discovered coloured ocelli in a medusa, and he ascribes a sense of taste to the polygastrica. The indications, however, of the special senses in the Acrita are feeble and obscure, and in the least doubtful instances the organs are evidently of the simplest and most elementary nature. For the most part all the different systems seem blended together, and the homogeneous granular parenchyma possesses many functions in common. Where a distinct organ is eliminated it is often repeated indefinitely in the same individual. Thus in the polypi the nutritious tubes of one individual are generally supplied by numerous mouths, and it has, consequently, the semblance tf Animalia gelatinosa polymorpha, interaneis nullis medullaque indistincta. " Os interdum indistinctum, sed nutritio absorp- tioue externa vel interna semper sistit. Anus nullus. " Reproductio fissipara vel gemmipara, gemmis modo exteris, modo internis, interdum acervatis. " Pleraque ex individuis pluribus semper cohae- rentibus animalia composita sistunt." Horae Ento- mologicae, ii. p. 224. See also Lamarck, Anim. saas Vertebres, ii. p. 2. ADHESION. of a composite animal ; the polygastrica derive their name from an analogous multiplication of the digestive organ itself. Among the sterel- niintha vve find instances where the generative system is the subject of a similar repetition, each joint of the lamia 1 being the seat of aseparate ovary, though all are nourished by continua- tions of one simple system of nutritious tubes. The calcareous and siliceous sponges, again, which, in eliminating the first sketch of an in- ternal earthy skeleton, seem to lose the few characteristics of animal life which they before possessed, are limited to the repetition of a simple spiculum. The formative energies of the Acrita being thus expended on a few simple operations, and not concentrated on the perfect development of any single organ, it is not surprising that the different classes should exhibit the greatest diversity of external figure.* But it has been well observed that Nature, so far from forgetting order, has, at the commencement of her work, in these imperfect animals given us a sketch of the different forms which she intended after- wards to adopt for the whole animal kingdom. Thus in the soft, sluggish sterelmintha we have the outline of the mollusca ; in the fleshy living mass which sui rounds the earthy hollow axis of the polypi natantes, she has sketched a verte- brated animal ; and in the crustaceous covering of the living mass, and the structure more or less articulated of the polypi vaginati we trace the form of the annulose or articulate classes. (Richard Owen.) ADHESION, ('from ad-hoerere, Lat. adhesio, Fr. adherence, Germ, wiederanheilung, Ital. ade- sione, ) that process, by the occurrence of which, when two living surfaces, naturally or artifi- cially separated the one from the other, are brought into mediate or immediate contact, and inflammation is developed, those surfaces may become adherent the one to the other. This adhesion may be effected either by the intervention of a stratum of exhaled fibrino- albuminous matter, inorganic in the first in- stance, but at a subsequent period acquiring organization, and becoming a perfect and per- manent cellular bond of union ; or it may not occur until after suppuration has been estab- lished and granulating surfaces are presented ; these surfaces enter into adhesion, and in this case the bond of union is not so decidedly cellular in character as in the former; it is more or less dense and fibro-cellular. In either case, the medium of union pre- sents peculiar modifications dependent upon the tissue on which it is developed. This circum- stance, and especially the deposition of osseous matter, where bony union is required, was one of the strongest arguments used for the purpose of establishing the existence of the presiding intelligent principle of Stahl. If the first process, that in which the fibrino- albuminous exhalation obtains, be interfered with, that is, if a more intense degree of in- " Macleay, ibid, p. 123. flammation be developed, such exhalation can no longer occur, but the second state, that in which a purulent exhalation shall be the pro- duct, may be induced. It is upon tli is principle, viz. that a certain quantity of inflammation shall predispose to the first species of union, which is termed union by the first intention ; and that a greater quantity may produce a purulent exhalation, and therefore be opposed to such union, that is founded the following precept. " When it is deemed prudent to prevent union by the first intention, we have merely to introduce between the surfaces, and retain there from eighteen to twenty-four hours a piece of lint, by which a sufficient degree of inflammation will, usually, be excited to ensure a suppurating surface." From the time when the phenomena of in- flammation were first carefully studied, until very recently, it has been commonly, if not uni- versally maintained, that adhesion could never be accomplished in the absence of inflamma- tion. In the present day, Breschet* and some others have endeavoured to establish that adhesion does not, necessarily, imply the pre-existence or co-existence of inflammation ; and as it appears to me upon very insufficient evidence. They say that adhesion may result from a " primitive disposition of the organization" and as evi- dence of the existence of this disposition, they refer to certain congenital affections, occlusion of the eyelids, and of the lachrymal canal, irnperforations of the mouth, the anus, and so on. Why they should assume that phenomena, the mechanism of which appears identical, should be effected by a totally different agency in intra and in extra-uterine life, it is not easy to understand, and I believe such is not the fact. We may have certain of these occlusions, accomplished in extra-uterine life, but never without the intervention of inflammation ; and what possible reason have we for supposing that if these occlusions do commonly, nay always, occur in consequence of the develop- ment of inflammatory action, that this agency shall be wanting during uterine life ? None, I apprehend, beyond simple assumption. Imperforation of the eyelids and occlusion of the lachrymal canal differ from imperfora- tion of the mouth and of the anus, in that the former result, not from the presence of an anomalous membrane, but only from the union of existing membranes, which are normally separated the one from the other. In the greater number of cases the eyelids are simply adherent, either at one or many points, or along the whole length of their border, and I would say are always so in consequence of inflammation. The other imperforations to which allusion has been made, are dissimilar to those of the eyelids. Imperforation of canals opening upon the surface of the body is a case in which, al- most always, there has been an arrest of de- velopment ; all the canals which in the adult are lined by a mucous membrane, continuous with the skin at their orifice, are naturally, at * Diet, de Med. art. Adherence. 50 ADHESION. a certain epoch of embryo life, imperforate. These organic states, which nosologists have so often considered as diseases, are, therefore, simply primitive conditions preserved by ano- maly, and become permanent instead of tran- sient.* It may, therefore, be inferred that the greater number of cases adduced as evidence of adhesion in intra-uterine life are not in point, and if they were it may still be asserted, and the assertion be borne out by analogy, that they had not occurred in the absence of inflammation. John Hunter seems to have had the idea that adhesion may occur in the absence of inflam- mation in certain cases, namely, in those where blood has been effused, that this blood may become organized and form a bond of union. He says, " It does not seem necessary that both surfaces, which are to be united, should be in a state of inflammation for the purpose of effecting an union ; it appears only necessary that one should be in such a state, which is to furnish the materials, viz. to throw out the coagulating lymph, and the opposite unin- flamed surface accepts simply of the union ; nor is it even necessary that either surface should be in a state of inflammation to admit of union : we often find adhesions of parts which can hardly be called inflamed ."f I believe that no solution of continuity can be obliterated in the absence of inflammation, the injury which has occasioned the solution of continuity, and the effusion of blood, being sufficient to excite inflammation. The only circumstance under which it seems to me to be possible that union could be produced in the absence of inflammation, is one which can only rarely occur; and even then, although the possibility of the occurrence can hardly be denied, its reality may be reasonably ques- tioned. If a portion of blood, for instance, be effused into a serous cavity, its colouring matter is, after a time, removed, and a fibrino- albuminous coagulum remains. This coagulum coming in contact with a previously uninflamed serous membrane, may become united to this membrane : and it is believed by some pa- thologists that this union occurs without the supervention of inflammation. Another si- tuation where it is believed by certain patho- logists that union is produced by similar means, is in a portion of artery included be- tween two ligatures, the blood which has been included between the two points undergoing a similar change to that which I have already described, and adhesion of the clot to the in- ternal tunic of the artery being effected in the absence of inflammation. Such cases may carry conviction to the mind of a superficial observer, but a more careful in- vestigation will lead to an opposite conclusion. My own observations induce me to think, that of all the causes by which adhesive inflam- mation of serous membranes maybe produced, the most remarkable perhaps is an extravasation * Isid. Geoff. St. Hilaire, Hist, des Anomalies de 1'Oreanization, t. i. p. 532. t On the Blood and Inflam. Ed. 1828, p. 319. of blood into their cavities, which appears to excite just the precise quantity of inflammation necessary for the production of adhesion. If we examine the point at which such coagula are maintained in contact with serous mem- branes, before perfect union is established, we shall find between the coagulum and the mem- branes a stratum of exhaled matter, the exist- ence of which would lead to the conclusion that the clot has excited in the membrane as much inflammation as is necessary for the pro- duction of such exhalation. In solutions of continuity where blood has been effused between the edges, it was main- tained by John Hunter* that this blood was the provisional bond of union ; this, I appre- hend, is not the case. Whether protected from the atmospheric air, which appears to exercise a very decided influence in decomposing it, as in some fractures, or directly exposed to it, as in ordinary solutions of continuity, this coagu- lum never, during the early periods, adheres with sufficient firmness to attach to each other the borders of a wound If, however, any por- tion of the coagulum remain after a fibrino- albuminous exhalation has been formed upon the divided surfaces, it may become in this way organised, and permanently adherent. After the preceding remarks, it will therefore be held in this article that whenever an adhe- sion has been effected between two surfaces, naturally or artificially separated, that that adhesion must have taken place through the in- tervention of inflammation ; that inflammation arrived at a certain height will be accompanied by afibrino-albuminous exhalation; that if the inflammation be carried beyond that point, a purulent secretion may be established, and when this is developed, union, by what is termed the first intention, cannot occur ; granu- lations are then developed, and union by what is termed the second intention, may follow. The process by which each kind of union is effected I shall now proceed to describe in de- tail. In all cases, whether two naturally separate tissues are to be united, or whether a solution of continuity is to be repaired, there appears to be a certain uniformity in the means by which the union is accomplished. Inflammation is developed, and a material susceptible of or- ganization is exhaled, which becomes the con- necting medium. This matter in its greatest state of simplicity is exuded under the form of lymph, upon the surface of the parts to be united ; it is coagulated, and transformed into a soft pulp ; it gradually increases in density, acquires a reticular or porous aspect, a first rudiment of organization, and as a second de- gree exhibits in its substance red spots, then striae, which have the appearance of vascular ramifications, and at last bloodvessels. It is hardly possible to collect this lymph in a state of purity except in the canal of an artery where it has been exhaled between two ligatures. It is then presented under the form of a whitish matter, of a soft and fibrinous consistence, which * Loc. cit. p. 253. ADHESION. is rendered particularly evident when the lymph is submitted to the action of boiling water ; it dissolves almost completely in a warm solution of caustic potash, though less promptly than thickened albumen, but more rapidly than fibrine. This matter, which is probably the same with that by which all parts of the body are nourished and preserved, but in the case before us secreted in increased quantity and preserving a strong tendency to coagulate, has nothing in it which is necessarily opposed to the healthy action of the animal economy. In fact we may consider exudation as a nutrition, much exalted by in- flammatory action, which is itself only an exaltation of the vital properties. We may admit four periods or states of change to which this material which consti- tutes the medium of adhesion is subject a first, the period of development; a second, a period of increase ; a third, that of organi- zation; and a fourth, that of mutation; in which it is changed into a cellular tissue. In the first period, we find that in twenty- four, and sometimes even in nineteen hours after we have irritated a serous membrane, the pleura of a dog, or of a rabbit for instance, that this membrane is much injected, and that there has been formed upon its surface an extremely thin, pulpy stratum, which may very easily be removed : the second period commences when this exudation has assumed a membraniform appearance, and is characterized by an aug- mentation of thickness and of density : the third period is characterised by still greater density and the presence of vessels. Stoll believed that these membranes might become organised in twelve, nine, or even eight days after the inva- sion of the disease. Home believed that vessels might appear in twenty-four hours. In the fourth period, the membrane loses some of its thickness, and every day assumes more and more of the appearance of cellular tissue ; and when perfected, there is not only identity of appearance between cellular tissue and these membranes, but also, according to Laennec,* identity of use, and even of disease, except that this tissue very rarely contains adi- pose matter, f Nothing in our subject is more curious or more important than the organisation of these membranes ; their vessels are thin, delicate, and similar to those of the pia mater ; their form and their direction are extremely simple ; they are not tortuous, and they proceed, usually, in fasciculi, almost like the lymphatics of the extremities. We may easily convince ourselves that their formation is sometimes very prompt, by the perusal of the following case. A por- tion of strangulated intestine, which, after the incision of the herniary sac, did not present many bloodvessels, was examined after the death of the individual, which occurred in twenty-nine hours after the operation, by Sir Everard Home : he found the portion of in- * De 1'Auscultation Mediate, torn. ii. p. 293. t Laennec states that he has " quelquefois " seen fat developed in these cellular laminae. Loc. cit. ED. testine which had been strangulated profoundly inflamed, and covered in many points by a " layer of coagulable lymph :" this intestine was injected with very fine size, and two small bloodvessels were found passing along through the new membrane into which the injection had penetrated. According to Laennec* we may observe the following phases in the organisation of these membranes. The rudiments of bloodvessels are at first presented under the form of striae of blood, which are more voluminous than the vessels by which they are to be succeeded. The blood appears to have penetrated into the tissue of the membrane, as if pushed by a strong injection ; yet in examining the points of the membrane,on which the layer of" coagulable lymph " is depo- sited, we find no destruction, nor any orifice of a vessel, but only spots of blood. Soon, ac- cording to Laennec, " these lines of blood take a cylindrical form, and ramify in the manner of bloodvessels, still preserving a considerable diameter. If, at this epoch, we carefully ex- amine them, we find that these vessels have an external coat which is soft, and formed of blood scarcely concrete, to which they owe their colour. After having incised this coat, we withdraw a sort of mould, or rounded fasci- cular body, whitish and fibrous, evidently formed of concrete fibrine, and of which the centre appears perforated and permeable to the blood. Uowever small be the canal, it is these fibrous fasciculi which should, by thinning, form the tunics of the bloodvessels." These delicate observations have not, so far as I know, been confirmed by other observers : those authors who have spoken of newly deve- loped vessels, among whom we may name Hunter, Monro, Soemmering, do not speak of this mode of development. Hunter and Home explain it differently; they say there is at first a formation of small ampullae, containing only a colourless fluid : second, a union of these ampullae, and production of a vascular net- work, not yet supplied with blood : third, an inosculation between the newly developed vessels, and those of the inflamed membrane, and next the ingress of blood. Beclard was of the same opinion.f Gendrin thinks that the new vessels are developed by the action of the primitive vessels ; he says, " that the blood is excreted by the adjoining capillaries, opening into the soft and fibrinous tissue deposited in the inflamed part; this blood becomes concrete, and the vascular impulsion, a tergo, being con- tinued, new blood is pushed into it and hollows it. Thus the little vascular rudiment is pro- longed into an irregular, flexuous, and unequal stria, which meets another and unites with it, continuing in this way to prolong itself into the least resistent portion of the fibrinous de- position. "J To some extent the opinions of Laennec and * Loc. cit. t Anat. Generale, p. 195. t Hist. Anat. des Inflam. torn. ii. $ 1303. and 1571. E 2 ADHESION. Gendrin are alike ; they believe that the forma- tion of the new vessel consisted in this, that the little clot was perforated, and that it was pene- trated by liquid blood. The experiments of Brande* would, however, lead to a different conclusion ; he shewed that the air contained in the blood had much in- fluence in the formation of bloodvessels. This air is carbonic acid gas, and its quantity appears to be nearly equal in the two kinds of blood ; being estimated at a cubic inch for every ounce of blood. This gas maybe separated from the blood by the air-pump, and it escapes with a kind of bubbling or effervescence, causing the ascent of the mercury in a barometer attached to the apparatus. It has been remarked that during the coagu- lation of the blood, a large quantity of carbonic acid gas escapes; this coagulation, observed under the microscope, has shewn that the gas, by escaping in all directions, forms a net-work of canals, the branches of which anastomose with each other ; and that this net-work pre- serves its form after desiccation. It has also been established that it is this gas which forms those canals in coagulated blood ; because, if by means of the air-pump we deprive the blood of it, before it is coagulated, they do not occur. Sir E. Home has even injected the vessels which were developed in the coagulum soon after the blood was taken from a vein. If the formation of new vessels occur even in a coa- gulum of blood removed from the living body, but preserving still a certain quantity of its heat, and of its vitality, with more reason might we expect that a similar phenomenon should obtain during life : and this fact has been de- monstrated by experiments performed on a rabbit, in which had been produced a hemor- rhage from a small branch of the mesenteric artery : after twenty-four hours, the coagulum which was formed was injected. The formation of vessels in coagulated blood, by means of the carbonic acid gas which tra- verses it in all directions, is in perfect accord- ance with the observations which have been made by M. Bauer upon germinating wheat, which were instituted for the purpose of shewing the influence of the globule of air. These globules are manifested below a bud of mucilaginous substance ; they push it forward, elongate it, and thus form a filament. I do not, however, believe that either of these theories correctly explains the pheno- menon. It was for a long time believed that false membranes were never organised ; that nature had given to the parts of our economy an almost unlimited power of development, but not the faculty of communicating life to the products of the circulation; that false mem- branes appeared to be organised only because they constituted a kind of frame-work through which vessels from the inflamed tissue might be prolonged : ulterior observations, however, have shewn that these media are really or- ganised. We have no general rules as to the time when such organisation shall commence. It seems to be dependent upon inexplicable individual dispositions. It may, however, be remarked, that the greatest analogy exists be- tween the mode of development of vessels in these media of adhesion and their mode of production in the membrane of the yolk in the chick, saving always this remarkable circum- stance, namely, the inconstancy, the irregu- larity of the work of organisation in the former, and, on the contrary, the constancy and the regularity of the occurrence in the latter case. These media are in fact secreted by a tissue, the vitality of which is exalted to a certain extent, and it appears to impress upon the pro- duct of its secretion a commencement of vitality, as in generation. All these circumstances ap- pear to me to demonstrate that these vessels are the product of a spontaneous generation a true epigenesis ; so indeed, to a certain extent, thought Hunter. lie says, " In a vast number of instances I have observed, that in the sub- stance of the extravasation there were a great number of spots of red blood, so that it looked mottled. The same appearance was very ob- servable on the surface of separation between the old substance and the new, a good deal like petechial spots. Was this blood extra- vasated along with the coagulating lymph ? In this case I should rather have supposed it would have been more diffused. I have there- fore suspected parts have the power of making vessels, and red blood, independent of the circulation."* If the inflammation be not strictly confined to that state in which the albumino-fibrinous exhalation is accomplished, but proceeds to the next stage, the exhalation entirely changes character ; pus is produced, a granulating sur- face is developed, and union is accomplished by the intervention of another tissue, and by a slower process than that which we have already described. This is the process which is always observed in mucous membranes, scarcely ever in serous; for in the former, the albumino-fibri- nous matter never becomes organised, and can therefore never be the medium of a permanent union. In these membranes, if adhesion occur, the inflammation must proceed to the succeed- ing stage. Adhesion of mucous membranes, however, does not often occur it is not com- patible with the performance of their functions. Soon after the secretion of pus is established granulations are developed, and a state favour- able to adhesion is produced. The develop- ment of granulations occurs in the following manner : upon the surface, about to suppurate, is exuded a layer of" coagulable lymph ;" this lymph becomes penetrated by bloodvessels, nerves, and absorbents, which give birth to granulations. These granulations are developed much earlier in some tissues than in others in a stump, for instance, we see them first upon the cellular tissue, then upon the mus- cular, then the fibrous, and lastly upon the osseous tissue : they appear to form as much Phil. Trans. 1818. pp. 172 and 185. * Loc. cit. pp. 388-9. ADHESION. more readily as the tissue may be more cellular and vascular. That these organs are very va.s- cular is evident from the rapidity with which they bleed upon the slightest contact ; that they contain nerves is shewn by the pain which is produced in them by the slighest touch : does not their prompt destruction by slight causes seem to indicate the existence of absor- bents / No one has made more interesting researches into the nature of these bodies than Sir Everard Uome.* lie carefully observed the changes which occurred in an ulcer of the leg. By using a lens which enlarged objects eight times, he saw that granulations were formed in the fol- lowing manner : first, is seen a mass of capil- lary vessels differently arranged ; secondly, small sinuosities containing pus. The ulcer ob- served during ten minutes, offered, in the first place, an extremely thin and transparent pel- licle, under which were disengaged globules of gas, then canals having a horizontal direction, and containing blood. The tunics of these vessels were so delicate that they were ruptured by the simple motion of the leg. These canals anastomose with each other, taking different directions ; those which are developed the first were the next day changed into true vessels. Soon these new vessels have enough of solidity to admit of our passing a needle under them and raising without rupturing them. The forma- tion of all these parts is due, according to Home, to the coagulation of pus, and the de- velopment of carbonic acid gas ; " for if the puriform matter be wiped off, these phenomena are not produced." \Vhen, on the contrary, he employed substances, calculated to coagulate the pus, the formation of those vessels was accelerated. He concludes from his experiments that bloodvessels are developed, almost as it were under the eye of the observer ; that they are not a prolongation of pre-existing vessels ; that they are formed independently of the action of the subjacent solid parts. So far, therefore, although the processes may differ, yet the general points of union between the two modes is singularly similar. While suppuration is proceeding, another operation is in progress under the layer of gra- nulations. A stratum of cellular tissue, at first simple and not very resistent, afterwards fibro- cellular, and lastly fibrous, is organised insensi- bly to serve as the base of the succeeding me- dium of union. When granular surfaces are brought into con- tact, and the tendency to secrete pus has ceased, they enter into adhesion. This tendency is marked by a diminution of activity in the gra- nulations; the membrane ceases to secrete pus, and the granulations become firmer and con- tracted : before union can be effected, the sup- purating surface must, therefore, change its nature must be destroyed. A state like that in simple union by the first intention is produced ; the secretion becomes plastic, and somewhat analogous to that which accompanies that mode of union. * Home on Ulcers. When these new tissues or media of union are developed between surfaces naturally free, the structure of the two portions of the organ between which they are seated becomes changed. In serous or mucous membranes, as well as in those surfaces which are immediate modifica- tions of these two systems, this may be ob- served. When, for example, the pleura costalis becomes adherent to the pleura pulmonalis, the point of union is no longer a serous membrane ; the free surface having disappeared, an un- interrupted continuity is established between the subserous cellular tissue of the pleura cos- talis, and the interlobular cellular tissue of the lung. This conversion is frequent in the peri- toneum ; in the tunica vaginalis a similar effect is produced by the common operation for hy- drocele ; in synovial membranes a similar effect occurs in what is termed false ankylosis. Having described the general laws by which the phenomena of adhesion are governed, 1 shall now point out, generally, the modifica- tions which are impressed upon it in different tissues. It is upon serous membranes that we may with most advantage study the process of ad- hesion, not only because it is more rapidly developed there, but because it much more frequently occurs there than in other tissues. If we examine the surfaces of two such mem- branes which have been recently united, com- mencing at a certain distance from the point of adhesion, we see the layer of coagulable matter effused between the two surfaces become thinner as we approach the point of contact. If the adhesion be sufficiently recent to admit of our separating the surfaces, we see the intermediate layer tearing, but remaining adherent to the inflamed surfaces. If the inflammation be more advanced, and the pseudo-membrane be more dense and organised, we find that the very thin layer of new deposition by which the union has place is more resistent than the thicker layer of organisable matter by which it is surrounded ; and at a later period we may discover vascular filaments attaching the ad- herent portion of the new tissue to that upon which it has been developed. These filaments are as much more evident as the adhesion is more immediate : of this we may very easily assure ourselves by cutting transversely two portions of digestive tube which have become to a certain extent adherent by their external tunic. The adhesion may be already veiy solid at the points where contact is so imme- diate that we can scarcely distinguish the in- terposed matter. Very delicate red capillaries creep through this matter, whilst perhaps at the distance of some lines, and even at the centre of an already organised point, the contact having been less immediate, a plastic layer of one, two, or more lines in thickness, may be seen uniting the surfaces, but not presenting either the solidity or the organisation of the exces- sively thin layer which adjoins it. When these adhesions have existed for a cer- tain time, the serous structure completely dis- appears. This destruction of serous membranes at the adherent point is very evident around 54 ADHESION. herniae which have been inflamed ; the intestines engaged in the tumour are enveloped by a more or less dense layer of cellular tissue ; and hence many herniae thus circumstanced have been described as having no hernial sac. This sac has, however, originally existed, but has disappeared by the adhesions which have been formed between it and the displaced organs, adhesions by which the cellular tissue which replaces the serous membrane has been deve- loped. If we consider these adhesions in relation to their frequency in the serous cavities, we see that they exist most frequently in the pleura, existing in nearly half the adult bodies ex- amined. After the pleura comes the perito- neum, then the pericardium ; those of the tunica vaginalis are less common, but the arachnoid is, of all serous membranes, especially relative to its extent, that where these adhesions are most unfrequent. The absence of mobility appears singularly to favour this phenomenon : thus in the pleura they most frequently occupy the superior parts, and in the peritoneum most frequently occur between the viscera forming a hernia, and be- tween the convex surface of the liver and the diaphragm. The membranes between which such adhe- sions occur, must usually, of course, be in intimate relation, the one with the other during the time when the process is in progress of accomplishment, though now and then the distance is considerable ; but they may after- wards become separated to great distances : those cellular bands which are so commonly seen in the thorax are evidences of this fact. Some circumstances tend to demonstrate that these bands in serous structure may at a certain period of their existence be absorbed and disappear, and the secreting surface be reproduced. M. Ribes states that occasi- onally we do not find any trace of such bands, nor any adhesion in the peritoneum of persons who have had penetrating wounds of the ab- domen. Beclard examined an insane person who had several times stabbed himself in the abdomen. At the points where the more recent of these wounds had been inflicted considerable adhesions were found; beneath the older cicatrices no vestige of adhesion was found. A case of artificial anus occurred in the practice of M. Dupuytren, by which faecal matter passed during twelve days. The pa- tient died at the end of seven months. At the examination after death, it was found that the portion of intestine in which the accidental opening had existed, was distant from the ab- dominal cicatrix between four and five inches. A very attenuated cellular band extended from the cicatrix to the portion of intestine. Doubt- less a short time would have sufficed for the absorption of this band, when the intestine would have been set at liberty and the serous surface restored. In the course of lectures which Bichat de- livered only a few months before his death, he maintained that adhesion was never pro- duced between mucous surfaces, and that con- sequently the cavities lined by this tissue were never obliterated. Few statements have given rise to more extensive discussion than this ; few discussions have up to the present moment been attended by less satisfactory results. In his first dictum I believe he was clearly right, in the second as clearly wrong. Mr. Hunter's opinion was in accordance with that of Bichat : he says, " that in all the outlets of the body called mucous membranes, the order of inflammation differs from that which occurs in cellular membrane, or in cir- cumscribed cavities. In these latter adhesive inflammation is immediately admitted to ex- clude, if possible, suppuration," In internal canals, where adhesions would in most cases prove hurtful, the parts run immediately into the suppurative inflammation, the adhesive in- flammation being in common excluded.* Mucous membranes, when unchanged by disease, are not capable of becoming adherent the one to the other, and the reason of this is simple. 1 have already stated that no per- manent adhesion can occur in the living body without the intervention of a new tissue, which at a certain indefinite or undetermined period of its existence becomes organized. A pseudo-membrane of considerable extent may be thrown out upon an inflamed mucous surface; but this membrane, 1 apprehend, never becomes organised, and union between mucous surfaces cannot therefore be permanent unless some other agency be called into action. But, as soon as inflammation has destroyed the characters from which these membranes derive their name ; when the mucus, which like an inorganic layer appears to oppose itself so successfully against immediate contact, thereby preventing the organization of the effused mat- ter, no longer exists ; when the cellular element which forms the basis of this membrane is developed, then adhesion by means of the union of granular surfaces is effected with the greatest facility ; of this we have evidence in most of the mucous canals. It is not rare, for instance, to meet with complete obliteration of the vagina, of the cystic duct, and so on. It is stated very generally that the opinion of Bichat is entirely unfounded ; that inflam- mation of the vagina is followed by complete occlusion, without destruction or transforma- tion of the mucous membrane, and that similar effects may occur in the Fallopian tubes, the uterus, and other mucous canals. That these are produced is perfectly true, but never until the disorganization to which I have alluded has occurred. It is maintained triumphantly as a con- firmation of the opinion that no transformation occurs, that when these adhesions are sepa- rated, we have the healthy mucous membrane performing its functions as before. This, how- ever, is not the case ; the membrane is essen- tially different, and it is not without difficulty that we can overcome its tendency to enter into adhesion again. That a membrane is pro- duced, which performs functions analogous to * Loc. cit. p. 305. ADIPOCERE. the primitive membrane, is true. If we ex- amine a fistulous canal which has existed for a certain time, we find it invested by a mem- brane similar in appearance, and performing an analogous function to the primitive mucous membrane, so rapidly does nature under cer- tain circumstances adapt an organ to the per- formance of the function to which it is des- tined. As it is therefore upon the organization of this pseudo-membrane that the species of union of which I am treating is dependent, some re- mark upon that subject becomes necessary. It has been maintained by Albers, Suemmering, andLarrey, that these new formations upon mu- cous membranes may become organized. The former of these gentlemen believes that the false membrane of croup is commonly organ- ized. Soemmering, it is said, possessed pre- parations which demonstrated the fact. Cail- leau* supports this opinion, as well as Vil- lermef and Guersent.J I have never seen this membrane present the slightest vestige of organization, nor have I ever found any one, with the exceptions I have named, who has, although, to my knowledge, they have been sought for during many years, by a number of the most competent observers of the present day. And as I believe the investigations of morbid phenomena are more accurately made at present than at any former period, I adhere to the opinion that organization of these mem- branes upon mucous surfaces never occurs; and that union by " the first intention " can never occur in those canals which are invested by mucous membrane. But when the com- position of the mucous membrane becomes destroyed or disorganized by inflammation, and a granular surface is presented, adhesion may be and is frequently produced. The epidermis with which the skin is fur- nished forms an inorganic stratum which is opposed to all adhesion; but remove this epidermis, render the surface bleeding, or sup- purating, and adhesion may be produced with the greatest facility. It is against this ten- dency we have constantly to struggle for the purpose of preventing the adhesion of fingers to each other, to the palm of the hand, and so on, so common a consequence of burns. Adhesion may in this tissue occur, therefore, by the development of the fibrino-albuminous medium, or by that of granulations. The synovial membrane of joints may become adherent, constituting a species of ankylosis, which is termed " false." In these cases the secretion of synovia diminishes and ultimately ceases, the contiguous surfaces lose their polish, become rugous, and contract adhesions. (See JOINTS.) In osseous tissues, adhesion may be effected either through the agency of the albumino-fibrinous exhalation already de- scribed, or that of granulations. (See BONE.) In cartilaginous tissues the mechanism of ad- * Rapport du Concours sur le Croup. t Diet, des Sc. Med. torn, xxxii. p. 260. t Diet, de Med art. Croup. hesion is different ; and in speaking of the process in these tissues, it is necessary to di- vide the tissue into those which are invested by a more or less dense fibrous perichondrium, and those which are without it. To the first appertain the cartilages of the ribs, of the larynx, and all those which Bichat termed fibro- cartilages. The second class comprehend the diarthrodial. It is in fact, I believe, upon the presence or absence of the perichondrium, that are dependent the principal differences which are presented in the pathological condition of these organs. The non-diarthrodial as well as the fibro-cartilages, when they are ruptured or divided, are not united by a cartilaginous substance. In the wounds of cartilages, with loss of substance, there is formed a kind of cellulous matter, which is a secretion from the perichon- drium ; in fact no phenomena of reproduction are observed where this membrane does not exist ; thus it is never observed in diarthrodial cartilages. We may cut and mutilate these latter, and after many days we shall find the wound almost as it was on the first day. When the cartilages of the ribs are ruptured, their union is often effected by an osseous ring which surrounds the two fragments. See the articles ARTERY, ENCEPHALON, NERVE, FI- BROUS TISSUE, MUSCLE, VEIN, for the pheno- mena of adhesion in these structures. BIBLIOGRAPHY. Freeke, on the art of healing, cicatrising, incarning, &c. 8vo. Lond. 1748. Bezoet, De modo quo natura solutum redintegrat. 4to. Lugd. Batav. 1763. (Rcc. in Sandifort Thes. Diss. vol. iii. p. 147.) Spallanzani, Prodromo, &c. sopra la reproduzione animali, 4to. Modena, 1768. Ejus, Opiiscoli de fisica, &c. 2 vol. 8vo. Modena. 1776. Eyting, De consolidatione vulnerum. 4to. Argent. 1770. Moore, On the process of nature in the filling up of cavities, healing wounds, &c. 4to. Lond. 1789. Nannoni, De Similium partium corp. hum. constit. regeneratione. (In Roemeri Delect. Opusc. Ital. vol. i.) Arnemann, Versuche neber die Regeneration an lebenden Thieren. 8vo. Gotting. 1782. Murray, De redintegratione partium, &c. 8vo. Cassel, 1786. Bell, Discourses on wounds. 8vo. Edin. 17951812. Balfour, Obs. on Adhe- sion. 8vo. Lond. 1815. Stoll, Ratio Medendi, pars v. & vii.8vo. Vienna, 1768. Hunter on the Blood, Inflammation, &c. Bichat, Anatomie Gen. Beclard, ditto. Breschet, Diet, de Med. art. Adherence. Cruveilhier, Diet, de Med. et Chir. Prat. art. Adhesions. Laennec, De 1' Auscultation Mediate, torn. ii. pp. 111. et seq. Brande, in Phil. Trans. 1818. Gendrin, Hist. Anat. des Infl. passim. 2 torn. Paris, 1826. Andral's Pathological Ana- tomy. Home on Ulcers. 8vo. Lond. 1801. (Benjamin Phillips,) ADIPOCERE, from adeps and cera: a term given to a peculiar fatty matter, somewhat re- sembling spermaceti in appearance, and sup- posed to partake of the properties of fat and wax. In the year 1789, Fourcroy communi- cated to the Royal Academy of Sciences at Paris a curious account of the changes sus- tained by the human bodies interred in the cemetery of the Innocents in that city; some of these had been piled, for a succession of years, closely upon each other, in large cavities containing from one thousand to fifteen hundred ADIPOSE TISSUE. individuals. One of these graves, opened in Fourcroy's presence, had been full, and closed for fifteen years. When the coffins were opened, the bodies appeared shrunk and flattened, and the soft solids were converted into a brittle cheesy matter, which softened and felt greasy when rubbed between the fingers. The bones were brittle ; and the texture of the abdominal and thoracic viscera no longer discernible, but lumps of fatty matter occupied their places. It is not uncommon to find masses of this adipocere in the refuse of dissecting-rooms, especially when heaps of such offal are thrown into pits and wells, and suffered gradually to decay. The carcases of cats and dogs and other drowned animals also often exhibit more or less of a similar change ; and Dr. Gibbes (Phil. Trans. 1794) found that lean beef, se- cured in a running stream, underwent a change into fat in the course of three weeks. Fat, and the adipose parts of animals, also undergo a change in appearance and composition under similar circumstances: tallow becomes brittle and pulverulent, and may be rubbed between the fingers into a white soapy powder.* Gay Lussac, Chevreul, and some other emi- nent chemists, conceive that muscular fibre, skin, &c. is not convertible into adipocere, but that this compound results entirely from the fat originally present in the substance, and that the fibrin is completely destroyed by putrefaction. There are cases, however, in which the conversion of muscle and of fibrin into fat can scarcely be doubted, (Annals of Philosophy, xii. 41,) though the propriety of applying the term adipo- cere to such fatty matter may be questionable. The action of very dilute nitric acid upon some of the modifications of albumen is also attended by their conversion into an adipose substance. The chemical properties usually ascribed to adipocere are the following: it fuses at a tem- perature below 100; it dissolves in boiling alcohol, and the greater portion is deposited as the solution cools; the action of ether resembles that of alcohol ; it is saponified by the fixed alkalies, but not by ammonia. It would ap- pear, however, from Chevreul's experiments, that adipocere is not a mere modification of fat, or a simple product, but that it is a soap composed of margaric acid and ammonia. These combinations of adipose substances and their further chemical history will be given under the article FAT. BIBLIOGRAPHY. Fourcroy,Acad.Rle.des Sciences de Paris, 1787. Gibbes, Conversion of animal muscle into a substance resembling spermaceti. Phil. Trans. 1794. Conversion of animal sub- stances into fatty matter. Phil. Trans. 1795. Vide also'Annules de Chimie, t. v. 154 ; t. viii. 17 72 ; Crell's chemische Annalen for 1792 and 1794 : and John's Tabellcn. 1. B. p. 35. ( W. T. Brande.) * If a portion of the fatty degeneration of the liver be immersed for some time in water, it will furnish an excellent specimen of adipocere. The writer of this note had lately an opportunity of observing the process of the conversion of a large portion of liver into this substance. R. B. T. ADIPOSE TISSUE. (Lat. Telaadiposa Fr. tissu adipeux, tissu graisseux, Germ, das Fttt, Ital. adipe. Many of the old anatomists, as Mondini, Berenger, Vesalius, and Spigelius, represent the fat (adeps vel pinguedo) of the animal body as entirely distinct from the membrana carnosa, or cellular membrane. The separate existence of a proper adipose membrane, however, si- tuate between the skin and the filamentous tissue, or membrana carnosa, was first taught by Malpighi, then distinctly maintained by De Bergen and Morgagni, and finally demon- strated by William Hunter. Collins, James Keill, and other anatomists adopted the views of Malpighi, and Haller was disposed latterly to imitate De Bergen and Morgagni, in assigning to the fat of the animal body a situation dis- tinct from that of the cellular membrane. And in this country the independent existence of the adipose membrane was recognized by Bromfield, John Hunter, and others. It was still, however, confounded with that of the filamentous tissue under the general name of cellular membrane, adipose mem- brane, and cellular fat, by Winslow, Dionis, Portal, Sabatier, Bichat, and Meckel, and described as a variety or modification of the cellular membrane; and Blumenbach considers it as a secretion into that membrane. Its dis- tinct existence from the cellular membrane was finally admitted by M. Beclard, and its anato- mical and physiological relations as well as its chemical properties have been since minutely investigated by M. Raspail. According to the dissections of De Bergen and Morgagni, the demonstrations of Hunter, and the observations of M. Beclard, the struc- ture of the adipose membrane consists of rounded packets or parcels (pelotom) separated from each other by furrows of various depth, of a figure irregularly ovoidal, or spheroidal, va- rying in diameter from a line to half an inch, according to the degree of obesity in the part submitted to examination. Each packet is composed of small spheroidal particles which may be easily separated by dissection, and which are said to consist of an assemblage of vesicular bags still more minute, aggregated together by very delicate filamentous tissue. These were originally described by Malpighi under the name of membranous sacculi, and by Morgagni under that of sacculi pinguedi- nosi. The appearance of these ultimate vesicular pouches is minutely described by Wolff in the subcutaneous fat, and by Clopton Havers* and the first Monro in the marrow of bones, in which the two last authors compare them to strings of minute pearls. If the fat with which these vesicles are generally distended should disappear, as happens in dropsy, consumption, chronic dysentery, and other wasting diseases, the vesicular sacs collapse, their cavity is obli- terated, and they are confounded with the con- * Osteologia Nova, Lond. 1691, and Obs. Nov. de Ossibus, Amst. 1731. ADIPOSE TISSUE. tiguous cellular tissue without leaving any trace of their existence. Hunter, however, asserts that in such cir- cumstances the cellular tissue differs from the tissue of adipose vesicles in containing no similar cavities, remarks that the latter is much more fleshy and ligamentous than the fila- mentous tissue, and contends that though the adipose vesicles are empty and collapsed, they still exist. When the skin is dissected from the adipose membrane, it is always possible to distinguish the latter from the filamentous tissue, even if it contain no fat, by the tough- ness of its fibres and the coarseness of the web which they make. The distinguishing characters between the cellular or filamentous and the adipose tissue may be stated in the following manner. First, the vesicles of the adipose membrane are closed all round, and, unlike the cellular tissue, they cannot be generally penetrated by fluids which are made to enter them. If the temperature of a portion of adipose membrane be raised by means of warm water to the liquefying point of the contents, they will remain un- moved so long as the structure of the vesicles is not injured by the heat. If again an adi- pose packet be exposed to a solar heat of 104 Fahrenheit, though the fat be completely lique- fied, not a drop will escape until the vesicles are divided or otherwise opened, when it ap- pears in abundance. The adipose matter, therefore, though fluid or semifluid in the living body, does not, like dropsical infiltra- tion, obey the impulse of gravity. Secondly, the adipose vesicles do not form, like cellular tissue, a continuous whole, but are simply in mutual contiguity. This arrangement is de- monstrated by actual inspection, but becomes more conspicuous in the case of dropsical effu- sions, when the filamentous tissue interposed between the adipose molecules is completely infiltrated while the latter are entirely unaf- fected. Thirdly, the anatomical situation of the adipose tissue is different from that of the filamentous tissue. The former is found, 1st, in a considerable layer extended immediately beneath the skin ; 2dly, in the trunk and ex- tremities round the large vessels and nerves ; 3dly, between the serous and muscular tissues of the heart ; 4thly, between the peritoneal folds which form the omentum and mesentery ; 5thly, round each kidney; and, Gthly, in cer- tain folds of the synovial membranes without the articular capsules. In each of these situations it varies in quan- tity and physical properties. In the least cor- pulent persons a portion of fat is deposited in the adipose membrane of the cheeks, orbits, palms of the hands, soles of the feet, pulp of the fingers and toes, flexures of the joints, round the kidney, beneath the cardiac serous membrane, and between the layers of the me- sentery and omentum. In the more corpulent, and chiefly in females, it is found not merely in these situations, but extended in a layer of some thickness, almost uniformly over the whole person; but is very abundant in the neck, breasts, belly, mons Verier is, and flexures of the joints. It has been long observed that the subcu- taneous adipose layer presents considerable differences from the adipose matter found be- tween the folds of the serous membranes ; and the older anatomists, aware of these differences, distinguished the former by the name of pin- ft uc do, and the latter by that of xebuiti. The subcutaneous adipose membrane is, when viewed as a whole, more elastic, softer, and less granular than the omental fat, and evi- dently presents the arrangement of vesicular bags much more distinctly than the omental. It is in the subcutaneous adipose membrane indeed, almost exclusively, that the vesicular arrangement can be recognized. The subcu- taneous cellular fat also contains a greater quantity of oil than the omental, which abounds chiefly in firm, brittle, granular fat. The situation where the vesicular structure of the adipose membrane is most easily de- monstrated is in the hips between the skin and the gluteal muscles, and at the flexures of the joints generally. In the former situation especially, the constituent fibres of the vesi- cular bags are tough, firm, and ligamentous, and the bags themselves are large and distinct. It is a remarkable anatomical character of the sebaceous or tallow-like fat that its distri- bution is confined chiefly to the external or commutual surfaces of several of the serous membranes; and this arrangement presents a series of interesting anatomical analogies. Thus sebaceous fat is found on the external surface of the pleura costalis, between it and the inter- costal muscles, and between the layers at the posterior and anterior mediastinum. It is also found between the cardiac pericardium and the muscular substance of the heart, especially around the vessels of the organ. In some of the large mammalia even this circumstance is connected with peculiar anatomical appear- ances. Thus, in the heart of the dolphin ( del- p/iinus tursio) we find the cardiac pericardium formed into broad prominent fringes, consisting each of two folds of the membrane, between which is interposed a considerable quantity of sebaceous fat. In the same manner the several amenta, or peritoneal duplicatures in the abdo- men, may be recognized as analogous fringes containing more or less sebaceous fat; and the omental appendages (appendices epiploictz) of the colon must be regarded as examples of the same arrangement. Lastly, in the interior of the articular capsules we find the synovial membranes forming large prominent fringes, which, if immersed in water, show to what extent they are made to recede from the cap- sule and bone, and forming cavities of dupli- cation in which sebaceous matter is contained. It thus appears that none of the serous mem- branes is exactly applied either to the parietes of cavities or to the surface of the contained organs, but that they form intervals on their outer or attached surfaces, on which various quantities of sebaceous fat are deposited. In all these substance^ we do not recognize the 58 ADIPOSE TISSUE. same distinct arrangement of an appropriate organ, but simply masses of adipose, or rather sebaceous matter, interposed between the at- tached surface of the serous membranes and the adjoining or the contained organs. Fat occurs in a third modification in the marrow of bones. The adipose granules, which are soft, whitish-yellow, and oleaginous, are here contained in a peculiar membrano-cellular web, forming numerous vesicles, which may be regarded as an ultra-osseous adipose tissue. It is a remarkable proof of the influence of the vital principle that during life the substance of the bones is never tinged with this animal oil, but the moment life is extinct, the marrow begins to transude and impart to the bones a yellow tint and a greasy aspect. Fat, though chiefly observed to occur in the bodies of animals, is nevertheless not confined solely to these bodies. Thus not only do va- rious kinds of oil and consistent oleaginous matter occur in certain vegetables, but sub- stances similar even to tallow are found in some vegetable productions. A sort of tallow is obtained from the Valeria Indie a, a forest-tree of the camphor family, indigenous in the Indian Archipelago. In a species of croton indigenous in China, namely, the croton sebiferum of Linnaeus, the stillingia of Mi- chaux, or tallow-tree, the seeds are covered with a quantity of fat, bearing so close a re- semblance in all its properties to tallow, that it is used by the Chinese in the manufacture of candles ; and the fruits of the aleurites triloba, a native of the Sandwicli Islands, of the same natural family with the croton, are the candle- nuts of the inhabitants of these remote regions. It is chiefly in the subcutaneous layer that the organization of the adipose membrane has been investigated. The constituent vesicles or bags consist of firm, tenacious, ligamentous, gray, or whitish-gray coloured substance, mu- tually united by means of delicate filamentous tissue. These vesicles or sacs receive arterial and venous branches, the arrangement of which has been described by various authors, from Malpighi, who gave the first accurate account, to Mascagni, to whom we are indebted for the most recent. According to Malpighi,* the bloodvessels divide into minute ramifications, to the extremities of which are attached the membranous sacs, containing the globules of fat so as to bear some resemblance to the leaves attached to the footstalks of trees. These ve- sicular or saccular arteries are afterwards di- vided into more minute vessels, which then form upon the vesicular sacs a delicate vascular network. According to Mascagni, who repre- sents these vessels in accurate delineations, the furrow or space between each packet con- tains an artery and vein, which, being subdi- vided, penetrates between minute grains or adi- pose particles, of which the packet is composed, and furnishes each component granule with a small artery and vein. The effect of this ar- rangement is that each individual grain or adipose particle is supported by its artery and vein as by a footstalk or peduncle, and those of the same packet are kept together not only by contact, but by the community of ramifications from the same vessel. These grains are so closely attached that Mascagni, who examined them with a good lens, compares them to a cluster of fish-spawn. Grutzmacher found much the same arrangement in the grains and vesicles of the marrow of bones.* It has been supposed that the adipose tissue receives nervous filaments; and Mascagni con- ceives he has demonstrated its lymphatics. Both points, however, are so problematical, that of neither of these tissues is the distribution known. The substance contained in these vesicles is entirely inorganic. Always solid in the dead body, it has been represented as being fluid during life, by Winslow, Haller, Portal, Bichat, and most authors on anatomy. The last writer, indeed, states that under the skin it is more consistent, and that in various living animals he never found it so fluid as is represented. The truth is that in the human body, and in most mammiferous animals during life, the fat is neither fluid nor semifluid. It is simply soft, yielding, and compressible, with a slight degree of transparency, or rather translucence. This is easily established by observing it during incisions through the adipose membrane, either in the human body or in the lower animals. The internal or sebaceous fat, however, espe- cially that interposed between the fat of the serous membranes, is much more consistent and solid. The reason of these differences will be understood from what is now to be stated re- garding the proximate principles of animal fat. The microscopical and atomical structure of fat has recently formed the subject of investi- gation by M. Raspail.f By placing a portion of lacerated fat upon a sieve, with an earthen vessel below it, and directing upon it a stream of water, numerous amylaceous granules are de- tached and pass through the sieve, and after foiling to the bottom of the water afterwards rise to the surface, in the form of a crystalline powder, as white as snow. When these par- ticles are collected by scumming, and dried, they form a starchy powder, though soft and somewhat oleaginous to the touch, and which does not reflect the light in a manner so cry- stalline as an amylaceous deposit does. According to M. Raspail,' when examined microscopically, these granules present forms and dimensions varying in different animals, in the same animal and even in animals of dif- ferent ages, but in all clearly resembling grains of fecula. In the human body these particles are polyhedral and not susceptible of isolation. As they are more fluid also than in other animals, it is necessary to immerse the portion subjected to examination in nitric acid or liquor potasses, either of which has the effect of consolidating the inclosed or central portion * De Qmento, Pinguedine, et Adiposis Ductibus, p. 41. * De Ossium Medulla, Lips. 1758. t Repertoire Generale d'Anat. 1827. ADIPOSE TISSUE. of each granule, and disintegrating the granules by the contraction of chemical agency. The borders of these granules appear by refracted light a little fringed an effect which M. Ras- pail attributes to the corrosive action of the nitric acid. When magnified to 100 diameters, they ap- pear like irregular hexaedral or pentaedral bodies, from two to four lines in diameter, and all accurately fitted or conjoined to each other. The actual diameter of these granules in the adult human subject varies according to Ras- pail from .00117 to .00562 of an English inch. In youth and infancy they are stated to be still smaller. The chief point to bear in remembrance is that the adipose tissue consists of two distinct parts, one a vital organic and secreting part, the other an inorganic and secreted product, which is void of vital principle. The chemical constitution of fat has been investigated by Chevreul, Braconnot, and more recently by M. Raspail. According to the researches of M. Chevreul fat consists essentially of two proximate principles, stearine (arsae.^, sebum, sapo,j and elainc, (gXatov, oleum.} The former is a solid substance, colourless, tasteless, and almost inodorous, soluble in alcohol, and pre- serving its solidity at a temperature of 176 Fahrenheit. Elaine, on the contrary, though colourless, or at most of a yellow tint, and lighter than water, is fluid at a temperature of from 63o to 65 Fahrenheit, and is greatly more soluble in alcohol. To the presence of stearine in a large proportion, the intra-serous sebaceous fat owes its solidity and firmness ; whereas the elasticity and softness of the sub- cutaneous adipose tissue, and the marrow, depend upon the predominance of elaine. It is farther important to attend to the ele- mentary composition of fat. Each variety of fat consists of carbon, hydrogen, and oxygen ; and a few, as hog's lard, blubber, nut oil, and almond oil, contain a small trace of azote. The proportion of the carbon is greatest and varies in general from 7-10ths to 4-5ths of the whole. The proportion of hydrogen varies from l-10th to l-5th. That of oxygen varies from four or five parts in the hundred to 12 and 13. It appears, therefore, that fat and each of its constituent principles are a highly carbonaceous animal substance. Little doubt can be entertained that animal fat is the result of a process of secretion. But it is no easy matter to determine the mode in which this is effected. Previous to the time of Malpighi it was a very general opinion that the blood exuding from the vessels was con- verted into adipose matter. This fancy was refuted by Malpighi, who, departing, however, from strict observation, imagined a set of ducts, (ductus adiposi) issuing from glands, in which he conceived the fat to be elaborated and pre- pared. To this fancy he appears to have been led by his study of the lymphatic glands, and inability to comprehend how the process of secretion could be accomplished by arteries only. The doctrine, though embraced by Perrault, Collins, and Hartsoecher, was over- thrown by the strong arguments which Ruysch deduced from his injections; and Malpighi afterwards acknowledged its weakness and re- nounced it. In short, neither the glands nor the ducts of the adipose membrane have ever been seen, unless we admit the testimony of the Members of the Parisian Academy, who state that they saw them in the civet cat, and to this we must oppose the fact that Morgagni, by anatomical evidence, disproved their ex- istence. Winslow, though willing to adopt the notion of Malpighi, admits, nevertheless, that the particular organ, by which the fat is sepa- rated from the blood, is unknown. Haller, on the contrary, aware of the permeability of the arteries, and inferring from the phenomena of injections either of watery liquors or melted tallow, their direct communication with the cells of the adipose tissue, and trusting to the testimony of Matpighi, Ruysch, Glisson, and Morgagni, that fat exists in the arterial blood, saw no difficulty in the doctrine of secretion, or rather of a process of separation ; and upon much the same grounds is this opinion adopted by Portal. Bichat, again, contends that no fat can be recognized in the arterial blood, and justly adduces the fact, that none can be dis- tinguished in blood drawn from the temporal artery. To the accuracy of this fact I can bear direct testimony, having repeatedly ex- amined with the view of recognizing the buffy coat, and detecting oily particles, blood, which I had drawn from this vessel, the latter sub- stance invariably without success. In wounds in the human body during life, and living animals, oily particles may be seen floating on the surface of the blood ; but these, it may be said, proceed from the division of the adipose vesicles; and hence it has been inferred that the arterial blood contains no adipose or olea- ginous matter. It may be doubted, however, whether facts of this kind are adequate to prove whether adipose or oily matter does not naturally exist in the blood, and both from the experiments of Chevreul, and those of Lecanu and Boudet it appears that small quantities of adipose or puriloid matter may be obtained from this fluid. M. Chevreul, for example, shows that fatty matter may be obtained from the fibrine of arterial blood ; and from a series of elabo- rate and accurate experiments, estimates the quantity of fatty matter in fibrine at from four to five per cent.* Lecanu and Boudet have also recently shown that crystals of pearly- coloured matter having the characters of an adipose substance exist in, and may be ob- tained in small proportion from the serum of the blood .f These inferences apply, according to the authors, to blood in its healthy state. In certain states of the system the blood drawn from the veins has presented serum of an opaque or milky appearance, and which has been proved to depend on the presence of adipose or oleaginous matter. Thus, indepen- dent of opaque or milky serum noticed by * Journal de Physiol. torn. iv. p. 119. t Journal dc Pharmacia, 1830-33. 60 ADIPOSE TISSUE. Schenke, Tulpius, Morgagni, and others, Hewson and several cotemporary observers remarked instances of opacity and milkiness of the serum of the blood, and from ocular inspection as well as experiment and obser- vation, inferred that these appearances arose from the presence of oil in the blood or its serum. Soon after Dr. Gregory, in his Con- spectus, or View of the Institutions of Medicine, was led to infer apparently from the fact stated by Hewson, that in persons in whom the serum was opaque or milky, this depends on the presence of fat which is undergoing ab- sorption, or resumption into the system. This representation, however, was entirely conjec- tural ; and no direct proof of the fact that oil does exist in certain states in the venous blood was given till Dr. Traill, in 1821 and 1823, furnished accurate chemical evidence on the point. The inferences of Dr. Traill have been since confirmed by the experiments of Dr. Christison, who found that milky serum con- tains oleaginous or adipose matter, consisting of the two adipose principles elairie and stearine.* The general conclusions, therefore, that may be deduced from the facts now stated are that in the healthy state adipose matter in small proportion exists in the fibrine of the blood, and in a still smaller portion in the serum ; and that in certain morbid conditions of the system, in which there is any process of mis- nutrition or paratrophia, oily matter in con- siderable quantity may be found in the blood, either in consequence of absorption or non- deposition. To account, however, for the secretion of adipose matter, it is not absolutely requisite to prove that oleaginous or adipose matter exists in the circulating fluid. Even were it ascer- tained that oil or adipose matter does not exist, or cannot be detected in any of the elements of healthy blopd, the fact would not form a stronger argument against its formation from that fluid, than in the case of several other principles which enter into the composition of the animal tissues, and which nevertheless do not exist in the blood. Thus neither gela- tine, which exists abundantly in skin, tendon, cartilage, ligament, and bone, nor osmazome, which is found in muscle, are contained in healthy blood. But we know that the chemical element of these substances exist in the blood, and we farther know that gelatine consists very nearly of the same chemical elements as albu- men ; and we must infer, therefore, that it is the faculty of the living tissues or vessels to arrange these elements in that manner and proportion in which they may constitute re- spectively gelatine and osmazome. The same reasoning may be applied to explain the for- mation of fat in the adipose tissue. Its ele- ments already exist in the blood, and the living agency of the tissue seems all that is requisite to effect its deposition. Its composition and history would also show that it is a secreted product which consists of superfluous chemical * Edin. Med. and Sure. Journal, vol. xxxiii. P . 274. elements not required in the formation of the albuminous and gelatinous tissues. On this subject the interesting experiments of Berard* and Dobereinerf may, perhaps, fur- nish some intelligible means of illustration. The former chemist found that by mixing one measure of carbonic acid, ten measures of carburetted hydrogen, and twenty of hydrogen, and transmitting the mixture through a red-hot tube, he procured artificially several white crystals which were insoluble in water, soluble in alcohol, and fusible by heat into an oily fluid. The latter chemist prepared a similar substance from a mixture of coal-gas and aque- ous vapour. It may therefore be inferred that while ani- mal fat is chiefly a combination of bicarbonated hydrogen with oxygen, or, in other words, a highly carburetted hydrate of oxygen, and con- tains either little or no azote, it is the animal substance which makes the nearest approach in chemical constitution to the vegetable prin- ciples. So close, indeed, is this approxima- tion that Raspail thinks it may be in this re- pect compared with starch; and as the different forms of fecula are prepared by the vegetable tissues for the nutritious stores of the vegetable during the process of development, he ob- serves that, in like manner, fat is deposited whenever the nutritious function is in excess in the animal organs. It was a singular fancy of Fourcroy that the deposition of fat in animal bodies was in- tended as a sort of vent for the superfluous and unnecessary proportion of hydrogen, since the idea is at variance with chemical facts ; and it is not less singular that such a hypothesis should receive any countenance from Blumen- bach. Carbon is the principle which predo- minates most largely in fat ; and if any atten- tion is to be given to such views, the adipose tissue ought to be regarded as the outlet for superfluous carbonaceous matter, or at least carbonaceous matter in a much larger pro- portion than hydrogen and oxygen. The pro- per physiological view, however, of this ques- tion appears to be, that as the tissues of the animal body consist chiefly of carbon, hy- drogen, oxygen, and azote united in variable proportions, and as most of these tissues either contain or seem to require azote, the adipose appears to be destined to receive whatever carbon, hydrogen, and oxygen, are not re- quired to be united with the azote, in the forma- tion of the albuminous, the gelatinous, or the albumino-gelatinous tissues. On the mechanism of the deposition of fat we possess no exact information. But various facts may tend to throw some light on the cir- cumstances under which it takes place, and the history of the state of the adipose tissue at different periods of life is instructive. In the foetus the adipose tissue contains a sort of whitish, solid, granular matter, which resembles adipocere rather than genuine fat. * Ann. de Chimic, 1817, t. v. p. 290. t Zur Pncumatischcn Phytochcmie, 8vo. Jena. 1822. ADIPOSE TISSUE. 61 Thus it is less oleaginous, and more brittle and friable than true fat. In the infant this layer continues the same in quantity, but a little more oleaginous, till the period at which the individual begins to exert the muscles of loco- motion. The fat then rapidly diminishes in quantity, and after the child has begun to walk and run, the fat has almost entirely dis- appeared from most parts of the adipose tissue, except the orbits, cheeks, neck, buttocks and the flexures of the joints ; but even in these regions it is much less abundant and much more consistent. The marrow presents similar changes. The bones of the foetus are void of a distinct me- dullary canal, and present merely a reddish, homogeneous, vascular pulp, some\vhat con- sistent, but presenting soft compressible por- tions. This state continues some time after birth. As the individual passes from infancy to childhood, the interior of the bone is formed into cancelli, adipose or oleaginous matter is deposited in the intra-osseous tissue within the cancelli, and as the vessels of the medullary membrane gradually mould the medullary canal, this oleaginous matter is most abun- dantly deposited in the interior of the cylin- drical bones. The marrow, however, is much less oleaginous, and more like a pulpy paste than it is in the adult. During the periods of boyhood and youth fat continues very sparing in the adipose tissue, and especially in the male sex. After puberty, however, it becomes more abundant, especially in females. After this period the deposition of fat depends more or less on the habits of the individual, as to eating and drinking and corporeal exertion. In general the deposition of fat becomes more copious and general after the age of forty or forty-two than previously. From these several facts it appears to result that fat is to be regarded as a secretion by the capillary vessels of the adipose tissue from the blood, and that the tissue and its vessels are to be distinguished from the fat or the matter secreted in the relation of vital agents and organic products. Upon the whole the idea of Haller as modified by Mascagni regarding the origin of the fat appears to be the most probable, viz. that, while the arteries secrete an imperfectly formed oily fluid, the thinner parts are absorbed either by lymphatics or by veins, and the residue is left in a more con- sistent and solid form. I think, in conclusion, that, taking all the circumstances already stated into consideration, it may be inferred that adipose matter, or its constituent elements exist in the blood, chiefly as complementary elements of the albuminous, gelatinous, osmazomatous, or gelatino-albu- minous principles employed in the nutrition of the several tissues ; and that, as the carbon, hydrogen, oxygen, and azote are employed in the formation of the latter tissues, the great excess of carbon, and the smaller excess of hy- drogen and oxygen, not employed in the for- mation of these tissues are arranged by the capillaries in such proportions as to form adi- pose matter; and that this adipose matter, though fluid, when first formed, becomes more consistent and fixed after deposition in its appropriate tissues. The pathological conditions of the ad i pom: tissue. \. Inflammation. From various facts, and especially, observing the phenomena of certain cases of what have been denominated diffuse inflammation of the cellular membrane, 1 for- merly inferred that the peculiar phenomena of certain intense and malignant forms of this disorder, depend on inflammation not of the cellular membrane, but of the adipose tissue. This conjecture I have since had opportunities of completely verifying as to certain, if not the majority of cases of diffuse inflammation. a. In cases of diffuse inflammation affecting the arm, the inflammation has spread along the adipose membrane, producing sero-puru- lent suppuration and sloughs of the adipose tissue. In cases of inflammation at the verge of the anus, the disease spreads along in the same manner, and affects, almost exclusively, the adipose tissue around the anus and rectum, and along the gluttei muscles. It is in the same manner that the adipose cushion, with which the bloodvessels are surrounded, is oc- casionally the seat of a species of bad inflam- matory action terminating in fetid and sloughy suppuration. That these forms of diffuse inflammation truly depend on inflammation of the adipose membrane, I must further maintain, from the fact that the disease occurs not only in the ex- ternal adipose cushion, but in the internal or sebaceous fat. I have seen an example of in- flammation in the adipose cushion surrounding the left kidney, in which the whole of this substance was converted into an ash-coloured, fetid, semifluid pulp, mixed with shreddy fila- ments, and in which this suppurative slough- ing process had opened a passage from the fat of the left kidney into the interior of the trans- verse arch of the colon. The instance of in- flammation and subsequent mortification of the adipose membrane surrounding both kidneys, detailed by Dr. Thomas Turner, in the fourth volume of the Transactions of the College of Physicians in London, is an example of the same species of disease. In the case witnessed by my- self, the disease gave rise to the usual symptoms said to attend diffuse inflammation. Though no great degree of pain was felt, the pulse was quick and small, the tongue brown and dry, the countenance dingy and lurid, and the eyes heavy, the bowels difficult to be affected by medicine, the urine scanty and high-coloured, and at length suppressed ; and the patient, after muttering delirium and typhomania on the second day of the attack, with subsultus tendi- num, passed into a comatose state, which ter- minated on the fourth day in death. h. This doctrine further does not rest upon evidence deduced from the mere symptomatic characters of the disorder. In fatal instances of diffuse inflammation, we find the adipose membrane not only partially mortified and suppurated, but that part of it adjoining to the skin and to the bloodvessels very much loaded, 62 ADIPOSE TISSUE. with injected vessels containing dark-coloured blood. c. It is chiefly in the corpulent, either by habit or by age, that this disease assumes its most exquisite, intense, and unmanageable forms. In persons of this description, who it is matter of common observation are generally not only plethoric but bloated, and liable to imperfect circulation, and disorders of the cir- culation and secretions generally, and in whom very slight causes often induce serious disor- ders, the adipose tissue appears to lose a great proportion of the small degree of vital energy which it possesses, and the more abundant its secreted product is, the less active are its vessels and the inherent properties of the membrane. In consequence of this greatly impaired energy, slight causes, as cold, injury, punctures, &c. produce suddenly a complete loss of circula- tion and action in the tissue ; for it is not in- creased but diminished action ; and this im- paired energy continues, until the natural func- tions of the tissue become extinct. It is thus that the secreted or inorganic matter of the adipose tissue becomes, as it were, a cause of strangulation of the tissue itself, or at least leads so directly to suppress the energies of its organic part, that it is incapable of resisting morbific agents of ordinary power, and hence the organic part either may be smitten with immediate death or is very easily made to assume a very low and imperfect form of mor- bid action, which speedily terminates in death. On this subject it is further proper to ob- serve that Mr. Bromfield, surgeon to St. George's Hospital, who sixty years ago main- tained the distinct characters and situation of the adipose membrane from the cellular, taught also that the former was liable to inflammation, but erroneously imagined that this inflamma- tion was of the circumscribed kind only.* 2. Hemorrhage. Effusion of blood into the adipose tissue is not very common. It is ob- served in the same circumstances nearly in which it occurs in the filamentous tissue. Thus it has been seen in land and sea-scurvy. Hux- harn observed it in fevers with petechial erup- tions. And Cleghorn states that one of the appearances after death in the continuous and malignant tertians of Minorca was extravasa- tion of blood in the form of black patches in the adipose layer of the mesentery, omentum, and colon. 3. Excessive deposition. In certain subjects, and in peculiar circumstances, the quantity de- posited is enormous. The average weight of the human subject at a medium size is about 160 pounds, or between eleven and twelve stones. Yet instances are on record of its attaining, by deposition of fat in the adipose membrane, the extraordinary weight of 510 and 600 pounds, or from thirty-five to forty stones. Cheyne mentions a case in which the weight was 448 pounds, equal to thirty-two stones. In the Philosophical Transactions are recorded two cases of persons so corpulent, that one weighed 480 pounds and another 500 pounds. * Chirurgical Observations, vol. i. p. 94. And the Breslau Collections contain cases in which the human body weighed 580 and 600 pounds. In females and in eunuchs it is more abun- dant than in males ; in females deprived of the ovaries it is more abundant than in those pos- sessed of these organs ; and it is well known that sterility is frequent among the corpulent of both sexes. In some circumstances this accu- mulation may be so great as to constitute dis- ease, (polysarcia adiposa of several nosolo- gists); and in other circumstances the deposi- tion of fat is a means which the secreting system seems to employ to relieve fulness and tension of the vessels, and if not to cure, at least to obviate morbid states of the circula- tion. (Parry.) Accumulations of fat are said to take place in some animals in a few hours in certain states of the atmosphere. During a fog of twenty-four hours continuance, thrushes, wheat-ears, ortolans, and red-breasts are report- ed to become so fat that they are unable to fly from the sportsman. (Bichat.) 4. Extreme diminution. The diminution or disappearance of fat is much more frequent than its extraordinary abundance. This dimi- nution is said to depend on one or other of the following causes. 1st. Long abstinence, as in fasting, and the periodical sleep of dormant animals ; 2d, organic diseases, as consumption, cancer, disease of the liver, of the heart, ulce- ration of the intestines, &c. ; 3d, purulent col- lections or secretions ; 4th, leucophlegmatic and dropsical states ; 5th, gloomy and melan- choly thoughts or passions ; 6th, long and un- interrupted effort of the intellectual powers ; 7th, preternatural increase of the natural evacu- ations, as in cholera, diarrhoea, diabetes, &c. mucous discharges, especially from the pulmo- nary and intestinal membranes, as in chronic catarrh, inflammation of the intestines, and dysentery ; 8th, long and intense heat, whether natural, as during hot summers, or artificial, as in furnaces, hot-houses, &c. ; 9th, running, riding, and every species of fatiguing exercise long-continued, as is exemplied in the case of grooms at Newmarket, Doncaster, &c. ; 10th, states of long disease, not organic; llth, night- watching and want of sleep in general; 12th, immoderate use of spirituous liquors; 13th, habit of eating bitter and spiced or acid aliments. Yet even in these states the fat of the animal body is seldom entirely wasted. In several organic diseases, in which great emaciation takes place, a considerable quantity of fat is always found in the orbits behind the eyeball, round the substance of the heart, around the kidneys, in the colon, and in the mesentery and omentum. Thus one or both lungs may be extensively occupied by tubercles and indu- rated portions giving rise to the usual symptoms of pulmonary consumption terminating fatally, yet without removing the fat from the subcuta- neous layer of the chest and belly; and in various organic affections of the brain espe- cially, a considerable quantity of fat is found, not only in the subcutaneous layer, but at the outer surface of the serous membranes. ADIPOSE TISSUE. According to the observations of William Hunter, anasarcous dropsy is the only disease in which the fat of the adipose membrane is entirely consumed. " This disorder, when in- veterate, has that effect in such a degree, that we find the heart or mesentery in such subjects as free from fat as in the youngest children." This, however, is in some degree denied by Bichat, who contends that it is not uncommon to find much subcutaneous fat in subjects greatly infiltrated.* It is obvious that much will depend on the stage of the disease. It cannot be expected that the moment serous infiltration appears in the filamentous tissue, all the fat should be at once removed from the adipose. The process of absorption is gradual as is that of deposition ; and the infe- rence of Hunter may be regarded as nearly exact in reference to long-continued, or what he terms inveterate dropsy. It is certain, that while it is very difficult to deprive the bones of ordinary subjects of oil, those of dropsical sub- jects are the only ones which it is possible to obtain free from this substance. In certain diseases, especially those the ter- mination of which is attended with serous effusion into the cavities of the serous mem- brane, the fat is partly absorbed or may be converted into a sort of sero-gelatinous fluid. In chronic dysentery, for example, the subcu- taneous fat and that of the heart and omentum, in a great measure disappear, while in their place we find effused an orange-yellow coloured sero-albuminous fluid, of a jelly-like aspect, which coagulates on the application of heat or the addition of re-agents. In the bodies of those, also, cut off by scirrhous disorganization or cancerous ulceration, the greater part of the fat is in like manner absorbed, and in its place appears a dirty orange-yellow coloured sero- albuminous fluid. The removal of the fat from its containing membrane is effected by the process of absorp- tion, the agents of which are supposed by William Hunter, Portal, Bichat, and Mascagni, to be the lympathics. According to the results of the experiments of Magendie, Mayer, Tiede- mann and Gmelin, Segalas and others, it must, in some measure at least, be ascribed to the in- fluence of minute veins. It is a point of some interest to know in what form it is absorbed, whether as oily matter, or after undergoing a process of decomposition The observation of Dr. Traill, above quoted, would lead to the former view; but it is not easy to conceive that this should be uniform. We want, in short, correct facts on the point at issue. 5. Adipose sarcoma. This consists in an un- usual deposition of firm fatty matter in cells, the component fibres of which are sufficiently firm to give it consistence. The tumour, which is generally globular, is always surrounded by a thin capsule, formed by the condensation of the contiguous filamentous tissue. The tumour is supplied by a few bloodvessels, which pro- ceed from the capsule, but which form so '^nder an attachment that they are readily * Anat. Gen. vol. i. p. 57. broken, and the tumour is easily scooped from its seat. This sort of tumour occurs almost invariably in the adipose membrane, and seems to consist in a local hypertrophy of the part in which it is found. It may have a broad basis, but is often pendulous, or attached by a narrow neck or stalk. It is the most common form of sarcomatous tumour, and may occur in any part of the body in which there is adipose mem- brane, but is chiefly found on the front and back of the trunk, and not unfrequently on two places at the same time. 6. Steatoma. In adipose sarcoma the adi- pose matter is deposited in cells, and the tumour derives a degree of firmness from the fibres with which it is thus traversed in every direction. In other instances, however, the adipose matter is deposited in a mass in the cavity of a spherical or spheroidal cyst, formed in the filamentous or adipose tissue ; and the tumour is soft and compressible, and seems to contain fluid or semifluid matter. When cut open it is found to contain a soft semifluid matter of the consistence of honey, but of oily or adipose properties. In such circumstances the inner surface of the cyst, or at least the vessels of this surface, are the agents which secrete the fatty matter. This tumour may occur either in the filamentous or the adipose tissue, but is to be regarded as an example of local deposition of adipose matter. It may appear in any region of the filamentous tissue, but is most frequent about that of the head and face. Small steatoms are not unfrequent in the eyelids and in the scalp. Larger ones are more frequent about the neck. 7. Lipoma. This name was first applied by Littre to a wen or cyst, filled with soft matter, possessing the usual properties of ani- mal fat. The matter of steatom, according to this surgeon, is either not or imperfectly in- flammable, by reason of its degeneration or commixture with some other animal secretion. The propriety of this distinction has been de- nied by Louis and others, who maintain that these tumours differ in nothing, unless per- haps in degree. It has been favoured, never- theless, by Morgagni, and adopted by Plenck, Desault, Bichat, and various foreign surgeons, and is defended by Boyer, who represents the steatom as differing from llpoma in the matter being white, firm, and changed from its origi- nal character, and in possessing the tendency to degenerate into cancer. Plenck had previ- ously distinguished the llpoma by its being destitute of a cyst, a circumstance not required by Littre. Though thus admitted to differ, the anato- mical character, as given by Morgagni, and confirmed by Boyer, is in both nearly the same : a cyst, containing unchanged fat, or granular adipose matter, in cells formed by the original fibres of the adipose membrane, ac- cording to Morgagni, or those of the filamen- tous tissue, according to Boyer. At the base or stalk, in the case of pendulous steatom, the cells are compressed, but loose in the body of the tumour. This description, with the alleged cancerous 64 AGE. tendency, accords more with the characters of the adipose sarcoma than those of the genuine wen. Personal examination enables me to say, that, in the case of small steatoms of the scalp, eyelids, face, &c. no fibres of this kind are re- cognized ; and to such, if any distinction be adopted, the name of llpoma should be con- fined. In the case of such larger steatoms as 1 have seen in other regions of the body, though the contents are firmly connected together, and some filamentous threads may be seen here and there, or the tumour may even be separa- ble into masses, I have not been able to trace the distinct arrangement of cells, mentioned by Morgagni and Boyer. Weidmann mentions, that in one case the matter of steatom was a sort of liquefied fat, and in another firm and dense, and not divided into lobes or cells. The other forms of encysted tumours, distin- guished by the names of atheroma, (a0?&;^a, pulticula, ab oe,^tx,^oe.,pultis genus, ) and mtliceris (pefaKrigu;, met and cer, honey wax,) are to be viewed rather as varieties of the steatom than as generically different. The substance con- tained may differ in consistence, but is nearly the same in essential qualities. 8. Melanosis. The adipose membrane is a frequent seat of this singular deposition. The black or melanose matter is found in the sub- cutaneous adipose membrane, arid the subja- cent cellular tissue of the chest and belly ; it is not uncommon in the fat of the orbit ; it is very commonly seen in the adipose cushion on the forepart of the vertebral column, on that sur- rounding the kidneys, and in the fat of the anus and rectum ; it is found in the anterior and posterior mediastinum ; and it is found be- tween the folds of the mesentery, of the meso- colon, and of the omentum. It is also found in the substance of the marrow of bones ; and, perhaps, in most cases in which the osseous system appears to be stained with the melanose deposite, the dark matter may be traced to the medullary particles, the situation of which it is found accurately to occupy. In all these situations it appears in various degrees of perfection, and in different forms. It may be disseminated in black or inky spots, through the adipose membrane ; it may be ac- cumulated in spherical or spheroidal masses of various size and shape ; or it may be found in the form of brown or ebon-coloured fluid or semifluid, enclosed in a cyst formed of the contiguous tissue, more or less condensed. The melanose matter is entirely destitute of organization, and is to be regarded as the result of a peculiar secretion. No vessels have been traced into it; and when bodies affected with this deposite are minutely injected, the vessels can be traced no farther than the enveloping cyst. (Breschet.) It is also to be noticed that it is never deposited exactly in the site of orga- nic fibres, but always between them, and very generally in the precise situation of the adipose particles. These several circumstances show that the melanose disease consists not in a de- generation or conversion into another substance, but in the deposition of a new form of matter in the manner of a secretion. In what form the melanose substance is first deposited we have few accurate facts to enable us to form a judgment. Laennec is of opinion that it is first deposited in a solid form, and afterwards becomes fluid. The former he con- siders the stage of crudity, the latter that of softening (ramollisement.) Several facts, how- ever, would lead to the conclusion, that when first deposited it was fluid, and afterwards ac- quired consistence. Thus in several dissec- tions performed by Drs. Cullen and Carswell,* the matter of the small tumours, which are supposed to be of short duration, were found to be softest, and sometimes as fluid as cream. In like manner, in a case recorded by M. Chomel, in which the disease was found in the liver in the shape of large cysts, the melanose matter was more fluid in the centre than in the circumference of the cysts. Upon the whole, if the melanose deposite be, as is supposed, an inorganic secretion, the idea of its bring poured forth from the vessels at first in a fluid or semi- fluid state is most probable, and most consis- tent with the usual phenomena and laws of animal processes. BIBLIOGRAPHY. Mnlpighi, de omento, pingue- dine, et adiposis ductibus. Op. Omn. fol. Lond. 1686. C. A. De Berqen, Programma de Mem- brana Cellulosa in Haller Disp. Anat. Select, torn. iii. Haller, Elerae: ta Physiologiae, lib. i. sect. 4. W. Hunter, On Cellular Memb. in Med. Obs. and Inquiries, v.ii. p. 26. Bachiene, Diss. de Adipe humano, 4to. Ultraj. 1774. Janssen, Pin- guedinis Animalis consideratio. 8vo. L. B. 1784. Redhead, Diss. de Adipe. 8vo. Edinb. 1789. Vogel, Diss. sur la graisse. 8vo. Paris, 1806. Allmer, Diss. In. De pinguedine animali, 4to. Jena; 1823. Heusinger, System der Histologie. 8vo. Gruetz- macher, De Medulla Ossium. (Rec. in Haller. Disp, Anat. vol. vi.) Lorry, Sur la graisse (Mem. Soc. R. de Med. 1779. Kuhn, De pinguedine. 4to. Lips. 1825. Bedard, Anatomie Generate, p. 156. Chevreul, Rf.cherches Chimiqties sur les corps gras d'origin animale, 8vo. Paris, 1823 ; and Ma- gendie's Journ. de Phys. torn. iv. Raspail, in Repertoire Gen. d'Anat. torn. iii. et iv. et Nouveau Systeme de Chimie Organique, or Henderson's Translation. (David Cralgie.J AGE. (Lat. fctas. Gr. SiAma. Germ. Alter. Fr. age. Ital. eta.} This word, in its most extended sense, may express any period of duration. In reference to the human body it is used to denote either the whole time occu- pied by this system in passing through its several stages from birth to decay, or, in a more limited signification, that particular por- tion of existence commonly designated old age. It is in the former of these meanings that we employ the prefix to the following arti- cle ; in other words, we propose to give an account of the organic and functional changes which the human system undergoes, from the commencement of extra-uterine life to the period of its dissolution by natural decay. The term of human existence has been va- riously divided, and in many instances with a view to adapt its divisions to certain fanciful notions respecting the power of num- * Trans. Med. Chir. Soc. Edinb. vol. i. p. 264. AGE. bers; but the only rational principle on which we can distinguish certain definite periods, must be that of observing alterations in the condition of the whole body or of its several organs, and the correspondence which they bear to particular epochs. The old Aristo- telian division of human life into three stages, growth, maturity, and decline, is founded on this principle ; for, viewing man as a whole, the conditions in which he is an imperfect, a complete, or a declining member of his species, are well marked. But these conditions are capable of subdivision according to the changes which particular organs have undergone ; in other words, man, in the progress of his pcr- J'ectionnement, makes certain acquisitions in his structures and functions, and in his decline suffers certain losses and impairments ; the more striking of these additions to, or sub- tractions from his resources, suggest the well- known division of existence into infancy, boy- hood, puberty or adolescence, manhood, old age, and decrepitude. It is not our intention to discuss the subject of age by describing the characteristics of the stages last enumerated ; we think it better to take a view of the general revolutions which transpire in the human economy during growth, maturity, and decline, and under each of these heads to mention the changes which particular organs undergo in the course of time, without limiting ourselves to distinct stages, the determination of which must be, to a certain extent, arbitrary. The consideration of the alterations which take place in the body during its progress from infancy to manhood might very properly be preceded by some remarks on those ultimate processes which are essential to growth, viz. nutrition, secretion and absorption ; but, for information upon this interesting subject, the limits prescribed to this article compel us to re- fer the reader to that upon NUTRITION, in which the processes alluded to will be viewed in rela- tion not only to the development, but also to the maintenance, and to the decay of the tissues. On comparing a young with an adult animal we are at first struck by the difference in bulk ; but immediately afterwards our attention is attracted by the difference in their respective capabilities of action, a difference not merely proportionate to that of size. A closer ex- amination informs us, that in the infant many of the parts of the body are absolutely incomplete, as organs or instruments, and we proceed to in- vestigate whether this imperfection holds with all the organs or only with some of them; and if the latter be the case, whether the parts thus existing only in a rudimentary state belong to a particular class. Now, the organs and func- tions of man, in common with those of other animals, are divided into those which he shares with organic beings in general, and those which distinguish him as an animal ; the former subserving his own independent existence, the latter his existence in relation to external ob- jects of his consciousness ; these more or less subjected to the control of volition, those re- moved, under ordinary circumstances, from the VOL. I. government of this principle. Hence these tvro classes have been variously named organic and animal, nutritive and relative, automatic and voluntary ; and, as life is a term employed to designate the collective functions according- to some physiologists, or the cause of them ac- cording to others, we have organic life and animal life, &c., &c. But the animal functions are truly supplemental ; they could not subsist but by virtue of the organic ; while, on the other hand, the latter are perfectly capable of a separate existence, as in the vegetable world, or in those conditions of animal life in which its characteristics are all but suspended, such as profound sleep and apoplexy. Yet, al- though the functions of relation are thus de- pendent on those of nutrition, it is evident, at a moment's glance, that the latter viewed col- lectively in an animal structure, would present an aspect altogether incomplete, and different from that which we notice in the system of a vegetable. In the one case they were obviously intended to act only for themselves and for one another ; in the other they have an ulterior object to fulfil, but for which they would not have been called into existence and opera- tion; this object is the production and support of the functions that constitute the animal. If we now look at the new-born infant in con- trast with the full-grown man, we at once per- ceive that the essential difference between them has reference to the life of relations ; in other words, the immaturity of the former is not de- termined by the state of the vegetative organs, which, as organs, are perfect, but by the unde- veloped conditions of the parts which are to receive impressions from, and to re-act upon surrounding objects. Thus, on the one hand, we observe that the food adapted to the little being is rapidly converted into chyle, that the blood, after undergoing its requisite changes, performs its circuit freely and effectively, and that the activity of the nutritive, secernent, and absorbent processes is evidenced by the quick increase of growth, and by the abundant fluids contained in the various tissues. But, on turning to the relative functions, we find the case altogether reversed ; sensation is dull, faint, and flitting; voluntary motion scarcely ex- ceeds the amount necessary for obtaining nutri- ment from the parent ; while the demonstra- tions of intelligence are the very lowest com- patible with our belief in the possession of such a principle by the being in question. An examination of the organs devoted to these several actions leads to results in accordance with what we observe in the functions them- selves; in the one class the organization is complete, in the other much remains to be accomplished. If the apparatus of digestion be inspected, the parts employed in deglutition, viz., the tongue, pharynx, and oasophagus, will be found fully formed ; in the stomach the parts required for accommodating the aliment during its stay and for mixing certain fluids with it, are properly developed; no deficiency is observable in the structure of the liver and pancreas ; and the chyliferous vessels are pervious, extensile, and perhaps contractile. If AGE. we proceed to the organs of circulation, similar conditions are observable. In the heart the seve- ral cavities, valves, and fibrous arrangements are duly proportionate to each other, and possess such qualities of firmness, pliancy, extensibility and contractility as are required for receiving, expel- ling, agitating, and keeping in separate compart- ments the two different kinds of blood ; the arteries are found resistent enough to hold the blood within their calibres, and at the same time elastic enough to adapt themselves to the varying quantity of their contents, while the veins are found so organized both as to the muscularity of their coats, and to the perfection of their valves, as to be quite capable of con- veying the fluid back to the heart. Not less complete is the apparatus of respiration, whether we regard the development of the diaphragm, or the elasticity of the thorax, or the cellular and tubular arrangements in the lungs and their appendages. For affording the necessary conditions for the occurrence of those molecular motions which constitute deposition and absorption, and upon which secretion also depends, we find an infinite number of capillary tubes well formed for supplying the fluids from which new particles may be taken, and to which old ones may return, and so disposed as not to interfere with the action of any supposable chemical affinities. If we next direct our at- tention to the organs of the animal functions, an opposite set of facts will directly meet us. In the locomotive system, the bones are dis- covered imperfectly ossified, the muscles de- ficient in fibrin, and the tendons and ligaments in firmness and density. Of the organs of sensation it may be said, in general terms, that the mechanism employed in the application of the appropriate stimulus is, for the most part, incomplete, while a difference is also observa- ble in certain properties of the nervous sub- stance. From this view it might at first be con- cluded that, in order to trace the changes that ensue between the commencement of extra- uterine life and the attainment of maturity, we have only to look for them in the organs of the relative life. But the survey that we are about to take of the changes in question will show that the other class of organs are by no means exempt from alteration, although the changes are not those of development. They will be found to have reference to degree or amount of function rather than to capacity. The external characters of the infant just eliminated from the uterus at the full period of gestation are as follows: the integuments are thin, tender, and covered with a white unctuous matter ; the nails just reach the ends of the fingers ; the trunk and limbs are round and plump; and the articulations are in a state of flexion. The average weight of the body is about six or seven pounds ; the length varies from seventeen to twenty-one inches, sometimes falling short of or exceeding these limits. The point which lies midway between the two extremities is at the umbilicus. The dimensions of the head and of the abdomen are very large in proportion to the other cavities, and as compared with their own measurements in after periods of life. The pelvis looks con- tracted, the thorax flattened at its sides and prominent in front, and the lower extremities are less developed than the upper. A line drawn from the occiput to the chin measures five inches and three lines ; from the occiput to the forehead four inches and three lines ; and from the vertex to the base of the skull three inches and six lines. The circumference of the head, taken along the course of the median line, is from thirteen to fourteen inches ; but taken horizontally, and passing over the parietal protuberances, it seldom measures more than ten or eleven inches. The contrast between this general aspect and that of a full- grown man is too obvious to require any repre- sentation of it here. The characters of the interior will be best described and understood by examining ana- lytically the several apparatuses of the func- tions. Of the latter the most simple and primitive is assimilation, consisting of certain molecular motions which maintain, repair, and mould the organic tissues. We have already observed that the requisites for this function are perfect in the new-born infant; a copious supply of the fluid from which the textural particles are to be elaborated, a ready ingress for this fluid, and a no less ready egress for that which receives the particles no longer required in the process. All that we know of the mechanism employed is a porous ex- tensile substance, varying in its chemical con- stitution according to the nature of the tissue. Porosity is resolvable into a collection of infinitely minute tubes, and the degree of porosity is, therefore, determined by the number of the tubes ; the extensibility depends on the composition of the tubes. The tissues of the infant are soft, they abound in fluids, and are more capable of imbibition or artificial injection than at later periods of life ; this being consequently possesses a complete me- chanism of nutrition. But this mechanism can be of little utility unless the nutrient fluid be supplied liberally, and after furnish- ing the atoms for the formation of the several textures give place to fresh supplies. These conditions are afforded by the arteries and veins. There is no period of human existence in which the processes of interstitial growth are so active as in infancy, whether they be instanced in the accretion of matter, in the change of composition, or in the modification of form. This fact is in harmony with the state of the capillary system just described, and it will be found to correspond no less with the relative construction of the arteries and veins. The function of the former of these is to convey the blood into the tissue, of the latter to take it away ; consequently in a part where the growth is most energetic, we might, a priori, expect that the former would be more numerous, capacious, and distensible. This is well known to be the case from actual observation, partly of the effects of artificial injection, and partly of AGE. the phenomena of disease. An examination commences, and rapidly proceeds until the of the textural properties of the two sets of thickness of the latter is to that of the former vessels leads to the same conclusion. Sir as 1:4. This change corresponds with the Chfton Wintringham, in his Experimental closure of the foramen ovale, tin- <>llit< ration Enquiry, fully demonstrated that the venous of the ductus arteriosus, and the consequ. nt coats in the young animal far exceed the execution of the systemic circulation by the arterial in density, and that, consequently, left ventricle only. The relative capacitV they are less subject to distension. When the right and left cavities begin to maturity is attained, the disproportion between after birth. From tables given by M< : longer appears that, while at birth the capacity of the former compared with that of the latter is as 1 : 1$, at the age of 50 it is nearly 3:1.* The lungs at the moment of birth undergo vessels, these can be of no avail unless the a more remarkable alteration in their form, fluid they contain possesses certain chemical their texture, and their contents, than any properties. Now the blood in early extra- other organ in the system ; but during infancy uterine life presents the same general characters and childhood they present no appreciable as in more advanced periods ; but there is yet change in their organization, although a change no the resistances of these vessels exists. However well provided the infant may be with the mechanical apparatus of pores and wanting a comparative analysis of this fluid at different ages.* Inferentially we can enter- tain no doubt that it is fully adapted to the purposes of nutrition, when we consider the conditions of the chylifactive and respiratory functions, and that, although the differences of its composition in early and in more mature must be inferred from the increase of their function. In infancy there is a smaller con- sumption of oxygen ; and the power of gene- rating heat, a function so intimately connected with respiration, is inferior to that possessed in later periods. Much light has been thrown on this subject by the researches of Dr. Ed- periods have not been denned by experiment, wards; and practical observations of the highest they must bear a relation to the different de- grees of nutrition and secretion. The differ- ence, however, between the blood of the infant and that of the aged is perceptible to the senses, and will be noticed hereafter. Pursuing the channels of the blood to the heart, we find this organ, as stated above, mportance in the management of infants, founded upon the facts which he has ascer- tained, are to be met with in his valuable work.f The inspirations and expirations are more frequent at this early period, although the chemical actions between the air and the blood are less considerable. This greater fre- complete in its functions. Its volume, how- quency is a necessary accommodation to the ever, is large in proportion to the size of the rapidity of the circulation. At puberty there body. Its parietes are less firm in texture, is a marked development of the organs of and of a paler colour than they afterwards respiration ; the volume of the lungs increases become ; but their contractility is more active, in conformity with the expansion of the thorax; The pulsations are from 120 to 140 in a minute. The large volume is in harmony while the greater determination of the blood to their vessels is indicated by the deeper hue with the quantity of the fluid, the comparative of the parenchyma, by the liability to pulmo- weakness of its parietes with the small extent to nary hemorrhage, so characteristic of this which their impulse requires to be propagated, period, and perhaps also by certain diseases and with the trifling resistance ; and the quick which affect the nutrition of these organs. successions of its contractions furnish the fresh The corresponding activity of function is null- supplies of the nutriment required by the cated by the increased power of calorification, energy of growth. In the progressive develop- the energy of muscular motion, and the exalta- ment of this organ we notice that the bulk, although increasing so long as general growth continues, is proportionately smaller, a cir- cumstance that corresponds with the diminution tion of the cerebral actions; functions well known to have a direct relation with that of respiration ; while the establishment of the generative faculty appears to own a connexion, of the circulating fluid ; the fibres become though somewhat more remote, with the pul- stronger and of a deeper hue, so that the contractions are more capable of propelling monary development. We pass from the system which imparts v^wii 1. 1 a,VsiiwLio cue niv/ic* Vsu.ijci.uii' \Ji |*v|/v*au v j; . , -. . , the blood through the greater extent which it new properties to the blood to tn; has now to traverse, or, more strictly speaking, supplies it with nutriment. No imper of communicating a shock to a greater column; is discoverable in the apparatus < but the pulsations are slower, agreeably to the in the new-born infant ; every 01 diminished requirements on the part of the plete as an organ but passes throi capillary actions. We must not omit to ob- rious changes in adaptation on the . serve that at birth the parietes of the left to the food that is supplied, and to the mode ventricle scarcely exceed those of the right in of receiving it, and on the other hand tn the thickness; but from this period an alteration demands of the other parts of the t ody. Ih organs employed in conveying and modifying * De Blainville states, on the authority of the chyle, viz. the lacteals and the mesent Fourcroy, that in infancy the albumen of the blood is more abundant, that the fibrin is softer and more gelatinous, and that the phosphates are in -- J - Cours de Physiologic, t. ii. p. 262. * Manuel d A aat. t. translated by p. 284. &c. AGE. glands, are in a state of high development, as indicated both by their size and by their tendency to disease. The stomach and duo- denum are fully formed, but the sensibility of their mucous membrane is adapted only to the milk of the mother; any other kind of food has a greater or less tendency to produce irritation. This membrane is thick, extremely villous and vascular, and consequently of a rose-colour.* In young persons it assumes a milky or satin-like appearance; in the adult it becomes slightly ash-coloured, especially in the duodenum and in the commencement of the ileum ; in the old subject it is more de- cidedly ashy. Its whitish appearance, according to Andral,f is found either in very old persons or in younger subjects who have died of ma- rasmus. In the adult the small intestines, according to Orfila,J bear a proportion of eight to one as compared with the distance from the mouth to the anus ; in the infant the propor- tion is no less than twelve to one. The large intestines are longer with respect to the small intestines in the infant than in the adult; but their calibre is proportionally smaller. Ascending to the mouth we might be tempted to say that there is evidence of incompleteness in the ab- sence of teeth; but a moment's consideration assures us that the organs collected in this part are all eminently adapted to their function. The food is already prepared by the mother, and only needs to be extracted and conveyed into the pharynx ; actions which are perfectly achieved by the lips, cheeks, and tongue. When the period has arrived at which this food can no longer be furnished with safety to the mother, and when all the purposes are accomplished which were intended in this close connexion between the two beings purposes in all probability of a moral as well as a physical character the infant is prepared for a more independent existence by the emer- gence of teeth. This event generally begins about the sixth or seventh month by the appear- ance of the two middle incisors in the lower jaw ; these are followed by the corresponding teeth in the upper jaw; next are seen the lateral incisors below and above : the rest appear in the following order ; the first molars, the canines, and the second molars ; those of the lower jaw having generally the priority of emergence. The milk-teeth, as they are called, by the end of the seventh year have given way to the second and permanent series. For the different characters of the two sets, the order of their appearance, and other par- ticulars, we beg to refer the reader to the article TEETH. That the first series should be only temporary is a necessary provision, in conformity with the change in the conforma- tion of the maxillary bones which ensues at the same time. We must not leave the alimentary tract with- * Billard, Traite des Maladies des Enfans, &c. t Precis d'Anat. Pathol. i } Lemons de Med. Leg. t. i. p. 62. This statement is at variance with that, of Meckelj, who says that the small intestine is much shorter in the early periods. Op. cit. t. iii. p. 424. out observing that the fibres of the stomach and intestines in infancy and childhood are, like those of the heart and other involuntary muscles, more irritable than in after life ; hence the contents of these viscera are propelled more rapidly, and the evacuations are more frequent; their tissue is also softer, and their colour more approaching: to white. The liver undergoes a great change after birth both in form and in function. The pecu- liar circulation of which it formed so important an organ during foetal life being abolished, the left lobe which nearly equalled the right in volume, is diminished to a third of its original size. But while the umbilical vein and the canalis veriosus are obliterated, the vena portse is developed, and the bilious secretion becomes the predominant function. Of the further changes which this organ experiences, we have very little knowledge, except that the whole bulk is greatly lessened, and that the colour of its parenchyma becomes darker, and that it is more subject to disease in after periods. Oc- casionally we meet with instances in which the foetal proportions of the liver continue through life (Andral). The bile has not been carefully examined with reference to particular ages, but it is known to be less viscid and to contain a smaller quantity of its peculiar principles in infancy ; while its greater liability to con- cretions at more advanced periods indicates an alteration in its composition. The gall-blad- der, though small at birth, contains bile, green in colour and bitter in taste, and soon becomes enlarged. The spleen also increases in volume, but what alteration takes place in the ' progress to maturity, in its function, must, of course, be doubtful until the function itself be better understood. Probably its enlargement is con- nected with the distended condition of the venous system. Of the changes in the pan- creas and salivary glands, we know little more than that their texture increases in firmness. The lacteals, lymphatics, and their respective ganglions have a very marked development. It is to be regretted that no observations have as yet been made upon the composition of the chyle at different ages. There are doubtless many alterations corresponding to the varying activity of the digestive function, and to the kinds of aliment used at those periods. So much for the organs and functions which are concerned in augmenting or modifying the nutrient matter. Before proceeding to those of the relative life, we must allude to the organs of excretion. The kidneys at birth have not lost the traces of their lobular forma- tion, but these are soon effaced. The weight of these organs at birth is to that of the whole body as 1-80; in the adult 1-240. The me- dullary portion is more abundant than the corti- cal in early life. The supra-renal capsules soon be- gin to shrink from their foetal size. The ureters are large, and the bladder has a more elongated form than in after periods ; it also occupies a higher situation above the pelvis. The func- tional qualities of these forms are not so well ascertained as the analogy of their organization to AGK. that of inferior animals. The urine is retained a shorter time in the bladder ; it is more aqueous and less impregnated with saline and animal ingredients than in after life; there is also a particular deficiency of urea. Of the intes- tines we have already spoken ; their contents are copious but less feculent than they after- wards become. The perspiration affords a si- milar character to that of the other excrernenti- tious secretions, being more aqueous, less sa- line, and less odorous. On the whole it may be said that less activity is indicated in the egestive than in the ingestive system. Of the defensive organs, or those which are exposed to surrounding agents, we may remark, in general terms, that although fully adequate to the demands of the infant under the circumstances of his existence, they acquire a development proportionate to his growing in- dependence of the care of others. The skin increases in firmness, and the epidermis in thick- ness ; the sebaceous follicles become larger and more numerous, and the hair is more abundant. There is a portion of the nervous system which we have every reason to consider more related with the functions which have been just reviewed, than with those of the animal life, and which might a priori be expected to bear a corresponding ratio of developement. We allude to the ganglions; they appear to be fully formed at birth, but what changes they undergo between that period and maturity we do not profess to know. In old age their tissue is found hardened, shrunken, and of a greyish colour. (Bichat.) The changes that we have next to take notice of are of a totally different character from the foregoing. They consist not merely in augmentations of size, correspondently with the general increment of the body, or in modi- fications of organs according to the altered circumstances under which they have to act, but in processes essential to the completeness of certain organs. These are the parts em- ployed in locomotion, voice, sensation, and thought. We shall begin with the osseous system. Bones are not subservient to locomotion only ; they have, in some parts of the body, the important office of enclosing and defending 'from external injury the more delicate organs of the system. We shall find, therefore, that in the young animal, according as they fulfil the one office or the other, their development will differ. But whatever be the functions of the bones, they require, for the perfection of that function, three mechanical properties, firm- ness, lightness, and tenacity. They must not admit of flexion, and, at the same time, the density of their substance must not render them cumbrous by weight, or brittle in texture. To present these three conditions, the organs in question consist of two principal ingredients, an animal matter and an earthy matter, most intimately interwoven ; the one preventing such vibrations as would occasion risks of fracture, the other affording the necessary strength in supporting weights, and in resisting the divellent tendencies of antagonist muscles. The pro- portion which these parts bear to e ,d, ,nh- vanes with . the tgea of the hum;,,, subject! Viewed as u part of the system cl v,,u ,1 ,.', ,1 ,.' lite of relations, bones aiv used u ,, support, as levers in various attitudes and mo- tions, and as />,///> r/V//,/>/// to the mus, k tendons. On examining the constitution of these portions of the osseous syM.-m in the new-born infant, we find the quantity of i>iv,,. ( i,,l the precise period however ur ,1,, , u,^.' In correspondence with this ohtusity \M- (i,,,! the organ incomplete, but tin- incompl has reference rather to the external th;m to t| 1( . internal ear. Thus the pinna is very i and therefore unfitted for collet tin- viliiMtions the same may be said of the meatus auditorial! In like manner, the membrana tynipan, oblique, and scarcely more than'a continuation of the superior surface of the meatus, and thus little calculated to receive the vibrations. Tin M. parts are also covered with a .soft matter very unfavourable to vibrations ; the tympanum is very small, and the mastoid cells do not .AM. In the progress of age all these parts gradually increase in hardness, and consequently are bet- ter adapted to their function. There are mus- cles attached to this sense also, but we are deficient in observations on their degree of de- velopment, though we may infer their condition from analogies in the rest of the muscular system. Lastly, we come to the organ of vision, of which, however, there is not much to be said. The differences between the visual organ in the in- fant and in the adult consist more in degree than in kind; thus the sclerotic membrane is less elastic, and the cornea is less conical, in conse- quence of the smaller quantity of aqueous hu- mour; (the greater thickness of this coat is pro- duced by the serosity contained between its la- minae;) thecrystalline lens is lessdense, but more convex in form. The pigmentum is in smaller quantity at birth than afterwards; while the retina is thicker and more pulpy than in more ad- vanced periods. The yellow tint of the foramen of Soemmering does not become visible till some time after birth, but deepens with the progress of life, till the stage of decline, when it grows paler. It has been ascertained that perfect images are formed on the retina ; and yet for the first few days the child gives no indication of visual sensation, and when objects appear to attract its attention, they are only those which are vividly illuminated. The de- ficiency therefore must exist in the optic nerve, though we are ignorant of the organic condition on which this insensibility is dependent. We observe, moreover, that the eye is much more passive than in the adult, that it follows the motion of luminous bodies, or is fixed upon them with little or no apparent interference of the will. This muscular incompleteness, then, tallies with what we have noticed with respect to the other senses. The eye is known in its advance towards manhood to increase in the capability of adapting itself to different distances; but as we are ignorant of the mechanism made use of for this purpose, it is useless to look for cor- responding organic alterations. We must not omit to notice those appendages to the appara- tus of vision, called eyebrows, which become much more prominent as life advances, by the development of the frontal sinuses, and are therefore belter adapted for shading the eyes. The generative apparatus is situated inter- mediately to the animal and the organic s\ >t in. 74 AGE. The evolution of the organs connected with this function marks the age of puberty; and the changes in which this evolution consists, both in the male and in the female, are too well known to require their specification here. The influence of this development on the mental and moral characters of either sex, is likewise sufficiently familiar even to the most superficial observer. The human being is related with the external world passively and actively, independently of those organic actions and reactions that are constantly occurring in his system with regard to outward agents. He derives perceptions from objects about him, and he reacts on them by his power of muscular motion. But in his growth we mark that the perfection of those organs, which are scarcely more than passive in his relative life, advances much more ra- pidly than those which enable him to take a more active part. Thus the eye and the ear attain a certain maturity of organization and function, long before the bones and muscles, which officiate in locomotion. The bones and muscles connected with the organs of sensation, and therefore partaking of the passive character, are also equally forward in their development. What is the probable final cause of this arrangement? If all our voluntary motions were the immediate consequences of our sen- sations, as some of them undoubtedly are, such as those which close the dazzled eyes, or refuse the bitter food, or withdraw from pain- ful contact; if all these followed directly on sensations, it would indeed be a strange ano- maly, if the systems that belong to each were not precisely on the same level of development. But this is not the case ; all the more impor- tant motions, important as it regards that world in which man exists, as an intelligent and social creature, though less so as it respects his individual being, are the results of a mental condition, no less distinct from sensation than from muscular motion. This state is desire, or as it is commonly called when the antecedent of action, will or volition. Probably no men- tal state is more simple than this, and it may follow any other. It is therefore the more necessary that it should be preceded by such intellectual changes as will give it a right direction ; in other words, that it should come under the dominion of certain faculties. But in early life the faculties to which we allude , are very imperfectly developed; those only have attained any thing like maturity which are in immediate relation with the senses; such are perception, memory, association, and imagination ; while the reflective faculties, such as comparison, reasoning, abstraction, all in fact that constitute man a judicious expe- rienced agent, are rudimentary. The conse- quence is that the desires or volitions are pro- verbially vain and dangerous. Let us observe a child of seven years old ; his senses are suffi- ciently acute for all ordinary purposes, although they are deficient in precision and delicacy; he has seen many attractive objects, he has heard many wouderful stories, and tasted many exquisite delights ; he remembers them vividly, he associates them rapidly, and often in shapes very different from those in which they were formerly combined. Desires follow which would prompt him to execute the most ridicu- lous and mischievous schemes. But happily the muscular system, by which alone he could accomplish them, is too immature and feeble for his puerile purposes. Here then is the final cause that we were in search of; the active corporeal functions of relation must not ad- vance beyond the governing faculty of the mind. But why, it might hastily be asked, should not the senses, the mental faculties, and the motive powers, all have been equally deve- loped? The question is absurd, if we consider but a moment the manner by which the mind accomplishes its growth ; that its higher powers result from the accumulation of innumerable sensations, by which in fact the former are nourished and exercised. We shall now introduce a brief account of some researches upon the height, weight, and strength of the human body, at different ages, prosecuted by M. Quetelet, of Brussels. Not having room for the numerical tables, or the particular observations, from which his general conclusions are derived, we must content our- selves with a statement of the latter, and refer those of our readers who may be desirous of seeing the former, to the author himself. His deductions as to the growth of human stature are as follows: (1) the growth is most rapid immediately after birth ; it amounts in the first year of infancy to about two decimetres (nearly eight inches.) (2) The growth dimi- nishes as the child advances towards the fourth or fifth year; thus, during the second year his increase of height is only half what it was the first year, and during the third year it is not more than one-third. (3) After the fourth or fifth year, the stature increases pretty regularly until the age of sixteen, and the an- nual growth is about fifty-six millim, (two inch.) (4) After puberty the stature still increases, though slightly ; thus, from the sixteenth to the seventeenth year, the increase is about four centim. (If inch); and in the two following years, only two centim, and a half (one inch.) (5) The stature does not appear to be quite completed even at the age of twenty-five. These observations refer only to absolute growth, but if the annual increase of stature be com- pared with the height which has been attained, it will be found that the infant, after birth, increases in the first year by two fifths of his height; in the second by one-seventh; in the third by one-eleventh; in the fourth by one-fourteenth; in the fifth by one-fif- teenth ; in the sixth by one-eighteenth ; &c. so that the relative growth continually dimi- nishes after birth. In addition to these statements M. Quetelet has ascertained that the rules of growth are not the same in both sexes; 1st, because the female at birth is less than the male; 2dly, because her development is completed earlier; 3dly, because her annual growth falls short of that of the male. It appears likewise that the stature AGE. of persons living in towns, taken at the age of nineteen, exceeds that of residents in the coun- try by two or three centim (1 or l\ inch); and that the children of persons in easy circum- stances, and those of studious habits, are gene- rally above the middle height.* A memoir by the same author devoted to an examination of the weight of the human subject at different ages, contains a series of interesting conclusions, from which we select the following. (1.) At' the period of birth there is an inequality both as to weight and to stature, in the two sexes ; the medium weight of males being 3 kil. 20, (rather more than 7 Ibs.), that of females 2 kil. 91, (about 6 Ibs.); the height of the former Om. 496, (about 19 inch.); that of the latter Cm. 483, (about 18 inch.) (2.) The weight of the infant diminishes the first three days after birth, and does not begin to increase till the second week. (3.) At the same age the male is generally heavier than the female; it is only about the twelfth year that their weights are equal. Between the first and eleventh year the difference of weight is fiom 1 kil. to 1 kil. and a half; between sixteen and twenty, about 6 kil. and after this period from 8 to 9 kil. (4.) At full growth the weight is almost exactly twenty times what it was at birth, while the stature is only about three and a quarter more than it was at that period. This holds good with both sexes. (5.) In old age both sexes lose about 6 or 7 kil. of their weight, and 7 centim. of their height. (6.) During the growth of both sexes, we may reckon the squares of the weights, at the different ages, as proportional to the fifth powers of the heights. (7.) After full growth in each sex, the weights are very nearly as the squares of the heights. (From the two prece- ding statements it may be deduced that the increase in the longitudinal direction exceeds that in the transverse, including in the latter both width and thickness.) (8.) The male at- tains his maximum weight towards the fortieth year, and begins to lose it sensibly towards the sixtieth. The female does not attain her maxi- mum weight till about the fiftieth year. (9.) The weights of full-grown and well-formed persons vary in a range of about 1 to 2, while the heights vary only from 1 to 1$. This state- ment is deduced from the following table :f Male weight Female Male stature Female . Maximum. Minimum. Medium. KIL. KIL. KIL. 98.5 49.1 63.7 93.5 63.7 55.2 MET. MET. MET. 1.990 1.740 1.684 1.740 1.408 1.579 * Recherches sur la loi de la Croissance de I'Homme, par M. Quetelet. Annales d'Hygiene Publique, &c. t. vi. p. 89. t Ann. d'Hygiene, t. x. p. 27. To the above memoir M. Villerme has appended some extracts from manuscript notes found among the papers of M. Tenon, and written about the year 1783. They contain observations which correspond, in many re- spects, with those of Quetelet. The last researches of this industrious ob- server have been devoted to the muscular p. of man at different ages, and have Wn hm very recently published. In the course of Ins memoir he refers to two tables; one statin - tin- relative power of draught (la force r6nale), at the several periods ; the other, the relative ma- nual strength (la force manuelle) ; in each > estimated by the dynamometer. The results are very much what might be expected a priori. It appears that the maximum of the " force renale " is at the age of twenty-five ; and that the difference in the extent of this kind of mus- cular power between males and females, is less during childhood than at the adult age. Thus, in the former period the male surpasses the female by one-third, towards puberty by one- half; and at full growth, his strength is double that of the other sex. The manual force is greatest at the age of thirty, and at all ages is greater in the male than in the female ; before puberty, in the ratio of 3 : 2, after this period, in the ratio of 9:5. The average manual strength of a man is equivalent to 89 kil. and exceeds his weight by 19 kil., so that he might support himself by his hands only, even with a considerable weight attached to his feet.* This and the preceding memoirs, we are told by M. Quetelet, are extracted from a work which he is about to publish, entitled " Sur I'Homme et le developpement de ses faculte"s ; ou, Essai de Physique Sociale." We need scarcely add that we are justified inspecting from the specimens already presented to us, a series of valuable and highly interesting facts, together with deductions of no ordinary im- portance and originality. Having thus briefly traced the changes that precede maturity, we may ask what is it that prevents the processes of growth from advancing at the same rate as they have hitherto done ? Why, so long as they are undisturbed by dis- ease or unnatural circumstances, should they not advance ad infinitum, or at least why should they not raise man to the strength and dimensions which poets have fabled in their Titans ? The same food, the same atmosphere, the same light and heat, the same electric agencies, by which the organs have been main- tained or excited, are still around them and exerting their influence. Why, then, should they never transcend a certain point? Why should the stature, however much it may vary between a Boruwlaski and an O'Brien, yet never rise above a certain measure ? Why does the strength never exceed the powers of a Milo or a Desaguliers, or the intellect surpass the limits of Aristotle, Shakspeare, or Newton? These are interesting but impossible problems. If we say that a certain quantum of vital power is allotted to the growth of man, and that while a portion is expended in raising him to matu- rity, the residue must be husbanded for con- ducting him through the remaining portion of his duration, else he might suddenly stop short * Ann. d'Hygiene, &c. Oct. 1834, t. xii. p. 294. AGE. in his career without passing those stages that prepare him for the cessation of his existence ; what do we gain by such an explanation ? Nothing ; for the term vital power which we employ is but a hypothetical cause, or if more closely examined, is scarcely even this ; it is but an abstract term applicable to a number of actions that do not occur in the inorganic world. The vital power of a body is but the collective manifestation of its vital actions, and to say therefore that only a certain quantum of vital power is inherent in it, is but to express in other words the simple fact that those actions are circumscribed. Discarding this explana- tion, shall we say that the fact must be referred to some deficiency in the media of the being's existence; that, although the aliment, the air, the light and caloric are competent to the pro- duction of a certain degree of growth, they cannot extend it, and that, were their conditions different, the animal development would be more perfect. It is easy perhaps to suppose this, but we do not see how it can be proved, nor indeed that existing analogies favour it. On the surface of our globe there is every variety in the temperature, in the humidity, and in the electric conditions of the atmosphere, and every diversity in the articles of food em- ployed; in more limited spheres there are the greatest diversities in these several respects produced artificially by the various occupations of mankind ; and although we find, both among races and individuals, great varieties of deve- lopment, which may occasionally be traced to some relation with the media in which they live, these varieties are by no means in propor- tion to the differences of the media, and in the majority of cases the former are independent of the latter. In the temperate zone, with a due proportion of animal and vegetable diet, man appears to attain his most perfect deve- lopment, and with however great skill he adapts these circumstances, he never surpasses a certain point, and from what we know of his physiology no great alteration in any one of the external stimuli of his existence could be tole- rated. A different proportion of the oxygen, nitrogen, and carbon in the atmosphere, we know full well to be noxious ; a larger or smaller quantity of aqueous vapour suspended in it will occasion many well-known maladies ; the same may be said of alterations in the ba- lance of the electricity that surrounds us. Great" extremes of heat and cold may be borne for awhile, but it is obvious that they are not so well adapted to a healthy state of the system, and therefore to its growth, as intermediate de- grees ; and consequently it is not easy to con- ceive any degree either above or below these limits consistent even with existence. Fami- liar enough also are we with the effects of full and sparing, of simple and mixed dietetics, and with the fact that between certain well- known bounds lie the. salutary quantities and qualities. From all which it appears suffici- ently evident, that we cannot conceive any difference iu the amount or properties of the known stimuli of life, that would be more favourable to the growth of man, than those which are to be found in the range of the known variations, whether natural or artificial. From the beginning there must have been established a direct relation between the organization of the body and the outward elements; the latter are nothing but stimulants adapted to co-exist- ing susceptibilities, or to put it more closely, man is not made by, but for or with, the sur- rounding agents ; his lungs are fashioned in cor- respondence to the atmosphere which he breathes, his digestive organs to the food that is spread so plenteously before him, and his nervous system to the subtle imponderable agents that play about him ; consequently as his organs only act in concert with, and do not result from the media of his existence, a development be- yond that which he is known to acquire must proceed quite as much from the former as from the latter; and the supposition, the value of which we have been endeavouring to estimate, thus falls to the ground. If man could become a. larger, more powerful, or more sagacious animal than he now is, he must not only live in different media, but must possess a different constitution ; in other words, the characters that distinguish him as a species must be altered. The question, then, that offered itself remains to our apprehension unsolved by either of the hypotheses. The limitation of man's development is like the definite period of his duration, and a hundred other circumstances connected with his existence, an ultimate fact ; no event that we are able to discover intervenes between its production and the will of the Deity. Maturity, though varying with every indi- vidual, may be said to take place somewhere between the ages of twenty-five and thirty. It is a general opinion that it is a stationary con- dition ; that when such changes have taken place in the frame, as render the human being capable of undertaking the various duties and occupations to which adults alone are adequate, there are no further alterations till the period of declining age ; that, in short, growth has entirely ceased. But this idea is not strictly correct, for there is in all probability no period when the system is absolutely stationary; it must either be advancing to or receding from the state of perfection. This is of course more obvious when we know that augmentation of bulk is only a part of that process which per- fects the organization. (See NUTRITION.) It is true that at the adult age the determinate height and figure, the settled features, the marked mental and moral character, naturally give rise to the idea that a fixed point has been attained ; but a little inquiry soon teaches us that the individual is still the subject of some progressive changes. It is the stature only that is stationary, for this depends on the skeleton, which ceases to lengthen before the period we speak of. But the capability of powerful and prolonged muscular exertions increases for some years ; there must consequently be a change in the muscular tissue. The intellectual faculties have not attained their maximum, although we AGE. 77 do not hesitate to consider them mature; we structures are supplied with nmt.nals by the Mb fluids in those structures, it is rvidn.t tint th.-y the must at any time be incensed, dimmish,-.!, at must therefore infer that there is a correspond- ing organic development of some kind in cerebral substance. Maturity then would, ac- cording to this view, require to be dated at a period much later than that which is usually assigned to it. It is enough, however, without referring further, to know that although at the adult period the organs of animal life are so developed, that we cannot consider them im- perfect instruments, they are even afterwards the subjects of a perftctionnement. What is commonly meant then by maturity, is in strict- ness that period of human existence, during which the processes of growth and decline are passing into each other by such slow degrees as to be imperceptible. In this important era of the life of man, more important even than the season of adole- scence, we must leave him in the full posses- sion of all the faculties and energies which his Maker has allotted him, fulfilling his destiny of good and evil, encountering and triumphing over peril, toil, and pain, scaling the rough steep of ambition, threading the dark intricate paths of gain, labouring for the happiness or misery of his fellow-creatures, supported all the while by the consciousness of a strength that seems never to fail him, of resources never to be exhausted ; we must allow a few years to roll by, and then return to him, when weary, wayworn, and broken with the storms of life, he has discovered that there are limits to his powers of action and endurance ; that of the objects which he proposed as the ends of his labours, while a few have been accomplished, the majority are either vain or unattainable; and that a race fresh in vigour, and high in hope, the images of his former self, are over- taking and thrusting him away from the scenes of his exertions. What are the revolutions that have transpired in his system ? The formative organs of all the tissues of the body are in reality the tissues themselves ; whether it be a muscle, or a gland, or the coat of a vessel, the parts which essentially produce its growth are nothing more or less than its own constituent molecules, the mutual attrac- tions of which in deposition and absorption constitute assimilation ; for there is no proof that vessels are used for any other purpose than that of conveying the nutrient fluids to and from the places, where the ultimate mole- cules arrange themselves in the form of tissue. The altered qualities, then, which are presented by the tissues, in whatever organs, in the de- cline of life, must depend immediately upon alterations in their own molecular motions and affinities. The nature of these alterations will of course correspond to the nature of each tissue ; and unless we mistake, they will all be found to agree in one character, viz. a sim- pler composition, a lower kind of organization than they formerly possessed. But the discussion of this point will be more conveniently deferred till we shall have briefly recited the principal changes in the more important parts of the body. As the nutritive secretions of the various otherwise modified by changes ... thr quantity and properties of these fluids. Jt ii therefore a natural commencement of the subject to begin with the circulating system. Nothing is more obvious in the condition of the aged as contrasted with the young than tin- different ratio between the fluids'and ih ( - solids, the former being remarkably deficient. There is not only a notable diminution in the quantity of oleaginous or serous secretions, which ;' generally contained in the cellular parts ,f tin- body, but it is manifest that the tissues are per- meated by a much smaller proportion of blood. This fluid moreover is very different in quality from what it was in earlier life; it is I, rial, its colour has not the same bright red it once presented, it has a large proportion of serum, and its coagulum is less firm in con- sistence.* Correspondently with the defi- ciency of fluids, many parts which once contained them are shrunk or obliterated. The capillary system becomes infinitely less ex- tended than it once was ; many of the extreme branches of the arteries themselves are no longer to be penetrated, and those which remain per- vious, are far less distensible than formerly. There is indeed a remarkable change in the coats of these vessels ; they are not only con- tracted in diameter, but are become denser and more rigid in texture. In this respect they dif- fer from the veins, which in old age are more dilatable than in youth, and consequently con- tain a larger quantity of blood. The final cause of this is evident ; in youth the arteries must convey a relatively larger quantity to sup- ply the increasing structures ; in the decline of life, when the latter are decreasing, there can no longer be any need for the same supply; the permission, however, of an accumulation in the veins, where it is less likely to be productive of injury, appears to be an accommodation to the diminution of the circulating powers. If we trace the arteries from their extremities back to the heart, we shall find their calibres every where diminished, their coats less elastic, less capable of adapting themselves to the varying quantity of their contents, in some places resembling the texture of ligament, in some that of cartilage, and in others studded with deposits of osseous matter. The heart itself presents marks of degeneration no less decided ; its cavities are shrunk, its fibres pale, and but feebly contractile, and fat will some- times seem to take .the place of the muscular substance. Frequently, also, the coronary arte- ries are found ossified, and the same alteration is not uncommon in the valves. All these facts account for the slow, languid, staggering circulation characteristic of advanced life ; there is less blood to be transmitted to the various organs, and that which is sent is pro- pelled with a degree of feebleness that shows how little energy is required in its motion, when * De Blainville is of opinion that these change* arc exaggerated. Cours Ue Physiologic, i. 26'2. 78 AGE. so few nutritive actions are transpiring. We have spoken of the altered character of the blood, of its being less arterial and of a darker tint : this change is explained by the alteration in the respiratory system. The lungs are be- come lighter, the cells being relatively much larger,'* and the parenchyma, which consists principally of bloodvessels, being greatly di- minished. This alone would not explain why the blood is imperfectly arterialized, because, although the respiratory surface is diminished, less of that fluid enters the organ. But the bronchial membrane is always in a more or less unhealthy condition, being covered with a thick and copious secretion, that constitutes the " old man's catarrh," and prevents a due intercourse between the air and the blood. Besides this circumstance, the expansion of the chest is less perfect in consequence of the diminished elas- ticity of the parietes of the chest produced by the ossification of the cartilages and other causes : the muscles also participate with less energy in the respiratory movements. Every thing in the history of advanced life indicates the diminution in the vigour of the circulation and respiration. The apathy and languor of mind, the deficiency of many secretions, and the general decrease of animal heat, but par- ticularly in the parts most distant from the heart, are all more or less intimately connected with the failure of these vital actions. On turning to the digestive apparatus we have abundant marks of deterioration. The teeth fall out, the alveolar processes are ab- sorbed, and the gums become hardened. In addition to these there is a change in the mus- cularity of the stomach ; it has become weak, attenuated, and less contractile. The same is true of the intestines. The lacteal vessels are much fewer in number, and scarcely any lym- phatic glands are to be met with. Every thing intimates that the food is less perfectly acted upon, and that consequently less chyle is ex- tracted, and transmitted to the circulation. Since, then, in these several systems, we find marks of diminution, impairment, depravation, it is not wonderful that nutrition, which is per- formed by means of the materials supplied by those systems, partakes of the same characters. But as nutritive changes must have occurred in the various deteriorated parts just spoken of, it would be incorrect to say that alterations of tissue depend solely on the alterations of these * M. Andral, in his description of the atrophy of the lung which occurs in aged persons, says, " In some cases the walls of the cells disappear alto- gether, and we only find in their stead some delicate laminae or filaments, traversing in different directions cavities of various sizes. In the parts of the lung where these alterations exist, there are no longer to be found either bronchial ramifications, or vesicles properly so called, but merely cells of greater or less diameter, divided into several compartments by im- perfect septa or irregular laminae. Many of these cells bear a perfect resemblance to the lung of the tortoise tribe, and they all approach to it more or less as to a type of organisation, towards which the human being in this case seems to descend. Pathol. Anat. v. ii. p. 528, translated by Drs. Townsend and West. systems, though they are promoted by them ; they must, in fact, have assisted each other. The altered tissues could not have been easily thus changed, without a defect in the quantity or quality of the matters out of which they are formed ; nor could the latter defects have easily occurred without some alteration in the texture of the parts employed in conveying and ela- borating the nutrient fluid. It is an old saying, that the functions of the body form a circle : if this be true of their healthy condition, it is not less so of their diseases and decline. The organs and tissues subservient to the organic life having undergone vitiation and diminution, we may expect to find equal or even greater decay in the parts which are alto- gether dependent upon them, or the organs of the supplemental life. These indeed, as they are the last to be developed, are some of the first to present marks of decline, and evi- dently for the same reason, viz. because they are appended to and generated by the other parts of the system, and also are more open to our observation. The body is indeed, in this respect as in many others, not unlike a poli- tical community ; no great change can occur in its internal arrangements, such as a failure or derangement of its energies and resources, without a manifestation of this weakness or disorder in its foreign relations. Let us proceed, then, to examine the ravages which are wrought by the hand of time on the organs of locomotion and sensation, in the same order in which we have traced the deve- lopments and amplifications, once lavished by the self-same agent. And first of the bones. The process of development in these parts consisted of a certain adjustment of the animal to the earthy matter, in order to give the requisite firmness, toughness, and solidity. As life advances, the phosphate and carbonate of lime are found to exceed the proportion of the cartilage and gelatine. The general conformation of the bones is less regular ; they look shrunken and worn. When handled they feel lighter, not- withstanding the osseous substance is in excess; a fact, which results from the diminished quantity of the fluids, and one or two other circumstances to be mentioned presently. The processes and ridges, once so eminent and dis- tinct, are comparatively effaced ; this alteration accords with the wasting and diminished exer- cise of the muscles that were attached to these eminences. On looking for the lines and spaces, which are occupied in early life by cartilages or membranes, and which are visible even in manhood, we now find every trace of them vanished. Thus, the divisions between the epiphyses and shafts of the long bones, the line of union between the bones of the pelvis, and, in a still more marked degree, the sutural outlines of the bones of the head, are no longer perceptible. They are all filled up with bony deposit, and the pelvis and cranium form single bones ; even the foramina by which the nutrient arteries entered the tissue are con- tracted or obliterated. The cellular structure between the tables of the cranium is removed ; AGE. and the outer plate has approximated and indeed become identified with the inner; hence we see more depressions on the surface of an aged skull. On inspecting the internal structure of these organs, we find the cavities that contain the marrow much more extensive than formerly, and the medullary tissue reduced to a con- sistence scarcely exceeding that of oil. The cells also of the short bones and of the ex- tremities are more expanded, and the laminae which form them are very much attenuated. The deficiency of animal matter renders the bones of the aged fragile ; they are broken by the most trivial accidents. It is also the cause of their slowness to unite; for the activity of assimilative, and consequently of reparative processes, is dependent on the vascularity and fluidity of a tissue. The lightness, however, of these organs produced by the same cause is beneficial, or at all events in harmony with the state of the muscular system. If we next turn our attention to the ar- ticulations, we shall find that similar pro- cesses of disqualification for former functions have ensued. The spinal column, which once adapted itself with such ease and flexi- bility to the motions and curves of the body, has become almost as rigid as a single bone by the drying up of the intervertebral cartilages, and sometimes by the encroach- ments of ossification.* Scarcely any traces of cartilages between the ribs and the sternum can now be found ; one of the causes to which we alluded above, in connection with dimi- nished respiration. The same deficiency of cartilage is observable in the bones of the wrist and of the tarsus. A change, the opposite of mobility, may also be detected in the liga- ments which embrace the joints; they are dense, dry, and inelastic. The gelatine which enters so largely into their composition has become altered in its chemical properties ; it is less easily soluble in water, and has all the characters of glue rather than of jelly. Ill-adapted as this state of the articulations is to the purposes of motion, it is, we think, not altogether difficult to discern its appropriateness to the human being at this advanced period. Were the joints supple and flexible, while the muscles have so little power, how much greater would be the risks of accidents to the aged man in the slight motions which he achieves. In order to preserve their frames from falling, those whose joints move easily upon each other are compelled to exercise those ' *' Cependant il est rare que les fibro-cartilages s'ossifient chez les snjets avances en age. A la verite on voit souvent les vertebres se reunir avec les autres au moyen d'une substance osseuse, mais cette souture depend bien plus rarement de 1'ossi- fication des fibro-cartilages que de la formation de lames osseuses a la circonierence des deux faces par lesquelles se regardent les coups des vertebres. Cependant j'ai observe quelquefois aussi I'ossifica- tion des fibro-cartilages intervertebraux, et j'ai trouve alors, en sciant longitudinalement la colonne epiniere, que plusieurs vertebres etaient soudees ensemble, et confondues en une seule masse." Meckel, Manuel d'Anat. t. i. p. 364. muscles which keep the limbs in the rvm.isite degrees of extension ami stability, durin - cer- tain attitudes and motions; but tins end accomplished in the feeble old subject by tin- very stiffness of his articulations. The muscles are subject to dian^o no less decided than those in the organs jusl ,, tioned. They are pale, flabby, atrophied, and indisposed to contract on the application of stimuli ; but the fibre itself is tough and not easily torn, and the true muscular suhst .,: seems to have given way in some places to a sort of dense cellular membrane, or a yellow- ish degeneration of tissue particularly de- scribed by Bichat. Their tendons are often studded with calcareous matter, and the sheaths in which they play are rigid and unmoistened with synovia. They obey the stimulus of the will tardily and irregularly; the uncertain tremulous movements, the tottering gait, the stooping posture, the unsteady grasp of the aged, are familiar to every one. The organ of voice comes next to be con- sidered. The larynx, once composed of seve- ral cartilages that moved freely on each other, is now a cavity capable of much less variation in its dimensions, owing to the rigidity of its parietes; the extent of the cavity gives in early old age that depth of tone, which by its gravity and solemnity excites our homage. In more advanced age, however, the tone becomes hoarse, shrill, and piping; this in all pro- bability is produced by the contraction and stiffness of the rima glottidis, but still more by the want of vigour in the muscles of the mouth and throat. The incapability of ma- naging the tone, and the tremulous articu- lation, are also results of changes in the muscles of the larynx, pharynx, and tongue, similar to those which transpire in other parts of the muscular system. Many senile impediments of speech are also produced by the loss of teeth, by the falling in of the cheeks, and by the disproportion of the lips to the space which they occupy. In our investigation of the signs of decay in the parts that are subservient to sensation and thought, we shall be met by the same difficulties which formerly opposed our way, when inquiring into the phenomena of their development. We traced the progress of the nervous substance both in the nerves and in the cerebro - spinal centre from the almost pulpy state recognized in the infant, to its firm consistence in the adult. If we now inves- tigate the anatomical quality presented by the tissue in advanced life, we shall find that it has shared the alteration of nearly all the other tissues, that in short it has increased in density. This fact viewed in connection with another, namely, that ramollissement and induration produce very nearly the same lesion of func- tion, will account for the failure in the sensific powers of old age. Besides this alteration in the substance of the nerves, they are found to be diminished in diameter; their neurilemmes are become, like other membranous parts, much harder and stronger. Moreover, Bichat has remarked that the nervous tissue of old ani- 80 AGE. mals is much less easily affected by reagents than that of younger ones ; so that there would appear to be an alteration in the chemical composition as well as in the mechanical con- sistence. That which has been said of the matter of the nerves is also true of the brain. The whole bulk is diminished arid the density greater than in earlier years. Some, however, assert that it is even softer than in manhood. M. Blandin makes a remark of this kind, in commenting upon Bichat's statement of a greater hardness in the tissue, and says that it might be expected a priori, since there is so strong a correspondence between the two ex- tremes of life. There is reason, however, to think that this remark, if true at all, applies only to the cerebral organ of persons very far advanced ; and it is not improbable that dis- eased softening has in other cases been mis- taken for the natural effect of age. The mem- branes investing the brain like the neurilemmes (for they belong to the same system) are also thicker and more resistent. The vascularity of the organ is greatly diminished ; on a di- vided surface no red dots are visible as at periods less advanced. The alterations in the mechanism of the senses must next be considered. The skin, which is the medium between the nerves of tact, and external agents, undergoes great changes in the progress of life. It becomes drier, harder, less flexible, and at the same time looser, in consequence of the absorp- tion of the adipose substance. By the latter qualities the function of the skin is more evidently impaired, in that modification of it more expressly denominated touch, or the sense of tact united with certain muscular feelings in the fingers and hands. By the looseness of the integuments, the slowness and weakness of the muscles, the stiffness of the digital joints, and that dulness of sensation which exists in this as in every other part of the system more or less, the hand is notably deteriorated in old age. In the olfactory apparatus we find that, although the cavities and sinuses, through which the Schneiderian membrane is ex- tended, are rather increased than diminished in size, the membrane itself is attenuated and less pulpy. The nerve also is mentioned by Rulher* to be evidently contracted and wasted. The sense of taste so closely connected with that just spoken of survives to the extremes! limit of existence ; the final cause of which is evi- dent. It is too intimately connected with one of the processes of organic life to be easily dispensed with, although one of the functions of the superadded life. It is, however, feebler than at periods less advanced, and requires the excitement of more piquant aliment ; this is partly owing to the diminished sensibility of the gustatory nerve itself, and partly to the diminution of the sense of smell, on the per- fection of which depends our appreciation of the more delicate species of sapidity. The * Diet, de Med. art. Aye. surface of the tongue is more rugose than in younger subjects, and there is generally a de- ficiency of moisture, which is an additional cause of diminished sensation. The ear, both in its external appendages and in its internal structure, presents certain conditions which very well account for the frequency of deafness among the aged. It is true the cartilages become harder, more elastic, and therefore more vibratory, but the internal surface of the meatus is often thickened, and obstructed by a dense cerumen. The mem- brana tympani is more rigid and therefore less capable of varying with the degree of the vibra- tions. In the internal cavity, although the mastoid cells are enlarged as life advances, the deficiency of the liquor cotunnii in the vestibule, the cochlea, and the semicircular canals, must greatly interfere with the produc- tion of hearing. In addition to all these cir- cumstances there is probably an idiopathic insensibility of the nerve. The modifications of the organ of vision are familiar to all who have paid even the most superficial attention to the science of optics. The cornea is less transparent and less convex, partly from the diminution of the aqueous humour, and partly from the condensation of its texture. The latter change is more marked at the circumference, where a nebulosity is often formed, which has gotten the name of gerontotoxon, or arcus senilis. The pigmentum diminishes, and the iris grows paler in con- formity with the altered colour of the hair. The crystalline lens is denser, less transparent, and often acquires a yellow tint ; the vitreous hufnour likewise suffers a decrease. The retina is considerably attenuated, but has increased in firmness. The punctum luteum is paler, and not unfrequently altogether effaced ; a change which, in the opinion of Meckel,* bears a direct ratio to the diminution of the transparency of the cornea. These several .alterations are ne- cessarily followed by two results diminished refraction of the rays of light, and torpor of the nervous function, both of which prod uce pres- byopia. That long sight bears a relation with nervous as well as more mechanical causes is, we think, attested by the fact that this kind of vision is modified by temporary excitement of the brain, as in phrenitis.f If we now take a retrospect of the revolu- tions which have occurred in the several struc- tures enumerated, and endeavour to arrange them under specific heads, it will be found that diminution of bulk, deficiency of fluid, and condensation of substance, comprehend them all or nearly all. The attenuatjon has been generally ascribed to a preponderance of absorption over deposition, or a reverse of that condition in which incremental growth consists. But we cannot enter upon the question here, and must refer to the article NUTRITION, con- tenting ourselves with the remark that it seems a superfluous multiplication of causes to sup- * Op. cit. t. iii. p. 261. t See Abercrombie on Diseases of the Brain. AGE. pose that absorption increases, when the cessa- tion or diminution of deposition fully explains the fact, provided the absorption is only main- tained in its usual ratio. Concerning the lessened quantity of fluid we have already made some remarks, and hinted at its relation with impaired digestion and slackened circulation. Here it is sufficient to observe that the fact is a sign of diminished vitality, by which we mean merely a diminu- tion of vital actions, especially of those of nu- trition. The abundance of fluid in the young succulent body is adapted to the constant accu- mulation of new particles, and to the increasing complexity of the organization of the tissues, as well as to the reparation of waste, or to the counteraction of decomposition; by the still abundant though diminished quantity in the adult the composition is maintained and ren- dered more exquisite; in the old man there is only enough required to keep up that degree of renovation, which is necessary to the integrity of the structure, and even this action is less than in former periods, because the organiza- tion, from its chemical nature, is less prone to decomposition. This brings us to the con- sideration of the third general fact, or the condensation of tissue, which will require more particular notice, because great impor- tance has been assigned to it by some writers. The condensation is a result of the deficient humidity just spoken of; but this is not all, otherwise the condensation would be merely that of dryness ; the tissue itself is of firmer materials. Thus membrane becomes ligament, ligament cartilage, cartilage bone, and bone increases in its earthy proportions. This har- dening of the whole body is spoken of by many writers as the cause of decay, and ulti- mately of death, by the gradual closure of all the small vessels, and the obstruction to vital motions ; while the methods of averting old age, proposed by the same authors, turned chiefly upon an artificial supply of moisture to the body. Galen constantly alludes to this condition when treating of old age, and the means of resisting its tendencies.