Digitized by the Internet Archive in 2015 https://archive.org/details/cyclopaediaofana1183todd THE CYCLOPAEDIA OF ANATOMY and PHYSIOLOGY, VOL. I. A D E A 1835-1836 THE CYCLOPAEDIA OF ANATOMY AND PHYSIOLOGY. EDITED BY ROBERT B. TODD, M.D. F.R.S. FELLOW OF THE ROT A L COLLEGE OF PHYSICIANS; PHYSICIAN TO KING’S COLLEGE HOSPITAL ; AND FORMERLY PROFESSOR OF PHYSIOLOGT AND OF GENERAL AND MORBID ANATOMY IN KING’S COLLEGE, LONDON, ETC. ETC. YOL. I. A DEA 1835—1836 15700 LONDON LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS. CONTENTS OF THE FIRST VOLUME Page Page Abdomen Dr. Todd 1 Bladder, Normal Ana- j Dr. Harrison .... 376 Absorption Dr. Bostock .... 20 tomy ............ Acalephse . Dr. Coldstream . . 35 Bladder, Abnormal | B. Phillips, Esq. . 389 Acids, Animal W.T. Brande, Esq. 47 Anatomy A nv! fn R. Owen , Esq. . . B. Phillips, Esq. . 47 49 Blood ............. Dr. Milne Edwards 404 Adhesion Blood, Morbid Condi- ) Dr. Babington .. 415 Adipocere W. T. Brande, Esq. 55 tions of the s Adipose Tissue Dr. Craigie 50 Bone, Normal Anatomy Dr. Benson 4"0 Age Dr. Symonds .... 64 Bone, Pathological I W.H. Porter, Esq. 438 Albino Dr, Bostock. ..... 83 Conditions of. ..... Albumen W. T. Brande, Esq. 88 Brachial Artery . Dr. Hart 465 Amphibia T. Bell, Esq 90 Bursae Mucosae Dr. Brenan 467 Animal Kingdom .... Dr. Grant ...... 107 Carnivora T. Bell, Esq. .... 470 Animal Dr. Willis ...... 118 Carotid Artery . Dr. Hart 482 Ankle, Region of the. . Dr. Brenan . . .... 147 Cartilage. .......... Dr. Benson 495 Ankle, Joint of the . . Dr. Brenan ...... 151 Cavity Dr. Todd 500 Ankle-joint, Abnormal j R. Adams, Esq. .. 154 Cellular Tissue R.D. Grainger, Esq. 509 Condition of the . . * Cephalopoda ....... R. Owen, Esq. .. 517 Annelida Dr. Milne Edwards 164 Cerumen W.T. Brande, Esq. 562 Anus R. Harrison, Esq. 178 Cetacea ........... Moils. F. Cuvier . . 562 Aorta Dr. Hart 187 Cheiroptera . T. Bell, Esq 594 Arachnida Dr. Audouin .... 198 Chyliferous System . Dr. Grant 000 Arm Dr. Hart 216 Cicatrix ........... A. T. S. Dodd, Esq. 002 Arm, Muscles of the. . Dr. Hart 219 Cilia. . Dr. Sharpey .... 600 Artery Dr. Hart 220 Circulation Dr. Allen Thomson 638 Artery, Pathological Conditions of . . . . ^ W. H. Porter, Esq. 226 Cirrhopoda Dr. Coldstream . . 683 Cirronosis Articulata R. Owen, Esq. . . 244 Conchifera . M. Deshay es .... 694 Articulation Dr. Todd 216 Contractility Dr. Alison ...... 716 Asphyxia Dr. Alison 257 Cranium . J. Malyn, Esq. .. 724 Aves R, Owen, Esq. . . 265 Cranium, Regions and | Dr. Todd 746 Axilla Dr. Benson 358 Muscles of the. . . . Axillary Artery Dr. Hart ........ 363 Crustacea ......... . Dr. Milne Edwards 750 Azygos.... Dr. Harrison .... 364 Cyst . B. Phillips, Esq. . 787 Back .............. 367 374 Bile W.T. Brande, Esq. Analytical Index. , , . 15700 * P 11 E F AC E. To collect a sei'ies 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 Cyclopaedia, 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, and 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 Cyclopajdia 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 the 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 Cyclopcedia. 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. 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. Duteochet, 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 hut 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 Cyclopcedia, hear 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 Cyclopaedia, 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 Eisher, an. 1832. PREFACE An important article on Animal Chemistry in this Cyclopmdia (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 OF THE CYCLOPEDIA OF ANATOMY AND PHYSIOLOGY. HUMAN ANATOMY, DESCRIPTIVE. Vol. Dr. Hart i. 219 Abdomen Dr. Todd . Ankle-joint Dr. Brenan . Aorta Dr. Hart..., Arm, Muscles ofv the J 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 Yagum ; 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 Fcetus Dr. Montgomery ... Foot, Bones and "i Joints of the j Dr. Todd Fourth Pair ofi ,T 1 Dr. Alcock Nerves J Generation, Or- -> T. Eymer Jones , "i gans of J Esq. J Glosso-pharyngeal | Page 1 151 187 Nerve j Hand, Bones and-) Joints of the J Dr. Reid. 246 363 364 37 6 465 482 724 1 65 154 171 235 267 268 316 Dr. Todd., ii. 338 ii. 370 ii. 406 ii. 494 ii. 505 Vol. Page Hand, Muscles of -| Bishop MacDou- the J gall | ii. 519 Hearing, Organ of T. TV. Jones, Esq ii. 529 Heart Dr. Reid ii. 577 Heart, Arrange- ment of the Fi- bres of the L Id. Searle, Esq. . . ii. 619 Hip-joint II. Hancock , Esq. ii. 776 Iliac Arteries Dr. Alcock ii. S27 Innominata Arteria H. Hancock, Esq. ii. 850 Kidney. See Ben. Knee-joint A. Higginson, Esq. iii. 44 Lachrymal Organs T. TV. Jones, Esq. iii. 78 Larynx J. Bishop, Esq. .. iii. 100 Leg, Muscles of. A. T. S. Dodd, Esq iii. 137 Liver E. Wilson, Esq. ... iii. 160 Mammary Glands S. Solly, Esq iii. 245 Mucous Membrane W. Bowman, Esq. iii. 484 Nervous Centres ... Ninth Pair of j Nerves J Dr. Todd iii. 712 G. Stokes, Esq. ... iii. 721 Nose J. Paget, Esq. iii. 723 GCsophagus Dr. G. Johnson ... iii. 758 Optic Nerves Dr. Mayne iii. 762 Orbit Dr. G. Johnson ... iii. 782 Pacinian Bodies ... IF. Bowman, Esq. iii. 876 Pancreas Dr. Hyde Salter... s. 81 Par Yagum Dr. J. Reid iii. 881 Pelvis John Wood, Esq. 5. 114 Penis E. Wilson, Esq. ... iii. 909 Perineum Dr. Mayne iii. 919 Peritoneum S. R. Pittard, Esq. iii. 935 Pharynx W. Trew, Esq. ... iii. 945 Pleura <5?. R. Pittard, Esq. iv. 1 Prostate J. Adams, Esq. ... b iv. 146 VOL. T. CLASSIFIED CONTENTS. Radial Artery Dr. Brinton Vol. iv. Page 221 Eadio-ulnar Arti- | culation J Dr. Brinton iv. 228 Eon Dr. Johnson iv. 231 Eespiration, Or- 1 gans of I Dr. Thos. Williams s. 258 Salivary Glands ... N. Ward, Esq. ... iv. 422 Scrotum Dr. Brinton iv. 438 Serous and Syno- | vial Membranes J Dr. Brinton iv. 511 Sesamoid Bones ... S. P. Pittard, Esq. iv. 541 Seventh Pair ofl Nerves J Dr. Brinton iv. 543 Shoulder-joint Dr. M'Dowel iv. 571 Sixth Pair of Nerves Dr. Brinton iv. 621 Spinal Accessory i Nerve / Dr. John Reid iv. 745 Spinal Nerves N. Ward, Esq. ... iv. 750 Spleen . Professor Kdlliker iv. 771 Stomach and In- ~| tcstinal Canal J Dr. Brinton s. 293 Vol. Page Subclavian Arteries Dr. M'Dowel iv. 814 Supra-renal Cap- a > Prof. Heinrich Frey iv. 827 SlllCS J Sympathetic Nerve Dr. Drummond ... s. 423 Temporo-Maxil- lary Artieula- l S. II. Pittard, Esq. iv. 937 tions J Testicle T. B. Curling, Esq. iv. 976 Thorax Dr. Hutchinson ... iv. 1016 Thymus Gland Dr. Handfield Jones iv. 1087 Thyroid Gland ... Dr. Handfield Jones iv. 1102 Tibio-fibular Ar- ticulations Tongue Dr. Hyde Salter ... iv. 1120 Urethra John Adams, Esq. iv. 1244 Uterus and its Ap-0 _ , , _ J Dr. Arthur Farre s, 545 pondages J Venous System ... Dr. M'Dowel iv. 1403 Vesicula Prostatica Prof. Leuckhardt iv. 1415 Vesiculx Seminales S. if. Pittard, Esq. iv. 1429 Wrist-joint Dr. M'Dowel iv. 1505 j Dr. M'Dowel iv. 1118 HUMAN ANATOMY, SURGICAL OR TOPOGRAPHICAL. Ankle. Eeaion of the Dr. Brennn i. 147 Fore- arm, Muscles'! Anus A. Holly, Esq ii. 361 P. Harrison, Esq. i. 173 and Regions of J Arm Dr. Hart i. 216 Glutxal Region ... A. T. S. Dodd, Esq. ii. 500 Axilla Dr. Benson i. 358 Groin, Region of the Dr. Todd ii. 503 Back i. 367 Hand, Eegions of ^ the J Bishop Mac Dougall Cranium, Eegions n. 523 and Muscles of > Dr. Todd i. 746 Leg, Eegions of the A. T. S. Dodd, Esq. iii. 126 the J Neck, Muscles and 4 J. Simon, Esq. ... Elbow, Region of the Dr. Hart ii. 62 Eegions of the J in. 561 Pace P. Partridge, Esq. ii. 207 Parotid Region ... Dr. G. Johnson ... iii. 902 Poot, Eegions and 1 Muscles of J A. T. S. Dodd, Esq. ii. 350 Popliteal Region ... TP. Trew, Esq. ... iv. 60 Scapular Region ... Dr. M'Dowel iv. 433 ANATOMY, GENERAL Adipose Tissue... .. Dr. Craigie i. 56 Artery .. Dr. Ilart i. 220 Bone j 4 3D Bursx Mucosal... .. Dr. Brenan i. 467 Cartilage i. i. 405 Cavity .. Dr. Todd 500 Cellular Tissue ... .. P.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 OR PHYSIOLOGICAL. Fibrous Tissue ... if. D. Grainger, Esq. ii. 263 Ganglion P.D. Grainger, Esq. ii. 371 Gland P.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 S J. A. Salter, Esq. iv. 1367 CLASSIFIED CONTENTS. ANATOMY, ABN OHM AL AND MON BID. Vol. Page Adhesion I>. Phillips, Esq.... i. 49 Ankle-joint , B. Adams, Esq. ... i. 154 Artery , W. H. Porter, Esq. i. 226 Bladder , B. Phillips, Esq.... i. 389 Blood Dr. Babington ... i. 415 Bone . IF. H. Porter, Esq. i. 438 Cicatrix . A. T. S. Dodd, Esq. i. 602 Cirronosis., Dr. Todd i. 694 Cyst B. Phillips, Esq i. 787 Elbow-joint . B. Adams, Esq. ... ii. 67 Foot . A. T. S. Dodd, Esq. ii. 347 Hand . B. Adams, Esq. ... ii. 510 Heart . Dr. Todd ii. 630 Hermaphroditism. . . Dr. Simpson ii. C84 Hernia . IF. II. Porter, Esq. ii. 738 Hip-joint . B. Adams, Esq. ... ii. 780 Vol. Page Hyperaemia and Anosmia Hypertrophy ando ^ _ ,, •u 1 J Da Todd ii. 826 Atrophy J Knee-joint B. Adams, Esq. ... iii. 48 Larynx IF. H. Porter, Esq. iii. 114 Lymphatic System Dr. Todd iii. 232 Nervous Centres ... Dr. Todd iii. 712 J Dr. Todd ii. 825 Products, Adven- ' titious . Dr. Walslie . 71 Shoulder-joint B. Adams, Esq. ... iv. 577 Softening and In- ■) duration I Dr. P. M. Duncan iv. 703 Teratology Professor Vrolik ... iv. 942 Wrist-joint B. Adams, Esq. ... iv. 1508 ANATOMY", COMP AH ATI YE. Chyliferous System Dr, Grant i. 600 Osseous System .. Prof. B. Jones .. . iii. 820 Digestive Canal ... Dr. Grant ii. 27 Shell Dr. Carpenter .... 556 Lymphatic and j £ Lane, Esq. ... iii. 205 Teeth Professor Owen . . iv. 864 Lacteal System J Tegumentary Or- Muscular System... Prof. B. Jones ... iii. 530 gans (Hair, Nails, - T. Hurley, Esq. .. . s. 473 Nervous System ... J. Anderson, Esq. iii. 601 Feathers, &c.) ZOOLOGICAL ANATOMY AND PHYSIOLOGY. Acalephae Dr. Coldstream ... i. 35 Insectivora .. T. Bell, Esq ii. 994 Acrita B. Owen, Esq. ... i. 47 Mammalia . . Professor Owen ... iii. 234 Amphibia . T. Bell, Esq i. 90 Marsupialia .. Professor Owen ... iii. 257 Animal Kingdom Professor Grant i. 107 Mollusca .. Professor Owen ... iii. 363 Annelida Dr. Milne Edwards i. 164 Monotremata .... .. Professor Owen ... iii. 366 Arachnida Dr. Audouin . i. 198 Myriapoda .. Prof. B. Jones ... iii. 545 Articulata Professor Owen ... i. 244 Pachydermata .... .. Prof. B. Jones ... iii. 858 Aves . B. Owen, Esq. ... i. 265 Pisces .. Prof. B. Jones ... iii. 955 Carnivora T. Bell, Esq i. 470 Polygastria .. Prof. B. Jones ... iv. 2 Cephalopoda . B. Owen, Esq. ... i. 517 Polypi fera .. Prof. B. Jones ... iv. 18 Cetacea M. F. Cuvier i. 562 Porifera .. Prof. B. Jones ... iv. 64 Cheiroptera . T. Bell, Esq i. 594 Pteropoda .. Prof. B. Jones iv. 170 Cirrhopoda . Dr. Coldstream ... i. 683 Quadrumana .... .. Professor Yrolilt iv. 194 Conchifera . M. Deshayes i. 694 Reptilia .. Prof. B. Jones ... iv. 264 Crustacea . Dr. Milne Edwards i. 750 Rodentia .. Prof. B. Jones iv. 368 Echinodermata. . . . . Dr. Sharpey ii. 30 Rotifera . . Dr. Lankester iv. 396 Edentata . T. Bell, Esq ii. 46 Ruminantia j" Dr. T. Spencer \ s. 506 Entozoa . Professor Owen ... n. 111 \ Cobbold Gasteropoda .... .. T. B. Jones, Esq. ii. 377 Solipeda .. Prof. B. Junes ... iv. 713 Insecta . G. Newport, Esq. ii. 853 Tunicata .. Prof. B. Jones iv. 1 185 CLASSIFIED CONTENTS. PHYSIOLOGY. Absorption Dr. Bostoch Vol. i. Page 20 Age Dr. Symonds i. 64 Albino Dr. Bostoch i. 83 i. i. 118 Asphyxia Dr. Alison 257 Circulation Dr. Allen Thomson i. 638 Contractility Dr. Alison i. 716 Death Dr. Symonds i. 791 Digestion Dr. Bostoch ii. 6 Dr. Brenun ii. 55 Electricity, Animal Dr. Coldstream ... ii. 81 Endosmosis Dr. Dutrochet ... ii. 98 Generation Dr. Allen Thomson ii. 424 Hearing Dr. Todd ii. 564 Heat, Animal Dr. W. E. Edwards ii. 648 Hibernation Dr. Marshall Hall ii. 764 Instinct Dr. Alison iii. 1 Irritability Dr. Marshall Hall iii. 29 Life Dr. Carpenter iii. 141 Luminousness, Dr. Coldstream ... iii. 197 Animal J Motion, Animal; including Loco- > J. Bishop, Esq. ... iii. 407 motion -> Vol Page Muscular Motion... W. Bowman, Esq. iii. 519 Nervous System ... Dr. Todd iii. 720 g. Nutrition Dr. Carpenter iii. 741 Ovum Dr. Allen Thomson s. 1 Parturition Dr. Bigby iii. 904 Pulse Dr. Guy iv. 181 Reproduction, Ve- , getable (Vege- table Ovum) J Dr. J. B. San- 4 derson j s . 211 Respiration Dr. John Beid ... iv. 325 Secretion Dr. Carpenter iv. 439 Sensation Dr. Todd iv. 508 Sensibility Dr. Todd iv. 510 Sleep Dr. Carpenter iv. 677 Smell Dr. Carpenter iv. 697 Symmetry S. B. Pittard, Esq. iv. 845 Sympathy Dr. Todd., iv. 852 Taste Dr. Carpenter iv. 856 Temperament Dr. Todd iv. 935 Touch Dr. Carpenter iv. 1163 Varieties of Man- ) kind J 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. Branch, Esq. i. 47 Adipocere W. T. Brunde, Esq. i. 55 Albumen W.T. Brande,Esq. i. 88 Blood Dr. Milne Edwards i. 404 Bile W. T. Braude, Esq. i. 374 Cerumen W. T.Brande, Esq. i. 562 Bat W.T1. Branch, Esq. ii. 231 Bibrine W. T. Braude, Esq. ii. 257 Gelatin W. T.Brande, Esq. ii. 404 Ilaematosine Dr. G. O. Bees... ii. 503 Milk Dr. G. O. Bees ... iii. 358 Mucus Dr. G. O. Bees ... iii. 481 Organic Analysis... Dr. Miller iii. 792 Protein Prof. J.E. Bowman iv. 162 Saliva Dr. Owen Bees ... iv. 415 a f Drs. Wanner and' 1 . L Leuckhardt J Sweat Dr. G. O. Bees ... iv. 841 Synovia Dr. G. O. Bees ... iv. 856 Urine Dr. G. O. Bees ... iv. 1268 GENERAL SUBJECTS. Medical Statistics .... Dr. Guy iv. 801 | Microscope Dr. Carpenter. Vital Statistics Dr. Guy iv. 1469 iii. 331 THE CYCLOPAEDIA OF ANATOMY AND PHYSIOLOGY. ABDOMEN, (in anatomy,) with which the terms venter and alvus are sometimes used synonymously. Gr. yccur'/iq- Germ, bauch, un- terleib, hinterleib. Ital. ventre , panda, abdo- mine : the French anatomists use the word abdomen as we do, and also the term ventre as we do belly ; also bas-ventre. It is so called, “ quod abdi et tegi soleat, aut quod alimenta in eo abdantur, aut intestina ibi sint ubdita.”* The term denotes a particular region and cavity in a large proportion of the animal series, being found in most of the classes from Mam- malia down to Articulata. It is impossible to give such a definition of this region as will apply to all ; it appears, however, to have one property sufficiently general, viz. that it con- tains in all these classes more or less of the digestive organs. Thus, to ascend from the Articulata : — It is in the class Insecta of the Articulata that we find the most defined region bearing this name. This region is the most posterior of the three portions into which the body of an insect is divided, and is composed of a series of seg- ments which unite to form a cavity enclosing the viscera subservient to nutrition, respiration, and reproduction ; it does not contain any of the organs concerned in locomotion. It is com- posed of a series of simple hoops, united to each other by a ligamentous connexion, which allows the abdomen to be flexible or otherwise, according to the closeness of the union .f The abdomen is united by its anterior extremity to * Facciolati, in verb. t See a very good engraving from Cams, of the segments of an insect, in Roget’s Bridgewater Trea- tise, vol. i. p, 321. VOL. "I. the thorax. (See Insecta.) In the Arachnida there is also a similar division of the body, to which the name of abdomen has been applied, united in front with the cephalo-thorax, and separated from it by a deep groove, which leaves only a slender pedicle between them ; like that of the Insecta it contains the principal viscera. (See Arachnida.) In all the divisions of the Vertebrata there is an abdomen. In fishes the abdomen is situated towards the posterior extremity of the body, and is separated from the heart in front by a strong membrane analogous to the diaphragm ; it contains the digestive and generative organs. In reptiles the abdomen is that region which lies immediately anterior to the anus ; in many classes it is not separated from the cavity con- taining the lungs, so that the lungs, heart, organs of digestion and generation are all con- tained in one great cavity ; in the crocodile, however, a layer of muscular fibres, having the appearance of a diaphragm, covers the perito- neum, where it is connected with the liver, so that the lungs do not project into the abdomen. In birds, the abdomen extends from the posterior extremity of the sternum to the anus ; it is, as in fishes, separated from the thorax by a mem- brane which, though not muscular, is analogous to the diaphragm, but is perforated so as to allow the air to pass into the abdominal cells. In Mammalia, the abdomen is placed between the pelvis and thorax, with the former of which it is continuous ; but it is separated from the latter by the diaphragm ; its principal contents consist of the digestive organs, and its size varies in reference to their respective degrees of development. n 2 ABDOMEN. ABDOMEN (in human anatomy.) In ex- amining the human skeleton, we notice that from the apex of the thorax to the inferior out- let of the pelvis, there exists one great oblong excavation. The two superior fifths of this cavity are separated from the remaining portion in the entire subject by a musculo- tendinous lamella, which, thrown into a vaulted form, constitutes the partition between the cavity of the thorax above and that of the abdomen below. This latter cavity communicates inferiorly with the space circumscribed by the ossa innominata, denominated the cavity of the pelvis; nor is there any natural line of demarcation between the two cavities. The communication between the two cavities is as free in the recent subject as it is in the skeleton, and under various con- ditions the contents of those cavities pass from the one to the other. A plane extended hori- zontally from the linea iliopectinea on one side to the corresponding line on the other would constitute an artificial floor to the cavity of the abdomen, properly so called, and a limit be- tween it and the pelvis; and this artificial divi- sion of a cavity, naturally single, may be useful in describing the positions of viscera, but to understand the functions of the abdomen, it will be expedient to consider that cavity and the pelvis as one. Some anatomists ob- ject to the use of the term cavity as applied to the abdomen, because no cavity can be said to exist, except in the skeleton or in the evisce- rated subject; neither can there properly be said to be a cavity of the thorax or of the cra- nium, inasmuch as that cavity is obliterated so long as the viscera are in a stale of integrity. I apprehend that the objection is hypercriti- cal, as it must be evident that the cavity does not become apparent till the viscera have been removed ; nevertheless, it is perfectly correct to say that it contains the viscera, nor is it in- correct to make use of the expression “ anatomy of the abdominal cavity,” to imply the anatomy of its contents when in their natural position. Hence, then, we derive a natural subdivision, in treating the subject of this article, into two heads : 1. the anatomy of the walls of the abdomen; and, 2. the anatomy of the cavity of the abdomen. I. Of the walls of the abdomen. — One of the most striking differences between the abdomen and the other great visceral cavities consists in the small proportion of bone that exists in its walls. The osseous boundaries of the abdomen may be thus enumerated : superiorly, towards the posterior and outer part, the false ribs; posteriorly, the lumbar region of the spine, which by its transverse processes affords strong points for the attachment of muscles, and by the bodies projects into the cavity, forming an imperfect septum, slightly convex on its anterior surface, and dividing the cavity into two symmetrical portions. Inferiorly, the alae of the ilia afford lateral expansions, which support some of the contents of the abdo- men, and the pelvic brim completed behind by the promontory of the sacrum, forms the opening by which the cavity of the true pelvis communicates with that of the abdomen. Between the inferior margin of the thorax and the superior margin of the false pelvis are stretched muscular lamellae and tendinous ap- oneuroses, the cingulum abdominis rnusculoso- aponeuroticum of Albinus and Haller, which, with integument, cellular membrane, &c. form the anterior, lateral, and for the most part the posterior walls of the abdomen, and circum- scribe that space to which we have already alluded under the name of the cavity of the abdomen. The superior wall of the abdomen is the diaphragm, and the inferior wall of the abdo- men, strictly so called, is formed by the ilia and their muscles, and is open in the centre at the superior outlet of the pelvis; but if the abdominal and pelvic cavities be considered as one, then those parts which fill up the inferior outlet of the latter must be considered as likewise constituting the inferior wall of the former. In the male adult the abdomen presents an expanded convex surface anteriorly (the ante- rior wall or proper abdominal region ) ; poste- riorly a broad surface not so extensive, situated between the last ribs and the superior margin of the pelvis, and divided into two by the lumbar portion of the spine (the posterior wall, the loins, or lumbar regions.) The anterior and posterior walls are connected with each other on the sides by two narrow regions (the lateral walls or the flanks.) The outline of the anterior wall or pro- per abdominal region constitutes an oval, whose long axis is vertical. The surface is generally more or less convex during life, proportionally with the degree of embonpoint of the indivi- dual, and also according to the condition of the diaphragm. After death, excepting in very fat subjects, or where the intestines or peritoneal cavity are much distended from any cause, this surface is in a variable degree collapsed, and more or less concave, but especially so in very thin and emaciated subjects. There is a con- stant adaptation in the condition of this surface to that of the abdominal viscera, so that the practitioner can in general argue pretty accu- rately, from the state of the abdominal surface, respecting that of the abdominal viscera, ex- cept in cases where every thing is masked by a superabundant deposition of adipose substance. So close is the apposition of the abdominal wall to the surfaces of the subjacent viscera, that in some cases of extreme emaciation the peristaltic movement of the intestinal canal is manifested by the successive elevation and depression of small portions of the walls corresponding to the dilated and contracted portions of intestine. This surface is divided into two equal and symmetrical portions by a groove which exists along the middle line, and which is chiefly ap- parent in the two superior thirds. This groove commences below the ensiform cartilage, where there is a slight depression, denominated the scrobiculus coi'dis, (creux de l’estomac.) In this line, about midway between the pubis and xiphoid cartilage, is the round depression called the umbilicus or navel. Just over the pubis there is a prominent surface in both sexes covered ABDOMEN. 3 with hair ; in the female it is much more pro- minent than in the male, and is called the mons Veneris. In subjects where the muscular sys- tem is well developed, there exists on each side of this median groove an oblong convexity, ex- tending from the anterior surface of the lower part of the chest to the pubis ; these convexities indicate the situation of the recti muscles. In statues representing athletic men, the promi- nences occasioned by these muscles are gene- rally very well shewn, and are divided by trans- verse superficial digressions into small qua- drilateral portions, generally three in number. External to these prominences there is, in similar muscular subjects, a fissure extending from the border of the chest, in a slightly curved course with external convexity, to a point a little to the inner side of the anterior superior spine of the ilium ; this fissure has internal to it the prominence from the recti muscles, and external that from the broad muscles of the abdomen. Gerdy calls it the lateral groove or furrow of the abdomen.* (See Jig. 1.) ' The posterior wall or the region of the loins, ( lumbar region ,) is in every way of less extent than the anterior. Its vertical height is equal to the distance between the last rib and the margin of the ilium. It is continuous on the sides with the flanks, and is divided along the middle line by a groove, corresponding to the lumbar spinous processes, into two symmetrical portions, each of which forms a large and pro- minent relief. Each relief corresponds to a great muscular mass, which almost wholly oc- cupies this region, and its prominence is greatest when those muscles are in a state of contrac- tion, as during the erect posture. Each relief is concave from above downwards, and in a degree directly proportionate to the contrac- * Gerdy, Anatomie des FormesExterieures, p.189. The above engraving is reduced from the folio plate? which accompany this work. 4 ABDOMEN. tion of the muscles, insomuch that in some in- dividuals the concavity is habitually very con- siderable, as in those who carry burdens on the head or in front of the body, in pregnant wo- men, &c. (See Jig. 2.) The limit of this wall on each side is indicated by a groove or fissure which passes obliquely upwards and outwards towards the ribs, and corresponds to the outer margin of each relief, or that of the lumbar muscles ; these lines also indicate the posterior limits of the lateral walls of the abdomen, or the flanks. Anteriorly the flank of each side is continuous with the anterior wall of the abdo- men ; above it is limited by the margin of the thorax, and below by the margin or crest of the ilium. It is concave on its surface from above downwards, (except in cases of great embon- point, where the concavity is obliterated,) and convex from before backwards. Gerdy remarks that in subjects in which the muscles have a considerable development, a relief is formed just above the crista ilii by the broad muscles of the abdomen at their insertion into this osseous border. Upon antique statues this relief is in general made too prominent. The anterior or proper abdominal region has been subdivided into smaller compartments, with a view to facilitating descriptions, patho- logical or otherwise. This subdivision is com- pletely arbitrary, and therefore some differences will be found among the various anatomical authors as to the precise limits of each region. That which is here subjoined, however, appears to be pretty generally agreed upon in this country. Lines connecting particular points drawn upon the surface, mark out these subdi- visions, and if planes be supposed to be carried from these lines horizontally backwards to the posterior wall, the cavity of the abdomen will thus be divided into segments, each of which has its particular portion of the abdominal viscera. It is an instructive exercise for the student to practise himself in examining the particular viscera which correspond to particu- lar regions. We are thus enabled, as Blandin has remarked,'* to resolve the problem, “ a point of the surface of the abdomen being wounded deeply in a given direction, to de- termine what organs have been injured ; and reciprocrally, an organ having been wounded in a particular part of the abdominal cavity by a sharp instrument, which entered in a given direction, to determine what part of the abdominal walls must necessarily have been injured.” f The limits of these several regions or com- partments may be thus indicated :J let aline be drawn horizontally from the extremity of the last rib on one side to the same point on the other, and let another line parallel to the pre- ceding be drawn between the two anterior superior spinous processes of the ilium : the * Anatomie Topographique, p. 423. t The division of the surface of the abdomen into regions is as old as Aristotle. t See an engraving exhibiting these subdivisions, in the article Abdomen of the Cyclopaedia of Practical Medicine. abdominal surface is thus divided into three great regions, each of which is subdivided into three by means of a vertical line let fall on each side from the anterior extremity of the seventh or eighth rib to a point a little external to the spine of the pubis. Nine regions are thus marked out, the relations and boundaries of which may be described as follows. The superior region, or that above the first horizontal line, is the Epigastrium, which name it derives from its close relation to the stomach ; (etti, upon, over; ycio-rrig, 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 (vtto, under, 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, (vrro, beneath, 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 infenorly 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 the most common forms of hernia.* (See Gkoin, 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 filamen- 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 zone 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 umbo, 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, f 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 lamina, 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 fibro-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 Beclardj- 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 ;+ 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 partakes 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 l’Abdomen, p. 11. t Diet, de Medecine, art. abdomen. | Vid. Blandin , Anat, Topog. B 2 4 ABDOMEN. below and carrying it upwards ; tbe 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, j- 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 glutteal 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 lamella 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 internus; 3, trans- versalis; 4, rectus abdominis ; 5, pyramidalis, which last is frequently absent. 1 . Obliquus externus. ( Obliquus descen- dens ; costo-abdominal ; iliu-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 VVishart, p. 22; also Todd on Hernia, Hub. Hosp. Reports, vol. i. p. 246; and Flood’s plates of Inguinal and Femoral Hernia. f Camper, leones 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. 5 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 Gimbemat's 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-pubienne 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 w'ithin 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 the 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 hernias 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 glutsei, 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. G 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. Obtic/uus interims (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 ofPoupart’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 laminse, 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 laminse going to be inserted into the ensiform cartilage and linea alba, the one in front, the other behind, the rectus muscle. (S eefig. 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 divrdes into two laminre,the aponeurosis of the obliquus externus and that of the transversalis 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 the 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 (x.^[xctu, 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. 7 Fig. 3. c, tlie internal oblique ; e, the descending fibres ; f, 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 aloDg 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 aponeurotic lamella after the manner of the digastric muscles. In general the external bundle is larger than the internal, but Cloquet has seen the reverse three times; and on referring to my notes, I find I have seen two instances in which the internal bundle exceeded the external in size. Many anatomists have noticed 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 totbeexternal abdominal ring. Hereit 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, lutnbo- 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. a i * “ The obliquus internus corresponds to the in- ternal intercostals by the direction of its fibres, by its being situated under cover of the obliquus externuSy and because its fleshy fibres extend much further forwards than those of the last-named mus- cle.”— Meckel. 8 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 ofthe quadratuslamborum and the commencement of the fleshy fibres of the muscle, extending vertically from the last rib to the crista ilii. ( Fig. 4, l.) 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 J'uscia 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, li); 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, j). 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 Pou part’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 external 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 th e folded jibres 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 (sterno-pubien). 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. f “ 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.” — Meckel. ABDOMEN. 9 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 linee 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.— Wirnluw. They are, says Meckel, incontestably 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 vesicre 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 integuments 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 ot the umbilicus, which apparatus does not exist at the inguinal ring or femoral arch.”* In the fcetus 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. ABDOMEN. 10 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 transversalis 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 certainly not a rare occurrence. which lies immediately before it, are seen through it. This muscle is the Quadratics 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 vertebra: 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 vertebra. 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, lurnbus ) ( prelombo , trochanterien, lunibaris.) 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 vertebra- 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 ramus of the pubis. It descends over the capsular ligament of the hip- * See fig. 4 , f ; see also fig. 5, where on one side the muscle has been removed from between the lamina; 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 vertebras ; this expansion, the arcus interior of Senac and Haller,* also called ligamentum arcuatum, 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 interiorly. 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, tom. 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 space 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 that 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 oeso- 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- terna} 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 the 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 eircumflexa 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 arcuatum, 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‘ Whinnie. 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 sheath 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. Colies 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 crurule. 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 hernise, 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 Colies’ 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 margiu, 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 herniae ; 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 oesophageal 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 oesophageal 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 crus 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 tlie 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_/as«’a iliuca, 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 vesicre 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 vertebra, 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, leones cavitatum thoracis et abdominis a tergo apertarum. Leipzig, 1789. ABDOMEN. 15 wall of the inguinal canal between the two rings ; it is distributed in the integuments and fasciaof 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 semdunaris. 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 hernite, 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- 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 the iliacus 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, obstruction-)- 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 inferior vena cava from the pressure of an aneurismal tumour observed by Reynaud. Journal Hebdom. de Med. vol. ii. p. 110. Diet, de Mcdecine, art. Abdomen. 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 port®. 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 port®. 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 tbegenito- 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 Manec, Dissertation inaugurale. Paris, 1826. t Diet, de Med. art, Abdomen . to the ribs, the vertebra, 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 viribus atque aliquando vomitum perficere. Plerumque tamen irrita- tionem in ventriculo natam et sensum summae anxietatis, quae vomitum praecedunt, facere ut ad levandam aegrimoniam vires diaphragmatis et musculorum abdominis excitatae atque mo- lestiam de liomine amoliturae, vomitum per- * Vide Haller, Elementa Physiologite, t. vi. sect. iv. § xiv. VOL. I. ficiant. Unde neque a solri voluntate in pie- risque eerte mortalibus vomitus cieri potest neque a sola absque voluntate natura — Quare recte conjunctas vires ventriculi et organorum respirationis Cl. Viri fecerunt. Et videtur dia- phragma etabdomen plusvirium habere, quando ventriculus aut cibis repletus est, aut clausis ostiis distentus : tunc 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 and 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 tleves 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- ologie par Ecrard, art. Digestion, § xxiv. t Medical Quarterly Review for April, 1835. p.100. c 18 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- temi,) 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 sinistiad 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 the aponeuroses of those muscles are connected. Another use has been assigned to these intersections by Bertin, 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 { fig. 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 vertebrae very * Berard, loc. cit., et Bertin, sur l’usage des enervations des muscles droits du bas-ventre, in Mem. dc TAcad. 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 19 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 fetus theabdomen is proportionallylarger 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,andthepancreas: 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 fetus 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 will 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, lioyer, Portal, Bichat, Meckel, Cloquet, Maijolin, 11 ildcbrandt , &c. for the titles of whose respective works see the Bibliography of A N ATOM Y, Introduction. ) — Velpeau, Anat. Chirurgicale. Paris, 833. t. ii. Blandin, Anat. Topographique. Cm- veilhier, Diclionnaire de Med. et Chirurg. art. Abdo- men. Beclard et Berurd, Diet, de Mcdecine. 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 l’Abdomen, or the trans- lation by McWhinnie. Load. 1835. Scaipa, on Hernia, by Wishart. Lawrence on ditto. Todd, on ditto. Dub. IIosp. Reports, vol. i. Flood’s plates of Inguinal and Femoral Hernia. Lond. 1834. Cam- per, leones Herniamm. Guthrie, on Inguinal and Femoral Hernia. A. Cooper, on ditto, and on the Testicle. Manec, Dissertation Inaugurale sur l’Her- nie.1826. Colies’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 einsuugung, 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. cup. 19 ; An sanguis in arteriis &c. cap. 5. parts of the absorbents had been seen by Erasistratus and Ilerophilus, 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. ft 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. J 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 9 “ 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. f 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 Horne 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 ABSORPTION. 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 Joliffe distinctly re- cognized and exhibited the lymphatics of many of the abdominal viscera, previously to the alledged discovery of either Rudbek or Bar- tholin.-}- But even if we allow Joliffe 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., and 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 ; Bibl. Anat., t. i. §. 378 and 415; and Not. 4. ad £.121. Iloer. Prael. 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. f For the most original and correct description of the lacteals, the reader is referred to Haller, El. Phys, xxv. 1. 4 . . 8 ; Mascagni, Vas. Lymph. Corp. 21 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 carry 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 Lymphaticisg Hew7- 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 EUiotson’s Physiol, ch. 9. p. 140 . .2, we have a "short account of the first discovery of the absorbent system.” Soemmer- 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 et 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 ordinary 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. f See Ciiyliferous System; Lac- teal. * 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, t. i. p. 185, does not admit their existence; 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,” Diet, 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. lxxxiv. p. 499 et seq. Similar observations were after- wards made by Valentin, t. lxxxvi. p. 231, et seq. ; this action was not, however, supposed to depend on contractility. Wrisberg informs us that be has frequently seen spasmodic contractions in the large vessels and 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. 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 subclavian 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 Magendie, 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. ; Bolius 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. t 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. 1Q< TO-T V b ’ 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 glands} 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 et seq., and Magendie, Journ. t. i. p. 21. t Some of 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 Ins been doubted by some anatomists; see Hewson, pt.2. p. 44, 5. § See Fleming’s Zool. t. i. p. 338 ; Blumenbach’s Comp. Anat. by Lawrence, ch. xiii. p. 256 ; Diet, des Sc. Med. art. “ Lymphatique,” par Chaussier et Adelon, p. 249 ; Breschet, art. “ Lymph. Syst.,” Diet, de Med. t. xiii. p. 397. Hewson in- forms us that birds have lymphatic glands in the 24 ABSORPTION. glands,' * the moderns hare 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 question 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. J 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. + 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 ; Bedard, 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 ; Boyer, Anat. t. iii. p. 243 . . 257 ; Mascagni, ps. i. sect. 5. p. 31 ; Rullier, ubi supra, p. 120 et seq. ; Breschet, ubi supra, p. 394. For plates of the glands, see Mas- cagni, tab. 1 . fig. 8 . . .12, tab. 2. fig. 4 . . 8, tab. 4. fig. 2. tab. 8, 16, 26; Cruikshank, pi. 3; Sheldon, tab. 3, 5. f Bocrhaave, Praelect. § 103. and § 247 ; Haller, in not. 1. ad §106, Boerhaave, Pradect., and not. 1. ad § 245 ; also El. Phys. ii. 1.28; Monro secun- dus. Do Ven. Lymph., p. 14 . . 21 ; Walter, sur la Resorption, Nouv. Mem. Berlin, pour 1786.. 7, §15 et seq. ; Magendie, Physiol, t. ii. p. 238. experiments referred to consisted in passing injections from the veins to the absorbents, or the reverse, thus proving, as was supposed, that a direct connexion subsisted between these vessels. They were performed by the most skilful anatomists of the age, and were gene- rally acquiesced in, without either the accuracy with which they were conducted, or that of the conclusions deduced from them, being ever called in question. Another class of experi- ments consisted in passing ligatures round the thoracic d uct, so as to render it impervious to the passage of the chyle, when it was supposed that under these circumstances the nutrition of the animal was not interrupted,* and the same conclusion appeared to be substantiated by various cases of natural obstruction of the duct, or by certain malformations of the part, where it was either defective, or did not convey its contents, in the ordinary manner, into the veins. The other set of arguments, which are more purely anatomical, were derived from the supposed fact that various parts of the body, which were evidently subject to the operation of absorption, were without lymphatics, and that this was likewise the case with large classes of animals, the general structure of which, as far as regards their growth and nutrition, was analogous to that of the mammalia. Admitting these data, it seemed to be a necessary conse- quence that absorption must in these instances be performed by the veins, and hence it was inferred that in all classes of animals, and in all parts of the body, the veins co-operated with the lacteals and the lymphatics in the function of absorption. The doctrine of venous absorption was first formally called in question, nearly at the same time,f by Wm. Hunter and by Monro se- cundus,J who, as it would appear, to a certain extent, entered upon the investigation inde- pendently of each other. The priority of dis- covery in this, as in so many points connected with anatomy, was for a long time the subject of warm controversy. We may remark con- cerning this question, that if the judgment of the present age should incline to ascribe to Hunter the original conception of the hypo- thesis, it is also disposed to allow to Monro the merit of establishing his opinion by a skilful and laborious process of experiment and observation. The method which these illustrious rivals adopted was, first, to repeat the experiments of their predecessors, when, by noticing with scrupulous accuracy all the circumstances con- nected with them, they were able to demon- strate, or at least to render it highly probable, that in all those cases where injections had passed between the absorbents and the veins, either rupture or extravasation had taken place, and that, when this was carefully guarded w Some experiments of this kind are referred to by M. Majendie, as having been performed by M. Dupuytren, Physiol, t. ii. p. 167. See also Ri- cherand, Siemens de Physiologie par Berard. t Medical Comment., passim ; Cruikshank, In- trod.; Walter, § 10 et seq. f Dissert, de Sem. et Test, in Smcllie, Thes. t. ii. and De Ven. Lymph. Valv. ABSORPTION. 25 against, the supposed connexion between the two sets of vessels could not be demonstrated.* In those experiments, where the thoracic duct had been artificially obstructed, or in the cases where the same thing had occurred as the result of disease or malformation, they were enabled to detect some supplementary vessels or some indirect channel, by means of which the chyle had been conveyed to the veins. With respect to the parts of the body, or to the animals of an inferior order, which were supposed not to be furnished with ab- sorbent vessels, by prosecuting their examina- tion with more care they gradually detected the existence of these vessels in many cases where they had not been previously known to exist ; and they were discovered in so many new situations that it became a fair inference that every part of the body, and every animal whose structure is generally analogous to that of the mammalia, is provided with an appropriate apparatus of absorption, although, from the texture or the peculiar nature of the vessels, it may be very difficult actually to demonstrate their existence. In this train of investigation the labours of William Hunter and Monro were ably seconded by various anatomists, both in this country and on the continent, among whom we may select the distinguished names of John Hunter, Hewson,f Cruikshank, and Mascagni. * We must, however, bear in mind that we have the high authority of Meckel in favour of the com- munication between the lymphatics and the veins ; “ Sur Resorption,” Nouv. Mem. Acad. Berl. ann. 1770, p. 19 et seq. The researches of some of the most accurate among the anatomists of the present day seem also to show that occasional communications exist be- tween some of the lymphatics and the contiguous veins; but this is a different kind of relation from that which was contemplated by the older anatomists between the sanguiferous and the absorbent systems. This point is fully discussed by Fohmann, in his late work, “ Sur le commun. des vaiss. lymph, avec les veins,” where we have an account of his own observations, as well as those of preceding anatomists ; he conceives that the observations of Lippi, of which an account is given in his “ Illus- trazioni fisiol.”, are not correct : see also the remarks of Antommarchi, Ann. Sc. Nat. t. xviii. p. 108, 9. The observations of Fohmann have been confirmed by Lauth, in his “ Essai sur les Vaisseaux Lymph.” We may here refer to the observations of Bleuland, which were made fifty years ago, on what he styles the arteriolas lym- phaticae, by which a communication was supposed to be maintained between the sanguiferous and absorbent systems; see his “ Experim. Anat.” Panizza of Pavia also opposes the doctrine of Lippi ; Osservazioni, c. 3 and 5. Mr. Abernethy, in examining the vascular system of the whale, discovered certain communications between the sanguiferous and the lymphatic vessels ; but the nature of the connexion is perhaps a little doubtful ; Phil. Trans, for 1796, p. 27 et seq. For further information on this subject, see a lecture on the lymphatic system lately published by Dr. Graves. Mr. Kiernan, in his elaborate researches into the anatomy of the liver, gives it as his opinion that the doctrine of Lippi has been ‘ ‘ satisfactorily con- futed ” by Panizza ; Ph. Tr. 1833, p. 729. See Elliotson's Physiol, p. 128,9 ; s. 1. also a paper in Ann. Sc. Nat. t. 21. p. 252 et seq. t Phil. Trans, for 1768 and 1769; in these vo- The experiments of Hunter may deserve to be particularly noticed, because they consisted not merely in repeating and correcting those of preceding anatomists ; but, in addition to these, he entered upon a series of original researches, winch are highly characteristic of that ingenuity and acuteness for which he was so eminently distinguished. The experiments essentially consisted in filling portions of the small intestines with a fluid, the sensible pro- perties of which might be easily recognized, and retaining it there so as to allow of its entering into the veins of the mesentery, were they capable of absorbing it ; the result, however, is stated to have been that in no instance could the fluid be detected in these veins. These experiments appeared to have been so carefully conducted, and so frequently repeated, as to have impressed the minds of anatomists and physiologists with a conviction that the lacteals were the only vessels which are concerned in the absorption of the chyle ; and although it was not possible to perform analogous experi- ments on the lymphatics, yet it seemed a natural inference, that we might extend to them the conclusion which had been established with respect to the lacteals.* In proof of lymphatic absorption various facts were brought forward, which seemed clearly to show that when extraneous or noxious substances were introduced into the system, it was done.by the medium of the lymphatic vessels rather than of the veins ; and it was thence argued that, as these vessels perform the func- tion of absorption under certain circumstances, and that we are not acquainted with any oiher office which they serve in the system, we may conclude that they are the sole agents in the action of absorption. Although the argument, as applied to the lymphatics, was far less direct and conclusive than to the lacteals, yet the analogy between the two organs appeared so strong, and so many concurring circum- stances appeared to favour the doctrine, that it was very generally received, and may be considered as having been the established opinion at the conclusion of the last century .f This unanimity of opinion was, however, of very short duration; for anatomists had scarcely ceased to contend for the honour of the dis- covery of the exclusive action of the lacteals and the lymphatics in the function of absorp- tion, when the doctrine itself was impugned by physiologists of the first eminence, who supported their views by a powerful train of arguments, enforced by numerous experiments, lumes are contained his account of the lymphatics of birds and fishes. * Med. Comment, c. 5 p. 42. .8; Cruikshank, c. 5. p. 21. t See the judicious summary of opinions in Mascagni, ps. i. sect. 2, 3: and in Rullier, ubi supra, p. 136 et seq. The doctrine of venous ab- sorption was, however, still maintained by many intelligent anatomists, especially by the high au- thority of Meckel, De Fin. Ven. et Fas. Lymph. 1772; and of Walter, Sur la Resorption, ubi supra. See particularly hi3 general conclusion, $ 92 : he conceives that the veins are the only agents in the absorption which is carried on at the. surface and from the cavities of the body. ABSORPTION. 26 and by various pathological considerations. Of these authors, one of the first, both in point of time and of ability, is M. Magendie, whose opinions on this subject, connected as as they are with some of those of his most distinguished countrymen, have been brought forward in a form which entitles them to the fullest and most respectful attention. Of the two sets of observations by which Hunter and Monro attempted to establish their hypothesis respecting lymphatic absorption, those derived from the analogy of the lacteals may still be considered as maintaining their ground ; while the conclusion which they de- duced from their experiments has been called in question, partly because it was thought not to be the legitimate inference from the experi- ments, and partly in consequence of the ex- periments themselves having been conceived to be imperfect or incorrect. It is principally upon the latter ground that the force of the objections has been rested ; and it has been, first, by repeating the experiments of Hunter, and afterwards by varying them in different ways, that their insufficency has been attempted to be proved. It has been stated above that the main support of the doctrine of the ex- clusive action of the lacteals and the lymphatics was derived from those experiments of Hunter, in which it appeared that, when the circum- stances were the most favourable for the re- ception of substances into the veins of the mesentery, they could not be proved to have entered these vessels ; and hence it was con- cluded that the veins did not, under any cir- cumstances, possess the power of absorption. We are informed, however, by M. Magendie that experiments have been performed by him- self and by M. Flandrin, which afforded directly contrary results, and that these experiments were so frequently repeated, and varied in such a manner, as to leave no doubt of their accuracy.'* We have here the opposing testi- mony of individuals, both of them of the highest authority in science, and eminent for their skill in experimental research. From personal considerations it might be difficult, if not impossible, to decide between them ; but when we take into account the circum- stance that the experiments of MM. Magendie and Flandrin were executed subsequently to those of Hunter, and with the benefit of his experience and that of the improved state of the science during the last half century; when, moreover, we are informed that the experiments of the French physiologists were more nu- merous than those to which they were opposed, and that their results were uniform and un- equivocal, we can scarcely refuse our assent to the conclusion, that the experiments of John Hunter do not afford a sufficient foundation for the doctrine of the non-absorption of the veins. But the French physiologists have not sa- tisfied themselves with repeating the experi- ments of Hunier ; they have extended them * Physiol, t. ii. p. 181 et seq. ; Journ. Med. t. lxxxv. p. 372 et seq., and t. lxxxvii. p. 221. et seq., and t. cx. p. 73 et seq. in various ways, and have obtained results supposed to be still more decisive in favour of venous absorption. Among the most im- portant, or at least the most curious of these, is an experiment which was performed by M. Magendie, in conjunction with M. Delille, and which was conceived by these physiolo- gists to afford the most unequivocal proof of their hypothesis. It consisted in dividing all the parts of one of the posterior extremities of a living animal except the artery and the vein, and in applying to the foot a poisonous substance ; when, in the short space of a few minutes, the effects of the poison on the func- tions of the animal were most distinctly ap- parent.* It was argued that in this case there was no mode of communication by which the poison could be conveyed from the extremity to the centre of the system except the vein, and that, therefore, the vein must have acted as the absorbing vessel. The experiment was rendered more striking, and, as was conceived, more conclusive, by dividing the bloodvessels themselves and introducing metallic tubes between the divided ends, through which alone the two currents of the arterial and venous blood respectively could pass in forming the communication between the extremity and the trunk of the animal, yet, under these appa- rently unfavourable circumstances, the delete- rious effects were manifested on the system as in the former case.f Experiments of this description appear to have been sufficiently multiplied to establish the fact, that the poison in these cases passed along the vein, and was conveyed in the general mass of the blood. The result of these experiments is no doubt very remarkable, and what would scarcely have been anticipated ; yet we may remark, that there is one circumstance connected with them, which, in a great measure, invalidates the conclusion that has been supposed to follow so necessarily from them. It may be inferred from the expression made use of, that the poison employed, which was the extract of the upas tree, was inserted by a puncture or incision into the foot of the animal, and would, therefore, in the first instance, be mixed with the blood ; so that the only deduction which we are warranted to draw from the experiment is, that the venous blood, being infected with the poison, had the power of communicating the infection to the system at large.}; On this view of the subject we should not regard the above as a case of absorption, but merely as an instance of the power of extraneous sub- stances, under certain circumstances, of uniting with the venous blood and retaining their specific properties. In connexion with these experiments of M. Magendie and his associates, we have another series which were performed by MM. Tiedemanu and Gmelin, and which bear di- rectly upon the question of venous absorption. Their object was to ascertain whether there * Magendie, Journ. t. :. p. 25 . . 7. t Journ. t. i. p. 23 et seq. ; Elem. t. ii. p. 183 . . 5. f See Rullier, ubi supra, p. 150 . . 2 : and Adelon, “ Absorption,” Diet, de Med. t. i. p. 148. ABSORPTION. 27 was any direct communication between the organs of digestion and the bloodvessels except by means of the lacteals. For this purpose they mixed with the food of an animal various substances, which by their colour, odour, or other sensible and physical properties, might be easily detected in the fluids of the body. After some time the animal was examined, and the result was that unequivocal traces of the substances were not unfrequently detected in the venous blood and in the urine, while it was only in a very few instances that any in- dication of them could be discovered in the chyle. The colouring matters employed were various vegetable substances, such as gamboge, madder, and rhubarb ; the odorous substances were camphor, musk, assafoetida, &c. ; while, in other cases, various saline bodies, such as muriate of barytes, acetate of lead and of mercury, and some of the prussiates, which might be easily detected by chemical tests, were mixed with the food. The colouring matters, for the most part, were carried out of the system without being received either into the veins or the lacteals ; the odorous substances were generally detected in the venous blood and in the urine, but not in the chyle, while of the saline substances many were found in the blood and in the urine, and a very few only in the chyle.* The conclusion, which we are disposed to regard as the fair inference, from the facts and arguments that have been adduced on the subject of venous absorption, is that, although there are strong analogies and various patho- logical considerations which would induce us to confine the function of absorption to the lacteals and the lymphatics, yet that the result of the experiments, although not uniform, is upon the whole in favour of venous absorption. It only remains for us to inquire how far the state and actions of the parts on which the experiments were made, were so far neces- sarily deranged by the process to which they were subjected as to render the results inapplicable to the natural condition of these organs. Now this certainly appears to be the case in the experiments of MM. Magendie and Delille, where the poisonous substance was introduced into the blood ; and the same remark may probably be applied to a number of pathological occurrences that have been supposed to afford a proof of venous absorp- tion, such, for example, as the case of ulcerated surfaces, where pus has been detected in the veins, and still more extraneous bodies, which may have been either accidentally or designedly inserted into the ulcerated part.f But it is * Ed. Bled. Journ. vol. xvii. p. 455 et seq. On the absorption of foreign bodies see the early experiments of Lister and Musgrave, Pli. Trans, for 1683 and 1701 ; also Lowthorp’s Abrid. vol. iii. p. 101 . .5, and La Motte’s Abrid. par. 2. ch. iv. p. 75, 6 ; with Haller’s sanction of their accuracy, El. Phys. xxiv. 2. 3 ; see also J. Hunter, in Med. Coin. p. 44 et seq., and Cruickshank, ch. viii. On the other hand, the experiments of M. Magendie and his friends would lead us to form an opposite conclusion ; Elem. t. ii. p. 168, 9. See Elliotson’s Physiol, p. 126. f See the experiments of Mr. Key, in Med. Chir. Trans, vol. xviii. p. 212, 13. not unreasonable to suppose that in these in- stances, in consequence of the erosion and partial destruction of the organs, the small branches of the veins will present an external orifice, through which the pus or other ex- traneous substance may be immediately re- ceived into the sanguiferous system, nearly upon the same principle as in the experiments related above. The experiments of MM. Magendie and Flandrin, the results of which were so opposite to those of Hunter, do not indeed lie open to the same objection ; but even here there is perhaps some ground for inquiry, before we implicitly adopt the conclusion that has been deduced from them. The experiment, as origi- nally performed by Hunter, necessarily implies a degree of mechanical violence, which must produce a considerable derangement of the actions of the parts concerned. Acute inflamma- tion of a peculiarly irritable and sensitive organ must have ensued, the vessels of all descriptions must have become much distended ; rupture and extravasation may have been not an impro- bable consequence of this inflammation and distention, and, in short, a general derangement both of structure and functions may have oc- curred, which must prevent us from drawing any positive inference respecting their natural condition. These observations will apply with much greater force to a subsequent variation of the experiment, which consisted in entirely detach- ing a portion of the intestine from the remainder of the tube, and filling this divided portion with the fluid, which, as in the former case, was detected in the vein of the mesentery. This arrangement was supposed to afford a still more decisive proof of venous absorption than the ex- periment in its original state, and if we con- sider the mechanical disposition of the organ only, we may admit that this would be the case. But it is obvious, on the other hand, that the vital actions of all the parts concerned must have been much more deranged, and that, on this account, we ought to be proportionally cau- tious in the application of such experiments to our physiological theories. We would venture to suggest, that the re- markable discrepancy which exists between the experiments of Hunter and of the French phy- siologists may perhaps be reconciled, by having recourse to the supposition, that in the former case there was less violence used to the parts, and that they were left more in their natural condition ; whereas M. Magendie, as we pre- sume, from a desire to render the effect more certain or more decisive, either produced a greater degree of distention of the intestines, or, in some other way, caused a greater derange- ment of the parts, so as to produce a difference in the results. But this idea is offered merely as a conjecture, from which we do not venture to deduce any of our conclusions. Upon the whole we feel disposed to regard the experiments of MM.TiedemannandGmelm, and those of an analogous kind, in which extra- neous substances were found inthevenousblood, and in some of the secretions, when they could not be detected in the chyle, as more directly ABSORPTION. 28 favouring the doctrine of venous absorption, because they are free from the objection which must always attach to those operations, where any considerable degree of mechanical violence has been employed. It may indeed be ob- jected, that in these cases, the examination of the body did not take place at the proper point of time; that, in some instances, it was made at too early a period, before the extraneous body had time to enter the lacteals, and, in other cases, not until it had left them, and had been discharged from the thoracic duct into the veins. But this contingency must be regarded as rather a possible than a probable occurrence, and it is obvious that if any considerable num- ber of experiments were performed, we can scarcely suppose it to exist. The conclusion that we are disposed to draw from all the facts and arguments that have been brought forwards on the subject is in favour of the possibility of venous absorption, at least under peculiar circumstances ; at the same time that there are strong anatomical considerations, which would induce us to suppose, that in the ordinary actions of the system, the function of absorption is confined to the lacteals and the lymphatics.'* §. 3. Inquiry into the mode in which the ab- sorbents act. — In entering upon this inquiry there are two distinct subjects which present themselves for our consideration ; we must first ascertain by what means the substances that are absorbed enter the mouths of the vessels, and, in the second place, after they have entered the mouths, how they are conveyed along the ves- sels themselves. With regard to the first of these points we may remark, that while there is so much uncer- tainty respecting the anatomical and physio- logical structure of the mouths of the lacteals, and still more, while we are completely igno- rant of that of the lymphatics, we cannot ex- pect to arrive at any definite conclusion con- cerning the mode of their action. We may, however, venture to say, that there is strong reason to believe, that the absorbents terminate in very minute or capillary vessels, that have open mouths, and that these mouths are brought into contact or close approximation with the substances to be absorbed. Hence, by an ana- logy, which it must be acknowledged is some- what vague, the action of these minute vessels has been referred to capillary attraction. But * A summary of M. Magendie’s experiments and deductions is contained in his Journ. t. i. p. 18 et seq. and his Elem. t. ii. 238 . .243 ; on this subject see also Bichat, Anat. Gen. t. ii. 104, 5, with the remarks of Beclard, p. 130. We must not omit to notice the experiments of M. Segalas, who by dividing the bloodvessels of a portion of the intes- tine, and leaving the lacteals, thus, as it were, re- versing the experiments of M. Magendie, found that no absorption took place, and hence concludes that the lacteals do not possess this power ; Magendie’s Journal, t. ii. p. 117 et seq. So singular a conclu- sion must.we conceive, lead us to place but little con- fidence in the result of such complicated experiments. Franchini of Bologna thought that the lymphatics absorb “ la sostanza assimilabile,” but that the sub- stances which do not directly contribute to nutrition are absorbed by the veins; Consider. Fisiol. sull’ Assorb. p. 44. it may be doubted whether in this inference, as in so many other cases of physiology, we have not been misled by a mere nominal resem- blance, and have applied the term capillary to the action of the lacteals, because it had been used to denote their dimensions. Perhaps, strictly speaking, there is scarcely a single cir- cumstance, in which the action of the lacteals can be assimilated to that by which fluids are taken up by capillary tubes. The structure and consistence of the tube itself, the nature of the substance on which it is supposed to act, and their relative situation, are all of them more or less different from what occurs in the ordinary cases of capillary attraction. And if there is a difficulty with respect to the lacteals, where we have at least some indistinct evidence of the mechanical disposition of the parts, which may seem favourable to this hypothesis, in a much greater degree will it exist with respect to the lymphatics, where we have nothing to direct our opinion, except the analogy which may be presumed to exist between the two spe- cies of absorbent vessels. In consequence of these difficulties, and of the supposed inadequacy of the mechanical theory, many physiologists have had recourse to a certain specific action of the vessels, and have conceived that the chyle was taken up by a power, which has been supposed to be ana- logous to an elective attraction between the vessel and the substance that is absorbed.* There are indeed many circumstances which would appear to indicate, that a certain kind of selection is exercised by the mouths of the vessels, for, as far as we are capable of judging, when substances possessed of the same con- sistence and physical properties are placed in contact with these mouths, some of them are received, while others are rejected. But we must remark, that the same objection may be urged against this as against the former expla- nation, that the term elective, which is borrowed from the chemical relation of bodies to each other, is perhaps as little applicable to the case under consideration jas that of capillary, which refers more to their mechanical action. Discarding therefore all these analogical illustrations, which are at least of doubtful application, we may remark, that the lacteals ought to be regarded, like every other part of the animal frame, as vital organs, possessed of appropriate and specific powers ; that, in this instance, we are not able to refer to any general principle the train of events now under con- sideration, and that we must therefore be satis- fied with simply stating the fact, that the lac- teals have the power of taking up by their extremities certain substances, with which they are in close approximation ; that, for the most part, the substances which they receive are the elements of the chyle, that they select these from the contents of the intestinal canal, and * See Bichat, Anat. Gen. t. ii. p. 125 ; Dumas, Physiol, t. ii. p.397, 8; Young’s Med. Lit.p. 112 ; Bell’s Anat. v, iv. p. 290. M. Magendie, however, is disposed to reject all these hypothetical explana- tions ; Elem. t. ii. p. 162,3, and Journ. t. i, p. 3. ct alibi. ABSORPTION. 29 that, except under peculiar circumstances, they reject every other substance.* When the elements of the chyle have been received into the lacteals, it appears to undergo a certain degree of elaboration, by which it is farther assimilated and perfected, an operation, the intimate nature of which we are unable to explain, but which, as well as its entrance into the mouths of the vessels, we correctly refer to their vital action. After the chyle has entered the lacteals, there is less difficulty in conceiving the subsequent steps of the process. We are at least able to generalize theoperation, by referring it to contractility, the same power which ori- ginates motion in other parts of the system. It must, no doubt, be admitted, that the exis- tence of the muscular fibres of the lacteals has not been satisfactorily demonstrated, and that, until this has been accomplished, our opinion can only be regarded as hypothetical : but we have here the advantage of being able to assign a probable and sufficient cause of the effect, and are aware of the point towards which we must direct our future investigations.f Before we conclude this branch of the subject, we may remark concerning the contents of the lacteals, that, under ordinary circumstances, we have no decided proof of these vessels containing any substance except the elements of the chyle, and that, although in some of the experiments referred to above, extraneous bodies have been occasionally found in them in minute quantity, these cases must be regarded as exceptions to the general fact. With respect to the chyle itself, it has been a subject of examination by the chemists, whe- ther its properties are always uniform in the same animal, or class of animals, under the various circumstances of age, constitution, and still more of diet, to which they are subject. But it may be necessary, before we enter upon this inquiry, to premise a few remarks upon the meaning of the terms chyme and chyle. By the older physiologists they were very gene- rally employed as synonymous, and this is still the case with some of the modern writers, more especially on the continent-! A clear distinc- tion between them has, however, been pointed out and recognized, and as there appears to be an essential difference between them, it is desi- rable that it should be generally adopted. The first of these substances is the immediate pro- duct of the action of the gastric juice on the aliment, as received into the proper digestive stomach, while the latter is the substance which is produced by a subsequent part of the pro- cess of digestion. The conversion of chyme * See the remarks of MM. Chaussier and Ade- lon, ubi supra, p. 272 et seq. ; also Adelon, Physiol, t. iii. p. 85 et seq. ; and Alison’s Out- lines, p. 79. t This is essentially the doctrine of Haller, Prim. Lin. c. xxv. §.568. Sheldon, p. 28, and Cruik- shank, c. 12, are advocates for this doctrine ; but it is opposed by the high authority of Mascagni, ps. i. sect. 4. p. 27, 8. t This appears to be the case with M. Rullier, art. “ Chyme,” in Diet, de Med. t. v. p. 241 . . 4 ; M. Adelon, however, clearly marks the distinction. Physiol, t. iii. p. 25, et alibi. into chyle seems to commence shortly after it leaves the stomach, and while it still remains in the duodenum, is so far advanced as to be reduced into a condition proper for being re- ceived into the lacteals. There is, however, reason to believe that the completion of the process takes place in the lacteals themselves, and even that it is not until the chyle arrives at the thoracic duct, or at least at the great trunks of the lacteals, that it is fully elaborated. The nature of the change which the chyme expe- riences in the duodenum, and the agents by which this change is effected, what share the secretions of the part itself, the bile, or the pancreatic juice have in the operation, are questions that still remain in discussion, and which will be considered in the appropriate parts of this work.* For the analysis of the chyle we are prin- cipally indebted to Vauquelin, Marcet, and to Dr. Prout. Vauquelin employed the chyle of the horse, as taken from the large trunks of the lacteals and from the thoracic duct.f The experiments of Marcet were principally directed to the inquiry, how far the chyle of the same kind of animal was affected by dif- ferences in the diet, according as it consisted principally of animal or vegetable substances.! Dr. Prout’s experiments on the chyle extended both to its general properties, and to the dif- ferences produced by different kinds of diet, while, in addition to these points, he entered into a very interesting examination of the suc- cessive changes which it experiences, from its first entrance into the lacteals until its final deposition in the thoracic duct.§ The result of these experiments, as far as our present inquiry is concerned, tends to shew that the vegetable chyle differs somewhat, in its physical and chemical properties, from that of animal origin, and that the chyle, when it first enters the lacteals, is in a less perfect state, while it be- comes more assimilated to the blood in pro- portion as it advances towards the thoracic duct. With respect to the means by which the animalization of the chyle is perfected after it enters the vessels, we have no certain informa- tion, and we have scarcely any analogy which may assist in guiding our opinion. What is termed by modern physiologists the action of the vessels, by which so many operations of the animal economy are supposed to be effected, we may regard rather as an expression which serves as a convenient veil for our ignorance, than as throwing any light upon the process. We have no evidence that any addition is made to the chyle while in the lacteals ; and indeed we can scarcely suppose it possible that this is the case, so that the only conceivable effect of this action is reduced to the motion which is imparted to the chyle by the alternate contrac- tion and relaxation of the vessels, in conse- * See the remarks of Adelon, art. “ Chyliferes,” Diet, de Med. t. v. t Ann. Chim. t. lxxxi. p. 113 et seq. ; Ann. Phil, v. ii. p. 220 et seq. t Med. Chir. Trans, v. vi. p. 618 et seq. § Ann. Phil. v. xiii. p. 22 . . 5. 30 ABSORPTION. quence of which the constituents may be more completely mixed together, and to a certain degree of pressure and temperature to which it is exposed, which may modify any spontaneous change that might otherwise take place in the arrangement of its elements. But to whatever cause it may be referred, we must consider the chemical and physical change in the nature of the chyle as one effect produced by the lacteals, as well as the progressive motion which is im- parted to their contents. In the present state of our knowledge on the subject, it remains for us to consider whether we have any independent evidence of the exist- ence of the muscular fibres of the absorbent vessels, whether, if their existence be proved, and their contractility thus established, it would be necessary for us to search out for other causes of the effects, and lastly, to what other principle the acknowledged effects might be attributed, should it appear, upon full con- sideration, that the assigned cause is insufficient or inadequate. The above considerations lead us to give an account of the hypothesis of the action of the absorbents, which has been proposed by M. Magendie. He had ascertained, by a previous train of experiments, that according to the con- dition of the system as to depletion or plethora, the process of absorption was respectively acce- lerated or retarded. Hence he draws the con- clusion, which, however, we conceive not to be a necessary consequence of the premises, that the function depends on a mere mechanical principle, independent of any vital action. The mechanical principle to which he has recourse, and which he thinks can alone account for the effect, is that of capillary attraction ; but this he conceives not to take place from the open mouths of the vessels, according to the ordinary conception of the subject, but that the fluid is imbibed by the substance of the vessel itself, and is, as it were, filtered through its pores.* He explains its further progress by supposing, that when it has entered these pores, it is car- ried forwards by the current of the fluid pre- viously in the vessel. To prove his idea of the permeability of the parietes of the vessels, he instituted a series of experiments on the veins of an animal shortly after death, when he found that they were capable of imbibing and transmitting certain fluids with which they were placed in contact. Still farther to substantiate the hypothesis, M. Magendie repeated a set of analogous ex- periments on the vessels of a living animal. They consisted essentially in detaching a por- tion of one of the great veins, and applying to * Journ. t. i. p. 6 et seq. and Diet, de Med. et Chir. Prat. “ Absorption,” t. i. p. 91 et seq. The doctrine of transudation was maintained by many of the older physiologists ; see Kauw Boer- haave, de Persp. ; also Haller, El. Pbys. ii. 2. 23 ; more lately it was supported by W. Hunter, Med. Com. ch. 5 ; by Walter, ubi supra, § 28 . . 35 ; and by Mascagni, ps. 1. sect. i. and is zealously main- tained by his commentator Bellini, t. i. not. 4. p. 33 . . 0. The “ penetrabilite” of the cellular tex- ture was one of the fundamental doctrines of Bordeu, Recherches sur le Tissue muqueux, § 72. its surface the solution of some narcotic or poisonous substance, the effects of which were, in a short time, manifested in the system at large.* This doctrine of imbibition and transudation has been embraced by M. Fodera, who has endeavoured to confirm the opinion of M. Ma- gendie by additional experiments, which he conceives tend directly to prove that the vessels of the living body possess this power of im- bibition. The method which he adopted to prove this point, in the most unequivocal man- ner, was to inject into two separate cavities of the body two fluids, which by their union pro- duce a compound, the presence of which may be easily detected, and which could be formed by no other means except by this union. For example, into the cavities of the pleura and the peritoneum were respectively injected the solutions of the ferro-prussiate of potash and of the sulphate of iron, when it was found, after a certain length of time, that various membranes and glands, connected with the thorax and the abdomen, were tinged with a blue colour. M. Magendie afterwards performed an ex- periment, which seemed more directly to bear upon the question, where a solution of the ferro-prussiate was retained in a portion of the intestine, at the same time that its external surface was placed in contact with a solution of the sulphate of iron : the part was then ex- posed to the galvanic influence, the result of which was that a blue tinge was communicated to the sulphate. We are further informed, that according to the direction of the galvanic cur- rent, the blue colour was produced either in the sulphate or in the ferro-prussiate. From these experiments M. Fodera draws the con- clusion, that the processes of absorption and of exhalation may be referred to the mechanical operations of imbibition and transudation, which take place through the pores or capillary open- ings of the various textures of the body.f On these experiments, and the conclusion deduced from them, we shall remark, that the facts appear to prove that membranes, perhaps during life, and certainly after death, before any visible decomposition has taken place, are capable of transmitting fluids through their tex- ture ; but we conceive that the analogy between this case and that of the entrance of chyle into the lacteals is so incomplete, that we can draw no inference from the one of these events which can be fairly applied to the other. Both the mechanical and the physiological properties of membranes and vessels differ much from each other, while the nature of the fluids employed in * Journ. t. i. p. 9, 10. t “ Recherches sur l’Absorption et l’Exhalation,” and Magendie’s Journ. t. iii. p. 35 et seq. -, see, also Med. Repos, v. xix. p. 419, et Med. Journ. v. xix. p. 488, 9. On this subject see the remarks of Tiedemann, Traite de Physiol, par Jourdan, § 168. p. 242. Mr. Mayo remarks, that the principle of imbibition and transudation affords a more easy ex- planation of the experiments of MM. Magendie and Segalas, than that of venous absorption ; Phy- siol. (3rd ed.) p. 97 et seq. See the remarks and objections of Sir D. Barry, Exper. Researches, p. 80 . . 2 et alibi ; also Elliotson’s Physiol, p. 133. ABSORPTION. 31 the experiments is totally different from any thing to which the parts are exposed under ordinary circumstances. It may be further remarked, that if the texture of the vessels is so permeable to fluids of all kinds and in all directions, it is difficult to conceive of any cause which can retain them there when they have entered, and which should prevent their escaping through the same pores when any pressure is made on the contents of the vessels by its contractile power or by any extraneous force. And it may be further remarked concerning these experiments, without impugning the accu- racy or the dexterity of the operator, that they imply a degree of minuteness in the execution, and of attention to a variety of concurrent cir- cumstances, and are altogether of so extremely delicate a nature, as to render it undesirable that any physiological conclusion should be founded on them. If a single bloodvessel be divided, however minute, and its extremity be exposed, or even if a single cell of the membranous texture be laid open, so as to admit of the introduction of the fluid, the essence of the experiment is destroyed, and its results must become equivocal. Another hypothesis respecting the nature of absorption has been lately brought forward by Sir D. Barry, according to which it immediately depends on atmospheric pressure, either ex- ercised directly on the surface of the body, or acting indirectly on the absorbents through the medium of the great internal cavities. The experiments on which the hypothesis rests con- sisted in introducing a portion of some poison- ous substance into a wound, and forming a vacuum over it by means of a cupping-glass; when, by contrasting the effect of the poison in this case with that which ensues from the same application where the cupping-glass was not employed, he concludes that the process of ab- sorption was suspended by removing the at- mospheric pressure, and he hence infers that this pressure is the cause of absorption.* The results of these experiments, in a prac- tical point of view, are of great interest, but with respect to the physiological conclusion that has been drawn from them, there are various circumstances to be taken into account, which appear not to have been duly attended to. In the first place, a similar kind of objection occurs in this case as in the experiments of MM. Magendie and Delille related above, that the poison was introduced into a wounded part, and would therefore be immediately mixed with the blood and carried into the general circulation. The effect of a vacuum formed over the divided extremity of a vessel, must be to retard the progress of its contents, whatever be its description, or in whatever cause it ori- ginates. This effect is therefore not specifically applicable to absorption, even in the natural state of the parts ; and when we consider that in this case there was an artificial opening * Barry’s Exper. Researches, pt. 2 " On Ab- sorption Alison’s Outlines, p. 85 ; Bostock’s Phy- siol. v. ii. p. 593 et seq. made into the vessel, we may venture to affirm that the conclusion which was drawn from it is in no respect the necessary inference from the facts. And besides this general objection, it may be fairly questioned how far the removal of pres- sure from the surface of the body could act in retarding the progress of a fluid along a vessel which has no external opening, and which is provided with valves, such as is strictly the case with the lacteals, and may be almost said to be so with the lymphatics. And with re- spect to the lacteals, it appears a very obvious objection to the hypothesis, that they are alto- gether defended from the effects of atmospheric pressure, either as applied directly, or as in- directly acting on them through the medium of any of the internal cavities. Besides, we have sufficient proof of the spontaneous and inde- pendent action of these vessels, whatever may be our opinion respecting the existence of their muscular coat, and to whatever principle we may refer this action, and we have thus an actual cause for the propulsion of their con- tents, although it is impossible to estimate its actual amount, it would appear unnecessary to search for any farther agent, unless we have good ground for concluding that the existing cause is inadequate to produce the effect re- quired. Cutaneous absorption. — There is a branch of the subject to which we must now direct our inquiry, the existence and extent of what has been termed cutaneous absorption. When we trace the progress of the lymphatic vessels from their great central trunks, and follow them through all their minute ramifications, we find that many of them appear to have their origin from the surface of the body,* and hence we are led to suppose that the function of ab- sorption is exercised, to a certain extent, by the cutis, or the parts immediately connected with it. That this is the case is proved by various pathological facts; we have daily opportunities of observing, that various medicinal substances, by mere application to the surface, and still more when aided by friction, produce the same effect upon the system as if they had been received, in the ordinary way, through the medium of the stomach. By this means mercury manifests its specific action on the salivary glands, the salts of lead destroy the contractility of the muscular fibre, while opium, tobacco, and other narcotics produce their pe- culiar effects on the nervous system. But, besides this kind of absorption, which is brought about by the substances being, as it were, mechanically forced into the pores of the skin, and thus applied to the mouths of the lymphatics, it was an opinion very generally embraced by the older physiologists, and still retained by many of our contemporaries, that the lymphatics, which are distributed over the surface, possess the power of imbibing water, when simply applied to it by the immersion of the body, or even when it is exposed to * See Haase, De Vas. Cut. et latest. Absorb., tab. fig. 2 ; also, Mascagni, tab. 2. fig. 9 . , 28, tab. 3. 32 ABSORPTION. aqueous vapour diffused through the atmos- phere. This supposed power of cutaneous ab- sorption was called in to account for various physiological or pathological facts, for which it appeared to afford a plausible explanation, while, on the other hand, the easy mode in which it appeared to account for these facts was made use of as the great argument to prove its existence. The statical experiments of Sanctorius, which have, since his time, been so much multiplied and extended, were supposed to prove unequivocally that the body is capable of gaining weight independently of any substance received into the stomach, and to account for this addition, recourse was always had to the cutaneous absorption. Of late, indeed, it has been discovered, that a part of the effect ascribed by Sanctorius to the action of the skin is in reality due to the lungs, but still, after making the necessary deduction for the operation of the latter organ, there re- mained a certain increase of weight, which it was supposed could only be accounted for by admitting the existence of the cutaneous ab- sorption.* The doctrine of cutaneous absorption has, however, been altogether called in question by Seguin, who performed a series of experiments, which consisted in immersing a part of the body in a saline solution, for example, that of corrosive sublimate, the effects of which on the system at large would be easily recognized, if any part had been absorbed. The result was, that when the cuticle was entire, no effect that could be attributed to absorption took place, and the conclusion seemed not unna- tural, that under ordinary circumstances it did not exist. f Currie was led to form the same conclusion by accurately weighing the body before and after immersion in the warm bath, under circumstances which were conceived to be favourable to the process,! and as the re- sults of his experiments coincided with those of Seguin and others, the doctrine of cuta- neous absorption, except under the particular circumstances mentioned above, was very generally abandoned. Experiments have been adduced to prove, that even under these par- ticular circumstances, when substances are ap- plied by friction to the surface, they do not enter into the mouths of the vessels, but being volatilized by the heat of the body, that the vapour thus produced is inhaled by the lungs ;§ an opinion which one might be inclined to think was almost too extravagant to be seri- ously maintained. The subject of cutaneous absorption has been lately investigated by Dr. Edwards, with that skill and address which he has applied to so many departments of physiology. By a number of experiments, which were performed on cold-blooded animals, where it was more * Mascagni, p. 22, 3; see also Kellie, in Ed. Med. Journ. v. i. p. 170 et seq.; and the article “ Integuments” in Rees’s Cyclop. t Fourcroy, Med. Eclair, t. iii. p. 232. . 241, and Ann. Chim. t. xc. p. 185 etseq. t Med. Reports, ch. xix. $ Ed. Med. Journ. v. ii. p, 10 et scq. easy to observe the effects, he found that ab- sorption was carried on, to a considerable extent, when the animal, or a part of it was immersed in water. The conclusion which the experiments seemed to warrant was, that transudation and absorption are, at all times, going forwards at the surface, but that the operations proceed at different rates, according to the circumstances in which the animal is placed, and that the body gains or loses weight, in proportion to the excess of one of them above the other. The analogy of the cold- blooded animals he applies to those with warm blood, and he supposes that they are subject to the same double action, a conclusion which appears to be confirmed by some experiments that were performed on guinea-pigs immersed in moist air, when an increase of weight was found to have taken place, which, after taking every circumstance into consideration, seemed necessarily to depend on absorption.* With respect to the experiments of Seguin, Dr. Ed- wards is not disposed to call their accuracy in question, but he points out various circum- stances connected with them, which he con- ceives would tend to increase the transudation, and to diminish, or even entirely to suspend the absorption .f The experiments of Dr. Ed- wards, considered in all their relations, are generally conceived to decide the question respecting the existence of cutaneous absorp- tion, under the ordinary circumstances, and in the natural conditions of the system. §. 4. Of the specific uses of the different parts of the absorbent system, and of the rela- tion which that syste?n bears to the other vital functions. — Whatever opinion we may form on the controverted question respecting venous absorption, and in whatever manner we may explain the action of the lacteals and the lym- phatics, there can be no doubt that their spe- cific use is to absorb certain substances which are presented to their extremities.! There is, however, so well marked a distinction between the situation and the anatomical relations of these two kinds of vessels, as well as between the substances that are found to be contained * De [’Influence des Agens, &c. ch. xii. p. 345 et seq. t lie l’lnfiuence, &c. ch. xiii. p. 556 et seq. See on this subject, Magendie.'Physiol. t. ii. p. 189 . . 196, and Diet, de Med. et Chir. Prat. “ Absorp- tion;” where he endeavours to prove, that it is the veins and not the lymphatics which are the agents in cutaneous absorption. See also the remarks of M. Rullier, ch. ii. ; and of M. Adelon, Physiol, t. iii. p. 10 et seq. ; also art. “ Absorption,” Diet, de Med. t. i. p. 124 et seq. M. Chaussier found that sulphuretted hydrogen gas, when ap- plied to the surface of the body, manifested its deleterious effects on the system, Bibl. Med. t. i. We have already had occasion to notice the opinion of Walter on this subject, p. 25, which is similar to that of M. Magendie. M. Buisson attempts to establish a distinction between the absorption which is carried on by the membranes and by the cellular texture, De la Divis. des Physiol. Phenom. p. 251 et seq. 1 M. Magendie indeed doubts this position so far as the lymphatics are concerned ; Journ. Phy- siol. t. i. p. 18 et seq. and Physiol, t. ii. p. 238. . 243. ABSORPTION. 33 in them, that we are naturally led to conclude, that they are destined for different uses, and serve different purposes in the animal economy. With regard to the lacteals, their use seems to be clearly marked by their connexion with the digestive organs, and by their contents, as constituting the channel by which the chyle is conveyed from the intestines to the thoracic duct, and ultimately to the bloodvessels. We cannot doubt that their primary function is to supply the body with the elements which com- pose the blood, and thus become the imme- diate agents in its nutrition. Although, from the experiments which have been related above, it will appear that, on certain occasions, the lacteals are not incapable of receiving extraneous bodies, yet we may conclude, that this is the case only under extraordinary cir- cumstances, or in an unnatural state of the parts. With respect to the lymphatics, their specific use is less obvious. As their contents are ul- timately mixed with those of the lacteals, we may suppose that they contribute indirectly to the nutrition of the body ; but this would appear not to be their primary, or even their principal destination. Still we can scarcely refuse our assent to the position, that absorp- tion is the specific function of the lymphatics ; and this will be equally the case, although we may suppose that the veins cooperate with them in this action. We are indebted to the genius of John Hun- ter for a consistent or plausible theory of the use of the lymphatics, which, with certain mo- difications, is generally admitted to be correct. Conceiving that the appropriate and specific action of the lacteals is to nourish the body, and to support the system by the addition of new matter, that of the lymphatics is to mould and fashion the body, to admit of the growth and extension of the whole, while each in- dividual part retains its proper form and position. When we consider in what manner an organized part increases in its dimensions, wc immediately perceive that it is not by mere accretion, nor by simple distention; it is, on the contrary, by an addition to every individual portion, while they retain the same relation to each other and to the whole. If we take the case of a muscle, we find that each particular fibre must be increased in length, so that the distance may be augmented between the ten- dinous extremities, while probably the number of fibres that are contained in the membranous covering is also increased ; the whole organ consequently becomes larger in every one of its individual parts, while they each retain their former proportions and connexions.* We may apply the same train of reasoning to the bones, which offer a still more remark- able example of this change of form, inas- * See Winterbottom, de Vas, Absorb, in Smel- lie’s Thes. Med. t. iv. ; also Cruikshank, p. 108, 9. For the more recent views of physiologists on the subject the reader is referred to Adelon, art. “ Absorption,” Diet, des Scien. Med. t. i. VOL. i. much as the firmness of their texture must render it less easy to conceive of any alteration in their dimensions and in the disposition of their component parts. Here it is still more obvious than in the case of the muscle, that the change cannot be effected either by accre- tion or by distention, but that a completely new disposition of the integrant parts must have taken place. The only means, however, by which this can be accomplished is by the former particles of the body being gradually removed, and new ones deposited to supply their place ; the process being so gradual, that, although the deposition of the new particle is not precisely in the same situation with the former, yet that of each particle is so nearly so as to cause no obstruction or interruption to the action of the organ. Now it is evident that this removal of the old matter can be effected by no process but by absorption, and we may therefore conclude that the lymphatics, either alone or in conjunction with the veins, are the agents destined to perform this office. With respect to the actual nature of the con- tents of the lymphatics there appears to be some uncertainty. We have the analysis of the fluid taken from the vessels of a dog by M. Chevreul,* from which it would appear that the lymph contains nearly the same in- gredients with the blood, but diluted with a much larger proportion of water. We must, however, suppose that the fluid contained in the lymphatics will vary very considerably in its composition, according to the part of the body from which it is taken, or the condition of the same part at different times; yet we are scarcely able to detect an actual state of things which altogether corresponds with what we might have been led to expect would have been the case.f It may indeed be presumed that in the ordinary condition of the system, the process by which the parts of the body are absorbed is so very gradual, that the change in the chemical constitution of the lymphatic fluid is as inconspicuous as the change in the organs from which it is absorbed, and that it is only in morbid cases, where there is some extraordinary quantity of matter to be re- moved, that we should expect to be able to detect it in the lymph. And this, to a certain extent, agrees with the fact; for when the ab- sorbents are called into action to remove col- lections of pus, or when they become the vehicles of any poisonous or morbid body, the substance in question has been occasionally found in them. The doctrine of the removal or absorption of all the parts of the body is rendered evident by a variety of cases, in which any particular organ or texture is broken down or removed, merely by cutting off the supply of fresh matter. It is upon this principle that we explain the * Magendie, Elem. t. ii. p. 171, 2. j Magendie, Elem. t. ii. p. 196, 7, et alibi. Mascagni, however, states that the lymph varies according to the parts to which it is contiguous, ps. 1. §. 4.; see also Blumenbach, §. 438. D 34 ABSORPTION. removal of a part by pressure. If a muscle, or even a solid bone be exposed to constant pres- sure, by which its nutritive arteries are ob- structed, it will be gradually diminished in bulk, and at length completely abstracted. And this is frequently effected by the action of a body much softer than the substance which is removed, as, for instance, we observe a bone to be absorbed by the pulsation of a blood- vessel, or the growth of a fleshy tumour.* But although we may venture to affirm that this moulding of the body, or rather of its in- dividual parts, is effected by the lymphatics, either alone or in conjunction with the veins, there is considerable difficulty in forming a distinct conception of the mode in which they operate. The operation cannot, strictly speak- ing, be mechanical, nor have we any evidence of the existence of a chemical solvent, by which the parts may be reduced to a liquid state, so as to fit them for entering into the mouths of the vessels. We may conceive of the source of supply being cut oft by pressure or in other ways, but still we are at a loss to account for the mode in which the solids are either dissolved or broken down, so as to adapt them to the process of absorption. There is, however, one principal or general fact in the animal economy, which will probably some- what assist us in our inquiry, viz. that it appears to be essential to the well-being, or even to the existence of the corporeal frame, that all the materials of which it is composed should un- dergo a constant change. It appears that these materials, after a certain length of time, expe- rience some alteration in their nature, by which they are rendered unfit for the further perform- ance of their functions as constituents of the living body. They are therefore removed and are replaced by fresh matter, this interchange being brought about in the gradual manner which was described above. Now this process implies a constant decomposition of the parts of the body, and as this decomposition is effected particle by particle, it may not be un- reasonable to conjecture, that each particle, when it ceases to form an integral part of an organ, is left in a state proper for being taken up by the absorbents. But independent of any hypothetical views of this description, we may assume it as a probable conclusion, that the configuration and moulding of the body is the specific and appropriate office of the lymphatics, while its nutrition is effected more immediately by the lacteals. With respect to the lymphatic glands we have seen above that their structure is involved in considerable obscurity, and we may remark, that their use is at least equally obscure. Among other opinions that have been entertained on * For the absorption of the solids, see Monro on the Brain, c. 5 ; also Blumenbach, $. 436 ; and Bell’s Anat. vol. iv. p. 311, 2. Ribes, who is a zealous defender of the doctrine of venous absorp- tion, remarks that the absorption of the bones must be effected by the veins, because they are not fur- nished with lymphatics; Mem. Soc. d ’Emulation., t. viii. p. 621. the subject, some physiologists have supposed that the glands are proper secreting organs, which are destined for the purpose of preparing a peculiar substance that is mixed with the chyle and the lymph, or that they merely serve the mechanical purpose of mixing together more completely the constituents of the fluid that is contained in the vessels, and thus produce some change in its nature or consistence.* There do not appear to beany arguments, either anatomical or physiological, by which this point can be decided ; but we may remark, that while the number and mode of distribution of these glands in the mammalia would seem to point them out as performing some important office in the animal economy, their rarity in birds and fishes proves that they are not essen- tial to the existence of most of the functions of animal life, nor have we any mode of explaining the cause why they should be more necessary to the mammalia than to the other classes, which in many of their functions so nearly re- semble them. It only remains for us to offer a few remarks on the connexion between the function of ab- sorption, and the other vital actions of the system, especially with the two leading princi- ples of contractility and sensibility. We have already had occasion to remark on the con- nexion of absorption with muscular contracti- lity, and although it may be difficult, or even impossible, to demonstrate the muscular fibres, or to exhibit any apparatus of this description, by which the action of the vessels can be ac- counted for, still we have strong reason for supposing that the absorbents possess this power, and that it is the main cause by which their contents are propelled. With respect to the relation which subsists between the nervous and the absorbent systems, we are induced to suppose, both from anato- mical and from physiological considerations, that it is merely of an indirect nature. From the researches of the anatomists, we learn that there are few nerves sent to the absorbent vessels or glands, and that even these seem rather to pass by them, in order to be transmitted to some other organs, than to be ultimately des- tined for the use of the absorbent system. The action of the mouths of the lacteals, or the power by which they are enabled to take up the substances that are afterwards transmitted along them, is involved in much obscurity, as is likewise the case with the power which these vessels seem to possess of changing the nature of their contents. Both of these have been re- ferred to the nervous influence, but this has been done in that loose and general way, which * On this subject we may refer to Haller, El. Phys. ii. 3. 25; Blumenbach, Inst. Phys. §. 425, 442; Richerand, Elem. p. 153; Mascagni, ps. i. sect. 5. p. 33 ; Magendie, Elem. t. ii. p. 166, 201 ; Chaussier et Adelon, ubi supra, p. 278. Rullier, art. “ Inhalation,” in Diet. Sc. Med. ; Meckel, Manuel, sect. 6. ch. i. ; Adelon, art. “ Lymphatique (Physiologie),” Diet, de Med. t. xiii, also art. “ Chyliferes,” ihid. t. v. p. 239; Desgenettes, Journ. Med. t. xc. p. 322, et seq. ACALEPH/E. 35 is too frequently met with in the reasoning of physiologists. We do not perceive, in either case, how it can be referred to this power, nor how it can be employed in any way to explain or elucidate the effects that are produced.* It is admitted that the chyle is elaborated during its passage along the lacteals, and be- comes more nearly assimilated, both in its phy- sical and chemical properties, to the blood. Still, however, its complete sanguification does not take place until it leaves the lacteals, and it becomes a very interesting subject of inquiry, by what means this is effected ; in what degree the function of respiration contributes to it, whether the abstraction of carbone and the in- troduction of oxygene, which is supposed to be effected by the passage of the blood through the lungs, is the immediate cause of the con- version of chyle into blood ; whether it be brought about more gradually, by the removal of the various secretions and excretions, or whether there be any particular organ, which may more especially produce the change in question. These are all of them points of high interest, but as they are concerned in an indi- rect manner only with the subject of this article, and as they will be considered in the appro- priate parts of this work, we shall not pursue the inquiry any further. Bibliography. — Abernethy, in Phil. Trans. 1776 and 1796. Adelon, in Diet. Scien. Med. “ Absorption” and “ Lymphatique Ditto, Phy- siologie ; Ditto, in Diet, de Med. “ Absorption ” and “ Chyliferes.” Albinus, Tab. Vas. Chyl. fob Lugd. Batav. 1757. Alison’s Outlines of Physio- logy. Aselli, de Lactibus. 4to. Mediol. 1627. Antommarchi, Prodromo di Mascagni ; Ditto, in Ann. Sc. Nat. t. xviii. Barry’s Exper. Researches. 8vo. Lond. 1826. Bartholin, De Lact. Thor. ; Ditto, Anat. Reform ; Ditto, Vas. Lymph, hist, nov. 12mo. Hafn. 1652, &c. Beclard, add. a Bichat. Bell's Anat. Bellini, Istor. Vas. linf. di Mascagni. Bichat, Anat. Gen. Bleuland, Exper. Anat. 1784. Blumenbach’s Comp. Anat. by Law- rence. Boerhaave, Praelect. a Haller. Bolius, in Haller, Disp. Anat. t. i. Bordeu, sur le Tissu Muqueux. Bostock’s Physiol. Boyer, Anat. Bre schet, in Diet, de Med. “ Lymph. Syst.” Buisson, Divis. de Phys. Phen. Chaussier, in Diet. Scien. Med. “ Lymphatique.” Ditto, in Bibl. Med. t. i. Cheselden’s Anat. Cloquet, Manuel. Cooper , in Med.Rec. and Res. Cruikshunk, on the Absorbents ; Ditto, Letter to Clare. 4to. Lond. 1786. Currie’s Med. Rep. Desgenettes, in Journ. Med. t. lxxxiv. Douglas, Bibl. Anat. Dumas, Physiol. Duvernoi, in Mem. Petrop. t. i. Edwards, sur l’lnfluence des Agens, &c Elliotson’s Physiol. 5th edit. Eustachii Oper. Anat. Fallopii Opera. Feller, Vas. Lymph. Desc. Flandrin, in Journ. de Med. t. Ixxxv, lxxxvii, xc. Fleming’s Zoology. Fodera, Recherch. sur l’Ab- sorption ; Ditto, in Magendie’s Journ. t. iii. Fok- mann, Commun. Lymph, et Veines. 4to. Liege. 1832. Fourcroy, in Ann. Chim. t. xc. ; Ditto, Medecine Eclairee. Franchini, Consid. fisiol. suit’ Assorb. Galeni Opera, a Charterio. Glisson, Anat. Hepat. 12mo. Lond. 1654. Gordon’s Anat. Graves, Lect. on the Lymph. Sys. House, Vas. Cut. et Inst. Abs. Haller, Bibl. Anat. ; Ditto, Elem. Phys. ; Ditto, Opera Min. ; Ditto, Prim. * On this subject the reader is referred to Mas- cagni, p. 30; Hewson, pt. 3. p. 52 ; Cruikshank, p. 64 ; and Gordon’s Anat. p. 77. Linete. Hedwig, Disq. Ampull. Lieb. Hewson’s Enquiries ; Ditto, in Phil. Trans. 1768, 9. Hodgkin, Appendix to his Translation of Edwards Sur les Agens, &c. J. Hunter, in Med. Com. W. Hunter, Med. Com. Kauw Boerhaave, De Perspir. Kellie, in Ed. Med. Journ. vol. i. Key, in Med. Chir. Trans, vol. xviii. Kiernan, in Phil. Trans. 1833. La Motte’s Ab. of Phil. Trans. Lauth, Sur les Vaiss. Lymph. 4to. Strasb. 1824. Lieberkuehn, Fab. Vill. Intest. Lippi, Illust. Fisiol. Lowthorp’s Ab. of Phil. Trans. Lyster, in Phil. Trans. 1683. Magendie, Phvsiol.; Ditto, Journal de Physiol. ; Ditto, in Diet. Med. et Chir. Prat. “Absorption.” Marcet, in Med. Chir. Tr. vol. vi. Mascagni, Vas. Lymph. Hist. fol. Senis, 1787. Mayo’s Physiol. Mechel, Diss. de Vas. Lymph. 4to. Berob 1757; Ditto, Manuel d’Ana- tom. par Jourdan et Bi'es< het ; Ditto, sur Re- sorption, in Nouv. Mem. Berl. 1770; Ditto, de Fin. Ven. et Lymph. 4to. Berol. 1772. Monro (2 ), de Sem. et Test, in Smellie, t. ii. ; Ditto, de Venis Lymph. 8vo. Berob 1757. ; Ditto, on Fishes ; Ditto, on the Nervous System ; Ditto, Three Treatises. Monro (3 ), Elem. of Anat. Musgrave, in Ph. Tr. 1701. Nuclt, Ade- nologia. 12mo. Lugd. Batav. 1691. Panizza, Osservazione. Pecquet, Exper. Nov. Anat. 4to. Paris, 1651. Portal, Mem. Acad. 1770. Prout, in Ann. Phil. vol. xiii. Quoin’s Elem. of Anat. Rees’s Cyclop. Ribes, in Mem. Soc. d’Emulat. t. viii. Richerand, Elem. Physiol. ; Ditto, par Berard. Rudbek, Nov. Exerc. Anat. 4to. Arses. 1653. Rullier, Diet, de Med. “ Chyme;” Ditto, Diet. Sc. Med. “ Inhalation.” Ruysch, Dilucid. Valv. Sabatier, Med. Acad. 1786. Salzmann, in Haller, Disp. Anat. t. i. Santorini, Tabula, fob Parma. 1775. Segalas, in Majendie’s Journ. t.ii. Sheldon, on the Alts. Sys. fob Lond. 1784. Soemmering, Corp. Hurti. Fab.; Ditto, de Morbis Vasor. Abs. 8vo. Traj. :ui Moen. 1795. Tiedemann, Physiol, par Jourdan. Valentin, in Journ. de Med. t. Ixxxvi. Vauquelin, in Ann. Chim. t. lxxxi ; Ditto, in Ann. of Phil. vol. ii. Vesting, Synt. Anat. Walter, in Nouv. Mem. Berlin, 1786, 7. Watson, in Phil. Trans. 1769. Werner, Vas. Lact. et Lymph. Desc. Winterbottom, De Vas. Abs. in Smellie, t. iv. Wrisberg, Observ. Anat. Vas. Abs., in Com. Gott. t. ix. Young’s Medical Literature. (J. Bostock .) ACALEPHiE (from ay.aXrilpn, a nettle); syn. urticee marina. Fr. Acalephes; Germ .Acalephen; the name of a class of invertebrate animals. They are all inhabitants of the sea, and are such as are commonly known by the names of sea- jelly, sea-nettle, Portuguese man-of-war, &c. It is from the property, which many of these animals possess, of irritating the surface of our skin so as to produce nearly the same effect as that resulting from the sting of a common nettle, that the class derives its name. Aristotle used the word a.y.a.’K-ofpr, to de- signate some of these animals ; but it was by Cuvier that the class was formed, and the term acalephae applied to it. As this class now stands in the last edition of the Regne Ani- mal,, (t. iii. p. 274,) it is formed chiefly by the animals constituting the Linnaean genus Medusa and les acalephes hydrostatiques of Cuvier. On many accounts the acalephae are objects of extreme interest to the anatomist and phy- siologist. They have occupied the attention of the most learned naturalists of every age, from the time of Pliny until the present day ; their numbers are, perhaps, greater than those i> 2 36 ACALEPII/E. of any other class of marine animals : they exist in all seas ; and yet we remain very ignorant with regard to several points in their structure and history. The peculiar nature of their tissues, the singular arrangements of their organs, the anomalies in their functions, present as many objects of interesting inquiry to the physiologist, as the wonderful variety and striking elegance of their forms, and their splendid colouring present to the admiration of the naturalist. Peron,* in his animated description of the Me- dusa, observes, “Among the animals of this family we find the most important functions of life performed in bodies which offer to the eye little more than a mass of jelly. They grow fre- quently to alargesize, soas to measure several feet in diameter; and yet we cannotalways determine what are their organs of nutrition. They move with rapidity, and continue their motions for a long time ; and yet we cannot always satis- factorily demonstrate their muscular system. Their secretions are frequently very abundant, and yet the secreting organs remain to be dis- covered. They seem to be too weak to seize any vigorous animal, and yet fishes are sometimes their prey. Their delicate stomachs appear to be wholly incapable of acting upon such food, and yet it is digested within a very short time. ' Most of them shine at night with great bril- liancy, and yet we know little or nothing of the nature of the agent which produces so re- markable an effect, or of the organs by which it is elaborated. And, lastly, many of them sting the hand which touches them ; but how, or by what means, they do so still remains a mystery.” It is, therefore, but a very imperfect account of the anatomy and physiology of this class that can be at present given . The following are the names and characters of the groups into which the acalephae have been divided by M. De Blainville,j- whose arrangement is nearly the same as that adopted by Eschscholtz. £ I. Physograda. Body regular, symme- trical, bilateral, fleshy, contractile, often very long, provided with an aeriferous sac. Bran- chiae in the form of long cirri, very con- tractile. 1. Organ of natation simple and lamellated. Gen. Physalus. ( Physalia, Lam.) 2. Locomotive organs complex and vesicular. Gen. Physsophora. Diphysa. Rhizophysa. 3. Locomotive organs in the form of smooth scales, disposed in transverse series. Gen. Stephanonna. Agalma. Protomedea. Rho- dophysa. II. Diphyda. Body bilateral and symme- trical, composed of a visceral mass of small size and of two swimming organs, hollow, * Peron. Ann. du Mus. xiv. 220. t Diet, des Sc. Nat. 41 Zoophytes.” 1830. f System der Acalephen. Berlin, 1829. The most complete treatise on the anatomy and history of the acalepha hitherto published. Its learned author enjoyed excellent opportunities of studying these animals in the course of the two voyages round the world undertaken by Kotzebue, of whose expeditions he was naturalist. contractile, somewhat cartilaginous, and placed one before the other, the anterior one being in more direct connexion with the central visceral mass, which it seems to surround ; the other posterior, and very slightly adherent. Mouth at the extremity of a stomach more or less extensile. Anus unknown. A long filamentary organ, ovigerous, rises from the root of the central mass, and is prolonged more or less posteriorly. Gen. Cucubalus. Cucullus. Cymba. Cu- boides. Enneagona. Amphiroa. Calpe. Abyla. Diphyes. Ersaea. Eudoxia. Py- ramis. Praia. Tetragona. Sulculeolaria. Galeolaria. Rosacea. Noctiluca. Doliolum. III. Ciliograda. ( Ctenophora, Esch.) Body gelatinous, free, varying in form, marked on the surface with narrow ambulacra formed by rows of vibratile cilia. Intestinal canal complete, with two orifices.* Gen. Beroe. Eucharis. Mnenia. Cal- ymma. Axiotoma. Callianira. Pandora. Medea. Alcynoe. Cestum. Cydippe. Idya. IV. Pulmograda. (Discophora, Esch.) Body entirely gelatinous, circular, without any solid part internally, margin provided with cirri of various forms, or with foliace- ous appendages pendent from the inferior surface. 1 . Simple : without true tentacula, peduncles or arms. Gen. Eudora. Ephyra. Phorcynia. Eu- lyrnene. Carybdea. Euryale. 2. Tentaculated : the circumference of the body, and sometimes the mouth, surrounded by tentacula. Gen. Berenice. Equorea. Foveolia. Pe- gasia. Cunina. iEgina. Eurybdia. Thau- mantias. Obelia. Linuche. Eirene. 3. Subproboscic : gastric cavity prolonged into a short peduncle, at the extremity of which is the mouth, surrounded by four brachial appendages. Gen. Oceania. Aglaura. Melicerta. Sa- phenia. Tima. 4. Proboscic : the lower and central part of the body prolonged into a proboscis-like appendage, either simple or provided with arms. Gen. Orythia. Geryonia. Dianoea. Fa- vonia. Cytseis. 5. Brachigerous : lower surface furnished with more or less numerous appendages, bra- chial, ramified. Gen. Ocyroe. Cassiopea. Medusa (Au- relia of Peron). Callirhoe. Melitea. Eva- gora. Cephea. Rhizostoma. Chrysaora. Cyanea. Pelagia. Sthenonia. V. Cirrigrada. (Velellida, Esch.) * M. De Blainville regards the animals included in this and the two preceding sections as being more allied in structure to the Mollusca, ( his Mala- cozoaires,) than to the Radiata, with which they are arranged by most zoologists. Accordingly he sepa- rates them from the two succeeding sections, which are truly radiate animals, and of which he forms a class in his great division Actinozoaires, under the name of Arachnoderma. ACALEPHiE. 37 Body oval or circular, gelatinous, supported by an internal, solid, subcartilaginous body, and provided with very extensile tentacule-like cirri pendent from the whole of the lower sur- face. Gen. Velella. Porpita. Rataria.* Of the genera above enumerated, Eschscholtz has described about two hundred species. Messrs. Quoy and Gaimard have made us ac • quainted with several others ; but of all these a comparatively small number only have been described in detail : so that, although in the account which we are now to give of the anatomy and physiology of the acalephae, we shall, for the sake of brevity, make use of the sectional designations, it must be understood that the descriptions apply only to a few species, and that, with regard to the others grouped along with these, we can only say it is probable that they are similarly con- structed. I. Locomotion. The principal organ of locomotion in the physograda is the air-filled vesicle or bladder, which exists, of various sizes, in all the species. In physalus, ( Fig. 6.) it is a large organ, forming a great portion of the general mass of the animal. It is placed * The following neat but artificial arrangement of acalepha forms the subject of a communication lately made to the Zoological Society by M. Lesson, foreign member of that body : we are indebted for it to our friend Mr. Owen. I. Without a central solid axis. A. Body simple, entire. 1. Symmetrical, termi- nated at each pole by an opening .... 1 Beroidcc. 2. Non-symmetrical, the upper pole disciform or umbelliform, imper- forate .2 Medusa. B. Body multiple or aggre- gated. a. Homogeneous. 3. Composed of two pieces adhering together, and capable of separation . 3 Diphydcs. 4. Composed of numerous pieces aggregated toge- ther 4 Polytoma. b. Heterogeneous. 5. Animal furnished with appendages of different kinds. * Vesicle small, regular, placed at the summit of a kind of stalk fur- nished with lateral am- pulla, and terminal suckers 5 Physsophoree. ** Vesicle large, irregular, without stalk or am- pullae, but having ter- minal suckers and cir- riferous processes . . 6 Physaliae. II. With a central cartilaginous axis. 6. Body simple, with suckers and lateral ten- tacula. a. Body irregularly oblong, with a vertical lamina on its upper surface . 7 Velella. b. Body discoid, fiat above. 8 Porpitee. R. B. T. superiorly, and, for the most part, rises above the surface of the water. It has an elongated form ; the longest diameter being the hori- zontal. It is somewhat pointed at one end, at the other truncated ; and at either there is a small opening, the place of which is marked by a superficial dimple, surrounded by delicate muscular fibres, acting as sphincters. When (Fig. 6.) Physalus Utriculus, (Esch.) the bladder is squeezed by the hand, so as to force the contained air towards one of these openings, the air makes its escape through it ; but whenever the pressure is taken off, the opening again closes. M. De Blainville states that he has satisfied himself that this air-blad- der is really a dilatation of the intestinal canal; and that he regards the two openings mentioned above as the mouth and the anus. We are ignorant of the data upon which M. De Blain- ville grounds his conclusion. It does not ap- pear that any observer has found alimentary matter lodged within the air-sac. But whether or not it be an organ of digestion, it is cer- tainly an organ of locomotion, although only a passive one; for it is by its contained air that the animal floats on the surface of the water, so as to expose a large superficies of its crest and bladder to the wind, by which it is driven to and fro frequently with great velocity. The walls of this sac are muscular, so that by their contraction its cavity can be considerably dimi- nished. And thus, partly by the escape of air forced out through the openings, and partly by the compression of what remains, the specific gravity is so much altered as to admit of the 38 ACALEPIliE. Fig. 7. animal’s sinking into the deep when danger threatens. In the other physograda, the air-ve- sicle is so small in pro- portion to the general mass of the animal that it is not sufficient to raise it above the sur- face of the water. It is generally an ovate sac, with an opening at its upper end, closed by a sphincter muscle. It is probable that its walls are muscular, and that by pressing out a portion of the contained air, and by secreting more, alternately the animal can sink and rise at pleasure. The nature of the air con- t>,. i tained in these vesicles K/iizoprn/sa Melon. , , , 1 J has not yet been ascer- tained. In rhizophysa ( Fig. 7.) there are, pen- dent from one part of the body, certain peculiar organs, arranged very re- gularly in pairs, of a mus- cular structure, hollow, and furnished each with a round orifice. They differ from the tentacula in structure, and are, pro- bably,organs of natation. Similar tubes, but only two in number, exist in diphysa ; and, anterior ings. Their attachment is so slight as to admit of their being separated by agitation of the water. It is at the bottom of the anterior ca- vity that the essential parts of the animal are placed. Locomotion is effected by means of the impulse of a current which is kept up by the successive contractions and dilatations of the organs above described. The contractions of the two bodies are not synchronous ; but they succeed one another within a short time, so that a steady progression is maintained ; and in some species it is very rapid. In the ciliograda, the locomotive organs are large cilia, disposed in longitudinal bands on the surface of the body. These bands are ge- nerally eight in number; but in some species, (e. g. axiotoma Guedii, Esch ,) there are only four. The arches supporting the cilia are of firmer texture, and are less transparent than the rest of the body. In many species they extend from one end of the body to the other ; in some only along a part of the circumference. The structure of the cilia themselves has lately Fig. 8. \ a Agalma okenii. to them, in the same animal, there is a two-lobed organ, the use of which is doubt- ful. In agalma, (Jig. 8.) and some of the genera allied to it, there are certain cartila- ginous plates disposed in an imbricated manner along the sides of the body. These, Eschscholtz regards as loco- motive organs. The mus- cles by which they are set in motion must be extremely delicate, as a slight touch is sufficient to separate the plates from one another. The chief bulk of the sin- gularly formed diphyda is made up of the swimming organs, which are two sub- cartilaginous bodies, poly- gonal, generally pointed an- teriorly, truncated posteri- orly, placed one behind the other, and one a little within the other; the posterior por- tion being lodged in a little excavation which exists in the anterior. These two parts differ somewhat from one another in form, but both are hollow, and have large open- Diphyes Campanulifera. been examined by Dr. Grant,* with his usual care, in the Beroe pileus; f and he has found that they are fin-like processes, and that each is composed of several short, transparent, some- what curved filaments, placed parallel to each other in a single row, and connected together by the skin of the animal, like the rays sup- porting the fin of a fish. The rays in the middle of the cilium are a little longer than those at the sides. All the rays appear as transparent tubes under high magnifying pow- ers. They are so curved that their extremities are directed backwards towards the closed ex- tremity of the animal. There are about forty cilia attached to each arch in this species, which is nearly an inch in length. The cilia are so large as to be visible to the naked eye. Most of the ciliograda have their cilia quite exposed; but Pandora is provided with moveable folds of the skin along the cilia-bearing arches, which can be brought over the cilia, in whole or in part, at the animal’s pleasure, so as to cover them more or less completely. These cilia are moved nearly in the same manner as the pec- toral fins of fishes. But their motion is so rapid, when the animal is vigorous, that the eye cannot follow it. The existence of motion is pointed out, however, by lines of beautiful iridiscent colours playing along the arches, and * Trans. Zool. Soc. of London, i. 10. t Pleurobrachia pileus. Fleming. Brit. Anim. 504. Cydippc p. Esch. ACALEPIIyE. 39 by the currents which are generated in the cir- cumambient fluid. The animal has the power of arresting completely the motion of one, two, or more rows of cilia, while the others are moving. When all are set in motion together, the animal moves onwards with the inferior or oral surface (inferior in a state of rest) directed forwards. When the motion of some is ar- rested, the whole body acquires a rotatory mo- tion, and advances in a curvilinear path. The animal has also the power of changing the direction of the currents caused by its cilia, so that it can ascend or descend in the water at pleasure. It can also increase and diminish at will the velocity of the motions of the cilia. Those animals which have the largest cilia, (e. g. Medea,) swim with the greatest rapidity. The cilia continue to move for some time after having been separated from the body, in con- nexion with part of their arches. Immediately beneath the arches there are vessels conveying a fluid, which is in motion during the vibrations of the cilia. Whether these vessels are destined only for the conveyance of the circulating fluid to the cilia, (which in all probability act as organs of respiration as well as of locomotion,) or carry a stimulus fitted to excite their vibra- tions, is not yet determined. Eschscboltz com- pares these vessels to those which Tiedemann has described as connected with the feet in the echinodermata. And Dr. Grant is of opinion, with MM. Audouin and Milne Edwards, that it is not improbable that the motions of the cilia are somehow dependent on the movements of the fluids contained in the above-mentioned vessels, seeing that in the actinia the tentacula are projected by water being forced from below into them. In the other classes of the acalephae also the same kind of structure prevails. Such of the pulmograda as have cilia around their margins have also circular vessels running along their bases; and almost all projectile and exten- sile tentacules and filaments are provided with sacs and canals, containing fluids, at their roots. In addition to their cilia, several of the cilio- grade acalephae have other organs of locomo- tion in the form of long filamentary arms or ten- tacules, with which they can poise themselves in the water without moving their cilia. In Cy- dippe* these are two in number. They are lodged in two tubes placed alongside of the sto- mach, from which they issue near the mouth. They can be extended to four times the length of the animal. They terminate in very fine points, and along their whole course present minute filaments placed at equal distances, which are coiled up spirally, close to the ten- tacules, when these are about to be withdrawn into their sheaths. The tentacules are also coiled up in a spiral form when completely contracted. They are sometimes suddenly sent forth from their tubes to their full length by one impulse, and then their lateral filaments are gradually uncoiled ; a process this of no less interest on account of the gracefulness of the motion than on account of the peculiar mecha- nism which it indicates. * Grant. Trans. Zool. Soc. i. 10. The principal organ of motion in the pulmo- grada is the large campanulate, or mushroom- shaped, disc, of gelatinous consistence, which constitutes the great mass of the animal. In this, for the most part, no muscular fibres can be seen, and yet the animals move about with some quickness. They have the power of con- tracting and dilating their discs at pleasure, in whole or in part. By alternately contracting and dilating their inferior surface, they strike the water in such a manner and with such force as to raise themselves ; when they discontinue this motion, they again sink, being of greater specific gravity than the sea-water. They move onwards horizontally, by acting only with one side of the margin of their disc. Lamarck was of opinion that these isochronous move- ments of the disc, by means of which the pul- mograda seem to swim, were fitted merely to facilitate the internal vital processes, and not to move the animals through the water ; and he regarded them as dependent entirely on the influence of imponderable agents existing in the circumambient fluid, and alternately enter- ing into, and flowing from, the general mass of the animal. He compared the motions with those of the fluid in Franklin’s thermoscope, when held in the hand.* In the course of the ordinary progression of the large Medusa aarita of our seas, the contractions of the disc take place from twelve to fifteen times in a minute. The convex surface of the disc always advances foremost. No fibrous structure has hitherto been dis- covered in the general mass of the disc. In- ternally, it is cellular, uniform, and veiy soft. The quantity of solid matter in the disc, and, indeed, in the whole body, is very small. Some medusa, which, when recently taken out of the water, weighed fifty ounces, on being dried, left remains weighing scarcely more than five or six grains. “ It is therefore evident, that the sea-water, penetrating the organic tex- ture, constitutes the greater part of the volume of these animals.” f But in some species there exists a fine muscular membrane, stretched over a certain extent of the lower surface just within its outer margin. Under a lens, this has the appearance of being composed of nu- merous fleshy fibres, forming little bundles, arranged in a radiate manner as regards the axis of the animal, and closely adherent to the gelatinous tissue of the disc. When portions of the disc are cut off from living medusa, without any part of this muscular membrane being attached to them, they remain motionless ; but when their connexion with the membrane is preserved, even small portions continue their motions of contraction and dilatation for a considerable time. The tentacula of the pulmograda (which are always pendent from the inferior surface) may be regarded as supplementary organs of loco- motion, although they are, in all probability, subservient chiefly to the nutritive function. They are all simple, not branched, generally * Anim. sans Vert. ii. 454. t Spallanzani, Travels in the Two Sicilies, iv 218. 40 ACALEPII7E. Fig. 10. hollow ; and, when connected with the appen- dages of the digestive cavities, or when they have a vesicle at their base, very extensile. Several genera have suckers at the extremities, and along the sides, of their tentacula, by means of which the passing prey is seized. The tenta- cula which are extensile seem to be projected by the forcing of water into their internal cavity, by the contractions of the vesicles at their base. The extent to which the filamentary organ is thus lengthened, in some species, is very extra- ordinary.* It seems to be shortened again by means of the contractions of circular muscles, which force back the water into the vesicle, and of longitudinal muscles which draw it in. Peron thought that some of the pulmograda were furnished with internal air-bladders ; but Eschscholtz, on directing his attention to this point, satisfied himself that what Peron had taken for air-bladders were merely appendages of the gastric cavities, into which air had acci- dentally been introduced during the removal of the animals from their native element. In the cirrigrada, locomotion is effected Fig. 11. * In the tentacula of some of the physograda, also, a similar extensibility exists. The lower sur- face of physalus, for instance, which itself seldom exceeds six inches in length, is provided with ten- tacula sixteen and even eighteen feet long. partly by the movements of the tentacules which hang down from the inferior surface ; but chiefly, perhaps, by the action of the wind on the raised crest, with which most of these animals are provided. Immediately around the mouth are placed numerous small tubular suckers, similar to the feet of many echinoder- mata. Exterior to these there are longer tenta- cula, for the most part in a single row, and simple; sometimes branched. Neither of these two kinds of organs is very extensile. The disc from which the tentacules hang, and the crest, are supported internally by a calcareous plate, which is the only organ of the kind in the whole class of acalephae. It somewhat re- sembles in structure the calcareous axis of retepora, being cellular and porous. Its nu- merous cells are filled with air, which renders the whole animal so buoyant that it floats on the surface of the water, and is wafted along by the winds. In velella (Fig. 11.) there are two plates, one placed horizontally, the other perpen- dicularly upon the upper surface of the former. They are marked with lines of growth, enlarg- ing from within outwards, like the extravascular shells of the mollusca. The perpendicular plate in velella supports the crest, which stands upright, and exposes a large surface to the wind. Rataria ( Fig. 12.) has its crest provided with strong muscular bands run- ning perpendicularly. It lies on the surface of the water, with the crest stretch- ed out, so that its whole side touches the water. When it is alarmed, the crest is suddenly contracted, and the centre of gravity is so al- tered in consequence, that the position of the body is almost reversed. When the crest is again raised, the body imme- diately resumes its former position. Porpitu has a simple plate supporting its disc, without any crest, and long tentacula, which are so delicate as scarcely to bear the slightest touch when the animal is taken out of the water. When the position of the animal is altered by the hand, so as to make the surface covered with suckers the upper one, all the tentacula of one half of the body turn round to the dorsal surface, and all those of the other half stretch over their own surface, and thus the animal very soon regains its old position. II. Motility and Sensation. — Almost all observers have failed to discover anything re- sembling a nervous system in the Acalephae. Even Eschscholtz,* who devoted so much atten- tion to their anatomy, could not see nerves in the largest that he examined. But in Cydippe, according to Dr. Grant, f there is a structure which can be regarded only as belonging to the nervous system. It consists of a double transverse filament of a milky white colour, running round the body, near its surface, at a short distance above the mouth. The two cords of which this filament is composed unite in the middle of each of the spaces between * System, p. 19. t Trans. Zool. Soc. of bond. i. 10. Fig. 12. Rataria cordata. ACALEPIIyE. 41 the ciliated arches to form eight ganglia, from each of which two nerves go to the adjoining bands, and one, larger than the others, runs upwards in the middle of the transparent space between the bands, and can be traced to be- yond the middle of the body. In the course of these last-mentioned nerves, two or three smaller ganglia are visible, from which fila- ments pass inwards to the viscera. Dr. Grant likens these nerves and filaments to the abdo- minal nerves of pectinaria and other transpa- rent animals. The circular fibres forming the sphincters of the orifices of the air-bladder in physalus have been mistaken for nerves.* There is no evidence that the acalephre possess any other sense than that of touch. But, al- though they cannot be said to have the sense of sight, they are evidently affected by light. At least some of the smaller tribes shun a bright light, and sink into the deep to escape from it. In most of the tribes of acalephae, the sense of touch seems to have its seat chiefly in the tentacula and cirri, with which almost all are provided. The degree of sensitiveness with which these are endowed varies much. In some, the slightest touch, even agitation of the water, is sufficient to excite them to contrac- tion. These organs of touch, as has been al- ready mentioned, are subservient chiefly to the nutritive functions. Other parts of the bodies of most acalephae also manifest, by their con- tractions, a certain degree of sensitiveness. Several of the ciliograda alter the shape of their general mass when touched. In physalus the crest appears to be more sensitive than any other part. Many species, particularly of the pulmograda, give no signs of their feeling even the deepest and most extensive wounds of their discs. But it was observed by Spallanzani, that, by friction, and by punctures of the mus- cular membrane of the disc, the movements of contraction and dilatation could be excited in medusae, which, having been kept in a dry place during twenty-four hours, had discon- tinued their ordinary motions, and had lost nearly two-thirds of their bulk by the running out of their contained fluids. f * Isis. Nov. 1819. t Professor Ehrenberg has very recently attempted to shew that medusa aurita is possessed of eyes, in the form of minute red points, which are seen on the surface of the eight brown-coloured masses set round the circumference of the disc. These masses, according to his observations, consist each of a yel- lowish, oval, or cylindrical little body, which is at- tached to a small and delicate pedicle. This short pedicle arises from a vesicle, in which there is placed a glandular body, unattached, presenting a yellow colour when viewed with transmitted light, a white colour under reflected light. It is upon the dorsal aspect of the yellow head, which surmounts the pedicle, that the well defined red point is seen, which Ehrenberg considers as an eye. Hp. compares the eyes of medusa to those of some rotifera and entomostraca. The glandular body situated at the base of the pedicle, he regards as an optic ganglion, which, he seems to have satisfied himself, is connected with two filaments that decus- sate one another at about the middle of their course. These he describes as forming part of a nervous III. Digestion. — The structure and action ofi'the organs concerned in the function of digestion in the acalephae are still involved in much obscurity. Even in the large and fre- quently examined physalus, it is difficult to ascertain the functions of the various parts in a satisfactory manner; and, accordingly, there exists so much difference of opinion amongst anatomists with regard to them, that some will not even admit that it has a mouth, while others assign to it both a mouth and an anus, as well as ccecal prolongations of the stomach. Eschscholtz concluded, from his numerous ob- servations on the living animals, that, in all the physograda, the digestive organs consist merely of absorbing tubes or suckers, all of which are simple, and pendent from the inferior sur- face. He seemed to think that the action of these filamentary organs was analogous to that of the roots of plants ; — that they were en- dowed with an endosmosic power, which en- abled them to imbibe nutritious matter from the water. However this may be with regard to the simple filaments, or cirri, it appears pro- bable that the suckers are provided with orifices at their extremities, through which proper ali- mentary matter passes into the interior ; for several observers agree in stating, that both the physograda, and the diphyda apply their suckers to the bodies of other animals, and re- main adherent to them for some time, during which they seem to take up some nourishing matter. Eudoxia has only one sucker. Messrs. Quoy and Gaimard have described in detail the singular filamentary organ which bears these suckers in diphyes. Generally it is seen, at first, only as a shapeless opaque mass, of a reddish colour, lying contracted within the swimming cavity. But, gradually, it is ex- tended, and then there are perceptible, along the whole of one side of a fine transparent tube, numerous suckers, of a lengthened form ; each is covered by a very delicate bell-shaped case, and has its base surrounded by groups of mi- nute vesicles, which are, probably, the ovaries. From the base there arises also a little tenta- cule or filament, susceptible of very great elongation, and which sends off many secon- dary filaments.* The digestive organs of the ciliograda are less dubious. In these we find uniformly a straight alimentary canal with two orifices, the mouth inferior, the anus superior, in the ordi- nary position of the animal. In some species there are lips formed by short and broad folds of the integument, four in number, and very sensitive. In cydippe, Dr. Grant found these lips capable of rapid extension and retraction. circle placed, throughout the greater part of its course, immediately along the bases of the row of tentacules that surround the disc, so as to form, as it were, the outer wall of the circular vessel, or ap- pendage of the intestinal cavity, which runs round the margin of the disc. The same observer de- scribes another nervous circle, composed of four ganglion-like masses, disposed around the mouth, each being in connexion with a corresponding group of tentacules. (Ehrenberg, in Muller’s Archiv fur Anat. Physiol., &c. 1834. p. 562.) * Ann. des Sc. Nat. x. 8. 42 ACALEPIIAh The mouth is large, the oesophagus straight and wide; the stomach is, for the most part, of an ovate form, the intestine passes in a straight line, and with a uniform diameter, to its ex- tremity. The anus has a prominent circular margin in cydippe. No absorbent vessels can be seen arising from the gastric cavity. In many species, the alimentary canal is so large as to occupy the greater part of the interior of the body. When there is no food within it, it remains open at both extremities, and, as the animal swims generally with its mouth fore- most, there is a current of water continually passing through it. Eschscholtz observed, that when suitable aliment was carried by this cur- rent against the walls of the stomach, the orifices were immediately contracted, and the digestive process begun. Minute Crustacea, sal pa? , &c., have been found in the stomachs of ciliograda. The diligent observer just men- tioned seemed to regard the canal leading from the stomach to the dorsal surface, (which we have called the intestine,) as forming no part of the digestive organs. He termed it “ the water-canal,” and considered it as connected merely with the peculiar mode of locomotion, inasmuch as he observed it so patent while the animal was swimming and not digesting as to admit of a free passage for the water ; which, otherwise, in entering the open mouth, would have much impeded progressive motion. It was generally believed, until within a very recent period, that some of the pulmograda were destitute of stomachs. Hence the term of agastric medusa: which was applied to them by Peron. The researches of Dr. Milne Ed- wards, however, have rendered it probable that this supposition was erroneous, and founded on inaccurate observations. We have now rea- son to believe that all the pulmograda have gastric cavities ; but all have not true mouths. There are some in which the only communica- tion between the stomach and the outer surface is through numerous ramified canals in the pendent arms, which open externally by ex- tremely minute orifices, barely sufficient, even in large species, to admit the smaller ento- mostraca. Such a structure exists in rhizostoma. By injecting milk into its gastric cavity, the canals in its arms, and their oscules can be rendered visible; and it is then discovered that from the minute oscules, which are situ- ated in indentations along the margins of the arms, small vessels proceed inwards, and, uniting in twos and threes together, open into one large canal which runs through the middle of each arm. These arms are large, fleshy, foliated organs, eight in number ; each of which has a triangular shape. The eight canals above mentioned unite two and two, so as to form four great trunks, which open into a large central cavity, — the only one in the body. This cavity is situated at the base of the central process pendent from the lower surface of the disc. The base, in rising upwards, enlarges into four fleshy columns, which lose them- selves in the disc. It is between these four fleshy columns that the cavity of the stomach is placed. The intervals between the columns would form so many openings into this cavity were they not closed by a fine and plaited membrane, which bulges outwards when the stomach is filled. From the circumference of the stomach, at equal distances, sixteen vessels arise, and run directly towards the margin of the disc. These vessels may be regarded as arteries, and will be hereafter described along with other structures more nearly resembling the parts of a circulating system. But Cuvier* was disposed to consider them as cceca; although he ad- mitted that he could discover no other vessels fitted to discharge the functions of arteries. He remarked that if we regard them as arteries, we must look upon the little vessels which lead from the appendages or arms to the central cavity, as veins, or as lymphatics ; and then we might say that the sea is as a stomach to the rhizostoma, in the same way as the earth acts as a stomach for plants. But, at all events, Cuvier was convinced by his dis- sections that alimentary matter enters the body through the marginal oscules of the arms, and that it is accumulated in the internal cavity before passing into the radiating vessels. By experiments on the living animal, Dr. Milne Edwards has recently provedf that the circumambient fluid and its contents of mi- nute size do really enter the body of the rhizostoma through the margins of the arms. He placed a living rhizostoma in sea-water, artificially coloured red. The animal did not appear to suffer from the presence of the colouring matter. Within a very short time, the puckered membrane which borders the arms was distinctly tinged red, and, gradually, the colour ascended, until the whole body assumed the same tint. Dr. Edwards does not state, however, whether he traced the progress of the coloured fluid through the brachial canals and the vascular system. On placing the same individual again in pure sea-water, the colouring matter which had been absorbed disappeared gradually, and it seemed to Dr. E. that it was thrown out chiefly from the brachial fringes, but partly also from the margin of the disc, and from the capillary orifices situated at the extremities of the arms. Dr. Edwards satisfied himself that it is impossible for ani- mals larger than small animalcules to enter the central cavity of the rhizostoma. But most of the pulmograda have large central mouths, either simple and sessile, or placed at the ex- tremity of a projection from the lower surface of the disc. In some, the mouth is more or less patent, but capable of being closed by the approximation of the base of the arms. In others it is surrounded by a ring of conside- rable density, in which muscular fibres can be distinctly seen. In medusa aurita, there are, just within the cavity of the mouth, four open- ings, which lead, by as many short but wide canals, into four spherical sacs of considerable size. These are completely separated from one another by membranous partitions. That they are stomachs is proved by the circurn- * Journ. de Phys. xlix. 438 t Ann. dcs Sc. Nat. xxviii. 24!). ACALEPH/E. 43 stance of fishes being found in them.* * * § From each sac, four vessels arise, which run out- wards to the circumference of the animal. Other species (e. g. medusa cupilluta ) have the four gastric sacs in free communication with one another; and, frequently, (e. g. in pelagia, chrysaora, and ceginu ,) in connexion with these, there are four other sacs, lined with a more dense membrane than the former. These gas- tric appendages have the form of simple canals in equorea and tuna ; and of branched vessels in medusa and sthenonia. They were chiefly such pulmograda as have their disc bell-shaped that were formerly sup- posed to be agastric. It was imagined that alimentary matter being received within the campanulate depression, its orifice was con- tracted, and nourishment taken up by im- bibition through the walls of the disc. But an attentive examination of Carybdea mar- supialis, (Peron,) one of the animals which was believed to be agastric, has satisfied Dr. Milne Edwards that a mouth and an internal cavity connected with it do really exist. The great transparency of this animal renders the dis- covery of its internal structure a matter of con- siderable difficulty, excepting when coloured injections are used. Dr. Edwards found within the funnel-shaped cavity of Carybdea, and, as it were, pendent from its roof, a projection of very delicate tissues, evidently forming tenta- cula surrounding a central mouth, and a stomach, from which proceed four long canals leading to the tapering filaments which hang down from the margin of the body of the animal. These canals, Dr. Edwards believes to be analogous to the radiating vessels of rhizostoma. There exists just at the com- mencement of each canal, and opening into it, a group of minute cylindrical sacs, which may be regarded as biliary organs.f But in most of the pulmograda these organs are situated on the margin of the disc. Generally, they pre- sent the appearance of glands, being distinctly granular in their structure. They are opaque, have a lengthened form, and are lodged in little depressions, and surrounded by cup- shaped folds of the external integument. They are connected with the gastric appendages by small tubes.} In Aurelia phosphor ea, (Lam.) (Pelagia, Esch.) which formed the principal subject of Spallanzani’s observations on the acalephae, there are four groups of membranous tubes, convoluted, and resembling in structure the intestines of vertebrate animals. Although he did not trace their connexions, Spallanzani appears to have regarded them as truly parts of the alimentary canal. He observed that they exhibit a peristaltic motion, both in the water and in air, which can be increased by the application of stimuli.§ The food of the pulmograda consists of various marine animals — small fishes, mollusks, * Gaede, Beytriige zur Anat. iind Phys. der Medusen. t Ann. des Sciences Nat. xxviii. 251. f Eschscholtz, op. cit. § Travels, iv. 228. crabs, and worms. Even large fishes are some- times found entangled amongst the arms and tentacules. They are probably killed by the peculiar excretion which covers the surface of these organs, and which produces a stinging effect on man. The long filamentary appen- dages which hang from the margins of the disc in Carybdea and others, are covered with a glutinous matter to which passing objects ad- here ; the animal has the power of stretching them out and withdrawing them at pleasure, and of so folding them inwards as to carry to the mouth whatever may be attached to their sides. It would appear that some species are endowed with the power of discriminating the food most suitable to their owm nature. Gaede remarks that he has never found fishes in the stomach of medusa capillata, but often worms ; while in that of medusa aurita there are fre- quently fishes, rarely worms. In none of the pulmograda have either masticatory or salivary organs been discovered. The cirrigrada have, in the middle of their lower surface, a large flask -shaped stomach, the mouth of which is formed like a sucker. There appears to be a communication between this organ and the numerous tentacula which surround the mouth, through minute canals. The food consists of small animals, such as entomostracous Crustacea; the undigested re- mains of which are again ejected through the mouth. IV. Circulation. — No distinct circulating system has hitherto been discovered in the acalephas. But perhaps the peculiar apparatus of radiating vessels connected with the gastric cavities in the pulmograda, and the aquiferous canals of the ciliograda, which seem to per- form nearly the same functions as the vascular system of higher animals, may be conveniently and properly considered under this head. In the physograda, Eschscholtz saw what he considered as the rudiments of a circulation ; namely, distinct vessels arising from the roots of the tentacula, and ramifying on the in- ternal surface of the air-bladders ; but it does not appear that he traced these further, or that he saw the movements of a fluid within them. The vessels in the ciliograda, within which a fluid is seen to move, are situated chiefly beneath the cilia-bearing arches. This fluid is supposed by most modern anatomists to be merely water ; but by some it is regarded as a peculiar fluid, the product of the animal’s digestive powers. If it be water only, the canals in which it moves must be considered as being analogous to those of the aquiferous system of other classes of invertebrate animals, which has been so fully illustrated by the re- searches of Delle Chiaje,* and which is pre- sumed to be subservient to the respiratory function. The vessels in question arise in Bertie from a vascular circle which surrounds the intestine near the anus. They are eight in number, and one runs beneath each cilia-bear- ing arch, from one extremity of the body to * Mem. sur la Storia e notomia degli animali senza Vertebre, 4to. Napoli, 1823-25. 44 ACALEPII7E. the other. They then terminate in another annular vessel, which surrounds the mouth. In their course they give off numerous branches. From the oral circle of vascular structure arise two large vessels, which run along the walls of the gastric cavity, and ap- pear to unite with the other circle at the anal extremity. These last Eschscholtz regarded as veins, and the eight external vessels as arteries. He supposed that the veins, passing along the walls of the stomach, absorbed the nutri- ment, and then carried the circulating fluid to the cilia for aeration. In the course of his observations on the Beroe uvatus, Dr. Fleming* distinctly saw a fluid moving “ backwards and forwards” in the external vessels ; and he states that “ while the animal was active, there were numerous small spaces in the different vessels where the contained fluid circulated in eddies.” Dr. Fleming failed to detect any structure in the vessels which could produce these partial motions. In cestumnaiadis, Eschscholtz thought that he saw the system of vessels more dis- tinctly than in any other of the acalephae. He thus described it: “ From the base of each of the two tentacules, a vessel takes its rise, and goes towards the bottom of the stomach. Here the two vessels unite, and form a little vascular circle around the water-canal (intestine). From the upper margin of this circle, four straight vessels arise, which go towards the two rows of cilia-bearing organs placed on the dorsal sur- face. Under these they run, two in one di- rection, and two in the other. At either extremity of the body, these unite with certain vessels running superficially along the sides, and which complete the circulation by entering the first set of vessels just before they begin to run beneath the ciliated organs. All these vessels are simple canals, of the same diameter throughout, without any visible branches. They contain a colourless watery fluid, in which mi- nute yellowish globules are seen to move. In the vessels which arise from the bases of the tentacules, the globules mount upwards ; they assume a rotatory motion in the vascular circle; and, in the four dorsal vessels, they seem to move, some in one direction, others in the other. It is probable that what appears to the eye as one vessel, is, in reality, composed of two vessels, running parallel and close together.”f Seeing that the radiating vessels which arise from the gastric cavities of the pulmograda seem to carry out the nourishing material to all parts of the body, and that they are, in some species at least, connected with other vessels which form a complete circle, we are disposed to class them under this head along with the vascular structures already described. The exact analogies of their functions, however, have not yet, we conceive, been distinctly made out. From the stomach of rhizostoma, formerly described, sixteen vessels arise, and pursue a straight course outwards to the margin of the disc, near which they all enter, at equal dis- * Mem. Wern. Soc. iii. 401. t Op. cit. p. 14. tances, a circular vessel, which passes com- pletely round the circumference of the animal. Four of the radiating vessels correspond with the four fleshy pillars of the process supporting the arms, and there exists on the internal sur- face of each of these pillars, a groove, which establishes a direct communication between the corresponding vessel, and one of the large vessels of the central process. The other twelve are distributed by threes in the intervals between the first four, and arise from those parts of the stomach which are closed by the plaited membranes. The space intervening between the circular vessel and the margin of the disc is occupied by an innumerable multi- tude of little vessels which form a net-work like the finest lace.* In medusa aurita, there are also sixteen radiating vessels, four of which arise from each of the four sacs, into which the gastric cavity in this species is divided. Two of the four vessels in each group are simple, the other two are several times bifurcated ; both the simple main trunks and all the brandies so formed, enter a circular vessel sur- rounding the disc, which seems to be connected also with the tubular cavities of the numerous cilia which surround the margin like a fringe, and which are capable of elongation and con- traction.f Carus remarks with regard to the circular vessel, that “ it may be considered as an extremely simple rudiment of the great cir- culation of superior animals, in case we view the radiating as chyliferous vessels.”}; V. Respiration.- — It is probable that the air- bladders of the physograda, the swimming organs of the diphyda, and the cilia of the ciliograda are all subservient, in a greater or less degree, to the respiratory function, as well as to locomotion. The vessels in the last men- tioned class, which have been described above as appertaining to the circulating system, are regarded by some as respiratory organs ; and by Lamarck were compared to the tracheae of insects. They have been called aquiferous trachea:. Those who consider them in this light believe that they are open at two points, so as to admit the circumambient fluid to pass freely through them. The most recent and accurate observations, however, leave it doubt- ful whether this really takes place in the ciliograde acalephae. With regard to the pulmograda, several parts and organs have been pointed out by different observers as being, in all probability, the seats of the respiratory function. Cuvier thought that the delicate plaited membranes which exist between the fleshy pillars of the central process in rhizostoma, and which form in part the walls of the stomach, might be re- garded as the organs of respirarion. Eisenhardt supposed that he saw them in certain tentacu- lated processes attached to the membranous partitions which divide the gastric sacs of some species from one another ; while Gaede looked upon the four small sacs which overlie the * Cuvier, Journ. de Phys. xlix. 438. f Gaede, Anat. der Medusen. f Carus, Comp. Anat. (by Gore,) ii. 266. ACALEPHfE. 45 gastric cavities in medusa aurita as subser- vient to the same function. These sacs com- municate directly with the gastric cavities by means of openings in the membranous par- titions which separate them. The partitions bear on their inferior surfaces, plaited mem- branes, which, under the microscope, present the appearance of being studded with vesicles containing a little watery fluid. A row of filamentary organs is also attached to these membranes, which move like external cilia, even for some time after they have been re- moved from the body of the animal. VI. Secretion. — The existence of this func- tion in the acalephae is made known to us by the emission from their bodies, under certain circumstances, of a glairy mucus ; by the stinging effect which some unknown product of their organization has upon our skin ; and by the remarkable phenomenon of luminousness, which a large number of them present. The organs by which the mucus is secreted have not been satisfactorily observed. Dr. Milne Edwards saw reason to conclude with regard to the rhizostoma, that a large quantity of this fluid is secreted by a glandular structure situated along the margins of the arms. The stinging property possessed by several animals of this class has been the subject of inquiry since the time of Aristotle, but to this day we remain in doubt with regard to the nature and mode of production of the agent which causes this effect. Some men seem to be in- sensible to the irritation generally produced by the contact of living acaleph®. But, for the most part, a slight touch of any part of their surface, and chiefly of the pendent tentacula, is followed within a few minutes, at most, by a burning pain, redness, swelling, and some- times even a vesication, of all that portion of the skin which touched the animal. Sloane said of the physalus, (“ what the seamen call caravels, or Portuguese men-of-war,”) “ They burn violently — they do suck themselves so close to the skin that they raise blisters, and cause sometimes St. Antony’s fire.”* Even on our own coasts, severe cases of inflammation of the skin are occasionally seen, which have been produced by the irritation received during bathing from some of the larger pulmograda. In physalus, the stinging property seems to reside chiefly in the fluid with which the ten- tacula are filled. It continues to act power- fully even after the organs containing it have been detached from the body. And not only so, but it is said by some observers that its peculiar properties are so permanent, that vessels in which the animals have been placed must be washed several times in water, and carefully scoured before they can be used without inconvenience. On one occasion it was found that linen, which bad been merely rinsed in soap and water, had this quality of * Nat. Hist, of Jamaica, ii. p. 273. Sloane re- commends acajou oil as “ the remedy for the sting- ing of this nettle.” Mr. Bennett has lately found (Lond. Med. Gaz. xiv. 908.) that the application of vinegar to the irritated surface in some degree alleviates the pain. irritation fifteen days after it had been used in making observations on the physalus.* None of the cirrigrada hitherto examined possess the stinging property. The organs by which the luminous matter is elaborated are unknown. In some species, it is evidently mixed with the mucous fluid, which is so abundantly poured out from the margins of the arms and the disc. It has been frequently observed that the ciliograda are luminous chiefly along their rows of cilia, and that these continue to emit light for some time after their removal from the body. Perhaps the greater number of the acaleplr* are lumi- nous. According to Dr. M'Culloch, all inhabiting the British seas are so ; and indeed it is chiefly to the emission of light by animals of this class that the beautiful phenomenon of the luminousness of the sea is owing in all situations. Spallanzani, however, whose observations and experiments on this subject were as extensive as they were careful and ingenious, came to the conclusion that “ the medusa which are possessed of lumi- nous properties are extremely few compared with those which are destitute of it.” The same philosopher remarked, with regard to some of the pulmograda, that they emit light more strongly during the contractions of their disc than at other times ; that the intensity of their light increases when they are pressed in any way ; that the luminousness resides chiefly in a peculiar fluid secreted by glands situated around the margins of the disc, along the edges of the tentacula, and in the fringed partitions of the gastric cavities ; that this fluid being mixed with other fluids, as with fresh and salt water, and especially cow’s milk, imparts its lumi- nousness to them ; that when spread over solid bodies it continues to shine for several minutes ; and that in it there generally exists that irri- tating substance which produces the stinging effect. Spallanzani applied some of this fluid on two occasions to the tip of his tongue. It excited a burning sensation, which lasted more than a day. A similar feeling, but much more painful, followed the accidental application of a singledrop of the same fluid to the conjunctiva.j- In most of the acalephae, the external cover- ing is very fine, smooth, and delicate ; but sometimes it is granular, or even warty. It does not appear that these differences in its structure have been observed by any naturalist to be connected with corresponding differences in the power of emitting light. (See Lumi- nousness, ANIMAL.) VII. Generation. — The organs of this func- tion cannot always be satisfactorily ascertained. This may, in a great measure, be owing to their minuteness and transparency when not in action. Ovaria and oviducts, however, are dis- tinctly seen in several species ; but no other organs connected with the generative function have hitherto been discovered. According to Eschscholtz, the ovaria in the physograda con- sist of several groups of vesicles and filaments, * Journ. Roy. Inst. 1831, p. 205. t Travels in the two Sicilies, iv. 250. 4G ACALEPILE. loosely attached to the lower surface of the air-bladder. In the diphyda, they are in the form of numerous vesicles, having thick tunics filled with an opaque white fluid, and situated within one of their swimming organs. Such parts were seen by Eschscholtz only in some individuals, and on this account he was dis- posed to regard them as ovaries. But Messrs. Quoy and Guimard seem to consider it more probable that the minute botryoidal bunches of vesicles, which surround the base of each sucker on the lengthened filaments, (before alluded to as being subservient both to nutri- tion and to locomotion,) are the ovaries.* It does not appear that either Eschscholtz or Messrs. Quoy and Gai- mard saw the ova. In the ciliograda, the ovaries are more obvious. They consist of two or four vesicular organs, each placed between two of the cilia-bearing arches. In cydippe, they are of a red colour, and nearly cy- lindrical shape. The ova are spherical. The parts in the pul- mograda corresponding to the organs just referred to, are eight round bodies, of small size, situated near the margin of the disc, each formed of a vesicle, containing, at its free ex- tremity, many minute hexagonal corpuscules ; there is attached to each vesicle a digitated appen- dix, which seems to be hollow, and to com- municate with the circular vessel. These organs were seen by Gaede and by Muller in medusa capilluta, and M. aurita, and by Eschscholtz in some species of cyanea, sthe- nonia, pe/agia, and chrysaora ; Dr. M. Ed- wards has observed them also, at certain seasons, in rhizostoma ; and in carybdea mar- supialis, he found, midway between each pair of pendent filaments, and immediately above a little notch in the margin, four spots of a deep brown colour, each of which appeared, under the microscope, to be formed partly by a minute spherical body, having a granular aspect, as if it were filled with eggs, and partly by a little sac, with puckered sides, which is imbedded in the gelatinous substance of the body. These he regards as the ovaries. f But, notwithstanding their having found gra- nular bodies like ova in the organs above described, neither Gaede nor Muller considered them as ovaries. Muller regarded the granules as excrementitious matters ; and Gaede thought that he saw the ovaries in the plaited mem- branes of the gastric cavities ; whence he observed the ova descend into certain minute * Ann. des Sc. Nat. x. 8. t Ann. des Sc. Nat. xxviii. 250. vesicles imbedded in the margins of the arms- He remarked that, in medusa aurita , when the cells in the arms were filled with eggs, the plaited membranes had none; and, on the other hand, when there were no eggs in the arms, the plaited membranes were studded with them. Cuvier was also of opinion that the ova are formed in the plaited membranes above men- tioned, and that they are matured in the mar- gins of the arms.* No observations, so far as we know, have hitherto been made on the development of the ova ; but Dr. Grant has recently stated that the ova of equorea are furnished with cilia, and have locomotive powers, like the ova of the porifera and polypi f era. -f The colours of the acalephae often depend on the tints of their ova: these are generally red, but sometimes brown, yellow, or purple. VIII. Ideographical distribution. — We con- ceive that a brief notice of this part of their natural history may, in some measure, illus- strate the physiology of the acalephre. They are met with in all seas ; but certain families exist more abundantly in some localities than in others. The ciliograda and pulmograda, for instance, are inhabitants chiefly of the colder regions, while the physograda are seldom found beyond the limits of the tropical zone. Some float in bays, and near land, but the greater number in the high seas. Medusa and cyanea are met with only in the cold and tem- perate zones of the northern hemisphere. Cy- dippe lives in the North Arctic Ocean, as well as in the Pacific, under the equator. One species of cestum inhabits the Mediterranean, — another the South Sea. It frequently happens that enormous numbers of one species are met with closely grouped together, so as somewhat to impede a ship’s progress for two or three suc- cessive days ; after which, not a single indi- vidual of the same species is seen. In the European seas, it is chiefly in summer and autumn that the acalephsc swim on the surface. In winter, they probably sink to the bottom. BIBLIOGRAPHY. — Madeer, Tentamen systematis Medusarum stabiliendi, in Nova Acta AcaL Natur. curios, vol. viii. Append, p. 19 ; and Papers in the Svenska Vetenskaps nya Handlingar An. 1791, transl. into Germ. s. t. Neue Abhand. der Schwed. Akademie, &c. Jahr 1791 ; Seite 75, 149, 227. Dana, De quibusdam urticae marinae differentiis : Miscel. Societat. Taurinens. v. iii. p. 206. Muller, Beschreibung zweier Medusen : Beschaeft. der Ber- liner Gesellsch. Naturfor. Freunde Bd. 2. S.290. Cuvier, Sur l’organizaiion de quelques Meduses ; Societe Philomat. A. 3, F. 2, p. 69. Strom, A paper in Danish on the Medusa palliata in the Skrifterder Kiobenhab. Selskabs nye Sami. Deel.3, S. 250. Swartz, Medusa pelagica beskrifven ; Svenska Vetens. Acad. Hand. A. 1791, S. 188 in the German transl. T. 1791, S. 172. Gaede, Bey- traege zur Anatomie und Physiologie der Medusen, 8vo. Berl. 1816. Quoy et Gaimard , Zoologie d’un Voyage autour du Monde, 2 vols. 4to. Atlas fol. Paris, 1824. Duperrey, Voyage autour du Monde 4to. Atlas fol. Paris, 1826-1834. (John Coldstream.) * Regne Animal, second edit. iii. 277. See also Carus, Comp. Anat. ii. 307. t Lectures, Lancet, No. 565. p. 483. Fig. 13. ovigerous filament of Dijdiyes much magnified. ACIDS, ANIMAL. ACRITA. 47 ACIDS, ANIMAL, Several acids are found in animal products, some of which are peculiar to organized bodies, and others com- mon to them and to the other kingdoms in nature. The former are characterized by their analogy to other organic compounds, and are ternary or quaternary combinations of carbon, hydrogen, oxygen, and nitrogen. The latter are for the most part binary compounds, such as the phosphoric, carbonic, muriatic, sul- phuric, and fluoric acids. With the exception of lactic acid, the exis- tence of which as a distinct definite compound is doubtful, there is only one acid which can strictly be called peculiar to animals, namely, the uric acid. The oxalic, benzoic, and acetic acids are common to animals and vegeta- bles. The other animal acids are not found ready formed, but are artificially produced by various chemical processes in which animal matters are concerned. Such are the various acids from fat and oil, the animal pyroacids, the purpuric acid,* * * § and a few others. There are also cer- tain acids almost peculiar to individual animals, such as the formic, f the allantoic or amniotic,| the bombic, &c.,§ and one or two which are the products of disease. Under the articles fat, urine, milk, and bone, will be found the details respecting the principal animal acids. (W. T. Brande.) ACRITA (a, priv. y.^nu, discemo ,) 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 Radiataof Cuvier, which Rudolphi^T 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. f Supposed by Vauquelin to exist in the liquor amnii of the cow. § Extracted by Chaussier from the silk- worm, but its existence is very problematical. || Hone Entomologicte, vol. i. pt. ii. p. 202. ’ll Synopsis Entozoorum, p. 572. ** Lamarck observes, ‘ 1 Les animaux apathiques (as he terms the Acrita) furent tres-improprement appeles zoophytes: ils ne tiennent rien de la nature vegetale, 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 absolument 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- fusoria of Ehrenberg, the Polypi of Cuvier, the Entozoa parenchymatosa , Cuv. or Sterel- mintha, and the Acalephte, differs in the absence or obscure traces of nervous filaments from the second division, including the Echinoderma, the Entozoa cavitaria or Ccdelmintha, the epi- zoa, and the Rotifera, Ehr., in which nervous filaments are always distinctly traceable, either radiating from an ora] 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 . W ith 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 sterelmintha 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 planari®, and parasitic trematoda, and also in the echinorhynchi, in some species of which genus the cutaneous canals form a rich net- work.* In the acaleph® 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 planari® 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 acaleph® ; and thus constituted it may be characterized as follows. Sub-kingdom Acrita. — Gelatinous polymor- phous animals, without distinct nervous fibre, or visceral cavities. Alimentary canalexcavated in the parenchyma of the body, generally without an anus. Sanguiferous system composed of reticulate canals without proper tunics. Generation in most fissiparous or gemmi- parous ; in some oviparous. f The Acrita have been termed Protozoa, as * Rudolpbi' terms one species echinorhynchus vasculosus, from this circumstance. — Synopsis Ento- zoorum, p.581. f The definition of the Acrita given by Macleay is confessedly a negative one as referred to animals; 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 constantor 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. 1 hat, 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 planari®, 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 “ Animalia gelatinosa polymorpha, interaneis nullis medullaque indistincta. “ Os interdum indistinctum, sed nutritio absorp- tione externa vel interna semper sistit. Anus nullus. “ Reproductio fissiparavel gemmipara, gemmis modo exteris, modo internis, interdum acervatis. “ Pleraque ex individuis pluribus semper coha:- rentibus animalia composita sistunt.” — Horae Ento- mologies, ii. p. 224. See also Lamarck, Anim. sans Vertebres, ii. p. 2. ADHESION. 49 of a composite animal ; the polygastrica derive their name from an analogous multiplication of the digestive organ itself. Among the sterel- mintha we find instances where the generative system is the subject of a similar repetition, each joint of the taenia being the seat of a separate 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 suiTOunds 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, ('front ad-hxrere , 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. VOL. I. 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 this 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, imperfo rations 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 1 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. E 50 ADHESION. a certain epoch of embryo life, imperforate. These organic stales, 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, lie 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 may be produced, the most remarkable perhaps is an extravasation * Isid . Geoff. St. Hilaire, Hist, des Anomalies de l’Orcanization, t. i. p. 532. t On ihe 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 striffi, 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 * Hoc. cit. p. 253. ADHESION. 51 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 horns 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, j- 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, tom. 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. However 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, M . nro, 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 ampulla, 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. Bedard was of the same opinion.-}- 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. To some extent the opinions of Laennec and * Loc. cit. t Anat. Generale, p. 195. $ Hist. Anat. des Inflam. tom. ii. § 1XJ3. anj 1571. E 2 52 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 pro'onged : ulterior observations, however, have shewn that these media are really or- ganised. We have no general rules as to the * Phil. Trans. 1818. pp. 172 and 185. 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 j 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 | * Loc. cit. pp. 388-9. ADHESION. 53 more readily as the tissue may he more cellular and vascular. That these organs are very vas- 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 Home.'* He 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: hrst, 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.” When, 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, I 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 move 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 very 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 hernia: 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. llibes 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. I 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, Soemmering, 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- lermep 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 I 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 da Concours sur le Croup, t Diet, des Sc. Med. tom. xxxii. p. 2b0. $ 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 tire 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. — Freelte, on tlie art of healing, cicatrising, incarning, &c. 8vo. Lond. 1748. Bezoet, De modo quo natura solution redintegrat. 4to. Lugd. Batav. 1763. (Rec. in Sandifort Thes. Diss. vol. iii. p. 147.) Spallanzani, Prodrome, &c. sopra la reproduzionc animali, 4to. Modena, 1768. Ejas, Opuscoli de fisica, &c. 2 vol. 8vo. Modena. 1776. Eating, 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 ueber die Regeneration an lebenden Thieren. 8vo. G-otting. 1782. Murray, De redintegratione partium, &e. 8 vo. Cassel, 1786. Bell, Discourses on wounds. 8vo. Edin. 1795 — 1812. Balfour, Obs. on Adhe- sion. 8vo. Lond. 1815. Stoll, Ratio Medeudi, pars v. & vii.8vo. Vienna, 1768. Hunter on the Blood, Inflammation, &c. Bichat, Anatomic Gen. Beclard, ditto. Breschet , Diet, de Med. art. Adherence. Cruveilhier, Diet, de Med. et Chir. Prat. art. Adhesions. Laennec, De 1’ Auscultation Mediate, tom. ii. pp. Ill, et seq. Brande, in Phil. Trans. 1818. Gendtin, Hist. Anat. des Infl. passim. 2 tom. 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 56 ADIPOSE TISSUE. individuals. One of these graves, opened in I ourcroy’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 iutoabrittle 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. Bibltogh APHY. — 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 Tabellen. 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. — fLat. Tclaadiposa Fr. tissu udipeux, tissu graisseux, Germ, dus Fctt, Ital. adipe. Many of the old anatomists, as Mondin i, 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 Ilaller 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 ( pelotons ) 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 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 ; Stilly, round each kidney ; and, 6thly, 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 TISSUE. 57 neck, breasts, belly, mom Veneris, 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- gurdo, and the latter by that of sebum. 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 - phinus 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 omenta, or peritoneal duplicatures in the abdo- men, may be recognized as analogous fringes containing more or less sebaceous fat; and the omental appendages (appendices epiploicce) 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 substances we do not recognize the 68 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 vateria Indica, 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 Linmeus, the stillivgia 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 Sandwich 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 inorganio. 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 translucenee. 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 falling 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 J'ecula. 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 potassw, either of which has the effect of consolidating the inclosed or central portion * be Omento, Pinguedine, et Adiposis Ductibus, p. 41. * Do Ossium Medulla, Lips. 1758. t Repertoire Generate d’Anat. 1827. ADIPOSE TISSUE. 59 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 (crreag, sebum, sapo,j and elaine, (eA;, vita. Fr. Amphibies. Germ. Amphibian. 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 branchiae 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 branchiae, 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. — Ampiiipneurta. 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 palpebroe. 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, Otilopha, 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. — Apoda. 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, Ccecilia. 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 be 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; Fig. 15. 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 alte 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. 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 menubranc/ius, 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, b), 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 vertebra, 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 trails- AMPHIBIA. 94 verse processes are only found on a few of the most anterior vertebra;. 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. fig. 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, (fig. 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, (fig. 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, (fig. 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 rouuded 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 (fig. 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, l,) 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 ( fig. 16, n ) is even a little longer than the femur. It is succeeded by two bones of considerable length, (fig. 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 calc is and the astragalus. Between these elongated bones and the metatarsal are four small tarsal bones. The metatarsal bones (fig. 16, p) are much elongated, as are also the phalanges, (fig. 1 6, qfi) 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. 95 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. Tire 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 vertebra 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 urodela, 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 tire 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 gastrocnemii, 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. — Tire 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 lme, 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 AMPHIBIA. 96 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 fort)' on each side of the upper jaw, of which eight belong to the intermaxillary bone. Thesalamanderhas about sixty above 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 cesophagus 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, fkc. 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 tire 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 tire change in the respiratory organs. The newts, or water-salamanders, afford the most satisfactory opportunity of observing these * Sopra il sistema linfatico dei rettili. fob 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. * Tabular view of the circulation in vertebrated animals. VOL. I. The first period, previous to any change having taken place in the branchiae, is given in Jig. 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. 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 (1 1 and 12) have increased in size, but the original continuation of 1 going to the bran- chial, 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, (Jig. 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 98 AMPHIBIA. 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, J 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. } Part iii. p. 213. to which its organs ate 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 branchiEe 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. rf extent, and forming the basis to which the branchial apparatus is suspended, by means of a rather thick angular portion, (figs. 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, (figs. 21, 22, b,) 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 branchiEe 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, (figs. 23, 24,) we find the branches which support Fig. 23. Fig. 24. d the branchial apparatus (a) 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 ; (fig. 25, a,) the single piece ( b ,) and the two rhomboidal pieces (r, r,) in the meantime become united and extended, (figs. 25, 26,) and gradually lose by absorption Fig. 25. Fig. 26. 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. Tire minute filiform branchise, 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, (fig. 27, a.) and passes, along Fig. 27. 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 (5), 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 the 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 branchise, 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 oeso- 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. Gotting, 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 branchiee 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 broad 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 Fig. 28. 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 merits of the spinal cord are observed to take place, and the contraction of the coccygeal ver- tebrae 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 laminse, 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 palpebr® ; or perhaps, with greater strictness of analogy, it might be said that there are two palpebrae, and a sort of expansion of the inferior, serving as a memhrana 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 eveiy 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 hoilowed as it were out of the temporal bone, at the bottom of which cavity is the sacculus with its creta- ceous body ; the fenestra ovalis 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 perennibrancliiate 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 tegumentary 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 ccecilia 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 witli 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 !s 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 ot' cuticle hanging about the terrestrial salamander, which would lead to the opinion that this animal does not disengage itself from its deciduous skin in 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. Sirmlar results followed ex- periments made under running water. The effects of temperature in these experiments were very striking, and pirove 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 obstetricans, 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. ■water, described by Dr. Milne Edwards, formed by duplicatures of the lining mem- brane of the branchial cavity. The eel too, as is 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 branchi® for a considerable time, thus preserving those organs in a respirable state. XIII. Of transpiration and of secretion. — The particular condition of the skin already described, 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 dies. 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 afford 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 degrees 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 ready 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- veyed to the surface for the purposes just men- tioned. When 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 always 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 anouru. 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 ages. The actual multipli- cation of the species in many, perhaps all the polygastric animalcula, by spontaneous sepa- ration,— -that of the hydra by artificial division, - — the restoration of lost arms 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 for 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 excess, in others by defect. One of the most extra- 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 mar- moratus. 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 * CEuvres, in 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 ofteu 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, an i 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 back 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 ate 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 A m- hibien, in Berl. Gesels. Naturf. Freunde B. ii. S. 69. 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. Vien. 1768. Meyer, Synops. Reptil. 8vo. Gotting. 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. Gatlung. der Amphibien. 4to. Munich. 1811. Merrein, Tent. System. Amphib. 8vo. IVlarb. 1820. lioesel von Rosenhof, Hist, nat. Ranar. nostrat. fob Norib. 1746-61. Ed. Alt. auct. germ. s. t. Naturgesch. der Froesche, &c. fob Niirnb. 1800-15. Steinlieini, Entwickelung d. Frdsche.8vo.Hamb. 1820. Hasselt, De metamorph. ANIMAL KINGDOM. 107 Ranas temp, droning. 1820. Kohler, Obs. Anat. in Appendices, &c. Ranar. 8vo. Tubing. 1811. Steffen, De Ranis Obs. Anat. 4to. Berl. 1815. JlJerlens, Anat. liatrachiorum prod. 8vo. Halle. 1820. Breyer, Fabric. Ranae Pip*. 4to. Berl. 1811. Klotue, De Rana cornuta. 4to. Berl. 1816. Zenker, Batrachomyologia. 4to. Jen* 1825. Rathke, De Salamandr. corp. adip. ovariis, &c. 4to. Berl. 1818. Rusconi, Descr. Anat. delle larve rielle Sa- lamandre, &c. 4to. Pavia, 1817. Ej. Amours des Salamandres fol. Milan. 1821. Ej. Develop, du Grenouille com. 4to. Mil. 1826. i Dvges, Sur 1'os- teologie et la myologie. des Batraciens. 4to. Paris, 1834. Funk, De Salamandrae terrest. vita, &c. fol. Berl. 1827. Cuvier, Rech. sur les Reptiles dou- teux. Par. 1807. 4to. Wayler, Descrip, et icones Amphib. Monad). 1828. Treviranus, Protei anguin. Enceph. & c. 4to. Gotting. 1820. Rusconi e Conficj- liachi, Del Proteo Anguino, &c. 4to. Pav. 1819. Barton on the Siren. 8vo. Pliiiad. 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., jlssipara, 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 primary 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 apathic 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, &e. 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 ci/clo-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 oesophagus, a character which is expressed by the term cyelo-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 alengthened 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 . Polygaslrica, 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 papillaris, 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 (/>), and escaping by the larger vents (c, d.) (See Porifera.) 3. Pulypifera, 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 dicliotuma, (Jig . 30), where 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, (fg. 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- Fig. 31. pose of attract- ing food and of aerating the surface and fluids of the II body, as repre- V If sented in Jig. s ' 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. 109 external vibratile cilia, as in the beroe pileus represented in fig. 32. Tliis figure represents Fig. 32. careous spines. These animals are for the most part 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 coeca, 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 fig. 34. The mouth (a) is here surrounded with Fig. 34. one of the ciliograde acalephae in which the mouth (a) 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 (Jfi) extend from two curved lateral sheaths. (See Aca- X.EPH.E.) 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 (b) is here in the centre 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- 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 (Jfi) open from" the cloaca ; the great systemic artery receives the aerated blood from the branchiae, and the organs of generation (ra) 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. Rotifiera, 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 ANIMAL KINGDOM. 1 10 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. Fig. 35. 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 b). 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, //,) 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- r's 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 antennas and numerous simple eyes, and the mouth with maxillae ; the organs of motion in the form of simple setae or cirrhi extending from the sides of the body in a sin- gle or double row. The vascular system of the atinelida 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, hirudo medicinalis, Fig. 36. (Jig. 36.) These lateral cceea (b, c, d, e,J\ g, b, i, 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 tracheae, 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 that of a phytophagous melolontha vulgaris, {Jig. 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 (Esophagus 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,c), which is covered like the crop with minute glandular cryptee 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 (d). The short small intestine (e) opens into a wide colon {f), which terminates in the anus (g). In the vegetable-eating insect, {Jig. 38) the alimentary canal is more lengthened, con- voluted, and capacious, with more numerous dilatations, and the glandular organs are more developed. The crop (a) of the melolontha is succeeded by a minute rudimentary gizzard, and to this succeeds a long and sacculated glandu- lar or chylific stomach, which becomes narrow and convoluted below, and terminates in a small pyloric dilatation, which receives the four terminations of the biliary organs. The succeeding part of the intestine is also con- voluted, and has three enlargements in its course to the anus (e). The liver (c c) is here of great magnitude, and has its secreting surface much extended by the development of innumerable minute coeca from its primary ducts. Insects also often present distinct urinary organs, and numerous glands in both sexes connected with the organs of generation. (See Insecta.) 12. Arachnida, with the head and thorax united, generally four pairs of legs ; with- out antennae, or compound eyes, or wings, or metamorphosis ; the trunk divided into a cephalo-thorax and abdomen ; the head is often provided with two pairs of chiliform manduca- tory organs'; the eyes are simple. The respi- ration is aerial, sometimes performed by tra- chea, and sometimes by pectinated pulmonary sacs opening on the sides of the abdominal surface of the trunk. In their nervous, res- piratory, and circulating systems they indicate a higher grade of development than insects, and like them are generally inhabitants of the land, attaining considerable size and strength, with cunning, cruel, carnivorous habits, and often provided with poisonous instruments. (See Arachnida.) 13. Crustacea, with the head and thorax generally united, two pairs of antenna, two 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. 112 ANIMAL KINGDOM. compound eyes, more than four pairs of legs, the respiration effected by gills, and the shell generally hard and calcareous. These ento- moid aquatic animals are generally carnivorous, and have a short and'straight alimentary canal. Their circulating system is often aided by a muscular ventricle. The sexes are separate, and the organs of generation are double and symmetrical in both sexes. Their biliary or- gans have a conglomerate form, being com- posed of minute glandular follicles grouped together into lobules and larger lobes. Some of these animals are fixed and parasitic, and breathe by their general exterior surface ; most are free, and respire by means of branchiae placed under the sides of the carapace or ex- posed on the under-surface of the post-abdomen. (See Crustacea.) The THIRD, or CYCLO-GANGLIATED Or mol- luscous division of the animal kingdom, com- prehends five classes, viz. : — 14. Tunicata, soft, aquatic, acephalous animals, breathing by internal branchiae, never in form of four pectinated laminae, and covered by a close external elastic tunic furnished with at least two apertures. The exterior tunic is lined by a muscular coat; sympathetic ganglia are observed in the abdominal cavity, and the respiratory organs are ciliated as in higher molluscous classes for the production of the respiratory currents. The mouth, unprovided with tentacula or other organs of sense, opens at the bottom of the abdominal cavity, as seemn the cynthia dione. (Fig. 39. a.) The short oesopha- Fig. 39. gus leads to a capacious stomach (b), sometimes surrounded by the lobes of a small liver, which pours its secretion into that cavity as in higher mollusca. From the stomach a short wide convoluted intestine proceeds to near the ven- tral orifice ( d ) of the sac, where it terminates in the anus (c). The thoracic orifice (e), or the entrance to the respiratory cavity, is generally provided with numerous delicate tentacula (_/'), and a nervous longitudinal filament (A) is ge- nerally observed to encompass that opening, and to terminate in a small glanglion ( g ). These ani- mals are entirely marine, most are fixed, some are free ; they are all female, like the conchifera ; the circulation is aided by a muscular heart. Many are organically connected in groups, others are isolated, (See Tunicata.) 15. Conchifera, acephalous, aquatic ani- mals, covered with a solid calcareous shell, consisting of at least two pieces, and breathing by internal branchiae in form of four pectinated laminae. These bivalved animals have the mouth, as in the former class, situated at the bottom of the respiratory or thoracic cavity; the stomach is surrounded and perforated by the lobes of the liver; the circulation is aided by a bifid or a divided auricle and by a mus- cular ventricle, which is generally perforated by the rectum, as seen in the annexed figure of the organs of the spondylus, (Jig. 40. ) The two fimbriated lips Fig. 40. (a) which surround the mouth are pro- longed laterally into four tapering flat pec- tinated tentacular ex- pansions (b). The stomach fcj and the intestine are sur- rounded by the large mass of the liver (i ), and the rectum, near the adductor muscle (in), penetrates the ventricle of the heart (d), at some distance from the anus (ej. The branchial veins (g, h ) return the aerated blood to the two lateral divisions of the auricle, these pour it into the ventri- cle, by which it is pro- pelled forwards and backwards through the system, so that the heart is here, as in other invertebrated classes, a systemic organ. (See Conchifera.) 16. Gasteropoda, body invertebrate and in- articulate, provided with a head which for the most part supports tentacula and simple eyes, and furnished with a muscular foot, extended under the abdomen, and adapted for creeping. These animals are sometimes naked, more generally covered with a univalve, unilocular, solid, external shell. Some gasteropods breathe by a pulmonary cavity, most by branchiae va- riously disposed on the surface or under an open mantle. Most are marine, many inhabit fresh waters, and some reside on land. The higher forms are mostly carnivorous, and the lower orders phytophagous, and this difference affects principally their alimentary apparatus, 113 ANIMAL KINGDOM. as seen by comparing that of the carnivorous buccinum undatum, (Jig. 41,) with the same Fig- 41. apparatus in the phytophagous patella vulgata, (fig. 42.) Like most of the predaceous gas- teropods the buccinum is provided with a long muscular proboscis, (fig. 41, a, b,) capable of being extended to a distance from the mouth, and enclosing a bifid tongue covered with sharp recurved teeth. The oesophagus near the sto- mach dilates into a small crop (c), and to this succeeds a round membranous stomach (c/, e). The whole remaining intestine is shorter than the oesophagus, and dilates into a wide colon (_/',) before terminating in the anus (g), on the right side of the body under the open mantle. The liver, of great size, and accompanying the testicle (i) in the turns of the spire, pours its secretion into the stomach as in the acepha- lous classes. The vas deferens following the right side of the body terminates at the end of the male organ ( h ) in a small tubular styhform duct. In the patella, (fig- 42,) however, which feeds on marine plants, the mouth (a) is provided with a long slender convoluted tongue covered with numerous rows of teeth like a long file. The wide and sacculated oesophagus (d) leads to a capacious and lengthened stomach {J\ g), surrounded by the large liver, and the long convoluted intestinal canal ( h ) makes several turns imbedded in the mass of the liver before it arrives at the short dilated rectum (i) and anus ( k ). The salivary glands are generally of great size in this class, and present some- times in the same species both the simple follicular and the conglome- rate forms. The pancreas likewise is often present in form of a single follicle opening into the sto- mach along with the biliary ducts. The inferior orders are mostly male and female, but VOL. i. in the higher forms the sexes are distinct. (See Gasteropoda.) 17. Pteropoda, body organized for swim- ming, mantle closed above, branchiae external, no muscular foot for creeping, shell, when present, always thin, pellucid, unilocular, and dnoperculate. These soft, minute, floating ani- mals are all marine, and are enabled to swim bv means of two lateral musculo-cutaneous fin- like expansions, on the surface of which the respiratory branchiae or vascular plexuses are placed. These lateral fins are never supported by rays. The head is generally provided with retractile or sheathed tentacula, seldom with eyes. The body is sometimes entirely naked, often protected by a delicate thin transparent shell, which encloses the abdomen and is covered with a fold of the skin. They appear to be most closely allied to the inferior testaceous cepha- lopods in the nature and form of their shells and in their locomotive powers, and also in the general simplicity of their internal struc- ture, especially of their generative organs. The structure of one of the naked pteropods, clio borealis, is represented in fig. 43, where the abdominal cavity is exposed by the mantle Fig. 43. being opened from behind. The mouth (a) leads to a long oesophagus ( b ), which is sur- rounded by a circular series of nervous gan- glia (f). The stomach (c c) is imbedded in the lobes of the liver (g), which open by numerous short ducts into its cavity. The oesophagus is accompanied by the two long simple salivary follicles ( k ), and at the left or pyloric extremity (i d ) of the stomach is placed the heart ( i ), en- closed in its pericardium, which receives the arterialized blood from the branchial veins, and sends it through the system. The bottom of the abdomen or cavity of the mantle ( h ) is occupied as in the cephalopods with the gene- rative organs, which consist of an ovary (/) and long oviduct ( m , o), into which a short wide ccecum ( n ), commonly considered as a testicle, pours its secretion. The oviduct termi- nates on the left side, near the anus (e), in a small glandular sac ( q ), beneath which is the rhenal sac ( p ). The pteropods are commonly found floating in immense numbers at thesur- Fig. 42. 114 ANIMAL KINGDOM. face of the water in still warm evenings in tro- pical seas ; some, as the clio borealis, figured above, abound in the Arctic seas. (See Pte- ropoda.) 18. Cephalopoda, free cyclo-gangliated or mulluscous animals, with the feet disposed around the head, respiring by internal branchiae, and with the abdominal cavity enveloped by a muscular mantle open anteriorly. The cepha- lopods are all marine animals capable of swim- ming by means of membranous or muscular expansions, which are never supported by rays. The surface of the body is often naked, some- times covered with a shell, which is generally po- lythalamous, rarely monothalamous, and always inoperculate. There is often a concealed, loose, dorsal, calcareous or horny shell contained in a shut subcutaneous sac. The mouth is fur- nished with two horny or calcified mandibles, and the rudiments of an internal organized cartilaginous cranium and vertebral column are generally perceptible, together with some de- tached parts of the skeleton of vertebrata. The oesophagus is surrounded by a nervous collar, from which two supra-abdominal nervous co- lumns generally extend along the middle of the back, and sympathetic ganglia are observed in the abdominal cavity as in the inferior mollus- cous classes. These are predaceous animals, and the alimentary canal, though generally furnished with three enlargements, forming a crop, a gizzard, and a spiral or proper chylific stomach, is always very short. There are two pairs of salivary glands ; the liver is of great size, and pours its secretion, with that of the pancreatic follicles, into the stomach, as in the inferior classes. There is always a strong mus- cular systemic ventricle, and generally a di- vided auricle placed at the beginning of the branchial arteries. The common form of the chvlopoietic organs is seen in those of the luligopsis guttata, (fig . 44,) where the liver (a a a a) pours its se- cretion by ducts (b), which are surrounded and pene- trated by the pancrea- tic follicles (c c), and which unite into a single canal before they open by a valvular aperture into the third or chylific stomach (fig). The crop (d) ends in the strong muscular giz- zard (e), and from the third stomach (fi g) the short intestine (h) ascends in front of the liver to terminate by a valvular anus at the base of the funnel. The naked species have a glandu- lar sac for secreting a black inky matter, which appears to be wanting in those protected by an external shell, excepting in the argonauta, where the shell is seen in the ovum, and where there is a slight membranous connexion be- tween the animal and its thin delicate calca- reous covering. The sexes are generally sepa- rate, but the lowest foraminiferous cephalo- pods appear to approach to the pteropods in the male and female character of the genital organs. (See Cephalopoda.) The last or highest division of the animal kingdom, comprehending the vertebrated or red-blooded animals, or spin i-cerebrata, con- sists of five distinct classes, characterised chiefly by their generative, their sanguiferous, and their tegumentary organs, viz. — 19. Pisces, cold and red-blooded oviparous vertebrated animals, with one auricle and one ventricle to the heart, breathing by permanent branchiae, and with fins for progressive motion. They have a vertebral column and cranium, enclosing a spinal cord, and brain consisting of a medulla oblongata, optic lobes, cerebral hemispheres, olfactory tubercles, and a cere- bellum. The hands and feet are always formed like fins for progressive motion in a watery element. The fins are supported by rays pro- longed from the skeleton, the body is generally covered with scales, the trunk is organized for the lateral motion of the tail, there is no sacrum, and the pelvic arch is unconnected with the vertebral column. The bones are elastic or cartilaginous, and the centres of ossification for the most part remain perma- nently detached. The bodies of the vertebrae terminate in two cup-like cavities, they move on elastic tense intervertebral sacs, and the transverse processes are directed vertically downwards in the coccygeal region of the skeleton to facilitate the lateral motion of the trunk. The muscles, of a white colour, are disposed in oblique strata on the sides of the trunk for the movement of the elastic vertebral column. The mouth, destitute of salivary glands, is generally furnished with numerous unequal, irregular, fangless, osseous teeth, and the wide oesophagus, short like the neck, leads to a capacious stomach, from which the in- testine, shorter than in the higher classes, and nearly equal throughout, proceeds, without ccecal enlargement, to terminate in a cloacal sac on the inferior surface of the trunk. The liver is large, and pours its secretion generally by a single duct into the duodenum, near the pyloric extremity of the stomach and close to the opening of the pancreatic duct, as shown in the annexed figures of these parts in the frog-fish (fig. 45, A) and the cod (fig. 45, B). The oesophagus (a) of the frog-fish (fig 45, A) leads to a large globular stomach (c) with a strong muscular cardiac sphincter fib). The pyloric extremity is also surrounded with strong muscular bands (d), and beyond its pyloric valve two pancreatic simple glandular follicles (e e) open into the duodenum (g) close to the opening of the ductus communis chole- dochus (,/’). In the cod ( fig. 45, B) the wide oesophagus (a) leads to a long and capacious muscular stomach shut below, and immediately beyond the pyloric valve, formed by a circular fold of the mucous coat, open the ducts of numerous straight and simple pancreatic folli- Fig. 44. ANIMAL KINGDOM. Fig. 45. eles ( e e ) along with the ductus communis choledochus (f). The cartilaginous plagi- ostome fishes, the most complicated of this class, have a conglomerate form of the pan- creas opening in the same situation. In the sturgeon and in the sword-fish an interme- diate form is seen between the simple pan- creatic follicles of the invertebrated classes and the more complicated conglomerate organ in the higher vertebrata. This is shown in the annexed figure of the chylopoietic viscera as I found them in the xiphias gladius (fig- 46), where the liver (a) is raised up to show Fig. 46. the three hepatic ducts uniting with the cystic from the curved gall-bladder (c) to form a very short ductus communis choledochus. The pancreas ( d ) forms a large reniform mass com- posed of numerous straight follicles produced by the successive divisions of the great termi- nal duct (e) of this organ. This large inter- mediate organ is surrounded with a distinct muscular tunic to force its contents into the duodenum immediately beyond the pyloric valve ( b ). The tortuous small intestine ends by a valvular orifice (f) in a very short but distinct colon, which presents no coecum in its course to the anus ( g ). The bilocular heart 115 of fishes is entirely branchial ; it is often pre- ceded by a sinus venosus, and is always succeeded by a bulbus arteriosus, which often presents numerous internal valves in its course. The venous blood is entirely sent through the gills, and the branchial veins, after giving- branches to the anterior parts, unite to form the aorta which sends the arterialised blood through the rest of the system without the aid of a systemic heart. The respiration is effected by the transmission of water through the mouth or through distinct spiracula, and over the surface of the branchiae, which are internal in the adult, and are often preceded by external branchiae in the young. The lungs are always rudimentary, when present, sometimes in form of a shut single air-bag, sometimes divided or ramified, and most generally communicating by a ductus pneumaticus with the intestine or stomach, or oesophagus, but seldom employed for respiration. Fishes are oviparous and have the sexes separate ; the ovaries are continuous with the oviducts in osseous fishes, and de- tached from them in the plagiostome chon- dropterygii, and impregnation sometimes takes place internally and sometimes after the ova are separated from the body. (See Pisces.) 20. Amphibia, cold and red-blooded, verte- brated, oviparous animals, with three cavities of the heart, with a naked skin, and breathing, in the young state, by gills. These animals com- mence their career like fishes with one auricle and one ventricle, which send the whole of the blood through the branchiae, and they have at this period also double concave bodies of the vertebrae, as in fishes. Many retain the gills through life, accompanied with pulmonic cavi- ties, from which the arterialised blood is sent to a small left auricle. These animals are termed amphibia from the metamorphosis to a terres- trial from an aquatic life seen in most of the species. Their skeleton is imperfectly con- solidated, their ribs very short or wanting, their pelvic arch free or nearly so, and their atlantal and sacral extremities often very imperfectly developed or partly deficient. Their toes are destitute of claws, as their skin is of scales, and the respiration through their naked, highly sensitive, and secreting surface compensates for the imperfect development or limited use of their lungs, especially during submersion or hybernation. Some reside constantly in the water, others occasionally, and others continue on land. The male organ of intromission is rarely developed, and impregnation of the ova is generally effected externally. The genital organs are double and symmetrically developed in both sexes. The perennibranchiate amphi- bia, especially the axolotl, have been shown by Weber to possess a double auricle like the caducibranchiate species. (See Amphibia.) 21. Reptilia, cold and red-blooded, ovipa- rous, vertebrated animals, with two auricles and one ventricle, not breathing by gills in their young state, covered with scales, and with the means of internal impregnation. These animals, whether aquatic or terrestrial, breathe only by means of lungs, and their pulmonic respiration and the left auricle of the heart are i 2 ANIMAL KINGDOM. 1 16 greater than in the amphibia. Their bones are more consolidated than in the lower vertebrata, theirpelvicarch, when developed, is more firmly attached to the vertebral column, the centres of ossification, especially of the cranial bones, generally remain detached, the extremities are for the most part more competely developed, and the toes are generally provided with claws. Their cerebellum is remarkably small, their muscular irritability languid, and they have great tenacity of life. This ventricle, which receives both the venous and arterialised blood, is more or less divided by an ascending imperfect septum. The thoracic and abdominal cavities are not separated by a muscular d iaphragm, and the lungs extend backwards over the abdominal viscera. Their organs of generation are double in both sexes, and symmetrically developed on the two sides of the body. The two portions of the corpus cavernosum are often detached and bifid ; the chorion of the ova is generally thin or coriaceous, seldom calcified or hard, and the instincts of the parent generally extend to the protection of the young. (See K-eptilia.) 22. Aves, warm and red-blooded, ovipa- rous, vertebrated animals, with four cavities of the heart, covered with feathers, and with their arms organized for flight. Their bones are the most compact and dense in texture, the most extensively anchylosed, and generally contain air admitted from the cells of the lungs. Their tympanic bone is moveable, they have horny mandibles in place of teeth, their coracoid bones reach the sternum, the sternal ribs are ossified, and they want the tarsal bones. Their diaphragm never forms a complete partition between the thoracic and abdominal cavities. The hemispheres of the brain are without con- volutions, the optic lobes are large and hollow, the cerebellum is large and sulcated, and the posterior enlargement of the spinal chord of great size. The great irritability of their mus- cular system corresponds with the great extent of their respiration, the high development of their nervous system, the rapidity of their cir- culation, and the increased energy of all their functions. Their alimentary canal is furnished with a crop, a glandular infundibulum, a giz- zard, and generally with two cceca-coli, as seen in the annexed diagram (Jig. 47), showing the Fig. 47. common form of these parts in a gallinaceous bird. In these gallinaceous birds the oesopha- gus (a) sends out at a right angle with its course a large crop (6), with a contracted neck, and supplied with glandular follicles. Beneath this is the infundibulum or glandular stomach (c), with numerous large follicles placed between the mucous and muscular coats, and this opens into the large muscular gizzard ( d ), provided externally with two strong digastric muscles (e). The cardiac and py- loric orifices of the gizzard are close to each other (/*), and towards the lower part of the small intestine a minute ccecum often indi- cates the original entrance of the yolk-bag. The two long cceca-coli (g) commence by nar- row entrances (A), and the short colon ends in a common cloaca (/) for the genital and urinary secretions. In the predaceous birds, as the eagles (JigAQ), the oesophagus (a), the crop (b), the infundibu- lum (c), and the gizzard ( de ), are capacious, thin, Fig. 48. a and membranous, and form a continuous cavity for the prey, from which the indigestible parts can be thrown out in a bolus. In these birds the coeca-coli (g) are very small, sometimes unequal, or wanting. The urinary (it) and genital organs (kk) enter the cloaca ( l ) near the anus. The right ventricle of birds has the tricuspid valve in form of a thick strong mus- cular fold, and the aorta descends on the right side. The lungs form two undivided, light- coloured lobes, fixed by pleurae to the back part of the trunk, the last rings of the trachea form an inferior larynx, the bronchi pass in a mem- jj branous form through the lungs, and the lungs open into large membranous abdominal air- cells, which communicate with the interior of the bones. This extensive aeration of their systemic as well as their pulmonic vessels gives energy to their muscles for their aerial life and their distant migrations, and a high tempera- ture to their body for the incubation of the egg. Their plumage and their downy covering are the best suited for their aerial life and their high internal heat. Their organs of generation are double and symmetrical in the male, and animal kingdom. 117 generally unsymmetncal in their development in the female. The testes are internal, and the vasa deferentia terminate in the cloaca, where there is sometimes a grooved organ of intro- mission. In the female the left ovary and oviduct are developed, the right for the most part atrophiated and useless. The cavity of the cloaca in most birds, as seen in that of the great condor of the Andes {fig- 49), receives the end of the rectum (a), which forms a wide Fig. 49. rectal vestibule (6) : beneath this lies the part analogous to the urinary bladder (c d). Lower than the urinary sac are found the two openings of the ureters {h h), with the pervious oviduct on the left side {f), and the remains of the impervious oviduct ( g ) on the right side. The bursa Fabricii and the clitoris (when present) are placed more posteriorly in the preputial cavity. The most distinct forms of these gene- rative and urinary parts, and the nearest ap- proach to the mammalia are seen in the cloaca of the ostrich {fig- 50), where the rectum {a) opens into a wide and distinct rectal vestibule (6), which extends into a large urinary bladder {d). Beneath the urinary bladder is the ure- thro-sexual canal (e), into which the two ureters Fig. 50. {h h h * h*) and the oviducts ( f f * f * g) open towards the dorsal and lateral part. The pre- putial cavity (i) is the terminal portion in which the distinct clitoris is here lodged. The ova are impregnated internally, their chorion is calcified, and their development is effected by incubation. (SeeAvES.) 23. Mammalia, warm and red-blooded ver- tebrata, having four cavities of the heart, with a viviparous mode of generation, and possessing mammary glands ; with the lungs free in a distinct thoracic cavity, and generally having the body more or less covered with hair. The bodies of their vertebrae unite by flat surfaces, the tympanic bone is fixed, the jaws are gene- rally furnished with teeth lodged in deep alveoli, the coracoid bone rarely reaches the sternum, and the posterior extremities, when present, are always attached by the pelvic arch to a solid sacrum. The thoracic and abdominal cavities are separated by a muscular diaphragm. The hemispheres of the brain contain large ventri- cles, and rarely want convolutions, the optic lobes are small, concealed, solid, and divided by a transverse sulcus, the commissures of the brain and cerebellum, and the hemispheres of the cerebellum are large. The alimentary canal is of great length, the colon long and wide, with a single coecum, and sometimes with a vermiform appendix, and the anal open- ing is generally distinct from the urinary and genital passages. The tricuspid valve is thin and membranous, the aorta descends on the left side, there is no inferior larynx, the epi- glottis is distinct, and the bronchi continue cartilaginous into their ramifications in the lungs. The lungs, generally divided into lobes, move freeely in a distinct thoracic cavity, and have no abdominal cells or perforations on their surface, as in birds. There is always a urinary bladder, and the urethra in the male passes through a tubular penis. The organs of gene- ration are double in both sexes, symmetrical in the male, and rarely unsyrometrical in the female. The oviducts commonly unite at their lower part to form a uterus, in which the ovum becomes again connected with the parent, and is hatched. There are mammary glands open- ing externally for lactation during the helpless condition of the young. (See Mammalia.) These are the primary and secondary divisions of the animal kingdom, the struc- ture, classification, and history of which it is proposed to consider in this Cyclopaedia, under the heads of the several classes as enumerated in the subjoined table. animalia. I. Sub-regnuni, Cyclo-neura vel Radiata. Classis 1 . Polygastrica. 2. Porifera. 3. Polypifera. 4. Acalephse. 5. Echinoderma. II. Sub-regnum, Diplo-neura vel Articulata. Classis 6. Entozoa. 7. Rotifera. 8. Cirrhopoda. 9. Annelida. 10. Myriapoda. 1 1 . Insecta. 12. Arachnida. 13. Crustacea. 118 ANIMAL. III. Sub-regnum Cyclo-gangliata vel Mollusca. Classis 14. Tunicata. 15. Conchifera. 16. Gasteropoda. 17. Pteropoda. 18. Cephalopoda. IV. Sub-regnum Spini-cerebrata vel Vertebrata. Classis 19. Pisces. 20. Amphibia. 21. Reptilia. 22. Aves. 23. Mammalia. For the Bibliography of this article see that appended to each of the articles on the classes of animals and COMPARATIVE ANATOMY ( Introduc- tion. ) ( R. E. Grant.) ANIMAL (from anima, breath, the living principle. Lat. animal. Gr. Fr. animal. Germ. Thier. Ital animate). The objects of the material universe were long considered as arranging themselves naturally into three grand divisions, or kingdoms, as they were called: the animal, the vegetable, and the mineral. Closer attention, however, and a more careful study of the qualities and actions of the various bodies composing these kingdoms, lead to the con- clusion that two of them have much in com- mon, and consequently that a two-fold division suffices to comprehend the whole of the objects in nature, — these are the inorganic, or lifeless, and the organic, or living ; the first embracing minerals, fluids, gases, or the various forms in which simple brute matter presents itself to our observation ; the second including vegeta- bles and animals. As the subject Animal may be regarded in the light of the very kernel and epitome of the entire matter treated in the pages of our Cyclopsedia, we shall give such extension to this head as its importance seems to demand, studying brevity nevertheless, and embracing in general views the particular points which will be illustrated in detail in the different articles on anatomy and physiology, human and comparative. COMPARISON OF THE ORGANIC AND INORGANIC WORLDS. Physical qualities and elementary composi- tion of unorganized and organized bodies. — - The organic and inorganic kingdoms of nature are distinguished from one another by many strong features of difference, — first, in reference to their general physical qualities, external form, volume, and elementary composition ; and second, in regard to their capacities of action. The forms of the objects composing the inorganic world, indeterminate when they are Considered in their masses, are reducible to a very few simple crystalline shapes when they are regarded in their parts. The cube, the hexa- hedron, the rhomb, the prism, &c. are the ele- mentary forms of the inorganic world : plane surfaces and straight lines uniting under differ- ent inclinations, and originating angles that measure certain determinate numbers of de- grees are the accidents, which give them their characteristic and individual shapes. But the inorganic world has not absolutely even this limited perfection of form, if the ex- pression may be allowed. In order that the ob- jects which compose it may exhibit themselves under the form of crystals, solution of some kind, rest, time, and space are required; and these or any of these being denied, the ob- jects of the unorganized world present them- selves or exist as simple aggregates of mo- lecules, shapeless in their component parts as in their masses. And further, even when the objects of the inorganic world do present them- selves under definite forms, these are not ne- cessary and invariable. Carbonate of lime, to take a single instance, occurs crystallized not only in rhombs, but in hexahedral prisms, in dodecahedrons, the several faces of which are pentagons, in solids terminated by twelve triangles with unequal sides, &c. In their material composition, too, unorganized bodies are essentially homogeneous: one part of a mineral does not differ from another. This is very different from what occurs in the world of organization. From the lowest to the highest of living beings the shape is determinate for the individual, not only as a whole, but even as each of its component parts is concerned. Instead of being cir- cumscribed within angles and right lines like the objects of the inorganic kingdom, those of the organic are mostly rounded in their forms, or they are branched, or articulated and made up of several parts, which present varieties of conformation in harmony with the kinds of offices they have to perform, or the conditions surrounded by which the beings thus fashioned exist. Neither do they consist of homogeneous particles like minerals, but are made up in general of heterogeneous parts : in plants we have roots, leaves, branches, flowers, &c. ; in animals muscles, nerves, bones, and a great number of organs besides, each itself reducible to a variety of simpler parts or elements, en- titled tissues. The organic world also presents an immea- surably greater variety of forms than the in- organic : the myriads of animals and vegeta- bles that people and possess the earth differ to infinity from each other in their forms and physiognomies. Size. — Neither is there less discrepancy be- tween the inorganic and the organic world in the quality of size, which, in the first, is perfectly indeterminate, being greater or less, simply as the constituent molecules happen to be aggregated in larger or in smaller num- bers. The volume of organized bodies, on the contrary, is determinate ; every animal, every vegetable, has a particular stature, a cer- tain bulk, which is that of its species also, and is within narrow limits alike in regard to all the individuals composing the kind. Composition. — Contrasted in their chemical nature, organized and unorganized bodies pre- sent numerous and striking points of dis- similarity. Modern chemistry enumerates no fewer than fifty-two elementary or simple sub- ANIMAL. 119 stances,* besides the imponderables — light, caloric, and electricity. The whole of these are met with in the mineral or inorganic world; but no more than nineteen of them have been detected in the constitution of organized bo- dies.f Six of this number, indeed, — oxygen, hydrogen, carbon, azote, phosphorus, and cal- cium, occur in such abundance as to compose almost the whole mass of organized bodies ; the remaining thirteen are met with but spa- ringly distributed, and some of them even appear to be adventitious, and by no means essential to the constitution of the bodies in which they are encountered. Speaking 'generally, the chemical composi- tion of inorganic objects may be stated to be the more simple, many of them consisting of a single element only, and when more com- pound generally presenting binary, and at most ternary combinations of known elements. Organized bodies, on the other hand, are never made up of single elements, they are not even binary combinations, vegetables in the aggre- gate being at least ternary, and animals at least quaternary compounds. Though the elements which compose inanimate objects, therefore, are more numerous, the combinations they enter into are less complex than those they form in the constitution of living things. Another difference in the chemical consti- tution of unorganized and of organized bodies consists in the mode or form in which the che- mical elements exist in each. In the former they present themselves immediately as it were, the chemist in his analyses coming upon them at once ; in the latter they occur under two forms, the one immediate as in minerals, the other mediate, or arranged under a variety of new and peculiar shapes, which, with reference to the bodies they mainly constitute, are con- veniently and fairly spoken of as elements, with the prefix organic, they being exclusively the products of life and organization ; these are also frequently spoken of as the immediate principles of vegetables and animals. In the inorganic world, again, the con- stituent elements of bodies are always united by virtue of, and in harmony with, the general laws of chemical affinity, whilst in the organic the compounds formed are very often even the opposites of those that would have been originated under the dominion of these laws. From this it comes that, whilst the chemist finds almost as little difficulty in recomposing * Oxygen, hydrogen, carbon, phosphorus, sul- phur, borium, silenium, iodine, fluor, chlorine, bromine, azote, silicium, zirconium, aluminium, yttrium, glucynium, magnesium, calcium, stron- tium, baryum, potassium, sodium, lithium, man- ganese, zinc, iron, tin, arsenic, molybdenum, tung- sten, columbium, chromium, antimony, ciranium, cerium, cobalt, titanium, bismuth, cadmium, cop- per, tellurium, lead, mercury, nickel, osmium, silver, gold, platinum, palladium, rhodium, and iridium. t Oxygen, hydrogen, carbon, azote, phosphorus, sulphur, iodine, bromine, chlorine, fiuor, silicium, aluminium, magnesium, potassium, 6odium, cal- cium, manganese, iron, and copper. as in disintegrating inorganic objects, he has hitherto failed in compounding any one of the higher organic products or immediate prin- ciples of plants and animals.'* Chemical analysis we may therefore imagine to be a process of a very different nature as applied to inorganic objects from what it is when ap- plied to organic substances. With reference to the former it signifies a simple disintegra- tion, with an inherent capacity in the elements separated to reunite into the compound ana- lysed ; in the latter it constantly implies de- struction, without any such continuing power of recombination among the constituent ele- ments. Chemical synthesis, consequently, is an expression that can only be logically used in connection with inorganic objects. Considered with reference to their intimate texture, organized beings are no less strikingly different from unorganized bodies. The last are either solid, or fluid, or gaseous ; they never occur commingled, each subserving the ex- istence of the other. The water of crystalli- zation, and the globules of this and other fluids occasionally found included within the sub- stance of minerals, are but adventitious, being in the first instance entangled among their component molecules, in the second imprisoned within accidental cavities in their substances but contributing in nowise to the existence or duration of the matter that surrounds them. Organized bodies, on the other hand, consist, uniformly of solid and of fluid parts : whilst the vegetable has its woody fibre and constituent parenchyma, it has its sap also ; and animals with their firmer bones, muscles, cellular sub- stance, &c. have likewise blood circulating through their bodies, or various fluids de- posited within their tissues, which are just as essential to their constitution and continuance as the containing parts themselves. It is even by the mutual play of the solids and fluids which enter into the composition of organized beings that they manifest themselves in action or exhibit the phenomena which are peculiar to them, and which we denominate vital. It were indifferent whether we took away the solids (were such a thing possible) or the fluids of a vegetable or an animal ; in either case it must perish. The solids and fluids of organized beings consequently are in intimate and inseparable relationship one with another. Consistence. — From this admixture of solids and fluids in the world of organization results the variety of consistence which its objects pre- sent. In the inorganic kingdom, rigidity, — rigidity, too, which is uniform, — is one of the distinguishing characteristics. In the organic, on the contrary, pliancy and softness, which vary as well in every individual as in almost ' The exceptions to this position are scarcely worth noticing — one or two of the more simple organic elements, oxalic acid anil urea, for ex- ample, have been formed synthetically, and a substance bearing a remote affinity to fat has also been produced. No one, however, has ever suc- ceeded in forming tibrine, neurine, fecula, gum, &c. synthetically. 120 ANIMAL. every part of the same individual, are no less strongly marked and inherent features. So- lidity or hardness may be looked upon as the term of perfection of a mineral ; softness, on the other hand, often appears to be the term of perfection among vegetables and animals, the parts in these being generally softer in proportion as they have more important or noble offices to perform. The tender fibrils of the root, the leaves, flowers, stamina and pistilla in plants ; the brain, vessels, viscera, &c. in animals, are softer than the bark and woody fibre, than the bones, ligaments, skin, &c. which form, as it were, but the frame and covering of the proper fabric. This quality also varies in the organic world according to the age of the in- dividual: the nearer any organized being is to its birth or origin, the softer will it generally be found to be ; the longer it has lived, the harder wrill it as uniformly be ascertained to have become. Many organized beings, indeed, in the first stages of their existence, are wholly fluid ; they only acquire consistence as they are evolved and approach maturity. It is almost needless to speak of the ex- tent to which inorganic bodies differ from or- ganic in these respects; they are rigid and hard in all their parts alike, and never vary in consistence from the moment of their forma- tion to that of their disintegration or decom- position. The elementary particles or molecules en- tering into the composition of organized and unorganized objects, also differ in their essen- tial nature. All organized beings, in fact, whether their solids or fluids are regarded, appear to be made up of or to contain glo- bular or oval and sometimes flattened cor- puscles. The simplest plants, — the conferva, tremellre, &c., and the simplest animals, — the infusoria, polypi, &c., are alike composed of globules and a fluid ; nor is the case different as regards the most complicated vegetable or animal that exists. The elementary globule has now been discovered in almost all the solids and fluids both of vegetable and of animal bodies, — in the sap and cambium or succus proprius of vegetables, and in the blood, chyle, milk, and other fluids of animals ; in the fecula, albumen, parenchyma of the leaves, cells of the flowers, &c. of plants, and in the cellular membrane, muscle, brain, nerve, gland, &c. of animals. Nothing of the same kind has yet been de- tected among inorganic bodies. Angular par- ticles separable to infinity into others of a like description are the elements of composition in minerals. Globules, then, are to be regarded as the elementary constituents of organized bodies, as the ultimate molecules possessing a distinct form, which by their aggregation compose them The first step, indeed, in the singular pro- cess by which infusory animals are eliminated during the decomposition of organized sub- stances, is the formation of globular corpuscles; these, by their subsequent aggregation in some cases and individual evolution in others, appear to give birth to the organized atoms that by-and-by make their appearance; and, as we have said, globules are now admitted to form the basis of the different tissues which enter into the composition of the very highest among animals. These various tissues, in fact, would seem to result from the different modes in which the elementary globules are disposed ; and it is not improbable that the difference of function they exhibit may yet be found in harmony with, and perhaps depending on, pe- culiarity of arrangement in their constituent molecules. This aggregation of the organic molecules into a variety of tissues and peculiar organs forms another essential feature of difference between the organized and the unorganized world. Minerals, indeed, as they manifest no variety of phenomena analogous to those of life, required no diversity of elementary con- stitution in their different parts ; they are con- sequently homogeneous. In minerals the com- ponent molecules are arranged in layers placed one upon another, so that their crystals can be readily cleft in a variety of directions, according to the elementary arrangement of these. In vegetables and animals, on the other hand, the constituent molecules always form tissues, the fibres of which interlace or cross one another ; in no living or organic thing do we observe aught similar to what is called the cleavage itr minerals. From this it comes that minerals are as com- plete in their parts as they are in their masses : the minutest spark of carbonate of lime has all the properties of a crystal of this substance, were it as large as a mountain. The case is very different in regard to organized beings ; these consist of a number of organs, the sum of whose actions constitutes the peculiar vitality of each being, and no individual part or organ enjoys capacity to manifest itself abstractedly from the system to which it belongs. All the parts, of organized bodies are mutually en- chained by bonds of the strictest causality ; this even follows necessarily from the manner in which they originate and are evolved. Ihe radicle that bursts from the fecundated seed of a plant determines the growth of the stem, which subsequently and in its turn plays the same part with reference to the leaves and flowers, — the parts that appear first are the cause of the appearance of those that follow at later stages. No relation of this kind exists among inorganic bodies. When a crystal is formed in the midst of a fluid, the particles composing it unite, in conformity with the mere laws of cohesion and affinity, not in consequence of any determining influence in the particles which cohered the first, — each stage or period of the process of crystallization is independent of that which preceded it. Whilst the parts of an inorganic body, therefore, can exist with all their qualities, as well in a state of disin- tegration as in one of aggregation, the com- ponent parts of organic bodies can only exist w’ith their distinguishing properties when united to the entire being. Individuality in the or- ANIMAL. 121 game world, far from existing in the integral molecule as it does in the inorganic, can only be said to exist in the mass of integral mo- lecules united into that congeries of organs which constitutes a particular being. As a consequence of this independence on the one hand, and dependence on the other, we find, that whilst in the inorganic world the several parts may be modified without the others feeling the influence of the change in- duced, in the organic, implication of one part and modification of one action are commu- nicated to and manifested in the state and actions of all the other parts. Considered with regard to their duration, the objects composing the organic and the inorganic world differ essentially. In the former this period is determinate and definite, and, although it varies greatly, it depends in a great measure on circumstances inherent in the in- dividuals; in the latter it is indeterminate and indefinite, and when the objects composing it cease to be, it is generally in consequence of circumstances exterior to themselves. Organized beings exist for a limited time and in oppo- sition to many of the physico-chemical laws ; unorganized beings exist indefinitely, and only in harmony with the whole of these laws. Organic beings continue to exist in conse- quence of a kind of reciprocal action with external things, and especially by virtue of an incessant change and renewal in their con- stituent elements. The very condition of ex- istence of an unorganized body is quiescence ; any new action between its molecules them- selves, or between these and others external to them, any addition to, or subtraction from, its component parts, implies the destruction of its individuality. In the organic world, new forms result from the actions of forms already existing, which have the wonderful property of producing others similar to themselves ; and this in virtue of no general physico-chemical law, but of an especial power inhering in each organized being individually. There is nothing like this faculty of procreation or of generation in the in- organic world. When a crystal is produced, it is necessarily at the expense of one or of others that have already existed, or of a combination of the elements of these ; destruction is here a necessary preliminary to production, and the process is simply one of re-formation, not of genesis or creation. Neither in the re-forma- tions of the inorganic world do we find that the forms are always necessarily the same as those which preceded them : the crystalline form does not depend on the nature of the integral molecules, but on their mode of aggregation and number. In the organized world, again, nothing is more certain and fixed than that the form of the new being shall resemble that which gave it birth. The last distinction we shall mention under this head of material composition and physical qualities between organic and inorganic bodies is, perhaps, less striking, though not less in- teresting on that account : it is this, — that whilst in inorganic bodies the composition is quite de- terminate, in organised beings, although con- stituting particular species, the composition may present individual differences or modifica- tions. These are designated by the titles tem- perament, constitution, 4'C- There is no corres- ponding modification recognizable in the in- organic world. From what has now been said, it appears that organized and unorganized bodies differ essentially from one another in their general physical qualities and material constitution. The form of the organized being is determinate, and its outline is rounded or undulating; its size is limited ; its duration is temporary ; its composition is an assemblage of heterogeneous parts, of solids and fluids, arranged so as to compose a variety of fibrous and cellular tissues, and aggregates of organs or parts differing from one another in their form, struc- ture, and functions, but all nevertheless mu- tually dependent one upon the other, and con- curring to a common end, — the preservation of the individual, which has place by virtue of an internal activity denominated life, amidst incessant changes and renovations of the matter entering into its composition, and the continuation of the species, which is a genesis or creation, implying neither destruc- tion nor alteration in the mode of being of the individual or individuals from whom the new formation springs. Actions of unorganized and of organized objects. — But form, size, material composi- tion, duration, mode of origin, &c. are not the only particulars in the history of or- ganic and inorganic bodies which are capa- ble of being contrasted, and in which differences may be made to appear. All that exists is active; every entity performs actions, or manifests forces by which its own ex- istence is continued, and by which it participates in the various phenomena of the universe. Of these actions or forces there are two grand classes, the one general, the other special : the first are the physico-chemical laws which per- vade space and include the universe ; the second are the vital laws, which embrace within their dominion plants and animals, or things organized and having life. The most general of all the forces possessed are those of attraction and repulsion, which inhere in, and are manifested by, all existing things, organic as well as inorganic. Every object gravitates or has weight, coheres in its several parts, exhibits chemical affinities, and yields to the expansive influence of caloric. Inorganic objects exhibit these general forces alone, and are absolutely under their control. Organized bodies are also subjected to the same general forces ; but they are often modified, nay, they are sometimes even abrogated and set at nought by vegetables and animals alike, in virtue of the special powers inherent in themselves. These special powers have, in fact, the singular property of subtracting, in various degrees, the beings they actuate from the in- fluence of the general laws of creation. In- 122 ANIMAL. stead of obeying the universal law of gravita- tion, vegetables, for instance, shoot upwards, and propel their juices from the roots to the leaves; animals also distribute their blood in opposition to the laws of gravitation, and by their powers of motion overcome the universal physical law that tends to fix them in one place. The force of cohesion is not a merely passive property in the organized as it is in the unorgan- ized world, and the laws of chemical affinity are especially set at nought both by plants and animal?, their constituent elements being even generally united into combinations the con- trary of those which these laws ordain. Animals and vegetables are farther abstracted from the general law of caloric, the more perfect of them at least having a specific temperature, inde- pendent of that of the medium which sur- rounds them, and which varies in conformity with changes in the peculiar actions of which in them it is the product. There is even a distinction between the organized and unorganized world to this extent, —that while the physico-chemical laws do- minate the inorganic world rigorously, and the bodies that -belong to it seem to have begun to be as they continue to exist through, or in harmony with, their prescriptions, no organized body known has either sprung- into being or continues to exist through the agency of purely physical or purely chemical forces. The whole of the special properties of organized beings consequently must be held to be effects of the agent denominated life, and of the laws which this agent originates. The organized world is, therefore, a creation within a creation, a some- thing superadded to the material universe and to the generally pervading forces that keep its parts in their places, and endow them with what may be called their necessary pro- perties. Nor is it only whilst endowed with life that organized differ from unorganized beings. Many of the distinguishing and peculiar pro- perties of these remain for a season at least after life has left the organization it had built up. The extensibility and elasticity of the tissues of animals especially, were held by the distinguished Bichat as even independent of life, which he owned increased their energy, but which he denied as their cause, seeing that they continue to exist after death. These pro- perties are undoubtedly peculiar, and are at all events effects of forces which life has called into play, both the tissues which possess elasticity and contractility, and these qualities themselves having been engendered under the influence of vitality. In these properties, forces or capacities of action common to all the objects of nature, unorganized as well as organized, we see the objection to the old denomination of inert, which was applied to one of the great classes. Nothing that exists is inert or inactive ; but organized have an infinitely wider field of action than unorganized bodies. Let us, in illustration of this position, examine in succes- sion the various actions by which bodies gene- rally originate, continue their existence, un- dergo such modifications as they present in the course of their existence, and by which they come to an end or die. Origin. — Unorganized bodies, minerals for example, commence their existence from the instant that circumstances exterior to them- selves detach them from the mass of some other mineral, precipitate them from a state of solution in a fluid, or bring their constituent elements into a position in which they can combine together. In this, it is evident, there is nothing like generation, as the term is applied to organized bodies, which all alike, vegetables as well as animals, spring from a molecule, an atom, which has once belonged to, and which has proceeded from, a being similar to themselves. Vegetables spring from seeds, animals from eggs. Organized beings, therefore, are engendered, their existence is a consequence of that of other beings like themselves ; and in their succession they depend one upon another. Minerals, on the contrary, have no powers of reproduction ; they cease to be, if at any time they originate another mineral, and they are individually in a state of perfect independence.* In the mode in which organic and inorganic bodies continue their existence, there is also a striking dissimilarity. In the inorganic world we observe no actions tending to preserve the individual, other than those which have pre- sided over its formation : it continues to exist through the continuing agency of the affinities and of the attraction of cohesion which called it into being. Animals and vegetables, on the contrary, have special powers for their pre- servation superadded to those by the peculiar * It were long to enter here into the discussion of what has been called equivocal generation, which, if admitted, militates against several of the in- ferences just deduced. It is quite certain that infusions of any organized substance do speedily become filled with animals distinct in their kinds and lately shown to be much more complicated in their structure than was long supposed. It is almost as difficult to conceive that these infusory animals proceed from eggs contained in the fluids in which they appear, as to imagine that they proceed from the combination, per se, of their con- stituent elements. Did we incline to admit the reality of equivocal generation, it is certain that its occurrence must be referred to other than the general laws of nature, with which we have al- ready had occasion to show the laws of life to be in opposition, much rather than in harmony. It would be absurd to believe that these general physico-chemical laws, absolutely inimical to life, should at any time call it into being. Equivocal generation being acknowledged, therefore, it would seem necessary to infer a third order of laws be- sides the physico-chemical and the vital, the nature of which is altogether unknown to us. The number of creatures which were presumed to owe their being to equivocal generation, has been very much curtailed by the progress of science in modern times ; and it is not impossible that the mystery which still overhangs the genesis of the infusoria may one day be dissipated, and their pro- duction demonstrated to be in harmony with those laws which are known to preside over the origin of higher classes of vegetables and animals. ANIMAL. 123 agency of which they have been created. Inorganic bodies exist through the absence of all change in their interior; organized beings exist by force of change : there are two pro- cesses, one of renewal, the other of decom- position, perpetually going on within them ; they are continually appropriating from bodies exterior to themselves a quantity of matter which they have the singular faculty of ela- borating into their proper substance, and they have at the same time the power of withdraw- ing portions of the matter which already forms them, and rejecting these from their interior as no longer fitted for their preservation. Vege- tables, by means of their roots and their leaves, draw from the earth and from the air materials which they elaborate into juices fitted for their nourishment, at the same time that they throw off, especially by means of their leaves, a por- tion of the matter which had been absorbed, either as superfluous or as improper to enter into their composition. In the same manner ani- mals appropriate to themselves various amounts of matter in the shape of atmospheric air and food, from which they prepare a fluid proper for their maintenance, at the same time that they, by virtue of peculiar processes, with- draw from their bodies such portions of mat- ter as have already fulfilled their destination, and cast them out under the form of excre- tions. Organized bodies, consequently, are preserved as individuals by a process of nu- trition, a process which implies dependence on other bodies, and alternate appropriation and rejection of the particles of these ; the ex- istence of an organized being, in fact, only con- curs with the presence and appropriation of substances external to itself, with a perpetual accession of matter on the one hand, and of its rejection on the other, whilst unorganized bodies are more certainly continued, as their state of isolation or abstraction from all ex- ternal influences is more complete. Organized beings, in a word, continue to exist by virtue of certain inherent especial powers ; un- organized simply by virtue of the general powers that pervade the universe in harmony with which they were originally framed. The modifications undergone by organized and unorganized bodies are peculiar and cha- racteristic in each class. In the first place modification or change is no necessary con- dition to the existence of an unorganized body, as it is of one that is organized. A mineral in a state of complete isolation might remain eternally unchanged ; a plant or an animal, on the contrary, cannot be conceived as existing for a moment abstracted from the universe around it, and without undergoing change. A mineral, in the instant of its formation, acquires all the properties that distinguish it at any after-stage of its existence ; in plants and animals, on the other hand, as we witness an origin, so we observe a series of modifications denominated ages, — they commence their ex- istence, they increase in size, they attain ma- turity, and they decline and ultimately die. Any change which unorganized bodies ex- hibit is accidental, and happens under the influence of agencies external to themselves ; the changes which organized beings undergo in the course they run from incipience to their end, are on the contrary necessary, and take place in consequence of powers inherent in themselves. Any change which an unorganized body ex- periences happens on its surface : its mass is increased or diminished by simple addition to or subtraction from its particles ; it does not increase, neither does it shrink and decay in all its parts like plants and animals, in which increase and diminution take place at one and the same time from within and from without. Increase in the unorganized world happens through juxta-position, in the organic through intussusception. Organized bodies, conse- quently, as they alone are generated, as they alone possess powers of self-preservation and of reproduction, so do they alone grow, advancing necessarily from infancy to maturity and old age, or exhibit what are called ages. (See Age ) Organized bodies further meet our obser- vation in two different states, — those, namely, of health and of disease, nothing correspond- ing to which is encountered in the inorganic world. Whatever has a beginning has also an end. But the mode in which organized and un- organized bodies cease to be, and the influences that determine their periods of being, are ex- tremely different. A mineral ends when the affinities that combined it, and the attraction of cohesion that held its particles together, are overcome. This language implies that its destruction is effected by agencies external to itself — by the action of other bodies, and of circumstances over which it has no controul. The destruction of a mineral is, therefore, in nowise necessary, neither is it spontaneous : abstract a mineral, as we have said, from all external agency, and its endurance is inde- finite. Very different is the case with regard to animals and vegetables ; as their continuance depends on the process of nutrition, their end hangs upon the cessation of this act; and as the tenure by which they enjoy existence is temporary, the machine of organization being calculated to endure but for a season, their death or destruction is both spontaneous and necessary. Organized bodies which alone owe their being to generation, which alone continue their existence, reproduce their kinds, grow, attain maturity, and become aged by virtue of powers inherent within themselves, so do they alone die. The period of endurance of unorganized bodies may often be calculated approximatively according to their masses, their densities, the aptitudes of their elements to enter into new combinations, &c.; that of organized bodies cannot be inferred from these or any other merely mechanical principles. Indeed, data from which the duration of organized bodies may be estimated are altogether wanting. We only know that every species has within nar- row limits a period which it cannot pass ; but why this period should, in particular instances, 124 ANIMAL. be confined to a few weeks, mouths, or years, or be extended to centuries, we cannot tell. Nor is it only whilst endowed with all their peculiar and inherent properties that organized differ from unorganized bodies. No longer manifesting their especial powers, organized bodies begin to be disintegrated ; their con- stituent elements, held together in opposition to the laws of chemical affinity, become ame- nable to these, and forthwith enter into new combinations, which imply the utter destruc- tion of the organization as it had been formed, and hitherto preserved. Organized beings, as they alone die, so do they also alone undergo putrefaction — a process nothing precisely si- milar to which occurs in the inorganic world. From this review of the distinguishing pecu- liarities of organized and unorganized bodies, it appears that organization implies vitality, and that organization and life are insepara- ble conditions. It would be going too far to say that they were synonymous terms : organization is the mode of structure proper to living beings ; life is the series of actions they exhibit. And this in fact appears to be about the least objectionable definition of life than can be given : life is the scries of actions manifested by organized beings; would we go farther, we must condescend upon an enumera- tion of these actions, — namely, incipience by a genesis or creation; temporary endurance as individual by nutrition, and indefinite continu- ance as species by reproduction, modification during the term of existence known by the title of age, and end by death, to which spe- cific acts or phenomena must be added the peculiar inherent power which living beings possess of overcoming the general physico- chemical laws that dominate the rest of the universe. Thus far we have discussed and contrasted the physical qualities and phenomena common to organized or living beings at large, with such as inhere or are manifested by unorganized bodies generally, more especially minerals; we have still left untouched those that severally pertain to the two grand divisions of the or- ganized world, and that are peculiar to each living thing individually ; and here we shall find that the manifestations of vitality are al- most as various as the species that people the earth. In the same manner as we have hitherto gone on contrasting first the material compo- sition, and then the actions of organic and inorganic bodies, we shall still proceed by comparing the material composition and the capacities of action of the different classes of organized beings first, and next of the several individuals composing these classes one with another. Comparison of animals and vegetables. Animals and vegetables were longheld essenti- ally and irreconcilably distinct from one another. We have already had occasion, however, to observe in how many particulars they are iden- tical. The material composition of both is often in opposition with the general physico-chemical laws, both are made up of a combination of solids and fluids, both consist of a variety of heterogeneous parts, and both have determinate sizes which they cannot exceed. Moreover, both are possessed of vitality, — in other words, both commence by a genesis, preserve them- selves as individuals by nutrition, and as spe- cies by reproduction ; both grow by intussus- ception, undergo the mutations which are denominated ages, endure for a time, present themselves in health or labouring under disease, and both decay and die. How intimately ani- mals and vegetables are associated, how nearly they resemble one another, will farther appear as we advance in the following Comparison of the general physical qualities and material composition of Vegetables and Animals. — As a general axiom the material constitution of vegetables may be said to be less complex than that of animals; this at least is more especially the case as the individuals at the top of the two scales are concerned. No distinguishing feature of either class is derivable from general diversity of Size. Be- tween the microscopic lichen and infusory ani- mal, and the gigantic adansonia and whale, plants and animals of every intermediate mag- nitude are encountered. Neither is there much to be said upon the differences which vegetables and animals pre- sent when their Forms are contrasted. The forms of many are alike amorphous, or simply globular; certain pulverulent fungi in the one class, and monads in the other, resemble each other greatly. Among both, individuals also occur whose parts are disposed around a centre; yet we do not advance far before we discover a peculiarity in animals, namely, composition by the union of two similar or symmetrical halves along a middle line or axis, nothing similar to which has even been imagined in the vegetable world, the members of which on the contrary often exhibit a horizontal division, but without anything of symmetry, into root and branches. As a general law the animal kingdom may be said to affect the globular or simply produced form, with radii in the shape of extremities sent off from a central part ; the vegetable to exhibit a greater tendency to ramification or division into branches. In point of chemical composition animals and vegetables consist very nearly of the same elements: oxygen, hydrogen, carbon, nitrogen, phosphorus, sulphur, iodine, bro- mine, chlorine, potassium, sodium, calcium, silicium, magnesium, manganese, and iron have been detected in both; aluminium and copper have hitherto only been discovered in vegetables, and fluor only in animals. But these elements are united in each in very dif- ferent relative proportions. Carbon predomi- nates greatly in the more solid parts of vege- tables, nitrogen in the bodies of animals gene- rally,although to this rule there are many notable exceptions ; albumen, fibrine, and gelatine all contain much more carbon than nitrogen, and certain fungi include a very large proportion of nitrogen in their composition. Several ele- ments, met with abundantly in animals, occur but sparingly distributed among vegetables, ANIMAL. 125 phosphorus, for example, and sulphur. The earth afforded by animal bodies incinerated, is mostly lime in a state of saline combination ; whilst that yielded by vegetables, besides lime, consists of alumina, with an admixture, greater or smaller in amount, of scilica. The peculiar combinations which form what are called immediate principles, are much more numerous in the vegetable than in the animal kingdom, and are also generally more simple in the former than in the latter, the immediate principles of vegetables being mostly ternary compounds, whilst those of animals are gene- rally quaternary, nitrogen being added in these last to the carbon, hydrogen, and oxygen, which form the organic elements of the first. The immediate principles in both classes are divided into acids and oxides ; and many of these they have in common. Vegetables, however, have a third order of substances entering into their composition, of which we discover no traces among animals ; these are the vegetable sali- fiable bases. There are but few acids which exist in the vegetable and animal kingdoms in common ; and whilst their number is small among ani- mals, it is very great among vegetables. The hydrocyanic acid has only been dis- covered in vegetables; when it is procured from animal substances, it is always formed un- der peculiar circumstances, or during their de- composition. Of the organic oxides, some — albumen, osma- zome, sugar — are common to both animals and vegetables ; but they occur in very different proportions in each : sugar, which is so abundant among plants, is scarcely to be detected among animals ; and osmazome, which is so univer- sally distributed among animals, has only hitherto been discovered in a few fungi. Of the ternary com pounds of carbon, hydrogen, and oxy- gen, such as starch, gum, sugar, the resins, woody fibre, fixed oils, volatile oils, camphor, extractive matter, SjC. which enter so largely into the consti- tution of vegetables, there are but a very few to be discovered among animals, such as the sugar of the milk and urine, the resin of the bile and of the urine, the elaine and stearine of the fat, the volatile oily principle of castoreum, &c. and the camphor of cantharides. The quaternary organic compounds of car- bon, hydrogen, oxygen, and nitrogen, which form the principal elements in the composition of the bodies of animals, are, on the contrary, very rare among vegetables. The most com- mon of these are albumen, gelatine, fibrine, animal mucus, and osmazome ; the less com- mon enumerated are the matter of the saliva, caseous matter, urea, and the pigmentary mat- ter of the eye. Still vegetables are not without several of these quaternary compounds, such as albumen and osmazome, and they even possess others which are peculiar to themselves, such as gluten, the matter of the pollen of flowers, indigo and several extractive colouring principles ; to say nothing of the whole exclusive class of salifiable bases, quinia, cinchonia, veratria, strychnia, morphia, &e., &c., which appear to be com- pounds of carbon, united in large proportion with a little oxygen, hydrogen, and nitrogen. Comparison oj' the organic composition or texture of animals and vegetables. — VVe find many and much more striking differences in the texture than in the chemical composition of the two great classes of organized beings. Both are made up of solids and fluids ; but with a few exceptions, the proportion wtiich the solid bear to the fluid parts is much greater in vegetables than in animals. The fluids contained in the bodies of the higher animals, the blood, chyle, spermatic fluid, bile, urine, &c. have in general a very different character from those that constitute the sap of the more perfect vegetables, or that are deposited as secretions in the nectaries and various cavities of their flowers, leaf-stalks, stem, See. But the solids, entering into the composition of each class, are still more widely dissimilar both in their outward and in their intimate characters. The most simple vegetables, the cryptogamia, appear to consist of a homo- geneous tissue, forming rounded or oblong cells filled with fluids or a granular substance, with- out any trace of proper tissue ; it is only when we come to the phanogamous vegeta- bles that vve find any distinction of tissues, namely, a cellular and a tubular tissue, the whole body of the plant being surrounded with a distinct integument or bark. The cellular tissue of vegetables, whilst still young, is soft, homogeneous, and contains cellules filled with a fluid often charged with globules; when full grown, this tissue is made up of cells properly so called, being spaces surrounded with solid membranous parietes of various forms and sizes containing different matters. These cells appear composed of vesi- cles placed side by side and running one into another, surrounding the spiral and nutrient vessels of the stem and bark, and opening so as to form reservoirs filled with air, or resinous, oily, or mucilaginous fluids. The tubular or vascular tissue of vegetables occurs under two different forms — spiral vessels, and nutrient vessels. The former present themselves in great abundance amidst the woody fibres, but penetrate also into the leaves, and even into the stamina, pistilla, and fruit. They are not met with in the bark. These vessels seem specially destined to include and conduct the sap, which from the root ascends to the extreme branches and leaves of all vege- tables. The nutrient vessels, so called from con- taining a fluid, the cambium or succus proprius, different from the sap, prepared from this by elaboration in the leaves, have now been demon- strated in a great number of vegetables; they are principally contained in the soft inner layer of the bark, but they also penetrate every part for the purpose of conveying the essentially nutritive juice or blood of the plant. These elementary tissues, combined and arranged in a great variety of modes, constitute the root, trunk, leaves, flowers, and fruit of all vascular vegetables; and it is wonderful how nearly the whole of this tribe, however dis- 126 ANIMAL. similar in their outward appearance, resemble one another in their intimate structure. The tissues that enter into the composition of animals are much more numerous than those of vegetables. The most universally distributed of these in the more perfect species of animals are the cellular, the vascular, the nervous, and the muscular, to which must be added the tendinous or fibrous, the osseous, the cartila- ginous, and the horny, which are less uniformly diffused among the individuals composing the animal kingdom. The cellular is the tissue the most universally encountered among animals ; it is demonstrable from the very lowest to the very highest. Its general appearance is that of a soft, homo- geneous, whitish, semi-transparent, extensible, and during life slightly contractile substance. It is permeable to air and liquids, and is easily distended by either of these, when it forms a series of continuous cavities or cells, strangers at first to its constitution, but so readily pro- duced as to have given the tissue its distin- guishing title. The cellular tissue is dispersed abundantly through every part of the animal body ; it enters as a principal element into the composition of many other tissues; it pervades the innermost parts of almost all organs, and in a modified shape forms a covering for them externally ; it may be said to constitute the frame-work of the organs generally, supporting them in their particles as it does in their masses ; it connects them together also, includes and accompanies the bloodvessels that supply them with nourishment, fills the intervals between them, and establishes continuity between every part of individual organized beings. The cellu- lar tissue consists of filaments and laminse, mingled and entangled together; the interstices it contains, and which may be blown up into cells, appear to be moistened during life by a thin vapour, or a variable quantity of serous fluid* The cellular substance appears to constitute the element of the various membranes encoun- tered in animal bodies : the fibrous membranes, the skin, the mucous membranes, the serous membranes, and the synovial membranes, are all readily resolvable into cellular tissue ; they in fact appear to consist of this tissue in dif- ferent states of condensation. The vascular is another tissue extensively distributed among animals. Three modifica- tions of the vascular tissue have been reckoned by anatomists, occurring respectively in arteries, veins, and lymphatics. The third tissue which is peculiar to animals is the nervous. This may be held the most eminently distinctive of this class of organized beings, as it is by its intermedium that they exhibit almost all the faculties which place them so immeasurably above vegetables in the * Rudolphi assigns as a distinction between animal cellular tissue and that of vegetables, that the latter exhibits cells of a more or less regular form with firm walls, nothing of which kind exists in the former : Rudolphi Anat. der Pflanzen, S. 26, quoted in Tiedemann, Physiologie, lster Band, S. scale of creation, and as, generally speaking, they may be reckoned by so much the more perfect as particular portions of this system are more fully developed. The element of tlie nervous tissue is a soft, whitish, and little consistent substance, composed of mi- nute globules surrounded by a semifluid sub- stance, and connected together by a tissue of cellular membrane of extreme tenuity. The globules are mostly disposed longitudinally, when they form the medullary fibres of the brain ; surrounded by denser sheaths, they take the form of nerves. In all the higher animals at least, two orders of nerves are distinguished, each, however, being intimately connected with the other, — the nerves of animal, or, better, of phrenic life, and the nerves of organic or vege- tative life. The nerves of the first order are connected in the higher classes of animals with a brain and spinal cord ; those of the second proceed from small bodies of a reddish grey colour, and irregular shape, named ganglions. The functions of the first take place with con- sciousness, those of the second without this mental phenomenon.* The fourth tissue peculiar to animals is the muscular. In several of the very lowest tribes of these, indeed, the existence of this tissue cannot be demonstrated ; yet its actions begin to be manifested at a very low grade in the scale. The element of the muscular tissue is a fibre, on the ultimate constitution of which there have been many disputes. The ultimate muscular fibre would appear to consist of a series of solid globules longitudinally disposed, and connected into larger and larger fasciculi, which at length compose the distinct bundles denominated muscles. Fibrine is the organic element of the muscular tissue. Its peculiar and distinguishing property is its capacity to contract or to become shorter, and to relax again or return in its quiescent state to its first lentgh. The muscles, like the nerves, are divided into two classes or orders, the one under the influence of the will, the other independent of it. The texture is different in each of these two orders : in the voluntary muscles, the fibres and bundles of which the peculiar tissue con- sists are very regularly disposed, and generally in straight and parallel lines relatively to one another; in the involuntary muscles again, the fibres appear of different degrees of density, run parallel or obliquely with regard to one another, are superposed in layers, intermingled and entangled like a kind of felt, &c. * Some physiologists have gone so far as to suppose a rudimentary nervous system among vegetables, which would imply consciousness on their parts of their existence. This, at least, is a very doubtful presumption, but we are not with- out abstract arguments which might be adduced in favour of the supposition. How immensely would the sphere in which the bounty of the Creator had displayed itself then appear enlarged 1 The number of beings conscious of the joys of exis- tence would be increased a thousand fold ; and it is even delightful to imagine these lower parta- kers of organization with ourselves and animals, also enjoying the light and sunshine, the sequence of day and night, the freshness of spring, and the fulness of autumn. ANIMAL. 127 The fifth tissue which prevails among ani- mals is the Jibrous. This is or may be divided into the tendinous and ligamentous. These are alike subservient to the muscular tissue and to the function of voluntary motion. They con- sist of fibrous, parallel bundles, of a white colour and pearly lustre, of great strength, and possessing little elasticity. The sixth tissue which is peculiar to animals (the first of those less universally distributed) is the osseous. This forms the frame-work or skeleton which gives form and fixity to all the other parts entering into the constitution of the higher animals. The essential organic element of bone is a cellular net-work consisting of gelatine, within the meshes of which certain calcareous salts, the phosphate and a little carbonate of lime especially, are deposited in order to give them greater solidity. The cartilaginous is generally reckoned as the seventh among the elementary tissues of animals ; it may and has been very properly assimilated to the osseous : the bones are car- tilaginous at first, and with the progress of years many of the cartilages show a tendency to, or do actually become, converted into bone. The cartilages that cover the articular heads of the bones are almost the only ones that show no disposition to undergo this change. The organic element of cartilage is gelatine. The fibro-cart ilaginous is a mere modification, although an interesting one, of the cartilaginous or rather of the fibrous tissue. The fibro-car- tdages are very strong, and particularly elastic. The horny and calcareous coverings of in- sects, and the Crustacea have uses corresponding to those of the bones. The calcareous shells of the mollusca, too, bear a certain, though a very remote analogy to the skeletons of the higher animals. The horny or eighth tissue peculiar to ani- mals might with propriety be reckoned among the number of those that are very widely dis- tributed. We meet with it in the epidermis of man, and as low in the scale at least as the molluscs and annelides ; it is the most universal clothing provided by nature for the bodies of animals. So much for the simple tissues entering into the composition of animals, to many of which nothing analogous can be discovered among vegetables. But these are by no means the only solid elements that make up the aggregate of animal bodies. The organs, as we entitle them, for the performance of certain functions so generally encountered among animals, — the lungs, liver, stomach, kidneys, testes, ovaries, &c., &c., are so many peculiar compounds of the more simple tissues, occasionally with ad- ditions denominated parenchyma, nothing cor- responding to which has ever been discovered among vegetables. These various organs are associated in animals into groups, denominated systems, which severally tend to the accom- plishment of the individual functions mani- fested by the creature examined, — the teeth, tongue, salivary glands, oesophagus, stomach, liver, pancreas, and intestinal canal, constitute one great and important system, subservient to the conversion of food into nourishment, and the preservation of the individual ; the testes, penis, vagina, uterus, and ovaries, in the two sexes, compose another great system by which the species is continued, and so on. Besides these solids we have a great variety of fluids, which in animal bodies subserve various and important purposes : we have, for instance, the general nutrient fluid distributed to all parts of their bodies, denominated blood. We have a variety of fluids prepared for aiding or accomplishing the act of digestion, — the saliva, gastric juice, pancreatic juice, and bile ; we have various fluids as emunctories of the worn-out parts and particles of the system, — the perspiration and the urine ; and we have a peculiar fluid prepared as a means of con- tinuing the species — the spermatic fluid. Fluids corresponding in their destination to one or two of these are also met with among vege- tables, but there they are greatly modified. Comparison of the vital manifestations, or ac- tions of vegetables and animals. — In considering generally the manifestations of vitality in vegeta- bles and animals, we immediately become aware of very distinct and peculiar tendencies in each class. A disposition to produce diversity of parts, and a symmetrical arrangement of these, are as striking features in the acts by which animals are evolved, as the opposite or a disposition to reproduce to infinity similar parts without sym- metry is a character inherent in vegetables. The liver, spleen, heart, intestinal canal, pancreas, and vertebral column, are the principal asymmetrical parts in animals : the organs of the senses, the lungs, kidneys, testes, ovaries, lateral bones of the head, and extremities, and the muscles, are the principal symmetrical parts ; and these seve- rally cannot be said to be repeated, — they only exist in pairs, on either side of the mesial plane. Such accessory and unessential organs as hair, scales, feathers, &c. are the only ones that are found repeated among animals. The very opposite of this tendency prevails among vege- tables; we find nothing like symmetrical ar- rangement on either side of a middle plane, and we see the same parts repeated again and again to infinity, so that any single part, a branch, for instance, becomes an epitome of the entire tree. Another peculiarity in the mode in which the vital processes build up vegetables and animals consists in the situation and disposition assigned to the various organs entering into their composition. Whilst in plants the whole of the organs destined to the manifestation of particular functions, — the leaves, flowers, sta- mina, pistilla, roots, &c., — are placed externally, and their interior or trunk is a mere prop upon which these parts are hung, in animals the whole of the essential organs destined for the preservation of the individual and continuation of the species are concealed, so that their ex- terior is the shell, their interior the receptacle for the especial lodgement and protection of these. Such diversity in the arrangement of the parts composing vegetables and animals does away with the necessity for the existence among 120 ANIMAL the former of any thing like those central organs found in the latter, which, from the interior of the body, and generally from the mesial plane, send off radii of communication to every atom of the organization, and prove the media that unite their several and often widely separated parts into a whole. We discover nothing like prolongations from central organs — from a heart, an artery, a stomach, and a spinal cord or ganglionic system, among vegetables. Hence the independence of the several parts of vegetables one upon another, hence their susceptibility of being multiplied by cuttings, and even of some species arising complete from their leaves. A third and very important peculiarity in regard to the mode in which the vital processes are performed in the animal and vegetable kingdom is that many take place with con- sciousness or knowledge of their occurrence, in the one, whilst they all occur unconsciously in the other. In vegetables the whole of the acts whose sum constitutes their vitality are perfectly irresistible, and take place in them without their knowledge, and uninfluenced by their will. A great many of the vital acts, in- deed, take place without consciousness among animals also, such as the circulation of the blood, the digestion and assimilation of the food, &c., but the moment the animal passes the sphere of its individual existence, whenever it lias to act beyond itself, we find conscious- ness of the action superadded to the capacity to act. The very lowest animals select their food, search for and appropriate their aliment as it presents itself to them ; the most perfect vege- table, on the contrary, absorbs irresistibly, and without perception or will, the materials brought into contact with its roots in the earth, and its leaves in the air. The same wide differences are apparent in the act by which the species is continued: animals search for, and, by an inherent virtue denominated instinct, implying consciousness, distinguish the other individual of opposite sex, of which they have need in order to procreate their kind ; in vegetables, on the contrary, all is passive ; the pollen or fecundating powder is projected or falls upon the pistillum, or is even left to be brought into contact with this part by accident, without participation in the act, without consciousness of or will in its performance. These two last named manifestations, the one subservient to the preservation of the in- dividual, the other to the continuance of the spe- cies, are accompanied with such circumstances in animals as presuppose in them other two peculiar faculties : these are perception and the power of locomotion. To preserve themselves as individuals and as species, they required powers which should make themacquainted with and enable them to establish relations between their own bodies and the world beyond them. By the faculty of perception, which may be taken as synonymous with sensibility in its widest acceptation, an animal is made aware of his individual existence, as well as of that of the material universe without him. This faculty also takes cognizance of all the internal sentiments, feelings, or desires of which by his constitution he is susceptible, and which are always in harmony with the part he is destined to play in creation. Sensibility may therefore be defined : the faculty by which impressions from without as well as sensations, emotions, and intellectual acts from within are perceived. The organ of this faculty is by universal con- sent admitted to be the nervous system. The faculty itself, as the above definition indicates, is susceptible of being considered under two heads : as the impressions perceived or percep- tions come from without, or as they emanate from within. The organs of the senses are the media through which external impressions reach the percipient principle which resides in the brain and medulla oblongata in the higher animals, the nervous ganglia in the lower, and these same parts are the instruments or elabo- ratories of the internal sensations. Both of these kinds or modes of perception were alike necessary to the beings endowed with them. The external sensations are the watchmen of the system, admonishing animals of the pre- sence of the objects they require for their pre- servation ; the internal feelings, in like manner, are centinels which admonish them of their wants and lead to the employment of the organs by which these may be supplied. By the faculty of locomotion, again, an animal accomplishes all the promptings of his inward nature ; he places himself in relation with the beings and the things which he is ad- monished by his instincts or internal faculties are necessary to him for his preservation as individual and continuance as species. Made aware of his wants by perception, by the faculty of locomotion he is enabled to minis- ter to them. These two powers, let us ob- serve, always exist together; the one, indeed, necessarily supposes the other. Sensibility or perception is the monitor, locomotion the agent. Without perception locomotion could have sub- served no end ; without some capacity of loco- motion perception would have been a vain in- heritance. Vegetables evidently possess no power of locomotion analogous to that inherent among the higher animals, — where the seed falls there the plant springs, there it attains maturity, and there it dies. Neither do they manifest any thing like sensibility in outward act that can be ascribed to volition or consciousness : their nature, in fact, made perception unnecessary to them ; and having no power of locomotion, it would have been useless in the two great acts by which organized beings minister to their pre- servation as individuals and to their existence as species. Still it is impossible to deny every thing like capacity of outward motion to vege- tables. Although they have no power of trans- porting themselves over the surface of the earth or through its waters like animals, many of them exhibit motions in their leaves and flowers in relation with the state of the atmosphere, and the diurnal revolution of the earth ; the sexual organs in several species move the one towards the other; and about the foot-stalks and petioles of the mimosa pudica and other plants we observe particular organs that con- ANIMAL.. tract when stimulated, very much in the same way as the muscular fibre among the higher animals. Moreover, the motions by which the radicle constantly seeks the ground or tends downwards and the plumula shoots into the air, that by which some of the higher phano- gamous plants twist in spirals around objects near them, and by which all preserve one side of their leaves towards the light, cannot be held as accidental or merely mechanical acts. Seve- ral genera of the confervae and tremellse even exhibit such remarkable oscillatory movements as have induced different naturalists and phy- siologists to reckon them among the number of the animals. With all this, however, locomotion among vegetables is a very limited power contrasted with the faculty among animals. These exhibit all the automatical motions of vegetables, and have in addition a particular system, the mus- cular, superadded to their organization, by which many of the most important offices of the eco- nomy are performed : not only instrumental in procuring the food by which they are main- tained, but in putting into play the digestive and respiratory apparatus by which the nutri- tive juices are prepared and assimilated, and finally distributed among the higher tribes to every part of the body. The existence of this system is in fact one of the grand characteristics of the more perfect animals. By its means they react upon the external world and modify it according to their wants ; by its means they guide their senses and enlarge the sphere of their acquaintance with things beyond them- selves; by its means they impress the air with the tones and articulate sounds, or execute the signs by which they make known the various states of their affective or moral and intellectual being to one another; finally, by its means the sexes approximate, and those acts take place which lead to the engenderment of new indivi- duals and the continuance of species. The best informed among physiologists, how- ever, do not confine the motions of all animals to the act of the particular tissue we denominate muscular. The polypes and many even of the massy acalephs, to say nothing of the smaller infusories, rotifers, &c. though they move freely, cannot be shown to possess muscular fibres in their constitution ; neither indeed can any nervous system, upon which muscular contractions and voluntary motion have always been held dependent, be demonstrated in these creatures. It is consequently probable that the means by which spontaneous motion takes place in these lower animals are peculiar, as indeed we must acknowledge the evident mo- tions which occur under many other circum- stances in the world of organization to be. But let us now turn to the special manifesta- tions of vitality of the two great classes of organized beings we are engaged in examining. These we shall consider in the following order, which is also that we have adopted in contrast- ing the manifestations of activity of unorganized and organized beings, — namely, origin or repro- duction, nutrition or self-preservation, changes VOL. i. 129 undergone during the period of existence, or the ages, and death, or end. Origin, or the acts by which species are con- tinued.—Vegetables and animals alike derive their origin from a birth or genesis accom- plished in two different modes, either without the concurrence of opposite sexes, or with such a concurrence. When organized beings are pro- duced without the concurrence of opposite sexes, the parent either divides into several pieces, each of which becomes an independent individual, or throws out burgeons or buds from its surface, which, being detached in due season exist as self-sufficing types of the spe- cies. When organized beings spring from the concurrence of sexes, again, two sets of organs minister to the generation, the one denominated male, supplying a fecundating matter, the other entitled female, furnishing a germ, which sub- sequently to its impregnation by the male organ undergoes a series of evolutions that end in the issue of an individual resembling the parents, and fitted by its own acts to preserve itself and to continue its kind. Both of these modes of reproduction are common to vegetables and animals. Confervas and polypi alike exhibit the first mode, almost without a difference : buds or sprouts arise from the surface of both ; these adhere for a time, acquire a certain size, and are finally detached to become independent beings. Again, the polype divided into several pieces, gives origin in each of these parts to distinct polypi, exactly as the cuttings of vegetables take root and grow into perfect trees, shrubs, &c. The second mode of reproduction — that by the concurrence of sexes, or of organs deno- minated respectively male and female, — is also exhibited by vegetables and animab; indiffer- ently; but there are numerous circumstances distinguishing this manner of reproduction in the two classes of organized beings. In the first place, the sexual organs do not exist from the earliest period, and during the whole course of the life of vegetables, as they do in animals ; the sexual organs, in fact, only occur among vegetables at the time of flowering, and perish whenever the end of their evolution has been accomplished, never serving oftener than once for the generative act. The sexual organs of all animals, again, that live for more than a year, suffice repeatedly for their office ; and if they are not required to accomplish this oftener than once in the short-lived tribes, it is probably from no inherent incapacity to serve again, or any destruction of the organs them- selves, but simply because the term of existence of the organism of which they formed a part is complete, — they perish with the system to which they belonged. Another grand though not an invariable dis- tinction between vegetables and animals is the mode in which the sexes, or sexual organs — for these may be taken as synonymous terms — are distributed among the individuals of each class. Speaking generally, it may be said that the sexual organs are as commonly divided be- tween two individuals among animals by whom K 130 ANIMAL. the species is represented, as they are confided to one among vegetables, which is, therefore, singly the type of its kind. In both classes, indeed, there are exceptions to this general law : the flowers of all vegetables do not contain stamina and pistilla, or male and female organs, neither are the opposite sexes invariably repre- sented by two different individuals among animals. In many plants the male organs are known to exist in one flower, the female in another, but both developed on the same branch ; in many others, again, they exist on dif- ferent stems, and are often evolved widely apart from one another. In the same manner, many of the lower tribes of animals include within their individual organisms male and female organs; this is the case with several tribes of the genus mollusca, gasteropoda, the helix, limax, and lepas, for instance, with the whole of the extensive classes of the annelida, en- tozoa, echinodermata, &c. But though there be resemblance to this extent among vegetables and animals in regard to organs, in the act by which fecundation is accomplished there is a wide and essential difference ; for whilst vegetables impregnate themselves, or, rather, whilst the impregnation of vegetables is a purely passive process, with- out perception of or concurrence in its accom- plishment on their parts, — the pollen of the anthers of those flowers that have male and female organs being simply shed upon the pistilla, the impregnation of animals, so far as our knowledge goes, appears to be almost as generally a consequence of a connexion be- tween two different individuals, and of volition with consciousness on their several parts. Although many animals have both male and female parts included within the same organism, it would seem that comparatively few have the power of impregnating themselves : two in- dividuals of the like species meet, and give and take reciprocally ; so that there is, in fact, much less difference between the highest and the lowest tribes of the animal kingdom in the essentials by which races are continued, than at first sight appears, much less certainly than there is between the vegetables and animals that are most nearly allied. The modes in which fecundation takes place in vegetab'es at large, and in animals probably without exception, are inherently and essentially distinct : an her- maphrodite animal is still a very different thing from an hermaphrodite flower. Another difference between vegetables and animals, less important, indeed, but still in- teresting, lies in the number of the organs pos- sessed by each destined for the continuation of the species. In many vegetables the organs are single, one flower being taken as a repre- sentative of the, sexes ; in a much larger pro- portion of plants, however, the organs are mul- titudinous. Among animals, on the contrary, with a few exceptions in the very lowest tribes, the asterias, &c. where they are multidinous, the essential male and female organs, the testes and ovaria, exist singly or in pairs only. A third diversity, and one that is striking and almost universal, between those species of plants and animals in which the sexes are represented by two individuals, lies in the difference of conformation, size, and general character of the individuals in the one class, and their perfect similarity in the other. There are very few dioecious plants the males of which are distinguishable from the females; there are very few trihes of animals, on the contrary, in which the distinction of sex is not extremely apparent, the males being generally larger, stronger, and more courageous ; the females smaller, more delicately formed, and more timid in their disposition.* A fourth distinction which deserves to be noted betwixt animals and vegetables is in the diversity of the act by which the new being is separated from the parent, and commences its independent existence. The period at which this happens, indeed, is determinate, and fixed in both alike, but it is accompanied with con- sciousness among animals, whilst it is alto- together unwittingly accomplished among ve- getables. From this review of the mode in which animals and vegetables are called into being, or of the acts which lead to their creation, the main and most striking differences observable in the two classes are these : whilst in vegeta- bles the whole of the acts that constitute re- production,— the union of the sexes, the fe- cundation of the ovum, and the birth of the new being are accomplished without the will and without the consciousness of the indi- vidual, but irresistibly and necessarily, they are left in some particulars, at least, to the will, and take place with the consciousness of the individuals among animals. Nutrition, or the acts by which the indi- vidual is preserved. — Every thing in nature changes, and organized beings only con- tinue their existence with their aptitudes to manifest the acts that draw so wide a line of demarcation between them and unor- ganized bodies, by a perpetual renewal or re- composition, and as incessant a rejection or decomposition of their elements. Nutrition is, therefore, at least, a two-fo’d act, implying absorption or appropriation of nutritive matter, and excretion or rejection of the old and worn- out particles that have already served their office in the economy : it consists, in fact, as we have said, of an incessant decomposition and reconstruction of the fabric of the living organized being. Nutrition, however, is a very comprehensive term, and includes the whole of the vital acts by wh.ch the individual continues * One of the most striking exceptions to this law occurs among some especially of the smaller species of the birds of prey. In many of these the female is much more powerful, heavier, and even more courageous than the male. The care of the off- spring, by one of nature’s ordinances, devolving principally upon the female, the supply of flesh for the brood — a supply procured by violence — might often have failed had she not in these tribes been provided with superior strength and courage to insure its regularity and abundance. ANIMAL. 131 its existence, — namely, among the higher tribes of living things, the absorption or ingestion of food or alimentary matter ; the preparation of this food by the processes of digestion and respiration ; the distribution of the nutritive matter fitted for its ends, to every part of the system by means of a circulation ; the conver- sion of the nutritive matter into the solids and fluids or proper substance of the indi- vidual, and finally the depuration and rejection of the worn-out parts and particles by means of certain secreting organs. These various pro- cesses in themselves will be particularly con- sidered in the article Nutrition, to which the reader is referred. Meantime let us contrast these different functions as they manifest them- selves in each of the two grand divisions of the organized world. Assumption of aliment. — The earth and the atmosphere, and the carbonic acid and water they contain, are the sources whence vegetables derive their food. Here they find aliment ready prepared for their use, or rather, as passive agents, they depend on the earth and the atmosphere for a supply of the elements required for their continuance. Those physiologists are now admitted to have been mistaken who supposed that the food of ve- getables was furnished by the inorganic earth, air, and water, with which their roots and leaves are in relation ; more accurate experi- ments have shown that plants are as dependent as animals on supplies of substances that have once had life for their support. When plauts are made to grow in pure earth and in distilled water, they appear to do so by a kind of de- composition of themselves, one part perishing and affording food to that which continues to live. To base a distinction between animals and vegetables, consequently, on the presump- tion that the one lived on organic, the other on inorganic substances, was incorrect : animals and vegetables are alike in this respect ; both feed upon organized matter, and this not al- ways or necessarily in a state of decomposition, as we observe among parasitic tribes, which subsist on the living juices of the individuals they cling to. The food of animals, however, may be stated generally to be both more various and also more complex in its chemical com- position than that of vegetables, and whilst vegetables take all their food in a liquid shape, animals much more commonly live on a mix- ture of solids and fluids. The assumption of food by vegetables and animals takes place under very different cir- cumstances. In vegetables it is necessary and independent of the individual ; it is also in- cessant ; and, farther, it takes place from the external surface, inasmuch as it is with this that the materials which supply the nutriment are in contact. Animals, however, have not generally their food prepared for their use brought into con- tact with their bodies, neither are they passive in its assumption ; they have mostly to search for it abroad, and are provided with special organs for this purpose. The act by which -hey take it is not necessary, neither is it in- cessant. They have also to select their food, and are, therefore, furnished with faculties which guide them in their choice; namely, taste and smell. Lastly, the absorption of the truly nutritious matter is accomplished from their interior, the crude material assumed as food having been first prepared by elaboration in a cavity called a stomach. As organized living beings, the soundest philosophy and best ordered experiments lead us to infer that there is little if anything me- chanical in the mode in which either vegetables or animals absorb nutriment. The absorption of their aliment by vegetables is influenced by the seasons, their state of health or disease, their age, and external circumstances gene- rally,— the temperature, state of dryness or moisture, &c. of the air with which they are surrounded ; the cause of the absorption of their food lay vegetables is, therefore, some- thing different from wrhat is called capillary attraction, or the law by which fluids ascend in tubes of small calibre. The proper passage of the nutriment into the bodies of animals occurs from their interiors, and in a very large proportion (probably in every somewhat perfect member) of the class, by means of a special set of vessels denomi- nated lacteals or lymphatics, no system cor- responding to which exists among vegetables. The very lowest tribes of the animal king- dom, the entozoa, acaleph®, polypi, &c. having no proper vessels of any kind, the cellular membrane of which they consist absorbs, and by virtue of a peculiar vital process, distributes the nutritive juices extracted from the matters received into the stomach and alimentary canal to all parts of their bodies. Those tribes of animals which have naked skins have the faculty of absorbing by their exterior also. Still less than in vegetables, can we suppose that the process by which in animals nutriment is ultimately absorbed into the body, whether from the exterior or the interior, is akin to mechanical or capillary attraction. The tissues of which animal bodies consist are, indeed, permeable to fluids, but this does not explain the collection of these fluids in so many tribes into particular canals, and still less does it solve the problem of the continued motion onwards in determinate directions within these channels. Absorption of alimentary and other matters, therefore, in both of the grand divisions of the organized world, must be held as a vital act, — as one of the particular laws superadded in organized beings to the general system of phy- sico-chemical ordinances that rule the universe and its parts. This quality is common to vegetables and animals. By far the greater number of animals have one or more special openings, — a mouth or mouths, by which they take in such sub- stances as are fitted for their nourishment. Even the greater number of animals as low in the scale as the infusoria, have been recently demonstrated (by Ehrenberg) to be provided with an opening of this kind. Several, how- ever, seem to receive aliment by the way of k ‘i ANIMAL. 1 32 absorption alone. The mouth is a cavity of extremely varied character and construction adapted universally to the circumstances in which animals exist. Nothing analogous to a mouth is met with in any vegetable. The food having been selected and seized is next transferred to the cavity in which it un- dergoes an elaboration that fits it to be received into the proper system of the animal and con- verted into its own substance. We do not find anything like the pouch denominated a stomach in any member of the vegetable king- dom. The matter fitted for its nourishment, absorbed by the root, is transmitted to the stem, and from thence makes its way into the leaves of the vegetable. It does not pass un- changed, however, from the earth into the root, or at least it has advanced but a very short way on its course to the leaves, before it is found to have undergone certain changes, which are also known to be greater in amount as it is examined at a greater height or distance from the root. Although growing from the same soil too, the sap of vegetables, i. e. the fluid which is passing upwards through the woody fibres, is found to be universally different. Whether the peculiar qualities thus acquired by the simple moisture holding certain salts, &c. in solution, which is the food all vege- tables derive through their roots, be the effect of vital elaboration within the cells of the woody fibre, or result from an admixture of the cambium or fluid which has already undergone assimilation in the leaves, is still uncertain. We are inclined to believe that a process ana- logous to digestion does actually take place within the woody conduits of the sap of vege- tables; — why should it not, or why should any new properties acquired by matters sub- jected to the influence of the peculiar laws of vitality be held as resulting from mere ad- mixture ? The very same thing, in fact, happens among the lowest tribes of animals which takes place in all vegetables : the substances fitted for their nourishment penetrate or are absorbed into their systems, and are there assimilated without the intermedium of any special apparatus. We mount but a very short way in the scale of the animal creation, however, before we meet with a peculiar pouch, destined for the reception of the aliment, and accomplishment of the first steps in the processes by which, in the more perfect animals, it is finally assimi- lated. This pouch is the stomach, and with the rest of the digestive apparatus with which it is connected, is in intimate and uniform re- lationship with the kind of food upon which animals are led by their instincts to live. All the accessaries of the assimilating cavity or stomach which we find in animals, from the organs of sense that guide them in their choice of aliment, to the lips that seize it, the teeth or jaws that bruise it or destroy its vitality, the muscular actions by which it is swallowed, and the chemico-vital processes by which it is dissolved, and the purely vital sen- sibilities by which such parts as are proper for nourishment are retained, and such as are im- proper for this purpose are expelled, — all of these are wanting among vegetables. There are yet other processes which form an essential item in the acts by which organized beings universally continue their existence, which it is necessary we should include in this summary of the common, particular, and dis- tinguishing attributes of vegetables and ani- mals. One of the most important of these is Respiration. — -The leaves in the more per- fect vegetables are the instruments of respi- ration ; their place is supplied by the general surface in those plants that are aphyllous. Vege- tables that live in air act immediately by means of their respiratory organs upon the ambient medium ; those that live in water, upon the air held in solution by the fluid around them. Vegetables are well known to exhale abun- dantly from the surface of their leaves, or stems, in case they have no leaves. The mat- ter exhaled is principally water. They have also the farther property of decomposing one of the elements of atmospheric air, namely, carbonic acid gas. In the sunshine the leaves of vegetables fix the carbon which enters into the composition of this gas, and set the oxy- gen at liberty ; in the dark, however, a very different process goes forward ; they then actually absorb oxygen and exhale carbonic acid gas; the balance, however, in the aggre- gate is not equal between these opposite pro- cesses, a much larger quantity of carbon being fixed by the decomposition of carbonic acid gas and oxygen set at liberty, than there is of oxygen absorbed and carbonic acid gas set free. These acts are essential to the life and health of vegetables ; their end and object appear to be the preparation of their proper nutritive fluids or cambium : the sap which reached the leaves, colourless, not coagulable, without glo- bules, mere water holding carbonic acid, acetic acid, a muco-saccharine matter, and various salts in solution, is in them converted into a greenish fluid, partly coagulable, and full of globules, which special vessels then distribute for the growth and maintenance of the different parts. The respiratory act is necessary, and goes on without the aid or concurrence of the indi- vidual among vegetables. Animals are no less dependent than vege- tables on communication with the air of the atmosphere, either immediately or mediately, for a continuance of their existence, or the manifestation of those acts whose sum con- stitutes their lives. In the very lowest tribes the communication between them and the air of the atmosphere takes place over the surface of the body generally, without the intermede of any particular organ or organs for the pur- pose. The fluids absorbed into their bod.es are brought into contact with the atmospheric air in those points where they approach the external surface, and there appear to undergo the changes necessary to fit them for being converted' into the substance of the animals themselves. Simple as this process may ap- ANIMAL. 133 pear, slender as the means of accomplishing it may seem to be, it is nevertheless essential : interrupted for any length of time, the animal inevitably perishes. A process of such im- portance, as may be imagined, is not long left without its appropriate and special apparatus. This varies extremely in its structure, in the different tribes of animals, and according to the circumstances surrounded by which they live. Some have lungs, branchise or gills, and traches opening by spiracula, of infinitely va- ried construction. Respiration is also carried on vicariously in a very large proportion of animals, if not perhaps in all to a certain extent, by means of the skin, and in some even by the instru- mentality of the alimentary canal. The changes effected in the atmospheric air by the respiratory apparatus of all animals are similar, but they differ from those that are produced by the corresponding implements in vegetables : the proportion of oxygen it con- tains universally diminishes, and the quantity of carbonic acid gas it holds in solution as invariably increases in amount. A quantity of water or of watery vapour is at the same time thrown off. This is exactly the opposite of what we have seen to be the effect of respi- ration among vegetables; in these the quantity of oxygen is augmented, whilst that of car- bonic acid gas is diminished. The nutritive fluids newly prepared by the apparatus of digestion, or that have already gone the round of the system, are by a variety of means ex- posed, in the special or common apparatuses mentioned, to the influence of the atmospheric air, from the contact of which they undergo certain important and often manifest changes that fit them for their ultimate office in the animal economy, — the maintenance of its parts, with their inherent capacities to execute the various functions imposed upon them. The respiratory act among animals takes place with the knowledge and with the assist- ance and implied will of the individual. Animals are informed of the necessity of re- spiring by the feeling of a want, an uneasiness, just as they are admonished of the necessity of taking aliment by the painful sensations denominated hunger and thirst. The essence of respiration in the two grand classes of organized beings would therefore appear to be different, and might be made the ground of a definitive distinction between the members of each kingdom. Carbon is the object for which the respiration of plants is instituted ; oxi/gen the end for which re- lations are established between animals and the atmosphere. Another grand difference be- tween the respiration of plants and animals is the involuntariness of the act in the one, and its voluntariness in the other, its occurrence with unconsciousness in the one, and with con- sciousness in the other. The nutrient juices thus prepared have iow to be distributed ; this is done by means f a peculiar motion impressed upon the fluids ;i virtue of a vital law with the nature of which we are still very imperfectly acquainted. Let us use the word circulation in a sense implying motion generally, not motion in a circle to designate the act by which in the organized world the nutritive juices are dis- tributed through the frames of the objects composing it. Circulation. — There can be no doubt of the existence of a circulation among vegetables ; in many species currents in opposite directions have even been seen with the aid of the micro- scope, and this not only among the lowest and most simple in their structure of the class, but also in the highest and most complicated. The circulation of vegetables appears to take place within two different congeries of vessels, ex- tremely numerous, and disposed according to their nature in different parts of the plant. The vessels that pump or transmit the sap from the roots to the leaves, for instance, as we have already had occasion to state, run within the woody parts of plants ; those that receive the modified juices of the leaves, again, take their course downwards within the bark. These two sets of vessels anastomose within the substance of the leaves, but no where else ; the second set can alone be said to have a distribution throughout the vegetable, for every part appears to depend on them for its supply of nourish- ment, even the extreme points of the roots, which were themselves the first instruments in collecting the aliment still unfit for the purposes of nutrition. The best informed vegetable physiologists are of opinion that the nutritive fluid once sent off from the leaves never finds its way back to these organs again ; it is ab- sorbed or fixed by the different parts or struc- tures to which it is distributed, ministering to their increment generally, and enabling each to manifest its specific function in the vegetable economy. In this motion of the fluids of vegetables it is evident that there is little analogous to what we find within the bodies of animals somewhat elevated in the scale. But let us first cast a hasty glance at what does take place within this other division of the organic kingdom be- fore instituting a comparison between the func- tions of circulation in the two. All animals, from the mammalia downwards to the entozoa, - — birds, reptiles, fishes, the mollusca, Crustacea, arachnida, insecta, and, among the radiata, the holothuriae, echini, and asteriae, include within their organisms particular canals or vessels for containing and distributing their nutrient juices, and within which, moreover, these are in motion in a circle. In the acalephse we still find canals branching off from the digestive cavity and dis- tributing the nourishment there prepared to the different parts of the body : in these, however, we no longer find any contrivance for establish- ing a circular motion in the nourishing juices. Still lower in the scale, among the polypes and actineas, for example, we discover no branched appendages or canals for the distribution of the nutrient fluids; those prepared in the stomachs of the animals appear to penetrate their sub- stance directly, and to permeate the homo- geneous cellular tissue of which they consist. 134 ANIMAL. In the tribes which have a circulation, in the strict sense of that word, we find two or- ders of vessels, — arteries and veins, in which the nutritive juices, or blood, moves respec- tively in opposite directions, from the trunks towards the branches in the one, from the branches towards the trunks in the other. These vessels anastomose freely by their ex- tremities, which terminate and originate in every part of the body, and, farther, meet in a common central cavity, which, when furnished with muscular parietes, is entitled heart. With- in the circle of vessels thus established, the nutrient fluid of animals is in perpetual or next to perpetual motion during the term of their lives. In the higher classes the main agent in producing this motion is the central organ in which the veins and arteries meet; but it is not the only cause of the circulation, this act going on vigorously in circles and in situations wherein the heart’s action can have very little influence, and in some tribes where the heart is even altogether, wanting. The circulation in the greater number of animals, however, is a more complicated pro- cess than that which has just been described ; it consists, in fact, of two parts perfectly dis- tinct from each other; one whereby the blood is exposed to the action of the air in the appa- ratus which, in connexion with the respiratory process, we have denominated lungs, gills, &c., another by which it is finally distributed for the uses of the system. This double circula- tion is accomplished by a great variety of con- trivances (vide articles Heart and Circula- tion). In some tribes we find more than one vessel, — two, or three, each apparently inde- pendent of the other, though communicating together, which are subservient to the distri- bution of the nutrient fluid to the different parts of the body of the animal. The chief differences between vegetables and animals with respect to their circulation, con- sequently, appear to be these : in vegetables the motion of the sap or aliment takes place through the whole of one of the tissues of which they consist ; that of the cambium or proper nutritive fluid through the whole of another of these tissues, in opposite directions simply, and by the intermedium of fascicu- lated, very numerous, and independent vessels ; whereas the aliment of animals does not cir- culate through their bodies, but the nutritive fluid prepared from it is collected and con- fined within peculiar channels, connected at both extremities in such wise as to form a con- tinuous circle. In vegetables we perceive nothing like tendency towards or distribution from a central reservoir, nothing like ramifica- tion from larger to smaller branches, &c. ; con- sequently nothing like a heart, as we do in animals above the very lowest. In vegetables, again, we see nothing like the two-fold distri- bution of the nutrient fluid within different orders of vessels, the one to the organs of respiration, the other to the system at large, as occurs among all animals possessing a some- what complicated organization. We have recognized the heart as the princi- pal cause of the motions performed by the fluids within the bodies of animals ; but as neither all animals have a heart and yet exhibit their nutrient fluids in motion ; indeed, as a distinct circulation of the blood may be demonstrated in many animals, and probably takes place in all at periods of their evolution anterior to the existence of a heart ; and further, as vegetables exhibit a motion or circulation of their fluids without the agency of any special organ, it is necessary to acknowledge a new law by virtue of which the fluids of organized beings generally go their round or reach their destination. This law has been designated as the propulsive, — a power inherent in the nu- tritive globules of living beings, and one of the special laws superadded to the general and all-pervading forces that regulate the universe. One fundamental distinction between the bodies of the organic and inorganic kingdoms we have found based upon the permanence of the parts, the constancy of the relations, affi- nities, See. of the component elements of the one, and the incessant changes or renewals and decompositions which these parts or elements undergo in the other. The various processes by which the aliment of vegetables and animals is converted into a succus proprius, the final means of their individual conservation and evolution we have now examined ; we have only farther to discover this nutrient juice con- verted into the different tissues and substances of which organized beings consist, to have a complete view of the vital act of nutrition. But here we are compelled to pause. Of the processes by which this transformation is ac- complished we know next to nothing; all we are assured of is, that each tissue and organ seizes upon and converts into its proper sub- stance those particles enveloped in the general mass of circulating fluids brought into rela- tionship with it, and which are adapted to this purpose, at the same time that the particles which have already been consolidated and served their office are reduced to the fluid state, absorbed back into the torrent of the circulation, and afterwards either abstracted and thrown out of the body by the operation of certain organs charged with this duty, or being subjected to the action of the atmos- pheric air in the lungs, gills, skin, &c. are restored to their fitness once more to enter as temporary constituents of the organization. It is evident, therefore, that we are only ac- quainted with this operation in its effects. The act of ultimate nutrition has been happily entitled one of continuous generation in each living being and its parts ; it takes place m conformity with the laws of vitality instituted, and probably originating and ending in living organized beings. This subject, however interesting, we must reluctantly forsake, referring to the article on Nutrition, and to the consideration of what has been called the nisus formations, or plastic power in our article on Fcetal development. Vegetables and animals, from this review, appear to differ little from one another in all 135 ANIMAL. that regards their nutrition. The processes that lead to this conclusion may be, and, indeed, are more complicated among animals than among vegetables ; but the essence of the final act is very nearly the same in both. Neither shall we be able to demonstrate any great want of uniformity between these different classes of organized beings in several of the actions which we shall next discuss ; in others, however, we shall discover an impassable line of demarcation between them. The first of these actions which we shall consider is Secretion. — We have already had occasion to mention the watery exhalation and oxygen thrown off by the leaves of vegetables. Divers other substances are excreted by the same parts, — water, various acrid, glutinous, saccharine, and balsamic substances. It is even by means of the leaves that vegetables throw out those substances which they may have absorbed by their roots, and which seemed calculated to injure them. We are at no loss, moreover, to demonstrate numerous apparently glandular organs in vegetables for the elaboration of a variety of substances, many of them very acrid. The flowers of vegetables secrete, in the first place, certain matters, the infinite variety of whose odours proclaims them to be different; the nectaries are also filled with fluids, which are sweet in many tribes. Lastly, in the flowers, the male fecundating matter, and the fluid that moistens the pistillum are secreted. Nor are vegetables without internal secretions, among the number of which certain aeriform fluids are not the least curious. The other secretions of vegetables are of infinite variety, — gummy, oleaginous, balsamic, camphoric, &c. &c. These are all stored up in cells con- tained in different parts of each individual plant, and undoubtedly either subserve im- portant purposes in their several economies, with the nature of which we are very imper- fectly acquainted, or are in relation with some other system in the universe, affording food to numerous tribes of insects, or materials which stand in relation to animals and man as means of accomplishing a variety of ends, the impulses to which they bring into the world with them, though they are launched upon existence un- furnished with the materials. We have also hinted at the watery and gazeous products of the respiration of animals, and consideration for a moment enables us to make a long catalogue of other secretions both with reference to individuals and to species. We have, for instance, the limpid fluids that bedew the cellular and serous mem- branes, serum and synovia, and fill various cavrties in the body— the chambers of the ear and of the eye particularly ; those that moisten and defend the surfaces of the mucous membranes, the tears and mucus ; those that are subservient to digestion, the saliva, gastric juice, pancreatic juice, and bile ; those that lubricate and prevent the surfaces exposed to the air from drying, the sebaceous or oleaginous fluids of the skin, and cerumen of the ears ; those that are laid up as reservoirs of nutriment or defences from the cold, the fat, marrow, &c.; those that are the vehicles for the worn-out particles of the body, the urine and perspira- tion ; those that minister to the reproduction of the species, the fluids of the female germ or ovum, the spermatic and prostatic fluids of the male ; and finally, those that are poured out among the mammalia as the first aliment for the newly-born being, the milk. Nor is the list exhausted, for numerous species of animals have peculiar fluids which are useful to them in the places they hold in the system of creation ; among these are the venomous fluids of serpents, and of the stings of numerous insects, the inky fluid of the cuttle fish, the fetid fluids of the anal glands of the carnivora, rodentia, &c.; the fluid with which spiders weave their web ; the wax with which bees build their cells, kc. Secretion is, therefore, a much more extensive function among animals than among vegetables; the products are still more various, and the apparatus by which they are eliminated is, generally speaking, far more complicated among the former than among the latter. Certainly, in the very lowest tribes of animals, secretion is an exceedingly simple process contrasted with what it becomes in the higher, whose organization is more complex. Among the polypi, medusae, and entozoa, the whole of this function seems to consist in a kind of transudation, or exhalation from the surface of their homogeneous bodies, without the intermedium of any special organ. Among animals higher in the scale we find secretion performed in two modes, — by vessels, when the act is entitled exhalation, and by means of certain special organs named glands, an arrangement which we also find among vege- tables. The skin and pulmonary surface are the great implements of exhalation among animals, as the leaves are among vegetables ; almost all the rest of the secretions take place by the instrumentality of glands. In vegetables secretion seems to be limited to the preparation of the nutrient fluid by the elimination of certain matters, and, so far as our knowledge extends of the end to be an- swered by any act, for the formation of the generative fluids ; we do not, in fact, find among vegetables any apparatus set apart for the excretion of matters derived from a change in the constituent particles of the organs once formed. Among animals, again, the apparatus by which this depuration of the system is ac- complished is one of the most important of all to the preservation of the individual. Secretion among vegetables is a function much more under the influence of external circumstances than it is among animals ; it is also more sub- ject to periodical changes among the former than among the latter, and whilst the function is mostly called into activity by the stimulus of light, heat, kc. in the one, it rather obeys cer- tain internal and peculiar stimuli transmitted through the medium of the nervous system in the other. ( Like all the other special modes of activity manifested by organized beings, secretion is 136 ANIMAL. one of' the products of the laws of vitality with the essence of which we are altogether un- acquainted. Besides the secretion of the various gaseous, fluid and solid matters mentioned, vegetables and animals appear in common to possess the power of disengaging certain imponderable elements — heat, light, and electricity. lieut. — There has been considerable variety of opinion among physiologists with regard to the extent to which vegetables have the power of maintaining a temperature of their own inde- pendently of that of the surrounding media. Nor is this question, in our opinion, yet com- pletely set at rest. It is certain that trees in high northern latitudes endure a cold many de- grees below zero without injury, whilst in in- tertropical countries they are frequently ex- posed even in the shade to a heat above that of any animal without perishing ; actual ex- periment, indeed, proves that they preserve a temperature intermediate between that of the extreme heat and extreme cold of the diurnal variations of those latitudes in which they are indigenous. This circumstance is explained variously, some attributing it to a vital property in plants to regulate to a certain extent their own temperature, others alleging that it is merely owing to the indifferent conducting qualities of the materials of which vegetables are composed. The thermometer has been seen several degrees below the freezing point of water within the trunks of fir trees, without their vitality being affected ; but it is probable that the constitution of this tribe renders them capable of enduring such a reduction of tem- perature with impunity as would prove fatal to other trees with simple watery sap. On the other hand, it is quite certain that the flowers of many vegetables have the power of disengaging heat, a difference of ten, twenty, and even more than thirty degrees having been observed at sun-rise between the temperature of the atmosphere and that of the flowers of different vegetables in southern latitudes, and the same thing is known to occur, though to a less extent, in northern countries. It would therefore be unfair, with such facts before us, to deny altogether to vegetables the faculty of disengaging caloric. Arguments, in- deed, a priori, might be adduced to show that they must almost necessarily possess such a property : they are the subjects of incessant change; and one of the most universal of the physical laws involves a change of temperature on any change of constitution. If the faculty of vegetables generally to secrete or eliminate caloric be doubtful, how- ever, it is indisputable that among all animals a little raised above those at the very bottom of the scale, there is an inherent power of gene- rating caloric, which in their state of maturity is nearly determinate as regards each particular species. Mammalia and birds have universally the highest temperatures. Reptiles or cold-blooded animals, as they are improperly called, have also the power of engendering heat, and of regulating their own temperature : this faculty, however, and the degree of heat they possess at different times, are influenced to a very considerable degree by the heat of the media in which they live. The same statements may be made with regard to fishes. The temperature of these creatures is generally several degrees above that of the water they inhabit; but it also varies with the tem- perature of their native element. Many insects have a very decided power of engendering heat and of regulating their tem- perature ; and similar faculties have been de- monstrated in the Crustacea, the mollusca, and the annelida. These tribes, however, are all very much influenced by the temperature of the media surrounded by which they live. No great difference is therefore discernible between vegetables and animals in the faculties they possess of engendering caloric and regu- lating their own temperature ; the faculty is only much more decided, and possessed to a far greater extent among the more perfect classes of animals generally than among vege- tables at large. It may very fairly, in the present state of our knowledge, be ascribed as a common property. As to the mode in which heat is engendered, opinions are still very much divided. The chemical and mechanical explanations that have been given of the phenomenon are not universally applicable. All we can say at the present day is that the production of heat and the power of regulating their temperature pos- sessed by organized beings is another of the hidden and singular laws or properties intro- duced into the system of the universe with their creation. Light. — Many unorganized bodies have the property of shining or giving out light for some time after they have been exposed to the bright rays of the sun, or have been heated in the fire, or when they are struck together or smartly compressed, and this certainly without any decomposition of their substance. The disen- gagement of light, again, is a very uniform accompaniment of the decomposition and com- position of inorganic substances, and it appears to be a very constant attendant upon electrical phenomena. Various organic substances and products of organization have a similar property ; living vegetables, too, particularly the flowers, have been seen to give out light by authorities so respectable, that though the fact has been called in question by others of great name, there seems no sufficient reason for treating all that has been said on the subject as illusion : in the physical sciences negatives cannot be received as evidence of equal value with posi- tives. No one thinks of calling in question the luminousness of animals ; most of the innu- merable inferior tribes that live in the sea, appear to possess and to manifest this pro- perty at different seasons. The luminous- ness of the ocean itself, so familiarly known, seems to depend on the presence of multitudes ANIMAL. 137 of infusory animals within its bosom. Many tribes of insects shine in the dark. The phe- nomenon is not certainly known to be mani- fested by any of the class of reptiles, birds, or mammalia. It appears to depend, in insects particularly, on the presence of a peculiar matter, secreted by their bodies and stored up in particular points, which, under the influence of a temperature elevated in a certain degree, and the contact of atmospheric air, enters into a kind of combustion during which light is emitted. Is the phenomenon dependent on one common cause in both vegetables and animals, supposing that it does really occur among the former? Electrical phenomena are extensively ex- hibited by the objects composing the unor- ganized and the organized world. In fact, wherever there is composition and decompo- sition going on, there are electrical phenomena manifested. The action of the immense mass of vegetables on the air, the evolution of oxygen in the sunshine, and the formation of carbonic acid during the dark, has even been supposed by an ingenious natural philosopher of Trance (Pouillet) to be the principal source of the electricity of the atmosphere. Galvanic electricity is excited by the contact of the different parts of which animal bodies consist, particularly of the nerves and muscular flesh ; the nerve of a frog’s thigh exposed and isolated, touched with a piece of quivering flesh from the body of a bullock just slain, also isolated, causes the muscles to which the nerve is distributed to contract energetically (Hum- boldt). The same phenomenon occurs when different other parts and fluids, particularly the blood, are used to form a chain. But the electrical phenomena manifested by animals at large, are weak when contrasted with those exhibited by certain fishes provided with spe- cial voltaic piles or galvanic batteries by which they give at will, but not otherwise, electrical shocks of such violence as to stun larger ani- mals and even to deprive smaller ones of life. This electricity of animals must be held as a vital phenomenon ; several of them have in- deed a peculiar apparatus for the preparation of the shock, to speak of the phenomenon by its effects, in our ignorance of its essence or efficient cause, but this loses its power when the nerves that are abundantly distributed to it are divided. Electrical phenomena are not so obviously displayed by any other tribe of animals as by fishes ; but it has been rendered next to certain that muscular contractions are uniformly accom- panied by a kind of electrical discharge from the nervous fibrils distributed to the special or- gans of voluntary motion. Animals, from this brief review, appear to pos- sess electrical capacities in a much higher de- gree than vegetables, in which the phenomenon is even explicable on ordinary chemical prin- ciples, whilst among animals it is unquestion- ably one of the effects of vitality. We have already indicated the existence of two faculties among animals which become necessary or complemental to them as a°-ents entrusted with their preservation as individuals, and their continuation as kinds; these are voluntary motion and sensation. But motion in the abstract is a phenomenon of much more extensive occurrence among organized beings than the notion we form of the act as connected with the existence of a muscular system. Mo- tion is in fact a quality inherent in organized beings ; they cannot be conceived as existing without change, and change implies motion. In most, or indeed in the whole of the actions which we have glanced at as manifested by them, we have supposed motion. The simplest of all animals, the infusoria, move about in many cases with great briskness; the polypes, composed of an uniform gelatinous mass, also move in various directions; the acalephs, with a similar structure, rise from the bottom and propel themselves through the waters of the ocean by a succession of contractions of their disc, of their tentacula, or of the fringe-like or foliaceous bodies with which several orders of the genus are provided. Many of the en- tozoa too, whose bodies consist of a simple gelatinous or mucous tissue, execute motions in various senses. But it is not only as a whole that a body endowed with life and organization possesses a capacity of motion. Many of its parts, and particularly the globules which enter as essen- tial and integral parts of the fluids contained in organized bodies, have inherent powers of motion ; the globules of the blood, for instance those of the spermatic fluid, and perhaps also' the germ included within the ova of the polype, mollusc, &c., have all been observed in motion' and the means by which it is accomplished' even demonstrated in many cases. But there is nothing absolutely peculiar in such indivi- dual instances, for we must need conceive motion in the first constituent elements of all organisms without exception, long before a muscular, a cellular, a nervous, or any other distinct system has existence.* Motion of all kinds, therefore, automatic as well as that which is voluntary, must be held as a quality inherent in organized or living beings. The cause of this phenomenon, as of so many others manifested in the world of or- ganization, has been the subject of much dif- ference of opinion and of much dispute amon° physiologists, and many titles have been ima- gined by which the agent or primary cause of the act has been sought to fie designated, or the act itself to be explained. It is quite certain that the capacity to com- mence and to continue the phenomena which we designate as vital, or the motions which constitute these phenomena, depends first on a variety of external conditions, such as a * Such motion is indubitable. The organic glo- bule has capacities of motion inherent in itself different from the motions of unorganized objects in a state of extreme division, as is proved by the motions of each kind of body being different, and those of organized globules being interrupted by the electric spark, or whatever destroys their vitality — acids, alkalis, poisons, &c. 138 ANIMAL. certain temperature, intercourse with the air of the atmosphere, supplies of aliment, and the access of light, and it is indubitable that organized beings exhibit phenomena that may be designated excitability, irritability, vital force, &c., which are only other names for these manifestations; but it is also certain that external conditions are of themselves ina- dequate to originate manifestations of vitality, and that the phenomena of living organized beings, generally designated excitability, irrita- bility, incitability, &c., are consequences of a state of things to explain which they have been conceived as causes, under the title of life, vital principle, soul, ike. The term excitability should be used in physiology, in the very widest sense, to signify a property inherent in organized matter generally, to be determined to manifestations of activity under and in con- formity with external influences (Tiedemann). We in fact see organized matter of every de- scription-— the green matter of Priestley, con- ferva, infusory animals, &c., acquiring organic forms under the dominion of outward influences, and every species of organized being existing within a determinate circle of external agency. It. were a grave mistake to suppose this agency either chemical or mechanical in its na- ture ; when of such potency as to act either chemically or mechanically it is destructive instead of productive of vital phenomena. These phenomena, therefore, and external influences are rather in opposition to one another than identical. External influences ex- cite organized beings to manifest their inherent capacities; they do not bestow these capacities ; all organized beings, indeed, and each parti- cular tissue of every individual among them, are excited in different modes by the various influences from without ; the stimulus is iden- tical, the effects are infinitely different. But organized beings, and especially ani- mals, are not dependent on external influences alone for the manifestation of their peculiar properties; they have themselves the additional power of engendering stimuli proper to arouse into activity the various organs and systems of which they are composed. The fluids circu- lating through every part of their bodies may be regarded in the light of the most generally distributed stimuli of this description. The nrevous system is another and important source of excitation, the influence of which is felt in every part of the organism of all animals above the very lowest. The various instincts, appe- tites, propensities, sentiments, and intellectual faculties, also, which all emanate from the nervous system, are inherent causes of a vast variety of manifestations of activity among the more perfect animals. There are yet other stimuli of a mechanical, or chemical, or pecu- culiar nature, which excite unusual or ano- malous manifestations ; m this category may be placed contagions of different kinds, the causes of epidemic diseases, medicines, &c. With regard to the essence or cause of this property of the organic globule to commence, and of the perfectly developed organism to manifest the various phenomena whose sum constitutes their vitality, and endows them with their various cognizable properties, all we can say is that it appears to inhere immedi- ately in the particular state of matter which composes them. What this state is in itself we cannot tell ; but we are familiar with the phenomena which ensue from, and which in- deed reveal to us its existence. It is evidently as diversified as species, and as the systems or organs possessed by the individuals severally composing these : there is a power — the nisus formations, the vis plastica, in the matter sus- ceptible of formation, — the organic globule, the germ, — which presides over and regulates its acts; and there are powers inherent in the parts or organisms to which the plastic force gives rise, in accordance with which they manifest the special acts that distinguish them. It would be improper, however, to regard this power or these powers as forces apart from and other than the globules, germs or organisms themselves ; in the present state of our know- ledge we cannot separate exciting causes from manifestations of activity; all we can venture to say is that germs exist, that organisms exist with inherent capacities of action in harmony with the peculiar states of their constituent elements, thus : the germ of the infusory ani- mal exists with its inherent capacity to en- gender an infusory animal, the germ of the polype with its inherent power to produce a polype; in the same way the various tissues, vessels, glands, &c. of vegetables and animals exist with their special capacities of excitation, which are manifested in the particular functions they severally perform. Excitability is there- fore a multiform property and a consequence, not a single peculiar power inherent in orga- nized beings, the fundamental cause of their actions and identical with or itself the living principle. Dependent on the integrity and continuance of the functions of nutrition, how can it be the cause of these? Only manifested in kind, with the occurrence of specific organs, how can it be the cause of their several ma- nifestations ? We are altogether in the dark with regard to the mode in which the motions and other actions of organized beings are performed, how or by what law the globule that in the infusion of organic matter is to become an infusory animal moves, as well as of the manner in which the contractility of a muscle is excited by the stimuli fitted to call this quality into action. The contractility of the infusoria, po- lypi, medusae, and other similar tribes appears to be peculiar. The motions exhibited by the confervas, tremellae, and simplest vegetables are also peculiar to them, they differ from those manifested by the simplest animals in being entirely under the influence of external influences, and showing nothing like spon- taneity. The tissues of all animals, even the most complicated, show traces of a vital ten- sion or contractility, different from simple elasticity and not depending on muscularity; the cellular membrane, skin, fibrous tissues generally, excretory ducts, and vessels of all descriptions tend to contract upon the parts ANIMAL. 139 and fluids they surround and include. This tonicity or peculiar contractility disappears in great part with the cessation of life : a wound made in a dead body never gapes as it does in a living one. Something of the same kind exists in vegetables ; the sap as- cends with greatly increased velocity in the young shoots under the influence of stimuli of different kinds, and its flow is checked by nar- cotics and altogether arrested by poisons ; it is probable, therefore, that it takes place in con- sequence of a vital tonicity or contractility in the sides of the sap-vessels which contain it. From this general review of the physical construction and vital phenomena of the two grand classes of organized beings, vegetables and animals, it is impossible not to remark the strong features of resemblance, and yet the numerous points of difference they exhibit. Both have a beginning, which happens very much in the same way in each ; both live as individuals by the susception of aliment and its prepration by a variety of processes, which, in their essence, differ but little from one an- other ; both continue themselves as kinds in a surprisingly similar manner ; both exhibit the changes denominated age ; both have a merely temporary existence, consequently both exhibit the phenomenon entitled death, and both are decompounded after the cessation of life, their constituent elements assuming new shapes, in obedience to the general laws of chemical affinity, which had been set at nought during the existence of the individuals in either class. Notwithstanding these striking points of re- semblance between vegetables and animals in all that is essential or general, it is impossible, as we have seen, to condescend upon par- ticulars without immediately detecting differ- ences that distinguish in the most marked manner the individuals of the one class from those of the other. It is always in their lowest or most simple species that we remark the most striking similarity between vegetables and animals, and it is among these that we constantly find ourselves most at a loss for characters distinctive of each. We observe no evidence of anything like a connected chain of being from the lowest or most simple, to the highest or most complicated vegetable, and from this through the most inferior animal upwards to man ; it is, on the contrary, in the extremes or lowest grades of each that the greatest similarity prevails ; here vegetables and animals approximate very closely, here they literally inosculate, but from this common point they begin to form two distinct series, which diverge ever more and more widely from one another as they ascend. Without attention to particulars, it would seem impos- sible to adduce as ultimate terms of distinction between vegetables and animals, other faculties than those of voluntary motion and sensation as peculiar to the latter, in virtue of the one of which powers they are rendered in a great mea- sure masters of their own existence, whilst by the other they are endowed with consciousness of many of the various acts that take place within, and of the phenomena that occur without them. Even this distinction, how- ever, is only applicable as regards species con- siderably raised above the lowest; would we indicate the differences between the most in- ferior members of either series we must con descend upon particulars, and, in some in- stances, even call in analogy and inference to our aid in laying down the chart of their re- semblances and dissimilarities. COMPARISON OF ANIMALS WITH ONE ANOTHER. This head is also comprised within that of our entiie 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. Physical qualities and material constitution of animals — 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. The form 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 heteramorph ous. 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 binaria 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, are added to the alimentary mass in its progress through the intestinal canal. In addition to the digestive apparatus and general external 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 trachea 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 to 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. When 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 vertebra ta 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, externa/ 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, w7e 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- cheze, 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 trachea 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,wheu 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. W'e 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 only, 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 forcirfg 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, when 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 ail 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, 'oy swimming, by running, leaping, flying, &c. &c. Every partial movement ex- ecuted by the higher animals has, farther, its own special apparatus : the intestinal canal has its muscular panetes ; 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 oneanother; 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 art, it is evident, suffices for its own existence, n 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 VOL. i. contain the organs of every one ol 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 jissiparous, 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- L ANIMAL. 146 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 ovo-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 mtra-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 rnixti et vivi, 4to. Hake, 1707. Berzelius, in Afhandlingen 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, Lchrbuch der Chemie, B. 3. Dresd. 1827 ; Traite de Chemie Trad, par Jourdan, t. v. Gay-Lussac et Thenanl, Proportion des principes des sub- stances vegetales et animales, 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. 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Lond. 1770. Sprengel, Kenntniss der Gevvaechse, 8vo. Halle, 1802-1807. Ejus, Vom Baue und Natur d. Gevvaechse, 8vo. Halle, 1812. Brisseau-Mirbel , Anat. et Physiol, vegetale, Paris, 1802. Ejus , Expos, et defense, 8vo. Amst. 1808; Paris, 1809. Petit- Thouars, Organization des Plantes, 8vo. Paris, 1806. Treviranus, Inwendigen Bau derPflanzen, 8vo. Gotting. 1806. Link , Anat. u. Physiol, d. Pflanzen, 8vo. Gotting. 1807 ; Nach- trag ib. 1809. Moldenhauer, Anatomie derPflanzen, 4to. Kiel, 1812. Kieser , Organization des Plantes, 4to. Harlem, 1814. De Candolle, Organographie vegetale, 2 vol. 1827. * * ** Blumenbach , Handb. d. Vergleichenden Anatomie, 8vo. Gotting. 1805, Anglice by W. Lawrence, 8vo. Lond. 1807. Cuvier, Lecons d’Anat. comparee, 5 tom. 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. Cams, 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 tom. 8vo. Paris, 1835. Meckel, System der vergleichenden Anatomie, 6 Bde, 8vo. Halle, 1821-33. ; Gallice partim, Paris, 1828- 29. De Blainville, De Forganization des Animaux, 8vo. Paris, 1822. Ejus, Cours de Physiologie ge- nerate et comparee, 3 tom. 8vo. Paris, 1829. * * * * Duhamel-Dumonceau , La Physique des arbres, 2 vol. 4to. Paris, 1758. Van Marum, Dissert, qua REGION OF THE ANKLE. 47 disquirinir quousque qiiaedam animalium planta- rumque fimctiones consentiunt, 4to. Gotting. 1773. Mustel, Traite, &c. sar la vegetation, 8vo. Rouen, 1781. Fryar, De vita animantium et vegetabi- lium, 4to. Lugd. Batav. 1785. Dumas, Essai sur la vie, Montp. 1785. Compuretti , Prodromo di fist- ca vegetabile, 8vo. Padua, 1791. Kielmeyer , V e r- haltnisse der organische Kraefte, 8vo. Stuttg. 1793; Tubing. 1814. Humboldt, Aphorism, aus d. Phy- siologie der Pflanzen, a. d. Lat. uebers. 8vo. Leipz. 1794. Brera , Program, de vitae vegetabilis et animalis analogia, 4to. Ticin. 1796. Rafn, Ent- wurf einer Pflanzen-physiologie a. d. Dan. uebers. Kopenhagen, 1798. Senebier, Physiologie 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. Goetiing. 1811. Kieser, Aphorismen aus der Physiologie 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, Ueber die Temperatur der Vegetabilien,Tubing.l826. 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 notturne dell’acqua marina, Venez. 1749. Viviani, Phos- phorescentia maris illustrata, 4to. Geno®, 1805. Murray, Exper. 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 electricitate, Bo- logn. 1794. Pfaff, Ueber thieresche Electricitcet 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. * * * * Glisson, De irritabilitate fibrarum (in Eg. De ventriculo et intestinis Tract. 12mo. Lond. 1677.) Stahl, Theoria medica vera, 4to. Halle, 1708. Whytt On the vital, &c. motions of animals, 8vo. Lond. 1751. Darwin, Zoonomia, 4to. Lond. De Garter, Exercitat. medic®, 4to. Amst. 1737-48. Tups, De irritabilitate, 4to. Leid. 1748. Haller, Prim® line® Physiologiaa, 8vo. Gotting. 1747 ; Ej. Ele- menta Physiologic ; 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. Beil. 1797. Bichat, Rech. sur la Vie et la mort, 8vo. Paris. Anatomie generale. The systems of Physiology of Adelon, Bostock, Burdach, Magendie, Mayo, Richerand, Rudolphi, and Tiedeman. (To the admirable Physiologie 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 dorsum 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 fourwell-marked prominences, one on either side, termed malleolus, ( interims 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 is 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 l 2 148 REGION OF THE ANKLE. of the skin as possible. Owing to the same peculiarities of the integuments in this situ- ation, no less 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 ermit the accumulation of adipose substance ere; 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- j 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 pollieis tendon which lies immediately external to the last-named tendon ; and lastly in those of the extensor digitorum longus andperoneus 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 REGION OF TilE ANKLE. 149 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, the 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 isubcutaneous 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, eateris paribus, be more likely to prove dangerous than that of the tibialis posticus : for, as the synovial shears of the former extend along the whole sole of fhe 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 synovial 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 calc is ; 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 injury7 to the articulation or wound of any7 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- riorly7 the bone and tendon are not even in con- tact, for here a distinct synovial bursa is inter- posed between them. The liability7 of this large bursa to inflammation and effusion should be carefully borne in mind by7 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 eren 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 necessary7 it is to maintain the extended position in our treatment of this important accident. b. Aluscles . — 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 wav upon the tendon. c. Arteries. — The arteries about the ankle, from their liability to injury7 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, Tunning upon and in front of the inner ankle, and anastomosing with others passing forwards from the posterior tibial, thus insuring a sufficient supply ofblood to the joint, even w hen 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 intemus. It is here occasionally7 the subject of operation, and hence its course and relations should be very7 carefully7 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 artery7, 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 thb situation, yet owing to the heel, the ankle, ar.d 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 very7 erroneous idea of its true position — hence it is that ail 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 ralher 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 151 JOINT OF THE ANKLE. 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 iu 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. Lymphatics. — 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 ly mphatic 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 TIIE.— (Normal ana- tomy.) (Fr. articulation du coude-pied. Germ. Fussgelenk. Ital. caviglia.) Tire 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 and Cloquet 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 upper 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 part 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 hones. The inner edge is prolonged downwards nearly an inch in length, forming the prominence known by the name of malleolus interims ; 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 tovyards 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. Th e fibula, 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 isnamed the malleolus externus ; it is much larger than the internal, and placed behind and somewhat below it. The external surface of this fibular malleolus is covered merely by the integuments ; the internal surface 152 JOINT OF THE ANKLE. is tipped with cartilage, and convex in the ver- tical direction, being received upon a corres- ponding concavity or. 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, which 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 itsantero-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 internalmalleolus 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 being 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 inferior tibiofibular articulation. We shall not now describe the ligaments which here unite the tibia and fibula, referring to the article on the Tibio-fibt lar Articulation ; but we 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 as 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 W eitbrecht 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. fibula 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 subdivide1 1 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 Weitbrecbt. It is related superficially to the peroneus longus tendon, and by its deep sur- face to the synovial membrane, to die astra- galus, and os calcis. In flexion of the foot this JOINT or THE ANKLE. 153 ligament is rendered tense ; hence it appears designed to limit motion in this direction : in extension it is of course relaxed. 5. The pos- teriorfibulo-tarsal\iga.ment( lig. fibula posterius, Weitb., posterior external lateral, 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 (fig. 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, (fig. 61.) From the circumference cf 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 TIIE. — 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 hones. 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 peronaei 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 experiment '-, 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 bones, are contingences which frequently render greater effort produces a separation of the the dislocation of the tibia at the ankle-joint lateral ligament from one or other of the mal- a very complex accident. leoli by laceration of its compact tissue, or of The most superficial view of the structure the periosteum which covers it, while the liga- of the ankle-joint will convince anyone that ments themselves remain unbroken. Oppor- no lateral displacement of the bones of the tunities do not often occur of discovering leg can occur, without its having been 1m- 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 tom from the bone. Mr. Wilson found, in a case where the patient died five days after a severe sprain of the ankle-jomt, 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 tom. 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 cedema 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 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. We 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 Uarle, 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 leave 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. 'im- partial luxation of the Tilua 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, and when the peronaei 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 fig. 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. 51, 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, (fig. 52, c,) 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 perontei muscles, when the patient has at- tempted to walk after the fracture has occurred. It is on these combined movements w'hen 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 j 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 l’Extremite infericure Hu 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 the Dissection of a case of tibia inwards or of the foot the same class as fig. 53, outwards and upwards. — from the museum of St. ( Dupuytren. ) 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 astragalus ( vid.Jig . 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 wTell as those 1.58 ABNORMAL CONDITION OF TIIF. 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 (Jig. 54, «, 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 preserved in the collection of St. Thomas’s Hospital 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 “ Annuuire" 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 f racture 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 (jig. 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 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 ). (Fig. 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 (jig. 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 Dupuytren, Annuaire. 159 ABNORMAL CONDITION OF THE ANKLE-JOINT. malleolus internus 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 heemorrhage 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 bi / 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- ronsei 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- ternumwhich 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 observations 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, (fig. 57, a, 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 161 ABNORMAL CONDITION OF THE ANKLE-JOINT. Partial luxation forwards of the tibia at the external ankle, with fracture of the fibula near the malleolus. Fig. 57. Fig. 58. a, b, semicircular excavation posteriorly, and projection of the heel backwards; e 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 ; 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 ffag- Fig. 59. Fig. 60. Skeleton preparations of fig. 57 and 58. M 162 ABNORMAL CONDITION OF THE ANKLE-JOINT. merit 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 more or less inti- ' ’ mately unded or even blended together, and equal in number to the number 111/:-—- of rings. (See fig. 65. repre- senting the nervous system of the aphrodita aculeata). The ganglions give origin to lateral branches, and -J! A— 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-oesophageal 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 * See Annates des Sciences Nat. tom.xxii. + See Cuvier, Anat. Comparee, tom.i.; Trevi- ranus, liber der stachlichten Aphrodite, Zeitschrift fur Physiologie, 3 Band; Moquin Tandon, “Mo- nograph. des Hirudines,” Morrem, “ Sur le Lom- bric,” & c. proboscis of a phyllodoce, and Jig. 67, that of a nereis). The surface is frequently beset with small papillae, and its extremity armed with Fig. 67. horny jaws (m), 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 analogous 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 terebelhe); 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, thalassemee. 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 coecums, (as in some hirudines, Jigs. 68 and 69.) Lastly, ANNELIDA. 169 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 aphroditse 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- cis, b b, the ap- pendages.) This type of structure leads to that which is manifested in the planarire, 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 coeca ; 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 thalassemas, 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- nidas 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 (jig. 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.; Home, ‘ Lectures on Comp. Anat.’ Fig. 70. Fig. 71. v_> 170 ANNELIDA. sides (c/), 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 ( b ), 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.4' In the genus ndis 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 oesophagus, 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, ‘ Reclierches sur les Annclides abranclies,’ Annalcs dcs 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 nai's; 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 ‘ lesser circulation,’ (fig. 72) : Fig. 72. this is effected in the branches ( b , e ) of the dorso- lateral vessels (a), which are for the purpose of bringing the blood into contact with the aerated water contained in the small membranous vesicles (f) situated at the sides of each seg- ment of the animal, and opening externally upon the inferior aspect.* Respiration.— ¥ rom 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 skin 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. 1 ANNELIDA. 171 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, f,f, f.) 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, (fig. 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 com plicated, for the filaments are extremely subdivided, (fig. 63, f.) In the arenicolte, 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 serpulse, 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 liirudinae 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 ‘ pulmonary sacs,’ and some authors think that they receive into their interior atmospheric air in a gaseous form. Their nuijiber 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 lumbrici 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 Blainville, and Audouin and Milne Edwards. Fig. 73. 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 nais.* Generation.-— The generative apparatus is only very imperfectly understood in the anne- lida. It appears that all these animals are hermaphrodite, but that they caunot 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 (■ d ) 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 deferens (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 I’Histoire Naturelle des Sangsues.’ Home ‘ Lec- tures on Comp. Anatomy,’ Moquin Tandon, op. cit. Morten de Lumbric. terrest. l)uges, op. cit. 172 ANNELIDA. is contained in the rest of the apparatus. These organs (Tig. 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 Fig. 76. pouch (i). This, accord- ing to some authors, is analogous to an ute- 7i rus, but in the opi- nion of other natura- lists is merely a copu- - 1 lutive 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, a) 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 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 lledi, 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 foetus 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 Dugbs, 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 nais 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.f 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 j ova contain severally as many as eighteen j embryos. One might at first view suppose that the same circumstances obtained in the nai's; 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- i ration, but enjoy the singular faculty of pro- ducing new individuals by a transverse division ! of the body. A nais 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 JVI. Dugfes, Sangiovanni, and many other observers : the anterior portion of the j 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- ther, 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 . Fig. 77. 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. This 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 he 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 nais, 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 des Sciences par la Societe Philoma- thique, an vii. et x. Lamarck, Discours d’ouver- ture du cours des animaux sans vertebras, pro- nonce en Mai 1806, et Histoire des animaux sans vertebres. Blainville, De l’organization des ani- maux, t. i. tab. 7. — Dictionnaire des Sciences Naturelles, art. Vers, t. lvii. Audouin Milne Edwards, Recherches pour servir a l’histoire natu- relle du littoral de la France, t. ii. Muqum Tandon, Monograph, des Hirudines, 4to. Montp. 1827. Morrem, De lumbrici terrest. hist. nat. 4to. Brass. 1829. Pallas, Miscellanea Zoolog ica, 4to. Lugd. Bat. 1775. Home, Lectures on Comp. Anat. Duqes, Annales des Sc. Nat. t. xv. Thomas, Memoires pour servir a Fhistoire nat. des sangsues, 8vo. Paris, 1806. Muller , Vermium terrestrium et fluviatilium, &c. historia, 2 parts, 8vo. Copenhag. and Lips. 1773-74; Ej us. Von Wiirmern 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 do Zoologie.’ logia Danica, fob Copenh. 1788-1806. Schweigger, Handb. d. Naturgeschichte d. skeletlosen ungeglie- derten Thieren, 8vo. Leipz. 1820. Weller, Circa animalium quaedam classium inferiorum incremen- tum et vitam, 8vo. Halle, 1817. Klein, Descript. Tubulorum marinorum, 4to. Danz. 1777. Otto, De Sternapside el 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. Kuntzmunn, Anat.-Physiol. un- tersuchung iiber d. Blutigel, 8vo. Berl. 1817. Knolz, Naturhist. Abhandlung uber d. 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 Syavans 1697, Phil. Trans. 1697. Mo - rand, Anatomie 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. Wickmann, Vom Giirtel des Regenwurms : Besch'aft. der Gesells. Naturforsch. Bd 3. Chamisso, De ani- malibus e classe Vermium in circumnavig. terras observatis, 4to. Berol. 1819. Belle Chiaje, Mem. sulla storia degli animali senza vertebre del regno di Napoli, 4 vol. 4to. Nap. 1823-29. Derheims, Hist. Nat. des Sangsues, 8vo. Paris, 1825. Nicolai, Diss. de strnctura 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 l’Egypte, fol. Paris. ( II. Milne Edwards.) ANUS, (in anatomy,) from Anus vel An- nus, a round, a circle, (syn. ostium recti, podex, cuius. Gr. w^wxro;. Fr. anus. Germ. After. Ital. ano.) is a term commonly applied to the lower extremity of the rectum : properly speakiug, 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 time : 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 hody of the animal, a single orifice admits the food necessary for its support, and the excremen- titious portion (if any) is ejected through the same opening. In the actiniae, also, where a 174 ANUS. 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 asteriee, 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.'* In the sipunculi the anus opens near the mouth, and in the holothurfe 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 (he 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 sepias 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 Leet. on Comp. Anat. vol. ii. p, 76. t 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 deferentia, 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 feces 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 fecal 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 perinseum ; 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 glutffii 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 perinteal 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 raphh 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 defoecation; 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 levator es ani, to which may be added the two transversi perilled, and the two coccygcd 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- fundus vel orbicularis. Sphincter ani cutaneus (crtpiyyu, constringo,) coccygeo-anul, 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 perinamm ; 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 rccto-coccygaal 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 urinse 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 the 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 intestinale, Winsl.) is of much less extent than the former, and is situated more ANUS. 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 defacation 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 permaeal 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 perinsei, and posteriorly the VOL. i. eoccygeus muscles bound this hollow. Each of these triangular recesses is lined on all sides, except towards the skin, by fascire, 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 off 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 obturate?- 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 perinreum the obturator in- ternus muscle, and the internal pudic nerves and vessels, the perinajal and hemorrhoidal branches of which pierce it as they proceed to their destination. The internal layer, or the Ishio-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, w'hilst a general firmness and elasticity is imparted to the w'hole 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 fasciae 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. Transversi perilled muscles ( Ischio-peri- N 173 ANUS. iieul ). — 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 perinseum, where it is also partially attached to the cuta- neous sphincter of the anus, and to the acce- leratores urinte 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 aud 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 perinseum, 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 pevinseal, and the deep trans- verse, or the artery of the bulb. These muscles are enveloped between the layers of the perina?al 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 perinreal aponeuroses, and thus they can support, strengthen, and compress generally the parts in the perinseum ; 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 perinseal 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-p u b io-cocajg ien ) . — This pair of broad, thin, flat, and nearly square muscles form a septum somewhat broader above than below, between the pelvis and perinaum, 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. 1 1 appears more correct to considerthese muscles as one circular muscular septum extended across and 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 perinseum, 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 puba! portion, des- cend a little obliquely backwards on each side ANUS. 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-coccygeeus 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 fascias, to the glutasus maximus and transverse perinatal 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 coccyx after it has been forced back lf9 by abdominal pressure in parturition, or in the ordinary evacuation of the bowels, and further, by raising and compressing the trigonb 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 urethra, &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-coccygai 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 defaecation, 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 arid 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 N 2 ANUS. 180 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 defecation. 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 has 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 defecation 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 perinseum 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 fecal 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, and 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 feculent 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 lacunae. It is here very loosely connected to the muscu- lar fibres, and is frequently found thrown into irregular folds ; these are protruded somewhat during defecation, 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 fecal 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. Nerves and 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 nerves; 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 hypogastric plexus of nerves is composed of filaments from the sacral plexus, which interlace with some from the inferior mesenteric 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 perinaeum, 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 luemorrlioidal, and are derived from three sources, viz., the abdominal aorta, the internal iliac, and the internal pudic arte- ries. The superior haemorrhoidal 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 perinceal 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 fistulas, and some- times give rise to a haemorrhage, troublesome and difficult to restrain. In such operations the external haemorrhoidal 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 perinaeum, 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 htEmorrhoidal 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 fcetus 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. 1. 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 l’Academ. 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 Du set* 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 sometime; 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 perinseum 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 staff1 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 perinseum 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 troehar, if at a considerable distance from the anus. * Recueil Periodique de la Societe de Med. de Paris, t. iv. p, 45. t Diet, des Sciences Med. t. xxiv. p. 126. f Mem. do l’Acad. de Chirurg. t. i. p. 385. ANUS. 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 situation 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 skm 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. cle l’Acad. de Chirurg. t. i. p. 378. other appearances 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 usua'ly 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 wdl 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 ulcera- 184 ANUS. lions 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 feces, and from die 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- fecation, 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 scroti ” 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 defecation : 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 defecation, 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 defecation, 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 feces 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- fecation, 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 defecation, 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 front j gangrene, be reduced by pressure properly ANUS. 185 applied, and by attention to posture. In the procidentia of old persons, Mr. Iley 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 fissures, 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 m 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 hamorrhoid 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 ihe 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. Trom 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, &c., 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 hcemorrlioids 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 defascation ; 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 haemorrhoidal tumours, external as well as internal, must be regarded 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 htemor- 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 haemorrho.ds, 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 w'ith 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 w'hich 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 defeca- 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 fistulas 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, hut 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 he 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 foecal 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 fistula, 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 defsecation ; in this state, when the fistula or abscess remains discharging through the skin only, it constitutes what is termed a blind external fistula ; 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 fistula is then said to exist. Fistula; 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 fasci® 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 cox® 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). — ( Arieria magna. Fr. aorte. Germ. Aorta, die grosse Schlugader. Gr. ao^rb.) Hippocrates applied the term aograi to the lower part of the bronchi. Aristotle called the great trunk of the arterial system i pAsi}/ cco^rb- The aorta, one of the two great arteries which spring from the heart, is the trunk of the arterial system of the general circulation ; it arises from the extreme right part of the base of the left ventricle of the heart, which, from this circumstance, is sometimes called the aortic ventricle. There is a ring of tendinous structure surrounding the aortic opening of the ventricle, which in the stag and some others of the ruminantia is more or less partially ossified; into this ring the muscular fibres of the heart are inserted. The middle tunic of the aorta is divided at its commencement into three .semicircular flaps by an equal number of angu- lar notches, forming thus a festooned edge which is bordered throughout its whole extent by a marginal tendinous cord. These three semicircular flaps touch the aortic opening of * The etymology of this term is by no means clear. The following extract from Spigelius (de corp. hum. fabrica) gives a not improbable origin for it.— “ Veteribus Graecis aop-rov dictam fuisse vaginam cultrorum Macedonibus familiarem, quo- rum manubrium nonnihil incurvatum erat, ad quam sane figuram quam proxime accedere videtur arte- riae magnae t uncus, qua parte ex corde onginem suam ducit.” Cloquet suggests the theme, aopTBOfxcu, suspendor, <( parceque l’aorte consideree dans sa t Halite parait comme suspendue au coeur.” Aris- totle, by whom the term seems to have been first employed, generally denominated it i’Ka.rtm, 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 fetus 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. Bedard* 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. Generale, 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 tile 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 pleur® 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 thorucic 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- tebra 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 arutid and left subclavian , which, arising from the transverse portion of the arch, are distributed to the head, neck, and upper extremities, and the primitive iliac 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 panetes 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. Bondon, 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. (SeeOvuM.) 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 pulmonary 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 of 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. f 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 of!' 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.J 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. f Vide Abhandlungen des Josephinischen Mcdi- cinisch-Chirurgischen Akademie. Band, i. S. 271. Taf. 6. Wien. 1787. :J Meckel Handbuch der Menschlichen Anatomie. Band iii. Halle and Beilin, 1817. Abernethy in Phil. Trans. 1793. § Desault in Journal de Chirurgie, tom. ii. Dr. Goodison in Dublin Hosp. Reports. Brasdor Recueil Periodique de la Societe de Medecine. Paris, tom. iii. |] Handbuch der Menschlichen Anatomie. Band iii. Halle and Berlin, 1817. AORTA. 1©1 kind, the number of branches is most fre- and superior mesenteric arise by a common 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 coming 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 twro 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, weazel, several rodentia, &c. ; b. sometimes there are two arteriae innominata?, 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, and the other into the sub- elavians ; 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 ; 6, 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 ; d, 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 cceliac ; sometimes the coeliac 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 Artert and Heart. The aorta, as Bedard 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- * Diclionnaire de Mcdeeine, 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 the 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 artery,* or, taking a direction backwards, have opened into the trachea, cesophagus, 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 vertebra. 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 if 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 (fig. 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. 73. E, common iliac artery. y, middle sacral 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 along 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, oesophageal, 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 (esophageal 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 (Esophagus, 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. Irferior 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 and fourth intercostal spaces, w'e often meet with but eight pairs of intercostal arteries coming immediately from the aorta (fig.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 inter- 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 tranverse process of the superior of the two vertebrae, with which the head of the rib is articulated ; it gives some branches to the bodies of the ver- tebras, 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, cceliac, 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 the fleshy substance of the ala oftlie 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 off 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 oesophageal arteries. The ceeliac. artery, called, also, cceliac axis, is one of the largest and shortest of the vessels given oft by tire 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 cceliac 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 coeliac; 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 oesophageal 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. W hile 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 communis 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 casliac. 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 (pancreaticte magnte et parva ), which anastomose with the pancreatic branches of the right gastro-epiploic. It gives a large branch, the left gastro-epiploic, which some- times arises from one of the branches in which the splenic terminates. This branch passes onwards to the left until it reaches the greater arch of the stomach, along which it descends, passes to the right until it meets the right gastro-epiploic, with which it anastomoses. In its course it gives off, like the right gastro- epiploic, superior branches, which pass over the anterior and posterior surfaces of the sto- mach to anastomose with the branches of the coronary and inferior branches which descend in the great omentum, where they have a simi- lar distribution with the descending branches of the right gastro-epiploic : near the fissure of the spleen, the splenic artery divides into five or six branches, which anastomose by arches, and enter the substance of that organ. Before entering the substance of the spleen these branches give off large vessels, called vasa 'orevia, which bend to the right, and are dis- tributed to the great extremity of the stomach, spreading over its anterior and posterior sur- faces, where they anastomose with branches of the coronary and right gastro-epiploic. The superior mesenteric artery, often larger than the cceliac, arises from the aorta imme- diately after the cceliac ; sometimes from a trunk common to both vessels, as in the tortoise. This artery is at first concealed by the pancreas, it descends perpendicularly behind that gland and crossing the termination of the duodenum arrives at the root of the mesentery, between the two layers of which it descends. In the middle of this fold of the peritoneum it forms a considerable curve, the convexity of which is to the left, and directs its course towards the ter- mination of the small intestine in the right iliac region, forming near its termination a second curve, the concavity of which is to the left. Near its origin this artery gives some branches to the duodenum and pancreas, by means of which it anastomoses with the branches of the hepatic and splenic sent to these organs : in the mesentery it sends off from its left side the arteries of the small intestines, and from its right the arteries which it supplies to the great intestine. Arteries of the small intestines. — These arise from the left side of the superior mesenteric, varying in number from fifteen to twenty; the superior are longer and larger, those which succeed them appear to diminish progressively in length and size, they all advance between the two layers of the mesentery to the concave side of the intestine ; at a certain distance from their origin they divide into secondary branches which diverge from each other at acute angles ; these secondary branches subdivide into still smaller branches, which, diverging in a similar manner, form arches of anastomoses with cor- responding branches of the adjoining arteries ; the convexities of these arches are all turned towards the intestine, and from them numerous branches arise, which, by dividing and anasto- mosing like the larger trunks, form a second series of smaller arches ; other branches arising from the convexities of these arches divide and anastomose to form still smaller and more numerous arches ; thus we have three, some- times four, and occasionally five series of arches, formed by the subdivisions of these arteries before they reach the intestine, and presenting in the mesentery a network with large meshes. From the convexities of the extreme arches which form the outer border of this network, thousands of small arteries pass in a straight direction to the tube of the intes- tine ; these form two series, an anterior and a posterior, which apply themselves to the oppo- site surfaces of the intestine, and anastomose with each other on its convex border. The detailed description of their further distribution will come under consideration in the article Intestinal Canal. Colic arteries. — The superior mesenteric sends off three, sometimes only two, branches from its concavity, called right colic arteries, dis- tinguished as superior or colica media, middle or colica dextra, and inferior or ileo-colic ; when there are but two, the superior and middle form but a single trunk ; the inferior is generally distinct. The right superior colic or colica media arises a few inches distant from the origin of the supe- rior mesenteric; it passes forwards between the layers of the meso-colon towards the middle of the transverse colon, and divides into a right o 2 196 AORTA. and left branch ; the right follows the right part of the transverse colon, and anastomoses with the superior branch of the colica dextra ; the left branch follows the left portion of the transverse colon, and communicates with the left colic branch of the inferior mesenteric artery. The colica dextra or middle right colic artery arises close to the colica media, sometimes from a trunk common to both, and sometimes from the ileo-colic. After its origin it passes for- wards, upwards, and to the right in the meso- colon towards the ascending colon, and divides into two branches ; one superior ascends to anastomose with the right branch of the colica media, the other descends along the concavity of the ascending colon, and communicates with the ascending branch of the ileo-colic. The ileo-colic, ccecal, or inferior right colic passes downwards, and to the right towards the coecum, and then divides into three branches; the first ascends in the meso-colon, and anas- tomoses with the descending branch of the colica dextra; the second communicates in the mesentery with the termination of the superior mesenteric; and the third, arising in the angle between the two preceding, passes behind the junction of the ileum with the ccecum : at this place it gives off a branch which forms a small arch in the mesentery of the vermiform appen- dix, and then divides into two branches, one of which passes upwards on the colon, and the other descends on the ccecum. The colic arte- ries, by their anastomoses with each other, form arches, from the convexities of which, turned towards the intestine, numerous branches arise ; each of these again divides into two, which with the contiguous vessels form smaller arches, and straight branches finally arise from the ultimate arches, which, passing on either side of the intestine, include it between them, and anastomose on its convex edge. In the foetus we have the omphalo-mesen- teric artery arising from the superior mesen- teric ; this vessel, which passes along the um- bilical cord to the vesicula alba, becomes obliterated towards the end of the second month of gestation. The inferior mesenteric artery arises from the front of the aorta to its left side, at about an inch or an inch and a half above the origins of the primitive iliacs ; it sometimes arises from the left primitive iliac, especially when the aorta has divided higher than usual ; instances of the absence of this artery are very rare, but interest- ing as presenting an example of the normal condition in birds and reptiles, in which the inferior mesenteric artery is much reduced in size or entirely absent. The inferior mesenteric artery runs obliquely downwards and to the left, and gets between the layers of the left iliac meso-colon, where it divides into many branches, distributed to the left portion, and sigmoid flexure of the colon and the rectum ; the superior branches are dis- tributed to the descending portion and sigmoid flexure of the colon, and are called left colic arteries, while the lower branches go to the rectum under the name of superior hemor- rhoidal arteries. The left colic arteries are three in number, the superior, iniddle, and in- ferior. The superior left colic is the largest of the three ; it arises from the inferior mesen- teric immediately after its origin, passes trans- versely to the left, and divides near the left lumbar colon into two branches, one of which ascends to the transverse meso-colon, and anastomoses with the colica media of the supe- rior mesenteric ; the other branch descends towards the left iliac meso-colon, where it anastomoses with the ascending branch of the middle left colic. The middle left colic is sometimes a branch of the preceding. It divides into two branches; one ascends along the left colon, and anas- tomoses with the descending branch of the left superior colic ; the other, inferior, smaller com- municates with the ascending branch of the left inferior colic. The inferior left colic goes to the sigmoid flexure of the colon, and soon divides into two branches; one superior anastomoses by an arch with the descending branch of the preceding, and the other inferior meets a branch of the haemorrhoidal in the meso-rectum. They are distributed to the intestine in a similar manner with the branches of the right colic arteries, as already described. When the inferior mesenteric has given off' the colic arteries, it diminishes, takes a perpen- dicular direction, and reaches the posteror sur- faceof the rectum lodged between the layersofthe meso-rectum, here it takes the name of superior haemorrhoidal artery. It soon divides into two branches, a right and left, which apply them- selves to the sides of the rectum, sending branches backwards and forwards round that intestine, by which they communicate with each other, and anastomose below with the middle and inferior haemorrhoidal arteries ; some branches anastomose with the lateral sacral of the internal iliac. The lateral branches of the abdominal aorta consist of the capsular, renal or emulgent, spermatic arteries, small twigs to the ureters and adipose substance in the vicinity of the aorta, and the four pairs of lumbar arteries. For an account of the capsular, emulgent, and sper- matic arteries we must refer to the articles Renal Capsule, Kidney, and Testicle. The lumbar arteries are four in number on each side (fig. 78, f); they arise from the lateral and posterior part of the aorta nearly at right angles, they pass outwards across the middle of the bodies of the four superior lumbar or abdo- minal vertebrae to the roots of their transverse processes, covered by the psoas muscle and the crura of the diaphragm. When the lumbar arteries have reached the roots of the transverse processes of the lumbar vertebrae, they divide each into two branches, one posterior and the other anterior. The posterior or dorsal branches are smaller and pass backwards between the transverse processes of the lumbar vertebrae, opposite the intervertebral foramina, where they each send a branch inwards to the spinal cord and cauda equina; they then plunge into the substance of AORTA. 197 the great sacro-lumbar mass of muscles, in which they are lost, anastomosing frequently with each other, and with the dorsal branches of the low- est intercostal and ileo-lumbar arteries. The continuations or anterior divisions of the lum- bar arteries pass outwards between the psoas andquadratuslumborum muscles, to which they give small branches, as well as to the diaphragm, kidney, renal capsule, and surrounding cellular membrane; they then continue their course forwards between the layers of the abdominal muscles, in company with branches of the lum- bar nerves, and anastomose with the lower in- tercostals, mammary, epigastric, and circum- flexa ilii. The middle sacral artery arises from the back part of the abdominal aorta, immediately above the origins of the primitive lliacs, from one of which it arises in some rave cases, it descends exactly over the middle of the anterior surface of the bodies of the last abdominal vertebra, false vertebrae of the sacrum and os coccygis, lying close on the surfaces of those bones ; the branches which it gives off are distributed in a lateral direction ; the first is the largest and not unfrequently is the fifth lumbar artery, the size of which sometimes exceeds that of the continuation of the trunk of the middle sacral itself. This branch divides into an anterior and a posterior, the distribution of which is similar to that of the superior lumbar arteries. Two transverse branches usually arise from the middle sacral on the body of each false vertebra ; these pass- ing outwards give branches to the periosteum and the substance of the sacrum, anastomose with branches of the lateral sacral arteries, and enter the anterior sacral foramina, where they give some branches to the origins of the sacral nerves, and emerging from the posterior sacral foramina are lost in the muscles arising from the back part of the sacrum ; finally, the middle sacral terminates at the extremity of the coccyx in small branches, which it sends to the rectum and surrounding fat. The middle sacral artery is sometimes found double ; in the foetus this artery is propor- tionally larger than in the adult, especially in the earlier periods of gestation. In some ani- mals, the size of the middle sacral artery is scarcely inferior to that of the aorta itself, as in the cetacea and fishes. In all animals fur- nished with tails, the size of this artery bears a constant relation to the size of that member. Aneurism rarely affects any of the branches of the aorta above described ; it, however, occa- sionally occurs in the cceliac or mesenteric arte- ries, or some of their branches. An interesting case of aneurism of the hepatic artery unat- tended by pulsation during life, and which produced jaundice by pressing on the ductus communis choledochus, is reported by Dr. Wil- liam Stokes, in the Dublin Journal of Medical and Chemical Science, for July 1834. We once witnessed the dissection of a female aged forty, under the care of the late Professor Todd, in the Surgical Hospital of the House of Indus- try in Dublin, in whom three distinct aneurisms of large size were found in the epigastric region ; one of the hepatic artery, which communicated with that vessel by a longitudinal fissure, and which had opened into the cavity of the gall- bladder; one of the trunk of the coronary artery of the stomach, and a third of the splenic artery. A remarkable feature in this case, and that of Dr. Stokes, was the absence of pulsa- tion during life, in consequence of which the nature of the disease was not discovered until the post-mortem examination ; the above cir- cumstance may be attributed to the want of resistance in the surrounding parts, and it is one which frequently obscures the diagnosis of abdominal aneurisms. Bidliograph Y. — Diet, de Medecine, art. Aorte. Beclard, Elemens d’anatomie generate, 8vo. Paris, 1823. Wintringham, Exper. inquiry on some parts of the animat structure, 8vo. Lond. 1740. A. Thomson, in Jameson’s New Philosophical Journal for Oct. 1830. Malacarne, Osserv. in Cirurgia, 2 pte, 8vo. Torino, 1784. Hommel, in Com. Noric. An 1737. Klintz, in Abhand. d. Joseph. Med. Chirurg. Akademie, Bd i. 4to. Wien. 1787. Meckel, Hanbd. d. menschlichen anatomie, 3 Bde 8vo. Halle and Berl. 1817. Abernethy, Phil. Trans. 1793. Desault, in Journal de Chirurgie, t. ii. Goodison, in Dub. Hosp. Repts. Brasdor, in Rec. period, de la Societe de Medecine, t. iii. 8vo. Paris. Stokes, in Dublin Journal of Med. and Chem. Science, 8vo. * * * * Buyer, Pr.es. Tiedemann, Diss. de ramis ex arcu aortas prodeuntibus, 4to. Salzb. 1817. Varieties in the number and origin of the principal branches of the aorta are signalized by Tiedemann, (Tabulae arteriarum corporis hu- mani fol. mag. Carolirh. 1827,) in great numbers ; also by Hunauld (Mem. de Paris 1737 and 1740) ; Neubauer (De Art. thyrodea ima) ; Meckel, ( Epist. ad Haller, iii.) ; Walter (Mem. de Berlin, 1785) ; J. F. Meckel (Tab. anat. pathol. fasc. ii. fol. Lips. 1817-26); Haller (Elementa Phvsioiogiae, t. ii.) ; Meckel (Pathol, anatomie, 3 Th. 8vo. Leipz. 1812, and in Archiv. Bd. vi.) ; Huber (Acta Helvet. viii.) ; Loder (Progr. de nonnul. variet. arteriarum, 4to. Jenae, 1781 ) ; Herold (Diss. exh. obs. quasd. ad corp. hum. partium struct. Marburgas, 1812) ; Nevin (Edinb. Med. Comment. Dec. 2, vol. 9) ; Ryan (De quarundum arteriar. in corp. hum. dis- tributione, 8vo. Edinb. 1812) ; Schoen ( De nonnul. arteriar. ortu et decursu abnormi, 8vo. Hal. 1823) ; Schmiedel (De varietatibus vasor. pier, magni mo- menti, 4to. Erlang. 1745); Ludwig (Obs. quaed. angiolog. 4to. Lips. 1764) ; Sandifort (De notabil. vasor. aberrationibus, in Obs. anat. pathol. 4to. Lugd. Batav. 1774); Koberwein (De vasorum decursu abnormi ejusque vi, &c. 4to. Viteberg. 1810) ; Barkow (Disq. circa originem et decursum arteri- arum, 4to. Lips. 1829); Otto (Seltene Beobach- t ungen ; ii Sammlungen, 4to. Berl. 1816-24 ; Ejus Handbuch. d. patholog. anatomie, 8vo. Berl. 1830 — Englished by J. South, 8vo. Lond. 1831, where there are copious references) ; Boehmer (De 4to et 5to ramo ex arcu aortas prod, in Haller. Disp. Anat. Collect, t. ii.); Petsche (Sylloge Obs. Anat. Halas, 1736); Penada (Saggio di Osserv. pathol. anatomiche, Padova, 1801); Burns (Obs. on the diseases of the heart, 8vo. Edinb. 1809) ; Nicolai (De directione vasorum) ; Biumi (Obs. anatomicae) ; Bertin (Maladies du cceur,8vo. Paris, 1824) ; Bernhard (Diss. de arter. e corde pro- deunt. aberrationibus, 4to. Berol. 1818) ; in the various systems of anatomy, particularly those by Heister, Winslow, and Hildebrandt, by Weber, in Morgagni, (Epist. &c. De Sinubus arteriae magnae Com. Bonon. t. i.) Hunauld, (’Obs. Anat. sur une conformation singul. de l’aorle, Mem. de Paris, 1735); Fiorati, (Osserv. sopra un insolita positione dell’aorta, e stravagante origine de suoi priini rami, in Saggi de Padova, t. i.); Murray, (Sonderbane Stellung einiger grosseren Pulsader-stamme, Ab- hand. der Schwed. Akad. Jahr 1768); Vicq d’Azyr, 198 ARACHNID A. ( Manque de 1’anastomose qui reunit les deux arteres mesenteriques, Mem. de Paris, 1776) * Du Verney , (Sur les vaissaux omphalo-mesenteriques, Mem.de Paris, 1700) • CJuiussier , (S ur les vaissaux ompha- lo-mescnteriques ; Nouv. Mem. de Dijon, A. 1782. Societ. Philomath, anil); and Tyson, (Unusual con- formation of the cmulgents, Philos. Trans. 1678.) ( J. Hurt.) ARACHNIDA; a^ci^vri, uranea; Eng. arachnidans ; Fr. aruchnides ; Germ. Spinne ; Ital. Ragni. This class of animals was for a long time confounded with that of insects, but it has been distinguished therefrom by many modern natu- ralists, and more especially by Lamarck, who has applied to it the term ‘ arachnides,’ now universally adopted. The characters indeed which the arachnidans present are perfectly distinct, and prevent them from being confounded either with crustaceans or insects, although one cannot avoid perceiving that they have numerous relations with the animals of these two classes, and they are con- sequently placed in natural arrangements be- tween the crustaceans and insects. Zoologists have assigned the following cha- racters as peculiar to and distinguishing this class. Body divided into thorax and abdomen ; apterous. Legs, eight in the adult state. Head continuous with the chest. Eyes smooth. Sex- ual orifices situated either on the thorax or base of the abdomen. To these external characters may be added others derived from the anatomical conditions of different organs. Thus all arachnidans pos- sess exclusively an aerial respiration, either effected by a sort of lungs, or by means of tracheal tubes, as in insects. This difference in the respiratory organs is accompanied with one not less marked in those of circulation ; for example, all the pulmonary arachnidans possess vessels which cany blood, while, on the contrary, all those which have trachea; are deprived of bloodvessels. Lastly, the latter species (or trachearies) alone undergo metamor- phoses analogous, in some respects, to those of insects ; while the former (or pulmonaries) suffer only changes of integument. We shall treat further on these peculiarities hereafter. Our object here not being to treat of classifi- cation, we shall refer the reader for this subject to the works of Cuvier, Leach, Latreille, Walcknaer, Dughs, and limit ourselves at pre- sent to a tabular exposition of the principal divisions and subdivisions admitted in this class down to the genera with which it is most essential to be acquainted. Latreille, whose method is that most gene- rally adopted by zoologists of every country, divides the arachnidans into two great orders, as follows : — Class. Orders. ARACHNIDA / Pulmonary sacs for respiration, 6 to 12 ocelli Pulmonaria. \ Trachea for respiration, not more than 4 ocelli Trachearia. The same author establishes in the first order two families, which are characterized as follows : Palpi simple, pediform; mandibula armed with a moveable and perforated claw, emitting a poisonous liquid Abdomen inarticulate, terminated by spinnarets Palpi produced, cheliform, or shaped like pin- cers Mandibida provided with a moveable digit . . Abdomen articulate, without spinnarets M. Walcknaer, who has made a special of life, has very recently considered them with study of the family of uraneida or spinning the express view of arriving at a natural arrange- arachnida, and who has published many works ment of them ; the result of his labour may be on their methodical distribution and their habits seen in the following } Families. , ARANEIDJE. .PEDIPALPI. \st Order. Arachnida Pulmonaria. TABLE OF THE SUBDIVISION OF THE ARANEIDjE, OR ARACHNIDA FILOSA INTO GENERA. GENERA. ARACHNIDA. 199 200 ARACHNIDA. ARACHNIDA. 201 Of the external covering or tegumentary system. — Although the external covering of the arachnidans varies in consistence, according to the part of the body which is examined, yet it may be said in general to be more or less soft, rarely acquiring the solidity of the integument of certain insects, and still less the hardness of that of many crustaceans.* Where it is of the greatest consistency it is elastic, of a deep brown colour, and has an aspect analogous to horn. In chemical com- position, however, it is always widely different, as has been proved by the researches of M. August Odier, and some other chemists. It contains, in fact, a substance sui generis, called ‘ chitine,’ which is insoluble in potassa, but, on the contrary, is soluble in warm sul- phuric acid, does not turn yellow with nitric acid, and does not curl up when burnt, but leaves an ash, which, if the part experimented on is sufficiently thick, preserves the form of the organ. The solidity of the outer covering is gene- rally greater on the thorax than on the abdo- men. The genera Scorpio, phrynus, theli- phonus, and phalangium, afford an exception to this rule, the rings of the abdomen being distinct and solid, especially on the dorsal aspect. In the spiders properly so called, ( aranea ,) and in the greater number of the mites ( acari ), the skin of the abdomen is very soft, coria- ceous, papiraceous, or even membranous, transparent, and susceptible sometimes of be- ing greatly extended. It is on this account that the abdominal segment of the body shrinks and loses its form after death, and from the transparency of the integuments the same arachnidans present during lifetime the various markings and lively colours which depend on a kind of pigment situated in the interior of the body. The head, as we have remarked in our ex- position of the characters of the class, is always consolidated with the thorax; this is readily ascertained to be the fact in scorpions and spiders, and in order to express this dispo- sition, which obtains also in many of the Crustacea, the two united segments are termed ‘ cephalo-thorax the term abdomen is applied to the part properly so called, and thus the body of the arachnidans may be divided into two parts. The abdomen may be either sessile or pediculate, i. e. it may either inclose at its anterior margin the posterior part of the thorax, as in the scorpions, or it may adhere to the thorax by a very circumscribed part of that margin, as in the spiders properly so called. Anatomically speaking, the abdomen has a very simple structure : it is formed of annular segments sometimes distinct and hard, as in the scorpions ; sometimes blended together and soft, as in the spiders and mites. The other division of the body or cephalo- thorax is not so simple. To facilitate the study * This composition being precisely analogous to that of the integuments of insects, we shall treat of it in the article relating to these animals. of this part it is necessary to consider the cephalic portion separately from the thoracic division. This it is easy to do, where, as in many cases, the junction of the two parts is perfectly distinct, and made obvious by the ex- istence of a furrow along all the whole superior part of the line of union, (see the traces of it m the thorax of a pholque, pholcus rivulatus, fig. 79.) But in every case the head (a) is recog- nizable by constant characters: it supports the eyes and all the pieces belonging to the oral apparatus, while the thorax ( b ), on the contrary, gives insertion to the four pairs of legs, which on account of their ex- treme length are repre- sented in the figure as truncated. The head is often as narrow as the chest, abruptly truncated anteriorly, and terminated by a point posteriorly, so that it appears by its backward prolongation to separate the right from the left side of the thorax, and to be placed between them like a wedge, (as in the pholcus.) The suture is very close, and sometimes so far effaced that it is no longer possible to decide where the head ter- minates and the chest commences. We have already observed that the head sup- ports the eyes on its upper paid, and has the oral instruments attached to its lower surface. These consist, first, of a pair of mandibles or forciples ; secondly, of a pair of maxilla: ; thirdly, of a sternal labium. The number of annuli or segments which enter into the composition of the head of an arachnidan may yet be determined at some future period : we have made some attempts to unravel this subject, but our observations are not yet sufficiently matured to permit us to decide so difficult a question. Our researches on the thorax of articulate animals have led to more decisive results, which we shall now expound, but for the complete understanding of which we must refer the reader to the article Insecta, where a more general theory of the thorax, and a description of all the pieces that enter into its composition will be given. In the arachnidans many of these pieces are entirely wanting ; and their thorax is consequently more simple than that of insects : it is even more simple than the thorax of crustaceans, to which, however, it bears a great resemblance in many points. If, for example, we take a large spider, as a mygale avicularia, and strip off the hairs which clothe the thorax, we shall easily perceive a plate, or plastron, interme- diate to the right and left series of legs. This plastron is the sternum, or, to speak more cor- rectly, the union of several sternums, which, were it not for this union, would manifest themselves as four distinct pieces ; that is to say, corresponding in number to the pairs of legs which arise from them. This sternal plas- Fig. 79. a ARACIINIDA. 202 tron is distinctly shewn in fig. 100, e, which represents the inferior surface of the body of the house-spider, ( tegenaria domestica.) On the upper surface of the chest we find another plate much more extended than the sternum, and joined anteriorly with the head by means of a fissure or triangular V-shaped notch which receives it. This plate or dorsal shield exhibits divisions or rather lines of suture which the eye readily distinguishes. They represent arcs of circles arising from the base of the legs and all ending in the centre of the thorax, where there is a depression varying as to extent and depth according to the individual. In other arachnidans this structure is not so clearly shewn on account of the close union of the different pieces ; but it is easy to detect or at least explain the un- important modifications which obtain in these cases. In the figure, which we have taken from Savigny, of the pholcus rivulatus, the traces of the division may be readily followed, (fig. 79, b.) Continued comparative researches have convinced me that this dorsal plate of the thorax of the araneidtz is formed, not of the dorsal pieces of the thorax of insects, but only of the lateral pieces or those of the flancs. For the arachnidans being deprived of wings, the intermediate thoracic element or tergum, so largely developed on account of the pre- sence of those organs in the thorax of insects, being no longer necessary, has completely dis- appeared. How has this taken place? The flancs ( pleura : ) which in insects were diva- ricated and pushed to the sides by the tergum, when that obstacle was removed, have mutu- ally approximated and become united toge- ther in the middle line, precisely at the place where the little depression exists which we have already mentioned. We believe that we have placed these facts beyond all doubt in our ‘ Researches on the Thorax of Articulate Animals,’ presented to the Academy of Sciences of Paris in 1820.* Now it is worthy of remark that what has hap- pened to the arachnidans, being animals de- prived of wings, is also found in the crusta- ceans, which are equally destitute of these organs. Only that there exists in some of the latter, as the decapods, a vast carapace which occurs independently of the flancs, and covers them. For if the carapace is raised in a crab, the flancs or pleura are seen beneath, extending obliquely towards one another as in the thorax of a mygule , with this single difference, that in the cancer, where the carapace covers the flancs and protects them as well as the internal soft parts, the pleura or side pieces remain divaricated and are not joined at their apices as in the mygule. f * See the Report by Cuvier, in the Analysis of the Works of the Royal Academy of Sciences for the year 1820. t We must again refer to the articles CRUSTACEA and Insecta for the full comprehension of the facts which presuppose an anatomical knowledge of the external covering of the animals of these two classes. To those who already possess that infor- mation 1 shall observe that a single piece of the Digestive system. — The arachnidans, whose habits have been made the subject of obser- vation, feed for the most part on animal matter, not in a state of decomposition or even re- cently dead, but in the living state. They either boldly seize their prey, which consists of insects of greater or less size, or they attach themselves to animals much larger than themselves, and live parasitically upon their blood or some other nutritious fluid. The latter species are generally very minute : many of them, as the mites ( acari ), require our best optical instruments for their detection. The above differences in habits of life are accompanied with important modifications in the organs of nutrition, and especially in the oral apparatus, which we proceed to de- scribe. In the non-parasitic species, as the pulmo- nary and part of the tracheary arachnidans, the mouth consists essentially, first, of two mandibulee or forciples (fig. 80, a) in close ap- Fig. 80. position, endowed with little lateral motion, but rather acting vertically and provided each with a hooked claw (6), which, near its point, is perforated, and emits a poisonous fluid, secreted by a gland, hereafter to be described. In other arachnidans of the same order the mandibulte are a species of pincers, one nipper of which is alone moveable, as in the scor- pions. Secondly, of two maxilla: (c c), each in the form of a more or less flattened and villous lobe, provided with a palp or jointed appendage (d) projecting more or less from the mouth, and terminated sometimes by pincers as in the scorpions, sometimes by a simple flancs of insects ( epimera ) forms the back-part of the thorax of spiders ; the other piece ( episternum) already in a rudimentary state in the c.ustaceans, has completely disappeared from the thorax of the arachnidans, each segment of which consequently consists only of two pieces, the sternum below, the epimera above. ARACHNIDA. 203 claw, as in the spiders, at least the females, for in the males this palp is frequently the seat of a singular apparatus (e), hereafter to be described. Thirdly, of a sternal labium (f), which, as its name implies, is inserted into the sternum, and does not give origin to any arti- culated appendage or palp. With respect to the composition of the mouth in the parasitic species, such as most of the mites, and we may take as an example an argas, although it is concealed under the form of a beak, sometimes with a sharp point, yet it is essentially the same. The principal difference consists in the dart - shaped mandibles (a «), being joined toge- ther so as to form a kind of lancet, the sides of which are sometimes denticulated, so as to cause them to adhere firmly to the flesh which they have penetrated. The maxilla with their palp (b) and the inferior Head of a mite ( Argas.) lablum (cj are ]iere more or less intimately blended together, so as to form a case or sheath. In some instances the maxillary palp remains free, as in the argas. Savigny admits that in the interior of the mouth of arachuidans there exist three pharyn- geal orifices, and not a single one as in crus- taceans and insects. These three orifices, which are of almost imperceptible minuteness, are situated at some distance from one another, and disposed in a triangular form. He has observed this structure in spiders, scorpions, and phalangians : but he represents only two orifices in a genus allied to galeodes. Latreille denies the fact, and Trevjranus, in his anato- mical description of arachnidans, mentions only one pharyngeal orifice. However this may be, Savigny confines the assumption of food in spiders to a true suction : “ The mandibles,” says he, “ do not serve for bruising the food, but for seizing it, and for piercing and retaining it in firm contact with the maxillre ; these subject it to alternate pres- sure, and express the juices which afterwards pass into the pharynx.”* This is a matter of daily observation when a spider seizes an insect. The intestinal canal of the arachnidans is always short, and is never disposed in convo- lutions as in certain herbivorous insects. This disposition is in accordance with their preda- ceous habits, and confirms the general rule, (but which to our knowledge is not without many exceptions,) that the intestinal canal is longer in herbivorous than carnivorous animals. In the spiders, (araneee,) and we may take the common species ( tegenaria domestica ) as * Sec Description of Egypt, Arachnidans, pi. 8, fig. 7, E, v, y. Savigny at first admitted but two pharyngeal openings, ( Memoir sur les Animaux sans Vertebres, p. 57); but subsequently admitted three. Fig. 81. Fig. 82. an example, the alimentary canal (fig. 82 ) com- municates with the mouth between the maxilla: ( a a) by an oesophagus, rather short and of a de- licate texture (6). This terminates in four sacs (c), which M. Treviranus calls “ stomach,” but which, in our opinion, merit rather the name of gizzards ; the digestive tube then continues, as a straight narrow canal (cl) of moderate length, which dilates (e) and adheres, by its parietes, to a kind of epiploon filled with adi- pose granules (fi). Posteriorly the dilated part becomes stronger in texture, insensibly con- tracts (g), then undergoes a second dilatation (A) before it opens into the rectum (i). It is near the latter part, in a kind of pouch, that the slender vessels open which M. Treviranus calls biliary vessels, and which he is, with reason, surprised to see terminating in so extraordinary a position. These vessels, in fact, which cha- racterize so well by their presence the chilific stomach of insects, and are situated in these animals more or less anteriorly, always pre- ceding the small intestines which have a greater or less length, terminate in the spiders in the rectum itself, and close to the anus. 204 ARACIINIDA. Now if the observations of M. Treviranus are correct, and the four vessels which he de- scribes are really analogous to the biliary tubes of insects, we do not hesitate to consider all the part which precedes and is intermediate to them and the four sacs, as the stomach, or chilific cavity. It would thus result, that the tegenaria domestica would be deprived of an intestine properly so called, and would pos- sess no part destined to transmit along a greater or less extent the residua of the digestive pro- cess. And, indeed, such residua must neces- sarily be very inconsiderable in an animal which is sustained by juices, and these already animalized. We are, indeed, led to this con- clusion by the structure presented by the he- mipterous insects which are nourished, like the spiders, by suction, and which also have the intestines, properly so called, so short that the biliary vessels, which always accompany the posterior extremity of the stomach, are found close to the anus. We may form an idea of this disposition by casting an eye over the beautiful figures which our friend M. Leon Du- four has just published in his “ Anatomical and Physiological Researches on the Hemiptera.” Fig. 83. In the alimen- tary canal of the a scorpions the biliary vessels d d are inserted much higher up, but this is not d the only pecu- liarity which the anatomy of these animals presents. Their digestive tube extends without any marked di- latation straight from the mouth (a) to the anus which opens at the extremity of c the tail. It pre- sents in this course a very singular struc- ture : five small canals ( b ) 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- Scurpio. posed, especially if we regard as coecums 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 myself f have made known under the name of Nicotho'e, the intestinal canal sends out considerable lateral prolongations. In the leech, and es- pecially the Clepsina, there exist numerous coecums. Lastly, certain minute arachnidans (acaridas) 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 aranese 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, fig. 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, tom. viii. p. 431. 1806. t Annales de. Sciences Naturelles, first series, tom. ix. pi. 49. ARACHNIDA. 205 Fig. 84. Fig. 85. Fig. 86. an infinite num- ber of small holes, between which in the centre we may remark a larger circular plate (b.) Each little aperture is as it were stellated at the margins (r,) by which the air penetrates the body and gets into the a tracheae. These tracheae 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- i Ixodes Erinacei. gins of which adhere to the horny circle or peritrema of the stigma before described. We here subjoin figures copied from those of Professor Muller of Berlin, which represent these parts in a scorpion. Fig. 87 shows one of Fig. 87. a c Fig. 88. > ! i ! I I 1 I I I VV ddddddddd dd 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 bronchia 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. Muller 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 JJca, 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, 206 ARACHNIDA. 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 ala 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 (aranece ), more par- ticularly in Clubione atrox and Tegenaria do- mestica, Fig. 89. In both these species nu- b 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- a dition to these ves- sels there exist two a others of larger B size (d d,) which communicate in “ one direction with a the heart, in an- other, by very fine ramifications, with the pulmonary branchiae. In Clu- bione atrox these two vessels do not give out any branches in their course. No doubt remains 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 e e) that come from the pul- monary branchial. 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 not by the dissection of the organs merely. The experiments which I 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-cardiae 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 branch io-cardiac vessels ( ed ) 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 Scorpionidce we find the following structure (Jig. 90): — the Jirst ganglion, which is commonly called the brain (a), and which supplies the nerves to the parts of the mouth ( b,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 (12 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 Jour remaining ganglions (4 5 6 7) occupy the entire length of the post-abdomen, or that contracted portion of the body which is incor- ARACIINIDA. 207 Fig. 90. ci> i,c rectly termed the tail. In the Aran- ° idoE the ganglions are fewer than in the Scorpionidw : t is opake, so that the globules of the yolk 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 thafi a fourth part of the circumference of the yolk; its form is already pretty well marked, and two parts may be distinguished in it ; one large (6), the other small (a), 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 fce 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 cephalicum. 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 the pectoral 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 araneee 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 diadema 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 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 do not reach so low down, but leave a triangular 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 (b). 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, (a) 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 that 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 thevitellus. Itis 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 (fig. 110) now presents a Fig. 107. 214 ARAGHNIDA. very important pecu- Fig. 140. 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 greatest portion of the abdomen. If the inferior surface of the abdominal region be examined, there will be seen, in addition to a spot 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. ah 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 coniine 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 con- 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. 1 10, 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, See. In proportion as the fetus 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 fetus 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 alternatingwith 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 fetus 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 les Insectes, t. vii. p 195. ARACHNIDA. 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 legs, 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 itselTof 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 others 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 acaridc t, 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, ( aranea ,) 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. Serie, tom i. and ii. , 1834. t See Bulletin de la Societe 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 remain- ing 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 j unction 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, (aranea,) and M. Lepelletier has ob- served them repeatedly in many of the common species. The following experiments have been made only on the domestic spider, ( Tegenaria domestica, Walck.) because it can be preserved in a lively condition, and for many years in a glass vessel. We have successively observed a great num- ber of individuals of this species which were mutilated of one or more legs. It was not without surprize that the author of this article observed the first spider that was experimented upon, and which wanted a leg, change its skin, and after that operation reappear with eight legs. The like occurrence was frequently ob- served ; the new leg was two or three lines in length wLen it first appeared, that of the oppo- site side being less than an inch : each of the joints of the former continued to grow during the whole of the year. 216 ARM. The general result of these observations, and of many others of the same kind, is, 1st, that the legs of spiders can be reproduced when they have been torn off; 2d, that this repro- duction can only take place when the limb has been detached as high as the moveable base ; for otherwise an hemorrhage supervenes which kills the animal; 3d, that the reproduction takes place only at the time of the moult, and that the new leg is at first slender, but with all its parts or joints, each of which increases pro- gressively, until the whole has acquired its natural relative size.* Bibliography. — Lister Sf Way, Obs. concerning the darting of spiders, Phil. Trans. 1669 and 1670. Homberg, Stir les araignees, Mem. de Paris, 1707. Clerck , Vom fangen und Ern'ahren der Spinnen Abh. d. Schwed. Akad. J. 1761. Boissier de Sauvages Obs. sur une araigne, Mem. de Paris, 1758. Ha - gedorn, De Araneis, Miscel. Acad. Nat. cur. Dec. II. an 3, 1684. Valentini, C'uriosa in araneis ob- servata, ib. Dec. ii. an 7, 1688. Berthes, Obs. on the structure and ceconomy of some curious species of aranea ; Trans, of Linn. Soc. vol. ii. Paullini, De aranea rara, Misc. Ac. Nat. cur. Dec. iii. an 3, 1695. Garmann, Aranea aere nutriuntur ib. Dec. i. an 1, 1670. Wurmb, Beschryving van te groote tuin-spin vant’Eiland Java; Verhand. v.h. Bataaf. Genoot. Duel 3. Latreille, Sur la famille des araignees mineuses, Soc. Philomathique, an 7. Prevost, Sur les araignees mineuses : Mem. de la Soc. d’Hist. Nat. de Paris, Oah. i. Murtyn, Aranei ; or, a natural history of spiders, 4to. Lond. 1793. Hahn, Monographie der Spinnen, _4to. Nurnb. 1820-22- Ej. die Arachniden liv. 1—10. Clerck, Aranei Suecici, 4to. Upsal. 1757. Mueller, Uydra- rachse quas in aquis Daniae, &c. 4to. Lips. 1781. Lister, Hist. Animal. A n elite, 4to. Lond. 1678; Germanice cum add. a Martini et Goeze, 8vo. Quedlingb. 1778. Meyer, Ueber ein. Spinnen d. Lotting. Gegend. 8vo. Gotting. 1790. Treviranus, Ueber den innern Bau der Arachniden, 4to. Nurn- berg, 1812. Heroldt, Exercit. de animal, verteb. carent. formatione in Ovo Pars prima: De genera- lione aranearum, fol. Marb. 1824. Walchenaer, Fauue Parisienne, 2 tom. 8vo. Paris, 1802; Ej. Tableau des Araneides, 8vo. ib. 1805 ; Ej. Hist, des Araneides, Fasc. 5, 12mo. ; Ej. et de Blainville, &c. Araneides de France. Lyunnet, Rech. sur l’anatomie et les metamorphoses de differentes es- peces d’insectes, 4to. Paris, 1832. Roesel, Insecten- Belustigungen, 4 tom. 4to. Niirnberg, 1746. ( Victor Audouin.) ARM. (Surgical anatomy.) (The arm, Gr. Lat. Bruchium. Fr. Bras. Germ. Oberarm. Ital. Braccio.) The ancients ap- plied this term to the whole of the upper or thoracic extremity collectively, as most persons do in ordinary discourse, at the present day ; but in anatomical language the term is restricted to that section of the upper limb included between the shoulder and the elbow. The arm taken in this limited sense is somewhat cylindrical, a little flattened, however, on its internal and external surfaces, particularly towards its middle ; it varies * Mr. Blackvvall, in the paper already referred to, has related an accidental discovery of the power of some spiders to abstract respirable air from water. Several individuals have preserved an active state of existence under water for six, four teen, or twenty- eight days, spinning their lines and exercising their functions as if in air, while others have not sur- vived for a single hour. — Ed. much in its proportions as to length and volume: it is more rounded in fat persons, and especially in females, in whom it assumes more or less of a conoid form, tapering to- wards its lower part. (S eeflg. 1 and 2, p. 3.) The arm is composed of a single bone, the humerus, several muscles, bloodvessels, ab- sorbents, and nerves connected together by cellular tissue, and inclosed in an aponeurosis, which lies immediately beneath the common integuments. Viewing the arm extended, the hand being placed in a state of supination, we observe at its superior and external part a prominence of a triangular form, the base of which is superior; this is formed by the deltoid muscle, and is bounded before and behind by two slight grooves, which unite below in a depression called deltoid fossa, situated immediately over the insertion of the deltoid muscle; this deltoid fossa is the most eligible part of the arm for the insertion of issues, as it contains a considerable quantity of cellular tissue, affording a favourable bed for the reception of peas or other bodies in- serted for the purpose of exciting suppuration, while it possesses this additional advantage, that no muscular fibres extend across it, whose contractions might have the effect of deranging the surface of the ulcer or the dressings neces- sary to be applied to it, and thus causing an unnecessary degree of pain. From the deltoid fossa a superficial depression extends along the outer edge of the arm, and terminates in the triangular fossa in front of the bend of the elbow : along the course of this depression blisters are frequently applied by the Parisian and other continental physicians in inflam- matory affections of the thoracic viscera, a mode of treatment not generally employed in such cases by the physicians of this country. Another depression extends along the inner side of the arm from the axilla to the hollow in front of the elbow, where it joins the external depression. Between these two depressions there is an oblong prominence an- teriorly, formed by the biceps muscle, and a more flattened prominence intervenes poste- riorly, formed by the triceps which occupies the whole of the posterior surface of the arm. Skin und subcutaneous tissue. — The skin covering the arm is soft and delicate; sebaceous glands and hairs are not very evident on it, especially in front ; it is thicker and stronger, however, on the posterior surface. The basilic vein is generally visible at the lower part of the internal brachial depression, and the pul- sations of the brachial artery may be felt along the whole of its course : the cephalic vein is sometimes visible, especially in thin persons, along the course of the external brachial de- pression. As the skin of the arm is loosely connected to the subjacent parts, the edges of simple incised wounds in this region are easily retained in contact. The subcutaneous layer of cellular tissue or superficial fascia contains more or less adipose substance, in greater abun- dance in women and chddren than in men, and in greater quantity in the depressions than over the muscular prominences ; the filaments ARM. of the cutaneous nerves of t'ne arm and the superficial veins and absorbents lie imbedded in it : thus the cephalic vein and twigs of the external cutaneous nerve appear along the outer edge of the arm, and along the inner edge are found the internal cutaneous nerve, the brachial branches of the second and third intercostal nerves, the cutaneous nerve which arises from the ulnar high in the axilla, the basilic vein, and a few lymphatic glands, which lie at from one to three inches above the internal condyle. Aponeurosis. — Beneath the subcutaneous layer of cellular tissue lies the aponeurosis or fascia, which invests the muscles and the deep- seated vessels and nerves of the arm : this fascia commences above at the superior attach- ment of the deltoid muscle; externally and internally it is continuous with the fascia, which extends over the axillary space; descend- ing along the arm it is strengthened by ex- pansions which it receives from the tendons of the deltoid, pectoralis major, and coraco- brachialis in front ; and behind it derives an accession of strength from the aponeurosis which covers the infra-spinatus and teres minor, and from the tendons of the latissimus dorsi and teres major. At the lower part of the arm the fascia is attached to the condyles of the humerus; laterally and posteriorly it is at- tached to the olecranon, on either side of which it is continuous with the fascia on the posterior surface of the fore-arm. In front of the elbow this fascia receives a fasciculus of fibres from the tendon of the biceps, and becomes continuous with the fascia covering the anterior surface of the fore-arm. The fascia of the arm varies in strength in different parts ; it is very indistinct over the deltoid, thin but very fibrous on the posterior surface of the arm where it covers the triceps ; it is much stronger over the biceps, and the thickest portion of it is found along the inner edge of the arm, where it covers the brachial artery and its accompanying veins and nerves. A strong aponeurotic septum passes in from the fascia of the arm to each of the lateral ridges of the humerus ; these septa are called intermuscular ligaments, and, together with the humerus, divide the space included within the general fascia into an anterior and a posterior sheath ; the external intermuscular ligament extends from the insertion of the deltoid to the external condyle ; the internal extends from the inser- tion of the coraco-brachialis to the internal condyle. Both intermuscular ligaments are narrowest above, and grow broader as they approach the condyles : their surfaces give at- tachment to fibres of the triceps posteriorly and to the braehiaeus anticus, supinator radii longus, and extensor carpi radialis anteriorly. The posterior sheath, formed as above described, is chiefly occupied by the triceps muscle, be- neath which, in the spiral groove on the pos- terior surface of the humerus, lie the musculo- spiral or radial nerve and the superior pro- funda artery : this nerve and the anterior or musculo-spiral branch of the superior pro- funda artery perforate the external inter- muscular ligament and enter the anterior 217 sheath of the arm to get between the braehiaeus anticus and supinator radii longus, while the posterior branch of the profunda descends within the posterior sheath to the back part of the external condyle ; the ulnar nerve and the inferior profunda artery enter this posterior sheath together at its internal side, about the middle of the arm, and descend within it to the back of the internal condyle. A considerable branch of the brachial artery, the ramus anas- tomoticus, perforates the internal intermuscular ligament above the internal condyle, and enters the lower part of the posterior brachial sheath. The anterior sheath of the arm contains the biceps, coraco-brachialis, braehiaeus anticus, and the origins of the long supinator and long radial extensor muscles ; the external cutane- ous nerve traverses this sheath, perforating the coraco-brachialis above, and descending ob- liquely outwards between the braehiaeus anticus and the biceps it gets to the outer side of the latter, between the tendon of which and the supinator radii longus it pursues its course to the fore-arm ; the radial nerve and the branch of the superior profunda artery accompanying it are to be found in the lower and external part of the anterior sheath, which they enter as above described : these lie deep between the braehiaeus anticus and supinator longus. Along the internal side of this anterior sheath, through its whole extent, run the brachial artery, and its two venae comites included in a sheath proper to them, and accompanied by the median nerve, which has very important relations to these vessels : this nerve is external to the artery above, crosses it in the middle of the arm, and lies internal to it below. Superiorly the ulnar nerve lies to the inner side of the brachial artery, from which it se- parates to enter the posterior sheath, as already noticed ; the internal cutaneous nerve, the cutaneous twig of the ulnar nerve, and the basilic vein for a short part of its course before it enters the brachial vein, also lie within this sheath; and deeply situated in its lower part is the ramus anastomoticus magnus of the brachial artery. Developement. — In the progressive deve- lopement of the upper extremity in the feetus, the arm is formed subsequently to the hand and fore-arm, and at an earlier period than the shoulder. In men the deltoid is fuller, and the biceps in front and the triceps behind are more prominent than in women : the greater fulness of these two latter muscles, with the smaller quantity of subcutaneous fat, give to the male arm a greater diameter from before backwards than in the transverse direction ; while the more slender character of the muscles and the greater abundance of subcutaneous fat laterally cause the arm of the female to assume a more rounded form. In the course of the brachial artery two trunks are often found to exist, in consequence of a high branching of that vessel, which sometimes occurs even at the lower border of the axilla: the supernumerary branch in such cases is most frequently the radial : in some instances it is the ulnar and less fre- quently the interosseous or median artery of the fore-arm. When this irregularity occurs, the ARM. 218 brachial artery usually preserves its ordinary relations to the surrounding parts, while the supernumerary trunk lies to its internal side and takes a more superficial course, some- times getting above the fascia of the arm, as we have witnessed in a few rare cases. It occasionally happens that the brachial artery divides at its commencement into two trunks, which again unite at its lower part. It is ob- vious that the surgeon, in performing operations on this artery, should constantly bear in mind that it is subject to the above-mentioned irre- gularities, and that he should cautiously guard against committing the error of including the wrong vessel in his ligature. The internal side of the arm in the middle of its length is the most eligible place for making compression on the brachial artery ; here this vessel is superficial, so that its pul- sation can be felt at once, whilst it has nothing interposed between it and the bone but the tendinous insertion of the coraco-brachialis muscle. It happens, however, that the median nerve lies immediately over the artery in this situation, a circumstance which causes com- pression of the latter to be attended with con- siderable pain, and productive of injury to the nerve if maintained for too, great a length of time. As the trunk of the brachial artery and several large nerves traverse this part of the arm, it is obvious that wounds in this region are liable to be attended with more serious consequences than those of any other part of the arm. A wound in the posterior region of the arm may be attended with considerable haemorrhage, if it should happen to penetrate so deep as to divide the profunda artery, or it may cause paralysis of the extensor muscles of the hand and fingers by dividing the radial nerve. When the humerus is fractured, the con- sequent derangement of the fragments varies according to the part at which the bone hap- pens to be broken ; when fracture occurs im- mediately above the insertions of the pectoralis major and latissimus dorsi, the lower fragment is brought inward towards the axilla by the action of these muscles, and drawn upwards by the action of the deltoid, biceps, coraco- brachialis, and long head of the triceps, whilst the extremity of the upper fragment is rather turned outwards by the supra-spinatus. In cases where the humerus is fractured imme- diately above the insertion of the deltoid and below the attachments of the latissimus dorsi and pectoralis major, the deltoid will draw the lower fragment upwards and outwards, whilst the upper fragment will be drawn inwards towards the axilla by the pectoralis major and latissimus dorsi. If the bone be broken im- mediately below the insertion of the deltoid, little or no displacement of the fragments may ensue, as the opposing forces exercised on the superior fragment by the deltoid on the ex- ternal side, and the pectoralis major and latis- simus dorsi on the internal, pretty nearly counterbalance each other; it more generally happens, however, that the upper fragment is turned outwards by the preponderating action of the deltoid upon it, whilst the lower frag- ment is drawn upwards by the action of the biceps, coraco-brachialis, and triceps. Frac- tures of that portion of the humerus which is covered by the brachfreus anticus in front and the triceps behind, are often unattended by any very obvious displacement, in consequence of these muscles being inserted into both frag- ments; fractures near the elbow are occa- sionally followed by deformities presenting some of the characters of dislocations of the elbow, of which more notice will be taken in the article Elbow. General inflammatory enlargement of the arm is rare ; it sometimes appears as a con- comitant affection with inflammation of the veins of the arm consequent on the operation of phlebotomy, in which case it not unfre- quently happens that abscesses form along the course of the sheath of the brachial artery ; red streaks along the course of the lymphatics and enlargement of the lymphatic glands are sometimes present in consequence of disease or inflammation affecting the hand or fore-arm. Amputation of the arm below the insertion of the deltoid may be performed either by the circular incision or the double flap ; when the latter method is practised, the flaps should be formed on the external and internal sides, by which the more important vessels and nerves will be included in the internal flap. When circumstances require the performance of amputation above the insertion of the del- toid, the circular operation should never be practised, for the following reason ; — in order to obtain a sufficiency of covering for the bone, the pectoralis major, latissimus dorsi, and teres major would all be detached from their inser- tions, a consequence of which would be that the contractions of these muscles in opposite di- rections, by drawing asunder the edges of the wound, would not only render complete appo- sition difficult in the first instance, but more- over their continued action would have the effect of converting the wound into an ulcer, which it would be extremely difficult if not impossible to heal ; therefore, whenever we have to amputate so high up, it is the more judicious mode of proceeding to make a flap including so much of the deltoid muscle as will form a sufficient covering for the stump. The importance of attending to the foregoing circumstances was first pointed out by Louis, the learned secretary to the French Academy of Surgery.* The arteries which require to be tied after amputation of the arm below the insertion of the deltoid are the brachial and inferior pro- funda on the internal side ; on the external side there are often two branches of the superior profunda requiring a ligature, one of which accompanies the musculo-spiral nerve, and the other runs in the substance of the triceps. When it becomes necessary to tie the bra- chial artery on account of a wound or aneu- rism, the varieties of its relation to the median nerve should be carefully borne in mind; at the upper part of the arm this artery has the median nerve external to it, and the ulnar nerve to its inner side ; in the middle of the * Memoires de l’Academie de Chirurgie, tom. v. •219 ARM, MUSCLES Of THE. anil the median nerve crosses the artery in general superficial to it, but sometimes under- neath it, while in the lower part of the arm this nerve is invariably on its inner side. When called upon to expose the brachial artery for the purpose of tying it, the surgeon should recollect that the course of the artery may be readily determined by a line drawn from the coracoid process to a point midway between the condyles of the humerus on the anterior surface of the elbow ; hence his in- cision for the purpose of exposing the brachial artery should be always made along the course of this line and perpendicular to the axis of the os humeri. (See Brachial Artery.) For Bibliography, see Anatomy (Intro- duction.) (John Hart.) ARM, MUSCLES OF THE.— The mus- cles which clothe the os humeri are part of the deltoid , the biceps, coraco-brachialis , brachiaus anticus, the origin of the supinator longus in front, and the triceps behind. The deltoid belongs to the shoulder, and will be described with the other muscles of that part. (See Scapular Region.) 1. Coraco-brachialis ( coraco-humeral ). — The coraco-brachialis arises from the point of the coracoid process, in common with the short head of the biceps, tendinous in front and fleshy behind ; it separates from the biceps at its middle third, passes inwards, and is in- serted tendinous into the internal surface of the humerus a little above its middle between the triceps and brachiaus anticus. This muscle has in front of it the deltoid and pectoralis major, which cover and conceal from view its upper part; behind it the tendon of the subscapularis, the tendons of the latissi- mus dorsi and teres major, the axillary artery, the median and the external cutaneous nerves. The latter nerve perforates the muscle about its middle, and passes through its substance to reach the outer side of the arm ; hence the epithet perforatus has been applied to this muscle. The coraco-brachialis can carry the arm forwards and inwards; when the humerus is fixed, it can act upon the scapula, and by depressing its coracoid angle, elevate the in- ferior angle and separate it from the ribs. 2. Biceps flexor cubit i ( scapulo-coraco-ra- dial). — This is a long muscle swollen in the centre, divided above into two portions called heads, one internal short, the other external long. The internal or short head arises from the coracoid process of the scapula in common with the coraco-brachialis. The long head is attached by a long slender flattened tendon to the upper part of the margin of the glenoid cavity, and is united by a dense cellular tissue to the glenoid ligament. This tendon passes over the head of the humerus, and enters the groove between the two tuberosities in which it is bound down by the fibres of the capsular ligament of the shoulder-joint; a pro- longation of the synovial membrane also lines the groove, and forms a synovial sheath for the tendon ; the tendon terminates in a fleshy belly which unites with the short head to form the large belly of the biceps ; the muscle ter minates below in a tendon, which, passing over the brachiaeus anticus and the front of the elbow-joint, sinks into a triangular hollow between the prouator teres and supina- tor longus to be inserted into the back part of the tubercle of the radius ; but before it sinks into this triangular space, it sends off from its internal side an aponeurosis (the semilunar fascia of the biceps), which is inserted into the internal condyle, and the fascia which covers the muscle at the inner side of the bend of the elbow. The biceps is covered by the deltoid, the pectoralis major, the fascia of the arm and integuments in front ; behind it lies on the humerus, coraco-brachialis, brachiaeus anticus, and the external cutaneous nerve ; internal to it lie the coraco-brachialis and brachial artery. It bends the elbow and makes tense the fascia of the fore-arm ; it is also a very powerful supinator of the hand by virtue of its insertion into the radius. If the fore-arm be extended and fixed, it will depress thescapula on the humerus. 3. Brachiaus anticus ( B. internus, hume- rocubital ). — When the biceps has been raised from its situation, we observe the brachiaeus anticus deeply situated on the front of the arm ; it arises by two fleshy tongues, one on each side of the insertion of the deltoid ; from the whole of the anterior surface of the humerus, and the internal intermuscular ligament which separates it from the triceps, its fleshy fibres pass downwards in front of the elbow, and end in a broad tendon which is inserted into a triangular roughness on the anterior surface of the coronoid process of the ulna. This muscle is covered in front by the biceps, supi- nator longus, the fascia of the arm and integu- ments, the musculo-cutaneous and median nerves, the brachial artery, and the pronator teres ; behind it covers the front of the lower part of the humerus and the elbow-joint. This muscle is the most powerful flexor of the fore- arm upon the arm. As Bichat remarks, flexion of the fore-arm takes place directly if the bra- chiaeus combines its action with that of the biceps ; if either acts alone, the flexion is in the direction inwards or outwards ; inwards when the biceps acts alone, outwards when the brachiaeus. 4. Triceps extensor cubiti (brachiaus posti- cus, tri-scapulo-humero-olecranien.) — The tri- ceps muscle of the arm is situated on the poste- rior surface of the humerus, and, as its name implies, has its origin by three heads. The long head arises by a short, flat, thick tendon from a rough portion of the inferior costa of the scapula, immediately below the glenoid cavity, and passing downwards in front of the inser- tion of the teres minor, and behind the teres major it forms a large belly, which covers the posterior surface of the os humeri. The se- cond or short head arises from the outer and back part of the os humeri, beginning by a pointed origin immediately below the insertion of the teres minor ; it continues to arise from the external ridge of the humerus as low down as the external condyle ; from the surface of the bone behind this ridge, and from the back part of the external intermuscular ligament. The third head, which is the shortest, called 220 ARTERY. bruchimuS cxternus, arises by an acute point from the internal ridge of the os humeri, be- ginning immediately below the insertion of the teres major; it also arises from the internal ridge as far down as the internal condyle, from the surface of the humerus behind this ridge, and from the posterior surface of the internal in- termuscular ligament. The three heads unite above the middle of the os humeri, and cover the whole of the back part of that bone; they form a thick broad tendon, which is inserted into the rough surface on the superior part of the olecranon process of the ulna, adhering closely to the ligamentous fibres covering the posterior surface of the synovial membrane of the elbow-joint ; the lowest fibres of the second and third heads of this muscle, which arise from the back of the condyles, run nearly horizontally into the tendon. The triceps is covered posteriorly by the teres minor, deltoid, fascia of the arm and in- teguments ; in front it is in contact with the posterior surface of the humerus, the inter- muscular ligaments, and the back part of the capsule of the elbow-joint. This muscle ex- tends the elbow ; when the long head contracts, it draws the scapula towards the humerus, and, if the scapula be fixed, it draws the humerus backwards. For Bibliography, see Muscle, and Anatomy (Introduction). ( J . Hurt.) ARTERY, (normal anatomy): ag-r^ia, ano tov rov ctiQx Tygiiv, ab aere servando. Er. ur- tere. Germ. Pulsuder, Schlugudei'. I tal. arteria. The arteries are the vessels which carry the blood from the heart, and distribute that fluid throughout the body. The trachea was ori- ginally called artery from the circumstance of its containing the air which it transmits to the lungs. The term artery was exclusively ap- plied to the trachea by Hippocrates and his cotemporaries, by whom the vessels now called arteries were described as pulsating veins. Aristotle restricted the term artery to the tra- chea, and described the aorta as the lesser vein. We find these vessels called arteries in the writings of Aretasus, Pliny, and Hero- philus, probably on account of the adoption of the opinion of Erasistratus, who taught that they contained a vapour or spirit. The vessels now known as arteries, however, were more dis- tinctly so designated by Galen, who affirmed that they were full of blood, and described the arteries and veins as forming each a tree, whose roots implanted in the lungs, and whose branches distributed through the body, were united by a common trunk in the heart. There are two great arterial trunks — the aorta, which arises from the left ventricle of the heart, and the pulmonary artery, which arises from the right ventricle of that organ. Each of these vessels has an origin, a trunk, and branches, which divide and subdivide in an arborescent form, until they are reduced in size to the most delicate degree of minuteness, terminating in the capillary vessels, which can be traced entering into all structures except cartilage, hairs, and epidermoid parts. Striking as the contrast is between the size of the primi- tive arterial trunks and that of the almost in- visible capillary vessels, comparatively few divisions intervene between the two extremes of the arterial system, their number hardly exceeding twenty, as Haller ascertained by counting the divisions of the arteries of the mesentery between the place of their origins from the aorta, and their termination in the capillaries of the intestines.* That the arteries in general are circular tubes is evident from an inspection of their orifices when cut across, even in the dead body. The walls of the larger arteries, when empty, collapse, so as to present, on a trans- verse section, an aperture more or less ellipti- cal : when distended, however, either by the blood during life, or by injection in the dead body, these also are circular ; so that the circular form may be considered as universal in all parts of the animal system except at the origins of the aorta and pulmonary artery, where the circumference of each of these ves- sels is distended into three sacculated pouches of equal size, called the lesser sinuses ; and in the ascending portion of the arch of the aorta, which has a dilatation on its right side, in- creasing with years, called the greater sinus. The arteries in general become smaller in their course in proportion to the number of branches arising from them. To this, however, there are exceptions, of which the aorta pre- sents a remarkable example, being of as great a capacity near the origins of the primitive iliac arteries as it is in its thoracic portion, and the vertebral arteries are as large where they enter the foramen magnum of the occipital bone as where they arise from the trunks of the sub- clavians, notwithstanding that they have given off many branches in the intermediate part of their course. Wherever an artery runs for some distance without giving off branches, it appears to suffer no perceptible diminution in its size, as has been ascertained by the experiments referred to by Baron Haller, -f and repeated by Mr. Hunter, J in which the common carotids were found as capacious near the place of their division into the external and internal carotids as at their origins ; and the same remark being considered as equally applicable to all other arteries simi- larly circumstanced, it has been stated in general terms that the arteries and their branches are cylindrical, and that the whole of the arterial system is a series of cylindrical tubes. Although the cylindrical form is pretty general throughout the arterial system, it is by- no means accurately preserved. Several arteries increase in size in the progress of their course ; of this we have examples in the umbilical arteries, which expand as they approach the placenta, and the spermatic arteries, especially in the bull and wild boar, which enlarge con- siderably as they proceed to their destination. Moreover, Haller § and Martinus have shown * Ilaller, Elementa Physiologic, t. i. sect. 1. § 17. t Elementa Physiologic, t. i. s. 1, § 3. | Treatise on the Blood, &c., p. 168 et seq. 4to edit. Lond. 1794. $ Elementa, t. i. s. 3, § 3. ARTERY. 221 by experiments, that in every instance where an artery divides in the human body, it undergoes a dilatation immediately before such division; and this fact derives confirmation from the experiments of Mr. Hunter on the carotid arte- ries : it is much more unusual for an artery to diminish in size in its course unless it has furnished branches. Santorini* states, how- ever, that he observed the carotid artery of an ostrich (Struthio camelus) to have become nar- rovver in a portion of its course of six inches in length, for which space no branch had been given oft'. The arteries become smaller and more nu- merous by repeated divisions : the combined area of the branches of each artery, however, exceeds the area of the trunk from which they are given off, in every instance, in consequence of which the capacity of the arterial system, as a whole, is increased in proportion to the number of its divisions. It is from this cir- cumstance that the arteries have been said to represent a cone, the apex of which is at the heart, and the base in the capillaries. When an artery divides into several branches of unequal size, the largest usually continues its course in the direction of the original trunk. The branches of the arteries are for the most part given off at acute angles ; some few, as the superior aortic intercostals, go off at obtuse angles, and the lumbar arteries arise from the aorta at right angles. The arteries appear in general to take the shortest course to the parts they supply ; hence the tendency they have to run in straight lines. In many situations the arteries are remark- able for having a tortuous course, as is par- ticularly evident in the arteries of the stomach, intestines, bladder, uterus, lips, iris, &c., where this disposition appears to be a provision to obviate any interruption to the circulation which might result from the great or sudden changes of volume, form, or situation to which those organs are subject in the performance of their functions : in other instances the arteries appear to be contorted for the purpose of breaking the impulse of the systole of the ven- tricle on the blood, and thereby moderating the force with which that fluid is propelled into vessels partaking of the delicacy of structure of certain organs to which they are distributed, as the arteries of the brain, spleen, testicle, cue. The smaller arteries, running among loose structures, are rendered tortuous during each systole of the ventricle of the heart, a pheno- menon which we have frequently witnessed where such vessels were exposed for a few inches of their course during surgical operations. Anastomoses. — The several parts of the arte- rial system communicate freely with each other: and these communications, known by the name of anastomoses, f are more frequent between the arteries in proportion to the remoteness of these vessels from the heart. Three kinds of anas- tomosis have been distinguished by anatomists : first, two vessels of nearly equal size approach and join so as to form an arch in such a man- * Observationes Anatom, c. 7. n. 6. t From ava, per, nopa, os. ner as to render it impossible to determine the exact point of their union : this arch gives off smaller vessels. Of this kind is the anasto- mosis which takes place between the arteries of the intestines and the arteries in the neigh- bourhood of joints. Secondly, two arteries are sometimes connected by a transverse branch, as the two anterior cerebral in the arterial circle at the base of the brain. We find this kind of communication, also, between the two um- bilical arteries as they approach the placenta. Thirdly, two arteries join at an acute angle, so as to form a single trunk : thus the twro verte- bral arteries form the basilar, the two anterior arteries of the spinal cord unite in a single trunk ; and in the foetus the ductus arteriosus joins the thoracic aorta in a similar manner. Besides these more obvious communications between vessels of a larger size, the anastomoses of the capillaries are so frequent as to give to those vessels, when successfully injected, the appearance of a fine net-work. It is by means of the anastomoses that the circulation is carried on in a limb after the trunk of its chief artery has been obliterated by disease, injury, or a surgical operation ; and the well-known efficiency of the anastomosis of arteries in re-establishing the circulation in parts from which the direct supply of blood through the principal artery has been cut off, has led to the performance of some of the most brilliant operations by which modern surgery has been raised to the exalted rank it holds at the present day. The larger trunks of arteries are inclosed within the cavities of the body, or run their course on the sides of the limbs least exposed to external injuries, being in general deeply situated in the intervals between the muscles, so as to be protected against wounds or other external injuries, to which they are therefore less exposed than if they had been more super- ficially situated. The arteries and their branches are every where surrounded by a layer of cellular tissue, called the arterial sheath, connected more or less intimately with the neighbouring struc- tures, but having so loose an attachment to the arteries as to allow them to glide freely on its inner surface in all their motions, by which means they frequently escape being injured when penetrating wounds traverse parts con- tiguous to them ; and it is owing to the loose- ness of the attachment of the arteries to their sheath that they retract so remarkably within it when cut across. The sheath is generally strongest around the arteries most exposed to external injury : thus it is particularly strong where it surrounds the arteries of the limbs ; it is less distinct on the arteries within the thorax and abdomen, many of which receive coverings from the serous membranes; and it is so ex- tremely delicate around the arteries of the encephalon as to have its existence in this situation questioned by some anatomists. Structure of arteries. — The arteries are of a pale buff colour when empty. The absolute thickness of their parietes is greatest in the larger trunks, but more considerable in pro- portion to their calibre in the smaller branches. 222 AltTEUY. The parietes of arteries are divisible into three tonics, known by the names of external, mid- dle, and internal. The external tunic, called the cellular coat, ( tunica, cellulosa propria of Haller,) is of a whitish colour, thin, dense, and firm : it is formed of condensed cellular tissue, containing fibres closely interwoven and crossing each other at obtuse angles to the length of the vessels. The structure of this tunic is loose on its external surface, and connected by deli- cate laminae with the arterial sheath : its internal surface is very closely attached to the external surface of the middle tunic. The middle tunic of the arteries (the tunica musculosa of Haller) is dense, firm, of a red- dish yellow colour, and composed of fibres, which, on a superficial view, seem to run transversely : when this tunic is submitted to a closer examination, we find that none of its fibres are sufficiently long to form perfect rings encircling the whole of the circumference of the vessels; they are all short and straight, with a slight degree of obliquity in their direc- tion, and their extremities are lost among the neighbouring fibres. The middle tunic may be divided into several layers by the knife of the anatomist, and these are found to increase in density from the external to the internal surface. There are no longitudinal fibres in this structure. As Haller has remarked, the middle tunic of the arteries is not continuous with the mus- cular substance of the heart. For the descrip- tion of the manner in which the middle tunic of the arteries is connected with the heart, and of the fibrous structure interposed between the muscular texture of that organ and the middle tunic of the arteries, we refer to the article Aorta. The continuity of the middle tunic through all parts of the arterial system is uninterrupted. Although the absolute thick- ness of this tunic is greatest in the aorta and larger trunks, its thickness in proportion to the area of the vessels manifestly increases as these diminish in size ; wherever an artery is curved, it is thicker on the convex than on the concave side, and in all the angles formed by the divisions of arteries its thickness is more considerable than in other situations. The colour of the middle tunic is yellower in the larger trunks and more of a reddish tint in the smaller branches. The middle tunic of the arteries has a degree of firmness sufficient to preserve the circular form of the artery even in its empty state, and after the other tunics have been removed. This tunic possesses a slight degree of strength and elasticity in the longitudinal direction ; in the circular direc- tion it exhibits both these properties in a more marked degree. The strength and elasticity of this tunic diminish progressively from the larger to the smaller arteries. There is so close a resemblance between the substance of this tunic and the yellow elastic fibrous tissue of the ligamenta subflava connecting the crura of the vertebrae, as well in its yellow colour and the firmness of its fibres, as in its elastic property, that many anatomists regard both these structures as being nearly if not perfectly identical. Mr. Hunter instituted a variety of experiments to prove that this tunic possessed a power of contraction similar to that of mus- cular structure in addition to its elasticity ; but, notwithstanding the results of the re- searches of this great anatomist and physio- logist, by which he showed, in the clearest manner, that the arteries were endowed with a power of contraction totally distinct from their property of elasticity, he never demon- strated, in a positive and unequivocal manner, the presence of muscular fibres in it, nor has any other anatomist, who, since his time, may have investigated the subject of the structure of this tunic, been more successful in dis- covering in it any decided trace of muscular fibres. Beclard® considers it to be a pecu- liar elastic tissue having an intermediate charac- ter between muscular and ligamentous fibre. From carefully examining this structure, it appears to differ both from the yellow elastic fibrous tissue and from the muscular tissue ; possessed of the elasticity of the former, but differing from it in being composed of fibres of a softer consistence and more easily torn ; from the latter it differs not only in the colour and consistence of its fibres, but moreover in the slow and gradual mode of its contraction under the influence of mechanical or chemical stimuli ; unlike the muscular fibre, it retains its power of resistance as perfectly in the dead as in the living body. Bichatf asserted that there was a total ab- sence of cellular tissue in the structure of the middle tunic of arteries. Meckel, who ranks higher as an authority for matters of fact in anatomy, has admitted this assertion as if it were an established fact : neither of these authors, however, has advanced a single valid argument or brought forward a well-founded proof in support of the correctness of this statement; wherefore we feel the less reluc- tance in registering our dissent from such high authorities on this point, which we found on the consideration of the following circumstances First, there is no analogous instance of an organized structure receiving bloodvessels and nerves into which cellular tissue does not also enter as a component part. Secondly, we have the authority of the accurate and learned Haller, in testimony of the fact of the fibres of the middle tunic of the arteries having cellular tissue interposed between them, being, as he expresses himself, “ cellulositate paucissima separate.” Beclard entertains a similar opinion founded on the circumstance that when a portion of an artery is stripped of its external tunic, granulations will shoot up from the exposed surface of the middle tunic. Thirdly, we have frequently observed that, when a portion of an artery stripped of its external tunic, is divided longitudinally and macerated in water for several days, the mid- dle tunic increases in thickness, and its fibres become more distinct and are more easily separated from each other ; by continuing the * Anatomie Generale, p. 325. f Anatomic Generale, tom. iii. ARTERY. 223 maceration, the intervals between the fibres become greater, and as the putrefactive pro- cess sets in and advances, the whole substance of the middle tunic takes on the form of a spongy mass, and ultimately the fibres cease to be any longer discernible, having been re- duced to the state of a soft pulp, while the cellular structure is rendered more evident. The following appears to us to be the rationale of the phenomena above described : the in- crease in thickness which the middle tunic at first undergoes is owing to the cellular tissue interposed between the fibres imbibing the water in which it has been immersed, in virtue of its hygrometric property ; and the spongy appearance observable after the maceration has been continued for a length of time, is the result of the cellular tissue having the property of resisting decomposition by putrefaction much longer than the fibrous tissue. The internal tunic ( intima of Haller) is the thinnest of the three; it is continuous with the lining membrane of the heart, in extending from which into the arteries it forms a dupli- cature, contributing to the composition of the semilunar valves : in the larger arteries, when empty, it sometimes forms longitudinal folds ; in some arteries, such as the poplitaeal, and the brachial at the bend of the elbow, it presents transverse folds or wrinkles; it also forms transverse wrinkles in arteries which have re- tracted after amputation : its internal surface, which is in contact with the blood in the living body, is smooth, polished, and bedewed with a fine exhalation ; its external surface adheres to the internal surface of the middle tunics in the larger trunks of the arteries; this tunic may be divided into two layers, the internal of which is thm and transparent, while the external is whitish and opaque, having its struc- ture blended with that of the middle tunic ; it is the tunica cellulosa interior of Haller, and is the seat of the calcareous, steatomatous, and atheromatous deposits, which so frequently occur as morbid appearances in the coats of the arteries. We do not perceive fibres nor any other signs of organization in the inner layer of this tunic in its healthy state; it is almost completely inelastic and very brittle ; it tears with equal facility in every direction ; compared with other structures it bears the closest resemblance to the arachnoid mem- brane of the brain ; the smooth and highly polished condition of the free surface of this tunic is an admirable provision, whereby the effect of friction in diminishing the velocity of the passage of the blood through the arte- ries is reduced to the smallest possible amount. The following mechanical contrivance ob- servable in the interior of the arteries would appear to be a provision for facilitating the distribution of the blood through the divisions of the arterial system. As the branches of the arteries mostly arise from the trunks at acute angles, the portion of the circumference of their orifices on the side next the heart is smooth and depressed, forming a sort of chan- nel sloping gently from the trunk into the branch, while the opposite side, or that more remote from the heart, is bordered by a ridge of a semilunar valve-like form, composed of a duplicature of the lining membrane in which there is included a portion of the middle tunic ; the more acute the angle at which the branch arises, the greater is the prominence of this ridge ; it is altogether absent where branches arise at right angles, as in the case of the emul- gent arteries, and where branches arise at ob- tuse angles to the trunk, it is found at their orifices on the side next the heart. The aorta and pulmonary artery are each provided with three valves at their origins from the ventricles; these valves, called sigmoid or semilunar from their semicircular form, are attached by their inferior borders, which are convex, to the margins of the semicircular flaps or festoons, into which the edge of the commencement of the middle tunic of the artery is divided ; the superior edges of each of these valves, which are free and floating, form two concave lines, separated by a projection in the centre, in which is con- tained a small cartilaginous body, called tubercle, globulus Arantii or corpus sesa- moideum. The portions of the walls of the artery corresponding to the valves are dilated in the form of pouches, more marked in the aorta than in the pulmonary artery ; these are the sinuses of Valsalva. The semilunar valves are composed of a duplicature of the lining membrane of the artery, including within it a thin but strong fibrous expansion, continuous with the fibrous structure, which connects the middle tunic of the artery with the tendinous ring encircling the arterial opening of the ventri- cle; the free border of each valve contains a small fibrous cord, as described by Beclard, having the globulus Arantii attached to it in its centre. An increase or diminution in the number of the sigmoid valves is of rare occurrence, more frequently presented in the pulmonary artery than in the aorta, and oftener consists in the number of valves being increased to four than diminished to two.* The mechanism of these valves is such as to prevent the blood flowing in a direction con- trary to its regular course ; for when that fluid is propelled towards the ventricle, they are separated from the parietes of the artery, and being distended by the column of blood pres- sing against their superior surfaces, they are laid across the area of the vessel, which they completely fill up by their edges being thus brought into perfect contact and the globuli Arantii meeting in the centre. There are no valves in the arteries in any other situation. The arteries, like other organized struc- tures, are furnished with proper nutritious arteries and veins called vasa vasorum. The aorta and pulmonary artery at their commence- ment receive sorne branches from the coronary vessels of the heart ; in all other situations the vasa vasorum are supplied by the neighbouring bloodvessels ; the vasa vasorum are very evi- dent in the external tunic of the arteries, they can be traced until they penetrate the sub- . stance of the middle tunic, but not farther ; * Meckel, Handbuch der menschlicheu Anato- mie. Band. i. 224 ARTERY. they are more numerous and larger in young than in adult and old subjects. Absorbents are not visible on the coats of any arteries except the larger trunks ; however, the removal of coagula formed in the interior of all arteries after the application of ligatures may be regarded as proving the existence of absorbents in every part of the arterial system. The arteries are plentifully supplied with nerves, of which the aortic system receives more in proportion than the pulmonary artery, and the smaller arteries more than the larger trunks. The trunk of the aorta, the pulmonary artery, and the arteries of the head, neck, thorax, ab- domen, and those of the genital organs, receive their supply from the nerves of organic life. These form a very intricate plexus on their surface. The arteries of the extremities receive their supply of nerves from those of animal life in their neighbourhood. Two sets of nerves have been described as being furnished to the arteries ; one set, consisting of softer nerves, of a flattened form, are said to be lost in the cel- lular or external tunic, ncrvi molles ; the other set, more firm and round, penetrate the middle tunic, in which they form a thin membraniform expansion, containing distinct fibres. Meckel* justly considers the internal nerves as subdivi- sions of the larger flattened external branches. No nerves have yet been discovered on the umbilical arteries, and the arteries of the brain are supposed to be without any. The nerves of the arteries become less apparent in old age. The specific gravity of the arteries exceeds that of distilled water in the proportion of 106 to 100. They are proportionally lighter and less dense than the veins ; while the veins possess more power of resistance, and are not so easily ruptured as the arteries. Physical properties. — Of the physical pro- perties of the arteries the most remarkable are the firmness of their parietes, their power of resistance, and their elasticity. It is owing to the firmness, which principally resides in their middle tunic, that they preserve their circular form in the empty state. Their power of resistance has been made the subject of experiment by Wintringham,f and, more recently, by Bedard,! from which the following results have been obtained. Their power of resisting rupture is very great, and is generally in proportion to their thickness, being greater in the aorta than in the pulmonary artery. As the arteries diminish in size, their absolute resistance diminishes ; however, as their relative thickness and softness increase, their extensibility and relative resistance undergo a proportionate augmentation. The resistance of all arteries of equal volume is not the same : for instance, that of the iliac artery is greater than that of the carotid. It is in the external tunic that the power of resistance in the longi- tudinal direction resides ; the resistance in the circular direction is much greater, and is owing to the middle and external tunics conjointly; the internal tunic has very little power of re- E Op. cit. t Experimental Inquiry on some parts of the Animal Structure. Loud. 1740. t Anatomie Generate, p. 373. sistance in either direction. The middle and internal tunics are as remarkable for their fra- gility as the external is for its toughness and great power of resistance ; hence it is, that when a ligature is tightened on an artery, the two former are divided, while the latter remains unbroken, as proved by the experiments of Dr. Jones.* The successful employment of torsion of the arteries as a means of suppressing haemorrhage is in like manner owing to the greater power of resistance possessed by the external tunic as compared with the other two. The process by which arteries are obliterated by torsion is thus explained by M. Amussat,t to whom belongs the merit of having been the first to propose and practise it. The divided extremity of an artery is seized between the blades of a forceps, and drawn out beyond the surface of the wound : the vessel is then taken hold of with a second pair of forceps a few lines higher, and held firmly while the operator commences to twist the forceps with which he holds the extremity of the vessel in the direction of its axis, making from five to nine or ten turns, according to the size of the vessel operated upon. On examin- ing an artery which has undergone this process, it will be found that the middle and internal tunics of the twisted portion have been broken in several places by the external tunic, which, remaining unbroken, is formed by the twisting process into a sort of spiral ligature, so tightly applied round the inner tunics as to set at defiance every attempt to unravel it by twisting the vessel in the opposite direction. The arteries are highly elastic ; they admit of considerable distension in the longitudinal di- rection, and quickly contract to their original length on the cessation of the distending force. In the transverse direction they yield less, and after distension resume their previous state with greater force. When a fluid is injected with some force into the arteries in the dead body, they become distended and elongated ; and if, when they are in this state, the force with which the injection was propelled be removed, they will contract to their previous state, or nearly so, expelling a portion of the fluid which had been thrown into them. During life the arteries are in a state of elastic tension, so that, when divided, their cut extremities retract with- in their sheath. The arteries are endowed with the power of contracting in a gradual manner, which they exhibit under the following circumstances: — when the passage of the blood is stopped in the principal artery of a limb, the vessel gradually contracts, its cavity is reduced in size, and ultimately becomes obliterated by degenerating into a filamentous band of cellular tissue ; while the collateral branches, taking up its function of conveying blood to the distant parts, are proportionally enlarged, rendered more tortuous, and increased in length. In process of time the number of enlarged collateral branches diminishes, and one or more vessels of in- creased size become as it were promoted to * Treatise on Haemorrhage. Lond. 1805. f Archives Generales de Medecine, t. xx. Aout, 1829, p. 606. ARTERY. 225 the station which the principal trunk had held in the circulation while in its normal condition. Several distinguished anatomists and physiolo- gists have considered the property of elasticity of the arteries sufficient to account for all the phenomena of the circulation of the blood through these vessels. This opinion has been principally insisted on by Haller, Bichat, Nysten, and, at the present day, byMagendie; elasticity, however, can only account for contractions taking place in consequence of previous dis- tension, and is equally evident after death as during life : but observation and experiments have shewn that, in the living body, the arteries possess an additional power of contraction, by which their calibre may be diminished in various degrees; in some instances even almost to obliteration. And this power of contraction has been considered by many anatomists to indicate the existence of a property of irritability in the arteries, similar to, if not identical with muscularity. The existence of irritability in the arteries was denied by Haller in conse- quence of his not having succeeded in render- ing it evident by the application of chemical or mechanical stimuli. Bichat, Nysten, and Ma- gendie, embraced a similar opinion, on the strength of the following facts : — mechanical or chemical stimuli, even the galvanic fluid, ap- plied to the surfaces of the arteries, produce no motions; when the fibres of the middle tunic are dissected off in successive layers in living animals, they are not observed to display that quivering motion visible among the fibres of muscles similarly treated. When cut longi- tudinally, the inner surface of the arteries does not become everted like that of canals, such as the intestines, which have a decidedly muscular tunic : they do not contract when separated from the heart. The finger introduced into a living artery is not constricted; stimuli applied to the nerves of particular arteries, or to the nervous system generally, do not produce con- tractions ; strong acids applied to arteries pro- duce a corrugation or crisping of their struc- ture, not a contraction, like that of muscular structure. The contrary opinion as to the existence of irritability in the arteries has been maintained by some of the most distinguished and accurate anatomists and physiologists, among whom are Hunter, Scemmerring, and Verschuir. It may be stated in a general manner, as an objection to the arguments of Bichat, founded on the circum- stance of the arteries not having contracted when stimuli were applied to them in some experiments which he performed, that other irritable parts, even the muscles themselves, do not at all tunes contract on the application of stimuli. In fact, most of the experiments de- tailed by Bichat, as proving the absence of irritability in arteries, have been performed by Hunter, Verschuir, and Hastings, and with results directly contrary to those obtained by that very distinguished anatomist. Verschuir* found that the arteries contracted when stimu- Dissertatio de arteriarum et venarum vi irrita- bili. Gronigen 1766. VOL. I. lated by the mineral acids, by electricity, and the application of the point of a scalpel. Dr. Thomson* also saw them contract on the ap- plication of ammonia, and when punctured with the point of a fine needle in the living- body. Irritating the nerves by the galvanic fluid or by caustic alkalies has been fol- lowed by contraction of the arteries.f Mr. Hun ter j found that the exposure of arteries to the air was followed by their contraction to such an extent as to produce their obliteration. An instance of this we have twice witnessed in the brachial artery when exposed during the progress of an operation for traumatic aneurism at the bend of the elbow. The contraction of divided arteries is well known to be an efficient means of arresting haemorrhage, in op- position to the force with which the blood is propelled through them by the heart’s action. In conclusion, we may observe that the arteries are proved to be both elastic and irritable ; that elasticity predominates in the large trunks, and irritability in the smaller branches ; that their irritability, like that of muscles, is under the influence of the nervous system, and obeys the immediate application of chemical and mechanical stimuli, the effects of which must, however, be very much modified by the influence of the elasticity with which they are endowed. (See Circulation.) In men the arteries are said to have their tunics thicker, and to possess greater density and a higher specific gravity than in women. The arteries are larger, more numerous, and their coats are softer in young persons : they become more fragile, and their elasticity di- minishes, in advanced life. In the progressive development of parts the arteries appeal- before the heart; but in the chick, during its evolution, the veins of the yolk precede them in their development, as ascer- tained by the researches of Malpighi, § Haller, |[ Wolff,' H Pander,** and Rolando.j-f BIBLIOGRAPHY. — Hebenstreit, Progr. de arte- riarum corp. human, confiniis, 4to. Lips. 1739 (Rec. in Haller’s Coll. Disp. Anat. vol. ii.) ; Ejus, Progr. de vaginis vasorum, 4to. Lips. 1740 (Rec. in Haller, &c. vol. ii.); Ejus, Progr. de flexu arteri- arum, 4to. Lips. 1741 (Rec. in Haller, &c. vol. ii.) Monro, on the coats of arteries and their diseases, in Ej. Works, 4to. Edinb. De la Sone, Sur la structure des arteres in Mem. de Paris, 1756 and 1762. Van Swieten, De arteriae fabrica et efficacia incorp. human. 4to. Lugd. Bat. 1725. Albimis, De arteriae membranis et vasis in Ej. annotat. academic, lib. iv. * Lectures on Inflammation. Edinburgh, 1813. p. 75-89. t Vide a paper by Sir E. Home on the Influence of the nerves upon the action of arteries. Philoso- phical Transactions for 1814. J Treatise on the Blood, p. 114. $ De formatione pulli in ovo, || Opera Minora, t. ii. Hi Theoria Generationis. ** Journal de Progres des Sciences et des In- stitut. Medicales, t. v. and Journal de Physique, t. Ixviii. also his Beitrage zur Entwickelungsges- chichte des Hiinchens im Eie. Wiirtzburg, 1817. ft Journal Complementaire du Diet, des Sc. Med., t. xi. p. 323, et t. xii. p. 34. Q 226 ARTERY, PATHOLOGICAL CONDITIONS OF. Haller , Dc artcriarum et vcnarum fabrica in Ej. Op. minor, vol. i. Hunter, on the blood, &c. 4to. Lond. 1794. Letter ce , Essai, &c. sur la membrane interne des arteres, Thes. de Paris, 1829, and in Archiv. Gen. de Med. Nov. 1829. Haller resp. Berklemann , De nervorum in arterias imperio, 4to. Gotting. 1744, and in Halleri Op. Min. t. i. Wrisberg , De nervis arterias venasque comitantibus, in Ej. Comment, vol. i. 8vo. Gotting. 1800. Lucce, Obs. Anat. circa nervos arterias adeuntes et comi- tantes, 4to. Frft. a M. 1810, Germ, in Reil's Archiv. Bd. ix. Riles, in Mem. de la Soc. Med. d'Emulation, t. viii. 1817, and in Meckel’s Archiv. Bd. v. Verscliuir , De Arteriarum et Ven. vi irri- tabili, &c. 4to. Groning. 1786. Parry , of the pulse, &c. 8vo. Lond. 1816; Ej. Additional experiments on the arteries, 8vo. Lond. 1819. Jaeger , De ar- teiiarum pulsu, 8vo. Viceb. 1820. Hastings , De vi contractili vasorum, 8vo. Edinb. 1818; Ejus, on inflammation of the mucous membrane of the lungs, and inquiry respecting the contractile power of the bloodvessels, &c. 8vo. Lond. 1820. Meckel, Verlauf der Arterien und Venen, in Ejus Archiv. B. i. 285 and 450. Ehrmann, Structure des ar- teres, &c. 4to. Strasb. 1822. Belmas, Structure dcs arteres, &c. 4to. Strasb. 1822. Oppenheim, Experimenta circa vitam arteriarum, 4to. Mannh. 1822. Wreden, Arteriologische Tabcllen. fol. Hannov. 1721. Chirol , Tab. de toutes les arteres du corps humain, fol. Paris. Muriay, Descriptio arteriarum corp. human, in tab. redacta Diss. i.-iv. 4to. Upsal, 1780-83; 8vo. Lips. 1794; Anglice a A. Scott, 8vo. Edinb. 1801. Barclay , Description of the arteries of the human body, 12mo. Edinb. 1812. Harrison , Surg. anat. of the arteries of the human body, 2 vol. 12mo. Dubl. 1824-25. Her- matt , Locality and distribution of the arteries, 12mo. Lond. 1827 ; Ej. Illustr. of the arteries, fol. Lond. 1825. Haller , leones anatomic®, fasc. i.- vii, fol. Gotting. 1743-56. Bell, Engravings of the arteries, 8vo. Lond. 1811, 1824. Manec , Traite de la ligature des arteres, fol. Par. 1832. Tiedemann, Tab. Arteriarum corp. humani, fol. Caroliruh®, 1822. Froriep , Chirurg. Anat. der Ligaturstellen am mensch. K'orper, fol. Weimar, 1830. Richerand, Moyens de determiner exacte- ment la situat. et le trajet des arteres : Societ. Pliilomat An 13. Blizard , Lect. on the situation of the large bloodvessels, 8vo. Lond. 1798. * * * * The comparative anatomy of the arteries generally is treated of in the Introd. of Blumenbach , the Le9ons of Cuvier , the systems of Carus, Meckel, Ucelli, Grant , &e. Particular subjects are dis- cussed by the following writers : — Carlisle , Pecu- liarity in the distribution of the arteries sent to the limbs of slow-moving animals, in Phil. Trans. 1800. Rapp, Ueber das Wundernetz, in Meckel's Archiv. 1827. Uarkow, Eigenthiimlichkeiten im Verlaufe der Schlagadern der Eischotter, in Meek. Archiv. 1829, and in Ej. Disquisit. circa orig. et decurs. Arteriarum, 4to. Lips. 1829. Bauer, Nonnul. Avium systema arteriosum, 4to. Berol. 1825. Nitsch, De avium arteria carotide communi, Hal®, 1829. Barkow, Schlagadersystem der Vogel, in Meek. Archiv, Jahr 1829. Meckel, in Ej. Ar- chiv, Jahr 1826. Schlemm , Blutgefasssystem der Schlangen, in Tiedem. u. Treviran. Zeitschr. f. Physiologie, 2ter Bd. Tiedemann , Anat. der Fischherzens, 4to. Landshut. 1809. Rathke, Herz- kammer der Fische, in Meek. Arch. 1826. Cuvier Valenciennes , Hist. nat. des Poissons, t. i. Paris, 1828. Owen, on the Nautilus Pompiiius, 4to. Lond. ARTERY, PATHOLOGICAL CONDI- TIONS OF.- — Notwithstanding the brilliant success that has attended the labours of British surgeons in the department of their profession having reference to the arteries, a success that has deprived haemorrhage of its terrors, and aneurism of half its danger, the pathology of the arterial sys- tem is still far from being perfectly understood. Doubtless, the appearances of disease in its more advanced and destructive forms have been ac- curately described as they have been carefully observed, but that invaluable information which enables a practitioner to detect its early and silent approach, to trace its progress by con- necting each symptom with the morbid change that is going forward, and to predict with accu- racy the time and the manner of its termination, is as yet but very imperfect. Many circum- stances have unavoidably contributed to this. It is quite possible that arteries may be in an unhealthy condition without presenting any in- dication of disease during life, which is, therefore, in the subsequentexamination overlooked. It is more than questionable whether arteritis occa- sions pain, for it has been observed in situations in which the patient never complained, and as persons do not die from inflammation of the arteries, the intensity of the disease has time to subside, and its effects only remain for obser- vation in alterations in the coats of the vessels, or in an aneurism. Many able and intelligent practitioners who have met with aneurisms without number, have yet not seen an example of acute arteritis, and are disposed to consider the red colour of the internal membrane of the vessel observed in cases presumed to be so by others as a staining by the blood after death. These facts prove the imperfection of our know- ledge of the pathology of the arterial system ; and years of patient investigation must still be passed both by the bed-side and in the dissecting-room before the dreams of hypo- thesis give place to the certainty of scientific demonstration. In prosecuting this inquiry, that source of information so valuable in the elucidation of other subjects in physiology, the experimenting on animals, is wholly closed ; the artery of the animal bearing no analogy whatever to that of man, either in susceptibility of disease or in the powers of reparation after injury. It appears, from Dr. Jones’s* experiments, that the artery of a dog, if wounded only to a moderate ex- tent, is capable of re-uniting and of healing so completely that after a certain time the cicatri- zation cannot be discovered, either on its inte>- nal or external surface; whilst it is nearly certain that in man the wound of an artery can only be healed by the complete obliteration of the vessel at the spot where it has been injured. It is difficult if not impossible to bleed an animal to death by opening a moderately sized artery, whilst few surgeons would be willing to entrust a wound of a branch of the temporal in man to the resources of nature alone. The facts, too, that aneurism is a disease unknown among inferior animals, — that it cannot, by any inge- nuity of contrivance, be artificially produced, and that the earthy depositions so commonly met with in the arteries of aged persons are peculiar to the human species, would tend to shew that some difference of structure existed, some pe- culiarity favourable to the production of dis- ’ Jones on Haemorrhage, pp. 107 to 111 inch 227 ARTERY, PATHOLOGICAL CONDITIONS OF. ease in the artery of the latter. Indeed, in examining and comparing the artery of a sheep or a dog with that of man, some very obvious differences are apparent: the former is firmer if not actually thicker in its coats ; it maintains its circular form more completely, and seems to possess the quality of elasticity in a greater degree of perfection. These circumstances, however, are insufficient to account for that comparative freedom from disease ; and pro- bably the greater susceptibility of man may be traced to the indulgence of certain habits and propensities from which the animal is debarred, and which, in many other instances as well as in this, seem to be the predisposing causes of disease in the human race. The surgical pathology of the arteries presents itself in two different though equally interesting points of view, one having reference to the effects of a wound or other injury to a healthy vessel, embracing a consideration of the pro- cess by which such injury is remedied or re- paired by the efforts of nature alone or by the assistance of art, and the circumstances that influence its success or failure ; the other refer- ring to the appearances and consequences of disease, either as it commences idiopathically within the vessel itself, or is propagated from adjacent parts or structures to it. A lesion of the structure of an artery is of but slight importance provided its function is unimpaired, that is, as long as the blood it was destined to circulate passes through it or is conveyed by some other channel in the natural course of the circulation : even the aorta has been obliterated without any serious inconvenience to the indi- vidual in whom it occurred. But when the lesion is of such a nature as to interfere with this function, when the blood is allowed to escape either externally as from an open wound, or internally as in the different species of aneu- rism, results of a most formidable nature ensue, greatly modified, however, in their cha- racter and consequences by a number of cir- cumstances highly deserving of attention. Wounds and injuries of arteries. — It cannot have escaped observation that the nature of the wound or rather of the substance that occasioned it exerts a striking influence on the phenomena both of haemorrhage and of the process by which it is restrained. Lacerated wounds seldom bleed, although the torn artery may be left hanging out an inch or more be- yond the adjacent surface. Gun-shot wounds, also, if the artery is completely divided, are not often followed by haemorrhage, although some instances to the contrary occasionally happen ; but if the vessel is only notched or partially cut, the bleeding is as profuse as from any other cause. If an artery is wounded by a cutting instrument or by puncture, however, the blood is poured out most freely ; yet even here there are varieties, according to the size and importance of the vessel, the extent and direc- tion of the accompanying wound, and the cir- cumstance of the division of the artery being partial or complete. In like manner the sub- sequent progress of the case will exhibit con- siderable variety, and demonstrate the fallacious views of those who, grounding their opinions on experiment, would limit the process of recovery to one operation, and regard the efforts of nature as alike in all, whereas, as has been remarked by Mr. Guthrie, this process essen- tially depends on the size and variation of structure of the artery ; it is not the same in large as in small arteries ; and it is not even quite the same in the upper and lower ends of the same artery. When a limb has been torn off by a cannon- shot, by the fall of a tree on it, or by any simi- lar violence, the arteries do not bleed : very frequently the main trunk is seen hanging an inch or more from the wound, pulsating, or at least receiving an impulse from the sound portion of the vessel, though (as far as I have observed) not containing blood within it. It hangs white, bloodless, and flaccid in the wound, not very unlike a piece of narrow wetted tape, and is smaller at its extremity than at any other part. This narrow point, which, according to Mr. Guthrie, is formed by the contraction of the artery, is also in his opinion the only barrier to the escape of the blood ; for in a case of this description he cut off the end of the artery at less than an eighth of an inch from the extremity, when it bled with the usual vigour. The extraordinary op- portunities this gentleman has enjoyed, and the accuracy of observation which his writings evince, entitle his opinions to be received with great deference, although in a physiological point of view it is difficult to conceive how an artery subjected to such a lacerating force should not have its vital properties so much impaired as to prevent its contracting at all, more par- ticularly at the spot where it was torn across, and where, therefore, the greatest injury was sustained. At the same time there is no other mode of explaining the case. All that portion of the artery that is pendulous from the wound appears to be smaller in diameter than in its healthy state ; there is cellular tissue at its torn extremity, but it is not injected with blood, and the eoagulum, if any, within the vessel, is so small as to be incapable by its mechanical resistance of preventing the escape of the blood. As there are scarcely any two accidents at- tended by exactly the same degree of injury, it is probable that nature in such cases possesses different resources. In one case where the leg had been torn off by the falling of a tree, and left attached merely by a portion of the skin over the gastrocnemius muscle, the posterior tibial artery hung nearly three inches from the wound. As the man had been carried a dis- tance of eleven miles, and seemed much ex- hausted, it was not deemed right to attempt more at the moment than merely to relieve him of the annoyance of the pendulous portion of the limb by cutting through the skin. This was performed incautiously, for no inconve- nience was apprehended ; about an inch of the extremity of the artery was removed, and it bled just as in Mr. Guthrie’s case. In another instance where the arm was shattered by a steam-engine with such violence that some of the muscles torn from their attachments re- 's 2 228 ARTERY, PATHOLOGICAL CONDITIONS OF. mained upon the wheel, the artery, divided in the subsequent amputation more than two inches above the wound, did not pour out one drop of blood. In others, still, the cellular sheath of the artery has been seen injected with blood in a state of coagulation, the pres- sure of which on its orifice seemed to be sufficient to prevent bleeding. We are told that the observation made by Amussat,* that in gun-shot wounds where all the parts were lacerated, the extremities of even the larger vessels did not bleed, suggested to him the application of the phenomenon to practical surgery, and led to the practice of the torsion of arteries. This operation con- sists in laying bare a portion of the divided artery, and carefully detaching it from the sur- rounding cellular membrane until its own cel- lular tunic is distinctly to be seen ; it is then seized with a forceps, not unlike the common artery-forceps of Bell, and twisted on its axis until the extremity engaged between the blades is completely detached by the torsion. This forms something like a knot or knuckle at the end of the vessel, which mechanically blocks it up ; a coagulum is formed within, and the remainder of the process is said nearly to re- semble that which succeeds the application of a ligature. Not having practised torsion on a vessel of any considerable size in the human subject, nor had an opportunity of examining after death a case thus treated, I am unable to comprehend, with sufficient precision, the exact process that is established. In experimenting on the femoral arteries of dogs, I have always found that the immediate obstacle to the flow of blood was a coagulum situated at the orifice, and apparently entangled in the lacerated cel- lular coat; but for the reasons already men- tioned, little confidence can be placed in such investigations. Hitherto we have been considering those wounds of arteries, which, however important in other respects, are not attended by hemor- rhage, and although ignorant of the operations of nature in effecting this result, it is of the less con- sequence, inasmuch as it is not likely we shall attempt to imitate them, or entrust a large- sized vessel to torsion alone. The wounds of arteries, accompanied by loss of blood, present themselves under very different circumstances; there is always anxiety, agitation, and dismay on the part of the sufferer, and it may be that promptness and decision in the practitioner shall be required to preserve life. In any of these awful situations, coolness and self-pos- session can alone ensure a freedom from em- barrassment, and these qualities cannot be ex- pected in any individual who has neglected to make himself acquainted with the nature of the mischief that has occurred, and the means by which it may be remedied. The phenomena attendant on arterial hae- morrhage occasioned by incised and punctured wounds exhibit remarkable varieties, according to the size, and of course to the structure of the vessel ; to the circumstance of its having * Dictionaire de Chirurgie de Rust, tom. ii. been fairly divided, or only notched, or punc- tured ; to the wound being so large and patu- lous as freely to permit the escape of all the blood externally, or so small or oblique that the fluid, though withdrawn from the circula- tion, is still retained within the limb. There is still another condition of wounded artery in which the blood that escapes from it is poured into an adjacent vein, and continues to circulate, though not in its proper vessel. However, these latter cases are usually considered and described as forms of aneurism, and will, therefore, not be noticed until there is an op- portunity of comparing the different species of that disease one with another. When a large artery is divided in an open wound, it may happen that the patient dies almost instantaneously, not from the absolute quantity of blood lost, but from its being with- drawn too suddenly from the circulation, just as syncope is often produced by the rapid abstraction of blood in the common operation of phlebotomy. However, this is not uniformly the case, and experience has proved that vessels of such size and importance as the carotid and femoral arteries may be divided, and yet suffi- cient time allowed for the successful interposi- tion of art. Mr. Guthrie states, that when the femoral artery is cut across in the upper part of the thigh, the patient does not always bleed to death, although frequently lost; while if the division takes place in the middle or lower half of the thigh, the bleeding will probably cease of itself. When, however, an artery of still smaller size is divided, the powers of nature are almost always competent to restrain the haemorrhage, and consequently it is from an examination of vessels of this class under such circumstances that a knowledge can be ob- tained of the nature and extent of these powers. When a vessel of moderate size is divided, the blood is poured forth in jerks from its open mouth in a large and full stream; soon, however, this stream is seen to become dimi- nished in size, and most probably it ceases to flow per saltum. If the patient faints, the bleeding perhaps ceases altogether, nor will it be renewed unless accident or indiscretion gives to the blood an impetus sufficient to overcome the obstacle that opposes its exit, whatever that may be. When the artery is divided, its middle coat retracts immediately that its natural state of tension is removed, withdrawing with it the lining membrane, but leaving the cellular, to which it is but loosely attached, hanging out beyond it. It contracts, too, in diameter, as is evidenced by the diminished stream of blood. The power by which this contraction and re- traction are performed is a vital property inhe- rent in the artery itself; it has been called muscularity, and endless arguments have thus been raised about a name, as if no tissue in the body but muscle could be capable of contrac- tion. But it operates in a manner very different from the rapid and decided contraction ofmuscle ; it is slow, gradual, and continued, and, there- fore, is longer in bringing the large vessel into a state favourable for the suppression of haemor- 1229 ARTERY, PATHOLOGICAL CONDITIONS OF. rhage than the small one. The next step is the entanglement of blood in the cellular coat of the vessel and its consequent coagulation when it comes to press in the most advantageous direction on its open mouth, and the haemor- rhage is stopped. Thus the immediate agent of nature, in the suppression of haemorrhage, is pressure effected by the clot of blood, whilst the vessel is placed by its own properties in the condition most fa- vorable to the operation ; and it is curious to ob- serve how universally the principle has been acted on, though probably first suggested by accident -or empiricism. The burning iron of the older surgeons produced the pressure of an eschar; agaric and sponge entangled the blood and retained a coagulum on the spot ; even the more modern invention of the ligature is in the first instance only pressure, but with the mani- fest advantages of being applied directly and immediately, of being firm and not likely to slip, and independent of rest, position, and bandage, which are indispensable when other modes of compression are had recourse to. But the permanent suppression of arterial haemorrhage can only be effected by the actual obliteration of the vessel at the spot where it had been opened or divided, a process that is the result of inflammation of the lining mem- brane, and of the coagulating lymph thereby poured out, or of the artery ceasing to transmit blood through it, and thus becoming as it were useless in the economy. Both these influences are exemplified in the permanent cure of a wounded artery, for in an incredibly short space of time after the external coagulum has been formed, lymph is effused from the wound in the vessel : and internally, between this lymph and the nearest collateral branch, another coa- gulum of blood is formed, to which a consi- derable degree of importance has been attached, though probably without sufficient reason. It cannot be very instrumental in controlling hse- morrhage, because it does not occupy the entire capacity of the. artery : its shape is conical, the base lying on the lymph poured out from the wound, from which it gradually tapers to the next branch, and it seems to be formed of a small quantity of the blood, which, being pushed into that branch, remains there, is placed out of the current of the circulation, and must coagulate. The transmission of blood to the limb below is now to be effected through the medium of the anastomosing vessels, which for this purpose become proportionably enlarged. This quality possessed by arteries of increasing their own diameters, or in other words of accommodating themselves to their contents, is curious and interesting, and although not admitting of ex- planation, cannot for a moment be doubted. No fact has been more satisfactorily proved by dissection, and like the contractility of the artery already noticed, the effects of this power exhibit themselves gradually and slowly. The circu- lation of the limb seems scarcely to be inter- rupted, for in a few minutes the arteries below appear, as has been observed by Dupuytren, like soft cords under the finger, evidently filled with blood, but totally devoid of pulsation. It is a long time before this latter proof of a re- stored activity in the circulation comes to be perceptible, and perhaps is never again equal to what it had been before the occurrence of the accident. The external wound, of course, heals like any other of a similar nature, and it is rare that the limb experiences any incon- venience subsequently. The internal coagulum is soon absorbed, and in process of time the vessel, from the point of division to the next branch above and below, degenerates into an impervious ligamentous cord. Such is the progress of events when the efforts of Nature are sufficient to arrest the bleeding ; but after all it is a fortunate case that ends thus, and experience teaches that there is little wisdom in leaving a moderately sized artery to her resources alone. What more frequently happens is this : the artery retracts and contracts it is true, and a coagulum forms, which, as the patient becomes faint or weak, is allowed to become consolidated, and for that time is sufficient to save him. But he recovers, or perhaps he uses some stimulus or some ex- citement, and the renewed circulation gradually loosens the clot, and a fresh gush of blood takes place. This recurs frequently, and an liasmor- rhagic disposition is formed ; the patient be- comes pale and exsanguineous, anxious, and in continual agitation, and without the interven- tion of art has but a slender chance of sur- viving. In these cases, art adopts the principle of the natural cure, only regulating its force, and ensuring its continued operation for the requisite period. The first object to be at- tained is the application of a sufficient degree of pressure to control the bleeding : the second to maintain that pressure for a length of time to ensure the obliteration of the vessel. This is not the place to discuss the various methods that have been adopted for the accomplishment of these ends ; suffice it that the superiority of the ligature has been so far proved by expe- rience, that few surgeons of the present day would feel satisfied in entrusting a large or im- portant vessel to a less powerful or enduring compression. But the ligature is in itself not unfrequently a cause of great and frightful mis- chief, and, therefore, it will be necessary to examine into all the circumstances connected with this part of the subject. In practice, a ligature is applied around an artery under two different circumstances ; one, in the case of the wounded and bleeding artery, it is placed on the open orifice of the vessel ; the other, in the treatment of aneurism, the artery is taken up and tied at a part where it is supposed to be sound and uninjured. When, in either of these cases, an artery is tied, the first effect is obviously to bring its opposite sides into apposition, and to arrest the flow of blood through it. At the same time that the internal and fibrous coats being shorter and less tough yield under its pressure and are divided completely, leaving the cellular coat entire, still sustaining the ligature in its place. The consequences of this division of the internal coats are very similar to those already explained as following the complete section of the artery ; 230 ARTERY, PATHOLOGICAL CONDITIONS OF. there is the same effusion of lymph, the for- mation of internal coagulum of the same conical shape and to the same extent, the diversion of the circulation through the collateral branches, and if the case proceeds favorably, the ultimate obliteration of the tube between the place occupied by the ligature and the next anasto- mosing branch. But the ligature is still to be attended to. The portion of the cellular coat included within its noose sloughs and dies, and is to be detached from the remainder by the absorption of the adjacent sound part. This process takes place at different periods of time according to the size of the vessel ; it separates from the subclavian about the twenty- second day after the operation, from the femoral about the sixteenth, and from the brachial so early as the twelfth or fourteenth. Unfor- tunately matters do not always proceed thus favorably, and the separation of the ligature is the commencement of a series of evils to the patient and of embarrassment to the surgeon, that can scarcely be paralleled in the practice of surgery. It has been found, however, by experience, that a ligature placed on an artery that has been fairly divided, is more rarely followed by those ill consequences that fre- quently ensue when its continuous tube is tied, and as this latter operation is so intimately connected with the subject of aneurism, and as it will be necessary to become acquainted with the phenomena of inflammation in these struc- tures, in order to understand those of secon- dary or consecutive haemorrhage, this part of the subject cannot at present be so favorably discussed. Morbid states of arteries. Aneurism. — 1 Aneurism (arEogicr/xo?, vel is a term of such extensive application as to pre- clude the possibility of an accurate definition. It has been employed by Corvisart and others to designate certain affections of the heart, but is now most generally used to express a disease produced by a dilatation of an artery, or by solution of continuity in one or all of its coats. It is also applied to any distended condition of a part of the vascular system, such as occurs when an unnatural communication is formed between an artery and vein, constituting the diseases of aneurismal varix and varicose aneurism. The name of aneurism by anastomosis has also been given to those bloody tumours, which, at first appearing only as marks or stains occa- sioned by a congeries of vessels, increase either with the growth of the individual, or according as the vascular system may be accidentally ex- cited, until finally they produce results of a most formidable description. Aneurisms have been classed, first, as to the condition of the coats of the artery, a dilata- tion of them being considered as the true aneu- rism, whilst a rupture or ulceration of them constitutes the false : and, secondly, as to the condition of the effused blood, which, if it is contained within a sac or bag, constitutes the circumscribed [form of the disease, or if it has been poured out throughout the circumjacent cellular tissue, forms the diffused aneurism. The nature of aneurism, however, will be better understood by considering it to consist of such a lesion of an artery as will permit the passage of a portion of the blood out of the usual course of the circulation, though not out of the vicinity of the injured or diseased vessel, and according to the different circumstances under which this can occur, the disease will be found to arrange itself under the following distinct species. In the first four of these the effused blood is either partially or entirely withdrawn from the circu- lation, and becomes coagulated in its new situation : in the others it passes from the usual course of the circulation, but is not withdrawn entirely from it, and consequently does not coagulate. 1. Where by rupture or ulceration of the internal and middle coats of the vessel, the blood is propelled against the external cellular coat, which becomes thus distended into a pouch containing within it the extravasated blood, in a more or less perfect state of coagulation, which pouch is termed the aneurismal sac. This is circumscribed false aneurism. 2. The true aneurism is when all the coats of an artery, in one particular part of its cir- cumference, are so far deprived of their elastic properties as to yield, become distended, and form a pouch, in which the contained blood is similarly circumstanced. 3. It is not difficult to conceive that the sac of a true aneurism, as just described, will not long endure its state of unnatural distension before its internal and fibrous coats either ulce- rate or rupture, and then an aneurismal sac is formed, consisting in one part of all the coats of the dilated vessel, and in the other of the cellular tunic alone. This is obviously a mixed form of aneurism. 4. When there is a wound, rupture, or ulceration of all the coats of an artery, in such wise as to permit the escape of the blood into the adjacent cellular tissue, a diffused aneurism is formed. This, for reasons that need not explanation, will be most frequently observed to succeed to wounds or punctures of vessels, but it may also be the consequence of an acci- dental rupture of the sac of a circumscribed aneurism allowing the blood to pass through it, and spread itself (as it generally does) in every direction throughout the loose cellular tissue of the entire limb. 5. A direct and immediate communication may be established between an artery and a vein lying close upon it, as by the passage of a lancet transfixing one vessel and entering the other. This is the aneurismal varix, obviously occurring with greater frequency as the result of a wound, but nevertheless occasionally seen as the product of disease. 6. A small circumscribed aneurismal sac has been found situated between an artery and vein so transfixed, communicating with both, and permitting a transmission of blood from one vessel into the other. This variety has been named the varicose aneurism. 7. A portion of blood may be contained within a new and diseased formation of cellu- lar structure, the precise nature of which is not understood . The trunks of the arteries in 231 ARTERY, PATHOLOGICAL CONDITIONS OF. the neighbourhood are neither distended nor ruptured, and the blood within it passes through the general circulation, and of course does not coagulate. It is difficult to class this disease with aneurism in any form, yet is it termed the aneurism by anastomosis. 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 the 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 with 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 to, 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 wfould shew it did not greatly interfere with the distensibility of the arterial tunics or render them more friable, * On Aneurism, page 90. 232 ARTERY, PATHOLOGICAL CONDITIONS OF. 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 consideied 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. II ow 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 hoemoptoe 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 233 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 aneurism be recent or of long 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 laminae, 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, and 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. Hosp. ltep. vol. iii. 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, w'hile 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 hremorrhage 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 externa 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 hasmorrhage 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 longstanding, 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 oi 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. 235 ARTERY, PATHOLOGICAL CONDITIONS OF. 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;’'5 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.— Ed. 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 irregular rugas 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, m 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 biood 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, 237 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- 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 eoagu- 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 eoagulum 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 hasmorrhages 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 and 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 remains 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 hcemorrhage. — 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 isremarkable thatthe 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 dlustration 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- 239 ARTERY, PATHOLOGICAL CONDITIONS OF. wards. 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, &c. 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. Qn 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, tom. iv. p. 573. 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 the 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- nnnata 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 hemor- 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 he- morrhage, seldom die (at least in this country) 240 ARTERY. PATHOLOGICAL CONDITIONS OF. 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 colour and nearly of its natural appearance, with the exception of one or two broad spots of a very light 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- j 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 241 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 hemorrhage, and that the practical arrangement of aneurism and its consequences, both fortunate and otherwise, might be as un- interrupted as possible. Aneurismal vurix. — 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. 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 vari.v. 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. R ARTERY, PATHOLOGICAL CONDITIONS OF. 212 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 held out a prospect of much benefit, he was soon discharged. This man (I believe) still lives, and as he resides in a distant part of the country, perhaps the true pathological nature of a case so very interesting may never be 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 part 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 tifco 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 disease 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 justify a passing notice of the subjecthere. This kind of tumour has also been called the naevus 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 manes 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 243 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 be 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 nasvus 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, hut immediately the pressure is removed it recovers its former level. It may be stationary for years, hut 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 ntevus 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 naevi are merely artificial ; the second can he made to pulsate and to increase by heat or intem- perance,'the third can often he 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 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 may be fatal, evidently shewing that these vessels are not endowed with con- tractility, and are a diseased and a new forma- tion. If a naevus is injected, it only affords a swollen and unshapely mass of whatever ma- terial had been used, and throws no light what- ever on the real pathology of the disease. Here, then, in the absence of demonstration, theory and conjecture are permitted, and all that is known, or supposed to be known, is only the fruit of speculation. Bell 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 a profuse discharge of blood. But still this explanation is defec- tive, as showing nothing of the nature of the cells themselves, or why blood poured oat into them should not coagulate as it would in any other cellular structure. It remained for Du- puytren 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 mamella 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 are 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, and 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 1835. — Ed. K 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. — Cowpcr, on ossifications or petrefactions of the coats of arteries; Phil. Trans. 1703. Stengel, lie stcatomatibus in aorta repertis, Vittobcrg, 1723 (Rcc. in Halleri Disp. ail Morb. Hist. vol. ii.) Lancisi, He motu cordis et aneu- rysmatilius, fol. Rom. 1728. Nichuls, Obs. on aneurisms ; Phil. Trans. 1728. Petit, Obs. See. de l’ancurysmc ; Acad, des Sciences do Paris, 1736. Arnaud, Obs. on aneurisms, 8vo. Lonrl. 1750, and in Kj. 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 ; Kj. 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. Kaselius, Dissert, sistens morbos arteriarum, 4to. Jonse, 1757. Langswerth, Theor. Med. de arteri- arum ct venar. adfectionibus, 4to. Prag. 1763. Monro, on the coats of arteries, their diseases, &c. in Edinb. Med. Ess. and Obs. vol. ii. Pold, De ossificatione vasorum. Lips. 1774. Heeleeren, De ostcogenesi prasternaturali, Lugd. Datav. 1797. Charitius, De arteria crurali ossca, Vitteberg. 1798. Lauth, Scriptorum Latinorum de anevrysmatibus collectio, 4to. Strasb. 1785. Lane, De arteriarum mor’bis, &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. Abcrnethy, in Surg. and Physiolog. Essays, 8vo. Lond. 1793. Guerin, Mem. sur Panevrysme * Journ. de la Soc. de Lyon. t. i. ; Sur la methode de J. Hunter; Hoc. Period, de la Societe de Sante de Paris, an v. t. ii. Caillot, Essai sur les anevrysmes : Theses de Paris, an vii. Ayrer , Ueberdie Pulsadergeschwiilste, 8vo. Gotting. 1800. Maunoir , Mem. sur Panevrysme, 8vo. Genev. 1802. Briot , Sur les tumeurs formes parlc Sang arteriel, 8vo. Paris, 1802. Scarpa , SulPanevrysma, fol. Pavia, 1804 ; Anglicc, by Wishart, 8vo. Edinb. 1806. Freer , Obs. on aneurism and some diseases of the arterial system, 4to. Binning. 1807. Jones on hemorrhage, Lond. 1810. Pelletan, Mem. sur les anevrysmes; Clinique Chirurg. t. i. and ii. 8 vo. 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. Lucce , De dcpositioliibus cretaceis intra cordis val- vularum arteriarumque 6ubstautiam. Marburg, 1815. Lobstein , Mem. sur les ossifications des arteres ; Mem. de la Soc. des Sciences, &c. de Strasbourg, t. i. Shchcllon, Dub. Hosp. Reports, v. iii. Spangenberg, Ueber die Entziindung der arterien, in Horn's Archiv. 1804, II d v. Meli, Storia d’una angiotide, &c. e consid. gener. intorno all’iufiamrna?. dei vasi sanguiferi, in Omodei Annali universali, 1821. Balbant, De Parterite ou inflam, des arteres. Theses de Paris, 1819. Barde, Observations, &c. inflammation general, des arteres. Revue Med. Mai 1821. Montesanto, Storia di un artcritide cronica, Annali di Omodei, 1825. Locatelli, Diss. de angioitide, Paviie, 1828. Breschet, Hist, de l’inflam. des vaissaux, Journ. de Progres. Gendrin, Hist. anat. des in- flammations, 2 tom. Paris, 1826. Dezeimeris, Memoire, &c. Apcriju rapidc des decouvertes cn anatomic patbologiquc, 8vo. Paris, 1829. * * * * Tnrnert 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. * * * * Manzoni, Consid. sugli anevrismi ; Mem. della Societa Ita- liana, t. xviii. Moden. 1820. Fleischer, Aneurys- inatis complicati historia, 8vo- Dorpat. 1822. Boring, Quiedam circa aneurysmatum pathologiam, 8vo. Berl. 1822. Levi, Saggio sugli anevrismi in- torni, 8vo. Venez. 1822. Casamayory Reflex, sur Panevrysme spontanc, 8vo. Paris, 1825. Mayer, De arteriarum regenerationc, 4to. Bonn. 1823. Sch'onberg, Sul ristabilmento della circolazione nclla legatura, &c. dei tronebi delle artcrie, Napoli, 1826. Fjbel, De liatura medicatrice sicubi arterice vulneratae et ligatse fucrint, 4to. Giessse, 1826. The papers of Lawrence and Travers on the ligature of arteries in the 4th, 6th, and 8th volumes of Med.-Chir. Trans. Zhuber, Neue Vcrsuchen an Thiercn und dcien Rcsultiite uber die Wiedcrer- zeugung der Arterien, &c. Wien. 1827. Coi'bin, Des anevrysmes spontancs ; Journ. Univcrs. t. ii. 1831. Mancc, Traite de la ligature des arteres, fol. Paris, 1832. Breschet, Mem. sur les anevrysmes in Mem. de PAcad. Roy. de Med. t. iii. 1833. Guthrie on the diseases and injuries of arteries, 8vo. Lond. 1833. Dupuytren, Leijons orales, t. iv. The reader should moreover consult the systematic works of Senae, Corvisa/rt, Burnsy Laermec, Kreysig, Bertin, Hopct Bouillaud, and Otto's Compcnd. of pathological anatomy, by South. (W. H. Porter.) ARTICULATA (articulus9 a joint,) a pri- mary division of the animal kingdom founded by Cuvier,* and characterized by him as follows: a 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 winch 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 bis earliest work, the te Tableau Elcmentaire de PHistoire Nalurelle des Animaux," although it was not defined with that clearness, nor its character's so fully developed as in the Regnc Animal. In the “ Tableau Elcmentaire ” the second section of f white-blooded animals,' including the Insecta 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. tom. i. p. 454.) AllTICULATA. 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 supraceso- 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 Regne Animal,” first placed the eirripeds 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. Burmeisterff have proved that in the immature state the Cirripeds un- dergo repeated metamorphoses or moults ; that 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.” “ Annates du Museum d’Histoire Naturelle, 4to, tom. xix. p. 73. t Beitrage zur Naturgesehickte dcr Rankenfuesser. 4to. Berlin, 1834. 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 branch i as 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 segments, of which the first, called the head, scarcely differs from the others, except by the presence of the mouth ancl of the principal organs of the senses. Many possess branchias, arranged the whole length of the body, or situ- ated at the middle ; others, which for the most part inhabit tubes, have the branchire 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 clhws; and in 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. With the exception of some genera, as the myriapoda, in which the body is divided into a number of nearly equal segments, and of the arachnidu and many Crustacea , in which the head and thorax are blended together, the body of the condylopes 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 insections 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 chitine, 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 I lid class of articulate animals or In- sects ( Insecta ), 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 trachese, or elastic 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 antennse. IV. The Arachnidans ( Arachnidu, Spiders, Scorpions, &c.), are octopod and apterous; they have no antennse, and have simple eyes. 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 tracheae, 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 bsick. They respire by means 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- pregnation of co-equal hermaphrodites, and, lastly, 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 tracheae 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. apfipor. Lat. articulus, arthrosis, junctura. Fr. articulation. Germ. Articulation, Gelenk. Ital. articolo ). The power of motion, to an extent however limited, seems to be inseparable from our idea 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 j body varies considerably, and increases in !| complexity as the forms of the animals them- j ARTICULATION. 2->7 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 superadded to the 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 stabilitatem 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-cai'tilage. 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. Dcor. 1. ii. c. 36. 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 ev.dently 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 vve 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 ; b, 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. Diarthrodiul curtilage. — 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. Tins 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 flosculi 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.”-j- * Loc. cit. p. 516. t Hunter, in loco citato. Hunter’s account of articular cartilage is completely confirmed by M. De J.asone in a paper in the Mem. de l’Academie Royale des Sciences, An 1752. He describes the cartilage as “ une multitude des petits filets adosses ctlieslesuns aux autres tons pcrpendiculaires au plan de l’os, en un mot parfaitement semblables par leur structure, oupar leur position a la substance emaillcedes dents, laquelle n’est composee, comine on sait, que de filets osseux, poses perpcndiculaiie- ment sur le corps do la dent : la comparaison cst des plus exactes.” ARTICULATION. 249 b. Synarthrodiul cartilage. — The cartilages of 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 lamina; 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 lamina; 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. Fibr o-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, forwhich 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.j; 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 laminae 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 vertebras 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 lamince must unquestionably be to guard 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-carlilage. b. The second class of articular fibro-carti- lages consists of those which Meckel designates fibro-cartilages ofi 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, (intervertebral 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- tebras, 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 fibro- cartilages generally assume more or less of the circular form, we find that the fibrorrs 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 lamina, are filled by cartilaginous tissue ; towards the centre the fibrous laminas 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 vertebra 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 vertebrae 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, (balcena 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 propria 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 fiexilibus, interdum elasticis, plerumque parallele concretis, in substantiam tenacem fibrosam, ruptioni fortiter resistentem, et solidam compacta, eum in finern creata ut duae pluresve partes quae alias divulsce per se subsisterent, adunentur atque in situ respectivo determinentur.”t Most of the articular liga- ments are employed to unite the bones which compose a joint ; theyalso will be found uniting some of the inlerarticular 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 synovial 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.); 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 ana enclosed within the ligamentous capsule. Liga- * Comp. Anat. vol. i. p. 83. t Syndesmologia, $ 5. t lieclard, Anat. Gen. ARTICULATION. 