* Lord Bacon, in his curious and highly interesting treatise, entitled Historia Vitae et Mortis, has much to say upon desiccation and the methods of pre- venting it, suqh as bathing and inunction. The fable of the restitution of old ^sop by the cauldron of Medea, he considers typical of the utility of the warm bath in softening the substance of the body. So much stress does Haller lay on the effect of the universal tendency to induration, that he tells us that one of the reasons why fishes are so long-lived is because their bones are never hardened to the same degree as in the higher animals " Inter animalia aves longaeviores sunt, longaevissimi pisces, quibus cor minimum, et lentissimum incrementum, et ossa nunquam indurantur." Primae Lineae, 972. There is, however, we think, but little foundation for the supposition that induration stands in the relation of cause * See his treatises De Sanitate Tuenda, and De Marasmo. VOL. I. to the general failure of the functions of the body. It is rather a symptom of decline, or one of the phenomena in \\hi< h decline con- sists, and is therefore itself the effect of the failure or alteration of some of the functions, more especially of the assimilative. It , deterioration of interstitial secretion, partly promoted by the changes in circulation, in di- gestion, and probably in innervation, and partly itself contributing to these changes, but pri- marily owing its origin, like the latter, to the ultimate law, which determines that at a certain period decay shall transpire. It is in one re- spect a descent in the scale of organization. This indeed is indicated by the paucity of fluids and by the slow nutritive motions, which conditions are always sufficient to warrant our application of the terms, diminished vitality or less vitalized structure; but the substance itself, indepen- dently of these deficiencies of action, belongs to a more simple organization. We examine a bloodvessel, and instead of finding its coats of that complex texture which enables it to ac- commodate itself by a property, known only in living bodies, similar but superior to elasti- city, we mean tonicity, we observe a plate of osseous matter, unyielding, insensible, immo- bile, possessing no other vital character than bare assimilation or molecular growth. We search for those admirably constructed sub- stances which are interposed between the ribs and the sternum, and by their elasticity give extent and facility to the respiratory move- ments, and we discover them converted into the same matter as the contiguous bones, with the coarse property of cohesion, and, as in the former instance, with nothing but its growth to redeem it from the character of mere inorganic matter. We untangle the muscle, and instead of the irritable fibre, soft in texture but firm in contraction, we find a torpid substance, scarcely fibrous in form, firm in mere physical cohesion, weak in vital contraction, and consequently of a degraded organization. The processes of induration about the joints, the glands, and the integuments, will all, when examined, be found to approximate more than the former conditions of these parts to the qualities of the inanimate world. Homogeneousness of sub- stance is alone an indication of a low organi- zation, and a body which possesses both this property and hardness, maybe considered on the very outskirts of the region of vitality. Such are the properties of osseous deposits. May we not here perceive an analogy with the animals of the inferior classes ? In many of the mollusca how trifling a degree of vitality seems adequate to the formation, growth, and reparation of their calcareous coverings and appendages; or to go down to the coralines, madrepores, and porifera, we observe that the very lowest structure that can be considered animal is sufficient to secrete or assimilate those vast collections of earthy matter which pave the ocean, and rise into islands, moun- tains, and mighty continents. In this har- dened constitution, this simplified but dege- nerate structure, we see that the frame of man, in its natural decay, loses the characters that AGE. once distinguished it from the dust, and that not less literally than truly it has become more and more " of the earth earthy." We have now traversed as far and as mi- nutely as our space would allow, the organs and tissues, with their various alterations. It remains for us to inquire whether any one of them may be considered to stand in the rela- tion of cause to the others. We have already dismissed the supposition, that rigidity and con- cretion are productive of the other alterations, and we also partly entertained the question, when treating of the relations between assimi- lation, the fluids, and the organs subservient to circulation and digestion. But there are one or two additional points which must be alluded to in this place. The decay of all the organs, concerned in the life of relations, has been shewn to depend on a failure in the actions which are necessary to their generation and maintenance; these organs may, therefore, be dismissed at once from our inquiry into the causation or priority of the processes of degeneration. Yet the observation of the marked declension of the function of the nervous system throughout the body, has led to the hypothesis, that the failure in this power is the ultimate fact in the history of our decline, the fact to which all the others may be traced. This view is suggested by Dr. Roget in his justly-admired article on Age, in the Cyclopaedia of Practical Medicine. He considers the general condensation of tissue throughout the system, to be occasioned by a diminished force of circulation, which allows the capillaries to collapse and become obli- terated; the weakened circulation this distin- guished author is inclined to attribute to a diminution of nervous power in the muscular fibres of the heart ; whence he infers that the declension of nervous power bears the priority in the chain of events. W 7 e do not feel pre- pared to adopt the inference ; for if we admit this failure in the innervation of the heart, (and whether its fibres are dependent on nerves for their contractility, is still an unsettled ques- tion,) are we to pass over the condition of the blood ? Might we not say that the enfeebled contractions of the heart are referable to an alteration in the properties of its appropriate stimulus ? It is known that this vital fluid has been less affected by respiration than in former periods of our existence ; we might therefore, when searching for the earliest antecedent in decay, stop at the imperfect arterialization of the blood. But this would be, in our humble opinion, to pause too soon. The deficient oxygenation of the circulating fluid is sufficiently well known to be the effect of certain changes in the apparatus of respiration. And to what do these changes belong ? To a variety of structural, functional, and nervous phenomena, which, if pursued, would lead us into a maze of events, from which it would be impossible to select that which was earliest in its occur- rence. Or if we leave the respiratory system, and follow the blood backward to the process of chylification, and ultimately to digestion, we shall, as was shewn above, be equally unsuc- cessful in obtaining satisfaction. Or finally, if we return to the heart, and investigate the dimi- nished nervous power, admitting this diminu- tion to be alone sufficient for the debility of circulation, is it possible to stop at this pheno- menon ? Nervous power is nothing but the function of nervous substance, and whether the latter belongs to the ganglionic system, or to the cerebro-spinal, it may have undergone some change, or have been stimulated differently from usual. We know that the sensibility of the nervous system is most intimately connected with the quality of the blood, and with the force of its impulse ; so that if it be true that diminished circulation is the effect of diminished innerva- tion, it is no less true that the latter is also the result of the former. Thus it appears that in this inquiry we are constantly arguing in a circle, and it can scarcely be otherwise ; the principal structures and functions of the organic life commenced simultaneously ; they must].de- cline simultaneously : they assisted one another to grow ; they accelerate each other in the way to dissolution. If, however, we are disposed in some measure to qualify this remark, and still hold that there must be some organic changes primary in the work of decay, all ana- logies must, we think, conduct us to the simple processes of assimilation and secretion, into which all the more complicated functions must be ultimately resolved ; but we can go no farther, for we know not what determines or modifies the play of those subtle affinities, motions, and contractions, in which such changes consist. Some fancy that the enigma is solved by the hypothesis of a diminished vital power ; but we have already attempted to show that the interpretation is without value, when applied to the cessation of development ; the same reasons render it equally useless as a key to the hiero- glyphics of decay. Not less vain were the endeavours of those who could satisfy their philosophy with such a subterfuge of ignorance as was afforded in the theory of a sum of exci- tability, originally allotted to the system, and gradually exhausted, &c.; as if excitability could possibly mean any thing more than an expression of the collective phenomena of ex- citement, or vital movement. It is exactly on a par with the doctrine of decreasing vitality.* Some talk prettily and poetically of the vital flame burning out, of oil gradually wasting, of fuel expended, phrases applicable enough as metaphors, but absurd when propounded, as they too often are, as statements of matters of fact. When philosophy has failed to discover an- tecedences, she may still find a prolific source of employment in the study of harmonies. There is no event to be found in the relation of cause to those organic changes which, without the intervention of accidental agents, ultimately affix a bound to the duration of man's existence. As no cause can be elicited for the termination of development, neither can we better explain * "La gene de 1'influence vitale s'accroit saus cesse." Cabanis. ALBINO. 83 why growth does not continue stationary, and maintain the bodily structures for a series of ages, so long as external circumstances remain the ratio of subsistence. The time ommi.-d in attaining maturity bean a lir- -t to the period of existence in tin- same. We live in the midst of agents consequently, if life were proloi its present limits, that time during which the offspring of man is either helpless or very the that both supply us with life and infest us with poison : for a time we resist the baneful tendencies, and then gradually succumb, but dependent on the parents, would be al- in what manner we are at present ignorant, ened, and the accidents of disease or other The prevalence of certain functions has been casualties remaining the same, it is cl- supposed to fortify certain animals against the confusion, distress, and manift.' outward agents or inward processes that would would accrue to a rising generation. otherwise urge them to dissolution. The in- the attainment of maturity and of its accompa- fluence of respiration upon nutrition is well known, and consequently a large sum of respi- ration has been alleged to account for the longevity of birds ; but there are equal or much greater instances to be found among fishes and reptiles, the amount of whose respiration is extremely small. In the one case the vitality is said to be less rapidly consumed, in the other to be more abundantly supplied ; expla- nations which amount to little more than statements of the same facts in different lan- guage. Lord Bacon was of opinion that birds owe their lengthened existence partly to the smallness of their bodies, and partly to their being so well defended by their teguments from the atmosphere ; while he accounted for the long life of fishes by the non-occurrence of desiccation in their aqueous element. There is nothing satisfactory to be obtained from speculations of this sort. The most that we can learn is the variation in the term of exist- ence by the influence of various outward agents and modes of life. But whatever variation may be discovered, it will still appear that climate, and time, and custom, and science have never prolonged the date beyond certain limits. The study of these circum- stances, and the appliances of art, undoubtedly tend to enable a greater number to attain the extreme goal, but can never give the power of transgressing it. Vain, then, as Boerhaave observes, are the hopes of men who look for an agerasia! Although at present, then, we cannot trace the causes of the bounded nature of our existence, yet it is not difficult to discern its fitness to our constitution, and to the universal frame of things. The brevity of life is an ancient com- plaint ; lamentations have been chaunted over it time out of mind : but its antiquity does not redeem this, any more than many other opinions equally hoary, from the character of nying faculties, it is not clear that any thin.? would be gained by the possession of for a longer period than is now allowed ; sii i know but too well that men, after a time, lost.- tin- spirit of enterprise once engendered by the con- sciousness of increasing or lately-acquired powers, and fall into habits of action which they are unwilling to abandon, but which do not advance the resources of the species beyond a certain limit. Hence the advan- tage of their giving way to others, to whom they can commit their knowledge, and who, by their unworn energy, will advance it fur- ther. " Life is sufficient for all its purposes if well employed," was well observed by Dr. Johnson ; and what follower of medicine can forget that the immortal sage of Cos, by the example which he afforded in his well-spent life, disarmed his own antithesis of its woful point: o /3/o? BIBLIOGRAPHY. Lord Bacon, Historia vitze ct mortis. Pollich, Diss. de nutrimento, incremento, statu, et decremento corp. hum. 4to. Strasb. 1763. Ploucquet, Diss. sistens aetates humanas eorumque jura, 4to. Tubing. 1778 ; (Recus in Frank Delect. Opuseul. vol. vii.) Daignan, Tableau des varietes de la vie bum. 2 vol. 8vo. Par. 1786. Rush, Med. inquiries, vol. iv. Esparron, Ess. sur les ages de rhomme, Thes. de Paris, an. xi. Ranque, Des predominances organiques des differens ages, Thcs. de Par. 1803. Wesener, Spec. hist, hominis varias ejus periodos, &c. sistens, 8vo. Kraebcrg. 1804. Lucce, Grundriss der Entwickelungsgeschichte des menschlichen Kb'rpers.8vo. Marburg, 1819. Burdach, Die Physiologie als Erfahrungswissenschaft, 8vo. Leipz. 1803. Renauldin, Diet, des Sc. Med. art. < Age/ Rullier, Diet, de Med. art. ' Ages/ Begin, Diet, de Med. et Chir. Prat. art. 'Age/ Roget, Cyc. of Pract. Med. art. < Age/ Copland's Diet. art. ' Age/ Also the anatomical and physiological systems of Adelon, Beclard, Bichat, Bostoch, &c. (J. A. Symonds.) ALBINO. ($yn.Albinismus,leucopathia, Icu- a prejudice. Every consideration of the fact in cathiopia). This term, as employed in phy- question with reference to the universe must siology, appears to have been first used by the "justify the ways of God to man" in the dis- Portuguese* to designate a peculiar condition position of this as of every other event. We have o f t he human body, which was occasionally only to conceive the circumstance altered, in cor- observed among the negroes in the west< respondence to the idle wish of some aspirant parts o f Africa. It consists in the skin and , .. i .1 , 1 -1 *, i /* j.1 .l.Ii/t nrVhil/* in fllO to longevity, and we see that every thing else also would require to be changed ; that, in short, the beautiful arrangements of the world and of our social relations would be broken. To notice one or two of these : if the life of man were longer than it now is, his progeny would need to be greatly abridged from their present numbers, or they would soon exceed the hair being perfectly white, while in the * Vossius, de Nili origine, cap. 19. p. 69 ; see also Ludolf, Hist, ^tbiop. Com. lib. i. cap. 14. No 100 p. 197. The name by which the African Albinoes are known among their countrymen Dondos : by the French they are frequently termed Blafards. G '/ 84 ALBINO. form of the features and in all other respects the individuals in question exactly resemble the negro race. Another striking peculiarity of the Albino is the state of the eye, which is of a delicate pink or rose colour ; it is likewise so sensible to light as to be unable to bear the ordinary light of the day, while in the evening, or in a dark shade, its functions appear to be sufficiently perfect. We learn from Wafer, who accompanied Dam pier in one of his voy- ages, and who relates his adventures in crossing the Isthmus of Darien, that Albinoes are not unfrequently found among the inhabitants of this district.* We are also informed by various travellers and naturalists that they are often met with in some of the oriental isles, more especially in Java and Ceylon ;f in all these cases exhibiting the peculiar appearance of the skin, hair, and eyes, while, in other respects, they conformed to the external and physical characters of the people among whom they are found. The same circumstance occurs in this country and in the other parts of Europe, al- though, if we are to place any confidence in the accounts of travellers, the Albino is much more frequently met with in tropical climates, especially in the western parts of Africa, and in Darien, than in the more northern regions.^ * Wafer's New Voyage, p. 134 .. 8 ; Buffon, Hist. Nat. t. iii. p. 500; WoodVTrans. v . iii. p. 419, 10 ; Pauw, Recherches sur les Americains, par. 4, sect. 1. t. ii. p. 1 et seq. ; Raynal, Hist, des Indes, t. iii. p. 288. The earliest account which we have of the South American Albinoes is by Cortez, in the narrative of his conquest of Mexico, which he transmitted to Charles V. In describing the palace of Montezuma, among other objects of rarity or curiosity which were found in it, he says, " In hujus palatii particula tenebat homines, pueros, fcemi- nasque a nativitate candidos in facie, corpore, ca- pillis, superciliis, et palpebris." De Insulis nuper inventis narrat., p. 30 of " Nar. Sec. ;" see also Clayton, in Manch. Mem. v. iii. p. 261 et seq. t Buffon, t. iii. p. 399 and 415 : Wood's Trans. v. iii. p. 328, 9 and 344. We have not been able to procure the " Voyages de Legal," which is re- ferred to by Buffon and others, as containing the original account of the Albinoes, or, as they have been termed, Chacrelos, of Java. With respect to the Bedas of Ceylon, as originally described by Ribeyro, Hist, de Ceylon, ch. xxiv., and more lately by Percival, Account of Ceylon, ch. 13, and by Cordiner, Desc. of Ceylon, v. i. c. 4, it seems evident that they are not to be considered as Albi- noes. The only remark which Ribeyro makes on their physical character is, " Us sont blancs comme des Europeens, et il y a meme des roux parrai eux," p. 178. Percival, who saw some of them, states that their complexions are fairer and more inclined to a copper colour, than those of the other inhabitants ; while all that is said by these writers respecting their habits and modes of life indicates that they are a distinct race or tribe. The term Beda, or Badah, appears to be a corruption of Vaddah, or Veddah, which Knox informs us is the name of the aborigines of the island ; Account of Ceylon, p. 61 ; see also Brown, in Brewster's Encyc. art. " Ceylon," p. 704 ; Cordiner and Per- cival, ut supra. t Vossius and Ludolph, ubi supra ; Argensola, Conquist. de las Islas Malucas, lib. ii. p. 71, speaks of Albinoes as not uncommon in these islands; De la Croix, Relation de 1'Afrique, par. iii. liv. ii. sect. ii. $. 13, " Albinos, hommes blancs, ou We meet with a few scattered remarks in the writings of the ancients, which render it evident that this peculiar state of the human body had fallen under their notice. We have the follow- ing passage in Pliny : " Idem " (Isigonus Nicaeensis) " in Albania gigni quosdam glauca oculorum acie, e pueritia statim canos, qui noctu plus quam interdiu cernant."* The same circumstance is referred to by Aulus Gellius : " . . . . in ultima quadain terra, quae Albania dicitur, gigni homines, qui in pueritia canescunt, et plus cernunt oculis per noctem, quam inter diem ;"f and by Solinus : he says that the Albanians " albo crine nascuntur ;" " glauco oculis inest pupula, ideo nocte plus quam die cernunt."]: Pliny, in speaking of the inhabi- tants of a certain district in the interior of Africa, names them Leucaethiopes ; and, as it has been supposed that in this passage he referred to the Albinoes, the term has been applied to them by some eminent modern naturalists; || but it appears more probable that the Leucaethiopes were a tribe of negroes whose complexion was rather less dark than that Mores blancs," informs us that they compose a considerable body of attendants at the court of the king of Loango ; the same statement is made by Ludolf, ubi supra, and by the author of the Hist. Gen. des Voyagesj t. vi. p. 250 et seq. : Bowdich, Mission to Ashantee, p. 292, observes, that the king had at his court " nearly one hundred negroes of different colours, through the shades of red and copper to white ;" he adds that they were " generally diseased and emaciated ;" some of these were probably Albinoes. Cook, in his first voyage, saw six Albinoes in the small population of Otaheite, v. ii. p. 188 ; in his second voyage he saw one in New Caledonia, v. ii. p. 113, 4 ; and in his third voyage, he met with three in the Friendly Isles, v. i. p. 381, 2. These, it may be remarked, must have belonged to the Malayan variety. See also Winterbottom, Account of Sierre Leone, v. ii. p. 166 et seq. ; Stevenson, in Brewster's Encyclopaedia, art. " Complexion," p. 41, 2; Bory St. Vincent, L'Homme, t. ii. . " Hommes Monstreux," p. 143-7 ; also in Diet. Class. d'Hist. Nat. art. " Homme," p. 166 et seq.; Renauldin, in Diet, des Scien. Med. art. Albino ;" Lawrence's Lect. p. 287 ; Is. St. Hi- laire, Anom. de 1'Organization, t. i. par. ii. liv. iii. ch. i. p. 296, 314, 5, and art. " Mammiferes," in Diet. Class. d'Hist. Nat. p. 113. Some of the earlier writers did not hesitate to affirm, that they were confined to the offspring of negroes, Monge, Journ. Phys. 1782, p. 401 et seq. Suppl. We have no very distinct account of Albinoes among the Chinese and Mongols, but they appear to be as frequent among the Malays and native Americans as among the ^Ethiopians. * Hist. Nat. lib. 7. cap. 2. See the note of Cuvier, in his edition of 7th . . llth books of Pliny, t. i. p. 18. t Noct. Attic, lib. 9. cap. 4. t Polyhistor, cap. 15. p. 25. See the remarks of Saumaise, Exerc. Plin. p. 134, and of Pauw, t. ii. note in p. 13. Lib. 5. cap. 8. We also find the same term in Pomponius Mela, lib. 1. cap 4, and in Ptolemy, Geog. lib. 4. cap. 6; but it is not accompanied by any description of the people so designated. [I Among others by Bltimenbach, Gen. hum. var. 78. See Is. St. Hilaire, p. 297, note. We may remark that the term is objectionable, as indi- cating that the Albino is confined to the ^Ethiopic variety. ALBINO. 85 of the Africans generally.* It has been like- wise supposed that Celsus alluded to the Al- bino, when he speaks of a peculiar condition of the skin under the name of Leuce ;f but this appears to be a morbid cutaneous affection, and to have no reference to the subject now under consideration. From the number of Albinoes which were supposed to exist in certain countries, as well as from the marked peculiarity in their ap- pearance, an opinion was long entertained that they formed a distinct race or variety of the human species,}; originating in some unknown cause, and bearing the same relation to the other inhabitants of the countries in which they are found that the acknowledged varieties of the human species bear to each other. But this opinion, although sanctioned by high authority, may be considered as decisively disproved by the well-ascertained fact, that Albinoes are born of parents who do not possess this characteristic peculiarity of the skin, hair, and eyes. Although Albinoes are of comparatively rare occurrence in Europe, yet we have had a suffi- cient number of examples to render us per- fectly familiar with the appearance which they present, and with the precise nature of the * See the note of Hardouin in loco, Valpy's ed. p. 1285, Le Maire's, t. ii. p. 438 ; also the remark of M. Marcus in M. Ajasson's Trans, of Pliny, t. iv. p. 185. It is, perhaps, to this lighter coloured negro, rather than to the proper Albino, that we must refer, in part at least, the accounts which are given by travellers of the great number of white Africans that have been collected in certain situa- tions. We may remark that all accounts of Albi- noes that are given in general terms only, should be received with a certain degree of caution, unless the peculiar state of the eye is distinctly noticed. Humboldt .remarks that the missionaries, when they t met with any Indians that were less black than ordinary, were accustomed to call them white ; Pers. Nar. by Williams, v. iii. p. 287 et seq. See Prichard, in Medical Cyclop. Art. " Tem- perament," p. 163. t De Medicina, lib. 5. cap. 28. 19. $ This appears to have been the case even with Haller, El. Phys. xvi. 4. 13. p. 492. Voltaire main- tains this hypothesis, Essai sur les moeurs, (Euvr. t. xiii. Introd. and p. 7, 8. Buffon inclines to it; but his opinion on this point is not decided or uniform, t. iii. p. 501. See Is. St. Hilaire, p. 295. $ In addition to the authors already referred to, we have a case of this kind by Helvetius, Hist. Acad. Sc. 1734, p. 15 . . 7. The Albiness described by Buffon was born of black parents : see also Castillon, in Berlin Mem. 1762, p. 99 . . 105 ; Dic- quemarc, Journ. Phys. 1?77, p. 357 . . 0, and 1788, p. 301 et seq. ; Hist. Acad. Scien. 1744, p. 12, 3; and Maupertuis, Ven. Phys. p. 135 etseq. : Jeffer- son, Notes on Virginia, p. 103 . . 5, mentions an in- stance of three Albino sisters born of black parents ; two of these had black children ; Firmin, Descrip. de Surinam, t. i. p. 153, 5 ; Goldsmith's Anim. Nature, t. i. p. 452, 3 ; Brue, Hist, des Voyages, t. iii. p. 370, 0. See on this point Is. St. Hilaire, p. 303. We have a decisive proof that the peculiarity of the; Albino is merely accidental and individual, and does not constitute a distinct variety, in the state of the offspring of an Albino and a black negro, which is not intermediate between the two, as in the case of the Mulatto ; Hunter, on the Anim. (Econ. p. 248 ; Is. St. Hilaire, p. 305.. .7. circumstances which characterize them.* The skin is of a milky whiteness, without the slightest admixture of the brown or olive tint which is found in the complexion of even the fairest European female ; the hair is also per- fectly white,f an d ' s generally of a soft or silky texture, while all the coloured parts of the eye are of a delicate rose colour. We are informed that the skin of the African and American Albino is not only completely free from any shade of brown or olive, but that it is also devoid of the pink tinge which is found more or less in the complexion of the European. It would appear, likewise, that the skin of the tropical Albino is frequently in a diseased state, being /covered with scales of a leprous nature, and with a serous exudation, which proceeds from the fissures or clefts that take* place in various parts of the surface.}: It has been a very general opinion, that be- sides the peculiar state of the integuments, the Albino possesses a general delicacy of habit and constitution, and that he exhibits a defici- ency even of mental power. For this latter opinion there appears to be no sufficient foun- dation, and with respect to the former we may remark, that any general weakness of the phy- sical frame, if it be actually found to exist, may be probably referred, at least in some degree, to the peculiar condition of the eyes and the skin, which are not well adapted either to a * We have a copious list of references in Blu- menbach, p. 278 . . 0, in Lawrence, p. 281 . . 9, and in Is. St. Hilaire, ut supra and $. 5. One of the earliest of what may be considered as the correct descriptions is that of Buffon, Supp. t. iv. p. 559 et seq. The descriptions of Blumenbach, $. 78, and of Saussure, Voy. . 1037 . . . 1043, are par- ticularly correct and characteristic : to this we may add the more recent account of Is. St. Hilaire, t. i. par. 2, liv. 3. ch. 1, . 2 and 5. We are informed by Ludolf, ubi supra, that the first modern writer who distinctly mentions the Albino is Tellez. f Blumenbach particularly characterizes the whiteness of the hair of the Albino as being " gilva, colori cremoris lactis quodammodo comparanda," p. 275. | See Vossius, Ludolf, De la Croix, Cook's First Voyage, and Winterbottom, ut supra ; Blumen- bach, p. 274 ; Buffon, in Hist. Acad. Scien. 1760, p. 17 ; St. Hilaire, p. 304, 5 : Wafer, in his de- scription of the white inhabitants of Darien, p. 134, et seq., says that there is a white down on their skin. $ Wafer, p. 134-8 ; Buffon, t. iii. p. 503 ; Wood's Trans, vol. iii. p. 420 ; Voltaire, t. xv. p. 269,70- Pauw, t. ii. p. 9, 10; Raynal, t. iii. p. 288; Du- bois on the People of India, ch. xv. p. 199 et seq. ; Firmin, t. i.p. 153. . 5; Dalin, in Amoen. Acad. t. vi. p. 74, note ; Isert, Voy. en Guinee, ch. xv. p. 199 et seq. ; Labillardiere, Voyage, t. ii. p. 141 ; Win- terbottom, t supra ; Rayer, sur le Peau, t. ii. p. 193 . . 203 ; Blandin, Diet. Med. Chir. Pr*c. "Al- binie;" Breschet, Diet, de Med. " Albino;'' Sonini, in his edition of Buffon, t. xx. p. 355-6, note. So far as regards the state of the intellect, the charge is repelled by M. Sachs, who gives a minute account of the peculiarity in his own person and that of his sister ; Hist. Nat. duor. Leuca3thio- pum. Jefferson informs us, that the Albinesses, of whioh he gives an account, were " uncommonly shrewd, quick in their appehension and reply," p. 103-5. ALBINO. bright light or to a high temperature, and there- fore render the individuals less able to bear exposure to the weather, or to perform the ordinary occupations of life. To the same cause may be ascribed the morbid condition of the skin, which, as was remarked above, occurs not unfrequently in hot climates, and which is not observed in the European Albino. Partly from the circumstances stated above, and partly from the idea of imperfection or defect, which is connected with their appearance, the tropical Albino is generally regarded by his country- men with a degree of compassion or even of contempt ;* and hence is derived one of their popular denominations, chacrelas, which is a corruption of kakkerlakken, the Dutch name for the cock-roach, as being, like those animals, able to leave their haunts only in the evening.^ Besides the complete Albino, which we have now described, there are occasional examples of individuals, where the whiteness of the skin exists in certain parts of the surface only, while the remainder of the body is of its ordinary colour 4 In the majority of cases the peculi- arities which constitute the Albino are connate, and continue during life without any change. There are, however, some instances, where the whiteness of the skin does not exist at birth, but makes its appearance at a subsequent pe- riod, generally by slow degrees, until the com- plete Albino character is induced. When * Vossius, p. 68, informs us that they are avoided by the other negroes, as supposed to be diseased. De la Croix says the negroes regard them as mon- sters, and do not permit them to multiply, ut supra. Dubois, p. 199 et seq. observes that they are named lepers by birth, and that when they die their bodies are not buried or burnt, but cast on dunghills. See also Firmin, ubi supra. t Blumenbach, p. 277 : Lawrence, p. 287 : St. Hilaire, p. 296. J Phil. Trans, vol. xix. p. 781, and Lowthorpe's Abridg. vol. iii. p. 8 ; Buffon, t. iv. p. 565. tab. 2, et p. 571, 'tab. 3 ; Arthaud, in Journ. Phys. 1789 .!pt. 2. p. 277,8 ; Rush, in Amer. Trans, vol. ii. p. 392 et seq. ; Gumilla, El Oron. Ilus. t. i. p. 109 et seq. ; Ditto, Hist, de 1'Oronoque, trad. t. i. p. 150 et seq. ; Jefferson, p. 105 ; Blumenbach, 48 ; Rayer, ut supra ; Is. St. Hilaire, p. 309 et seq. ; Isert, p. 156. Bell, in Travels in Asiatic Russia, p. 217,8, saw a number of persons -with white spots oil the skin, but it seems probable that this was the effect of some cutaneous disease. The partial Albino appears to have been ; noticed by the ancients ; Lucian, Prometh, t. i. p. 15. Blumenbach, p. 276, says it is " semper con- natus ;" see, also, Lawrence, p. 285. There are, however, certain well authenticated cases, where the skin of the negro has gradually changed its co- lour from black to white ; sometimes the change has been general, sometimes only partial ; Bates, in Phil. Trans, vol. li. p. 175 et seq. ; Gualtier, in Journ. Phys. t. Ixx. p. 248 et seq. ; Le Cat, sur le Peau, p. 112 et seq. ; Rayer, ut supra ; Fisher, in Manch. Mem. vol. v. p. 314 et seq. ; Rush's Re- marks on the same, Amer. Trans, vol. iv. p. 289 et seq. In one of the four cases which are men- tioned by Le Cat, the change of colour appears to have been the consequence of a severe burn or scald. Besides the partial Albino, we have what has been termed the imperfect Albino, where the peculiarity exists in a certain degree only ; Is. St. Hilaire, $. 4. p. 312 ct seq. once formed it does not seem that it ever dis- appears, or is even in any degree diminished, nor have we any authentic accounts of its being removed by any constitutional change, either natural or morbid, or by external applications. Although, as has been stated above, this peculiarity occurs in individuals, who did not derive it from their parents, yet, like all those deviations from the ordinary structure of the body, which have been styled accidental varie- ties, when once produced, it is disposed to propagate itself by hereditary descent. There are also certain individuals, who have a ten- dency to produce it; so that even among the few European Albinos, of which we have a minute account, we have cases of its occurrence in two or more members of the same family, either as connected by parental descent, or by collateral relationship.* We have no instance on record of the offspring of a male and female Albino. The whiteness of the skin and hair, both general and partial, is not confined to the hu- man race ; it is found in most, if not in all the species of the mammalia, and in some of these, as in the dog, the horse, and the rabbit, is the subject of daily observation ;f in most of them, however, the peculiar state of the eye does not exist. These white varieties, like other analogous cases among the lower animals, when once produced, are strictly hereditary, in which re- spect they differ somewhat from the human Albino. Various opinions have been entertained by physiologists respecting the nature of this pecu- liarity, whether it should be considered as a morbid affection,^ depending upon a diseased state of the constitution, and also respecting its immediate or efficient cause. The first of these points may be regarded as a verbal con- troversy, depending altogether upon our defi- nition of morbid action ; but we conceive, that according to the ordinary definition of the term, we should not consider it as a disease, but as a connate deviation from the perfect structure of the animal frame, not produced by an external cause, and not removable by a remedial agent. For a correct knowledge of its physical cause, we are indebted, in the first instance, to an in- genious conjecture of Blumenbach's, who ac- counted for the red colour of the eye, and its extreme sensibility to light, by the absence of the pigmentum nigrum. * See particularly Saussure's account of the two boys of Chamouni and Sachs's Narrative ; also Blu- menbach, p. 276 and 279, note ; Firmin and Jeffer- son ut supra ; Pauw, t. ii. p. 25 ; Bory St. Vincent, L'Homme, 'p. 144, mentions an Albino of the third generation; Is. St. Hilaire, passim. t Blumenbach, p. 281, 2 : Is. St. Hilaire, p. 297.. 9. | " Ad cachexias referenda videtur affectio," Blumenbach, p. 274 ; Is. St. Hilaire, . 6, supposes that there are two species of Albinism, one the eifect of disease, the other a true anomaly ; but we con- ceive that the term is not correctly applied to the former state. Comment, de Oculis Leucaethiopum, et De Gen. Hum. var. . 78. ALBINO. 87 This conjecture was shortly after verified by Buzzi of Milan, who took advantage of an opportunity which presented itself, of dissecting the eye of an Albino, in which the pigmentum nigrum could not be detected.* He also ex- amined the structure of the skin, which appeared to be deprived of the rete mucosum, that part of it in which its specific colour is supposed to reside ; the hair was also found to be deficient in its central coloured part.f Whether, in these cases, the pigmentum nigrum of the eye and the rete mucosum of the skin are absolutely deficient, or are only deprived of their colouring matter, so as not to be detected by the eye, is a point on which different opinions have been formed by anatomists ; J perhaps, upon the whole, we may be induced to consider the lat- ter opinion as the most probable. What are the circumstances in the consti- tution of the parents which should lead to this peculiarity in their offspring is entirely un- known, nor have any conjectures been formed on the subject which can be considered as even plausible. The hypothesis of Buffon, which at one time obtained a considerable degree of credit, that white is, as it were, the primitive colour of nature, which, by various external causes, is changed to brown or black, but which the body has always a tendency to resume under favorable circumstances,) | is completely without foundation : nor does it appear that we can explain it upon the principle, that do- mestication and the habits of civilized life have a tendency to produce a lighter shade of the complexion, because we trace no connexion between the supposed cause and the effect, * For some remarks " on the colour of the pigment of the eye," and its effect on vision, as applicable to the eye of the Albino, see Hunter, p. 243 . . 253 ; also Blumenbach, $. 51. " Capillorum cum cute consensus," and . 53, ' ' Irides oculorum cum capil- lorum colore consentientes." t Sachs gives us a minute account of the analysis of the hair of the Albino, compared with Vatiquelin's analysis of hair in its ordinary state, from which it appears that no iron could be detected in it. j Blandin, Diet. Med. Chir. Prat. ' Albinee ;" Rayer, . 630. Mansfeldt is disposed to ascribe the production of the Albino state to some shock given to the foetus, by an impression made upon the mother ; it is characterized as a " cessation totale, momentanee d'action cerebrale ; " Journ. Compl. t. xv. p. 250 et seq. Is. St. Hilaire essentially adopts this hypo- thesis, ascribing the peculiar state of the skin to an " arret de developpement," in consequence of which the colouring matter is not formed at the requisite period, p. 319,0. The idea, that it depends upon something peculiar in the seminal matter of the parent, which was maintained by Herodotus, Thalia, $. 101, and was controverted by Aristotle, Hist. Animal, lib. 3. cap. 22, has been revived by Mau- pertuis, Diss. 2, and by Pauw, t. i. p. 179, and t. ii. p. 21. Le Cat refers the colour of the negro to a pecu- liar substance, which he names " ^thiope animal," which he supposes is contained in their fluids, ana- logous to the black inky matter of the cuttle fish ; par. 2. art. 1 ; the absence of this substance con- verts the negro into an Albino. || T. iii. p. 502,3. ; Wood's trans, t. iii. p. 422. We may remark that this speculation of Buffon's is precisely the reverse of that of Hunter, p. 243 et seq. and because the production of the Albino is complete in the first instance, and not brought about by any gradual or progressive alteration. It appears that we must come to the con- clusion, that although the anatomical or phy- sical cause of the peculiarity is ascertained, yet that we are entirely ignorant of its remote cause, or of that train of circumstances which leads to its production.* * " The following cases have not been referred to in the body of the article; DelaNux, Hist. Acad. Scien. 1744, p. 13; Camelli, Phil. Trans. v. xxv, p. 2268; Duddell on the Eye, Suppl. to, sect. iii. $. 30 et seq. ; Percival, Irish Trans, v. iv. p. 97, 8 ; Hunter, Anim. (Econ. p. 250, 1 ; Traill, in Nich. Journ. v. xix, with an Add. by the editor ; Mansfeldt, Journ. Compl. t. xv ; Ansieux, in Journ. Med. de Corvisart, t. xiv, p. 263, 4. For the following epitaph, which appears to have been written on an Albino child, we are indebted to a literary friend, the Rev. Jos. Hunter. ' Upon Thomas, son of Ric. Elmhurst by Mar- garet his wife, daughter to Ric. Micklethwaite : whose promising parts, were interrupted by an early death. " . . . This boy no Albiau was, yet gray hair'd borne Who saw old age and night as soon as morne. His grave's a cradle ; there his God him lay'd Betimes to sleep lest he the wanton play'd. Bid him good night ! i'th bed of dust sleep on Until the morne of Resurrection. " Anagram. " Lo Earth misseth me, 1632." From the Church of Worsborough, Com. York. BIBLIOGRAPHY. Ansieux, in Journ. Med. de Corvisart, t. xiv. Argensola, Conquist. de las Islas Malucas. Lond. 1609.' Aristoteles, OperaaDuVal. Par. 1619. Arthaud, in Journ. Phys. pour 1789. Bates, in Phil. Trans, v. li. Bell's Travels. Glas. 1763. Blandin, in Diet. Med. Chir. Prac. "Albinie." Blumenbach, Gen. Hum. var. (ed. 3.) Gott. 1795; Ditto f Comment, de Oculis Leucaeth. Gott. 1786. Bory St. Vincent, in Diet. Class. d'Hist. Nat., " Homme ;" Ditto, 1'Homme. Par. 1827. Bostock, in Brewster's Encyc. " Albino." Bowdich, Mis- sion to Ashantee. Lond. 1819. Breschet, in Diet, de Med., " Albino." Brown, in Brewster's Encyc., Ceylon." Brue, in Hist. Gen. des Voyages, t. iii. Buffon, Hist. Nat. (ed. 2). Par. 1750. ; Ditto, by Sonnini. Par. An. 8; Ditto, (trans.) by Wood. Lond. 1812. ; Ditto, in Hist. Acad. Scien. pour 1766. Camelli, in Phil. Trans, v. xxv. Castillon, in Ber- lin Mem. 1762. Cehus, De Modicina, ab Alme- loveen. L. B. 1730. Clayton inManch. Mem. v. ii. Cook's first voyage, by Hawkesworth. 'Lond. 1773. Ditto, second ditto. Lond. 1777. Ditto, third ditto. Lond. 1784. Cordiner's Description of Ceylon. Lond. 1807. Cortesius, De Insulis nuper invent. Narrat. Colon. 1532. Dalin, Amcen. Acad. t. vi. De la Croix, Relation de 1'Afrique. Lyon. 1688. De la Nux, in Hist. Acad. Scien. pour 1744. Dique- marc, in Journ. Phys. pour 1777 and 1788. Dubois, on the people of India, (trans.) Lond. 1817. Dud- dell, on the eye, and Suppl. Lond. 1729. Firmin, Descrip. de Surinam. Amst. 1767. Fisher, in Manch. Mem. v. v. Gellius, Noctes Atticae. Basil, 1565. Goldsmith's Animated Nature. Lond. 1822. Gaultier, in Journ. Phys. t. Ixx. Gumilla, El. Oro- noco ilust. Madrid. 1745. Ditto, Hist, de 1'Oro- noque (trad.) Avignon. 1758. Holler, Elem. Physiol. Laus. 1757. Hehetius, in Hist. Acad. Scien. pour 1734. Herodotus, by Beloe (3d. ed.) Lond. 1812. Humboldt's Pcrs. Nar. by Williams. Lond. 1814. Hunter, on the Animal (Economy. Lond. 1792. Iscrt, Voyage en Guinec. Par. 1793. Jefferson's Notes on Virginia. Phil. 1794. Knox's ALBUMEN. Account of Ceylon. Lond. 1681. Labillardiere, Voyage. Par. 8. Lawrence's Lectures. Lond. 1819. Le Cat, Traite de la Peau. Amst. 1765. Lowthorpe's Abridg. of Phil. Trans. (2d. ed.) Lond. 1716. Lu- cianus a Graevio. Amst. 1687. Ludolf, Hist. JEthiop. comment. Franc. 1691. Mansfeldt, in Journ. Compl., t. xv. Maupertuis, Venus Physique. Haye. 1746. Monge, in Journ. Phys. pour 1782. Pauw, Recherches sur les Americains, Lond. 1760. Per- cival's Account of Ceylon. Lond. 1803. Ditto, in Irish Trans., v. iv. Plinius, Hist. Nat. a Valpy. Lond. 1826. Ditto, a Lemaire. Par. 1827. Ditto, lib. vii. . . xi., a Cuvier. Par. 1827. Pline, Hist. Nat. par Ajasson (trad.) Par. 1829. Pomponius Mela, a Gronovio. L. B. 1782. Prichard, in Cy- clop, of Pract. Med., " Temperament." Ptolemaeus, Geographia, a Bertio. Amst. 1618. Rayer, Traite des maladies de la Peau. Par. 1826. Raynal, Hist, des Indes. Neuch. 1785. Renauldin, in Diet, des Sc. Med., " Albino." Ribeyro, Hist. ;de Ceylon. Trev. 1701. Rush, in Amer. Trans., v. ii. and iv. Sachs, Hist. Nat. duor. Leucaethiopum. 1812. St. Hilaire, ( Isid.), Anomalies de 1'Organization. Par. 1832. ; Ditto, in Diet. Class. d'Hist. Nat., ' Mam- miferes." Saussure, Voyages dans les Alpes. Ge- nev. 1787. Soliiiiis, Polyhistor, cum Salmatii, Exerc. Plinian. Traj. ad Rhen. 1689. Stevenson, in Brewster's Encyc. " Complexion" Traill, in Nicholson's Journ. v. xix. Voltaire, CEuvres. Par. 1819. Vossius, de Nili Origine. Hag. Com. 1666. Voyages, Hist. Gen. des, Haye, 1747. Wafer's New Voyage. Lond. 1699. Winterbottom's Account of Sierra Leone. Lond. 1803. (J. Bostock.) ALBUMEN, (Fr.Albumine, Germ. Eyweis- sstojf,) is one of the most important proximate principles of animal bodies ; it is the leading ingredient of the blood, of many of the secretions, and of muscular fibre, cartilage, and membrane : the white of egg (whence the generic term albu- men) presents it in considerable purity, and it is from this source, and from the serum of the blood, that we chiefly obtain it for the purposes of experiment. In this article we shall describe the leading properties of albumen; and in others, refer to its principal modifications. The white of egg may be regarded as a combination of albumen with water ; it con- tains small quantities of saline substances, which are inseparable in its liquid state. When it is evaporated at a temperature below 120, it dries into a brittle, shining, transparent sub- stance of a pale yellow colour, inodorous and tasteless. Its ultimate constituents, exclusive of saline matters and a trace of sulphur, are carbon, hydrogen, nitrogen, and oxygen ; of these the relative proportions have been deter- mined by Gay Lussac and Thenard, who analysed the white of egg dried at 212; and by Dr. Prout, who employed the dried serum of slightly inflammatory blood ; the following table shows its theoretical composition as con- trasted with these experimental results : Atoms. Equivs. Theory. Carbon.. 8 48 51.61 Hydrogen 7 7 7.53 Nitrogen 1 14 15.05 Oxygen 3 24 25.81 G. Lussac. Prout. 52.883 50.00 7.540 7.78 15.705 15.55 23.872 26.67 1 93 100.00 100.000 100.00 White of egg, when heated to about 150, coagulates, that is, it becomes a white, translu- cent, and somewhat elastic substance, which, when cautiously dried, shrinks up and assumes the appearance of horn, becoming tough, yel- lowish, and insoluble in water. Two parts of white of egg and one of water entirely co- agulate when duly heated ; equal parts remain, under the same circumstances, semi-fluid; a mixture of one part of white of egg and ten of water becomes opaque, but is not coagulated ; and a milkiness is perceptible when the al- bumen only forms a thousandth part of the solution.* Fresh-laid eggs, and those which have been oiled upon the surface do not per- fectly coagulate when put into boiling water, in consequence, probably, of the dilute state of the albumen. One hundred parts of the fresh albumen of the egg, when carefully evaporated in vacuo, leave a residue == fifteen parts. One hundred parts of the coagulated white of a duck's egg (dried in vacuo with sulphuric acid) leave 13.65 parts, which, steeped in water, acquires its original appearance, but in four days only took up 68 of water, though it had lost 86. 35 .f When albumen is made part of the voltaic circuit, it presents appearances dependent upon the power used, which, when considerable, excites so much heat as to coagulate it; but with a feeble power and the poles sufficiently distant, coagulation ensues most plentifully at the negative platinum wire ; a coagulum also forms at the positive wire, where acid is also sparingly evolved. These phenomena are much interfered with by the evolution of gaseous matters at the respective poles, which occasion a froth, and the appearance of more extensive coagulation than actually occurs. When coagulated white of egg is boiled for several hours, it shrinks up and becomes har- dened, communicating traces of animal matter to the water. Heated by high pressure steam in a copper digester to 400, it blackens the interior of the vessel, and dissolves, leaving a small residue of unaltered albumen. The solution is brown, and has the odour of boiled meat (from osmazome ?). This action deserves further investigation.! White of egg soon runs into putrefaction, and evolves sulphuretted hydrogen. The se- rum of blood kept for two years in a well- stopped phial, blackened its interior, and be- came a stinking, pale, yellow liquid, still co- agulable by heat, and containing hydro-sul- phate, carbonate, and acetate of ammonia, and a fetid volatile matter : a portion of yellowish white purulent-looking matter, containing un- decomposed albumen, remained at the bottom of the phial. Coagulated white of egg, even under water, long resists putrefaction. * Bostock, Nicholson's Journal, vol. xiv. and Medico-Chirurgical Transactions, vol. i. and 11. t Chevreul, |Mem. du Museum vn. IbO. Ann. de Ch. et Ph. xix. 46. | Gmelin, Handbuch der Theoretischen Chemie, ii. 1053. 3rd ed. Frankfort, 1827. ALBUMEN. 89 One hundred parts of dried white of egg, subjected to destructive distillation, yielded carbonic acid, carburetted and sulphuretted hydrogen, prussic acid, carbonate of ammonia partly in solution and partly sublimed, stinking volatile oil, and 14.9 of spongy difficultly com- bustible carbon, which, by incineration, left 2.21 of ash composed of carbonate of soda, phosphate of soda, and phosphate of lime, (Hatchett.) Nitric acid, dropped into a solution of albu- men, forms a white, flaky precipitate, which is more or less abundant according to the state of dilution of the solution, and which is soluble in ammonia and potash. When coagulated white of egg is kept for some weeks in very dilute nitric acid, it acquires a yellow colour, and if digested in boiling water it dissolves, and has acquired the properties of gelatine, and is precipitated by tan and muriate of tin. Hatchett.)* Cold nitric acid sp. gr. 1.25, gradually tinges coagulable white of egg of a yellow colour, dissolving a little of it, and forming malic acid, with the evolution of nitro- gen ; its surface becomes tallowy, and in twenty-four hours it falls into a pale yellow powder, which is acid and composed of nitric, nitrous, and malic acids with albumen ; when thoroughly washed with water, it becomes more neutral and of an orange colour, still reddening litmus, and remaining insoluble in water, but soluble in caustic potash .f When coagulated white of egg is digested in hot nitric acid, nitrogen, nitrous gas, carbonic acid, and prussic acid are formed, and a dark yellow solution obtained, which is precipitated by the addition of water and ammonia, and which contains malic and oxalic acids, bitter matter, and fat. (Hatchett.)J Sulphuric acid is a less powerful precipitant of albumen than nitric acid. Dilute sulphuric acid dropped into an aqueous solution of albumen occasions a precipitate which is so- luble in excess of acid ; ferrocyanate of po- tassa throws it down. When coagulated albu- men is digested in sulphuric acid, very slightly diluted, it yields a deep crimson solution. Coa- gulated serum digested in sulphuric acid diluted with six parts of water, converts it into acid sulphate of albumen, which, when edulcorated with cold water, becomes more neutral, and is soluble in warm water, forming a gelatinous solution, which is precipitated by sulphuric, muriatic, and nitric acids, and by the alkalies. (Berzelius.)H Coagulated white of egg digested in hot sulphuric acid becomes carbonized without forming artificial tan. (Hatchett.) When a solution of recently fused phosphoric acid (pyro-phosphoric acid) is added to solution * Phil. Trans. 1799. t Berzelius Lehrbuch der Thier. Chemie, p. 38. Wbhler's Translation. Dresden, 1831. J Phil. Trans. 1799. According to Raspail, when sugar is previously dissolved in the sulphuric acid, the albumen is co- loured purple, which is deeper in proportion as the acid and sugar are in greater quantity. U Lehrbuch der Thier. Chemie. of albumen, it occasions an abundant pre- cipitate : the acid gradually loses this property, and again acquires it by fusion and ignition. (Berzelius.) Muriatic acid occasions a precipitate in al- buminous solutions, and entirely throws down the albumen when aided by heat; but the precipitate is soluble in excess of acid, and in ammonia and potassa. A muriated albu- men may be formed in the same way as the sulphate. (Berzelius.) Coagulated egg-albu- men digested in muriatic acid gradually ac- quires a purple colour. (Hatchett.) Albumen which has been precipitated by muriatic acid, often becomes reddish when collected and ex- posed upon a filter. When coagulated seralbumen is digested in acetic acid, it becomes soft and transparent, and, aided by a gentle heat, dissolves with the evolution of a little nitrogen. This solution is precipitated by the alkalies, but a slight excess again renders it clear : it is also precipitated by sulphuric, nitric, and muriatic acids, and by ferrocyanate of potassa. When this acetic so- lution of albumen is evaporated, it leaves a transparent sour residue, soluble in warm water acidulated by acetic acid. (Berzelius.) Albumen is slowly soluble in liquid ammo- nia. In solution of potassa it becomes gelati- nous, and yields a pale yellow green solution, precipitable by acids and alcohol, and by acetic acid. Heated in liquid potassa, albumen evolves ammonia. Alcohol and ether coagulate ovalbumen, but pure ether (free from alcohol) does not co- agulate seralbumen. (Gmelin.) When serum is shaken with ether, it soon separates upon the surface, holding fatty matter in solution. (Gmelin.) Coagulated serum digested in al- cohol or ether yields a solution of fatty matter. Coagulated ovalbumen, when long boiled in water, becomes bulky and falls into pieces, and a small portion is dissolved : the filtered so- lution, evaporated at 212, leaves a pale brown film, and is alkaline ; it is rendered turbid by mineral acids, acetic acid, and tincture of galls, and by many metallic salts. When albumen which has been cautiously dried at a low temperature (without coagula- tion) is triturated with four parts of water, it yields a solution resembling fresh al- bumen. A solution of the white of an egg in a pint of water occasions no precipitate in lime, bary- tic or strontia water, nor in solution of sulphate of lime. Some of the neutral salts render it more or less turbid, and it is copiously precipitated by solution of alum. Nitrate, acetate, and subacetate of lead are precipitated by albuminous solutions. One part of fresh ovalbumen in 2000 of water, or one of dried albumen in 10,000 of water is rendered turbid by subacetate of lead. A four-hundredth part of liquid, or a two thousandth of solid albumen is precipitable by corrosive sublimate. (Bos- tock.) The precipitate is blackened by potassa, and is probably a compound of muriate ofalbu- 90 AMPHIBIA. men and calomel. Nitrate of silver, muriate of gold , and of platinum , also precipitate album i- nous solutions. These precipitates are mostly triple compounds of acid, albumen, and oxide, and several of them are redissoluble in excess of liquid albumen. Albumen is precipitated by tannin in the form of a yellow viscid combination. Water, holding a thousandth part of solid or a two- hundredth of liquid ovalbumen, becomes tur- bid after some hours by the addition of a solution of galls containing 2.5 per cent, of solid matter. (Bostock.) The above are the principal chemical pro- perties of liquid and solid albumen as obtained from the egg and from serum of blood ; several of their modifications will be noticed under other heads, such as FIBRIN E, MILK, BILE, &c. The cause of the coagulation of albumen is, in many cases, obscure and even inexplicable. It ap- pears possible that the acids by which it is co- agulated enter into combination with it so as to form insoluble compounds; the same change pro- bably happens with certain metallic salts, and with tan ; its coagulation by alcohol has been ascribed to the abstraction of water. Having remarked the copious coagulation of albumen at the electro-negative pole in the voltaic cir- cuit, I was induced to ascribe the fluidity of albumen to combined soda, the evolution of which seemed to cause its solidification, and it appeared possible that the acids and even alcohol might also occasion coagulation by the abstraction of soda ; and that its more enigma- tical coagulation by heat only, might be as- scribed to the transfer of soda from the albu- men to the water. It has been objected to this statement that the addition of alcali to coagulated albumen does not reproduce liquid albumen, and that acetic acid causes no co- agulation ; but when albumen is once coagu- lated, its properties are essentially modified, and acetic acid, or even acetate of soda appear to form soluble compounds with it. (Gmelin.) Dr. Turner* supposes that albumen combines directly with water at the moment of being secreted, at a time when its particles are in a state of minute division ; but as its affinity for that liquid is very feeble, the compound is decomposed by slight causes, and the albumen thereby rendered quite insoluble. The or- ganization of albumen may certainly be con- cerned in its singular properties with respect to many coagulants : there are several albuminous fluids, which we shall hereafter refer to, which contain globules resembling thosexof the blood. In the voltaic coagulation of albumen, that which separates at the positive pole contains globules, which, under the microscope, resem- ble the blood-globules deprived of their co- louring matter.f The readiest tests of the presence of albumen in fluids are its coagulation by heat, alcohol, * Elements of Chemistry, 4th ed. 868. t Prevost et Dumas, Ann. de Chimie et Physique xxiii.52. and acids; when it is too dilute for such detection, it may be subjected to voltaic elec- tricity, or tested by corrosive sublimate, or by ferrocyanate of potassa; the alcali should, in the latter case, be previously neutralized by acetic acid. It would appear, from Orfila's experiments, that white of egg is an antidote to the effects of corrosive sublimate when taken into the stomach, and that, if administered in sufficient quantity immediately after the recep- tion of the poison, it prevents the progress of the symptoms. The white of one egg appeared sufficient to render four grains of the poison ineffective. The readiness with which some metallic oxides are received into the system may per- haps be ascribed to their affinity for albumen, with which some of them form compounds not easily decomposable, and in which the metallic oxide cannot be detected by the usual tests, till they have been subjected to heat sufficient to decompose the organic matter. Mercury and silver are thus, in certain cases, detected in the secretions and excretions. (W. T. Brande.) AMPHIBIA. (A^pK, utrinque, to $, vita. Fr. Amphibies. Germ. Amphibien. Ital. Amphibie.) A class of vertebrated animals, hitherto almost universally considered as an order of REPTILIA, constituting the Batrachia of the later erpetologists. To the retention of the latter appellation, as derived from the Greek name of a single form of the group, and as bearing no reference to any character either of structure or of habit, there is an obvious objection. The term Amphibia is therefore here adopted, as designating one of the most striking peculiarities of the class; namely, the change which takes place at an epoch of their life, more or less advanced, from an aquatic respiration by branchise to an atmospheric respiration by true lungs, and an equivalent and consequent alteration in their general structure and mode of life. The Amphibia may be characterized as " vertebrated animals, with cold blood, naked skin, oviparous reproduction, and most of them undergoing a metamorphosis or change of con- dition, having relation to a transition from an aquatic to an atmospheric medium of respi- ration." These characters, by many of which the am- phibia are distinguished from the reptilia, are sufficiently determinate and important to justify our considering them as a distinct class, ac- cording to the generally received principles of zoological arrangement ; notwithstanding most even of the modern writers on the subject have retained them as merely an order of reptilia. But it will also be seen that if in the adult state they approach the reptilia in many points of their general structure, their organization, during the early and imperfect condition of the tad- pole, partakes no less of that of fishes. As an osculant or intermediate form, connecting two others of higher typical importance, it may be, certainly of greater extent, and consisting AMPHIBIA. 91 of groups having more striking distinctive cha- racters, there is not, perhaps, a more interesting and satisfactory instance in the whole range of the animal creation than is afforded us in the class of amphibia : a circumstance which can only be fully appreciated by following out the structure of each system of organs, first as it exists temporarily in the tadpole, and ultimately in its permanent condition in the perfect animal. The class has been variously divided into groups according to the different views of the naturalists by whom they have been arranged. The division adopted by many zoologists of the present day, according to the mere presence or absence of the tail in the perfect state, is not only liable to the objections which belong to all merely dichotomous arrangements, but appears to be far less natural and less consistent with the physiological characters of the groups than that which may be derived from the absence or presence and the duration of the branchiae. Thus the frogs and toads, which in the adult state have not the vestige of a tail, and the salamanders and tritons, which retain that organ through life, all agree in the early possession of branchioa, which are subsequently lost and replaced by true lungs, and in un- dergoing consequently a total change in the medium of their respiration ; whilst the pro- teus and the siren retain their branchiae, with lungs, (rudimentary at least,) and probably throughout life possess synchronously the two- fold function of aquatic and atmospheric re- spiration. The amphiuma and menopoma have not as yet been observed to possess branchiae at any period of their existence, though further observations are necessary to warrant the con- clusion of an absolute non-existence of a meta- morphosis in these genera. It appears to me that no one arrangement hitherto given sufficiently distinguishes the different forms ; and I venture to propose the following modifications as more consistent with the diversities of structure in the different groups. Class AMPHIBIA. Order 1. AMPHIPNEURTA. Body elongate, formed for swimming. Feet either four, or two anterior only. Tail com- pressed, persistent. Respiration aquatic by means of branchiae, throughout life, co-existing with rudimentary lungs. Branchiae external, persistent. Eyes with palpebrae. Genera, Proteus, Siredon, Menobranchus, Siren, Pseudobranchus. Order 2. ANOURA. Body short and broad. Feet during the tad- pole state wanting ; afterwards four, the hinder ones long and formed for leaping. Tail before the metamorphosis, long, compressed ; after- wards totally wanting. Ribs wanting. Ver- tebrae few and anchylosed. Tympanum open. Respiration at first aquatic by branchiae ; after- wards atmospheric by lungs. Branchiae at first external, but withdrawn within the chest before the metamorphosis. Impregnation effected ex- ternally during the passage of the ova. Genera, Rana, Hyla, Ceratophrys, Bufo, Rhinella, Otilop/ta, Ductylethra, Bombinator, Breviceps. Order 3. URODELA. Body long, slender. Feet always four. Tail long, persistent. Ribs very short. Respi- ration at first aquatic by external branchiae, afterwards atmospheric by cellular lungs. Ver- tebrae numerous and moveable. Tympanum concealed. Impregnation internal. Genera, Salamandrina, Salamandra, Molge. Order 4. ABRANCHIA. Body long, formed for swimming. Feet four. Cranium solid. Tail compressed. Respi- ration by means of lungs only: branchiae none. No metamorphosis known. Genera, Menopoma, Amphiuma. Order 5. APOD A. Body elongate, slender, anguiform. Feet none. Tail very short, almost wanting. Lungs one larger than the other. (The existence of branchiae at any period of life unknown.) Ribs very short. Sternum wanting. Ears concealed. Impregnation unknown, probably internal. Genus, Cacilia. I. Osteology. The changes which take place in the habits and formation of these animals, in their passage from the tadpole or pisciform state to their adult and permanent condition, are not confined to any one system of organs or of functions. The skeleton, the organs of motion, of sensation,and of digestion are not less the subject of these changes than those of respiration and circulation : it will, therefore, be necessary, in treating of each system of organs, to describe not merely their structure in the perfect state, but the less advanced grade of organization from which they emerge in passing from the condition of a fish to that of a reptile. In the adult state, however, they are found to vary considerably in the form and composi- tion of the skeleton, according to their habits, and to the existence or absence of a tail. The principle of compensation, or, in other words, the extreme developement of one set of organs at the expense of another, which is so often seen to take place in every form of animals, is here strikingly illustrated. In the frogs, whose movements on land, from their feeding chiefly on terrestrial prey, are necessarily ex- tensive, we find the hinder legs developed to an extraordinary degree, for the purpose of enabling them to take enormous leaps, by which they not only seek or pursue their prey at a distance from the water, but rapidly escape from danger, and rapidly regain their place of refuge in the nearest pond or rivulet. As it is evident that a long tail and a generally elongated body, with a flexible spine, would Jbe not only useless but inconsistent with these habits, we find these animals absolutely tail- 92 AMPHIBIA. less, the body contracted longitudinally into as short a space as possible, the vertebrae very few, and anchylosed or soldered together into a single immoveable piece, and wholly devoid of ribs. On comparing with this formation, on the other hand, the extensive developement of the tail, the long flexible body, and gracile form of the newts or aquatic salamanders, and reflecting upon the obvious object of this structure in facilitating their motions in the water, we should hardly be prepared to find that the extraordinary extension of the hinder extremities in the frogs, the primary object of which is to afford the great powers of leaping just alluded to, is made subservient also to their aquatic life, by enabling them to swim with great facility, aided by a web of skin extending between the toes of the hinder feet. Now as we shall hereafter see, when treating on the respiration of these animals, that the occasional presence of water, and its applica- tion to the surface of the skin, is equally essential to the well-being of both these forms, it is very interesting to observe how admirably this peculiarity in the general re- quirements is provided for by the very different, and even opposite, construction of their form and limbs, which their individual habits of life demand. But to return to the detailed anatomy of the skeleton. On examining the general texture of the bones in this class, there is an obvious advance towards the firm calcareous substance of those of the higher forms of vertebrated animals when compared with the bones of fishes, they being more compact, and less tran- sparent and flexible than in the latter animals. The cranial bones, though they retain to a certain extent the character of those of fishes, in the permanent disunion of the different centres of ossification, at least in many in- stances, yet they do not overlap each other, as in that class, but, on the contrary, remain with their margins at least in contact, and in many cases actually united, though not by true sutures. The elements of which the cranium is essentially composed, and which in a higher grade of organization are found consolidated, are here still exhibited as distinct pieces ; a state of things which is strikingly imitated in the progress of the development of these parts in the highest classes during their growth. It is also to be observed that the bones of the face are more closely united to those of the cranium and to each other in the higher than in the lower forms of the class, exhibiting distinct and obvious links in the development of these parts, which we see so beautifully and gradually perfected in the as- cending series from fishes up to man. The following enumeration of the separate cranial bones of the amphibia, as existing in the menopoma alleganiensis, the gigantic sala- mander of America, will illustrate the general relations of the distinct centres of ossification, here remaining permanently detached. Fig. 14. In figs. 14 and 15 the different elements are thus designated: a. the frontal; b. the exterior frontal ; c. the parietal ; d. the nasal ; e. the occipital ; f. the pterygoid ; g. the tympanic ; h. the jugal ; i. the superior maxillary; k. the intermaxillary; /. the vomer; m. the sphenoid ; n. corresponding to the or- bitary processes or alae of the sphenoid. In the frog and most others the palatine bones are distinct. We here find that the separate portions or elements which in this class are permanently detached, correspond almost ex- actly with the number found in the cranium of fishes. It will be observed by a reference to the figures, that the intermaxillary bones and this is more or less the case in all the amphibia are much developed transversely, as in the fishes, an affinity which has been already so much insisted on, and which is borne out by the condition of all the other parts of the cra- nium. The lateral extension of the upper and lower maxillary bones, for instance, as well as of the tympanic and jugal, expands the general form of the skull, without involving any ex- pansion of the cavity of the cranium, which is restricted to a small, central, elongated space. The latter bones also terminate in a condyle, which is received into a shallow glenoid cavity of the lower jaw, a peculiarity which offers a AMPHIBIA. 93 still further illustration of the proximity of this class to the fishes. The lower jaw consists of three distinct pieces on each side, an anterior, a lateral, and a posterior or articular portion. The anterior bone supports the teeth in those genera which have teeth in the lower jaw, and unites with its fellow at the symphysis. In frogs the lower jaw is devoid of teeth, but they are found in the upper jaw, bordering the in- termaxillary and the maxillary bones ; and the vomers are also furnished, each with a trans- verse row of teeth ; but in the salamander, the menopoma, the proteus, and others, they are found occupying the margin of the lower jaw. In the toads there are no teeth in the lower jaw, but the edge of the jaw-bone is serrated. The second bone of the inferior maxilla occupies the side, and is larger even than the former. It has at the posterior part a coronoid process, behind and within which is placed the third bone, which forms the medium of articulation with the cranium. It is to the os hyoides that the principal interest attaches in the present class, as it is that bone which undergoes the most remarkable changes in its form and relations during their transforma- tion, passing from the office of supporting the branchial organs into a true os hyoides, and thus offering, as Cuvier has beautifully shewn, an elucidation of the true nature of this ap- paratus in fishes. As this bone, however, has a direct relation with the respiratory functions, I shall explain these changes while treating on that part of the subject. The spinal column varies exceedingly in the different forms of the amphibia. In the highest form the vertebrae are fewer than are found in any other animals. In the common frog Fig. 16. there are but nine, and in the pipa only eight. Of the nine vertebrae in the frog, the first, the atlas, a, has no transverse processes ; there are two articular surfaces situated anteriorly, by which it is articulated to the two occipital condyles. In the seven following vertebrae the anterior articular surfaces of the bodies are concave, and the posterior convex. This con- vex tubercle, which enters the concavity of the next vertebra, consists of the intervertebral car- tilage converted into bone. In the tadpole condition of the animal (and this remains per- manently the case in the perenni-branchial forms, as the menobranchus, the proteus, &c.) this intervertebral substance retains the soft con- sistence which characterises it in fishes ; and, as in that class, it is contained in the circum- scribed cavity formed by the cup-like hollows of the two articular surfaces of contiguous vertebrae. The elongated fish-like form of those amphibia which retain their branchiae throughout life, requires that this structure should also be permanent ; and we have thus another beautiful example of that perfect chain of organisation which is manifested by this class of animals, from the fish upwards to the reptilia. The vertebrae of the adult frog have long transverse processes (fig. 16, 6), but are wholly destitute of ribs a class of bones which would be utterly useless in the particular modes of locomotion to which these animals are restricted, and the absence of which implies a peculiarity in the act of respiration, which will be described hereafter. The spinous pro- cesses are very short ; the articular are oblique, the posterior of each being placed above the anterior of the following one. The last or sacral vertebra has large transverse processes (fig. 16, c) directed a little back- wards, to which the ilia (fig. 16, d) are at- tached; and to the body of this vertebra is united by two tubercles, a long single bone, extending backwards to above the anus. This bone (fig. 16, e) is considered by Cuvier as a second sacral vertebra ; but by Schultze, Altena, Dr. Grant, and others, it is regarded as the coccyx. The vertebral canal occupies the anterior third of a carina or crest, which runs along the upper surface of this bone, diminishing gradually in its course until it wholly disappears. The spinal column in the other orders of the class differs in a remarkable degree from that which has been just described. In the salamander there are thirteen dorsal, two sacral, and about twenty-five caudal vertebrae, which in the genus molge or newt are increased to upwards of thirty. In these the anterior surface of the body is convex, and the posterior concave, a contrary arrangement to that which occurs in frog. The transverse processes are directed a little backwards, each, excepting the atlas, supporting a small rib, which is scarcely curved. The menopoma has a similar arrangement. In the siren are found forty-three vertebrae in the trunk, and forty-four or more in the tail. They all retain in a great measure the form of those of fishes and of the tadpole of the higher orders of this class, particularly in the existence of the intervertebral cavity or double cone, formed by the apposition of two hollowed surfaces of their bodies, and filled by a semi-cartilaginous mass or intervertebral substance. Eight only of the vertebrae, commencing with the second, bear ribs, which are extremely small, and in fact merely rudimentary. In the tail the trans- 94 AMPHIBIA. verse processes are only found on a few of the most anterior vertebrae. The spine of the proteus is not sufficiently different from that of the siren to require any particular description. The construction of the members, both an- terior and posterior, especially the latter, will be found to be arranged on very different plans, according to the habits and requirements of the different groups, and particularly their mode of progression. In the apoda, as the ccecilia, there are not even the rudiments of limbs. In the other orders they exist under very different degrees of development, according as they are constructed for leaping and swimming, as in the frogs, toads, &c., or for creeping, as in the salamanders; or they are rudimentary, and without any very apparent use, as in the am- phiuma. It will be necessary to give a cursory description of these forms. Of the anterior extremity in the anoura. The shoulder of the frog (fig. 16, f. Jig. 17.) consists of the scapula, the clavicle, and the coracoid bone, which all combine to form the glenoid cavity for the head of the humerus. The scapula is composed of two very distinct portions. The upper, (Jig. 17, a,) which is Fig. 17. permanently cartilaginous, at least at its mar- gin, is articulated moveably to the inferior and more solidly ossified piece, (Jig. 17, b,) at the inferior and posterior part of which is the arti- cular surface forming its portion of the glenoid cavity, immediately anterior to which it is at- tached to the clavicle. (Jig. 17, c.) This bone is slender and straight, and is connected beneath with its fellow in the median line. The coracoid bone (fig. 17, d) is considerably larger than the clavicle, and is also connected with its fellow by its broad median margin. The sternum consists of several pieces, ex- tending from before the clavicles to some dis- tance behind the coracoid bones; the latter terminates in a broad xiphoid cartilage. These parts differ considerably in their relative pro- portions in different genera. The arm is developed in a very inferior de- gree compared with the hinder extremity. The humerus (fig. 17, g) is short and thick, having a rounded head, received into the glenoid ca- vity of the shoulder-joint. The opposite extre- mity forms an almost globular surface for its articulation with the bone of the fore-arm, which is still shorter, and consists of the radius and ulna united, (fig. 17, h,) having only a slight groove to show their line of union. The carpal bones (Jig. 16, i) are six in number, supporting the four metacarpal bones, (fig. 16, k.) The index and middle finger have each two phalanges, the others three. The index is particularly large in the male. The thumb is merely rudimentary. The posterior extremity is greatly developed in the frogs, for the purpose before mentioned, of enabling them to take long leaps, and to swim with great rapidity and energy. The pelvis consists of the three essential bones of this part, the ilium, ischium, and pubis on each side. The iliac bones, (fig- 16, d,) di- verging above, are moveably articulated with the sacrum . They then extend backwards, and form, together with the small ischiatic and pubic bones, (fig. 16, 1 9 ) the cotyloid cavities for the reception of the femur. This bone (fig. 16, m) is nearly twice as long as the humerus, cylin- drical, and having a slight double curve. The leg consists, like the fore-arm, of but one bone, the tibia and fibula being anchylosed through their whole length. This bone (Jig. 16, n) is even a little longer than the femur. It is succeeded by two bones of considerable length, (Jig. 16, o,) having very much the aspect of a tibia and fibula, but which must be considered as bones of the tarsus greatly modified, and are most probably the os calcis and the astragalus. Between these elongated bones and the metatarsal are four small tarsal bones. The metatarsal bones (Jig. 16, p) are much elongated, as are also the phalanges, (fig. 16, q) for the purpose of forming strong oars or paddles with the intervention of a broad web of integument. The inner toe is consi- derably developed, and the whole structure of the foot and leg thus combines to furnish a pow- erful and efficient organ of progression. The elongated forms of the aquatic sala- mander, the proteus, the siren, &c., in which the vertebrae are developed to so great an extent, present the opposite extreme in the structure of their limbs. These are small, feeble, and ap- pear as it were abortions. In the genus triton and in the salamandra, which possess both an- terior and posterior extremities, they differ but little in their general form and development. The bones of the fore-arm as well as of the leg, instead of being respectively anchylosed into a single piece, as in the frogs, are permanently separate, consisting of a distinct ulna and radius in the former, and an equally distinct tibia and fibula in the latter. The toes are four, both before and behind; they are short, slender, and of slight construction. This imperfect development of the extremi- ties is, however, as we have seen, admirably compensated by the extraordinary extent of the spine both in the body and the tail ; and while the limbs afford but very imperfect means of progression on land, the structure of the spine AMPHIBIA. is admirably adapted to the purpose of swim- ming, which is performed either by a succes- sion of curves, as in the amphiuma and the siren, or by the alternate flexure of the tail, as in the tritons and the menobranchus. Having given this general sketch of the os- teology of the amphibia in the adult state, it will be interesting to examine the structure of the skeleton in the tadpole. It has already been observed that in this early condition of its existence the animal resembles fishes in all the most remarkable characters of its organi- zation. We find accordingly that the limbs, which are at first scarcely perceptible by the most minute examination, become gradually developed, passing through a rudimentary form beneath the integuments, from which they do not emerge until they have acquired considerable size and a very defined figure. The hinder legs are first seen, and are early employed as a feeble assistance to the more effective tail, as instruments of progression. The tail is developed, however, to a great degree, occupying the same relative size and situation as it is found to do in fishes. The coccygeal vertebrae are numerous, forming a long column, not ossified, but retaining its cartilaginous structure, at least in those forms in which it is deciduous; but in the salamanders, the tritons, the proteus, and all others of the urodcht, it becomes ossified instead of being absorbed. In the frog and other anoura, as the permanent organs of progression acquire their full development, the tail is slowly re- moved by interstitial absorption, not suddenly falling off as some have supposed, but be- coming gradually smaller and smaller until it wholly disappears. The cranium under- goes no other important change than that of the gradual ossification and expansion of its different elements, the centres of ossification being at first wholly disunited as in fishes, and afterwards assuming the more consolidated structure and closer approximation to each other, by which they approach the reptilia. II. Muscular system. The similarity which has been already shewn to exist in the osseous system of fishes and of the tadpole and peren- nibranchiate amphibia, would naturally lead to the conclusion that a corresponding affinity would be found in the muscular apparatus. The muscles which are employed for progres- sion in those early forms of vertebrated beings, are found to consist of oblique layers, abutting upon a median line, and extending along the whole length of the tail on each side. A similar general direction obtains in the muscles both of the trunk and tail in the long-bodied forms of the permanently tailed amphibia. The direction of their action therefore is horizontal, and their progression is effected by the alternate action of the muscles on each side. These oblique caudal muscles in the tadpole of the tailless tribe, become absorbed with the vertebrae to which they are attached, as the animal gradually assumes its permanent form; but its aquatic habits are still provided for by the extraordinary magnitude of the flexors and extensors of the thigh, leg, and foot, which are in perfect ac- cordance with the great length of the bones of this extremity, which has been described. The muscles which form this important apparatus of motion are exactly analogous to those which are so peculiarly developed in the human leg. Thus the large glutei extend the femur, the rectus and triceps extend the leg, and by their united and sudden action forcibly throw the whole limb into a straight position, whilst the gastrocnernii, which are here as in the human subject of sufficient size to form a considerable calf of the leg, enable the foot with the wide expanse of its toes, connected as they are by a tense web, to strike with great force and effect the resisting medium in which they live, assisted by the flexors of the toes, which are called into action at the same instant. The same beau- tiful mechanism is no less adapted for the pe- culiar nature of their progression on land ; by it they are enabled to take those long and vigo- rous leaps which particularly characterize some of the genera of the acaudate family of this class. It is obvious that the same sets of muscles must be developed for the performance of the energetic and sudden movements above- mentioned as are required to sustain the upright form of the human subject in its erect position, those, namely, which extend at once the thigh upon the pelvis, the leg upon the thigh, and the heel upon the leg; and hence arises the remarkable similarity in the conformation of the leg in these otherwise remote forms, and hence too the act of swimming in man must be a tolerably accurate imitation of the same effort as exhibited by the frog. III. Organs of digestion. The foregoing consideration of the various structures of the organs appertaining to locomotion would pre- pare us for corresponding differences in those belonging to this important office. These variations, however, are not found exactly to follow those which have been described in the former class of organs. The tadpole condition of the higher amphibia does not correspond in the nature of its food, nor consequently in the structure of the alimentary canal, with the class of fishes, nor indeed with that per- manent tadpole, as it may be called, the larviform axoloth. The teeth, as has been already stated, vary in the different genera not so much in their size and form as in their situation. Thus the whole of the amphibia have teeth in the palate; the sala- manders have them also in both the upper and lower jaws, the frogs in the upper only, and the toads in neither. In the two latter genera the palatine teeth are placed in a trans- verse line, interrupted in the middle. In the salamanders they form two parallel lines, con- taining not less than thirty on each. In the menopoma they occupy the anterior palatine margin of the vomer, forming a line on each side parallel with the maxillary and inter- maxillary teeth. In the axoloth they are arranged in the quincuncial order, and are nu- merous. But the most remarkable form and arrangement of the palatine teeth is found in the siren, in which they have the quincuncial arrangement; they are placed on two small 96 AMPHIBIA. bony plates on each side, probably rudiments of the vomer and palatine bones. Each of the larger has six or seven lines of teeth, about twelve on each line; and each smaller bone bears four ranges of five or six teeth ; making in all nearly two hundred teeth in the palate. Those of the lower jaw in this animal are placed in similar order. In the proteus the teeth nearly resemble those of the salamander. The maxillary teeth are always slender, sharp-pointed, and closely -set. The frog has about forty on each side of the upper jaw, of which eight belong to the intermaxillary bone. The salamander has about sixtyabove and below. In the tadpole state of the frog the mouth is very small, and, instead of teeth, is occu- pied only by minute horny plates of just sufficient consistence to abrade the soft mixed food which it finds on the surface of animal or vegetable substances in the water. Its sto- mach and intestinal canal are of very different form from that which they afterwards assume. The intestine is of nearly equal size throughout its whole length. It is very long, being not less than ten times the length of the actual space from the mouth to the anus, and is coiled up in a circular form, occupying the greater part of the abdominal cavity. The canal, as we shall presently see, changes its character materially during the metamorphosis of the animal, becoming gradually shorter until it is not a quarter of the length, in proportion to the size of the animal, which it exhibited in its earlier condition. In the adult amphibia the whole alimentary canal is of a very simple character. The oesophagus is wide and comparatively short. The stomach single, consisting of a simple sac, elongated in the lengthened forms of the sala- mander, the proteus, and other aquatic species. The intestine is but slightly convoluted, even in the short tailless family ; and there is com- paratively little difference in the diameter of its two distinct portions. It terminates, as in the reptilia, in a cloaca, or pouch, which also receives the openings of the urinary and genital organs. The anus in the toads and frogs opens on the hinder part of the back ; in the other forms it is situated beneath at the commence- ment of the tail, as in the reptilia. The liver, the pancreas, and the spleen are found in the whole of the amphibia ; and these organs are observed, in the elongated aquatic forms, to assume a corresponding lengthened shape. The liver is of considerable size, particularly in the salamanders. The gall-bladder exists in all cases, varying, how- ever, in size and form in the different genera. IV. Lymphatic and lacteal system. This system is highly interesting in the amphibia, on account of its extreme development, and of its presenting several important and remark- able peculiarities in its structure. The investigations of Professor Muller of Berlin have lately brought to light the existence of pulsating cavities in the course of the lympha- tics, constituting a sort of ventricles for the pro- pulsion of their fluids towards the veins into which they are received. In the frog two pairs of these little pulsating sacs are found ; at the pos- terior part one is situated on each side of the extremity of the coccygeal bone, behind the hip- joint, and the anterior ones under the posterior edge of the scapula by the transverse process of the third vertebra. These cavities are of considerable size, and pulsate with some degree of regularity : the pulsations, however, do not coincide with those of the heart, nor are those on the one side always synchronous with those on the other. The posterior ones convey the lymph received from the legs and hinder parts of the body into the ischiatic veins, and the anterior pair, into which the absorbents of the arms and the anterior parts of the viscera, &c. open, convey this fluid into the jugular veins. The internal structure of these sacs is cellular; they communicate freely with each other on each side by anastomosing vessels. On inflating the organ, not only the lymphatic vessels are inflated, but the whole of the veins also. Dr. Marshall Hall had previously observed a somewhat similar pul- sating cavity in the eel. These lymphatic ventricles in the amphibia have still more recently received further exami- nation and illustration by Professor Panizza of Pavia, who published the result of his researches in the year 1833.* Professor Muller's discovery was published in the previous year in the Berlin Annals. The lymphatic system is developed to an extraordinary degree in the frogs, as well as in several other genera of this class, its vessels being found in numbers and of considerable size immediately under the skin. The lacteals ramify upon the surface of the intestine in two layers, anastomosing and forming intricate plexuses on the mesentery, and terminating in two trunks, or thoracic ducts, which pass forwards one on each side of the spinal column. V. Of the sanguiferous system. If the changes, so frequently alluded to, which the animals of this class undergo in passing from the condition of a fish to that of a reptile, have received repeated illustrations in the considera- tion of the structure of the skeleton, of the organs of motion, and of those of digestion, far more interesting and important are those which occur in the character of the circulation ; in which the view which has been taken of the true situation of the amphibia in the chain of animal development receives the most satis- factory proof. Beginning life with all the essential characters of the fishes, even in the functions of circulation and respiration, pos- sessing the single branchial heart of that class, how wonderful and beautiful are the changes which these systems of organs undergo, as the branchiae become obliterated to give place to pulmonic cavities, and the heart at the same time assumes the compound character and form of a systemic and pulmonic heart, in accordance with the change in the respiratory organs. The newts, or water-salamanders, afford the most satisfactory opportunity of observing these * Sopra il sistema linfatico dei rettili. fol. Pav. 1833. AMPHIBIA. 97 changes, as the branchiae are large in propor- tion, and remain external during the whole period of their existence ; the animal also acquires considerable size before these organs of aquatic respiration are lost. The heart in the early stage of these animals consists of a systemic auricle, which receives the whole of the blood from the system after circulation, and of a ventricle which propels it through a third cavity, the bulbus arteriosus, to the branchial arteries, of which there is one given to each branchial leaf. From the capillary branches of these arteries the aerated blood is received by the branchial veins, which, as in fishes, concur to form an aorta without an intervening ventricle. From the last, or posterior branchial artery, on each side is given off a branch which goes to the rudimentary pulmonic sac, and which ultimately forms the trunk of the pulmonary artery. But the most interesting and important change is that by which the continuous branches of what were originally the branchial arteries combine to form the two trunks of the aorta. This is effected by means of small communicating branches between the branchial arteries and the branchial veins, which, as the branchiae become absorbed, and their minute branches are obliterated and lost, gradually enlarge until they become continuous trunks; and the artery, which was originally branchial, then" becomes the single root of the two descending aortae, and at its base gives off the pulmonary artery. The two veins which return the blood from the rudimentary air-sacs gradually enlarge as these cavities become more important, and assume the character of lungs ; and at length they receive the name, as they perform the function, of pulmonary veins. These by de- grees become, as it were, distended at their point of union with the heart, and ultimately form the second auricle. This general description will be better un- derstood by a reference to the subjoined figures taken from the tabular views of M. St. Ange, of which an English edition has been published by Mr. Jones.* The following detailed description of those figures is necessary to the correct understanding of this intricate but interesting arrangement. Fig. 18. The first period, previous to any change having taken place in the branchiae, is given in fig. 18. Four pairs of trunks (1, 2, 3, 4) go off from the heart. The first branch on each side (1) gives off a small anastomotic branch (5) ; after which it becomes divided into numerous branchial filaments (6); these, by their ulti- mate subdivision, terminate in a capillary tissue or network (7), from which arise other minute returning vessels, forming, by their junction, a single large vessel (9), which brings back blood into the general circulation after it has been aerated in its course through the branchiae. The second branch (2) also gives off a small one (14) previously to its subdivision in the second branchial leaflet, which branch enters the returning vessel ; thus producing a com- munication between the two vessels 2 and 9, as in the former case. The returning vessel then terminates in the arch of the aorta, in which the two vessels 13 and 15 also terminate. The third principal vessel (3) is similarly distributed on the third branchial leaflet, and the corresponding returning vessel (16) termi- nates in the aorta, as in the other case. The arch of the aorta, thus formed, gives off a branch (21), which, after receiving the fourth branch from the heart (4), goes into the lungs (19). The second period, shewn in Jig. 19, occurs Fig. 19. * Tabular view of the circulation in vertebrated animals. VOL. I. w when the branchiae begin to contract. The anastomotic branch (5), shewn in the former figure, is not much enlarged, and assumes the character of a continuous trunk with 1 . The branches (11 and 12) have increased in size, but the original continuation of 1 going to the bran- chiae, has decreased in the same proportion. The anastomotic branch (14) has acquired the size of the arch of the aorta, whilst the continuation of 2 is diminished, and the branchial leaflet is contracted in a corresponding degree. The branch 3 has become exceedingly small; and 4, which was before the smallest, is now the largest of all. By these changes in the relative di- mensions of the different vessels, especially in the enlargement of the anastomotic branches, the whole system of the circulation is gradu- ally being altered, until, in the third period, (fig. 20,) it has assumed the character of that in the reptile, by the total obliteration of the branchiae and their vessels, and the enlarge- ment of those branches, which, at first only anastomotic, have now become principal. In the adult condition of the animal, there- H AMPHIBIA. Fig. 20. fore, the heart consists of a single ventricle, and of two auricles. The existence of a se- cond auricle was first demonstrated in the higher forms, the frogs and toads, by Dr. Davy,* and, although in the latest works of Cuvier and Meckel the auricle in these forms is de- scribed as single, yet the more complicated structure has since been amply confirmed by many other anatomists. Weberf especially has described the biauricular structure in a large American frog ; but he failed to demon- strate it in the perennibranchiate amphibia. From a very interesting paper by Mr. Owen, in the first volume of the Zoological Society's Transactions,} it appears that the biauricular structure of the heart was ascribed by Hunter to all the amphibia except the perennibranchiate forms; in which, however, the existence of the left auricle has been satisfactorily deter- mined by Mr. Owen, who has also given some very interesting illustrations of the mode in which the coexistence of branchiae and rudi- mentary lungs is associated with certain pecu- liarities of the circulation. The circulation in the adult amphibia, then, assumes exactly the character which we find in the reptilia, but in the most simple form. The little pulmonic auricle receives the blood perfectly aerated from the lungs by means of the pulmonary veins. The systemic auricle at the same time receives the impure blood from the system by the venae cavae. The blood from the two auricles is sent together into the single ventricle where it becomes mixed, and this mingled arterial and venous blood, thus but half purified, is propelled by the same impulse, partly into the pulmonary arteries to be more perfectly purified, and the remainder through the aorta and the whole circulating system to the different organs of the body. The aeration of the blood, therefore, is but imperfect; a condition which is met with equally in the whole of the reptilia. VI. Respiration. -~- The preceding observa- tions on the circulation have in some measure necessarily anticipated the account which we have to offer of the correlative function of re- spiration, and the character of those changes * Zool. Journal, vol. ii. t Beitrage von dem Herzen der Batrachier, 8vo. 1832. t Part iii. p. 213. to which its organs are subjected in the transit of the amphibia from the pisciform to the reptile state. Breathing water, in the first instance, exclusively, these animals are fur- nished in the tadpole condition with branchiae or gills, of a leaf-like form, considerably sub- divided, though far less so than in the fishes. These branchiae are, in the first instance, in all cases external ; but in the higher forms of the class they remain so situated only for a brief space, becoming, as in the frogs and toads, internal at a very early period of their ex- istence. They are supported by cartilaginous or osseous arches, connected with the os hy- oides, and the changes which they undergo are accompanied by alterations in the form of that bone, to which allusion has already been made, and an account of which will now be given. At that period of the tadpole's existence, at which its branchiae are in full action, and the lungs still restricted to the state of a black- ish, rudimentary tissue, we find the tympanic bones, (jigs. 21, 22, e,) developed to a great Fig. 21. Fig. 22. extent, and forming the basis to which the branchial apparatus is suspended, by means of a rather thick angular portion, f/gs.21, 22, a.) This has been shewn by Cuvier to represent what in the fishes is composed of three bones, and is the medium by which in them the whole branchial apparatus is suspended to the temporal, and which bears also the branchi- ostegous rays. Between these two lateral branches is a single piece, (Jigs. 21, 22, &,) which, according to the same authority, cor- responds to the chain of bones placed in most fishes between the two first branchial arches. To the posterior point of this bone are attached two rhomboidal portions, (c, c,) to the external margins of which are suspended the arches on which the branchiae are supported, and which represent the chain of bones in fishes, bearing the two last branchial arches. As the age of the tadpole increases, and its metamorphosis is proceeding unseen, (Jigs. 23, 24,) we find the branches which support Fig. 24. the branchial apparatus () gradually lengthen- ing, and becoming more and more slender, and at length exhibiting the two long cartila- ginous pieces, by which the os hyoides is AMPHIBIA. 99 attached to the cranium ; (fg. 25, ,) the single piece (/>,) and the two rhomboidal pieces (r, c ,) in the meantime become united and extended, (jigs. 25, 26,) and gradually lose by absorption Fig. 25. Fig. 26. d the branchial arches, and ultimately form a broad disc, the body of the os hyoides, the anterior margin of which on each side is di- lated into a scutiform process, and the posterior margin bears two bony appendages, which are, in fact, the posterior cornua of that bone. Such are the changes which this bone un- dergoes during the gradual passage of the amphibious animal from the tadpole state, in which it represents the class of fishes, to its perfect or reptile condition; and it affords a most interesting instance of the manner in which the true nature of an organ, existing under ambiguous circumstances in one class of animals, is often clearly illustrated by its cha- racters, or, as in the present instance, by its transformations, in another. The minute filiform branchiae, which are appended to the tadpole of the frog im- mediately behind the head, have essentially the same structure as is observed in the gills of the perennibranchiate family, as the siren and the proteus, though in a different form. In the proteus each branchia consists of three principal divisions or branches, from each of which proceed seven or eight leaves, again sub- divided into numerous regular leaflets form- ing the ultimate divisions of the branchiae, on which the extreme capillary branches of the vessels ramify, and in which the blood under- goes its necessary change. A minute rami- fication of the branchial artery, conveying the impure blood from the heart, enters each leaf- let at its base, (jig. 27, a.) and passes, along Fig. 27. fr- its shorter or inner margin, giving off capillary branches in its course, which, after meandering over the surface of the leaflet, and commu- nicating with each other in various directions, pass over to the opposite margin of the leaflet, and reunite in a corresponding ramification of the branchial vein (6), which passes out at the base to combine with the corresponding branches from the other leaflets, and convey the aerated blood back to the heart. This is the general structure, modified however in the different genera, by which this important func- tion is effected in all the amphibia, as long as they are confined to their aquatic life ; and whilst the higher groups lose these organs as they advance, and acquire the necessary organs for atmospheric respiration, those of the lower forms retain them throughout life, coexistent with rudimentary lungs ; and thus probably exhibit the remarkable phenomenon of a two- fold mode of respiration at one and the same time in the same individual. Such, then, is the general structure of the organs of aquatic respiration, whether in the early and transitory form in which it is seen in the frog and the salamander, or in the perma- nent character which belongs to it in the peren- nibranchiate group of the siren, the axolotl, the menobranchus, and the proteus. But as the former of these groups acquires gradually a per- fect and unmixed atmospheric respiration, and as the pulmonary cavity serving this office is only slowly developed, so we find in the pe- rennibranchiate forms that the lungs also exist, though in little more than a rudimentary state. The early condition of the lungs in the cadu- cibranchiate genera, in which they ultimately exhibit a somewhat advanced structure, is that of a mere rudimentary sac, without internal cells or any appearance of even the commence- ment of that more perfect structure which they afterwards acquire. Gradually, however, the inner surface is furnished with small processes, forming little sacs or cells, on which the capil- lary branches of the pulmonary vessels ramify, and through the infinitely attenuated surfaces of which the impure blood undergoes its essen- tial process of depuration. In the lower forms of the class, as in it\e pro- teus anguinus for instance, the air-bags, for they scarcely deserve the name-of lungs in this state, never arrive at this advanced stage of develop- ment, but remain permanently in the condition of simple membranous sacs. Every part of the apparatus belonging to that organ is equally rudimentary. The glottis consists of nothing more than a small slit in the lower part of the fauces, placed between the branchial apertures of each side. The margin of this little opening, which has no cartilaginous ring to support it, is furnished with a small soft pair of muscles, by which it is opened. The tube leading from this opening speedily bifurcates, and one passes to each air-bag. In this rudiment of a trachea and of bronchi, there is no appearance of car- tilaginous rings ; it is a mere membranous canal, each branch of which opens without any other apparatus into its air-cell. From the perfect condition of the branchiae, and the very H 2 100 AMPHIBIA. simple structure of these pulmonary sacs, it will readily be seen that the function of respiration could be only very ineffectively aided by the latter organs, even were there no other diffi- culty arising from the imperfect structure of the apparatus which in the air-breathing amphibia serves the office of conveying the air into the lungs. A short description of the means by which the act of inspiration is effected in the frog will enable us to judge how far it may be possible that the rudimentary lungs in the pro- leus and siren are to be considered as performing any such function. In the adult frog, toad, salamander, and all others of the higher orders of amphibia, the reception of air into the lungs is effected not by the primary expansion of the pulmonic cavity and the consequent rush of air into it, but by the act of forcing air into the lungs, or in fact by a simple act of swallowing. This is effected in the following manner. The os hyoides and tongue are brought downwards to a considerable extent, and the cavity of the mouth being thus much enlarged, the air enters by the nostrils. The pharynx is then shut at the posterior part, so as to prevent the passage of air into the ceso- phagus, and the cavity being suddenly con- tracted by means of the muscles acting on the os hyoides, the air is necessarily forced through the glottis and trachea into the lungs, as the posterior nares are closed either by their mar- gins acting as a valve, or by the pressure of the tongue against them. This view of the mode of inspiration explains the cause of the well- known fact, that if the mouth of frogs be held open they perish from actual suffocation ; for the motions of the os hyoides being thus im- peded, and an external passage being also afforded for the air, respiration by the injection of air into the lungs is obviously impossible. Any other mode of inspiration, connected with the primary expansion of the thoraco-abdo- minal cavity is obviously impossible in the frog and its congeners, from the total absence of ribs. It may not be out of place to explain here the mode in which the peculiar noise uttered by the male frog, called croaking, is produced.* Ac- cording to the observations of P. Camper, the inspired air is forced against the inferior surface of the tongue, the protuberance of which di- vides it as it were into two currents, which pass into the membranous sacs adhering to the lower jaw and existing exclusively in the males. From these sacs it is directed over the tongue, and by its vibration the peculiar sound in ques- tion is produced. It is an interesting question whether in the perennibranchiate amphibia, the organs which have just been described as rudimentary lungs, do ever serve the purposes of respiration in even the smallest degree ; and it is one of no small difficulty. The superficial structure of the nares in the siren and the proteus, in which they almost exactly resemble those of fishes, and which would preclude the mode of inspi- ration practised by the frogs, together with the slight and attenuated character of the mem- * Comment. Soc. Reg. Scient. Getting, v. ix. branous tube and sacs, would almost lead to the conclusion, assumed by Rusconi,that in the proteus at least these organs do not exercise any function appertaining to respiration. If these animals be confined for a considerable time in the same water, the branchiae become purple instead of having the florid red colour which characterizes them in a healthy state, and they die asphyxiated. On the other hand, the very excitement of the two sacs, accom- panied by tubes of such length, and opening to the pharynx by a sort of simple glottis, go- verned by a distinct muscular apparatus, would seem to warrant the opinion that a nearer affi- nity to true lungs is to be traced in these organs than in the air-bag of fishes, though recent observations have shewn the latter organ to be analogous to the lowest rudimentary state of lungs in the higher animals. The chain of affinities, therefore, is here perfect, as far as re- gards the pulmonary cavities. VII. The nervous system. The centre of the nervous system offers a not less striking in- stance of the progressive development of the am- phibia in their passage from the pisciform to the reptile state than those which we have already shewn in the organs of the other functions of the body. The condition of the brain in the early state of the frog tadpole, the genus in which the changes are most strongly marked, is almost ex- actly that which it possesses in the fishes. The linear arrangement of the different lobes, the bread and lobed form of the medulla oblongata, the small cerebellum, the large size of the op- tic thalami, with the distinct ventricles which they contain, and the very diminutive extent of the hemispheres, all evince a low degree of development, and one not yet emerged from that which we find in the brain of fishes. The same imperfect character is also observed in the spinal marrow, which even in the frog is con- tinued into numerous coccygeal vertebrae, and as the extremities are not yet in existence, is devoid of those enlargements which afterwards take place where the nerves of the anterior and posterior members are given off. The brain becomes developed, however, in a very short period ; the changes which take place being very rapid, though at last not very considerable; the hemispheres become enlarged, expanding laterally and in some measure upwards, con- stituting the first step towards that superiority in position, as well as in size, over the other lobes, which is so conspicuous a character of these important portions of the brain in the higher animals. Fig. 28. represents the brain 1, pneumogastric nerve; 2, ninth pair; 3, sixth pair ; 4, acoustic ; 5, fa- cial ; 6, the eye ; 7, optic nerve and its tubercle ; 8 and 9, base of the hemi- spheres ; 10, anterior por- tion of ditto ; 11, pedicle of olfactory lobe. in the common frog after Serres. As the limbs begin to make their appearance, the enlarge- AMPHIBIA. 101 ments of the spinal cord are observed to take place, and the contraction of the coccygeal ver- tebra; into a single linear bone, is accompanied by a corresponding diminution in the length of that part of the spinal marrow, which at length only extends, in the form of a small filament, into the anterior third of that bone. The inferior condition of the brain which has been described as existing in the tadpole of the higher species, is permanent in the proteus and other perennibranchiate genera ; so that the brain of the animal just named bears a very obvious resemblance to that of the larva of the aquatic salamander or triton. VIII. The organ of vision. The eye differs considerably in its form and magnitude in dif- ferent genera of the amphibia, and without any very apparent relation to either their habits or their circumstances. In the frogs and some others they are remarkably large and prominent ; in the salamanders they are comparatively small, though from their at least equally aquatic habits, this difference might perhaps have scarcely been anticipated, and in the coecilia, as the name imports, the eyes are scarcely if at all visible. In the latter animal the same object has doubtless been intended by this absence of vision, as in the mole and many other ani- mals, whose common subterranean mode of life would render the possession of acute sight not only generally useless, but an extreme inconvenience on their occasional appearance above the surface. In some points of their structure the eyes of the amphibia are not remotely related to those of the fishes ; as, for instance, in the flattened anterior surface of most of them, arising from the small supply of the aqueous humour, and in the depth of the crystalline. In some of the lower forms, there can scarcely be said to be a true orbit, the eyes being fixed as it were in the integuments, and surrounded by a mass of minute veins, intermixed with extremely small branches of nerves. Rusconi states that in the proteus he was not able to discover muscles, nor even the optic nerve ; though on carefully and gently raising the hemispheres of the brain a minute nervous filament was seen going to- wards the foramen which serves for the passage of the ophthalmic artery ; but whether this was the optic nerve or not, appears a matter of entire doubt. In fact, the structure of the eye in this animal, on the whole, is very imperfect. In the frog, on the contrary, the eye is fully developed, and all the essential parts of its structure sufficiently conspicuous. The globe of the eye is large and projecting ; the scle- rotic is considerably solid and tough, and semi- transparent ; the cornea is large, and though somewhat flattened, is much less so than in fishes, or in the lower forms of the elass. The inner surface of the choroid is extremely black, and the external of a silvery whiteness. The ciliary processes have not with certainty been discovered in these animals, unless, as Altena suggests, a little tubercular mass, occupying nearly their situation, and closely connected with the edge of the choroid and with the cap- sule of the crystalline, may be a modification of this structure. The iris is covered on its posterior surface with pigmentum nigrum ; the anterior having a shining metallic lustre, pre- cisely similar to that which we see in fishes. The contractility of the pupil asserted by Carus is denied by Altena and others. The retina is thick, and covers the whole internal surface to the capsule of the crystalline. The vitreous humour is, in proportion, abundant, and the lens is large and of a spheroidal shape, consisting of numerous concentric laminae, en- closing a nucleus of extreme density, exhibiting a close relation to the state of this part in fishes. There are in the frog three nalpebrae ; or perhaps, with greater strictness ot analogy, it might be said that there are two palpebrae, and a sort of expansion of the inferior, serving as a membrana nictitans. The superior pal- pebra is small, and is not possessed of any degree of mobility; the inferior is broad, ex- panded, and semitransparent. It has an in- ternal membranous expansion, which has just been alluded to, and which is capable of cover- ing the whole eyeball. IX. The organ of hearing. The function of hearing exists in very different degrees in the different groups of amphibia. The aquatic habits to which the lower forms are confined by their branchial respiration, would render an acute perception of sonorous impulses as unne- cessary as it would be incompatible with the dense medium in which they live ; and we find in this sense, as in every other function of the body, the most perfect concord existing be- tween the habits of the animal and its structural arrangements. The pisciform aquatic genera of this class, therefore, are found to possess as near an affinity to the fishes in the structure of the organ in question as in most others ; and in this they are also imitated by the tadpole state of the higher reptiliform groups, the adult condition of which exhibits a much more ad- vanced development of the acoustic organ. In the proteus and the allied genera, there is neither a tympanic cavity, nor membrana tym- pani ; it consists of a large cavity hollowed as it were out of the temporal bone, at the bottom of which cavity is the sacculus with its creta- ceous body ; the fenestra oval is is closed by a bony lamina, the representative of the stapes. Behind the sacculus are the membranous semi- circular canals. The whole organ is covered externally by the integuments, without any pos- sible communication with the atmosphere. In the frog, on the other hand, the whole structure is more complicated. The sacculus, which is membranaceous, is filled with the cretaceous matter, which is here semifluid, having the appearance of cream. The semi- circular canals are contained within the sub- stance of the temporal bone. The ossicula auditus are three, united, and contained within the tympanum, which they traverse, and are attached to the membrana tympani, a broad round membrane, perfectly superficial, and very distinct from the surrounding integument. The cavity of the tympanum is not capacious. It 102 AMPHIBIA. communicates with the external air by means of an Eustachian tube passing from it to the fauces. In all the essential parts of this struc- ture, there is but little variation from that which exists in the true reptilia. X. The organ of smell. The nares in the perennibranchiate amphibia are, like those of fishes, confined to little more than a slight cavity on the anterior part of the head, and having no continued canal by which they can communicate with the cavity of the mouth. In the proteus the similarity of this organ to that of fishes is so complete, that even the pli- cated radiations of the lining pituitary mem- brane are almost exactly imitated. It is of considerable size, and is contained in a length- ened canal or cavity, the parietes of which are in no part osseous. The nostrils terminate im- mediately under the upper lip. The olfactory nerves are rather large, and no sooner emerge from the cavity of the cranium than they divide into numerous branches of various lengths, which enter every part of the soft pituitary membrane. In the more highly developed genera the organ of smell has the more advanced structure which is observed in the reptilia. The nostrils are partly cartilaginous, partly osseous, and extend into the cavity of the mouth, though the posterior openings are placed much more for- ward than in the higher classes of vertebrata. The olfactory nerves enter the nostrils through two openings in the ethmoid bone. The ab- sence of the convoluted and extensive surfaces of the turbinated bones, the entire simplicity of the canal of the nostrils, and the small extent of its surface, must restrict these animals to a very circumscribed enjoyment of this function; and it is probable that the sensibility to odours is much more acute in the aquatic forms, in which the organs of sight and of hearing are so im- perfectly developed, than in the frogs, in which the organs of these senses are much more elaborately formed. XI. Of the organ of taste. The sense of taste, in all the amphibia, as well as in fishes, is probably very obtuse. The tongue in the urodela is small, and attached closely at every part. In the anoura, on the contrary, it is developed to an extraordinary degree; it is very long, bifid, and the anterior half is not only free, but, in its quiescent state, doubled back upon the posterior fixed part, and capa- ble of being thrown forwards and again re- tracted with the rapidity of lightning, serving as a most efficient means of arresting the quickest movements of insects, which it con- veys into the back part of the mouth to be swallowed. The application of the tongue as an assistant in respiration, by closing the posterior nares, in all higher groups of the class, has been before alluded to. XII. The dermal or tcgumentari/ system. The absence of all hard scaly adventitious covering to the skin of the amphibia is one of the most common, or perhaps it may be said, the only universal peculiarity by which they are, as a class, distinguished from all reptilia. The amphibious nature of their progressive development, or the existence at the earliest period of even rudimentary branchiae, can scarcely be said to be without exceptions, as several genera have already been mentioned as not having yet been observed in this condition. But the naked skin is a character belonging equally to all, from the serpentiform coecilia to the typically amphibious frog, and the pisciform axoloth and proteus. The skin of the aquatic genera is soft, smooth, and furnished with a secreting surface, by means of which it is kept constantly moist, and in a state suitable for that cutaneous respira- tion which strikingly characterises these ani- mals. Many of those which are generally inhabitants of the land, as the terrestrial sala- manders, the toads, and others, are provided with numerous cutaneous glands, which secrete a tenacious milky fluid, which is somewhat acrid, and may perhaps be deleterious if swal- lowed in any quantity ; though the old opinion of the poisonous nature of these animals is altogether without foundation. The fluid which is poured out from these cutaneous follicles in the common salamander is copious, of a milky colour, and consists of mucus, with the addi- tion of some acrid matter, the nature of which is not yet known. From the quan- tity which is suddenly secreted when the ani- mal is injured or any part of the surface irritated, it is not improbable that even the effect of fire may for a few moments be arrested by it ; and thus may have originated the fable of the salamander having the power of remaining unconsumed and unhurt when thrown upon burning coals. The acrid nature of the cuta- neous secretion of the toad was confirmed by the observations of Dr. Davy a few years since. The cuticle of these animals is frequently shed ; that of the aquatic species comes off in shreds, and is washed away from the skin. In the toads a very curious process takes place for its removal. When the cuticle has become dry and unyielding, and a new and softer surface is required, the deciduous layer splits down the median line of the back and of the abdo- men at the same time. The whole cuticle is thus divided into two parts. By numerous con- vulsive twitchings and contortions of the body and legs, this separation becomes more and more considerable, and the cuticle is gradually brought off the back and belly in folds towards the sides. It is then loosened from the hinder legs by similar movements of those limbs, and finally removed from them by the animal bring- ing first one and then the other forwards under the arm, and by then withdrawing the hinder leg its cuticle is left under the fore leg. The two portions are now pushed forwards to the mouth, by the help of which the anterior ex- tremities are also divested of it. The whole mass is now pushed by the hands into the mouth, and swallowed* at a single gulp. The new cuticle is bright, soft, and covered with a colourless mucus; the old skin was harsh, dry, dirty, and opaque. This curious AMPHIBIA. 103 process I have repeatedly watched. I have observed shreds of cuticle hanging about the terrestrial salamander, which would lead to the opinion that this animal does not disengage itself from its deciduous skin m the same manner as the toad; but as the .individuals under notice were not in health, the observa- tion is inconclusive. But the most interesting circumstance con- nected with the functions of the integuments of these animals, or indeed with any part of their economy, is their cutaneous respiration, or the power which the dermal surface possesses of effecting those changes in the blood, which are essential to life, and which are usually per- formed by particular organs set apart for that express object, and modified according to the aquatic or atmospheric medium in which the depurating agent is applied to them. Although the experiments of Spallanzani had long ago demonstrated that carbonic acid was produced by the contact of the atmosphere with the skin of frogs, the subject had never been examined with the care and attention which its importance demands, until the in- vestigations of Dr. Edwards of Paris, given in his work " On the Influence of Physical Agents on Life," set the question at rest, and esta- blished the proposition by a series of interesting experiments, so admirably arranged, so satis- factorily conducted, and so logically reasoned upon, as to leave no vacuity in the regular line of induction, nor doubt of the strict correct- ness of his conclusions. The existence of a cutaneous respiration in frogs was proved by the simple experiment of tying a piece of bladder over the head so tightly as to produce complete strangulation, and then placing them under water. On examining the air contained in the vessel after an hour or two, a sensible quantity of carbonic acid was de- tected. On placing frogs in vessels filled respec- tively with river water and with water which had been deprived of its air by boiling, and inverted over the apertures perforated in the shelf of a pneumatic trough, containing ninety- eight and a half pints, those in the latter lived on the average little more than half as long as those in the aerated water. On trying the effect of stagnant water renewed at intervals, they were found to live two months and a half, and then died from accidental neglect of renew- ing the water. Similar results followed ex- periments made under running water. The effects of temperature in these experiments were very striking, and prove that the duration of life under water is in an inverse proportion to the elevation of the temperature from 32 to about 107, at which point the animals die almost instantly. But these effects of tempera- ture were found to be modified by an increase of respiration, whether by their rising to the surface and breathing the atmosphere, or by the quantity of aerated water being increased. Such is a rapid glance at some of the results observed by this distinguished physiologist, on the cutaneous respiration of aerated water ; those which are connected with atmospheric respiration by the same surface are no less interesting. In order to render the experiments as rigorously satisfactory as possible, pulmo- nary respiration was prevented by actual stran- gulation, rather than by keeping the mouth open, a method which appears liable to some degree of uncertainty. A ligature was passed round the neck of six frogs, using the most rigid compression, so as completely to exclude any possible passage of air. One of them lived twenty days ; those placed in five ounces and a half of water had died in from one to three days. As the severity of the operation of strangulation might probably have hastened death, another mode was tried, namely, the total excision of the lungs, an operation which appeared to produce but little suffering; the animals were then placed on moist sand. Of three frogs thus treated, two died on the thirty- third day, and the remaining one on the fortieth. Other experiments were instituted to resolve the converse of the former proposition, whether life can be prolonged by pulmonary respiration alone, unaided by that of the skin ? The re- sult of the experiments made upon tree frogs and upon the bufo obxtetricans, was that pul- monary respiration is not sufficient to support life, without being accompanied by the influ- ence of the skin. The results of these experiments are not only highly interesting as regards the habits of the particular tribe of animals which were the subject of them, but still more so with refer- ence to some important questions in general physiology ; but as their bearing on these points can only be shown by viewing them in relation with all the other subjects treated of in the admirable work from which they are taken, it would be out of place to consider them here. It is impossible, however, not to be struck with the evidence they afford, that the respi- ratory organ, that surface through the medium of which the blood undergoes its necessary change by the action of oxygen, whether pul- monary, branchial, or cutaneous, and whether the medium of its access be water or the at- mosphere, is in all cases similar, being a modification of the cutaneous surface. And as we see in the instance before us, the same surface capable of performing either atmos- pheric or aquatic respiration, the inference is obvious, that pulmonary and branchial organs may, and probably do, possess an identity of structure.When it is considered too that moisture is absolutely essential to atmospheric respira- tion, whether pulmonary or cutaneous, the identity of the two processes becomes still more unequivocal. This view of the subject receives considerable confirmation from the fact that branchiae, are in many animals capable of exercising the office of atmospheric respiration through the medium of a very small quantity of water ; as the land crabs of torrid regions are enabled to traverse immense districts under a burning sun,, by means of those little reservoirs of 104 AMPHIBIA. r, described by Dr. Milne Edwards, formed by duplicatui-es of the lining mem- brane of the branchial cavity. The eel too, as i> well known, will live for a long time out of water, from its branchial cavity being capable of retaining a sufficient quantity of water to bathe the branch iiv for a considerable time, thus preserving those organs in a respirable state. XI II. Of' transpiration ami i>f secretion. The particular condition of the skin already d escribed, naked and consisting of a moist mucous surface, would render it probable that cutaneous transpiration should be exceedingly extensive and rapid in these animals : this is in fact the case to such an extent, that when exposed to too great a degree of heat, the eva- poration of transpired fluid is sufficient to pro- duce a very rapid decrease in the weight of the animal ; which, if exposed for a sufficiently long period to its influence, becomes almost dried up and d One object, and that not an unimportant one, of the sensible transpiration of fluid in these animals, the frogs especially, is un- doubtedly to preserve the skin in a condition fit for the" performance of that cutaneous respi- ration which has been described. But its still more obvious purpose is to aflbrd a quantity of fluid for evaporation from the surface, in order to reduce and equalize the temperature of the body when exposed to a degree of heat, sufficient to incommode or injure it. This will appear very reasonable when we reflect that these ani- mals will die in a few minutes, if placed in water of 107 decrees of Fahr., though respiring freely with the head above the water, whilst, on the contrary, they will support for hours the action of damp air of the same temperature. The water which is thus transpired is not the result of the absorption of fluids taken in by the mouth, for these animals do not appear to drink. It is received by absorption on the surface of the skin, to which part it is after- wards restored when necessary. But in order to be re idy whenever circumstances call for its use. the fluid thus absorbed is conveyed into a membranous cavity, formed generally of two lobes, opening into the cloaca, where it is re- tained, to be again absorbed, and again con- , d to the surface for the purposes just men- tioned. \Yhen a frog is suddenly alarmed, or seized, it ejects from its cloaca a quantity of pure, limpid water, for the purpose of lighten- ing itself, that it may leap with greater facility. This fluid is expelled from the sac in question, and is often mistaken for urine, and the sac for a urinary bladder. Hence, if a frog be kept in a moist situation, without having access to water in any form but in vapour, the skin is always kept moist, and the water-bag a filled. Such is the function attributed in the first place by Townson to the sac in question, and after him by Dumeril, Altena, and others : but Cuvier. Dr. Grant, and many other anato- mists consider that it is the true urinary blad- der. That Townson's opinion is correct ap- pears, says Altena, from the circumstance that the ureters do not terminate in the bladder, but in the rectum itself." Dr. Grant states, that on the contrary, "the bladder receives the ureters." The kidneys are of a lengthened form, in the aquatic genera, but are shorter in the frogs and other anoura. XIV. On the restoration of lost parts. The fact that parts lost by accident, or re- moved for the purpose of experiment, become reproduced in many of the lower animals, has been known for aces. The actual multipli- cation of the species in many, perhaps all the polygustrie animalcula, by spontaneous sepa- ration, that of the hydra" by artificial division, the restoration of lost anus in the different species of asterias, of the anterior or posterior extremity of the body in the earthworm, of the claws of the lobster, and other Crustacea, and of portions of the head in the pulmo- niferous mollusca, are, all of them, phenomena which have attracted the attention, and occu- pied the experiments of physiologists, at va- rious periods. The experiments of Plateretti, Spallanzani, Murray, Bonnet, and others, have shewn that it is not in the invertebrate forms alone that we are to look for this phenomenon, but that the amphibia, and even some reptilia, will reproduce either the limbs or the tail, when removed. This restoration of the tail in the saurian reptiles is indeed a common occurrence, and it often happens that the new tail is double through the whole of the restored length. Of all the observers of this curious phe- nomenon in the amphibia, Bonnet* stands pre- eminent for the laborious and patient zeal with which all his experiments were conducted, no less than tor the conscientious strictness with which they are recorded. In many experi- ments he cut off the anterior or posterior limbs of the common water salamander or triton, which he found to be invariably restored, and even the toes were reproduced, and acquired some degree of motion. The tails were also amputated at various distances from the base, and were always renewed. The same limb was in some cases removed and restored four times consecutively. In all cases it was ob- served that warmth encouraged and that cold retarded the regeneration of the part. The restored portions were not generally well- formed, but in some instances varied by t\ in others by defect. One of the most t ordinary results was that which followed the extirpation of an eye from one of these ani- mals. In the course of a year this organ was completely restored, and its organization was found to be perfect. Dumeril records a remarkable experiment of this nature, in his latest work on the rep- tilia. The subject was the triton mmr- monttus. Three-fourths of the head were cut off, and the animal was deposited at the bot- tom of a large vessel having half an inch depth of water, which was constantly renewed. It continued to live, and to move slowly. The * (Euvres. iu 4to. Neufchatel, 1769. AMPHIBIA. 105 nostrils, the tongue, the eyes, and the ears were gone; the animal could therefore enjoy no relation to external objects but by the sense of touch. It nevertheless evinced conscious- ness, creeping cautiously and slowly about, occasionally raising the neck to the surface as if attempting to breathe. The process of cica- trization at length completely closed the aper- tures of respiration and of deglutition. It lived three months after the operation, and then died from accidental neglect. After all, this expe- riment proves only the respiratory function of the skin, a fact already sufficiently established by the observations of Dr. Edwards before detailed, and its cruelty does not appear to be compensated for by its results. XV. Of reproduction. The impregnation of the ova in the amphibia, is effected without actual coitus ; that is to say, it either takes place out of the body, as in the anoura, or the impregnating fluid is received by the mere contact of the external opening of the cloaca in the two sexes, as in the tailed forms. The only exception to this statement is in the land salamander, the male of which has a small intromittent organ. The act itself of impreg- nation therefore differs materially in these two divisions of the class. The generative organs of both sexes are double, and are placed sym- metrically in the abdomen. The testes in the higher forms of the class, the frogs and toads, are small globular oval bodies, having exter- nally a bright white appearance, from the tunica albuginea, and internally a somewhat loose texture, and a yellowish colour. They are placed behind the liver, attached to the vertebral column ; the vasa deferentia are numerous, disposed in pairs; they form a small epididymis, and passing on the outer side of the kidneys back towards the cloaca, dilate into vesiculae seminales, just before they terminate in that cavity. These organs, as in many other animals, become much enlarged at the breeding season. The ovaria are situated in the anterior and upper part of the abdomen, and are internally divided into numerous sacs, by duplicatures of the peritoneum, by which also they are bound to each side of the spine. These sacs are torn at the period of depositing the eggs, whether by the pressure of the arms of the male, as asserted by Prevost and Dumas, or otherwise, appears uncertain. The oviducts are small at their commencement, and become large towards their termination in a sort of dilated sac, which Altena terms the uterus; they are of a pulpy substance, having an in- ternal secreting surface; and the eggs during their passage through them become enveloped in a gelatinous mass. They dilate into a sort of uterine cavity just mentioned, which opens into the cloaca. The mode by which the eggs of the frog pass from the ovaries into the oviducts appears yet to be doubtful. The observations of Pre- vost and Dumas on this subject are generally received as correct, but their statements are denied in some particulars by Altena, and doubted in others. They state that the ova, detaching themselves from the ovaries, are seized by the opening of the tube, but they do not state the mode by which this act is effected. It is a question which was long since examined with great care by Swammerdam, and which brought him into a controversy ; and he con- fesses at last his ignorance of the mode in which it actually takes place. The ovaries enlarge greatly at the breeding season, and the ova at the time of their depo- sition fill the body almost to bursting. At the time of impregnation the male placing himself on the back of the female, embraces the body with astonishing force with the anterior legs, which are pressed under the axillae, and the tuber- cular thumbs, which are at this period con- siderably enlarged to enable him to retain his hold, are so essential to this object, that if they be cut off, he can no longer clasp the female with the requisite force. The instinct which instigates the male frog to this act at the season of breeding is astonishingly powerful, and sometimes no less remarkably blind. Thus, it is recorded by Walter, and has been often observed by others since his time, though the object of this curious fact has been un- accountably overlooked, that frogs are occa- sionally found in the spring adhering with great force to different parts of the skin of pike ; and a near relative of the writer of this article has seen an instance of the same kind, where several frogs were so closely fixed to a large pike as to require some force to remove them. This instinct of adhesion is, in fact, sometimes fatal to its legitimate object. I have before now taken from the water a large con- glomeration of male frogs, amounting to per- haps twelve or more, with one solitary female in the middle of the mass, dead and putrid, and even some of the males, towards the in- terior, pressed into an almost lifeless and shape- less lump. While the male is thus closely embracing the female, an operation which sometimes lasts for more than a month, the eggs, to the num- ber of several hundreds, are gradually ejected from the cloaca, either in masses as in the frog, or in double chaplets as in the toad, and impregnated by the sprinkling of the semen, as they pass out under the male. In some species, as the bufo obstetricans, the female is assisted in the act of expulsion by the hinder legs of the male. When the eggs are thus deposited in the water, the jelly-like substance in which each is enveloped absorbs a large quantity of it, and the whole mass speedily enlarges to many times the size of the animal from which it was expelled. The male of the bufo obstetricans just men- tioned, when, by his assistance, the eggs are excluded, attaches them to his thighs by glu- tinous threads, and carries them about with him until the young are ready to leave them, when he seeks a pool of water in which he deposits them, and the young shortly afterwards come forth. The impregnation of the tailed aquatic 106 AMPHIBIA. genera, as the tritons, is effected by a totally different mode. During the spring, the males acquire a considerable dorsal membrane, which runs the whole length of the back and tail, and is sometimes curiously indented or fringed at its edge. This membrane is gradually lost after the breeding season, and its use appears to be to assist in the act of impregnation. The male, instead of adhering to the female like the frog, swims by her side pursuing her in all her rapid and changing courses through the water, till at length both remaining for a moment quite still, he suddenly turns up, by the assistance doubtless of the dorsal mem- brane, and places for an instant the edges of the cloacal aperture in contact with hers. It is at this instant that the semen is ejected and received. The eggs are afterwards deposited slowly, and comparatively few in number, upon some part of an aquatic plant, on which the female supports herself by holding by her hinder legs. When the embryo has gradually acquired its larva development, and is ready for its aquatic life, it bursts the thin membrane which encloses it, and emerges in the fish-like form which has been so often alluded to in this paper. XVI. Metamorphosis, The changes which take place in the different organs during the progress of this extraordinary phenomenon, have been already detailed. It remains to trace the general form of the animal from the egg through its larva condition till it receives its permanent form, and to point out some remarkable peculiarities observed in different genera. In the frog, the toad, and probably all the anoura, the respiratory organs undergo a double change, the branchiae being first external for a very brief period, and afterwards internal during the remainder of its larva existence. In all the other forms in which branchiae have been detected, they remain external till they are lost. The tadpole, whether of the anoura or of the urodela, possesses, at first, as we have seen, the same means of progression as belong to the class of fishes. That of the triton retains its branchiae, co-existent with four perfect legs, until it is about a third of its ultimate length. In the frog the legs which first make their appearance are the hinder ones ; and from the great development of the tail, and the con- tinuous form of the head or abdomen, they ap- pear as if they came through immediately be- hind the head. As the terrestrial salamander, though pre- ferring moist places, does not frequent the water, the young have not the opportunity of being developed in that medium ; but as the essential character of their organisation requires that the first portion of their existence should be passed in the condition of a tadpole or larva, we find that the whole of its metamorphosis takes place whilst in the oviduct, where it is found with small branchiae on each side of the neck, which are lost as the animal enters upon its terrestrial existence. Like the viper, there- fore, this animal is ovo-viviparous. The arrest of the metamorphosis in the lower or perennibranchiate forms is confined to the organs of locomotion in part, to those of cir- culation, and of respiration. The organs of reproduction receive their full development, though even in these there is a considerable resemblance to those of the fishes. One of the most remarkable peculiarities in the whole of this class, with regard to the sub- ject now under consideration, is the reproduc- tion and metamorphosis of the pipa or Surinam toad. It has long been known that the eggs are developed in cells on the buck of the mother; but the facts connected with this curious circumstance have only of late years been ascertained. It is now established that the cells on the skin of the female are not persistent, but grow as the eggs enlarge, and are removed after the young leave them. The male impregnates the eggs as the toad, but immediately places them on the skin of the mother's back; here they are attached by a tenacious mucus, and the skin gradually thickens in the interstices, forming at length a cell around each. In these cells the young ones not only leave the eggs, but actually undergo their metamorphosis ; and when they leave the back of the parent, they have lost all the characters of the tadpole, and have become perfect animals. It is impossible to contemplate the structure and habits of this remarkable class of animals without being struck by the many interesting points which they offer for the investigation of the physiologist. Whether we consider the evident and perfect transition which many of them present, from the form and structure of an inferior to that of a superior type or organiza- tion, the facilities which they afford us of tracing, as it were under the eye, those mys- terious changes and grades of development which in most cases are accessible only at par- ticular epochs, or are wholly concealed during their progress in the hidden recesses of the reproductive organs, or whether we view the modifications which they present of the respi- ratory and other important functions of life, it is not, perhaps, saying too much to aver that there is scarcely any class of animals which invites the study and contemplation of the lover of physi- ological science by phenomena at once so varied and so interesting as the Amphibia. BIBLIOGRAPHY. Boddaert, Abhand. von Am- phibien, in Bcrl. Gesels. Naturf. Freunde B. ii. S. 369. Gray, on the class of animals called by Lin- naeus Amphibia. Phil. Trans. 1789, p. 21. Schnei- der, Amphib. Physiol. spec. 4to. Frft. a M . 1790-92. Ditto, Hist. Amphib. nat. et literar. 8vo. Jena, 1799-1801. Laurenti, Synops. Reptil. 8vo. Vim. 1768. Meyer, Synops. Reptil. 8vo. Getting. 1795. Latreille, Contin. of Buffon. Hist. Nat. des Am- phib. Ditto, Hist. Nat. des Salamandres, 8vo. Paris, 1800. Brongniart. Essai d'une Classif. Nat. des Reptiles. 'Societe Philom. A. iii. T. 2. Oppel, Ord. Fam. u. Gattung. der Amphibien. 4to. Munich. 1811. Merrem, Tent. System. Amphib. 8vo. Marb. 1820. Roesel von Rosenhof, Hist, nat. Ranar. nostrat. fol. Norib. 1746-61. Ed. Alt. auct. germ. s. t. Naturgesch. der Froesche, &c. fol. Niirnb. 1800-15. Steinheim, Entwickelung d. Frosche.8vo.Hamb. 1820. Hasselt, Demctamorph. ANIMAL KINGDOM. 107 Ran.E temp. Groning. 1820. tCohler, Ohs. Anat. in Appendices, &c. Ranur. 8vo. Tubing. 1111. Steffen, De Ranis Obs. Anat. 4to. Berl. 1815. fllertetis, Anat. Uatrachiorum prod. 8vo. Halle. 1820. Breyer, Fabric. Ranae Pip*. 4to. Bf-rl. 1811. KCotxe, De Rana cornuta. 4io. Berl. 1816. Zenker, Batrachoinyologia. 4to. Jenae 1825. Rathke, De Salamandr. corp. adip. ovariis, c. 4to. Berl. 1818. Rwconi, Descr. Anat. delle larve (ielle Sa- lamandre, &c. 4to. Pavia, 1817. Ej. Amours des Salamandrcs fol. Milan. 1821. Ej. Develop, du Grenouille com. 4to. Mil. 1826. Duges, Sur 1'os- teologie et la myologie. des Batraciens. 4to. Paris, 1834. Funk, De Salainundrae terrest. vita, &c. fol. Berl. 1827. Cuvier, Rech. sur les Reptiles dou- teux. Par. 1807. 4to. Wayler, Descrip. et icones Amphib. Monach. 1828. Treviranus, Protei angnin. Enceph. &c. 4to. Gotting. 1820. Rusconi e Cortfig- liachi, Del Proteo Anguino, &c. 4to. Pav. 1819. Barton on the Siren. 8vo. Philad. 1808. Edwards, Influence des Agens physiques, &c. 8vo. Paris, 1824. Prevost et Dumas in Ann. des Sc. Naturelles. (T. Bell.) ANIMAL KINGDOM, an appellation given to that great division of natural bodies to which ANIMALS belong. Like the other kingdoms of nature, the mineral and the vege- table, it is divided into numerous sub-king- doms, classes, orders, genera, and other subor- dinate groups, according to the properties and forms of the objects which it comprehends. As the primary grand divisions of the mineral kingdom are founded on the primitive forms of crystallization, and those of the vegetable king- dom on the endogenous and exogenous modes of growth, zoologists have endeavoured to find some common principle for their first divisions of the animal kingdom. The most common function in animals, and in all organized beings, is generation, and we find the animal kingdom divided into four distinct groups by the modifi- cations of this function, viz., jissipara, gemmi- para, ovipara, and vivipara. But as the fissi- parous and gemmiparous modes of generation are effected without the presence of distinct permanent organs, as the fissiparous mode occurs in isolated species belonging to classes remote from each other in the scale, and as nearly all the classes of the animal kingdom belong to the oviparous division, the modifica- tions of this system do not present the means of establishing primaiy divisions suitable for the purposes of zoology. Although the pro- cess of internal digestion is not so universal as the function of generation, the internal alimentary cavity is the most universal organ of animals, and its forms therefore merit a first consideration in the establishment of pri- mary groups. It is found, however, that in animals whose general structure is nearly the same, the alimentary apparatus varies so much according to the nature of the food, as to render hopeless any attempt to subdivide the animal kingdom from its modifications; as from its having one or two apertures, from its being a simple sac or a lengthened intestine, from its having one, two, or more stomachs or glands developed in its course, or other modifications of this kind. In the circulating system we are presented with better means for such divisions than in the digestive, for the radiated classes have only vessels for their circulation, the articulated classes have a superadded ventricle, the mollus- cous classes and fishes a bilocular heart, am- phibia and reptiles a trilocular heart, and the birds and mammalia have four cavities in that organ. The respiratory organs likewise afford the means of founding primary divisions, as into ciliated, branchiated, and pulmonated classes, in ascending from the lowest to the highest forms of that system. The primary divisions of the animal kingdom adopted by Aristotle, viz., animals with red blood and animals without red blood, are ob- viously founded on a single principle of classi- fication, and correspond with the more recent divisions of vertebrata and invertebrata ; but from the number of distinct classes of animals now comprehended under each of these divisions, they are quite unsuitable as primary groups in the present advanced state of the science of zoology. Considering the functions of the nervous system or the intellectual conditions of animals as a means of classification, Lamarck proposed three great divisions, the lowest of which comprehended the animals regarded by him as apatliic or automatic, the second the sensitive, and the highest the intelligent, which, however, are too hypothetical to answer the purposes of the zoologist. Without any fixed principle for the establishment of his primary groups, Cuvier divided the animal kingdom into the radiated, the articulated, the molluscous, and the vertebrated divisions, which have been generally adopted by naturalists. From the importance of the nervous system in the living economy of animals, some have sought in its modifications a means of establishing primary or grand divisions of the animal kingdom on principles more uniform and philosophical than those commonly employed. In the radiated or lowest classes of animals, wherever the nervous system is perceptible, as in actinia, medusa, beroe, asterias, echinus, holothuria, &c. it is found in the form of filaments disposed in a circular manner around the oral extremity of the body. This lowest form of the nervous system is expressed by the term cyclo-neura, and although, like the radiated and every other character assigned to these classes, it is of partial application, it marks the uniform con- dition of that system on which the manifesta- tions of life are chiefly dependent, and which principally establishes the relations of animals to surrounding nature. A different form of the nervous system is found in the long cylindrical trunks of the helminthoid and entomoid classes, where we observe almost from the lowest ento- zoa to the highest Crustacea, a double nervous chord or column extending along the whole of the ventral surface of the body. This form of the nervous system, common to the articulated classes of animals, is expressed by the term diplo-neura, and it is found to accompany an organization generally more complex than that of the cyclo-neurose classes, and inferior to that of most of the succeeding divisions or sub- kingdoms, especially in the organs of vegetative or organic life, as the vascular, the digestive, and the glandular apparatus. The nervous 108 ANIMAL KINGDOM. system is more concentrated around the en- trance to the alimentary canal in the mollus- cous classes, where it generally forms a trans- verse series of ganglia, disposed around the O3sophagus, a character which is expressed by the term cyclo-gangliata. The dorsal position of the great ganglia and nervous columns of the cephalopods, and their partial protection by an organised osseous internal skeleton, leads to the condition of the nervous system presented by the vertebrated classes of animals, where its central parts are in the form of a lengthened dorsal nervous chord developed anteriorly into a brain, and protected by a vertebral column and cra- nium. The vertebrated classes are thus de- signated spini-cerebrata, from the form of the most influential part of their organization. To the lowest sub-kingdom or cyclo-neurose division belong five classes of animals; viz., 1. Polygastrica, microscopic, simple, transpa- Fig. rent, soft, aquatic animals, in which no nervous filament has yet been detected, generally pro- vided with eyes, with a circular exsertile dental apparatus around the mouth, and with vibratile cilia for respiration and progressive motion, and provided with numerous internal stomachs or cceca communicating with the alimentary cavity. (See POLYGASTRICA.) 2. Porifera, simple, aquatic, soft, animals, without perceptible nervous or muscular fila- ments or organs of sense, with a fibrous internal skeleton sometimes supported with silicious and sometimes with calcareous spicula, the body permeated with a soft gelatinous flesh, covered externally with minute absorbent pores, tra- versed by numerous ramified anastomosing canals, which commence from the pores and terminate in large open vents, as seen in the annexed figure of the halina pap'Ularis, Gr. (Jig. 29), which represents the animal as alive, 29. under water, with the usual currents passing inwards through its pores (a a), traversing its internal canals (6), and escaping by the larger vents (c, d.) (See PORIFERA.) 3. Polypifera, aquatic animals, of a plant- like form, generally fixed, of a simple internal structure, for the most part without perceptible nerves or muscles, or organs of sense, and nou- rished by superficial polypi, which are developed from the fleshy substance of the body, as in the campanularia dichotoma, (fig. 30), wher^ the Fig. 30. irritable fleshy tubular portion of the animal is seen to occupy the interior of the base, the stem, and the branches, and to extend in the form of polypi from the open terminal cells. The polypi of most zoophytes are provided with tentacula around their orifice, as seen at B, (fig. 31), and the margins of these ten- tacula are generally furnished with numerous minute processes, termed cilia, (see CILIA,) by the rapid vibration of which, currents are pro- duced in the surrounding water for the pur- pose of attract- ing food and of aerating the surface and fluids of the body, as repre- sented in fig. 3, A. (See PO- LYPIFERA.) 4. Acalepha, soft aquatic free animals, of a simple structure, generally of a gelatinous and transparent texture, and emitting an acrid se- cretion which is capable of irritating and inflaming the skin like the stinging of a nettle, from which the name of the class is derived. They rarely possess a solid skeleton or a per- ceptible nervous system. They are all marine, often luminous, sometimes they possess eyes with a crystalline humour, they feed on minute floating animals, and swim by the contractions of a highly vascular and irritable mantle or by means of air-sacs, or by the rapid movement of ANIMAL KINGDOM. external vibratile cilia, as in the beroe pileus represented in Jig. 32. This figure represents Fig. 32. one of the ciliograde acalephae in which the mouth () is directed downwards, and leads, by a narrow oesophagus, to a wide stomach (6), and from this the intestine proceeds straight through the axis of the body to the anus (c) at the opposite pole. The longitudinal nerves (g), as in holothuria, proceed from a nervous ring around the oesophagus. The ovaries (d) extend along the sides of the intestine ; the surface of the body is provided with eight longitudinal bands of pectinated broad vibratile cilia (M), and two long ciliated tentacula (Jf) extend from two curved lateral sheaths. (See ACA- LEPH^l.) 5. Echinoderma, simple aquatic animals, for the most part provided with a calcified ex- terior skeleton or a coriaceous skin, the body for the most part radiated, globular, or cylin- drical, often provided with a distinct nervous, muscular, respiratory, and vascular system. These animals have received the names of echi- noderma, from the spines or tubercles which generally cover their exterior surface, as seen in the annexed figure of the echinus esculentus (fig. 33.) The mouth (6) is here in the centre Fig. 33. of the lower surface, and the intestine (b,b.) connected to the shell by a mesentery (c), on which vessels are ra- mified, passes in a convoluted manner upwards to the oppo- site axis where the anal aperture (a) is surrounded by the five openings of the ova- ries (d,d.