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 accessory 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 enarthrosis 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 fibre-cartilage. In ginglymoid joints they are always placed on the sides, and are called lateral ligaments ; sometimes they cross or decussate with each other, whence the appellation crucial, ar.d 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 joint 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 jaune,) as well as by its elasti- city. We find it in the human subject most developed in the ligamenta subjlava of the vertebra. 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 2ol 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; and 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 epiploica.' 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, (fig. Ill,) representing a vertical section of the knee-joint. The cut margin of the synovial membrane is indicated by a, 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. Anat. Lect. 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 Soemmerring 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 MagendieJ Blandin,§ and more re- cently by Gendrin|| and Velpeau.^ 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 Bled. tom. 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. t Compcnd. of Physiology, by Milligan, p. 450. § Additions a Bichat, par Beclard et Blandin, p. 345. || Hist. Anat. des Inflam. t. i. p. 60. 11 Anat. Chir. cd. 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 : I, 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- tdage ; 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 9 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. f Vide the 17th, 18th, 19th, 21st, and 22d cases recorded in Sir B. Brodie’s work. t Cruveilhier, loc cit. § He confesses, “ ma conviction n’est pas cepen- dant pleine et entiere.” ARTICULATION. to explain without admitting either the exist- ence of the synovial membrane, or the organi- zation* of the cartilages. Velpeau ,f 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, 1 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 ait. ARTICU- LATIONS, Maladies des. Diet, de Med. f Loc. cit. v. i. p. 173. $ See Home’s Paper, in Trans, of a Soc. for the improvement of Med. and Chirurg. Knowledge, v. i. 1793. 253 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 H aversion glands. f 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 urticularis. 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 weie they kept together by an uncontractile ligamentous capsule alone ; hence the elongation of the arm which ap- * Osteologia Nova : Loud. 1691. t Weitbrecht railed these fatty bodies, “ Adi- poso-glanduloso? ; ” and Cowper, “ mucilaginous glands.” See them figured in Monro’s work on the Burste, 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 : 1 believe there is no fact in anatomy, more generally admitted or better 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, d 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 (avv, cum, and agS^or, 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 (ha., per, and agQgov): 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. c. 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, Vesab). — 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 veru, of which three kinds are distinguished : sutura dentata, where the processes are long and dentiform, as in the interparietal 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 (a^u, 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, lamina:, and spinous processes ofthe vertebrae 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. f See Giant’s Comp. Anat. p. 83, fig. 43. 4 Cuvier, Lecons d’Anat. Comp t.. i. p. 125. ARTICULATION. 25 5 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. b. Schindylesis Jissio, crpri £lw, diffindu ).- — This form of articulation is where a thin plate of bone is received into a space or cleft formed by the separation of two lamina of another, as is seen in the insertion of the azj'gos process of the sphenoid bone into the fis- sure on the superior margin of the vomer ; and in the articulation of the lacrymal bone with the ascending process of the superior maxillary. c. Gomphosis (yopipos, clavus. Clavutio, cone lava tio ). — When a bone is inserted into a cavity in another, as a nail is driven into a board, or as a tree is inserted into the earth by its roots, the articulation is by gomphosis. The only example we have of it in the human subject or in quadrupeds is in the insertion of the teeth into the alveoli. In the weapon of offence of the saw-fish we find also an example in the manner in which the strong- osseous spines are inserted like teeth into its lateral edges. Cuvier mentions a variety of gomphosis, the only modification of the above : it is where a bony process grows from the bottom of the recipient cavity, and is inserted into a cavity in the base of the received bone or hard part. This is the mode of articulation of the nails with the ungueal phalanges in animals of the cat kind ; the nail is received into an osseous sheath, from the bottom of which the body of the phalanx projects and fills up the cavity of the nail. A similar pivot grows from the bottom- of the alveoli, into which the long canine teeth of the walrus are inserted. d. Amphiarthrosis utrinque, a^^ov, articulus, i. e. a mixed form of articulation. Articulatio dubia, Bartholin . Synarthrosis diar- throdica). — This is a form of articulation where two plane or mutually adapted surfaces are held together by a cartilaginous or fibro-cartilaginous lamina of considerable thickness, as well as by external ligaments. In virtue of the elasti- city of the interposed cartilaginous or fibro- cartilaginous lamina, the amphiarthrosis pos- sesses a manifest, although certainly a very limited degree of motion, and hence most systematic writers class it with the diarthrodial articulations. To me it appears much more consistent to place it among the synarthrodia! joints, for, 1. its anatomical characters agree precisely with those of synarthrosis; 2. the surfaces in amphiarthrosis being continuous, it would make an exception in diarthrosis were * Meckel, Anat. Comp. (Fr. transl.) t. ii. p. 43. we to place it there; and, 3. its degree of motion is greater than that of suture, only because of the greater development of the in- terosseous substance. These points of similarity led some anatomists to call it Diarthrosis syn- arthrodica ; for the reasons above stated, as well as because it has one point of resemblance to diarthrosis in its greater latitude of motion, I propose the appellation Synarthrosis diar- throdica. The examples of this form of joint in the human body are the articulation between the bodies of the vertebrae, that between the two ossa pubis at what is called the symphysis, and that between the ilium and sacrum. We may also, I think, place here the articulation of the ribs with the sternum by means of the costal cartilages.* The bodies of the vertebrae in most of the mammalia are articulated in the same way ; so are they in fishes also ; but in these last there is a peculiarity already re- ferred to, which increases the degree of motion of which the joint is susceptible. f Like the sutures, the amphiarthrosis is liable to become obliterated by age, and from the same cause, namely, the ossification of the interosseous la- mina. This is very common in the costo-sternal joints, less so in the interpubic, and still more rare in the inter-vertebral and sacro-iliac. Diarthrosis. — Evident mobility is the dis- tinguishing characteristic of this class of joints; the articular surfaces are contiguous, each co- vered by a lamina of cartilage ( diarthrodial cartilage ), having a synovial sac, and in some cases two synovial sacs interposed, which are separated by a meniscus. The in- tegrity of the articulation is maintained by liga- ments which pass from the one bone to the other. Their mechanism is much more com- plicated than that of synarthrodial joints, being intended not only for security, but also to give a certain direction to the motions of which they are the centre. Before proceeding to the enumeration of the varieties of joints that come under this head, it will not be amiss to describe briefly the various motions which may take place between any two segments of a limb, and which it is the object of these joints to admit of. It is obvious that the most simple kind of motion which can exist between two plane or contiguous surfaces, is that of gliding : one surface glides over the other, limited by the ligaments which extend be- tween the bones. This motion, however, is not confined to plane surfaces, it may exist evidently between contiguous surfaces whatever their form. When two segments of a limb, placed in a direct line or nearly so, can be brought to form * It may be objected to this arrangement that at the sternal extremity of each cartilage there is a synovial membrane between it and the sternal depression. All anatomists agree in denying its existence at the articulation of the first cartilage, and all admit the great difficulty of fully demon- strating its existence in the others. For my own part I do not believe that it exists in any. f The articulation of the lower jaw in the whale- bone whale, above referred to, is a joint of this kind. 256 ARTICULATION. an angle wiih each other, the motion is that of flexion, the restoration to the direct line is ex- tension. These two motions belong to what Bichat calls limited opposition ; the flexion and extension of the fore-arm on the arm illustrate it. Sometimes a motion of this kind takes place in four directions, indicated by two lines which cut at right angles. This is best under- stood by a reference to the motions which take place at the hip-joint : there it will be seen that the thigh-bone may be brought forward so as to form an angle with the trunk, flexion — or it may be restored, extension ; it may be sepa- rated from the middle line of the body so as to form an angle with the lateral surface of the trunk, abduction — or it may be restored and made to approximate the middle line, adduc- tion. Bichat terms this “ opposition vague.” It is evident that a joint, which is suscepti- ble of these four motions, may also move in directions intermediate to them. When these motions are performed rapidly, one after the other, it appears as one continuous motion, in which the distal extremity of the bone describes a circle indicating the base of a cone whose apex is the articular extremity moving in the joint; this motion is called circumduction. Rotation is simply the revolving of a bone round its axis. It is important to bear this definition in mind : through losing sight of it many anatomists have attributed rotation to a joint which really does not possess it. The varieties of the diarthrodial joint are as follows : a. Arthrodia ( articulatio plana or plani- formis.J — In this species the surfaces are plane or one is slightly concave, and the other slightly convex: the motion is that of gliding, limited in extent and direction only by the ligaments of the joint or by some process or processes con- nected with the bones. The examples in man are, the articular processes of the vertebra;, the radio-carpal, carpal, carpo-metacarpal, infe- rior radio-ulnar, superior tibio-fibular, tarsal and tarso-metatarsal, temporo-maxillary, acro- mio-clavicular and sterno-clavicular joints. This last articulation and the wrist-joint possess a greater latitude of motion than the others ; the former, in consequence of the shape of its articular surfaces : each surface is convex in one diameter and concave in the other, so that the gliding that takes place in this joint is in the direction of the long and short diameters, which intersect each other at right angles. It is capable, therefore, of vague opposition in those lines, but certainly not in the interme- diate directions, the nature of the surfaces being calculated to prevent this. The wrist owes its mobility to the laxity of its ligaments, which permit it to move as well in its transverse as in its' antero-posterior diameters, as also in the in- termediate directions; it consequently admits of vague opposition and circumduction. The articulation of the metacarpal bone of the thumb with the trapezium, is also an arthrodia very similar to the sterno-clavicular, but with a greater degree of motion. Arthrodial joints are generally provided with ligaments, placed at the extremities of the lines in the direction of which the gliding motion takes place. b. Enarthrosis ( diarthrosis orbicularis — ball- and-socket joint.) — This is a highly developed arthrodia. The convex surface assumes a glo- bular shape, and the concavity is so much deepened as to be cup-like, hence the appella- tion ball and socket. The ball is kept in appo- sition with the socket by means of a capsular ligament, which is sometimes strengthened by accessory fibres at certain parts that are likely to be much pressed upon. The best example of enarthrosis is the hip-joint, and next to it the shoulder: in the latter the cavity is but imper- fectly developed. All the quadrupeds have their shoulder and hip joints on this construc- tion, and the same common plan is observed in the vertebrata generally whose extremities are developed. In birds and reptiles the bodies of the vertebrae are articulated by enarthrosis, and the solid calcareous spines on the external surface of the shells of echinida are adapted to round tubercles on which they move, thus ex- hibiting a very complete form of enarthrosis.* This species of joint is capable of motion of all kinds, opposition and circumduction being the most perfect, but rotation limited. Indeed what is called rotation at the hip-joint, is effected by a gliding of the head of the femur from before backwards, and vice versa in the acetabulum ; it is not a rotation of the head and neck, but of the shaft of the femur. c. Ginglymus (yiyyAt^Ao;, cardo, articulatio cardiniformis, articulation en charniere, enge- nou, hinge-joint.) — The articular surfaces in the hinge-joint are marked with elevations and depressions which exactly fit into each other, so as to restrict motion in all but one line of direction. They are always provided with strong lateral ligaments, which are the chief bonds of union of the articular surfaces. The elbow and ankle joints in man are per- fect ginglymi ; the knee also belongs to this class, but is by no means a perfect specimen, for in a certain position of the bones of this joint, the ligaments are so relaxed as to allow a slight rotation to take place. The phalangeal articulations, both of the fingers and toes, are ginglymi. This form of joint is most exten- sively employed among the lower animals. In quadrupeds, most of the joints of the extremi- ties come under this head. In amphibia and reptiles, too, there are many examples of the hinge-joint. The bivalve shells of conchiferous mollusca are united by a very perfect hinge, and a great number of the joints of Crustacea and insects are of this form. The true ginglymus is only susceptible cf limited opposition : hence the knee-joint can- not be regarded as a perfect example ; in fact, in the perfect ginglymus there is every possible provision against lateral motion. d. Eiarthrosis rotatorius ( commissura tro- choides.) — A pivot and a ring constitute the mechanism of this form of joint. The ring is * Vide fig. 9 in Grant’s Comp. Anat. p. 21. See also the article EcuiNODliRMATA. ASPHYXIA. 257 generally formed partly of bone and partly of ligament, and sometimes moves on the pivot, sometimes the pivot moves in it. The motion is evidently confined to rotation, the axis of which is the axis of the pivot. In the human subject the best example of this articulation is that between the atlas and odontoid process of the axis or vertebra dentata. The ring is formed by a portion of the anterior arch of the atlas, completed behind by a trans- verse ligament. Here the atlas rotates round the odontoid process, which is the axis of mo- tion. Another example is the superior radio- ulnar articulation : here the ring is formed one- fourth by bone, namely the lesser sigmoid cavity of the ulna, and the remaining three-fourths by the round ligament called the coronary ligament of the radius. In this case there is rotation as perfect as in that just mentioned, but the head of the radius rolls in the ring, and the axis of motion is the axis of the head and neck of the bone. Some anatomists consider this joint a species of ginglymus, which they designate lateral. The terms Symphysis, Synchondrosis, Syn- neurosis, Syssarcosis, Meningosis, have been employed by anatomists to designate certain kinds of articulation, chiefly in reference to the nature of the connecting media. Symphysis, although originally employed with great extent of meaning, seems to have been in later days applied exclusively to denote the articulations of the pelvis, which we have classed under Amphiarthrosis. I pass over the other terms, because they ought to be discarded from use, as only tending to encumber a vocabulaiy already too much crowded with difficult and unnecessary terms. The descriptive anatomy of the several joints will be found under the heads — Ankle, Cra- nium, Elbow, Face, Foot, Hand, Hip, Knee, Pelvis, Radio-ulnar, Shoulder, Spine, Temporo - maxillary, Tibio-fibu- lar, Wrist, and the morbid anatomy under the head Joint. Bibliography. — Havers, Osteologia nova, 8vo. Lond.1691. Saltzmann, De Arliculationibus Artuum, Argent. 1712. Walther, De Articulis, Ligamentis, &c. 4to. Lips. 1728. Neumann, Lehre von d. Articulationen d. menseh. Koerpers, Freiberg, 1745. Isenfiamm, Diss. de Ginglymo, 4to. Erlang. 1785. Bonn, De Suturarum co:p. hum. fab. et usu. Lips. 1763. Haase, De unguine articulari ejusqne vitiis, 4to. Lips. 1774; Ej. De fabrica cartilaginum, 4to. Lips. 1767. Petschel, De Axungia articulari. Lips. 1740 (Recus. in Halleri Diss. Anat. select.). Weit- brecht, Syndesmologia, 4to. Petrop. 1742 (decidedly the best work extant on the descriptive anatomy of the ligaments). Hunter, W. on the structure and diseases of articulating cartilages, Philos. Trans. 1743. Schaar schmidt, Syndesmologische Tabellcn, 8vo. Lange. 1782. Monro on the Bursas mucosae, fob Edinb. 1788. Heysigers , Diss. Phys. Anat. de fabrica intima articulationum, 8vo. Traj. ad Rhen. 1803. Loschge , Die Knochen, & c. des menseh. Koerp. fol. Erlang. 1804. Bichat, Mem. sur la membrane synoviale des articulations, Mem. de la Soc. Philom. An. 6. Dickinson, A syndes- mological chart, 8vo. Lond. 1821. Cooper, B. on the ligaments, 4to. Lond. 1825. Cruveilhier, Sur les cartilages diarlhrodiaux. Arch. Gen. de Med. Fevrier, 1824. Bichat, Anatomic generale. Beclard, Anatomie generale. (The older and likewise the VOL. i. newer systems of anatomy are mostly deficient in syndesmology ; the works of Bichat and Boyer, however, form exceptions, and are well deserving of a careful perusal : the descriptions in the Traite des Maladies Chirurgicales, t. iv. of the latter, are also very excellent ; and one of the most minute and accurate accounts we have of the ligaments is contained in the magnificent work of Messrs. Bourgery and Jacob, now in the course of publica- tion : Traite complet de l’anatomie de l’homme ; Anglice, The whole anatomy of the human body, by R. Willis, fol. Paris and Lond.) (R. B. Todd.) ASPHYXIA. (Gr. A<7ipufia. Fr. Asphixie. Ger. Scheintod, Asphyxie. Ital. Asfissiu) The word Asphyxia, according to its derivation (from a and acpv^n, pulsus,) ought to signify what is usually expressed by the term Syncope, i. e. failure of the heart’s action ; but it is now always used to express failure of the process of respiration. It is hardly necessary to say, that there is no more general law of vital action, in all classes of organized beings, than its dependence on oxygen, i. e. on a certain chemical action taking place between the nourishing fluids of that living body (whether animal or vegetable) and the oxygen of the atmosphere. This law is, indeed, as general as the dependence of vital action on heat, and in like manner as a certain elevation of temperature (short of what acts chemically on the organized textures) is destructive to life, so a certain concentration of oxygen in the air inhaled, at least by the higher orders of animals, affects them as a poison.* Many organized substances, as the seeds, roots, and stems of vegetables, the pupae of insects, eggs, even perfect animals of some of the lower classes, may retain their vitality, as is commonly said, i. e. remain susceptible of vital action, for very various periods of time, at low temperatures, without exercising any action on the oxygen of the atmosphere ; but whenever the phenomena indicating vital ac- tion take place in them, exposure to oxygen, and a certain alteration of the air surrounding them, very soon become necessary conditions of the continuance of vitality. The alterations which take place in the air in contact with different living bodies are some- what various. Water is exhaled probably in every instance. In the case of some animals, particularly fishes, there is certainly an absorp- tion of azote ; and in that of vegetables growing under the influence of light, there is a decided absorption of carbon from the carbonic acid of the atmosphere, and an evolution of pure oxygen. But it is now generally agreed, that, in all cases, the action between the atmosphere and the nourishing fluid which is essential to the motion and vivifying power of the latter, is that which is denoted by the disappearance of part of the oxygen from the air that comes in contact with that fluid, and the substitution of a quantity of carbonic acid. Some time since it was the prevalent opinion, that the nature of that action was merely an * See Broughton in Journal of Science, 1830. S 258 ASPHYXIA. excretion of carbon, which immediately on its being evolved from the nourishing fluid, en- tered into combination with the oxygen of the air, and was carried off; and the chief reason for this opinion was, that the volume of oxy- gen which disappeared in the process, was believed to be just equal, in all cases, to that of the carbonic acid that appeared. As it is known that the volume of any quantity of carbonic acid is just the same as that of the oxygen contained in that quantity of acid, if the fact had been as above stated, the coinci- dence could hardly have been accidental, and the inference would have been nearly inevitable, that the oxygen of the atmosphere did not enter the nourishing fluids, but merely dissolved and carried off the excreted carbon. But the numerous experiments of Dr. Ed- wards* * * § and of M. Du Long,f seem to have nearly established the proposition, that in the respiration of by far the greater number of animals, the volume of oxygen that disappears from, is somewhat greater than that of the carbonic acid that appears in, the air employed : the same result was obtained in experiments by Allen and Pepys on birds and if this be so, it is certain that the respiration of these animals is attended with an actual absorption of oxygen, at least to a certain extent. This conclusion authorizes us to inquire far- ther, whether it is not more probable, that the whole of the oxygen which disappears from air in contact with the nourishing fluid of living beings, is absorbed into that fluid, and that the carbonic acid which appears is exhaled, ready formed, in its place. And several facts shew that this is by far the more probable suppo- sition ; and that oxygen is essential to vital action, not merely as a means of carrying off superfluous carbon, which has become noxious; but as itself an ingredient in the nourishing fluids, necessary for the maintenance of their motion and vivifying power. But without entering at length into this question, which will be more fully discussed under the head of Respiration, it is obvious from what has been said, that provision must be made, in the oeconomy of all living beings, for the exposure of their fluids to the air of the atmosphere, in circumstances admitting of ex- halation and absorption ; and it may be farther stated, that, in the different classes of animals, the amount of this mutual action for which provision has to be made, must be proportioned to the energy and activity of vital action which each animal is destined to exhibit, these qualities being very generally found to be greater, as the consumption and vitiation of the air are more rapid.§ These principles explain the intention of many different contrivances and arrangements, afterwards to be described, which are em- ployed in different classes of animals for the performance of the function of respiration; and the variations of which may be said, in a gene- ral view, to be determined by two conditions, first by the medium in which each animal is destined to exist, and secondly, by the inten- sity and variety of vital actions which it is to be capable of performing. The importance, to all living beings, of the action of oxygen on their fluids is most un- equivocally shewn by the nature of the fatal changes which ensue, when that action is in any way obstructed ; i. e. by the nature of the changes which take place in death by asphyxia. The study of these has long been held to be of the highest importance, not only as a car- dinal point in physiology, but as affording the only precise information in regard to the fatal tendency of many and various diseases. It is chiefly in animals of the highest orders, i. e. in warm-blooded animals, that these phe- nomena have been studied ; and it is to be remembered, that in them the subject is ren- dered more complex by the higher endow- ments and greater power over all functions of the body, which the nervous system there possesses. When we trace the connection, in these animals, of the different changes that precede the fatal event, it is right to bear in mind, that the in- terruption of the process by which their fluids are exposed to the air is equally fatal, not only to those animals in which no action of the ner- vous system is concerned in that process, but also in vegetables, where no nervous system exists. The phenomena of asphyxia in the higher animals are very nearly the same, in whatever manner the access of air to the organs of respi- ration is prevented. This may be done, in the case of animals that breathe by lungs, in a great variety of ways ; by strangulation or suf- focation, i. e. by any mechanical means pro- hibiting the ingress of air by the trachea and bronchi ; by submersion in water or any other fluid ; by confinement in vacuo or in such gases as contain no oxygen, but are not them- selves poisonous, such as azote and hydrogen ; by forcible compression of the thorax, prevent- ing its dilatation ; or by the admission of air into free contact with the surface of the lungs on both sides of the chest, so as to prevent their distension, as in the celebrated experiment of Dr. Hooke ; or by the section, either of all the separate nerves which move the muscles concerned in the dilatation of the thorax in inspiration, or of the spinal cord in the upper part of the neck, above the origin of the phrenics, by which the whole of these nerves are simultaneously palsied, as in many ex- periments of Galen, Cruikshank, Le Gallois, and others.* In the case of fishes or other animals that * Dc Plufluence des Agens Physiques sur la Vie, p. 410, et seq. + Journal cle Physiologie, t. iv. $ See Hodgkin’s Translation of Edwards, p. 486. § Sec Cuvier, La Rcgnc Animale, t. i. p. 56; also Marshall Hall, Philosophical Transactions, 1832, p. 339. * These last are the lesions of the nervous sys- tem which cause sudden death by asphyxia. Sec- tion of the par vagum, the sentient nerve of the lungs, produces death by asphyxia also, but slowly, and through the intervention of disease and disorganization of the lungs, to be afterwards no- ticed. ASPHYXIA. 259 breathe by gills, where several of the methods above enumerated are inapplicable, asphyxia is produced, either by confinement in air, or in distilled water, or water impregnated with any gas that does not contain oxygen ; for no ani- mal has the power of decomposing water by its organs of respiration, to obtain oxygen, and all aquatic animals are dependent, either on the occasional respiration of atmospheric air by lungs, or on the more constant respira- tion of the air contained in water by gills or analogous organs. In the case of fishes breathing by gills, as the motion of these organs is dependent on nerves arising as high as the medulla oblongata, injury of the nervous system must be as high as that part, in order to produce asphyxia ; and on the other hand, in the case of birds, where the expansion of the thorax in inspira- tion is effected almost entirely by the motion of the ribs, asphyxia may be produced by section of the spinal cord in any part of the neck.'* We exclude here entirely the cases, often described under the name of asphyxia, in which gases positively noxious (such as carbonic acid, carburetted hydrogen, &c.) have been breathed, because accurate observation shows that these are in fact cases of poisoning, where the poison has been introduced by the lungs, and not simply cases of asphyxia. The phenomena of asphyxia, in all the cases above-mentioned, (as occurring especially in the warm-blooded animals,) may be divided into three stages. The first is characterized by the intensity of the sensation which prompts to acts of inspiration, and the consequently violent and laborious, though ineffectual attempts to appease that sensation by the action of all the muscles of inspiration; and in some in- stances by other actions, voluntary or instinc- tive, but still under the guidance of sensibility. Lividity of the surface takes place before the end even of this stage. The next is distinguished by insensibility, rapidly increasing, and attend- ed with irregular spasms or convulsions ; and the last by cessation of all effort, and of all outward signs of life, while the heart’s action and circulation are known still to go on for a short time. In the case of a warm-blooded animal (ex- cluding the cetacea, and animals that habitually dive) in the full possession of its vital powers, exposed to complete and sudden obstruction of the access of air to the lungs, it may be stated, that the two first of these stages are very generally over within three minutes, seldom extending to live, and that the circulation through the heart has very generally ceased within less than ten minutes from the commencement of the ob- struction. The time during which the priva- tion of air can be borne may be somewhat ex- tended by habit ; and there are instances of men trained to diving in India who have re- mained under water three, four, or even five minutes without loss of sensibility or subse- quent injury. In cases of disease, terminating in death by asphyxia, all these stages may often be observed to be distinctly gone through, although in a very gradual and somewhat irregular manner ; the dyspnoea and lividity being succeeded by delirium, often by spasms, and ultimately by coma, and the respiration coming to a stand in general a little before the action of the heart. The most characteristic appearance which is seen after death by asphyxia, is simply the great accumulation of blood in the vessels of the lungs, in the pulmonary artery, right side of the heart, and great veins, and the compara- tively empty state of the left side of the heart, the larger pulmonary veins, and the aorta. The left ventricle is not found empty after death, but seldom contains half as much blood as the right; and it is in this part of the heart that the contractions are soonest observed to cease. The accumulation of blood in the lungs and right side of the heart is greatest in cases where the asphyxia has been gradual, the access of air to the blood not having been absolutely obstructed.* Besides this appearance of congestion of blood in the thorax, the liver, the spleen, and the whole venous system in the abdomen, are generally observed to be unusually congested in such cases, especially those parts which are depending after death ; and even ecchymosis on the mucous membrane of the stomach, after strangulation, has been observed by, Dr. Yelloly and others. This congestion of blood in the liver, and in the veins of the abdo- men, is remarkably observed, and leads to important consequences, in various chronic diseases of the thorax, threatening death by asphyxia. The hlood after this, as after other kinds of sudden or violent death, is usually found fluid, and very imperfectly coagulated ; and in connection with this state of the blood there are frequently livid marks resembling ecchy- mosis, (though not depending on extravasation of blood,) in various parts of the surface of the body, and not exclusively in depending parts. This appearance is, of course, most remarkable in the face and neck after strangulation, and is much less observed on any part of the surface after drowning. After strangulation, if the body is soon ex- amined, congestion of blood in the vessels of the brain and pia mater may often be remarked, but there is seldom any morbid effusion. After drowning, a frothy fluid, in consequence of the introduction of a small quantity of water, and of efforts at respiration, is generally found in the trachea and bronchi. The successive steps by which physiolo- gists have been led to what we may regard as a satisfactory account of the phenomena now described, and of the death by asphyxia, may be recapitulated, as curious in themselves, and as affording the clearest view of the evidence on which the doctrine, which now appears to be wed founded, is supported. * Flourens in Annales d’Histoire Naturelle, * Bichat, Recherclies Physiologiques, Sec. (4th bb edit.) p. 333. ASPHYXIA. 2 GO 1. Tlie first opinion on this subject, which need be noticed here, is that which was sup- ported by the great Ilaller, viz. that the circu- lation, and with it all other functions of the body arc brought to a stand, because when the movements of respiration cease, and the lungs are no longer dilated and contracted, there is a mechanical difficulty to the propulsion of the blood through the pulmonary capillaries, by which the fatal stagnation in these vessels, ob- vious on dissection, is produced. This doctrine was satisfactorily refuted by Goodwyn, in his treatise on the Connection of Life with Respiration, who shewed that the air-cells of the lungs are not necessarily con- tracted at the time of asphyxia, and that after having once admitted air, these cells never are so much emptied of it again, or contracted on themselves, as to offer any considerable impe- diment to the free motion of blood in their parietes. Besides, we know that the same stagnation in the lungs takes place in the case of an animal confined in a gas which does not contain free oxygen, as in the case of drowning or strangulation, although in the former case, any impediment to the mechanical acts of re- spiration that can occur, must be the conse- quence, not the cause, of the fatal changes within the chest.* 2. The well-known theory of Goodwyn him- self on this subject was, that the venous blood is not an adequate stimulus to the left side of the heart, which in the natural state circulates arterial blood only, and which fails to contract upon or propel blood which has passed un- changed through the lungs, j- This doctrine was, in its turn, refuted by Bichat, who showed by experiment that in the case of strangulation the venous blood does penetrate the lungs and left side of the heart, and is delivered from the carotid arteries if these are punctured ; that the appearance of venous blood in these arteries is contemporane- ous with what was described as the second stage of asphyxia, viz. the insensibility and spasms ; and further, his experiments have been generally admitted as affording satisfac- tory evidence, that the circulation of venous blood through the brain is a sufficient cause for these symptoms, and produces them when the venous blood from the heart of one dog is sent to the brain of another. J He also found by experiment, that venous blood could be in- jected artificially into the left cavities of the heart, with the effect of exciting, not suppress- ing their action.§ 3. Bichat ascribed the cessation of the circu- lation in asphyxia, however, not to the penetra- tion of the brain by venous blood, and the consequent insensibility (which is now well known to be compatible with the maintenance of circulation for many hours, provided the * fins point has been further elucidated by some experiments, of which an account was read, by the author of this article, to the Medical Sections of the British Association. t Connexion of Life with Respiration, p. 02. t Recherches Physiologiques, &c. Art. vii. $ Recherches, &c. p. 327. blood can be arterialized,) but to the penetra- tion of the muscular substance of the heart by venous blood, sent to it by the coronary arte- ries, and which he held to be equally (although less rapidly) fatal to the vital action of this organ, as of the brain or nerves. 4. Later experiments and observations have, however, shewn that this explanation likewise is, in some measure, incorrect. In fact, while the free flow of venous blood in the carotid arteries of an asphyxiated animal was urged with perfect fairness by Bichat, as a refutation of the theory of Goodwyn, it was with equal justice argued by Goodwyn,* in opposition to Bichat, that if the heart’s actions ceased in asphyxia, only because its substance is pene- trated by venous blood from the coronary arte- ries, these actions could not be restored by blowing air into the lungs and arterializing the blood there. Bichat, indeed, foreseeing this objection, maintained that the artificial respiration never is successful in restoring the circulation, unless employed in the interval which, as was already stated, always exists between the occurrence of insensibility and the final cessation of the circu- lation. But subsequent and careful observa- tions (e.g. those of Roesler, Edinburgh Journal, vol. xxiii) show that life has been restored, by this means, after warm-blooded animals have lain from twelve to seventeen minutes after their immersion in water, i. e. until a time when all observations made by laying open the chests of similar animals show that their circulation must have ceased. The records both of the Humane Society in London and of a similar institution in Paris, seem sufficiently to show that resuscitation has occasionally taken place in the human body after fifteen minutes’ im- mersion.f And we are therefore well assured that the arterial ization of the blood at the lungs may, in some instances, restore the natural state of the heart’s action after the circulation has come to a stand. Farther, although there is a laboured attempt, by Bichat, J to explain the accumulation of blood on the right side of the heart, and the comparative emptiness of the left side, in as- phyxia, consistently with his own explanation of the failure of the circulation ; yet it seems obvious, that if that explanation were correct, the left side of the heart, receiving the venous blood and contracting on it until it loses its power from the penetration of its own fibres, should be found after death distended with that blood ; and that the accumulation of blood taking place in the lungs and right side of the heart, indicates that the capillaries of the lungs are the main seat of the cause which ultimately stops the circulation. That this is really the fact has been more unequivocally shown, first, by the experiments by Dr. Williams, and afterwards by those of * In a paper, not published till after his death, but contained in the Edin. Med. and Surg. Journal, July 1830. t See Cyclopaedia of Practical Medicine, art. Asphyxia. | Recherches, &c, art. 6. ASPHYXIA. 261 Dr. Kay,* which we know to have been care- fully performed, and sufficiently repeated, and which appear to solve satisfactorily all the diffi- culties that have been stated. Bichat had not adverted to the length of time during which the circulation of venous blood by the left side of the heart, is carried on in asphyxia; but the experi- ments of both Dr. Williams and Dr. Kay prove, that this time is very short, and that before this side of the heart has lost its contractile power, the pulmonary veins have ceased to deliver the blood to it, in such quantity as to maintain any effec- tive action. A short quotation from Dr. Kay’s paper will show the evidence for this propo- sition. u Experiment 1. The trachea of a large rabbit was tied, the abdomen and chest opened, and at the end of the second minute from the commencement of the experiment, the external iliac artery was divided ; a considerable quantity of dark blood flowed, but at the third minute it had almost ceased to escape. The heart continued contracting vigorously ; very small quantities of dark blood collected slowly every twenty seconds at the extremity of the artery. In five minutes all flow of blood had entirely ceased. The left heart contracted spontaneously for a very considerable period longer. I repeated this experiment with simi- lar results. ”f Again, one of the variations of the experiment was as follows : “ Experiment 3. A rabbit was asphyxiated by tying the trachea. The chest was opened. At the end of three minutes and a half no pulse could be discovered in the aorta. The left auricle was then opened, the blood contained escaped, and for a period of from one to three minutes, blood occasionally collected in very minute quantities, as though it gradually drained from the larger vessels of the lungs, but never , as often as the experiment was repeated, collected in quantity. The heart continued vigorous the usual period.” “ In general,” says Dr. Kay, “ the pheno- mena of the cessation of motion in the left heart in asphyxia are these. A smaller quantity of blood is received into its cavities, and expelled for a time vigorously into the arteries. The ventricle meanwhile diminishes in size, as the quantity of blood supplied becomes less, until at length, although spontaneous contractions still occur in its fibres, no blood issues from a divided artery, and the ventricle, by contrac- tion, has obliterated its cavity. After this, blood slowly accumulates in the auricle from the large vessels of the lungs ; and its con- tractility continues for a very considerable period. Farther experiments by Dr. Kay show, that after the aorta of an animal has been tied, and after the muscles of its lower extremities have, iu consequence, gradually lost all contractile power, that power is restored for a time by the injection of venous blood into the lower portion of the aorta ;§ and from these, and from some * Edinburgh Medical and Surgical Journal, vol. xix. and xxix. t Edinburgh Journal, vol. xxix. p. 42. t Ibid, p. 46. $ Ibid, p, 53 and 54. experiments by Dr. Edwards,* we learn, that the venous blood, though less powerful than arterial in maintaining the vital power of mus- cles, is by no means rapidly destructive to it. The changes in asphyxia, in the warm-blooded animals, have, therefore, of late been generally thought to be as follows :■ — that the venous blood, though more or less noxious to all parts of the body which it fully penetrates, is nevertheless transmitted through thelungs in the first instance, in sufficient quantity to stimulate the left side of the heart, and is sent from thence in sufficient quantity to penetrate the brain — that by its action there it destroys the sensibility, but that it passes more and more slowly through the pulmonary vessels, and after a few minutes is no longer delivered to the left side of the heart in such quantity as to keep up regular and efficient contractions there ; and that thus, while the animal life is suddenly extinguished by the noxious influence of venous blood on the brain, the organic life is more gradually brought to a stand by its noxious influence in the lungs, and the consequent failure in the supply of blood to the left side of the heart. This explanation is consistent with all the phenomena, and particularly with the very rapid restoration of the flow of blood by the admission of air to the lungs of half-asphyxiated animals, stated by Bichat himself as a difficulty in his view of the subject. The more recent experiments by Dr. Kay had, however, led him to question the validity, even of that part of Bichat’s doctrine, which has been most generally admitted, viz. the ra- pidly noxious effect of venous blood on the brain and nerves. He found, in various cases, that large quantities of blood from the veins of one rabbit could be injected (slowly and cau- tiously, so as to avoid all injury of the cerebral matter) into the carotid arteries of another, with- out causing more than muscular debility and lassitude ; so that he considers venous blood to be only a weaker stimulus to the brain than arterial, not a direct poison to it; and thinks the sudden insensibility of asphyxia is to be explained by the rapid diminution of the quan- tity, not by the change of quality, of the blood sent to the brain from the heart.f And when we bear in mind the fact stated in the outset of this inquiry, that the motion and vivifying power of the nutritious fluid is dependent on its exposure to oxygen, not only in the higher animals, but even in the lowest tribes, and in vegetables, where neither heart nor nervous system exists ; it appears reasonable to suppose, that the chief impediment to the blood’s motion, from the failure of the supply of oxygen, will be in the lungs themselves, where the venous blood is accumulated in the greatest quan- tity, and where all the minute vessels carrying it must be most completely exposed to its action, But before we can be completely satisfied upon this subject, it will be necessary to carry the inquiry one step further, and to ascertain in what manner the change from venous to * De rinfluencc, &c. p. i. ch. i. and p. iv. ch. 4- t Treatise on Asphyxia, p. 193 et scq. 202 ASPHYXIA. arterial blood so greatly promotes the flow of blood through the capillaries of the lungs, and how the presence of venous blood in the begin- nings of the pulmonary veins can so effectually retard it, that the action of the right ventricle of the heart, though continuing vigorous for a time thereafter, fails of its wonted effect, and the blood stagnates in those capillaries. The common expression employed on this subject is, that arterial blood is a stimulus peculiarly adapted to excite the capillaries of the lungs and pulmonary veins ; and that venous blood stagnates in those capillaries for want of power to excite them. But it must be remembered that we have no distinct evi- dence of the existence of coats, still less of irritable coats in the minute capillaries of the lungs that although the circulation there has been often examined with the microscope, no contraction of the vessels has ever been ob- served ; that the only vital power of contrac- tion which experiments authorize us to ascribe to any arteries, is a power of permanent or tonic contraction on their contents, which, when called into action, lasts for some time, and while it lasts must obviously impede the flow of fluids through these vessels ; that on these grounds Magendie and other eminent physio- logists believe the only power, which arteries can exercise over their contents, to be simply a power of either relaxing, so as to give them a free passage, or contracting so as to lessen and re- tard their flow ;j- and that, conformably with these views, it was found by Wedemeyer, that when he injected stimulating liquids into the arteries of living animals, they were much longer of making their way into the veins, than mild liquids were.J These considerations evidently point to the conclusion, that, if the difference depend on any vital action of vessels, venousblood, which makes its way so slowly through the capillaries of the lungs, must be the stronger stimulus to them, and that arterial blood, which is transmitted so readily, must act as a sedative, to the only vital action of which these vessels are susceptible. But this conclusion is again strongly opposed by the fact, that in all other instances, in relation to muscular contraction, to the functions of the nervous system, and of secreting organs, arterial blood, and the oxygenated fluids in general, manifestly possess the stimulating power, and venous blood or carbonized fluids the sedative. In this difficulty it is important to remember, that we have many facts to indicate the exist- ence of powers which move the blood and other organized fluids in living animals, inde- pendently of any contractions of moving solids. It. would appear that the power by which any texture is nourished, or secretion or excretion is formed from the blood, in any part of the circu- lation, is, to a certain degree, a cause of move- ment of the blood towards that part, and that any stimulus given to such act of nutrition or secre- * See Marshall Hall on the Circulation, p. 47. t Physiology, translated by Milligan, p. 409-10. Mayo’s Outlines, (2nd edit.) p. 87 et seq I Edinburgh Medical Journal, July 1829, p. 90, tion, although applied at the extremity of the capillaries, produces an effect on the circulation which, as Sir C. Bell expresses it, is retrograde along the branches of the arteries. Thus, the flow of blood to the mucous membrane of the stomach and bowels during digestion, to the uterus during gestation, to the mammae during lactation, to any part of the body during inflammation, sup- puration, or the growth of a tumour, is excited by causes acting at the extremities of the arte- ries of these parts ; although there is the same difficulty in all these cases, as in the case of the lungs, in understanding how a cause acting there, and exciting the only vital power which arteries can be shewn to possess, should in- crease the flow of blood through them. It is always to be remembered, that pre- cisely analogous phenomena are observed from the application of heat, or other stimuli, to single branches, or roots, of vegetables, where there is no evidence of the existence, either of a structure or of a contractile power, in the vessels or cells through which the fluids pass, capable of giving them a determinate direction towards the parts, which are thus stimulated; and where the movement of fluids that can be seen, (in the case of those plants that have milky juices,) is not only unattended with any visible contraction of solids, but is of a kind, (as the recent observations of Scliultze, Amici, Raspail, and others indicate,) which no contractions of solids appear capa- ble of producing. It is farther to be observed, that when venous blood becomes arterial, it acquires an increase of fibrin,* and that its tendency to coagulation is decidedly increased, + which implies such an increase of an attraction of aggregation in the particles of the fibrin, as may be held to be strictly vital. And on the other hand, when arterial blood becomes venous, according to the microscopical observations of Kalten- brunner, its globules seem to separate some- what from one another, and its whole bulk ap- pears somewhat increased-! Lastly, it is to be remembered, that when a vessel is opened in a living animal, and the blood exposed to the air, the consequence is, a movement of derivation of the blood, in all directions, towards the aperture ; which is cer- tainly altogether independent of the heart’s action, and which the elaborate investigations of Haller led him (and apparently with good reason) to think inexplicable likewise by any contraction of vessels.§ The consideration of all these facts may lead us strongly to suspect, that the stimulus to the circulation which is given by the arte- rialization of the blood, and which we have found to act chiefly in the capillaries of tlie lungs, is of the nature of an attraction of the venous blood towards the part where it is to '* Prevost and Dumas, -An. dc Chimie, t. xxiii. f See particularly Schiceder Van der Kolk, Com. dc Sanguine Coagulante. $ Expcrimcnta circa Statum Sanguinis, &c. § 201 & 357. $ Mem. sur lc Mouveinent du Sang, p. 386 et scq. ASPHYXIA. 263 undergo this change, and towards the arterial blood in advance of it in the vessels ; not of the nature of an increased contraction of the vessels themsleves ; and that it is in conse- quence of the failure of this auxiliary power in the circulation, that the stagnation of the blood in the lungs in asphyxia, and the extinc- tion of the organic life, are effected. What has been said of the manner in which death is produced in asphyxia, enables us to understand in what circumstances it can hap- pen, that life may be retained, even by a warm-blooded animal, for an unusual length of time, without respiration. As the stop to the circulation is the immediate cause of death, it is obvious that an animal which can exist for a time, in a lowered state of vitality, with little or no circulation, will during that time require no exposure of its blood to air, to maintain that grade of vitality ; and farther that in such an animal, as the brain will not suffer from the afflux of venous blood, and as the lungs will not be hurtfully congested, these organs will retain a condition much better adapted for the recovery of their functions, than they will in those cases where asphyxia is produced at a time when the circulation is vigorous. Hence we can easily understand, that per- sons who are in a state of syncope, (from a temporary cause,) in whom the circulation is nearly at a stand before the access of air to their lungs is obstructed, may survive a longer suspension of the acts of respiration than per- sons in health. This has been stated, by Des Granges and Fodere, as the explanation of some cases in which it appears certain, that recovery has taken place after fifteen minutes or more of submersion in water.* The case of hybernatitig animals was, until lately, considered to be of this nature, i. e. it was supposed that circulation is gradually sus- pended in those animals, simultaneously with respiration, and therefore that such animals, although consuming little or no air, did not suffer the noxious influence of venous blood on their solids, and remained susceptible even of sensation. But the experiments of Dr. Marshall Hall f appear to have established that in warm-blooded hybernating animals in the complete state of torpor, when respiration is quite at a stand for many hours, circulation, although slow and feeble, still goes on regu- larly ; so that we must suppose the essential peculiarity of these animals, during the state of lowered vitality, to which they are reduced by cold, to be this, that the venous blood has little of the noxious effect, in any part of the system, which it has, on them as on other animals, during the state of activity ; it has neither the same difficulty of making its way through the lungs, nor the same destructive influence on the brain.]; * Fodere, Med. Legale, $ 613. t Phil. Transactions, 1832. t Dr. M. Hall considers the essential peculiarity of these animals to be, that the left side of the heart in them, is irritable by venous blood ; but as it appears from the facts above stated, that the The nearest approach to this mode of vita- lity in the human body, is in the case of the new-born child, which has never felt the in- fluence of perfectly arterial blood, and which has been known to live, although its natural respiration was not established for nearly an hour after birth. The study of the fatal changes in asphyxia is also of peculiar importance as illustrating the manner in which the circulation, and the organic functions maintained by it, are con- nected with the nervous system. It will be observed, that as the vitality of hybernating animals, during the state of torpor, is inde- pendent of respiration, so it is also, in a great measure at least, independent of the larger masses of the nervous system ; and Dr. M. Hall found, by experiment in a hedgehog in this state, that the circulation went on regu- larly for ten hours after the gradual but com- plete destruction of the brain and spinal cord. Indeed, the maintenance of the circulation after the head of an animal has been cut off, by the artificial respiration, i. e. by inflating its lungs in a manner resembling its natural breathing, (which has been so often practised by Fontana, Cruikshanks, Bichat, Brodie, Le Gallois, Wilson Philip, and others,) is in it- self a clear proof that the circulation, and other functions of organic life* in animals, are necessarily and immediately dependent on the animal life, only inasmuch as the natural respiration of animals, and the arterialization of their blood, are dependent on sensation. And ac- cordingly we know, that in that stage of animal existence, where the supply of sufficiently arterialized blood is provided for without the intervention of sensation, i. e. in the foetus in utero, the whole organic life is altogether in- dependent of the animal, and goes on perfectly, not only before sensation is felt, but even in cases where the essential organs of sensation and of voluntary motion, the brain and spinal cord, do not exist. It is not until the moment of birth, when the arterialization of the blood is put in dependence on sensation, — that the brain and spinal cord become essential for the maintenance of organic life ; or that we possess any proof of influence being exercised by the nervous system, over that part of the animal (economy. It seems probable, that if we possessed the means of making the artificial respiration ex- actly similar to the natural, and neither injuring the structure of the lungs, nor introducing more air into them than is useful, in practising it, the circulation, and perhaps all the func- tions of organic life, might be maintained, after the head of an animal is cut off, until nearly the time when it must fail for want of nourish- ment; but it must also be remembered, that in the adult animal, as the experiments of Le stop to the circulation in asphyxia is at the lungs, the chief peculiarity of these animals must lie there also. * By organic life, we mean those vital acts which take place without the intervention or consciousness of the mind ; by animal life, those in which some mental act is ajt essential constituent. 264 ASPHYXIA. Ga'.lois, Dr. Wilson Philip, Flourens, and others have shewn, injuries of the brain and spinal cord, (particularly injuries suddenly in- flicted on any large portions of these organs,) may directly influence, or even wholly sup- press, vital actions belonging to the head of organic life, for the performance of which we have no evidence of their furnishing any ne- cessary condition. As the function of respiration thus appears to be the only link by which the organic life is immediately and necessarily connected with animal life, it is naturally to be expected that the extinction of animal life should affect the organic functions just in the same way as the suspension of respiration does, and therefore that in the case of death beginning at the brain, as Bichat expressed it, (i. e. of death consequent on the extinction of sensation and voluntary motion,) the circulation and other organic functions should be brought to a stand just in the same manner as in death by as- phyxia. And in what is strictly called death by coma, this is really the case; the sensations being gradually more and more impaired, the sense of anxiety in the chest, which prompts to the acts of respiration, is ultimately extinguished ; but even after the last breath has been drawn, the pulsations of the heart still continue, and the blood then gradually stagnates in the lungs, the circulation comes to a stand, and the blood is found after death congested on the right side of the heart, just as in the case of asphyxia already described. That this is truly the mode of fatal termina- tion in cases where death takes place strictly in the way of coma, was first unequivocally proved by Sir B. Brodie,* who found, by experi- ment, that animals poisoned by opium or other narcotics, and in which the acts of re- spiration had ceased, in consequence of the impression made on tire brain and the gradu- ally increasing insensibility, might be recovered by the artificial respiration, just as asphyxiated animals may be. Indeed the same expedient had been previously employed with success (although not suggested by an equally accurate view of its mode of action) by Mr. Whately.f The reason why the same expedient cannot be expected to avail in cases of disease termi- nating by coma is simply that in these cases the cause of the coma is not temporary, like the effect of a narcotic poison, but permanent. It seems possible that it may yet be found successful in some cases of insensibility with convulsion, in children, unconnected with or- ganic lesion. In so far, therefore, as the extinction of the organic life is concerned, the death by coma, or beginning at the brain, resolves itselfinto the death by asphyxia, or beginning at the lungs, the difference lying merely in the mode in which the arterialization of the blood is ar- rested. But although this is strictly true as to cases * Phil. Transactions, 1812. t London Medical Observations and Inquiries, vol. vi. of violent death, produced experimentally in such a way that a single cause only is allowed to operate ; and although we occasionally meet with cases of equal simplicity in disease, and ought always to keep in view the principles which these simple cases illustrate in the treat- ment of disease, yet it ought not to be sup- posed that either the death by asphyxia, that by coma, or that by syncope, often present themselves to the observation of the medical practitioner in the same simplicity as to the experimental physiologist. We can state from frequent observation, that it is only in a certain number of cases of disease, strictly belonging to the head, such as apoplexy or hydrocephalus, that death takes place exactly in the way of coma, as above described, or that the function of circulation can be observed to survive that of respiration ; and on the other hand there are many instances of disease of the lungs, particularly of phthisis, in which the ultimate extinction of life is rather in the way of syncope than of asphyxia. The simple principle, that the circulation, though not dependent on any action of the nervous system, is liable to be influenced in various ways by causes acting on the nervous system, enables us to under- stand that death may often take place, in the course of diseases, in a way different from that which the seat of the disease may lead us to anticipate. Nevertheless it may often be of real and practical importance, with the view of ac- quiring clear and precise ideas of the modes of fatal termination which are to be expected in the course of diseases, and particularly of such diseases as fever — where the symptoms immediately preceding death, and the causes evidently inducing death, are remarkably various in different individual cases, — to study atten- tively the phenomena, and causes, of the fatal termination, in the simpler cases of violent death, such as those which have been here considered . BIBLIOGRAPHY. — Testa, Della morte apparente, 8vo. Firenz. 1780. Coste, Mem. sur les asphyxies, 8vo. Pliilad. 1780. Preainaire, Traite sur les as- phyxies, 8vo. Paris, 1788. Kite, Essay on the recovery of the apparently dead, 8vo. Lond. 1788. Goodwyn, The connexion of life with respiration, 8vo. Lond. 1789. Portal, Obs. sur les effets des vapours mepliitiques dans l’homme, &c. 8vo. Paris, 1791. Coleman, A dissertation on suspended respi- ration, 8vo. Lond. 1791. Curry on apparent death, 8vo. Lond. 1792. Fotheryill, Preservative plan; or, hints, & c. 8vo. Lond. 1798. Graf, Dis. sur l’asphyxie, Strasb. 1803. Bichat, Sur la vie et la rnort, Paris, 1805. Guillebout, Indie, des affec- tions qui produisent subitement la mort, &c. 4to. Paris, 1812. Colurini, Sulle varie morti apparent!, 8vo. Pavia, 1813. Lehel, Consid. sur la maniere dont la mort arrive dans quelques maladies des organes dc la respiration, 4to. Paris, 1815. Orfila, Secours a donner aux personnes empoisonnecs ou asphyxiees, 12mo. Paris, 1818. White, A disser- tation on death and suspended animation, 8vo. Lond. 1819. Gummer, De causa mortis submer- sorum, Groning. 1761. Recus. in Sandif. Thes. vol. i. Champeaux et Faisole, Exper. sur la cause de la mort des noyes, 8vo. Lyon. 1768. Du Chemin d'Etany, Mem. sur la cause de la mort des noyes : reponse a MM. Champeaux et Faisole, 8vo. Paris, AVES. 1770. Fothergill, New inquiry into the suspension of vital action, &c. 8vo. Lond. 1795. Caillau, Mem. stir l’asphyxie par submersion, 8vo. Bordeaux, 1799. Fine, De la submersion, 4to. Paris, 1805. Berger, Essai sur la cause de l’asphyxie par sub- mersion, 4to. Paris, 1805. Ploucquet, Animadvers. in statum ac therap. submersorum, 4to. Tubing. 1799. Hunter, Animal (Economy, 4to. Leroy, Rechercbes sur les asphyxies, 8vo. Paris, 1829. JDevergie, Diet, de Med. et Chir. Prat., art. As- phyxie. Roget, in Cyclopaedia of Practical Medi- cine, art. Asphyxia. Kay, on asphyxia, 8vo. Lond. 1834 ( the most complete and able work on this subjict in the English language ). Edwards, Sur l’influence des agens physiques, Englished by Drs. Hodgkin and Lister, Appendix, p. 463. (W. P. Alison.) AVES, birds; (Gr. O guSr; ; Fr. Oiseaux ; Germ. Vogeln; Ital. Uccelli:) a class of ovi- parous vertebrate animals, with warm blood, a double circulation, and a covering of feathers. Birds are organized for flight, and as this, the most vigorous kind of locomotion, demands the greatest energy in the contractility of the muscular fibre, so the respiratory function finds its highest development in the present class. Not only the ramifications of the pulmonary artery, but many of the capillaries of the sys- temic circulation, from the singular extension of the air-cells through the body, are sub- mitted to the influence of the atmosphere, and hence birds may be said to enjoy a double re- spiration. Although the heart resembles in some parti- culars that of the Reptilia, the four cavities are as distinct as in the Mammalia, but they are relatively stronger, their valvular mechanism is more perfect, and the contractions of this organ are more forcible and frequent in Birds in ac- cordance with their more extended respiration and their more energetic muscular actions. As Birds exceed Mammals in the activity of those functions on which the waste and renovation of the general system more imme- diately depend, so they possess a higher stan- dard of animal heat : their ordinary tempera- ture is 103° and 104°, and according to Cam- per is occasionally as high as 107° Fahr. The modification of the tegumentary cover- ing characteristic of the present class is to be regarded rather as dependent upon, than oc- casioning, this high degree of internal tem- perature, which requires for its due mainte- nance against the agency of external cold an adequate protection of the surface of the body by means of non-conducting down and imbri- cated feathers ; and this warm clothing is more especially required to meet the sudden vari- at.ons of temperature to which the bird is exposed during its rapid and extensive flights. The generative product is always excluded from the oviduct in an undeveloped state, in- closed, in a liquid form, within a calcareous case or shell. The female organs are, therefore, developed only on the left side of the body. The ovum is subsequently perfected by means of incubation, for which action the bird is es- pecially adapted by its high degree of animal heat. Birds form the best characterized, most dis- 265 tinct, and natural class in the whole animal kingdom, perhaps even in or ganic nature They present a constancy in their mode of generation and in their tegumentary covering, which is not met with in any other of the vertebrate classes. No species of Bird ever deviates, like the Cetacea among Mammals, the Serpents among Reptiles, and the Eels among Fishes, from the tetrapodous ttype of formation which so peculiarly characterizes the vertebrate division of animals. The anterior extremities are invariably con- structed according to that plan which best adapts them for the actions of flight; and although, in some lew instances, the development of the wings proceeds not so far as to enable them to act upon the surrounding atmosphere with suffi- cient power to overcome the counteracting force of gravity ; yet, in these cases they assist, by analogous motions, the posterior extremities; either, as in the Ostrich, by beating the air while the body is carried swiftly forward by the action of the powerful legs ; or, as in the Pen- guin, by striking the water after the manner of fins, and by the resistance of the denser me- dium carrying the body through the water in a manner analogous to that by which the birds of flight are borne through the air. In a few exceptions only are the wings reduced to mere weapons of offence, as in the Cassowary and in the singular Apteryx of New Zealand, in which they are represented by a single spur. In no instance do the anterior extremities take any share in stationary support or in prehension. Birds are therefore biped, and the ope- rations of taking the food, cleansing the plumage, &c. are almost exclusively performed by means of the mouth, which consists of two unlabiate and edentate mandibles, sheathed with horn. To facilitate the prehensile and other actions thus transferred to the head, the neck is elongated, and the body generally in- clined forwards and downwards from the hip- joints. The thighs are accordingly extended forwards at an acute angle from the pelvis to- wards the centre of the trunk, and the toes are lengthened and spread out to form an adequate base of support. The actions of perching, walking, running, scratching, burrowing, wa- ding, and swimming, require for their perfect performance different modifications of the pos- terior extremities. The mandibles, again, present as many varieties of form, each corresponding to the nature of the food, and in some degree in- dicative of the organization necessary for its due assimilation. Ornithologists have, there- fore, founded their divisions of the class chiefly on the modifications of the bill and feet. Since, however, Birds in general are associated to- gether by characters so peculiar, definite, and unvarying, it becomes in consequence more difficult to separate them into subordinate groups, and these are necessarily more arbi- trary and artificial than are those of the other vertebrate classes. A binary division of the class may be found- ed on the condition of the newly-hatched young, which in some orders are able to run about and provide food for themselves the mo- 2GG AVES. ment they quit the shell (Aves pracoces ) ; while in others the young are excluded feeble, naked, and blind, and dependent on their pa- rents for support ( Aves altrices). Scot’OLi, in his ‘ Introduction to Natural History,’ published in 1777, proposed a dicho- tomous systematic distribution of Birds, found- ed on the form of the scales covering the tarsus. The species which have these scales small and polygonal are the lietepedes of this author ; those which have the legs covered anteriorly with unequal semicircular plates are the Scutipcdes. Nitzscu,* the celebrated professor of natural history at Halle, has synthetically grouped to- gether the feathered tribes under three grand orders, according to the great divisions of the terraqueous globe which form the principal theatres of their actions.! The first order con- sists of the birds of the air par excellence, Aves aerece (Luft-vogeln) ; the second order em- braces the birds of the earth, Aves terrestres (Erd-vogeln) ; the third great division includes the birds which frequent the waters, Aves aqua- ticee (Wasser-vbgeln). The Eagle and the Sparrow may be named as examples of the first ; the Ostrich and the common fowl of the second ; the Heron and the Gull of the third of these extensive divisions. A more definite arrangement of Birds, in which a similar principle may be traced, has been proposed by a distinguished naturalist of our own country, Mr. Vigors. He divides tire class Aves into five orders. The first includes the birds which soar in the upper regions of the air, which build their nests and rear their young on the highest rocks and loftiest trees, and which may be regarded as the typical species of Nitzsch’s Aerial Bii'ds ; this order is termed I laptores, from the rapacious habits and animal food of the species so grouped to- gether. The second order affects the lower regions of the air ; the birds composing it are peculiarly arboreal in their habits, and are therefore term- ed Perchers or Insessores. The third order corresponds to Nitzsch’s Arcs terrestres, and is denominated Rasores, from the general habit which these granivorous species present of scratching up the soil to obtain their food. By dividing the aquatic birds of Nitzsch into those which frequent the fresh waters, and are limited to wading into rivers, lakes, &c. in search of their food, and those which possess the power of swimming in the great ocean, we ob- tain the two remaining orders of the quinary arrangement of Mr. Vigors, viz. the Grallatores, or Waders, and the Natatores, or Swimmers. The merit of this system is not, however, confined to the defining of the different groups in as clear and readily appreciable a manner as the subject will admit; but it also aims at * See Schoepfs, in Meckel’s Archiv fur Physio- logic, B. 12, p. 73. t Blumenbach more vaguely proposes a Binary arrangement of Birds on the same principle ; he divides the class into Land-Birds and Water-Birds, In Lawrence’s Blumenbaxh, Comp. Anat. p. xxxiii. displaying the natural affinities by which the several orders and families are connected with and pass into one another. In the ornitholo- gical systems of other naturalists, who have made this branch of zoology their particular study, we find the greatest discrepancy both as to the number and value of the primary divi- sions of the class. Sandewall has four orders or cohorts. Vieillot, like Vigors, has five orders. Linnaeus, Cuvier, Carus, and Dumeril have six orders. Illiger has seven. Scopoli, Latham, Meyer, Wolf and Elain- ville have nine. Temminck (1820) has sixteen. SchoefFer has seventeen. Brisson has twenty-eight, and Lacepede has thirty-eight orders. Where so many masters of the science differ, it is difficult for one less profoundly versed in ornithology to select the most unexceptionable system of arrangement, and as Kirby* ob- serves, ‘ the choice perplexes.’ We have here adopted the arrangement proposed by that dis- tinguished naturalist as being the one which facilitates the expression of the leading ana- tomical differences which obtain in the class of Birds, and which may therefore be considered as the most natural. Orders. 1. Raptores, Vig. Syn. Accipitres, Linn. Cuv. Birds of Prey or Haveners.! II. Insessores, Vig. Passeres, Linn. Cuv. Perchers. III. Scansores, Illig. Cuv. Climbers. IV. Rasores, Illig. Gallinee, Cuv. Scratchers. V. Cursoues, Illig. Brevipennes, Cuv. Coursers. VI. Grallatores, Illig. Grallrz, Linn. Cuv. Waders. VII. Natatores, Illig. Palmipedes, Cuv.; Anseres, Linn. Swimmers. The following are the characters of these orders. Class Aves ( Birds.) Animal vertebrated, oviparous, biped. Anterior extremities organized for flight. Integument plumose. Blood, red, warm. Respiration and circulation double. Lungs fixed, perforated. Negative characters, no auricles, lips, teeth, epiglottis, diaphragm, fornix, corpus callosum, scrotum. Order I. RAPTORES. Body, very muscular. Beak, strong, cur- ved, sharp-edged and sharp-pointed, often armed with a lateral tooth ; upper man- dible the longest. (Fig 112.) * Bridgewater Treatise, vol. ii. p. 444. t This word is proposed by Mr. Kirby as the English for Ilaptores it is the substantive of rave- nous, from the verb to rewen. AVES. 267 Legs, robust, 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; Vulturida, Vultures; and Gypogeranidre, which 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 prey, viz. noxious reptiles, serpents, &c. The Nocturnal Raptoreshavetheeyesdirected forwards, and include the Strigida or owl-tribe. Fig. 113. Order II. INSESSORES. Legs slender, short, with three toes before and one behind, the two external toes united by a very short membrane.* The Ferchers 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 nidification, 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 J 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 Fig. 114. The genus Ceyx, Laccp. ( Alcedo 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. Tlte 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, (Jig. 115) characterized by their insect food, and the notch near the extremity of the upper man- dible, include the families termed Laniadw or Shrikes ; Mcrulida, Thrushes; Sylvi- Rostrum, of a Shrike adee, Warblers ; Fipridce, Tits ; and Muscica- pidee. Fly-catchers. The Conirostres (fig. 116) include the two Rostrum of a Crow. orders of M.Temminck, termed Omnivores and Grunivures ; 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 : Sturnidee, Starlings ; Cot'- vidcc, Crows ; Buceridee, Ilornbills ; Loxiadce, Cross-bills; Fringillida, Finches, Larks. The I 'enuirostres (jig. 117) or suctorial birds form, Mr.Vigors observes, “ the most interesting group, per- haps, of the animal Rostrv/mof theOrthorhynchus, world. Deriving their or Straight-billed Humming subsistenceforthemost Bird. part from the nectar of flowers,* we never fail to associate them in idea with that more beautiful and perfect part of the vegetable creation, with which in their delicacy and fragility of form, their variety and brilliancy of hues, not less than by their extracting their nourishment from vegetable juices, they appear to have so many relations. As the tribe is confined exclusively to the torrid zone and southern hemisphere, the naturalists of our northern latitudes have little opportunity of observing their manners or of inspecting their internal construction.” f Fig. 117. * In the Humming-Birds which we have dis- sected, we have found the remains of minute insects in the gizzard. f We have selected the skeleton of the Humming- bird, one of this tribe, as a striking illustration of the 2G3 A.VES. Fig. 118. ' jirrmnii/s^ Rostrum of the Cujnimultjus. This distinguished ornithologist proposes to divide the Tenuirostres into the following families: Cinnyridre, Sugar-eaters ; Trochilida, Humming-birds; — in which families the beak and feet are more remarkable for their tenuity and length : and Promeropida, Hoopoes ; Me- liphagidte, Honey-suckers; Nectariniada, Nec- tar-birds;— in which the slenderness of the beak and feet is less remarkable. The Fissirostres, (fig. 118J, like the Tenuirostres, are distinguished by a habit of feeding on the wing, but as their food, instead of vegetable juices, consists of , „ living insects, the form of the beak is modified accordingly, and is re- markable for its shortness and the wideness of its gape, especially in the typical families. In these the mode of catching the prey is con- formable to their distinguishing characters ; they receive it in full flight into the cavity of their mouths, which remain open for that purpose, and where a viscous exudation within and a strong fence of vibrissa on the exterior, assist in secur- ing the victim. The longer-billed Fissirostres, on the other hand, seize their food by their bills. The following are the families of the Fissirostral tribe : Hirundinidte, Swallows ; Caprimulgida, Goat-suckers; these are characterized^ by the short, wide, and weak bill. Todidee, Todies ; Halcyonida, King-fishers ; eaters ; these latter fa- milies are characterized by their stronger and longer bill, and fur- ther differ from the preceding in having the external toe nearly as long as the middle one to which it is united as far as the penultimate joint; they are therefore termed Si/nductyles by Cuvier. Fig. 119 represents the foot of the King-fisher. Meropidee, Bee- Fii r. 119. Order III. SCANSORES. Feet with two toes before and one behind. (Fig. 120.) The disposition of the toes which re- sults from the ex- ternal one being turned back like the thumb, gives the Scansores great fa- cility in climbing the branches of trees, but proporti- onally impedes their progression along level ground.'* Their Fig. 120. Foot of the Woodpecker. adaptation of the vertebrate skeleton to powers of flight. * There are peculiar exceptions to the general character in this as in most other orders of birds. nests are less skilfully constructed than those of the Insessores, and are generally made in the hollows of old trees ; one family, indeed, is remarkable for depositing its eggs in the nests of other birds. Their powers of flight are moderate ;* their food consists of insects and fruit. The scansorial families are the Psittacida, Parrots; Picida, Woodpeckers, Wry-necks; Cuculida, Cuckoos; Rhamphas- tidtc, Toucans. OrderIV. RASORES. Upper mandible, vaulted ; nostrils, pierced in a membranous space at their base, covered by a cartilaginous scale. Legs, strong, mus- cular; three toes before united at their base by a short membrane, and one behind, higher than the rest, furnished with short, blunt, and robust nails, for the purpose of scratching up the food . Tail-fea- thers 14 — 18. The food of the Scratchers, or gal- linaceous birds, be- ing vegetable sub- stances, as grains and seeds, they have a large crop and ex- tremely muscular gizzard. They most- ly deposit and hatch their eggs on the ground in a rudely constructed nest of straw. Each male has ordinarily many females, he takes no partin nidification or in rearing the young; and these are generally numerous and able to run about and provide for themselves the mo- ment they quit the shell. The families of the Rasores are the Colum- bida, or Dove-tribe ; Cracida, Curassow-birds , Phasiunidte, Pheasant, common Fowl ; Tetra- onidee, Grouse, Partridge. Beak of the Guinea-fowl. Order V. CURS ORES. Wings very short, not used for flying; legs robust; Sternum without a keel. This order includes the Brevipenncs, which constitute a tribe of Waders (Grails) in the Cuvierian system ; and form in the system of Mr. Vigors, a family of Rasores under the term Struthionida. They differ remarkably from one another, both in the form of the beak and feet, and each known species forms the type of either a separate genus or family. Among the Cuculidee, the ‘ Traveller’s Friend, of South America,’ and among the Psittacida;, the * ground parrots’ of New South Wales, are remark- able for their preference of the ground, for progres- sion along which their elongated naked tarsus, and slender toes, of which one of the hind ones can be brought forward to the front row, favourably adapt them. * The Triclioglossi of New Holland afford as re- markable an exception in respect of powers of flight ; for instead of the usual short rounded wings of the parrot tribe, they have them elongated and pointed like those of a hawk, and dart through the forests with inconceivable rapidity. AVES, *2cg The Coursers with a depressed beak have the longest and strong- est legs, and run with remarkable velocity ; these include The Ostrich ( Stru- thio Camelus ) which has only two toes. (Fig. 122.) The Rhea ( Rhea A ricana.) The Cassowary ( ( suarius galcatus.) The Emeu ( Drotn ater.) Of these four giants of the class the first inhabits the continent of Africa, the second South America, the third Java, and the fourth Australia. The Coursers, with a compressed beak, are represented by a single and now extinct genus, the Dodo, ( Didus ineptus, Linn.) This bird is known from a description given by one of the early Dutch navigators, and preserved in Clusius ( Exoticorum libri de- cern descr. 1605, pp. 99 and 100) ; by an oil- painting of the same period, copied by Ed- wards (Gleanings, plate 294); from a de- scription and figure in Herbert’s Some Years Travels in Africa, Asia, fyc. 1677 ; and from the Historia Naturalis et Medica, of Jacob Bontius, 1658. A foot of the Dodo is preserved in the British Museum, and a head in the Ashmolean col- lection at Oxford. The beak resembles that of the Penguin or Albatross rather than that of a Vulture, to which it has been compared. The foot would resemble that of the Apteno- dytes, if it were webbed, which however it is not nor has been. It is very similar to, but proportionally stronger than, the foot of the Curassow. We have examined carefully the foot in the British Museum, and also the head of the Dodo at the Ashmolean Museum, and derived a conviction that they are the remains of a bird sui generis. A third form of beak among the Brevipennes or Cursores is presented by the Apteryx Aus- tralis ; a bird inhabiting and apparently pecu- liar to the island of New Zealand. The man- dibles are elongated and slender, the upper one is marked on either side by a longitudinal furrow. The toes are, as in the Dodo, four in number; but the fourth, or posterior one, is smaller, being reduced almost to a spur, and the three anterior ones have the lateral skin, notched as in the Phaleropes. The wings are shorter than in any other known bird, are quite concealed by the feathers, and terminate in a sharp spine or claw. The feathers are narrow like those of the Cassowary. OrdoVI. GRALLATORES. Legs with the tibia, and especially the me- tatarsus very long, stretched out behind in flight; the distal end of the tibia unfeathered ; toes elongated, straight. Wings long. Body i slender ; neck and beak long. Fig. 122. rne->. Foot of the Ostrich, , a which have three ,as' V toes, all turned for- ward. Fig. 123. The Waders, — or Gralla, as they were termed by Linnaeus from being raised on their long legs, as on stilts, — frequent for the most part the banks of lakes and rivers, marshes, and the shores of estuaries, and derive their food, some exclusively from the waters, feeding on small fishes, aquatic mollusks, worms, small reptiles, and insects, as well as their spawn, while others are of more terrestrial habits and food. Of the latter kind are the Gruidtz, or Stork tribe, which are chiefly vegetable feeders, and resemble the land birds in their bill and feet ; the former being more obtuse than in the typical waders, and the latter shorter. Then follow the Ardeidee, or Heron tribe ; the Scolo- pacida, Snipe, Woodcock ; the Rallida, Rail, Coot; and the Charadriada, Plover, Sander- ling, &c. The Waders are remarkable for their power of preserving a motionless position upon one leg for a considerable length of time ; the mechanism by which this is effected will be afterwards described. During flight they stretch out their long legs behind to counter- balance their long neck, and the tail is always extremely short, its function as a rudder being transferred to the legs. They mostly make or choose their nests on the ground, and the young are enabled to run about as soon as hatched, excepting in those Waders which live in pairs. Ordo VI I . NA TA TO R ES. Body closely covered with feathers, and coated with a thick down next the skin. Legs short, placed behind the point of equilibrium. Toes united by a membrane or web, which is The Swimmers, or Palmipedes, are of all the orders of birds the most easily recogniza- ble by the structure and position of their oar- like feet : this peculi- arity which occasionsan awkward gait on land, is extremely favourable to those birds ‘ whose business is in the great waters.’ Their body is boat-shaped, and ge- nerally elongated, as is sometimes divided. 270 AVES. also their neck. Their dense plumage is oiled and lubricated by the secretion of the coccy- geal glands, which are remarkably developed for that purpose. In general the males have many females, and in harmony with this spe- ciality the young are hatched in a condition which renders the cooperation of both parents for their support unnecessary, being able to take to the water and swim about in search of food the instant that they are liberated from the egg-coverings. The families of Swimmers are'th e Anatida, Swan, Goose, Duck; Co - lymbidtc, Divers; A leaden, Auks ; Pelecanida, Pelican, Cormorant, Gannet ; Lurid a, Gulls. 1. Osteology. — The skeleton of Birds is re- markable for the rapidity of its development and the light and elegant mechanism displayed in the adaptation of its several parts. The osseous substance is compact, and exhibits more of the laminated and less of the fibrous texture than in the other vertebrate classes. This is more especially the case in those parts of the skeleton which are permeated by the air. The bones which present this singular modifi- cation have a greater proportion of the phosphate of lime in their composition than is found in the osseous system of the mammalia, and they are whiter than the bones of any other animal. In the bones where the medulla is not dis- placed or dessicated by the extension of the air-cells into their interior, the colour is of a duller white. In the Silk or Negro-fowl of the Cape de Verd Islands ( Gallus Morio, Temminck) the periosteal covering of the bones is of a dark brown, and in some parts almost black colour ; but this ought to be re- garded as a peculiarity of the cellular rather than of the osseous texture, which does not differ in colour from that of other birds ; indeed the thin aponeurosis covering the lateral tendons of the gizzard of the Silk-fowl is observed to have the same dark hue as the membrane which invests the bones. Although in the disposition of the parts of the osseous system of birds the plan which pervades the vertebrate type of structure is nowhere absolutely violated, yet the variations from that plan required by the peculiar exigen- cies of the class are of the most striking and interesting kind. We shall successively con- sider the relations of these modifications to the powers and habits of the bird as they present themselves in the vertebral axis, in the bones of the head and thorax, and in those of the anterior and posterior extremities. The vertebral axis or spine is divisible into a cervical (Jig- 125, a), dorsal (5), sacral (c), and caudal (cl) region ; the vertebras immediately succeeding those which bear ribs have a lateral anchylosis with the iliac bones, and therefore there is no part of the spine which possesses the characters of the lumbar vertebrae of mam- malia and reptiles. The vertebrae are the first parts of the osseous system which make their appearance in die development of the embryo, and they are of all parts of the skeleton the most constant in their existence and general characters. The dorsal or costal vertebrae in birds rarely form more than a fourth part of the entire vertebral column, and in some of the long- necked Grallatores, as the Stork, form only an eighth part of the spine ; they have not been observed to be fewer than six nor more than eleven in number throughout the class: the latter obtains in the Swans ( Cygnus canorus et olor) and Sheldrake; the most common numbers are seven or eight. The dorsal vertebras are short, as compared with the cervical : they appear broad when viewed superiorly, in consequence of the great development of the transverse processes; but their bodies are much compressed in the lateral direction, so as to be reduced almost to the form of vertical laminae towards the sacral region. This is especially observable in the Penguins ( Aptenoclytes, Catarrhactes) ; but in the Ostrich the bodies of the dorsal ver- tebra retain their breadth throughout. The bodies are not united by intervertebral substances, but by capsular ligaments and synovial membranes ; the anterior articular cartilaginous surface is convex in the vertical direction, and concave in the transverse ; the posterior surface is the reverse. The Penguins, however, present a remarkable exception to this rule. The posterior surface of the third dorsal vertebra is uniformly concave, to which the opposed end of the fourth vertebra presents a corresponding convexity : the ball and socket joint is continued between the several ver- tebra to the last dorsal, which is anchy- losed to the sacrum. This is an interesting affinity to the Rcptilia, in addition to numerous others displayed in the construction of thc-se^ singular birds. In most birds the bodies of some of the middle dorsal vertebra are an- chylosed together ; and in general those which are nearest the sacrum. In the Flamingo we have observed this anchylosis extending from the second to the fifth dorsal vertebra. In the Sparrow-hawk the second, third, fourth, and fifth dorsal vertebra; are conso- lidated into one piece, while the sixth enjoys con- siderable lateral motion both upon the fifth and seventh, which last is an- chylosed to the sacrum; so that the body can be rapidly and extensively in- flected towards either side AVES. 271 during the pursuit of prey. This structure and its uses were first pointed out by Mr. H. Earle. The bodies of the anterior dorsal vertebrae send down processes from their inferior or ventral surfaces for the advantageous origin of the recti antici majores muscles of the neck. These processes differ from the inferior spines of the tail in not being perforated for the passage of an artery. This part of the spine is further strengthened by the extension of osseous splints from the transverse processes, which unite those of contiguous vertebrae to- gether, and also by the anchylosis of the spinous processes. But where a similar ne- cessity for the fixation of the trunk does not exist, as in the Struthious birds and Penguins, which cannot fly, all the dorsal vertebras are moveable upon each other. When it is con- sidered that the head, posterior extremities, and viscera are suspended in flight from this central portion of the trunk, and that it has almost exclusively to sustain the shock of the violent contractions of the principal muscles of the wings, the necessity for the mechanism consolidating the dorsal vertebrae will be readily appreciated. Immobility and strength are still more ob- viously required in that part of the spine by which the weight of a horizontal body is to be transferred to a single pair of extremities articulated to the trunk behind the centre of gravity. The anchylosis of the bodies of the vertebrae, which already begins to appear in the last dorsal, is, therefore, continued through all the sacral vertebra as far as the caudal region; and this consolidated mass (bloc) is united laterally to the iliac bones, lienee it is always difficult to determine the number of vertebrae of which it is composed. We have made sections of the sacrums of many different birds with a view to determine this fact, and have generally found the number greater than that which is indicated in the tables of Cuvier. Thus the Stork has twelve, instead of eleven sacral vertebrae ; the Coot thirteen, instead of seven ; the Kingfisher eleven, instead of eight : while the Ostrich, on the other hand, has but seventeen, instead of twenty bones of the sacrum. The bodies of the sacral vertebrae are broad, but shallow, and towards the tail the floor of the vertebral canal is formed by a mere lamina of bone : the canal is remarkably dilated in this part of the spine for the enlargement of the cord which gives off the nerves to the posterior extremity. It is a curious fact that the roots of these nerves pass out of the osseous canal by separate orifices, the ganglion on the posterior root and the union of the two being external to the spine. The aspect of all these orifices is la- teral, in the intervals of the transverse pro- cesses of the different vertebrae, which are not united together as in the mammalia. The first four or five sacral vertebrae give off two sets of transverse processes, one ventral, the other dorsal ; the ventral ones are wanting in the succeeding four, and then suddenly reappear to abut against the symphysis of the ilium and ischium, and are 90 continued double to the end. The spinous processes which are prin- cipally developed from the anterior sacral ver- tebrae, give off from their extremities lateral expansions, which anchylose with the iliac bones, and form an osseous roof, arching over and concealing the transverse processes. The coccygeal vertebrae of birds, though never prolonged into a conspicuous caudal appen- dage, are in general moveable upon each other, and are frequently nine in number. With the exception of the last, they are broad and short and perforated for the lodgement of the spinal marrow. With the exception of the last also they have spines on both the dorsal and ventral aspects ; and the anterior vertebra have also transverse processes. The last caudal vertebra (d, Jig. 125) is so singularly shaped, that were it found alone in a fossil state it would hardly be recognized as a bone of the spine. It has no medullary canal and no processes ; but is compressed laterally and terminates above and often also below in a sharp edge ; its posterior extremity is obtuse. It supports the coccygeal oil-gland, and affords a firm basis to the tail feathers, which, from their use in guiding the motions of the bird through the air, Linnseus termed the rect rices* In the Toucan the three last caudal vertebra are anchylosed together; the six anterior ones are articulated by ball and socket joints, the ball and the socket being most distinct in the two last of these joints ; that between the sixth and seventh vertebra is provided with a capsule and synovial fluid, the others have a yielding ligamentous mode of connexion. The spinous processes of these vertebra, both superior and inferior, are of moderate size, but smallest in the sixth, where the greatest degree of motion takes place ; the transverse pro- cesses on the contrary are large and broad so as almost to preclude lateral motion. We have given a more particular description of these vertebra because of the singular move- ments observable in the tail of the Toucan ; it can be inflected dorsad till the superior spines of the vertebra are brought in contact with the sacrum ; and in the performance of this motion the lateral muscles, which at first tend rather to oppose the elevators, become, at a certain point of inflection dorsad of the centre of motion, elevators themselves, and thus com- bining with the elevators jerk the tail upon the back ; it is thus that the tail turns as if on a hinge operated upon by a spring. As the prehensile functions of the hand are transferred to the beak, so those of the arm are performed by the neck of the bird; this portion of the spine is therefore composed of numerous, elongated, and freely moveable ver- tebra, and is never so short or so rigid but that it can be made to apply the beak to the coccy- geal oil-gland, and to every part of the body for the purpose of oiling and cleansing the plumage. In birds that seek their food in * In the tail-less variety of the common Fowl the coccygeal vertebra have degenerated into a single unshapely knotty process. 272 AVES. water it is in general remarkably elongated, whether they support themselves on the surface by means of short and strong natatory feet, as in the Swan, or wade into rivers and marshes on elevated stilts, as in the Crane, &c. The articular surfaces of the bodies of the cervical vertebrae, like those of the dorsal series above mentioned, are concave in one direction and convex in the other, so as to lock into each other, and in such a manner that the superior vertebrae move more freely forwards, the middle ones backwards, while the inferior ones again bend forwards; producing the ordinary sigmoid curve observable in the neck of the bird. This mechanism is most readily seen in the long-necked waders which live on fish and seize their prey by darting the bill with sudden velocity into the water. In the common Heron, for example, ( Ardea einerea ) the head can be bent forward on the atlas or first vertebra, the first upon the second in the same direction, and so on to the sixth, between which and the fifth the forward inflection is the greatest; while in the opposite direction these vertebrae can only be brought into a straight line. From the sixth cervical vertebra to the thirteenth the neck can only be bent backwards ; while in the opposite direction it is also arrested at a straight line. From the fourteenth to the eighteenth the articular surfaces again allow of the forward inflection, but also limit the opposite motion to the straight line. Two transverse processes are ordinarily con- tinued from the anterior part of the bodies of the cervical vertebrae : the inter-space of these is filled up externally to the vertebral artery by a rudimentary styliform rib, which is sepa- rated in the young bird, but afterwards ancliy- losed, and directed backwards parallel to the body of the vertebrae. These processes give attachment to numerous muscles of the neck, and being, with the transverse processes, more strongly developed in the rapacious birds, give a greater breadth to the cervical region in that order. The superior spinous processes are but feebly developed ; they are most distinct on the vertebrae at the two extremities of the cervical portion of the spine. Inferior spinous processes are also found on the vertebrae at the commencement and termination of the neck, but are wanting m a great proportion of the intermediate cervical vertebrae. The atlas is a simple ring. In general it is articulated with the occipital tubercle by a single concave facet on the body ; but in the Penguin and Ostrich there are two other facets, continuous with the middle one, but corresponding with the anterior articulating pro- cesses of the rest of the vertebrae and applied to the condyloid portions of the occipital bone, while the middle facet is articulated to the ba- silar portion as in other birds. The body of the dentata is joined to the atlas by a single synovial capsule, its odontoid process is tied down by a strong transverse ligament stretched above it, and by a longitudinal one extending from its extremity to the posterior part of the occipital condyle. In the articulations of the bodies of the remaining cervical vertebrae a moveable inter-articular cartilage is found in- closed between reduplications of the synovial membrane, as in the joint of the lower jaw in mammalia. The articulations of the oblique processes have no peculiarities worthy of no- tice. A remarkable difference is found in the diameter of the spinal canal contained in the cervical vertebrae. If, e. g. the sixth cervical vertebra of a Stork be sawed down verti- cally, the antero-posterior diameter is greatest in the middle, least at the ends ; but if it be sawed lengthwise horizontally, the transverse diameter is the reverse, being narrowest at the centre and widest at the ends. In the Ostrich, the Swan, and many other birds the spinal canal is widened in every direction at the extremities of the vertebra ; and on the dor- sal or posterior aspect of the spine, the canal remains open for some extent in the intervals of the vertebrae, the cord being there protected only by membrane and the elastic ligaments which connect the roots of the spinous pro- cesses together. The final purpose of this structure has been ably illustrated by Mi'. Earle in the Philosophical Transactions, (1822, p. 276.) where he shews that it is adapted to pre- vent a compression of the spinal cord during the varied and extensive inflections of the neck. The vertebra of the different regions of the spine bear a different proportion to each other in respect to number among birds, from what we observe in the mammalia and reptilia. The cervical portion in this class is generally com- posed of a much greater number of vertebra than any of the other divisions of the spine ; in this respect the fossil reptilian genus called Plesiosaurus alone resembles the bird. This singular animal was an inhabitant of the waters, and it is interesting to observe that the peculiarity which distinguishes it, viz. the great length of neck, is chiefly characteristic of the Aves aquatica of Nitzsch. In the Gral- latores the length of the neck is determined by the height of the legs : in the Natutores it is necessary for the purpose of obtaining their food while swimming the waters. The dorsal vertebra are usually less numerous than in mammalia. The caudal vertebra are subject to few variations; they never project in the form of a tail, but are most numerous in those birds which make the greatest use of the tail- feathers, as in the Swallows, to direct their rapid flight, and in the Woodpeckers, where they serve as a prop or climbing pole. The following table, which, with some cor- rections, is extracted from Cuvier’s Lepons d’Anatomie Comparee, exhibits the variety that exists with respect to the number of ver- tebra in different species of birds. Table of the number of vertebra in birds. Order. Raptoiies Vertebra. Species . Cervical. Dorsal. Sacral. Caudal. Vulture 13 7 11 Eagle 13 8 11 Osprey 14 8 11 Sparrow-hawk .. 11 8 11 AVES. 273 Species. Cervical. Dorsal. Sacral. Caudal. Buzzard 1 1 7 10 8 Kite 12 8 11 8 Great Horned Owl 13 7 12 8 Hawk-owl .... 11 8 11 8 Order. Insessores. Flycatcher 10 8 10 8 Black-bird .... 11 8 10 7 Tanager 10 8 9 8 Crow 13 8 13 7 Magpie 13 8 13 8 Jay 12 7 11 8 Starling 10 8 10 9 Gross-beak .... 10 7 12 7 Bull-finch .... 10 6 11 6 Sparrow 9 9 10 7 Goldfinch .... 11 8 11 8 Titmouse .... 11 8 11 7 Lark 11 9 10 7 Redbreast .... 10 8 10 8 Swallow 11 8 11 9 Night-jar .... 11 8 11 8 Humming-bird 14 9 10 8 Hoopoe 12 7 8 7 King-fisher .... 12 7 11 7 Order. Scansores Woodpecker . . 12 8 10 9 Toucan (Ariel) 12 8 12 9* Parrot 11 9 1 1 8 Order. Rasores. Pigeon 13 7 13 7 Peacock 14 7 12 8 Pheasant 13 7 15 5 Turkey 15 7 10 5 Crested Curas- sovv 15 8 10 7 Order. Cursores. Ostrich 18 10 17 9 Cassowary .... 16 10 19 7 Rhea 14 9 ?+ ? Emeu 19 9 19 9 Order. Grallatores. Heron 18 7 10 7 Stork 19 7 12 8 Crane 19 9 12 7 Al gal a 14 7 13 7 Spoon-bill 17 7 14 8 Avoset 14 9 10 8 Plover 15 8 10 7 Lapwing 14 8 10 7 Wood-cock .... 18 7 13 8 Curlew 1 3 8 10 8 Oyster-catcher . . 12 9 15 7 Rail 13 8 13 8 Coot 15 10 13 8 Jacana 14 8 13 7 Flamingo .... 18 7 12 7 * Cuvier says “plus de 7 : ” we have ascertained the above number in a dissection of a recent spe- cimen of this singular genus ( Rhamphastos Ariel, Vigors) Zool. Proceedings, vol. 11. p. 42. t This part of the spine is singularly modified and interrupted by a natural atrophy of many of the vertebrae. VOL. r. Species. Cervical. Order. Natatores. Dorsal. Sacral. Caudal Pelican . . . . 7 14 7 Cormorant . . . . 16 9 14 8 Tern 8 10 8 Gull . . 12 8 11 8 Petrel 9 13 9 Catarrhactes . . 13 9 13 8 Swan . . 23 11 14 8 Goose ....... . . 15 10 14 7 Barnacle . . . 10 14 9 Duck 8 15 8 Sheldrake . . .. 16 11 11 9 Scoter .. 15 9 14 7 Merganser . . . . 15 8 13 7 Grebe 10 13 7 The skull in all the Vertebrated Classes is composed of a considerable number of osseous pieces, which, in the Mammalia, unite in defi- nite numbers and proportions, so as to form the bones termed occipital, temporal, sphenoidal, &c. In the cold-blooded Vertebrate the com- ponent parts of these bones generally remain separated throughout life, giving an appear- ance of great complexity to the skull, and occa- sioning much difficulty in tracing their cor- respondence with the cranial bones of the higher classes. Equal difficulty is experi- enced in determining the component parts of the head in Birds, but from a very different cause. In the cold-blooded Crocodile, and Fish, this difficulty is caused by the tardiness of ossification, which prevents the coalition of the several elements of the cranial bones into their determinate groups ; while, in Birds, the T 374 AVES. energetic respiratory and circulating functions occasion so rapid an evolution of the osseous system, that the bones of the cranium become at an early period anchylosecl into one piece, with a total obliteration of the original har- monise; it is necessary, therefore, to examine the skull of the Bird at an early period of ex- istence, and to compare it with the fatal con- dition of the skull of the Mammal, when it will be found to be ossified from analogous centres, which, in their expansion and subsequent union, obey the same laws of, as it were, elective attraction. The occipital bone is originally composed of four pieces: the basilar , below, ( a, Jig. 126,) the two condyloid, laterally, (b, b,) and the expanded spinous process, or supra-occipital piece above (c ). These fulfil the usual functions of the occipital bone, protecting the cerebellum and medulla oblongata, and form- ing the medium of connection between the cranial and cervical vertebra;. The head is articulated to the spine by means of a single hemispherical tubercle (x, Jig. 1 26,) which plays in a corresponding cavity of the atlas. In most birds the tubercle is formed exclusively by the basilar piece of the occipital bone, but in the Ostrich and Penguin the condyloid portions also contribute to its formation, which is an approximation to the structure of the occipital condyle in the Chelonian reptiles. In all birds, however, the articulation is such as to allow of a much greater extent and freedom of motion to the head than exists in the Mammalia. The temporal hone consists of the petrous por- tion, the squamous portion, (d, d,Jig. 126, 127) and the tympanic bone, or os quadratum ( e.) The petrous bone includes the complex parts of the internal ear, and is soon anchylosed to the condyloid portions of the occipital bone, which fulfil the functions of the mastoid pro- cesses. The squamous, or, as it may be termed, the zygomatic portion of the temporal bone (d) remains for a longer time separate; it forms the lateral boundary of the cranial cavity, as in quadrupeds, and the tympanic element is move- ably articulated to its inferior part. The parietal bones (f, f, Jig. 127) retain their separated condition till after the union of the occipital pieces, they then unite and protect the posterior part of the cerebral hemispheres. The sphenoid bone is composed of a basilar portion , (g,Jig. 1 26,) two orbital plates, ( h, Jig. 1 27,) forming the floor and part of the septum of the orbits, and which rapidly anchylose with the preceding; two cranial portions, or alas ma- jores, (g, Jig. 127, 128,) which remain longer separate, and form the posterior part of the or- bits, and two pterygoid portions (‘interarticular’ or ‘ omoid ’ bones), (i, i. Jig. 126,) which, in birds, abut against the tympanic or quadrate bones. The great alee of the sphenoid join the parietal, and separate the temporal from the frontal bones. Th e frontal bone (k, fig. 127) continues for a longer period than the parietal to be sepa- rated into two lateral halves by the continuation of the sagittal suture through its whole length. Fig. 127. The ant-orbital processes ("13, Jig. 127) are elongated and pointed, ex- tending for- wards to join the lachrymal bones, (o, a, jig. 127,) con- siderably be- yond the ori- gins of the nasal bones, and are separated from each other by these and by a process of the ethmoid bone. The post-orb i- lal processes are most de- veloped in the Parrots and Maccaws, in the latter of which they join Skull of a young Ostrich. the lachrymal bones, and complete the bony circumference of the orbits, (Jig. 128.) In the Emeu they remain for a long time distinct bones, as in the reptiles. The frontal bone thus forms the whole of the superior, and, more or less, of the outer boundary of the orbits, and protects the anterior part of the cerebrum. It supports the horn-like prominences which are seen upon the heads of the Cassowary, Pintado, and Cu- rassow, the bony bases of which commence by distinct ossifications.® A small part of the ethmoidal bone (l, fig. 127) is seen, in the Ostrich, on the ex- 1 terior of the cranium lodged between the ant-orbital processes and nasal bones (n, n.) The ethmoid separates, as usual, the orbits from the cavity of the nose, and forms a great part of . the inler-oibital septum where this exists, as in the parrots, ( rn, Jig. 128.) In the mature bird the whole of the prece- ding bones, with the exception of the tym- panic elements of the temporal bone, are usually found anchylosed into one piece. The internal surface of the cranium exhibits a well-marked transverse ridge, which divides j the cavity into two principal depressions. In the anterior division the hemispheres of * * A most remarkable sexual difference appears in the skull of the crested Hens: in these the frontal portion of the cranium i9 dilated into an immense cavity, on which the crest of feathers is placed. This degeneracy of the formative impulse, which is propagated to the offspring, is quite unparalleled in the whole animal kingdom : I have lately ex“ amined several heads of such hens in afresh state, and have found that this peculiar dilatation of the cranium is filled by the hemispheres of the cere* brum, and is separated from the posterior part which holds the cerebellum, as in the common hen, by an intermediate contracted portion/ — Law- rence's Blumenbach's Comp. Anat. p. 61. AVES. 275 the cerebrum are lodged, the rest of the brain is contained in the posterior division. The relative proportion of these divisions varies in the different orders; in the Insessores and Ac- cipitres the anterior superior depression is the largest; in the Rasores, the posterior inferior depression equals, and in some species, ex- ceeds the former in size. The orbits form two slight projections in the anterior fossa of the cranium, which is partially divided longitu- dinally by a ridge corresponding to the inter- space of the cerebral hemispheres. This is developed in the Gallinaceous birds into a thin falciform osseous crest, which is especi- ally remarkable in the Partridge, Turkey, and Capercailzie. It is also well developed in the Parrot tribe. The sella turcica in all birds is a deep round cell, lodging the pituitary gland, as in the Mammalia. The foramen magnum (1 ,Jig. 126) is formed, as usual, by the union of the four pieces of the occipital bone : its size is considerable, having relation to the mobility of the cranium upon the spine. The foramen lacerum posterius (2, 2, Jig. 126) is situated immediately below the membrana tympani (8, 3, Jig. 126.) There is no fissure analogous to the foramen lacerum medius. The carotid foramina (3, 3, Jig. 126) are transversely oblong, and situated on the body of the sphenoid ; the same bone, in the Ostrich, is perforated immediately anterior to the carotid canal by the Eustachian tube, (4, 4.) The posterior palatine foramina are wide spaces, (5, 5,) separated from each other by the vomer (q, fig. 126). Anterior to these, in the base of the skull, are seen the still wider posterior apertures of the nostrils (6, 6). In the inside of the cranium the internal auditory foramina are distinctly seen. The foramen lacerum an- terius is divided into several distinct foramina. The optic foramina, on the contrary, are closely approximated, and frequently blended into one. The olfactory nerves escape each by a single foramen, and are continued to the nose either along a deep groove on the upper part of the orbital septum, or, as in the Toucan, pass through a complete osseous canal. The bones of the face correspond in number and relative position with those of the Mam- malia, but differ considerably in their forms and proportions ; they bear most resemblance to the facial bones of the Rodentia. They are always moveably connected with the bones of the cranium, and retain much longer than these their separate condition Fig. 128. The nasal bones ( n, n, jig. 127, 128) are a large and elongated pair, extend ing from the inner side of the ant-orbital SMUf.rm the froiual to the outer side of the ascending processes of the intermaxillary bones, expanding as they ad- vance forwards, and giving off from their outer sides a process which curves downwards to join the superior maxdlary bone, to which it has erroneously been considered to belong. The nasal bones soon anchylose with the frontal, ethmoidal, inter-maxillary, and superior maxillary bones. The lachrymal or ungueul bones Jo, o, fig A 27, 128, l, Jig. 125) are also of considerable propor- tionate size. They are more exposed than in mam- malia, and are usually moveably articulated by their mesial or anterior edge to a varying number of the bones of the skull. These are commonly the frontal, nasal, and malar bones ; but in the ostrich the lachrymal articulate with the palatine bones ; in the Parrot they extend backwards beneath the orbit to the post-orbitals, and thus complete the bony circumference of that cavity, while in the Owls they do not at all articulate with tire frontal bone. They are smallest in the Rasores and Natatores, and attain their greatest development in the diurnal Rap- tores. In these the separated supra-orbital bones give additional protection to the eye, over which they form, in conjunction with the lachrymal, the projecting arch so characteristic of the physiognomy of the bird of prey. The palatine bones ( p, p,fg. 1 26,) are of great proportional size : each is of an elongated, slender, depressed figure, becoming narrower anteriorly, forming the posterior part of the pa- latine arch, and completing with the vomer the boundary of the posterior nostrils. In the Rap- tores the palatine bones are united together only by a small part of their anterior extre- mities. In the Owls the posterior extremities are widely separated from each other. In the Insessores they are not united together in any part of their extent, except in the Gross- beak, ( Loxia Coccothraustes,) at the anterior extremity. In this bird and in the Parrots, the palatine bones have not a horizontal but a ver- tical position, contrary to what they are in most other birds. They are least developed in the Rasores. Th evomer (q,Jig. 126) is rapidly anchylosed in the Ostrich with the sphenoid, appear- ing as a long, moderately compressed, pointed process, extending forward from the spine of the sphenoid in the interval of the palatine bones, and dividing the posterior aperture of the nose into two lateral halves. In most other birds it remains distinct from the spine of the sphenoid, as it is also in the ostrich at a very early period. The intermaxillary bone (rn, Jig. \'25,r,r. Jig. 126, 127, 128) determines the form, and constitutes the greater part, of the upper man- dible. It consequently presents considerable variety in its figure and proportions, and also in its mode of articulation, in different birds; but in every species it is of considerable size. When completely ossified, which it is at a very early period, the intermaxillary bone consists of three processes which diverge from, or unite to form, the extremity of the upper mandible : the superior mesial process or nasal plate is lamellate, depressed or flattened hori- zontally, extends backwards between and above the lower ends of the nasal bones, and becoming t 2 2 76 AYES. wedged, as it were, between their upper ends, is articulated in general by an anchylosis to them and the ethmoid bone. This union, however, always allows of a certain elastic or yielding- motion to pressure from below. In the Parrots, where the upper mandible is an important in- strument in their climbing habits, the nasal plate of the intermaxillary bone is joined to the cra- nium by a ligamentous substance (11, fig. 12B). The two lateral or mandibular processes ( r, r, jig ■ 127) of the intermaxillary bones diverge and extend backwards, external and superior to the superior maxillary bones ; and, in the Ostrich, they articulate with the anterior extremities of the malar or zygomatic bones. Throughout their whole course the mandibular processes are in close contact with, and soon become an- chylosed to the superior maxillary bones. The ossification of the intermaxillary bone obeys the ordinary law of centripetal development. The lateral moieties are still separate in the chick at the conclusion of incubation; and in the duckling they do not anchylose until six weeks after that period. The union commences at the anterior extremity, while at the opposite or cranial end of the nasal process, traces of the original separation may frequently be observed in. the full-grown bird ; these are very con- spicuous in the Gulls, ( Laridee). The superior maxillary bones ( s , s, Jig. 126, 127) are very seldom united together in birds. They are comparatively of small size. Each may be said to commence mesiad of the ori- gin of the mandibular processes of the in- termaxillary bone ; it then expands as it pro- ceeds backwards, and, opposite the anterior end of the palatine bone, divides into two processes. The mesial or palatine process ex- tends along the outside of the palatine bone, and soon becomes anchylosed to it; the ex- ternal or malar process is articulated obliquely to the under part of the anterior moiety of the zygomatic bone. At the origin of this process a small projection meets the descending pro- cess of the nasal bone. In most Gallinaceous birds, the body, or part anterior to the palatine and zygomatic processes, is wanting; but in the common fowl it extends towards the mesial line, and unites with the vomer, so as to divide the palatal fissure into an anterior and posterior cavity. In the Ostrich, where the body of the upper maxillary extends for- wards to the symphysis of the intermaxillary bone, a process is also given off at the origins of the palatine and zygomatic bones, which passes inwards to the vomer, and completes, in the adult, the boundary of the anterior pa- latal fissure. The movement of the bony framework of the upper mandible resulting from the union of the intermaxillary, superior maxillary, and palatal bones, is immediately effected by the elongated malar or zygomatic bone, ( o,fig. 125, t, t,fg. 126, 127, 128,) which transfers to the zygomatic process of the superior maxil- lary the movements of the tympanic bone, being so placed as to form the medium of communication between these parts. It ex- tends in a straight line from one to the other, this being the form best adapted to resist the pressure upon its two extremities. With the superior maxillary bone it is soon anchylosed, but with the tympanic bone it is in most Birds articulated by a moveable ball and socket-joint, the articular surfaces being connected by a fibro-cartilaginous substance; in the Capri- inulgi, however, it is anchylosed at both ex- tremities. The malar bone is commonly of a compressed or vertically flattened form, but sometimes, as in the Ostrich, it is cylindrical. It is originally composed of two pieces placed in a parallel line, one above the other; the superior being pointed at both extremities, and much smaller than the other. The tympanic, pedicellate, or quadrate bone (i, Jig- 125, e, fig. 126, 128,) is never anchy- losed with the other elements of the temporal bone, but is freely moveable as in most of the cold-blooded ovipara; and it is interesting to observe that in the rodent quadrupeds, which exhibit many other affinities to birds, the tym- panic element remains for a long period a de- tached bone, but is situated altogether posterior to the maxillary articulation. In birds, where the base of the cranium is remarkably shortened in the antero-posterior diameter, the tympanic bone is, as it were, thrust forward and wedged in between the inferior maxillary bone and the zygomatic process of the temporal, thus inter- cepting, and articulating with, both the lower jaw and cheek-bones. The membrana tympani continues, however, to be attached by about half its circumference to the posterior part of the os quad rat urn, and for the remainder of its extent to the occipital and sphenoidal bones. The upper end of the tympanic bone is articulated by two distinct transverse condyles with the zygomatic portion of the temporal bone; below these it is contracted, and then expands as it descends, giving off a strong- process from the middle of its anterior surface, which projects into the orbit, then a smaller process from its posterior surface extending backwards, and lastly, sending off at its lower extremity an external process for the malar bone, and an internal one for the pterygoid, between which processes are two oblique oblong convexities for the articulation of the lower javr. Having an immediate connection with the mo- tions of the whole beak, it necessarily presents varieties of form in different birds, without, however, losing the characteristic figure which has been described. By whatever cause the tympanic bone is carried forwards, whether by the action of the pterygoid muscles in- serted into its orbitar process, or by the pres- sure of the lower jaw upon its inferior surface, that motion is communicated to the pterygoid and malar bones, which transfer it, the one to the palatine, the other to the superior max- illary bones, and thus the upper mandible is elevated at the same time that the lower one is depressed. The elasticity of the union of the nasal process of the intermaxillary bone with the cranium restores the upper jaw on the cessation of the pressure from below, to the position from which the move- ment of the tympanic bones had displaced it. AVES. 2 77 These movements are freely allowed in most birds from the nature of the articulation of the tympanic bone; but in the Struthious birds they are more restrained, from the connection of the bone with the descending zygomatic process of the temporal bone ; the extent of this attachment is greatest in the Emeu, where it almost produces a complete fixation of the tympanic bone. The inferior maxillary bone ( p , jig. 125, v, jigs. 126, 128,) is originally composed of twelve distinct pieces, each lateral moiety being made up of six. The anterior symphyseal or dental portion of each ramus first unites with its fellow at the symphysis ; the two portions which form the condyle (v, jig. 126) next an- chylose; the angular ( v , fig. 126), supra- angular and opercular, or splenial pieces are consolidated at a later period. The anterior extremities of the angular and supra-angular pieces are wedged into corresponding grooves of the symphyseal element ; and the opercular portion is extended like a splint along the inner side of the gomphosis, by which the preceding portions are united. The traces of the original separation of these bones long remain in the semi-aquatic and aqua- tic birds ( Grallatores and Natatores ), which, as the lowest of the class, manifest their affinity in this respect to the cold-blooded Ovipara, where this complex structure of the lower jaw continues throughout life. As the lower jaw, thus constituted, forms with the upper jaw the principal organ of pre- hension in birds, it presents many variations of form and magnitude, which immediately relate to, and are consequently indicative of their mode of life, food, &c. These general modifications will be treated of in relation to the digestive function, but some of the less conspicuous characters of the lower jaw may be more appropriately considered in this place. The rami are in general completely anchylosed at the symphysis, the extent of the united por- tions varying considerably in different birds, but occupying in most cases only a small pro- portion of the jaw. In the Pelicans the rami are united by the mere extremities, appearing as if bent upon each other at the symphysis, and supporting the dilatable sac which fills up the intermediate space, like the hoop of the fisher- man’s landing-net. The symphysis is also of very small extent in most other Palmipeds. It is small in the Rasores and Cursores. In the Storks and Cranes it extends along a third part of the entire jaw. In the Flamingo, where the anterior part of the jaw is bent down at an obtuse angle, nearly half of the rami are united. In the Skimmers ( Rhyncops ), Ilorn- bills, and Toucans, two-thirds. In the Curlew the two rami are in apposition for two-thirds of their anterior extent, but are not anchy- ! losed, and form, in this respect, the only known exception to the rule. In diurnal Birds of Prey, in many of the Parrot-tribe, in the Herons and Swans, each ' ramus of the lower jaw forms an entire bony plate. In the rest of the class a membranous j unossified space is left at the place of union of the symphyseal with the angular, supra- angular, and splenial elements. This defi- ciency is of a longitudinal form, and is always situated behind the middle of the ramus. In the Bustards, Woodcocks, Curlews, Gulls, Skimmers, Guillemots, Petrels, and Pen- guins, there is a second foramen, of a rounder figure, posterior to the preceding, and resulting from a defective union of the angular, supra- angular, and condyloid pieces. In the Casso- wary this space is subdivided into several small foramina. In the Emeu ( Dromaius) and Ostrich ( Struthio ) there is a single small fora- men at the corresponding part. At the posterior part of each ramus the fol- lowing processes are developed in various degrees in different birds. The suprangular piece ascends in a greater or less degree in the form of a thin lamina with a gently rounded outline, representing the coronoid process. From the inner side of the condyloid piece there extends a more marked process, which may be called the internal angular ; and from the posterior part of the ramus a third process is continued, which may be termed the posterior angular process. The coronoid process is most developed in the Parrots, Gulls, Herons, and Cross-bills ( Loxia), in some of which, as the Loxia coccothraustes, cardinalis, and pulverulentus, the lower jaw presents the following peculiarity. A large sesamoid bone of a triangular form, but rounded and transverse, with the base directed outwards and the apex inwards, is situated at the posterior and internal aspect of the articular ligament of the lower jaw. It com- pletes the maxillary articulation posteriorly, and corresponds by its anterior articular surface to the posterior part of the outer condyle. The__ar- ticular surface of the lower jaw of the Parrots is a simple narrow longitudinal furrow, open at the two extremities. That of the Toucans is almost equally simple, but of a rounder figure. In most other birds the articular surface is divided into two distinct portions, of which the internal is an oblique concavity, the exter- nal also oblique, but terminating in a convex eminence behind. In the Rasorial birds the coronoid process is feebly developed, but the internal and angular processes are of large size. The latter is very remarkable in the great Cock of the woods, ( Tetrao urogallus,) where it extends upwards and backwards in a curved form for the extent of an inch, affording attachment to the power- ful muscles required to produce the wide ex- pansion of the mandibles necessary to seize the large fir-cones which constitute its food. In the lamellirostral Palmipedes not only are the internal, and the posterior angular processes of large size, but there are also two eminences for muscular attachment on the outer side of each ramus anterior to the articular surface. In the Gulls an oblique ridge is continued from a single eminence similarly situated. The articular capsule of the lower jaw is strengthened by ligamentous fibres arising from the lower extremity of the tympanic bone, and passing backwards to be inserted into 278 AVES. the outer side of the internal angular process. This ligament assumes a fibrocartilaginous structure at its anterior part : it is attenuated internally, and is situated between the two bones in the outer part of the capsular ligament. At the posterior part of the joint a strong fibrous band extends from the end of the mas- toid process to the internal angular process of the lower jaw, so as to restrain the forward movement of the jaw. The skull presents fewer varieties of form in birds than in any other class of vertebrate ani- mals. With the exception of a few species, in which the beak assumes what may almost be termed a monstrous development, it has the form of a pretty regular five-sided pyramid, of which the occiput forms the base, and the an- terior extremity of the beak the apex. The posterior facet or base of the pyramid is formed by the upper and larger poition of the occiput, together with part of the temporal bones. It is the smallest facet of the head, and is larger in the transverse than the vertical diameter. It presents the vertical prominence corresponding to the narrow cerebellum, which is separated by a venous foramen and furrow (8, Jig. 126) from a broad muscular depression on either side ; below these are the large occi- pital foramen, (1, jig. 126); the hemispheric tubercle, which unites the head to the atlas ; and on either side of this tubercle a smaller muscular depression, separated by a transverse ridge from the larger one above, and per- forated by the pneumogastrie and hypoglossal nerves; these depressions are bounded laterally by the mastoid processes. (10, 10, fig. 126.) The inferior facet or base of the skull joins the posterior and lateral facets almost at a right angle. It is bounded anteriorly and at the sides by the lower jaw, which, on account of the compressed form and divarication of the rami, scarcely intercepts any part of the view of this very complicated surface. The occipital condyle, with the muscular depressions on either side and the mastoid processes, may be considered in some, and more especially in the Struthious birds, as forming part of the base of the skull. Anterior to the basilar portion of the occiput comes the body of the sphenoid, which in the Struthionidee sends outwards and forwards two rounded processes (jj,fg. 126) to abut against the flattened pterygoid bones. Between the origins of these, and anchylosed to the spine of the sphenoid, the vomer extends forwards to a distance varying in different birds. The tympanic bones are seen on either side of the body of the sphenoid, and external to these the zygomatic processes of the temporal ; the space circumscribed by these bones, with the mastoid processes behind, forms the expanded external passage of the ear, which is closed in the recent state by the large convex membrana ti/mpuni, (8, 8, Jig. 126.) Anterior to the tympanic bones the pterygoid processes (i i, Jig. 126) extend forwards and inwards to join the palatine bones; which are then continued forwards to the superior maxillary, leaving between them the large posterior nasal fissure divided longitudinally by the vomer. These fissures arc commonly continuous with the anterior palatal fissure, (7, 7, Jig. 126,) but in the full grown Struthious and some Gallinaceous birds, the palatine and maxillary bones unite with the vomer and separate the two fissures, thus increasing the bony floor of the nasal cavities. External to the rami of the lower jaw, the malar or zygomatic bones may in ge- neral be seen converging from the tympanic to the superior maxillary bones, the elongated triangular space between these bones and the pterygoid and palatine leads directly from below into the large orbits. The two lateral facets present posteriorly the tympanic or auditory cavity, (8, Jig. 128,) ante- rior to which is the tympanic bone, with the malar and inferior maxillary bones extending forwards from its lower extremity. Above the tympanic bone is the zygomatic process of the temporal, (d, jig. 128,) arching over it in the Struthious and Psittaceous birds, as if to effect its normal connection with the malar bone. Between the zygomatic and post-orbital pro- cesses is the crotaphyte depression, (g, Jig. 128,) always well-marked, but bounded by ridges more or less developed in different birds. At the lower part of this depression may be per- ceived the large foramen common to the supe- rior and inferior maxillary divisions of the trifa- cial nerve. Then come the spacious rounded orbits, bounded above by the supra-orbital lamella, behind by the sphenoid and frontal ex- pansions, which form, at the same time, the an- terior walls of the cranium ; separated from each other, but always more or less incompletely, by the thin sphenoidal and ethmoidal plates, the deficiencies of which are supplied in the recent state by aponeurotic membranes, and defended anteriorly by the largely developed lachrymal bones and the ethmoidal alee, between which there are always present apertures varying in size. The pterygoid and palatine bones, with the styliform malar bone, form a very incom- plete floor of the orbit. Anterior to the orbits the sides of the skull become gradually narrower to the end of the beak ; between the lachrymal and the superior maxillary bones a large triangular or rounded space is left, (11 ,jig. 128,) which conducts to the nasal cavity. A second vacancy occurs, anterior to this, bounded by the nasal, superior maxillary, and intermaxillary bones, forming the osseous boundary of the wide external nostrils. (12 ,jigs. 127, 128.) The superior surface of the cranium is gene- rally convex in relation to and indicative of the development of the brain ; it is round- ed posteriorly, where it is generally widest. Here on each side is seen the temporal de- pression : the interorbital space in the Gulls, Petrels, Albatrosses, Penguins, and other sea- birds, presents also two depressions, scarcely less marked, of a semilunar form, the convexi- ties meeting in the mesial line, and lodging a gland, whose secretion is carried into the nose to lubricate the pituitary membrane. Slight traces of these glandular depressions may be seen at 13, fig. 127, in the Ostrich. In other birds the mterorbital space is moderately con- AVES. 279 cave or flattened. Anterior to this part the cranium in the Parrot presents the moveable junction of the upper mandible, but in other birds a continued osseous surface converges more or less gradually to the end of the beak, only interrupted by the anterior orifices of the nasal cavity. The skull in the Raptores, especially in the nocturnal division, is short, broad, and high, in proportion to its length, and the cranium is large compared with the face. The posterior facet is convex, and remarkably extended up- wards_and laterally, and is continued insensibly at an obtuse angle with the upper surface. The occipital foramen is almost horizontal. The temporal fossa: are not very deep, and do not meet above at the middle line. The cere- bral convexities are not strongly marked ; the frontal region is flat. A longitudinal furrow extends along the whole upper surface of the cranium, and is especially remarkable in the Owls. The cranium and face are separated by a sudden contraction. The orbits are very complete, on account of the development and complete junction of the frontal, ethmoidal, ungueal, and palatine boundaries. The cranium of the Warblers presents a more regular sphericity, but the interorbital space is very concave. The anterior parietes of the orbits are large and very complete from the size of the lachrymal bone and of the trans- verse lamina of the ethmoid ; the internal and posterior bony parietes are, on the other hand, remarkably defective ; the optic foramina are indeed commonly blended into one, and con- tinuous with the larger fissures above. The distinctive characters of the skull of the Scansores are the most remarkable, especially in the Parrots and Toucans. In the former the upper surface of the cranium is flattened or slightly convex, and greatly extended in breadth between the orbits. These cavities are very complete ; and the nasal inlets on the sides of the skull are much limited in size by the extent of ossification. However, the breadth of the posterior part of the base of the cranium and the large size of the pterygoid bones occasion a very considerable interval between these and the body of the sphenoid. In the Toucans the cranium slightly in- creases in breadth to the anterior part where it is joined to the enormous bill. Its superior surface presents an equable convexity. The temporal fossae, like those of the parrots, are small, and wholly confined to the lateral aspects of the cranium. The posterior sur- face, which is absolutely concave in the Mac- caws, from the backward extension of the mastoid processes, is slightly convex in the loucans, where it is separated from the upper surface by a regularly arched ridge. The cerebellic prominence extends over the occi- pital foramen, the plane of which inclines forwards and downwards from the horizontal line at an angle of 45°. The circumference of the orbit is uninclosed by bone at the pos- terior part, the postorbital processes of the frontal not being developed as in the parrots. The zygomatic process of the temporal, with the ligament extending between it and the malar bone, forms here the posterior boundary of the orbit. The septum of the orbits is very incomplete. The ungueo-maxillary fissure and the external nasal apertures are very small, and situated on nearly the same perpendicular line, tire nostrils open on the posterior part of the upper mandible, and the remainder of tb.e lateral facet is, therefore, a smooth entire osseous surface formed by the thin parietes of the dilated cellular mandibles. In the Hornbills the skull presents the same characters as in the Toucans, with the exception of that extraordinary species the Ilelineled Ilornbil! ( Bucerus Guleatus.) In this bird the whole outer surface of the skull is sculptured with irregular furrows and risings, a character which it presents in no other bird, and which can only be compared to the surface of the skull in the Crocodiles. The posterior surface is concave, and separated by a strongly deve- loped ridge from the temporal furrows, which almost meet at the vertex. The bony rim of the orbit is completed by the extension of the zygomatic process of the temporal to that of the malar bone, which, however, are not an- chylosed, but joined by a ligamentous union. The bony septum of the orbits is complete, and formed by two strong plates, separated by an intermediate cellular diploe, except at the pos- terior part. The optic foramen is directed transversely outwards. In all the Hornbills the malar bone is moveably connected with the maxillary as well as the tympanic bones, as in other birds. In the Wood-peckers the cranium is round- ed, the temporal fossae shallow, the internal wall or septum of the orbits incomplete, but the anterior boundary is well developed. The posterior facet of the cranium is raised. The superior surface is traversed by a wide furrow extending longitudinally forwards, generally to the right, but sometimes also to the left, as far as the lachrymal bone. It is in this furrow that the elongated cornua of the os hyoides are lodged, which relate to a peculiar mechanism hereafter to be described. In some of the larger species of M ood-pecker, as the Picus major , L. the cranial furrow is more symme- trical. In the Humming-birds it is double, the hyoidean furrows being separated at first by the cerebellic protuberance, and afterwards by a mesial longitudinal ridge. The skull in the Rasorial birds is narrow, but slightly raised, and without ridges. In the Capercailzie ( Tetrao Urogallus ) it is almost square, flattened on the posterior and superior surfaces, and impressed with a con- siderable longitudinal furrow anteriorly. The orbit is very incomplete, the anterior pa- rietes being almost entirely wanting, and the ungueo-maxillary vacancy being consequently continuous with the orbit. In the Bustards the posterior boundary of the ungueo-maxillary fissure is complete, but in other respects the cranium resembles that of the Rasores. The skull is remarkable for its length in the majority ot the Waders. In the Herons and Bitterns the occipital region is low, and inclines 280 AVES. from below upwards and forwards ; it is sepa- rated from the upper and lateral regions by a well developed, sharp, lam bdoidal crest; and it is divided into two lateral moieties by a slight longitudinal ridge. The temporal fossa; are deeper and wider than in any of the preceding orders ; and they now extend upwards, as in many of the carnivorous mammalia, to the sa- gittal line, along which an osseous crest is developed to extend the surface of attachment of the temporal muscles. The cranium is ex- panded, anteriorly to the above fossae, as if to allow of a compensating space for the develop- ment of the cerebral hemispheres, the interspace of which is indicated by a deep longitudinal furrow, almost peculiar to these genera of birds. The roof of the orbits is expanded late- rally, which gives great breadth to this part of the head, but the posterior orbital walls are very imperfect, and the internal walls or septum almost wholly wanting. The optic foramina are blended with each other and with the smaller foramina, which in other birds represent the foramen lacerum orbitale. The anterior boundary of the orbits is also very imperfectly completed, the ungueo-naso-maxillary and an- terior nasal fissures are not remarkable for their extent. Woodcocks, Snipes, Curlews, and Lapwings, resemble Herons in their defective bony orbits; but they want the extended superior parietes of those cavities, and differ much in the al- most spherical form of the cranium, which is smooth and devoid of the muscular ridges characteristic of the fish-feeding Gralla. In this order the intermaxillary bones present some of their most eccentric forms. They are narrow, elongated, and curved downwards in the Ibises and Curlews; bent upwards in the contrary direction in the Avosets; extended in a straight line in the Snipes ; singularly widened, and hollowed out in the Boat-bill ( Cancroma); widened, flattened, and dilated at the ex- tremity in the Spoon-bill ; thickened, rounded, and bent downwards at an obtuse angle in the Flamingo. Among the Natatores, the sea-birds, as the Divers, ( Colymbus ), Grebes, ( Podiceps ), and Cormorants ( Carbo ), are characterized for the defective condition of the bony orbits, and of the anterior parietes of the cranium ; the septum of the orbits is almost entirely wanting; in place of the posterior parietes there are two lacunae leading directly into the cranial cavity, one superior, of large size, and one inferior, smaller ; they are, in general, separated by a narrow osseous bar, but in the Coulterneb, ( Fratercula arctica ) this is also wanting, so that all the anterior cerebral nerves escape by a common open- ing. But in this species it must be observed, that the vertical lamina of the tethmoid is ossified at its posterior part. In the Petrels and Albatrosses, the internal and posterior walls of the orbits are more complete. In the Diomedea exuluns the optic foramina are separated both from each other, and from the neighbouring outlet. The occipital re- gion is low, and divided into a superior and an inferior facet, the latter being concave from side to side. The plane of the occipital foramen is almost vertical. The occipital or lambdoidal crista is well-marked, and the temporal fossa; nearly approximate in the middle line. In these sea-birds and in the Gulls, the lateral lacuna in the bony parietes of the face are very considerable. A most remarkable characteristic of the cra- nium of both the Brachypterous and Macro- pterous Sea-birds is the presence of the two deep, elongated, semilunar glandulardepressions before mentioned, extending along the roof the orbits. In theiaquatic birds which frequent the marshes and fresh waters, as the Anatida or Lamellirostres, these glandular pits are want- ing, or very feebly marked, as in the Swans. They are, however, again met with of large size, though shallow, in the Curlews ( Nume- nius) and Avosets ( Recurvirostra) ; and are also found, though of smaller size, in the Flamingo. Of the thorax. — In every part of the skele- ton of Birds, we may observe that there is a close adherence to the oviparous modification of the vertebrate type of structure. This is manifested in the forms and connections of the several vertebra;, and of the cranial bones. It is no less conspicuous in the structure of the thorax. The ribs are apparently in moderate num- ber, but when their analogues are closely sought for, they are found to extend, as in the Crocodile, along the greater part of the cervical region. In fact the small styliform processes which point backwards from the lateral projections on the anterior parts of the bodies of these vertebra remain separate after , the true elements of the vertebra have coalesced. In an Ostrich which had attained half its growth, we have found these spurious ribs still moveable. They anchylose, however, with the 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 i determining the commencement of the dorsal vertebra. 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 furculutn, from which ( point, either one, or two, as in the Humming- bird, (see p, fig. 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 Uroyallus ), 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 Rasores seven or eight ; in the Struthiones the number of ribs varies ; in the Ostrich ( Stru- thio ) we find ten pairs, of which the 3d, 4th, 5th, and 6th, are articulated with the sternum ; in the Nandou (Rhea) 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 ( Casuarius ) there are ten pairs, and of these the 4th, 5th, 6th, 7th, 8th, and 9th, have sternal portions. The last pair of ribs in Struthio and Rhea are extremely short, and abut against the expanded iliac bones. Among the G ra llatores we find seven pairs of ribs in the Herons ( Ardea ), and Gigantic Stork ( Ciconia Argula) while the Cranes ( Grus ) 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 (TJria troile ) 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. 1 25, 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 vertebras allows of this mode of articu- lation ; but it is an interesting circumstance that in the Ostrich, where the costal vertebrae 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 corresponding 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 vertebra, 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,Jig. 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 fibro-eartilaginous 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 powders 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, fig. 125, a, fig. 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 20! 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. 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,figs. 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, figs. 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 Ilawks 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 Raptures the sternum is short, convex as in the preceding tribe, hut 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 Barn Owl ( Strix Jlammea ) 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 on either side, and a single lateral process, the extremity of which is constantly dilated. The lateral margins are slightly excavated. In the Curvidee 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, fig. 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 ( Ccrthia ) and Hoopoes AVES. 233 (Upupa), 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 costal processes are also long, and curved forwards; the posterior margin has four deep notches 129 ). In the Trogons, Toilers ( Corackis), King- fishers, Bee-eaters ( Merops ), Toucans, and Touracos, the sternum is characterized by two fissures on either side at the posterior margin. In the Parrot tribe the sternum again singu- larly resembles in its integrity that of the higher If uptores, being 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 turn 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 Rasores 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 Ardeidm 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 • 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, and 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 Anutida 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. ]n 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 Geoffroy St. Hilaire the entosternal ( a, fig. 129) ; two anterior lateral pieces, the hyoster- nals (b, b, jig. 129), and two posterior lateral pieces, the hyposternals (c c, fig. 129). The posterior cartilaginous appendages he terms xiphi-sternals ( g g,fig. 129, 130). If to these be added the two portions or episterruils 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, h, 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. 130), a coracoid bone ( i ), and a clavicle ( k ), — the clavicles being mostly anchylosed together at their mesial extrem ities, constitute a single bone, which, from its peculiar form, is termed the osfwrcatorium ox fare alum. 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 is 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 backwardsfrom theshoulder, 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,) ft 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. 1 25, i,figs. 129, 1 30), or posterior clavicle, is always the strongest ol the bones composing the scapular arch : its ex- panded extremity is securely lodged below in the transverse groove at the anterior part ol 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 AVES. 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, (l, fig. 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, whicli Mr. Vigors re- gards as composing the typical orders of the class, viz. the Raptores and Insessores, (the uves aerea. 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 humero-scapulare, and is regarded as the analogue of the scapula inferior of reptiles. In the Aberrant orders of birds, as the Rasores, 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, fig. 125, b, fig. 130) in birds, 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, the fiurculum, 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 processitself 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 Psittacula Galgnla. those species in which we have examined it, be- longing to the genus Trochilus, Lacep. 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, fig. 125, m, fig. 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, AVES. 2&6 the humerus presents a notable process at the outer side, near its lower extremity; and in the Puffin ( Frutcrcula arc tied ) 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 llaptores,and in the Swifts. In the Penguins it is double ( n, n, fig. 130.) Of the two bones of the antibrachium (y, jig. 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 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 . 130); 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. 130) of moderate length ; to which, in some birds, a third smaller phalanx is added. The ulnar finger consists of a single phalanx only ( t,Jig. 1 30). 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 Primaries 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, Spuria, 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 flic 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 j 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 125, Pelvis and bones of the ley of the Diver , or ioon.^-Colymbus glacialis. a, fig. 131.) is the only AVES. 267 bone of the pelvis which comes in con- tact with the vertebral column, and it ex- tends from the posterior dorsal vertebra; 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,fig. 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 supporting 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 pubis (£, fig. 125, b b, fig. 131J does not extend to meet its fellow on the mesial line, but is commonly directed backwards like a long bent styliform process (3, fig. 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 (f, fig. 131), behind which another fo- ramen is occasionally formed by a second union with the ischium, as is seen in the Ilum- 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, fig. 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 vertebra; is in consequence so much impeded, that they can scarcely be detected at this part ; beyond which, however, the coccygeal vertebra; 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 /e??wr (b,fig. 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 readdy 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, ( Gallinula 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 ( i,fig.\25, hh, fig.\3\) is the prin- cipal bone of the leg — the fibula ( y-,fig . 125, fig. 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 , fig. 131) directed inwards and forwards, anterior to, but not supplying the place of, the patella, (l, fig. 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 AYES. of the latteF 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, fig. 131) in which the above tendons are inserted, and which is very prominent in the Itasores, Gral- latores, and Natatures, 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, Jig. 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- torcs and Slrut/iiones, 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 pf 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 thecre 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 Birds. N umber of Phalanges in the First or inner- most toe or Calcar. Second, com- monly called the Hallux. Third. Fourth. Fifth or outer- most,or little toe. 1 Cock ( Gal- los ), Phea- sants ( Pha- sianus ), Tur- keys, Pea- cocks ( Pavo and Lopho- phoms ) . . p 2 3 4 5 2 Raptores, Tn- sessores, Co- lumbidce, Cra- cidce, Tetrao- ?iidcz?,and the rest of the class, except 2t 3t 4$ 5|| 3 The Genera, Rhea, Dro - mains, Cam- arias, Otis, Cursorius, Charadrius, Hcematopus Arenaria, Falcinella , H imantopus , Halodroma , Diomedea . 4 The Ostrich ( Struthio ) . 3 4 4 5 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 Tnsessores, and Hemipodius among the Rasores, this toe is wanting. In all the rest, with the exception of the Swifts ( Cypselus ) it is directed backwards. f 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 Switt ( Cypselus J have only three phalanges like the third, in the Goat-suckers ( Caprimulgus ) and Herons ( Ardea) the claw of this toe is provided with dentations similar to a comb on its inner side. || Tilts 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 joir in the Bee-eaters ( Merops ), the Motmots ( Pru nites), the King-fishers ( Alcedo ), the Todic ( Todus ), and the Hornbills ( Buceros ), which fon in consequence the family Syndtictyli of Cuvie: In the Scansores this toe is turned backward: and assists the Ilallu. v in opposing the other toe: lhe Owls have the power of turning back tli 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. Fig. 132. 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 characta's 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 vertebras ; in short, that their whole organization was regulated by the same general v 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 Sparrow-hawk . These characteristic properties are mani- fested in the greatest degree in the muscles of those families of the Insessures which take their food on the whig, as the Hirundinides and Trochilida, (Swallows and Humming-birds); in the Diurnal Haptores 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 sternum, 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 Opisthotenur, 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 vertebras. 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 Cerviculis uscendens (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 filth 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 - versules (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 AYES. 291 spinous processes of the dorsal vertebras and from the anterior part of the cervical vertebrae, 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 cervicis 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 vertebras, 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 Complexus (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-mastoideus (8) arises from the articular processes of the cervical vertebrae 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 anticus major may be seen at 4. This muscle is largely developed, arising from the anterior part of the sixth, seventh, and eighth vertebra, and inserted into the basis cranii. There are also muscles ana- logous to the Rectus capitis anticus minor, the Recti postici majores et minores, the Obliquus externus 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. VYhen 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 fieanser of the plumage, we cannot sufficiently idrnire the endowments of length, flexibility, md muscularity, by which it is enabled to ulfil the important functions of an additional xtremity. In the caudal region of the spine the fol- owing muscles present themselves. On the orsal aspect, the Levutor coccygis (10) ex- 'nds 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 Interspinales mus- cles. The Quadratics coccygis (\1) arises from the transverse processes of the coccygeal vertebrae and is inserted into the shafts of the rectrices 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-coccygeus (13) extends from the posterior margin of the ilium to the last coccy- geal 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- coccygeus (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 vertebra, 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-frontalis (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 Masseter; 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 ; v 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 scpiamous 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 vertebra are met with abundantly in the inferior vertebrate classes, especially in fishes, where they extend frecjuently 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 audilorius ; they are in- serted into the back part and angle of the lower jaw. A similar disposition of the digostricus is met with in many of the mammalia ; even in the Orang-utan ( Simia 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 Ilorn-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 Yarrcll ‘ 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 process 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 hone 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 vertebra. The Intercostales externi appear to be con tinuations of the Levatores costarum, and are ; usually divided mto an anterior and posterior moiety corresponding to the marked separation and moveable articulation between the vertebral and sternal portions of the ribs ; the anterior 1 division arises from the costal appendage and 1 extends to the anterior extremity of the rib ; . to afford a more advantageous origin to this inspiratory muscle would appear, therefore, to i be one of the uses of the costal appendages, as well as to strengthen the connection of the ! ribs to each other. The Internal intcrcostals 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- I tions of the ribs ; arising from the superior and Bj 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 rectus abdominis. 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 Transversalis is a muscle of greater extent; it arises from the whole anterior margin of the puhic 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 lohes 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. Ehe 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 vertebra, 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 Rhomboideus 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 vertebra 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 Serratus magnus auticus (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 Serratus 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 vertebras, 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 Deltuides (26) is comparatively a small muscle ; it arises from the anterior part of the 294 AYES. scapula, and is inserted along the middle of the outer side of the humerus ; it brings the wing upward and backward. Birds have the Pectorulis 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. The first 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 longana widein 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 here remarkably developed. The great pec- toral is very long, but not very thick in the Rasores. 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 mto 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 coracoideum, 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-bruchialis, 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 Struthionida, is of small size in the Heron and Goose, is much more developed in the Raptores 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 two flexors 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 Cams 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 AVES. along the edge of the aponeurotic expansion of the wing. In this situation it acquires exactly the structure and elasticity of the liga- mentum subflavum or ligameDtum nuchse ; 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, fig. 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. Tnthe Penguin this muscle is extremely feeble, and the tendon is lost in that of the tensor plica alaris. 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, Ehasianidu , 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 295 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 quadratus lumborum 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 Glut ecus medius: Carus calls it the Gluteus muximus. But the latter, according to Meckel, is represented by the posterior part of what Carus terms the Rectus fiemor is latissimus (40). Anterior to the Gluteus 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 Gluteus minor of quadrupeds. It is wanting in many of the Natatores, 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 Mechel as the Iliacus interims, 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 P yramidalis 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 flanoris (40) arises by a thin but wide aponeurosis from the spines of the sacrum, after a short course it joins the Crurtxus and Vasti (42), and is inserted into the head of the fibula. It corresponds according to Meckel with the Tensor vagina femoris and the Glutaus mugnus. 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 perforates of the toes. Meckel con- siders that the muscle now described represents the Rectus femor 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 Raptures. Scansores, 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 fibro-cartilage appertaining to the fie xor 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- tacidie 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 for 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 perfloratus seu 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 ofthelegand constitute one fleshy belly which gives off three tendons ; these proceed to the proximal phalanges of the three outer toss where they bifurcate to give passage to the ten- dons of the flexor perforans. The Flexor poll ids (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 condyle of the femur; when it has reached the region of the calcaneum, 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 profundus performs (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 communis 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 three 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 Aves terrestres. 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, fyc., 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 uater 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, 208 AVES. itis 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, ike., 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 liace-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. 134, a, b,c,d) and medulla spinalis (e,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" 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 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 j medulla oblongata, (d,)\ ( Fig . 134J * 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. V' I Brain and Spinal Cord of a Goose. AVES. 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. The optic lobes (b, Jg. 135) are rounded tubercles, situated be- low and behind the hemispheres, in the la- teral interspace between these and the cerebel- lum. The cerebellum is „ . , . . composed of the middle Base of the brain of a , , 1 , , . r Pigeon. lobe only> and ls 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 Rep- tiles and Fishes, and some of the least intel- ligent orders of Mammalia, as the Roden tia, Marsupi.ata, 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, (Jg. 136,J they are 'JiJr i seen to be disunited mW through the whole of their vertical extent, and to be joined only by the round anterior commissure of the brain (k,Jg. 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 striatum ( 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, (h,) 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, (j\) 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 (l) 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 orlamelliform commis- sure of the optic lobes. Caras 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 vyith 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, nouv. eJ. i. p. 88, pi. xv. fig. 6. 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 foetus. The substance of the cerebellum does present the admixture of the two substances, or arbor vitie (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 vertebra;, 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,fig. 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, fig. 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 rhomboidalis.’ 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, fig. 13.5.) These nerves are of a cylin- drical figure and small 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, figs. 1 35, 1 37,) 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*, fig. 137,) in which, on making a horizontal section, some transverse stria; may be perceived, apparently resulting from the decussating fibrils of the nerves. The distribution of the third, ( 3, figs. 135, 137,) fourth, (4, figs. 135, 137,) and sixth cerebral nerves, (6, figs. 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% fig. 137, as far as its termination in the superior oblique muscle to which it is, as in other vertebrata, exclusively distributed. The fifth or trigeminal nerve (5, figs. 135, 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", fig. 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 Anatida: and other Water-fowl, where the upper mandible is notched on the edge, each denticu- lalion receives four or five nervous filament?, 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 confirmed to the anterior end of that mandible. In the Anatida it gives off AVES. 301 nerves 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, ox 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 heart, and proceed along the tfisophagus to terminate in anasto- moses with the great sympathetic nerve. The glosso-phuiyngeal 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 vertebrae 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 vertebra. 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 (V iC, fig. \ 34 ) 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,fig. 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 AYES. 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. “ 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 thecourseof 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 tibia l and the peroneal nerves. “ The tib'uil 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 auticus 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.” — llees ’ 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 AVES. 303 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 tire cardiac plexus of the par vagum ; three other filaments proceed inwardly to the projection formed by the bodies of the vertebra 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 the 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 trie sympathetic con- tinues along the bodies of the vertebra, 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. 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, (fig. 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,fig . 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 isrnain- tained by a circle of osseous plates or scales (f, ,/?g.l37)mterposed between the exteriorand 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 (c,Jig. 138) is delicate in its texture, which under the lens appears composed of a fine net-work of interlacing fibres, but itis 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, and 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 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, rnnning 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, (cl, Jig. 138,) the extremities of which adhere firmly to the capsule of the chrystalline. These processes are the most numerous, close set, and delicate m the Owl ; they are proportionally larger and looser in the Ostrich. The chief peculiarity in the eye of the Bird is the marsupiutn or pecten, (f,fig. 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 f 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 centralis retine, enter the eye between the laminae of the retina, along the whole extent of the oblique slit above men- i 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 marsupium 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 plica 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 to Soem- 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 Home,]: 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 Marsupium or Bourse. The origi- nal description is as follows : — “ De cet entonnoir (the termination of the optic nerve) sortoit une membrane plissee, faisant comme me bourse qui abou- tissoit en pointe vers le bord du Christallin le pins prochain de l’entree du nerf optique. Cette bourse, qui estoit large de six lignes par le has, a la sortie du nerf optique, et qui alloit en pointe vers le baut, estoit attachee par sa pointe aubord du Chrystallin, par le moyen de la membrane qui le couvroit du eoste de l’humeur vitree, et qui couvroit aussi toute la bourse qui estoit noir mais d’un autre noir que n’est celtty de la choro'ide.” — Duvernoy, in ‘ Me- moires pour servir a 1’Hist. Nat. des Animaux,’ p. 375. t Croonian Lecture, Phil. Trans. 1796. VOL. I. it does not extend to the chrystailine, 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 chrystailine, it can only move it obliquely. Some physiologists have supposed that this black membrane was extended towards thecentre 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 lo the vitreous humour. The chrystailine 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 chrystailine is of a rounder figure, and this is peculiarly the case in the near- sighted Owls which hunt for prey in obscure x 300 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 — the one in front and the other behind the lens, — leave round its circumference the sacculated canal 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 retinas. 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 {i,Jig. 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 ,fig. 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 Fig. 139. ismoved 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 * Meckel’s Arclriven, B. xii, pi. x. 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 Jig. 140, a' is the rectus superior or uttollens ; U the rectus inferior or deprimens ; c' the rectus ex- ternus or abducens ; d‘ the rectus internus or adducens ; e‘ the obliquus superior ; f the ob- liquus inferior ; g' the quadratus ; h ' the pyra- midalis. 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 palpe.bree superioris 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 h an example, as also the Horn-bills and the Owl.s, 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 sheath, having no express or fixed insertion. The second muscle, called Pyramidalis nictitantis, (h, fig. 139,) arises from the sclerotica 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 quadratus, 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- dratus, 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 recti. 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 Glandula Harder iana ( 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, fg. 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, (k\ fig. 140,) and is inclosed in an ex- tremely dense fibrous niembrane. 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 Se. par la Soc. Philomath, iii. an 6. p. 267. f Nitzsch, Meckel’s Archiv. vi. p. 234. x 2 308 AVES. 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 . 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 auditories, which serves in some degree the office of an external ear. The Ostrich and Bustard ( (l,fg. 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, jig. 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 jlammea ). This species is also remarkable in having the membrana tympani attached ex- clusively to the bony meatus (b,fig. 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 eav, 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) lias 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 j'oramen 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, ts moved by one muscle (f', _pg. 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, AVES. 309 in consequence of the connections of the ossi- culum, 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 vibratile 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, canales 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 ampullte (/), 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 lube (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 1 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. I he 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 s 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 Smelt.- — The close affinity subsist- ing between the cold and warm-blooded ovipara 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 the 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 Corvidte 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, fig. 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, Le<;ons d’Anat. Comp. tom. ii., and Macartney in Rees’ Cyclopaedia, Art. Birds. t See Montague’s Ornithological Dictionary. 310 AVES. the orbit, the external terminates behind the middle turbinated lamina in a cul-de-sac. These olfactory lam in* 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 Ilorn- bill and Toucan. We have found this to be the case in the recent Toucan. The organ of smell in this singulai species is confined to the base of its enormousbeak,f 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, fig. 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: Grullatores, Natatures, Ruptores, Scansures, Inscssores, 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. Roget 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 for 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 ol 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, Bridgewater Treatise, vol. ii. p. 406. AVES. Organ of Taste. — 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 (h,fig. 152), and is destitute of papillee except at its base ( o, fg. 152) near the aper- ture of the larynx ; these papilke 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 papilfe ; 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 Gluucopis 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 311 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. Geoflfoy St. Hilaire has described a structure in the bill of birds which presents a closer approach to a dentary system. In a fetus 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. Cateris 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 Comparee, tom. ii. p. 192. AVES. 312 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 Trey 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 {fig. 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. Bill of the Petrel. batrosses, Frigate-bird, and Tropic-bird. But in the Raptores 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., {fig. 1 16) ; 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 lb's it is curved down- wards {fig. 123); in the Jabiru (fig. 143) it is curved in the contrary direction. 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 {fig. 145), which is also ser- rated at the edges. Some t ^ speciesofFly- y (O' catcher and Tody have this form of beak on a small scale . Hiif of 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 {fig. 146), it serves to seize a large but feebly resisting prey, as fishes. 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. {fig. 147.) 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, tire 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 A.VES. 313 of the mandibles are bent downwards abruptly {fig. 148), have all transverse horny lamina Bill of the Flamingo. arranged along their edges, which, when the bird has seized any object in the water, serve, like the whalebone lamina 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 ), which are nearly allied to the Anatidz, 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. The bills of the Toucans and Hombills 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 com- Fig. 150. 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, fig. 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 m 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 (in, Jig. 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, fig. 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 IJornbills 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 (fig. 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 (fig. 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 Rampkastidce, 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 bird, ob- serves that, notwithstanding M. Buffon’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, l 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 byoides very much resembles that of lleptiles. Its parts have been minutely studied by Geoffroy St. Hilaire, who has bestowed upon them separate names: (a, fig. 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 m the Swan and other Lumelli-rostres. * Zool. Journal, vol. iv. p. 464. AVES. Fig. 151. 315 In 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, Os hyoides and larynx Swan. 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 Woodpecker 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, fig. 153, 154.) Fig. 153. 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 from twenty to twenty-five recurved spines, from one to three lines in length. These spines are arranged in an irregular alternate series : the outer ones being the smallest, which 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 Raptores 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 31G 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 oerato-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. Gth. 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 Ceraio- tracheales, ( A, 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- ation, anterior palatine: in the Pica they correspond to the parotid and sublingual of Quadrupeds. The sublingual glands of the Woodpecker are of extraordinary size, extending from the angle to the symphysis of the lower jaw. The single ducts of each gland unite just before their termination, which is a simple orifice at the apex of the month. The structure of these glands is shown at i, k, fig. 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 ( Gallinula chloropus ) there is a series of coecal glandular tubes along each side of the tongue ; and it is interesting to note that glan- 317 AVES. dular 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- chial 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 ernbued 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 papilla: 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 has 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, fig 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(7ig.l55). In the male there is a membranous sac extendingforsome 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 durmg the breeding season _ r uncial bag of the Bustard. Sec 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 Bustard ; it is also proportionally of less extent. A similar structure obtains in the Rook and probably in other Insectivorous birds. The oesophagus ( H , fig. 171 : a, 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 tire 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 Rap tores, 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 cesophagus 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, fig. 159), in the internal longitudinal (b, fig. 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 cesophagus 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, fig. 156). the Pigeon it is double, consisting of two lateral oval cavities (b c,fig. 158). The dilatation of the cesophagus 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 cesophagus, but the muciparous follicles of the lining membrane are larger and more numerous. This 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 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. 158. Crap of a Pigeon. 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 * A ■ 1 ,-v 0‘AFk AVES. 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 ‘ 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(6), shows the ordinary structure of the parts, the other ( e ), the state of the cavity during the period of rearing the young [Jig. 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 succenturiatus, bulbus glandulosus, echinus, infundibulum, the 1 cardiac cavity ’ of Home), (c, Jig. 156, 157, 166). In birds with a wide oesophagus ( a, fig. 165), 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. jig. 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 Psittucidc e 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 fundus, 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 Fig. 159. Part of the proventriculus of a Swan dissected. 319 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. lvi.) show the different forms of the solvent or proventricular glands in different birds. Fig. 160. •d r o o Eagle. Gannet. O PH l Sea-gull. I Pigeon. Swan. Goose. Fowl. 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 Naiatores 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 form a complete zone. In general the muscular or pyloric division of the stomach immediately succeeds the glan- dular or cardiac division ; but in some Birds, as the Auk and Parrots, there is an intervening portion 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 sacrud of the liver, on the left side and dorsal aspect of the abdomen, generally resting on the mass of intestines ; although, according to Bluinen- 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 (6, Jig. 161) ; below these apertures the cavity extends to form a cul-de- sac (c, fig. 161, 162.) At the middle of the anterior and posterior parts of the cul-de-sac there is a tendon ( e , fig. 156, 157) from which the muscular fibres radiate. AVES. 321 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 Raptores the gizzard (d, fig. 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 (e. Jig. 156), and there are some longitudinal fibres beneath the radiating or external layer. In the Rusores 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 {e, fig. 157, 162); they constitute the sides of the gizzard, and are termed the digastric muscles or ‘ musculi laterales’ (d, fig. 161, 162) : between these, at the end of the gizzard, are the two smaller and thinner muscles called ‘ musculi intermedii’ (, f,fig . 162). There are likewise irregular bands placed about the cir- cumference of the gizzard. Fig. 161 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. The internal coat of the gizzard (c, h, fig. 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. 162). It is here that the fibrous structure of the lining membrane can be most plaiuly 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, fig. 161, 162), which vary in different birds, but are pretty constant in the same species. Carus* has recently figured the gizzard of a Petrel ( Procellana 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 ‘ 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 subgenus Eup/iones, 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 parietes 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 Hunterian 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 ‘ Caesalpinus 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 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. * Tabulas AnatomiamComparativam illustrantes, fol. pars iv. 1835. f 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. t 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 lledi’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, ( Dc Gcneratione Animalium, in Opera Omnia, 4to. p. 208,) “ Fal- conibus, aquilis, aliisque avibus ex preda viven- tibus, si aurern 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. Soe. 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 ccECum, but most generally by those of two cocca, which are always opposite to one another. In a few instances there is no such distinction. The small intestines and cocca 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, (jf, Jig. 163,) Fig. 163. which fold receives the pancreas (, q, fig. 168, 169) which correspond to the mitral valve in Mam- malia. Of these valves, the one next the aorta(etween the jugular vein and the sinuses of he brain ; and in every instance the external eins of the head appeared to be sufficiently uge of themselves to produce the trunk of ie jugular. It may, therefore, be presumed iat if any branch analogous to the internal igular vein passes through the posterior fora- ien lacerum, it is very inconsiderable, and 339 incapable of transmitting the blood of the brain. “ The sinuses of the brain seem to discharge their contents principally into some veins which lie in the membrane forming the sheath of the spinal canal, and these appear to dispose of their blood gradually, as they descend in the neck by means of lateral communication with the vertebral veins. The sinuses, which immediately open into the spinal veins, are situated upon the back of the cerebellum, aud produce, by anastomoses with each other, with the superior longitudinal sinus, and with others along the side of the brain, an union of vessels of a diamond shape. “ The sinuses of the brain in birds generally are irregular in their form, and consist of flat- tened canals; and not only the sinuses on the back of the cerebellum, but the spinal veins appear so like extravasation, that accurate and repeated observations are necessary to discover them to be real vessels. “ The principal sinuses, besides those upon the cerebellum, are the superior longitudinal, and one which runs along the lower edge of each hemisphere of the cerebrum; there appears to be also one upon the side of the cerebellum, corresponding to the lateral sinus. All these sinuses communicate with each other on the back of the cerebellum as already mentioned. The superior longitudinal sinus is continued at its -anterior part under the frontal and nasal bones, and anastomoses with the ophthalmic and nasal veins. There are other sinuses in the several duplicatures of the dura mater, which are too small to be easily traced or to deserve much regard. “ The veins of the wings, or superior ex- tremity, have a less curious distribution than those of the head. The branches which are derived from the parts within the chest, the muscles about the scapula, and the pectoral muscles, accompany the arteries of the same parts so regularly that their course does not require description. “ The axillary vein (T) lies considerably lower in the axilla than the artery, but still continues to receive corresponding branches; ( m indicates the great pectoral vein). The trunk of the vein descends in the course of the humeral artery, but more superficially; in this situation it may be called basilic, or more pro- perly the humeral, vein ( n ). There is no vein in birds which deserves the name of the ce- phalic ; there are branches of the humeral vein, accompanying the articular and profunda arte- ries, and at the middle of the humerus a large branch of the vein enters the bone ; there are also two very small branches which lie in close contact with the humeral artery, which they accompany nearly its whole length. “ The principal vein of the wing divides into two, opposite to the joint of the humerus with the fore-arm. One of these branches (o) belongs to the sides of the radius ; it receives blood from the muscles and skin on the upper part of the fore-arm, but its chief vessels lie be- tween the integuments of the fold of the wing. The other branch of the humeral vein (p) crosses z 2 3-10 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 join's from the opposite side of the fingers. 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 ( tom. iv, p. 450. AVES. 347 Barn-Owl ( Strix Jiummea ) and Horn-Owl ( Otus aurita). 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 ( i 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, is the Owls, that in them they resemble some- what in their superficial position the kidneys of nammalia. 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 * Dc Glandularum Structura, p. 92. 3+8 AVES. trunks to the branches, are seen to become con- joined 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, fig. 171) to the hypogastric vein (z). 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 uvipara, 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, h,jig. 176) has 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 papillae of the ureters are situated with the orifices of the genital ducts, in the same segment of the cloaca, which is therefore termed the urethra-sexual cavity (e,jig. 176). The space intervening between the urethra- sexual cavity and the valvular termination of the rectum ( c,ftg. 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 Felecan, 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 (d,fg. 176). Fig. 176. Cloaca of the Ostrich .* The Supra-renal Glands, Renal capsules, Glandules succenturiate (d, d, Jig. 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 ol 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 wiih 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 Memoires du Museum, tom. xv. pi. 2 ,Juj. 1 AVES, 349 Peculiar Secretions. — 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 which 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 rcte mucosum. The corium, or true skin, is very thin, as in the cold-blooded Ovipara. It adheres to 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 colonies 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, Cassowary, the Apteryx, and the Palamedea ; and upon the tarsi of the Gallinaceous Birds. The claws which sheath the ungueal phalanges of 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 Jiummea ), the Goat-sucker genus ( Caprimul- gus ), the Heron and Bittern kind (Ardeida, 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- cida, 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 1 Scu- tipedes.’f 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 seriated claw the function of freeing the plumage from vermin, because its presence is partial in the class of Birds. “ To suppose,” says he, “ 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. t In one section' of the Tyranni , Cuv. the scut® 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-extendcd 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 (he 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 Fig. 177.* of size, consis- tence,and colour, all feathers are composed of a quill or barrel Oh fig ■ 177), a shaft (b b), and a vane or beard. (c c) ; the vane consists of barbs (e e, fig. 178) and burbulesfffi, 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 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 ■ 1 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 homy material similar to that This figure and fig. 179, 180, 181, are copied from the Monograph of F. Cuvier, Surle developpe- ment des Plumes,” M6moires du Museum, tom. xiii. of which the quill is formed, and they inclose a peculiar white, soft, elastic substance, called the pith (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 the bases of the barbs of a feather magnified. The barbules (f f, 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 j 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 doc-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 1 the accessory plume. It is usually a small downy tuft, but varies both in different species, and even in the feathers of different parts ot the body of the same bird. In the quill- feathers of the wings and tail, it usual!) 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. thp infprinr of tVip nnill AVES. 351 In the Ostrich the feathers have no accessory plume : in the Ilhea 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 4 auriculars.’ Those which lie above , the scapula and humerus are called the 4 scapulars.’ The small feathers which lie in several rows upon the bones of the antibrachium are called the 4 lesser coverts ’ C tectrices primes ). Those which line the under or inner side of the wings are the 4 under coverts.’ The feathers which lie immediately over the quill-feathers are the 4 greater coverts’ ( tectrices secunda ). The largest quill-feathers of the wing, which arise from the bones of the hand, are termed 4 primaries’ (prirnores). Those which rise from the ulna, towards its distal end, are the 4 secondaries’ ( secondaries ). Those which are attached to its proximal ex- tremity are the 4 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 ; m which, although the pectoral muscles are immensely developed in order to counteract die disadvantage resulting from the disposition of the primaries, yet they are only able, in consequence of the form of the wing, to carry he bird rapidly forward for a short distance, md that with an exertion and vibratory noise veil known to every sportsman. The texture of the quill-feathers has also a oaterial effect on the powers of flight. In he Falcons each primary quill-feather is longated, narrow, and gradually tapers to a oint; the webs are entire, and the barbs 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, 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 to the feather which it incloses, and the formation of which has, in the meanwhile, been * 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. and at the sides Fig. 179. a a Matrix of a grow- ing Feather, with the Capsule laid open. 352 AVES. gradually proceeding from the apex downwards. The capsule of the matrix (a a, fig. 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 (d, Jig. 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 septa?, the matter of the vane (c. fig. 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 from 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, 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 whichis moulded between the two striated membranes until the entire feather is completed. If the striated membrane inclosing the bulb be attempted to Fig. 181. W Wi U m Structure of the Bulb. be reflected from below upwards, it will lie found to be connected with a series of mem- branous cones f 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 the 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-jj phere. The bulb itself, when examined in a half-formed quill-feather,* is composed of twi 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 feather in the goose. A^ES. 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. Its 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 bulb, 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 die quili. 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 one 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 me years, and several birds rear a progeny before they acquire the plumage of maturity. " hen the male bird assumes a vestment vol. r. 353 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, tire 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 * Yavrell, 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 ,fg. ICO, a, ii, Jig. 182) are 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 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 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 °fa Cock. 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 testesof 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. 1 1 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. 182. Fig. 183. © © 1. January. © 2. Middle of February. 3. Beginning of March. 4. Latter end of March 5. 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 bin« 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 (b, Jig. 182). This part frequently pre- sents a colour strikingly different from that of the testes: thus it has been observed in the Bustard and Curassow to be black; in tin Cassowary, yellow ; and in the Anthropoids 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 meters without undergoing any remarkable convo- lution ; but in the common Cock it is lent 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 m the diameter of the tube composing them, and they are so closely compacted as to present m a longitudinal section the appearance of a series of cells, which are capable of retaining, as in a vesicula seminalis, a quantity of t a seminal secretion. , Each vas deferens in the Common cock, terminates on a separate rudimentary penis oi papilla, situated in the urethro-sexual d. vision of the cloaca at a little distance from cacti 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, :'b fig. 171) which serve as an erectile organ during the venereal orgasm, when the turgid papillae ai AVES. 355 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 Natalores 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. it is in the unexcited state coiled up like 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 off 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 b, Jig. 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 papilla: 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 glandula odorifera ; but there is no vestige either of prostatic or other urethral glands. Female organs of generation. — An ovarium or productive organ, (a, b, c, d, fig. 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 CEconomy, 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 papillae, on which the vasa deferentia termi- nate. 2 a 2 35G AVES. Fig. 1B5. excitement is found in those species of which the males have a penis. Birds difler 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 vaginae 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 Rodentia, 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 Zoolomie.’ 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 Rap tores. In the Falcons Nitzsch found the right ovary more developed than the left, and also in 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 ot 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 tiie 1 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 iri 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 ‘ germinaiive vesicle,’ states that it is most easily detected in the ova of the common I owl, when they have attained the size of from four to six lines. The vesicle is at this period lodged in a mam- AVES. 357 miliary pile ( cumulus ) of white granular sub- stance, 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- bmna 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, d, 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,Jig. 185) distributed in a pectinated manner, and converging towards a white transverse line, called the stigma ( c, .fig- 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 (J), 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 tne article Generation; and we resume he consideration of the female organs. The calyx of the ovum, when emptied of its contents (d,Jig. 185)- collapses, shrinks, and is ultimately absorbed, not forming a permanent yrpus luteum, as in Mammalia. In Birds that have but few young at a brood, Is 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 duplicature 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,fig. 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, fig- 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 left 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 mem- 356 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. Bidliograph Y. — Perrault, Description A nato- mique de six oiseaux appelles Demoiselles de Numidie, Mem. de Paris, t. i. et t. iii. Duverney, Observation Anatomique sur le pevroquet arras, sur la cigogne, sur le casuel, Mem. de Paris, t. i. Vicq-d’ Axyr, Memoives pour servir a l’anatomie des oiseaux, Mem. de Paris, A. 1772, 73, 74, 78. Tiedemann, Zoologie, 2ter u. 3tter Bd. Anat. und Naturgeschichte d. Vogel, 8vo. Landsh. 1808-14. Nitxsch, Aufsatzen, in Meckel’s Archiv. B. i. B. ii. and B. iii. * '* * * Colter, Divers, animalium sceletorum explicationes, fol. Norimb. 1575. Camper, Memoire sur la structure des os duns les oiseaux et de leurs diversites dans les differentes cspeces, Mem. de Mathem. et Pliys. A. 1773. Nitxsch, Osteographische Beitr'age 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, Miag. of Nat. Hist, 8vo. Lond. * * * * De Reuumur, Sur la digestion des oiseaux, Mem. de l’Ac. des Sc. de Paris, A. 1752. * * * * Bauer, Disquis. circa nonull. Avium systema arteriosum, 4to. Berl. 1825. Nitxsch, Obs. de A vium arteria carotidc communi, 8vo. Halae, 1829. Burliow, Untersuchungen liber das Schlagadersystem d. Vogel, 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. 1708. Hewson on the absorbents of Birds, Phil. Trans. 1769. Lautli, 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. * * * ® Haller, De cerebro avium et piscium, Verh. van het Maatsch. te Haarlem, Deel 10. Malaearne, Esposizione anatomica delle parti relative all’en- cefalo degli uccelli, Mem. de Verona, t. i. ii. iii. iv. vi. vii. Nvman, De medulla spinali avium, &c. 8vo. Hallae, 1811. Frank, De avium encephali anatome, 8vo. Berl. 1812, et in Red's Archiv. B xi. * * * * Vicq-d’ Axyr , De la structure de l’organe de l’ouie des oiseaux, Mem. de Paris, A. 1778. * * * * Mery, Observation sur le cercle osseux autour de la cornee de l’ocil de 1’aigle, du corbeau, et sur la sclerotique de l’autruche, Mem. de Paris, t. ii. p. 24. Tannenberg, De partibus genitalibus masculis avium, 4to. Gotting. 1789 ; Germanice auct. 4to. Gotting. 1810. Spangenberg, Disq. circa partes foemineas genitales avium, 4to. Gotting. 1813. Cuvier, Lecjons d’Anat. Comparee, 5 vol. 8vo. passim, Rees’s Cyclopaedia, art. Birds, by Macartney. ( Richard Owen.) 5 Purkinje, Symbolae ad Ovi Avium Historians, 4to. 10. fig. 19. AXILLA (surgical anatomy) — (Fr. Aisselle, Ger. Acliselgruhe.) Syn. region axillaire, 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 meaut 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 ti uncated 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 nume.'ous 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 j! 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 I is drawn a few inches from the side, and sup- 1 ported without any effort of the patient. AXILLA. 359 Immediately under the skin vve 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 m detail. The anterior wall consists of the pectoralis major and minor muscles. The pecturalis 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 horn the seventh rib to thehumerusand 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 eorning 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 continuouswiththe triangular or coraco-acvomial ligament, and in some rare instances the entire tendon runs across the coracoid process, and through this ligament to join the capsular liga- ment of the shoulder-joint. The tendon is about an inch broad ; very short on the posterior 3(30 AXILLA. surface, longer on tire anterior, and longer still at the lower edge. The surface now exposed was covered by cellular tissue, and concealed by the pecloralis 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 costo-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-clcido-coracoid. The name ligdmentum bicorne is sometimes applied to in- dicate its horn-shaped extremities ; Blandin denominates it fascia clavicular is, and Gerdy, ligament suspenseur de I’aisselle. 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 ot 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 Bel 1, by whom it lias 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 costo-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 magnus 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, tkc. 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 been recorded. Velpeau mentions one, which resulted from a blow inflicted on the inner wall of the axilla 1 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 both 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 tlie circulation of the linrb. 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, dine subscapular, and six others of much jreater size, viz. the external cutaneous, median, nternul cutaneous, ulnar, musculo-spiral, and ircumflex. The thoracic branches are most commonly hree in number ; the anterior, arising from the seventh cervical, runs in front of the great ves- els and is lost in the pectoralis major and lectoralis minor muscles ; the middle, very mall, passes under the vessels and is lost in ie lesser pectoral ; the posterior, the largest, ; the respiratory, and has been already de- nt bed. The subscapular branches are also three in umber generally ; they come from different oints ai the upper and back part of the plexus : ie smallest quickly enters the subscapular uscle : the other two sometimes arise by a >mmon trunk, or one of them comes from the jreumflex, both run along with the sub- apular artery, the larger pierces the teres ;ajor and is lost in the latissimus dorsi, the nailer is distributed to the subscapularis, teres ajor and teres minor. Hie external cutaneous, or per forans Casserii, mes 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 t.he 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. Round 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 tibres 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 dor si, 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-bracliialis, 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 d oes 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 or 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. 1 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 j 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 putty swelling marks the effusion of serum into tin cellular membrane, which may or may not b( followed by suppuration. The glands frequently take on the disease under which the neighbouring mamma labour.' as cancer, fungus hEematodes, &c. Thesj must be removed if the breast be amputated They are generally in the course of the extern; mammary artery, and no other vessel is it terested in their removal, yet the looseness c the tissue in which they lie renders it unsafe tj cut the little vessels derived from this moot siderable artery. Surgeons usually twist < tear away the glands, or else apply a hgatui 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 the BIBLIOGRAPHY see 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 subclavius 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 stale 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 hsemor- 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. the acromial; 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 off 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 3(34 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- mion 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 ( thoracica 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 mammuria 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. Soemmerring describes a fourth thoracic ar- tery, under the name of alaris sive axillaris glundulosa 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 Soemmering, passes backwards through a triangular space formed by the sub- * Do Hum. Corp. Fab. t. v. p. 109. scapularis above, the teres 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-spiuatus, 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-spmatus 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-scapularand 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 oft’ 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 j 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, ji to which and the other parts entering into tiie 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. For the Bibliography see that of ANATOMY (Introduction) and of Artery. (J. Hart.) AZYGOS, (a, Ifvyoz, 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. 65 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, Prclum- ho-tlwracique, Vena sine pari, 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 vertebrse; it serves to receive the blood from most of the intercostal spaces, from the phrenic, bronchial, and medi- astinal veins, as also from the vertebra 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 aud 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 crus 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 .'.issue ; the aorta is to its left, and in the in- tervening adipose matter the thoracic duct is {placed ; the right splanchnic nerve is external o it or on its right side. Opposite to about lie fourth dorsal vertebra the vein leaves the I’Pine, increases very much in size, arches onvards 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 oeso- 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 soinetines 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 vertebras 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- tebras, 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 vena; innominatas. 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 vertebra; it communicates with the1! 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 between1 the two cavae, 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 ol the lower segment of the body. Cases have even occurred in which the inferior cava has been obstructed or nearly obliterated by thejl pressure of a tumour or of a diseased liver and in these this anastomosis, and indeed tin whole vena azygos have been found greath increased in size. The vena azygos appear moreover to have been formed as a convenient means for receiving numerous venous branche which could not reach any of the large vessel BACK. 3t>7 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 fllBLIOGRAPH Y 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 ihe absence of a spinous process in the atlas, while the muscles on either side, chiefly 'the complexi, stand out boldly. In fat persons i quantity of adipose substance fills up this lollow and nearly obliterates it. The upper bird of the neck, and in some persons much nore, is covered with hair. This part is tech- lically called nucha, a term of Arabian origin, ts common appellation is nape of the neck. See jig. 2.) The dorsal region corresponds in length to the twelve dorsal vertebra*, with their intervertebral 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 raplrfe 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 BACK. 3G3 never be followed by troublesome haemorrhage. In the fascia we generally find 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 clostly : 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, rliom- boideus major , rhomboideus minor, levator an- guli scapula, serratus posticus superior, serratus posticus inferior, splenius capitis, splenius colli, sacro-lumbalis, longissimus dorsi, spinalis dorsi, semi-spinalis dorsi, cervicalis descendens, trans- versalis colli, trachelo-mastoideus, eomplc.rm, spinalis colli, multijidus spina, inter-spinales, inter-transversales, rectus capitis posticus major, rectus capitis posticus minor, obliquus capitis in- ferior, and 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. The first 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. Thefourth 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 complexes. The sixth layer, again, is formed of short mus- cles, rotating and erecting the head or minute j1 portions of the spinal column ; these are the recti and obliqui of the head, the spinalis colii, inter-spinales, inter-transversales, and multifidus spinas. 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 vertebrae. 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 tendmou: fibres which are from half an inch to an mcl;j long in the occipital portion ; in the cervical! they are very short until we come down to the sixth cervical vertebra, where they begin tej lengthen; at the first dorsal they are an inch and a half in length, again they diminish, and aj the fourth dorsal spine they are scarcely to b seen ; but at the tenth they again increase i length, and form a triangular tendon. Itsom< BACK. 369 times happens that this muscle has no connexion with the eleventh and twelfth dorsal vertebrae. The long tendinous fibres of the two trapezii, at the junction of the cervical and dorsal re- gions, form an oval aponeurosis of considerable size, called the cervical aponeurosis, 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 and 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 complexus, 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 cucullares 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- ralus 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 nucha, 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 tuberosity 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 ligamenta subflava of the spine, and is of great impor- tance by supporting the head without much muscular effort. In man it is quite rudimental. The trapezius presents much variety in differ- ent animals. In the carnivora and 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 scapuke. 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. Latissimus 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 B 370 BACK. conceals the one above it, and so on. The muscle on its way to the humerus 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 rhomboidei and levator 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 rhomboideus minor arises from about half an inch of the ligamentum nuclise 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 foui- 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 scapula-, 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 !i point of the shoulder. \V ith the trapezius they 1 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 nuchas. The levator anguli scapula is a long strap- shaped muscle, situated on the side of the neck, and extending from the superior cervical vertebrae to the upper angle of the scapula. ], Its origin is by four (sometimes three) ten- j dinous bundles from the posterior tubercles li of the transverse processes of the four superior cervical vertebras ; that which arises from the atlas is the largest ; they are intimately con- nected with the splenius colli behind, and |j with the scaleni before. The fleshy fibres pro- !1 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 die 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 simiae 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 vertebra, 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 nuchae, from the last cervi- cal and the first two or three dorsal spines. The fleshy fibres which succeed form a thin plane, pass downwards 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 ingles. This muscle is covered by the rhomboid, the trapezius, and, when the shoulder is drawn sack, by the serratus magnus. Its origin is rnited to the two former. It covers the splenii, he longissimus dorsi, transversalis colli, sacro- umbalis and cervicalis descendens ; while on hese it is tendinous ; then it becomes fleshy ind covers the ribs and intercostal muscles. Sometimes it has only three points of insertion. Iccasionally we find a bundle of fibres passing "om the upper part of this muscle along the Jvator anguli scapulae to be inserted into the ■ansverse process of the atlas. This muscle elevates the ribs and expands ie thorax as in inspiration. It binds down ie muscles on which it lies, enabling them to with more effect. Ihe serratus posticus inferior is very like the •st muscle, but a little broader and thinner. arises from the last two dorsal and first three mbar 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 lowrest 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 abdominis, 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 aponeurosis, 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 vertebra. Covered below by the rhomboid and serratus posticus superior, higher up by the trapezius and levator anguli scapulas, 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 vertebra, 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 vertebra, 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 vertebrae and of the seventh cervical, and from the ligamentum nuchae as high as the fourth cervical. At the origin it is tendinous ; it =oon 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 complexi 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 1 ( Turton’s 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 fifth layer of muscles, consisting of the sacro- lumbalis, longissimus dorsi, spinalis and semi- spinalis dorsi, cervicalis descendens, trans- versalis colli, trachelo-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 spince. The saero-lumbalis, 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 vertebras ; 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 vertebree, 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 flat 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 muscles 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 saero-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 vertebrae. 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 saero-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 rihs These are at first blended with those of the saero-lumbalis ; then they unite and form slender muscle, which runs upwards, out wards, and forwards, to be inserted into the transverse processes of the third, fourth, fifth and sixth cervical vertebra, between the trails! versalis colli and the levator anguli scapulae. This muscle may elevate the ribs or extern! the neck, turning it to one side. It is oftejj considered as a portion of the sacro-lumbalf. and sometimes called musculus accessorial or cervicalis ascendens. The name cervical descendens, that by which it is best known, wr given to it by Diemerbroeck, who describe! * Under the denominations transversatre epv which may be latinized tramversus spintr, hich and some other continental anatomists include tl I spinalis dorsi, semi-spinalis dorsi, spinalis colli, ai multijidus spinal, — Et>. 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 vertebrae 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 iide. The complexus is thicker and broader than he muscles we have been now describing in he cervical region. It arises from the trans- verse and articulating processes of the four or ive superior dorsal vertebrae, and from the ransverse processes of the four inferior cervical, iy tendinous slips : these are followed by leshy and tendinous bundles. The muscle hus formed passes upwards and inwards, to be nserted into the os occipitis between its supe- or and inferior oblique ridges. The complexi re close to each other above, separated only y cellular tissue which is connected with the gamentum nucha ; lower down, however, tere is some space between them. This mus- e is covered by the trapezius above, by the rlenii in the middle, and by the Irachelo- astoideus and longissimus dorsi at its lowest irt. Ii rests on the spinalis colli, the oblicjui id recti capitis. The name is derived from e complicated intermixture of tendinous and shy fibres of which it is composed. A su- ■rficial portion of it is described by Albinus the biventer cervicis, but it does not usually mit of subdivision. This muscle draws the head back on the inal column. In the muscles of this layer there are no i' 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 rectus capitis posticus major and minor. These, with the spinalis colli, form a sixth layer. The spinalis, or rather semi-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 vertebra 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 to its own side. The rectus capitis posticus major is triangu- lar; its apex arises from the spine of the den- tata; 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 multijidus spina?. 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 vertebra. 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-trunsversales are similar fibres, scarcely to be demonstrated except in the neck, where they are in pairs, corresponding to the divided transverse processes. The multijidus spinee 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 Ibis article see that of Anatomy (Introduction). ( Charles Benson.) BILE. Syn. Gall. (Gr. ypM ; Lat .bills; Fr. bile ; Ger .die Guile; Ital .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 cducts 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 bo 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, anil often seems in some way to modify its other charac- ters: in general, however, (ox-gull,) it is a green liquid, varying much in tint, of a pecu- liar odour, a bitter and nauseous taste, and aj! specific gravity fluctuating between 1.020 and;: 1.030. It does not coagulate when heated, and although it may possibly contain albumen, oi something very like it, it is not immediately coa- gulated by alcohol or by dilute acids. The rela, tive proportion of solid matter obtained byevapo ration is between eight and ten per cent. 11; means of acetic acid, the mucus which is mixeiij with the bile may to a great extent be separatet;; In the mammalia, generally, the bile exhibit nearly the same characters; and in birds an fishes its components seem to be the same, bt rather more dilute in the former and more cot centrated in the latter : it is always alcaIine,froi the presence of soda, apparently in the san, state of combination as it exists in the seru j of the blood . When bile is evaporated very car fully to about half its bulk, and alcohol adde (in the proportion of about four parts to one the evaporated bile,) a coagulated matter thrown down, which has some of the prop1 * Thenard, Memnires d’Arcueil, i. f Lehrbuch der Thierchemie. Dresden, loo and Mcdico-Chirurgical Transactions, iii. f Uber die Verdauung (Essay on Digestion). § Scliweigger’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 filtered 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 filtration, 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 off 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 GuLknstojf) has probably beenmistaken 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- men 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 Phosphaleofsodaand lime and traces of a substance insolu- ble in alcohol 0.11 100. 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 (mucusand 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: l.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 Gallenaspa- 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. Schweigger’s Journal, vol. 1. p. 8. f L. Gmelin, Handbuch der Thcoretischen Che* mie, ii. 1012.' Frankfurt, 1829. 376 BLADDER, NORMAL ANATOMY. 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 gall-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 p^oArj, bile , and o-rrgeo;, solid,) with more or less colouring matter, muco-albumen, and inspissated bile ; they are accordingly of various colours and textures, but generally brittle and friable. Those which are chiefly cholesterine, or as it should more properly be termed cholestearine, are white and crystalline, and lighter than water; the others are more tough, coloured, and dense ; their specific gravities, therefore, vary from 0.803 to 1.06. Their chemical ex- amination maybe conducted as follows : they may be powdered, and digested in water to separate the inspissated bile : then boiled in alcohol, and the solution filtered whilst hot ; as it cools it deposits the cholesterine, and often retains common fat and its acids in solu- tion. The portion which resists the action of alcohol may be digested in a weak solution of caustic potash, which takes up colouring matter and muco-albumen : the solution, supersatura- ted by acetic acid, deposits these, and the co- louring matter may afterwards be removed by alcohol. Any common albumen may be de- tected by ferrocyanate of potash added to the acetic solution. Cholesterine separates in white pearly scales from its hot alcoholic or etherial solution during cooling; it fuses at about 280°, and when heated to about 400°, it sublimes : in the open air it burns like wax. Its ultimate components are 85 carbon, 12 hydrogen, 3 oxygen. It is the most carbonaceous of all the varieties of fat. The gall-stones of the ox frequently consist chiefly of the yellow colouring matter of the bile, which is occasionally used by painters on account of its brightness and durability : it is in- soluble in water and alcohol, but readily solu- ble in weak solution of potash, from which it * Annales de Chimie, xcv. 5. is thrown down in green flocks by muriatic acid : nitric acid cautiously dropped into a solution of this colouring matter gives it various shades of green, blue, and red. Bibliography. — Bianchi, Historia hepatica,2 vol. 4to. Genev. 1725. Rwderer, Experimenta ciica bilis nat. 4to. Argent. 1767. Cadet, Exper. sur la bile des homines et des animaux : Mein, de 1’Acad. de Paris, 1767. Bordenave, Analyse de la bile, ibid, (Savans etrangers, t. vii.) Mqclurq, Experiments upon the human bile, 8vo. Lond, 1772. Goldwitz, Nene Versuche zu ein waliren Physiologie der Galle, 8vo. Bamb. 1782. Ploua/uet, Exper. circa vim bilis cliyliferam, 4to. Tul.inv. 1792. Thenard, Deux mem. sur la bile : Mem. d’Arcueil, t. i. Saunders, A treatise on the struc- ture, &c. of the liver, 8vo. Lond. 1793. John, Chemische Tab lien : Tableaux chimiques, 4to. Paris, 1816. Chevreul, Note sur la presence de cholesterine dans la bile de l’liomme : Joum. de Chim. Med. t. i. and Ann. de Chimie, No. xcv. Bracconnot, Rech. sur la bile : Ann. de Phys. et de Chimie, Oct. 1829. Orjila, Elem. de chimie, 2 vol. 8vo. Berzelius, Traite de chimie : Ruspail, Nouv. systeme de chimie organique, 8vo. Paris, 1833; Anglice a Henderson, 8vo. Lond. 1834. ( W. T. Brande.) BLADDER, (in anatomy.) (Gr. nvtrm. Lat .vesica, vesiculu. Fr. vessie, vesicule. Germ. Blase. I tal. vescica ). — This term is employed to denote a membranous sac, more or less complicated in its structure, with one or more orifices, and destined as a reservoir for parti- cular fluids. We have, for instance, in most animals provided with a liver, a gall-bladder or reservoir for the bile ; in fishes we have a swimming-bladder, vesica natatoria; and in the females of several insects, mollusca and crustaceans, a bladder, recently described hy Audouin, Milne Edwards, Des Hayes, and others, the function of which is to receive, during copulation, the prolific fluid from the male, and which has, therefore, been called vesicule copulatrice. In fine, in a great num- ber of the animals provided with a urinary ap- paratus we have a urinary bladder, vesica urinaria. For a particular description of the first three varieties of bladder we refer to the articles Liver, Pisces, and Insecta; — that of the urinary bladder forms the subject of the succeeding article. (R. B. Todd ) BLADDER OF URINE (normal anato- my).— (Kvcttk ov(o^oypq, vesica urinaria. ' Germ. Harnblase. Commonly known as the Bladder.) The urinary, like the biliary appa- ratus, consists of four principal organs, each accomplishing a different purpose, yet all con- tributing to the same end, namely, the sepa- ration from the circulating medium of a consi- derable portion of aqueous and saline matter : these are, first, the kidney or kidneys, which are the principal, indeed the sole agents in this function ; secondly, the ureters, the excre- tory ducts, whose office it is to convey the fluid secreted, drop by drop, as fast as it is formed, which is by a slow and gradual pro- I cess, to, thirdly, the urinary bladder, which I serves merely as a temporary receptacle for it ; I and, fourthly, the u ethra, or terminating ex- I BLADDER, NORMAL ANATOMY. cretory tube, whereby this fluid is wholly discharged from the system. A urinary bladder has not been ascertained to exist in any of the invertebrate division of animals, and in the vertebrate there is a great diversity with respect to it : thus in the class Pisces, this organ is absent in all the osseous family, in most of whom, however, the two ureters unite below, and form a slight heart- shaped dilatation which opens externally be- hind the anus in common with the sexual organs: this vesicle, though somewhat analogous to, cannot be considered as a perfect reservoir. In most of the cartilaginous fishes it is absent also, as in the ray and shark, in whom the ureters open as in birds into a cloaca, or reser- voir common to the renal, sexual, and intes- tinal discharges ; in some, however, of this family it is present, as in the cyclopterus or lump-fish, the lophius piscatorius, &c. ; in the latter it is very capacious, and its coats are so thin as to be transparent; it receives the ureters anteriorly, and opens, as is usual in fish, behind the anus, in common with the genital ducts. In Reptilia, the bladder is present in some, as the Batrachia and Chelonia ; it is absent in all the Ophidia, and in many of the Sauria, as the crocodile, the gecko, and the lizard ; while again it exists in many of the same division, as the iguana, chameleon, draco, &c. In the Batrachia, as the frog and the toad, it is situated in front of the rectum or cloaca, into which it opens ; the ureters open into the latter poste- riorly, from whence the urine is directed into the bladder by the muscular contraction of the cloaca and of the sphincters of the anus. In the frog its cavity is large, parietes thin, and its fundus divided into two cornua. In the Chelonia, as the tortoise, it is very large, and the ureters open into the urethra anterior to its cervix, the urine must therefore return or reas- cend to enter the bladder. In the Ophidia or the Serpent tribe, each ureter dilates inferiorly into a small vesicle, which then opens into the cloaca, and there is no other approximation to a bladder; in such of the Sauria as this organ exists, it opens into the cloaca. In Aves the bladder is always absent ; in the whole of this extensive class, the ureters open into the cloaca, and the urine, which is so earthy as to appear almost solid, is there min- gled with the fseces, in common with which it is discharged at short and repeated intervals. In the Ostrich and Cassowary the cloaca is very dilatable, and its muscular structure is so organized as to be enabled to retain within it, and to discharge occasionally a considerable quantity of urine; hence in these animals a vesica urinaria has been by some erroneously supposed to exist. In all mammalia this organ exists, and in every member of this class the ureters enter it obliquely at a little distance behind the cervix, with the exception of the ornithoryncus and monotrematous animals generally ; in these the ureters open into the urethra a little beyond or anterior to the cervix of the bladder, so that the urine must return or ascend, in order to enter its cavity ; this curious arrangement is 377 similar to that adopted in the chelonia, and would appear to indicate, as Carus ingeniously suggests, that in these strangely formed animals, in the same manner as in reptiles and in birds, the allantois (the remains of the urachus of which form the bladder in mammalia) arises from the expansion of the rectum or the cloaca, whilst in other quadrupeds it is solely connected to the genital passages. In all mammalia this organ presents a tolerably uniform appearance both as to structure and shape, but great diver- sity as to capacity or size ; the latter appears to be in an inverse ratio to its muscularity : hence in Carnivora, the bladder being more muscular, appears smaller in proportion to the size of the animal than in some of the Herbivora, where its coats are thinner, and therefore more dila- table ; in others, however, of the latter order, in whom it is very muscular, its capacity is inferior to that of some even of the carnivora : in the Rodentia it is muscular and small, par- ticularly if contrasted with the genital appa- ratus. In quadrupeds the bladder is usually more covered by the peritoneum, and hence it appears more loose and free in the abdomen than in the human subject; its figure is usually rounded, pyriform, or oval ; and it may be re- marked (and the remark will even apply to the human child and embryo) that the younger the animal the more elongated is the bladder, a fact which is indicative of its derivation from, or original continuity with the urachus and allantois. The urinary bladder in man is deeply seated in the anterior inferior part of the pelvis : it is composed of different tissues, membranous and muscular, both calculated to yield and to expand to a slightly distending force, so as to form a recipient reservoir, while the latter is fitted by its contractile power to obliterate the cavity of the organ, and forcibly to eject its contents. This musculo-membranous viscus demands the particular attention of the surgical anatomist, not merely as to its structure, but as regards its situation and connections, as it is the seat of many very severe and often fatal morbid affections, several of which admit of a perfect cure, and most of considerable relief, from operation and from various kinds of local treatment, the safe performance and judicious application of which greatly depend on a cor- rect knowledge of the structure and relations of the organ. We propose first to consider the form and structure of the bladder in the normal state, and afterwards to describe its situation and connections. Shape. — The figure of the bladder must vary according to its state of contraction or distention, in reference to which it is usual to consider it under three conditions, viz. the empty or contracted, the full or ordina- rily distended, and the over-distended. Its figure in these different states also varies ac- cording to the sex and age of the individual, the bladder of the infant differing materially from that of the adult, and that of the adult female from that of the male ; the bladder of the embryo also differs from that of the fully developed foetus. The younger the animal, the 378 BLADDER, NORMAL ANATOMY. more does its form resemble that of inferior animals, and it is an organ very fully developed in the young of all animals who possess it. This organ, in the adult male, when empty or contracted, is a flattened triangle, the transverse and vertical axes being considerably greater than the antero-posterior one ; in this con- dition the bladder is buried deep in the pelvis, behind and partly below the symphysis pubis ; the base of the triangle is in front of but not very closely applied to the rectum, unless the cavity of the latter be fully distended. When the bladder is expanded in the adult male to that moderate degree which in perfect health usually excites a slight feeling or desire to void the urine, and when the quantity accumulated may amount to half a pint or upwards, its figure is then somewhat oval, its vertical axis being considerably greater than either the transverse or the antero-posterior, the two latter being then nearly equal. The larger end of this ovoid sac rests interiorly and posteriorly on the rectum, and is of an irregular form ; the smaller end, which is more regularly sphe- roidal, is directed upwards towards the abdo- men, and somewhat forwards, and occasionally also a little towards the left side. When the bladder is over-distended from any cause, it becomes considerably increased in every dia- meter ; it first expands in its lower and middle portions, until the pelvic parietes resist ; it then enlarges superiorly to an indefinite degree, and at the same time the whole organ rotates a little forwards by its superior, and a little backwards by its inferior fundus. Its figure in this over-distended condition is not merely enlarged, but it also presents a totally different, or rather a reversed shape : the larger extremity of the oval is now superior, occu- pying the hypogastric region, which it ren- ders prominent and tense in a degree propor- tioned to its distension. These observations as to the form of the bladder will not apply in every instance, as occasionally this viscus pre- sents irregularities both in size and shape, as well as in the density and delicacy of its tunics. The bladder in the female child does not differ from that of the male of the same age, but in the adult of each sex it presents peculiarities. In the contracted state it is nearly similar in each, only somewhat flatter in the female. When distended, in the latter it presents a more triangular form, the sides somewhat rounded, than it does in the male, where the ovoid form prevails ; in the female its lower fundus admits of greater lateral extension in conformity with the shape of the pelvis, and its transverse axis is longer in proportion than in the male ; hence it assumes the triangular more than the oval figure. This character is more remarkable in the female who has borne children than in the virgin ; in the former the bladder, when dis- tended, appears to exhibit the effects of the pressure of the uterus posteriorly, and of the pubes anteriorly, being flattened in each of these aspects : in some instances it resembles a small barrel placed tranversely. In the fcetus and infant of a year old the bladder in figure more resembles that of a qua- druped ; when distended, it is pyriform, like a bottle or a flask reversed, the larger end, or the superior fundus being in the abdomen, and the smaller extremity tapering into the urethra. This is the only portion in the pelvis ; at tins age its vertical axis greatly exceeds its other diameters, and even when empty the greater portion of it is in the abdomen. As the child increases in years and size, its pelvis expands, the bladder gradually descends into this region, and in the same proportion its lower fundus enlarges, so that at about six or seven years of age it presents a more oval form, both extremi- ties being nearly equal, and very little of it rising above the pubis, unless when distended. From this period it continues to acquire gra- dually the adult figure; that is, its inferior fundus and body enlarge, while the superior re- mains stationary ; hence it becomes shorter in its proportions, and broader below, so as to assume the triangular shape when empty, and the ovoid when distended. About two months before birtn the bladder is very much elongated, its upper extremity being somewhat pointed, and ap- proaching the umbilicus in the direction of the urachus. When distended, it presents some- what the appearance of a cylinder contracted at each extremity. Soon after birth the upper fundus becomes rounder, and then it acquires the pyriform figure, which in the course of a few years undergoes the gradual alterations that have been already noticed . The capacity of the bladder in the adult cannot be accurately ascertained, as it varies from a number of circumstances, such as age and sex, health and disease: thus irritation general or local, ischuria renalis, cholera, &c.., will cause it to contract, while retention of urine, paralysis, fever, & c., will allow it to enlarge. Custom or habit will also affect it, likewise the position of the body, pregnancy, the nature or peculiar quality of diet, the tem- perament of the individual, the temperaHire of the atmosphere, the state of society, &c. In the same individual it will at one time contract so as to retain only a few drops, and at another it will dilate so as to contain one, two, and even three pints. Generally it is more capa- cious in women, particularly in those who have borne children, than in men. In children the bladder, although very dis- tensible under certain circumstances, is usually less capacious in proportion than in the adult or old, probably because it is more muscular and irritable ; and hence, too, the more fre- quent desire to contract and empty its contents. When the bladder is moderately distended, anatomists and pathologists have been in the custom of dividing it into four regions for the purpose of more accurate description ; viz., the superior part or the upper fundus, the middle part or body, the inferior part or the lower fundus, and the cervix or neck. This arrange- ment is not very correct, for it can only apply to this organ when distended ; the term su- perior fundus also is obviously objectionable, and was probably derived from examining this viscus in other animals, or in the human fetus where the lower fundus does not exist ; neither BLADDER, NORMAL ANATOMY. 379 can any exact distinction, or even an approxima- tion to such, be made between these several compartments. A more accurate knowledge of this organ may be obtained by examining both internally and externally its several aspects, which are six in number, and which may be regarded as distinct regions ; viz., an anterior and posterior, two lateral, and a superior and inferior. We shall examine each of these ex- ternally, and defer any remarks on their in- ternal aspect until we come to speak of the lining membrane or the mucous coat of the bladder. The anterior region, in consequence of the obliquity of the pelvis, looks also downwards. When the bladder is contracted, this region is behind and in contact (cellular tissue only in- tervening) with the lower half or three fourths of the symphysis pubis, and with the pubic and triangular or interosseous ligaments ; when dis- tended, it rises above the bone, and is connected by an abundance of cellular and adipose tissue to the lower portion of the recti and transversi muscles ; and as no peritoneum is there inter- posed, this part can be punctured with safety during life. At the lower border of this region is the neck of the bladder, the upper surface of which is firmly attached to the lower edge of the symphysis pubis by two horizontally placed fibrous cords, which are named the anterior ligaments of the bladder, and which will be more particularly noticed presently. Between and beneath these, some veins also run upon this surface of the bladder. The whole of this region is deprived of any peritoneal or serous covering. The posterior region has an aspect upwards also ; it is smooth and covered throughout with peritoneum. When the bladder is contracted, this small region in the male pelvis is in con- tact with the fore-part of the rectum, or with such of the floating abdominal viscera as may chance to intervene ; in the female with the fore-part of the uterus. When this region is distended, it presents a broad smooth convex surface, which presses more against the rectum and supports the convolutions of the small in- testines. The lateral regions, when the bladder is contracted, are little more than margins or edges, and present nothing worthy of notice; but when distended, each becomes a broad surface, somewhat triangular, the base below and the apex above, the posterior portion, nearly the half, is covered by peritoneum, the anterior portion is connected by cellular tissue to the parietes of the pelvis : the obliterated umbilical artery ascends along its superior posterior por- tion, and the vas deferens, which crosses to the inside of the latter, runs along this region in an oblique direction downwards and backwards, and marks the anterior limit of the peritoneum. From this region the broad lateral fold of this membrane extends to the iliac fossa, and at its inferior border is that reflection of the vesical fascia which is named the true lateral ligament of the bladder. The superior region, by some called the superior fundus, is, when the bladder is empty, little more than a point prolonged into the urachus; but when distended, it presents its large and convex surface upwards and forwards ; to it is attached the superior ligament of the bladder, which consists of three fibrous cords, the urachus and the obliterated umbilical arte- ries ; behind these this region is covered by peritoneum, but anterior to them it is not. The former portion is in contact with the con- volutions of the small intestines, the latter with the recti muscles. The inferior region, or the inferior fundus, or the base of some authors, always exists as a distinct surface, whether this organ be contracted or distended, but of course larger in the latter condition. It is rather more exten- size in a transverse direction than from before backwards, and is larger and more distinct in the male than in the female : its lateral por- tions in each sex are in contact with the leva- tores ani muscles, and correspond to the spaces between the anus and the tuberosities of the ischium. In the female its middle portion is in contact with the vagina, in the male with the rectum in the middle line, and with the vasa deferentia and vesiculae seminales on either side ; to the latter it is closely connected. The cel- lular and adipose tissue on and around this region in the adult is very abundant, and con- tains numerous veins. This region is covered posteriorly by peritoneum, which extends to a transverse line connecting the centre of each vesicula seminalis. This line corresponds to the convexity of the cul-de-sac formed by the reflection of this membrane from the bladder to the rectum. In front of this line this region is covered in the middle only by a fascia and by some cellular tissue as far as the base of the prostate gland, which extends for some dis- tance along its anterior portion, and on either side are the vasa deferentia and the anterior terminations of the vesiculae seminales. When the bladder is distended in the adult, this surface is enlarged, not only in superficial extent, but it also swells backwards and downwards towards the rectum, and even presses against and into that intestine, so as in some rare cases to admit of being felt by the finger introduced per anum. To this portion the name of ‘ bas fond ’ is com- monly applied. In the adult this bas fond, that is, the posterior part of this region, is the lowest portion of the bladder, and hence cannot be evacuated except by the contraction of the organ or by surrounding pressure. In man, in advanced life, it is often found dilated into a sort of pouch, which is behind and quite below the level of the anterior part of this region, as well as of the neck of the bladder, forming in some instances of debility a sort of permanent reservoir, and one in which calculi are not un- frequently contained. In the foetus this pouch or fundus does not at all exist, the cervix or the urethral opening being then the most depend- ing part, which circumstance offers another reason for the power of retention of urine being less at that age than at a later period of life. Some writers limit the inferior region to so much of this aspect of the bladder as is uncovered by peritoneum, and therefore consider the posterior 380 BLADDER, NORMAL ANATOMY. part of it as appertaining to the posterior region. Anatomically we consider this incorrect, as the vesiculae seminales are acknowledged by all to be situated on the inferior region, and the cul- de-sac of the peritoneum certainly descends between these bodies to within nearly one-half or three-fourths of an inch from the prostate gland. In a practical point of view it is most essential to keep this in mind, because in the operation of recto-vesical paracentesis this mem- brane is endangered, and would certainly be perforated if the trochar faere passed through the posterior portion of this region. The sur- face of the bladder which can be opened from the rectum in that operation is comparatively small; it is of a triangular form, nearly equilateral, situated on the anterior part of this region. The base is behind marked by the convex border of the peritoneal cul-de-sac : the apex is at the notch in the base of the prostate gland, and the sides are the vasa deferentia and vesiculae seminales. While all these parts are in situ, this space is but small ; when, however, the bladder has been removed from the subject, distended, and dissected, this space appears much more ample, because the peritoneum recedes from it in proportion as the attach- ments of the former have been loosened. The bladder presents to our notice three diameters, viz. the transverse, antero-posterior, and the vertical ; the latter is also called its axis. In the contracted state the antero-pos- terior can scarcely be considered as existing ; but when distended, this and the transverse diameters are nearly equal. In all states, at least in the male, the vertical diameter or axis is the longest ; this line leads in the adult from the centre of the upper region to that of the lower region or fundus : in the foetus and infant it leads from the urachus to the orifice of the urethra; if this line be contrasted with the axis of the trunk or abdomen, and with that of the pelvis, it will be found to correspond very nearly with the direction of the latter, and to pass very obliquely with respect to the former. The axis of the trunk may be regarded as nearly a vertical line, descending through the thorax and abdomen to the pubis, whereas the axis of the pelvis, or rather of its superior orifice, will pass obliquely downwards and backwards, and if produced at either end, it will pierce the recti muscles between the um- bilicus and pubis anteriorly, and the lower end of the sacrum posteriorly. The vertical axis of the bladder in the adult is on a lower plane, but nearly parallel to that line ; in the foetus it is more parallel to that of the trunk, the blad- der at that age being placed more in the ab- domen, and in a more vertical direction than in the adult. The bladder is composed of several mem- branous laminae, called coats or tunics : these are essentially three in number, a serous, a muscular, and a mucous. They are connected together by cellular tissue, the laminae of which being two in number are also considered coats ; so that the whole number of tunics is stated by most writers as five. First, the serous or peritoneal is but a partial coat ; it covers those portions only which come in contact with some of the abdominal or pelvic viscera, namely, all the posterior region, and the posterior portions of the lateral, and of the superior and inferior regions ; consequently it is deficient on all the anterior region, and on the anterior part of the superior, and of the lateral and inferior regions. The course of the vasa deferentia marks the extent or the limits of this mem- brane on the bladder; all that portion which is behind and between these tubes is covered by it, except the small triangular area already noticed on the inferior region; all that which is anterior to these vessels is uncovered by this membrane. The peritoneum arrives at this viscus from the fore-part of the rectum in the male, and from that of the uterus in the female, and is continued from its lateral regions to the iliac fossse, and from its superior fundus to the inside of the recti muscles. This membrane is not very closely attached to the subjacent coat ; it can be easily separated from it ; it is much stronger and more elastic on this organ than on any of the chylopoietic viscera. When the bladder is distended, there is more in pro- portion covered by peritoneum than when it is contracted. The female bladder has more of the peritoneum on its upper fundus, and less on its lower fundus than the male bladder, and in the foetus and infant it is still more extensively covered by this membrane, which then extends over the whole of the upper region and over a small portion of the anterior. As the peritoneum passes from the sides of the bladder to the iliac fossae, it forms folds, improperly called the lateral ligaments, and in passing from the back of the bladder to the rectum or uterus, a similar fold on each side, called the posterior ligaments of the bladder. Between these the cul-de-sac of the peritoneum descends ; this in the male subject is the lowest portion of the peritoneal cavity, it extends to within about three inches and a half of the anus : in ascites it has been known to be somewhat lower, and has even been tapped in this situation from the rectum. 2dly. The external or first cellular coat con- nects the serous to the muscular tissue ; it also covers those regions of the bladder where the serous membrane is deficient. In the lateral regions it is more distinct and thick, and is particularly abundant anteriorly between it and the pubes, where it is also very lax, to allow this organ when distended to move freely as k rises out of the pelvis into the abdomen. Jt contains some but not much adipose matter; towards the inferior and lateral parts it con- tains many bloodvessels, chiefly venous, and a great number of nerves, which can be distinctly traced from thence in all directions over the bladder. Towards the vesiculas it is dense and white, and supports a number of veins: this coat is strong, resisting, and elastic ; it binds together, supports, and assists the muscular fibres. The third coat of the bladder is the muscular : this is composed of fasciculi running in dif- ferent directions, and which, though they appear pale and feeble when contrasted with the volun- tary muscles, are yet much stronger and redder BLADDER, NORMAL ANATOMY, 38i than those in the corresponding coat in most of the other hollow viscera, being intermediate in these respects to those of the stomach and oesophagus ; this tunic, however, presents great diversity as to colour and density in different individuals. In the contracted state of the bladder, it of course appears more dense than in the distended ; in the latter, but particularly in the over-distended state, it appears thin and imperfect in some places, in consequence of the fasciculi being separated from each other. In the young, cateris paribus, it is stronger than in the old, and in the female than in the male ; but long-continued irritation at any age and in either sex has the effect of thickening it, as also any disease which causes obstruction to the flow of urine. If the bladder be removed from the body, slightly distended and sub- jected to maceration for a few hours, this tunic will admit of more distinct examination ; its fibres will then be seen to take such different directions as to admit of a tolerably easy, though not a perfectly natural separation into distinct lamin®, the fibres in the first or super- ficial of which have a longitudinal course ; be- neath this is a second stratum, whose fibres are transverse or circular ; and in some situa- tions even a third lamina can be distinctly seen, the fibres of which are by some des- cribed under the name of oblique, but the term reticular would appear .more correct : in general these three laminae can be made dis- tinct, particularly on the anterior part of the bladder. The first or longitudinal lamina con- sists of the longest, strongest, and most nu- merous fasciculi ; many of these are connected superiorly to the urachus, thence they descend principally on the fore and back part of the bladder, a few only along the sides ; inferiorly they terminate about the neck. These fibres are very parallel, and much stronger on the an- terior and posterior aspects than upon the sides, where they run more obliquely or irregularly, and decussate with one another. The inferior attachment of these fibres in the male subject may be ascertained by careful dissection to be as follows : — those on the fore part of the bladder are connected chiefly to the anterior ligaments, or to the reflections of the fascia from the pubis on this organ ; these appear as shining and dis- tinct as tendons, and have been by some con- sidered as such to these muscular bands. Above this insertion these longitudinal fibres appear very numerous, and those on the right and left of the median line distinctly decussate or interlace. Several here also take a transverse or an arched or semicircular course; some of these are very distinct and are inserted laterally ; they must serve to strengthen and to bind down the longitudinal fasciculi. The latter in this situation can be divided into layers, the superficial of which only are inserted, as has been described, into the anterior ligaments of the bladder, and through these into the pubis. The deeper set are inserted, some into the dense cellular tissue about the upper surface of the prostate, and some pass deeper, and intermingle with that circular mus- culo-cellular tissue which surrounds the cervix, and which constitutes the true sphincter. Some of those longitudinal fibres, particularly more laterally, pass so deep in this situation as to be very distinctly seen, when the bladder is opened, through the mucous lining of the orifice of the urethra. This disposition of the longitu- dinal fibres we consider as important, as it must enable them during their contraction to draw out or expand the sphincter, so as to allow of the escape of the urine. Laterally these longi- tudinal fibres are attached, a few of them to the margin of the prostate, while others expand over the lateral lobes of this gland, and are in- serted into the fascia which covers it. Poste- riorly these fibres are very distinct, particularly near the inferior surface of the bladder between the two ureters ; to these last-named tubes seve- ral of these fibres are connected : some ascend upon them in arches concave upwards; these we have traced several inches along the ureters ; while others descend in the same course with them, and are inserted into the trigone of the bladder. The longitudinal fibres collect into a strong flat band between and beneath the two vcsiculae, over which however no fibres pass as they do over the prostate, which circum- stance clearly separates these vesicles from, while the contrary disposition rather connects the prostate with, the urinary excretion. This band of fibres can be followed near to the base of the prostate ; some of its fibres are then in- serted into the submucous fibrous tissue in this situation, others into the base of the gland itself ; and very generally one long delicate but distinct band enters the notch in the base of the gland, passes beneath the uvula and middle lobe of the prostate, into which it is sometimes insert- ed, but it can frequently be traced nearly an inch further forward to be inserted by a delicate tendon beneath the seminal caruncle or the verumontanum, which is partially covered over by a fold of mucous membrane or by a sort of prepuce. The effect of this band of the longitu- dinal fibres must be to depress the uvula, and thus to open the orifice of the urethra, and also to depress and to draw the seminal caruncle (a sort of organized glans) downwards and back- wards within the prepuce or sinus pocularis, which covers it, and thus protects it from the irritation of the urine. In the female the lon- gitudinal fibres are inserted anteriorly and late- rally into the cellular, glandular, and vascular tissue which surrounds the neck of the bladder, and posteriorly into a more dense tissue which connects the urethra to the vagina; some fibres also pass in deep, as in the male, to be attached to the sphincter. This muscular lamina is de- scribed by the older authors as a distinct mus- cle, the ‘ detrusor urinre,’ arising from and around the urachus by numerous fibres, which thence descend and expand over the whole surface, and again concentrate towards the neck of the bladder to be inserted by one or two tendons into the ossa pubis. This account, however, is by no means perfectly correct ; for on attentively examining this muscular lamina, we frequently find strong transverse fasciculi crossing superficially to the longitudinal fibres, most frequently on the anterior region, but also 382 BLADDER, NORMAL ANATOMY. near the neck. Occasionally some of the longi- tudinal fibres alter their direction gradually or abruptly, as may be particularly noticed about the ureters and also on the lateral regions. Great diversity exists as to the arrangement of this tunic in the lower animals : thus in the dog this plane consists of strong and regularly parallel fibres, whereas in the ox they assume a reticular and irregular course : in man they re- semble the arrangement of the carnivorous more than that of the graminivorous animals. This tunic must have the effect of compressing the bladder towards the ossa pubis, and of course urging the contents of the cavity in that direc- tion, while at the same time some of its fibres will expand the orifice of the urethra by draw- ing out the sphincter above and on either side, and below by depressing the uvula and the verumontanum. This stratum of muscular fibres can be raised with a little careful dissec- tion; a few fibres must be divided, which now and then change their direction, and join some of the deeper orders : this separation is difficult and can be but imperfectly made on the lateral regions, but on the anterior and posterior it can be fully accomplished. The second order of muscular fibres is circular or transverse; they are paler, weaker, and more scattered than the former, particularly towards the superior part of the bladder, where they are often indistinct. As they descend they increase in thickness, par- ticularly near the cervix, where they are so close and distinct as to have induced many to consider them as a sphincter to the bladder, — a term, however, to which they do not appear to have been entitled, for there is no distinction between the fibres in this situation and those which have a parallel course at a greater dis- tance ; and inasmuch as the latter are obviously designed to contract the organ and to expel its contents, it is most probable that the former must contribute to the same effect, and forcibly expel the last drops which it contains : indeed it is impossible to draw such a line of distinc- tion in this lamina as could denote the limit between the expelling and the retaining or sphincter fibres. In addition to this plane of circular fibres, several others may also be ob- served taking a parallel direction ; thus we oc- casionally find transverse bands superficial to the longitudinal plane, both on the anterior and posterior regions in different situations. We very generally also find them near the superior fun- dus, and constantly on the. anterior and lateral parts of the neck, where they cover the decus- sation of the longitudinal fibres. In the inter- val between the ureters, these transverse fibres are very distinct, particularly above, where they usually form a very distinct cord, arched a little upwards : this semilunar band or projection may be better seen when the bladder is opened; it corresponds to the base of the trigone, ex- tends from one ureter to the other, and is im- mediately in front of the pouch or bas fond of the bladder, which is so well marked in the adult and old. Throughout the rest of the trigone the circular fibres are by no means so distinct or strong as they are behind it, or as they are towards the anterior and lateral parts of the cervix. This circular plane of fibres may next be raised ; it is almost impossible to do this completely, because many of them deviate from that course, and join into the next or third lamina, taking a totally different course; the separation, however, can be accomplished suffi- ciently to demonstrate the peculiar artange- ment of the third plane of fibres, not all over the bladder, but only in particular situations, namely, in the greater part of the anterior and posterior regions, but only very imper- fectly on the superior fundus, and on the sides, and not at all on the trigone. Wherever this third layer is exposed, the fasciculi appear very large and thick, and present a very remark- able appearance and course, not unlike the inner surface of the cavities of the heart. Large fleshy bundles, bearing some resemblance to the carne* columnae, separate, unite again, and again subdivide, the fibres taking various direc- tions, and inclosing interstices of the mucous surface of various size and form : several of the fibres also join those of the circular plane. It is owing to this reticularly arranged stratum of muscular fibres that the bladder, when opened, presents its peculiar irregular surface, which in some cases, particularly if the bladder have been hardened in alcohol, resembles a honey- comb surface. If the bladder which has been opened be everted, then carefully closed and distended, this reticular coat will become very distinct when the mucous membrane has been removed. Its action during life must obviously be to contract the capacity of the bladder in every direction. When the internal surface of the bladder, even in the healthy state, is in- spected, the different orders of muscular fibres become very apparent; and when this coat has become thickened from any of those causes which are well known to produce thickening, some of the fasciculi often project into the bladder: such a condition of the organ is named a co- lumnar state of the bladder. In cases of irritable bladder, when calculous symptoms have been present, and the bladder has been sounded in consequence, these fleshy projections meeting the extremity of the sound, have in some in- stances deceived the surgeon into the idea of the existence of a calculus, and this is still more likely to occur should there be any gritty mat- ter adhering to their surface. Some of those recorded cases of the operation for lithotomy, in which no stone could be detected, although the symptoms of the disease previously existed, may admit of explanation by a knowledge of this fact. In the bladder of some persons the muscular fibres do not perfectly cover the mu- cous surface, particularly if the organ be very capacious. In such cases the mucous membrane may be pushed through some of the cells or meshes of the muscular fibres, and thus a hernia of the mucous coat be produced; that is, a small pouch or purse of this membrane will protrude between the muscular fasciculi, and will be covered only by peritoneum or by cellular tissue. This pouch may continue to increase in size, because it possesses no power of empty- ing itself, and the muscular fibres around its orifice can only contract the latter without 383 BLADDER, NORMAL ANATOMY. affecting the sac itself ; hence a process of this sort may enlarge indefinitely, and has been known in some cases to have formed a part of the contents of an inguinal hernia. Pouches of this nature, for there may be several in the same individual, sometimes contain calculi, the latter having probably been the cause of the former, inasmuch as the muscular coat having been excited by the irritation of the stone to increased action, has forcibly pressed the latter into one of the cells of the mucous membrane, which has then become enlarged and protruded, so as to contain the calculus impacted in it. The consequence of this occurrence to the indi- vidual, however, is often a fortunate remission of suffering, because the stone being now fixed in a cell, ceases to excite pain or irritation : it is by occurrences of this nature that the boasted and sometimes fortunate efficacy of certain lithontriptie medicines as cures for stone is to be explained. The exact arrangement of the muscular fibres at the neck of the bladder has not been very accurately explained ; some describe them as arranged circularly so as to constitute a true sphincter: this opinion is maintained by John Bell, System of Anatomy, vol. iv. p. 159; also by Palfin, Anat. tom. i. p. 163; by Meckel, Anat. vol. iii. p. 564 ; by Bayle and others. Sir Charles Bell also describes a sphincter vesieae to exist, but places it in a different situa- tion from that usually assigned. Ilis description of this muscle is as follows : — “ to exhibit it, cut off all the appendages to the bladder except the prostate gland, make an incision into the fundus and invert it, dissect off’ the inner mem- brane from around the orifice of the urethra ; a set of fibres will be discovered on the lower half of the orifice running in a semicircular form round the urethra ; these make a band of about half an inch in breadth, particularly strong on the lower part of the opening, and having mounted a little above the orifice on each side, they disperse a portion of their fibres m the substance of the bladder; a smaller and weaker set will be seen to complete their course surrounding the orifice on the upper part, to these sphincter fibres a bridle is joined which comes from the union of the muscles of the ureters; this is the most posterior part of all the muscles which embrace the urethra, it re- sembles the sphincters of the other hollow vis- cera; forexample,thatof the pyloric orifice of the stomach.”'* The great advantage of the sphincter as thus described must be, as Sir C. Bell says, to prevent the fluids from the seminal vessels and from the ducts of the prostate gland, falling back iuto the bladder, as also to protect the ori- fices of these ducts from exposure to the urine when the bladder is closed, and that without this arrangement it would be inconceivable how the contents of the vesiculre seminales could be discharged forwards, or how the urine could be retained while the seminal discharge was being made. We must remark, that after frequent examinations of this region, we cannot satisfy ourselves of the existence of this particular ar- Treatise on Diseases of the Urethra, &e. p. 14. rangement, although we are convinced that the orifice is furnished with a sphincter such as we shall presently describe. Moreover, we believe that the prostatic secretion is more or less ex- pressed at each evacuation of the urine, inas- much as the longitudinal, the principal detrusor fibres of the bladder, are fixed into, expand upon, and must compress this gland, especially at the commencement of the process, although they obviously can have no effect on the vesi- culae seminales, vasa deferentia, or their contents. The existence of a true muscular sphincter is denied by Sabatier, Anat. tom. ii. p. 403; Marjolin, tom. ii. p. 473; also by Bichat, Anat. desc. tom. v. p. 447 ; by Boyer, Anat. tom. iv. p. 490 ; by Cloquet, Anat. tom. ii. p. 1050; by Portal, Anat. tom. v. p. 401; the latter, however, describes the urethral orifice as surrounded by oblique muscular fasciculi. Winslow also, Anat. tom. ii. p. 210, denies a true sphincter, but ascribes the office of such to the muscular fasciculi which pass from the pubis to the bladder. Wilson (Lectures on the Urinary and Genital Organs, p. 57,) denies the existence of any regular sphincter, but thinks, from the distribution of some fibres at the beginning of the urethra, and which pass round it semicircularly from the forepart and meet the descending fibres behind, that the contraction of these, assisted by those of the urethra nearer the penis (compressores urethra), may be considered as sufficient to prevent the urine passing from the bladder into the urethra. Several of the foregoing writers who deny a muscular sphincter to the bladder, consider, nevertheless, that its orifice is closed by a pe- culiar tissue which resists the ordinary tendency of the muscular coat to expel its contents, but which is capable of yielding to the increased force which is exerted in the ordinary evacua- tion. Thus Bichat describes, as placed between the mucous lining and the external cellular tissue, a dense white fibrous substance, con- tinuous with the muscular fibres which are in- serted into it, a small process of this prolonged posteriorly to the uvula, and another anteriorly to the verumontanum. This substance is not muscular, and presents a passive organic resistance. Cloquet, Boyer, and Marjolin con- cur in the same account ; it is difficult, how- ever, to reconcile with such a condition of parts the phenomena which not un frequently occur in disease, such as paralysis and incontinence of urine in cases of injury of the spine, or of the nervous system ; or again, retention of urine from irritation in this situation caused either by local inflammation, or through sympathy with some adjacent diseased organ, or by some pe- culiar acrimony in the urine. A muscular struc- ture is more reconcilable with these, and with many other pathological facts, than an elastic, or fibrous, or resisting tissue, such as this part is stated to be furnished with. The result of our examination convinces us that the organization of this part is very peculiar, and that the neck of the bladder is closed by a power more than thatof a mere elastic tissue. Elasticity no doubt resides in this structure, and we admit to a con- siderable extent, as it does in almost every ani- 304 BLADDER, NORMAL ANATOMY. raal tissue, except perhaps mucous membranes: elasticity exists at the pylorus and at the anus, although true muscular and sphincter fibres are evident at both these outlets. When this region is carefully examined in the male subject, we shall find that immediately behind the pubis, on the anterior and lateral reflections of the pelvic fascia, to these ligaments numerous muscular fibres of the bladder are attached ; these are chiefly longitudinal, but there are also several transverse arched or semilunar, some upon, and others underneath the longitudinal fibres, and with which many of them are continuous. None of these arched fibres pass around or behind the prostate so as to encircle this region. The longi- tudinal, the transverse and decussating or inter- lacing fibres in this situation, are in greater abundance, and may be raised in successive laminae. Veins and nerves are very manifest in and between these; several of the longitudinal fibres of the deeper laminae pass in so deeply as to approach the mucous surface. When the several strata of longitudinal fibres have been raised from the front and lateral parts of this region, the circular fibres of the bladder become distinct, but do not appear so proportionably increased as were the longitudinal ; but on de- taching more completely the longitudinal strata down to the circumference of the very opening of the urethra, a distinctly fibrous, that is, mus- cular tissue, is evident, bounding this opening laterally and superiorly, but not below. This muscular fasciculus is not intimately connected to the general circular coat ; it appears redder, and of a closer texture, and will be found to be attached to the fibrous or tendinous substance forming the anterior part of the trigone on each side of the uvula, behind which it does not pass. The longitudinal fibres are inserted partly into this semicircular muscle, much in the same manner as the levatores ani are inserted into the circumference of the anus. This structure we consider to be partly elastic, but essentially muscular; it bounds the urethral opening late- rally and above, but not below; the slight pro- jection of the uvula in the latter situation, and the elasticity and gentle state of contraction natural to all the sphincter muscles, will pre- serve this opening in a constantly closed state during the quiescent and normal condition of the parts. This arrangement is on a level with the uvula, and, of course, behind the orifices of the prostate ducts, although the base of that gland extends further back than this sphincter. We have repeatedly examined beneath the uvula for muscular fibres, but have found none in a transverse direction ; there is, therefore, no portion of a sphincter in that spot, and hence one advantage of the slight elevation caused by the uvula and by that portion of the prostate gland denominated its middle lobe, which cor- responds to it : indeed sphincter fibres in this spot would be not only useless, but injurious, as they could scarcely exist without interfering with the ejaculatory ducts. We conceive, then, that the urine is retained in the bladder partly by the relaxed or passive state in which its muscular coats usually remain until they are excited by the sense of distension, partly also by the urine, when only in a moderate quantity, gravitating, not towards the neck, but distending the inferior fundus, which lies on a level lower than that of the former, and principally by the dense muscular, elastic, vascular, and nervous tissue which surrounds three-fourths of the orifice of the bladder. The gentle contraction of the latter raises the uvula into the calibre of the opening, while the remaining sides are pressed into contact with it, and thus the bladder is closed. When distension excites the usual feel- ing, the muscular coat contracts, the sphincter relaxes, phenomena exactly corresponding to those which take place under similar circum- stances in the rectum and anus ; and as the levatores ani expand the anal opening by draw- ing the sphincter fibres outwards at the time the expulsive powers of the rectum are dis- charging its contents, so the longitudinal fibres of the bladder draw out from the axis of the urethral opening the relaxed sphincter which encompasses three-fourths of it, while the middle band of the posterior longitudinal will plainly depress the uvula and expand the orifice in that aspect, and will even retract and depress the verumontanum, thereby freeing the passage into the urethra, and retracting that sentient caruncle from the irritating influence of the urinary stream. The next coat of the bladder, the fourth of some anatomists, or the second common of others, is the deep cellular, or more properly the submucous cellular coat, by some also de- nominated the nervous tunic. This coat invests the whole organ and connects the muscular and mucous tissues intimately yet loosely ; it con- tains no adipose matter, but is very filamentous, f extensible, and elastic: in it are found those vessels and nerves which are to supply the in- ternal surface of the bladder, and which, except in some situations, are not very numerous when compared with those in the other hollow vis- cera. This coat, though essentially cellular, pre- sents very many fibrous threads through it, on which much of its strength appears to depend, particularly in those places where the muscular coat is deficient. When the bladder is fully distended, if we dissect off the muscular fibres carefully without injuring this tissue, the mu- cous membrane still remains supported; but as soon as a portion of this coat is detached, f the mucous membrane projects in an unsup- ported sacculated manner. This coat corre- sponds with that elastic tissue in the parietes of the small intestines in some animals, out of which the substance, commonly termed catgut, is formed. The third proper coat is the mucous or fining membrane, to expose which the bladder must be opened by a perpendicular incision along its anterior region. This tunic is but a portion of the genito-urinary mucous membrane, and is continuous with that lining the ureters above, and the urethra below. The vesical portion of tins membrane is very thin, has a soft and smooth feel1 caused by the mucous fluid which lubricates it ; its colour is very pale in the natural condition although in catarrh or in chronic inflammation it presents a general vascular appearance; bu 385 BLADDER, NORMAL ANATOMY. in health the mucous surfaces of the intestinal tube and of this organ form a strong contrast, more particularly if the vessels of both have been injected with coloured size; the former will then assume the colour of the injection, the lat- ter will continue pale, although numerous ves- sels become apparent in the submucous tissue. The mucous lining of the bladder in the healthy state does not present any distinct follicles or crypt® except near the cervix, which become veiy distinct in chronic disease. A cuticular or epidermoid covering cannot be detected in health, although in certain states of disease a substance very similar to cuticle is occasionally discharged in shreds and flakes. W hen the blad- der is empty and contracted, the mucous mem- brane is thrown into numerous rugs, existing chiefly in a transverse direction, which are most distinct if a very recently contracted bladder be examined. When the organ is distended, these rugs disappear, so that their existence may be considered as evincing a want of elasticity in this tissue. This membrane presents some pecu- liarities throughout the extent of a small region named the ‘ trigone’ or the ‘velum’ of the bladder : this term is applied to a small triangular space, nearly equilateral, situated about the middle of the inferior region, and leading to the neck of the bladder. The base of this space is a lunated line leading from the orifice of one ureter to the other ; the sides are marked by lines which converge forwards from these open- ings to a slight projection at the neck of the blad- der named the ‘ uvula,’ which is immediately behind or rather in the orifice of the urethra. Throughout the area of this space the mucous membrane is very smooth and free from rugie or folds, as it adheres closely to the fibrous or compact cellular substance beneath : it is also more vascular, being generally of a delicate rose colour, or variegated with fine vessels, and when minutely examined with a magnifying lens numerous fine villi can be discerned. On the whole this surface appears to be delicately and peculiarly organized, and no doubt possesses higher sensibility than the remainder of the in- ternal surface of the organ. The posterior part of the trigone is thinner than the anterior ; the hue which marks its base is a thickened band of the circular or transverse muscular fibres, behind which the inferior fundus of the bladder is fre- quently dilated into a pouch which presses against the rectum, and where a calculus some- times rests, so as to elude the search of the sound unless the finger be introduced into the ectum : in old persons this pouch sometimes ernains constantly full of urine, the muscular :oat of the bladder not being able to contract t. The lines which form the sides of the tri- ;one, and which extend from the orifices of ach ureter to the uvula, are composed of a light projection of the mucous membrane, be- eath which is some cellular tissue, and in ame cases a few pale muscular fibres are dis- nctly seen. These lateral lines are not in eneral very distinct, at least in the healthy adder; their distinctness is owing to little ore than being the borders of this space. In VOL. i. some cases, particularly when the prostate has been enlarged or the urethra obstructed, they are found very distinct, the muscular fibres they contain being thickened even in a greater degree than the other portions of the muscular coat of the bladder. These lateral fasciculi appear to be little more than some of the lon- gitudinal muscular fibres of the bladder con- verging towards its cervix. Sir C. Bell, however, has attached a particular importance to these muscles, which he denominates the “ muscles of the ureters his description of their attachments and use is as follows, in his own words :• — “ The use of these muscles is to assist in the contraction of the bladder, and at the same time to close and support the mouths of the ureters.” “ They guard the orifices of the ureters by preserving the obliquity of the passage, and by pulling down the extremities of the ureters according to the degree of the con- traction of the bladder generally.” * It appears very questionable how far this statement as to the structure of these lines is generally correct, and it is still farther doubtful whether the use assigned is correctly ascribed or not ; for it may be remarked that these lines are often very faintly traced, that the muscular structure within them is sometimes very in- distinct, that in females it is scarcely observable, in very young children also of either sex it is not well developed ; whereas if such an import- ant office as that of guarding the ureters de- pended on these muscular fibres, it is most probable, and indeed is even certain that their presence would be constant and their deve- lopment more uniform. Again, the fact of the dead bladder when fully distended with fluid, or even with air when the urethra is tied, and the contents not escaping through the ureters, is a strong proof that the oblique or valvular direc- tion of the latter is the true cause of the non- regurgitation, and that it does not depend on the contraction of any particular muscular fibres. Again too, in animals this structure, as described by Sir C. Bell, is not at all obvious although the ureters have the same oblique course as in man ; it would rather appear that these muscular bands, which are occasionally very distinct along the sides of the trigone, are only portions of the longitudinal fibres, and that their action will be to shorten the trigone, to draw its base forward, and thus to assist in emptyingthe bladder. They may doubtless assist in fixing the orifice of the ureters and moving these in proportion as the surrounding parts are affected, but the opiniorr That -the preservation of the valvular or oblique course is depending upon them appears to be invalidated by the fore- going remarks, as well as by the following expe- riment. The healthy bladder of an adult male, recently dead, was opened to a small extent on its fore-part, and the sides of the trigone were cut by a sharp-pointed bistoury passed beneath each of them ; the urethra was then tied, and the bladder carefully closed : its cavity was next fully distended with water, and the fluid was * Medico-Chir. Trans, vol. iii. p. 178. 2 c 386 BLADDER, NORMAL ANATOMY. retained for a considerable time although it was subjected to pressure, and was afterwards eva- cuated through the urethra when the ligature on the latter was removed. No alteration whatever from the ordinary appearances was observed either during the distension or the subsecpient emptying of its cavity, nor did any regurgi- tation take place into the ureters in either state. The same experiment with air instead of water was repeated and with the same effect. It may be further observed that the ductus communis choledochus enters the duodenum in a similar oblique way, that no regurgitation from the intestine ever occurs into it, and yet there is no peculiar muscular fasciculus attached to its orifice which could execute the office ascribed to these lateral boundaries of the tri- gone. To these muscles Sir C. Bell also attributes the projection into the bladder of the third lobe of the prostate gland, usually called the middle or Homes lobe, when this part is in a state of enlargement. There are, however, such plain and simple reasons for this tumour be- coming prominent in this direction rather than in any other, that it is unnecessary to search for an explanation in the action of these muscles, the undoubted development of which in such cases may with a much greater degree of pro- bability be considered as one of the effects and not as the cause of this projection. The uvula or apex of the trigone varies very much in its appearance in different persons. In the normal state it is very small, and is most distinctly seen by making only a small opening in the upper region of the bladder when in situ, and looking down towards the cervix ; it then appears as a small projection in the middle line of the orifice of the urethra, which opening it thus assists to close or to fill. It is much effaced by opening the bladder from the urethra after its removal from the subject, the mucous membrane being then easily ex- tended. This projection is only a slight full- ness or prominence of the mucous membrane with an increase in the submucous tissue, in which small follicles or cryptoe may be dis- cerned . This part appears rather vascular, and probably possesses some peculiar organization ; the situation also which it holds, as well as its structure, appear to indicate it to be the seat of a proper sensibility, which, when affected, ex- cites the irritability of the whole organ. Many facts which manifest themselves in the treat- ment of urinary diseases seem to corroborate this idea : thus, when a calculus is pressed against this part of the mucous membrane, the pain is insupportable, whereas when it falls or is directed into the inferior fundus, the pain is comparatively trifling ; also when a bougie or catheter is being passed into the bladder, a peculiarly acute sensation is experienced as the instrument comes in contact with this par- ticular prominence. The uvula in the child is the most depending part of the bladder, at least in the erect posture; this is not the case in the adult ; hence probably we have in part the reason why calculus is more painful in the former than in the latter. The trigone in the female bladder comprises a smaller area, but is broader in proportion than in the male ; it is not so distinct or firm in the former as in the latter, where it is sup- ported not only by a dense substratum, but also by the vasa deferentia, vesiculse seminales, and prostate gland. This portion of the bladder is so firm and incompressible that it is probable the cavity corresponding to it can never be wholly obliterated, so that in the most contracted bladder a few drops of fluid are still retained. The uvula, like other similar portions of the mucous membrane, is subject to infiltration and increase of size in acute in- flammatory affections, as also to chronic and permanent enlargement ; and as it lies nearly over, but a little anterior to the middle lobe of the prostate gland, it is therefore difficult, and in most cases impossible to distinguish affections of the latter from those of the former. The uvula is smaller in the female than in the male ; hence the opening from the bladder into the urethra is larger in the former than inlhelatler. Organization of the bladder. — a. Arteries .— In the normal slate the bladder is not very j vascular ; we have already mentioned that its 11 inner surface is pale and free from any red jj vessels. The arteries, however, of the bladder I are very conspicuous when they have been in- jected ; they are long and tortuous, and are distributed chiefly along the sides, inferior region, and cervix. They are derived from various sources. The internal iliac or hypo- gastric on each side, just before its ligamen- tous termination, sends off one or two vesical branches, which ramify on the superior and lateral regions ; the middle hemorrhoidal and internal pubic also very generally send some considerable branches to its inferior region and cervix; the obturator and epigastric vessels also very frequently send small arteries to it anteriorly. When the bladder is distended, all these vessels are seen very distinctly, and in the muscular coat much more than in tire sub- mucous tissue, contrary to what may be ob- served in the other hollow viscera ; this, how- ever, is accounted for by recollecting that the mucous coat of the bladder does not in it' normal and healthy condition possess, nor doc; it indeed require any high degree of organi- zation, as it is simply a reservoir, and has nc important function to execute further than t( secrete a fine mucous fluid which lubricates it surface and defends it from the irritation of tin urine. This secretion mingles with the urine the properties of which it alters in a remark able manner whenever it is increased in quan tity, as occasionally occurs in chronic diseas of this organ. The muscular coat of the blac der is the essential agent in expelling its coi tents, and is therefore more fully supplied wit vessels than any other of its tunics. b. Veins.- — The veins of the bladder ail large and numerous inferiorly, and in old pe sons in particular. There are but few on tl superior and lateral regions except towards tii inferior part of the latter. In the child tl veins are very inconsiderable : this differed: 38? BLADDER, NORMAL ANATOMY. depends on this circumstance, that the veins which are seen at the inferior region of tire bladder, and which return the blood from its tunics, do not belong exclusively to this organ, but are principally derived from the dorsal veins of the penis ; they also receive several branches from the vesiculae and the prostate, also from the rectum and intervening adipose substance. In the adult and old these latter veins are very numerous, indeed they may be said to form a perfect ‘ venous plexus’ on each side, extending from the termination of the ureter to the prostate gland. All these veins are considerably less developed in children, inasmuch as the organs, at least those of gene- ration, from which they are principally de- rived, are comparatively small. The vesical ■veins ultimately discharge their blood into the internal iliac or hypogastric veins. c. Lymphatics. — The lymphatic vessels are tolerably distinct, more particularly inferiorly and about the cervix. They intermingle with the lymphatics of the rectum and of the neigh- bouring organs, and ultimately lead to the internal iliac or hypogastric glands. Indepen- dent of dissection, the existence of absorbents in the bladder is proved by its functions, or by the changes which the urine undergoes when long retained in this cavity, — a portion of its water is absorbed, and the residue be- comes pungent, high-coloured, and acrid. d. Nerves. — The nerves of the bladder are derived from the hypogastric plexus, which is constituted of two orders of nerves, viz. some from the sacral plexus of the spinal system, and others from the sympathetic or ganglionic system. This two- fold supply of nerves accords with the functions of this organ, and entitles it to be placed, as far as relates to the properties of its muscular coat, among the mixed muscles, being in part voluntary and in part involuntary : the former endowment will, of course, depend on its ’share of spinal nerves, the latter on the sympathetic. It may also be observed that the branches of the latter are principally distri- buted about the cervix and inferior region, while those of the former are seen distinctly on the sides and superior regions ; but in all these situations these nerves are more or less intermingled. The cervix of the bladder is of a com- pressed conical form, longer below and on the sides than above. It is surrounded in the male by the prostate gland ; only a small portion of this is upon its upper surface : in the adult the neck is placed nearly horizontally below the pubis and behind the triangular ligament. In the female the cervix vesicaa is closely sur- rounded by a whitish compact follicular tex- ture, not possessing any perfect capsule, and therefore without the accurate form of or any resemblance to the prostate gland in the male. The cervix in the child is more distinctly conical, and is placed in a more oblique or vertical direction than in the adult. The term cervix is not very definitive, as there is no exact limit, at least in the human subject, to mark this region as in quadrupeds ; according to most writers on human anatomy, it is syno- nymous with the prostatic portion of the urethra, and the full description of it is given by such in connexion with the anatomy of the urethra. We consider the neck of the bladder to be that contracted portion of the viscus which is embraced by the base only of the prostate gland, and which contains internally and below the slight elevation named the uvula of the bladder, and laterally and above the peculiar structure which fulfils the office of a sphincter. Having particularly noticed the situation of the bladder, and the slight change of position it admits of in consequence of its change in form, we shall next consider its attachments, or the media by which it is retained in its posi- tion, for it may be considered as nearly a fixed viscus. The bladder is held in its position principally by three connexions ; first, by the peritoneum ; secondly, by the reflections of the pelvic fascia; and, thirdly, by the continuity of its cervix with the urethra, the commence- ment of the latter being fixed by ligamentous connexions to the arch and rami of the pubes. First, the bladder is connected by certain folds of the peritoneum to the parietes of the pelvis and abdomen; these folds are named the “ false ligaments” of the bladder, and are five in number, two lateral, two posterior, and one superior. Each of the lateral ligaments or folds extends from the lateral region of the bladder to the iliac fossa, and contains in its duplicature thevasa deferentiain the male, and the round ligament of the uterus in the female. The posterior folds or ligaments are also two in number; they lead from the fore-part of the rectum to the back part of the bladder. Each of these folds is of a semilunar form, (the concavity looking forwards and upwards,) and contains the ureter posteriorly, and the obliterated hypogastric artery anteriorly. When the bladder is distended, these posterior folds are very short; but when it is contracted, they are distinct and long. Between them the pelvic cul-de-sac of the peritoneum descends, which in the empty state of the bladder and rectum appears deep, narrow, and distinct, but in the distended condition of these organs, particu- larly of the former, it is of much less extent and depth, as the bladder in becoming dis- tended rises upwards and draws with it the cul-de-sac of the peritoneum : hence in the distended state of this organ the triangular portion of its inferior region which is uncovered by peritoneum is increased in extent, and is larger than when the organ is contracted. Between the two posterior ligaments one or two semilunar folds of the peritoneum may- be generally observed on the posterior surface of the bladder, provided the latter be in a con- tracted state ; these folds are expanded as the bladder enlarges, and thus they serve to ac- commodate the serous membrane to the varying conditions of the bladder without stretching or extending the former — a purpose which perito- neal folds or ligaments in general are intended to answer. 2 c 2 BLADDER, NORMAL ANATOMY. 388 The superior fold or ligament extends from the summit of the bladder to the posterior surface of the recti muscles, and is partially reflected over the remains of the urachus and hypogastric arteries. This fold rather consists of three folds which diverge below and con- verge towards the umbilicus; they present a falciform appearance towards the abdomen, particularly when the bladder is contracted. In the foetus these superior folds, particularly the lateral, are very distinct, as they each con- tain the umbilical artery. The urachus, which is in the centre, is also at that age very distinct though shorter; its vesical end is often pervious for about an inch : it is always closed before it arrives at the umbilicus, it then becomes fila- mentous, and is soon lost on the umbilical arteries. The second medium of connexion between the bladder and the parietes of the pelvis is the vesical fascia, the reflections of which con- stitute the true ligaments of the bladder. The vesical is the internal lamina of the pelvic fascia reflected from the latter at the upper border of the levatores ani muscles : it covers the internal surface of this muscle on each side, and descends as low as a line drawn from the inferior border of the symphysis pubis to the spinous processes of the ischia. On this level it is reflected on the prostate gland and on the sides of the bladder, and posterior to this organ on the rectum and on several of the pelvic vessels and nerves. The anterior or vesical portion of this fascia is distinct and strong, and forms a pouch on each side of the bladder which assists in closing the pelvis; posteriorly this fascia is thin and cellular, being perforated by several vessels. Its anterior reflections constitute the true anterior liga- ments of the bladder, which are described as arising from the lower margin of the pubis on either side of the symphysis, then passing back- wards and upwards on the upper surface of the prostate gland, and expanding on the an- terior region of the bladder; many of their fibres become continuous with the muscular fibres of the bladder. A depression exists between these two ligaments, along which the dorsal veins of the penis run from beneath the arch of the pubis to the side of the bladder in their course to the internal iliac veins, in which they terminate. The fascia, however, is not deficient in this depression between these ligaments, but is continued from one to the other so as to line this hollow' and to cover the upper surface of these veins. The anterior ligaments present a smooth concavity towards the abdomen or pelvis; their perineal or infe- rior aspect is convex, and has inserted into it the posterior lamina of the inter-osseous or triangular ligament of the urethra. The true lateral ligaments of the bladder are also two in number, one on each side ; each is continuous with the anterior, and is formed by the reflection of the vesical fascia from the internal surface of the levator ani muscle to the side of the prostate gland, and of the bladder immediately above and outside the vesiculre seminales. The pelvic and vesical fascia? will be more particularly noticed in the article Pelvis. Lastly, the bladder is retained in situ by the attachments of the cervix; these take place not only directly by the ligaments which have been just described, but also indirectly through its connexion to the urethra and of the latter to the pubes through the medium of the trian- gular ligament of the urethra. This ligament, for a fuller description of which we refer to the article Perineum, is a strong aponeurosis intimately connected to the rami of the pubes and ischia, and there continuous with the obtu- rator fascia of each side. It is strong, tense, and unyielding, and closes all the anterior portion of the inferior orifice of the pelvis; it is perforated by a small opening, through which the urethra passes about an inch inferior to the bony edge of the pubes; the edges of this opening are continued on the urethra both to- wards the perineum and towards the pelvis. The process which extends in the former or inferior direction is lost on the bulb of the urethra, while that which extends in the pos- terior or superior direction, and which is more distinct and strong, encompasses the mem- branous part of the urethra, (which, while in situ, is very short,) and is then inserted or becomes continued into that reflected portion of the vesical fascia which forms the true anterior and lateral ligaments of the bladder; thus the commencement of the urethra, the prostate gland, and the neck of the bladder, which must be nearly synonymous with the prostatic portion of the urethra, are all retained in a nearly fixed position, and the continuity of the different aponoreuses in this region serves to afford mutual strength and general security. The bladder, notwithstanding the foregoing connexions, is subject to displacement. In the male this occurrence seldom happens, although in some cases of very large inguinal or scrotal hernia? this viscus has been gradually drawn into the sac, in consequence, most probably, of adhesion between it and the omentum or some other of the protruded parts. We have already mentioned how a portion of the lining membrane may become protruded between the muscular fasciculi and form a sac which may increase to a considerable size, and extend into some new and even remote situation. In the female the bladder is very liable to partial pressure as well as to displacement, owing to different conditions of the uterus, such as retroversion, inversion, and prolapsus. Bibliography. — Mangetus, Ureterum et vc- sicae urinaria? hist, ex variis in Bib. Anat. v. 1. Vogelmann resp. Jamon , Diss. sist. fab. &c. renum et vesicae urinaria?, 4to. Moguut. 1732. Parsons, Description of the human urinary bladder, &c. 8vo. Lond.1742. Beudt, De fabrica et usu viscerum uropO'- eticornm, 4to. Lugd. Bat. 1744 (Rec. in Kalleri Disp. Anat. vol. iii.f. Waltlier, De collo vrrilis vesicre, 4to. Lips. 1745 (Rec. in Haller, Coll. diss. Anat. vol. v.). Lieutaud, Ohs. anat. stir la structure de la vessie, Mem. de I’Acad. de Paris, 175c Weitbrecht , De figura et situ vesica? urinaria;, torn. BLADDER, ABNORMAL ANATOMY. Petrop. vol. v. Noot, De structura ct usu vesicse urinari® atque urcterum, 4to. Lugd. Bat. 1767. Boeckkoven de Wind, Do ureteribus et ves. urin. 4to. Lugd. Bat. 1784. Richerand, Mem. sur l’ap- pareil urinairc, in Mem. de la Soc. Med. d’Emulat. An viii. Bell on the muscles of the ureters, Med. Chir. Trans, v. iii. Wilson, Lectures on the struc- BLADDER, ABNORMAL ANATOMY OF THE URINARY.— Under this deno- mination it is proposed to include all variations from the natural condition of the organ, whe- ther the particular variety be a congenital vice of conformation or a consequence of extra- uterine disease. 389 turo and physiology of the male urinary organs, &c. 8vo. Lond. 1821. See also the different systems of anatomy, the Tabula: Septendecim of Santorini and his Observations anatomic®, and the recent Memoir of 3Ir. Guthrie on the anatomy and diseases of the neck of the bladder, &c. 8vo. 1834. ( li. Harrison. ) In the following synopsis may be seen the several affections included, as well as the order in which they will be described in the present article. Changes Congenital Acquired 'Of conformation Of position Of structure ^_Of function To some persons, the introduction of two functional diseases, paralysis and spasm, in an article on pathological anatomy, may appear objectionable ; but as they are sometimes con- sequences of structural change, we hold that we have a perfect justification for their ap- pearance. CONGENITAL CONDITIONS. Numerical changes. — Absence. — Among the single organs of the body, one degree of nu- merical diminution only is possible, namely, their absence. Such an anomaly, if we except true cases of monstrosity, should be extremely rare, and indeed it is so; for as all unique portions of the organization are called upon to perform functions, to which they are more or less exclusively devoted, it is rarely that any other can supply their place, and in conse- quence, when the organ is wanting, the func- tion is also wanting. There are upon record a certain number of instances of absence of the urinary bladder; in some of these cases the ureters have been round to terminate directly in the urethra, in others they have been inserted into the rectum, ln others they have communicated with the ragina. Of the first species we have the fol- owing examples : Lieutaud * mentions the ■ase of a man, aged thirty-five, in whom the rreters, the capacity of which was much aug- Hist. Anat. Med. Liber primus. Obs. 1361. i NumeriCal \ Plurality. \ i Septa. Of conformation . . < Extrophy or extroversion, ( Persistance of the urachus. c Sacculi or cysts. ) Capacity, increase of. i decrease of. v. Introversion. c Hernias, inguinal. ) femoral. \ perineal. v. vaginal. ("Inflammation with its consequences. Idiopathic softening. Rupture. \ Fistula?. ' ( Hasmorrhage. Fungoid tumours, j Varices. IjSeirrhus. t Paralysis. ' ’ \ Spasm. mented, terminated immediately below the pubis near the orifice of the urethra. Binnin- ger* describes the case of Abraham Clef, in whom there was no urinary bladder, and the ureters opened upon the urethra. A stylet, introduced into the urethra, passed alternately into the one and the other ureter ; the ureters were afterwards separated from the kidneys, and the stylet, introduced in the opposite di- rection, met with no obstacle to its passage into the urethra. Of the second species we have, in the se- venth volume of the Philosophical Trans- actions, the history, given by Richardson, of a lad residing in Yorkshire, who lived to the age of seventeen, without ever having passed urine through the urethra, and who had still enjoyed good health. The only inconvenience he suf- fered was a consequence of the passage of the urine into the rectum, by which a troublesome diarrhoea was kept up. Camperf speaks of five similar cases, one of which was that of a female. Klein J also speaks of a case. In the Nov. Acta Acad. Nat. cur. ann. i. obs. 38, there is another in which “ ureter in rectum intestinum insertus fuit.” And in the Hist, de l’Acad. ann. 1752, n. 4, there is one de- * Obs. Med. 24, cent. 2. t In Mem. pour le Prix, &c. 8vo. edit, tome v. p. 9. t Rachit. congenit. Nov. Eph. Ac. Nat, Gur«. vol. i. obs. 38. BLADDER, ABNORMAL ANATOMY. 390 scribed under the head : “ Uretra in intestlnum 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,| 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 ! 1 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 Academia; Csesarere Nat. Curios, vol. i. obs. * Element. Physiologic, vol. vii. p. 297. t Nov. Ephem. Acad. cur. Nat. vol. i. obs. 38, ct 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 tho 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 (ccecum). — Ed.] Dissert. Anat. Pathol, lib. vi. cap. 7. 83, may be found a well-marked case of 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. Hilaire, 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 cavee, and so on. Now if there exist two vaginas, two bladders, two uteri, at a certain epoch of embryotic life, the evolution of these organs should necessarily present three successive 1 periods : a first, characterised by their du- J plicity and their complete isolation; a second, by their mutual approach and union upon the median line ; a third, by their complete fusion, which constitutes their permanent condition I in man and the mammalia. We can therefore !j conceive that at the moment of the second period, when the two primitive organs are united, the parietes of both being entire and in contact on the median line, there will be a perfect septum separating the one organ from the other. At the commencement of the third period in the process of develop- ment, the septum is destined to disappear, the two cavities merge into one, and the work of development in the organ is com- plete. Now, in the evolution of all the organs, 1 development may be arrested at any period of its progress : it may be arrested before the organs come into contact, in which case there would be two bladders; it may be arrested after they have formed a junction, in which case a complete septum would exist, as in the case described by Blasius ; or the check may not occur until a greater or less portion of the septum shall have disappeared. To distinguish the congenital affection which is a consequence of arrested development, from the acquired affection which is an extra- uterine disease, and is commonly an effect of retention of urine, is not difficult. In the former we shall always find that the entile of each pouch is invested by a layer of mus- cular fibres ; in the latter, it will be found that GLADDER, ABNORMAL ANATOMY. 391 in one of the two compartments no such mus- cular investment is present. Extrophy ox extroversion. — Extrophy of the bladder was, up to a comparatively late period, almost universally regarded as a hernia of that organ; and it was not until about the middle of the last century, and after Tenon had dissected two such cases, that this opinion was shown to be erroneous.'* Tenon dis- covered that there was a complete “ absence ” or destruction of the whole of the anterior parietes of the bladder; and that the tumour which is found at the hypogastrium is only the posterior parietes of this sac, with the “trigone” pushed forward by the abdominal viscera, as if for the purpose of blocking up the opening caused by the deficiency of sub- stance below the umbilicus. On the surface of the tumour which is there presented, and at its inferior part, we see the urine almost con- tinually exuding through two holes, pierced in the centre of two small nipple-like eminences, which are the orifices of the ureters. The insertion of these conduits of the urine at the inferior part of the tumour indicates that the portion of the bladder, which appears upon the exterior, is precisely that which, in the natural state, is found most deeply situated in the pelvic cavity, the internal surface of the posterior and inferior portion of the organ. The researches of anatomists have most posi- tively confirmed these indications, by shewing that in extroversion of the bladder the anterior part of this organ is more or less completely wanting, and that the posterior part is pushed from behind forwards, through the large open- ing which results from this absence, causing a “ hernia,” either between the two pubes and the two recti muscles, or, which is very rare, only between the latter, the mucous mem- brane being presented externally. By this displacement the external posterior surface of the bladder forms a concavity in which some portions of the intestinal tube may be impacted, as in a true herniary sac, especially when the abdominal muscles and the diaphragm are strongly contracted. The volume of the tu- mour is on this account variable, not only as between one subject and another, but in the same subject at different ages. Thus in new- born infants onlya slight projection is presented: the tumour may not occupy a larger space than from half an inch to an inch. In adults it may project to the extent of two or more inches and present a transverse diameter of four or five. The tumour is then smooth and frequently appears divided into two lobes. When extroversion of the bladder exists, the umbilicus commonly is, as in the embryo and the young fetus, not far removed from the symphysis pubis, nor consequently from the vesical tumour. The umbilicus is almost always found immediately above the tumour. ' Sometimes, however, the superior extremity of the latter is observed beyond the umbilicus, which is then entirely concealed ; and in con- l'cs Sciences, 1761, tom. cxiv, in 12mo, ‘ p. 67. sequence of this circumstance, some author have believed that the umbilicus was not pre- sent in infants affected with extrophy, and they have drawn from this fancied absence phy- siological consequences as erroneous as the facts upon which they were based are ground- less. This affection was until recently supposed to occur only very rarely in the female; this opinion, however, is incorrect. In many of the cases on record the sex is not specified, and it is not improbable that many women may from a sense of shame be desirous of concealing such a disgusting deformity. Even with these reasons why the cases should be less numerous, we have been enabled to collect twenty-one examples. In women the affection does not produce so much derangement in the sexual functions as when it exists in man, by whom, the penis being almost constantly deprived of urethra, fecundation must be al- most impossible. In the other sex, on the contrary, the vagina being ordinarily free, though more or less contracted, coitus may have place, as in a well conformed female, and fecundation may follow, as in the case detailed by Drs. Huxham and Oliver and Mr. Bonnet, of a woman who lived at Lantglasse near Fowey ;* and that of Thiebault, in which the delivery occurred through the perineum. Among the anatomical varieties by which it is accompanied, none are more singular than that mentioned by Bartholin, f in which there was neither anus nor penis, all the ingesta return- ing from the mouth during forty years. It has been over and over again maintained that this affection was incompatible with long life. The child of which Highmore speaksf was ten years old, and in good health ; the case of which Montagne speaks§ was at the time a person of thirty ; that of Flajani || was seventy. Baillie,^' Mowatt,** Innes,ff and Labourdette,j.j; all describe the cases of adults. Quatrefages §§ describes the cases of a person of forty-nine and of another of forty- six. Most authors who have written on this sub- ject have strenuously maintained the constancy of the separation of the bones of the pubis. Duncan, even in spite of the case of Mr. Coates, with the details of which he was fami- liar, retained that opinion apparently unshaken. We are in possession of the particulars of cases in which no such separation existed, re- corded by Coates, mi Denman, Roose,*j[^[ * Phil. Transact, vol. xxiii. 1723, p. 408, 413, and vol. xxxiii. p. 142. t Hist. Anat. cent. iv. hist. 30, p. 293. f Disquis. Anat. part iv. cap. 7. § Acad, des Sciences, tome cxiv. in 12mo. p. 67. |1 Malattie Spettanti alia Chirurg. 1786. Morbid Anat. p. 309. ** Mem. de Desgranges. tt Arch. Gener. vol. ii. p. 286. Journal dc Sedillot. §§ Theses de Strasbourg, 4to. 1832. ||[| Edinburgh Med. and Surg. Journal, vol. i. Dc nativo vesicas urinaria: invers. &c. n. 19. 392 BLADDER, ABNORMAL ANATOMY. Walther, and one of Quatrefages ;* and there are still one or two others, about which some doubt exists. What proportion these cases would bear to those in which the separation was demonstrated, it is almost impossible to determine, because there can be no doubt that, of the numerous recorded cases, many of the descriptions appertained to the same indivi- dual, the total number of cases being in my opinion much less than is supposed. It is easy to explain how this source of error has been introduced. The unfortunate persons who are subjected to this infirmity are often objects of general curiosity. They wander from town to town for the purpose of obtaining a livelihood by exhibiting themselves to me- dical societies and to private individuals, and the history of a single person may thus be found repeated in the different periodicals of the same and even of different countries. To determine the mode in which this vice of conformation is effected is very difficult. We cannot admit that Duncan’sf explanation of the mode of its formation is correct, because it is opposed to every principle which we are ac- customed to recognize as presiding over the developement of our organs. He attempted to prove that an obstacle to the expulsion of urine affords a satisfactory explanation of this phenomenon, and he believed that the bladder, by its distention, removes the bones of the pubis from each other, ruptures the hypogas- trium, and then disorganises itself. We should have conceived that a very little reflexion would have removed from his mind so singular an opinion. The disease is almost always conge- nital, although during intra-uterine life the fcetus can have but little urine to void, and cannot, consequently, have a distended blad- der. Duncan himself, however, strangely enough states the case of a little boy who was affected by the disease, although the urethra, placed in front of the root of the penis, strongly curved towards the anus, allowed of the easy passage of the renal secretion. And there are cases on record well authenticated, where no separation of the pubis existed. Isenflamm also states that the disease was manifested, in his experience, ten weeks after birth. The opinion of Duncan, therefore, cannot, it is apprehended, be sustained. Those persons who believe this disease to be a primitive monstrosity are divided into two classes. The one suppose it to be merely an organic deviation, in which the urethra is placed above instead of gliding beneath the pubis. This, however, is not the prevailing doctrine; that which has obtained the most general currency is based upon the theory of arrested development. Supposing that the two moieties of the body do not, until late, meet upon the median line anteriorly, they say, if, by any cause, the sides of the hypo- gastric parietes cease to advance, the one to- wards the other, during their allotted time, the bladder will pass between them, and will * Theses de Strasbourg, 1832. t Edinburgh Med. and Surg. Journal for 1805 soon lose its anterior moiety, supposing this moiety to be already formed, from whence the fungous state which it offers after birth. So powerful are the authorities by which this mode of explaining the phenomena is supported, so completely is it said by the ardent supporters of teratology to be in consonance with its principles, that it would appear to be almost heretical to support a somewhat different view of the subject taken by M. Velpeau, lie be- lieves that extrophy of the bladder is not simply owing to an arrested development, first, because in the normal state the bladder is neither split nor open, neither anteriorly nor posteriorly ; secondly, because the pubic circle is completely formed before the bladder is per- ceptible; thirdly, because the aspect of the fissure that the urinary sac should present never exists ; and, fourthly, because the theory in question has for its support only such ana- logies as do not appear to us to have been completely established. If an hypothesis he required, it appears to be more in conso- nance with observation to assume that this vice depends upon an alteration of the abdo- men, either pathological or purely mechanical, contracted during embryo life. The parietes of the abdomen are extremely attenuated and fragile up to between the second and third months, and for some time beyond this the parietes do not acquire any thing like the density below that they do above the umbilicus. At this time the space is so small between the umbilicus and the sexual organs, that the smallest fissure may become the origin of a large ulceration, and such lesions are seen at all degrees. Indeed it is scarcely possible to set forth the variety of lesions to which the young foetus is subject : foetuses have been seen in which the parietes of the abdomen were alone destroyed. In one of three months the bladder was already comprised in such a perforation, and the borders of the whole weie so jagged, thin, and unequal, that it could be referred to nothing else than a laceration. It is held in this place, therefore, that extrophy is frequently a disease, or the effect of a diseases, but not a monstrosity ; an ulceration, a perfo- ration of the penis or of the hypogastrium, being the common point of origin. The bladder is only secondarily altered. If the fcetus continues to live, the borders of the de- stroyed bladder are united to the circumference of the abdominal opening, or, at least, to the posterior surface of the remaining portion ol the hypogastrium. The cicatrisation once ef- fected, the rest is explained by the mucous nature of the organic septum, which occupies the place of the pelvic or abdominal parietes. The umbilicus may or may not be implicated in the loss of substance; the pubes, which are commonly destroyed, and not simply sepa- rated as has been believed, may be also pre- served ; and the vesical tumour may in some cases only occupy a space of a few lines, whilst in others it may implicate a great por- tion of the hypogastrium. Those organs which are normally in relation with the pubis present certain anomalies in BLADDER, ABNORMAL ANATOMY. extroversion of the bladder, which should be mentioned in this place. The ureters, of course, open immediately upon the surface of the body ; the urethra no longer serves for tite emission of urine, and is often incomplete. Commonly in woman it opens above the cli- toris, in man above the penis. Occasionally the testicles do not descend. Meckel has remarked that there is commonly a separation of the two lateral moieties of the external genital organs, like that of the abdominal muscles and the pubis. It has been remarked by Duncan (loc. cit.) that this infirmity more commonly happens to the male than the female. Meckel doubts this proposition, and adds many cases to those cited by Duncan, in which the disease affected the female. Isidore Geoffroy St. Hilaire, who has carefully examined the recorded cases, which are now very numerous, supports the conclusion of Duncan : he says that of these one-fourth appertain to females, nearly two-thirds to males, and in the re- mainder tlie sex was undetermined. Ex- trophy of the bladder is a very serious af- fliction, because of the incontinence of urine winch is its inevitable consequence, and the deformity of the genital organs by which it is constantly accompanied, and which, in man especially, very commonly occasions impo- tence. It constitutes a more serious disease in the male than in the female, for in the latter the external genital organs, except the want of projection of the pubic eminence, commonly suffer only slight modifications of form ; the ovaries, the uterus, and their appendages may not even present any anomalies.* Persistance of the urachus. — The last of the congenital malformations to which I shall allude is the persistance of the urachus some- times even to adult age. For a considerable time much doubt was expressed whether the urachus was ever a canal, pervious from the bladder to the umbilicus ; and it was not gene- rally admitted until the fact had been re- peatedly demonstrated by Haller and his pupil Noreen. In January, 1787, Boyer exhibited a bladder taken from a man aged thirty-six, in which the urachus formed a canal an inch and a half long, and containing twelve urinary calculi, each of the size of a millet-seed; and it was demonstrated that this canal was not a vesical sac or a prolongation of the mucous membrane. But these cases of persistance of the cavity of the urachus in adult or even in infant life are unquestionably extremely rare ; * For more minute details of this affection the reader may consult Blasius, part iv. obs. 6. Stal- part Vanderwiel, vol. ii. p. 56. Bartholin, cent, ii. hist. 65, the Edinburgh Essays, vol. iii. p. 257, the Journal Encyclopedique, August, 1756, the Journal de Medecine of Paris, t. v. p. 108, et t. xxvii. p. 26, the Memoirs of the Academy of Sci- ences of Paris, 1761, where we find an observation of Leinery made in 1741, and three facts observed by Tenon, also the second volume of Medical Commentaries by a Society of medical men at Edinburgh, p. 437, and the Memoirs of Duncan Mdirrb. Med. and Surg. Journ. 1805), and Velpeau Mem de l’Acad. lloyale de Med. tom. iii.) 393 and it is certain that a protrusion of the mu- cous tunic in the form of a canal at this point has been mistaken for the canal of the urachus ; it is even probable that generally where the urine is prevented from escaping by the urethra, and where it escapes by the umbi- licus, it results from the rupture of the species of hernia formed near the situation of the urachus by the mucous tunic of the bladder, and not from the ddatation of this membranous cord. When this canal remains pervious only in a part of its extent, the anomaly is not indicated externally. When its cavity is preserved even from the bladder to the umbilicus, nothing marks its existence at the exterior if the urinary passages are unobstructed ; in the opposite condition a very remarkable physiological ano- maly accompanies it, and reveals the presence of the anatomical anomaly; it is the total or partial excretion of urine by the umbilicus, either constantly and from the moment of birth, which is the case when a vice of confor- mation or a disease prevents the urine from passing by its natural channel or tempo- rarily, when the course of the urine, which was at first by the urethra, comes to be inter- rupted by any cause. Sigismund Kbnigj- relates the case of a woman in whom the urine, usually excreted by the urethra, passed by the umbilicus during some days in consequence of a severe labour ; but this example and others which might be mentioned do not appear to possess the authen- ticity which is required to establish that this infirmity may be acquired. It is probable that many of these cases were simply a hernia of the mucous membrane of the bladder, such as occurred in the case detailed by Portal .J. acquired changes. Succuli or cysts. — A sacculated or encysted condition of the bladder is never a congenital vice of conformation of that organ, but an effect of disease. Sacculi may be produced by any thing which can oppose itself to the excretion of urine, or which may enfeeble the muscular tunic of the organ. In this way the urine becomes collected in the bladder, the parietes are distended, the internal tunic is forcibly applied upon the muscular coat, and if at any point this tunic be weakened, less resistance is offered, a separation between some of its fasciculi takes place to a sufficient dis- tance to admit of the mucous membrane pass- ing between them, and in this way sacculi may be formed. This, however, is not the only way by which this state may be produced ; in some bladders the muscular tunic is so developed, probably by irritation, that its fasciculi are grouped and a columnar aspect is produced, not very unlike to the appearance of the interior of the ven- tricles of the heart. * Littre, Mem. de l’Acad. des Sciences, 1701, p. 23. Sabatier, Traite d’Anat. t. ii. p. 402, et t. iii. p. 498. — Cabrol, Alphabet Anat. obs. 20. This case occurred at Bcaucairc in 1550. t Phil. Trans, v. 16. t Mem. de l’Acad. dcs Sciences, 1769. BLADDER, ABNORMAL ANATOMY. 394 Certain portions of the parietes of the organ are in such cases unprovided with the muscular fibre necessary to enable them to offer the usual resistance, and a similar effect is pro- duced to that which I have already described, the mechanism being somewhat different. These sacs may attain great size, even supe- rior to that of the bladder itself; commonly the point by which communication with the bladder is maintained is only a narrow neck , and in consequence of this circumstance the organ has occasionally been described as dou- ble, triple, and so on. It is always easy to determine whether it be really so or not, first, by examining the parietes of each, and, secondly, by ascertaining the points at which the ureters are implanted. In the first case we shall find only one of these compartments invested by a muscular tunic : in the second an ureter has never yet been known to pene- trate directly the adventitious cavity. There is scarcely any point of the surface of the bladder in which such a state may not be produced, but there are certain regions where the affection is much more frequently met with than others. They are most commonly formed at the lateral parts, or at the summit, near the insertion of the urachus. Occasionally many of these sacculi are found in the same bladder.* A species of sacculi or appendices may, however, be produced by an extension, at a given point, of the whole of the vesical tunics; and even these may be a consequence of re- tention of urine, but more frequently of the sojourn of a stone, which forms a cell. Some examples of this species are given by Morgagni.f A woman, two years before her death, introduced into the urethra “ a long hair pin ;” this instrument slipped from her grasp and passed into the bladder, where it became arranged transversely, so that whilst the point rested upon the left, its head rested on the right side of the organ. The head became incrusted with calcareous matter; a stone of the size of a nut was thus formed, which was contained in a quadrilateral sac produced by the extension of the whole of the tunics of the bladder. Cells or cysts may be otherwise formed at the expense of the vesical parietes. Calculous concretions may be formed in the kidney, and may pass unobstructed through the ureter into the bladder; but if the magnitude of the stone be disproportioned to the capacity of the canal of the ureter, it may sojourn at any point of the continuity of this canal, or at the point where it terminates in the bladder. If also the cal- culous matter be abundant in the urine, it will be deposited upon this nucleus, which will more or less rapidly augment in volume, and will be impacted at or near the point where it may have acquired this augmentation. The first author who speaks in a clear and precise man- ner of this affection is the celebrated Pierre * Hcistcr. t De Setl. &c. cp. xlii. art. 18. Franco* Since Franco, it has been described by by many others, particularly by Alexander Mon- rof and Iloustet.j The existence of this affection is certainly not frequent, but its occasional occur- rence is amply proved : formed in the way I have described, these calculi occasionally glide between the mucous and muscular tunics of the organ by means of an opening which they form at the point where the ureter obliquely pierces the bladder, instead of entering the bladder by the natural channel. The volume of these cysts is never very considerable, for such calculi do not acquire anything like the volume of those which are commonly found moving freely in the cavity of the bladder. The reason of this is ob- vious ; they are not exposed to the action of any considerable quantity of urine, and they cannot consequently receive a large accession of calcu- lous matter. CovilIard§ and Garengeot|| have seen them of the size of a hen’s egg, but such cases are rare. Commonly they are very little removed from the insertion of the ureters. The reason of this is not, however, that which was assumed by Littre,^[ because the contraction of the muscular fibres is made towards the fundus, and that in consequence the calculus would be forced towards that region, but by reason of the resistance offered by the membrane of the cyst by which they are surrounded. CHANGES OF CAPACITY. The bladder may suffer certain modifications of capacity as consequences of disease. It may become so distended as to contain nine pounds of urine (in puella pro hydropica liabila, Koenig)'*'* novem chopines ab ischuria, La Motte;)ff or even twelve pounds, Felix Pascal: or it may become so diminished that its volume shall not exceed that of a small walnut. In 1764, M. Portal found at Montpellier, in the dead body of a woman aged sixty, the bladder so small that its volume did not exceed that of a hazel-nut. Decrease.' — In persons who pass urine fre- quently, the bladder is small ; still more so in those whose kidneys do not perform their func- tions properly. It is small in those cases of irritation by which frequent contractions are excited. Lithotomists have frequently remark -d that in calculous patients the bladder clos.dy embraced the stone. Morgagni, in opening the body of a girl of fourteen, found the bladder adherent to the parietes of the abdomen imme- diately above the pubis, and so contracted around a needle, which had been introduced sixteen months before her death, that this viscas could scarcely have contained anything more. 51 Trait6 des hernies, chap. xxxi. p. 107, Lyon, 1561. t Essays and Observations of the Medical So- cicly of Edinburgh, vol. vi. p. 257. I Mem. dc l’Acad. des Sciences do Paris, ann. 1702. $ Obs. 11. U Mem. de 1’Acad. dc Chir., t. i. p. 411. y| Mem. dc l’Acad. des Sciences, an 1702. ** Lith. spec. Epist. 11. ft Traitc des Accouchmcns, Obs. 44. 1} Do Scd. cp. xlii. art. 20. BLADDER, ABNORMAL ANATOMY. The bladder is also very small in cases of incontinence of urine and in vesical fistulas. Increase. — The volume of the bladder aug- ments when the whole or a great portion of the urine is retained in its cavity, and under the opposite conditions to those which have just been named. To such an extent may this in- crease proceed, that it may be mistaken for ascites.* * * § Inflammation of the bladder com- monly accompanies its excessive dilatation, but many circumstances related by Morgagni and others prove that this viscus may be con- siderably distended by urine without becoming inflamed. It may, however, lose its contractile power, and the assistance of art may be neces^ sary for the evacuation of the urine. A fact stated by Mauchartj- shews that a man had ischuria, which had commenced four days before he was sounded. Some days after this he died ; the bladder was found inflamed in different points. It was entirely empty and yet very voluminous, without being contracted as it is commonly after death. Introversion. — Among the acquired changes of conformation of the urinary bladder, there is one which may be termed introversion. In this affection, which is rare, the superior por- tion of the organ is so depressed as to be brought near to its neck, to project into the urethra, and in woman to make its appearance at the external orifice of that canal. Chopart j relates from Percy the following observation : — The patient was an abbess aged fifty-two, in whom the fundus of the bladder was impacted in the neck, having also passed along the urethra, and forming at its external orifice a tumour of the volume of the eye of a pigeon, red, fleshy, unequally tumefied, which, when pressed upon with the finger, returned into the canal and reappeared without any violent exertion. An analogous case occurred to Foubert.§ The patient died, the body was examined after death, and it was found that the posterior and superior region of the bladder was depressed into the form of a cone whose apex had pene- trated the neck of the bladder, a portion of ileum about six inches long being lodged in this depression. When, in the female, the summit of the bladder is engaged in the neck, the simple inspection of the tumour, its increase after walking or in consequence of a fit of coughing, its disappearance with compression, are sym- ptoms sufficient to enable us to recognize the disease. Those aged persons whose bladders are very capacious, and who are become feeble, are most subject to this affection, which is produced by the pressure which the other viscera exercise on this organ. Hernia. — The absence of information in old authors on the subject of hernial displacement of the urinary bladder induced an opinion which was current for very many years, that the * Chopart, Smellic, Black. t Epliemeridcs Acad. Nat. Cur., cent. ix. obs. 41. f l'vaite dcs Maladies des Voies Urinaires, t. i. d. 399. Edit. 1830. § Mem, de l’Acad, de Chir,, t. ii. p. 36. 395 affection we are about to consider was of ex- tremely unfrequent occurrence. This, however, is an erroneous opinion, for the experience of modern times has demonstrated, that though less frequent than hernia of the intestines or of the epiploon, cystocele is not an unfrequent disease.* The inguinal ring, the crural arch, the peri- neum, and the anterior walls of the vagina may become the seat of a hernia of the blad- der. At whichever of these points the disease may be manifested, the bladder, fixed deep in the pelvis and hidden behind the pubes, is never completely displaced ; only prolongations of the organ can pass these several points. It must be at once evident that besides the dila- tation of the opening through which it passes, there must be a great increase in the capacity of the organ itself, and a great relaxation of its parietes, occasioned most commonly by retention of urine, or by a habit of only rarely attending to a desire for its evacuation. Whe- ther the protrusion occur at the one or the other of the several regions I have named, there are certain general characters by which it may be more or less readily detected. We shall find a soft tumour, accompanied by a fluctuation which is as much more sensible, and which acquires a volume as much more considerable as the time which may have elapsed without an evacuation of urine is greater. This tumour may be easily lessened by compression, but the reduction is immediately followed by an urgent desire to pass the urine. This species of hernia is only partially co- vered by peritoneum. Dominique Sala is, according to Bartholin, f the first person who mentioned this peculiarity. The reason of this circumstance is obvious : when the bladder is distended, it is raised to the level of the crural arch and of the inguinal ring ; it pushes before it the peritoneum, and insinuates itself between the peritoneum and the abdominal muscles. If at this time a violent effort determine the escape of the corresponding part of the organ by one or other of these openings, it is the anterior, superior, and lateral part of the organ which will be presented, and this is the portion which is without a peritoneal invest- ment; so that at this time the hernias we have described are completely deprived of a sac. It usually happens, however, that the posterior portion of the organ soon follows, dragging with it the peritoneum by which it is covered ; this portion in turn drags down that which is in the vicinity of the ring; and in this way a hernial sac is formed, ready for the reception of the intestine or the omentum. This is the reason why a hernia of the bladder is so fre- quently accompanied by an intestinal or omen- tal hernia. * For a confirmation of this opinion, see Blegny, Traite des Hcrnies, 1688; Mery, Mem. de l’Acad. des Sciences, 1713; Petit, memo ouvrage, 1717; Le Dran, Garcngeot, and La Faye. Hcister anti Plainer, Instit. Chir. J. G. Gunzii, Obs. an. Chir. de Hernia, Lipsia:, 1744 ; Monro, Levret, Sharp, Pctt, Scarpa, Lawrence, and others. " f Hist. Anat., cent, xviii. BLADDER, ABNORMAL ANATOMY. 306 It does not appear to be well established whether a primitive hernia of the bladder occurs in the direction of the inguinal canal, or whether it escapes directly through the aponeurotic opening of the external abdominal muscle, though the latter opinion is the most probable. It has been remarked in some cases that the spermatic vessels were external to the hernia. In consecutive vesical hernia an intestinal hernia primarily exists ; the intestine pushes before it the peritoneum which surrounded the ring, and in proportion as the hernia increases in volume, does the sac augment, the peri- toneum in the neighbourhood of the ring is drawn down, and, as a consequence, that which invests the posterior surface of the bladder, which in its turn is also drawn down, if, on the one hand, the adherence of the peritoneum to the bladder be sufficiently strong, and if, on the other, the latter organ be voluminous and sus- ceptible of displacement. The primitive peri- neal and vaginal hernise are similarly situated as to the non-existence of a hernial sac, and of the existence of consecutive hernia in these situations we have no record. The species of vesical hernia which Is most commonly seen is the inguinal ; the tumour is usually confined to the groin, but it may descend into the scrotum, gliding along the spermatic cord.® Hernia of the bladder at the crural ring is very rare. It presents the same characters and is subject to the same complications as that which occurs at the inguinal ring. Its form and its seat only are different; it is developed at the same point as a merocele, and like it takes a globular form. Vesical hernia at the perineum is an ex- tremely rare disease, and for some time was supposed to occur exclusively in pregnant women, but the observation of Pipelet is con- clusive as to the possibility of its existence in man. In these cases a portion of the bladder passes between the fibres of the levator ani muscle, and it is presented in the form of an ovoid tumour placed at the side of the anus. In each of the three species of hernia which we have described, the bladder suffers certain changes of form: it is contracted at the level of the opening through which it passes, and is again dilated below this point. This circumstance has been observed by Keate, Pott, and Ber- trandi. Sometimes even calculi have been found in the displaced portion of the blad- der.f Few occasions have occurred of observing hernia of the bladder through the vagina. In this affection the fundus of the bladder de- presses the anterior parietes of the vagina, and forms a round projection, which is frequently visible externally when it passes the level of the orifice of the vulva. The disease is usually developed during pregnancy when pressure is made by the distended uterus upon the neigh- bouring organs; but cases have occurred at an * Pott’s Surgical Works, vol. i. case 26. t Pott, loc. cit. advanced period of life. Of all the species of hernia of the bladder, that by the vagina occa- sions the most pressing symptoms, and these symptoms are principally owing to the devia- tion which is produced in the canal of the urethra, which is drawn downwards and for- ward by the fundus of the organ, so as to prevent the passage of the urine along it. In this way a complete retention of urine is pro- duced, together with tension, pain and aug- mentation of volume in the abdomen, agitation, sleeplessness, sympathetic irritation of the heart and the brain. Considerable doubt has usually been ex- pressed, whether hernia of the bladder is sus- ceptible of true strangulation ; whether the sensibility of this organ is of the same na- ture as that of the intestines, and whether its constriction might give rise to similar sym- ptoms. In the case described by Plater,* strangulation does, however, appear to have occurred, but the symptoms which he detailed were not well marked. The symptoms given by J. L. Petit f do not appear sufficient to enable us to distinguish strangulation where the bladder is implicated from that in which the intestine suffers. Hiccup, says Petit, pre- cedes vomiting in hernia of the bladder, while in intestinal hernia the latter precedes the former symptom. If strangulation should occur, the method of relief proposed by Du- rand, viz. to empty the tumour by puncture with a trocar, appears rational. Inflammation. — Inflammation of the blad- der may be produced by a variety of causes- among them we may mention external violence, incised wounds of the organ, contusions on the hypogastric or perineal region, concus- sions of various kinds, the bladder being dis- tended, the compression consequent upon pregnancy, upon a laborious accouchement, upon the use of the forceps, upon the pre- sence of a pessary or a hernial displacement; the presence within the organ of foreign bodies, whether introduced from without, generated within, or derived from the kidneys, distention consequent upon retention, and the use of eantharides and certain other diuretic me- dicines. It may also be communicated to the bladder by neighbouring organs, such as the kidneys, the urethra, the prostate, the uterus, and the rectum. It may be developed during the progress of acute gastro-enteritis, may succeed to certain articular inflammations, to certain cutaneous affections, and to the sup- pression of a hemorrhoidal or menstrual flux. The affection is more common in men than in women, and at the approach of age than at any other period of life. Boisseau describes the disease in a male child of two years old ; Lesaive in a female child of two years and a half. Acute inflammation commonly affects at the same time more than one of the vesical tunics; there are, however, on record two cases in which acute inflammation was limited to * Obs. lib. iii. p. 830. t Traitc des Mai. Cliir. tome ii. p. 368. BLADDER, ABNORMAL ANATOMY. the peritoneal tunic of the organ.* Dr. Bail- lie suggests, as a reason for such limitation to this particular tunic, the quantity of cellular tissue interposed between the serous and mus- cular tunic, and the laxity of their connection the one with the other. Chronic inflammation is frequently confined solely to the mucous tunic of trie organ. Acute cystitis may terminate by complete resolution ; it may cause a secretion of pus, which is either diffused in points over the greater part or even the whole of the surface of the organ, or circumscribed under the form of abscess ; may produce ulceration, may ter- minate in gangrene, or it may assume a chronic form. If death supervene during the intensity of acute inflammation, we find the mucous mem- brane strongly injected, patches being pre- sented of a brownish colour, commonly in the vicinity of the neck and fundus of the organ ; nor does it appear that the occurrence of such patches in these situations can be attributed to the irritation occasioned by the prolonged con- tact of acrid urine. At other times the mucous membrane is thickened, and the veins much dilated ; pus is disseminated over the surface, or collected into foci ; patches of false mem- brane are extended over portions of the organ or floating in the contained fluid, and gan- grenous points are presented ; these points may only affect the mucous tunic, or they may affect the entire thickness; it is sometimes studded with small ulcerations, which are more or less concealed by folds of the membrane, and not unfrequently it is softened. Usually the organ is very much contracted, so much so as to present only a very small cavity. This effect is induced by the contraction of the muscular fibres which is excited by the exten- sion of the irritation from the mucous mem- brane. When the disease terminates by resolution-, ordinarily, in a short time, all trace of the existence of the affection disappears. In cer- tain cases, however, where it has existed long, the parietes of the bladder have been found slightly thickened; one or more branches of veins have become varicose and consequently more apparent. If the disease have had a still longer existence, we may find the mucous membrane thickened ; but this effect is more frequently manifested in the muscular tunic. When a purulent secretion is produced, pus is found diffused through the substance of the parietes, more particularly, however, in the cellular and muscular layers, and an appear- ance of hypertrophy is here produced ; or it is poured out upon the surface of the mucous tunic. Occasionally, but unfrequently, abscesses are formed between the tunics, but these are commonly a consequence of wounds or con- tusions of this organ, or of the operation for stone. In such cases the abscess may open iitself on the external surface of the bladder, or upon the interior. Sometimes it is pre- * See Baillic, Wardrop’s edition, vol. ii. p.259, nnd Nauchc, Maladies des Voies Urinaires, p. 27. 397 sented upon the sides of the rectum, but according to Chopart it is usually in the neighbourhood of the neck of the organ that suppuration commences. When an abscess opens upon the internal surface of the bladder, the pus passes out, mixed with the urine ; in such cases we discover after death more or less extensive and profound fistulous openings, which are sometimes surrounded by varicose veins, sometimes covered by dark grumous blood, extravasated from the small vessels which ramify on them : they all exhale a fetid odour. Ulceration of the bladder as a consequence of acute inflammation is unfrequent ; indeed, of this affection there are only a very small number of cases on record. When it occurs, it is commonly caused by the opening of a purulent collection upon the mucous surface of the organ. A case, detailed by Marechal in the 28th vol. of the Recueil Periodique des Travaux de la Societe de Medecine de Paris, is the best marked case of the affection with which we are acquainted. It was that of a hussar, in whom the affection appeared to be brought about by a violent attack of gonor- rhoea : the patient died on the fifth day. Upon an examination of the organ after death, it was found rather contracted ; though not filled with urine, its parietes sustained themselves ; it contained eight ounces of a greyish thick matter ; the mucous membrane was extremely thick, and covered by a glutinous stratum. It presented, however, many ulcerations of varied extent ; the parietes of the organ w'ere six lines in thickness. Occasionally it happens that inflammation of the mucous membrane of the bladder pro- ceeds to gangrene, which is characterised by a change in the volume of the hypogastric tu- mour, supposing the organ to be distended, the cessation of pain, the sudden prostration of the vital powers, the complete suppression of the flow of urine, the excessive distention of the bladder and the ureters, and sometimes by the escape of urine by the umbilicus more frequently, however, by the rupture of the organ and the extravasation of its contents into the abdominal or pelvic cavity. In cases which are a consequence of retention, the gan- grenous points may be presented either at the fundus or at the summit of the organ ;f but most commonly the affection is a consequence of the irritation or pressure made upon the bladder by a foreign body, and in these the point implicated is that upon which the body lias directly exercised its influence. When we examine the mucous surface of an organ so affected, we discover that the disease exists under two distinct forms, the diffuse and the circumscribed ; but the latter of the two forms is not often witnessed except as a consequence of local violence. Dr. Carswell, however, bears testimony to its occasional existence ; he states that the congestion is extreme, and often ac- companied by hemorrhage, which gives to the * Walther, loc. cit. t Sec Hunter, Hey, and others. BLADDER, ABNORMAL ANATOMY. 398 membrane a uniform deep red colour. More- over, dark brown or black patches are found to occupy portions of various extent of tho mucous membrane, which, as well as the submucous tissue, is easily torn, and other portions of this membrane are seen partially detached, and converted into a soft spongy substance having a strong gangrenous odour. In the circumscribed form of gangrene, we sometimes see a number of black eschars, which are soft and nearly putrid : sometimes greyish pulpy points are presented, which appear to implicate only the mucous tunic, but in the greater number of cases we see the different stages of their progress ; they are at first whitish, they then become yellowish, grey, slate colour or brown, and blackish ; but these changes are much more marked when the organ has been subjected for a short time to the action of the atmosphere. Where the whole of the parietes are involved, the eschar is characterised by a greyish slaty tint. These eschars are frequently confounded with the violet or brown portions or patches by which they are surrounded ; these latter are simply extreme congestion, bordering, it is true, upon gangrene, but susceptible of being restored to a healthy state, whilst the death of the other points is inevitable. When acute inflammation affects the mus- cular tunic of the bladder, the organ usually becomes strongly contracted, and the parietes present an appearance of considerable thicken- ing; at the same time pus is commonly in- filtrated through the tissue, or it is circum- scribed into the form of abscess ; the tunic is then of a dark red colour and strongly in- jected. In a case which was seen by Gendrin, where the patient refused to submit to the operation for stone, the internal tunic was ulcerated and of a red-brown colour ; the mus- cular tunic was more than half an inch in thickness, and contained two abscesses, each of the size of a small nut. Velpeau saw in a patient who had died of a diarrhoea, the blad- der reduced to the size of a small fist ; it was hard and elastic ; its parietes were more than an inch thick. In the cases described by Martin Ripaux, Molat, Maret, and Berard,* the mucous membrane was not in any way implicated, the hypertrophy being entirely limited to the muscular tunic. In these cases the bladder was reduced to very small dimen- sions, and the mucous coat made many pro- jections into the cavity; the summit of these projections was red and vascular. It is not unlikely but that, it may be owing to the excess of extent of the mucous over the contracted muscular tissue in such cases, that the former so easily becomes engaged in the formation of appendices. The muscular tunic may be much increased in thickness in the absence of acute or even chronic inflammation of the organ ; any irritation by which a frequent con- traction of the organ may be excited will most probably produce a great increase of thickness of this tunic. Among these causes we may * Vide Transact, dc la Societe Anatomique. range tho existence of fistula or calculi in the organ. Sometimes the thickening is limited to the mucous tunic. M. Portal, in examining the bladder of an old man, the parietes of the organ being eight or nine lines in thickness, found the internal tunic like cartilage, and that this was the only tunic which had acquired an increase of substance ; the peritoneal tunic was in its natural state, the muscular scarcely apparent. Chopart made a similar remark with regard to the bladder of an adult. Mor- gagni mentions a like case.* Instead of either of the modifications which have been described, acute cystitis may dege- nerate into a chronic form of the disease. This form of the affection does not commonly succeed to a single and simple attack of the acute affection ; almost always there will have been sundry recurrences of the acute form before this degeneration takes place. Most frequently chronic cystitis occurs without hav- ing the acute disease as a precursor, and it is upon chronic inflammation that extensive dis- organisations of the various tissues of the eco- nomy are mainly dependent ; and the altera- tions of texture in the parietes of the bladder ! are, therefore, most commonly produced by its agency. In such cases we may see the mucous mem- brane of an uniformly dark violet colour, thick- ened and unyielding, the organ so contracted as to present only a very small undilatable cavity, incapable of containing more than a jj few drams of fluid. Fungous excrescences are sometimes developed upon its internal surface, especially in the vicinity of the neck. In some cases ulcerations will be found to have destroyed the muscular tunic and pene- trated to the peritoneum ; in others, the mucous follicles present a most exaggerated development, communicating to the membrane a considerable increase of thickness, but with- out change of colour. In other cases, the muscular tunic having acted with increased energy, its fibres have become more volumi- nous and project into the interior of the organ in the form of columns, between which the mucous membrane sometimes forms what is termed ‘ hernia.’ But the more ordinary consequence of chronic inflammation of this |) organ consists in the thickening and more or less uniform induration of the vesical pa- rietes. The tissue of the bladder is then con- verted into a homogeneous, lardaceous sub- 11 stance, similar in appearance to that of the un- impregnated uterus; the vessels which surround 1 the organ are dilated, varicose, and form on the external surface considerable plexuses, jl which attest the long existence of its excitation, and the continuance of the afflux of blood of which it has been the seat. Ulceration as a consequence of chronic in- flammation of the mucous membrane of this * organ is unfrequent, but as an effect of the! presence of a calculus is less so. Of the firsiji species a description, with a fine plate, is given, by Baillie, of a case in which the mucous,! * Ep. 41, art. 6. BLADDER, ABNORMAL ANATOMY. 399 membane covering the posterior and superior surface of the bladder was destroyed ; a simi- lar case is given also, with a plate, by Walter; another is described by Pare.* A case is described by Jalon,j- in which the whole of the muscular tunic was as well displayed as if it had been prepared by dissection. There are several well-marked cases on record in which this species of ulceration, consequent upon chronic inflammation, had extended to the whole of the tunics and caused an extrava- sation of urine. These ulcerations are some- times very numerous, almost like erosions, and they are often concealed between the folds of the relaxed mucous membrane, so that they are not discovered until the membrane is stretched out. Under the influence of either acute or chronic inflammation, pseudo-mem- branes are now and then generated upon the surface of the mucous tunic of the organ, usually during the suppurating period of the affection. These membranes are either ad- herent or free, and they are sometimes ex- pelled through the urethra : this circumstance has induced a belief in an often repeated error, that the mucous tunic of the bladder may be entirely detached and expelled with the urine; among those who have perpetuated this error are Ruysch and Morgagni. J Under the influence of chronic, and much more rarely of subacute inflammation, the mucous membrane of the bladder furnishes in large quantity a species of muco-purulent fluid. This affection was termed by Lieu- taud § catarrh of the bladder. When the affection presents the subacute form, it is fre- quently extended to the other tunics of the organ ; and if we examine it after death, we shall find similar appearances to those which have been described in speaking of acute in- flammation. When the disease is chronic, it often lasts for years, and we then discover little change of colour in the membrane, but we find it often prodigiously thickened, the vessels varicose, and the cavity much con- tracted. Idiopathic softening. — During the progress of some acute and many chronic diseases, the mucous membranes of the body not un- frequently become softened, in the absence of inflammatory action in their tissues : in the bladder, however, this state has been only very rarely witnessed. This fact is important, espe- cially when we reflect upon the functions of the organ and the great variations to which the liquid of which it is the reservoir is exposed. M. Louis, || in a very careful examination of five hundred bodies, found this idiopathic softening in only two cases. In these the mucous membrane in a great portion of the 5 Lib. xvii. ch. 59. t Eph. Nat. Cur. D. 11. an 11. obs. 129. f A case of the kind is detailed by M. Dcstrees in the Journal General de Medecine, tome lxviii. p. 206. § l\led. Prat. tom. i. || Repertoire General, tome iv. part i. Faits relatifs a«x lesions de la membrane muqucusc de la vessie. fundus of the organ was reduced into a “ mucilage ” possessing a consistence little if at all superior to that of mucous pseudo-mem- branes. The membrane thus altered was pale, even at the limits of the softening ; there was no injection or vascular congestion at any point of the bladder, nor in any of the vessels which existed on the exterior of the organ ; neither was there at the interior any erosion or other product of inflammation. It is probable that it is in such cases that even a careful intro- duction of the sound has occasioned a per- foration of the bladder; it may be as well to mention that no true friability of the mucous membrane, so commonly found in inflam- mation, existed in these two cases ; the tunic was soft, as if formed of a viscid jelly, but it did not present either the redness, the infil- tration or the induration by which inflam- mation is characterised. So general is the opinion that softening is uniformly a conse- quence of inflammation, that in taking an opposite opinion it appears to be incum- bent upon us to state our reasons for doing so. Although the differences which may be remarked between softening of this tissue and its inflammatory condition appear to be very great, yet able observers have still be- lieved themselves justified in regarding all softening as the result of inflammation. It is so important to have correct ideas on this point, that we ought here to refute the reason- ing by which that opinion is supported. It is stated that softening of mucous tunics is, in the greater number of cases, united to evi- dently inflammatory alterations ; such as a more or less vivid redness of the softened parts, together with an injection and tume- faction. This assertion is gratuitous; for in all cases where the condition has been well observed, softening in the first degree has scarcely ever been united to unequivocal in- flammatory alterations. In the second degree of softening, the existence of inflammation is frequently demonstrable. It is especially by studying the anatomical characters of the early stage of softening that we shall be enabled to establish the non-existence of inflammation ; we may go farther, and say that the characteristics of sof- tening are directly opposed to those of in- flammation. In the latter we find injection and vascular congestion ; in the former the capillaries have disappeared; — in inflammation, thickening, and at first augmentation of density in the membrane, which becomes rugous to the touch ; in softening we find thinning and diminution in the density of the tunic, with loss of its tenacity, and it is soft to the touch ; — in inflammation we observe specific inflam- matory products at the surface and in the sub- stance of the tissue ; in softening a diminu- tion and absence, then a total extinction of this secretion, which is not only not augmented at the commencement of the disease, as in the first stage of inflammation, but is immediately diminished. Inflamed tissues at a certain epoch do, it is said, become soft and friable ; why should it 400 BLADDER, ABNORMAL ANATOMY. not be so in mucous or villous tissues ? Although this reasoning proves nothing, — for we cannot judge from analogy in a graphic science like pathological anatomy,- — yet it is the simple expression of the truth, because it is certain that mucous tunics are softened by inflammation, but this softening does not re- semble in any thing the idiopathic softening. Rupture. — Rupture of the bladder is a more frequent occurrence than that of the oesophagus, the stomach, or the intestines ; it occurs sometimes without external violence, simply by a distention of the organ, from a prolonged retention of urine ; most commonly, however, it is produced by a violent blow, or the passage of the wheel of a carriage over the hypogastrium, or the violent efforts to which a woman is subject during the pains of labour, the bladder being in a state of plenitude. In the first case, the rupture usually occurs near the insertion of the ureters or the neck of the bladder, because it is at these points that the distended organ usually begins to thin and tear. In the second case it is usually at the inferior fundus of the organ that the rupture is found. We have already pointed out the circum- stances under the influence of which the blad- der may be ruptured, and we have stated that the extravasation of urine by which it is fol- lowed is commonly productive of fatal con- sequences. In a certain but small number of cases, the patient is able to resist the inflammatory symptoms which are developed, urinary ab- scesses are formed, which may open either in the vicinity of the umbilicus, at the hypo- gastrium, in the inguinal region, in the vagina, at the perineum, or in the rectum, and a fistu- lous canal is organised. Fistula. ■ — - Fistulous communications be- tween the bladder and the vagina or in- testines are commonly the result of purely mechanical causes, such as the action of a calculus which may destroy the recto-vesical septum, the action of a foreign body introduced into the anus and penetrating the bladder, the lateralised or recto-vesical operation for stone, the operation of lithotrity, or as a con- sequence of the pressure produced by the head of the child in parturition. Vesico-in- testinal fistulas sometimes establish a com- munication between the bladder and the ileum or colon,* and then the summit of the bladder is usually the seat of injury. When the com- munication is established between the bladder and the rectum, the posterior surface of the bladder is commonly implicated; the neck of the bladder may, however, be similarly affected, and then it is commonly owing to the action of a calculus or other foreign body directed upon this portion of the vesical parietes. At other times the lesion succeeds to chronic in- flammation, or to a cancerous ulcer which has extended from the rectum to the bladder ; and then the perforation almost always exists near the neck of the latter. The communication of * London Med. Journal for 1784, part 2 ; Edin- burgh Medical Commentaries, vol. ii. part 2. the intestine with die bladder is sometimes established without abscess, without external inflammation. Sometimes the urine does not escape by the rectum, while lineal matter and flatus pass from the rectum into the bladder. Ordinarily, however, the urine passes into the rectum and often causes diarrhoea; the bladder, distended by intestinal gas, forms a sonorous and painful tumour at the hypo- gastrium. Vesico-vaginal fistulce are sometimes though rarely occasioned by the action of a foreign body introduced into the vagina ; sometimes they are the result of the progress of a uterine cancer ; but in general the cause by which they are produced is a laborious accouchement, during which the head of the infant has re- mained long in the passage, and has by its pressure determined gangrene of the vesico- vaginal septum. The accident may be pro- duced by the imprudent use of instruments; but this is a rare occurrence, perhaps for the reason that instruments are comparatively un- frequently employed. In a few days the eschars which are the result of that gangrene are thrown off, and the consequent loss of sub- stance may then be demonstrated. We find that these fistulae have not always the same form, the same direction, nor the same extent. In some cases they are longitudinal, at other times transverse; in others their form is irre- gular. The extent of the loss of substance is also very variable: sometimes the fundus of the bladder is extensively destroyed, so much so as to allow of the opposite parietes of the organ being implicated in the opening, and forming a true vesico-vaginal hernia. When the disease is a vesico-umbilical fistula, the com- munication is with the summit of the bladder, and is commonly caused by a dilatation of the urachus or by the prolongation of the mucous membrane of the bladder, which is directed along the cord produced by the conversion of the urachus and the vessels by which it is accompanied into a cellular structure.* In either case the disease is almost invariably a consequence of the existence of some oh- i| stacle to the passage of urine along the urethra. The pubic and inguinal fistulae succeed to an accidental opening of the bladder, which, : having formed a tumour in those regions, has been taken for an abscess, a hernia, or an encysted tumour; to wounds, to ruptures, f puncture, or incision of the organ ; to its per- foration in consequence of a purulent focus being in contact with its parietes, or by a suppu- ration in these parietes themselves. All fistula: of the bladder have this in common, that the urine escapes from their orifice drop by drop, almost continually, often without contraction : of the bladder, and without the patient having wished to urine ; sometimes it escapes in greater quantity during those motions of the i body which excite the pressure of the abdo- minal muscles. In consequence of the habit which the bladder has acquired of remaining * See Yan-der-Wicl, Liltre, Tenon, and Roux. BLADDER, ABNORMAL ANATOMY. empty, it almost always becomes contracted ; in all cases its capacity is considerably di- minished. Hemorrhage from the bladder. — Instead of the mucus which is furnished by the mucous membrane of the bladder when in the state of health, it may be the seat of a sanguineous exhalation. When a sanguineous fluid is excreted from the bladder, it does not of neces- sity follow that it has proceeded from the mucous membrane of that organ ; it may be brought by the ureters from the kidneys. When the fluid is produced within the vesical cavity, the mode of production is not uniform : it may be a simple exhalation from the mu- cous membrane, or it may be a consequence of the destruction of the mucous membrane by gravel, by a calculus, or by a foreign body introduced from without ; or it may be a con- sequence of the rupture of varicosed vessels. Blood is, however, rarely exhaled at the in- ternal surface of the bladder, unless the mu- cous membrane be in a state of structural disease : yet this exhalation is occasionally manifested as a result of intemperance, or the use of certain irritating diuretic medicines, concussions of the pelvis ; in woman the sud- den suppression of the menstrual evacuations, and in man of a hemorrhoidal discharge. It is very difficult, and sometimes even al- most impossible to determine whether the fluid be derived from the kidney or from the bladder; and to arrive at any thing like a sound opinion, it is necessary to consider carefully all the circumstances of the case. Much as it has been relied on, we cannot consider as a sym- ptom peculiar to vesical haemorrhage, the mix- ture of blood with the urine, and the sensation of burning and weight behind the pubis, at the perineum, and at the extremity of the penis ; for these symptoms occur in some cases where there is no effusion of blood, and in others where the blood has arrived from the kidneys. It is also very difficult to decide as to what is the exact state of the bladder, even when we are convinced that the blood discharged from the urethra is derived from that organ, Chopart found the vesical mucous membrane, more particularly at the fundus, studded with red points in an old man subject to haematuria; these points appeared to him to be vascular orifices.’6 In other persons who have suffered from a similar affection, different kinds of fungus have been discovered on this mem- brane. A man, aged seventy-three, had hrema- uria, but there was no stone in the bladder, ^■s there was no appearance of disease about he kidneys, it was attributed to the rupture of ome varicose vessels in the neighbourhood >f the neck of the organ. After death the •ladder was found of great size, and within the ngone was a fungous rounded ulceration, six ines in diameter, surrounded with varicose eins and small fungous excrescences. Ordi- arily, however, gravel or calculi appear to be ie exciting causes of this disease. * Loc. cit. tome ii. p. 52. VOL. i. 401 Fungous tumours. — The information which we possess on the subject of fungous tumours or excrescences of the bladder is not sufficiently precise to enable us to attempt to arrange them according to their variety in structure or development. The tumours which we pro- pose to describe are those which do not im- plicate the whole of the parietes of the organ, but project into its cavity under the form of more or less perfectly pediculated excrescences. We are, therefore, under the necessity of con- sidering simultaneously all those tumours, however variable in structure, which come under the definition which we have given. Many eminent pathologists have expressed an opinion that these tumours are always directly connected with the prostate ; but their occa- sional existence in the female sufficiently proves that this opinion is incorrect. In 1750 Mr. Warner removed from the bladder of a woman a fungous tumour of the shape and size of a turkey’s egg. Walter* details the case of a young woman in whose bladder he discovered what he calls a polypus, which ex- tended itself nearly to the external orifice of the urethra. It is true that these morbid products are more commonly seen at the fundus of the blad- der than at any other point of its surface, and it is equally true that a large number of those affections which are described as fungous tu- mours of the bladder, were really morbid products arising from the prostate, which will be described in the article on the Prostate Gland. The circumstances necessary for the develop- ment of these tumours are unknown, but it would appear that the larger number occur under the influence of irritation produced by calculus. Ordinarily only one of these tumours is found, and then occasionally it attains a considerable volume. Fabricius Hildanusf describes one of the size of a hen’s egg, and weighing two ounces. Zacutus LusitanusJ found one of these polypi of the size of a goose’s egg, and so hard that he could not cut it with scissars. There are, however, many examples in which a greater number existed, but in these cases the tumours are usually small. Chopart§ de- scribes a case which he examined at the Hotel Dieu, in which there were found three tumours, the largest being nearly as large as a cherry. Ludwig describes a case in which he found two of small size in the bladder of a man of sixty-three. Desault once saw the whole of the cavity of the bladder studded with small “ fungous tubercles.” Lobstein || has seen three, and Bartholin^]- two. This affection is rarely seen before adult age. Morgagni** has never seen them in infants or in young persons. * Einige Krankhciten d. Nieren und Harnblase, 4to. Berlin, 1800, tab. iii. t Cent. ii. obs. 65. j Prax. Med. Ader. lib. ii. obs. 71. § Loc. cit. tome ii. p. 77. |1 Diss. de Dysuria. 51 Anat. cent. ii. Hist. 52. p. 243. ** De Sed. ep. lxvi. art. 12. 2 D 402 BLADDER, ABNORMAL ANATOMY. Deschamps, in 1791, whilst removing a cal- culus from the bladder of a boy of twelve years, discovered on the anterior and lateral parieles of this organ, a small fungous tumour of the size of a cherry, which projected to the distance of half an inch from the surface. Baiilie, in his Morbid Anatomy, has given a plate of a polypus of the bladder which he found in a child, and which not only occupied the whole of the cavity of the organ, but sent prolongations into the urethra. The structure of these tumours is very va- rious ; the greater number appear to possess a fibrous structure, others present a white homo- geneous, lardaceous texture at their base, whilst their free surface may be red, vascular, or even carcinomatous; sometimes they are hard and almost cartilaginous in their whole thickness ; at others they present calcareous concretions. Around the points from which these tumours arise the bladder is ordinarily thickened and indurated : this is, we apprehend, a consequence of the continued irritation which has attended their development. Varices. — The arteries and veins of the bladder present numerous ramifications in the cellular stratum, which separates the muscular from the mucous tunic of this organ ; and in the neighbourhood of its neck they form an immediately apparent plexus. This vascular structure in inflammation be- comes so marked that the mucous membrane appears to be entirely formed of these vessels. Though it might be expected that during the existence of inflammation these vessels would become more dilated and manifest, yet it cannot be regarded as a true varicose condi- tion, there being neither partial dilatations nor projecting indurations like those which characterize varices situated in other parts of the body. Bonnet describes the case of a man, who during life had suffered from the ordinary symptoms of stone, but in whose bladder no stone was discovered after death. The veins around the neck of the bladder were varicose and very much distended with blood.* Morgagni discovered in the body of a man aged sixty, in which the tunics of the bladder were very thick, large vessels creeping along its internal surface around its neck. They were so distended with blood, that at first he almost believed they were haemorrhoids rather than parallel vessels.f A similar case is described by Chopart, in a calculous patient. There cannot, therefore, be any doubt that such a disease may exist. It appears to occur principally when the parietes of the bladder are thickened, when it contains calculi or fungi, or when its neck or the prostate are tumefied. It is not unfrequent in old men and in inhabitants of warm countries. The disease has much analogy with haemorrhoids, and appears to increase under similar sources of irritation. It may contract the neck of the bladder and so cause * Sepul. lib. iii. sect. 25, p. 263. t lie Sed. ep. 63 ait. 13. retention. These veins may become inflamed and produce divers alterations in the mucous tissue. This membrane may be thinned, take a fungous appearance, give rise to hsemor- rhage, in fact assume somewhat of an erectile character. Scirrhus and Cancer. — Cancer primitively affecting the membranes of the bladder is ail extremely rare disease. Chopart relates only one example of the kind.* Desault describes another ;f Lallemand another, j Soemmering appears to doubt whether the disease ever exists.§ In each case to which I have alluded the disease occurred in man, and I know of no case on record in which the disease has primarily existed in the bladder in woman. In the whole of the cases the disease was characterized by lancinating pains behind the pubis, and by the emission of particles of de- composed animal matter ; these were the only symptoms which were calculated to excite suspicion as to the nature of the disease. In every one of them the scirrhus was situated in the fundus of the bladder and near its neck. The whole of the membranes at that point were transformed into a scirrhous lardaceous j substance, varying in thickness from two to four inches, and in two cases the tumours were somewhat funnel-shaped, the internal surface of which was unequal, bristling with very projecting vegetations of a cauliflower cha- racter. Most commonly the affection is the result of the extension of a similar disease from the uterus or the rectum, and the symp- toms by which the affection might be announced , are confounded with those of the affection of the uterus or of the rectum. This affection may exist with dilatation or contraction of the cavity of the organ, with or without ulceration with or without hypertrophy of the muscular tunic. When derived from the uterus, the affection is manifested at the fundus of the organ, and a communication is usually soon brought about between it and the vagina, and as a consequence the urine flows involuntarily from the vulva. When derived from the rec- tum, the fundus is commonly affected ; and in either case these productions are manifested within the vesical cavity under the form of fungous vegetations. Paralysis. — The bladder is not an excep tion to the rule, that “ all parts of the body may become unfit for the functions which they are destined to perform it may lose the fa- culty of contractility, which is indispensable tf the accomplishment of excretion. Under many circumstances it may contract with too muc! force; in a still greater number its contracti lity is enfeebled and ultimately destroyed Apoplexy, hemiplegia, paraplegia, concussion! * Traite des Maladies des voies urinaires, tome p. 466. Edit, de 1821. t Traite des Maladies des voies urinaires, 3d edi p. 177. | Obs. sur les maladies des organes gemt< urinaires, p. 8. § Traite des Mai. de la vcssie et de l’uretre, tra< de H. Hollard, 1824. 403 BLADDER, ABNORMAL ANATOM Y. and inflammation of the brain and its meninges, extravasations within the cranium, and still more concussion and inflammation of the spinal marrow and its membranes, and extravasations within the spinal canal, consequences of con- tusions of this part; the excessive distention of the bladder by the accumulation of urine within its cavity, either in consequence of neglecting to attend to the desire of excretion, or because the want has been resisted by false delicacy, or because an obstacle exists at the neck of the bladder or in the urethra ; inflam- mation of the mucous membrane, especially when it affects the neighbourhood of the neck of the organ ; the sudden cessation of articular pains, inflammations of the skin or of the genital organs ; exasperated gastro-enteritic af- fections which are accompanied by affections of the brain and the spinal marrow ; abuse of the sexual organs ; — these are among the cir- cumstances under the influence of which the bladder loses partially or completely its con- tractility. We must not therefore regard all cases of paralysis of the bladder as evidence of feeble- ness, nor confound the inability to contract, with those mechanical obstacles which, acting on the bladder or the urethra, oppose the ex- cretion of urine. We should always endeavour to ascertain whether there be a real paralysis of the bladder in cases where the brain or the spinal marrow is injured, and where there is detected abuse of the sexual organs. When retention is primitively the effect of inattention to the desire to pass urine, there is only exces- sive distention of the muscular fibres, but that distention is formidable in its effects ; for no fact is better established than this, that when we submit muscular fibre to excessive distention or contusion, it loses the faculty of contracting. Again, in cases of inflammation of the bladder, there is less of paralysis than a suspension of contraction in the muscular tunic, in conse- quence of the proximity of the mucous tunic, which by reason of its inflammatory state be- comes still more painful when its tissue is ruffled by contraction. There may, however, be atony or even a real paralysis of the mus- cular tunic during the existence of inflammation of the mucous tissue. It is important to distinguish the case where paralysis is simple from those in which it is complicated by inflammation of the mucous membrane of the bladder or that of any other organ, and for that purpose it is necessary to analyse with care the symptoms. We must also bear in mind that from simple, complete, and primitive paralysis of the muscular tunic to inflammation of its mucous tunic, the inter- val is only very short, in consequence of the irritating impression which is exercised by the accumulated urine which has become much deteriorated in its qualities by its prolonged retention. From the time when paralysis is fairly established, the bladder is quite insensi- ble to the stimulus of the urine — it is merely an inorganic sac, which may become enor- mously distended. Ilaller found in a drunkard the bladder so dilated that it was capable of containing twenty pounds of water.* Frankf saw a similar bladder which simulated ascites; he evacuated from it at onetime twelve pounds of urine without removing all that it contained. William Hunter, in his Anatomy of the Gravid Uterus, plate 26, has given a fine repre- sentation of a bladder which extended as far as the xiphoid cartilage of the sternum. This affection may, according to Baillie,J exist during two distinct states, one when the muscular tunic of the bladder has lost its contractile power, the other while that power is still retained. He adds, that after death these two cases cannot be distinguished the one from the other, but that by an attentive examination of the symptoms the existence of each may be recognised during life. It may be complicated with inflammation of the organ, and in this case rupture of the bladder may occur, § to which may be added the case of the celebrated Tycho Brahe. || ZuberIT dis- tinguishes this affection into that of the neck and that of the body, and this distinction is important, for the second being sometimes accompanied by a species of spasm or want of consent in the neck, a retention of urine must be the result, whilst the former occasions incontinence of that fluid. Spasm. — Spasm of the bladder is an affec- tion of frequent occurrence ; it accompanies the various forms of cystitis, calculus, and often in- flammation of the urethra. In fact it may be ex- cited by any kind of irritation of the bladder or urethra, or by certain affections of the kidneys and of the rectum. It is not our purpose to con- sider in this place any other than what may be termed the idiopathic species of this affection. Hoffmann describes the case of a man who sank under the numerous and violent attacks of this disease, and in whom, after death, except in one particular, the bladder was found perfectly healthy ; this was in the thickening and dilatation of its vessels, in which there was still much blood. Of course, although no anatomical lesion was found in this case, some irritation capable of exciting the spasm must have existed. BIBLIOGRAPHY. — Rutty, A treatise on the urinary passages, &c. 4to. Lond. 1726. Zuber, Diss. de vesicas urinariae morbis, 4to. Argent. 1771. Adams on stone and gravel, diseases of the bladder, &c. 8vo. Lond. 1772. Lentin, Krankheiten der Harn- blase der Alten, in Ej. Beytrage iii. Bd. 1780. Troja, Mali della vesica orinaria, 2 vol. 8vo. Nap. 1785-88. Frank, J. P. Orat. de vesica urinaria ex vicinia morbosa aegrotante, 8vo. Ticin. 1786, in Ej. opusc. No. 4. Malacarne, Osserv. anat. e pathol. sugli organi uropoetici, in Mem. della Soc. Ita'. vol. iii. et vol. v. 1780. Chopart, Des ma- * Elementa Physiologic, art. Vesica, f Oratio de signis morborum ex corporis situ, partiumque positione patendis, Ticini, 1788. J Path. Anat. chap, xiii, § See cases related by Ploucquet, Bibl. Med. Pract. || Petri Gassendi Tychonis Biahei vita, Paris, 1654, in 4to. p. 206. Diss. de Morbis vesicae. 2 D 2 404 BLOOD. ladies des voies urinaires, 8vo. Paris, 1791. Mac- beath on affections of the urinary organs among ne- groes. in Edinb. Med. Comment. Dec. 2, vol.x.1798. Desault, Des maladies des voies urinaires (a, Bichat Ed.) 8vo. Paris, 1799. Sherwen on diseased and contracted urinary bladder, 8vo. Lond.1799. Walter, Einige Krankheiten der Niercn und Harnblase un- tersucht, 4to. Berl. 1800. Bell , Engravings of morbid parts, fol. Lond. 1803. Schmidt , Ueber derj. Krank. der Harnblase, & c. 8vo. Wien. 1806. Soem- mering, Ueber todtlichen Krankheiten der Harn- blase, 4to. Frft. a M. 1809. Nauche, Des mal. de la vessie, &c. 8vo. Paris, 1810. Wadd, Cases of diseased bladder, Lond. 1815. Howship on the diseases of the urinary organs, 8vo. Lond. 1816. Coquin da Martel , Vice de conformation des voies urinaires, &c., in Bullet, de la Soc. Med. d’Emulat. Jnin 1824. Lallemand, Sur les malad. des organes genito-urinaires, 8vo. Paris, 1824. Brodie, Lectures on the diseases of the urinary organs, &c. 8vo. Lond. 1834. * * * * De- t hording , De haemorrhoid, vesicae, Rost. 1754 (Rec. in Haller Disp. Pathol, t. vii.). Ludwig, De ischuria ex tumoribus vcsicae, 4to. Lips. 1767, in Ej. Advers. Med. vol. ii. * * * * Salzmann, De hernia vesicae urinariae. Argent. 1732 (Rec. in Haller Disp. Chir. t. iii.) Camper , De vesicae herniis, in Ej. Demonst. Anat. Pathol, lib. ii. Sandifort, De hernia vesicae, in Ej. Obs. Anat. Pathol, lib. i. Roose, De nativo vesicae urin. inversae prolapsu, 4to. Gotting. 1793. Baillie, Remarkable deviation from the natural structure in the urinary bladder, &c.. Transactions of a Society for the Improvement of Medical and Chi- rurgical Knowledge, vol. i. Goeckel , De vesica spongiosa extra abdomen posita, Miscel. Acad. Nat. Curios. Dec. 2, A. 5. Raijfer, Diss. sur la cysto- cele ou hernie de la vessie urinaire, 4to. Paris, 1805. Beugin , Diss. sur la cystocele, 4to. Paris. 1805. Isenflamm , Beschreibung, &c. angebornen, vorgefallenen, ungestiilpten Harnblase, &c. 8vo. Dorpat. 1806. Fuchs, Hist. anat. prolapsus nativi vesicae urinariae inversae, 4to. Jenae, 1813. * * * * Cases of double bladder, by Bordenave, in Mem. de Chirurg. t. ii. ; by Lebenwaldt , in Miscell. Acad. Nat. Curios. Dec. 2, A. 8, 1689; by Tenon , in Mem. de Paris, A. 1768 ; by Bussiere , in Phil, Trans. 1701. * * * * Cases of absence of the bladder, by Preuss, in Miscel. Ac. Nat. Cur. Dec. 2, An. 7 ; by Rengger , in Museum der Heilkunde, B. 2 ; by Labourdette, in Sedillot’s Rec. Period, t. xxxii. Cases of rupture of the bladder, by J. Johnstone , in Mem. of the Med. Soc. of London, vol. iii. ; by Kundmann, in Acta Acad. Nat. Curios, vol. vii. ; by Montagu, in Med. Communications, vol. ii. ; by Zuinger , in Ephem. Nat. Curios. Cent. 7 et 8 ; by Berchelmann , in Acta Hassica, A. 1771 ; by Berner, in Ephem. Nat. Curios. Cent. 9 et 10; by Schlich- tung , in Acta Ac. Nat. Curios, vol. vi. ; by Hey, in Med. Obs. by a Soc. of Phys. vol. iv. ; by Lynn, in the same work, vol. iv. ; by Sedillot , in Rec. Period, t. i. ; and by Cusack, in Dub. Hosp. Rep. vol. ii. ( Benjamin Phillips.) BLOOD, (Gr. Lat .sanguis. Fr .sang. Germ. Blut. Ital. sangue ). This is the title given to the peculiar fluid which carries into the living tissues of animals the materials necessary to the nutritive processes going on within them. The physical qualities of this fluid vary extremely ; among almost all the lower animals it is so far from resembling what we are accus- tomed to regard as essential to the blood in man and the vertebrata generally, that its nature is at first sight apt to be mistaken, and we cannot be surprised that the inferior tribes of creation should have been long supposed to be without blood. In the mammalia, birds, reptiles, fishes, and several of the annelida, the blood is of a red colour ; among the whole of the invertebrata, a few of the annelida excepted, it is, on the contrary, nearly colourless ; fre- quently it has a decidedly blue tint, and in many instances it is bluish, greenish, or yel- lowish. A celebrated chemist (Berzelius) has lately slated that the common fly (one of the insecta) had red blood in the head, and colour- less blood in the other parts of its body. It is true, indeed, that if the head of one of these insects be crushed, a reddish fluid is forced out ; but this is not blood ; it proceeds from the eyes of the insect, whose blood, in the head as elsewhere, and among all the other species of the genus, as well as among the arach- nida, Crustacea, and mollusca, is almost co- lourless. From these differences in the appearance of the nutrient fluid, the animal kingdom has been divided into animals having red blood and animals having white blood. But these modifications of colour are not perhaps of so much consequence as has commonly been be- lieved, for they are met with among animals having in all other respects the most striking analogy one with another, as has already been seen in our particular article on the Anne- lida. The blood is an opaque, thickish fluid, of a specific gravity greater than that of water. In man its density varies from 1,052 to 1,057. It has a saline and rather sickly taste, and it diffuses a peculiar odour, which varies somewhat in different tribes, and occasionally in the different sexes of the same species. In all the vertebrata, it is, as we have said, red ; but the shade of this colour varies in different animals, as it is familiarly known to do in the same animal, according as it is ex- amined in its course to the tissues which it is destined to supply with nourishment, or after it has already traversed these, and is returning to the centre of the circulation ; the colour, how- ever, may be stated to be generally deep. Examined by the naked eye, the blood ap- pears to be perfectly fluid and homogeneous; but if it be spread in a very thin stratum upon the object plate of a microscope, and viewed under a lens having a magnifying power cf between 200 and 300, it will be seen to con- sist of two distinct and heterogeneous parts, viz. a transparent yellowish watery fluid, and a number of solid corpuscles, of extreme mi- nuteness, suspended in this fluid. To the fluid portion, the name serum is given ; the minute corpuscles are spoken of as the globules of the blood. The discovery of the globules of the blood is almost contemporaneous with that of the microscope ; it is due to Malpighi and to Leuwenhoeck. A considerable number of ob- servers have since engaged in the micro- scopical study of the blood ; but it is to Hew- son and to the Messrs. Prevost and Dumas that science is indebted for the most important facts BLOOD. 405 and the best connected series of inquiries into the composition and qualities of this fluid.* The form of the globules of the blood varies in different animals, but appears to be at all times essentially the same in individuals of the same species; this at least is the case if we except the first periods of their embryotic existence ; for in the embryo the globules have been found to be different before the formation of the liver, from what they are after thp deve- lopment of this organ. The globules of the blood of all the mam- malia that have been examined are of a circu- lar shape, whilst in birds, reptiles, and fishes, they are elliptical; in the invertebrate animals, however, they are again circular. The whole of the microscopical observers of modem times are agreed in the above points; but they differ in opinion with regard to the nature of these bodies. This discrepancy, however, does not appear to us to be owing so much to any optical illusion to which the microscope exposes those who use it, as to the choice of objects made by the different observers. Too many of them have been satisfied with the study of the human blood, the globules of which are extremely small and always seen with great difficulty, whilst, had they made use of the blood of certain animals, as of the frog, or, bet- ter still, of the water-newt ( Salamandra cris- tata), they would have escaped much of the uncertainty that surrounds their conclusions. The globules of all animals having red blood are more or less flattened, and in the greater number of cases they resemble a small circular or elliptical disc. Leuwenhoeck was aware of this fact in reference to birds, reptiles, and fishes, but he believed that in the human sub- ject and the other mammalia these bodies were spherical. f This error, which was sanctioned by Fontana and various others of the older observers, and has even very recently been adopted by Sir E. Home and M. Bauer, J was, however, completely refuted by Hewson, Prevost and Dumas, Hodgkin and Lister, Muller, &c.; my own observations also con- firm the conclusions of these physiologists, and even go to prove that the globules of the blood in the invertebrata have the general form of flattened vesicles. The greater number of observers appear to think that the whole of the globules of the blood of any animal are of the same dimen- sions. When blood in which these globules are very minute is examined, and a low mag- nifying power is employed, it is quite true that no perceptible difference in point of size can be detected ; but by estimating the mag- nitudes of a great number of these globules com- paratively and under a powerful microscope, r have satisfied myself that they differed in size * Vide Hewson on the Blood, and Prevost and Pumas, Examen du Sang et de son action dans les diverses phenomenes de la Vie, in Biblioth. onivers. de Geneve, t, xvii. t Philos. Trans. No. 165, 1684, p. 788. t Ibid. 1818. in the same individual. Among the lower animals, the river-crab ( astacus jluviatilk) for instance, it is by no means difficult in the same drop of blood to perceive globules of very dif- ferent dimensions ; and although this inequality is much less remarkable among the higher ani- mals, I may affirm that it exists. Thus, in the same drop of a frog’s blood, I have seen globules that differed from one another in the proportion of 39 to 45, without my being able to ascribe these variations of diameter to any circumstance connected with my mode of observing, or to any optical illusion : the globules were spread in a single layer upon the object plate, and so close together as to be exactly within the focus of the instrument. Their apparent diameters, I may state, were estimated by tracing, with the assistance of the camera lucida, the out- lines of their images, upon a board eight inches distant from the eye-piece. I found corresponding differences of dimension among the globules of the human blood ; in the same drop 1 have measured several which were to each other in the ratio of 112 to 140 : in ge- neral, however, the differences are scarcely appreciable. The globules of the blood appear to be identical in every part of the circulating sys- tem, and hitherto no difference in their size or shape has been detected in individuals of the same species, though of different ages and sexes. It was long found a matter of considerable difficulty to determine the precise diameter of the globules of the blood ; we consequently find marked discrepancies in the conclusions come to by different microscopists. At the present day, however, and since our means of observation have been improved, the estimates have become gradually less and less discordant, and therefore may be held worthy of the greater confidence. From a very great number of measurements taken by means of the process of M. Amici (with the camera lucida), and under a mag- nifying power of 900, I have obtained as the mean term of the diameter of the globules of the human blood gL of a line (English,) or in decimal fractions 0,00030 of a line. But as I have already said, I have found considerable variety in the sizes of the globules; some, and these were the largest, were 35 ten thou- sandth parts of a line, and others, the smallest, no more than 28 ten thousandths of a line in diameter. These estimates accord very nearly with the last admeasurements published by M. Dumas, and taken by a different method. He gives 31 ten thousandths of a line as the mean dia- meter of a globule of the human blood accord- ing to his latest observations.* The conclusions come to by Dr. Hodgkin and Mr. Lister are also very nearly the same, these observers estimating the diameter of the * Annales des Sciences Naturelles, tom. xii. p. 59. 406 BLOOD. globule of the human blood at 33 ten thou- sandths of a line. These dimensions exceed, it is true, the mean of the measurements I have taken, but they are still within the limits of the individual variations which I have en- countered among these corpuscles ; and as the physiologists quoted do not say whether their estimate was made from the mean of a number of observations, or from the measure- ment of only a few globules more apparent than the rest, it is impossible for me to deter- mine whence this discrepancy in our conclu- sions (arises, whether from actual varieties, from the manner of proceeding in determining the magnifying power of the microscope, or from an error in taking the limits of the image projected by the camera lucida.* The observations made some twelve years ago by Messrs. Prevost and Dumas do not differ from the measurements already given. The diameters they then assigned to the glo- bules of the blood, amounted to 33 ten thou- sandths of a line (yjf, of a millimetre) ; but the magnifying powers they at that time employed did not exceed 300, and consequently the difference between the diameter of a globule 315TC5i5iJotlls of a line and one 367^^1118 of a line might fail to be detected ; further, the errors which arise from the determination, always somewhat arbitrary, of the limits of the image, are sufficient to explain such slight differences as occur in the results of these very delicate observations. We must also add that Messrs. Prevost and Dumas at this time made use of a method, much less accurate than the camera lucida, for taking the apparent diameters of objects under the microscope, causing the image seen in the instrument with the right eye to coincide with the divisions of a scale placed laterally under the left eye. We therefore believe our- selves justified in the preference we accord to the more recent observations of these gentle- men. The late Captain Kater, at the request of Sir E. Home, also made some observations with a view to determine the diameter of the globules of human blood, taking his measure- ments in the manner formerly employed by Messrs. Prevost and Dumas, but making use of a power not higher than 200, by which the chances of erroneous conclusions were greatly increased. His first observation, nevertheless, comes extremely near what we are inclined to regard as the truth (22TBL33ths of a line); a se- cond observation, however, gives a much smaller diameter (1 Sixths of a line), but it is possible that in this case the observer may have taken his measurements from a globule divested of its colouring matter, or perhaps from one of the albuminous globules which abound in the Vide, Some microscopical Observations on the Blood, &c. in Philos. Mag. Aug. 1827. serum, and which are in fact very nearly of the dimensions indicated.* Mr. Bauer and Sir E. Home had pre- viously assigned S&jjVjjths of a line as the di- ameter of these globules ; but their obser- vations having been made with the ordinary micrometer are necessarily defective, inasmuch as the globules placed upon this instrument, and the divisions drawn on its surface, can never be simultaneously in the focus of the object glass.f Dr. Wollaston held that the globules of the human blood did not exceed 20-1jAJosths of a line in diameter, which is considerably different from our mean ; and Dr. Young did not esti- mate them at more than 16 loibdh8 of a line.f It is also possible that both of these eminent individuals have measured the central nuclei of globules divested of their vesicular envelope. The results just specified having, farther, been come to by the aid of the eriometer, an in- strument which we have searched for in vain through all the instrument-makers and col- lections of philosophical apparatus in Paris, and as we are altogether ignorant of the degree in which its indications may be relied on, we cannot discuss these conclusions with an adequate knowledge of the elements from which they are derived. As to the measure- ments published long ago by Jurine, they are so discordant that no confidence can be placed in them ; the first diameter he assigned to the globules of the blood was 1 Qj^ths, the se- cond 5 ljjjjjjjgths of a line. From all that has gone before, then, and particularly from those researches which have been conducted urrder circumstances tire most favourable to accurate conclusions, we may assume the mean diameter of the globules of the human blood to be about the 31-njjfifi;ths, or in vulgar fractions the 5TKth part of a line. Messrs. Prevost and Dumas have given the dimensions of the globules of the blood of a great number of other vertebrate animals; in these observations they employed the same means of estimating the diameters as in their earliest researches on the size of the globules of the human blood, so that to me their valu- ations appear to fall somewhat short of the truth. This slight presumed inaccuracy, how- ever, scarcely detracts from the interest of the general results ; for the measurements being all taken by the same means and therefore comparable one with another-, are adequate to show in the clearest light the differences that occur in the dimensions of these corpuscles in different animals. The following is the table of admeasurements given by the physiologists quoted. * Vide Additions Philos. Trans. 1818. t Loc. cit. 1 Young, Elem. Load. 1818. to the Croonian Lecture, I of Med. Literature, 3vo. BLOOD. 407 NAMES OF THE ANIMALS. MAMMALIA. Man Canis familiar is } L. : Sus scrofa, L Mus ponellus, L. Mus avellanus, L Lepus cuniculus, L. . . . Erinaceus Europeus, L. . . Simla Sabica, L Eguus asinus, L Velis catus, L Mus masculus . . . . Equus caballus, L. ... Equus hybrid as, L. . . . Bos taurus, L Ovis aries, L Antelope rupicapra , L. . . Capra hircus, L Cervus elapkus, L. . . . AVES. Strix flammea , L. Columba domestica, L. Didus ineptus, L. Anas boschas, L. . . Phasianus gallus, L. . Pavo cristatus, L. . . Anas anser, L. . . . Corvus corax , L. . . Fringilla carduelis, L. Fringilla domestica Purus major , L. . REPTILIA. Testudo terrestris, L. . Colubra berus, L Angitis fragilis, L. . . Coluber Razomouskii . Lacerta grisea, L. . . Salamandra cincta, L. Salamandra cristata, L. Rana bufo, L Rana esculenta, L... Rana temporaria, L. . . PISCES. Gadus lota, L. . . . Cyprinus phoscinus, L. . Cobitis barbatula, L. Murcena anguilla, L. X X X Diameter of the globules in vulgar fractions of an English line. Diameter of the globules in decimal fractions of an English line. 550 0,000231 1 353 0,000328 nh 0,000335 1 133 0,000220 si 5 0,000196 333 0,000181 0,000104 Great diam. Small diam. Great diam. Small diam. 195 l 135 0,000526 0,000231 l 500 id. 0,000500 id. 1 id. 0,000488 id. l 513 id. 0,000463 id. l 5T5 id. 0,000458 id. l 53? id. 0,000316 id. l T35 1 153 0,000757 0,000512 l 135 l 531 0,000657 0,000316 l Tg 7 1 555 0,000598 0,000342 l 135 1 531 0,000658 0,000316 137 555 0,000598 0,000354 1 55 115 0,001132 0,000704 1 in l 155 0,000877 0,000526 i 155 0,000526 0,000319 From my own observations I am inclined ■•o tbmk that the globules of the blood of the rog have a mean long diameter of about ^ToMuthsofaline; but the individual differences observable among the several globules ranged oetween 87TBLn5 and lOO^J^ths of a line. In the olood of the water-newt ( Salamandra cristata) have obtained in my measurements of the mg diameters of the globules the following ex- treme individual varieties: minimum lOdjj^ths of aline, maximum 1 27-io^jjjjtlis. The outline of the globules in all the verte- brate animals is extremely well defined ; but they are readily deformed or put out of shape. Even during life their pressure mutually, or the pressure they experience between the cur- rents in which they move and the parietes of the vessels against which they are driven, suf- 408 BLOOD. fices to alter their form ; they are then fre- quently seen to become elongated, to bend, in a word, to alter their figure considerably ; but they are extremely elastic, and readily and soon resume their pristine state. Among the invertebrate animals the globules of the blood are much less regular in their forms. Their surface is uneven and tubercu- lated, like that of a raspberry ; their contour is extremely variable; they change their figure with the greatest facility, and their size is considerable. In the blood of the river crab for example ( astacus jiuviatilis ) I have found their mean diameter to be 70-rj^jgths of a line. Several, however, were measured which were no more than 67-[ggj0ths of a line across, and others which were as much as 72Tugggths. In the oyster I have detected still wider differences in the size of the globules of the blood. In the same drop of this creature’s blood I found some globules 601g^5Bths, others only 54-igj^gths, and some no more than 40-fijiWths °f a l'ne in diameter. It is well ascertained that the blood differs during the earlier periods of embryotic existence from what it is in after life. Messrs. Prevost and Dumas have shown that the globules of the blood in the chick in ovo are circular at first, and only become elliptical at the period when the liver is developed.* And M. Prevost found that in the foetus of the goat these corpuscles were at first the double in diameter of those in the adult animal.f The structure of the globules of the blood, as well as their magnitude, has been a subject of great variety of opinion. The differences in the conclusions, however, appear to me to depend principally on the circumstances in the mode of experimenting. Della Torre and Styles believed that the globules of the blood were perforated in the centre and fashioned like rings. When they are examined with lenses of low magnifying power, they look like small black points; when viewed under an instrument rather more powerful, they assume the appearance of a white circle with a black point in its middle ; this is evidently what has given rise to the opinion we have quoted ; but the appearance in question by no means de- pends on the existence of a central hole in the globules; it is merely the effect of the light; for by using a magnifying power of 300 or 400, the central point assumes the appearance of a luminous spot, and by varying the position of the globule, as well as the direction of the rays of light, the observer may easily convince himself that the globules are entire. Hewson, to whom we are indebted for so many good observations on the blood, was the first who arrived at accurate conclusions in regard to its globules. He considered them as flattened vesicles, in the interior of which there is a central corpuscle or nucleus. The accuracy of this opinion, which has been maintained in our * Mem. sur le developpement du Cceur, &c. Annales des Sciences Nat. 1 Serie., t. iii. t Ann. des Sciences Nat. t. iv„ own day by Messrs. Prevost and Dumas and others, has been called in question by Dr. Hodg- kin and Mr. Lister ; nevertheless to me it ap- pears to be founded on unquestionable data. In studying the blood of the Reptilia, in which the globules are of very considerable magni- tude, Messrs. Prevost and Dumas have even seen the outer envelope of these corpuscles tear, and expose the central nucleus naked. In 1826 I myself observed that by acting with a little weak acetic acid on the globules of the blood, previously placed on the object-plate of a microscope, they are very speedily stripped of their envelope, and their central nucleus is obtained isolated.* Professor M filler ,f who does not appear to have been acquainted with this observation of mine, has lately arrived a- the same conclusions, and has varied his ex- periments in such wise as to place the results that follow from them in the clearest possible light. I shall only further add that at the moment of writing this article I have again assured myself of the facts as stated, by sub- jecting the blood of the river-crab and that of the frog to renewed examination. The existence of a solid, white, central nucleus in the globules of the blood conse- quently appears to me to be completely de- monstrated ; and there is, further, every reason to believe that the peripheries of these cor- puscles are membranous vesicles formed of the matter which gives the blood its peculiar colour, or rather that they enclose this colour- ing matter between their inner surfaces and the central nuclei. This vesicular part of the glo- bule is very elastic : whilst engaged in examin- ing the capillary circulation in the lungs of the water-newt, Messrs. Prevost and Dumas frequently saw the globules change their figure ji under the pressure of the moving column of J fluid, and mould themselves in some sort upon the parts that opposed their advance, but they resumed their original form the instant they escaped from the influence of the unequal pressure.]: In general the tegumentary vesicle is collapsed upon the central corpuscle, and thus forms a kind of disc of different degrees of thinness near the edges, but plump or filled out towards the middle. By observing the globules of the blood of the frog and water-newt in diffe- rent positions, the existence of this central tumi- dity may be so positively ascertained as to be be- yond the reach of farther doubt ; but in the hu man blood, the globules of which are extremely small and almost entirely occupied by thei central nucleus, it is more difficult to be satis-j fled of its occurrence; and Dr. Young hasj even been led to think that these globules are discs concave on both sides, an opinion which has been revived and advocated anew by Dr. Hodgkin and Mr. Lister. The ap * Mem. sur les tissus : Ann. des Sciences Nairn t. ix. t Observations sur l’analyse de la I.ymphc dj| Sang,&c. Annales des Sciences Naturelles, 2 Serb Zoologie, t. i. p. 559. f Vide Magendie, Physiologic, t. ii. BLOOD. pearance or disposition of the globules in question, when it occurs, seems to me to depend on an alteration of these corpuscles. In examining the blood of frogs diluted with thin syrup, the globules occasionally appeared to me to become turgid, but not to be distended equally in every part; the exterior vesicle then remained attached to the centre of the internal nucleus, whilst it became puffed all around. I have seen a globule thus altered in its form, presenting three very distinct en- largements in the course of its long diameter, the two lateral of which exceeded the median one in extent. I should therefore be led to imagine that by the effect of an endosmosis these vesicles may occasionally absorb the water of the serum, and that this fluid, accu- mulating around the central nucleus, without, however, separating this corpuscle from its envelope, gives to the globule in general the form of a biconcave disc, as described by Dr. Young. This appearance, which is very com- mon in the human blood, agrees extremely well with the description of Dr. Hodgkin and Mr. Lister, but we do not imagine that this is the normal condition, and we are persuaded that if these very scrupulous observers would but extend their inquiries to the blood of those animals in which the globules are most easily studied, they would return to and espouse the opinions of Hewson and of Prevost and Dumas in regard to the particular point at issue. In the normal state, the membranous vesicle of the globules of the blood appears perfectly smooth among vertebrate animals ; but among the invertebrata its surface is uneven and nodulated like that of a raspberry, as we have already said. Hewson, however, observed that when the blood of the vertebrata began to putrefy, the globules then presented an appearance analogous to what we have remarked in those of the Crustacea and mollusca. In the mammalia the central nucleus is circular and depressed, and in all this class of animals it appears to be similar in size. In the oviparous vertebrata, it is on the contrary elliptical in figure, though, according to Messrs. Prevost and Dumas, it acquires this figure in consequence of a par- ticular substance being fixed around it, itself being in reality circular, as among the mam- malia. It frequently happens that other smaller corpuscles than the globules of which we have treated hitherto are observed swimming in the serum. These are of a whitish colour and simi- lar to the molecules that occur in almost all the fluids of the animal economy. The resem- blance that exists between these corpuscles and the central nuclei of the proper globules of the blood might lead to the belief that they were nothing more than the central nuclei divested of their coloured envelope ; but in several of the inferior tribes, as the river-crab and certain mollusca, in the blood of which they occur in very considerable numbers, the central nuclei of the globules are much larger, and it is impossible to confound the two toge- 4 09 ther. These then are to be regarded, not as globules of the blood, properly so called, altered in any way, but as globules of albumen or fibrine. These substances, in fact, have always the appearance of being made up of circular corpuscles of extreme minuteness when by any means they are brought into the solid state ; and we are led to believe that even when dissolved or suspended in water they still preserve this peculiar disposition, and only escape detection under the microscope by their dissemination and transparency. To recapitulate, then, we find : — 1st. That the globules of the blood are mem- branous sacs inclosing a solid flattened nu- cleus in the form of a disc, in their interior. 2d. That their form and their dimensions vary among animals of different species, but that in the same animal they all bear the strongest resemblance to one another. 3d. That in the mammalia these corpuscles are circular and smaller than in any other class of animals. 4th. That in birds the globules of the blood are elliptical and larger than in the mammalia ; their dimensions vary slightly in different genera, but this variety does not seem to ex- tend further than to the admeasurements of their long diameters. 5th. That in vertebrate animals with cold blood the globules are also elliptical, but that their dimensions are much greater and vary more extensively in different classes ; reptiles, more especially the batrachia, are of all animals those in which the globules of the blood are the largest. 6th. That in the invertebrata the globules of the blood are more or less regularly circular in shape, and are also of very considerable dimen- sions. It appears to be especially owing to the presence of the globules, the common physical properties of which we have thus far studied, that the blood owes its power of arousing and keeping up vital motion in the animal economy. We observe, in fact, that if an animal be bled till it falls into a state of syncope, and the further loss of blood is not prevented, all muscular motion quickly ceases, respiration is suspended, the heart pauses from its action, life is no longer manifested by any outward sign, and death soon becomes inevitable ; but if, in this state, the blood of another animal of the same species be injected into the veins of the one to all appearance dead, we see with amazement this inanimate body return to life, gaining accessions of vitality with each new quantity of blood that is introduced, by-and- bye beginning to breathe freely, moving with ease, and finally walking as it was wont to do, and recovering completely. This operation, which is known under the name of transfusion , proves better than all that can be said the importance of the action of the globules of the blood upon the living tissues; for if, instead of blood, serum only, deprived of globules, be employed in the same manner, no other or further effect is produced than follows the in- BLOOD. 410 jection of so much pure water, and death is tio less an inevitable consequence of the he- morrhage. A variety of other experiments upon trans- fusion, for which we are equally indebted to Messrs. Prevostand Dumas, show the influence which the form and volume of the globules of the blood exert upon its physiological proper- ties. If the blood introduced into the veins of a living animal differs merely in the size, not in the form of its globules, a disturbance or derangement of the whole economy more or less remarkable supervenes. The pulse is in- creased in frequency, the temperature falls rapidly, the alvine evacuations become slimy and sanguinolent, and death in fine generally happens after the lapse of a few days. The effects produced by the injection of blood having circular globules into the veins of an animal the globules of whose blood are ellip- tical, (or vice versa,') are still more remarkable ; death then usually takes place amidst nervous symptoms of extreme violence, and comparable in their rapidity to those that follow the intro- duction of the most energetic poisons. We know by observation and experiment that it is the blood that supplies the living tissues with the materials which they assimilate to repair their losses resulting from the vari- ous processes of which they are the seat, as well as to add to their masses during the period of their growth ; thus, when by mechanical means we lessen in a notable and permanent manner the quantity of this fluid received by any organ, we soon find it declining in size, and often shrinking almost to nothing; whilst on the other hand we see that the more blood any part receives, the more does it tend to in- crease in size. It has also been demonstrated that it is at the expense of the blood that the different glands prepare the fluids they are destined to secrete, for the ligature of the ves- sels which run to one of these organs is followed by the immediate cessation of its secreting function. From this it became an interesting question to determine whether or not the blood contains, ready formed, the various substances of which these tissues and these secreted fluids are composed, and if the organs it traverses do anything more than merely separate these from its mass, or whether the general nutrient fluid only supplies to the different parts of the economy the primary elements necessary to the formation of the substances of which we have spoken, which would then be originated by the tissues or glands in which they are encoun- tered. To resolve this question, it became necessary to contrast the chemical composition of the tissues and fluids of the economy with that of the blood, and to ascertain whether the last-named fluid contained all the variety of substances which are met with elsewhere in the animal organization. This very important part of organic chemistry is not yet sufficiently advanced to enable us com- pletely to answer the question : all we know, however, goes to prove that the component parts of the tissues and secreted fluids exist in the blood ready formed, and are only sepa- rated from its general mass by the organs which at first sight seem to produce them. In the blood we discover — 1st, water, an element which enters in large proportion into the com- position of all the fluids, and even forms a considerable item in the constitution of all the tissues : 2d, fibrine, which forms the basis of the muscles : 3d, albumen, which is met with in variable but still considerable quantities in the brain, cellular substance, membranes generally, and in the greater number of the secreted fluids which are not excrementitious : 4th, a fatty phosporated matter, which enters into the composition of the nervous system: 5th, a peculiar colouring matter of a yellow hue, which, slightly modified, is perchance the same as the pigmentum nigrum of the choroid, coat of the eye, and of melanosis : 6th, phos- phate of lime and phosphate of magnesia, salts which form the inorganic basis of the bones : 7th, alkaline salts, which are met with in almost all the fluids of the body : 8th, cholesterine, a peculiar fatty matter existing very abundantly in the bile : 9th, urea, a substance characteristic of the urine : lastly, various other matters more or less accurately defined. Under ordinary circumstances our means of analysis are inadequate to demonstrate the presence of urea in the blood ; but if the ac- tion of the organs destined to separate this substance from its current in proportion as it is formed, be arrested, the amount contained goes on increasing continually, so that before long it becomes easy to distinguish it. Messrs. Prevost and Dumas have shown that, after the extirpation of the kidneys, the blood always contains urea in appreciable quantity.'* This experiment, the results of which have been confirmed by Messrs. Vauquelin and Sega- las, is of the highest importance, and shows that if we have hitherto failed to discover uric acid, easeum, and the other compo- nent elements of the principal fluids in the blood, we are not, therefore, to conclude that they do not exist there ; analogy would even lead us to infer that they are actually present, and that if we were to interrupt the different glands in the performance of their functions, they would be discovered in appreciable quantity. Experiments con- ducted in this view would be extremely in- teresting. Another subject of inquiry, too, net less important, would be to discover the source of the gelatine which forms the basis of the cartilages, tendons, ligaments, & c. and which does not appear to exist in the blood. The most complete analysis of the human blood we possess is that published lately by M. Lecanu, a chemist of Paris.j- The careful examination of the blood of two strong and healthy men afforded the following results. * Bihl. Univers. de Geneve, and An. de Chemie, 2dc Serie, t. xxiii. t Journal dc Pharm, No. ix. and x., 1831. BLOOD. 411 Water Fibrine .... Albumen .... Colouring matter . Fatty chrystallizable matter .... Oily matter . . . Extractive matters soluble in alcohol and in water . . Albumen combined with soda . . . Chloruret of po- tassium . . . Chloruret of sodium Alkaline sub-carbo- }■ nates .... Alkaline phosphates Alkaline sulphates . J Sub - carbonate of 0 lime .... Sub - carbonate of magnesia . . . Phosphate of lime . > Phosphate of mag- nesia .... Phosphate of iron . Peroxide of iron . J Loss 1st Analysis. •2d Analysis. 780.145 785.590 2.100 3.565 65.090 69.415 133.000 119.626 2.430 4.300 1.310 2.270 1.790 1.920 1.265 2.010 8.370 7.304 2.100 1.414 2.400 2.586 Total 1000.000 1000.000 Since the publication of the preceding ana- lysis, M. Boudet has discovered a new substance in the serum of the blood, which he denomi- nates seroline. This is a white slightly opa- lescent substance, fusible at 36 cent., (about 94° Fahr.), not forming an emulsion with water, soluble in alcohol, not saponifiable, and appearing to contain azote. This chemist has also shown that the oily matter mentioned by M. Lecanu is a mixture of cholesterine and an alkaline soap, similar to that which is met with in the bile; lastly, he has determined the identity of the fatty chrystallizable phosporated matter contained in the blood with that dis- covered by Vauquelin in the brain (cere- brine).* The study of the colouring matter of the blood has engrossed a large share of the atten- tion of chemists ; nevertheless its nature is still very imperfectly known. It is very com- monly designated under the name of hemato- zine or hematine, and can be readily shown to have the greatest analogy to albumen, from * Ann. dc Chimie, 2de Scrie, t. hi. which it is indeed always separated with great difficulty. This matter is soluble in pure water, insoluble in serum and in water impreg- nated with salt or sugar, coagulable by heat, capable of absorbing oxygen, carbonic acid, and various other gases which modify its colour. According to M. Lecanu the hematine of chemists is a combination of albumen and the pure colouring matter of the blood, which he proposes to designate globuline.* But his researches into this delicate subject do not seem to us altogether satisfactory, and we have reason to believe that his globuline is neither more nor less than some of the globules of the blood which have escaped the action of the sub- acetate of lead employed to precipitate the un- combined albumen. However this may be, the colouring matter of the blood after incine- ration leaves a large quantity of ashes, in which a considerable proportion of oxide of iron can be demonstrated, to the presence of which several chemists have ascribed the red colour of the blood ; such an opinion, however, does not seem tenable at the present day. The experiments of Berzelius have shown that the serum of the blood of the ox does not differ essentially from that of the blood of man.f But we are still without comparative analyses of the nutrient fluids of the different classes of animals. This desideratum has been partially supplied in regard to the vertebrata by Messrs. Prevost and Dumas, they having carefully determined the proportions of water, and of albumen contained in the serum, and those of the fibrine, and other solid parts which swim suspended in this fluid. From these expe- riments we learn that the composition of the serum varies in the same animal at different times, and that it differs still more widely in different animals, without its being possible to connect such changes with the physiological state of the individual. The case is otherwise, however, as concerns the globules ; in the majority of cases there exists a remarkable relation between the quantity of these cor- puscles and the degree of heat developed by the vital actions. Of this we may be easily convinced by inspecting the following table, in which Messrs. Prevost and Dumas have pre- sented us with the comparative weights of the solid particles (globules and fibrine) contained in 1000 parts of blood, with the habitual temperature of different animals, taken in the rectum, the number of pulsations of the heart per minute, and the number of inspirations made in the same interval of time. 9 Ann. de Chimie, 2de Serie, t. xlv. t On animal fluids, in Med. Chirurg. Trans, vol. iii. i 412 BLOOD. Names of the Animals. Weight of the solid particles in 1000 parts of blood. Composition of the serum. Mean temperature. Normal pulse per minute. Normal number of inspirations per minute. Albumen. Water. Birds. Pigeon 15.57 55 945 42° centigr. 136 34 Common fowl . . 15.71 75 925 41.5 140 30 Duck 15.01 99 901 42.5 110 21 Crow 14.66 66 934 . . , . , , Heron 13.26 68 932 41 200 22 Mammalia. Monkey .... 14.61 92 908 35.5 90 30 Man 12.92 100 900 39 72 18 Guinea-pig . . . 12.80 100 900 38 140 36 Dog 12.38 74 926 37.4 90 23 Cat 12.04 96 904 38.5 100 24 Goat 10.20 93 907 39.2 84 24 Calf 9.12 99 901 . , . . . , Rabbit 9.38 109 891 38 120 36 Horse 9.20 99 901 36.8 56 16 Sheep 9.00 •• •• 38 •• •• Reptilia. Frog 6.90 50 950 9. in water. 20 Tortoise . . , . 15.06 96 904 7.5 that of the air. •• 3 Fishes. Trout 6.38 77 923 O 0 , . • • Loach 4.81 69 931 # , . . Eel ...... 6.00 100 900 •• • • From these experiments it follows that of all animals birds are those whose blood is richest in globules and in fibrine, as they are those also whose temperature is highest and whose respiration is most active. The blood of the mammalia contains rather less, and there is a difference to be noted in this respect between the carnivorous or omnivorous tribes, and the herbivorous, the proportion of solid particles being larger in the two former than it is in the latter. We see, indeed, that in man, the dog, and the cat, they enter in the proportion of twelve or thirteen per 1000, whilst in the horse, sheep, calf, and rabbit, they form no more than from the seventh to the ninth per 1000 of the general weight of the blood. But the number of species hitherto examined is not so considerable as to enable us to say that the circumstance, now announced, is to be regarded in the light of a physiological law. Among the cold-blooded vertebrate animals the blood becomes much influence on the composition of the blood : M. Lecanu found in regard to The blood of man (in 1000 parts.) Maximum Solid particles. ... 148 Water. 805 Minimum ... 115 778 Mean . . ... 132 791 Maximum The blood of woman. ... 129 853 Minimum ... 68 790 Mean . . ... 99 821 The quantity of albumen did not appear tc differ in the blood of the two sexes. The richness of the blood also varies ac- cording to the temperament of individuals as may be seen by the following table. Men. poorer in solid particles ; the tortoise, indeed, seems, from the results in the table, to form an exception to this fact, but the circumstances under which the estimates were made in regard to it, and which it would be too long to enter upon here, explain the anomaly.* The proportion of serum and of solid parti- cles also presents considerable varieties in the blood of different individuals of the same species. From the investigations of M. Lecanu we observe that the proportion of water in the human blood varies from 853 to 778 in 1000, and that of the solid particles from 148 to 68. The differences of sex have also a certain Sanguine tempe- rament. Lymphatic tempe- rament. 1 Solid particles Water Solid particles Wale Maximum 148 801 117 805! Minimum 121 778 115 V95| Mean 136 786 116 800l[ Women. Maximum 129 796 129 827 Minimum 121 790 92 79C Mean 126 793 117 802 * Ann. de Chimie, t. xxiii. BLOOD. 413 Lastly, the composition of the blood may also vary in the same individual according to a variety of circumstances. Prolonged absti- nence from diluents, for example, tends to di- minish the proportion of the watery particles of the blood, and, consequently, to render it richer in nutrient elements. Bloodletting pro- duces the contrary effect; not only is the mass of circulating fluid by this means diminished, but it is also rendered poorer. Messrs. Prevost and Dumas having bled a cat largely, found its blood to consist of 791 of water, 87 of albumen, and 118 of globules. Two minutes afterwards they repeated the bleeding, and now only found 116 of globules, and 74 of albu- men to 809 of water; after an interval of five minutes more the bleeding was repeated for the third time, and they found the blood to consist of 829 of water, 93 of solid particles, and 77 of albumen. M. Lecanu obtained similar results from the analysis of human blood taken from patients who had been bled several times in quick succession, or who were labouring under haemorrhagic affections ;* and the circumstance is readily explained, by sup- posing that the diminution of the mass of blood tends to accelerate absorption, the first effect of which must needs be to introduce a much larger proportion of water than of solid particles into the torrent of the circulation. In its ordinary state the blood is always fluid, and consists, as we have seen, of a watery part, holding solid globules in suspen- sion; butundercertain circumstances its physical properties change completely: this happens whenever it is withdrawn from the vessels in which it is contained in the bodies of living animals, or in the event of an animal ceasing to exist. The blood left to itself changes within a few minutes into a mass of a gelatinous con- sistence, which gradually separates into two parts, one fluid, transparent, and of a yel- lowish colour, formed by the serum ; another solid, quite opaque, and of a red colour, to which the name of cruor, crassamentum, or 'lot is given. The mode in which this phenomenon hap- pens, and the cause that occasions it, have engaged the attention of a great many physio- ogists. The experiments of Hunter and of nany others show that the coagulation of the flood depends mainly on the cessation of the notion to which it is constantly subjected in ne course of the circulation ; for this condition done suffices to make it coagulate even in the nterior of the vascular system, and we are of 'pinion that the great physiologist just quoted rred in attributing vital properties to the blood, lest, then, cessation from motion, is that vfiich contributes most generally and most essentially to cause coagulation of the blood ; ither circumstances, however, such as its ooling, its being brought into contact with he air, &c. may also contribute to accelerate fis phenomenon, which appears, from the xperiments of Dr. John Davy, to be unac- ompanied with any evolution of caloric. * Journal de Pharmacie, 1831. If a clot of blood be gently kneaded and pressed under a stream of water, it gradually becomes paler, and finally loses its red colour entirely, the colouring matter being washed away ; what remains in the hand is a mass of whitish and very elastic filaments composed of fibrine. Or otherwise, if, instead of being left at rest, a quantity of freshly drawn blood be quickly stirred with a bundle of rods, a stringy mass of fibrine will be found adhering to these after a time, and the blood thus treated will not coagulate. This experiment shows that it is to the fibrine that the blood owes its pro- perty of coagulating. The filaments of fibrine studied under the microscope are found to be formed by the aggregation of a multitude of white globules, bearing the greatest resemblance to the central nuclei of the proper globules of the blood. It was, therefore, natural to suppose that the formation of the coagulum depended on the spontaneous decomposition of these globules and the aggregation of their internal corpuscles. And such, indeed, is the theory which Messrs. Prevost and Dumas have given, and which has been adopted by the greater number of the physiologists of the present day. “ The at- traction,” say they, “ which keeps the red matter fixed around the white globules having ceased along with the motion of the fluid, these globules are left at liberty to obey the force which tends to make them combine and form a net-work, in the meshes or amid the plates of which the colouring matter is included along with a great quantity of particles which have escaped this spontaneous decomposition.”* It would appear, however, that this is not an exact explanation of the phenomenon, for Professor Muller, of Berlin, has succeeded in demonstrating that the coagulation of the blood is altogether independent of the globules, and that the fibrine which determines the pheno- menon exists dissolved in the serum. By filter- ing with great care the blood of frogs, diluted with sugar-water, he separated the globules completely from the serum before coagulation took place : the fluid part of the blood alone passed the filter, the solid particles remained upon it ; nevertheless, a coagulum formed within the fluid after the lapse of a few mi- nutes; this, of course, was colourless instead of red, as it is when the red globules are en- tangled in the mass. This curious and in- teresting experiment does not succeed so well when human blood is employed, inasmuch as the globules, being much smaller than those of the blood of the frog, pass along with the serum through almost any filter that can be used. Still Professor Muller has succeeded in proving the existence of fibrine in the serum by means of the following procedure. If to a little blood contained in a watch-glass a few drops of a highly concentrated solution of sub- carbonate of potash be added, the coagulation of the fluid is so much retarded, that the glo- bules have time to sink to the bottom before it occurs. When coagulation takes place at * Ann. de Cliimie, t. 23, p. 51. 414 BLOOD. length, the clot extends as usual through the whole mass, but it is colourless on its upper part, and only red in the part into which the globules have subsided. Professor Muller believes that the fibrine exists in a state of solution in the serum, an opinion which to us appears hardly reconcilable with the known che- mical properties of this substance ; we are more inclined to suppose that, like the proper glo- bules, it is merely suspended in the mass of the blood in a state of extreme subdivision, and possessed of transparency too perfect to admit of its being distinguished amidst the sur- rounding fluid. There are circumstances under which the blood only coagulates with difficulty, or in which it even loses this property entirely. In cases of poisoning with hydrocyanic acid, for instance, the blood remains fluid and thick after deatli ; the same thing also occurs after death from fever of a typhoid type, from lightning, &c. Another phenomenon presented by the blood which is of very common occurrence, and depends on the manner in which it coagu- lates, consists in the formation of what is called an inflammatory crust or huffy coat : the coagulum, instead of being uniformly red, then appears covered with a greyish or yel- lowish viscid and very tough pellicle of various degrees of thickness. The pheno- menon in question is principally observed in individuals labouring under acute inflammatory affections of the serous or synovial membranes, of the substance of the lungs, &c. but also occurs among persons in good health, although plethoric. The experiments of M. Ratier go to prove that various circumstances, altogether independent of the physiological state of the individual, may also exert great influence on the formation of the buffy coat : thus, cateris paribus, it is more readily produced if the blood withdrawn be received in a deep and narrow vessel, and if the opening in the vein be large, and the jet be free. The cause of the buffy coat has been very satisfactorily ex- plained ; it depends on the more rapid subsi- dence than usual of the red globules, in con- sequence of which the more superficial parts of the coagulum contain none. From the ex- periments of Professor Muller it would also appear that this subsidence of the globules takes place more quickly if a thick solution of gum be added to the blood, so as to increase its density, whilst, when it is deprived of its fibrine by stirring with rods, these bodies remain for a very long time suspended. Now it follows, from the investigations of Sir C. Scudamore, that buffy blood contains a larger proportion of fibrine than usual, a state to which the more rapid deposition of the glo- bules, and the formation of the inflammatory crust, which is its consequence, may be at- tributed. Thus far we have only spoken of the blood in a general manner, and without respect to the part of the system in which this fluid is examined ; it is, however, very far from being- identical in every part, and there are wide differences between the physical and physio- logical properties of arterial and of venous blood. The blood which is tending to the several parts of the body is in the first place of a bright vermilion red colour (arterial blood); whilst that which has already passed through the different tissues, and is on its way back from them, is of a dusky or blackish red of various degrees of intensity ( venous blood). Arterial blood also coagulates more quickly than venous blood, and, from the researches of Dr. John Davy, appears to have rather a less capacity for caloric,* and a somewhat in- ferior specific gravity (1,049 : 1,051); wears, however, led to think that in the normal state the contrary of the latter proposition will he found to obtain, for Messrs. Prevost and Di - mas have shown that in this case arterial blood contains a larger proportion of globules than venous blood.f VVhen the physiological action of arterial and of venous blood is investigated, still more striking differences are discovered ; the first maintains vital excitation in the economy, and the second is insufficient to support life. Physiologists have even gone so far as to regard the influence of the venous blood upon the brain as deleterious ; J but more recent experiments show that though inadequate to keep up life, it is far from being a poison ; on the contrary, it rather tends to prolong existence, for frogs whose vascular system is filled with this liquid die less speedily than those placed under similar circumstances, but which have lost almost the whole of their blood by haemorrhage^ The blood thus modified by the influence of the organs it permeates, is still susceptible of resuming its primary colour, and of ac- quiring at the same time its vivifying- pro- perties : it is enough to expose it to the con- tact of oxygen, to give it back all its peculiar qualities. We find, in fact, that if venous blood be agitated with atmospheric air, j or better still with oxygen gas, it speedily assumes the vermilion tint that characterizes arterial blood, and if the air thus employed be afterwards analysed, a certain quantity of oxygen will be found to have disappeared, and its place to be occupied with a corresponding measure of carbonic acid. Now that, which happens here under the influence of mere chemical affinity, also takes place in the ani- mal economy, and it is even thus that venous blood in being exposed to the contact of atmospheric air in the respiratory apparatus, whatever its nature, changes into arterial blood and again becomes fit to minister to life. (See Respiration.) On the other hand, if ver- milion-coloured blood be subjected to the action of carbonic acid, it speedily acquires a * Philos. Trans. 1815. + Ann. de Chimie, t. xxiii. p. 67. f Bichat, sur la Vie et la Mort. See also the article ASPHYXIA. j § M. Edwards, Influence des Agens Physiques) sur la Vie, translated by Dr. Hodgkin. 415 BLOOD, MORBID CONDITIONS OF THE deep or blackish hue, and then resembles venous blood in its appearance and pro- perties. It now became a question of the very highest importance in the theory of respiration to ascertain whether the oxygen acting upon the blood in the manner specified, produced the carbonic acid disengaged, by combining directly with carbon supplied by the colouring matter or some other element of the blood, or whether the oxygen was simply dis- solved by the blood and in dissolving ex- pelled the carbonic acid which existed in it ready formed. Various experiments satisfy us that venous blood contains carbonic acid already formed. My brother, Dr. W. F. Edwards, has shown that those animals which possess the greatest powers of resisting asphyxia continue for a long time to disengage carbonic acid when kept in vessels filled with pure azote or hy- drogen, circumstances under which it is im- possible that the carbonic acid evolved can proceed from the direct combination of in- spired oxygen with the carbon of the blood. By placing venous blood under the receiver of an air-pump, several inquirers had indeed already found that bubbles of carbonic acid gas were disengaged from it, when the pres- sure of the atmosphere was withdrawn. This fact, first observed by Vogel,* * * § has been verified by Messrs. Brande, Bauer, f and others. The quantity of carbonic acid disengaged in this way, however, is very small, and altogether inadequate to explain the phenomena accom- panying respiration ; but if, after having freed a quantity of blood as completely as possible from its carbonic acid by means of the air- pump, it be agitated with hydrogen or any other gas, this will be absorbed, and a fresh and corresponding disengagement of carbonic acid will be determined.^ On the other hand there is an experiment of Girtanner, mentioned by Hassenfratz,§ which goes to prove that arterial blood contains a portion of free oxygen in its constitution ; but this conclusion appears to require confirmation. The bright vermilion or dusky red colour of the blood, however, does not depend solely on the nature of the gas it holds in solution, or with which its colouring matter is in com- bination. The recent experiments of Dr. Hoffmann shew that the presence of the saline matters it contains is necessary to the phe- nomena in question. Blood freed from these saline ingredients is black, and cannot be brought to the vermilion red tint as usual by the action of oxygen. The same physiologist also ascertained that the presence of an over- dose of saline matter in blood charged with carbonic acid, equally prevented the ordinary action of oxygen in changing its colour. The blood does not invariably exhibit the properties and the mode of composition which * Schweigger’s Journal, Bd. xi. t Home, Croonian Lecture, Philos. Trans. 1818. t Hoffmann, Lond. Med. Journ. May, 1828. § Ann. de Chimie, liere Serie, t. ix. we have just ascribed to it in the normal state. There was a time when physicians ascribed the greater number of internal maladies to alterations of this fluid ; the general errone- ousness of this opinion, however, was at length detected, and at the present day patho- logists have probably fallen into the opposite extreme, namely, that of neglecting the study of the changes which the blood does actually undergo, although these are sufficiently striking in many cases, and undoubtedly exert an im- mense influence upon the animal economy. A careful examination of their kinds and effects were undoubtedly fraught with results of equal importance in a medical as in a physiological point of view. ( H. Milne Edwards.) BLOOD, MORBID CONDITIONS OF THE. — The nature and properties of blood in its normal condition having been considered in the foregoing article, we proceed to notice those changes to which it is liable in a state of disease. That a fluid which is destined to receive and convey materials for the formation, increase, and repair of every structure in the animal frame, which carries away whatever is useless, and is brought into perpetual contact with the external atmosphere, should itself be subject to morbid alterations, is a notion so natural, so entirely in accordance with what might d priori be ex- pected, that, independently of all reasoning, and antecedently to all proof, it has existed in the common belief of every age and of every nation. To preserve a healthy state of the blood has accordingly ever been considered an object of primary importance. The greatest pains have been taken to maintain its purity, as well in the individual as the species ; not only in man, but in all those animals which he has domesticated for his use ; and there is no belief more generally received than that which attributes the origin of many of the cutaneous eruptions, and of most of the cachectic diseases, to the degene- racy and poverty of this vital stream. When from this general and popular notion we advance to the more especial assumption that the origin of all diseases is to be found in the blood and other fluids ; when we classify these into hot and cold, moist and dry, or into blood, bile, black bile and phlegm, and attribute morbid changes and even natural dispositions to the prevalence of one or other of these supposed humours, we quit the belief of the people to follow theories far less tenable, invented at a period when authoritative assertions had the weight of proof, and when the dogmata of a philosopher were preferred to facts plainly re- corded in the book of nature. It would be out of place here to enter into a discussion of the merits of the humoral pa- thology as compared with the various doctrines which have supplanted it, and to which it is not unlikely that in an improved form it may again succeed. Under the triple relation of vital phenomena, intimate structure, and chemical composition, as 416 BLOOD, MORBID CONDITIONS OF THE. Andral* justly remarks, we can draw no definite line of demarcation between the blood and the solids. Physiologically speaking, we cannot conceive that of these two facts which form a single whole, the one can be modified without affecting the other. Since the blood nourishes the solids, they must necessarily be influenced by its state ; and since the solids furnish ma- terials from which the blood is formed, and abstract materials by which it is decomposed, any alteration in the nature or quantity of these must necessarily have its influence on this fluid. Suffice it then to observe that the further we extend our knowledge of pathology, the less shall we feel inclined to admit the exclusive claims either of fluidism or solidism, and the more shall we strengthen our belief that the animal structure is composed of parts, every one of which may not only partake of disease, but, under certain circumstances, become its cause. Quitting, therefore, all unprofitable specu- lations on this subject, we proceed at once to a detail of facts, and to such observations in elu- cidation of them as occasion may suggest. Blood may be excessive in quantity, thus constituting a state of plethora in which the circulating system is supplied more abundantly than is needed for the due performance of the functions of nutrition and secretion. A ten- dency to accumulation in the capillaries and in the different internal organs is induced, and con- gestion with its consequences, or actual rupture of the bloodvessels, is the result. Drowsiness, vertigo, headache, epilepsy, apoplexy, mark this state as existing in the head ; dyspnoea, and a livid or purple hue of the skin, as affecting the lungs; palpitation and irregular action with syncope mark the ineffectual struggle of the heart to propel its contents. Haemorrhages from the mucous membranes of the nose, the lungs, or the intestines, are often the consequence of congestion in the vessels which ramify on their surface; while indigestion, torpor, and biliary redundancy, are connected with a plethoric condition of the abdominal viscera. Although the existence of such a state, as deducible from the symptoms just enumerated, as well as from the effect which depletion has in removing them, admits of no doubt, it has, nevertheless, not been made the subject of direct proof. The proportion which the circulating blood, even in a healthy animal, bears to its total weight has not been, and, perhaps, cannot be ascertained with precision. Haller collects together many authorities at variance with each other on this point, and at length comes to the conclusion, “ Neque dissimulandum est, obiter hsec et vage definiri. Infinita enim procul dubio in ratione sanguinis ad reliquam corporis molem varietas est.” f Fat men and animals have less blood than lean, old than young ; and yet plethora is oftener found in the former than the latter, obviously on account of the mechanieal im- * Precis d’Anatomie Pathologique, p. 526. t Elementa Physiologic, tom. ii. p. 5. pediment which the encumbered tissue or the rigid fibre offers to the circulation. The state of anaemia, or a deficiency in the quantity of circulating blood, whether induced by natural or artificial causes, is no less detri- mental to health than its excess. Its symptoms are general pallor, weak circulation, languor, syncope with palpitations, oppressed respi- ration, flatulency, general oedema, and, in extreme cases, effusion into all the serous cavities. Neither plethora nor anaemia necessarily imply, though they are generally complicated with some morbid change in the blood itself. We therefore pass them over with this slight notice, referring for further information to the excellent observations of Andral, in his work on Pathological Anatomy. The circulating blood consists essentially of a homogeneous fluid and red particles, and the former, when removed from the body or froru the circulation, separates into a fluid and a solid portion. The solid, when washed and freed from the serum and red particles which are mechanically entangled in its substance, consti- tutes the proximate animal principle called fibrine. The fluid contains water, albumen, oil, animal extractive, and salts, alkaline, earthy, and metallic. With the exception of the oil and fatty matter, which, in a healthy state of the blood, do not amount to four parts in a thousand, its constituents are all heavier than water, and something is to be learned by ascertaining its specific gravity. In the information thus gained, however, we are limited to the al- ternative, either that some one or more of these constituents is in a state of excess or of de- ficiency, the proportion of water remaining normal, or that the water itself is either su- perabundant or deficient. The specific gravity of healthy blood has been variously stated by different authors. Haller makes it on the average 1,052; Blu- menbach, 1,054; Berzelius, from 1,0527 to 1.057 ; Denis, 1,059; but none of these au- thors note the temperature at which it was taken, although, from their manner of ascertain- ing it, there must have been considerable variety in this respect. By experiments which I have often repeated with an accurate specific gravity bottle holding 1,000 grains of distilled water, I find that with that fluid four degrees of Fahrenheit’s thermometer corresponds with a difference of '001 of specific weight, water being 1,000. Consequently, if one author states the specific gravity of blood at its circu- lating temperature 98° Fahrenheit, while an- other states it at 60° Fahrenheit, the usual- standard, the former will make it -0095 lighter than the latter. The heaviest blood of which I find a record among my own observations was that of a man suffering under diabetes mellitus. At a tempe- rature of 87° Fahrenheit it was of specific gra- vity 1'0615, while that of the serum was under the average standard of health, namely, 1 -027 at 60° Fahrenheit, and of the medium propor- tion ho the crassamentum, being, after twelve 417 BLOOD, MORBID CONDITIONS OF THE. hours’ rest, as 1000 to 1323. The specific gra- vity of the crassamentum was 1-088. The lightest blood which I have met with was of specific gravity 1-031, at 90° Fahren- heit. It was taken from the arm of a female, aged 22, who was bled on account of headach, and had a full pulse of 1 17. The red particles being the heaviest of all the constituents of the blood, their relative quantity must greatly affect its specific gravity ; and as Messrs. Prevost and Dumas have shewn that they bear a general proportion to the de- gree of animal heat, we might reasonably sup- pose that, ceteris paribus, the heaviest blood would be found in those diseases which are marked by high action and increased tempera- ment. In a fluid so complicated, however, in which every constituent is liable to such variety in quantity, it is difficult to estimate the precise influence of each. I am not aware that any experiments have been made on this subject. Blood diminishes in specific gravity in pro- portion to its frequent abstraction, for the red particles and the fibrine are reproduced with more difficulty than the serum or the salts. The serum also becomes lighter from a gradual di- minution of its solid contents. A recent paper by Mr. Andrews, in the fifteenth volume of the Medical Gazette, p. 592, proves these facts very satisfactorily by experiments made on calves. They have, however, been long known. The specific gravity of morbid blood, says Thackrah, differs little from that of healthy blood ; but this observation is only true of an average deduced from numerous specimens of blood examined under different forms of dis- ease. It would be equally true, perhaps, according to the same mode of obtaining a result, were we to affirm that the temperature of the body or the state of the pulse differed little in health and disease, since there might be as many instances of deficiency as of ex- cess in heat or action. The assertion is not applicable to particular cases, and is, therefore, without value. Blood may be morbid from an undue proportion of any of its constituents, and it will be heavier or lighter than healthy blood according to the preponderance of the heavier or lighter principles. Where the spe- cific weight is increased, it is generally owing to a deficiency in the proportion of water, as in the blood of cholera and diabetes ; sometimes to an increase of fibrine and red particles, as in plethora, gout, and rheumatism. The following table, containing the specific gravities of blood under several forms of dis- ease, is compiled from a few cases of my own which were recorded for another purpose. Though short, it will be sufficient to shew that tonsiderable variety occurs, and may collaterally iuggest that in determining the propriety of de- pletion, it may in some cases become impor- ant thus to ascertain the proportion of solid natter existing in the circulation. A specific gravity bottle, holding 1000 grains of distilled vater, was employed in all the experiments, so !iat the proportion of serum to clot was not Pfluenced by variation in the shape or material f the receiver. VOL. I. 418 BLOOD. MORBID CONDITIONS OF THE. The specific gravity of morbid serum lias been much oftener ascertained than that of morbid blood, and it leads to more precise information. The normal proportion of salts does not raise the specific gravity of serum above that of distilled water more than five parts in 1000.* The excess beyond this increase is owing to the presence of albumen. The quan- tity of other animal matter is too small to be worth taking into the account. Hence the spe- cific gravity of serum indicates with tolerable accuracy the quantity of albumen it contains. In some states of disease, where albumen is rapidly carried out of the system, as in dis- eased kidneys, in dropsies, and in profuse haemorrhages, the specific gravity of serum has been observed as low as 1013, f whilst in other states, where water and even salts are removed, as in cholera, it is found as high as 10414 Neither the specific gravity of fibrine nor of red particles has been hitherto stated by authors. The former, by immersion in solution of salt, I find to be 1 079 at 60° Fahrenheit. Some of the latter will fall to the bottom of a solution of specific gravity 1- 1 *29, and when agitated with a solution of even specific gravity 1-207, which is the point of saturation, will not rise to the top; but the experiment is not con- clusive, for the red particles certainly undergo some change by the addition of salt in solution. The temperature of the blood is materially influenced by disease. In fevers it is generally though not always above the healthy standard. In the cold stage of an intermittent the tempe- rature of the skin has, according to Dr. Wilson Philip, been observed as low as 74° Fahren- heit, while in its hot stage it has increased to 105°. A corresponding diminution or increase in the temperature of the blood in all probability occurred in these cases. Haller cites authorities to prove that in pleurisy and yellow fever the temperature of the blood has been known to rise to 102° and 104°, in intermittent fever to 106° and 108°, and in continued fever to 1 09°. Mor- gagni devotes several pages to the history of a woman, as related in the journal of a cotempo- rary, Media Via, whose blood flowed in an icy cold state from the arm. The serum of this blood was in small proportion and of a yellow colour; the crassamentum black and viscid. This person seems to have undergone repeated venesection. Thackrah witnessed a similar phenomenon. Whatever theory may be adopted respecting the generation of animal heat, it is a fact which is generally admitted, that it is effected through the medium of the blood, that it is, cater, is paribus, increased in proportion to the velocity, freedom, and force of the circulation, and that it is mainly dependent for its development upon the presence of the red particles. Wherever these are deficient, either from natural disease or artificial depletion, animal heat is deficient likewise. Chlorotic females and those who are subject to habitual losses of blood usually * Med.-Chir. Trans, vol. xvi. part i. p. 57. f Bright’s Reports, vol. i. p. 85. t O Shanghnessy’s Report on Cholera, p. 29. suffer from coldness of the extremities. The phenomenon of fainting is always accompanied by diminished temperature; and whenever we cut off the supply of blood from a limb, it loses its natural warmth as an immediate conse- quence. Plethoric subjects, on the contrary, provided their circulation be unimpeded at its capillary extremities, or in the process of the pulmonary ventilation, are liable to preter- natural heat of the surface and profuse perspi- ration. As an actual diminution or increase in the quantity of the red particles produces a corresponding increase or diminution of animal heat, notwithstanding the natural change of venous to arterial blood, so likewise any cause which impedes that change, although the red particles be not deficient in quantity, will produce a like effect. Thus, in diseases of the heart, in pulmonary obstructions, especially of a spas- modic character, in the cold fit of ague, and lo Asiatic cholera, there is a diminution of the natural warmth, although there is no reason to suppose that the red particles are actually less abundant than in health. Fibrine may undergo alterations in qua'ily during disease. In the healthy state it is com- posed of definite quantities of oxygen, hydrogen, azote, and carbon ; and it is quite possible that some variety in the proportion of these consti- tuents may give rise in disease to morbid states of that principle. Huxham observes that in malignant petechial fevers the crasis is so broken as to deposit a sooty powder at the bottom of the vessel, the upper part being either a livid gore, or a dark green, and exceedingly soft jelly. De Ilaen saw the blood in a dis- solved state, and in the plague the blood is said not to coagulate. In some persons there exists a state of con- stitution, bordering no doubt upon passive hae- morrhagic disease, in which the blood is ob- served either to coagulate very imperfectly or not at all. Alarming hremorrhages from the slightest wounds are the consequence of such a diathesis, and the most powerful styptics will not always succeed in preventing their fatal j| termination. Dr. Wardrop, in a small work just published, has collected together several interesting cases of this kind, and from some ol these it is demonstrated that such a condition may exist in many members of the same family, and even sometimes become hereditary. In the dead body blood is sometimes found in a liquid state, resembling water, holding in suspension a red, brown, or black colouring matter.. In this case, according to M. Andial, it has been demonstrated chemically that it still contains fibrine, but altered in its character, so as to be no longer coagulable. This dis- solved state of blood observable after death is probably the same as that which exists in sea- scurvy, in putrid and typhous fpvers, and in the latter stages of fatally terminating diseases characterized by defective nervous energy. It is matter of more common observation, how- ever, that fibrine alters materially in its relative quantity. We often find that the clot is large^ in proportion to the serum, which may indeed arise from its being loose and defective in con- 419 BLOOD, MORBID CONDITIONS OF THE. tractility, so as to contain a large portion of fluid, or from its bolding entangled among its meshes an unusual number of red particles ; but it will often also arise from there being a more than ordinary quantity of fibrine present, in which case it will be firm and contractile as well as voluminous. Blood thus circumstanced is said to be rich and thick, and is generally met with in those whose complaints are con- nected with a plethoric habit. A deficiency in the proportion of fibrine is likewise not unfrequent among those who suffer from complaints of debility, or who have lost much blood by natural or artificial depletions. In this case the clot is small, and has but little contractile power. It is, I conceive, a possible case, that the fibrine may separate imperfectly or not at all, in consequence of an augmented proportion of salts, which out of the body we know to be capable of suspending coagulation altogether. The continued use of alkaline remedies will probably tend to produce a like effect. Fibrine coagulates the more speedily in porportion as the circulating and nervous sys- tems become more feeble. The experiment has been repeatedly made with animals that are killed by bleeding, and the last por- tions of blood invariably coagulate soonest. “ The principle of the blood’s speedy con- cretion in debility is important in a curative point of view. The first natural check to hae- morrhage is known to be the formation of a clot on the mouth of the vessel. If the longer the hremorrhage the less had been the disposition to form such a clot, the wounded on the field of battle, and those injured by common accidents, who cannot promptly procure the aid of a surgeon, must inevitably have perished.”* One of the most remarkable and frequent de- viations from the normal condition of blood removed from the body by venesection, is the occurrence of the buffy coat, which is a layer of fibrine occupying the surface of the crassa- mentum. The blood, whilst circulating within its vessels, consists, as I have already remarked, of a fluid which I have elsewhere ventured to call liquor sanguinis, and of insoluble red par- ticles. These being in constant motion are uniformly diffused throughout this liquor ; but their specific gravity being much greater than that of the medium in which they are sus- pended, they have a tendency to gravitate when- ever that motion ceases. In healthy blood the fibrine coagulates so quickly that the red par- ticles have not time to subside, so as to leave any portion of the liquor entirely free from them. By protracted fluidity this result is effected ; the red particles do then gravitate to a greater or less depth before the liquor separates into two parts. A general coagulation of the fibrine at length occurs, and a clot is formed. That part of it through which the red particles had fallen becomes a layer of fibrine free from colour, and merely having some serum mecha- nically retained in its meshes, while the sub- jacent portion is of intense depth of shade, especially at the bottom, and of less than ordi- nary cohesion. In extreme cases, such an abundance of red particles reaches the bottom of the vessel that they are there found in a state of fluidity. The buffed layer sometimes assumes a cupped form, which is clearly owing to unequal contraction. The upper surface being freer from intervening red particles, con- tracts more powerfully than the under, and a concavity of the surface is the necessary con- sequence. Where, however, the contraction is weaker, the weight of the subjacent red clot, which is one and the same mass with the upper colourless portion, weighs this down, and keeps it in a horizontal position. The crassamentum of arterial as well as of venous blood has frequently been observed to exhibit a buffy coat. It is rarely seen in blood extracted by cupping-glasses, and never in that pressed from leeches. It occurs in the lower animals, and is observed as frequently in the horse as in the human subject ; indeed, from the quantity of blood usually drawn from that animal, it is still more strikingly apparent, being occasionally several inches thick. It has been denied that the cupped appearance is ever met with in the blood of the horse ; but if this be received into a sufficiently small vessel, it will be in some instances as complete as in blood taken from the human subject. There are va- rieties in the appearance of the buffed coat which it is worth while to notice. It is gene- rally of a firm uniform consistence, and of a light yellow or buff colour, whence its name. Sometimes, however, it is of a more spongy texture, and of a white or bluish, and more transparent hue. Two layers of buff are occa- sionally seen ; the upper soft or friable, the in- ferior more compact. “ There is a difference,” says Sir Gilbert Blane, “ in the appearance of the blood when sizy, perhaps not sufficiently insisted on by practical writers; for though there should even be a very thick buff, yet if the surface is flat, and the crassamentum tender, no great inflammation is indicated in com- parison of that state of the blood wherein the surface is cupped, the crassamentum contracted so as to form the appearance of a large pro- portion of serum, and where it feels firm and tenacious, though perhaps but thinly covered with buff.”* From the examination of several specimens of buffed blood, I was at one time led to be- lieve that its serum was always deficient in its due proportion of albumen; but this I have since found not to be the case, having met with blood thickly buffed, the serum of which at 60° Fahr. had a specific gravity of only T024, and with another specimen where the layer of fibrine was equally thick, of which, at the same temperature, the serum had a spe- cific gravity of 1-040. Dr. John Davy examined the specific gravity of buffed blood in eleven cases. In five of them in which the buffy coat was slight, the specific gravities were 1-047, 1-051, 1-054, 1-055, 1-054 ; in five others in which the buffy coat was moderately thick, the * Blane on the Diseases of Seamen, note to page 314. ' 6 Thackrah, p. 188. 2 e 2 4 20 BLOOD, MORBID CONDITIONS OF THE. specific gravities were 1-044, 1 038, 1-052, 1-056; and in one instance in which it was thick, the specific gravity was 1-057. Taking the mean gravity of healthy blood at 1-044, which 1 believe will be found correct, it would thus appear that the buffy coat is more frequent in blood above than below the mean weight; but it is also clear that it may exist in either state, and the number of experiments is not sufficient to lead to any conclusive result. De Haen, Hewson, and others have met with cavities in the crassamentum of buffed blood containing clear fluid (liquor sanguinis), which, on being evacuated several hours afterwards, separated into fibrine and serum. This fact is analogous to that of fluid blood having been found by Hewson in the heart of a dog thirteen hours after death, which blood, on being re- moved, coagulated soon after exposure to the air. A similar coagulation will occasionally take place in fluid blood taken from the human heart several hours after the extinction of life. The remote cause on which the occurrence of the buffy coat depends appears to be an increased action in the circulating system, de- pendent on increased nervous energy, and this is capable of being very speedily excited. Thus it has happened* that blood from the same orifice drawn into four cups has exhibited this appearance in the second or the third cup, and not in the first or last, the difference being plainly owing to a faintness felt at the com- mencement and termination of the venesection. Thus also the blood of healthy horses drawn immediately after a smart gallop while the cir- culation is powerful and rapid, will exhibit a buffy coat, while that previously abstracted will of course shew no such appearance. Scudamore, it is true, arrived at an opposite result in the case of a young man whom he bled, and after causing him to run two miles, bled again. Neither before nor after the race was the blood buffed, but it is obvious that such severe exercise after depletion would exhaust rather than augment the powers of the nervous and circulating systems. Accordingly he found the proportion of fibrine diminished in the blood last drawn, while the specific gravity of the serum was increased from 1-030 to 1-035, thus shewing how large a quantity of moisture must have been carried off by perspiration. The buffy coat, as might be anticipated from its cause, is usually found in connexion with those diseases and even conditions of health in which vascular action is preternaturally increased — in the active stages of peripneu- mony, in pleurisy, in inflammatory fever, scar- latina and the eruptive diseases generally, and very uniformly in acute rheumatism. It is also occasionally but not always met with in the blood of pregnant women, in persons of sanguine temperament and full habit, and those who resort to frequent bloodletting ; in chronic rheumatism, gout, enlargement of the heart, and other affections where no inflammation exists. On the other hand, it may be absent even in the most intense inflammation; for the * See Hewson on the blood, vol. i. p. 82 et seq. circulation may be so overcharged either actually or relatively, or the nervous power so oppressed, that the requisite degree of propul- sive force is not exerted by the heart and arteries, nor the vital energy on which slow coagulation depends imparted to the blood. In such instances the buffed coat generally appears on a second or third repetition of venesection. Louis found the blood covered by a firm thick buff at each bleeding in nineteen cases of fatal peripneumony out of twenty-four. In two-fifths it was cupped. In fifty-one out of fifty-seven cases of recovery the blood was buffed, and in twenty-three cupped. In nine tenths of rheumatic patients the buff was firm and thick. The form of the receiving vessel, the degree of motion to which it is subjected, and the size of the orifice in the vein, materially in- fluence the phenomenon. M. Belhomme, the experimenter under M. Recamier, has made aboutone hundred and fifty experiments onblood drawn in health and disease. He has come to the conclusion that a medium orifice one line in the vein, a strong, rapid, and continuous jet in the form of an arch, and a narrow vessel for the reception of the blood, are the external circumstances most favourable for producing the buffy coat.* Fibrine is more abundant in buffed than in healthy blood. Dr. Davy, from his observa- tions, infers that there is no constant relation between the appearance of this covering and the proportion of fibrine in the crassamentum, yet his own tabular report contradicts him. “ From all the examinations we have made,” says Thackrah, who has made many experiments to determine this point, “ I infer without hesita- tion that buffed blood contains a considerably greater proportion of fibrine than healthy blood.” This is a fact of much interest and importance, for as very slight aud sudden causes may give rise to the formation of a buffed coat, we are thence led to infer that the quantity of insoluble matter which separates from liquor sanguinis by coagulation is variable, and that there is so far reason to believe that fibrine and albumen are principles convertible into each other. In connection with the appearances depen- dent upon the slow coagulation of fibrine, I may here notice the occurrence of what have been termed polypi, or more recently and cor- rectly, false polypi in the heart and larger ves- sels. These are so common, that, as Haller ob- serves, scarcely a body is met with in which they do not exist. They are found in both auricles and both ventricles and in the larger arteries and veins, as well of the trunk as of the extremities. They consist essentially of fibrme, and partake of all the varieties that are obser- vable in the fibrinous coat of buffed blood. Haller affirms, as usual, supporting his opinion by numerous authorities, that these have been known to exist even during life, not only in ! * See also Med.-Chir. Trans, vol. xvi. p. 296, note. BLOOD, MORBID CONDITIONS OF THE. man but in the larger warm-blooded animals, and adverts to a disease, la gourme , common among horses, which arises from a coagulation of the blood in the large arteries and veins and in the heart. Thackrah is of the same opinion, and Dr. George Burrows, who has made the changes which take place in the blood when its circulation is stopped in the living body, the subject of the Croonian Lectures of the present year, states that “ there can be but little doubt that in some cases the blood coa- gulates in the heart during life. The firmness of the clots found in its cavities after death— their close adhesion to the lining of the heart — the presence of various fluids in the centre of these clots — the occasional organization of the coagulated masses, and their partial conversion into structures which are similar to new growths in other parts of the body — are facts which lead us to the conviction that the blood often coagulates in the heart long prior to death." That such coagulation may take place during life I am willing to admit, but I am by no means led to the conviction that such an event often occurs. To the formation of a firm coa- gulum I am persuaded that rest is absolutely necessary, and I must consider it as a very rare occurrence that the contents of the cavities of the heart should be at rest during life. The usual appearance of false polypi is such as would take place in blood that coagulated very slowly, ■whether in or out of the body. Mr. Thackrah has proved that the blood when at rest coagu- lates much more slowly in living vessels, among which his experiments include vessels recently removed from living animals,* than in those that are dead ; and I conceive that the human body, long after the heart has ceased to beat, and when it is, in the common accepta- tion of the term, dead, is still endowed, like the vessel just separated from the living animal, with a sufficient share of vitality to keep the blood which is in the heart and larger vessels in a fluid state, and thus to permit its coagula- tion to take place at length far more slowly than under ordinary circumstances. The fol- lowing fact will perhaps be considered to have some interest as bearing on this point. I was engaged in the post-mortem examination of a gentleman who had died apoplectic from soft- ening of the brain, which had given rise to effu- sion into the ventricles and under the pia mater; and being desirous of examining the fluid thus effused, I collected it with a clean sponge, by successively dipping this into the ventricles, and squeezing the fluid into a small cup. With a view to increase the quantity, I used the sponge also in soaking up some of the same fluid which had been caught in the calvaria, but was somewhat tinged with red particles. The cup was set apart till the conclusion of the ex- amination, which lasted an hour and a half, when, on proceeding to transfer its contents to a phial, I was not a little surprised to find that a bulky clot of a rose colour and perfectly dis- tinct was formed in the fluid. The examina- tion in question took place twenty -two hours lhackrah on the Blood, p. 85, expt. lii. & liii. 421 after death. As long as galvanism will stimu- late the muscular structures to convulsive movement, so long at least may we conceive such a portion of vitality to remain as will in- fluence the state of the blood. The fluid thus circumstanced exhibits the same phenomena, though in a more marked degree, which we ob- serve in buffed blood out of the body. The red particles subside and leave the liquor san- guinis free from colour. In due time this separates into fibrine and serum : the coagula- tion takes place uniformly and universally, and in the larger cavities and vessels a colourless clot is left, which is moulded into their exact shape. The serum drains off, and washes away the red particles into the more depending and distant vessels. Thus it is that where we find polypi in the heart, we often find the descend- ing aorta and the vena cava inferior filled with fluid, in which there is no fibrine at all. The firmness of a polypus affords no proof that it existed during life, or rather before respiration and circulation had ceased ; for what can be firmer than the buffed coat which we often see formed out of the body ? Its close adhesion to the lining of the heart is generally in appearance only, and is occasioned by the exactness with which it has adapted itself to every cavity and sinus, and enveloped every column, and the force with which the heart itself has contracted upon it. The presence of fluid in the centre, however difficult to account for, is also occa- sionally met with in the crassamentum of blood abstracted from the arm ■* and even purulent matter, said to be found in false polypi, is oc- casionally formed out of the body. “ In some rare cases I have seen the fibrine,” says Andral, “ assume a different aspect. The blood had no clot, and instead of it we observed at the bottom of the basin a kind of homogeneous purulent matter of a deep brown or dirty grey colour, and rather resembling sanies than blood.” With regard to the existence of organization, it seems to me that sufficient distinction has not usually been made between those cases w'here the lining membrane of the cavities of the heart or vessels has been ruptured, and which in so far are of the character of aneu- rism, and those where that membrane has re- mained entire. I am willing to admit that where there is a lesion of surface, adventitious growths will readily spring from it; but their substance is furnished from the structure be- neath, and not from the circulating fluid. As an instance, I may mention the case of a youth who, being in perfect health, received a sudden shock from the unexpected discharge of a pistol close to his ear. He immediately felt conscious that something had given way in his heart, and from that hour suffered from palpitation, occa- sional syncope, with the usual symptoms of obstructed circulation, and died of general dropsy at the end of eighteen months. On ex- amination after death the mitral valve was found to be obstructed by a fringe of excre- scences, originating no doubt from a rupture of * See Hewson, p. 69 and 70. 422 BLOOD, MORBID CONDITIONS OF THE. the valve itself, which had taken place at the time of the sudden surprise. This kind of growth, as well as that winch is formed on the inflamed surface in endocarditis, lias a suffi- ciently evident origin. We can also readily account for organized structures arising from aneurisms of the heart or arteries, accidental wounds of the latter vessels, ruptures of their inner membrane by ligatures, or its destruction by inflammation. I can, however, imagine nothing more unlikely than that an insulated mass of fibrine owing its origin to the mere coagulation of the blood from rest, and there- fore only by gravitation brought in contact with the sides of the vessel which may contain it, should assume an organized structure, and that, too, at a time when the powers of life are so much enfeebled that the heart itself ceases to perform its office. I have looked carefully for unequivocal signs of vitality in these false polypi, and I confess that 1 have never been able to satisfy myself of its existence. The albumen has not been demonstrated to be subject to alteration in quality. Its distin- guishing characteristic of coagulating by heat is preserved even after it has become in the high- est degree offensive from putridity.'*' It may be excessive or defective in proportion, and M. Gendrin has shewn that under inflammation of the system, the serum contains twice as much albumen as in the healthy state. Andral affirms that even by the touch, we may, from its vis- cidity, recognise serum that is surcharged with albumen. Its specific gravity, however, of which the French writers seem to take little note, would be a far better guide, and would indicate alike the defect as the excess of this principle. M. Gendrin has occasionally ob- served a mucous layer either at the bottom of the serum, or suspended in it. This is, in all probability, a minute portion of fibrine se- parating in the form of a flocculent cloud ; for serum is capable of holding a certain portion of fibrine in solution, which after a time separates from it. This was first proved by Dr. Dowler,f who, on pressing the buffed coat of blood, ex- tracted from it a liquid serum, which, on being allowed to rest for some time, exhibited signs of coagulation. With regard to the relative proportions of the serum and the clot, I have proved elsewhere J that this depends much on the vessel into which the blood is received. I shall show experimentally, however, in treating of diseased kidney, that an opposite state to that above alluded to as occurring, according to M. Gendrin, in inflammation, takes place under certain forms of disease where albumen is passing out of the system by the urinary pas- sages. Thackrah lays it down as a law, to which he has found no exception, that in all cases in which the proportion of fibrine is con- siderably above the normal standard, the solid matter in the serum is below it. He cites ten examples in proof of his assertion, and puts it * See a paper by M. Vauquelin, in the 16th vol. of the Ann. de Cliimie, new series, p. 363. t See Med.-Chir. Trans, vol. xii. p. 89. I Med.-Chir. Trans, vol. xvi. p. 296. as a question whether we may not hence sup- pose that the albumen is taken from the serum for the formation of fibrine ? The fact itself, however, requires confirmation, being in direct opposition to M. Gendrin’s statement, that the proportion of albumen is greatly increased in an inflammatory condition of the system, winch is precisely that condition when in general we find buffed blood, and therefore, according to Thackrah, an increase in the proportion of fibrine. The hrematosine is the least destructible of all the elements of the blood, retaining its quali- ties in that fluid after having been kept for several years. It is liable to much variety in its proportion, and in all those diseases and states of system in which hemorrhages occur, it gradually diminishes, at least to a certain point, in proportion to their extent and duration. In what part of the system the red particles are elaborated remains for the present a mys- tery. That they are reproduced slowly is manifested by the fact that those who have suf- fered large losses of blood, remain exsanguine for many months or even years afterwards. The same conclusion may also be deduced from the circumstance that women have a smaller proportion of red particles than men, the difference having been shewn by M. Le- canu to be attributable to the monthly loss which they habitually experience. Besides change of colour, to which the red particles are liable during disease, and which, among other causes, may arise from an altered proportion in the saline matters contained in the blood, they also appear to undergo structural alterations. I n fevers, in malignant diseases, in sea-scurvy, in cases of poisoning, and of asphyxia from light- ning, a permanently liquid state of the blood occurs, wherein the colouring matter of the globules appears to have lost its character of insolubility in the serum, and to be capable of percolating those tissues which are otherwise il destined to contain it. Passive hemorrhages, ij petechioe,and ecchymoses, are the results during life; and, after death, a stained condition of the lining membrane of the heart, the arteries, and veins, which has often been mistaken for va.s- cular congestion of these parts. The oil or unctuous soft solid which is now ascertained to be one of the constituents of healthy blood,* is liable to morbid increase f under various forms of disease. Morgagni cites two cases of malignant fever in which the serum was milky. Hewson, besides enumerating in- stances to be met with in authors, gives three cases sent him by medical friends : one of Jj amenorrlioea with dyspepsia and vicarious dis- charge of blood by vomit and stool ; another of violent and continued epistaxis, and a third of dyspepsia with slight asthma. In all three cases there were symptoms of plethora ; but milky serum is by no means necessarily connected with this state. The most marked instance that I have met with was in a case of diabetes, where bleeding was several times repeated at long in- tervals, and on each occasion the same morbid * Med.-Chir. Trans, vol. xvi. p. 46. 423 BLOOD, MORBID CONDITIONS OF THE. condition of serum was observed. This was quite opaque, and nearly as white as milk ; and on standing for a few hours, a film of mattter re- sembling cream covered the surface. The clot could not be seen when it was scarcely a tenth of an inch beneath the surface. It had a firm, very thick, white coat of fibrine, and the red particles were almost diffluent beneath. The patient, a female, could not be called ple- thoric, having been the subject of her emaci- ating complaint more than a year and a half. Milky serum, though of a far less marked cha- racter, having occurred in persons who have been bled shortly after making a hearty meal, the notion has been entertained that it is owing to the passage of liquid chyle into the circu- lation. This was Haller’s opinion, while others have attributed its appearance to admixture of fat. To the former notion it may be objected, that whereas it is certain that the milky appear- ance of serum is owing to the presence of oily particles, it is very doubtful, from the discord- ant opinions of eminent chemists, whether the chyle contains more oily matter than the blood itself. Berzelius, indeed, makes its solid part to consist of more than twenty-one per cent, of fat, and Raspail considers it as differing little from milk. Prout, however, whose analysis is adopted by Turner, only admits an unappre- ciable trace of oily matter in chyle, and makes its composition differ little from blood ex- cept as respects the absence of red particles. In milky serum the oil exists in superabun- dance at the expense of the albumen, which, in all the specimens I have examined, has been remarkably deficient in proportion, its specific gravity varying from 1-019 to 1-024. This cir- cumstance naturally leads to a question whether this oil may not owe its origin to some chemical change in the albumen itself, of which it seems to supply the place. The ‘ remarkable blood ’ described by M. Caventou,* and alluded to by M. Raspail, f which was evidently nothing more than blood with milky serum, affords ad- ditional ground for supposing that such a change takes place. “ This blood issuing from the vein was turbid, of a pale dirty red colour, and became marled and of a whitish red as it cooled in the basin, and some drops which fell on the floor assumed this colour in a few seconds, and looked like drops of chocolate made with milk. After half an houracoagulum of moderate size was formed in it, which floated in a large quantity of a white opaque fluid ex- actly like milk.” Raspail, who had evidently never seen a marked example of milky blood, gives the following fanciful explanation of the appearance. “ Under the influence, or in the absence of one of the causes which together produce the circulation, an acid had been formed, which, saturating the alkaline men- struum of the albumen, had caused it to coagu- late. Now this irregular coagulation could not take place without disguising the colour of the olood and rendering it rose-coloured, while it would give the serum the appearance of milk.” If the albumen had really been coagulated by ■Annales de Olnmie. vol. xxxix. p. 288. t Sect. 941. an acid, a distinct clot would not have been formed by it, but a curdled precipitate ; nor would the serum have borne any resemblance to milk. But what is important as confirming my view respecting the conversion mentioned above, M. Caventou, to his great astonishment, could not find any albumen in the milky serum here described. The probability of this change is heightened by the consideration that some- thing analogous must necessarily occur in the formation of true milk, the oil of which, when separated as butter and melted to clarify it from curd, remarkably resembles the oil of milky serum. The attention of pathologists to the salts of the blood, which, considering the visible effects they produce on this fluid, had been strangely neglected, has of late years been roused by the observations of Dr. Stevens, who certainly may claim the merit of having advanced our know- ledge of facts on this subject. It appears that in the last stages of tropical fevers the saline ingredients of the blood are so much diminished that they are no longer capable of giving a red colour to the hamatosine. The black blood that is found in the heart after death from either the climate fever or the African typhus, remains black even in an atmosphere of pure oxygen, but it instantly changes colour when we add it to a clear fluid that contains even a small portion of any neutral salt. Nor is it in fever alone that this deficiency of salts is observed. Dr. O’Shaughnessy has shewn that it likewise exists in malignant cholera, and it is probable that in sea-scurvy, and in those analogous dis- eases produced by want and unwholesome nourishment, a similar state occurs. The saline matters may be in excess as well as in defect, and this is marked by excitement of the circulating system, and either local de- terminations or general febrile disturbance. The stimulant effect of saline springs has been known time out of mind, while the thirst and heat pro- duced by the too copious use of common salt is in every body’s experience. If we couple these facts with the certainty that the neutral salts will pass unchanged through the circu- lation so as to admit of detection in the urine, we may infer that their superabundance in the bood is not only a possible, but, in all proba- bility, a frequent occurrence. They are occa- sionally fouud after death deposited in a crys- talized form, as was observed by Sir Everard Home, who, in dissecting an aneurismal tumour, found a mass of crystals, which were analyzed by Mr. Faraday, and are stated to have been salts usually met with in the blood. Having thus concluded such remarks as the present state of our knowledge has enabled me to offer respecting the morbid changes which take place in the separate constituents of the blood, I now proceed to notice some of the more important diseases in which those changes have been observed to occur. Inflammation. — The usual appearances of blood in inflammatory diseases have already been described in treating of the buffed coat. The crassamentum is commonly supposed to be increased in bulk, but this is somewhat doubtful; and indeed it so much depends upon 424 BLOOD, MORBID CONDITIONS OF THE. extraneous circumstances, such as the form of the vessel in which the blood is received, the time allowed for the contraction of the clot, which it is well known goes on for many hours, and even the quantity abstracted, that no accu- rate deduction can be drawn from its appear- ance. The collection of the fibrine itself is easily effected, and it will thus be perceived that, under inflammation, it is more abundant than in the normal state. Scudamore has made numerous experiments on the relative quantity of fibrine contained in healthy and diseased cras- samentum, and the following short list selected from them satisfactorily establishes this fact. In 1000 grs. of clot as deduced from eight specimens of healthy blood, average of dry fibrine 3-53 grs. Maximum 4-43, minimum 2'37 Slight pleurisy, blood slightly buffed 7-05 Pain in the side, ditto 11-37 Cough . „ 7-24 Acute gout, blood not buffed, firm texture 5’88 Disease not named, clot compact, buffed, and cupped 12'41 Ditto 13-73 Average 9-62 Mr. Jennings, in his report on the blood in the Transactions of the Provincial Medical As- sociation for 1834, likewise gives a table, the result of which is, that in eight cases of in- flammation, the proportion of fibrine in the blood was increased from 2-1, which is Le- eanu’s standard of health, to 9, 8, 11, 6, 5-3, 7, 6-9, 7 ; average 7-525, and that the alkaline salts were diminished from 8'37, the healthy standard, to 4'9, 4‘8, 5-1, 4-3, 4-2, 4-4, 4, 5-6; average 4-61. Among all the varieties of inflammation it is in acute rheumatism where we find the blood most decidedly loaded with fibrine. Owing to the powerful action of the heart and arteries, it is intensely arterial in character, and sometimes issues from the vein with a distinct pulsation. Fever. — In those fevers which arise from marsh miasmata or from contagion, it is an opinion held by Dr. Stevens, and supported at great length in his work on the blood, that a diseased condition of that fluid is the first in the train of symptoms which occur, and the immediate cause of those which follow. The blood itself, says Dr. Stevens, is both black and diseased even before the attack. During the cold stage it is very dark. When first drawn it has a peculiar smell, and coagulates almost invariably without any crust. There are black spots on the surface of the crassamentum, the coagulum is so soft that it can easily be separated by the fingers, and during its forma- tion a large quantity of the black colouring matter falls to the bottom of the cup. In the hot stage it becomes more red, and, in some cases, it is even florid for a time, but during the remission it is darker in colour than the blood of health, and decidedly diseased in all its properties. In milder cases, the blood which is drawn may coagulate without a crust on the surface ; but in the more severe forms of this fever, when the blood was drawn at an advanced period of the disease, a part of the albumen coagulated on the surface of the fibrine, and formed a diseased mass, which in appearance had a greater resemblance to oatmeal gruel than to blood drawn from a healthy person. The serum which separated was also diseased ; it had a brownish colour, and in some cases an oily appearance, which is never met with in the clear serum of healthy blood. In the climate or seasoning fever of the West Indies, which is not considered contagious, but a fever of excitement, the blood drawn in the first stage flows from the vein with great force, but is neither cupped nor buffed. It is so florid, being charged with salts which ought to have been removed by the organs of secretion, that it resembles arterial blood. The fibrine coagu- lates firmly, and in some cases the serum which separates from it has a bright arterial colour, the colouring matter being not merely diffused through, but combined with the serum. During the progress of this kind of fever the blood loses a large proportion of its fibrine and albumen, and becomes so thin that it oozes from the mu- cous membranes without any abrasion of sur- face, and in the last stage turns quite black from a diminution in the proportion of its salts. Such are the appearances which the blood presents in the more severe fevers of hot cli- mates. In this country, at the commencement or stage of depression the blood is dark and tarry, coagulates quickly, and forms a large clot with but little serum. As the stage of excitement advances, the blood becomes thinner and more florid, and flows more freely. Coa- gulation takes place more slowly, and a bufiy crust is frequently formed on the surface of the clot. In the latter stage, when the powers are giving way, the blood becomes thinner, darker, and more dissolved. It scarcely coa- gulates at all, and is deficient in saline matter, and probably also in fibrine, thus nearly re- sembling menstrual blood, or the fluid mixture of serum and red particles, already mentioned as often found in the larger vessels after death. Such are the alterations which the blood usually undergoes in the different stages of simple con- tinued fever, but in its more malignant forms, as in typhus, the blood is generally very watery, even from the commencement. As the disease advances, it gradually loses its power of coagu- lation, and in the last stage seems almost en- tirely deprived of fibrine. Magendie has artificially produced an analo- gous state of blood by injecting putrid liquids into the veins of animals, and the speedily fata! disease which he thus caused had a strong ana- logy with typhous fever.'* To Dr. Stevens belongs the merit of having especially directed general attention to the cir- cumstance that the saline matter of the blood gradually disappears in the progress of fever, and is almost entirely lost in its last stage. This he ascertained by direct experiment,! and his facts have since been confirmed by Jennings, who in the interesting report already alluded to, gives an analysis of the blood in six cases of continued fever, in which the * Journal de Physiologie, tom. iii. p. 83. t On the Blood, &c. page 209. BLOOD, MORBID CONDITIONS OF THE. alkaline salts were found diminished in the fol- lowing proportions : — In healthy serum, according to Lecanu, salts 8T0 In the serum of a male, aged 31, first day of fever, salts 4 Ditto ditto aged 34, first day of fever, salts 5 Ditto female, aged 14, fourth day of fever, salts 4-2 Average of three other cases 4'4 Scurvy. — It seems to be the universal opi- nion of those who have seen and written on scurvy, that it owes its origin to a morbid change in the fluids, and especially in the blood; and even those who have been the most strenuous opposers of the humoral pathology in general, among the most celebrated of whom we may reckon Willis, Hoffmann, Boerhaave, Cullen, and Sir John Pringle, have made an exception in favour of this disease. Notwith- standing this general belief there has been no attempt up to the present time at any chemical examination of the properties of scorbutic blood, and we have only the general obser- vation made by the surgeons of Lord Anson’s expedition, (Messrs. Ettrick and Allen,) that in the beginning of the disease it flows from the arm in different shades of light and dark streaks ; that as this advances, it runs thin and black, and after standing turns thick and of a dark muddy colour, the surface in many places being of a greenish hue, without any regular separation of its parts ; that in the third de- gree of the disease it is as black as ink, and though kept stirring in the vessel for many hours, its fibrous parts have only the appear- ance of wool or hair floating in a muddy sub- stance; and that in dissected bodies the blood in the veins is so fluid that by cutting any con- siderable branch, the part to which it belongs may be emptied of its black and yellow liquor, the extravasated blood being precisely of the same kind. The prevalence of scurvy where there has been a long-continued use of salted provisions has given rise to the supposition* that the salt itself actually finds its way into the circulation, and acts as it is known to act on blood out of the body by preventing its coagulation. This, however, is very evidently not the case, first, because salt provisions are not necessary to its production, since scurvy has often made its appearance where no salt provisions were used; as, for instance, in the Milbank Penitentiary in 1819, where the diet consisted of pease, barley soup, and brown bread ; and, secondly, because the appearance of the blood, especially as the disease ad- vances, is exactly the reverse of what it would be on the addition of salt, which, instead of making it black, and causing it on standing f° become thick, muddy, and of a greenish pue, would impart to it a fine scarlet tint that ifvould remain permanent until it began to nitrefy. Since the modern advances in ani- nal chemistry, opportunities for examining the ,'lood in true scurvy have been very rare ; and * Jennins’s Report. 425 it is therefore the more to be regretted that Drs. Latham and Roget, philosophers every way so competent to determine the precise morbid changes which it undergoes, did not, when they had it in their power, make a particular ex- amination of it. Venesection, it seems, was practised at the Penitentiary in a few cases, but nothing is stated respecting the appearance which the blood assumed.* The description of Lord Anson’s surgeons does not by any means apply to the blood which is found in purpura hasmorrhagiea, a complaint that was, prior to the appearance of Dr. Bateman’s work on diseases of the skin, generally considered closely allied to scurvy. In two cases of pur- pura related by Dr. Parry, | of Bath, blood drawn from the arm exhibited a tenacious contracted coagulum covered with a thick coat of lymph ; and in one instance which occurred under my care, where the patient, a man of forty-five years of age, had most of the sym- ptoms of sea-scurvy, such as general cachexia, with anasarca of the lower limbs, great depres- sion of spirits and prostration of strength, ex- tensive ecchymosis on the trunk and the ex- tremities, fetid breath and extravasations of blood from the gums, the stomach, and the bowels, as well as from a large foul ulcer on the leg; a copious venesection demonstrated that the blood had not in any degree lost its crasis, the crassamentum being covered with a thick buffy coat, and having as much firmness as is usual under the existence of such a state. It is proper to observe that Lind’s description of the blood in scurvy differs from that of Lord Anson’s surgeons, as he found it generally either natural or buffed. J Jaundice. — In jaundice the blood, both arterial and venous, is tinged with bile, and this is apparent not only in the serum, but still more strikingly in the crassamentum, provided it be covered with a buffed surface. If this be removed and dried in a state of tension, it exhibits a deep yellow hue, particularly when viewed by transmitted light. Although the bile is thus rendered very visible in jaundiced blood, yet, owing to its combination with albumen, which defends it from the action of acids, it is difficult of de- tection by chemical re-agents, so that many chemists of eminence have sought in vain to ascertain its presence. Lassaigne, however, succeeded in demonstrating that the colourino- matter of the bile is really to be found in the circulation, and Berzelius tells us that Collard and Martigny pretend to have discovered even the resin of bile in jaundiced blood. M. Le- canu has more recently confirmed these facts and Mr. Kane has verified his results.§ To the medical inquirer who does not follow the minutise of animal chemistry, the identity of the colouring matter in the serum of jaundiced * Account of the Disease lately prevalent at the General Penitentiary, by P.M. Latham,M.D. 1823 p. 39. t Edinburgh Medical and Surgical Journal, vol. v. p. 7. I Lind on Scurvy, page 512. $ Dublin Journal, vol. ii. p. 346. 426 BLOOD, MORBID CONDITIONS OF THE. blood with that of the bile itself will be ren- dered sufficiently evident by adding to it an equal quantity of sulphuric acid diluted with twice its bulk of water. The serum will thus change its yellow hue for the characteristic green colour of acid bile. Experimentalists have failed in producing this effect, being pro- bably misled by having found that the small proportion of acid which is required to strike a green colour with urine charged with bile, produces no such effect when added to jaun- diced serum. Disease of the kidney. — In those organic diseases of the kidney which are characterized by anasarca and the passing of urine coagu- lable by heat and acids, the albumen of the blood is more or less deficient in proportion; and this is marked by a corresponding dimi- nution in the specific gravity of the serum. In a letter to Dr. Bright, published in the first volume of that author’s Reports of Medical Cases, page 83, Dr. Bostock states, in re- ference to the blood in these diseases, that the crassamentum was for the most part co- vered with a thick buffy coat, and was gene- rally of a firm consistence. The appearance of the serum was more varied. It was occa- sionally turbid, and upon standing for twenty- four hours a white creamy substance rose to the surface ; but no proper oily matter could be detected in it. On exposing it to heat, it coagulated in the ordinary manner, except that the coagulum seemed to contain an unusual number of cells, and that a greater quantity of serosity separated from it. “ I think I may venture to say,” adds the writer, u that the serum generally in these cases contained less albumen than in health, although I am not able to state precisely the amount of this dif- ference. The serosity which drained from the coagulated albumen on being evaporated was found to consist in part of an animal matter possessing peculiar properties which seemed to approach to those of urea; it was partially soluble in alcohol, and was acted upon in a somewhat similar manner by nitric acid.” The above remarks were made on specimens of blood furnished from time to time by Dr. Bright. The number is not stated, nor was the specific gravity of the serum taken. Dr. Bos- tock gives a case, however, (page 85,) where, after stating that the crassamentum was re- markably buffed and cupped, he adds, “ The serum was also worthy of attention, as taken in connexion with the state of the other fluids. Its specific gravity was almost exactly the same with that of the urine, being no more than 1-013, which I believe to be lower than had ever occurred to me in the numerous expe- riments which I have made upon this sub- stance. We have here, therefore, an example of blood exhibiting a very great deficiency of albumen, at the same time that we observe the mode in which it passes off from the system by means of the kidney, while this organ has its appropriate office of secreting urea nearly suspended. I regret that I did not attend particularly to the specific gravity of the other specimens of dropsical serum which you sent me. From some incidental remarks in my notes, I suspect that its specific gravity would have been found lower than ordinary ; but it is a circumstance which I shall be anxious to ascertain when any opportunity occurs.” This suspicion is completely confirmed by other cases that have occurred to myself, in which the fact was also established beyond doubt, that the animal matter found by Dr. Bostock in the serosity was not merely an approach to urea, but that principle itself possessing all its usual characters. The following may serve as an example of light serum. William Squires, aged 54, labouring under or- ganic disease of the kidneys and chronic bron- chites with anasarca, had for many months voided urine which coagulated on the appli- cation of heat or the addition of nitric acid. The specific gravity of his blood at 88Fahr.was 1041 Do. Serum at 68 1-021 healthy standard 1 030. This blood contained in 1000 parts, 3-845 fibrine : healthy standard 2- 1 to 3 56 55-000 albumen : healthy standard 65 to 69 In this case 100 grains of urine contained 6'666 albumen. There was consequently nearly one eighth as much albumen in the urine as in the blood, and the patient lost as much of that con- stituent daily, as if he had been bled to the extent of four ounces. The following cases are from notes with which I have been favoured by Dr. G. II. Barlow, who has devoted much attention to the exami- nation of the blood and urine in this disease. No. 1. A patient affected with general ana- sarca— Urine copious, clear, pale, coagulable by heat and nitric acid : specific gravity 1-011. Blood cupped and buffed, serum milky : spe- cific gravity 1-019. No. 2. Man aged 48, anasarcous — Urine dingy brown, natural in quantity, acid, coagula- ble ; specific gravity 1-017, contained 4^ per cent, of albumen. Serum of the blood, specific gravity 1-013. No. 3. A man who was found on post-ir.or- tem examination to have granulated kidneys. Urine reddish brown, very scanty, coagulable; S specific gravity 1-008. Blood cupped and buf- fed ; specific gravity (of the whole blood) 1'037. In my paper on the blood in the Medico- Chirurgical Transactions, vol.xvi. I have stated the case of a woman forty-eight years of age, who for ten weeks had complained of pains in her loins, anasarcous swelling of her legs, and ge- neral debility, and who passed urine which was in a high degree coagulable. 1 examined her blood, and found it to contain 0"43 percent. of fibrine, and only 1-61 per cent, of albumen. The specific gravity of the serum was 1'020 at 60° Fahr. In that paper I have also observed that in several cases marked by coagulable urine, I have examined the specific gravity of serum with which Dr. Bright has fur- nished me, and have always found it much below the healthy standard. It is not, however, in this complaint ex- 427 BLOOD, MORBID CONDITIONS OF TIIE. clusively that the albumen of the blood will be found deficient in proportion. In other dropsical affections it will sometimes happen that a proportion of albumen more than equi- valent to the fibrine effused will disappear from the circulation. Eleven days after tap- ping a young woman, in whom ascites had supervened upon rheumatic affection of the heart, she was observed to be filling again very fast. A few ounces of blood were taken from the arm, and this blood was found to contain 0-319 per cent, of fibrine, and only 3-51 per cent, of albumen. Her serum had a specific gravity of 1-023. The experiments of MM. Prevostand Dumas (Annales de Chimie, vol. xxiii.) which have since been repeated by Gmelin and Tiedemann (Poggendorff’s Annalen), prove satisfactorily that urea exists in the blood after the kidneys have been extirpated, and consequently that it is not formed, but merely abstracted by those organs. So long, however, as the kidneys act, we cannot expect to find it, since it is removed from the circulation as fast as it is formed, and never exists in any considerable quantity. In these cases of diseased kidney a result analogous to that which follows extirpation occurs, for while that organ is permitting albu- men to pass through it unchanged, the urea which it should separate is very generally if not always found in the blood. This I have proved in repeated instances, and it is now so generally admitted from the experiments of Prout, Chris- tison, and others, that it is scarcely worth while to cite cases. Dr. Bright, vol. ii. p. 447, al- ludes to several specimens of serum from patients under this disease, which he had sent me for examination, in some of which I did, and in others I could not detect urea. In one very remarkable instance of a young woman, the albuminous state of whose urine constantly existed for above three years, the urine con- tained less than one-third of the normal pro- portion of urea, while about one per cent, of albumen supplied the deficiency. The serum of the blood was, as I have already remarked to be usual in this disease, of very low specific gravity, being only 1-021. The quantity of al- bumen in 1000 grains amounted, after careful drymg, to only 50 grains instead of 78 (Le- eanu’s healthy standard), and it contained fully as much urea as the urine itself, the 1000 grains yielding nearly 1 5 grains of that principle. It may not be out of place here to observe, that in this disease not only does the blood it- self contain urea, but all those effusions also which are formed from it, and which take place m the different serous cavities. I have repeat- edly detected urea in these cases in the serous effusion into the ventricles of the brain ; and Dr. Barlow found it in one case, 1st, in abun- dance in the ventricles of the brain ; 2dly, scantily in the effusion into the pleura and peri- cardium ; and 3dly, in [abundance in the peri- toneum. In a second case of a similar nature area was obtained in abundance from the fluid ,ff the pericardium. In a third the effusion 'ollected after death from the pleura of a man vho had suffered from general dropsy and mot- tled kidney, yielded a very satisfactory specimen of urea. I have dwelt at some length on this subject, as it is only of late years that the attention of the medical world has been drawn to it through the writings of Dr. Bright, and still more re- cently that the morbid changes presented in the blood have been investigated. Diabetes. — In this complaint the blood un- questionably undergoes some material change, although its nature has not hitherto been very successfully investigated. This may be inferred from the great length of time during which it is capable of resisting putrefaction, a circumstance first noticed by Rollo, and which, though doubted by some authors, I have had oppor- tunities of confirming in several instances. Nicolas and Gieudeville* have observed that it contains an increase of serum and very little fibrine, but this is not borne out by my own experience as deduced from many specimens of diabetic blood which I have examined; neither can its antiseptic qualities be attributed to any deficiency in the proportion of azote, for Dr. Prout, who has made accurate experiments to determine this point, has found it not to differ in this respect from the standard of health. The most eminent chemists both abroad and in this country have endeavoured in vain to de- tect sugar in diabetic blood. Dr. Wollaston ascertained that the smallest portion of saccha- rine matter added to serum previously to its coagulation by heat, prevents the subsequent crystallization of the salts it contains, yet that in diabetic serum those salts crystallized with the same facility as in that procured from a person in health. The same reasoning as that which has been adduced to prove that urea may be formed in the blood, although it is not to be detected there while the kidneys perform their office, will also apply to the existence of sugar in the blood of those affected with this disease. I am not aware that the arterial blood has been made the subject of experiment, and yet it is possible that it might exist in the arteries alone, for we have only to suppose it to enter the cir- culation with the chyle, and after having been carried through the lungs, the left cavities of the heart, and the aorta, to be again withdrawn from the circulation by the kidneys. I do not pre- tend, however, that this supposition carries with it any degree of probability. Cholera .- — There is no disease in which the blood undergoes more remarkable changes than in malignant cholera; not indeed in the in- cipient stage, as affirmed by Dr. Stevens, but in direct proportion to the intensity and duration of the collapse. In appearance it is thick and dark, bearing a strong resemblance to treacle or tar. It is of high specific gravity, the serum varying from 1 040 to 1-045 at 60 Fahr.; and according to M. Lecanu, the solid matter which it contains is sometimes double that of the healthy proportion. Most of its physical cha- racters are satisfactorily accounted for by its analysis, which has been accurately made by several eminent chemists, among whom we may * .dnnalcs de Chimie, vol. xliv. p. 69. 428 BLOOD, MORBID CONDITIONS OF THE. mention Dr. Turner, M. Lecanu, and Dr. O’Shaughnessy. Cholera blood, according to these authorities, contains less water and more albumen and hsematosine than healthy blood, and its salts are in unusually small quantity, or almost entirely wanting. Dr. O’Shaughnessy, who has detected urea in cholera blood, states that the summary of his experiments denotes a great but variable deficiency of water in the blood of four malignant cholera cases ; a total absence of carbonate of soda in two ; its occur- rence in an almost infinitessimally small propor- tion in one ; and a remarkable diminution of the other saline ingredients : lastly, the micro- scopic structure of the blood and its capability of aeration are shewn to be preserved. The cause of the dark colour of the blood in cholera is a point which vve are told by Dr. Turner is by no means decided. Dr. Thomson and Dr. O’Shaughnessy are at variance on the question of its susceptibility of arterialization. Dr. Stevens rather unphilosophically makes its dark colour to depend primarily on the poi- sonous cause of contagion, yet attributes it also to a deficiency in the proportion of saline matter. It is probably not owing to either of these causes, but to a defective circulation through the lungs, from which the blue livid tint frequently observed over the surface of the limbs likewise originates. The corresponding diminution of animal heat gives countenance to this supposition. Chlorosis. — Among other changes which oc- cur in the progress of chlorosis, there is none more constant than an impoverished condition of the blood, which is thin, light-coloured, and weakly coagulable, being deficient in fibrine, and still more so in the proportion of the red par- ticles. To the latter cause is to be attributed the diminished temperature of the surface, to- gether with the universal pallor and waxy ap- pearance which those who are the subjects of this disease generally exhibit. The deficiency of colour in the catamenia, and the pale stain which haemorrhages from the nose leave on linen, are also referable to the same cause. In aggravated cases, if blood be drawn from the arm, the crassamentum is observed to be of a pale rose colour, and small in proportion to the serum. We have to regret that in this, as in most other cases of morbid blood, pathologists have contented themselves with a general ob- servation of facts without attempting to inves- tigate them with that degree of precision which can alone lead to a further advancement of our knowledge respecting their causes. The only analyses of chlorotic blood of which I can find a record are given by Mr. Jenkins in two well- marked cases of chlorosis ; the one of a girl aged fifteen, the other of a young woman aged twenty-one. In these the blood contained 871 and 852 parts in a thousand, of water, respec- tively, instead of 780, the healthy standard; and the colouring matter amounted to 48'7 and 52, instead of 133. The albumen and salts were in the usual proportions. Melanosis. — Although it would be foreign to my present object to treat of the various morbid products which may l e supposed to have their origin in a diseased state of the blood, yet there is one which seems so evidently to be the result of an accidental change in that fluid, that it must not be passed over without a brief notice. The similarity of chemical composition in the blood and in the matter of melanosis is such as to leave little doubt that the material of which the latter is composed has its origin in the circulation, and is afterwards deposited in the various parts in which it is found. The different analyses of melanosis, says Andral, all concur in one important point. They all shew that the accidental production called melanosis is formed of the different elements of blood, and especially of a colouring matter which more or less resembles that of the blood, but which is, nevertheless, not identical with it. M. I’oy, in his analysis, calls this altered cruor. Dr. Carswell, to whom we owe the most detailed and best account of melanosis which we possess, states that he has fixed its seat in the blood, not only because it is seen there, but because his anatomical researches shew that it is there formed. He makes a grand division of melanosis into true and spurious ; the former of which occasionally makes its appearance in the circulating system, a fact which is well established, while the latter is more decidedly the result of chemical action. Whenever healthy blood comes in contact with an acid, whether in or out of the body, its colour changes from red to brown or I; black, in proportion to the strength and abund- [ ance of the acid employed. It is to this cause that we are to attribute the appearance of brown or black ramifications, patches, or points, as ob- served after death in the stomach and intestines. To this cause also are owing the accumulations, ; during life, of black pitchy matters in the ali- |i mentary canal, and it is by the acidity of the * black vomit and its power of reddening litmus paper, as we learn from Dr. Stevens, • that it can alone be distinguished from blood rendered black by defective decarbonization or the ab- sence of saline ingredients. Where a haemor- 1 rhage occurs, whether by the rupture of a large vessel or by a general oozing from the mucous |j membrane into the stomach or bowels, we shall find the fluid ejected assume the appearance of jj red blood or of brown or black matter, accord- ing to the presence or absence of the gastric juice in an acid state. Upon this almost acci- dental circumstance, then, will it depend whether we are to designate the disease haematemesis or melasna, there being in reality no essential dif- ference between the two diseases. The black discolouration of blood which occurs whenever it becomes stagnant from retarded or interrupted circulation, will, by those who follow the views of Dr. Stevens, be attributed to a similar cause. According to that author it is the presence of carbonic acid which acts like other acids in ren- dering venous blood dark, and it is its abstrac- tion by oxygen which, combined with the action of the saline matters it contains, restores it to its scarlet hue. The foregoing are among the more pro- minent diseases in which the blood has been, observed to undergo changes either directly 429 BLOOD, MORBID CONDITIONS OF THE. cognizable by our senses, or discoverable by those chemical and mechanical means which we are enabled to call to our assistance. There are, however, other morbid conditions the ex- istence of which is equally certain, although their essence is of such a doubtful nature that it defies detection by the coarse instruments and the limited skill which man, in the present state of his knowledge, is enabled to employ. In the exanthematous diseases the blood par- takes of the general disorder of the system. Dr. Home of Edinburgh* succeeded in reproducing measles by inoculation with blood drawn from a superficial vein in one of the patches of eruption which cover the skin in that disorder ; and though others have failed in this experi- ment, it has been successfully and often re- peated by Professor Speranza of Mantua. Pregnant females affected with small-pox, or even exposed to its virus, though they may have had the disease, have often imparted it to the foetus in utero,f and syphilis has been communicated in the same manner. Professor Coleman has proved by experiment that the blood of a glandered horse will impart glan- ders if infused into the veins of a healthy animal. Dupuy and Leuret have thus pro- duced malignant pustule ; transfusion of the blood of a mangy dog has produced mange in another; and, according to Dr. Ileitwich of Berlin, the blood of a rabid animal will by inocu- lation communicate the disease. A remarkable instance is related by Duhamel, in which a butcher became affected with a malignant pus- tular disease in consequence of having put into his mouth the knife with which he had slaugh- tered an over-driven ox. Another individual lost his life from sphacelus of the arm in con- sequence of a wound in the palm of his hand, accidentally inflicted by a bone of the same animal; and in two women who received some drops of its blood, the one on her hand, the tther on her check, inflammations ensued which •apidly terminated in gangrene. Although in all these instances there can be 10 doubt that the blood was in a poisonous tate, there is no reason to suppose that this »uld have been foretold by any thing remark- ble in its appearance or sensible qualities. Scarcely more successful in general has been he search for extraneous poisons, which never- heless have appeared from collateral circum- tances to have entered the circulation, or have ven been purposely introduced into it. Dr.Chris- 'sonj has cited a sufficient number of cases 'here poisons swallowed have been afterwards lund in the blood, to shew that we must not ifer their absence from our inability in most ases to abstract them in a separate form ; and e further demonstrates how erroneous such an iference might be by stating that Dr. Coindet id himself, after destroying a dog in thirty iconds by injecting grains of oxalic acid ito the femoral vein, endeavoured in vain to * Duncan’s Medical Commentaries, vol. xix. 213. t Edinb. Med. and Surg. Journ. for April 1807. ed.-Chir. Trans, vol. i. p. 272. t Christison on Poisons, p. 14. detect any portion of it in the blood of the iliac vein and vena cava collected immediately after death, although it is highly improbable that it could have passed off by any of the secretions in so short a time. The chief obstacles by which we are opposed in such researches are minuteness of quantity and decomposition. When only a few grains of a poison are absorbed, and thence diffused not only through the whole mass of circulating blood, but likewise among all the various tissues and solids of the body, being moreover carried off by the kidneys, perhaps nearly as fast as they enter by the circulation, it cannot be matter of surprise, however delicate our tests may be, that they are seldom to be met with even where still retaining their chemical characters. When we consider, however, that reagents which produce a change of properties in those bodies with which they are brought in contact do probably themselves undergo a cor- responding change, we shall readily perceive that our difficulties will be still further in- creased on this account. The products of diseased action, and espe- cially pus, have been often met with, as well in the arteries and veins, as in the cavities of the heart ; but it yet remains a matter of doubt whether these are actually formed in the blood, or whether, as seems to me more probable, they are not rather carried into the circulation from other parts in a degenerate or diseased state, or are the products of inflammation in the lining membrane of the bloodvessels them- selves. With respect to those cases where worms and insects are said to have appeared in the blood, whereof many are recorded, some are referrible to the head of false polypi, the shape of which has misled the observer, others to deception or the accidental presence of insects or their ova in the receiving vessel ; and though we cannot deny the possibility that parasitical animals may exist in the fluids as well as in the closed cavities and solids of the body, yet we require better evidence than has yet been ad- duced to confirm our belief in the existence of entozoa in the circulating current. In a recent case brought forward by Mr. Bushnan,* and learnedly illustrated by that gentleman, it would, I confess, have carried more conviction to my mind, had he himself watched the blood from the moment of its quitting the vein until the larvee which he describes were seen swim- ming in its serum. In such extraordinary cases the mind is not satisfied with anything short of moral certainty. From what has been set forth in the fore- going pages, it will be perceived that our knowledge on the subject discussed in them yet remains extremely defective. We learn, indeed, that under the existence of disease the different constituents of the blood are liable to morbid increase or diminution as well as to certain alterations in their sensible qua- lities, hitherto less accurately examined ; that * History of a case in which animals were found in blood, &c. 430 BONE, NORMAL ANATOMY. there are instances in which principles not usually met with in the healthy circulation may he detected in it, and others where those which are always preseni in a state of health do nearly if not altogether disappear. But that which still remains unknown, and to which it is of the highest interest and importance that our investigations should be directed, is the con- nexion that these morbid changes have with the diseases which they accompany ; the position which they occupy in the relation between cause and effect. Perhaps our present information is not sufficiently minute to give fair expecta- tions of any considerable advances being made in this line of inquiry ; for when we contemplate the variety of materials for the formation and removal of morbid as well as of healthy secre- tions and structures, which are stealing unper- ceived along the vital current, we are forced to confess how small is the sum of all we know compared with that of which we are still igno- rant, and how ample is the harvest which yet remains to be gathered by future labourers in this field of research. Bi BLIOGRAPH V. — (The following comprehends the most esteemed writings on the blood in its healthy as well as its morbid states.) — R. Boyle, Mem. for a nat. hist, of human blood, 8vo. Bond. 1684, and Analytical observ. on milk found in veins instead of blood, Phil. Trans. 1665. Albinus, De Massac Sanguinis corpusculis, 4to. 1688 (Kecus. in Haller Disp. Anat. t. ii.) ; Ejus, De Pravitate Sanguinis, 4to. Franc. 1689. De Sandris, De naturali et praster- naturali sanguinis statu, 4to. Bon. 1696. De Haen, De sanguine humana, in Ej. Ratione medendi. N. Davies, Exper. to promote the analysis of tho blood, 8vo. Lond. 1760. Fontana, Nuove osserv. sopra i globetti rossi del sangue, 8vo. Lucca, 1768. Hewson, Exper. inquiry into the properties of the blood, 8vo. Lond. 1771-78. Spallanzani, Fenomeni della circolazione, 8vo. Moden. 1773 ; Anglice by Hall, Lond. 1801. Haller, El. Physiol, t. ii. Bordeu, Analyse Med. du sang, Par. 1771. Thou- venel, Mem. sur le mechauisme et les produits de la sanguification, Mem. de l’Acad. de St. Petersbourg, an. 1776. Della Torre, Oss. microscopiche, 4to. Neap. 1776. Hey, Observations on the blood, 8vo. Lond. 1779. Blumenbach, De vi vitali sanguinis deneganda, 4to. Gutting. 1788. Deyeux Sf Par- mentier, Mem. sur les alterations du sang, 4to. Par. 1797. Hunter on the blood, &c. 1794. Wells on the colour of the blood, Phil. Trans. 1797. Kreysig, De sanguine vita destituto, Prag. 4to. 1798. Tollard, Diss. sur la fibrine, 4to. Strasb. 1803. Le Gallois, Le sang est il idcntique dans tous les vaisseaux, 8vo. Par. 1805. Henke, Uber die vitaliliit des Blutes,8vo. Berl. 1806. Bostoch, Med. -Chir. Trans, vol. i. Douiler on the products of inflammation. Mi d. Chir. Trans, vol. xii. Thackrah on the properties of the blood, 8vo. Lond. 1819. Wilson, Lectures on the blood, &c. Lond. 1819. Kolk, Sanguinis coagulantis historia, &c. Diss. Inaug. Groning. 1820. Cotte, Sur les diff. caracteres du sang dans l’etat de sante et de maladie, 8vo. Aix, 1821. Davy on the buffy coat, Phil. Trans. 1822. Krimer, Versuch einer Physiol. desBlutes, 8vo. Leipz. 1823. Stoker, in Pathological Observations, Dublin, 1823. Scudamore , Essay on the blood, Lond. 1824. 3/i- chaclis, De partibus constitutivis sing, partiitm sang, art. et ven. 8vo. Berol. 1827. Babington on fatty matter in the blood, Med. -Chir. Trans, vol. xvi. Christison in Ed. Med. and Surg. Journal, No. ciii. Velpeau, Recherches sur les alterations du sang, 8vo. Par. 1826. Trousseaux , in Arch. Gen. de Med. t. xiv. Segalas, in ibid, t. xii. Gendrin, Recherches sur les fievres, and Hist. anat. des inflammations. Andral, Pathological anatomy. by Townsend. Denis, Rech. exper. sur le sane hum. 1830. Stevens on the blood, 8vo. Lond. 1832. O’ Shaughnessy , Keport on the chemical pathology of cholera, Lond. 1832. Prevost lV Dumas, Exarnen du sang, &c. Bibliotheq. Univ. de Genev. t. xvii. See also Rudolphi , Blumenbach , Sprengel, Adelun, &c. in their systems of physiology. ( B. G. Babington.) BONE, (general anatomy in the normal state.) Gr. octtsov. Lat. os. Fr. os. Germ. derKnochen. Ital. osso. The important offices fulfilled by bone in the animal economy, and its almost imperishable nature, could not but give it im- portance in the eyes of the philosopher ; whilst every language bears testimony to the high place it holds in popular estimation. We see it forming a framework to give shape and sun- port to the body, cases and cages to protect the more delicate organs, levers by which loco- motion is performed and force exerted. Again, we find it, among the tombs, successfully resist- ing those destructive agents which a century before reduced the softer portions of the body to dust; and we speak of laying our bones m the grave as if they constituted the essential element of our frame. W e propose to treat of the general anatomy of bone under the following heads, viz.— 1. its physical properties and intimate structure in man : 2. its periosteum and medulla, and its organization as a part of the living system ; 3. its chemical composition: 4. its peculiarities in other animals. 1. The physical properties and intimate structure of bone in man. — The most remark- able property in bone, and that which first arrests attention, is its extreme hardness com- pared with other parts of the system. It is, indeed, the only substance in the body which deserves to be called hard ; all others are mere or less soft, and are consequently destitute of that resistance and firmness by which bones are so admirably adapted for the offices they have to fulfil in the animal machine. The hardness usually increases with age. It varies a little in different situations, and depends, as we shall see, on the earthy matter which enters largely into the composition of the bones. The colour of bone in the living person is a pale-rose colour, inclining, in early life to red, in old age to a yellowish white. Bones assume a beautiful white when macerated and deprived of the oily and sanguineous fluids which pervade them. The specific gravity of fresh bone is greater than that of any other animal substance. Bone is opaque or only slightly diaphanous. Bones are flexible and elastic. We find that the ribs may be bent and afterwards recover their form perfectly; every schoolboy, indeed, knows the value ol a horse’s rib as a bow. This elasticity frequently saves them from fractures, and lessens the shock which would otherwise be communicatee to the nervous centres and delicate structure; they defend. It is possessed by every bone and may be demonstrated in the oldest am most rigid by cutting them into thin slices. Shape. — Bones assume every variety of shape as might be expected from the use made c BONE, NORMAL ANATOMY. them in so complicated a piece of machinery as the skeleton. These varieties have been reduced by anatomists to four classes, viz. 1. the long or cylindrical ; 2. the broad or flat ; 3. the short or thick ; and 4. the mixed or irre- gular bones. The long bones are distinguished by their length, which greatly exceeds their other dimensions. They are to be found only in the extremities, and are adapted for locomo- tion and for supporting the weight of the body. They are never exactly cylindrical, being al- ways contracted in the middle or shaft , and enlarged at each end ; and their transverse sec- tion is oval or triangular, never round. The broad or flat bones are thin, generally arched, and fitted to protect delicate organs ; we find the best specimens of them in the cranium. The short have nearly equal length, breadth, and thickness; they are seen in the carpus and tarsus. The mixed or irregular bones are usually classed with the short, but it is more convenient to separate them : the vertebrae are good examples of these. The ribs and bones of the pelvis may also be ranged with them, combining the characters of two of the pre- ceding classes. Each of these divisions exhibits certain peculiarities of structure to which we shall allude hereafter.* If we prepare bones by careful maceration and drying, and then saw them through, or, what is better, fracture them with a smart blow of a hammer, we observe the density of texture 431 to differ very much in different portions. The outer part is generally much more dense and close than the interior, and is called the com- pact, vitreous, or cortical substance. The inte- rior, open and areolar in its appearance, is the spongy, cancellated, or reticular substance. These two are arranged in a peculiar manner in each class of bone. In the long there is a considerable thickness of compact substance in the shaft, surrounding a cavity, and but little of the spongy, whilst towards the ends the compact gradually becomes thin as paper, the spongy increasing in quantity and filling up all the interior, as if formed by the expansion of the compact tissue (jig. 186, a). In the flat bones the compact substance is formed into two plates with a thin stratum of spongy substance called the diplbe between ( flg . 186, b). In very thin bones the diplbe is often absent. The short bones are spongy throughout, with a thin layer of the compact tissue on the surface ; they are like the extremities of the long bones: and the irregular , resembling in shape two or more of the former classes, have a corresponding arrange- ment of the two tissues. A vertical section of three long bones is re- presented at flg. 186, where A is the head and neck of the femur, and B the upper extremities of the tibia and fibula : a indicates the com- pact tissue; b the reticu'ar; at c it may be seen how thin is the layer of compact tissue cover- ing the head of the femur. Fig. 186. In the shaft of the long bones there exists a cavity of considerable size filled with marrow, and called the medullary cavity. This is widest in the centre, gradually getting smaller towards * See further particulars respecting foramina, processes, epiphyses, &c. as connected with mecha- nical contrivance,, under the article Skeleton. the extremities, where its place is occupied with spongy substance. The interior of this cavity is rough ; bony processes project into it, and form a kind of net-work resembling the spongy substance at the ends, but with more open and less regular cells. By some anatomists the term spongy is confined to the cellular arrange- ment at the ends, that in the middle being 432 BONE, NORMAL ANATOMY. denominated reticular or cancellated. Such a distinction is useless. There is no line of demarcation between them. At first view a great difference appears to exist between the compact and the spongy substance, but in reality this is not the case. The degree of condensation is the only dis- tinction. The spongy substance would become compact were the sides of its cells pressed together, and the compact would become spongy or reticular were its texture loosened by en- larging the minute cells which may be detected even in it. Such changes actually occur by the processes of absorption and deposition in growing bones. In the perfect bone the cells are compressed towards its middle to diminish its bulk, and thereby to accommodate the bel- lies of the muscles ; and they are expanded at its ends for the purpose of giving security to the joints by a more extensive surface, and allowing more room and power to tendons, &c., whilst the osseous matter in equal lengths of bone, whether at centre or extremity, is of nearly equal weight. The surface of bone in many places presents a striated appearance ; and small holes or canals are seen on it especially near the ends of long bones. Simple inspection of dried and divided bone carries us thus far in the knowledge of its structure. But the question still arises, what is the arrangement of the particles which com- pose the compact and spongy tissues ? Is bone laminated, or fibrous, or cellular ? or does it partake of a texture in which these three varieties of disposition are to be found ? One might imagine there could be no great difficulty in answering these questions, where bone is so readily procured, so easily pre- served, and admits of such varied modes of examination. It can be viewed in the living subject, or after death while fresh, or when prepared by injection, or when all its moisture is removed. It was long ago discovered to consist of an earthy and an animal portion, either of which can be removed, leaving the other undisturbed in its original form. Yet, with all these “ appliances and means to boot,” anatomists have entertained opposite opinions, and are not yet quite agreed upon the subject. Malpighi, the first author who deserves to be mentioned, thought that bone consisted of fibres and filaments with an intermediate os- seous juice : “ constat igituf, ossa eoagmentari filamentis, et fibris per longum ductis in rete implicitis, quae affuso osseo succo ferrumi- nantur in solidam densamque ossis naturara.” (Gp. Posth. p. 47. Lond. 1636.) He also allowed the existence of lamellae, though he does not put forward its lamellar structure in a prominent way.* Gagliardi adopted his no- * We aTe told by an interesting writer that Mal- pighi compared these lamella; to the leaves of a booh. Could this writer have taken “ Him,” in the fol- lowing passage, to mean book instead of bark, of which last Malpighi had just been speaking ? “ Pari incremento procedit natura in ossium aug- mento. Foetus os a, et cranium precipue, fila- mentorum progressum exhibent ; h«ec non omnino sibi parallela sunt, et hinc inde breves appendi- tions of a laminated structure, but made additions, from which Malpighi, at a subse- quent period, expressed his dissent. He exa- mined bones long exposed to the weather, or softened by boiling, and concluded that they were formed of plates, (lamell®, squamuls, bractese,) held together by processes, in the form of nails, the shape and direction of which he minutely describes.* Clopton Havers found bones composed of plates connected by an osseous juice, with pores which ran, some transversely through tire plates, others longitu- dinally through the entire length of the bone.f Leuwenhoeck thought that the filaments of Mal- pighi were hollow tubuli.j Duhamel observed concentric layers as in wood.§ Haller says, “ Fi- brosum est (os) sive in laminas et fila divisum qua; snlcis separantur.’)| And Monro lays it down that “ bones are composed of a great many plates, each of which is made up of fibres or strings united by smaller fibrils.”!!’ About the close of the eighteenth century the celebrated Scarpa published his work “ De penitiori ossium structura,” in which he com- bats former opinions, and asserts that bone is in every part of a cellular or reticular texture. In the first place he shows that we have no proof of its lumellated structure ; the appear- ances produced by calcination, the weather, disease, &c. on which former anatomists relied, proving nothing. Calcination is a rude pro- cess, and acts with different power on the dif- ferent parts of the same bone as they vary in density, and divides them irregularly as it happens to overcome their force of cohesion. The same thing may be said of the weather. And exfoliation takes place in the skin, whose culas filamentosas promunt, quibus invicem col- ligata rete efformant parurn a libri natura distans, cujus potiores are* et tota fibrarum compagcs exsudante osseo succo repletur et tnmet.” Here we have a tissue of fibres and filaments run- ning in various directions, and forming a net-ivork not unlike a booh ! ! From this quotation, indeed, it might be thought that our author entirely denied the existence of plates. However, in the next sentence he speaks of plana, lamella;, and bruetea: “ Successivis increinentis nova fibrarum plana su- perinducuntur, quae prasexistenti lamellae osseo agglutinata succo, debilam molem et firmitatem | excitant. Patent autein singula plana resolutions facta per longum ossium maceratione ; integras namque osseae reticulares bractece evelluntur. In abortibus verb in cranio inchoatum rete evi- denter conspicitur.” — Anatome Planturum. Op, Omn. p. 19, Lond. 1686. * “ Natura prudens ossiculis eas transfixit. The nails were of four kinds for the outer plates, viz. “ perpendiculares acuti, perpendiculares ca- pitati, oblique si'.uati, et inflexi angulum eftor- mantes.1' The inner plates, forming tiie spongy substance, differed from the outer, and were of three kinds, the corrugated, the per! orated or cri- briform, and the reticulated. These had a system of nails peculiar to them : “ alia sine cuspids, plurima ramusculos rescissos efformant, nounulla breviora.” — Anatome Ossium. Lugd. Bat. 1723. t Observationes de Ossibus, Auctore Cloptone Havers. Amstel. 