} The mouth is surrounded with a maxillary apparatus containing five teeth, and the exterior of the complicated and solid shell is seen to be provided with moveable cal- --J 109 careous spines. These animals are for the most pait free, but some are fixed, as the crinoid echinoderma, the vascular system is unpro- vided with auricle or ventricle, and the diges- tive canal is seldom furnished with distinct glandular organs. There is sometimes a simple stomach with one aperture and numerous late- ral cceca, and sometimes a lengthened intestine with two terminal openings. Some marine animals without an echinodermatous covering are placed in this class from the similarity of their structure in their more essential organs, as is the case with the holothuria represented in Jig. 34. The mouth (a) is here surrounded with 34 ramose tenta- cula (c) and an osseous ap- paratus. The intestine is long, convolu- ted, vascular, supported by a mesentery, and termi- nates in a cloaca (i) at the opposite axis of the bo- dy. The rami- fied internal branchiae (ff) open from the cloaca ; the great systemic artery receives the aerated blood from the branchiae, and the organs of generation(wi) open near the anterior part of the body. The irritable coriaceous skin is supported by five broad longitudinal subcutaneous muscular bands, and five crowded series of tubular mus- cular feet extend from its surface. (See ECHI- NODERMA.) The SECOND SUB-KINGDOM Or DIPLO-NEU- ROSE DIVISION comprehends four classes of helminthoid animals and the same number of entomoid classes, viz. 6. Entozoa, parasitic, simple, internal,or fixed animals, for the most part of a lengthened cylindrical form, without distinct organs of sense or any internal skeleton, the mouth or anterior part of the body generally provided with recurved sharp spines, the body generally covered with an elastic white transparent inte- gument, the nervous system seldom distinct, the vascular system without auricle or ven- tricle, without respiratory organs, and with the sexes generally separate. (See ENTOZOA ) 7. Rotifera, minute aquatic animals with distinct nervous and muscular systems, provided with eyes, lateral maxillae, a dorsal vessel, an intestine with two apertures, and with vibratile cilia disposed generally in a circular form 110 ANIMAL KINGDOM. around the anterior part of the body. They are termed rotifera from the appearance of revolving wheels produced by the rapid move- ment of the cilia disposed around the mouth. One of these minute wheel-animalcules, the hydatina senta, is represented highly magnified in Jig. 35, where the mouth (a) is surrounded with long vibratile cilia (b 6). The oesophagus (c) leads to a capacious stomach (d), which becomes a narrow intestine below, opening into the cloaca (e), where the genital organs (i,i,g,g,h,) also terminate. Several ganglia surround the oesophagus, and a dorsal vessel (o o) is seen extending along the middle of the back and sending out regular transverse branches. All the rotifera are free, most are naked, many are sheathed or loricated, they exhibit no branchial or pulmonary organs, they are remarkable for their fertility and their tenacity of life. (See ROTIFERA.) 8. Cirrhopoda, aquatic, articulated, diplo- neurose animals, with articulated cirrhi, and branchiae for respiration, body covered with a fleshy mantle, and fixed in a multivalve shell. These animals are all marine, the branchiae are fixed to the bases of the articu- lated cirrhi, the mouth is provided with man- dibles and maxillae, there is a pulsating dorsal vessel, and a double longitudinal knotted sub- abdominal nervous chord. The cirrhopoda have been commonly placed among the molluscous classes from the form of their exterior coverings. (See CIRRHOPODA.) 9. Annelida, with a long cylindrical body generally divided into transverse segments, and covered with a soft skin; the head commonly provided with antennae and numerous simple eyes, and the mouth with maxilla? ; the organs of motion in the form of simple seta? or cirrhi extending from the sides of the body in a sin- gle or double row. The vascular system of the annelida consists of arteries and veins, without a distinct auricle or ventricle, and the blood is generally of a red colour. The re- spiratory organs are generally in form of external branchiae, sometimes of internal air-sacs, and the alimentary canal passes straight through the body with two terminal openings, and with numerous lateral coeca developed in its course, as seen in that of the leech, hinido mcdicinalis, Fig. 36. (fig. 36.) These lateral coeca (b, f> d > e >f> g> h> h k, m,} increasing in length and size from before backwards, are often much more lengthened and divided, as in the halithea. Many of the red- blooded worms are fixed in cal- careous, arenaceous, or other tubes, and many are free and naked. (See ANNELIDA.) 1 0. Myriapoda, with a length- ened articulated body equally developed throughout ; the head provided with antennae and sim- ple eyes ; the segments of the trunk free, without distinction of thorax and abdomen; the segments furnished with one or two pairs of articulated legs adapted for progressive motion on land; the respiration is aerial, and performed by trachea?, which ramify from their commencement in stigmata which open along the whole extent of the body. They do not undergo me- tarmorphosis, nor possess compound eyes nor wings, and they have always more than six pairs of feet. (See MYRIAPODA.) 1 1 . Insecta, with six articulated legs extend- ing from an articulated trunk, which is divided into a head, thorax, and abdomen ; the head is provided with a labium, a labrum, mandibles, and maxillae, with compound and often also with simple eyes, and a pair of antennae and palpi ; the thorax supports the six legs, and commonly one or two pairs of wings, and has attached to it the moveable segments of -the abdomen, which embrace the principal organs of digestion, circulation, and generation. The respiration is effected by tracheae, which form continuous lateral trunks before they ramify through the body. The circulation is aided by a pulsating dorsal vessel provided with nu- merous valves, and the alimentary canal is furnished with salivary and hepatic, and often with pancreatic glands. The sexes are sepa- ANIMAL KINGDOM. Ill rate, and the genital organs, slow in their development, are highly complicated in the perfect state. These animals generally pass through a series of metamorphoses, and throw off their exuvial covering five or six times during their development. This class is the most numerous in the animal kingdom, com- prehending about a hundred thousand species. The greater part of their life is spent in the larva state, during which they are generally most voracious, like the young of other classes. In the adult state the masticating organs and the digestive apparatus vary much according to the kind of food in the different species, as is seen in comparing the alimentary canal of a carnivorous cicindela campestris (Jig' 37.) with Fig. 37. Fig. 38. that of a phytophagous melolontha vulgaris, (fig. 38.) In the carnivorous insect (Jig. 37.) the intestine passes nearly straight through the body with few enlargements in its course, and the glandular organs have a simpler struc- ture. The oesophagus passes down narrow from the head, and dilates into a wide glandu- lar crop (a), which is succeeded by a minute gizzard, and this is followed by the chylific stomach (6,r), which is covered like the crop with minute glandular cryptae or follicles. At the pyloric extremity of the chylific stomach, the liver, in form of simple biliary ducts, pours its secretion into that cavity by two orifices on each side (e Cyclopaedia. The glance we shall cast over the field it embraces will, therefore, be very cursory, and the views taken of the objects it presents extremely general. JPkysicut qualities and material constitution of annuals In point of size, animals differ most widely from one another. The existence of some is only made known by the aid of a powerful microscope, the length of others ex- ceeds a hundred feet, and their weight amounts to many tons. These extremes include animals of every intermediate bulk. Tbejorm assumed by animals presents many more interesting particulars for study and in- vestigation than the mere bulk of their bodies. The consideration of this accident has even been made the ground of a classification of the objects included within the animal kingdom by several naturalists, and although not adopted as the sole basis of any one now generally received, it nevertheless furnishes the element upon which several of the classes even of the most recent are established. Some animals present themselves in the likeness of a globule, others of a filament, and others of a small fattened membrane (the cyclides). Various animals, again, from exhibiting no uniform or regular shape, have been entitled amorphous or heteramorphous . Animals which exhibit a determinate form naturally arrange themselves into two classes ; their bodies are either disposed around a centre, or they consist of two similar halves cohering along a middle plane or axis; the first are the radiata, the second the bin aria or symmetrica of naturalists. The radiata are not a very extensive class of animals, neither is their organization extremely complicated. The symmetrical is a much more numerous class than the radiated, and includes within its limits creatures of such simple structure as the en- tozoa, and of such complicated fabric as quad- rupeds and man. Of the symmetrical animals, some consist of a mere trunk without appen- dices or limbs ; those that are provided with limbs, again, have them in the shape of feet, fins, wings, or hands, according to the media in which they live. In some the body forms as it were a single piece, in others it is divided into portions, such as head, trunk, and tail. Sometimes it is naked ; at others it is covered with shells, scales, spines, hair, &c. Some- times the general integument is continuous, unpierced by any opening that leads to the interior, at others it is reflected inwards, and lines extensive cavities there contained. 140 ANIMAL. With regard to structure, as may be imagined, the amorphous tribes, at the bottom of the scale, are the most simple of all. The bodies of some of these are without any internal cavity, and without any division of parts; they are homogeneous masses, generally gela- tinous in appearance, and simply cellular in structure, without arrangement into tissues or particular organs. The external surface of these animals imbibes the matters which are fitted to subserve the purposes of nutrition, and we may presume that it throws off by transpiration such particles as are worn out or have accomplished this end. The external surface is also the organ of respiration in these animals. They procreate by the evolution of gemmi from their surface, and if they possess sensibility the element to which it is attached must be generally diffused throughout their sub- stance. The organization of the radiata becomes con- siderably more complicated. Fluids are no longer absorbed from the external surface of the body ; we meet with an internal cavity, the rudiment of a digestive apparatus, having a single opening in some of the species, which serves consequently for both mouth and anus, but in others presenting two openings, a mouth properly so called on one side of the body, and an anus on the other. Through the walls of this cavity the nutritive fluids make their way, and infiltrate the general mass of the animal's body. In this class we also discover the rudiments of a nervous and of a muscular sys- tem. The nervous system consists of rounded masses of a soft whitish substance, equal in number to that of the radii composing the animal, connected together by slender white cords, and sending off filaments of the same description to all parts of the body, but espe- cially to the outer integument, and to the inter- nal digestive apparatus. The muscular system consists of reddish and whitish fasciculated fibres disposed in the line of the motions. The external surface of these animals is still the only organ of respiration they possess. The three systems now enumerated the digestive, the nervous, and the muscular are readily demonstrated in the majority of the symmetrical animals, and are even very soon found to have acquired complication, and to have sundry other parts and organs superadded to them. The digestive apparatus consists of a mouth for the susception of aliment, of a stomach for its elaboration, of an intestinal canal from which the nutrient juices are ab- sorbed, and of an anus from which the un- digested residue is expelled. Whilst in the radiata the nutritious fluids passed through the parietes of the digestive cavity to impregnate the body of the animal, and be assimilated with its substance ; in the binaria we find vessels, the rudiments of a circulating system, employed in receiving the juices prepared in the digestive apparatus and transmitting these to all parts of the body. Digestion, too, in this class becomes a more complicated process than in the radiata, and various secreted fluids, saliva and particularly bile, the special products of large and evidently important organs, arc added to the alimentary mass in its progress through the intestinal canal. In addition to the digestive apparatus and general exteinal respiratory surface we by-and- by find an especial system dedicated to the aeration of the juices prepared for nutrition; this is the respiratory apparatus. Of extreme simplicity in the first instance, being little or no more than a fold of integument turned inwards, and forming a simple cavity or sac within the body of the animal, it is soon rendered more complex in its structure, being distributed in the manner of vessels under the name of tracheae or canals to different parts of the body, or being confined to a particular district, and entitled lungs or gills as it is fitted to receive the atmospheric air immediately, or lo make use of this elastic fluid suspended or dissolved in water. The existence of this separate respiratory apparatus presupposes that of another system, namely, the circulatory. The fluids prepared by the organs of digestion are not yet fitted to minister to the growth and nutrition of the organization ; to be made apt for this purpose they require exposure to the air in the lungs or gills wherever these organs exist, and these be- ing distinct, or contained in a particular region of the body, a series of conduits were re- quired, first to carry the fluids thither, and to transmit them subsequently to every part of the organization for its support. Like all the other systems of animals, the circulatory exists of various degrees of complexness; when first encountered it consists of a series of simple canals or vessels, which diverge on every hand ; by-and-by it has several, and finally one, forc- ing piece, or heart superadded to it, which impels the fluids by its contractions to every the most remote part of the organization. Among animals, however, nutrition is not a process simply of addition or composition ; it is also, perhaps universally, one of subtrac- tion or of decomposition. We have seen the composition provided for by special systems in animals occupying very low grades in the scale of creation ; we mount but a short way before we encounter an apparatus which pre- sides over the decomposition also in the shape of another system of vessels, the veins and especially the lymphatics ; these collect the superfluous and worn-out particles from every part, pour them into the general current of the circulation, wherein being exposed in the vital elaboratory of the lungs they are either assi- milated anew and made fit once more to form an integral part of the organization, or, being subjected to the action of certain glands, they are singled out, abstracted, and finally ejected from the system entirely. In the most com- plicated animals therefore a peculiar appa- ratus for the depuration of the system is su- peradded as complementary to the absorbents. This we find in the glandular bodies familiarly known as the kidneys ; the vehicle in which the decayed particles are withdrawn is the urine. W hen we examine the instruments of sensa- tion, we find them becoming gradually more ANIMAL. 141 and more numerous, and the nervous system generally more and more complicated as we rise in the scale of animal creation. The ner- vous system is before long found to consist of other parts than a series of similar ganglions supplying at once the organs of sensation and those of digestion ; it has a central part super- added, from which issue immediately the nerves that supply the organs of the senses, sight, hearing, taste, and smell, which at the same time make their appearance with their especial capacities. This central superadded portion is the brain, with its prolongation in the vertebrata entitled spinal marrow. Nor in the more perfect classes of the animal king- dom is the nervous system even thus simple ; among them it consists essentially of two grand divisions, the one including the brain and spinal cord and the nerves thence pro- ceeding, the other constituted by the system of the great sympathetic, or that series of ganglions which, situated on either side of the vertebral column, from the head to the pelvis, are con- nected with one another, and with the cerebro- spinal system, by branches of communication, and furnish the digestive apparatus with almost the whole of the numerous nerves it receives. The nervous system in its relative degree of development and complexity becomes the ultimate standard by which the perfection of animals is estimated, and their place in the scale of creation assigned to them : if man stand alone and unattended, as he undoubtedly does, upon the summit of the pyramid, it is only because he possesses in his brain the organs of certain moral and intellectual facul- ties which occur in no other living thing; these confer on him his humanity; these are the ma- terial parts to which the soul is wedded during his existence. In intimate connection with the functions of phrenic or animal life, and developed nearly in the same ratio, is the muscular system, the most universal agent of locomotion. Exceed- ingly simple at first, and operating at great disadvantage through a want of levers and points of support, we trace it becoming gra- dually more complicated as we ascend, and, finally, provided with a complementary skeleton or frame-work by means of which it acts to the best advantage. The skeleton among animals is of two kinds, external and horny, internal and osseous. In the first case the muscular system is inclosed within the resisting pieces which it has to move; in the second it is without these, and is arranged around them. The bones and muscles together compose the numerous and variously fashioned instruments with which animals accomplish the promptings of their inward appetites and instincts. They form feet, fins, hands, the prehensile tail, &c. The muscular system, and a modification of the osseous, the cartilaginous, moreover, com- pose the most universal instrument by which animals communicate their vicinity, their states, their dispositions or affections, &c. to one ano- ther this is the larynx. The means by which species are continued, are extremely varied. The very lowest tribes of animals we have seen shooting forth buds exactly like vegetables, and these being in due season detached from the body of the parent, find themselves fitted to commence an inde- pendent existence. At the next step we take in ascent, however, we meet with particular organs of reproduction ; and, singular enough, the moment these exist they are not of one, but of two kinds, denominated male and fe- male. Sometimes these organs are possessed by single individuals, far more commonly, however, they are divided between two, whence the so uniform division of the beings com- posing the animal kingdom into sexes. The simplest form of the male organ of generation is a gland secreting a fecundating fluid (the testis) and an excretory duct: the simplest form of the female apparatus of generation is a gland or body producing germs (the ovary) and an excretory duct. In a greater state of complication or development these essential parts in the male have an instrument super- added to them by which the fecundating fluid is carried directly into the body of the female, and in the female the ovary has a dilatable cavity superadded in which the germ remains for a season, and until its included embryo attains such a state of development as is com- patible with its more independent existence surrounded by the circumstances amid which it is afterwards to live. In the higher classes, the connection between the parent and offspring does not cease immediately on the birth of the latter, and in the highest of all we find the female furnished with a complementary apparatus (the mammae), from which she fur- nishes her young with food during the first period of Its existence. Actions of animals. The foregoing rapid sketch of the grand features of distinction among animals with reference to their struc- ture naturally leads to the inference of di- versity of function in harmony with the pecu- liar organization possessed by each. In the lowest grades of animal existence we have seen to how simple a process the act of nutrition this act so complicated among the more elevated tribes, is reduced. It consists merely of imbibition or absorption by and of exha- lation from the general surface of the body. The matters absorbed appear to be assimilated incontinently, or to be made a part of, and to receive the form proper to, the animal in the instant of their assumption: applied imme- diately to the homogeneous organism, the nutriment is forthwith made a portion of its substance. The vital decomposition of the bodies of these lower animals is accomplished with the same simplicity and directness : the surface that absorbs is also that which exhales the worn-out particles of the system. The first step by which nutrition becomes more complex, as we rise in the scale of cre- ation, is the institution of a process of solution (digestion), by which the matters appropriated as aliment are prepared for reception into the body. This process of solution is accom- plished by powers inherent in the animal itself, within a cavity destined for the purpose. In 142 ANIMAL. our survey of the structure we have already seen to how great an extent the organization became complicated as a consequence of* this centralization of the office of digestion, and with what variety of superadded function this complication was attended, namely, external absorption, sanguification or the formation of a fluid, the pabulum of nutrition, confined within vessels, respiration, circulation, and, finally, assimilation, in regard to the compo- sition ; whilst with reference to the vital de- compositions we have discovered another spe- cies of interstitial or internal absorption, and depuration of the system by one principal apparatus, the kidney, to which the cutaneous and pulmonary exhalations may be added as supplementary. But every one of these functions, and its organic apparatus, are themselves modified, according to internal aptitude, and in con- formity with the circumstances surrounded by which animals commence and continue their existence. Digestion is a very simple process in those cases in which it takes place within a single cavity, having but one opening, and no complementary apparatus of any kind, compared with what it is when connected with an apparatus for bruising the food, for mixing it with saliva, for macerating it in a crop or a series of reticulated and foliaceous pouches, mixing it with bile, pancreatic juice, &c. &c., and transmitting it along a muscular canal, of six, eight, or ten times the length of the body to which it belongs. Absorption, in like manner, among the most inferior classes is essentially one and undi- vided either in kind or destination. It is in itself adequate to the entire office of nutrition, seizing and transmitting the matters which are fitted for this end, elaborating the food and atmospheric air at the same instant of time, and effecting immediately the composition of the whole animal organism. In animals higher in the scale, we perceive, in the first place, that there are several species of absorption : there is, in the first place, the absorption from the surface of the digestive passages and that from the surface of the lungs, gills, skin, &c. or of the respiratory apparatus. Again, absorption is not limited to furnishing materials for the com- position of the organism ; it is also entrusted with the office of abstracting from its interior the particles which are worn out and no longer fit to continue the ends of their existence in the places they occupy. Nor is this all ; for it is by absorption that the amount of those exhaled fluids which moisten internal cavities, having no external communications, is regu- lated, and by which, as it would appear, many of the secreted fluids, the bile, and the sper- matic fluid in particular, are inspissated and rendered more fit to accomplish the important ends they subserve in the economy. Absorp- tion in the highest classes of all is even per- formed by two, and perhaps three different orders of vessels, the lacteals, namely, the lymphatics, and the veins. Further, absorption is not in the higher as it is in the lower classes of animals a function effecting immediately the composition and de- composition of the parts and particles of the organization. It is intermediate to the pre- paration of the nutritious juices and their ap- propriation or assimilation by the organism. The lacteals or absorbent vessels of the in- testines collect the fluid called chyle from the pultaceous alimentary mass in its progress through the intestines. But this fluid is not yet fitted to subserve nutrition; as a pre- liminary it has to be subjected to the action of the atmospheric air in the gills, lungs, &c., where, being converted into arterial blood, it first becomes apt to minister to the growth and reparation of the body and its parts. So also in regard to decomposition : the fluids collected from all parts by the lymphatics and veins, are not immediately rejected from the economy, as useless and having already accom- plished all of which they are susceptible, but being first exposed to the contact of the at- mosphere, and then made to undergo the scrutiny of the depurative organs, they are either retained, being restored to their pristine capacity to subserve nutrition, or are abstracted from and thrown out of the body as no longer fit to aid in its growth and maintenance. Intercourse with the air of the atmosphere is essential to every living thing, and we should a priori have anticipated very considerable variety in the means by which, as well as the mode in which this intercourse is established. Among the inferior tribes which are nourished by ab- sorption immediately from the surface of their body, and which find the materials of their nutrition ready prepared for their use in the circumambient media, we may presume that the matters absorbed have either undergone the needful changes by exposure to the air previously to their assumption, or that these changes take place at the time they are ap- propriated. Where digestion is a preliminary to absorption and assimilation, it is evident that this could not have been the case; and hence the necessity for that modification of the function of aeration entitled respiration. Look- ing generally, we observe two principal varieties in the mode by which aeration is accomplished : in some classes there are a number of holes arranged symmetrically along the sides, and communicating with air-vessels entitled tra- cheae, which are subsequently distributed to every part of the body. The air in this case is evidently brought into communication with the nutrient juices already arrived at their destinations ; and the necessary changes are wrought in them at the instant of their assimi- lation. Here the respiration is very properly said to be diffuse or disseminated. In other classes, again, in which the respiration is local or concentrated, in harmony with the existence of a special apparatus, which we have spoken of under the title of lung or gill, aeration is accomplished by the access of the air on the one hand, and the exposure to its action of the nutritive fluid on the other, the effect of which is to convert the latter into arterial blood, and to make it fit, upon its distribution by appro- priate channels, to accomplish the ultimate and ANIMAL. 143 immediate nourishment of every part of the organization. The different media in which animals live involves the supposition of another modifica- tion as to the mode in which the blood or nutritive fluid is aerated. Those that live in air respire this elastic fluid immediately; those that live in water, again, respire it mingled with or dissolved in the surrounding medium. The tracheae of those animals whose respira- tion is diffuse, and that exist on the surface of the earth, consequently are filled with air; those of the creatures that exist in water are conduits for the constant transmission of this fluid. When the respiration is concentrated, corresponding modifications in the function are encountered according to the medium in which animals live : the air is either received immediately into the body, when the apparatus is known as a lung, or, suspended among water, it is passed over the surface of the respiratory organ, which is then denominated gill. Quadrupeds and birds respire univer- sally by means of lungs, fishes and the mol- lusca by means of gills. In certain reptiles the function is carried on by means both of lungs and gills, and as it would appear even by the general surface of the body either vica- riously, or at one and the same time. These are the only true amphibious animals. A circulation, properly so called, is the ap- panage of an organization already somewhat complicated, consequently of an animal con- siderably raised in the scale of creation. This function, it is evident, as implying in its sim- plest sense a progressive motion of the general nutritive fluid or blood, can only exist where such a fluid is encountered. It is altogether wanting, therefore, among those animals in which nutrition is accomplished immediately. We ascend but a little way in the scale before we find the function consisting not only of an outward or progressive motion of the nutritive fluids, but of a retrograde motion also of these same fluids modified in their nature, and re- quiring exposure to a greater or less degree in some form of respiratory apparatus to fit them anew for distribution to the organization at large. The fluid in this instance parts from a centre, and returns thither after having made the round of the system. Circulation in this acceptation only occurs among those animals that have a separate respiratory apparatus, and in which we meet with absorption of nutri- ment from without, and of lymph, &c. from within. The pabulum of nutrition is taken up by lacteals and veins from the digestive apparatus, and by veins and lymphatics from the rest of the organism for transmission, under the name of venous blood, to the apparatus of respiration, whatever its form. In this the fluid, still immature and unapt for assimilation, is exposed in vessels of infinite minuteness and extreme tenuity to the action of the at- mospheric air, and having undergone in these a certain change, it begins to be collected by another set of vessels, which form branches suc- cessively of larger and larger size, until finally it is projected from the respiratory apparatus in one or more trunks, under the name of arterial blood, fitted for assimilation by the organization at large, and proving the principal stimulus under the influence of which its various par- ticular organs accomplish their offices. Circulation, however, as a function, is com- plicated in the same degree as the apparatus by which it is effected. In some classes we find the circulation taking placing through vessels ow/y, one set distributing the blood from the respiratory apparatus to the body generally, another collecting this fluid again, and the newly-absorbed matters from the body at large, and transmitting these for elaboration anew in the organ of respiration. In other tribes, and this invariably after the very lowest grades of the scale are passed, we find the hollow muscle, or forcing apparatus, which, in glancing at the differences of structure, we have spoken of as the heart superadded to the circle of vessels, which even in its simplest state consists of at least two cavities communicating with one another, one for the reception of the blood from, the other for the projection of this fluid to the general system. But the blood does not follow the direct and simple course here supposed in almost any case. There is the aeration of the fluid in the way, and means to accomplish this important end must of course be provided. Among many animals it would appear by no means necessary that the whole of the blood should undergo exposure in the respira- tory apparatus, in order to fit it for the wants of the organization ; a part only is sent thither, and this on admixture with the remainder suffices to revivify the mass. In this case it is not imperative that the two kinds of blood the unaerated or venous, and the aerated or arterial should be kept distinct; there is con- sequently no occasion for more than one re- cipient cavity or auricle, into which the aerated blood from the organ of respiration, and the unaerated blood of the system are poured in common and mingled, and one projecting cavity or ventricle from which the mixed cur- rent is distributed partly to the respiratory ap- paratus and partly to the system at large. Here the blood in its course describes no more than a single circle, beginning and ending in the heart, which is then characterized as simple, consisting, as has been said, of a single auricle and a single ventricle. Among other tribes of animals, however, the whole mass of blood requires to undergo aeration in the respiratory apparatus each time it completes its round before it can again subserve the wants of the organization. In this instance it is evident that the aerated and unaerated blood require to be most particularly prevented from commingling, and that a single or simple heart will no longer suffice as the implement of circulation. This complex circulation is met with among ani- mals so low in the scale as to be unprovided with a heart, v\hen of course it is accomplished by means of vessels only. In some tribes the one portion of the function is performed by the medium of vessels, the other by the agency of a heart which is now connected with the gene- 144 ANIMAL. ral systemic circulation, now with the pul- monic, being situated in the one case in the course of the aerated, in the other in that of the unaerated current of blood. In the most elevated classes of animals, finally, the double circulation is effected by means of two hearts, one dedicated to the projection of the un- aerated blood into the lungs, the other to the propulsion of the aerated fluid through the general system. These two hearts, indeed, adhere to one another, and are usually spoken of as if they constituted no more than a single organ, having however four cavities, two auricles and two ventricles, but they are not less distinct on that account, and are severally the centre of a particular circula- tory system, one of which commencing in the cavities for the venous or unaerated blood, ex- tends through the respiratory apparatus (then uniformly a lung), and back to the cavities for the arterial aerated blood ; the other, com- mencing in the cavities just named, extends to every part of the organization, and terminates in the cavities for the unaerated blood, where the lesser round recommences, to be followed in its turn by the greater, and so on, during the whole period of existence. Assimilation appears to be identical in all animals; it is the ultimate term of nutrition, and however varied the apparatus that minis- ters to the act, the act itself we may presume not to differ in its essence in one animal from what it is in another. Akin to assimilation we have secretion, and this is a function that offers extensive differences in every class of the animal kingdom. It is generally spoken of as of two kinds, excretion, and secretion, properly so called. In the lowest tribes excretion is quite simple, consisting of a mere exhalation from the general surface of the body. In the more elevated we find another and very important form of excretion super- added, that, namely, of the urine, the nature of which, and the mode in which it takes place, we have already indicated in speaking of the structure. Secretion, however, even in the classes but a little raised above the lowest, is a function of much more varied import, and con- sists of a great many other processes than that by which the bodies of animals are depurated and their blood maintained in a state fit to supply all the wants of the system. We ad- vance but a little way before we begin to detect distinct organs destined for the secretion of peculiar fluids from the general mass of cir- culating nutriment, evidently subservient in many cases to the most important ends of the economy, and by no means destined to be rejected from the system as useless, like the excretions properly so called. It seems even that it is by a process analogous to secretion that the imponderable matters the heat, light, and electricity, which we have acknowledged as elements in the constitution of organized beings, are eliminated. All animals possess sensibility or sensation, though evidently in the most dissimilar degrees. Some have been supposed to possess the faculty of perceiving impressions made upon them by external objects, but to have no power of re- acting upon external nature, they being without the faculties which in the higher classes prompt to action. This state ; however, of animal ex- istence is rather hypothetical than demonstrable, and in animals generally we observe not only the aptitude to be impressed, but inherent capacities inducing reaction upon the world around them. The sensitive life of these beings consequently consists of two items the senses and their organs, external and internal, by which im- pressions are received and cognized, and the affective and intellectual faculties by which the motives to action, the propensities, sentiments, instincts, appetites, &c., are originated, and the means and modes of accomplishing their promptings are supplied. Animals evidently differ immensely in the degrees in which they are endowed with ex- ternal and internal senses. Some appear to possess none of the external senses save touch ; others, in addition to this, have taste and smell ; the most perfect besides these three reckon sight and hearing. The internal senses, in like manner, are more or less acute, more or less numerous, according to the consitution of ani- mals : those of hunger and thirst are probably universally distributed, and the most keenly felt ; then come those which induce the respira- tory act, the sexual act, &c. ; and here we find ourselves among the propensities which exist in very different numbers and kinds in every different species of animal. Some tribes tend their offspring, others leave their progeny to the care of accident, which in this case always suffices for their protection ; some con- gregate in herds or shoals, others live solitary or in pairs; some are bold and rapacious, Others timid and gentle, &c. When we ex- amine animals generally, with reference to the sentiments or moral faculties, we find them still more or less like each other in many respects, some being cautious or cowardly, proud or haughty, persevering or obstinate, &c., in various proportions. When we contrast all other animals with man, however, in regard to moral endowment, we immediately perceive the broad, the impassable line of difference that runs between the lord of creation and all the other beings that with him partake of life. The feeling which leads man to view his actions in their bearing upon others or in relation to jus- tice, is extremely weak among animals, if in- deed it do actually exist among them at all. The same may be said of the sentiment which leads mankind to wish well to all, and to succour and relieve those that are suffering and unfortunate. The feeling, again, that raises man to the imagination of a something beyond nature, the sentiment that inclines him to reve- rence and adore his Maker, thus in one way re- vealed to him, and the wonderful impulse that leads him to look beyond time and his merely temporary existence, and thence to conceive in- finity and eternity, are so many moral attributes which man alone, of all created things, possesses. Similar diversities in intellectual endowment are apparent when we survey the animal king- dom at large. Intelligence appears utterly ANIMAL. 145 wanting in numerous and extensive classes, and it varies conspicuously in the members of every tribe among which it is apparent. In his in- tellectual powers man is not less eminently raised above all the other beings of creation than in his moral constitution : he alone takes note of the phenomena that pass around him with ulterior views, and he alone perceives the relation between effect and cause, preparing and foreseeing consequences long before they happen. Locomotion is a function so evidently in re- lation with the circumstances surrounded by which animals exist, and with the apparatus by which it is accomplished, that it is enough to refer back to the structure for proof and illustra- tion of its infinite modifications among the various genera and species of the animal king- dom. Some, by their constitution, are inca- pable of motion from place to place, but they still perform those partial motions which their preservation as individuals require taking their food, respiring, voiding their excretions, &c. Those that can move from one place to another have organs in relation to the mode in which this motion is accomplished, whether it be by creeping, by swimming, by running, leaping, flying, Sec. &c. Every partial movement ex- ecuted by the higher animals has, farther, its own special apparatus : the intestinal canal has its muscular parietes; the necessity that is felt to communicate internal sensations and ideas has its pathognomonic means in the looks, gestures, sounds of the voice, and so on. Nor is it only in the greater or less degree of complexity of their general structure, in the num- ber and diversity of their particular organs, or in those of the actions whose sum constitutes their vitality,that animals differ from one another; they vary farther in the degree in which these organs and these functions are enchained or mutually dependent. In the most simple animals so complete is the independence of the several parts, that their bodies may be divided into numerous pieces without injury to the vitality of any one of them, each possessing in itself the capacity to commence a separate existence. In animals somewhat more elevated in the scale we observe very extensive powers of reproduc- tion at least, of parts that have been lost, and even of continuing existence in very insignificant remainders of their bodies. In the most ele- vated tribes, however, the dependence of every part upon the whole becomes such that neither will the body essentially mutilated survive, nor will any part of the slightest consequence con- tinue to live. Among the beings at the bottom of the scale we have in fact found the organiza- tion to be homogeneous, or without distinction of parts, and nutrition to be accomplished by means of an immediate absorption and exhala- tion; and as every part possesses the structure which makes it capable of these two acts, every part, it is evident, suffices for its own existence. In the higher classes of animal existence, how- ever, nutrition requires the concurrence of a mul- titude of peculiar acts ; and in order that life may be continued in any fragment of one of the mem- bers of these, it is plain that this fragment must vor. i. contain the organs of every one of the functions essential to nutrition. Further, it is certain that the nervous system, when once it has fairly made its appearance, strictly dominates the nutritive function, and that every part of the nervous system itself becomes progressively more and more dependent on one of its portions, the encephalon or brain, as animals stand higher in the scale of creation, and as the functions over which the nervous parts preside respectively are themselves of a higher order. These are new and additional reasons for the centraliza- tion of life, or for the complete dependence of the organs and their functions one upon another among the more perfect animals man, the quadrumans and quadrupeds, birds, &c. So much for the acts that minister to the preservation of the individual. Let us now turn to the interesting series by which species are continued. In the very lowest grades this end is accomplished without the concurrence of sexes : at a determinate period of its life the animal either separates into several fragments, which become so many new and independent individuals, or it throws out a number of buds or germs from its external surface or from a particular internal cavity. The first of these modes of reproduction is entitled fissiparous, the second external gemmiparous, and the third internal gemmiparous. When we examine animals in the next grade, we find reproduction taking place by the con- currence of sexes, or rather of two kinds of organs which we afterwards discover divided between different individuals, who are then said to be of opposite sexes. When the male and female organs are united in the same indi- vidual it is denominated an hermaphrodite ani- mal, and in some cases seems to suffice for its own impregnation ; more generally, however, hermaphrodite animals are not capable of per- forming this act upon themselves, but require the concurrence of another individual of similar constitution: the two hermaphrodites meet and severally impregnate one another. Among the more perfect classes of the ani- mal kingdom the organs of reproduction are universally allotted to two different individuals, males and females, which consequently become in their dualism representatives of their species. Agreeing in this single feature, the modifica- tions in the process of reproduction are never- theless extremely numerous. In some cases the fecundating fluid of the male is only ap- plied to the egg or germ of the female after its extrusion from her body, as happens among fishes, several reptiles, &c.; in others the male fluid is injected into the body of the female, and made to fecundate the germ still attached to its parent. This act is generally, though not invariably, accomplished by means of a penis, or male external organ, with which many birds and all the animals above them in the scale of animal creation are then provided. With this contact or intermixture of bodies we have the following varieties in the after-parts of the process : the egg or germ now fecun- dated is either forthwith expelled from the body, and it is only subsequently, under the in- 146 ANIMAL. fluence of a certain temperature, and after the lapse of a certain time, that the young being bursts the shell and commences its independent existence ; this is the case among oviparous animals. Or otherwise : the fecundated egg makes its way so slowly through the passages that lead from the ovary outwards, that it is hatched before it can escape, so that the young one passes from the body of the mother imme- diately. Animals in whom this happens are justly said to be ova-viviparous. In the third and last place, the fecundated ovum is imme- diately loosened from the ovary, but instead of being laid, or extruded from the body immedi- ately, it only passes along a canal to a certain distance from the ovary, where it meets with a reservoir or cavity (the uterus) to which it at- taches itself, and within which it commences a series of evolutions, at the expense of the mother, preliminary to its final expulsion with instincts ready formed, and an organization so perfect as enables it to begin its separate ex- istence. The classes in which this mode of reproduction obtains, and they are the highest of all, including quadrupeds and man, are en- titled viviparous, so that in these, besides the connection of the sexes and the fecundation of the germ, we have the phenomena of utero- gestation and labour. And here the proper work of reproduction ends; but the young are so generally born in some sort immature, that in the higher classes the connection between the offspring and pa- rent does not cease immediately. In the class of mammalia, indeed, the connection is little less intimate during the earlier periods of extra uterine life than it was during the whole term of intra-uterine existence ; the young being still depends upon its mother for the whole of its nourishment, and very generally for the supply of warmth it requires and the protection needful to it till able to provide for itself. Many of the particulars now merely glanced at, and numerous others, the mention of which has been omitted entirely, will be found de- tailed, and their bearing and importance illus- trated in the article on GENERATION, to which the reader is therefore referred. BIBLIOGRAPHY. Stahl, De diversitate corporis mixti et vivi, 4to. Halae, 1707. Berxelius, in Af handlingen i Fisik, Kemi, &c. (on the means of ascertaining the definite and simple proportions in which the component elements of organic bodies are combined), t. iii. Stockh. 1810, and in Thom- son's Annals of Philosophy, vols. iv. and v. ; Ejus, Lehrbuch der Chemie, B. 3. Dresd. 1827 ; Traite de Chemie Trad, par Jourdan, t. v. Gay-Lussac et Thenard, Proportion des principes des sub- stances vegetales et animates, in Rech. physico- chymiques, t. ii. 8vo. Paris, 1811. Ure, Ultimate analysis of vegetable and animal substances, in Phil. Trans. 1822. Emmet, Chemistry of animated nature, 8vo. New York, 1822. Chevreul, Sur 1'analyse organique, 8vo. Paris, 1824. Robinet, Sur 1'affinite organique, 4to. Paris, 1826. Fray, Sur 1'origine des substances organizees et inor- ganizeea, Berl. 1807 ; Ejus, Essai sur 1'origine des corps organizes, &c. Paris, 1817. Treviranus, Ueber die organische elemente des thiereschen Koerpers. in Verm. Schrift. B. 1. Edwards, Sur la structure elementaire des tissues organiques, in Archiv. Gen. de Med. t. iii. Rudolphi, Anatomie der Pflanzen, 8vo. Berl. * * * Nitsch, Beitrage zur Infusorienkunde, Halle, 1817. Moerklin, Ueber die Urformen der niedern Organismen, Heidelb. 1823. Schweigger, Naturgesch. der skelettlosen ungeglie- derten Thiere, 8vo. Leips. 1820. Cams, jEussern lebensbedingungen d.weiss und kaltbluetiger Thiere, 4to. Leipz. 1824. Wrisberg, Obs. de animalculis infusoriis, 8vo. Getting. 1765. * * * Ciassi, De natu- ra plantarum, 12mo. Venet. 1677. Phile, De ani- malium proprietate, Traj. ad Rhen. 1730. Feld- niann, Comparatio plantarum et animalium, Lugd. Batav. 1732, iterum, Berol. 1780. Camper, Oiat. de analogia inter animalia et stirpes, 4to. Groning. 1764. Bonnet, Parallele des plantes et des ani- maux, Contemp. de la nature, Amsterd. 1764. De la Methrie, Vues physiol. sur 1'organiz. animate et vegetale, 8vo. Amst. 1787. Gleditsch, Gleichheit zwischen den Thieren und Gewachsen. Bondt, Overeenkomt tweschen Dieren en Planten, 8vo. Amst. 1792. Nitsche, Momenta quaedam compa- rationis regni animalis cum vegetabili, 4to. Lips. 1798. Decandolle, Snr les Proprietes des Plantes, 8vo. Paris, 1804. Samelson praes. Schweigger, De corporum naturalium affinitate, 8vo. Regiom. 1814. Schweigger, Verwandschaft desThier-und Pflanzen- reichs (Handb. d. Nature, d. Skelettlos. ungegl. Thiere, 8vo. Leipz. 1820). Schultz, Ueber die Pflanzen und Thiere im Allgemeinen, 8vo. Berl. 1823.*** Cartheuser, De genericisquibusdam plan- tarum principiis, 8vo. Francof. ad Viadrum, 1754. 1764. Bucquet, Etude des corps tires du regne vegetal, 2 torn. 12mo. Paris, 1773. Riche, Chimie des vegetaux, 8vo. Paris, 1787. Von Hum- boldt, Aphorismi ex doctrin. physiol. - chemica plantarum (in Florae Fribergensis Spec. 4to. Berl. 1793). Johnson, Hist. &c. of animal chemistry, 3 vol. 8vo. Lond. 1803. De Saussure, Recherch. chimiques sur les vegetaux, Paris, 1804. Wahlen- berg, De sedibus materiariini immediatarum in Plantis, 4to. Upsal, 1804, 1807. Davy, Elem. of agricultural chemistry, 4to. Lond. 1813. Berzelius, Fbrlasningar i Djurkemien, 2 Del. 8vo. Stockh. 1806-8. Ejus, Progress and present state of animal chemistry from the Swed. 8vo. Lond. 1813 ; Germanice, 8vo. Nurnberg, 1815. Berard, Analyse des substances animates (in Annales de Chemie, t. v. 1817). Dobereiner, Zur pneuma- tischen Phyto-chemie, Jena, 1822. Desvaux, Essai d'une classification des principes immediate des vegetaux (Journ. de Pharmacie, t. ii.) * * * * Malpighi, Anatome Plantarum, fol. Lond. 1675. Grew, Anatomy of Plants, fol. Lond. 1682. Hill, On timber, 8vo. Lond. 1770. Sprengel, Kenntniss der Gewaechse, 8vo. Halle, 1802-1807. Ejus, Vom Baue und Natur d. Gewaechse, 8vo. Halle, 1812. Brisseau-Mirbel, Anat. et Physiol. vegetale, Paris, 1802. Ejus, Expos, et defense, 8vo. Amst. 1808 ; Paris, 1809. Petit- Thouars, Organization de Plantes, 8vo. Paris, 1806. Treviranus, Inwendigen Bau derPOanzen, 8vo. Getting. 1806. Link, Anat. u. Physiol. d. Pflanzen, 8vo. Gotting. 1807 ; Nach- trag ib. 1809. Moldenhauer, Anatomie der Pflanzen, 4to. Kiel, 1812. Kieser, Organization des Plantes, 4to. Harlem, 1814. De Candolle, Organographie vegetale, 2 vol. 1827. * * * * Blumenbach, Handb. d. Vergleichenden Anatomie, 8vo. Gb'tiing. 1805, Anglice by W. Lawrence, 8vo. Lond. 1807. Cuvier, Lecons d'Anat. comparee, 5 tn. 8vo. Paris, 1798- 1809. ; Anglice, partim, by W. Ross, 2 vol. 8vo. Lond. 1802. Jacopi, Element, di Fisiologia e Notomia compar. 3 vol. 8vo. Milan, 1808. Carus, Lehrbuch der Zootomie, 8vo. Leipz. 1818 ; Ang- lice by W. Gore, An introduction to the compara- tive anatomy of animals, 8vo. Lond. 1827 ; Gallice a Jourdan, 2 torn. 8vo. Paris, 1835. Meckel, System der vergleichenden Anatomie, 6 Bde, 8vo. Halle, 1821-33. ; Gallice partim, Paris, 1828- 29. De Blainmlle, De 1'organization des Animaux, 8vo. Paris, 1822. Ejus, Cours de Physiologic ge- nerale et comparee, 3 torn. 8vo. Paris, 1829. * * * * Duhamel-Dumonceau, La Physique des arbres, 2 vol. 4to. Paris, 1758. Van Marum, Dissert, qua REGION OF THE ANKLE. 147 disquiritnr quousque quaedarn animalium planta- rumque t'unctiones consentiunt, 4to. Gotting. 1773. Mustel, Traite, &c. stir la vegetation, 8vo. Rouen, 1781. Fryar, De vita animantium et vogetabi- lium, 4to. Lugd. Ratav. 1785. Dumas, Essai sur la vie, Montp. 1785. Compuretti, Prodrorao di fisi- ca vegetabile, 8vo. Padua, 1791. Kielmeyer, Ver- haltnisse der organische Kraefte, 8vo. Stuttg. 1793; Tubing. 1814. Humboldt, Aphorism, a us d. Phy- siologie der Pflanzen, a. d. Lat. uebers. 8vo. Leipz. 1794. Brera, Program, de vitae vegetabilis et animal is analo-.ua, 4to. Ticin. 1796. Rafn, Ent- wurf einer Pflanzen-physiologie a. d. Dan. uebers. Kopenhagen, 1798. Senehier, Physiologic vege- tale, 5 vol. 8vo. Genev. 1800. Darwin, Phyto- tomia, 4to. Lond. 1800. Carradori, Sulla via delle Piante, 8vo. Milano, 1807. Treviranus, Beitrage zur Pflanzen-physiologie, 8vo. Goetting. 1811. Kieser, Aphorismen aus der Physiologic der Pflanzen, 8vo. Goetting. 1808. Keith, A system of physiological botany, 2 vol. 8vo. Lond. 1816. * * * * Treviranus, Biologie, 6 Bde, 8vo. Gotting. 1802-21. Scheubler u. Haider, Ufber die Temperatur der Vegetabilien/Fubing. 1826. Hunter, Obs. on certain parts of the animal economy, 4to. Lond. 1786, 1792. Edwards, Influence des agens physiques sur la vie, 8vo. Paris, 1824 ; Anglice, 8vo. Lond. 1832. * * * * Vianelli, Luci notturae dell'acqua marina, Venez. 1749. Viviani, Phos- phorescentia maris illustrate, 4to. Genoae, 1805. Murray, Ex per. researches on the light and lu- minous matter of the glow-worm, &c. 8vo. Glasg. 1826. Heinrich, Ueber die Phosphorescenz der Koerper. * * * * Galvani, Mem. sull' elettricita animale, Bologn. 1797. Volta, Sull' elettricita ani- male, 1782. Valli, Sull'elett. animale, Pavia, 1792.' Aldini, Diss. de animali electiicitate, Bo- logn. 1794. Pfoff, Ueber thieresche Electricitaet und Reizbarkeit. Leipz. 1795. Ritter, Beweis dass Galvanismus den Lebensprocess in dem Thierreiche begleite, Weimar, 1790. Ejus, Beitrage zur kennt- niss des Galvanismus, Jena, 1800. * * * * Gliston, De irritabilitate fibrarum (in Ej. De ventriculo et intestinis Tract. 12mo. Lond. 1677.) Stuhl, Theoria medica vera, 4to. Halle, 1708. Whytt On the vital, &c. motions of animals, 8vo. Lond. 1751. Darwin, Zoonomia, 4to. Lond. De Gorier, Exercitat. rnedicae, 4to. Amst. 1737-48. Lups, De irritabilitate, 4to. Leid. 1748. Holler, Primae lineae Physiologies, 8vo. Gotting. 1747 ; Ej. Ele- menta Physiologiae ; Ej. Mem. sur la nature irrita ble et sensible des parties, &c. 4to. Lausan. 1756 ; Ej. Op. minora, 4to. Humboldt, Ueber die gereitzte Muskel-und Nervenfaser, t. ii. 8vo. Berl. 1797. Bichat, Rech. sur la Vie et la mort, 8vo. Paris. Anatomic generale. The systems of Physiology of Adelon, Bostock, Burdach, Magendie, Mayo, Richerand, Rudolphi, and Tiedeman. (To the admirable Physiologic of the last mentioned judi- cious, learned, and laborious author, the writer of the present article stands greatly indebted. The work has been lately translated into English by Drs. Gully and Lane.) ( R. Willis.) ANKLE, REGION OF THE, (surgical anatomy), (region tibio-tarsienne, Velp.) The relative positions and other particulars con- nected with the parts found in the region of the ankle, owing to the numerous accidents which occur here, are matters of great interest to the surgeon. The extent and boundaries of this re- gion are by no means so distinctly defined as those of many others ; hence, in isolating it for special description, the surgical anatomist is obliged to assign to it arbitrary or imaginary limits. We propose to adopt the following boundaries for this region, viz. superiorly a hori- zontal line drawn round the leg two inches above the malleoli, and inferiorly a line drawn across the dorsurn and sides of the foot at the same distance from those bony prominences. In this space are comprised the ankle-joint and several important vessels, tendons, and other soft parts well worthy of attention. In examining the external characters of this region we notice four well-marked prominences, one on either side, termed malleotus, (internus v. externus) ; a third posteriorly, which cor- responds to the tendo Achillis; and a fourth in front, resulting from the projection of the astra- galus. The malleoli do not accurately corres- pond either in situation or shape to each other : the internal lies upon a plane superior and anterior to the external, and in a well formed person is much less sharp and prominent, a fact, the recollection of which is of great im- portance in estimating deformity or dislocation of the joint. The cylindrical prominence be- hind, as it depends upon the tendo Achillis, will of course vary in size and tension accord- ing to the relaxation or contraction of the gastrocnemii muscles. Upon either side of the tendo Achillis, between it and the malleo- lus we meet with a deep groove, called by some the calceo-malleolar furrow : that upon the outside is extremely well marked, and we may here distinctly feel through the integu- ments two of the peronei tendons : the internal calceo-malleolar groove is broader and shal- lower, but of much greater interest, for through it, in addition to certain tendons, we have transmitted the principal vessels and nerves des- tined for the sole of the foot. The anterior prominence, named in popular language, " the instep," is rounded in the transverse direction, and in some individuals projects much more than in others. On throwing the foot and toes into action, as in walking, we can here dis- tinctly recognize the tendons of the tibialis anticus, extensor pollicis, extensor digitorum longus, and peroneus tertius, and almost in the mesial line may be felt pulsating distinctly the anterior tibial artery. Having thus examined the landmarks which are to guide us in our anatomical investigation of this region, we may next proceed to inquire into the nature and relations of its constituent parts. Besides the bones, cartilages, and liga- ments which immediately constitute the joint, and form the basis of the region, we have like- wise several other structures entering into its formation ; integuments, muscles, vessels, nerves, and fasciae are here arranged in suc- cessive layers beneath each other. We shall accordingly describe four layers, namely, 1. the skin; 2. the subcutaneous cellular tissue; 3. the fasciae; and 4. the tendons, vessels, and nerves, which lie in immediate contact with the articulation. 1. The skin forms a complete investment for the whole region, but its structure and properties differ considerably in different situ- ations. Upon the inner ankle it i:i smooth and thin, and possessed of but little extensibility ; so that in operating here, if we look forward to union by the first intention, it becomes a matter of great moment to preserve as much i. 2 148 RKGION OF THE ANKLE. of the skiu as possible. Owing to the same peculiarities of the integuments in this situ- ation, no lebs perhaps than to the frequent motion of the part, wounds and ulcers occur- ring upon the inner ankle are extremely tedious and troublesome, in many instances laying bare the bone, and finally even occasioning its destruction. Upon the outer ankle, the skin is more pliant and extensible; hence the greater facility of healing wounds and ulcers in this part; and hence, too, the more frequent occur- rence of abscess and extravasation beneath the surface. At the posterior part of the region the skin acquires great strength and thickness, becoming as it passes downwards still more dense and unyielding, approximating in fact to the character of the plantar integument. Upon the instep it is also of tolerable thick- ness, particularly in those individuals whose feet are usually uncovered. In this situation, however, it is soft and extensible : its natural pliancy being still further increased by the secretion of numerous sebaceous follicles thickly scattered throughout its substance. It is here, owing to the frequent motions of the joint, thrown into transverse rugae, and hence, in making an incision, to give exit to matter, it may be proper to prefer a transverse to a vertical direction. 2. The subcutaneous cellular tissue. The structure and properties of the subcutaneous cellular tissue are not the same throughout the whole region, but like the skin, which we have just considered, its characters vary in dif- ferent situations. Thus, upon the instep, it is at the upper part loose and distensible, full of adipose cells, and similar in every respect to the subcutaneous tissue of the leg, of which it is a prolongation : as it descends, however, it becomes more dense and unyielding, and ad- heres more closely to the skin which covers, and to the annular ligament which is placed beneath it. This anatomical fact at once ex- plains why it is that when subcutaneous ab- scess or infiltration occurs on the anterior part of the leg or foot, the passage of the fluid either upwards or downwards is, for a time at least, impeded at the ankle-joint. It is like- wise owing to the density of the subcutaneous tissue across the ankle, that its cells do not permit the accumulation of adipose substance here; hence in very fat persons and also in children whose subcutaneous fat is usually abundant upon the leg and foot, the instep is as it were strangulated by a deep transverse furrow. Upon the malleoli the characters of the subcutaneous tissue present great differ- ences: upon the inner one it is scanty and delicate, but of a compact structure, and con- tains few if any adipose cells. Upon the outer one it is, on the contrary, much more copious, of a loose and yielding texture, and usually contains a greater quantity of fat. These dif- ferences of texture will explain why, after severe contusion, extravasations so frequently occur upon the outer part of the joint and so seldom upon the inner ; why abscess is so much oftener met with in the one situation than in the other ; and why the transmission of pus and serum from any of the neighbour- ing regions takes place so much more easily about the outer than about the inner ankle. At the posterior part of the region, the sub- cutaneous tissue assumes again new characters : losing here its soft lamellated texture it be- comes suddenly dense and filamentous, ad- hering with great firmness to the integuments above, and to the fascia beneath : as we trace it down it becomes more dense and elastic ; the cells formed by the decussation of its filaments become loaded with a firm granular fat; in a word, it already begins to put on the characters of the dense fibro-adipose cushion, which is found in the sole of the foot. Hence it is that wounds and abscesses of the part we are now considering, approach in character those of the plantar region : hence the slight swelling, the severe pain ; hence in both cases the necessity of a prompt and free evacuation of the matter. Before leaving this subject we should ob- serve that the subcutaneous tissue of the region we are now considering transmits certain ves- sels and nerves. In front of the inner ankle we meet with the incipient branches of the great saphena vein and the ultimate filaments of the saphenus nerve : the venous branches are here of such a size that they have fre- quently been selected by the phlebotomist as the seat of operation. Anteriorly we find the filaments of the musculo-cutaneous nerve, and externally the roots of the lesser saphena vein, and its accompanying nervous filaments. 3. The fascia or aponeurosis forms the next stratum we have to examine: it is placed be- tween the subcutaneous tissue and the tendons. The fascia, like the two preceding layers, forms a general investment for the whole region. Its structure and properties, like those of the preceding layers, vary considerably, according to the situation in which we view it. Upon the instep it becomes continuous, above with the aponeurosis of the leg, and inferiorly with the dorsal aponeurosis of the foot, but, for very obvious reasons, surpassing both of these in strength. This additional strength is owing to the accessory band of fibres which passes transversely across the instep, interlaced with the proper oblique fibres of the fascia, and to which is given the name of anterior annular ligament. Arising from the anterior edge of the inner ankle this annular ligament passes outwards and soon meets with the ten- don of the tibialis anticus : at this point it splits into two layers ; the one passes before, the other behind the tendon, and they unite again at its outer edge. The same mechanism is repeated in the case of the extensor pollicis tendon which lies immediately external to the last-named tendon ; and lastly in those of the extensor digitorum longus and peroneus tertius. In contemplating the mechanism and uses of this ligament, the surgical anatomist cannot but perceive that certain inconveniences must result from its division : its use being obviously to bind down the tendons in this situation, and to form canals for their free and separate trans- mission, it is clear that after its division in the KECiiON OF THE ANKLE. living subject, when the individual attempts to flex the foot or extend the toes, these tendons will not only form an unseemly projection upon the instep, but also the accuracy and per- fection of these motions will be much im- paired. Upon the lateral parts of the region, the fascia is so intimately united to the peri- osteum, that it is almost impossible to separate them from each other, and hence some have denied its existence here. Behind both mal- leoli, it becomes however again very distinct, forming in both situations a band similar to that which we have just seen upon the instep. The internal annular ligament arising from the posterior edge of the inner malleolus passes backwards to the os calcis; it is thrown like a bridge across that deep gutter which divides the heel and ankle from each other, and it is destined like the anterior liga- ment to form a covering to the tendons and other parts which pass through this region. Like the anterior, the internal ligament also consists of two layers closely united to each other. To express more distinctly the me- chanical disposition of these layers, we may say that the bridge formed by the internal annular ligament consists of two arches ; through the anterior arch are transmitted the tibialis posticus and the flexor digitorum longus tendons, wrapped each in its own synovial theca : the posterior arch is occupied with the posterior tibial vessels and nerves, and the tendon of the flexor longus pollicis muscle. Having thus safely conducted these important organs, the superficial layer of the ligament fixes itself into the os calcis, while the deep one passes backwards and upwards to become continuous with the deep fascia of the leg. Behind the external malleolus, the fascia forms another but less remarkable liga- ment, which Blandin calls the " external an- nular:" this passes from the fibula to the astragalus, and forms with the posterior edge of the malleolus a deep osseo-fibrous canal for the transmission of the peroneus longus and brevis tendons. At the back part of this region, t!ie fascia is also found covering the great tendo Achillis ; this tendon also, like the smaller ones we have just spoken of, is not merely covered super- ficially, but is contained within a sheath, formed by the splitting of the fascia into two layers : the posterior layer we may regard as the continued fascia itself; the deep one passes in front of the tendon, and if we trace this up- wards, we shall find it becoming ultimately continuous with the deep fascia of the leg. An acquaintance with the disposition and structure of the fascia we have thus described, will en- able the surgical anatomist, in almost every in- stance, to explain the time, situation, and pro- gress of abscesses occurring in this region: he will at once comprehend that three distinct sorts of abscess may form here : one in the subcutaneous tissue, and which being super- ficial to the fascia can hardly penetrate deeply toward the joint ; another, occurring between the two layers of that membrane, in those situations where it splits to include the ten- dons ; such an abscess will have little tendency to point in front, being bound down by the superficial layer of the fascia, or to penetrate deeply for a similar reason ; but to its free passage upwards or downwards in the course of the tendons, little or no obstacle is presented. Lastly, matter may accumulate under both layers of the fascia, where its deep position and close confinement render it alike dangerous, and of difficult detection. 4. The next stratum is perhaps less entitled to that name than those we have hitherto described. Instead of forming, like them, a general investment for the whole region, it consists of several distinct and independent or- gans scattered irregularly about the joint : we shall enumerate them in the order in which we propose to treat of them, viz., tendons, mus- cles, arteries, veins, lymphatics, and nerves. a. Tendons. Upon the instep we find no fewer than seven tendons passing towards the foot : the internal is the largest of all, it is that of the tibialis anticus running obliquely for- wards and inwards to the inner cuneiform bone. Close upon its outer side is the tendon of the extensor pollicis ; still more outwards we meet with the four tendons of the extensor digitorum longus, and most externally of all, or nearest to the outer ankle, that of the peroneus tertius. We need not revert to the subject of the fibrous sheaths furnished to these tendons by the fascia or annular ligament; but we should here care- fully observe, that both sheaths and tendons are completely lined by a synovial apparatus. He who is at all acquainted with the general patho- logy of synovial membrane will understand why it is that effusions so frequently form about the instep ; why adhesion of the opposite walls of these synovial sheaths will almost destroy the power of extending the toes and of flexing the foot ; and, lastly, he cannot but draw the im- portant practical deduction, that in operations about the instep we should avoid, if possible, cutting into these synovial sacs. Behind the inner malleolus we meet with three tendons, that of the tibialis posticus most anterior, and in close connexion with the posterior surface of the malleolus internus; that of the flexor digitorum longus a little further back ; and still more posterior, and at a little distance from the others, the tendon of the flexor pollicis longus. These are included, as we have already explained, in fibrous sheaths formed by the internal annular ligament, each sheath and tendon having its own synovial lining. We may here observe a good anatomical reason, why inflammation affecting the sheath of the flexor digitorum will, cateris paribus, be more likely to prove dangerous than that of the tibialis posticus : for, as the synovial sheaths of the former extend along the whole sole of the foot, little or no obstacle is presented to the disease extending itself into that region : whereas the tendon of the tibialis being inserted, not. upon the sole, but rather upon the inner edge of the foot, its synovnl membrane forms here a cul-de-sac, no doubt presenting some obsta- cle to the inflammation extending beyond this point. Behind the outer malleolus there exists 150 REGION OF THE ANKLE. a deep groove, in which two important tendons are contained, those, namely, of the peroneus longus and brevis. They are lodged in a canal which we have already described as formed by the bone and the external annular ligament, and this canal is lined by a distinct synovial membrane reflected upon it from the tendons. Having passed over the ligaments of the outer ankle, the peronei tendons are next applied upon the surface of the os calcis; and here, though previously in close apposition, and in- deed contained within the same synovial sheath, they become separated by a ridge projecting from the bone. The peroneus longus tendon plays behind it as upon a pulley, and instances have occurred, where, owing to the fracture of this little osseous septum, the peroneus longus has been dislocated forwards upon that of the brevis. It has also happened that both peronei tendons have been dislocated forwards from their groove behind the malleolus, and thrown in front of that eminence. Were such an acci- dent left without surgical interference, it is inte- resting to reflect how completely altered would be the action of these two muscles, if that action were not completely suspended by the inflam- mation and obliteration of the synovial sheath consequent on the accident ; instead of extend- ing the foot and pointing the toe, as they do in their natural state, they would become con- verted into flexors and abductors of the foot. At the posterior part of the region, the tendo Achillis forms a remarkable projection. In our account of the fascia, we have described the sheath within which this tendon is contained. We may further observe that this tendon is separated from the joint, and also from the deep vessels and nerves of the leg, by a consi- derable interval, so that it has frequently been cut across without injury to the articulation or wound of any other important part. Its mode of insertion into the os calcis is also worthy attention ; instead of being fixed into the whole posterior surface of that bone, it occupies by its insertion merely the lower half of it ; supe- riorly the bone and tendon are not even in con- tact, for here a distinct synovial bursa is inter- posed between them. The liability of this large bursa to inflammation and effusion should be carefully borne in mind by the surgeon : and he who is aware of its office, placed as a friction roller between the tendon and bone, will duly estimate how much disease of this bursa will impede the motions of progression. Owing to the interposition of the bursa, rupture of the tendo Achillis has occurred even below the upper edge of the os calcis ; and if, having cut across the tendon, we forcibly extend the foot so as to elevate the heel, we shall at once com- prehend how indispensably necessary it is to maintain the extended position in our treatment of this important accident. b. Muscles. There are bu t few muscular fibres met with in the region of the ankle : the flexor digitorum brevis arises upon the instep ; and posteriorly we find some of the fibres of the flexor pollicis longus, which are here continued down a considerable way upon the tendon. c. Arteries. The arteries about the ankle. from their liability to injury and disease, become of great interest. Upon the instep the course and relations of the anterior tibial artery de- mand particular attention; the vessel here does not run exactly in the median line of the foot, but is somewhat nearer to the inner than to the outer malleolus : we may always reach it with perfect certainty, by cutting between the tendon of the extensor digitorum longus, and that of the extensor pollicis ; these overlap it upon either side, and afford considerable protec- tion against wounds or other injuries. Not- withstanding the facility of reaching the vessel in this situation, it is by no means advisable to do so when it is at all possible to avoid it, inas- much as to expose the artery here it is necessary to wound the synovial sheaths, and inflammation and adhesionwould be the probable consequence of such an injury. The branches of the in- ternal malleolar artery are found upon the inner part of the region, running upon and in front of the inner ankle, and anastomosing with others passing forwards from the posterior tibial, thus insuring a sufficient supply of blood to the joint, even when the trunk of the anterior tibial itself has been tied. But these vessels are of much inferior importance compared with the posterior tibial, whose main trunk lies in the fossa between the heel and the malleolus internus. It is here occasionally the subject of operation, and hence its course and relations should be very carefully noted. We have al- ready enumerated the tendons passing beneath the annular ligament in this situation ; the most anterior is that of the tibialis posticus, imme- diately behind it lies that of the flexor digi- torum, and still more posteriorly, at the interval of about an inch, is found the tendon of the flexor pollicis ; in this interval between the two" latter tendons runs the posterior tibial artery, not however equidistant from both, but nearer to that of the flexor digitorum ; it rests upon the tibia and internal tibio-tarsal ligament, and is covered by the integuments and annular ligament; its venae comites run one upon either side ; and the posterior tibial nerve lies close behind it, but as the vessel descends get- ting gradually to its inner side. Notwith- standing the few coverings of the artery in this situation, yet owing to the heel, the ankle, and the tendo Achillis projecting around, and bearing off as it were those coverings from it, the vessel is here at a considerable depth from the surface ; and any one who supposes it can be easily found in the living subject, will form a very erroneous idea of its true position : hence it i* that all good writers on surgical anatomy recommend us to take up the artery in the lower third of the leg, rather than in the calceo-malleolar groove. Several small vessels ramify about the outer ankle, the external malleolar coming from before meets here with the terminating branches of the peroneal artery from behind, but these small vessels are interesting to the sur- gical pathologist rather than to the regional anatomist or operative surgeon. d. Veins. Two veins, the " venae comites," accompany each of the larger arteries : in all operations upon the artery, the close apposition JOINT OF THE ANKLE. 151 of the veins, and the possibility of mistaking one for the other, should be remembered by the surgeon. In front of the inner malleolus we observe one or two openings in the fascia, through which small branches of communication pass between the superficial and deep veins; these, no doubt, are the principal channels through which the venous blood of the integu- ments about the foot and instep is returned, after the operation of tying the great saphena vein. e. Lymphatic*. The lymphatics consist like- wise of two sets ; the one lying beneath the integuments and scattered irregularly over the region ; the other lying beneath the fascia, and for the most part accompanying the blood- vessels. Some anatomists speak of a lymphatic gland lying upon the instep, and receiving several of these deep absorbents ; in the majo- rity of cases there is no such gland, and its existence in any appears to us extremely doubtful. f. Nerves. The nerves in this region have the same general distribution as the arteries. In our account of the larger arteries, we have already minutely assigned the relation which their accompanying nerves bear to them. We may thus briefly enumerate them : in front, the musculo-cutaneous and anterior tibial ; on the inner side the terminal ramifications of the internal saphenus and the posterior tibial ; and on the outside, the terminal branches of the external saphenus. For further particulars re- specting the nerves, we refer to the articles LUMBAR NERVES; SACRAL NERVES. For the BIBLIOGRAPHY of this article and all others on surgical anatomy, see the Bibliography of ANATOMY (INTRODUCTION.) (John E. Brenan.) ANKLE, JOINT OF THE. (Normal ana- tomy.) (Fr. articulation du coude-pied. Germ. Fusagelenk. Ital. caviglia.) The ankle-joint, or tibio-tarsal articulation, results from the junc- tion of the leg and foot. For reasons which will appear when we come to explain its mo- tions, it is ranked in the excellent and com- prehensive classifications of Bichat andCloquet as a perfect angular ginglymus. The security of the ankle-joint, more perhaps than of any other in the body, is owing to the peculiar form of its bones, and to their exact adap- tation to each other; in this respect it has aptly been compared to the tenon and mortise joint, so frequently used by mechanics, the strength of which, as is well known, is chiefly owing to the peculiar form and close fitting of its component parts. Upon the "pper part of the foot, we meet with, it is said, a true and well defined tenon, and upon the lower part of the leg a tolerably perfect mortise for the reception of the tenon. The comparison, though perhaps not strictly correct, will however assist us in understanding how much the security of this joint depends upon the form and fitting of its bones ; and will explain to the beginner why, in treating of the ankle-joint in particular with a view to demonstrate its use and mechanism, a brief account of its bones becomes par) of our description no less essential than of its liga- ments themselves. In our account, therefore, of this articulation, we shall, in the first place, describe its bones; next its ligaments; and, lastly, shall offer some remarks upon its me- chanism and uses. a. The Bones. Three bones contribute to the formation of the ankle-joint; the tibia and fibula form, by the union of their inferior por- tions, a deep depression, into which the head of the astragalus is received. The tibia, as it ap- proaches the joint, looses gradually its prismatic shape, and assumes a well-defined cubical or quadrangular form. On its lower extremity it presents a quadrilateral articulating cavity, covered in the recent state with cartilage ; this cavity is transversed from before backwards by an obtuse ridge which subdivides it into two smaller cavities. Of the four sides or margins of this articulating cavity, the anterior is almost straight transversely, but convex or rounded off in the vertical direction, with the obvious design of permitting a greater flexion to the foot; the anterior tibio-tarsal ligament arises from this margin. The posterior margin is also straight transversely, but vertically convex, to permit an increased extension to the foot ; the posterior tibio-fibular ligament is connected here : a shallow oblique groove is met with upon the outer part of this surface, for the transmission of the flexor longus pollicis tendon. The ex- ternal side presents a depression for the reception of the fibula ; this articulating portion is pro- longed upwards for nearly an inch, is of a triangular form with the base below ; the sides of the triangle give attachment to the anterior and posterior tibio-fibular ligaments ; and the area of the triangle is rendered rough, except at its lowest part, by the attachment of the inferior interosseous ligament, another strong bond of union between these bones. The inner edge is prolonged downwards nearly an inch in length, forming the prominence known by the name of malleolus internus; this is placed upon a plane superior and anterior to the malleolus externus; it is somewhat flattened in shape, and has one surface looking inwards or towards the mesial line ; this in the living subject is covered only by the integuments ; the outer surface enters into the formation of the joint, hence it is tipped with cartilage to permit the astragalus to play upon it; the anterior edge is sharp and gives origin to the anterior tibio-tarsal ligament; the posterior edge is traversed by a broad and generally well-marked groove, which transmits the tendons of the tibialis posticus and flexor digitorum longus ; the apex of the malleolus is below, and gives attachment to the deltoid or internal tibio-tarsal ligament. Thejibula, as it approaches the foot, becomes suddenly enlarged in size, applies itself firmly to the tibia, and then descends nearly an inch and a half below its point of union with that bone. The prominence formed by the fibula in this situation is named the malleolus externus ; it is much larger than the internal, and placed behind and somewhat below it. The external surface of this fibular maHeohis is covered merely l>y the integuments ; the internal surface JOINT OF THE ANKLE. is tipped with cartilage, and convex in the ver- tical direction, being received upon a corres- ponding concavity on the outer side of the astragalus; upon the lower and back part of this inner surface may be seen a deep depres- sion, where the posterior fibulo-tarsal ligament arises; the anterior edge of the malleolus is sharp, and gives origin to the anterior fibulo- tarsal ligament ; the posterior edge is marked by a deep groove, whieh transmits the tendons of the peronei muscles, longus and brevis. The apex of the malleolus is below, and gives origin to the middle fibulo-tarsal ligament. The astragalus enters into the formation of the ankle-joint by its superior surface, and a portion of its two lateral surfaces. On the superior surface we observe, anteriorly, a well marked groove forming part of the neck of the astragalus ; into this groove the anterior tibio- tarsal ligament is inserted. Immediately be- hind the groove we meet with an articulating eminence of an oblong quadrilateral form, an inch and a half in its antero-posterior, and about an inch and a quarter in its transverse measure- ment; (this transverse measurement is, however, a little greater in front than behind ;) the emi- nence is remarkably convex from before back- wards, and concave from side to side ; the outer edge somewhat more elevated than the inner ; it is completely covered with cartilage, and cor- responds to the articulating cavity upon the in- ferior exremity of the tibia. Upon the inner side of the astragalus, we find a small articu- lating surface of a triangular form, with the base above and apex below; it is convex in the vertical direction, and is tipped with car- tilage prolonged ftom the superior surface: upon thetriangular surface the internal malleolus plays ; the remaining portion of the inner side of the astragalus is rough, and occupied chiefly by the insertion of the internal tibio-tarsal ligament. The external side of the astragalus is also marked by an articulating surface of a much greater size for the reception of the ex- ternal malleolus : it too is of a triangular form with the base above ; concave in the vertical, and slightly convex in the antero-posterior direction. b. Ligaments. We have already compared the mechanism of this joint to that of the tenon and mortise ; the mortise cavity, however, is not, as we have seen, cut out of a solid bone, but teing formed in great part in the lower extremity of the tibia, is completed on the outer, side by the fibula, which is firmly united with the tibia by strong ligaments, forming what is called the i nferior tibw-fibulur articulation. We shall not now describe the ligaments which here unite the tibia and fibula, referring to the article on the TlBlO-FIBULAR ARTICULATION ; but W6 must observe that, however it may be advisable, in anatomical descriptions, to separate this last named articulation from the ankle-joint, they are perfectly inseparable in their functions, the integrity of the latter being essentially dependent on that of the former : indeed it may be said, that, by virtue of the great strength of the liga- mentous connexion between the tibia and fibula in the former articulation, the mortise is n* strong, nay, in some respects stronger, than if it had been formed out of solid bone. The ligaments which connect the tenon and mortise together, or to speak more literally, which tie the tibia and fibula with the tarsus, are five in number, namely, two tibio-tarsal and three fibulo-tarsal ligaments. 1 . The internal tibio-tarsal ligament is also called the internal lateral, and by Weitbrecht the deltoid ligament. There is, however, no reason why we should not apply to it likewise that principle of nomenclature which is so gene- rally and with such advantage applied to other ligaments. It arises by a truncated apex from the point of the inner malleolus, and from the little fossa at its outer surface ; its fibres change as they proceed downwards and are fixed into the inner surface of the astragalus and os calcis, some proceeding as far forwards even as the scaphoid bone. The posterior fibres are strong but short ; the anterior are much larger and not so thick. Its internal surface is lined by the synovial membrane of the joint; and on its internal surface it is covered by the tendon of the tibialis posticus, and it sends some of its fibres to the sheath of the flexor longus digitorum tendon. In flexion of the leg the anterior fibres are relaxed, and the posterior are rendered tense: in extension the reverse of course takes place. 2. The anterior tibio- tarsal ligament (lig. tibio-tarsal, Cloquet) con- sists of a few loose fibres scattered over the synovial membrane, and in some instances so delicate and so separated by pellicles of fat as to be scarcely perceptible. They arise from the fore part of the inner malleolus and the adjacent anterior portion of the tibia, and de- scend obliquely downwards and outwards to be inserted into the neck of the astragalus. This ligament is covered anteriorly by the ten- dons of the tibialis anticus, extensor proprius pollicis, and extensor digitorum longus : poste- riorly it is in contact with the synovial mem- brane. 3. The anterior fibulo-tarsal ligament (lig.fibule anterius, Weitb., anterior external lateral, Boyer) arises from the anterior edge of the outer malleolus, a few lines from its ex- tremity; it descends obliquely forwards and inwards, and is fixed into the astragalus imme- diately in front of the articulating surface which receives the fibula: it is scarcely an inch in length, of an oblong quadrilateral form, and is frequently subdivided into two distinct parts. In extension of the foot it is rendered tense ; in flexion it is relaxed. 4. The middle fibulo- tarsal ligament ( lig. fibula medium perpen- diculare, Weitb., external lateral ligament, Cloq.) is a round fasciculus of fibres having almost the appearance of a tendon which arises from the apex of the external malleolus, de- scends obliquely backwards, and is attached to the outside of the os calcis. It does not appear to us that in any position of the joint this ligament takes a perpendicular course, although that epithet has been applied to it by Weitbrecht. It is related superficially to the peroneus longus tendon, and by its deep sur- face to the synovial membrane, to the astra- galus, and os calcis. In flexion of the foot this JOINT OF THE ANKLK. 153 ligament is rendered tense ; hence it appears designed to limit motion in this direction : in extension it is of course relaxed. 5. The /ws- teriorjibulo-tarsal\\ga.mei}t( lig. fibula postcrius, Weitb., posterior external later at, Boyer) arises from the little fossa upon the inner and back part of the outer malleolus ; it passes backwards and inwards almost horizontally, or at least de- scends very slightly, and is inserted upon the back part of the astragalus into the outer edge of that groove which transmits the flexor longus pollicis tendon. This ligament is stronger than either of the two preceding, and is frequently divided into several distinct fasciculi. From its superior edge an accessory band sometimes passes upwards and inwards over the synovial capsule to be fixed into the tibia. Walther has described this band under the name of the oblique ligament, and it is well represented by Weitbrecht (jig. 65, tab. xxii.) The synovial membrane of the ankle-joint is of very great extent : it lines not only the articular surface of each malleolus, the several ligaments we have just described, and the articulating cavity upon the lower portion of the tibia, but it is prolonged upwards between the tibia and fibula, forming in that situation a little cul-de-sac : this, however, is merely for the extent of a few lines, for its further progress up- wards is interrupted by the inferior interosseous ligament, (Jig. 61.) From the circumference of the tibio-fibular mortise the synovial mem- brane passes downwards upon the astragalus, covers its superior articulating eminence, and sends prolongations upon its lateral articulating surfaces. It is remarkably loose upon the anterior and posterior parts of the joint, and is said to contain a greater quantity of synovia than any other synovial membrane in the body. Certainly its strength is much increased by those scattered fibres to which we have given the name of anterior tibio-tarsal ligament : posteriorly it is weakest, for here few if any ligamentous fibres can be detected, though Boyer and Weitbrecht speak confidently of such. c. Mechanism and function of the ankle-joint. To understand properly the mechanism and function of the ankle-joint, we must carefully contemplate it in the opposite conditions of rest and motion. 1. Viewing it, then, in the first place, as the individual stands at rest, we observe that the leg and foot meet each other in the ankle-joint at a right angle, and we are particularly struck with this fact upon finding that this disposition occurs in scarcely any other animal than man. This interesting fact in comparative anatomy is by no means an accidental arrangement; its design is obviously in reference to the proper position of the body in each animal. It has, for instance, frequently been alluded to as one of the many anatomical proofs that the erect position is natural to the human subject : had the leg and foot been articulated at any other than a right angle the upright position of the body could not be maintained, at least without great and incessant muscular exertion. Another point worthy of our attention is that when the ankle is at rest and the body in the upright position, the fibula plays no part in the func- tion performed by the joint : it is the tibia alone which receives the weight of the body, and transmits it to the astragalus. This fact should be carefully borne in mind, for it has considerable influence upon the accidents so frequently occurring here. The astragalus, from the way in which it supports the body, has often been compared to the key-stone of an arch, the arch being represented by the foot. That the foot presents an arched concavity at its lower part cannot be doubted ; but it is by no means so certain that this is designed upon the prin- ciple of the architectural arch to support the weight of the body : in fact, the astragalus, which receives the entire weight, does not cor- respond to the centre of this arch. The true design of the vaulted form of the foot is to permit its accommodating itself to the several irregularities of surface which, both in standing and progression, it must encounter. The motions of flexion and extension are the only ones permitted at the ankle-joint. In flexion the astragalus rolls from before back- wards in the tibio-fibular mortise; it maybe continued until the foot and leg form with each other an angle of about sixty degrees ; at this point further flexion is prevented, partly by the tension of the middle fibulo-tarsal liga- ment, and still more effectually by the neck of the astragalus coming into contact with the lower edge of the tibia. In flexion the anterior tibio-tarsal and fibulo-tarsal ligaments are both relaxed ; the posterior and middle fibulo-tarsal are rendered tense ; the internal tibio-tarsal ligament has its posterior fibres stretched and its anterior ones loosened. 2. In extension the foot not only returns to its rectangular posi- tion with the leg, but may even be carried beyond this, so as to form with the tibia an obtuse angle of about one hundred and fifty degrees.* Further extension is at this point prevented by the tension of the ligaments which lie in front, and also by the astragalus behind coming into contact with the lower edge of the tibia. During extension the astragalus rotates forwards in the tibio-fibular mortise ; the pos- terior ligaments are relaxed, the anterior are put upon the stretch, the state of each individual ligament is, in short, reversed from what we have just described as its condition in the opposite motion of the joint. 3. A slight degree of lateral motion of the ankle is perceptible in the dead subject, but during life it cannot be said to exist : hence, in the classification of Cloquet and Bichat, the joint is properly ranked under that variety of ginglymus to which we apply the term "perfect." The ankle is the analogue of the wrist-joint in the superior extremity, and accordingly, though there are certain points of difference between them, the general character of both is * According to Hildebrandt the angle of flexion is 45, and the angle of extension according to Rosenthal (Handb. der Chir. Anat.) is 175. ED. 154 ABNORMAL CONDITION OF THE ANKLE-JOINT. the same. It is no less interesting than instruc- tive to contrast these two articulations with each other, for in doing so we find that the modifications of structure here, as well as in all other instances, are referable to the peculiar function which each part is destined to perform. The hand in the human subject is exclusively an organ of prehension ; the foot is one merely of support : now this simple fact at once fur- nishes us with a clue to all difficulties. The great strength and sudden expansion of the tibia and fibula at the ankle, are evidently a provision to sustain the weight of the body and to increase the basis of its support; in the radius and ulna such size and strength would have been to no purpose, and hence these bones at the wrist are comparatively thin and delicate. At the ankle we should naturally have expected frequent dislocations, owing to the great weight from above, and to the great mobility which for the purposes of progression must at the same time necessarily exist here ; these are two most formidable causes of displacement ; but, as if in compensation, we find two strong buttresses (the malleoli) projecting one upon either side of the joint, and rendering such displacement, under ordinary circumstances, almost impossible. At the wrist, where there is no weight to be sup- ported, such lateral splints would have been superfluous : hence the imperfect and almost rudimental malleoli of the radius and ulna; hence the shallow and imperfect cavity ; hence, in a word, the anatomical confor- mation which constitutes the ankle-joint a ginglymus, and the wrist an arthrodia. In the motions of the ankle and wrist-joints we observe likewise a striking difference: in the former, lateral motion would have been super- flous in reference to the function of the foot ; at the wrist, on the contrary, a free lateral mo- tion is indispensable to increase the sphere of action of the hand. For the BIBLIOGRAPHY of this article, see that of ARTICULATION. (John E. Brenan.) ANKLE-JOINT, ABNORMAL CONDI- TION OF THE. The deviations from the na- tural or normal condition of the ankle-joint may be classed under those which are referable to accident and to disease : any defects which may be considered to result from congenital malformation shall be elsewere treated of. (See FOOT.) Accidents. The different structures which immediately compose the ankle-joint, as well as those which surround this articulation, and are merely accessary to its functions, are, each and all, liable to numerous accidents, the most important of which we shall here advert to. These accidents may affect the tendons, the ligaments, or the bones. Tendons. Those tendons which pass behind the inner and outer malleoli are occasionally displaced ; and, although the accident must be considered a rare one, it ought not here be overlooked. " The two peronaei extensor muscles," says the late Mr. Wilson,* " where they pass behind and below the fibula over a smooth lubricated surface of that bone, are bound to it by a strong ligament ; but should the ligament give way, one or both of these tendons may escape from the groove or pulley in which they usually play, and being thrown forwards over the edge of the bone, in this new situation their action on the foot will be to bend it on the leg, when in their natural position it was to extend it. The peronsei having been habituated to act with the extensor muscles, continue to contract at the same time with them, but now they oppose the effect which formerly in conjunction with the extensor muscles they produced upon the foot, and by so doing excite much pain and irritation in addition to the lameness. When this situation of the tendon is discovered early, the tendon can be readily restored to its proper place, but if this is not done, it forms a new groove on the fore part of the bone, and the old one is filled up, or otherwise so altered that it cannot receive the tendon, and thus the pain and lameness may continue for life. I have seen this occurrence sometimes in the living body early enough to return the tendon, and have been consulted in cases where it could not be returned ; in one, where the pain was so violent that I recommended the divi- sion and removal of part of the tendon ; the muscle then contracted to its full extent, and afterwards shrunk, and no inconvenience was felt after the operation. I have met with two or three instances of this kind of displacement of tendons in bodies brought into the dissect- ing-room ; but of the previous history of the cases I could know nothing." Mr. Wilson adds, " Those tendons which pass in grooves behind the inner ankle are liable to a similar displacement.'' Of the latter accident we have known but one instance, but of the former several. Ligaments. Accurate anatomical investi- gations of the actual condition of the various structures which compose the ankle-joint, when affected by a sprain, have shown that in slight cases of sprain of this joint no- thing unnatural has been discovered, as the bonds of union between the bones have been merely stretched or strained. In others more severe, the ligaments have been found broken or torn from their attachment to the bones, the synovial sac opened, and its fluid to have escaped from the cavity of the joint ; the cel- lular tissue around has been filled with extrava- sated blood, and with synovial and serous fluids. In these cases the nerves, bloodvessels, ten- dons, even the skin itself, have been subjected to a degree of stretching and extension, more or less considerable. Baron Dupuytren, from nu- merous observations on the living subject, from post-mortem examinations, and experiments, is of opinion that a slight accidental torsion of the foot inwards or outwards, amounting to a sprain, only produces an injury, in which * Wilson's Lectures on the Bones, &c. ABNORMAL CONDITION OF THE ANKLE-JOINT. 155 the ligaments are merely stretched ; but that a greater effort produces a separation of the lateral ligament from one or other of the mal- leoli by laceration of its compact tissue, or of the periosteum which covers it, while the liga- ments themselves remain unbroken. Oppor- tunities do not often occur of discovering the effects of sprains on the joints by anato- mical examination made at various periods after the accident ; but although Dupuytren's opinion may be correct as to the majority of cases, still others have found the lateral liga- ments ruptured across, instead of having been torn from the bone. Mr. Wilson found, in a case where the patient died five days after a severe sprain of the ankle-joint, that the del- toid ligament binding the tibia to the foot was lacerated, and that the synovial membrane of the ankle-joint was also much torn. In older cases he found evidences of chronic inflamma- tion in the ligamentous structures around the joint ; that these structures were thickened and vascular, and had lost much of their plia- bility. The pain and inability to walk, the sudden effusion around the injured ankle, the ecchy- mosis, tenderness of the skin and tension, the signs of this injury expressed by the living structures, are all accounted for by the lesions which an anatomical examination of these in- juries of the ankle-joint discovers. This also explains what practical writers have noted of sprains, viz. that sometimes the ankle-joint which has been affected by this accident, rapidly and perfectly recovers, that, on the other hand, it is not unfrequently so weakened by the injury, as to become peculiarly suscep- tible of a renewal of the sprain from slight causes ; sometimes the articulation contracts a rigidity, by which for a time, or even for life itself, its proper functions are interfered with, and a permanent osdema of the soft parts around the joint is too often in these cases established. Bones. The bones which contribute to form the ankle-joint are liable to fracture and to luxation. These bones, we know, are the tibia, fibula, and astragalus ; for an- account of the accidents which affect the latter particularly, we refer to the article FOOT, and shall here, as succinctly as we can, notice the various dis- placements of the bones of the leg at the ankle-joint, which have been observed to be the result of a fracture through one or both of the malleoli, or of an accidental rupture of the ligaments which tie these eminences to the foot. When we reflect on the great strength of the ligaments which connect the astragalus to the tibia and fibula, and the support which the ar- ticulation derives from the prolongation down- wards of the malleoli, we can easily perceive that a luxation of the foot must be the effect only of some very violent cause, and that this accident can very rarely (in a true sense) be a simple one. Effusions of blood, rupture of all the surrounding ligaments, fracture of the external or even of both the malleoli, wounds of the soft parts, and even protrusion of the bones, are contingences which frequently render the dislocation of the tibia at the ankle-joint a very complex accident. The most superficial view of the structure of the ankle-joint will convince any one that no lateral displacement of the bones of the leg can occur, without its having been im- mediately preceded by a fracture of either the tibial or peronaeal malleolus ; but such a view would warrant the conjecture, that a luxation in the direction forwards or backwards may possibly take place, simply from the rupture of the ligaments of the joint alone, and the action of muscles. Such a luxation as this last, when no fracture exists, should be best entitled to the name of simple ; yet those luxations of this articulation (such is the vagueness of surgical language), whether ac- companied with fracture or not, are all called simple, provided there be no wound through the integuments communicating with the cavity of the joint. In this latter case alone the luxation is denominated compound, of which it is not our intention here to treat. W T e shall arrange the luxations of the bones of the leg at the ankle-joint in the above sense called simple luxations, into those which occur in the direction inwards, outwards, forwards, and backwards, and each of these, it is be- lieved, may be a partial or a complete lux- ation. Luxation of the Tibia inwards. This luxa- tion may be complete or incomplete : we shall first treat of the most common form of it or that termed partial Dislocation of the Tibia inwards from the Astragalus, or Pott's luxation. Mr. Pott, in describing this accident, observes, " that the support of the body, and the due and proper use and execution of the office of the joint of the ankle, depend almost entirely on the perpendicular bearing of the tibia upon the astragalus, and on its firm connexion with the fibula. If the former bone is forced from its just and perpendicular position on the astragalus ; or, if it be separated by violence from its connexion with the latter, the joint of the ankle will suffer a partial luxation inter- nally : this is the case when, by leaping or jumping, the fibula breaks in its weak part, within two or three inches of its lower ex- tremity. When this happens, the inferior frac- tured end of the fibula falls inwards towards the tibia, that extremity of the bone which forms the outer ankle is turned somewhat out- wards and upwards, and the tibia, having lost its proper support, and not being of itself capable of steadily preserving its true perpendicular bearing, is forced off from the astragalus, in- wards, by which the ligaments are torn, thus producing a perfect fracture and a partial dis- location."* If we are called to examine a patient who has recently suffered this accident, we find that the ankle-joint now possesses some degree of lateral mobility. In the normal state of the ankle-joint we know that the quadrilateral cavity formed by the tibia and fibula for the * Pott's Works by Earle, vol. i. p. 327. 156 ABNORMAL CONDITION OF THE ANKLE-JOINT. reception of the astragalus, makes with the latter a perfect mortise joint, which admits of motions of flexion and extension, but allows of no motion whatever laterally or horizontally; for it must be recollected that those motions of inclination of the foot, known under the names of adduction and abduction, are not movements in the ankle-joint, but take place in the joints of the tarsus : but the un- natural mobility in question is very great when the fibula is broken at its lower part; this is shewn, when, after the surgeon has bent the limb to relax the muscles, the leg is fixed by one hand placed at its lower extremity, whilst the other moves the foot from within outwards; the foot is then seen to move in a transverse line and to quit the axis of the leg ; the mal- leolus internus projects inwards, and the mal- leolus externus is moved upwards and out- wards, and all these appearances vanish, when by a contrary movement we bring the foot to its natural position. When we le,ave the limb for a moment to itself, we notice that there is a remarkable change in the point of incidence of the axis of the leg upon the foot. The tibia and upper fragment of the fibula, although really remain- ing in their natural position, appear driven in- wards, while the foot is rotated outwards. The changes of direction of the leg and foot are such, that if the axis of the leg were pro- longed inferiorly, instead of falling on the astragalus, it would leave this bone, and con- sequently the whole foot, more or less on its outer side; hence the impossibility patients experience of bearing upon the foot , which only presents its inner edge to the ground. Fig. 51. Fig. 52. Partial luxation of the Tibia inwards, or Pott's luxation. This change is a necessary and constant effect of the displacement of the foot, when the fibula ceases to support it on the outer side, arid when the peronsei muscles begin to con- tract. The foot and external malleolus which make part of one system, move in one direc- tion ; the tibia and upper fragment of the fibula move, or, to speak perhaps more correctly, remain, in another. The centre of this new motion is no longer in the articulation, but, in an oblique line, passing through the joint, and extending from the malleolus internus to the point of fracture of the fibula: this line is well expressed in Jig. 51, representing the frac- ture of the fibula, and taken from the engrav- ing which accompanies the work of Pott. The retiring angle seen (fig.5\, 52, a) in this partial luxation of the tibia inwards, on the outer part of the articulation, and the pro- jecting one (b) existing at the inner, consti- tute the most striking features of the accident ; these angles correspond exactly to the extremi- ties of the line above-mentioned, in the direc- tion of which the weight of the body acts, when the foot being turned outwards this line may be seen to traverse the leg obliquely from the lower part of the upper fragment of the broken fibula to the malleolus internus. We cannot omit to notice also, that there is in all these cases a remarkable rotation of the whole foot on its long axis, in such a direction that the upper surface of the astragalus looks obliquely upwards and inwards, f/g.52,cj the inner edge of the foot is turned downwards, the sole inclined outwards, the outer edge raised, and the dorsum turned directly upwards. The extent of this rotatory motion is besides always proportioned to the displacement out- wards ; both are attributable to the same causes, viz. the weight of the body, and the action of the peronaei muscles, when the patient has at- tempted to walk after the fracture has occurred. It is on these combined movements when not corrected by a proper mode of treatment, that the deformity of the foot, and all the consequent difficulties in walking, depend. Complete luxation of the tibia inwards from the astragalus, complicated with a simple frac- ture of the fibula. This is a very severe, and, fortunately, a very rare accident. In alluding to it, Dupuytren says,* that " the foot is not only susceptible of being carried outwards, but also upwards at the same time;" a double displacement, which he had observed to occur only once in 200 cases of fractures of the fibula treated in the Hotel Dieu for fifteen years, " but the case was so marked," he says, " that in future it cannot be mistaken or passed over in silence." It cannot occur unless the fibula is fractured ; for this condition is indis- pensable to any displacement of the foot in- wards or outwards ; it requires besides a com- plete laceration of the short thick ligaments placed between the tibia and fibula, the strength of which is such that, in most experiments on * Sur la Fract. de 1'Extremite inferieure du Pe- rone, in Annuaire Med. Chir. des Hopitaux de Paris, 1809, 4to. and folio. ABNORMAL CONDITION OF THE ANKLE-JOINT. 157 the dead subject, they resist more powerfully than the structure of the bones themselves. It was as a consequence of the fracture of the fibula and a rupture of these ligaments, that, in the case alluded to, the astragalus was seen dislocated outwards, and then drawn up on the outer side of the tibia. In short, the astragalus, the malleolus externus, and the foot, which formed but one system of parts firmly connected, were drawn first to the outer side of the leg, and then two inches upwards on the tibia. A carpenter, aged fifty-four years, was ad- mitted into the Hotel Dieu, in February, 1816. His right leg presented all the signs of fracture of the fibula at its inferior part, such as devia- tion and rotation of the foot outwards, promi- nence of the tibia, and of the internal malleolus inwards, depression and crepitation above the outer ankle ; but that which most attracted the attention was, 1st, the shortening of the limb, and, 2dly, the enormous increase in breadth of the space which should naturally intervene be- tween the two malleoli. The sinking down of the lowest part of the tibia, even to the level of the sole of the foot, where the projection of the internal malleolus could be felt, the elevation of the astragalus, of the peroneal malleolus, and the whole of the foot along the external surface of the tibia, even to two inches, were all symp- toms quite unusual in fracture of the fibula, and left no doubt that the ligaments which stretched inferiorly from this bone to the tibia had been lacerated, and that the foot, yielding to a violent effort from within outwards, and from below upwards, had been luxated in these directions, and had carried with it the peroneal malleolus. This then is evidently a case of complete dislocation of the tibia inwards, or, as the French writers would call it, a luxation of the foot outwards and upwards. Although this species of luxation has not been specially described in any of our English works, I doubt not but such an accident has been observed, although it is possible that its nature was not always clearly understood. Sir A. Cooper, in his valuable work on Disloca- tions and Fractures, states that the foot has also been known to be thrown upwards, between the tibia and fibula, by the giving way of the ligament which unites these bones; but he adds that this accident is only an aggravated form of an internal dislocation. We find but little difficulty in comprehend- ing how the accident described by Dupuytren may occur, because, the fibula having been first fractured, the broken bone and ruptured ligaments permit the foot to yield to the powerful action of the muscles on the back part and outside of the leg, which draw it at first outwards, and then upwards ; but on the contrary, it is not easy to imagine any force capable of overcoming the resistance of the many inter-osseous ligaments which exist, and of the fasciae and annular membranes which surround the bones of the leg : a force must be great indeed which can overcome the muscles also, and cause a divarication of the bones of the leg sufficient to permit the astragalus and rest Fig. 53. Fig. 54. Complete luxation of tlie tibia inwards or of the foot outwards and upwards. (Dupuytren.) Dissection of a case of the same class as fig. 53, from the museum of St. Thomas's Hospital. of the foot to be thrown upwards between the tibia and fibula. Supposing this last case pos- sible, the shortening of the limb and its newly- acquired breadth between the malleoli might lead to error, and the two cases here alluded to be at first sight confounded ; but in Dupuy- tren's case, the fracture of the fibula, the over- lapping of its fragments, and above all the ascent of the external malleolus, so much above the level of the internal, will always constitute such characteristic marks, that when such an accident presents itself, we conceive it cannot be confounded with any other injury of this articulation. What are the anatomical characters of this complete luxation of the tibia inwards, with displacement of the foot and outer malleolus upwards and outwards? It is evident that there must be very extensive injury done in such cases to the ligaments and bones ; the fibula must be fractured near the ankle, and it is probable that some fragments of the tibia may be carried off with the fibula, for such is the strength of the ligaments between the lower part of the tibia and fibula, where these unite for the reception of the astragal us (vid.fg. 61), that there is reason to believe that the bone itself would break before the ligaments would yield. If a portion of the tibia, however, is not broken off and carried with the fibula, these transverse fibrous bands must be torn, as well as those 158 ABNORMAL CONDITION OF THE ANKLE-JOINT. oblique ligaments which pass before and be- hind from the fibula to the tibia. The proper interosseous membrane itself must be detached from between the bones to allow the astragalus to ascend along the outside of the tibia. While the ligaments which connect the outer malleolus to the tibia must be torn, those which unite it to the foot remain entire, the deltoid or internal lateral ligament must be completely torn across, as well as the synovial sac of the articula- tion ; nor should it be forgotten that the annu- lar ligaments and strong fasciae at the lower part of the leg, must, in so severe and ex- tensive an injury, be lacerated; the tendons, muscles, and other structures may escape injury, the astragalus and outer malleolus are dragged up (fg. 54, a, 6), their ascent being only limited by the lower point of the upper fragment of the fibula (c), which remains in its natural relation to the tibia, except that it must be somewhat approximated to it ; the lowest point of the superior fragment of the broken fibula rest upon the summit of the articular pulley of the astragalus, as is well seen in a preparation B'eserved in the collection of St. Thomas's ospital Museum, the delineation of which we have borrowed from Sir A. Cooper's work. The preservation of this specimen, which in our mind is a true example of the complete dislo- cation of the tibia inwards, and of the external malleolus astragalus and foot upwards and outwards, is a new proof of the truth of the observation we have above made, that this severe accident had not altogether escaped the notice of English surgeons, although the 11 Annuaire" contains the first accurate account of the external signs by which it may be recog- nized in the living subject. Luxation of the tibia outwards, complicated with simple fracture of one or both of the mal- leoli. This, it is said, is one of the most dan- gerous of the dislocations to which the ankle is liable, for its production has been noticed to be attended with greater violence, and to be accompanied by more contusion of the integu- ments, more laceration of ligaments, and greater injury to bone, than we have occasion to ob- serve in the production of the other luxations of this joint. The astragalus in this accident is carried towards and below the external malleolus(7zg. 55), whilst the outer edge of the foot is turned downwards, its inner edge upwards, and the sole inwards, the tibial malleolus disappears, and is hidden at the bottom of a retiring angle formed by the inner side of the leg and foot, and the peroneal malleolus forms, with the astragalus, a salient angle rounded off on the outside. Looking only to the change of form, situation, and rela- tive position of the leg and foot, we might sup- pose the case one of congenital club-foot.* The luxation of the tibia outwards, with inversion of the sole of the foot, is one of the most rare and most difficult cases to explain. Its pro- duction must be the result, we suppose, of co- incidences rare and unusual. There may be a certain obliquity in the line of direction of the * Dupuytren, Annuaire. Fig. 55. Fig. 56. Luxation outwards of the Dissection of the luxa- tibia and fibula with ob- tion outwards (Museum lique fracture of the tibia. of St. Thomas's Hospi- tal}. [Fty.55.] fracture coinciding with a considerable degree of resistance in the lower fragment of the fibula : thus, if we can suppose that a fracture shall traverse the tibia obliquely from above down- wards, and from within outwards, so that the point of the upper fragment be directed down- wards and outwards, and the lower fragment point upwards and inwards, and if to this obliquity we suppose added a certain resistance on the side of the lower fragment of the fibula, it is plain that the foot being unable to turn out- wards, must be carried inwards by the action of the muscles, and with this inversion, &c. some little shortening of the limb, at least when measured on its inner side, may be ex- pected. If this accident be neglected, the cure which nature attempts is very imperfect, the ankle-joint becomes stiff and rigid (fg. 56), the interval be- tween the internal and external malleolus is much increased^ the latter presses heavily against the integuments, which, when the limb is much exercised, have a strong tendency to inflame and suppurate, the outer edge of the foot throughout its whole line presses the ground, whether the patient be standing or walking, while the inner edge is somewhat elevated and curved inwards. In the dissec- tion of this accident, it will be found that the ABNORMAL CONDITION OF THE ANKLE-JOINT. 159 malleolus interims is fractured, and in general, we suppose, with the obliquity from above downwards, and within outwards, above de- scribed. The deltoid ligament remains un- broken, the capsular membrane is torn in front, the fibula has been found obliquely fractured, as well as the tibia, or the three ligaments which connect it to the tarsus have given way; none of the tendons suffer, and haemorrhage to any extent in these cases seldom or never occurs, as the large arteries generally escape injury. Luxation of the tibia and fibula forwards, and also luxation of these bones backwards from the articular pulley of the astragalus, without fracture. In the simple and complete luxa- tion of the bones of the leg forwards at the ankle-joint, (without fracture,) the articular pulley of the astragalus is placed behind the inferior extremity of the tibia, which last rests partly on the superior surface of the neck of the astragalus, and partly on the os naviculare. In the simple and complete luxation of the tibia backwards, (without fracture,) the inferior extremity of the tibia is placed behind the arti- cular pulley of the astragalus, and corresponds to the posterior part of the superior surface of the os calcis. In both these luxations, the na- tural connexion with each other of the bones of the leg remains undisturbed, and the two mal- leoli advance or recede together, according to the direction in which the displacement has occurred. In both, the capsular membrane and the posterior and lateral ligaments must be ex- tensively lacerated, and most of the flexor and extensor tendons, in some degree, put upon the stretch. The luxation of the bones of the leg forwards cannot take place, but in a forced and sudden extension of the leg on the foot, when the latter being retained by some obstacle, and solidly supported, we fall backwards. The luxation of the tibia backwards, on the contrary, cannot happen unless when the foot is strongly flexed, the toes being elevated and retained in this position, we fall forwards. Authors have seldom failed to notice these simple luxations forwards and backwards of the bones of the leg, yet for our part, no mat- ter to what source we apply for information, we cannot satisfy our minds that we can adduce a single well-marked example of luxation of the bones of the leg at the ankle-joint, unac- companied by a fracture of one or both of the malleoli ; we would not, however, be under- stood to deny the possibility of such an occur- rence, but merely to state our conviction that such an accident must be exceedingly rare. We have now to consider luxations of the tibia from the astragalus, forwards and back- wards, when complicated with a simple frac- ture of the fibula or tibia close to the articula- tion : these may be complete or partial. Complete luxation of the tibia forwards from the articular part of the astragalus compli- cated with a simple fracture of the fibula. This accident may arise from the same causes nearly as those which may be supposed to influence the more simple luxation in the same direction; and as we know that when the fibula is fractured near its malleolus, the pe- ronaei muscles may under certain circumstances effect a luxation of the tibia inwards, so that displacement which we are now considering may be the result of the action of the gastro- cnemius and solaeus. These acting on the foot, which in consequence of the fracture is no longer fixed by the malleolus externus, cause the astragalus to slip from before backwards, and the lower end of the tibia forwards, and move the lower fragment of the fibula in such a manner that its malleolar extremity is carried backwards, and the upper part forwards. This action of these muscles, however, only pro- duces a very incomplete dislocation whenever the internal malleolus is uninjured, or the foot in this case being carried outwards and back- wards at the same time; but when, as often happens, either the internal malleolus or del- toid ligament is broken, this displacement may be as complete and direct as the simple dis- location forwards of the tibia. We then find the foot lengthened behind and shortened in front ; a semicircular excavation occurs in the former direction, and an osseous tumour raises the tendons and ligaments on the front of the ankle, but it is to be particularly remarked that, whilst in the simplest form of luxation of the tibia, i. e. where there is no fracture, the external malleolus follows the tibia and fibula, and forms a projection corresponding to that of the internal, it is in this case dragged backwards with the foot to which it is attached by the lateral ligaments, and no longer has the same direction as the bones of the leg. In the dislocation forwards of the tibia (whether simple or complicated with a frac- ture of the fibula) from the astragalus, the articular pulley of this bone is placed behind the inferior articular cavity formed for it in the tibia ; but this latter bone at the same time, it will be recollected, must now rest on the dor- sum of the tarsus, where it is formed by the upper part of the neck of the astragalus and os navi- culare. When the tibia has thus once advanced before the articular pulley of the astragalus, the luxation forwards is as complete as it well can be ; in our opinion, to imagine any more com- plete luxation of the tibia forwards, we should be obliged to presume that this bone in its advance on the dorsum of the foot had com- pletely cleared the astragalus, and then rested " on the os naviculare and os cuneiforme in- ternum" * which last form part of the anterior * The weight that so justly attaches to any ob- servations from Sir A. Cooper, induced us to con- sider well the account he gives of the dissection of this complete luxation of the tibia forwards, in his work on Dislocations and Fractures ; and we find that we cannot reconcile it with our ideas of the anatomy of the injury. We are sorry in this in- stance to be obliged to differ from an authority, to which we feel indebted for many observation^ copied into these pages ; but we think there must be error in the following passage taken from the valuable work to which we allude, page 178, 8th edition. " On dissection, the tibia is found to rest upon the upper surface of the os naviculare and os cunei- 160 ABNORMAL CONDITION OF THE ANKLE-JOINT. range of the tarsus, a situation which the tibia could not well occupy, without a previous lesion of the tendons of the tibialis anticus, and stretching of the other extensors : from such a relative position of the bones of the leg and foot would result a shortening of the dorsum of the foot and an elongation of the heel to an extent which, we believe, has never been no- ticed. Partial luxation of the tibia forwards, with simple fracture of one or both of the malleoli. The complete 'luxation forwards of the tibia from the astragalus, which we have described in the preceding section, all writers look upon as the more common form of dislocation for- wards ; while the partial luxation in this di- rection is considered a rare accident. My opinion upon this subject is quite different; for some experience in these accidents leads me to say, that a complete luxation of the tibia forwards from the articular pulley of the astra- galus is rare, but that a partial luxation in this direction accompanied with a simple fracture of one or both of the malleoli, is an accident by no means uncommon. The signs of this partial luxation of the tibia forwards are nearly the same as those we have stated to belong to the complete luxation in this direction ; they are, however, as might be expected, more faintly marked, and, conse- quently, may more easily be neglected ; but, after all, these signs are so evident, that it is wonderful how with common attention they can be overlooked. It may not be amiss to subjoin the following case as illustrative of the common partial luxation forwards : A man, aged twenty- two years, was ad- mitted into Jervis - Street Hospital, at three o'clock, A.M. of the 26th of December, 1833. He stated that he and a friend had been drinking together in a public house, that in the middle of the night they quarrelled, that he was knocked down, and was unable to rise, in consequence of his having received a severe injury of his left ankle : his friend then pro- cured some assistance and carried him to the hospital; at my visit, I found him in bed, complaining of much pain, his leg extended and resting on its outer side ; the heel was re- tracted, and between it and the calf of the leg, instead of the ordinary line which marks the course of the tendo Achillis, there was a conspicuous semicircular curve, (Jig- 57, , b); in a word, the heel was lengthened, and the dorsum of the foot seemed much shortened ; in the situation of the ankle-joint in front, there was a remarkably hard, prominent, trans- forme internum, quitting all the articulatory sur- face of the astragalus, excepting a small portion on its fore part, against which the tibia is applied." Now, a single glance at the skeleton of a foot will shew us, that a portion, however small, of the ar- ticulatory surface of the astragalus, together with, secondly, the upper part of the neck of this bone ; thirdly, the os naviculare ; and, fourthly, the os cuneiforme internum, nearly form a space equiva- lent to a third of the length of the whole foot, an extent of surface, which, manifestly, the arti- culating portion of the dislocated tibia could not occupy. verse ridge made by the advance of the lower extremity of the tibia and extensor muscles of the toes, while beneath this there was a marked depression, where the skin and annular liga- ment seemed, as it were, pinched in, drawn under the lower edge of the articular part of the tibia; the foot was pointed downwards, no movement of flexion or extension could be communicated to the ankle-joint, but it ad- mitted of some little motion in a horizontal, and also in a lateral, direction, when the leg was firmly grasped with one hand and the foot moved with the other. It was remarkable that, although the man had no power whatever over the motions of the joint, he could, while he lay in bed, move his whole limb about with much freedom, and (as there was probably a locking of the bones with each other) these voluntary movements were not accompanied by any increase of pain. The fibula could be felt to be fractured about an inch and a half above the lowest point of the outer malleolus, " the foot, the outer malleolus, and short portion of the broken fibula, formed one system of parts," and were carried for the length of an inch or more horizontally backwards, while there was a projection forwards, of the lower articular part of the tibia, and the internal malleolus itself was advanced in the same proportion : it is to be observed, that there was no crepitus, because it was the deltoid ligament only which was torn ; the tibia was not broken, and the ends of the fractured fibula were evidently far separated from each other. When the luxation was reduced, which was effected with- out much difficulty, crepitus could be felt, proving the restoration to its place of the lower fragment of the fibula. This is a species of fracture and luxation, which can, by proper management, be readily redressed, and no deformity remains, if time be not lost after the accident has occur- red ; but if the fibula become solidly united in its new situation, the motions of the ankle- joint are for ever lost, and the patient is doomed to lameness for life. In the month of September 1833, a woman, aged fifty-three years, was admitted into Jervis- street Hospital, whose left ankle-joint presented all the characters above assigned to the partial dislocation forwards of the tibia, combined with a simple fracture of the fibula ; she stated that she had, two months previously, broken her leg close to the ankle joint, and had been at- tended at her own house, from a dispensary, by a pupil, who applied pads and lateral splints, but when after a time all the splints were re- moved, she found that her limb was deformed, her ankle stiff, her foot rigidly extended, and pointed downwards, so as to be nearly useless to her; as two months had elapsed since the accident, before she applied, no promise of relief could be held out to her. She there- fore left the hospital, but not before I was enabled, through the kindness of Mr. Sutton, to obtain a cast of the leg and foot, from which figures 57 and 58 are copied. As I ABNORMAL CONDITION OF THE ANKLE-JOINT. 161 Partial luxation forwards of the tibia at the external ankle, with fracture of the fibula near the malleolus. Fig. 57. Viewed on the external side. Fig. 58. Viewed on the internal side. a, b, semicircular excavation posteriorly, and projection of the heel backwards ; c prominence formed by the tibia projected on the dorsum of the foot; d displacement of the external malleolus backwards along with the foot. was anxious, before these pages went to press, again to examine this case, I requested Mr. S. to make inquiry about her; he learned that the woman died dropsical a few days before, and with much difficulty procured for me an opportunity to examine the limb, which on careful dissection presented the following ap- pearances: the whole extremity was somewhat wasted, the skin on the sole of the foot was smooth and fine, shewing that she had been able to walk but little since the accident; the foot was in a position of almost rigid extension, the toes were directed downwards, the range of motion of flexion and extension did not exceed one inch, in short, all the usual characters assigned to the partial dislocation forwards of the tibia and displacement of the foot back- wards were seen; when the skin was re- moved from the fascia of the leg and foot, the intervening cellular membrane was found infiltrated with serum, the skin was adherent to the inner malleolus, the vena saphena and the nerve of the same name were thick- ened and firmly connected together, the ex- VOL. i. tensor tendons were stretched over the tibia, and were somewhat flattened, and the grooves which transmit the tendons that play behind the inner and outer malleolus were deepened. We now directed our attention to the state of the bones; we found that the tibia was dis- placed forwards, that its anterior edge was ad- vanced more than one inch beyond its natural situation, and that it much overhung the os naviculare, but such was the direction and state of obliquity of the tibia with respect to the foot, that it could not be said to rest upon that bone ; between the os naviculare and the infe- rior articular extremity of the tibia there inter- vened much fat of a yellow hue and fibrous texture, like intervertebral substance ; the inter- nal malleolus itself had not escaped injury, the deltoid ligament had not in this instance as in the former given way f the internal malleolus itself had been broken, and a small portion of the back part of the edge of the articular cavity of the tibia was detached, and both malleoli were retracted, or carried backwards with the foot; the fibula above the fractured portion was directed down- wards and a little forwards, and was somewhat parallel to the tibia, yet. more than naturally approximated to it, a circumstance which ac- counted for the contracted rounded form the middle of the leg possessed ; the lower frag- Fig. 59. Viewed on the external side. Fig. 60. Viewed on the internal side. Skeleton preparations of fig. 57 and 58. M ABNORMAL CONDITION OF THE ANKLE-JOINT. ment of the fibula was directed from below upwards, a little inwards, and very much for- wards, so as to make with its shaft a remark- able angle salient anteriorly; this bone had been traversed by the fracture obliquely, from above downwards and from before backwards. The external malleolus was placed about one inch and a quarter behind its usual situa- tion, and was consequently dislocated at its tibio-fibular articulation, having burst those strong ligaments which connect these bones together, and which are so seldom found to yield. Luxation of the bones of the leg backwards at the ankle-joint. A luxation of one or both bones of the leg at the ankle-joint backwards, whether the accident be what has been called complete or incomplete, whether accompanied with a fracture of the fibula, or merely with a rupture of the ligaments, is a displacement which must be considered exceedingly rare. Boyer, in his valuable work, gives no case of it from his own observation ; and in alluding to such an accident, states that no author, to his knowledge, has given a single example of it. Sir A. Cooper evidently has not seen it; for he says, " 1 have seen the tibia dislocated in three different directions, inwards, forwards, and outwards ; and a fourth species of disloca- tion is said sometimes to occur, viz. back- wards." Baron Dupuytren states that he has never seen this accident.* Mr. Colles has given me the notes of one case, and it is the only one he can, in his exten- sive experience, recollect to have met with, of a partial dislocation of the lower part of the tibia and fibula backwards, and has also shewn me the cast he had taken of the leg. In this case the tibia seemed thrown partially back- wards, from the articular pulley of the astraga- lus; the fibula was unbroken, and was also carried backwards with the tibia; the foot, measured from the instep upon its dorsum, was longer than that of the opposite side, the heel was shorter and less pointed, the space in front of the tendo Achillis, near to the os calcis, was partially filled up, and a hard swelling oc- cupied the lower and back part of the tibia, which was evidently formed by a quantity of callus, which had cemented together the frag- ments of a fracture of the lowest part of the tibia; the leg was shorter than the opposite limb. It would have been interesting to have learned the precise manner in which this accident had occurred ; but as to this, or the immediate symptoms which followed the injury, I could get no satisfactory information. The man did not apply to Stevens's Hospital until the bones were united in their new and faulty position. Besides the partial dislocation backwards of the tibia, this bone with the outer malleolus of the fibula was inclined somewhat outwards; and the man walked lame and most awkwardly on * Je n'ai jamais vu de luxation du pied en avant, dans les fractures du perone et de Textremite du tibia. Annuaire Medico-Chirurgical, 1819, Paris p. 159. the outer edge of the heel and foot, the inner side of which was somewhat curved inwards. I have had occasion to notice a displace- ment of the tibia backwards on the os calcis, in a case where the astragalus sloughed in con- sequence of a compound injury to the external malleolus and ankle-joint; but such a case is different from that now under our considera- tion, although the possibility of such an occur- rence should not be lost sight of. 2. Morbid anatomy, a. Acute inflammation of the synovial membrane of the ankle-joint produces changes in the synovial fluid of the articulation both in quantity and quality, and alterations very generally in the appearance and structure of the membrane ; I say very generally, for I have known an exception to the rule, in a case* of acute synovitis of the ankle-joint which caused the death of the patient in fifty hours from its first onset ; during the whole of the time the patient never slept nor ceased to com- plain of the agonizing pain of the ankle-joint. At the post-mortem examination, before the skin was removed, the extensors of the toes were observed to be displaced by the fluid which distended the synovial sac of the articulation, and fluctuation was now, as during life, to be felt in two tumours which existed in front of the two malleoli ; the interior of the joint was occupied by a turbid oily synovial fluid; no false membrane existed, and if there had been increased vascularity during life, no trace of it was discoverable at the time of examination : increased quantity with altered quality of the synovial fluid were the only deviations from the normal condition which could be noticed. Portions of the synovial membrane are, how- ever, occasionally found covered with false membrane. Pus has also been found in the joint, sometimes laudable, sometimes foetid, and of a brownish red colour; the membrane has been found thickened, and has afforded evidence of increased vascularity, and even in some points has presented a villous ap- pearance. In very young subjects I have known acute inflammation of the ankle-joint in a few days extend itself to the epiphysis, and produce separation of it from the shaft of the tibia ; and in such cases a displacement of the shaft inwards, and of the epiphysis and foot outwards, occurs from the action of the muscles, as in Pott's luxa- tion. Acute inflammation commencing in the synovial membrane of the ankle-joint sometimes extends farther than this : there have been cases in the Richmond Hospital, and the specimens have been preserved in the museum, of acute synovitis of the ankle in which the inflammation extended through the vascular junction of the epiphysis and shaft of the tibia, and having occupied the cellular junction of the periosteum with the anterior and inner surface of the tibia, soon ended in the formation of pus and lymph, which detached from the bone its immediate covering, and produced effects which termi- nated in the death of the patient. I have seen this detachment of the lower epiphysis of the tibia in an infant six days old, the result of acute * See Dublin Journal, vol. iv. p. 1. ABNORMAL CONDITION OF THE ANKLE-JOINT. IGiJ synovitis, with purulent deposition in the joint, and in a young man aged twenty, but have not observed it ever to occur in older subjects ; and conclude that it is one of the consequences of synovitis of the ankle-joint, which is only to be noticed at an age when the epiphyses are not yet consolidated with the shaft of the tibia. In these very acute attacks of inflamma- tion, its ravages are seldom confined to the structure which seemed to be the 'point du dipurC of the disease ; the cartilages are in some cases removed from the tibia, fibula, and upper surface of the astragalus with astonishing rapidity; the porous surface of the bones has also been found exposed, and their substance to afford evidence of its having been in a state of inflammation. Surgeons should ever bear in mind, that the synovial membrane of the ankle-joint passes very far forwards on the upper surface of the astragalus, even as far as within a few lines of the junction of this bone with the os naviculare, so that an accidental wound high upon the instep might very readily give rise to a fatal synovitis of the ankle-joint. Moreover, by an experiment on the dead sub- ject, it may be shown that a very slight direc- tion too much upwards of the edge of the knife when the operation of partial amputation, ac- cording to Chopart, is performed, may wound the most anterior part of the synovial sac of the ankle-joint, and the consequences of such a mishap might prove fatal, or at all events greatly aggravate the ills which even without such cause too frequently follow Chopart's operation. Again, the synovial membrane extends very low down, even to the lowest point of the inner side of the peroneal malleolus, along the outer or fibular surface of the astragalus (fig- 61, ). It has very frequently happened to the wri- ter's knowledge, that inflammation commencing in the body of the os calcis, or in the fibrous or synovial tissue of the articulation between the os calcis and under surface of the astragalus, has crept up to the ankle-joint by this route between the fibula and astragalus; when, therefore, opera- tions and cauterizations are performed by surgeons to cure the carious state of the os calcis, the close contiguity of such an important articulation as that of the ankle should be recollected. The great proximity of the ankle-joint to that be- tween the under surface of the astragalus and os calcis can only be estimated by making a vertical section of the tibia, fibula, astragalus, and os calcis, passing transversely across these bones and through the malleoli, as may be seen in fig. 61 ; and if a subject be selected in which the epiphysis has not been consolidated with the rest of the bone, a useful view may be had illustrating many of the preceding practical observations, and explaining clearly how in- flammation, traumatic or idiopathic, once esta- blished in the ankle-joint, can pass through the epiphysis to the periosteum of the tibia ; and ori- ginating either in the body of the os calcis, or in some of the structures composing the articulation between this bone and the under surface of the astragalus, can be propagated to the ankle-joint : such a view as this will shew the necessity of con- Fig. 61, sidering, in connexion, the normal and abnor- mal state of these important articulations. b. Chronic disease. The effects of chronic diseases on the tissues composing the ankle- joint are next to be considered ; these are vari- ous, and may be referred to the influence of specific diseases, such as gout, syphilis, struma, rheumatism, &c.; but the effects of most of these on this particular articulation need not here be discussed, as they will be sufficiently dwelt on elsewhere in this work (see JOINT): we deem it, however, right to enter somewhat into detail in the description of those morbid appearances of the ankle-joint which are supposed to be of a scrophulous origin, and which are denominated white swelling of the ankle-joint. The external characters of the affection are pretty much those in common with the same melancholy disease, in whatever articulation of the extremity it is situated ; the swelling, at first soft, and appear- ing in front of each malleolus, seems divided into two by the extensor tendons ; after a time it becomes more solid, and assumes somewhat of a globular form ; here as elsewhere, however, it does not completely surround the joint. The limb above is wasted and the heel is retracted ; the foot is cedematous, and the toes are pointed downwards, no motion of flexion or extension can be communicated to the foot ; but when the bones are moved laterally, an unnatural motion is communicated to the foot, and a grating of rough and carious surfaces in advanced cases can be felt : the sides of the swelling are studded over with numerous fistulous orifices, from which even now a thin sanious matter can be pressed ; a probe introduced passes either directly through one or other of the malleoli, or by a circuitous route into the interior of the joint through the sinuses, which are, as M 2 164 ANNELIDA. it were, the excretory ducts leading from the interior, and conducting out the sanious and sabulous matter which proceed from the dege- nerated cartilages, synovial membranes, and bones of the diseased joint. The skin is thin, soft, and shining, and moveable on the sur- face, except where the tistulous orifices exist. The anatomical characters of this disease in its advanced stage affecting this articulation we have many opportunities of observing. When the superficial coverings of the swelling are removed, the fat is remarked to be consistent and yellow, the cellular tissue interposed be- tween the ligaments, tendons, and muscles is infiltrated with a viscid, semi-fluid, spongy, homogeneous mass ; sometimes this tissue be- comes so thick, and is so connected with the lateral ligaments of the ankle-joint, and so in- terposed among their softened fibres, as to render a clean dissection of these last impracticable ; so that the ligamentous and cellular structures around the joint appear to have undergone a species of fibre-cartilaginous degeneration ; the viscid glairy matter infiltrated around the joint with the tumefied ligaments are the parts which cause the principal swelling, and give to the fingers examining it that deceptive feeling of fluctuation which characterises the white swelling wherever situated. The few muscular fibres to be found near this joint are pale and of a gelatinous appearance, being infiltrated with the same matter as that which pervades the more superficial structures. The tendons, nevertheless, preserve their natural colour and consistence. The periosteum will be found much thickened and easily detached from the bone. The bones of the joint, and those in its vici- nity, are very usually more or less atrophied, and have undergone a process of degeneration ; notwithstanding, however, what has been said on high authority to the contrary, these bones are occasionally enlarged and expanded ; they have lost much of their specific gravity, their spongy tissue is softened, yellowish, and easily penetrated by a knife, and filled with a matter resembling adipocere, or a yellow semi-fluid fat. The heel it has been noticed is elongated, and the foot measured from the tibia to the toes on the dorsum is shortened very generally, and pointed downwards. Dissection discovers the cause of this frequent phenomenon in a par- tial dislocation of the tibia forwards on the astragalus, the softened ligaments allowing the action of the gastrocnemii and solaei to drag the whole foot backwards. In the interior of the articulation, a more or less considerable quantity of a sanious matter is found; while the cartilages covering the end of the tibia and fibula, and surfaces of the astragalus, are softened, adhere but slightly to the bones, and have been partially removed, leaving exposed the porous structure of the latter. The arteries, veins, and capillaries present no peculiarity, except that the naturally white ligamentous tissue is more freely supplied than usual with red vessels. The neurilema of the posterior tibial nerve is evidently much thick- ened, so as to give it an appearance of enlarge- ment; the small nerves around the joint seem also hypertrophied. ( R. Adams.) ANNELIDA, (a generally adopted, but barbarous latinization of the French term ' Annelidas,' from ' Annellus,' a little ring ; ought rather to be written < Annulata'or ' An- nellata.') The natural group of Annelida comprehends all the invertebrated animals which have a soft body divided into transverse segments or rings; a distinct central nervous system disposed in the form of a longitudinal gangliated chord, blood coloured (generally led), and contained in a system of appropriate and very distinct vessels ; and, lastly, organs of locomotion, consisting either of flesjiy appen- dages provided with bristles, or of bristles only ; or of a prehensile cavity situated at each ex- tremity of the body ; but never of articulated members, as in the Arachnida, Crustacea, and Insecta. The establishment of this class is due to Cuvier. Prior to him, Pallas, Miilhsf, and Otho Fabricius, had made observations of great interest on the animals of which it is com- posed; and we find in the writings of the author of the Miscellanea Zoologica the most happy ideas respecting the natural relations which these animals bear to one another. Nevertheless, these works had at first but little influence on the classification of the Inverte- brata, and for a long time naturalists persisted in following the method of Linnaeus, who united under the term Vermes,theMollusca, Zoophyta, and Annelida, and dispersed the latter in three different sections of that great class; confound- ing some with the Entozoa (intestinal worms), others with the Acephalous Mollusca, and others again with the Testacea. It was in the work entitled " Tableau Ele- mentaire de 1'Histoire Naturelle des Animaux," published in the years 1797-8, that M. Cuvier laid the first foundation of a natural distribution of invertebrated animals. He collected together in the class Vermes the species which more lately have constituted the groups of Annelida and Entozoa, and established in it the two divisions corresponding to those which are generally adopted at the present day. Having subse- quently determined the presence of red blood in the leech, and having investigated the circu- lating apparatus in these animals, Cuvier sepa- rated the " red-blooded'' from the " intestinal" worms, and constituted for the former a distinct class, to which Lamarck afterwards gave the name of " Annelides," which has been gene- rally adopted, and is used at the present day by most naturalists.* This classification being based essentially on anatomical structure, has been adopted by Lamarck, Dumeril, Savigny, Leach, Latreille, * See Cuvier, Bulletin des Sciences par laSociete Philomathique, an vii. et x. Lamarck, Discours d'ouverture du cours des Animaux sans Vertebres prononce en Mai 1806, et Histoire des Animaux sans Vertebres, ANNELIDA. 165 &c., but is not received by all zoologists of the present day. M. De Blainville, in his metho- dical distribution of the animal kingdom, has adopted another plan. Taking the exterior organs for the base of his system, this naturalist divides the articulate animals, which he terms " Entomozoaires," into seven classes, of which the penultimate, viz., the " chetopodes," com- prehends the Annelidans provided with loco- motive bristles, and of which the last, viz, the " apodes," is composed of the Annelidans des- titute of those organs, together with the planariae and intestinal worms.* The general plan of organization exhibited in the animals which are grouped together by Cuvier under the name of " vers intestinaux," and the numerous affinities which connect the planarivE and several helminlha to the Annelida, appear to us fully to justify a partial adoption of the innovations introduced by M. De Blain- ville, and to indicate that the natural position of the white-blooded worms is by the side of those with red blood, at the bottom of the sub- kingdom of articulate animals; whilst in the system of Cuvier the Annelida are placed at the head of that great division of the animal kingdom, and the entozoa are left among the zoophytes. But, on the other hand, similar reasons appear to us to oppose the adoption of the divisions which M. De Blainville has proposed for the articulate animals. That zoologist, in fact, establishes a distinction between his che- topoda and apoda as wide as between the former and the insecta, arachnida and Crustacea, and thus separates from the setiferous annelidans to place among the intestinal worms the hirudines, which approximate to the former and deviate from the latter in many of the most important points of their organization ; for example, in the existence of a gangliated nervous system. This arrangement does not appear to us to accord with the spirit of a natural classification, in which the several divisions ought to be in- dicative of the different degrees of importance which the modifications of the animal organiza- tion present. In the present state of science the class An- nelida ought in our opinion to be preserved nearly as it was established by Cuvier, but should be joined with the entozoa and rotifera, to form a great division of the sub-kingdom articulata, distinct from the natural group, con- sisting of insecta, myriapoda, arachnida, and Crustacea. The affinities, indeed, between the setiferous annelidans and the hirudines are too close to admit of their being arranged in sepa- rate classes ; and, on the other hand, every day discloses new facts of a nature which demon- strate that the vermiform animals pass from one to another by almost insensible gradations. Thus the researches of M. Dugbs on the planariae show how closely their structure ap- proaches that of certain red-blooded worms, and the distinction founded on the colour of the nutritious fluid no longer suffices to separate * See the Bulletin de la Soc. Philomathique, 1818 , De 1'Organization des Animatix par M. de Blainville, torn. i. table 7 ; and the article Vers' of the Dictionnaire des Sciences Naturelles, torn. Ivii. them ; for on the one hand it is proved that the colour of the blood is yellow and not red in some of the annelidans properly so called; while on the other hand 1 have recently ob- served on the shores of the Mediterranean an animal which differs from the genus prostoma only in the possession of red blood. We now know intestinal worms which have a circulation and a vascular system as well formed as that of the annelida, which they already resemble so much by their outward form. The absence of a rudimentary nervous system in the entozoa is called in question by skilful anatomists. Lastly, the excellent works of Ehrenberg on the in- fusoria of the class rotifera prove the analogy that exists between these minute beings and the articulate animals generally, but more espe- cially to the annelida. The differences which the annelida present among themselves have necessitated their di- vision into many secondary groups or orders. In the latest work* that has been published on the classification of these animals, they have been divided into four orders, under the names of Annelida errant ia, Annelida tubicola, Anne- lida terricola, and Annelida suctoria (suceuses). This classification is based on the combination of the modifications which exist in the struc- ture of these beings, and does not materially differ from that proposed by M. Cuvier in the Regne Animal, and by M. Savigny in the great work on Egypt. The following is a table of the principal characters which distinguish these groups. First Order. ANNELIDA ERRANTIA. Body, with soft appendages (cirri, branchiae, or antennae), generally disposed over the whole length of the animal, and not collected towards the cephalic extremity. Feet generally very distinct, armed with seta: or bristles, which have very rarely the form of hooks. Head generally distinct, and provided with eyes, antennae, and a retractile proboscis, often with jaws. (This order, which nearly corresponds to that of the Annelida dorsibranchiata of Cuvier, com- prehends the genet*. Apkrodita, Polynoe,Polyo- dontes, Acoetes, Sigalion, Palmyra, Amphinome, Chloeia, Euphrosyne, Hipponoe, Eunice, Onu- phis, Diopatra, Lysidice, Lombrincreis,Aglaura> (Enone, Nereis, Syllis, Hesione, Alciope, Myri- ana, Pftyllodoce, Nephtya, Goninada, Glycera> Aricia, Aonis, Ophelia, Cirrhatulis, Peripatus, Chetopterus, Arenicola.} Second Order. ANNELIDA TUBICOLA. Body, with soft appendages, for the most part collected together at the cephalic extremity. Feet, almost always of two kinds, generally de- prived of cirri, and armed with hooked bristles. Head not distinct, without eyes, antennae, pro tractile proboscis, or jaws. (This order corresponds to that established by Cuvier under the same name, and includes the * See Classification des Annelides et description des especes qui habitent les cotes de la France, par MM. Audouiu et Milne Edwards, torn. ii. des Recherches pour servir al'Hist. Nat. du littoral de la France. 166 ANNELIDA. genera Serpula, Sabella, Tercbella, Amphitrite, Hermella, and Siphostoma.') Third Order. ANNELIDA TERRICOLA. Body, completely destitute of soft appendages. Feet, scarcely or not at all distinguishable, and represented only by some bristles. Head not distinct, without eyes, antennae, or jaws. This order comprehends the genera Clymena, Lumbricus, Na'is, fyc. In the classification of M. Cuvier it is united to the Hirudinida to form the order Anne- lides abranches. Fourth Order. ANNELIDA SUCTORIA. Body destitute of bristles for locomotion, com- pletely apodous, and without soft appen- dages. A prehensile cavity in the form of a sucker at each extremity of the body. Head, not distinct, but generally provided with eyes and jaws. This order is composed of the family of Hiru- dinida, and of the genus Branchellion. External conformation. The Annelida have always an elongated, generally cylindrical, and vermicular form; sometimes, however, they are flat or more or less oval. The body is com- posed, as we have already observed, of a series of rings, not of a horny or calcareous texture as in the majority of insects and Crustacea, but membranous and separated from each other only by a transverse fold of the integument; as is seen in certain larvae. The number of these rings is occasionally very considerable (some nereida have more than 500), and in many annelida it varies considerably indifferent individuals of the same species, and seems to increase with age. In some instances these segments are sub- divided into two or more transverse bands by furrows. In general each ring supports a pair of mem- bers, and when an apparently single segment gives origin to a greater number of these or- gans, it is easy to perceive that it results from the union of many rings blended together. The two extremities of the body are sometimes dilated in the form of suckers (in the suctorious annelidans), but in general nothing of the kind exists, and the anterior extremity either resem- bles the rest of the body, or it terminates in a head more or less distinct (as in the nereida, see Jig. 62), often supporting eyes (a), and fili- Fig. 62. form appendages called antennae, (b,c), the num- ber of which is generally three, four, or five. The mouth is situated at the extremity of the body, and in the acephalous annelida is di- rected forwards, but in the cephalous species this opening is situated below the base of the head. The anus is placed at the opposite ex- tremity, and is almost always found on the dorsal aspect of the body. A certain number of Annelida are completely apodous, and do not present the least trace of an appendage on any of the segments of the body (the hirudinidse). Others exhibit on either side many rows of bristles, which fulfil the office of feet (the terri- colae). In others, again, the bristles of which we have spoken are supported on a fleshy tubercle more or less prominent, and more or less complicated in structure, and to these organs the name of feet is applied. The feet of the Annelida, when they present the maximum of development of which they are susceptible in that class of animals, are com- posed each of two very distinct portions, placed one above the other, and appertaining the one to the dorsal, the other to the ventral arch of the ring. (See/g. 63,which represents one of the feet Fig. 63. of an amphinome.) M. Savigny, who was the first to study with due care the zoological cha- racters furnished by these appendages of the annelida, gave to these portions of the feet the names of dorsal oar (a) and ventral oar (6) (rame dorsal et rame ventral). Sometimes these oars are pretty distant from one another, (fig. 63.) sometimes they are separated only by a shallow fissure (Jig- 64. which represents the foot of a nereid), and occasionally they are so intimately blended together that they can hardly be dis- Fig. 64. ANNELIDA. 