1731. t Opera Omnia, Lugd. Bat. 1722. S Mem. de l’Academie Hoy. des Sciences, 1739, 41, 42, 43. |j Opera Minora, tom. ii. Laus. 1767. ! Monro’s Works, Edin. 1781. 433 BLOOD, NORMAL ANATOMY. cellular texture no one denies. In the next place he endeavours to establish its reticular texture; 1st, by observations and experiments on the bones of a chick, made during its growth; 2d, by treating bones with dilute muriatic acid, and then putting them in oil of turpentine to render them transparent. In every bone, he says, the net-work was conspicuous. He observed the same in rickets, in exostosis, and in callus ; and still more remarkably in the bones of the amphibia, reptiles, and fishes. The conclusion at which Bichat arrived is not very different: “Ces lames osseusesne me paroissent point exister dans la nature.” “ Considerons le tissu compact comme un assemblage de fibres rapprochees mais nullement separees par couche.”* Blumenbaeh and Meckel in- cline to the lamellar arrangement. More re- cently bone has been submitted to microscopic examination by Mr. Howship, who agrees with Scarpa that the ultimate texture of bone is not lamellated but reticular. He coincides, too, in opinion with Havers and Leuwenhoeek as to the existence of minute longitudinal canals in it; and he adds that the canals communicate freely with each other, and that a fine vascular membrane lines them in the foetus, where they may be seen projecting into the temporary car- tilage during the growth of bone in the form of fibres which are tubular.f Bostock says, “ the membrane of bone is composed of plates very similar in their general form to those of the cellular texture, and it is probable that the earthy matter is inserted between these plates, and thus is likewise disposed to assume the laminated structure.” And again : “ As we may presume that the earthy part of the bone is moulded into its appropriate form by the membrane into which it is deposited, we may judge of the structure of the latter by that of the former, which, from its firmer consistence, it is more easy to ascertain. Now, whether we examine bone during its formation in the foetal state, or after it has had its membrane destroyed by the action of fire, we find the earth to assume the appearance of fibres, which, when the bone is perfected, have a tendency to a laminated arrangement.”! It is plain, from the quotations we have made from some of the most distinguished writers on the structure of bone, that all before the time of Scarpa considered it laminated, or fibrous and laminated, while all, after his publication, looked upon it as cellular. In the former, however, we see some intimations of a reticular texture ; in the latter we hear of a tendency or a disposition to a laminated ar- rangement. If, with these opinions before us, we come to examine for ourselves, I think we shall have no hesitation in agreeing with Scarpa that it is cellular. At the same time it must be confessed that the sides of the cells are, in the compact tissue, so pressed together that the appearance of laminae is often very striking, * Anat. Gener. tome iii. pp. 24-6. Par. 1812. t ftledico-Chirurgical Trans, vols. vi. and'vii. t Bostock’s Elementary System of Physiology, vol. i. VOL. I. and, again, that the sides of the cells have, in most places, the appearance of fibres. When the earthy portion is removed by an acid, we can teaze out the membranous portion with a pin, and almost demonstrate the fibres. But a closer examination will show that we have torn the cells and destroyed the true texture. The laminated disposition supposed to be shown by exfoliation, the weather, burning, &c. may all be proved to be deceptive ; and, indeed, there seldom can be exhibited a plate, however small, of equal thickness throughout, which has been removed by any of these agents. There is, however, an approach to the laminated ar- rangement, and every cell is formed of parti- cles which approach to the form of fibres. The longitudinal canals of Havers, Leuwenhoeek, and Howship, probably result from the flattened cells, and may be deceptive appearances in the old bone, or the channels for bloodvessels, &c. 2. The periosteum and medulla, and the organization of bone us a part of the living system. A. The periosteum is a fibrous membrane of a dull white colour. It covers bone on every part of its circumference, except where enamel takes its place as on the teeth, or car- tilage as on the articular extremities, or fibro- eartilage as where tendons play, or tendon as on sesamoid bones. The fibres which compose it run in different directions and form a tissue of great strength. On the long bones the greater number of fibres take a longitudinal direction. The superficial ones extend for a considerable length without interruption ; the deep are short. All interlace with the liga- ments of the articulations, and become in- separably united to them, but there is not, as was formerly imagined, a continuity of fibres from one bone to the other by means of the ligaments; on the contrary, the direction of the fibres in these two organs seldom co- incides. The external surface of the periosteum is in contact with a great variety of parts : muscles, synovial burs*, mucous membranes, vessels and nerves, rest on it immediately, or are separated from it by cellular tissue, and thus permitted to move freely on it. The other surface is connected to the bone by vessels, and by numerous prolongations which pass into the osseous substance and are lost there. This connexion is weak in early life, and espe- cially in the centre of the long bones ; but in the more advanced periods the deeper sub- stance of this membrane becomes identified with that of the osseous tissue ; thus its union is rendered more intimate, its thickness di- minished and its density increased. The union is so close in old age and even in middle life, that the inner fibres of the periosteum are sup- posed to be the seat of calcareous deposition, and to be converted into bone. The vascularity of the periosteum may be easily shown by injection, especially in the young. Its vessels freely anastomose with those of the surrounding soft parts, and there is no point of the external osseous surface 2 F BONE, NORMAL ANATOMY. 434 which is not perforated with the communi- cating branches. Some lymphatics have been discovered in its tissue, but no nerves; how- ever, the diseases to which it is subject, the symptoms to which these give rise, and the changes that follow, leave no doubt of the existence of both. That cellular substance enters into its formation is inferred from some of its morbid phenomena, as gra- nulation ; and independently of this argument, on which we do not lay much stress, its exter- nal fibres are evidently of a mixed nature, com- bining common cellular membrane with its own peculiar substance. The proper and essential part is the dense, inelastic, and very resisting fibre, by which it is associated with other fibrous membranes. (See Fibrous Tissue.) The older anatomists believed that the periosteum had its origin from the dura matei, and might be traced as one continuous membrane over every bone in the body. Boer- haave asserts (Praelectiones Academic®) that if we could remove it without rupture, we should have an exact mould of the skeleton with all the joints. Its origin from the dura mater was said to take place through the fora- mina which transmitted the nerves ; there the dura mater separated into two layers, one of which enveloped the nerves as neurilema, the other the bones as periosteum. But there does not appear, on close inspection, to be any actual identity between the dura mater and periosteum, although they are most intimately connected ; and there certainly is no continuity of the latter membrane over the joints. It is true that we may, at least in young subjects, after boiling, tear oft' the articular ligaments with the periosteum, but the tendons come off with it too ; and in both cases the fibres are seen to be interlaced, not continuous. Various uses have been assigned to the peri- osteum, such as modelling the bone in its growth and adding new layers to it, for the further consideration of which we refer to the article Osteogeny. It is, moreover, also said to be useful for the purpose of protecting the bone from the impression of surrounding muscles, arteries, &c., and vice versa, shield- ing them from the rough and unyielding osseous substance ; permitting the soft parts to move freely without injury ; and serving as a centre for the fibrous system in general. This last is, in Bichat’s opinion, a most important use; he considers its attachment to bone is more for the purpose of affording a point d'appui to the fibrous system than for any office it can fulfil with regard to the osseous system.* B. Medulla or marrow. — When a longitu- dinal section of a long bone is made, we ob- serve a large tubular cavity occupying the shaft, becoming smaller as we recede from the centre, and replaced in the extremities by the spongy tissue. This tube is rounded, not having exactly the triangular form so commonly presented by the bone externally. Its surface is rough, especially near the ends, as if it had * Anat. Gen. tome iii. Par. 1812. originally contained cells which were in some way or other broken up. All this cavity is filled with a peculiar, soft, adipose substance — the medulla (quasi in medio), contained in a membrane of extreme delicacy. The medullary membrane, or internal peri- osteum as it is often called, resembles the pia mater in structure, being composed of vessels ramifying minutely in fine cellular tissue. Its tenuity is such that some anato- mists have doubted its existence, but we have only to look into any well-boiled marrowbone, and we shall no longer doubt. It may be shown too by roasting a bone, or macerating it for some time in a diluted mineral acid. This membrane sends numberless prolonga- tions from its inner surface into the medulla which it contains. It is to these processes that the marrow is indebted for its consistence; they form cells and areolse which support and maintain the vesicles in which the medullary fat is lodged. They are exquisitely fine, and almost invisible; we lacerate them with a touch. The oily substance of the marrow is not in immediate contact with these cells. It is contained in distinct vesicles, which are beau- tifully figured by Havers. The vesicles are little bags which do not communicate with each other, but look like a cluster of pearls, as Monro observes. When bones have been long buried or macerated, the marrow often assumes a granular appearance depending on this vesicular arrangement. A fine artery runs to each, ramifies on it minutely, and is the source of its secretion. This vessel may be demonstrated. Each artery has its accompa- nying vein, and, though we cannot see absor- bents and nerves, their presence is inferred from analogy and various phenomena. Mar- row is merely a variety of adipose substance, ; and to the article on that subject we refer for the chemical properties and some generalities j respecting it. Marrow is not confined to the medullary canal. It is to be found in the cells of the spongy extremities of the long bones, and in the areol® of the short. It exists in the diploe of the flat bones, and even in the longitudinal canals and pores of the compact tissue every where. In all these situations a membrane ' lines the osseous cell or pore, and secretes the contents. The membrane is still finer than that of the medullary canal, and the oil is less consistent. The communication between the membranous lining is kept up by vascular prolongations, not by a continuity of cavity. In the bones of the head we find certain cells, called sinuses, which contain air, not marrow. They are distinct from the cells of the diploe, with which they have no communication. There is a free anastomosis between the vessel*) of the medullary membrane and those of the bone and periosteum everywhere. Near the middle of the long bones a fora- men is observed by which an .artery of con- siderable size passes in to the medullary cavity, where it divides into two branches, one for either end. These extend to the extremities I, of the canal in a beautiful network on its lining BONE, NORMAL ANATOMY. membrane. The artery is erroneously called the nutritious vessel of the bone. It is ob- viously intended for the marrow. A vein is seen to accompany it ; and nerves may also be demonstrated. The medullary membrane is possessed of sensibility. This was long ago shown by Du- vemeyA According to Bichat it enjoys a very high degree of sensibility in the centre, but much less towards the ends. Anatomists do not agree with him in this observation, nor is it found very sensible in any part. Patients seldom complain of pain when, in amputations, it is rudely lacerated by the teeth of the saw ; but sometimes they do complain loudly, and in those cases especially where the operation is performed below the entrance of the nerve ; in the opposite case the nerve is probably di- vided with the soft parts, and the sensibility, of course, destroyed. The marrow and the medullary canal vary much in different periods of life, and under different circumstances. No medullary cavity exists in the cartilage which precedes bone ; but Bichat asserts that the membrane is pre- sent, filled with gelatine of the same ap- pearance as the rest of the cartilage. An assertion so improbable a priori, and so con- trary to all observation, seemed to require some proof to support it, yet he offers none. When a cavity is formed at a later period, it is at first occupied entirely by the artery ; a membrane soon shows itself which contains a reddish watery substance, of a gelatinous appearance, not fatty : it may be dried away before the fire and will not stain paper. To this the true marrow succeeds, more unctuous and more abundant as the individual advances in years. In subjects, however, which have been wasted by slow disease, and in the very aged, the marrow again becomes watery, though not so red as in the fcetus. In the cells of the verte- brae there never is well-formed marrow. It there remains through life sanguineous and almost destitute of oil. The use of the medullary membrane seems to be to act as an internal periosteum, or a bed in which the vessels may ramify before they enter the osseous substance. Its destruction to any extent is followed by the death of the bone. But is the adeps contained in it of any Jse ? Doubtless it is to the general system a itore of nutriment, which is absorbed, in cases >f wasting or marasmus, for the general good ; >ut to the bone itself perhaps it is of no more ise than so much of any other soft animal ubstance would be — it fills a space which in the "techanism of the bone was not to be occupied pith calcareous matter. Marrow was lighter ian the heavy earth of bone, and could at (ny time be used for the necessities of the aimal. Me see young bones filled with a alatinous fluid, and in birds air takes its 'ace — a proof that marrow is no wise essen- ii to the existence of the osseous system, arious other uses have been assigned to the arrow, which will not bear examination. * Memoires de l’Acad. des Sc. 1700. 435 Blumenbach, Haller, and their predecessors conceived that it rendered bones more flexible ; but the bones of children, which have little or no marrow, are much more flexible than those of adults. Burning a bone renders it brittle, and this w’as said to be owing to the destruc- tion of its oily part ; but it is occasioned, clearly, by the destruction of all its animal ingredients. Some were of opinion that it contributed essentially to the growth and nu- trition of bone and to its union when fractured, but bones are far advanced in growth before it appears at all, and they unite faster in the young than in the old. They unite also readily in birds. Others looked on it as the source of synovia ; but the very same objec- tions hold to that supposition, and indeed the two fluids axe quite dissimilar. According to the law of development, so generally observed, we find fishes and amphi- bia, like the human foetus, for the most part destitute of a medullary canal. The crocodile and other lizards are, however, exceptions. Some of these have considerable cavities. Birds, when young, have an imperfect medulla in all their bones, but at a later period the canal in many of them becomes remarkably developed, and then no longer contains mar- row ; air takes its place, and fulfils important offices in the economy of the class. In mam- malia the internal structure coincides with that of the human bones, except in those species which have fins. These approximate to fishes, and either contain no cavity or a very small one filled with fluid oil. The medulla of car- nivorous animals generally is softer than that of herbivorous. Organization of bone as a part of the living system. — The physical properties of bone are so very peculiar that we cannot much wonder at the mistakes of the ancient anatomists re- specting its organization. Some classed it it amongst the bloodless organs ; others even supposed it to be destitute of vitality; and superficial observation might countenance the supposition, for no pain is excited by sawing, scraping, or cauterizing a bone ; but experi- ment and observation, analogy and disease, all convince us that it possesses well-developed systems of arteries, veins, nerves, and most probably lymphatics, not differing essentially from those of the soft parts. These are ob- scured by the presence of calcareous matter, not obliterated. “ Scrape a bone, and its ves- sels bleed ; cut or bore a bone, and its granu- lations sprout up ; break a bone, and it will heal ; or cut a piece away, and more bone will readily be produced ; hurt it in any way, and it inflames ; burn it, and it dies ; take any proof of sensibility but the mere feeling of pain, and it will answer to the proof.”* Animal sen- sibility was unnecessary, it would even be incon- venient ; it is, therefore, not to be found, ex- cept in diseased bone, where it sometimes exhibits itself too acutely. The presence of bloodvessels may be shown in various ways. 1st. The colour of healthy * Bell’s A natomy. 2 F 2 436 BONE, NORMAL ANATOMY. bone in the living animal is a pale pink, which becomes much deeper in case of inflammation, whilst a deadened portion puts on a yellowish white appearance. When animals are drowned or strangled, their bones assume a darker hue ; and in cholera the colour is so deep, and so thoroughly pervades the osseous tissue, that no length of maceration will remove it. In all these cases the colour obviously depends on the blood contained in the osseous vessels. 2d. It was discovered accidentally by Belchier, in 17 36, that the bones of animals fed on food I tinged with madder very quickly become red ; (a sensible change is produced in young ani- mals in twenty-four hours ;) now, whether we explain this, with most physiologists, by saying that the earthy matter is coloured in the blood before it is deposited, or, with Gibson, that it receives its dye in the bone, the presence of bloodvessels is equally necessary to account for the phenomenon. (See Osteogeny.) 3d. The most satisfactory proof of vascularity in bone is afforded by injection. A young bone may be completely coloured in this way : the vessels are seen to enter it, and if the earthy part be removed by an acid, they may be followed in their fine ramifications through its tissue. Arteries are found to enter bone under three modifications. 1st. Numerous small vessels fill the minute foramina, which may be seen in the compact substance every where : 2d, a larger set enter the holes which we see on the short bones, and near the extremities of the long ones : and 3d, about the centre of the long bones considerable branches pass into the medullary canal, and ramify on the medullary membrane. These last have been called the nutritious arteries, a name to which they have no claim : they are destined for the marrow. The two first sets are the true nutritious ves- sels. All, however, freely anastomose with each other. The veins merit particular notice. They Fig. 187. Fig. 188. b have been investigated by Dupuytren,'* and their course in some of the bones, espe- cially the flat bones, splendidly figured by Brescbet.f In figs. 187, and 188, copied from one of Breschet’s plates, a indicates these veins | in the diploe of the cranium : they may be very easily exposed in the cranium by filing away the external table with a coarse file. The first two sets of arteries have no accom- panying veins, but with the last there always |j are veins of a corresponding size. These do not appear large enough to return all the blood; we therefore have others leaving the bone by foramina, which are proper to them, and through which no artery passes. They arise in |i the spongy tissue by numberless radicles, re- ceive branches like other veins in their course, |i and, after issuing from the compact tissue by li a constricted opening, empty themselves into ■ the vessels of the neighbouring soft parts. The canals through which they pass have a lining of compact substance continuous with the external surface. The veins, while in the bone, have only one coat, the internal, which adheres closely to the osseous canal, and can enjoy no change of size or form. They are, notwithstanding, furnished with valves. Nerves, doubtless, exist in bone, although we cannot demonstrate them in the osseous substance. But it is not to be supposed that a part so highly vascular would be destitute of nerves. Nerves are seen to enter with the nutritious vessels, and minute filaments pass into some bones, as the frontal. These nerves we may be sure, ramify through every part The sensibility of an inflamed bone indeec settles the question. Lymphatics have not been found in the iute rior of the osseous substance; but they ma be seen on the surfaced In a tissue such ait that of bone it would be no easy matter t< * Propositions sur quelques points d’Anatomu de Physiologie, et d’Anatomie Pathologique IJa; 1803. ' t Recherches Anat. sur le systeme veiuetu Par. 1829. X Bedard. Grainger. BONE, NORMAL ANATOMY. exhibit them,' even if they existed in great numbers. That they do so exist we have reason to think from the phenomena of mollities, exfoliation, and various other morbid actions, as well as the changes which daily occur in the growth of bone. 3. Chemical composition. — When bone is heated to redness in an open fire, some of its ingredients are consumed, and a white friable earth is left behind. Again, if bone be ex- posed for some time to the action of an acid, it becomes soft and flexible. In both cases the form and size of the original are retained, but there is considerable loss of weight. These facts were well known in the infancy of science ; they were too obvious to escape notice; but it does not appear that they were explained before the time of Nesbit in 1736,'* nor very satis- factorily then. The existence of an earthy and an animal matter was afterwards proved by Herissant, who showed, by experiment, that acids did not soften the osseous substance as a whole, but removed from it the earthy portion; and that the soft animal matter was always present, but concealed by an earthy “ incrus- tation” of its fibres.f The action of fire on the animal portion was easily explained. Some time after this Gahn discovered that the earth was principally a phosphate of lime ; and later chemists, especially Berzelius, have minutely investigated the nature and proportions of these different ingredients. It is now ascertained that bones contain several earthy salts, varying a little in different animals; that the earthy and the animal parts do not always bear the same proportion to each other in the different classes; and that even in the same individual age and situation give rise to varieties. It was long believed that fat formed an essential part of bone, and that very important properties depended on its mixture with the osseous tissue ; but this opinion was quite erroneous. Fat is not always present, and when it is, it invariably belongs to the medulla, which may be looked upon as a distinct struc- ture superadded to bone. It is, as it were, an accidental deposit, and is not to be con- sidered in the analysis. On removing the fat and periosteum, if we suspend a bone for some days in diluted mu- riatic acid, the earthy part is dissolved, whilst nearly all the animal portion remains untouched. This last is soft, translucent, and of a yellowish white colour. It is called the cartilage of bone. When washed and dried it contracts a little, assumes a deeper colour, though still retaining some translucency, becomes hard and tough, and weighs about one-third of the original bone. This substance yields, on being boiled, a quantity of gelatine, which in young subjects is very considerable, forming nearly all the cartilage, but in the old a soft, white, elastic substance still remains, possessing the figure of the bone. According to Hatchet’s experiments Human Osteogeny, by It. Nesbit, M.D. p. 31. Lond. 1736. * t Memoires dc l’Academic Royalc des Sciences, 1758. 407 this last has the properties of coagulated albu- men.* Berzelius, f however, shows that all the cartilage may be resolved by boiling into a clear colourless gelatine, which leaves on the filter only a very small quantity of fibrous sub- stance, the debris of vessels. He does not admit the existence of any albuminous nidus, and even looks upon the gelatine as the pro- duct of a decomposition effected by coction on the peculiar cellular basis of bone. The earth of bone is principally subphos- phate of lime; it also contains carbonate of lime and minute quantities of other salts. The following is the analysis, as given by Berzelius, of bone deprived of its oil, blood, and perios- teum : — Bones of man. Of the ox. Cartilage completely solu- a ble in water 32-17 > 33-30 Vessels 113a Subphosphate of lime with a little fluate of lime. .. . 53'04 57-35 Carbonate of lime 1130 3 85 Phosphate of magnesia .. 1-16 205 Soda, and a very little mu- riate of soda. . 1-20 3-45 100-00 100-00 The proportion of earthy and animal matter is the same generally in man and the other mammalia. In birds there is more of the animal part which does not perfectly dissolve than in mammalia. In reptiles and osseous fishes the cartilage of bones approaches in its nature to the substance which, in cartilaginous fishes, is the substitute for bone. This substance is of a peculiar nature ; it yields neither gelatine nor albumen, but is more analogous to inspis- sated mucus than to any thing else. The earthy salts are not always in the same proportion to each other in different animals. We have seen that they are not the same in man and the ox. Banos gives the following table -. — Lion . . Phosphate oflime. Carbonate of Sheep . . 83 0 ... IQ-3 Fowl . . Frog .. 95 2 . . . Fish . . With respect to varieties depending on age and situation, we have a table of the proportions of animal matter and earth as found by Dr. John Davy in several experiments, from which it appears that old bones contain more earth than young ones, and that the bones of the head have a greater proportion than those of the extremities.J As to the exact nature of the earthy salts, we have given the results obtained by Ber- zelius as the latest and most accurate. But it may be right to state that differences of * Philosophical Transactions, 1800. t Traite de Chimie, Par. 1833. 1 See Monro’s Elements of Anatomy, vol. i. Edinb. 1825. 438 BONE, PATHOLOGICAL CONDITIONS OF. opinion exist on this point. Even Berzelius expresses a doubt whether magnesia is met with as a phosphate or a carbonate. We find iron mentioned by Fourcroy and Vauquelin as present in bone. This, according to Berzelius, depends on the red blood which its vessels happen to contain. They also mention silica, alumina, and phosphate but no fluate of am- monia. 4. Its ■peculiarities in other animals. — In the course of this article we have noted the most striking of those peculiarities, so that little need be said under the present head. The Radiata, Articulata, and Mollusca have coverings which somewhat resemble bone, and are considered by some physiologists as the osseous system of these classes. This opinion will be examined in another place. Fishes. — Cartilaginous fishes have very little earthy matter in their skeleton, so that their bones scarcely deserve the name. They are very flexible, elastic, homogeneous, and semi-trans- parent, and in chemical composition resemble inspissated mucus. Osseous fishes have bones properly so called. They are more flexible than in the higher classes, have no medullary cavity, little of the spongy tissue, and make no approach to the laminated arrangement. Amphibia have no appearance of laminaj in their bones, nor, with the exception of the crocodile, a medullary cavity. In chemical composition they resemble those of fishes. Birds have firm, elastic, and thin bones, shewing less of the cellular and more of the laminated disposition than we meet with in the other classes. They have large and well deve- loped cavities, which contain air instead of medulla. Mammalia . — The bones of the cetacea are coarse and fibrous externally. Within they are spongy or cellular, but the cells assume a re- markable tubular disposition. There is no medullary canal. The bones of quadrupeds do not differ much from those of man. In general they are of a coarser texture, and in some, as in those of the head of the elephant, we find very extensive air-cells. Bibliography. — Leuwenhoeck, Microscop. Obs. in Phil. Trans. 1674 and 1678. Malpighi, De ossium structura, in Ej. Anat. Plantar, fol. Bond. 1675, et in Ej. Op. Posth. Venet. 1743, Lond. 1697. Havers, Osteologia nova, 8vo. Lond. 1681. Gagli- ardi, Anatoine ossium, 8vo. Lugd. Bat. 1723. De La Sone, Mem. i. et ii. stir 1'organization des Os. Mem. de Paris, 1751. Albinus , De construc- tione ossium, in Annot. Acad. lib. vii. Scarpa, De penitiori ossium structura Com. 4to. Lips. 1799 ; 4to. Paris, 1804 ; Ticin. 1827, s. t. : De anat. et pathol. oss. Malacarne, Auct. ad osteologiam, &c. Ltidwigii et Scarpae, Padov. 1801. Caldani, Mem. sulla struttura della ossa umana e bovina, 4to. Padov. 1804. Howship, Microscopic observations on the structure of bone, in Med. Chir. Trans, vol. vii. Medici, Esperienze intorno alia tessitura organ, delle ossa, in Opusc. Scientif. t. ii. Bologna, 1818. Speranza, Consid. sul. tessitura organ, delle ossa, Bo!og. 1819. Ilmoni , Physiol, syst. oss. spec. i. et ii. 4to. Aboas, 1825,-6. See also the various systems of general and descriptive anatomy anti of physiology, and further in the Bibliography of Osseous System and Osteogeny. ( Charles Benson.) BONE, PATHOLOGICAL CONDI- TIONS OF. — The bones, as the foundations of the animal system, as the passive organs of loco- motion, required necessarily to be firm and com- paratively inelastic and unyielding, qualities which we have seen in the preceding article are imparted to them by the addition to their original animal elements of a saline or earthy substance, consisting principally of phosphate of lime. It is obvious that this difference of structure and constitution must have considerable in- fluence in modifying the diseases to which they are liable, and in giving to the affections of these organs many of their distinguishing peculiarities. In considering, therefore, the phenomena exhibited in the various patholo- gical conditions of the osseous system, not only must the presence of this unorganized earthy substance be constantly borne in mind, but even its relative amount, its abundance or deficiency must command attention. In early life, when the animal material preponderates in quantity, the bones are highly vascular, and comparatively soft, flexible, and springy, and though liable to many serious diseases, they are very apt to escape the effects of injury: fracture is uncommon in infancy; and in child- hood the bones, bending rather than breaking, often exhibit that partial fracture which has been likened to a “ branch of a tree that yields to an attempt to break it while it still retains its sap.”* The powers of repair are commensurate with the extent of vascular or- ganization at this period; fracture is quickly re-united, and its effects so regulated by the subsequent growth of the bone that permanent deformity is a very infrequent occurrence. But this activity in the osseous system in early life has its evils. The period of youth, between absolute childhood and puberty, is that in which disease is most easily and, there- fore, most frequently developed, and although extensive powers of reparation are constantly exhibited in recovery after caries, in re- production after necrosis &c., still are the operations that lead to these results languid and too often inefficient, — circumstances that may be attributed partly to peculiarity of or- ganization in the structure affected, but per- haps with more propriety to the influence of some general constitutional taint over which medicine exerts but slender control. The osseous system cannot be considered as having attained maturity until a period sub- sequent to the age of puberty, most commonly somewhere between the twenty-seventh and thirtieth years. At this lime bone is calculated most perfectly to answer its purposes in the animal economy : it is then least liable to disease ; and if fractures and other injuries are more frequent, it is only because indivi- duals are now more exposed to them. The effects of these injuries are in general repaired sufficiently well, but if deformity has been produced it will be permanent, because the bone has ceased to grow. * See a paper on this subject by Dr. Hart, vol. i- Dublin Journal of Medical Science. 439 BONE, PATHOLOGICAL CONDITIONS OF. As life advances, the osseous system un- dergoes many obvious alterations. The shape of some bones is altered : the natural curvatures of the long bones, for example, are increased ; the direction of the processes and parts of others is changed, the most remarkable example of which occurs in the neck of the thigh-bone ; and their powers of affording sup- port and resisting violence are obviously en- feebled. This senile fragility has been gene- rally supposed to arise from an increase in the earthy material of the bones. The opinion, however, has not been invariably borne out by the results of chemical analysis of bones at different periods of life, and has been objected to by M. Pubes,'* who, after extensive obser- vation and enquiry, was led to believe “ that the fragility of bones depended essentially on a change of action being established within them, and that all the parts entering into the texture of bones are really in less quantity in the aged than in younger individuals.” If by “ a change of action” in the above passage is meant that gradual decrease of the vital properties observed in every organ and in every tissue as man declines into the vale of years, we cordially agree in the opinion ; being satisfied that the results of chemical or me- chanical enquiries, however true in themselves, will always be insufficient to explain the ope- rations carried on within a living body. Having offered these preliminary remarks, we proceed with an attempt at an arrangement of the pathology of the osseous system, fully aware, indeed, that every classification of dis- ease must be more or less artificial, and, there- fore, open to objection. Perhaps it may be advantageously considered under the three fol- lowing heads. 1. Cases in which there is a real or supposed derangement or imperfection in the processes carried on within the bone itself in order to its maintenance in the normal or healthy condition. 2. Cases in which there is inflammation of the bone, whether produced by injury, appearing idio- pathically, or connected with some specific taint. The pathological conditions of the pe- riosteum are so intimately connected with this part of the subject, that some reference to its diseases must of necessity be made. 3. Cases in which there is alteration of the original struc- ture or development of a new one ; as thus : — a. b. c. d. b. d. e. /• DISEASES OF THE OSSEOUS SVSTEM. Class i. Derangements of internal functions. Deficiency of the calca- reous deposit Rachitis. Superabundance of the calcareous deposit ..Fragility. Absorption of the calca- reous deposit Mollities. Absorption of both con- stituents Atrophy. Class it. Inflammation. Simple inflammation ..Adhesion Union of fracture. Suppuration Abscess in bone. Ulceration Caries. Mortification Exfoliation. Death with regeneration Necrosis. Specific inflammation . .Scrofula Absorption of cancelli. Deposit of a cheesy substance. Softening of the bone. Abscess. Caries. Syphilis Deposit of fluid between the periosteum and bone. Node. Caries. Class iii. Structural diseases. Spina ventosa .Development of a new cavity within a bone, with unnatural contents. Exostosis Growth of a tumour in or from a bone, Cartilage. Both structures mixed. Osteo-sarcoma Alteration of structure with deposit of a new material. Cancer.f Fungus hsematodes-f Bloody cellulated tu- mour within bone. * We refer our readers for a summary of M. Ribes* opinions, &c. to the Dietionnaire dcs Sciences [Medicales, vol. xxxviii. p. 456 ct soq. t These diseases are generally, if not always, propagated from a jacent parts or structures. 440 BONE, PATHOLOGICAL CONDITIONS OF. Rickets. — The consideration of this subject has been too frequently mixed up with that of the disease entitled mollities ossium (osteo- mulaxie ), or with that of the interstitial absorp- tion of bone which occurs in aged persons. Rachitis seems not to be so much a softening of bone that had previously been solid and perfect, as an interruption in the first instance of the process of ossification. It is a disease of early life, generally commencing, or at least first observed about the period when the infant should make its earliest attempts to walk, and rarely appearing after the age of two years. It would appear that the disease should be considered as connected with inadequate nu- trition throughout the body generally, rather than as being confined to the osseous system ; its effects are only most obviously marked on that system ; and it is quite certain that all the bones of the skeleton are more or less af- fected, although particular local causes com- monly produce much greater deformity in one than in another. The early symptoms of rickets are invariably those of imperfect or deranged nutrition, pale- ness of skin, flaccidity of fibre, &c. Along with these symptoms or shortly succeeding to them the deformities appear which cause the disease to be ranked amongst the affections of the osseous system. In mild cases these ex- tend no farther than to an increase in the cur- vature of some of the long bones and an aug- mented expansion of their extremities. Whether from its supporting the whole weight of the body or from the action of the strong muscles behind it, the tibia generally suffers in a remarkable degree : the legs are not only bent forwards, the curve being sharp and sudden about the lower third of the bone, but they are twisted in such a manner as to bring the internal ankle below its proper level, deformities which, not- withstanding a perfect recovery, are never com- pletely removed afterwards. Rickets, consi- dered alone, is not very dangerous to life : in most instances it proceeds no farther than has been already described — the visceral derange- ments are either subdued or subside sponta- neously, the healthy functions are re-estab- lished, and amongst them that of ossification, and the patient soon becomes enabled to per- form the ordinary motions, while the deformity in some slight degree disappears. But if the disease is severe or protracted, or complicated with a scrofulous taint, it generally leaves tokens behind it which embitter the patient’s future existence, or hurry him to a premature grave. Sometimes the head becomes flattened, or pushed so as to project backwards, or is otherwise strangely deformed. More frequently still the chest suffers in shape, either in the ribs, the spine, or in both, and the compressed and contracted thorax, or laterally curved spine, with all their accompaniments and consequences of deranged respiration, will be the result. But of all the parts which suffer from this disease, perhaps the pelvis is that which is most fre- quently engaged. Placed between the spine and the thighs, it is the fulcrum and centre on "hich numerous motions are performed ; it is surrounded by powerful muscles and subjected to irregular and unequal pressure ; and it also sustains the weight of the principal part of the body. Hence arise the strangest and some- times the most complicated distortions, and woe to the female who at the age of woman- hood becomes pregnant under such circum- stances. The remote consequences of rickets may, therefore, be far more formidable than the immediate. The actual condition of a bone with reference to its structure is the next point to which we must direct our attention. Is there an absolute deficiency in the quantity of ossific matter secreted, the place of which is supplied (espe- cially about the epiphyses of the bones) by a soft substance which increases their bulk ? or is the earthy material removed by absorption previous to the deposition of this softer sub- stance ? The question is not easily answered, for patients seldom die of rickets alone; and when they perish, it is generally in consequence of some complication of scrofula producing hydrocephalus, tabes mesenterica, glandular abscesses, or, it may be, caries ; and it is evi- dent that the examination of a case so mixed cannot afford a satisfactory demonstration of the disease itself. It cannot, therefore, be a matter of surprise if some difference of opinion has existed. The following is the description of a ricketty bone as given by Boyer.* It is lighter, of a red or brown colour, pierced by a great number of dilated bloodvessels, porous and spongy, soft and compressible, moistened with a sort of sanies that may be pressed out as from a sponge, or rather from leather that has been soaked to maceration. The walls of the medullary cylinder of the long bones of the extremities are greatly thinned, whilst the bones of the skull are increased in thickness and become spongy, and, as it were, reticulated. Both the one and the other, but especially the long bones, have acquired a remarkable sup- pleness, but when bent beyond a certain point they break : and the fracture takes place more easily if the inflexion is made rapidly. The medullary cavity of the long bones contains, instead of marrow, a reddish serosity, totally devoid of that fat and oily character which appertains to marrow in its natural state. The result of Mr. Stanley's-} experience is that the consistence of a ricketty bone is but slightly different from that of common cartilage, an opinion more consonant with our notions of the disease than Boyer’s exaggerated descrip- tion is calculated to convey. We ourselves have never met with that extreme degree of softness which has been occasionally described, or which would permit of the bone bemg di- vided by a knife. Meckel} states that the bones of ricketty patients are soft, spongy, flexible, and curved, both in situations where they are subjected to muscular actions, and where they have some weight to support. In the meantime '* Boyer, Traite des Maladies Chirurgicales, loro. iii. p. 625. + Medico-Chirurgical Transactions, vol. vii. | Meckel, Manuel d’Anatomie, tom. i. p. 344. 441 BONE, PATHOLOGICAL CONDITIONS OF. they receive more blood. The periosteum has undergone analogous changes. The chemical composition is not the same throughout. Thus, on theonehand, there is not always the same rela- tion between the respective proportions of phos- phoric acid and lime — sometimes too much, sometimes too little of the acid : on the other, the proportion between the animal and earthy substance varies considerably. Sometimes the quantity of animal matter is greatly increased, so that the relation is 74 : 26, or even 75,8: 24,2, or so far as 79,54 : 20,6. Often it is the same as that met with in the healthy condition, or it is even less, as 25,5 : 74,5,* although the bones are spongy. These differences depend probably on the intensity, and, more particularly, on the period of the disease ; but they prove, at least, that the essence of rickets does not consist in an original deficiency of earthy material. It is unnecessary to quote any farther autho- rities to shew that no universality of opinion prevails as to the pathology of this important disease, and that it still requires careful and accurate investigation. It seems, however, to be agreed on, that when the patient begins to recover, a great activity may be observed in the deposition of the earthy material, and that it is principally deposited where it is most wanted, viz. on the concave surfaces of the curves. Fragilitas. — We have classed a brittle con- dition of the bones under the head of a dispro- portionate abundance of the earthy substance, rather in compliance with a doctrine that was once universally believed, and perhaps is still pretty generally admitted, than as the statement of a fact that may be supported by evidence. It was supposed that the presence of a greater quantity of phosphate of lime rendered the hone short-grained and dry, and therefore more liable to snap across ; and this condition of bone, as peculiarly appertaining to old age, has been placed by Boyer among the predis- posing causes of fracture.)- The opinions of Ribes on this subject, and the doubt cast by chemical analysis on the ordinary explanations of a softened condition of bone on the one hand, and of its fragility on the other, have been already noticed, and, notwithstanding some attention to the subject, we are obliged to leave it without even attempting a solution of the difficulty ; the results even of several series of experiments, which were instituted in the years 1831 and 1832, with a view to the elucidation of this difficult question, scarcely deserve to be stated, as they were in every respect unsatis- factory. We compared the respective thick- ness of the thigh-bone in the adult and the aged, the section being made exactly in the middle : we weighed equal lengths of similar bones — we softened equal lengths and equal weights by means of dilute muriatic acid — and we burned equal portions and weights also, with a view of comparing them under these different circumstances, but could never * These chemical results are quoted by Meckel from Monro’s Outlines of Anatomy. t Traite des Maladies Chirurgicaies, tom. iii. p. arrive at any fixed or certain conclusions. In one remarkable instance the bone of a wo- man, who must have been seventy or eighty years of age, was thicker, stronger, and con- tained more both of the animal and earthy materials than any adult bone with which it was compared. We were, therefore, obliged to adopt M. Ribes’ theory of “ a change of action,” just as we see the muscle of an old man incompeteut to such a display of strength as would be easy to that of a younger person, although the latter may be smaller, and pos- sessed apparently of less toughness of fibre. Fragility seems to exist under two different conditions, one derived from, or having rela- tion to, some defect or imperfection in the bone itself ; the other being rather a symptom of some other disease than a disease itself, and arising from some vice or taint in the constitu- tion. The former of these is exhibited in the fragility occasionally observed in the bones of some young persons, and more constantly in those of the old ; but it may be remarked that the causes that produce this fragility (whatever they are) do not interfere with the restorative powers of the part. True, a fractured bone is tedious in uniting, and is frequently followed by unpleasant consequences in aged persons, but in such all the vital powers exhibit evi- dence of sluggishness and debility; whilst in youth, so far from fragility interfering with the process of union, fractured bones have been observed to be consolidated in even less than the usual period. But when any particular condition of constitution or any disease seems to be the exciting cause of fragility, it may also be regarded as a cause of subsequent non- union. Of these, cancer, fungus hsematodes, and sea-scurvy, seem to furnish the most nu- merous and best authenticated instances ; sy- philis has been added, probably from the fact of some fractures remaining disunited until the patients had been subjected to a course of mercury; its influence, however, is question- able, unless where it had previously produced caries. A state of pregnancy or of lactation has been mentioned as predisposing to fracture, and impeding or delaying the process of re- union ; but however the observation might have been occasioned by a few solitary cases, it is not borne out by general experience. In the fragility of early youth, and where union would take place quickly and kindly, it is not to be expected that the bone (if there was an opportunity of examining it) should present any morbid appearances unless the evidences of its physical weakness in the small- ness of its diameter and the thinness of its walls should be so considered. In the aged, as all persons are not afflicted with this fragility, so are there some whose bones cannot be dis- tinguished from those of the healthy adult. As to the ordinary characters of the bones of old persons, Mr. Wilson remarks they are never found so friable and fragile as to crumble like a calcined bone, but, on the contrary, they contain a large quantity of oil ; and when dried after death, they are so greasy as to be unfit to be preserved as preparations. Their 442 BONE, PATHOLOGICAL CONDITIONS OF. organized vascular partis diminished, but their oily animal matter is increased. Mollifies ossium is a disease, the phenomena of which are directly the reverse of those we have just considered. In fragilitas the bone snaps across from the most trifling causes : in mollities it is flexible, bends in every direction, and, of course, is useless for the purposes of support or motion. The morbid condition seems to arise from a want of accordance be- tween the secreting and absorbing vessels of the bones affected : if the earthy material is not secreted at all or in insufficient quantity, or if it is absorbed too rapidly, mollities will be the consequence, and we may presume that there will be variety in the rate of its progress and in the intensity of its symptoms, according to the degree of derangement of function ex- isting at different times. It may thus be easily comprehended how fragility of bone may be an early symptom of mollities, at a period when the earthy material has been removed to an extent which renders the bone completely flexible. Of the causes that produce this curious dis- ease, or of the change of structure that occurs at an early period, nothing is certainly known, indeed, it is so rare an affection that little oppor- tunity for anatomical or chemical examination in any of its stages has occurred. Boyer seems to regret our deficiency in this branch of pathological knowledge, and doubts that there are a sufficient number of authentic cases to establish such a difference between the fragility and the softness of bone as to authorize them being considered distinct diseases. There can be no doubt that in the cases of cancer, &c. which have occasioned, or been attended by, a softening of the bones, the symptom of fra- gility has been observed at one period or another, and perhaps there is no such thing as a softening of the bones independent of some malignant taint in the constitution. “ There is scarcely any case,” observes the author just quoted, “ of a pure and simple softening (ramollissement) of the bones:” not one (we believe) in which they have been found merely deprived of their earthy constituent, leaving the animal material healthy and unaltered, like a bone that had been prepared by macera- tion in muriatic acid; whilst all the dissections of mollities exhibit such decided alterations of structure as to justify an opinion of the exis- tence of some malignant disposition in the entire system. This view of the case ought to remove the disease from the position it holds in our classification, and place it among the derangements of structure, only that there is some reason for supposing that the first and early stages may be accompanied with the absorption of the phosphate of lime, and it must therefore signify little where we place an affection, of the nature of which we are con- fessedly so ignorant. There is, however, a softness and pliability of bone (we use the word softness in opposi- tion to softening) in which there is no malig- nant tendency whatever. It is original and congenital, that is, from birth the process of ossification is suspended in some part or limb. We have seen two instances of this : the most remarkable occurred in a poor man forty years of age, whose right arm was perfectly flexible, and of course powerless. He stated that lie had been so from birth, but in every other re- spect had enjoyed the very best health; he earned his livelihood with the other arm, with which he had become wonderfully dextrous. Ou the nature of the cause that could suspend a particular process of nutrition in one limb, the remainder of the body being perfectly healthy, it would be useless to speculate at present. The most extraordinary instance of mollities ossium on record is that of Madame Supiot. It may be found at length detailed by Brom- field, to whom it was communicated by M. Supe, surgeon to the hospital of La Chari tc.* This woman appears to have been an in- valid for fifteen years, during the first five of which she suffered from great weakness in her loins and lower extremities, accompanied by great pain, which, however, did not prevent her giving birth to two children within the time. When M. Supe saw her, “ the trunk was extremely shortened, and did not exceed twenty-three inches in length. The thorax was exceedingly ill-formed, and the bones of the upper extremity were greatly distorted ; those of the lower were very much bent; and the thigh-bones became so extremely pliable as to permit the legs to be turned upwards, insomuch that her feet lay on each side of her head. The softness of her bones daily in- creased to the hour of her death.” It is unne- cessary to dwell on the symptoms under which she laboured, as it must be obvious that no one viscus could perform its function properly in such an extraordinary mass of deformity as she eventually became. On dissection, M. Supe says, “ the bones, one may truly say, had arrived at the utmost degree of softness, as we have not heard of any observations similar to this case. In effect we have, now and then, remarked that bones become mem- branous and of the consistence of flesh, but I believe there never was before seen an instance of the osseous particles in the great bones of the extremities being so totally dissolved, Lav- ing no more than the form of a cylinder by the periosteum remaining unhurt.” Mr. Goochf relates a case which lasted five years, and which at an early period exhibited the symptoms of fragility, the patient having broken her leg as she was walking from the bed to her chair and heard the bones snap. The winter after breaking her leg, she had symptoms of scurvy, and bled much at the gums, and throughout her illness her legs and thighs were oedematous, and subject to excoriate, discharg- ing a thin yellow ichor. From the commence- ' ment of the attack the bones continued to grow softer, and a year before her death she breathed with difficulty, and the thorax ap- peared so much straitened as necessarily to * Bromfield’s Surgery, vol. iii. p. 30. t The Chirurgical Works of Benjamin Gooch,; vol. ii. p. 393. 443 BONE, PATHOLOGICAL CONDITIONS OF, impede the expansion of the lungs : her spine was much distorted, and any motion of the vertebrae of the loins excited extreme pain : her legs and thighs being quite useless, she was confined to her bed in a sitting posture : the bones she rested upon, having lost their solidity, were much spread, and the ends of her fingers and thumbs, by frequent efforts to raise herself, were become very broad, with a curvature of their phalanges : she now mea- sured but four feet, though before this disease she was five feet and a half high and well shaped.’’ After death she was found wanting in her natural stature two feet and two inches. “ All her bones except her teeth were more or less affected, and scarcely any would resist the knife : those of the head, thorax, spine, and pelvis were nearly of the same degree of softness; those of the lower extremities were much more dissolved than those of the upper or of any other part ; they were changed into a kind of parenchymatous substance like soft dark-coloured liver without the least offensive smell. I cut through the whole length without turning the edge of the knife, and found less resistance than firm muscular flesh would have made, meeting only here and there with bony laminae, thin as an egg-shell. “ Those bones were most dissolved which in their natural state are most compact, and contain most marrow in their cavities. This circumstance may appear more worthy of ob- servation as it held throughout, and looks as if the wonderful change they had undergone was occasioned by the marrow having acquired a dissolving quality ; for it was evident the dissolution began internally by the bony laminm remaining here and there on the outside and no where else, and the pain in the beginning of the disease not being increased by external pressure.” Mr. Wilson* met with three cases, of one of which he gives the dissection, which in some respects resembles the preceding. As it exhibited the symptom of fragility, — indeed the symptoms throughout were rather such as should appertain to fragilitas than mollilies, for most of the bones of the skeleton had given way, some of which were imperfectly united, and many not at all,- — as the bones were altered into a substance not very unlike that described by Gooch, and as the disease evidently com- menced within, we subjoin an extract from ihe dissection, which will be sufficient without entering into the more minute details. “ All the bones were diseased. The ossa brachiorum were so soft that I very readily divided them with a common scalpel from their heads until near the condyles. Immediately at the condyles both bones were hard, and the articulating cartilages had a natural healthy appearance ; both bones had been fractured ; n one the fracture had not united, and in the ather there were several fractures which had anited very imperfectly. The compact sub- stance of the bone was in some places not Wilson’s Lectures on the Bones and Joints, Q£0 thicker than an egg-shell : the cancelli were totally destroyed, and the cavities in the mid- dle of the bones were filled up with a substance which seemed to have been originally extra- vasated and coagulated blood, but which had become vascular, and had much oil deposited in the cells within it. These substances ap- peared to have produced absorption of part of the bone from their enlargement and internal pressure, for in some places the external surface of the bone was removed and tumours allowed to extend through the openings.” In confirmation of the opinion that this disease is produced by some malignant taint in the constitution, it may be proper to add that hitherto it has baffled every mode of treatment. It continues its progress without stop or inter- ruption, and is inevitably fatal. Inflammation — osteitis. — The exact process that is carried on within an inflamed part* seems not to be satisfactorily understood, al- though the subject has exercised the ingenuity and employed the research of many who have distinguished themselves in the cultivation of pathological science. If this position is true with regard to the softer and more external structures which are open to examination both by the touch and eye, it must be still more so with reference to the osseous system, the parts of which are more or less deep-seated and concealed from observation. We know, how- ever, that the process of inflammation is greatly modified by the structure of the part affected, or perhaps more particularly by its vascular organization, some powerfully resisting the inroads of disease, and repairing its ravages with wonderful activity, while others exhibit as remarkable a want of energy, seem scarcely capable of a struggle, and run at once into mortification. But as the bones, besides their animal ingredients, contain an earthy material which must exert considerable influence on the phenomena, the progress, and the results of inflammation, it will be necessary to examine the subject with reference to the nature of the structure particularly affected. A bone in its healthy condition is copiously supplied with bloodvessels. f When examined on its external surface stripped of its perios- teum, it exhibits a bluish-grey colour, evidently produced by a quantity of blood contained within it. When it is cut, or when the perios- teum is torn from it, a number of bloody specks are seen ; and the cancellated structure in which the marrow is lodged is always red, particularly in young subjects. By Mr. How- ship’s observations it appears that “ the small space occupied by the bloodvessels of the canals (within the bones) compared with that which is found to be allotted to the secretions and membranes of these cavities, distinctly proves that the circulation must, under all circumstances, enjoy as much freedom here as elsewhere ; and the intimate connexion formed by these canals between all parts of the bones * Generally spoken of as the proximate cause of inflammation. r See Howship’s Papers in the Mcdico-Chirurgi- cal Transactions. 444 BONE, PATHOLOGICAL CONDITIONS OF. and the surrounding soft parts affords the strongest grounds for believing that the minute vascular and membranous organization of the bones is as susceptible of impressions from irritation or sympathy as the muscular, glandu- lar, or other soft structures of the body.” The bones in common with other parts are conse- quently subject to inflammation with all its consequences of adhesion, suppuration, granu- lation, ulceration, &c. &c., but subject to the following modifications which result from the peculiarities of structure and material compo- sition indicated, and the intimate connexion just alluded to between them and the adjacent soft parts. 1. The connexion between the bone and periosteum is so complete that it is not easy to conceive how inflammation of a bone can occur without its membranes being more or less en- gaged, and therefore it is difficult to meet with a case of diseased bone unaccompanied by periostitis. 2. The effects of inflammation on the mem- brane and on the bone must be different. One structure can swell, the other in the first in- stance cannot; and hence the vessels of the bone itself in a state of debility and compressed by an unyielding substance are very liable to die, whilst those of the periosteum tumefy and exhibit a more mitigated form of disease. Thus the periosteum in inflammation is gene- rally found swollen or thickened, and detached from the bone underneath, which is then usually either carious or necrosed. 3. Those bones or parts of bones which are hardest and firmest usually die soonest, whence Mr. Wilson’s remark that “ they are the soonest cured,” the process of exfoliation being set up by the surrounding living parts in order to remove that which is dead. 4. In the various processes of repair and re- production the periosteum largely participates, and if this latter membrane has been injured or torn off, the vessels of the adjacent cellular tissue seem to assume a new function in order to supply its place. Thus, if a portion of the scalp is torn down, leaving the cranium per- fectly denuded, it by no means follows that the bone must exfoliate if the flap has been carefully laid down and still preserves its vitality; but perhaps the best illustration may be drawn from some cases of necrosis succeed- ing to injuries by which the periosteum had been removed, in which the process of regene- ration is commenced and completed notwith- standing. Tlius far, then, we have seen that there is little difference between the inflammatory process in bone and in any other structure of similar or equal vascular organization; the chief or cha- racteristic peculiarities must therefore depend on the presence of the earthy material, which we shall find influencing the phenomena of the disease, but perhaps more especially its progress. Thus, whether the operation is sana- tive or otherwise— whether adhesion is to be accomplished, ulceration or granulation is to be set up, or a spoiled or dead portion of bone is to be removed — the progress of the work is more sluggish, and its ultimate accomplishment deferred to a much later period, than in any other animal structure. When a bone is wound- ed, coagulating lymph is thrown outas quickly and with as much facility as from any other tissue, but nothing can be more familiarly known than that it will require a length of time before consolidation is effected, and the solution of continuity is repaired. The process of ulcerative absorption in any structure is scarcely understood either as to the stimulus which first determines the vessels to this action or their modus operandi subse- quently; still less can we comprehend how a solid unorganized material like the earthy phos- phate of bone comes to be thus removed. That this process is not performed with the same facility as in softer structures of equal or inferior vascularity is obvious from the tedious- ness of its progress, a delay that is therefore attributable to the presence of this earthy sub- stance. The absorption of the earthy particles takes place under two different conditions; one without the secretion of purulent matter (dry caries), examples of which may be seen in the caries of bones compressed by aneurisma! tu- mours, and in some cases of angular curvature of the spine. It is of importance to remark this kind of caries, and to observe that its pro- gress is equally or perhaps more rapid than that in which purulent matter is secreted. Many writers have assumed that pus possessed a solvent quality, and by thus preparing the ossific matter for absorption, materially assisted in the process — an idea which the preceding observation strongly militates against. In the other there is a secretion of purulent matter, and the case is analogous to suppuration and ulceration in the softer tissues, except that the process is still very slow, and in general the odour of the matter is very offensive. Adhesion* Formation of callus. — The phe- nomena attendant on this process are most easily and familiarly observed in the re-union of fractures. It is very remarkable, however, that considering the number of celebrated men who have directed their attention to this subject, and the opportunities for observation that are so constantly occurring, nothing has yet been positively determined. We have theories in abundance, apparently founded on and sup- ported by experiment, but still so contradictory that it is impossible not to entertain a suspicion that the theories were in general formed in the first instance, and the facts, if they did not immediately apply, wrested a little in order to support them afterwards. Hence this part of our pathological studies consists of little more than a history of opinions and doctrines neces- sary to be known as constituting part of the literature of the profession, but totally unavail- able to any practical purpose. The most ancient explanation of the process by which callus is formed is, that it was per- fected by means of a viscous fluid poured out.1 around and between the fragments of a dividea bone, which were thus mechanically glued to- * The adhesive ossihc inflammation of Hunter. 445 BONE, PATHOLOGICAL CONDITIONS OF. gether. This fluid, which was termed tiie osse- ous juice, was supposed to acquire the requi- site consistence afterwards, and thus became the medium of a firm union. Nothing, how- ever, was said of the time or manner in which the consolidation was effected, nor of the absorption of the superabundant part of this fluid subsequently. The first who doubted this theory of the osseous juice, or rather who thought it insuffi- cient, was Duhamel, a man of extraordinary ingenuity, but unfortunately not a physician, and therefore not qualified to examine or to explain the results of vital actions. He adopted his ideas as to the formation and growth of bone analogically from trees and vegetables, and supposing the periosteum to answer the same purpose to bone that the bark did to the wood, he conceived that ossification went for- ward by the conversion of the internal layer of periosteum into bone. It was natural, having formed this theory as to the original conforma- tion, to advance it still farther into an explana- tion of the mode of re-union in fracture. He said that the extremities of the torn periosteum covering the fragments swelled ; that they met, and uniting, formed a kind of brace or ferule inside and outside of the fracture; sometimes, in case of the external membrane being torn off, the internal answered every purpose alone; sometimes the external periosteum was suffi- cient, but in every case it was this that perfected the operation. It is needless now to canvass a theory that has long since been given up as untenable, yet as if to show how little of novelty can be expected in physiological rea- soning, it will be found that an opinion not very far removed fiom this in its bearings was the one entertained by Dupuytren, so recently lost to science. The next opinion to be noticed is that of Haller. This great physiologist, who was a cotemporary of Duhamel,* quite dissatisfied with the ideas entertained in his time on this subject, endeavoured to develope the truth by experiments, and conducted many, in conjunc- tion with a pupil of his named Dethlef. The result was, that the process of re-union ap- peared to him to be the same as that of the original ossification ; 1st, that a gelatinous or gluey substance is poured out around the ends of the fragments; 2d, that this substance be- comes converted into genuine cartilage ; and lastly, that an osseous deposit is laid down in the cartilage, forms a ring of bone, and gra- dually increases until the entire ossification is completed. This theory is principally objec- tionable in the regularity with which these changes are said to take place, whereas it is more than questionable whether this gelatinous fluid, the origin of the callus, ever becomes car- tilage at all. Doubtless it is altered in con- sistence and becomes hard and firm, opaque and elastic, and thus far resembles cartilage in its sensible qualities ;f but it is tinged of a red * Haller was born a short time after Duhamel, and died before him, this latter philosopher having attained the age of 82. t Macdonald. colour by feeding the animal with madder, which is not the case with cartilage; and che- mical analysis shews its nature to be osseous and not cartilaginous. However, the experi- ments of Haller and Dethlef are entitled to great attention from the care with which they were conducted, and with a little modification their results are probably not very remote from truth. Hunter, so happy in the doctrine of adhe- sion, endeavoured to extend it as widely as possible, and has certainly simplified both our notions with respect to divided parts and our practice in procuring union, although his cor- rectness in considering effused blood to be the medium of that union has been frequently doubted. According to him, the first effect of fracture is, the effusion of blood from the ruptured vessels of the bone and the adjacent structures: this blood becomes organised by vessels shooting into it ; whilst in the mean time the ends of the fragments inflame, and this inflammation produces adhesion in the surfaces that are even, and a disposition in the scales or points of the broken edges that re- main, to be removed by absorption. Pretty nearly the same are the conclusions to which Mr. Howship arrived after a series of expe- riments conducted with great accuracy and minuteness. This paper is in the ninth volume of the Medico-Chirurgical Transactions, in which these experiments (performed on the fractured bones of rabbits) are detailed and illustrated with engravings. They refer to the appearances observed on the third day, on the fifth, the ninth, the fifteenth, the twenty-third, and thirty-second days after the fracture. The relation of these experiments singly would occupy more space than can be appropriated to this part of the subject, and we must therefore confine ourselves to the conclusions as drawn from them by the author himself. He concludes that the first effect of fracture is extravasation of blood into the surrounding cellular struc- tures, principally that of the periosteum ; into the medullary cavities of both fragments and between their fractured extremities. This blood soon coagulates ; after some further time its colouring matter disappears ; and the thick- ened periosteum becoming more firm assumes the sensible characters of cartilage. The de- position of osseous matter takes place within the coagulum, beginning at the part nearest the fracture and extending gradually from this point: it even commences in the clot situated within the medullary cavity before the coloui- ing matter is removed ; but under every cir- cumstance and in every situation, we are to understand that the coagulum of blood is the nidus of ossification and the medium of union between the fragments. Notwithstanding the respect due to such high authority, there are many who do not believe in the possibility of effused blood becoming organised, and look with doubt and suspicion on every experiment and every observation by which such a doc- trine is sought to be established. They reason, that if, under any circumstances, blood became the medium of union, we ought to leave the 446 BONE, PATHOLOGICAL CONDITIONS OF. surface of a stump or other wound covered with clotted blood, and spare ourselves all the labour and pains we employ in removing it and placing the cut surfaces cleanly in appo- sition with each other. And they also remark that when a clot of blood is left behind, how very commonly, instead of becoming organised, it lies as a dead substance in the wound, im- pedes the union, promotes suppuration, and imparts to the discharge a putrid and offensive odour. These pathologists suppose that in many instances the fibrine of the blood has been mistaken for coagulating lymph, which is the natural product of the vessels in the adhesive stage of inflammation, is capable of becoming organised, and ought to be the legi- timate seat of any deposit to be afterwards laid down in completing the process of union. We now pass to the theory of Bordenave, Bichat, and Richerand, who make the union of fractures analogous to that of the soft parts by the second intention, or by means of 'granu- lation. Like other pathologists, they have supported their opinions by observation and experiment ; and without entering into the minuter circumstances connected with this hy- pothesis, it will be necessary to mention some very familiar facts that bear upon the case. In necrosis, the surface of the new or grow- ing bone is often seen covered with granu- lations. In cases of amputation, when the bone protrudes after eight or ten days, the cut extremity is observed to be fungoid and granu- lated. And in some cases of compound frac- ture we can observe the process of granulation going forward, and actually see that it is thus the union is completed. It nevertheless ap- pears very doubtful whether granulation has any part in the process of uniting a fracture, unless where a communication exists between the broken ends of the fragments and the ex- ternal air. In a compound fracture, or in the case of a bone protruding from a stump, there will be granulations, often to a degree of excessive exuberance ; and in them there will be a deposit of osseous substance, because new structures always assume to a certain extent the nature of the parts from which they are produced ; but in a case of simple fracture, where there is no wound, no communication with the atmosphere, and not a single drop of purulent matter is formed, it is very doubt- ful whether granulations could exist; at least their existence has never been demonstrated. Amongst modern pathologists, Meckel’s'* opi- nion is entitled to very great respect, although we may not be disposed to accede implicitly to his views. He ranks among those who consider the process of consolidation in frac- ture to be similar to that of original ossi- fication, and states, that at first there is an effusion of a gelatinous substance which gra- dually becomes firmer and more solid in con- sistence, and is converted into cartilage, in the interior of which osseous nuclei appear that join to each other and to the broken ends of the bone, and also envelope any fragments that * Manuel d’Anatomie, tom. i. p. 335. may have been detached. At the same time the spiculae or scales become rounded off' in order that the surrounding parts may not suffer injury or irritation. It is not necessary to the perfection of this union that the ends of the fragments should be accurately in contact: it is sufficient if they lie against each other, and then the union occurs by the same means, and exactly on the principle of anchylosis taking place between different bones. It must be understood that this ossific deposit is laid down both external to and within the bone ; that when union is complete, the bone is di- vided into two cavities internally; and that, for a length of time afterwards or for ever, it may be known, by making a longitudinal section, whether a bone had ever been broken or not. lie further states that the part sur- rounded and joined by ossified callus is stronger and firmer than any other, and to all appearance this observation is correct, but it is contrary to one of Mr. Ilowship’s experiments, who saw the callus break down and crumble away in an attempt to calcine it, and therefore concluded that it was softer and more highly animalized. Hitherto we have noticed a number of the- ories, all of which, with the exception of that of Duhamel, bear a strong similarity to each other, the principal points of difference being, 1 . as to whether the soft gelatinous substance, which all agree in having seen, was the fibrine of the blood deprived of its colouring matter, or genuine coagulating lymph effused by in- flamed vessels : 2. whether this in process of time was changed into real cartilage, or the osseous deposition took place into this lymph very much inspissated : and, 3. whether any- thing like adhesion happened, or the conso- lidation was perfected after the manner of union by the second intention, namely, by granulation. We now proceed to take a view of a new theory bearing some resemblance to that of Duhamel, and supported by the autho- rity of Dupuytren. He supposes that there are two distinct and different processes in the j union of bone. First, that there is a callus formed like a brace or ferule round the frag- i ments externally, with a plug of the same material within, the object of this provision being, to hold the ends of the fracture in ap- position whilst the union that is to he per- manent is going forward : thus we arc to imagine a kind of natural splint placed around and within the fractured pieces in order to preserve them in situ. This preliminary pro- cess commences almost immediately after die accident, and is completed in the space of from four to six weeks. Matters remain thus, while the ends of the bones are becoming per- manently united, which they are in about eight months, during the latter period of which time the mass of new material is declining in size, and is eventually removed so as to leave the bone of its natural extent and figure. The formation of this first callus, which he calls “ cal provisoire,” is attributed to the perios- teum and occasionally to all the surrounding structures, and in the centre of it he sup- 447 BONE, PATHOLOGICAL CONDITIONS OF. poses the fracture to remain for a considerable time un-united, the limb being, of course, weaker here, so that, in the event of the occur- rence of a new fracture, this will be the spot in which it will give way. The second or per- manent callus, which he calls “ cal definitif,” is the actual medium of union between the fragments, and remains like the cicatrix of a wound in the soft parts. It must appear curious to the reader that no positive conclusion should have been obtained on a point which has occasioned so much inquiry, and which apparently was so easy of determination. It is open to experiment; obvious to the senses ; and there are few sources of fallacy except such as might arise from previously adopted views of the expe- rimentalist, and perhaps from different periods puring the progress of ossification being chosen for making the observations, and the same thing, of course, being seen under different circumstances. We think it might have been reasonably suspected from analogy, (and the experiments of Breschet and Villerme have confirmed the idea,) that nature, in the sim- plicity of her operations, produced every where similar effects from similar causes, and that, in whatever manner the re-union of divided soft parts was accomplished, the same would hold good as to bone, only allowing a longer time in order to admit of the consolidation of the lymph by osseous deposition. And such is probably the fact. In an incredibly short space of time after the receipt of a fracture, the process of repair seems to be actively com- menced : coagulating lymph is effused in con- siderable quantity, probably mixed with blood, as the coagulum is found to possess a more than ordinary firmness and consistence. At the end of the second day the torn edges of the periosteum are evidently thickened, pulpy, aDd vascular, easily receiving coloured in- jections. At the end of the fourth day, we have seen the sharp edge of the fracture be- ginning to be rounded off. Where the surfaces of the fragments are broad and thick, it is easy to observe them coated with a deep layer of lymph, which adheres to them tenaciously from a very early period. If the fragments are in apposition, the torn extremities of the peri- osteum are united by the intervention of this lymph, the membrane appears greatly thick- ened also, and seems to afford a kind of pro- tection to the fracture ; or, otherwise, an im- mense and irregular mass of lymph is thrown out around both fragments, filling up all the space that has been occasioned by the dis- placement of the bones and the laceration of the soft parts. In effecting this deposition, all the vessels of the part, those of the bone, periosteum, and adjacent structures, seem to he equally engaged. In process of time this ymph becomes organised, assumes a ligamen- ts rather than a cartilaginous appearance, dthough, strictly speaking, the new structure possesses not the true characters of either, and inally is converted into bone by the simul- taneous establishment of numerous but irre- ular specks of ossification. This process varies as to the time required for its com- pletion according to a number of circum- stances, such as the situation of the bone, the part of it broken, the apposition of the frag- ments, rest, and many others that need not be enumerated here ; as well as the age and con- stitution of the patient, which exert such marked influence on all cases, that it is im- possible to lay down certain rules for calcu- lating the time that may be required for the union of any given fracture. The process of re-union, however, is some- times very imperfectly performed ; sometimes it is suspended indefinitely, and occasionally it is not performed at all. Of the causes that occasion these deviations from the natural and usual progress of ossific union we are in ge- neral ignorant, although there are many cases in which former experience may enable us to predict the occurrence of such an event. It has been already stated that the diseases which occasion a fragility of bone will be likely to interfere with its subsequent union, and in these cases little more is accomplished than the removal of the sharp spiculated edges by ab- sorption : the presence of such a constitutional derangement as would occasion a bone to give way in the effort to turn in bed will be suf- ficient to explain its want of re-union. But these are not the cases generally met with. When there is an un-united fracture, or as it has been termed, a false joint, the ends of the fragments are not smooth and polished moving on each other like articulated surfaces, but are joined together by the intervention of a liga- mento-cartilaginous substance, which, accord- ing to its extent, is more or less flexible, and of course incapacitates the bone from the per- formance of its functions of support and mo- tion. This imperfect union occurs in some bones with wonderfhl regularity ; we may, for instance, calculate on such an event in frac- tures of the neck of the thigh, and in the trans- verse fracture of the olecranon and patella ; but it happens at other times quite unexpect- edly, in cases wherein we could suspect no possible cause, in which there may have been no neglect, no impropriety of treatment, to lead to such a result. We have lately seen two cases of fractured femur remain un-united at the end of five and six months in the per- sons of fine and apparently healthy young men, although the ends of the bones were kept in apposition, and in every other respect the treatment was correct. The chief causes* to which this imperfect union has been attributed are a removal, or rather a withdrawing of the broken surface of one fragment from the other, a want of vascu- larity in one of the fragments, and the fracture not being maintained in a state of uninter- rupted repose. The frequency of this occurrence in fractures of the above-mentioned bones, in which the fragments are always withdrawn from each other, was too remarkable not to lead to the connexion of the circumstances as cause and * Sir A. Cooper on Dislocations and Fractures. 448 BONE, PATHOLOGICAL CONDITIONS OF. effect, the only objection being that the result is not uniform and universal. Fractures have been submitted to each of the above con- ditions, more especially to the maintenance of exact co-aptation for months, yet has no ossific union been produced ; and again a firm consolidation has taken place between two bones, the extremities of which had been sawed off and the parts placed under circum- stances that could not permit of the approxima- tion of the divided surfaces. We have a case published as having occurred in the hospital of La Charite in Paris, in which the os calcis was broken ; and although the surfaces of the fragments were never completely separated, yet the usual kind of ligamentous connexion took place ; and for proof that a solid union may occur under the circumstances above- stated, we refer our readers to Mr. Crampton’s second case of extirpation of the knee-joint.* * * § If we can subscribe to Larrey’s opinion that only the vessels of the bone itself can minister to osseous union, and that those of the peri- osteum and adjacent structures are incom- petent to such function, (an opinion in which he is to a certain extent supported by Mr. Liston, f) it is obvious that a union between fragments at a distance from each other would be difficult if not impossible. Here, however, as well as in every other part of the history of ossific union, it is only conjecture. We have nothing like substantial definite proof, and must only rest satisfied with a knowledge of the fact without being able to explain it, that the medium of union between fragments, the faces of which are withdrawn from each other, is in general not osseous. Whatever may be the operation of this cause, that of the other two is by no means so ob- vious. The second J has been generally ad- duced in explanation of the non-union of fractures of the neck of the thigh-bone, but perhaps without being entitled to the impor- tance that has been attached to it. If a part is only possessed of a degree of organisation barely sufficient to preserve its vitality in ordi- nary circumstances, but inadequate to accom- plish any process of repair, it should follow that any violence offered to it ought to cause its death, or at least its removal by the ab- sorbents, and in such case the caries or exfo- liation of a fragment of bone might be easily understood. But these are not the results of fracture of the neck of the femur except in very rare and anomalous cases ; and, on the contrary, there is scarcely an example of exami- nation after death that did not exhibit a conside- rable display of reparative energy, although the results were not such as to produce ossific union. Professor Colies § has published twelve cases of post-mortem examinations of this accident, in some of which he observed the appearance of ivory-like patches on the surface of the superior fragment, evidently proving the ex- * Dublin Hospital Reports, vol. iv. p. 236. t Elements of Surgery. t Cooper’s Surgical Essays. § Dublin Hospital Reports, vol. ii. p. 334. istence of considerable ossific powers in this part. Besides, this condition of the head of the bone has been assumed rather than proved. On the most attentive examination, we have not been able to observe any deficiency of vascu- larity within it; and if there is any difference between the head and neck and shaft, we are rather disposed to believe the head to be pos- sessed of the highest degree of organization. The advantage of the most absolute rest to the cure of fracture has been observed in all ages, and yet is it doubtful how far its influence on the question under consideration can be appre- ciated. Few fractures can be kept in a more perfect state of repose than those of the patella or of the heel, yet the union in both these cases is always ligamentous. It would appear as if constant although very trifling motion was more prejudicial than occasional shocks however rude and productive of greater dis- turbance, and this perhaps is the reason why false joints so frequently occur after fractures of the clavicle, even although the fragments have never suffered displacement, as occurs when the bone is broken near its acromial extremity. Suppuration may occur in the osseous tissue under a variety of conditions, as to situation, as to the character of the matter, and as to whether it is produced by or connected with any constitutional or specific taint. Pus is occasionally, though not frequently contained in a cyst or sac within a bone, as the result of inflammation, and resembling the common ab- scess in the soft parts. These collections are never very large ; they are usually situated in the thick and spongy parts of the bones, and have a strong tendency to burst into the neigh- bouring joint. We have seen a case of abscess in the head of the tibia, which appeared to have opened into the knee-joint even after ii had burst externally. The disease had pre- viously existed for months, the patient suf- fering very little either locally or constitutionally until the communication with the cavity of the articulation was established, when the symp- toms became so aggravated as to demand the speedy removal of the limb. The symptoms of suppuration within a bone are exceedingly obscure, nor is there any certainty until the abscess has burst and a probe can be passed into the cavity, particularly if the inflammation has not been attended with enlargement of the bone. The pain is said to be agonizing, but this is not universally true, and we may infer that suppuration has taken place “ by the violent symptoms of active inflammation les- sening, by cold fits and shivering occurring, j by a remission of pain with an increased sense of weight in the part ; but all these are fab lacious, and no external marks of suppuration are at first to be observed, the disease affecting parts too deep to be seen with the eye or fob with the finger.”* Suppuration on the surface of a bone is o very common occurrence, and so constantl; complicated with affections of the periosteum * Wilson on the Bones and Joints. 449 BONE, PATHOLOGICAL CONDITIONS OF. that it is difficult to say which structure is the source of the purulent secretion; the disease, indeed, is generally described under the name of periostitis. We are disposed, however, to regard it as inflammation of the bone in the first instance, although the membrane comes very soon to be engaged ; because in many cases the pain in the commencement is not ag- gravated by external pressure, which it uni- formly is when the periosteum is engaged, and also because in very severe cases, such as paronychia periostei, a portion of the bone becomes carious, and is lost even from the earliest period. It is most frequently ob- served in connexion with some constitutional taint, such as scrofula or syphilis,* but it may and very often does appear purely as an idio- pathic disease. “ Inflammation of the pe- riosteum, unconnected with any known con- stitutional disease, is an affection with which practical surgeons are well acquainted. It is remarkable, however, that a disease so impor- tant in its consequences and of such frequent occurrence, should not have been noticed in any systematic work, nor have been made the sub- ject of any separate inquiry .”f Whether we consider this affection to belong primarily and principally to the bone or pe- riosteum, it is certain that the former structure always is engaged, and shews the most evident marks of activity in the disease, although this, perhaps, may in part be explained by the fibrous texture of the membrane and its defi- cient organization. The bone is always in- flamed. Even in the most chronic case that leads only to a thickened condition of the pe- riosteum, the bone is preternaturally vascular, and so soft that it is often difficult in such cases to distinguish the limits between the sof- tened bone and the condensed periosteum. J In the severer forms, the bone, unable to sus- tain itself under the excitement, is always dead, and must be gotten rid of by ulceration or exfoliation : in these cases the periosteum is detached, and a fluid, very generally thin, ichorous, and fetid, is interposed between them. Between these extremes there is every possible variety, and, therefore, there will be vast diff- erences in the results of the inflammation, * Of all the causes that produce these affections >f the bones, an irregular or protracted use of mer- ’uty seems to be the most efficacious. Many sur- ;eons of the present day doubt whether a suppu- rating node is a true or genuine venereal symptom. iVe have learned from an experienced army surgeon, rho spent many years on the western coast of Africa, vhere the venereal disease is not known, but where aercury is profusely employed in the treatment of iver complaints and other diseases incident to the limate, that affections of the bones, resembling hose considered to be venereal, are of exceeding requency. It is a remark worthy of attention to jae curious in such matters, that nodes, &c. formed o part of the symptoms of syphilis as first observed nd described, and that the first practitioner who oticed them (John de Vigo, 1519,) is mentioned y Astrnc, (page 158,) as an eminent promoter of ,'e mercurial method of cure, and as having by that leans acquired great reputation and riches. : t See a paper by Mr. Crampton, in the Dub. ! osp. Reports, vol. i. f Ibid. VOL. I. sometimes in the mere thickening of the pe- riosteum, sometimes in the deposition of more bony matter, or the apparent ossification of the membrane (exostosis) ; occasionally in the ab- sorption of the bone, and most frequently, particularly in specific diseases, in that which is our more immediate object, the deposition of purulent matter. A node is a swelling situated over a bone, hard, firm, and exquisitely tender to the touch, not round or circumscribed at its base, but gradually subsiding to the level of the adjacent parts, and not discoloured on the surface. It is at all times painful (except in some scrofulous cases), and when arising from a venereal cause, is subject to nocturnal exacerbations of great severity. The morbid anatomy of the disease is not always the same even when examined at the same period of duration, being modified by a number of circumstances, such as the age of the subject and consequent vascularity of the bones; the structure of the bone en- gaged being solid and firm or soft and spongy ; but more particularly by the fact of the disease being idiopathic, or produced by some consti- tutional affection. The scrofulous diseases of bones seldom or never exhibit the symptom of nodes, although attended by suppuration, be- cause they affect their substance rather than their surfaces : idiopathic nodes, or those pro- duced by injury, do not suppurate unless the violence used is great ; on the contrary, these are cases which so frequently terminate in thickening of the periosteum, &c., and often, when cut into, scarcely afford any perceptible discharge. The venereal or mercurial node offers the best example of suppuration. At an early period, if an opportunity occurs for exa- mination, the periosteum round the margin of the effusion shews a more than ordinary degree of vascularity ; immediately covering the tu- mour it is somewhat paler, more opaque and thickened. The bone underneath is denuded and soon runs into caries ; between it and the membrane the matter is deposited, thin in con- sistence, dark-coloured, and sanious. There are other forms of suppuration on the surface of a bone of too much interest and im- portance to be omitted, such as those large de- pots which occasionally occur after severe in- juries or operations, as the accompaniments of inflammation of the veins, or as the sequelae of acute fevers. In general, the matter is in great quantity and of a good and healthy cha- racter, though sometimes it is otherwise, and particularly in that form which attacks a stump after amputation. We have seen the entire remnant of the bone up to the next articulation denuded of its periosteum, while quantities of green and fetid pus could be pressed from the very depths of the wound. In these cases the veins are generally inflamed, the divided ends of the muscles pale, flaccid, and sloughy, and the patient seldom or never recovers. Where the deposition has taken place after fever, if the patient is young and the constitution has enabled him to combat the original disease, a recovery very frequently takes place by the process of necrosis. 2 G 450 BONE, PATHOLOGICAL CONDITIONS OF. Caries from a scrofulous cause, generally, if not always, commences in the cancellated structure ; that from syphilis affects the firmer and more external parts of the bone. The former attacks the ends of the long bones and the spongy and cuboid bones generally ; the latter, the centres of the long bones and the flat ones. Venereal nodes principally affect the bones which are nearest to the surface of the body, the skull, the tibia, or the sternum; it being rare to see the humerus or femur thus diseased, whilst they are by no means exempt from idiopathic or strumous inflammation. But the most remarkable differences to be ob- served between caries arising from a specific cause, and that which occurs idiopathically or from injury in a constitution otherwise good, occur in the progress and termination of the disease. The process seems to be analogous to that of ulceration in the softer tissues, and when recovery takes place, it is by granulation and cicatrization in like manner. Thus, if we suppose an abscess to occur on the surface of a bone in a healthy man, when it is opened or has burst, we find that a scale or shell has lost its vitality and must be thrown off by exfo- liation, and soon exuberant and florid granula- tions are seen springing from below as if to force the offending substance off, and the dis- charge from the cavity is healthy pus. On the other hand, if a venereal node is opened on the skull, the pericranium is here detached, the table is carious and will exfoliate, but there is (as long as the taint remains) no effort at re- paration ; the discharge is thin, ichorous, and unhealthy ; and if we may judge by the repre- sentations we see of venereal caries, (for in modern times mercury is not so unsparingly used and real specimens are not numerous,) the disease would progress until the skull was fairly corroded through. Again, the lymph secreted in scrofulous inflammation is not healthy, and there are seldom granulations ; whilst the matter is either of that whey-like appearance so remarkable in such affections, or else a foul and fetid sanies. Every one con- versant with surgery must know how tedious and obstinate a scrofulous caries is, and how frequently it involves the loss of limb or of life. The true scrofulous affection of the bones occurs so frequently in this country as to re- quire particular attention ; it constitutes the vast majority of the diseases of the osseous system that we are called upon to see and to treat. It commences (as we have said) in the cellular or cancellated structure. In the first instance there is an increase of vascularity, which, though not always apparent to the eye, may easily be proved by injection. Next, there is an absorption of the natural contents of the cancelli, and in their room a substance is deposited of a yellow or white colour that has been described as resembling cheese in consistence ; it is, however, most probably a species of that flocculent unorganized lymph, such as is seen coating the cysts of scrofulous abscesses. The cancelli themselves are oc- casionally removed, and masses or patches of this unorganized material deposited in their stead, hence the bone becomes lighter, and so soft as to allow of being cut with a knife. It is remarkable that the disease may have existed up to this period, when it is probably incura- ble, without much pain and without external swelling to attract attention to the mischief underneath. In the Museum of the School of Anatomy, &c. of Park-street, Dublin, there is a preparation to illustrate necrosis of the centre of the shaft of the thigh-bone, for which the limb was amputated. The patient during life never complained of the knee, neither was there the smallest enlargement of the articula- tion ; yet after removal the condyles of the femur internally were completely softened, the external shell of solid bone being reduced in thickness nearly to that of parchment, the can- cellated structure completely removed, and its place occupied by this cheesy substance. This condition of the bones is considered by Mr. Lloyd* as constituting the first stage of scrofulous disease, and he justly remarks that it is quite uncertain how long they may con- tinue in this state without further mischief taking place. The next step is the erosion or absorption of the cartilages, if the affection is situated in the head of a bone, (see Joint,) or otherwise near an articulation, and probably about the same period the external soft parts sympathise, and lymph is extensively deposited around the deep fibrous tissues in the neigh- bourhood. This lymph is afterwards to be- come the seat of abscesses, which always communicate with the diseased bone, and very generally with the cavity of the adjacent joint. 1 The limb or part is now swollen : the tume- faction is round and well defined, tolerably firm in consistence, and elastic to the touch ; the colour of the skin is of a more than ordi- nary paleness, and its surface is marked by the meandering lines of numerous small blue veins. The growth of the tumour seems to be limited, for having reached a given size it becomes stationary and never increases, al- though the disease may appear at times even ! more fully developed. Subsequently the pain is very variable ; that attending on scrofulous j diseases being generally described as dull and heavy rather than acute, but this idea must be received with some limitation, for occasionally the very reverse is the truth. We have seen some patients the victims of most intense irri- tation and suffering throughout every stage of carious ulceration ; and even when it is other- wise, they are always liable to severe exacer- bations on any injudicious attempt at motion, any improper diet or other irregularity. In all cases there seems to be a considerable ag- gravation of symptoms, both local and consti- tutional, about the period when suppuration is established, and whilst the matter is progress- ing towards the surface. It may be a long time before the tumour gives indications of being about to burst exter- nally, partly perhaps from the imperfect organi- zation of the lymph by which the matter is * See Lloyd on Scrofula. 451 BONE, PATHOLOGICAL CONDITIONS OF. secreted, and partly because it seldom takes the shortest route to the surface, but proceeds by devious and intricate windings. At length the tumour, at one limited and almost circum- scribed spot, becomes soft, then assumes a dark red or purple colour, finally a small slough forms on the surface and it bursts, giving exit in general to a greater quantity of matter than the size of the abscess would have led us to anticipate. The abscess does not collapse, and although the discharge may continue in pro- fusion for months, the size of the tumefaction is never proportionally diminished. After it has burst, a small papilla of very red granu- lation (a most unfailing symptom of the exis- tence of a diseased bone underneath) is pushed out through the aperture. From the centre of this a small drop of matter can generally be pressed, and through it the discharge flows ; never for obvious reasons profusely at a time, but still so constantly as to soil the dressings and the bed-clothes extensively in a single night. When a probe is passed down to the bottom of this ulcer, which it is not easy al- ways to accomplish, the bone is felt completely denuded, soft and rotten, and the instrument sinks into it with very little resistance. Most frequently the earthy material of the bone is removed by the absorbents ; sometimes a small portion of it thus detached is washed off by the discharge, and is occasionally found block- ing up the little orifice, occasioning a good deal of irritation and pain, and almost always an access of fever. Sometimes the remains of the bone come away in a larger mass, quite dead, light, and porous, and, when dried, per- fectly friable. Previous to the formation of the matter, however, the pathological state of the bone has undergone a remarkable change. Hitherto we have seen that an increase of vascularity oc- curred at an early period, and preceded the deposition of the soft and cheesy substance ; but in proportion as this deposit is increased in quantity, the vascularity decreases, and with it the vitality of the bone. “ If a scrofulous bone be injected at an early period,” says Mr. Lloyd, “ or before the whole of its cancellous structure is altered, the injection very freely enters its vessels ; but if it be injected at a more advanced period, there evidently appear to be fewer vessels, though it is very probable that a fine injection may be forced into vessels which had previously ceased to carry blood.” In the correctness of this observation Sir B. Brodie coincides, as well as in the opinion “ that this diminution of the number of ves- sels, and, consequently, of the supply of blood, is probably the proximate cause of those exfo- liations which sometimes occur, where the disease has existed for a considerable length of time, especially in the smaller bones.”* Although carious ulceration, or, as it would be more correctly termed, absorption of bone, is so frequently attended by the formation of matter and abscess, yet such is by no means a See Lloyd on Scrofula, p. 123, and Brodie on me Joints, last edition, p. 195. necessary consequence— at least, we have ex- amples of the removal of large portions of bones without any such unfortunate accompa- niment. These principally appeal’ under two distinct forms : one, where such absorption is the result of inflammatory action within the bone itself, the most familiar illustration of which is to be found in the caries of the spine attending on some cases of angular curvature : the other, where the absorption has been occa- sioned by the pressure of an aneurism, an abscess, or other tumour in the immediate neighbourhood. Mr. Pott, and others who have described this caries of the spine, mention that, at first, the bodies of the vertebrae seem to spread so as absolutely to become larger than in a state of health; that the ligaments are loose and detached, and the intervertebral cartilages sepa- rated from the bone. The first part of this description is certainly not correct, for in all the subjects we have had opportunities of ex- amining, nothing like an enlargementorswelling of the bone appeared. It must be recollected that dissections of this disease at an early period are rarely met with — never unless the patient had been accidentally seized by some mortal affection soon after the spine had been attacked. It may, therefore, be supposed that these early descriptions were taken from ana- logy with what other bones suffer in scrofulous disease, and it is well known that, until a com- paratively recent period, it was a universally received opinion that the heads of bones be- came actually enlarged under similar circum- stances. Sir B. Brodie, who has given the clearest as well as the most succinct description of caries of the spine we have met with, considers that its pathological history may be arranged under three heads. 1. “ It has its origin in that peculiar sof- tened and otherwise altered condition of the bodies of the vertebrae, which seems to be connected with what is called a scrofulous state of constitution. In these cases ulceration may begin on any part of the surface, or even in the centre of the bone, but in general the first effects of it are perceptible where the interver- tebral cartilage is connected with it and in the intervertebral cartilage itself.”* As this is an instance of scrofulous caries, such as has been already noticed, it should perhaps have come more legitimately under consideration in that part of our article. We prefer, however, to take a distinct and separate view of caries of the spine, because the locality invests the disease with some peculiarities. For instance, this scrofulous caries is almost invariably attended by abscess, and we find these collections to be much larger in quantity of contents, and, if possible, more sluggish in approach to the surface than when situated elsewhere. Their existence, therefore, may not only not be suspected, but the symptoms occa- sioned by them during life may be attributed to a totally different cause. They are least * Brodie on the Joints, p. 243. 2 c 2 452 BONE, PATHOLOGICAL CONDITIONS OF. frequently met with in the neck, but when so situated it is easy to conceive how they may occasion dysphagia or difficult respiration. We have seen a case where such an abscess occasioned symptoms resembling those of com- pression of the brain, and we have the notes of one in which death was produced in a very sudden and unexpected manner, the matter having burst into the sheath of the spinal marrow. They may also occur in connexion with disease of the dorsal vertebrae, and within the chest give rise to symptoms resembling the different forms of deranged respiration — tho- racic aneurism — and, under peculiar circum- stances, even of empyema. Such difficulties are now not so likely to occur, as we have auscultation to assist the diagnosis ; but we recollect to have seen more than one case treated as a pulmonary affection, the real nature of which was caries of the dorsal vertebrae, complicated with abscess pressing forward within the posterior mediastinum. Abscess in the loins connected with diseased vertebrae is too familiar an occurrence to require any lengthened details. As far as our own observation can guide us, we believe the appearance of abscess as an accompaniment of spinal disease to be almost always a fatal symptom ; and when, in the course of a wasting and protracted discharge, spiculae of carious bone, or portions of a sub- stance resembling ivory or enamel are seen to come away, the aspect of the case is still farther formidable — very few, if any, ever recover under such circumstances. 2. “ In other cases the vertebrae retain their natural texture and hardness, and the first indication of the disease is ulceration of one or more of the intervertebral cartilages, and of the surfaces of bone with which they are con- nected.”* “ There is still another order of cases, but these are of more rare occurrence, in which the bodies of the vertebrae are affected with chronic inflammation, of which ulceration of the intervertebral cartilages is the consequence.” We shall now proceed to detail the results of our own observations, in order to see how far they coincide with those of the learned and accurate surgeon already quoted. In two instances we have, in the dissecting room, seen the intervertebral substance eroded at the anterior edge, the bodies of the adjacent bones remaining unaltered in shape or consis- tence, and to every appearance in a perfectly healthy condition. These were, at the time, regarded as specimens of the very earliest and incipient stage of the disease, and although no clue could be obtained as to the history of the cases, it is worthy of remark that not a trace of scrofulous disease could be discovered in any other parts of the bodies. In general, however, it is otherwise. The body of the bone seems to be seized with scrofulous inflammation, and the peculiar ef- fects of this morbid action are produced within it. It becomes softer in consistence, in conse- * Brodie, loc. citat. quence of the absorption of its osseous parti- cles, and a deposition of the cheesy lymph in its stead. At this time, although so soft as to admit of being cut with a knife, the bone ap- pears unaltered as to size or shape, but its absorbents begin to act upon the ligaments and intervertebral cartilages, and hence is it that the separation and ulceration of these are amongst the earliest appearances. In many instances the connexion between the cartilage and bone is so much impaired, that if we wanted to separate them with a knife, the former would come off in one entire flake. The edges then begin to be eroded and ulcerated, as if gnawed by a mouse ; and at this period also the ligaments are often found thickened and softened, and matted up together into a confused and indistinct mass. The body of the bone then becomes carious, and the ulce- ration commences at the anterior part of it : very rarely is the posterior layer of firm bone, that forms the front of the canal for the spinal marrow, affected ; and never does the caries spread to the processes. Up to this period it may be, and often is, a specimen of purely dry caries, being unattended by the formation of a single drop of purulent matter. As the disease proceeds, and the bodies of one or more vertebrae are removed, those which remain approximate more or less above and below : the spinous processes project, and a bending of the body forward is produced. The character of this curve is influenced by the extent of the destruction that has been accomplished within ; it is sharper and more angular when the body of one vertebra only has been removed; it is more sweeping and gradual when three or four have suffered. Never, we believe, is the angle so sharp as to permit the denuded surfaces of the vertebra above and I below to come into actual contact, the sound 1 condition of the bony parietes of the spinal |j sheath effectually preventing this ; and hence, I when recovery takes place, it is not by the I adhesion of these surfaces, but by the forma- I tion of a quantity of new bone which fills up I the vacant space, producing a perfect example I of true anchylosis. j The developement of such a curative pro- I cess as this is scarcely to be expected in a K scrofulous system, yet is it satisfactory to know I that even under such circumstances the case is !,' I not utterly hopeless. We have seen repeated I instances of angular curvature without the Q occurrence of abscess, in patients apparently I deeply tainted with scrofula, one of which is E so very remarkable as to deserve particular I notice, because it illustrates a mode of union || that frequectly occurs in scrofulous cases, and jjl because the preparation is in existence to de- ■ monstrate the fact. In July, 1830, a wretch' 1 I young girl was brought into the Meath hospital M with a very acute angular curvature of the | ■ dorsal vertebra. Almost every joint in her K5 body was diseased, and the knees so extensively! ■ that the eroded condyles of the thigh-bones were exposed, from the surface of one of which thej H mud of the street was wiped away after ■ her admission. It need scarcely be added H BONE, PATHOLOGICAL CONDITIONS OF. that her sufferings were not of long duration, and an opportunity was speedily afforded for examining the pathological condition of the back. It appeared that three of the vertebra had been engaged, the spongy portion of one of which had been completely removed. There was nothing like a reproduction of osseous material, although the caries had long ceased, and the spine was sufficiently strong for every ordinary purpose of support; but the space that had been left by the absorption of the bone was filled up by a ligamento-cartilaginous substance, which, attached like a new and adventitious ligament to the vertebra above and below, held them with a sufficient tight- ness to prevent the smallest motion, and gave to the entire column a tolerable degree of firm- ness. We have also seen examples of true bony anchylosis in patients apparently scrofu- lous, but it seems to occur generally in males rather than in females, and more particularly in patients about or approaching to the age of puberty, a period at which it is generally sup- posed some important change takes place in the Constitution of scrofulous subjects. Where there is no such taint, or where, as Sir B. Brodie expresses it, the bones retain their na- tural texture and hardness, it may be easily conceived that a cure is effected in less time and with less difficulty. There is another specimen of caries or ulce- ration of bone without the formation of matter, occasionally observed in the neck of the thigh- bone of very old persons, the symptoms of which have particular relation to the hip-joint; we shall therefore postpone our remarks on it until we come to discuss the pathology of joints. Necrosis. — There are few subjects more in- teresting either to the pathological inquirer or to the practical surgeon than the death of a portion of the osseous system, and the circum- stances connected with this event. Neither is there any one with respect to which the ideas of medical men generally are less definitively settled. Thus also some confusion has crept into our nomenclature, and necrosis and ex- foliation have been often indifferently used, as if they applied to one and the same diseased action ; or, perhaps, to speak more correctly, the term necrosis has been made to extend to every case in which a bone or a portion of a bone is deprived of vitality, no matter how the dead material is to be removed or replaced. According to the etymology of the term such s in fact its true meaning ; nevertheless, we ire hardy enough to dissent from this applica- lon of the word, and to confine its use to one orm of the death of a bone, exfoliation more iroperly belonging to another. And we do so he more readily because not only do these two . flections present different pathological pheno- jnena, but there are such practical discrepancies •etween them that it is essential to every sur- eon to have a distinct and separate notion of ach. | Exfoliation, then, expresses the death of a ortion of bone which is either never replaced, r replaced by a process which is set up after 453 its death, and is analogous to mortification in the soft parts, where the slough is thrown off, and the consequent ulcer subsequently heals by granulation and cicatrization. Necrosis is the death of a bone or part of a bone accompanied by a process of regeneration established at a time coeval or nearly coeval with the inflammation or accident that deprives it of vitality. In this point of view the disease is singular, there being nothing like or ana- logous to it in any affection of the soft parts. Necrosis is rarely a disease of early and never of advanced life, being, except in cases where it attacks the lower jaw, almost exclu- sively confined to the period between the ages of ten and twenty-two : exfoliation may occur at any time, but is more likely to appear in the adult or the aged. Necrosis, although it may succeed to acci- dent, as in this manner compound fractures and other injuries are not infrequently repaired, yet is it more generally an idiopathic disease, or may be the sequela of continued fever; whilst exfoliation in the great majority of instances is the consequence of injury. According to the acceptation in which we employ the term, it is extremely questionable whether necrosis is ever a disease of the flat bones; at least, except in the instance of the lower jaw, we have never met with an example of the death of one of these structures accom- panied or even followed by a regenerative pro- cess. As necrosis, then, presents a solitary exam- ple of the efforts of nature in counteracting, or rather in providing against the ravages of dis- ease, the process by which it is accomplished becomes an exceedingly interesting subject of inquiry. Different opinions are entertained upon this subject. It seems to be agreed upon all sides that the commencement of the disease is marked by inflammation of the bone: at this period it is red, vascular, and receives the tinge of coloured injections. How this in- flammation may be caused or why it is followed by the formation of new bone, are points not so easily determined. Troja introduced a sharp instrument through a bone, by which he con- trived to destroy the internal periosteum and marrow, and thus produced a number of cases of necrosis, which presented the same sym- ptoms and ran the same course as if they had been examples of idiopathic disease. Hence it came to be believed that the death of the inter- nal periosteum was a necessary prelude to necrosis, until it was observed that the parts surrounding a bone had assumed those actions which end in the formation of a new one before the absolute destruction of any part of the old one whatsoever ; and therefore that, although the injury inflicted on the internal periosteum might cause necrosis, yet it was only one cause, and acted by creating inflammation within the substance of the bone. Thus we are obliged to return to the point from which we set out : we know that inflammation is established within the bone, and, coeval with this or nearly so, that nature commences the process of repro- duction ; but why this latter is confined to a 454 BONE, PATHOLOGICAL CONDITIONS OF. limited period of our existence, or v»hy even amongst young persons it may occur in one individual and not in another, form questions to which, in the present state of our knowledge, we can give no answer. We are not even agreed on the different steps of the process or on the structure principally engaged. It has been observed that the portion of the bone which is to die, and for some space above and below it, is surrounded by a dense thick- ened mass, of rather a gelatinous character ; that this mass, after a very short time, becomes opaque in detached spots, and that depositions of osseous material are found within it, so that a case of bone may be constructed around the original one before it actually dies, and thus the limb never be entirely deprived of support.* As soon as the dead bone separates from this surrounding mass, the internal surface of this new material becomes, under some circum- stances, covered with a layer of lymph, and under others with regular ossific granulations, which gradually increase until a new bone is formed, nearly as serviceable, though not so symmetrical or so beautiful as the old one. It next becomes a question, what is this gelatinous mass, and whence is it derived ? It has been supposed that it was the periosteum of the old bone swelled and thickened, and at the same time softened in consistence; and this opinion has been strengthened by Dr. Macartney,-)- the present Professor of Anatomy in the University of Dublin, who stated that he had opportunities of watching the progress of the disease from its earliest periods upwards. According to this gentleman, “ the first and most important cir- cumstance is the change that takes place in the organization of the periosteum : this membrane acquires the highest degree of vascularity, be- comes considerably thickened, soft, spongy, and loosely adherent to the bone ; the cellular sub- stance, also, which is immediately connected with the periosteum, suffers a similar alteration : it puts on the appearance of being inflamed, its vessels enlarge, lymph is shed into its inter- stices, and it becomes consolidated with the periosteum.” Next, “ the newly organized pe- riosteum, which, for the sake of distinction, one might call the vascular sheath or investment, separates entirely from the bone, after which it begins to remove the latter by absorption, and during the time that this process is carrying on, the surface of the vascular investment, which is applied to the bone, becomes covered with little eminences, exactly similar to the granula- tions of a common ulcer.” To this doctrine Mr. Russell, of Edinburgh, strongly objected. He stated that if the osseous matter was depo- sited between the layers of periosteum, both the external and internal surfaces of the new de- posit ought to be perfectly smooth, whereas the contrary is observed — they are rough, irregular, and one of them is covered with granulations. He instanced cases of fracture in which, one fragment overlapping the other, and being thus * See Russell on Necrosis. t See Crowther on White Swelling. Edition 1808, p. 183. permanently entangled, the periosteum between the two can have no share in the reproduction, and yet the whole is united by a cylindrical shell of bone, on the principle of reproduction in necrosis. It is also known that compound fractures, where the fragments have been exten- sively stripped of periosteum, have united in the same way, and the regeneration of bone, in these instances, could not be attributed to peri- osteum, inasmuch as that had been destroyed. It must be owned that this is a very unusual occurrence in compound fractures, but one sin- gle example will be sufficient to prove that the reproduction can take place independently of the periosteum. And again, in cases where disease has caused the sloughing and destruc- tion of the periosteum, as for instance in deeply seated paronychia, still reproduction is some- times accomplished by a process resembling necrosis. These arguments seem to be very decisive in overturning the doctrine of the sur- rounding shell being formed by the periosteum, and accordingly Russell supposed that a depo- sition takes place from all the surrounding structures ; that it is at first gelatinous ; that it soon assumes the appearance of cartilage ; and that at the end of twenty-four days bony specks I may be discovered within it. The external surface of this deposit is rough, and attached to the surrounding parts : its thickness is quite unequal, being greater in proportion to the du- ration of the disease, and always more so than the bone it is destined to replace. The internal surface, or that next the old bone, is more smooth, and covered either with lymph or gra- nulations. Boyer, Meckel, Weidmann, and I other continental surgeons, attribute the process |j nearly altogether to the periosteum, and there- fore their opinions need not be particularly dis- cussed ; but it is proper to mention that all the very accurate descriptions we read, of the pro- gress from gelatine to cartilage and from carti- lage to bone, must be received with the utmost caution. It is by no means usual to meet with cases exemplifying these descriptions ; and amongst a considerable number of dissections of necrosis, it will perhaps be difficult to find one in which the existence of cartilage car, be separately and distinctly shown. Such is an outline of the chief opinions en- tertained on this interesting subject, and it is probable that, to a certain extent, they arc all correct. When the poeriosteum has not been removed or spoiled, there can be no doubt that, it is deeply and even principally engaged in the process of reproduction. In the museum all Park-street, the specimens exhibiting the earliesj period of the disease show the periosteum a| slightly thickened, smooth on its internal, bu more rough and flocculent on its external sur face, detached from the bone, the surface oj which is smooth, and scarcely appears ciiangei1 from its natural and healthy condition. At more advanced period, the periosteum is sti! thicker, but is not softened ; on the contrary it has nearly the firmness of ligament, an there are small osseous depositions within it the bone then being rough and uneven on i surface and evidently having lost its vitalit 455 BONE, PATHOLOGICAL CONDITIONS OF. But although we concede to the periosteum the principal office in the process of reproduction, we can also conceive that the adjacent tissues are also more or less engaged, for the thicken- ing of parts is found to extend on the outside of this membrane, and Dr. Macartney himself speaks of the cellular tissue external to the periosteum becoming altered and condensed. Now, supposing the periosteum to be destroyed, these structures may be capable of supplying its place and producing the secretion of gelati- nous substance, which is afterwards to become bone, just as we see that if the periosteum is torn off a bone, the adjacent tissues laid down upon it may prevent exfoliation, and answer every purpose of nutrition and preservation that the original membrane did. From what- ever source derived, this deposition begins while yet the original bone is in a state of in- flammation, and the part that is to die still un- detached. If tendons or muscles are inserted into this part of the bone, they, being living and organized substances, separate from that which is dead : but the previous deposition has ex- tended about them, and fastened them in their situations, and hence not only is the limb capa- ble of support during the progress of necrosis, but unless in exceedingly rapid, acute, and un- favourable cases, its motions may not be very materially impaired. Soon after the investing shell has been form- ed, the dead portion of the bone separates from its attachments, and lies within its osseous case. It is now termed the sequestrum, and presents some remarkable and peculiar charac- ters that distinguish it from diseased bone otherwise circumstanced. Its extremities are always jagged, pointed, and uneven : its mar- row and internal periosteum have disappeared : its length and its diameter are always much less than ought to be anticipated from consi- dering the size of the bone that has died ; and its surface is uneven and marked with slight depressions, as if part of its substance had been taken up by the absorbents. This ap- pearance is more distinctly observable, and the sequestrum is always smaller where the surface of the new shell is covered with granulation, than when it is only smeared over with lymph. And here, as in other cases, it maybe observed that the existence of granulation or of lymph on the new bone seems greatly to depend on the free admission of air to the cavity. Where the bone is deep-seated, as in the thigh, and there are but a few sinuous apertures that can scarcely render the cavity analogous to an open sore, the surface is covered by a layer of lymph ; but where it is more superficial, as when the shaft of the tibia has come away and left the new osseous deposit totally uncovered, its entire surface is seen studded over with healthy gra- nulations, which, on passing the handle of a scalpel over them, are found to be gritty, and give sensible indications of containing bony matter. From the first formation of the newT deposit, small holes or perforations exist in it, the edges of which are bevelled down and thin, and not- withstanding that the new bone may and usually does become extremely thick and spongy, these apertures still remain thin : it is through them the matter makes its way to the surface and forms the fistulous ulcers that attend on this disease, and are to be described hereafter. These apertures remain as long as there is a single spiculaof sequestrum within to keep up irritation and protract the suppuration. After the sequestrum has completely disap- peared, the growth of osseous material still continues internally until the new shaft appears one solid mass devoid of any cancellated or medullary cavity whatever. At this period the ulcers are healed up, and the patient enjoys a wonderful use of his swollen and deformed limb, but the pathological condition of the bone is still deserving of attention. At first it is a mass of soft and spongy texture. After the lapse of a few years, though still clumsy in shape and undiminished in diameter, the bone has become much more firm and solid, and in these respects, at least, equals the original structure. At a more remote period the osseous part is wonderfully solidified, being, in some instances, as firm as ivory, and a new medul- lary cavity, with an internal periosteum, is formed. When a transverse section of a tibia so circumstanced is made, the osseous walls are found to be hard, thick, and very firm, the medullary cavity much narrower than in the healthy bone, being scarcely capable of admit- ting more than a goose-quill, and it does not seem to be cancellated or reticulated, but merely to consist of one continuous cell. In this state the bone possesses nearly three times the weight of one in the natural condition, and when dried is of a dirty brown colour, never assuming the white tint or polished appearance of the remainder of the skeleton. Necrosis once formed is variable in its pro- gress and indefinite as to the time that may be necessary to its completion. Sometimes the affection of the bone is exceedingly acute, ac- companied by external inflammation resemb- ling phlegmonoid erysipelas : in these cases the bone soon dies, the sequestrum separates and protrudes very rapidly, perhaps even before the new deposit has attained strength to sup- port the limb, so that it is necessary to preserve it artificially as to shape and length until the process is complete. Within the last year we nave seen a case in which, through neglect of this precaution, the tibia is bent nearly into the shape of the letter C. In other instances the disease is extremely tedious, requiring years before the sequestrum is either removed or ab- sorbed : we possess a preparation exhibiting a specimen of necrosis of more than six years’ duration, in which the sequestrum is of a more than ordinary size. Between these extremes of great rapidity and as great tediousness there is every possible variety, and perhaps these me- dium cases are the most unfavourable, for the very rapid are over before the constitution is broken down, and the very slow produce their effects on the system so gradually as not to make any decided or severe impression ; whilst those which exhibit the symptoms of abscess, with an extraneous body working to gain the 456 BONE, PATHOLOGICAL CONDITIONS OF. surface and not able to accomplish it quickly, occasion much suffering, and if there is ever danger to life or limb from the disease, such cases are most likely to produce it. The sequestrum or dead bone is disposed of either by presenting externally and permitting of its removal by the process of ulceration or by manual operation, or else it is never seen, and is entirely carried off by the absorbent vessels. Mr. llussell accounted for the disap- pearance of the sequestrum in a very unsatis- factory manner. He considered the dissolution of the dead bone to be “ greatly accelerated by the solvent power of the purulent matter,’' a property, the existence of which in pus both observation and experiment render question- able : and when thus macerated, he conceived it to be prepared to be removed by absorption or washed out by the discharge of the matter. But, if the surfaces of a sequestrum are exa- mined, that which is next to the granulations of the new bone will be found to be irregularly marked and indented, as if by the action of the mouths of the absorbents, whilst the other is’ comparatively smooth ; and as every part ex- posed to the action of the fluid should suffer equally if the removal of the osseous particles was effected by maceration, there are strong reasons for believing that the disappearance of the sequestrum depends not on any power chemical or mechanical, but on some vital pro- cess, and therefore probably on the action of the absorbents. When the sequestrum presents externally, either one end of the bone (almost always the superior one) protrudes through the soft parts and remains there dry, hard, and dead for a longer or shorter time, until it becomes de- tached by the slow process of nature, or is separated by a surgical operation ; or else the middle of it presents, and can be seen or felt through an aperture in the surrounding new bone whilst its extremities are confined. In either case the process of removal is extremely tedious. W'hen the end presents, it is gene- rally moveable, and seems as if very little force would be sufficient to detach it altogether ; yet if an attempt is made to pull it away, it is by no means easily accomplished, and a con- siderable time elapses between the first pro- trusion and its final and complete separation. When the middle presents, the process is still more protracted. All bones do not seem equally liable to necrosis. Perhaps the tibia is as fre- quently attacked as all the other bones of the skeleton taken together ; next in frequency is the humerus, the bones of the fore-arm, the thigh, the clavicle, and lastly the lower jaw. Thus far, it will be seen that we have con- sidered necrosis as a disease, distinct and dif- ferent from every other affection of the bones whatever, and that its chief and most marked characteristic is the process of regeneration. Kegarded in this point of view, it is as much and even more an action of health than of dis- ease, and it can easily be understood why the constitution suffers so little, why the hectic fever is of so mild and mitigated a form, and why in a simple and uncomplicated case re- covery is nearly certain. It is also evident that this disease will not be likely to occur in a constitution contaminated with syphilis, scro- fula, scurvy or any of those other vices which the continental surgeons not only think it may be united with, but which they adduce as its occasional exciting causes. Doubtless, if the death of a bone from any cause or under any circumstances — if caries, exfoliation, and other such destructive maladies are to be included as species under the generic name of necrosis, such affections may not be inconsistent with the existence of any poison or any taint ; but if the idea of a process of reproduction co- existent with that of disease must be admitted as appertaining to this affection, it will be im- possible to recognise scrofula or syphilis as connected with it in the remotest possible de- gree. Perhaps we shall incur censure for thus attempting to limit the signification of the term, but it has been observed that the nomen- clature of surgical pathology is too loose and undefined, and in no instance is the remark more applicable than with reference to the dis- eases of the osseous system ; and again, patho- logy to be useful must be practical, and we can by no means assimilate caries which is so des- tructive of the limb or fatal to life — or exfo- liation, which is always attended with loss of substance — with necrosis, the essential cha- racter of which is a process of reproduction, and its natural termination recovery. In attempting to describe, or even to arrange the remaining diseases of the osseous system, the pathologist has to encounter difficulties al- most insurmountable. Some of these are na- tural to and inseparable from the subject, as 1st, the depth at which a bone maybe situated will render it difficult to discover a change of shape or size, much more to ascertain an altera- tion of structure. 2d. The bones do not al- ways exhibit a very active sensibility; when attacked by chronic forms of disease, they do not cause very great pain, and consequently the evil may be well established and irreme- diable before the patient is fully sensible of his condition. 3d. These affections are not fatal at an early period ; they run a long and ted'ous course before they destroy life or render the removal of the limb indispensible. And hence in any individual case it may be difficult to learn even the early history or commencing symptoms, much more the nature of that pecu- liarity of constitution that disposes to these diseases, or the first changes that take place from a healthy to a morbid structure. Little, indeed, can be ascertained with certainty as to the nature of osseous tumours until the part has been removed, and then the information comes too late for any useful purpose. Another source of embarrassment exists in a want ol ac cordance as to the nomenclature of these affec- tions. One surgeon calls that exostosis which another has named osteo-sarcoma, and a third has designated as cellular exostosis an affection which he himself in another place has named spina ventosa. In order, in the present in- stance, to avoid similar confusion, we must endeavour to construct an arrangement which 457 BONE, PATHOLOGICAL CONDITIONS OP. shall give to each class of disease its own ge- neric term ; and although occasionally such deviations from the usual operations of nature will present themselves to the pathologist as to baffle all his attempts at classification, still we believe such a foundation as we allude to will be eminently useful, whatever superstructure may be raised upon it. Spina ventosa. — In our museums of morbid anatomy, there is no want of specimens exhi- biting the separation, or rather expansion of the solid walls of a bone, leaving one or more cavities within it; these cavities having during the patient’s life been filled with a secretion that presents considerable variety in different cases, sometimes possessing a moderate degree of firmness and consistency, but more frequently consisting of a fluid of a serous character and reddish colour. This is the disease to which we apply the name of spina ventosa in contra- distinction to abscess within a bone, from which it differs in its extremely chronic nature and tedious progress ; in its not containing purulent matter ; in its having no tendency to burst into any contiguous joint; and (until at a very ad- vanced period) in its not being complicated with caries.* Boyer divides this disease into two species, one of which is peculiar to chil- dren, and continues to the age of puberty ; the other, the spina ventosa of adults, which ex- hibits the characteristic features of the disease more perfectly. It is, indeed, difficult to separate the first- mentioned of these affections from our com- monly-received notions of caries, and in the various instances we have seen we have always regarded them as such. Boyer attributes it to the influence of a scrofulous taint within the system, and says that it attacks the metacar- pus, the metatarsus, and the phalanges. It commences and continues for a length of time either without pain or with very trivial suffer- ing ; the tumefaction of the parts is moderate, their motions scarcely interfered with, and re- covery finally takes place about the age of pu- berty by a species of necrosis. Its course is thus described : “ The progress of the disease and the distension the soft parts undergo, cause them to ulcerate at a spot always corresponding to some aperture in the osseous cylinder, and permitting the introduction of a probe within its cavity. The external aperture becomes fistulous, and for a long time discharges a moderate quantity of ill-digested serous matter. The part, however, remains indolent, the con- stitution does not suffer, and if the patient can thus attain that epoch of life at which nature commonly can struggle with success against scrofula, this form of spina ventosa may be cured by necrosis of a part of the spoiled bone. Then the sequestrum is detached, the re- mainder of the osseous parts subside, resolu- tion is established, and the disease ends by a deep, adherent, and deformed cicatrix.” We hav e not met with the affection as here described — we have never seen any thing like the rege- i neration of a bone thus lost, nor can we con- * Diet, des Sciences Medicates, tom. lii. p. 311. ceive necrosis, which is essentially a reproduc- tive process, to be in anywise allied to or con- nected with scrofula ; we therefore still regard this disease, which after all is not very frequent of occurrence in these countries, as a modifica- tion of caries. “ The other species, fortunately more rare but much more serious, most frequently attacks adult persons, and affects the extremities of the long and cylindrical bones of the limbs.” Its exciting cause seems to be involved in utter obscurity, nothing being known with certainty concerning it. Very often the patient traces it to the receipt of some injury, bnt it occurs so frequently without any such provocation, that it must be considered as an idiopathic disease. It is found most frequently, as Boyer has re- marked, in the long bones, where the medullary cavity is best developed, but it is seen in the flat bones also, and in so many instances in the lower jaw as to render it an object of attention with reference to this bone alone. Its com- mencement has no characteristic by which it can with certainty be known, and its progress is equally variable, being generally slow, but sometimes remarkably rapid. It commences with pain, occasionally deep and dull, occa- sionally severe to excess, either when its pro- gress is rapid, or it presses on some sensible or important part. This pain, with very few ex- ceptions, precedes the swelling, and when the disease attacks the lower jaw is almost con- stantly mistaken for common tooth-ache — a mistake that leads to the extraction of one or more of the teeth and the consequent exacerba- tion of morbid action. The tumour seems to engage the entire circumference of the bone, if it be a round one; if flat, the swelling is more oval, and sometimes it is irregular and lobula- ted. It is hard, firm, unyielding, and incom- pressible : pressure on it does not occasion an aggravation of pain, unless it shall have hap- pened that the periosteum is inflamed, when of course the smallest pressure will occasion suffering. In the commencement it bears a strong resemblance to necrosis of the long bone, except in not being preceded or accompanied by fever, and in not being so painful or so rapid in its progress. In the flat bone it has a greater likeness to osteo-sarcoma, from which it is so difficult to distinguish it that many cases of spina ventosa have been operated on and removed as examples of the other disease. Nevertheless at a more advanced period the diagnosis is more easy, for spina ventosa does not reach the great, or rather the illimitable size to which osteo-sarcoma may attain. In a pathological point of view, spina ven- tosa should not be considered as a malignant disease : it often endures for a length of time or during life without engaging adjoining structures or contaminating the constitution, and if removed by operation it does not recur in another place or seize on some other bone. It is, moreover, not infrequently capable of relief or even of cure by the simple operation of exposing the cavity and evacuating its con- tents We have at this moment before us the details of a case in which the patient referred a 458 BONE, PATHOLOGICAL CONDITIONS OF. spina ventosa of the lower jaw to a blow re- ceived forty-one years previously, during the last twelve of which the tumour had been opened or given way spontaneously three seve- ral times. In hospital it was punctured through the mouth, and found to consist of three dis- tinct cells, each containing its own collection of a fluid of the consistence of oil, varying from a straw colour to that of coffee, the darkest being lodged within the largest cell. This patient, though at the advanced age of sixty- seven, was relieved by the operation, and left the hospital convalescent. If, however, by the term malignant is meant a disease that may prove destructive of life or limb, spina ventosa can occasionally lay claim to the title. For it sometimes happens that small dark red or pur- ple elevations appear on the surface of the skin, which soon ulcerate and burst, discharging a quantity at first of the material contained within the bone, the character of which subsequently alters into a brown, unhealthy, fetid, and often putrid sanies. This ulceration is much more likely to take place when the surface of the tumour is uneven and lobulated, and at this period the disease in appearance bears no very faint resemblance to fungus bsematodes. The external sores next become fistulous and fun- goid ; they lead down to the cavity or cavities within the bone, and the patient, worn and wasted by an ill-formed irritative hectic fever, sinks exhausted and dies. Boyer* in his description recognizes these two forms of spina ventosa. “ Sometimes,” says this author, “ having attained a size dou- ble or triple that of the natural dimension of the bone, the tumour ceases to make further progress : it no longer causes pain ; it does not interfere with the motions of the part, but re- mains stationaiy, and continues thus during life, without any alteration of the soft parts, which accustom themselves by degrees to the state of distension in which they are placed. But much more commonly it continues to in- crease, until it slowly arrives at an enormous size, still preserving its inequalities of surface or acquiring new ones.” Having proceeded to the period of ulceration, the conclusion of the case is thus delineated. “ Arrived at this point, the local disease exercises a baneful in- fluence on the constitution of the patient: the edges of the fistulous apertures become de- pressed and inverted towards the interior of the tumour ; the discharge becomes every day more copious and more fetid ; the fever which ap- pears commonly at the period of ulceration, but which at first is intermittent and irregular, comes at last to be continued, and assumes the character of hectic : the pains are unceasing, and sometimes intolerable; sleep and appetite are deranged or lost ; consumption establishes itself, and the patient dies exhausted and worn out.” Other authors, however, have considered spina ventosa in all its forms as a malignant disease. Such must have been the opinion of Mr. B. Bell,* of Edinburgh, not only from his descriptions, but from the practice he incul- cates. “ The treatment,” he says, “ of spina ventosa is very simple, as the surgeon, when he is insured of its existence, must at once have recourse to the amputating knife. If the dis- ease is seated in the bones of the metacarpus or metatarsus, as is generally the case in child- hood, they should be removed at the articula- tions. If it has attacked the tibia and fibula, or radius and ulna, the amputation may be performed either at the knee or elbow, or a short way above these joints. The general rule to be observed is, that the entire bone in which the disease has its seat should be removed.” The morbid anatomy of spina ventosa throws but imperfect light on its pathology, principally because the first and early changes induced by the disease are wholly unobserved, and there- fore are we ignorant both of the peculiarity of constitution that disposes to it, and of the local alterations that are first developed. Even at a more advanced period, when an opportunity is afforded of examining the part after death or removal, there is no striking uniformity of ap- pearance. The bone itself, as Boyer remarks, seldom seems to have suffered any actual loss of substance : on the contrary, it often appears rather to have gained in weight, the walls ex- panding and becoming thinner in proportion as the cavity within increases in size. As to the number, size, and shape of these cells, there is an infinite variety as well as in the appearance of the surface, which may be smooth, irregular, or lobulated, and in the character of the mem- brane lining the cells and the material secreted by it. There is in the museum of the Anato- mical School, Park-street, Dublin, a very curi- ous specimen, exhibiting a perfect bony cyst developed within a spina ventosa of the supe- rior maxilla, and completely contained within the expanded walls of the bone. It is a very remarkable circumstance connected with these alterations of structure, that although they usu- ally commence near the extremities of the long bones, they never attack the joints, and conse- quently the motions of the adjacent articulation may be but slightly impaired, even although the size of the tumour may be such as to inter- fere with the natural shape of the joint, and render its usual appearance obscure and indis- tinct. Exostosis. — We employ this term to indicate certain tumours growing from the outer sur- face, or rather the external structure of a bone, in the production of which neither the medul- lary substance within nor the periosteum with- out have any participation. And although our notions of the nature of the disease may not be perfectly correct, and our descriptions lame and incomplete, we still prefer this arrange- ment in order to separate the disease under consideration from spina ventosa on the one hand, and osteo-sarcoma on the other. It will be necessary also to distinguish it from nodes and some other affections of the periosteum, in * Loc. citat. * Treatise on Diseases of the Bones, by Benjamin Bell, edit. 1828. 459 BONE, PATHOLOGICAL CONDITIONS OF. which a deposit is found between it and the bone, or between the laminae of this ifiembrane. Exostosis, then, may consist of different struc- tures^— -of cartilage alone — of cartilage mixed with some material resembling ligament — of cartilage mixed with osseous structure, which is by far most frequent of occurrence — of pure bone — and lastly, of a much harder, firmer, and closer substance, nearly resembling ivory. It may attack any bone whether flat or round, and may be found in more than one bone at a time : perhaps the femur and the tibia are most frequently engaged. Like most other affections of the osseous system, the causes that lead to the production of this disease are involved in the greatest obscurity. Unquestionably they sometimes appear as the results of accident, but then, when other and more severe injuries constantly occur without inducing such a consequence, the unavoidable conclusion must be that some peculiarity of constitution predisposing to the disease exists in the individuals who suffer from it. Exostosis has been seen, though not frequently, at a very early period of life; it has occurred idiopathically and attacked several bones in the same individual at the same time ; after complete removal it has grown again with an inveterate pertinacity, and we have seen it in two or more individuals of the same family. Boyer* considers the venereal poison to be the most common cause of exostosis, scrofula to have but little connexion with it, and scurvy still less. Other French writers! take a more extensive range, and adduce as causes, accident, cutaneous affections, scrofula, scurvy, cancer, and venereal. We cannot coincide with any of these opinions. Scrofula, when it attacks a bone, produces a destructive caries, and not an adventitious growth; scurvy, a softness or brittleness of bone. If there is any idiopathic disease of bone bearing the smallest resem- blance to cancer, it is osteo-sarcoma, and vene- real or even mercury we suspect to have a closer connexion with caries than exostosis. In every form of exostosis, no matter from what cause proceeding, (and we have seen that its exciting causes are sufficiently obscure,) the surface of the bone and its substance to some depth become altered into a structure nearly resembling that of the morbid growth. Patho- logists are not agreed as to whether this altera- tion should be attributed in the first instance to au inflammatory process within the perios- teum or the bone itself. Mr.CramptonJ makes the terminations (as they are technically called) of chronic inflammation of the periosteum to consist in cartilaginous thickening of the mem- brane, absorption of the subjacent bone, or the deposition of an undue quantity of bony matter upon its surface, the first and last of which are evidently forms of exostosis. How- ever, leaving this part of the subject, which after all is not of much practical importance, still unsettled, it may be remarked that whether * Traite des Maladies Chirurgicales, tom. iii. p. 549. r t Diet, des Sciences Medicales, art. Exostose. J Dub. Hosp. Rep. vol. ii. p. 433. the morbid action commences in tire bone or not, this latter structure is always extensively engaged. Exostosis is seldom to be met with like a circumscribed tumour in the soft parts connected by a narrow neck or bounded by a well-defined base ; on the contrary, the bone forms a considerable portion of the swelling, which generally seems to spring gradually from an extended portion of its surface. The symptoms of exostosis may be arranged into those produced by the inflammatory or other diseased action within the bone or perios- teum, and those occasioned by the pressure of the tumour on the adjacent organs. In general it is said not to be very painful nor very sen- sitive to the touch, but this opinion must be received with great limitation. We have wit- nessed the case of a young gentleman who had exostosis on the front of both tibiae. Here was neither nerve to be compressed nor muscle to be interfered with, yet the pain was so great that he insisted on their removal. The part was as hard and firm as ivory, and removed by the mallet and chisel. His sufferings were extreme : he was subsequently attacked with erysipelas, and his life brought into extreme danger, yet did he not regret his pain and the risk he ran when considered as the price of the relief he had obtained. The pain in this case could not be regarded as the result of pressure on any very sensible structure. However, the situation of the tumour may not only occasion a great aggravation of suffer- ing, but be the cause of very formidable occur- rences. We have seen a very small exostosis, not larger than half a marble, prove the apparently exciting cause of epilepsy, which for years embittered the patient’s existence, and at length brought it to a termination. Indeed, it can scarcely be necessary to adduce instances in order to prove that morbid growths from the internal table of the skull may prove detrimen- tal or even destructive in a variety of ways. Such growths from the bottom of the orbit very generally destroy vision by protruding the eye from its socket; from the maxillae they may interfere with respiration or deglutition ; and in any situation where there are muscles, they must more or less change their direction or otherwise impair their motions. But beyond this they cannot be considered as malignant. — they do not involve adjacent structures in a disease similar to themselves, they do not ulcerate, neither do they contaminate the sys- tem through the medium of the absorbents. The vascular organization of an exostosis seems to be inferior to that of the bone from which it springs, and to the healthy structures whether bone or cartilage that it may appear to resem- ble; its growth is therefore in general slow and its size moderate ; but its increase is progressive, and there is no limit to the size it may ulti- mately attain, in this respect differing from the node, which soon attains its proper dimensions and does not increase subsequently. The same deficiency of organization causes it to endure an attack of inflammation but badly, and therefore, when subjected to any irritation or even exposed to the influence of the atmos- 460 BONE, PATHOLOGICAL CONDITIONS OF. phere by the ulceration of the superincumbent tissues, it is prone to fall into mortification, which is one of the methods by which a natural cure may be accomplished. Not very long since a man was operated on in the Meath Hospital for the removal of an ivory-like exos- tosis from the tibia, but the tumour was so hard as to resist chisel and mallet and every instrument that could be employed, and, finally, the operation was abandoned ; yet was the case ultimately successful, for the exposed tumour sloughed, exfoliated, and the patient left the hospital perfectly well. It is remarkable that if the exostosis has been removed by operation, the same degree of certainty as to its not returning does not exist as when it has thus sloughed away. On the contrary, when the tumour has been completely extirpated and only the sound part of the bone left, a new growth is often formed with so much certainty and rapidity as to justify the expression we have already used, of its “ grow- ing again with an inveterate pertinacity.” On this subject we recollect a story (told, we be- lieve, by Bell) which might be considered as ludicrous if it was not but too instructive. A dancing-master had exostosis on both tibiae ; they gave him no inconvenience, but the de- formity was intolerable to his eyes, and he thought it interfered with his popularity and therefore with his profits. lie persuaded a surgeon to lay them bare and scrape them down to his ideas of genteel proportion, but unfortunately the surgeon forgot that bones could granulate and grow. They did so in this case, and after a long confinement and much suffering the last condition of the patient was worse than the first' — the deformity was much increased. We distinguish a node from a truly exostotic growth by the rapidity of its formation, by its becoming stationary when it has been formed, whereas the increase of exostosis is progressive and may be unlimited ; by its being exquisitely tender to the touch ; its being subject to noc- turnal exacerbations, and by its capability of being, relieved or removed by medicine in a great number of instances. When composed of osseous material alone, the almost stony hardness of an exostosis will serve to distin- guish it, and when of cartilage, it is lobulated or nodulated on its surface, which is never the case with respect to nodes. There is a fungoid disease of the periosteum which, under particular circumstances, may be mistaken for exostosis, an error which we have witnessed, and which might be attended with serious consequences. It is fortunately of very rare occurrence, and as far as we know has not been hitherto described. In the four speci- mens which have fallen within our observation, its situation has been in the periosteum of the tibia. During life, when covered by a dense and resisting fascia, the tumour is very hard, its growth slow, and not attended with much pain ; neither is the use of the limb much impaired, as we have known a patient with this disease travel on foot a distance of six miles to the hospital. When not so restrained, its growth is more rapid : it is softer to the feel, and lias most of the external characters of malignant fungus. Frequently its surface is lobulated or otherwise uneven, when it very much resembles exostosis. When the skin gives way and ulce- rates, or if the tumour is unfortunately cut into, a bleeding fungus protrudes, that runs rapidly into a gangrene, which involves the adjacent parts; and if the limb is not speedily removed, the patient dies. When examined after death or removal, the tumour is found to be situated within the laminae of the periosteum. There is a speci- men in the museum of the school in Park-street, in which the membrane may be seen as if split, one layer passing in front of the diseased mass, and another still more distinctly, behind, be tween it and the bone. The consistence of the tumour is tolerably solid and firm, but not so solid as cartilage ; its colour is white or gray, and its vascular organization apparently very deficient. This latter circumstance is very re- markable, for in some instances these tumours exhibit a pulsatility scarcely inferior to that of an aneurism, a symptom that may render dia- gnosis extremely difficult, and which cannot be explained by any post-mortem examination. The substance of the bone beneath the tumour is always removed by absorption to a consider- able depth. Osteosarcoma. — This disease, as its name im- plies, is a degeneration of the bone into a sub- stance of a softer consistence, not, however, resembling flesh ; or rather it is an alteration of structure accompanied by a deposition of new material, and therefore attended by tumefaction to a greater or less extent. As such, it is evidently irremediable except by the knife, and if there is a disease of the osseous system to which the term malignant can be applied, it certainly is this. Its malignancy, however, has no resem- blance to that of cancer or fungus hsematodes, although like the latter it very frequently attacks ,j persons in the earlier periods of life; but it does not involve adjacent structures in a disease similar to itself, neither does it contaminate the system through the medium of absorption. The most terrific feature in its character is its ten- dency to recur after its removal from one situa- tion, being in this respect more formidable than cancer, which is, in many instances, at first but a purely local disease, and may be extirpated with complete success. This predisposition to the disease is evidently constitutional, but as we are totally ignorant of the circumstances that conduce to it, and will probably remain so, it is wholly uncontrollable by medicine or . medical treatment. This disease may possibly affect persons at every period of life, although we have not seen it in the aged. In children, particularly about the fingers, the wrists, the fore-arm, &c. nodu- lated swellings are frequently met with ot a ; large size and firm consistence, which go on progressively increasing until they arrive at a destructive termination to be described here- after. On examination a tumour is found, the external surface of which is bone, as tlnn, it may 461 BONE, PATHOLOGICAL CONDITIONS OF. be, as paper, and in some spots nearly entirely absorbed evidently shewing that the morbid action had commenced and increased from within ; the substance of this newly-formed mass being neither cartilage nor ligament, but per- haps something between both, and yet not so entirely so as to deserve the name of ligamento- cartilaginous, or to be likened to any natural animal product whatever. It has been de- scribed by Bell as a substance much resembling callus.* Again, in another specimen as it ap- pears in the adult, (in the lower jaw for in- stance,) the part of the bone in which the dis- ease commenced is completely spoiled and changed into a mass of this new material, assu- ming a rotund tuberculated appearance. From thence downwards, towards the spot where the bone is not spoiled, there is an admixture of this new material with gritty particles of bone generally disposed in a radiated form ; the en- tire containing cells filled here and there with a dark-coloured fluid, and traversed throughout by a foul and fetid 'ulceration. But osteo-sar- comatous tumours, although generally consist- ing of this firm material, are by no means so invariably. In one remarkable instance in which the disease occupied the femur, a vertical section of the inferior end, which was mon- strously enlarged, exhibited a mass of much softer consistence, and cellulated or porous. Its colour was a mottled dark brown, and it re- sembled nothing so much as a dirty sponge that had been soaked in blood and matter. Sometimes the tumour is so soft as almost to resemble brain : sometimes there are cysts con- taining fluid like blood : in the long bones there is constantly a fracture in the centre of the tu- mour, or if the swelling occupies the shaft, the articulating surfaces are broken from it.f Very often this fracture is, or seems to be, the com- mencement of the disease. We collect from these observations and dis- sections that osteo-sarcoma, as we understand the term, consists in a morbid alteration inte- resting the entire structure of a bone ; com- mencing in its interior, and incapable of re- medy or removal unless by amputation. We have already stated that its chief malignancy consisted in some constitutional predisposition which originally led to its formation, and in- duces a recurrence of it in some other situation after removal, and we wish to examine into the correctness of this opinion in order to separate it from cancer and fungus haematodes, because some diversity of opinion obtains on this part of the subject, which after all is the only one of practical importance. Boyer, j who considers malignancy as constituting the very essence of the disease, nevertheless recognizes two species. “ lo one, the osteo-sarcoma is propagated by the continuity of some cancerous affection, which had commenced in the adjacent soft parts, as is seen, for example, in the bones See Bell’s Principles of Surgery, 4to edition, vol. iii. part 1. t VVe have taken the above descriptions entirely from preparations in the school of Park-street, Dublin. t lraite des Maladies Chirurgicales, tom. iii. which form the walls of the nasal fossas, and more particularly in the superior maxilla when they become spoiled as the result of a hard and cancerous polypus, which had previously existed for a long time insulated, and without any other local affection. In the second species the bone is the original seat of the disease, its own proper tissue is degenerated, and the sur- rounding soft parts only partake of the same species of alteration consecutively and in a secondary manner.” Dupuytren,* in describ- ing the disease as it attacks the lower jaw, offers pretty nearly a similar opinion. If, says he, the osteo-sarcoma is primitive, it remains a long time confined to the bone, and mav ac- quire a very considerable volume before the lips and cheeks are affected. It then presents itself under two principal forms : in the one, the disease consists in cancerous fungi, which spring from the substance of the bone, within which the disease is often superficial, that is, it may only affect the alveolar edge or the surface, the body of the bone remaining without any enlargement, and particularly its base continu- ing sound. The second form is that in which the disease commences in the centre of the bone, which becomes fleshy, and swells through- out its entire thickness. Most tumours of this description acquire a considerable size, and oc- casion a most repulsive deformity. The teeth, loosened and displaced, appear implanted here and there in the substance of the bone. It is impossible to close the jaws. The lips, dis- tended, thinned, and closely applied to the tumour, no longer retain the saliva, which trickles off continually. It is, however, worthy of remark that these tumours, or at least many of them, are slow to ulcerate or pass into the condition of cancer. Sir A. Cooperf has evi- dently made a similar division of osteo-sarco- matous tumours, and described them with his accustomed accuracy and clearness, but under the names of cartilaginous and fungous exosto- sis. Mr. Crampton,j in his paper on osteo- sarcoma, also divides it into two species, the “ mild and the malignant,” stating, at the same time, that the nature of either previous to dis- section after removal or after death is involved in the greatest obscurity. He considers the encysted condition of the tumour, its lying in a bed of cellular tissue unconnected with the surrounding parts, as indicative of mildness : the characters of the malignant, as laid down by him, are evidently those of genuine carci- noma. “ The soft bleeding fungus, which makes its way through the integuments before the tumour has acquired any very considerable size; the profuse and peculiarly fetid discharge, slightly tinged with the red particles of the blood ; the tubercles of a purple colour on the surrounding skin, which adheres firmly to the subjacent tumour ; the pain, and above all the altered health, sufficiently point out the malig- nant character of the disease.” We have thus laid before our readers the * Le5ons Orales, tom. iv. p. 636. f Cooper and Travers’s Surgical Essays. t Dub. Hosp. Reports, vol. iv. DONE, PATHOLOGICAL CONDITIONS OF. 462 opinions of the highest and most respectable authorities, although we cannot coincide with them in classing cancer as a species of osteo- sarcoma. Pathologically they are distinct and different diseases, appearing in patients of dif- ferent ages, habits, and conditions of health, and exhibiting totally different phenomena; and practically they are not alike, for it would be as insane to attempt the removal of a bone contaminated by an adjacent cancer, as it would be cruel to refuse the chance of an ope- ration to one afflicted with true osteo-sarcoma. The disease is only malignant in its tendency to re-appear, nor can it be previously ascer- tained by the symptoms, or subsequently by examination of the tumour, whether it is likely to show this disposition or not. Those nodu- lated tumours that occur on the fingers and wrists of children, and which are so admirably described and delineated by Bell,* almost in- variably reappear in some other situation after removal. This we have seen remarkably ex- emplified in the case of a little girl who was admitted into hospital with the two fore-fingers and thumb affected with this disease : they were amputated, but in nine weeks afterwards both the radius and ulna were attacked, and the arm was cut off. In seven weeks both clavicles were engaged, and the little patient was sent to the country, from which she never returned. Besides the development at an early age, a rapidity of growth, accompanied by in- tensity of pain, is considered as indicative of a most unfavourable disposition in the system. Yet is the contrary no assurance of safety, for we have seen a case in which the disease had lasted for five years and without much suffer- ing, return after removal, and destroy the pa- tient in less than twelve months. In general, however, the remark seems to be grounded on experience. The presence of a deep and foul ulceration within the tumour is rather unpro- mising : in Mr. Cusack’s six cases of excision of the lower jaw, the disease returned in one only, and in that this kind of ulcer had pre- viously existed. It may, too, be laid down as an unvarying rule that the secondary appear- ance of osteo-sarcoma is more painful and more rapid in its progress than in its first and original attack. It is uniformly fatal. The first approaches of osteo-sarcoma are usually insidious, and as it is in general not a very painful affection, it may (particularly in children) escape obseivation at its very earliest periods. Any bone may be attacked by it, but in the adult it is more frequently situated in the spongy extremities of the long bones and in the lower jaw, whilst the phalanges, carpal and metacarpal bones, the radius, the ulna, and the clavicle furnish the best and most frequent spe- cimens in the younger subject. It occurs often idiopathically, and on the other hand it occa- sionally follows or seems to follow a fracture or other injury, as if the disposition existed in the system, and only required some stimulus to direct it to any one situation. It commences usually by a small, firm, immovable tubercular- * Loc. cilat. like tumour appearing to spring flom some part of the bone : soon after another of these may make its appearance, but these, in the first in- stance, are free from pain and insensible to pressure. As it increases, the pain assumes a dull and aching character, in the jaw frequently mistaken for tooth-ache, in other bones for rheumatism. The degree of suffering, however, is not a very strong characteristic, for it will depend on the rapidity of growth, the disten- sion suffered, the sensibility of the parts com- pressed, and a number of other circumstances too obvious to require detail. In ordinary cases, it has been remarked that the pain ob- serves a more than progressive increase with the size of the tumour, particularly if its growth has been accelerated by any accidental injury. In the advanced stages it is always severe, and in some instances dreadful. In one of Bell’s cases, it is stated that there was no hour cf the night or day in which the patient’s wild cries could not be heard miles off. In most in- stances the sufferer is completely deprived of sleep, and in some he complains of nocturnal exacerbations. Once formed, it grows with greater or less rapidity, often appearing stationary for some time, and then suddenlyand quickly increasing: sometimes, on the contrary, it increases rapidly 8 from the commencement, and we have removed an osteo-sarcoma of the lower jaw, which at- tained to the enormous weight of 4 lbs. 1 oz. avoirdupoise in the short space of eight months. Whilst the tumour is comparatively small, the skin is pale and glassy and stretched, and blue veins are seen meandering on its surface : when large, its colour is dark red, verging to purple, and multitudes of these little veins appear upon I it. It is, generally, firm to the touch, solid 1 and heavy ; but occasionally an examination with the fingers discovers the osseous covering of the tumour to be very thin, and it yields on i pressure with a peculiar sensation of elasticity, j such as one might conceive parchment to con- vey if not stretched very tightly. At length it gives way, and a foul ulcer is formed, dis- charging an unhealthy fetid pus, often mixed with blood. The character usually attributed to this ulceration is fungoid, but we have never seen it thus. It commences generally in the centre of the tumour by a slough, and gradually makes its way outwards to burst by two or three apertures, and we have seen an immense osteo-sarcoma of the lower jaw completely tra- versed by ulceration, one opening being in the mouth and the other at the inferior and most depending part of the tumour. These ulcers are usually hollow, attended with loss of sub- stance, and we have not observed one that could have been easily mistaken for fungus hsematodes. Independent of any malignancy inherent in the tumour, it is evident that osteo-sarcoma may destroy life by being so situated as to compress some important or even vital organ, more par- ticularly if such situation precludes the possibi- lity of removal by a surgical operation. Such, for instance, was Mr. Crumpton’s case, in which the diseased growth sprung from the root of the 463 DONE, PATHOLOGICAL CONDITIONS OF. orbit, projecting forwards on the eye-ball and backwards on the brain, both of which organs it must have destructively compressed.* We have seen an osteo-sarcoma of the lower jaw in a young boy occasion death by suffocation ; and another in a young female impede deglutition so entirely that she died or seemed to have died of actual starvation. This, however, was at a period before an operation for the removal of the jaw had been attempted, at least in this country, and both were considered as specimens of fungus heematodes. When the tumour re-appears after operation, it does so in a very short space of time, often before the wound has cicatrized and healed ; and as its situation is in the immediate neigh- bourhood of the former disease, the fungus protrudes through the wound, and seems to grow from it. In these cases the progress to a fatal termination, which is inevitable, is per- haps, fortunately for the patient, extremely rapid also. Indeed in all cases of relapse, the growth of the tumour goes on much more quickly than in the original disease, and the patient’s sufferings are considerably augmented also. We have seen cases in which the pain was so intense and so unremitting, that, night or day, not a moment’s rest could be obtained, even under the influence of the largest doses of opium that could be administered with safety. Cancer. Fungus hamatodes. — We have al- ready more than expressed a doubt that either of these diseases ever originated in the osseous structure, or could be considered as properly appertaining to it, although it must be conceded that, in a few insulated cases, a cancerous dis- position has seemed to produce a fragility of bones, and that this loss of the power of resist- ance has preceded the development of the dis- ease in the softer structures. But with the utmost diligence of research we have not been able to discover one case in which a morbid alteration of structure, analogous to those chan- ges in the soft parts which we call cancer, and which contaminate the system through the me- dium of the soft parts, has been found within the bone itself, or indeed to have existence therein, independent of some similar degenera- tion in the adjacent structures. On this sub- ject, however, our knowledge must be extremely limited. We do not well know what cancer is, or what is meant by a cancerous diathesis. We know not how to define or even to describe it as a generic form of disease. The dissection of these tumours exhibits an almost infinite diversity of structure, and during life, previous to the actual contamination of the system, when the information too frequently avails but little, it is difficult to say whether any given tumour possesses this quality of malignancy or not. We therefore do not offer a very positive or de- cided opinion on this subject. But that the bones in the vicinity of can- cerous disease often suffer from a malignant and incurable species of caries, quite distinct and separate from that absorption which might be the result of pressure, and that this caries * Dub. Hosp. Reports, vol. iv. illustrates Mr. Hunter’s position of the exist- ence of a cancerous disposition in parts ap- parently sound, which will afterwards become developed even though the cancer is removed by operation, admits, we think, of most irre- fragable proof. Several years since, we re- moved a very large cancerous ulceration in- volving most of the under lip, the angle of the mouth, and part of the upper lip also. The diseased parts were most unsparingly taken away, and a minute and careful examination could not detect the smallest hardness in any part of the extensive resulting wound. Never- theless, in less than a year afterwards a tumour appeared at the angle of the jaw, with a hard and unyielding band striking from it deeply into the neck. The tumour increased and pressed deeply: an operation was altogether out of the question, and the man died of open cancerous ulceration. On dissection the bone was found to be deeply and extensively eaten away by caries : its entire structure was pre- ternaturally softened, and on attempting to dry it, as an anatomical preparation, its earthy material crumbled away and was altogether lost. At this moment we have another case affording a similar example of cancer attacking the lower jaw after being apparently removed from the lip. The bone is swollen, hard, nodulated, and extremely painful ; but not- withstanding the urgent entreaties of the poor man, no operation can be performed, and he too will die of open cancer. But the point is too well understood by operating surgeons to require further elucidation. Every one must have met with cases of extirpation of the breast where the ribs had been found softened and diseased, although little indication might have previously existed of such an unfortunate complication. But with reference to fungus hamiatodes the question is by no means so easily settled. In very many cases of extirpation of the eye in consequence of this disease, the bones of the orbit, even at a very early period, have been found softened, altered, and spoiled, new and more irritable growths have sprung from their substance, and the affection has re-appeared in a worse, because a more incurable form. Operations about the upper jaw have too fre- quently proved failures from a similar cause. Again, although the immediate points of re- ference have escaped our recollection, we have read of cases of fungus hsemotodes, the very first and earliest symptom of which was a fracture of the bone or bones of the member in which the disease afterwards was extensively developed. In our own note book are two such cases. One, a poor boy admitted into the Meath Hospital in the year 1820, with the most frightful enlargement of the thigh per- haps ever witnessed, the circumference of the limb being much larger than that of the body of an ordinary man. He attributed the dis- ease to the almost spontaneous breaking of the thigh-bone whilst he was riding on an ass. The tumour never ulcerated, but as an ope- ration, even at the hip-joint, was decided on in consultation to be practicable, be left the 464 BONE, PATHOLOGICAL CONDITIONS OP. hospital, went to the country, and was lost sight of. A case nearly similar occurred shortly afterwards in the shoulder of a young woman, the first symptom of which seemed to have been a fracture of the humerus. Both these cases were at the time regarded as spe- cimens of fungus haematodes, and as they were not examined, the question must still remain undetermined ; but from what we have since observed, we should be disposed to think they were osteo-sarcoma. It is, perhaps, right to state that many surgeons of high attainments and great experience do not separate these diseases in their own minds, and still regard the affection of the bone, which we would en- title osteo-sarcoma, as a species of fungus hae- matodes. It is, however, only in the first and middle stages that these morbid growths can be easily confounded one with the other. Both appear small at first, but increase with great rapidity ; and both attain a size not often observed in other tumours, the fatty tumour alone ex- cepted. The same purple colour, the same meandering of blue veins, and the same in- equality of surface are found on both ; and when the osteo-sarcoma is about to ulcerate, it may be observed to be soft in some places and firm in others, like fungus haematodes. But here the resemblance ends. Throughout the entire case the osteo-sarcoma is harder, firmer, and more unyielding: it attains to a much greater size previous to ulceration, and when ulcerated it does not shoot out (at least in its more common forms) a soft and spongy and bleeding fungus ; neither does it destroy its victim with such rapidity. In the Repertoire Generale d’Anatomie et de Physiologie Pathologiques (4 trimestre de 4826), there is an account of a disease of the tibia related by Lallemand and commented on by Breschet, who considered it to be some species of aneurismal tumour, more particu- larly as it is stated to have been cured by the application of a ligature on the femoral artery. The precise nature of this tumour, however, is only conjectural, as it was never demonstrated by dissection ; neither is it right in the present state of our knowledge to question the cor- rectness of these authors’ opinions. Nature sometimes makes extraordinary deviations from the ordinary courses bdth of disease and re- covery, and the circumstance of our inability to explain the processes adopted by her is not sufficient to warrant a denial of their existence. It may, however, be remarked that if the case alluded to was, as is said, an aneurism situ- ated within a bony case and cured by the operation already stated, such recovery must have been based on principles totally different from those on which an artery is tied in an ordinary case of aneurism. In the museum of the school in Park-street, there is a preparation perhaps in some de- gree illustrative of this eellulated aneurismal disease. It exhibits a morbid expansion of the walls of a humerus removed from a woman in Stevens’s Hospital : the entire shaft of the bone seems to have been engaged, and the transverse diameter of the tumour is about five inches and a half. Within are a number of cells lined by a vascular membrane of an exceedingly dark red colour, the deep tinge of which has scarcely been weakened by the immersion of the preparation in fluid for more than seven years ; and it is known that during life this enormous tumour imparted an in- distinct sense of pulsation. It appears by no means improbable that the commencement ol' this disease was in the medullary membrane, which gradually became altered and poured out the material, whether blood or otherwise, with which its cells were filled. In proportion as this accumulated, the cells must have en- larged and the bone swelled. In many places the external parietes are seen thinned down to the strength of parchment or paper, and had the disease been allowed to progress, they might have been removed by absorption. Had such an event occurred, and the integu- ments subsequently given way, it is easy to conceive that a fungus might have sprung from this vascular membrane, which, occasionally pouring forth an abundant and incontrollable flow of blood, would in every particular have so far resembled fungus haematodes, that even an experienced practitioner might have found it difficult to distinguish between them. BIBLIOGRAPHY.— Isenflamm, Anmeik. fiber d, Knochen, 8vo. Erlang. 1782. Bonn, Thess. oss. morbos. 4to. Amst. 1783 ; Ejus, Tab. oss. morbos. fol. Amst. 1785-87. Heckeren, De osteogenesi preternat. 4to. Lugd. Bat. 1797. Boyer, Lecons sur les maladies des os, par Richerand, 2 vol. 8vo. Paris, 1803; A nglice by Farrell. Sandifort, Museum anatomicum. Weidmann, De necrosi ossium, fol. Frfti. a M. 1793. Augustin, De spina ventosa ossium, 4to. Halas, 1797. Howship on the morbid structure of bones, &c., in Med. Chir. Trans, vol. viii.; Ejus, Experiments, &c. on fractured bones ; Op. cit. vol. ix. and Sequel to the pre- ceding paper in Op. cit. vol. x. * * Glisson, De rachitide, l2mo. Lond. 1651. Stanley, Obs. on bones in rickets. Op. cit. vol. vii. * * Scarpa, De anat. et pathol. ossium, 4to. Ticin. 1827. B. Bell, on the diseases of the bones, 8vo. Edinb. 1828. * * Miiller, Diss. de callo ossium, 4to. Norimb. 1707. Bohmer, Diss. de ossium callo, 4to. Lips. 1748. Trqja, De novornm ossium, &c. regenca- tione, 8vo. Lutet. Paris. 1775. Russel, Etsay on necrosis, 8vo. Edinb. 1794. Koehler, Ex- per. circa regenerationem ossium, 8vo. Gotting. 1786. Bonn u. Marrigues, Abhand. liber die Natur und Erzeugung d. Callus, &c. 8vo. Leipz. 1766. Rebel, Reflex, sur la regeneration des os, in Journ. Complem. vol. v. Breschet, Rech. sur la formation du Cal. 4to. Paris, 1819 (parmi les Theses du Concours). Meding, Diss. de regeneratione ossium, |, 4to. Lips. 1823. Kortum, Exper. et obs. circa rc- generat. ossium, 4to. Berol. 1824.* *** Spondli, jj Diss. de sensibilitate ossium morbosa, 4to. Gotting. 1814. Observations more or less connected with the subject of the foregoing article will also be jj found in the surgical works of Bromfield, Gooch , Pott, &c., in Mechel's Handbuch d. anatomie or Manuel d’anatomie, in Wilson's Lectures on the bones and joints, Lloyd on scrofula, Cooper Tracers s Surgical essays, Crowther on white swelling, Cope- land on the spine, Brodie on the joints, besides the various articles already referred to in the Diction- naire des Sciences Medicales, papers in the Dublin Hospital Reports, Dublin Journal, Medico-Chirur- gicai Transactions, &c. ( W. H. Porter.) 465 THE BRACHIAL OR HUMERAL ARTERY. BRACHIAL OR HUMERAL ARTERY ( arteria brachialis, humeraria. Germ, die Ar- marterie.) This artery is the continuation of the trunk of the axillary. It commences at the inferior margin of the tendons of the teres ma- jor and latissimus dorsi, whence it extends to about an inch below the bend of the elbow, where it usually divides into the radial and ulnar arteries ; but not unfrequently this divi- sion takes place high in the arm. The brachial artery lies on the internal side of the arm above, but in its course downwards it gradually advances in an oblique direction until it gets completely to the anterior surface of the limb, where it is found situated nearly midway between the condyles of the humerus in front of the elbow joint; it is superficial in the whole line of its course, in every part of which its pulsations can easily be felt, and sometimes, in the arms of thin persons, are distinctly visible. Relations. — Anteriorly the brachial artery is overlapped, for about its upper fourth, by the coraco-brachialis muscle and the median nerve; for the greater part of its course down the arm it is covered by the brachial aponeurosis, to which is added, where it crosses the elbow, the falciform expansion sent off from the tendon of the biceps to the internal condyle : the median basilic vein also lies in front of it opposite the bend of the elbow. Posteriorly, for about a third of its length from its commencement it lies in front of the triceps, from which it is se- parated by a quantity of loose cellular tissue which envelopes the musculo-spiral nerve ; in its inferior two-thirds it rests on the brachiteus anticus. Internally it is covered by the bra- chial aponeurosis at its superior part, where the ulnar nerve is also in contact with it. The me- dian nerve which crosses it, sometimes super- ficially, and at other times passing more deeply, in the middle of the arm gets to its internal side, and continues to hold this relation to it in the remainder of its course. Externally it lies at first on the internal side of the humerus, from which it is separated as it descends by the thin muscular expansion in which the coraco-brachi- alis terminates at the lower part of its insertion ; in the remainder of its course the inner edge of the biceps bounds it. The fleshy belly of this muscle also partially covers it in front, a little below the middle of the arm. At the bend of the elbow, the relations of the brachial artery become more numerous and complicated ; here it inclines obliquely outwards and backwards, and sinks into a space which is bounded on the inner side by the origins of the pronator and flexor muscles of the forearm, and on the out- side by those of the supinators and extensors, the floor of which space is formed by the bra- chi®us anticus muscle, from which the artery is separated by a layer of adipose cellular mem- brane. The artery is accompanied in its passage into this space by the tendon of the biceps and the median nerve, the former being situated to its radial side, the latter to its ulnar ; and it is at the bottom of this space, opposite the coro- noid process of the ulna, that the subdivision of the artery into radial and ulnar usually takes VOL. i. place. As it enters the space the artery is crossed by the semilunar fascia of the biceps, by which it is separated from the internal cutaneous nerve and median basilic vein. (For further par- ticulars on this stage of the artery, see Elbow, Region of the.) Two venae comites accompany the brachial artery : they are included in its sheath, and lie one on either side of it, often communicating by several transverse branches which cross the artery in front. So superficial is the position of this artery from its origin till it enters the region of the bend of the elbow, that it may be exposed during life in any part of its course with facility, and, if the operator use only common caution, with safety. In all this course the artery may be felt, and in the upper third the operator may avail himself of the inner side of the coraco-brachialis muscle as a guide, and in the middle third, of the inner edge of the belly of the biceps. In both situations the operator has to avoid in- juring the cutaneous nerves, and the median and ulnar nerves, as well as the basilic vein, which sometimes passes up as high as the axilla. He should also bear in mind the po- sition of the inferior profunda artery, which is sometimes of a large size; and from its direction, as well as its relation to the ulnar nerve, presents a considerable resemblance to the brachial trunk. Branches. — The brachial artery furnishes a variable number of branches from its external side, none of which is of sufficient importance to be distinguished by a name ; they are dis- tributed to the os humeri, the deltoid, coraco- brachialis, biceps, and brachiasus anticus muscles, and to the integuments. From its internal side, however, there usually arise, in addition to several small twigs sent to the triceps, teres major, latissimus dorsi, and the integuments, three branches of more considerable size, and which derive their principal importance from being the leading channels of anastomosis be- tween the brachial trunk and the arteries of the forearm. These are, 1, the superior profunda, 2, the inferior profunda, 3, the anastomotica magna* 1. The superior profunda (profunda humeri , Haller and Scemm. collaterale externe, Boyer, grand musculaire du bras, Chauss.) arises from the posterior side of the brachial artery, close to the border of the axilla. It sometimes comes from the axillary artery by a trunk common to it and the posterior circumflex, and occasionally it arises from the subscapular. Immediately after its origin the profunda superior gives several branches to the coraco-brachialis, triceps, latissimus dorsi, teres major, and deltoid mus- cles. Some of these latter, ascending towards the acromion process of the scapula, anastomose with the thoracicaacromialis, supra-scapular and posterior circumflex ; while the branches sent to the latissimus dorsi and teres major anas- tomose with the subscapular artery. The supe- ® Sometimes the subscapnlar, and one or both of the circumflex arteries, derive their origin from the brachial. 2 II 466 THE BRACHIAL OR HUMERAL ARTERY. rior profunda passes backwards between the os humeri and the long head of the triceps, and in company with the musculo-spiral nerve enters the spiral groove on the posterior surface of the bone, passing between the second and third heads of the triceps. About the middle of the arm it divides into two branches, the internal or ulnar, and the external or radial. The ulnar branch descends in the substance of the triceps to the olecranon process, around which it anas- tomoses with the posterior ulnar and inter- osseous recurrent arteries, having in its course supplied the triceps with several branches. The radial branch comes forward with the musculo- spiral nerve as far as the external intermuscular ligament, where it separates from the nerve and taking a more superficial course, descends along the outer margin of the humerus over the supinator radii longus and the triceps, to which and the integuments it gives several branches. On arriving at the external condyle it gives branches to the elbow-joint, and anastomoses with the radial recurrent in front, and the recur- rent of the interosseous artery posteriorly. Below the origin of the superior profunda a small artery, called nutritia humeri , frequently arises either from the superior profunda or the brachial trunk : it enters the nutritious foramen of the humerus, and is distributed to the can- cellated structure of that bone. 2. The inferior profunda ( ramus alius pos- terior humeri, Haller) arises from the internal side of the brachial artery, generally about the lower part of the insertion of the coraco-brachialis into the os humeri ; passing backwards, it per- forates the internal intermuscular ligament, be- hind which it descends, having the ulnar nerve internal to it until it arrives at the posterior side of the internal condyle, in the grooved depres- sion between which and the olecranon it lies close on the periosteum, and is covered by the ulnar nerve : here it divides into several branches, some of which are distributed to the elbow joint and the muscles attached to the internal condyle and olecranon, and it anasto- moses freely with the posterior ulnar recurrent artery. Sometimes the inferior profunda is a branch of the superior artery of that name ; it varies very much as to its size in different subjects, being sometimes a very insignificant twig, while in other instances it is so large that it is liable to be mistaken by an ope- rator for the brachial trunk. In reference to this latter circumstance Professor Harrison ob- serves,* “ In the dissected arm, the inferior profunda artery appears at some distance from the brachial, but if the triceps be pressed for- ward towards the biceps, so as to place these muscles as nearly as possible in their natural relations, those vessels will be found very close to each other ; so that, in cutting down upon the brachial artery in the middle of the arm, in the living subject, the inferior profunda, from its situation, and from its being accompanied by the ulnar nerve, may be mistaken for the brachial. This error, however, may be avoided by recollecting that the brachial artery is the t Surgical Anat. ol the Arteries, vol. i. p. 176. nearest to the triceps, and is a little covered by that muscle : in general, also, there is a material difference in size between the two vessels.” The remarks contained in the foregoing quo- tation do not apply to a merely hypothetical case, but to one which has actually occurred in practice, the following instance of which I once had an opportunity of witnessing. A late emi- nent surgeon undertook to tie the brachial artery for the cure of an aneurism at the bend of the elbow : the inferior profunda, which was un- usually large, was exposed and tied on the supposition of its being the brachial artery, the pulsation in the tumour continuing un- diminished pointed out the nature of the mis- take which had been committed, and the patient had to submit to a second operation at a sub- sequent period, in which the brachial artery was tied with a successful result as to the cure of the aneurism.* 3. The anastomotica magna, ( ramus anusta- moticus , Haller, collaterale da coude, Ch.) arises generally at nearly a right angle from the inner i side of the brachial, at a little distance above the elbow-joint. Several similar vessels, but of much smaller size, arise from the same source in its vicinity: at first it passes inwards across the brachieeus anticus, and perforates the internal [j intermuscular ligament, giving branches to the ; brachiocus anticus, the triceps, the cellular tissue and lymphatics above the internal condyle : having got upon the triceps, it descends to the back part of the internal condyle, where it anastomoses with the inferior profunda and posterior ulnar recurrent arteries. When the inferior profunda happens to be very small, or is absent, this vessel supplies its place by giving branches to the articulation, to the muscles at- tached to the internal condyle, and for anasto- i mosis with the posterior ulnar recurrent. Where t the anastomotica magna is absent, small branches 1 from the brachial, inferior profunda, and ulnar recurrent arteries, supply its place. When a high division of the brachial artery occurs, the branch which is to become the ulnar usually gives off the two profundre, and the anasto- ,j motica magna : this last, however, sometimes jj comes from the radial in such cases.f * [Such a mistake as that alluded to in the text may likewise occur where there has been a high bifurcation of the brachial artery. — Ed.] f [The frequent occurrence of irregularity as to the position at which the brachial trunk divides into its terminal branches, the radial and ulnar, constitutes a point of great interest in the anatomical history of this artery. I believe it may be said that it never happens that the bifurcation takes place beh'/tu the coronoid process of the ulna ; on the contrary, the division above that point is by no means uncommon, occurring, according to the calculation of Professor Harrison, once in every four subjects. This bifur- cation occurs at all points in the arm, and in some cases the radial and ulnar arteries proceed at once from the axillary. In general the anomalous artery is the radial, and is subcutaneous in its course, while the ulnar follows the normal course of the brachial trunk. Sometimes the reverse is the case : sometimes both radial and ulnar are subcutaneous, and sometimes the radial is at its origin ulnad, but afterwards crosses the ulnar artery at a very acute angle, to get to the radial side. In some rare cases the brachial artery is regular in its course, BURSiE mucos/e. 467 Anastomoses ■ — The ascending branches of the superior profunda anastomose in the sub- stance of the deltoid muscle with the anterior and posterior circumflex and the cephalic branch of the acromial thoracic, and with the subsca- pular and the axillary branches of the thoracica longior in the axilla. If the brachial artery be obliterated by disease or the application of a ligature above the origin of the superior pro- funda, the blood will be carried by the circuitous route of these anastomoses into the brachial artery and all its branches from the superior profunda downwards. When the brachial artery is obliterated near the elbow, the circulation is maintained in the forearm and hand by the anastomoses of both profund® and the anastomotica magna with the recurrent branches of the radial, ulnar, and in- terosseous arteries. The anastomosis kept up between all the branches of the brachial artery along the periosteum of the humerus, in the substance of the muscles and in the integu- ments of the arm, is so free as to be sufficient to ensure the circulation in the limb even if the brachial artery were obliterated throughout the whole of its length. For the Bibliography, see that of Anatomy (Introduction) and of Artery. (J. Hart.) BRAIN. See Enkephalon, and Nervous System (Comp. Anat.) BU RS/E MUCOS/E. (Fr. bourses synovi- ales; Germ, die S/ileimbeutel) — This name was first given by Albinus to small shut sacs, filled with an unctuous fluid, which he found in certain parts of the body, interposed between the tendons and bones. The name, however, is now much more extensively applied, for ana- tomists have ascertained that those smooth membranes, previously noticed by Winslow, covering the tendons and lining the tendinous sheaths about the wrists and ankles, are strictly of the same nature as those described by the Dutch anatomist. The number of bursae known to Albinus, and described by him in his “ His- toria Musculorum,” was but sixteen pairs. Monro, who first properly explained their ana- tomy and uses in his excellent monograph upon this subject, has made us acquainted with no less than seventy pairs, all situated in the ex- tremities : and since his day the number has been further increased by the discoveries of Beclard and others : so that anatomists are now acquainted with upwards of one hundred pairs, many of them situated in the head and trunk. Bursae mucosae, though of the same structure and answering the same ends in every situation but gives off the interosseous high up, which has all the appearance and many of the dangers of the high bifurcation. Mr. Harrison mentions a case in which the brachial divided into three branches, two of which united to form the radial, which gave off the anterior interosseous, the posterior being derived from the third, the ulnar. Mr. .Burns re- marks, that when, as rarely happens, the ulnar is the anomalous branch, the bilurcation generally takes place nearer the axilla, than when the radial is the abnormal vessel. — Ed.J where they occur, may nevertheless be divided, with advantage, into two great classes ; viz., I. the subcutaneous bursa, or those placed be- tween the skin and fascia; and, II. the deep bursa, or those which lie beneath the latter membrane. I. The subcutaneous or superficial bursa were unknown not only to Albinus, but even to Monro and Bichat ; at least there is no mention made of them in the works of any of these authors. Beclard, in his “Additions to the General Anatomy of Bichat,” appears to be the first anatomist who refers distinctly to them. The most remarkable are, — 1, a large one placed between the skin and the liga- mentum patellae ; 2, one between the skin and fascia covering the great trochanter of the femur ; 3, one between the skin and fascia over the olecranon. These are all extremely well marked. There are others likewise, which, though less perfectly developed, are, however, evidently of the same nature ; such as that between the skin and fascia over the angle of the lower jaw, and those found upon the dorsum of the hand beneath the phalangeal and meta- carpo-phalangeal articulations. These super- ficial bursae are not equally perfect in all in- dividuals : they are best developed in those whose limbs are actively and habitually exer- cised. On cutting into their cavities we gene- rally find them traversed by numerous fila- ments : the appearance indeed is extremely similar to that presented by the subcutaneous cellular tissue in certain parts of the body, — in the palpebra and penis, for example ; and this no doubt is the reason why these burs® were not distinguished from cellular membrane- by Monro and others. That they are different structures, however, or at least that they are independent of the cellular system, is sufficiently proved by the simple process of inflating their cavities through asmall opening made into them ; we then find that the air is circumscribed within a definite boundary, and cannot, as in the palpebra and penis, be made to pass into the surrounding cellular membrane. II. The deep bursa, or those placed beneath the fascia, are much more numerous and much better marked than the preceding. They are almost uniformly found in connexion with ten- dons, and, generally speaking, are interposed between them and the bones over which they play. Like the superficial ones, they too are always shut sacs, in most instances of an ex- tremely simple form, but in some cases much more complex ; and hence they may with pro- priety be subdivided into two sets, — the vesi- cular and the vaginal. a. The deep vesicular bursa, when fully dis- tended, represent each a simple globular bag, one of whose sides is in contact with the bone, and the other with one side of the tendon, without, however, enveloping it. {See fig. 1 1 1, b.) On opening into its cavity, it is found to con- tain a viscid fluid, more or less abundant, and this is sometimes traversed by fila- ments passing from one wall of the sac to the other. They generally occur in the neighbourhood of the great articulations of 2 a 2 468 BURS/E MUCOS/E. the hip, shoulder, knee, and ankle, but are not, as it was supposed until of late years, con- fined to the extremities, for we shall presently point out instances of their occurrence both in the head and trunk. Amongst the most re- markable in the inferior extremity we find, in the neighbourhood of the hip-joint, a very large one between the tendon of the psoas muscle and the capsular ligament ; a large one between the great trochanter and gluteus maximus; one between the gluteus maximus and vastus externus ; one between the gluteus medius and trochanter; one between the gluteus minimus and trochanter ; one between the pectineus and femur. These are all large and regular in their existence ; but there are other smaller ones fre- quently met with, particularly at the posterior part of the joint connected with the small ten- dons and muscles placed there. About the knee-joint there are likewise several vesicular burses : immediately above the articulation, be- tween the extensors and front of the femur, there is an extremely large one, oftentimes ex- tending several inches upwards, and still more remarkable in many instances for communi- cating with the synovial membrane of the joint; a fact which has been well appealed to by the general anatomist in proof of the anatomical identity of these two structures. There is a large one, likewise, at the inner and lower part of the articulation between the tibia and the tendons of the sartorius, gracilis and semi- tendinosus : posteriorly between the origins of the gastrocnemii and the bone there is also found a bursa; and a similar one between the popliteus muscle and the joint. These, like the large one in front, generally communicate freely with the articular synovial membrane. There is also a bursa generally found between the semi-membranosus and the internal lateral ligament. Around the ankle there are but few vesicular bursae : posteriorly, however, between the tendo Achillis and os calcis, there is found a very large one ; and smaller ones are frequently met with connected with the flexor pollicis longus, and some of the other muscles in their passage here. In the superior extremity we find, likewise, several vesicular bursae : around the shoulder-joint there is a very large and regular' one placed between the deltoid muscle and the capsular ligament ; there is one between the clavicle and coracoid process ; one between the scapula and subscapular muscle ; one be- tween the subscapular muscle and the capsule. Lower down there is a bursa between the humerus and the tendons of the teres major and latissimus dorsi; and also a bursa fre- quently between these two tendons, at a little distance from their insertion. About the elbow- joint there is a vesicular bursa between the tendon of the triceps and the olecranon ; one in front, between the tendon of the biceps and the tubercle of the radius : there is also one between the head of the radius behind, and the extensor muscles passing over it. Around the wrist-joint there are no vesicular bursre of any size or importance. There is in the trunk a large vesicular bursa, usually found between the latissimus dorsi and scapula. In the head we often see a distinct bursa interposed between the two divisions of the masseter muscle. b. The deep vaginal bursa are invariably found connected with tendons and with the fibrous sheaths through which these tendons are transmitted. They are somewhat more complex than the preceding, for instead of representing a simple shut sac, they form, like serous membranes, by reflexion a double sac, one of whose portions, corresponding, for ex- ample, to the plura costalis, lines the interior of the fibrous sheath, while the other, answering to the plura pulmonalis, invests the surface of the tendon. There is, however, this difference between the pleura and the synovial sac, that in the latter there is no longitudinal septum, no mediastinum resulting from the reflexion of the membrane ; for the reflexion occurs not along the channel, but at either extremity of the fibrous sheath : thus the bursa, if completely detached from all surrounding structures, would represent a large tube, containing within itself a smaller one ; these two being continuous by their extremities alone. The deep vaginal bursa? generally occur in the neighbourhood of ginglymoid articulations, and by far the largest and most interesting are those connected with the flexor tendons of the wrist and ankle. They are always of very great j size, not only passing a considerable way up- wards upon the forearm and leg, but likewise extending downwards into the palm of the hand and sole of the foot, and branching out at their distant extremity into several distinct sheaths ! for the respective tendons belonging to the different toes and fingers. Upon the phalanges J the synovial sheath is firmly bound down by j a dense unyielding fibrous membrane, a cir- cumstance well worthy of remark; for, as we shall presently see, it modifies in a very im- ’ j portant degree the characters of inflammation occurring here. Besides these, we have a re- markable vaginal bursa connected with the long head of the biceps muscle ; and smaller ones are found investing the tendons of the circum- flexus palati, obturator internus, &c. Having thus considered the forms and rela- tions of the different sorts of bursae, we may next proceed to offer a few remarks applicaole j alike to all, upon their structure, contents, uses, j development, and diseases. Here, however, our labour is much abridged by the fact already alluded to, and now admitted upon all hands, that the membrane forming the bursae, and the synovial membrane of joints, are anatomically and physiologically the same. They are, in fact, the same in form, being both shut sacs; the same in structure, being both essentially composed of cellular membrane; the same in function, for they are both designed to facilitate the motion of contiguous organs; and, as we shall presently see, they are both similarly af- fected by disease. Were we to enter at length into these particulars upon the present occasion, we should but anticipate details belonging pro- perly to a more general head, that, namely, of synovial membrane. Hence the few remarks we are now about to offer must be received as merely supplementary to those found under that article. BURSiE MUCOSA. 469 1. Structure.- — The opinion of Haller, that these membranes are ultimately composed of cellular substance, though controverted by Monro and others, is, however, now universally admitted. They are, in fact, like all synovial membranes, essentially composed of cellular substance, entirely destitute of fibre, scantily supplied with vessels, and remarkable for their softness and flexibility. The vaginal bursas are, however, much more delicate than the vesicular. The fatty bundles, mistaken by Havers for glands, are frequently found in their substance. Rosenmiiller speaks of distinct synovial follicles as likewise demonstrable, but the existence of any such bodies appears to us more than doubtful. 2. Contents. — Experiments have been made by Monro and others, to shew that the fluid contained in bursae is similar to that contained in synovial membranes. These, however, may now be looked upon as superfluous, inasmuch as this question has merged in the general one, viz , the identity of the two structures. Chemistry, in fact, has proved that their fluid and that of synovial membranes are, if not completely, at least essentially the same. In the subcutaneous bursae it is scanty and thin; in the larger and deeper ones it is said to be somewhat more viscid. 3. Function. — The use of bursae is in all cases the same ; they serve tS isolate certain parts and facilitate the motions performed by them : hence they are found only in those situations which are the seat of motion. Their fluid, from its oily consistence, must of course tend considerably to diminish the effects of fric- tion. 4. Development . — Bursee are developed at a very early period, and are relatively more pliant and perfect in the child than in the adult, to facilitate, as it would appear, the almost incessant movements natural to that period of life. They become more dense and unyielding in the adult, and in extreme old age are said to become dry and rigid. This, no doubt, is amongst the causes which render the movements of old age slow and laboured. A curious fact connected with this subject is the accidental development of bursse in cases where their presence becomes necessary. When the superficial bursa in front of the patella has been removed by operation, its place is ulti- mately supplied, as Sir Benjamin Brodie has seen, by a newly formed one, similar in every respect to the original sac. In cases of club- foot a large subcutaneous bursa has been found developed upon that portion of the swelling which has been the chief seat of pressure and motion: and in cases of diseased spine, at- tended with considerable angular curvature, a bursa has become developed between the pro- jecting spinous process and the skin. Pathological conditions of burs#: mu- cos#:. — Bursae mucosae, superficial as well as deep, are not unfrequently the seat of inflamma- tion, resulting either from external causes, such as cold or local injury, or from constitutional causes. In the majority of cases inflammation in these structures assumes a chronic form, and its ordinary effects are either to increase the quan- tity of the synovial fluid, to determine the effusion of a turbid serum loaded with flakes of lymph, or to end in the formation of matter. The general phenomena of bursal inflamma- tion may be studied with most advantage in the large subcutaneous bursa in front of the knee- joint : it is more frequently inflamed than any other in the system. This, however, is not owing to any peculiarity of structure predis- posing it to disease, but merely to the accidental circumstance of its situation, which exposes it more than any other to external injury. In those persons who continue for a long time in the kneeling attitude, in devotional exer- cises for example, and still more remarkably in those whose occupation obliges them not only to support the body but also to move upon the knees (as carpenters, housemaids, and others), inflammation of this bursa is very frequently met with. In many instances it occasions little general or local disturbance, merely causing an increased effusion of the proper synovial secretion, without producing any change whatever in its natural properties. In other cases the fluid is not only increased in quantity, but becomes changed likewise in quality; it assumes the appearance of a turbid serum, with numerous flakes of lymph floating in it; or where the disease has been of long standing, the fluid is frequently found loaded with a number of loose bodies, almost of the consistence of cartilage, and of a flattened oval form. Sir Benjamin Brodie compares their appearance not inaptly to that of melon-seeds, and he considers them as portions of lymph originally of an irregular shape, but which, by the motions and pressure of the surrounding parts, have had their angles worn off, and assumed by degrees a firm consistence. They have been found likewise in the smaller bursas. Monro has seen upwards of fifty extracted from the small bursa of the flexor pollicis longus tendon, where, by excessively distending the surrounding parts, they had produced severe pain. When the great vaginal bursie of the flexor tendons have become the seat of effusion, a very remarkable appearance may present itself, at once explicable, however, by referring to the anatomy of the part. The fluid can by pressure be forced downwards under the annular liga- ment, and into the palm of the hand, and thence upwards again into the forearm. Some authors have deemed it proper to designate by a par- ticular name this termination of the disease by effusion, and the words thygroma and ganglion have been applied with a good deal of con- fusion by different persons; but it appears to us that there exists no necessity for a specific name to refer to this accidental mode in which inflammation terminates. A much more important termination of the disease is that in which, owing to local or con- stitutional causes above alluded to, the inflam- mation, having run a severer course, ends in suppuration. Sir Benjamin Brodie has in this case observed that the matter may take either of two courses : it may come directly to the surface ; or, without pointing forwards, it may 470 CARNIVORA. penetrate the side of the sac, and so become extensively diffused through the surrounding cellular membrane, involving the whole anterior and lateral portions of the joint. In such a case the practitioner is very liable to be de- ceived as to the true character of the abscess, and to confound it with those which originate in the cellular membrane. There are certain cases in which acute inflam- mation of a bursa becomes even a more serious disease than that just alluded to. In the syno- vial sheaths of the flexor tendons, for example, the progress and termination of the inflamma- tion are often modified in a remarkable manner by the anatomical peculiarities of that part. In that form of the paronychia affecting the ante- rior part of the finger, and seated in the synovial sheath of its flexor tendon, the inflamed mem- brane is closely bound down by a dense and unyielding fibrous layer : hence not only death of the contained tendon may be produced, but even extension of the disease to the bone itself. Such are the morbid changes usually met with in the contents of inflamed bursae; but if the disease have been of long standing, changes scarcely less remarkable are produced in the structure of the bursa itself. Instead of the delicate synovial membrane we have above described, it is frequently found converted into a firm gristly substance, sometimes half an inch in thickness. In such cases no tact, how- ever delicate and experienced, could, previously to operation, have detected the presence of matter. Monro seems to regard, in certain cases at least, the communication above alluded to be- tween certain bursae and the neighbouring joints as the result of rupture or of friction : he even considers it remarkable that in such instances neither lameness nor pain had been complained of during the lifetrme of the individual. It ap- pears to us, however, much more probable that in those instances the synovial membrane of the joint and that of the bursa have been ab initio but different parts of one and the same structure ; at least, in our dissections of the subcrureus bursa in young subjects, we have more than once observed it communicating freely with the joint. For Bibliography, see ;hat of Synovial Mem- brane. ( John E. Brenan .) CARNIVORA ( euro, carnis, and voro,) an interesting and highly important group of the mammifera, constituting the typical order of that great division of the class which feed upon animal aliment. Whether the present group can with propriety be considered as en- titled by its organization to the ordinal rank which we have assigned to it above, or whether it does not rather form a subdivision of a great order, answering nearly to the Carnassiers of Cuvier, is a question which, as it is variously viewed by different naturalists, may be safely left undecided in a work like the present, in which structure rather than arrangement is the principal object of research, and in which the nomenclature of a system is of little importance, compared with thedevelopement of anatomical and physiological truth. The Carnassiers of Cuvier (excluding the Marsupiata, which may unhesitatingly be considered as a distinct order,) includes a natural and tolerably well defined assemblage of animals, to which the term Zoophaga may with propriety be applied as the classical equivalent to the French phrase of that distinguished zoologist ; but however the stricter rules of zoological arrangement may render it difficult to divide this group into the three orders of Cheiroptera, Insectivora, and Carnivora, it has appeared to the author of this essay as more convenient on the present occasion to assign that designation to each of these divisions, and to make the structure of each the subject of a separate article. The characters of the Carnivora as distinct from the rest of the digitate animals possessing the three distinct classes of teeth, (which, be- sides the other Zoophaga, include the Quadru- mana and the Marsupiata,) are such as point them out as especially formed for the pursuit and destruction of vertebrate animals. They possess in the upper and in the lower jaw six incisive teeth, a large, strong, and pointed ca- nine tooth on each side, and molar teeth which partake in a greater or less degree of the charac- | ters distinctive of the class, according to the habits of the different genera. These molars con- sist of three distinct kinds: the anterior, which 1 immediately follow the canine, are more or less pointed, and are termed false molars; the next class, formed especially for cutting in pieces the flesh on which the animals feed, are termed by M. Frederick Cuvier Carnassiers; and the posterior are tuberculated. The proportion which these different classes of teeth bear to each other in number or developement, accords with the degree of the carnivorous propensity in the animal. ii In agreement with these characters of the teeth, the feet are digitate, the toes furnished with claws, which in some are retractile ; the stomach is simple, the intestines are short, and ij the ccecum is either very small or altogether l| wanting. The animals of this order differ in the form 1 and position of the posterior feet; in some, hence termed plantigrade, the whole foot rests on the ground ; in others, called digitigrade, the toes only touch the ground, the heel being considerably raised. Of the former structure the bears exhibit the type, and the cats of the latter. A third and most remarkable form of the extremities is shown in the Seal tribe, in which the anterior as well as the posterior feet are formed for swimming, being spread into fin- like paddles. The families of which this order is pom- posed are perhaps as follow : — 1. Ursid®, typical genus Ursus, bear. 2. Mustelid®, do. Mustela, marten. 3. Canid.®, do. Canis, dog, wolf. 4. Felid®, do. Felis, cat. 5. Phocid®, do. Phoca, seal. Of these families the Felid® constitute the type of the order, possessing the carnivorous CARNIVORA. 471 propensity and structure in a higher degree prey on which, in a state of nature, they than any of the others. wholly subsist. In the less typical forms we Skeleton. — The structure of the skeleton in find these attributes possessed to a modified the cat tribe exhibits, in the greatest imaginable extent, but still admirably adapted to their degree, all the requisites of fleetness, activity, respective habits. and power, for the purpose of pursuing, sur- As an example of the typical structure, the prising, overpowering, and tearing the living skeleton of the lion (Jig. 189) shews, in the Fig. 189. of muscular attachment, such a combination of servient to the object in question. The cra- lightness of form with vast power, as must nium is broad and short, and fitted for the strike every one as being exactly equivalent to exercise of almost incalculable force in holding the natural requirements of the animal. The and tearing their food. spine is flexile, yet of great strength, and the In the weasel tribe the legs are shorter, the extent and robustness of the lumbar portion of vertebral column elongated and in the highest the vertebral column seem at once adapted for the degree slender and flexible, the lumbar region exercise of that flexibility, and for the location being as long even as the dorsal, a structure of powerful muscles. The ribs are narrow by which they are enabled to creep with almost and far asunder; the limbs long, powerful, and a serpentine motion in quest of the small and so constructed as to afford the greatest facility sometimes subterraneous animals on which and extent of motion, an object which is they subsist. greatly promoted by placing the point of rest In the bear tribe (Jig. 190) there is a still Fig. 190. 472 CARNIVORA. greater aberration from the type, in the planti- grade form of the foot, by which the animal is enabled to walk with that solidity and firmness which the less degree of mobility in the rest of the skeleton renders necessary, or to climb trees, or dig the ground, in pursuit of the various food from which the different genera of this family derive their nutriment. The small extent of the lumbar portion of the spine com- pared with the dorsal which we find in some of this tribe, is equally characteristic. In the Phocidae or Seals, (fig. 191 ), on the Fig. 191. other hand, the most remarkable deviation from the typical struc- ture is seen in the adaptation of the limbs to the aquatic residence and habits of the animals. The posterior members are extended backwards in a horizontal direc- tion, forming two broad fins, by which they swim with great facility and strength . The anterior feet are similarly constructed, but they serve also in some measure for progres- sion on land, though to a limited extent. The cranium is thin and round, and the teeth, sharp and many-pointed, are formed for seiz- ing, holding, and tearing fish, the activity of whose motions, no less than their scaly surface and even, rounded form, render such a structure absolutely necessary. The cranium.— The peculiarities by which the cranium of this order is distinguished have reference, not to the form and developement of the brain only, but particularly to the character of the food, and the consequent necessity of peculiar powers of mastication, and of the other acts preparatory to the function of diges- tion. We shall find, therefore, not only that the general form of the skull in the whole of the Carnivora is diffe- rent from those of every other group, but that the families composing it differ in minor points of structure, with the same relation to aliment and habits. The cranium in this order then is cha- racterized, when com- pared with that of most other orders, especially those which feed on grain or other substances requiring long and la- borious trituration, by great shortening of the bones of the face. This is particularly con- spicuous in the cats, (fig. 192,) the seals, Fig. 192. (fig. 193,) and even] the hyenas, but i3 less so in the bears (fig. 194) and dogs. The Fig. 194. CARNIVORA. 473 posterior aspect is generally small, directed backwards, and separated by a strong occipital crest from the anterior parts of the skull. From this, in many instances, a strong, elevated, me- dian crest passes forwards, which is remarkably short in the lion, the white bear, the hyena, the badger, and many others. It is remarkable that in many of the Phocidas this crest does not exist, whilst in other species it attains a con- siderable size. The orbit and the immense temporal fossa are confounded in one great excavation ; the zygomatic arch is perfect and of considerable size. The anterior opening of the nares is large, and directed forwards, ex- cepting in certain seals, in which it is placed almost vertically, for the obvious purpose of facilitating its exposure to the atmosphere when these animals come to the surface to breathe. A remarkable peculiarity exists in this order, in the existence of a bony process arising from the internal surface of the occipital and parietal bones, and separating the lobes of the cerebrum from the cerebellum. This process, of mode- rate size in the dogs, is much larger in the seals, and still more developed in the cats. In the dogs it is considerable from before backwards, but small from side to side ; it is formed by the parietal and the squamous portion of the occipital. In the seals the parietal bone is not concerned in its formation ; in the cats, on the contrary, it entirely arises from this bone, not being at all connected with the occipital. The object of this bony tentorium is obviously to support the different portions of the brain, and prevent their pressing upon each other during the sudden and violent movements of the ani- mal, when springing upon its prey or leaping with great violence. With regard to the substance of the bones of the cranium in this order, although it may be observed generally that they are of a medium degree of thickness and solidity, there are re- markable exceptions in some of the seals, in which they exhibit an extreme degree of tenuity, the object of which, in reference to the medium in which the seals reside, and the necessity of often rising to the surface to breathe, is suffici- ently obvious. In the cats and other genera, where extraordinary and sudden exertion is frequently necessary, the bones altogether are found to be remarkably compact and solid. A few details of the structure of the indivi- dual bones composing the cranium will be necessary, in order to shew how admirably every portion is made to bear upon the general objects of the whole organization. The frontal bones, (Jig. 192, 193, 194, e ,) which, as in most other instances, are separate, have a considerable developement of the zygo- matic or external angular process, especially in those whose habits are preeminently carnivorous, as in the cats, the mustelidae, &c. In the ichneu- mons it even extends so far as to meet the orbi- tary process of the malar bone, and thus form a complete orbitar circle ; the cats exhibit an approach to such a formation, but in the other tribes it is less and less marked, and in the seals there is scarcely the vestige of this process to be perceived. The parietal bones ( f) are of a quadrate form ; they are early united in the mustelse, the cats, the hyenas, and the bears ; in the dogs and in the seals, &c. they remain more durably separated . The interparietal bone, as it is called, (a large os triquetrum ,) which is found in many ani- mals, particularly during the young state, is considerable in the dogs, in which it remains permanently distinct from the parietal and oc- cipital. Its form in these is that of an elon- gated triangle, which extends forwards, sepa- rating the two parietal bones for more than half their length. In this instance it proceeds from a single point of ossification, whilst in many of the rodentia it arises from two centres of developement. The crest which is formed along the median line of the cranium, at the junction of the parietal bones, and which forms a continuation forwards from the ridge of the occipital, is greatly developed in the older cats and others. The lion and tiger, the wolf and the bear, the badger and many others, exhibit it in an extraordinary degree. Its object is evidently to afford a strong and extended sur- face of attachment to the powerful temporal muscles, which are required to be enormously developed for the purpose of cutting and tearing in pieces the hard tendinous portions of the animal’s prey. The temporal bone (g) is divided, as in the other mammalia, into a cranial or squamous, and a petrous or acoustic bone. The former constitutes the posterior and superior portion of the zygomatic arch, and beneath the root of this process is situated the articular cavity for the reception of the condyle of the lower jaw. Its transverse form, and the depth of its ante- rior and posterior boundaries, afford a strong and secure hold of the condyle, which, whilst it thus moves freely within its limited sphere of action, is restricted from any other than a simple hinge-like motion. This circum- stance adds greatly to the power of this parti- cular kind of mastication. The squamous portion is but small, and is externally more or less convex. The acoustic portion is greatly developed in the cats, and still more so in the seals, a circumstance which will be further alluded to hereafter. The occipital bone varies much in the car- nivora. In the seals the superior or squamous portion is large, obtusely triangular, and much flattened, being in many species devoid of the strong occipital ridge which is so prominent a feature in all the other families of the order. In the cats this process is very prominent and strong, forming a solid attachment for those powerful muscles which are necessaiy for the forcible and even violent raising of the head in tearing the prey to pieces. It is also strongly marked in most of the Ursida, particularly in the white bear, the badger, the coati, &c. The inferior portion, answering to the cuneiform process, is in the seals remarkably broad and thin, much more so than in any other of the mammifera; and in this part there is in some species of that family an oval hole of consi- derable size, placed near the inferior margin of the foramen magnum. This exists only in cer- 474 CARNIVORA. tain species, in Ph. vitulma for instance, and ap- pears to harmonize with the tendency to scanty deposition of bony matter, which characterizes the whole cranium in this family. The con- dyles in these animals are also very much larger than in the other carnivora. The sphenoid bone has nothing very remark- able in its structure, excepting the greater developement of its aim in these than in most others of the mammalia, and the small com- pressed triangular form of the pterygoid pro- cesses which in the cats are long and hooked backwards. The superior maxillary bone consists of the true or posterior maxillary (c) and the intermax- illary (a) portions. For the sake of clearness they may be described as distinct bones. The body of the maxillary bone extends very high up in the cats, and is remarkably strong and compact. In the seals it is encroached upon by the nasal opening, so as to leave only a narrow neck be- tween that opening and the orbit. The infra - orbitar foramen is remarkably large in the cats and in the seals, in which animals the long elastic setaceous whiskers are so useful as feelers, and are supplied with large filaments of the infra-or- bitary branch of the fifth pair of nerves. The length of the body of this bone depends on the number and nature of the teeth which are imbedded in it, and is shorter in proportion to the predominance of the strictly carnivorous appetite. The canine teeth and the molares are those which occupy this bone, the incisores being placed in the intermaxillary ; and in the cats the body of the bone is remarkably short, being occupied only by four molar teeth, the first of which is small and rudimentary, as well as the posterior one, which is small and tubercular ; the two middle ones are formed for cutting asunder the flesh, and are exceedingly strong. In the bears the teeth assume more of a tubercu!arform,and are, infact, adapted for mas- ticating vegetable substances as well as animal matters; the jaw-bone is, therefore, much longer than in the cats. In the dogs, which hold an intermediate place in this respect, the molar teeth are six in number, and the two posterior ones are more or less tubercular. The anterior part of the jaw is enlarged and rounded for the location of the large and powerful canine teeth. In the Walrus (Jig- 195,J the anterior part of this bone is greatly enlarged for the enormous canine teeth, which form powerful weapons, with which the animal strikes directly down with immense force. The intermaxillary bones contain each three small incisor teeth : these in the cats are very small, excepting the external one, which is somewhat larger than the others. In the seals they are pointed. These bones are con- siderably smaller in the carnivora than in most other orders. The nasal bones ( b ) are smaller in this order than in many others. In the cats they are rather broad anteriorly, but short; they are longer in the dogs and bears, agreeably to the greater length of the face generally. In the seals they are much shortened, in order to allow of the great expansion, in an upward direction, Fig. 195. of the nasal aperture, by which, when in the water, they more readily raise their nostrils to the atmo- sphere for the purpose of breathing. The malar bone ( h) per- forms a very important office in the carnivorous group, as the zygoma re- quires to be very exten- sively developed for the protection of the enormous masses of mus- cle which are needed in tearing the food of these animals, as well as for the attachment of the musseter. The zygomatic arch in this order is convex upwards as well as curved outwards, by which form a great increase of strength is acquired in the direction of the muscular force. The lacrymal bone is said to be wanting in the seals. I believe I have seen a trace of its existence in a rather young cranium of Phoca vitulina. The remarkable vacancy which oc- curs in some of this tribe in the orbito-temporal fossa, between the frontal, the maxillary, and the sphenoid bones, has been supposed by Meckel to indicate the place which the lacry- mal bone should occupy; but as this hiatus does not exist in several species, in which the absence of this bone is equally evident, this supposition is probably not correct. The inferior maxillary bone ( i ) follows of course the general structure of the superior. It is remarkably short in the typical forms of the carnivora, and more elongated in the others, particularly in the bears. Indeed this bene, like the upper jaw, is shortened exactly in pro - portion to the carnivorous propensity of the animal. The ascending plate is also remarkably developed, and offers a surface of great extent for the insertion of the elevators of the lower jaw. The character of the vertebral column in the Carnivora offers some interesting varieties of form, depending principally on the degree of exertion, of activity, or of flexibility re- quired by the habits of the different genera. The strength and size of the two first cervical vertebra, the atlas and dentata or axis , have already been alluded to. The first is exceed- ingly broad and robust, with strong transversej processes; the second is long, with an enormous spinous process. The remainder of the cervi- cal vertebra are generally rather elongated in most of the genera, but in the seals they are short and but little developed. In general, also, the spinous processes are considerable, and either CARNIVORA. 475 perpendicular or directed rather forwards, par- ticularly in the cats, the coatrs, the badger, and some others. In the dogs there are also small inferior spinous processes. The dorsal region varies much in its relative proportions with the lumbar region and with the size of the animal ; a point which will be more particularly alluded to presently. The spinous processes are very strong and strait, and directed backwards. The number of the dorsal vertebra, and, con- sequently, of the ribs, varies in the different genera of the order, from thirteen, which is the most common number, to sixteen, of which we have an example in the Glutton (Gulo articus). The lumbar vertebra are remarkably strong in almost all the Carnivora , though less so than in some other orders. The spinous processes are long and directed forwards, particularly in the cats and dogs. The transverse processes are also very large and strong ; but the most im- portant circumstance connected with the cha- racter of these vertebrae is the relative propor- tions which exist between them and the dorsal in different species, not so much with regard to number, as to the proportional extent of the two regions. In respect even to number, the variations of the lumbar vertebrae are not in- considerable : thus, the Ratel and the Hyena have only four, whilst the cats and many others have seven. But we find that in those species which, from their habits, require gieat power of springing, of rapid running, or of great flexibility of motion, the relative extent of the lumbar region is increased in proportion. Thus, whilst in the Hyena the lumbar region bears to the dorsal only the proportional length of four and a half to fourteen, and in the Ratel of three to eight and a half ; in the Lion we find it as fifteen to eighteen, and in the Panther, the Wild Cat and the Civet, the extent of the two regions is almost exactly equal. This is a con- sideration of great importance, not in the Carnivora only, but in the Ruminantia and other orders, where the different groups are found to vary much in their powers of spring- ing and their general activity : for the propor- tion of the lumbar to the dorsal regions will invariably be found in exact accordance with the extent of those powers. The Sacrum is composed of several vertebrae, as in most other mammifera ; in the present order there are generally three or four, though in the Brown Bear there are six (Cuvier says five), and in the White Bear seven; in the Coati there is but one, and in the Hyena only two. The spinous processes of the Sacrum are more developed in this order than in many others. Cuvier observes that, in those animals which, from their habits, occasionally rise upon their hinder legs and hold themselves upright, the Sacrum is broader than in others of the same order, and he instances the Brown Bear in the present order as an example. The tail, consisting of the coccygeal vertebra, varies excessively amongst the Carnivora, and this in many cases in the same family, and with but little obvious relation to the habits of the species. As a general rule it may be ob- served that the most active, and those which possess the most flexible spinal column, have the greatest number of caudal vertebrae. Thus, while the Brown Bear has only about six, the Lion has twenty-three, and the Panther twenty- four. In many of the Carnivora which have long tails, the spinous processes are generally di- rected from before backwards, but are always very small, and exist only on the few anterior vertebrae of the tail. The middle and posterior coccygeal vertebra are therefore more deve- loped in length and become almost cylindrical, excepting that they are thicker at each extre- mity. As in other orders, the anterior portion only of the tail conveys the spinal marrow, the posterior being impervious. The most im- perfect developement of this portion of the vertebral column is found in the Seals, in which generally it is only the first vertebra which possesses even a trace of spinous and transverse processes, the remainder being al- most cylindrical, without even any enlargement at each extremity. The ribs correspond in number with the dorsal vertebrae. Their curvature varies con- siderably both as regards the different portions in the same species and the general form in different groups. In many of the mammifera the difference in this respect between the an- terior and middle regions of the thorax is very striking; this, however, is generally not so much so in the present order, in which, as a general rule, the anterior ribs are not less arched than the others. The anterior ones, however, are very much smaller and shorter than the middle and posterior. The relative number of true and false ribs would, a priori, appear to have some relation to the degree of rapidity or of flexibility in the animal’s move- ments ; and hence that those which leap or swim would require greater mobility of the thorax, and consequently a greater proportion of false ribs. Now, although this is strikingly the case with regard to some of the cetacea, which have only from one to five fixed ribs, and from ten to seventeen false, yet no such rule is observable in the present order; the Seal and the Lion having even a less propor- tion of moveable ribs than the Bear and the Glutton. The sternum in the Carnivora does not vary greatly in breadth in its different portions. It is much more developed longitudinally in these animals than in most others, and is scarcely broader than it is deep. The anterior piece of this bone in the Seals is remarkably long, and is also moveable. The shoulder, composed of the same ele- ments as in the other mammifera, varies, how- ever, considerably in the degree of develope- ment of the bones of which it is formed. The scapula is depressed and remarkably broad from the anterior to the posterior margin, and in some cases — as in the Badger especially, and in some degree in the Bear — it assumes almost a quadrate form. The spine of this bone, which in the Seal is very small, is of great size and strength in the bear tribe, par- 476 CARNIVORA. ticularly in the Badger. The acromion is small and slight in all the true Carnivora, but in those of the Insectivora which have true cla- vicles, it is long and robust. The coracoid process is generally present, but is wanting in the seals. The clavicle in the whole of this order is very slender, and must be considered as merely rudimentary. In the Hyena and the Dog it is extremely small ; larger in the Mus- telidce, and still larger in the Cats. It is not attached to the sternum or to the scapula, but suspended, as it were, between these two bones, generally occupying not much more than half the space between them. The humerus is in general rather slender, long and nearly cylindrical when compared with that of the Pachydermata, Ruminantia, and some others. It is somewhat arched, and the great tuberosity is very much developed ; this bone is short and broad, the superior two- thirds being widened from before backwards, and the lower third from side to side. The fore-arm is here, as in the other orders, composed of the radius and the ulna. The latter bone is generally placed immediately behind the former, and they have but little motion one on the other, excepting in the bear tribe, whose habits require more freedom of movement in the anterior extremity. That tendency to the expansion of the members into instruments fitted for swimming, which is so obvious in the Seals, is found to obtain in the two bones in question, which in this family are short, flattened, and very broad. The carpus in this order offers a few pecu- liarities which may be slightly glanced at. The os scapho'ides and the os similunare form but one bone, which is of considerable size. The os pisiforme is much elongated, forming a little spur or heel to the anterior feet, a peculiarity, however, which is wanting in the seals. The os trapezium is very small in the Hyena, in which the thumb is but rudimentary. The metacarpal bones in the digitigrade car- nivora are much larger than in the plantigrade. In the latter the shortness of these bones, with the comparative length of the phalanges, gives somewhat of a plantigrade character even to the fore-feet, although the metacarpal bones do not actually rest upon the ground : whilst in the digitigrade families, and especially in the cats, the metacarpals being much produced, and the phalanges very short, the part which rests upon the ground is greatly abbreviated. The phalanges offer some very interesting points of structure, particularly in the Felida, in which the terminal phalanx is retractile, or, on the other hand, can be thrust out and rendered the basis of a most formidable weapon. This character of the retractile claw is, in its full developement, peculiar to the family just named ; and the Lion may be selected as offering, from its great size, the most conve- nient opportunity for its examination. In all the Carnivora the claw is fixed on the extremity of the last phalanx (Jig. 196, a, a), the hooked form of this part of the bone being an accurate model of the interior of the claw, and the base of the claw is secured within a thin lamina or hood of bone which covers it on the sides and above. In the animal just named this is par- ticularly strong and large. It is considerable also in the Badger, but less so in the Bears, the Dogs, the Hyenas, &c., and in the Civets it is very small. The penultimate phalanx is of a peculiar form. Its transverse section would be triangular, two of the sides being lateral, and the third inferior. On the inner face or side, there is a hollowing or twist of the bone, which leaves an oblique excavation in the middle. It is by the inferior portion of the last phalanx that it is articulated to the penul- timate, and beneath the joint a process of the last phalanx extends downwards, for the at- tachment of the muscles by which the toes are flexed, and consequently the claw protruded. When the claw is retracted or in a state of rtst, the last phalanx is brought upwards and thrown completely hack on the inner side of the se- cond phalanx, being partly lodged in the lateral hollow before described. This is the condition of repose, and the last phalanx is held in this situation by the elasticity of the capsular liga- ment, and particularly by two lateral ligaments which arise from the second phalanx. The posterior extremity. — The pelvis in the Carnivora is shorter than in many other orders, and the ossa ilii particularly are flattened and rather broad. Their internal surface also is not turned forwards as in most other orders, but for the most part directed towards the spine, so that the ventral aspects of these two bones face each other. In most of the seals the ilia are short and small, compared with the other bones of the pelvis. The posterior or descending branch of the ischium, and the anterior portion of the pubis are, in particular, much elongated in this family. The femur is strait, cylindrical, and mode- rately long in most of the Carnivora. In the Seals it is, however, extremely short, as may be observed in jig. 191. In this tribe this bone does not assume the direct backward direction of the leg-bones, but stands outwards and downwards, by which a great extent of motion is obtained for the hinder paddles. f. The tibia and fibula,* (jig. 196, ls m; jig. 197, i, k; jig. 198, l,m;j are detached in most of the Carnivora; but in the Dog the fibula is attached to the back part of the tibia. In the Phocida these bones are long, flattened, directed backwards, and the tibia has a double , curvature. The tarsus consists of the same bones in the Carnivora as in Man, (jig. 196, /, g,h, i, k, fg. 1 97 , e,f, g, h,fgA98,f,g,h, k,) the os calcis has a very long and robust tube-, rosity both in the digitigrade (jig. 196, k) and plantigrade (jig. 197, h) forms. In the former there is also on the inferior surface a small tubercle which is wanting in the others. * The figures representing the hinder foot arc selected for the purpose of shewing the three prin- cipal types of progression in the Carnivora. Fig. 196, that of the Lion, exhibits the digitigrade, fig. 197, that of the polar bear, the plantigrade ; and fig. 198, that of the seal ( Phoca vitulina), the natatory. CARNIVORA. 477 Fig. 197. Fig. 196. b 'c The metatarsal boties (Jig. 196, 197, 198, d ) are generally five. In the cats and the dogs, indeed, the inner one is merely rudimentary, a defect which is perfectly consonant with the absence of a posterior thumb in these two genera. Those of the seal tribe are remark- ably long and slender. The first is the longest, the fifth the next, then the second, the fourth, and the middle one which is the shortest. The toes consist of three phalanges (Jig. 196, 197, 198, a, b, c,) and in most genera there are five toes; the bears and other plantigrades having the inner toe or thumb in the same range as the others ; in the mustelidce it is a little smaller, and in the cats and dogs it is wholly wanting. The toes in the seal tribe are developed to considerable length, and being much extended, and covered with an entire skin which extends from one to the other, a very perfect finlike paddle is thus furnished. The types, then, of the three different varie- ties of progression are here distinctly shewn. In the foot of the bear (Jig. 197) we find that every thing in its formation is made subser- vient to the action of walking; the heel, the tarsal and the metatarsal bones, and the pha- langes all rest upon the ground, and these bones arc elongated for that purpose. In the Lion (Jig. 1 96) the last phalanges only rest on the ground, the heel being drawn upwards, and the whole of the foot, excepting that small portion which is applied to the ground, is thus made an additional lever for the increase of the animal’s powers of leaping and bounding in its course. In this form the limb consists of three joints (the pelvis being the fixed point) moveable in alternately different directions, | capable of being all approximated to each other, and then suddenly and simultaneously extended with prodigious force. In the third type, that of the Seal (Jig. 198), the bones are all much flattened, and, excepting the foot, greatly shortened ; the foot itself being de- veloped both longitudinally and laterally into a finlike expansion. The Muscular System. — The general cha- racter of the muscles in the Carnivora is that of combined power and irritability. The ele vators of the lower jaw, the masseters and the temporals, are enormously large, for the pur- pose of cutting and tearing the flesh and the harder portions of their food. The muscles of the face also, those of the lips, of the nose, of the eyelids, and of the ears, are all of them greatly developed and capable of the most extensive and powerful motion. A moment’s reflexion upon the habits of these animals, and particularly on those of the cats, will shew the necessity of enormous power in the muscles which raise the head upon the spine. A Lion, it is said, can kill a moderate-sized bullock, throw it on his back by a toss of the head, and trot off with it to his hiding-place. All the muscles, therefore, which arise from the vertebrae of the neck and are inserted into the projecting ridge of the occipital bone, are of prodigious strength. The same remark holds good of all the muscles of the limbs, particularly those of the anterior extremity, but which do not require a par- ticular description or demonstration. The mus- cles of the tail, which are for the most part similar in this order to those in the tailed Qua- drumana and Kuminantia, will be described in the articles devoted to the anatomy of those animals. The digestive organs. — The structure which has been already detailed in the skeleton of the Carnivora, and alluded to in their muscular 478 CARNIVORA. system, will be found altogether subservient to the office of procuring that peculiar kind of food to which these animals are restricted, and the modifications of that structure which have been described as appertaining to different types of form in the order, are equally con- sonant with the modified nature of their ali- ment. Thus, whilst the powerful yet active and flexible movements of the typical Carni- vora are adapted only to the pursuit and de- struction of living prey, the more sluggish habits of most of the bear tribe, their peculiar mode of progression, and the modified structure of the skull, the teeth, and the limbs, are all equally applicable to the mixed nature of their food ; and the third principal type — that of the amphibious carnivora, the Seals — exhibits an arrangement of these organs not less admirably fitted for the pursuit and capture of their aquatic and scaly prey. The digestive organs of each of these prominent groups are not less perfectly formed for the digestion of their vari- ous food, than the organs which have already been described are for its capture. The teeth have already been slightly alluded to, but they deserve a more particular description. In the cats, the character of the teeth is typically car- nivorous. The incisores are very small, as indeed they are throughout the whole order. The canine teeth are, on the contrary, pre- eminently strong, long and sharp, and are evidently adapted for seizing and holding their prey and afterwards tearing in pieces the flesh and other soft parts of the animals. These teeth are conical and very slightly curved, a form which, united with their sharpness and strength, is the best that can be imagined for effecting this object. The cheek teeth, instead of having flat grinding surfaces, have, for the most part, only cutting edges ; and those of the lower jaw shut within the upper, passing them so closely as to form an accurate instru- ment either for shearing off pieces from the flesh or for cutting into morsels the portions which have been torn by the canine teeth. On each of them are sharp triangular processes which much facilitate the entrance of the tooth into the flesh. The range of these teeth is short, as is also the whole jaw, by which great power is gained in this particular direction. The articulation of the lower jaw is also cir- cumscribed to a perpendicular motion, the only one which the structure of the teeth would permit. The strong muscles of the lips also enable the animal to raise them out of the way of injury during this process. The animals of the bear tribe, on the other hand, have an elongated jaw, canine teeth, although very large and strong, yet less so than in the cats, and molares, the surfaces of which, instead of being raised into cutting edges, are depressed, tuber- cular, and require a certain degree of lateral motion in the jaw to bring them into action. In the seals a very different structure of the teeth is observed. The canines are not par- ticularly large and prominent ; and the molares, neither adapted on the one hand for shearing nor on the other for grinding their food, either of which actions would be unavailable in their particular case, are numerous and furnished with several angular points, which are fitted for holding the slippery, scaly surface of fish, and equally so for crushing them before they are swallowed. The teeth of the Walruses, however, are very different from those of many other of the Phocida. The tusks (jig. 195) which are enormous canine teeth of the upper jaw, are directed downwards, and constitute formidable weapons of defence, and the mu- lares are formed rather for grinding than for merely holding their prey. The food then being thus variously prepared by the different groups of this order, passes into the stomach more or less masticated. The salivary glands in the meantime have been performing their important office. The vari- ations in form and situation of these glands are slight and unimportant. The submaxillary glands are generally as large as the parotid, which in the dogs and cats are of a crescentic form, embracing by their concave margin the conch of the ear ; and in the dogs the inferior portion is distinct from the rest. The sub- lingual are wanting in the cats. The stomach in all the animals of this order is perfectly simple, and its interior smooth, with the exception of that of the Seal, which has a villous coat. In the cats (that of the Lion is shewn at jig. 199) it is elongated, and Fig. 199. the two openings are placed nearly at each end: there is a small pouch however at the cardiac extremity. In the Wild Cat it is somewhat pyriform, the pyloric portion being, as in the Lion, doubled upon the other part; and in the Lynx the cardiac and pyloric openings are more distant than perhaps in any other species. In the other genera the form varies a little. It is nearly globular in the Racoon ; that of the Hyena is large and short. In the seals it is elongated from before backwards, the pyloric portion being turned forwards upon the other; at the bend there is a pouch, at which point a glandular layer is found between the internal coat and the cellular. The intestinal canal is in these animals re- markably short, particularly in the cats ; in the Lion and in the Wild Cat the whole alimentary canal is but three times the length of the body. In the Seal it is much longer. The distinction between the small and large intestines varies considerably. In the Badger this distinction can scarcely be said to exist : in the Lion it is considerable, and still more so in the seals and CARNIVORA. 479 others. The ceecum exists, but is very small and short in the cats : (Jig. 200 shews that of the Lion.) In the dogs it is spi- Fig. 200. ral. The whole canal is almost destitute of val- vuIib conniventes, nor is the large intestine tucked up into sacs as in other orders. The mustelida generally have no ccecum nor valvula coli. A short comparative view of the structure thus hastily sketched, with that of the digestive system in the typical herbivora, the ruminant animals, will not be uninteresting. The Car- nivora feeding on aliment which requires but little elaboration to convert it into nourish- ment, the whole process of digestion appears to be as rapid as possible, and we find that every part of the organisation is admirably adapted to this object. The strength of the jaws, the form of the teeth, the structure of the maxrllary articulation are all contrived for preparing the food by simple division. The stomach is sim- ple and almost straight, the intestines short, and without any structure to retard the passage of the food. In the ruminantia, on the contrary, the jaws are much elongated, the molar teeth flat and formed for affording the greatest pos- sible extent of triturating surface, the maxillary joint allowing of the most extensive lateral mo- tion, the stomach complicated, and a second and more complete mastication is performed after the food has been long macerated in the paunch. The intestines are exceedingly long, (in the ram twenty-eight times the length of the body,) very large, and tucked up into folds and sacs throughout their whole length. Here every thing is arranged for the thorough com- minution and maceration of the food, and for the greatest possible retardation of its passage through the body, as well as for an immense extent of absorbing surface for the extraction of every particle of nutritious matter. The liver in the Carnivora is deeply divided into lobes, which vary in number in different species. Thus in many of the plantigrades there are five, as the brown bear, the coati, and the racoon ; in the otter also, and in the martens and generally in the dogs there are the same number. The Badger has but four. The cats generally have from five to seven, though that of the jaguar has but four, and that of the lynx eight. This numerical variation appears, therefore, to have no reference to any physio- logical law, nor to any peculiarity of habit. The hepatic ducts offer some peculiarities worthy of notice. In the cats there are always several, which correspond with the different lobes of the liver. Before the ductus com- munis opens into the duodenum after passing the muscular coat of the intestine, it forms a i considerable enlargement, divided by an in- ternal contraction into two cavities, into the first of which the pancreatic duct opens. In the dog the ductus communis enters the intes- tine with one of the pancreatic ducts. In the otter, the common duct forms a second reser- voir near the duodenum. The gall-hladcler exists in all the Carnivora. It varies in some measure in form, being py- riform in most, elongated and almost cylin- drical in many of the mustelida, and rounded in the bear, the racoon, and some others. It is of great size in several of the plantigrades. The pancreas is similar in its general struc- ture to that of the other mammifera. It varies in form, but not in any way that can be sup- posed to give it a peculiarity in function. The pancreatic ducts vary also in number and in the situation at which they open into the liver. In some instances, as in the cats, the pan- creatic and common biliary ducts are united and enter the intestine at one orifice, though this circumstance is not uniform in the genus, nor even in all individuals of the same species. As a general rule in this order the ducts of these two important glands terminate together. The spleen requires also to be merely glanced at, as its characters and situation do not ma- terially differ from those in the other orders of the class. It is generally elongated and narrow, and either flattened or somewhat pris- matic. The chyliferous system. — The chyle in the Carnivora has always been remarked for its whiteness and opacity, a circumstance which greatly facilitates the tracing the course of the lacteals in this order, and which in fact gave rise to their discoveiy in these animals before they were seen in man. The mesenteric glands are united either into one large mass only, as in most examples of the order, into two as in mustela, or the larger substance is associated with several smaller ones, as in the cats, the otter, the seal, and some others. This glan- dular mass has been termed Pancreas Asellii, from its having been erroneously mistaken for a pancreas by that anatomist. The thoracic duct, in the dog is double, and in the Sea Otter it has been found by Sir Everard Home that two ducts go from the receptaculum chyli to form this duct, which in its course sometimes divides into two, three, or four, again uniting at intervals. Organs of circulation. — The heart and blood- vessels offer but few peculiarities in this order worthy of particular notice. The heart varies but little in form ; its parietes are remarkably strong in the larger cats, in the lion particularly. The general structure of this viscus does not differ materially from that of the other mam- mifera. There is, however, a question of some interest which has been often debated ; this is, whether the foramen ovale and the ductus arteriosus remain pervious in the seals and the otter. The testimony of Cuvier and of Blumen- bach goes to prove that, at least in many in- stances, these openings are closed. Cuvier states it to have been so in a seal, and Blumen- bach says that this is its general condition. On the other hand Sir Everard Home has given two examples in which the foramen ovale remained pervious in the sea otter ; Blumen- bach also states that he possesses the heart of 480 CARNIVORA. an adult seal, in which both these channels of communication remained open ; and the writer of this article dissected a seal some years since which was nearly full grown, in which the foramen ovale was so open as to allow the tip of the little finger to enter, and the ductus arteriosus would admit with ease the bulb of a common probe. Upon the whole then it appears that, al- though the pervious condition of these chan- nels cannot b« considered as general in the adult state of these diving animals, as has sometimes been supposed, it must be allowed that this exception is far more frequent in them than in any other mammiferous animals, and that, as a general rule, these holes remain open later in such animals than in others. There is, however, in the otters and in the seals, a con- siderable dilatable enlargement observed in the inferior cava, which serves doubtless as a re- servoir to retain part of the returning blood during submersion, until the animal rises again to breathe. Organs of respiration. — The lungs are di- vided into lobes varying but little in number in the terrestrial families of the order. These all have four lobes to the right lung, and either two or three to the left. The seals have the right lung divided into two lobes, and the left undivided. The cartilaginous portions of the rings of which the trachea is composed vary in the proportions which these bear to the whole circle; in the genus Mustela and some others, the cartilage forms about two-thirds of the circle ; in the bear, the coati, and the cats, about three-fourths ; and in the ichneumon as much as four-fifths. The nervous system. — On viewing the dif- ferent orders of mammifera in the ascending series, the brain of the Carnivora (fig. 201 being an upper and a lateral view of that of the Lion) will be found to exhibit a higher degree Fig. 201 . of developement than exists either in the cetacea, in any of the forms of the herbivora, or in the marsupiata ; the hemispheres have here a well-marked superiority of develope- ment over the cerebellum and tubercula quadri- gemina. On the other hand the brain of the Carnivora is less developed anteriorly than in the Quadrumana, the anterior lobes being some- what narrowed and depressed, and the con- volutions, (although deeper than in the orders just mentioned,) instead of the labyrinthine duplicatures which are observable in the Qua- drumana and in man, are, generally speaking, longitudinal in their direction, the principal being but two on each side of the median line, crossed by a transverse anterior one. The cerebellum is almost wholly uncovered as seen from above, not more than one-fifth of it lying under the posterior edges of the hemispheres. The optic thalami, however, are concealed not only from above but even on a lateral view, by the hemispheres. Of the tubercula quu- drigemina, the posterior are the larger. 'The eye possesses but few peculiarities of any importance. The relative proportions of the different humours are here more nearly equalized than in any order of the mammalia, at least in some of the genera, as the following comparative view will shew : — Aqueous. Crystalline. Vitreous. Dog & ... $ ... ^ ^an I, ... j4, ... 'ji DX 37 • • • ^7 • • • 3? The vitreous humour, therefore, is much less than in either of the other cases, and the crys- talline smaller in proportion than that of man. The crystalline lens in the Seal fulfils the gene- ral law which gives to it a degree of sphericity in relation with the aquatic habits of the animal. Thus the crystalline of fishes is ab- solutely spherical, that of the cetacea nearly so, and that of the seal and of the otter very much less flattened than in those animals which re- side and seek their food on land. In the sea) also the sclerotic is considerably thickened anteriorly and still more dense at the posterior part, whilst the middle zone is very thin and flexible, — a structure which must offer great facility for the action of the different muscles which compress the globe, and alter the rela- tive proportion of its diameter to its axis. The form of the pupil differs in different groups. In the diurnal carnivora, and even in some nocturnal, it is permanently round ; but in the cats it is perpendicular during its contracted state, and in a very bright light it is almost linear, but even in these it becomes perfectly round in the dark, and the ellipse which it forms in its contraction is more or less length- ened or acute according to the degree of light. The inner surface of the choroid is partially lined with a brilliant greenish tapetum, similar to that which is found in the ruminantia, and occupying nearly the same situation. The lachrymal gland exists throughout this order, and the glandula Harderi is also found in its members as well as in the ruminantia, pachydermata, and some if not all the ro- dentia. The organ of hearing is developed to a very considerable degree in most of the Camwora. Ij The external ear varies much in size and form; it is moderate in the cats, small in the bears,!: and rudimentary in the seals, but enormously large in the Fennec, a species of the family Cunidce. There is in these, as wrell as in many other mammiferous animals, especially the ro- dentiu, a remarkable hollow appendage to the CARNIVORA. true tympanum, taking the place of the mastoid process, and probably performing the same office as the mastoid cells. This, in many, forms a large rounded process beneath the cranium. In the cats it is remarkably large and globose ; in the bear, on the contrary, it is not visible externally. The object of this en- larged cavity is doubtless to give additional volume to the sounds which are brought to it, a circumstance especially required by the noc- turnal habits of those species in which it is most largely developed. Tb q fenestra rotunda, which is covered by a membrane stretched across it, is believed by Cuvier to be intended for the reception of the sounds produced by the resonance of the bony case just described ; an opinion which is perfectly consonant with that of Scarpa, who considers the hole in question, with its membrane, as a sort of se- condary tympanum. The fenestra rotunda is the larger of the two apertures of communi- cation with the internal ear in the present order generally; in some of the most nocturnal, the cats and the civets, it is almost double the size of the fenestra ovalis. The passage answering to the Eustachian tube is remarkably short and can scarcely be called tubular; in the cats and civets it is nothing more than a narrow cleft in the suture which unites the tympanum to the true petrous bone. The organ of smell is generally extensive in the carnivorous animals, and in addition to the principal apparatus of this sense, the different sinuses which augment the nasal cavity, par- ticularly the frontal, are of considerable extent, especially in the canida. But the most re- markably developed of the surfaces on which the pituitary membrane is distributed, are those of the superior and inferior turbinated bones. The inferior are very complicated in their convolutions in the dogs, the bears, seve- ral of the cats, and particularly in the otters and the seals. This complication consists of repeated and multifarious bifurcation ; and the ultimate divisions of this bone, which all as- sume a parallel direction, form a great number of channels which the air traverses in the act of inspiration, and which are all covered by the pituitary membrane. The ethmoidal cells and the superior turbinated bones are likewise greatly developed in the Carnivora, and par- ticularly in those in which the before-men- tioned structure of the inferior turbinated bones is most conspicuous — a remark which also applies to the numerous foramina in the cribriform plate of the ethmoid. In the bear, and particularly in the coati, the cartilages of the nose form a complete tube, which is articulated moveably to the bony nos- trils. The same structure is still more remark- able in the mole. The organ of taste. — The structure of the 1 surface of the tongue in the Felida is very remarkable with regard to the characters of the various papillae with which it is furnished. The edges are everywhere covered with small soft conical papillae, as well as with the papilla \petiolata, such as are found in most other VOL. i. 4$1 animals. The whole of the middle part is covered with papillae of two kinds very dif- ferent from each other, and these two kinds are arranged in alternate rows in a quincuntial order. Those of one kind are soft, rounded, and appear to consist of bundles of filaments, which are supposed by Cuvier to be the ulti- timate extremities of the gustatory nerves, though this opinion appears from the recent observations of Breschet to be very doubtful, The others are conical and pointed, and each of them is covered by a sharp horny case curved a little backwards. It is these horny spines which render the tongue of the cats and the civets so exceedingly rough as that their continued licking would soon abrade the hu- man skin. The tongue in all the other Carni- vora scarcely differs in its structure from that of the human subject. Secretions. — The urine. The structure of the kidney in some of the Carnivora is wor- thy of notice. Instead of being a compact and united mass as in man, it is subdivided into numerous portions similar to those of the human foetus. In the cats this division is scarcely perceptible, the surface being only in- terrupted by superficial fissures or sulci. But in the bears, the otters, and the seals, the sepa- ration is so deep as to resemble in some sort a bunch of grapes. In the otter there are only ten of these divisions in each kidney ; in the bear there are about fifty, and in the seal from a hundred and twenty to a hundred and forty. As this peculiarity of structure is found to exist in a still more remarkable degree in the cetacea, Cuvier has suggested whether it may be connected with the occasional longer or shorter suspension of respiration, as it obtains in the cetacea, the seals, the otters, which are often submerged, in the bears which re- main torpid during the winter, and in the human foetus which has never breathed. Its existence, however, in the elephant, the ox, and many other animals whose respiration is never interrupted, renders this explanation, as Cuvier himself observes, extremely unsatis- factory. The existence of follicles producing a pecu- liar secretion is not an uncommon circumstance in several orders of the mammifera, as well as in many reptiles. In the Carnivora these fol- licles are found in almost all the genera, and in some attain to a large size. They are situ- ated one on each side of the anus, and the excretory duct opens near the termination of the rectum. The substance usually secreted by these glandular surfaces is strongly odor- ous, and in some cases intolerably fetid. The annexed engraving (fig. 202) is taken from a specimen of Gallictis vittata, which I dis- sected some time since, and is selected, because it has not been before figured, and because the glands are of large size and very distinct. Each follicle is covered by a muscle of no inconsiderable strength, the object of which is to compress the follicle, and to force out the secretion through the duct. One of the follicles is represented covered by ' its 2 i 462 CAROTID ARTERY. Fig. 202. muscle ; the other has had the muscle re- moved. Besides these follicles there is in several species a pouch, somewhat resembling those above described, but differently situated. It is always single, and in the badger and hyena is placed between the anus and the tail ; in the ichneumon it surrounds the anus, and in the civet it is found between the anus and the opening of the prepuce in the male, and be- tween the anus and the vulva in the female. The secretion of this sac in the latter animal is well known as a scent of a most powerful musk-like odour. The sac opens by a longi- tudinal slit, and in the interior are seen two cavities in which the substance is secreted, and which are furnished with a muscular coat for its expression. Generative system.- — Male organs. The structure of the testes is similar to those of the other mammiferous animals, but they vary con- siderably in situation. In most of the genera, as in the bears, the cats, the martens, the hy- enas, the ichneumons, &c. they are perma- nently suspended in a pendulous scrotum. In the civets they are enclosed under the skin of the perineum, and in the otter under that of the groin. In the seals, in which a pendulous scrotum would be exposed to continual danger of injury or destruction, they remain con- stantly within the abdomen, being retained in their situation by a production of the peri- toneum, resembling the broad ligaments of the uterus. The vesicula seminales do not exist in most of the Carnivora. They are found in the coatis, but not in their congeners. The pros- tate gland, or at least a glandular body ap- parently analogous to it, is found throughout the order. It varies in form and exceedingly in size ; in the otter and the other mustelidie it consists of a thin layer only, whilst in the dogs and cats it forms a large and conspicuous bulb around the urethra. Cowper's glands also are found in many of these animals, but are wanting in the planti- grades, in the mustelidee, the dogs, and the seals. In the Felida (the cats and the civets) and still more in the hyena, they are on the other hand of great size, and the muscle which envelopes them is of considerable thickness. The penis is found to vary but little in its form and direction in this order. It is, in al- most all, directed forwards, and contained within a sheath formed of an extension of the integuments of the abdomen. In the cats the extremity, during its relaxed state, is turned backwards, and the urine is consequently voided in that direction, but during its erect condition it assumes the same position as in the other Carnivora. Almost the whole of the carnivorous order possess a bone of the penis, of various size and length. The hyena is a remarkable exception, as in its congeners, the dogs, &c., it is of considerable size. This is the case also with the ursidce and the mustelida ; but in the cats and the ichneumon it is small. The anterior extremity of this bone is fixed in the glans, and the posterior is attached to the corpus caver nosum. In some genera, particu- larly the dogs, the corpus spongiosum under- goes a remarkable degree of tumefaction, which retains the two sexes in coitu for a considerable time. The female organs. — The clitoris is found in all the Carnivora. It is contained in a sort of pouch within the vulva in the wolf, and at some distance in front of this partin the civet. In some of those species in which the penis of the male is furnished with a bone, the clitoris of the female has also a rudimentary one. This, however, is not constant. It is not found in the dogs or civets, but exists in the cats, the bears, and the otter. The uterus is two-horned, and resembles that of most other mammifera. ( The mammary glands are situated along the sides of the belly, and the number of teats varies greatly, without any general law as regards the affinities of the species. Most of the plantigrades have six ; but the lion has four, the cat eight, and the panther six ; the bitch, again, has from eight to ten. I The placenta consists, in the cat, the dog, the marten, and others, of a perfect zone sur- rounding the foetus, and attached by its whole external surface to the uterus; in the polecat it is formed of two rounded masses connected together. For the Bibliography, see that of Mammalia. (T. Bell.) CAROTID ARTERY, (human anatomy,) (urteria carotis; Gr. xugvTn; ; Fr . carotide ; Germ, die Carotis, Kopfpulsader ; ) the great artery which on each side distributes blood to the different parts of the head. The term carotid, derived from xupoi;, sopor, appears to have been first applied to the arteries of the head by the ancients from a supposition that a state of drowsiness or deep sleep depended on compression or some other affection of these vessels exercising an influence over the circula- tion of the blood in its passage through them to the brain : in accordance with the same CAROTID ARTERY. 483 opinion they have been also called arteria soporijera. The carotid arteries consist of — 1 st, the pri- mitive carotids, of which the right arises from the arteria innominata, while the left comes directly from the arch of the aorta ; 2d, the ex- ternal carotid ; and, 3d, the internal carotid: these last two vessels on each side being pro- duced by the bifurcation of the primitive ca- rotid. Both primitive carotids are of equal size according to Bichat, Boyer, and Cloquet ; nei- ther Meckel nor Tiedemann make any remark as to a difference in their size, while, according to Soemmerring, the right is one-twenty-fifth larger than the left in the majority of in- stances. The origin of the right carotid from the arteria innominata is opposite the right sterno- clavicular articulation. The left carotid arises from the transverse portion of the arch of the aorta behind the first bone of the sternum, on a plane with the centre of the junction of the cartilages of the first pair of ribs with that bone in front, and corresponding with the superior edge of the second thoracic vertebra posteriorly; owing to this difference in their origins, the left primitive carotid is from one inch to one inch and a quarter longer than the right, and is con- tained within the thorax in the commencement of its course; it may therefore be divided into a thoracic and a cervical portion. The thoracic portion of the left primitive carotid, by which 1 mean that portion which extends from the origin of the artery to a point on a level with the stemo-clavicular articulation, has the following relations : — anteriorly it is covered by the left vena innominata, the remains of the thymus gland, some loose cellular tissue, and occasionally a few lymphatic glands ; in front (if these the origins of the sterno-thyroid and sterno-hyoid muscles separate it from the sternum ; posteriorly it rests on the oesophagus, left recurrent nerve, the origin of the left sub- clavian artery, the left par vagum, the thoracic duct, and some loose cellular tissue, in addition to which the longus colli is interposed between it and the front of the spinal column ; on its right side it is bounded by the trachea, and on its left by the phrenic nerve and the mediasti- nal portion of the left pleura, which gives a loose covering to a small portion of its surface, against which the internal side of the apex of the left lung is applied. The right primitive carotid and the cervical portion of the left are of equal length, and have similar relations : at first, in the lower part of the neck these vessels of opposite sides are only separated by the breadth of the trachea : as they ascend, however, they diverge from each other, and are separated by the larynx and thyroid body : in their ascent they seem to pass backwards, owing to the prominence of the larynx forwards, but in reality they cannot re- cede, as they are closely applied to the front of the spinal column ; they are not contorted in their course, nor do they furnish any branch until they arrive as high as the superior margin of the larynx, where each bifurcates by dividing into the external and the internal carotids. Relations of the trunk of the Primitive Carotid. — Anteriorly the primitive carotid is covered by the three following layers of mus- cles from the sterno-clavicular articulation to the level of the cricoid cartilage; 1st, the pla- tysma myoides, beneath which lies the superfi- cial layer of the cervical fascia; 2d, the sternal portion of the sterno-cleido-mastoid ; and 3d, by the sterno-hyoid, sterno-thyroid, and the omo-hyoid, which latter muscle crosses the sheath of the artery, having its internal edge connected with the outer edge of the sterno- thyroid by a dense fascia, a part of the deep layer of the cervical fascia, which is firmly con- nected to the posterior margin of the clavicle inferiorly : between the lower part of the sterno- mastoid and the front of the artery there is an interval of about an inch on the left side, and something less on the right, in consequence of the origin of the right carotid being so much more anterior on that side ; this interval is filled by cellular and adipose tissue, some large veins, one or more of the sub-clavicular branches of the cervical plexus, and occasionally a few lymphatic glands ; at the level of the cricoid cartilage the sterno-mastoid passes backward, and the omo-hyoid coming from beneath, it passes forwards to its insertion into the os hyoides. Above the crossing of these two muscles the carotid has no muscular covering, except the platysma, from which it is separated by cellular membrane, several veins from the thyroid body and larynx, and some lymphatic glands ; the nervus descendens noni also lies in front of the primitive carotid at its upper por- tion, being found sometimes within, sometimes outside, and occasionally embedded in the sub- stance of the wall of its sheath ; the thyroid body also generally overlaps the carotid by its outer edge. Posteriorly the carotid is bounded by the longus colli and rectus capitis anticus major, which separate it from the anterior surface of the spinal column; the cervical cord of the sympathetic nerve and its superior and middle cardiac branches are closely connected to the posterior part of its sheath; the vertebral artery and vein are behind it at its lower part ; and higher up it crosses the inferior thyroid artery at a point corresponding to that at which it is covered in front by the omo-hyoideus ; some- times the inferior thyroid crosses over the ca- rotid : the arteria cervical is ascendens often lies behind the carotid towards the upper part of the neck ; moreover, the recurrent nerve on the right side, in its course from behind the sub- clavian artery to the side of the trachea, passes behind the origin of the right carotid. From the relations of the primitive carotid posteriorly, it is evident that it can be most effectually compressed against the front of the spinal co- lumn, but to continue such pressure for any length of time would obviously be followed by injurious effects, from the lesion to which the nerves behind the sheath of the vessel would be thus subjected. 2 i 2 484 CAROTID ARTERY. Externally the carotid artery is bounded by the internal jugular vein and the pneumo-gas- trie nerve, both of which are contained within its sheath ; the vein when distended advances in front of it and partly conceals it ; the nerve lies in the posterior part of the sheath, behind and between the artery and vein, more closely attached to the latter vessel; on the left side the internal jugular vein lies closer to the ca- rotid, in front of which it passes at the lower part of the neck in its course to the vena inno- ininata; on the right side the jugular vein is separated from the carotid inferiorly by a small intervening space, principally occupied by cel- lular tissue, in consequence of the vein of this side descending to join the commencement of the superior cava in a perpendicular course further from the mesial line than the point at which the carotid is given off from the arteria innominata. Internally the carotid is bounded by the trachea at its lower part ; higher up by the thyroid body and the inferior constrictor of the pharynx, by which it is separated from the cricoid and thyroid cartilages ; the recurrent nerve also lies on its inner side, but separated from it by a quantity of loose cellular tissue; in addition to the foregoing relations, the left carotid lies in contact with the oesophagus. The varieties to which the origins of the carotid arteries are subject are the following : 1. the right carotid sometimes arises separately from the aorta ; this variety occurs when there are four large trunks arising from the arch of the aorta, of which the right carotid is the first, and the right subclavian the last in order ; 2. sometimes the arteria innominata gives origin to the left carotid, in addition to the right ca- rotid and right subclavian, in which case the left carotid has to cross in front of the lower part of the trachea to enter upon its cervical course ; 3. the right and left carotids some- times spring from a common trunk, which arises from the arch of the aorta between the right and left subclavian arteries ; in this variety as well as in the preceding, the situation of the carotids in front of the trachea exposes them to the danger of being wounded in the operation of tracheotomy, in performing wmch the sur- geon should always be prepared to meet with the existence of such irregularities of distribu- tion: 4. the left carotid sometimes arises from a left arteria innominata, which also gives off the left subclavian. (See Aorta.) The bifurcation of the primitive carotid most frequently occurs opposite the superior margin of the thyroid cartilage, in front of the third cervical vertebra ; it may, however, take place above or below that point. It sometimes bifur- cates opposite the cornu of the os hyoides, or, which rarely happens, behind the angle of the lower jaw ; in cases where the bifurcation is higher than usual, the primitive carotid often furnishes some of the branches ordinarily arising from the external carotid. The high bifurcation is an approximation to that condi- tion of the carotid in which no bifurcation takes place, but where the primitive carotid, after having given all the branches which the external carotid usually supplies, enters the cranium and becomes the internal carotid. 2. The primitive carotid sometimes bifurcates lower down in the neck than usual. I have seen such a bifurcation occurring on both sides in an old female subject, as low as the inferior border of the thyroid body. The bifurcation of the carotid has the same relation to the larynx at all periods of life : it is more distant from the angle of the jaw in the infant than in the adult; the depth of the lower jaw in the former being much less, owing to the non-development of the roots of the teeth and alveolar processes : in old persons who have lost their teeth, and whose alveolar processes have been absorbed, the jaw being in the edentulous condition, the angle of the jaw is carried forward and thus removed farther from the bifurcation of the carotid. By de- pressing the head the angle of the jaw is brought nearer to the bifurcation ; while the distance between these parts may be consi- derably increased by throwing the head back- wards. The bifurcation of the primitive carotid gives origin to the external and internal carotids; the former of these supplies the larynx, thyroid body, pharynx, throat, face, and external parts of the head ; the latter is distributed to the brain and the internal parts of the organs of hearing and vision. These two vessels lie close together at their origins. The internal is at first more superficial and more external in situation than the external, but becomes the more deeply situated of the two as they ascend |! They are nearly of equal size in the adult when the bifurcation occurs at the usual place; while in the infant the internal is larger than the external. The external carotid, ( arteria carotis externa, superficial is vel anterior, Scemm.Ja- ciale of Chaussier,) extends from the bifurca- tion of the primitive carotid to the neck of the condyle of the lower jaw, where it terminates by dividing into the superficial temporal and internal maxillary arteries. In this course it describes a curve, the concavity of which is outwards and a little backwards, as it ascends ,j between the ear and the ramus of the lower jaw. At first it is superficial, merely covered by the integuments, platysma and cervical i fascia; it then ascends under the ninth or hypoglossal nerve and the posterior belly of the digastric and stylo-hyoid muscles, and buries itself in the substance of the parotid gland. In- ternally it rests at first on the commencement of the internal carotid, then over the middle con- strictor of the pharynx, the stylo-pharyngeus and stylo-glossus muscles, the glosso-phaiyn- geal nerve and the styloid process of the tem- poral bone; the superior and inferior pharyn- geal nerves coming from the par vagum also pass under it in their course to the pharyngeal plexus. The part of the parotid gland which the external carotid first enters is the internal surface of its lower extremity, consequently the whole thickness of the gland covers it at CAROTID ARTERY. 485 that part; but in passing through the gland the artery becomes more superficial as it ascends and is covered only by a very thin layer of the glandular substance at the place where it ter- minates. The branches of the portio dura forming the pes anserinus cross the course of the carotid in the substance of the gland, being superficial to it and separated from it by the posterior facial vein and part of the glandular substance. Branches of the external carotid* — The ex- ternal carotid gives off eight principal branches ; three anteriorly, the superior thyroid, the lin- gual, and the labial or facial; two posteriorly, the occipital and posterior aural ; one internally, the ascending pharyngeal ; and two superiorly, the superficial temporal and internal maxillary, besides several smaller branches, the number and origins of which are subject to great irregularity, and which are distributed to the sterno-mastoid muscle, the superior cervical ganglion of the sympathetic nerve, the digastric, stylo-hyoid, stylo-pharyngeus, and stylo-glos- sus muscles, &c., to the parotid gland, the external ear, and to the integuments. Anterior branches. — 1st. The superior thyroid artery ( A . thyroidea superior) gene- rally arises opposite the cornu of the os hyoides a few lines above the bifurcation of the primi- tive carotid ; in some rare cases it comes from the trunk of the primitive carotid : it has been aiso seen to arise from the lingual. It takes a tortuous course downwards and forwards, and passing under the omo-hyoid, sterno-thyroid, and sterno-hyoid muscles, arrives at the supe- rior and external part of the thyroid body to which it is chiefly distributed : at first it is Superficial, being covered by the integuments, platysma, cervical fascia, some lymphatic glands and small veins coming from the superior part of the larynx to join the internal jugular ; it is also crossed by the branch of the nervus de- scendens noni which is sent to the superior belly of the omo-hyoid muscle, and the supe- rior laryngeal and several filaments from the sympathetic nerves to the larynx, &c. lie be- neath it. In its course the superior thyroid artery, besides furnishing a variable number of smaller branches, to the muscles and other parts in its vicinity, generally gives off the three following : a. The hyoidean branch, which runs along the inferior border of the os hyoides between the hyo-thyroid muscle and the mem- brane of the same name, to both which it gives branches ; it inosculates with the corresponding artery of the opposite side in the mesial line, and with the lingual by a twig which passes up on the front of the body of the os hyoides. lhe hyoidean branch is often absent, b. The superficial branch passes downwards and out- wards over the sheath of the carotid artery to the sterno-mastoid muscle, to which and the neighbouring lymphatic glands and integu- ments it is finally distributed, anastomosing In the arrangement of the branches of the III tC£ i c^rot'^. artery the writer follows that of leckel. See his Anatomic Descriptive, &c. trans- ited into French by Breschet and Jourdan. in the substance of the sterno-mastoid with branches coming from the occipital above and others from the thyroid axis inferiorlv. c. The laryngeal often arising from the external carotid, an occurrence which, according to Meckel, takes place in one case in eight, passes into the larynx through the hyo-thyroid membrane, sometimes through a hole in the thyroid carti- lage ; it usually accompanies the superior laryngeal nerve : its branches are lost in the internal muscles and mucous membrane of the larynx and the epiglottis. Before it enters the larynx it gives branches, some of which ascend to anastomose with the hyoidean, others de- scend to the thyroid body ; one of these latter is remarkable for running across the front of the crico-thyroid membrane to anastomose with a similar branch from the opposite side ; it generally lies in the situation in which laryn- gotomy is performed . Having given off the above-mentioned branches, aud arrived at the superior extremity of the thyroid body, the thyroid artery divides into two branches, one of which descends along its external edge, sending off numerous branches which are lost in its substance, anastomosing freely with the inferior thyroid, the other branch descends coursing along the superior border of that body on which it expends its branches, and arriving at the mesial line below the cricoid cartilage, anastomoses with the corresponding artery from the opposite side : occasionally this branch supplies the small artery which crosses the crico-thyroid membrane. 2. The Lingual Artery (A. lingualis ) arises after the thyroid, and sometimes, but rarely, from a common trunk with the thyroid, comes at other times and not unfrequently from the facial. This artery forms in its course a con- siderable curve, the convexity of which is upwards ; it passes forwards and inwards above the cornu of the os hyoides, between the mid- dle constrictor of the pharynx and hyo-glossus, and mounts up towards the base of the tongue, between the hyo-glossus and sublingual gland which lie to its outer side, and the genio-glossus which is internal to it ; then taking a horizontal direction, it passes forwards under the name of ranine artery, in company with the hypo-glossal nerve, coursing between the genio-glossus and lingualis muscles, as far as the point of the tongue where it anastomoses with its fellow of the opposite side. After its origin and before it passes under the posterior edge of the hyo- glossus muscle, this artery runs superficially be- neath the common coverings of the neck, lying- on the middle constrictor of the pharynx above the cornu of the os hyoides; superior to it lie the tendon of the digastric muscle, the stylo- hyoid muscle and the hypo-glossal nerve, which after sending a filament across it to the hyo-thyroid muscle, continues its course for- wards on the cutaneous surface of the hyo- glossus muscle which separates the lingual nerve and artery in this part of their course. Branches. — Having given a few inconsi- derable twigs to the middle constrictor, stylo- glossus, digastric, and stylo-hyoid muscles, and to the sublingual gland, &c.; the lingual 48<3 CAROTID ARTERY. artery sends off the following branches, a, The hyoidean branch, arising at the external edge of the hyoglossus muscle, passes be- tween the genio-hyoideus and genio-glossus, and coming forward in the mesial line, de- scends over the front of the body of the os hyoides, and anastomoses with the hyoidean branch of the thyroid artery, giving branches to the muscles, in the vicinity of which it passes and to the integuments, b, The dorsalis lingua;, arising under cover of the hyoglossus, passes upwards and outwards, crossing the stylo-glossus and distributes its branches over the posterior part of the dorsum of the tongue, the tonsils, velum palati, and epiglottis, where it anastomoses with the laryngeal branch of the superior thyroid. At the internal edge of the hyoglossus the lingual artery divides into the sublingual and ranine, c, The sub- lingual branch passes forwards between the mylo-hyoid and genio-glossus muscles and above the sublingual gland, to which it is principally distributed, as well as to the muscles of the tongue and the mucous mem- brane of the mouth. Occasionally we find the place of the sublingual artery supplied by the submental, a branch of the facial, d, The ranine artery, which is the continuation of the trunk of the lingual, passes forward between the genio-glossus and lingualis, and running along the under surface of the tongue by the side of the attachment of the fraenum, sends nu- merous branches into the substance of that organ, and ends by anastomosing with the ranine of the opposite side. It is this artery which is endangered if the scissors be directed too much upwards in dividing the frcenum linguae in children. 3. The labial artery, called also facial or external maxillary, (a. facialis v. maxillaris externa,) varies very much in its origin, size, and the extent of its distribution. It is usually the largest of the three anterior branches of the external carotid, and supplies the whole of the anterior part of the face ; sometimes, however, it only extends as far as the angle of the mouth, beyond which its place is supplied by the temporal artery. There is, perhaps, no other artery which presents so many varieties, even on opposite sides of the body in the same subject. From its origin it proceeds, in a tortuous course, inwards and forwards, towards the internal part of the angle of the lower jaw, covered by the hypo- glossal nerve, the digastric and stylo-hyoid muscles : it then passes between the lower jaw and submaxillary gland, lodged in a groove in that gland ; after which it turns over the inferior border of the lower jaw, and arrives on the external surface of that bone a little in front of the anterior edge of the masseter muscle : from this it ascends tor- tuously towards the commissure of the lips, covered by the skin and the platysma ; thence passing upwards and inwards under the zygo- matic muscles, and over the buccinator and levator anguli oris, it continues to ascend in the groove between the cheek and the upper lip and by the side of the nose, to the internal canthus of the eye, where, very much dimi- nished in size, it terminates by anastomosing with the nasal branch of the ophthalmic artery. Brunches. — The branches of the labial artery are very numerous, a, The inferior palatine, which arises from the labial close to its origin; this vessel sometimes comes from the trunk of the carotid itself, it passes upwards between the stylo -pharyngeus and stylo-glossus, to which it gives branches : it then attaches itself to the superior and lateral part of the pharynx, supplying this region, the tongue, and the tonsil. Having reached the velum palati, it divides into many branches, which are dis- tributed to the muscles, mucous membrane, and glands of that organ, and to the Eustachian tube. These branches anastomose with the superior palatine branch of the internal max- illary. The tonsillitic artery, (arteria tonsil- laris of Soemmerring,) enumerated as a dis- tinct branch of the labial by Professor Harrison, is, more properly speaking, a branch of the inferior palatine. In passing through the sub-maxillary gland, the labial artery gives off several branches to this gland, the internal pterygoid muscle, and the mucous membrane of the mouth : as it is about to turn over the side of the lower jaw, there arises from it a branch of more considerable size, namely, b, the submental branch. This artery passes forwards beneath the base of the lower jaw, covered by the platysma and anterior belly of the digastric, between which and the mylo-hyoideus it takes its course towards the symphysis of the chin, distributing branches to supply the muscles and integuments in this region and to anasto- mose with the sublingual ; some of its branches mount over the chin and communicate with the arteries of the lower lip : the submental 1 artery sometimes furnishes the sublingual, and at other times it is given off by this latter. From the inferior border of the lower jaw to the commissure of the lips, the labial gives several branches, some of which are anterior and some posterior : the posterior are com- paratively insignificant branches distributed to the masseter, platysma, buccinator, parotid gland and duct, the cellular tissue and in- teguments of the cheek, which communicate with branches of the transverse facial. Besides j, smaller branches given off anteriorly to trie ■ lips, there are two considerable branches and one of lesser size, which require a more par- ticular description ; viz. c, the inferior labial coronary arises about midway between the commissure of the lips and the base of the lower jaw, it passes under the triangularis oris muscle, to which, as well as to the quadratus, levator labii inferioris, and mucous membrane of the mouth, it gives numerous branches and anastomoses with its congener, and the mental branch of the inferior dental. This artery is sometimes smaller on one side than on the ■' other; it is sometimes absent on one side, when its place is supplied by the artery of the opposite side ; sometimes it arises from the superior labial coronary ; sometimes it is double. After having given off this branch, CAROTID ARTERY. 487 the fecial artery continues its course upwards and inwards, and, opposite the commissure of the lips, gives off d, the superior labial coronary artery. This vessel passes inwards among the fibres of the orbicularis oris, runs above the free border of the upper lip nearer to its mucous membrane than to its cutaneous surface, gives branches to the various parts composing the upper lip, and meets the co- ronary of the opposite side, with which it very freely anastomoses. The superior labial coronary always sends off from the place where it anastomoses with that of the opposite side a branch, which ascends towards the septum of the nose, and which is called the artery of the septum of the nose, ( arteria septi nasi.) The place of this artery is some- times occupied by two or more branches ; it divides, near the septum of the nose, into at least two branches, which pass, one on either side, along the inferior border of the septum to the extremity of the nose, where it anasto- moses with branches of the lateral nasal : sometimes the superior coronary gives off a branch (ramus pinna lis), as it passes the ala of the nose, to which, and the external part of the nostril, it is distributed. After the origin of the superior labial the facial artery is reduced to a very small size, and its continuation is by some called the external nasal, arteria nasalis externa com- munis. It continues to pass obliquely up- wards, forwards, and inwards under the levator labii superioris, to which it gives branches : after anastomosing with the infra-orbital artery and giving off branches, which pass forward on the lateral surface of the nose, namely, e, laterales nasi, and /j dorsales nasi, which freely anastomose with each other, with the artery of the septum, and those of the opposite side on the dorsum of the nose, it emerges from between the two heads of the levator labii superioris, and becoming subcutaneous, ter- minates at the inner canthus of the eye by anastomosing with the termination of the nasal branch of the ophthalmic, at which place it has received the name of the angular artery. Irregidarities of the labial or facial artery. It sometimes happens that the facial artery is smaller than usual, and terminates at the angle of the mouth or even below the situation of tne usual origin of the inferior coronary; in this case the transverse facial branch of the temporal generally fnrnishes the branches which the coronary has failed to produce ; on the other hand the labial artery is sometimes of a larger size than usual, as happens when it furnishes supernumerary branches, such as the ranine or sublingual. The facial artery is the principal source of communication between the superficial and deep branches of the external carotid by its anastomoses with the infra-orbital, nasal and dental arteries ; and of the external carotid with the internal, by its anastomoses with the ophthalmic. Internal branch of the external carotid, Inferior pharyngeal artery, ( a. pharyngea in- ferior v. ascendens,) arises commonly from the internal side of the external carotid close to its origin, sometimes from the bifurcation of the primitive carotid, more rarely from the internal carotid, and occasionally from the occipital ; sometimes its place is supplied by the inferior palatine or by branches from the trunk of the facial; sometimes it is double, in which case only one of its branches arises from the external carotid, the other being furnished by one of the smaller arteries already mentioned, or by the internal carotid ; this artery is always the smallest branch of the external carotid; it passes perpendicularly upwards internal to the external carotid between the trunk of that vessel and the pharynx, lying on the rectus capitis anticus major muscle, and closely re- lated to the superior cervical ganglion of the sympathetic. Having furnished branches from its inner side, both ascending and descending, to the constrictors of the pharynx and other muscles, which also supply the mucous mem- brane, and from its external side to the deep muscles of the neck, it terminates at the basis cranii, near the petrous portion of the temporal bone, by giving off its terminal branches, of which one, the proper pharyngeal, is princi- pally distributed to the parietes of the pharynx, and communicates by anastomosis with the inferior palatine from the superior thyroid ; a second, the posterior meningeal artery, enters the cranium by the foramen lacerum posterius, or by an opening in the vicinity of the condyle of the occipital bone, and is distributed to the dura mater lining the inferior occipital fossa : and a third ascends to the basis cranii, and per- forates the cartilaginous lamella, which fills up the foramen lacerum posterius, to enter the cranium and be distributed to the dura mater. Posterior branches of the external carotid. — 1st. The occipital artery (a. occi- pitalis) arises from the posterior side of the external carotid, opposite the lingual or the facial ; it sometimes but rarely comes from the internal carotid ; it passes at first a little ob- liquely backwards along the lower border of the posterior belly of the digastric muscle which overlaps it ; it crosses over the ninth pair of nerves which winds beneath it just at its origin, the internal carotid artery, internal jugular vein, and spinal accessory nerve ; and passing backwards between the transverse pro- cess of the atlas and the mastoid process of the temporal bone it is lodged in a groove in this latter bone, which is internal to the inser- tion of the posterior belly of the digastric; it crosses the outer border of the rectus capitis lateralis muscle, and continuing its course beneath the sterno-cleido-mastoid, trachelo- mastoid, splenius capitis and trapezius, and over the obliquus superior and complexus, it ascends tortuously over the superior part of the occipital bone, where it becomes cutaneous and anastomoses with branches from the tem- poral, posterior auris, and opposite occipital. The first branches of the occipital are small, and are distributed to the sterno-mastoid, di- gastric, and stylo-hyoid muscles, and to the lymphatic glands in the neighbourhood ; the branches which enter the sterno-mastoid are sometimes considerable, and anastomose freely 488 CAROTID ARTERY. >n the substance of that muscle with the branches which it receives from the superior thyroid. The sterno-mastoid muscle very frequently receives a large branch at this part arising dis- tinctly from the external carotid. This Professor Harrison considers should be classed among the regular branches of the external carotid, and he has described it under the name of a. sterno-mastoidea.* While the occipital artery is covered by the sterno-mastoid, trachelo-mastoid, and splenius, it gives branches to these muscles, some of which descending anastomose with branches of the cervicalis profunda and the vertebral ; those which ascend are distributed to the supe- rior attachments of these muscles ; amongst them there is one branch occasionally found which penetrates into the cranium by the mas- toid hole, and is distributed to the dura mater, under the name of posterior meningeal of the occipital. When the occipital artery comes out from beneath the splenius muscle it divides into those branches which are distributed over the posterior surface of the occipital bone, sup- plying the occipito-frontalis and the scalp, to- gether with the pericranium, and anastomosing, as already mentioned, with the opposite occi- pital, posterior auris, and temporal. One of these branches frequently enters the cranium by the parietal hole, and spreads over the dura mater. The occipital artery sometimes gives small twigs, which enter the cranium by the foramen lacerum posterius and the anterior condyloid foramen. 2d. A. posterior auris, v. auricularis pos- terior, arises immediately after the occipital, in the substance of the parotid gland; it is generally a much smaller vessel than the latter, from which it is mostly separated by the stylo- hyoid muscle : sometimes it comes from the occipital. It passes upwards and backwards under the parotid gland between the mastoid process of the temporal bone and the cartila- ginous tube of the ear ; it first sends branches to the parotid gland, the stylo-hyoid muscle, the posterior belly of the digastric and the external ear ; it then gives off the stylo- mastoid artery, which, among other branches to the external ear, gives off one to be dis- tributed to the membrana tympani. Then the stylo-mastoid traversing the aqueduct of Fallopius finds its way into the cavity of the tympanum, on the lining membrane of which, and its prolongation into the mastoid cells, its branches are expended, where it anas- tomoses with a branch of the middle menin- geal, which enters the hiatus Fallopii, and arrives in the tympanum along with the chorda tympani nerve. Sometimes the stylo-mastoid artery comes from the middle meningeal. When the posterior auris gets to the front of the mastoid process it divides into two branches, one of which is anterior and the other pos- terior; the former spreads its branches over all Sm-gical Anatomy of the Arteries of the Human Body, vol. i. parts of the internal surface of the ear; the latter ascends in front of the mastoid process, passes under the posterior auris muscle, and divides into many branches, which are distri- buted to the occipito-frontalis and temporal muscles, integuments, &c. These branches anastomose with the temporal and occipital arteries.* While traversing the parotid gland the ex- ternal carotid gives several small branches to the masseter and pterygoid muscles, to die substance of the gland itself, and a few to the front of the external ear ; occasionally it gives origin to the transversalis faciei in this course. Behind the neck of the condyle of the lower jaw the external carotid divides into its two superior and terminal branches, the temporal and internal maxillary. 1. Temporal artery, ( a. temporalis.) The temporal artery ascends at first a little obliquely outwards between the ramus of the jaw and the tube of the ear, covered by the parotid gland ; crossing the zygoma at its posterior part, and passing under the anterior auris muscle, it mounts up over the temporal apo- neurosis, and becomes subcutaneous for the remainder of its course. Immediately after its origin the temporal gives off anteriorly a very considerable branch, which is called the transversalis faciei : this artery sometimes arises from the trunk of the external carotid ; it passes forward over the neck of the condyle of the lower jaw, and, crossing the masseter muscle, runs superior to the duct of Steno, which it accompanies across the face; it anastomoses with the labial, buccal, and infra-orbital arteries. The branches which the transversalis faciei usually gives oil' are distributed to the parotid gland and its duct, the masseter, zygomatic, and orbicularis pal- pebrarum muscles, and the integuments. I have seen an instance in which this artery arose i from the external carotid opposite the angle of the jaw, beneath which it passed forwards, and joined the labial at the anterior edge of the masseter muscle. When the temporal artery has arrived at the zygoma, it gives a branch called middle tem- poral, which pierces the temporal aponeurosis, and ascends in the substance of the temporal muscle, to which it is distributed, and winch anastomoses with the deep temporal arteries. Having given off a few small branches to the parotid gland, integuments, and external ear, the temporal artery ascends on the temporal aponeurosis, and divides into two branches, 1 the anterior and posterior. The anterior branch ascends in a serpentine course towards the forehead, and sends off’ many branches, which are distributed to the occipito-frontalis, the orbicularis palpebrarum, and integuments, and which anastomose with the superciliary and * [The surgical anatomist cannot fail to notice the relation of the posterior auris artery to the portio dura nerve, as it lies superficial to and nearer the mastoid process than that nerve, so as to be consi- derably, although not necessarily, endangered when the operator proceeds to divide the nerve at its emergence from the stylo-mastoid foramen. — Ed.-J CAROTID ARTERY. 489 frontal brandies of the ophthalmic and with the opposite temporal. The posterior branch passes upwards and backwards in a tortuous course, and supplies the integuments, tem- poral aponeurosis, pericranium, &c. These branches anastomose with the anterior branch, with die opposite temporal, the occipital, and posterior auris. 2. The internal maxillary artery, ( a. maxil- laris interna,) is larger than the preceding; im- mediately after its origin it passes downwards and inwards under the neck of the condyle of the lower jaw; it then mounts forwards and in- wards between the temporal and external ptery- goid muscles, and usually passing between the two origins of the latter, it enters the pterygo- maxillary fossa, where it ascends as high as the level of the inferior wall of the orbit, oppo- site which it takes a horizontal direction. At this place it divides into numerous branches, which are distributed on one side inwards to- wards the nose, and on the other side to the external part of the face. The branches of the internal maxillary are, a. the middle meningeal, b. the inferior dental, c. the posterior deep temporal, d. the masseteric, e. pterygoid branches, f the buccal, g. the an- terior deep temporal, h. the alveolar, i. the infra-orbital, l. the superior palatine, m. the vidian, n. the ptery go-palatine, and o. the spheno-palatine : in addition to these the in- ternal maxillary artery gives several branches to the cellular tissue and other parts surrounding it. a. The middle meningeal artery ( a. meningea media, spinosa ) arises from the superior part of the artery and passes directly upwards on the inside of the external pterygoid muscle, to which, to the superior constrictor of the pharynx and muscles of the velum palati it sends branches, and passing between the tensor palati muscle and internal lateral ligament of the temporo-maxillary articulation, enters the cranium through the foramen spinale of the sphenoid bone, and immediately gives off some small branches, which pass through the hiatus Fallopii to the cavity of the tympanum, where they anastomose with the stylo-mastoid artery; other branches pass forwards towards the orbit into which some of them occasionally enter by the foramen lacerum. The meningeal artery then divides into two branches, an anterior and a posterior; the anterior, which is the larger, might be considered as the continued trunk; it mounts forwards towards the anterior inferior angle of the parietal bone, where it is lodged in a groove, and sometimes in a canal in the sub- stance of that bone. This branch at first gives twigs to the foramen lacerum, which anastomose with the lachrymal ; after which it mounts on the parietal bone, principally following the course of the coronal suture, sending its bran- ches upwards and backwards between the dura mater and the inner surface of the parietal bone. The posterior branch passes backwards m a curved direction on the inner surface of the squamous portion of the temporal bone, and , advancing towards the inferior border of the parietal bone, is expended on the posterior and lateral part of the dura mater. The branches of the middle meningeal artery spread over the external surface of the dura mater, and occupy the grooves which are disposed in an arbores- cent form on the internal surface of the parietal bone. The middle meningeal artery anasto- moses with that of the opposite side and with the other arteries of the dura mater. b. The inferior maxillary or inferior dental artery sometimes coming from the middle me- ningeal, descends to the posterior dental hole by which it enters the dental canal, passing be- tween the inner surface of the ramus of the jaw and the outer surfaces of the internal pterygoid muscle and the internal lateral ligament of the temporo-maxillary articulation, to which it gives small twigs : before it enters the dental hole, it gives off a small branch, which passing down- wards and forwards in a groove on the inside of the lower jaw, is distributed to the mylo- hyoid muscle and mucous membrane of the mouth. In the dental canal this artery passes forwards beneath the alveoli of the molar teeth, sending upwards in its course several branches which penetrate into the alveoli, and enter the cavities of the teeth by the holes in their roots ; having arrived opposite the mental hole, it sends a branch which passes onwards beneath the alveoli of the canine and incisor teeth, to which it is distributed ; while the continuation of the artery coming out through the mental hole is distributed to the muscles of the lower lip, where it anastomoses with the labial. c. The posterior deep temporal artery arises after the dental ; it passes upwards between the temporal and external pterygoid muscles, and sinking into the substance of the former, divides into a great number of branches, which spread over the squamous portion of the temporal bone, and are distributed to the temporal mus- cle and pericranium. This artery anastomoses with the anterior deep temporal, the middle, and the superficial temporal. d. The masseteric is a small branch often arising from the posterior deep temporal ; it passes outwards between the posterior border of the temporal muscle and the condyle of the lower jaw, and enters the masseter muscle, where it anastomoses with the transversalis faciei. e. The pterygoid arteries are irregular as to number, size, and origin; they either come from the trunk of the internal maxillary or the posterior deep temporal, and are distributed to the pterygoid muscles. f. The buccal artery does not always arise from the internal maxillary itself; it sometimes comes from the anterior deep temporal, the alveolar, or infra-orbital. It passes downwards and forwards between the internal pterygoid muscle and ramus of the lower jaw, and ad- vances over the surface of the buccinator mus- cle, to which it gives branches, as well as to the zygomatic and other muscles of the lip : it anastomoses with the labial, infra-orbital, and transversalis faciei. g. The anterior deep temporal arises from the internal maxillary, near the outer wall of the temporal fossa beneath the temporal mus- cle, to which it is distributed ; some of its 490 CAROTID ARTERY. branches enter the orbit through the malar bone, and spread over the lachrymal gland, communicating with the lachrymal artery. h. The alveolar artery descends forwards over the superior maxillary bone, very tortuous in its course ; it gives two or three twigs, which pass into the inferior and posterior dental fora- mina to be distributed to the lining membrane of the antrum maxillare and the molar teeth ; the other branches of the alveolar artery are distributed to the gums, to the buccinator, to the periosteum of the superior maxillary bone, and to the cellular substance of the cheek : they communicate with the infra-orbital, labial and buccal. i. The infra-orbital artery arises from the internal maxillary at the superior part of the pterygo-maxillary space ; it enters the infra- orbital canal, through which it passes forwards and inwards, sending branches into the orbit and maxillary sinus; passing out by the infra- orbital hole it comes forward on the face behind the levator labii superioris, and termi- nates in a number of branches, which pass into the muscles of the upper lip, and anastomose with the labial, alveolar, buccal, and nasal branch of the ophthalmic. The remaining branches of the internal max- illary are given off in the pterygo-maxillary space ; of these the first is l. The superior palatine descends behind the tuberosity of the superior maxillary bone in the palato-maxillary canal : it usually gives off two branches, which descend through holes in the pterygoid process of the palate bone, and are distributed to the soft palate ; while the trunk of the superior palatine passing out of the posterior palatine hole, directs itself for- wards and inwards in a groove on the surface of the hard palate, and divides into numerous branches, which are distributed to the mucous membrane and glands of the palate, to the gums, and to the superior maxillary bone ; one of these branches sometimes passes up through the foramen incisivum to the nasal fossae. m. The vidian artery is an insignificant branch which traverses the vidian canal from before backwards, and coming out of its poste- rior opening is distributed to the Eustachian tube and the roof of the pharynx : it anasto- moses with the inferior pharyngeal. n. The pterygo-palatine or superior pha- ryngeal is a small insignificant branch, which passes through the pterygo-palatine hole, and is distributed like the former to the roof of the pharynx and Eustachian tube, sending some branches to the sphenoid bone and the mem- brane lining its sinuses. o. The spheno-palatine artery may be con- sidered the termination of the internal maxil- lary ; it enters by the spheno-palatine hole into the posterior part of the nasal fossae, and divides into two principal branches ; an external and an internal; the internal branch passing across the roof of the nasal fossae arrives at the septum, on which its branches are principally distri- buted; it also supplies branches to the roof of the pharynx and the posterior ethmoidal cells; the external branch descends on the lateral wall of the nose, sending its branches over the spongy bones and into the antrum maxillare : these branches anastomose with the ethmoidal branches of the ophthalmic artery. The internal carotid artery, ( carotisin - terna seu cerebralis, Samrn. cerebrate ant'erieure, Chaussier.) This artery is larger than the external carotid in the foetus, but in the adult is only equal in size to that vessel, aud sometimes even smaller. At its origin it takes a curve outwards so as to get external to the commencement of the ex- ternal carotid ; it then mounts upwards and forwards in front of the three superior cervical vertebrae, and making a few contortions along the side of the pharynx, enters the foramen carotieum of the temporal bone, traversing the carotid canal of that bone internal to the ca- vernous sinus, perforates the dura mater internal to the anterior clinoid process of the sphenoid bone, where it divides into two large branches, the anterior and middle cerebral. The internal carotid artery has the following relations from its origin to the place where it enters the foramen carotieum : anteriorly it has the external carotid and its branches in contact with it at its origin, also the hypoglossal or lin- gual nerve, and as it passes under the digastric muscle it also slips beneath the following parts which lie between it and the external carotid, the styloid process, with the muscles attached to it, part of the parotid gland, the glosso- pharyngeal and inferior pharyngeal nerves. Posteriorly it lies on the rectus capitis anti- cus major, having the par vagum and superior laryngeal nerve behind it, and higher up the trunk of the hypo-glossal nerve coming from between it and the internal jugular vein. The internal jugular vein bounds it externally at first, but passes to its posterior side above where it gets to the internal side of the root of the styloid process. Internally the carotid ar- tery lies on the side of the pharynx to which it is more closely applied towards its upper part, lying on the stylo-glossus and the outer surface of the superior constrictor muscles, which with some cellular membrane and a venous plexus separate it from the tonsil, external and poste- rior to which it lies, at the distance of from six to eight lines in the natural state of the parts; but when that gland is enlarged in consequence either of acute inflammation or chronic disease, the distance between it and the artery is dimi- nished so much as to expose the latter to some risk of being wounded in opening abscesses in the tonsil, an occurrence of which the records of experience are not without examples. In this stage of its course the internal carotid seldom gives any branches; occasionally, how- ever, the inferior pharyngeal or the occipital arises from it. Having entered the carotid canal, the artery ascends vertically, then turns forwards and inwards, and passing out of the canal opposite the posterior clinoid process, it takes a second turn upwards, then forwards along the side of the sella turcica, between the layers of the dura mater which include the ca- vernous sinus, between which latter and the bone the artery is situate. At the anterior extremity of the side of the sella turcica it makes CAROTID ARTERY. 491 a’ third turn upwards under the anterior clinoid process, and passing backwards and a little in- wardsit perforates thedura mater between thein- ternal side of this process and the commissure of the optic nerves. The only vessels which it gives from its entrance into the foramen caroticum to the place where it perforates the dura mater are one or two small branches which perforate the petrous portion of the temporal bone, and pass to the cavity of the tympanum, and as it lies beside the cavernous sinus, two or three little twigs to the dura mater, pituitary gland, body of the sphenoid bone, and to the third, fourth, fifth, and sixth pairs of nerves which lie ex- ternal to it and in contact with the outer or inner wall of the cavernous sinus. The ophthalmic artery arises from the an- terior side of the carotid while that vessel is passing into the dura mater, by the side of the anterior clinoid process; it enters the foramen opticum at first external and inferior to the optic nerve, over which it mounts obliquely towards its internal side, passing between it and the superior rectus muscle of the eye ; it then directs its course along the superior and internal part of the orbit between the obliquus superior and rectus internus, towards the inner canthus of the eye where it terminates. Before entering the orbit it gives off a few small twigs to the dura mater and cavernous sinus, and within the orbit it furnishes the following branches: — 1. the lachrymal ; 2. the arteria centralis retinae; 3. the supra-orbital; 4. the ciliary; 5. the muscular; 6. the ethmoidal ; 7. the palpe- bral ; 8. the frontal ; and 9. the nasal. The order in which these arteries arise from the ophthalmic presents many varieties; but they are constant in their distribution. 1. The lachrymal artery is one of the largest branches of theophthalmic: it sometimes comes from the middle meningeal, and enters the orbit by the foramen lacerumorbitaleof the sphe- noid bone. It runs forwards between the ex- ternal wall of the orbit and the rectus externus, giving branches to that muscle, the periosteum, levator palpebrse superioris and sheath of the optic nerve. One of its branches traverses the malar bone, and entering the temporal fossa anastomoses with the anterior deep temporal ; another little branch frequently traversing this bone passes outwards through the same hole with the nervus subcutaneus malee, and anas- tomoses with branches of the transversalis faciei. The continuation of the artery then divides into several branches which are distributed to the lachrymal gland and the external part of the upper eyelid, anastomosing with the palpebral and the temporal arteries. 2. The central artery of the retina ( arteria centralis retina ) penetrates the substance of the optic nerve to enter a canal in its centre, the porus opticus, in which it passes forwards, and is distributed to the retina, the vascular layer of which it forms by its ramifications. 3. The supra-orbital arises after the centralis retime, passes forwards along the superior wall of the orbit above the levator palpebra; supe- rioris and superior rectus, giving branches to hese muscles, the periosteum, and the scle- rotic: on reaching the margin of the orbit, it passes out through the superciliary foramen, along with the frontal branch of the ophthalmic nerve, giving in its passage a branch which enters the substance of the frontal bone ; this arteiy then mounts beneath the corrugator su- percilii and orbicularis palpebrarum muscles, and is expended on these muscles, the occipito- frontalis and the integuments ; it anastomoses with branches of the lachrymal and frontal. 4. The ciliary arteries sometimes amount in number to thirty or forty; they consist of three sets : the posterior or short, the long, and the anterior. The posterior ciliary arteries are very numerous, sometimes amounting in number to thirty or forty : although mostly arising from the ophthalmic, some of them come from the inferior muscular, the supra-orbital, posterior ethmoidal or lachrymal ; they run along the optic nerve very tortuous, and entangled with the ciliary nerves, anastomosing freely with each other. The posterior or short ciliary arteries pierce the sclerotic close to the entrance of the optic nerve ; some of their branches are distributed to that membrane in which they anastomose with branches from the muscular arteries ; while all the others advance nearly parallel, dividing at very acute angles into numerous smaller twigs ; these branches are at first ex- ternal to the choroid ; but in their course for- wards they penetrate to the internal surface of that membrane, and becoming more numerous from having undergone new subdivisions, form a network of anastomoses from which several branches are sent to the ciliary margin of the iris, where they anastomose with the anterior ciliary, but a greater number are given to the ciliary processes in the centre of which they form a very fine network, and finally end in a circle of anastomoses surrounding the margin of the circle in which these processes terminate internally. The long ciliary arteries are two in number, one internal, the other external ; they are larger than the short ciliary arteries among which they arise, but pierce the sclerotic obliquely at a greater distance from the optic nerve ; they pass forwards between the sclerotic and cho- roid, and having arrived at the ciliary ligament, they divide each into two long branches which separate from each other at obtuse angles, and, coursing along the ciliary margin of the iris, form a circle around the greater circumference of that membrane which receives branches of anastomosis from the short ciliary arteries. From the interior of this circle numerous branches arise, each of which divides into two, which diverge at obtuse angles, and, anastomo- sing with each other and with the anterior ciliary, form another arterial circle within the former. Thus there are two arterial circles, one within the other at the greater circumference of the iris. From the concavity of this inner circle the arteries of the iris arise. These arte- ries are very numerous ; they converge in ser- pentine lines towards the papillary margin of the iris, where they anastomose, in the manner of the mesenteric arteries, to form the lesser 492 CAROTID ARTERY. arterial circle of the iris. All these arteries, however, do not contribute to form this lesser arterial circle ; a great number pass beyond it, and, along with the branches which arise from its concavity, advance towards the pupil. There are thus three arterial circles in the iris, two close together at its greater circumference or ciliary margin ; the third much smaller, sur- rounding its pupillary margin, and commu- nicating with the preceding by a radiation of branches situated on the anterior surface of the iris. The anterior ciliary arteries are two or three in number; sometimes coming from the palpe- bral or from the branches which go to the recti muscles ; they pass forward to the anterior part of the globe of the eye, where they each di- vide into many branches, the smaller of which are distributed to the conjunctiva and the scle- rotica, the others pierce the sclerotica, near the circumference of the cornea, pass through the ciliary ligament, and join the arterial circles of the greater circumference of the iris ; some passing beyond that circle go to the iris, and others are distributed to the anterior part of the choroid. 5. The muscular arteries generally consist of two, an inferior and a superior. The inferior muscular artery is a branch which is generally present ; it sometimes gives off the centralis retinas and one or more ciliary; it passes in- wards to supply the inferior and internal recti muscles, and sends some branches into the nasal fossa;. The superior muscular is less regular than the former; it passes forwards im mediately under the superior wall of the orbit, and di- vides into many branches, which are distributed to the superior and internal recti, the superior oblique, the levator palpebrae superioris, the periosteum, and the sclerotic. 6. The posterior ethmoidal artery sometimes arises from the lachrymal or supra-orbital ; it passes inwards between the superior oblique and rectus interims, and enters the foramen orbitarium internum posterius, giving branches to the anterior ethmoidal cells and their lining membrane ; it then enters the cranium, where it is distributed to the dura mater, over the cribriform plate, through the holes of which it sends some branches to the pituitary mem- brane, and anastomoses with the anterior ethmoidal. The anterior ethmoidal artery is given off by the ophthalmic towards the anterior part of the orbit ; it passes through the foramen orbi- tarium internum anterius with the nasal branch of the ophthalmic nerve, and after giving branches to the interior of the frontal sinus and anterior ethmoidal cells, it enters the cranium and divides into many branches, some of which go to the dura mater, and others descend into the nasal fossae by the holes in the cribriform plate of the ethmoid bone, and are distributed to the pituitary membrane. 7. The palpebral arteries sometimes arise by a common trunk and sometimes separately. The superior palpebral arisag a little further forward than the inferior; they are distributed to the conjunctiva and to the eyelids, in which they spread out their branches between the skin and the orbicularis muscle. They princi- pally divide each into two branches, one of which runs along the tarsal margin, supplying the tarsal cartilage, Meibomian glands, and con- junctiva, and the other nearer to the base of the eyelids in an oblique course from within outwards. The superior palpebral anastomoses with the lachrymal, superciliary, frontal, and an- terior branch of the temporal. The inferior palpebral anastomoses with the infra-orbital, the lachrymal, and nasal. After the ophthalmic artery has given off the palpebral, it divides into two branches, one of which is the frontal and the other the nasal. 8. The J'rontal artery is usually the smaller of the two ; it passes out of the orbit at the superior and internal part of the base of that, cavity, and divides almost immediately into two or three branches, which ascend on the forehead, over which they ramify, and are dis- tributed to the orbicularis, corrugator super- Jj cilii, pyramidalis nasi, and occipito-frontalis muscles, to the periosteum and common inte- guments : these anastomose with the opposite artery, the superciliary, and the temporal. 9. The nasal urtery varies in size, being sometimes only a very trifling branch, which terminates at the root of the nose; sometimes its size is considerable, as, when it descends ' very low, contributing with the lateral nasal branch of the facial to supply the place of the dorsal artery of the nose, in which case it ex- tends to the lower part of that organ; it always anastomoses with the facial and inferior pal- pebral, and gives branches to the integuments, cartilages, and bones of the nose, to the la- chrymal sac, to the corrugator supercilii, and the internal part of the orbicularis palpebrarum. The internal carotid, after it has furnished the ophthalmic artery, is distributed entirely to the brain, especially to its anterior part, the posterior part of that organ receiving its prin- cipal supply of blood from the vertebral. Having pierced the dura mater at the external side of the anterior clinoid process, and ex- ternal to the optic nerve, the internal carotid artery gives several minute branches to this nerve, to the pituitary gland, the infundibulum, and anterior part of the brain; shortly after this it gives a branch which is very variable ;u size, frequently differing in this respect on opposite sides in the same subject; this is the lateral or posterior communicating branch of Willis, which passes backwards and a little inwards, external to the commissure of the optic nerves, infundibulum, tuber cinereum, and the corpora mammillaria, and joins the 1 posterior artery of the cerebrum, which is a branch of the basilar : the motor oculi lies ex- ternal to it. In its course it gives small branches to the corpora mammillaria, the crus cerebri, the optic nerves, and the choroid plexus. After having given off the communicating artery, the carotid sends a branch to the choroid plexus, the arteria choroidea ; the artery passes CAROTID ARTERY. 498 backwards and outwards, enters the tractus opticus, supplies the pia mater of the middle lobe of the brain and the optic thalamus, and, entering the inferior cornu of the lateral ven- tricle, spreads out its branches in the choroid plexus. After having given off the choroid artery, the internal carotid divides always at an obtuse angle, and at the internal extremity of the fis- sure of Sylvius, into two branches, the an- terior and the middle cerebral, of which the latter is much the larger vessel : sometimes the lateral communicating artery arises at the place of this division, and forms with these branches a sort of tripod. The anterior cerebri, also called the artery of the corpus callosum, is always smaller than the media cerebri ; it passes upwards, forwards, and inwards to the fissure which separates the anterior lobes of the cerebrum, passing over the optic nerves, and inferior to the internal origin of the olfactory : on entering the above- mentioned fissure, it approaches closely to the corresponding branch of the opposite side, with which it communicates by a large and very short transverse branch, called the anterior communicating artery, by which the circle of Willis is completed anteriorly: sometimes this branch is double, and occasionally we find it partially double, in consequence of a forking of one of its extremities; its place is sometimes supplied by a fasciculus of small branches ; it gives off, especially when it is unusually long, a number of small twigs, which pass upwards and backwards to the septum lucidum, fornix, and corpus callosum. From the place of this communication the trunk of the anterior cerebri passes forwards under the corpus callosum, giving off consi- derable branches to the inferior and internal part of the anterior lobe of the cerebrum ; it then turns round to the anterior extremity of the corpus callosum, mounts up on the internal surface of the hemisphere of the cerebrum, and divides into many branches, the anterior and superior of which supply the convolutions on their internal surface, while the posterior take a lower course along the upper sur- face of the corpus callosum, at the posterior extremity of which they take an ascending lirection. All these branches extend to the superior surface of the cerebrum, and anasto- nose with those of the media cerebri and the posterior cerebri, which is furnished by the ver- ebral. Besides these large branches into which the rteria callosa divides superiorly, it gives off rom its inferior and concave side a vast number >f smaller branches, which penetrate the corpus allosum. Sometimes, instead of being connected by ie communicating branch, the anterior cerebral rteries of opposite sides unite, forming a single 'unk, which runs forward for some little dis- use, and then divides into a right and left ranch ; this junction is the more remarkable, n account of its analogy to the union of the jvo vertebral arteries in forming the single unk of the basilar on the median line. The media cerebri, from its greater size com- pared with the anterior branch, appears, as it were, the continuation of the trunk of the carotid ; it passes outwards and backwards, in the fissure of Sylvius, and divides into two branches, the subdivisions of both of which are distributed over the pia mater of the anterior and middle lobes of the brain, anastomosing in front with the anterior cerebri, and behind with the posterior cerebri from the basilar: this artery at first gives branches at the base of the brain to the pia mater on the crus cerebri ; one of these, larger than the others, enters the inferior cornu of the lateral ventricle, where it is lost in the choroid plexus. The anterior and middle cerebral arteries are not always similarly disposed on opposite sides ; it not unfrequently happens, as Haller has remarked, that the two large trunks of the middle cerebral arteries are given off by the right carotid, and the two anterior from the left carotid, while the three others come from the right : considering these anomalies with that of the union of the two cerebral already mentioned, we here find a very remarkable repetition of many of the varieties exhibited by the mode in which the trunks that spring from the arch of the aorta take their origin. For the BIBLIOGRAPHY, see that of Anatomy (Introduction), and of Artery. (J. Hart.) The following observations are to be regarded as supplemental to the preceding article. There is no fact more worthy of the atten- tion of the practical surgeon, as regards the anatomical history of the carotid artery, than the free anastomosis which exists between the external and internal carotids of both sides at nearly all the stages of their course. This is especially the case with the external carotid arteries which anastomose at numerous short intervals from their origin to their termination, where they likewise communicate with some small ramifications of the internal carotids. Nor is the communication between the internal carotids less free, although it is less frequent : this communication is formed within the cra- nium at the anterior segment of the circle of Willis. Moreover, by means of the posterior communicating artery the internal carotid anas- tomoses with the posterior cerebral, and there- by with the subclavian, through the medium of the vertebral artery. And farther, by the anas- tomoses of the superior thyroid artery with the inferior, and of the occipital with the cervicalis ascendens, profunda, and vertebral, a commu- nication is established between the external carotid artery and the subclavian. From the knowledge of the communication thus existing between these several portions of the arterial system of the neck and head, we may deduce some very useful inferences. 1. It is evident that the carotids of both sides may be injected by even a coarse injec- tion, from a pipe introduced into the artery of one side. This is a fact well known to every practical anatomist. 494 CAROTID 2. With the knowledge of this freedom of communication between the carotids, no sur- geon will look for uniform success after the application of a ligature, in cases of wounds of either carotid or of one of its branches, if the ligature be applied only below the situ- ation of the wound. Nevertheless, experience tells us, that such a plan of treatment has been successful in several instances ; and it is wor- thy of notice that iri almost all the successful cases the primitive carotid was tied very shortly after the infliction of the wound, at a time when the collateral branches could not have become sufficiently enlarged to admit of the full circulation in them ; while, on the other hand, in two unsuccessful cases, the primitive carotid was not tied for some days after the receipt of the wound, and secondary hemor- rhage ensued in each case. 3. The free anastomosis of the two internal carotids with each other and with the sub- clavians through the vertebrals within the cra- nium, sufficiently evinces that the circulation of the brain after the obliteration of either carotid, by ligature or otherwise, may be easily maintained ; and experience fully confirms this inference from anatomy. That a disturbance of the cerebral circulation does occur occa- sionally after the operation of tying the carotid is fully proved ; but it would appear that it is an occurrence much more rare than might, a priori, be expected. Of seventy cases, col- lected by Berard,* in which this operation was performed, symptoms arising from cerebral affection appeared only in a very few, and in two only of these instances the patients died from the effect produced upon the cerebral cir- culation. One of these cases occurred in the practice of Mr. Aston Key ; the patient fell into a deep sleep after a severe fit of coughing, and died shortly afterwards without awaking. On examination it was found that the carotid of the opposite side was obliterated by a eo- agulurn nearly as low as its origin from the aorta, so that the cerebral circulation could only have been maintained by the two vertebral arteries, which in this case were smaller than usual. In the second case, which was ope- rated on by Langenbeck,-)- immediately after the application of the ligature the patient be- came motionless, with closed eyes, without speaking, except when addressed several times in succession; he sank gradually, and died in thirty-four hours after the operation.}; In three of the cases collected by Berard, some disturbance or indistinctness of vision, on the same side as that on which the artery was tied, followed the operation ; in one of these the impairment of sight was accompanied by syncope, and a sensation of cold affecting * Diet, de Medecine, art. Carotide. f Arch. Gen. de Med. t. xix. p. 118. f Dr. Mussey, of New Hampshire, in America, has recorded a case in which he tied both primitive carotids within twelve days of each other, and without any untoward result. The reader will find the case quoted at length in Mr. Guthrie's valuable work on the Diseases and Injuries of Arteries, p. aso. ARTERY. the whole of that side of the face ; in a second, related by Mr. Mayo, the impaired vision was only on the right side, the carotid of which side had been tied, and the sense was perfectly restored in a few hours. In the third case one eye was completely deprived of sight, and the sense of hearing greatly weakened in the ear of the same side. Berard remarks that the loss or impairment of vision on one side is un- favourable to the opinion that such an occur- rence is to be attributed to disturbed cerebral circulation ; it is sufficiently accounted for by the fact that there is a considerable diminution in the quantity of blood sent to the eye ; for that organ is supplied by a direct branch of the internal carotid, viz. the ophthalmic, which anastomoses at its termination with several of the terminal branches of the arteries of the face ; and it is not improbable that in the cases above referred to, the branches which form this anastomosis, as well as those forming the circle of Willis at the base of the brain, were much smaller than usual. In other cases hemiplegia, more or less ge- neral and perfect, followed the operations after a longer or shorter period. In a case related by Magendie, that of a young girl, in whom the loft carotid was lied, there appeared on the sixth day paralysis of the right arm, of the pharynx and larynx, and numbness of the right lower extremity. The paralysis gradually di- ; minished, but the intellect was so far impaired that the patient lost the power of reading/' In Sir A. Cooper’s first case, the right arm and leg were deprived of sensation and in part of motion on the seventh day after the operation ; ;i and a man, in whom Mr. Vincent tied the right carotid for aneurism, was attacked with com plete hemiplegia of the left side in half an hour after the operation, and continued in that state till his death on the seventh day. It is re- markable that, in all these cases, the paralysis j was situated on the side opposite to that on which the artery was tied ; a fact which alone would indicate that the cause of the paralysis } was seated in the brain. Aneurisms do not occur so frequently in the carotid arteries as in the aorta or in the large arteries of the extremities. They are most frequently found situated at the bifurcation of the common carotid, where also calcareous;1 and atheromatous deposits are very often met with. In the lower part of the common ca-J rotid an aneurism is, of course, a more for- midable disease than if it were situated high; up, in consequence of the impossibility of applying a ligature between the artery and the heart. Sometimes an aneurism of the aorta1 projects upwards into the neck, compressing and obliterating the carotid, and simulating: al the characters of aneurism of its lower portion I am not aware that there is on record any! instance of aneurism of the internal carotid artery in its cervical portion, although our mu| seums are not without specimens of aneurisma dilatations of it after it has entered the cranium and as it lies by the side of the sella Turcicaj * Journal de Physiol. April, 1827. CARTILAGE. 495 We sometimes find the cervical portion of this artery in a tortuous state, but we rarely see in it those atheromatous and earthy deposits which are met with in other parts of it. In the dead body there is no difficulty in exposing the common carotid artery in any part of its course, but during life much em- barrassment is occasioned by the alternate di- latation and collapse of the internal jugular vein, corresponding with expiration and inspi- ration, and sometimes by some small veins which lie in front of the artery. It may be cut down upon either above or below the omo- hyoid muscle, but in the former situation the superficial position of the vessel and the less complexity of its relations render it more easy to be got at. In both situations the anterior margin of the sternomastoid muscle forms a useful guide to the artery; but much more careful dissection is required when the operation is done in the region below the omohyoid muscle. Here great care is de- manded in dissecting back the sternomastoid muscle, and in drawing the sternothyroid inwards; the thyroid body and, on the left, the oesophagus must be avoided, and in pas- sing the ligature round the artery, the ope- rator must take care to avoid not only the vein and par vagum but also the inferior thyroid artery, the recurrent and sympathetic nerves and the cardiac branches of the latter, and on the left side the thoracic duct. As anomalies in the distribution of some of the arteries in the neck are occasionally met with, the surgeon should be on his guard against such an occur- rence, especially in operating in the low region where they are most likely to be met with. Two arteries may be found here occupying pretty nearly the situation of the carotid artery. One of these will be the carotid itself, the other the vertebral, which sometimes passes high up in the neck in front of the rectus capitus anticus muscle, before it enters the canal in the transverse pro- cesses of the cervical vertebra. In a case related by Mr. Allan Burns,* the vertebral artery en- tered this canal only a few lines below the bifur- cation of the carotid, and in its passage up the neck, parallel to and behind the carotid, it was separated from that vessel only by its sheath. A low bifurcation of the carotid artery would be equally likely to occasion embarrassment; and the possibility of such a condition of the cer- vical vessels as well as of the anomalous course of the vertebral artery before alluded to are strong arguments in favour of the recommenda- tion of Mr. Burns, that, “ when the surgeon has reached the sheath of the vessels he ought uniformly, before opening it, to press the carotid between the finger and thumb. If the pulsa- tion of the tumour be not in this way con- trolled, he will do well to pause before he pass a ligature round that vessel.”t In fine we sometimes find the inferior thyroid artery cros- sing in front of the common carotid in the inferior region. * Surgical Anatomy of the Head and Neck, p. 170. t Loc. cit. It is very easy In the dead body to find the primitive carotid low down in the neck by cutting in the cellular interval between the clavicular and sternal portions of the stemo- mastoid muscle, but it is not so easy to pass a ligature round it; and this difficulty is greatly magnified in the living subject, in consequence of the necessarily limited space in which the operator has to work ; the difficulty too is greatly increased by the contractions of the sternomastoid muscle. To expose the external carotid artery shortly after its origin, it is only requisite to follow the same steps as are necessary for cutting down on the common carotid above the omohyoid muscle. It is in general advisable to apply the ligature below the point at which the di- gastric muscle crosses the artery and below the origin of the superior thyroid. Some embar- rassment is likely to result from the plexus of veins which in this region often lies in front and on the sides of tbe artery. A ligature, however, may be passed round this artery above the digastric muscle, but it will be re- quisite that the external incision shall com- mence higher up. The needle must be passed between the parotid gland and the digastric tendon, the distances between these parts hav- ing been previously increased by drawing down the tendon of the muscle. (R. B. Todd.) CARTILAGE (Lat. cartilago, quasi car- nilago ; Gr.^ovJgo;; Fr. cartilage; Germ .Knor- pel ; Ital. cartUagine) is a firm elastic sub- stance, of pearly whiteness, and uniform or homogeneous in its appearance. It bears a considerable analogy to bone, and is to be found in situations where less rigidity and more elasticity are required than the osseous system presents. Several tissues, differing a good deal from each other, were formerly comprehended under this term. These have been variously classified by modern anatomists ; but the division of them into cartilages and Jibro-cartilages, proposed by Bichat,* is that which is now generally adopted. Although Bichat was happy in the choice of names for these tissues, yet, in arranging the individual pieces under the two heads just mentioned, he has not been found quite correct. Some of the true cartilages are placed by him amongst the fibro-cartilages, an error which Meckel perceived and rectified .f Cartilages may be divided into the temporary, the permanent, and the accidental. A. The temporary cartilages are substitutes for bone in the earlier periods of life, and after a certain time become ossified. We find them at birth forming the extremities and larger emi- nences of long bones, a great part of the short bones, and the margins of the broad ones. These gradually disappear, and at puberty cease to exist. It is unnecessary to say more of them here. (See Osteogeny.) B. Permanent cartilages are met with under * Anatomie Generate, tom. iii. Par. 1812. f Manuel d’Anatomie, tom. i. Par. 1825. 496 CARTILAGE. two forms : 1, the articular, attached to bone, and entering into the formation of joints ; 2, the non-articular, forming canals more or less per- fectly. I. The articular cartilages are called diar- throdial, obducent, or of incrustation, when they belong to the moveable articulations; synarthrodial when connected with those very limited in their motions, or the immoveable articulations of some authors. We think it unnecessary to do more than refer to these cartilages here, as their characters will be found fully described in the article Articulation. II. The non-articular cartilages are usually much more flexible than the articular. In some cases they are attached to bones, and lengthen them out, as the preceding class. Of this we see examples in the nose, the auditory canal, and the Eustachian tube. In other cases they are insulated, forming the basis of distinct organs, as the larynx, the trachea, the eyelids. All the cartilages of this class have a well- marked perichondrium.'* Some of them, as the epiglottis, the tarsal cartilages, and those of the alee nasi, are so thin, so flexible, and assume so much of a fibrous appearance from their perichondrium, that Bichat placed them amongst the fibro-cartilages ; but these last never have perichondrium, and their fibrous texture is distinctly independent of their investment, as is easily seen without any preparation. (See Fibro-cartilage.) The structure of non-articular cartilage, like the other forms, may, by protracted maceration, be shown to be fibrous ; but the arrangement of its fibres is different; they interlace a good deal more. The physical properties of cartilages are such as to fit them admirably for the functions which they have to perform. They are solid, resisting, and incapable of extension, that they may be able to preserve the form of certain parts as effectually as bone; and they are flexible and elastic, to enable them to yield in some degree, and immediately to resume their original shape. Elasticity is the property most essential to them, and on this their usefulness mainly de- pends. Its existence is easily demonstrated. If the blade of a knife be pressed into a diar- throdial cartilage, the reaction of the displaced fibres expels it with force ; and a piece of any cartilage, if bent between the fingers, returns with a spring to its former shape. The elastic fibres of diarthrodial cartilage are so placed as to receive impressions on their extremities ; they yield a little to force, and only a little, else the ligaments would be too much relaxed ; but they yield enough to let the opposite sur- faces accommodate themselves to each other, and to deaden the shocks which would other- wise have an injurious effect on the nervous centre. In fact, these articular cartilages serve as a series of springs between the ground and the delicate organs which they support. The * If we except the capsule of the lens and the posterior layer of the cornea, supposing these structures to belong to the cartilaginous system. See Eye. elasticity of the costal cartilages is obvious and essential. They are subject to torsion in the act of inspiration, and by their reaction become an important agent in expiration. Differences depending upon age. — Cartilages are soft, transparent, and like jelly in the very young foetus. Gradually, as the individual advances to maturity, they become opaque, white, firm, and elastic; and in the adult these qualities are in their greatest perfection. In old age they lose again their elasticity and flexibility ; a yellowish colour takes the place of their beautiful pearly white; they become dry and brittle, and shew a great tendency to ossify. Organization. — Cartilage appears at first sight to be perfectly homogeneous throughout, like a concrete jelly, not shewing any traces of organization, nor exhibiting the least appear- ance of vessels. But, as an attentive examina- tion proved it to be fibrous, so we shall be able to satisfy ourselves that it possesses an organ- zation similar to other parts of the living sys- tem. In healthy cartilage, it is true, no red vessels can be demonstrated, neither can the finest injection be made to penetrate it, nor will madder used in food colour it. But dis- ease sometimes shows red vessels ramifying through its substance ;* and several other phe- nomena lead us to the conviction that it is at all times permeated with vessels, though they may be too fine to admit the red globules. For instance, we find cartilage assume a yellow tinge in jaundice. If we slice off a bit, the dry surface is soon moistened with a serous fluid, which, doubtless, comes from its colourless vessels. Exposed cartilages have been known to granulate, which implies the existence of j, vessels, and perhaps of cellular substance. And we know that in the old and laborious there is often not the least sign of wear, although die enamel of the teeth be quite worn away. Where a perichondrium is present, we may suppose the vessels first ramify in it before they enter the cartilage. Dr. William Hunter describes j the arrangement of the vessels which supply diarthrodial cartilage to be very peculiar. He says, “All around the neck of the bone there !| are a great number of arteries and veins which ramify into smaller branches, and communicate with one another by frequent anastomoses, like those of the mesentery. This might be called the circulus articuli vasculosus, the vascular border of the joint. The small branches divide into still smaller ones upon the adjoining sur- face, in their progress towards the centre of the cartilage. We are seldom able to trace them into its substance, because they terminate ah- |j ruptly at the edge of the cartilage, like the vessels of the albuginea oculi when they come to the cornea.”t It does not appear that nerves or absorbents have ever been traced into cartilages ; but the phenomena of disease, pain, ulceration, &c., convince us that they are supplied with both. Even in their healthy condition, though their * Brodie on Diseases of Joints, p. 183, third edition. f Phil. Trans. 1743. , CARTILAGE. 497 animal sensibility is exceedingly low, scarcely perceptible, yet it probably does exist, and •will manifest itself whenever any cause is operating upon them which might destroy their texture. We may, indeed, cut an exposed car- tilage without pain, and the violent pressure it undergoes in a sound joint is unheeded. But the former is a kind of injury from which car- tilage may be said to be totally exempted, and the latter is that for which it is peculiarly adapted. In either case sensibility would be useless or inconvenient. Let but a foreign body however get into a joint, between its cartilages, such as might disorganize them, and then an alarm is set up too great to be attributed to the synovial membrane alone, and depending, we may suppose, in part at least, on the cartilage itself. C. Accidental cartilage. — By this name we designate the cartilaginous concretions which are occasionally found in situations where they do not ordinarily exist. They present them- selves in several organs, under various forms, and in different stages of development. Laennec divides them into perfect and imperfect ;* but it is not easy to point out any line of distinction between these two classes; they differ only in degree, the one passing gradually into the other as its development becomes more complete. We rarely, indeed, meet with accidental car- tilage which deserves to be called perfect ; in one part it is fibrous, or of a dense cellular nature, in another it is cartilaginous, while a third portion of the same piece is passing into the osseous state. The forms and situations in which they occur, will permit an arrangement of them under three heads : — 1. The insulated or loose cartilages, which are found either (a) in joints or (/>) in serous sacs. a. Those of the joints are rounded or ovoid, usually flattened, sometimes lohulated, always smooth, polished, and lubricated with synovia, frequently osseous in their centre. They vary in magnitude from the size of a mustard-seed to that of an almond ; and in one instance Mr. S. Cooper found in the knee a concretion of this kind, which was as large as the patella. They also vary considerably in numbers ; Ilaller saw twenty in the articulations of the lower jaw, and Morgagni met with twenty-five in a knee-joint. Their most usual seat is in the knee, but they have been found in the hip, jaw, elbow, and wrist. They are commonly “ loose,” moving freely in the cavity, but some- times connected to the synovial sac by slender membranous attachments. With respect to the origin of these bodies various opinions have been entertained. Ilaller and Reimarus supposed that they were frag- ments of the original cartilage, accidentally de- tached. Cruveilhier found fifteen of them in a hip-joint some years after it had been injured, and conceived that he saw an exact correspon- dence between them and certain depressions in the cartilages of that articulation. Bichat con- jectured they might be altered portions of the * Diet, des Sciences Med. VOL. I. synovial membrane. According to John Hunter, they may have had their origin in a coagulum of blood poured into the joint from an injured vessel, and there becoming organized. This coagulum would, he thought, assume, as in all other situations, the peculiar organization of the parts in its immediate vicinity. Laennec and Beclard were of opinion that they might be formed outside the synovial membrane, and push it before them so as to form a pedicle, which in some cases remained, but more gene- rally w'as ruptured. This opinion Laennec sup- ported by observations made on similar sub- stances in serous sacs, where he traced them through all the degrees of their development, from the incipient stage, in which they formed a slight projection behind the membrane, to the period when they became perfectly isolated bodies. Sir Benjamin Brodie, whose authority on this subject is of so much weight, remarks, “ It is generally supposed that these loose bodies have their origin in coagulated lymph which has been effused from inflammation of the inner surface of the synovial membrane, and which has afterwards become vascular. In the majority of cases, however, which I have met with, no symptoms of inflammation pre- ceded their formation ; and hence it is probable that, in some instances, they are generated like other tumours, in consequence of some morbid action of a different nature. They appear to be situated originally either on the external sur- face, or in the substance, of the synovial mem- brane ; since, before they have become de- tached, a thin layer of this latter may be traced to be reflected over them.’’* When inflammation is of long standing in a bursa mucosa , it is not unusual to find in it a number of loose bodies, of a flattened oval form, and of a light brown colour, with smooth surfaces, resembling small melon-seeds in ap- pearance. There seems to be no doubt that these bodies have had their origin in the coagu- lated lymph effused in the early stage of the disease.f From the resemblance which these concretions bear to loose cartilages, we might infer that they both have had a similar origin ; but, as there can be no doubt that loose car- tilages sometimes begin to be formed outside the synovial membrane, we must not conclude that this is the only mode. From the evidence before us, therefore, and from observations made on the second species of accidental cartilage, to be mentioned by-and- bye, we are inclined to admit two distinct sources from which these loose cartilages may have commenced. One, a deposit in the cel- lular tissue outside the synovial membrane; the other a deposit within this membrane. The ori- gin of both being lymph, which becomes cartila- ginous, and often proceeds to an osseous state. b. Insulated cartilages are sometimes found in connexion with true serous cavities. They are seldom larger than a pea, rounded, floating, or attached by a pedicle to the inside of the * Pathological and Surgical Diseases of the Joints. Lond. 1834. t Idem. 2 K CARTILAGE. 498 sac, and, in some instances, distinctly outside it. Laennec often found them between the tunica vaginalis testis and the tunica albuginea, and on one occasion in the lining membrane of the lateral ventricles of the brain. Andral saw three of these bodies in the serous mem- brane of the brain ; one of them floated loose and unattached in the sac of the arachnoid ; the other two were attached to the choroid plexus by a delicate cellulo-vascular prolonga- tion. Me also often found them in the peri- toneum, sometimes perfectly isolated, at other times appended to the serous membrane.* 2. Accidental cartilages of incrustation, occurring in plates, are very irregular in size and shape. They are most frequently found in fibro-serous membranes, as the dura mater, the pericardium, and the immediate coverings of the testis and spleen. Upon this last viscus they are seen more frequently than in any other situation whatsoever. Bichat supposed they vvere altered portions of the fibrous membrane, having so generally met with them where the latter existed. The subserous cellular tissue is the proper seat of them. We often find them between the middle and internal coats of ar- teries, in what may likewise be called a sub- serous cellular tissue. (See Artery.) It is exceedingly rare to meet with them under mucous membranes. Andral saw one solitary instance of a true cartilaginous mass developed in the submucous cellular tissue of the stomach. The subcutaneous cellular sub- stance is likewise nearly exempt from them ; but the same experienced pathologist relates, that one of the lower extremities of a woman who died in La Churite in the year 1820, was affected with elephantiasis ; underneath the skin, and occupying the place of the muscles, which were reduced to a few pale fibres, was found an enormous mass of condensed hard cellular tissue, possessing, in many places, all the physical characters of cartilage. In all these instances there is every reason to believe, from the closest examination, that the newly formed substance is developed at the expense of the cellular tissue alone, and that neither the fibrous nor the serous membranes are al- tered, nor indeed any adjoining texture. These last seem to be replaced by the accidental for- mation, but they are only absorbed to make room for it, and not transformed into the new substance. An exception must, perhaps, be made in favour of mucous membrane, which appears capable of undergoing this change. Laennec relates the case of a child, in the membranous portion of whose urethra he found a large calculus. The mucous mem- brane of the part presented several patches, of the size and thickness of a man’s nail, which appeared to him semi-cartilaginous, and were incorporated with, and formed part of, the mucous membrane. In like manner Beclard found the mucous membrane of the vagina, in a case of prolapsus uteri, studded over with cartilaginous spots ; and he observed a similar A ndral’s Pathological Anatomy, translated by Townsend and West. appearance on the prepuce of an old man, who had had phymosis from the time of birth. What is the cause of these formations ? Most probably they have their commencement in some obscure inflammatory action. It is true we often find them where there is no other appreciable lesion whatsoever, nor any trace of inflammation in the neighbourhood ; but, on the other hand, they seem to be but a step re- moved, in structure, from coagulable lymph, and are sometimes imbedded in it ; and the irritation and consequent inflammation pro- duced by foreign bodies must be allowed to have occasioned them in the instances just related from Bichat and Beclard. 3. The irregular or amorphous masses which we sometimes see in the thyroid gland, ovaries, uterus, testes, brain, liver, lungs, spleen, kidneys, and heart, are supposed to differ from the preceding classes, not only in form, but in connexions and origin. They appear to be united by continuity of substance with the tissues in which they are developed, and, in fact, to be altered portions of them. But it is by no means proved that cellular tissue may not, even in these cases, be the nidus of such concretions, and that the organs have not rather been absorbed to make room for them, than transformed into them. In false articulations, old cicatrices of the liver, lungs, &c., we find a substance resembling car- tilage ; but its description belongs to “ Fibro- cartilage,” to which we refer. Chemical composition. — On this subject there is some difference among writers; Dr. Davy* found diarthrodial cartilage to consist of Albumen 44'5 Water 55-0 Phosphate of lime ...... 00 5 1000 Berzelius professes his ignorance of its com- position. Neither diarthrodial nor non-articular cartilage yielded gelatine, and he doubts “ whe- ther the mass which constitutes them be of a peculiar nature, or similar to what we find in the fibrous coat of arteries.” f By boiling costal and synarthrodia l cartilages, gelatine is developed. lie looks on them to be imperfectly developed bone, and to have the composition of its animal part, with the addition of 3-402 per cent of earth in the false ribs of a man of twenty. In 100 parts of this earth he gives the fol- lowing analysis from Frommherz and Gugert: Carbonate of soda .... 35 068 Sulphate of soda 24-241 Muriate of soda 8 231 Phosphate of soda .... 0-925 Sulphate of potass .... 1-200 Carbonate of lime .... 18-372 Phosphate of lime .... 4-056 Phosphate of magnesia . 6'908 Oxyde of iron, and loss . 0 999 100-000 * Monro’s Elements of Anatomy, vol i. t Traits de Chimie, tom. vii. Par. 1833. CARTILAGE. 499 Pathological conditions.- — Cartilages are not subject to many diseases. Inflammation, ulce- ration, and ossification are almost the only ones to which they are liable ; and of these the first is very indistinctly marked ; the last scarcely deserves to be called disease. Cartilages are supposed to owe this exemption from morbid actions to their extremely low degree of vitality. Destitute of red vessels, and supplied with no more nervous influence than is barely sufficient to constitute them a part of the living system, they escape those changes to which highly organized parts are exposed ; and, were it not for their connexion with more delicate and excitable tissues, their exemption would be still more complete. Some eminent pa- thologists have gone so far as to consider them incapable of any morbid action; espe- cially the diarthrodial cartilages. “ Les carti- lages diarthrodiuux ne jouissent point de la vie," says Cruveilhier, who asserts that he could not excite disease in them by any of his experiments ; and that he saw them perfectly sound in the midst of every other diseased structure. Mr. Key* also seems to allow them very little vitality in health, and to consider them very nearly passive in what are called their diseases. Inflammation is rarely to be met with. Its characters are so slightly marked in diarthro- dial cartilage, that we infer its existence, not so much from the signs which are present, as from observing that ulceration is a common occur- rence— a state which we suppose to have been preceded by inflammation. The only marks of inflammation to be seen, even when most de- veloped, are a softening of the cartilage, and in two instances detailed by Sir B. Brodie, vessels injected with red blood could be traced extend- ing from the bones into the cartilages covering them. Severe pain accompanies this disease; but, as in all the cases on record, ulceration, or some other disease was also present, it cannot be determined how much of the pain belonged exclusively to it. The costal cartilages are subject to painful affections which usually occur in patients who have had syphdis, or to whom mercury has been administered inju- diciously. These depend on inflammation of the perichondrium. They may terminate in ulceration or in osseous deposition, and have a close resemblance to periostitis. Ulceration of cartilage is a very common occurrence in joints, but is extremely rare in other situations. It may be met with at any period of life, or in any articulation, but it is in the hip and knee we mo.-t frequently find it, and in persons who have passed the age of puberty and are under thirty or thirty-five. A striking peculiarity attends this affection, namely, that the formation of pus is by no means a constant accompaniment. The form and situations of ulcers in diarthrodial cartilages are very various. Sometimes they are small and deep ; sometimes very superficial, like an abra- sion— at one time attacking the free, at another the attached surface; and may commence in * Medico-Chirurgical Transactions, vol. xviii. the centre or at the circumference. These ulcers may be divided into primary and secondary, the former arising independently of any disease in the adjoining tissues, the latter being preceded by a morbid state of the bone or synovial membrane. Tire primary ulcer commences towards the centre of the cartilage, and always on its free surface. It is accompanied with much pain, but when exposed to view exhibits no sign of inflammation. There is no vascularity to be observed, no granulations, frequently no pus, nor any unhealthy appearance of the synovial membrane. Should the ulcer, however, have extended itself quite through the cartilage to the bone, the latter usually becomes carious, pus is secreted abundantly, and the synovial membrane sympathizes. The surface of the ulcer differs very much in different cases ; in some it appears smooth, and of the colour of healthy cartilage, as if a portion were chiselled out. In others, and more generally, it is a little yellowish, dull looking, and slightly irregular. The edges are often irregular, never elevated nor undermined. The ulceration sometimes spreads superficially over a large extent; at other times it is small and deep, or it may destroy all the cartilage and expose the bone, which will also be found diseased. Most generally the remaining cartilage, if any, retains its healthy structure to the very edge of the ab- sorbed portion. Another appearance is often observed ; a part of the cartilage is reduced to a fibrous state, the fibres being attached at one extremity to the bone, while at the other they are free, and have no lateral connexion. This condition of carti- lage is said, by Sir B. Brodie, to be frequently, but not constantly, the first stage of ulceration ; and he conceives it may often exist where no ulceration is ever to follow. Mr. Key looks on it as “ a disease of a peculiar character.” And we have frequently found it in the dissecting- room, where there was not the slightest mark externally or internally of any other morbid action. The writer has observed it oftener on the patella than elsewhere ; and as this is so seldom the part first involved in the ulcerative process, it probably depends on an action of a different nature. The writer has also seen it oftener in joints long dead than in the more recent, and has therefore thought it might possibly be caused, in some cases at least, by the action of the synovial fluid, or by decomposition. Secondary ulceration may commence in the bone or in the synovial membrane. ( a ) When the bone is previously diseased, that side of the cartilage which was turned to it is first affected. The adhesion of the two tissues is diminished ; we find it more easy to separate them. After some time a separation actually takes place, and a vascular net-work, sometimes a layer of granu- lations, occupies the interval. The surround- ing cartilage is softened. The ulcer, with cha- racters differing little from the primary form, goes on more or less rapidly, until an openin is made quite through into the cavity of th joint. When this opening is effected, the mat- ter, which in this form of ulcer is always pre- bo 500 CAVITY. sent, finds its way into the synovial sac, and ex- cites inflammation there. The disease of the bone commonly giving rise to this ulcer is the slow strumous affection of the spongy extremities, so accurately de- scribed by Sir B. Brodie, the symptoms of which are familiar to every surgeon. A more acute inflammation of the osseous tissue is oc- casionally to be seen, and may be followed by a disease of the same nature, or differing only in the quickness of the course it pursues. (5) Secondary inflammation extending from the synovial membrane is most apt to attack the edges of the cartilages in the first instance. These are thinned, as if abraded, and over- lapped by the vascular or disorganized mem- brane. The bone remains sound, as in the primary ulceration. For further particulars on the ulceration of cartilage, see Joint. Does fractured cartilage ever unite by cartilage? It probably never does. The costal cartilages, when broken, unite by lymph, which soon after is converted in bone, but never appears to form true cartilage. When a fracture extends into a joint, as we often see in the condyles of the humerus and femur, the divided cartilage is united by a cicatrix, which is not truly car- tilaginous. Neither does it appear that car- tilage is ever regenerated. Laennec believed it was: “ in examining a knee-joint, he found in the centre of the articulating surfaces, in place of the natural cartilage, a thin cartilaginous lamina, semitransparent, adherent to the bone; the old cartilage formed around it a projecting border, as if fimbriated.”* This observation certainly was not enough to establish its power of regeneration. We often find in cases of gout and rheumatism, and especially in the disease designated morbus coxa senilis, that the cartilage is removed, and in its place a compact shining layer of osseous sub- stance like ivory deposited. This is not owing to an ossification of the cartilage, for the cartilage is often found completely absorbed, and the rough bone exposed, which, if seen at a later period, would doubtless be covered with this deposit to prevent the disintegration of its cancellated structure. BIBLIOGRAPHY. — Hunter on the structure and diseases of articulating cartilages, Philos. Trans. 1743. Haase, De fabrica cartilaginum, 4to. Lips. 1767. Authenrieth, De gravioribus quibusdam cartilaginum mutationibus, 8vo. Tubing. 1798. Mayo, Acute form of ulceration of the cartilages of joints, Medico-Chirurg. Trans, vol. xi. Cru- veilhier, Ohs. sur les cartilages diarthrodiaux, et les maladies des articulations. Archives Gen. de Med. t. iv. 1824 ; JEj. Usure des cartilages articu- laires, Nouv. Biblioth. Med. t. i. Observations on accidental or loose cartilages may be found, by Cruikshank, in Med. and Philos. Comm, of Edinb. vol. iv. ; by Coley, in Med.-Chir. Trans vol. v. ; by Horne, in Trans, of a Society for Improv. Med. and Chirurg. Knowledge, vol. i. ; by Desault, in his Jonrn. de Chirurg. t. ii. ; by Abernethy , in his Surg. Observations; by Laennec, in the art. Car- tilages dccidentels of the Diet, des Sc. Med. ; by Cruveilhier , in Nouv. Bib. Med. t. i. 1827 ; &c. And remarks on special forms of disease affecting the cartilages occur in the general treatises on dis- * Op. cit. p. 240. eases of the joints, as those of Cooper, Biodie, Schreger, Wilson, and Scott. — Vide Bibliography of Articulation. ( Charles Benson .) CAVITY, in anatomy, ( cavitas ; Fr. cavite; Germ. Hohle; Ital. cavita.) — This term is used, in anatomy, to signify any excavation or even depression of more than ordinary depth, which may exist in or between solid parts. Hence we find cavities existing in bones, or formed by the junction of one or more bones, which, as they are severally destined for articulation with other bones, or for the reception or transmis- sion of certain tendons, vessels, &c. are de- signated articular or non-articular. (See Bone.) But we have likewise large excavations whose walls are of a more complicated arrangement, and which are destined to receive and protect those organs which are concerned in the func- tions of innervation, respiration, and digestion, and throughout a large proportion of the classes composing the animal kingdom are three in number, namely, the Cephalic or Cranial cavity, containing the brain — the Thoracic cavity, containing the organs of respiration— and the Abdominal cavity, containing the organs of digestion and of the secretion of urine. To this last is appended, as a continua- tion, the Pelvic cavity, which is chiefly de- voted to the organs of generation, as well as to some of those connected with the urinary ex- cretion. We refer for particulars connected with the other cavities to the articles Cranium, Thorax, and Pelvis, and proceed to consider succinctly the anatomy of the Abdominal Cavity in its Normal as well as Abnormal conditions.* Abdominal Cavity, (in human anatomy.) The annexed woodcut exhibits a vertical section of the body intended to show the tbo racic and abdominal cavities, from which the viscera have been removed. A simple reference to it and to fig. 204 will sufficiently explain the form and boundaries of the latter cavity, which have been already fully described in the article Abdomen. Our object in the present article is to examine the abdominal cavity as it is brought under the eye of the anatomist, when its contents have been exposed by removing or cutting through the abdominal parietes. * Some anatomists object to the use of the term cavity, because, say tljey, every hollow in the animal body is full. Such an objection, on the principle of nature’s abhorrence of a vacuum, would go to discard the use of the term, even from ordinary discourse. Considering the word in re- ference to its etymology, it is synonymous with excavation, which in no way implies emptiness, and it is in this sense that we must employ it in anatomical description. I apprehend that con- fusion has arisen from employing the same word to denote the excavation bounded by bone or by bone and muscle, in which the viscus or viscera are lodged, and to indicate the bag or sac of the serous membrane by which each of the three great cavi- ties is lined. In this latter sense, the term cavity is certainly not appropriate, at least it may be most advantageously laid aside ; and we can use, without the same risk of confusion, the expression bag or sac of the peritoneum, pleura, & c. CAVITY. 501 Fig. 203. It rarely happens that vve meet with an in- stance in which the abdominal viscera have not been more or less disturbed after death from their natural relations to one another. During life the contractile walls of the ab- domen, ever active, maintain such a uniform degree of pressure on the contained organs, that displacements or alterations of positions are very rare occurrences excepting through some preternatural opening in the abdominal parietes. It is advisable to study the positions of the contents of the abdomen in a body re- cently dead, and which has not experienced any degree of disturbance. When the anterior wall of the abdomen has been removed or freely laid open by a crucial incision, the contents of the cavity are brought into view in the following order : — In the right hypochondriac region the liver projects to a slight extent below the inferior border of the chest. This, however, is not to be regarded as the position of the liver during life ; the descent of that organ from behind the shelter of the ribs is attributable to its gravita- tion in consequence of the removal of the support which it obtained from the pressure of the anterior abdominal wall. The liver will thus be found to extend more or less into the proper epigastric region, covering and con- cealing the lesser curvature of the stomach with the gastro-hepatic omentum and the ante- rior, or more correctly, the antero-superior surface of the stomach to a variable extent. In this region we likewise see, corresponding pretty nearly to the cartilage of the ninth rib, the fundus of the gall-bladder in some in- stances completely covered by the liver, in others projecting beyond it or only covered by a duplicature of serous membrane which fills up a natural notch in the liver. In the epigas- Fig. 204. trium more or less of the stomach is seen, its greater curvature projecting forwards, having pendent from it the middle portion of the great omentum ; and the left hypoehondrium often (especially when the stomach is full) seems to be wholly occupied by the splenic extremity of the stomach, immediately below which there is a portion of the transverse colon, just where it is forming an angle with the descending colon. Sometimes the anterior margin of the spleen projects before it, and sometimes a still greater portion of the spleen is visible, if that organ be in a state of turgescence. Along the 502 CAVITY. inferior boundary of the epigastric region, and projecting partly into that region and partly into the umbilical below, the transverse arch of the colon runs with a slight curve concave backwards and downwards. The position of this important portion of the great intestine is always lower in the abdomen of a subject thus opened than it can possibly be during life. In fact, when the abdominal wall is unimpaired and the usual compression is maintained, the stomach and colon must be in very close appo- sition with each other, so that it must be diffi- cult, if not impossible, to make pressure from without on the one without affecting the other nearly to the same degree. The arch of the colon is loosely covered on its anterior surface by two lamina of peritoneum, which descend from the greater curvature of the stomach and entering into the umbilical region are reflected upwards after a descent as far as the lowest part of that region, forming a curtain which covers the convolutions of the small intestine beneath the transverse arch of the colon. This curtain is the great Omentum or Epiploon, ( Omentum majus,) which, in the natural con- dition of the parts during life, there is every reason to believe is closely applied to the an- terior surface of the small intestine ; much variety, however, may be observed as to the extent of its relation to this portion of the intestinal canal, and it is difficult to account for this variety. Thus we sometimes find the in- testine uniformly covered by this membrane more or less loaded with fat, descending as low as the upper outlet of the pelvis ; this may be regarded as the normal state in the adult. But at other times we find the omentum so crumpled up or contracted, that the small intestine is completely exposed, and it is only by pulling down the omentum from the arch of the colon towards which it is folded up or crumpled, that we can form an estimate of its extent. Again, in other cases we observe that it is only long enough to descend halfway or a little lower over the surface of the small intes- tine. It is said to have less extent in females who have borne many children than in any others ; I cannot confirm this statement, inas- much as I have not unfrequently seen it of its full dimensions in such subjects. In the na- tural state of the parts, then, the whole of the central portion of the umbilical region is oc- cupied by the omentum, forming a moveable curtain over the anterior surface of the con- volutions of the jejunum and ilium. The iliac region of the right side is occupied by the coecum or caput cob, and in the lumbar region of the same side the ascending colon is visible, sometimes when distended projecting considerably, at other times so contracted as to appear sunk towards the posterior wall of this region, and to allow of being overlapped and concealed from view by some of the convo- lutions of the small intestine. In the corres- ponding regions of the left side the remaining portions of the colon are seen, and they too are very frequently, if not generally, closely applied to the posterior wall : in the lumbar region the descending colon is much more frequently in a contracted than in a distended state, and in the iliac region, not occupying it to the same extent as its fellow is occupied by the coecum, we find the sigmoid flexure of the colon winding its curved course over the psoas muscle, and sinking into the pelvis to assume the name of rectum. The lower convolutions of the small intestine invariably fill up the superior outlet of the pelvis, and are found to a greater or less extent in that cavity, in pro- portion as the bladder and rectum are empty or the reverse. Such being the position of the parts as they appear when the anatomist lays open the ab- domen in a recent subject, we proceed now to examine what parts are found in each com- partment of this cavity, and the relation which they bear to each other. We may observe, in passing, that there cannot be much difference in the position of the abdominal organs during life, even in the varied attitudes of the body, from that which we find them to possess in a body recently dead. Making allowance for the pressure which is maintained upon them by the abdominal parietes, it is obvious that the position of each organ during life will be higher in the abdomen than that which it occu- pies in the dead body; all the organs are more J firmly applied to one another and to the pos- terior wall of the abdomen. It is not, however, unimportant to bear in mind that such is the nature of the contents of the hollow abdominal viscera, and such the rapidity with which they become accumulated, that changes of relation may be rapidly effected. Thus the stomach, or any part of the intestinal canal, may by a rapid accumulation f of air or any other matter within it, occupy a much more extensive portion of the abdo- men than it usually does in the natural state. This is allowed by the extraordinary com- pressibility of the other viscera, a com- pressibility which is every day exemplified in i pregnancy, aud in cases of ovarian dropsy, j of ascites, &c. 1 . The epigastric region.— The right extre- mity of this region or the right hypochondrium is occupied almost entirely by the liver, which is connected with the diaphragm and anterior wall of the abdomen by the folds of perito- neum which form what are called the ligaments of the liver. When the left lobe of the liver is raised up, we see the lesser or gastro-hepaiic omentum extended between the lesser curvature of the stomach and the transverse fissure of the liver. A defined margin terminates the gastro-hepatic omentum on the right side, just adjoining the neck of the gall-bladder : if the finger be pushed underneath this margin from right to left, it passes through an opening which leads into the cavity of the omentum, and if continued downwards behind the stomach will separate the lamina; of the great omentum- This opening is commonly known under the name of the Foramen of Winslow : the lesser omentum bounds it in front, behind it lie the supra-renal capsule, the vena cava ascendens,and the psoas muscle, covered by a lamina of perito- neum which ascends towards the diaphragm.. CAVITY, 503 after having partly covered the duodenum.* The lesser splanchnic nerve will also be found in this situation lying on the quadratus lum- borum muscle and on the psoas, and descend- ing to throw itself into the renal plexus. On a plane posterior to the lesser omentum the inferior surface of the liver is in contact with the kidney, and with the angle of junction of the ascending and transverse portions of the colon, as is proved by the frequent adhesion of this intestine to the liver. The situation of the gall-bladder in this region demands atten- tion ; — its fundus corresponds to the cartilage of the ninth rib, beneath which it sometimes projects to an extent proportionate to the de- gree to which it is distended ; hence it is evi- dent that an unusually distended gall-bladder is not unlikely to form a tumour below the margin of the ribs presenting all the characters of an hepatic abscess.f The gall-bladder is, in this region, in close connexion either by its neck or body, with the duodenum or tranverse colon, a fact which explains the evacuation of gall- stones into either of those intestines. The left lobe of the liver projects more or less into the central portion of the epigastric region, or that which is called the proper epigastrium. Here it is in contact by its concave surface with the anterior superior surface of the pyloric half or third of the stomach. This latter viscus when contracted lies very far back in the epigastric excavation, and extends towards the left side, so as to occupy the left hypochondrium to a great extent. Its pyloric third or half is in contact with the liver, the remaining or cardiac portion is in contact with the diaphragm ; hence it is always the displaced organ in dia- phragmatic hernia. This close connexion of the stomach and diaphragm likewise explains the peculiar sonorousness which percussion frequently elicits over the left hypochondrium and even for some distance up the anterior surface of the thorax, so that when the sto- mach is large and flatulent, it is often very difficult to ascertain whether the sound pro- duced and heard in this region results from an effusion of air and liquid into the thorax, or from such a stomach filled partly with liquid and partly with air. When the stomach is full, the aspect of its superior surface is more directly upwards and less forwards than in the empty state ; but a considerable portion of the anterior part of this surface, as well as of the greater curvature, is in contact with the abdo- minal parietes. The great curvature of the stomach for three-fifths of its extent towards the pylorus is closely connected with the upper * Blandin records a remarkable case of internal strangulation which took place by the introduction if a considerable portion of the small intestine hrough the foramen of Winslow into the cavity of he omentum, from which it escaped through a acerated opening in the transverse mesocolon vhich firmly constricted a knuckle of the intestine tnd occasioned mortification of it. — Anat. Topoq. >. 442. r u t See cases recorded by Andral, Clin. Med. t. iv. md Graves, Dublin Hosp. Rep. vol. iv. surface of the transverse arch of the colon, and with the two anterior laminae of the great omentum which come in contact along the line of that curvature, enclosing between them the anastomosis of the gastro-epiploic arteries. Hence we sometimes find that, in cases of per- foration of the stomach, the opening is filled up by the adhesion of the wall of the colon to the serous coat of the former viscus, and the effusion of its contents is thereby prevented ; and it has been said that fluids may pass through an ulcer of the great curvature and be effused between the laminae of the omentum, so as to point externally as an abscess.* The extent of the relation of the stomach to the liver varies; in some instances it extends as far outwards as the gall-bladder ; and Cruveilhier mentions a case in which gall-stones were discharged into the stomach in consequence of an adhesion formed by its anterior surface with the gall- bladder. The stomach rests by its posterior and inferior surface on the superior lamina of the transverse mesocolon, which forms a natural floor to the epigastric region, and separating it from the umbilical region. Posteriorly the same lamina of the transverse mesocolon sepa- rates it from the inferior transverse portion of the duodenum and from the head of the pan- creas, which again are separated from the spine by the aorta and crura of the diaphragm. The lobulus Spigelii of the liver is seen behind, and to the left of the lesser curvature of the stomach, and when the latter is drawn down- wards and the liver forwards, this lobe projects, pushing the gastro-hepatic omentum before it ; the lesser curvature has likewise among its connections posteriorly the cceliac axis and solar plexus, and like the great curvature has an arterial anastomosis running along it formed by the superior pyloric and gastric arteries. The spleen is very intimately connected by the gastro-splenic omentum to the left extremity or great cul-de-sac of the stomach, and seems, as it were, moulded upon it, following it in its movements, and each accompanying the other in its displacements : behind this portion of the stomach are the tail of the pancreas, the left kidney, and supra-renal capsule. The point of entrance of the oesophagus into the cardiac extremity of the stomach is overlapped by the left lobe of the liver and its left lateral ligament, and it rests upon the decussating muscular bundles of the diaphragm.j- In the epigastric region we likewise find the first portion of the duodenum passing from left to right slightly upwards and backwards, terminating at the neck of the gall-bladder, with which it often contracts preternatural adhesions. Behind this superior portion of the duodenum, a little to the left of its ter- mination, the ductus communis choledochus * Ledran, quoted by Velpeau, Anat. Chir. t. ii. p. 165. t From the relations of the stomach to the abdo- minal parietes we are not surprised to read of fistu - lous communications being formed between that viscus and various regions of the abdominal surface. 504 CAVITY. descends to enter the middle portion of this intestine, the upper part of which is likewise found in this region. Here, too, we have the upper half of the head of the pancreas, the right gastro-epiploic and the gastro-duodenalis arteries. In proceeding to remove the parts which lie most superficially in the epigastric region, we notice on the right side the vessels and nerves enclosed between the laminae of the lesser omentum, viz. the hepatic artery and its terminal branches, the vena portae, and the hepatic and cystic ducts, with the com- mencement of the ductus communis chole- dochus, and entwining its filaments chiefly around the hepatic arteries is the hepatic plexus of nerves ; several lymphatic vessels of considerable size are also found here, and some lymphatic ganglions, the enlargement of which latter, whether acute or chronic, may retard the passage of the bile and give rise to jaundice. All these parts are invested and connected to each other by the dense cellular membrane called the capsule of Glisson. Behind the liver, and closely lodged in a groove, and sometimes a canal in its posterior thick margin, is the vena cava ascendens, which is still more intimately connected with the liver through the branches of the vena cava hepatica, which open into that portion of the ascending vein which is lodged in the groove. To the right of the vein are the supra-renal capsule and tlie upper part of the kidney, and to its left, and closely connected with the supra-renal capsule, is the semilunar ganglion. Here, likewise, are the renal or emulgent vessels and the renal plexus of nerves. In the centre of the epigastric region, on removing the stomach, we open into the lesser cavity of the peritoneum, of which the stomach forms, in part, the anterior and superior boun- dary. This cavity is bounded inferiorly and posteriorly by the descending layer of the trans- verse meso-colon, which covers the upper part of the pancreas ; above this latter gland is the coeliac axis, surrounded by the solar plexus of nerves, giving off its terminal branches, of which the hepatic passes towards the right side, and forwards to the transverse fissure of the liver, while the splenic directs itself tortuously towards the left side, along the upper margin of the pancreas. The pancreas itself is to be counted among the parts contained in this region ; here it is covered by the superior layer of the trans- verse mesocolon, which alone separates it from the posterior surface of the stomach ; hence this gland has sometimes, by contracting an adhesion with the stomach, served to fill up a perforation by an ulcer. Behind the pan- creas are the vena port® and the conflux of the splenic and superior mesenteric veins, the superior mesenteric arteiy, and the nervous plexus of the same name ; by all of which the gland is separated from the aorta, which, again, with the pillars of the diaphragm and some lymphatic glands, separates the pancreas from the spine. To the right of the aorta, and intervening between it and the right crus, are the thoracic duct and the vena azygos, and external to each crus of the diaphragm the great splanchnic nerve is seen to connect itself with the semilunar ganglion. On the left side the gastro-splenic omentum contains the vasa brevia and splenic arteries, the splenic plexus of nerves, and the com- mencement of the left gastro-epiploic artery ; the great cul-de-sac of the stomach, and the spleen cover here the left supra-renal capsule, the semilunar ganglion and great splanchnic nerve, the upper part of the left kidney, and the renal vessels and nerves. From the vast number and importance of the parts contained in the epigastric region, it cannot be a matter of surprise that it is fre- quently the seat of disease, and that the most serious consequences will often ensue upon strong pressure or violence inflicted upon it. It is universally known that syncope may he induced or even sudden death occasioned by a blow upon the epigastrium, even in a healthy individual ; and it seems to be the favourite opinion that such results arise from the influence exerted upon the immense nervous plexus which is found here. Sometimes, however, one or more of the viscera have experienced injury, and cases of rupture of the spleen, liver, gall-bladder, or duodenum from violence inflicted on this region are not uncommon.4 Every practitioner is familiar with the existence of epigastric pulsations, which, as they arise from a variety of causes, form a subject of great interest. Ur. Copland thus enumerates these causes, and, indeed, most of them may be deduced a priori from a knowledge of the anatomy of the region : a, nervous suscepti- bility; b, inflammation of the aorta ; c, aneu- rism of the aorta ; d, adhesion of the pericar- dium to the heart; e, tumours at the root of the mesentery ; f, tumours of the stomach or scirrhus of the pylorus; g, enlargement of the pancreas; h, hypertrophy of the heart, parti- cularly of its right side; i, enlargement of the inferior vena cava; k, hepatisation of the lower portion of the lungs ; /, enlargement of, or abscess in, the liver. f Umbilical region. — This region is distinctly and naturally separated from the epigastrium by the transverse arch of the colon and the transverse mesocolon. It is almost entirely occupied in the centre by the small intestines, and on each side by the colon, either ascending or descending. Deep seated and at the upper part of the region, we notice the inferior portion of the duodenum, which is covered by the infe- rior lamina of the transverse mesocolon, and ter- minates on the left side of the spine, just where the mesentery commences. The superior me- senteric artery crosses above and in front of the duodenum, a few lines to the right of its termination, and when the body is laid on the back the intestine seems to suffer a constriction1 from the artery. Such a constriction can hardly * See an interesting paper by Dr. Hart, in th' Dub. Hosp. Reports, vol. v. t Diet. Pract. Med. art. Ejiiyaslrium. CAVITY. 5«5 exist during life, when the viscera of the abdo- men are under the influence of the action of its walls, for then the direction of the superior mesenteric artery is so little downwards and so much forwards that it cannot be said to exert any pressure upon the intestine ; yet it is remarkable that in many cases of ruptured intestine, the seat of the rupture has been a very short way below the continuation of the duodenum into the jejunum. The inferior portion of the duodenum rests upon the vena cava and the aorta, and is in contact with these vessels by its posterior wall. The inferior margin of this intestine descends to very near the bifurcation of the aorta, leaving no more than from one-half to three-fourths of an inch interval. We notice, moreover, in this region the obliquity of the mesentery, the arterial and venous, nervous and lacteal ramifications existing between its laminae and the mesenteric glands or ganglions connected with the lacteals, which ganglions are often very few and much atrophied in old subjects. The convolutions of the small intestine are covered in front by the omentum, and are very closely in apposition with each other : hence they become ‘ matted together ’by the lymph effused in peritonitis, and hence, too, in per- forations, effusion of the intestinal contents by no means necessarily takes place. The looseness of the intestinal convolutions and of the mesentery by which those convolutions are tied to the spine, admits not only of their being liable to frequent introsusception, but also of being strangulated by the twisting of a knuckle of intestine. For the same reason it is that we find this intestine forming most of the herniae which protrude from the various regions of the abdomen. The small intestine occupies the whole central umbilical region, extending likewise on either side into the lum- bar regions and downwards into the pelvis. Thus it forms a considerable mass interposed between the anterior and posterior abdominal walls, and it is easy to conceive how, during an irregularly distended state of the intestine, violence applied to the abdomen in front can cause a rupture of a part of it without occa- sioning any solution of continuity in the wall of the abdomen. The laminae of the mesentery pass back- wards and outwards along the sides of the spine, and entering the lumbar regions become continuous with the right and left mesocolons. By their divergence in front of the spine they orm a triangular enclosure, the basis of which s formed by the bodies of the vertebrae. In his space we find the aorta, and lower down he primitive iliac arteries, the commencement >f the thoracic duct, the receptaculum chyli, ind several tributary lymphatics and lacteals vith their ganglions, the vena cava ascendens, md the left renal vein, the lumbar arteries and ems, and many nervous ramifications from he sympathetic, and more on the sides the umbar ganglia of the same nerve; here also 'e notice the fibrous insertions of the crura f the diaphragm, and the anterior common gamentof the vertebrae. Each lamina of the vol. r. mesentery, as it passes outwards, crosses over the ureter lying on the psoas muscle, and the spermatic artery with the accompanying veins, and some of the musculo-cutaneous branches of the lumbar plexus, and having entered the lumbar region, covers the right and left colons, forming, at its reflections on and off the intestine, the mesocolons. Each of these portions of the colon lies very nearly con- nected to the posterior wall of each lumbar region, having only the lower portion of the kidney, with its surrounding adeps, interposed above. In some instances a mesocolon does not exist, and the colon is bound down to the posterior wall of the lumbar region, so that the posterior surface of the intestine uncovered by peritoneum is in direct contact with the quadratus lumborum muscle or the kidney, having only cellular membrane or fat inter- vening, and this occurs much more frequently at the left than at the right side : hence the not uncommon occurrence of lumbar abscess, or renal abscess, or calculi being discharged into the colon, and so finding their way out by stool. The proximity too of the portions of the colon to the ureters serves, as Velpeau has remarked, to explain how pins, or beans, or pieces of lead find their way into the bladder and become the nuclei of calculi there, or being impeded in their progress through the ureter, the calculous matter concretes around them in that canal. In confirmation of this explanation, he relates a case which occurred at La Pitie. A pin, the head of which was still found in the colon, in which it had excited considerable ulceration, had passed also into the ureter, so that a calculus, of which the pin formed the axis, projected partly within and existed partly without the canal of the ureter.* Whether the mesocolons exist or not, the right and left colons are in general so fixed in situ, that they rarely form the contents of a hernial sac. Hypogastric region.- — The central portion of this region is occupied by the continued con- volutions of the small intestine. The right iliac region is in general entirely or almost entirely occupied by the coecum, which sometimes has a mesoccecum and sometimes not. In the latter case, a little reticular cellular membrane, and the fascia iliaca, are all that separate the intestine from the surface of the iliacus in- ternus muscle. Beneath the fascia the ilio- scrotal and the inguino-cutaneous nerves are seen passing outwards to their destination. The internal iliac artery and vein lie along the inner margin of the psoas muscle, covered by a thin fibrous expansion, which is a process fro m the iliac fascia, and deeply seated between the psoas and iliacus internus muscles is the ante- rior crural nerve. The external iliac arteries are crossed at their origin by the ureters, and along their course a few glands may be found either at the sides or in front. This region is one of great interest to the pathologist, in con- sequence of the frequent occurrence of disease * Velpeau, Anat. Chir, t. ii. p. 175. 2 L . CAVITY. •i06 in it, whether originating in the wall or in the coecum. There is no part of the intestinal canal in which accumulations are more likely to take place than in the ececum; and it is now pretty well ascertained by the researches of various observers that inflammation is often pro- pagated from the coecum distended with har- dened faeces to the cellular tissue and muscles of the iliac fossa, thus exciting abscess, which may open either externally through the abdo- minal parietes or internally into the ccecum * By careful manual examination of the anterior abdominal wall corresponding to this fossa, we are in general able to detect even a slight distension of the coecum, and percussion em- ployed here will often afford considerable assistance in forming a diagnosis. The ver- miform appendix of the coecum frequently hangs down into the pelvic cavity connected to the coecum by a fold of serous membrane ; at other times it lies in the iliac fossa, being folded up under cover of a projecting portion of the coecum, sometimes as a natural result, and at others as an effect of morbid adhe- sions. The left iliac fossa contains the sigmoid flexure of the colon, which from its cylindrical form, as well as from the circumstance of its being in general much contracted, does not occupy that region to the same extent as the right side is filled by the ccecum. The sig- moid flexure is here connected by a mesocolon similar to that of the descending colon, and its relations to the other parts contained in the iliac fossa are pretty much the same as those of the coecum on the right side. In the centre of the hypogastric region we observe that the posterior wall is formed by the last lumbar vertebra and the promontory of the sacrum, and this region is open below, whereby it com- municates with the pelvis through the superior outlet. Hence along the posterior wall we find therectum withits mesorectum,themiddlesacral artery, and the hypogastric plexus of nerves ; and some of the pelvic viscera under particular conditions pass forwards into this region, and even admit of being examined during life through the anterior wall. Thus the bladder under distension comes forward, and, as the distension increases, ascends, so as often to occupy the whole of this region to the ex- clusion of its natural contents; so also the uterus. The vas deferens in the male and the round ligaments of the uterus in the female, and in both the obliterated umbilical arteries, the urachus and the spermatic vessels, are also among the parts belonging to the hypogastric region. The preceding account of the abdominal cavity as it is found upon dissection, has re- ference chiefly to the adult male subject; but there are certain differences in the relations and positions of parts, dependent on sex and age, to which it is highly important to pay due * See Dance in Rep. Gen. d’Anat. et de Phys. t. iv. p. 74; Meniere, Arch. Gen. de Med. t. xvii.; and Ferrall, Ed. Med. and Surg. Journal. No. 108. attention. In the adult female, the chief dif- ference arises out of the great size of the pelvis and the consequent increase in the magnitude of the lower part of the abdomen, the trans- verse measurement of which will be found to exceed that of the epigastric region, more especially where that region has been arti- ficially compressed and consequently dimi- nished in its capacity, by the custom of wear- ing tight stays. During pregnancy, which, as being a natural change, may be not inap- propriately noticed here, the female abdomen experiences a very considerable alteration in its form, capacity, direction, the relations of its organs, and the order of its circulation. “ In the first month,” says Blandin, “ it seems to contract, and its walls to fall in upon themselves; but afterwards opposite changes take place. By reason of the resistance offered by the pelvis, when the uterus begins to in- crease, and especially when it has acquired a certain size, it makes, as it were, a protrusion, upwards, and is carried into the supra-pelvic part of the abdominal cavity, which it dilates, especially in front, in consequence of which the obliquity of the axis of that cavity for- wards is diminished. The dilated uterus is placed entirely in front, behind the anterior | abdominal wall, and presses the small intestine |, and omentum towards the spine : the omen- turn, however, is sometimes, though rarely, found in front of the uterus. The diaphragm |i is also pushed upwards and raised as high as the level of the sixth dorsal vertebra : all the peritoneal folds of the uterus are obliterated ; ji the peritoneum no longer descends into the j. pelvic excavation, the bladder and the rectum J; are strongly compressed, and are in some de- j, gree impeded in performing their functions;? the uterus itself is inclined to one side, in con- sequence of the projection of the vertebral i column, and generally to the right side, which, | according to Chaussier, is attributable to the greater shortness of the round ligament of the ,| right side. Notwithstanding all this enlarge- ment of the abdominal cavity, the viscera are compressed more strongly than usual, and canjj become protruded with greater facility, when the distended and attenuated walls have lost; much of their power of resistance. The nor- mal irritation of which the uterus is the seat, causes a greater afflux of blood into the whole inferior part of the vascular system, and into its own vessels in particular.”* During the development and growth of the, walls of the abdominal cavity some interesting changes are observed to take place in its shape capacity, and in the positions of the container viscera. The most remarkable characteristic o the abdomen at the earliest period is its ver great capacity when compared with the othe3 cavities; this arises from thegreatdevelopmentc its contained organs. This great size, howeve^ is manifest entirely in die umbilical region, fc neither the epigastric nor the hypogastric ca be said to exceed their proportional magnitud in the adult. On the contrary, both thesj * BlanJin, Anat. Topog. p. 431. CAVITY. regions are proportionally much smaller than in the adult; the epigastric, in consequence of the contracted diameters of the thorax, but more particularly in consequence of the small size of the vault which is formed by the diaphragm ; and the hypogastric by reason of the imper- fectly developed state of the pelvis. Hence, then, we find that most of the viscera extend more or less into the middle or umbilical region, which thus exhibits a very great en- largement. The liver is the viscus which exhibits the most remarkable degree of enlarge- ment; its two lateral lobes present but little difference in size, it extends laterally so as to occupy nearly the whole epigastrium, leaving but a small space at the left side for the stomach and spleen ; it passes considerably beyond the inferior margin of the ribs, so that a great portion of it is found in the umbilical region, extending even to the hypogastrium. This great extent of space occupied by the liver necessarily causes corresponding altera- tions in the positions of the neighbouring vis- cera, and of none more than the'stomach. The direction of this organ is nearly perpendi- cular, its pyloric extremity is found a little to the right in the umbilical region, while the aspect of its splenic end is upwards and to the left; its great curvature looks to the left side and downwards, and its lesser cur- vature to the right and upwards. The spleen is not altogether contained in the left hy- pochondrium, but also extends into the left lumbar region, and may be felt below the false ribs. The duodenum does not change its positive situation with reference to the spine, but, in consequence of the position of the stomach, its curves are more marked, the superior portion passes more decidedly up- wards, and the whole duodenum is to a greater extent covered by the stomach. The rest of the small intestine is crowded backwards against the spine, and in consequence of the non-deve- lopment of the pelvis is found entirely in the umbilical region ; nor is it covered by the omentum, which as yet has attained but a very small size. At this early period, moreover, the bladder is an abdominal viscus ; in general, very capacious and of a cylindrical form, it extends out of the pelvis to within a very short distance of the umbilicus, to which it is con- nected by the urachus, so that it occupies a considerable portion of the hypogastric and a small part of theumbilical regions ; consequently, as Portal remarks, the shortest route by which the bladder can be reached at this early age is according to the method of the suprapubic operation, and it is only a small portion of the neck of the bladder which is at all in relation with the perinaeum. A considerable portion of the rectum, also, is found in the hypogastrium, and in the female the uterus and ovaries and the Fallopian tubes. Prior to the seventh or .eighth month of intra-uterine life, when the tes- ticles enter the scrotum, they are found suc- cessively as they descend in different regions of the abdominal cavity, at first in the lumbar regions immediately beneath the kidneys, and hen at different heights along the inner side of 507 the iliac fossae ; we also observe here that pro- cess of peritoneum connected with the testicle, and extending from it to the inguinal canal, which is known by the name of the diverticu- lum of Nuck : a similar process exists in a much less developed condition in the female connected with the round ligament. The prin- cipal difference observable, as regards the large intestine in the fcetus at its full period, consists in the great curvature of that portion of it that is found in the left iliac region, occasioned by the narrowness of the pelvis admitting but a small part of the rectum.* In the progressive development which takes place during intra- uterine life, the position of this as well as of the other portions of the intestinal canal presents dif- ferences which it does not belong to the present article to examine. (See Intestinal Canal.) The capacity of the abdominal cavity and the position of some of its contained organs, as they thus exist in the fcetus at its full period, continue pretty nearly the same for some time after birth. The enlargement, however, of the vault of the diaphragm increases the capacity of the epigastrium, while the gradual diminu- tion of the liver affords room for the passage of more organs from the umbilical region up- wards, and the stomach is allowed to take a more horizontal direction. These changes, which are gradual in the periods of life prior to puberty, become most manifest when the arrival of that period gives rise to the enlarge- ment of the pelvis ; then the umbilical region is as it were relieved from its overloaded state ; the belly is less prominent, for the bladder now occupies its proper place in the pelvic cavity; the rectum, too, sinks into it, and many of the convolutions of the small intestine are found in it: thus, by the enlargement of the hypochondria in the first instance, and subse- quently by the development of the pelvis, the three subdivisions of the abdominal cavity assume those proportions in their respective magnitudes which are characteristic of the adult period. In considering the probable amount of in- jury inflicted by wounds which may have pene- trated the abdominal cavity, we must take into account the changes which the different atti- tudes of the body occasion in the positions of the viscera. These changes cannot be exten- sive, and only regard the position of each viscus with reference to the whole cavity, the relations of that viscus to the neighbouring ones being unaltered, or nearly so. They take place in obedience to the law of gravitation, and it is so easy, by a little reflection, to de~ duce what the changes must be, keeping in mind the various means made use of to limit and prevent displacement, that it seems unne- cessary to do more here than allude to the fact that the viscera are altered in position under the influence of such a cause. Abnormal conditions of the abdomi- nal cavity. — All the abnormal conditions of * See on this subject Portal, Anat. Med. tom.^v. Blandin, Anat. Topog. and Meckel, Anat. Gen. Desc. et Path. tom. ill. •2 l 2 508 CAVITY. the abdomen may be considered under two heads : 1 . as they regard the parietes of the cavity; and, 2. as they refer to the positions of the contained organs. We shall first examine the abnormal conditions of the parietes. Congenital malformations oj' the abdominal parietes. — The first class of these malformations which demands consideration is that which de- pends on a defect in the development of the structures which form the abdominal walls, and these are by far the most numerous. In ex- amining them it is to be borne in mind that many of the abdominal viscera exist before the walls of the cavity, which are formed around the viscera, and that the anterior wall is later in its formation than any of the others. The ca- vity containing the viscera seems at first to be a continuation of that of the umbilical cord, its walls being continued from the sheath of the cord. A distinct separation does not appear to take place until the skin has become deve- loped, when a line of demarcation is evident between the skin of the abdomen and the sheath of the cord. The anterior wall may be deficient on both sides to a greater or less extent, the lateral and posterior being also more or less involved. The maximum is when the defect extends not only throughout the whole anterior abdominal wall, but also to that of the thorax, leaving all the viscera of both abdomen and thorax visible, being covered only by a thin membrane ; and frequently congenital deficien- cies of the lower part of the anterior wall of the thorax are accompanied by a more or less ex- tensive defect of the upper part of the same wall of the abdomen, and the heart is included with the abdominal viscera, which are rendered visible, and which, in some instances, protrude forwards. There may, however, be a con- genital deficiency of, or fissure in the deeper seated elements of the anterior abdominal and thoracic wall, and yet the skin remain per- fect and cover the protruded viscera.'*' But the thoracic parietes may be perfect, and yet there may exist an imperfect condition of the abdominal parietes to a greater or less extent, which imperfection evidently results from the continuance of a greater or less portion of the abdominal wall in that condition in which it naturally exists in the early stages of fcetal development. In such cases the viscera are covered by an expansion which is continuous with the sheath of the umbilical cord. When the deficiency of the abdominal wall exists to a great extent, the tumour formed by the pro- truding viscera is designated by the term even- tration ; but if the defect be very limited, and exist, as it generally does, at the base of the umbilical cord, then the protrusion is an exom- phalos or congenital umbilical hernia. Both, as Isidore Geoffioy St. Hilaire remarks, are results of an arrest in the development of the abdominal walls, with this difference, that in the former the cessation of development takes * See Geoffroy St. Hilaire’s description and plate of an hyperencephalous foetus : Monstruosites Humaines, pp. 183 & seqq. plate 15. place at an early period of foetal existence, but in the latter at a late period. In conformity with the same laws, under the influence of which the arrest of development took place, we find that, as in the progress of the natural formation, the small intestine is the last to enter the abdominal cavity, so a larger or smaller portion of that intestine is generally found in the tumour of a congenital exom- phalos. The nature of the contents of an eventration depends evidently on the extent of the deficiency and the region of the abdomen which is most involved. In some instances the peritoneum is deficient to an extent corresponding to that of the defi- ciency of the abdominal parietes. This is a rare occurrence, and is generally met with where the defect of development is very extensive.* There are cases, however, where, although the defect was small, the peritoneum was absent to a corresponding extent, and the intestines protruded through the opening in a naked state.f The congenital inguinal hernia must likewise be referred to an arrest in the development of a very small portion of the anterior abdo- minal wall. The canal of communication which at one period exists between the peri- toneal sac and the sac of the tunica vaginalis remains pervious, the natural process by which j it is closed having been arrested. This mode J of explaining the formation of congenital bubo- nocele does not preclude the possibility of its accidental occurrence, the material which closes the canal having given way under the influence of some force applied to it. The superior wall of the abdomen sometimes presents a defect of development, giving rise to the congenital perforation of the diaphragm, through which hernia; take place into the thorax. Such a perforation may exist on either side, although it is much more frequently found upon the left. (See Diaphragm.) The malformation commonly known under the name of ‘ extroversion of the bladder,’ has also connected with it an imperfect state of the anterior abdominal wall inferiorly, in conse- quence of the separation of the ossa pubis and of the recti abdominis muscles, and I be- lieve, in general, the absence of the pyra mi- dales. (See Bladder, Abnormal Anatomy.) In these cases the umbilicus is generally situ- ated much lower than usual, and some writers have fallen into the absurd error of supposing that it was absent altogether, in consequence * See a case by Ruysch, (observat. Ixxii.) in which the stomach, intestines, and spleen were situated externally to the cavity of the abdomen. Also one by Robinson, in which the defect ex- tended from the abdomen to the umbilicus. Amer. Journal of Med. Sc. Feb. 1833, p. 346; and a very interesting and well-narrated one by my learned friend Dr. Montgomery, in the Trans. Coll. Pbys. Dub. vol. i. New Series. See also several othercasea referred to in Meckel, Handbuch Der Patbol. Anatomie, Hand. i. p. 97 — 139. t See Fried, de feetu intestinis plane nudis extra abdomen propendentibus nato, in SandifortThesaur. dissert, t. i. Also Howell, in London Med. and Phys. Journal, vol. xlv. 1821. CELLULAR TISSUE. 509 of its having escaped their notice by being covered and concealed by the protruded blad- der. A second class of congenital malformations of the abdominal parietes arises from an excess in the development of certain parts, as a nu- merical increase in the muscles, vessels, or nerves entering into the formation of the abdo- minal parietes, or from the development of a part of a second foetus in connexion with the abdomen. Of the former it is extremely rare to meet with instances among the muscles or vessels of the abdomen ; occasionally we do find an unimportant increase in the number of the costal attachments of one or more of the muscles. As to the latter several cases are recorded in which foetuses exhibited an arm or leg, or even a portion of the trunk of another implanted upon the abdominal wall, or, as is a very rare occurrence, included in it; con- stituting a subdivision of that form of mon- strosity which has been called Diplogenesis. We refer to the article Monstrosity for details on this subject. Morbid conditions of the abdominal parietes. — These are such as are common to all parts compounded of the same elements as enter into the formation of the abdominal walls, which it would be superfluous to particularise here. Congenital malformations of the abdominal cavity. — In many acephalous foetuses the ab- dominal cavity is more or less curtailed of its due proportions, the deficiency existing at its superior part. Where the inferior part of the thorax or the pelvis is malformed, the abdo- minal cavity wdl also be necessarily more or less affected. Under this head we may refer to the ano- malies which arise from the congenital mal- position of the viscera, which may extend to the whole contents of the abdomen, or may affect only one or more viscera. Such are the cases of complete transposition of the viscera, where those which in the normal state are on the right side are found upon the left, and vice versa; thus the liver is found on the left, the pylorus on the left, the cardiac extremity of the sto- mach and the spleen on the right, &c. &c. The aorta and vena cava too change places, and the openings in the diaphragm alter their po- sitions along with the parts which respectively pass through them. The same transposition generally extends also to the thoracic viscera. In many of the instances in which this trans- position has been observed, the individuals have lived to the adult period of life without ex- hibiting any symptom indicative of the unusual position of the internal organs.* Single viscera are likewise often found trans- posed or in unusual positions, occasioning necessarily corresponding changes in the parts which are connected with them. It is unne- cessary to allude further to them here, as they * See Metzger de Translocatione Viscerum,1779 ; also instances in Haller, Op. Minora, t. iii. ; and several cases of modern date, of which one of the most complete is that published by Bryan in the Transactions of the Irish College of Physicians, vol. iv. will be treated of in the articles appropriated to those viscera. The morbid conditions of the abdominal cavity are the results of disease affecting its lining membrane or its contained viscera and other parts intimately connected with it. See Peritoneum and Intestinal Canal. For the Bibliography see that of ABDOMEN and Intestinal Canal. (R. B. Todd.) CELLULAR TISSUE.— Tela cellulosa, textus mucosus, corpus, cribrosum, cellular mem- brane, reticular membrane, filamentous, areolar, laminar tissue, &c. (Fr. tissu celluleux ; Germ. Zellgeweben.) The cellular tissue is the most universally diffused element of organization, and constitutes the basis of every animal body. It consists of a soft, areolated, and elastic sub- stance. A somewhat similar structure also exists in vegetables, constituting their most simple or elementary texture. In systematic works the cellular tissue is generally considered as a solid substance ; but as it really exists in the animal body, it is a compound of solid and fluid materials ; for in no part of any animal is the cellular membrane ever entirely devoid of fluid. This union of fluid and solid parts is indeed indispensable to organization, since there is no animal, or even vegetable, in which it may not be demonstrated. In the zoophyte the entire body appears to consist of the cellular tissue, and even in man it enters so largely into the formation of the different organs, pervading equally the most delicate and the most solid parts, that it con- stitutes a species of mould of the whole body and of its individual parts ; indeed, if we ex- cept the enamel of the teeth, and, as some authorities contend, also the nails, the hairs, and the epidermis, there is no solid in which it may not be detected. Many anatomists have included the adipose tissue under the general denomination of cel- lular membrane, but as the vesicles of the former are distinct from the cells of the latter, both as regards their formation and the nature of their contents, we rather incline to adopt the views of Malpighi, W. Hunter, Beclard, and others, who contend that the adipose and cellu- lar tissues are distinct and separate structures. (See Adipose Tissue.) Arrangement. — The most striking and im- portant fact relative to the cellular tissue is its uninterrupted continuity throughout the whole body, there being no part or region, however insulated it may appear to be, in which this communication may not be demonstrated. Whilst we fully admit this general communica- tion, it is yet necessary to state that the cellular tissue may be appropriately divided into two parts: the first division, called from its dis- position the common or interstitial portion ( textus cellularis intermedins vel laxus ), is that which occupies the spaces left between the various organs in all parts of the body ; the second division is distinguished by the name of the special cellular membrane ( t. cellularis CELLULAR TISSUE. 510 striclus, t. cellularis stipatus ), because it is proper to the several constituent parts of the body, investing each of them, and penetrating into their internal structure. Of the common cellular membrane. — It is in this division that the connection to which we have just referred is most free. Thus in the subcutaneous tissue placed between the skin and the fasciae of the muscles, there is an uni- versal and evident communication. Again, in the head, the cellular membrane of the exter- nal parts communicates with that of the internal through all the natural apertures — through the foramina of the base and other regions of the skull. From the face and cranium the con- nexion may readily be traced to the neck, whence, after having pervaded all its parts, it passes in one direction behind the sternum and upper ribs to the thoracic cavity ; and in another underneath the clavicle and scapula on either side, to the arm-pit, which may be re- garded as the common point of junction be- tween the cellular substance of the neck, the trunk, and upper extremity. The cellular tissue of the thorax is continuous with that of the abdomen through the openings of the diaphragm, and particularly beneath the sternum, around the aorta, the inferior vena cava, and the oesophagus. In a similar manner the connexion may be followed from the abdo- men to the pelvis ; from the former of these cavities under the crural arch to the inguinal region, which constitutes the point of union between the trunk and the lower extremity ; whilst from the pelvis the communication ex- tends in one direction by the side of the rectum and urethra to the perineum, scrotum, and penis ; and in another by the obturator fora- men and the ischiatic notch to the thigh. In addition to these, which are the principal connexions, the common cellular membrane is united in every direction with the special di- vision ; the details, however, of these commu- nications belong to the descriptive anatomy of the several regions, to the articles on which the reader is referred. The quantity of the interstitial tissue varies according to the age and temperament of the individual, and to the region of the body in which it is examined; but, independently of any original differences which exist, it is well known that the mode of living and habits of the individual have a great influence in this respect: thus an habitual full diet, especially if con- joined with indolence, causes a great accumu- lation of the cellular substance ; whilst, on the contrary, a spare or moderate diet and exercise will reduce it in a remarkable degree. These differences depend, probably, more on the accu- mulation of serous fluid and on the repletion of the bloodvessels, than on the actual increase of the proper filamentous tissue : we can in this manner, and in no other, understand how, by by what in England is called training, the bulk of the body may be so rapidly diminished. The proportion of this tissue varies also in the different regions of the body ; but as it is in an especial manner subservient to the pro- duction of free motion, it is principally accu- mulated in those parts which are most move- able. It is on this account that it abounds on the face, especially around the globe of the eye and about the cheeks, and also on the forepart of the neck and of the trunk in general. In the limbs it is met with in considerable quantity in the flexures of the joints, in the axilla, the elbow, the wrist, and in the palm of the hand; also in the groin, in the ham, in the front of the ankle, and in the sole of the foot. The super- ficial muscles, which are very moveable, are separated from each other by thicker layers of membrane than the deeper-seated and more fixed. It may also be remarked that those important organs, which are most liable by their structure or connexions to rupture or other effects of external violence, are carefully pro- tected by being lodged in a large quantity of cellular substance. It is thus that we find the pancreas and the kidneys enveloped in this tissue in the abdomen ; the bladder and genital organs in the pelvis ; and the bloodvessels and nerves in all parts of the body. Of the special cellular membrane. — Each organ in the body is invested in a proper cover- j ing of the cellular tissue, and also receives into its interior, processes which envelope and join together its component parts. The investing cellular membrane (t.cellu- I laris strictus ) is united by one of its surfaces, the external, with the general cellular tissue, and by the other or internal with that entering || into the organ. It presents many peculiarities | as to the mode of its connexion ; the solid parts, for instance, as the glands, muscles, and nerves, are entirely surrounded by cellular envelopes ; and a somewhat similar disposition ! is observed around the bloodvessels, lympha- i tics, and excretory tubes. On the contrary, the skin, the mucous and serous membranes, !; having one surface free or unattached, are only connected on one side with the cellular tissue, jj which is distinguished according to its situation, by the terms subcutaneous, submucous, and subserous cellular tissue. The covering thus afforded to each individual organ serves in a certain degree to insulate and separate it from the surrounding structures, and in this manner it often tends to limit the progress of disease; but as we have just seen that this covering is united both to the interstitial and to the pene- trating cellular tissue, it would be equally con- trary to reason and experience to expect that a should constitute, as some authorities have con- tended that it does, a species of atmosphere ji around the various organs, confining their natu- ral actions and morbid phenomena. The penetrating cellular tissue (t. cellularis^ stipatus) constitutes so essential a part of organized structures, that there is no organ in which it may not be detected. It exists in the substance of bone, cartilage, and ligament, although it is distinguished in these structures with difficulty, in consequence of their great density ; it penetrates between the most minute fibres of the muscles and nerves ; between the coats of the bloodvessels and lymphatics ; also between the layers composing the skin and mucous membranes; and lastly, it enters into CELLULAR TISSUE. 510 the substance of the absorbent and secreting glands, investing their several component parts. Structure and organization. — If a portion of cellular tissue void of adipose substance be ex- amined with the naked eye, and for this purpose that which intervenes between very recent muscu- lar fibres may be advantageously selected, it will be seen that it is composed of an immense num- ber of delicate and semi-transparent filaments, having very much the appearance of the finest threads of a spider’s web. These fibrils cross each other in various directions, and in this manner intercept innumerable spaces, which communicate one with another, and exhibit a vast variety of figures. The small spaces or areolae which are thus produced constitute what are called the cells of this tissue ; but as there is nothing determinate either in their size or shape, which evidently vary according to ihe degree of traction exercised in separating the filaments ; as they communicate together, and consequently are not circumscribed ; as they are in fact simply the interstices left between the fibres, the expression in common use is calculated to convey an erroneous idea of the real nature of these spaces. If the investigation be prosecuted with the aid of a powerful microscope, a very beautiful appearance will be presented, of which it is impossible to convey an adequate idea by any description. We shall still observe fibres cross- ing in all directions ; but although I have had many favourable opportunities of making these observations, I have never been able to detect in the cellular fibre that linear arrangement of globules described by Dr. Milne Edwards, and which has of late years been very generally supposed to pervade all the elementary fibres of the body. A number of globular particles may, it is true, be seen at irregular distances, either clustered together or dispersed in an isolated manner, but they do not enter into the forma- tion of the fibre. The results, then, of careful inspection disprove the ideas of former anato- mists, some of whom, Ruysch and Mascagni for example, supposed that the cellular fibre was entirely vascular, whilst others imagined it to be an expansion of the nerves : it is now generally admitted that the basis of the cel- lular substance is a solid and elementary fibre; and although to the naked eye it often presents a membranous form, yet microscopical observa- tion evinces that the plates of membrane are distinctly composed of solid fibres. The in- terstices or cells always contain in health a very thin albuminous fluid, which has a great resemblance to the secretion of the serous mem- branes, and also to the serum of the blood ; and hence it is often termed the cellular serosity. This fluid, which must be regarded as an in- tegrant part of this tissue, has a great influence on its properties, so that if it be entirely re- moved, as by desiccation, the membrane be- comes hard and brittle, and its elasticity is almost lost ; or if it be accumulated in excess, as we often see it in disease, the elastic force is also destroyed. Bloodvessels and lymphatics. — An inquiry into the relations which exist between the cel- lular and vascular tissues, would lead to the important question, how far vascularity is essen- tial to organization? Without entering into this investigation, it may be remarked that the cellular substance is provided with blood- vessels; and although the greater number of these merely traverse the membrane in order to reach other parts, yet the phenomena of nutri- tion and absorption shew that a vascular appa- ratus must exist in connexion with the cellular tissue. Nerves. — It is impossible to trace any ner- vous filaments to the cellular fibres, although such threads may be seen passing between them to the neighbouring organs. The insensibility in its healthy state also seems to indicate the absence of nerves; but as pain is experienced during inflammation, we must admit the ex- istence of some communication with the senso- rium. Chemical composition. — The cellular sub- stance contains, like all the soft solids of the body, a large quantity of water: when this is evaporated, the fibres and cells adhere to each other, and present a membranous appearance. Analysis shews that albumen and gelatine com- pose this substance; the former predominating, and being in a state of coagulation, bestows on it the necessary degree of firmness and re- sistance. Properties. — As we shall have occasion in a future article (see Membrane) to consider this subject more minutely, it will suffice if we here remark that the most important property of the cellular substance is a species of contrac- tion which produces in all the soft parts a con- stant state of tension or tone, which is one of the most remarkable qualities of living bodies. The cause of this peculiar condition, in what- ever part it is evinced, — in the skin, in the cellular tissue, in the muscles, in the vessels, &c. — is the result of a property inherent in mem- branous matter, which some authorities refer to muscular contractility, and others to elasticity ; whilst many eminent physiologists, denying both these hypotheses, conceive that the con- traction to which we are alluding is of a character sui generis, and which they have called tonicity , vis cellulosa, tonic contraction, contractility of tissue, &c. I confess that none of these theories have ever been to me satisfactory ; because, as regards the first, there is no resem- blance between the phenomena connected with the contraction of membranous parts, and those of muscular contraction ; whilst, as respects the second, the resiliency by which the skin re- covers itself after pressure has been made on the external surface, and the retraction and separation of the sides of an incision inflicted on the integument, being observed only during life, and never after death, prove that the results of cellular contraction are, in some important respects, different from those of common elas- ticity. Those writers who, in consequence of the difficulty of referring the phenomena under consideration to either of the known causes of contraction, viz., muscular contractility and elasticity, have imagined the existence of a new kind of contractile power, have> without ad- 512 CELLULAR TISSUE. during any sufficient proof in corroboration of their views, had recourse to an expedient but too frequently adopted by physiologists when the real nature of any vital process escapes their detection. The only way in which the apparently con- tradictory results of experiment and observation can be reconciled, is by attending to a combina- tion of vital and physical processes, that has been too much neglected in investigating the characters of living bodies ; that is to say, it must be recollected that “ life,” to borrow the philosophic expression of Dr. Arnott,* “ is a superstructure on physics and chemistry,” and that those phenomena which are essentially de- pendent on the ordinary laws of matter are controlled and modified by the superior prin- ciple of life. In the case of the cellular sub- stance this remark is peculiarly applicable ; and from reflecting on all the facts relative to that tissue both in a state of health and disease, I have arrived at the conclusion that the phe- nomena of its contractile force are the com- bined results of one of the common proper- ties of matter, viz., elasticity; and of a vital process, viz., nutrition. It is a well-known fact that the existence of elasticity in any inor- ganic substance requires a particular state or arrangement of its particles, and that if the necessary condition be but partly fulfilled, or be entirely wanting, that property is only slightly displayed, or is totally absent. The same principle strictly applies to the living- body; and in the cellular substance the required condition is, a definite proportion between the solid fibres and the interstitial fluids, which state is maintained by the agents of the circu- lation and secretion, namely, the bloodvessels and lymphatics. Any thing which interferes with this proportion, either the excess of fluids, as in anasarca or phlegmonous erysipelas, or the diminution of the humours, as in old age and in many diseases, will impair or destroy the phenomena observable in the sound state of the cellular membrane, and will explain in the former case, th e pitting which is seen on making pressure on the skin ; and in the latter, that flabbiness and wrinkling of the integument about the face and other parts of the body, so characteristic of those advanced in life or re- duced by disease. We can in this manner understand how a class of phenomena may be dependent on a physical property, and yet be modified by the condition of the vital powers, so as to become impaired by disease, and destroyed by death. The exhalation and absorption of which the cellular substance is the seat, have been sup- posed by many high authorities to be effected by its elastic contractility ; but it is probable that these phenomena, although in part de- pendent on that property, are principally pro- duced by the power of imbibition, which, ac- cording to the experiments of MM. Magendie and Fodera, exists in all the soft parts of the body. Functions. — The offices accomplished by * Elem. of Physics, Introd. p. xxvi. this substance in the economy seem to be, first, that of uniting together the various constituent parts of the body, and of keeping them in situ by its contractile force ; secondly, of facilitating their movements by means of its lubricating fluid, and thus preventing the injurious effects of friction and concussion ; and lastly, of fur- nishing an appropriate structure for their recep- tion. It has also been supposed that, being a bad conductor of caloric, it will tend to pre- serve the uniform temperature of the body. Development. — The first trace of an organized substance observed in the embryo consists of a very soft and pulpy cellular tissue, which at this early period is loaded with fluid ; and being homogeneous in its nature, it presents neither fibres nor interstices, although it may be readily permeated by air or liquids, so as to produce small cells, and may likewise be drawn out into glutinous filaments. In proportion as the several organs become developed, itacquires greater consistency, and is at the same time diminished in quantity. At the period of birth it is still, however, in a very soft and imperfect state, and only acquires its proper density by slow degrees; in old age, being deprived of a large portion of its fluid, and perhaps otherwise deteriorated, it loses much of its elastic force; and this circumstance, joined to its diminished bulk, is a principal cause of that loss of rotun- dity so conspicuous in the bodies of aged persons, and of the flabbiness of the several organs. The power of reproduction is greater in this than in any other tissue, so that it is not only readily formed again within certain limits when j, it has been destroyed, but it even appears to supply the place of other and dissimilar struc- | tures which may have been lost by disease. The cellular substance presents but few -mo- difications of importance when examined in the different classes of animals, except, indeed, || that it is generally believed to constitute the entire body in those species that are placed at the bottom of the scale. The Porifera afford an example of the simplest form of the cellular tex- ture with which we are at present acquainted ; the body of these animals consists of a soft gelatinous substance composed of translucent || globules, which, however, are not perceptibly joined together ; so that there is in this instance nothing of that fibrous structure, which is the great characteristic of the cellular membrane in the human body and in the higher orders of ani- mals. In the semifluid and jelly-like body of the Polypifera and of some of the Acalephae, there is merely a pulpy substance, which, although ;t may exhibit a distinct digestive cavity, and even tubes communicating with this, yet no mus- cular tissue has hitherto been discovered. In these animals, however, rapid movements are seen in the cilia ; and the tentacula, when pre- sent, together with the entire body, are capable of spontaneous motion ; it is evident, then, in these and other instances, that if, as is gene- rally supposed, there be an absence of muscles, the cellular tissue must be endowed with a pro- perty totally wanting in that substance as it exists in the higher animals. When it is con- CELLULAR TISSUE. 513 sidered how little is known respecting the real structure of the Infusoria, Zoophytes, &c., and when the numerous discoveries which have of late years been made in these and much higher animals, of parts whose existence was formerly doubted or denied, are recollected, we shall be inclined to think that there are special organs of motion provided ; for it would be in direct oppo- sition to the simple but constant laws observed in the animal creation, were the organic tis- sue, entitled the cellular, to acquire in the lower classes a power of contraction, which in the higher it does not possess, and which property is the endowment of a totally distinct system of organs, namely, the muscles. Whichsoever of these opinions be correct, there is no doubt that in the least perfect animals, a soft and gelatinous matter, analogous to the cellular tissue, and loaded with fluids, greatly predominates. As we advance in the scale, it is found that organ- ized substances of a diversified character are developed in the nidus afforded by this cellular texture, the proportion of which to the other structures becomes thus diminished. Morbid conditions of tiie cellular tissue. — As the cellular membrane is so in- timately united with all other organs, it is very liable to be involved in diseases commencing in these parts ; but morbid action also very frequently arises primarily in this tissue. It is subject to — 1, inflammation, acute and chro- nic, circumscribed and diffused; to the effects of inflammation, thickening and induration, suppuration, ulceration, and mortification; 2, in- filtration of blood, serum, air, and occasionally of other substances, as urine; 3, induration, occurring in new-born infants ; 4, morbid growths, such as fibrous productions, cysts, melanosis, scirrhus, vascular sarcoma; 5, foreign bodies ; 6, preternatural increase or hypertro- phy, and degeneration, or atrophy. I. Inflammation. — -This tissue is very fre- quently affected by inflammation, which may either present itself under the form of a distinct affection, as when it attacks the subcutaneous cellular membrane especially, or it may- occur as a part of some other disease, as when inflam- mation of the parenchyma of the lungs, liver, &c., spreads to the cellular tissue in which this substance is universally involved. a. Acute circumscribed inflammation, or phleg- mon.— The anatomical characters of this form of inflammation of the cellular substance are essentially the same in whatever part of the body it may arise, either in the subcutaneous tissue, or in that part which penetrates into the interior of the various organs ; it will, therefore, be proper to trace the effects of it in a general manner. 1 Congestion of the bloodvessels. — The ef- fects of irritation on the capillary vessels, in which the phenomena of inflammation are prin- cipally observed, may be beautifully seen with the aid of a sufficiently powerful microscope in the transparent membrane of the frog’s foot. After having familiarized the eye by watch- ing the circulation for a short time, we shall find that the first effect produced by the appli- cation of an irritant is a distinct and evident acceleration of the blood’s motion. I have not been able to satisfy myself of that diminution of the calibre of the vessels which is said by some observers to accompany this acceleration. If the irritation be repeated, or if its power in the first instance were considerable, it will be seen after a certain time that the capillary ves- sels become dilated, that the blood moves more slowly, and often that it oscillates and circulates apparently with difficulty ; its constituent parts become less distinct, the particles being crowded together. If the effects of the irritation now subside, the dilated vessels contract and recover their proper calibre, the blood again moves more freely, and the circulation regains its natural state ; but, on the contrary, if the mor- bid action still persists, the membrane begins to grow opaque, either in consequence of the engorgement of the vessels, or, as it has appeared to me, from an extravasation of one or other of the constituents of the blood ; or, lastly, the circulation altogether ceases, the vessels are further enlarged, the blood is stagnant, and is evidently deteriorated in quality, and the colour becoming deeper and deeper, is at length per- fectly brown, or even black. This is the order in which the phenomena in the derangement of the circulation occur ; and although they have been more particularly studied in microscopical observations on the lower animals, yet many of them are daily to be observed in the human body during the progress of inflammation. Whilst the inflammatory action is confined to the first of the above stages, in which there is merely a preternatural excitement of the circu- lation, it may be arrested and put an end to without any further morbid change ; and this may even happen in the second stage, where the blood, although accumulated and retarded in its motion, still circulates in its proper ves- sels. This speedy termination of the disease has been called by the French writers deli- tescence. 2. Effusion. — When the bloodvessels are greatly congested and dilated, it usually hap- pens that a part of their contents escapes, and the cellular tissue becomes loaded with coagulable lymph, more or less tinged with blood accord- ing to the vascularity of the affected part, pro- ducing that condition which has been called red induration. This substance, by agglutina- ting together the fibres and layers, causes the hardness which is so perceptible on pressing the diseased part. At the same time that this solid deposition takes place in the centre, it is found that the circumference of the inflamed part is soft and oedematous, in consequence of the cells being distended with a fluid which appears to be the serum of the blood. Although the cellular tissue is rendered more firm to the touch by the effusion of lymph, yet, as happens in the other organized structures of the body when attacked by acute inflammation, the co- hesion of its fibres is diminished, and it is, con- sequently, more easily torn than in its natural state, and its elasticity is also greatly impaired. The preceding changes may be very beautifully observed in the progress of pneumonia, when the substance of the lungs is passing into that 514 CELLULAR TISSUE. condition which is called red hepatization. I have in my possession a specimen of com- mencing hepatization, taken from a lung in another portion of which that change was quite complete. In this preparation a portion of the pulmonary tissue is of a reddish brown colour, and evidently infiltrated with a solid substance, consisting, it may be presumed, of fibrine mixed with the colouring matter of the blood. The manner in which this deposition took place in the cellular tissue of the organ is distinctly seen, the reddish colour being gradually shaded off till it is lost in the healthy structure. It sometimes happens that the morbid action now ceases, and that by a process of absorption the interstitial effused matter is removed, so as slowly to restore the part to its proper condition : this is the termination of inflammation to which the term resolution is applied. 3. Suppuration. — It usually happens in acute inflammation of the cellular tissue, that after the lapse of a certain period, a softening takes place towards the centre of the circumscribed hardness, in consequence of the diminution of cohesion above described gradually increasing, and of the deposition of purulent matter. It is not certain how the pus is formed in the first in- stance; several modern pathologists, especially in France, imagine that the lymph and serum which were previously effused experience a change by which they are converted into pus, a theory which is rendered probable by the physical properties of pus so nearly resembling those of the blood : according to other autho- rities, pus is a proper secretion derived from the neighbouring arteries. I believe that in the beginning the purulent matter results from changes in the effused matters; but that when suppuration is fully established, the pus is poured out or secreted from the bloodvessels. In the commencement the pus is observed in the cells of the tissue, under the form of whitish spots; subsequently the walls of these inter- stices are broken down by the softening alluded to, and the purulent matter is collected together so as to constitute an abscess, which is sur- rounded by a rather dense layer of cellular tissue, still retaining the characters of inflam- mation. This layer constitutes the sac of the abscess, and presents at first a rough and reddish surface; but it soon happens that the walls acquire a greater firmness, and that the surface of the sac assumes very much the appearance of a mucous membrane. 4. Ulccrution. — When an abscess has thus been formed, the cellular tissue intervening be- tween it and the external surface of the body, is removed by the action of the absorbents. This process, which is always preceded by inflam- mation, and accompanied by suppuration, is distinguished from various other morbid actions of the absorbents by the term of ulceration. Other instances of ulceration occurring in the cellular tissue might be adduced; ex. gr. the separation of the slough in carbuncle, after extravasation of urine, &c. 5. Mortification. — If the inflammatory action be sufficiently intense, it causes the destruction of the vitality of the part affected, and pro- bably in the manner suggested by Professor Andral. “ In the most acute form of hyper- scmia,* the circulation of the blood is sus- pended, and if this stagnation be prolonged so as to become complete, the parts being gorged with blood that is no longer renewed, and which, therefore, soon becomes unfitted to sup- port nutrition and life, must necessarily perish, and in this manner gangrene is produced, as in the experiments performed by Dr. Hastings, In these cases the black colour announces the stagnation of the blood, and this stagnation being prolonged, must of necessity lead to gangrene. Such, in my opinion, is the manner in which the species of gangrene usually attri- buted to excess of inflammation, is produced.” M. Gendrin has ascertained by dissection that some of the vessels are filled with coagulated blood ; whilst others are actually ruptured, and allow their contents to escape. The cessation of the circulation has for a long time been remarked as the most striking character of mor- tification ; in fact, that cessation, in whatever manner it may have been induced, whether by inflammation, by continued pressure, by the application of tight bandages to a limb, &c., is in the great majority of instances the imme- diate cause of mortification. The consequence of this loss of vital action is, that the natural ! properties and appearance of the cellular tissue are destroyed ; the affected part becomes dis- coloured, usually assuming a black or ash- coloured appearance; the proper texture is lost, and the part is infiltrated with a dark sanious fluid, and is subsequently converted C into a shapeless mass of pulpy substance, which is cold to the touch, and extremely offensive to the smell, owing to the gases which are generated by putrefaction : in fact, the part is ' dead, and presents the usual appearances caused J1 by the decomposition of animal matter, con- joined with those which result from the pre- vious effects produced in the circulation by the inflammatory action, especially the engorge- ment of the bloodvessels. These are the changes jj induced in the cellular substance when it is attacked by humid, or, as it has been called, inflammatory gangrene. In dry gangrene, on the contrary, the black and discoloured part shrivels up, and does not undergo the same changes which are produced by the decompo- sition of a texture which is loaded with fluids. ! b. Chronic inflammation. — As we find that in phlegmon there is a great tendency to the formation of pus, so in chronic inflammation there is usually a deposition of solid matter, which produces more or less of induration and enlargement. This deposition seems almost in every instance to occur in the cellular tissue, either where it is interstitial, or where it pene- trates into the interior of the several organs. This is observed among other parts in chronic * This is a general term employed by M. Andral to designate the increased quantity of blood which is contained in the capillary vessels of any organ, without any reference to the cause which produces the accumulation. In the passage above quoted, he is speaking of acute hypertemia, which is syno- nymous with acute inflammation. CELLULAR TISSUE. 515 inflammation of glands, as the testis, mamma, liver, tonsil, &c. ; in the lymphatic glands, especially in scrofulous persons ; in various dis- eases of the joints ; in the hard swellings so often seen in scrofula, gout, and rheumatism; in imperfectly cured erysipelas, pellagra, and ele- phantiasis ; in the callous edges of old ulcers ; in the uterus, labia pudendi, and prepuce of the penis; and, according to Otto,* in that pe- culiar induration of the cellular tissue which occurs- in new-born children. This distin- guished pathologist, in common with many other continental writers, attributes phlegma- sia dolens to the same cause. The incorrect- ness of this opinion has been demonstrated by the researches of Dance, Arnott, Lee, and others. (See Vein.) The great induration often induced by long- continued chronic inflammation was called by the older writers scin-hus ; and even in the present day most of the French pathologists apply that term to the hardness thus induced, as well as to the malignant disease, to indicate which English practitioners restrict the word. The substances that are effused into the cel- lular tissue in chronic inflammation are various, according to the part attacked, the circum- stances of the disease, constitution, &c. It generally consists of a whitish or greyish matter, of a lardaceous, homogeneous appearance, caus- ing whatis called by modern pathologists, white induration ; and sometimes it is of a yellowish, or even bluish colour. It is doubtful whether this substance consists of the fibrine or albumen of the blood, or of some newly formed material. In scrofulous individuals the deposition consists of the well-known caseous matter, so characteristic of the strumous diathesis; lastly, this form of inflammation, especially in strumous constitu- tions, often leads to the formation of chronic abscess, the contents of which, as Gendrin, Mayo, and others have observed, do not, how- ever, consist of true pus, but of serum generally mixed with a flakey matter, or even tinged with blood. c. Spreading or diffuse inflammation.- — The cellular tissue, constituting in all parts of the body an uninterrupted secreting surface, is sub- ject to spreading inflammation, which, from the extent of the parts implicated, the disorganiza- tion induced, and the alarming character of the attendant constitutional disturbance, must be regarded as one of the most formidable diseases to which the human body is subject. In what- ever manner this disease originates, whether from poisoned wounds, from phlegmonous ery- sipelas, from external injury, or from any other cause, it progressively and rapidly attacks a large extent of the cellular tissue, often invading an entire limb, or even a considerable part of the trunk. In examining parts thus affected after death, they are found to be variously altered, according to the duration of the dis- ease and the order in which they became in- volved ; in those which are most recently im- plicated, the cellular substance is merely oede- * Compcnd. of Pathol. Anat. by South, vol. i. p. 91. matous, containing a large quantity of limpid or reddish-coloured serum, which readily flows out on making an incision, and which after- wards acquires more consistence, and becomes more deeply coloured. In the subsequent stages, pus, sometimes pure, sometimes dis- coloured, is effused : the matter is at first con- tained in the cells, which are gorged with a whitish semifluid matter, but afterwards depots of matter take place in the disorganized tissue ; there being, however, no proper cyst, owing to the want of that barrier of lymph which is effused in common phlegmon. These abscesses are often numerous, but insulated and distinct from each other : at other times they occupy a great extent, and contain a large quantity of pus, often mixed with shreds of mortified membrane. In the more severe forms of this affection the natural organization is in some places totally destroyed, and the cellular substance, from the effects of gangrene, is converted into a greyish or dark-coloured slough. These changes are not confined to the sub- cutaneous membrane, in which, however, they are principally observed, but are seen in the cellular sheaths of the muscles, and even in the processes which separate their different fasciculi. The muscles themselves, under these circum- stances, partake in the disorganization, and lose their proper colour. The progress of this formidable disease would seem to shew that an acrid and irritating hu- mour is effused into the cellular substance, where it rapidly causes suppuration and slough- ing, in the same manner as when urine is ex- travasated into the perinreum and scrotum. That a vitiated state of the blood is often pro- duced is a now well-known fact, and such a condition appears to be induced in the disease under consideration, either in consequence of the introduction of a poison into the system, as from the bite of a venomous serpent, or from a deterioration of the constitution, as in draymen, coal-porters, and others, who in large towns con- sumeenormous quantities of fermented liquors; or, lastly, from both these causes combined, as from punctures received in dissection by indi- viduals who at the time are in an indifferent State of health. II. Infiltration, or effusion.- — -The escape of various fluids from their proper receptacles into the cellular tissue is of extremely frequent occurrence. a. Blood. — This is effused either as a conse- quence of external violence acting on the arte- ries and veins, or from an internal cause, of which the nature is more obscure. When the hemorrhage is extensive, the surrounding tissue is unable to resist the progress of the blood, and the infiltration becomes of considerable ex- tent. It is by effusions of this kind that ecchy- moses, false aneurisms, &c. are formed. b. Serum.— A very common morbid change is the infiltration of a thin watery fluid into this tissue, consisting of an accumulation of the serum naturally exhaled into its cells. The effused fluid, apparently owing to its contain- ing a larger proportion of albumen than usual, is occasionally of a more viscid nature, so as MG CELLULAR TISSUE. to escape but imperfectly on a puncture being made ; and in other cases, as in the diffused swelling so often occurring in bad constitutions after serious local injury, compound fractures, poisoned wounds, &c. the effused fluid is of an acrid character. The effusion is often restricted to a particular region, ( oedema ;) at other times it is more extensive, and may even occur in all parts of the body (anasarca ). In all instances in which effusion takes place, it ought to be regarded simply as an effect, resulting from some previous change in the vessels of the cellular tissue, which stands in the relation of a cause. This change consists, I believe, in the great majority of cases, if not in all, in a preternatural con- gestion of the bloodvessels, which may be induced by inflammation, debility, mechanical obstruction to the free return of the venous blood, or the suspension of any of the great secretions of the body. c. Air. — Emphysema, in its usual form, arises from an unnatural communication being formed between some part of the air-passages and the cellular tissue ( traumatic emphysema ) ; it is thus an occasional consequence of fracture of the ribs, in which the neighbouring portion of the lung is lacerated ; of penetrating wounds of the chest; of rupture of the air-cells by violent exertions ; of ulceration of the air- cells ; of rupture of the membrane of the larynx, and even of the lachrymal sac and windpipe, and of fractures in the vicinity of the frontal sinuses, causing a laceration of their mucous membrane. Emphysema has been likewise known to arise spontaneously, the air appear- ing to be secreted from the bloodvessels ; and it is also a frequent attendant on gangrene, in which case the effused air is the result of the decomposition of the fluids previously col- lected. d. Urine. — Effusion of urine may arise from a wound or ulceration of any of the organs through which the urine passes ; usually, how- ever, it is a consequence of an injury of the bladder or urethra. The accident particularly demands notice on account of the destructive effects which result from it. These effects are extensive mortification of the cellular tissue, and, in a somewhat less degree, of the skin, followed by profuse suppuration, attended with constitutional symptoms of so serious a nature as often to cause the death of the patient. III. Induration. — Induration occurs as a special disease in new-born infants, and in a large proportion of those who are attacked, there is a fatal termination from the sixth to the thirtieth day ; in very severe cases, and in infants prematurely born, death may take place in two, three, or four days. Some idea of the mortality in this disease may be formed from the following facts : in the Foundling Hospital in Paris, the mortality of late years has been one in three ; out of twenty- seven cases occurring in 1809, at La Charite in Berlin, only two were saved; in fifteen cases seen by Lobstein, four recovered. The disease is very prevalent in the large foundling hospitals on the continent, as many as 240 eases occurring in one year in the Hos- pice des Enfans Trouvfis of Paris, out of 5392 received into the institution. In this country, where, fortunately for humanity, no such establishments exist, and where conse- quently new-born infants are but rarely deserted by the mother, the disease is very rare. Dr. Copland states that he has not met with an instance of it in the Queen’s Lying-in Hospital, and that even in the Infirmary for Children, such cases are very rarely presented. I have made inquiries of several very extensive prac- titioners of midwifery, some of whom are con- nected with public institutions, and they have very rarely or never seen the disease. The parts which are attacked, usually the legs, hands, and face, are more or less swollen, hard, and rigid to the touch ; and the skin assumes a red or violet colour in consequence of the respiration being imperfectly performed. The affection consists of an cedematous state of the cellular tissue, the areolae being loaded with a concrete albuminous matter and a sero- sanguineous fluid, which oozes out when a section is made and quickly coagulates ; it is this infiltration that is the cause of the peculiar' hardness, for according to M. Billard, who has carefully investigated the characters of the dis- ease, the cellular fibres and layers preserve all their flexibility, and present no signs of having undergone any organic change. According to M. Chevreul, in this disease the serum of the j; blood contains an abundant quantity of a matter distinct from fibrin, but which spontaneously coagulates ; this substance is perfectly identical with the material to which the cellular tissue I owes its apparent induration. The history of this disease, and the results obtained by dissection, prove that venous con- gestion is a very constant morbid appearance; and it is a question that has not hitherto been decided, how far this congestion is the exciting cause of the disease. IV. Morbid growths. — These are of very common occurrence and of very various characters ; some consisting of the trans- formation of the cellular membrane into other tissues, the fibrous and osseous for example; whilst others are entirely new productions, and occasionally prove of a malignant nature, such as cysts, vascular sarcoma, scirrhus, melanosis, &c. We do not often meet with bony or fibrous formations in the common cellular structure, although I have occasionally seen growths with these characters. From an ex- amination of many specimens, I am induced to believe that the ossific deposits not unfre- quently observed in connection witii the fibrous and serous membranes, as the dura mater, pleura, &c. are formed in the cellular tissue of these structures. V. — Foreign bodies are sometimes intro- duced into the cellular tissue from without, such as bullets, needles, &c. Certain para- sitic animals, the origin and characters of which are very obscure, are also occasionally met with in the substance of the human body, and especially in the cellular tissue. At the present day it is generally admitted that hy- CEPHALOPODA. 517 datids are bodies endowed with vitality, the most common species of which is the acepha- locyst ; another species is the cysticercus cel- lulosus. The Jilai'ia medinensis, or guinea- worm, is another parasitic animal which has been seen in the human body. Lastly, the cellular tissue may vary in the degree of its consistence, colour, &c. ; and owing to some derangement in the function of nutrition, it may present a preternatural in- crease or a wasting of its substance: (hyper- trophy or atrophy.) Bibliography. — Bordeu, Recherches sur le ti3su muq., in his works by Richerand. W. Hunter, in Med. Obs. and Inq. vol. ii. p. 17. Haller, Elementa Physiolog. The systems of Portal, Bichat, Meckel, Beclard, Craigie, and ^Grainger, Blandin Sf Beclard, Add. a l’Anat. Gen. de Bichat. Diet, de Med. art. Cell. Tissue. M. Edwards, Recherches microsc. sur la struct, intime des tiss. organ, des anim. Hodgkin, Annals of Phil. Aug. 1827. The systems of physiology by Blumenbach, Majendie, Bostock, and Tiedemann. Fodera, Journ. de Phys. t. iii. p. 35. Lindley, Introd. to botany. Roget, in Bridgwater Treat., Anim. and Veget. Phys. Grant’s Lectures, Lancet, 1833, 34, vol. ii. p.257. He Blainville , De 1’organis. des animaux. Hunter, Treatise on the blood, &c. Thomson’s Lectures on inflammation. James, Observations on inflammation. Portal, Cours d’anat. med. t. ii. t. v. Lawrence, Lectures on inflammation, in Lancet, vol. i. 1829, 30. Hastings, Treatise on the lungs, p. 57. Billard, Traite des mal. des enf. nouv.-nes, p. 169. Gendrin, Hist. anat. des inflam. t. i. p. 14 ; t. ii. 358. Andral, Precis d’anat. pathol. Otto, Com- pendium of pathological anatomy, by South. Cop- land, Diet, of Pract. Med. art. Cellular Tissue. Wells, Transactions of a Society for Improvement of Medi- cal and Chirurgical Knowledge, vol. iii. Breschet, Reclier. sur les hydrop. actives, f c. Paris, 1812. Blackall, Obs. on dropsy, London, 1813. Aber- crombie, in Edin. Med. and Sur. Journal, vol. xiv. Ayre’s Researches into the nature and treatment of dropsy, p. 1 etseq. Cyclop, of Pract. Med. art. Anasarca. Diet, de Med. et de Chir. Prat. art. Acephalocystes , Anasarque, Emphyseme, Entoxoaires, Inflammation. Mayo, Outlines of human patho- logy. Lobstein, Traite d’anat. pathol. p. 201. Duncan, in Trans, of Med. Chir. Soc. Edin. vol. i. ( R. D. Grainger.) CEPHALOPODA — (xstpaToi, caput, iron;, pes); Eng. Cephalopods ; Fr. Cephalopodes ; Germ. Kopffiisslern, Blackfische, Tintenfiische ; Ital. Seppie, Polpi. Syn. MaXar.la., Aristotle ; Mullia, Pliny ; the genera Nautilus, Argo- nauta, and Sepia, Linne ; Octopodia, Schneider; Mollusca brachiata, Poli ; Mollusca Cephalo- poda, Cuvier ; Cephalopoda, Lamarck, Leach ; Brachiocephala, Cephalophores, De Blainville ; Pterygia, Latreille, (including the Pteropoda of Cuvier); Antliobrachionophora, Gray. Definition. — A class of Molluscous Inver- tebrate animals in which the head ( A, figs. 206, 209,) is situated between the trunk ( B) and the^/eef (C), or principal organs of loco- motion. Characters of the Class. — The trunk or body is thick and soft ; varying in form from a 'sphere, to a flattened ellipse, or elongated cylinder ; sometimes protected by a shell, sometimes naked ; consisting of a membranous or muscular sheath or mantle, with a transverse anterior* aperture (a, figs. 206, et seq.) and containing the respiratory, circulating, gene- rative, and principal digestive viscera : the mantle sometimes supports a pair of fins (6, figs. 207, 208, 209,) and, in the naked species, lodges in its substance the rudiments of a shell. The head is distinct from the trunk, of large size, and of a rounded figure ; it contains the organs of sense, mastication, and deglutition, and gives off from its anterior circumference or exter- nal surface, a number of fleshy processes which encircle and more or less conceal the mouth. These processes, by some naturalists termed the feet, but which we prefer to call, with Poli, the arms, are either very numerous, short, and hollow, containing each a long, slender retrac- tile tentacle (figs. 205, 213) ; or they are eight (figs. 206, 210), or ten (figs. 207, 208), in number, solid, supporting on their internal surface numerous suckers (antlia, ucetabula) ; and being more or less elongated and flexible in every direction, they act as powerful organs of adhesion, prehension, and locomotion. The eyes are a single pair, of large size, varying in relative perfection of structure ac- cording to the locomotive powers of the spe- cies, and either pedunculated or sessile. The mouth is anterior, and situated at the bottom of the conical cavity formed by the base of the feet ; it is provided with two horny or calcareous jaws, shaped like the mandibles of a Parrot, playing vertically on each other, and inclosing a large fleshy tongue, which is armed with recurved horny spines. The branchice are concealed within the man- tle, and are symmetrical in size, form, and posi- tion. The systemic circulation is aided by a muscular ventricle. The infundibulum, (i,figs. 206, 208,) or pas- sage through which the respiratory currents and the excrements are discharged, is a muscular tube, situated at the anterior part of the neck, shaped like an inverted funnel, with the pipe projecting from the visceral cavity, and directed forwards. The sexual organs are separate and exist in distinct individuals ; but whether impregnation takes place by copulation or after the ova are excluded is not determined ; the former is most probable. All the species are aquatic and marine. Division of the Class into Orders. — The type of organization which characterizes the Cephalopods, and of which the preceding is a general outline, presents two principal modi- fications, according to which the class is di- vided into two orders.f ® Throughout the present article the terms of aspect and position relate to that in which the animal is represented in _/?rra B^ovcra; SiXo-rtiXov.* “ All (mollia) have eight feet, provided with a double series of suckers, except in one genus of Polypi.f The Sepiae, Teuthides, and Teuthi,j; have, besides, two long proboscides, the extremities of which are beset with a double series of suckers.” Pliny gives, after the Stagyrite, the fol- lowing notice of their functions, “ Sepia et Loligini pedes duo ex his longissimi et asperi, quibus ad ora admovent cibos, et in fluctibus se, velut ancoris, stabiliunt.” German authors generally term the ordinary feet, ‘ arms,’ ( arme,) and the tentacles ‘ seizers,’ (fangarme.) In the Cephalopods which have only the eight normal feet, these present many vari- ations ; and, although they are generally re- markable for their length, yet in some species, as the Octopus brevipes, they are extremely short, resembling the digital processes of the Nautilus. In Octopus Ei/lais, the first or dorsal pair is alone developed so as to serve as a locomotive organ, and the animal mustcrawl along the ground by means of this pair only. In most Octopods the first pair of feet is the longest. In Octopus Aranea, in which the feet apparently present the maximum of de- velopment, the dorsal feet are ten times, and the ventral ones five times, the length of the body. Besides their superior length the dorsal feet present other peculiarities in this family of Cephalopods. In the genus Argonauta (fig. 206, c 1,) they are provided with expanded membranes, the fabled use of which has af- forded a beautiful subject for poetic imagery in all ages ; but similar appendages occur in Octopus violaceus, and in Octopus velifer, in which both the first and second pairs of feet support broad and thin membranes at their extremities. Now neither of these species in- habit a shell, in which the expanded mem- branes could be used to waft the animal along the surface of the ocean, as has been said or sung of the Argonaut from Aristotle to Cuvier, from Callimachus to Byron. The physiologist, in contemplating the structure of the velated arms, is compelled to disallow them the power of being maintained erect and expanded to * Ibid. lib. iv. c. 1. 4. f The genus -Efedone of Aristotle, the eight feet of which have only a single series of suckers upon each. f Species of Loligo or Calamaries, supposed to be the Loligo vulgaris and Loligo media of modern naturalists. CEPHALOPODA. 528 meet the breeze. What their real function may be is still to be determined; but the re- moval of the erroneous impressions entertained on this subject is the first step towards the at- tainment of the truth. In our common Oc tupux, and most other species of this genus, the feet are connected together for some distance beyond the oral sheath by membranes and muscles which form a circular fin. This is their sole locomotive organ when swimming ; and by its powerful contraction they are driven through the water with a quick retrograde motion. In a species which we have recently described* ( Octopus semipalm atm) the fin is extended only between the four dorsal arms : a structure which must occasion a characteristic difference in its mode of swimming. The disposition of the muscles of the web- like fin is as follows. There are two transverse layers of fibres, the external arises from a white line extending along the back-part of each foot ; the internal from the sides of the same feet between the attachments of the suckers. These two strong muscular bands are con- nected together as they pass from arm to arm in the middle of the webs, and decussate one another, so that the external become internal and vice versa. Within these a thin layer of longitudinal fibres extends to the free margin of the webs ; and there is also a layer of ob- lique longitudinal fibres externally, which arise from the white line at the middle of each foot : these fibres are shown at (k, k,fig. 216,) the transverse fibres at l, l. In the Cephalopods which possess the re- tractile peduncles, the ordinary arms are gene- rally short, and the first or dorsal pair are commonly exceeded in length by the second ; sometimes, indeed, as in the species of Loli- gopsis, of which the figure is subjoined, (Jig- 209,) they go on progressively increasing in length to the ventral or fourth pair, which here resembles in its great development the arms of the Octopods. The peduncles are always longer, and more slender than the arms; they exhibit these characters in the highest degree in the genus Loligopsis, in which they are frequently mutilated and lost ; but the examination of the nerve proceeding to the mutilated stump sufficiently attests, in such cases, the importance of the organ of which this animal has been accidentally deprived. The tentacles serve to seize a prey which may be beyond the reach of the ordinary feet, and also to act as anchors to moor the Cepha- lopod in safety during the agitations of a stormy sea. Each arm is perforated near the centre of its axis for the lodgment of its nerve (a, fig. 214) and artery ( b ) ; and upon making a transverse section of the arm, these are seen to be lodged in a quadrangular or rhomboidal space (c) of a light colour and apparently soft homogeneous texture, but in which a few radiating fibres may be discerned. This part is surrounded by four * See Proceedings of the Zoological Society for March, 1836. Fig. 214. Section of an Arm arid Suckers of a Poulp. groups of transverse striae forming as many seg- ments of a circle, external to which there are two thin circular strata of fibres. On making a longitudinal section of the part the striated segments are seen to consist of longitudinal muscular fibres, and of the surrounding strata, the fibres of the internal are longitudinal, and those of the external transverse. It is easy to conceive that, like the tongue in Mammalia, the arms thus organized may be lengthened, shortened, curved, and bent in all conceivable directions. The acetabula or suckers with which the in- ternal surface of the arms of the Dibranchiales are provided, vary in relative position, in size, in structure, and in mode of attachment, not only in different species, but in different arms in the same individual, and sometimes in diffe- rent parts of the same arm. Thus in the pe- duncles of Loligopsis Veranii, the suckers on the long cylindrical stem are sessile, while those on the expanded extremity are supported on long peduncles ; and another remarkable instance will presently be mentioned of suckers having different structures for different functions in the same arm. In the Dibranchiate genera which are charac- terized by a soft thin skin, as the Argonaut, Octopus, and Eledone, the suckers are soft and unarmed ; in those genera which have a hard and thick skin, as the Calamary and Onychoteuthis, cuticular appendages are deve- loped in the cavities of the suckers. An excellent description of the unarmed acetabulum as it exists in the genus Octopus, is given by Dr. Roget. The circumference of the disc is raised by a soft and tumid margin (e, Jig. 214); a series of long slender folds of membrane (f), cover- ing corresponding fasciculi of muscular fibres, converge from the circumference towards the centre of the sucker, at a short distance from which they leave a circular aperture (g)‘- this opens into a cavity (h), which widens as it descends, and contains a cone of soft substance CEPHALOPODA. 529 (i) rising from the bottom of die cavity, like the piston of a syringe. When the sucker is applied to a surface for the purpose of adhe- sion, the piston, having previously been raised, so as to fill the cavity, is retracted, and a vacuum produced, which may be still further increased by the retraction of the plicated cen- tral portion of the disc. So perfect is the me- chanism for effecting this mode of adhesion, that in the living Cephalopod, “ while the mus- cular fibres continue contracted, it is easier to tear away the substance of the limb than to release it from its attachments : and even in the dead animal the suckers retain a considerable power of adhesion.”* Still there are circumstances in which even this remarkable apparatus would be insufficient to enable the Cephalopod to fulfil all the offices in the economy of nature for which it was created ; and in those species which have to contend with the agile, slippery, and mucus- clad fishes, more powerful organs of prehension are superadded to the suckers. In the Calamary the base of the piston is inclosed by a horny hoop, the outer and ante- rior margin of which is developed into a series of sharp-pointed curved teeth. These can be firmly pressed into the flesh of a struggling prey by the contraction of the surrounding transverse fibres ; and can be withdrawn by the action of the retractor fibres of the piston. Let the reader picture to himself the projecting margin of the horny hoop developed into a long, curved, sharp-pointed claw, and these weapons clustered at the expanded terminations of the tentacles, and arranged in a double alter- nate series along the whole internal surface of the eight muscular feet, and he will have some idea of the formidable nature of the carnivo- rous Onychoteuthis. Banks and Solander, in Cook’s first voyage, found the dead carcase of a gigantic species of this kind floating in the sea, between Cape Horn and the Polynesian Islands, in latitude 30° 44' S. longitude 110° 33' W. It was surrounded by aquatic birds, which were feeding on its remains. From the parts of this specimen, which are still preserved in the Hunterian Collection, and which have always strongly excited the attention of natu- ralists, it must have measured at least six feet from the end of the tail to the end of the tenta- cles. The natives of the Polynesian Islands, who dive for shell-fish, have a well-founded dread and abhorrence of these formidable Cephalopods, and one cannot feel surprised that their fears should have perhaps exaggerated their dimensions and destructive attributes. We cannot quit this part of our subject without noticing a structure which adds greatly to the prehensile powers of the uncinated Calamaries : at the extremities of the long ten- tacles, besides the uncinated acetabula, a cluster of small simple unarmed suckers may be ob- served at the base of the expanded part. When these latter suckers are applied to one another, * Roget, Bridgewater Treatise, i. p. 260. See also Baker, An Account of the Sea-Polypus, Phi- losoph. Trans, vol. 1. p. 777. the tentacles are firmly locked together at that part, and the united strength of both the elon- gated peduncles can be applied to drag towards the mouth any resisting object which has been grappled by the terminal hooks. There is no mechanical contrivance which surpasses this structure : art has remotely imitated it in the fabrication of the obstetrical forceps, in which either blade can be used separately, or, by the interlocking of a temporary joint, be made to act in combination. (S eefig. 215, where d marks Fig. 215. the stemsof the peduncles, e the parts joined together by the mutual apposi- tion of the un- armed suckers, f the terminal expanded por- tions bearing the hooks.) The great muscular coni- cal basis which gives origin to the feet is at- tached, as be- fore mention- ed, to the an- terior part of the annular cephalic carti- lage : it is also provided with distinct fasci- culi of museu- lar fibres, which connect it to the mantle and to other parts of the body. In the Octo- pus a great pro- portion of these fibres arise from the posterior part ofthe man- tle, and, di- verging as they pass forwards, spread over the posterior and lateral parts of the head, rece- ding at the sides to leave a space for the eye ; they then di- vide into five bundles, each of which again subdivides into two, which are lastly inserted into the sides of the six dorsal and lateral feet. fSee a a fig- 21 6-) 530 CEPHALOPODA. Fig. 216. Muscles of the Poulp, Octopus Vulgaris. Fasciculi of muscular fibres (b, b, 216,) are continued from the ventral pair of feet and the back part of the cranium, across the base of the funnel to the muscular septum, which divides longitudinally the branchial cavity. Other fibres descend to join the muscular tunic enveloping the liver and oesophagus ( d, d) ; but the fibres of this part rise principally from the posterior part of the cephalic cartilage. The septum of the branchial chamber above- mentioned is the strongest and most complete in the genus Eledone, where, with the excep- tion of a very small part of its posterior termi- nation, it is muscular throughout.'* In the Poulp, in which this septum (c,Jig. 216) is well described by Cuvier as the “ bride ante- rieure qui lie la bourse a la masse viscerale,” a greater proportion of the posterior part is membranous. In the Argonaula the muscular part of the septum is reduced to two narrow and delicate fasciculi, which arise from the back part of the cranial cartilage, descend ob- liquely forwards, intercept the termination of the rectum and ink-duct, to which they serve as a sphincter, and then expand in the vertical direction to be inserted along the middle line of the inner surface of the anterior part of the mantle. A membrane is continued from the upper margin of the muscular septum to within * See Carus’ original figure, Vergleich. Zooto- mie, pi. iv. fig. 4, g. in Octopus ( Eledona J Mos- chatus. a short distance of the anterior margin of the mantle, and another from the lower margin ex- tends downwards, and terminates opposite the base of the gills ; the branchial chambers in- tercommunicate both above and below this septum. In Sepiola the muscles corresponding to the “ bride anterieure” of the Octopus are developed in the same degree as in the Argo- naut, arising not from the back of the funnel, but from the cranial cartilage ; the septum is completed below by membrane. In the Cuttle- fishes and Calamaries these muscles and the septum of the branchial chamber are wanting. The muscular parietes of the funnel are formed by an external longitudinal (e) and an internal transverse (f) layer, strengthened by the insertion of the extrinsic muscles of this part. The principal of these are the lateral muscles (g, fig- 216,) which in the Poulp take then- origin from the capsules of two small styles, hereafter to be described, at the sides of the mantle, and are inserted into the sides of the funnel and the muscular tunic of the liver. In the Cuttle-fishes and Calamaries they are at- tached to the cartilaginous articular cavity at the sides of the base of the funnel, as well as to its fleshy parietes. These muscles serve to retract and depress the funnel ; it is raised and drawn forwards by two pair of muscles (h) which descend from the under and lateral parts of the head to be inserted into its back part. But neither of these muscles pass through a sheath, as do the corresponding muscles in the Nautilus. A pair of muscles, whose important charac- ter is only perceived by tracing them through their successive stages of development to the Nautilus, are those small fasciculi which Cuvier terms “ la bride laterale qui joint la bourse it la masse viscerale.” (i.) They arise in con- junction with the fibres of the fleshy tunic of the liver, but soon quitting these, extend, as distinct fasciculi, downwards and outwards, being perforated in their course by the great lateral nerve, and are inserted into the upper part of the capsule of the rudimental shell, which the styles above-mentioned represent. In the Sepia they are proportionally large-, corresponding to the greater development of the shell. They are not inserted, in the Octo- pus, into the cartilaginous substance of the in- closed style; nor, in the Sepia, into the calca- reous substance of the cuttle-bone; neither are they attached to the calcareous matter of the shell in the Nautilus, where they acquire their maximum of development. They termi- nate in this, as in the preceding genera, in tee epidermic capsule of the shell, which has a much closer and more intimate adhesion to the testaceous substance in the Nautilus than to the internal rudiment of the same part in the naked Cephalopods. It is well known that zoologists are divided in opinion as to whether the shell called Argo- nauta is formed by the cephalopod which in- habits it or not. Having traced out the mus- cles in the naked Cephalopods which are ana- logous to those of the shell in the Nautilus, vie next examined the Ocythoe, with the view of CEPHALOPODA. ascertaining if these muscles presented a corre- sponding degree of development, but found them proportionally smaller even than in the naked Octopus. All trace of internal shell has disappeared in the Ocythde ; yet there is no muscular connexion between the body and the external shell which contains it. The fleshy fibres of the mantle being white like the rest of the muscles, and very compact, are extremely difficult to follow in dissection. Cuvier* observes, that in the Octopus those which are external are evidently longitudinal ; those which are internal, transverse ; and that there are short fibres which pass through their thickness from one surface to another. In the Cuttle-fish the muscular fibres of the posterior part of the mantle recede laterally to leave a large space for the lodgement of the sepium or cuttle-bone, which is covered exter- nally by a thin and flaccid skin : the rest of the mantle is formed by a thick muscular tissue, as in the Pou/p. The lateral fins are connected not only by the skin, cellular tissue, and vessels, as Cuvier describes, but by a distinct though thin stratum of muscular fibres ; these arise from the lateral and dorsal aspects of the apo- neurotic capsule of the rudimental shell, and are inserted into the spinal ridge of the alar cartilage (h, h, jig. 212) ; from this ridge pro- ceed the fibro-cartilaginous laminae and inter- mediate muscles, which are disposed perpen- dicularly to the ridge, and extend to the mar- gins of the fin. In the Calamaries the muscles which con- nect the terminal fins to the body are still more distinct. By means of these fins they are enabled to propel themselves forward in the sea; and there is good reason for believing that some of the small slender-bodied subu- late species of this genus are enabled to strike the water with such force as to raise them- selves above the surface, and dart, like the flying fish, for a short distance through the air.f Digestive System. — The animals which we have thus seen to be endowed with so various and formidable means for seizing and over- coming the struggles of a living prey are pro- vided with adequate weapons for completing its destruction, and preparing it for deglutition. These consist of a pair of strong, sharp, hooked mandibles, which are of a horny texture in the Dibranchiate Cephalopod, ( a, b, jig. 218,) where they are fitted for cutting and tearing the softer animals which they are enabled to catch ; but are strengthened by a dense calcareous sub- stance in the Nautilus, (a, b, jig. 217,) which, from its more limited sphere of action, is pro- * Memoire sur le Poulpe, p. 11. t See Proceedings of the Zool. Society, Pt. i, 1833, p. 90. The faculty possessed by the Cala maries of darting through the atmosphere was not unknown to the ancients. Pliny ( Hist. Nat. lib. ix. tom. ii. p. 105, Cuvier’s Ed.) says, “ Loligo etiam volitat, extra aquam se efferens, quod et pectunculi faciunt sagittoe modo and so general appears to have been this belief that Varro sup- posed the name Loligo to be a corruption of Voligo. “ Loligo dicta, quod subvolat, littera commutata, primo Voligo.” — He Ling. Lat. lib. iv. p. 21. 531 bably restricted in regard to food to such crus- taceous and testaceous animals as it may sur- prise by stealth, and whose defensive armour it is thus enabled to break up.* The mandibles, which are hollow sheaths, like the horny covering of the beak of a Bird or Tortoise, are fixed upon a firm fleshy sub- stance, (c, c, jig. 217,) which resembles the Fig. 217. animal part of bone after the earth has been removed by means of an acid. At the base of the mandibles the fibrous structure of this part becomes apparent, and a strong stratum, (g, Jig. 217,) passing between the bases of the mandibles, serves for their divarication ; their closure is effected by fasciculi of muscular fibres, which surround them externally near the reflection of the circular lip. When the mouth is closed, the lower mandible (6) over- laps the upper (a). The oral aperture is in the centre of the base of the feet, and appears in the form of a small circular orifice, formed by the contracted fleshy lip which surrounds and more or less conceals the mandibles. In the Nautilus the margin of the lip (c) is beset with several rows of elongated papilla?, irregularly disposed ; external to which are the labial processes with their tentacles : these, in the specimen we dissected, com- pletely overlapped and concealed the oral ap- paratus. In the Calamaries the jaws are surrounded, external to the fringed circular lip, by a thin membrane, which is produced into short pyra- midal processes, corresponding in number to the eight feet, and supporting minute rudimen- tal suckers ; thus imitating the external feet, as the labial processes of the Nautilus repeat the structure of the digital processes. In the genus Sepioteuthis the circular lip immediately surrounding the jaws is tumid and plicated, but not papillose ; external to it are two cir- cular ridges of membrane, then a thin mem- brane with jagged margins, and lastly a mem- brane with its margin produced into eight angular processes, which are not, however, free, as in Loligo, but are tied down in the interspaces of the eight legs ; small rudimental suckers may be observed on these processes. * The digestive canal of the Nautilus was found filled exclusively with the remains of a species of crab. 532 CEPHALOPODA. In Onychoteuthis the inner lip (d, fig. 218) is tumid, and merely subplicated ; the angles of the external labial membrane are extended along the middle of each foot for a short dis- tance. In Sepia the inner lip is fringed, as in Nautilus. The outer lip is tied down by mus- cular bands to the bases of the arms, but sends forward eight short, conical, unarmed processes. In Loligopsis and Cranchia the outer-lip sends off a muscular band to the base of each arm, but has no free processes. In Octopus the suckers commence immediately round the mar- gin of the oral aperture, which is so con- tracted that the mandibles can seldom be seen without dissection : the inner-lip is fimbriated, as in Sepia. In Ocythoe it is tumid and entire, but pli- cated both circularly and transversely. The tongue is a large and complicated organ, and is constructed on the same plan in both orders of Cephalopods. In the Nau- tilus it is supported by an oblong horny transversely striated substance, which appears to represent the body of an os hyoides (a, fig. 236.) The posterior ex- Section of the tremity of this substance is free, or connected only by a few filaments with the parts above, but its anterior extremity is embraced by a pair of retractor muscles (5), which originate from the posterior margins of the lower mandible. The fleshy substance of the tongue, thus supported, is produced ante- riorly, and forms three caruncles (c), very soft in texture, and beset with numerous papillae, having all the characters of a perfect organ of taste. The anterior or terminal caruncle is the largest, and four delicate retractor or depressor muscles ( d ) are inserted into it. Behind the caruncles the dorsum of the tongue is encased with a thin layer of horny matter, about five lines in length, from which arise four longitu- dinal rows of slender prickles (e), wdiich are from one to two lines in length, and are in- curvated backwards. The number of these prickles is twelve in each row, singularly cor- responding with the number of tentacles given off from the labial processes. It is unnecessary to allude to the obvious utility of this structure in seizing the morsels of food, and directing them towards the gullet, after they have been broken up by the mandi- bles. Behind this horny part the tongue again becomes soft and papillose (_/), but the papillae are coarser and larger than those on the anterior portions. Two broad fleshy processes (g, g,) project forwards from the sides of the fauces : these also are papillose, and are perforated in the middle of their inner surfaces by a small aperture (A, h), which leads into a glandular cavity, situated between the folds of the mem- brane, and analogous to the superior pair of salivary glands in the Poulp, Calamaries, &c. In the Dibranchiate Cephalopods the tongue Fig. 218. Beak, with the Tongue of an Onychoteuthis . is similarly composed of an anterior and pos- terior papillose and a middle spiny portion. In the specimen from which the figure (218) was taken, the anterior fleshy portion (e) was slightly divided into three parts, but was retracted by a single round muscle, and the papilla; were relatively fewer and coarser than in the Nautilus : at its sides there were several orifices of glandular follicles. The horny plate, covering the middle part of the tongue, is bent at right angles; the recurved hooks in the Onychoteuthis are confined to the anterior and vertical surface ; they commence above or be- hind in seven rows ; but, as they descend, first the two outer on each side blend together, and then each united row joins the next, so that there remain but three rows at the lower part of the sheath. In the Cuttle-fish the seven rows of lingual spines continue distinct. In the Onychoteuthis the posterior portion of the tongue (g) is inclosed, as in the Nau- tilus, between two faucial or pharyngeal folds of membrane (A, A), but their inner surfaces, instead of being merely papillose, are beset with rows of small recurved spines, which must greatly assist the act of deglutition. The superior salivary glands (f) are not con- fined to the outside of the buccal mass, as in the Octopus, but extend between the layers of membrane which form the pharyngeal fold, forming here a flattened mass (i) ; their duct opens at the bottom of a longitudinal fissure on the inner surface of the fold ; styles are repre- sented passing into the ducts of these glands in the figure. In most of the Dibranchiata a second and generally larger pair of salivary glands are CEPHALOPODA. 533 found below the cartilaginous cranium, situ- ated in the hepatic cavity, on either side of the cesophagus. A single excretory duct is continued from each gland, and the two unite and form one, as they are passing through the cranium. The common duct penetrates the lower or central surface of the buccal mass, and is continued along the concavity of the lower mandible, through the tongue to the lower part of the spiny plate, where it termin- ates. In the Octopus these glands are very large, and have a smooth surface (q,Jg- 233) ; but in many Cephalopods, as in Ocytho'e, Sepiola, and Rossia, they are relatively smaller, and have agranular surface. It is in the genus Loligopsis alone that these glands have hither- to been found wanting. With respect to the ultimate structure of the salivary glands of the Cephalopoda, Muller* observes that they are not composed of solid acini or granules, but of hollow canals or cells. Before the description of the abdominal viscera is proceeded with, it is necessary to make a few observations on their position and connections. In the veutricose and short-bodied species of Cephalopoda the mantle-sac is almost wholly filled with the viscera, but in those of an elon- gated form they are more or less confined to the lower part of the sac, and a vacant space intervenes between the visceral mass and the opening of the mantle, which is traversed by the respiratory currents : the part of the mantle unoccupied by the viscera is most remarkable for its extent in the genus Loligopsis (Jig- 223.) If the mantle of the common Octopus or Poulp be laid open longitudinally, and a little to one side of the mesial line, a cavity will be exposed, separated by the longitudinal muscular1 septum ( c,Jig. 216) from the corresponding one of the opposite side; in these two cavities are contained the branchiae ( r,Jg. 216), the termi- nations of the oviducts ( p), and the pericardial apertures ( q). Below and behind the branchial cavities, the peritoneum is seen enveloping the rest of the viscera ; but this great serous sac is subdivided into many compartments. If the point of the scissors be inserted into the project- ing orifice internal to the root of the gill (i, Jig. 226), and the cavity of which it is the outlet be laid open, the branchial ventricle, the branchial division of the vena cava, and its appended follicles will be exposed ; this cavity is sepa- rated from a corresponding one on the opposite side by the systemic heart and the great vessels, which are contained in a distinct serous com- partment. In the Nautilus the two lateral and the middle cavities form one large pericardiac chamber, appropriated to the heart and great vessels, and the venous appendages. Behind these cavities, the peritoneum is disposed so as to form several compartments : one, which commences at the cranial cartilage, extends downwards as far as the middle of the branchiae, and contains the oesophagus, the inferior salivary glands, the crop, and anterior aorta : in front of this, but commencing a little * De structura glandularum penitiori, fol. p. 54. lower down, is a second, which includes the liver and ink-bag. These two cavities are sur- rounded by a common muscular tunic, of which we have already spoken, and the lower part, which resembles a diaphragm, is per- forated by the gullet, the aorta, and the two biliary ducts, each of which has a distinct aperture. The receptacle which contains the gizzard is situated immediately beneath the oesophageal sac ; that in which the spiral py- loric appendage is lodged lies immediately behind the left compartment of the pericar- dium. The intestine is principally contained in a serous cavity behind the right division of the pericardium ; and the bottom of the sac is occupied by the cavity containing the organs of generation. The digestive organs in the Tetrabranchiate Cephalopods would appear to differ in a less degree than other parts of their organization from the structures observable in the higher order : in the Nautilus they present the following con- formation. The pharynx (f, Jig. 217) or commence- Fig. 219. Digestive Organs, Nautilus Pompilius. rnent of the gullet, has numerous longitudinal rugae internally, and is evidently capable of con- siderable dilatation. The oesophagus, after having passed beneath the brain, or commissure of the optic ganglions, dilate into a capacious pouch or crop (k,fig. 219) of a pyriform shape, two inches and three lines in length, and an inch in diameter at the broadest part. From the bottom of this crop is continued a contracted canal {l, Jig- 219,) of about three lines in diame- ter, and half an inch in length, which enters the 534 CEPHALOPODA. upper part of an oval gizzard (in, Jig. 219) situated at the bottom of the pallial sac. Close to where this tube enters, the intestine (n, Jg. 219) is continued from the gizzard, and after a course of a few lines communicates with a small round laminated pouch or ap- pendage (p, Jg. 219) analogous to the spiral ccecum of the Cuttlefish, into which the biliary secretion is poured : from thence the intestine is continued, twice bent upon itself, but with- out varying materially in its dimensions, to its termination (o, Jg. 219). In this course it first ascends for about an inch and a half, then makes a sudden bend down to the bottom of the sac, and returns as suddenly upon itself, passing close to the pericardium, and terminat- ing between the roots of the branchiae. The alimentary canal is every where con- nected to the parietes of the abdomen by numerous filaments ; the only trace of a me- sentery exists between the two last portions of the intestine, which are connected together by membranes including the ramifications of an artery and vein.* The longitudinal rugae, into which the lining membrane of the oesophagus is thrown, disappear at its entrance into the crop. The muscular coat of the crop con- sists of an exterior layer of close-set circu- lar fibres and an inner layer of more scattered longitudinal ones. The lining membrane is thin but tough, with a smooth surface : when the cavity is empty, it is probably thrown into longitudinal folds by the action of the circular fibres. In the canal which leads to the gizzard, the lining membrane puts on a villous appearance and is disposed in distinct close-set longitudinal rugae. The gizzard is girt by two broad radiate muscles, of the thickness of two lines, arising from opposite tendons : it is lined by a thick cuticular membrane, delicately furrowed and adapted to numerous fine ridges which tra- verse longitudinally the whole interior of the cavity. This, as is commonly found in gizzards, was detached from part of the parietes and adhered very slightly to the remainder. The pyloric orifice is close to the cardiac, and is guarded by a valve, to prevent a too ready egress of matter from the gizzard.* The globular cavity (p, Jg. 219) which communicates with the intestine at a little dis- tance from the pylorus, is occupied with broad parallel laminae, which are puckered trans- versely, so as to increase their surface for vas- cular ramifications ; their texture under the lens is follicular and evidently fitted to secrete. The bile enters this cavity at the extremity furthest from the intestine by a duct large enough to admit a common probe. The two laminae on each side the entiance of the duct increase in breadth as they approach the in- testine, and are continued in a curved form Fig. 220. Alimentary Canal of the Poutp.t * In the specimen of the Nautilus from which the preceding account is derived, the whole alimen- tary canal was tilled with fragments of some species of crab, among which portions of branchial, claws, and palpi, were distinctly recognizable. The crop in particular was tensely filled with these substances, and the capability of propelling such rude and angular particles through a narrow canal in the gizzard, without injury to the thin tunics of the preparatory cavity, is a remarkable example of the superior powers of living over dead matter. * The contents of this part of the alimentary canal were in smaller pieces than in the crop, but of the same nature ; the fragments of shell were comminuted apparently by mutual attrition, as there were no particles of sand or pebbles present. t From Ferussac’s Monograph on the Cephalopoda Acetabuliferes. CEPHALOPODA. along that canal, being gradually lost in its inner membrane, the lamina next the gizzard is peculiarly enlarged, so as evidently to pre- sent an obstacle to the regurgitation of bile towards the gizzard. The inner surface of the rest of the intestinal canal presents a few lon- gitudinal rugs, with slightly marked transverse puckerings. In the Dibranchiate Cephalopods the gul- let, in consequence of the position of the stomach near the lower part of the visceral sac, is of great length (a, a, fig. 221), but varies in this respect according to the form of the animal. We have seen that in the Nautilus it is dilated into a pyriform crop; a similar dilatation occurs in the genus Octo- pus ; but its position is reversed, the larger end of the sac being uppermost, and probably as the result of the habitually reversed position of the animal with the head downwards, the crop is extended into a large cul-de-sac above the part where the oesophagus opens into it ( b , fig. 220). From this part the crop gradually contracts to its termination. In the Argonaut the crop commences by a similar lateral dilatation, but is continued of almost uniform breadth to the stomach. In the Sepia, Sepiola, Rossia, Onychoteuthis, Loligopsis, and Loligo, and probably in the other Decapods, there is no crop, the gullet being continued of uniform breadth to the stomach (a, a, fig. 221).* The stomach (c, figs. 220, 221,) in all the Dibranchiate Cephalopods is a more or less elongated sac, having its two orifices, the car- dia ( d ) and pylorus (e), close together at the anterior or upper part of the sac, as in the gizzard of birds : the muscular fibres are simi- larly disposed, and radiate from two opposite tendons; they form a stratum of about the same thickness as in the stomachs of omnivo- rous birds. The epithelium, which is con- tinued from the oesophagus and crop (a', b', fig. 220) acquires a greater thickness in the gizzard, and is disposed in longitudinal rugae ; it is readily detached from the muscular tunic. The intestine, at a short distance from the pylorus, communicates with a glandular and laminated sac, analogous to the pyloric ap- pendages in Fish, but which in the Cephalo- pods is always single. In the Nautilus, we have shewn that this rudimental pancreas (p, fig. 219) is of a sim- ple globular form, as in the Doris and some other Gasteropoda. It presents a similar form in Rossia and Loligopsis, in the latter of which it is of large size (g, fig. 223). In Argo- nauta it is triangular; in some species of * From this difference I conclude that Aristotle took his description of the digestive viscera of the Malakia from the Sepia or Teuthis : he says, Mira b to 0-t opa E^ourtv olffotyayov paxpov xai ctevov, iiWtEV8'1 ^E toutou orpoXo (2ov fxiyav xal g ■ 219,) as that artery winds round the bottom of the sac to gain the dorsal aspect of the crop. It is from the arterial blood alone, in this, as in other Mollusks, that the secretion of the bile takes place, there being but one system of veins in the liver, corresponding to the hepatic, which returns the blood from that viscus, and conveys it to the vena cava at its termination. The colour of the liver is a dull red with a violet shade ; its texture is pulpy and yielding. hen the capsule is removed by the forceps, the surface appears under the lens to be mi- nutely granular or acinous, and these acini are readily separable by the needle into clusters hanging from branches of the bloodvessels and duct. The branches of the duct arising from the terminal groupes of the acini, form, by repeated anastomoses, two main trunks, which unite into one at a distance of about two lines from the laminated or pancreatic cavity. There appears to be one example in the Dibranchiate Order where the liver is divided into four lobes, as in the Nautilus; this occurs, according to Dr. Grant, in the Loligopsis guttata ; but in the figure which is given of this structure the lobes are each distinct from the rest, and divided at the middle line; while in the Nautilus the four lobes are united together. Rathkd, on the contrary, who has given an elaborate account of the Anatomy of Loligopsis under the name of Perothis,* describes and delineates the liver, in the two species of that genus dissected by him, as a simple undivided viscus, of an ellip- soid figure, situated in the middle line of the body (12, jig. 223). In Onychoteuthis Banksii the liver is a single elongated laterally com- pressed lobe, obtuse and undivided at both extremities. In the Sagittated Calamary it is single, elongated, and cylindrical. In Sepia and Rossia it is divided into two lateral lobes, both of which are notched at the upper extre- mity. In the Argonaut the two lobes are united for a considerable extent along the mesial line, but are greatly produced laterally, and advance forwards, narrowing towards a point, so as partially to enclose the alimentary canal. In Octopus the liver is a single oval mass, flattened anteriorly. In Eledune it pre- sents a spherical form, corresponding to the ventricose form of the visceral sac. In the two latter genera the ink-bag is enclosed within the * n>)pai0u;, mutilatus, a name applied to this genus by Eschscholtz, in consequence ot the gene- rally mutilated condition of the tentacles. See Mem. de l’Acad. Imp. de Petersbourg, tom. ii. pt. 1 & 2, p. 149. 1 VOL. r. 537 capsule of the liver, but in the Argonaut and in all the Decapodous genera this is not the case. The proper capsule of the liver is very delicate, and apparently nothing more than the outer ter- mination of the cellular tissue which connects the lobules of its parenchyma. When this is inflated from the biliary ducts, it is seen to be composed of cells, formed by the ulti- mate ramifications of the duct, with very thin parietes, and re- latively larger than those of the liver of the Snail. Thisisthe structure observable in the liver of the Octopus, according to Muller, * and Rathkd observed the same structure in the terminal coeca of the hepatic duct in Loligopsis. In the Octopo- dous Dibranchiates, which have a large crop, and the lower pair of salivary glands of corres- pondingly large di- mensions, the two biliary ducts are simplecanals, which are continued from the lower end of the liver, embracing the origin of the intes- tine, and uniting be- low it to terminate by a common orifice in the pyloric ap- pendage. Butinthe Decapodous tribe they continue to send Viscera in situ, Loligopsis. off branches, which Lol. Eschscholtzii. subdivide and form clusters of coecal appendages, through a greater or less proportion of their entire course. The follicles thus appended to the biliary ducts are larger than those which form the liver ; they are figured by Monro in the Loligo sagittata as the ovary, but were considered by Mr. Hunter to represent the pancreas in the Cuttle- fish, from which species he took the preparation of these parts in his collection.f These folli- cles are described with much care and detail by Rathke in the genus Loligopsis, and, ac- cording to him, in one species (10, Jig. 223), ( Lol. Eschscholtzii ,) they terminate, not in the hepatic duct, but separately and directly in the pyloric appendage. We have found these cystic follicles appended to the hepatic duct in Sepiola, Onychoteuthis, Sepioteut/iis, and in the genus Rossia, in which they present the largest proportional development hitherto ob- * De Glandularum Struct. Pen. p. 71. f See No. 775, Physiological Catalogue, 4to. vol. i. p. 229. 533 CEPHALOPODA. served in the class. Here the biliary ducts, as soon as they emerge from the liver, branch out into an arborescent mass of larger and more elongated follicles than those constituting the hepatic parenchyma; these ramifications extend full half an inch from the hepatic duct, and conceal the upper halves of both the stomach and pyloric appendage. Organs of Circulation. — Prior to the dis- section of the Nautilus Pompilius the Ce- phalopoda were regarded as having three dis- tinct hearts, a peculiarity which is not found in the circulating system of any other class of animals. In the Nautilus, however, there is but one ventricle, which is systemic, as in the inferior Mollusks ; and the three hearts are, therefore, characteristic only of the Dibran- chiate or higher order of Cephalopods. These differences in the circulating system of the two orders are accompanied with equally well marked modifications of the respiratory organs; and hence the primary divisions of the class are each distinguished by characters of equal value, and derived from modifications of those organs which afford the most natural indica- tions of the corresponding groups in the other classes of the Molluscous division of Inverte- brate animals. In the Nautilus the veins which return the blood from the labial and digital tentacles and adjacent parts of the head and mouth, termi- nate in the sinus excavated in the substance of the cephalic cartilage. From this sinus the great anterior vena cava (a, jig. 224) is continued, running in the interspace of the shell-muscles on the ventral aspect of the abdominal cavity, and terminating in a sinus (6) just within the pericardium, where it receives the venous trunks of the viscera. (These are indicated by bristles in the figure.) The structure of the vena cava is very remark- able ; it is of a flattened form, being included be- tween a strong membrane on the lower or ventral aspect, and a layer of transverse muscular fibres, which decussate each other on theupperor dorsal aspect; both the membrane and the muscle pass across from the inferior margin of one shell-muscle to the other; they consequently increase in breadth as those muscles diverge, and complete the parietes of the abdomen on the ventral aspect. The vein, however, main- tains a more uniform calibre by its proper internal coat, leaving a space on either side between the membrane and muscle. The ad- hesion of the proper membrane to the muscular fibres is very strong, and these, though ex- trinsic to the vessel, form part of its parietes on the dorsal aspect. There are several small intervals left between the muscular fibres and corresponding round apertures ( a ') in the mem- brane of the vein and contiguous peritoneum, by which the latter membrane becomes continuous with the lining membrane of the vein : from this structure it would seem that the blood Fig. 224. a Circulating and Respiratory Organs , Nautilus Pompilius, CEPHALOPODA. 539 might flow into the peritoneal cavity, or the fluid contents of that cavity be absorbed into the vein.* In the structure of the other veins of the Nautilus nothing uncommon is observed : their principal termination is in the sinus above-mentioned, where the greater or systemic circulation ceases, if we are to consider the lesser circulation to commence where the blood again begins to move from trunks to branches. Four vessels, which, according to the above view, are analogous to branchial arteries, ( c, c,J arise from the sides of the sinus, and proceed, two on each side, to their respective gills. In this course they have each appended to them three clusters of short, pyriform, closely aggre- gated, glandular follicles ( d, d). The larger cluster is situated on one side of the vessel, and the two smaller on the opposite. Each of these clusters is contained in a membranous receptacle communicating with the pericar- dium, and formed by partitions projecting from its inner surface. In these partitions we ob- served a fibrous texture, which conveyed an impression that they were for the purpose of compressing the follicles and of discharging such fluids as might exude through their pa- rietes into the pericardium, whence it might be expelled by the papilliform apertures at the base of the gills into the branchial cavity.f The follicles, however, terminate by their pro- per apertures in the interior of the dilated parts of the vessels to which they are appended : (these are shewn on the right side at d',d'.) We shall revert to these singular bodies in the de- scription of the circulating organs of the Di- branchiata. The branchial arteries having reached the roots of the gills become contracted in size, and their area is here occupied by a valve which opposes the retrogression of the blood. Each vessel, then, penetrates the fleshy stem of the branchia ( e ), where it dilates into a wide canal, which presents a double series of orifices through which the blood is driven by the contraction of the surrounding muscular sub- stance, into the vessels which extend along the concave margins of the branchial laminae. The branchial vein (f) receives the aerated blood from vessels extending along the convex margins of the respiratory laminae, by a series of alternate slits, and is continued down the anterior or inner side of the gill. After quit- ting the roots of the gills each vein crosses its corresponding artery on the dorsal aspect, and is continued, without forming a dilatation or sinus, to the systemic ventricle, where regurgi- tation is prevented by a single semilunar valve at the termination of each vein. The ventricle (p ) is of a somewhat com- pressed and transverse quadrate form : its mus- cular parietes are nearly a line in thickness, and present internally a decussated structure. * For a further description of this structure, its analogies, and probable uses, see ‘ Memoir on the Pearly Nautilus,’ p. 27 et seq. t We found the pericardium in the specimen dissected filled with coagulated matter accurately moulded to the different parts which contained it. Two arteries arise from it ; one superior and small (h), whose orifice is furnished with a double valve ; the other inferior and of large size (i ), coming off from near the left angle of the ventricle, and furnished with a muscular bulb about five lines long, at the termination of which there is a single valve ; and which ought rather to be considered as a continuation of the ventricle. The lesser aorta gives off a branch to the great gland of the oviduct; a second, which is continued down the membra- nous siphuncle of the shell ; and a third to the fold of intestine (l). The larger aorta passes downwards between the gizzard and ovary, and renders vessels to both these viscera. It then winds round the bottom of the pallial sac, sends off large branches to the liver, and gains the dorsal aspect of the crop, along which it is continued, distributing branches on either side to the great shell-muscles, to the cephalic cartilage, where it divides into two equal branches, which pass round the sides of the oesophagus, and furnish branches to the mouth, the sur- rounding parts of the head and the funnel. In the Dibranchiata the veins of each arm form two principal branches, which descend along the lateral and posterior parts of those appendages; each lateral vein unites at the base of the arm with the opposite vein of the adjoin- ing arm; the united vessel is joined by another similarly formed ; and the whole of the venous blood is thus ultimately conveyed to an irre- gular circular sinus, from the anterior part of which, between the head and the funnel, the great anterior cava is continued. In the Octo- pus this vessel ( a, jig. 226) is provided with two semilunar valves, where it communicates with the venous circle. A little below this part it receives the veins of the funnel ; then those of the anterior part of the liver (b ) and of its muscular envelope. Upon its entrance into the pericardium the vena cava divides without forming a sinus as in the Nautilus ; and sometimes before, sometimes after its divi- sion it is joined by two large visceral veins (c). Thus reinforced, each of the divisions ( d, d) proceeds downwards and outwards to the lateral or branchial heart of its correspond- ing side ; but previous to opening into the ventricle it dilates into a sinus (e), which also receives the venous blood from the sides of the mantle and the fleshy and vascular stem of the branchia, by the vein marked f. Both the divisions of the vena cava and the two visceral veins, after having entered the pericar- diac or venous cavity, are furnished with clusters of spongy cellular bodies (g, g), which open into the veins by conspicuous foramina, like the venous follicles of the Nautilus above described. In no species of Cephalopod which has hi- therto been anatomized, have these appendages* been found wanting ; but they vary in form in different genera. In the Genus Eledonef they * From a consideration of the different particu- lars given in Aristotle’s anatomical description of the Cephalopods, Kohler supposes the part which he calls ptu'rtc, mytis, to have been the glandular appendages of the veins above described. f Carus, Vergleich. Zootomie, tab. ivi fig. viii. x, Elcdone Moschata. 2 N 2 540 CEPHALOPODA. Fig. 225. Circulating and respiratory organs — Cuttle-fish form thin colourless pyriform sacs, extending nearly an inch from the vein. They are ar- ranged in distinct clusters, and are relatively shorter in Argonauta. In Sepioteuthis the whole extent of the superior and inferior tranks of the veins contained in the pericardium pre- sent an uniform and continuous cellular en- largement of their parietes. In Loligo the coats of the corresponding veins in like man- ner present only a spongy thickening. In Sepia the cells are more elongated, but are large, irregular, and flocculent ( c,c , Jig. 225), and continued without interruption not only upon the divisions of the vena cava (a), but upon the visceral veins, two of which ( b, b) present remarkable dilatations. In Loligopsis the venous follicles are in distinct groups, as in Nautilus ; and Rathk6 describes them as presenting a laminated and glandular structure. With respect to the function of these bodies nothing is as yet definitely known. They are well supplied with blood from the neighbouring arteries, and are undoubtedly glandular ; but the matter which they secrete has not yet been subjected to chemical analysis. If the spongy coats of the vena cava of a Calamary be pressed, a whitish fluid escapes, which is al- 51 From Home’s Comparative Anat. vol. iv. See the original figure and description by Hunter, in Descr. Catalogue of Mus. R. Coll, of Surgeons, vol. ii. pi. xxii. ways thicker and more turbid than the blood which circulates in the vein. The elongated cells of the Poulp yield in like manner an opake and yellow mucus. Some physiologists suppose that the secreted matter is not expelled by the orifices of the sacs into the veins to be mixed with the current of blood, but that the venous blood passes into the cells by those apertures, and that the matter secreted from it exudes from the parietes of the cells or follicles into the great serous cavity surrounding them. Mayer, considering that the urine is secreted from venous blood in the lower vertebrate animals, regards these venous appendages as the renal organs of the Cephalopods; the serous sacs (h, fig. 226), therefore, which Cuvier calls the ‘ great venous cavities,’ and which we have termed the ‘ pericardium,’ the German Physi- ologist calls the ‘ urinary bladder;’ and the papillary orifices (i ) leading into the branchial or excrementory chamber, which we have com- pared with the orifices leading from the peri- cardium of the Ray and Sturgeon into the peritoneal cavity of the abdomen, f Mayer calls the urethra. It must be observed, however, that this Physiologist does not advance any proof from chemical analysis in support of his theory. Cuvier, on the other hand, believing that the water of the branchial chamber might have access by the orifices to the cavities containing the appendages in question, supposes that they t Memoir on the Nautilus, p. 33. CEPHALOPODA. 541 * From Mayer, Analecten fur Vergleichende Anatomie, tab. v. Systemic Ventricle, Onychoteuthis. Viscera of Poulp .* may serve as accessory respiratory organs. The valvular structure of the orifices is opposed, however, to this view; while it supports the doctrine of their being excretory outlets. The venous follicles may, therefore, serve as emunctories, by means of which the blood is freed of some principle that escapes from their external pores ; or they may alter the blood by adding something thereto; or, like the spleen, they may assist in converting arterial to venous blood. As a secondary function they may serve as temporary reservoirs of the venous blood whenever it accumulates in the vessels either from a general expansion, or from a partial impediment in its course through the respi- ratory organs ; and thus the cells or follicles, which are endowed with a motion of systole and diastole, like the auricles of the heart, may serve to regulate the quantity of blood trans- mitted to the gills. The branchial ventricles ( d, d,fig. 225) are appended to the roots of the gills : in the Octo- poda they are simple pyriform muscular cavities (k, k,fig. 226,) generally of a blackish grey co- lour ; in the Decapoda they are elliptical or trans- versely oblong, of a light grey or pale red co- lour, and have a white fleshy appendage ( e, e, fig. 225,) hanging to their lower surface or their external side. The connecting pedicle is hollow, and communicates with a small cavity in the substance of the appendix. Internally these ventricles are deeply impressed writh cells and decussating carneae columnae (k,fig. 226), and where they com- municate with the ve- nous sinus two semi- lunar valves (l) are placed to prevent re- gurgitation . Their func- tion is to accelerate the circulation through the branchiae ; and by this simple addition to the respiratory appa- ratus, the two gills of the Dibranchiata are rendered equal to the office of preparing the blood to maintain the increased muscular ex- ertions, and repair all the corresponding waste which the vita! economy of this highly organized group of Molluscous animals occasions. The branchial veins (m, m, figs. 225, 226) return, as in the Nauti- lus,along the internal or unattached side of the commissure of thebran- chial laminae ; and, as they approach the sys- ic ventricle, generally dilate into a sinus (n) Fig. 227. 