167 languished, and form, as it were, but a single organ ; lastly, there are cases in which only one of the oars would seem to be developed. If one were disposed to compare the loco- motive system of the annelida with that of tlie other articulate classes, the ventral oar should be regarded as analogous to the members which in the Crustacea, Insects, &c. are variously modified to constitute the legs, the jaws, or the antennae : and the dorsal oar ought to be considered as representing the appendages, which, though wanting in the greater number of articulate animals, yet acquire a considerable develop- ment on the last two rings of the thoracic segment of most insects and constitute the wings. In this particular the annelida afford an example of the greatest uniformity in the development of the appendicular system in the articulate division of the animal kingdom. Each oar is essentially composed of a fleshy tubercle more or less prominent, which sup- ports different productions of the integument, incloses the bristles (c), and which is more especially designated by the name of foot. Towards the base of the setiferous tubercle there is generally a membranous appendage, sometimes filiform, sometimes lamelliform, called the cirrus (d, e) ; lastly, it is also above the margin and near the base of these organs that the branchiae (/) take their origin, but in general it is only the dorsal oar that supports them. All the above parts may exist simul- taneously, but- it often happens that one or more are atrophied to a greater or less degree, or are altogether deficient; and this either along the entire body or on certain segments only. Thus in the terricolous annelida there are no cirri; in the hermellae they are pre- sent on the ventral, but not on the dorsal oar ; while in the cirrhatulae the reverse obtains. In most of the annelida errantia the setiferous tubercle of both oars is wanting on the first rings which follow the head, whilst the cirri assume a very great development, and form the appendages termed by systematic authors ten- tacular cirri. (Fig. 62, d.} A similar modification may be frequently remarked in the composition of the appen- dicular system of the last ring of the body, and thence results a certain number of filiform pro- ductions called styles. Lastly, the antennae of the annelida, which must not be confounded with the antennae of insects and Crustacea, may also be considered as representing the cirri of the dorsal oar of those rings, the union of which constitutes the head.* The annelida pass in general a somewhat stationary life, and a great number among them remain constantly buried in the earth or * For further details regarding the external struc- ture of the annelida the reader may consult the excellent work of M. Savigny, intitled " Systeme des Annelides," principally of those found on the coasts of Egypt and Syria; the article ' Vers ' of the Dictionnaire des Sciences Naturelles, torn. Ivii. by M. De Blainville ; and a more recent publica- tion on the same subject inserted in the Annales dos Sciences Nature-lies, torn, xxviii, xxix, and xxx, and in the second volume of the Rcchf-rches pour servir a 1'Hist. Nat. du littoral de la France, par MM. Audouin et Milne Edwards.' enclosed in tubes formed by the mucus which is secreted by the skin, and which, while hard- ening, commonly agglutinates together frag- ments of shells and sand. The formation of these sheaths is very quick. I have seen them fabricated in the course of a few hours. Some- times they are of extreme tenuity, occasionally they are as tough as thick leather, and there are some which possess very considerable hardness and are composed in great proportion of carbonate of lime, like the shells of mol- lusca. In the greater part of these animals locomotion is produced by general undulations of the body determined by contractions of a layer of muscular fibres extending from one ring to another, and fixed to the inner surface of the skin. But in other species the change of place is effected by the action of the feet, of which we have spoken ; or by the contrac- tion of the tentaculae which surround the mouth, as in the terebellae, and which, by shortening themselves, drag on the body of the animal in the same manner as the arms of the cephalopods : lastly, by the action of the suckers with which the extremities of the body are furnished. The bristles (Jig. 63 and 64, f,) with which the feet of the annelida are provided, do not serve merely as little levers to facilitate their move- ments, but are also offensive arms, and their structure is very curious. They differ con- siderably from the hairs of other articulate animals, which are nothing more than small tubular prolongations of the epidermic layer. By their mode of connexion with the integu- ments and their mode of formation they ap- pear to approach the hair of mammalia, but their disposition is of a more complicated na- ture. They are inclosed in sheaths provided with muscular fibres, by the aid of which the animal can protrude and retract them again : in general, also, they are not merely simple conical filaments, but their extremity is often shaped like a harpoon, a lance, or a barbed arrow, and the annelidan uses it to inflict a wound upon its enemies.* Sensation. Tactile sensibility is considerable in these animals, and it seems to reside prin- cipally in the antennae, the cirri, and the tentacula. They do not appear to possess a sense of hearing, and there are many among them which do not manifest any sign of sen- sibility to light ; but in others, eyes (jig- 62, ,) exist, the number of which is sometimes very considerable, but the structure very simple. They are coloured points, (generally black,) and situated on the dorsal aspect of the head or on the cephalic sucker. In the setiferous anne- lida there are never more than two pairs, but in the hirudinidae or leeches their number often increases to eight or ten. The anatomy of these eyes has recently been studied by Professor Muller of Berlin, and according to his researches it would seem that these organs do not contain a crystalline lens, or a trans- parent body analogous to the vitreous cones of * Sec Observations sur les Foils des Annelides consideres rotnme moyen de Defense, par MM. Audouin et Milne Edwards, op. cit. torn. ii. p. 31. 168 ANNELIDA. the Crustacea and insecta, but consist simply of a terminal ganglion of the optic nerve covered by a layer of black pigment and placed imme- diately beneath the integument, which is thin and transparent at that part.* Nervous system. In like manner the ner- vous system of the annelida Fig. 65. is verv simple. It occupies ._ a the middle line of the ventral c aspect of the body, and con- sists of a double series of mi- nute ganglions of medullary matter, more or less inti- mately united or even blended together, and equal in number to the number of rings. ( See Jig. 65. repre- senting the nervous system of the aphrodita aculeata). The ganglions give origin to lateral branches, and are connected together by two chords of communi- cation, sometimes separate, sometimes united into a sin- gle trunk, so as to constitute a longitudinal chain extended through the entire length of the body. The first of these ganglions (a) is lodged in the head, or at least at the ante- rior extremity of the animal, in front of or above the di- gestive tube; the rest are placed below that canal ; whence it results that the two nervous chords which form the media of communi- cation between the cephalic ganglion and the first of the sub-cesophageal series pass along the sides of the oeso- phagus, and form around that canal a species of collar or ring ; a character which is common to all the articulate animals. f Organs of' digestion. The alimentary canal in the annelida extends from one end of the body to the other, and has an external com- munication at both extremities. The mouth is generally provided with a projectile proboscis, which is formed by the anterior portion of the digestive canal, which can be inverted and pro- truded like the finger of a glove, and possesses muscles for the express object of effecting these movements (see Jig. 66, which represents the Fig. 66. * See Annales des Sciences Nat. torn. xxii. + See Cuvier, Anat. Comparee, torn. i. ; Trevi- ranus, iiber der stachlichten Aphrodite, Zeitschrift f iir Physiologic, 3 Band ; Moquin Tandon, *' Mo- nograph, des Hirudines/' Morrem, " Sur le Lom- bric/' &c. proboscis of a phyllodoce, and^g. 67, that of a nereis). The surface is frequently beset with small papillae, and its extremity armed with Fig. 67. horny jaws (ni), the disposition of which varies in different genera. It is to be observed that these jaws are almost always placed laterally like the mandibles of other articulate animals, and cannot act upon one another in the direc- tion of the axis of the body, as in the vertebrata, but are not to be regarded as analogous to the mandibles and maxillae of insects and Crustacea. In their structure, the jaws of the annelida ap- proximate rather to the solid plates with which the interior of the stomach in some Crustacea is provided, and to the hooks which arm the mouth of certain gasteropodous molluscs. This conformation of the oral apparatus is met with only in the annelida errantia ; in the annelida terricola there is scarcely a vestige of a proboscis, and never any teeth or jaws. In the annelida suctoria, the mouth, which is placed at the bottom of the cephalic sucker, is also occasionally protruded in the form of a small tubular proboscis, and in other species its margins are armed with little horny jaws ; lastly, in the annelida tubicola, nothing of the kind is to be seen, but in general the superior border of the mouth forms a sort of projecting lip, which is provided with long tentacles, sometimes simple and filiform, sometimes pec- tinated and resembling tufts. In certain erratic annelida, the Agliope, for example, there are also found around the mouth small tentacula, which are quite distinct from the tentacular cirri, and which appear to be analogpus to the appendages of which we have just made mention. The oesophagus which succeeds the pro- boscis or mouth presents nothing worthy of notice, but it is in general quite distinct from the stomach. The conformation of the latter organ varies much. Sometimes the stomach is a simple enteroid tube (as in the nereida and terebellae) ; sometimes it is composed of two pouches, of which the first is membranous and may be compared to a crop, while the second is muscular and is analogous to a gizzard, as, for example, in the lumbrici, thalassenuB. In other cases the stomach pre- sents on either side a succession of enlarge- ments which have in general the form of rounded cells, but which sometimes consti- tute sacs or vast and much elongated ccecums, (as in some hirudihes,/gs. 68 and 69.) Lastly, ANNELIDA. 169 Fig. 68. Fig. 69. we may observe that these ccecums are replaced by blind canals, either simple or ramified; thus in the arenicola, or sand worm, we find that there communicate with the second sto- mach two ccecums terminated by a soft point, with thick parietes of a yellow colour ; and in the aphroditae the stomach opens on either side into a score of membranous appendages, which commence of very contracted diameter, but afterwards insensibly become dilated and di- vide into many branches : (see Jig. 70, a, the retracted probos- Fig. 70. cis, b bj the ap- pendages.) This type of structure leads to that which is manifested in the planariae, and also approximates to what one sees in the parasitic arachnida. The intestine which succeeds the stomach is generally narrow, and in the majo- rity of the anne- lida extends in a direct line to the anus. In some species, as the amphitrites, it presents a greater or less number of convolutions. There does not exist in these animals a gland which can be re- garded as a liver, properly so called : the appendages which are grouped around the stomach in the arenicola: may, indeed, be biliary vessels analogous to those of insects rather than true cceca ; but in the earthworms and many other annelides the bile would seem to be secreted by a peculiar organ of a yellow colour and pulpy texture, which surrounds like a sheath a great part of the digestive canal. Lastly, in certain annelida, as, for example, the thalassemae, there exists on either side of the oesophagus a small organ, which would seem to have a secretory office, and may very probably be a salivary gland.* Circulation. The blood in almost all the annelida differs from that of every other in- vertebrate animal by its red colour; some- times, however, this fluid has scarcely a tinge. According to M. De Blainville the blood of the aphroditae is yellow, and MM. Mayor and Gosse, of Geneva, assert that the circulating fluid of the genus clepsina, one of the hirudi- nidae or leech-tribe, is even altogether white. When the blood of an annelide is examined with the microscope it is seen to contain circu- lar globules, but of a much larger size, and in far less number than in human blood : it coa- gulates after rest like the blood of the higher animals, but it appears to contain a very small proportion of fibrine. The blood circulates, as we have already stated, in peculiar vessels, which its red colour renders easily distinguishable. The vascular system has been best studied in the earthworm : above the alimentary canal there runs along the entire length of the body a contractile vessel (fig. 71, a,) which is con- sequently dorsal, and in which the blood passes generally from behind forwards, some- times in large waves, some- times by small quantities pro- pelled by the successive con- tractions of the divisions which this vessel forms through its entire extent. A portion of the circulating fluid then passes into another vessel (c), which originates at the anterior ex- tremity of the one above- mentioned, and which runs backwards along the ventral surface of the body below the nervous column, from which circumstance it has been cal- led the sub-nerval vessel by Duges. But the greater part of the blood which is con- tained in the dorsal vessel, in- stead of following this chan- nel, passes into seven or eight pairs of large lateral branches composed each of a series of dilatations or rounded ve- * See Willis, ' De Anima Brutorum ;' Pallas, * Miscellanea Zoologica ;' Cuvier, ' Anat. Comp.' Treviranus, op. cit. Moquin Tandon, op. cit. ; Duges, op. cit. j Home, < Lectures on Comp. Anat.' Fig. 71 170 ANNELIDA. sides (d), which are highly contractile. These ' moniliform vessels' are placed in a situation corresponding to the ovaries : they are directed downwards and open into a ventral vessel (6), which occupies the middle line of the inferior aspect of the animal, following the same track as the sub-nerval vessel, but situated less superficially. Its parietes are contractile, and it may be seen alternately dilating and con- tracting simultaneously at every part along the whole of its extent. The blood flows into this ventral vessel from before backwards, and leaves it to re-enter the dorsal vessel by passing through the branches (e) which ascend perpendicularly to join the latter, on either side of the alimentary canal, which they thus embrace, and to which they furnish a great number of ramifications. The blood con- tained in the sub-nerval vessel flows equally from before backwards, and ascends to re-enter the dorsal vessel by lateral channels (/), ana- logous to the anastomosing vessels which we have just described, but situated more superficially than those. These superficial transverse or dorso-abdominal vessels, as they are termed by M. Duges, severally receive a large branch from their corresponding deep-seated dorso- abdominal vessel, and distribute to the skin a number of ramifications which appear to be specially destined to bring the blood into contact with the oxygen necessary for respi- ration.* In the genus na'is the moniliform vessels, which in the earthworm perform in some degree the office of a composite heart, seem to be re- placed by a single pair of wide veins, which are contractile and analogous to a divided heart, and both the superficial and deep-seated transverse vessels by which the blood ascends to the dorsal trunk seem to rise from one and the same ventral trunk; so that the circulatory appa- ratus is more simple in these annelida than in the earthworms. The same plan pervades the sanguiferous system in the other setiferous an- nelidans, in which the branchiae are distributed throughout the entire length of the body ; but when these organs are collected together at a determinate point of the anterior extremity of the body it is a little different. Thus in the terebellae the ventral vessel is seen to bifurcate and to form two lateral branches which have the form of an arch, and which, after having passed over the sides of the O3sophagus, re-unite above that tube to form a single trunk. This trunk reaches the anterior extremity and gives origin to three pairs of primary branches, which descend to the vesi- cular receptacles at the base of the branchiae, and distribute the blood to these organs. In the leech-tribe the vascular system, on the contrary, is more complicated, for the san- guiferous circle is composed of four longitu- dinal trunks, and the branches which bring them into communication with each other. Of the four longitudinal vessels two occupy the dorsal and ventral aspects of the mesial * See Duges, ' Recherches suv les Annclides abranches,' Anuales des Sciences Nat. t. xv. line, and two the sides of the body. The dorsal and ventral trunks communicate toge- ther by dorso-abdominal branches correspond- ing to each segment of the body. The lateral trunks also render to the dorsal trunk a series of dorso-lateral branches, and, moreover, mu- tually communicate by a series of abdomino- lateral branches which glide transversely be- neath the nervous chords. The dorsal and ventral vessels are evidently analogous to those which we have designated by the same names in the earthworm and na'is; and the lateral vessels may be compared to the sub-nerval trunk of the earthworm, except that, instead of being single and situated in the mesial line, they form a circle in which the blood undu- lates sometimes in one direction, sometimes in another, but always pursuing an opposite course in the two canals. Lastly, in addition to the above * general circulation,' there is observed in the leech-tribe something ana- logous to the l lesser circulation/ (fig- 72) : Fig. 72. this is effected in the branches (6, e) of the dorso- lateral vessels (), which are for the purpose of bringing the blood into contact with the aerated water contained in the small membranous vesicles (./) situated at the sides of each seg- ment of the animal, and opening externally upon the inferior aspect.* Respiration. From what has been said of the mechanism of the circulation in the annelida, it will be seen that respiration must be effected either in the vesicles above mentioned, or on the surface of the body. Such in fact is the case ; the skiu is in general the seat of that function ; but in the greater number of instances, the integument, instead of maintaining the same texture throughout, and acting upon the air in the same manner at every point of its extent, presents at particular spots peculiar modi- fications, and thus gives rise to special organs of respiration called ' branchiae.' The branchiae of the annelida are almost universally membranous appendages, highly vascular, fixed to a certain number of the feet of the animal, or inserted upon the back near the base of these organs. In the nereida and some other congeneric annelida, the appendages which are designated branchiae, and which in fact seem to be in an * See Moquin Tandon, op. cit. Duges, op. cit. ANNELIDA. 171 Fig. 73. especial manner subservient to respiration, are simply a kind of papillae or laminated cutane- ous productions very little or not at all sub- divided, attached either to the extremity or base of the feet and distributed in an almost uniform manner over the entire length of the body, (fig. 64, /*,/,/.) In the eunice, and other allied genera, their position is the same, but they assume the form of an elongated filament, furnished with a series of prolongations of a similar filiform shape, disposed like the teeth of a comb, and traversed longitudinally by a canal filled with red blood, (Jig. 73,./'.) In the amphinomian family, as in the former groups, these branchiae are placed on almost every segment of the body, so that these organs form along the whole extent of the back a double row ; but here their struc- ture is more complicated,for the filaments are extremely subdivided, (fig. 63, /.) In the arenicoltf, the form of the branchiae is almost the same as in the amphinomes, but they are limited in their position to the middle seg- ments of the body. In the genus terebella the branchiae are also highly ramified vascular appendages to the integument, but their num- ber is inconsiderable, and they are all inserted near the cephalic extremity of the back. In the serpulae, the membrane which forms a sort of thoracic disc near the cephalic ex- tremity of the body, ought to be regarded as an organ of respiration, and it is probable that the tentacles surrounding the mouth like a crown of plumes are subservient to the same function.* In the hirudinse respiration is in part effected by the external skin, but there exists in these annelida a series of small mem- branous sacs, which communicate externally each by a minute orifice situated on the ven- tral aspect of the body : these sacs derive from the numerous vessels which ramify upon their parietes a considerable quantity of blood. Water penetrates into these organs and seems to subserve a true respiratory purpose. These sacs are commonly denominated sacs, 7 and some authors think that they receive into their interior atmospheric air in a gaseous form. Their number varies from fifteen to twenty, and it may be observed, when a living leech is irritated after being recently removed from water, that a small quantity of liquid escapes from their apertures. In the lurnbrici terrestres there is in like manner found in each segment and on eitherside of the digestive tube, an enteroid vessel folded upon itself, containing a liquid and opening outwardly by a particular pore. These sacs are less vascular than in the leeches; never- theless there is reason to believe that they fulfil an analogous office, and perform a more or less * See, for additional details, the works already cited of Savigny, De Blainvillc, and Audouin and Milne Edwards. important part in respiration. Lastly, it has been proved that in the annelida there are other pores, placed on the back, which tra- verse directly the dermo-muscular envelope, and communicate with a cavity intermediate to the muscles and intestines, and imperfectly divided by transverse septa, into which air or water can penetrate. This structure may, indeed, belong to the respiratory apparatus, but science does not yet possess sufficient data to solve that question. An analogous dis- position has been observed in the nai's.* Generation. The generative apparatus is only very imperfectly understood in the anne- lida. It appears that all these animals are hermaphrodite, but that they cannot fecundate themselves ; the intercourse of two individuals being necessary for the accomplishment of the act of generation. It is in the earthworm and leech that this part of their anatomy and phy- siology has been most completely studied. In the leeches the sexual apertures are placed at the inferior surface of the body towards the anterior third, and separated from one another by the intervention of five segments. The anterior aperture belongs to the male organs, and at the season of reproduction a filiform and highly contractile penis is observed to be protruded from that part, (fig. 74, 75, a.) Fig. 75. This communicates in- ternally with a narrow cylindrical canal (b\ which in its turn opens into a kind of whitish vesicle of a pyriform shape (c) commonly cal- led the vesicula semi- nalis. On each side of this vesicle there is an oval whitish body (rf) composed of con- torted tubes filled with a whitish liquid : each of these organs is a testicle ; and they seve- rally give origin to a slender vas deferem (fig. 75, e) of the same colour, which opens into the vesicula seminalis. Lastly, from the posterior extremity of the testicle, another fili- form duct (/) is continued,which passes back- wards on each side of the nervous cord, and gives origin to a series of pedunculated vesicles filled with a whitish fluid similar to that which * For the structure of the pulmonary sacs, see Willis, op. cit. Thomas, ' Memoires pour servir a 1'Histoire Naturclle des Sangsues.' Home ' Lec- tures on Comp. Anatomy,' Moquin Tandon, op. cit. Morren de Lumbric. tcrrest. Duges, op. cit. 172 ANNELIDA. Fig. 76. is contained in the rest of the apparatus. These organs (Jig. 74, g) are generally regarded as accessory vesicles, and they vary both in number and form in different species. The female apparatus is of much less mag- nitude, but also presents a sufficiently com- plicated structure : it is situated between the two canals leading to the accessory vesicles of the male apparatus, and is a little posterior to the penis. The external orifice, of which we have already spoken, communicates with a short canal (jig. 74 and 76, //), of a greyish colour, which leads to a sort of pouch (i). This, accord- ing to some authors, is analogous to an ute- rus, but in the opi- nion of other natura- lists is merely a copu- lative vesicle for the pur- pose of retaining the fecundating liquid which is there deposited by the male in the act of copulation. This sac is bent upon itself, and a duct (j) may be observed to be continued from the anterior extremity which leads to the ovaries (k) : these are small whitish bodies two in number, and in close approximation to one another. In the earthworm, the only parts that can be regarded as male organs are some sacs or vesicles varying in number from two to seven, and situated in a longitudinal series on either side of the ventral aspect of the body towards its anterior extremity. Each of these vesicles adheres to the parietes of the splanchnic cavity, by a small canal opening directly outwards by pores placed on the posterior and inferior part of the corresponding ring: there is farther a canal of communication, which is continued directly from one vesicle to another of the same lateral series ; and at the season of co- pulation there is found in the interior of these organs a viscid liquid abounding with seminal microscopic animalcules. The outlets of the female apparatus occupy the sixteenth segment of the body, and are continuous internally with two narrow canals directed forwards, and situated on the internal side of the above mentioned vesicles. Having reached the ova- ries, each of these canals (Jig- 77, ) divides into two branches (6), which bend inwards and terminate by a globular enlargement (c). This is seen with the assistance of the microscope to be itself formed by a continuation of the canal puckered up into numerous folds, which are enveloped in a com- mon membrane. To each of these enlargements are appended a pair of ova- ries, the entire number of which is consequently eight, four on either side. The colour of these ovaries is whitish, their texture pulpy, and their interior is beset Fig. 77. with numerous minute vesicles, which are the ova. At the period of copulation the ovaries are filled with a whitish fluid, which is pro- bably the spermatic secretion, but it is not easy to comprehend how the male apparatus can introduce it into that part.* According to Redi, the ova, after being detached from the oviduct, pass along the whole extent of the body towards the vicinity of the anus, whence they are expelled by two orifices stated to be near the termination of the alimentary canal or to open in its interior. According to Mon- tegre it is the fetus and not the ovum which traverses the body to escape by the above passages, and the lumbrici according to this view are viviparous. This statement has been adopted by many authors without perhaps sufficient examination; but, according to recent observations by Duges, it would seem not to be correct, and that what have been regarded as the young of the earthworm are in fact a species of intestinal worm. In the na'is the male organs are less nume- rous than in the lumbrici, but differ very little in other respects. They consist of a single pair of vesicles opening externally by a wind- ing canal, which terminates by a small fissure on the eleventh segment of the body. The ovaries are disposed in four principal masses, between which there winds a long oviduct, of which the extremity can be protruded out- wardly like a penis.-j- In some annelida, as the clepsina carena, the ova are developed and hatched before exclusion, so that the young are born alive; but most of the class are oviparous, and what is very remarkable, the same ovum sometimes incloses the germs of many embryos : this is the case in the earthworm, each ovum of which produces two individuals, and in the leech the ova contain severally as many as eighteen embryos. One might at first view suppose that the same circumstances obtained in the na'is; but what appears to be an ovum with multiplied germs is in reality nothing more than an aggregate of simple ova. Reproduction. Some annelida not only per- petuate the race by the ordinary modes of gene- ration, but enjoy the singular faculty of pro- ducing new individuals by a transverse division of the body. A na'is or an earthworm cut in two and placed under favourable circum- stances, will continue to live, and each moiety will become, in appearance at least, a perfect animal. This fact, which was first determined by Reaumur and Bonnet, has since been veri- fied by M. Duges, Sangiovanni, and many other observers : the anterior portion of the animal reproduces a new tail, and the posterior portion developes a head. That faculty which the two portions of the earthworm's body possess of manifesting the vital properties independently of one ano- her, and even after having been separated, may be explained to a certain degree by the known structure of these animals and * See Willis, Duges, &c. f See Duges, op. cit. ANUS. 173 the general laws of physiology. With the exception indeed of the generative organs which are concentrated in a peculiar part of the body, it is easy to observe that each seg- ment of the body is almost the exact repe- tition of all the rest : they all possess the same organs, and, however the total number of rings may vary, there results no change of any im- portance in the general structure of the animal. Now it may be laid down as a law in phy- siology, that a parity of organization neces- sitates a similitude of action ; and it results that as in depriving an earthworm of a given number of segments no organ is removed of which it does not still retain the analogue, no function is completely destroyed; and conse- quently that if such a mutilation should weaken the vital action, it does not change its nature. Tin's holds good for both the segments of the animal : each continues to possess all the organs essential to individual existence, and consequently if their resisting energy be suf- ficiently great, there can be no reason why they should not continue to live independently of one another, and become two distinct worms.* But if the anterior moiety thus becomes a perfect animal, it is probable that this may not happen to the posterior portion, but that the new individual formed by this part will always continue deprived of generative organs. For the anterior moiety retains exclusively the reproductive organs of the original individual, and there is nothing which authorizes the belief that the earthworm possesses the power from being simply mutilated, of reproducing the whole apparatus on any part of the posterior moiety. This, however, is a circumstance which it would be easy to determine. From the sketch that we have given of the organization of the annelida, it will be seen that there exists in this branch of zoology many hiatuses. Anatomists, in fact, have hardly paid attention to any but the leech, the earth- worm, and the na'is, and we possess only a vague notion of the internal structure and physiology of the erratic and tubicolar species; their comparative study would form an interest- ing subject of research. BIBLIOGRAPHY. Cuvier, Anat. Comparee, t. i. Bulletin dcs Sciences par la Societe Philoma- thique, an vii. et x. Lamarck, Discours d'ouver- ture du cours des animaux sans vertehres, pro- nonce en Mai 1806, et Histoire des animaux sans vertebres. Blainville, De 1 'organization des ani- maux, t. i. tab. 7 Dictionnaire des Sciences Naturelles, art. Vers, t. Ivii. Audouin fy Milne Edwards, Recherches pour servir a Fhistoire natu- relle du littoral de la France, t. ii. Moquin Tandon, Monograph, des Hirudines, 4to. Montp. 1827. Morrem, De lumbrici terrest. hist. nat. 4to. Bruss. 1829. Pallas, Miscellanea Zoologica, 4to. Lugd. Bat. 1775. Home, Lectures on Comp. Anat. Duges, Annales des Sc. Nat. t. xv. Thomas, Memoires pour servir a 1'histoire nat. des sangsues, 8vo. Paris, 1806. Muller, Vermium terrestriura et fluviatilium, &c. historia, 2 parts, 8vo. Copenhag. and Lips. 1773-74 ; Ejus, Von Wurmern des siissen und salzigen Wassers, 4to. Kopenhag. 1771 ; Ej. Zoo- * See the article Organisation of the ' Dictionaire Classique d'Histoire Naturelle,' and the Intro- duction to my ' Elemens de Zoologie/ logiaDanica, fol. Copenh. 1788-1806. Schweigger, Handb. d. Naturgeschichte d. skeletlosen ungeglie- derten Thieren, 8vo. Leipz. 1820. Weller, Circa animalium quaedam classium inferiorum incremen- tum etvitam, 8vo. Halle, 1817. Klein, Descript. Tubulorum marinorum, 4to. Danz. 1777. Otto, De Sternapside et Liphostomate diplochaito, vermibus duobus marinis, 4to. Bresl. 1820. Leo, De struc- tura lumbrici terrestris, 4to. Regiom. 1820. Clesius, Beschreibung d. medicinischen Blutigels, 8vo. Hadamar, 1812. Kuntxmann, Anat.-Physiol. un- tersuchung iiber d. Blutigel, 8vo. Berl. 1817. Krtolg, Naturhist. Abhandlung uberd. Blutegel, 8vo. Wien. 1820. Johnson, A treatise on the medicinal leech, 8vo. Lond. 1816 Further Obs. on the leech, 8vo. Lond. 1820. Poupart, Anat. Hist, of the leech from Journ. des Svavans 1697, Phil. Trans. 1697. Mo- rand, Anatomic de la Sangsue : Mem. de Paris, 1739. Bebiena, De Hirudine sermones quinque : Comment. Bonon. t. 7. Cuvier, Sur les vaissaux Sanguins des sang-sues : Soc. Philom. An 7. Wichmann, Vom Gu'rtel des Regenwurms : Beschaft. der Gesells. Naturforsch. Bd 3. Chamisso, De ani- malibus e classe Vermium in circumnavig. terrse observatis, 4to. Berol. 1819. Delle Chiaje, Mem. de structura lumbrici terrestris, 4to. Berl. 1820. Olivi, Zoologia Adriatica,4to. Bassano, 1792. Sorg, Circa respirationem insectorum et vermium, 12mo. Rudolst. 1805. Savigny, Mem. sur les animaux sans vertebres, 8vo. Paris, 1816 ; Ejus, Systeme des annelides, dans le grand ouvr. sur 1'Egypte, fol. Paris. (H. Milne Edwards.) ANUS, (in anatomy,) from Anus vel An- nus, a round, a circle, (syn. ostium recti, podexj culus. Gr. 9T&;xTo$. Fr. anus. Germ . After. Ital. ano.) is a term commonly applied to the lower extremity of the rectum : properly speaking, it is the inferior orifice of the alimentary tube, through which, in the higher orders of animals, the excrementitious portion of the food, as also the excretions from the di- gestive apparatus, are discharged ; for obvious reasons it is endowed with powers to assist in expelling, as also with the faculty of retain- ing these for a considerable tiine : such oppo- site but important qualities would infer the existence of a somewhat complicated muscular apparatus, more or less under the influence of the will, as also a structure in other respects worthy of attention. The presence of an anus indicates a complex system of digestive organs ; hence in many of the inferior or simpler classes of the invertebrate division of animals it is absent, and in many of the superior of this division, as well as in several of the vertebrata, it presents considerable variety as to structure, function, and position. In some of the zoophytes, such as the in- fusory animalcules there is no central digestive cavity, and of course no distinct outlet. In them absorption takes place by imbibition through pores into cells, in a manner somewhat similar to a sponge ; and most probably excretion (if any occurs) takes place through the same orifices. In others of this class, such as the acalephae, where a rudimental cavity appears in the body of the animal, a single orifice admits the food necessary for its support, and the excremeri- titious portion (if any) is ejected through the same opening. In the actiniae, also, where a 174 AN-US. distinct stomach exists, and where the retained matter obviously undergoes certain changes, the one orifice serves the two-fold purpose of admission to the food, as well as of exit to its residuum. Even in some of the echino- dermata, as the asteriae, in which the digestive apparatus is more developed, the central cavity becoming more complex, the latter is still but a cul de sac, which can be protruded at the mouth, the only orifice it presents. In other species, however, of this class, the anus ap- pears ; thus in the English echinus, where the masticating apparatus is so remarkable, this opening exists on the surface of the animal, opposite to the mouth.* Jn the sipunculi the anus opens near the mouth, and in the holothuriae near the respira- tory organ .f In the several families of the articulata, viz. insecta, Crustacea, and vermes, the anus exists, and is always found at that end of the animal opposite to the mouth, and most generally on its inferior surface. In the mollusca it is also present, but it holds situations singularly differing in the different orders and genera of this class ; thus in the cephalopoda, as the cuttle-fish, the rectum opens into a sort of cloaca, which is situated . before the neck, and which also re- ceives the semen and ova, as well as the secretion from the ink-bag. In the gastero- poda, as the slug, it is generally found near the pulmonary cavity. In the patella or limpet, however, it opens on the head, and in the doris on the back, surrounded by a delicate fringe, a sort of branchial tuft. In most of the acephala, except the oyster, the rectum extends along the back of the animal, beneath the hinge, and above the respiratory organs ; it then passes through the heart, and opens above the posterior muscle of the shells, into the cavity of the maulle, or between its edges, the anal opening presenting the appear- ance of a fleshy disc or sphincter. Among fishes the anus varies, in the osseous and cartilaginous divisions of this class ; in the former it usually presents the appearance of a round opening leading into a longitudinal groove ; it is placed in front of the anal fin, and of the urinary and genital aperture, contrary to what occurs in all other vertebral animals. In the cartilaginous fish, as the ray and shark, this groove is deeper, and has the appearance of a true cloaca, through which are discharged, as in the sepiae and in birds, not only the alvine, but also the urinal and seminal excretions. In reptiles the anus serves as the opening of a cloaca, or common receptacle of the re- siduum of the food, as well as of the urine, semen, or ova ; in the batrachia, as the frog, it is situated at the end of the back, and there- fore above the body of the animal. In the chelonia, as the tortoise, it is under the tail. In the sauria and ophidia it is a transverse cleft, but in the salamander it is a longitudinal fissure with two prominent lips. * Home's Lect. on Comp. Anat. vol. ii. p. 76. f Cuvier's Comp. Anat. t. iv. p. 143. In birds the rectum expands above the anus into the cloaca, which also receives the ter- minations of the ureters, the ends of the vasa deferent! a, and the penis (when the latter exists) ; also the openings of the oviducts, and of the bursa Fabricii. In all the mammalia the rectum terminates in a distinct anal open- ing, which is placed at the posterior or in- ferior extremity of the trunk, directly under the origin of the tail, and usually in a direc- tion opposite to the mouth, and in all it is placed behind, and not, as in fish, before the urinary and sexual orifice ; in some few of the quadrumana, as the mandril, it is directed upwards. In almost all mammalia it is a dis- tinct orifice, giving passage to the faeces only ; in the beaver and sloth, however, the rectum and urethra have a common termination. The monotrematous animals also, such as the echidni and ornithorhynci, form a complete ex- ception to this statement; in these singular and anomalous creatures a single opening gives exit to the faecal and urinary secretions, and also subserves sexual purposes. (See INTES- TINAL CANAL.) ANUS (in human anatomy). In the present article we propose to examine not merely the structures which immediately bound this open- ing in man, in their normal and healthy state, as well as in their abnormal and diseased condi- tions, but we shall also examine the parts which enclose and surround it, and which can exert an influence, direct or indirect, on its functions ; that is, we shall consider the anatomy, normal and abnormal, of the parts contained in the Anal Region. The Anal Region is synonymous with the posterior portion of the perinaeum ; its triangular area is denoted by the following outlines : the apex, which is posterior and superior, is marked by the extremity of the os coccygis ; its base, which is before and below the latter, is defined by an imaginary line extending transversely from one tuber ischii to the other, and each side is denoted by a line drawn from the last named process to the point of the coccyx : these lateral boundaries correspond to the mar- gins of the glutaei maximi muscles, which over- lap the inferior or the great sacro-sciatic liga- ments; the base or the transverse line before mentioned, separates the anal from the anterior perineal or urethral region : in the adult male this line will be found to be about three inches, or nearly three inches and a quarter in length ; in the female it is about half an inch longer, and more certainly so if the individual ex- amined have borne children ; great variety, how- ever, has been found to exist in this measure- ment, the extremes of which may be stated at two and four inches. In children under twelve years of age this transverse diameter of the perinaeum is considerably less, in consequence of the extreme narrowness of the pelvis prior to puberty. The anal region contains the lower portion of the intestinum rectum, several muscles, and fasciae, some nerves and vessels of importance, and an abundance of adipose substance. The ANUS. 175 quantity and consistence of the adipose substance found in this region vary considerably in dif- ferent individuals at the several periods of life, and under various conditions of health ; a fact most important for the surgeon to bear in mind, inasmuch as this diversity causes corresponding differences in the physical characters which this region presents under these particular circum- stances. In children, and in the female, in youth and middle age, as also in the robust and healthy male, this region will be found plump, or convex around the anus, whereas in the ema- ciated, the sickly, or the old, it often presents the very opposite appearances; and a proportional difference may be observed in the depth of the perinaeum, or in the distance between the neck of the bladder and the surface : the greatest extremes of this difference have been found between two and four inches, a circumstance which bears materially on the lateral operation of lithotomy. So much of the Rectum as lies beneath the cul de sac of the peritoneum, may be consi- dered as appertaining to the anal region, and must, therefore, be noticed at present; below the reflection of that membrane, this intestine descends obliquely forwards between the sacrum and bladder, in the male as far as the prostate gland, and in the female as far as the vagina; it is there on a level with the inferior extremity of the coccyx, and then it bends downwards and backwards, and ends in the anal opening ; the perinaeal portion of the Rectum, therefore, is convex forwards and concave towards the coccyx ; hence in introducing into this intestine the bougie, enema pipe, or even the finger, it should be directed at first upwards, and for- wards, and then upwards and backwards : in the child, however, this precaution is not ne- cessary, as the course of this intestine is not so much curved, the name of Rectum being then more correctly applied than in the adult. In order to examine the several parts con- tained in the anal region, the thighs should be fully separated, flexed, and fixed on the pelvis; the first object which attracts attention is the Anus. This opening is situated in the median line, at the bottom as it were of a deep excavation, which is bounded on either side by the tube- rosity of the ischium, with the superincumbent muscular and adipose substance ; in the erect position it appears at a great depth from the surface, in consequence of the approximation of the nates. In the adult the anus is from one inch to an inch and a half distant from the point of the coccyx, and three inches from the arch of the pubis ; it is in some measure, but not perfectly, fixed in its situation, anteriorly by an indirect attachment to the interosseous or triangular ligament of the urethra, and pos- teriorly by a dense fibrous tissue, which forms a sort of raphe between it and the coccyx, and to which the muscles and integuments adhere. In the natural and healthy state, the anus pre- sents the appearance of a small rounded, or rather elliptical orifice, whose border is thrown into numerous small plaits, or ruga, which during the extended state of the opening are effaced ; these rugae are occasionally so deep as to admit of the escape of a small quantity of fluid. As the skin approaches the margin of this opening it becomes very fine and delicate, is gathered into those several radiated folds or plaits, which sink into it, and in the same man- ner as at the other outlets of the body, it be- comes continuous with the lining mucous mem- brane of the intestine, there being no exact line of demarcation, except that of an increased vascularity, to distinguish the one from the other. This plaited condition of the skin which lines this opening arises from the close contraction of the subjacent muscle, and is doubtless de- signed to admit of the more easy dilatability of the anus during defecation; this opening, however, is never equal to the diameter of the rectum at a little distance above it. In the child the integument surrounding the anus is smooth and red, in the adult it is of a deep brown colour and studded with several fine hairs, which, however, are usually absent in the female. In this situation also the cutaneous follicles are very distinct and numerous, but not so prominent as in the scrotum ; they secrete a mucous or sebaceous matter which gives to the skin a shining or oily appearance, and adapts it to the functions of the part: from the absence or from the vitiated condition of this secretion, painful and troublesome excoriations not unfrequently ensue. In the healthly state the margin of the anus feels firm and resisting, and together with the surrounding muscles forms a floor or support to the inferior part of the pelvis, in the centre of which floor the rectum and its contents are maintained, and on either side a mass of cellular and adipose substance. Muscles. The muscular apparatus connected with the lower extremity of the rectum consists of the superficial and the deep sphincters of the anus, also the right and left levatores am, to which may be added the two transversi perincei, and the two coccygcei muscles. The first two, namely, the sphincter muscles, surround the anus, and may be regarded as a modification, or as a particular development of the general circular muscular tunic, which is continued around the whole alimentary tube from the mouth to the anus, and which in dif- ferent situations exhibits a considerable increase in colour and consistence, for example, in the lips, around the fauces, the oesophagus, the pylorus, &c. The name of these muscles in- dicates their principal function, while the other muscles which have been alluded to proceed from certain fixed points to be inserted into the lower extremity of the rectum, and must, therefore, rather serve to retain the anus in its situation or to restore it to its natural condition, when in the exercise of its functions it has been con- siderably dilated, or slightly displaced by the expulsive efforts of the diaphragm and abdo- minal muscles. We shall first examine the descriptive anatomy of these individual muscles, and then consider their several powers or pur- poses in the economy of the surrounding organs. Although there are two sphincter muscles of the anus, yet this name is generally applied to the 176 ANUS. more superficial of these ; we shall distinguish these muscles by the names of sphincter ani cutaneus vel ellipticus, and sphincter ani pro- J'undus vel orbiculuris. Sphincter ani cutaneus (ertytyyu, constringo,) coccygeo-anal, sphincter externus, constrictor ani} is the first muscle which meets the eye of the anatomist in the dissection of this region. It may be exposed by dividing the integuments from the coccyx to near the back part of the anus, and thence extending an incision on each side, and about half an inch distant from the edge of this opening to its forepart, whence it should be continued indefinitely along the me- dian line of the perinaeum ; the integument should then be carefully dissected off from either side of this elliptical incision. The muscle thus exposed is thin and flat, of an elongated and elliptical form, and cleft in the centre to embrace the opening of the anus ; it arises posteriorly fleshy and cellular from the point of the coccyx, and from a tense fibrous or cellular tissue, called the recto-coccygceal liga- ment, which extends from the coccyx to the back part of the anus, where it divides and is lost in the cellular tissue on either side. From this origin the fibres of the sphincter collect into a rounded fasciculus, which proceeds for- wards and downwards, increasing in size, and at the back of the anus divides into two bands which pass one on either side of this opening, each spreading out till it is an inch or even more in breadth ; again converging in front of the anus, these bands unite into a fasciculus, which in the male is very long and passes for- wards and upwards between the skin and the acceletatores urinae muscles, to be partly in- serted into the median line of the superficial fascia of the perinaeum, and partly confounded and interlaced with the transversi perinaei, and with the muscles which cover the bulb of the urethra; through the medium of these last it is even attached to the common cellulo- tendinous central point of the perinaeum, be- tween the rectum and the bulb, whereby it is enabled to act on this part of the urinary canal. This anterior insertion is very variable in different persons ; in some it stops abruptly at Ihe bulb, while in others it continues to run forwards between the skin and the acceleratores as far as the dartos, in which it terminates. In the female this anterior fasciculus is much shorter, and ends in the sphincter or con- strictor vaginae ; in the male its attachment to the muscles of the bulb is often deficient, so that in the course of the dissection, when the superficial fascia has been removed, this ex- tremity of the muscle will be found detached and its insertion isolated. The entire of the inferior surface of this muscle is in contact with the integuments, its superior surface is related to the levatores ani, acceleratores urinae, and transversi perinaei muscles ; in front of the anus it is confounded with the two latter, and immediately behind it with the formerly named muscles ; its external border is, of uncertain ex- tent, and is imbedded in adeps, while its inter- nal edge is in close relation with the delicate inflected anal skin, being separated only by a fine cellular tissue. This muscle is composed entirely of fleshy fibres, occasionally intersected by cellular and imperfect tendinous bands; these fibres are placed in concentric arches, those of opposite sides unite at acute angles, and sometimes interlace before and behind the anus ; the fasciculi are frequently separated by considerable intervals, so that they appear like different muscles ; some of the internal fibres assume a circular arrangement ; in the female this muscle is shorter, broader, and more rounded, particularly in front. In structure and appearance this muscle presents great diversity ; in some it is red, strong, and large, in others, so pale and weak as to be difficult of perfect demonstration ; it is also probable that during life great differences exist as to its power of contraction. The use of this muscle is obviously to close the anus, the skin of which it throws into small rugae ; hence when the sphincter is paralysed, there is incontinence of the contents of the rec- tum ; the most internal fibres will tend to close the opening more perfectly than the external or elliptical, which will reduce it rather to a cleft or fissure ; this muscle can also raise the anus somewhat, and at the same time draw back and compress the bulb of the urethra; it will also express the secretion from the anal glands and follicles. The sphincter ani may be properly said to belong to the class of mixed muscles, both as relates to its structure and function ; as to the former, its paleness, scattered fibres, connection with the commencement of the mu- cous surface, and absence of true tendon ally it to the muscular system of organic life; while on the other hand the parallel direction of its fas- ciculi, and the arrangement of many of the latter in the surrounding adeps, assimilate it to the muscles of voluntary motion. In its functions also it appears to border on the province of each division of the muscular system ; thus without the efforts of the will, or even without any in- ternal cognizance, it continues in a state of al- most permanent contraction, and as uncon- sciously relaxes when the functions of the part impress upon its sensibility the necessity of so doing ; while on the other hand the will can exert a considerable control over its powers, and can cause it to contract with considerable and continued energy, as well as throw it into a state of atony and .relaxation. Although this muscle belongs to the same class with the other sphincters, the orbiculares oris and palpebra- rum, yet it manifests a considerable difference in its vitality. The natural and, therefore, the usual condition of these other sphincters is relaxation ; hence the mouth continues open, and partly from the same cause too, the eyelids are apart ; whereas the natural condition of the sphincter ani when at rest is contraction, and hence the anal opening is always closed, although the muscle is still capable of contracting with con- siderably more energy when any of the contents of the rectum suddenly approach the orifice, or when any irritation exists in its vicinity. The Sphincter ani internus vel orbicularis (Sphincter infest male, Winsl.) is of much less extent than the former, and is situated more AN IS. 177 deeply; it is closely connected to the mucous membrane, or the fine lining integument, and appears a particular development of the circular fibres of the intestine, like those which surround the pyloric extremity of the stomach. This cir- cular muscular ring consists of several fine and pale fasciculi of fibres, which are closely con- nected together, and when contracted form a thick ring around the intestine immediately with- in the anus ; this muscle may be exposed either by detaching the lining membrane which is but loosely attached to it, or removing the rectum from the subject, everting and distending it. The mucous membrane being then detached, the muscle will be distinct ; its upper border is continuous with the circular fibres of the rectum, and a distinct cellular line separates it from the cutaneous sphincter ; anteriorly it is connected with the levatores ani muscles. The action of this muscle must be to assist the former sphincter in closing the lower ex- tremity of the rectum and supporting its con- tents ; in the process of defsecation it assists in the expulsion of the residual portions of the faecal matter, by the sudden or almost spas- modic action which succeeds its relaxation ; moreover, it strongly opposes the entrance of any foreign body by the anus ; so that from its power of resisting the ingress or egress of any substance, it may be considered as constituting a perfect pylorus. The subcutaneous adipose tissue in perineo is very abundant in some situations ; close to the anus, or between the sphincter and the skin, there is but very little ; hence abscesses but seldom form there, except of very limited size, such as small furunculi, or as the result of circumscribed inflammation in some of the fol- licles around the opening; whereas at either side of the anus and rectum there always exists a considerable quantity of cellular and adipose matter, the former remarkable for the large size of its cells, which, are intersected by irre- gular bands or fibres from the perinaeal fascia, and which give the whole some degree of elasticity ; the adipose substance is abundant, very soft, loose, sometimes reddish, and fills those large spaces which exist on either side of the rectum. In no part of the body do ab- scesses so frequently form as in these ischio- rectal spaces ; and as such abscesses are very generally attended with consequences tedious, troublesome, and dangerous, it may be right to make a few remarks on the anatomy of these regions. Each Ischio-rectal space is a deep triangular hollow, the base being situated towards the integuments, the apex towards the cavity of the pelvis ; the outer side is formed by the ischium, and the inner by the rectum with its muscles; this intestine, together with the attachments of the levatores ani behind and before, separates the two spaces from each other, but the cellular membrane of one side communicates with that of the opposite, and hence in cases of diffused or extensive suppu- rations, the fluid is occasionally observed to pass from one side to the other; anteriorly the transversus perinoei, and posteriorly the VOL. I. eoccygeus muscles bound this hollow. Kach of these triangular recesses is lined on all sides, except towards the skin, by fasciae, a view of which may be obtained by dissecting out of either all the contained adeps. There may then be observed near the apex, or the deepest part of the recess, a strong and tense aponeu- rotic line, which is the inferior folded surface of the pelvic fascia, which in this situation sends oft' its inferior or descending layer ; this latter immediately divides into two laminae, an internal and an external ; the latter is called the obturator, the former the ischio-rectal fascia ; the former is very strong and distinct, the latter very thin and cellular. The obturator fascia descends a little ob- liquely outwards and is inserted into the falci- form process of the great sacro-sciatic liga- ment, and into the tuberosity and ramus of the ischium. It is very dense, being composed of strong aponeurotic fibres, and it conceals and separates from the perinseum the obturator in- tern us muscle, and the internal pudic nerves and vessels, the perinaeal and hemorrhoidal branches of which pierce it as they proceed to their destination. The internal layer, or the Iskio-rectal fascia, is much weaker and more cellular than the last; from the before-men- tioned aponeurotic line it descends obliquely inwards along the lower and outer surface of the levator ani as far as the sphincter, when it becomes thin and cellular, and is lost in the surrounding adipose tissue. Thus, by the unfolding or division of the inferior layer of the pelvic fascia into these two laminae, the obturator and ischio-rectal fasciae, these re- cesses are completely lined, and by the gradual degeneration of the last named aponeurosis into cellular and fibrous bands, which inter- lace in every direction, the large mass of adi- pose substance is enclosed and supported, whilst a general firmness and elasticity is imparted to the whole region. Towards the posterior part of each of these regions a cul de sac is enclosed between these fasciae and overlapped by the glutaeus maximus, on the surface of which the fascise become extended, and ulti- mately lost. A somewhat similar but smaller cul de sac exists anteriorly behind each trans- versus perinaei muscle. An inspection of the Ischio-rectal spaces will serve to explain not only the great size to which abscesses here attain, but also the difficulty in effecting a cure when they have been of long standing and of considerable magnitude ; the constantly-vary- ing form of the rectum on one side, the im- moveable surface of the pelvis on the opposite, a muscle above, and the integuments below, all tend to prevent the possibility of effecting any permanent apposition between the sides of the cavity, while very generally the state of the constitution is equally unfavourable to any healthy action in the part. These several facts have impressed surgeons with the propriety of opening all such abscesses in a very early stage, otherwise a large cavity will be formed, the rectum denuded, and very frequently opened by ulceration. Trunsversi perintfi muscles ( Tachio-peri- 178 ANUS. neal). This pair of small muscles extends in a direction nearly parallel to the ante- rior border of the anal region ; each arises from the inside of the tuber ischii, passes inwards, forwards, and downwards to join its fellow in the median line of the perineum, where it is also partially attached to the cuta- neous sphincter of the anus, and to the acce- leratores urinae muscles, or in the female to the constrictor vaginae. These muscles are very unequal in appearance in different subjects; in some they are feeble and indistinct, in others very strong, and sometimes divided into two on one or both sides, the additional or minor muscle being superior and anterior. In the female these muscles are often found more dis- tinct than in the male, but even here much variety exists ; in many subjects they appear to be simply composed of some of the anterior and partially detached fibres of the middle portions of the levatores ani muscles. The transversi perinsei muscles form the bases of the two lateral triangular regions contained in the anterior or urethral perinaeum, and one of them, the left, is necessarily divided in the lateral operation for lithotomy; they are surrounded by much adipose matter ; two arte- ries, both branches of the internal pudic, take a course parallel to them, viz., the super- ficial transverse perinaeal, and the deep trans- verse, or the artery of the bulb. These muscles are enveloped between the layers of the perinaeal fasciae. The superficial layer, which is continu- ous with the Ischio-rectal, covers them in their course forwards to the urethral muscles, and the deep layer, or the triangular ligament of the urethra, which is continuous with the ex- ternal or Ischiatic layer or obturator fascia, lies between them and the pelvis. These muscles, therefore, will have the effect of making tense the different perinaeal aponeuroses, and thus they can support, strengthen, and compress generally the parts in the perinaeum ; they can also compress, and thus assist in clearing the orifice of the anus, at the same time that they draw back and raise this part, somewhat in the same manner as the levatores ani muscles. According to some anatomists these muscles are considered as dilators of the bulb of the urethra, as well as of the vagina ; but it is more than doubtful whether they can exert any such action. When these muscles are divided, the base of the deep perinaeal fascia, or triangular ligament of the urethra, is exposed. This will be observed to have some influence in main- taining the rectum and anus in their situation ; its posterior border, being attached to the levatores ani muscles, and to the bulb of the urethra, serves to maintain a close connection between these parts, which is still further ef- fected by the interlacement of the muscles of the anus with those which cover the bulb. (See PERINEUM.) Levatores ani (sous-pubio-coccygien). This pair of broad, thin, flat, and nearly square muscles form a septum somewhat broader above than below, between the pelvis and perinaeum, which, together with the aponeu- roses covering its upper and lower surfaces, and with the coccygeal muscles and the trian- gular ligament of the urethra, completely in- tercepts all communication between these two regions except through the natural passages for the urethra, vagina, and rectum. Although these muscles are described as two, there ap- pears no good reason for the division, for the fibres of opposite sides have a common in- sertion, partly into the circumference of the rectum and partly into a middle cellulo-ten- dinous raphe before and behind that intestine. It appears more correct to consider these muscles as one circular muscular septum extended across arid within the lower opening of the pelvis, concave towards this cavity, and convex to- wards the perinaeum. The fibres attached by their circumference to the interior of the pelvis, and converging thence towards the median line of the perinaeum, are inserted into and around the rectum ; in fact the muscle resembles the diaphragm in form, in the circumference being its origin or fixed attachment, and the central portion being its insertion, also in its being perforated for the transmission of certain parts ; the analogy only fails in the absence of a central tendon, and in the fibres being prin- cipally inserted into the parts passing through it. The fact, however, of there being an inter- ruption in the origin of this muscle in the middle line both before and behind, in which respect again there is a resemblance to the sternal and vertebral deficiences in the dia- phragm, is the cause of its being described as consisting of a right and left muscle, which dis- tinction, it should be observed, is only an artificial one, for during life the fibres of both sides act together, and in all respects constitute but a single muscle. The origin of the levator ani muscle may be exposed by tearing the peritonaeum from the parietes of the pelvis, together with a con- siderable quantity of loose cellulo-adipose membrane. The recto-vesical layer of the pel- vic fascia should then be divided near to the neck and sides of the bladder, and carefully raised towards the wall of the pelvis. The muscle will then be seen to arise on each side by three attachments, which, however, form one continuous semicircular line extending from the pubis to the spine of the Ischium; its anterior portion is attached to the back part of the pubis, a little above its arch, and imme- diately below the anterior vesical ligaments by short aponeurotic fibres commencing a little distance from the symphysis, and extending outwards as far as the notch in the thyroid hole ; its second or middle attachment is to a strong tendinous arch, which extends from the pubis to the spine of the Ischium, and which is formed at the separation or junction of the pelvic fascia into its superior or recto- vesical layer, and its inferior or perinaeal layer ; its third or posterior attachment is to the spinous process of the ischium. All the fibres pass downwards and towards the median line to their insertion ; the inferior border of this muscle is shorter but thicker than the superior. The fibres of the first, or pubal portion, des- cend a little obliquely backwards on each side ANUS. 179 of the prostate gland and membranous portion of the urethra, and converging beneath the latter are inserted in common between the bulb and the fore-part of the rectum into the central point of the perinaeum ; these portions in their descent present a well-defined edge inwards or towards the median line. The middle, or aponeurotic portion, is broad and thin above, the vesical fascia adhering so closely to it as to render its separation difficult. As it descends it increases in thickness, expands close to the rectum, and is inserted into the coats of that intestine, intermingling with its longitudinal, fibres, and with the sphincter ani ; in the female it is intimately attached to the vagina also. The posterior or Ischiatic portion passes al- most transversely inwards, and is inserted into the coccyx, and into the cellulo-tendinous line which extends from the latter to the rectum ; some fleshy fibres are continuous from one muscle to the other. This portion of the le- vator ani is more aponeurotic than the pre- ceding, and its posterior border is connected to the Ischio-coccygaeus muscle. The external or inferior surface of this muscle is inclined down- wards, and is more or less related to the obtu- rator and ischio-rectal fasciae, to the glutaeus maxim us and transverse perinaeal muscles and vessels, and to the mass of anal fat. The internal or concave surface looks upwards, and is closely covered by the vesical fascia, below which it is in contact with the rectum, bladder, prostate gland, and urethra, or with the uterus and vagina. This muscle is disposed on the rectum in the same manner in the female as it is in the male; the fibres are also inti- mately connected to the vagina. The action of the levator ani muscles is two-fold, and not confined to the mere ele- vation of the anus, as its name would im- ply. First, they act as a moveable floor to the abdomen and pelvis, which can antago- nize the diaphragm ; these two fleshy planes being opposed to each other, can, by a slight action of one or both, materially alter the perpendicular axis of the abdomen, which extends between them. This axis is at its great- est length during the state of expiration, and is most diminished when both these muscles are forcibly contracting. The levatores ani, how- ever, have less influence in effecting this change than the diaphragm ; they serve chiefly to support the lower region of the pelvis and the several viscera this cavity contains against the combined protruding forces of the diaphragm and abdominal muscles in violent exertions of the body, or in forcible efforts of respiration, or in the evacuation of the contents of the rec- tum and bladder ; and, secondly, they not only raise, but dilate the anus, by drawing out its circumference so as to overcome the sphinc- ters ; at the same time they compress and assist in emptying the rectum, particularly the dilated pouch, which is a little above the anus; they also resist the prolapsus of the mucous coat of the intestine, and raise it after it has been to a certain extent protruded by the action of the abdominal muscles. They raise and draw forward the coccvx after it has been forced back by abdominal pressure in parturition, or in the ordinary evacuation of the bowels, and further, by raising and compressing the trigone of the bladder, they assist in expelling its contents, and for the same reason they can also empty the vesiculae seminales of their fluid. The anterior portions of these muscles are intimately con- nected to the membranous part of the urethra, and are variously modified in different indi- viduals and in different animals; we consider those muscular fasciculi which have been de- scribed differently by anatomical writers under different names, compressores urethrae, &c., as parts of or appendages to these muscles : these urethral portions of the levatores ani can cer- tainly compress the membranous part of the urethra and empty its canal ; they can even interrupt or suddenly stop the stream of urine, and thus they may occasionally aid the neck of the bladder in retaining the contents of that organ. The Ischio-cocct/gcei muscles are situated at the posterior inferior part of the pelvis ; they are thin, flat, and triangular, composed of a mix- ture of fleshy and tendinous fibres. The apex or origin of each is attached to the spine of the Ischium, and its base is inserted into all the side of the coccyx, and a small portion of the sacrum ; they are partly covered by the great sciatic ligaments. The superior and posterior border is connected to the lesser sciatic liga- ment, and the anterior border is in part con- tinuous with the levator ani muscle ; the an- terior or pelvic surface is connected to the rectum and the surrounding adipose substance. This pair of muscles appear as a prolongation of the levatores ani, and are of use in com- pleting the inferior boundary of the pelvis; they thus support the rectum and the pelvic viscera, and they also serve to retain the coccyx and restore it to its situation when protruded by the diaphragm and abdominal muscles in the pro- cess of parturition, and in the act of defalcation, or when drawn too much forward by the levatores ani muscles. If the several muscles in this region be now partially removed on one side, the lower extremity of the rectum will become more distinct, and will be found surrounded by a quantity of loose, fatty, cellular tissue, sepa- rating it from the surrounding muscles and bones; this contains many nervous filaments and numerous bloodvessels, particularly veins. (See INTESTINAL CANAL.) Anteriorly in the male subject a small triangular space, the bulbo-rectal hollow, will now become distinct ; this is situated between the anus and mem- branous portion of the urethra ; the base of it is at the skin of the perinaeum ; the apex at the prostate : to the last the rectum will be seen rather intimately connected. The bulb and the membranous portion of the urethra bound this space in front, and the rectum behind. (See PERINEUM and URETHRA.) Rectum. In addition to the several muscles which have now been severally noticed, and which thus serve not only to retain and support the rectum and anus, but which even enter into the structure of the former, we have further to consider the parts more immediately composing- 180 ANUS. the parietes of the lower extremity of the in- testine ; these are the longitudinal muscular fibres, the mucous membrane, and the sub- mucous cellular tissue. The longitudinal fibres of the alimentary tube exist through its whole extent, but like the circular are differently mo- dified in different situations; thus along the oeso- phagus they are very fully developed, also along the arches of the stomach; in both these situa- tions the fibres are strong and somewhat red ; whereas on the parietes of the small intestines they are very indistinct and pale ; on the coecum and colon they are still pale, but very distinct, being collected into three flat fasciculi or bands. On the rectum, as on the oesophagus, they are again fully developed as to thickness and num- ber ; their colour is still rather pale. In the two superior thirds of this intestine, or as low down as the prostate gland, they predominate over the circular fibres, which are internal, whereas in the lower third the latter prevail; the former terminate, some by becoming con- tinuous or intermingled with the fibres of the levatores ani, others with the cutaneous sphinc- ter so low as the border of the anus, and some are inserted into the submucous tissue of the intestine ; these fibres are continuous superiorly With those of the colon ; they serve to continue that successive series of contractions or shorten- ings of the intestine, which essentially assist in the process of defaecation. As the longitudinal fibres of the rectum resemble those of the oeso- phagus, so the inferior circular fasciculi or the sphincters are like the muscles of the pharynx, not merely in their increased strength and colour, but also in their vital power. Over the lon- gitudinal fibres the will lias no control, whereas the inferior circular are to a certain extent under its influence. Here, then, as in the organs of deglutition, we perceive the animal and organic powers still distinct as to their elementary na- ture, but becoming intimately, nay inseparably associated for wise and obvious purposes. In the act of defaecation the offices of the se- veral muscles connected with the anus may be summed up as follows : When the contents of the rectum, particularly if of a solid con- sistence, are being expelled, the whole rectum descends, and the perinaeum becomes promi- nent in consequence of the viscera being forced against it by the contraction of the diaphragm and abdominal muscles. The presence of the faeces irritates the muscular fibres of the rectum; the longitudinal fibres shorten the intestine, while the successive actions of the circular urge down the faecal mass; these two orders of muscular fibres are the true antagonists to the sphincters. During this stage, however, the sphincters are relaxed, and the anus be- comes dilated, partly by the contents of the rec- tum distending it, ana partly by the levatores ani muscles, which are nevertheless in a suffi- ciently relaxed condition to allow the protru- sion of the rectum and anus, while they still support the latter to a certain extent, and thus exert a sort of check against its forcible de- scent ; they also tend to open the orifice of the anus. During this forcible expulsion, a small portion of the mucous lining is frequently protruded. The expulsion of the last portion of faeculent matter is then effected by the sub- sequent strong and gradual contraction of the levatores ani compressing the rectal pouch, and raising the rectum and anus to their former position, and lastly, the sudden action of the sphincters clears and closes the orifice. The mucous membrane lining the rectum is in every respect highly organized, it is thrown into several folds, and is larger and looser than the other coats, hence portions can be easily removed by operation, and are not unfrequently detached by gangrene. As it approaches the anus, it is very red, soft, and fungous, being highly vascular, presenting the orifices of several glands, follicles, or lacunas. It is here very loosely connected to the muscu- lar fibres, and is frequently found thrown into irregular folds ; these are protruded somewhat during defaecation, and when morbidly enlarged or thickened, are not unfrequently the source of considerable pain and inconvenience. As the mucous membrane is not contractile, these folds are necessarily increased when the longitudinal fibres of the rectum contract and shorten the intestine; they are then protruded together with the faecal matter. Immediately above the plaited margin of the anus the skin and mu- cous membrane become continuous ; the ter- mination of the cuticle appears rather abrupt, just within the internal sphincter. Some de- scribe it as continued higher up, and gradually lost on the surface. I have not been able to exhibit it satisfactorily higher than the point indicated, nor does it appear to me that it extends through this orifice by any means to the same extent as through the other outlets of the body, the mouth, nose, urethra, or va- gina. In the latter passage in particular 'it is very distinct, even in health ; and in disease, as in cases of prolapsus uteri, its develop- ment becomes considerable; whereas in pro- lapsus ani, that is, a protrusion of the mucous lining of the rectum, at a little distance above the anus, I have not found the protruded mass to become covered with cuticle : I have seen cases of long standing in which the surface presented the same soft, vascular tissue as it does at first. It does not controvert this state- ment to find tumours about the margin of the anus (hemorrhoids or polypi) covered with a thickened or developed cuticle; for in such cases the cutaneous covering is derived from the elongation of the surrounding skin, which has increased in density from exposure to the air, and from continued irritation. The same remark will apply to cases of artificial anus, no matter in what situation : in all these the villous surface, which protrudes during the peristaltic acton, retains its mucous charac- ters, and does not become covered with cu- ticle. From these facts it may be inferred that cuticle is never developed in any situation in which it did not originally exist, but that circumstances favour the increase or more full development of it in those situations where it naturally occurs, even though its normal con- dition be extremely delicate and fine. nd vessels. The submucous tissue ANUS. 181 in the vicinity of the anus is very loose, and the seat of nervous and vascular plexuses ; in the latter the venous system predominates. A consideration of the functions of the rec- tum and of its surrounding muscles, its re- markable irritability and sensibility in health, as well as its sympathies in disease, would lead us to infer what dissection proves to exist, namely, that this organ is largely supplied with neives; numerous branches are furnished to it from the sacral plexus, which is formed by the union of the inferior spinal nerves, also from the hypogastric plexus, which is chiefly com- posed of filaments of the sympathetic. The sacral plexus of spinal nerves furnishes, in addition to many others, the hemorrhoidal, vesical, and pudic branches ; the hemorrhoidal nerves are directed principally towards the in- ferior part of the rectum, some ascend to the colon, others descend even to the sphincter ani : they divide into numerous filaments, which are chiefly distributed to the muscular fibres of the rectum and the adjacent muscles; the vesical nerves in their course to the bladder give some filaments to the rectum, and the in- ferior or perinaeal division of the pudic nerves also send several branches to the levator and sphincter ani muscles. The ht/pogastric plexus of nerves is composed of filaments from the sacral plexus, which interlace with some from the inferior rnesenteric plexus, and with nume- rous branches from the sacral ganglions of the sympathetic nerves. This plexus supplies the rectum, as also the other pelvic viscera; the branches accompany the bloodvessels, and are distributed principally to the mucous and sub- mucous tissue. The cellular tissue, also, about the coccyx, and the adjacent muscular fibres receive some filaments from the coccygeal plexus of the sympathetic. This supply of nerves from these two very different sources, the one presiding over voluntary, the other over in- voluntary motion, corresponds with the well- known functions of this organ, and causes its muscles to be classed by the physiologist under the head of mixed muscles, that is, partaking of the common characters of the animal or voluntary, and the organic or involuntary sys- tems. Its supply of spinal nerves serves to explain not only the influence which the will can exert over its functions, but also the impaired or altered state of its powers in case of disease or injury of the brain or spinal cord ; thus irrita- tion of the latter may cause morbid irritability and contraction of the rectum, and, necessarily, constipation of the bowels; or, again, paralysis of the spinal cord from injury or compression may lead to perfect atony of the sphincters, and to the involuntary discharge of the contents of the rectum. The general distribution of the branches of the sacral and hypogastric plexuses to the several pelvic viscera, and to the muscles, &c. in the perinseum, associates these different organs with each other, which is so necessary to their functions, and with the urinary and genera- tive organs, connecting more particularly the muscles of the anus with the muscular coat of the urinary bladder and with the parts about its cervix. This interlacement and subsequent general distribution of these nerves serve also to establish those several sympathies which are found to exist in acute and chronic diseases of the rectum and anus, between this intestine and the other pelvic viscera. In some the uterus and vagina partake of the irritation, in others the urinary bladder is almost incessantly irri- tated to expel its contents ; or, on the other hand, when the sympathetic irritation engages its cervix and the parts in its vicinity, the most painful retention of urine is endured. Chronic disease of this intestine is also very generally attended with occasional attacks of pain and irritation in different portions of the alimentary canal, as also with pain in the sacrum and loins, and in various other direc- tions, which may in most cases be explained by referring them to nervous irritation extending in the course of some of the nervous communica- tions which are found to exist in such num- bers in the pelvis. The rectum, like the rest of the alimentary canal, is freely supplied with blood. Its arte- ries are named h(emorrhoidal, and are derived from three sources, viz., the abdominal aorta, the internal iliac, and the internal pudic arte- ries. The superior hsemorrhoidal is the con- tinuation of the inferior mesenteric, a branch of the aorta ; the middle hemorrhoidal is derived either from the internal iliac or from some of its branches ; and the inferior or external he- morrhoidal branches from the perinseal division of the pudic. The latter are destined directly to the confines of the anus, and are lodged in the subcutaneous adeps. The two former be- long properly to the rectum, and are above the levatores ani muscles. These arteries divide into several small branches, which anastomose together, and form a continued chain of inos- culations along this intestine, somewhat similar to that which is continued along the whole of the alimentary tube. They form a complicated vascular net-work between and within the mus- cular fibres, and are largely distributed to the mucous and submucous tissues. Some branches of considerable size not unfrequently descend so low even as the sphincter, particularly at its posterior parts. These are liable to be divided in operations for the cure of fistulae, and some- times give rise to a haemorrhage, troublesome and difficult to restrain. In such operations the external hsemorrhoidal arteries also are very commonly opened, and bleed smartly ; they can be secured, however, with much less difficulty than the divided extremities of the superior or middle haemorrhoidal vessels. The whole of the rectum, particularly its lower portion, is encompassed by numerous veins, which in some persons are very large and plexiform. In the perinacum, also, many venous plexuses are found in the subcutaneous adeps. The external haemorrhoidal arteries have their external venae comites, which run outwardly to end in the internal pudic veins (branches of the internal iliac). Some of their branches ramify around the anus, and in some cases form a plexus, in which hrcmorrhoidal 182 ANUS. tumours are frequently developed; the mid- dle haemorrhoidal veins are uncertain as to number, size, and situation, but the superior are very large and numerous; their branches form repeated anastomoses in the submucous tissue around the intestine, and frequently present all the appearance of erectile tissue, particularly in front, communicating below with the perinaeal veins, before with a plexus of vaginal or prostatic veins, and above with the trunk of the inferior mesenteric which leads to the vena portae. This latter communi- cation, as also the absence of valves in the portal system, has laid the foundation of the practice of applying leeches to the anal region in chronic inflammatory affections of the liver and bowels. The same facts also have been adduced to explain the frequency of haemor- rhoids, varices, and vascular congestion about the anus and rectum in cases of diseased and hardened liver, which, under such circum- stances, is supposed to obstruct the circulation by impeding the returning blood through the venae portae. ABNORMAL CONDITION OF THE ANUS AND NEIGHBOURING PARTS. Congenital malformations. The lower ex- tremity of the rectum and anus not unfre- quently present in the new-born foetus con- genital malformations, some of which are in- compatible with continued existence, while others admit of protracted suffering, with great inconvenience and imminent danger to life; while, again, some may be relieved by the in- terference of art. Hence it is necessary to con- sider these anomalous appearances with a view to discriminate those which are curable from those in which all remedial attempts are totally useless. The following congenital malforma- tions have been noticed by surgical writers, some of which have come under our own ob- servation. \. The anus has appeared at first view to be natural, but on a more accurate examination no canal has been found above it; and after death it was discovered that the rectum was absent, that the left colon ended in a cul de sac, and that a dense fatty substance occupied the situation of the rest of the canal. It is plain that no operative interference could avail in such a case. In some cases of this want of rectum the anus has been absent also.* 2. The anus and rectum have appeared natural, but after death it has been found that the latter was interrupted in one part of its course, and that the intestine had ended above that in a cul de sac. This state of parts must lead to the same practical conclusion as that last mentioned. In these and in such like cases of unhappy malformation, some have suggested, as a " dernier resort," the propriety of opening the intestinal canal at some point in the abdo- men, so as to evacuate its contents and establish permanently an artificial anus. The proposal was first made by Littre,f of opening the * See Diet, dcs Sciences Med. t. xxiv. p. 129. t Mem. de FAcadem. des Sciences, 1720. sigmoid flexure of the colon in the left iliac region. A successful case of this operation is recorded as having been performed by Duset* on a boy twenty-four hours after birth : the child was reported, at twelve years of age, to be in good health, with an artificial anus esta- blished in the left iliac fossa.f 3. No anus, but the rectum has opened into, and its contents escaped either by the urethra in the male, or by the vagina in the female. This condition is an approximation to the cloaca of birds, and of some fishes. Life may continue under such an arrangement, particu- larly in the female, when the intestine opens into the vagina, with great inconvenience no doubt ; but in the male the prognosis cannot even be so favourable, as the urethra can scarcely suffice to give exit to the faeces after some time ; and as the bladder and organs in its vicinity will be subject to constant irrita- tion. Cases are, however, recorded of life being protracted for several months; and in one case, a boy, who lived for eight months, on examination after death it was found that a cherry-stone had blocked up the passage of communication between the rectum and ure- thra. In such a state of parts it has been ad- vised to cut through the perinaeum in the situa- tion of the anus, and endeavour to open the extremity of the rectum. The bladder should be previously emptied of urine, and a sound or staff be retained in it, as a guide to the operator to protect it from injury. In the other somewhat parallel condition of these parts in the female, the exit for the alvine mat- ters is usually more free ; and several cases are on record of life being continued for several years. These cases offer more encouragement for operative interference than the former. A curved probe may be passed from the orifice in the vagina into the rectum, and then directed towards the perinaeum to the situation of the anus. An incision is to be then made upon it ; and when the canal of the rectum is thus opened to the surface, the channel is to be kept carefully dilated, in order to oppose the natural tendency in the parts to close. 4. The anus may be open, but the con- tents of the intestine retained, in consequence of a congenital contraction of the rectum at some distance above, owing either to a mem- branous septum extending across it, or to a circular thickening and contraction. Such cases may be overlooked, and their cause remain unknown until after death : in cases, therefore, of obstinate constipation at this early age, this part should be particularly examined. Petit J describes this condition, and mentions a case in which he detected such an obstruction in the rectum, about an inch above the anus. This he divided by a pharyngotome, with success. The division may be effected by a bistoury, if situated low down ; or by a trochar, if at a considerable distance from the anus. * Recueil Periodiqtie de la Societe de Med. de Paris, t. iv. p, 45. t Diet, des Sciences Med. t. xxiv. p. 126. f Mem. de FAcad. de Chirurg. t. i. p. 385. AM S. 183 5. No anus, but the rectum is continued pervious as far as the integuments, which in some cases are then prominent, and of a violet colour, from the meconium appearing through in the siiuation which the anal opening should occupy. In other cases the skin is thick and hard, and gives no indication of the situation of the rectum. In such circumstances the surgeon must divide the integuments, either by a crucial or by a transverse and longitudinal incision, and then proceed cautiously until he exposes the dis- tended rectum. When the skin only inter- venes, the prognosis as to the result of this operation may be favourable, as the sphincters are probably perfect ; but when the cul-de-sac of the rectum is deep-seated, then experience affords but little encouragement to hope for success. Death is inevitable in such cases, unless relief can be afforded, and but very few cases of successful operations are on record.* 6. The anus and the continuous portion of the rectum are so contracted as scarcely to admit of any fluid discharge : we have even seen it scarcely pervious to air, so that on forcing in a grooved director, a considerable burst of flatus has escaped. This contraction may exist be- low, and yet the rectum be perfectly natural above. This contraction is sometimes not sufficiently noticed for several days or perhaps weeks after birth, because occasionally there is a small discharge of fecal matter ; it ultimately, however, excites attention from the great diffi- culty, straining, pain, and crying manifested at each evacuation. This condition of the parts sometimes admits of relief, by simple dilatation, by introducing a soft bougie, or some prepared sponge, which should be re- placed after each evacuation, and secured, if possible, by adhesive plaster and a bandage. Should these means fail, an effectual cure may be obtained, as we have seen, by a division of the circumference. This may be done by intro- ducing into the rectum a button-pointed bis- toury for about an inch on a director, and dividing the wall of the intestine transversely, towards the ischium, first on one side, and then on the other, to the depth of about one quarter of an inch. The part must be carefully dressed, and the edges of each wound kept separate by lint. The success of the operation greatly de- pends on the care in the after treatment, par- ticularly in renewing the dressing whenever it has been displaced. The anus is occasionally found much con- tracted in new-born children who are con- taminated by syphilis, and may be mistaken for a congenital malformation, especially of the kind last noticed, though not one in the strict sense of the expression; yet as it generally occurs at birth, it deserves the consideration of the practitioner in midwifery, whose attention is often first called to it by the same symptoms that attend the congenital malformation of this opening, namely, pain, difficulty, and straining at each evacuation, and a peculiarly small aper- ture. On examination, however, there are * See some observations by Petit, Mem. de 1'Acad. de Chirurg. t. i. p. 378. other appe-.ira.nces which will assist in explain- ing the real nature of the case, such as brown or dark discolouration of the surrounding parts, also considerable moisture, frequently excoria- tion, and even superficial ulceration in the adja- cent structures. Small fissures in the anus, also, are observable, discharging tenacious matter. Similar appearances may exist about the com- missures of the lips ; some soft granulations or condylomata are also often present in the im- mediate vicinity of the anus ; these frequently extend into the canal for a very little way. Other constitutional symptoms also are usually present, such as copper-coloured blotches on the skin, a tendency to cracking and excoriation of the skin about the hands and feet, and but- tocks, an imperfect development of, or a ten- dency to a separation of the nails, general emaciation, suspicious appearances about the mouth and tongue, and a remarkable and peculiar hoarseness in crying. Many, if not most of these symptoms, aided sometimes by the history of the parents, will lead the prac- titioner to distinguish this contraction of the anus from the congenital malformation before described. The distinction is important, as the treatment in both is totally different; the syphi- litic contraction invariably yields to gentle courses of mercury, administered in such form and dose as the circumstance of the case shall denote to be necessary. The local complaint disappears as the constitution is restored to health. Soothing, emollient applications are the best topical remedies ; should there be any ulceration or excoriation about the part, the surface should be slightly stimulated daily, either by caustic or by the ordinary mercurial lotions. Morbid conditions. The anus is the seat of several morbid affections, some of which pro- ceed from a specific cause ; others are merely local. The specific diseases are syphilis and cancer ; and the most common local derange- ments to which the anus is subject are, super- ficial ulcerations, excoriations, fissures, with or without contraction of the orifice from exces- sive irritability of the sphincter muscle, pro- lapsus ani, haemorrhoids, fistula in ano, polypi, &c. Some of these last mentioned affections must, strictly speaking, be considered as ap- pertaining to the rectum, under which head the reader will find them noticed. As, how- ever, the anus is more or less engaged in these diseases, we shall make some observations on each. The anus is also subject to laceration in parturition, and from other causes. Syphilis affects the anus at all ages ; its ap- pearances in the infant have been already noticed. In the adult it may present the primary venereal ulcer, which will have the same cha- racter here as elsewhere, only somewhat modi- fied by the position and function of the part. The primary ulcer may be produced either by the direct application of the virus, or by ex- tension of ulceration from the neighbouring organs, as not unfrequently occurs in the female. When the chancre is confined to the anus, which is very seldom the case, it may be difficult to discriminate between it and ulccra- 184 ANUS. ions from other causes. Ulcers in this region are very generally difficult and slow to heal, owing to the irritation to which they are exposed from the passage of the faeces, and from the motion, pressure, and changes of form to which the parts are necessarily subject. Syphilis frequently appears here in the form of fissures, clefts, rhagades : these are very distinct, and different from the fissures attending the irri- table anus. The syphilitic fissure is chiefly in the integuments; it seldom extends to any distance within the anus : the edges are some- what elevated and thickened, and the surface secretes an adhesive pus, which forms crusts or scabs. Although in some instances these fissures or rhagades are attended with pain in de- faecation, yet we have met many cases in which they caused very little uneasiness, and thus contrasted remarkably with the simple or the irritable fissure. Warts, condylomata, or ex- crescences about the anus are also frequent effects of syphilis in this region. These are generally on the cutaneous side of the anus, and very rarely, I believe, extend within it : they are not, therefore, difficult to distinguish from those vascular excrescences which are of mucous origin, and which so commonly pro- trude at the anus. Syphilitic warts and con- dylomata have generally a broad base; their surface is flattened by pressure against the op- posite nates, soft and moistened with an offen- sive sero-purulent fluid. In these cases the surrounding skin is often excoriated, and clefts and superficial ulcers frequently exist in the vicinity of the anus. Cancer is a disease to which the rectum is very liable, and may attack any part of the intestine, but usually exists at some inches above the anus. This opening, however, may become implicated by the extension of the dis- ease. We occasionally see that form of cutaneous cancer called " cancer scrott" extend along the perinaum and involve the circumference of the anus. Its parietes may, however, be prima- rily affected by cancer, in which case the disease will commence by a chap or fissure, or more frequently by a tubercle, which, gra- dually increasing in size and in breadth, at length ulcerates and shoots out a cauliflower mass of granulations which protrude through the opening, causing great uneasiness, pain, and dif- ficulty in defaecation : the surrounding parts in time become involved, ulceration extends, and a bleeding surface, very unhealthy, sloughy in some parts, and fungoid in others, discharging sanious and unhealthy matter, is an almost in- cessant source of pain and irritation, which in time wastes the health and strength of the patient. As no local application or consti- tutional treatment has yet been able to arrest this disease, it has been proposed to extirpate the anus and the lower end of the rectum when in this condition. Unfavourable as this opera- tion may appear, and rarely as it has been undertaken in this country, it has been fre- quently performed in France, and with some success.* * See Velpeau, Med. Oper, t. iii. p. 1033. The anus is often affected with warty ex- crescences, which by a superficial observer might be condemned as cancerous, yet these are not of a malignant character, and may be cured by local remedies and due attention to the gene- ral health. I have seen a warty tubercular appearance about the anus, extending through it, and even involving the mucous surface for some height, and contracting the orifice so much as to cause great pain and difficulty in defaecation, and also materially impairing the general health by continual irritation ; yet this state of parts is not malignant, nor is it prone to ulceration. Attention to the consti- tution, to the functions of the bowels, with local applications, will effect a cure. The anus is also frequently affected, and even incon- venienced by the growth of common warts ; these, however, can be speedily removed either by the scissors or by caustic. Excrescences frequently protrude through the anal opening, which are not warty or cutaneous growths, but elongations of the mucous mem- brane from a little distance above the anus. The anatomical disposition of these parts, before alluded to, together with a very relaxed state of the mucous membrane, accounts for the fre- quency of this occurrence. In some these pro- trusions only appear during defaecation, in others they are permanent, but much increased in volume during that act ; and, indeed, in some they are so large and fill up so much of the canal, that they must be extruded before the faeces can escape. These excrescences are soft, and very vascular ; they often appear without any assignable cause, though frequently they are attributed to haemorrhoids, to constipation of the bowels, to violent straining efforts in de- faecation, to fistula, or to long-continued irrita- tion from any cause. Prolapsus ani, or procidentia ani, although a term in somewhat common use, is rather an incorrect one, as the anus itself is too well maintained in its situation to descend, at least to any appreciable distance; the term rather implies a protrusion of a considerable portion of the relaxed mucous membrane of the rectum, or a portion of the large intestine itself, which must have become " invaginated or introsuscepted," and then protruded through the anus ; in these conditions the anus is rather dilated, the mu- cous membrane sometimes remains protruded after defaecation, but in others it returns after this process, or it can be returned by the gentle pressure of the hand : this is not uncommon in children and in elderly persons. This disease has been ascribed to a relaxation of the sphincter ; a circumstance which, however, does not seem to be proved, for in paraplegia and in paralysis of the sphincter, we do not find that the mem- brane protrudes, although the anus is often in these cases very dilatable ; the condition referred to ought perhaps rather to be considered as one of the effects, than as the cause of the disease ; moreover in some other instances the sphincter appears rather irritable, and painfully and dan- gerously constricts the protruded mass, which must then, in order to save the intestine from gangrene, be reduced by pressure properly ANUS. 185 applied, and by attention to posture. In the procidentia of old persons, Mr. Hey conceives that the relaxed state of the lower part of the intestine and of its surrounding cellular tissue, are in fault, and that hence the folds or ex- crescences about the anus remain, even when the parts have been returned ; he therefore sug- gests the removal of these flaps from the cir- cumference of the opening, and relates some well-marked cases in support of this practice, in which the operation had been successfully performed. The margin of the anus, like that of the mouth, is subject to Ju*ure$ t chaps, and super- ficial excoriations, sometimes caused by lace- ration induced by the passage of large and hardened faeces, but sometimes arising spon- taneously, and sometimes connected with a peculiarly irritable and contractile condition of the sphincter ani. This disease must not be confounded with haemorrhoids; on examin- ation it is not easily seen, but little is appa- rent, the anus is much contracted, the orifice somewhat redder than natural, slightly tender on pressure, but exquisitely so on dilating it by introducing the finger; this must be done cautiously and slowly, a cleft will then be observed just where the skin and mucous membrane join, generally on one side extending a little way, from half an inch to an inch and a half, longitudinally up the intestine; on di- lating the part still more, the surface of the fissure will be seen slightly ulcerated, and when touched it is exquisitely painful ; the surrounding muscle is in a state of rigid con- traction. It is doubtful whether the contrac- tion is the cause of the fissure, or whether the latter is the cause of the irritable and con- tracted condition of the muscle. Both expla- nations may be occasionally correct; but it is most probable that the irritable state of the muscle induces the ulcerated fissure, inasmuch as this muscular contraction occasionally exists without any fissure, and is then equally pain- ful ; and fissures frequently exist, as in syphilis, without inducing any spasmodic constriction of the muscle, and accordingly are attended with little or no pain. Contraction of the anus also frequently ex- ists without any fissure ; sometimes it is con- genital, sometimes it appears in the adult; the pain and other symptoms are nearly analogous, and as severe as in the case of fissure ; the examination by the finger however does not detect one part to be more painful than another, as is the case in that disease ; and this is almost the only symptom distinguishing these two affections. The term luemorrhoid has been applied by writers, practitioners, and invalids to any con- dition of the rectum and anus in which a discharge of blood takes place. It is, how- ever, more correctly applied to the small tu- mours which are frequently seen at and very close to the inner border of the anus or even occupying the very aperture, also to somewhat similar productions situated within the rectum, at the distance of one, two, or even three inches above the anus. From such tumours occupying these different positions, they have been arranged by all writers into external and internal haemorrhoids; the latter are very im- portant and demand the close attention of the surgeon, both as to their pathology and sym- ptoms, as being frequently obscure and liable to be mistaken not merely for the ordinary diseases of the anus, such as fissure, blind internal fistula, &cc., but also to be confounded with a varicose condition of the veins of the rectum, which is by no means an uncommon condition, or with those vascular tumours which are productions of the mucous mem- brane occasionally protruding at the anus, that have been already noticed, and are of a wholly different character from true hae- morrhoidal tumours, or with the protrusions of the mucous membrane itself, the effect of the relaxation of its cellular connections. As the full consideration of this important branch of pathology belongs to the article on the mor- bid anatomy of the rectum, we shall here con- fine ourselves to a few observations on external haemorrhoids and analogous tumours. External hemorrhoids appear at the border of the anus as small bluish tumours, the colour however varying according to the con- dition of the tumours, being sometimes of a dark and deep red or black, at others pale and almost white ; in size they vary from a grain of small shot to a large cherry ; they are some- times full and almost bursting, at others they are soft like a flaccid nipple, empty or with- ered ; they are covered on the anal side by the delicate cuticle which is smooth and glossy, and on the outer side by the common integu- ment; when small, they are moveable and can be distinctly felt to be in the subcutaneous cellular tissue; when large and tense, they ap- pear more connected with the skin itself; an attentive examination can always distinguish between these and the several excrescences, vegetations, or condylomata, which have been already mentioned as the effects of syphilis, as also the folds or crests of integument and mucous membrane which are found so fre- quently prolonged from the border of the anus. These tumours remain in many persons for years free from pain, and productive of little, if of any, inconvenience ; occasionally, however, and periodically in some, they en- large, inflame, and interfere with the functions of the anus, and by sympathy engage the ad- jacent organs, and are relieved either by a copious discharge of blood, or by suppuration, or by the interference of art. The liability of the veins immediately about the anus to varicose enlargement appears in some measure founded in anatomical structure. If we inject the intestinal veins in the adult with wax injection, we shall often find a little above the anus, just where the skin and mu- cous membrane unite, a sort of constriction on the vessels; the veins appear larger imme- diately above it, and again below it, and many of the branches in the venous plexus around the anus appear to be enlarged, while in the very spot or circular line alluded to, the vessels appear to be compressed. It may 186 ANUS. occur, then, that hardened faeces impacted in the rectal pouch, which is above this point, may assist in obstructing the more free flow of blood, and thus encourage the enlargement of these anal veins, and the same effect may be still further induced by the muscular pres- sure employed in defaecation ; in support of this view we find that children are almost free from, this varicose condition of these veins, unless under peculiar circumstances ; and in the adult it usually occurs in those of con- stipated habit of bowels ; it is also relieved or removed by attention to their functions. The true hsemorrhoidal tumours, external as well as internal, must be rega'rded as essentially dif- ferent from a varicose condition of the anal veins, although they are often connected with the latter, and it must be admitted that in some cases they may owe their origin in a great -measure to venous dilatation. Varices of the anal veins are simple dilatations either of a trunk or of some of the branches of these vessels ; their cavity is continuous with that of the vein, and freely communicates with it, and pressure on the varix empties it of its contents ; its tunics are the venous coats and the membrane of the intestine; whereas hremor- rhoidal tumours are wholly distinct from the veins, and are either simple cysts, lined by a smooth membrane, or they are composed of a spongy cellular texture, not unlike the erectile tissue. This latter is usually the con- dition of recently formed haemorrhoids, whereas in those of long standing the single or divided cyst is the ordinary structure ; this cyst will be found to contain a little blood, partly fluid and partly coagulated ; and when the internal surface is minutely examined, one or more fine pores will be visible, the orifices of ca- pillary vessels, through which warm water, if steadily injected by the inferior mesenteric artery, will exude on the surface. In the cellular or more recent haemorrhoids the texture ap- pears very vascular, soft, and spongy, as also the surface of the tumour, from which blood or serum will sometimes exude during life. These cellular haemorrhoids in time become circumscribed, the cellular texture becomes more or less perfectly absorbed, and the cyst- like structure becomes more developed ; how- ever a very recently formed haemorrhoid may, and sometimes does, present a distinct cyst or cavity, as may be readily conceived when we consider the process whereby these tumours come to be developed, which, as far as our observation extends, is as follows : from con- tinued irritation from any exciting cause, such as disease of the intestine or anus, worms, or from a local plethoric condition, spontaneous, as far as we can know, the capillary circulation is increased in the loose submucous tissue in this region, a small quantity of blood, or lymph, or serum, is effused into it, perhaps from the rupture of some small vessels, or exhaled from their dilated extremities. A slight degree of inflammation attends this con- dition : the part affected, that is, the cellular tissue, becomes more highly organized, thick- ened, vascular, and spongy. After some time, this increased vascular action subsides, and in process of time the whole may nearly dis- appear, but in general a part of this more highly organized spongy tissue remains, it being fully supplied with nourishment; the absorbents in due course modify its appear- ance ; the surrounding thickening is removed, as also some portion of the cellular mass, and thus the formation of the haemorrhoidal cyst is completed. A structure like this, con- nected with the capillary system, must be influenced by the same causes as can affect the latter ; thus irritation local or general, me- chanical injury, or general or local plethora are all capable of exciting increased action in it, and of inducing all those symptoms and changes which are so well known to attend during haemorrhoidal inflammation. Fistula in ano is a disease of such very fre- quent occurrence, and so well understood and described by every surgical writer, that it is scarcely necessary to do more than allude to it in this place : strictly speaking it is not a disease of the anus, as that opening is in general totally unaffected, except as regards its functions : it should rather be regarded as a disease of the anal region. There is one form of fistula in ano, however, which is seated on the very confines of this opening ; it is trou- blesome and distressing, attended with heat, itching, and excoriation, pain during defaeca- tion, and constant purulent or sero-purulent discharge : without due attention it may be overlooked by the surgeon, as the orifice is so close to the anus as to be concealed by the natural rugae, and so small as only to admit a lachrymal probe ; the sinus is not more than an inch or half an inch long; its internal opening is on the very edge of the anus, the whole is immediately under the skin, and does not involve any other structure ; it is not pre- ceded by regular abscess, neither does it or the treatment necessary for its cure involve the sphincter or any other structure, except the fine integuments ; it most probably originates in irritation of some of the anal sebaceous follicles, and sometimes two or three of such fistulae may exist at the same time. The true or deep fistula in ano has its origin in deep-seated abscess commencing close to the rectum, or in the centre of the ischio-rectal space of either side : when in the former, some mechanical irritant or some disease of the intestine may have been the cause or origin of the abscess ; when in the latter, it often arises without any obvious reason, but frequently appears to have been connected with some peculiar delicate or morbid con- dition of the constitution. All abscesses in this situation do not necessarily end in fistula ; if they have been small, superficial, opened early, and treated judiciously, they may be healed as perfectly as abscesses in any other situation; but when deap-seated, of slow growth, and long continuance, and when de- pending on some deep-seated mechanical irri- tant or on constitutional causes, then the ab- scess usually attains considerable size, and having opened either into the rectum or through AORTA. 187 the integuments, or in both these directions, it continues to secrete and to discharge a con- siderable quantity, and shews no disposition to alter its action or to heal. We have already detailed all the local peculiarities of the ischio- rectal region (the seat of this abscess) which can satisfactorily explain the difficulty or the impossibility of keeping at rest or retaining in apposition the sides of the cavity, a condition almost essential to the healing of an abscess in any situation, and hence the necessity of sur- gical interference. Abscess in this region frequently originates close to the rectum in consequence of irritation and ulceration in this intestine; this irritation may be caused by disease, such as cancer or stricture of the rectum, or by some foreign body becoming impacted in one of the lacunae. Above the sphincter is the rectal pouch, and an irre- gularly shaped or sharp substance, such as a pin, a fish-bone, or one of the small bones of a fowl, &c. brought into this in the fcecal mass, may catch in its villous or rugous surface, the muscular powers of the intestine are excited by this irritation to increased and repeated efforts of expulsion ; these only serve to im- pact more closely the foreign body in the parietes of the intestine ; the submucous tissue, which may now contain the whole or part of this substance, becomes inflamed, suppuration follows, an abscess is formed close to the intes- tine; in some time the matter is discharged either through the rectum and anus, or coming to the surface of the nates it receives exit by puncture. In this case of abscess, which we suppose to have been caused by a foreign body impacted in the intestine, the matter is usu- ally discharged by the rectum, at least at first, although this exit will not always prevent it still tending towards the cutaneous surface : in cases of fistula, however, arising from such a cause, we are most likely to meet with the blind internal jistula, at least in the early period; whereas, when abscess forms spon- taneously in this region, and opens on the surface, the intestine is often at first and for some time wholly disengaged from the disease, even after the abscess has opened, notwith- standing which it is productive of great in- convenience and more or less of pain during defaecation ; in this state, when the fistula or abscess remains discharging through the skin only, it constitutes what is termed a blind external jistula ; by degrees the rectum be- comes denuded, and ultimately ulceration opens it by one, and sometimes, but rarely, by more orifices ; this opening is usually about half an inch above the edge of the anus, and between the two sphincters. I have observed it to hold this situation in a great number of cases, which I have examined both in the living and the dead ; in a few instances, how- ever, I have found it opening at a higher point. When the abscess arises from irritation in the rectum, then I have observed the internal opening to be higher, that is, in the dilated pouch of the rectum, which during life will appear to be from an inch and a half to two inches from the anus ; but when the abscess has commenced spontaneously in the anal adeps, and opened on the surface first, I have then in general found the rectal opening less than an inch distant from the anal orifice, and in a groove or recess between the two sphinc- ters. When the abscess discharges by two openings, that is, through the skin and through the rectum, a perfect or complete jistula is then said to exist. Fistulas occasionally appear in the anal region which have their source at a much greater dis- tance; thus, any diseases of the uterus or vagina in the female, of the prostate or urethra in the male, which end in suppuration, may cause collections of pus which will burrow under the fasciae and skin to the vicinity of the anus, and open near it or even into the rectum. Psoas and lumbar abscesses also may descend into the pelvis and approach the sur- face, either in front or at one side of the anus. In morbus coxae also chronic abscesses which form about the nates not unfrequently open in the same situation. Polypus is seldom a disease of the anus ; it most usually grows from the rectum, and pro- trudes occasionally only at the anus. (Robert Harrison.) For the Bibliography of this article see that of INTESTINAL CANAL. AORTA* (human anatomy). (Arteria magnet. Fr. aorte. Germ. Aorta, die grouse Schlagader. Gr. O^T.) Hippocrates applied the term ao^ra* to the lower part of the bronchi. Aristotle called the great trunk of the arterial system Xs4- t'ha.rrw, in reference to the vena cava, which he considered the greater vein. R. B. T. 188 AORTA. the ventricle at three equidistant points by the centres of their convex edges, where the fibres of their marginal cord become intimately blended with those of the tendinous ring of the aortic opening of the ventricle ; between these points are three triangular intervals, each of which is occupied by a thin tendinous expansion of considerable strength, having one of its sides continuous with the tendon which encircles the aortic opening of the ventricle, and the other two continuous with the marginal ten- dinous cord of the festooned commencement of the middle tunic of the aorta. The convex margins of the sigmoid valves of the aorta are attached to the margins of the semilunar flaps, and are composed of thin ex- pansions sent off from their marginal tendinous cord, covered by a reflexion of the lining mem- brane common to the heart and arteries. Hence it follows that the fibres of the middle tunic of the aorta are not continuous with the muscular fibres of the ventricle, being sepa- rated from them by the tendinous structure above described ; this tendinous connexion is strengthened and supported externally by a layer of dense cellular membrane, which may be regarded as the commencement of the cellular or external tunic of the arterial system. The lining membrane of the heart, after being reflected over the sigmoid valves, extends itself into the aorta, and becomes continuous with the lining membrane of that vessel. The muscular substance of the heart rises in form of a swollen annular border around the commencement of the aorta for a little distance, and is connected to it by dense cellular membrane. The serous layer of the pericardium passes loosely from the surface of the heart over the aorta; a quantity of soft adipose substance, which is absent in the foetus during the earlier months, begins to collect under the serous membrane in this situation, sometimes before, sometimes after birth, and, increasing as life advances, is found in considerable quantity in old age. The fore- going description of the connexion of the aorta with the heart has been determined by my own dissections repeatedly performed, and agrees, in its leading particulars, with the account given of it by M. Beclard* The aorta, arising from the left ventricle of the heart opposite the left side of the body of the fourth thoracic vertebra, ascends at first obliquely forwards, and to the right behind the middle bone of the sternum, until it arrives at the right side opposite the second intercostal space, and behind the sternal articulation of the cartilage of the second rib ; it then stretches backwards and to the left, opposite the junction of the upper and middle portions of the ster- num, on a level with the body of the second thoracic vertebra, and curving downwards it reaches the left side of the body of the third thoracic vertebra, on which there is a slight depression for lodging it; from this point it descends through the posterior mediastinum, * Diet, de Medecine, art. Aorte. Elemens d'Anat. Generate, par Beclard. Paris, 1823. advancing in its course downwards from the left side to the front of the bodies of the ver- tebrae ; it passes through the aortic opening of the diaphragm, enters the abdomen, and on the body of the fourth abdominal vertebra gives off the two primitive iliac arteries, in which it seems at first view to terminate; the aorta, however, does not end here, but is continued, although greatly reduced in size, under the name of the middle sacral artery, as far as the extremity of the os coccygis. The aorta is usually divided by anatomists into three portions; the curved portion fiom the heart to the third thoracic vertebra is called the Arch of the aorta ; the remaining portion of the vessel, to which the name of descending aorta has been sometimes given, is called Thoracic aorta above the diaphragm, and Ab- dominal aorta below that muscle. The Arch of the aorta is divided into three portions, for the purpose of describing its nu- merous important relations to surrounding parts with greater accuracy; these are, first, the ascending or anterior limb ; second, the trans- verse portion ; and, thirdly, the descending or posterior limb. The commencement of the aorta is covered anteriorly and to the left by the pulmonary artery, on the right by the right auricular appendage, the tip of which overlaps it in front, and behind it rests on the sinus of the left auricle. The ascending limb of the arch lies first in front of the right pulmonary artery, as that vessel crosses behind it in its course to the right lung, and then it gets in front of the right bronchus, and the cluster of bron- chial glands which fill up the angle formed by the bifurcation of the trachea; it is bounded on the right side by the superior vena cava, and on the left by the pulmonary artery ; an- teriorly it is separated from the sternum by the anterior margins of both lungs, which here approximate, and by the narrowest part of the anterior mediastinum, where the attached sur- faces of the opposite pleurae touch. This portion of the aorta is contained within the bag of the pericardium, the serous layer of which invests it in every part except where it lies in contact with the pulmonary artery. The transverse portion of the arch is shorter than the ascending limb. The three great arte- ries of the head and upper extremities arise from its superior sides ; inferiorly it rests on the left bronchial tube ; in front it has the cellular membrane of the anterior mediastinum, the thymus gland, and the inferior part of the vena innominata; behind it rests on the trachea a little above its bifurcation, and on the left re- current nerve. The posterior limb is the shortest portion of the arch; it lies immediately behind the division of the pulmonary artery, which is connected to it by a ligament, the remains of the ductus arteriosus ; and it is crossed by the left par vagum ; on the right side it is in con- tact with the oesophagus, thoracic duct, and left side of the body of the third thoracic ver- tebra ; the rest of the circumference of the thoracic aorta is covered by the left pleura, and is in contact with the internal surface of the left lung. In the generality of adults having AORTA. 189 the chest well formed, and the heart and the arch of the aorta free from disease, the origin of the aorta is opposite the sternal articulation of the cartilage of the fourth rib of the left side in the male, and the intercostal space above it in the female; the ascending limb of the arch, which is behind the middle bone of the sternum in the greater part of its length, may be felt pulsating on the right side of the sternum in the second intercostal space ; the highest part of the transverse portion of the arch is on a plane with the centre of the sternal extremities of the first pair of ribs, and about an inch below the upper margin of the ster- num : the arch of the aorta terminates oppo- site the lower edge of the cartilage of the second rib of the left side. The t/wracic aorta descends in the posterior mediastinum, and advances from the left side to the front of the thoracic portion of the spine, crossing in its course the left intercostal veins, and the left vena azygos when that vein exists ; in front it is covered by the left bronchus, the pos- terior surface of the pericardium, the lower ex- tremity of the oesophagus, and the left stomachic cord of the par vagum ; on the right side it is bounded by the oesophagus, thoracic duct, and vena azygos ; on the left side it is covered by the pleura, and in contact with the internal surface of the left lung, and at its lower extremity the left splanchnic nerve comes into contact with it, and most frequently accompanies it through the diaphragm. The abdominal aorta, which enters the abdo- men between the crura of the diaphragm, des- cends along the front of the abdominal ver- tebrae and the left lumbar veins; it is covered in front by the solar plexus of nerves, the stomach, pancreas, transverse portion of the duodenum, the splenic and left renal veins, the small intestine, and the root of the mesentery ; on the right side it is bounded by the abdomi- nal vena cava, and the commencement of the thoracic duct, and on the left it is covered by the peritoneum going to form the left layer of the mesentery. The termination of the aorta in the common iliacs and the middle sacral arteries is a little below the level of the um- bilicus. A remarkable deviation from the cylindrical form, which is one of the general characteristics of the arterial system, is observable in two parts of the arch of the aorta ; the first of these occurs at the commencement of this vessel in form of three dilatations corresponding to the semilunar flaps already described ; they were first pointed out by Valsalva, and have received the name of the lesser sinuses of the aorta ; they exist at all periods of life, and increase in size with years ; the other deviation from the cylindrical form is a dilatation on the right side of the ascending limb of the arch at its junction with the trans- verse portion ; this dilatation, which does not exist in the foetus, grows larger as life advances, and appears to be produced by the impulse of the blood striking against this part of the aorta at each successive systole of the left ventricle. The aorta in the succeeding part of its course gradually grows smaller in a degree proportionate to the size of the branches it gives off. The thickness of the aorta is proportionally less than that of its branches; it is thinner at its commencement than in the arch, in which part, according to Haller, it is thicker by an eighth on the convex than on the concave side; it gradually diminishes in thickness as it descends through the thorax and abdomen, but its power of resisting distention instead of being dimi- nished in an equal degree was found by Win- tringham to be greater at its lower part than near the heart.* The structure of the aorta is the same as that of the rest of the arterial system in general ; its external tunic, however, is slighter than that of all other arteries except those of the brain, it is weaker the nearer it is examined to the origin of the aorta ; it is strengthened near the heart by the covering which the serous layer of the pericardium gives to the aorta, and by an expansion from the fibrous layer of that mem- brane, which is lost on the transverse portion of the arch. The cellular sheath of the aorta in which the soft fat around its origin is deposited, becomes so fine where the vessel is passing out of the pericardium as to lead some anatomists to deny its existence in this situation ; it becomes more evident in the course of the descending aorta through the mediastinum, and is still more considerable around the abdominal aorta, where it is usually loaded with a considerable quantity of adipose substance. The branches which arise immediately from the aorta may be divided into orders, according to the degree of remoteness or the relative size and importance of the parts which they supply with blood ; first, the branches which convey blood to the two extremities of the trunk and the limbs attached to them ; these arteries, which are of considerable size, are the arteria innominata, the leftc arotid and left subclavian, which, arising from the transverse portion of the arch, are distributed to the head, neck, and upper extremities, and the primitive ili&c arte- ries which arise from the lower part of the abdominal aorta supplying the pelvis and the lower extremities. 2nd order. Branches some- what smaller going to the thoracic and abdomi- nal viscera and the parietes of the chest and abdomen ; the coronary arteries which supply the heart arise from the aorta immediately after its origin ; the bronchial arteries which supply the substance of the lungs, and the intercostal arteries supplying the parietes of the chest arise from the thoracic aorta; the cceliac, su- perior and inferior mesenteric, which supply the digestive organs ; the renal arteries which supply the kidnies ; the spermatic going to the organs of generation, the inferior phrenic sup- plying the diaphragm, and the lumbar arteries going to the parietes of the abdomen and lum- bar region of the spine, are the vessels of this order which arise from the abdominal portion of the aorta. 3rd order. Branches of much smaller size are sent from the aorta to se- * Experimental Inquiry on some parts of the Animal Structure. London, 1740. 190 AORTA. condary parts which lie in its vicinity, as the thymus, the pericardium, the oesophagus, the lenal capsules, ureters, &c. 4th order. Small arterial twigs lost in the neighbouring cellular substance, lymphatic glands, and in the coats of the aorta itself. Development. The aorta appears to be formed in the foetus prior to the heart and sub- sequently to the system of the vena porta, with which, according to Baer, Rathke, and Meckel, , it is connected by a small dilatation described by Dr. Allen Thomson* as a curved tube, which is the rudiment of the heart. (See OVUM.) Whilst the heart has but a single ventricle, the aorta and the pulmonary artery form a common trunk, which afterwards becomes divided by the de- delopment of the contiguous portions of the circumference of both vessels ; during the remaining periods of intra-uterine life, and for a short time after birth, the pulmonary artery communicates with the aorta by the duc- tus arteriosus, which appears as a continuation of the trunk of the pulmonaiy artery opening into the concavity of the arch of the aorta at its termination. The ductus arteriosus becomes impervious soon after birth, and having under- gone a process of complete obliteration, is finally concerted into a ligamentous cord. The size of the arch of the aorta is less in proportion in the foetus than in the adult, whilst the thoracic aorta is larger, being increased in size below the ductus arteriosus. The arch lies closer to the spine in the foetus in consequence of the tra- chea and bronchi behind it being so much less developed than in the adult, and the thymus which is between it and the sternum being so much larger during foetal life. In old age the curvature of the arch of the aorta is much greater in consequence of the great sinus having increased considerably in size. Anomalies. The aorta presents occasional varieties or anomalies in the mode of its origin, its course, termination, and the number and situation of its branches. It is an interesting fact, that almost every irregularity hitherto observed in the course and branching of the aorta in the human subject, represents the dis- position which that vessel constantly exhibits in some of the inferior animals. The anomaly pf the aorta arising from both ventricles, and causing that condition called cyanosis, will be more properly considered in the article HEART, The following anomalies of the course of the aorta have been recorded by anatomists : 1st. The aorta sometimes divides imme- diately after its origin into a right and left trunk, which, after having each given off the arteries of one side of the head and one upper extremity, join to form the descending aorta. Malacarnef has described a remarkable case of this anomaly; the aorta was of an oval form at its origin, its greater diameter being to its lesser in the proportion of three to two, it had five sigmoid valves in its interior, it divided immediately after its origin into a right * Vide Edinburgh New Philosophical Journal, by Dr. Jameson, for October, 1830. t Osservazioni in Chirurgia. Torino, 1784. and left trunk, from each of which arose a subclavian, an external and an internal carotid : after the two trunks had run for a space of four inches distinct, they joined to form the descending aorta. Hommel, a Norwegian ana- tomist,* relates a case in which the transverse portion of the arch of the aorta divided into two trunks, one of which passed before and the other behind the trachea, after which they joined to form the descending aorta, having encircled the trachea with a sort of ring : this anomalous division of the arch of the aorta is the more remarkable as it approaches the con- dition of the vessel which is constant in all known reptiles. 2d. The arch of the aorta is sometimes absent, in consequence of the vessel dividing, immediately after its origin, into two great trunks, one of which gives off the arte- ries of the head and upper extremities, whilst the other becomes the descending aorta.f This distribution is similar to that in the horse, rhinoceros, and other pachydermata, in the ruminantia, and some of the rodentia. 3rd. Varieties in the course of the arch sometimes, although rarely, occur, as, for instance, when the arch of the aorta, instead of crossing to the left in the usual manner, curves over the right bronchus, and gets to the right side of the spine, whence it either immediately crosses behind the trachea and oesophagus to the left, or continues its course along the right side of the spine to the lower part of the thorax ; in cases of complete transposition of the vis- cera, where the heart is in the right side of the chest, the arch of the aorta is also reversed, in which case its thoracic portion descends along the right side of the spine.| Instances are recorded in which the descending aorta, a little below its arch, was very much con- tracted in its area or even completely obliterated for a certain distance, below which it resumed its full size : the circulation in these cases was carried on by the anastomosing of large col- lateral branches arising above and below the constricted or obliterated part. Anomalies of the branches of the aorta are more frequent : according to Meckel the branches arising from the arch deviate from the normal condition in one person out of every eight.|| The branches arising from the arch of the aorta present three kinds of ano- maly, which, as to their frequency, occur in the following order : 1st, an increase in their num- ber; 2d, a diminution; and 3d, an anomaly in the identity or order of the branches arising from this part without any increase or diminu- tion of their number. In anomalies of the first * Comm. Noric. ann. 1737. t Vide Abhandlungen des Josephinischen Medi- cinisch-Chirurgischen Akademie. Band, i. S. 271. Taf. 6. Wien. 1787. $ Meckel Handbuch der Menschlichen Anatomic. Band iii. Halle and Berlin, 1817. Abernethy in Phil. Trans. 1793. Desault in Journal de Chirurgie, torn. ii. Dr. Goodison in Dublin Hosp. Reports. Brasdor Recueil Periodique de la Societe de Medecine. Paris, torn. iii. || Handbuch der Menschlichen Anatomic. Band iii. Halle and Berlin, 1817. AORTA. 191 kind, the number of branches is most fre- quently increased to four, by the left vertebral arising from the arch between the left carotid and left subclavian, as in the phoca vitulina ; next to this in frequency is the instance of the inferior thyroid arising from the arch between the innominata and left carotid, then the in- ternal mammary, and, lastly, the most un- usual is the thymic artery : it is more unusual to find the number of branches coining from the arch increased to four, in consequence of the innominata being absent, the right carotid and right subclavian arising separately ; in such a distribution the right subclavian most fre- quently arises from the left extremity of the arch after the left subclavian ; it may, how- ever, be the first branch of the arch to the right, or it may arise between the two carotids, or, as more rarely happens, between the left carotid and left subclavian. The number of branches arising from the arch will be in- creased to five or upwards, when two or more of the above-mentioned anomalous branches arise from it at the same time. Of the second kind of anomaly, or that by diminution of the number of branches, the most frequent is where these are reduced to two, of which there occur the following varieties : a. the in- nominata sometimes gives off the left carotid as an additional branch, and the left subcla- vian arises separately, as in many quadrumana, several of the carnivora, as the lion, cat, dog, \veazel, several rodentia, &c. ; 6. sometimes there are two arteriae innominatae, each dividing in a symmetrical manner into the subclavian and carotid of its own side, as in cheiroptera and the dolphin ; c. sometimes when the arch gives off but two trunks, one of them divides into the two carotids, ^nd the other into the sub- clavians ; d. the right subclavian may arise distinct, and a common trunk give off the two carotids and left subclavian ; the origin of a single trunk from the arch of the aorta sup- plying the arteries of the head and upper extremities is equivalent to a division of the aorta into an ascending and descending trunk, already noticed. The third kind of anomaly partakes of the characters of the two pre- ceding, although the number of branches is the same as in the normal state : its varieties are, a, the left vertebral arising from the arch, whilst the left carotid comes from the inno- minata ; b, the two carotids may arise from a common trunk between the origins of the right and left subclavians, as in the elephant ; c, the right subclavian and right carotid may arise as distinct branches, whilst the left carotid and left subclavian come from a common trunk, forming a complete inversion of the usual order ; rf, the left carotid may arise from the innominata, whilst the right carotid comes from the part of the arch in the situation usu- ally occupied by the origin of the left carotid. Anomalies of the branches of the descending aorta are less frequent ; the following are among the more remarkable : a, the coeliac and dia- phragmatic may arise above the diaphragm ; one or both of the diaphragmatics may be given off by the coeliac ; sometimes the coeliac and superior mesenteric arise by a common trunk as in the tortoise; sometimes there are two or more renal arteries on one or both sides, and sometimes the primitive iliacs are given off much higher than usual, in which case they are sometimes connected by a cross branch before they divide into the external and in- ternal iliacs : it sometimes happens, when the iliacs are given off higher than usual, that the inferior mesenteric arises from the left of them. The diseased conditions of the aorta are described in the articles ARTERY and HEART. The aorta, as Beclard remarks,* is more sub- ject than any other artery to the ovoid dila- tation in its ascending, and the lateral dila- tation in its descending portion ; it is also very subject to osseous or calcareous deposits, to fissures and ulcerations, to tubercles and small abscesses in its parietes, and to aneurism. Wounds of the aorta are constantly mortal. Laennec has observed a particular lesion of this vessel ; it was a fissure of the internal and middle coats, from which the external tunic was extensively separated by a quantity of blood which had been effused between it and the middle tunic. The late Mr. Shekelton has described, in the Dublin Hospital Reports, a form of aneurism of the lower part of the abdominal aorta, in which the blood forced its way through the internal and middle coats, dissected the middle from the external for the space of four inches, and then burst into a lower part of the canal of the artery, forming a new channel which eventually superseded the old one, which the pressure of the tumour obliterated. Granular excrescences are sometimes formed on the valves of the aorta, which Corvisart conjectured to be of venereal origin. The in- ternal tunic of the aorta sometimes presents a red appearance, not peculiar, however, to this vessel, and occurring in certain forms of fever. Obliteration or constriction of the aorta is a condition rarely met with; its existence may be traced either to pressure on the vessel from without, morbid thickening of its coats, or the formation of coagula internally ; this latter occurrence being most usually a consequence of the spontaneous cure of aneurism. Aneurisms of the aorta produce various effects on surrounding parts ; thus the heart, lungs, trachea, oesophagus, pulmonary artery, large veins, thoracic duct, and the various organs in the abdomen placed in their vicinity, may suffer derangement of their functions, displacement, atrophy or partial destruction, according to the degree of pressure to which they are subjected. Aneurisms occurring in the ascending por- tion of the aorta, which is within the pericar- dium, are often attended during life by many symptoms very similar to those of disease of the heart itself, while their pressure may produce a diminution of the calibre of the pulmonary artery, obstruct the free passage of the blood through the vena cava superior, and even in- * Dictionnaire de Medecinc, art. Aorte. 192 AORTA. terfere with the full distension of the auricles. Aneurisms of the transverse portion of the aorta, when directed forwards, usually project at the right side of the sternum about the second intercostal space : when the sac extends upwards towards the neck, it frequently be- comes a matter of extreme difficulty to dis tinguish an aneurism of the aorta from an aneurism of the innominata or some other large arterial trunk in the neighbourhood ; cases are on record, where the pressure of such aneurisms of the aorta caused obliteration of the subclavian and common carotid. When aneurisms extend backwards, they produce a variety of effects, interfering with respiration and deglutition from their pressure on the trachea and oesophagus, sometimes producing obliteration of the thoracic duct. The pres- sure produced by aneurisms of the thoracic and abdominal aorta occasionally cause ab- sorption of the bodies of the vertebrae, and give rise to an appearance not very dissimilar to that produced by caries. Aneurisms of the arch of tj^j aorta do not so often terminate fatally by making their way through the anterior parietes of the chest, and opening externally as by bursting internally : when they occur in that part of the arch of the aorta covered by the pericardium, they most usually burst into the sac of that membrane ; cases are recorded in which aneurisms of the aorta have burst into the pulmonary arterv,* or, taking a direction backwards, have opened into the trachea, oesophagus, or the substance of the lungs. Aneurisms of the thoracic por- tion of the aorta sometimes burst into the left pleura, sometimes into the posterior medi- astinum : they have been known to point at the left side of the spine, after having caused ab- sorption of the heads of the ribs and sides of the bodies of the vertebrae. In two cases observed by Laennec and Mr. Chandler, aneu- rism of the thoracic aorta burst into the spinal canal. Aneurisms of the abdominal aorta most usually burst into the cellular tissue of the lumbar regions behind the peritoneum, seldom into the sac of that membrane. An aneurism of the abdominal aorta has been observed to make its way backwards by the side of the spine, and point in such a situation as to have been at first mistaken for lumbar abscess. Branches of the aorta. I. Branches arising from the arch. From the arch of the aorta five branches are given off; two from its com- mencement, the coronary arteries, and three vessels of considerable size (jig. 78 a b c), from the upper part of its transverse portion to supply the head and the upper extremities. The coronary arteries of the heart or the car- diac arteries arise from the aorta close to its origin, and immediately above the free borders of the sigmoid valves ; they are usually two in number, one for each ventricle. The right, anterior or inferior coronary artery is often larger, seldom smaller than the * Dr. Wells in Trans, of a Society for Improve- ment of Medical and Surgical Knowledge, vol. iii. Fig. 78. A B, arch of the aorta. C, thoracic aorta. I), abdominal aorta. E, common iliac artery. g, middle sacial artery. left; it arises from the anterior side of the aorta above the anterior sigmoid valve, coming out from between the roots of the aorta and pulmonary artery, it passes downwards and to the right side in the groove between the right auricle and ventricle, turns round the right edge of the heart until it reaches the groove of the septum on the inferior surface of that organ, when it changes its direction, coursing afong that groove until it arrives at the apex of the heart, where it anastomoses with the left coro- nary artery ; in its course it gives off to the right and left many tortuous branches arising nearly at right angles, the right branches are smaller and go to the right auricle, the left are larger and belong to the right ventricle, which they traverse in a longitudinal direction to- wards its apex. From the origin of the right coronary artery two small branches are given off, one to the commencement of the pul- monary artery and the surrounding fat, which anastomoses behind the pulmonary artery with a branch of the left coronary; the se- cond branch anastomoses with the bronchial arteries. The left posterior or superior coronary artery arises between the left auricle and the posterior surface of the pulmonary artery, de- AORTA. 193 scending to the left between the left auricle and pulmonary artery, and, having reached the groove at the base of the heart, dividing into two or three branches ; one anterior longitu- dinal descends along the anterior groove of the septum to the apex of the heart, where it anas- tomoses with the termination of the right coronary artery, with which it holds frequent communication by branches which it sends over the anterior surface of the right ventricle, while it sends some large branches to the left ventricle; this branch at its commencement gives small twigs to the aorta and pulmonary artery. The second branch of the left coronary artery covered by the great coronary vein passes from right to left in the groove between the left auricle and ventricle, to both of which it gives many branches, turns round the left border of the heart, changes its direction, and descends by the side of the right coronary artery to the apex ; the third branch sinks into the substance of the septum and continues its course to the apex; this branch sometimes arises directly from the aorta ; in this latter case, of course, there will be three coronary arteries arising from the aorta; Meckel has once seen four ; the supernumerary coronary artery does notarise above any particular valve, but usually close to the origin of one of the normal branches. It is rare to find but one coronary artery in the human subject, which corresponds, according to Camper, with the normal con- formation in the elephant. The three large branches arising from the transverse portion of the arch of the aorta and sent to the head and upper extremities, will be described in a separate article. II. Branches of the thoracic aorta. These may be divided into anterior and lateral. The anterior branches are, the bronchial, cesophageal, and posterior mediastinal. The lateral are the inferior or aortic intercostal arteries. The bronchial arteries are usually two in number, one for each lung ; sometimes, however, there are two for each lung, and sometimes the right and left bronchial arise from a common trunk, which usually springs from the first aortic in- tercostal of the right side. The right bronchial artery most usually arises from the first aortic intercostal artery of the right side, which supplies it after having arrived at the right side of the spinal column behind the oesophagus, sometimes it comes direct from the aorta; it proceeds in a tortuous course under the right bronchus, to the root of the right lung, after having given small branches to the oeso- phagus, the pleura, the back part of the peri- cardium and the bronchial glands. The left bronchial artery arises immediately from the aorta and passes in front of the oeso- phagus to the left bronchus, to the posterior side of which it attaches itself. Both bronchial arteries are similarly distributed through the lungs, dividing with the bronchi, along each branch of which they send two or more tortu- ous twigs. The relation of the bronchial arte- ries to the other vessels of the lungs will be more particularly noticed in the article LUNG. The asophageal arteries vary in number from VOL. i. two to seven : they are inferior to the bronchial in size : they arise from the front of the thoracic aorta, and are distributed to the oesophagus, on which they anastomose freely with descending branches of the inferior thyroid from above, in the middle of the oesophagus with the bronchial, and below with branches of the phrenic and coronary artery of the stomach, The posterior mediastinal arteries are nume- rous and small; they send branches to the oesophagus, thoracic aorta, thoracic duct, ab- sorbents, and cellular membrane of the pos- terior mediastinum, anastomosing with the bronchial, oesophageal, and some branches of the right thoracic intercostal arteries. Inferior or aortic intercostal arteries. Of the eleven intercostal spaces the two superior are mostly supplied with arteries from the superior intercostal branch of the subclavian ; and as the first aortic intercostal artery frequently supplies the third arid fourth intercostal spaces, we often meet with but eight pairs of intercostal arteries coming immediately from the aorta (jig. 78, d). The first right aortic intercostal is usually the largest of the series in consequence of giving origin to the right bronchial ; the size of the ifrter- costal arteries diminishes in general from above downwards. All the intercostal arteries arise rather from the posterior part of the aorta, those of opposite sides arising very near each other, and sometimes springing from a common trunk. At first they descend obliquely on the vertebral column, at an acute angle to the trunk of the aorta. The right intercostal arteries are longer than the left, in consequence of the position of the thoracic aorta on the left side of the spine. Each artery is lodged at first in a groove on the side of the body of each vertebra, enters the intercostal space passing behind the ganglia of the sympathetic nerve, and immediately divides into two branches, one posterior or dorsal, the other anterior or intercostal. The posterior branch passes backwards through a space above the neck of each rib and below the tran verse process of the superior of the two vertebrse, with which the head of the rib is articulated ; it gives some branches to the bodies of the ver- tebrae, and in passing the intervertebral hole it sends branches inwards to the spinal cord, which anastomose with the spinal arteries. The continuation of the vessel is distributed to the longissimus dorsi, sacro-lumbalis, and other muscles along the side of the spine, as well as to the integuments of the back. The ante- rior or proper intercostal branch is usually larger than the posterior, and traverses the intercostal space. At first it is situated be- tween the pleura and external intercostal muscle, it shortly divides into two smaller branches, a superior and an inferior, which get between the two layers of intercostal muscles. The inferior branch, usually the smaller, runs forwards along the superior border of the in- ferior rib, and passes obliquely over its surface to the periosteum covering it. The superior branch, larger than the former, enters a groove in the lower edge of the superior rib, about its angle, in company with the intercostal nerve, and passes forwards between the two layers of o 194 AORTA. intercostal muscles, towards the junction of the rib with its cartilage, where it descends from the rib towards the middle of the intercostal space, and there anastomoses with the anterior intercostal arteries sent off from the internal mammary. Besides supplying the intercostal muscles, pleura, and ribs, the intercostal arteries give several branches, which pierce the external layer of intercostal muscles, and carry blood to the muscles and integuments covering the thorax. The lower intercostalsalso send branches to the abdominal muscles, diaphragm, and quadratus lumborum, which freely anastomose with the internal mammary, epigastric, phrenic, lumbar, and circumflex iliac arteries. Anastomoses. The intercostal arteries have a chain of anastomoses with each other by communicating branches which cross the heads of the ribs. By this means the superior freely communicate with the subclavian by its inter- costal artery. Inferiorly, their anastomosis with the phrenic, circumflex ilii, and lumbar arteries, is equally free; internally they anasto- mose with the arteries of the spinal cord, and in front with the internal mammary and epi- gastric. III. Branches of the abdominal aorta. They may be divided into anterior and lateral. The anterior branches are, the inferior phrenic, cctliac, superior and inferior mesenteric. Phrenic arteries. The phrenic arteries are two in number; they arise from the aorta im- mediately after its entrance into the abdomen, generally distinct, sometimes from a common trunk, and occasionally one or both arise from the coeliac artery, or one of its branches. Each phrenic artery passes outwards in front of the crus of the diaphragm, and along the upper edge of the renal capsule of its own side. The right artery passes behind the vena cava, and the left behind the oesophagus. They run on the abdominal surface of the diaphragm, and at the posterior edge of the cordiform tendon each vessel divides into an external and an anterior branch. The external branch supplies tiie fleshy substance of the ala of the diaphragm, and sends several branches towards the external attachments of that muscle which anastomose with the lower intercostal and lumbar arteries ; while the anterior branch, coursing round the margin of the cordiform tendon, supplies the anterior part of the diaphragm, and anastomoses with its fellow of the opposite side, behind the ensiform cartilage, sending forwards branches to anastomose with the internal mammary. Minute branches are given oft by the phrenic arteries near their origins to the semilunar ganglia and renal capsules : a small twig from the right phrenic ascends along the vena cava through the diaphragm to anastomose with the comes nervi phrenici of the internal mammary. Another similar twig, given to the oesophagus by the left phrenic, while passing behind that tube, anastomoses with the middle cesophageal arteries. The ccdiac artery, called, also, caliac axis, is one of the largest and shortest of the vessels given off by the abdominal aorta. It generally arises from the aorta, between the crura of the diaphragm opposite the junction of the last dorsal and first abdominal vertebra, having the renal capsules and semilunar ganglia on either side of it, with the lobulus Spigelii to the right, the cardiac orifice of the stomach to the left, the superior border of the pancreas inferiorly, and the stomach and lesser omentum in front : it is closely embraced by branches of the solar plexus. The coeliac artery, which is often scarcely half an inch in length, immediately divides into three branches, the gastric or coronaria superior ventriculi, the hepatic, and the splenic, which constitute the tripod of Haller. Sometimes the cceliac axis gives off the phrenic and superior capsular. Coronary artery of the stomach. The coro- nary artery is the smallest of the three branches furnished by the trunk of the caliac ; it some- times arises from the aorta itself. Passing upwards, forwards, and to the left, it arrives at the cardiac orifice of the stomach, from which it proceeds forwards and to the right, following the direction of the lesser arch of the stomach until it arrives near the pylorus, where it anastomoses with the pyloric branch of the hepatic. When the coronary artery has arrived at the cardiac orifice of the stomach, it sends one or more branches upwards along the oesophagus which supply that part with blood, and anastomose with the cesophageal arteries from the thoracic aorta : it then sends branches round the cardiac orifice, which nearly encircle that part, and ramify over the great extremity of the stomach, where they anastomose with the vasa brevia of the splenic. In its course along the lesser arch of the stomach the coronary sends many branches over both surfaces of that viscus, which anastomose with each other and with the right and left gastro-epiploic. The ter- minal branch of the coronary which ends at the pylorus is sometimes called superior pyloric. Sometimes the coronary artery gives off the right hepatic immediately before reaching the cardiac orifice of the stomach. The hepatic artery passes forwards and to the right under the lobulus Spigelii to the neck of the gall-bladder. In this part of its course it gives a few twigs to the gastro-hepatic omen- tum and the inferior surface of the liver ; when it reaches the pylorus, it gives two considerable branches called the pyloric and the right gastro- epiploic. The pyloric passes from right to left along the lesser arch of the stomach, where it meets the coronary with which it anastomoses, sending several branches over the anterior and posterior surfaces of the stomach to anastomose with the right gastro-epiploic artery. The right gastro-epiploic artery, much larger than the pyloric, arises after that vessel ; it passes down- wards behind the pylorus, and arrives at the greater arch of the stomach, along which it courses from right to left and anastomoses with the left gastro-epiploic. While passing behind the pylorus, it gives several branches to the pancreas and duodenum, one of which, somewhat larger than the rest, called pancreatico- duodenalis, lies concealed between the duo- denum and head of the pancreas, and anasto- AORTA. 195 moses with the branches which the pancreas receives from the superior mesenteric. As the gastro-epiploic artery courses along the greater arch of the stomach, it gives off numerous branches, some of which ascend on the anterior and posterior surfaces of the stomach, and anastomose with the coronary and pyloric ; others descend in the anterior layer of the great omentum : some branches from these ascend in the posterior layer of this fold of membrane until they reach the arch of the colon, where they anastomose with the colic branches of the superior mesenteric. After having given off these branches, the hepatic artery ascends towards the right within the capsule of Glisson, in front of the vena porta, and to the left of the ductus com munis choledochus. Having reached the transverse fissure of the liver, it divides into the right and left hepatic arteries which enter the liver by divisions corresponding to those of the vena porta, the right branch having previously given off the cystic artery, which arises opposite the junction of the cystic and common hepatic ducts, attaches itself to the neck of the gall- bladder, and soon divides into two branches, one of which ramifies over the inferior surface of that reservoir, while the other sinks between the liver and the gall-bladder. For further particulars relating to the hepatic artery vide LIVER. The splenic is the largest of the three branches of the cueliac. Immediately after its origin it passes with numerous contortions to the left, behind the stomach and along the superior border of the pancreas to the fissure of the spleen. In this course it gives off pancreatic branches (pancreatic^ magnee et parv) go off at right angles from either side, above the place of communica- tion of the bili- ary vessels, and terminate by ramifying in the fatty masses which make a sort of epiploon (c.) This tru- ly remarkable structure is not, however, so an- omalous as might be sup- posed,especially if we regard as ccecums these kind of lateral ves- sels. For the alimentary canal presents a still more ramified condition in some crustaceans, we would cite as an example the argulus studied by Jurine;* and in another animal of the same class which M. Milne Edwards and myselff have made known under the name of Nicothoe, the intestinal canal sends out considerable lateral prolongations. In the leech, and es- pecially the Clepsina, there exist numerous co3cums. Lastly, certain minute arachnidans (acaridae) are remarkable for analogous lateral dilatations. It is to be observed that all these beings are sustained by animal juices, and the great part, for the better gorging of the same, are fixed either momentarily or during their whole life upon the body of their victim. We now come to speak of the epiploon and the fatty globules which it contains. The fat, or the substance which appears as such, is ex- tremely abundant in the bodies of insects and arachnidans. In the latter it assumes the form of granular masses or globules of various co- lours, and sometimes these are united together by a thin membrane. In the araneae the fat is especially abundant in the abdomen, of which, indeed, it determines the form. The use of this fatty apparatus cannot be mistaken, and it has been placed beyond doubt by experiment, that it supplies the place of nourishment to the animal, either when the latter passes the winter in a state of torpidity, like the hibernating ani- mals, or when in particular seasons circum- stances are not favourable for catching prey. Respiratory system. The division which has been established in the class Arachnida of Pul- monaries and Trachearies indicates that there are in these animals two very different modes of respiration. In both cases the atmosphere penetrates to the interior of the body by orifices situated on different points of the body, and called stigmata. The stigmata of the Pulmo-* nary Arachnidans, and especially those of scor- pions, are very conspicuous ; they occupy the inferior part of the abdomen, and are four in number on either side, (1, 2, 3, 4, fg. 84.) They are in the form of narrow fissures, sur- rounded as in insects with a circle of more solid substance than the rest of the integument, and to which we have given the name of pe- ritrema. In the spiders (araneae) not only do they differ in form but in number and position. Treviranus counts four pairs in the thorax above the insertion of the legs, four pairs on the upper part of the abdomen, and one pair on the lower surface ; the latter is the most constant and important, (Jig. 100, d.) The stigmata of the Tracheary Arachnidans are less easy to be distinguished, more espe- cially on account of the small size of the species constituting a part of that group. We have here carefully figured them in an Acaroid species (Ixodes Erinacei), where they are situated below the sides and on the lower part of the abdomen, (Jig. 85, a,) in shape like a spherical tubercle, (Jig. 86, a,) perforated by * Annales du Museum, torn. viii. p. 431. 1806. t Annales de.> Sciences Naturelles, first series, torn. ix. pi. 49. ARACHNIDA. 205 Fig. 84. gins of which adhere to the horny circle or peritrema of the stigma before described. We here subjoin figures copied from those of Professor Miiller of Berlin, which represent these parts in a scorpion. Fig. 87 shows one of Fig. 86. an infinite num- ber of small holes, between which in the centre we may remark a larger circular plate (6.) Each little aperture is as it were stellated at the margins (c,) by which the air penetrates the body and gets into the ... n tracheae. These trachese are ana- logous in struc- ture and posi- tion to those of insects ;they are elastic, ramify after the man- ner of vessels in the interior of the body, and penetrate to even the minutest organs. With regard to the internal respiratory organs of the Pulmonary Arachnidans they have a very different character ; presenting the ap- pearance of membranous sacs formed by la- mellae applied to one another like the leaves of a book, each of these little receptacles opens into a common cavity, the membranous mar- Ixodes Erinacel Fig. 87. Fig. 88. ddddddddd d d d the pulmonary branchiae entire, seen in profile : a is the edge by which it adheres to the circum- ference of the stigma ; b the simple membrane without folds ; c the folds or leaves. Fig. 88 shows a portion of the same pulmonary branchia laid open : a is the horny margin of the stigma, or peritrema, to which the simple membrane 6 adheres ; c the common cavity into which each of the spaces opens which are formed by the laminae. These organs resemble closely in their struc- ture the branchial laminae, and hence Trevi- ranus and Meckel compare them to branchiae. Miiller on the other hand maintains that they are lungs, because, he says, they can be dis- tended with air. The name of pulmonary branchiae, which we have given them, seems to reconcile the two contending opinions, although we believe that the distinction between lungs and gills is in itself of very slight importance when applied to articulate animals. It is, for example, quite impossible to establish such a distinction in certain crustaceans, as the Onis- cus, the Asellus, the Cymothoa, which are all provided with organs of an analogous structure, although some live in water, and others in air more or less humid. Moreover, certain crabs, as the terrestrial species called Cancer Uca y Ruricola, &c., of Linnaeus, possess branchiae which are much better adapted for respiration in air than in water. The Cancer Manas, so common on our coasts, is almost in the same case, since it passes a great part of its life out of the sea, and it is well known that lobsters and shrimps can live a long time out of water, provided that the air in which they are kept is humid. M. Milne Edwards and myself have demonstrated, by decisive experiments, the conditions in which the branchiae in these animals act as lungs. Circulating system. The function of cir- culation, which is always so intimately con- nected with that of respiration, presents, as might be supposed, two different conditions in the arachnidans. Those which breathe by means of tracheae have not an apparent circu- lation ; and in this respect they resemble in- sects : we attribute to them simply a dorsal vessel without any ramifications. Those, on the contrary, which possess branchial lungs, 205 ARACHNIDA. d 'have an apparatus for circulation pretty well developed. It consists of an elongated vessel placed immediately beneath the integument along the middle line of the dorsal aspect of the back, on which account it has received the name of dorsal vessel (jig. 89). It is kept in. its situation by small ligaments or muscles, (a a), which in insects are called alts cordis. The texture of the dorsal vessel is membranous, and pretty firm ; it contains a colourless fluid. This heart is in communication with numerous vessels, but hitherto it has not been discovered which of these terminate in, or which arise from the organ, or, in other words, it is not known by what route the blood arrives at, or proceeds from the heart. We believe that we are able to dissipate the doubts which still exist as to this subject, but before we state our opinions we shall speak of the anatomical disposition of the apparatus. Treviranus has described it vaguely in the scorpions, but has well elucidated its structure in the spiders (araneee), more par- ticularly in Club tone atrox and Tegenaria do- mestica, Fig. 89. In both these species uu- merous vessels are observed to arise from the heart, es- " pecially from its posterior part (c c.) These proceed to a ramify indefinitely, d distributing them- e selves over every organ ; and we a have no doubt e with respect to d their true arterial nature. But in ad- dition to these ves- sels there exist two o others of larger a size (d d,*) which communicate in a one direction with a the heart, in an- other, by very fine a ramifications, with the pulmonary branchiae. In Clu- bione atrox these b two vessels do not Tegenaria domestica. branches in their course, in our mind but that these vessels maintain a direct communication between the heart and respiratory organs. The subjoined figure (Jig. 89) will facilitate the understanding of these facts. It represents the heart and its appendages in the house-spider, (Tegenaria domestica,) and shows the two canals which communicate with the heart and receive the small vessels (e e ee) that come from the pul- monary branchiae. Treviranus, to whom we owe these observations, has not, however, at- tempted to explain the manner in which the circulation takes place in the arachnidans, and indeed this is to be determined by physiolo- gical experiment and riot by the dissection of the organs merely. The experiments which I give out any No doubt remains have made, in conjunction with my friend M. Milne Edwards, on the circulation of the crus- taceans, enable me to give a satisfactory and doubtless true explanation of that of the arachni- dans. The organs which exist in these animals, and we admit the precision of the anatomical facts detailed by Treviranus, are essentially the same as in the crustaceans. We find a heart, of the nature of which no one can entertain a doubt : then there are arteries proceeding from the heart and ramifying over every part of the body; lastly, the heart receives on each side vessels which bring it into communication with the respiratory organs. These latter vessels are the analogues of the branchio-cardiac vessels of crustaceans. With respect to veins, of which the latter animals are destitute, they are equally wanting in the arachnidans, and are doubtless replaced by cavities of an irregular form which exist between all the organs of the body. Tre- viranus, indeed, has remarked in the abdomen of Tegenaria domestica two small intervals which are discoverable through the integument, and in which he says the blood may be ob- served to be collected. These reservoirs are perhaps the analogues of the venous sinuses of the Crustacea. The nature of the vessels being thus deter- mined, it becomes easy to conceive how the circulation takes place in the arachnidans the blood, leaving the heart, is distributed through all the arteries to the different organs for their nutrition : this being effected, and the nutrient fluid being thereby converted into ve- nous blood, it begins to circulate through the sinuses before mentioned, and arrives by an insensible course at the pulmonary branchiae. There it is changed by contact with air into arterial blood, and returns to the heart by means of the branchio-cardiac vessels (e d} to be finally again propelled through the arteries (c.) Thus the ascertained anatomical facts, few as they are, permit us already to appreciate the mode of circulation in the arachnidans ; and we repeat that it is in every respect analogous to the circulation in the crustaceans. Nervous system. The nervous system is gangliated, as in all the articulate animals; but it presents considerable differences of dis- position in the different arachnidans : the scorpions in this respect vary much from the spiders. In the Scorpionidte we find the following structure (Jig. 90): the first ganglion, which is commonly called the brain (a), and which supplies the nerves to the parts of the mouth (6,c) is intimately blended with the nervous mass giving origin to the nerves of the legs (d). The succeeding ganglia are distinct from one an- other, and are seven in number : the Jirst three (1 2 3) are situated in the abdomen proper; they have this peculiarity, that they are united together and with the ganglion, which may be termed cerebro-thoracic, by three instead of two chords of communication (e), which is the number found in all other articulate animals; the^bwr remaining ganglions (4567) occupy the entire length of the post-abdomen, or that contracted portion of the body which is incor- ARACIINIDA. 207 Fig. 90. c b be rectly termed the tail. In the Aran- a idee the ganglions are fewer than in the Scorpionidff. : rf the first pair, or that which consti- d tutes the brain, QSg. 9 1,0,) is quite distinct from the e thoracic ; these are Jour in number (66) but have under- gone a remarkable fl degree of centrali- zation, being inti- mately connected together so as in- deed to form a mass in which all traces of junction are lost > except at 3 the sides, which have remained free and in the form of smallconoid bodies directed outwardly so as to resemble, in the aggregate, the figure of a star. From the apex of each of these small cones the nerve is given off to each leg. In the abdo- men there does not exist any ganglion, but only a double longitudinal ner- vous cord (c),which swells out at its ter- mination. From this swelling (d) a great number of nerves (ee) pass off, which are distri- buted to all the organs contained in the abdominal cavity. Organs of sense. We have no- thing particular to observe with re- spect to the smell or hearing of the arachnidans, for we are ignorant of the existence of these senses in the class, or at least of the parts of the body in which they are seated. With re- gard to taste, the choice which the arachnidans make of their food sufficiently indicates that it exists in variable degree ; the organ is situated probably at the entrance of the pharynx. With regard to touch, the delicacy of that sense is in the ratio of the tenuity of the integument; but the extremities of the legs, and more especially of the maxillary palps seem to be expressly destined to bring the individual \ *%*. into relation with sur- rounding objects. The sense of sight is the only one respecting which no doubt can exist ; particularly in the species which are the most perfect of the class, such as the spi- ders, scorpions, &c. The eyes belong to that kind which are termed simple, in op- position to those de- nominated compound, and which are found exclusively in insects and crustaceans. These simple eyes (ocelli) in arachnidans are two, four, six, or eight in number ; they are situated on the an- terior part of the body either superiorly or la- terally. With respect to size they differ not only in different spe- cies, but in the same * individual, as in the Platyscelum, (Jig. 92,) and especially in the Attus. Fig 92. In the Scorpions (Jig. 93) there are two eyes (a a) situated on the dorsal aspect of the Fig. 93. cephalo-thorax, and closely approximated to the mesial line : these are of much larger size than the minute simple eyes (b 6), which are placed on the sides and near the outer margins of the same segment. The two mesial eyes, on account of their size, have been selected by Miiller for the subject of his researches, which he published at Leipsic, and which have been translated by extract in the 17th volume of the first series of the " Annales des Sciences Natu- relles." The following are the principal re- 208 ARACHNIDA. suits of the labours of this accomplished na- turalist. He finds that each of these simple eyes is composed, 1st, of a cornea; 2dly, of a crys- talline lens; 3dly, of a vitreous body; 4thly, of a kind of chamber; 5thly, of a choroid; 6thly, of a retina. The cornea, as is shewn in jig. 94, which represents a vertical section of the eye, is smooth and con- Fig. 94. vex externally (,) its superficies pre- a senting none of those divisions which characte- rize the cornea of the compound eyes of insects. The internal sur- face is deeply concave, and in the hollow he- misphere thus formed is lodged the anterior part of the crys- talline lens. This body (6) is of a spherical figure, of a hard and transparent texture, resem- bling in these respects the crystalline lens of Fishes. Posteriorly it rests upon but does not penetrate the vitreous humour. The vitreous humour (c) is composed of a granular, soft material, is larger than the chrystalline, plano- convex anteriorly, wholly convex behind. As the crystalline lens rests upon without sinking into the vitreous humour, there remains a cir- cular channel or space filled with an aqueous humour, to which the term chamber may be appropriately given, and which may be com- pared to the posterior chamber of the eye of some of the vertebrata. The retina (e} is applied to the back part of the vitreous humour, and is in some degree an expansion of the optic nerve (g). It is lined by a choroid, or membrane saturated with a co- loured matter, or kind of pigmentum (/), which is afterwards reflected over the anterior margin of the plano-convex surface of the vitreous humour so as to form there a sort of pupil, the aperture of which exceeds the diameter of the crystalline, but is less than that of the vitreous humour. Such is the somewhat complicated structure of one of the large eyes of a scorpion, by the knowledge of which physiologists are now enabled better to understand the mode in which vision is effected in the arachnidans. Organs of secretion. We designate thus the organs that emit outwardly a matter which is sometimes liquid, and sometimes becomes con- crete by contact with the atmosphere. The position of these organs varies; in one case they occupy the anterior part of the body, in another they are observed at the opposite extre- mity. The nature and properties of the matter secreted is not less variable ; in some instances it is an irritating or poisonous liquid which the animal introduces by means of a more or less sharp pointed hook into the interior of the body to which it may be applied ; in other instances, again, it is a substance which is at first in a liquid state, but soon becomes solid in its Fig 95. passage through a sort of sieve, or, if I may be permitted the comparison, a cullender pierced with excessively minute holes. We shall treat separately of these two kinds of apparatus. Of' the apparatus for secreting the irritating or poisonous liquid. Every one knows how quickly a fly that has been bitten by a spider expires : the effect is instantaneous. It is by means of the mandibulae or forciples that the spider has inflicted the wound. These mandi- bulae are each armed with a moveable and ex- tremely sharp claw, fjig. 95, a,) near to the point of which is a minute orifice (6), from which there escapes a drop of poisonous liquid, which spreads itself over the whole wound the instant that it is inflicted. This orifice, which from its minuteness is very difficult to be perceived even with a high magnifying pow- er, communicates with a fine or narrow excretory canal (c ), situated in the interior of the -d mandible and given oft" from the true secreting organ. This gland is lodged in the inter- space of the muscles of the thorax; it is in the form of an elongated and slightly curved vesicle, the parietes of which have a singular structure. Treviranus describes it as consisting of filaments adhering together and united by a membrane so as to resemble a spirally disposed band. This structure presents, he thinks, some analogy to that of the trachea of insects. Ly- onnet, in his posthumous work, has described this part somewhat differently : he considers each little band as being composed of two sub- stances, one fleshy, which contracts upon drying, the other squamous, which is disposed like a watch-spring, or rather like Archimedes' screw, and which always remains in the same state. He supposes that these fibres, upon contracting, force the poisonous liquid into the excretory canal. Such a construction is not, however, necessary, since it may be readily conceived that that vesicle, being placed in the midst of very powerful muscles, it is sufficient that they contract in order to its compression and the consequent propulsion of the fluid contained in its interior, which probably the parietes have secreted. This apparatus appears to us to correspond, by its position, to that which is termed, in in- sects, the salivary apparatus, and in silk-worms the silk-glands : it is even possible that the poisonous fluid itself, mingling with the ani- mal juices which the spider introduces by suction into its stomach, serves to facilitate digestion. Spiders are not the only animals of their class that are provided with this kind of organs. Scorpions have also a poison-apparatus, but in a very different position. It is not placed in the mandibles, but at the posterior part of the body, in the last segment of the tail-like abdo- men. Every one is familiar with that pyrifonn ARACHNIDA. 209 dilatation which the scorpions carry at the end of the tail ; it is terminated by a little sharp hook generally curved backwards. Near its termination there may be observed, as in the mandibnlous hook of spiders, a very minute orifice, or, according to some authors, two dis- tinct lissnres. It is from this part that a lim- pid fluid, having strongly-marked poisonous qualities, exudes; and, corresponding to the fo- ramen within, there is the neck of a Tittle blad- der which is the true secretory organ. Little is known respecting its structure: according to the observations of Treviranus it is surrounded by a horny substance and provided with a muscle, which most probably has for its func- tion the compression of the vesicle and the consequent expulsion of the poison. Apparatus for secreting t lie fluid which con- cretes in the air. This apparatus is peculiar to certain arachnidans : it does not exist in the scorpions nor in many other genera ; but when present it is always situated at the posterior part of the body. The threads by which the spiders suspend themselves, and of which they spin their webs, are emitted from the extre- mity of the abdomen. There we find, in the vicinity of the anal aperture, several small appendages, which it is important not to con- found with one another, (Jig. 9t3.J Of these there are two which are small articulated hairy Fig. 96. and filiform processes (b b ; )* the others are spinnarets, or the or- gans by which the c silky threads are emit- ted. Of the latter, d four may generally be b counted, (c d.} Their structure is very re- markable ; it has been described by many anatomists, and among others by Lyonnet in his posthumous Memoirs. This patient anato- mist has discovered that the surface of each of the spinnarets is pierced by an infinite number of minute holes, from each of which there escapes as many little drops of a liquid, which, becoming dry the moment it is in contact with the air, forms so many delicate threads. Im- mediately after the filaments have passed out of the pores of the spinnaret, they unite, first together, and then with those of the neighbouring spinnarets to form a common thread ; so that the thread of the spider, as it is employed in the manufacture of the web, or such as the creature suspends itself by when hanging from one's "* Mr. Blackball, who has published some inter- esting observations on the structure and functions of spiders in the third report of the British Asso- ciation (1833), and more at length in a recent volume of the Linnaean Transactions, considers these pro- cesses to be also spinnarets. They are provided with tubes, which, arranged along the under side of the terminal joint, present the appearance of fine hairs projecting from it at right angles ; if examined, when in operation, by a powerful magnifier, the function of these tubes may be ascertained without difficulty, as the fine lines of silk proceeding from them will be distinctly perceived. Mr. B.'s observations were made on Agelena labyrinthica (Walck.) ED. VOL. I. finger, is composed of an immense number of minute filaments, perhaps many thousands, of such extreme tenuity that the eye cannot detect them, until they are all twisted together into the working thread. Lyonnet has made a still more curious observation: he detected in Tcgc- naria civilis (Walck.) a different anatomical structure of the four spinnarots. The pair which is above and a little longer than the other, presents on its surface a multitude of small perforations, (flg- 97,J the edges of which do not project, and which, therefore, Fig. 97. resemble a sieve. This structure has also been well described by Leuwenhoeck, Roe- sel, Treviranus, &,c. The other pair, shorter and lower than the preceding, differs still further by having pro- jecting or mamillary tubes independent of the perforations which also exist and are analo- gous to those above de cribed. The tubes are hollow,and perforated at the extremity (fig. 98, a). Lyonnet supposes that agglutinating threads issue from these tubes, while those which are Fig. 98. emitted from the per- forations do not poss- ess that property. We may observe, indeed, upon throwing a lit- tle dust on a spi- der's web, such as the circular one ofaranea diadema, that it ad- heres to the threads which are spirally dis- posed, but not to those that radiate from the centre to the circumference; the latter are also stronger than the others. . 99. Internally there a exists in the abdo- men of spiders a special secretory ap- paratus, which con- sists of intestiniform canals, united toge- ther, and variable in number and extent according to the species. In Clu- bione atro.r, they consist, according to Treviranus, of four vessels, two large (fig. 99, a a) and two small (b b} ; near their base, and not far from the point where they open into the spinnarets, a number of small supplementary canals (c c) maybe observed. (Fig. 96 represents the spin- narets in the same species.) Generative system. In the arachnidans the sexes are placed, as in insects, in different in- dividuals. It is not always an easy matter to distinguish outwardly the male from the female ; 210 ARACI-INIDA- but in some cases there exists a well-marked character. The greater part of the aranese of the male sex have, at the extremity of their maxillary palp, a swelling containing a compli- cated structure, which is not found in the female. Until lately this protuberance was considered, notwithstanding its anomalous po- sition, as the penis of the male; and even now this opinion is maintained by many naturalists. All observers indeed, both ancient and mo- dern, agree in stating that copulation takes place by means of this part. They have repeatedly observed the fact, and have described the pro- cess with all the details that can inspire con- fidence in their observations. Nevertheless it appears to us certain, if the anatomical facts we are about to disclose are accurate, that there is some mistake on their part, and that what they have taken for the act of copulation was in reality only a prelude to it. It is indeed true that the male spiders are distinguished from the females by the swelling at the extre- mity of the maxillary palp, and that that swel- ling presents a very complicated structure. Treviranus, Savigny, and, earlier than these, Lyonnet, have given detailed figures of it, which may be consulted with advantage: our descrip- tion will be after that of Treviranus, and from observations made on the common spider, Tc- genaria domestica. The male of this species, when arrived at the adult state, presents a considerable dilatation at the extremity of its maxillary palp (Jig. 100, ). On carefully observing this swelling, it is per- Fig. 100. ceived to arise from the penultimate joint (6), which is enlarged and spiny. The swelling it- self, or what has been termed penis, (Jig. 100 and Jig. 101, a,) is a con- cave body from which a membranous, vesi- cular, and glandiform body (c) protrudes, ter- minated by several horny pieces (d), which are curved and pro- ject but slightly in this species, but ac- quire, in others, a con- siderable development, and protrude in the form of long hooks having a much greater complication of structure. Fig, 101. In order that this part should be a penis, as has been supposed, and as many naturalists still believe,itought to be perforated for the emission of the prolific liquor. Now, Treviranus is certain that it is not perforated by any foramen, and also that there does not exist in the interior of the palp any excretory duct which could have brought to this part the secre- tion of the testicles. Lastly, and this proof is still more conclusive, on examining carefully the under surface of the abdomen of a male, he discovered at its base, i. e. at the point where it is inserted into the thorax, between the aper- tures of respiration, and at the part correspond- ing to the vulvary opening of the female, two very small orifices, placed in a transverse fissure, which he ascertained to be the true outlets of the male apparatus. He found in the inte- rior of the abdomen two cylindrical dilated vessels, which he determined to be the testes. (Fig. 102, b } b.) These two organs open into two long, slender, tortuous, Fig. 102. excretory canals (c), which , terminate at the two orifices of which we have spoken (a), but without the appear- ance of any superaddition of a firm or horny part that can be compared to a penis. From this description it is certain that what has been regarded as the act of copu- lation, has been only preli- minary, and that the intro- duction of the extremity of the maxillary palp of the male into the vaginal aper- tures of the female was for the mere purpose of opening the oviducts in order that the ac- tual coitus should be effect- ed with facility and with- c out doubt instantaneously ; which explains why no ob- server has hitherto witness- ed the act.* The remarkable sexual differences which obtain in a the araneae are not found in other arachnidans. Thus in the scorpions the maxil- lary palps have a similar organization in both sexes, being terminated by pincers, both in the male and female, (jig. 84, b.) The external aperture of the male apparatus is placed behind the thorax, and manifests itself by the presence of a valve formed by two semi- circular pieces (fig. 84, c.) The internal struc- ture of these organs is but imperfectly known. Treviranus believes that he could distinguish the testicles which terminated at the extremity in a kind of horny penis. Leon Dufour has given a more detailed description of these or- gans, together with a figure which represents each testis, as being a large network of three meshes formed by cylindrical tubes. The male, like the female scorpion, presents at the inferior part of the body on either side of * Mr. Blackwall denies the accuracy of Trevi- ranus's opinion, and supports that of Lister and the older observers, as to the sexual function of the maxillary palp, founding his remarks on observa- tions made on various individuals of the genera, Epeira, Theridion, and Agelena. We must refer for the details to the memoir before quoted from the Transactions of the Linnaean Society. ED. ARACHNIDA. 211 the valve certain organs of a singular structure which are called combs, pectines, (Jig. 84, d,) on account of the disposition of a series of small appendages of which they are formed, and which are arranged on the lower surface one beside the other, like the teeth of a comb. Many speculations have been offered respecting tlu'ir uses. Many naturalists believe that they render some assistance in the act of impregna- tion. Some suppose that they are extended during progression, and prevent the abdomen of the scorpion from trailing on the ground : others, auain, regard them as hygrometrical organs, by means of which the animal judges of the humidity of the atmosphere. These are, however, all mere gratuitous hypotheses un- supported by any observation ; and the fact is that we have yet to learn the use of these pec- tinated appendages. ()/' the female generative system. It has been long known that the orifices of the gene- rative organs in female spiders are situated at the base of the abdomen. We observe on that part of the body two distinct cavities, (fg.103, a, aj which are closed by opercular pieces of Fig. 103. a more or less solid texture, and it is at this part that the oviducts terminate. In the tege- naria domestica, these oviducts (b, bj are con- tinued internally in an insensible manner with the ovaries, which consist of a kind of bags (c, c) situated on each side of the intestinal canal, and to whose parietes the ova are attach- ed in a racemose manner. In the epeira diadema the ovaries are divided by two longitudinal membranous septa, and each is again subdivided by a transverse septum. The longitudinal sep- tum has no orifice, but the transverse one is perforated. There is, therefore, no communi- cation between the principal chambers of each of these ovaries, but there is a passage from the anterior to the posterior division, and the ova which are in the former must pass into the lat- ter before being extruded. This structure ex- plains how it happens that the epeira diadema lays its eggs at two distinct periods. Another spider (theridion quadripunctatum, \A alck.) presents a very analogous organization. The female generative apparatus of scorpions has not hitherto been studied with that degree of care which it deserves ; and there is a consi- derable difference among authors with respect to this subject; it therefore requires farther ex- amination. Treviranus and Leon Dufour have described these organs as consisting of three elongated tubes ; of these, two are lateral and mutually communicate at their apices, the third is mesial and communicates with the lateral by three branches which we observe on either side. All of them, lastly, terminate at the vaginal orifice which is concealed by a more or less rounded plate, and is situated on the middle line of the body anterior to the pectines and between the coxae of the fourth pair of legs, at the same point where the penis is placed in the male (^. 84, c./ Copulation, oviposition, and development of the ova. Metamorphosis, and reproduction of the extremities. Natural observers have hitherto given but very few details respecting the man- ner in which the male spider approaches the female, in accomplishing the sexual act : and we have already observed that they have been de- ceived in considering a preliminary step as the entire process. The preliminaries are accom- panied with very curious circumstances, the account of which may be found in all the me- moirs and works which treat of the animals of this class. It will be there seen with what precaution and fear the male makes his ap- proaches to the female, who is always ready to attack and devour him, whether before or after copulation. The majority of the arachnidans deposit their eggs in great numbers. The female guards them with the utmost care, some- times carries them about with her, and always prepares a silken nest for them which is fre- quently covered with a solid exterior. Some arachnidans, as the scorpions for example, are ovo-viviparous ; the ova are developed in the interior of the body of the female who brings forth her young possessing the faculty of loco- motion ; but they rest for a certain time at- tached to the back of the mother, who guards and feeds them, and gives them a kind of edu- cation. The changes which occur in the ova of spiders (araneae) have been studied vith mv.ch care. We are indebted to M. Heroldt for highly interesting observations on this subject, published in the work entitled " Exercita- tiones de animalium vertebris carentium in ovo formatione," folio, Marburg, 1824, from which an extract is given in the Annales des Sciences Naturelles, first series, vol. xiii. p. 250. From the importance of these re- searches we here present an analysis of them. The exterior covering of the ovum is formed by a very delicate and transparent membrane, in the composition of which no pore or fibre can be distinguished on microscopical in- spection. Within this membrane there is a liquid matter in which Heroldt has distinguished several essential parts, which in relation to their functions appear to us to correspond to the vitellus, the albumen, and the cicatricula of the egg in birds. An idea of the disposi- tion and size of these parts may be formed by inspecting the subjoined figure (Jig. 104), p 2 212 ARACHNID A. Fig. 104. representing a vertical section of a fecundated ovum at the moment ofexclusion,and before any organ has been de- veloped. The vitellus or yolk (a) forms the greatest part of the contained liquid mat- ter, and the egg is almost entirely filled by it : its colour is gene- rally that of yellow ochre, and sometimes has a saffron tiiv,e. In some species the yolk is grey, white, or reddish brown; and in each case the colour of this part determines the ge- neral tint of the egg. If the yolk be consi- derably magnified, it is seen to be composed of an infinite number of minute globules of various sizes, swimming in the albumen, or surrounded by it, and resembling so many small yolks. The albumen (6) is a transparent crystalline liquid, without distinct organical parts, and consequently not presenting any globules, sur- rounding the vitellus as far as the cicatricula, and intermediate in bulk or quantity to these. If an ovum be opened, and the liquid which it contains be poured out upon glass, the albu- men is seen to surround the globules of the vitellus and cicatricula exactly as the serum of the blood envelopes the crassamentum. In the interior of the egg the albumen is situated, like the cicatricula, externally to the yolk, and fills the interspace between the yolk and the exterior membrane of the egg. It is in this interspace that the first lineaments of the embryo appear, and here the head, thorax, members, integuments, and their appendages, and all the internal organs, without excepting the intestines, are successively developed. The cicatricula or germ (c) is the smallest and most important part of the ovum. It is situated immediately beneath the exterior co- vering, and at the centre of the circumference of the egg. It is distinguished by the naked eye in the form of a little white point. If it be examined with more care, we perceive that it is of a lenticular figure, and is composed of an innumerable quantity of whitish granules. Under the microscope these granules are seen to be of a globular figure, somewhat similar in this respect to those of the yolk, but more opake, and of a smaller diameter. When segregated and diffused they present a striking analogy to the grains of pollen, but with this difference, that the pollen of vegetables is composed of vesicles filled with organic molecules, whilst each of these globules of the cicatricula must be regarded as simple. The cicatricula or perm is the centre of radiation of all the changes which take place in the ovum. All the parts which it contains seem subordinate to it, as we shall see by carefully tracing their development. A remarkable fact observed by Heroldt in the ova of some undetermined species of spiders is this, that in place of a single cicatricula, there appear to be several spread over different points of the surface of the ovum ; but these small germs rapidly coalesce into one mass, which soon assumes . 105. the ordinary form of the single cicatricula. The component parts of the ovum being known, we proceed to the metamorphoses which they undergo up to the time when the young spider breaks through the shell. First period. The im- pregnated ovum being de- posited , and the te m perature being favourable, develop- ment commences. The changes always begin at the margins of the cica- tricula, which appear to be resolved into granules,which extend into the albumen and vitellus. The centre of the germ remains the same, the only appreciable difference is the enlargement of its circumference: (A, gives the natural size of the ovum.) Second period. The germ is much larger, its margins are dispersed in numerous granules ; the centre is not yet affected by this tendency to molecular dispersion, but has undergone a notable modification. It changes its situation and begins to move towards the extremity of the ovum, leaving in the place which it for- merly occupied a train of globules; it now, to compare small things with great, bears some resemblance to a comet, the nucleus of which is represented by the centre of the germ; the tail, which is formed by the dispersion of the globules, is transparent, and the vitellus which it covers may be as distinctly seen through it as the fixed stars through the tail of a comet. Third period. The nucleus of the germ (jig- 106, a), which has contimied to change its Fig. 106. place, is arrived near the extremity of the ovum, but has not quite reached it. The tract which it has traversed is marked by an infinity of granules, which are then so much dissemi- nated that they extend al- most to the opposite extre- mity of the ovum. It is then that the kind of comet which it represents is seen at its greatest development, and with all the characters that have been indicated. The movement of the nucleus of the cicatricula authorizes the supposition that that body has not, at least at die earlier periods, a very intimate connexion with the vitellus. Fourth period. The nucleus of the germ has not gone beyond the point which it had attained, but it presents a new change. The molecules are disseminated into an infinity of granules, nothing remains of the comet but the tail, which is still more extended ; but we see then that the granules dispersed in the albumen have a tendency to reassemble at the point where the germ was originally situated. Fifth period. The germ of the ovum, which appears to be disseminated in the albumen, has undergone a very curious transformation. Its nucleus has disappeared, all its granules are decomposed into almost imperceptible mo- lecules, which, in destroying the limpidity of the albumen, have given it a clouded appear- ARACHNIDA. 213 ance, through which, however, the globules of the vitellus may be distinguished. A single point remains perfectly transparent, and this is observed at the extremity of the egg (fig. 107, ,) opposite to that which the germ occupied Fig. 107. a f ter i ts displacement. Herokltcalls this clouded a]bumencolliqnamcnt/im. Up to this period the vitellus seems not to un- dergo any change ; all that has been hitherto observed takes place in the albumen and in the circular space between the yolk and the shell. Sixth period. The colliquamentum, or clouded albumen, which was extended over the yolk so as to conceal it, is now concen- trated upon the point last occupied by the nucleus of the germ, and has assumed a pearly colour (fig. 108). Its consistence is pretty Fig. 108. solid ; it is opake, so that the globules of the yolk ~ a can no longer be distin- guished through it, al- though they are elsewhere more conspicuous on ac- count of the retreat of the clouded albumen towards this single point; from this moment the colliqua- mentum, which seems to have changed its nature, receives a new name, and is designated by Heroldt the cambium. The cambium covers more than a fourth part of the circumference of the yolk; its form is already pretty well marked, and two parts may be distinguished ;n it; one large (&), the other small (), which are separated by a kind of contraction. The form of the larger division is elliptical, and it is in its substance that the thorax, the legs, and the essential internal parts of the foetus will soon be perceived to develope themselves. The smaller division is of a rounded form, and seems, as it were, an appendage to the preceding; it is destined to give origin to the head, the or- gans of sense, and the appendages of those of mastication. So much being premised, we may call, with Heroldt, the larger division cambium thoracicum, the lesser one cambium cephalicurn. We may also, for the better comprehension of the changes which are about to succeed each other, divide the superficies of the ovum into four regions. That which contains the cambium may be called \hepectoral region, the opposite portion may be called the dorsal, and the two intermediate parts the lateral regions. We may observe that in other species of aranese where the ova are spherical, the germ is at once converted into colliqua- mentum, and then into cambium, without a change of situation. The Aranea c/iadema offers an example of this circumstance; in other re- spects there is no important difference observable. Seventh period. The two portions of the cambium, the cephalic and thoracic, have as yet presented only the appearance of an opake and homogeneous mass, but now we Fig. 109. may distinguish traces of rings, four in number on either side ; these are the rudiments of the legs. (Fig. 109, 1, 2, 3, 4.) They occupy the lateral aspects of the anterior part of the ovum ; they are also visible on the pectoral region, towards which they are prolonged in- feriorly. The extre- mity of the first leg is contiguous to that of the opposite side ; but the three others, though of greater length, yet own, but leave a triangular do not reach so lo\ interspace between them, which is filled with a cloudy and somewhat transparent matter, through which the vitelline globules are visible. This triangular space, which is subsequently to be covered by the legs, seems to give origin to the trunk and to many parts contained in the abdomen. In tracing the two portions of the cambium through the changes which they have undergone, we find that the thoracic portion is represented by the legs and their intermediate space, and that the cephalic por- tion is anterior to this. The alterations of the latter part are not less remarkable ; instead of being rounded anteriorly it is truncated, and we may perceive a ring at the sides, which is not divided on the inferior middle line of the body, and which represents the maxillary palps (6). One may even distinguish, as if through a cloud, the rudiments of the mandibles. It is probable that all the parts which appertain to the head, as the eyes, the mandibular hooks, and the maxillae, have their limits well defined from this period. With respect to the head, (ct) it is neatly separated from the chest ; and this fact it is of importance to dwell on, since in all the full-grown spiders the conflu- ence of the two parts is most intimate, and their original separation only indicated by a groove of greater or less depth. The ovum, also, now presents some other new appearances; these are a kind of furrows or arched folds (c c), which are seen on the vitellus behind the legs ; and which deserve attention, since they indicate the formation of the common teguments of the foetus. And we must here observe thaf the parts which are already de- veloped have an intimate connection with the vitellus. Thus if an ovum be opened with all the precautions requisite for so delicate an operation, and if the matter of it be extended on a piece of glass, we see that the parts formed in the cambium preserve their general figure, and that the internal layer of the mucous and whitish matter of which it consists is in intimate communication with the vitellus. It is implanted upon the yolk just as fungi and other parasitic plants are attached to the trunk of a tree: the yolk, then, is subservient to the nutrition of the most exterior parts of the body. Eighth period. The exterior parts which are developed in the cambium, viz. the feet, the mandibles, and the head, are more neatly de- fined. The ovum (Jig. 110) now presents a 214 ARAGHNIDA. Fig. 110. very important pecu- liarity, but which was in some measure in- dicated in the pre- ceding period. Its size is slightly di- minished anteriorly, and the vitellus con- sequently is divided * e into two portions. The smaller and an- terior part (a) is rea- dily distinguishable from the dorsal part of the foetus, and occupies the place which sub- sequently becomes that of the corslet; M. Heroldt consequently terms it the thoracic re- gion. The other part is the abdominal region, which is very conspicuous, occupies more than one-half the bulk of the ovum, and seems to constitute the grpatest portion of the abdomen. If the inferior surface of the abdominal region be examined, there will be seen, in addition to a srx>t which ornaments that part, some addi- tional oblique and curved folds, which indicate the formation of the integuments ; another and a more important change has now taken place on the middle line of the superior surface; viz. an obscure straight band (b) which commences at the thoracic-abdominal constriction, and reaches to the extremity of the ovum, becoming gradually narrower in that direction. This band, which does not give off lateral processes in any part of its course, is to be considered as the rudiment of the heart or dorsal vessel. The fluid which it doubtless contains in its interior is motionless. Heroldt thinks that the forma- tion of the fluid is anterior to that of the parietes in which it is enclosed : he also be- lieves that it is the albumen which gives origin to the circulatory apparatus, and further attri- butes to it the origin of all the integuments. These are, doubtless, important questions to solve, but as they are the result of speculation rather than direct observation, we have deemed it proper to omit the theories by which they are supported, and confine ourselves to a simple enunciation of the facts The eyes (d) are now distinguishable. Ninth period. The ovum presents a more sensible diminution anteriorly, and is more dis- tinctly divisible into two parts. The anterior and narrow portion constitutes the smaller ex- tremity, and includes the head, the thorax, and their appendages ; the other portion, which is spherical and of much larger size, constitutes the greater extremity and corresponds to the abdomen. At the same time that these modi- fications take place the ovum becomes slightly elongated, and all the parts which can be dis- tinguished therein have proceeded towards their perfection. The legs now present slight traces of a division into joints, and they have increased so far in length that they cover almost the whole of the lower surface of the thorax. Tenth period. The small extremity, which is still more elongated, is now found to be dis- tinguished from the large one by a true conr striction, dividing the ovum into the parts de- nominated in the perfect spider ' thorax' and * abdomen.' The visible parts of the thorax are the mandibles, the palpi, and the legs ; these latter appendages are folded upon the chest, and have grown so long as to cross the middle line of the body; they are locked in the interspaces of each other, like the fingers when the hands are clasped together. The abdomen presents nothing remarkable, except the elon- gated opake streak which exists along the middle of the inferior surface from the feet to the termi- nation of the abdomen, and which was already visible at the preceding periods. (Fig. 110, e.) Heroldt imagines this streak to be an indication of the development of the internal parts of the abdomen, viz. the intestinal canal, the secreting vessels of the web, and the genital organs, &c. In proportion as the foetus increases, the ex- ternal membrane or covering of the egg is ap- plied more exactly to its body, and seems to represent an exterior skin, of which the young spider soon divests itself, almost in the same manner as the caterpillar sheds the skin in which it is enveloped. Eleventh period. By the progressive in- crease of the foetus the membrane of the egg becomes so much stretched, and is applied so exactly to the surface of the body of the animal that the different parts can be distinctly seen through it, like the nymph or chrysalis of certain coleopterous insects. The essential parts of the thorax are the head and the feet. The head is of a white colour, and is surmounted by eight brown streaks ; the legs, which are also white, are closely applied to the chest, with their extre- mities alternating with each other. One may dis- tinguish in each a hip,a thigh, a leg, and a tarsus. The articulations of the palps and mandibles are also visible through the general envelope of the egg. The inferior streak of the abdomen is much more extended, and seems to be divi- ded into two parts, one large and elliptical in figure, the other small and rounded ; the latter corresponds to the anal aperture; at this last stage of the development, the foetus or the im- prisoned young spider, as it may be called, gives no sign of motion. Exclusion or hatching of the spider. At length the spider bursts the egg by tearing through the exterior membrane. De-Geer* has described this phenomenon. The outer mem- brane or pellicle of the ovum becomes fissured along the corslet, and the spider protrudes by this aperture, first the head, the mandibles, the thorax, and abdomen, after which there remains the more difficult operation of extracting the legs and maxillary palps from that part of the outer membrane with which these parts are, as it were, enveloped. This is at length effected, though slowly, by alternately dilating and con- tracting the body and legs, upon which the animal is liberated, and capable of progression. In proportion as the parts are disengaged from the pellicle, it is pushed towards the extremity of the legs, and is reduced to a little white bag which is all that remains. Sometimes the pel- licle is found still slightly adherent to the ab- * Mem. sur Ics Insectes, t. vii. p 195. ARACIINIDA. 215 domen, but the spider soon entirely frees itself from it. This is the mode in which the young spiders of every species disembarrass themselves of the egg-covering, and the operation is analo- gous to that of moulting. This is, however, only the first birth: all the parts of the spider, the head, the jaws, the le^s, the abdomen, are still enveloped by a membrane which furnishes to each a sort of sheath. The spider is embar- rassed in all its movements ; it changes its situation with apparent pain, and is unable to construct a web and seize its prey : it seems in- deed to be stupified and indisposed to action. To this end, and in order to be fit for locomo- tion, it is necessary that it should free itself of this other covering ; and it is only then that it can be said to see the light. This last operation, or as it may be termed the first moult, takes place after a period, varying according to the de- grees of atmospheric heat and moisture. Some- times it is observed within the first week, at ethers it is not effected before the end of several weeks. In every instance the moult takes place in the woolly nest or general envelope of all the eggs, and the young spider does not quit this common nest, except in fine weather, generally in the months of May and June. Before arriving at the adult state the spider changes its skin many times, and even after that period it is still subject to moults, which occur every year in the spring, and after the exclusion of the eggs. Up to the present time it has been admitted that the Arachnidans, from the moment of their exclusion to their adult state, undergo no metamorphosis, but are subject only to the moultings of which we have just spoken. This circumstance has even been em- ployed by zoologists as a character distinguish- ing the arachnidans from the class of insects, which generally undergo metamorphoses in pas- sing through the conditions of the larva and chrysalis. The observation holds good for the greater part of the Arachnidans, but there are many of this class, which, in passing to their adult condition, undergo changes which cannot but be compared with the metamorphoses of insects. Such, for example, are many of the acaridff, upon which M. Duges has recently fixed the attention of naturalists.* We cannot conclude the present article, without briefly noticing a very curious phy- siological phenomenon which has been ob- served in the Arachnidans, and which has long been noticed in the class Crustacea : we allude to the faculty which these animals possess of reproducing their limbs when these have been accidentally lost. This property, which belongs to the spiders, (aranetf,) was generally doubted, until a distinguished natu- ralist, M. Lepelletier, published the result of his experiments ; the fact is of too much im- portance in science not to be dwelt upon with some detail. Spiders which have lost a limb, according to this observer,! are always found * See his interesting Memoir in the Annales des Sciences, Nouv. Scrie, torn i. and ii., 1834. t See Bulletin de la Socicte Philomathique. Paris, Avril, 1813. to have lost it entirely, that is, the femur, tibia, and tarsus, are all wanting. A portion of a leg is never found detached at one of its joints, nor bro- ken off between two joints, nor the femur remuin- inj, adherent to the body by itself,or with the tibia, the rest of the leg being lost. If by accident a spider should be met with in any of these con- ditions, it is either dying or dead. But M. Lepelletier remarks that those which have lost one or more entire legs, are not less lively on that account. To explain these circumstances our author commenced a series of experiments on spiders, in the year 1792, with the following results: The smallest wound in the thorax or abdo- men of a spider is mortal, and that in a very short time, on account of the loss of the internal nutrient fluid, which cannot be staunched. If a leg of a spider be cut off with a sharp instrument either at one of its joints, or in the interval of two, leaving a part of the limb ad- hering to the body, the spider appears to suffer considerably ; it endeavours to tear off the rest of the leg ; if it succeeds, it again acquires its powers of moving, and the hemorrhage soon ceases ; in the contrary case it perishes in twenty-four hours. The luxation of one of the joints, or the frac- ture of the femur or tibia in the middle are equally mortal, if the spider does not soon dis- embarrass itself of the leg which has received the injury. It is necessary here to make a remark upon the anatomy of the legs of spiders and crusta- ceans ; they have the first joint short, which connects the leg to the thorax; M. Lepelletier calls this the haunch, coxa. If a spider be seized by the extremity of one of its legs, and is left at liberty to make its efforts to escape, the leg will be separated from the body at the junction of the femur with the coxa ; and the same thing takes place when the body of the spider is held fast, and the leg is pulled off. In both these cases the spider seems not to suffer pain ; it experiences only a very little loss of the internal fluid, and does not die in consequence ; it spins, seizes its prey, and oviposits in the or- dinary manner. The preceding facts are applicable to all spiders, (aranei/ OtUUtomotU. No part of the natural history of any disease can be more interesting than that which has reference to its causes, whether predisposing and remote, or immediately exciting. Cer- tainly, when an aneurism has been formed, a knowledge of the circumstances that occa- sioned it will not be very useful in contributing to its removal, although it may often assist in forming a prognosis as to the result of an operation : yet if it can be made available in tin; prevention of the disease, it must prove of no inconsiderable value. It is admitted that aneurism frequently appears suddenly as the result of a blow, a strain, or some violent exer- tion, the patient being conscious of something having torn or given way within him. With still greater frequency it occurs without any such consciousness on the part of the sufferer, and persons have borne this formidable disease about them for months, and even for years, not only without being themselves aware of its existence, but, if situated internally, without its being recognized by their professional at- tendants ;* and it often happens that a patient complains of the crookening of the fingers or the numbness of the foot, unmindful of the tumour under the clavicle or in the popliteal space. Without denying that an artery, in a perfectly healthy condition, can become the seat of aneurism, because there are too many facts apparently in support of such an opinion, it may be remarked that if such was generally or even frequently the case, the disease ought to be much more common amongst the labouring poor, and also that it should prevail amongst some particular trades. These considerations lead to a belief, that previous to the occurrence of spontaneous aneurism, the artery has under- gone some change predisposing to it, although it may not be so easy to point out the nature of that change, or the causes that lead to its production. It is observed that aneurism is of far less frequent occurrence in woman than in man ; a comparison between the numbers of internal cases proving this fact in a remarkable manner, and in cases of external aneurism still more so. It is very rare to meet w r ith a popliteal aneu- rism in a female. Certainly, the more labo- rious habits and constant exposure to accident in the one sex may in some respects serve to account for this circumstance, but to those who know that in many places women are obliged to undergo at least as much hardship and fatigue, the explanation will be far from satisfactory. Again, it has been stated that certain pursuits of life predispose to aneurism, inasmuch as it prevails amongst coachmen and postilions, but there never has been even a plausible reason offered to explain this greater * A very curious case of this description is related in the Dublin Hospital Reports, vol. v. p. 167. liability of particular callings. It cannot be the bent positions of the limbs of such per- sons, because many other classes, studious persons for instance, maintain similar postures for a longer time and with greater frequency, yet is not aneurism common amongst them. Neither will the sudden stretching of the limb by pressing the foot against the stirrup or foot- board in managing the horses throw any light upon the subject, for it is found by experiment that no force will rupture a healthy artery short of what would also tear asunder the ligaments of the adjacent joints. Allowing, therefore, the accuracy and truth of these observations, their explanation is still to be sought for. Some have supposed that old age, and the deposit of earthy material which is formed in the arteries at that period, are predisposing causes of aneurism ; yet, if this was the case, the disease should be very prevalent indeed among those advanced in life, whereas it is in reality almost as rare as in infancy or early youth. Of fifteen cases of large aneurism operated on, only two had exceeded the age of forty years, the average of all being but thirty-one and a half ; and if a larger number of cases (inclusive of the internal forms of the disease) were collected and compared, it would probably be shewn to be considerably less. With respect to the earthy deposit alluded 1o, it is found between the fibrous and internal coats closely adhering to the latter, from which it can scarcely be separated : it is disposed in thin laminae or plates of different sizes, the largest being seldom greater than a spangle, and these earthy spots are distinct and separate, not running into or connected with each other, and never encircling the vessel with an un- interrupted bony ring. They are supposed to render an artery friable and brittle, and there- fore to predispose to aneurism, and have been considered by some to be the products of arterial inflammation. Unfortunately the origin and progress of this earthy degeneration have not yet been satisfactorily traced. Scarpa* seems to regard it as arising from the same cause that produces the steatomatous deposit, and states that it cannot be said to be proper to old age, as it is sometimes met with in patients who are not much advanced in life. I have seen these earthy depositions in the aorta of a female not twenty -five years of age, which was also highly inflamed and covered with spots of soft steatomatous deposit, but still that is far from proof of its being the product of active inflammation, or of its rendering the artery weak or disposed to aneurism. Of any number of subjects above the age of sixty brought into a dissecting-room, three- fourths will be found with this earthy dege- neration in some of the arteries, yet the in- frequency of aneurism amongst old patients has been already remarked. Again, this de- posit has been seen in the sac of a true aneu- rism, a circumstance that would shew it did not greatly interfere with the distensibility of the arterial tunics or render them more friable, * On Aneurism, page 90. ARTERY, PATHOLOGICAL CONDITIONS OF. 232 and, lastly, a large and important vessel in this condition has been tied without its being crushed or broken down short, and being fol- lowed by consecutive haemorrhage. From these observations some reasonable doubt may be entertained of these deposits being the result of inflammation, more particularly as, at the period of life alluded to, there is an evident disposition to the formation of earthy deposits in many structures and organs as well as in the arteries. When a large aneurism runs its course with great rapidity, an opportunity is frequently afforded of observing a condition of the vessel most favourable to the production of the dis- ease, and which therefore may be considered as one of its direct or immediate causes. The vessel in this case, on being slit up, exhibits its internal lining membrane less smooth and polished than in its natural state ; its colour is changed to a deep roseate carmine, and it sepa- rates "from the subjacent fibrous coat with com- parative facility. This latter structure is also changed in colour, but not to so bright a red as the other. Between these coats, but more closely attached to the internal, (for they peel off with it,) are numerous specks of a soft steatomatous material of a white or pale grey colour, presenting, on a superficial inspection, somewhat of the appearance of the calcareous deposit already spoken of. An artery in this condition has lost more or less of its elastic properties; it is distended, and its calibre increased equally around. As the arteries are always full, the impulse of every new wave of blood driven on the greater quantity con- tained within the distended vessel increases its apparent pulsation, for it is in the diastole or expanded condition of the artery that the pulse is felt. This loss of elasticity must obviously weaken the vessel, and cause it to be less re- sisting: a fact that can be proved by expe- riment after death, when an artery so circum- stanced will be found to yield and tear under a distending force that would have little effect on it if in health, and will explain how an apparently trifling exertion may produce aneu- rism in one man, whilst numbers of others exposed to similar or even greater violence escape safe and unharmed. If arteritis can be justly considered as an immediate cause of aneurism, it follows that any thing tending to produce this condition of the vessel will predispose to the disease. An investigation of the natural history of this affection would, therefore, prove equally useful and interesting, but as yet a sufficient num- ber of facts have not been collected from which any useful practical induction can be drawn. The experience of an individual cannot be sufficient to establish a fixed and general posi- tion, but may be valuable if it induces others to a similar line of investigation, in order to its being verified or contradicted ; and from a minute attention to the previous history of several cases, I have frequently been able to connect intemperance, particularly in the use of spirituous liquors and repeated or ill-con- conducted courses of mercury, with the pro- duction of arteritis. How far these can explain the comparative infrequency of the disease in females and its prevalence amongst men sub- ject to exposure, and too often of reckless and dissolute habits, must be determined by future observation ; but, in corroboration of the latter part of this opinion, it may be remarked, that few old persons are subjected to a course of mercury that do not perish shortly after by the bursting of a bloodvessel, of apoplexy, or haemoptoe most frequently. When arteritis has proceeded to the extent of producing these steatomatous deposits, if aneurism is not inevitable, it is certainly very likely to ensue. In some instances the loss of elasticity is so great as to cause all the coats of the vessel to yield and become distended into the sac of a true aneurism : in others, (and far more frequently) the process of ulce- ration commences, the lining membrane cover- ing one of these spots first becoming soft, then exhibiting a distinct ulcer which proceeds from within, eroding the middle coat either through its entire thickness to the cellular, which is then easily distended into the aneu- rismal sac ; or so far as that it shall be likely to give way and tear under a trifling shock, even under the impulse of the circulation. In the pathological collection of the medical school of Park-street, Dublin, there are pre- parations exhibiting these forms of aneurism and the different stages of dilatation, of soft' ening, and of ulceration in the most satisfactory manner. Circumscribed false aneurism. When a person experiences a sensation as if something had given way or been torn within his limb, or even without such previous warning, per- ceives a small hard, pulsating tumour situated somewhere immediately on the course of a large or leading artery, it is to be suspected that an aneurism has formed. And' this suspicion is confirmed, if the tumour becomes larger or smaller, according to the diastole or systole of the artery, or is diminished by pressure, or almost disappears if the patient should happen to faint. If pressure be applied on the trunk of the artery between the tumour and the heart, its pulsation ceases, its size is sensibly diminished, and it becomes soft and flaccid; if on the farther or distal side of the tumour, its size is increased, and its throbbing rendered far more evident. The pulsation is said to become more faint in proportion to the growth of the tumour, and this, though generally true, is not so universally, for this symptom will presently be found to be influenced by a num- ber of circumstances, such as the blood within the sac being fluid or coagulated, the situation and depth of the tumour within the limb, and the coverings of fascia it may possess. In most instances there is a peculiar whizzing sound, plainly perceptible on applying the ear or a stethoscope to the tumour, termed by the French the " bruit de soufflet;" but its pre- sence or absence is by no means pathogno- monic, for it may be artificially produced by pressure on the trunk of any large artery. On examining a circumscribed aneurism ARTERY, PATHOLOGICAL CONDITIONS OF. after death or the removal of the limb, the artery should, if possible, be always slit up on the side opposite to that from which the tumour springs. The appearances of inflam- mation will probably depend on whether the ;HU urism be recent or of lung standing, and obviously on whether it has been the result of accident or disease. Also, if it be recent, the aperture leading into the sac is generally well defined, circular, and circumscribed, its edges remarkably thin and fine : if, on the contrary, it is old, the aperture is large, smooth, and so even as to present an appearance as if the lining membrane had been prolonged from the artery into the sac. On cutting into the sac some fluid blood is usually found, and always a quantity in a state of coagulation. Besides, there is always more or less of fibrine, the remains of former coagula deposited in irre- gular lamina?, and varying in colour from a pale red or grey. The most external layers are closely fastened to the internal wall of the sac by means of large depositions of flaky lymph, from which, however, they can be separated by careful washing or maceration. This lymph thickens the walls of the sac, and imparts to them considerable firmness and resistance. The sac, itself, is most generally of an oval form, but to this there are some exceptions, amongst which the occasional oc- currence of a dissecting aneurism is the most curious. This happens when the internal and middle coats having ulcerated or given way, the blood insinuates itself between the fibrous and cellular coats, detaching them from each other to a considerable extent, whence the dis- ease has derived its name.* Such is an outline of the appearances on dissection, but they will avail little in explaining the nature of aneu- rism, unless combined and compared with the phenomena of the disease during life. And, in the first instance, it must be recol- lected that the tumour is pulsatile, a quality that proves the entrance of a quantity of fluid blood, arid its return back again into the artery by the resistance or reaction of the sac. It was this circumstance that principally led Fer- nelius to believe and to teach that aneurism consisted in a dilatation of all the coats of the artery, inasmuch as he could not understand how pulsation occurred if the tumour did not possess an elastic covering, and moreover imagined that if the blood was driven into a sac otherwise constituted, it must of neces- sity remain there and become coagulated. It is, however, unnecessary now to discuss the question as to whether the sac of an aneurism possesses elasticity or not, when it is daily observed that any tumour (an enlarged gland for instance) situated on an artery, and re- ceiving an impulse from the heart, may com- municate the sensation of pulsation, provided the skin and other elastic tissues covering it are sound. Nay, farther, it may be remarked that the pulsation of an artery, even with its elastic coat uninjured, is much more apparent * See Dissections of Aneurism, by John Shekel- ton, Dub. Uosp. Rep. vol. iii. 233 than real, and when felt ab externo, is greatly influenced by the skin and its other coverings. It is a fact too well known to every operating surgeon to be for a moment controverted, that an artery when exposed exhibits nothing like the force of pulsation that it did before the skin was divided ; sometimes it is difficult to ascertain it satisfactorily at all. The late Pro- fessor Todd has strongly pointed out this circumstance in his case of axillary aneurism, published in the third volume of the Dublin Hospital Reports, where he says, " For some time I could not be convinced that the feebly pulsating vessel, to which the point of my finger was applied, was really an artery of such magnitude as the subclavian ;" and similar observations could be adduced, if necessary, from other sources. It is of little consequence, then, whether the aneurismal sac possesses an elastic covering- proper to itself or not, the resistance of the external structures being sufficient to explain the phenomenon of pulsation, and the impor- tance of the integrity of these structures in the progress and termination of the case is ex- tremely interesting. If even a small quantity of blood was thrown at each pulsation of the heart into a yielding, unresisting bag, it must of necessity remain there, and in a very short space of time the accumulation would be enormous; but if there is a re-acting force capable of returning a portion of this blood and restoring it to the circulation, the accumula- tion and consequent growth of the tumour will be measured by the quantity of blood thus left behind. The volume of blood sent into an aneurismal sac must be proportioned to the aperture through which it has to pass, while the actual quantity lost must depend not so much on this as on the non-resistance of it and its coverings, and their incapability of return- ing the fluid back into the circulation. Hence the growth of external aneurisms is in general rapid or slow according as they have existed a greater or less length of time ; for in old aneu- risms the aperture into the sac is generally large, and the elasticity of the external coverings is weakened by over-distension. The pathology of aneurism arranges itself under two distinct orders, one having relation to the open and bleeding artery, the other con- sequent on the haemorrhage being internal. This latter circumstance is interesting to the surgeon, because the presence of the blood in the limb, the position it occupies, and the pressure exercised by it on the adjacent structures and organs, very often form the most prominent and important features of the disease, and nearly as frequently cause the destruction of the patient as the bursting and bleeding of the tumour. But the consideration of this part of the sub- ject does not immediately belong to the patho- logy of the arterial system, to which these re- marks are more particularly directed. To re- turn, then, to the open or ruptured artery. The condition of the vessel is scarcely different from that of one wounded by a knife. It is a bleeding artery, and the same principle that is applicable to haemorrhage under any other 234 ARTERY, PATHOLOGICAL CONDITIONS OF. circumstances is also available here, for if a wound of this species of vessel cannot heal whilst its calibre remains open, neither can an aneurism be cured until the artery from which it springs is completely obliterated at the spot where the aperture into the sac exists. The complete closure of the vessel is to be accom- plished by placing its opposite walls in contact and under the influence of such pressure as will occasion inflammation and the effusion of coagulating lymph, a pressure that can be applied either ab externo by means of com- press and bandage, or from within, by placing the blood in the sac in a condition that will admit of its perfect and complete coagulation. Pressure on the tumour, if it could be ex- actly applied and firmly maintained, ought to succeed, and, in truth, has often been success- ful, particularly when the disease is consequent on a wound; but there are so many difficulties to be surmounted and dangers to be encoun- tered in its use, that few entertain much confi- dence in it, and perhaps it never would be resorted to but from a dread of consecutive haemorrhage after a ligature. A bandage, if applied with sufficient firmness to operate with rapidity, occasions such excruciating pain that it can scarcely be endured ; and if loosely, it is liable to slip ; and if even it does finally work a cure, the progress of the case is so protracted that many patients become wearied with the trial. Again, the large trunks of arteries throughout the extremities are generally accom- panied by nerves and veins in such close apposition with them, that a compress can scarcely be applied to one without interfering with the other; and instances have occurred of dreadful mischief having been occasioned by interruption of the venous circulation in such cases, even in the course of one night. Finally, pressure has very frequently caused the rupture of the sac, and the aneurism, from being cir- cumscribed, has suddenly become diffused ; and if there was no other source of apprehension but the possibility of this latter occurrence, it should make a surgeon pause before he adopted so hazardous a mode of treatment. Pressure from within is effected by re- moving the impulse of the heart from the blood within the sac for a sufficient time to permit of the sac becoming perfectly filled with blood, and for that blood to become coagulated. This object will be accomplished by interrupt- ing the flow of blood under the impulse of the heart through the leading trunk of the vessel for a given time : in cases of small aneurisms forty-eight hours being sufficient, but the larger and older requiring a longer period. A ligature placed around the vessel between the tumour and the heart effects this purpose ; but it does more than is requisite, for it divides its in- ternal and middle coats, occasions the effusion of lymph and the obliteration of the artery there, and involves the risk of consecutive haemorrhage afterwards on its final separation. To avoid these inconveniences, the presse artere of Deschamps and a number of other con- trivances for arresting the flow of blood through an artery, and admitting of easy removal after the object has been accomplished, have been proposed and tried, but success has not been so great as to warrant their general adoption, and the operation by ligature is still very generally preferred. It may be applied either at the cardiac side of the tumour, when it acts in the manner above stated, or between the aneurism and the capillary circulation, in which case the principle of its operation is somewhat different. In the former instance, when a ligature is applied to the trunk of an artery, the supply of blood to the limb below it is interrupted for a few moments; the aneurism loses its pulsa- tion, and sinks and diminishes in size more or less according as its contents had been fluid or coagulated. Soon the blood begins to flow through the collateral branches, and enters the aneurismal sac also, but it passes into it slowly and without impetus, and no part of it is again forced back into the circulation. It coagulates and comes to press upon and close the ruptured vessel, which is soon obliterated by lymph, and in process of time becomes degenerated into little more than a ligamentous cord. A beau- tiful illustration of this entire process was seen in Mr. Crampton's case* of ligature of the com- mon iliac artery. The patient had two aneu- risms, one of very large size at the groin, the other in the popliteal space of the same limb, firmer, and of much smaller dimension. A liga- ture of catgut was placed round the common iliac, which either rotted or by some accident became detached on the sixth day : the pulsa- tion returned in the larger tumour, which soon afterwards burst, and the patient perished. The sac of the popliteal aneurism being so much smaller had time to become perfectly filled with blood, which was there coagulated and firm. The ligature had accomplished all that was necessary for it, and the cure would have been complete even although the ligature had loosened whilst the opposite was the fact with reference to the larger tumour. Sometimes, soon after the ligature has been applied, pulsation reappears in the tumour. This must always be considered as an untoward circumstance, but does not necessarily involve the failure of the operation; for it may take place under two different conditions of the parts. 1. In aneurisms of very long standing, in situations where there is a free and extensive collateral circulation, probably increased by the pressure of the tumour. In these the pulsation does not return for some time after the vessel has been tied, and is never so strong as before the operation. It may continue for several days, but gradually diminishes in force, and at last ceases. The progress of the case then resembles that of the ordinary forms of the dis- ease, except that in this the cure is much more protracted. Apparently, such was Sir A. Cooper's first successful case f of ligature of the common carotid artery, as also the case of carotid aneurism published in the fifth volume of the Dublin Hospital Reports.} It is not un- * Medico-Chirurg. Transactions, vol. xvi. t Medico-Chirurg. Transactions, vol. i. t Page 208. ARTERY, PATHOLOGICAL CONDITIONS OF. 235 likely that Mr. Turner's case of aneurism in the fore-arm, in which he secured both radial and ulnar arteries, was of a similar description also. 2. Where by an irregular distribution there exist two trunks in the limb, both con- veying blood to the aneurismal tumour. Sir C. Bell had a case of popliteal aneurism in the Middlesex Hospital, in which, just below the origin of the profunda, the femoral artery divided into two branches of nearly equal size, which ran parallel to each other until they arrived at the spot where the artery perforates the tendon of the triceps muscle, and there they united again. Only one of these was tied, and although the pulsation in the tumour ceased for a moment, yet it soon returned, and never disappeared until the patient's death, which happened a few days afterwards, from erysipelas. A preparation of a similar distribution is pre- served in the Museum of the Royal College of Surgeons in Dublin;* and it is quite clear that where such exists in an aneurismatic limb, the securing of one of the trunks could produce no benefit. It has been already stated that one of the effects of the ligature on an artery is the eventual obliteration of the entire calibre of the vessel between it and the nearest collateral branch at each side, and, therefore, it might be supposed that if it be tied immediately close beyond an aneurismal sac in such wise that no branch shall intervene between the cord and it, the whole of the canal to the next branch, in- cluding the spot where the rupture had taken place, ought to become obliterated, and the aneurism thus be cured. This is the principle that led to the performance of the operation of tying the artery at the distal side of the aneu- rism. It was (I believe) originally proposed by Delpech, and put in practice by Desault, but the termination of the case gave little en- couragement for future trials, and it fell into disuse until of late years, when it has again been tried in England, and still subsequently by Mott, in New York, but not with a success to justify its general adoption. There is but one artery in the body (the common carotid) so circumstanced as to answer the design of the operation ; and even in this, if the smallest and most trifling branch happened to intervene be- tween the aneurism and the ligature, it must defeat the principle of the operation altogether, and perhaps tend to aggravate the disease. True aneurism. Two different pathological conditions of an artery have been regarded as constituting this disease ; one in which the entire circumference of the vessel is distended, forming a tumour of an oval shape, pulsating strongly during life, and not containing coagu- lated blood : the other is where all the coats of an artery at one particular spot are dilated in such wise as to form a sac springing from the side of the vessel, and containing blood with- drawn from the circulation, and in a state of coagulation. Perhaps it would be more cor- rect to regard the former of these as a state of There is a similar preparation in the Museum of St. Bartholomew's Hospital. Eu. vessel predisposing to the formation of a false aneurism, whilst the latter, presenting during life the same phenomena, and curable on the same principles that have been already laid down, must be considered as offering truly a specimen of the disease. When in consequence of arteritis, or from any other cause, the elasticity of the arterial structure becomes impaired or weakened, a dilatation of the vessel at the spot so debilitated ought to be the result ; and this probably takes place in all arteries previous to the formation of idiopathic aneurism. But the circumstances that determine an artery to become dilated rather than to ulcerate are very obscure, for the same morbid appearances in the vessel are observed to precede both. In the eleventh number of the Dublin Journal of Medical Science there is an account of two cases of internal aneurism, one formed by ulceration of the internal and middle coats of the artery, which burst into the oesophagus; the other, evidently by dilatation, which destroyed the patient by pressure on the trachea : and in both the aorta exhibited the same appearances of inflammation and steatomatous deposit be- neath the lining membrane. The preparations are preserved in the collection of the school in Park-street, and as showing this pathological fact are extremely satisfactory. Again, it is not easy to say what dilatations should be con- sidered aneurismal or not. The aorta, in a great proportion of subjects above the age of forty, is dilated ; yet such dilatation is not regarded as an aneurism. Other arteries present a similar appearance occasionally; and a case occurred not very long since in the Meath Hospital, in which all the arteries of the inferior extremities in an aged man were dilated to more than twice their natural calibre. These vessels were found after death filled with coagulated blood, yet as the fluid seemed to circulate through them during life, and the patient never ex- perienced any inconvenience, it is difficult to admit them as specimens of true aneurism. On the other hand, nearly at the same time, a man died in another hospital who for years had a small aneurism of the femoral artery, with every observable symptom of the disease except that the growth of the tumour was un- usually slow ; and on dissection this appeared to have been a species of true aneurism, caused by an equal dilatation of the entire circum- ference of the vessel, and did not contain coa- gulated blood. It would seem, then, impos- sible to pronounce during life on the real nature of an aneurismal tumour, nor is it always easy to demonstrate it after death. In most instances of aneurism, particularly those of long standing, the edges of the aperture into the sac are smooth and even, and the lining membrane seems to be prolonged into it. The internal wall of the sac is so thickened, and all the parts so matted together and confused by depositions of lymph and fibrine, that the appearances altogether become so deceptive as almost to countenance the old opinion as to the pathology of the disease. Professor Scarpa, who principally opposed the doctrine of aneu- 236 ARTERY, PATHOLOGICAL CONDITIONS OF. rism by dilatation, was obliged to support his opinions more by argument than by facts de- monstrable by dissection ; and although later in- vestigations, particularly those of Mr. Hodgson and Mr. Guthrie, have satisfactorily proved the occasional existence of both true and false aneurism, yet it must be a favourable case and patient examination that will enable the morbid anatomist to exhibit its nature and structure without possibility of error. When cases of inflamed or diseased artery are seen, compli- cated with aneurism, and the same depositions are observed in the artery and in the sac, it proves beyond doubt the identity of structure in both. Thus, if an aorta be found studded over with specks of a soft steatomatous deposit situated between its internal and middle coats, and if on one side of it an aneurism is placed, in the sac of which, throughout its entire ex- tent, the same appearances and the same de- posit are observed, it follows that the same structures must exist in both, and that one is a prolongation of the other. One of the cases already noticed as being a true aneurism, that destroyed the patient by pressure on the trachea, exhibited such evidence of its nature : and a similar one, but still more satisfactory, occurred in the person of a gentleman, who died some years since. This patient had laboured under some anomalous cerebral symptoms, and on inspecting the brain a small aneurismal tumour was seen at the bifurcation of the basilar artery, in the sac of which were found the same kind of earthy depositions that pervaded all the arteries of the body the same so generally observed in the arteries of aged persons. These examples are sufficient to prove that aneurism by dilatation may exist, and perhaps its occur- rence in the aorta and larger vessels is more frequent than has been supposed. During the past spring two opportunities occurred of examining into the nature and condition of aneurism, both in its early stage and long after it had been apparently cured by operation. They were, probably, both ex- amples of what has been termed true aneu- rism, although unquestionably all the coats of the artery were not engaged : and as the mor- bid appearances have not been hitherto de- scribed, it may be useful to take notice of them here. A man was admitted into the Meath Hos- pital, with popliteal aneurism in each ham : one of these had existed for several weeks ; the other was of very recent occurrence. The limb in which the older and larger one was situated was first made the subject of opera- tion, the femoral artery was tied, but the patient died on the sixteenth day afterwards, of venous inflammation, the ligature on the vessel still remaining firm and undetached. On examining the aneurismal tumour exter- nally it appeared of an oval shape, and to have been formed by the gradual expansion of all the coats of the vessel. On being cut into, however, it was found that the lining mem- brane was wanting throughout the entire extent of the sac, the edge of it terminating sharply and abruptly, above and below, at the junc- tions of the tumour with the more healthy parts of the vessel, and being as accurately defined as if made by a careful dissection. The fibrous coat was. evidently continued into the tumour, which seemed to be formed of an expansion of it and the cellular. It was, moreover, otherwise diseased, being thickened, greatly softened and thrown into irregalar rugae or folds, the interstices between which were filled with coagula of lymph or fibrine. As the sac of this aneurism was in a state of sup- puration, the deficiency of the lining mem- brane was attributed to that circumstance until the other aneurism came to be examined when the same appearances were observed. The second tumour was not so large as a walnut and evidently formed by the gradual expan- sion of the fibrous coat, for the abrupt ter- minations of the lining membrane at the healthy extremities of the artery were still more exactly defined. The other case is even more interesting, be- cause it exhibits a cure of aneurism after operation in a manner that has not been de- scribed, the principle of which it is not easy to understand. A man was operated on by Mr. Collis, in the Meath Hospital for popliteal aneurism on the 22d of January, 1831. The ligature came away on the seventeenth day, the tumour diminished ; in short, every thing went on well and the patient left the hospital per- fectly cured. So far as the aneurism was con- cerned, he remained healthy and free from inconvenience until his death, which hap- pened in March 1835, from fever, and such an opportunity for pathological inquiry was not neglected. The tumour which had been origi- nally of the size of a turkey's egg, was found to have diminished to little more than that of a walnut : externally it felt hard and as if com- pletely solidified : on being cut into, however, neither artery nor sac was obliterated, the latter being occupied by a coagulum of a deep red colour, through the centre of which was a canal of a sufficient size to allow the blood from the portion of the artery above the tumour to flow freely into that below it. It seemed as if the current of blood through the sac had never been interrupted, the only effect of the former ligature having been the removal of the im- pulse of the heart from it. This aneurism appeared to have been a true one, so far as the fibrous and cellular coats were concerned, but the fact could not be so satisfactorily demon- strated as to admit of no dispute ; however, the absence of the lining membrane and its sharp and abrupt terminations at the healthy portions of the vessel were sufficiently ob- vious. If it be difficult to demonstrate the nature and constitution of the small and recent aneu- rism, it becomes impossible when the tumour has attained to a considerable size. It seems probable, however, that the arterial structures will not long endure this state of unnatural distension, and they either ulcerate or tear in their internal and middle coats. A mixed aneurism will thus be formed, having its sac at first composed of all the structures of the artery, ARTERY, PATHOLOGICAL CONDITIONS OF. and subsequently in the largest portion of its circumference, of the cellular coat alone. The long continuance and gradual increase of some aneurisms, as contrasted with their sudden and rapid growth afterwards, have been explained on this supposition. Diffused aneurism. An aneurism is termed diffused when the blood, removed from the circulation, is not confined within a pouch or sac, and therefore passes in every direction throughout the cellular tissue of the limb. This may be occasioned by the rupture or ulceration of an aneurismal sac, but far more frequently by some violence applied to the artery itself in such a manner as to open its cellular as well as its other coats. Thus a spicula of a fractured bone, or a pointed sequestrum, in coming from a necrosed limb, may produce the disease ; but the most common examples that fall under a surgeon's observation are furnished by awkward or ignorant persons in their at- tempts to perform the operation of phlebotomy. In the latter case there is an external wound communicating with the injured vessel, and then it also presents a familiar illustration of traumatic aneurism. When the blood is thus diffused throughout the cellular tissue, there is always the greatest danger ; not so much from the loss of a large quantity to the circulation as from the rapidity with which a limb so circumstanced runs into a gangrene, a rapidity so great that the mor- tification either is not or seems not to be pre- ceded by inflammation, and its occurrence is often the first notice a surgeon receives of the extent and nature of the accident. When the injured artery lies deep and is covered by a dense and resisting fascia (as in the instance of the posterior tibial artery being ruptured by a blow), it may bleed for some time without affording any indication beyond the pain and tension complained of by the patient, and a slight tumefaction of the limb. When, how- ever, the fascia has yielded or sloughed and per- mitted a more extended diffusion of the blood, the part becomes swollen, glassy, and cedema- tous, pale if the blood did not occupy the cellular tissue underneath, but of a livid colour, like that of a bruise, if it does. The joints in the neighbourhood are kept flexed, and any attempt at motion gives intolerable pain. In a very short space of time circumscribed spots of gangrene appear, which, on separating, per- mit masses of very dark coagula to protrude, accompanied by an oozing, or perhaps, a flow of arterial blood, under which a patient will very soon sink. And it may be, the real nature of the case has not been suspected until this blood has made its appearance. Doubtless, if a diffused aneurism has been occasioned by a wound, the rush of blood at the moment, its colour, and the difficulty of controlling the hae- morrhage will point out what has happened ; or if there had been a circumscribed aneurism that on a sudden lost its defined character while the limb began to enlarge above and below it, there would be good grounds for suspicion ; but in any other case it is so difficult to sepa- rate the pain and tension and the other symp- 237 toms from those which might naturally super- vene on a severe injury, that the appearance of a tendency to gangrene is too often the first circumstance to create alarm. There are many symptoms in which the diffused aneurism differs from the circumscribed, that render the diagnosis of the former particularly diffi- cult. It has been already stated that the " bruit de soufflet" is, even when present, not a pathognomonic symptom, and if the vessel lies deep it is not to be heard at all. Pulsation of the tumour, the most satisfactory symptom of an aneurism, is generally absent, and when otherwise, is very weak, fluctuating, and indis- tinct. To those who reflect that the effused blood is thrown out amongst inelastic and unresisting structures, that no portion of it is returned to the circulation, but that it lies a coagulated mass amongst the surrounding cellular tissue, the absence of these symptoms will not require explanation. Traumatic aneurism. But if, as very fre- quently happens, the accident that caused the aneurism has also created an external wound communicating with the injured vessel, and permitting the escape of a portion of the blood through it, although still a diffused aneurism, the leading circumstances of the case are essentially altered. This is the form of disease termed by the French traumatic aneurism, the name having reference not so much to the fact of its having been produced by violence, as to the co-existence with it of a solution of continuity in the skin and other structures external to the vessel. Thus, although an aneurism may be caused by the prick of a lancet in the bend of the arm, or by a bayonet- wound in the thigh, yet if the external wound is healed, or, being unhealed, if it is so oblique or devious that the blood flowing from the artery does not escape from the limb, it may not be called traumatic, whilst a common pop- liteal aneurism that had arisen spontaneously, if it is accidentally opened, assumes the cha- racter just designated. The chief peculiarity of this case, then, is the external wound, and if it be conceded that it is the resistance of the unyielding structures that presses the coagu- lum against the vessel, and thus accomplishes the cure of those forms of aneurism already described, it will be seen that a material part of the process must be deficient, and, therefore, that the principles applicable to the former cannot be made available here. In order to the proper understanding of this part of the subject, it will be necessary to take a familiar case for illustration. A person in attempting to open a vein in the arm strikes his lancet into the artery, and is, perhaps, unconscious of the extent of the mischief he has occasioned. The arm is tied up, but it swells and becomes intolerably painful. When the bandage is removed, the wound is found not to have united, and a coagulum is pro- bably seen plugging it up, which loosens occa- sionally and allows the escape of a considerable quantity of red and florid blood. In the meantime the diffusion throughout the limb is extending in every direction, and the hsemor- 238 ARTERY, PATHOLOGICAL CONDITIONS OF. rhages from the external aperture are more frequent. If this case is treated by ligature at a distance from the situation of the aneu- rism, although the patient may appear relieved at the moment, that relief is but delusive. The blood may coagulate, but being unsupported by any external resistance, it cannot make suf- ficient pressure on the orifice of the bleeding vessel. Fresh blood is carried round by the collateral circulation, and as it constantly oozes from the punctured artery, it disturbs the coagu- lum in the neighbourhood, and bursts out into new and repeated haemorrhages until the sur- geon is obliged to end where he ought to have begun, by cutting down (if he has still the opportunity) directly on the injured part of the vessel, and tying it above and below the aper- ture. The great difference between the trau- matic aneurism and the other forms of the dis- ease is, that in it the haemorrhage is external as well as internal, and that the coagulum within the limb being unsupported may press out- wards through the wound more freely than inwards upon the vessel. The coagulum, therefore, is not available in the cure, and the treatment must have reference to the wounded artery alone. If the radial artery was opened arid bleeding freely from the ex- ternal orifice, few surgeons would think of taking up the brachial high in the arm, know- ing that the inosculating branches would still supply abundance of blood to the wound, and although the pathology of traumatic aneu- rism is somewhat different, inasmuch as a portion of the blood lost still regains within the limb, yet the principle of treatment is unchanged. It may be objected that in very many in- stances of traumatic aneurism success has at- tended the application of a ligature on a dis- tant part of the artery ; but every one of these cases will require to be accurately examined before the treatment here laid down can be impeached. The definition of traumatic aneu- rism must be borne in mind, and that it im- plies not only the existence of a wound, but of one through which coagulated blood may pro- trude and fluid blood may trickle. The only case in which such practice could succeed is, where, after the ligature had been tied, a suffi- cient degree of pressure ab externo could be maintained to lay the opposite sides of the wounded artery together, and produce sufficient inflammation to procure its complete oblitera- tion, in short that it shall effect that which the resistance of the skin and fascia and other superincumbent structures would have accomplished in a limb less injured. Such pressure as this must occasion intolerable suf- fering; and experience has proved, in nume- rous instances, how little reliance can be placed on it. Secondary hemorrhage. Hitherto the ap- plication of a ligature has been noticed only as a curative process, its advantages have been discussed, and the manner in which it may be supposed to operate explained ; but it has been also stated that " the ligature is in itself not infrequently a cause of great and fearful mis- chief," and as the consideration of the different cases that might require the operation has been just concluded, perhaps this may be a fit op- portunity for examining into the nature of these unfavourable cases. Secondary or consecutive haemorrhage occurs, as its name implies, at some period subsequent to the application of the ligature, and the blood flows from the place where the vessel has been tied. In many instances the patient has a kind of presenti- ment of that which is about to happen, and becomes restless, uneasy, and agitated ; in other instances there is not the slightest warn- ing, and the first notification of the mischief is the appearance of the dressings soaked in blood. In general it has been stated that it is on the separation of the ligature that this bleeding takes place, but this is not the fact, for com- monly it happens whilst the cord is fixed and firm, and three or four days before its fall ought to be expected. The longer the ligature remains, provided no nerve or fascia had been included with the vessel, the safer the patient is, and it must be rare to meet with secondary hae- morrhage after the cord has become detached and been quietly withdrawn. It is remarkable that the blood comes from the inferior portion of the artery; it wells up abundantly from the bottom of the wound, and never flows with a gush or per saltum ; it is easily restrained by pressure on the bleeding orifice ; and if such pressure is accurately applied, and can be maintained during a very few days, the cure is permanent, and the patient would be safe but for a number of collateral circumstances, which, however important in the management of the case, form, properly speaking, no portion of the pathology of arteries. Various causes have been assigned as pro- ducing secondary haemorrhage, the chief of which is the too extensive detachment of the vessel from its surrounding connexions during the operation, an opinion that I cannot think is borne out by observation. If it is supposed that this dissection of an artery is injurious by depriving it of its vascularity, and diminishing its supply of nutrient blood, the result should be analo- gous if not exactly like that which takes place when the vessel is deprived of its cellular coat from any other cause, that is, a slough should form on it, on the separation of which the haemorrhage should occur violently and with a gush. An illustration of this is familiarly observed in the phagedenic ulceration of buboes in the groin, where the artery for a time appears to resist the destructive process, and lies de- nuded like a white cord at the bottom of the sore ; but one or more black spots form upon it, which are really specks of mortification, on the detachment of which the bleeding commences with awful violence. Perhaps consecutive haemorrhage does occasionally occur from the burrowing of an abscess along the coats of an artery, an example of which is on record in Mott's case of ligature of the innominata, in which the bleeding occurred ten days after its removal, was so violent from the first as to be with much difficulty restrained, and de- stroyed the patient on the day but one after- ARTERY, PATHOLOGICAL CONDITIONS OF. wiirds. But it may be observed that the phe- nomena attendant on these cases are different from those already described as characteristic of the common forms of the accident that they usually occur at a later period, even long after the separation of the ligature might have inspired confidence in the result, and they are evidently more hopeless, for neither pressure nor ligature can here be of the slightest avail. Farther, to appeal to experience, the best and surest foundation of every scientific principle, is it not a matter of daily observation that this much-dreaded insulation of the artery can have but little effect on the ultimate termination of the case, as operations performed in this respect in the most bungling and clumsy man- ner occasionally end well, whilst the utmost caution in not exposing more of the artery than will barely permit the passage of the ligature cannot ensure the patient from secondary hae- morrhage ? When the bleeding is occasioned by any defect in the operation, such as tying the cord too loosely, including adjacent structures, &cc. it usually appears so early as from the third to the fifth day after the operation, and there is another form of early consecutive haemorrhage that occurs in consequence of the artery itself being inflamed or otherwise diseased at the time of the operation. An example of this is too often met, when, as a means of controlling con- secutive haemorrhage, a fresh ligature has been tied on the trunk somewhere higher up or nearer to the heart. It has been remarked by Dupuytren, that an artery under such circum- stances is in a most unfavourable condition for an operation ; it is surrounded by cellular tissue in a state of inflammation, in which it par- ticipates ; its coats are rendered so brittle that they break down immediately under the liga- ture, and the haemorrhage returns in a few hours.* It is worthy of remark that in this case also the bleeding comes from the orifice of the vessel below the ligature; indeed, in all cases of divided artery, whether by a cutting instrument or by a cord, the remedial process seems to be different in the two fragments, being far more perfect in the upper. On this point the statements of Mr. Guthrie are most valuable because founded on extensive ob- servation, and he remarks in the case of an artery, the bleeding from which had ceased of itself, that if it recurs it is more likely to proceed from the lower than the upper portion. This latter fact is the more important as it bears upon another supposed cause of secondary haemorrhage, namely, the state of tension in which an artery inclosed in a ligature is ne- cessarily placed. Many years ago it occurred to Mr. Aber- nethy that, " as large arteries do not ulcerate when they are tied upon the surface of a stump after amputation, it would be right to tie them in cases of aneurism as nearly as possible in the same manner and under the same circum- stances." It is familiarly known that he re- commended for this purpose the application * Le9ons Orales, torn. iv. p. 573. 239 of two ligatures with the division of the artery between them ; and he argues that the divided portions would be like the large vessels on the surface of the stump in possession of all their surrounding connexions, whilst they are left in a lax state in consequence of their division. But the cases after all are not analogous, be- cause in the stump there is no inferior portion of vessel from which it has been seen the chief cause of apprehension arises it has been cut away, and only the superior remains, from which it is rare to meet with haemorrhage under ordinary circumstances. In Mr. Aber- nethy's operation it is only the upper division of the vessel that bears analogy with the artery of the stump, and the insufficiency of the removal of the tension in preventing haemor- rhage from the inferior is proved, first, by the fact that consecutive haemorrhage occurs in cases that have been thus treated proportion- ally as often as in others ; and, secondly, by Mr. Guthrie's observation that in the case of a wound there is no tension : the artery has been fairly divided, and its surrounding con- nexions are undisturbed ; yet the bleeding, having ceased spontaneously, or, in other words, having been controlled by the power of nature alone, may recur, and when it does the blood flows from the lower orifice. Others have believed that the accidental position of a collateral branch near to the ligature might be a cause of consecutive haemorrhage by interfering with the formation of the internal coagulum. I have already stated that 4he importance attached to this coagulum was greater than it deserved ; and it will be only necessary here to add, that I have tied the common carotid artery within an eighth of an inch of its origin from the inno- minata without the slightest ill consequence from that circumstance. It has been pretty generally believed that in those cases which have ended favourably, a mild, healthy, and mitigated process of inflammation had been established which terminated in the effusion of lymph and the obliteration of the vessel, whilst in the unfavourable the inflam- mation was more violent and ran into ulce- ration. Nothing is more familiar than to hear of the ulceration of an artery in connexion with and as the cause of secondary haemor- rhage, yet the existence of such ulceration is very questionable. Arteries are not prone to ulcerate. It has been shewn.that in the midst of phagedenic destruction, the artery escapes for a length of time, and when it is attacked, it is rather by mortification: and the appear- ance of arteries traversing in safety the cavities of tubercular abscesses in the lungs, where they have lain for weeks or months bathed in purulent matter, should make us hesitate in speaking so boldly of ulceration in these struc- tures. The fact, as observed on dissection, appears to be quite otherwise, and the haemor- rhage to be occasioned not by a hyper-activity of inflammation tending to ulceration, but by an absence or failure of the process altogether. As persons, the subjects of consecutive hae- morrhage, seldom die (at least in this country) ARTERY, PATHOLOGICAL CONDITIONS OF. 240 of actual loss of blood, it is not easy to pro- cure a dissection which can satisfactorily shew the condition of the vessel at the moment it begins to bleed, and no subsequent examination can be relied on, because the pressure or other means used to stop the bleeding may in the course of a very few days alter the appearances completely. I have availed myself of every opportunity that occurred, and state the results, not with the presumptive hope of being able to establish any general principle, but to excite others to inform themselves on every case fa- vourable to the further prosecution of the in- quiry, and, perhaps, in some respects to justify the opinions I have formed. It is worthy of re- mark, that secondary haemorrhage occurs much more frequently in the arteries of the lower than of the superior extremities or of the neck, and all the specimens I have examined were of the femoral that had been tied from half an inch to an inch and half below the profunda. In all, the portion of the artery above the ligature gave indications of inflammation extending nearly as high as the common iliac ; the lining membrane more or less vascular ; the portion of the vessel between the ligature and profunda of its natural size or slightly diminished ; its cavity occupied by the remains of a coagu- lum. Above that point the calibre of the trunk was evidently increased, and the texture of its coats less resisting. The inferior por- tion resembled a vessel simply cut across, its calibre diminished, its internal coat dis- coloured, its divided edge smooth and even, not rough, jagged, or irregular, as would pro- bably be the case if it had been the seat of ulceration. When a ligature is tied tightly round an artery, every thing included within its noose is killed, but this is only a very small ring of the cellular coat, the internal and middle being as completely divided as if it had been done with a knife. When the absorbents have de- tached the connection of this ring with the remainder of the cellular coat, there is nothing (so far as the vessel is concerned) to retain it farther, nor is it of use in preventing haemor- rhage : it might be withdrawn, only that being entangled in lymph or granulations from the adjacent parts, such a proceeding would dis- turb the divided vessel before the curative process was complete. This process is in some instances, perhaps, never attempted in the inferior portion, although such a deviation from the usual course is probably not frequent ; when it does happen, the cure is more tedious and longer of accomplishment, and when inter- terrupted prematurely, of course it is from this portion that the blood is poured out. Whatever the process is by which the ex- tremities of the two segments are closed, it is certainly not the same in both. This fact I was enabled to verify in one of the cases al- ready alluded to, namely, that of the man who died on the sixteenth day after the operation for popliteal aneurism, and whilst the ligature still remained undetached from the artery. The vessel was carefully removed from the body, and on being slit up, the lining mem- brane of the portion at the cardiac, side of the ligature was of a pale yellow cftlour and nearly of its natural appearance, with the exception of one or two broad spots of a very li^ht pink colour. A large coagulum extended upwards from the seat of the ligature, the base of which was attached to the lymph situated there. The ligature was still firm, but on attempting to tear it away, the lower portion of the vessel easily separated from it, leaving it still fixed firmly on the upper section : a circumstance which explained a fact I had frequently wit- nessed, that of secondary haemorrhage occur- ring before the final separation of the cord. Below the spot where it had been tied the vessel appeared to be of a deep pink colour approaching to carmine, the seat of which colouring matter was in the cellular tissue between the fibrous and internal coats. This cellular substance seemed to be hypertrophied and largely congested with blood, whilst it caused the lining membrane to be thrown into transverse rugae or folds. On pulling off this membrane, it was pale, transparent, and colour- less devoid of any proper vascularity : and on looking along the slit-side of the vessel the fibrous coat and the internal membrane were seen like white lines with the congested cellu- lar tissue between them. There was not a particle of coagulum either of blood or lymph in any portion of the vessels below the liga- ture. It may be objected that in this very dissec- tion, the appearances would warrant a belief that a more active form of inflammation was present in the distal portion of the vessel, because of the deeper tint of colour and the superior thickness of the cellular tissue there observed. Such, however, was not the im- pression of those who witnessed the dissection. There was no result of inflammation visible after seventeen days, neither adhesion, nor sup- puration, nor ulceration : there was merely a congested condition of the part a condition not found in other structures or situations to lead to any of the usual products of inflam- mation. An artery, the coats of which have been divided by a ligature, is subject to the same conditions as if it had been severed with a knife : its cavity must be obliterated from the wounded spot to the next collateral branch above and below. Now, the constitutional causes that can delay or impede this oblite- ration, if any, are not sufficiently known ; but it is obvious that any local interference may (as in a case of open haemorrhage) prove sin- gularly perilous. During the first few days, whilst the continuity of the cellular coat is still unbroken, there is no cause for apprehen- sion; but afterwards, any irregularity of diet, any excitement of the circulation, any unwary motion, any injudicious meddling with the ligature; in short, any one circumstance that can interfere with or disturb the operations of nature within the part before they are perfect and complete, will have a much more intimate connexion with the production of secondary haemorrhage than any of the causes hitherto ARTERY, PATHOLOGICAL CONDITIONS OF. advanced. Hence it is, that the bleeding occurs some two or three days earlier than the period at which the ligature naturally separates and comes from the wound. When the bleeding has commenced, it is a case of haemorrhage from an open wound, and must be managed on similar principles, that is, pressure to a sufficient extent must be applied directly on the orifice of the vessel. I have never seen a second ligature applied on the mouth of the vessel, either in consequence of the difficulty of finding the artery in a wound swollen and matted up with lymph and gra- nulations, or from an apprehension of the ex- istence of such a diseased condition of its coats as would cause it again to break down under the cord. But I have frequently witnessed the effective operation of direct pressure, par- ticularly in three cases, which occurred within the last few months, two of which were patients in the Meath Hospital, and all of whom recovered. In the application of this pressure, however, much caution is required. It should not be greater than is absolutely necessary to command the haemorrhage; it ought to be maintained by means of some me- chanical contrivance, and be independent of all bandages which are liable to stretch, to loosen, or to slip, and it should be removed the very moment this can be done with safety. If the bleeding has been perfectly restrained during three or four days, it is probable it never will return. The sequelae of secondary haemor- rhage ought always to have been regarded as more important and more perilous than the bleeding itself. I have invariably found the wound to become the seat of unhealthy sup- puration : very frequently abscesses form in different parts of the limb, and occasionally gangrene supervenes. It is sometimes diffi- cult to connect any of these occurrences with a lesion of any structure within the limb ; but too frequently the mischief can be evidently traced to the pressure being directed on the vein, and being either too forcible or too long continued. Having thus, however imperfectly, sketched the pathology of the arterial system in con- nexion with the use of the ligature, it will be necessary to revert to other forms of disease, which have hitherto been postponed, in order to permit the introduction of the subject of secondary haemorrhage, and that the practical arrangement of aneurism and its consequences, both fortunate and otherwise, might be as un- interrupted as possible. Aneurismal varix. In the year 1761, Dr. William Hunter* directed the attention of the profession to a disease that had not been before observed, one not indeed very formidable in its consequences, but exceedingly curious as to its exciting cause and subsequent progress. When an artery and vein lying in close con- tact are transfixed by a cutting instrument in such a manner that the aperture in one shall exactly correspond with that of the other ; and * Medical Observations and Inquiries, vol. i. and ii. VOL. i. 241 when subsequent inflammation has so glued and fastened these apertures together, that, whilst a mutual transmission of blood between the vessels is freely permitted, not a drop will be allowed to escape in any other direction, a disease is formed, to which the discoverer gave the name of aneurismal varix. All and each of these several conditions are absolutely indispensable, and there are so many chances of their not being fulfilled in a case of wounded artery, that the infrequency of the disease may be easily explained. It does, however, occasionally occur, and for obvious reasons will most generally be found in the arm as a consequence of phlebotomy. Soon after the infliction of the injury that has been the cause of the disease, a small tumefaction is observed in the vein; its ap- pearance is irregular and knotted, but it is soft, yielding, and disappears on pressure. On laying the finger on it, a peculiar thrilling sen- sation is perceptible, and on applying the ear, a whizzing noise is heard, very much re- sembling that occasioned by a fly inclosed in a small paper bag. These phenomena dis- appear on either current of blood being in- terrupted by pressure on the artery above or on the vein below : at the same time that the tumour subsides a little, (though it soon regains its original size) and the peculiar noise is no longer heard. If the disease is allowed to advance uninterruptedly, the calibre of the artery above the point of communication be- comes enlarged, but it is diminished below : the vein also enlarges chiefly in the direction of the current of its blood, rarely in the opposite, and then but very slowly. Another interesting circumstance is, that the peculiar thrill is heard and felt all over the dilated portion of the vein, at a distance from, as well as in the immediate neighbourhood of, the point of communication between the two vessels. It seldom produces any inconvenience that can- not be remedied by the use of a moderately tight bandage, and if thus managed in time never requires a severer treatment. From the circumstance of pressure, either on the artery or vein, diminishing the size of the tumour and removing the thrilling sen- sation it imparted, it may be fairly inferred that both these phenomena are produced by the meeting of the two currents of blood, and their mutual resistance to the escape of either from its proper vessel. And further, it is ob- vious that if the disease should by any chance prove troublesome or alarming to the patient, its growth might be checked and its progress altogether stopped by permanently obliterating the canal of either the artery above or the vein below : but no operation that a surgeon would be justified in undertaking can remove the tumour, inasmuch as the blood still will con- tinue to flow into and through the enlarged vein. The dangers of secondary haemorrhage after an artery is tied, or of venous inflam- mation if the other vessel is tampered with, ought to inculcate the greatest caution, and it may be easily understood why in such cases Dr. Hunter thought it advisable not to interfere. B 242 ARTERY, PATHOLOGICAL CONDITIONS OF. This disease must, in the great majority of instances, be the result of accident, and its probable situation has been already pointed out, but it is also possible that it may appear as an idiopathic affection without any previous violence. Some years since a young female applied at the Meath Hospital as an out- patient, in whom aneurismal varices existed between every artery and vein in the body that lay in a state of approximation to each other. In the neck, in several parts of the arms, the thighs, &c. the peculiar thrill and sound were remarkably distinct and plain. She did not seem to experience much uneasiness, nor could any probable exciting cause be assigned for such a singular form of disease. She had pre- viously suffered from syphilis and been sub- jected to irregular mercurial treatment, but it would be scarcely fair to assume as the cause of a solitary specimen of disease in one indi- vidual, influences that operate so very differ- ently on others. Varicose aneurism. When a vein and artery communicate with each other in a manner similar to that already described, excepting that an aneurismal sac formed of condensed cellular tissue and containing some coagulated blood is interposed between their orifices, the disease is termed a varicose aneurism. As this disease is generally the result of some accident in bleed- ing, as it occupies the same situation at the bend of the arm, and as the sac in that case never attains to any considerable size, it is difficult and frequently impossible to distinguish during life between the two affections: nor is the diagnosis of much importance, for as the patho- logical changes in the artery and vein, and the phenomena produced by them, are exactly the same, so will be the rationale of the treatment. Some few years since, a patient was admitted into the Charitable Infirmary with a popliteal aneurism of the size of a child's head, and with all the veins of the limb, particularly of the thigh, enormously distended so as to appear like ropes twisted and knotted under the in- teguments. In every one of these veins the peculiar thrill and sound of aneurismal varix could be distinctly perceived. The account he gave of himself was this : he had a pulsating tumour in the ham for fourteen years previ- ously, which gradually increased to its present size, until the veins began to swell, when the large tumour became stationary. He expe- rienced but little inconvenience, and said he was able to walk eleven or twelve miles a day. ; He was frequently permitted to leave the hos- \ pital, and exhibited himself to several profes- ; sional men for money. As he refused to sub- mit to any treatment, and indeed no operation i held out a prospect of much benefit, he was | soon discharged. This man (I believe) still Hives, and as he resides in a distant part of the \ country, perhaps the true pathological nature Jof a case so very interesting may never be f ascertained. Could it have been that this was { originally a case of popliteal aneurism that had burst into the popliteal vein ? The position of this vein, and its very intimate connexion with the artery, cause it to -appear to be a pan of the sac of every popliteal aneurism, and it is not difficult to conceive that the tumour might have given way in this particular situation, and a communication been thus established between the artery and vein through the medium of the aneurismal sac. It may not be unimportant to observe, that rare as these latter forms of disease are acknow- ledged to be, they are still more so in reality than is generally imagined. It often happens- that a congeries of knotted and contorted veins forms a tumour strongly resembling the aneu- rismal varix in its external characters, and im- parting similar sensations of thrill and sound. If one of these happens to occupy a situation favourable to the production of aneurismal varix,. it might easily occasion a mistake, and perhaps it would be very difficult to point out a satisfactory diagnostic. I have seen two of these tumours dissected, which during the lives of the patients were supposed to have been aneurismal varices,. in neither of which could the slightest commu- nication with any neighbouring artery be dis- covered. Aneurism by anastomosis. The d isease which was so named by John Bell, and by him first placed in the class of aneurismal tumours, has- no title to such a position, unless that it forms a reservoir of blood, and occasionally exhibits the phenomenon of pulsation. But it mate- rially differs in that the blood contained within it is fluid, is not withdrawn from the circulation, and therefore does not coagulate. The circum- stances, however, of these tumours being in- creased or diminished in size by those influ- ences which excite or depress the activity of the circulation, and of the leading trunks of the vessels supplying them having, however erroneously, been made the subjects of opera- tion for their cure, serve to connect them in some respects with the pathology of arteries, and j ustify a passing notice of the subject here. This kind of tumour has also been called the nsevus maternus or mother mark, because it so often- appears from birth or at a very early age, and its shape, colour, size, or situation is explained by the mother on the supposition of some sub- stance having been thrown at her, or from other causes of affright. It may, however, appear for the first time in more advanced life, in the form of a speck or pimple, which gradually enlarges until it constitutes a disease of a most important and sometimes dangerous nature. The external characters of aneurism by anas- tomosis are somewhat varied, and have admitted of its classification under three forms apparently distinct from each other : 1. Where the mark or stain is merely cutaneous, does not increase in size, and is never pulsatile. These marks may be of different colours, sometimes red, sometimes of a brassy yellow, or perhaps brown ; and as they occasion no inconvenience beyond the unsightliness of their size and situation, they can scarcely be considered as diseases. Indeed, if the common mole be admitted un- der this class of naevi, in many instances it seems to constitute a beauty rather than a defect. 2. Where the disease is situated in both the skin and sub-cutaneous cellular tissue. It ARTERY, PATHOLOGICAL CONDITIONS OF. appears as a patch, slightly elevated, of a red or purple colour, being generally of a brighter hue on the face or breast, and darker on those parts usually kept covered. The colour of the naevus also seems to depend on the quality of the blood with which it is altogether or prin- cipally supplied, as sometimes tumours are met with which might he termed venous aneurisms of this description, consisting evidently of veins indurated, knotted, and contorted on each other, increasing gradually, and never pul- satile; these frequently occur in different parts of the body of the same individual, and are always attended more or less with pain. The arterial nan -us is, however, most intimately connected with the present subject. It sometimes pre- sents an appearance as if irregularly granulated; more frequently is it smooth and velvety. The deep stain possesses a sharp and circumscribed edge, yet a net-work of minute vessels may be seen like an areola around it, conveying blood to nourish the tumour, and therefore forming an important part of the diseased structure. The tumour is increased in size and intensity of colour by every thing that accelerates the circu- lation by exercise, intemperance, paroxysms of passion, and even by an elevation of tem- perature, and hence the supposed marks of currants and other fruits are said to grow red and ripen at the proper season. Its feel is doughy, and communicates a sensation as if it contained a jelly. It sinks, and is diminished by pressure on its surface, but immediately the pressure is removed it recovers its former level. It may be stationary for years, but the contrary is generally observed ; its growth, however, is always irregular, being more rapid at one period than another. 3. The distinguishing charac- teristic of the third form of n&vus is its pulsa- tility. It beats synchronously with the heart and arteries. When wounded, blood of a bright red colour flows from it, often in such abundance as to occasion syncope or even more dangerous consequences. As it grows larger, the skin gradually becomes thin ; it bursts and bleeds ; masses of coagula lie upon its surface, putrefying and occasioning the most unsightly appearance and most offensive odour. This is a condition that cannot endure long, the patient soon becomes irritable and weak, and falls a victim to that irregular, ill-formed hectic which is seen in every disease accompanied by extensive haemorrhages. It is manifest that the distinctions between these latter forms of nacvi are merely artificial ; the second can be made to pulsate and to increase by heat or intem- perance, the third can often be restrained by cold, by abstinence, and other means that debilitate the circulation. The external appearances, however, yield no information as to the condition' of the parts within, or the nature of this newly-formed struc- ture; and on this subject anatomical investiga- tion affords but little satisfactory knowledge. When a nsevus is extirpated, it seems to consist of a mass of cellular tissue, collapsed and flaccid, which cannot be unravelled, and seems to bear no proportion in size to that of the 243 tumour before removal. If it be cut away close to its defined edge, and without the ex- tirpation of the zone of small vessels already described, the bleeding is frightful, and in very young children nay be fatal, evidently shewing thiil these vessels are not endowed with con- tractility, and are ;> diseased and a now fbroia- tion. If a nicvus is injected, it only ai'lbrds a swollen and unshapely mass of whatever ma- terial had boon used, and throws tio light what- ever on the rea' pathology of the disease. Here, i lion, in ihe absence of demonstration, theory and conjecture are permitted, and all that is known, or supposed to be known, is only the fruit of speculation. Ficll supposed the tumour to consist of a congeries of cells, into each of which an artery and vein opened; that these cells increased both in number and in size, with the growth of the patient, until they became immense reser- voirs of blood ; and, finally, that they became so distended as to burst and destroy life, as any other aneurism would, by u profuse discharge of blood. Gut still this explanation is defec- tive, as showing nothing of the nature of the cells themselves, or why blood poured out into them should not coagulate as it would in any other cellular structure. It remained for Du- pnytren to offer an ingenious and extremely probable hypothesis relative to these points, and he conceived the aneurism by anastomosis to be a " tissu erectile," analogous to that naturally found in many parts of the body.* In the penis of man, and in the clitoris and mamclla of woman, there is a particular structure, capable of receiving, retaining in a fluid state, and afterwards returning a given quantity of blood. These organs are provided with strong fibrous sheaths, that prevent their distension beyond a certain size, and arc fur- nished with a number of nerves that preside over the circulation through them, and deter- mine their conditions of erection and col- lapse. The abnormal " tissu erectile" consists of a cellulated structure, in itself of the same or a similar structure, but not being invested by a fibrous sheath or capsule, its growth is unrestrained, and the size to which it may attain has no limit; and as it has not a similar distribution of nerves, there is nothing to occa- sion either unwonted distension or collapse, and it is left solely under the influence of those causes that act upon the circulation. (See * The late Mr. Shekelton of Dublin injected one of these tumours with wax from a large artery in its vicinity, aud corroded away the animal matter by immersing it in a weak acid solution, by which it was shewn to consist of a congeries of vessels arranged in a retiform manner, dilated at some points and contracted at others. An able and in- teresting paper was read on this subject, and on the tortuosity of arteries generally, to the medical section of the British Association, which lately met at Dublin. The great attainments of its author (Mr. Adams) in pathological science lead us to look, not without some degree of impatience, for the full publication of the paper, of which but an imperfect report has appeared in the Dublin Medical Journal for September 1U35. ED. R 2 244 ARTICULATA. ERECTILE TISSUE.) Thus an aneurism by anastomosis is made to increase by heat, by passion, or by excess of any description, and by the removal of these, or by the application of opposite influences, its growth may be checked, or its pulsation stopped. But when once formed, it remains for ever, unless re- moved by spontaneous ulceration, by adhesive inflammation of the cells, or by operation; for although, if the general circulation be depressed, that in the tumour will be less active also, yet the structure is there still unaltered and ready to receive the blood and to exhibit all its wonted phenomena whenever the requisite sti- mulus is applied. BIBLIOGRAPHY. Cowper, on ossifications or petrefactions of the coats of arteries; Phil. Trans. 1703. Stenzel, De steatomatibus in.aorta repertis, Vitteberg, 1723 (Rec. in Hallcri Disp. ad Morb. Hist. vol. ii.) Lancisi, DC motu cordis et aneu- rysmatibus, fol. Rom. 1728. Nichols, Obs. on aneurisms ; Phil. Trans. 1728. Petit, Obs. &c. de 1'aneurysme ; Acad. des Sciences de Paris, 1736. Arnaud, Obs. on aneurisms, 8vo. Lond. 1750, and in Ej. Mem. de Chirurgie, t. i. Hunter, W. Hist, of an aneurism of the aorta, with remarks on aneurisms in general ; Med. Obs. and Inquiries, vol. i. 1755 ; Ej, Sing, observ. on particular aneu- risms, ib. vol. ii. Armiger, A letter to W. Hunter on the varicose aneurism, ib. vol. iv. White, Two letters to W. Hunter on varicose aneurism ; Med. Obs. and Inquiries, vol. iv. Monro, Cases of aneurism; Essays physical and literary, vol. iii. Faselius, Dissert, sistens morbos arteriarum, 4to. Jenae, 1757. Langswerth, Theor. Med. de arteri- arum et venar. adfectionibus, 4to. Prag. 1763. Monro, on the coats of arteries, their diseases, &c. in Edinb. Med. Ess. and Obs. vol. ii. Pohl, De ossificatione vasorum, Lips. 1774. Heekeren, De osteogenesi praeternaturali, Lugd. Batav. 1797. Charitius, De arteria crurali ossea, Vitteberg. 1798. Lauth, Scriptorum Latinorum de anevrysmatibus collectio, 4to. Strasb. 1785. Laue, De arteriarum morbis, &c. 4to. Lugd. Bat. 1787. Hunter, J. An account of his method of treating aneurism by E. Home ; Trans, of a Society for the Improvement of Med. and Chirurgical Knowledge, vol. i. and ii. 1793-1800. Abernethy, in Surg. and Physiolog. Essays, 8vo. Lond. 1793. Guerin, Mem. sur 1'anevrysme ; Journ. de la Soc. de Lyon. t. i. ; Sur la methode de J. Hunter ; Rec. Period, de la Societe de Sante de Paris, an v. t. ii. Caillot, Essai sur les anevrysmes : Theses de Paris, an vii. Ayrer, Ueberdie PulsadergeschwUlste, 8vo. Getting. 1800. Maunoir, Mem. surFanevrysme, 8vo. Genev. 1802. Briot, Sur les tumeurs formes par le Sang arteriel, 8vo. Paris, 1802. Scarpa, Sull'anevrysma, fol. Pavia, 1804 ; Anglice, by Wishart, 8vo. Edinb. 1806. Freer, Obs. on aneurism and some diseases of the arterial system, 4to. Birming. 1807. Jones on hemorrhage, Lond. 1810. Pelletan, Mem. sur les anevrysmes ; Clinique Chirurg. t. i. and ii. 8vo. Paris, 1810. Hodgson, on the diseases of arteries and veins, 8vo. Lond. 1815; translated into German, with notes, by Koberwein and Krey- sig, Hanover, 1819, and into French by Breschet, Paris, 1819; Ejus, Engravings to illustrate some of the diseases of arteries, 4to. Lond. 1815. Lucte, De depositionibus cretaceis intra cordis val- vularum arteriarumque substantiam. Marburg, 1815. Lobstein, Mem. sur les ossifications des arteres ; Mem. de la Soc. des Sciences, &c. de Strasbourg, t. i. Shehelion, Dub. Hosp. Reports, v. iii. Spangenberg, Ueber die Entziindung der arterien, in Horn's Archiv. 1804, Bd v. Meli, Storia d'una angiotide, &c. e consid. gener. intorno all'infiammaz. dei vasi sanguiferi, in Omodei Annali universal! , 1821. Dalbant, De Tarterite ou infhiin. des arteres, Theses de Paris, 1819. Barde, Observation?, &c. inflammation general, des arteres, Revue Med. Mai 1821. Montesanto, Storia di un arteritide cronica, Annali di Omodei, 1825. Locatelli, Diss. de angioitide, Paviae, 1828. Breschet, Hist, de 1'inflam. des vaissaux, Journ. de Progres. Gendrin, Hist. anat. des in- flammations, 2 torn. Paris, 1826. Dezeimerit, Memoire, &c. Aper9u rapide des decouvertes en anatomic pathologiqne, 8vo. Paris, 1829. * * * * Turner, on the sudden spontaneous obstruction of the canals of the larger arteries, and Supplement ; Transactions of the Medico-Chirurg. Soc. of Edinb. vol. iii. Syme, Case of obstruction of the arteries from an internal cause ; Edinb. Med. and Surg. Journ. vol. xxix. 1828. * * * * Manxoni, Consid. sugli anevrismi ; Mem. della Societa Ita- liana, t. xviii. Moden. 1820. Fleischer, Aneurys- matis complicati historia, 8vo. Dorpat. 1822. Doring, Quaedam circa aneurysmatumpathologiam, 8vo. Berl. 1822. Lem, Saggio sugli anevrismi in- terni, 8vo. Venez. 1822. Casamayor, Reflex, sur 1'anevrysme spontane, 8vo. Paris, 1825. Mayer, De arteriarum regeneratione, 4to. Bonn. 1823. Sch'onberg, Sul ristabilmento della circolazione nella legatura, &c. dei tronchi delle arterie, Napoli, 1826. Ebel, De natura medicatrice sicubi arteriae vulneratae et ligatae fuerint, 4to. Giessae, 1826. The papers of Lawrence and Trovers ou the ligature of arteries in the 4th, 6th, and 8th volumes of Med.-Chir. Trans. Zhuber, Neue Versuchen an Thieren und deren Resultate uber die Wiederer- zeugung der Arterien, &c. Wien. 1827. Corbin, Des anevrysmes spontanes ; Journ. Univers. t. ii. 1831. Manec, Traite de la ligature des arteres, fol. Paris, 1832. Breschet, Mem. sur les anevrysmes in Mem. de 1'Acad. Roy. de Med. t. iii. 1833. Guthrie on the diseases and injuries of arteries, 8vo. Lond. 1833. Dupuytren, Le9ons orales, t. iv. The reader should moreover consult the systematic works of Senac, Corvisart, Burns, Laennec, Kreysig, Bertin, Hope, Bouillaud, and Otto's Compend. .of pathological anatomy, by South. (W. H. Porter.) ARTICULATA (articulus, a joint,) a pri- mary division of the animal kingdom founded by Cuvier,* and characterized by him as follows : " Body jointed externally, corresponding to the divisions of the nervous system internally : a very small brain placed above the oesophagus gives off two filaments which extend along the abdomen and unite together from distance to distance by means of ganglions, which resem- ble as many small brains, from which nerves are given off. The muscular system is disposed on the inside of the rings or segments of the body so as to separate and approximate these segments; when there are articulated mem- bers, the muscles of these parts are also placed within the hard parts. The divisibility of the body, and the power which the fragments possess of retaining a kind of independent *This division was virtually established by Cuvier in his earliest work, the f< Tableau Elementaire de 1'Histoire Naturelle des Animaux/' although it was not defined with that clearness, nor its characters so fully developed as in the Regne Animal. In the " Tableau Elementaire " the second section of ' white-blooded animals,' including the Insecta and part of the Vermes of Linnaeus, corresponds pre- cisely with Lamarck's division of invertebrate animals, which he first denominated ' Articulosa/ (Hist. Nat. des Animaux sans Vertebr. torn. i. p, 454.) ARTICULATA. 245 vitality corresponds to the distribution of the nervous system into as many centres as there are corporeal segments."* With respect to the agreement between the number of segments of the body and the ganglions of the nervous sys- tem, it must be observed that in the higher crustaceans, arachnidans, and insects, the gan- glions, though originally as numerous as the segments, subsequently become concentrated by progressive development into masses which are fewer in number, and that also in some of the lowest annelidans, as the leech-tribe, the ex- ternal segments are more numerous than the internal ganglions. In many of the molluscous class two nervous cords proceed backwards from the supraoaso- phageal ganglion or brain, and are afterwards brought into communication by ganglionic masses on the ventral aspect of the body ; but in the Articulata the uniting ganglions are always confined to the mesial line of the body, are perfectly symmetrical in their arrangement, and are accompanied by a symmetrical or bila- teral form of the whole body. It is this homo- gangliate disposition of the nervous system which essentially distinguishes the Articulate from the Molluscous and other divisions of the Animal Kingdom, and it is an infallible guide to the true affinities of the classes possessing it. The Cirripeda present a striking example of this fact : these animals, on account of their inarticulate body enveloped in a fleshy mantle and protected by a multivalve shell, were for a long time classed with the mollusca : but the views of those naturalists who considered that they had closer relations to the Arti- culata, although that opinion was founded on a knowledge of their nervous system only, has since been corroborated by every additional fact which has been discovered respecting them. Latreille, in his " Families Naturelles du llegne Animal," first placed the cirripeds in the Articulate series, but being guided by their adult organization, and supposing that they were deficient in visual organs, and underwent no metamorphosis, he joined them with the an- nelidans, to form a division of Articulate ani- mals, " Elminthoida," distinct from the " Con- dylopeda" which include the insects, arach- nidans, and crustaceans, or the Articulata with jointed feet. The later researches of Mr. I. V. Thompson and Dr. Burmeisterf have proved that in the immature state the Cirripeds un- members, and as their nervous cords are sim- ple and not brought into communication by a regular series of ganglions, we prefer to leave the Rotifera and Ccelelmintha with the Entozoa and Echinodermata, as a separate and higher subdivision of Cuvier's Radiata, and thus pre- serve the Articulata as a distinct and well de- fined subkingdom, characterized by a dispersion of the nervous system in a series of ganglions, symmetrically arranged and brought into com- munication by a double nervous cord ; by an articulate or jointed structure of the body or its appendages, by the lateral position and hori- zontal movements of the jaws, when these are present, and by the presence of distinct respi- ratory organs. The subdivisions of this sub- kingdom are not founded on the modifications of any single system, but principally rest on the conditions of the sanguiferous and respira- tory organs, in connexion with exterior form, modes of locomotion and generation. I. The Cirripeds, (cirripedia, cirripeda, cir- rhopoda) ; oceanic animals called barnacles and acorn shells : they are characterized by their fixed condition, being either sessile, or attached to foreign bodies by means of a peduncle; their generation is, consequently, hermaphrodite, without the intercourse of se- parate individuals, but the male and female organs are distinctly developed in each animal. The blood is colourless and is propelled by a dorsal vasiform heart, but the venous system is diffused. The branchiae are internal. The cir- ripeds undergo metamorphoses, but are ulti- mately inclosed in an inarticulate defensive covering of shelly pieces varying in number, form, and size. II. The Annelidans, (Annelida, red-blooded worms,) are always locomotive; and, conse- quently, although hermaphrodites, they enjoy the intercourse of the sexes, and reciprocally fecun- date each other. Their blood, which is gene- rally red, like that of the vertebrate animals, circulates in a closed system of arteries and veins, which sometimes has appended to it several well-marked propulsive cavities or hearts ; they respire by means of organs some- times developed externally, sometimes remain- ing on the surface of the integument, or lodged in its interior. Their body, which is of an elongated form, and covered with a soft skin, is always divided into numerous transverse mat m me immature state the Cirripeds un- segments, of which the first, called the head, dergo repeated metamorphoses or moults ; that scarcely differs from the others, except by the presence of the mouth and of the principal organs of the senses. Many possess branchije, arranged the whole length of the body, or situ- ated at the middle ; others, which for the most part inhabit tubes, have the branchise collected at the anterior part of the body; in others, again, the respiratory organs are in the form of internal air sacs. The annelidans never possess articulated limbs, but many have, instead thereof, stiff bristles, or hooks, frequently inclosed in tubular prolongations of the integument. The other articulate classes, viz., insects, arachnidans, and crustaceans, differ from the preceding classes in the possession of arti- culated limbs, terminated by claws; and in they move freely in the water by means of setiferous articulated members, and during this period guide their wanderings by the aid of distinctly developed, though simple eyes. Besides the cirripeds the higher organized infusoria and intestinal worms have been proposed by some naturalists to be added to the articulate division of Animals : but as they are neither articulated nor possess articulate * See his celebrated memoir, " Sur un nouveau rapprochement a etablir entre les classes qui com- posent le regne animal." " Anwiles du Museum d'Histoire Naturelle, 4to, torn. xix. p. 73. t Beitnige zur Naturgeschichte tier Kaukeufuesser, 4to. Berlin, 1834. 246 ARTICULATION. connexion with the superior powers of loco- motion afforded by these appendages, the sexes are separate, and the organs of vision are well developed, and often highly complicated. Witli the exception of some genera, as the myriapoda, in which the body is divided into a number of nearly equal segments, and of the arachnida and many crustac<.a, in which the head and thorax are blended together, the body of the condylupes of Latreille is divided into three principal parts, viz., the head, which bears the antennae, the eyes, and the mouth ; the thorax, which supports the feet and the wings, when the latter are present; and the abdomen, which contains the principal viscera. These segments present different degrees of hardness in the different classes of condylopes, being most flexible in the arachnidans, firmer in the insects, and calcareous in most of the crustaceans. The origin of the insertions or articulations of the body which form so marked an external character of these animals, is as follows : The integument is composed of two layers or pellicles, viz., the epidermis and the corium, and is originally of equable consistence, and presents an uninterrupted continuity, save by some slight transverse superficial wrinkles. The epidermis subsequently becomes solidi- fied, in arachnidans and insects, by the super- addition of a peculiar substance termed chitinc, and in crustaceans by a calcareous deposition, so as to be divided into bands or rings. As the external development proceeds, these epidermic pieces are detached posteriorly from the inferior pellicle, or corium ; and the intervals of the segments remaining membranous, and preserv- ing their flexibility, yield readily to the various movements and inflections of the body. The 1 1 Id class of articulate animals or In- sects (Insccla), are either myriapod or hexapod. Most of the latter are furnished with wings, which they acquire at a certain age, after undergoing metamorphoses varying in kind and degree. In every state they respire by tracheae, or clastic vessels which receive the air by stigmata, situ- ated along the sides of the body. A dorsal vessel propels the circulating fluid, which is afterwards diffused throughout the cellular tissue of the body. They have conglomerate or compound eyes, and antennae. IV. The Arachnidans (Arachnida, Spiders, Scorpions, &c.), are octopod and apterous; of gills, and have no stigmata, or spiracles on the surface of the skin. In the Articulate sub-kingdom, as in the ver- tebrate, there may be traced one general plan of structure pervading all the classes, but with such variations in it as are, in each case, de- manded by the particular exigencies of the individual to which it is applied; but these variations are of such a nature, that a gradation of complexity or perfection may be followed through all the organic systems. With regard to locomotion, we commence with a class (the Cirripeds) as fixed and immoveable as the polypes and sponges of the Acrite sub-king- dom ; and afterwards trace a series of forms adapted first to slow and tortuous reptation ; next to swifter progression, as creeping, run- ning, or leaping ; and, lastly, to a rapid flight through aerial space. Generation, in like manner, is effected, in the lowest class, without the intercourse of separate individuals; afterwards by the reciprocal im- J)regnation of co-equal hermaphrodites, and, astly, as in the vertebrate division, by indi- viduals of distinct sexes. The perfection of the nervous system results from the approximation of many separate gan- glions into fewer masses of nervous matter. The organs of the senses also augment in number and complexity. The Articulata present, in the organs of the vital functions, as strongly marked differences as are met with in the vertebrate animals. With respect to the sanguiferous system, a gradation may be traced from a circulation in closed vessels to a diffused condition of the nutritious fluid ; and a corresponding pas- sage from the articulata which respire by means of circumscribed branchiae* to those in which indefinitely ramified trachese carry the air to all the parts of the body. The amount of respiration thus produced occasions the same effects here, as in the Vertebrate sub-kingdom, and the Insects thus constitute, as it were, the Birds of the Articulate division of animals. (Richard Owen.) ARTICULATION (in anatomy), synony- mous with joint. (Gr. aftyov. Lat. articulus, arthrosis, junctura. Fr. articulation. Germ. Articulation, Gclctik. Ital. articolo). The power of motion, to an extent however >JV-'VJ.|^lV/llk5j VVV^.Ij lilt V^tWJJWVL C*UU Cll7LC.l.^U.a . J.11C IH.IVYC1 ^-'1 iUVLlV^Mj C< / Clll \^ALV^l-ll. UVSTVW^^ they have no antennoe, and have simple eyes, limited, seems to be inseparable from our idea Their circulation is effected by a dorsal vasi- form heart which transmits arterial branches, and receives the returning blood from veins. Their organs of respiration vary, some pos- sessing true pulmonary sacs which open upon the sides of the abdomen, others receiving the air by trachese, like insects. In both cases, however, the air is respired by lateral orifices or true stigmata. V. The Crustaceans (Crustacea) have never less than ten feet; they have two compound eyes, and also antennae, which are generally four in number; their blood, which is white, is circulated by means of a muscular ventricle situated on the back. They respire by means of an animal, and in looking through the animal series we find none which do not appear to be endowed with this power whether for the pur- pose of progression, or simply of altering the po- sition or condition of some part of their bodies with respect to the others. The organic structure which is the immediate agent in this motive power (the muscular fibre), is one and the same throughout the whole chain of animals, va- riously modified according to the degree and force of the motions necessary for the particular individual. The mechanism by which this structure acts upon the different parts of the body varies considerably, and increases in complexity as the forms of the animals them- ARTICULATION. 247 selves become more complex. In the lowest grade of animals the structure is so soft and pliant that nothing more is required to produce motion than this contractile tissue, which acts in obedience to certain stimuli. But when hard parts are superaddcd to tlie structure of the animal, we then find a peculiar me- chanism to allow of the motion of these hard parts on each other without the risk of injury. It is obvious that such motion could not take place were these hard parts united in one piece. Hence we find that they are subdivided into segments, and these segments are joined to each other through the medium of some struc- ture more flexible than that of the segments themselves, or by an apparatus of such a con- struction as to admit of the motion of one segment upon the other. It is to these join- ings of different segments of an animal body that the term articulations or joints has been applied. An articulation may, therefore, be defined to be the union of any two segments of an animal body through the intervention of a structure or structures different from both. The most perfect and elaborate forms of articulations are those which are seen in ani- mals that possess a fully developed internal bony skeleton, and in none may they be studied with more advantage than in man. We propose to treat of the forms and structure of the ar- ticulations in man, and at the same time to in- quire what modes of mechanism are employed for analogous purposes in the lower classes. In the human subject and in the vertebrated ani- mals generally, we shall, indeed, have particular occasion to admire the articulations, as mira- biles commissuras, et ad stabilitatern aptas, et ad artus finiendos accommodatas, et ad mo- tum et ad omnem corporis actionem.* It will be observed that the definition here given of articulation is of the most compre- hensive nature. In most instances, in man, two parts articulated together are joined by their solid portions, which are never in immediate apposition with each other, but have some elastic structure interposed which may or may not form a bond of union ; and it is obvious that the fact of the intervening substance being, or not being also a bond of union will greatly in- fluence the extent of motion of which the joint is capable. Before inquiring into the variety of forms of joints, we shall first examine briefly the various structures which enter into their composition, and which essentially contribute to the perfection of their mechanism. These parts may be enumerated as follows, and we propose to observe the same order in treating of them: 1. Bone. 2. Cartilage. 3. Fibro-cartilage. 4. Ligament. 5. Synovial membrane. 1. Bone. The osseous or an analogous structure constitutes the fundamental portion of an articulation in all the vertebrated animals, in the mollusca, and in some of the articulated classes. In the human subject and all ver- tebrated animals we find that certain parts of * Ciccr. de Nat. Deor. 1. ii. c. 35. the bones have surfaces marked upon them in correspondence with similar surfaces on others with which they are connected, or that, as in the long bones, the extremities are expanded or enlarged, and present sur- faces which are adapted to similar surfaces on contiguous bones. In this way are formed the articular portions of the bones, and we observe that these portions present considerable varieties in their characters according to the nature of the articulation which they con- tribute to form. In fact, in examining these articular portions of the bones we cannot fail to notice the diversity of their form, so that some are adapted to each other in such a manner as evidently to favour motion, and others are so framed as to limit and restrict it. The articular surfaces in dry bones are ge- nerally characterised by a peculiar smooth- ness, indicative of the existence on them of a cartilaginous incrustation in the recent con- dition. The expansion of the extremities of the long bones on which the articular surfaces are formed is to be attributed to the accu- mulation there of a considerable quantity of the reticular texture, covered by a thin lamina of compact tissue, whereby a large surface is obtained without the inconvenient increase of weight which would necessarily result did that portion of the bone contain compact tissue to any extent. In the neigh- bourhood of the articular portions of the bones we find certain eminences, depressions, or rough- nesses, which indicate the points of attach- ment of those bonds of union by which the joints are secured and strengthened. In ge- neral it may be observed that the long bones are articulated with each other by joints which possess a considerable extent of motion; the flat bones, again, have articulations very limited in their mobility, and this is likewise the case with the irregular bones. 2. Cartilage. Pure cartilage enters into the composition of almost all joints, but more particularly of those which are very moveable, and indeed the chief purpose for which it is employed in the economy of adult animals is as an important and valuable element in these moveable joints. Articular cartilage, there- fore, constitutes a primary subdivision of this texture by systematic writers. Its hardness, its elasticity, and the limited degree of or- ganization which it possesses, peculiarly adapt it for the purposes to which it is applied in the mechanism of the articulations. Although cartilage is chiefly employed in those joints which possess considerable mo- bility, it nevertheless also exists in joints which are limited in their motions, and as it possesses peculiar characters according as it belongs to one or other of these classes of articulations, we may very conveniently subdivide it into a, cartilage of moveable articulations, or ar- ticular cartilage properly so called, or diar- throdial cartilage ; 6, cartilage of articula- tions very limited in their motions, or cartilage of sutures, or synarthrodial cartilage. Under these heads we propose to treat of articular cartilage. 248 ARTICULATION. a. Diarthrodial cartilage. The general characters of this class of articular cartilage may be best examined on the articulating ex- tremities of the long bones. Here we observe it moulded exactly to the forms of those sur- faces, insomuch that, after a little maceration, the cartilage may, by careful dissection, be removed from the bone, to which it adheres with great firmness, and will be found to ex- hibit an exact mould of the articular ex- tremity ; hence these cartilages have been called "cartilages of incrustation" This cartilage is perfectly distinct at the early periods of life from the temporary cartilage which forms the nidus of the future bone, and cannot be re- garded as a portion of that cartilage left un- ossified ; this may easily be seen by examining a vertical section of a femur or tibia at this period ; and the peculiar arrangement of the fibres of the articular cartilage, hereafter to be noticed, constitutes an additional proof that it is completely distinct from that which is after- wards transformed into bone. The physical properties and general charac- ters of this form of cartilage do not differ from those of the others ; it possesses the same pearly whiteness the same apparent homoge- neousness of structure the same elasticity the same absence of vessels carrying red blood. It is not covered by a perichondrium ; the surface towards the joint is peculiarly smooth and glis- tening, and is generally supposed to owe these properties to its being lined by a layer of the synovial sac of the joint; this point, however, has been controverted, as we shall notice in a subsequent part of the article. The first and the most complete investigation of the true anatomical construction of articular cartilage was that announced by Dr. William Hunter so long ago as 1743.* His paper still deserves the most attentive perusal, not only for the actual information it affords on its professed subject, but as a specimen of the careful and original method of observation pursued by its distinguished author. To examine the structure of articular cartilages, it is necessary to subject them to boiling or along-continued maceration .f " When an articulating cartilage is well pre- pared," says Dr. Hunter, " it feels soft, yields to the touch, but restores itself to its former equality of surface when the pressure is taken off. This surface, when viewed through a glass, appears like a piece of velvet. If we endeavour to peel the cartilage off in lamellae, we find it impracticable, but if we use a certain degree of force, it separates from the bone in small parcels, and we never find the edge of the remaining part oblique, but always perpen- dicular to the subjacent surface of the bone. If we view this edge through a glass, it appears like the edge of velvet, a mass of short and nearly parallel fibres rising from the bone, and terminating at the external surface of the carti- lage : and the bone itself is planned out into * Of the Structure and Diseases of Articular Cartilage, Phil. Trans, vol. xlii. t The articular cartilage on the patella may be selected as very favourable for this purpose. See the plate annexed to W. Hunter's paper. small circular dimples where the little bundles of the cartilaginous fibres were fixed. Thus we may compare the texture of a cartilage to the pile of velvet, its fibres rising up from the bone, as the silky threads of that rise from the woven cloth or basis. In both substances the short threads sink, and bend in waves upon being compressed, but by the power of elasti- city recover their perpendicular bearing as soon as they are no longer subjected to a compressing force. If another comparison was necessary, we might instance the flower of any corymbiferous plant, where the fiosculi and stamina represent the little bundles of cartilaginous fibres, and the calyx, upon which they are planted, bears analogy to the bone."