542 CEPHALOPODA. on each side : these sinuses are relatively larger in the Sepia than the Octopus. In both species the branchial vein resumes its ordinary dimen- sions before terminating in the ventricle; but in the Cuttlefish the sinus is placed closer to the ventricle. The systemic ventricle (o) is situated in the mesial plane between the bifurcation of the vena cava above, and the ovary or testis below. In the Octopus and Eledone it presents a glo- bular form, rather extended tranversely, and with the branchial sinus entering at its superior and lateral aspects. In the Loligo and the Onychoteutliis (fig. 227) it is lozenge-shaped, with the long axis in the axis of the body; giving off the two aorta; (c, d) by the anterior and posterior angles, and receiving the bran- chial veins ( a, a,) at the lateral angles. In the Sepia, ( o, fig. 225,) Sepioteuthis, and Rossia, the systemic ventricle is a fusiform body, bent upon itself at right angles. About one-half on the right side lies in the axis of the body, the remainder extends transversely to the left side ; the extremity of this part receives the left bran- chial vein, the other extremity gives off the an- terior aorta ( q, fig, 225). The bulb of the posterior and generally the larger aorta ( p, fig. 225) is continued from the middle of the transverse portion ; the right branchial vein enters the middle of the right side of the lon- gitudinal portion of the ventricle. In all the Dibrancliiata the parietes of the systemic heart, though thin, are firmer and more muscular than those of the branchial hearts; and its cavity is generally about three times greater than that of either of the others : its inner surface shows the regular interlacement and decussation of the column® carneae, none of which, however, project into the cavity. The termination of each branchial vein is defended by a pair of membranous semi- lunar valves (b, fig. 227). The origin of the lesser aorta (p), arising from the anterior part of the ventricle, is defended by a single valve (e, fig. 227); that of the great aorta, (q1, fig- 226,) which, though posterior in its origin, is de- stined to supply the head and anterior parts of the body, is generally provided with a mus- cular bulb, as in the Nautilus. In the Octopus it is defended, according to Cuvier, by two semilunar valves; but in the Calamary and Onychoteutliis by a single valve (f, fig. 227), In the Octopus there is also a third small artery (r, fig. 225) given off directly from the ventricle, which is distributed to the generative organs, and presents considerable periodical variations of size in relation to the functions of those parts. In the same genus the small aorta, which arises from the anterior part of the ventricle, first gives off two long and slender branches (s, s, fig. 226), which are distributed to the venous follicles, whose arterial vascularity we have before mentioned. The trunk then di- vides into two arteries, of which the largest ( t) ascends in front of the vena cava to be distri- buted to the mantle; the other supplies the folded intestine and surrounding peritoneum. The large aorta first passes backwards and to the right between the layers of peritoneum which separate the intestinal sac from that of the pyloric appendage and that of the stomach; winds round the latter, and passes, by a proper opening, to the right of the cardia through the muscular septum, and into the cavity behind the liver, and ascends on the right side of the dilated oesophagus to the cartilaginous cranium. Here, after distributing branches to the sur- rounding parts, it bifurcates and completely encircles the gullet; and from this vascular ring, which is strikingly analogous to the bran- chial arches in Vertebrata, the head and all its complex radiating appendages derive their nu- triment. Respiratory Organs. — The branchiae pre- sent the same general form and structure in both orders of Cephalopods, but differ, as before ob- served, in number, and also in their mode of attachment to the mantle. They are always entirely concealed and protected by the mantle, which is extended forwards so as to form a peculiar chamber for them anterior to the other viscera, and into which the rectum and gene- rative organs open. It is interesting to perceive the respiratory cavity retaining, iu the highest organized Mollusks, that relation with the ana! extremity of the digestive canal which we trace through the whole of this type of animal con- formation, and which forms so well-marked a line of distinction between the Molluscous and Vertebrate divisions of the animal kingdom. In the Nautilus the four branchi® are at- tached by their bases only to the inner surface of the mantle ; but in the Dibranchiates a thin fibrous membrane connects the fleshy stem of each gill to the contiguous surface of the man- tle. In the Nautilus the branchiae are subject to contortions from the want of this support ; and in the specimen which we dissected, we found the gills on one side closely bent upon themselves, with their apices turned down; this circumstance does not probably impede a cir- culation which flows with an equable and con- tinuous current through the gill ; but where the blood is driven in jerks by the contractions of a powerful ventricle, a necessity then exists for theprovision of a free channel for the passage of the fluid ; and accordingly we find that the obstruction of the branchial artery by the bending of the fleshy stem of the gill is obvia- ted by the simple but effectual means above described, viz. the superaddition of a connect- ing membrane, which always preserves the gill in a straight position. In both orders of Cephalopoda the branchia; present an elongated pyramidal figure, with their apices directed forwards : they are compressed from before backwards in the Nautilus (n,m, fig. 224), and from side to side in the Cuttle-fish ( i, k, fig. 225) and most other Dibranchiates. They are composed of a number of triangular vascular lamin® extendingtransversely from each side of a central fleshy stem ( h,fig. 225), having an alternate disposition : each lamina is com- posed of smaller transverse lamin®, which are again similarly subdivided ; the entire gill thus exhibiting the structure called by botanists ‘ tri- pinnate,’ by which an extensive surface is afiord- edfortheminutedivisionof the branchial vessels. CEPHALOPODA. 543 In the Nautilus (Jig. 224) there is a larger and smaller branchia on each side; the larger and external branchia (m ) presents forty-eight pairs of laminae; the smaller branchia ( n ) thirty-six. In the Dibranchiates the gills vary in the relative size and number of laminae in different genera ; they are, perhaps, proportionally small- est in the Loligopsis, where, according to Rathke, the number of branchial laminae does not exceed twenty-four pairs ; and it is inte- resting to observe in this genus that the mus- cular structure of the mantle has a correspond- ingly feeble development. In the Cuttle-fish the branchiae are each composed of thirty-six pairs of triangular laminae : in the Sagittated Calamary of sixty pairs of laminae. As the branchiae of the Cephalopods are un- provided with vibratile cilia, respiration is effected by the alternate dilatation and contrac- tion of the branchial chamber ; in the first ac- tion the sea-water rushes in by the anterior aper- ture of the mantle ; by the second it is expelled through the cavity of the funnel. As in other classes, respiration is performed more quickly in the young than in the full-grown animals : Dr. Coldstream witnessed an Eledone, which measured one inch and a half in length, respire eighteen times in a minute ; while one of the same species, which measured four inches in length, respired ten times in a minute. The proper direction of the respiratory currents is insured by various mechanical contrivances ; in the Nautilus, the funnel passes through a hole in the substance of the mantle, which fits it so closely, that at the moment when the funnel is distended by the expiratory stream, no space is left external to it by which the water can escape ; and the greater the force by which the water is driven into the funnel, the closer is it girt by the mantle. In the Poulp and Eledone, where the funnel is connected to the fore part of the neck, and the mantle passes across its base, two large valvular folds (one of which is shown at v,jig. 216) are extended from its sides; these are concave towards the respiratory sac; they subside during inspiration, and the parietes of the funnel at the same time are collapsed ; the latter during expiration are dilated, while the valves are raised and expanded, and thereby prevent the ejected currents from passing out- side the funnel. In the Argonaut, and in all the Decapods, except the Loligopsis and Cranchia, the sides of the funnel are articula- ted to the opposite sides of the mantle by ball- and-socket joints, which produce so close an apposition of the anterior free margin of the mantle with the parts it surrounds, that upon its contraction, no other outlet, save the funnel, is left for the expiratory currents. In the Ar- gonaut the pallial eminence is a round tuber- cle, below which is a small cavity, and these are adapted to a cavity and tubercle of corre- sponding form at the side of the funnel. In Sepia, the articular tubercle is elongated in the direction of the axis of the body, and is of an oval form. In Loligo and Onychoteuthis it is still more elongated and narrow, and the arti- cular depression is conformable : in Loligopsis the corresponding cartilage is no longer sub- servient to an articulation with the funnel, but is represented by a series of wart-like knobs. Tegumentary System. — The skin of the Cephalopods is thm and lubricous, and can be more easily detached from the subjacent muscles than in the inferior Molluscous classes. In the Poulp, Eledone, Argonaut, Cuttle-fish, and Sepiola, its texture is soft and tender, and the whole mantle is semitransparent in some species, as the Octopus hyalinus ; but in the Calamaries and Onychoteuthides it is thicker, harder, and more unyielding ; it is interesting to observe that it is in these latter genera that the epidermoid system is most developed, as is exemplified in the horny denticulations and hooks upon the acetabula. In the Cuttle-fish the suckers are provided with simple unarmed horny rings. In the Octopods the epidermis is reflected over the interior of the suckers without being thickened into a horny substance at that part. In the body generally the epidermis is readily de- tached by maceration, and forms a thick, white, elastic, semitransparent, external layer. The colorific stratum of the integument forms, both in its structure and vital phenomena, one of the most curious and interesting parts of the organization of this singular class of animals ; and the nature of which, when thoroughly un- derstood, may be expected to elucidate the mysterious operations of light in producing and affecting the colours of animals. This stratum, which is analogous to the rete mucosum, consists of a very lax and fine vascular and nervous cellular tissue, con- taining an immense number of small closed vesicles, which vary in relative sizes in different species of Dibranchiata. These vesicles are of a flattened oval or circular form, and contain a fluid in which is suspended a denser colouring matter. The colour is not always the same in all the vesicles, but in general corresponds more or less closely with the tint of the secre- tion of the ink-bag. This, for example, is the case in Sepiola, in which all the vesicles con- tain material of the same colour. In Sepia, be- sides the vesicles which correspond to the ink in the colour of their contents, there is another series of an ochre colour. In Loligo vulgaris there are three kinds of coloured vesicles, yel- low, rose-red, and brown. In Loligo sagittata there are four kinds, saffron, rose-red, deep blue, and light blue. In Octopus vulgaris there are also four orders of vesicles, viz. saffron, red, blackish, and blueish. The Argonauta Argo possesses vesicles of all the colours which have been observed in other Cephalopods, and hence the variety and change of colour which the surface of its skin presents when exposed to the light. These vesicles have no visible communica- tion either with the vascular or the nervous systems, or with each other : yet they exhibit, during the life-time of the animal, and long after death, rapid alternating contractions and expansions/* If, when the animal is in a state * Conf. Dr. Coldstream in Edinb. Journal of Natural and Geographical Science, vol. ii. p. 297. 344 CEPHALOPODA. of repose, and the vesicles are contracted and invisible, the skin he slightly touched, the co- loured vesicles show themselves, and in an in- stant, or sometimes with a more gradual mo- tion, the colour will be accumulated like a cloud or a blush upon the irritated surface. If a portion of the skin be removed from the body and immersed in sea-water, the lively contractions of the vesicles continue ; when viewed in this state under the microscope by means of transmitted light, the edges of the vesicles are seen to be well defined, and to pass in their dilatations and contractions over or under one another. If the separated portion of integument be placed in the dark, and exa- mined after a lapse of ten or fifteen minutes, all motion has ceased; but the vesicles, when re-exposed to a moderately strong light, soon, in obedience to that stimulus, recommence their motions. As the vibratile microscopic cilia have been recently traced through the higher classes of the animal kingdom, it is not an un- reasonable conjecture that equally inexplicable motions of the colouring parts of the integu- ment may also be detected in other classes than that in which we have just described them, and thus a clue may be obtained towards the explanation of the influence of geographical position on the prevailing colours of the animal kingdom. Besides the colouring matter, another kind of product is secreted between the corium and cuticle, viz. the shell : this presents diffe- rent degrees of development in different genera. M. De Blainville in France, and Leach, Broderip, Gray, and Sowerby, among the able naturalists of our own country, maintain that the Argonaut shell is not the product of a Cephalopod, but of some inferior Mollusk, allied to the Carinarise, whose shell Linnceus indeed placed in the same genus with the Argonauta, in consequence of the close rela- tionship subsisting between them, both in form and structure. The principal grounds for this opinion are the following. The Ocythoe has no muscular or other attachment to the Argo- naut shell. When captured, and placed alive in a vessel of sea-water, it has been seen vo- luntarily to quit the shell, and in one instance without manifesting any disposition to return to it. In this state, viz. without its shell, it was described by Rafinesque as a new genus of Cephalopod under the name of Ocythoe, and De Blainville, who first recognized this genus as being founded on an animal identical with the Cephalopod of the Argonaut, or the Nautilus primus of the ancients, retained the name in orderto distinguish the supposed parasite from the shell which it had, according to this theory, adopted. Agreeably with the absence of any natural connexion between the Ocythoe and the shell in question, is the fact that this animal is not found in any constant or regular position in the shell. In most examples we have found the funnel and ventral aspect of the bodyturned tow'ardstheexternalwall of theshell, as in the figure (fig. 206). The Cranchian speci- men figured by Mr. Sowerby was in the same position. In the specimen which M. De Blain- ville* has carefully delineated for this pur- pose, the back of the Ocythoe is next the invo- luted convexity of the shell, the funnel is towards the opposite expanded concavity, but turned out of the middle line, and separated from the parietes of the shell by the retracted feet. In the figure which illustrates Brode- rip’s excellent Memoir, f the animal is repre- sented with the funnel next the involuted crest of the shell. In another specimen in the unique collection of the same Naturalist, the Cephalo- pod is retracted on a mass of ova, its arms hud- dled together, and its funnel projecting from the middle of one side of the shell; on the op- posite side numerous suckers are seen expand- ed and applied to the inner surface of the shell, demonstrative of the abnormal mode of its ad- hesion to that body. Whatever be the position in which the Ocythoe is found, the whole of the exterior surface of its mantle is coloured as in the naked Cephalopods, which seems to indicate that it has not been permanently excluded from light by an opake calcareous covering, such as the Argonauta shell must have formed if it had been applied to the body of the Ocythoe ah ovo. What is more remarkable, and con- trary to the analogy of true testacea, is, that there is little or no correspondence between the disposition of the colour of the Ocythoe and that of the Argonaut shell. The external sur- face of the skin of the Ocythoe has the same entire epidermic covering as in the naked Poulp, yet the Argonaut shell is furnished with a delicate epidermis in its natural state. All Mollusks which are naturally pro- vided with external shells have them for pro- tecting either a part or the whole of the body ; and in the latter case the interior of the shell is always kept clear, that the animal may retire to it for safety; but this retraction into the hol- low of the shell is impossible to the Ocythoe, at least in those numerous cases in which the shell is found more or less filled with masses of ova. Other Cephalopods, with external shells, indubitably their own, as the Pearly Nautilus, have adequate muscular attachments ; and it may reasonably be asked does the Argo- naut afford a valid exception to this rule? Such an exception indeed it must form if the shell be really secreted, as the Continuator of Poli asserts, by the Cephalopod inhabi- tant ; and not only in this particular, but in every principle which has been established in reference to the relations of a shell to the body and the reciprocal influences affecting them in the Molluscous classes. The naturalists who maintain that the Ce- phalopod of the Argonaut and the shell are parts of one and the same animal, insist on this unde- niable fact, that from the time of Aristotle to the present day the Argonaut shell has never been found with any other inhabitant than the Ocythoe ; and, what is of more weight, that the Ocythoe has never been found in any other shell than the Argonauta. Whereas the Hermit-Crab * Malacologie, tom. ii. p- 1, f Zoological Journal, vol. iv. CEPHALOPODA. 545 adopts different species as they happen to fall in his way. And further, that the different species of Argonauts, as the A. Argo, A. tuberciilata, and A. hians, have each different species of Ocy- tho'e. We may add that the light fragile tex- ture of the Argonauts shell, like that of Ca- rinaria, bespeaks a floating oceanic species, and not a Mollusk that creeps at the bottom, and therefore the probability is less that its real inhabitant should have escaped the notice of the Naturalist, supposing the Cephalopod to be a parasite. In the posthumous volume of Poli’s great work on the Sicilian Testacea, it is stated that that naturalist watched the daily development of the ova of an Ocythoe contained in an Ar- gonaut shell, and that, by means of the micro- scope, he detected the rudiment of the shell in the embryo : the completion of the experi- ment was, however, accidentally interrupted ; and the figure which the editor Della Chiaje has published of the ovum, which it was hoped would have determined the question, seems to shew the yolk appended to the embryo instead of the shell. Air. Gray,'* on the other hand, has recently stated that the nucleus of the Argonaut shell, or that part which, from analogy, must have been formed in the egg, is too large to have been formed in the egg of the Ocythoe. The arguments drawn from the microscopical exa- mination of the ova of the Ocythoe before the commencement of the development of the embryo, are obviously inconclusive; since, whatever the subsequent products of the egg might be, at this period only the granular and oily particles of the vitelline nidus could be expected to be seen. With respect to another argument against the legitimate title of the Ocythoe to the shell, founded on the supposed uniform occurrence of a deposition of eggs in the same shell, we can adduce three exceptions in which the Argonaut shell was exclusively occupied by the Cephalopod ; these specimens were taken along with several others, by Captain P. IJ. King, R.N., from the stomach of a Dolphin, caught upwards of six hundred leagues from land, and were kindly presented to us by that gentleman. In these examples, as in others, we were struck with the exact correspondence between the size of the shells and that of their inhabitants, every trifling difference in the bulk of the latter being accompanied with proportional differences in the shells which they occupied. The consideration of all these circumstances has prevented a satisfactory con- clusion being formed with respect to this long- agitated and nicely-balanced question, and we are compelled to repeat after the Stagyrite, wept Si ywi/Ttox; xai truvav^nrtwt; tov orTpaxov aKpifiu; yh olnai SwTai.-j- Observation of the development of the Ocythoe until the period when it is ex- cluded from the egg, would decide the point. * See Proceedings of the Zoological Society, September, 1834. f “ But as touching the generation and growth of the shell nothing is as yet exactly determined.” — Hist. Anim. lib. ix. But this must be done satisfactorily, and with the requisite knowledge, care, and good faith on the part of the observer. Before, however, quitting this subject, we will mention one example of a naked Ce- phalopod, nearly allied to Ocythoe, having manifested a parasitic propensity similar to that which is laid to the charge of that genus. A medical gentleman, (Dr. Moffat, of the Hon. East India Company’s Ship, Flora,) who had collected objects in Natural History in the East Indies, amongst other specimens' brought home an Octopus, which was caught in the Madras roads in his presence, by means of a baited book and line, and, when drawn out of the water, was found to have its ven- tricose body firmly imbedded in a ghee-bowl, (one of the small round pots in which the fluid butteris brought on board ship,) which had been thrown overboard. The Doctor disengaged the Cephalopod from the bowl before placing it in spirits, and when we related to him the interest which the fact possessed in consequence of the problematic nature of the Argonaut shell, of which he was not before aware, he regretted much that he had not preserved the Octopus in the singular domicile which it had chosen. Another instance of the parasitic appropriation of a dwelling-place by a Poulp is related by M. Desjardins, in the Report of the Natural History Society of the Mauritius ; he found an Octopus Arenarius in the shell of a Dolium. The parasitic occupation of shells by the Octopi for the purpose of depositing the ova in them was not unknown to Aristotle. K«; mo riXTEi o yh vro'hinrovq d; t a; SaXayap h dp xepayiov n ri aXXo Ko~\ov oy.o-.oV, &c. “ And the Polypus oviposits in cavities or in shells, or some such hollow places.”* To return to the shells of the Dibranchiate Cephalopods; these, then, with the doubtful exception of the Ocythoe, are always internal, and either camerated and siphoniferous, or laminated and more or less rudimental, and concealed within the substance of the mantle. In Octopus and Eledone the traces exist in the form of two small amber-coloured styli- form bodies, lodged loosely in capsules, (im- bedded in the sides of the mantle,) and ex- tending downwards from the insertion of the shell muscles, close to the base of the bran- chiae. When the capsules are laid open, the styles frequently fall out in pieces, being of a friable texture. In the Octopus the styles are straight and elliptical ; in Eledone they are largest at their upper extremities, and become filiform as they pass in a curved direction downwards. In all the Decapoda in which the shell is rudimental, it is represented by a single piece lodged in the middle line of the dorsal region of the mantle. It is of a horny texture in all the genera except the Sepia, and has generally more or less the form of a feather, as in the Calamary (Jig. 228), or of a straight three- edged sword. * Hist. Anim. v. c. 16. 546 CEPHALOPODA. According to Aristotle the hard dorsal body of the Cuttle-fish was called by the Greeks ‘ sepion,’ that of the Calamaries ‘ xiphos.’* In Sepiola and Rossia the gladius does not reach half-way down the back, beginning at the anterior margin of the mantle, which in the latter genus is free. In Loligopsis, Cran- chia, Onycoteuthis, and Loligo, it extends the whole length of the posterior part of the mantle. In Sepioteuthis it rivals in breadth the Sepium or Cuttle-bone, but is horny and elastic, as in the Calamary. In the latter the gladius is multiplied by age, and several are found packed closely one behind another in old specimens. Fig. 229. Gladius of the Calamary. Rudimental Shell of the Cuttle-fish. The Sepium or Cuttle-bone (fig. 229) is a well-known substance, and formerly figured in the Materia Medica as an antacid. It is a light cellular calcareous body, of a peculiar form and structure ; and, as it is confined ex- clusively to the genus Sepia, its presence alone serves to characterise that section of Cepha- lopods. Its form is an elongated oval, de- pressed, convex on the dorsal surface, partly convex and partly concave on the opposite side: it terminates posteriorly in a very thin, * “ T r. /Mtv ovv arimla, xal in TtufhSi Xal rti TEiifla) EVTflC Ift 7a (TTEfJEa £V TOO 7TpaVH Too o'chy.ctTot;, a xa- XoSa-i to fj.h rinov, to Js £l54 CEPHALOPODA. liquely downwards and backwards, and if air be blown or fluid injected through it, the large cavity surrounding the anterior part of the eye- ball will be distended, and the cornea ren- dered convex. In the Poulp the corresponding aperture (o,Jig. 216) is somewhat larger, and situated more in the axis of vision : its inferior and posterior margin is extended beneath the opposite margin, so as to form a semi-transpa- rent curtain behind the external opening. In the common Calamary and the Onychoteuthis the corneal perforation is stdl larger, vertically oblong, and through it the capsule of the cry- stalline lens, which projects through the scle- rotic aperture, is immediately exposed to the external medium. Organ of Hearing. — This organ has hitherto been found only in the Dibranchiate division of the Cephalopods. It consists, as in the C'yclostomous or lower organized cartilaginous Pishes, of an acoustic vestibule, containing a limpid fluid and a calcareous body or otolithe suspended in a delicate sacculus to the filaments of the auditory nerve, but without the semi- circular canals, cochlea, or other parts which progressively complicate the Organ of Hearing in the higher animals. The vestibular cavities ( a , a, Jig. 235) are situated, not at the sides, but at the base of the cranium in that thick and dense part of the carti- lage which supports the sub- cesopbageal cerebral masses. In the Cuttle-fish the cavities are of a sub-quadrate form, separated only by a thin septum (cj ; and they are every where closed, except at the entrance of the nerve. From their inner surfaces project several obtuse moderately elongated processes ( b , b, fig. 235), of a soft elastic texture, which support the central sacculus (d) and otolithe (e), and doubtless serve to convey to it the vibrations which affect the body generally. The sinuosities in the intervals of these pro- cesses seem to be the first rudiments of those which in the higher classes are extended in the form of canals and spiral chambers within the substance of the dense nidus of the labyrinth. The otolithe in the Sepia officinalis is of an ir- regular flattened quadrangular figure, with two of the angles produced so as somewhat to re- semble the human incus : the surface next the parietes of the sacculus is convex and smooth, the opposite one concave and broken : it is white and transparent. (In Jig. 235, the oto- lithe is seen as exposed in the sacculus on the right side.) In the Octopus vulgaris the vestibules are nearly spherical, and their panetes are smooth ; the otolithes are of an hemispherical figure at- tached to the dorsal part of the membranous sac, of a white colour on the adherent surface, and yellow on the opposite side : the rest of the sacculus is filled with a transparent gelatinous fluid. The auditory nerve divides into three branches, which spread over the sacculus, and convey to the sensorium the vibrations which affect the otolithe and its sac. Fig. 235. Organ of Hearing, Cuttle-Jish. In the Eledone cirrosa the otolithe is shaped like the shell of a limpet, with the apex rounded and curved backwards ; of a pink colour on the sides, but of a white semitransparent texture internally. The otolithes in all the Dibranchiates effer- vesce with acids, like other substances com- posed of carbonate of lime; and in the Poulp, Eledone, and all the Decapods except the Cuttle-fish, they are the only earthy substances which enter into the organization of these animals. Organ of Smell.— The sense of smell has been attributed to the Cephalopods by all natu- ralists who have written on their habits ; from Aristotle, — who mentions the strong-scented herbs which the Greek fishermen attached in his day to their baits, in order to prevent their being destroyed by the Mollia, — down to Cuvier, who expressly asserts that they are at- tracted by the odour of different substances. But no organ expressly appropriated to the ex- ercise of the olfactory sense has been deter- mined in the Dibranchiate Cephalopods. In dissecting the Nautilus Pompilius, our attention was directed to a series of soft mem- branous laminae ( h,fg . 231) compactly arran- ged in a longitudinal direction, and forming a circular body very closely resembling the lami- nated olfactory organ in Fish. The position of these lamina, as well as their form and arrange- ment, supported the belief that they exercised the functions of an olfactory organ ; being situated just before the entrance of the. mouth, 1 between the internal labial processes : nerves were also traced to them from the inferior labial ganglions. From analogy we are inclined to suppose that the external lips in the Dibranchi- 1 ate order may be the seat of the olfactory sense. '' Organ of Taste. — From the elaborate struc- ture which the tongue displays in both orders ; of Cephalopods, there can be no doubt but that these destructive creatures fully relish the prey that they devour, and, in correspondence to their particular tastes, are led to select those species the limitation of whose increase is assigned to their charge. The anterior soft papillose lobes of the tongue of the Nautilus are shewn in the sub- joined figure (fig. 236), in which they are Fig. 236. d denoted by the letter c; e indicates the middle spiny plate, f the posterior coarser papillose surface, and g the faucial folds. The nerves of this part are derived from the brain itself, or supra-cesophageal mass. CEPHALOPODA. Organ of Touch. — With respect to the sense of touch, the exposed part of the integument of the Nautilus presents numerous papillary eminences ; and several of the naked Cepha- lopods are remarkable for the irregular surface of the skin, which seems designed to increase its natural sensibility. Thus, in the Cranchia scabra, flattened processes terminating in nu- merous pointed denticulations, project from the surface of the mantle ; in the Sepia papil- lata the integument is beset with branched papillae ; in Sepia mammillata with more sim- ple obtuse eminences ; in Sepia tuberculata, with tubercles; in Octopus aculeatus, with pointed tubercles, &c. That these projections serve to warn the creature of the nature of the surfaces which come in contact with its body is highly probable; and it is not at all uncommon to find in those species, which have smooth skins over the body generally, that there are tubercles in the immediate neigh- bourhood of the eyes, as in the Octopus vulgaris, Octopus Lichtenaultii , Octopus Wes- terniensis, &c. In the Nautilus, the more exposed pedun- culate eyes are expressly provided with re- tractile sensitive tentacles on each side, as has been already mentioned. With respect to the organs destined for the active exercise of touch or exploration, we must suppose that the numerous tentacles with which the Nautilus is so remarkably provided, from the softness of their texture, their an- nulated surface, and liberal supply of nerves, serve in this capacity as well as instruments of prehension and locomotion. The less nu- merous but more highly developed arms of Fig. 237. 555 the Dibranchiates doubtless exercise the same faculty, especially at their attenuated flexile extremities. The internal fringed circular lip surrounding the mandibles, in both orders of Cephalopods, presents another example of the dermal co- vering so disposed as to be the seat of delicate sensation. Generative System. — The individuals of the present class are, as before stated, of distinct sexes, which in the Dibranchiate order are re- cognizable by diversity of size, external form, colour and shape of the internal rudimental shell. In the common Calamary, for example, the gladius of the male is one-fourth shorter, but broader than that of the female. As only the female, organs are known in the Tetrabranchiate order, we are limited in the description of the male parts, to those which exist in the Dibranchiate Cephalopods ; but from the close resemblance subsisting in the two orders in the form of the organs of the female sex, little difference can be expected to exist in the structure of the male apparatus. In the Poulp the male organs consist of a testicle, a vas deferens, a kind of vesicula seminalis, a gland compared by Cuvier to the prostate, the sac containing the moveable fila- ments which Needham’s description rendered so celebrated, and lastly the penis. The testicle is situated at the bottom of the visceral sac, and is composed of a membra- nous pouch (a, Jig. 237), to one part of the inner surface of which are attached a number of branched elongated glandular filaments (6), which swell at the breeding season, and dis- charge an opake white fecundating fluid into the sac. From this cavity the fluid escapes by the orifice (c), and passes into the vas de- ferens (d). This is a narrow tube, indefinitely convoluted upon itself; it opens into another larger canal (e), the interior of which is di- vided by ridges and incomplete septa ; its texture seems to be muscular, so that it pro- bably serves by its contractions to eject the fluid carried into it by the vas deferens. From the vesicula seminalis the semen next traverses the extremity of an oblong gland (f), which is of a compact gratiular structure, and, like the prostatic or Cowperian glands, contributes some necessary secretion to the fecundating fluid. Next follows the muscular pouch (g) con- taining the filaments or animalcules of Need- ham (Ji). When first exposed, they present the appearance of white filaments, from six to eight lines in length, packed closely and regu- larly in parallel order, in three or four rows one above another, from the fundus to the aperture of the pouch ; and they are kept in that position by a spiral fold of the membrane of the pouch, without, however, having the slightest adhesibn to that part. For a long time after being removed from their position they continue to exhibit, when moistened, motions of inflection in different directions. A short and narrow canal (i) leads from the pouch to the root of the penis (A), which is a short pyramidal body, hollow within, and terminating by a small anterior aperture. 2 o 2 Male Organs , Poulp. 556 CEPHALOPODA. In the Sepiola the part corresponding to that called the prostute by Cuvier exists, but is relatively smaller, and the duct by which it communicates with and is appended to the vas deferens is relatively longer; the sac of the filaments is relatively larger, exceeding doubly the dimensions of the testis; the penis is much shorter. In the Onychoteuthis the penis is merely grooved, as in the Pectinibranchiate Mollusks, not perforated, and such may be expected to be its structure in the Pearly Nautilus. With respect to the act of impregnation in the Cephalopods, Aristotle gives two accounts. In the fifth book of the Historia Animalium it is stated that the Octopus, Sepia, and Cala- mary, all copulate in the same manner ; the male and female having their heads turned to- wards one another, and their cephalic arms being so co-adapterl as to adhere by the mutual apposition of the suckers. In this act the Poulpsaredescribed as seeking the bottom, while the Cuttles and Calamaries are stated to swim freely in the water, the individual of one sex moving forwards, the other backwards. Aris- totle also observes that the ova are expelled by the funnel, which the Greeks called physetera ((fivcri TYiga), and some, he adds, assert that the coitus takes place through that part. From the position of the oviduct at the base of the funnel, and the inclination of the penis to the same part, from the left side, the latter supposition derives some probability, espe- cially with respect to the Sepia and Sepioteu- this, in which the penis is of large size, although true intromission is physically impossible in these, as in all other Cephalopods. There may, however, be an imperfect connexion, analogous to that of the Frog, Toad, See. and it is worthy of remark that the differences in the situation where the coitus is said to take place, in Aristotle’s remarkable account, corresponds with the modifications of the locomotive powers in the three genera treated of ; it is only, for example, in the Sepia and Loligo that the indi- viduals are provided with posterior fins for swimming forwards. In the twelfth chapter of the sixth book of the Historia Animalium , where the generation of Fishes is treated of, the Stagyrite ob- serves — ‘ When they (fishes) bring forth, the male following the female sprinkles the ova with his semen : — the same thing happens in the Malakia; for in the genus Sepia, where the female deposits the ova, the male follows and impregnates them : this possibly happens in like manner to other Malakia, but, hitherto, it has been observed in the Sepiae alone.' It reflects, perhaps, little credit on modern Naturalists, that the knowledge of this part of the eco- nomy of the Cephalopods should remain in the same unsatisfactory and conjectural state as it was two thousand years ago. The female organs exhibit four principal types of structure in the Cephalopods. The ovary is single in all. In the Nautilus there is one oviduct, and one superadded glandular appendage. In the Sepia and many others, there is also Fig. 238. Female Organs of the Nautilus. s : one oviduct, but there are two separated ni- damental glandular laminated organs which open near its extremity. In the Loligo sagittata there are two distinct oviducts, and two separate nidamental glands. In the Octopoda there are two distinct ovi- ducts, each of which, as in the Ray and Shark, passes through a glandular organ in its course towards the base of the funnel, but there are no detached glands. In the Nautilus the ovary (a, fig. 238) is situated, as in the higher Cephalopods, at the posterior part of the visceral sac, in a distinct compartment of the peritoneum ; and the gizzard, which here descends lower down than in the Dibranchiata, is lodged by its side. The ovary is of an oblong compressed form, and in the specimen dissected, measured one inch and a half in length and one inch in breadth. It consists of a simple undivided hollow sac, with thick and apparently glan- dular parietes, rugose on the inner surface, and having an anterior aperture (b) with puck- ered margins, directed forwards. The ovisacs (c, c) are numerous, of an oval form, and attached by one extremity, in a linear series, along the internal surface of the ovarian sac on the dorsal aspect. In the specimen here described they were collapsed, and had evidently recently discharged their ova; the rent orifices by which these had escaped were still patent and conspicuous. T lie tunics of the ovisacs, as in the Dibranchiata, were glandular, but the internal plic* did not present the reticulate disposition characteristic of the corresponding parts in the Sepia , &c. The exterior thin membrane (d) of the ovary is continued forwards to form the oviduct : the thick glandular tunics of this canal com- mence by a distinct aperture (e), just above the outlet of the ovary, and continue increasing in thickness to the extremity of the oviduct, where the glandular membrane is disposed in numerous deep and close-set folds: the CEPHALOPODA. 557 length of the glandular part of the oviduct is one inch ; its termination is at the base of the funnel close to the anus, and immediately behind an accessory glandular apparatus. This body is analogous to the laminated ovarian gland of the Pectinibranchiate Tes- tacea, and, as in them, forms no part of the oviduct; but in the Nautilus it is extended in the transverse direction, and composed of two lateral convex symmetrical masses, resem- bling the corresponding separate symmetrical glands in the Decapoda, but which are here united by a third middle transverse series of lamina;. All the laminae are deep, pec- tinated, and close-set, and are supplied by a large artery. The lateral groups form conspicuous projections on the external sur- face of the ventral aspect of the Nautilus, and are covered internally by a layer of thin tough membrane ; the middle laminae are exposed. The female organs of the Dibranchiate Ce- phalopods present different structures, as be- fore observed, in the Decapodous and Octo- podous tribes. In the former the oviduct or oviducts have laminated glandular termina- tions, near to which are placed two detached nidamental glands : in the latter there are al- ways two distinct oviducts which pass through laminated glands, but there are no detached superadded glandular organs. The Sepia, among the Decapodous Cephalo- pods, manifests in its generative, as in its prehensory and testaceous organs, a near affinity to the Tetrabranchiate order, while the form of the female apparatus in the Octopods more closely corresponds, on the other hand, with the same parts in the Oviparous Cartilaginous Fishes. The ovarium in both tribes is a single organ, situated at the bottom of the pallial sac, and consisting of a capsule and ovisacs di- versely attached to its internal surface. The ovisacs are proportionally larger in the Decapods than in the Octopods. In the Cuttle-fish they are extremely numerous, and are appended by long and slender pedicles to a longitudinal fold of membrane extending into the ovarian cavity, from the dorsal aspect of the sac. The pltcee of the internal glan- dular surface of the ovisacs or calyces are disposed in a reticulate manner, forming cor- responding light-coloured opake lines on the external surface, which, being contrasted against the dark-brown tint of the contained ovum shining through the transparent areolar space, occasions the beautiful and characteristic ex- terior reticulate markings of the undischarged ovisacs. In the Genus Rossia, from which the sub- joined illustration of the Decapodous type of the female organs is taken (Jig. 239), the ovisacs have the same structure and mode of attachment as in Sepia, but they are rela- tively of double the size and fewer in num- ber. In the specimen which we dissected, we found the greater part of the ovisacs con- taining the ovum in various stages of deve- lopment, as at a, a. One was in the act of shedding the ovum, as at b, f; others were Fig. 239. discharged, collapsed, and shrivelled, and in progress of absorption, as at c, c. The pa- rietes of the ovarium consist of a thin and almost transparent membrane, which is con- tinued forwards to form the oviduct ( d , d). This canal commences in the Cuttle-fish by a round aperture, about a third of an inch in diameter, immediately beyond which it dilates, and continues forwards of the same thin and membranous structure to within an inch of its extremity, where, as in the Nautilus, its pa- rietes are suddenly thickened by the develop- ment of a number of broad, close-set, glan- dular laminae. The chief difference between the Sepia and the Nautilus obtains in the greater extent of the membranous part5 of the oviduct in the former. In the Rossia the oviduct (rf) differs only in greater relative width : the terminal gland (e) is composed of two lateral semioval groups of transverse glandular lamellae, each group being divided by a middle longitudinal groove; the oviduct was contracted immediately before opening into the interspace of the glands, and a deep but narrow groove, which is probably dilated during the passage of the ova, was continued between the two groups of lamellae to the termination of the oviduct. This was situated towards the left side and behind the orifices of the nidamental glands. The female organs of the Sepiola present the * In the original description of the Nautilus, this membranous part of the oviduct was regarded, from its brief extent, and the sudden commence- ment of the glandular tunic, as a connecting process of the peritoneum ; it was accurately represented, however, in the figure, (pi. viii. fy.9.) 558 CEPHALOPODA. same structure as in Sepia and Russia, but the single oviduct is relatively wider than inthe latter genus, the ova being of remarkably large size. In the Calamary the ovary is more elongated, and the ovisacs and ova are relatively smaller than in any of the above genera. In the common species ( Luligo vulgaris ) the oviduct is single, but narrower, and more elongated than in the Sepia, and, like the vas deferens in the male, it is disposed in convolutions ; its terminal gland is relatively larger and longer; and the detached nidamental glands are correspond- ingly restricted to a smaller development. In the great Sagittated Calamary, which is not uncommon on our north-western shores, we found in a large specimen taken before the beginning of the breeding season, that the oviducts commenced by separate apertures about two inches apart from the anterior sur- face of the great ovarian bag, and were imme- diately disposed in sixteen short transverse folds, beyond which they continued straight to the terminal ovarian gland. The whole length of each oviduct was two inches ; the convoluted portion occupying one inch ; the straight and glandular parts each half an inch. Monro, in his anatomy of this species of Luligo, conjectured that the glan- dular appendages of the biliary ducts, of which he gave a figure, were the ova : of the oviducts and nidamental glands he had no knowledge. The latter parts are situated external to the terminations of the oviducts; they are of a narrow, elongated, flattened form, about one inch and a half in length, with a wide cavity for moulding the secretion of the two lateral series of glandular laminre. The ova which are contained in the mem- branous part of the oviduct of the Sepia, consist of a deep yellow vitellus, inclosed, first, in a very delicate vitelline membrane, and, externally, in a thin, smooth, shining, easily lacerable, cortical tunic, or chorion. We have generally found them in great num- bers, squeezed together in a mass, so that few retained their true form. The external tunic of the ova in Russia is stronger than in Sepia, and the form of the ovum, which is elliptical, is consequently bet- ter preserved : the oviduct, in the specimen dissected by us, contained several ova detached from one another, in progress of exclusion, as represented in the figure at f, f The ova in Sepiola, as in the two preceding genera, are devoid of any external reticulate markings, which belong only to the ovisac or formative calyx. The delicate ova are defended by additional layers of a horny substance deposited on their external surface by the terminal gland, which may be compared to the shell-secreting segment of the oviduct in the Fowl. When the ova quit the oviduct, they are connected together by, and probably receive a further covering from, the secretion of the two large super- added glandular bodies {gigifig- 239), the wide ducts of which converge and open close to the termination of the oviduct. These bodies, in the Cuttle-fish, Sepiola, and Rossia, are of a pyriform shape with the apices, converging and turned forwards; of large size, especially at the reproductive season, situ- ated on the ventral aspect of the abdomen, but not attached, as in the Nautilus and in- ferior Mollusks, to the mantle. They are each composed of a double series of transverse, parallel, close-set semi-oval laminae, the straight margins of which are free and turned towards each other along the middle line of the gland. When the gland is laid open, an impacted layer of soft adhesive secreted sub- stance is found occupying the interspace of the two series of laminae ; in which, in Rossia, it is evidently moulded into a filamentary form, whence it escapes by the anterior orifice above mentioned. (See h, h, fig. 239.) The laminae are attached by their convex margins to the capsule of the gland, which is thin, and probably contractile; it is com- pletely closed at every part save the anterior outlet, forming a shut sac posteriorly, and having no communication with the oviduct or oviducts, for which these glands have some- times been mistaken.* In the Cuttle-fish the extremities of the ovarian glands rest upon a soft parenchymatous body of a bright orange colour : the correspond- ing part is rose-red in the Sepiola, and of a bright colour in all the congeneric species. In the Sepia this body is trilobate, consisting of two lateral slightly compressed conical portions, whose obtuse apices are directed forwards, and a smaller middle portion connecting the lateral ones at their posterior and internal angles. The dorsal surface of the lateral lobes is flat- tened, the opposite side excavated to receive the superincumbent extremities of the ovarian glands. To these the substance in question is closely attached by a tough connecting mem- brane, but has no correspondency of structure nor any excretory outlet. Its texture is dense and granular, with minute cells, the largest of which are in the centre of the body, and are filled with a yellowish brown caseous substance. , In Sepiola the corresponding body is single, and is similarly attached to the anterior extre- mities of the two nidamental glands. In the s In the description of the anatomy of the Loliriap - sis by Dr. Grant, contained in the first volume of ;he Zoological Transactions, it is stated that “ the usual large glands of the oviducts appear to be wanting,” p. 26 ; whence we are led to conclude that the oviducts are double in that genus as in the Octopods. Rathke, however, describes the oviduct as being single, and states that it is continued downwards to terminate at an aperture situated on the ventral surface of the hinder extremity of the body. This is so singular a deviation from the Cephalopodous type of structure, and makes so important a step towards the Vertebrate Organiza- tion, that we have selected the figure (fin- 223) in which the learned author above quoted illustrates this part of his observations on Loligopsis, where 14 represents the ovary, 15 the oviduct, and lb its posterior terminal aperture. Further dissection of this remarkable genus is, however, evidently re- quired, in order to reconcile the discrepancies in the accounts of the anatomy of these animals which have hitherto been published, both as to the ge- nerative system and in reference to other important structures. CEPHALOPODA. 559 Loligiiies and in Rossia it is double ; each portion (i, i,fig. 239) in the latter genus is at- tached by cellular tissue to the anterior part of its corresponding nidamental gland, and is excava- ted by a deep groove close to the aperture of the gland : from this structure and their position it would appear that they assisted in moulding the nidamentum, and, perhaps, in applying it to the ova. Considering the texture of these singular bodies, their ordinarily bright colour, and their relative position to the generative apparatus, we believe ourselves justified in regarding them as the analogues of the glan- dule succenturiate or ‘ supra-renal bodies’ of the Vertebrate animals. In the Octopodous Dibranchiates the ovary is a spherical sac with thick parietes (l, fig. 226). The ovisacs (2) are racemose or connected in bunches, and attached in the Poulp to a single point of the ovarian capsule, but in the Eledone to about twenty separate stalks suspended from the upper part of the ovary. The ova, when detached from the ovisacs, escape by a single large aperture (3), leading from the anterior part of the sac into a very short single passage, which then divides to form the two oviducts. These tubes, in the unexcited state of the ge- nerative system, are membranous, straight, and of an uniform narrow diameter, except where they perforate a glandular laminated enlarge- ment (4), situated about one-third from their commencement; but, towards the period of ovi- position, the parietes of th£ oviducts increase in thickness and extent, forming longitudinal folds internally. The laminated glands doubtless serve to pro- vide an exterior covering to the ova, and con- nect them together, thus performing the func- tion of the accessory external glands in the preceding tribe. The oviducts ascend behind the lateral hearts and venous cavities, and open on each side of the mediastinal septum of the branchial cavity opposite the middle of the gills (5, 5). A glandular body surrounds each oviduct in Eledone, but is situated nearer the lower end of the tubes, and is of a darker colour than in Octopus. In Argonauta the oviducts are continued by a short common passage from the ovary, and form several convolutions before they ascend to their termination, which is the same as in Oc- topus ; they differ, however, from both the preceding genera in having no glandular lami- nated bodies developed upon them : the minute ova of this genus are, therefore, connected together by the secretion of the lining mem- brane of the long and tortuous oviducts. In correspondence with the striking differences which the female organs present in the Cephalo- podous class, it is found that almost every genus has its own peculiar form and arrangement of ova after their exclusion. Of these, therefore, we proceed to give a short description of the principal varieties. The ova of the Argonaut are invariably found occupying a greater or less proportion of the bottom of the shell ; they are of an oval form, about half a line in length before the develop- Ova of the Argonaut. Fig. 241 . Fig. 243. Fie. 242. Ova of the Calumary, Loligo Vulgaris * From Ferussac, Monographic des Cephalopodcs*. 560 CEPHALOPODA. merit of the embryo has commenced, and are connected together in clusters by long filamen- tary processes. in the figure subjoined, (fig- 240), A repre- sents the ova of the natural size, B a group of ova at an early stage of embryonic develop- ment, magnified, C a single ovum, still more highly magnified, showing the embryo a, the rudimental feet b, and what would be regarded as the vitellus c, in the ovum of any of the naked Cephalopods, but which the continuator of Poli states to be the germ of the shell. With respect to the Poulp ( Octopus') Aristotle states that the animals of this genus copulate in winter and bring forth in spring : that the female oviposits in a shell or some secure cavity ; that the ova adhere in clusters, like the tendrils of the wild vine or the fruit of the white poplar, to the internal parietes of the cavity; that the young Poulps are hatched on the fifteenth day, and are then seen creeping about in prodigious numbers.'*' The ova of the Calamary (fig. 241) are in- closed in cylindrical gelatinous sheaths, mea- suring from three to four inches in length, and about a quarter of an inch in diameter at the thickest part, narrowing to an obtuse point at one end, and attached at the opposite extremity by a filamentary process, varying from half an inch to an inch in length, to some foreign body, as floating wood, &c.; each sheath or nidamen- tum contains from thirty to forty ova, of a spherical figure, about a line and a half in diameter when newly excluded. As the num- ber of cylinders attached to one body some- times exceed two hundred, the prolific nature of the species may be easily conceived. Fig. 242 shows the first appearance of the head and eyes a, at the stage prior to the development of the arms and funnel ; b is the Fig. 244. Ova of the Cuttle-fish, Sepia Officinalis. "* Hist. Animal, lib. v, cap. 16. elongated body, c the yolk-bag. Fig. 243 is another ovum at a more advanced stage of development : the pigmentum is now deposited both in the rete mucosum and in the eye; the arms are just beginning to shoot from the ante- rior circumference of the head ; and the little funnel may be observed rising above the ventral margin of the mantle. The ova of the Sepioteuthis are also spherical and enveloped in cylindrical sheaths, but these are much shorter than in the Loligo, and contain much fewer ova, making an approach in this respect, as in the general organization, to the Sepiae, in which each ovum has its own nida- mentum. The eggs of the Cuttle-fish (fig. 244) are of an oval form, attenuated at the extremities, enveloped in a flexible horny covering, of a blackish colour, which is prolonged into a pe- dicle at one extremity, and twisted round some foreign body. The length of ovum from the point of its attachment is generally an inch, and as a number of these ova are always found attached close together, and sometimes to one another, they resemble in this state a bunch of grapes, as the name ‘ sea-grapes,’ com- monly given to them by the fishermen, implies. In the development of the Cephalopod the most interesting circumstance, and one which had not escaped the notice of Aristotle,* is the point of attachment of the yolk-bag ( c,fg. 245), which is suspended from the head of the embryo, its pe- dicle being surrounded by the cephalic arms, and passing down anterior to the mouth to communicate with the pharynx. The yolk is a trans- parent gelatinous fluid of a spherical form. In the embryo of the Cuttle-fish all the organs, the exercise of which is essential to its future welfare, are adequately developed before its exclusion. The gills are very distinct, and the respiratory actions are vigorously performed by the alternate dilatation and contraction of the mantle and a corresponding elevation and falling of the funnel (rf), by which the little streams are expired. The ink-bag has already provided a store of secretion sufficient to blacken a considerable extent of water, and baffle any enemy which may be ready to remove the little Cephalopod from the world into which it is about to enter. The pigment of the rete mucosum is developed in several large spots, as in the Calamary (fig. 243). Five concentric layers of the dorsal shell at least are deposited ; these are, however, horny, white, and transparent, except at the narrow and thick end; and the innermost layers are marked with irregular opake spots. The lateral fins are broad, and the ventral arms are furnished with a fin-like expansion, so that the young animal is enabled to execute movements either retrograde or progressive ; and the eyes are well Fig. 245. Faslal Sepia. * npocF7Ti to ,5, or j. The intermaxillary bones are always very small and short ; they contain small incisores, varying in number according to the genera, from two to four in the upper, and in the lower jaw from two to six, there being always either the same numberin the two jaws, or two more in the lower than in the upper; thus there is always one of the following formula — 1 f g- The articu- lation of the lower jaw is transverse. The ascending ramus, with its coronoid process, is large and strong, rising very high above the level of the condyle. The vertebral column. — The cervical verte- bra• are in general very little raised, but they are developed laterally, so as to present the broadest portion of the whole vertebral column, CHEIROPTERA. 597 and the spinous processes are wanting from the second to the sixth vertebra. The Atlas is large, the dentata small, and its spinous process inconsiderable. The dorsal vertebra are of a very simple construction ; they are almost without spinous processes, which are replaced by a small tubercle : the bodies are, however, much compressed at the sides, so as to form a sort of crest. The vertebral canal is very large in this region. These vertebrae are twelve in number in both forms, excepting in some species of the single genus Vespertilio, in which they are only eleven. The lumbar vertebra retain the peculiar characters which have been mentioned as belonging to the dorsal. They are elongated, and still almost devoid of spinous processes ; they are also compressed into a sort of continuous crest. The number of these vertebrae is four in Pteropus, five in Phyllostoma and Vespertilio, six in Rhinolophus, seven in Noctula. The sacrum is particularly elongated and narrow, and the spinous processes large. The number of sacral vertebra varies much. In Pteropus (fig. 280) there is but one. In the other genera they are either three or four. In Pteropus the sacrum is united at its extremity to the tuberosities of the ischium. The coccygeal vertebra are slender, elon- gated, and nearly cylindrical; the tail being always included within the flying membrane, the only use of this part is to assist in sup- porting the interfemoral portion of that mem- brane. In most the tail reaches to its margin, in some much beyond, in others only half-way, and in Pteropus (fig. 280) there is not the least appearance of a tail, there is not even a rudi- ment of a coccygeal bone. The number of these vertebra is but six in Noctula, twelve in Ves- pertilio and some others. The number of vertebra in the whole co- lumn is said to be less in Pteropus than in any other mammiferous animal, being only twenty- four, namely, 7C+12D+4 L+lS=24. The ribs are the same in number as the dorsal vertebra. The first rib is very short and remarkably broad, and its cartilage, which is ossified, is still more so. The rest of the ribs follow the usual variations of form. The Bats are remarkable for the extraordinary proportional length of their ribs, in which they probably exceed all other Mammifera. The sternum is altogether greatly developed in the whole of this order. Its length is con- siderable, and this circumstance, with the length of the ribs, tends to afford a great protection to the thorax in the violent movements re- quired by the act of flight. But the most re- markable peculiarity exhibited in the structure of this part, is the extraordinary lateral deve- lopment of the anterior portion of this bone, termed the manubrium. This expansion is conspicuous in all the Bats, and appears to be intended to afford the strongest possible attach- ment for the clavicles, which are also very much developed. In the genus Rhinolophus (the Horse-shoe Bat), this expansion seems to have reached its maximum of development. Its breadth is four times as great as its length, and yet it is nearly as long as the whole remaining portion of the sternum. The inferior surface of the manubrium is also furnished with a crest, which is continued, though much smal- ler, on the next piece of the sternum ; it varies in size in the different genera. The remaining bones composing the sternum are of nearly equal size. The anterior extremity is the part of the skeleton which in the true Cheiroptera offers the most remarkable deviation from the nor- mal form, especially in the metacarpal and pha- langeal bones. The clavicle, from the extensive motion of the anterior extremities, requires to be much elongated in these animals ; some of which in fact exhibit proportionally a greater develop- ment of this bone than is to be found in any other order. It is always arched above and intimately articulated both to the scapula and to the sternum, and in some species is half as long as the greatly elongated humerus. As far as I have had an opportunity of observing, the clavicle, as well as the other portions of this extremity, is more developed in the in- sectivorous than in the frugivorous Bats, for the very obvious reason that the former require more extensive powers of flight in the pursuit of their swift and active prey, than the latter in merely flying from place to place, in search of their stationary food. The scapula is also developed to the greatest extent, and particularly in the insectivorous Bats. It is greatly elongated towards the base and posterior angle, which in some species reaches nearly to the last rib. The inner surface is very concave, and the fossa above and below the spine are deep, for the attach- ment of the powerful muscles which are in- serted to it. The humerus is very long, slender, and cy- lindrical, as may be observed in the skeleton of Pteropus in fig. 280. The head of the bone is round and large. The whole anterior part of the inferior articulation or elbow-joint cor- responds to the head of the radius. The fore-arm consists, as in the other mam- mifera, of the radius and the ulna. The latter bone is, however, in all the Cheiroptera ex- ceedingly small, and in some merely rudimen- tary. In several species of Vespertilio, for instance, it forms nothing more than a flat process, only partially separated from the radius.' In the example shewn at fig. 280 it is more considerable ; but even here it presents nothing more than a small styliform bone, united to the radius at the head, and diminishing to a thin point, towards the carpal extremity ; the olecranon too is wholly wanting. The radius, like the other bones of the an- terior extremity, is remarkably elongated, and rather robust. The absence of rotation in the forearm of these animals forms an admirable adaptation to their habits. Not only would the pronation and supination of the hand be wholly useless to them, but at every impulse of their flight such a motion would deprive the whole limb of its resistance to the air, or 598 CHEIROPTERA. it would require die constant exertion of such a degree of antagonizing' muscular force to prevent it, as would be incompatible with the essential structure of these organs of flight. The carpus is of a very peculiar structure. The first series of bones consists but of two ; one very large, on which the radius rests, and which is probably formed of the three outer bones, the scaphoid, the semilunar, and the cuneiform bones ; the other extremely small, which is undoubtedly the pisiform, on the ulnar side. The second series consists of the four bones of which it is usually constituted. The metacarpal bones and phalanges of all the fingers excepting the thumb are extremely elongated. They extend outwards and down- wards in a slightly curved direction to the margin of the flying membrane, the second finger being the shortest and extending to the upper angle of the outer margin, the third, fourth, and fifth to the inferior margin of the membrane. There is a slight enlargement at the articulation of the metacarpal bones with the phalanges ; but otherwise these bones are extremely slender and cylindrical. The thumb is of no extraordinary length, and the ultimate phalanx is hooked and sustains a nail, by which the animal is enabled to climb on any rough perpendicular surface, or to suspend itself from some projecting part. The pelvis is remarkably strait, rather elon- gated, somewhat wider mferiorly. The ilia are narrow and elongated ; the ischia in several species, instead of receding from each other, approach so that their tuberosities touch each other, and in some instances come in contact with the coccygeal bones. In some species of Pteropus, the anterior portion of the ossa pubis, instead of meeting at the median line, recede more or less from each other, and the space is filled by ligament. In some species there is a sexual difference in this respect; the two pubic bones being in contact in the male and sepa- rated in the female. The sacrum and the ilia are connected by absolute bony union at an early period. The femur is of moderate length, slender and cy- lindrical. It is turned outwards and upwards, so that the side which is usually anterior is directed nearly backwards. The tibia offers no peculiarity which requires particular notice. The fibula is exceedingly small, slender, pointed towards its femoral extremity, and has this singular peculiarity, that it does not rise to the head of the tibia. In other cases where this bone is defective, it is at its inferior ex- tremity, but in the present case it is the supe- rior portion which is wanting. As the femora are directed outwards, the leg-bones are in some measure turned round, so that the fibulee are at the inner side of the tibia and a little behind them. The foot of the Cheiroptera does not ex- hibit the same deviation from the normal structure which we have seen in the hand. On the contrary, it is not extraordinarily developed, and the different parts of which it is composed are in the usual relative proportions. The tarsus is composed of the usual bones. There is a peculiarity in the heel, however, which is worthy of notice. There is a long, slender, pointed, bony process from the pos- terior part of the foot which is inclosed within the folds of the margin of the interfemoral membrane, and extends about half-way to the tail. Whether this process is a portion of the os calcis, according to Cuvier, or a distinct bone according to Daubenton, it is perhaps difficult to decide ; but the opinion of Meckel is probably the correct one, that it is nothing more than a development of the tuberosity of that bone, remaining disunited from its body. The metatarsal bones are rather short, slender, and of nearly equal length. The phalanges of the five toes are nearly equal, the inner toe reaching almost to the same length as the others, in consequence of the greater elongation of its first phalanx. The ultimate phalanges are furnished with hooked nails, by which these animals constantly suspend themselves when at rest with the head downwards. The whole of this structure is so perfectly adapted to the peculiar habits of the animals, as to require no comment. The great deve- lopment of the ribs, sternum, and scapula, for the attachment of strong muscles of flight, the length and strength of the clavicle, the exten- sion of all the bones of the anterior extremities, all admirably tend to fulfil their obvious end. The existence of a tail for the support and extension of the interfemoral membrane, which is found in the insectivorous Bats, compared with its absence or comparative inefficiency in many of the frugivorous, also points out an interesting relation to the different habits of the two groups, the former structure being calcu- lated to afford a powerful and effective rudder in guiding their rapid and varying evolutions in the pursuit of their insect food. The general nervous system in the Cheiro- ptera does not exhibit any very remarkable peculiarity, but some of the organs of sense require a particular notice. Organs of the Senses. — The organ of vision is principally remarkable for its diminutive size. The eye in many of the insectivorous group, in which the external ear is very largely developed, is placed within the margin of the auricle and almost concealed by hair. In the frugivorous group, on the other hand, it is of the usual proportional size. The organ of hearing, on the contrary, though in the latter forms not more developed than in most other quadrupeds, in the former seems to take the place of the diminutive organ of vision, being greatly extended both in its external and internal organization. The external ear in Pteropus is of the usual form and dimensions, and the eminences are not in any respect extra- ordinary : but in most of the insectivorous Bats the conch of the ear is enormously large ; in many species being considerably larger and longer than the head, and in the common long- eared Bat of this country, Plecotus auritus, it is nearly as long as the body. The tragus is proportionally larger than in any other animals; CHEIROPTERA. 599 in most species it is more or less lanceolate in its form ; in Vespertilio spasma it is forked, and in the great Bat of Britain, Vespertilio noctula, it is short, blunted, with a rounded head, thickish, and I have observed it beset with numerous minute glands, which do not occur in those species having the thin lan- ceolate form of this part. Its use is probably to prevent the rush of air into the open ear during flight ; and where it does not exist, as in the Horse-shoe Bats ( Rhinolophus ), its place is supplied by a large rounded lobe which is capable of still more effectually closing the external meatus. In the internal ear there is an equal diver- sity of structure in the two groups in question. The cochlea is particularly developed in the insectivorous group; being much larger than the semicircular canals; the circumference of that of Rhinolophus is no less than four times the circumference of the canals, and its cavity exhibits ten times the diameter of one of them. In Rteropus this disproportion is very much less. The meatus is short and, as well as the tympanic cavity, extremely large and open. But it is in the sense of touch probably that the most extraordinary and interesting pecu- liarities are to be observed. Spallanzani hav- ing observed the power which these animals possess of flying with perfect accuracy in the dark, and of avoiding every obstacle that pre- sents itself with the same unerring certainty as in the light, instituted a series of experiments, the results of which proved that bats when deprived of sight by the extirpation of the eyes, and, as far as possible, of hearing and smell by the obliteration of the external pas- sages of those senses, were still capable of directing their flight with the same security and accuracy as before, directing their course through passages only just large enough to admit them without coming into contact with the sides, and even avoiding numerous small threads which were stretched across the room in various directions, the wings never, even by accident, touching any of them. These marvellous results led him to believe that these animals are endowed with a sixth sense, the immediate operation as well as the locality of which is, of course, unknown to and unap- preeiable by us : but the sagacity of Cuvier* removed the mystery without weakening the interest of these curious facts, by referring to the flying membrane as the seat of this extra- ordinary faculty. According to this view of the subject, the whole surface of the wings on both sides may be considered as an enor- mously expanded organ of touch, of the most exquisite sensibility to the peculiar sensation for which it is intended ; and it is, therefore, by the varied modification of the impulsion of the atmosphere upon this surface, that the knowledge of the propinquity of foreign bodies is communicated. This membrane is every where furnished with oblique or transverse bands, consisting of lines of minute dots re- * Le9ons d’Anatomie Comparee, t. ii. p 582. sembling in some measure strings of very small glands or cutaneous follicles. May there not be some connexion between these peculiar little bodies and the extraordinary function just described ? The tendency to an extraordinary develop- ment of the dermal system is not confined to the organs now mentioned, of the senses of touch and of hearing. The organ of smell is in many insectivorous Bats, as in the whole family Rhinolophida, furnished with foli- aceous appendages, formed of the integument doubled, folded, and cut into the most curious and grotesque forms. These nasal leaflets are found principally or exclusively to belong to a group, the habits of which are more com- pletely lucifugous and retired than any others ; they are found in the darkest penetralia of caverns, and other places where there is not even the imperfect light which the other genera of Bats enjoy. It is probable that this deve- lopment of skin around the nose is intended to give increased power and delicacy to the organ of smell, as well as to regulate the access of the odoriferous particles, and thus to super- sede the sense of vision, in situations where the latter would be unavailable. In the genus Nycteris a curious faculty is observed, namely, the power of inflating the sub- cutaneous tissue with air. The skin adheres to the body only at certain points, where it is connected by means of a loose cellular mem- brane ; it is therefore susceptible of being raised from the surface, on the back as well as on the under parts. These large spaces are filled with air at the will of the animal, by means of large cheek pouches, which are pierced at the bottom, and thus communicate with the subcutaneous spaces just mentioned. When the animal therefore wishes to inflate its skin, it inspires, closes the nostrils, and then contracting the cavity of the chest, the air is forced through the openings in the cheek pouches under the skin, from whence it is prevented from returning by means of a true sphincter, with which those openings are furnished, and by large valves on the neck and back. By this curious me- chanism the bat has the power of so com- pletely blowing up the spaces under the skin, as to give the idea, as Geoffroy observes, “ of a little balloon furnished with wings, a head, and feet.” The digestive organs of the Cheiroptera ex- hibit as distinct a division into the two prin- cipal groups before-mentioned, as any other part of their anatomy. The teeth have been already alluded to, and the characters of these important organs, important as indicating, in the most unerring manner, the nature of the food, are well-marked in the two groups. The flattened crowns of the molares, so similar to those of the Quadrumana which are found to belong to the frugivorous Bats, are strikingly contrasted with the many-pointed tuberculous teeth of the insect-feeders, and exhibit an in- teresting affinity to the two important orders of animals to which the Cheiroptera may be con- sidered intermediate; the former division re- 600 CHYLIFEItOUS SYSTEM. ferring evidently to the Quadrumanous type in the structure of the teeth, and the latter to the type of the insectivora. The tongue presents a peculiarity in the genus Phyllostoma, which is worthy of being particularly noted. It consists of a number of wart-like elevations, so arranged as to form a complete circular suctorial disk, when they are brought into contact at their sides, which is done by means of a set of muscular fibres, having a tendon attached to each of the warts. By means of this curious sucker, these bats are enabled to suck the blood of animals and the juice of succulent fruits. This power has been attributed by mistake to some of the genus Pteropus, merely because their tongue is rough, and it was calculated that by means of such a surface the skin may have been abraded. The stomach is no less indicative of the nature of tlie aliment than the teeth ; offering, in the Pte- ropus (Jig. 287 ), a very striking affinity to that an identity with that of the carnivorous type. In the former the oesophagus swells out before it enters the general cavity, and that dilatation, as Home observes, appears, from its structure, to belong to the stomach. To the left of the oesophagus there are two dilatations, the far- thest of which has a smooth surface and thin coats ; the other is furnished with several deep longitudinal rugae, some of which are con- tinued from similar ones in the oesophagus. Four of the rug® are continued towards the pylorus, giving a direction to the food in that course ; about one-third of the stomach to- wards the pyloric extremity is turned back upon itself, and the pylorus is consequently placed externally close to the entrance of the oesophagus. At the pylorus is a very small opening into the intestine, which when con- tracted seems scarcely pervious to air. Such is the complicated form of the stomach in the frugivorous division ; whilst that of the insect- feeders is as simple as possible, being only divided into a cardiac and a pyloric portion with scarcely the slightest contraction. The intestines present a no less marked distinction. In the Pteropus they are no less than seven times the length of the body, whilst Vesper- tilio noctula offers the shortest proportional length of the canal, it being only twice as long as the body. The latter is also wholly devoid of a caecum. The organs of generation. — The male organs of the Bats bear a near relation to those of the Quadrumana and of Man, in some striking respects. The penis is pendulous, and the proportions between the different organs are not very dissimilar; but the testes do not descend from the abdomen excepting during the breeding season, when they are found on each side of the anus, whilst the large epididymis is seen just behind them, on each side of the origin of the tail. The vesicula seminales are of moderate size, and consist of two round white sacs, which are perfectly simple, form- ing each a single cavity with a secreting in- ternal surface. They have a prostate gland, which surrounds the whole circumference of the urethra, and appears to be composed of numerous small lobes. They have also Cow- per’s glands. The penis is very similar to that of the other more highly organized forms, the Quadrumana and Man. It is of moderate size, pendulous, and supported by ligaments, as in the other cases. There is a small bone of the penis. The muscular portion of the urethra is rather long. The glans is in some species enlarged by a small process or button on each side ; the urethra opens at the extreme point. The female organs offer nothing very par- ticular. The vulva is round, and exhibits a slight appearance of a clitoris near its edge; the mouth of the uterus stands out into the vagina. The uterus is two-horned and the horns are very short. There are but two teats, which are placed on the breast. The additional ones said to exist in the groin of the Rhinolophi are most probably ordinary cutaneous glands, as Kuhl could discover no trace of mammary glands beneath them. They were first discovered by Montagu in this country, and by Geoffroy in France. The Bats are among those animals in whom we notice the remarkable phenomenon of Hy- bernation, of which it is unnecessary to say any thing here, as a distinct article is devoted to the subject. (See Hybernation.) For the Bibliography see that of Mammalia. (T. Bell.) CIIYLIFEROUS SYSTEM (in Compa- rative Anatomy) is that portion of the vascular system of vertebrated animals which is destined to convey the nutritious part of the food, or the chyle, from the alimentary canal into the san- guiferous vessels. The function of these chy- liferous vessels appears to be performed by the veins in the invertebrated classes, where the white colour of the blood causes them to re- semble more closely the lacteals or chyliferous vessels of vertebrata. Several parts, however, of the invertebrated animals have been taken by anatomists for this lacteal system, as the C II YLI FERGUS SYSTEM. tSOl nervous system of Molluscaby Poli, the biliary tubuli of Insects by Sheldon, the mesenteric vessels of Echinodermata by Monro, the radi- ating prolongations from the stomach of Me- dusas by Cams. The chyle of vertebrata, derived from the chyme of the digestive canal, and much resembling the white blood of the lower divisions of the Animal Kingdom, varies in its physical properties and chemical com- position in the different tribes of animals, and in the same animal according to the kind of food on which it subsists, (see Chyle,) being- most allied to red blood in the highest animals and those which subsist on the most nutritious animal food, and being most remote from that condition in the lowest fishes and the most imperfect animals. The vessels which con- vey, and still further elaborate, this fluid, the chyliferous system, like the other systems of the body, present very different grades of de- velopment in the different classes of vertebrata. In fishes they consist of simple vessels in which we cannot separate the two usual tunics ; they are destitute of internal valves and me- senteric glands, they form two strata of vessels between the coats of the small intestine, and they convey a limpid chyle to the receptaculum chyli, from which it is sent by one or two thoracic ducts to the branches of the su- perior cava or the jugular veins. They com- municate freely with the veins, they already present numerous constrictions as rudimentary valves, they present valvular orifices at their entrances into the veins, and their numerous convoluted plexuses supply the place of me- senteric glands. The chyliferous vessels are nearly in the same condition of development in the amphi- bia, where they form two layers on the parietes of the alimentary canal, are destitute of con- globate glands, form plexuses on the extended mesentery, and terminate in two thoracic ducts which proceed forwards along the sides of the vertebral column. (See Amphibia.) In the class of reptiles the lacteals pre- sent a more advanced stage of formation, chiefly in the development of the internal valves in the trunks and branches in all these animals, and in the white milky condition of their contents in the crocodilian family. (See Reptilia.) They are still without mesenteric glands, their valves are less perfect than in birds and quadrupeds, and the chyle is still limpid and colourless in the serpents, lizards, and tortoises. The coarse vegetable food of the chelonia, and the great length of their small intestine, give occasion for the numerous large chyliferous vessels which cover their alimentary canal and mesentery. The place of mesenteric conglobate glands is yet supplied, as in the inferior vertebrata, by numerous complicated networks of lacteal vessels, formed in different parts of their course ; and, as in fishes, two or more ducts are here observed passing forwards from a single wide receptaculum. The tho- racic ducts form numerous free anastomoses with each other in their course forwards to the neck, accompanying the left branch of the aorta to the anterior part of the trunk, where VOL. i. they pour their contents into the jugular or subclavian veins, or into the angle between these vessels. Before entering the veins these ducts receive the lymphatic trunks, as in other classes, from the head and arms. The chyli- ferous vessels of the chelonia coming from the outer and inner layers spread on the small in- testine, unite into considerable trunks, which pass along the mesentery in close proximity to the bloodvessels. The thoracic duct of the tortoise surrounds and almost conceals the trunk of the aorta by its numerous large anas- tomosing branches. The inferiority of the chyliferous system of birds to that of quadrupeds is seen even in the properties of the chyle, which is still, as in the lower tribes of vertebrata, a thin, colourless, and limpid fluid. The lacteal ves- sels are now, however, more obvious, and more regular in their distribution, and are spread in more crowded layers above the mu- cous and above the muscular coats of the in- testine. They collect from the intestine and form numerous anastomosing plexuses on the mesentery, in place of the conglobate glands of mammalia, and then proceed, with the lym- phatics, to the receptaculum, which sends for- ward two thoracic ducts to terminate, on each side of the neck, at the junction of the sub- clavian with the jugular veins. (See Aves.) The coats of the lacteals are still very thin and distensible in birds ; their valves, which are more abundant on the trunks and branches than in reptiles, are still so incomplete as to allow injections to pass easily against their course, and although conglobate glands are not yet developed on the chyliferous system, they are already perceptible on the lymphatics, especially in the neck. The chyliferous system of the mammalia, though more developed than that of all the inferior classes, is still imperfect as a hy- draulic apparatus when compared with the sanguiferous system. The lacteal and lym- phatic systems may still be regarded as mere appendices of the venous, performing the func- tions which are assigned to veins in the inver- tebrated classes, and serving as inlets to the materials which renovate the blood. No pul- sating sacs have yet been detected in the lym- phatic system of quadrupeds, nor any distinct motion in the lacteals, the receptaculum, or the thoracic duct. The chyliferous system of this class presents a superiority of develop- ment in the almost sanguineous characters of the chyle, in the more perfect structure of the vessels and their valves, in the development of the conglobate mesenteric glands, in the frequent unity or concentration of the thoracic duct, and in the more isolated condition of this system from the sanguiferous. The mesenteric glands are chiefly confined to the mesentery of the small intestine ; they are generally placed apart from each other ; sometimes they are united into a -pancreas Asellii ; they are firm in texture, highly vascular, and composed of con- voluted lacteals, like more concentrated forms of the plexuses of the lower vertebrata. ( R. E. Grant.) 2 K CICATRIX. eo2 CHYLIFF.ROUS SYSTEM (Human Ana- tomy). See Lacteal. CICATRIX. (Fr. Cicatrice; Germ. Narbe .) When from accident or disease a portion of any organ in the body has been destroyed, a process is set up by Nature for the repair of the breach, a new structure is generated, which possesses many properties of conside- rable interest and importance both in a phy- siological and a pathological view. The new formation constitutes what is termed a cicatrix, and the process by which it is completed, the process of cicatrization. We shall in this article give a general view both of the mode of of repair and of the product when completed. The restorative process, when a part of the skin has been destroyed, is extremely in- teresting. The first stage varies according as the part is removed at once, as by exci- sion, or secondarily, as by sloughing. The immediate effect of removing a portion of skin is, that the surrounding integument, by its inherent elasticity, retracts, and to a certain extent, enlarges the breach made by the wound. In a short time after the infliction of the injury inflammation and suppuration take place. As the next step, fibrine is effused, which very shortly becoming organized, constitutes those red, soft, roundish elevations known by the name of granulations. As these form, a con- traction of them occurs, by which the edges of the sore, which had at first retracted, are now brought back again towards their original si- tuation. - John Hunter informs us that this contracting tendency in the granulations is in some degree proportioned to the general healing disposition of the sore, and the looseness of the parts on which the granulations are formed, for when there is not a tendency to skin, the granulations do net so readily contract.* The contraction continues till the whole is healed over, but its greatest effect is at the beginning; one cause of which is that the resistance to it from the surrounding parts is then least. While this is going on within the circum- ference of the sore, and immediately pre- ceding the commencement of actual cicatri- zation, the surrounding old skin, close to the granulations, becomes smooth and rounded with a whitish cast, as if covered with some- thing white, and the nearer to the cicatrizing edge, the more white it is. At this moment the process of cicatrization is actually begin- ning, and the new cuticle may now be ob- served to be spreading from the circumference of the sore towards the centre, not uniformly, but creeping irregularly over the granulations, or rather formed irregularly from them, but always, in recent sores, spreading in a con- tinuous surface from the circumference. In large and old ulcers, however, in which the edges of the surrounding skin have but little tendency to contract, or the cellular membrane underneath to yield, the old skin also having but little disposition to skinning in itself, the 581 On the Blood, 8vo edit. nearest granulations do not receive from it a cicatrizing tendency. In such cases new skin forms in different parts of the ulcer, standing upon the surface of the granulations like little islands. The rapidity with which the skinning process takes place in this stage is but an un- certain criterion whereby to judge of the time that will be occupied in the cure. Generally speaking, the latter stages of the process are much slower than the earlier, particularly when the breach of surface has been large. And here a question arises : is the new skin that is formed the result of an altered state of the granulations themselves, or is it an entirely new product from them ? Bichat inclined to the former opinion, holding that the granu- lations having discharged their fluid contents, collapsed, and uniting one to another, became converted into the uniform smooth membrane in question. Hunter, on the contrary, con- sidered the new cutis as a new product, the secretion of the granulations. Our own ob- servations lead us to adopt the opinion of Bichat. It seems that, as soon as the surface of a granulation is covered over with epidermis, which is often the case before the least shrink- ing or collapse of the granulation occurs, then the secreting orifices of those numerous vessels of the granulation which had hitherto been pouring out pus are now sealed up, and having no longer any use, the same change takes place which occurs in other parts of the system similarly circumstanced : an or- gan no longer in use shrinks and the fluid parts become absorbed, and the elevated soft and spongy granulations shrink into the thin and somewhat dense fibrous structure of the cicatrix. We cannot agree with the opinion of M. Dupuytren, that the chorion is formed first, and the epidermis added subsequently, since we have often detected the epidermis creeping over granulations so little altered in appearance that its presence could only be dis- covered by placing the part in such a light that its dry shining surface could be distin- guished from the soft villous appearance of the neighbouring granulations. The process of contraction, we believe, generally, if not always, does not precede but follows the formation of the cuticle, and consequently the cutis formed by this contraction does in the order of time follow the cuticle. The reason of this we can- not explain, but of the fact we cannot doubt; and this fact accounts for the very slow formation of the cuticle in the first healing of an ulcer where that membrane is formed from the granulations. The organization of these bodies may be said to be much inferior to that of the cutis when completed ; hence, when the cuticle of a cicatrix is abraded, it is readily formed again, because it has now a more perfect organ to secrete it. As the new cuticle covers the granulations, then, these two striking changes immediately take place in their state; the secretion of pus is stopped, the surface becoming dry, and that process of shrinking or contraction begins which we shall find to continue for a conside- rable period after the whole sore is apparently CICATRIX. 603 healed. The contractile action takes place in every direction, producing that depression of the cicatrix which is observed to follow the spreading of the cuticle over the granulations. Thus those parts which were soft and spongy now acquire firmness, and form a condensed layer, which occupies the position, and per- forms some of the functions of the original cutis which had been destroyed. It is an interesting question, why the cuticle in covering an ulcer, though evidently formed from the granulations, is arising not over the whole surface of the ulcer at once, as it is when abraded from the healthy skin, but creeps from the circumference towards the centre, in a slow, progressive manner ? It seems that a greater perfection of organization is necessary for the production of cuticle than for the for- mation of granulations capable of secreting pus. If we examine the vascular structure of these newly formed parts, we find that the bloodvessels apparent on the granulations are few and very irregular in their course, and often in figure also, having an appearance re- sembling a varicose or unequally dilated state ; this we take to be an indication of a feeble and incomplete state of organization. On the contrary, the vessels in the immediate vicinity of the new skin, are more regular in form and direction, and may often be seen running on- wards through the neighbouring granulations towards the centre of the sore, having a good deal the appearance of the vessels of the in- flamed cornea ; and where this is not remark- ably apparent, the granulations in the imme- diate neighbourhood of the parts in which the skinning process is going on are more vascular than the internal ones. Our observations would lead us to believe that this more perfect system of circulation commences by an anasto- mosis newly set up from the vessels of the edge of the healthy skin first, and by the action of these newly formed vessels the cuticle is secreted. From these, others are still sent on over the surface of the sore, or immediately under it, and thus by progressive steps the necessary degree of perfection of structure is acquired, and is immediately followed in its progress by the development of the cuticle. This, be it remembered, is still a different state of the granulations from the contracted un- secreting layer which constitutes the new cho- rion. If this description of the process is consistent with Nature, it is reasonable to sup- pose that the new vessels shooting from the edges of the healthy skin would be more per- fect, and more equal to the task required than those which would pass through the granu- lations from the subjacent cellular tissue; and in the same way we may suppose that one part being in the before-mentioned manner com- pleted, is better fitted to send on new vessels for the organization of the next portion of granulations than the granulations themselves. It is moreover to be expected that the power of organizing its neighbouring parts must be superior in the healthy skin to that of any newly formed structure, and that this power will in an extensive sore gradually diminish as the distance from the healthy parts in- creases ; and this accords with the well-known fact that the cicatrization goes on much more slowly in the latter stages of healing than at the commencement Thus the external process of skinning is completed, but the internal changes are not yet finished. A slow but remarkable change is going on for a considerable time longer, by which the appearance and structure of the cicatrix becomes modified. From a red colour it becomes gradually paler, till it is almost white ; this at least is the general rule, though under circumstances, to be presently mentioned, the result is different. The cicatrix also conti- nues to contract in all its dimensions, thus not only diminishing in extent, but sinking below the level of the surrounding skin, and becoming more dense and thin and more perfect in its organization, till it has assumed the appearance and character which it will retain through the rest of life. It is this power of contraction resident in the new chorion of the cicatrix, that produces those bridles which are such frequent causes of deformity after the healing of extensive burns. In these cases there does not seem any neces- sity to have recourse to any peculiarity of hypothesis in explaining the great degree of shrinking that so commonly occurs. On the contrary, we conceive that the phenomena at- tending the healing up of burns are to be ac- counted for by means of the usually recognized causes of the shrinking in the cicatrices of wounds in general. We have now described the process of re- pair in wounds in the skin, with loss of the entire substance of the cutis. When the de- struction has been more superficial, the process of restoration is more rapid, and the result more perfect, inasmuch as the part upon which the burden of repair devolves, is the inner layers of the original cutis, a part much more highly organized and more equal to the task than the cellular tissue.* In wounds which are united by the first intention, the stage of suppuration does not take place. The sub- stance which would have formed suppurating granulations here becomes an immediate means of union, and the only portion of new skin formed is in the mere line where the divided edges met, a line always visible by the white colour before mentioned. In the healing of ulcers in any of the mucous membranes, the process would appear to go on much in the same way as on the skin. Granu- lations shoot up from the bottom of the ulcer ; the surrounding healthy membrane is drawn inwards by their contractile power, and the edges of the ulcer are turned in and become continuous with the new membrane, which at length covers the ulcer. When the destructive process has merely gone through the mucous membrane, the granulations shoot from the mus^ cular coat, and the contraction is of course ex- ercised only upon the surrounding mucous coat; but when the muscular tunic is destroyed, the * See Hunter on the Blood, 8vo edit. p. 274. 2 R 2 604 CICATRIX. granulations grow from the bottom of the wound, that is, from the cellular tissue in contact with the peritoneum; but the contraction of the sur- rounding parts now diminishes the circumfe- rence of the ulcer very considerably by puck- ering up this thin layer of membrane, so as to give it externally an appearance as if a small portion of the intestine had been taken up by the forceps and tied with a ligature on the in- side.* When the process of repair is com- pleted, a fine web-like production from the edges of the ulcer overspreads its base, and forms fine wrinkles converging towards its centre. This production is destitute of villi, and slightly depressed. When the ravages of the disease have been very extensive, the cica- trix is covered by puckered cellular tissue, formed of white thread-like filaments, crossing each other in all directions, and leaving pitted interstices.f When the ulcer was small, the cicatrix has sometimes a considerable resem- blance to the scar of small-pox.} That cicatrization takes place in the lungs after tuberculous excavations, the observations of Laennec§ and Andral|| among others, have put beyond a doubt; and since these patholo- gists have made public their observations of the fact, and pointed out the signs by which it may be known, most observers have borne tes- timony to the accuracy of their statements. According to Laennec there are three ways by which this desirable object is accomplished ; one, by the walls of the cavity becoming lined with a membrane of a semicartilaginous struc- ture and smooth polished surface, which seems often continuous with the lining mem- brane of those bronchial ramifications which open abruptly into the cavity. This state of the restorative process constitutes a sort of in- ternal cicatrix, analogous to a fistula, and is in many cases not more injurious to health than the species of morbid affection just mentioned. The second mode of cicatrization consists in the obliteration of the morbid cavity by adhe- sion of its sides. In the complete state they exhibit, when cut into, a band of condensed cel- lular substance or of fibro-cartilaginous struc- ture. The bronchial tubes which run towards this structure are obliterated as they reach it, and there is generally an unusual quantity of the peculiar black matter of the lungs in the parts bordering upon the cicatrix ; and where this is the case, the structure of the lungs is more flabby and less crepitous than natural. These internal cicatrizations are indicated on the surface of the lung by a depression of the pleura, the depth of which corresponds with * Dr. Latham on the Disease of the General Penitentiary, p. 51. t Dr. Hope’s illustrations of Morbid Anatomy, vol. i. p. ‘203. See also Billard’s Recherches d’Anat. Pathol, p.534. J Bright’s Medical Reports, vol. i. p. 182, where are some very interesting illustrations of this por- tion of pathological anatomy. See also on this subject a valuable paper by M. Troillet in the Jour- nal Gen, de Medecine. Reported in the Med. Chir. Rev. vol. v. p. 192. § On Mediate Auscultation, translation by Dr. Forbes, 2d edit. p. 300. || Clinique Medicale, tom. iii. p. 382. the size of the previous excavation, and is sometimes so deep as to form a large over- lapping prominence of the neighbouring sound parts. Here we have another instance of the same contractile tendency in newly formed structures, which is so striking in cicatrizations of the skin; a tendency resulting from the gene- ral law by which the labour of restoration is, as much as possible, spared to the animal system. The third species of cicatrix in the lungs is that formed by the fibro-cartilaginous walls in- creasing in thickness till they fill up the cavity, thus leaving a blueish or greyish white mass, in which large bronchi terminate abruptly as in the preceding case. Cicatrices of the two last kinds are not uncommon.* In the healing of common abscesses, whether in the subcutaneous cellular tissue or in the more deep-seated parts, the mode of cicatriza- tion is much the same as in the second species just described. As the fluid contents are re- moved by evacuation, the cavity of the abscess is diminished in extent partly by the contrac- tion of the surrounding tissue and partly by the granulations arising from the sides of the ca- vity, and as the opposite sides are thus brought in contact they adhere, and at length leave a fibrous cicatrix, whitish and more dense than the surrounding cellular tissue. It is remark- able that few or no abscesses granulate till they are exposed, and that after they are opened there is one surface that is more disposed to granulate than the others, which is the surface next the centre of the body in which the sup- puration took place. The surface next the skin hardly ever granulates, but on the contrary has an ulcerative tendency The proximate cause of this remarkable difference is not evi- dent, but the utility of it in the healing of the abscess is clear and striking.! We have now considered the processes by which nature repairs the breach in the healthy structure; let us in conclusion shortly examine the characters which mark the cicatrix when completed. This new formation, though in many points it resembles and fulfils the func- tions of the old and perfect skin, yet differs from it in many material respects. 1. It occupies, as we have stated, a smaller space, having by its contraction drawn the surrounding skin inwards, and thus, by the wise economy of nature, diminished the surface requiring new skin to cover it. This is of course most strikingly seen in those parts where the cellular texture is loose and yielding, as in the scrotum, where a large loss of skin is often healed with only a very small cicatrix. On the contrary, parts that cannot so yield are healed with a proportionately large cicatrix, as in wounds of the scalp, &c. 2. The texture of the cicatrix is frequently harder and thicker than the natural skin. This circumstance varies considerably, but we believe this variation will be found to bear a pretty exact relation to the degree of contraction, to the length of time occupied in the cure, and to the irritation to * See Hope’s Illustrations of Morbid Anatomy, vol. i. p. 34. t Hunter on the Blood, p. 593. CICATRIX. 605 which the ulcer was subjected in the process of healing. When these have been considerable, the hardness is correspondingly gTeat, while, if the cure has been expeditious and the part been kept extended and irritation avoided, the cicatrix remains soft, thin, and pliable, a point of great importance in practice as applied to the healing of burns. 3. The colour of the new skin is different from the natural parts. This arises from the want of rete mucosum, which is not regenerated till long after the other tissues, and sometimes not at all. For this reason a cicatrix in a Black is as white as that in an European ; but after a considerable lapse of time, this structure is sometimes formed anew, and in some instances becomes even of a darker colour than before. 4. The surface is perfectly dry from the want of ex- halent pores, which are never found to be restored even in the oldest cicatrices. Indeed, in cases where the chorion has not been de- stroyed through its entire thickness, the loss of substance reaching only through its outer layers, these pores are generally obliterated, and the important exlialent function of the skin is annihilated; and even when the injury has extended only through the external vas- cular structure of the skin, as is the case in the healing of a blister which has been long in- flamed, we have observed a drier state of the parts, and more polished than the surrounding skin which had not been injured. From this pe- culiarity in the cicatrix, when the whole body is bathed in sweat these parts are dry and po- lished. This state of dryness, however, partly results from another anatomical deficiency, namely, of the perspiratory glands, which are destroyed in cases where the entire integument has been injured, and these are of course never regenerated. 5. The new tissue contains no hairs, and if, after superficial wounds, a few scattered hairs appear on the surface, they are feeble and white. 6. After the healing of a large ulcer of long standing, the new surface is sometimes much lower than the surround- ing skin. Nature seems, in these cases, to have exhausted her energies in the long en- deavour to heal the ulcer, and the granulations never rise to the level of the surrounding skin, as in recent cases. The new cuticle there- fore commences upon those granulations which shoot from the elevated edges of the ulcer, and the cicatrizing process is thus led as it were into the hollow of the ulcer, and spreads along its surface, completing the cicatrix in an exca- vated form. 7. The elasticity of the cellular tissue under the new chorion is less than that of the ordinary cellular web; nor does it allow of distension to the same degree. This is seen in oedema and emphysema, where this part will often remain depressed while the sur- rounding parts are raised and distended ; it is also seen in the impediments which large pica- trices prove to the movements of the joints. The same circumstance perhaps also gives a reason for there being no fat contained in these parts. This want of extensibility seems to be but one consequence of the law which regu- lates the products of inflammatory action. The elastic power is materially diminished in the natural cellular tissue by inflammation, a de- gree of stiffness and difficulty of movement remaining for a long time after ; and as the tissue of a cicatrix is, ab initio, the product of inflammatory action, it is to be expected that it should shew the same effects. How far are the vascular and nervous func- tions of the lost part restored in the cicatrix ? It is probable that the new structure receives nerves, but in small number. Of those senses which can be implicated in the destructive process of ulceration, that of touch alone seems to be restored. This is so in a marked though still imperfect degree, the sensation in these parts being somewhat of that dull kind expe- rienced after paralysis. On the temperature of the cicatrix we have not made sufficient observations to generalize, but we have found that the actual temperature of the bridle from a burn, while it retains its hardness, is several degrees above that of the healthy skin, while the power of retaining its temperature, or of resisting the extremes of heat and cold, is much inferior in the cicatrix to that which the healthy skin possesses, although the actual temperature, under ordinary circum- stances, is the same as the surrounding skin. Almost every traveller to the Poles or to the Tropics mentions the liability of old ulcers that had been healed, to announce the extremes of temperature by pain and inflammation. The bloodvessels of the new structure are at first numerous, as indicated by the redness and the readiness with which it bleeds, but after- wards they diminish much in size and number, so that, in an old cicatrix, it is often impos- sible to force an injection into them. M. Du- puytren tells us that in scars upon the face the greatest heat from exercise, or the influence of the mind in producing blushing, leaves this part uncoloured amid the surrounding redness.* Bichat assures us that even the new epidermis itself is overrun with bloodvessels.-)- We have certainly never been able to discover the least trace of vascularity in it, nor have we found that sensibility in this part which he describes. It seems to be a matter of doubt at present how far the function of secretion exists in the new production. Dr. Bright seems to believe in its restoration, since he says that the scar in one of his observations appeared to be covered with a true mucous membrane ; but it is right to state that the proof he gives of this is rather equi- vocal, namely, that the surface was quite con- tinuous with the membrane lining- the rest of the canal; “ indeed,” he adds, “ when inspect- ing the ulcer in the process of healing, we per- ceive the vessels of the mucous membrane running over the surface to be repaired.”! M. Troillet mentions in round terms that the cica- trix had the thickness, consistence, and ap- pearance of mucous membrane ;§ but neither he nor Dr. Bright says any thing in particular as to the villous structure, which we conceive to be an essential characteristic of some forms of * Reckons de Clinique Chir. tom. ii. p. 47. t General Anatomy, Transl. vol. ii. p. 899. t Med. Reports, vol. i. p. 182. § Med. Chir. Rev. vol. v. p. 194. C 06 CILIA. mucous membranes.* Dr. Hope’s and M. Bil- lard’s cases were destitute of villi, and the latter expresses a doubt whether it ever takes place. Our own observations decidedly incline us to the same opinion. Like all adventitious organic products, cica- trices are very readily irritated and are de- stroyed by ulceration with amazing rapidity. A few days and even a few hours are sometimes sufficient to undo the restorative labours of many months; but this destruction is often su- perficial, and then the after-healing is as rapid as the previous ulceration. M. Dupuytren-f informs us that the cicatrix resulting from an entire destruction of the skin is not liable to be affected by many exanthe- matous diseases, such as scarlet fever, measles, and small-pox; it remains pale in the midst of the inflammation and eruption which covers the neighbouring parts. The contrary takes place only in superficial cicatrices, under which some layers of the original cutis exist, and which participate in the properties as well as in the inflammatory tendencies of the rest of the skin. In conclusion we may state, that it appears, from the previous considerations, that in the repairing of the injuries in question, beautiful as is the process and useful as are the results, yet nature’s great object does not consist so much in an endeavour to restore the lost struc- ture in all its functions and perfections of organization, as merely to produce a covering for those parts which remain uninjured, to act as a defence to them from external irritations and injuries, and possessed therefore only of such a degree of vitality and of such properties of structure as shall be sufficient for its own preservation and repair. (A. T. S. Dodd.) CILIA,j 0n anatomy, Fr. Cils; Germ. Wimperhaare.) This term is used to desig- nate a peculiar sort of moving organs, re- sembling small hairs, which are visible with the microscope in many animals. These organs are found on parts of the body which are habitually in contact with water or other more or less fluid matters, and produce motion in these fluids, impelling them along the surface of the parts. The currents or other motions thus produced serve various purposes in the economy of the animals in which they occur. In other circumstances the cilia serve as organs of locomotion, some aquatic animals propelling themselves through the water by their means. Cilia have now been ascertained to exist in a great many invertebrated and in all verte- brated animals, except Fishes ;§ having been very recently discovered by Purkinje and Va- lentin on the respiratory and uterine mucous membranes of Mammalia, Birds, and Reptiles. The terms “ vibratory motion ” and “ ciliary motion” have been employed to express the * Med. Chir. Rev. vol. x. p. 324. t Op. cit. tome ii. p. 48. t For another signification of this term, see the articles Fye and Lachrymal Apparatus. $ Fishes are no longer an exception ; see note at page 632. appearance produced by the moving cilia ; the latter is here preferred, but it is used to express the whole phenomenon as well as the mere motion of the cilia. A considerable space has been allotted to the present article, more perhaps than its re- lative importance may seem to demand, chiefly for the reason that, with one exception, no attempt has been hitherto made to collect and describe under appropriate heads, the facts known on the subject. The exception alluded to is a work by Purkinje and Valentin,* which appeared while this article was in progress, and which contains not only an account of their own discovery, but a history of all preceding obser- vations. But the manner of treating the sub- ject in the work alluded to is for the most part so different from that which is here followed, that its publication has not seemed to warrant any material abridgement of the following article, which, on the contrary, it has increased by affording much new and important matter, as will be acknowledged in its proper place. Another ground on which indulgence may be claimed for details which are, perhaps, greater than may seem commensurate with the impor- tance of the subject, is that many of the facts are here described for the first time, and it was felt desirable to state them in their full extent, which could not be done intelligibly without considerable length of description. The article is divided into two parts ; the first comprehends the particular facts, or an account of the phenomena as they occur in the different tribes of animals considered in Zoo- logical order, with the history of their dis- covery; the second part consists of general deductions from the first, and also treats of the structure and mode of action of the cilia in general. This method has been adopted as appearing on the whole best suited to the pre- sent state of knowledge on the subject. PART i. 1. Infusoria. — Cilia exist very extensively in the different tribes of Infusory Animalcules; indeed they constitute the principal organs of motion in these small animals. When a drop of water containing Infusoria is brought under the microscope, these creatures are seen swim- ming rapidly through it in various directions ; and as they move along, small particles of foreign matter which happen to lie near their path are thrown into agitation, obviously in- dicating the existence of currents in the neigh- bouring water. When the animals remain steady in one place, these currents become much more distinct, setting in particular di- rections, and causing the small particles to run in a stream to and from the animal. If the magnifying power be sufficiently strong, small transparent filaments will be distinguished, projecting from the surface of the animalcules and moving in a very rapid manner. These are the cilia ; they serve like fins or paddles to carry on the animal in its progression through the water, and when it is stationary, they impel the water in a current along the surface, which * Dc phenomeno motus vibratorii, &c. 4to. Wratisl. 1835. CILIA. bor is beset with them. They may be often most distinctly seen when their motion be- comes languid or impeded, as is the case when the water round the animal is diminished by evaporation to such a degree as not to afford scope for their full and rapid play. The cilia of the Infusoria in their arrange- ment are either separate and independent, or combined, forming in the latter case the rota- tory or wheel-like organs of the rotiferous tribes of animalcules. In the first or simple form, which exists in the Polygastric Infusoria (fig. 289), the cilia are usually set round the mouth or spread over the Fig. 289. body generally, in which case they are often disposed in regular rows. Their struc- ture has been carefully in- vestigated by Professor Ehren- berg, who states that each is furnished with a bulb at the root, to which minute muscles are attached. A slight degree of rotation communicated to the bulb causes a much more extensive motion in the rest of the organ, which in its re- Leucophrys volution describes a cone. patula. From time to time the animal sets its cilia in motion, and then, if its body be free, the cilia, acting like fins or oars, move it onwards through the water, serving in this case as organs of lo- comotion. If the body is fixed, the cilia com- municate an impulse to the surrounding water and excite a current in it. This may always be made evident by mixing with the water some colouring matter, the particles of which are hurried along by the current. Many of these particles are conveyed towards the mouth, where some are swallowed and the rest thrown back, the cilia in this case serving the animal as a means of seizing its food. In their combined form the cilia constitute the singular and well-known rotatory or wheel- like organs of the Rotiferous Infusoria. These are formed of one or more circles of cilia, placed on the fore part of the animal, as in Philodina (fig. 290), in which the organ is double, consisting of two cir- cles of cilia set on two short processes, one on each side of the mouth. This apparatus can be retracted or pushed out at the will of the ani- mal. When in motion, the circles of cilia have the ap- pearance of toothed wheels turned round on their axes, first in one direction and then in the opposite. Various ex- planations of this apparent revolution have been given. According to Ehrenberg it is Philodina an optical deception, which erythropthalma. he thus explains : the individual cilia com- posing the rotatory organ move in the same manner as the separate cilia above men- tioned, that is, they each revolve in such a way as to circumscribe a conical space. When viewed sideways, in performing this revolution they must necessarily pass at one moment a little nearer, at another a little more distant from the eye, or, in other words, become alter- nately more and less distinct to the view at short intervals ; and this alternation occurring over the whole circle gives rise to a seeming change of place in every part of it, and a con- sequent appearance of rotation. Perhaps it would be an equally satisfactory and a more simple explanation to consider the appearance as occasioned by an undulatory motion of the cilia, such as that produced by the wind in a field of corn; the undulations following one another in every part of the circle would give the appearance of rotation. Such a waving motion of the cilia undoubtedly occurs in other animals. The Rotifera set in motion or retract their ciliary organs apparently by a voluntary act; they use them for similar pur- poses as other Infusoria use their simple cilia ; when the body is free, the rotatory organ pro- pels it through the water; at other times the animal fixes itself by its tail, and setting in motion its wheels, produces currents in the water, by means of which it seizes its food. These currents in most of the Rotifera have a determinate and regular direction. The cilia of the Infusoria, then, serve as organs of locomotion ; and in the greater number of species they are the only visible organs for this purpose; indeed it is not im- probable that they may exist in others in which from their smallness they have hitherto eluded observation ; as in such cases cur- rents are observed which are most probably produced by invisible cilia. Secondly, the cilia are employed by the animals in catching their food. Thirdly, it is extremely probable that, by bringing successive portions of water into contact with the surface of the animal, they serve also for respiration. Soon after the invention of the microscope, the animalcula of infusions became a favourite subject for its employment, and the cilia and the motions which they produced did not escape the notice of the earlier microscopic observers. Leeuwenhoek observed them dis- tinctly and recognised their use, and probably he was the first that did so. He repeatedly makes mention of them in his writings. At one place* he describes them in an animalcule, which seems to have been the volvox , as short slender organs projecting a little from the body, by means of which the animal produced a re- volving motion and moved onwards. Again, f in speaking of the animalcules which he ob- tained from an infusion of pepper, he states that these animals produced a great commotion in the water by means of divers organs placed on the fore part of the head, which organs also the animals used in swimming. “ In this way,” says he, “ they occasioned such a cir- cular eddy in the water that not only several * Continuatio Arcanorum Natural, 1719, p. 382, Epist. 144. t Continuatio Epistolarum, 1715, p. 95, Epist. 17, Oct. 1687. 608 CILIA. small bodies floating in the water were moved in a circular manner, but even many very minute animalcules, though able to swim vigorously, when they approached the larger animalcules, were whirled about for some time in a circular manner.” In announcing his discovery of the wheel animal,* * * he describes its rotatory apparatus as two projecting discs set round with very slender elongated organs. “ Imagine,” says he, “ two wheels set round with points of needles, and moved very swiftly round from west by the south to the east.” He adds that he cannot comprehend how such motion takes place in a living body. Lastly, in describing a small animal which he found adhering to the water-lentil, (probably a species of vorticella,) and speaking of the currents which it excites, and by which it attracts its food, he adds the following reflection : j- “ More- over it is necessary that these animals, and in general all such as are fixed and cannot change their place, should be provided with an appa- ratus for stirring up motion in the water, by which motion they obtain any matters that float in the water, for their nourishment and growth and for covering their bodies.” Baker,j next to Leeuwenhoek, takes notice of the cilia of animalcules. He observed them in many species, and named them fins, or feet, and sometimes fibrillte. He distinctly recog- nised the currents produced by them, and in- ferred the existence of cilia as the cause of visible currents in cases where the cilia them- selves could not be seen.§ In particular, he bestowed much pains in investigating the eco- nomy of the wheel animal previously disco- vered by Leeuwenhoek, and addressed a letter to the Royal Society on the subject, in 1744.|| He there describes its rotatory apparatus as “ a couple of semicircular instruments round the edges of which many little fibrillae move themselves very briskly, sometimes with a kind of rotation, and sometimes in a trembling or vibrating manner,”!]—— — 1 “ by this means a cur- rent of water is brought from a great distance to the very mouth of the creature, which thereby is supplied with many little animalcules and va- rious particles of matter.”** He also states that the wheels are instruments of locomotion by which the creature swims. ff Baker drew a distinc- tion between the rotatory and vibratory motions of the cilia, these organs being moved in some animals in the one way, in some in the other, while in others they seemed capable of being- used in both ways-!! It appears that he was aware of the true structure of the so-called wheels, and though he often speaks of their * Continuatio Arcanorum Naturae, 1719, p. 386, Epist. 144. t Epistolae Physiologic*, 1719, p. 66. Epist. 7. f 1 cite his work entitled ‘ ‘ Of Microscopes, and the Discoveries made thereby,” London, 1785, although his observations were previously related in separate memoirs of a much earlier date. § Of Microscopes, vol. i. p. 71, p. 80. || Reprinted in op. cit. ii. p. 267. It P.271. •* P. 273. ft P. 284. XX P. 292. being turned round, he was still doubtful of the reality of the apparent rotation. * Spallanzani, in his curious and interesting researches on the production and economy of the Infusoria, made observations similar to those of Baker on the cilia and their motions. He describes them as small filaments or points agitated with a vibratory or oscillating motion. He conceived them to be organs of locomotion which the animals used in swimming,* and that they also served to excite a vortex or cur- rent by means of which food was brought to the mouth. “ The oscillating filaments cause the vortex; the vortex draws the floating par- ticles into the aperture or mouth of the animal- cule, and the latter chooses for its aliment the most delicate, or at least those which suit it best.”f He afterwards describes the ciliary apparatus of the vorticella in a similar man- ner.! In the account of his singular experi- ments on the apparent resuscitation of the Rotifer, he describes its wheel organs as two circles of filaments, exactly like the vibrating filaments of other Infusoria, which by their continued motion give rise to the appearance of two moving wheels; but he distinctly states that the rotation is only apparent, not real. These organs, he adds, serve the same purposes as the simple cilia.§ Needham, || about the same time as Spallan- zani, correctly observed the cilia, and recog- nized their uses. Saussure!! observed the cur- rents, but did not perceive the cilia. Pallas,** in his systematic work on Zoophytes, describes the eddies or currents produced by certain Roti- fera, and notices their cilia, but far less clearly than his predecessors. Wrisbergff observed the currents and eddies produced by the vorticellae; at least he saw smaller Infusoria and particles of floating matter hurried on towards their mouths, but he seems not to have perceived the cilia. Otto Frederick Muller,!! in his systematic work on the Infusoria, described the appear- ance and arrangement of the cilia in each species, and represented them in figures. He named them cilia and pili, and ascribed to their action the currents and vortices which the Infusoria excite. But while he assigns to them the office of locomotive organs, he denies that they are employed in seizing food ; for, what is singular, in his long-continued and elaborate inquiries into the economy of these animals, he could never perceive that foreign matters drawn into the mouth were retained there as nourishment, but believed that they were always again thrown out. In this, however, he was undoubtedly mistaken. * Opuscules de Physique, torn. i. p. 180. f P. 183. x P. 199. $ Tom. ii. p. 227. || Spallanzani, Nouvelles Recherches sur les Decouvertes Microscopiques, &c. 1769, p. 161. !f See Letter by Bonnet, in Spallanzani Opus- cules, tom. i. p. 176. ** Elenchus Zoophytorum, 1766. ■ft Observationum de Animalculis Infusoriis sa- tura, 1765, p. 52. p. 63. ;; Vermium Terrestrium et Fluviatilium His- toria, 1773, and Animalcula Infusona, 1788. CILIA. 609 Gleichen,* * * § in 1778, described the currents produced by the vorticellae. In an earlier work he ascribed an agitation of small bodies, which he had observed in the neighbour- hood of one of the Infusoria, to an electric or magnetic force, not having perceived the cilia.f Fontana J described the rotatory apparatus of the Rotifer and its use ; he conceived that its apparent rotation was produced by the succes- sive elevation and depression of the cilia which encircle it. Of the more recent writers who have inves- tigated or described these phenomena in the Infusoria, I may mention Dutrochet,§ Gruit- huisen,|| Agardh,H Raspail,** and Ehren- berg.ff Raspail denies the existence of cilia, attributing their appearance to an optical de- ception, an opinion which is undoubtedly erroneous. Ehrenberg, who, of all recent ob- servers, has contributed most to the knowledge of the economy and natural history of the Infusoria, has particularly investigated the structure and mode of action of their cilia. The substance of his observations has been already given. The ciliary motion has been recently ob- served in the embryoof Infusoria while enclosed in the ovum.JI 2. Polypi and Sponges. — a. Fresh-water polypi. The phenomena in question have not been discovered in the Hydra, which is the largest and best known of the Fresh-water Polypi; but they have been seen and described by many observers in another sort, viz. that known by the names of the Polype a panache, or Plumed Polype of Trembley, the Bell- flower animal of Baker, and Plumatella, Cris- tatella, Alcyonella, &c. of other naturalists. The Polypes of this kind are connected in groups on a common stock or stem, (a, a, Jig. 291, which represents the animal magnified,) and each is furnished with a tube ( b , b' ), into which it can wholly withdraw itself. From time to time they advance a little way out of the tubes and display a double row of arms or tentacula (c ) ranged round the mouth in the figure of a horse-shoe. When the arms are spread out in this manner, cur- rents appear in the surrounding water, which are made evident by the motion of any small particles that may accidentally or intentionally be suspended in it. The currents pass along the tentacula, the water being drawn towards * Abbandlung ueber-die Saamen -und Infusions Thierchen, 1778. f See Muller, Infus. p. 87. 1 Traite sur le venin de la Vipere, etc. 1781, tom. i. p. 87. § Sur ies Rotiferes, Ann. du Musee d’Hist. Nat. 1812, tom. xix. et 1813, tom. xx. |j Salzburg. Med. Chir. Zeitung, 1818, iv. p. 222. H I'cber die Zauberkraft der Infusorien, Nov. Act. Acad. Caes. Leop. tom. x. p. 127. ** Hist. Nat. de l’Alcyonella Fluviatile, etc. Mem. de la Soc. d'Hist. Nat. tom. iv. and Chimie Organique, 1833. tt Abbandl. d. Akad. der Wiss. zu Berlin fur 1831. Wagner, Isis, 1832, p. 383. , Fig. 291. them from every side, and the main stream at last issues from the midst of them, appearing as if it came out of the mouth, from which, however, it really is not derived. The arms are fringed on their two borders with a mul- titude of cilia, (see A, a single arm mag- nified,) set close together, which vibrate in regular succession, their motion appearing like progressive modulations along the ten- tacula. When one of the arms is cut off, it affects the water in the same way as when con- nected with the animal, its cilia impelling the fluid in a current, or carrying the separated arm through it, according as it is fixed or free. As to the use of these motions, it may be stated that they serve undoubtedly for renew- ing the water in respiration, and probably also to convey food to the animal. Steinbuch, however, remarked that the currents were most lively in pure water, and that the extraneous matters which they conveyed seemed rather to incommode the animal, which endeavoured to avoid them ; and from this he inferred that the currents served chiefly if not solely for respiration. Trembley* and Bakerf observed the currents produced by this polype, but both erroneously conceived them to be caused by agitation of the tentacula. Roes el J correctly remarked that, during the production of the currents, the tentacula were motionless, but not perceiving the cilia, nor being aware that the arms when detached still produced motion in the water, he supposed that the currents were occasioned by a stream issuing from the mouth. At length Steinbuch§ discovered that separated tentacula retained the power of impelling the water; he distinguished the cilia and their motion as the cause of the impulsion, and * Mem. pour servir a 1’Hist. d’un genre de Polype d’eau douce, 1744, p. 212. t Of Microscopes, ii. p. 309. t Insecten Belustigungen, tom. iii. 1755, p. 458. § Analccten neuer Beobachtungen und Unter- suchungen fur die Naturkunde, 1802, p. 89. 610 CILIA. more correctly described the course of the cur- rents : the foregoing description is in a great measure taken from his memoir. Since then several others* have made similar observations, among whom we may mention Raspail as more particularly deserving of notice, though he here, as in other cases, denies the existence of cilia. b. Marine Polypi. — The polypi of marine Zoophytes, on which observations relating to the present subject have been made, may for our purpose be conveniently arranged under three principal forms. The first form of polype (fig. 292) is found in Flustrae and cellular polypi generally; it ex- Fig. 292. ists also in some spe- cies which have been classed among the Ser- tulariae, and probably prevails very extensively in different tribes of Zoophytes. The body (a, b, c), which is gene- rally contained in a cell, is bent on itself, some- what like the letter Y or V ; the one branch (a) being the mouth and throat, the other ( b ) the rectum opening by an anus, and the middle part (c), which is of a dark and often of a brown co- lour, being the stomach probably with some accessory organ. The mouth is surrounded with a variable number of long straight ten- tacula or arms, fringed on both of their lateral margins with cilia. When the arms are ex- panded, the cilia are thrown into rapid motion, which has the appearance of undulations pro- ceeding along the fringes, upwards on one side of the arm or from its root to the point, and downwards on the other. While the cilia are thus moved, they produce currents in the water, as described in the Fresh-water Polype, and here also the currents in all probability serve for respiration and the prehension of food. Besides these motions in the water in the neighbourhood of the tentacula, a revolving motion of particles is observed within the body : small particles of extraneous matter which enter the throat are moved round within it ; and the contents of the stomach and rectum undergo a very singular revolving motion round the axis of the cavity. These internal motions, Dr. Grant conjectured, might be owing to internal cilia; and I have been able to satisfy myself of the actual existence of such internal cilia, by means of a Wollas- ton’s doublet of one-thirtyfifth of an inch focus ; they are very evident in the throat; in the stomach they are most distinct in the part adjoining the rectum (indicated by d in the * Vaucher, Bull, de la Soc. Philom. An xii. ; Raspail, Mem. de la Soc. d’Hist. Nat. de Paris, for 1827 : Meyen iiber Polypen, Isis 1828, p. 1225. figure), and they are clearly to be seen on the whole internal surface of the rectum (6). I have nowhere more clearly seen the above- mentioned phenomena than in a zoophyte, whose polype, though differing somewhat from the first form, may yet be referred to it. This zoophyte (fig. 293, A, B) has a creeping stem Fig. 293. w. (a, a), which adheres to shells, or twines round the stems and branches of other zoophytes, (as b in the figure) ; the polypes are supported on soft pliable fleshy stalks (c), which the crea- ture moves from time to time ; their body ( d , and B more magnified) is bell-shaped and consists of a transparent brownish skin or envelope containing the mouth and throat (e), the stomach ( g ), and rectum ( h ). The mouth, or expanded aperture of the animal, is sur- rounded by a prominent lip or border ( i , i), to which the arms are attached. Cilia are distinctly visible on the arms, and within the mouth and stomach ; they are moved very briskly, and small extraneous particles indi- cating currents in the water are hurried onwards towards the arms, as pointed out by the arrows at k,k; many of these particles descend along the inner side of the arms to their base, as shown by the dotted arrows o, o, o, and thence into the cavity of the mouth, from which, after being moved about for some time, the greater number are thrown out. It would seem that the particles of food or other solid matter, after being conveyed to the inside of the arms, take then a different course from the stream of water. The latter passes inwards between the arms, and issues from the middle of the irregular circle which they form (as at m, m), carrying with it such solid matters as are not arrested on the arms; but the bodies which enter the mouth are slowly carried along the inside of the arms (as at o, o ), and in close contact with them till they reach their base. The motions of the contents of the stomach and its cilia appeared as in the Flustrae. I could perceive none in the rectum. Mr. Lister has described the same phenomena in a zoophyte closely resembling this one in the structure of the polypi, but differing in the character of the stem.* * Phil. Trans, for 1834, p. 385. CILIA. 611 In the second form (fig. 294) the stem and Fig. 294. branches are formed externally of a tough (generally horny) substance, and within this of a transparent soft tissue, which is tu- bular and contains a granular matter. The polypi resemble hydras ; each is lodged in a horny cell («, a), from which it partially protrudes itself ; one orifice surrounded with tentacula serves both for receiving aliment and discharging faeces ; this leads to a stomach ( b ) , which communicates through an opening (c) at the bottom of the cell with the interior of the tubular stem and branches, the attached part or base of the polype being continuous with the soft internal tube, of which the po- lypes might be regarded as a prolongation. In this form of polype, which exists in most true species of Sertularia, Campanularia, and Plumularia, and in allied genera, the tentacula or arms are destitute of cilia and incapable of giving an impulsion to the water. But a very remarkable motion has been observed by Cavolini* and Mr. Listerf in the granular matter contained in the stem and branches. Although this motion has not been traced to the agency of cilia, yet as it is connected with our subject, I shall briefly notice it here. When the stem and branches of the above- named zoophytes are examined with a high magnifying power, a current of granular par- ticles is seen running along the axis of the tube. The current, which is compared to the running of sand in a sand-glass, after con- tinuing one or two minutes in the same direc- tion, changes and sets in the opposite one, in which it continues about as long, and again resumes the first, thus alternately flowing along the stem to the extremities of the branches, and back again. The change of direction is sometimes immediate, but at other times the particles are quiet for a while, or exhibit a confused whirling motion for a few seconds before the change takes place. Mr. Lister has discovered that the currents extend into the stomachs of the polypi, in which and in the * Memorie per servire alia storia de’ Polypi Marini, p. 121 and 197 ; p. 56 and 91 of the Ger- man Translation. f Phil, trans. 1834, p. 369. mouth a remarkable agitation of particles is perceptible. When these particles are allowed to escape from a cut branch, they exhibit, according to Mr. Lister, something very like spontaneous motion. The immediate cause of these currents is not apparent ; it seems not to be muscular contraction of the tube ; perhaps, like the agitation within the stomach, they may be owing to internal cilia. As to their use Mr. Lister supposes the circulating matter “ to be a great agent in absorption, and to perform a prominent part in the obscure pro- cesses of growth; and its flow into the stomach of the polypi seems to indicate that in this very simple family (the Sertulariae) it acts also as a solvent of the food.” — Page 77. Perhaps the polypi of the Pennatula and Virgularia should be referred to this head. In these Dr. Grant* discovered a constant vibratory motion within the mouth, apparently pro- duced by cilia placed round the entrance of that passage, and he saw minute particles oc- casionally propelled from the mouth. Their tentacula, as in the zoophytes last referred to, did not excite currents. The third form of polype is found in Tubularia. Fig. 295 represents a magnified view of a common species, the Tubularia indivisa. There is a transparent horny tube (a, a), containing a soft mat- ter, which at the extremity of the tube is continuous with the stomach (6) and the mouth (c). There are two rows of tentacula or arms, one ( d ) immediately surrounding the orifice of the mouth, the other (e) further back, be- tween the mouth and stomach. The arms are destitute of cilia and excite no movement in the water; but Mr. Listerf has discovered a remarkable motion of particles within the tube, which has some re- semblance to the circulation of globules observed in plants of the genus Chara. These particles moved in a current within the tube, the general course of the stream being parallel to the slightly spiral lines of spots on the tube, and in the directions marked Tubularia by the arrows. On the greater indivisa. part of the side first viewed (the one represented) it set as from the poly- pus ; but on the other side the flow was to- wards the polypus, each current thus occupy- ing half the circumference. The tube had a granulated appearance between the lines of spots, and beneath this the particles ran. Their course was even and uniform without any starting or dancing motion, such as is observed in the Sertularia;. At the nodous parts of the * Edin. Ph:l. Journ. t Phil. Trans. 1834, p. 366. 612 CILIA. tube (in, n) were slight vortices in the current, and at o near the end of the tube it came over from the opposite side. Two currents were continually going on in the mouth and the stomach, one always flowing down the sides in the direction e, e, and the opposite one in the axis. Neither the cause of these currents nor their use has been ascertained. Such are the phenomena of the ciliary and other apparently allied motions in the Marine Polypi. Spallanzani seems to have first noticed them ; he observed the currents produced by the Flustrae, but erroneously attributed them to the agitation of the arms, the cilia on which he had not perceived. Dr. Fleming* described the current along the tentacula in the Valkeria cuscuta (a genus which he has separated from the Sertulariae, among which it was previously included,) and distinguished the cilia with their undulatory motion. Dr. Grantf discovered the cilia on the arms of the F’lustrae and described their undulatory motion, to which he ascribed the motion in the water. He also pointed out the revolving motion of particles within the mouth, stomach, and rectum, and conjectured that it was owing to the action of internal cilia, which conjecture I have been able to verify. Dr. Grant also discovered the vibratory and probably ciliary motion within the mouth of the polype of the Pennatulae. LoeflingJ first observed the agitation of granular matter within the stem and branches of the Sertu- lariae. Cavolini afterwards more correctly de- scribed this as a current of fluid holding granules in suspension, running first in one direction and then in the other. Lastly, Mr. Lister observed anew these internal currents of the Sertulariae, described them more mi- nutely, and showed that they extended into the stomach of the polypes. Mr. Lister has also described the phenomena in the Flustrae previously observed by Dr. Grant. He dis- covered the currents within the stem of the Tubularia, which, as far as I know, had not been previously noticed. c. Sponges. — In the various species of sponges, water, the element in which they live and grow, passes in currents through pores and canals in their substance, in a con- tinuous manner, entering at one place and issuing at another. This phenomenon has not been directly traced to the agency of cilia; it comes nevertheless to be considered here, as such an agency is highly probable, and at least the motion of the water is not owing to any contraction of the canals in which it flows, but is obviously caused by some other kind of impulsion communicated to it by the surface along which it passes. In a common sponge we see a number of pretty large orifices on the surface, each opening on the summit of a conical eminence or pa- pilla (jig. 296, a ). These openings are named * Mem. of Wern. Soc. fol. p. v. p. 488. t On the Structure and Nature of Flustrae. Ed. New Phil. Journal, vol. iii. 1827. t Schwedische Abhandlungen, 1752, p. 121. Fig. 296. by Dr. Grant the “ faecal orifices.” Innume- rable small pores occupy the rest of the surface, and give to it its peculiar character. These pores penetrate to a certain depth, and lead into canals ( b ), which, uniting together and gradually growing larger, terminate in wide tubes, which open at the faecal orifices. The pores, excretory canals, and faecal orifices thus form continuous passages through the sponge. In the fresh state they are lined throughout with a smooth gelatinous coating. When a living sponge is examined atten- tively in its native element, the water is per- ceived entering at the pores and issuing from the fecal orifices, its course being indicated by the motion of any floating particles that may be present. The issuing currents are stronger than the entering, and are rendered con- spicuous by excrementitious matters or some- times ova, conveyed out at the fecal orifices. When sections of the sponge, including a greater or less extent of the internal canals, are placed in water, the fluid, according to Dr. Grant’s observations, is still evidently moved along the internal surface of the portions of canals, although their continuity with the rest is destroyed. Dr. Grant could not detect cilia either in these canals or the pores which lead to them, but he discovered these organs on the ova of the sponge, which there- by execute remarkable spontaneous motions, and he is inclined to attribute the currents in the adult sponge also to cilia, which he conceives may probably exist, though, from their small- ness, he has not been able to perceive them. At any rate he has shewn by most satisfactory observations, that the current cannot be ascribed to contractions in the canal, for in none of his numerous experiments instituted for the pur- pose, could he discover any sign of irritability, at least any sign of contraction of the tissue of the sponge on the application of stimuli. Naturalists even of the earliest times, whose attention was directed to the phenomena exhi- bited by the living sponge, have remarked that water entered and passed out from its porous substance, but the true course of the fluid seems to have been unknown, it having been erroneously supposed to enter and issue by the same orifices. Dr. Grant,* to whose labours we owe most of the correct information ob- tained respecting the structure and functions of the sponge, demonstrated that the current is continuous, and flows always in one direction as above described, and proved that the motion * Edin. Phil. Journal, vols. xiii. xiv. Edin. New Phil. Journal, vols. l. and ii. CILIA. of the water was not produced by contraction and dilatation of the tissue of the sponge, which he showed to be destitute of irritability. Dutrochet had made observations on the same subject, which were published subsequently* to those of Dr. Grant, and not anteriorly as he supposes ; he perceived the constant direction of the current, and ascribed the phenomenon to endosmosis and exosmosis. 3. Ciliary motion of the ova of Polypi and Sponges. — The ova or gemmules of several of these zoophytes execute independent move- ments, and produce currents in the surrounding water. This singular fact was, it appears, first noticed by Mr. Ellis in 1755,f in ex- amining a species of Sertularia, the Campanu- laria dichotoma ; but he described the ova or embryos which he had seen in motion, as young polypi, already somewhat advanced in their formation. Cavolini,j in 1784 and 1785, observed the same phenomenon in the ova of the Gorgonia and Madrepore, and investigated it more fully. He saw the egg-shaped gem- mules or ova, on quitting the parent, rise to the surface, and sw'im with their large end for- wards, in a horizontal direction, till they fixed themselves on some spot where they were deve- loped. Dr. Grant, § in 1825, discovered similar motions in the ova of the sponge, and detected the moving cilia. The cilia covered the whole surface of the ovum, except the pos- terior tapering extremity, and in its motions the large end of the ovum was always directed forwards. When an ovum fixed itself, its cilia still continued to play, by which a current along its surface was kept up for some time. Dr. Grant also investigated the movements of the ova of the Campanularia, previously seen by Ellis, and of the Plumularia falcata. The ova of both these zoophytes are contained within transparent capsules, two or more being in each capsule, surrounded by a clear fluid. Dr. Grant distinctly perceived cilia vibrating on the surface of the ova, and causing, while within the capsule, an eddying motion of the surrounding fluid, but propelling the ova through the water when extracted from their capsule, as in the sponge. The ciliary motion has also been found in the ova of fresh-water polypi, having been discovered by Meyen|| in those of the Alcyonella stagnorum, which is probably the same with, or at least nearly allied to the Bell-flower Polype. By means of the remarkable provision here de- scribed, the ova of these fixed zoophytes are dis- seminated, and conveyed to situations suitable to become the abode of the future individuals. The same provision undoubtedly serves also to move the water along their surface for the pur- pose of respiration. It exists, as will be after- * L’agent immediat dumouvement vital devoile, 1826, p. 179, and Annales des Sciences Naturelles, 1828, tom. xv. p. 205. t Hist. Nat. des Corallines, p. 116. | Memorie per servire alia storia de’ Polypi Marini, Nap. 1785, p. 8, p. 48 of German trans - lation. Edin. New Phil. Journal, vol. i. p. 150. Isis, 1828, p. 1225, sqq. Isis, 1830, p. 186. 613 wards shown, in the ova of many other ani- mals. 4. Acalephce. — Many species of Medusas are furnished with cilia, or at least with moving organs bearing a close resemblance to the cilia of other animals, though in the Meduste they present several peculiarities. The cilia are found in all the Medusae belonging to the order Ciliograda of Blainville, or Ctenophora of Eschscholz, of which the genus Beroe is a good example. Eschscholz* describes them as small pectinated or comb-like organs, ranged in longitudinal rows or stripes on the external surface of the body, with their flat surfaces in apposition. Each comb-like organ consists of many small, flattened, pointed filaments, united together by a common base, the points being directed towards the posterior extremity of the body. They are moved like fins, being slowly raised and suddenly struck back, by which means the body is carried through the water. In the Beroe and others of similar form, the cilia point towards the closed extremity of the body, so that the opposite or open end is carried forward. The animal seems to have the power of moving more or fewer of these organs as it may incline, by which means other motions besides direct progression are per- formed. The cilia, when separated from the body with a piece of skin, continue to move briskly for some time. A longitudinal vessel runs under each row of cilia, com- municating with the rest of the vascular system, and containing a fluid, in which yel- lowish particles are suspended. Eschscholz regards these vessels as arteries, and considers the cilia as respiratory as well as locomotive organs. Dr. Grant, in describing the cilia of the Beroe pileus,j- represents the parallel fila- ments of which the comb-like organs consist, as united together by a membrane as far as their points, like the rays in the fin of a fish. Schweigger compares the vessels which run underneath the rows of cilia, to the canals com- municating with the tubular feet of the Sea- urchin and Asterias ; and Dr. Grant seems also inclined to ascribe the motion of the cilia, whose filaments he conceives to be tubular, to their being alternately filled and emptied of fluid derived from the longitudinal vessel, like the tubular feet of the Echinodermata. This view of their mode of action, however, is scarcely reconcilable with the observed phe- nomena, as will be afterwards shown in con- sidering the structure of the cilia in general. Audouin believed that in the Idya, a genus nearly allied to the Beroe, the fluid of the longitudinal vessel, which he supposes to be water, is sent into the cilia; lie therefore regarded them as respiratory organs. If the vessel under the cilia in this case, as 'in the Beroe, communicate with the rest of the vas- cular system, and its contained fluid be re- garded as blood, then the cilia of the Idya, which, according to Audouin, are permeated by the fluid, would bear a certain analogy to the gills of fishes. * System der Acalephen, p. 3. t Zoological Trans, vol. i. p. 9. 614 CILIA. Cilia appear also to exist in other tribes of Medusae besides the Ciliograda, but they differ in form and situation from those described, and have not been investigated with equal accuracy. In Rhizostoma there are certain membranous appendages attached to the arms or tentacula, and bearing on their free edge a fringe of short filaments which are constantly in motion, and continue so for some time after the arm or portion of membrane supporting them is de- tached from the body. These filaments are described and figured by Eysenhardt,* who regards them as organs of generation ; they are probably of the nature of cilia. Similar fila- mentary organs seem also to exist within the body in some Medusae. (See Acalephze, p. 48.) 5. Actinia. — In a paper published on the present subject in 1830,| I mentioned that I had found the ciliary motion in the Actinia or Sea-anemony, but gave no description of it. 1 have since re-examined various species of Actiniae with this view, and shall now describe the appearances ; but to make the description intelligible, it may not be improper to remind the reader of some points in the anatomy of these animals which require to be kept in view. The body of the Actinia, of which Jig. 29 7 Fig. 397. is a plan, consists entirely of a soft but tough substance, exceedingly contractile and irritable. It is usually cylindrical in shape, one end, (a, a,) named the base or foot, serving to fix the animal by adhering to rocks or other ob- jects ; the other extremity is named the disc, one-half of which is seen at b, b, the other half being removed by a section ; it is sur- rounded at its circumference by the arms or tentacula (c, c,) in concentric rows, and in its centre is the mouth (d), or opening of the stomach, which serves both for the entrance of food and discharge of undigested remains. * Nova Acta Acad. Cars. Leop. vol. x. p. 404. t Edin. Med. and Surg. Journal, vol. xxxiv. The stomach ( e ) is plaited longitudinally on its inside ; vertical membranous partitions ( g , g, g, g',) pass from its outer surface to the inside of the parietes of the body, and to the base, dividing the intermediate space into numerous compartments or cells, which com- municate with each other by openings, as at g', g, and also open into the tentacula, as at h. The latter are conical muscular tubes, commu- nicating at their base with the cells, and open- ing at their point by a small orifice, surrounded by a sphincter muscle. The cells seem also to communicate with the cavity of the stomach, and, according to Rapp,* they open in some species by small orifices on the surface of the body. The cells and tentacula contain sea- water, with which the animal can distend the whole body or any particular part of it. The protrusion of the tentacula, as is well known, is effected by their distension with water. The stomach also is often partially everted and pro- truded from the mouth by an accumulation of water behind it. It has not, so far as I know, been clearly shewn by which of the communi- cating orifices the water enters. Though I took considerable pains, I have not been able satisfactorily to ascertain this point ; I may remark, however, that I have repeatedly no- ticed water entering at the mouth. The ovaries and oviducts {k, k,) are lodged in the cells, and are consequently bathed in water ; of these it is unnecessary here to say more than that one part of them consists of a waving membranous fold like a mesentery, at- tached by one edge to the sides of the cell, and at its free border supporting the oviduct, which resembles a white opaque chord, termi- nating, after numerous serpentine windings, in the stomach. In regard to the ciliary motion in the Actinia?, I am led from my observations to conclude that it exists to a greater extent in some species than in others. In all cases I have found it on the sur- face of the oviducts and their supporting mem- branes, which is covered with cilia of very minute size ; also on the internal surface of the sto- mach, which has similar cilia, and there the currents follow the direction of the folds of the membrane. In one small but full-growm species I found currents commencing near the centre of the disc, and proceeding outwards in a radiating manner to its circumference, whence they continued along the arms as far as tiie points. On examining this species, which was semitransparent, by transmitted light, I distinctly perceived moving particles in the water contained within the tentacula and be- hind the protruded stomach.j- The motion of these particles obviously indicated a current in the water along the surfaces containing it, which current, like that on the oviducts, it may be inferred was produced by cilia, for it went on while there was no perceptible con- traction taking place in any part of the ani- mal. The particles indicating the currents * Ueber die Polypen und die Actinien. Weimar, 1829, p. 47. t Some of these particles were no doubt the ova. CILIA. 615 within the tentacula, were moved in two diffe- On the under surface of the Asterias, (I rent directions, namely, from the base to the speak of the Asterias rubens in particular, point, and from the point to the base ; and Jig. 298, A, B, C, as it is a large species and (supposing the arm spread out horizontally,) common on our shores,) we observe the mouth the outward current was along the under part in the centre, and the tubular feet ( l, fig. B) of the tube, and the returning one along the projecting in rows along the under part of the upper: (see h.) I also observed these internal rays. Nearly the whole surface of the animal currents of the tentacula in a young specimen of is beset with three kinds of eminences. First, Actinia senilis, which seemed to have been very hard calcareous processes, (a, fig. C,) placed recently discharged from the parent; in it also like studs at some distance from each other, there were radiating currents on the disc, but Secondly, claw-like processes (6, b) ; these sin- they stopped at the base of the tentacula. gular organs are more thickly set ; they consist Thus the external currents on the disc and ten- of a solid stem of soft substance, bearing at the tacula were found in one species, and they extremity a sort of pincers or forceps of hard occur on the disc in some other species in the calcareous matter, like the claw of a crab, young state, but their occurrence in this situa- They resemble analogous organs found on the tion is by no means general in adult Actiniae. Sea-urchin, only that the maxillae or pincers in The phenomena described are in all proba- the latter consist of three pieces ; they were bility connected with the processes of nutri- named antennae or feelers by Monro, but Miil- tion and respiration. They bear a striking ler regarded them as parasitical animals. The analogy to those I have observed in the Echino- third sort of processes (c, c,) are named the dermata. respiratory tubes, and are the most important The ova of the Actiniae were observed by in regard to our present subject. They are Rathke to revolve round their axis, and occa- short, conical, membranous tubes, communi- sionally to move straightforwards in the eating at their base with the internal cavity of water. He could detect no cilia or other the body, and perforated at their point by an moving organs.* orifice which can be very perfectly closed. 6. Echinodermata. — The animals of this Most of them are placed in groups or patches, class in which I have observed the ciliary and, corresponding with each group of tubes, motion, are different species of the Sea-star the fibrous membrane forming the wall of the (Asterias), and the Sea-urchin (Echinus). In body presents on its inside a pit or shallow proceeding to describe the phenomena in the depression (e), perforated with holes, through Asterias, I must first take the liberty of ex- which the tubes communicate with the general plaining some points in the anatomy of that cavity. Like the tentacula of the Actinias, animal, referring the reader for other details to which they resemble in several other respects, the proper sources, especially the monograph they can be distended with water and elon- of Tiedemann.j- gated, or emptied, contracted, and shortened. Fig. 298. * Dorpater Jahrbiich. fur Litt. Stat. und Kunst. Dalyell, who had long before observed it. The cilia Bd. i. Heft. ;. p. 84 — 86, quoted by Purkinje and could be distinctly perceived. Valentin, p. 32. I have since seen the indepen- t Anatomie der Rohren Holothurie, &c." Land- dent motion of the ova when extracted from the shut, 1816. animal. It was shown to me by Mr. Graham 616 CILIA. In the inside of the body the membranous stomach (g) occupies the middle part, and from it a pair of lobed cceca (h, h,J (and i, i, cut short) pass into each ray. Within the rays also we find inferiorly the rows of vesicles (k,k) which form part of the feet (1,1), and the ovaries. All the rays communicate through the middle part, and the whole inside is lined by a transparent membrane (n, n), which, like a sort of peritoneum, covers the stomach and cceca, attaches each of the cceca by a me- sentery (o, o) to the roof of the ray, lines the fibrous parietes of the body, and is probably reflected over the vesicles of the feet and the ovaries. Each mesentery encloses a space ( o, fig. B) between its sides, which opens into the general cavity at the root of the cceca. The lining membrane passes into the perforated pits ( e), by which the tubes (c) communicate with the cavity, and sends prolongations through the perforations into the tubes lining them to their points. The space ( s, s, fig. B) lined by this membrane contains sea-water, which is generally described as entering and issuing by the respiratory tubes.* I find the ciliary motion in four situations, namely, 1. on the external surface; 2. within the cavity of the body, or in the space (s) between its parietes and the viscera ; 3. within the stomach and cceca ; 4. within the feet. In all these situations moving cilia are visible with the microscope on the respective surfaces; they are every where comparatively small, in some parts excessively so. Though I have not traced them over the entire extent of each sur- face, I have no doubt they exist at every point where currents are produced. 1. On the external surface. The ciliary mo- tion as indicated by the application of pow- dered charcoal, occurs over nearly its entire extent, but with different degrees of intensity. The strongest currents pass along the outer surface of the tubes from the base to the point, as at c ; they are also pretty strong on the claw-like processes (b' ) and intermediate skin; on the feet they are evident but less vigorous. 2. Within the body the currents take place on the lining membrane and its reflections. A longitudinal current runs along the roof, and another along the floor of each raj', forwards or towards its point : (see the arrows in fig. A.) These advancing currents are confined to the median line and its immediate vicinity; two retiring currents (r, r,) run backwards (one on each side) at the place where the sides join the floor of the ray. Two longitudinal currents also exist on each of the cceca, an advancing one (li ) on the inferior surface, and a retiring one superiorly (A, //, fig. A) in the space (o,fg. B) inclosed within the mesentery, which, as already mentioned, opens into the general cavity. The longitudinal currents, except those within the mesentery, are, if for the sake of explanation * Without denying this mode of entrance, 1 may yet mention, that though I have often seen the animal slowly distending itself with water, and again partially emptying itself, 1 could never per- ceive the fluid entering or issuing at the orifices described. we may so express it, connected by others which run vertically and transversely on the cceca and on the roof and sides of the cavity, (see the arrows in fig. B ;) on the vesicles of the feet the course of these cross currents is varied by the curved surfaces. As the lining membrane of the cavity extends into the respiratory tubes, so currents exist within these likewise, as at t, fig. C. This is proved by injecting turbid fluid into the ray, when particles are seen moving within the tubes; and if a few of the tubes with a portion of the skin be cut off and placed under the microscope, the fluid which will still be retained by some of them may be seen to be in motion, the floating particles moving from the base to the point and back again, as in the arms of the Actiniae. 3. The motion is very distinct on the inner surface of the stomach and cceca; the currents within the cceca follow the same direction as on their external surface, that is, an advancing current runs inferiorly from the root to the point and a returning one superiorly ; and at the sides currents run upwards, following the ridges or folds of the internal membrane which result from the lobulated structure of the coeca. 4. The ciliary motion exists distinctly within the feet, though the cilia are very small ; these became visible on viewing the edge of a folded portion with Wollaston’s doublet of one-thirty- fifth of an inch focus. The currents described, as far as I have been able to perceive, preserve always the same determinate direction. Even when portions of the ciliated surface are detached, the motion on them continues, and its direction is the same as before their separation. As to the use of these motions, it is most probably connected chiefly with respiration ; and if such be the case, it would show that in this animal a great extent and variety of parts are concerned in that function. The ciliary motion on the inner surface of the stomach and coeca is probably subservient also to the process of digestion. It is conceivable that by means of this provision the dissolved or digested food might be introduced into the cceca, and spread over their internal surface, there to be duly mixed with secreted fluids ' and subjected to the process of absorption ; the returning cur- rent serving to bring back the residue, or to convey secreted fluids into the stomach. Or, considered as subservient to respiration, the cili- ary motion, in diffusing the digested food over the internal surface of the cceca, may at the same time expose it to the respiratory influence of the water on their outside. These phenomena in the Asterias seem not to have been previously noticed. Tiedemann,* it is true, had observed an eddying motion of the water in the vicinity of the respiratory tubes while the animal was slowly distending or emptying itself, but he conceived it to be nothing more than the commotion necessarily produced by the passage of the water through the tubes. There can be little doubt that the * Anat. der Rohren Holothurie, etc. p. 40. CILIA. phenomenon he saw was caused by the ciliary motion on the external surface, though he was not aware of this. Having entered into these details respecting the Asterias, I may describe more briefly the phenomena in the Sea-urchin, the more so as my opportunities of observing this animal have been less frequent. The species submitted to examination was the common large Sea-urchin of our shores, Echinus esculentus, described by Monro.* Its body consists of a globular shell, containing the viscera. The mouth is placed underneath, the anus opposite on the upper surface. The tubular feet are disposed in vertical rows from the mouth to the anus, the intermediate part of the shell being covered with moveable spines, and the singular claw-like organs referred to in describing the Asterias. As in the Asterias, there are membranous respiratory tubes, but they are comparatively few in number, forming ten small bunches or groups, which are placed on the under surface not far from the mouth, and open internally in ten small perforated pits, like those of the Asterias ; they are supposed by Tiedemann and others to be the channels by which the sea-water gets into the interior of the body, and fills the space between the inside of the shell and the contained viscera. The ali- mentary canal, commencing at the mouth, rises through the curious dental apparatus named Aristotle’s lantern, turns in a waving manner twice round the inside of the shell, and termi- nates above at the anus ; it is supported by a mesentery derived from a membrane which lines the cavity of the shell, and which is reflected over its contents like a peritoneum. Inside the shell we also find the ovaries and the rows of feet. The internal parts of the latter, instead of being round vesicles as in the Asterias, are broad lamina; enclosing vessels,! canals or branched cavities, which canals, like the vesicles of the Asterias, communicate on the one hand with the tubes of the feet, and on the other with a common vessel which runs along the middle of each double row of laminae. The vessels or spaces within the laminae are much branched ; they form a plexus surrounded by a principal vessel at the border. I have found the ciliary motion over nearly the whole surface of the cavity of the body and the contained parts, which surface, as mentioned already, is covered by a lining membrane or peritoneum. Two longitudinal currents run on the intestine in the same direction, viz. one along the line of attachment of the mesentery, the other at the opposite part of the tube. On the remaining circumference of the intestine the impulsion is directed obliquely towards the nearest longitudinal current. In regard to the laminae of the feet, a current runs down the middle of each of the double rows, following the course of the longitudinal vessel there situated, the direction being from the anus to- wards the mouth. Lateral currents pass over the surface of the laminae from their external * Anatomy of Fish.es, &c. f Accurately described by Monro, 1. c. VOL. I. 617 to their internal border, where they join the middle current; they follow the irregular eleva- tions on the surface of the laminae occasioned by the canals or vessels in the latter; hence, when charcoal powder is applied, the particles follow winding paths in crossing from one edge of the lamina to the other, and they are fre- quently caught in a hollow between two cur- rents, and whirled about for some time before they resume their way. Currents were visible also on the reflections of the lining membranes which cover and pass between different parts of the lantern, and at the internal openings of the respiratory tubes. The cilia on the parts de- scribed are excessively small, but distinctly per- ceptible. The ciliary motion wras not detected on the external surface of the body nor within the alimentary canal ; but in regard to these parts the observations could scarcely be consi- dered as conclusive; nor could 1 determine whe- ther, as in the Asterias, the phenomenon occurs within the feet or within the spaces or vessels of their membranous laminae, though from an observation of Carus, who states that he saw globules circulating within these laminae, its existence in that situation is not improbable.* This provision in the Echinus is probably, as in the analogous cases already described, chiefly subservient to respiration. Tiedemann, who ascribed a respiratory office to the water within the animal, expresses himself at a loss to con- ceive by what mechanism it can be made to enter and issue from a cavity with unyielding sides incapable of being expanded and con- tracted by muscular action ; perhaps the provi- sion here described may be adequate for this purpose. Since the above observations 'were made, a fact has been mentioned by Ehrenberg,! from which it appears that tire ciliary motion exists on the external surface of the Echinus on the spines. The species observed by him was the Echinus sexatilis. The observations of Carus and Ehrenberg here referred to comprehend the only facts hitherto published on the ciliary motions of the Echinus which have come under my notice. 7. Annelida. — In proceeding to describe the ciliary motion in animals of this class, in several of which it occurs, it seems advisable to begin with the Aphrodita, as the phenomena in this animal present a remarkable analogy with those we have been considering in the Eehinodermata. A great part of the body of the Aphrodita aculeata, or Sea-mouse, (of which Jig. 299, A, represents a cross section,) is occupied by the abdominal cavity, (a, a, a.) Along the superior wall of this cavity a row of cells (b ) is placed on each side, which below open into the abdo- men, but above, or exteriorly, project on the dorsal surface as oblong transverse eminences. Each alternate cell on the back bears a broad membranous scale (c, c), and each of the in- termediate ones a small indented process. On the back a covering of felt-like substance (d) is stretched from side to side like a roof over * Analecten zur "Katur-wissenscliaft, etc. Dres- den, 1829, p. 152. t Muller’s Arcbiv. Band 1, p. 578. 2 S CILIA. CIO Fig. 299. B. Alimentary canal and cosca, seen from above. the cells and scales, inclosing them in a space (e) to which the water has free access. Re- turning to the abdomen, we find the nearly straight alimentary canal, its anterior third (f, Jig. B) forming the stomach, the remaining part or intestine ( g, fig. A and B) being fur- nished on each side with a number of long cceca Hi), whose branched extremities ( i , i) are in part lodged in the before-mentioned cells. The abdomen is lined with a de- licate peritoneal membrane, which also lines the cells, and is reflected over the viscera. In the living Aphrodita the water freely enters and issues from the space (e) beneath the felty membrane, passing over the external surface of the cells and their appendages. The flow of the water in this passage is produced, as I have repeatedly observed, by the elevation and depression of the scales, and on no part of the surface over which the fluid passes is the ciliary motion to be observed. But the water also enters the cavity of the abdomen, though it is doubtful by what orifices this takes place, for my endeavours to find those de- scribed by Treviranus* in the alternate in- tervals of the feet have never been successful. In whatever way it may happen, however, there can be no doubt of the fact that the water enters the abdomen, and consequently fills the dorsal cells and surrounds the intestine and its coeca, which last organs, according to Sir Everard Home and Treviranus, exercise a respiratory function, an opinion which derives additional probability in considering the phe- nomena of the ciliary motion to be here de- scribed. The ciliary motion exists in two situations, 1st, on the external surface of the intestine and cceca and the internal surface of the cells, which surfaces are in contact with the contained water ; 2dly, within the intes- tine and cceca, or on their internal surface. The motion as usual persists for some time in de- tached parts, and the direction of the currents is constant. On the intestine the currents pass from the inferior surface round the sides to the upper part (as marked by the arrows). On the cceca the direction is outwards or towards the cells, and the motion is very distinct at their extremities. The direction on the inner surface of the cells was not completely made out, but it seemed to be chiefly downwards. Nor was the direction of the impulsion satis- factorily ascertained on the internal surface of the intestine and coeca, though of the ex- istence of the phenomenon in that situation there could be no doubt. From what has been stated, it appears then, first, that in the Aphrodita the water finds access to the outside of the cells, over which it is conveyed by the elevation and depression of the dorsal scales, and to the inside of the cells, over which, as well as over the external surface of the intestine and its coecal appen- dages, it is moved by the action of cilia. In both situations the motion of the fluid is pro- bably subservient to the respiratory function, and if it really be so, we must reckon the scales, the cells, the alimentary canal, and its appendages, as constituting the respiratory ap- paratus. Secondly, that the ciliary motion exists also on the internal surface of the in- testine and cceca, where it is likely connected both with respiration and digestion. In all this we cannot overlook the analogy which subsists between the Aphrodita and Asterias. In both the water is conveyed, though by a different mechanism, over the external surface of the body ; in both it enters the cavity con- taining the viscera ; in both it is moved along the parietes of the cavity and surface of the viscera in a determinate direction by the agency of cilia ; and, lastly, in both the ciliary motion occurs on the internal surface of the digestive organs. I first observed the ciliary motions in the Aphrodita aculeata in 1 830, at the same time with the late Mr. Cheek, who gave notice of the fact in the journal of which he was conductor ;-f- but most of the observations on * Zeitschrift fur Physiologie, Band iii. p. 158. f Edin. Jour, of Nat. and Geog. Science, April, 1831, p. 246. CILIA. 019 which the preceding account is founded, were made more recently. There is no mention of the existence of the phenomenon in the Aphro- dita to be found in systematic works on com- parative anatomy, nor in any of the special memoirs on that animal which I have had an opportunity of consulting. The ciliary motion exists in several other animals belonging to the class Annelida. It is remarkably distinct, and easily observed, on the branchiae or gills of the Serpula. These organs consist of two bunches of pinnated or feather-like processes, which the animal pushes forth from the calcareous tube in which it lives, and spreads out in a radiating form. The edges of the branchiae, both of the stems and of the leaflets, are fringed with cilia, which exhibit their vibrating and undulating motions, and cause a constant current of water over the surface of the gills, serving here, no doubt, as in analogous instances, at least chiefly for respiration. In a paper already referred to,* I mentioned having observed the phenomena in question in the Amphitrite. The animal meant was a com- mon marine tubicolar worm (fig- 300), which Fig. 300. Amphitrite alveolata. A. Dorsal surface, natural size. B. Part before a, b, magnified. C. A gill magnified. D. One still more magnified, to show the spiral ridges and cilia. appeared to be the same with that figured by Ellis (Corall. plate 36), and described by Cuvier as the Amphitrite a ruche, with which figure it agrees, except that it bears two rows of simple filaments on the back, which, for reasons that will appear, I was led to regard as gills. But if these are really gills, the animal must, it seems, be arranged with the Dorsibrauchiata, probably as a Sabella. The currents in this worm proceed forwards along the back, be- tween the rows of gills (as marked in fig. B), and along the gills themselves (see C), whose points are directed forwards. The conical fila- ment of which each gill consists is marked on one side by ridges (see C, D), crossing it obliquely like segments of a spiral; and on these ridges as well as on the point of the gill the most conspicuous cilia are placed. The cilia are comparatively large and curved, their points being turned towards the summit of the gill, which figure they retain when their motion is stopped. The gills contain large Edin. Med. and Sur. Jour. vol. xxxiv. bloodvessels, which when distended give them a bright red colour. The ciliary motion occurs also on what seem to be the branchiae of another tubicolar worm, the name of which is unknown to me; the organs in question are placed at the anterior extremity of the animal, concealed by a pro- fusion of long serpentine tentacula. Lastly, Mr. Cheek* observed the ciliary motion in the Sandworm ( Arenicola piscato- rum ). It was seen on the inner surface of the internal vesicles, which Sir Everard Home de- scribes as livers. Nothing similar exists on the tufts of filaments which form the gills.f 8. Mullusca. — The ciliary motion prevails very extensively in this division of the animal kingdom. It seems to exist generally in the Gasteropodous and Acephalous Mollusca. There is some uncertainty as to its existence in the Cephalopoda; I have repeatedly sought for it in that class, hut without success. It occurs on the surface of the respiratory organs, and often on other surfaces over which the water has to pass in the act of respiration. It also exists within the alimentary canal, at least this has been ascertained in several spe- cies of Gasteropoda and Acephala, and may be presumed of the rest. Moreover, in some of the Gasteropoda, it is very manifest on the horns or feelers, which suggests the possibility of its aiding in these instances in the exercise of the sense of touch or smelling. In all cases the impulsion maintains a determinate direction, which continues the same in parts detached from the animal. In salt-water spe- cies, the action of the cilia and impulsion of the fluid, are instantly stopped by putting the parts into fresh water. The ciliary motion also occurs in the embryo of the Mollusca within the egg, which pheno- menon will be considered in the next section. A. Gasteropodous Mollusca. — Of this class the phenomena have been observed by myself and others in the orders of Nudibranchiuta, Cyclobranchiata, Pectinibranchiata, and the aquatic P ulmonifera, in one or more species of each. a. Nudibranchiuta. — In this order, in which the gills are entirely exposed, the currents can he very easily observed. The Doris, a species of which is represented in the adjoining figure (301), may serve as an example. The arbo- rescent gills («, a ) are ranged in a circle round the anus, and their stems and branches are covered with cilia. Currents pass over their surface, the general direction being towards the points ; small portions detached still ex- cite currents in the same direction, and, if free, move through the water in the opposite one. I have examined three species of Doris, and * Edin. Journ. of Nat. and Geog. Science, April, 1831, p. 245. t The ciliary motion has also been observed in Planariae, on the surface of the body, by Gruit- huisen, (Salzb. Med. Chir. Zeit. 1818, vol. iv.) and by Purkinje and Valentin Gruithuisen also discovered it in the Nais proboscidea, in the pos- terior part of the intestine, (Nov. Act. Acad. Ca»s. Leop. xi. p. 238.) 2 S 2 (ito CILIA. Fig. 301. in one of them, the D. cornuta, the ciliary motion was very strong on the club-shaped feelers; perhaps it may be the same in all. I also examined the Tritonia and Eolis belong- ing to this order, and found the ciliary motion in corresponding parts. b. Cyclobrunchiata. — In the Patella or Limpet (fig. 302, representing the under surface), the gills form a series of simple Fig. 302. A B. Portion inclosed between the lines c and d, magnified to show a, a, the branchial la- minae, and b, b, the circular border of the mantle. laminae (a, a) attached within the circular* border of the mantle ( b , b ). The currents pass inwards from the edge of the mantle to the gills, then over the surface and along the border of each branchial lamina, from its outer or lower to its inner or upper edge, as indicated in the figure by the arrows. In the Limpet the ciliary motion is also found on the inner surface of the alimentary canal. In the Chiton or Oscabrion (fig. 303), the only other genus of this order, the gills are situated as in the Limpet, but are of a more complex structure. Each consists (at least in the species examined by me) of a triangular lamina, with a series of smaller laminae set on each side of it, Fig. 303. diminishing in size as they approach its point. The currents on each of the gills are directed towards its apex, and also pass between the secondary laminae over their surface and along their edges : a, a, are the gills ; b one of the gills magnified, showing its laminae ; c the same viewed endwise. The arrows mark the direction of the currents. c. Pectinibranchiata. — The common Buc- cinum (fig. 304) may serve as an example of Fig. 304. this order. The gills, as accurately described by Cuvier, are attached to the roof of a bran- chial cavity or recess formed between the man- tle (a, a) and upper part of the body (6) in the last turn of the shell, and opening anteriorly by a broad slit. At the left end of the slit the edge of the mantle is prolonged in the form of a groove (c), which prolongation is called the syphon, and is lodged in a corresponding groove of the shell. On detaching the roof of the branchial cavity at the left side, and reflecting it (as represented in the figure), we find attached to it, first, the gills, consisting of a short double row ( d ) and a longer single row (e) of laminae, the latter being larger ; secondly, to the right of the gills, the so-named mucous laminae (ff); thirdly, still more to the right, the rectum ( g ). The water enters by the syphon, and issues at the right extremity of the branchial slit. The ciliary motion and currents take place on the gills, mucous laminae, and rectum, and on CILIA. 621 the inner surface of the mantle, where it forms the roof of the branchial cavity. Their situ- ation and direction are indicated in the figures by the arrows. B is an enlarged view of a few laminae from the larger series, h the at- tached border, i point, m left, and n right border. Currents pass between these laminae along the surface and border of each, as shewn in B ; C is a magnified view of the laminae of the smaller set, on which the di- rection of the currents is marked ; the direc- tion on other parts will be understood by re- ferring to figure A. The ciliary motion is very manifest within the alimentary canal, in the gullet, stomach, and intestine; the direction of impulsion is from the mouth towards the anus. The ciliary motion has been observed by myself and others in the Paludina vivipara, a fresh-water snail belonging to this order, Fig. 305. A m m g Mytilus Edulis. F. Portion of a bar of the gill, with the cilia, highly magnified. in which also Purkinje and Valentin state that they observed it within the alimentary canal ; and Gruithuisen* has described the phenomenon as seen on the branchiffi of another fresh-water snail, which he names Valvata branchiata. He saw moving cilia, which caused an incessant agitation in the water ; but he does not state whether the motion followed any constant direc- tion, although we may infer that this was the case. He rightly attributed to these motions a respiratory function, but seems not to have observed that similar pheno- mena existed in other Mollusca. d. Pulmonifera. The ciliary motion is not confined to those Mollusca which breathe by gills, for it occurs also in the Lymnaea and Planorbis, which, though they live in water, breathe air by a pul- monary sac. In these instances the impulsion of the water takes place on the surface of the tentacula, which is covered with cilia. If these parts are to be regarded as organs of sensation alone, the ciliary motion observed upon them, as well as that which occurs on the tentacula of bran- chiferous species, must be considered as connected with the function of sensation; but the tentacula, which in the Lymnaea are broad vascular laminae, might be conceived also to perform the office of accessory organs of respiration, in which case the pulmoniferous Mollusca here mentioned would possess organs both of aerial and aquatic respiration. In the Lymnaea the motion has also been observed by Purkinje and Valentin within the alimentary canal. B. Conchiferous AcephrJa. — The motion in question has been found in several bivalve Mollusca, both of salt and fresh water, and there can be little doubt that it exists in all. The common Sea-mussel (Jig. 305) will serve as an example of the class. It will be recollected that the gills of this animal ( fig . A, c, c', d,) have the form of * Nova Acta Acad. Caes. Leop. x. p. 437. 622 CILIA. leaves, there being two on each side inclosed between the lobes of the mantle ( a, a, a, a"). Between the gills are interposed what is called the foot (f) and the prominent part of the abdomen, which separates the two of the right side from those of the left. Each gill or leaf consists of two layers, which are made up of vessels set very close to one another (Jig. D,) like the teeth of a comb, or like parallel bars, across the direction of the gill, and perpendicular to the great vascular trunks running along its base, with which they communicate. The two layers composing each gill are connected together at its edge, and by a few points of their contiguous surfaces. At the base only one layer is fixed, the other ter- minating at this part by a thick unattached border (e, e), under which a probe may be passed into the interior space between the two layers. This is further explained by Jig. B, which represents a section of the two gills of one side cut parallel to the bars. The layers (e c, fc,) are united at the edge of the gill (c), but separated at the base, the one being fixed at f, the other ending by a free margin, e. g, g, is the space between the layers ; it com- municates with the excretory orifice (h,Jig. A). Fig. C shews the upper part of the gill, (c, fig • B,) viewed similarly, but magnified eighteen diameters. Two bars, (e c, f c,) be- longing to opposite layers, are seen ; they are shaped somewhat like the blade of a knife, with a thick round external border (e), and a thin internal edge (A) opposed to the corres- ponding one of the other layer, with which it is connected at a few places by cross slips, i, i, Jig. C, and k, k, Jig. B, where they are longer, the space at this part being wider. Fig. D is a small portion of one of the layers, (t, t, Jig. A,) magnified eighteen diameters. The bars are connected laterally with the adja- cent ones of the same layer at short intervals, by round projections on their sides, (a, a, a, a, in Jigs. D, C, and E,) in which last they are still more magnified. Each of these projec- tions adheres but slightly to the corresponding one of the collateral bar, and its surface is covered with small filaments resembling the cilia in the other parts, only their motion is very slow. Besides the gills, the mussel has four triangular laminae (in, m, n, Jig. A,) placed round the mouth, which probably serve for respiration ; they have been named labial ap- pendages, tentacula, or accessory gills. When a live mussel is placed in a vessel of salt water, it is soon observed to open slightly the two valves of its shell, and at the same time a commotion is evident in the water in its vicinity . This is occasioned by the water en- tering at the posterior or large end of the animal into the space between the lobes of the mantle in which the gills are lodged, and issuing near the same place by a separate orifice in a continued stream, as represented by the arrows, (g and h. Jig. A), g being the entering and h the issuing stream. The existence of this con- tinuous current is well known, but the agency by which the water is set in motion appears not to have been, at least generally, understood. It can readily be shewn that here, as in the in- stances already described, the water receives its impulse from the ciliated surface of the gills and other parts over which it passes, and that it is carried along these surfaces in a determi- nate direction. The whole surface of the gills and labial appendages or accessory gills, the inner surface of the cloak, and the surface of some other parts produce this effect, and the combined action of the cilia over this extensive surface gives rise to the main current which enters and issues from the animal. On removing one of the valves, turning down the cloak, as represented at. o, and putting moistened charcoal powder on the surface of the gills, the finer part of the powder soon dis- appears, having penetrated through the inter- stices of the bars or vessels into the space between the two layers of the gill. On arriving there a part is often forced out again from under the border of the unattached layer at the base of the gill, but most of it is conveyed rapidly backwards between the two layers, and is carried out at the excretory orifice with the general current, its course being indicated by the dotted arrows in the figure. The coarser particles remain outside the gill, and are slowly carried to its edge, following the direction of the bars ; they then advance along the edge of the gill towards the forepart of the animal, as shewn by the entire arrows. It thus appears that the water first passes in between the lobes of the mantle to the external surface o. the gills ; it is then forced into the space inclosed between their layers, from whence it is driven out at the excretory orifice, to which the inclosed spaces of all the gills lead. As this process continues to go on after the shell and lobe of the mantle of one side are removed, it is evident that the motion of the water must be mainly produced by the cilia of the gills, to be immediately described. By their agency the fluid is forced into the space within the gills, and this operation taking place over the whole extent of the gills, must, by its concentrated effect, give rise to a powerful issuing stream at the excretory orifice, of which the entering stream seems to be a necessary result. The cilia are found on the gills, the acces- sory gills, the inside of the mantle, and the foot. Only those on the gills require particular notice. Most of them are arranged along the sides of the vessels or bars (a, a, Jig. F), com- posing the gills, in two sets, one nearer the surface consisting of longer and more opaque cilia, (6, b,) the other close to the first, but a little deeper, and consisting of somewhat shorter and nearly transparent cilia, (c, c.) Both sets are in constant motion, but of this it is difficult to convey a correct idea by description. The more opaque cilia, or those of the exterior range, appear and disappear by turns, as if they were continually changing from a horizontal to a vertical* direction and back again. The * By vertical is here meant a direction perpendi- cular to the plane of the gills, which direction is vertical when the gills are spread out under the microscope. CILIA. 623 motion of the other set consists in a succession of undulations, which proceed in a uniform manner along the sides of the bar from one end to the other. It might be very easily mistaken for the circulation of globules of a fluid within a canal, more especially as the course of the undulations is different on the two sides of the bar, being directed on one side towards the edge of the gill, and on the other towards the base. But besides that the undulations continue for some time in small pieces cut off from the gill, which is incon- sistent with the progression of fluid in a canal, the cilia are easily distinguished when the un- dulatory motion becomes languid. When it has entirely ceased, they remain in contact with each other, so as to present the appearance of a membrane, ( d , d, jig. F.) Besides the two rows of cilia just described on each side of the bars, others are placed in a less regular manner on their external and internal borders. The in- ternal (A, jig. C) are exceedingly small ; they extend upon the cross slips, ( i,Jig . C). Those on the external borders are very numerous and thick-set, and of considerable size, especially on the extremity of the bar at the edge of the gill (c, Jig. C) ; their points are directed to- wards the edge of the gill. It is probably by the agency of these last-mentioned cilia that the particles of food or other foreign matter are conveyed along the surface of the gill to its edge, and then onwards to the mouth, while the others may serve principally to force the water through the interstices of the bars into the space inclosed between the layers, and from thence out at the excretory orifice. As in other instances, detached portions of the ciliated parts excite currents in the same direction as before their separation, or swim through the water in the opposite direction. It is very remarkable that when the parts are immersed in fresh water, the currents and mo- tion of the cilia are almost instantaneously stopped. The ciliary motion is equally apparent on the respiratory organs of the Oyster, River-mus- sel, and other bivalve Mollusca which have been submitted to examination. Purkinje and Valentin pointed out its existence also in the alimentary canal of the River-mussel, which observation I have confirmed, and I have found the same to be true of the Sea-mussel. The impulsion appeared to me in both instances to be chiefly directed onwards, that is, towards the anus. c. Tunicata (Ascidie ). — In the paper pre- viously referred to, I stated that I had not been able to perceive the ciliary motion in the Ascidia, but added that the observation seemed inconclu- sive, as the specimens examined had been some time out of the water. Since then I have seen the phenomena as distinctly in the Ascidiae as in other Mollusca. The observations were made on a common species found adhering to rocks in the Frith of Forth at low water-mark, and as far as they go they agree with those lately made by Mr. Lister,* on a small aggregated * Phil. Trans. 1834, p. 378. species, the substance of which being nearly transparent enabled him to trace the currents more completely. For this reason it seems preferable to borrow his description. The annexed figures (A and B) represent Fig. 306. one of these Ascidia; on its peduncle, with the opening of the mouth (g) and the funnel {J'') in front. The outer covering is a tough coat («), lined internally with a soft sub- stance or mantle (b). A great part of the interior is occupied with the branchial sac (c), whose cavity terminates upwards at the oral opening, and is closed at the bottom. It is united to the enve- lope or to the mantle above and behind ; the juncture (e, e,) beginning in front of the oral open- ing, extends backwards on each side of it, and then downwards along the middle of the back ( a , Jig. A.) A vacant space ( f,f- ,) is left between the sac and mantle at the sides and front, which ends in the opening of the funnel. The sac opens infe- riorly into the (Esophagus (/i), which leads to the stomach (j), the intestine passing forwards and opening by the vent (k) into the funnel. On its sides and front the branchial sac is per- forated by four rows of narrow vertical slits or spiracles (m, m), and through these the water, which flows constantly in at the mouth when its orifice is open, appears to be conveyed to the vacant space (/') between the sac and mantle, and it then escapes at the funnel. The sac seems extremely thin between the spiracles, but their edges are thickened, and they are lined with closely set cilia, which, by their motion, cause the current of water. When they are in full activity, the effect upon the eye is that of delicately toothed oval wheels, re- volving continually in a direction ascending on 624 CILIA. the right and descending on the left of each oval, as viewed from without ; but the cilia them- selves are very much closer than the apparent teeth, and the illusion seems to be caused by a fanning motion given to them in regular and quick succession, which will produce the ap- pearance of waves, and each wave answers here to a tooth. Whatever little substances alive or inanimate the current of water brings, if not ejected as unsuitable, lodge somewhere on the surface of the branchial sac, along which each particle travels horizontally with a steady slow course to the front of the cavity, where it reaches a downward stream of similar materials (li); and they proceed together, receiving accessions from both sides, and enter at last, at the bottom, the oesophagus (h); this is a small flattened tube which carries them, without any effort of swallowing, towards the stomach. Mr. Lister observed similar phenomena in a species of Polyclinum, another form of com- pound Ascidia, in which an excretory funnel is common to several individuals. Mr. Lister, p. 385, has adverted to the resemblance be- tween the Ascidiae and a zoophyte of a similar form to that here described at page 610. I may here point out an analogy on the other side, no less striking, between the Ascidise and bivalve Mollusca, in regard to the phenomena now under consideration. In both cases the water enters at one opening, and meeting with the surface of the membranous gills, passes through slits or interstices between their vessels into a space on the other side of the gill, which space terminates at another external opening, by which the water issues. In both cases also the mar- gins of the slits in the gills are fringed with cilia which exhibit a waving motion, the waves proceeding in opposite directions on the two borders of the slit. Lastly, in both cases, while the water and finer particles of matter floating in it pass through the slits, the coarser matters are conveyed along the first surface of the gills towards the mouth. The difference lies chiefly in the nature and form of the ex- ternal covering and the form of the gills in each; the membranous gills in the mussel being folded into double leaves on each side, and in the Ascidia being formed into a tubular sac ; the space between the laminse of each leaf in the mussel corresponding with the space (f) enclosed between the branchial sac and mantle in the Ascidia, both these spaces leading to the excretory orifice. The remarkable appearances in the Mollusca described above could not wholly escape the notice of naturalists and microscopic observers. Thus we find Ant.de Heide,* a Dutch physician of the end of the seventeenth century, observing the appearance produced by the ciliary motion in the Sea-mussel; he names it “ motus radio- sus,” or “ tremulus.” He found it in most parts of the animal, but in none more evident than the gills (cirri pectinati), in which it is most easily examined. “ I call the motion radiant,” says he, “ because it proceeds from the whole sur- 1 Anat, Mytuli, &c. !2mo. Amst. 1684 face of the cirrus (gill) almost in the same way as air-bubbles issue from crabstones or metals while undergoing solution ; it may be called tremulous, because the parts affected by it vibrate. This motion goes on not only in the entire gill connected with the rest of the mussel, but even in the smallest pieces cut off from it, which by their radiant motion swim briskly through the sea-water.” Leeuwenhoek likewise appears, from various passages in his writings,* to have perceived the moving cilia in the Oyster and Mussel; he noticed also the existence of the motion in detached portions. His observations, so far as they go, are correct; but he takes no notice of the currents in the water ; nor does he seem to have perceived the relation of the phenomenon to the respiratory or other functions, or indeed to have formed any opinion regarding its phy- siological use. Baker alludes to Leeuwenhoek’s discoveries, and relates an appearance observed by himself in the Fresh-water Mussel, which must have been caused by the ciliary motion.f He states that “ on snipping off a piece of the transpa- rent membrane (gill), and viewing it with the microscope, the blood will be seen passing through numbers of veins and arteries, and if the extremity of the membrane be viewed, the true circulation or the return of the blood from the arteries through the veins will be shewn.” Dr. Hales, in his Statical Essays, (vol. ii. p. 93,) plainly alludes to the same phenomena. Among more recent writers, Professor Ehrman of Berlin, in a memoir on the blood of the Mollusca, published in the Transactions of the Royal Academy of Sciences of Berlin for 1816-17, l has described an appearance no- ticed by him in Mya, Anodonta, the Oyster, and other Bivalves, which seems evidently to have been produced by the ciliary motion. He states that on viewing the inner side of the labial appendages, accessory gills, or tentacula of these Mollusca, while it was illuminated by a strong light falling in a particular direction, he perceived a very rapid and incessant motion along the transverse stripes or furrows obser- vable on the surface of the part. The motion proceeded along each stripe like a series of oscillations. It continued for some time in portions cut off from the organ. He next ob- served that a number of round vesicular bodies escaped from the furrows or stripes at the part where they were cut, which bodies moved to and fro and as it were spontaneously in the water; and it seemed to him that in proportion as these bodies escaped, the oscillatory motion relaxed in intensity. From these facts he con- cluded that the motion apparent on the surface of the part was produced by the agitation of these vesicles or animated molecules within the furrows ; that is, he supposed the furrows to be covered by a membrane to which an * Epist. 83, in Opp. i. p. 463 , 482. Anat. et Contemp. p. 52 in Opp. ii. Ibid. p. 27. Contin. Arcan. p. 17 in Opp. ii. f Of Microscopes, &c, vol. i p. 128. t P. 214, seq. CILIA. oscillatory motion was communicated by the agitation of the globules underneath it. lie perceived the motion in question in no part but the labial appendages, and he imagined it to be connected with the male generative func- tion, of which he therefore conceived the parts mentioned to be the organs. It is obvious that the appearance seen by E'nrman was the undu- lating motion of the cilia, which organs, how- ever, he had not recognised. He makes no mention of currents, and consequently could not perceive the connexion of the phenomenon with respiration, which was also less likely to occur to him, as he supposed the motion to be confined to the appendages mentioned. The observations of Ehrman led Treviranus to investigate the subject;* and he distin- guished two different motions, the one a mus- cular contraction, the other the peculiar motion alluded to by Ehrman. The latter motion had the appearance of a trembling or flickering of innumerable points, and seemed at some places as if produced by a moving fluid, and at others by the agitation of oblong vibrating organs. It was peculiarly distinct alongside each of the bars of the gills and appendages. He farther perceived that the agitation on the surface of these parts caused an eddying mo- tion in the water in which they lay, and also set in motion globules of blood which had escaped from the vessels. On breaking down the parts into small fragments, he found that each retained its power of motion, by which they moved in most manifold directions, the larger masses at the same time contracting and dilating themselves. From these observations Treviranus concludes that the bivalve Mollusca afford an example of a structure in which the integrant parts possess an independent vitality. Their independent vitality shews itself in the persistence of their automatic motion after solution of organic connexion with each other, and this motion is intermediate in its nature between the spontaneous movements of organic molecules in infusions, the male semen, &c. and the motion of muscular parts, which re- quires the integrity of the texture and the application of a stimulus. These reflections on the relation of the phenomenon to the general laws of organization are the sole infe- rences which he draws from his observations. He notices the motion of the water only as a concomitant and subordinate circumstance, not having been aware of its determinate direction, its relation to the respiratory process, or, in short, of its being the chief end and effect of the motion of the cilia. The next researches on the subject are those of Iluschke, narrated in a paper in the Isis for 1826-t Not having seen the original, we must content ourselves with a brief notice of them to be found in Burdach’s Physiologie-I It is there stated that on detaching a portion of the gill of the Fresh-water Mussel ( Unio pictorum), Huschke found that the water “ moved up- * Vermischte Schriften, Band iii. p. 234. + P.623. j Band iv. p. 434. 625 wards on one side, and then in an eddying manner back again.” Raspail, in a memoir on a species of fresh- water polype, published in 1828,* pointed out the analogy between the phenomena exhibited by the gills of Mollusca and those observed in infusory animalcules and polypi. Ciliary currents were now described by vari- ous other writers of eminence, but their causes were very commonly mistaken : among the number may be quoted Poli,f Delle Chiaje,J Carus,§ De Blainville,|| and Unger.^f Having observed currents produced in other instances by an impelling power inherent in the surfaces over which the fluid passed, I was myself led to suspect that the respiratory cur- rent in bivalve Mollusca was of the same kind, or that it was caused by an impulsion commu- nicated to the water by the surface of the gills and other parts over which it was conveyed in its passage, without being aware of any similar view having been entertained by others. I then observed the determinate direction of the impulsion along the surface, together with the arrangement and action of the cilia. These observations were published at the time (1830) in a paper already mentioned,** in which also the respiratory currents of the bivalve Mollusca are considered as a particular example of a more generally prevailing phenomenon. In a paper on the circulation of the blood, in Magendie’s Journal for 1831, ff there are some remarks pertaining to the present subject, from which it appears that the author, M. Guillot, had observed the ciliary motion of the gills of the Sea-mussel and Oyster. He has, however, like Baker, mistaken the regular un- dulations of the cilia for the circulation of a fluid within vessels. He takes no notice of any motion or current excited in the water. Carus, II in a memoir on the development of the River-mussel, states that he observed an undulatory or oscillatory motion of the gills, and that by this motion, which he conceives to be in the substance of the gill, the water is propelled, and the general respiratory current through the branchial cavity produced. It is obvious that what he calls an oscillation of the substance of the gill, and which he erroneously supposes has previously escaped attention, is merely the undulatory motion of the cilia. The last researches on this subject which we have to notice are those of Purkinje and Va- lentin^ As above stated, they discovered the ciliary motion in the alimentary canal of the Mollusca, having found it in the Lymnaea, Pa- ludina, and the Fresh-water mussel. * Memoires de la Soc. d’Hist. Nat. de Paris, tome iv. p. 131, seq. Chimie Organique, 1833^ p. 246. f Testacea utriusque Sieiliae, t. i. 51. t Istituz. di Notom. e Fisiolog. comp. t. i. p. 278. ^Lehrbuch der Zootomie. || Malacologie, 157. il Uber die Teichmuschel, p. 10. ** Edin. Med. and Surg. Journal, vol. xxxiv. ft Tom. xi. p. 182. tt Nova Acta Acad. Caes. Leop. xvi. p. 58, seq, §§ Loc. cit. 626 CILIA. Such is an outline of the observations hitherto made relative to the ciliary motion in the bivalve Mollusca. We may now shortly con- sider those which refer to the other classes of these animals. Dr. Fleming,* ** in describing the cilia in some species of Polypi, states that “ analo- gous hairs” exist on the branchiae of the Tri- tonia, which may probably be considered as forming part of the aerating organs. He also mentions, in another place, f that these branchia: “ readily fall off, and, as if indepen- dent, are capable of swimming about for a short time in the water, by means of minute hairs with which their surface is covered, and which move rapidly, pushing forwards the distal extremity.” Gruithuisen, as formerly mentioned, observed the ciliary motion, and recognised its true nature in the Valvata bran- chiata, a species of fresh-water snail. Also Ilaspail,J having seen the phenomena pro- duced by the gills of the Fresh-water Mussel, was led by analogy to discover the same in the Lymnsea and Paludina. Without being aware of these previous researches, I observed the ciliary motion in several different tribes of marine Mollusca, and shewed that it prevailed extensively among Mollusca generally. Mr. Lister, as has been already stated, has subse- quently discovered that it exists in the Ascidia; and since then I have also found it in that animal, though in a different species. 9. Of the ciliary motion of the embryo of Mollusca. — The embryo of Mollusca exhibits, while withiu the egg, a peculiar rotatory mo- tion which belongs to the class of phenomena we are here considering, and is referable to the same cause. This motion has been observed in the Gasteropodous and Bivalve Mollusca, and may perhaps be found in others. Gasteropoda. — Swammerdam§ states that in examining the young of the viviparous water- snail, while they were yet inclosed in the mem- branes of the ovum, he observed the embryo turning round in the contained fluid with con- siderable rapidity, and, he adds, “ in a very elegant manner.” He again mentions the fact in another place. || Baker observed the same appearance in the ova of a fresh-water snail, which appears to have been the common Lym- naea. He says,1I “ when the eggs are about a week old, the embryo snail may be discerned in its true shape, turning itself very frequently within the fine fluid in which it lies.” These brief notices of this remarkable fact by Swam- merdam and Baker seem to have failed to ex- cite the curiosity of succeeding naturalists, for there would appear to be no account of any subsequent researches on the subject till those of St.iebel published in 1815,*'* who seems not * Mem. of Wern. Soc. of Edin. iv. p. 488. t Philosophy of Zoology, v. ii. p. 470. 1 Loc. cit. $ Biblia Naturae, p. 142. || Op. cit. p. 179. ’ll Of Microscopes, &c. vol. ii. p. 325, 329. ** Diss. sist. Lymnaei stagnalis anatomen, Goet- ting, 1815, and Meckel’s Deutsches Archiv fur die Physiologic, Bd. i. p. 424. Bd. ii. p. 557. to have been aware that the fact had been pre- viously noticed. Stiebel’s observations were made on the ova of the Lymnseus stagnalis. They were followed by those of Hugi* in 1823, and Carus in 1824, f on the same species, to which Carus afterwards}' (in 1827) added cor- responding observations on the Paludina vivi- para. About the same time (1827) Dr. Grant extended the inquiry to salt-water Gasteropoda, both naked and testaceous, and, as far as I know, was the first to point out the cilia, which are very conspicuous in salt-water species, as the agents which cause the rotation. The eggs of the Lymnseus (or Lyirmaea) are deposited in clusters, being imbedded in oblong masses of gelatinous matter that are found ad- hering to stones or water-plants. Each egg consists of an oval pellucid membrane, con- taining within it the yolk surrounded by a con- siderable quantity of limpid fluid. The yolk is at first round, without any obvious distinc- tion of parts, but in the progress of develop- ment it changes its figure, and is gradually converted into the embryo, of which the shell and several principal organs can soon be dis- tinguished. From the descriptions of the au- thors above mentioned, as well as from some observations made by myself, it appears that the embryo is at first motionless, but that as soon as the distinction can be perceived be- tween the anterior or cephalic extremity and the rest of the animal, its rotatory motion com- mences. This invariably goes on in the man- ner indicated by the larger arrows (c, c) in the annexed figure, the head or anterior extremity Fig. 307. a continually receding. After a time the rota- tion is combined with a progressive motion, by which the embryo, while turning on its axis, moves onwards at the same time along the inside of the egg, performing a circuit like a planet in its orbit. The path described by a point on the surface is indicated by the spiral line in the figure. Stiebel, as well as the earlier observers men- tioned, is silent as to the cause of this curious phenomenon. Carus§ at first denominated it a primitive or cosmic motion, without clearly * Isis, 1823, p. 213. t Von den aiissern Lebensbedingungen der weiss-und kaltblutigen Thiere. Leipz. 1824. j: Nova Acta Acad. Caes. Leop. vol. xiix. p. 763. § Von den aiiss. Lebensb, p. 59. CILIA. 627 explaining what he meant by the term. Having subsequently discovered that a current existed in the fluid in an opposite direction to that followed by the embryo, he ascribed the mo- tion to an attraction and repulsion exerted by the substance of the embryo on the surround- ing fluid,* more especially at the region of the body -where the respiratory organ was afterwards to be developed, and justly conceived that the chief purpose served by it was to renew the water on the respiring surface of the embryo. The attraction and repulsion again he supposed to be produced by an oscillatory motion which he perceived on the surface of the embryo. This oscillatory motion, although he describes it as taking place in the substance of the animal, seems to be nothing else than the usual undu- latory play of moving cilia, such as has been already described in other instances, — indeed he himself compares it to the undulation on the arms of polypi. I have distinctly perceived the cilia, though they are very small, in the embryo of the small species of Lymnaea com- mon in this country. It is the one represented in the figure, but considerably magnified. The current takes place along the whole of the sur- face indicated by the small arrows, which also mark its direction, being opposite to that in which the embryo moves. The cilia, though they probably exist over all this surface, were distinctly seen only on the part inclosed be- tween the dotted lines at a; it required a dou- blet of one-thirty-fifth of an inch focus to make them visible. Appearances similar to those described were discovered by Dr. Grant in the ova of Marine Gasteropoda. In examining the embryos of the Buccinum undatum and Purpura lapillus, which are inclosed in groups within transparent sacs, he was struck with a rapid and incessant motion of the fluid in the sac towards the fore part of the embryo, and he observed that this motion was produced by cilia placed around two funnel-shaped projections on the fore part of the young animal, which form the borders of a cavity in which he perceived a constant revolution of floating particles. He also ob- served these circles of cilia in the young of other testaceous Mollusca, as the Trochus, Nerita, &c. in which the embryo was seen re- volving round its axis. He met with the same appearance in the naked Gasteropoda, as the Doris, Eolis, &c. The embryo of these re- volves round its centre, and swims rapidly forward by means of its cilia, when it escapes from the ovum. My own observations on the ova of the Buccinum agree generally with those of Dr. Grant. The larger cilia are placed round the prominent border of a cavity on the fore part of the body, but the surface of the foot and other neighbouring parts is also ciliated, though the cilia are there much smaller. Dr. Grant assigns various uses to these motions ; it seems not to have occurred to him that they were connected with respiration, although there can be little doubt that they are principally subservient to that function. Acephala. — The rotation of the embryo of bivalves was discovered by Leeuwenhoek, and described by him in one of his epistles, dated October, 1695.* On examining the ova of a species of Fresh-water Mussel with the micro- scope, he observed the embryo turning slowly round within the egg, like a sphere revolving on its axis. This was at a time when the shell could be distinctly perceived on the young mussel ; he had failed in discovering the phe- nomenon in some ova of the same species which he had examined at an earlier period of advancement.)- He adds, that he was so much delighted with the spectacle of the young Mus- sels turning round within the egg, that he spent two hours along with his daughter and his draughtsman in contemplating it. Baster,J who wrote in 1762, seems to have observed an appearance of the same kind in the ova of the Oyster, if we may judge from a reference by Cavolini, for I have not been able to consult the original. More recently (1827) Sir E. Llome and M. Bauer § perceived the motion in the embryo of the Fresh- water Mussel, as de- scribed by Leeuwenhoek, but erroneously attri- buted it to a small worm which pierces the egg and preys on the young mussel, and which, according to their view, by dragging on it pulls it round in the manner described. Lastly, Carus subjected the phenomenon to a more careful investigation, in the course of his re- searches on the development of the River Mus- sel.|| According to his observations the em- bryo, at the time the motion becomes percepti- ble, has acquired a flattened triangular shape (fig- 308), the two halves of the shell cover its two surfaces, and are united together by the hinge at the base of the triangle. When the ovum is placed under the microscope, the embryo is seen moving round in a ho- rizontal direction, as indica- ted by the larger arrows, ap- pearing as if it turned on the centre of the lowermost shell. When the embryo is extract- ed from the egg, a current is perceived in the water opposite that part where the current en- ters and issues in the adult animal, (as shown by the small arrow,) and Carus therefore attri- butes its rotatory motion to an attraction and repulsion exerted on the water by that part of the embryo, which is afterwards to form the respiratory organ. The attraction and re- pulsion of the water he supposes to be pro- duced by an oscillatory motion observable in the substance of the animal at its surface, as in the embryo of the snail, which motion, as we have already seen, is in reality an undulatory movement of minute cilia. As in the snail also, he conceives the phenomenon to be con- nected with respiration. For an account of his * Ep. 95. Corn. Arc. Nat. 1697, p. 26, 27, in Op. tom. ii. t Ibid. p. 20. ^ Opuscula Subseciva, tom. ii. p. 146. $ Phil. Trans. 1827, p. 39. || Nov. Acta, xvi. p. 27, sqq. Fig. 308. Embryo of 3IusseL Nova Acta, xiii. p. 771, 628 CILIA. observations on the velocity and direction of the motion, and its supposed influence in de- termining the figure of the animal, l must refer to the paper itself. The analogy of these motions of the embryo of the Mollusca with the phenomena exhibited by the ova of Infusoria, Polypi, Sponges, and Actinia:, already described, scarcely requires to be pointed out. We shall afterwards see that it extends to the ova of Batrachian Reptiles.* 1 1 . Phenomena of the ciliary motion in the. Vertebrata. — The ciliary motion exists very ex- tensively in vertebrated animals. Until lately it had been found only in the larvae of Batra- chian Reptiles, but Purkinje and Valentinf have recently made the important discovery that it exists also in adult Reptiles, Birds, and Mammiferous animals ; and it seems to prevail generally throughout the three classes, having been found by these naturalists in all the nume- rous examples of each class examined by them in the course of their investigations. It has not been found in Fishes, though many species have been submitted to examination. % The parts of the body which exhibit the ciliary motion in the Vertebrata are, the lining membrane of the respiratory organs, and that of the generative organs in the female. Besides this general situation, it is found on the external gills and surface of the body in the larvae of Batrachia, and on the surface of the embryo of these reptiles while contained within the ovum. A. Reptiles. — The ciliary motion has been discovered in all the orders of Reptiles. It has been found in every species submitted to ex- amination, and is therefore presumed to exist in all. Batrachian Reptiles. 1st. Larva and ova. — The Batrachian Reptiles, while in the foetal or larva state, breathe by means of gills or branchiae, and it was on the gills of the young Salamanderand Frogthat the phenomenon under consideration was first discovered as existing in vertebrated animals. The gills of the young Salamander might in appearance be compared to feathers or pinnated leaves ; there are three on either side, each consisting of a main stem bearing two rows of simple leaflets ; they are * In the preceding account of the ciliary motions in the Invertebrata no mention has been made of their existence in the class Crustacea : I think it necessary to state that I have examined this class, but without success ; and since these pages have been put into the printer’s hands I have re-exa- mined the crab and lobster with the greatest care; all the respiratory and alimentary surfaces, the inner surface of bloodvessels, &c. with lenses of all powers, but without finding the phenomenon. I suspect the respiratory currents in Crustacea which are produced by the motion of the branchiae them- selves, or of the plates or oars with which many are provided in order to renew the water, have been confounded with the currents produced by cilia, more especially as many of the organs employed for the purpose in the Crustacea are fringed with long hairs; but I would scarcely reckon such mo- tion as ciliary any more than those occasioned by the gill-covers of a fish. + Muller’s Archiv. 1834. Edinb. New Philos. Journal, xix. and Comm. Phys. de Phenomeno motus vibratorii continui. Wratislav. 1835, 4to. 4 See note at p. 29. wholly external, projecting backwards and out- wards from the side of the neck. The tadpole of the Frog (fig. 309) has at first gills resem- Fig. 309. bling those of the Salamander, but of a simpler form; they are also three on each side, but have each only five or six diverging branches. The gills of the Salamander, although not perma- nent, endure till the animal makes full use of its lungs, but the external gills of the Frog are of very short duration, being soon superseded by internal gills, more resembling those of a fish, with which the animal respires for the rest of the larva state. By means of the microscope the blood may be seen circulating through the external gills of the Frog and Salamander ; it passes outwards to their extremities by the branchial arteries, and returns in a contrary direction by the branchial veins. The water also is moved continually over these organs, for the purpose of respira- tion, in a constant and determinate direction, and this is effected by the peculiar impelling power we are here considering, viz. the ciliary motion on their surface. Steinbuch,* a German naturalist already mentioned, while examining the circulation of the blood in the gills of the Salamander, ob- served that small bodies floating in the water were carried, as if by attraction, to the surface of the gill, and again repelled from it. He also found that portions detached from the gill moved themselves through the water, or if kept fixed, continued as before to attract and repel small objects in their vicinity. From these and similar facts he was led to conclude that the water was continually propelled over all parts of the gill, that the current thus produced served to renew the water in the process of re- spiration, that the power producing the propul- sion resided in the gill, and was exercised in- dependently of the will of the animal ; and lastly, from the analogy of Infusoria and Polypi, in which currents are produced by cilia, he in- ferred that in this case also the water was pro- bably impelled along the surface by the action of cilia, though he could not actually perceive any such organs. Steinbuch next examined the tadpole of the Frog, and found that its ex- * Analektenneuer Beobachtungen und Untersuch- ungen fur die Naturkunde, Furtli, 1802. p. 46, sqq. CILIA, 629 ternal gills exhibited the same phenomena, but he could discover nothing of the kind on the internal gills. Gruithuisen* observed in the tadpole of the Green Frog that so soon as the circulation of the blood began in any part of the gills, small ob- jects were attracted and repelled from that spot, and that the same took place a few days later on the tail wherever vessels had been formed. He conceived that the motion of the water was for the purpose of exposing the blood to its in- fluence, and compared it to the current pro- duced by Infusoria by means of cilia. He does not say, however, that he had seen cilia in the tadpole. Huschkef observed that the water in the vicinity of the gills of the young Salamander was thrown into a boiling-like motion, while it flowed steadily at other parts of the body. Without being aware of these previous disco- veries, I was led in 1830, by an accidental ob- servation of my own, to go over nearly the same ground.J I had cut off one of the external gills of the tadpole of the Frog, and placed it with a drop of water under the microscope, with the view of measuring the size of the glo- bules of blood that might flow from it, and was astonished to perceive that the globules, on escaping from the cut part of the gill, moved rapidly along its surface towards the points of the branches in a constant and uniform manner. On further inspection it soon became evident that the blood-globules were entirely passive in their motion, and that other light particles brought near the gills were moved in a similar manner; their motion being manifestly owing to a current produced in the water along the surface of the gill in a determinate direction. A conclusive proof of this was afforded by put- ting the gill which had been cut off, into a watch-glass with a larger quantity of water. It was then seen that when the gill happened to be fixed by any obstacle, small bodies in its vicinity were moved along it as before towards the points of the branches, but when unim- peded the gill itself advanced through the water in a direction contrary to that in which the particles were moved, the trunk being turned forward ; the tendency to produce a current in one direction, thus causing the gill, now no longer fixed, to move in the opposite one. The current began at the root of the gill, and ran along the branches, at the points of which it did not continue its primitive direc- tion, but turned off sideways, and immediately ceased. (See fig. 309, C). I soon found that the gill was not the only part of the animal which excited motion in the water. Nearly the whole surface of the body produced the same effect. A general current commenced on the fore part of the head, pro- ceeded along the back and belly and the two * Salzburg. Medicinisch-Chirurgische Zeitung, 1819, ii. p. 447. f Isis, 1826, p. 625, (cited in Burdacb’s Physio- logie, from which I quote, not having seen the ori- ginal.) f Edinb. Med. and Surg. Journal, xxxiv. sides, to the tail, along which it continued to its extremity. It was not so strong as that on the gills, but agreed with it in other respects. I continued for some time to observe the phenomenon in the larva of the Frog, in order to find out whether it underwent any alteration in the progress of the developement of that animal. It is known that after a time the ex- ternal gills become covered by a fold of the skin, and inclosed in the same cavity with the internal gills, when they gradually shrink and at last disappear. On examining the animal while this change was taking place, and for some time after, it appeared that the external gills after their inclosure still retained their peculiar property, and continued to do so as long as any portion of them remained; the current on the body remained the same ; on the tail it acquired a twofold direction diverging from the middle part or continuation of the vertebral column, obliquely upwards and down- wards towards the upper and lower edge. As the animal advanced in growth, the currents gradually disappeared over the greater part of the surface, continuing longest at the posterior part of the body; at length, when the pos- terior extremities were so far advanced in growth that the thigh, leg, and toes could be discerned with a magnifying glass, which was the latest period of observation, the current existed only at the commencement of the tail, and on a small part of the body near the hind leg. The internal gills, though tried in various stages of development, did not exhibit the phenomenon. I next sought for the same appearances in the larva of the Newt or Water Salamander, which was first examined a few days after its exclusion from the egg when its gills are very simple. At this period the surface of the animal produces currents agreeing in almost every circumstance with those which take place in the larva of the frog at a correspond- ing stage of its development. Particles of powder diffused in the water are carried alon°- the surface of the body from before back- wards ; on the gills they are conveyed along each of the trunks from the root to the ex- tremity. The gills also, when cut off, move through the water with the cut extremity for- wards, in a direction contrary to the currents. I have since found nearly the same phenomena in the gills at a much later period. It was evident that the purpose of these currents was to effect a renewal of the water on the respiratory surfaces; respiration in these animals probably being performed not only by means of the gills, but also by the general sur- face of the body. It appeared that the power of impelling the water was wholly confined to the external sur- face of the animal; a portion of the skin bein<* raised and detached, floating bodies were moved along its external surface only. Parts cut off from the animal continued to excite currents for several hours after their separation, and the smallest portion produced that effect. In these cases the current always moved in the same direction relatively to the surface of 630 CILIA. the detached parts, as it had done previous to their separation. At the time of making these observations I had not been able to detect Cilia in these larva.', although, from the analogy of the In- vertebrata, I was led carefully to look for them. Since then I have succeeded in perceiving them with the aid of Wollaston’s doublet of one-thirtyfifth of an inch focus, especially when a portion of the gill is compressed under a plate of mica. They are to be distinguished chiefly by their waving motion, which is so charac- teristic as to remove all doubt of their ex- istence ; though here, as in other instances in which they are very minute, it is not always possible to demonstrate their existence by actual observation on every spot of the sur- face. Ova of the Batraehia. — In the course of the above-mentioned observations, I was led to enquire whether the phenomena in question appeared at a still earlier stage. With this view I examined the ova of the Newt, which for a considerable time may be procured in all degrees of advancement, and found that the ciliary motion presented itself in the embryo a considerable time before its exclusion from the egg. Since then I have observed the same with regard to the embryo of the Frog. In both cases the embryo is formed from the yolk or opaque central part of the ovum, by a series of changes sufficiently well known ; it is surrounded by a clear fluid, which is inclosed between it and the external pellucid membrane of the egg. By means of a lens, minute bodies may generally be perceived floating in the fluid, which by their motion serve to indicate the currents that take place in it; but with a little care the embryo may be extracted from the egg, and then the course of the currents along its surface can be ren- dered more evident by the usual means. A (jig. 310) is an enlarged view of the embryo Fig. 310. Embryo of the Frog. of the Frog at the earliest stage at which I have detected the motion. The vertebral canal is just closed, and at the fore part of the body three ridges on each side indicate the com- mencement of the gills. The arrows point out the course of the currents. They proceeded backwards along the dorsal surface, diverging in a direction downwards and backwards on the sides. They were visible but weaker on the abdominal surface. B represents the em- bryo farther advanced, the currents have nearly the same direction but are better marked, they are strongest on the lateral eminences of the head which correspond to the future- gills. In the embryo of the Newt, the phenomena are in a great measure similar; the currents seemed, however, to begin and to continue most vigorous on the abdominal surface; they are more particularly described in the paper re- ferred to. On extracting the embryo of the Frog, and viewing its surface in profile with Wollaston’s doublet, moving cilia may be perceived on various parts. They appear like a transparent undulating line on the surface, and, though very minute, are so distinct as to leave no doubt of their existence. No one can fail to perceive the analogy which subsists between the phenomena just described, and those which occur in the ova of Zoophytes and Mollusca. I have not been able distinctly to perceive a rotation of the embryo of the Batraehia, as observed in the other instances, but Purkinje and Valentin state that they have seen it, and Rusconi ob- served that the embryo of the Frog, when extracted from the ovum, turned round in a certain direction, which motion he supposed to be produced by water entering and issuing through pores in the skin.* The phenomena in the Batrachian larvte have since been observed by M filler, j- Raspail,J and Purkinje and Valentin.§ The last men- tioned naturalists also distinguished the cilia and perceived the motion within the egg. Adult Batraehia. — The ciliary motion was discovered in the adult Batraehia by Purkinje and Valentin; indeed, it may not be improper again to state that the discovery of the phe- nomena in adult Reptiles generally, and in Birds and Mammiferous animals, is due to these phy- siologists. According to their account, the ciliary mo- tion in the Batraehia, as well as in all other vertebrated animals in which they have dis- covered it, occurs in two situations within the body, viz. on the lining membrane of the respiratory organs and on that of the genital organs of the female. They state that it exists over the whole internal surface of the lungs, and in the nose, mouth, and pharynx, extend- ing as far back in the throat as the glottis, but no farther. They say nothing of the direction of the impulsion. Again, in the female, they discovered the motion on the internal surface of the oviduct. The result of my own ex- amination of the Newt, Frog, and Toad is somewhat different. In all the three I found the ciliary motion very distinct in the mouth, throat, and gullet ; in none could I perceive it in the lungs, notwithstanding very careful trials. In regard to the oviduct I have examined, it only in the Newt, and although I could per- ceive something like the motion on the edges of its superior orifice, I could not detect it on the internal surface of the tube.|| * Sur le Developpement de la Grenouille Com- mune. Milan, 1826. t Burdach’s Physiologie, Bd. iv. p. 434. t Chimie Organique, 1833, p. 250. $s Op. cit. || Edin. New Phil. Journal, xix. CILIA. 631 The ciliary motion in the mouth and throat occurs all the way from the opening of the mouth to the termination of the (esophagus. Its extent and the direction of the impulsion are easily ascertained by means of powdered charcoal ; they are pointed out by the arrows in the adjoining figures, A and B (jig. 311), Fig. 311. which are taken from the Newt, the ap- pearances in the Frog and Toad being not ma- terially different. a is the lower jaw detached from the head, b the tongue, c the glottis, d the oesophagus cut off from the head (at g, g, jig. B), and laid open from above, e the sto- mach, and j\ j\ the lungs. The general course of the impulsion, or, if in this case we might so express it, the currents, is longitudinal; they begin at the symphysis of the lower jaw and extend to the lower end of the oesophagus, where they terminate abruptly at the entrance of the stomach, thus differing from the de- scription given by Purkinje and Valentin; but it is worthy of notice that these observers de- scribe the motion in the Tortoise and Serpent as extending the whole length of the oesopha- gus. At particular parts the impulsion fol- lows the direction of the plaits of the lining membrane. Figure B represents the head and the roof of the mouth, from which the lower jaw has been separated. On this part of the mouth also the general course is longitudinal, from before backwards ; at the nostrils h, h, the particles are drawn in at one edge and issue at the other, as indicated in the outline of figure B. As regards the use of the ciliary motion on the internal membranes of the Batrachia, we can scarcely doubt that one purpose is to convey onwards the secretions of these mem- branes in the direction indicated. It is not impossible also that it may have some more intimate connection with the respiratory pro- cess; but on this point we have not as yet suf- ficient grounds for forming a probable opinion. Sauria, Ophidiu, and Chelonia. — The authors mentioned describe the appearances in these reptiles as being similar to what they have found in Batrachia. The ciliary motion oc- curs in the oviduct and in the nose, mouth, pharynx, Eustachian tube, and inner surface of the lungs. In the Serpent and Tortoise they state that it extends along the gullet to its termination at the stomach, as we have seen to be the case in the Batrachia. The motion of the cilia is remarkably vivid in the mouth of the Serpent, and in the Tortoise it endures for several days after death, not ceasing till the parts are destroyed by putrefaction. B. Birds.- — The same physiologists have discovered the phenomena in thirteen species of Birds, belonging to five different orders ; and as they met with it in every species sub- mitted to examination, they infer that it exists in all. In Birds, as in otherVertebrated animals, the motion shows itself on the lining membrane of the oviduct and that of the respiratory organs. It was detected in the nasal cavities and Eustachian tube, in the windpipe and its divisions, even in the smallest branches capable of investigation, and on the internal surface of the large sacs or receptacles into which the air penetrates. No trace of it could be found in the mouth and pharynx. In regard to the direction of the impulsion, the authors state that in the oviduct they had found it to be from the internal towards the external extre- mity of the tube, and in the windpipe from its orifice towards its branches, or from without inwards, at least they so observed it once in the domestic Fowl. The phenomenon exists in the foetus of the bird, having been distinctly seen in the foetal pigeon near the full period. C. Mammalia. — An accidental observation led Purkinje and Valentin to discover the ciliary motion in Mammalia, and they fol- lowed out that discovery by extending their inquiries to other vertebrated animals. While examining the Fallopian tube of a rabbit that had been recently impregnated, in order to discover the ova, they chanced to observe small portions of the mucous membrane of the tube turning round, and moving briskly, and recognized the appearance as an instance of ciliary motion. The whole uterus and organs of generation generally were then dili- gently searched, and these motions were dis- covered throughout their entire extent, though of very different degrees of intensity in dif- ferent places. They were particularly brisk in the tubes, less so in the cornua of the uterus, still less in the conjoined parts of the organ, most lively of all on its swollen and dark red lips, and of considerable strength in the vagina. After finding the same appearances in the oviduct of Birds and Reptiles, they succeeded also in discovering it in the lining membrane of the air-passages in all the three classes. In Mammalia the ciliary motion of the re- spiratory organs occurs on the mucous mem- brane of the nose and its sinuses, and that of the Eustachian tube, also on the lining mem- brane of the lower part of the larynx, the trachea, and bronchial tubes, extending to their smallest divisions capable of examination. No trace of it can be found in the glottis, nor CILIA. 632 in the mouth and pharynx. It was also sought for unsuccessfully in the lachrymal passages. The authors mentioned have now examined it in twelve species of Mammalia, and have found the same appearance in all of them ; they add that, although they have had no op- portunity of inspecting the parts in the human body so soon after death as to see the cilia in motion, yet by covering the surfaces to be examined with blood, which preserves the ap- pearance longer than any other fluid, they were able on examination, thirty hours after death, satisfactorily to distinguish the cilia both in the nose and windpipe. I have seen the phenomena in the nose, trachea, and Fallopian tubes of the Rabbit, and in the trachea of the Dog.* According to Purkinje and Valentin the motion occurs in the uterine mucous mem- brane, both in the impregnated and unimpreg- nated state ; but in gravid animals it appears only on those parts of the uterus which are not adherent to the chorion or external enve- lope of the foetus. The direction of the impul- sion they state to be from the internal ex- tremity of the tube, towards the orifice of the vagina. It seems, wanting on the genital mem- brane of young animals. On the other hand, it occurs in the respiratory passages of the foetus, it was detected in foetal calves and iambs, and in foetal pigs not more than two inches long. The authors could not with cer- tainty distinguish the direction of the im- pulsion in the air-passages of Mammalia. In some parts of the nose of the Rabbit, I have been able to trace it clearly enough by means of charcoal powder, the parts being placed in tepid water. On the inferior turbinated bone the grains of powder were slowly carried for- wards, following the direction of the project- ing laminae of the bone. On breaking open the maxillary sinus and trying its lining mem- brane in the same way, the impulsion seemed to be directed towards the back part of the cavity, where its opening ,is situated. By the same means I traced the direction in the wind- pipe of a young dog a few days old ; the im- pulsion was best marked on the posterior part of the tube, and there it was obviously di- rected towards the larynx, the direction being thus different from what Purkinje and Valentin observed in the domestic Fowl. PART II. 1. Summary of the animals in which the ciliary motion has been discovered. From the foregoing facts it appears that the ciliary motion is a phenomenon which prevails most extensively in the animal kingdom, hav- ing been found in the highest as well as the lowest members of the Zoological scale. Among Vertrebated Animals it has been dis- covered in Mammalia, Birds, and Reptiles, viz. the Batrachia, Sauria, Ophidia, and Chelonia. Of the Invertebrata it has been found in Mollusca, viz. Gasteropoda, Conchi- J'erous acephala, and Tunicata ; in Annelida, * Edin. New Philos. Journal, xix. viz. Aphrodita, Arenicola, and many Tubi- colar worms, also in Planaria; and Naiades; in Echinodermata, viz. the Aster ias and Echinus ; in Actiniae; in Medusae; in Poly.pi; in Sponges; and in Infusoria. It is a remarkable fact that no trace of it has been observed in Fishes. I at one time supposed that the pendent filaments of the gills of the fatal Skate and Shark might probably be found to exhibit it ; but my friend, Dr. Allen Thomson, has care- fully inspected those of the Skate without being able to perceive any appearance of it.* 2. Organs or parts of the body in which the ciliary motion has been ascertained to exist. These may be referred to four heads, viz. the skin or surface of the body, the respiratory, alimentary, and reproductive systems. Its use in all these cases, or the function in general of the cilia, is to convey fluids or other matters along the surface on which the cilia are placed, or, as in the Infusoria, to carry the entire animal through the fluid. a. Surface of the body. — Cilia have been found on different parts of the external surface, in Batrachian larvse, in Mollusca, Annelida, Echinodermata, Actiniae, Medusae, Polypi, and Infusoria. Their function in this situation is various ; in most cases it is evidently respi- ratory, but in many instances it is also locomo- tive, as in Infusoria and Medusae, or prehensile, as in Infusoria and Polypi ; and perhaps it is in some animals subservient to the sense of touch or smelling, as may be conjectured with regard to the cilia on the tentacula of some Mollusca. b. Respiratory system. — The ciliary motion has been observed on the lining membrane of the air-passages of Mammalia, Birds, and Rep- tiles ; and there, whatever may be its other uses, it at least serves to convey the secretions along the membranes, together with foreign matters, if any are present. It exists also on the external gills of Batrachian larvae, and on the gills of Mollusca and Annelida. In other Annelida, in Echinodermata and Actiniae, it is found on the external surface of the viscera and on the parietes of the cavity containing them, to which cavity the water has access. The pores and canals of the Sponge are pro- bably both respiratory and alimentary passages, and under this head we must refer again to the cilia on the external surface of Medusae, Polypi, and Infusoria, as belonging partly to the respi- ratory system. The use of the ciliary motion on the respiratory organs of animals with aquatic respiration is obviously to renew the water on the respiring surface. c. Alimentary system. — The motion occurs in the mouth, throat, and gullet of Reptiles, in the entire alimentary canal of Mollusca, on * Since the above was written, a short notice has appeared in i( l’institut” of 16th December, 1835, of the Transactions of the Leopoldine Aca- demy for 1834-35, from which it appears that Pur- kinje and Valentin have at last succeeded in detect- ing the phenomenon in Fishes. They found it in the organ of smelling and the internal genital organs of the female. No further particulars are stated. CILIA. 633 the internal surface of the intestine and eoscal appendages of the Aphrodita, within the sto- mach and coeca of the Asterias, in the stomach of the Actinia, in the canals of the Sponge, which no doubt belong partly to the alimentary system, and in the mouth, throat, stomach, and intestine of several Polypi. It is not easy to see the purpose of the motion in all these cases. In some it may merely convey secreted matters along the surface of the lining mem- brane; in Polypi it agitates the food within the alimentary cavity, and in several instances it seems almost to serve in place of ordinary deglutition, to carry food into the stomach. d. Reproductive organs. — The phenomenon occurs on the mucous membrane of the Fallo- pian tubes, uterus, and vagina of Mammalia, and of the oviduct in Birds and Reptiles. From the direction of the impulsion being from within outwards, it is difficult in the meantime to assign any other office to the cilia in this situation than that of conveying outwards the secretion of the membrane, unless we suppose that it also brings down the ovum. The phenomenon has been sought for in other parts of the body, but hitherto without success. Purkinje and Valentin state that on examination they could not find it in the fol- lowing parts of vertebrated animals, viz. the skin, serous membrane, the alimentary canal, (except the mouth and gullet of Reptiles,) the gall-bladder, the biliary and pancreatic ducts, the urinary organs, the seminal vesicles and ducts, the conjunctiva, cornea, and iris, the internal surface of the bloodvessels, the globules of the blood and lymph, the chorion, amnion, allantois, and yolk-sac of Birds. I have also repeatedly examined the foetal membranes of the common Fowl, and with the same result. 3. Of the ciliary motion in the embryo.- — According to Purkmje and Valentin the ciliary motion of the genital mucous membrane does not appear in the foetus, nor until the animals have made some approach to the adult state ; that of the respiratory passages on the other hand becomes apparent in the embryo long before it attains maturity. The ciliary motion, however, to which we would here refer is that which occurs at a much earlier period on the surface of the embryo of many animals, and generally causes it to perform a rotatory move- ment within the ovum. It has now been ob- served in the ova of Batrachia, Mollusca, Ac- tiniae, Polypi, Sponges, and Infusoria. While the embryo is contained within the ovum, the cilia produce a current in a certain direction along its surface, or cause the whole embryo to move in the opposite direction ; hence the very remarkable rotatory motion which occurs in many instances, and which is so well marked in the Snail. When it has escaped from the egg, the embryo moves about in the water by means of the cilia, as happens also with the naked gemmules of the Sponge after they are discharged from the parent. The ciliary mo- tion is subservient to the respiration of the embryo, by renewing the contact of the water or fluid contained in the egg on the respiring surface, and in some instances, the Mollusca VOL. i. for example, the motion is observed to be especially strong at the part where the respira- tory organ is afterwards developed. When the embryo quits the egg, the cilia serve also for locomotion, and by this provision the gem- mules of fixed zoophytes are disseminated, and conveyed to situations suitable for their future growth. 4. Figure, structure, and arrangement of the cilia in general . — The cilia are best seen when their motion slackens ; their shape, size, arrangement, and manner of moving may then be distinguished with tolerable accuracy, at least in the larger sort. Their figure is in general that of slender, conical, or sometimes slightly flattened filaments, broader at the base or root, and tapering gradually to the point. Their size differs greatly on different parts even of the same animal, but on corresponding parts of different individuals of the same species their size seems to be the same. The largest I have measured are those on the point or angle of the branchial laminae in the Buc- cinum undatum; they are at least ^ of an inch long. I have not attempted to determine the exact size of the smallest, but Purkinje and Valentin state it at 0.000075 of an inch, while they make the largest they have met with only 0.000908 in., which is considerably less than I have found them ; but they had no opportunity of examining marine animals, in which, gene- rally speaking, the largest cilia are met with. In the Sea-mussel the darker-coloured cilia are about of an inch long, the others consider- ably less. The cilia are very generally arranged in re- gular order. In some cases they are placed in straight rows, as on the gills of the Mussel ; in others they form circles or spiral lines, as in many Infusoria; and Purkinje and Valentin state that in animals of the higher orders the most prevalent mode of arrangement is in spiral lines or ridges. They are generally set close together in the same row ; on the gills of the Sea-mussel I find there are seven or eight of the larger cilia in the length of of an inch, or about seven or eight thousand to the length of an inch, but in other cases there are many more. In some instances they are erect, or at right angles to the surface on which they are planted, in others inclined, and then it would seem that the inclination is in the direction of the currents which they produce. In some parts they are straight, in others curved, not only when in action, but also when at rest, and the points are bent in the same direction in which the currents flow. The substance of the cilia is transparent, and for the most part colourless ; in some, however, it is coloured brown or yellowish brown. It appears as if homogeneous, even when highly magnified, and no fibres or globules are distin- guishable in it. It seems to vary somewhat in consistency, for the cilia on some parts appear extremely soft and pliant, and on others com- paratively firm and elastic, though still abun- dantly flexible. There is a peculiarity in the form of the cilia in some animals, of which the Beroe and other 2 T 034 CILIA. CiHograde Medusre afford a good example. In these, in place of cilia of the usual form and arrangement, there are rows of broad flattened organs, each of which is made up of several simple filaments joined together by a common base, according to Eschscholz, or according to Dr. Grant by a connecting membrane in their whole length. The entire organ is raised or depressed at once, so that the filaments are all moved simultaneously, like the eye-lashes. The compound cilia in some of the Rotatoria, de- scribed by Ehrenberg, are probably of the same nature. 5. Of the appearance of the cilia in motion. — On examining these organs with a lens of Js inch focus, when their motion is not very rapid, the manner in which the individual cilia move may be distinguished with tolerable cer- tainty. Most commonly they have a fanning or lashing motion, that is, the cilium is bent in one direction and returns again to its original state. The flexion takes place chiefly at the base or root, but not wholly there, for the rest of the organ is obviously bent and altered in figure ; nay, the more elastic cilia, when their motion abates in intensity, appear some- times to bend only near the point, the base and adjoining part remaining motionless. When a number of cilia are affected in suc- cession with this motion, the appearance of a progressive wave is produced, and as in such a case they are again and again moved in the same way at very short intervals, successive waves proceed along them in the same direc- tion, which might be compared to those pro- duced by the wind in a corn-field. Such at least seems to be the true explanation of the undulatory motion which so often occurs, although it must be confessed that the motion of the cilia individually cannot be distinctly seen when the undulation is most perfect. Tire undulations succeed one another along a range of cilia with great regularity, and except in the Rotifera, and perhaps some other Infusoria, they seem always to maintain the same direc- tion in the same parts. Purkinje and Valentin describe the motion of the individual cilia as being more frequently rotatory, or, as they term it, infundibuliform ; and Ehrenberg states this to be the common mode in the Infusoria; the cilium describing a circle with its point, while the base is the centre of motion. From my own observation, how- ever, 1 would be inclined to infer that this motion is by no means the most common. 6. Duration of the ciliary motion after death and in separated parts.— The continuance of the ciliary motion for some time after death, and the perfect regularity with which it goes on in parts separated from the rest of the body, are facts which have been already repeatedly stated, and sufficiently prove that the motion is quite independent of the will of the animal, and also that it is not immediately influenced by the circulation of the blood, even in the respiratory organs. The time which it continues after death differs in different species of animals, and also, but in a much smaller degree, in different parts of the same animal. Its duration is influenced also by the temperature of the air, and by the nature of the fluid in contact with the surface. In Mammalia and Birds the period varies from half an hour to four hours, being longer in summer than in winter; but it is still further prolonged when the parts are covered with blood. In the gills of Batrachian larvae I have seen the motion continue six hours ; but of all vertebrated animals it is most enduring in the Tortoise, in which animal Purkinje and Valen- tin atfirm they observed it fifteen days after death, when putrefaction was far advanced ; the irritability of the muscles remained in the same animal for seven days. Among the in- vertebrata the River-mussel affords an instance of the great pertinacity of the motion, which ceases only when putrefaction has advanced so far as actually to destroy and dissolve the tissues. 7. Effects of external agents on the ciliary motion. — Steinbuch, Purkinje, and Valentin allege that on touching the parts, or giving them a gentle shock by merely striking against the object plate of the microscope, the motion is rendered brisker when it has become languid, or is even renewed in parts where it has ceased . They, however, attribute more importance to this fact than it seems to deserve ; for it may be doubted whether the concussion in renewing the vivacity of the cilia does not act merely by removing obstacles which impede their play. Electricity and galvanism produce no visible effect. A powerful discharge from a Leyden jar was made to pass through the River-mussel by Purkinje and Valentin without causing any change in the ciliary motion. Portions of the external gills of the Tadpole were subjected by myself to the same experiment and with a similar result, except when the surface was abraded, which occasionally happened with a strong discharge. I have exposed portions of the gill of the River-mussel while viewed with the microscope, to the influence of a galvanic battery of twenty-five pairs of three-inch square plates, charged with solution of salt, without being able to perceive the slightest effect on the motion of the cilia. The authors above men- tioned obtained a similar result, both in the Mussel and the domestic Fowl. The effect of temperature is different in warm and cold-blooded animals. In the former, ac- cording to Purkinje and Valentin, the motion stopped on exposure to a temperature of 43° F. while it went on at 54° F. On the other hand they found that in the Fresh-water Mussel it was not affected at 32° F. ; and I found the same to be true of the Tadpole. A portion of the gills of the River-mussel, which I kept for five minutes in water at 96° F. shewed no change. Acids, saline solutions, and other substances applied to the parts, differ in their effects ac- cording to the kind of animals submitted to experiment. Thus, for example, fresh water instantly arrests the motion in the Marine Mol- lusca, and also in other marine animals in which I have tried its effect, though a satu- rated solution of sea-salt destroys it both in salt and fresh-water species. Purkinje and CILIA. 635 Valentin state the effects which they found to result from the application of various sub- stances, but erroneously coneeivinR, from some preliminary trials, that the same substance produced the same effect in all animals, they confined their experiments to the Fresh-water Mussel. According to their experiments, which were made with a great many different sub- stances, most of the common acid, alkaline, and saline solutions, when concentrated, arrest the motion instantaneously ; dilution, to a degree varying in different: substances, pre- vents this effect altogether, and a less degree of dilution delays it. The same is the case with alcohol, aether, aqua laurocerasi, sugar, and empyreumatic oil. Kreosote, muriate of baryta, sulphate of quinine, infusio pyrethri, and muriate of veratria, act less intensely. Hy- drocyanic acid and watery solutions or in- fusions of belladonna, opium, capsicum, ca- techu, aloes, musk, gum-arabic, acetate of morphia, and nitrate of strychnia, produce no effect whatever. They accordingly infer that the substances affect the motion only in so far as they act chemically on the tissue. The result of my own experiments differs from theirs in some points. In the River-mus- sel I found that hydrocyanic acid, containing ten per cent, of pure acid, invariably destroyed the motion. Solution of muriate of morphia, of medicinal strength, also arrested the motion in the Mussel, but not in the Batrachian larvae. The motion on the gills of these larvas also continues unimpaired in water deprived of air by boiling, or distilled, or impregnated with carbonic acid ; a sufficient proof, it may be remarked, that it is independent of the che- mical process of respiration. In regard to the effect of animal fluids, the authors already mentioned state that bile ar- rests the motion, while blood has the property of preserving it much beyond the time that it lasts in other circumstances, at least in verte- brated animals; thus it continued three days in a portion of the windpipe of the Rabbit, which had been kept in blood. But it is sin- gular that blood or serum, whether of Quadru- peds, Birds, or Reptiles, has quite the opposite effect on the cilia of invertebrated animals, arresting their motion almost instantaneously. Albumen and milk also possess the conserva- tive property, though in a less degree. 8. Effects of inflammation. — Purkinje and Valentin excited inflammation artificially in the nose and vagina of rabbits, and are in- clined to conclude from their experiments, which however are not numerous, that inflam- mation arrests the motion. 9. Of the power by which the cilia are moved. — It may next be inquired by what means or by what power the cilia are moved ; and, in particular, whether their motion, like other visible movements in the animal body, is effected by muscular action. Dr. Grant,* reflecting that in the Berbe a vessel conveying water runs beneath each row * Trans, of Zoological Society of London, vol. i. p. 11. of cilia, and that, according to M. Audouin, in an allied genus of animals the water enters the cilia, is disposed to liken the motion of the cilia to that of the feet of the Echinoder- mata. He seems accordingly to think it pro- bable that the cilia are tubular organs, which are distended and protruded by the injection of water into them from elastic tubes running along their base, in which the wTater is conveyed by successive undulations. This view, however, seems scarcely recon- cilable with the fact that the motion of the cilia continues in parts separated from their connexion with the rest of the body, portions so small that not more than two or three cilia are attached to them, and in which the ope- ration of the supposed undulating tubes can scarcely be conceived. Ehrenberg states that in the Infusoria he observed that the cilia were bulbous at the root, and that they were moved by small mus- cles attached to the bulb. Purkinje and Va- lentin also admit the existence of a bulb, and they conceive it likely that the cilia are moved either by muscular substance placed within the bulb, or by certain fibres which they be- lieve they have discovered in the adjacent tissue. They describe these fibres as existing in the substance of the membranes or other parts supporting the cilia, being situated at the surface, straight and parallel, and ap- pearing to be connected together by delicate cellular tissue ; and they think it highly pro- bable that they are of a muscular nature. The whole phenomena of the ciliary motion seem to me most consistent with the notion that it is produced by muscular action. I must confess, however, that I have never seen the muscular fibres described, nor the bulbs; and perhaps the cilia are not moved merely by muscular fibres attached to their base, like the whiskers of the seal and cat, but may con- tain muscular substance throughout a greater or less portion of their length, by which they can be bent and extended ; or perhaps they may in some instances be bent by muscular fibres, and resume their original shape and position by virtue of their elasticity. We need not hesitate to admit that the ciliary motion is the result of muscular action on account of the smallness of the muscular apparatus necessary ; for the researches of Ehrenberg on the Infusoria have brought to light examples of complex organization on as minute a scale as any here required. Nor need wre hesitate on account of the great ra- pidity of action ; for there are familiar instances of muscular motions of equal velocity. The continuance of the ciliary motion after death and in parts detached from the rest of the body, and its regularity in these circumstances, are appearances, startling at first, but which, though they differ in degree, may be fairly compared with those produced in similar cir- cumstances by involuntary muscular action, and may be attributed to the same cause. Thus the different parts of the heart, which during life contract in a certain order inde- pendently of the will, continue to act in the 2 t 2 636 CILIA. same regular order for a time, and in some animals for a long time, after death or sepa- ration from the body; and it is remarkable, although perhaps we are not warranted by ob- servation to lay it down as a general rule, that there is a correspondence in the duration of the ciliary motion after death and the persistence of muscular irritability. In the Tortoise, for instance, in which it is well known that the irri- tability of the heart and other muscles endures remarkably long after death, the ciliary motion is also of extremely long continuance ; while in Mammalia and Birds, the ciliary motion and muscular irritability are both comparatively soon extinguished. On the whole, therefore, without laying any stress on the alleged discovery of a muscular apparatus by Ehrenberg and the other authors mentioned, we may venture to conclude that the facts known respecting the motion of the cilia are all reconcilable with the opinion that it is produced by muscular contractility. 