* The total absence of vessels capable of car- rying red blood in articular cartilage is proved by the failure of even the minutest injections to pass into the cartilage, and a further confirma- tion of this opinion is derived from the fact that madder taken into the system of a young animal does not stain them. The attempts of anatomists to trace lymphatics and nerves into this structure have been equally unavailing. The design of articular cartilages, as means to break the violence of shocks, is well illus- trated by comparing the different arrangement of the cartilaginous incrustation on convex arti- cular surfaces from that on concave. In the former, we observe the layer of cartilage to be very thin at the circumference of the articular surface, its thickest portion being in the centre, while the opposite arrangement obtains on con- cave surfaces : there the thinnest portion of the cartilage is in the centre, and the layer increases in thickness as it approaches the circumference. " The articulating cartilages are most hap- pily contrived to all purposes of motion in those parts. By their uniform surface they move upon one another with ease : by their soft, smooth, and slippery surface mutual abra- sion is prevented : by their flexibility, the con- tiguous surfaces are constantly adapted to each other, and the friction diffused equally over the whole : by their elasticity, the violence of any shock, which may happen in running, jumping, &c. is broken and gradually spent; which must have been extremely pernicious, if the hard surfaces of bones had been immediately contiguous. As the course of the cartilaginous fibres appears calculated chiefly for this last advantage, to illustrate it, we need only reflect on the soft undulatory motion of coaches, which mechanics want to procure by springs, or upon the difference betwixt riding a chamber-horse and a real one. v f * Loc. cit. p. 516. t Hunter, in loco citato. Hunter's account of articular cartilage is completely confirmed by M. De Lasone in a paper in the Mem, de 1'Academie Royale des Sciences, An 1752. He describes the cartilage as " une multitude des petits filets adosses et lies les uns aux autres tous perpendiculaires an plan de 1'os, en un mot parfaitement semblables par leur structure, ou par leur position a la substance emaillee des dents, laquelle n'est composee, comme on sait, que de filets osseux, poses perpendiculaire- ment sur le corps de la dent : la comparaison est des plus exactes." . ARTICULATION. 249 b. Synarthrodial cartilage. The cartilages synarthrodial articulations are destined in some degree to act as bonds of union, as well as means of separation and for the prevention of the effects of concussion. They are simply cartilaginous laminae interposed between the osseous articular surfaces, very adherent to both, and adherent likewise by their margins to the periosteum or ligamentous expansions which may pass from one bone to another. We find instances of these cartilages in the sacro-iliac symphysis, or synchondrosis, as it has been called from the junction of the bones by carti- lages;* also in the sutures, where there are very thin cartilaginous laminae interposed be- tween the osseous margins. These laminae will be found to be triangular in their section, the thin edge or apex being internal, which, as Meckel observes, may in some degree account for the earlier obliteration of the sutures on the internal than on the external surface of the cranium. These cartilages of sutures are not strictly permanent ; they disappear with age : and according to Beclard, hold the midway, as to frequency of ossification, between permanent and temporary cartilages.f The cartilages of the ribs perform in some degree the office of articular cartilage ; they are situated between two osseous surfaces ; they form bonds of union, and their elasticity is eminently essential to the full performance of the movements of the thorax. In fishes most of the moveable articulations are provided with elastic cartilages, which serve the double purpose of forming bonds of union as well as of permitting motion by their elasticity. 3. Fibro-cartilage. This remarkable struc- ture, called by the older anatomists ligamentous cartilage or cartilaginiform ligament, is made much use of in the articulations ; and it is well adapted for a means of union, by reason of its great strength, which it owes to its ligamentous part, and of its elasticity, for which it is indebted to its cartilaginous portion. We find fibro- cartilage to be connected with the joints under three forms : a. In the form of laminae, free on both sur- faces to a greater or less extent, and lined to the same extent by the synovial membrane re- flected upon them. | These are the interarti- * No one can have failed to notice the peculiar yellow appearance of the cartilage in the sacro- iliac articulation. Does that arise from an admix- ture of the yellow elastic tissue with the pure carti- lage, by which the elasticity of the latter is in- creased ? t It is doubted by some whether these cartilagi- nous laminje can be admitted into the class of arti- cular cartilages; they being regarded as forming a nidus for the extension of the flat cranial bones, and the sutures being supposed to be useful only for this purpose, viz. to admit of the growth of these bones at their margins in a manner analogous to that of long bones at their extremities. See Soem- merring de Corp. Hum. Fab. t. i. p. 212, and Gibson on the use of sutures in the skulls of animals, Manchester Memoirs, 2d series, vol. i. t This point, however, is liable to the same objections as that of the continuity of the synovial membrane over diaithrodial articular cartilages, which will be considered in a subsequent part of the article. cular cartilages or menisci of authors. They are found in the temporo-maxillary, sterno- clavicular, and tibio-femoral articulations, some- times in the acromio-clavicular, between the bodies of the cervical vertebrae in birds, and in general in those joints where there is constant and extensive motion, and consequently where the articular surfaces are exposed to consider- able friction. The principal use of these fibro- cartilaginous laminae must unquestionably be to guaid against any bad consequences likely to arise from this continued friction ; this is particularly obvious in the sterno-clavicular articulation. To increase the depth of an arti- cular excavation is another object, as appears from the semilunar cartilages of the knee-joint; and moreover, in conjunction with the attain- ment of these two objects, to ensure in all the motions of the joint a perfect adaptation of the articular surfaces to one another, as will appear obvious to any one who carefully considers the construction of the temporo-maxillary or even of the knee-joint. It will be observed, that I do not include in the class of interarticular fibro-cartilages, the lamina which is commonly known by the name of the triangular cartilage of the wrist joint, as is done by all the systematic writers I have looked into ; for, first, it does not appear to me to be fibro-cartilaginous in its structure ; it is purely cartilaginous ; and, secondly, it is not interar- ticular, in the sense in which we here use that term, viz., as lying between two articular surfaces. This lamina seems to be merely an extension of the cartilaginous incrustation of the inferior ex- tremity of the radius, which completes the ar- ticular surface for the reception of the first row of carpal bones. The scaphoides and lunare are provided for by the radius; but as the ulna could not be brought into the composition of the wrist-joint without interfering with the motions of the inferior radio-ulnar articulation, a structure such as the triangular cartilage, was necessary one which would present a sufficient opposing surface to the articular portion of the os cuneiforme, and which would not impede or obstruct the necessary motions of the joint between the radius and ulna. In the cases of the temporo-maxillary and sterno-clavicular articulations, these fibro-carti- lages form, in general, complete septa between two portions of the joint : so that there are then two synovial sacs; but sometimes there is a per- foration in the centre of the fibro-cartilage. b. The second class of articular fibro-carti- lages consists of those which Meckel designates fibro-cartilages of circumference, or cylindrical fibro-cartilages. They form fibro-cartilaginous brims to certain articular excavations; they are triangular in their section, attached by their basis to the osseous margin of the articular cavity, and free at their apices, lined by synovial membrane on the whole of one side, and a great part of the other. They are to be found only in two joints, namely, on the margin of the acetabulum in the hip-joint, and on the edge of the glenoid cavity in the articulation of the shoulder ; in the former, this fibro-cartilage is much larger and stronger, and is evidently 250 ARTICULATION. intended to obviate the ill consequences which must have resulted from the violent application of the neck of the femur against the bony margin of the acetabulum : for, where the margin of that cavity is ligamentous, viz., at the notch on its inner side, this fibro-cartilage does not exist. c. The most remarkable and beautiful variety of this structure belongs to the third class. It consists of fibro-cartilaginous laminae, generally of considerable thickness, which intervene be- tween two bones and adhere intimately to each. Examples of it are to be found between the bodies of the vertebrae, (inter vertebral sub- stance) between the pieces of the sacrum in early life between the sacrum and coccyx, and between the pieces of the latter also, be- tween the ossa pubis at the joint called the symphysis pubis. In this class of fibro-car- tilages too, we may place that which is situ- ated between the scaphoid and lunar bones in the carpus. It is evident that these fibro-cartilages are useful, not only as very powerful bonds of union, but also as elastic cushions placed be- tween the bones to prevent the concussion which must necessarily result, did the unyield- ing bony surfaces come together with any de- gree of force. No where is this so beautifully exhibited as in that chain of bones which forms the spinal column in the mammiferous vertebrata, the strength and flexibility of which result from the fibro-cartilaginous discs, which, placed between the bodies of the ver- tebrae, are commonly called intervertebral car- tilages. As to the structure of articular fibro-cartilage, we can distinctly observe, without any process of dissection, that it is compounded of fibrous tissue as well as of cartilage. As these nbro- cartilages generally assume more or less of the circular form, we find that the fibrous tissue is most abundant towards the circumference, and that the cartilage is most manifest at the centre. In the intervertebral substance, the fibrous tissue is arranged in concentric laminae, placed vertically behind one another. Each lamina is composed of a series of interlacing fibres, which have intervals between them ; these intervals, as well as those between the laminae, are filled by cartilaginous tissue ; towards the centre the fibrous laminae diminish in number, the inter- vals become large, and at length the fibrous tissue disappears in toto ; hence the gradually diminishing density towards the centre, which characterises the intervertebral substance. In fishes, there is such a diminution of density, that the central part is fluid, but here the sur- faces of the vertebras are excavated, not plane as in the mammiferous vertebrata, and the cha- racter of the articulation is thereby materially altered. The incompressible central fluid forms a ball, round which the cup-like excavations of the vertebras play, while the fibro-cartilage at the circumference is made available in the la- teral motions of the spine. Of the three varieties of fibro-cartilage above enumerated, the menisci possess the most car- tilage in their structure, and the circumferential fibro-cartilages the greatest quantity of fibrous tissue. It may be questioned whether that peculiar structure which intervenes between the base of the skull and the condyle of the lower jaw in the whalebone whale, (baltena mysticetus) be- longs to the class of fibro-cartilages, although it seems to bear a nearer resemblance to that than to any of the other structures employed in the composition of joints. The following is Sir Everard Home's description of it.* " Be- tween the condyles of the lower jaw and the basis of the skull is interposed a thick sub- stance, made up of a network of ligamentous fibres, the interstices of which are filled with oil, so that the parts move readily on each other. The condyles have neither a smooth surface nor a cartilaginous covering, but are firmly attached to the intermediate substance, which in this animal is a substitute for the double joint met with in the quadruped, and is cer- tainly a substitute of the most simple kind." 4. Ligament. The term ligament, as it is used by systematic writers on descriptive ana- tomy, is by no means confined to portions of the " fibrous system" of Bichat, although all the articular ligaments (properly so called) be- long to that system. Weitbrecht comprehends under this term all fibrous structures in and about joints, including the fibrous sheaths of tendons, and also all membranous folds, which are in any way concerned in maintaining soft parts or viscera in proprio situ. I apprehend, however, that a better definition of articular ligament could not be given than the following, which is that of Weitbrecht, the words printed in italics being added," Ligamentum est par- ticula corporis, plerumque albicans, interdum jlava, ex fibris flexilibus, interdum elasticis, plerumque parallele concretis, in substantiam tenacem fibrosam, ruptioni fortiter resistentem, et solidam compacta, eum in finem creata ut duae pluresve partes quaa alias divulsae per se subsisterent, adunentur atque in situ respectivo determinentur."f Most of the articular liga- ments are employed to unite the bones which compose a joint ; they also will be found uniting some of the interarticular cartilages within joints, or passing from one part of a bone to another (forming the " mixed" class of liga- ments of Beclard) ; and such is the vagueness with which names are applied in descriptive anatomy, that folds of the sy no vial membrane often receive this appellation without the least title to it. Articular ligaments are divisible as regards their forms into two species, the capsular and the funicular or fascicular.J Capsular ligaments are generally cylindrical in shape, or rather barrel-shaped, being wider in the centre than at the extremes. Each ex- tremity envelopes one of the bones that enters into the formation of the joint, so that the arti- cular cavity is completely surrounded by and enclosed within the ligamentous capsule. Liga- * Comp. Anat. vol. i. p. 83. t Syndesmologia, 5. . T>__1_ -J A __ .. A. /~1 oynaesmoiogio., y t. Beclard, Anat. Gen. ARTICULATION. 251 merits of this kind are composed of fibres which are closely interwoven with each other, and they sometimes receive accessions from bundles of ligamentous fibres coming from neighbouring bony prominences (these fibres being generally called acceswri/ ligaments.) Capsular ligaments are not calculated to re- strict the extent or direction of motion be- tween the bones which they surround, and we consequently find them only in that kind of joint which admits of motion in all directions, viz. the enart/iroais or ball-and- socket joint, of which the only examples in the human subject are to be met with in the hip and shoulder. The internal or articular surface of capsular ligaments is to a. great extent lined by one lamina of the synovial membrane, which is reflected upon it from the articular portion of the most moveable of the bones which form the joint. Funicular ligaments are found in the form of rounded cords or flattened bands : they exist generally on the exterior of joints, very rarely on the interior, and always externally to the sac of the synovial membrane. They pass from bone to bone, adherent sometimes to the syno- vial membrane of the articulation, sometimes to the intervening fibro-cartilage. In ginglymoid joints they are always placed on the sides, and are called lateral liyaments ; sometimes they cross or decussate with each other, whence the appellation crucial, and sometimes a ligament of this class assumes a nearly circular course, and forms a greater or smaller portion of the circumference of a circle, the remainder of the round being completed by the bone into which the extremities of the ligament are fixed ; a ring is in this way produced within which the head, or a special process of another bone, is enclosed, as is seen to be the case particularly with the head of the radius in the superior radio-ulnar articulation, and with the processus dentatus in the j<>int between the axis and atlas : the ligament in such instances is called coronary. When a ligament is concealed in the interior of a joint, although situated exter- nally to the synovial sac, or, to speak more correctly, in the space between the articular surfaces, it is called an internal ligament, e. g. the ligamentum teres of the hip-joint, the mu- cous ligament of the knee, or the transverse ligament of the same articulation. Elastic ligament. Hitherto we have been examining ligamentous structure, one of whose most prominent characteristics is the want of elasticity ; but we now come to a kind of liga- ment which forms a most valuable constituent in the mechanism of some joints, and is emi- nently distinguished for the great elasticity which it possesses. It differs from ordinary ligament by its yellow colour, (whence the French ap- pellation tissu jaunCj) as well as by its elasti- city. We find it in the human subject most developed in the ligamenta subflava of the vertebrae. In joints, as elsewhere, this tissue is employed to restore to the position of quie- scence, parts which have been previously acted upon by muscular contraction. John Hunter fully appreciated the value and utility of this structure in supplying the place of muscle, with less expense of exertion to the economy, and assigned it a place in the arrangement of his museum.* The thyro-hyoid and crico-thyroid ligaments in man are formed of this struc- ture. 5. Synovial membrane. The articular syno- vial membranes, (by the older anatomists called, and confounded with, the capsular ligaments,) like all others, possess in common with serous membranes the form of a sac shut in all points; they line the whole interior of the joints, and secrete from their internal surface a peculiar fluid, obviously destined for the lubrication of the articular surfaces. These membranes are remarkable for their great tenuity; they are transparent; in a state of inflammation, their vascularity, which is imperceptible during health, becomes very apparent by the general redness which the membrane assumes ; arid their internal or secreting surface is easily dis- tinguished from the external, by contrasting the smooth and glistening appearance of the former with the roughness which the latter receives from the cellular tissue and ligamentous fibres which adhere to it. The internal surface of the membrane is sometimes thrown into folds with fringe-like margins, which project into its cavity or sac. These folds contain more or less of cellular tissue and a number of pellets of fat, which being supplied with ves- sels, the margin of the synovial fringe is some- times tinged red. These folds are compared, and certainly with much justice, to the epi- ploic folds of the abdominal serous mem- branes, more especially to the appendices epiploicre of the great intestine. Beclard sup- poses that these fringes are specially the seat of the synovial secretion, which being perspiratory likewise takes place, though less abundantly and manifestly, from the rest of the synovial surface. The best examples of these folds occur in the knee and hip-joints, in the former of which they have been absurdly called alar ligaments. Some idea may be formed of the manner in which the synovial membrane is related to the other articular structures by examining the an- nexed figure, (jig. Ill,) representing a vertical section of the knee-joint. The cut margin of the synovial membrane is indicated by , which after lining the posterior surface of the patella and ligamentum patellae, is reflected upon the condyles of the femur, whence it is carried in front of the crucial ligaments to line the arti- cular surface of the head of the tibia, and from that is again reflected upwards, and is con- tinuous with the portion lining the posterior car- tilaginous surface of the patella. This descrip- tion is founded on the opinion, which I believe to be correct, that the analogy between serous and synovial membranes is accurate, in so far as their possessing in common the form of shut sacs is concerned. On this subject, how- * Vide Home's Lect. on Comp. Aaat. Lcct. i. vol. i. 252 ARTICULATION. Fig. 111. ever, anatomists are by no means likely ever to be unanimous, because of the difficulty or impossibility of tracing by the ordinary me- thods of dissection the synovial membrane over the articular cartilages. The continuity of this membrane over the cartilage was first distinctly announced and described by Dr. W. Hunter, in the paper to which we have already referred in the Philosophical Trans- actions : after him Soemm erring described it, and still later Bichat, who insisted more par- ticularly on its analogy with serous mem- branes. Bichat's description has been followed by Meckel, Beclard, and most of the anato- mists of modern times; but its accuracy has been called in question by Cruveilhier,* Gordon,f Magendie,J Blandin, and more re- cently by Gendrin|| and Velpeau.^F The advocates for the continuity of the syno- vial membranes over the diarthrodial cartilages, found their opinion on the following facts : 1 . Synovial membranes elsewhere, lining ten- dinous sheaths or bursae mucosae, are distinctly and obviously shut sacs. 2. We do not find * Observations sur les Cartilages diarthrodiaux. Arch. Gen. de Med. torn. iv. p. 161. t Gordon says, " the continuation of the syno- vial membranes over the surface of articulating cartilages is, I am convinced from a number of ex- periments, altogether an anatomical refinement." System of Human Anatomy, p. 261 . $ Compend. of Physiology, by Milligan, p. 450. Additions a Bichat, par Beclard et Blaiidin, p. 345. (I Hist. Anat. des Inflam. t. i. p. 60. II Anat. Chir. ed. 2de, t. i. p. 176. cartilage to present the smooth and polished aspect exhibited by the articular surfaces, ex- cepting where it is connected with synovial membrane, as it evidently is to at least a cer- tain extent in the moveable articulations. 3. If by an oblique cut we raise a slice from an arti- cular cartilage, and turn it back so as to rupture it at its base, we shall find it still retained in connexion with the rest of the cartilage by a thin pellicle, which seems to have all the cha- racters of synovial membrane. A similar mem- brane may be seen by sawing a bone vertically down to the cartilage, and then breaking the cartilage by forcibly separating the segments. 4. Some observers state that they have seen the redness of inflammation affecting the synovial membranes prolonged over the cartilage,* but becoming gradually less marked towards the centre (this, I must confess, I have never seen). 5. Bands of adhesion are also said to have been met with in some cases of chronic inflammation of the synovial membrane, passing from the ar- ticular surfaces, as well as from other parts of the interior of the joint. 6. In that peculiar disease of the synovial membrane described by Brodie,the pulpy substance has been seen on the articular cartilages, as well as on the menisci.f On the other hand, the opponents of this opinion deny : 1, that the membrane demon- strable by slicing the cartilage in the way above described, is any thing else than a very thin lamina of cartilage ; 2, they say that by even the most successful injection the fluid cannot be made to pass beyond the margin of the car- tilage ; 3, they assert that inflammation always stops abruptly at the circumference of the car- tilage ; 4, and that if a synovial membrane did exist on the free surface of the cartilage, there would take place a continual exhalation of sy- novia from the articular surface, contrary to what was~found to be the case in an experiment tried by Cruveilhier : synovia was freely exhaled from the membrane lining the ligaments, and after having been wiped off reappeared with rapidity ; but not so over the articular cartilage, the sur- face of which became quite dry. J Cruveilhier, however, relates a case which in some degree invalidates his own conclusions ; it was one in which fungous granulations sprang from the articular surfaces of the femur and tibia in the knee-joint, and by their adhesion produced anchylosis of the joint : this fact Cru- veilhier very candidly expresses his inability * I am uncertain whether the fourth case related by Sir B. Brodie in the last edition of his work on the joints, may not be regarded as affording an in- stance of this. In the account of the post-mortem examination it is said, " The synovial membrane was everywhere of a red colour, as if stained by the secretion," p. 15. Beclard, whose powers and accuracy of observation few will be disposed to question, speaks with the confidence of one who had seen this extension of the vessels over the car- tilage. Anat. Gen. p. 214. t Vide the 17th, 18th, 19th, 21st, and 22d cases recorded in Sir B. Brodie's work. | Cruveilhier, loc cit. He confesses, " ma conviction n'est pas cepen- dant pleine et enliere." ARTICULATION. 253 to explain without admitting either the exist- ence of the synovial membrane, or the organi- zation* of the cartilages. Velpeau,t too, al- though he asserts that the synovial membrane " terminates at the circumference of the carti- lages," furnishes us with an argument in oppo- sition to his own views : namely, that no appre- ciable line of demarcation can be detected indicating where the synovial membrane ceases. " Viewed in this way," he says, " the synovial apparatus consists of surfaces, mem- branes, and glandular folds, between which there exists not the least interruption, and the use of which is to isolate the interior of the joint from the tissues which surround it." It will appear then sufficiently evident that the weight of argument preponderates in favour of the doctrine that the synovial membranes line the articular surface of the cartilages, and that maintains their analogy with the serous membranes, an analogy which receives the strongest support from the physical properties of the synovial membrane, from its obvious functions during health, and from the diseases with which it is affected ; and I apprehend, that nothing tends more fully to establish iden- tity or similarity in the nature of two mem- branes, than the fact of a close resemblance between their morbid conditions. We may add, what was long ago remarked by W. Hunter, that this question as to the continuity of the synovial membrane on the cartilages is very similar to that as to the continuity of the conjunctiva over the cornea of the eye; the affirmation of which latter question, Gordon considers equally an anatomical refinement as that of the former. VelpeauJ ascribes much importance to the dense and fine cellular tissue which is sub- jacent to the synovial membrane and is ana- logous to the subserous cellular tissue else- where. This would appear to be the seat of the vessels which in a state of inflammation give rise to the red colour of the synovial mem- brane. He particularly alludes to it as afford- ing a clue by which the formation of loose cartilaginous bodies in joints can be explained ; these he supposes to originate in sanguineous effusions into this tissue, which subsequently become indurated and cartilaginous, and push the synovial membrane before them into the cavity of the joint. It will be remembered by many readers that this opinion is very similar to that of John Hunter regarding the origin of these bodies. Allusion has already been made to the fatty bodies which are found in connexion with * This is a bad word ; we cannot' deny the orga- nization of cartilages, however we may deny that they are supplied with red blood. It has been said, I know not with what authenticity, that cartilages have become yellow in jaundice. f Loc. cit. pp. 172 and 174. He expresses his opinion much more decidedly in the art. ARTICU- LATIONS, MALADIES DES. Diet, de Med. t Loc. cit. v. i. p. 173. See Home's Paper, in Trans, of a Soc. for the improvement of Med. and Chirurg. Knowledge, most of the joints, and in general lying behind the synovial fringes formerly described. These fatty pellets were supposed by Clopton Havers* to be the agents of the synovial secretion, and, in consequence, have obtained much celebrity under the title of Haversian glands.^ The opinion of Havers and his followers as to their glandular nature was successfully combated by Bichat, who proved that they were merely composed of adipose substance, and in no way concerned in the function of synovial secretion : for 1st, the secretion of synovia takes place where no such bodies exist, as in almost all the bursae mucosae, and tendinous sheaths ; and 2d, these bodies have no trace of glan- dular structure, nor are they provided with any thing resembling an excretory duct ; whilst, on the other hand, they possess all the properties of fat. The synovial sac is lubricated by the sy- novia, also called unguen articulare, axungia articularis. How is this secreted ? We believe it to be a perspiratory secretion precisely similar to that of the serum from serous membranes. Its formation cannot be imputed to a com- bination of the serosity of the blood with the fat, nor to the transudation of the marrow through the extremities of the bones, nor, with Desault, to a sweating from all the parts which enter into the composition of the articulation, inas- much as the chemical analysis of synovia proves that it is essentially different from any oily fluid, and does not contain a trace either of elaine and stearine. In addition to the structures already named as entering intrinsically into the formation of joints, we find that the tendons and muscles, which lie in the immediate vicinity of or which surround the joints, contribute much to their strength and security. In joints of the hinge kind we generally see the anterior and poste- rior parts protected more or less by the tendons of muscles, and even by muscles themselves passing from one segment of a limb to an- other, and here it frequently happens that the tendon is bound down on the bones which form the member, by a fibrous expansion of great strength, lined by a synovial membrane of the same characters as the articular, but adapted in its form to the osseo-fibrous canal in which the tendon is placed, e.g. the tendons of the fingers. The protection and strength afforded by mus- cles is particularly evinced in the case of the shoulder-joint, where the capsular ligament is closely embraced by four muscles, whose tendons become identified with the fibrous capsule as they go to be inserted into the bone. A muscular capsule, as it were, is thus provided for this joint, by which the bones are main- tained much more firmly and powerfully in apposition than were they kept together by an uncontractile ligamentous capsule alone ; hence the elongation of the arm which ap- * Osteologia Nova : Lond. 1691. t Weitbrecht called these fatty bodies, " Adi- poso-glandulosa? ; " and Cowper, "mucilaginous glands." See them figured in Monro's work on the Bursae, Tab. viii. 254 ARTICULATION. pears as a consequence of paralysis, and hence also the greater liability to luxation which exists in a debilitated state of the system. Articular or capsular muscles thus placed, have also the effect, as it is said, of preventing the pinching of the capsule or synovial mem- brane between the articular extremities of the bones in the different motions of the joint. The joints are very generally copiously sup- plied with blood, and are remarkable for the arterial anastomoses which take place around them. The best examples of these are met with in each of the joints of the extremities. The parts supplied with blood are the synovial membranes, the ligaments, the fat, and the extre- mities of the bones; but the cartilages cer- tainly do not receive vessels carrying red blood : I believe there is no fact in anatomy, more generally admitted or belter determined than this. The vascular ramifications which proceed from these vessels may be seen, par- ticularly in young subjects, advancing in the subsynovial cellular tissue, and forming a vas- cular net-work there, as far as the margin of the articular cartilage where they stop abruptly; this is what W. Hunter described under the name of circulus articuli vasculosus. Of the forms and classification of the arti- culations. It is not difficult, by passing in review the various motions which take place between any two segments of a limb, to form an idea, a priori, as to the kinds and shapes of the articulations by which these segments will be united ; it is only necessary not to lose sight of the fact, that in the construction of a joint regard is had not to its mobility alone, but to its security, its durability, and the safety of the neighbouring parts. We may expect to find joints varying in the degree of motion, from the slightest perceptible quantity, to the freest that is compatible with the maintenance of the segments in their proper relation with each other, and also in extent of motion, from that which is so slight as to admit of almost no appreciable change in the position of the parts, to that which allows of the most ample variety of relation between the segments, consistent with the integrity of the articula- tion. It will appear, then, that the most simple kind of articulation is that by which two parts are so united as that the slightest appreciable degree of motion only shall exist between them. This constitutes the first great division of joints the Synarthrosis (jrvv, cum, and agO^ov, arti- culus) where the parts are continuous, i. e. not separated from each other by an intervening synovial cavity. Some anatomists consider all synarthrodial joints to be immoveable ; which, although not far from the truth, cannot be said to be strictly accurate. Had immobility been the object to be obtained, I imagine that that might have been more effectually accomplished by the fusion of the extremities of the segments together, as in anchylosis. In the second class of joints, motion is enjoyed freely and fully : this class is designated by the term Diarthrosis ($icx,,per, and the segments are interrupted completely in their continuity ; the extremities of the bones can only be said to be contiguous. Synarthrosis. The general characters of the articulations belonging to this class are, 1. that they are very limited in their motion, insomuch as to be considered by some as im- moveable ; 2. that their surfaces are continuous, i. e. without the intervention of a synovial cavity, but with that of some structure different from bone. The following varieties may be noticed among synarthrodial articulations. a. Suture (Germ. Nath or Naht. Com- missura cranii, Vesal.). When the margins of two bones exhibit a series of processes and indentations (dovetailing) which are received and receive reciprocally, with a very thin car- tilaginous lamina interposed, this is the ordi- nary kind of suture, sutura vera, of which three kinds are distinguished : sutura dcntata, where the processes are long and dentiform, as in the interparictal suture of the human skull ; sutura serrata, when the indentations and processes are small and fine like the teeth of a saw, as in the suture between the two por- tions of the frontal bone ; sutura limbosa, when there is along with the dentated margins a degree of bevelling of one, so that one bone rests on the other, as in the occipito-parietal suture. When two bones are in juxta-position by plane but rough surfaces, the articulation is likewise said to be by suture, and this is the false suture, sutura nolha, of which there are two kinds : sutura squamosa, where the be- velled edge of one bone overlaps and rests upon the other, as in the temporo-parietal suture, and harmonia (agu, adapto), where there is simple apposition : this last kind of articulation is met with, as Bichat* observes, wherever the mechanism of the parts is alone sufficient to maintain them in their proper situation, as may be seen in the union of most of the bones of the face. It is in the articulation of the bones of the skull and face of animals, as has been already noticed, that we see the best examples of su- tures. In the chelonian reptiles, as the tortoise, the bodies, laminae, and spinous processes of the vertebras are united by suture, and the same mode of articulation unites the elements of the sternum of the land-tortoise to each other .f The bones of the head of birds and fishes are united chiefly by the harmonic and squamous sutures. In the lateral parts of the heads of fishes, and in the opercula of their gills, as between the opercular and subopercular bones, there is a species of articulation, most re- sembling the squamous suture, but differing from it in admitting a considerable latitude of motion by which these bones can glide on one another.}: To descend still lower in the scale, we may observe a mode of joining very similar to suture, between the tubercular and * Anat. Gen. t. iii. p. 63. t See Grant's Comp. Anat. p. 83, fig. 43. J Cuvier, Lecons d'Anat. Comp t.. i. p. 125* ARTICULATION. 255 ambulacral plates which form the shell-like covering of the echinida.* The sutures have the peculiarity of a con- siderable tendency to become obliterated by age, the intervening cartilage being ossified ; it rarely happens that the sutures are all ma- nifest in a human skull past fifty years of age, and sometimes the obliteration takes place at a much earlier period. The frontal suture is by no means permanent; it is not often found at puberty. In birds and fishes this tendency to the obliteration of the sutures is particularly manifest. 6. Sc/tindi/lesis (crpn<^yAj0 > i$, fissio, c^^u, diffindo). This form of articulation is where a thin plate of bone is received into a space or cleft formed by the separation of two laminae of another, as is seen in the insertion of the azygos process of the sphenoid bone into the fis- sure on the superior margin of the vomcr ; and in the articulation of the lacrymal bone with the ascending process of the superior maxillary. c. Gomphosis (yo[AQo$, davits. dav*, robust, Fig. 113. short, with three toes before, and one behind ; all armed with long, strong, crooked talons. Fig. 1 13. All the Birds of Prey feed on the flesh of living or recently killed animals. They have a prompt, powerful, and rapid flight. They are mono- gamous; the female exceeds the male in size. They nidificate in lofty situations and rarely lay more than four eggs : the young are ex- cluded in a blind and feeble state. The Birds of Prey are either diurnal or noc- turnal. The Diurnal Raptores have their eyes di- rected laterally, and are divided into the fol- lowing families Falconidte, Eaglesand Hawks ; Vulturidte, Vultures; and Gypogeranida',\vh\ch includes the Secretary vulture. In the first two divisions the characters of the order are most strongly marked ; in the third the legs deviate from the ordinal character and are remarkably elongated, adapting it to an inferior kind of grey, viz. noxious reptiles, serpents, &c. The Nocturnal Raptores have the eyes directed forwards, and include the Strigidte or owl-tribe. Order II. INSESSORES. Legs slender, short, with three toes before and one behind, the two external toes united by a very short membrane.* The Perchcrs form by far the most nume- rous order of birds, but are the least easily recognizable by distinctive characters common to the whole group. Their feet, being more especially adapted to the delicate labours of modification, have neither the webbed struc- ture of those of the Swimmers, nor the robust strength and destructive talons which characterise the feet of the Bird of Rapine, nor yet the extended toes which enable the Wader to walk safely over marshy soils and tread lightly on the float- ing leaves of aquatic plants ; but the toes are slender, flexible, and moderately elongated with long, pointed and slightly curved claws. (Fig. 114.) The perchers in general have the females smaller and less brilliant in their plumage than the males ; they always live in pairs, build in trees, and display the greatest art in the con- struction of their nests. The young are ex- cluded in a blind and naked state, and wholly dependent for subsistence during a certain * The genus Ceyr, Lacep. ( Akedo tridactyla, Pall.) affords an exception, the inner toe being deficient; and the two other anterior ones being united as in the other Syndactyles, it appears as if there was but one toe in front opposed to one behind. period on parental care. The brain arrives in this order at its greatest proportional size ; the organ of voice here attains its utmost com- plexity, and all the characteristics of the bird, as power of flight, melody of voice, and beauty of plumage are enjoyed in the highest perfection by one or other of the groups of this extensive and varied order. The beak of the Insessores varies in form according to the nature of their food, which may be small or young birds, carrion, insects, fruit, seeds, vegetable juices, or of a mixed kind. The modifications of the rostrum have therefore afforded convenient characters for the tribes or subdivisions of the order ; these are termed, 1, Dentirostres ; 2, Coniros- tres; 3, Tenuirostres ; 4, Fissirostres. The Dentirostres, (jfifg115) characterized by their insect food, and the notch near the extremity of the upper man- dible, include the families termed Laniadte or Shrikes ; Merulidtf, Thrushes; Sylvi- Rostrum of a Shrike ad(E, Warblers; Pipridt?, Tits; and Muscica- pidte, Fly-catchers. The Conirostres (Jig. 116) include the two Fig. 116. Fig. 114. T -^ Rostrum of a Crow. orders of M.Temminck, termed Omnivores and Granivores ; and are characterized by a strong and conical beak, the margin of which is gene- rally entire; the greater part are omnivorous, the rest granivorous; these latter are the Hard- billed Birds of Ray. The families of the tribe are the following: Sturnida, Starlings; Cor- vidthe transverse processes in general long before the growth of the individual is completed, excepting towards the caudal extremity of the cervical region, where comparative anatomists, from this cir- cumstance, have always found a difficulty in determining the commencement of the dorsal vertebrae. If the moveable ribs had com- menced, as in Mammalia, by extending to the sternum, the determination of their number would have been easy; but they begin, some- times by a gradual and at others by a sudden elongation,* opposite the furculum, from which point, either one, or two, as in the Humming- bird, (see p, Jig. 125,) terminate by extremities imbedded in muscle, and unconnected with any corresponding portion extending from the sternum. Meckel considers the true number of ribs in the Diurnal Raptores to be nine pairs, of the Nocturnal eight; in the Insessores seven or eight; in the Scansores nine, except the Cuckoo, which has seven or eight ; in the * This is remarkably the case in the Wood- Grouse ( Tetrao Urogallus), where the penultimate and last cervical ribs, instead of gradually enlarg- ing, diminish in size, so that the determination of the first thoracic rib is easy. AVES. 281 RfiKores seven or eight ; in the Struthiones the number of ribs varies ; in the Ostrich (Stru- t/no) we find ten pairs, of which the 3d, 4th, 5th, and 6th, are articulated with the sternum ; in the Nandou ( R/iea) there are nine pairs, of which only the 3d, 4th, 5th, and 6th, are completed by sternal portions ; in the Emeu (Dromaius) there are nine pairs, the 3d, 4th, 5th, 6th, and 7th, being joined to the sternum; in the Cassowary (Casuurius) there are ten pairs, and of these the 4th, 5th, 6th, 7th, 8th, and 9th, have sternal portions. The last pair of ribs in Strut/no and Rhea are extremely short, and abut against the expanded iliac bones. Among the Grullutures we find seven pairs of ribs in the Herons (Ardea), and Gigantic Stork (Ciconia Argula) while the Cranes fGrus) have nine, and the Coots and Water- Hens have ten pairs. In the Natatores, which vary so much in their locomotive powers and habits of life, we find a corresponding variety in the number of ribs ; in the Willock (Uria troilc) there are twelve pairs, and in the Guil- lemots and allied sea-birds eleven; in the Swans eleven ; in the Penguins nine, of which six are articulated with the sternum. The true ribs are not joined to the sternum by elastic cartilages, but by straight osseous portions, called sternal ribs, (q, jig. 125, h, Jig. 129,) which are moveably connected at both their extremities. These are the centres upon which the respiratory motions hinge ; the angle between the vertebral and sternal ribs, and between these and the sternum becoming more open in inspiration, and the contrary when the sternum is approximated to the dorsal region in expiration. As the ribs are traced backwards, their vertebral extremities are seen to become gra- dually double or bifurcated from the in- creasing development of the part answering to the cervix and head of the rib in Mam- malia. The spurious cervical ribs may be plainly seen to be articulated, like the pos- terior spurious ribs of the Cetacea, by the -tubercle only; and, as they increase in length in the proximity of the thorax, the head of the rib is then seen to be thrown downwards to join a distinct tubercle on the side of the body of the vertebra close to its anterior margin, but without encroaching on the intervertebral space. The comparative immobility of the dorsal vertebrae allows of this mode of articu- lation ; but it is an interesting circumstance that in the Ostrich, where the costal vertebra? preserve their mobility, the heads of the ribs, at least of those of the anterior ones, evidently pass forwards to the intervertebral space. The tubercle of the rib has thus less the character of a subordinate process than in the ribs of mammalia ; it is supported on a pedicle, and is articulated by a simple synovial joint with the transverse process of the correspond ing ver- tebra. The ribs, below the union of the two articular processes, are thick and strong, but they gradually become flattened, and increase in breadth as they descend towards the sternum. This is especially remarkable in the second, third, and fourth ribs of the Woodpecker. The dorsal ribs are not only connected together by muscles and aponeurotic membranes, but cooperate with the anchylosed dorsal vertebrae, in giving stability to the trunk by means of small osseous splints, detached from the pos- terior margin of each true rib, and directed backwards and upwards to the next in suc- cession, to both of which they are united by means of oblique fibrous ligaments. In birds of powerful flight these connecting pieces are, as might be expected, most developed. In the Raptores they extend beyond and overlap the succeeding posterior rib, and in this order they are anchylosed. In some of the Struthious birds, as the Ostrich and Rhea, they exist from the third to the fifth rib, while in the Emeu and Cassowary there are only rudimentary traces of them. In the Penguins these accessory processes are remarkable for their breadth, but they are never anchylosed to the ribs, and consequently are apt to be lost if care be not taken in pre- paring the skeleton. The sternal ribs (h, h,fig. 129) are of a less flattened form than the vertebral ; they increase in length as they are situated further back ; their costal extremity is simply rounded, while their sternal extremity is extended transversely and divided into two smooth surfaces moveably articulated by two synovial capsules with cor- responding cavities in the sides of the sternum. The first sternal rib is, however, joined by fibre-cartilaginous substance only, while one or two of the posterior pieces are anchylosed with the rib immediately preceding them, and do not reach the sternum. In the Ostrich the last rib abuts against the ilium, to which it is anchylosed. In the Peacock, Pintado, and common Fowl, the vertebral and sternal portions of the last pair of ribs are unconnected with each other; the latter thus representing the ossified ten- dinous intersections of the rectus abdominis muscle, as in the Crocodile. This analogy is still more striking in the Herons, Storks, and Curlews, and in many of the Natatores, in which the sternal portions alone exist, and are remarkably elongated. The part of the skeleton which has undergone the most remarkable modifications in relation to the powers and functions of the anterior ex- tremities is the sternum, ( r,s, fig. 125 and 129,) which gives origin to their principal muscles. It is so developed, both in length and breadth, as to extend over the whole of the anterior or ventral aspect of the thoracic and of a great part of the abdominal cavities, reaching in some birds of great powers of flight even to the pubic bones, so as to require removal be- fore the abdominal cavity can be examined. In order to afford origin to the accumulated fasciculi of the pectoral muscles, which other- wise would become blended together over the middle of the sternum, an osseous crest (s, Jig. 125, a, Jig. 130) is extended down- wards, analogous to the cranial crest which intervenes to the temporal muscles in the carnivorous mammalia ; and as this crest in- dicates in these the powers of the jaw, so the 282 AVES. sternal keel bespeaks the strength of the ante- rior extremity in the bird. Besides the difference of form and deve- lopment of the mesial crest or keel, the ex- tended sternum presents many other varieties in the different orders and families of birds. A zoological arrangement of the class has even been founded on the modifications of this cha- racteristic and important part of the skeleton. In every species the sternum is more or less Fig. 129. Sternum, coracoida, and clavicles of a Woodpecker. quadrilateral, more or less convex outwardly, and each of its margins affords distinctive characters. The anterior margin presents two grooves (b, b, figs. 129, 130) extending along the greater part of either side, and affording a secure articulation to the coracoid bones ; and in many birds it sends forward a process from the middle part where the two grooves meet, as in the Woodpecker and Penguin (e, fig. 129). This mesial process we shall term the manubrial process, since it is analogous to that which extends from the manubrium or first sternal bone of the seal, mole, &c. The lateral margins are straight and excavated anteriorly, to a greater or less extent, for the lodgement of the sternal ribs. In some birds a process (d,jigs. 129, 130) is given off at each angle of the union of the lateral with the anterior margin- as this process seems to supply the sternal portions of the anterior floating ribs, it may be termed the costal process. The posterior margin is most varied in its contour, and is in general interrupted by fis- sures, (f,f,Jigs. 129, 130.) which are always symmetrical in their position, but vary in number and depth, so that this margin is some- times represented by the extremities of three or five long processes. In the Diurnal Raptores the sternum is a large elongated parallelogram, convex both in the direction of its length and breadth, but especially in the latter sense. The manubrial process is thick, the contour of the keel convex, and its margin extended laterally. In the Eagles and Secretary-bird the ster- num is entire, but in the Vultures and Hawks it is pierced on either side by a small round aperture situated near the posterior margin. Ossification sometimes extends along the apo- neurotic membrane stretched over this aperture so as to divide it into two, as has been ob- served in the Buzzard; or so as to obliterate it on one side only, as seen by Meckel in the Kite. In the Nocturnal Raptores the sternum is short, convex as in the preceding tribe, but weaker : there is no manubrial process. The keel is less developed, its margin less convex, and not thickened. The posterior margin is concave and presents two fissures, separated by a middle process, except in the common Darn Owl ( Strix flammca ) where it is wanting, and a large but shallow fissure is found in- stead. The greater part of the Insessorial Birds are characterized by the following form of sternum. It is large, a little longer than broad, and pinched in, as it were, at the sides, just behind the costal margin. The keel is prominent and convex along its inferior margin ; its anterior margin is slightly excavated, and terminates below in a slightly projecting angle. The ma- nubrial process is compressed, prominent, and curved upwards ; the costal processes are mo- derately developed. The posterior margin pre- sents a single deep fissure OB either side, and a single lateral process, the extremity of which is constantly dilated. The lateral margins are slightly excavated. In the CorvidfS the keel is more excavated at its anterior margin ; the manubrial process is stronger, and is bifurcated at the extremity ; the posterior fissures are shallower ; the angular processes directed outwardly and not dilated at the extremity. In the Swallows (Hirun- do) the sternum is large and the keel greatly developed ; there are two posterior fissures, but they are still shallower than in the Crows}; the angular processes are not dilated at the extremities. In the Swifts (Cypselus) the sternum is entire, and corresponds in its pro- portional magnitude with the superior length and power of wing which characterizes this genus. The manubrial process is wanting, but the costal processes are moderately long and pointed. In the Humming-birds, which sustain them- selves on the wing during the greater part of the day, and hover above the plant while ex- tracting its juices, the sternum (r, s, Jig. 125,) is still further developed as compared with the body ; it approaches to a triangular form, ex- panding posteriorly, where the margin is entire, and rounded. The depth of the keel exceeds that of the entire breadth of the sternum. The coracoid depressions are deep and approxi- mated ; the manubrial process is small, but evident, and directed upwards ; the costal pro- cesses are also present, but of small size. In the Creepers (Certhia) and Hoopoes AVES. 283 (Upupa)j the sternum again becomes dimi- nished in size, and presents the two fissures on the posterior margin ; the keel is moderately developed ; the manubrial process is produced anteriorly ; it is of a compressed form in the Hoopoe, but thick, and bifurcate in the Creepers ; there are no costal processes. In the Wood-peckers the keel of the ster- num is more feebly developed, its inferior margin is straight, and the angle formed by its union with the anterior margin truncate. The manubrial process enlarges as it advances forwards, and is bifurcate at the extremity. The co.stal processes are also long, and curved forwards; the posterior margin has four deep notches (ff,fig. 129> In the Trogons, Hollers (Coracias), King- fishers, Bee-eaters (Merops), Toucans, and Touracos, the sternum is characterized by two fissures on either side at the posterior margin. J n the Parrot tribe the sternum again singu- larly resembles in its integrity that of the higher Raptor&fbeing in some species simply perforated on either side near the posterior margin, and in others wholly ossified. It is, however, narrower in proportion to its breadth. The keel is well developed, its inferior margin concave, its an- terior one describing a sigmoid flexure ; their angle of union rounded. The costal depres- sions occupy almost the entire lateral margins of the sternum. The manubrial process is slightly developed, trihedral, and truncate at the extremity. In the Pigeons, which unite the In- sessorial to the Gallinaceous order, the ster- num is narrow, but the keel is deep, with its inferior border convex, and the anterior one curved forwards, thin and trenchant ; the ma- nubrial process is strong and bifurcated; the costal processes short. The posterior margin is cleft by two fissures on either side of the mesial plane, the lateral and superior fissures being the deepest ; the mesial ones are occasion- ally converted into a foramen. The costal surface of the lateral margin is, as in the Gallinaceous birds, of very little extent. In the Crown Pigeon the superior fissures are so deep and wide as to convert the rest of the lateral margin into a mere flattened process, which is dilated at the extremity. In the true Kasores the four posterior fis- sures of the sternum are so deep and wide from its defective ossification, as to give to the lateral parts of this bone, or hypo-sternal elements, the appearance of a bifurcated pro- cess extending backwards from the costal margin. The mesial fissures are here the deepest, extending as far as the anterior border of the keel. This part is short, straight, or very slightly convex inferiorly; concave at the anterior margin, which is formed by two ridges which converge to it from the anterior margin of the sternum. This margin is con- vex laterally, and largely excavated for the coracoid bones; the depressions are continuous with each other, and the compressed manubrial process, arching over the canal, converts it into a foramen. The costal processes are prolonged upwards and forwards ; the posterior lateral processes pass backwards exterior to the ribs, supporting them in the Capercailzie, like a semi-hoop ; these processes are dilated at their extremities. In the Grallatores or Waders the sternum corresponds in size to the shortness of the thoracic-abdominal cavity. In the Ardeida the grooves of the anterior surface pass reci- procally beyond the middle line, increasing the surface of attachment for the expanded lower and posterior extremities of the coracoid bone. In most of the genera the posterior margin pre- sents a single fissure on either side ; these in the Storks and Herons are wider at the com- mencement than at the termination. In the Plo- vers, Woodcocks, Avosets, and Oyster-catchers, it occupies the whole breadth of the sternum. In the Curlews, Ibises, and Spoonbills, there are two fissures on either side. In the Coots, and Water-hens the single fissures on either side of the keel are long and narrow, and the lateral portions of the sternum extend back- wards beyond the middle, and become larger towards their extremities. Among the Natatores, the Albatrosses, Petrels, Pelicans, and Cormorants present a strong wide convex sternum, similar to the Storks and Herons; the keel is moderately developed, but prolonged anteriorly ; the pos- terior margin presents a single slight fissure on either side. In the Penguins, these fissures are of considerable extent (f ? f,fig- 130,) ; but the keel of the sternum is well developed, even in the Aptenodytes ; its inferior border is straight. In the Gulls and Sea-swallows the sternum is of large size, wide, arid convex ; it presents posteriorly two small and shallow fissures on either side, of which the lateral and superior are sometimes converted into foramina. The keel extends along the whole of the ster- num, but is of moderate depth, and convex inferiorly. In the Anatida or Lamellirostral tribe the sternum is thin, but of large size, very convex transversely, and much elongated. The keel is of moderate depth, and of a triangular form, its inferior margin being straight ; there is only one fissure on either side posteriorly.* In the Divers (Colymbus) the portion of sternum intermediate to the two fissures is pro- longed beyond the lateral pieces, and the ma- nubrial process is strongly developed, and of a rounded form ; the whole bone is remarkable for its length. In the Grebes the sternum is characterized by a third mesial fissure of a chevron figure intermediate to the two ordinary fissures of the posterior margin. The sternum of the Cursorial Birds pre- sents few affinities of structure to that of the rest of the class, resembling rather the ex- panded plastron or abdominal plate of the Tortoises. It has neither a keel, nor manu- brial, nor costal processes, and may be com- pared to a square shield. It is most convex in the Rhea, and least so in the Ostrich ; * The modifications of the sternum in relation to the folded trachea will be treated of in the article on the Organs of Voice. 284 AVES. in the latter there may be observed slight indi- cations of the two ordinary posterior fissures. The ossification of the perfect sternum of the Bird commences from five centres, a middle one which supports the keel, termed by by Geoffrey St. Hilaire the entosternal (a, fig. 129); two anterior lateral pieces, the hyoster- nals (b, bj Jig. 1 29), and two posterior lateral pieces, the hyposternals (c c, fig. 129). The posterior cartilaginous appendages he terms xiphi-sternals (g g,fg. 129, 130). If to these be added the two portions or episternals of which he supposes the manubrial process to be composed, then nine elements may be reckoned to enter into the composition of the the coracoid element has been err neously re- garded as the clavicle, in consequence of its being moveably articulated with the scapular piece. In the Emeu ( Dromaius) it is interesting to observe that the clavicle commences by a dis- tinct ossification, and long continues separate ; it does not reach the sternum, but holds the same relative situation as the continuous acro- mial or clavicular process of the scapula in the other Struthious birds. The scapula (t, fig. 125, A, fig. 130) is most readily recognised as such, in the Pen- guins of the genus Aptenodytes, where it is broader and flatter than in any other bird : in these, however, it is of considerable length in Fig. 130. sternum; but, hitherto, we have only met with a single ossific centre in the manubrial process. Where the keel is absent, as in the Cursores, the entosternal piece appears to be wanting, and the ossification of the sternum here radiates from lateral centres only. Of the anterior extremity. The bones of the anterior extremity do not present that ex- traordinary development in the bird that might be expected from the powers of the member of which they are the basis. The great expanse of the wing is here gained at the expense of the epidermoid system, and not exclusively pro- duced by folds of the skin requiring elongated bones to support them, as in the Bats, Dragons, and Flying-fish. The wing-bones are, however, both in their forms and modes of articulation, highly characteristic of the powers and appli- cation of the muscular apparatus requisite for their due actions in flight. The bones of the shoulder consist, on each side, of a scapula (h, fig. 1 30), a coracoid bone ( i), and a clavicle (k), the clavicles being mostly anchylosed together at their mesial extremities, constitute a single bone, which, from its peculiar form, is termed the os furcator ium or furculum. In the Ostrich the two clavicles are distinct from each other, but are severally anchylosed with the coracoid and scapula, so as to form one bone on either side. In almost every other species of bird the scapula, coracoid, and clavicle remain separate or moveably articu- lated throughout life. In the American Ostrich (Rhea) and Java Cassowary (Casuarius) the acromial element or clavicle is anchylosed with, or rather is a continuous ossification from, the scapula ; but the coracoid bone is free ; and this condition is worthy of notice as it i's precisely that which the bones of the shoul- der present in the Chelonian Reptiles; where proportion to its breadth, and does not exhibit any trace of spinous process. In the rest of the class it is a simple narrow elongated bony lamina, increasing in thickness as it approaches the joint of the shoulder ; there it is extended in the transverse direction, forming externally the posterior half of the glenoid cavity, and being internally more or less produced to meet the clavicle, while it is strongly attached in the re- mainder of its anterior surface to the coracoid bone. The position of the scapula is longitudi- nal,being extended backwards from the shoulder, parallel to the vertebral column, towards which, however, it, in general, presents a slight convex- ity. In birds of strong powers of flight, as in the Swift, (Cypselus,) it reaches to the last rib, while in the Emeu, on the contrary, it extends over two ribs only. In the Humming-bird (Trochilus) its posterior third is bent down- wards at a slight angle. The coracoid (u,fig.\ 25, i,fgs. 129, 130), or posterior clavicle, is always the strongest of the bones composing the scapular arch : its ex- panded extremity is securely lodged below in the transverse groove at the anterior part of the sternum, from which it extends upwards, outwards, and forwards, but frequently al- most in the vertical position to the shoulder - joint, where it is united at an acute angle with the scapula and clavicle. It thus forms the AYE'S. 285 main support to the wing, and the great point of resistance to the humeri during the down- ward stroke of this aerial oar. The superior or humeral end of this bone is commonly bifur- cate ; the outer process is the strongest, and completes the glenoid cavity anteriorly, (I, Jig. 1 30,) above which it rises, to a greater or less extent, and affords, on its inner side, an arti- cular surface for part of the acromial end of the clavicle : the inner process is short and com- pressed, and is also joined by ligament to the acromial end of the clavicle. Just below the origins of these processes an articular surface extends transversely across the posterior part of the coracoid bone by which it is firmly united by fibro-cartilaginous substance to the scapula. The glenoid cavity resulting from the union of these two bones is not, however, always equal to the reception of the entire head of the hu- merus. In the birds, which Mr. Vigors re- gards as composing the typical orders of the class, viz. the Rap tores and Insessores, (the aves aerete of Nitzsch,) a small but distinct bone extends between the scapula and coracoideum along the superior part of the articular cavity for the humerus, which it thus completes. Nitzsch, the discoverer of this element of the scapular apparatus, denominates it the capsular bone, (Schulterkapselbeine) ; by Meckel it is called the Os humcro-scapulare, and is regarded as the analogue of the scapula inferior of reptiles. In the Aberrant orders of birds, as the Rasoi^es, Grallatores, and Natatores, there is, in place of this bone, a strong elastic ligament or fibro- cartilage extended between the scapula and coracoideum, against which that part of the head of the humerus rests, which is not in con- tact with the glenoid cavity. The clavicles (v, fg. 125, b, Jig. 130) in birfls, as in the mammalia, are the most variable elements of the scapular apparatus. In the Ground Parrots of Australia ( Pezophorus, II- liger) they are rudimentary or wholly deficient ;* they are represented by short processes in the Emeu, Rhea,and Cassowary; they do not come in contact inferiorly in the Ostrich, although they reach the sternum. In the Toucans they are separate, and do not reach the sternum. In the Hornbills and Screech Owl (Strix ulula) they are united at their inferior extremities by carti- lage. In the rest of the class they are anchylosed together inferiorly, and so constitute one bone, thefurculum, or merrythought. From the point of union a compressed process extends down- wards in the Diurnal Raptores, the Coniros- tral Insessores, the Rasores, most of the Gral- latores, and Natatores, in which a ligament extends from its extremity to the ento-sternum. The process itself reaches the sternum, and is an- chylosed therewith in the Pelicans, Cormorants, Grebes, Petrels, and Tropic-bird ; also in the Gigantic Crane, and Storks in general. In the Humming-birds, where the sternum is so disproportionately developed, the furculum ter- minates almost opposite the commencement of the keel, but at some distance before it; in * Mr. Vigors has noticed the absence of the os furcatorium in Psittacus mitratus, Platycercus eximius, and Psittucula Galgula. those species in which we have examined it, be- longing to the genus Trochilus, Lacrp. it is of equal length with the coracoideum, and not shorter, as Meckel asserts. As the principal use of this elastic bony arch is to oppose the forces which tend to press the humeri inwards towards the mesial plane, during the downward stroke of the wing, and restore them to their former position, the clavicles composing it are stronger, and the angle of their union is more open, as the powers of flight are enjoyed in greater perfection; of this adjustment the Swifts, Goat-suckers, and Diurnal Birds of Prey afford the best examples. Notwithstanding the anterior extremity is limited to one function, and the motions of its parts are confined to simple folding and exten- sion, it contains the same number of joints as the arm of the Monkey, or of Man himself. We shall now successively consider the bones of the Brachium, Antibrachium, Carpus, Metacarpus, and Digits. The brachium, or humerus (w, Jig. 125, m, fg. 130) is principally characterized by the forms of its extremities. The head, or proximal extremity, is transversely oblong to play in the articular cavity formed by the union of the scapula and coracoid bone. It is further enlarged by two lateral crests: of these the superior, or external, which is angular, with the thin margin turned forward, affords an adequate attachment to the great pectoral muscle: the opposite process has its margin rounded and curved backwards, and it is beneath the arch thus formed that the orifices are situated, by which the air penetrates to the cavity of the bone. There is always a deep depression at this part, even in birds which have no air in the humerus, as in the Penguins and Ostrich. The distal end of the humerus is not less cha- racteristic of the bird, and different from that of other vertebrate animals. The articular hinge is divided into two parts, one internal, which is the largest, for the ulna, of an almost spherical form, and one external, for the radius, of an elongated figure, extending for some distance along the anterior surface of the humerus. The radius is thus made to describe in the act of bending a greater portion of a circle than the ulna, and the whole fore-arm moves in a plane which is not perpendicular to the anterior surface of the humerus. The humerus is not always developed in length in proportion to the powers of flight; for although it is shortest in the Struthious Birds and Penguins, it is also very short in the Swifts and Humming-birds. In the latter, how- ever, it is characterized by its thickness and strength, the size of its muscular processes, and the consequent transverse extension of its extremities ; while in the Cursores it is as attenuated as it is short, and in the Penguins is reduced to a mere lamina of bone resembling the corresponding part in the paddle of the turtle. In the Rasores it rarely equals half the length of the body ; in most other birds it is about two-thirds that length; it attains its greatest length in the Albatross. In this and other sea-birds, as the Gulls, Awks, and Petrels, 286 AVES. the humerus presents a notable process at the outer side, near its lower extremity; and in the Puffin ( Fratercula arctica) an ossiculum is moveably articulated to this process. Another ossiculum may here be noticed, al- though it belongs rather to the ulna, being essentially the separated olecranon of that bone. This detached sesamoid bone is found attached (like the patella of the knee-joint) to the capsular ligament and the tendons of the extensor mus- cles, in many of the Raptores, and in the Swifts. In the Penguins it is double (n, n, fig. 130.) Of the two bones of the antibrachium (y> fig' 125) the ulnar (o, fig. 130) is always the strongest, and especially so in the Stru- thiones: both this and the radius (p,fig. 130) are in general slender and straight bones, slightly enlarged at their extremities, placed not by the side of, but one in front of the other, and so articulated together, and with the hu- merus, as to admit of scarcely any degree of pronation or supination, which, as Meckel justly remarks, adds to that firmness and resist- ing power in the anterior member which are so necessary during the actions of flight. In the Penguins, the bones of the fore-arm present the same modifications as the humerus in re- lation to the corresponding action in the denser element, or that of swimming : they are flat- tened, and are articulated with the anterior edge, and not the extremity of the humerus. The bones of the hand are extended in length, but restricted in lateral development. The carpus consists of two bones only, (q, fig. 130,) so wedged in between the antibrachium and metacarpus, as to limit the motions of the hand to those of abduction and adduction necessary for the folding up and expansion of the wing ; the hand is thus fixed in a state of Fig. 131. Pelvis and bones of the leg of the Diver, or Loon, Colymbus glacialis, pronation ; all power of flexion, extension, or of rotation, is removed from the wrist-joint, so that the wing strikes firmly, and with the full force of the contraction of the depressor muscles, upon the resisting air. The metacarpus is principally formed of two bones, anchylosed together at both extremities (r, r, Jig. \ 30) ; of these, the one which cor- responds to the radius is always the largest, and supports the finger which has the greatest number of phalanges : a third small rudi- mental bone is in most birds found an- chylosed to the outer-side of its proximal extremity, and this supports the single phalanx of what is usually called the thumb. The longest or radial finger is generally composed of two phalanges (s, s, Jig. 1 30) of moderate length ; to which, in some birds, a third smaller phalanx is added. The ulnar finger consists of a single phalanx only (t,fg. 130). These are strongly bound together by ligaments and in- tegument, so that the wing loses nothing of its force, while it preserves in these separated bones its analogy with the anterior extremities in- the other vertebrated classes. In Zoology the large feathers that are attached to the ulnar side of the hand, are termed Primarne or pri- mary feathers ; those which are attached to the fore-arm Secundaria, or secundaries, and Tec- trices, or wing-coverts ; those which lie over the humerus are called Scapularia, or scapu- laries ; and those which are attached to the thumb, Spurue, or bastard feathers. In some birds the wing is armed with a spur attached to a phalanx at the radial side of the so-called thumb, which, as Nitzsch observes, would therefore seem analogous to the index finger. The bones of the leg or posterior extremity (Jig. 131J do not exactly correspond, in their divisions or principal groups, to those of the wing, the segment corre- sponding to the carpus being invariably blended with the one that suc- ceeds. The pelvic bones present a remarkable contrast to those of the shoulder, being always anchylosed on either side into one piece, but being with one exception \ never joined in the mesial line, while this is the only place where the elements of the scapular apparatus are in general united by bone. In the young bird the os innominatum is seen to be formed by the usual three bones, viz. the ilium, ischium, and pubis, corre- sponding respectively to the scapula, coracoid, and clavicle, of the anterior extremity. The ilium ($,fig. 125, a, fig. 131.) is the only AVES. 287 bone of the pelvis which comes in con- tact with the vertebral column, and it ex- tends from the posterior dorsal vertebrae along the whole of the sacrum, to which it is early united by anchylosis. At its posterior extre- mity it is expanded laterally and becomes anchylosed with the ischium (c,fig. 131) pos- terior to the ischiadic notch (e,Jig- 131) which is thus converted into a foramen. The ilium is of a considerable size, of an elongated form, expanded at its extremities and contracted in the middle ; the anterior expan- sion is concave externally, the posterior on the contrary convex. Besides being anchylosed with the ischium and sacrum, the spinous and transverse processes of one or two posterior dorsal vertebrae are commonly joined to it by bony union. In the Penguins, however, where the posterior extremities are ill adapted for su pporting the body in progressive motion on land, the ilium appears at no time to be anchylosed with any part of the vertebral co- lumn. The os pnbis (^ fig. 125, b b, Jig. 131 ) does not extend to meet its fellow on the mesial line, but is commonly directed backwards like a long bent styliform process (3, Jig. 134), adapted to allow a safe passage to the large and fragile eggs. In general it unites with the ischium so as to complete the obturator fora- men (J\ fig. 131), behind which another fo- ramen is occasionally formed by a second union with the ischium, as is seen in the Hum- ming-bird ; while in other Birds, as the Stork, it is only united to the ischium at the cotyloid foramen, and the obturator hole communicates with a long fissure and is completed posteri- orly by ligament only. The cotyloid cavity for the head of the thigh-bone is always incomplete at its posterior or internal part, which is closed in the recent state by a strong aponeurosis. The ischium (c, jig. 131) is a small elon- gated bone, slightly convex externally, ex- tending from the acetabulum backwards, pa- rallel with the ilium. In the Struthious Birds the pelvis is pro- portionally very long, but narrow ; the ossa innominata cover the whole of the sacrum, meeting and joining above that part like the roof of a dwelling. In the Rhea, or Ame- rican Ostrich, the ischiadic bones meet below the sacrum, where they are united for a con- siderable extent by a symphysis, so that the sacrum is closely surrounded, and in fact its place is almost supplied by the ossa inno- minata, for the development of the included vertebrae is in consequence so much impeded, that they can scarcely be detected at this part; beyond which, however, the coccygeal vertebrae suddenly resume their ordinary mag- nitude. This union of the ischia does not take place in the other Struthious birds ; but the Ostrich presents the remarkable exception, among Birds, of the completion of the pelvic circle by the anchyloses of the pubic bones at their inferior extremities. The femur (Q,frg. 125, g,fig. 131) is a short cylindrical bone, deviating from the straight line by a very slight anterior convexity. The head is a small hemisphere; joined, without the in- tervention of a neck, at a right angle, to the shaft of the bone : it presents at its upper part, a considerable depression for the attachment of the round ligament. The single large trochan- ter generally rises above the articular eminence, and is continuous with the outer side of the shaft. The orifice for the admission of air into the bone is situated anterior to this ca- vity. The femur is most readily characterised by the form of its lower extremity : this pre- sents as usual two condyles, the inner one cor- responding to the tibia, the outer one, which is the largest and the longest, resting both upon the tibia and fibula; upon this condyle a semi- circular rounded eminence is observed extend- ing from the front to the back part, and being lost in a depression at both extremities; the result of this structure is to put the external lateral ligament upon the stretch when the fibula is passing over the middle of the condyle, and that ligament, being elastic, pulls the fibula into the cavity in which the ridge termi- nates, with a jerk whether the motion be that of flexion or extension, in either of which con- ditions the leg is by this structure the more firmly locked to the thigh. It has been denied that the spring-joint ever exists at the knee, and it is probable that all birds do not possess the requisite structure in the same perfection ; but a common indigenous species, the Water-hen, (Gullinula Chloropus) affords a good example of the beautiful mechanism in question. The femur attains its greatest development in the Ostrich ; but in this species it is short in com- parison to the other bones of the leg, the length of which in the Stilt-bird and other Waders is attained solely by the elongation of the tibia and metatarsus. The tibia (J%.125,M,./Zg.l31) is the prin- cipal bone of the leg thejibula (x,Jig- 125, ', Jig. 131) appearing as a mere styliform process tapering to a point below, and anchylosed for a greater or less extent to the tibia. The tibia is of a triangular form, especially at its enlarged superior extremity, the articular surface of which is unequal, being flat internally, convex at the centre, and concave externally and in front. The inferior articular surface of the tibia forms a considerable transverse trochlea, above which anteriorly there is a deep depression. In ge- neral an osseous bridge extends transversely across this depression, converting it into a foramen through which the tendon of the Exten- sor communis digitorum passes. In the Divers, Grebes, Guillemots, and Albatrosses the middle and internal crests of the tibia unite superiorly and are extended up- wards into a long pointed process (k, Jig. 131) directed inwards and forwards, anterior to, but not supplying the place of, the patella, (I, Jig. 131) which will be always found as a distinct bone behind this process. The process is most developed in the genus Colymbus, and affords extensive attachments by way of insertion to the extensors of the tibia, and by way of origin to the extensors of the metatarsus ; by means 288 AVES. of the latter disposition the power of the back stroke of the foot is increased. The Tarsus can only be recognized as a distinct segment of the leg when the bones of a very young Bird are examined. But in the Ostrich, even when it has attained a third of its natural size, the Astragalus re- mains ununited to the metatarsus. It is a flattened transversely oval bone, convex in the middle of its upper surface, and irregularly flattened below, where it is adapted to the three still partially separated bones of the metatarsus. A rudiment of the os calcis may be observed in the detached bone which is found in the tendons of the extensors of the foot near their insertion. The Capercailzie ( Tetrao urogallus) affords a good example of this structure. The process (m, Jig. 131) in which the above tendons are inserted, and which is very prominent in the Hasores, Gral- latores, and Natatores, must also be regarded as appertaining to the tarsal series, since it com- mences by a separate ossification. In most birds, however, the tendo Achillis has no sesamoid bone to add to its leverage, and in all birds the astragalus is soon anchylosed to the metatarsus, constituting with it one elongated tarso-metatarsal bone (A, fg. 125, n, Jig. 131). Traces of the number of laterally anchylosed pieces of which the metatarsus is composed are always more or less indicated by longitu- dinal grooves. In the Penguins, indeed, the anchylosis of the three metatarsal bones takes place at their extremities only, and they are consequently separated from each other in the greater part of their extent. They are also disproportionately short, and bent forwards upon the tibia, so as to increase the surface of support required by these birds when standing in their usually erect position. In the Gralla- tores and Struthiones, on the contrary, the tarso-metatarsal bone is remarkably elongated, the extraordinary length of leg in these birds depending chiefly upon the extent of this seg- ment of the limb. In the Stork and congeneric birds, which sleep^on one leg, the ankle-joint presents a mechanism analogous to that which we have above described in the knee-joint. Here, how- ever, the projection which causes the extension of the elastic ligaments in the motion of the joint is in the inferior bone. Dr. Macartney thus describes the mechanism : " There arises, from the fore-part of the head of the metatarsal bone, a round eminence, which passes up be- tween the projections of the pulley on the an- terior part of the end of the tibia. This emi- nence affords a sufficient degree of resistance to the flexion of the leg to counteract the effect of the oscillations of the body, and would prove an insurmountable obstruction to the motion of the joint, if there were not a socket within the upper part of the pulley of the tibia to receive it when the leg is in a bent position. The lower edge of the socket is prominent and sharp, and presents a sort of barrier to the admission of the eminence that requires a voluntary muscular exertion of the bird to overcome, which being accomplished it slips in with some force like the end of a dislocated bone."* It must be added, that the elastic lateral ligaments contribute also to jerk the metatarsal tubercle into the tibial cavities, and to resist its displacement. The lower extremity of the metatarsus is divided into three articular eminences, corres- ponding to the ordinary number of anterior toes. These eminences are convex from before backwards, and the middle one, which is the longest, is converted into a pulley by a mesial groove which traverses it in the same direction. The lateral surfaces are simply convex, and very narrow ; of these the internal is the short- est, except in the raptorial birds. At the extre- mities of the grooves which indicate the lateral juxtaposition of the metatarsal pieces, there are ordinarily foramina extending from before back- wards through the bone. A fourth articular surface is observable in most birds on the inner and posterior side of the metatarsal bone; this is situated on an ac- cessory piece which always commences by a separate ossification, although in some birds it afterwards becomes anchylosed with the inner- most of the other juxtaposed components of the metatarsus. When this does not take place, the metatarsus presents a rough, more or less irregular, oval surface, for the firm ligamentous attachment of the accessory bone which sup- ports the back toe, usually termed the hallux or posterior thumb. This articulating surface is important as affording a good distinctive cha- racter for identifying the bones of birds in a fossil state, and the more so as its position is indicative of the powers of grasping or perching being placed low down, on a level with the anterior toes, in those birds which enjoy the insessorial power in the greatest perfection, and being gradually removed higher and higher in the Waders, until it is at length wholly lost, as in the genus Cursorius, the Bustards, and the Struthious family. In the Petrel, however, this accessory metatarsal bone is wanting, al- though the hallux is present, the two bones of which are therefore united to the principal me- tatarsal bone by long ligaments. The tarso- metatarsal bone is further characterized by sharp longitudinal ridges of bone on the pos- terior surface, which afford attachment to the aponeurotic thecae confining the tendons which glide along the metatarsus to the toes. In birds, as in mammalia, the number of toes is subject to great variety; if the spur of the Gallinaceous tribe be regarded as one, we may then reckon the ordinary number of five in these birds, while in the Ostrich the toes are reduced to two. Birds are, however, the only class of animals in which the toes, whatever be their number or relative size, always differ in the number of their phalanges, yet at the same time preserve a constancy in that variation. The following is a tabular view of the nume- rical relation in the osseous parts of the feet of * See Transactions of the Royal Irish Academy, vol. xiii. p. 20. AVES. 289 birds according to the researches of Cuvier, the discoverer of this remarkable peculiarity in the anatomy of birds. Table of the number of toe phalanges in Jiirds. Number of Phalanges in the First or inner- most toe or Calcar. Second, com- monly called the Hnllux. Third. Fourth. Fifth'or outer- nost,or little toe. 1 Cock (Gal- lus), Phea- sants ( P/ia- sianus), Tur- keys, Pea- cocks ( Pavo and Lopho- pliorus) . . 1* 2 3 4 5 2 Raptores,Tn- sessores, Co- lumbidce, Cra- cidce, Tetrao- 7u'da?,and the rrst of the class, except it 3* m 5|| 3 The Genera, Rhea, Dra- in* ii us, Casu- al-ins, Otis Cursoriitx, Cfuiradrius, Hevmatopus, Arenaria, Falcinella, ffimatttopvt, Halodroma, Diomedea . 3 4 5 4 The Ostrich (Struthio) . 4 5 The above table shows what are the toes which are deficient in those birds that do not possess the ordinary number. The phalanges are expanded at their extre- mities, especially at the posterior ; the articular surfaces are concave at this end, but divided longitudinally by a narrow convex line, to which a corresponding unequal surface at the anterior * This is wanting in the Argus Pheasant ; the Pavo bicalcaratus, on the contrary, has two spurs on each metatarsal bone. t In the single genus Ceyx among the Insessores, and Hemipodius among the Rasores, this toe is wanting. In all the rest, with the exception of the Swifts (Cypselus) it is directed backwards. \ In the Dentirostral Insessores this toe is united by one or two phalanges to the fourth. $ According to Cuvier this toe and the fifth in the Swift ( Cypselus) have only three phalanges like the third. In the Goat-suckers ( Cuprimulyus) and Herons (Ardea) the claw of this toe is provided with dentations similar to a comb on its inner side. || This toe is stated by Cuvier to have only four phalanges in the Goat-suckers, and we have ascer- tained the correctness of the exception, and that it also obtains in the Rhea. This toe is united to the fourth toe as far as the penultimate joint in the Bee-eaters (Merops), the Motmots ( Prio- mtes), the King-fishers (Aleedo), the Todies ( Todus), and the Hornbills ( Buceros ), which form in consequence the family Syiuhtctyli of Cuvier. In the S ansores this toe is turned backwards, and assists the Hallux in opposing the other toes. The Owls have the j.ower of turning back the outer toe at pleasure. VOL. i. end of the preceding phalanx is adapted, con- stituting a ginglymoid articulation. The ulti- mate or ungueal phalanges are characterised by their anterior pointed terminations, which cor- respond in form, in some degree, to the nature of the claw. 132. Foot of the Goat-sucker. Of the fossil bones of birds. Birds differ from each other in a much less degree than qua- drupeds, less, perhaps, than any other class. The Penguin and the Ostrich have, indeed, but a remote external resemblance with the Eagle or the Swallow, but yet they have never been regarded as other than birds. The Por- pesse and the Whale, on the other hand, al- though their real affinities were pointed out by Aristotle, have been placed by many sub- sequent Zoologists in a very different class from the Lion or the Ape, and in the older systems of Natural History they always ob- tained their position among the true fishes. Osteological characters of the same value with those which serve to distinguish the genera, and for the most part the species of Mammalia, are, therefore, with difficulty found in the Class of Birds. Cuvier has declared that the differences in the skeleton of two species of an ornithological genus are some- times wholly inappreciable, and that the oste- ological characters of Genera can rarely be detected in any other part than in the bones of the mandibles, which, do not always con- form in a sufficiently characteristic manner with the modifications of the horny bill. The determination of the fossil bones of this class is, therefore, conjectural, or, at least, it wants much of that demonstrative character which the bones of quadrupeds afford. The fossil bones of birds described by Cu- vier are considered by him to appertain to a species of Buzzard, Owl, Quail, Woodcock, Ibis, Sea-lark, and Cormorant; and, although not remarkable for their number or for their zoological interest, yet they demonstrate that the species which existed at that remote period, when the Anoplotheriums and other extinct quadrupeds trod the face of the earth, had the same proportion of parts, the same length of wings and legs, the same articulations of the toes, the same form and numerical proportions of the vertebra; in short, that their whole organization was regulated by the same general u 290 AVES. laws of co-existence and all that relates to the nature of the organs and their essential func- tions, as at the present day. They afford no evidence, not even a trace of any part having been lengthened or curtailed, or otherwise pro- gressively modified, either by the operation of external causes or by internal voluntary im- pulse. Myology. The muscular system of Birds is remarkable for the distinctness and density of the carneous fibres, their deep red colour, and their marked separation from the ten- dons, which are of a brilliant shining colour, and have a peculiar tendency to ossification. This high degree of development results from the rapid circulation of very warm blood, which is highly oxygenated in consequence of the activity and extent of the respiratory func- tion. The energy of the muscular contraction in this class is in the ratio of the activity of the vital functions, but its permanent irrita- bility is proportionally low, as Carus has justly observed. Fig. 133. Muscles of a These characteristic properties are mani- fested in the greatest degree in the muscles of those families of the Insessores which take their food on the wing, as the Hirundinida and Trochilida (Swallows and Humming-birds) ; in the Diurnal Raptores and in the long- winged Palmipedes, as the Albatross, Tropic Bird, &c. In the more heavy and slow- moving Herbivorous families, and in the short- winged Swimmers, as the Penguins, &c. the muscles resemble those of the Reptilia in their softness and pale-colour. The mechanical disposition of the muscular system is admirably adapted to the aerial loco- motion of this class; the principal masses being collected below the centre of gravity, beneath the stev.ium, beneath the pelvis, and upon the thighs, they act like the ballast of a vessel and assist in maintaining the steadiness of the body during flight, while at the same time the extremities require only long and thin tendons for the communication of the muscu- lar influence to them and are thereby rendered light and slender. Muscles of the trunk. The muscles of the cervical region are the most developed, as might be expected from the size and mobility of this part of the spine ; the muscles which are situ- ated on the dorsal and lumbar regions are, on the other hand, very indistinct, feeble, and but slightly carneous ; they are not, however, entirely wanting. The Semi-spinalis dorsi or Opisthotenar, is easily recognizable, occupying the space be- tween the spinous and transverse processes, arising from the anterior margin of the ilium and the transverse processes of the sacrum, and attached by means of long tendons to the transverse processes of the costal vertebrae. It is most developed in those birds which have the greatest mobility in this part of the spine, as in the Penguins, in which the external venter of the muscle is well developed, inserted into the vertebral ends of the ribs, and adapted to support the body in the erect position which these birds assume while standing. On the mesial aspect of this muscle and somewhat covered by it, the Spinalis dorsi may be distinctly traced, passing from the spinous processes behind, to those at the anterior part of the trunk and beginning of the neck. The Cervicalis ascendens (1, Jig. 133) is the chief extensor of the neck : it rises from the spines of the anterior dorsal vertebrae, and is inserted by long and separate fasciculi into the posterior articular processes of the second, third, and fourth cervical vertebrae. In this course it receives descending slips of muscle from the spines of the inferior cervical vertebrae, and ascending fasciculi, which furnish tendons to the fifth and sixth vertebrae, and to the atlas, so that it is enabled to extend the neck even while the head is raised. Muscles corresponding to the Intertrans- versales (2) are continued on the neck from the external belly of the Opisthotenar ; these slips extend from the articular processes of the dorsal vertebrae to those of the inferior cervical. Posterior to the Intertransversales, the Semispi- nalis colli (3) is seen passing from the trans- verse to the spinous processes. The Longus colli arises from the anterior A\ spinous processes of the dorsal vertebrae and from the anterior part of the cervical vertebra', and these slips diverge to be inserted into the transverse processes, and their appended styles or spurious ribs. A superadded muscle, which may be re- garded as a continuation of the preceding, and which corresponds to the increased number of the vertebrae of the neck, passes from the transverse processes of the five superior ver- tebrae to the anterior spines of the vertebrae immediately anterior a portion of this muscle is shown at 5. No. 6 indicates one of the most remarkable muscles in the cervical region of Birds ; it is analogous to the Biventer ccrvicis of mam- mals, but has a much longer and more distinct middle tendon, a. 6. Its lower or pos- terior venter, b. 6, arises by a tendon, most com- monly from the short spinous processes of the lowest cervical vertebrae, the anterior fleshy part c is inserted into the squamous spine of the occiput. This muscle is well developed in the Ostrich, where it arises as low down as from the last lumbar vertebra, by a long ten- don, which is continued to the cervical region before it joins the fleshy portion, the whole muscle affording a striking example of the peculiar development of the tendinous over the carneous part which characterizes the mus- cular system of Birds. In the Parrots and Raptorial birds, however, the carneous exceeds the tendinous part of this muscle. The Contplexus (7) arises from the articular and transverse processes of a variable number of the superior cervical vertebrae, and passes obliquely backwards to be inserted into the occiput, crossing exteriorly the upper belly of the preceding muscle. The Trachelo-mastoidcm (8) arises from the articular processes of the cervical vertebra; from the second to the sixth, and is inserted into the posterior part of the basis cranii. Anterior to the preceding muscle a portion of the Rectus capitis an tic us major may be seen at 4. This muscle is largely developed, arising from the anterior part of the sixth, seventh, and eighth vertebrae, and inserted into the basis cranii. There are also muscles ana- logous to the Rcctns capitis anticus minor, the Kccti postici majores et minores, the ObLiquus cjcternus or superior, and in the Penguin, a strong tendon is given off from the Trachelo- mastoideus which represents the obliquus in- ferior of the neck. When it is remembered that the cervical re- gion of the spine in Birds is subservient and essential to all the movements and functions of the bill, as a prehensile instrument, and a cleanser of the plumage, we cannot sufficiently admire the endowments of length, flexibility, and muscularity, by which it is enabled to fulfil the important functions of an additional extremity. In the caudal region of the spine the fol- lowing muscles present themselves. On the dorsal aspect, the Levator cocci/gis (10) ex- tends from the transverse processes and lower extremity of the .sacrum to the superior spines of the coccyx and the base of the last or plough-share vertebra. This muscle may be regarded as a continuation of the spinalis dorsi. Beneath it are found strong Interspiuules mus- cles. The Quadratus coccygis (11) arises from the transverse processes of the coccygeal vertebras and is inserted into the shafts of the reclrices or tail-quills, which it separates and raises. On the lateral aspect we find the Pubo-coccy- geus (12) arising from the posterior margin of the pubis, and inserted also into the shafts of the exterior rectrices; it is by means of- these muscles in conjunction with the two preceding that the Peacock spreads its gorgeous tail. The Ilio-coccygetu (13) extends from the posterior margin of the ilium to the last coccy- ueal vertebra, and to the small inferior tail- feathers. On the ventral or inferior aspect of the tail, the muscles are in general more feebly developed than on the opposite side, except in the Wood- peckers, where the tail, by means of its stiff and pointed quill-feathers, serves as a prop to sup- port the bird on the perpendicular trunks of trees on which it seeks its food. In these the Ischio- cocci/geits (14) is of large size, extending from the lower edge of the ischiadic tuberosity, and from the transverse processes of the anterior coccygeal vertebrae to the inferior spines of the posterior coccygeal vertebrae, and to the sides of the last compressed or plough-share bone. The Depressor coccygis (15) extends from the ventral aspect of the bodies of the anterior coccygeal vertebra to the inferior spines of the posterior and to the base of the last vertebra. Of the Muscles of the head those which are attached to it for its general motions have already been described; the remaining mus- cles of this part are devoted to the movements of the jaws, the tongue, the eye, and the ear. The cutaneous muscles of the face are usually described as being entirely deficient, and the only ones that can be regarded as belonging to this series are the slips of panniculus car- nosus, analogous to an occipito-fronta/is (16), which are chiefly developed in order to elevate the crest-feathers in those birds which possess that ornament ; there are also cutaneous slips which belong more properly to the organs of hearing, and which raise the auricular circle of feathers in the Owls, Bustards, &c. The muscles of the jaws are chiefly mo- dified in relation to the moveable condition of the upper mandible and tympanic bone, and the subserviency of the latter to the actions of these parts. The Temporalis (17) fills the temporal fossa, which consequently indicates the bulk of that muscle in the dry skull. It arises from a greater or less extent of the temporal and parietal bones, and, as it passes within the zygoma, becomes closely blended with the Musseter; the united muscles derive an acces- sion of fibres from the lower part of the orbit, and are inserted into the raised superior margin, representing the coronoid process ; u 2 292 AVES. and into the sides of the lower jaw from the articulation as far forward as the commence- ment of the horny bill. In the Cormorant there projects backwards from the spine or squamous element of the occipital bone, an osseous style about an inch in length, of a trihedral figure and tapering to a point. It is not anchylosed as a process of the occiput, but is moveably articulated to it ; and its description has been referred to this section because it does not constitute a regular part of the skeleton, not representing any essential element of the bony fabric, but is to be regarded like the bony tendons of the legs as an ossification of the intermuscular aponeu- rosis of the temporal muscles to which it affords a more extensive and firmer origin. This, indeed, is its essential use,* for the mus- cles of the upper part of the neck are inserted into the occipital bone, and glide beneath the posterior or superadded fasciculi of the tem- poral muscle. Analogous parts appended to the true spinous processes of the vertebrae are met with abundantly in the inferior vertebrate classes, especially in fishes, where they extend frequently above the spines of the whole ver- tebral column, increasing the surface of origin of the lateral series of muscles. The muscle analogous to the Biventer maxilla: (18) arises by two portions, the one from the lateral depression of the occiput, the other from the depression behind and below the external meatus auditorius ; they are in- serted into the back part and angle of the lower jaw. A similar disposition of the dignstricus is met with in many of the mammalia; even in the Orang-utan (Simla Satyrus) it is equally devoid of a central tendon, and is unconnected with the os hyoides. The openers and closers of the mandibles present very slight differences of bulk in rela- tion to the development of the parts they are destined to move; their disproportion to the bill is, on the contrary, truly remarkable in the Horn-bills, Toucans, and Pelican, and the bill is but weakly closed in these in comparison with the shorter-billed birds. The upper mandible is moved by three muscles on either side. The first is of a radiated form, arises from the septum of the orbits, and converges to be inserted into the external and posterior end of the pterygoid bone, just where this is articulated to the tympanic bone. It draws forward the pterygoid bone, which pushes against and raises the upper jaw. The second muscle analogous to the External Pterygoid arises from the space between the posterior part of the orbit and external meatus auditorius, and is inserted into the internal process and contiguous surface of the tympanic bone ; it affects the pterygoid process, and con- sequently the upper mandible in the same way as the preceding muscles, and assists in opening the bill. The Pterygoideus Internus is a long and * See Yarrell ' On the Anatomy of the Cormo- ant/ Zool. Trans, v. iv. p. 235. slender muscle ; it arises from the pterygoid process and body of the sphenoid, and is in- serted principally into the inner side of the lower jaw and tympanic bone ; it also sends off a small tendon to the membrane of the palate. This muscle draws forward the lower jaw and depresses the upper one. In the Cross-bill ( Loxia curvirostra) there is a remarkable want of symmetry in the muscles of the jaws on the two sides of the head corresponding to their peculiar position. Those of the side towards which the lower jaw is drawn in a state of rest (which varies in different individuals) are most developed, and act upon the mandibles with a force that enables the bird to dislodge the seeds of the fir-cones, which constitute its food. The articulation of the lower jaw is strength- ened and its movements restrained by two strong ligaments, one of these (a) is extended from the ligament completing the lower part of the orbit, or from the zygomatic proce ss of the temporal bone, and is inserted at the outer protuberance near the joint of the lower jaw, and must prevent the bill from being too widely opened. The second ligament extends from the zygomatic process of the temporal bone directly backwards to the posterior part of the articular depression of the lower jaw, and is designed to guard against the backward dislo- cation of the lower jaw. The muscles of the ribs. The levatores costarum arise from the posterior part of the extremities of the transverse processes, and converge to be inserted into the anterior margin of the succeeding posterior rib. Those of the first and second ribs represent the Scalcni, and are of larger size, arising from the last and penultimate cervical vertebrae. The Intercostales externi appear to be con- tinuations of the Levatores costarum, and are usually divided into an anterior and posterior moiety corresponding to the marked separation and moveable articulation between the vertebral and sternal portions of the ribs ; the anterior division arises from the costal appendage and extends to the anterior extremity of the rib ; to afford a more advantageous origin to this inspiratory muscle would appear, therefore, to be one of the uses of the costal appendages, as well as to strengthen the connection of the ribs to each other. The Internal intercostal* commence at the sternal extremities of the ribs, as in mammalia, but extend backwards no farther than the costal appendages; their fibres run in an opposite direction to the external intercostals, and are shorter, the insertion into the posterior suc- ceeding rib being by a thin but wide aponeu- rosis : in the Penguin they are, however, wholly muscular. Two other layers of inter- costal muscles, corresponding to the triangu- laris sterni, and having the same direction of fibres, are extended from before backwards and outwards to the four anterior sternal por- tions of the ribs ; arising from the superior and external angle of the sternum. The muscles of the abdomen are small and AVES. 293 weak, in consequence of the protection which the extended sternum affords to the viscera of that cavity. The External oblique (19) is chiefly remarka- ble for the transverse arrangement of its fibres ; these arise anteriorly by short fleshy digitations from the inferior ribs, and by a large but very thin tendon from the posterior ribs and the edge of the ilium and pubis ; they are inserted by aponeurosis into the anterior margin of the pubis, and join the aponeurosis of the opposite muscle in front of the thin and tendinous rcctus abdominls. This muscle, by drawing downwards and backwards the posterior part of the sternum and sternal ribs, opens the angle between these and the vertebral ribs, depresses, in consequence, the anterior part of the sternum, and thus dilates the thorax, and becomes a muscle of inspiration. The Internal oblique comes off fleshy from the anterior moiety of the edge of the pubis, and tendinous from the posterior moiety of the same bone ; it is much smaller than the pre- ceding, and is directed forwards and inwards to the last rib, which it draws backwards, and thus assists the preceding in the compression of the abdomen and abdominal air-cells, and in the dilatation of the thorax. The Tramversalis is a muscle of greater extent; it arises from the whole anterior margin of the pubic bones by carneous fibres, and by digitations from the three posterior ribs ; its tendon unites with that of its fellow in the mesial line, extends immediately over the pe- ritoneum over the whole abdomen as far as the posterior margin of the sternum to which it is attached. The Rectus abdominis is not intersected by tendinous digitations ; its origin is by a broad thin tendon from the lower and posterior half of the pubis ; at about the middle third of the abdomen it becomes carneous, and is inserted into the posterior margin of the sternum. A mesial tendon or linea alba sepa- rates the fleshy portions of the two muscles. The Diaphragm arises by fleshy digitations from the sternal ribs; in the Ostrich these digitations are five in number on either side : the carneous fasciculi do not, however, extend so far upon the central aponeurosis as even to be united laterally to one another, and consequently this muscle has frequently been denied to birds. From the lungs being con- fined to the back part of the thorax, the dia- phragmatic aponeurosis attached to their inferior surface is not extended as a transverse sep- tum between the chest and abdomen, but allows the heart to encroach upon the interspace of the lobes of the liver, as in reptiles. The contraction of the muscle tends directly to dilate the lungs, but is less perfect as an inspiratory action from the aponeurosis or central tendon being perforated by large cribriform apertures for the passage of the air into the abdominal air-cells. The Wing-Muscles. The muscles of the anterior extremity, especially those inserted into the humerus, are prodigiously developed, and form the most characteristic muscles of the bird. The muscles of the shoulder, however, are but small, and those of the distal segments of the wing still more feeble. The Trapezius (20), the lower half of which seems only to be present in birds, arises from the spines of the lower cervical, and a varying number of the contiguous dorsal vertebrae, and is inserted into the dorsal margin of the sca- pula and the corresponding extremity of the clavicle ; the clavicular portion can commonly be separated from the scapular. The Hhomboideus lies immediately beneath the preceding, and is always single ; it passes in a direction contrary to the trapezius from the spines of the anterior dorsal vertebrae to the dorsal edge of the scapula. The Levator scapula arises by digitations from the transverse process of the last cervical vertebra, and from the first two ribs; it is inserted into the posterior part of the dorsal edge of the scapula, which it raises and pulls forwards. The Serralus magnus antic us (21) is most developed in birds of prey ; it arises by large digitations from three or four of the middle ribs, and converges to be inserted into the ex- tremity of the scapula. The Serrutus parvus anticus or Pectoralis minor, as it is termed in Man, arises by digita- tions from the first and second ribs, and is in- serted into the commencement of the inferior margin of the scapula. This is the largest of the muscles of the scapula in the Penguins. A muscle, which may be regarded either as a portion of the Pectoralis minor or as the ana- logue of the Subclavius muscle, arises from the anterior angle of the sternum, and is inserted into the external margin of the sternal extremity of the coracoid bone. The Supra-spinatus (22) arises from the ante- rior part of the outer surface of the scapula, and is inserted behind the largely developed inter- nal tuberosity of the humerus. The muscle which seems to represent both the Infra-spinatus and Teres major (23) has a more extensive origin from the outer margin of the scapula to its extremity, and is inserted into the internal tuberosity of the humerus. The Subscapularis arises from the anterior part of the inner surface of the scapula, and is inserted into the humeral tuberosity. It is divided into two portions by the Pectoralis minor. The Latissimus dorsi (24, 24,) is but a feeble muscle in this class, and is constantly divided into two very distinct slips. The anterior por- tion arises, more superficial than the trapezius, from the spines of the four or five anterior dorsal vertebrae, and is inserted near the tendon of the deltoid into the outer side of the humerus. The posterior slip comes from the spines of the dorsal vertebrae above the origin of the glutaus magnus, and sometimes from the anterior mar- gin of the same muscle, and is inserted by a broad and thin tendon immediately in front of the preceding portion. The Deltoidcs (26) is comparatively a small muscle ; it arises from the anterior part of the 294 AVES. scapula, and is inserted along the middle of the outer side of the humerus ; it brings the wing upward and backward. Birds have the Pectoralis muscle divided, as in many of the mammalia, into three portions, which are so distinct as to be regarded as sepa- rate muscles ; they all arise from the enormous sternum, and act upon the proximal extremity of the humerus. Thejirst or great Pectoral muscle (25) is ex- traordinarily developed, and is in general the largest muscle of the body. In birds of flight it often equals in weight all the other muscles of the body put together. It arises from the anterior part of the outer surface of the clavicle or furculum, from the keel of the sternum and from the posterior and external part of the lower surface of that bone ; it is inserted by an extended fleshy margin into the inner side of the anterior crest of the humerus. It forcibly depresses the humerus, and consequently forms the principal instrument in flight. This muscle is very longand wide in the Nata- tores generally, but in many of these birds, as the Penguin, its origin is limited to the external margin of the subjacent pectoral muscle, which is heie remarkably developed. The great pec- toral is very long, but not very thick in the Rusores. In the Herons it is shorter, but much stronger and thicker. Its size is most remarkable in the Humming-birds, Swallows, and diurnal Birds of Prey, where it is attached to almost the whole outer surface of the sternum and its crest, and has an extended insertion into the humerus. In the Ostrich its origin is limited to the an- terior and external eighth part of the sternum, and it is inserted by a feeble tendon into the commencement of the crest of the humerus, to which it gives a strong rotatory motion for- wards. The second Pectoral muscle is situated be- neath the preceding; it has the form of an elongated triangle : it arises from the base of the crest of the sternum and from the mesial part of the inferior surface of that bone ; it in- creases in size as it ascends, then again be- comes suddenly contracted, passes upwards and backwards round the coracoideam, between that bone and the clavicle, then turns down- wards and outwards, and is inserted, fleshy, above and in front of the great pectoral, into the upper extremity of the humeral crest. The interspace between the clavicle, cora- coid, and scapula, through which its tendon passes, serves as a pulley, by means of which the direction of the force of the carneous fibres is changed, and although these fibres ascend from below towards their insertion, yet they forcibly raise the humerus, and thus a levator of the wing is placed without inconvenience on the lower part of the trunk, and the centre of gravity proportionally depressed. In the Penguins, Guillemots, and Gulls, this muscle is almost the largest of the three, occupying the whole length of the sternum. It is remarkable for the length and strength of its tendon, which is inserted so as to draw forwards the humerus with great force. It is proportionally the smallest in the Raptores; and is very small and slender in the Struthious birds. We have already alluded to the use which the Penguin makes of its diminutive anterior extremities as water-wings, or fins; to raise these after making the down-stroke obvi- ously requires a greater effort in water than a bird of flight makes in raising its wings in air : hence the necessity for a stronger development of the second pectoral muscle in this and other Diving Birds, in all of which the wings are the chief organs of locomotion, in that action, and consequently require as powerful a deve- lopment of the pectoral muscles as the gene- rality of Birds of Flight. The third Pectoral muscle, which is in ge- neral the smallest of the three, arises from the anterior part of the inferior surface of the ster- num, and also by a more extended origin, from the posterior moiety of the inferior surface of the coracoid ; it is directed forwards, and is inserted by a short and strong tendon into the internal tuberosity of the humerus, which it depresses. It is proportionally large in the Penguins and Gulls, but attains its greatest development in the Gallinaceous order. Above the preceding muscle there is another longer and more slender one, analogous to the Coraco-brachialis, which arises from the middle of the posterior surface of the coracoid ; its direction upwards is less vertical than that of the third pectoral, along the outer side of which it is attached to the anterior tuberosity of the humerus. This muscle is wanting in the Struthionidtf, is of small size in the Heron and Goose, is much more developed in the Rapiores and many Natatores, espe- cially the Penguins, and attains its greatest relative size in the Rasores, where it arises from almost the whole of the coracoideum. Birds in general possess twojlexors and one extensor (27) of the fore-arm, analogous to those which are found in the mammalia. They have also the muscles corresponding to the pronators and supinators of this higher class, but their action is limited in the feathered tribes to in- flexion and extension of the fore-arm, and to adduction and abduction of the hand. A remarkable muscle, partly analogous in its origin to the clavicular portion of the deltoid, but differently inserted, is called by Carus Extensor plica alaris (30, a b) and forms one of the most powerful flexors of the cubit. It is divided into two portions, of which the anterior and shorter arises from the internal tuberosity of the humerus ; the posterior and longer from the clavicular ex- tremity of the coracoid bone. In the Ostrich and Rhea, however, both portions arise from the coracoid. The posterior muscle (b) sends down a long and thin tendon which runs pa- rallel with the humerus, and is inserted, gene- rally by a bifurcate extremity, into both the radius and ulna. The anterior muscle (a) terminates in a small tendon, which runs AVKS. along the edge of the aponeurotic expansion of die wing. In this situation it acquires exactly the structure and elasticity of the liga- mentum subflavum or ligamentum michae ; it then resumes its ordinary tendinous structure, passes over the end of the radius, and is in- serted into the style of the metacarpal bone. It combines with the preceding muscle in bending the fore-arm; and further, in conse- quence of the elasticity of its tendon, puckers up the soft part of the fold of the wing. (See 48, Jig. 133.) An analogous structure is met with in the wing of the bat. A lesser flexor of the fore-arm, and stretcher of the alar membrane (31) arises, as a portion of the serratus magnus from the ribs, and ter- minates in an aponeurosis inserted into the alar membrane and fascia of the fore-arm ; it is re- presented in the figure as turned aside. The Extensor metacarpi radialis longus (32) is the first muscle which detaches itself from the external condyle of the humerus (E), and it forms the radial border of the muscular mass of the fore-arm ; it terminates in a large tendon about the middle of the fore-arm, and this tendon passes along a groove of the radius, over the carpus, to the phalanx of the so called thumb, or spurious wing, into the radial margin of which it is inserted. It raises the hand, draws it forwards towards the radial margin of the fore-arm, and retains it in the same plane. In the Penguin this muscle is extremely feeble, and the tendon is lost in that of the tensor plica alar is. The Extensor metacarpi radialis brevis (33) arises below the preceding from the ulnar edge of the radius, and is inserted into the phalanx of the thumb immediately beyond the tendon of the preceding muscle. The two tendons are quite distinct from one another in the Birds of Prey, the Ostrich and Parrots, but unite at the lower end of the fore-arm in the Anatida, Phasianida, and Gruida. The muscle analogous to the Extensor carpi ulnaris (34) comes off from the inferior extre- mity of the outer condyle of the humerus, passes along the middle of the exterior surface of the fore-arm, and its tendon, after passing through a pulley at the distal end of the ulna, is inserted into the ulnar phalanx. It draws the hand towards the ulnar edge of the fore- arm, and is the principal abductor or folder of the pinion. The Flexor metacarpi radialis (35) is a short and weak muscle, which arises from the inferior part of the ulna, descends along the internal side of that bone, winds round its lower extre- mity and the radial edge of the carpus, passes beneath the tendon of the radial extensors, and is inserted, external to the latter, high up into the dorsal aspect of the radial phalanx of the metacarpus. In the Ostrich it arises from the lower third of the ulna. In the Penguin it is wanting. The Flexor metacarpi ulnaris (36) arises beneath the fore-arm from the internal pulley of the ulna, continues fleshy to the pinion, and is inserted, first into the ulnar carpal bone, then into the ulnar phalanx. The latter insertion is wanting both in the Ostrich and Penguin. The muscles of the pinion or hand are few, and very distinct from one another; the thumb or spurious wing is moved by four small mus- cles, viz. two extensors, an abductor, which draws the thumb forwards, and an adductor. The second digit receives three short muscles, two of which are extensors, and the third an abductor, in this action it is aided by one and opposed by another of the extensors. The lesser digit receives an abductor, which comes from the ulnar edge of the preceding phalanx. Muscles of the lower extremity. Notwith- standing the simplicity of the motions of the lower or posterior extremity, the muscles of this part are numerous, and present several peculiarities in birds. The femur can be moved freely forward and backward, but its rotation is limited by a strong ligamentum teres, and the structure of the hip-joint does not permit it to be carried under the body, or far outwards. In consequence of the form of the pelvis, the psoas magnus and parvus, the obturator externus and the quadratics lumborwn do not exist in birds. A large muscle, regarded by Cuvier as the Obturator internus, takes its origin from the internal surface of the ischio-pubic bone, it is directed from behind forwards, and gives off a strong and long tendon which passes through the small opening at the anterior part of the obturator foramen, which is situated between the pubis and ischium, (f, fig. 131.) In this situation a muscle, arising from the external border of the opening, attaches itself to the preceding, and is inserted conjointly with it into the posterior and outer aspect of the trochanter. Meckel compares this muscle with the pectineus, especially as it exists in the Sau- rian Reptiles, but observes that as it arises from both the internal and external surfaces of the circumference of the obturator foramen, it may represent both the internal and external obturator muscles. It is of an extraordinary size in the Ostrich. The femur is raised by three muscles. The most superficial and highest of these elevators (37) arises by a broad and thin aponeu- rosis from the anterior and external surface of the ilium, it is of a square form, descends al- most in a straight line, and is inserted into the posterior part of the trochanter. Meckel re- gards it as analogous to the Glutaus medius: Carus calls it the Glutteus maximus. But the latter, according to Meckel, is represented by the posterior part of what Carus terms the Rectusfemoris latissimus (40). Anterior to the Glutaus medius of Meckel, there is a much smaller muscle, which extends from the anterior margin of the ilium to the trochanter, where it is inserted in front of the preceding. It is of an elongated quadrilateral form, and it represents the Glutaus minor of quadrupeds. It is wanting in many of the Natatvres, and arrives at its greatest degree of development in the Raptorial Order. A third muscle, still smaller and longer than 296 AYES. the preceding and situated beneath it, which arises from the outer margin of the ilium, and is inserted into that part of the femur which corresponds to the lesser trochanter, is regarded by Meckel as the Iliacus internus, which Cu- vier states to be wanting in Birds. It is, how- ever, present in most, and is seen highly deve- loped in the Ostrich. The muscles analogous to the Pyramidalis and Gemellus superior exist in Birds. There are most commonly three adductors of the thigh. The inferior, external, and posterior one arises from the middle of the external sur- face of the anterior margin of the ischio-pubic bone, and is inserted into the greater part of the lower half of the femur at 38. The second and third adductors are situated internally to the preceding ; the latter of these may be compared to the Pectineus. The Sartorius (39) arises from the anterior point of the ilium, and passes down to be attached to the head of the tibia ; it is an ex- tensor of the leg upon the thigh. The Rectus femoris (40) arises by a thin but wide aponeurosis from the spines of the sacrum, after a short course it joins the Crurceus and Vasti (42), and is inserted into the head of the fibula. It corresponds according to Meckel with the Tensor vagina femoris and the Glutens magnus. The Gracilis (41) arises from the superior part of the pubis, descends along the inner side of the thigh, and towards the lower extre- mity of this part, is continued into a long and strong tendon, which passes in front of the knee-joint, and over the extensor tendon of the leg to the outer side of the fibula, whence it pro- ceeds inwards, anterior to the tendon of the pero- neal flexor, to become united to the outer origin of the flexor perforatus of the toes. Meckel con- siders that the muscle now described represents the Rectus Jemor is of mammalia, and regards as the Gracilis a small and thin muscle, whose origin has been transferred lower down, from the pubis to the femur, from the internal side of which it passes to the internal and superior part of the tibia. Be this as it may, the disposition of the former muscle is such, passing, viz. first, over the convexity of the knee-joint, and after- wards over the projection of the heel, that from its connection with a flexor of the toes, these must necessarily be bent simultaneously with every inflection of the joints of the knee and ankle. As these inflections naturally take place when the lower extremities yield to the superincumbent weight of the body, birds are thus enabled to grasp the twigs on which they rest whilst sleeping, without making any muscular exertion. There are three flexors of the leg : one (43) which, although single, is from its insertion into the back of the fibula, analogous to the Biceps flexor cruris of the human subject : ano- ther on the inside is attached to the tendon of the extensors of the foot as well as the tibia ; this muscle might be called the Semimembranosus (44) : the third flexor is in the middle (45), it comes from the ischium, and as it descends it receives a broad fleshy slip from the back of the femur. It is inserted on the back of the tibia, the tendon covering those of the extensors of the heel. The muscles of the feet present in Birds essential resemblances to the same parts in Reptiles. They are divided into muscles of the tarsus, of the metatarsus, and of the toes, the latter being subdivided into long and short. The principal points in which they differ from the same muscles in Reptiles and the Mammalia are the following: their origins and carneous portions are not situated on the foot but higher up on the tibia and even on the femur. The great length of the metatarsus occasions the smaller muscles to be of a greater proportional length than in other animals. The muscular portions are most developed in the Raptores, Scansoresy and Natatores ; the Insessores and Rasores present an intermediate proportion ; the Cursores and Grallatores have the longest tendons. The Gastrocnemius (46) has three distinct origins : two of these are superficial, one from the outer, the other from the inner condyle of the femur ; the third origin is lower down from the inner side of the tibia and fibula (47), They unite to terminate in a thin and broad aponeurosis, which after becoming closely con- nected with a fibre-cartilage appertaining to the flexor digitorum, proceeds to be inserted into both the outer and inner margins of the tarso- metatarsal bone. The Tibialis anticus (48) arises from the an- terior part of the upper extremity of the tibia, below which its tendon passes through an aponeurotic loop extended from the outer to the inner margin of the tibia. It has also a second origin, by means of a slender tendon, from the anterior part of the external condyle of the femur. It is generally inserted pretty high up into the tarso-metatarsal bone between the outer and inner margins ; but in the Psit- tacida it is attached lower down to the internal border, so as to turn the foot inwards as well as raise it, a disposition which is extremely favor- able fov the act of climbing. The Peroneus (49) is a much smaller muscle ; it extends from the lower region of the fibula, and the outer and anterior edge of the tibia to the tarso-metatarsal bone, into the outer side of the base of which it is inserted. The Flexor perforatus sen longus digitorum (50) forms the superficial and external mus- cular mass of the leg : it arises by one mass from the posterior part of the external side of the femur, immediately in front of the outer head of the gastrocnemius ; another portion arises from the outside of the lower extremity of the femur ; these two heads unite below the middle of the leg and constitute one fleshy belly which gives off three tendons; these proceed to the proximal phalanges of the three outer toes where they bifurcate to give passage to the ten- dons of \heflexor perforans. The Flexor pollicis (51) arises, by its anterior head, from the anterior and upper part of the tibia, and by its posterior head from the ex- AVES. 297 ternal condylc of the femur; when it has readied the region of the culcaneum, it passes backwards through a synovial capsule, and is inserted into the proximal phalanx of the thumb, where it is perforated by the tendon of the perforans muscle. The Flexor proj'undus perforans (52) arises as two distinct muscles, the one from the back of the femur and the other from the back of the tibia and fibula; the tendons of these two portions unite behind the metatarsal bone, and send off tendons to the last phalanges of the toes, which perforate those of the flexor sublimis. The Extensor longus com munis digitorum arises above from the anterior side of the tibia, below the tibialis anticus, passes beneath a strong restraining ligament, then lower down beneath an osseous bridge, and lastly across a strong ligament situated at the inferior ex- tremity of the tarso-metatarsal bone. Below this part its tendon divides into three slips which are inserted into the distal phalanges of the thiee outer toes (53). There are six long muscles lying on the metatarsal bone ; they are largest and best marked in those birds which walk most, as the Arcs ter retires. Two of these muscles are on the posterior surface ; one goes to the base of the external toe, which it abducts; the other is inserted into the root of the back toe, which it bends. The other four muscles are on the anterior part of the metatarsus : the first extends the back toe; the second goes to the base of the first toe, and abducts it; the third is spread on the root of the middle toe, which it extends ; the fourth lies along the out- side of the metatarsus, perforates the end of the bone, and is implanted into the inside of the external toe, and abducts it. Progression on land is generally effected in birds by the alternate advancement of the two feet; but sometimes they proceed by leaping or hopping, rather than walking ; both feet are then firmly fixed on the ground, and the body is propelled forwards by a sudden extension of all the joints of the legs. Birds which have sharp claws, as the Accipitres, #c., retract them when they hop, to prevent their being blunted. The Cat tribe, among mammalia, have a me- chanism effecting a similar purpose. Some birds derive assistance in terrestrial progression by the flapping of the wings, and this is especially the case with the Ostrich, which runs by the alternate advancement of its legs. The act of climbing is performed by means of a peculiar disposition of the toes, aided by prehension with the beak, as in the Maccaws and Parrots, or by the prop formed by the stiff tail-feathers, as in the Woodpeckers. The act of swimming is rendered easy to birds by the specific levity of their body, arising from the extension of the air-cells ; by the shape of the chest, which resembles the bottom of a boat ; and by the conversion of the hinder extremities into oars in con- sequence of the membranes uniting the toes together. The effect of these web-feet in water is further assisted by the toes, having their membranes lying close together when carried forwards, whilst, on the contrary, they are ex- panded in striking backwards. The oar-like action of the hinder legs is still further favoured by their backward position ; and by the meta- tarsus and toes being placed almost on the same perpendicular or vertical line with the tibia, an arrangement, however, which is unfavourable for walking. Sailing. Some birds, as the Swan, partially expand their wings to the wind while swimming, and thus move along the waters by means of sails as well as oars. The act of diving is performed by the rapid and forcible action of the wings, beating the water as in flight, by the feet striking the waters backwards and upwards, and assisted probably by the compression of the air-cells. Flight, the most important and characteristic mode of locomotion in birds, results principally from the construction and form of the anterior extremities, which have already been described. The form of the body has also especial reference to this power, the tiunk being an oval with the large end forwards. The spine being short and inflexible, the muscles act to great advantage, and the centre of gravity is more easily changed from above the feet as in the stationary position, to between the wings as during flight. The head of the bird is generally small, and the beak pointed, which is a commodious form for dividing the air. The long and flexible neck compensates for the want of hands and the rigidity of the trunk, and contributes to change the centre of gravity, according to the required mode of progression, by simply projecting the head forwards, or drawing it back. The position of the great pectoral muscles, as before observed, always tends to keep the centre of gravity at the in- ferior part of the body. The power which birds enjoy of raising and supporting them- selves in the air is undoubtedly aided by the lightness of the body. The large cavities in the bones diminish their weight without taking away from their strength, a hollow cylinder being stronger than a solid one of the same weight and length. But the specific levity principally depends on the great air-cells, which occupy almost every part of the body, and which are all in communication with the lungs. The air which birds inspire distends these cells, being expanded by the great heat of the body. Lastly, the feathers, and especi- ally the quills, from their lightness and elastic firmness, contribute powerfully to the act of flying by the great extent which they give to the wings, the length and breadth of which are fur- ther increased by the expanded integument situated in the bend of the arm and in the axilla. When a bird commences its flight it springs into the air, either leaping from the ground, or precipitating itself from some elevated point. During this action it raises the humerus, and with it the entire wing, as yet unfolded ; it next spreads it horizontally by an extension or ad- duction of the fore-arm and hand ; the greatest extent of surface of the wing being thus acquired, 298 AVES. it is rapidly and forcibly depressed; the resistance of the air thus suddenly struck occasions a reaction on the body of the bird, which is thereby raised in the same manner as in leap- ing from the ground. The impulse being once given, the bird folds the wings by bending the different joints, and raises it preparatory to another stroke. Velocity of flight depends upon the rapidity with which the strokes of the wings suc- ceed each other. A simple downward stroke would only tend to raise the bird in the air ; to carry it forwards the wings require to be moved in an oblique plane, so as to strike backwards as well as downwards. The turn- ing in flight to the right or to the left is prin- cipally effected by an inequality in the vibra- tions of the wings. To wheel to the right the left wing must be plied with greater frequency or force, and vice versa. The outspread tail contributes to sustain the posterior part of the body ; when depressed during a rapid forward flight, the anterior part of the body is raised, and flight retarded ; when the tail is raised the anterior part of the body is lowered. Some birds bend the tail to one side, using it as a rudder when the hori- zontal course of flight is required to be changed. The first launch of the bird into the air is pro- duced by an ordinary leap from the ground, and depends, in some degree, on the length of the legs. Those birds which have very short legs and very long wings, as the Swallows, &c., cannot leap high enough to gain the requisite space for the expansion of their wings, and consequently have much difficulty in raising themselves from the ground, and generally pre- fer throwing themselves from some high point. The manner of flight varies exceedingly in different birds, some dart forward by jerks, closing their wings every three or four strokes ; the Woodpeckers, Wagtails, and most of the small Insessores are characterized by this kind of undulatory motion : other birds, as the Swal- low, Crow, &c. fly smooth and even : the Kite and Kestrel Hawk and the great Albatross some- times appear to buoy themselves in the air with- out any perceptible motion of the wings. The rapidity with which a strong Bird of Prey flies in pursuit of his quarry is inconceivably great. The anecdote of the Falcon belonging to Henry IV. King of France, which flew in one day from Fontainbleau to Malta, a distance of 1350 miles, is well known, and many similar instances are on record. The flight of a Hawk, when its powers are fully exerted, is calculated at one hundred and fifty miles an hour. The Eider-Duck's usual flight has been ascertained to be at the rate of ninety miles an hour. The famous Race-horse Eclipse is said to have gone at the rate of a mile in a minute for a very short distance; but this speed, if it could be continued, would not be half so great as that which many birds put in practice during their long journeys of migration. Of the Nervous System. There is a remark- able uniformity in the form and structure of the brain (fig. \ 34, , b, c, d) and medulla spinalis (e y e) in the different orders of birds. These great divisions of the cerebro- spinal axis are always readily distinguishable from one another by the greater breadth and glo- bular form of the brain, which is proportionally much larger than in the other oviparous verte- brata. The high degree of development which the spinal cord and cerebellum present, as compared with the cold- blooded Reptilia, has an evident relation to the extraordinary loco- motive powers with which the feathered class is en- dowed . In a Pigeon weighing eight ounces with, and seven ounces without its feathers, or three thou- sand three hundred and sixty grains, the cerebro- spinal axis weighs forty- eight grains, the weight of the spinal cord be- ing eleven, and that of the brain thirty-seven grains. Of the Brain. The brain of the bird differs from that of the reptile in the superior size of the cerebrum, and the more complex structure 4 of the cerebellum ; it differs from the brain of a mammal in the smaller size of the cerebellum, resulting from the want of the lateral lobes, and in the absence or rudi- mentary condition of the fornix; and it differs from the brain of every other vertebrate class in 1 the lateral and inferior position of the optic lobes or bigeminal bodies.* * It cannot be at once distinguished, as Cu- vier asserts, by being composed of six out- ward and visible masses, since the two hemi- spheres, (a, a,) the two optic lobes, ( b, b,) the cerebellum, (c,) and medulla oblongata, (d,) * We have lately as- certained that the corpus callosum is wanting in some of the marsupial animals; its presence is therefore no longer characteristic of the class mammalia. 'g- 134.; Brain and Spinal Cord of a Goose, AVKS. 299 are equally obvious in the brains of reptiles. They are, however, differently disposed in birds ; the optic lobes, which in reptiles intervene and are visible between the cerebrum and cerebel- lum, being in birds displaced, as it were, by the hemisphere and cerebellum coming into close contact, so that the optic lobes are pushed downwards and to one side. The transverse convolutions of the cerebellum at once distin- guish, however, the brain of a bird from that of any reptile and most fishes ; but it is a curi- ous fact that the cerebellum in the sharks is similarly composed of a vermiform process only, transversely folded or convoluted. The cerebral hemispheres sometimes present the form of a flattened oval, as in the Parrot tribe, but in general are of a convex cordiform shape, with the apex directed forward. Fig. 135. The optic lobes (b, Jig. 135) are rounded tubercles, situated be- low and behind the hemispheres, in the la- teral i n terspace between these and the cerebel- lum. The cerebellum is Base of the brain of a composed of the middle Pigeon. lobe onl y> and 1S of a compressed arched form. The medulla oblongata presents neither a tuber annulare nor corpora olivaria or pyrami- dalia, but is a large uniform tract situated be- tween and behind the optic lobes. On the lower part of the side of each cere- bral hemisphere there is a depression which corresponds to the fissura magna Sylvii, and is the only appearance which the hemispheres present of a division into lobes. Elsewhere there are no traces of convolutions, the cere- brum in this respect resembling that of Kep- tiles and Fishes, and some of the least intel- ligent orders of Mammalia, as the Rodent ia, Marsupiata, and Edentata. The optic lobes are also devoid of the transverse fissure which bisects the optic lobes of mammalia. The cerebellum is marked by close and transverse anfractuosities, such as characterize the corresponding portion of the cerebellum in mammalia, called the vermiform process. Fig. 136. When the cerebral hemispheres are divari- cated from each other, (Jig. 136,^) they are seen to be disunited through the whole of their vertical extent, and to be joined only by the round anterior commissure of the brain (k,Jig. 136.) In fact both the corpus callosum and fornix are wanting ; or at most a rudiment only of the latter part can be perceived in the brains of some birds, as the Eagles, Vultures, and Parrots. The mesial surfaces of the hemispheres, which are in contact with each other, present a few striae which diverge from the commissure. These surfaces are composed of an extremely Brain of a Pigeon. thin layer of medullary substance, (g,) forming the internal parietes of the ventricle, and ex- tended outwardly over the corpus striutum (i.) This body is of very great size in birds, consti- tuting of itself almost the entire substance of the hemisphere, projecting into the ventricle, (/i,) not only from below, but from the anterior and outer sides of the cavity, and being covered by a smooth layer or fold of medullary matter, Up) which increases in thickness anteriorly. The ventricle does not extend below the corpus striatum to form an inferior horn ; and, as in most mammalia there is no extension of the cavity backwards to form a posterior horn, there is consequently no cornu ammonis. The vessel forming the plexus choroides penetrates the ventricle beneath the posterior part of the thin internal wall, and the lateral ventricles communicate together there, and with the third ventricle. They are continued anteriorly to the root of the olfactory nerve, which is itself a continuation of the apex of the hemisphere. Just above the orifice of communication there is a smooth flattened projection, rounded exter- nally, which advances into the ventricle from the internal wall ; this is a rudiment of the fornix. The round anterior commissure (k) is pro- longed on either side into the substance of the hemispheres, as in man and quadrupeds. The optic thalami (I) are of small size, and not united by a soft commissure: between them is the cavity called third ventricle (m) ; and above and behind they give off the peduncles of the pineal gland. This body does not hang- freely suspended by the pedicles, but seems to form a rounded and thickened anterior border of the valvulaVieussenii or lamelliform commis- sure of the optic lobes. Carus describes the pineal gland as adhering firmly to the conflu- ence of the great veins situated at the anterior orifice of the aqueduct of Sylvius. In Pigeons he states that it is composed of many segments, but that in general it is of a simple and "conical form ; the figure which he gives of it, from the Turkey, exhibits a pyriform shape.* The valve which closes the upper part of the passage from the third to the fourth ventricle, is a thin lamella of great width, in consequence of the distance to which the optic lobes are sepa- rated from one another. Anteriorly the third ventricle communicates with the infundibulum. The fourth ventricle (n) resembles that in the brain in mammalia, but is of less width ; its floor is indented with the longitudinal fissure called calamus scriptorius. Besides the cavities or ventricles above men- tioned, there are also two others situated in the optic lobes ( o) ? or bigeminal bodies, each of which, when laid open, is seen to be occupied by a convex body (p) projecting from the posterior and internal side of the lobe; these ventricles communicate with the others in the aqueduct of Sylvius. As there is no transverse furrow in the optic lobes, they cannot be distinguished into the protuberances called * nates ' and ' testes ' in * Anat. Comparee, uouv. cd. i. p. fig. 6. pi. xv. 300 AVES. the human brain ; they have most resemblance, however, to the latter bodies. With respect to the substance of which the brain of birds is composed, we may observe that the bodies analogous to the corpora striata do not merit that name, as there are no alterna- ting striae of grey and white matter. In this respect the bird's brain resembles that of the cold-blooded ovipara and of the human fetus. The substance of the cerebellum does present the admixture of the two substances, or arbor vita (q), but in a less complicated degree than in mammalia. The brain in birds is invested with the same membranes as are described in Mammalia. Medulla spinalis. The spinal cord is con- tinued from the foramen magnum to the canal formed by the coccygeal vertebrae, where, how- ever, it becomes extremely attenuated, and corresponds in extent to the shortness of that division of the vertebral column, terminating in a mere filament which expends itself in distributing a few pairs of nerves through the coccygeal foramina. As in the Mammalia, it appears externally to be composed of the white or medullary matter, but contains a small pro- portion of grey substance internally. It is of a cylindrical figure, and as in the cold-blooded ovipara, it is of great length in proportion to the brain. An anterior and posterior fissure may be distinguished, and also a narrow canal which extends through its entire length. Two enlargements occur in the course of the spinal cord, one corresponding to the wings, the other to the legs ; and from these swellings the nerves of the brachial and sacral plexuses come off respectively. As might be expected, therefore, these enlargements present differ- ences of relative size corresponding to the dif- ferent relative development and powers of the anterior and posterior extremities. In general the posterior enlargement is greater than the anterior; and this difference is very remarkable in the Struthious birds in which the whole business of progression falls upon the posterior extremities. Besides the difference in size, the spinal enlargements or ganglions, as they may be termed, differ also in structure ; at the anterior, alar, or thoracic enlargement (r, Jig. 134) the spinal cord merely receives an accession of grey and white medullary substance ; but at the beginning of the sacral swelling (s,fg. 134) the canal of the cord enlarges in a remark- able manner, so that the lateral cords separate from one another posteriorly or above, pre- cisely as they do to form the fourth cerebral ventricle: the cavity or spinal ventricle (s, Jig. 134) thus formed, is filled with a serous fluid inclosed in a pia mater. From the figure of this cavity it has been termed the ' Sinus rhomboidalisJ Of the Nerves. The cerebral nerves cor- respond in number to those of the Mammalia. The principal difference of form and structure is presented in the olfactory or first pair (1, jig. 135.) These nerves are of a cylin- drical figure and sihall extent, being continued from the anterior extremity or apex of the hemispheres. Instead of separating into fila- ments to pass out of the skull by a cribriform lamella, each nerve is continued along an osseous canal, accompanied by a venous trunk, as far as the pituitary membrane of the supe- rior spongy bone upon which its filaments are distributed in a radiated manner. The optic nerves (2, Jigs. 135, 137,) are in general of remarkable size ; they arise from the whole of the outer surface of the optic lobes, and form in front of the infundibulum, a perfect union, or chiasma, (2*, Jig. 137,) in which, on making a horizontal section, some transverse striae may be perceived, apparently resulting from the decussating fibrils of the nerves. The distribution of the third, (3, Jigs. 135, 137,) fourth, (4, Jigs. 135, 137,) and sixth cerebral nerves, (6, Jigs. 135, 137,) is almost the same as in Mammalia. The course of the fourth pair, immediately above the supra- orbital branch of the fifth pair is shown at 4*, j0g. 137, as far as its termination in the superior oblique muscle to which it is, as in other vertebrata, exclusively distributed. The Ji/'t h or trigeminal nerve (5, Jigs. \ 35, 137) has nearly the same distribution as in Mammalia. The first or ophthalmic division (5*, .fig- 137) passes out of the cranium by a peculiar canal situated externally to the optic foramen. It is of large size, and describes in its passage through the orbit a curve corresponding to the roof of that cavity; it generally penetrates the substance of the facial bones above the nasal fossae. It divides into three branches ; the first or supe- rior is the smallest and is lost upon the pitui- tary membrane; the second branch is the largest of the three and the longest ; it is re- ceived into an osseous canal, passes over the nasal organs, and terminates at the extremity of the beak in a great number of divisions ; the third branch of the ophthalmic nerve is entirely distributed to the skin which covers the circumference of the external nostrils. The second division, or superior maxillary nerve passes out of the same foramen as the in- ferior one (at 5", Jig. 137,) immediately above the tympanic bone or os quadratum ; it passes forwards along the floor of the orbit, and in this part of its course gives off two filaments, of which one joins the ramifications of the ophthalmic nerve, the other ascends, penetrates the substance of the pterygoid muscles and the maxillary bone, to be lost on the lateral parts of the bill. In those birds, as the AnatidtE and other Water- fowl, where the upper mandible is notched on the edge, each denticu- lation receives four or five nervous filaments, and the nerve is proportionally of large size. The inferior maxillary nerve separates from the superior, and proceeds obliquely down- wards, dispensing branches to the pterygoid and quadrangular muscles of the jaws; the trunk proceeds outwards to the lower jaw where it divides into two branches an internal and an external. The internal, which is a con- tinuation of the trunk, penetrates the maxillary canal, and is continued to the anterior end of that mandible. In the Anatute it gives off nerv AVES. 301 es to the dentations along the edge of the mandible. The external branch recedes from the internal, perforates the jaw, and is dis- tributed on its external surface beneath the tegumentary or horny substance which sheaths the extremity of the mandible. It supplies no gustatory branch to the tongue, which is an or- gan of prehension, not of taste, in Birds. The facial nerve, or portio dura, exists in Birds, but it is extremely small, its offices being hardly required, in consequence of the structure of the parts of the face in this class. However, a few branches may, with difficulty indeed, be traced, and the trunk of the nerve is constantly present. The auditory nerve, or portio mollis, is large, very soft and pulpy, and of reddish colour ; it is received into a deep depression on the internal surface of the cranium (at 7, fig. 137), whence it penetrates by several small foramina to the labyrinth. The pneumogastric nerve, or nervus vagus, generally passes out of the cranium in two or three filaments, which afterwards rejoin. On leaving the skull, this nerve communicates with the lingual and glosso-pharyngeal nerves, and is situated between them, the lingual being placed in front. Each nerve of the par vagum passes as a distinct strong cord along the neck in company with the jugular vein, and de- scending into the chest forms the cardiac and pulmonary plexuses, as in Mammalia. The two nerves unite behind the hearl, and proceed along the oesophagus to terminate in anasto- moses with the great sympathetic nerve. The gtosso-pharyngeal nerve of the eighth pair passes out of the cranium through the foramen behind the ear, which corresponds to the foramen lacerum posterius, by two filaments, which immediately unite to form an elongated quadrangular ganglion ; this sends off a small internal branch in front of the muscles of the neck ; a small posterior twig which unites with the par vagum, and a large inferior branch to the anterior part of the neck. The latter is a continuation of the nerve itself; it descends along the oesophagus and divides into two prin- cipal branches, of which one passes upwards to the muscles of the os hyoides, between which it is included, and this branch is re- markably tortuous in the Woodpecker in order to be accommodated to the extensile motions of the tongue. The other branch descends along the lateral parieles of the oesophagus, and sends off a twig to join the lingual nerve. The termination of the glosso-pharyngeal is expanded upon the oesophagus. The hypoglossal nerve (9th pair) escapes from the cranium posterior to the nervus vagus by the condyloid foramen. It is very slender at its origin; passes to the front of the nervus vagus, partly uniting with, as it crosses over this nerve, and in that situation it detaches a small filament analogous to the descendens noni, which accompanies the jugular vein to the chest. The trunk of the hypoglossal next crosses the glosso-pharyngeal nerve, then passes beneath the cornu of the os hyoides, and ad- vances towards the superior larynx, where it terminates by dividing into two principal branches, which are distributed, the one to the anterior and inferior, the other to the superior and internal parts, of the tongue. Spinal nerves, These correspond in number to the vertebra- of the spine. They arise, as in the other vertebrata by two roots, the ganglion on the posterior of which is proportionally very large. In the sacral region of the spine, the anterior and posterior roots escape by distinct foramina, and can be separately divided with- out laying open the bony canal, but they are deeply seated and well protected by the anchy- losed processes of the sacrum and the extended iliac bones. The cervical nerves vary considerably in number, the known extremes being from ten to twenty-three, corresponding to the number of vertebrae. They are proportionally larger than in man, are tortuous in their course, to be accom- modated to the extensive motions of the neck, and are principally lost in the integument. Only the last, or last two, pairs (u' u", fig. 134^) of cervical nerves concur in the formation of the brachial plexus, which is completed by the first two pairs of dorsal or thoracic nerves ( v). The dorsal nerves do not present any notable differences from those of mammalia. The sacral nerves have no other peculiarity than their mode of passing out of the spinal canal: they form exclusively the plexus ana- logous to the lumbar and sacral (w,Jlg. 134). The nerve analogous to the phrenic nerve is wanting in Birds, in correspondence with the rudimentary condition of the diaphragm. The brachial plexus, formed by the two last cervical and one or two first dorsal nerves, soon becomes blended into a single fasciculus whence all the nerves of the wing are derived. Accord- ing to Cuvier, the first four that are given off are of large size, and are distributed to the great and middle pectoral and subclavian mus- cles. A small filament is then detached which supplies the muscles surrounding the head of the humerus and capsule of the joint ; this re- presents the articular nerve. The rest of the plexus divides into two large nerves, which supply the wing. Macartney describes the course of the nerves of the wing in a somewhat different manner, and observes that they more nearly resemble those of the superior extremity in mammalia, than Cuvier has represented. The brachial plexus, according to this author, gives rise to three nerves which are distributed in the follow- ing manner : " The first is a very fine filament, which runs down on the inside of the arm, and is lost about the internal part of the elbow. This is analogous to the internal cutaneous nerve. The second is a large cord ; it gives off a very large branch, which divides into many others, for the supply of the pectoral muscles ; it sends several smaller branches to the muscles under the clavicle and about the joint, and then proceeds to the inner edge of the biceps muscle, along which it descends to the fold of the arm, after giving some large muscular branches. Before it reaches the joint, it divides into two branches; one of 302 AVES. which is analogous to the ulnar nerve, and the other soon divides again into nerves which are similar to the median and musculo-cutaneous. The median dips down amongst the muscles on the middle of the fore-arm, to which it gives branches, and afterwards runs along the inter- osseous space, passes under the annular ligament of the carpus, and is distributed to the short muscles of the digiti. The branch analogous to the musculo-cutaneous nerve, is expanded upon the muscles on the upper edge of the radius. 11 The ulnar nerve, although it appears to be incorporated with the median on the upper arm, can be easily separated from it, and traced to its proper origin in the brachial plexus. After this nerve leaves the median, it turns over the end of the foramen to get upon the edge of the ulna. It gives filaments to the muscles in this situation; but its chief branch runs down superficially upon the ligaments of the quills in company with a vein, and goes ultimately to be lost upon the ulnar edge of the hand. " The third cord furnished by the brachial plexus, supplies the place of the radial nerve. It detaches several filaments to the muscles on the inside and back of the scapula. It gives off also the articular nerve, and then winds round the humerus between the extensor mus- cles, to which it furnishes some large filaments. On coming to the outside of the humerus, it sends a branch between the integuments of the fold of the wing. The nerve now turns round the neck of the radius, beneath the muscles, and forms two branches ; of which one passes under the muscles to the outer side of the ulna, along which it runs superficially to the hand ; the other branch passes on the radial side, but more deeply amongst the muscles, goes under the annular ligament of the carpus, proceeds between the branches of the metacarpus, and is finally lost on the back of the digiti." The same anatomist describes the course of the nerves of the posterior extremities as follows. " Although Cuvier has given a more accurate description of the nerves of the lower extremity than those of the wing, it nevertheless needs correction in several particulars. " The obturator and femoral nerves arise from the same plexus which is formed by the two last lumbar nerves, by a communicating branch from the first sacral pair. The obtu- rator nerve passes through the upper part of the foramen ovale, and is distributed to the muscles around the hip-joint, especially the adductor. The femoral nerve passes out of the pelvis in company with the artery, over the upper edge of the ilium. It divides into three branches, which are dispersed among the muscles and integuments on the anterior and inner part of the thigh. Some of these filaments are long, and descend superficially for a considerable way upon the limb. " The ischiatic nerve is composed of the five superior sacral nerves ; and as soon as it de- parts from the plexus, even within the pelvis, is easily separable into its primary branches. Immediately after it passes through the ischi- adic foramen, it sends filaments to the muscles on the outer part of the thigh ; it then proceeds under the biceps muscle, along the back of the thigh, about the middle of which it becomes divided into the tibiul and the peroneal nerves. " The tibial nerve, even before it arrives in the ham, separates into several branches, which pass on each side of the bloodvessels, and are chiefly distributed to the muscles on the back of the leg. Two of these branches, however, are differently disposed of; the one accom- panies the posterior tibial artery down the leg, passes over the internal part of the pulley, and is lost in small filaments and anastomoses, with a branch of the peroneal nerve on the inner side of the metatarsus ; the other branch runs down on the peroneal side of the leg, along the deep- seated flexors of the toes, passes in a sheath formed for it on the outer edge of the moveable pulley of the heel, and proceeds under the flexor tendons along the metatarsal bone, to be distributed to the internal part of the two ex- ternal toes. " The peroneal nerve is directed to the outer part of the leg ; it dips above the gastrocnemii muscles, and runs through the same liga- mentous pulley that transmits the tendon of the biceps muscle; it then detaches some large filaments to the muscles on the anterior part of the leg, under which it divides into two branches, which proceed close together, in com- pany with the anterior tibial artery to the fore part of the ankle-joint, at which place they separate ; one passes superficially over the outer part of the joint, the other goes first under the transverse ligament which binds down the tendon of the tibialis anticus muscle on the tibia, and then over the inner part of the joint, below which it divides into two branches, the one is distributed to the inner side of the metatarsus and the tibial side of the pollex, and to the next toe ; the other turns towards the centre of the metatarsal bone, and pene- trates the tendon of the tibialis anticus just at its insertion, and then rejoins the branch of the peroneal nerve it accompanied down the leg. They continue'their course together again in the anterior furrow of the metatarsal bone ; and at the root of the toes, separate once more, and proceed to the interspaces of the three anterior toes, and each divides into two fila- ments, which run along the sides of the toes to the nail." Rees' Cyclopedia, Art. Birds. The great sympathetic nerve of birds resem- bles, in many particulars, that of mammals. It enters the cranium by the same orifice as that by which the nervus vagus and the glosso- pharyngeal make their exit; it there unites with the fifth and sixth pair of nerves. At the base of the cranium the first ganglion, or su- perior cervical, is of a lenticular form, and communicates at once with the ninth and eighth pairs of nerves, so as to seem as if it were blended with them. The remainder of the chain of cervical ganglions are very remarkably situated, being lodged on either side in the canal of the vertebral artery formed by the trans- verse processes ; into which it passes, or from which it escapes above, at the third cervical vertebra, while below the sympathetic again becomes conspicuous at the commencement of the thorax, where it sends a considerable branch from the first thoracic ganglion to join the pul- monary plexus formed by the par vagum. This ganglion also distributes seven other fila- ments, one of which goes to join the brachial plexus; a second is lost in the cardiac plexus of the par vagum ; three other filaments proceed inwardly to the projection formed by the bodies of the vertebrae to produce the commencement of the splanchnic nerve ; lastly, the sixth and seventh serve to unite the first ganglion with the second, one passing above, the other below the head of die rib, which they thus include in a lozenge-shaped space. Each of the succeed- ing ganglions forms, in like manner, a centre of nervous radiations, which are five, six, or seven in number, of which four, two anterior and two posterior, serve to bring the contiguous ganglia into communication with each other; one or two contribute to the formation of the splanch- nic nerve, and one joins the dorsal spinal nerve situated immediately behind the ganglion. The splanchnic nerves, formed by all the in- ternal thoracic branches of the great intercostal, accompany on either side the trunk of the aorta. When it has arrived at the cceliac axis, they surround it and form one, two, or three ganglions from which an immense number of filaments are thrown off, which surround the different arteries of the abdomen. These gang- lions are evidently the analogues of the semi- lunar ganglions of man, and the filaments pro- ceeding from them correspond to the solar plexus. The trunk of the sympathetic con- tinues along the bodies of the vertebrae, but the ganglions become less marked after the ribs cease to be given off; two or three filaments are given off from each of these small swell- ings, which, by uniting with the filaments of the opposite side, form a plexus around the aorta. The termination of the sympathetic may be readily traced along the coccyx, where four pairs of ganglions are observable in the Swan, the last of which join to form a ganglion impar. Fig. 137. Cerebral nerves, eyes, Sfc. in situ of a Goose. 303 Organs of Vision. The eye in Birds pre- sents many peculiarities, which chiefly relate to the extraordinary powers of locomotion in this class, tending to accommodate vision to a rapid change of distance in the objects viewed, and to facilitate their distinct perception through a rare medium. There is no species of bird in which the eyes are wanting, or are rudimentary, as occurs in the other vertebrate classes. The eyes of Birds are, in the first place, re- markable for their great size, both as compared with the brain and with the entire head, (jig. 137,) being analogous, in this respect, to the eyes of some of the flying insects. Their form is admirably adapted to promote the objects above named. The anterior segment of the eye is more prominent than in any other class of animals, and is in many birds prolonged into a tubular form, terminated by a very convex cornea (e,Jig. 137.) Dr. Macartney observes that " the owl furnishes the most striking ex- ample of the disproportion between the anterior and posterior spheres of the eye, the axis of the anterior portion being twice as great as that of the other. The obvious consequence of this figure of the globe of the eye is to allow room for a greater proportion of aqueous fluid, and for the removal of the chrystalline lens from the seat of the sensation, and thus produce a greater convergence of the rays of light, by which the animal is enabled to discern the objects placed near it, and to see with a weaker light; and hence owls, which require this sort of vision so much, possess the structure fitted to effect it in so remarkable a degree." The anterior division of the eye is least con- vex in the swimming birds. The sclerotic coat is divisible into three layers. It is thin, flexible, and somewhat elastic posteriorly, where it presents a bluish shining appearance, without any distinct fibres,but anteriorly its form is main- tained by a circle of osseous plates or scales (J\ fg.l 37) interposed between the exterior and mid- dle layers. These plates vary from thirteen to twenty in number, and are situated immedi- ately behind the cornea, with their edges over- lapping each other. They are in general thin, and of an oblong quadrate figure, becoming elongated from before backwards in proportion as the bird possesses the power of changing the convexity of the cornea. In the nocturnal Raptores the bony plates are strong and thick, and extend from the cornea over the whole of the anterior projecting division of the eye to the posterior hemisphere, which they also contri- bute to form. The figure of the eye is thus maintained, notwithstanding its want of sphe- ricity; and in other classes, as Reptiles and Fishes, where the eye recedes from the spherical figure from an opposite cause, viz. the extreme flattening of the cornea, that form is also pre- served by the introduction of an osseous struc- ture in the sclerotic. The bony plates are capable of a degree of motion upon each other, which is, however, restrained within certain limits by the attach- ments of their anterior and posterior edges to the sclerotic coat ; and by their being bound 304 AVES. together with a tough ligamentous substance, which seems to be the continuation of the scle- rotic between the edges that overlap each other. The cornea possesses the same structure as in mammalia, but differs with respect to form. When the posterior part of the eye is com- pressed by the muscles, the humours are urged forwards and distend the cornea ; which, at that time, becomes much more prominent in most birds than it is ever observed in mammalia ; and under such circumstances, the eye is in a state for perceiving near objects. When the muscles are quite relaxed, the contents of the eye-ball retire to the posterior part, and the cornea becomes flat or even depressed : this is the condition in which we always find the eye of a dead bird, but we can have no opportunity of perceiving it during life. It is only prac- tised for the purpose of rendering objects visi- ble that are placed at an extreme distance. From the well-known effects of form upon re- fracting media, it must be presumed, that the cornea possesses very little, if any, convexity, when a bird which is soaring in the higher re- gions of the air, and invisible to us, discerns its prey upon the earth, and descends with uner- ring flight to the spot, as is customary with many of the rapacious tribe. The degree of convexity of the cornea is also changed in birds by the action of muscular fibres especially appropriated to its motions. These were discovered by Crampton ; are dis- posed around the circumference of the cornea, and are attached to its internal layer; they draw back the cornea, in a manner analogous to the action of the muscles of the diaphragm upon its tendinous centre. The choroid coat re- sembles in its structure that of mammalia; it is copiously covered with a black pigment, similar to that in the human eye. Opposite the bony circle the choroid separates into two layers; the exter- nal layer is the thin- nest, and adheres at first firmly to the sclerotica, after which it is produced freely inwards to form, or be continuous with, the iris. The iris (e,fg. 138) is delicate in its texture, which under the lens appears composed of a fine net-work of interlacing fibres, but it is remarkable for the activity and extent of its movements, which seem in many birds to be voluntary. The contraction and dilatation of the pupil, inde- pendent of any change in the quantity of light to which the eye is exposed, is most conspicu- ous and remarkable in the Parrot tribe, but we have observed it also in the Cassowary and some other birds. The colour of the iris is subject to many varieties, which frequently display great bril- liancy, arid afford zoologists distinguishing spe- cific characters of birds ; although these cannot always be implicitly relied upon. The breadth of the iris varies in different species, but is greatest in Birds which take Fig. 138. their food in the gloom of evening, as the Owls and Night-jar, in order that the pupil may be proportionally enlarged to admit as much light as possible to the retina. Carus observes that in the eye of the Owl is exhibited with peculiar distinctness the remarkable dis- tribution of the ciliary nerves and vessels, which, running in the form of single trunks between the choroid and sclerotica, terminate anteriorly in several ring-shaped plexuses for the supply of the iris and of the muscular circle of the cornea. The pupil is usually round : in the Goose and Dove it is elongated transversely, and in the Owls is vertically oval. The inner layer of the choroid is thicker than the external, and is disposed in numerous thickly set plicae radiating towards the anterior part of the chrystalline lens, where they termi- nate in slightly projecting ciliary processes, (d, Jig. 138,) the extremities of which adhere firmly to the capsule of the chrystalline. These processes are the most numerous, close set, and delicate in the Owl ; they are proportionally larger and looser in the Ostrich. The chief peculiarity in the eye of the Bird is the marsupium or pec ten, (f,Jig. 138,) which is a plicated vascular membrane analogous in structure to the choroid, and equally blackened by the pigmentum; situated in the vitreous humour anterior to the retina, and extending from the point where the optic nerve penetrates the eye to a greater or less distance forwards, being in many birds attached to the posterior part of the capsule of the chrystalline. As its posterior point of attachment is not to the choroid but to the termination of the optic nerve, this requires to be first described. When the optic nerve arrives at the sclerotic, it tapers into a long conical extremity, which glides into a sheath of a corresponding figure, excavated in the substance of that membrane, and directed downwards and obliquely forwards. The central or inner layer of this sheath is split longitudinally, and the substance of the nerves passes through this fissure. A similar but longer fissure exists in the corresponding part of the choroid : so that the extremity of the optic nerve presents in the interior of the eye, instead of a round disc, as in mammalia, a white narrow streak, from the extremities and sides of which the retina is continued. Branches of the ophthalmic artery, which are quite dis- tinct from the vessels of the choroid, and ana- logous to the arteria ccntralis retinae, enter the eye between the laminae of the retina, along the whole extent of the oblique slit above men- tioned, and immediately enter or compose the folds of the marsupial membrane, upon which they form most delicate and beautiful arbore- scent ramifications. The marsupium is lodged like a wedge in the substance of the vitreous humour, in a vertical plane, directed obliquely forwards. In those species in which the marsupium is widest, the angle next the cornea reaches the inferior edge of the capsule of the chrystalline ; but where it is narrow, the whole anterior surface is in contact with the same point. This con- tact is so close in some birds, as the Vulture, AVES. 305 Parrot, Turkey, Cassowary, Stork, Goose, and Swan, that the rnarsupium seems absolutely to adhere to the capsule of the lens ; but in many other birds, on the contrary, it does not extend further than two thirds of the distance from the back part of the eye, and is attached at its anterior extremity to some of the numerous laminae of the hyaloid membrane which form the cells for the lodgment of the vitreous hu- mour. In these cases the marsupium can have no influence on the movements of the lens, unless it be endowed with an erectile property, and be so far extended as to push forward the lens. The researches of Bauer* have shewn that there is no muscular structure in the marsupium, and its changes of form, if such occur in the living bird, must be effected by changes in the condition of the vessels of which it is almost exclusively com- posed. The form of the marsupium varies in differ- ent birds ; it is broader than it is long in the Stork, Heron, Turkey, and Swan ; and of the contrary dimensions in the Owl, Ostrich, and Cassowary. The plicae of the membrane are perpendicular to the terminal line of the optic nerve ; they are of a rounded figure in most species, but in the Ostrich and Cassowary they are compressed, and so far inclined from the plane of the membrane, that their convergence towards its extremity gives it a resemblance to a close-drawn purse.f The folds vary in num- ber, being four in the Cassowary, seven in the Great Horned Owl, eight in the Goose, from ten to twelve in the Duck and Vulture, fifteen in the Ostrich, sixteen in the Stork, and still more numerous in the Insessorial Birds, amounting to twenty-eight, according toSoem- merring, in the Fieldfare. The exact functions of the marsupial mem- brane are still involved in obscurity. Its po- sition is such that some of the rays of light proceeding from objects laterally situated with respect to the eye must fall upon and be absorbed by it ; and Petit accordingly supposed that it contributed to render more distinct the perception of objects placed in front of the eye. The theory originally proposed by Sir Everard IIome,t which attributed to the marsupium the office of retracting the lens for the purpose of distant vision by its muscular contraction, is opposed by the numerous examples in which * Philosophical Transactions, 1822, p. 76. t The Parisian Academicians, who took their de- scription of this part from the Ostrich, first applied to it the name of Ufarsupium or Bourse. The origi- nal description is as follows : " De cet entonnoir (the termination of the optic nerve) sortoit une membrane p\issce f faisant comme une bourse qui abou- tissoit en pointe vers le hord du Christallin le plus prochain de 1 'entree dn nerf optique. Cette bourse, qui estoit large de six lignes par le bas, a la sortie du nerf optique, et qui ^lloit en pointe vers le bant, estoit attachee par sa pointe an bord du Chrystallin, par le moyen de la membrane qui le couvroit du roste de 1'humenr vitree, et qui couvroit aussi toute la bourse qui estoit noir mais d'un autre noir que n'est celuy de la choroide." Duvernoy, in ' Me- moires pour servir a 1'Hist. Nat. des Animaux/ p. 375. J Croonian Lecture, Phil. Trans. 1796. VOL. I. it does not extend to the chrystalline, and by the manner of its attachment in those cases in which it does; since, as in these the mar- supium adheres to the side of the chrystalline, it can only move it obliquely. Some physiologists have supposed that this black membrane was extended towards the centre of the eye, where the luminous rays are most powerfully concentrated in order to absorb the excess of intense light to which birds are ex- posed in soaring aloft against the blazing sun. Others have considered it as the gland of the vitreous humour, and that, as this fluid must be rapidly consumed during the frequent and energetic use made of the visual organ by Birds, it therefore might require a superadded vascular structure for its reproduction. We are inclined to consider the marsupium as an erectile organ, adapted to receive a vary- ing quantity of blood, and to occupy a variable space in the vitreous humour ; when fully in- jected, therefore, it will tend to push forward the lens, either directly or through the medium of the vitreous humour, which must be dis- placed in a degree corresponding to the in- creased size of the marsupium ; the contrary effects will ensue when the vascular action is diminished. From the analogy of other struc- tures introduced by Supreme Wisdom into the mechanism of organized bodies, it may reason- ably be supposed that the marsupium is not limited to a single function. The retina is continued from the circumference of the base of the marsupium, and after forming a few slight folds expands into a smooth layer of medullary matter, which seems to terminate at the periphery of the corpus ciliare. In the Owls, as Haller has observed, not more than half the globe of the eye is lined by the retina ; it ceases in fact where the eye loses the sphe- rical form at the base of the anterior cylindrical portion. The humours of the eye no less correspond to the peculiar vision of the bird, and the rare medium through which it is destined to move, than the shape of the globe and the texture of its coats. The aqueous humour is extremely abundant, owing to the extent of the anterior chamber gained by the convexity of the cornea, and its refractive power must be considerable in the higher regions of the atmosphere. The mem- brane inclosing it can be more readily demon- strated in birds than in most mammals, espe- cially where it adheres to the free edge of the iris. The large size of the ciliary processes may have the same relation to the repro- duction of the aqueous, as the marsupium is supposed to have with reference to the vitreous humour. The chrystalline lens is remarkable for its flat- tened form, especially in the high-soaring Birds of Prey ; it is also of a soft texture, and is without any hard nucleus, as in the eyes of Fishes and Reptiles. In the Cormorant and other birds which seek their food in water, the chrystalline is of a rounder figure, and this is peculiarly the case in the near- sighted Owls which hunt for prey in obscure x 306 AVES. light. It is inclosed, as in Mammalia, in a distinct capsule, which adheres very firmly to the depression in the anterior part of the vitreous humour; the capsule is itself lodged between two layers of the membrana hyaloidea, which, as they recede from each other to pass t'te one in front and the other behind the lens, leave round its circumference the sacculated c;inal of Petit. The vessels of the lens are derived from those of the marsupium, which, as we have before observed, are ramifications of the analogue of the arteria centralis retina. With respect to this vessel we may here observe, that it is not continued as a simple branch from its origin to the marsupium, such a course would be in- consistent with the important functions it is destined to fulfil in the present Class. Imme- diately before penetrating the coats of the eye it breaks into numerous subdivisions, the aggre- gate of which is much greater than the trunk whence they proceed, and these again unite, forming a plexus (s,fg. 139) close to the ex- ternal side of the optic nerve. The artery of the marsupium proceeds from this plexus, and runs along the base of the folds, giving off at right angles a branch to each fold, which in like manner sends off smaller ramuli. The plexus at the origin of the marsupial artery serves as a reservoir for supplying the blood required for the occasional full injection of the marsupium ; and a similar but larger plexus (4,^/iir. 139) is formed at the origins of the ciliary arteries which supply the erectile tissue of the ciliary processes and iris. These plexuses are described by Barkow, from whose Memoir* the subjoined figure is taken, but their relation to the erectile powers of the parts they supply appears to have escaped his notice. The vitreous humour presents few peculia- rities worthy of note ; compared with the aque- ous humour, it is proportionally less in quan- tity than in the eyes of Mammalia. The outer capsule formed by the hyaloid membrane is stronger, and can be more easily separated from the humour. The Eye-ball is moved in Birds by four straight and two oblique muscles. The Recti muscles a- rise from the cir- cumference of the optic foramen and expand, as they pass forward, to be inserted into the soft middle part of the scle- Muscles of the eye. rotic. We have not been able to trace their insertion distinctly to the osseous circle ; their aponeurosis cannot be reflected for- wards from the sclerotica without lacerating that membrane. The Obliqui both arise very near together from the anterior parietes of the orbit, and go * Meckcl's Archiven, B. xii, pi. x. Fig. 139. to be inserted, the one into the upper, the other into the lower part of the globe of the eye ; the superior obliquus does not pass through a pulley, as in Mammalia. All the muscles are proportionally short in this class, but especially so in the Owls, in which the eye, from its large size and close adaptation to the orbit, can enjoy but very little motion. In the subjoined figure and in fig. 140, ' is the rectus superior or attollens ; b' the rectus inferior or deprimens ; c' the rectus ex- ternus or abducens ; d' the rectus interims or adducens ; e' the obliquus superior ; f the ob- liquus inferior ; g' the quadrat us ; h'lhepyra- niidalis. The accessory parts of the eye in Birds are similar to those of the higher Reptiles. There are three eye-lids, two of which move vertically, and have a horizontal commissure, while the third, which is deeper-seated, sweeps over the eye-ball horizontally, from the inner to the outer side of the globe. The vertical, or upper and lower eye-lids, are composed of the com- mon integument, of a layer of conjunctiva, and between these of a ligamentous aponeurosis, which is continued into the orbit, and lines the whole of that cavity. The lower eye-lid is the one which generally moves in closing the eye in sleep, and it is further strengthened by means of a smooth oval cartilaginous plate, which is situated between the ligamentous and con- junctive layers. The orbicularis muscle is so disposed as by means of this plate to act more powerfully in raising the lower than in depressing the upper eye-lid. In the latter it is continued imme- diately along the margin : in the lower eye-lid the tarsal cartilage intervenes between the mus- cle and the ciliary margin. The levator palpebra sitperioris arises from the roof of the orbit, and is inserted near the external angle of the lid. There is also an express muscle for depress- ing the lower eye-lid, as in the Crocodile. In the Owls and Night-jar (Caprimu/gus) the eye-lids are closed principally by the depres- sion of the upper one. There are but few birds that possess eye-lashes ; of these the Ostrich is an example, as also the Horn-bills and the Owls, in which they are arranged in a double series ; but in these they are rather to be considered as feathers with short barbs, than true eye-lashes. The third eye-lid, or membrana nictitans, is a thin membrane, transparent in some birds, in others of a pearly white colour, which, when not in action, lies folded back by virtue of its own elasticity on the inner or nasal side of the globe of the eye, with which it is in close contact. Two muscles are especially provided to effect its movements, but are so placed as to cause no obstruction to the admission of light to the eye during their actions. One of these is called the Quadratus nictitantis, (g,fig. 139;) it arises from the sclerotica at the upper and back part of the globe of the eye, and its fibres slightly converge as they descend towards the optic nerve, above which they terminate in a AVES. 307 semilunar tendinous shenth, having no express or fixed insertion. The second muscle, called fyramidalii iiicfitantis, (h, fig. 139,) arises from the sclerolica from the lower and nasal side of the eye-ball ; its fibres con- verge as they pass to the upper side of the optic nerve, and there terminate in a small round tendon, which glides through the pulley at the free margin of the quadrat us, and wind- ing round the optic nerve, passes along a cellu- lar sheath at the lower part of the sclerotica, and is inserted into the lower part of the mar- gin of the third eye-lid, along which it is continued for some distance, and is gradually lost. By the simultaneous action of the two mus- cles, the membrana nictitans is drawn forcibly outwards and with an oblique inclination down- wards over the anterior part of the eye.* The tendon of the pyramidalis gains the due direc- tion for that action by winding round the optic nerve, and it is restrained from pressing upon that nerve during the action of the pyramidalis muscle by the counteracting force of the qua- drat us, which thus augments the power of the antagonist muscle, while it obviates any incon- venience from pressure on the optic nerve, which its peculiar disposition in relation to that part would otherwise occasion. To examine this singular and beautiful me- chanism, it is necessary to remove the muscles of the eye-ball, especially the rccti. Lachrymal Organs. There are two glands which secrete a fluid to lubricate the ball of the eye, and facilitate the movements of the eye-lids ; one of these relates more especially to the movements of the nictitating membrane, and is called from its discoverer the Harderian Gland ; the other corresponds to the ordinary Glandula lachrymalis. Fig. 140. * This oblique motion is most remarkable in the Owls, in which the nictitating membrane is ac- companied by the upper eye-lid in its sweeping movement across the eye-ball. The Glanduld Hardcriana (i, fig. 140) is a conglomeration of mucous follicles, which compensates for the absence of Meibomian glands in Birds ; it is generally of large size, situated at the internal angle of the eye, and pours out a thick viscid secretion by a small duct which opens beneath the nictitating membrane. The surface of the gland is di- vided into many small lobules, which, when injected with mercury, are seen to be com- posed of still smaller vesicles. It is interesting to find that some of the Rodentia, which manifest so many affinities to the Class of Birds, have a corresponding gland ; in the Hare, for example, it is of large size and bipartite, situated at the internal angle of the orbit, and opening beneath the internal eye-lid. The true lachrymal gland is situated at the external angle of the eye. In the Goose it is of a flattened form, about the size of a pea, opening upon the inside of the outer angle of the eye-lids by a short and wide duct. Its secretion is less viscid than that of the Har- derian gland : but this is not uniformly the case. The lachrymal duct consists of a wide mem- branous canal commencing by two apertures at the nasal canthus of the eye, and terminating below and a little before the middle or great turbinated cartilage. In the Ostrich there is a glandular prominence at the commencement of each of the lachrymal canals ; these seem analogous to the caruncula lachrymalis. In other birds this structure is wanting. Nasal gland, (k, Jig. 140.) Besides the lachrymal glands, or those which furnish a fluid for the purpose of lubricating, defending, and facilitating the movements of the eye-ball, there exists another gland, which, from its position within or near the orbit, seems at first sight to appertain to the preceding series, but the secretion of which is exclusively employed in lubricating the pituitary membrane of the nose. This gland, which corresponds to the nasal glands of serpents, and those described by Jacobson* in Mammalia, is situated in many aquatic and marsh birds above the supra-orbital ridge in a depression noticed in the description of the skull, (p. 278.) In most birds it is lodged within the orbit itself; in some it is found under the nasal bone, or in the cavity analogous to the maxillary sinus. In the Woodpeckers it is found in the sub- ocular air-cell. It appears to be present in every order of Aves.f In the Anserine Birds this gland is so situ- ated as to complete the superior margin of the orbit, f/c', Jig. 140,) and is inclosed in an ex- tremely dense fibrous membrane. Its duct (/, fig. 140) is long, and passes to the nose along an osseous groove, behind the lachrymal bone. Its structure is simple, like that of the salivary glands in the same class, being com- posed of ramified follicles from which the * Nouv. Bullet, des Sc. par la Soc. Philomath, iii. an 6. p. 267. t Nitzsch, Mcckel's Archiv. vi. p. 234. x 2 808 AVKS. acini of the cells proceed. In the Albatross and Penguin we have traced two or three distinct ducts leading from this gland to the nose. Organ of Hearing. The structure of the organs of hearing in Birds resembles most closely that in the higher Reptiles, especially the Crocodile. There is no concha, or projecting Fig. 141. Organ of hearing. Owl. auricle in this class, for collecting and con- densing the rays of sound ; but to compen- sate for this deficiency, the labyrinth, and especially the semicircular canals, are of large size in proportion to the cranium. In those Birds, however, which enjoy the locomotive or visual faculties in a less perfect degree than in the rest of the class, there is found a peculiar arrangement of the feathers around the external meatus auditorius, which serves in some degree the office of an external ear. The Ostrich and Bustard (d,fig. 155) are so provided, and these birds can raise the auditory circle of plumes to catch distinctly any distant sound that may alarm them. The Owls, again, are furnished with a large crescentic mem- branous flap, or valve ; and the membrana tympani is situated ^at the bottom of a cavity (a, fig. 141), the lining membrane of which is disposed in folds analogous to those of the human auricle. The opercular flap is largely developed in our common Barn-owl (Strix flammea). This species is also remarkable in having the membrana tympani attached ex- clusively to the bony meatus (b,Jig. 141), and not to the tympanic bone or os quadratum. The bony framework of the membrana tym- pani is sunk below the surface of the head, and rarely projects so far from the tympanum as to deserve the name of a meatus or canal : it is deficient anteriorly, where it is bounded by the tympanic bone, to which, with the ex- ception above mentioned, the membrana tym- pani is attached for a greater or less extent of its anterior circumference. The drum of the ear (c, Jig. 141) is more or less of an oval shape ; it has the same structure as in Mammals, but is extremely delicate ; it is convex externally, as in the Reptiles, not concave, as in most Mammals. The cavity of the tympanum is widest at its outer part, and very irregular in the rest of its extent. It communicates by the usual fora- mina with the internal ear, and is connected with the fauces by means of the Eustachian tube. It also communicates by three other apertures with the cells of the bones of the cranium. " These," Macartney observes, " are widened into something like canals, where the holes open into them. The largest of the foramina is in the back of the tympa- num, and leads to the posterior cells, and communicates above the foramen magnum with the cellular canal of the other side. The second opening is placed at the anterior part of the tympanum, and conducts to the cells on the lower and anterior part of the cranium. The third foramen is continued amongst the cells which surround the labyrinth. Thus each tympanum has a communication with the interior of all parts of the cranium, and with each other, from which they might be reckoned as making only one cavity. The end of the tympanic bone, also, where it contributes to form the parietes of the tym- panum, has a foramen by which it derives its supply of air. The auditory cells of the cra- nium of birds are analogous to the mastoid of the human subject ; but from their extent they multiply sound much more. They are of the greatest magnitude in the nocturnal birds of prey; the Night-jar (Caprimulgus) has them also very large : they diminish in size in other birds, in which the posterior canals have no direct communication with each other; they are little observable in the Struthious Birds, and are wanting in the Parrots, but in their place the cavity of the tympanum is enlarged posteriorly." The Eustachian tube (e, e, Jig. 141) is very large in birds; it is an osseous canal, and ter- minates by a small aperture close to the one of the other side, within the fissure of the posterior nares. In the Swan the Eustachian passages, after having reached the base of the skull, pass forwards for about half an inch and then unite to form one common tube, which gradually expands until it termi- nates just behind the posterior apertures of the nose. The foramina, which lead from the tym- panum into the labyrinth, are situated within a fossa. They do not merit the distinctions of foramen ovale and foramen rotundum, being both oval, and only' separated by a small bony process. The ossicula auditus are supplied by a sin- gle bone, analogous to the stapes, and some cartilaginous processes representing the rudi- ments of a malleus and incus. The ossiculum consists of a stalk or pedicle, crowned by an oval plate, which is applied to the foramen that leads into the vestibule of the labyrinth. At the other extremity it is united to two or three cartilaginous processes, which form a tri- angle that is attached to the membrana tym- pani. The elongated stapes, or tympanic ossicle, is moved by one muscle (f, fig- 141), which comes from the occiput and penetrating the cavity, is affixed to the triangle that is con- nected to the membrana tympani. This muscle, AVKS. 300 in consequence of the connections of the ossi- culuin, is a tensor, and draws the membrana tympani outwards. It is counteracted by two small tendinous cords that are extended to the internal parietes of the tympanum. The labyrinth of the ear of birds consists of the vestibule, the three semicircular canals, and the rudiment of the cochlea. These parts are included within the bones of the cranium, which form a dense vibraiile case (d) around the whole internal ear. The vestibule is small in proportion to the other parts, but is more elongated than in the cold-blooded Reptilia. The semicircular canals have been termed by Scarpa, from their gradation in bulk, caiuiles major, minor, and minimus. The largest is most superior, and has a vertical position* (h, fig. 141). The smallest is situ- ated horizontally (k,k). The canalis minor or second canal (i) is vertical, it ascends upon the horizontal canal, and opens into its side at m. They contain corresponding tubes of vascular membrane, and they also possess en- larged ampulla, 1 (/), on which the nerves are distributed in the same manner as in mam- malia. The place of the cochlea is supplied by a short obtuse osseous conical tube (n, fig. 141), as in the Crocodile, very slightly bent, with the concavity directed backwards. Its interior is occupied by two small cylinders of fine car- tilage, each a little twisted, and united by a thin membrane at their origin and termination. They proceed from the osseous bar, which separates the two foramina, corresponding to the foramen ovale and rotundum. The sulcus, which is left between the cartilages, is dilated near the point, and accommodates the same branch of the auditory nerve, which is sent to the cochlea in mammalia. This nerve spreads in fine fila- ments upon the united extremity of the carti- laginous cylinders. The tube is divided by the presence of the cartilages into two scala?, the anterior of which communicates with the vestibule and is not closed ; the posterior scala is shorter, and communicates with the tym- panum by the foramen rotundum, which is closed by a membrane. Besides these parts the cochlea still contains a trace of the cretaceous substance which forms so conspicuous a part of the organization of the internal ear in Fishes. The Struthious birds manifest their close relation to the Reptilia by having the tube corresponding to the cochlea, very small in proportion to the other parts. The seventh cerebral nerve is received into a fossa, and there divides into five branches ; one is the facial, or portio dura, and the others are sent to the semicircular canals and the tube. The facial nerve receives a filament from the par vagum, which traverses the ear, and is afterwards distributed to the palate. Comparetti has described two canals leading * In the Insessores this canal is generally the smallest of the three. from the labyrinth of birds, which correspond with the aqueducts of the mammalia.* Organ of Smell. The close affinity subsist- ing between the cold and warm-blooded ovi para is no where more strongly manifested than in the olfactory organs. The external nostrils are simple perforations, having no moveable car- tilages or muscles provided for dilating or con- tracting their apertures, as in mammalia. The extent of surface of the pituitary membrane is not increased by any large accessory cavities, but simply by the projections and folds of the turbinated bones. The olfactory nerve is sim- ple, as in the Tortoise, and passes out of the skull, as before observed, by a single fo- ramen. The external nostrils vary remarkably both in shape and position, and serve on that ac- count as zoological characters. They are placed at the sides of the upper mandible in the majority of birds, but in some species are situated at or above the base of the bill; the latter is the case in the Toucans; in the Ap- teryx Australis they are found at the extremity of the long upper mandible. In general they are wide and freely open to facilitate the inhalation of air during the rapid motions of the bird, but sometimes they are so narrow that, as in the Herons, they will scarcely admit the point of a pin ; and in ihe Gannet they have been supposed, but erro- neously, to be wanting altogether .f In the Rasores the nostrils are partially defended by a scale. In the Corvuta they are protected by a bunch of stiff feathers directed forwards. In the Petrels the nostrils are produced in a tubular form, parallel to one another for a short distance along the upper part of the mandible, with the orifices turned forwards (a, Jig. 142.) The septum narium is, in general, complete, and is partly osseous, partly cartilaginous. It is perforated in the Swan just opposite the external nostrils. The surface of the septum is very irregular in this bird, and the pituitary membrane which covers it is highly vascular. The outer side of each of the nasal passages gives attachment to three turbinated laminae. The inferior one is a simple fold adhering to the septum narium as well as to the side of the nose; the middle one is cartilaginous and is the largest. It is of an infundibular figure, and adheres by its base to the septum of the nose, and externally to the cartilaginous ala or side of the nostril. It is convoluted with two turns and a half in the Anserine Birds, but in the Grallatores it is compressed and forms only one turn and a half. The superior tur- binated lamina (m m, fig. 140) generally presents the form of a bell ; it is also cartila- ginous, and adheres to the ethmoidal and lachrymal bones. It is hollow, and divided into two compartments, which are prolonged in a tubular form ; the internal one extends to * See Cuvier, Logons d'Anat. Coinp. torn, ii., and Macartney in Hccs' Cyclopaedia, Art. Birds. t See Montague's Ornithological Dictionary. 310 AVES. the orbit, the external terminates behind the middle tu/binated lamina in a cul-de-sac. These olfactory laminae differ in regard to tex- ture. In the Cassowary and Albatross they are said to be membranous. Cuvier states that they appeared to him to be bony in the Horn- bill and Toucan. We have found this to be the case in the recent Toucan. The organ of smell in this singular species is confined to the base of its enormous beak, (d,e,fig. 150.) The canal, which is traversed by the air and odorous particles in inspiration, forms a sigmoid curve in the vertical direction. The external orifice is on precisely the same perpendicular line as the internal, or, as it is generally termed, the posterior nasal aperture. The external nostril (d, Jig. 150) being situated on the posterior surface of the upper mandible, where it is raised above the level of the cranium, is consequently directed backwards, secure from all injury to which it might be exposed while the bill was used in penetrating dense and interwoven foliage. The olfactory canal is at its commencement of a cylindrical form, and about two lines in diameter. It passes forwards for about half an inch, receiving the projection of the first spongy bone, then bends downwards and backwards, and is dilated to admit the projections of the two other spongy bones. From this point it descends vertically to the palate, at first con- tracted and afterwards dilating to form the in- ternal or posterior orifice, (e,Jig. 150.) The first or outermost spongy bone is almost hori- zontal, and has its convexity directed outwards. The second is nearly vertically placed, with its convexity directed backwards : it terminates in a narrow point below. The superior spongy bone is about the size and shape of a pea. All these bones are processes from the inner and posterior parietes of the nasal passage; they are cellular, and air is continued into them from the cranial diploe ; but the parietes of the nasal passage are entire and smooth, and lined by a delicate pituitary membrane, so that there is no direct communication between the cells, the turbinated bones, or of the man- dible and the nasal passages. In most birds the nasal cavities communicate with the pharynx by two distinct but closely approximated apertures. In the Cormorant, however, these join into one before their termi- nation posteriorly, which is consequently by a single aperture. The olfactory nerves are dis- tributed exclusively to the pituitary membrane covering the septum narium and the superior spongy bone. The pituitary membrane is of the most delicate structure, and is most vas- cular, where it covers the superior turbinated lamina, and becomes thicker and more villous as it descends upon the middle one. It every- where displays numerous pores of muciparous glands, which bedew it with a lubricating secretion. According to Scarpa the acuteness of smell is exactly in proportion to the development of the superior turbinated lamina, to which the size of the olfactory nerve corresponds. The following is the order in which, according to his experiments, birds enjoy the sense of smell, beginning with those in which it is most acute : Grallatores, Natatores, Raptores, Sccmsores, Insessores, Rasores. There is still, however, much obscurity with reference to the extent to which Birds make use of their olfactory organs. It has been generally asserted that birds of prey are gifted with a highly acute sense of smell, and that they can discover by means of it the carcass of a dead animal at great distances ; but those who have witnessed the rapidity with which the Vultures descend from invisible heights of the atmosphere to the carcass of an animal, too recently killed to attract them by putrefactive exhalations, have generally been led to consider them as being directed to their quarry by sight. " That this is the case," Dr. Koget observes, " appears to be now suffi- ciently established by the observations and experiments of Mr. Audubon, which show that these birds in reality possess the sense of smell in a degree very inferior to carnivorous quadru- peds, and that so far from guiding them to their prey from any distance, it affords them no indication of its presence even when close at hand . The following experiments appear to be perfect- ly conclusive on this subject. Having pro- cured the skin of a deer, Mr, Audubon stuffed it full of hay ; after the whole had become perfectly dry and hard, he placed it in the mid- dle of an open field, laying it down on its back in the attitude of a dead animal. In the course of a few minutes afterwards he observed a vulture flying towards and alighting near it. Quite unsuspicious of the deception, the bird immediately proceeded to attack it as usual in the most vulnerable points. Failing in this object, he next with much exertion tore open the seams of the skin where it had been stitched together, and appeared earnestly intent on get- ting at the flesh, which he expected to find within, and of the absence of which not one of his senses was able to inform him. Find- ing that his efforts, which were long reiterated, led to no other result than the pulling out large quantities of hay, he at length, though with evident reluctance, gave up the attempt, and took flight in pursuit of other game to which he was led by the sight alone, and which he was not long in discovering and securing. " Another experiment, the converse of the first, was next tried. A large dead hog was concealed in a narrow and winding ravine, about twenty feet deeper than the surface of the earth around it, and filled with briers and high cane. This was done in the month of July, in a tropical climate, where putrefaction takes place with great rapidity ; yet, although many vultures were seen from time to time sailing in all directions over the spot where the putrid carcass was lying, covered only with twigs of cane, none ever discovered it; but in the meanwhile several dogs had found their way to it and had devoured large quantities of the flesh."* * See Roget, Bridgcwater Treatise, vol. ii. p. 406. AVES. 311 Organ of Tasle. The gustatory sense is very imperfectly enjoyed in birds, which, having no manducatory organs, swallow the food almost as soon as seized. The tongue is organized chiefly to serve as a prehensile instrument, and its principal modifications will be treated of under the head of the Digestive Organs. It is generally sheathed at the anterior part with horn (hjjig. 152), and is destitute of papillae except at its base (o, fig. 152) near the aper- ture of the larynx ; these papillae are not, how- ever, supplied by a true gustatory nerve, but by filaments of the glossopharyngeal. No branch of the fifth pair goes to the tongue. The tongue is proportionally largest and most fleshy in the Parrot tribe, and the food is detained in the mouth longer in these than in other birds. It is triturated and commi- nuted by the mandibles certainly, and turned about by the tongue, which here seems to ex- ercise a gustatory faculty, since indigestible parts, as the coat of kernels, &c. are rejected. In the Lories the extremity of the tongue is provided with numerous long and delicate pa- pillae or filaments projecting forwards. Organs of Touch. With respect to the tactile instruments, but few observations can be made in the class of Birds. The anterior extremities have their digital extremities undivided and entirely unfitted for the exercise of this sense, and the posterior extremities are but little better organized for the purpose. The integument covering the toes is very sparingly supplied with nerves, and is of a texture scarcely fitted for ascertaining the superficial qualities of bodies. However, the villi on the under sur- face of the toes are observed to be remarkably long in the Capercailzie (Tetrao urogallus), but this is probably for the purpose of enabling them to grasp with more security the frosted branches of the Norwegian pine-trees. The Parrots seem to use their feet more like instru- ments of touch, but in them the action may be merely prehensile. The only organ of touch respecting which there can be no doubt is the bill. Even where this is covered with a hard sheath of horn, some filaments of the fifth pair (c,fig. 150) may be traced terminating in small papillae ; but in the Lamelli-rostral water-birds the bill is covered by a softer substance, and is plentifully supplied by branches of the fifth pair of nerves. (See Nerves.) In the Woodcocks and Snipes the long bill is so organized that it is used as a probe in marshes and soft ground to feel for the small worms and slugs that constitute their food. The cire in the Falconida, the wattles of the Wattle-birds (Philedon carunculatus and Gkmcopis cinerea) and of the Cock, the ca- runcles of the King-Vulture and Turkey, may also be regarded in some degree as organs of touch. Organs of Digestion. The digestive function in birds is necessarily extremely powerful and rapid in order to supply the waste occasioned by their extensive, frequent, and energetic mo- tions, and in accordance with the rapidity of their circulation and their high state of irrita- bility. * The parts to be considered with reference to this function are the rostrum or beak, the tongue, the oesophagus, the stomach which is always divided into a glandular and muscular portion, the intestines, and the cloaca. The glandular organs of the digestive system are the salivary glands, the proventricular fol- licles, the liver, pancreas, and spleen. The beak consists of the maxillary and inter- maxillary bones, which in place of teeth are provided with a sheath of horny fibrous mate- rial, exactly similar to that of which the claws are composed: this sheath is moulded to the shape of the osseous mandibles, being formed by a soft vascular substance covering these parts, and its margins are frequently provided with horny processes or laminae secreted by distinct pulps, and analogous in this respect to the whalebone lamina; of the Whale: M. Geoffrey St. Hilaire has described a structure in the bill of birds which presents a closer approach to a dentary system. In a foetus of a Perroquet nearly ready for hatching, he found that the margins of the bill were beset with tubercles arranged in a re- gular order and having all the exterior appear- ances of teeth : these tubercles were not, indeed, implanted in the jaw-bones, but formed part and parcel of the exterior sheath of the bill. Under each tubercle, however, there was a ge- latinous pulp, analogous to the pulps which secrete teeth, but resting on the edge of the maxillary bones, and every pulp was supplied by vessels and nerves traversing a canal in the substance of the bone. These tubercles form the first margins of the mandibles, and their remains are indicated by canals in the horny sheath subsequently formed, which contain a softer material, and which commence from small foramina in the margin of the bone. The different degrees of hardness and varieties of form of the beak exercise, Cuvier observes,f as much influence upon the nature of birds as the number and figure of the teeth do upon that of Mammals. The beak is hardest in those birds which tear their prey, as in Eagles and Falcons ; or in those which bruise hard seeds and fruits, as Parrots and Gros-beaks; or in those which pierce the bark of trees, as Woodpeckers, in the larger species of which the beak absolutely acquires the density of ivory. The hardness of the covering of the beak gradually diminishes in those birds which take less solid nourishment, or which swallow their food entire; and it changes at last to a soft skin in those which feed on tender substances, or which have occasion to probe for their food in muddy or sandy soils, or at the bottom of the water, as Ducks, Snipes, Woodcocks, &,c. C&teris paribus, a short beak must be stronger than a long one, a thick one than a thin one, a solid one than one which is flexible ; but the * The Cormorant readily devours six or eight pounds of fish daily. t Anatomie Compuree, torn. ii. p. 192. 312 AVES. general form produces infinite variety in the application of the force. A compressed beak with sharp edges and a hooked extremity characterizes both the Birds of Prey properly so called, which destroy the smaller quadrupeds and birds (fig. 112) ; and also the carnivorous species of a different order that live on fish, as the Petrels (Jig. 142), Al- Fig. 142. of being as deep as it is long), and the Skimmer (Rhyncops), in which the still more singular structure obtains of an inequality in the length of the two mandibles, the upper one being con- siderably the shortest; so that this bird can only get its food, which consists of floating marine animals, by pushing them before it as it skims along the surface of the water. Fig. 144. Bill of the Petrel. batrosses, Frigate-bird, and Tropic-bird. But in the Raptures it is comparatively shorter and stronger, and in some genera a tooth-like pro- cess on either side adds considerably to its destructive powers : hence the Falcons which possess this armature are reckoned the more ' noble ' and courageous Birds of Prey. The Insessorial Shrikes which have their bill similarly armed do not yield in courage to the Hawks, notwithstanding their small size, and the comparative feebleness of their wings and feet: (Jig. 11 5.) As the bill becomes narrower and straighter, it characterizes birds of a voracious habit, but less daring in their attacks on other birds, such as the Crows, Magpies, &c., (jig. 116) ; and the compressed knife-shaped bill is asso- ciated with similar habits in the Water-birds, as the Gulls, Grebes, Dabchicks, &c. Another kind of strong and trenchant bill, which is more elongated and without a hook, serves to cut and break, but not to tear : this form of bill characterizes the Waders which frequent the water and prey upon animals that make resistance in that element, as reptiles, fishes, &c. In the He- rons and Bitterns the bill is straight; in the Ibis it is curved down- wards (fig. 123); in the Jabiru (fig. 143) it is curved in the contrary direction. Fig. 143. Bill of the Skimmer. Lastly, there are trenchant bills which are depressed or flattened horizontally ; they serve to seize fishes and reptiles, and other large objects; the Boat-bill (Cancroma) exhibits a bill of this kind k (fig. 145), which is also ser- Fig, 145. rated at the edges. Some /^^- ^ , r~\\ speciesofFly- /^ catcher and Tody have this form of beak on a small scale . Biu f the Boat-bill. Of the blunt-edged bills we may first notice those which are flattened horizontally. When a bill of this description is long and strong, as in the Pelecan (jig- 146), it selves to seize a large but feebly resisting prey, as fishes. Fig. 146. Bill of the Pelecan. When it is long and weak, as in the Spoon- bill, which derives its name from the dilated extremity of the mandibles, it is only available to seize amid sand, mud, or water, very small Crustaceans, Mollusks, &c. (Jig. 147.) Fig. 147. Bill of the Jabiru. Some trenchant or sharp-edged bills are so compressed as to resemble the blade of a knife, and can only serve to seize small ob- jects, which are immediately swallowed : such is the form of the beak in the Auks, Puffins, Coulterneb, (where it has the further peculiarity Bill of the Spoonbill. The more or less flattened bills of Ducks, the more conical ones of Geese and Swans, and that of the Flamingo,* of which the extremities * It is singular that it should ever have been supposed that the upper mandible was alone move- able, and the lower mandible perfectly immoveable, in the Flamingo, since precisely the contrary is the AVES. 313 of the mandibles are bent downwards abruptly (Jig. 148), have all transverse horny lamina; Fig. 148. which are nearly allied to the Anat'ulee, the la- teral laminae are developed into small conical tooth-like processes, which serve to hold fast the fishes, which the Goosander destroys in great numbers. Fig. 149. Bill of the Flamingo. arranged along their edges, which, when the bird lias seized any object in the water, serve, like the whalebone laminae of the Whale, to give passage to the superfluous fluid. The aquatic habits of all these birds are in harmony with this structure. In the Goosanders (Mergus), Bill of the Goosander. The bills of the Toucans and Hornbills are remarkable for their enormous size, which is sometimes equal to that of the whole bird. The substance of the beak in these cases is extremely light and delicately cellular, without which the equilibrium necessary for flight would have been destroyed. The singularity of the structure of these bills demands a more particular consideration. The osseous portions of the mandibles of the Toucan (fig. 150) are adapted to cora- Fig. 150. Bitt of the Toucan. bine, with great bulk, a due degree of strength and remarkable lightness, and their structure is consequently of a most beautiful and delicate kind. The external parietes are extremely thin, especially in the upper beak : they are elastic, and yield in a slight degree to moderate pressure, but present considerable resistance if the force be increased for the pur- pose of crushing the beak. At the points of the mandibles the outer walls are nearly a line in thickness ; at other parts in the upper beak case. In the specimen which we dissected (see Proceedings of the Zoological Society, Part ii. p. 141) the upper mandible was so firmly fixed to the cranium as only to be moved with that part, while the lower mandible was freely moveable when the head was fixed. The Flamingo is remark- able for applying the upper mandible to the soil, which it shovels backwards in searching for its food. they are much thinner, varying from one- thirtieth to one-fiftieth part of an inch, and in the lower beak are from one-twentieth to one- thirtieth of an inch in thickness. On making a longitudinal section of the upper mandible (a,jig. 150) in the Rhamphastos Touco, its base is seen to include a conical cavity about two inches in length and one inch in diameter, with the apex directed forwards. The walls of this cone consist of a most beautiful osseous net-work, intercepting irregular angular spaces, varying in diameter from half a line to two lines. From the parietes of the cone a net- work of bony fibres is continued to the outer parietes of the mandible, the fibres which imme- diately support the latter being almost invariably at right angles to the part in which they are in- serted. The whole of the mandible anterior to the cone is occupied with a similar net-work, the meshes of which are largest in the centre of 314 AVES. the beak, in consequence of the union which takes place between different small fibres as they pass from the circumference inwards. It is worthy of observation that the principle of the cylinder is introduced into this elaborate structure : the smallest of the supporting pillars of the mandibles are seen to be hollow or tubular when examined with the microscope. The structure is the same in the lower man- dible (ntjjig. 150), but the fibres composing the net-work are in general stronger than those of the upper mandible. The medullary membrane lining these cavi- ties appears to have but a small degree of vascularity. Processes of the membrane, ac- companying vessels and nerves, decussate the conical cavity at the base of the beak. The air is admitted to the interior of the upper mandible from a cavity (b,fg. 150) situated anterior to the orbit, which communicates at its posterior part with the air-cell continued into the orbit, and at its anterior part with the maxillary cavity. The nasal cavity is closed at every part except at its external and internal aper- tures by the pituitary membrane, and has no communication with the interior of the mandible. * The horny sheath of the mandibles in the Hornbills and Toucans is so thin that it often becomes irregularly notched at the edge from use. The Hornbills have, besides, upon their enormous beak, horn-like prominences of the same structure and of different forms, the use of which is not known. The Trogons, Touracos, Buccos, &c. exhibit forms of the bill which are intermediate to that of the large but feeble bill of the Toucans, and the short, but hard, strong, and broad bill of the Parrot-tribe, which is also hooked, so as to assist in climbing, like a third foot: (Jig* 128.) The short, conical, and vaulted beak of the Rasores (fig. 121) serves to pick up with due rapidity the vegetable seeds and grains which constitute their food, as well as small insects, as ants, &c. with which the young are frequently nourished. The bills of the small Insessorial or Pas- serine birds present every gradation of the conical form, from the broad-based cone of the Hawfinch to the almost filamentous cone of the Humming-birds (jig. 117, 125), and each of these forms influences the habits of the species in the same manner as in the larger birds. The short and strong-billed Insessores live on seeds and grains ; those with a long and slender bill on insects or vegetable juices. If the slender bill be short, flat, and the gape very wide, as in Swallows, the bird takes the insects while on the wing (Jiff. 118) ; if the bill be elongated and endowed with sufficient strength, as in the Hoopoes, it serves to penetrate the soil and pick out worms, &c. Of all bills, the most extraordinary is that of the Cross-bill, in which the extremities of the mandibles curve towards opposite sides and * See Anatomical Appendix to Gould's Mono- graph on the Ramphastidfc , fol. cross each other at a considerable angle a dis- position which at first sight seems directly opposed to the natural intention of a bill. With this singular disposition, the Cross-bill, however, possesses the power of bringing the points of the mandibles into contact with each other ; and Mr. Yarrell, in his excellent paper on the Anatomy of the Beak of this b;rd, ob- serves that, notwithstanding M. Button's asser- tion to the contrary, it can pick up the smallest seeds, and shell or husk hemp and similar seeds like other birds. He further shows that the disposition and power of the muscles is such that the bill gains by its very apparent defect the requisite power for breaking up the pine- cones that constitute its natural food. In a pair of Cross-bills which were kept for some time in captivity, one of their principal occu- pations, Mr. Yarrell observes, " was twisting out the ends of the wires of their prison, which they accomplished with equal ease and dexterity. A short flat-headed nail that confined some strong net-work was a favourite object upon which they tried their strength, and the male, who was usually pioneer in every new exploit, succeeded, by long-continued efforts, in draw- ing this nail out of the wood, though not without breaking off the point of his beak in the experiment. Their unceasing destruction of cages at length brought upon them sentence of banishment." He concludes his memoir by observing that " the remarks of Buffon on the beak of this bird, which he characterizes as ' an error and defect of nature, and a useless deformity,' exhibit, to say the least of them, an erroneous and hasty conclusion, unworthy of the spirit of the science he cultivated. During a series of observations on the habits and structure of British Birds, t have never met with a more interesting or beautiful ex- ample of the adaptation of means to an end than is to be found in the tongue, the beak, and its muscles, in the Cross-bill." * The tongue, as has been already observed, can hardly be considered as an organ of taste in Birds, since, like the mandibles, it is gene- rally sheathed with horn. It is principally adapted to fulfil the offices of a prehensile organ in association with the beak, and it pre- sents almost as many varieties of form. Orni- thologists have not yet perhaps derived all the advantages which a study of the modifications of the tongue might afford in determining the natural affinities of birds. The os hyoides very much resembles that of Reptiles. Its parts have been minutely studied by Geoffroy St. Hilaire, who has bestowed upon them separate names: (a, Jig. 151) is the glosso-hyal, b the basi-hyal, d d the apo-hyals, e e the cerato-hyals, c the uro-hyal. The body, or basi-hyal element, is more thickened than the rest : in some birds it is cylindrical. The length of the tongue depends chiefly on that of the lingual process or glosso-hyal element. In most birds it is lengthened out by a carti- lage a' appended to its extremity. This is re- markable in the Swan and other Latnelli-rostres. * Zool. Journal, vol. iv. p. 464. Iii the Humming-bird, and especially in the Toucan and Woodpecker, the horny sheath of the glosso-hyal presents singular pecu- liarities. In the Humming-bird it is divided at its extremity into a pencil of fine hairs, well fitted for imbibing the nectar and farina of flowers. In the Toucan's tongue (fig. 152) the sheath gives off from the lateral margins stiff bristle-like processes which project for- wards ; this structure is continued to the apex, 99 Os hyoides and larynx Swan. Fig. 152. and the tongue so provided becomes an in- strument for testing the softness and ripe- ness of fruit, and the fitness of other objects for food, thereby acting as a kind of antenna or feeler. A similar but less developed struc- ture is found in the tongue of the frugivorous Touraco. In the Woodpeckers the apex of the horny sheath (a, fig. 153, 154) gives off at, the sides short-pointed processes directed back- wards, which thus convert it into a barbed instrument, fitted for holding fast the insects which its sharp point has transfixed, after the strong beak has dislodged them from their hiding places. The cornua of the os hyoides in the \Voodpecker extend backwards to the vertebral column, wind round the back of the head, and converge as they pass forwards to be inserted in a canal generally on the right side of the upper mandible (d, e, jig. 153, 154.) Fig. 153. Cranium and tongue of a Woodpecker. One of the most remarkable structures which the tongue presents in this class is met with in the Flamingo, where it is remarkable both for its size, texture, and singular armature. The tongue is almost cylindrical, slightly flattened above, and obliquely truncate anteriorly, so as to cor- respond with the form of the inferior mandible. The pointed extremity of the truncated part is supported beneath by a small horny plate. Along the middle of the upper surface there is a moderately deep and wide longitudinal furrow ; on either side of which there are ( fr "m twenty to twenty-five recurved spines, m one to three lines in length. These nes are arranged in an irregular alternate ies : the outer ones being the smallest, which Tongue of tJie Toucan. may almost be considered as a distinct row. At the posterior part of the tongue there are two groups of smaller recumbent spines di- rected towards the glottis. The substance of the tongue is not muscular, but is chiefly composed of an abundant elastic cellular sub- stance, permeated by an oily fat. In the Raptures the tongue is of a mode- rate length, broad, and somewhat thick, and has a slight division at the tip. In the Vultures its sides can be voluntarily approximated so as to form a canal, and its margins are pro- vided with retroverted spines. In the Raven it is bifid at the apex. In the Struthious birds, in many of the Waders, and in the Pelecanida:, the tongue is remarkably short. In the Parrots it is thick and fleshy, serves admirably to keep steady the nut or seed upon which the strength of the mandibles is exerted, and is applied to the kernel so extracted, as if to ascertain its sapid qualities. The following are the muscles of the tongue in birds. 1st. The Genio-hyoideus of Vicq d'Azyr, or the Mylo-hyoideus according to Cuvier. This is a thin layer of fibres attached to the lower and inner border of the lower jaw, and running transversely to a mesial tendon which separates them, and extends to the uro-hyal. It raises the tongue towards the palate. 2d. The Stylo-hyoideus arises from the upper and back part of the lower jaw, and divides into three or more portions : the posterior descends obliquely forwards, and is inserted into the tendinous commissure of the preceding mus- cle; the middle portion is inserted into the ' uro-hyal :' the anterior fasciculus is inserted into the side of the basi-hyal above the trans- verse hyo-glossus. The actions of these dif- ferent portions vary according to their insertion; the first and second depress the apex of the tongue by raising its posterior appendage, (uro-hyal,) the third raises the tongue and os hyoides, and draws it to one side when it acts singly. 3d. The Genio-hyoideus arises by two fleshy 316 AVES. bands from the lower and internal edge of the lower jaw; these unite and surround the cerato- hyals or cornua of the os hyoides ; and as they draw forward the os hyoides, protrude the tongue from the beak. 4th. The Cerato-hyoideus passes from the rerato-hyal to the uro-hyal, and is therefore subservient to the lateral movements of the tongue. 5th. The Sterno-hyoidei are replaced by a slip of muscle which extends from the anterior surface of the upper larynx to be attached to the base of the glosso-hyal. 6th. A small and short muscle is single or azygos ; it passes from the basi-hyal to the under part of the glosso-hyal ; it depresses the tip of the tongue and elevates its base. 7th. A short muscle which arises from the junction of the basi-hyal with the cerato- and uro-hyals, and is inserted into the upper and outer angle of the base of the glosso-hyal. All these muscles are remarkably large in the Woodpecker, in which there is a singular pair of muscles that may be termed Cerato- tracheales, (h, jig. 154.) They arise from the trachea about eight lines from the upper larynx, twist four.times spirally round the trachea, and then pass forward to be inserted into the base of the cerato-hyals. This is the principal re- tractor of the singular tongue in this species. Salivary glands. The salivary organs, being in general developed in a degree corresponding to the extent of the changes which the food undergoes in the mouth, and the length of time during which it is there detained, are by no means so conspicuous a part of the diges- tive system in Birds as in Mammals. Glands which pour out their secretion upon the food prior to deglutition are, however, met with in every bird, but vary in number, position, and complexity of structure. In some species, as the Crow, they are of the simplest structure, consisting of a series of unbranched, cone-shaped follicles or tubules, opening separately upon the mucous mem- brane of the mouth, along the sides of which cavity they are situated. They pour out a viscid mucus, and are the only traces of a salivary system met with in this bird. In many other birds, and especially in the Scratching, Wading, and Swimming Orders, glands of the conglomerate structure are found beneath the lower jaw, analogous to the sub- maxillary glands of quadrupeds. In the Goose they occupy the whole of the anterior part of the space included by the rami of the lower jaw, being of an elongated form, flattened and closely united together at the middle line. On either side of this line the mu- cous membrane of the mouth presents inter- nally a series of pores, each of which is the terminal orifice of a distinct gland or aggre- gate of ramified ducts. A third and higher form of salivary gland, in which the secretion of the conglomerate mass is conveyed into the mouth by a single duct, is found in the Woodpeckers and some species of the Rapacious Order. In the latter birds these glands are termed, from their situ- Fig. 154. Tongue and salivary glands, Woodpecker. ation, anterior palatine: in the Pica thej correspond to the parotid and sublingual Quadrupeds. The sublingual glands of the Woodpecker are of extraordinary size, extending from the angle to the symphysis of the lower jaw. The 1 single ducts of each gland unite just before their termination, which is a simple orifice the apex of the mouth. The structure of tl glands is shown at i, k, Jig. 154. Besides the preceding, which may be con- sidered as the true salivary glands, there are numerous accessory follicles in different parts of the oral apparatus of birds. In the Water- hen ( Galimula chloropus) there is a series o ccecal glandular tubes along each side of the tongue ; and it is interesting to note that glan- AVES. 317 clular follicles are found abundantly developed on the tongues of the Chelonian and Saurian reptiles. Similar elongated follicles are situated along the margin of the lower jaw, resembling in their parallel pectinated disposition the bran- chiae of Fishes. In the Goose the corresponding follicles are longer and wider, and are situated near the sides of the tongue. In the Raven these mucous follicles are narrower but longer. The food, after being embued with the secre- tion of the preceding glands, is poised upon the tongue and swallowed partly by means of the pressure of the tongue against the palate, partly by a sudden upward jerk of the head. The posterior apertures of the nostrils being generally in the form of narrow fissures are undefended by a soft palate or uvula ; and the laryngeal aperture, which is of a similar form, is in like manner unprovided with an epi- glottis, but is defended by the retroverted papillae at the base of the tongue. In many birds, indeed, as the Albatross and Coot, there is a small cartilage in the usual place of an epiglottis, but insufficient to cover more than a very small part of the laryngeal aperture. Nitzsch lias devoted a treatise to these rudimen- tary epiglottides in Birds.* With respect to the fauces the remarkable instance of a dilatation of these parts in the Pelecan must not be forgotten. The exten- sibility of the membrane between the rami of the lower jaw admits of its formation into a bag (a, Jig. 146), which is calculated to contain ten quarts of water, and serves as a receptacle for fishes, making in that state a conspicuous appen- dage to the huge bill ; when empty it can be contracted so as to be hardly visible. By means of this mechanism a quantity of food can be transported to the young ; and, as in disgorging the bleeding fishes the parent presses the bottom of the sac against her breast, this action has probably given rise to the fable of her wounding herself to nourish the young with her own blood. A remarkable provision of an analogous na- ture is met with in the Bustard as a sexual pecu- liarity^g.155). In the male there is a membranous sac extending for some way down the an- terior part of the neck capable of holding several quarts of water; it communicates with the mouth by an aperture be- neath the tongue. It is not found ex- cept in the mature bird. It is sup- posed to serve the purpose of provid- ing the female and young during the breeding season Fig. 155. Faucial bag of the Bustard. * See Meckel's Archiven, 1826, p. 613. with water, and hence may not be developed to its full extent except at that period. The Swift presents an analogous dilatation of the membrane of the fauces at the base of the lower jaw and upper part of the throat: it is most developed at the period of rearing the young, when it is generally found distended with insects in the old birds that are shot while on the wing. This receptacle is of a rounded form, and communicates with the fauces by a wider opening than that of the Bastard ; it is also proportionally of less extent. A similar structure obtains in the Rook and probably in other Insectivorous birds. The oesophagus (tf, fig. 171 : , fig. 156, 158), like the neck, is usually very long in birds : as it passes down, it generally inclines towards the right side ; it is partially covered by the tra- chea (G,fig. 171), and connected to the sur- rounding parts by a loose cellular tissue. It is wide and dilatable, corresponding to the im- perfection of the oral instruments as comminu- tors of the food. In the rapacious and especially in the piscivorous birds it is of great capacity, enabling the latter to swallow the fishes entire, and serving also in many Waders and Swim- mers as a temporary repository of food. When the Cormorant has by accident swal- lowed a large fish, which sticks in the gullet, it has the power of inflating that part to its utmost, and while in that state the head and neck are shaken violently, in order to promote its passage. In the Gannet the oesophagus is ex- tremely capacious, and, as the skin which covers it is equally dilatable, five or six herrings may be contained therein. In both these species it forms one continued canal with the stomach. In the Flamingo, on the contrary, the dia- meter of the gullet does not exceed half an inch, being suited to the smallness of the objects which constitute the food of this species. Besides deglutition the oesophagus is fre- quently concerned in regurgitation ; and in the Birds in which this phenomenon occurs, the muscular coat of the gullet is well deve- loped, as in the Ruminant Mammalia. The Raptores, for example, habitually regurgi- tate the bones, feathers, and other indiges- tible parts of their prey, which, in the lan- guage of the falconer, are called ' castings/ A Toucan, which was preserved some years alive in this country, was frequently observed to regurgitate partially digested food, and after submitting it to a rude kind of mastication by its enormous beak, again to swallow it. The oesophagus possesses an external cel- lular covering, a muscular coat, an internal vascular tunic, and a cuticular lining. The muscular coat consists of two layers of fibres ; in the external stratum they are trans- verse (a, jig. 159), in the internal longitudinal (b y Jig. 159); the reverse of the arrangement observed in the human subject. Ingluvies. In those birds which are om- nivorous, as the Toucans and Horn-bills, in the frugivorous and insectivorous birds, and in most of the Grallatores, which find their food in tolerable abundance, and take it in small quantities without any considerable inter- 318 AVES. mission, it passes at once to the stomach to be there successively digested, and the gullet pre- sents no partial dilatations to serve as a tem- porary reservoir or macerating receptacle. But in the larger Raptorial Birds, as the Eagles and Vultures, which gorge themselves at un- certain intervals from the carcasses of bulky prey, the oesophagus does not preserve a uni- form width, but undergoes a lateral dilatation anterior to the furculum at the lower part of the neck. This pouch is termed the ingluvies or crop (b, Jig. 156). a Fig. 156. Digestive canal of an Eagle. In those birds, again, the food of which is exclusively of the vegetable kind, as grains and seeds, and of which consequently a great quantity must be taken to produce the ade- quate supply of nutriment, and where the cavity of the gizzard is very much diminished by the enormous thickness of its muscular coat, the crop is more developed, and takes a more important share in the digestive process. Instead of a gradual cylindrical lateral dila- tation of the gullet, it assumes the form of a globular or oval receptacle appended to that tube, and rests upon the elastic fascia which connects the clavicles or two branches of the furculum together. In the common Fowl the crop is of large size and single (b,fig. 157 : I, fig- 171), but in Fig. 157. the Pigeon it is double, consisting of two lateral oval cavities (b c,Jig. 158). The dilatation of the oesophagus to form the crop is more gradual in the Ducks than in the Gallinaceous birds. The crop is wanting in the Swans and Geese. The disposition of the muscular fibres of the crop is the same as in the oesophagus, but the muciparous follicles of the lining membrane are larger and more numerous. Tins difference is most conspicuous in the ingluvies of the grani- vorous birds, where it is not merely a temporary reservoir, but in which the food is mixed with the abundant secretion of the glands, and be- comes softened and macerated, and prepared for the triturating action of the gizzard and the sol- vent power of the gastric secretion. The change which the food undergoes in the crop is well known to bird-fanciers. If a Pigeon be allowed to swallow a great quan- tity of peas, they will swell to such an extent as almost to suffocate it. The time during which the food remains in the crop depends upon its nature. In a common Fowl animal food will be detained about eight hours, while half the quantity of vegetable substances will remain from six- teen to twenty hours, which is one among many proofs of the greater facility with which animal substances are digested. Mr. Hunter made many interesting observations on the crop of Pigeons, which takes on a Fig. 158. secreting function during the breeding season, for the purpose of supplying the young pi- geons in the callow state with a diet suitable to their tender condition.* An abundant se- cretion of a milky fluid of an ash-grey colour, which coagulates with acids and forms curd, is poured out into the crop and mixed with * Animal Economy, p. 235. the macerating grains. This phenomenon is the nearest approach in the class of Birds to the great characteristic function, the presence of whose special apparatus, the mammae, has af- forded the universally recognized title of the higher division of warm-blooded Vertebrata ; and the analogy of the l Pigeon's milk' to the lac- teal secretion of the mammalia has not escaped popular notice. In the subjoined figure one side of the crop (/>), shows the ordinary structure of the parts, the other (e\ the state of the cavity during the period of rearing the young (fig. 158). The canal which is continued from the in- gluvies to the stomach was called by Hunter the second or lower oesophagus ; at its com- mencement it is narrower and more vascular than that part of the gullet which precedes the crop, but gradually dilates into the first or glandular division of the stomach, which is termed the * proventriculus ' (ventriculus tuccenturiatus, bulbus glandulosus, echinus, injundibulum, the * cardiac cavity ' of Home), (c, Jig. 156, 157, 166). In birds with a wide oesophagus (a, /?g.l65), as the omnivorous and piscivorous tribes, the commencement of the proventriculus (e, fig. 165), is not indicated by any change in the di- rection or diameter of the tube, but only by its greater vascularity, by the difference in the structure of the lining membrane, and by the stratum of glands which open upon its inner surface, and which are its essential cha- racteristic (c. fig. ' Fig. 159. AVES. 319 Part of the proventriculus of a Swan dissected. 159). Hence it is by some compara- tive anatomists re- garded as a part of the oesophagus. The proventri- culus varies, how- ever, in form and magnitude in dif- ferent birds. In the Rasores it is larger than the oeso- phagus, but much smaller than the gizzard. In the Psittacida and Ardeida: (Parrot and Stork tribe) it is larger than the gizzard and of a different form. In the Ostrich the proventri- culus is four or five times larger than the triturating division of the stomach, being con- tinued down below the liver, and then bent up upon itself towards the right side before it termi- nates in the gizzard, which is placed on the right and anterior part of this dilatation. The experiments of Reaumur, Spallanzani, and Hunter, and those of -Tiedemann and Gmelin, prove that the secretion of the pro- ventricular or gastric glands is analogous to the gastric juice in man and mammalia. In the majority of birds the gastric follicles are simple, having no internal cells, dilated fund us, or contracted neck; but from their external blind extremity proceed with an uniform diameter to their internal orifice. This form obtains in the zoophagous and omnivorous birds. In the Dove-tribe the follicles are of a conical shape. In the Swan they are tubuli- form ; in the Goose and Turkey they present internal loculi ; in the Ostrich and Rhea these loculi are so developed that each gland forms a racemose group of follicles, terminating by a common aperture in the proventriculus. The subjoined figures from Home's Com- parative Anatomy (vol. ii. pi. Ivi.) show the different forms of the solvent or pro ventricular glands in different birds. Fig. 160. Eagle. Gannet. Turkey. Rhea. Ostrich. The gastric glands are variously arranged. Among the Raptores, we find them in the Golden Eagle disposed in the form of a broad compact belt ; in the Sparrow-Hawk this belt is slightly divided into four distinct portions. In the Insessores the glands are generally arranged in a continuous zone around the pro- ventriculus; but in some of the Syndactyli, as the Hornbill, the circle is composed of the blending together of two large oval groups. Among the Scansores the Parrots have the gastric glands disposed in a continuous white circle, which is at some distance from the small gizzard. In the Woodpeckers the glands are arranged in a triangular form, with the apex towards the gizzard. In the Toucan they are dispersed over the whole proventriculus, but are more closely aggregated near the gizzard ; the lining membrane of the cavity is reticulate, and the orifices of the glands are in the inter- spaces of the meshes. Among the Rasores the Pigeon shows its affinity to the Passerine Birds in having the gas- tric glands of a simple structure, and arranged 320 AVES. in a zonular form : they are chiefly remarkable for their large cavity and wide orifice. In the Common Fowl and Turkey the glands are more complex, and form a complete circle. In the Cursores the arrangement of the glands is different in almost every genus. In the Ostrich they are of an extremely complicated structure, and are extended in unusual numbers over an oval space on the left side of the proventriculus, which reaches from the top to the bottom of the cavity, and is about four inches broad. The Rhea differs from the other Struthious birds in having the solvent glands aggregated into a single circular patch, which occupies the posterior side of the proventricular cavity. In the Emeu the gastric glands are scattered over the whole inner surface of the proven- triculus, and are of large size ; they terminate towards the gizzard in two oblique lines. In the Cassowary the glands are dispersed over the proventriculus with a similar degree of uniformity ; but they are smaller, and their lower boundary is transverse. Among the Grallatores, the Marabou, or Gigantic Crane, (Ciconia Argala and Ma- rabou,) has the nearest affinity to the Rhea in the structure and disposition of the gastric glands ; they are each composed of an aggre- gate of five or six follicles, terminating in the proventriculus by a common aperture; and they are disposed in two compact oval masses, one on the anterior, the other on the posterior surface of the cavity. In the Heron (Ardea cineria) the solvent glands are of more sim- ple structure, and are more dispersed over the proventriculus; but still they are most nume- rous on the anterior and posterior surfaces. In the Flamingo the gastric glands are short and simple follicles, arranged in two large oval groups, which blend together at their edges. The Natatores present considerable differ- ences among themselves in the disposition of the solvent glands. In the Cormorant ( Pha- lacrocorax carbo) they are arranged in two circular spots, the one anterior and the other posterior; while in the closely allied genus the Sula, or Gannet, they form a complete belt of great width, and consequently are extremely numerous. In this respect the Gannet, or Solan Goose, has a nearer affinity to the Pelecan, with which both birds were generically associated by Linnaeus. In the Sea-Gulls the gastric glands form a continuous zone ; and in the Little Auk ( Alca Alle) they are spread, according to Sir Everard Home, over a greater proportional extent of surface than in any other bird that lives on animal food, and the form of the digestive organs is peculiar to itself. The cardiac cavity or proventriculus appears to be a direct con- tinuation of the oesophagus, distinguished from it by the termination of the cuticular lining and the appearance of the solvent glands. The cavity is continued down with very gradual enlarge- ment below the liver, and is then bent up to the right side, and terminates in the gizzard. The solvent glands are situated at the an- terior or upper part of the cavity every where surrounding it, but lower down they lie prin- cipally upon the posterior surface, and where it is bent upwards towards the right side they are entirely wanting. In the graminivorous lamellirostral Water-birds, as the Swan, Goose, &c. the gastric glands have a simple elongated exterior form, but have an irregular or cellular internal surface : they are closely arranged so as to fofin,a complete zone. In general the muscular or pyloric division of the stomach immediately succeeds the glan- dulaK)r / cardiac division ; but in some Birds, as the Auk and Parrots, there is an intervening portioji without glands. It is always widely dif- ferent in structure, and hence has received a dis- tinct name, the ' gizzard ' (gigerium, ventriculus bulbosus). The gizzard is situated below or sacrad of the liver, on the left side and dorsal aspect of the abdomen, generally resting on the mass of intestines ; although, according to Blumen- bach, the Nutcracker and Toucan, as well as the Cuckoo, differ in having the gizzard situated on the abdominal part of the cavity. Hence this peculiarity not being restricted to the Cuc- koo affords no explanation, as has been sup- posed, why it should not incubate. In the Owl, also, the gizzard adheres to the membrane cover- ing the internal surface of the abdominal muscles. In all birds the gizzard forms a more or less lengthened sac, having at its upper part two apertures ; one of these is of large size, com- municating with the proventriculus (a, fig- 161, 162), the second is in close proximity with, and to the right side of the preceding, leading to the duodenum (b, fig. 161); below these apertures the cavity extends to form a cul-de- sac (c, Jig. 161, 162.) At the middle of the anterior and posterior parts of the cul-de-sac there is a tendon (e, Jig. 156, 157) from whicli the muscular fibres radiate. Fig. 161. Gixzard of a Swan. AVES. The differences in the structure of the gizzard resolve themselves into the greater or less extent of the tendons, and the greater or less thick- ness of the muscular coat, and of the lining membrane. In the Ruptores the gizzard (d, Jig. 156) assumes the form of a mere membranous cavity, in accordance with the animal and easily di- gestible nature of their food. The muscular coat is extremely thin; the fibres principally radiate from small tendons (<, Jig. 156), and there are some longitudinal fibres beneath the radiating or external layer. In the Rasorcs and lamellirostral Natatores it exhibits the structure to which the term giz- zard can be more appropriately applied. The muscular fibres are distinguished by their unparalleled density of texture and deep colour, and are arranged in four masses ; two are of a hemispherical form, and their closely- packed fibres run transversely to be connected to very strong anterior and posterior tendons (f, Jig. 157, 162); they constitute the sides of the gizzard, and are termed the digastric muscles or 'musculi laterales' (d, Jig. 161, 162) : between these, at the end of the gizzard, are the two smaller and thinner muscles called ' musculi intermedii' (f,Jig. 162). There are likewise irregular bands placed about the cir- cumference of the gizzard. Fig. 1 6 1 shows the relative thickness of the musculi laterales in the gizzard of a Swan, and fig. 162 that of the musculi intermedii and tendon. Fig. 162. 1 921 Gizzard of a Swan. The internal coat of the gizzard (c, h,Jig. 162) is extremely hard and thick, and being of a horny or cuticular nature, it is liable to be increased by pressure and friction, and as it is most subject to these influences at the parts of the gizzard opposite the musculi laterales, two callous buttons are there formed, (g, g, fig. 1 62). It is here that the fibrous structure of the lining membrane can be most plainly seen : and it is worthy of observation that the fibres are not perpendicular to the plane of the muscles but VOL. I. oblique, and in opposite directions, on the two sides. Elsewhere the cuticular lining is dis- posed in ridges and prominences (h, Jig. 161, 162), which vary in different birds, but are pretty constant in the same species. Carus* has recently figured the gizzard of a Petrel ( Proccl/aria glacialis), the lining membrane of which is disposed in a pavement of small square tubercles, like the gastric teeth of some Mollusca. The cavity of the gizzard is so encroached upon by the grinding apparatus, that it is necessarily very small, the two horny callosities having their internal flat surfaces opposed to one another, like ' millstones/ A crop is as essential an appendage to this structure as the 1 hopper' to the mill ; it receives the food as it is swallowed, and supplies it the gizzard in small successive quantities as it is wanted.f Between the stomach of the carnivorous Eagle, and that of the graminivorous Swan, there are numerous intermediate structures, but it is necessary to observe that the animal or vegetable nature of the food cannotalwaysbe pre- dicated of from the different degrees of strength in the gizzard. Hard-coated coleopterous in- sects, for example, require thicker parietes for their due comminution than pulpy succulent fruits. In the submenus Euphones, among the Tana- gers, the muscular or pyloric division of the stomach is remarkably small and not sepa- rated from the duodenum by a narrow pylorus.J The parieles of the gizzard, like those of other muscular cavities, become thickened when stimulated to contract on their contents with greater force than usual. In the Ilunterian collection this fact is well illustrated by pre- parations of the gizzard of the Sea-gull in the natural state, and that of another Sea-gull which had been brought to feed on barley. The digastric muscles in the latter are more than double the thickness of those in the Sea-gull which had lived on fish. The immediate agents in triturating the food are hard foreign bodies, as sand, gravel, or peb- bles. The well-known habit in the granivorous birds of swallowing stones with their food has been very differently explained. Blumenbach observes that ' Csesalpinus considered it rather as a medicine than as a common assistance to digestion ; Boerhaave, as an absorbent for the acid of the stomach ; Redi, as a substitute for d teeth; Whytt, as a mechanical irritation, adapt- ed to the callous and insensible nature of the coats of the stomach.' Spallanzani rejected all supposition of design or object, and hazarded the stupid observation that the stones were swallowed from mere stupidity. * Tabulae A natomiamComparativam illustrantes, fol. pars iv. 1835. t Thus we find in Parrots, where the gizzard is remarkably small, that a crop is present. A like receptacle exists also in the Flamingo, in which the gizzard is small but strong. J Carus ut supra, tab. vi. fig. iv. See Home, Comp. Anatomy, vol. i. p. 271, and Hunter, Animal (Economy, p. 221, where it is re- lated that a similar change was effected by changing the food of a tame Kite. Y 322 AVES. Pigeons, however, are known to carry gravel to their young. Gallinaceous birds grow lean if deprived of pebbles; and no wonder, since experiment* shows that unless the grains of corn are bruised, and deprived of their vitality, the gastric juice will not act upon or dissolve them. The observations and experiments of Hunter have completely established the rationa- lity and truth of Iledi's opinion, that the peb- bles perform the vicarious office of teeth. Hunter inferred from the form of hair-balls occasionally found in the stomach of Cuckoos,t that the action of the great lateral muscles of the gizzard was rotatory. Harvey appears to have first investigated, by means of the ear, as it were in anticipation of the art of auscultation, the actions which are going on in the interior of an animal body, in reference to the motions of the gizzard. He observes, (De Generatione Animalium, in Opera Omnia, 4to. p. 208,) " Fal- conibus, aquilis, aliisque avibus ex preda viven- tibus, si aurem prope admoveris dum ventricu- lus jejunus est, manifestos intus strepitus, lapillorum illuc ingestorum, invicemque colli- sorum percipias." And Hunter observes, (Animal (Economy, p. 198,) " the extent of motion in grindstones need not be the tenth of an inch, if their motion is alternate and in con- trary directions. But although the motion of the gizzard is hardly visible, yet we may be made very sensible of its action by putting the ear to the sides of a fowl while it is grinding its food, when the stones can be heard moving upon one another." Tiedemann believes that the muscles of the gizzard are in some degree voluntary, having observed that when he placed his hand oppo- site the gizzard, its motions suddenly stopped. The pyloric orifice of the gizzard is guarded by a valve in many birds, especially in those which swallow the largest stones. This valve in the Ostrich is formed by a rising of the cuticle divided into six or seven ridges, which close the pylorus like a grating, and allow only stones of small size to pass through. In the Touraco the pylorus projects into the duodenum in a tubular form. There is a double valve at the pyloric orifice in the Gannet, and a single large valvular ridge at the same part in the Gigantic Crane. In this species and some other Waders, as the Heron and Bittern ; also in the Pelecan, and, according to Cuvier, in the Penguin and * Grains of barley, inclosed in strong perforated tubes, pass through the alimentary canal unchanged. Dead meat, similarly introduced into the gizzard, is dissolved. t The hairs of caterpillars devoured by this bird are sometimes pressed or stuck into the horny lining of the gizzard, instead of being collected into a loose ball. They are then neatly pressed down in a regular spiral direction, like the nap of a hat, and have often been mistaken for the natural structure of the gizzard. One of these specimens exhibited as such to the Zoological Society was sent to me for exami- nation, when, upon placing some of the supposed gastric hairs under the microscope, they exhibited the peculiar complex structure of the hairs of the larva of the Tiger-moth ( Arctia Caja), and the broken surface of the extremity which was stuck into the cuticular lining was plainly discernible. See Proceedings of Zool, Soc, 1834, p. 9. Grebe, there is a small but distinct cavity inter- posed between the gizzard and intestine. An analogous structure is found in the Crocodile. The intestines reach from the stomach to the cloaca ; in relative length they are much shorter than in the mammalia. In the Toucan, for example, the whole intestinal canal scarcely equals twice the length of the body, in- cluding the bill. The canal is divided into small and large intestines, sometimes by an internal valve, sometimes by the insertion of a single coecum, but most generally by those of two coeca, which are always opposite to one another. In a few instances there is no such distinction. The small intestines and coeca are longest in the vegetable feeders. The large intestine is, with one or two exceptions, very short and straight in all birds. The course of the small intestine varies somewhat in the different orders of Birds ; it is always characterized by the elongated fold or loop made by the duodenum, (fj\ Jig. 163,) Fig. 163. Abdominal viscera of a Pigeon. which fold receives the pancreas (q q) in its concavity. In the Raptores the intestines are generally disposed as follows : The duodenum forms a long and broad fold, the lower part of which is commonly bent or doubled upon itself: the intestine then passes backwards on the right side of the ab- domen, crosses to the left, and is disposed in deep folds upon the edge of a scolloped mesen- tery ; towards its termination the ileum passes up behind the stomach and adheres to it, having here but a narrow mesentery; then passing down the posterior part of the abdomen the ileum makes another loose fold and ends in the rec- tum, which is continued straight to the cloaca.* In the Owls the last fold of the ileum is nearly as long as the duodenal fold, and the cceca adhere to each side of the fold. In the Diurnal Raptores the intestinal canal * la fig. 156 the intestines are not represented according to their natural arrangement. AVES. 323 is only twice the length of the body, except in lite fi.sh-eating Osproy, in which the intestines are very narrow, and are to the length of the bird itself as eight to one. In the Insessorcs the scolloped folds of the small intestine are narrower and longer than in the Raptores, and the ileum generally adheres to the duodenal mesentery and pancreas in- stead of to the stomach, prior to passing down to form its last fold and to terminate in the rectum. In the Raven the small intestines arc disposed at their commencement in concentric folds. Among the Scansorcs the Cuckoo presents the following disposition of the intestinal canal : after the usual long and narrow duo- denal fold, the ileum* makes a fold which is widened at the end, it then forms a close fold upon itself, at the termination of which the rectum commences. In the Maccaw the course of the small intestine is somewhat peculiar: after forming the duodenal fold, it is disposed in three distinct packets of folds : the intestine, after forming the first two, passes alternately from one to the other, de- scribing shorter folds upon each ; it then forms the third distinct fold, which is a long one, at the termination of which the ileum adheres closely to the right side of the gizzard, and then passes backwards and dilates into the rectum. In the Rasores the Dove-tribe have the small intestines disposed in three principal folds ; the first is the duodenal fold (ff, Jig. 163); the second is along and narrow fold, coiled and doubled upon itself, with the turns closely connected together, (k, Jig. 163); the third is also a long fold, which is bent or twisted, (k', jig. 163.) In the common Fowl the duodenum is disposed in a long simple loop ; the ileum passes towards the left, and is disposed in loose folds on the right and lower edge of the mesentery ; the ileum before its termination passes up behind the preceding folds, and is accompanied as far as the root of the mesentery by the two creca, which there open into the commencement of the large intestine. The Ostrich presents the most complicated course of the intestinal canal in the whole class of birds. The duodenal fold is about a foot in length, and the returning part makes a bend upon itself before it reaches the py- lorus ; the intestine then turns down again behind the duodenal folds and gradually ac- quires a wider mesentery. The ileum after a few folds ascends towards the left side, accom- panied by the two long cceca, and becomes again connected with the posterior part of the duodenal mesentery ; beyond which the cceca enter the intestine behind the root of the me- sentery, and the large intestine commences. This part differs from the rectum in other biids in its great extent, being nearly double the length of the small intestines, and being disposed in folds upon a wide mesentery. It terminates by an oblique valvular aperture in a large urinary receptacle. In the Bustard the * There is seldom any part of the small intestine empty so as to merit the name of jejunum. rectum is a foot in length, which is the nearest approach to the Ostrich which the rest of the class make in this respect. The small intestines in the Grallatorcs are characterized by their small diameter and long and narrow folds ; these are sometimes ex- tended parallel to one another, as in the Crane and Coot; or folded concentrically in a mass, as in the Curlew and Flamingo. In the latter species the duodenal fold is four inches in length ; then the small intestines are disposed in twenty-one elliptical spiral convolutions, eleven descending towards the rectum and ten returning towards the gizzard in the interspaces of the former. Many of the Na tat ores present a concentric disposition of the folds of the small intestines similar to the Flamingo. Home* has given figures of this structure in the intestines of the Sea-mew (pi. cviii.) ; the Gannet or Solan Goose (pi. cvi.); and the Goose (pi. cxi.). It likewise obtains in the Pelecan and Cor- morant. The arrangement of the muscular fibres of the intestine is the same as in the oesophagus, the external layer being transverse, the internal longitudinal. The villi of the lining membrane manifest an analogy with the covering of the outer skin, being generally much elongated, so as to pre- sent a downy appearance when viewed under water. There are, however, great varieties in the shape and length of the villi. In the Emeu they consist of small lamellae of the lining membrane folded like the frill of a shirt. In the Ostrich the lamellae are thin, long, and nu- merous. In the Flamingo they are short and arranged in parallel longitudinal zig-zag lines. In many birds a small diverticulum is ob- served in the small intestine, which indicates the place of attachment of the pedicle of the yolk-bag in the embryo (m, Jig. 157). We have found this process half an inch in length in the Gallinule, and situated seventeen inches from the pylorus. In the Bay Ibis (Ibisfalci- nellaj the vitelline ccecum is an inch in length. The birds in which the cceca coli have been found wanting are comparatively few, though such examples occur in all the orders. These exceptions are most frequent among the Scan- sores, in which the cceca are absent in the Wry- necks, the Toucan s, theTouracos, the Parrot tribe, and according to Cuvier in the Woodpeckers.f In the Insessores the cceca are deficient in the Hornbill and the Lark. Among the Gral- latores, we have found them wanting in a Spoon- bill. In the Natatores they are absent in the Cormorant. The Herons, Bitterns, and, occa- sionally, the Grebes afford the rare examples of a single ccecum, which is also remarkably short. In the Raptores the diurnal and nocturnal tribes differ remarkably in the length of the ccoca. They are each less than half an inch in length in the Eagles and Vultures, but are occa- sionally wanting in the latter. Cuvier states * Comparative Anatomy, vol. ii. t In the Poppinjay ( Picusviridis, Linn.) we have found two small coeca, so closely adhering to the intestine as easily to be overlooked. Y 2 324 AVES. that the cceca are deficient in the greater part of the Diurnal Raptores, but we have observed them in the Huliatus Albicilla, Aquila Chry- saetos, Astur palumbarius, and Buteo nisus. They seldom exceed the length above-men- tioned (g,Jig. 156), and in the Secretary Vul- ture they form mere tubercles. In the Barn Owl the caeca severally measure nearly two inches in length, and are dilated at their blind extremities; they are proportionally developed in the larger Strigida. In the Insessores they are invariably very short where present. Among the Scansoriat Genera which possess the cceca, these parts are found to vary in length, measuring in the Cuckoo and Wattle-bird (Glaucopis), each half an inch ; while in the Scythrops, or New- Holland Toucan, the cceca are each two inches Ions:, and moderately wide. In the Rasores the cceca present considerable varieties. In the Pigeons (g,fg- 163) they are as short as in the Insessorial order, and are sometimes wanting altogether, as in the Crown- pigeon. In the Guan (Penelope cristata) each coecum is about three inches in length; while in the Grouse each ccecum measures a yard long, being thus upwards of three times the length of the entire body. The internal surface of these extraordinary appendages to the alimen- tary canal is further increased in the Grouse by being disposed in eight longitudinal folds, which extend from their blind extremities to within five inches of their termination in the rectum. We have always found the cceca in this species filled with a homogeneous pulta- ceous matter without any trace of the heather buds, the remains of which are abundant in the fcecal matter contained in the ordinary tract of the intestines. In the Peacock the cceca measure ach about one foot in length; in the Partridge about four inches ; in the common Fowl and other Phasianida the cceca are each about one- third the length of the body ; they commence by a narrow pedicle, which extends about half their length, and then they begin to dilate into reservoirs for the chyme (g,fg- 157). In the Cursores the cceca again present very different degrees of development. In the Emeu they are narrow and short. In the Cas- sowary they are wholly deficient; while in the Ostrich they are wide and upwards of two feet in length, and their secreting and absorbing parietes are further increased by being pro- duced into a spiral valve, analogous to that which exists in the long ccecum of the Hare and Rabbit. In the Grallatores the two cceca are gene- rally short where present; they attain their greatest development in this order in the De- moiselle, where the length of each ccecum is five inches ; and they are also large in the Fla- mingo, where they each measure nearly four inches, and are dilated at their extremities, presenting with the gizzard, crop, lamellated beak, and webbed feet, the nearest approach to the Anatida of the following order. In the Natatores the cceca, where they are present, vary in length according to the nature of the food, being very short in the fish-eating Penguin, Pelecan, Gull, &c. and long in the Duck, Goo.se, and other vegetable feeding Lamellirostres. In the crested Grebe (Podiceps cristatus), Yarrell detected two cceca, each measuring 3-16ths of an inch in length. In the Canada Goose the same indefatigable observer found the cceca each nine inches in length, and in the White-fronted Goose the same parts mea- sured severally thirteen inches. They have the same length in the Black Swan. In the Wild Swan the coeca measure each ten inches in length, while in the tame species they are each fifteen inches long. As digestion may be supposed to go on less actively in the somnolent, night-flying Owls, than in the high-soaring Diurnal Birds of Prey, an additional complexity of the alimentary canal for the purpose of retaining the chyme somewhat longer in its passage, might naturally be expected; and the enlarged cceca of the Nocturnal Raptores afford the requisite adjust- ment in this case. For, although the nature of the food is the same in the Owl* as in the Hawk, yet the differences of habit of life call ibr corresponding differences in the mechanism for its assimilation. In the Rasorial Order, where the nature of the food differs so widely from that of the Birds of Prey, the principal modification of the digestive apparatus obtains in the more, complex structure of the crop, proventriculus, and above all the gizzard ; but with respect to the cceca, as great differences obtain in their development as in the Raptores. Now these differences are explicable on the same prin- ciple as has just been applied towards the elucidation of the differences in the size of the coeca in the Raptores. Where the difference in the locomotive powers is so great in the Dove-tribe and the common Fowl ; where the circulating and respiratory systems must be so actively exercised to enable the Pigeon to take its daily flights and in some species their an- nual migrations a less complicated intestinal canal may naturally be supposed with such increased energy in the animal and vital func- tions to do the business of digestion, than in the more sluggish and terrestrial vegetable feeders; and accordingly we find that the requisite complexity of the intestinal canal is obtained by an increased development of the ccecal processes in them, while in the Colum- bidfE the cceca remain as little developed as in the Insessores, which they resemble in powers of flight. If we regard the cceca as excretive organs, their differences in the above orders may be in like manner explained by their relations to the locomotive and respiratory functions. In the Cursores the development of cceca seems to have reference to the quantity of food, and the ease with which it may be obtained, according to the geographical position of the species. In the Cassowary, which is a native * The indigestible parts of the prey of the Owl do not pass into the intestine, but are regularly cast or regurgitated from the stomach ; the length of the creca cannot, therefore, be accounted for on Macartney's supposition of their being receivers of those parts. AVES. 325 of the fertile districts of a tropical country, ve- getable food of a more easily digestible nature may be selected, and it need not be detained un- necessarily long, where a fresh supply can be so readily procured. But in the Ostrich, which dwells amidst arid sands and barren deserts, every contrivance has been adopted in the struc- ture of the digestive apparatus to extract the whole of the nutritious matter of the food which is swallowed. In the Grallatores, where no material dif- ferences of locomotive powers or means of obtaining food exist, the coeca present in their development a direct relation to the nature of the food, and are most developed in the Gruidte. The same holds good in the Natatores. Why the increased extent of intestinal sur- face in the above different cases should be chiefly obtained by the elongation of the coeca, will appear from the following considerations. In consequence of the stones and other foreign bodies which birds swallow, it is necessary that there should be a free passage for these through the intestinal canal, which is therefore generally short and of pretty uniform diameter. In the Omnivorous birds of the tropics, as the Ilornbills, Toucans, Touracos, and Parrots, which dwell among ever-bearing fruit-trees, the rapid pas- sage of the food is not inconsistent with the extraction of a due supply of nourishment, but is compensated by the unfailing abundance of the supply. But where a greater quantity of the chyle is to be extracted from the food, and where, from the nature of the latter, a greater proportion of foreign substances is required for its tritura- tion, while the advantages of a short intestinal tract are obtained, the chyme is at the same time prevented from being prematurely expelled by the superaddition of the two ccecal bags which communicate with the intestines by orifices that are too small to admit pebbles or undigested seeds, but which allow the chyme to pass in. Here, therefore, it is detained, and chylification assisted by the secretion of the coecal parietes, and the due proportion of nutri- ment extracted. The large intestine is seldom more than a tenth part of the length of the body, and, except in the Ostrich and Bustard, is continued straight from the cceca to the cloaca ; it may therefore be termed the rectum rather than the colon. It is usually wider than the small in- testine, and its villi are coarser, shorter, and less numerous. The rectum (a, fig. 164) terminates by a valvular circular orifice (6), in a more or less dilated cavity, which is the remains of the allantois, and now forms a rudimental urinary bladder, (c d). The ureters (A A), and efferent parts of the generative ap- paratus (f, g,) open into a transverse groove at the lower part of the urinary dilatation, and beyond this is the external cavity which lodges, as in the Reptiles and Marsupial and Monotrematous Quadrupeds, the anal glands and the exciting organs of generation. The anal follicles in Birds are lodged in a conical glan- dular cavity, which communicates with the pos- terior part of the outer compartment of the cloaca, and has obtained from its discoverer the name of Rursrt Fabricii (A-). Berthold considers this part as a subdivision of the urinary bladder in Birds, and Geoffrey St. Ililaire as the analogue of Cowper's glands. *. 164. 1 Cloaca of the Condor. Digestive glands. The liver is large in Birds, and proportionally larger in the Aquatic species than in Birds of Prey. In the former Fig. 165. Posterior view of tlie biliary and pancreatic ducts, in the Hornbill. 326 AVES. it bears a proportion of one-tenth, in some of the latter of one-tvventy-ninth part of the entire body. The liver (m m, jig. 163, 165) is situated a little above the middle of the thoracic-abdo- minal cavity, with its convex surface towards the abdominal parietes,and its concavity turned towards the subjacent viscera : the right lobe covers the duodenum, pancreas, and part of the small intestines ; the left lobe covers the pro- ventriculus and part of the gizzard; and the apex of the heart is received between the upper ends of these principal lobes. The liver is, as it were, moulded upon all these parts, and pre- sents corresponding depressions where it comes in contact with them. It is generally divided into two nearly equal lobes, which are often separated for a short extent, and connected together by a narrow isthmus of the glandular substance. In some birds, however, as in the Pigeon, Cormorant, Swan, and Goose, there is a third, smaller lobe, situated at the back of the liver between the lateral lobes, which from its situ- ation appears analogous to the lobulus Spigelii of Mammalia. In the Common Fowl the left lobe is occasionally cleft so deeply as to form two lobes on that side. In some species the right lobe exceeds the left in size ; this is most remarkable in the Bustard, in which the right lobe extends into the pelvis. In the Eagle, however, the left lobe has been observed to be the largest. Each lobe is invested by a double membranous tunic, one embracing it closely, the other surrounding it loosely, like the peri- cardium of the heart. They are formed by laminae of the peritoneum, which seems to split at the exterior thin edge of the liver into four layers, two being continued upon the anterior and posterior surfaces adhering to them, the other two forming the loose exterior cap- sule. The principal ligament of the liver is formed by a large and strong duplicature of the peri- toneum, which divides the abdomen longitu- dinally like the thoracic mediastinum in Mam- malia. It is reflected from the liriea alba and middle line of the sternum upon the pericar- dium, and passes deeply into the interspace of the lobes of the liver ; it is attached to these lobes through their whole extent, and connects them.below to the gizzard on one side and to the duodenal fold on the other: the lateral and posterior parts of the liver are attached to the contiguous air-cells ; and the whole viscus is thus kept steady in its situation during the rapid and violent movements of the bird. The ligament first described is analogous to the fal- ciform ligament of Mammalia; and, although there is no free margin inclosing a round liga- ment, yet the remains of the umbilical vein may be traced within the duplicature of the membranes forming the septum. As the mus- cular septum between the thorax and abdomen is wanting, there is consequently no coronary ligament; but the numerous membranous pro- cesses which pass from the liver to the sur- rounding parts amply compensate for its ab- sence. The liver is of a lighter colour in Birds of flight than in the heavier Water-fowl. Each lobe has its hepatic artery and vena portae. The hepatic arteries are proportionally small, but the portal veins are of great size, being formed not only by the veins of the intestinal canal, pancreas, and spleen, but also by the inferior emulgent and sacral veins. The blood, which has circulated in the liver, is returned to the inferior cava by two venae hepaticoe. There are occasionally some smaller hepatic veins in addition to the two principal ones. The coats of the portal and hepatic veins ap- pear to be equally attached to the substance of the liver. The biliary secretion is carried out of the liver by two and sometimes three ducts ; one of these terminates directly in the intestine, and is a 'he- patic duct ' (w, n,Jig. 165); the other enters the gall-bladder, and is a ' cyst-hepatic duct ' (o',Ji-g. 1 65) ; the cystic bile is conveyed to the duo- denum by a < cystic duct ' (o,fig 165). Where, as in a few instances, the gall-bladder does not exist, both hepatic ducts terminate separately in the duodenum (n, n, Jig. 163); but in no case is there a single ductus communis cho- ledochus as in Mammalia. The gall-bladder (p, Jig. 165) is situated near the mesial edge of the concave or under side of the right lobe, and is commonly lodged in a shallow depression of the liver; but some- times, as in the Eagle, Bustard, and Cormorant, only a very small part of the bag is attached to the liver. It has the same structure as in Mamma- lia, manifesting no visible muscular tunic, and having its inner surface delicately reticulated. The gall-bladder is present in all the Rap- tores, Insessores, and Natatores. It is want- ing in a great proportion of the Scansores, as in the Genus Rhamphastos and in the whole of the Psittacida and Cuculida. Among the Rasores the gall-bladder is constantly deficient in the Columbidte. or Dove-tribe alone, in which the coeca are shorter than in any other vege- table feeder: (n n, jig. 163, are the two he- patic ducts terminating apart from one another in the Pigeon.) The gall-bladder is occasion- ally absent, according to the French Acade- micians, in the Guinea-fowl; and they also found it wanting in two out of six Demoi- selles ( Anthropoides Virgo). The gall-blad- der is small and sometimes absent in the Bittern : it is always wanting in the Ostrich. The bile, as before observed, passes directly into the gall-bladder, and not by regurgitation from a ductus choledochus ; the cyst-hepatic duct arises from the right lobe, and is con- tinued in some birds along that side of the bag which is in contact with the liver, where it penetrates the coats of the cyst and terminates about one-third from the lower or posterior end. In the Horn-bill we found it passing over the upper end of the bladder to the anterior or free surface, and the cystic duct continued from the point where the cyst-hepatic duct opened into the bladder; so that the cystic duct had a communicaton both with the reservoir and the cyst-hepatic duct; being somewhat ana- logous to the ductus communis choledochus; AVES. 327 (see fig. 165, where x represents the orifice by which the bile pusses both in and out of the gall-bladder.) In the Goose the cyst-hepatic duct termi- nates by a very small orifice, surrounded by a smooth projection of the inner mem- brane, which, aided by the obliquity of the duct, acts as a valve and prevents any re- gurgitation towards the liver. The cystic duct here passes abruptly from the posterior ex- tremity of the gall-bladder, which is not pro- longed into a neck. The duct makes a turn round the end of the bag, and is so closely ap- plied to it, as to require a careful examination to determine the true place of its commencement. The hepatic duct fn, fig. 165) arises by two branches from the large lateral lobes of the liver, which unite in the fissure or ' gates' of the gland. Two hepatic ducts have been found in the Curassow; but these and the cystic duct terminate separately in the duodenum. The place of termination of the cystic and hepatic duct is generally, as shown in Jig. 163 and 165, pretty close together at the end of the fold of the duodenum ; but in the Ostrich one of the hepatic ducts, which is very large and short, terminates in the commencement of the duodenum about an inch from the pylorus; while the other enters with the pancreatic duct at the termination of the duodenum. Both the cystic and hepatic ducts undergo a slight thickening in their coats just before their termination; and it is remarkable that, in some of the Marsupiata, as the Kangaroo, the termination of the ductus choledochus is si- milarly thickened and glandular. The passage of the bile-ducts in birds through the coats of the intestine is oblique, as in the Mam- malia, and they terminate upon a valvular prominence of the lining membrane of the gut. The Pancreas (q, q, Jig. 163, 165) consists of two and sometimes of three distinct por- tions in Birds; but these are so closely ap- plied together at some point of their surface as to appear like one continuous gland. It is of a narrow, elongated, trihedral form, lodged in the interspace of the duodenal fold, and generally folded upon itself like the duodenum, as in the Hornbill (fig. 165). The structure of the pancreas is conglome- rate, like that of the salivary glands, but the ultimate follicles are differently disposed. In the salivary glands these are irregularly branched, while those of the pancreas in Birds diverge in the same plane from digitated and pinnatifid groups.* The ducts (r r, Jig. 163, 165) formed by the reiterated union of the efferent branches from the component follicles of the pancreas are in general two in number, which terminate separately in close proximity to the hepatic and cystic ducts ; but occasionally there are three pancreatic ducts, as in the common Fowl, Pigeon, Raven, and Horn-bill ; in which case the third duct commonly terminates at a dis- tance from the other two: in the Horn-bill it proceeds from an enlarged lobe of the pan- * Mullcr dc Gland. Struct. Pen. fol. p. 66. creas at the end of the duodenal fold, and entering that part, as ut ?', Jig. 165. The Spleen (s, s, Jig. 163, 165) is compara- tively of small size in Birds; it is generally of a round or oval figure, but sometimes presents an elongated and vermiform shape, as in the Sea-Gull, or is broad and flat as in the Cor- morant. It is situated beneath the liver, on the right side of the proventriculus. It is, however, somewhat loosely connected to the surrounding parts, so that its position has been differently described by different authors. We have generally been able to trace a pro- cess of the pancreas passing into close contact with it, and connected to it by a continuation of vessels, as in the Horn-bill (fig. 165, ) crosses z 2 840 AVES. the fore-arm, just below the articulation in company with the nerve, and running along the inferior edge of the ulna, receives a branch from between the basis of each quill, is con- tinued along the ligament which sustains the rest of the quills to the extremity of the wing, receiving many veins of the joints from the opposite side of the ringers. Besides these large superficial veins of the fore-arm, there appears to be one, and sometimes two, small accompanying veins to the ulnar and interos- seous arteries (y). " The inferior vena cava (K), before it enters the auricle (A), receives as usual the hepatic veins (s) ; these are numerous, and open into the cava as it passes behind the liver, or more frequently within the substance of that viscus in the back part. We have reckoned in the Cock two large and two small hepatic veins from the right lobe, and one large branch from the left lobe, besides six minute veins, which came indifferently from both lobes. " The trunk of the vena cava is very short in the abdomen; it separates into two great branches analogous to the primary iliac veins (), opposite to the renal capsules ; these turn to each side, and experience a very singular dis- tribution. On coming near the edge of the pelvis each of these two veins forms two branches ; one of which collects the blood of the lower extremity, as hereafter described; the other passes straight downwards imbedded in the substance of the kidney, and admits the several emulgent veins, which are very large, and are seen to pass for some way obliquely in the kidney before their termination. Some- times the emulgent veins are double, as in the figure, (M). The descending branch of the iliac also receives the ovarian veins, and when arrived at the lower end of the kidney, divides into three branches; one transmits the blood of the muscles of the tail and parts adjacent ; another accom- panies the ureter to the side of the rectum, and is distributed about the anus and parts of gene- ration, answering to the htemorrhoidul veins ; the third (v, v) passes inwards to the middle line between the kidneys, and there unites with the corresponding branch of the opposite side.* The vessel which is in this manner produced (*) receives all the blood of the rectum from the anus to the origin of the cceca, anastomosing below with the branches of the hsemorrhoidal veins ; and at the upper part of the rectum, it becomes continuous with the trunk of the veins of the small intestines (.reforming the most remarkable anastomosis in the body, both on account of its consequences and the size of the vessels by which it is effected. By means of* this communication, the blood of the viscera and the external parts of the body flows al- most indifferently into the vena cava and vena portae (iv) ; for the anastomosing vessels are suf- ficiently large to admit the ready passage of a considerable column of blood in proportion to the whole mass which circulates in the body * It is these branches which Professor Jacobson supposes to carry venous blood into the kidneys, for the purpose of supplying material for the uri- nary secretion. of the bird ; for instance, in the Goose the com- municating veins of the pelvis are equal in size to a goose-quill, and in the Ostrich and Cassowary they are as thick as a finger. The advantage which appears to result from this remarkable union of vessels, is the prevention of congestion, or the overloading either the heart or liver with blood, as the one organ has the power of relieving the other. It would seem from this, as well as several other pro- visions of the same kind, that the circulation would be more liable to obstruction in birds than other animals.* It is difficult to say, how- ever, to what cause such an effect ought to be ascribed. Is it from the compression sus- tained by the heart and other viscera, by means of the air-cells during respiration ? or, is the mode of progression by flight capable of impeding the motion of the blood ? " The anastomosis of the pelvic veins, in being the means of conveying common venous blood into the liver, goes to prove that the blood of the vena portae does not require any peculiar preparation by circulation in the spleen or other viscera, which has been conceived as necessary by some physiologists to fit it for the secretion of bile. " The vena portce (w) belongs almost exclu- sively to the right or principal lobe of the liver. It is formed by three branches. The splenic vein is the smallest, and is added to the vena portae, just as it penetrates the liver on the side of the hepatic duct. The next is made of two branches; of which one returns the blood of the posterior gastric artery, and therefore may be called the posterior gastric vein ; and the other is furnished by the pancreas and duode- num, and therefore is the pancreatic vein. The third and largest branch of the vena portse is the mesenteric vein (x\ which not only collects the blood from all the small intestines, but likewise receives the inferior mesenteric (2), or vein of the rectum, which forms the com- munication that has been described with the pelvic veins. " The veins of the left lobe of the liver are furnished in the goose by those which accom- pany the anterior gastric artery, and some branches from the head of the duodenum. " The anterior gastric veins produce two small trunks, which enter at the two extremities of the fissure, in the concave surface of the left lobe of the liver, as it lies upon the edge of the gizzard; the veins from the head of the duodenum furnish a small vessel which passes backwards to penetrate the posterior part of the fissure in the left lobe. " In the c ock the veins that the left lobe of the liver derives from the anterior gastric, are more numerous than in the goose, " The veins of the zone of gastric glands, and of the lower portion of the oesophagus, do not * Besides their anastomoses the principal vis- ceral veins are remarkable for their large size in the Diving Birds. Cuvier (Lemons d'Anat. Comp. iv. p. 274 ) has especially noticed the dilatation of the inferior cava of the Grebes (Colymbus), which reservoir he compares with that formed by the hepatic veins in the Seal. AVES. 341 contribute to the secretory vessels of the liver, but proceed to the superior part of that viscus, to terminate in the vena cava, as does also the umbilical vein. " The vein which returns the blood of the inferior extremities is divided in the pelvis into two branches, which correspond with the femoral and ischiadic arteries; the one passes through the ischiadic foramen, and the other through the hole upon the anterior margin of the pelvis; but the proportion they bear to each other in magnitude is the very reverse of what occurs in the arteries ; for the anterior vein is the principal one, whilst the other is not a very considerable vessel, and receives its supply of blood from the muscles at the pos- terior part of the joint. " The femoral vein (a ), immediately without the pelvis, gives branches on both sides, which receive the blood of the extensor and adductor muscles at their superior part : the trunk passes obliquely under the accessory muscle of the flexor digitorum, and over the os femoris, where it liessuperficially ; it then winds under the adductor muscles, and gets into the ham (b 6), where it receives many muscular branches, and comes into company with the artery and nerve. It here divides into the tibial(c c) and peroneal veins. The first is joined by some branches from the surface of the joint answer- ing to the articular arteries; it also receives the anterior tibial vein which accompanies the artery of the same name. The tibial vein pro- ceeds down the leg along with the artery on the inside of the deep-seated flexors of the heel : it turns over the fore part of the articu- lation of the tibia with the metatarsal bone, in order to get upon the inner side of the me- tatarsus; above the origin of the pollex, it receives a communicating branch from the peroneal vein, and immediately after two branches from the toes: one of them comes from the inside of the internal toe ; the other arises from the inside of the external and mid- dle toes, unites at the root of the toes in the sole of the foot, and is joined by a branch from the pollex, before its termination in the internal vein of the metatarsus. " The peroneal vein derives its principal branches along with those of the peroneal artery, from the muscles on the outside of the leg. The trunk of the vein comes out from the peroneal muscles, and passes superficially over the joint at the heel, and along the outside of the metatarsus ; near the pollex, or great toe, it sends a branch round the back of the leg, to communicate with the tibial vein ; after which it is continued upon the outside of the external toe to the extremity, receiving anas- tomosing branches from the tibial vein. " Where the veins run superficially upon the upper and lower extremities, they seem to supply the place of the branches of the cepha- lic, basilic, and the two saphena; but the analogy is lost upon the upper arm and thigh, these branches forming deep-seated trunks ; this constitutes the greatest peculiarity in the distribution of the veins in the extremities of birds. 1 ' Respiratory organs. In the course of this article we have frequently had occasion to allude to the extent and activity of the respiratory func- tion in the Class of Birds;* nevertheless the organs subservient to this function manifest more of the peculiarities of the Reptilian than of the Mammalian type of formation. The lungs are confined, as in the Tortoise, to the back part of the thoracic-abdominal cavity, being firmly attached to the ribs and their interspaces ; and, as in the Serpent, they communicate with large membranous cells which extend into the abdomen and serve as reservoirs of air. In those aquatic Birds, which are deprived of the power of flight, as the Penguins, the air receptacles are confined to the abdomen ; but in the rest of the class they extend along the sides of the neck, and, escaping at the chest and pelvis, accompany the muscles of the extre- mities. They also penetrate the medullary cavities and diploe of the bones, extending in different species through different proportions of the osseous system, until in some birds, as the Horn-bill, every bone of the skeleton is permeated by air. There is, indeed, no class of Animals which are so thoroughly penetrated by the me- dium in which they live and move as that of Birds. Fig. 172. The lungs (w, fig. m) are two in number, of a lengthened, flattened,oval shape, extending along each side of the spine from the second dorsal vertebra to the kidneys, and laterally to the junc- tion of the vertebral with the sternal ribs. They are not suspended freely as in Mammalia, but are confined to the back part ' of the chest by cellular membrane, and the pleura is reflected over the sternal surface only, to which the strong aponeurosis of the ^' diaphragmatic muscles is attached. They are con- sequently smooth and even on the anterior Ri 9 ht Iun 9 f a Goo8e - surface, but posteriorly are accurately moulded to the inequalities of the ribs and intercostal spaces. The lungs in general are of a bright red colour, and of a loose spongy texture. The bronchi (u,fig. 163; a, Jig. 172) penetrate their mesial and anterior surfaces about one-third from the upper extremities; they divide into four, five, or six branches, which diverge as they run along the anterior surface ; some in- complete cartilaginous rings are found through their entire extent. The orifices of the air-cells of the lungs (c r, Jig. 172) open upon the posterior parietes of the bronchial tubes, while the extremities of these tubes terminate by wide openings (b b, Jig. 172) in the thoracic and abdominal air- receptacles. These orifices are oblique, ai.d * According to Lavoisier, two Sparrows consume as much oxygen in a given time as one Guinea-pig. 342 AVES. are partially covered by a slight projection of membrane. The pulmonary artery divides, almost im- mediately after its origin, into two branches, one to each lung; the ramifications of each artery form plexuses upon the air-cells, and freely anastomose with the pulmonary veins; these leave the lung by a single trunk, and the two pulmonary veins unite into one before terminating in the left auricle. The thoracic-abdominal cavity is subdivided and intersected by a number of membranes; the greater part of the cells thus formed are filled with air. The texture of their parietes possesses considerable firmness in the larger birds, as the Ostrich and Cassowary, in which they were described by the French Academi- cians as so many distinct bags. The innermost layer of the air-receptacles can be separated from the outer layer, and is a continuation of the lining membrane of the bronchial tube; the outer layer is a serous membrane, and appears to form the cells by a series of reflections of what may be regarded as the pleura or peritoneum. These large membranous receptacles into which the extremities of the bronchial tubes open are disposed with sufficient general regu- larity to admit of a definite description and nomenclature. Fig. 173. Air-receptacles of a Swan. The first or inter-clavicular air-cell (, 173) extends from the anterior part of ea< lung, forwards to the interspace of the fur- culum, anterior to which it dilates in the Gannet and many other birds into a large globular receptacle. In the Vultures it is di- vided into two lateral receptacles, between which the large crop is situated. A thin fan- shaped muscle is extended from the anterior edge of the furculum, over the interclavicular air-cell in these and some other birds The anterior thoracic cell (6) contains the lower larynx and bronchi, and the great vessels with their primary branches to the head and wings. It is traversed by numerous mem- branous septa, which connect the different vessels together, and maintain them in their situations. The air passes into the posterior part of this receptacle by two openings at the anterior part of the lungs. The deep-seated air-cells of the neck are continued from it anteriorly. The lateral thoracic cells (d) are continued on each side from a foramen on the inner edge of the lung, situated just opposite the base of the heart ; they are covered by the anterior tho- racic air-cell, and from them the air passes into the axillary and subscapular cells, into those of the wing, and into the humerus (e). They also communicate with the cellula cordis posterior (c), behind the heart and bronchi, which cell is often subdivided into several small ones. The cellula hepatica are of much larger size ; they are two in number, of a pyramidal figure, with their bases applied to the lateral thoracic cells, and their apices reaching to the pelvis : they cover the lower portions of the lungs and the lobes of the liver ; they receive air from several foramina situated near and at the external edge of the lungs. The cellula abdominales commence be- neath the cellulse hepaticae at the inferior ex- tremity of the lungs, where the longest branches of the bronchiae open freely into them. (A bristle is passed through one of these openings in the figure.) They are distinguished into right (f) and left (h) ; the former is gene- rally the largest receptacle in the body ; it ex- tends from the last ribs to the anus, and covers the greater part of the small intestines, the supra-renal gland, and kidney of the same side. The left abdominal cell (A) contains the intestines of its own side, and is attached to the gizzard. In some large Birds, as the Gannet, it is separated from the right recep- tacle by a mediastinal membrane (g) which is continued from the gizzard to the anus. Both the abdominal receptacles transmit air to the pelvic cells (i, k) of their respec- tive sides, and to several small and extremely delicate cells between and behind the coils of intestine. One of these is continued round the fold of the duodenum and pancreas to the gizzard, and has been termed the duodenal cell. From the inguinal cell are continued the in- termuscular glut&al and femoral cells, which surround the head of the femur, and commu- cate with that bone by an aperture (1} situated AVES. 343 immediately anterior to .the great trochanter, except in those Birds in which the femur retains its medulla. The cervical air-cells are continued from the large clavicular cell, and form in the Argala a singular appendage or pouch, contained in a loose fold of integument, which the bird can inflate at pleasure. In the Pelecan and Gannet extensive air- cells are situated beneath almost the whole of the integument of the body, which is united to the subjacent muscles only here and there by the septa of the cells and the vessels and nerves which are supported by the septa in their pas- sage to the skin. The large pectoral muscles and those of the thigh present a singular ap- pearance, being, as it were, cleanly dissected on every side, having the air-cavities above and beneath them. The axillary vessels and nerves are also seen passing bare and unsupported by any surrounding substance through these cavi- ties. Numerous strips of panniculus carnosus pass from various parts of the surface of the muscles to be firmly attached to the skin ; a beautiful fan-shaped muscle is spread over the inter-clavicular or furcular air-cell. The use of these muscles appears to be to produce a rapid collapse of the superficial air-cells, and an expulsion of the air, when the bird is about to descend, in order to increase its specific gravity, and enable it to dart with rapidity upon a living prey. The air-receptacles of the thoracic-abdominal cavity present varieties in their relative sizes and modes of attachment in different birds. In the Raptores they are principally attached pos- teriorly to the ribs, the diaphragmatic aponeu- rosis covering the lungs, and to the kidneys ; while in the Grallatores they have anterior attachments to the intestines in many places. The singular extension of the respiratory into the osseous system was discovered almost simultaneously by Hunter and Camper, and ably investigated by them through the whole class of Birds. The air-cells and lungs can be inflated from the bones, and Mr. Hunter injected the medullary cavities of the bones from the trachea. It is stated that if the femur into which the air is admitted be broken, the bird shall not be able to raise itself in flight. It is certain that if the trachea be tied, and an opening be made into the humerus, the bird will respire by that opening for a short period, and may be killed by inhaling noxious gases through it.* If an air-bone of a living bird, similarly perforated, be held in water, bubbles will rise from it, and a motion of the contained * " I cut the wing through the os humeri in a Fowl, and tying up the trachea found that the air passed to and from the lungs by the canal in this bone. The same experiment was made with the os femoris of a young Hawk, and was attended with a similar result. But the passage of air through the divided parts, in both these experiments, espe- cially in the last, was attended with more difficulty than in the former one ; it was indeed so great, as to render it impossible for the animal to live longer than evidently to prove that it breathed through the cut bone." Hunter's Animal (Economy, p. 94. air will be exhibited, synchronous with the motions of inspiration and expiration. The proportion in which the skeleton is permeated by air varies in different Birds. In the Penguin (Aptenodytcs), which we have examined for this purpose, air is not admitted into any of the bones. Its chief progression being in water, the specific levity of the body gained by the substitution of air for marrow would be rather a detriment than an advantage. The condition of the osseous system, therefore, which all birds present at the early periods of exist- ence, is here retained through life. In the large Struthious Birds, which are re- markable for the rapidity of their course, the thigh-bones and bones of the pelvis, the ver- tebral column, ribs, sternum and scapular arch, the cranium and lower jaw, have all air admitted into their cavities or cancellous struc- ture. The humeri and other bones of the wings, the tibiae and distal bones of the legs, retain their marrow. With the exception of the Woodcock, all Birds of Flight have air admitted to the humerus. The Pigeon tribe, with the exception of the Crown Pigeon, have no air in the femur, which relains its marrow. In the Owls also the femur is filled with marrow; but in the Diurnal Birds of Prey, as in almost all other Birds of Flight, the femur is filled with air. In the Pelecan and Gannet the air enters all the bones with the exception of the phalanges of the toes. In the Hornbill even these are permeated by air. Mr. Hunter* has given the following cha- racters as distinguishing the bones which receive air. They may be known " first, by their less specific gravity ; secondly, by their retain- ing little or no oil, and, consequently, being more easily cleaned, and when cleaned, ap- pearing much whiter than common bones : thirdly, by having no marrow, or even any bloody pulpy substance in their cells ; fourthly, by not being in general so hard and firm as other bones ; and, fifthly, by the passage that allows the air to enter the bones, which can easily be perceived." We have reserved for this section the de- scription of the foramina by which the air penetrates the different bones. These openings may be readily distinguished in the recent bone, since they are not filled up by blood- vessels or nerves, but have their external edges rounded off. In the dorsal vertebrae the air-orifices are small, numerous, and irregular ; situated along the sides of the bodies, and the roots of the spinous processes, the air passes into them directly from the lungs. In the two or three lower cervical vertebrae the air-holes are in the same situation, but receive the air from the lower cervical or clavicular air-cells : in the remainder of these vertebrae the air-holes are situated within the canal lodging the vertebral artery, and communicate with the lateral air- cells of the neck. * Animal (Economy, p. 91. 344 AVES. The air-holes of the vertebral ribs are situated at the internal surface of their vertebral extre- mities, and appear like those of the contiguous vertebrae to have an immediate communication with the lungs. The sternal ribs, or ossified costal cartilages, have also internal cavities which receive air from the lateral thoracic cells by means of orifices placed at their sternal ex- tremities. The orifices by which air is admitted to the sternum are exceedingly numerous, but are principally situated along the mesial line of the internal surface, opposite the origin of the keel, forming a reticulation at that part; the largest foramen is near the anterior part of the bone ; some smaller ones occur at the costal margins. All these orifices commu- nicate with the thoracic air-receptacles. The scapula is perforated by several holes at the articular extremity, which admit air into its cancellous structure from the axillary cell. The coracoid has small air-holes at both ex- tremities ; the largest is situated on its inner surface, where it is connected with the clavicle or furculum. The furculum receives air principally by a small hole in the inner side of each of its scapular extremities, which communicates with the clavicular air-celL The air-hole of the humerus is of large size, and situated at the back part of the head of the bone, below the curved inferior process. It communicates with the axillary air-cell, and transmits the air to the cavity of the bone by several cribriform foramina. The air-holes of the pelvic bones are situated irregularly on the inner surface upon which the kidneys rest, and must therefore receive air from continuations of the abdominal receptacles around the kidneys. The air-hole, or rather air-depression of the femur, is situated at the anterior part of the base of the trochanter; it receives air from the glutaeal cell, and transmits it by several small foramina into the interior of the bone. In the Ostrich, the air-holes are situated at the posterior part of the bone at both of its extre- mities. The cavities of the long bones into which air is thus admitted are proportionally larger than in the corresponding bones of Mammalia, and are characterized by small transverse osseous columns which cross in different di- rections from side to side, and are more nu- merous near the extremities of the bone ; they abut against and strengthen, like cross-beams, the parietes of the bone. We have sometimes succeeded in filling with fine size-injection the minute arteries which ramify on the membrane lining these cavities, but the vascularity of this membrane is by no means very remarkable. The lower jaw receives its air by means of an orifice situated upon each ramus behind the tympano-maxillary articulation. Mr. Hunter was in doubt as to whether the lower jaw derived its supply of air from the Eustachian tube or the trachea where it passes along the neck.* In a Pelecan which we dissected for the purpose we found it to be supplied by an air-cell which surrounded the joint, and was con- tinuous with the upper cervical air-cells. The bones of the cranium and upper jaw have com- munications with the Eustachian tube, but not with the nasal passages, which are every where lined with an impervious pituitary membrane. Various explanations have been given of the final intention of the condition of the respiratory system above described. The extension of this system by means of continuous air-receptacles throughout the body is subservient to the function of respiration, not only by a change in the blood of the pulmonary circulation effected by the air of the cells on its re-passage through the bronchial tubes, but also, and more especially, by the change which the blood undergoes in the ca- pillaries of the systemic circulation, which are in contact with the air-receptacles. The free outlet to the air by the bronchial tubes does not, therefore, afford an argument against the use of the air-cells as subsidiary respiratory organs, but rather supports that opinion, since the inlet of atmospheric oxygenated air to be diffused over the body must be equally free. A second use may be ascribed to the air- cells as aiding mechanically the actions of respiration in Birds. During the act of inspi- ration the sternum is depressed, the angle between the vertebral and sternal ribs made less acute, and the thoracic cavity proportion- ally enlarged ; the air then rushes into the lungs and into the thoracic receptacles, while those of the abdomen become flaccid : when the sternum is raised or approximated towards the spine, part of the air is expelled from the lungs and thoracic cells by the trachea, and part driven into the abdominal receptacles, which are thus alternately enlarged and dimi- nished with those of the thorax. . Hence the lungs, notwithstanding their fixed condition, are subject to due compression through the medium of the contiguous air-receptacles, and are affected equally and regularly by every motion of the sternum and ribs. A third use, and perhaps the one which is most closely related to the peculiar exigences of the bird, is that of rendering the whole body specifically lighter ; this must necessarily follow from the dessication of the marrow and other fluids in those spaces which are occupied by the air-cells, and by the rarefaction of the contained air from the heat of the body. Agreeably to this view of the function of the air-cells, it is found that the quantity of air admitted into the system is in proportion to the rapidity and continuance of the bird's motion; and that the air is especially distributed to those members which are most employed in loco- motion ; thus the air is admitted into the wing- bones of the Owl, but not into the femur; while in the Ostrich the air penetrates the femur, but not the humerus or other bones of the wing. A fourth use of the air-receptacles, which has not hitherto been suspected, relates to the * Loc. cit. p. 93. AYES. 315 mechanical assistance which they afford to the muscles of the wings. This was first suggested to us by observing that an inflation of the air- cells in a Gigantic Crane (Ciconia Argala) was followed by an extension of the wings, as the air found its way along the brachial and anti-brachial cells.* In large birds, therefore, which, like the Argala, hover with a sailing motion for a long-continued period in the upper regions of the air, the muscular exertion of keeping the wings outstretched will be les- sened by the tendency of the distended air-cells to maintain that condition. It is not meant to advance this as any other than a secondary and probably partial use of the air-cells. In the same light may be regarded the use as- signed to them by Hunter, of contributing to sustain the song of Birds, and to impart to it tone and strength. It is no argument against this function that the air-cells exist in birds which are not provided with the mechanism necessary to produce tuneful notes ; since it was not pre- tended by Hunter that this was the exclusive and only office of the air-cells. The latest writer on this subject has indeed proposed this suggestion of Mr. Hunter as a novel idea.f Air-passages. The air-passages in birds commence by a simple superior larynx, from which a long trachea extends to the anterior aperture of the thorax, where it divides into the two bronchi, one to each lung. At the place of its division there exists, in most birds, a complicated mechanism of bones and carti- lages moved by appropriate muscles, and constituting the true organ of voice : this part is. termed the inferior larynx. The tendency to ossification, which is ex- emplified in the bony condition of the costal cartilages and tendons of the muscles, is again manifested in the framework of the larynx and the rings of the trachea, which, instead of being cartilaginous, as in Reptiles and Mam- mals, are in most birds of a bony texture. The superior larynx (Jig. 151, 174, 175,) is situated behind the root of the tongue, and rests upon the uro-hyal element of the os hy- oides, to which it is attached by dense cellular texture. It is composed of several bony and cartila- ginous pieces, varying in number from four to ten. The largest oi these pieces constitutes the anterior part of the larynx. It is of an oval or triangular form, according as. its superior termination is more or less pointed : it is regarded by Cuvier as analogous to the anterior part of the cricoid cartilage, (Lecons d'Anat. Comp. iv. p. 489,) but by Carus it is considered as representing the thyroid cartilage (f y fig. 151). The cricoid cartilage in birds consists of the three osseous pieces, which are situated at the posterior * On relating this fact to Mr. Clift, he suggested another use of the air-cells which is more generally applicable, namely, that of assisting the actions of the muscles by compressing and bracing them, in a manner analogous to the action of the fasciae of the extremities in Man. t Jacquemin, Memoirc sur la pneumaticitc des oiseaux, 1835. Fig. 174. and inferior part of the upper larynx; the middle one (g,Jig. 151) is of an oblong form, and varies in size, being larger than the lateral ones in the Anatida, but smaller in the In- scssores. The lateral pieces are connected at one extremity with the thyroid piece, and at the other to the middle oblong piece above described, which completes the circle of the laryngeal frame-work posteriorly. Carus re- gards the first two incomplete tracheal rings (gg) as the anterior part of the cricoid. The arytenoid bones (h) rest upon the middle ob- long portion of the cricoid, and extend for- wards, being connected at their outer edge by means of elastic cellular substance to the thy- roid bone, and attached by their anterior ex- tremities to the uro-hyal bone by means oi" two small ligaments :* they form, by their inner margins, the rima glottidis or laryngeal fissure. This fissure (i,fig. 152) being thus bounded by inflexible rigid substances is only susceptible of having its lateral diameter varied according to the degrees of separation or approximation to which the arytenoid bones are subject. These different states are produced by (appropriate muscles, one pair of which may be regarded as analogous to the Thyreo-arytcnoidei, and the other may be termed Constrictores glottidis. The former of these muscles (k k,Jig. 174,) arise from the sides and posterior surface of the thyroid bone, and are inserted into the whole length of the inner edge of the arytenoid cartilages, which they draw out- wards, and consequently open the laryngeal fissure, The constrictores glottidis in the Gigantic Crane arise from the middle of the in- ternal or posterior surface of the thyroid bone, and are inserted into the extremi- ties of the arytenoid pieces. According to Mr. Yarrell, from whose Memoir the subjoined figures are taken, the constrictors of the glottis (l,fig.175) " pass from the upper portion of the cricoid (thyroid) cartilage along the cru'ra of the ary- tenoid cartilages, upon each outer edge of which they are inserted ."-f In either case these muscles are enabled to close the la- ryngeal opening with con- siderable force, and with such accuracy as to super- sede the necessity of an epiglottis. From the sim- plicity of the structure just described, from the situation of the superior larynx with relation to the rictus or gape of the bill, and from the absence of lips by which this might be partially or * Linn. Trans, vol. xvi. p. 06, pi. 17, figs. 3 and 4. t This description is taken from the Gigantic Crane. Ciconia Argala. Fig. 175. 346 AVES. entirely closed, it is plain that it cannot be considered as influencing the voice, otherwise than by dividing or articulating the notes after they are formed by the lower larynx. The superior larynx presents, indeed, but few varieties in the different species of Birds ; and these relate chiefly to certain tubercles which are observed in its anterior, but which vary in number, and do not exist at all in some spe- cies, as the singing birds ; being chiefly pre- sent in those birds which have a rough un- musical voice. In the Pelecan, the Gigantic Crane, and most of the Rasores, a process ex- tends backwards into the cavity of the upper larynx from the middle of the posterior surface of the thyroid cartilage, and seems destined to give additional protection to the air-passage. The trachea (G,Jig. 170, 171) in Birds is proportionally longer, in consequence of the length of the neck, than in any other class of animals, its length being further increased in many species by convolutions varying in extent and complexity. A species of Sloth (Bradypus tridactylus) among Mammalia, and a species of Crocodile (Crocodilus acutus) among Reptiles, present an analogous folding of the trachea. The trachea is composed in Birds of a series of bony, and sometimes, as in the Ostrich, of cartilaginous rings, included be- tween two membranes. In those cases in which they are of a bony structure, the ossi- fication is observed to commence at the anterior part of each ring, and gradually to extend on both sides to the opposite part. The tracheal rings, whether bony or cartila- ginous, are, with the exception of the two uppermost, always complete, and not, as in most quadrupeds, where the windpipe bears a different relation to the organ of voice, defi- cient posteriorly. They differ in shape, being sometimes more or less compressed. They are generally of uniform breadth, but in some species are alternately narrower at certain parts of their circumference and broader at others, and in these cases the rings are generally closely approximated together, and, as it were, locked into one another. This structure is most common in the Grallatores, where the rings are broadest alternately on the right and left sides : the French Academicians have given a good illustration of this structure from the trachea of the Demoiselle Crane. With respect to the diameter of the tracheal rings, this may sometimes be pretty uniform throughout, and the trachea will consequently be cylindrical, as in the Insessores, the Gralla- tores which have a shrill voice, the females of the Natatores, and most Raptores and Ra- sores: or the rings may gradually decrease in diameter, forming a conical trachea, as in the Turkey, the Heron, the Buzzard, the Eagle, the Cormorant, and the Gannet ; or they may become wider by degrees to the middle of the trachea, and afterwards contract again to the inferior larynx ; or, lastly, they may experience sudden dilatations for a short extent of the trachea; the Golden-eye (Anasclangula), the Velvet-duck (Anas fusca), and the Mergan- ser (Mergus sermtor), present a single en- largement of this kind, in which the bony rings are entire, and of the same texture as in the rest of the tube. In the Golden-Eye the trachea is four times larger at the dilatation than at any other part. In the Goosander ( Mergus merganser), the trachea presents two sudden dilatations of a similar structure to that above described. The trachea of the Emeu (Dromaius ater) is also remarkable for a sud- den dilatation, but in this instance the cartila- ginous rings do not preserve their integrity at the dilated part, but are wanting posteriorly, where the tube is completed by the membranes only. The bronchi (v, jig. 163) are straight, com- pressed, delicate, and easily lacerable tubes; their rings, in most Birds,* form only a small segment of a circle, and are situated at the outer side of the tube, which is convex ; the inner side is completed by a membrane (mem- brana tympaniformis) extended between the extremities of the defective rings, and is flat. The bronchial rings are weak and thin ; in Birds without true muscles of voice, they are either of uniform thickness, or become gradually thinner to their termination : in many Birds which have the vocal muscles they grow sud- denly thinner below the insertion of those muscles : this is remarkable in Owls. The muscles of the trachea are generally a single pair, the sterno-tracheales, to which, in some cases, a second pair is added, the cleido- tracheales. The sterno-tracheales, which are analogous to the sterno-thyroidei of mammalia, arise from the costal processes of the sternum, and ascend along the sides of the trachea, as far in general as the superior larynx. The cleido-tracheales (ypsilo-tracheens of Cuvier) arise from the furculum or conjoined clavicles, and pass along the sides of the trachea parallel to the preceding. Many birds possess only the tracheal and superior laryngeal muscles, and have no proper muscles of the inferior larynx. Cuvierf divides such birds into those which have the lower larynx simple or without dilatations, as the Rasores, and into those which have lateral bony cavities at that part, as the males of the Genus Anas, Cuv. and Mergus. His next division in the order of complexity of the vocal organs includes those birds which have one pair of vocal or inferior laryngeal muscles, the Broncho-tracheales ; these arise from the sides of the lower part of the trachea, and are inserted in one of the half-rings of the bronchi at a less or greater distance from the lower larynx in different birds ; as, for exam pie, in the first half-ring in the Genus Falco, in most of the Grallatores, in the Genus Larus (Gull), and Phalacrocorax (Cormo- rant) ; in the third half-ring in the King-fisher (Alcedo), and Goat-sucker ( Caprimulgus ) ; in the fifth half-ring in the Genus Ardea, Cuv. in the Cuckoo and the Eagle-Owl (Bubo maximus); in the seventh half-ring in the * In the Vultures, which have no true vocal muscles, but only the sterno-tracheales, the first four bronchial rings are entire. t Anat. Comparee, torn. iv. p. 450. AVES. 347 Barn-Owl (Strix flammea) and Horn-Owl (Otus uurita). The influence of these muscles upon the voice must obviously be in proportion as they shorten the bronchi and depress the lower larynx, according to the different inser- tions above mentioned. A further degree of complexity in the organ of voice is presented by the Psittacida or Par- rot-tribe, which, according to Cuvier, have three pairs of inferior laryngeal muscles. The Insessores, lastly, present five pairs of muscles appertaining to the lower larynx, and the organ of voice consequently attains its greatest perfection in this order. The peculiar structure of the lower larynx, and the modifications of the trachea in relation to its functions, will be treated of under the article Organs of' Voice. Urinary Organs. These consist in birds of the kidneys, ureters, and a urinary receptacle, which is more or less developed in all birds. The kidney of the oviparous vertebrate ani- mal is distinguished from that of the mammi- ferous by the homogeneity of its substance, which is not divided into a cortical and medul- lary part, and by the tubuli uriniferi extending to the surface of the gland there to form by reiterated unions the ureter, and not terminating in a cavity or pelvis in the interior of the kidney, from which the ureter commences. The kidneys (x x, fig. 182) of birds manifest all the essential characters of the oviparous type of structure. They are two in number, of an elon- gated form, commencing immediately below the lungs, and extending along the sides of the spine as far as the termination of the rectum ; in which course they are impacted in, and as it were moulded to the cavities and depressions of the pelvis. From this fixed condition it results that they are generally symmetrical in position, not placed one higher than the other, as in the mam- malia. The posterior surface of the kidney pre- sents inequalities corresponding to the risings and depressions of the pelvis; the anterior sur- face is smoothly convex or flattened ; but rising into a series of prominences which correspond, not to the eminences, but to the cavities of the bones on which they rest : their inner or mesial side is generally pretty regular and straight, but the external edge is more or less notched. From the nature of the integuments about to be described, and the small amount of cutane- ous transpiration in birds, the office of removing from the system the superfluous watery part of the circulating fluids devolves almost exclu- sively upon the kidneys, and they are conse- quently relatively larger than in the terrestrial mammalia. The kidneys vary in size in different birds, being for example smaller in most of the Grallatores, as the Bustard and Heron, where the pelvis is short, than in the Rasorial Order, in which it is of great extent. Where they are short they are in general more promi- nent, and this is so remarkable in some birds, as the Owls, that in them they resemble some- what in their superficial position the kidneys of mammalia. As might be expected from their relations to the pelvis, the kidneys in birds present as many varieties of outward configuration as there are differences in the part of the skeleton to which they are moulded. In some aquatic birds, as the Grebe ( PodicepsJ and the Coot (Fulica), the kidneys are more or less blended together at their lower extremities, as in most fishes. In the rest of the class they are distinct from one another. In the Tern they are each divided by fissures into seven or eight square-shaped lobes. In the Eagle they each present four divisions ; but in these cases there are not distinct ureters to each lobe as in the subdivided kidneys of mam- malia. The principal lobes are in general three in number, the anterior or highest one being, in some cases, the largest; while in others, as the Pelecan, the contrary obtains, the lowest division being most developed in this bird. In the Emeu (Dromaius ater) the kidney presents only two lobes; the superior or anterior one is the broadest and most prominent, being of a rounded figure, and constituting one-third of the whole ; the lower division is flattened, and gradually tapers to a point. In the speci- men we dissected we found the left kidney half an inch longer than the right. Each kidney is invested by its proper capsule, a thin membrane, which also extends into the substance of the gland, between its divisions : a delicate layer of peritoneum is reflected over their anterior surfaces. The texture of the kidneys is much more frail than in mammalia, readily yielding under the pressure of the finger, to which they give a granu- lar sensation as their substance is torn asunder. In colour they resemble the human spleen. Besides being divided into lobes, the surface of the kidneys may be observed to be composed of innumerable small lobules, separated by conti- nuous gyrations like the convolutions of the cerebral substance. The ultimate divisions of the lobules and their intimate structure can only be distinguished by observations on the embryo, unless when the component follicles are filled, as they occasionally are seen to be after death, with the white salts of the urinary secretion. The tubuli uriniferi, as Miiller ob- serves,* may then be seen under the microscope originating from every part of the internal sub- stance of the lobules, extending to the gyrations, uniting in the pinnatifid form, and coursing to the margins of the lobules, all the inflexions of which they follow. The pinnatifid ramification of the uriniferous tubules is sometimes opposite, sometimes alternate. Sometimes the branches are simple, sometimes dichotomously divided : but these ramuli appear scarcely smaller than the branches from which they spring, and never intercommunicate. They have been successfully injected with size and vermilion, without any of this material escaping into the secerning vessels, which are much more minute. The uriniferous ducts, when thus traced from the * De Glandularum Structura, p. 92. 348 AVES. irunks to the branches, are seen to become con- fined in pyramids, which adhere to the branches of the ureter, are sent out in the gyri of the lobules, and are outspread in a pinnatifid figure on the surface, one next another, and ultimately terminate in blind, rounded, but not dilated extremities. The branches from the convoluted lobules unite dichotomously, and ultimately escape by a single duct the ureter. The arteries and veins of the kidneys have already been described ; a difference of opinion, however, prevails as to the course of the blood in the veins which pass from the lower end of the kidneys (at v,fg. 171) to the hypogastric vein (*). Jacobson considers that the venous blood is carried into the kidney by these veins, for the purpose of affording the material for the urinary secretion, analogous to the portal vein in the liver ; but Cuvier regards these veins as having the same function as those which come from the upper ends of the kidneys, and that they return the blood from the lower ends of the kidneys to aid in the formation of the portal vein. Nicolai* also opposes the doctrine of a venous circulation in the kidneys of Birds. In favour of Jacobson's theory is the small size of the renal arteries, in consequence of which the kidneys are not more coloured than the liver, when the arterial system is in- jected from the aorta, and the disproportionate size of the veins, together with the analogy of the cold-blooded ovipara, in which the exist- ence of a secreting system of veins in the kid- neys is now generally admitted. The ureter (y,fig. 163, 182; h, k,fig. 176) lias the same structure as in the mammalia. It is continued down along the anterior surface of the kidney towards the mesial side ; here and there imbedded in its substance, forming a series of dilatations corresponding to the prin- cipal lobes or enlargements of the gland, and receiving the branches of the tubuli uriniferi as it passes along. But these slight reservoirs do not present any parts corresponding to the mammillae and their infundibula of mam- malia. Below the kidney the ureters pass be- hind the rectum, becoming connected to, and after a short distance involved in its coats ; they ultimately terminate upon valvular emi- nences, in a depression at the lower part of the urinary sac; the terminal papillse of the ureters are situated with the orifices of the genital ducts, in the same segment of the cloaca, which is therefore termed the urethro-sexual cavity (e, fig. 176). The space intervening between the urethro- sexual cavity and the valvular termination of the rectum (c,jig. 176) forms a cavity more or less developed in different birds, but always distinct in the smoothness of its lining mem- brane from the rectum, which has a more vas- cular and villous internal tunic. The birds in which this rudimental urinary bladder presents the largest capacity are the Owls, many of the aquatic birds, as the Pelecan, Willock, Grebe, Swan, &c. ; some of the Wading Order, as the * Oken's Isis, 1826, p. 414. Bittern and Bustard, but more especially the Ostrich, among the Cursorcs, in which the urinary receptacle is represented as laid open Cloaca of the Ostrich* The Supra-renal Glands, Renal capsules, Glandule succenturiatts (d, d, fg. 182) are small bodies, usually of a bright yellow colour, situated on the mesial or inner side of the su- perior extremities of the kidneys; closely at- tached to the coats of the contiguous large veins and in contact with the testes in the male ; and the left one adhering to the ovary in the female. They vary in shape, being sometimes of a round, flattened, oval, or irregularly triangular figure. They are proportionally smaller than in mammalia, being in the Goose each about the size of a pea. They present, like the kidneys, a homoge- neous texture throughout, and do not exhibit the alternate strata of different-coloured sub- stances as in mammalia. In the Gigantic Crane we found the texture of the supra-renal glands to be coarsely fibrous; in the Hornbill they were granular, similar to the kidney; in the Pelecan they were of a granular but more pulpy texture. There is no cavity in the supra-renal glands. The veins which return the blood from them are of proportionally large size, as in all the parenchymatous bodies without excretory ducts. The supra-renal glands have been found to present a slight enlargement corresponding with the increased development of the sexual organs; and it has been conjectured that their function is related to that of the generative system. Thyroid Glands. In many birds, as the Vultures, Falcons, Starling, Magpie, Heron, Bustard, and in most Aquatic birds, two glands are found, one on each side of the trachea, very near the lower larynx and frequently attached to the jugular veins. They are regarded as the analogues of the thyroid glands. In addition to these there are two small glands, in the Gan- net, attached to the upper part of the commence- ment of each bronchus. From Memoircs du Museum, torn. xv. -pi. 2,Juj.'I. AVES. 349 Peculiar Secret ions. The unctuous fluid with which Birds lubricate their feathers is secreted by a gland which is situated above the coccyx or uropygium. This gland consists of two lateral moieties conjoined. As might be expected, it is largest in the birds svhich frequent the water. In the Swan it is an inch and a half in length, and has a central cavity, which serves as a receptacle for the accumulated secre- tion; but this cavity has not been observed in other species. Each lateral portion is of a pyriform shape, and they are conjoined at the apices, which are directed backwards and are perforated by numerous orifices. The longitu- dinal central cavities also present internally nu- merous angular openings, in which there are still smaller orifices. The surrounding glandu- lar substance consists of close-set almost paral- lel straight tubules, and is not irregularly cellular. The tubules extend to the superficies of the gland, without ramifying or intercommunicating, and preserve an equable diameter to their blind extremities. The tubules are longest at the thickest part of the gland, and become shorter and shorter towards the apex. Tegumentary system. This is composed, as in Mammalia and Reptilia, of the corium or derm, epiderm, and its appendages, and an intermediate layer of unhardened epiderm with colouring matter, called rete mucosum. The corium, or true skin, is very thin, as in the cold-blooded Ovipara. It adheres io the subcutaneous muscles by cellular tissue, which is frequently the seat of accumulation of dense yellow fat ; and it is moved by muscles which at the same time raise and ruffle the plumage which it supports. The rete mucosum rarely contains any co- louring matter where the feathers grow ; at this part the skin is of a pale, greyish colour, or pink, from the colour of the blood which circulates in it. But in the naked parts of the integument, as the cire, the lore, the comb, the wattles, the naked parts of the head and neck in some birds, and the tarsi and toes, the rete mucosum frequently glows with the richest crimson, orange, purple, green, black, and a variety of other tints, of which the planches calorics and the different zoological monographs of families of birds afford nu- merous examples. The epidermis is in some places continued as a simple layer over the corium, following its wrinkles and folds, as around the naked necks of some Vultures. It is moulded upon the bony mandibles to form the beak, and in some birds adheres to osseous protuberances on the cranium, where it forms a species of horn ; and it is remarkable that these instances occur chiefly in those orders of birds, the Cursores and Rasores, which are most analogous to the Ru- minantia among quadrupeds: the Cassowary and Helmeted Curassow are examples. The cuticle is sometimes developed into spines or spurs, as upon the wing of the Secretary-bird, t Cassowary, the Apteryx, and the Palamedea; md upon the tarsi of the Gallinaceous Birds. The claws which sheath the ungueal phalanges >f the feet assume various forms adapted to the habits and manner of life of the different orders. A remarkable artificial form is given to the claw of the middle toe in certain birds ; the inner edge being produced and divided into small parallel processes like the close-set teeth of a comb (Jig. 132.) These teeth are not reflected or recurved, as they might be expected to be, if they had been intended to serve as holders of a slippery prey, but are either placed at right angles to the claw or are inclined to- wards its point. The Common Barn-Owl (Strix flammed), the Goat-sucker genus ( Caprimul- gus), the Heron and Bittern kind (Ardeidtg, Vig.), afford examples of this structure ; and as each species of bird appears to be infested by its peculiar louse (Nirmus), the solution of the final intention of so singular a con- trivance, which is limited to so few species, and these of such different habits, may yet be afforded by the entomologist. At least it would be worth while to examine the pa- rasitic animals of the species so provided, with the view of determining whether they pos- sessed superior powers of adhesion which might require the application of a comb in the birds infested by them.* With respect to the scales 'which defend the naked parts of the legs of birds, they do not differ from those of Reptiles. Their form and disposition, as has been already observed, have afforded distinctive characters to the zoo- logist. In most of the Raptores, the Psitta- cidte, the Rasores, the Grallatores, and the Natatorcs, the scales are polygonal, small, and .disposed in a reticulate form ; the birds so characterized formed the Retipedes of Sco- poli. In the rest of the class the tarsi are covered anteriorly with unequal semi-annular scales, ending on each side in a longitudinal furrow, and these birds were termed the * Scu- tipedes.'-^ The four classes of vertebrate animals have each their characteristic external covering : the cold-blooded Ovipara are naked, or their ex- ternal surface is defended only by hard scales or plates ( squama and scuta); but the warm- blooded classes require to be invested by an integument better adapted to maintain the high degree of temperature peculiar to them : hence quadrupeds are clothed with fur and hair, and birds with down and feathers. Feathers are the most complicated of -all the modifications of the epidermic system, and are quite peculiar to the class of birds. The eloquent Paley well observes that " every * Mr. Swainson objects to>. the theory which ascribes to the serrated claw the function of freeing the plumage from vermin, because its presence is partial in the class of Birds. ' To suppose," says he, t( that nature has given to one or two families of birds the exclusive power of freeing themselves from an enemy which in like manner infests all birds, is preposterous." The assertion that the different species of Nirmi infest all birds in like manner is much easier than the proof. fin one section of the Tyranni, Cuv. the scutae surround the tarsi as complete rings. Where the carneous parts of the muscles are continued low down upon the legs, as in the Owls, a covering of feathers is co-extended to preserve their tempera- ture. 350 AVES. feather is a mechanical wonder;" " their dis- position, all inclined backward, the down about the stem, the overlapping of their tips, their different configuration in different parts, not to mention the variety of their colours, constitute a vestment for the body, so beau- tiful, and so appropriate to the life which the animal is to lead, as that, I think, we should have had no conception of any thing equally perfect, if we had never seen it, or can now imagine any thing more so." Notwithstand- ing the varieties of size, consis- tence,and colour, all feathers are composed of a quill or barrel (a, fig. 177), a shaft (b b), and a vane or beard (c c) ; the vane consists of barbs (e e, fig. 178) and barbules (ff, fig. 178). The quill, by which the feather is attached to the skin, is larger and shorter than the shaft, is near- ly cylindrical in form and semi- transparent ; it possesses in an eminent degree the opposite qua- lities of strength and lightness. It terminates below in a more or less obtuse extremity, which is pierced by an orifice termed the lower umbilicus (e,fig. 177); a second orifice, leading into the interior of the quill, is situated at the opposite end, at the point at which the two lateral series of barbs meet and unite; this is termed the upper umbilicus (f, fig. \ 77). The cavity of the quill contains a series of conical capsules fitted one upon the other, and united together by a central pedicle. The shaft is more or less quadrilateral, and gradually diminishes in size from the upper umbilicus to its distal extremity. It is always slightly bent, and the concave side is divided into two surfaces by a middle longitudinal line continued from the upper umbilicus ; this is the internal surface (c, fig. 178). The opposite, or external surface ( b, fig. 178), is smooth, and slightly rounded ; both sides are covered with a horny material similar to that * This figure and fig. 179, 180, 181, are copied from the Monograph of F.Cuvier, " Surle developpe- ment des Plumes," Memoires du Museum, torn. xiii. of which the quill is formed, and they inclose a peculiar white, soft, elastic substance, called the /M (a, fig. 178). Fig. 178 * Section of the Shaft and Vane magnified. The barbs are attached to the sides of the shaft near the external surface, and consist of laminse, varying as to thickness, breadth, and length. They are arranged with their flat sides towards each other, and their margins in the direction of the external and internal sides of the feather ; consequently they present a con- siderable resistance to being bent out of their plane, although readily yielding to any force acting upon them in the line of the stem : e e, fig. 178, are th,e bases of the barbs of a feather magnified. The barbules (ff, fig. 178) are given off from either side of the barbs, and are sometimes similarly barbed themselves, as may be seen in the barbules of the great feathers of the Peacock's tail. Sometimes, as in these feathers and in the plumes of the Ostrich, the barbules are long and loose ; but more commonly they are short and close-set, and by their form and disposition constitute the mechanism by which the barbs are united together. The barbules arising from the upper side of the barb, or that next the extremity of the feather, are curved downwards or towards the internal surface of the shaft ; those which arise from the under side of the barb are curved in the contrary direction : so that the two adjoining series of hooked barbules lock into one another in a manner which the Pari- sian dissectors compare to the fastening of a latch of a door into the catch of the door-post. But besides the parts which constitute the perfect feather, there is also an appendage attached to the upper umbilicus of the quill which requires to be noticed. This is termed the accessory plume. It is usually a small downy tuft, but varies both in different species, and even in the feathers of different parts of the body of the same bird. In the quill- feathers of the wings and tail, it usually remains in the rudimentary state of a small tuft of down; but in the body-feathers of Hawks, Grouse, Ducks, Gulls, &c. it is to be found of all sizes, acquiring in some species a size equal to that of the feather from which it is produced. * Perrault, Hist. Nat. des Animaux, p. 336. AVES. 351 In the Ostrich the feathers have no accessory plume : in the Rhea it is represented by a tuft of down ; in the Emeu, on the contrary, the accessory plume equals the original feather, so that the quill supports two shafts ; and in the Cassowary, besides the double feather, there is also a second accessory plume, so that the quill supports three distinct shafts and vanes. The feathers vary in form in different parts of the bird according to their functions, and afford zoological characters for the distinction of species; they have, therefore, received in Ornithology distinct names. Those which surround or cover the external opening of the ear are termed ' auriculars.' Those which lie above the scapula and hurnerus are called the * scapulars.' The small feathers which lie in several rows upon the bones of the antibrachium are called the * lesser coverts ' (tectrices prinue). Those which line the under or inner side of the wings are the ' under coverts.' The feathers which lie immediately over the quill-feathers are the ' greater coverts ' (tectrices secunda). The largest quill-feathers of the wing, which arise from the bones of the hand, are termed ' primaries' (primores). Those which rise from the ulna, towards its distal end, are the ' secondaries' (secondaria). Those which are attached to its proximal ex- tremity are the ' tertiaries' (tertiaria). These in some birds, as the Woodcock and Snipe, are so long as to give them the appearance, when flying, of having four wings. The quill-feathers which grow from the phalanx, representing the thumb, form what is termed the bastard wing ( alula spuria). In considering the structures which deter- mine the powers of flight in different birds, it is necessary to take into account the structure, forms, and proportions of the wing-feathers, as well as the development of the bones and muscles which support and move them; as much depends upon the mechanical advantages resulting from the shape and texture of the expanded wing. When the primary quill- feathers gradually increase in length as they are situated nearer the extremity of the pinion, they give rise to the acuminated form of wing, as in the true Falcons, in which the second primary is the longest. In the Hawks the wing is of a less advantageous form, in con- sequence of the fourth primary being the longest ; when the primaries gradually decrease in length towards the end of the pinion, they give rise to a short rounded form of wing, such as characterizes the Gallinaceous Order; in which, although the pectoral muscles are immensely developed in order to counteract the disadvantage resulting from the disposition of the primaries, yet they are only able, in consequence of the form of the wing, to carry the bird rapidly forward for a short distance, and that with an exertion and vibratory noise well known to every spoilsman. The texture of the quill-feathers has also a material effect on the powers of flight. In the Falcons each primary quill-feather is elongated, narrow, and gradually tapers to a point; the webs are entire, and the barbs Fig. 179. closely and firmly connected together.* In the Owls the plumage is loose and soft, and the outer edge of the primaries is serrated ; so that, while they are debarred from a rapid flight, which would be dangerous in the gloom in which they go abroad, they are enabled, by the same mechanism, to wing their way without noise, and steal unheard upon their prey. Development of feathers. The first covering of the bird is a partial and temporary one, consisting of fasciculi of long filaments of down, which on their first appearance are en- veloped in a thin sheath, but this soon crumbles away after being exposed to the atmosphere. The down-fasciculi, which diverge each from a small quill, are succeeded by the fea- thers, which they guide, as it were, through the skin : and after the first plumage, at each succeeding moult, the old feathers serve as the gubernacula to those which are to follow. It is to be observed that feathers do not grow equally from every part of a surface of a bird ; they are not developed, for example, at those parts which are subject to friction from the movements of the wings and legs. They first appear in clumps upon those parts of the skin which is least affected by the pressure of superincumbent parts, or the movement of the parts beneath, as upon the head, along the spine, upon the exterior surface of the extre- mities, at the intervals of the joints on either side the projecting sternum, and at the sides of the abdomen. The matrix, or organ by which the perfect feather is produced, has the form of an elongated cylindrical cone, and consists of a capsule, a bulb, and intermediate mem- branes which mould the secre- tion of the bulb into its ap- propriate form. The matrix is at first an extremely minute cone, attached by a filamen- tary process to a follicle or papilla of the skin ; but it is not a development of that part, being of a different structure and adhering to it by a small part only of ts circumference. The matrix progressively increases in length ; its base sinking deep- ly into the corium, and ac- quiring a more extended con- nection by enlarged vessels and nerves, while its apex protrudes to a greater or less extent from the surface of the integument, when the cap- sule drops off to give passage MaMg of a to the feather which it incloses, ing Feather, with and the formation of which the Capsule laid has, in the meanwhile, been open. * Of so much consequence are the quill-feathers to the Falcons, that when any of them are broken the flight is injured and the falconers find it ne- cessary to repair them ; for this purpose they are always provided with perfect pinion and tail fea- thers, regularly numbered. 352 AVES. graduallyproceeding from the apex downwards. The capsule of the matrix (a a, Jig. 179) is composed of several layers, the outermost of which is of the nature of epidermis ; the inner ones are more compact, but have no appear- ance of organization. The sides of the cap- sule which correspond to the outer and inner sides of the growing feather within are indi- cated by a white longitudinal line. The axis of the capsule is occupied by a medulla or bulb, (e, fig. 179,) also of a cy- lindrical form, and of a soft fibrous texture, adhering by its base to the parts beneath, and there receiving numerous bloodvessels and a nerve. Between the medulla and the capsule there are two parallel membranes, one in- ternal (dj fig. 179); the other external, (b, fig. 179); from the latter membrane a number of close-set parallel laminae extend obliquely from one of the white longitudinal lines above mentioned to the other on the opposite side of the cylinder. The two mem- branes seem to be united together by the oblique septa. In the long and narrow spaces between these septae, the matter of the vane (c. Jig. 179) is deposited, and formed into barbs and barbules, nearly in the same way as the enamel of the teeth is formed between the external membrane of the pulp, and the in- ternal membrane of the capsule. The depo- sition of the material of the barbs commences at the apex of the bulb, and the stem is next formed in the following manner, The external longitudinal line fron> which the oblique laminae are continued, receives and moulds on the inner surface of the external capsule the horny covering of the back of the feather, or that longitudinal band, to the two sides of which the barbs are attached ; and on the opposite surface of the internal membrane are formed the pith or substance of the shaft 1 , and the horny pellicle which incloses it on the inner surface. The internal longitudinal line has no other use than to establish a solution of continuity between the extremities of the barbs of one side and those of the other, which meet at that part, and thus curve round and completely inclose the formative bulb. In fig. 180, the capsule of the matrix of a grow- ing feather has been laid open, and the nascent barbs (c) which surrounded the bulb have been unfolded, exposing that part at a b. A portion of the barbs and stem have been completed and protruded, and the bulb is beginning to undergo a process of absorption at that part, which will hereafter be described. The shaft and barbs at the apex of the cylinder are the first parts which acquire consistence, and the molecules composing the remainder are less compactly aggregated as they are situated nearer the base of the matrix. As the gela- tinous medulla increases, at the base, the first- formed shaft and barbs are protruded through the extremity of the capsule, the bulb con- tinuing to furnish the secretion which is moulded between the two striated membranes until the entire feather is completed. If the striated membrane inclosing the bulb be attempted to Fig. 180. Structure of the Bulb. be reflected from below upwards, it will be found to be connected with a series of mem- branous cones (abed e,fig. 181,) ranged one upon the other throughout the whole length of the bulb, and connected together by a tube running through its centre. In this figure (181) the pulpy matter which occupied the interspaces of the cones has been removed to shew their central connecting tube. As the development of the feather advances, the pulpy matter disappears from the summit of the medulla, and only the membranous funnel-shaped caps remain, which are pro- truded from the theca and ithe centre of the new-formed barbs, and fall off. as these ex- pand. The theca which incloses the whole is of a firm texture where the new moulded barbs are yet pulpy and tender, but it be- comes thinner as these acquire consistency, and lastly, dries and crumbles away after it has been exposed to the action of the atmos- phere. The bulb itself, when examined in a half-formed quill-feather,* is composed of two parts corresponding to the external and in- ternal aspects of the feather. The internal part represents a semi-cylinder or case, in- * The following description is taken from such a feather in the goose. AVES. 3J3 closing the external part, which is of a conical form ; the latter extends from the base of the bulb, and gradually diminishes to a point where the shaft is completed and the barbs begin to expand. Jts office is to deposit the pith within the shaft, and it is absorbed in proportion as this is effected. The internal part or case also commences at the base of the bull), and adheres closely to the cone, with which, indeed, its substance is continuous; it increases in thickness as the cone diminishes, its margins are beautifully scolloped or crenate, and the crenations are lodged in the interspaces of the oblique laminae or moulds, and deposit in them the material of the vane. The horny sides of the shaft are lodged and formed in the grooves between the external and internal parts of the bulb, and correspond in degree of formation to the depths of those grooves, and being progressively brought into contact from above downwards, the shaft is thus completed, leaving the longitudinal line at the internal side. When all the grooves, (wherein are formed the barbs, and the portion of the shaft which carries them) are filled by the horny matter, and the barbed part of the feather is finished, this horny matter lastly expands uni- formly around the medulla, and forms the quill of the feather. When the quill of the feather has acquired the due consistence, the internal medulla be- comes dried up, and is resolved, as before, into membranous cones arranged one upon the other ; but these latter never pass out, for the quill, which is now hardened and closed by the shaft at the opposite extremity to the lower umbilicus, will not permit their egress ; they remain, therefore, inclosed, and constitute the light dry pith which is found in the interior of the quill. The last remains of the bulb are seen in the ligament which passes from the pith through the lower opening of the quill and attaches it to the skin. Cuvier has justly observed that notwith- standing the complexity of the process just de- scribed, the formation of a feather differs only from that of a tooth in the nature of the substance which is deposited between the two tunics which constitute its mould ; but a tooth takes many years to be perfected, and there are but two series produced in one part of the jaw, and only oi:e in the other, in any warm-blooded animal. Feathers, on the other hand, are de- veloped in the course of some days ; they attain a length of from one to two feet or more in many birds, and they are almost all re- newed every year, in many species even twice a year. It may be conceived, then, how much vital energy the organization of birds must exercise, and how many dangers must accom- pany so critical a period as that of the moult. The plumage is commonly changed several times before it attains that state which is re- garded as characteristic of the adult bird. The time required for this varies from one to five years, and several birds rear a progeny before they acquire the plumage of maturity. When the male bird assumes a vestment VOL. i. differing in colour from the female, the young birds of both sexes resemble the latter in their first plumage ; but when the adult male and female are of the same colour, the young have then a plumage peculiar to themselves. Mr. Yarrell states a third law in addition to the preceding, viz. that whenever adult birds as- sume a plumage during the breeding season decidedly different in colour from that which they bear in winter, the young birds have a plumage intermediate in the general tone of its colour compared with the two periodical states of the parent birds, and bearing also indica- tions of the colours to be afterwards attained at either period. " There are three modes," the same author observes, " by which changes in the appearance of the plumage of birds are produced : " By the feather itself becoming altered in colour. " By the bird's obtaining a certain number of new feathers without shedding any of the old ones ; and " By an entire or partial moulting, at which old feathers are thrown off and new ones pro- duced in their places. " The first two of these changes are ob- served in adult birds at the end of spring, in- dicating the approach of the breeding season ; the third change is partial in spring and entire in autumn. " A fourth mode may be noticed, though its effects are limited. It is observable in spring, as the breeding season approaches, by the wearing off of the lengthened lighter- coloured tips of the barbs of the feathers on the body, by which the brighter tints of the plumage underneath are exposed, as was no- ticed by Sir William Jardine and Mr. Blyth. The effect is most conspicuous in the Buntings, Finches, and Warblers."* The experiments detailed in the Memoir above quoted, some of which we witnessed, prove incontestably, that notwithstanding the extravascular nature of feathers, they are subject to influences, apparently of a vital nature, which occasion a change of colour in them after they are completely formed. In yearling birds the winter plumage which suc- ceeds the autumnal moult gradually assumes the brighter tints characteristic of the adult without a change of feather. The new colour commences generally at that part of the web nearest the body of the bird, and gradually extends outwards till it pervades the whole feather. Organs of generation. The few varieties of structure which these organs present in the Class of Birds, are principally met with in those of the male, which we shall first de- scribe. The male organs of generation exhibit all the essential characteristics of the oviparous type of structure. The testes are situated high up in the abdomen, whence they never descend into an external scrotum. The intromittent * Yarrell, Zool. Trans, i. p. 13. 2 A 354 AVES. organ is either double, as in Serpents, when, however, each penis is extremely small ; or it is single, but in this case, to whatever extent it may be developed, it always consists of a uniform ligamentous and vascular elastic sub- stance, and, as in the Tortoise, is simply grooved along the upper surface or dorsum for the passage of the fecundating fluid. As there is no true urethral canal, so neither are the glands of Cowper or the prostatic glands present. The testes (x, Jig. 166, tf > a >fg' 182) nre two in number; in form more or less oval, situated above the upper extremities of the kidneys. They vary remarkably in colour in different birds; we may mention, as examples, that they are white in the Peregrine Falcon and and Dove ; pale yellow in the Horn-Owl, and 19 ~ Gallinule ; of a brighter yellow in the Magpie, Bay Ibis, Ruff, and Oys- ter-catcher; of a black colour in the Chough, Partridge, Heron, Sea- gull, but whitish towards the lower end in the last 9 two. They are invested with a strong and dense albuginean tunic. Their structure is evidently tu- bular, the contorted tu- bules are very slender, scarcely exceeding in di- ameter the seminal tu- Urinary and male organs bules of mammalia : they f a Cocft - are separated into packets by delicate and mem- branous septa, continued from the inner surface of the tunica albuginea. The arteries spread in an arborescent form beneath that capsule. The vas deferens (c c) is continued from the posterior and internal part of the gland. The periodical variations of size which the testicles undergo are very remarkable in the Class of Birds; and the limited period during which their function is in activity is compen- sated by the frequency and energy with which it is exercised. The proportional size which the testes ac- quire at the breeding season is immense, as may be seen in the subjoined figures (183) of the testes of the House-Sparrow;* which commences with the glands as they appear in January, when they are no bigger than pins' heads, and ends with their full development in April. It rarely happens that both testes are deve- loped in exactly the same degree, but the increase of size is not limited to the one on the left side. The right testis is as often the * See John Hunter, in the Animal (Economy, plate vii. Fig. 183. O 1. January. ^ 2. Middle of February. o 3. Beginning of March. 4. Latter end of March. Middle of April. Testes of the House-Sparrow. largest, and we have seen an example, in a Rook, where it alone had taken on the action of sexual increase, and had acquired a bulk compensating for the want of development in the left testis. In most Birds, the only appearance of an epididymis is a remnant of the Wolffian body or primordial matrix of the genital and urinary organs (6, Jig. 182). This part frequently pre- sents a co!6ur strikingly different from that of the testes: thus it has been observed in the Bustard and Curassow to be black ; in the Cassowary, yellow ; and in the Anthropoides Virgo to be of a green colour. In the Ostrich the epididymis is folded upon itself at the side of the testis. The vas deferens commonly passes down to the cloaca by the side of the ureters without undergoing any remarkable convo- lution ; but in the common Cock it is bent upon itself in short transverse folds from side to side almost from its commencement; the folds gradually but slightly increase as they approach the cloaca, both in extent and in the diameter of the tube composing them, and they are so closely compacted as to present in a longitudinal section the appearance of a series of cells, which are capable of retaining, as in a vesicula seminalis, a quantity of the seminal secretion. Each vas deferens in the Common Cock terminates on a separate rudimentary penis or papilla, situated in the urethro-sexual division of the cloaca at a little distance from each other, and anterior to, or sternad of the inser- tions of the ureters. The base of each papilla is surrounded by a remarkable plexus of arteries and veins (M, M, Jig. 171) which serve as an erectile organ during the venereal orgasm, when the turgid papillae are AVES. everted, and the semen brought into contact with the similarly everted orifice of the oviduct in the female, along which the fecundating fluid is impelled by the vibrations of the cilia of the mucous surface through all the windings of that tube to its ultimate destination. In the Natatores which copulate in water there is an obvious necessity for a more effici- ent coitus than a simple contact of everted cloacae, and consequently in these birds, as the Swan, Gander, Drake, &c. a long, single penis is developed. Fig. 184. Penis of a Drake. This body arises from the front part of the outer compartment of the cloaca ( (t, a, Jig. 184) immediately below the urethro-sexual cavity ; it is in the unexcited state coiled up lik^ a screw from the elasticity of the internal liga- mentous structure. The external coat is a pro- duction of the membrane lining the outer cavity, and gives oft' a number of small pointed processes, which in the Gander are arranged in transverse rows on either side the urethral groove, and near the extremity of the penis are inclined backwards. The body (b 6, fig. 184, where it has been cut open) is composed of a white elastic ligamentous substance, and a vascular pulp, but without any of the cellular structure which characterizes a corpus caver- nosum. A groove (d d), commencing widely at the base is continued along the side of the ligamentous substance, and follows all the spiral turns of the penis to its extremity. The vasa deferentia terminate in papilloe at the base of this groove, along which the semen is transmitted to the vagina of the female.* The penis of the Ostrich is also single, and the urethra is represented by a dorsal groove ; it is disposed in a slight spiral bend when in a retracted state. It arises by two strong liga- mentous crura from the cartilage uniting the bones of the pubis, and descends into the external or preputial compartment of the cloaca. There are four muscles to the penis of the Ostrich : two arise from the inside of the os sacrum, and descending along the preputial cavity, are inserted into the base of the penis : two other muscles pass from the internal part of the iliac bones, to be attached to the sides of the penis. The Guan (Penelope cristata) presents a singular exception to the other Rasorial Birds in having a single linguiform pointed penis developed, the sides of which are provided with retroverted papillae, as in the Anserine Birds. In the Gallinule, which seeks its food in water, there is no penis ; it, therefore, most probably copulates on land. The tumid margin of the preputial cavity of the penis is well provided with large mu- cous follicles which secrete a sebaceous lubri- cating substance ; of these there are twelve in the Gander, arranged six on each side. These may be regarded as analogous to the glandule odorifera? ; but there is no vestige either of prostatic or other urethral glands. Female organs of generation. An ovarium or productive organ, (a, 6, c, d, Jig. 185,) with an oviduct or efferent tube ( e, f, g, k, /,) are present in all birds, and a clitoris or organ of * We cannot account for the error into which Sir Everard Home has fallen, in describing the urethra of the drake as a complete canal, and the penis as being enclosed within a prepuce. (Phil. Trans. 1802, pp. 361, 363.) Repeated dissections of different species of Anas, Cuv. have satisfied us of the accuracy of Mr. Hunter's statement, that " birds have no urethra, some having merely a groove, as the Drake and Gander, and many being even without a groove, as the common Fowl." Animal (Economy, p. 40. The letter c, in Sir Everard Home's figure, (jig. 184,) points to the orifices of mucous glands or cut vessels, and not to the papilla?, on which the vasa deferentia termi- nate. 2 A 2 356 AVES. Fig. 185. -d FowIS excitement is found in those species of which the males have a penis. Birds differ from all the other oviparous vertebrata in having the canal which completes and carries out the ovum single, and in this respect they manifest an analogy to many mammalia. When, however, the whole of the circumstances from which this condition re- sults come to be investigated, the nature of the part in the two classes will be found to be widely different. In the Mammalia the single efferent canal results from a blending together of the vaginas and uteri of the two sides of the body for a greater or less extent along the mesial line; which junction is continued from the external outlet towards the ovaria, but never extends beyond the uteri, the Fallopian tubes always remaining distinct. And in proportion as the generation approximates the oviparous mode, the efferent tubes remain separate for a greater extent. Thus, among the Kodentia, we find the uterus completely divided into two lateral tubes, as in the Rabbit; and in the Marsupiata the division is continued through the whole extent of the true vagina. In the true Oviparous classes the oviducts are always double and open separately into the cloaca, and the exception in the class of Birds to this rule is only apparent. At an early period of existence the two oviducts exist of equal size, but the left one alone attains that state of development which qualifies it for the exercise of the sexual func- tions. Hitherto no exception has been found * This figure, and those numbered 133, 134, 135, 136, 138, 151, 153, 163, 182, are copied from the plates of the second edition of Carus's ' Verglei- chenden Zootomie.' to this rule, and the uniformity in the condition of the excluded ovum in Birds corresponds with the sameness which prevails in the structure of the organs concerned in its evolution. The ovarium is in general single like the oviduct, and developed only on the left side, as in the Rasores. But two ovaria have been observed in many of the Raptores. In the Falcons NITZSCH found the right ovary more developed than the left, and also m some species of Eagle and Owl. In the Sparrow- Hawk the same distinguished anatomist found two ovaries equally well developed. In the Common Fowl the ovary first makes its appearance as a membrane beset with small pellucid vesicles adhering to and apparently developed from the coats of the vena cava. The substance of the ovary is invested by a thin and extensible capsula propria, covered by a reflection of peritoneum. The ova are imbedded in a stroma of delicate and yielding cellular substance, and consist each of a mi- nute pellucid vesicle, surrounded by the yolk, which at this period is as clear as the fluid of the vesicle itself, and both are inclosed in a distinct transparent capsule. When the ovum has attained the diameter of a line, the vitelline liquid presents a turbid whitish appearance. When it is about the size of a pea the yolk begins to assume a slight straw-coloured tint, and the seat of this colour- ing matter may be observed to be certain glo- bules of oil now superadded to the albuminous and serous fluid. As the oily material prevails, the yolk gradually assumes a more viscid and tenaceous consistency, and a deeper and deeper tint, until it presents the rich orange colour characteristic of the mature ovarian ovum. If one of these ova be transversely divided after being hard-boiled, the cut surfaces of the yolk will present three concentric strata of diffe- rent colours ; the external one is of a pale straw colour, the middle one of a deeper yellow, and the internal one is again light-coloured, and surrounds a substance of a whitish colour and more fluid consistency, from which a canal surrounded by a similar substance is continued to the cicatricula. The central substance and continuous canal are composed of albuminous fluid containing white granules, similar to the colliquamentum of the cicatricula. The primitive vesicle of the ovum around which the material of the yolk is accumulated, by no means grows with the growth of the ovum ; it is not more than one-half larger in the largest ovarian ovum, than it was when the ovum exhibited its smallest dimensions, and when the vesicle formed its most con- siderable part. Throughout the whole of this period it is, however, the most important part of the ovarian ovum; forming the essential element of the cicatricula, and the centre from which all subsequent development radiates. Purkinge, the discoverer of the ' germinative vesicle,' states that it is most easily detected in the ova of the common Fowl, when they have attained the size of from four to six lines. The vesicle is at this period lodged in a mam- AVES. 357 millary pile (cumulus) of white granular sub- stanre, which is surrounded by a whitish zone, and is continuous with the granular stratum applied to the internal surface of the membrana vitelli, but not adherent to that membrane. The common envelope of the germinal vesi- cle, cicratricula, and yolk, is called the mem- brana vitelli. It is extremely delicate and transparent, without any perceptible organi- zation, and forms an entire or shut sac. It is at first scarcely distinguishable from the stra- tum of granules forming the periphery of the yolk, and at this period the germinal vesicle closely adheres to it. Subsequently, however, a separation is effected by an interposed stra- tum of granules. The external membranes of the ova are thick in proportion to the vitelline membrane, and can with difficulty be detached from without lacerating it. The part of the ovary in which the ovum is lodged is termed the calyx (a, a, fig. 185). It consists of two membranes; the external one is highly vascular; the internal one is somewhat smooth and pellucid, and is beset with equidistant, minute, and apparently glan- dular bodies. As the ovarian ovum advances to maturity, a pedicle is developed from which the calyx with its contained ovum depends, and which permits it to be brought in contact with the infundibular orifice of the oviduct (e,Jig. 185). The external vascular tunic of the calyx then becomes covered with a rich profusion of vascular twigs (b,fg. 185) distributed in a pectinated manner, and converging towards a white transverse line, called the stigma (c, jig. 185). This stigma begins to appear when the ova have attained the diameter of an inch, in the form of a whitish streak, which con- tinues to increase in breadth, and the membranes at that part to be thinned by absorption until they readily yield, and are rent by the compressing force of the infun- dibular opening of the oviduct, when the ovarian ovum escapes, and is received into the efferent passage. The membrana vitelli is at this period sufficiently strong and ductile to permit the ovum being compressed into an elliptical form to facilitate its passage through the con- tracted part of the oviduct (f), but during this process Purkinge conjectures that the germinal vesicle of the cicatricula is ruptured and its pellucid contents diffused. It is certain at least that it can no longer be de- tected either in the cicatricula of the ovum of the oviduct, or in that of the excluded egg. The further changes which take place in the generative product, now no longer forming a part of the maternal system, will be described in the article GENERATION ; and we resume the consideration of the female organs. The calyx of the ovum, when emptied of its contents (d,fg. 185) collapses, shrinks, and is ultimately absorbed, not forming a permanent corpus luteum, as in Mammalia. In Birds that have but few young at a brood, as the Eagles or Doves, the number of enlarged yolks is correspondingly small; but in the more prolific species, as the Common Fowl, they are more numerous. The number of young pro- duced may be, by this means, in some degree inferred, if the female of a rare species happen to be killed during the breeding season. The oviduct commences by the infundibular orifice, where its parietes are very thin ; as it descends, these increase in thickness, and the efferent tube gradually acquires the texture and form of an intestine. Like this, it is attached to and supported by a duplicating of perito- neum called the mesometrium, but which also includes muscular fibres, to be presently de- scribed. The oviduct in the quiescent state is generally straight, but at the period of sexual excitement it is augmented in length as well as capacity, and describes three principal convolutions be- fore reaching the cloaca. The lining membrane presents a different character in different parts of the oviduct; at the infundibular extremity it is something like the mucous coat of the intes- tine, then it becomes rugous, and afterwards, at the part where the egg is detained and the chorion calcified, it presents a number of long close-set villi (k,fy. 185). This part is by some anatomists termed the uterus, but by a loose analogy, as the ovum is developed out of the body of the parent. The rest of the canal, which, pari modo, is termed vagina, opens into the urethro-sexual segment of the cloaca, anterior to the termination of the left ureter, and its termination (f,Jig- 164, 176) is provided with a sphincter. The mesometry (m, fig. 185) differs most from the mesentery when the female organs are in full sexual action. It presents at that period a true muscular structure. It is divided into two parts, one superior, the other inferior. The inferior mesometry has its point of attach- ment at the lower part of the uterine portion of the oviduct, and forms a somewhat dense and cruciform plexus of muscular fibres ra- diating from that part. The transverse fasci- culi are spread out on either side and around the uterus. The lower fasciculus surrounds the vagina more laxly, and contributes to the expulsion of the ovum. The upper fasciculus spreads out like a fan upon the oviduct from its insertion into the uterine portion to the com- mencement of the infundibulum. The superior mesometry commences by a firm elastic ligament, which is attached to the root of the penultimate rib of the lefl side, whence the muscular fibres are continued to the upper part of the oviduct, upon which they form a delicate muscular tunic, whose fibres embrace the oviduct for the most part in the transverse or circular direction, except at the infundibular aperture, where they affect the longitudinal direction, which enables them to dilate that orifice. Longitudinal muscular fibres begin again to be distinctly seen in the uterine portion of the oviduct, whence they are continued along the so-called vagina. An in- ternal stratum of circular fibres is also situ- ated immediately behind the calcifying mesr 368 AXILLA. brane of the uterus. In the vagina the circular fibres are concentrated at its termination to form the sphincter above mentioned.* The clitoris in the Ostrich is continued from the anterior margin of the preputial cavity of the cloaca, and is grooved like the penis of the male; it has also the same muscles inserted in it. A corresponding projection, as before observed, is met with in those birds of which the males have a well developed intromittent organ. BIBLIOGRAPHY. Perrault, Description Anato- mique do six oiseaux appelles Demoiselles de Numidie, Mem. de Paris, t. i. .et t. iii. Duverney, Observation Anatomique sur le perroquet arras, sur la cigogne, sur le casuel, Mem. de Paris, t. i. Vicq-d'Azyr, Memoires pour servir a 1'anatomie des oiseaux, Mem. de Paris, A. 1772, 73, 74, 78. Tiedemann, Zoologie, 2ter u. 3tter Bd. Anat. und Naturgeschichte d. Vbgel, 8vo. Landsh. 1808-14. Nitxsch, Aufsatzen, in Meckel's Archiv. B. i. B. ii. and B. iii. * * * * Cotter, Divers, animalium Bceletorum explicationes, fol. Norimb. 1575. Camper, Memoire sur la structure des os dans les oiseaux et de leurs diversites dans les differentes especes, Mem. de Mathem. et Phys. A. 1773. Nitsssch, Osteographische Beitrage zur Naturgeschichte d. Vogel, 8vo. Leipz. 1811. * * * * Herissant, Observations anatomiques sur les mouvemens du bee des oiseaux, Mem. de Paris, A. 1748. Yarrell, on the structure of the beak and its muscles in the Cross-bill, ^Mag. of Nat. Hist. 8vo. Lond. De Reaumur, Sur la digestion des oiseaux, Mem, de I'Ac. des Sc. de Paris, A. 1752. * * * * Bauer, Disquis. circa nonull. Avium systema arteriosum, 4to. fieri. 1825. Nitzsch, Obs. de Avium arteria carotide communi, 8vo. Halae, 1829. Barkoio, Untersuchungen liber das Schlagadersystem d.Vbgel, Meckel's Archiv. Jahrg. 1828. Monro, State of facts, &c. and on the lymphatic vessels of oviparous animals, Edin. 1770. Hunter on the absorbents of Birds, in Phil. Trans. 1768. Hewson on the absorbents of Birds, Phil. Trans. 1769. Lauth, Mem. sur les vaissaux lymphatiques des oiseaux, Ann. des Sciences Nat. 1825. * * * * Daubenton, Observations sur la disposition de la trachee- artere de differentes especes d'oiseaux, Mem. de Paris, A. 1781. Latham, Essay on the tracheae, or windpipes, of various kinds of birds, Linn. Trans, v. iv. Fuld, De organisquibus aves spiritus ducunt, 4to. Wirceb. 1816. Yarrell on the trachea of Birds, in Linn. Trans. 1827. Hunter, An account of certain receptacles of air, in birds, which communicate with the lungs, and are lodged both among the fleshy parts and in the hollow bones of these animals, Phil. Trans. Y. 1774. * * * Holier, De cerebro avium et piscium, Verb., van het Maatsch. te Haarlem, Deel 10. Malacarne, Esposizione anatomica delle parti relative all'en- cefalo degli uccelli, Mem. de Verona, t. i. ii. iii. iv. vi. vii. Numan, De medulla spinali avium, &c. 8vo. Hallae, 1811. Frank, De avium encephali anatome, 8vo. Berl. 1812, et in Reil's Archiv. B x i. * * # * Vicq-d'Azyr, De la structure de 1'organe de 1'ouie des oiseaux, Mem. de Paris, A. 1778. * * * * Mery, Observation sur le cercle osseux autour de la cornee de 1'oeil de 1'aigle, du corbeau, et sur la sclerotique de 1'autruche, Mem. de Paris, t. ii. p. 24. Tannenberg, De partibus genitalibus masculis avium, 4to. Getting. 1789 ; Germanice auct. 4to. Getting. 1810. Spangenberg, Disq. circa partes foemineas genitales avium, 4to. Gotting. 1813. Cuvier, Le9ons d'Anat. Comparee, 5 vol. 8vo. passim. Rees's Cyclopaedia, art. BIRDS, by Macartney. (Richard Owen.) - * Purkinje, Symbola; ad Ovi Avium Historiam, 4to. 10. fig. 19. AXILLA (surgical anatomy) (Fr. Aisselle, Ger. Achselgrube.) Syn. region axillaire y Velp. is the Latin name for the armpit, and is used by anatomists to designate an important region situated between the upper extremity and the thorax. The axilla in man is the seat of so many diseases and accidents ; it contains so large a number of nerves, arteries, and lymphatic glands ; and is so frequently interested in sur- gical operations, that a pretty full description of it is allowable on the present occasion. When the arm is separated a little from the side, we observe, in the angle between them, a hollow space, which, in the adult, is always covered with hair. This is, in popular lan- guage, the armpit ; but to the anatomist the term axilla conveys a very different notion. By him it is understood to mean a large region, bounded anteriorly by the greater and lesser pectoral muscles, posteriorly by the subsca- pular, the teres major, and a part of the latis- simus dorsi, and internally by the ribs, the intercostal muscles, and the serratus magnus. It presents a basis below, formed of skin and fascia, and an apex above, which opens into the cervical region between the clavicle, scapula, and first rib. Its walls form, therefore, a kind of triangular pyramid, very unequal in their extent, very irregular, and continually under- going alterations in size and shape. Its height is greater in the male than in the female, but its other dimensions are nearly equal. It is to be found in all animals which have an upper extremity, and its uses are subservient to the motions of that limb. In the following description the adult male axilla is always supposed to be meant unless otherwise specified. When the arm is raised to the horizontal position, we see the floor of this region, the base of our pyramid. This floor is triangular, having its truncated apex at the humerus, its base at the side of the thorax, and its sides formed by the folds of the axilla, that is, the great pectoral in front, the teres major and latissimus behind. It is concave, the concavity looking downwards and outwards. The skin is fine, covered with hair at its upper part from the time of puberty, and secreting, by numerous follicles, a fluid of a peculiar odour. By raising the elbow higher than the head we convert the concave into a convex, the folds of the axilla are removed, the skin made tense, and the head of the humerus by descending is made to touch the floor of this region. Press- ing the arm close to the side lowers the floor, shortens the margins, and relaxes all the parts composing the axilla. When the elbow is drawn a few inches from the side, the axillary artery and nerves may be felt along the humerus, and the head of this bone may be distinguished. In searching for disease in the axilla the arm must be placed in all these positions, but we are most likely to detect any abnormal condition of the parts when the elbow is drawn a few inches from the side, and sup- ported without any effort of the patient. AXILLA. 359 Immediately under the skin we find some cellular substance, containing a small quantity of fat ; and next a fascia of considerable thick- ness, which gradually loses itself on the side of the thorax, in the general superficial fascia of the trunk. It will be found extremely variable in different subjects, according to the embon- point of the individual, sometimes loaded with fat, at other times thin, firm, and somewhat aponeurotic, with its principal bands stretched across from the anterior to the posterior wall of the axilla. In raising it, layer after layer may be removed, until it opens up into that ex- tremely lax cellular tissue which attaches itself to the walls of the axilla, loosely supporting glands, vessels, and nerves, and permitting all the motions of which this part is capable. It is obviously cellular membrane. When enlarged glands, or abscesses, or tumours of any kind, form under it, it readily yields, and stretches before the distending force, never exerting any painful pressure on them. The cellular tissue under it is very loose. Numerous vessels ra- mify through it which are chiefly derived from the thoracica alaris artery. These vessels are occasionally ruptured, when extensive ecchy- moses ensue. Matter formed here passes easily from one part to another, and gives rise to obstinate sinuses, not easily remedied on account of their length and tortuous course. On carefully removing the dense cellular membrane of the floor, and that more loose tissue which it conceals, the edges of the axillary folds will be seen. Close to the an- terior of them we observe the thoracica longior artery, with its accompanying veins and several lymphatic glands, and, under cover of the posterior, the subscapular vessels and nerves ; whilst a great bundle of arteries, veins, and nerves, with the biceps and coraco-brachialis muscles, stretch along the humerus. To this view of the parts, the operating surgeon will look with peculiar interest. It is from below that we generally operate on the axilla, and the three sets of vessels just now mentioned con- stitute the most important subjects for consi- deration when the scalpel is to be used. It is obvious that free incisions may be practised in the centre of this space or upon its thoracic side, but that all its other boundaries are beset with dangers. To follow up the anatomy of this region with advantage, each of its walls must be examined in detail. The anterior wall consists of the pectoralis major and minor muscles. The pectoralis major is a large flat muscle, of a tri- angular shape, extending over the front of the thorax, from the clavicle and sternum to the humerus. The origin of this muscle is curved, its con- vexity being directed upwards and inwards; this may be called its base. The insertion or apex is outwards and downwards. One surface looks outwards and forwards, the other back- wards and inwards. The inferior margin extends from the seventh rib to the humerus and is nearly horizontal, folded on itself and free. The outer edge is nearly vertical, at first about an inch dis- tant from the deltoid, but soon coming into con- tact with it, and so continuing to its insertion. The triangular space between the deltoid and pectoral may be seen even in the living person when the shoulders are shrugged up, especially if the individual be thin. It is in this situation that the axillary artery commences, and might be cut down upon without dividing any muscular fibres except those of the platysma ; it is however protected by the costocoracoid ligament, and by the edge of the pectoral mus- cle. In this interval we see the cephalic vein and a small artery, the thoracica humeraria, which is the descending branch of the thoracica acromialis. The cephalic vein is derived from a plexus on the outer and back part of the hand. After various communications in its superficial course it gets between the deltoid and pectoral muscles, and on arriving at the triangular interval above mentioned, it dips in under the edge of the great pectoral and just above the lesser, to empty itself into the axillary vein. When the pectoralis major has been raised, we bring into view a stratum of cellular tissue, in which several branches of the thoracica suprema artery and some nervous filaments ramify before they enter the muscles. Under- neath this tissue lies the pectoralis minor, still concealing the cavity of the axilla. The posterior surface of the great pectoral is not nearly so extensive as the anterior ; its fibres arise from the cartilages of the ribs, and, there- fore, the extreme limit of the axilla in front is not to be estimated by the superficial dimensions of the muscle. A line drawn obliquely downwards and outwards, beginning one inch outside the sterno-clavicular articulation, and ending an inch outside the nipple, will nearly mark the junction of the anterior and internal walls. This muscle is sometimes torn across by ex- ternal violence. We have seen this occasioned by the passage of a railway carriage over it, and marked by a deep depression, but without any laceration of the integuments. The pectoralis minor is shaped like the major, but it is considerably smaller. Its base is ap- plied to the ribs, its apex to the coracoid pro- cess of the scapula. One surface is turned outwards and forwards to the greater pectoral, the other back to the axilla. Attached on the one hand to the upper edge and the external surface of the third, fourth, and fifth, and some- times the second, true ribs, near their cartilages, by so many distinct slips, (hence its occasional name serratus minor anticus,) and an aponeu- rosis which covers the intercostal muscles, it terminates in a flat tendon which is inserted into the inner border of the coracoid process near its apex. In this situation it is intimately con- nected with the coraco-brachialis and short head of the biceps, sometimes sending fibres to be continuous with the triangular or coraco-acromial ligament, and in some rare instances the entire tendon runs across the coracoid process, and through this ligament to join the capsulur liga- ment of the shoulder-joint. The tendon is about an inch broad ; very short on the posterior 360 AXILLA. surface, longer on the anterior, and longer still at the lower edge. The surface now exposed was covered by cellular tissue, and concealed by the pectoralis major every where except a small part of its lowest digitation, which is generally to be seen below it, in contact with the integuments. The upper edge of this muscle is nearly hori- zontal, and placed about an inch below the clavicle. In the space between, when some fat is carefully removed, and some absorbent glands, we see the axillary artery running down- wards and outwards, internal and anterior to which is the axillary vein, and behind it the nerves. The cephalic vein is observed passing upwards and inwards from the edge of the del- toid muscle to the axillary vein, and the tho- racica suprema artery standing forwards from the axillary artery and resting on this edge of the pectoral. The thoracica acromialis artery runs in this space out towards the acromion process, and is often a branch of the suprema. Here, too, we see the lower surface of the sub- clavius muscle, turned forwards, and covered by a pretty strong fascia which terminates in the costo-coracoid ligament. The coslo-coracoid ligament is very thin, but strong. It extends from the cartilage of the first rib, just below the origin of the subclavius muscle, to the coracoid process of the scapula, in an arch across the vessels and nerves. It is concave inferiorly, and appears to be only the thickened edge of the fascia which covers the subclavius and descends a little below that muscle. This view of its true mode of forma- tion is favoured by the fact that it has an at- tachment also to the clavicle, and consequently may be called costo-cleido-coracoid. The name ligamentum bicorne is sometimes applied to in- dicate its horn-shaped extremities ; Blandin denominates it fascia clavicularis, and Gerdy, ligament suspenses de I'ai&elle. As a ligament it has little power, but as an aponeurosis it pro- tects the vessels, and sends down a thin process upon them. Below the lesser pectoral the vessels and nerves again come into view, and the thoracica longior or external mammary artery is seen passing downwards and forwards along its lower edge. For a fuller description of the pre- ceding muscles, see THORAX, MUSCLES OF THE. The inner wall of the axilla exhibits the ribs, intercostal muscles, and serratus magnus, with some vessels and nerves. One of these last is remarkable for its length and vertical direction; it lies on the serratus magnus, and appears as if flattened against the side of the thorax. It arises generally by two branches from the back of the anterior division of the fifth and sixth cervical nerves (counting eight in the neck). It communicates with the phrenic, descends be- hind the brachial plexus, under the clavicle and trapezius, appears upon the serratus magnus, on which it runs a great distance and enters its lowest division by many filaments. It is classed among the respiratory nerves by Sir Charles Bell, by whom it has been named the inferior ex- ternal respiratory nerve of the trunk, its function being, according to his views, to associate the muscle to which it is distributed with the ge- neral respiratory movements. It was known to antecedent anatomists as the posterior thoracic branch of the brachial plexus.* Crossing the axilla from the thorax to the arm, we see two nerves, frequently called nerves of Wrisberg. They are the external branches, or co&to-humeral, of the second and third inter- costal nerves. They pierce the external layer of intercostal muscles opposite the origin of the serratus magnus, between the second and third and the third and fourth ribs, and pass out ob- liquely to the arm, where they are lost in the in- teguments on the inner and back part of the arm. and elbow. The superior of them is the larger. The great vessels and nerves are seen pass- ing from the first rib to the lower border of the teres major muscle, forming an arch whose con- cavity is downwards. By raising the arm to the horizontal position we obliterate the arch, and by supinating the hand strongly we bring them more into view. In the upper third of this curve the order of the parts, proceeding outwards, is, the axillary vein, axillary artery, and plexus of nerves. In the middle the vein is situated as before, and then the nerves sur- rounding and hiding the artery ; and in the inferior third we first meet the vein, then the nerves, and lastly the artery. The axillary vein is about three inches in length, commencing a little above the edge of the teres major ; thence it runs upwards, in- wards, and forwards to the second rib, which it touches, as also some fibres of the serratus rnagnus there arising ; next it gets on the first intercostal muscles, after which it becomes the subclavian vein, crosses over the first rib, under the clavicle, before the scalenus anticus muscle, and then enters the thorax. It is formed by the confluence of three veins, viz. the basilic and the two vena comites which convey their fluid from the fore-arm, and it is afterwards en- larged by the accession of those veins which accompany, usually in pairs, the subscapular, the thoracic, and the circumflex arteries. It also receives the cephalic a little higher up, as before described. The axillary artery traverses this region from above downwards in a course doubly ob- lique, from within outwards, and from before backwards; at its upper part it rests on the chest separated by the serratus magnus muscle, and lies close under the anterior wall of the axilla, whilst below it rests on the subscapularis muscle (posterior wall), and is very near the arm. Its complicated relations with the nerves, veins, glands, &c. come more properly under consideration in the next article (AXILLARY ARTERY), to which we refer. * One or two cases of paralysis of the serratus magnus muscle from injury to this nerve have heen recorded. Velpeau mentions one, which resulted from a blow inflicted on the inner wall of the axilla : a permanent projection of the posterior edge of the scapula backwards, and inability to bring that bone into close apposition with the thorax, were the signs on which ho founded his diagnosis. (Sec Cy- clop, of Pract. Med. art. PARALYLSis.) ED. AXILLA. 361 It is plain from this view of the parts that a wound in the axilla, near the clavicle, might penetrate botli the artery and vein, and be fol- lowed by aneurismal varix, but that no such consequence could follow a puncture of these vessels lower down. We see too that there would be much difficulty in compressing the axillary artery through the anterior wall of the axilla, (formed as it is of the two pectorals,) ex- cept in the triangular interval between the great pectoral and deltoid muscles close to the clavicle, and that the subclavius muscle and the ligamentum bicorne would bear off pres- sure even there to a great extent. In this place the vein and artery lie closer to each other than they do above the clavicle, a circumstance to be remembered in attempting to command the circulation of the limb. Collections of pus are often met with in the cellular tissue under the great pectoral muscle. In children they will frequently be found to have been occasioned by laceration which the tissue has suffered in the act of raising them up by the arm. These abscesses elevate the muscle considerably, and do not always point in the lower part of the axilla as might be expected. They approach the surface directly in front in some cases. But if an early opening were not made, it is pro- bable they would oftener extend themselves all through the axilla. The nerves in the axilla are large, numerous, and complicated. The principal ones are in a bundle, at first behind the axillary artery and then surrounding it. They arise in the cervical region, interlace in a remarkable way to form the axillary or brachial plexus, give off some branches in the neck, and on reaching the axilla separate to supply the arm, forearm, and hand. (For a particular description of this plexus we refer to the article CERVICAL NERVES.) The nerves we meet with in the axilla, besides the costo-humeral, are, three thoracic branches, three subscapular, and six others of much greater size, viz. the external cutaneous, median, internal cutaneous, ulnar, musculo-spiral, and circumflex. The thoracic branches are most commonly three in number ; the anterior, arising from the seventh cervical, runs in front of the great ves- sels and is lost in the pectoralis major and pectoral is minor muscles ; the middle) very small, passes under the vessels and is lost in the lesser pectoral ; the posterior, the largest, is the respiratory, and has been already de- scribed. The subscapular branches are also three in number generally ; they come from different points at the upper and back part of the plexus: the smallest quickly enters the subscapular muscle : the other two sometimes arise by a common trunk, or one of them comes from the circumflex, both run along with the sub- scapular artery, the larger pierces the teres major and is lost in the latissimus dorsi, the smaller is distributed to the subscapularis, teres major and teres minor. The external cutaneous, or perforam Cotterif, comes from the external part of the plexus, chiefly from the fifth and sixth cervical branches, and leaves the axilla by running downwards and outwards. It is superficial and external to the axillary artery. The median arises from the front of the plexus by two roots, one of which is placed on each side of the artery ; they soon unite, the nerve then lies on the artery, and inclining a little outwards escapes from the axilla, being destined principally for the hand. The internal cutaneous issues from the inter- nal and inferior part of the plexus, lies very su- perficially along the inner side of the artery, and quits the axilla where the basilic vein is entering. The ulnar, arising from the internal and pos- terior part of the plexus, inclines backwards, separating itself slowly from the inner side of the artery. The musculo-spiral arises still farther back, and is concealed from view by the other nerves. The circumflex nerve arises above and be- hind all the others, and completely concealed by them ; it descends before the subscapular muscle for a little, then turns backwards and outwards, close to the capsular ligament of the shoulder-joint, and in company with the pos- terior circumflex artery ; then it appears on the outside of the neck of the humerus, between the long head of the triceps, the bone, and the teres major and minor muscles, and soon enters the deltoid in two branches. The situation of this nerve accounts for the paralysis of the del- toid muscle which sometimes follows dislo- cation of the head of the humerus into the axilla. Lymphatic glands are found in great num- bers in the axilla; some are scattered over the internal wall, but there the majority of them will be found in a chain along with the external mammary, or thoracica longior artery. On the posterior wall they form a chain also, in the course of the subscapular vessels. Some will be seen above the lesser pectoral, and several along the axillary vein. Hound this last vein we see numerous lymphatic vessels twining. When the clavicle has been detached "from its connexion with the trunk, and along with the scapula raised from the side, the serratus magnus may be seen to form the greater part of the internal wall, but extending far below it. This is a flat irregularly quadrilateral muscle ; one surface of it is in contact with the side of the thorax ; the other, looking externally, touches the subscapular muscle, the axillary vessels and nerves, the two pectorals, the latissimus dorsi, and the integuments. The anterior edge pre- sents a convexity forwards, and consists of digi- tations or fleshy slips which arise from the first eight or nine ribs. The fibres all run back to the posterior margin of the scapula, along the whole of which they are inserted. The thoracic surface of the muscle, which may be seen by cutting through the trapezius and rhomboid muscles, and pulling out the base of the scapula from the ribs, rests on loose cellular tissue, which connects it with 362 AXILLA. the ribs, intercostal muscles, and serratus pos- ticus superior. The posterior wall of the axilla is formed by the subscapular muscle, the teres major and the latissimus dorsi, to which the long head of the triceps may be added. Along the inferior margin of the subscapular muscle, the subsca- pular artery runs. This is a vessel of considerable size, and deserves the attention of the surgeon. It arises from the axillary artery at the tendon of the subscapular muscle, and passes all along the inferior or anterior edge of this muscle to the inferior angle of the scapula, where it ter- minates by branches which supply the muscles connected with that point. The teres major is a long, flat muscle, strap-shaped, one inch and a half or two inches in breadth, extending from the inferior angle of the scapula, to the poste- rior margin of the bicipital groove of the hu- merus. Its lower edge is in part covered by the latissimus dorsi and then by the inte- guments, and forms, principally, the poste- rior fold of the axilla. The posterior surface is covered by the latissimus, nearer the arm by the integuments, and then by the long head of the triceps and the humerus. Its anterior sur- face corresponds to the subscapular, latissimus, coraco-brachialis, biceps, and the axillary ves- sels and nerves. The latissimus dorsi forms a very small part of the axilla ; we see it passing over the inferior angle of the scapula and twisting round the teres major, so that its posterior surface be- comes anterior, and the tendon in which it ends gets internal to that of the teres. Its edge does not go quite so low as that of the teres major, but, except there, it prevents that muscle from touching the axillary vessels. It is some- times connected to the great pectoral by a fleshy slip which passes across the axilla. The axilla has all the conditions which ex- pose a part to frequent disease ; a position which puts it in the way of many external injuries; an important joint closely related to it ; bones, liable to fracture ; arteries, veins, and nerves of great size ; numerous lymphatic glands, connected with the most delicate parts of the body, lying in it ; and then a quantity of cellular tissue, loose, vascular, and con- stantly undergoing alterations. To the observations made on these points in the course of the present article, we shall now make a few additions. Wounds penetrating into the axilla endanger the nerves, artery, and vein, if inflicted near the humerus below, or close to the clavicle above. In the latter situation, as mentioned before, they may give rise to aneurismal varix. At the lower margin of the anterior wall the external mammary artery may be injured, and along the inferior border of the posterior wall the subscapular vessels lie exposed. The shoulder-joint is more liable to disloca- tion than any other in the body, and in most cases the head of the humerus comes into the axilla. The great vessels and nerves are dis- placed inwards, the circumflex vessels and nerve often torn. The head of the humerus lies just below the subscapular muscle, and forms a tumour in the axilla easily felt from below. (See SHOULDER, ARTICULATIONS OF THE.) The neck of the humerus is often broken above the insertion of the arm-pit muscles. The lower fragment is drawn inwards by them and upwards by the deltoid, whilst the supra- spinatus directs the upper fragment out. In this state of things the rough extremity of the lower piece irritates, perhaps lacerates the ves- sels and nerves, and if not properly managed leaves a permanent osseous tumour in the axilla. Collections of matter are very frequently met with in the axilla. These occur either about inflamed glands, or in the cellular tissue connected with these glands, or they may have found their way into this region, their focus being somewhere else. The abundance of cel- lular membrane here, its vascularity, its in- cessant movements, and the dragging and stretching to which it is exposed, render it very liable to formations of pus. Irritation of the delicate integuments may occasion them, and they may be formed in the neck and pass into this region through the opening at its apex. The looseness of the texture is such as to allow suppurations to go on to a great extent, whilst the movement of the walls pre- disposes to their termination in sinuses. The absorbent glands, however, are the or- gans which most frequently take on disease in this place. These may become inflamed and enlarged from sympathy with disease or injury in any part of the corresponding limb, the back, the surface of the thorax, or the upper part of the abdomen. When inflamed, they often run on to suppuration, or resolution may follow on the removal of the exciting cause. Slight lesions of the skin of the parts men- tioned may determine the formation of ab- scesses, as a scratch on the finger, a blister on the chest, &c. Paronychia is not an unusual exciting cause. Formidable inflammations of these glands, often attended with fatal consequences, follow the absorption of poisons. The cases most familiar to us in this country arise from wounds received in dissecting. The glands seem to arrest the poison in its progress to the circu- lation. They become excited and congested. The cellular tissue surrounding, imbedding, and partly forming them, inflames ; a puffy swelling marks the effusion of serum into the cellular membrane, which may or may not be followed by suppuration. The glands frequently take on the disease under which the neighbouring mamma labours, as cancer, fungus haematodes, &c. These must be removed if the breast be amputated. They are generally in the course of the external mammary artery, and no other vessel is in- terested in their removal, yet the looseness of the tissue in which they lie renders it unsafe to cut the little vessels derived from this incon- siderable artery. Surgeons usually twist or tear away the glands, or else apply a ligature to the vessel before they cut it. AXILLARY ARTERY. 363 In almost every disease in the axilla the arm swells on account of the pressure exerted on the absorbents and veins. For tho BIBLIOGRAPHY sec that of ANATOMY (INTRODUCTION). (Charles Benson.) AXILLARY ARTERY (arteria axillaris). This artery, which is the continuation of the subclavian trunk, commences at the outer border of the first rib, beneath the lower mar- gin of the subclavitis muscle : lying at first on the external surface of the superior part of the thorax, it traverses the axillary space, applies itself to the internal side of the upper extre- mity, and terminates at the lower edge of the tendon of the teres major muscle. The ave- rage length of this vessel is about six inches : when the arm hangs by the side it describes a curve in its course, the concavity of which is downwards and inwards, but it is brought to a nearly horizontal right line by raising the arm to a right angle with the trunk, and it may be made to describe a curve, the concavity of which is turned upwards, by raising the arm to the greatest possible extent of elevation. The depth of this artery from the surface is greatest at its commencement, whence to its termination it gradually becomes more superfi- cial. Relations. Anteriorly the axillary artery is covered by the following parts ; on first emer- ging from under the margin of the subclavius muscle, it is covered by the costo-coracoid li- gament, beneath which the anterior thoracic nerves coming from the brachial plexus cross it in their course to the pectoral muscles, the vessel then passes under the pectoralis minor muscle, from the lower edge of which to its termination the coraco-brachialis lies in front of it. Posteriorly it rests at its commence- ment on the first intercostal muscle, then, with the interposition of a considerable quan- tity of cellular tissue, on the first digitation of the serratus magnus, which separates it from the external surface of the second rib, it next crosses the tendon of the subsca- pularis muscle, from the lower edge of which to its termination it lies on the anterior sur- face of the tendon of the teres major. Ex- ternally it is bounded by the lowest cord of the brachial plexus, until it arrives at the supe- rior edge of the subscapularis, and for the re- maining part of its course by the commence- ment of the external cutaneous nerve. Inter- nally it is bounded by the axillary vein, which is in contact with it in the whole of its course, except while crossing the subscapularis, where the internal root of the median and the ulnar nerve separate the vein from the artery. The lesser pectoral muscle, in crossing the axilla at the lower part of the upper third of that region, divides the axillary artery into three stages. The first extends from the clavicle to the upper edge of the lesser pectoral ; in this stage the most important relation which the artery has, is to the vein, which lies upon its inner side and upon a plane anterior to it, so that in a state of distension the vein would overlap the artery. All the nerves are behind and external to it. In the second stage, which is that concealed by the lesser pectoral, the vein, still on the thoracic side and more an- terior, is separated from the artery by the nerves, which, forming the axillary plexus, are so closely applied to it, behind and on each side, as to form, as Velpeau remarks, a complete nervous sheath. In the third stage, which is below the lesser pectoral and in immediate connexion with the subscapularis muscle, the artery is still in the midst of nerves, having on each side a root of the median, together with the external cutaneous nerve on the outside and the internal cutaneous and ulnar on the inside, the circumflex and musculo-spiral being posterior to it. In this stage the vein is in- ternal and superficial to the artery, but sepa- rated from it by the nerves which lie on its internal side. A ligature cannot be placed on the axillary artery in any stage of its course without endan- gering parts of great importance ; in the second stage, however, the connexion of the artery with the axillary plexus is so intimate as com- pletely to preclude the possibility of tying it there without incurring the greatest risk of serious injury. Hence there are but two situ- ations in which it can be deemed prudent to expose this artery. Of these the operation in the third stage may be accomplished with greater facility, because the artery is here much more superficial, and although its relations are numerous, and in some degree complicated, they admit of being separated from the artery to such a distance as will guard them from injury. To tie the artery in the first stage, however, is much more difficult, chiefly in consequence of the great depth at which it lies, the necessity there is for cutting through large muscles, and the almost certainty of troublesome and unavoidable venous haemor- rhage. The principal part which the surgeon has to avoid in applying the ligature needle is the vein. Branches. The axillary artery usually gives off six branches, viz.; 1. theacromial; 2. the superior thoracic; 3. the inferior or long tho- racic or external mammary ; 4. the subscapu- lar; 5. the posterior circumflex; 6. the ante- rior circumflex. 1. The acromial artery (thoracica acromia- lis) arises from the anterior side of the axillary artery above the edge of the lesser pectoral muscle, and after having given oft some branches to the subclavius, serratus magnus, and first intercostal, it passes obliquely down- wards and outwards, piercing the expansion of the costo-coracoid ligament, and arrives at the posterior surface of the deltoid muscle, where it divides into a superior and an inferior branch. The superior branch mounts by a tortuous course towards the clavicle ; this branch, which is more particularly designated by the term acromial, after having given off one or more branches to the deltoid muscle and the integu- ments, runs along the anterior border of the clavicle, behind the origin of the deltoid, until 364 AZYGOS. it arrives at the acromial end of that bone, where it is expended in a number of branches which go to supply the scapulo-clavicular and scapulo-humeral articulations, and also the supra-spinatus and deltoid muscles. This ar- tery anastomoses with the supra-scapular and posterior circumflex in the vicinity of the acro- rnion process. The inferior or cephalic branch descends in company with the cephalic vein in the cellular interval between the deltoid and pectoralis major muscles, and is distributed to these muscles and the integuments. 2. The superior thoracic (thoracic a suprema, Seem.) is very irregular as to the place of its origin, coming as frequently from the acromial as from the trunk of the axillary; it passes ob- liquely forwards between the greater and lesser pectoral muscles, and divides into several branches, which are distributed to these two muscles, the integuments, and more deeply to the serratus magnus and the two or three supe- rior intercostal muscles, anastomosing with the intercostal and internal mammary arteries. 3. The inferior thoracic (thoracica longior or mammaria externa) is subject to the same variety of origin as the superior thoracic; it sometimes arises from the subscapular. This artery descends on the surface of the serratus magnus muscle along the inferior border of the pectoralis major; its branches are distributed to the glands and cellular tissue of the axilla, to the serratus magnus, and pectoralis major and minor, and the intercostal muscles ; it also supplies the mammary gland and the integu- ments ; it anastomoses with the intercostal, in- ternal mammary, superior thoracic, and sub- scapular arteries. Scemmerring describes a fourth thoracic ar- tery, under the name of alaris sive axillaris glandulosa,* which is distributed principally to the axillary lympathic glands; this artery is very irregular in its origin, sometimes coming from the trunk of the axillary artery, and as often arising from the thoracica longior or the subscapularis. Instead of a single artery going to the glands of the axilla, these parts are more usually supplied by several small twigs which arise from the arteries in their vicinity. 4. The subscapular artery is generally the largest branch of the axillary ; it arises at the lower edge of the subscapularis muscle, lying at its origin behind the brachial plexus; it gives three or four branches to the glands and cellular tissue of the axilla and to the subscapularis muscle, after which it divides into two branches, one inferior, the smaller, the other, larger, called the external scapular. The inferior branch de- scends along the inferior border of the subsca- pularis muscle and the inferior costa of the scapula between the latissimus dorsi and the serratus magnus, to which muscles, the teres major, and the integuments it is finally distributed, anastomosing with the posterior scapular artery at the inferior angle of the scapula. The external branch, circumflexus scapula of Scemmering, passes backwards through a triangular space formed by the sub- * DC Hum. Corp. Fab. t. v. p. 189. scapularis above, the tercs major inferiorly, and the tendon of the long head of the triceps ex- ternally, and after having given several branches to these muscles, it divides into two branches, a superficial and a deep-seated ; the superficial branch is distributed to the teres major, teres minor, infra-spinatus, latissimus dorsi, and the integuments; the deep-seated branch winds round the neck of the scapula under the teres major, and entering the fossa infra-spinata, supplies the infra-spinatus muscle, the scapula, and the scapulo-humeral articulation. This branch anastomoses freely with the branch of the supra-scapular, which descends under the root of the acromion process. 5. The posterior circumflex, next to the sub- scapular, is the largest branch of the axillary artery, from the posterior side of which it arises; frequently it comes from the infra-scapular. It passes backwards through a quadrilateral space, bounded in front by the neck of the humerus, behind by the long head of the triceps, above by the subscapularis, and below by the teres major; coursing round the neck of the humerus, it passes below the inferior edge of the teres minor, and attaching itself to the under surface of the deltoid, is principally distributed to that muscle, giving branches in its course to the capsular ligament of the shoulder-joint, the subscapularis, teres major and minor, infra- spinatus, and triceps ; it anastomoses with the supra-scapular and acromial thoracic by branches which it sends to the acromion, and with the anterior circumflex by the branches which it gives to the articulation of the shoulder. 6. The anterior circumflex is a very small vessel, arising either from the axillary or the posterior circumflex ; it passes forwards round the neck of the humerus under the coraco-bra- chialis and short head of the triceps, to both of which muscles it gives branches; arriving at the bicipital groove, it sends off several branches, some of which descend along that groove, and others spread over the surface of the head and neck of the humerus, supplying that part of the bone and the tendons which are inserted into its tuberosities ; while the continuation of the vessel entering the bicipital groove ascends by the side of the tendon of the long head of the biceps, passes under the capsular ligament, to which and the other parts entering into the formation of the shoulder-joint it is ultimately distributed. This artery anastomoses with the posterior circumflex and ascending branches of the superior profunda of the brachial artery. see that of ANATOMY ARTERY. ( J. Hart.) For the Bibliography (INTRODUCTION) and of > AZYGOS, (a, fyyo?, jugum.) The term azygos is applied by anatomical writers to cer- tain parts of the human body, which, being situated in or near the mesial line, appear singly, and not symmetrically or in pairs : thus we read of the azygos process of the sphenoid bone, of the azygos uvulae muscle, of the azygos artery, vein, &c. This term, however, (strictly speaking,) is seldom very correctly applied, for in the cases of the bony AZYGOS. 365 process and muscle quoted, each is composed of parts that were originally double or sym- metrical., which have coalesced in the middle line so completely as to appear single ; as to the vessel, the description of which will form the subject of the present article, there is very frequently an analogous trunk, only somewhat smaller, on the opposite side of the spine. AZYGOS VEIN, Posterior thoracic, Prelum- bo-thoracique, Vena sine part, Azygos major. This vein exists in the posterior part of the cavity of the thorax, on the right side of the bodies of the dorsal vertebrae; it serves to receive the blood from most of the intercostal spaces, from the phrenic, bronchial, and medi- astinal veins, as also from the vertebne and vertebral sinuses, and to convey it into the superior vena cava ; it also establishes a com- munication between this last-named vessel and the inferior cava through some of its lumbar branches, and thus connects the veins of the upper and lower segments of the body, in the same manner as the internal mammary and epigastric, and several others of the thoracic and abdominal arteries inosculate. In the present article we shall consider not only the greater and lesser vena azygos, but also the principal branches which each receives namely, the intercostal and bronchial veins. The right or great vena azygos presents many varieties as to the size and number of its branches, as well as in its exact origin; it usually commences very small opposite the first or second lumbar vertebra, on the upper extremity of the right psoas muscle from the confluence of several minute veins, which com- municate with branches from the superior lumbar, capsular, renal, and spermatic veins, and thus indirectly with the abdominal cava ; it not unfrequently, however, arises by a branch from the cava itself, in which case it appears even in this region as a vessel of considerable size. The abdominal portion of the vena azygos is but short, ascends obliquely inwards, crosses the right cms of the diaphragm, and enters the posterior mediastinum between the crura of this muscle in company with, and to the right side of the thoracic duct and aorta ; it is here surrounded by so much cellular and adipose tissue as to be frequently very indistinct; it sometimes enters the chest along with the right splanchnic nerve through an opening in the right crus itself, or external to the latter, between the attachments of the diaphragm to the body and transverse process of the first lumbar vertebra. The thoracic portion of the vena azygos ascends along the right side of the vertebral column in front of the right inter- costal arteries, and covered by the right pleura, to which it is closely connected, being, in fact, contained in the subserous cellular tissue ; the aorta is to its left, and in the in- tervening adipose matter the thoracic duct is placed ; the right splanchnic nerve is external to it or on its right side. Opposite to about the fourth dorsal vertebra the vein leaves the spine, increases very much in size, arches forwards and to the right, around and above the right pulmonary artery and bronchial tube, and opens into the back part of the superior vena cava, immediately above the reflection of the serous layer of the pericardium on that vessel. A small fold of the lining membrane of the azygos vein, a mere rudiment of a valve, exists at its junction with the cava ; sometimes, however, this fold is well developed, it is even observed to be double. Similar folds or valves are occasionally found lower down in the vena azygos, but generally it is destitute of valves. The vena azygos has been seen by Cheselden to open into the vena cava within the pericar- dium close to the right auricle ; it also occa- sionally opens into the cava at a point higher than that which has been stated as its regular termination, and it now and then joins the right or even the left vena innominata. The vena azygos receives several veins; in the abdomen and in its passage through the diaphragm it is joined by one or two of the superior Inmbars, and by small branches from the diaphragm; in the thorax it receives the intercostals; the seven or eight inferior inter- costals of the right side enter it distinctly ; the corresponding number of the left side some- times join it in a similar manner, but most com- monly they first unite into a trunk, called the left or minor azygos, of which we shall speak presently. The three or four superior inter- costal veins of the right side unite into one or two branches which end in the convexity at the upper extremity of the azygos major, which also receives the right bronchial veins in the same situation, and at a lower point the ceso- phageal ; the latter, like the arteries of the same name, are irregular in number and in situation. The left vena azygos, azygos minor, semi- azygos, is smaller, but in other respects similar to the right ; it commences by small branches from the superior left lumbar, capsular, and renal veins, which unite into a delicate vessel that sometimes communicates with the right azygos, and sometimes with the inferior cava ; it then passes through the aortic opening in the diaphragm, or through or external to its left crus in company with the left splanchnic nerve, and ascends along the anterior and left side of the dorsal vertebrae as high as the seventh or eighth ; it then crosses the spine behind the aorta, oesophagus, and thoracic duct, to join the right or great vena azygos. The azygos minor receives the six or seven inferior left intercostal veins, and as it is passing across the spine it is generally joined by a large descending branch which is formed by the confluence of some of the superior of these vessels; the azygos minor also receives the left bronchial veins as well as some branches from the diaphragm, oesophagus, and medias- tinum. In some subjects this vein is wanting; in such cases the left intercostals join the proper azygos either individually, or by two or three uniting into a large branch. The intercostal veins are eleven or twelve in number on each side ; in their course and dis- tribution they correspond to the intercostal 366 AZYGOS. arteries ; they commence each by the union of small branches near the sternum, which anas- tomose with the internal mammary veins ; they then accompany the intercostal arteries along the groove in the lower border of each rib ; near the spine they increase in size, being joined by several veins from the exterior mus- cles of the spine, which pass through the internal part of each intercostal space along with the posterior branches of the intercostal arteries ; in this situation also they receive veins from the vertebral canal, communicating with the vertebral sinuses on the posterior surface of the bodies of the vertebrae, and passing through the intervertebral holes along with the spinal nerves. All the intercostal veins com- municate with each other over the heads of the ribs, either by many small or by a few larger branches ; the veins of the opposite sides also communicate by transverse branches, so as to give to the anterior surface of the dorsal ver- tebrae, in a successful injection of the venous system, an appearance somewhat analogous to the vertebral sinuses on their posterior sur- face. The first intercostal vein of the right side generally ascends over the neck of the first rib, and over the first dorsal ganglion of the sympathetic nerve, and joins the subclavian vein or some of its deep cervical branches ; the second intercostal frequently joins the first, and sometimes the third also terminates in a similar manner, but usually the fourth, third, and often the second open into the arch of the azygos by one or two branches : these superior intercostal veins always communicate with each other and with the azygos below, as well as with the subclavian above. The remaining intercostal veins of the right side enter the azygos separately, or two or three occasionally unite and end by a common opening; the infe- rior ascend, the middle take a transverse course, and the superior descend ; near the spine they all anastomose freely with each other, so that the heads of the ribs support a chain or net- work of these vascular inosculations, as is well represented in Breschet's plates of the venous system. The superior intercostal vein of the left side always joins the left subclavian or some of its large branches, the internal mammary in parti- cular ; it is usually a large vein, but it presents great varieties ; in some it appears as a third vena azygos, and might be named the left superior azygos; in such cases it communicates below with the inferior azygos about the sixth dorsal vertebra and above with the left subcla- vian ; in the intermediate space it receives the corresponding intercostal veins, also the ceso- phagaeal, mediastinal, and left bronchial ; this vein sometimes also communicates directly with the right azygos. The remaining left intercostal veins enter the lesser azygos, or if this vessel be absent, they cross the spine behind the oesophagus, aorta, and thoracic duct, and enter the great azygos separately, or two or three conjoined. The superior and in- ferior azygos veins of the left side are some- times continuous, and enter the left subclavian, thus taking a parallel and very similar course to the vein on the right side, particularly when the latter opens so high as into either of the vense innominatae. The bronchial veins arise in the cellular tissue of the lungs from the extremities of the bron- chial arteries ; as the branches unite into larger vessels, these are found to accompany very closely the divisions of the bronchial tube ; they leave the root of each lung two or three in number ; on the right side one joins the arch of the azygos or the superior vena cava, the others open into the azygos lower down, or into some of the mediastinal or intercostal branches. The left bronchial veins arise in a similar manner, escape from the root of the left lung, and open either into some of the superior in- tercostal veins, or into the superior or inferior azygos minor. In minute injections of the lungs these veins are found to inosculate with the capillary terminations of the pulmonary arteries. Both the right and left vena azygos receive numerous branches from the posterior mediastinum, from the coats of the aorta, pericardium, oesophagus, bronchial glands, trachea, &c. &c. ; these veins pursue no regular course; they receive names either from the arteries they accompany, or from the organs whence they are derived ; they require no par- ticular description. The vena azygos is the principal vein apper- taining to the parietes of the chest; it not only serves to receive the several branches which have been mentioned, but also maintains numerous communications between different portions of the venous system, which must prove of essential service in case of obstruction to the circulation in any of the principal trunks : thus, its abdominal portion communi- cates either directly with the inferior vena cava, or indirectly through the medium of the lumbar, phrenic, renal, or spermatic veins, while its thoracic end joins the superior cava, and at the same time anastomoses on either side with the subclavian vein or some of its branches. On both sides of the thorax again it inoscu- lates by its intercostal communications not only with the internal mammary, but also with the thoracic branches of the axillary veins, and along the vertebrae it communicates with the vertebral sinuses, opposite each foramen of conjunction. This vein, consequently, ap- pears not only as one of the roots of the cava, but also as a loop or second channel between the two cavffi, which, in case of the obstruction of either, more particularly of the inferior, would convey the blood to the heart, and thus obviate any impediment to the venous circulation of the lower segment of the body. Cases have even occurred in which the inferior cava has been obstructed or nearly obliterated by the pressure of a tumour or of a diseased liver, and in these this anastomosis, and indeed the whole vena azygos have been found greatly increased in size. The vena azygos appears moreover to have been formed as a convenient means for receiving numerous venous branches which could not reach any of the large vessels BACK. 307 without some more complicated provision ; thus the inferior intercostal veins could not join the inferior cava, where the latter is imbedded in the liver, without perforating the diaphragm ; neither could the middle and superior inter- costal, the mediastinal, and the bronchial veins arrive at the superior cava or at the right auricle of the heart without a much more complex disposition of all these parts than we observe. For the BIBLIOGRAPHY see that of VENOUS SYSTEM. (Robert Harrison.) BACK, REGION OF THE (surgical anatomy). Under this denomination, which is of Saxon origin, it is intended to describe the posterior regions of the body situated between the head and the pelvis, including a cervical, a dorsal, and a lumbar region, varying in breadth in these different portions, and corresponding in length to that of the spine. The skeleton of this extensive region consists of the spinal column, and a portion of the ribs, and to the former of these it is chiefly indebted for its longitudinal curvatures. Thus we find it con- cave in the cervical and lumbar portions, convex in the dorsal. (See SPINE.) In its whole course from the os occipitis to the base of the sacrum, we observe a central depression occasioned by the prominence of muscular masses on each side. In weak and emaciated subjects a rugged ridge takes the place of this depression ; the ridge is the series of spinous processes which have little or no muscular covering, and are hid when the mus- cles on each side are much developed. At the junction of the cervical and dorsal portion, however, the ridge is scarcely ever obscured, because there the spines are very long and the muscles thin ; and again, the depression at the top of the neck is only rendered deeper by emaciation. The length of the cervical region is well de- fined by the external tuberosity of the os occi- pitis above, and by the prominent spine of the last cervical vertebra below. Its breadth, at the upper part, extends from one mastoid process to the other; in the middle it becomes nar- rower, and inferiorly it again spreads out almost to the acromio-clavicular articulations. Its length and breadth vary in different indi- viduals. In general it is broader, propor- tionally, in the male than in the female, espe- cially at the upper part, where, according to Gall, it may be considered a measure of ama- tiveness. At the top of this region we see a remarkable depression, called the suboccipital fossa, or cervical fossa ; its existence depends on the absence of a spinous process in the atlas, while the muscles on either side, chiefly the complexi, stand out boldly. In fat persons a quantity of adipose substance fills up this hollow and nearly obliterates it. The upper third of the neck, and in some persons much more, is covered with hair. This part is tech- nically called nitcha, a term of Arabian origin. Its common appellation is nape of the neck. (See/g.2.; The dorsal region corresponds in length to the twelve dorsal vertebra?, with their intcrvertebral substances, and in this dimension it is well de- fined, but its breadth is not so settled ; anato- mists bound it by the angles of the ribs on either side, while surgical writers extend it somewhat farther. This region is convex from above downwards, and from side to side also, if we overlook the slight central depression. The lumbar region extends from the last dorsal vertebra to the base of the sacrum, and on each side to the outer margin of the sacro- lumbalis muscle. These bounderies can gene- rally be seen and felt without difficulty. It is a little concave from above downwards, convex, or nearly plane, from side to side, with the central depression slightly marked. integuments. The integuments of the back are every where strong and coarse. They are particularly so over the spinous processes, where an imperfectly marked raphe exists; they are also more fixed along that line than elsewhere, on account of the density of the cellular tissue which connects them to the su- pra-spinal ligament, and in many subjects the raphe is hairy. The sensibility of the skin is much less on the posterior than on the anterior surface of the body ; the nerves and vessels are not so numerous, nor is its organization so high. Hence its resistance to the action of vesicatories and rubefacients, which must be stronger, or applied for a longer period to produce the required effect. The skin is also very unyielding, so that col- lections of matter do not readily make their way to the surface, and if not opened early may spread under it extensively. Subcutaneous cellular tissue. On raising the integuments a layer of cellular substance is observed, not containing much fat. It is strong, coarse, and filamentous, and adheres to the skin more than to the muscles. In passing a seton in the neck we pinch it up with the skin, and transfix it without touching the muscles, which could not be wounded with impunity. Along the middle line this fascia is more con- nected to the deeper parts than it is on either side, and especially in the dorsal region. This cellular tissue is frequently the seat of post-mortem congestions and effusions arising from the gravitation of the fluids to so depen- dent a position; hence we generally find it either very vascular or infiltrated with fluid, in a state quite resembling anasarca. A very fine layer of cellular tissue, under- neath this again, closely adheres to the mus- cular fibre, and a good deal of motion may take place between these two layers. The arteries which supply the skin and fascia in the neck are branches of the occipital, the cervicalis profunda, and the transversalis colli, to which the vertebral and transversalis humeri may contribute a little. In the dorsal region the posterior scapular and the dorsal branches of the intercostals principally supply these parts ; and in the lumbar region we have the posterior branches of the lumbar arteries. None of these approach the skin in their undi- vided state, so that superficial wounds here can 368 BACK. never be followed by troublesome haemorrhage. In the fascia we generally tint! a vein, described by Godman of Philadelphia under the name of the dorsal azygos. It arises at the lower part of the back by irregular roots, runs up single for some time along the middle line, and then divides into two branches, one of which pierces each trapezius, and enters into the transversalis colli vein. It is small and of little importance. The other veins are not of sufficient size to deserve particular notice ; they are found in company with the arteries. Nerves. The nerves of this region are the posterior branches of all the spinal nerves. The cervical and brachial plexuses also send some filaments ; but its nervous supply is, like its vascular, very scanty. Lymphatics, The lymphatics, too, are not so numerous as elsewhere. We trace them running to the cervical, axillary, and inguinal glands, according to their proximity to these. With the exception of two or three on the cer- vical portion of the trapezius, lymphatic glands are not met with here. The back is peculiarly subject to anthrax in debilitated constitutions, and in some cases the tumour acquires great magnitude. It some- times happens that several anthraxes occur in succession, until a large portion of the integu- ments and fascia is destroyed, and the patient sinks under the disease. Pressure is frequently the exciting cause. By pressure the vessels are so obstructed that the vitality of the part is impaired, and its organization is too low to enable it to recover from the deadening effects, especially if the constitution be previously in- jured. Here too we often meet with furunculi : they are most common in the nape of the neck. Fistulae in the lumbar region, depending on diseased kidney, sometimes present themselves. There is no peculiarity in the cutaneous or other diseases to which it is liable in common with other regions. BACK, MUSCLES OF THE. The mus- cles of the back are very numerous and complex. There is much variety in their origins and inser- tions in different subjects, and in many cases it is not easy to decide with which of two adjoining muscles we are to connect certain bundles of fibres ; a distinct impression, therefore, is not always obtained from an examination of the part, nor will a repetition of the dissection pre- sent us with the same view in another subject. Hence it happens that anatomists differ as to the number of muscles to be met with, some dividing into two Or more muscles what others consider as one ; this proves another source of difficulty. The names and the enumeration of them, as given by Albinus, we shall follow pretty closely : we esteem them the best on the whole, and they have the advantage of being generally adopted in these countries : viz. the trapezius or cucullaris, latissmus dorsi, rhom- boideus major, rhomboideus minor, levator an- guli scapula, serratus posticus superior, serratus posticus inferior, splenim cupitis, splenius colli, sacro-lum'balis, longissimus dorsi, spinalis dorsi, semi-spinalis dorsi, cervicalis desccndens, trans- versalis colli, (rachelo-mastoideuS) complexes, spinalis colli, multifidw spina;, inter-spinales, inter-transversales, rcctus capitis posticus major, rectns capitis posticus minor, obliquus capitis in" ferior, arid obliquus capitis superior. These muscles are placed in pairs, one on each side of the median line ; none of them can be said to be exactly in the middle. We shall examine them in the order they present themselves to us in dissecting. We find these muscles disposed in layers, and each layer differing from the others in the shape or use of the pieces which compose it. Six such layers may be enumerated. Thejirst consists of the trapezius and latissimus dorsi, muscles somewhat triangular in form, and destined to act principally on the upper extre- mity. The second consists of the rhomboidei and levator anguli scapulae. These are qua- drangular, approaching a square shape, and act on the scapulae. The third layer is formed of the serrati, of similar shape, but acting on the ribs. The fourth consists of the splenii ; these, more elongated than the last, rotate and erect the head and neck. The fifth layer is com- posed of very long muscles, acting chiefly as erectors of the spine and head, viz. the sacro- lumbalis, longissimus dorsi, spinalis, and semi- spinalis dorsi, cervicalis descendens, transver- salis colli, trachelo-mastoideus and complexus. The sixth layer, again, is formed of short mus- cles, rotating and erecting the head or minute portions of the spinal column ; these are the recti and obliqui of the head, the spinalis colli, inter-spinales, inter-transversales,and multifidus spinae. First layer. The trapezius and latissimus dorsi, which form the first layer, almost com- pletely conceal all the other muscles of this region, and in superficial extent are scarcely succeeded by any two muscles in the body. The trapezius is thin, triangular, and very extensive. One of its surfaces is turned to the integuments, and covered by the superficial fascia, and by a fine layer of cellular tissue which closely adheres to it. The trapezius arises from the internal third of the superior oblique ridge of the os occipitis, from the liga- mentum nuchse, and from the spinous pro- cesses of the last cervical and of all the dorsal vertebras. The superior fibres run downwards, outwards, and a little forwards, the middle transversely, and the inferior upwards and out- wards ; all converge, and are inserted into the external third of the posterior border of the clavicle, the acromio-clavicular ligament, the acromion process, the upper edge of the spine of the scapula, and the tubercle which termi- nates this spine at the base. The origin of this muscle is by tendinous fibres which are from half an inch to an inch long in the occipital portion ; in the cervical they are very short until we come down to the sixth cervical vertebra, where they begin to lengthen ; at the first dorsal they are an inch and a half in length, again they diminish, and at the fourth dorsal spine they are scarcely to be seen ; but at the tenth they again increase in length, and form a triangular tendon. It some- BACK. 369 times happens that this muscle has no connexion with the eleventh and twelfth dorsal vertebra). The long tendinous fibres of the two trapezii, at the junction of the cervical and dorsal re- gions, form an ovul aponeurosis of considerable size, called the cervical aponeurotis, which is supposed to give greater strength to this part. All the spinal origin has its fibres blended with those of the opposite muscle, and supraspinal ligament. The insertion is by a mixture of tendinous ami fleshy slips, except at the extre- mity of the spine of the scapula, where a little tendon is formed which glides over a small triangular surface to be inserted into the top of the tubercle. The plane which this muscle forms is curved on the side of the neck, and its fibres are there a little twisted. Instead of three sides this muscle has actually five: 1st, a superior; 2nd, an internal these are its ori- gins; 3rd, an external, which is its insertion, and two others which are unconnected, viz. 4th, an inferior external, and 5th, a superior external. Of these the first is so short that it attracts no notice ; the other four are of un- equal lengths hence the name trapezius. But the third and fourth sides are so nearly in one continuous line that the whole muscle appears triangular. The trapezius covers the cornplexus, the splenii, the levator anguli scapulae, the serratus posticus superior, the rhomboidei, the supra- spinatus, a small portion of the infra-spinatus, the latissimus dorsi, the sacro-lumbalis and longissimus dorsi. It touches all these mus- cles, and glides on them by means of a fine cellular tissue, which contains little or no fat except over the supra-spinatus. The anterior superior edge forms the posterior boundary of the great lateral triangle of the neck, and at its upper extremity is often connected with the sterno-mastoid. The two trapezii have some resemblance to the monk's cowl hanging over the neck, hence the name citcullares often given to them, By its superior fibres this muscle raises the clavicle and scapula; by its middle it draws the scapula towards the vertebral column, and by its inferior it pulls the tubercle of the spine of the scapula downwards. If all the fibres act together, it will cause, the scapula to rotate on the thorax, so as to elevate the shoulder-joint, and in this it is powerfully assisted by the in- ferior portion of the serratus magnus, as in carrying heavy burthens on the shoulder. It serves to keep the head from falling forwards, and will, by its superior fibres, draw the head to the shoulder and turn the face to the other side. We use it in shrugging up the shoulders. It becomes a muscle of inspiration by raising and fixing the clavicle and scapula, so that the subclavius, the lesser pectoral, part of the ser- ratus magnus, &c. may elevate the ribs. The spinal accessory nerve (the superior external respiratory of the trunk) terminates in this muscle, and, according to Sir Charles Bell, associates it with the other respiratory muscles. The ligamentum nuchte, from which the chief part of the cervical portion of the muscle arises, is a line of dense cellular tissue, extending from VOL. I. the external luberosity of the os occipitis to the spine of the seventh cervical vertebra. It is interposed between the two trapezii. A thin septum extends from it to the spines of all the cervical vertebrae. In no part does it deserve the name of ligament in the human subject. In quadrupeds, however, especially where the neck is long or the head very heavy, as in the horse, stag, elephant, &c. it is a powerful elastic ligament, resembling in structure the ligarnenta subflava of the spine, and is of great impor- tance by supporting the head without much muscular effort. In man it is quite rudimerital. The trapezius presents much variety in differ- ent animals. In the carnivoraand rodentia the clavicular portion joins with the masto-humeral, (a muscle not found in man,) and is separated from the scapular portion by the levator anguli scapulae. In the horse the only part of the muscle developed is that which corresponds to the as- cending fibres in man, and which are inserted into the tubercle at the extremity of the spinous pro- cesses. In the dolphin it is thin, covers all the scapula, and is inserted into that bone near its neck. In the mole a fleshy bundle coming from the loins replaces it. In birds it consists of two portions, one for the furca, the other for the scapula. In reptiles there is no trapezius. Latts4tnus dorsi.- This muscle is also thin, triangular, and very extensive, covering the lumbar region, a part of the dorsal and of the side of the thorax, and contributing to form the posterior boundary of the axilla. It is exposed by raising the integuments, superficial fascia, and lower angle of the trapezius. Then we find it arising from the tops of the spinous pro- cesses of six, (sometimes of four or five, some- times of seven or eight,) of the inferior dorsal vertebrae, of all the lumbar vertebrae and from the supraspinal ligament, from the spines and other eminences of the sacrum, from nearly the whole posterior half of the crest of the ilium, and from the three or four lowest false ribs. The fibres all converge, the uppermost running transversely, the lowest vertically. It is in- serted into the posterior edge of the bicipital groove of the humerus. The costal origin of this muscle is fleshy, all the rest is tendinous. The tendinous fibres on the vertebrae are blended with those of the opposite muscle, and on the sacrum and ilium with the glutaeus maximus. They form a tendon of great extent, narrow on the sacrum, very broad on the lumbar region, and again becoming narrow as we ascend to the dorsal. It is to this tendinous expansion that the name of lumbar fascia is given; its fibres are for the most part in the direction of the fleshy fibres which succeed, but they are crossed irregularly by some others. This fascia covers and binds down the lumbar muscles, giving great strength to the loins; it is intimately connected with the tendon of the serratus posticus inferior, the internal oblique of the abdomen, and the posterior tendon of the transversal is, all of which are inseparably connected with its anterior surface. The costal origin is by fleshy slips which indigitate with similar slips of the obliquus externus abdominis; these are so disposed that the inferior almost 2 n 370 BACK. conceals the one above it, and so on. The muscle on its way to the Immerus glides over the inferior angle of the scapula, from which it receives a small fasciculus of fleshy fibres; then it bends under the teres major, forms a tendon about an inch broad and an inch long, which is connected at first by cellular tissue, and after- wards by a bursa mucosa to the front of the teres major; and is inserted into the inner or posterior edge of the bicipital groove. Some fibres of this tendon line the groove, a few pass up along its edge to the lesser tuberosity. The axillary vessels and nerves, the biceps and the coraco-brachialis, are in contact with its tendon. The upper edge of the latissimus is nearly horizontal, slightly curved its concavity up- wards and free. The anterior edge is nearly vertical, and for the most part free also. The posterior or inner edge is connected throughout, and takes an extensive irregular sweep. On raising the muscle, we shall find that it was in contact with the serratus posticus inferior, the sacro-lumbalis and longissimus dorsi, the inter- nal oblique and transversalis of the abdomen, the inferior rhomboid, the serratus magnus, the inferior angle of the scapula, the infra-spinatus and teres major, also with some of the ribs and intercostal muscles. We sometimes meet a fasciculus of muscular fibres passing from the latissimus dorsi to the pectoralis major across the axillary vessels and nerves. In the Edinburgh Medical and Sur- gical Journal, vol. viii. Dr. Ramsay states that it is found in one subject out of every thirty, and may prove inconvenient to the axil- lary artery, vein, and nerves. The latissimus dorsi depresses the arm, draws it backwards and inwards, rotates the humerus so as to turn the palm of the hand first in- wards, then backwards. It serves to keep the lower angle of the scapula in its place. When the arm is raised and fixed, it draws the body up, as in climbing, or elevates the ribs, as in difficult respiration. In using crutches the arm is fixed by grasping the handle of the crutch, then the pectoralis major and latis- simus pull up the body on the cross-bar to- wards their insertions ; and when the body is so raised, it is impelled forwards by the action of this muscle, aided by the feet and by the body's own gravity. In quadrupeds it is a muscle of progression, pulling the trunk forwards to the fore-leg, which was previously fixed. The panniculus carno- sus, which is inserted close to it into the hu- merus, assists in this action. In birds it is small, and consists of two portions. Second layer. This layer consists of the rhomboidci and leva-tor anguli scapula. They are seen on raising the trapezius. The rhomboidei form a broad thin plane, separated only by a line of cellular tissue into the minor and major, extending from the spine to the scapula, and nearly concealed by the trapezius. The rhomboidens minor arises from about half an inch of the ligamentum nuchte and from the spine of the seventh cervical vertebra; its fibres run downwards and outwards to be inserted into the base of the scapula at and a little above the commencement of the spinous process of that bone. The rhomboideus major, three or four times as broad, arises from the four or five uppermost dorsal spines, runs downwards and outwards, and is inserted below the last into the base of the scapula from its spinous process to its inferior angle. These two muscles are of the same length, thickness, and appearance in every respect, differing only in breadth. Their fibres are parallel to each other, being tendinous at their origin, where they are blended with those of the trapezius, and are inserted between the serratus magnus and the supra- and infra- spinati. The insertion of the major is peculiar; a tendinous band runs along the base of the scapula from its spine to its inferior angle, and it is into this > not into the bone, that the mus- cular fibres are inserted,, nearly at right angles. This band is attached only at its two extremi- ties ; it is not seen till we cut a few of the posterior fleshy fibres which do reach the bone. This arrangement is supposed to allow of greater freedom, of anastomosis between the scapular vessels. The minor is overlapped at its insertion by the levator anguli scapulae,, in the rest of its extent by the trapezius. The major is covered by the trapezius principally ; a very small part of its inferior Angle is covered by the latissimus, and between these it is separated from the integuments only by the superficial fascia. The rhomboids get their name from their shape. Their opposite, but not their adjacent sides and angles are nearly equal. Their internal and external edges are attached; their superior and inferior are free. The inferior edge of the major is a little longer than any other. The deeper surface of these muscles touches the splenii, the serratus posticus superior, sacro-lumbalis and longis- simus dorsi, some ribs and intercostal muscles. These muscles draw the base of the scapula towards the spine, acting with most effect on the inferior angle, and thereby depressing the point of the shoulder. With the trapezius they draw the shoulders upwards and backwards. In the simiae the rhomboids extend to the oc- ciput. In carnivora the levator major scapula? seems to be their occipital portion. In the horse the levator proprius scapula is the ante- rior part of the rhomboid, arising from the ligamentum nuchae. The levator anguli scapula is a long strap- shaped muscle, situated on the side of the neck, and extending from the superior cervical vertebras to the upper angle of the scapula. Its origin is by four (sometimes three) ten- dinous bundles from the posterior tubercles of the transverse processes of the four superior cervical vertebra ;. that which arises from the atlas is the largest ; they are intimately con- nected with the splenius colli behind, and with the scaleni before. The fleshy fibres pro- ceeding from them unite, and passing down- wards, outwards, and backwards, are inserted into the inner surface and posterior margin of the scapula, from its superior angle to near its spine. Here it overlaps a little of the lesser BACK. 371 rhomboid, and is so united with the serratus magnus that Dumeril considers it a portion of this muscle. The dissection of it in some quadrupeds favours this opinion, but in man it appears rather in connexion with the rhom- boid. This muscle is covered by the sterno-mastoid at its upper part, then by the integuments, and afterwards by the trapezius. It rests on the splenius colli, cervicalis descendens, transver- salis colli, serratus posticus superior, and lesser rhomboid. This muscle pulls the superior angle of the scapula upwards and forwards, and by rotating that bone on the thorax becomes a depressor of the shoulder-joint. The rhomboids act with it in depressing the joint; but the inferior portion of the serratus magnus is its direct antagonist. When the trapezius acts with this muscle, the scapula is drawn directly upwards. If the scapula be fixed, this muscle will incline the neck to its own side. This muscle undergoes many modifications in the different families of the mammalia. In simite it is inserted into the spine of the sca- pula, not into its angle. In carnivora and rodentia it separates the two portions of the trapezius, and is inserted near the acromial end of the spine of the scapula. In the cat it arises from the basilar process of the os occi- pitis and from only one of the cervical vertebrae, the atlas. In the horse it does not exist at all. In the dolphin it forms a thin tendon which spreads over the scapula. As to birds and rep- tiles, it is replaced in them by other muscles. Third layer. Two very thin muscles, the serratus posticus superior and serratus posticus inferior, constitute the layer. The serratus posticus superior is quadrilateral. It arises by a thin tendon from the lowest part of the ligamentum nucha, from the last cervi- cal and the first two or three dorsal spines. The fleshy fibres which succeed form a thin plane, pass dow r nwards and outwards, and are inserted by four digitations into the superior border and external surface of the second, third, fourth, and fifth ribs, a little external to their angles. This muscle is covered by the rhomboid, the trapezius, and, when the shoulder is drawn back, by the serratus magnus. Its origin is united to the two former. It covers the splenii, the longissimus dorsi, transversalis colli, sacro- lumbalis and cervicalis descendens ; while on these it is tendinous ; then it becomes fleshy and covers the ribs and intercostal muscles. Sometimes it has only three points of insertion. Occasionally we find a bundle of fibres passing from the upper part of this muscle along the levator anguli scapulae to be inserted into the transverse process of the atlas. This muscle elevates the ribs and expands the thorax as in inspiration. It binds down the muscles on which it lies, enabling them to act with more effect. The serratus posticus inferior is very like the last muscle, but a little broader and thinner. It arises from the last two dorsal and first three lumbar spines by a thin tendinous expansion, which is intimately connected with the tendon of the latissimus dorsi, and often destroyed in removing the latter. The fleshy fibres which succeed pass upwards and outwards to be inserted by digitations into the four lowest false ribs. The uppermost digitation is the largest, and is attached to the rib near its angle ; the others become smaller as we descend, and their insertions are more remote from the angles. The lowest is connected with the cartilage of the last rib. This muscle covers the longissimus dorsi and sacro-lumbalis, the ribs and inter- costals. It also covers the posterior tendon of the transversalis abdomiriis, to which it is in- separably united. This muscle draws down the ribs as in ex- piration, and binds down the deep lumbar muscles. A thin semitransparent fibrous layer, called the vertebral aponeurosiSj covers the spinal muscles in the interval between the two ser- rati. It is continuous with their adjacent edges, and assists them in binding down the long muscles of this region. The fibres of which it is composed pass for the most part trans- versely, from the spinous processes to the an- gles of the ribs. These muscles are generally present in the inferior animals, when ribs exist, and have no peculiarity worthy of being noticed here. The splenii form the fourth layer. They appear as one muscle, extending from the lower cervical and upper dorsal spines obliquely upwards, outwards, and forwards, to the head and to the transverse processes of the superior cervical vertebras. Covered below by tha rhomboid and serratus posticus superior, higher up by the trapezius and levator anguli scapulae, and higher still by the sterno-mastoid, it is only about the middle of their course that they become distinct from each other, for they arise as one. The splenius colli (or splenius cervicis) is the inferior portion, not so thick or broad as the superior, but of greater length. It arises from the spines of the third, fourth, fifth, and sixth dorsal vertebrae, and from the interspinal ligaments, by tendinous fibres which are long, and form an acute angle below. The flat band of fleshy substance which proceeds from this tendon passes upwards, outwards, and for- wards, then divides into two or three fasciculi, which are inserted tendinous into the trans- verse processes of the two or three superior cervical vertebrae, blended with the attach- ments of the levator anguli scapulae and the transversalis colli. The splenius capitis, the superior portion, arises from the spines of the two superior dorsal vertebras and of the seventh cervical, and from the ligamentum nuchae as high as the fourth cervical. At the origin it is tendinous ; it soon becomes fleshy, passes upwards, out- wards, and forwards, to be inserted into the back part of the mastoid process of the tem- poral bone, and into the external part of the depression on the occipital, between the supe- rior and inferior transverse ridges. These two portions ought not to be con- 2 B 2 372 BACK. sidered distinct muscles. They are inseparable below ; their structure, direction, and uses are alike ; and they are inserted similarly the one into transverse processes, the other into a part of the cranium perfectly analogous. The splenii cover the longissimus dorsi, the complexus, the transversalis colli, and the trachelo-mastoideus. The splenii of opposite sides pass off from each other as they ascend, leaving a triangular space at the upper part of the neck, in which the complex! appear. The action of these muscles is to incline the head to one side, and rotate it. If the sterno- mastoideus of the same side act with them, the head is inclined directly to the shoulder. If the splenii of opposite sides act together, the head and neck are kept erect, and in this they are assisted by the complexus and trapezius. They strap down the deeper muscles. Their name is said to be derived from some resem- blance to the spleen! (Turtorfs Glossary.) The splenii are generally better marked in other mammalia than in man. In the mole they are particularly strong. In carnivora there is no splenius colli. In the horse the splenius capitis is inserted into the mastoid process by a tendon common to it and to the trachelo-mastoideus. Birds have no splenius. Reptiles have analogous muscles; but fish have not. Fifth layer. On removing the splenii and all those previously described, we expose the Jift/i layer of muscles, consisting of the sacro- lumbahs, longissimus dorsi, spinalis and semi- spinalis dorsi, cervicalis descendens, trans- versalis colli, traehelo-mastoideus, and com- plexus. These, excepting the last, are long and slender, quite different from those hitherto described. They are also less distinct from each other. The first four of them fill up the vertebral groove from the sacrum to the neck, and might well be considered as one muscle the erector spirits. The sacro-lumbalis y placed most externally, arises from the posterior surface of the sacrum, from the margin of the ilium where the latter overlaps the former, from the sacro-iliac liga- ments, and from the extremities of the trans- verse processes of the lumbar vertebrae ; pas- sing upwards, and tapering in form, it is in- serted by tendinous slips into the angles of all the ribs. It is reinforced in its ascent by acces- sory fibres (musculi accessor ii), which arise at the upper margins of the five or six lowest true ribs, internal to their angles, run upwards and outwards over one or two intercostal spaces under cover of the longer fibres, and are in- serted with them into the angles of the ribs. These accessory fibres constitute almost the entire of the muscle at its upper part. The longissimus dorsi, placed along its inner side, arises from the spinous and transverse processes of the lumbar vertebrae, and from the spines of the sacrum and its posterior surface down to its apex. It forms a thick, somewhat square, mass in the loins ; on the dorsum it becomes fiat and tapering, and ends in a point at the top of the thorax. It is inserted by two rows of tendinous and fleshy slips one row into the transverse processes of all the dorsal vertebrae, the other row, externally, into the lower edge of the ribs near their articulations with those processes. The costal slips are seldom inserted into all the ribs, the first two or three and the last two or three being often without them. The posterior surface of these two rmiscles consists below of a strong tendinous layer, from which a great part of their fleshy fibres arises ; it is common to the two as far as the middle of the lumbar region ; there it terminates on the sacro-lumbalis, but ascends much higher on the longissimus dorsi, separating into several distinct bands, between which vessels and nerves come out. This tendon is not to be confounded with the fascia lumborum, which is much thinner and adheres to its posterior surface. The spinalis dorsi* lies close along the spi- nous ridge, arising from the two superior lum- bar, and three inferior dorsal spines. It forms a thin muscle and is inserted into the nine superior dorsal spines. Below it is in contact with the longissimus; above it is separated from it by the next muscle. The semi-spinalis dorsi arises from the trans- verse processes of the dorsal vertebrae from the eleventh to the sixth inclusive by so many distinct tendinous fasciculi which pass up, be- come fleshy, unite and are inserted into the spines of the four or five superior dorsal and two inferior cervical vertebra. The name of this muscle is intended to denote its attachment to the transverse as well as to the spinous pro- cesses. It is at first concealed by the longis- simus dorsi, then lies along the inner side of that muscle and the outer side of the spinalis dorsi, with which last it is often united in description. These four muscles elevate the spine, and give it an inclination to their own side. The sacro-lumbalis will also depress the ribs slightly. The cervicalis descendens looks like a con- tinuation of the sacrolumbalis, between which and the longissimus dorsi it arises. Its origin is by tendinous slips from the angles of the second, third, fourth, fifth, and sixth ribs. These are at first blended with those of the sacro-lumbalis ; then they unite and form a slender muscle, which runs upwards, out- wards, and forwards, to be inserted into the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, between the trans- versalis eolli and the levator anguli scapulae. This muscle may elevate the ribs or extend the neck, turning it to one side. It is often considered as a portion of the sacro-lumbalis, and sometimes called musculus accessorius, or cervicalis ascendens. The name cervicalis descendens, that by which it is best known, was given to it by Diemerbroeck, who described * Under the denominations transversaire epineux, which may be latinized transversus spines, Bichat and some other continental anatomists include the spinalis dorsi, semi-spinalis dorsi, spinalis coUi, and mvltifidus spinee. ED. BACK. 373 it as descending from the neck to act on the ribs and elevate them. The transversalis colli appears like a con- tinuation of the longissimus dorsi, and as such is often described. It arises along its internal side by tendinous and fleshy slips from the transverse processes of the second, third, fourth, fifth, and sixth dorsal vertebrae. These unite, form a flat fleshy belly, which passes upwards, outwards, and forwards, to be in- serted by similar slips into the transverse pro- cesses of the cervical vertebras from the sixth to the second inclusive, between the cervicalis descendens and the complexus. The origin and insertion of this muscle are connected only to transverse processes hence the name. This muscle elevates the neck and inclines it to one side. The trachelo-mastoideus lies to the inner side of the transversalis colli, by which it is in great measure concealed. It arises by ten- dinous slips from the transverse processes of two or three superior dorsal, and of three or four cervical vertebrae. The slender muscle enlarges as it ascends, passes a little outwards, and is inserted into the posterior border of the mastoid process, underneath the splenius ca- pitis. Its inner side rests on the complexus, then it covers the obliquus capitis inferior and superior, and the origin of the digastric, also the occipital artery. It is by some called the complexus minor, from the resemblance it bears to the complexus in its structure. Some anatomists consider it as the cranial portion of the longissimus dorsi and transversalis colli. The origin of its name is obvious. When in action, this muscle extends the neck, drawing the head back and to its own side. The complexus is thicker and broader than the muscles we have been now describing in the cervical region. It arises from the trans- verse and articulating processes of the four or five superior dorsal vertebrae, and from the transverse processes of the four inferior cervical, by tendinous slips : these are followed by fleshy and tendinous bundles. The muscle thus formed passes upwards and inwards, to be inserted into the os occipitis between its supe- rior and inferior oblique ridges. The complexi are close to each other above, separated only by cellular tissue which is connected with the ligamentum nuchae ; lower down, however, there is some space between them. This mus- cle is covered by the trapezius above, by the splenii in the middle, and by the trachelo- mastoideus and longissimus dorsi at its lowest part. It rests on the spinalis colli, the obliqui and recti capitis. The name is derived from the complicated intermixture of tendinous and fleshy fibres of which it is composed. A su- perficial portion of it is described by Albinus as the biventer cervicisj but it does not usually admit of subdivision. This muscle draws the head back on the spinal column. In the muscles of this layer there are no very striking differences to be observed in the other mammalia, nor in birds. Reptiles and fishes differ too widely to allow of a com- parison. Sixth layer. On raising the complexus and trachelo-mastoideus we observe a beautiful series of muscles for moving the head, viz. the inferior oblique, the superior oblique, the rcctus capitis posticus major and minor. These, with the spinalis colli, form a sixth layer. The spinalis, or rather scmi-spinalis colli, arises by four or five fasciculi from the trans- verse processes of as many superior dorsal vertebrae ; these unite, pass upwards and in- wards, to be inserted into the second, third, fourth, and fifth cervical spines, forming a thicker muscle than the spinalis or semi-spinalis dorsi. This muscle commences between the longis- simus and semi-spinalis dorsi, then it lies be- tween this last and the complexus. It is almost concealed by the complexus. It ex- tends the cervical vertebrae and inclines them to its own side. The obliquus capitis inferior arises from the spine of the second vertebra, passes outwards and a little upwards and forwards, to be in- serted into the transverse process of the first. Its origin is connected with that of the rectus posticus major, and the insertion of the spi- nalis colli. Its insertion is blended with the origin of the obliquus superior. It is fusi- form in shape, the largest of the four muscles to be met with here, and is often called obli- quus major. It covers the vertebral artery and the lamina of the second vertebra, and is itself covered by the complexus and trachelo-mas- toideus, and by the posterior branch of the first cervical nerve. It rotates the first vertebra on the second, thus turning the face to its own side. The obliquus capitis superior (or minor) has a pointed origin from the transverse process of the atlas; runs upwards, inwards, and back- wards, becoming broader, and is inserted into the os occipitis between its transverse ridges, just above the insertion of the rectus posticus major. This muscle is covered by the splenius capitis, trachelo-mastoideus and complexus. It covers the vertebral artery and the interval between the atlas and occiput. Its action is to extend the head, giving it some inclination toils own side. The rectus capitis posticus major is triangu- lar; its apex arises from the spine of the deri- tita; it passes upwards and a little outwards, to be inserted by its base into the inferior transverse ridge of the os occipitis. This muscle and its fellow arise close together; passing up they separate. The insertion is overlapped by that of the superior oblique. The complexus covers the greater part of it. This muscle draws back the head, turning the face a little to its own side. The two obliqui, with this last muscle, en- close a triangular space, in which we see the posterior branch of the sub-occipital nerve enveloped in adipose tissue, the vertebral artery, the posterior half ring of the atlas, and 374 BILE. the thin ligament which connects this last with the edge of the foramen magnum. Here we find the nerve dividing into three branches for these three muscles. On removing some cellular tissue from between the recti majores, we observe the Rectus posticus minor, shaped like the last, but much smaller. It arises close to its fellow from a little tubercle on the back of the atlas, passes upwards, outwards, and backwards, to be inserted into the os occipitis between the inferior oblique ridge and the foramen mag- num. It is partly concealed by the rectus major. This muscle can draw the head back- wards. In quadrupeds these four muscles are pro- portionally larger than in man. The inferior oblique and the rectus major are considerably larger. Birds have three recti, and only one oblique the inferior. Reptiles and fishes may be said to want them, as the analogy is very remote. On removing the spinalis colli and all the muscles of the fifth layer, we observe nume- rous fasciculi of muscular fibres, which are named inter-spinalis, inter-transversalis, and multifidus spince. These might be considered a seventh layer ; but they are very analogous to the small muscles just described, and nearly on the same plane. The inter-spinales are short bundles of fleshy fibres placed between the spinous processes of contiguous vertebrae. They are in pairs in the neck, where the spine consists of two laminae. Here also they are well marked. In the dorsal region they are scarcely visible, and in the loins they are not easily distinguished from an interspinal ligament. They are analogous to the recti postici. They extend the spine. On the lips of the spinous processes of the neck some fibres may be shown, to which the name supra-spinal muscles has been given. They extend farther than from one vertebra to the next. The inter-transversales are similar fibres, scarcely to be demonstrated except in the neck, where they are in pairs, corresponding to the divided transverse processes. The multifidus spines consists of separate bundles of fibres, extending from each trans- verse process obliquely upwards and inwards to the spinous process of the vertebra next above, or sometimes to the second above. The first bundle runs from the side or transverse process of the sacrum to the spine of the last lumbar vertebra ; the last from the transverse process of the third cervical to the spine of the second. They are smaller as we ascend, and are not easily separated from the spinales and semi- spinales. They support the spine, and rotate one vertebra on the other slightly. In the article SPINE, the practical utility of a knowledge of the muscles of this extensive region will be demonstrated. For the BIBLIOGRAPHY of this article see that of ANATOMY (INTRODUCTION). (Charles Benson.) BILE. Syn. Gall. (Gr.^oXTj; Lat. bills; Fr. bile ; Ger. die Guile ; \\3\.jiele.j This im- portant secretion has been laboriously examined by several modern chemists of eminence, among whom we may especially enumerate Thenard,* Berzelius,f Tiedemann and Gmelin,J and Frommherz and Gugert. Their results, how- ever, are so much at variance, that it is impos- sible to draw any general conclusions from them respecting the real nature and chemical components of the bile ; these discrepancies seem partly to arise from the extreme facility with which chemical agents react upon this secretion, so that many of the supposed educts or component parts which have been enume- rated, are probably products of the different operations to which it has been submitted, or at all events modifications of its true proximate elements : it has been therefore well observed by Berzelius, that our present chemical know- ledge of the nature of bile can only be consi- dered as a foundation for the more extended and satisfactory researches of future experimen- talists. We shall here endeavour to select some of the least disputable and most import- ant facts respecting the chemical properties of the bile, remarking at the outset to those who may be inclined to repeat the experiments which we shall cite, that the indications of re- agents upon different specimens of bile are apt to vary, and that their action is often much modified by temperature, quantity, and the mode in which they are used. There always appears to be mixed with bile a variable proportion of mucus, probably deri- ved from the gall-bladder and its ducts, and not, therefore, a true component of the secre- tion : this gives the bile its viscidity, and often seems in some way to modify its other charac- ters: in general, however, (ox-gall,) it is a green liquid, varying much in tint, of a pecu- liar odour, a bitter and nauseous taste, and a specific gravity fluctuating between 1.020 and 1 .030. It does not coagulate when heated, and although it may possibly contain albumen, or something very like it, it is not immediately coa- gulated by alcohol or by dilute acids. The rela- tive proportion of solid matter obtained by evapo- ration is between eight and ten per cent. By means of acetic acid, the mucus which is mixed with the bile may to a great extent be separated. In the mammalia, generally, the bile exhibits nearly the same characters ; and in birds and fishes its components seem to be the same, but rather more dilute in the former and more con- centrated in the latter : it is always alcaline,from the presence of soda, apparently in the same state of combination as it exists in the serum of the blood. When bile is evaporated very care- fully to about half its bulk, and alcohol added, (in the proportion of about four parts to one of the evaporated bile,) a coagulated matter is thrown down, which has some of the proper- * Thenard, Memoires d'Arcueil, i. t Lehrbuch der Thierchemie. Dresden, 1831 ; and Medico-Chirurgical Transactions, iii. $ Uber die Verdauung (Essay on Digestion). Schweigger's Journal, v. 1. BILE. 375 ties of albumen; yet neither solution of corro- sive sublimate, nor of ferrocyanate of potassa, which are such delicate tests of that proximate animal principle in other cases, enables us to detect it in the original bile. When alcohol is added to bile which has been evaporated nearly to dryness, it acquires, when tillered off, a brownish green colour and bitter taste ; when evaporated, it leaves a residue which is almost totally soluble in water; and in this aqueous solution, dilute sulphuric acid slowly throws down a grey substance, which appears to be a compound of the acid and the bitter principle of the bile; when it has been washed with water (in which it is not soluble), it dissolves in alcohol, and if the sulphuric acid be then separated from it by carbonate of baryta and nitration, the filtered solution leaves on evapo- ration a green, transparent, bitter residue, which appears to be the characteristic princi- ple of the bile, and which Berzelius calls Gal- lenstoff'. As thus obtained, it is not quite free from foreign matters, and ether digested upon it takes up a little fatty matter ; indeed when bile, concentrated by evaporation, is agitated with ether, and the latter, after having separated upon the surface, is poured oft' and evaporated, it always leaves traces of a fatty substance, probably identical with cholesterine. The pu- rified bitter residue, to which we have just adverted, is apparently the picromel of Thenard; it has a bitter, pungent, and sweetish taste, is inflammable, deliquescent, soluble in water and alcohol, but insoluble in ether ; its solu- tion is precipitated by many acids, (not by acetic or phosphoric,) and the precipitate is nearly insoluble in water, of a greenish colour, resinous appearance, and fusible at 212. This precipitate (consisting of picromel combined with the acid used to throw it down) dissolves in alcohol, and is again thrown down by water : it dissolves in solution of acetate of potash, the alcali of which combines with the acid of the precipitate, whilst the acetic acid unites to the picromel to form a soluble acetate. Picromel dissolves in weak alcaline solutions apparently without decomposition. It will be seen from many of the above cha- racters, that picromel (by which we mean Ber- zelius's Gallenstoff) has probably been mistaken for albumen, and that it is not improbable that the only true albuminous part of the bile may be in that equivocal state which is often called mucus, and which is especially distinguished by being precipitable by acetic acid. Berze- lius has suggested an analogy between picromel and the peculiar saccharine matter which is contained in liquorice-root; and in many re- spects their chemical properties are identical. In the preceding statement, drawn princi- pally from Berzelius, we have endeavoured to give the simplest view of the analysis of the bile ; namely, the separation of its muco-albu- mcn by acetic acid or alcohol, and of its picromel, by precipitation with acids and subsequent decomposition of the precipitate by carbonated baryte or alcali; its saline contents appear closely to resemble those of the serum of the blood ; like which it has an alcaline reaction, due to soda. We have also selected such ex- periments, as, with us, have invariably suc- ceeded : the following results, therefore, of the analysis of the bile, as given by Berzelius, will now be intelligible. Water 90.44 Picromel, (Gallenstoff,) inclu- ding fat , . 8.00 Mucus of the gall-bladder .. 0.30 Extractive, common salt, and lactate of soda 0.74 Soda 0.41 Phosphate of soda and lime and traces of a substance insolu- ble in alcohol 0.1 1 100. The details of the other analyses of the bile as given by the authorities to which we have referred above, would be unintelligible if abridged, and are too voluminous, and too ex- clusively chemical, to be inserted here; and moreover, we have generally failed in arriving at satisfactory conclusions in our endeavours at a repetition of the various analytical operations which are described; we must therefore rest satisfied with giving, in a condensed form, a general statement of their results. According to Thenard, human bile contains, water 90.90 ; yellow bitter resin 3.73; yellow matter gene- rally diffused through the bile (mucus and colour- ing matter?) 0.18 to 0.90 ; albumen 3.82 ; soda, by which the resin is dissolved, 0.51; phos- phate, sulphate, and muriate of soda, phosphate of lime, and oxide of iron, 0.41. Tiedemann and Gmelin give the following as the compo- nents of human bile: 1. fat; 2. brown resin; 3. sweet principle of bile; 4. salivary matter; 5. mucus; 6. gall-brown (colouring matter?); 7. oleic acid, salts, and minute quantities of other substances, Frommherz and Gugert* have arrived at yet more complicated results: namely, 1. fat ; 2. resin ; 3. sweet principle; 4. osma- zome; 5. salivary matter (Speichelstoff); 6. ca- seum; 7. mucus; 8. margaric and other fatty acids, with phosphate, muriate, and sulphate of soda and potash ; and carbonate, phosphate, and sulphate of lime. The above, and other chemists, have published analyses of bile, taken after death in various diseases, but they present nothing very important. Tiedemann and Gme- lin's elaborate analysis of ox-gall deserves the perusal of all chemists concerned in such in- quiries : it contains, according to L. Gmelin,f a substance not to be found in any other bile, and which he has called Taurin or GailentiKpa- ragin : it may be obtained as follows : add muriatic acid to ox-gall and filter ; after a few days a fatty matter appears, which is separated by filtration ; the filtered liquid is evaporated to a small bulk, when it separates into two parts, a resinous mass and a sour fluid : the latter, upon further evaporation, yields more resinous matter, and at length crystals of com- * M. Scbweigger's Journal, vol. 1. p. 8. f L. Gmelin, Handbuch der Thcoretischen Cbe- mie, ii. 1012. Frankfurt, 1829. BLADDER, NORMAL ANATOMY, 376 mon salt and taurin, which are to be separated, and the latter purified a second by crystalli- sation. Taurin, when purified, is in prismatic crystals, neither acid nor alkaline, not altered by exposure to air, inodorous, of a peculiar taste : soluble in about fifteen parts of cold wa- ter, and nearly insoluble in absolute alcohol : it is fusible, and not decomposed by nitric acid. In concluding this subject, we must again express our conviction that many of the sup- posed proximate components of bile are pro- ducts of the various operations and re-agents to which it has been submitted, and that the ana- lysis of Berzelius, which is the simplest, is probably the most correct: from the uncertain operation of various precipitants upon bile, and from the facility with which the results vary, apparently in consequence of very trifling causes, there seems to be a peculiar tendency in its component parts to undergo hitherto unex- plained modifications. BILIARY CALCULI, or gull-stones. These concretions have been especially examined by Gren, Thenard, Fourcroy, and as to the fatty matter which they contain, by Chevreul.* Human gall - stones are, for the most part, composed of a crystalline aggregate of a species of adipocere, or as it has been termed by Chevreul, cholesterine, (from %o^j, bile, and vol. i, obs. 38. BLADDER, ABNORMAL ANATOMY. 390 scribed under the head : " Uretra in intestinum patens." Of the third species, cases are cited by Haller* and by Schrader.f In these cases there was no other malformation. In the foregoing enumeration we have purposely avoided the introduction of cases of general monstrosity in which the urinary bladder was absent. Plurality. There are upon record a certain number of cases in which two or more urinary bladders are said to have existed. Of these some appear to me to have been cases in which the plurality was maintained merely because the organ was divided into compartments, either as a consequence of arrested develop- ment or of the formation of pouches, by the protrusion, or hernia of the mucous membrane of the organ. The following case related by Blasius belongs, I apprehend, to the former species. A person died phthisical, having a " double bladder." When the external sur- face was examined, it appeared to be an unique organ, but upon being opened a membranous septum was discovered, by which the organ was divided into two distinct cavities. The narrator adds, that by dissection he separated the one from the other, so that the longitudinal septum was formed by the parietes of the two bladders, which were in contact, and had become united the one to the other. There is a case of a similar nature described by Brom- field; and many more are recorded by Mor- gagni and others. We know of no instance in the human sub- ject, with the exception of that related by Molinetti,J in which a plurality of urinary blad- ders distinct from each other existed. In this case there does not appear to have been any thing abnormal in the organisation except in so far as concerned the urinary organs. " A woman had five urinary bladders, as many kidneys, and six ureters, two of which were inserted into a bladder which was much larger than the others ! ! the remaining four ureters terminated in as many small bladders, which poured their urine by particular canals into the larger bladder." Another but less carefully described case of the same kind is mentioned by Fantoni, in his Anat. Corp. Hum. diss. 7; and in the Acta Physico-Medica Academiae Csesareae Nat. Curios, vol. i. obs. * Element. Physiologies, vol. vii. p. 297. t Nov. Ephem. Acad. cur. Nat. vol. i. obs. 38, et die 42, obs. 68. [The Editor has in his posses- sion the preparation of a female foetus which lived some days, where the ureters opened through the abdominal parietes on each side of the pubic region in the form of little pouches or sacs, in which was a continuation of their lining membrane. The urine, as it distilled from the kidney, accumulated in each of these sacs (in very small quantity, as they were incapable of containing more than a drop or two,) prior to its oozing out upon the raw cutaneous surface. This latter was deficient of cuticle for a surface about an inch and a half in diameter ; the pubic bones and the inferior fourth of the recti and tendinous expansions of the obliqui were absent. There was also only about an inch of large intestine (coecum). ED.] Dissert. Anat. Pathol, lib. vi. cap. 7. 83, may be found a well-marked case oi duplicity of the urinary bladder described by Zuinger, whose account is accompanied by a plate, which perfectly confirms the description ; but this case occurred in an ox. Septa. Occasionally, within the cavity of the bladder, more or less perfect septa are found, by which that organ is divided into two or more compartments. This condition is met with or occurs under two very different circum- stances: in one it is a congenital affection, and this it is our business to consider in this section ; in the other it is produced by and is not an uncommon consequence of retention of urine during extra-uterine life. In the de- scription of these two very dissimilar affections much confusion has occurred, in consequence of an almost universal impression that they were similar the one to the other. If the theory of the eccentric development of organs, proposed by Geoffroy St. IJilaire, and extended by M. Serres, be admitted, all difficulty in explaining this seemingly singular congenital phenomenon vanishes. M. Serres conceives that he has triumphantly established the fact, that the hollow organs, which are single and placed on the median line, are composed of two moieties, primitively distinct and sepa- rate; so that according to him, at a certain period of uterine life, there exist two aortas, two basilar arteries, two superior cavae, and so on. Now if there exist two vaginae, two bladders,