10. Strange as it may seem, after what has been said, some observers maintain that the cilia have no real existence, even in cases where the appearance of them is the most perfect, and that the whole is an optical de- ception. I allude particularly to Raspail ; according to him the water which quits the respiring surfaces has, in consequence of the change produced in it by respiration, acquired a different density, and consequently a dif- ferent refractive power from the surrounding fluid ; it therefore produces the appearance of lines or streaks at the surface of the parts, which streaks are the supposed cilia. It is scarcely necessary to repeat that the cilia are seen when at rest, when all motion of the water has ceased, and that they are evident in circumstances in which no interchange of ma- terials can take place between the tissue and the water in contact with it; and indeed, after the details already given, it is needless to say more in refutation of this view. 1 1 . Of the motion caused in fluids by the tiliu. — One of the most remarkable characters of the motion produced in water and other fluids by the ciliary action, is its definite di- rection, which, except in some of the Infusoria, appears to be always the same in the same parts ; at least I have never been able to per- ceive any exception to this rule. Appearances would rather lead to the belief that in the Infusoria the motion of the cilia is under the influence of the will, which would account for this and other possible cases of exception. We have hitherto taken it for granted that the currents in the water are owing to the mechanical effect of the moving cilia, without formally adducing proofs in support of the opinion; but at the same time the details already given must have served as such. The currents cease when the motion of the cilia stops, they are strong and rapid when it is brisk, and feeble when it languishes ; and though there are modifying circumstances or perhaps exceptions, yet in general the mag- nitude and velocity of the current seem to be proportionate to the size and activity of the cilia. It is true that while doubts remained as to the existence of cilia in several well- marked instances where the water unequivo- cally received its motion from the surface over which it flowed, and, independently of any visible contractions of the animal tissue, there was also considerable room to doubt whether, even in the cases where cilia were manifest, the effect of these organs was wholly mecha- nical, and whether the motion of the water was not rather due to some peculiar impulsive power in the tissue, differing from mechanical action. But more extended observation has almost wholly removed these exceptions, while it has considerably increased the number of conforming instances, insomuch that there seems at present no necessity for having re- course to any other explanation of the motion of the fluids than that it is produced by the action of the cilia, and that their action is the result of muscular contractility, a known pro- perty of animal tissues. The phenomena of the ciliary motion seem therefore of themselves to afford no counte- nance to the notion of a peculiar impelling power of the animal tissue, in virtue of which fluids are visibly moved along its surface, in- dependently of impulse communicated to them mechanically by cilia or by contraction of in- closing solids; nor am I aware of other facts which either alone, or viewed in connexion with the former, warrant such a notion. But as some physiologists believe in the existence of such a power, and found their opinion, at least partly, on alleged examples of visible motions of fluids in organized bodies, pro- duced without cilia and independent of con- traction of the solids, it may not be amiss here shortly to consider the principal facts which have been adduced as instances of this kind. First, Three cases have been already men- tioned in which currents, more or less re- sembling those produced by cilia, take place on surfaces on which cilia have not been de- tected ; these are the currents in the Sponge, those of the Tubularia indivisa, and those within the stem and branches of Sertulariae. In regard to the Sponge, it is true that cilia have been diligently sought for and without success; still, considering the difficulty of the investi- gation, it is not impossible they may exist in some part of the passages through which the water runs, though not yet discovered, espe- cially as the ova possess evident cilia. With respect to the currents described by Mr. Lister within the stem of the Tubularia, it will be seen, on referring to the account of these, that farther observations would be required to settle the points here in question, viz. whether the floating particles receive their impulse from the surface over which they move independently of any contraction of the stem, and whether or not that surface is covered with cilia. To de- cide these points satisfactorily it would be necessary to lay open the tube and make trial of detached portions of the tissue as in other instances. The same remark is in a great measure applicable to the currents in the stem and branches of Sertulari®. Indeed both CILIA. instances have been described above only be- cause of their seeming analogy with the rest, but further investigation is still required to determine their true nature. Neither these, therefore, nor the Sponge afford unequivocal examples of the peculiar motion of fluids al- luded to taking place independently of cilia. Of course we may pass over without notice the cases in which the appearance of the moving cilia has been mistaken for a circu- lating fluid,* or ascribed to other causes than the real one, and their existence erroneously denied. Secondly, It is well known that in cold- blooded animals the blood continues to move in the capillary vessels for some time after the heart has been cut out. This motion for the most part goes on at first steadily from the smaller to the larger vessels in the arteries as well as the veins, and afterwards becomes oscillatory. Haller, who particularly investi- gated the phenomenon, was of opinion that it could not be attributed to contraction of the large vessels, to gravitation, nor to capillarity; he therefore attributed it to some unknown power which he conceived to be exerted by the solid tissues on the blood and also by the glo- bules of blood on each other, and to this power, until farther investigation should eluci- date its nature, he gave the name of attraction. The same opinion or a modification of it has been taken up by succeeding physiologists ; accordingly many maintain the existence of a peculiar propulsive power in the coats of the capillary vessels different from contractility, or that the globules of blood are possessed of the power of spontaneous motion. Among others, Dr. Alison has adopted and extended this view in so far as he regards the motion of the blood in the capillaries as one of the effects produced by what he calls vital attraction and repulsion, powers which he conceives to be general attri- butes of living matter, or at least to manifest themselves in other processes of the living economy besides the capillary circulation. The motion in question has certainly not been as yet satisfactorily accounted for by re- ferring it to the operation of known causes. At the same time we can scarcely admit that the influence of such causes has been wholly avoided in the experiments in which the phe- nomenon has been observed. It is not im- possible, for example, that a certain degree of agitation may be occasioned in the blood by the elastic resilience of the vessels reacting on it, after the distending force of the heart has been withdrawn. The necessity of the case there- fore, though great, seems scarcely such as alone to warrant the assumption of a peculiar attrac tive or repulsive power acting on the blood at sensible distances, of whose existence in the animal economy we have as yet no other evi- dence. It may be remarked, finally, in regard to the phenomenon alluded to, that it cannot properly be termed a continuance of the circu- lation, for the blood does not necessarily pre- * .4s by Baker, Guillot, and others. 637 serve its original course, nor indeed any con- stant direction. (See Circulation.) Thirdly, In several plants motions have been observed in the fluids which are contained in their cells or vessels in determinate directions, and seemingly independent of any contraction of the parietes of the containing cavities. The best known example of this is in the Chara. Its jointed stem consists of a series of elon- gated cells, which contain a clear fluid with globules suspended in it. The globules are moved up one side of the cell and down the other in continual circuit. No contraction can be perceived in the parietes of the cells, which are indeed of a rigid texture, and this myste- rious movement has therefore been ascribed to some unknown and invisible impelling power. It is doubtful, however, whether the motion can go on unless the cell is entire, the experi- ments of different observers on this point being contradictory, and it certainly has never been shewn that separated portions of the tissue continue to excite the motion. In this state of knowledge on the subject we can scarcely admit this or similar motions of vegetable juices as unequivocal examples of the opera- tion of an impulsive power of the kind referred to; and even on the contrary supposition it does not follow that such a power exists in animals. On the whole therefore, from what has been said regarding the several examples adduced, we may conclude that they do not afford une- quivocal evidence of visible motions being produced in fluids in the animal body, inde- pendently of contractions of containing solids or of the action of cilia; and, consequently, that viewed in reference to the ciliary motion, they form no adequate reason for doubting that the fluid is moved mechanically by cilia. I may conclude this article by observing, that though the general existence of the ciliary motion in the Animal Kingdom is already suffi- ciently established, yet many particular in- stances of it must still remain to be found out, especially in invertebrated animals; and who- ever has opportunities and inclination to cul- tivate this field of inquiry will find his labour rewarded by much curious and interesting discovery. Bibliography.— ( The works more especially de- serving of attention are marked with an asterisk.) — *Ant. de Heide, Anatome mytuli, &c. 8vo. Ainst. 1684. Swammerdam, Biblia Naturae, fol. Leid®, 1787. * Leeuwenhoek, Opera, 4to. Delph. et Lugd. Bat. 1695-1719. *Baker, Of microscopes. &c. 8vo. Lond. 1785. Hales, Haemastaticks, 3d edit. 8vo. Lond. 1769 Ellis , Hist. Nat. des Corallines, 4to. La Haye, 1756, (a translation from the Eng. lish, with the(author’s additions). Roesel, Insecten- helustigungen, vol. iii. 4to. Niirnberg, 1755. *Spal - lanzani, Opuscules de Physique, 8vo. Pavie, 1787. *0. F. Muller, Hist, vermiuin terrestrium etfluvia- tilium, 4to. Hafniie, 1773, and, Animalcula Infu- soria, 4to. Hafniie, 1786, *Cuvolini, Memorie per servire alia storia dei polipi marini, 4to. Napoli, 1785; translated into German by W. Sprenirel, Niirnb. 1813. Poli, Testacea utriusque Siciii®, fol, Parmae, 1 792. Stiebel, Lymnasi Stagnalis anatome, 4to. G’ott. 1815, and in Meckel's Deutsches Archiv, fur die Physiologie, Bd i. and ii. Ehrmmi, 638 CIRCULATION. in Abliandl. der k'onigl. Akad. der Wissensch. zu Berlin fur 1816-1817. * Gruithuisen, in Salzb. Med. Chir. Zeitung, 1818, Bd iv. ; Nov. Act. Acad. Cass. Leop. vol. x. G. R. Treviranun, Vcrmischte Schriftcn, 4to. Bd iii. Bremen, 1820. Huqi, in Isis for 1823. *C«ras, Von den anssern Lebens- bedingtingen der weiss-und kahbluetigen Thiere, 4to. Leipz. 1824 ; Nov. Act. Ac. Cses. Eeop. vols. xiii. and xvi. Fleming , in Mem. of Wer- nerian Society, vol. iv. *Huschke, in Isis for 1826. *R. Grant, in Edin. Phil. Journal, Edin. New Phil. Journ., Elin. Journal of Science, and Trans, of Zoological Society. Sir E. Home, Phil. Trans. 1827. *Raspail, Mem. de la Soc. d’Hist. Nat. de Paris, 4to. vol. iv. 1827 ; Chimie Or- ganique, 8vo. Paris, 1833. Meyen, Isis for 1828. E. H. Weber, in Meckel’s Archiv. 1828. Fr. Esch- scholz, System der Acalephen, 4to. Berlin, 1829. Dutrocliet, in Annales des Sc. Nat. t. xv. 1828. * W. Sharpey, in Edin. Med. and Surg. Journal, vol. xxxiv. July, 1830. Guillot, in Magendie Journal de Physiologie, xi. 1831. * Eh/renberg , Ueber Infnsorien, in Abhandl. der k. Acad, der Wissensch. zit Berlin fur 1830 and 1831, Miiller’s Archiv. i. 1834. R. Wagner, Isis for 1832. Jo. Muller, Handbuch der Physiologie, Bd i. 8vo. 1833. H. Rathhe, in Dorpater Jahrbiicher, &c. Bd i. 1833. *Jos. J. Lister, in Phil. Trans. 1834. *J. E. Purkinje Of G. Valentin, in Miiller’s Archiv. Bd i. translated in Dublin Journ. of Med. and Chem. Science for May, 1835, and in Edin. New Phil. Journ. vol. xix. July, 1835; also, by the same authors, Commentatio Physiologica de Phe- nomeno Motus vibratorii continui, &c. 4to. Wratislav. 1835, (the only systematic treatise on the subject.) ( W. Sharpey.) CIRCULATION (in Physiology), ( Circu- latio, Circulus, Circuitus Sanguinis ; Fr. Cir- culation du Sang; Germ. Blutlauf; Ital. Cir- colazione del Sangue;) designates in its more extensive signification the course through or- ganised beings of their nutritious fluid ; as limited to man and the higher orders of ani- mals, the course of the blood from the heart to the most minute vessels, and from these back to the heart. By modern writers on physiology the circu- lation of the blood is generally included under the nutritive functions, because one of the most important purposes served by the motion of this fluid through the various textures and organs of the body is the supply of those new ingredients which are necessary to carry on the process of growth and the changes of nu- trition. A very slight acquaintance with ani- mal physiology teaches us, however, that the function of circulation has another very im- portant and immediate use, viz. the support of that condition of the textures and organs which is necessary to enable them to exercise their vital properties. It was on account of the apparent necessity of a constant supply of blood for the support of the animal powers, that Galen placed circulation, along with re- spiration, among the vital functions. In the following article it is intended to de- scribe more particularly the course of the blood in the human body and the powers by which it is moved, and also to state the general facts ascertained regarding the function of cir- culation in other animals. For the sake of clearness it will be neces- sary to divide the subject into several de partments. The first, of these will compre- hend a description of the course of the blood in man ; the second of its course in animals. In the third will be considered the phenomena presented by the blood during its motion, the properties of the organs in which it circulates, and the powers by which it is propelled ; and in the fourth will be mentioned the more im- portant circumstances connected with the other functions which modify the circulation. The term circulation applied by its cele- brated discoverer, Harvey, to the motion of the blood, is sufficiently expressive of the general fact that this fluid, or the greater part of it at least, in being carried through the body, moves in a circular course, or, that in performing its jour- ney through the body, the blood always re- turns to the same place from which it set out. The term is equally applicable to the func- tion by which a supply of nutritious fluids is kept up in the lowest animals, in which a pro- gressive motion of a fluid of the nature of blood takes place, as well as in the highest ; for in nearly the whole of them there is a central part of the circulatory organs, which forms the rallying point, as it were, of the rest, from which the blood begins its course and to which it is brought back, in a longer or shorter period of time, after having passed through the dif- ferent organized parts. I. Course of the blood tn man. The organs of circulation consist of the heart, arteries, veins, and capillary vessels. Werefer the reader to the articles on thesedifferentorgansfor all details relative to their anatomical structure. In man and warm-blooded animals there are two passages through the interior of the heart, through each of which a stream of blood is propelled at the same time, so that the heart is alternately receiving and giving out a certain quantity of blood upon each side. The two auricles serve as receiving cavities for the blood which is constantly flowing into the heart from the veins or those vessels which have the office of returning blood to the centre of the circulation. By the contraction of the muscular parietes of the auricles, the blood is propelled from these cavities into the ventricles, which, in their turn, contract with force and thus propel their contents into the arteries, or those vessels which serve to transmit blood outwards from the centre of the circulatory organs. The auricles and ventricles of the opposite sides acting simultaneously, and the size of these cavities on the right and left sides of the heart being nearly equal, the quantity of blood which is made to pass through each of them at one and the same time must also be nearly equal. The cavities on the left side of the heart are adapted to propel the blood into those arteries which are subservient to the nutrition of the body, while those on the right side of the heart send the blood to the lungs for the purposes of respiration. The construction of the heart and the connection of its parts with the arte- ries and veins are such that the whole of that CIRCULATION. 639 blood which has served the purposes of nu- trition, and the other uses for which the blood is destined throughout the body, on being re- turned to the heart, is directed by the cavities on the right side of that organ to the lungs, and made to pass through them before returning to the left side of the heart to repeat its course through the nutritive vessels of the body. In all those animals in which there exists a disposition of the heart and bloodvessels such as that described, the circulation is said to be double, because the blood is moved in two circles at once, and the respiration is said to be complete, because the whole of that blood which has passed through the nutritive vessels of the body is subjected to the respiratory action of air in the lungs. The blood returned from the lungs of a bright red colour, or arterial blood, on being expelled from the left ventricle (fig. 312, H) Fig. 312 * * In all the figures relating to the circulation in different animals the same letters indicate corres- ponding parts as follows : H, the heart or the common ventricle ; h, the common auricle ; A, the aorta or trunk of the systemic arteries ; a, its branches ; a*, the carotids. V, the great systemic veins or vena cava infe- rior; v, its branches; v*, the vena cava superior ; c, the capillary vessels ; P, the pulmonary artery ; p, the pulmonary vein ; B, the branchial artery ; b, the branchial vein ; 1), the ductus arteriosus ; d, ductus venosus ; f, foramen ovale ; U, umbilical arteries ; u, umbilical vein ; by the muscular contraction of that cavity, passes into the aorta or great artery of the system (A), and is distributed in various pro- portions to all parts of the body by the branches of the aortic trunk (a) and their in- finitely minute ramifications. The smallest arteries lead, by an intermediate set of minute tubes to which the name of capillary vessels is given, into the systemic veins ( v ), all of which (the veins of the intestinal canal excepted) join- ing gradually together into larger and fewer branches, form at last the great trunks of the superior and inferior venae cavse ( V, v*), which carry back to the centre of the circulation the whole of the blood that had passed from the left ventricle into the aorta. In passing from the arteries to the veins through the capillary vessels, the properties of the arterial blood are changed ; its colour is altered from bright scarlet to dark purple, it expends some of its substance in the nou- rishment of the textures, and a considerable quantity of its thinner part transudes through the small vessels, constituting the lymph that is taken up by the absorbent vessels. The venous or dark blood, as it approaches the heart upon its return, has its composition fur- ther changed by its admixture with the chvle or imperfectly formed blood, which is the pro- duct of digestion, and which is poured along with the lymph from thp thoracic duct into the great veins of the head and superior ex- tremities. By the changes thus produced in its com- position, &c., the venous blood which returns to the heart is rendered unfit for nutrition, until it has been acted upon by the atmos- pheric air in the lungs, which restores to it its bright red colour and arterial composition and properties. The great systemic veins are therefore con- nected with the right side of the heart (fP), and the stream of venous blood brought by them to the right auricle (//), next issues from the heart by the pulmonary artery (P), into which it is propelled by the contraction of the right ventricle ( H' ) as it passes through that cavity. The minute branches of the pulmo- nary arteries and veins (F, p), and the capil- lary vessels by which they communicate with one another, are wholly distributed on the membrane lining the air-cells of the lungs. In passing through these vessels then, the venous blood is exposed to the action of the at- mospheric air contained in the pulmonary cells ; and, after having acquired arterial properties, is returned to the centre of the circulation by /, arteries of the intestine or alimentary canal ; i, the coeliac artery ; L, vena portae ; l, hepatic vein ; /*, hepatic artery ; K, advehent renal veins ; k, renal veins ; K* , renal artery. In those instances in which the parts are double, those on the right side are distinguished by the accentuation of the letters indicating them, thus P' right pulmonary artery, P left ditto. We beg to remind the reader that most of these figures arc merely plans, and that strict anatomical accuracy is not to be looked for in them. 640 CIRCULATION. the pulmonary veins ( p ). The left auricle (/<) receives the newly arterialized blood from the pulmonary veins, and transmits it to the left ventricle ( H ), from which it is ready to start again, when the ventricle contracts, on the same course as has just been described. In this double circulation, the path which the blood traverses in passing from the left to the right side of the heart through the aortic arteries and the corresponding veins, has been called the greater or systemic circulation : and the route of the blood from the right to the left side of the heart through the pulmonary arte- ries and veins has been termed the lesser or pulmonic circulation. The names of pulmonic and systemic, indicating the parts of the body in which each of these circulations respectively occurs, are on the whole preferable to the cor- responding terms of lesser and greater. There is still one part of the course of the blood to be mentioned, viz. that of the venous blood of the principal abdominal viscera through the liver, or what has been termed the system of the vena portae. The blood supplied by the cceliac and me- senteric arteries (I, i) to the abdominal viscera is not returned directly to the heart by their corresponding veins, as occurs in other parts of the body. The veins of the stomach and intestinal canal, of the spleen, pancreas, me- sentery, omenta, and gall-bladder, unite to- gether below the liver into one large vessel (L), the trunk of the vena portae, which branches out again and distributes to the liver by its ramifications the whole of the venous blood coming from the above-mentioned organs. The blood of the vena porta?, being joined in the minute branches by that of the hepatic artery (/*), passes into the smallest ramifica- tions of the hepatic veins, by the principal trunks of which ( l ), the venous and arterial blood circulated through the liver is carried to the inferior vena cava, and thus reaches at last the right side of the heart. Proofs of the circulation. — After this brief outline of the course which the blood takes through the circulatory organs in man and warm-blooded animals, it may be proper to introduce an enumeration of those circum- stances which are generally adduced as af- fording the most satisfactory “ proofs of the circulation’’ or evidence that the blood pursues the paths above detailed. As proofs of the circulation, besides those derived from the connection of the different orders of great vessels with the cavities of the heart to which they are respectively attached, may be mentioned — • 1st. The structure and disposition of the auriculo-ventricular valves of the heart, and semilunar valves of the aorta and pulmonary artery, which admit of the passage of blood from the auricles to the ventricles, and from the latter cavities to the great arteries, but not in a reverse direction. 2nd. The mechanism of the valves of the systemic veins which allow of the motion of fluid only in the direction towards the heart. 3rd. The fact that when a ligature is applied to an artery, or any other impediment opposed to the free passage of blood through it, the vessel becomes dilated on the side next the heart, while the application of a ligature to the trunk of a vein is followed by a turgescence of the vessel beyond the place where the obstruc- tion occurs. 4 th . That on opening one of the larger arteries, blood issues in a jet from the end next to the heart at the time of every contraction of that organ, and that in general no blood flows from the orifice of the remote part of the artery: and that on opening a vein the converse is ob- served, the blood issuing freely in a continued stream from the remote part, but none proceed- ing from the part of the vein adjoining the heart. 5th. That the passage of the blood from the arteries to the veins in the small or capillary vessels has been observed by means of the microscope in transparent parts of animals, and, though it has not been seen in man, we are entitled from the general analogy in the struc- ture of the organs of circulation to infer that the same passage occurs in the human body. 6th. That, by mechanical arrangements, fluids may easily be made to pass in the dead body through the whole course of the double circulation, but not in a direction different from that which the blood has been stated to pursue. 7th. That by the operation of transfusion, the blood of one animal may be made to circu- late through the heart and vessels of another, by connecting together the bloodvessels (whe- ther arteries or veins) of the two animals, in such a manner that the course in which the blood is directed by the action of the heart of (he animal from which the blood is derived is that of the natural circulation in the animal into which it is introduced. 8th. The phenomena presented by the circu- lation of the blood in various diseased condi- tions of the heart and bloodvessels may be ad- duced as affording additional illustration of the natural course of the blood, by pointing out the effect of morbid obstructions and other varieties in different parts of the circulatory organs. Course of the blood in the fatus before birth. — The double circulation just described is the course performed by the blood from the time of birth during the whole of life. The circulation of the blood, however, begins at a very early period of foetal life; but the difference in the mode in which respiration is effected in the child so long as it is contained in the uterus, induces a modification in the course of the blood to which we shall now advert. There being no inhalation of air into the lungs of the foetus, the blood is sent only in small quantity to these organs, and does not undergo in them any change of properties. A considerable portion of the blood of the foetus passes out of its body through the umbilical cord (fig. 313, U, u) into the placenta of the uterus. The minutely divided foetal vessels are bathed by the blood of the mother contained in the placental sinuses, and, though no direct CIRCULATION. 641 Fig. 313. continuity of tube exists between the maternal and fetal vessels, the blood of the child seems to undergo a respiratory alteration, or a certain degree of arterialization, in being brought into near proximity with the maternal blood. The blood of the fetus, after passing through the minute ramifications of the umbilical arte- ries ( U', U) in the placenta, returns by the umbilical vein (u) into its body. The umbilical vein carries part of its blood directly by the ductus venosus ( d ) to the vena cava inferior, and part is distributed by the branches of the vena port® ( L), with which the umbilical vein unites, through the sub- stance of the liver, and is then conveyed by means of the hepatic veins ( l ) into the general current of the returning blood. The right auricle of the heart (Ji), therefore, receives not only the blood which has circu- lated through the body of the fetus, but also that which has passed through the placenta, consequently a mixture of venous and arterial blood ; — the blood in the superior vena cava (v*) being entirely venous, that in the inferior vena cava ( V) being mixed. The blood which is brought to the right auricle is in much greater quantity in the fetus before birth than in the child which has breathed air ; a part of this blood passes from the right into the left auricle ( h ) by the foramen ovale (f) in the sep- tum auricularum, and it would appear that it is chiefly the blood from the inferior vena cava which takes that course. The rest of the blood entering the right auricle takes the same route as in the adult, viz. into the right ventricle ( H' ), and thence into the pulmonary artery, but, as very little blood is sent to the collapsed lungs, a passage of communication is established in the fetus from the pulmonary artery into the descending aorta through the ductus arteriosus ( D), and thus the greater mass of the blood, which in the adult would have proceeded to the lungs, is in the fetus immediately transmitted to the aorta (A). From the disposition of the Eustachian valve, it is believed that nearly the whole of the blood of the inferior vena cava passes from the right to the left auricle through the foramen ovale, while the blood brought from the head and superior extremities (parts which are compara- tively large in the fetal condition) passes through the right side of the heart. The as- cending aorta, rising from the left ventricle, delivers almost all the blood expelled by the contraction of that cavity into the carotid and subclavian arteries, while the ductus arteriosus passing between the trunk of the pulmonary artery and the descending aorta directs the blood which passes through the right ventricle to the lower regions of the body. In this manner the upper regions of the body are sup- plied with the most arterialized part of the blood from the left side of the heart and aorta, while the purely venous blood is propelled from the right ventricle through the pulmonary artery and ductus arteriosus into the descend- ing aorta, and consequently into the lower part of the body, and by the umbilical vessels to the placenta. The foramen ovale in the septum of the au- ricles, the ductus arteriosus passing from the pulmonary artery to the aorta, the ductus ve- nosus leading from the umbilical vein to the vena cava inferior, and the umbilical vein and arteries are the structural peculiarities of the fetal circulating organs. These passages are all closed up, and the umbilical vessels obliterated at the navel after aerial or pulmonic respiration is established at birth.* II. Course of the blood in various ANIMALS. We now’ leave for the present the history of the circulation in man, in order to give a brief sketch of the varieties of this function in other animals, the study of which is calculated to throw considerable light upon some of the pro- cesses of the human economy, and to illustrate the anatomical and physiological relations of the circulatory and respiratory organs. f It has been shewn that a regular and pro- gressive circulation of the nutritive fluids occurs in those animals only in which the aeration of the blood is performed by a separate and dis- * Sabatier, Mem. de 1’Acad. An 8. Kilian, Kreislauf im Kinde, &c. Karlshruhe, 1826. Bur- dach’s Physiologie, &c. vol. ii. Jeffray, Pecu- liarities of the Foetal Circulation. Glasgow, 1834. t In the following view of the comparative phy- siology of the circulation, besides the different works referred to under the separate heads, we have been guided chiefly by the following, viz. the works of Cuvier, Home, Meckel, Blumenbach, Trevira- nus, Carus, and R. Wagner; Roget’s Bridgewater Treatise, and the excellent chapter upon this sub- ject by J. Muller in Burdach’s Physiologie, vol. iv. and in his Handbuch der Physiologie, vol. i. 642 CIRCULATION. tinct respiratory apparatus ; and that, amid the immense varieties of form which the circulatory organs present in different animals, the course of the blood bears a more close relation in all to the form of their respiratory apparatus than to any other part of their organization. This general law of the relation between circulation and respiration, satisfactorily established by the extended researches of modern comparative anatomists, receives farther confirmation from manj’ facts connected with the performance of these functions in the adult human body, and is illustrated in a peculiar manner by the re- markable changes which take place in the cir- culatory and respiratory organs of the child before and after birth. In treating of the varieties in the course of the blood in different animals, we are at once freed from any embarrassment regarding the order proper to be pursued, by the circumstance that the form of the circulatory organs consti- tutes one of the principal bases upon which the modern classification of animals is founded ; so that, in following the zoological arrange- ment, we take the order best adapted for our present purpose. As our object in giving this sketch is principally to illustrate the structure and functions of the human organs of circula- tion, we shall begin with the consideration of the course of the blood in those animals which most nearly resemble man ; and trace the varie- ties in this function, as far as our knowledge permits, through the descending series of the animal chain. 1 . Course of the hlood in warm-blooded animals. — In Mammalia and Birds, the form of the organs of circulation and the course of the blood are essentially the same as in Man, for in all of these animals the heart contains four distinct cavities, — two auricles and two ventricles, and there is consequently a double circulation and a complete respiration. Some considerable varieties in the form of the circulatory organs, which seem to have a relation to peculiarities in habits or mode of life, occur in certain mammiferous animals, such as the Cetacea, Amphibious Carnivora, the Sloths, Hybernating Animals, &c.; but we shall not at present enter upon the considera- tion of these varieties, because they do not amount to any deviation from the type or general plan of construction of the human organs of circulation, and consequently are not accompanied by any material difference in the course of the blood, but seem rather to have the effect merely of modifying the quantity of blood sent to particular organs, or of influen- cing its velocity and force.* In the organs of circulation of the various tribes of Birds, we observe the same remarka- ble uniformity of structure which pervades the rest of their internal organization. It may be remarked that, as in Birds a cer- tain respiratory action takes place in the large air-cells distributed over the trunk of the body, and as the pulmonary vessels seem in most birds not to extend to these cells, but to be * Sco p. 678. confined to the thoracic lungs, the blood con- tained in the small branches of the systemic arteries and veins, ramifying upon the lining membrane of the air-cells, must be made to undergo some respiratory alteration of its com- position ; but we have not as yet obtained the means of judging accurately of the extent to which such a respiratory change may be effect- ed in the vessels of the systemic circulation, nor how far the minute branches of the pulmo- nary vessels may in some instances be pro- longed from the lungs into the air-cells.* Very frequent anastomoses take place among the veins of Birds. We may here mention one of these which induces an important modifica- tion in the portal circulation. By means of a communicating branch which passes from the united caudal, hemorrhoidal, and iliac veins to the vena port®, the blood of the viscera of the abdomen and of the posterior part of the body may flow indifferently either into the vena cava inferior or the vena porta?, a disposition which may have for its object to prevent congestion of blood in the parts from which these veins pro- ceed .f A still more remarkable modification of the venous circulation in Birds was supposed to exist by Professor Jacobson of Copenhagen, consisting in the distribution of branches of the vena cava inferior to the interior of the kidneys and their subdivision in these organs, in the same manner as the vena portae subdivides in the liver. Such veins transmitting venous blood to the kidneys, in the manner of a vena portae, have been ascertained by Professor Jacobson,! and are admitted by others making subsequent researches, to exist in Reptiles and Fishes ; but Nicolai§ has shewn that the lower veins, described by Jacobson in Birds as vena advehentes of the kidney, do not differ from the other branches of the vena cava, and serve to carry away from these organs, like the superior renal veins of Birds and the renal veins of Quadrupeds, the venous blood derived from the arteries. Course of the blood in cold-blooded vertebra- ted animals. — Of cold-blooded vertebrated ani- mals, some, as the adult Batrachia, Chelonia, Ophidia, and Sauria, breathe air by means of lungs, while the rest, as the young Batrachia, the Protean, and Siren-like Reptiles and Fishes, are constant inhabitants of water, and breathe the air contained in that medium by means of gills or branchiae. Of the aquatic cold-blooded animals, Fishes breathe by gills only, while the aquatic Reptiles or Amphibia are furnished with lungs as well as gills during the greater part of their aquatic life. * See the article Aves, p. 330. t It is a remarkable fact that there have been found, between the hemorrhoidal veins in Man and some branches of the vena port®, anastomoses by small branches, which correspond in some respects with the disposition of the veins referred to above. These anastomoses were known to Haller, and are lately described by Retzius. See his Researches in Tiedemann’s and Treviranus’ Zeitschrift, vol. v. 1. t Meckel’s Archiv. vol. ili. p. 147. Edin. Med. and Surg. Jonrn, vol. -xix. p. 78. § Isis, 1826, p. 414. CIRCULATION. 643 Reptiles.—' The structure and functions of the circulatory organs in Reptiles form a sub- ject of great interest on account of the nume- rous varieties which they exhibit in different orders and genera, for in this respect the class of Reptiles may be said to present to us an anatomical analysis of the circulatory and re- spiratory organs, and to constitute a gradually simplifying series of forms, the observation of which enables us to trace in the most clear and interesting manner an analogy and correspon- dence between the forms of these organs in warm-blooded animals and in fishes, which, but for the study of their structure in reptiles, must very probably ever have remained hidden from our view. In Fishes the heart consists of one auricle and one ventricle, and a single current of blood only passes through it. The structure of the heart is very similar in some of the Batrachia breathing by gills, but among other reptiles, we find a gradual transition in the form and structure of the heart from that just mentioned as peculiar to animals with aquatic respiration, to the double heart possessed by warm-blooded and air-breathing animals. Among the Reptiles provided with lungs and breathing air, some, as the Sauria, Ophidia, and Chelonia, have the ventricular part of the heart partially divided into two cavities (Jig. 314, Fig. 314. H, It J which correspond in structure, relative situation, and connections to the right and left ventricles of the heart of warm-blooded ver- tebrata ; the anterior or right compartment fH) giving off chiefly the pulmonary ( P), the left or posterior ( H), the systemic arteries ('A ) . In the others, viz. the Batrachia and Protean reptiles, the ventricle forms a single cavity (figs. 317 and 318, H), and gives origin to one large artery only (A), so that the pulmo- nary and systemic arteries derive their blood from the same trunk. In all of these, how- ever, the auricle is double,* so that the venous * The auricle of the Batrachia was generally de- scribed as single until the discovery of the left or pulmonary auricle in the Frog and Toad by Dr. John Davy. Mr. Owen has shewn this to be the case also in the Newt and Protean Reptiles; blood from the system and the arterial blood from the lungs are received into separate auri- cular compartments of the heart, and are sub- sequently mingled together in the common ventricular cavity. In the Heart of the Croco- dile of the Nile, Cuvier* has described three compartments, one of which corresponds to the left, the other two to the right ventricle, the septum between the right and left sides being incomplete. The heart of the Crocodilus Lu- cius is described by Hentz, Meckel, f and others as consisting of two ventricles, between which the septum is quite complete, so as to permit of no direct passage of fluid from one side to the other, possessing therefore in this respect, the same structure as the heart of warm- blooded animals. In those of the above-men- tioned reptiles in which the septum is so nearly complete as to divide the ventricle into two separate compartments communicating by a small orifice, the arterial and venous blood are believed to be kept separate from one another by a valvular apparatus. Among the rest of the Saurian, Ophidian, and Chelonian Reptiles, in Fig. 315. all of which the septum of the ventricular part is less complete than in the Crocodile, there is considerable variety in the extent to which the division of the cavity is effected by the septum. In a few of them the septum projects so little into the ventricular cavity that it cannot be supposed to divide to any extent, or to prevent the complete mixture of the two kinds of blood propelled from the opposite auricles. In the Crocodile, and in those Reptiles in which the ventricular septum is nearly com- plete, the circulation, so far as regards the heart at least, may be considered as almost double, or the same as in warm-blooded ani- Zool. Trans, 1834, p. 213. See also Martin St. Ange’s Plate of the Circulation, and M. Weber, Beitr. zur Anat. und Physiol. Bonn, 1832. , * Lemons, vol. iv. p. 221. f Verglcich. Anatomic, vol. v. p. 231. CIRCULATION. 644 raals, that is to say, the arterial blood returning from the lungs to the left auricle (fig- 314, h) is directed entirely into the arteries of the system (A) from the left compartment of the ventricle ( H J, and the venous blood brought back to the right auricle (h') by the venae cavae (V v*) is directed wholly into the pul- monary vessels ( P ) by the right ventricular compartment ( H‘ ). Fig. 316. In all Reptiles, however, the descending aorta is formed by the union of two branches, the right and left aortic arches (figs. 314, 315, 316, and 317, A', A); the right corresponds with the systemic aorta of birds, and rises from the left ventricular compartment, the left arch joins the right on the back, and leads generally from the right ventricular cavity into the descending aorta. The arteries of the head and upper extremities (fig. 314, a*), arising from the right aorta (A'), which corres- ponds with the aorta of birds, and is con- nected with the left ventricular compartment, are supplied with highly arterialized blood proceeding directly from the lungs. The left arch of the aorta (A), being connected on the other hand with the right ventricular com- partment (H'), obtains, like the pulmonary artery, venous blood from the right auricle; and consequently the common trunk of the aorta, formed by tiie union of the right and left aortic arches, must carry to the posterior parts of the body a mixture of arterial and venous blood.* It may be remarked, however, that in theTurtle and some Lizards the left aortic arch does not join the right upon the back until after it (the left) has given off the great cceliac or rather visceral artery, which supplies the whole of the alimentary canal and digestive organs with ve- nous blood (fig. 315, I). The leftaorta is thus much diminished in size before it sends its com- paratively small communicating branch to the right. f From this disposition of the parts, it is obvious that in these animals the abdominal viscera must receive the greater part of the venous blood brought from the right side of the heart by the left aortic arch, while the right aortic arch which gives the carotid, brachial, ver- tebral, intercostal, and other arteries must carry to the parts it supplies in the first part of its course nearly pure arterial blood, and, after it is joined by the left, blood which contains a small proportion only of the dark or venous kind. In the Turtle, some Lizards and Ser- ents again, the arterial and venous blood must e mixed in the ventricular cavity though par- tially divided ; the two streams of blood pro- pelled into the aortic and pulmonary vessels must therefore be nearly of tbe same kind, and thus a part only of the blood which is sent to the lungs is made to undergo a respiratory change. In some of the Chelonia, the exis- tence of ductus arteriosi, leading from the pul- monary artery on each side into the arch of the aorta, insures a still more complete mixture of the arterial and venous blood.} In most of the adult Batrachia the ventricle (fig. 317, II), being single and giving rise to one arterial trunk only (A ), the pulmonary arteries ( F', F ) derive their blood from the great systemic aortic trunk of which they are branches; one coming off from each of the aortic arches which unite to form the descend- ing aorta. The venous blood returning from the system ( V v*) to the right auricle, is mixed in the common cavity of the ventricle with the arterial blood returning to the left auricle by the pulmonary veins ( p ), and this mixed blood being propelled into tbe aortic bulb is distri- buted in part to the system and in part to the lungs. In these animals then, only a small quantity of a mixed blood is exposed to the action of the air in the lungs, which, from the simplicity of their structure, offer only a con- * In the Crocodile, the left branch coming from the right ventricle is small and very short. t See Bojanus’ beautiful Anat. Monography of the Tortoise. J In this respect, as well as in the mode of origin of the left aortic arch, the Tortoise and Tur- tle differ from otie another. CIRCULATION. 645 Fig. 317. fined surface for the distribution of the pulmo- nary capillary vessels. In the aquatic Reptiles having gills, such as the larvae of the Frogs and Salamanders in their transitory conditions, and the Protean animals, Fig. 318. which are very similar to them, but do not un- dergo, so far as is known, any further metamor- phoses, the branchial organs are formed by an extension or minute subdivision of branches of the aortic trunk, supported upon the arches of the hyoid bones. In all of these Reptiles, the ventricle consists of a single cavity (Jig. 318, H), which propels its blood into the bulb or commencement of the aortic trunk (A). The aortic trunk divides into two branches, each of which subdivides again into three or four ves- sels upon each side of the neck. These vessels ( B), passing round the gullet or upper part of the alimentary canal in the form of lateral arches, unite again together behind, to form the descending aorta. The branchial apparatus of the animals now under consideration is formed entirely upon these lateral arches of the aortic trunk. In the larva of the Salamanders, in the Proteus, Axolotl, Menobranchus, and Siren,* the small branches of each gill are formed by the minute subdivision of a loop of vessel prolonged from the outer part of three of the arches on each side into leafed processes of the cuticular system attached to the hyoid ar- ches (B, b). The larva of the Frog has, in the earliest stage of its existence, gills of the same kind as those just described ; but in its more advanced condition these external gills disappear, and the larva of the frog breathes by internal gills more resembling those of fishes than the ex- ternal branchiae of the Newt or Proteus. The gills of the tadpole of the Frog are covered by the skin, and consist of a great number of small leaflets, receiving the minutely subdi- vided loops of vessel given off for some way along each of the four vascular arches as they pass round the neck along the cartilaginous hoops of the hyoid bone. The vascular arches are double in that part of their course where they are connected with the gill, the blood being transmitted from one branch to the other in passing through the leaflets of the gill. In the larvae of the Batrachia, from a very early period of their existence, as well as in the Pro- tean Reptiles, there are lungs which seem to be used as adjuvant respiratory organs, for they are generally filled by the animal with air from time to time. These lungs, more or less per- fectly developed in different kinds of Protean Reptiles, and at different stages of the existence of the Batraehian larvae, all receive a pulmo- nary vessel from the vascular arch of the aorta which is nearest the heart, whether this arch is connected with a branchial apparatus or not. In all these animals the anatomical relations and the mode of development of the blood- vessels of the gills proves distinctly their re- turning vessels to be, as much as those which conduct the blood into them, branches of the arterial system; but the lungs on the other hand, however rudimentary, are almost always furnished with proper pulmonary veins which lead to the auricle of the heart. The following is the course which the blood takes in this interesting class of animals. The * We omit the consideration of the Amphiuma, Menopoma, and Coecilia. 64G CIRCULATION. heart (A, H) receives tire whole venous blood of the body by the right auricle, and a small quantity of arterial blood from the lungs by the left. These two kinds of blood, mixed together in the common ventricle, proceed from thence into the aortic bulb and its branches ( A , B, b). In the larva of the Sala- mander and Protean Reptiles, a part of the blood is sent by pulmonary vessels to the lungs, from which it is returned by the pul- monary veins to the heart ; a part passes di- rectly round the arches, and gains the descend- ing aorta ; the greatest quantity passes out into the gills, and after being arterialized returns to be mixed with that in the aorta, so that a mixed blood must permeate all the vessels of the systemic circulation. In the Siren, accord- ing to Cuvier and Owen, the whole blood goes at once to the gills, from the want of any com- municating twigs across the root of these organs. It is interesting to remark that the arteries of the head and upper extremities («) are not given off by the aortic arches until after they are joined by the returning branchial vessels, a disposition which is in some respect similar to what we find in higher Reptiles, and which seems to have for its object the supply of a more pure arterial blood to the cerebral organ. In the larva of the Frog, the course of the blood is very similar to that of Fishes. The whole of the venous blood propelled through the heart is sent into the gills, and is made to pass through them before reaching any other part. From the posterior parts of the first arches are given off the vessels of the head, the second form the right and left roots of the de- scending aorta, and the fourth are continued upon the lungs in the form of a pulmonary artery. There is however also in the larva of the Frog a short anastomosis between the out- going and returning artery of each of the gills, which allows of a direct passage of some blood round the arches of the aorta. In the Protean Reptiles and larva of the Batrachia a greater quantity of blood is sent to the respiratory organ than occurs in the adult Frog or Salamander. Portal circulation in Reptiles.— In the class of Reptiles there are two lesser venous circula- tions besides those already described ; the one, similar to the portal circulation of warm-blooded animals, belongs to the liver; the other, which does not appear to occur either in Birds or Mammalia, belongs to the kidneys. According to Jacobson, who was the first to point out the existence of veins carrying blood to the kidneys in the Amphibia, and the later researches of Nicolai and others, there are two principal ves- sels which carry back blood from the posterior parts of the body, viz. the anterior abdominal, and the inferior renal veins. These two vessels are formed by the union of the iliac, caudal, posterior cutaneous, pelvic, visceral, abdominal, and umbilical veins; and in most Reptiles, ex- cepting the Ophidia, the renal and portal vessels proceeding from the posterior parts of the body arise together. In some Reptiles the whole of the blood returning from the posterior parts of the body is divided between the portal veins of the liver, and the vena advehentes of the kidney ; in others a part is also sent into the abdominal vena cava. The inferior renal or advehent veins of the kidneys (Jigs. 316, 317, and 318, K) carry venous blood to these organs, and distribute it minutely through their substance. It is removed from thence and returned into the great circulation by the revehent or superior renal veins (k) which lead into the vena cava* The anterior abdominal vein (Jig. 316, u) is the same to which Bojanus has given the name of umbilical in the Tortoise, in which class of ani- mals it is of very large dimensions, and receives not only the venous blood from the posterior extremities and shell, but also some from the anterior extremities. The persistence of those umbilical veins which proceed from the large urinary bladder in many of the adult reptiles is a fact of some interest, because it points out a resemblance between the permanent distribu- tion of the vessels in these reptiles and the foetal condition which we find in the higher animals, and likens the bladder of the scaly Reptiles, as well as of the Batrachia in which during fatal life no allantoid membrane is ever formed, rather to an allantoid receptacle than to a proper urinary bladder. Fishes. — In fishes there is no vestige of a pulmonary organ, and the respiration is wholly effected by means of the gills. The branchial apparatus of fishes is internal or covered, like that of the larva of the frog ; it is placed on the cervical part of the alimentary canal, and is formed by the fine subdivisions of aortic arches (Jig. 319, A, B, b), which are prolonged into the fringed or leafy processes of the hyoid branchial arches. The respiratory organ is thus placed in this class in the course of the arterial circulation. The venous blood from the body generally, and from the liver, enters the single auricle (A) through the great sinus (V), and is wholly propelled into the arterial bulb by (A ) the single ventricular cavity ( H). No systemic arteries come from the aortic bulb, but this vessel carries by the arches into which it divides ( B), the whole of the venous blood into the gills. The number of these arches subdividing and ramifying in the gills varies in different fishes. In a few, as the Lophius, there are only three on each £ide. -In most osseous fishes there are four. In the Skates and Sharks there are five. In the Lampreys there is the greatest number known, namely, six or seven. The blood, after having undergone arteria- lization in the gills, is not returned to the heart, but proceeds directly through the branches of the aorta (Jig. 319'*, b b, A ) to different organs. The force of the heart acts therefore through the whole of the capillary system of the gills (be ), and continues to propel the arterialized blood * It must be remarked that Meckel, who appears to have examined the distribution of the above men- tioned vessels with great care, denies entirely the advehent function of the lower veins of the kidneys both in fishes and reptiles, considering all the veins of the kidney as revehent. Vergleich. Anat. B.V. S. 201 and 253. CIRCULATION. 647 Fig. 319. through the branches of the aorta (A) in the various parts of the systemic circulation. Dr. Marshall Hall* and J. Miillerf have observed a dilated contractile part of the caudal vein in the tail of the Eel, to which Dr. Hall has applied the name of caudal heart, which may assist in promoting the flow of blood in the caudal branches of the vena cava. The position and anatomical relation of the heart of fishes with the bloodvessels as well as other parts shew that it corresponds to the whole heart of higher animals, and that the arterial vessel which receives the whole of the fish’s blood from the ventricle may strictly be considered as the commencement of an aorta entirely destitute of any pul- monary branches. Although there is no dis- tinct right ventricle to propel the blood to a pulmonary organ, and the whole of the blood issuing from the heart is sent directly to the gills, there is not on this account any suf- ficient reason for considering, as some have done, the heart of the fish as corresponding to * Essay on the Circulation of the Blood, p. 170. Lond. 1B31. f Handbuch der Physiol, vol. i. the pulmonary or right cavities of the heart in warm-blooded animals, for we have seen that in some of the reptiles when they have gills, the blood is driven into these organs through the aorta or systemic trunk. The branchial arteries in fishes, as in reptiles, are therefore branches of the great aortic trunk, and the returning vessels on the posterior side of the arches, or branchial veins as they are called, are as much of an arterial nature both in their structure and relations as the anterior vessels or branchial arteries are. When these return- ing vessels unite together on the back to form the descending aorta, it is not necessary there- fore to suppose them to undergo a change from the venous to the arterial structure. So far then as general structure and relative position are concerned, the heart of the fish corres- ponds to the whole heart of warm-blooded animals, and not to one or other set of its cavities. Nor does the contemplation of its function or uses in the circulation induce us to modify this view, for it is manifest that the heart of the fish, as it serves to propel the blood through the gills into the vessels of the system, and as the branchial vessels may be considered as belonging to the aortic system, acts at once as a branchial and a systemic heart.* We have abstained from entering at this place into the detail of those remarkable changes formerly alluded to, which the circulatory and respiratory systems and the systemic and branchial or pulmonary circu- lations undergo during the development of the young of animals, although these afford the most direct proofs of the justness of the view now taken. Under the head of Ovum we shall have a more fitting opportunity of ex- plaining these fully. Suffice it for the present to say that the heart of the highest warm- blooded animals passes, during the progress of its development at different periods or stages, through the same general outline of various forms which that organ retains permanently in the adults of fishes or different reptiles ; and that the aortic arches and a semblance of a branchial apparatus connected with them is not confined to those animals which necessarily employ gills for a time as respiratory organs, but are to be found also in the foetus of the scaly reptiles, birds, and mammalia in the early stages of their existence. The ductus arteriosus, double in birds and single in mam- malia, is, we may remark, the last of those transitory structures which remains in the foetus. Portal circulation of fishes. — In fishes, as in reptiles, both the liver and kidneys have venous blood distributed to them by the sub- division within these organs of veins (L&Jf) from the abdominal viscera and posterior parts of the body. The vena portae of the liver consists generally of veins from the stomach, intestinal canal, spleen, pancreas, and some- times from the genital organs, swimming blad- * Blainville, Sur la Degradation du Coeur, &c. Bull, de la Soc. Philomathique, 1818-19, p. 148. G48 CIRCULATION. der, and tail. There is, however, considerable variety in regard to the distribution of the posterior abdominal veins in fishes; and com- parative anatomists do not appear as yet to have connected these varieties with any general view of their uses. In the Gadus the venous blood from the tail and middle of the ab- domen goes to the kidneys only by venae ad- vehentes. In the Silurus the blood of the posterior parts of the body is carried to both the kidneys and liver; and in the carp, pike, and perch, to the kidneys, liver, and vena cava at once. The blood from the testicle, ovary, swimming bladder, and kidneys, most frequently goes to the vena cava.* Course of the blood in Invertebrate Animals. — In investigating the course of the blood in animals destitute of a vertebral column and cerebro-spinal nervous system, we are no longer guided by any such analogies of form, posi- tion, and use, as those just attempted to be traced in the circulatory organs of the Ver- tebrata ; for each class of Invertebrate animals, as Mollusca, Articulata, and Zoophyta, and even their subordinate orders, differ so widely from one another in their organization, that we are at a loss to discover any general plan or type to which their circulatory organs may be referred. In all of the Invertebrate animals in which there is a regular progressive motion of the nutritive fluids, there exists also a central con- tractile organ to which the name of heart is applied, from its functional rather than struc- tural analogy to the central propelling organ of the circulation in Vertebrate animals; and in many of them, the outgoing and returning vessels in which the circulation is performed may be distinguished into arteries and veins, by a difference of structure as well as of office. From the same kind of analogy, the name of auricle is given to the weaker part of the heart of Invertebrate animals, which serves to re- ceive the returning blood from the veins, when such a cavity exists, and we call ventricle the stronger and more muscular part which propels the blood into the arteries. The general form of these parts, however, and their position relatively to the other systems, render it ex- tremely difficult, if not altogether impossible, to trace any strict anatomical correspondence between the heart and bloodvessels of Verte- brate and Invertebrate animals. In the Inver- tebrate animals, the heart and principal artery are generally placed on the upper part of the body, above the alimentary canal and largest ortions of the nervous system ; while in all 7ertebrate animals the order is reversed, the brain and spinal marrow being above, the heart below the alimentary canal. In the Invertebrata, as in the higher animals, the respiratory change of the blood is the most important function to which its course or cir- culation bears a constant relation. In the Vertebrata the blood flows from the heart to * See the papers of Jacobson and Nicolai al- ready referred to, and the extended Researches of Rathke, Meckel’s Archiv, 1826, and Annal. des Sciences Nat. tom. ix. the respiratory organ, while in the Invertebrata the blood very generally arrives at the heart after having passed through the respiratory organ, and is propelled from the heart into the systemic circulation : the vessels, therefore, in which respiration is effected in the lower ani- mals may be considered as belonging in ge- neral to the venous circulation only, while in the higher classes of animals, arteries alone, or arteries and veins together, conduct the blood through the respiratory organ. Another remarkable difference between the circulation of the nutritive fluids in Vertebrated animals and that in the Invertebrate classes consists in this, that in the first the digested food or chyle and the lymph are taken up by a system of vessels distinct from those circulating blood, and are poured into the venous circulation at one or more determinate places; while in the latter animals, the bloodvessels, so far at least as we yet know, perform the office of lacteal and lymphatic absorbent vessels as well as of circulatory organs. In the Invertebrate animals also, there is no vena portae, as in the Vertebrata, and the liver is supplied with blood only by a hepatic artery. In investigating the structure of the circu- latory organs in different classes of Inverte- brate animals, we at once perceive that no accurate correspondence can be traced between the varieties of their forms and the places assigned to the animals in a Zoological arrange- ment; for we find among the Mollusca some tribes having a highly developed and compli- cated circulatory apparatus, and others with heart and bloodvessels comparatively simply organized. The same discrepancy occurs among the Crustacea, Annelida, and Insects; and among the Entozoa and some other tribes of Zoophytes, while some possess a simple circulatory apparatus, in others we are not able to discover any vestige of a vascular system. There is a considerable number of the lower animals in which no vascular system has yet been discovered, and in which the nutritious juices are supposed to pass from the alimentary cavity by interstitial transudation through all the parts of their bodies. The circulation has, how- ever, been recently shewn to exist in animals formerly believed to be without it, and the farther progress of Comparative Anatomy may diminish still more the number of animals believed to be destitute of circulating organs : in the present state of our knowledge, it is therefore as difficult to say with certainty in what animals this function is deficient, as it is to fix in which it is of the most simple or most complicated kind. Mollusca. — The greater number of the Mol- lusca live in water and breathe by means of gills, but many aquatic Mollusca, possessing a branchial apparatus, appear to have their blood aerated in other parts of the body also. There is a strong muscular heart in all the ani- mals belonging to this class, which when single is always systemic, (figs. 320,321, and 322, H .) In the Cephalopoda, besides the aortic or sys- temic heart, which has only one cavity or ventricle, each vessel (fig. 320, B) leading to CIRCULATION. 649 Fig. 320. the gills has a dilated contractile portion (B*), which dilatations may be considered as bran- chial hearts, so that there are three separate contractile portions of the circulatory system. In the Gasteropoda and Pteropoda, there is only one heart. This organ is strong and mus- cular, provided with valves, and consisting of an auricular and a ventricular cavity (Jigs. 321 and 322, h, JET). In the Testaceous Acephala, the heart is nearly of the same structure as in the orders just mentioned, but less fully deve- loped. In most of them, as also in the Gas- teropodous Mollusca, the rectum passes through the ventricle. The auricle is occasionally double. The Brachiopoda have two aortic hearts, but of a very simple structure, not being divided into auricular and ventricular portions. The naked Acephala, such as the Ascidiae, have the simplest heart of all the Mollusca, consisting of a thin membranous ventricle apparently without valves. In all these animals, the course of the blood is generally considered to be the following: Arterial blood only passes through the systemic or aortic heart (or hearts where this organ is double), and is carried to the system by the branches of the systemic arteries (A, a). The von. r. altered blood, returning in the veins of the system, is collected into one or more trunks ( V), and carried in the subdivided branches of these (Jig. 321, fig. 322, B) to the re- Fig. 321. Fig. 322. spiratory organ, which consists of branchial plates or fringes in the greater number, but in some of the Gasteropoda, as in the Garden- Snail, of pulmonary sacs. In most cases, the whole of the blood returning from the system passes through the respiratory organ. In others, especially in some Bivalves, the vena cava or systemic veins send branches directly to the auricle as well as to the gills. In the compound Ascidi®, Mr. Lister* has recently discovered one of the most remarkable modifications of the circulation with which we * Philos. Trans. 1834, p. 378. 2 u 050 CIRCULATION. are acquainted. Mr. Lister finds that the dif- ferent Ascidiae of a branched animal are not only connected together by the polypiferous stem, but have a common circulation. In each indi- vidual there is a heart consisting of one cavity only, and pulsating about thirty or forty times in a minute. In the common stem, the mo- tion of the globules of the blood indicates distinctly two currents running in opposite directions. One of the currents enters the Ascidia by its peduncle and proceeds directly to the heart ; the blood issuing from the heart is propelled into the gills as well as the system at once, and upon its return from thence the returning current proceeds out of the animal by its peduncle again into the common stem, whence it goes to circulate through another of the ascidiae attached to the stem. The direc- tions of the currents appeared to be reversed every two minutes or less. According to Mr. Lister, when one of the ascidiae is separated from the common stem, its circulation goes on in an independent manner; the blood return- ing from the body being conducted into the heart, but the alternation of the directions still continues, — a circumstance which points out an important difference between the compound and the simple ascidiae, in which last the cir- culating fluid is generally believed to pass from the gills into the heart, and to hold continually the same direction. Articulata. — In this class of animals, varied as the forms of the circulatory organs appear, the position of their principal parts is much more constant than in the Molluscous animals. In some, as the Decapodous Crus- tacea, there is a short and thick muscular heart connected with the systemic arteries. In others, the contractile part of the vascular system is much more like a dilated artery than a circumscribed heart, as occurs in some other Crustacea, spiders, and insects ; and in the Annelida the greater part of the large vessels seem to be endowed with a contractile power by which they propel the blood. Annelida. — Although the Annelida form the highest division of the class Articulata in the arrangement of Cuvier, their circulatory organs may for the most part be regarded as more simple than those of most of the others. The circulation is best known in the Naides, the Leech, Earthworm, avid Sandworm. In all of these, the blood, which is generally red, moves gradually forwards in the vessels situated on the upper surface of the animal, and backwards in the vessels placed below or on the abdomi- nal side. There are also numerous cross vessels which transmit the blood from one side to another, or from above downwards, or from be- low upwards, in each of the compartments or joints of the animal. The upper vessels, being generally the most contractile, are considered as the arteries; the lower vessels as veins.* The organs of circulation appear to be sim- plest in the Naides. In these animals, the contractile part or heart is represented by an artery above. This vessel turns round at the * See the article Annelida, p. 169. head into the vein which is below. The artery sends its blood partly into the gills, placed along the whole length of the body, from which it again receives the returning blood, and by numerous lateral branches, which may be re- garded as the only capillary vessels, it sends blood across the body of the animal into the vein. The motion of the blood appears to be partly progressive and partly oscillatory. Lumbricus.— In the common earthworm, there are two principal vessels, the one (Jig. 323, a,) placed above and the other (v) below, and extending the whole length of the body ; these two principal ves- sels communicate together by very numerous small cross branches (c), and, in the neigh- bourhood of the ovaries, by from five to eight very remarkable neck- lace-shaped or moniliform ves- sels (h, H ). At the place of junc- tion of these mo- niliform vessels with the lower longitudinal one, there are small di- latations of that vessel, which are believed to aid in propelling the blood by their con- tractions. There are also three other longitudinal ves- sels, much smaller than the principal or median ones, which join with the cross anas- tomosing twigs. The upper principal vessel pulsates in an un- dulatory manner, the contraction taking place first at the posterior part, and proceeding gra- dually forwards. In these animals, however, the course of the blood does not appear to be very well known. It is believed to be from behind forwards in the upper vessel and from before backwards in the lower, but there must be also lateral motion. Both the upper and lower vessels are said to give off pulmonary branches. Arenicola — In the sandworms also, besides the principal upper and lower vessels, there are two smaller ones, placed one on each side of the abdominal nervous cord, and two others upon the intestine ; between these there is a very minute net-work of smaller branches. The branchial arteries are derived from the upper longitudinal vessel, the branchial veins lead into the lower. The greater part of the blood proceeds from the' upper vessel into the gills by the branchial arte- Fig. 323. CIRCULATION. 651 ries ; by the branchial veins it gains the lower vessel. This vessel may be regarded as the systemic artery, and sends the arterial blood, by the numerous anastomosing branches, up- wards across the intestine, and through the other parts into the upper vessel. The upper vessel communicates also with the lower ante- riorly by the lateral dilatations named auricles, which are supposed to furnish some blood to the upper vessel. A part of the blood at the anterior extremity of the lower vessel is said to be propelled into the two subordinate vessels placed along the sides of the nervous cord. In this course which the blood is stated to follow, it does not appear to be known whether its motion is of a regular progressive kind or only undulatory. Leech. — Tn the leech the principal and most highly contractile longitudinal vessels are placed one on each side (fig. 324, a, a), and there are also two lesser longitu- Fig. 324. dinal vessels, one supe- rior and the other inferior (a*), all which commu- nicate freely together by small cross branches along the whole body (c). It is remarkable that the lower median vessel (a*) incloses the ganglionic nervous cord, so as to bathe it with blood. Both pulmonary arteries and veins are branches of the lateral ves- sels ; a capillary network between them distributing the blood minutely over the pulmonary sacs or vesicles. The pulmonary veins form very remarkable dilated and coiled por- tions, which seem to be endowed with a high de- gree of contractility. Ac- cording to J. Muller, for a certain number of pul- sations, the middle and the lateral vessel of one side contract together, and pro- pel the blood into the lateral vessel on the other 4|l ]t|k side, and then the order ' is reversed, and the middle Erpobdella or Leech. vessel acts along with the lateral vessel of the other side, so that one lateral vessel is always dilated while the median and opposite lateral ones are contracted, and vice versa. According to some there is thus only an alternate motion of the blood from one side to the other, while others believe that there is at the same time a gradual progressive motion of the blood for- wards in the upper vessel and backwards in the lower one.* The course of the blood in the principal * See a full account of most of the opinions of observers on this subject, as well as original obser- vations by Rudolf Wagner, in the Isis for 1832, p. 643. parts of the circulatory organs is nearly the same in the rest of the Articulata, viz. Crustacea, Arachnida,and Insects, as in Annelida. In all of them the central propelling organ, whether in the form of a heart or consisting only of a dilated arterial vessel, such as the dorsal vessel of in- sects, is situated on the upper surface of the animal, above the alimentary canal, while the returning vessels are situated on the lower sur- face of the body, on each side of the nervous ganglionic cord. The respiratory circulation, when occurring in a distinct set of vessels, forms a part of the venous system, and the heart, which has no auricle, is systemic or aortic. Insects. — All perfect Insects, whether inha- bitants of air or water, breathe air alone. In these animals there is not a separate and dis- tinct respiratory organ in one part of the body only, but the atmospheric air is carried by minute elastic and tough tubes ramified to an infinite degree of minuteness into every part of their body. The dorsal vessel of insects forms a long and wide contractile artery, larger in general behind than before, in which the contractions begin at the posterior extremity, and proceed gradually forwards with an undulatory motion. In the greater number of perfect insects, we are not acquainted with any other vessels or passages in the body, through which the blood moves, and this fluid seems in these insects to oscillate backwards and forwards in the dorsal vessel alone. This state of the circulation in insects, according to the ingenious views of Cuvier, is related to the distribution of the respiratory organ over the whole body, in consequence of which the air is brought in contact with the more perfect blood contained in the dorsal vessel, and the nutritious fluids supposed to pervade interstitially the rest of the body. The recent discovery by Carus of a continuous cir- culation of the blood through arteries and veins in a few of the perfect insects, and more espe- cially in some larva, must modify the above views, which, ingenious as they must appear to all, do not account so satisfactorily for the ab- sence of a systemic as for the want of a pulmo- nary circulation. The circulation of the blood of Insects may be most easily seen in the aquatic larvae of Neuropterous Insects, as the Agrion, Ephemera, Semblis, and Libellula,* in which it was first discovered. In these larvae it may be described generally as follows. The dorsal vessel (fig. 325, H) is connected anteriorly and posteriorly by several branches with the inferior or returning vessels ( v , v), which, running along the whole body, receive the blood from the anterior extremity, and carry it into the posterior extremity of the dorsal vessel. The antennae and first joint of the legs, as well as the fin-shaped caudal pro- cesses, receive each a loop of vessel from the abdominal current; and from the motion of the globules in these transparent parts, the circula- tion can be more easily seen in them than in * We have ourselves seen the circulation in the larvae of two Neuropterous Insects. 2 u 2 652 CIRCULATION. Fig. 325. any other parts (fig. 325 *«, a, v). A net- work of vessels is also distributed over the surface of the imperfectly formed wings. As the metamorphosis from the larval to the perfect state advances, and shortly after the insect leaves the water to assume the aerial condition, the circulation of the blood be- comes gradually confined to a more and more circumscribed space. The loops extend- ing into the wings, limbs, caudal processes, and antennae, become shorter ; when the meta- morphosis is complete, they become entirely closed, and in general this change is followed by the disappearance of the inferior lateral or returning currents also. These remarkable changes in the circulatory organs at once indi- cate an interesting relation of their condition to the changes in the mode of life of the insect. In the aquatic state, the caudal and lateral laminas, antennae, and wings may be considered as serving the purposes of gills, for the blood is carried to them, and exposed upon their surfaces to the action of the water. The larvae of the neuropterous insects generally feed largely, but their life during the perfect condi- tion, when the circulation has ceased, is of short duration, and they either take very little food, or live in absolute abstinence. It has been also shewn that the dorsal vessel consists of different compartments, between each of which a valvular apparatus (fig. 325*, ,r) prevents the passage ot the blood in a retrograde direction. 1 here are lateral openings in the neighbourhood of the valves, by which it would appear that the blood is admitted into the dorsal vessel from cross branches (Jig- 325 **, y) passing directly from the lateral streams. It may be mentioned that the larger returning streams of blood, situ- ated on the lower side of the body, are said by Cams and Wagner, we cannot judge with what reason, not to be inclosed within vascular pa- rietes, but to run loose in the texture of the insect A complete circulation is not, how- ever, confined to the larvae of insects, having been discovered by Cams and others in some of the perfect insects. Caras saw it in the wings of the Semblis developed for flight. The circulation has also been seen by Cams in the larvae of Water-beetles, Hydrophilus, and Dy- tiscus, and by Ehrenberg and Hemprich in the Mantis, so that the circulation has now been discovered in insects belonging to four orders, viz. Coleoptera, Diptera, Orthoptera, and Neu- roptera. Crustacea.- — -In the Slomapoda, Isopoda,and Branchiopoda, or in the Squill, Oniscus, and Monoculus or Daphnia, the circulation is ge- nerally described as being of the same simple kind as that just stated to occur in the larva of insects, with this exception, that the blood is carried to gills for the purpose of undergoing a respiratory change. In most of them the venous blood which is sent to the gills comes directly from the systemic veins. From the description given by Gruithuisen of the circu- lation in the Daphnia,* it would appear, if his observations are correct, that the venous blood is sent to the heart before going to the gills, — a distribution very dissimilar from that which exists in the rest of the articulated animals. In this animal, Gruithuisen also describes an au- ricle and ventricle in the heart. The investigations of Messrs. Audouin and Milne Edwards have pointed out very clearly the structure of the circulatory organs and the course of the blood in the larger Decapodous and some other Crustacea. The aortic heart (Jig. 326, H ), consisting of a single ventricular cavity, and situated below the posterior margin of the thoracic shield, gives off six systemic arteries (A, a), which convey the arterial blood to the various organs of the body and to the liver (l*). The venous blood, returning thence in the systemic veins ( v , v ), is collected on the lower surface of the body into sinuses ( V, V), from which the branchial arteries ( B ) take their origin ; the branchial veins (6) return the blood which has passed through the gills to the heart. Arachnida. — In those of the Arachnida in which the respiratory organ consists of tracheae like that of insects, the circulation has been supposed to be much the same as in these latter animals. The dorsal vessel, however, approaches to the form of a heart posteriorly, being there more dilated at one part than in the rest of its course, and considerable lateral vessels are known to be given off from it upon either side. In others of the spiders, in which the respiratory organ consists of pulmonary ca- vities admitting air, it is conjectured that the blood is distributed on the surface of the plates * Nova Acta Nat. Cur. xiv. p. 404. CIRCULATION. 653 Fig. 326. within these sacs, as upon the gills or lungs of other animals, but the exact course of the blood does not appear as yet to have been satisfacto- rily ascertained in these animals. Audouin* believes it to be essentially the same as in the Crustacea. The long-shaped dorsal vessel or heart gives off arteries to both sides, and re- ceives at one place branches from the gills. The veins form only spaces or sinuses, and not vessels on the abdominal side of the animal. The blood propelled from the artery is passed through the system, returning from which, it is collected into the venous sinuses below, thence it proceeds to the pulmonary organs, and after passing through them, returns to the heart. Zoophytes. — The general character of the circulation in this class is exceedingly ob- scure ; for while in some of the animals be- longing to it, comparative anatomists have not succeeded as- yet in pointing out any distinct vascular system ; in others, they have been at a loss to determine, among various vascular or- gans, which of them forms the proper circula- tory system corresponding with that of higher animals. Echinodermata. — Among the Zoophytes the * See the article Arachnida, p. 206. Echinodermata present the most fully deve- loped vascular system with which we are ac- quainted. According to the observations of Tiedemann and Delle Chiaje, who have inves- tigated the structure of these animals with great success, there are two principal divisions of the vascular system, described by the first of the above-mentioned authors as distinct from one another, by the other as communicating toge- ther. We do not feel inclined to consider, in ac- cordance with the view of these authors, that series of cavities which is employed in loco- motion as a part of the nutritive circulatory organs. That part of the vascular system of these animals again, which is situated in the neigh- bourhood of the alimentary canal, very proba- bly corresponds with the circulatory organs which we have been describing in other ani- mals ; since arteries and veins can be distin- guished in it, and there is good reason to be- lieve that a circulation of fluid takes place through its vessels in all the kinds of Echino- dermatous animals. In the Ilolothuria, the principal artery or heart is connected with a ring situated round the commencement of the alimentary canal, from which the systemic arteries are given off : the systemic veins send branches to the gills, and the returning vessels from these organs transmit the circulating fluid through one large trunk into the heart. The intestinal vascular system of the Asterias and Echinus is somewhat similar to that of the Ilolothuria, consisting of annular vessels, from which arteries and veins are given off, and con- nected with a dilated contractile canal, consi- dered as a heart. P lanaria. — Next to the Echinodermata in respect of the degree of perfection of their cir- culatory organs, may be mentioned the Plana- ria?, in which M. Duges* has pointed out a very remarkable system of vessels which ap- pear to constitute circulatory organs (fig. 327, a, a). For some time previously to the disco- very of these vessels, the sin- gularly branched intestinal ca &c. Annal. d. Sc. Nat. xi. p. 113. Borelli, De motu animalium, 1743. Passavant ( Bernouilli ), De vi cordis, 1748. Hales’s Statical essays, vol. ii. 1733. Poiseuille , Sur la force du coeur aortique, Breschet’s Repert. vi. 1828, and Ma- gendie’s Journ. Whytt on the heart. Works, p. 16. Williams on the motive powers of the heart, Edin. Med. and Surg. Journ. xxi. 268. Bartholin on the suction-power of the heart, Anat. 8 vo. p. 371. Senac, Traite du coeu* , 1749. Wil- degans on the same, 1772. A. Wilson , Inquiry into the moving powers employed in the circulation of the blood, 8vo. Lond. 1774. Jurin. De po- tentia cordis, Phil. Trans. 1718 and 1719. James Keill, Essays on several parts of the animal economy, 4th ed. with a Diss. on the force of the heart, 8vo. Lond. 1738. Prochaska, Opera Min. 1800, Controv. physiol. Arteries. — In addition to the works referred to CIRRIIOPODA. 683 in the Bibliography of ARTERY', the following are deserving of notice : — Thomson's Lect. on Inflam- mation. Roulin on variations of the pulse at different heights, Magendie’s Journ. Jan. 1826. Poiseuille on the contractility of arteries, Magendie's Journ. vol. viii. On the dilatation of arteries, ibid, vol. ix. 44. Weber, H. E. De pulsu in om- nibus arteriis plane non s> nchronico, Annotat. Academ. 1835. Mich, Jager, Tract, anat. physiol, de arteriaruin pulsu, Wirceb. 1820. Reinarz , Diss. de arteriarum irritabilitate propria, Bonnae, 1821. Kramp , De vi vitali arteriarum, Argentor. 1786. Veins, arul connection of respiration with circu- lation.— James Carson , Inquiry into the causes of the motion of the blood, Liverpool, 1815. On the empty state of the arteries after death, Med. Chir. Trans, xi. Sir D. Barry, Experimental researches on the influence of atmospheric pressure on the flow of blood in the veins and on absorption, Lond. 1826. On the application of the barometer to the study of the circulation, Annal. d. Sc. Nat. x. Cams, Remarks on the above theories, Meckel's Archiv. iv. 1818, p. 413. Ellerby, Davies, and Serle, Lancet, xi. p. 606, &c. Poiseuille , in Ma- gendie's Journal, x. Arnott's Physics. H. Marx, Diatribe anat. phys. de structura et vita venarum, Carlsruh. 1819. Refutation of the theories of Carson and Barry, Edin. Journ. of Med. Sc. ii. 462. Wedemeyer on the same, Edin. Med. and Surg. Journ. xxxii. p. 86. Macfadyen on the cir- culation, in same work, xxii. 271. Wilson Philip on the effect of derivation in promoting the flow of blood in the heart. Inquiry, p. 9, See. Lugeiibuhler , De motu sanguinis per venas, 1815. J. W. Tur- ner's Remarks on the same subject, Med. Chirurg. Trans, of Edin. vol. iii. Magendie, Influence of Respiration on the motion of the blood in the arteries. Journal, t. i. Bourdon, Rech. sur le mecanisme de la respiration et sur la circulation du sang, Paris, 1820. Defermon on the mutual dependence of respiration and circulation, Ann. d. Sc. Nat. xiii. 425. Hales on the force of the blood in the veins, Med. Statics, vol. ii. p. 27 & 31. Flourens, Sur la force de contraction des prin- cipals veines de la Grenouille, Ann. d. Sc. Nat. xxviii. 65. Nic. Oudemann, De venarum, prascipue mesaraicarum fabrica et actione, Groning. 1794. Kellie on the circulation in the head, Edin. Med. Chirurg. Trans, vol.i. Carson on the same, Edin. Med. and Surg. Journ. vol. xxi. p. 252. Capillaries and small vessels. — Doellinger, Munich Transactions, vol. vii. and Journal des Progres. Do. Was is Absonderung, &c. ? Wiirtzburg, 1819. Gruithuysen, Beitrage zur Phvsiognosie und Eau- tognosie, &c. Munchen, 1812. Organozoonomie, Sec. Miinchen, 1811. Kaltenbrunner, Experimenta circa statum sanguinis in inflammatione, Stutt. 1826. Leuret, on the same. Journal des Progres. Whytt on the circulation in the small vessels. Works, p. 211. Schultz, Journal Complement, vol. 19; also Der Lebensprocess im Blute, Sec. Berlin, 1822. R. Wagner, Zur Vergleich. Phy- siologie des Blutes, Leipzig, 1833. Baumgartner , Beobacht. iiber die Nerven und das Blut, Sec. Freiburg. 1833. Oesterreicher, Versuch einer Dar- stellung der Lehre des Kreislaufs. Nurnberg. 1830. Marshall Hall . Essay on the circulation of the blood, 8vo. Lond. 1831. J. Muller, capill. circul. in the liver of the Salamander, Meckel's Archiv, xvi. 1829, p. 182. Wedemeyer, Additions to his work, Meckel's Archiv, 1828, p. 337. J. W. Earle on the irritability of the small vessels, Med. Gaz. 1834-35, No. 29, p. 70. Kaltenbrunner , Magendie's Journ. viii. John Evelyn on the passage of blood from arteries to veins in quadrupeds, Phil. Trans, xxiii. 1702, p. 1177. Molyneux in another volume of the same. Jas. Black , Essay on the capillary circulation, London, 1825. Alison's Outlines of Physiol. Appendix to 2nd edition, 1836. Hunter on the blood and inflammation. Thomson's Lec- tures on inflammation, Edin. 1813. Burns on inflammation. Gendrin, Hist. anat. des inflam- mations, Paris, 1825. Reuss , Electrical theory of the capill. circulation, Edin. Med. and Surg. Journ. Meyen , De primis vitte phasnom. et de circulatione sanguinis in parenchymate, Berol. 1826. Kruger, Diss. de theoriae physical tubulorum capillar, ad corp. human, applicatione, Halas Magd. 1742. Infuence of the nerves on the circidation. — Trevi- ranus, Vermischte schriften, i. p. 99. Home , Philos. Trans. 1814. Flourens , Action of the spi- nal marrow on the circulation, Ann. d. Sc. Nat. viii. 271. Krimer , Physiolog. Untersuchungen. Leipzig. 1820. Legallo'is, Exper. sur le principe de la vie, Paris, i 812. W. Philip, Laws of the vital functions. Clift on the heart, Philos. Trans. Bracket, Exper. sur les fonrrions des nerfs sym- pathiqnes, Paris. Milne Edwards 8f Vavasseur , Ann. d. Sc. Nat. vol. ix. p.329. Influence of the cervical ganglia and their nerves on the action of the heart. ( Allen Thomson.) CIRRIIOPODA; Cirripedia ; Cirripeds ; (y-iggog and n rove;, cirrus and pes, from the curl- like form which the coiled feet or arms present. Fr. Cirripedes. Ger. Rankenfuesser .) A class of invertebrate animals, composed chiefly of the barnacles and acorn-shells. They are re- lated in some points of structure with the annu- lated or diploneurose animals, particularly with Crustacea ; in other points they resemble Ace- phala (Conchifera). All are marine and fixed. The soft parts are, for the most part, encased in a multivalve shell. The body is somewhat conical in form, tumid, and bent inwards at the oral extremity, tapering towards the oppo- site extremity, where it terminates in a long pointed tube. Placed along the abdominal surface, there are two rows of fleshy lobes, (six on either side,) each having two long horny processes, jointed and ciliated. In some species, these constitute the chief bulk of the whole animal. The head is indistinctly de- fined, and has neither eyes nor tentacles; mouth with lips, and three pairs of horny jaws ; anus at the base of the tubular process. Respiration is effected by branchiae, which, in some species, are filamentary, in others foli- ated. Mantle membranous, sacculated, pro- vided with a slit-like opening for the passage of the arms, &c. Between each two pairs of arms, the abdominal surface is marked by six slight depressions, which may be regarded as an approach towards complete articulation. The animals thus characterized have had dif- ferent places assigned to them in the various systematic arrangements of modem zoologists. Cuvier formed of them the sixth and last class of his Mollusca. Lamarck was at one period inclined to place them amongst the Crustacea, but latterly he constituted for them a distinct class, and placed it between Annelida and Conchifera; still, however, regarding them as more closely allied to Crustacea than to any other class; u for,” as he remarked, u they have the nervous system of Crustacea, they have jaws analogous to those of the animals of that class, and their tentacle-like arms resemble the antennas of the lobsters.”* Bur- * An. sans Vertebres, v. 377. 2 y 2 684 CIltRHOPODA. meister also places them amongst the Crus- tacea. De Blainville arranges them, under the name of Nematopoda, as a class of his subtype of the Mollusca — Mollusc-articulata ; the other class of the subtype being formed of the Chitons (Polyplakiphora). He regards them as Crustaceous Mollusca, but admits that they seem to form a transition group uniting the Crustacea with the Annelida. M. St. Ange,* however, would rather class them with the Annelida, on account of the closer resemblance which the arrangement of their nervous system bears to that of these animals. Professor Wagner does not doubt that they are really articulated animals, but he would rather place them in a distinct class between the Mollusca and Articulata. Setting aside their nervous system, M. Serres sees, in the other parts of their structure, points enough to in- duce him to arrange them with the Mollusca. The same views are entertained by Wiegmann, Coldfuss, and others. Dr. Leach regarded them as truly annulose animals. Dr. Grant (who calls them “ entomoid animals enclosed in shells”) places them amongst the Articulata, or diploneurose animals, between Rotifera and Annelida, making of them a distinct class, but admitting their great resemblance in many points to the entomostracous Crustacea. Mr. J. V. Thompson (whose admirable researches on the development of the Cirripeds have thrown a new interest around them) holds it as proved by his observations that the Cirripeds do not constitute a distinct class; but that they are naturally and closely connected, on the one hand, with the Decapod Crustacea, through the Balanids, and, on the other, with the Entomostraca, through the Lepads ; further, that they have no relation with the Testacea. All the known Cirripeds may be naturally grouped into two families, one pedunculated, the other sessile. The former includes all the barnacles, properly so called ; the latter, the acorn-shells. The barnacle family have had the name of Campylosomata applied to them by Dr. Leach, who calls the other family Acamtosomata : but we shall use De Blain- ville’s synonyms of Lepadicea and Balanidea. The following are the names of the genera generally used at present : — I. Lepadicea. 1. Otion. 2. Cineras. 3. Anatifa. 4. Pollicipes. 5. Scalpellum. II. Balanidea. 1. Balanus. 2. Ochthosia. 3. Conia. 4. Creusia. 5 Clrsia. 6. Pyrgoma. 7. Acasta. 8. Coronula. 9. Tubiei- nella. 10. Chelonobia. External coverings and organs of support. — There are three principal modifications of the tegumentary organs in this class. The first is that seen in Anatifa, in which it assumes the form of calcareous plates, united by horny ligament, and attached to a cartilaginous pe- duncle. The second form is that common to all the Balanids — a calcareous cone, composed of separable pieces, sessile, and provided with * Mem. sar !es Cirripedes. Paris, 1835. an opercule of shelly plates. The third form is a general cartilaginous covering, sometimes strengthened by small calcareous plates. The shells of the Cirripeds are similar in general appearance to those of many Acepha- lous Mollusca. They are most fully developed in Anatifa, which has five separate plates, four placed laterally in pairs, and one median. One pair is conside- rably larger than the other (c. Jig. 332) ; it covers all the anterior part of the animal, and the greater part of the internal organs. The bases of these shells are attached to the car- tilaginous peduncle ; the lower halves of their anterior edges form part of the mar- gin of the slit-like opening through which the arms are protruded (f,g, fig. 332). The inferior pair of shells (d) are of a triangular form ; the smallest side completes the margin of the brachial ori- fice ; another side is united by ligament to the upper valve ; the third is connected with its fellow by the common intervalvular ligament. The median piece (e) covers the dorsal aspect of the animal. It has an elongated lanceolate shape, curved and grooved internally. Its upper point only is inserted into the peduncle. Its margins are imbedded in the intervalvular ligament. This piece may be compared to the unpaired valve of the shell of Pholas : it oc- cupies nearly the same situation. The surface of these shells is generally denuded of epi- dermis, excepting just around their margins. All three are strongly and regularly marked with lines of growth, from which it is seen that the two pairs of lateral valves increase in size, chiefly, by additions to their margins, which look towards one another ; so that the parts first formed are, in the adult animal, re- moved to the greatest possible distance from one another. In the upper valve, the umbo or centre of growth is situated in the anterior- superior angle, close to the termination of the peduncle ; in the lower, it is situated in the anterior-inferior angle; and in the dorsal valve, in the point next to the peduncle. All the shells are thin, diaphanous, of nearly the same thickness throughout, yet much less fragile than shells of Acephalous Mollusca which otherwise resemble them. It has been re- marked by Burmeister that the shells of Cir- ripeds resemble those of crustaceous animals more than those of Molluscs : to us it appears that they have a greater degree of density, and a more compact crystalline structure than are commonly met with in Crabs ; and that their well-marked lines of growth give them a closer resemblance to shells of acephalous mollusca. In some genera, as Pollicipes, in addition to Fig. 332. CIRRHOPODA. 685 the five valves just described, there are other eight smaller calcareous plates arranged around the junction of the peduncle with the shells. The shells of the Balanids present several striking peculiarities of structure, and, in their mode of growth, offer to the physiologist an interesting subject for investigation. They form truncated cones, the bases of which, without the intervention of peduncles, are fixed to rocks, floating wood, integuments of marine animals, &c. These cones are composed of several pieces, closely cemented together so as to admit of no motion between them, excepting during the process of enlargement of the shell. In the common acorn-shells (Jig- 333), which cover our litto- Fig. 333. ral rocks and the bottoms of ships, there are seven of these pieces, six form- ing the walls, and one dis- coid, forming the base. The outer surface of the parietal valves is mark- ed by the lines a of growth in such a manner as to give it the appearance of being com- posed of twelve pieces. These may be termed compartments. They are all conical. Six of them have their bases applied to the common base of the shell, and the other six are inserted between these, with their apices towards the common base. The first six we shall refer to under the name of th ejirst series of compart- ments (a, a, Jig. 333) ; the other six constitute the second series (b, b, Jig. 333). The opening in the summit of the cone is closed by an opercule composed of four shelly pieces so arranged as to leave a longitudinal fissure be- tween them, through which the arms are pro- truded (c, Jig. 333). The two series of com- partments differ much from one another in their external aspect, owing to the differences in the directions and appearances of the lines of growth. The second series have a smoother surface, and are marked with very delicate lines, both longitudinal and transverse; they are also less prominent than the first series. The lines on the first series are chiefly trans- verse, and correspond with the outline of the base. On the internal surface of the walls there are six deep grooves, in the bottoms of which are seen the openings into certain cham- bers, constituting a sort of diploe of the valves, hereafter to be described. These grooves run from the summit to the base of the shell, and are the internal edges of the sutures of the six parietal valves. Around the internal margin of the common base there is a series of holes opening into certain tubes that terminate on the outer margin of the shell. When all the valves are separated at the sutures, it is found that each of four of the six compartments of the first series, as they appear externally, has attached to its dorsal margin one of the second series, and that the union between these two is exceedingly intimate, in fact that they form one piece, notwithstanding their apparent division externally. Two of the second series of compartments are attached to the anterior valve, while the dorsal valve has none. The anteal margins of the lateral valves and both margins of the dorsal valve are marked by transverse depressions corresponding to the numerous partitions of the chambered com- partments which are fitted into them ; and, externally, each has a projecting margin. To the upper part of the inner surface of each valve there is attached a laminated process, form- ing part of a circle of calcareous plates which gives support to some parts of the mantle. The internal structure of these shells pre- sents some peculiar features. They all contain numerous tubes and cavities, regularly ar- ranged, and forming a sort of diploe. The suture-holes mentioned above open each into a separate canal, chamber, or tube. Those which occur in rows on the walls of the cone lead to small chambers within the second series of compartments, running parallel with the general base, and separated from one another by delicately-formed partitions, each of whicli is deeply grooved on both sides. The par- titions are placed at equal distances, and their grooves are most regularly formed. The whole presents one of the most beautiful and delicate pieces of structure with which we are ac- quainted in the whole range of extravascular skeletons. These are from thirteen to fifteen on either side of each partition. Fig. 334 repre- sents a perpendicular section of a few of these grooved par- titions considerably magnified. Fig. 335 represents a horizontal section of one of the six valves. The holes forming the sutures are at a. The grooved floor of one of the chambers of the piece is be- Fig. 335. tween a, d, and c. d, c is the outer e wall of the compartment of the se- cond series, a, b is a section of that part of the valve which appears outside as a compart- ment of the first series. Its diploe is com- posed of tubes, running from the apex to the base, gradually enlarging below. Horizontal sections of those tubes shew them to be of an ovate form, tapering inwardly (Jig. 336). They are placed nearer Fig. 336. the outer wall than the inner. The spaces intervening between the taper- ing sides of the tubes are marked with lines of growth, shew- ing a gradual filling up of the tubes from within outwards ; and also the previous ex- istence of furrows or grooves on the surfaces of the partitions between the tubes. These Fig. 334. 686 CIRRHOPODA. grooves are very strongly marked in some spe- cies, as in Balanus Spinosus (Jig- 337), where the tubes are large, and Fig. 337. the walls comparatively thin. In all they run in atsgy straight diverging lines from the apices of the compartments to their bases. There they open close to the margin of the general base. In most species, however, their orifices are, in part, filled up by an extension of the base (a, fig. 338). In some small species, the tubes of which are wider than those of larger ones, there is hardly any opening discoverable externally, or at most a very narrow fissure just around the margin. Very near their terminations on the mar- gin, these tubes of the diploe are joined by the very short canals which proceed from the inner circumference of the base (6, fig. 338), and it is at their junction that the grooves in the walls of the partitions are most obvious. These two sets of tubes communicate freely all around the margin with the diploe of the base. All the Balanids — with the exception of the Coronules — have calcareous bases. The struc- ture of the base differs from that of the walls in being composed internally of large oval cells irregularly arranged. These cells seem to communicate freely with one another and with the tubes of the valves. The Coronules have no base : their soft parts are in immediate contact with the integuments of the living animals in which they are generally imbedded. The form and arrangement of the opercule vary. There are generally four triangular valves, two larger than the others, all deeply grooved on their upper surfaces by the lines of growth. These valves cover more or less completely the soft parts beneath, to which they are attached, so as to be very moveable one upon the other, and to admit of the pas- sage of the feet through the slit that exists be- tween the two pairs. In some of the coronules, the greater part of the opercule is soft. Coro- nula diadema has two small shelly plates in its opercule. Keeping in view the complex but beautiful structure just described, it is not difficult to determine how the whole shell increases in size. It is obvious that the parietal compart- ments of the first series are enlarged by addi- tions to their basilar edges and internal surface, and that thus the whole cone is lengthened, and consequently widened at its base ; but, in all the species, it is also widened above ; and, as the summits of the first series of com- partments are, evidently, not at all, or, at most, very slightly, abraded by the friction of the opercule, it is certain that the apices of these compartments — originally very closely approx- imated— must be moved outwards and sepa- rated from one another by the gradual increase in breadth of the intervening wedge-like com- partments of the second series. This process implies the insertion of soft parts endowed Fig. 338. a with vascular action between the valves so as to admit of lateral additions being made to the second set of compartments. There can be no question that these soft parts (foliated processes of the mantle) pass into the sutures along their whole length, and deposit the shelly matter on the edges of the partitions forming the chambered structure of the se- cond series of compartments ; each valve, with the exception of the dorsal one, is thus added to in breadth; and as the distance between the original valves is enlarged, and the whole shell lengthened, new chambers are formed below. Of course, as the cone is lengthened, its base is widened ; and this is effected by the excretion of shelly matter from such parts of the mantle as can easily pass through the numerous holes placed around the inner cir- cumference of the base. The valves of the opercule are imbedded in the margins of the mantle between the epidermis and true skin, and are increased by marginal additions in the same way as the shells of molluscs. The mode of growth of these shells engaged the attention of Cuvier, who concluded that an addition to the sides of the valves could take place only in an early age; for it appeared to him that they are, in a more advanced stage, so firmly cemented together as not to admit of separation. In large species, however, we find that the valves are easily separated at the sutures, and that the calcareous matter along the sides of the sutures is loosely aggregated ; so that, to us, there seems to be no impro- bability in the supposition that in the living animal the prolongations of the mantle pass between the terminations of the minute tubu- lar processes of the second series of compart- ments, and the corresponding depressions in the edges of the first series already noticed. There is no indication, we think, of each of the valves being “ detached from its neighbour only at certain times that it may receive addi- tional calcareous matter along its sides,” as Brugieres and Cuvier imagined. The process of growth seems to be carried on in uniform progression until adult age. So puzzling did the problem of the mode of growth in these shells appear to Dufresne, that he concluded that, like crabs, the Balanid casts its old shell, and forms a new one, as it increases in size.* Cuvier remarked that, “ while the mode of growth of the shells of the Mollusca resembles that of simple teeth, the organization and in- crease of the shells of balanids may be com- pared to that of certain compound teeth, par- ticularly those of diodons and tetrodons.” Tubicinella, a parasite of the Whale, differs much from the other balanids in the formation of its shell. The widest part of its six-valved cone is superior; the whole surface is strongly ribbed, and marked with transverse lines of growth ; and it appears that the additions to the cone are made on the upper margin ; this margin is surrounded internally by a thick and fleshy production of the mantle, which is never altogether covered by the opercule. The base * Ann. du Mus. i. 467. CIRRHOPODA. 687 is open, and of little less diameter than the upper part, which led Dufresne to conclude that the animal does not form a shell until it be considerably advanced in growth. This seems to be very probable, as the base is im- bedded deeply in the integument of the Whale, and descends lower the more it increases in size, so as to leave only the summit of the shell visible. The imbedded portion is gene- rally deeply coloured by the tegumentary pig- ment of the Whale. In coronula, which also inhabits the backs of Whales, but has the same general structure of shell as the majority of Balanids, the valves are deeply partitioned, and provided with toothed processes, fitted to fix the animal in its site. The only other calcareous coverings that re- main to be noticed are the rudimentary valves in Otion and Cineras, animals that bear a general resemblance in form to Anatifa, but which are covered chiefly by a semicartila- ginous tunic. There are two small valves in Otion, which are attached to the anterior as- pect just above the brachial orifice. In Cine- ras they are five in number, two in the same situation as those of Otion, two along the ter- minal margin of the outer tunic, and one unpaired along the dorsal aspect. These are imbedded by their margins in the semi-carti- laginous tunic, and seem to be formed by it ; calcareous matter being added to their margins in successive layers. The ligamentous membrane, by which the valves in Anatifa are connected one with the other and with the peduncle, is strong but pliant. It is an extension of the outer cover- ing of the peduncle. At the brachial orifice, it is reflected inwards to join the mantle. In addition to this, each valve has a membrane of its own, which closely invests its inner sur- face, and is not continuous with those of the other valves. The peduncle of this and the allied genera may be considered as a kind of developed ligament. If we regard the upper pair of valves as analogous to the valves of Acephalous Mollusca, the peduncle is found to be attached to them at points corresponding to the situation of the ligament in those shells. This organ is sometimes of great size. In the British seas it occasionally occurs two feet in length. Its epidermis is generally rough, wrinkled transversely, coriaceous, and elastic : Otion, however, has it very smooth and stiff, nearly cartilaginous, diaphanous. In some species it is so e'ast c as to admit of exten- sive lateral motion, and much elongation and contraction. These movements are effected by a layer of strong muscular tissue beneath the skin, within which there is a large organ, granular in its structure, regarded by some anatomists as the ovary. Burmeister is of opinion that the peduncle is merely an organ of support : and he suggests that the granular parenchymatous mass, which fills its interior, is destined solely for its own nutrition, which he seems to think is independent of the other parts of the animal. In mostspecies,itisbyits epider- mis that the peduncle adheres. The peduncle pre- sents still other varieties than those just mention- ed. Pollicipes villosus has itcovered partly with imbricated scales, and partly with a hairy coat; and Pollicipes quadrivalvis has its valves wholly encased in a large prolongation of the pe- duncle, which, on its upper surface, bears four valves arranged nearly in the same way as those of the opercule of the Balanids. The base of Coronula is closed by a strong fibrous membrane connected with the body of the animal only by a process of the epidermis. It is regarded by Burmeister as the analogue of the peduncle of the Lepads. The cartilaginous tunic of Otion Cuvieri, at its summit, is enlarged into two large auri- form appendages, hollow, having a crescentic orifice externally, and internally commu- nicating with the visceral cavity of the animal ; no organ is discoverable within them, but their cavities receive the terminations of a duct, which descends on the dorsal aspect of the body, in the groove of the dorsal valve, from the peduncle. Of the mantle, as one of the tegumentary organs of the Cirripeds, little more need be said, than that it is generally a very thin trans- parent membranous sac, surrounding the vis- ceral mass, open only at the brachial orifice, where it joins the epidermis and intervalvular ligament, and is reflected so as to form an inner lining for the visceral cavity. It has neither fringes of filaments, nor foliated pro- cesses. M. St. Ange describes another tunic of the visceral mass, which, he says, is con- tinuous with the horny covering of the arms. Locomotion. — Their base being permanently fixed, the principal motions of the Cirripeds are those of the arfns, which seem to be sub- servient at once to the respiratory and to the digestive functions. But, as has just been mentioned above, the peduncle of Anatifa and other allied genera is moved both laterally and in the way of contraction and extension, and the valves, in the same animals, are so moved as to open and close the brachial orifice. The motions of the arms are, in many species, very rapid, and are performed with great re- gularity ; proving the existence of a complete muscular apparatus both at their bases and within their numerous joints ; but the parts are too minute to admit of a satisfactory examina- tion being made of their structure. The Lepads have a strong transverse adductor muscle placed between their superior valves, just above the brachial orifice (a, fig. 340); this muscle seems to be every way analogous to the same organ in Acephala. Its action closes the brachial slit very accurately ; while its relaxation admits of its being opened by the advance of the arms grouped together into the form of a wedge. This movement of the arms cannot be per- formed without the whole body being carried outwards; which is effected apparently by the contraction of certain delicate muscular fibres spread over the mantle, and attached around the margin of the orifice. Cuvier describes a similar set of fibres, “ attached to the mantle opposite the insertion of the peduncle, by 688 CIRRHOPODA. the action of which the general mass of the body is drawn deeply within the shell.” This we have failed to observe in the species which have come under our notice. When the arms are fully exserted, they are separated one from the other, fan-like. This motion is probably produced by a muscular expansion, described by M. St. Ange as covering the visceral mass dorsally, the fibres of which are grouped into six bundles on either side, cor- responding to the arms. The same observer describes also certain tendons which he found crossing one another at the median line ; these are probably connected with another layer of muscles, expanded over the dorsal surface of the visceral mass, fitted to approximate the arms of either side towards one another. The muscles of the jaws cannot be satisfactorily examined on account of their minuteness. In the Balanids, the valvular opercule is moved by a set of muscles attached to the circle of shelly plates that surround the opening of the parietal cone. Its adductors, which close the aperture with great force, are attached to the extremities of the valves on either side. The visceral mass is, in the Balanids, fixed to the shell by three muscular bands, partly attached, around the mouth, to a process of the epider- mis, and partly spread over the mantle. Motility and Sensation. — The nervous sys- tem of the Cirripeds consists essentially of two nervous cords running along the abdominal surface, and swelling out into distinctly formed ganglions, at intervals corresponding to the feet-bearing lobes. The first pair of ganglions is situated above the oesophagus (Jig. 339). They are united by a very short nervous cord. — From this supra- oesophageal gan- glion and the u- niting cord, there arise anteriorly three or four nerves, which are distributed to the muscular tunics. The principal ner- vous cords, leav- ing the first gan- glion posteriorly, descend to encir- cle the oesopha- gus. In this course, they give off branches to the salivary glands and other neighbouring parts, and particularly, (as M. St. Ange has pointed out,) a nerve of communication with a small lateral ganglion (/c, k,Jig. 339) on either side, situated near the stomach and below the salivary organs. This is connected also with the second pair of ganglions. From this se- cond pair, several branches arise, some of which go to the stomach, and two to the first pair of arms. The other arms receive only one branch each (t, i), which is divided into two, one for each of the jointed processes. In its course along the abdominal surface, the double ganglionic cord — the centre of the nervous system — lies immediately beneath the skin, between the bases of the arms. The fifth and the sixth pairs of ganglions have the appearance of being closely united. The tu- bular process, which terminates the anal ex- tremity of the body receives two nerves, one from each of those going to the sixth pair of arms. Dr. Grant directs our attention to the fact that all the anterior parts of this system are very imperfectly developed compared with the posterior parts, and with the same parts in other articulated animals, which have their heads free, and organs of sense more com- plete. The sense of touch is the only one enjoyed by the Cirripeds, so far as we can discover. The ciliated arms of some of the species are acutely sensitive : they are withdrawn imme- diately on being touched by any foreign body, and when the surrounding fluid is unfit for respiration. Some observers have also re- marked that they shrink from a strong light brought to shine upon them suddenly. In the adult animals, there are certainly no organs which can be regarded as eyes; but, according to Mr. Thompson, what he be- lieves to be the free-moving young have very well developed eyes, like those of some Crus- tacea. Some of the littoral Cirripeds, when left dry at ebb-tide, seem to be sensible of certain changes being produced in the state of the sur- rounding air by the approach of a living being to the place of their habitation. We have frequently remarked, on drawing near a spot densely peopled by the small acorn-shells that so abundantly cover most of our rocks on the sea-shore, a peculiar faint crackling noise, sud- denly produced, gradually subsiding after the lapse of a few seconds, and not repeated until a movement was made towards another spot ; and, on searching for the cause of this singular sound, we have satisfied ourselves that it is uniformly produced by the sudden closing of the opercules of the Balanids, which seem generally to remain open in ordinary cir- cumstances. We have seen this motion again and again follow immediately the movement of the hand towards particular spots, (not, however, nearer the shells than twelve or four- teen inches,) so that we could not but con- clude that the animal was made sensible, through the medium of the air, of the pre- sence of some foreign body, and, fearing dan- ger, closed its shell for self-protection ; just as the limpet, warned of the approach of hurtful agents by the slightest touch of its shell, fixes itself more securely to its rocky footing. What the nature of the sense is which is thus used by the Cirripeds, we have no means of determining. Digestion. — The minute swimming Crus- tacea appear to constitute the principal food of the Cirripeds. Sometimes, however, the shells of minute Mollusca are found in their CIRRHOPODA. 689 Fig. 341. stomachs, and Burmeister once found part of an annelid of unknown species. The food is carried towards the mouth by currents pro- duced by the rapid motions of the arms, which, in most of the species, are constantly Fig. 340. spread out and drawn in, alternately, with great regularity. The mouth is situated just at the bottom of the funnel-shaped cavity formed by the spread arms (b,Jig. 340). In the Lepads its position is close to the trans- verse adductor muscle. Its jaws form a round protuberance, which presents itself very con- spicuously immediate- ly on separating the arms. It might al- most be regarded as a head, so prominent is it (jig. 341, b,b ); but we find it composed only of the lip and jaws, with their muscles. The lip over-arches the jaws ; it is horny, and furnished with minute palpi. There are three pairs of jaws. The first or outer pair are thin horny plates of an oval form, fringed along their opposing sides with long stiff hairs. The other two pairs are curved and deeply serrated on their opposed surfaces. The middle pair bears a small palp on its lateral margin. In some species, a small tongue has been found. All these parts bear a close re- semblance to the same organs in some of the Crustacea. The oesophagus is short ; its lining membrane is somewhat horny, stiff enough permanently to distend the whole canal ; be- fore entering the stomach, its diameter is con- siderably enlarged. It receives the ducts of two salivary glands. The stomach ( c,fig . 341) is capacious ; externally, it presents an irre- gular mamillated surface, studded with nu- merous small prominences closely set, which are the outer surfaces of hepatic cells, formed in a layer of glandular tissue that closely in- vests the walls of the stomach. These cells communicate directly with its general cavity {a, Jig. 342). There is no other organ that can be regarded as a liver.* Two coecal appen- * IJurmeister’s recent researches have led him to conclude that both the Lepads and the Balanids have large livers. He has satisfied himself that the organs, regarded by Cuvier as the ovaries, and by more recent authorities as the testicles, communicate by ducts with the upper part of the intestinal canal, and not at all with the seminal vessels. Hence he supposes that they are lobes of the liver and not organs of reproduction. Our own dissections lead us rather to agree with Messrs. Wagner and St. Ange, who believe them to be the testicles. dages, also saccu- lated internally, and embossed outwardly, are attached to the stomach. The intestine is wide, nearly without convolutions, and ta- pering towards the anus (d, e, fig. 341). In the Lepads the stomach is situated in that part of the visceral mass near- est to the peduncle ; from which point the intestine runs on the dorsal aspect of the body, and terminates in the anus just at the base of the articulated tubular process. It is slightly dilated near the anus. The walls of the in- testine are perfectly smooth and free from folds and duplications. The number of their tunics cannot be satisfactorily determined. M. St. Ange has described a singular piece of struc- ture which he has found within the intestinal canal of certain Anatifae (c, c, fig. 342). It is a kind of second intestine, which floats within the cavity of the one just described. It is nearly equal in length to the outer canal. Its upper extremity is expanded, funnel-shaped, with edges cut into fringed processes like the mouths of the Fallopian tube in vertebrate animals. These processes are lodged in the cells of the walls of the stomach, and furnish the only means of attachment to the outer walls with which the organ is provided. It thence tapers towards the anal extremity, where it is pointed and closed. Its walls are very thin and delicate. It is generally filled with alimentary matter, which must pass from its cavity by a kind of rumination, so as to enter the stomach a second time. Circulation. — The sanguiferous system of the Cirripeds has not yet been fully investigated. Only the vessels of the arms, and a central canal, situated on the dorsal aspect of the body, have been discovered. Poli asserted that he saw a heart pulsating a little above the anus : but it does not appear that any other observer has made the same remark. Burmeister has searched, in vain, for a heart, in the large Coro- nula diadema. The vessels of the arms can be distinctly seen through the transparent integu- ments of the ciliated processes; there are, in each process, two vessels, one of which runs very superficially between the two rows of hairs. ( Fig. 343.^) Cuvier regarded the anterior canal of the peduncle in Anatifa as the nourishing vessel of that organ. Respiration. — The principal organs concern- ed in respiration are, in the Lepads, certain tapering filamentary processes attached to the sides of the anterior part of the body, which are regarded as the branchiae ( d, g, fig. 340) : in most of the Balanids, they assume the form of two leaf-like membranes with fringed mar- gins, and are attached to the inner surface of 690 CIRRIiOPODA. the mantle. Professor Burmeister describes the gills of Coronula diadema as broad mem- branous expansions, of a semicircular form, attached to the sides of the visceral mass by a narrow pedicle. They are composed of two tunics arranged in deep and narrow transverse plaits. The number of the branchiae in the Lepads varies from four to sixteen. They are composed of soft cellular tissue, and have a smooth surface. The arms ( h, h, Jig. 340), which constitute so large a portion of the general mass of all the Cirripeds, and which form their most distinc- tive feature, must be regarded as subservient chiefly to the function of respiration; although, by producing currents in the water, which bring food within reach of the jaws, they minis- ter also to the digestive function. In all the known species, both of Lepads and Balanids, these arms are twelve in number, six on either side, arranged symmetrically. Each arm is composed of a short fleshy peduncle, having three articulations, and two horny articulated processes, compressed laterally, of equal length, ciliated on their internal surfaces, and coiled up in a spiral of one turn. On their internal surface there is a coating of a black pigment in spots. Each joint is provided with a double row of hairs of different lengths. ( Fig. 343.) Fig. 343. A part of one of the arms considerably magnified. In Anatifa, the first pair of arms is thicker and stronger than the others ; the sixth pair is the longest. Dr. Grant says, “ the arms are not only minutely jointed to their extreme points, but, also, the innumerable fine cilia which pro- ject inwards from their surface are themselves minutely jointed, and by the aid of the micro- scope, we can perceive that these jointed cilia are also ciliated on their margins.” When the animal is at rest, with the valves of the shell closed, the arms are coiled up, and lie close to one another; but, at other times, circumstances being favourable to the perform- ance of the function of respiration, they are ex- tended simultaneously so as to project from the shell, — radiate and plumose in their arrange- ment. Many species extend and contract their arms with considerable rapidity, as often as forty or sixty times in a minute; the smaller species more frequently than the larger. Considering how extensive the surface is which is exposed in the arms between the two rows of cilia, and that a vessel seems to run immediately beneath the delicate covering of these organs in that situation, it appears proba- ble that the arms are very efficient agents in the function of respiration. Secretion. — We have failed to ascertain satis- factorily the structure of the secreting apparatus by which the shells of the Cirripeds are formed. In the Lepads, the organs must be imbedded in the ligamentous membrane by which the valves are united : and in the Balanids, they are arranged in six rows along the outer surface of the mantle, and around the base; but, as in acephalous mollusca, they are too small to ad- mit of their structure being particularly exa- mined. The external surface of the mantle in the Balanids has also the power of secreting calcareous matter, with which to increase the thickness of the shell. Reproduction. — It is not yet accurately de- termined what are the organs of reproduction in these animals. That which was regarded by Cuvier as the ovary in the Lepads, is supposed by Professor Wagner and M. St. Ange to be the testicle ; while Professor Burmeister has satisfied himself that it is the liver. The ex- tent, structure, and relations of the ovary are still doubtful. It is certain, however, that all the known Cirripeds are hermaphrodite. The testicle, according to Professor Wagner and M. St. Ange, is a large granular organ (y, Jig. 344), expanded over the sides of the Fig. 344. visceral mass, and around the digestive canal, from the stomach to the anus, passing even into the bases of the arms, immediately beneath the muscular tunics which cover the body on both sides. It is composed of numerous minute lobules, about gijth of an inch in diameter in the common Lepads, soft, white, grouped toge- ther by branched ducts ( q , q, jig. 344), which, after uniting into three or four principal trunks,* meet in a large central receptacle ( r ), some- what analogous in relative function to the vas deferens of vertebrate animals. The seminal fluid passes from this central receptacle by a short and straight duct into a large canal (l, t ), which may be compared to the seminal vesicle. It pursues a tortuous course towards the base of the tubular process, where fk) it is joined by its fellow of the other side, and enters the canal * This description does not accord with the result of Professor liurmeister’s researches. Instead of a regular scries of branched vessels, he says that he met with .nothing but an irregularly arranged mesh of thready fibres lying between what he be- lieved to be the liver ( described above as the testi- cle) and the intestinal canal. CIRRHOPODA. 691 of the process which forms a kind of caudal prolongation of the abdomen ( f', f). This canal runs to the distal extremity, and opens by a minute orifice fringed with very fine hairs. In Otion Cuvieri the Iwo canals are continued distinct to the very point of the process, where there are two openings.* The walls of the organ, which we have compared to the seminal vesicle, have a glandular structure, which Cuvier imagined to be the testicle. The re- searches of Professor Burmeister have led him to the same conclusion. He says it can be no- thing but the testicle. f Cuvier, as well as Lamarck, regarded what we have called the testicle as the ovary, and believed that the ova were impregnated, in the course of their passage along the oviducts, by the seminal fluid flowing from the testicle investing these canals. The granular lobules of the true testicle, which were supposed to be immature ova, are found always in the same state, and what are more distinctly ova are found within the peduncle.J The lengthened tubular process ( t', t', fig. 344), through wfliieh the excretory duct of the testicle passes, is articulated ; the margin of each joint is fringed with minute hairs. In Otion and Coronula, Burmeister found large canals closed at both extremities, within the process, in addition to the ducts from the testi- cle. This organ is generally found after death bent upwards on the abdominal surface ; but, during life, it is in continual motion. Its use is, probably, to carry the seminal fluid back- wards beyond the current caused by the move- ments of the arms, in the event of there being mutual impregnation between separate indivi- duals; or towards the mouths of certain ducts which communicate with the ovary within the peduncle, in case of self-impregnation taking place. In this view it must be regarded as the penis ; and it is so called by the most recent authors on the subject — Wagner and Burmeister. Mr. Thompson calls it an ovipo- sitor ; and conjectures that, after their expul- sion from the ovary, (understanding by this what we regard as the testicle,) the eggs are conveyed by it into the cellular texture of the pedicle. How they pass from this depository into the general cavity, where they afterwards form two or three foliated groups, he confesses himself unable to explain. The peduncle of the Lepads was formerly regarded merely as an organ of support, and even Cuvier discovered within it nothing but what appeared to him to be a homogeneous pulp, surrounded by muscular tissue. But, at certain seasons of the year, at least, there are, very distinctly developed, throughout the greater art of the soft matter which constitutes the ulk of the organ contained within the dense cartilaginous and muscular tunics, certain oval granules, regular, and uniform in shape, and gradually increasing in size. Poli and Lamarck * Burmeister, Beitr'age, p. 46. f Op. cit. p. 44. } Professor Wagner is satisfied that nothing but the discovery of spermatic animalcules can assure us against error in our attempts to determine what is the testicle. were of opinion that these w ere truly eggs, but held that they were originally formed in the granular organ surrounding the intestine, (now regarded as the testicle,) and merely deposited here temporarily. But the recent researches of Professor Wagner and M. St. Ange have ren- dered it probable that it is the ovary which is contained within the peduncle. The organ in question seems to occupy the whole of the pe- duncle within the layers of muscular tissue. It is separated from the visceral cavity by a fine membrane which lines that cavity, and is a reflexion of the mantle. A transverse section of the ovary shews the eggs most fully deve- loped towards the outer margin, and scarcely formed in the centre. There are also seen in the same section two canals which run longitu- dinally through the organ, one near that side of the margin which corresponds to the anterior aspect of the body of the animal, the other in a similar situation on the dorsal aspect. Of these canals, the anterior is the larger ; and it alone was described by Cuvier, who regarded it as connected with the circulating system. The other was first described by M. St. Ange, who satisfied himself that it is a true oviduct. In Anatifa, he traced it pursuing a straight course through the ovary, and leaving it as a perfect canal just at the posterior and inferior angle of the organ, thence passing on the outer surface of the lining of the visceral cavity, in the groove of the dorsal valve, and terminating in an orifice opening into the visceral cavity not far from the brachial slit.* We have found a structure exactly resembling the above in Otion, where, however, instead of opening into the general cavity of the visceral sac, the duct is bifurcated just between the two auriform appendages, into each of which one of the branches of the duct enters and opens. M. St. Ange found eggs in progress through this duct; and they are frequently found, arranged in groups or packets, two or three in number, within the cavity of the mantle. We have not yet seen them in the duct ; but the whole structure of the parts in question seems to indicate their adaptation to the function assigned to them by M. St. Ange. This being the case with regard to Anatifa, it appears to be very probable that the use of the singular auriform appendages in Otion is to afford a convenient lodging for the eggs before the young are hatched. Their deep sinuosities and folds seem to adapt them admirably to this purpose. Packets of eggs, however, are found within the cavity of the mantle in this species as in others. According to Burmeister, these packets are unattached, excepting in the earliest stage of development; but Wagner has generally found them fixed to a process of the mantle, situated near the adductor muscle of * Professor Wagner says, “ at the base of the dorsal valve there exists a slit in the mantle which leads into the canal that runs through the peduncle. I presume that this canal serves as an oviduct, and that the slit is analogous to the opening of the branchial canal in the bivalves/’ (in Archiv fur Anat. Physiol. & c. von D. J. Muller, 1834, No. 5, quoted in Ann. des Sc. Nat. iv. n. s.) We are not aware what species was anatomized by Professor Wagner. 692 CIRRIIOPODA. the shell ; which process is, at times, so much elongated as to admit of the eggs hanging out in groups from the brachial aperture, beyond the extremities of the arms. Burmeister has observed that, after the escape of the embryo, the shells remain connected with the parent, forming a loose net-work. This author seems to regard these groups of eggs within the man- tle, and the tissue in which they are imbedded, as constituting the true ovary. In each of the individuals of Anatifa striata which came under his observation, he computed that there were about 4000 eggs in the ovary. Mr. Thompson calls these groups of ova conceptacles ; and says that “ each has a separate attachment at the sides of the animal to the septum, which divides the cavity occupied by the animal from that of the pedicle.”* The retention of their ova, grouped in separate packets on the surface of their bodies, after their expulsion from the ovary, constitutes another point of resemblance between the Cirripeds and Crustaceous animals. With regard to the anterior canal within the ovary, little has yet been determined. We have particularly examined it in Otion, and find that, like its fellow of the dorsal aspect, it leaves the ovary at its inferior edge, whence it opens into a small cavity situated between the intervalvular ligament and the lining membrane of the visceral cavity. We have not succeeded in discovering any orifice in the walls of this cavity, although, from the results of some of our experiments we think it probable that there exists a small one just above the brachial slit. If so, is it not likely that this is the passage in- tended for conveying the fecundating liquor from the orifice of the tubular process connected with the male organs to the ovary ? When the body is exserted through the brachial slit, the point of the process can easily be brought into contact with the outer surface of the cavity above described. The development of the egg and the young of the Cirripeds has recently become an object of interesting inquiry in consequence of the novel results announced by Mr. J. V. Thomp- son in his “ Zoological Researches,” (1830, 4th Memoir.) This gentleman has published an account of observations made on what he believed to be the young of Balanids, from which he concludes that, on their first exclusion from the egg, they closely resemble some of the branchiopodous Crustacea, — that they pos- sess the power of free locomotion through the water by means of setiferous arms projecting from within a bivalve shell, — and that they have very obvious pedunculated eyes. Minute animals, bearing these characters, and having some resemblance to species of the genus Cypris, were placed by Mr. Thompson in a glassful of sea-water. Soon after, on looking for them, he could not find them in the water, but he found in their room several very young balanids, which, from the appearance they pre- sented, he concluded to be really the same animals that he had originally placed in the water, changed by metamorphosis. Mr. Thomp- * Phil. Trans. 1835, 356. son has not seen the change actually going on, but he has satisfied himself that what he re- gards as the free-moving embryo fixes itself by a spot on its dorsal aspect between the two shells, which spot can be seen during its free state. When fixed, the base of adherence ap- pears to be broad like that of an Actinia : from this it rises in a conical form, truncated. The flat sides of this cone are coated with six shelly plates, so arranged as to leave a large space in the middle uncovered. This space is closed by the old shells of the embryo state, which are made to move up and down as the opercule does in the adult animal, admitting of the egress and ingress of the arms at the animal’s pleasure. Through this shell two large black spots like eyes can be distinguished. Mr. Thompson found in the young of the Balanids, six pairs of arms, cleft ; each arm with two ar- ticulations. The first casting of the shell, after the animal has fixed itself, is followed by an increase in the number of articulations in each arm ; and this number is further added to at every succeeding shell-casting. Even the old full-grown animals, according to Mr. Thomp- son, cast their shells. Very recently Mr. Thompson has made a still more satisfactory series of observations on the development of some of the Lepads, of the genera Cineras, Otion, and Lepas. These he obtained from the bottoms of vessels in the harbour of Cork. They hatched eggs in large numbers, and afforded him the means of ascer- taining, entirely to his own satisfaction, that, at its first exclusion from the egg, the Lepad, like the Balanid, is a natatory crab, lie found a considerable difference between the larvte of the two classes. The newly-discovered one of the Lepads he describes as “ a tailed monocu- lus, with three pairs of members, the most an- terior of which are simple, the others bifid, having its back covered by an ample shield, terminating anteriorly in two extended horns, and posteriorly in a simple elongated spinous process.” The general appearance of this larva is not unlike that of the Argulus armiger of La- treille.® Very recently Messrs. Audouin,j- Wagner,]; and Burmeister, § have corroborated the state- ments and supported the views of Mr. Thomp- son. Professor Burmeister has detailed the results of his observations with great minute- ness. It appears that they were made chiefly on individuals of Anatifa striata, procured in the North Atlantic Ocean, and preserved in spirits ; partly also on Lepas anserifera. (Linn.) The results of these observations have led Pro- fessor B. to divide the development of the Cir- ripeds into five stages or periods. The first of these is the state of egg ; the second is that of * Phil Trans. 1835, pt. ii. 355. “ Discovery of the Metamorphosis in the second type of the Cirri- peels/* &c. f Ann. des Sc. Nat. n. s. iii. 31. j Muller's Archiv, No. 5, 1834, and Beitrage zur vergleich. phys. des Blutes. Leipzig, 1833. $ Beitrage zur Naturgcsch. der Rankenfusser. Berlin, 1834. r CIRRHOPODA. 693 free locomotion ; the third is that in which the young becomes encased in a shell, and fixes itself; in the fourth stage, the young gradually assumes the characters of the adult ; the fifth stage is that of perfect development. First stage. — The egg. Its outer covering is a very delicate membrane. The yolk is yel- lowish-red, clouded, and marked with two rows of small spots, globule-like, distinct at one end, running together at the other. The eggs in the central parts of the ovary are consi- derably further advanced than those in the cir- cumference. Through the transparent covering of the egg the general form of the embryo can be seen. Second stage. — In this stage the young Cir- riped resembles the fry of Cyclops or Daphnia in its external characters. It is provided with two long antennae and three pairs of feet (arms?) placed along its ventral surface.* Each foot of the first pair is single, and is furnished with bristles at its free extremity. Each of the other pairs is divided into two members, also tipped with bristles. The posterior part of the body is tapering, compressed, and slightly bifurcated at its extremity, where it is beset with bristles. No eyes could be seen in this stage, but Pro- fessor Burmeister nevertheless conjectures that they really do exist. The appearance of two rows of small globules on the surface of the body continues to present itself, but here they are more numerous, although not larger. The middle part of the body is clear and transparent. Third stage. — Materials for the description of this stage were obtained by Burmeister from the examination of only one individual, which was found attached to the frond of a fucus hard by the bases of some adult indivi- duals. The shell, in this the first stage of its growth, is of leathery consistence, and formed of one piece, placed dorsal ly. A fleshy protu- berance serves as the peduncle. The organs by which the young animal fixes itself are evi- dently the long antennae situated near the mouth. Behind these are placed the very large eyes. Burmeister satisfied himself of the ex- istence of a single transparent cornea, and saw behind it a round black spot, but no lens. The two eyes are very closely approximated by their bases. Both the eyes and the brownish con- tents of the alimentary canal can be distin- guished through the translucent shell. In the structure of the posterior part of the body there is no great change from the former stage. Each arm of the first pair is single, and consists of three articulations, of which the basilar is the greatest : the smallest and terminal one bears four long stiff bristles. The arms of the follow- ing pair are not single, but each is divided into two small articulated processes. The little globules of the two former stages are not dis- cernible in this. * The circumstance of there being a smaller number of arms in the young than in the adult, re- minds us of the same being the case in several of the Branchiopodous Crustacea ; and the want of the shell in young Cirripeds seems to point out a closer analogy between them and Crustacea, than between them and Mollusca, the young of which are covered with shell in the egg. Fourth stage. — This stage was observed by Professor Burmeister in the Lepas anati- fera from the coasts of Chili. All the indi- viduals examined were about three-fourths of a line in length. Soon after the animal fixes itself the old integuments are thrown off. The eyes and the antennae are entirely cast off along with these. After this process had been completed, the space within the man- tle was found to be filled with a granular pulta- ceous mass, at first occupying the greater part of the cavity of the shell, and covering all the young animal. This appeared to M. Burmeis- ter to be the same that is found in the pedicle of the older animals, and to resemble closely the matter contained within the cavities of the shells of Coronulae and other Balanids. It is by a sack-formed process of the mantle filled with this yellowish matter that the peduncle is first formed. At the time of the animal’s fixing itself the shell has no calcareous points, but in the course of this stage it becomes firm and gradually more and more solid. There are now six pairs of feet, each of three articulations, and terminated by bristles. A small tail of two articulations also appears, the rudiments of which, however’, can be detected in the former stage. In the fifth stage the process of deve- lopment is completed. It must be admitted that the evidence in favour of Mr. Thompson’s opinions on this subject is by no means conclusive. There is stili wanting a series of minute and careful ob- servations on the first appearance and motions of the embryo immediately after its exclusion from the egg ; and nothing but the results of such a series can settle the question as to whe- ther there be a real metamorphosis or not. Mr. Gray’s observations have led him to conclude that no great changes of structure, such as Mr. Thompson’s views presuppose, actually take place ; although, in examining the mature egg of Balanus Cranchii, he found the appearance of the embryo nearly the same as is described by Burmeister as being that of the Lepads in the second stage of development. The egg of this Balanid Mr. Gray ascertained to be one-fiftieth of an inch in length. He de- scribes the inclosed animal as being of an ovate form, tapering at one extremity, truncated and ciliated at the other ; bearing a general resem- blance to the adult animal, but furnished with only three pairs of ciliated ar ms ; the base of each arm being two-jointed. He found only one lengthened process attached to the lower pair of arms ; but, connected with the two upper pairs, two fusiform, thick, articulated and ciliated processes, similar to those of the anterior part of the perfect animal, but less elongated. He saw no shelly covering.* We have not yet had proper opportunities of devoting attention to this interesting subject so far as observations on the living animals are concerned ; but we have no doubt of its very soon meeting with a clear and satisfactory elu- cidation ; meanwhile we may remark that the structure of the embryo within the mature egg * Proceedings of Zool. Soc. Lond. 1833, pt. i. 115. CIRRONOSIS — CONCIIIFERA. 694 (about which there can be no doubt) is such as strongly to indicate its adaptation to free loco- motion ; and that, after a review of all the ob- servations that have been published on the subject, we are inclined to conclude in favour of Mr. Thompson’s opinion that, in the early stages of its development, the young Cirriped really enjoys locomotive powers, and then un- dergoes such changes of structure as are re- quired to fit it for its altered circumstances in adult age. Bibliography. — Leeuwenhoek, Opera, iii. 472. Lister, Exercit. anat. 1696, p. 96. Cuvier, Mem. pour servir a l’histoire des Mollusques, 1817. La- marck, Anim. sans vertebres, v. 377. J.V. Thomp- son, Zoological researches, 1830 ; Fourth Memoir ; and Phil. Trans. 1835, 355. Wagner, in Archiv fur anat. physiol. &c. von I). J. Miiller, 1834, No. v. Burmeister, Beitrage zur Naturgeschichte der Raukenfuesser, Berlin, 1834. Martin St. Ange, Memoire sur [’organization des Cirripedes et leurs Tapports naturels avec les animaux articules, Paris, 1835. ( John Coldstream.) CIRRONOSIS. (Ki ffo?, fulvus ; voao;, morbus.) In a memoir published by M. Lob- stein in the first volume of the Repertoire d' Anatom ie and de Phpsiologie* for the year 1826, this term was applied to what that author considers to be a disease affecting the foetus at an early period of intra-uterine life. The essential characteristic of the malady consists in the serous or transparent membranes being dyed of a beautiful deep golden yellow colour. “ The disease is,” says M. Lobstein, “ an internal jaundice of the peritoneum, of the pleura, of the pericardium, of the arachnoid, differing from the ordinary jaundice, in that it does not affect the parenchymatous cellular tissue of organs, nor the subcutaneous tissue, nor the skin, the usual seats of that disease.” Lobstein published the first account of the •occurrence of these appearances in two five- month foetuses, in his Rapports sur les travaux executes a 1’Amphitheatie d’Anatomie de Strasbourg.! Since that time additional cases were presented to his attention, from which he ascertained that the yellow staining was not confined to the serous membranes only, but also was found in the nervous tissues, espe- cially those of the spinal marrow and encepha- lon. By the aid of the microscope he perceived that the substance of the marrow seemed to be composed, as it were, of small grains of a lemon yellow colour, mixed with a white and pulpy substance, as if a very fine gold-coloured powder had been intimately mixed with a soft and semi-transparent jelly. In these cases the thoracic portion of the sympathetic also exhi- bited a similar colour, and the ganglia were somewhat swollen, and it was ascertained by the microscope that the stain was equally inherent in the nervous substance of the ganglia as in that of the spinal marrow. It is impossible to remove the yellow stain * Rep. d’Anat. et de Phys., t. i. p. 141. t Page 26, ed. in 4to. from the structures in this condition either by ablution or immersion for any length of time in alcohol or water. The intensity of the colour was not diminished in preparations which had been preserved in spirits for seven- teen years, neither was it affected by the action of light. The difficulty of accounting for the pheno- mena which constitute this disease of the embryo is much increased by the fact that cirronosis has hitherto been observed only in three or five month foetuses. As at this period the biliary secretion has not begun to be formed in the usual way, we cannot attribute the occurrence of this disease to any of the causes which give rise to ordinary jaundice, so com- monly met with in the foetus at and shortly after birth. There seems, however, to be no reason to doubt that the elementary constituents of the biliary secretion may already exist in the blood at an early period of intra-uterine life, and that from them the stain may have been communicated to the serous membranes and nervous tissues. But we cannot but express our concurrence in the opinion of Andral, that cirronosis differs only in situa- tion from the ordinary icterus infantum or neonatorum ; there being this remarkable dis- tinction also, that the tissues which are the seat of the colour in cirronosis are rarely affected in jaundice. Although the observations of Lobstein were first published ten years ago, I do not find that they have been confirmed by any subse- quent observer. The preceding account, there- fore, of this disease rests entirely upon his authority, and is drawn up chiefly from his paper in the Repertoire already referred to. ( R. B. Todd.) COLLOID. See Sciriihus. CONCIIIFERA. Fr. Conchiferes. When we take a general view of the organization of the extensive series of Mollusca, two prin- cipal classes are readily distinguished, one of which has been raised to the rank of the pri- mordial division of the animal kingdom by Lamarck ; this class, comprising the whole of the Acephala of Cuvier, as well as the Bra- chiopoda, has received the name of Conchi- fera. The mollusks included in the class of Conchifera present peculiar characters which prevent their being confounded in any point of the series with the other classes of the same sub-kingdom. They are all contained within a bivalve shell, generally articulated after the manner of a hinge ; to this shell the animal is attached by one or several muscles, and the shell itself is secreted by a fleshy envelope, generally thin, but having the edge thickened, to which naturalists agree in giv- ing the name of mantle. The animal, of a structure more simple than other mollusks, has no head; the mouth is pierced at the anterior extremity and is the entrance to organs of di- gestion, consisting of a stomach, an intestine of different lengths, an anus, and an organ CONCHIFERA. 695 for secreting bile. Circulation is performed by means of a heart generally symmetrical, the ventricle of which surrounds the rectum. Respiration is effected by means of four bran- chial leaflets, equal in size and symmetrical, arranged on either side of the body. Gene- ration is simple ; the Conchifera are endowed with hermaphrodism adequate to the continu- ation of the species ; every individual has an ovary included among the general mass of the viscera. The nervous system does not form a complete ring around the oesophagus ; ganglia are found towards the anterior and posterior parts of the animal, and lateral and very long filaments form a ring within which the visceral mass is included. Before entering upon the more particular description of the organs which have just been mentioned, it is essential as a preliminary to institute some order among the members of the class Conchifera, to throw them into a few grand divisions by which the labour of de- scription, in many particulars, will be very much abridged. Lamarck divided the Conchifera into two grand orders, Dimyaria and Monomyaria. We are of opinion that this division may be preserved with some slight modifications ; and, farther, that it is necessary to establish a third order equal in importance to the two others, and including the Brachiopoda. The ana- tomical inquiries of Cuvier, and those, still more recent in their date, of Mr. Owen into the structure of the Brachiopoda will not allow us any longer to regard these animals as per- taining to the family of monomyary Conchi- fers. These inquiries also prove that Cuvier, in forming the Brachiopoda into a particular class of Mollusca, disjoined them in too great a degree from their congeners. It is from re- garding both of these views as carried too far, that we have been led to propose a new divi- sion which to us appears to be called for, and to be preferable to either of the others ; this is to restore the Brachiopoda to the type of pro- per Conchifera, and to establish a third order of this family for their especial reception, to which the title of Polymyaria might be given. Instead of placing this order at the end of the Conchifera, however, it appears better to set it at the head, especially if the analytic method of Lamarck be adopted as the basis of the classification. The Conchifera we should, then, propose to arrange in the following order : < a w s u z o u r < First sub-class. BRACHIOPODA, or POLYMYARIA 1 Second sub-class. DIMYARIA ^ 1st sub-order : valves articulated, t 2nd sub-order : valves free. Order 1st. The ( 1st sub-order : shell regular, lobes of the mantle < more or less united ( 2nd sub-order : shell irregular. Order 2nd. The r 1st sub-order : shell regular, lobes of the mantle < disjoined . . . C 2nd sub-order : shell irregular. Third sub-class. flstorder: a foot- MONOMYARIA |2ndorder. nofoot. The organization of the Brachiopoda being more simple than that of the other Conchifera, renders it proper to place this order at the be- ginning of the class. The Dimyaria having an organization somewhat less complex than the Monomyaria constitute an intermediate order, which is the most numerous of the three ; the Monomyaria terminate the series. To facilitate the comprehension of the brief descriptions which we shall give of the dif- ferent parts of the Conchifera, it seems neces- sary to state precisely the position in which the animal must be placed in order to be suit- ably observed. The animal, then, is supposed to be walking before the observer, included within six planes to which its different parts are referred. The head or the oral aperture indicates the anterior extremity of the creature. This extremity is directed forwards, its pos- terior extremity backwards. The back cor- responds to the superior plane ; the belly and foot correspond to the inferior plane, and the flanks of the animal to the lateral planes, one of which is to the right, the other to the left. The two accompanying figures (fig. 345) will suffice to give an idea of the relations of one of these animals to the different planes within which it is supposed to be included. The organization of the Conchifera is simple enough. The researches of anatomists have shown that these animals are provided digestion, circulation, respiration, generation, and (in the greater number) of locomotion; with a skin or envelope common to the whole of these organs ; and a nervous system bringing the different systems into mutual relation with each other. Of the organs of digestion. — In the Con- chifera, as among other animals, these organs begin at the oral aperture. This aperture 690 CONCHIFERA. Fig. 345. (a, fg. 346) placed at Fig. 346. the anterior part of the animal is deeply hid- den between the foot {b, Jig. 346), and the anterior retractor mus- cle (c) in the Dimyaria, and under a kind of cowl formed by the « mantle in the Mono- myaria. The mouth is in the form of a trans- verse slit, comprised between two lips, ge- nerally thin and nar- row, as in almost all the Dimyaria, or lo- bated and digitated, as in some of the g Monomyaria, (a, fig. 348). The lips ex- tend on either side in the form of two flat- tened smaller appendages, more or less elon- gated, occasionally truncated, streaked or laminated on their internal surface, and to which the title of labial palps has by general consent been given, (d, fig. 346, c,fig. 348.) The mouth in the Conchifera never presents any part that is hard. In the greater number of these animals it terminates without any intermediate passage in a stomach, the form of which is subject to but little variety. When there is an oesophagus (a, fig. 347), it is variable both in point of length and capacity; it has nothing constant, relatively to the other distinctive characters of the groups established among the conchifera generally : thus it either occurs or is wanting indifferently among the individual members of the dimyarian and mo- nomyarian families. Fig. 347. The stomach (b, fig. 347, d,Jig. 348) is a membranous pouch, commonly pear-shaped, CONCHIFERA. 697 sometimes globular, rarely elougated and narrow. When the cesophagus exists, it opens into the upper part of the stomach ; but when that canal is absent, the mouth termi- nates directly in the stomach. Examined internally, the stomach presents several de- pressions irregularly dispersed over its surface, by means of which the bile is brought into its cavity ; it is on this account that these minute depressions have received the name of the biliary crypts. The intestine (c, Jig. 347, e, Jig. 348) arises from the posterior wall of the stomach, and a very singular ap- paratus is occasionally found in its vicinity (d,fg. 347), the use of which is not yet de- termined. It consists of a small appendage which may be compared to the vermiform process of the coecum in the higher animals ; it communicates with the stomach, and is filled by a horny process or stylet of different lengths and thickness, according to the genera and species examined. The anterior extremity of this body is attached to the parietes of the stomach by means of small extremely thin and irregular auricular processes ( oreillettes ). It is to be presumed that quantities of the food may fall during the act of digestion between the parietes of the stomach and the horny body, by it to be pressed or bruised in some particular manner. Yet when those conch iferous ani- mals which are furnished with the apparatus just mentioned, are examined by dissection, no particle of food is found in such a position. We may therefore be allowed to conjecture that this part accomplishes some other purpose in the economy of the conchifera. Whatever this may be, it must, we should imagine, be connected with the function of digestion. The intestinal canal in the conchiferous Mollusca is generally slender, cylindrical, and from one extremity to the other almost always of the same diameter. After having made a variable number of convolutions within the substance of the liver and the ovary, the in- testine comes into relation with the dorsal and median line of the animal’s body. It con- tinues in this direction to the posterior extre- mity, there to terminate in the anus ( e,fig . 347, f, jig. 348) ; the whole of this dorsal part of the intestine is named rectum. The rectum is generally longer in the Dimyaria than in the Monomyaria, because the anus is found above the superior adductor muscle in the former, whilst in the Monomyaria the rectum twists round behind the central muscle to terminate in an anus which floats between the edges of the mantle. The liver (J\ fig. 347, g, fig. 348) is a bulky organ enveloping the stomach and part of the intestine. It pours the product of its secretion directly into the stomach by means of the biliary crypts. The liver alone con- stitutes a very large portion of the visceral mass, and consequently of the body of the animal; it consists of a great number of fol- licles connected together by means of lax and extremely delicate cellular membrane; this structure renders the organ very easily torn. We shall see by-and-bye that it is traversed in VOL. i. Fig. 348. the greater number of mollusks by several muscles belonging to other parts, an arrange- ment which contributes to support and give it greater strength. The exposition which has now been given of the structure of the organs of digestion, affords a ready explanation of all that bears upon this function in the conchiferous mol- lusca. These animals not having the mouth armed with any hard part are unable to seize and swallow any kind of solid food, so that in general nothing more is found in their sto- machs than segregated particles, proceeding without doubt from the decomposition of aquatic animals and plants. The lips, and unquestionably the labial palps also, are do- stined to give the animal perception of the aliment it takes. Once in the stomach, this aliment, impregnated with bile and probably also with a gastric juice secreted by the lining membrane of this pouch, is subjected to a first digestive elaboration ; it next passes the pylorus when it exists, and then traverses the intestinal canal and supplies to the absorbent system the elements necessary to the nutrition of the animal. It does not appear that there is any par- ticular system of absorbent vessels in the con- chiferous Mollusca; the veins perform the office of absorbents, and they transmit with- out any intermedium, and without their under- 2.z 690 CONCHIFERA. going any glandular elaboration, the fluids ab- sorbed to the general current of the circulation. After having thus had all the nutritious ele- ments it contains abstracted, the alimentary mass, having reached the rectum, there com- monly presents itself under the form of minute globules ; it is soon afterwards expelled through the anus. Organs of circulation. — The organs of cir- culation in the acephalous Mollusca consist of two vascular systems forming together a simple circuit, namely, a ventricle and an arterial system, and a venous system and two auricles. The ventricle in the majority of acephalous mollusca is single, symmetrical, situated in the dorsal median line of the body, and rests upon the rectum, which it embraces in its evolution (g, fig. 347, h, Jig. 348) on every side so closely, that the intestine appears to pass through it. It is to be presumed, however, that the intestine does not pass im- mediately athwart the heart, but that this canal is only embraced so intimately by the central organ of the circulation, that it is impossible to separate without tearing them. The ventricle, which is regular and symmetrical in the greater number of the genera (a, Jig. 349) is irregular and unsymmetrical in the Ostracean family, (a, Jig. 350). It is generally elongated and fusiform ; Figs. 349 & 350. j its parietes are thin, formed of muscular fibres variously interlaced, and often projecting in- ternally. From either extremity issues one of the two main arteries of the body, the one superior giving branches to the whole of the anterior parts of the animal ; the other pos- terior supplying branches to the principal vis- cera,— the stomach, liver, intestinal canal, and ovary. Many superficial branches penetrate the mantle, and may be observed ramifying more especially upon the thicker parts which constitute its edges. When the back of the animal is very broad, and as a necessary consequence of this struc- ture, the branchifE of one side are at a consi- derable distance from those of the other side, we find, as among the Archid®, that there are then two ventricles (a, a, fig. 351,) and two auri- cles (6, 6, fig. 351) to secure the perfect per- formance of the important business of circula- tion. This interesting modification of the organs of circulation is of slight significance as regards the mere results of the function, for it still con- tinues no more than a simple circuit, exactly as if it were effected by a single ventricle. The auricles are two in number ( b , b, Jigs. 349 & 351, i, fig. 348) in the whole of the genera of Conchifera except those of the family of the Ostracea, in which there is no more than a single irregular auricle (b’fig- 350), just as there is but one ventricle. The most general figure presented by the au- ricles is the triangular. They communicate with the ventricle by one of the angles of the triangles, and they receive the blood of the branchiae by the most extensive of their three sides. These organs are altogether membra- nous ; in their interior, however, we discover, with the aid of the magnifier, a great number of small fibrous fasciculi, by means of which the regular contraction of the ventricles appears to be effected. The venous system is of very considerable magnitude. In his magnificent work, Poli* has given a very satisfactory account of its anatomy. It is more particularly remarkable in the Archid®, the Pinna, &c. It is destined to receive the blood of the general circulation ; it is also destined to collect the whole of the fluids absorbed, and to direct these towards the branchial apparatus, in which the blood with these added fluids undergoes a fresh elaboration. It is after having traversed the branchial vessels (c, c,c, c, fig. 349, 351, j, Jig. 348) that the blood revivified is carried to- wards the auricle by the pulmonary veins, from whence it is sent to the ventricle, and by it forced anew to perform the round of the arterial cir- culation. The blood in the Conchiferous mollusks is colourless, or of a bluish white, very different from the hue it presents in the vertebrata ; it is but slightly viscid, and when it coagulates exhibits but a very small quantity of crassa- mentum or solid matter. Circulation then is an extremely simple function in the Conchiferous mollusks: an aortic ventricle gives the blood impulse enough to carry it through the two systems of vessels, to expel it from the heart and to bring it back again to the auricle. In other branchiferous animals, the auricle is sometimes adapted to give the blood a new impulse when it is about to pass through the branchi® ; here, on the * Testacea Utriusque Sicilise, fob 3 tom. CONCHIFERA. Fig. 351. 699 contrary, the auricles do not receive the blood until it has been exposed to the revivifying influence of the organs of respiration. Of the organs of respiration. — The whole of the Conchiferous mollusks respire by means of branchiae {e,e,Jig. 346). These or- gans are variously disposed according to the form of the animal. They are symmetrical ; and in almost all the genera there are two on each side. The branchiae generally present the form of membranous leaflets, of a qua- drangular shape, though often unequal. They are broad and short when the animal is glo- bular, elongated and narrow when the animal is lengthened in its general form. In the greater number of genera the branchiae are formed of two membranous layers or laminae (a, b, Jig. 352) within the substance of which the branchial vessels descend with great regu- larity. In several genera, as the Archidae and Pecten, the branchial vessels, instead of being connected parallel to one another within the thickness of a common membrane, continue unconnected through their entire length, and they are thus formed of a great number of extremely delicate filaments attached by the base within a membranous pedicle, in which the branchial veins pursue their way towards Fig. 352. the auricle. In a great many families and genera the branchiae of one side have no com- munication with those of the opposite side ; in some others however, as in the genus Unio, the four branchial laminae meet under the foot, and the whole of their vessels empty them- selves into a venous sinus of considerable size. 2 z 2 700 CONCHIFERA. A remarkable phenomenon is observed in a great many of the Conchiferous mollusks : the eggs on escaping from the ovary, instead of being cast out altogether, are deposited between the two membranes of the branchial laminae, and there undergo a kind of incubation, during which they acquire a considerable size. In some genera, such as the Unio, the shell is even developed within the egg before this is cast loose from the branchiae, and this circum- stance has led several anatomists to mistake these small shells for parasites. As in all the other animals having branchiae, the organs of respiration are destined to restore to the blood the oxygen which it had lost in its circulation through the body. This necessary element to the maintenance of life is restored to it during its passage through an organ contrived so as to bring it almost into contact /with the ambient fluid in which a considerable quantity of atmo- spheric air, and consequently of oxygen, is found dissolved. Organs of generation. — The organs of ge- neration are of extreme simplicity in the Con- chiferous mollusks. They consist of an ovary included in the visceral mass. Not a trace of any other organ of generation can be detected, and the Conchifera must therefore be allowed to possess what has been called sufficient herma- phrodism, generation in them taking place without coition. The ovary is a glandular mass situated at the superior and posterior part of the body; it is in connexion with the liver; and it often receives a portion of the intestine, if it happens to be developed laterally between the two fleshy laminae which form the walls of the foot. In thesiphomferous acephala having the foot short and rudimentary, the ovary, in its state of complete development, forms a very great part of the abdominal mass, amid which it is easily distinguished by its soft consistency and yellowish white colour. In those acephala in which the siphon is short and the foot well developed, the ovary forms a mass less promi- nent at the superior and posterior parts of the viscera. In the Conchifera monomyaria the ovary resting upon the central muscle is situated in the upper and posterior part of the body, and in its state of development constitutes a whitish mass of considerable size, which is readily seen in the Ostracea through the walls of the mantle. This ovary occupies the whole superior part of the animal, and it is seen de- scending along the lateral and posterior parts when the animal is examined at the time of laying its eggs ; a rent in the ovary allows a fluid of a milk-white colour to escape. This fluid under .the microscope is seen to contain a very great number of small whitish granules, each of which is an egg capable of reproducing an individual similar to that from which it de- rives its origin. There is a singular genus placed by the generality of writers in alliance with the Oyster, and designated by the name of Anomia, in which the ovary forms no part of the common mass of the viscera, but extends between the two walls of the mantle, which it separates in proportion as it increases in size. This position of the ovary in the substance of the skin is analogous to what is observed in the Terebratulae, in which the ovary is divided into four segments comprised within the substance of the mantle and in the direction of the prin- cipal branchial vessels. Notwithstanding the minute dissections which have been made of the acephalous mollusks, there are a great many in which the oviduct remains unknown. In two of these animals in which it has been sought for in vain, it has yet been seen running to- wards the middle and anterior part of the branchia;, and opening to the right between the folds of this side. It is not yet known whether or not it be by this opening that the ova escape after they have undergone incubation in the branchire, or whether they escape by the edges of these organs. M. Prevost of Geneva has made some important observations on the generation of the Uniones, which appear to prove that although coitus cannot take place between the acephala, it is nevertheless necessary to their propagation that a certain number of these animals be found together near the same spot. From these experiments we may infer that a fecundating fluid is diffused in the water and absorbed by the ovary, which is thus fecun- dated without the contact of two individuals. This phenomenon is comparable to that which we know takes place in the fecundation of the ova of fishes ; these are deposited by the female, and afterwards sprinkled by the male, who places himself above them, with the prolific fluid. Before adopting definitively the results of M. Prevost’s experiments, however, it were necessary to repeat them a great number of times, in order to leave no doubts on this ques- tion, so interesting to the naturalist as well as to the physiologist, touching the generation of the hermaphrodite mollusca. The number of eggs extruded by each in- dividual is very great, and explains the rapidity with which these animals are propagated in certain seas, and the production by accumulated generations of those extensive beds of shells which are so frequently found covering the sur- face of actually existing continents. Organs of motion. — The organs of motion are of two kinds : one is destined to move the two valves with which the animal is covered; the other is peculiar to a special organ, by means of which the animal moves its whole body. The muscles may therefore be arranged into two classes : 1st, adductor muscles of the valves ; 2d, locomotory muscles, or muscles proper to certain organs. Those fleshy and fibrous fasciculi attached between the two shells, and which by their contraction approxi- mate and close these two shells, are denomina- ted the adductor muscles. In the greater num- ber of the conchiferous mollusca, two of these muscles can be demonstrated, the one anterior (c,fig. 346; h,fig. 347; a, fig. 362) situated in front of the oral aperture, and the other pos- terior (f fg. 346; i, fig. 347; b, fig. 362), CONCHIFERA. 701 Lamarck has given the title of Dimyaires to all the mollusca having two adductor muscles, a character which he has invested with a consi- derable degree of importance, because it is con- stantly proclaimed by the interiors of shells, upon which the impression left by these mus- cles is very distinctly seen (a, b,Jig. 367). One of these muscles, the anterior, diminishes gra- dually as we descend in the series of the Con- chifera ; in the family of Mytilacea it only exists in a rudimentary state ( a, fig. 353); and after these it disappears entirely. In propor- tion as the anterior muscle disappears, the pos- terior one increases in size, and approaches more nearly to the middle of the valves. When no farther trace of anterior muscle can be dis- covered, the posterior muscle continues singly (k,Jig. 348), and the mollusca having a single muscle, very distinct from the former which have two, have received the name of Mono- myaires from M. Lamarck. Poli, however, has shewn that the muscle of the Monomyaria consists in reality of two por- tions, readily separable from one another, and even differing considerably in their appearance. This leads us to presume, with every show of reason, that the single muscle in the Mono- myaria is the result of the approximation of the two muscles, which are parted in the Dimyaria. This fact would incline us to regard the num- ber of the muscles as a matter of but small im- portance in the classification of the conchiferous mollusks, and we may suppose that it was with such inductions before him that Cuvier was led to attach such slight significance to the division of these animals proposed by La- marck. The organ denominated foot in the acepha- lous mollusks is a part which presents very different forms, and is destined to locomotion. This part is particularly well developed among the Dimyaria, and we shall pass in rapid re- view its most general features. The foot (b,fig. 346) is usually situated at the anterior and middle part of the abdominal mass, and is directed forwards. It is so placed as to hide the mouth in a deep sinus between its base and the anterior adductor muscle. In those conchiferous mollusks in which the lobes of the mantle are united through a great por- tion of their circumference, the foot is com- monly very small and meiely rudimentary ; it then forms a kind of little nipple projecting from about the middle of the abdominal mass, a form which is very distinctly seen in the Mya, Saxicava, &c. In others of these mol- lusks the foot, more anteriorly situated, is ex- tremely short, broadly truncated, and similar to a cupping-glass; this configuration is observed in the Pholadia. In proportion as the foot be- comes more free, the lobes of the mantle are distinct from one another, the foot becomes flattened and elongated in the form of the human tongue, and is subservient to motion by digging a hole or furrow in the sand into which the animal sinks. This form of the locomotory organ is met with more especially in the Tellina, the Donata, and a very great number of other genera, the shells of which are more or less flattened. Lamarck had attached some consequence to the shape of the organ of locomotion, and Goldfuss has proposed a clas- sification based upon the modifications pre- sented by this organ ; but the groups establish- ed in accordance with such considerations are in reality of no importance; the several forms proper to the organ pass too insensibly one into another to make it possible to say where one terminates and another begins ; the boundary between one family and another, with a few rare exceptions, is altogether indefinite. In the present day, consequently, naturalists no longer admit into their methods of arrangement the groups established by Lamarck under the names of Tenuipeda, Crassipedu, &e. The foot exists developed in a greater or less degree in the whole of the Dimyaria. If in some species it is found merely rudimentary, it is yet never altogether wanting in any member of this first division of the Conchifera. The organ is also met with in a very considerable number, but by no means in the whole of the Monomyaria, and the presence or absence of the foot might be taken as the basis of a division of this great family into two series, in the one of which the foot was rudimentary but present, whilst in the other it was no longer to be found. Whatever the form of the locomotory organ, and whatever the degree of its development, it is always organized in the same manner. It is essentially composed of several planes of mus- cular fibres (1, 2, 3, fig. 347), which by their various courses and interlacements enable it to perform a great variety of different motions, either in part or as a whole. When the foot is short or vermiform, its mass is entirely muscu- lar from the apex to the base. It is at the base that the fleshy fibres separate into two fasciculi (4, 5, fig. 347), which, after having circum- scribed the visceral mass, proceed backwards, where they are attached to each valve of the shell near the implantation of the posterior ad- ductor muscle in the Dimyaria; and towards the superior part of the valves, and occasion- ally in the interior of the hook, or incurved part of the shell in the Monomyaria. In the Conchifera denominated Lamellipeds and Crassipeds by Lamarck, in a word, in the whole of the Conchiferous mollusks in which the foot constitutes a principal part of the body, this organ presents remarkable differences in its composition and its rela- tions with the internal organs. It is then formed of two lateral planes of fibres, uniting and blending together near the free edge. These two planes, more or less separate ac- cording to the general form of the animal, have between them an internal space, within which is included a considerable portion of the visceral mass. In the generality of conchife- rous mollusks furnished with a large foot, it is here that a portion of the liver is situated, the greater part of the intestinal canal, and a notable portion of the ovary. These organs are bound down in the place they oqcupy, and the 702 CONCIIIFERA. parietes of the foot are preserved in immediate communication by means of a great number of small muscles, sometimes straight, sometimes oblique, and variously interlaced, to which Poli has given the name of funicular muscles (j,j, fig ■ 347). They are particularly conspi- cuous in the cylindrical foot of the Solens, in the flattened foot of the Tell in®, and of the Uniones, and they have a remarkable arrange- ment in that of the Cardiac. They appear to be wanting in the foot of those Conchiferous mollusks that attach themselves by means of a byssus. In them the foot is reduced to the functions of spinning ( de filer ) the threads of the byssus, and it is not therefore surprising that its organization should be found to be peculiar. Reduced to a purely rudimentary state, the foot in the Monomyaria (b, fig. 348) appears rather as an appendage to the mass of the viscera than as their defensive envelope. The muscular fasciculi that terminate it pos- teriorly are small ; they pass through the vis- ceral mass to be attached either to the superior part of the central muscle, or within the in- terior of the hooks or beaks of the shell. Almost the whole of the Monomyaria furnished with a foot, have a byssus also ; to this rule there are indeed a small number of exceptions, among others the Lim®. Up to the present time the faculty of pro- ducing a bi/ssus is not known to belong to any other class of animals, and it is limited to a few only of the Conchiferous mollusks. Among the Dimyaria the genus Byssomya may be quoted as an example, also the members of the family of the Mylilacea; and, if the horny plates of certain Arch® be likened to the Fig. 353. byssus, it would also be necessary to include this genus in the group of byssiferous Dimyaria. In the Monomyaria provided with a foot, the whole of the genera are byssiferous, with the exception of those which attach themselves im- mediately by their shell. The byssus (b, fig. 353) is a bundle of horny or silky filaments, of different degrees of fine- ness and of different thicknesses, and flexible in various measures, by means of which the animal is, as it were, anchored to any solid body sunk in the sea. The filaments, for the most part distinct from one another, are, how- ever, occasionally connected into a single mass of a subcylindrical form, and terminated by a broad expansion, which serves as the point of attachment. This disposition is to be ob- served in the Avicul®, and leads to the belief that the horny mass of certain Arch® is a mere modification of the byssus. In those species of which a byssus is formed of separate filaments, these are all seen to be detached from a com- mon pedicle ( c,fig. 353), situated at the infe- rior base of the foot (cl, fig. 3.53). If the byssus be examined before any of the filaments are torn, it is easy to perceive that these are attached to submarine bodies by means of a small disc-like expansion of their extremities, of various extent according to the genus and species (a, a, a, fig. 354). Attentive examina- tion of these filaments shews that they are of equal thickness through their entire length, and that they have nothing of the structure of the hair of the higher animals. Fig. 354. If the byssus and foot of a byssiferous mol- lusk be placed under a powerful lens, the last filaments of the byssus are first seen to be nearest to the base of the foot; and if the infe- rior edge of the foot be inspected, a fissure will CONCHIFERA, 703 be found running completely along it, at the bottom of which a brownish and semi-corneous filament is often to be perceived ; this is neither more nor less than a filament of the byssus prepared to be detached by the animal, in order to which the animal stretches forth its foot until it encounters the object upon which the other fibres of the byssus are fixed ; to this it applies the point of the foot, which then se- cretes a small quantity of glutinous matter, continuous with the silky filament lying along the bottom of the furrow of which we have spoken. When the pasty matter has acquired sufficient consistency, and is firmly fixed to the stone or other body at the bottom, the animal retracts its foot, and in doing so detaches the new fibre to the base of the pedicle. The mode in which the filaments of the byssus are formed, is consequently entirely different from that in which hair or the horns of the higher animals are evolved, and it is easily under- stood when the intimate structure of the foot of the byssiferous mollusks is known, when we are aware that this organ consists in its centre of a pretty considerable fasciculus of parallel and longitudinal fibres. By a faculty peculiar to the class of animals that now engages our attention, the fibres situated at the bottom of the groove of the foot become horny, and are detached in succession in the form of threads as they become consolidated. Certain genera are celebrated for the abundance and fineness of the byssus ; that of the Pinnae, among others, which was even known to the ancients, may be spun into threads like silk or wool, and may be used to manufacture tissues of an unchangeable colour, and of great strength and durability. With reference to form, the foot presents a variety of interesting modifications. Some- times it is short and truncated, as in the genus Pholas; sometimes more elongated, but still truncated at the summit, as in certain Razor-shells (Solen), (a, fig. 355); in which the edges of the truncation are regu- larly toothed. A few of the acephalous mollusks have the foot cylindrical (a, fig. 356), as the So- lenes ; when it presents this form, the organ is generally terminated by a kind of glutinous point, or disc, which enables the animal to fix itself at different heights in the deep cylindrical hole it digs for itself in the sand. The foot, which is shaped like a tongue, is named linguiform, as in the Solen strigilatus; it is claviform when it is thicker at its extremity than at its base : it is found of this shape in certain other Solens. The Fig. 355. Fig. 356. foot again is vermiform when it is very slender and much elongated, as in the Loripes and Lima. When it is thus formed, it appears to us to be incapable of subserving motion. In a considerable number of species the foot is conical, as in the Cockle, («, fig. 357); and in this case it is generally folded into two nearly equal portions, so that by its means Fig. 357. the animal can leap pretty actively. It is secu- riform when its free edge is arched like the cutting face of an axe, as in Petunculus, (a, fig. 358). When it presents this form its edge Fig. 358. is generally divided into two lips, which, being separated, present with some degree of ac- curacy, although much contracted, the sem- blance of the locomotive plane of certain Gas- teropoda. When this structure occurs, the Fig. 359. foot is said to be bifid, as in Nucula, Trigonia. It is said to be flattened when it is thin and laterally depressed, as in Tellina and Donax ; to conclude, it is designated as bent when it consists of two portions connected at an angle with one another (5, fig. 359), of which the genera Cardium, Nucula, and Trigonia present examples. Various other modifications, of less importance than those we have particularized, 704 CONCHIFF.RA. also occur; these can be aptly enough alluded to in the anatomical description. From what has now been said it is easy to understand the offices performed by the foot. In the lithophagous and xilophagous Con- chifera, the foot, reduced to its rudimen- tary condition, is probably without any par- ticular use, unless perhaps it be among the Pholades, where, being in the form of a sucker, it may enable the animal to fix itself to the parietes of the cavity it inhabits. Among the Conchiferous mollusks that live at large, the chief use of the foot is to dig a furrow, into which the animal forces itself partially, and then advances slowly by making slight see- saw or balancing motions, a circumstance which has led Poli to designate the whole class of acephala by the title of Mollusca subsilentia. Several of these Mollusks not only make use of the foot in the way we have just mentioned, but also employ it as a means of executing sudden and rapid motions, true leaps, by which they are enabled to change their place with great celerity. It is of course unneces- sary to say that in those genera whose shell is attached immediately to the bodies at the bot- tom of the sea (Chama), the foot is of no use as an organ of locomotion at all events. In the byssiferous species, again, the organ, al- though but slightly developed, is the agent in spinning the filaments of this cable. Nervous system.- — Anatomists were long ig- norant of the existence of a nervous system in the Conchiferous mollusca. Poli first disco- vered it in the course of his dissections, whilst preparing subjects for the plates of his magni- ficent work, entitled, Testacea TJ triusque Sici- lia ; but he mistook the nervous system, occa- sionally of considerable magnitude, for one of absorbent or lymphatic vessels, and spoke of it under the name of lacteal vessels. In a very interesting memoir, Mangili exposed the error which Poli had committed, and rectified it by assigning to the vasa laclea of his learned countryman their true place as portions of the nervous system. The acephala have no brain properly so called. The nervous system is symmetrical in the Dimyaria, but loses this character in some measure in the Monomyaria. This diversity in the nervous system, coinciding with the number of the muscles, gives a higher value to the character which is established on the existence of one or two adductor muscles. In the Dimyaria we find, on each side of the mouth, a small ganglion above the (esophagus, towards the base of the labial palps (1, 1, Jig. 360). Each of these ganglions is of an oval or sub-quadrangular shape, and the two are connected by means of a transverse filament (2, Jig. 360) running across or over the oeso- phagus. From the edges of the ganglions many fi'aments arise, some of which on the sides descend into the substance of the labial palps (3, Jig. 360); others anterior are distri- buted to the edges of the mouth ; and others run to the lateral parts of the anterior adductor muscle, gain the thick portion of the edge of Fig. 360. the mantle, and detach numerous branches. From the posterior edges of these anterior ganglions there is one, and occasionally there are two nervous branches of considerable size sent off (4, 4, Jig. 360) ; these descend along the body towards the base of the branchiae, concealed amidst the visceral mass, and give off filaments in their course to the neighbour- ing organs, first to the stomach, then to the liver and heart, and next to the ovary and branchiae. A considerable branch descends on each side of the foot, and is expended upon this organ. When the lateral filaments have arrived opposite to the posterior adductor muscle, they advance along its internal sur- face, approach one another, and at their point of junction give origin to one or two ganglions of different sizes, but always larger than the anterior ganglions. When the posterior gan- glions are some way apart, a nervous filament always connects them. It is from these pos- terior ganglions that the nervous cords are detached, the branches of which are distri- buted to the whole posterior parts of the ani- mal Some run towards the anus, others to the thin portion of the mantle, and a consi- derable number to the thickened margin of the same organ. When the lobes of the mantle are conjoined posteriorly, and are continued from this part by means of siphons, among the nervous branches which follow the thick- ened edge of the mantle, one is distinguished of larger size than the others, which terminates at the point of commissure in a small ganglion. This little ganglion is not met with in the Dimyaria without a siphon; neither does it appear in the Monomyaria. When the siphons occur, however, a retractor muscle, peculiar to them, is almost invariably found also, as we have already seen. When these two parts CONCHIFEIIA. 705 exist, nervous branches are likewise discovered, destined for them, one for each of the retractor muscles, and one for each of the siphons. The posterior part of the nervous system of the Dimyaria is so considerable in comparison with the anterior part, that some anatomists have maintained that the title of brain should be given to the posterior ganglions, conceiving them to be of much greater consequence in the organization of these animals, and of more avail in regulating their functions than the anterior ones. In the Monomyaria the nervous system is in general less perfectly developed than in the Dimyaria. It is not quite symmetrical, and the posterior are not larger than the anterior ganglions. The nervous cords, too, are much more slender, and not nearly so easy of de- monstration as in the Dimyaria; it was not without difficulty that we discovered them in the common Oyster, the Pecten and the Spon- dylus. Poli has said nothing upon the nervous system of these genera. Our own researches in quest of it were perfectly fruitless at first ; but having bethought us that in the Dimyaria the nervous cords of the labial palps were always to be discovered without difficulty, we sought for the same filaments in the Mono- myaria, and were lucky enough to find them ; these led us by-and-bye to the anterior gan- glions, and by degrees to the detection of the entire nervous system. The anterior ganglions in the Monomyaria are extremely small ; they send a principal filament to each of the palps; a cord proceeds from them to the anterior part of the mantle which covers the mouth ; another runs from the ganglion of one side to that of the other, passing above the oesophagus ; and from the posterior angle several branches are detached to the liver, the stomach, and the branchiae. Among these there is one, and sometimes two, which, resting on the internal aspect of the central muscle, bend obliquely over its surface, and finally unite occasionally to form a small posterior ganglion. This gan- glion sends branches to the heart, to the ovary, and to the posterior parts of the mantle. The parallel cords traverse the thin part of the man- tle, sometimes radiating in a slight degree, and divide into numerous branches within its thick margin and the tentacular ciliary processes that fringe it. There is one among the monomyary genera, the nervous system of which we have not been able to study with due attention; this is the genus Lima. From what we have seen of it, however, it would appear that the ner- vous system in this genus is every way as perfectly symmetrical as in the Dimyaria. But before admitting this as a fact definitively, it were necessary to have verified its accuracy at least several times, which we have as yet had no opportunity of doing. When we consider the great simplicity of the nervous system of the acephalous mol- lusca, we can only conceive these animals endowed with sensibilities extremely obscure, and with instincts extremely limited. No especial organ of sense can be detected among them, unless perhaps it be that of touch, which appears to reside in every part of the body and of the mantle, and probably also the sense of taste, of which in all likelihood the maxillary palps are the organ. The manner of existence of these animals is in perfect accordance with the great simplicity of their nervous' system. Many genera live attached to submarine ob- jects, either by the shell immediately or by means of a byssus, taking no pains to avoid or to protect themselves from danger, and giving no sign of existence but by opening and shut- ting their shells : they shut them when any foreign body comes in contact with their mantle ; and they open them to admit the water which brings suspended in it the nutri- tious particles which they seize upon for their subsistence, and which is in itself necessary for the purposes of respiration. Among the acephalous mollusca which are not fixed in the manner of those now mentioned, those which have no siphon, or which have this part very short, live at the bottom of the sea, in spots covered with sand or mud, amidst which they burrow by means of the foot, and support themselves in an oblique position by resting upon the half-open valves of their shell. The acephalous mollusca again, which are furnished with a siphon, almost all bury themselves more or less deeply amid the sand or the mud of the bottom, contenting themselves with an ascend- ing or a descending motion, the latter sufficient in the moment of danger to gain the limits of their retreat, the former to enable them to protrude the free extremity of their siphon when they would establish the current of water necessary to their nutrition and respi- ration. It is easy to imagine that among ani- mals whose functions of external relation are so limited, the nervous system must continue extremely simple, a fact which could in some measure be predicated from observation of the habits of the extensive class whose structure and economy we are now engaged in consi- dering. Of the skin and its appendages. — The mantle. — The acephalous mollusca are enve- loped by two very thin fleshy laminae, which are seen covering or closely applied to the whole of the inner surface of the shell ; this is the part to which the name of mantle has been given (c, fig. 359 ; a, a, fig. 360). This name has been very appropriately given to this cuta- neous envelope, for it appears to be applied over the back of the animal, and to be extended over the lateral parts, to meet by its edges along the anterior middle aspect of the body. The mantle is composed of two parts generally equal, or nearly equal, each of which has been designated one of its lobes. In the natural position of the animal, one of these lobes is in relation with its right side, the other in relation with its left side ; they adhere intimately to the superior and posterior part of the body ; they become free at the origin of the branchiae, and form around the whole inferior part of the animal a cavity of various dimensions, within which the abdominal mass, the foot, and the 706 CONCHIFERA. branchiae are included. It is in this palleal sac that the animal establishes a current of water, destined to minister to the function of respiration, and to carry towards the mouth the alimentary particles with which it is fed. The median parts of the lobes of the mantle are ex- tremely thin and transparent, and a great number of vessels (c, fig. 362), and a few nervous filaments (7, 8, fig. 360) are perceived ramifying through their substance, and running towards the anterior and inferior edges. These edges, which extend as far as those of the shell, are thickened , and it is at the point where the thickening begins that the mantle adheres to the shell by means of a great number of minute muscles ( t , l, fig. 347; d,fig. 362), which leave a linear impression upon it. The thickening of the edges of the mantle is owing to the pre- sence of a great quantity of muscular fibres, fre- quently to several rows of contractile tentacular cilia ( m,m , fig. 347; e, fig. 361 &362); and, lastly, to that of an organ, which is the secerning apparatus of the shell. The muscular fibres are Fig. 361. Contractile cilia magnified. distributed some to the edges of the mantle, and others to the tentacula with which it is fringed. The whole of these parts are extremely retractile, and are endowed with such sensi- bility that the slightest contact is perceived, as is evinced by their instantaneous contraction. Zoologists have taken advantage of certain modifications in the lobes of the mantle to establish divisions in their methodical arrange- ments of the conchifera. This artificial means is sufficiently convenient, inasmuch as no anatomical inquiries are necessary in order to get at the distinguishing characters which these modifications supply. Latreille, in his ‘ Fa- milies du Rfegne Animal,’ as well as other zoologists, have also made use of the conjunc- tion or disunion of the lobes of the mantle to establish the principal divisions of their classifi- cation ; but they have perhaps given too much consequence to these characters, inasmuch as they bear no relation to the number of the muscles. Nevertheless, none of the Mono- myaria has yet been found which presents the lobes of the mantle conjoined, whilst the Dimyaria exhibit the two modifications which we have had occasion to mention, and which gives an opportunity to divide them into two grand series, the first comprising the whole of the Dimyaria whose mantles are united, the second all those whose mantles are open, or unconnected one lobe with another. The con- chiferous Dimyaria which exhibit the lobes of the mantle uniled are modified in this respect in a remarkable manner, a circumstance which induces us to enter somewhat in detail into this part of the anatomy of the conchifera. In making the series of acephalous mol- lusca commence with those which have the lobes of the mantle completely distinct, we may place near them certain genera in which the branchiae, conjoined in their posterior parts, form a kind of canal, within which the anus proceeds to terminate. This conjunction of the branchiae, extending as far as the edge of the mantle, forms a kind of band towards the pos- terior commissure; but, notwithstanding this, it may still be said that these animals have the lobes of the mantle altogether unconnected (Unio) (fig. 360) ; in other genera which have been held allied to this, the posterior band is not found, and already the lobes of the mantle appear united in the posterior part, to a very small extent, leaving a particular perforation for the anus. The mantle still continues open in its circumference (Mytilus). By-and-by neighbouring genera, and even particular spe- cies of the same genus, instead of a single per- foration, present two (f g, fig. 362) ; the second is destined to carry the water directly upon the branchiae. When these two perfo- rations have the faculty of being projected beyond the shell in the form of fleshy and con- tractile tubes of various lengths, they have re- ceived the special denomination of siphons; and the term perforation has been reserved to be applied to the holes of the mantle, which never pass the edges of the shell. When the two siphons begin to appear, the lobes of the mantle still continue disjoined in a portion of their circumference; and this opening (b, b, fig. 356, h, fig. 362), is destined for the passage of the foot. Fig. 362. In proportion as the foot is modified in its form, in proportion as it becomes more rudi- mentary, the two lobes of the mantle are ob- served in the succession of genera to become more and more extensively united, and it hap- pens at length that in certain genera (Mya, Saxicava, &c.) a very minute submedian or anterior perforation, corresponding to the rudi- mentary foot, is all that remains of separation CONCHIFERA. 707 between them. It is a circumstance worthy of remark that the siphons are observed to be- come elongated and thickened in proportion as the lobes of the mantle are more extensively united. This circumstance, however, is only true in a general way, for it would be easy to quote many striking exceptions to it. 2. Siphons. — We have already had occasion to see the siphons commence in certain genera by simple perforations ; they increase in length in the succession of genera ; and in a certain number they always continue unconnected through their entire extent ( g , h, Jig. 346 ; b, c, fig. 355). In other genera, however, the siphons are seen at first united towards their base, then conjoined nearly to the middle, co- hering almost to their ends, and finally blended through their whole length, so as to form a single elongated subcylmdrical fleshy mass, pierced through its entire length by the canals of the two siphons, one of smaller size, situ- ated superiorly for the anus, the other larger, situated under the former, and destined to transmit the water to the branchiae. Whether connected or not, the superior siphon is always characterized as the anal, the inferior as the branchial siphon. The structure of the siphons is entirely mus- cular, so that their free extremities are capable of contracting and of being elongated to a very considerable degree. They are beset around their external orifices with a great number of papillae, (n, o,Jig. 347), occasionally truncated at their extremities and of exquisite sensibility. The water has to pass over these papillae before it can enter the mantle, and un- doubtedly they apprise the animal of the pre- sence of every foreign body that might injure it. In a few genera the siphons contract by means of their component muscular fibres; but in the greater number they have a parti- cular retractor muscle running on each side of the animal, and in relation, in point of mag- nitude, &c. with the length and degree of con- tractility possessed by the siphons ( P,fg ■ 347). The existence of this muscle, and consequently of siphons, is manifested on the interior of the shell by a posterior sinuous furrow of various depth, and indicating upon a narrow line the point of implantation of the retractor muscle of the siphons. In some of the acephalous mollusks the siphons are too large to he received within cover of the shell, in which case the retractor muscle is generally small, inasmuch as it is then of little use (Mya, Glycimeris); but in those species in which the siphons are of mid- dling size, or not so large as to be incapable of entering the shell, the retractile muscle is of considerable size and power (Tellina, Psammobia). 3. The shell.- — The lobes of the mantle appear to be the efficient parts in determining the form of the shell, and it is by their thick edges that this covering is in great part secreted. The whole of the Gonchiferous acephala, without exception, are included within a bivalve shell, the two parts of which are joined by a point in their upper edge, to which the title of hinge has been given by naturalists, and very pro- perly, because it is in truth upon it that the motions of the valves take place. General structure. — When examined with due attention, the shell is found to be composed of two kinds ol laminse very distinct from one another (a, b, Jig. 363) ; the one, secreted from within outwards by the edges of the mantle, present themselves under the form of greatly elongated cones, the thick parts of which are turned towards the outer surface («, c, c, Jig. 363) ; the other, in parallel layers, secreted by the central and posterior parts Fig. 363. of the mantle, line the interior of the shell, and in many species at length fill up the cavity of the hooks. These two layers of the shell are frequently found in cer- tain fossil species almost com- pletely separated from one an- other. At other times the inner layer is seen to have been dissolv- ed away, whilst the external one continues without appealing to have undergone any great change. It is in the genera Chania, My- tilus, Pinna, Spondylus, more es- pecially that the two laminae of which a bivalve shell is formed can be studied to greatest advantage, and this study is of importance as leading to a more accurate knowledge of certain fossil genera, in regard to the charac- ter of which some uncertainty has always pre- vailed, by reason of one of the constituent portions of their shell always being found dis- solved, as in Patillus. In some genera the ex- ternal layer is very readily distinguished, from having a fibrous structure (a, a, Jig. 369), a structure observed more especially in the shells of the Pinna family and those of the Malleacea. The two layers of the shell are in the inverse ratio of one another in point of thickness : the external layer, extremely thin towards the hook, increases continually towards the edges, whilst the inner layer, thick at the hook, becomes thinner and thinner as it ap- proaches the edges, around which it is usually exceeded a little by the outer layer. A fact well deserving of attention is this — that the muscular impressions and the whole articular aspect of the hinge are formed in the substance of the inner layer of the shell, and these parts, of so much consequence, do not leave a trace upon the external layer when this alone is pre- served. It is only from having neglected to study the structure of the shell with sufficient attention that naturalists have found themselves at a loss to discover the true characters of certain fossil genera, as Podopsis, Spherulites, which, in consequence of their position in porous chalky beds, never occur with more than the outer layer of their shell in a good state of preser- vation. The hinge. — The part of the edge of a shell by which the two valves are conjoined, is, as we have already had occasion to state, deno- minated the hinge. This part is entirely formed by the inner layer of the shell. The part of 708 CONCIIIFERA. the shell, of various length and thickness, upon which the hinge occurs, is called its cardinal edge. In the hinge two structures are appa- rent: 1st, an elastic ligament, the position of which is variable; 2d, projections and corres- ponding cavities on either valve, destined un- doubtedly to give additional strength to their union. 1. The ligament.- — The ligaments of bivalve shells are distinguished into two kinds, accord- ing to their structure and their position: they are internal when they are completely hidden by the cardinal edge of the shell ; they are external when they appear on the outside be- yond this edge. The internal ligament is com- posed of a great number of highly elastic fibres, parallel to one another, and perpendi- cular to the valves they connect. They are secreted by a lamina of the mantle, projecting upon the back of the animal, and penetrating between the edges of the two shells. The fibres of the ligament secreted when the shell is partially open, are of too great length when it is shut, so that when the valves are ap- proximated to one another these fibres are forcibly compressed, and their elasticity is brought into play, by which it is only necessary for the animal to relax its adductor muscles in order to have the fibres of the ligament, in their effort to regain their natural length, force the valves apart from one another to a deter- minate extent. When the ligament is external, it rests upon the prominent parts of the cardinal edge, parts to which the title of nymplue has been given («, a, fig. 365). When the ligament is of this kind, it consists of two distinct layers, one external, thin, and very strong, composed of transverse fibres, which extend from one nympha to the other, and are strongly inserted within a groove hollowed out of the base of each of them. The other portion of the external ligament is of precisely the same structure as that of internal ligiments, and is comprised between the nymphs and the outer layer, of which we have just made mention. The action of this ligament is also precisely the same : it forces the valves apart when the animal ceases to maintain its adductor muscles in a state of contraction. In the extensive series of Conchiferous mol- lusks, some modifications, as might have been anticipated, are met with in the conformation of the ligament, external as well as internal. If many members of the family of the Dimy- aria be examined, the ligament, very prominent, outwards, will be seen bearing upon nymph® more prominent externally than the cardinal edges, but contracting gradually under this edge in proportion as the nymph® become shorter, until in some species we find that, still preserving the structure of the external ligament, the whole of this apparatus is never- theless entirely hidden under the superior edge of the shell. This point attained, the external ligament alters by insensible degrees into a ligament completely internal ; that is to say, the exterior fibrous layer diminishes gradually, and at length disappears entirely when the ligament is much developed upon certain in- ternal parts of the hinge. Our own opinion is, that the ligament is internal when the nymph®, having undergone certain modifications, have been transferred to the interior, and have as- sumed the form of acetabula. The ligament is sub-internal when the nymph®, of less depth, still show a portion of the ligament externally; finally the ligament is external when the nymph® are situated towards the upper edge of the shell. This displacement of the ligament, and of the solid part which gives it insertion, is very well seen in the succession of the following genera : Solen, Punopus, Thrac.ia, Calcinella, Amphidesma, Lutraria, Macira, Mya, Crassatella. In those shells in which the beaks or hooks are of great size, and spirally turned to one side, the ligament, in keeping pace with the growth of the covering, bifurcates at its anterior part, and this bifurcated part then becomes useless. This circumstance is particularly remarked in the Isocardium and the Chama. The ligament also presents a very remarkable peculiarity in the three genera of the Area family. The superior surface of the hooks in these genera (Area, Pectunculus, Cucullcea ) is of greater or less breadth, flattened, triangular, some- times furrowed, and has a thin ligament, re- sembling an elastic web, strongly attached to it. The ligament in the greater number of the genera of the Monomyaria is situated within a triangular groove or depression of a breadth corresponding to its dimensions. In one fa- mily, that, namely, of the Malleacea of La- marck, several genera ( Perna, Crenatula ), instead of having a single ligament, have a regular series of fossicul®, in each of which a ligament is implanted. Cardinal edge.— The cardinal edge presents a great number of modifications. Sometimes it is simple, and of various degrees of thick- ness, in which case the hinge is said not to be articulated; sometimes it presents projections and reciprocal cavities, in which case the hinge is said to be toothed or articulated upon the cardinal edge. These projections and hollows are remarkably regular in their formation, and every change in their appearance commonly coincides with one of greater moment in the organization of the animal. This remarkable coincidence, to which only a very few exceptions are yet known, has led conchologists to attach great value to the characters derivable from the hinge, and Lamarck, among others, has grouped several families and a great number of genera after them. We believe, with this celebrated naturalist, that the hinge supplies excellent characters for the distinction both of families and genera, but we have been led to this con- clusion by viewing the subject in a different point of view from that taken by Lamarck. Every conchologist knows the interesting genus denominated Pholas. In the interior of the valves of this genus there always exist two kinds of large curved processes, extend- ing from the interior summit of the hooks (a, fig. 364), and advancing nearly to the middle of the valves. According to our views CONCHIFERA. 709 Pholas. Petricola. 364. these appendages are the first parts of the cardinal teeth. There i is one fact which deserves to be insisted on in connexion with this genus ; it is that there are no ligaments found, and that the cardinal edge, folded in upon itself (rentre sur lui- meme), is not flattened and placed in the same manner as in the other conchifera. Another circumstance of equal impor- tance to be mentioned is that the processes, of which we have just spoken, are buried in the substance of the animal, and covered wflth a duplicature of the mantle which accompanies them as they plunge amid the visceral mass. Without leav- ing the genus Pholas, the cuil- lerons may be seen gradually contracting in their breadths, be- coming shorter, and approaching nearer and nearer to the edge. But if other shells be examined, which obviously form the links of transition from the Pholada to the Saxicava, or Petricola, the processes are found to turn upon the edge, to become coherent with it so as to form a salient margin, and by their free extremity to produce a projection ( b , Jig. 364). In our opinion the toothings of ihe hinge of all the other bivalve shells are produced in the same manner; but with such modifications as rarely admit of those relations being traced which are to our mind obvious in those genera that have just been particularly mentioned. With regard to the shells of the genera in which the hinge is complicated, of which the cardinal edge is thickened, and the cavity of the hook partly filled by the external layer of the shell, it is difficult to imagine in what manner the suc- cessive growth of the hinge has taken place, and to make out its analogy in point of struc- ture with that of the Petricola pholadiformis and of the Pholada generally. To discover this it is necessary to break a great number of the shells, or to make various sections of the edge, when the direction of the denticulations with which it is furnished must be followed. The teeth of the hinge will then be seen arising from the summit of the book (c, jig. 364), becoming developed, and forming a solid arc, surrounded and hidden by the matter of the cardinal edge itself, and these arcs thus disen- gaged will be found to present the strongest analogy with those of the Pholada. It is from viewing the hinge in this manner that we have been induced to think that its structure was in reality of sufficient importance to make it be constantly appealed to for the distinguishing characters of genera. Naturalists have agreed to designate as the cardinal teeth those solid projections which arise on the edge of the hinge. These projec- tions on the one valve are for the most part accompanied with corresponding depressions on the other for their reception mutually. The depressions are called cardinal pits. These cavities and these projections present a great variety of modifications which cannot be well understood without a long and careful study of the conchiferous tribes generally. When the teeth are collected under the hook, they pre- serve the title of cardinal ( b , fig. 365) ; when Fig. 365. one or two in number, and remote from the centre of the hinge, they are named lateral teeth. Of these lateral teeth one is an- terior (c, fg. 365), the other posterior ( d , fig. 365). The anterior lateral tooth is com- monly situated at the extremity of the lunule, and the posterior lateral tooth at the extre- mity of the ligament. The cardinal teeth, properly so called, vary in number. When there are but two, the one is anterior, the other posterior ; when there ate three or more, those in the middle are entitled median teeth. If the hinge be composed of a great number of teeth, it is said to be serial (6, b, fig. 366). Fig. 366. 710 CONCHIFERA. The teeth are commonly simple and conical ; occasionally they are flattened either lengthwise or transversely. In a considerable number of species they are grooved to different depths on their summits, and the teeth are then said to be bifid (e, fig. 365). There are other parts still which present themselves upon the cardinal edge, and of which it is important to have a sufficient know- ledge,— namely, those destined for the implan- tation of the ligament when it is external ; to these parts the name of nymphte is given. These form two callosities more or less promi- nent, which are seen along the posterior and superior edge of the shell. When the ligament is internal, it rests upon a cavity generally pro- minent towards the interior of the valves, and designated by the name of cuilleron or spoon- shaped cavity. This cuilleron is generally situated in the centre (c, d, Jig. 367) of the Fig. 367. hinge ; sometimes, however, it becomes a little oblique, elongated, narrower, and runs in the direction of the posterior and superior edge. When we direct our attention to the external forms of thebivalve shells, we observe numerous modifications, of the principal of which it is necessary to take some notice. In a consi- derable number of species the two valves are alike, when the shell is said to be equivalved. When one of the valves is larger than the other it .is of course inequivulved ; to constitute it so it is not necessary that the shell should be irregular. A regular shell is that which at liberty always presents the valves alike in all the individuals of the species ; an irregular shell is not only inequivalved, but farther, the whole of the individuals of the same species are not exactly of the same form, and want the same peculiarities of external conformation generally. The Oysters are inequivalve and irre- gular shells ; the Corbules are inequivalve and regular shells; the Venus and many others are perfectly equivalved and regular ; the Placunes, to choose a particular example, are in like manner equivalved but irregular. The length of a shell is always calculated from the summit of the hooks to the inferior edge. All that are of greater length than breadth are entitled longitudinal, ( Mytilus, Pinna, &c. Jig. 353) ; and all that are of greater breadth than length are named transversal : the breadth is estimated by a line passing from the anterior to the posterior extremity, and cutting the posterior axis of the shell at a right angle, ( Solen, Tel- lina, &c. The number of transverse bivalve shells is very great : Jig. 367). If the position of the hooks with relation to the transverse and longitudinal lines be considered, the shell is said to be symmetrical, when, the hooks being in opposition, the anterior segment is equal to the posterior, and of the same form in consequence of this symmetry ; a perfectly symmetrical bivalve shell might in fact be held to be composed of four similar parts ; but this perfection of symmetry, which exists in many Brachiopods, never appears among the conchifera properly so called, even those which are the most symmetrical in external character, ascertain Petuncula, Jig. 358, would be more correctly designated as sub-symme- trical. When the hooks are inclined to one side of the shell, and divide it into two equal parts, it is said to be equilateral. But if the hook be carried further forwards than back- wards, so that one of the sides of the shell then becomes larger than the other, it is said to be inequilateral. In the greater number of the conchifera the two valves of which the shell consists join each other accurately around their whole circumference, in which case the shell is said to be shut or closed. When, on the contrary, the two valves present a vacancy between them in some part of their circum- ference, when they are approximated as nearly as possible to one another, the shell is said to be patulous. This open space is vari- ously situated in different species, sometimes in the anterior surface, rarely in the inferior edge, but pretty frequently in the posterior edge, especially in those species of the class whose mantle is prolonged on this side into one or two syphons. Surfaces of the valves. — Every bivalve shell has two surfaces, an external surface and an internal surface. Various parts are distin- guished on the external surface, — the hooks, the belly, the edges, the lunule, and the corslet. External surface. 1 . The hooks. — The protuberant opposed parts, often inclined to- wards the anterior side, and presenting an apex of various degrees of sharpness or blunt- ness, are thus denominated. When these hooks are very much inclined forwards, they are styled lateral. If they are particularly CONCHIFERA. 711 prominent, they are said to be cordiform. When they are inclined towards one another, so that their summits approximate, they are said to be opposed. The hooks in no case in- cline to the posterior side ; but occasionally they disappear almost entirely, and, as in the Solens, exhibit no kind of prominence. In other instances again they project a great way, and form the most prominent part of the shell (Mytilus, Pinna), in which case the hooks are said to be terminal. 2. The belly of the shell comprises the greatest part of the exterior surface. It is bounded at the base of the hook, as also by the lunule and the corslet. It is more or less rounded or flattened according to the general form of the shell, and we shall speak of the dif- ferent points worthy of consideration con- nected with it when we come to define the various particulars of the external surface con- sidered in a general manner. Fig. 368 A. f- a, superior edge ; b, uncus ; c, lunula ; e, anterior edge ; f, inferior edge ; g, posterior edge. Fig. 368 B. b a, anterior edge; b, inferior edge; e, posterior edge ; d, edges of the shield ; /, ligament ; f to h, nympha ; h, other extremity of the liga- ment ; i, point of the uncus or hook ; l to n, lunula; l, anterior cardinal tooth; j, median cardinal tooth ; g, posterior cardinal tooth ; m, anterior lateral tooth ; o, anterior muscular im- pression; p, posterior muscular impression; r, palleal .impression ; s, sinuosity of the palleal impression. 3. The edges. — These are indicated, pre- serving the shell in the position which we have mentioned; they are anterior, posterior, inferior, and superior. The extent of these edges is very various, and depends entirely on the form of the shell and the position of its hooks. Upon this particular the simple in- spection of a collection of shells will give much more information than we can hope to do by the most laboured description ; so that we shall only say that the anterior edge cor- responds to the head of the animal, the pos- terior to its posterior extremity, the inferior to its ventral aspect, and the superior to its back. The edges in themselves, however, present a few particulars which it were well to mention. Sometimes they are thin and cutting ; very com- monly too they are thick and continue simple. In those species especially whose shells are marked externally with longitudinal strite, they are notched and toothed alternately, the pro- jections of the one valve in almost all instances being received into the cavities of the other. When these projections and notches are very fine, the shell is said to be crenate; if larger, toothed; when very large and few in number, with their summits blunt, again, the edge is undulating as in the Tridacna; on the con- trary it is angular when the prominences con- tinue sharp as they do in certain of the Ostrese; in the latter case the edge is also said to be widely or deeply dentated. f 4. The lunula does not occur in every genus of bivalve shell. It is met with, how- ever, among the greater number of the Mono- myaria ; it is also met with among many Dy- myaria, and is particularly conspicuous in the Venus. It is a space comprised on the ante- rior surface immediately under the hooks, and is generally circumscribed by a particular line or depression. The lunula presents certain pe- culiarities which it is often of consequence to attend to, in order to distinguish certain spe- cies otherwise apt to be confounded with one another. Its form is various, sometimes cordi- form, a shape which almost peculiarly belongs to inflated and subglobular species; sometimes lanceolate, sometimes very narrow, especially in species whose shells are flattened. The lunula is very rarely prominent, unless it be towards the centre. Sometimes it is super- ficial, pretty frequently depressed, and there are a few genera or species in which it is deeply hollowed. 5. The corslet occupies a part of the su- perior and posterior edge of the shell. It is only met with in the Dimyaria ; it is not so accurately bounded as the lunula ; it is also wanting in a great number of genera, in which its presumed position is arbitrarily determined. It is towards its upper part that the nymphse are observed in those species whose ligament is external. In a very considerable number of Mono- myarians the lunula and corslet are replaced by certain projecting parts to which the name of auricula or auricles has been given. These occur more especially in the Pecten family — the Pectinites of Lamarck ; they are distin- 712 CONCHIFERA. guished into anterior and posterior, and they are frequently unequal. If we now turn to the particulars of the external surface of the shell of the conchi- fera, we shall find many points worthy of being attentively noted. In a very great number this surface is covered with a thin and frequently deciduous lamina of a sub- corneous and often filamentous substance, to which the title of epidermis has been given. This matter is secreted by the most external edge of the mantle, but observers have not yet stated in what manner the secretion takes place, and what means the creature employs to make this epidermis adhere so strongly to its shell. The epidermis often occurs both of considerable thickness and extent (Glycimeris, Solemya), and thus constitutes an important portion of the shell. In other genera the epi- dermis appears to be wanting entirely, and in others bears some resemblance to velvet of thicker or thinner pile, and then consists of a large quantity of short hair, standing erect, and more or less closely set. In some species these hairs become more scanty, but increase greatly in length, as we perceive in certain Archidae and Bucarides. When it occurs in certain species the successive growths of which are manifested by irregular ridges, the epider- mis is irregularly squamous. The epidermis is insufficient to furnish any generic character that can be depended on ; for there are certain extremely natural genera in which some species are covered with it whilst others are entirely naked. The other particulars of the external surface of the shell are soon glanced at : they consist of stria, ridges or ribs, and furrows, which, according to their direction, are distinguished into longitudinal when from the hook they run towards the inferior margin, and transverse when they follow an opposite course, that is to say, when they run from before backwards ; they are oblique, again, when they follow a line in any way inclined to the longitudinal or the transverse. These stria, ridges, and furrows, may cross one another, and the shell is then trellised. They may also severally present a great variety of particular appearances, the de- finitions of which maybe found in the ordinary elementary works on Conchology , but which may all be learned much more rapidly from even a very moderately attentive study of the shells themselves than from any written description, however minute and accurate. Internal surface. — The inner surface of bi- valve shells is commonly smooth and polished, and often presents different colours which de- pend on the secretion of that part of the man- tle which produces the solid laminae of the inner surface. The greater number of shells are white within, and many of them are na- creous or like mother-of-pearl. Mother-of- pearl would appear to be the consequence of a molecular arrangement of the calcareous matter intimately united in a constant ratio with the animal matter by the combination of which the shell is formed. The pro- portion of the two substances does not ap- pear to be the same in the non-nacreous and the nacreous shells ; there are some which afford a much larger proportion of calcareous, and others which yield a much larger propor- tion of animal matter when analysed than is usual. Naturalists are now generally aware of the experiments, an account of which is to be found in the Philosophical Transactions, from which it appears that the nacreous lustre is owing to the decomposition of light by an infinity of asperities of excessive minuteness which beset the surface of the shell. It has, indeed, been found possible by means of an impression from a mother-of-pearl surface taken in sealing-wax especially, to transfer the power of exhibiting corresponding phenomena to the surface of the wax.* There is a variety of characters exhibited by the interior of the valves which it is of con- sequence to be familiar with. In shells which have belonged to dimyary mollusks, two muscular impressions of variable depth are constantly to be found in the interior. Some- times they are so superficial that they escape an examination which might even be charac- terized as minute. One of these impressions is on the anterior side of the shell, the other on the posterior. They are generally sub- rotund ; sometimes, however, they are elon- gated, which serves as an announcement that the muscles were flattened. In some genera these muscular impressions are of a particular form, as may be observed in the Lucina for example. It is a circumstance worthy of ob- servation that the muscles of the animal shift their place and come forward in the shell in proportion as it grows, and it might have been concluded, a priori, that this could not be otherwise, when the mode of increment pecu- liar to the class is taken into consideration. On escaping from the ovum, a conchiferous mollusk is already provided with its shell, of course of very small size, and its two adductor muscles; and the relations of these muscles to the shell and the other internal organs are the same as at every subsequent period. When the animal has attained to some lines in length, and by the lapse of time to much larger di- mensions, did not the muscles undergo a gradual displacement the shell would be found as thin at the summit as it was on escaping from the egg, and the muscles prolonged into the interior of the hook. Now, not only does the shell go on increasing in thickness and the hooks fill up, but observation shows that the adductor muscles always preserve the same relations and the same proportions. To study in the best possible manner the successive dis- placements of the muscular impressions, the best mode is to saw a fossil oyster-shell length- wise in a line passing from the summit through the centre of the muscular impression. The ; impression will then be seen beginning towards * [We have heard this point disputed. The power which the sealing-wax had certainly gained in some instances of exhibiting the mother-of- pearl lustre was afterwards shown to depend on the wax having detached a minute film from the sur- face upon which it had been pressed. — Ed.] CONCHIFERA. 713 the summit and increasing gradually in its dimensions, so as to form a long triangular imprint, running obliquely through the thick- ness of the shell. When, at a very early age, the shell was extremely thin, the muscular im- pression existed very near to the external sur- face; but in proportion as the animal has become older, and new layers of calcareous matter have been successively added to the former, the muscular impression is found to have become farther and farther removed from the external surface. It is generally on the surface of the muscular impressions, and in the substance of the adductor muscles them- selves, that those peculiar solid and highly prized excrescences called pearls are produced. These excrescences are engendered in a very considerable number of genera, and it is to be presumed that they may occasionally exist in all ; it is, however, among the Monomyaria that pearls are most constantly formed. Various causes have been assigned to explain the formation of pearls. But it seems enough to be aware in a general way of the manner in which bivalve shells grow to understand how pearls are produced. Their production, it would appear, may be assigned to some accident hap- pening to the animal ; sometimes a few grains of sand getting between the mantle and the shell prove nuclei for their formation, but still more frequently they are consequences of per- forations made by a species of Annelidan, to the attacks of which bivalve-shelled animals are obnoxious. In either case the animal, feel- ing itself injured, deposits over the grain of sand or the small orifice made by the Annel- idan, a thin layer of nacreous matter, secreted accidentally and superabundantly with re- ference to its regular laminae of progressive growth. In consequence of this, the shell at the point where the grain of sand lodges or where it is wounded acquires more than its usual thickness. This thickening, from the mere fact of its presence, becomes a perma- nent cause of excitement to the mantle of the animal, so that this organ goes on secreting an unusual quantity of calcareous matter, in con- sequence of which there results an elevation that increases with the age of the animal, so much the more rapidly as the annoyance has been greater and more permanent. When the mass has increased so much as to penetrate somewhat deeply into the substance of the organs, it is then apt to go on increasing by depositions of nacreous matter upon one of its extremities, by which we have pedunculated and elongated pearls produced. Zoologists have also asked how those pearls that are found perfectly free in the interior of conchi- ferous mollusks were formed. We shall first observe that these pearls are met with more especially in the substance of the adductor muscles ; now if it be remembered that these muscles shift their place in proportion as the animal grows, it may readily enough be al- lowed that a pediculated pearl developed on the surface of the muscular impression itself, might be detached from its connexion with the shell by the advance of the muscle, be- VOL. I. come free in the substance of this muscle, and there continue to increase vvith more or less rapidity. This explanation, which we advance for the first time, appears to us sufficiently plausible ; but, before admitting it as an esta- blished fact, it would be well to institute some experiments in regard to the successive changes of position undergone by the adductor muscles of a conchiferous animal. Fig. 369. The mantle, as we have seen, is attached to the shell by a determinate portion' of its sur- face. In the Dimyaria the part that is ad- herent is not far from the thickened edge of the mantle ; it adheres by means of the small muscles which regulate its contractions, as well as those of the tentaculary papillae with which it is commonly fringed. In the Monomyaria the adhesion of the mantle is situated much higher, and very nearly at the place where the lobes of the mantle are detached from the general mass of the body. From the adhe- sion of the mantle to the shell there results a linear impression, to which M. de Blainville has given the name of palleal impression ; in the Dimyaria it extends from before backwards, from the anterior to the posterior adductor muscular impression, following the circum- ference of the edge. This linear impression is simple when it presents no inflexion in its course. In a considerable number of the Di- myaria it is observed to form a notch of dif- ferent depths in different species, directed towards the mantle. This notch appears to be 3 A 714 CONCHIFERA. produced, as we have already said, by the pro- per retractor muscle of the siphons. Besides the muscular impressions of which we have now spoken, several others of much less importance have been particularized in the greater number of the conchiferous mollusks. All tire species that have a foot have peculiar muscles to move this organ, and these have their fixed point of action on some point of the interior of the shell. They are generally divided into two principal fasciculi; the one runs to be inserted within the hooks, the other in the Dimyaria proceeds to be attached before and above the posterior adductor muscular impression. In the Monomyaria, the foot of which is generally rudimentary and without use, we observe nothing more on each side of the body than a single small fibrous fas- ciculus, the impression of which is found on the inside of the hooks. In some genera of Dimyaria, and particularly in the Unio, we observe three and sometimes four muscular im- pressions belonging obviously to the adductor muscles of the valves, which are occasioned by the anterior adductor muscle in particular being divided into two fasciculi, often of un- equal size, as in certain Uniones, and some- times equal and of considerable magnitude, as among the Iridines. From the summary and concise view we have taken of the principal facts in the organi- zation of the Conchifera, very important con- clusions may be drawn with reference to the classification of these animals. Taking the Conchifera, properly so called, and looking narrowly into that which is of most importance in their organization — the ner- vous system, vve find two principal modifica- tions, coinciding in a very remarkable manner with the number of the muscles. This num- ber of the muscles, permanently proclaimed by the impressions they leave on the shell, presents an important character by means of which, while we define their limits somewhat more strictly, we feel authorized in retaining the two grand orders of Lamarck, — the Conchi- fera Dimyaria, and the Conchifera Mono- myaria. A fact of some importance, and brought to light by the observations of Poli, is that a small nervous ganglion exists at the point of commissure in those acephalous mol- lusks which have the lobes of the mantle con- joined. This peculiarity gives new conse- quence to the characters drawn from the con- joined or disunited state of the lobes of the mantle. Unfortunately the circumstance is not always indicated upon the shell ; it is, in fact, only obvious upon those inhabited by siphoniferous animals; it is quite inapprecia- ble upon those the inhabitants of which have siphons so short as not to require a particular retractor muscle to draw them within cover of the shell. With regard to the other organic characters which furnish data available in clas- sifying the Conchiferous mollusks, these are all of so little permanency that they are only useful in supplying secondary hints for the arrangement of families and genera. Thus neither the branchiae nor the heart present any character susceptible of generalization or of contrast. Better data might perhaps be ob- tained from the conformation of the organs of digestion ; but these organs have hitherto been examined in comparatively so small a number of genera and species that they cannot be brought forward usefully in supplying cha- racters for a general classification. If, as we ourselves feel inclined to do, the hinge be taken as the point of starting in the Pholades, this part may be made the means of giving excellent characters in its principal modifica- tions for the establishment of genera. It is, indeed, very remarkable that we should find the characters as indicated by the hinge almost constantly in harmony with those af- forded by the rest of the organization ; and with a few exceptions, relative to several ex- tremely natural families, that of the Unios for example, all that is valuable in the generic cha- racters generally may be preserved along with the characters supplied by the hinge. Ano- ther character which may be usefully employed in classification is assumed from the regularity or irregularity of the shell of the animal ; in generalizing upon this, like groups are obtained in the two principal divisions of the Conchifera, and the two principal divisions of the classi- fication are referred to the simplicity or exact- ness of the dichotomy, whilst natural groups are preserved as much as may be in the linear arrangement. Method, it must ever be remembered, is an artificial means of introducing order among a series of observed facts, and of approximating, according to the analogy of their organization, the beings which nature has scattered over the face of the earth ; method is a human creation altogether, and in this light must it be viewed. To be all it ought, every known fact must be included, and the greatest possible amount of organic relationships between the individuals of each great class must be indicated. In an exposition of facts seriatim, and as they occur in a book, every thing has to be arranged in sequence, and therefore in the linear mode, now so generally followed by naturalists. In this way, however, it is impossible to express the enchainment, the inosculation, so to speak, of the different groups. To counterbalance this inconvenience, we are of opinion that the clas- sification ought to be made with lateral offsets, now terminating abruptly, now divided once or twice, sometimes inosculating variously, an! again, departing from a common trunk, dispo- sed in one case in a right line, in another in a curved line, and in a third in a circle. We conceive that it is according to these new views only that the acephalous mollusks can be pro- perly arranged ; it is accordingly upon the principles just announced that the following table is constructed. Although in the present state of our know- ledge of these animals many important parti- culars are still unquestionably wanting, this division of the molluscous tribes nevertheless presents fewer gaps than any of the others, in- asmuch as opportunities have occurred of ex- amining some one or other of the animals be- longing to the whole of the genera. CONCHIFERA. 715 Galeonnucca, Saxicava, Petricola, Venerupist siiaiapiCif) ‘e/Cuiaiog 'uaps ‘BaSdouej ‘snjjauaios- QS rt — g a. a ■o I V° -5 c, E S’® 5.2-0 ■§* m c J2 O 3 bfi y ® rt g.2 ■ -- e — d z c >>e hi oa E-Z ££< £ V* — ' Oi «J .Sg.sS 6 -o o c u = i S’ c & O w Q, CO 75 O 3 : -3 • O O « 5 s H S cs < ft < -i O X Ph fr> < fcd ft O w H cfl o L-. ( L c c >- h E f. C i c k E i- C. 5 2 < og> S<5 3 A 2 I CONTRACTILITY. 716 This tabular view of the classification exhibits certain particulars, upon which we deem it necessary to offer a few explanatory remarks. As we said before, the series as a whole may be regarded as a common trunk, from which various branches spring, sometimes anastomo- sing, sometimes ending abruptly. It is thus that from the Clavigella we observe a lateral line departing, formed of the genera Fis.tu.lana, Galeomma, and those of Lamarck’s family of Petricola. These genera descend parallel to the common trunk of the classification, so as to approximate in as great a degree as possible the genus Venerupis to the genus Venus. The genus Pandora has numerous analogies on one side with the Corbula, but it has also many with the members of the genus Osteodesrna, on which account it is made to depart laterally fiom the Corbula, and to ascend towards the Osteodesmata. The Lutraria are also variously related to several genera of the Osteodesmata, and this genus is joined to that of the Thracia by means of the genus Anatinellu, which we place crosswise to connect the genera just men- tioned. In the Mactraceu, we pass without any very great stride from the Lutraria to the Mactra, from the Mactra to the Erycina and to the Amphidesma. Farther, in order not to interrupt this series of relation- ships, we place upon a lateral line departing from the Mactra the two genera Mesodesma and Crassatella. Every naturalist knows how great the resemblance is between the flat and broad Solens ( Soletellina, De Blainv.) and the Psammobite ; but we also know that the genus Psammobia has so many analogies with the family of the Tellinida, that it is impossible to detach it from this family in order to include it within the family of the Solenaceae. To avoid interrupting the relations of this genus to those of the Solen family, we have recourse to an ascending line composed of the genera Sulen- ertus, Panoptea, Solen, Solemya, and Glyci- meris, by which means we approximate, as much as possible, these last genera to the fa- milies Pholadia and Osteodesmata, with which they have in fact unequivocal relationships in point of organization. We consider the family of the Lucinidtz as a lateral and truncated branch of the Conclude, divaricating from the genus Astarte. W ith regard to the Cyclada, we place the genus Glaucoma of Mr. Gray laterally, between the Cyrenas and the Venuses, so as to establish the connexion between the two ge- nera; whilst departing also from the genus Cyrena we place our genus Cyrenella obliquely in order to make it join that of Lucina, this genus of Cyrenella being to Cyrena and Lucina that precisely which the genus Glaucoma is to Cyrena and Venus. To us the family of the Chamacea is a lateral offset from that of the Cardiacea, and although the Etherice and the family of the Rudisles are in reality among the number of those Conchife- rous mollusca which have the lobes of the mantle disjoined, stdl as they do not imme- diately arrange themselves in any particular part of this section, we have placed them to the side in continuation of the family of the Cha- macea, but underneath them. The family of the Ostracea we now believe to consist of the single genus Ostrea, and we propose under the name of Placunide a family containing the three genera P lacuna, Placunonomia, and Ano- mia, which according to our views constitute a descending and lateral line really intermediate to the Conchiferu and the Brachiopoda. Bibliography. — The following works and essays may be referred to as still interesting on the natural history of the Conchifera. Reau- mur, De la formation et de l’accroissement des eoquilles, Acad, de Paris, An 1709 et An 1716; Ej. De la maniere dont plusieurs especes d’animaux de mer s’attachent au sable, aux pierres, &c. ibid, An 1711. Walch, Vom Wachsthum und den Farben der Konchilienschaalen. Besch. der Berlin. Naturforsch. Gesell. B. i. S. 230. Muller, Anmerk. ueber Walch, ibid, B. ii. S. 116. * * * * Cuvier, Nouvelles Rech. sur les eoquilles bivalves, Societe Philomath. A. 7, p. 83. Lister, Anatomy of the Scallop, Philos. Trans. Year 1697. Ant. van der Heide, Anatome Mytuli, 12tno. Amst. 1684. Bojanus, Sendschreiben an G. Cuvier liber d. Athrnen und Kreislaufswerkzeuge d. Zwei- shaaligen Muscheln, 4to. Jena, 1820. Mangili, Ricerche nuovi zootomiche sopra alcune specie di Conchiglie Bivalvi, 8vo. Milano, 1804. Brack, De ovis ostreorum, Misc. Ac. Nat. cur. Dec. 2, An 8. Koehlreuter, Obs. anat. physiol. Mytili cygnei (Lin.) concernentes, Nov. Act. Petrop. ( G. P. Des Hayes.) CONTRACTILITY. — Since it has been generally understood, that all the most striking and conspicuous movements which take place in living animals, depend on peculiar contrac- tions of certain of their solids, the circum- stances of these contractions, the causes by which they are excited, and the laws by which they are regulated, have been justly regarded as objects of the highest interest, and of fun- damental importance, in physiology. The term Irritability was employed by Haller and his followers, to denote all such contractions in living bodies, as they judged to be peculiar to the living state ; but more recent inquiries have shewn the necessity of distinguishing different species of these contractions ; and the more comprehensive term Contractility is now pretty generally employed. To this the epithet Vital, in physiological discussions, may usually be understood as prefixed. It is to be remembered, however, that several of the animal textures are endowed with a pro perty of contraction, in certain circumstances, which is not peculiar to their living state, but subsists as long as their structure remains unal- tered after death ; and the distinction between the phenomena resulting from this cause, and those which are strictly vital, has not always been accurately observed. Thus many of the soft animal textures, muscles to a certain de- gree, tendons and ligaments in a greater degree, and arteries in a still greater degree, are elastic, and liable to contractions from that cause when stretched. The Contractility de Tissu of Bichat is in most cases to be considered simply as Elasticity, although in some cases (as when he assigns this property as the reason of the re- traction of the cut extremities of a living muscle CONTRACTILITY. 717 or of the stiffening of limbs after death,) he gives this name to contractions which are strictly vital. Almost all animal substances are liable to contraction from heat, and from the application of various chemical agents which affect them as astringents, to which property Bichat gave the name of Contractilite par racomissement ; and it is easy to perceive that this property also, although persistent in the perfectly dead body, and therefore inde- pendent of life, may give occasion to contrac- tions which may sometimes be mistaken for indications of the strictly vital contractility. Confining our attention, however, to such contractions of the solids of organized bodies, as are exhibited by them only in their living state, i. e. so long as they present that assem- blage of phenomena, to which we give the name of Life,- — we proceed to state the facts which seem to be most important and best ascertained, first, as to the modes in which they are excited ; secondly, as to their pheno- mena, and varieties ; thirdly, as to the condi- tions necessary to their manifestation; and, lastly, as to the laws which regulate them. I. It is universally known, that the most striking examples of vital contractions are seen in the effects produced by various stimuli acting on muscles, particularly those of volun- tary motion, and the heart. The essential cha- racters of muscular fibres, their composition nearly akin to the fibrin of the blood, their arrangement in parallel fasciculi, which are bound together by cellular membrane, their soft texture, and slight elasticity are also ge- nerally known. The change excited by sti- muli acting on them is a contraction in the direction of the visible fibres of the muscle, which in the healthy state always rapidly alternates with relaxation; and by these two circumstances, — the excitation by stimulus, and the quickly ensuing relaxation, — we dis- tinguish that form of Vital Contractility, to which the term Irritability is most correctly applied. The stimuli which produce this effect are very various; and the experience of our own bodies points out the obvious distinction of these into physical and mental. Of the first kind, air and water, especially if aided by heat, act decidedly in this way; but those w'hich have been chiefly used in experiments are, dis- tension, especially in the case of the hollow muscles, such as the heart or bladder,- — che- mical acrids, such as acids, alkalies, various alkaline, earthy, or metallic salts, — and elec- tricity or galvanism. The effect of all these stimuli is much increased by their being sud- denly applied. It has also been long known, that many muscles are excited to contraction by such sti- muli, when applied to certain nerves, entering their substance, or to certain parts of the spinal cord or brain, even more effectually than by applications to themselves; and likewise, that it is only when those nerves are entire, up to the brain, that those muscles which are natu- rally obedient to the mental stimulus of the Will, can be excited by voluntary efforts. From these different modes of excitation of the contractile power of muscular parts, diffe- rent names have been given to the power itself, as by Haller, who applied the term Vis Tonica to the contraction from distension, Vis Insita to the contraction from irritation of the muscular fibres themselves, Vis Nervosa to the contraction from irritation of a nerve, and Vis Animalis to the contraction from volition, acting at the brain and transmitted through a nerve ; or again by Bichat, who applied the term Contractilite Organique Sensible to the contractions excited by any kind of irritation, acting on muscular fibres themselves, and the term Contractilite Animate to those excited by stimuli, whether mental or physical, acting on the nerves, spinal cord, or brain. But it is obviously more correct to distinguish the dif- ferent varieties of the vital power according to the phenomena, which the contracting part presents, than according to the manner in which the contractions are excited ; and there- fore those terms have fallen much into disuse. In most instances, it is the same vital power of Irritability, as above defined, which is called into action in these different ways. It is only of late years, that it has been fully ascertained, as to the excitement of vital contractions through nerves : 1, that it is, almost exclusively, in the case of muscles which are naturally subject to the Will, that even physical irritation, confined to the nerves, has power to excite contraction; and 2, that these muscles have nerves, or nervous filaments, from two distinct sources, viz. from the anterior and posterior columns of the spinal cord, and their prolongations within the cranium ; and that it is by irritation of the first of these only, (or almost exclusively,) that the muscular con- tractions are excited.* From these facts, it appears obvious, that the grand and eternal law of separation, as Ilaller calls it, of the Vo- luntary and Involuntary muscles, consists essen- tially, not in different powers of the muscular parts, but in different endowments of the ner- vous filaments which enter them. In regard to the excitation of muscular con- traction through nerves, it is also to be ob- served, that although the action of muscles in obedience to the will is the most obvious and striking example, in the living body, where the intervention of a change in a nerve is known to be an essential condition of the act, yet there are many examples of movements, per- formed by voluntary muscles, in obedience to mental stimuli, but not to volitions, — to sensa- tions, or other involuntary acts of mind, even in opposition to efforts of the will. These con- stitute a very important class of vital motions, and are known to be equally excited through the motor nerves of the muscles concerned in them. Of this kind are not only the irregular agitations of the limbs produced by tickling, or the convulsive writhing of the body from pain, but also, such regular and admirably precise movements as shrinking when pain is excited * See Mayo’s Outlines, 2d edit. ji. 50 et seq. and Sir C. Bell, Phil. Trans. 1826, 718 CONTRACTILITY. on the surface, closing the eyelids when the eyes are offended by bright light, swallowing, breathing, coughing, sneezing, vomiting, ex- pulsion of faeces and urine, &c. consequent on certain sensations of the fauces, lungs, air- passages, nostrils, stomach, rectum, or blad- der. Such muscular actions, excited by irri- tation of distunt parts, have been generally but vaguely described as the effects of Sympathies of one part of the living body with another. It is well ascertained that they are effected through the motor nerves (or certain of the motor nerves) of the muscles concerned in them ; and their dependence on the Sensations, and therefore on the sensitive nerves, of the parts from the irritation of which they originate, has been sufficiently illustrated by Haller, Whytt, Monro, and others.'* * * § It has also been observed, by Haller and Whytt, but more frequently and carefully by Legallois,f I’lourens, and Mayo,) that in many animals, (most remarkably in cold- blooded, or young warm-blooded animals,) even after the removal of the brain, as long as the circulation can be maintained, move- ments of the kind now in question go on, or may be excited by irritation of the sur- faces; and that if the spinal cord be divided into several parts by transverse sections, such movements may still be excited in the muscles supplied from each part, by irritation of the portion of the skin which has its nerves from that part of the cord. These facts have (as is believed) usually been thought to denote, that a certain degree of Sensation remains under these circumstances, in connection with the living state of the spinal cord, or of portions of the spinal cord, and medulla oblongata, indepen- dent of the brain ; and that it is still through the intervention of sensation, that irritation of the surface of the body excites any con- traction of muscles. Dr. Marshall Hall has lately described phenomena precisely of this description, under the title of Excito-motory phenomena, and as proofs of what he terms the Reflex Function of the Spinal Chord § — a power of exciting contraction in mus- cular fibres connected with it, which he supposes that organ to possess, equally inde- pendently of sensation as of volition ; 1 1 and as it seems hardly possible to be quite certain of the existence of Sensation in the case of the mutilated animal, this language is perhaps philosophically correct; but the probability of the existence of Sensation in such circum- stances must be allowed to be very great ; and at all events, that sensation is an essential part of * It is obvious that such motions, excited di- rectly by sensations, cannot be accurately distin- guished from those voluntary actions which are called Instinctive, as being prompted by the in- stincts, distinct from strictly intellectual acts, which are linked by nature with the sensations of certain parts of the body. t Experiences sur le Principe de la Vie. t Outlines of Physiology, second edit. p. 282, and Anat. and Physiol. Comms. § Phil. Trans. 1833, p. 635. Il See particularly p. 640. the connection between the irritation of distant parts, and the excitement of involuntary mus- cular contractions of voluntary muscles, for useful purposes, in the entire and healthy body, — may be held to be a point well esta- blished by the observations of Haller, Whytt, Monro, and others, on such sympathetic actions. Accordingly, those actions, in the entire body, which Dr. M. Hall ascribes to the reflex func- tion,* are the same, or similar to those, which have been fully treated by Dr. Whytt and others as sympathetic actions, or actions of voluntary muscles excited by sensations. But Dr. Hall has fixed the attention of phy- siologists on this class of facts, and has illus- trated by experiments their independence of the Brain, and dependence on the Spinal Cord exclusively, and in this conclusion he is sup- ported by many facts previously recorded by Le Gallois, Magendie, Flourens, and others. It is further to be observed, that the contrac- tions of voluntary muscles, which are supplied by thp nerves of the Symmetrical class of Sir C. Bell, while they are excited through the one set of filaments comprising those nerves, are made known to our consciousness by the others or sensitive filaments, and constitute the im- portant class of Muscular Sensations. Of the movements of the strictly involuntary muscles, the heart, stomach, and bowels, and even the bladder, (supplied by irregular nerves,) we have, in the perfectly healthy state, no intima- tion, although they frequently become percepti- ble to us in disease, or when over-excited. But contractions of some of these involuntary mus- cles also are pretty certainly excited by certain Sensations, as, e. g. a certain degree of antipe- ristaltic movement in the stomach by the feel- ing of nausea, and a certain movement of the pharynx and oesophagus by the sensations in the fauces, which prompt the act of deglutition ; and in such cases, although not attended with consciousness, they are in all probability excited through the nerves of these muscular parts. Accordingly, the pharynx and oesophagus have been observed by Mr. Mayo, and the stomach by Bresehet, Milne Edwards, and others, to be exceptions to the general rule of involuntary muscles being inexcitable by irritation of their nerves. The old distinction of muscles into Volun- tary, Involuntary, and Mixed, is very deficient in precision, so far as the last class is concerned. The true distinction is, of muscular contrac- tions, into those excited in the natural state by Mental Stimuli, and through the intervention of Nerves (qui soli in corpore mentis sunt mi- nistri) — and those excited by Physical Stimuli, acting on the muscles themselves, whereas the intervention of nerves is a theory, not an esta- blished fact. The first class admits obviously, from what has been stated, of a division into movements excited by the Will, which depend on the Brain, and movements excited by invo- luntary mental acts, especially by Sensations, which depend only on the Spinal Cord and medulla oblongata. The Will acts only on * P. 653 et seq. CONTRACTILITY, 719 muscles provided with sensitive nerves, by which the mind is informed of the contractions, and so enabled to regulate or guide them. The Sensations act chiefly on this description of muscles likewise, but partly also on muscles the nerves of which give no such distinct inti- mation of their contractions, and which are uniformly and strictly involuntary; and the chief excitants of this last class of muscles in the Animal Economy are physical stimuli, ap- plied to themselves and to their lining mem- branes. II. In regard to the vital power or property of Irritability, as exhibited in any of these ways, the following facts demand particular notice. 1. The minutest fibres, of which the mus- cles, exhibiting this property, consist, or what have been called by some authors the primary filaments of muscular fibres, appear under the microscope to consist of rows of globules, or at least to be marked by transverse stria, at equal distances. 2. When contraction takes place, these fila- ments, or rows of globules, are thrown into a zigzag form ; the angles being always at the same points on each contraction, and being generally obtuse, rarely and only on occasion of very forcible contraction, acute.* At the points where these angles are formed, the fila- ments are crossed, according to the observa- tion of Prevost and Dumas, by nervous fibrils; but it is important to remember, that this last observation has been made only on muscles of voluntary motion, and on them only in cold-blooded animals, where they are somewhat translucent. 3. According to the best observations, not made on entire limbs or even entire muscles, which involve various fallacies, but on small portions of muscles, removed from living bodies, it appears that no alteration of the bulk of the filaments attends this alteration of their form, so that neither the size nor distance of the particles or globules appears to be changed, but merely their position in regard to one another, j- 4. W’hen by any stimulus, applied to mus- cular fibres, the filaments directly stimulated are thrown into action, the contractions very generally and rapidly extend to many others in their neighbourhood, frequently even to the whole muscle of which they form a part ; but the contractions of single fibres appear to be of short duration, and the more enduring efforts to be made by many short successive contractions and relaxations or vibrations of the individual fibres. From these facts it would appear, that each exertion of this property of Irritability essen- tially consists in a greatly increased attraction among the particles or globules constituting 9 This appearance, with slight variations, has been repeatedly seen, both in warm-blooded and cold-blooded animals, in the lower classes and even in the infusory animals, under the micro- scope. t See Prevost and Pumas, in Journal de Phy- siologie, tom. iii.; and -Mayo’s Outlines. the muscular fibres, and alteration of the di- rection in which this attraction acts, — rapidly communicated from one particle to another, both along the same fibre, and among adjacent fibres, — and rapidly succeeded by repulsion, or return to the previous state of the cohesive attraction existing among these particles. When a muscular mass, consisting of many such fibres, is thrown into this kind of action, it is easy to understand that its breadth and thickness, and its rigidity or resistance to com- pression will be increased ; that its extremities will be approximated ; and that if it be dis- posed around a cavity, containing a fluid and provided with an outlet, that fluid will be expelled, it is by such contractions, that all the more conspicuous movements, even of the organic life, of the higher animals, are per- formed, and that their locomotive and vocal powers are exerted ; and it is worth while to pause for a moment to consider the almost in- conceivable amount of moving power, and ra- pidity of motion, which various facts indicate iu muscles thus contracting, whether under the influence of the will, or from other stimuli. It seems well ascertained that the contrac- tions of the left ventricle of the human heart, in its ordinary unexcited state, are sufficient to expel its fluid contents, in free space, a dis- tance of 7J feet, and to balance a weight of above 50 lbs. ; and this power is exerted regu- larly more than once in every second, and often, even independently of disease, twice in every second, during the whole of human life. The ordinary action of the left ventricle of the Whale's heart suffices to expel, according to Dr. Hunter’s statement, at each pulsation, above ten gallons of blood, with a great velo- city, through a tube of a foot in diameter. Two instances given by Haller, and quite within the limits of ordinary experience, suf- ficiently exemplify the great power occasion- ally exerted by voluntary muscles ; and which will appear the more extraordinary when it is remembered, that the direction of muscular fibres, as regards the line in which they are to act, — the points of their insertion into the bones they are to move,— and the line in which they act, as regards the motion which they give to these bones, — are ali, very ge- nerally, such as to render their action dis- advantageous, and requiie a greater amount of moving power than might otherwise have been necessary. The instances recorded are, the case of a man, who could raise a weight of 300 lbs. by tlie action of the elevator mus- cles of his jaw ; and that of a slender girl, afflicted with tetanic spasm, in whom the ex- tensor muscles of the back, in the state of tonic contraction or opisthotonos, resisted a weight of above 800 lbs., laid on the abdomen with the absurd intention of straightening the body. In some of the lowest classes of ani- mals the intensity of the muscular power ap- pears to be greater than in any of the largest. Thus, a flea has been known to leap sixty times its own length, and to move as many times its own weight. 720 CONTRACTILITY. Again, the rapidity of the changes of po- sition of the component particles of muscular fibres may be estimated, although it can hardly be conceived, from various well-known facts. The pulsations of the heart can some- times be distinctly numbered in children at more than 200 in the minute ; and as each pulsation of the ventricles occupies only one- third of the time from the commencement of one pulsation to the commencement of the next, this implies that each contraction takes place in g^th part of a minute, or that ten times in each second, for many hours toge- ther, the whole of the convoluted muscular fibres of the ventricles must be thrown into folds, and again smoothed out. Again, it is certain that by the movements of the tongue and other organs of speech, 1500 letters can be distinctly pronounced by some persons in a minute. Each of these distinguishable sounds must require a separate contraction of muscular fibres; and the production and ces- sation of each of these sounds must imply, that each separate contraction must be followed by a relaxation of equal length. Each con- traction must, therefore, have been effected in arooth part of a minute, or in the 50th part of a second. Haller calculated that in the limbs of a dog at full speed, muscular contractions must take place in less than the 200th part of a second, for at least many minutes in suc- cession.* But the property of Irritability, which acts throughout so great a portion of the animal creation, as a moving power of this extra- ordinary efficiency, is not the only contractile power, which certain organic textures possess, or which the conditions of their existence re- quire them to exert during the living state. Even in muscular fibres themselves, in certain organs, and still more in other textures of animal bodies, contractions are often observed, peculiar to the living state, but differing essen- tially from those which come under the defi- nition of Irritability already given. In all the different tribes of animals, indeed, differences in the contractile power of the diffe- rent living solids may be observed, exactly cor- responding to their circumstances and wants. The slow and languid movements of the bodies of most of the Zoophyta, and the rapid vibra- tions of the Cilice with which parts of many of these animals (particularly of the order Infusoria) are provided, are examples, even in the lowest class, of the great variety of moving powers, with which the living solids of different animals are endowed. In the human body, and analogous animals, it is obvious that the contractile power exerted by the stomach and intestines in performing their peristaltic movements, although of the same general characters as that of the heart, — the contraction of each portion of the tube being followed by a relaxation of that portion and a contraction of the portion next in ad- vance^— is yet materially different; both con- * Sec Haller’s Hlem. Phys. tom. iv. p. 481. traction and relaxation in the peristaltic move- ment being of longer and less definite du- ration, and of more variable extent. In the bladder and in the uterus, in the healthy state, we see contractions excited by peculiar stimuli, and repeatedly recurring as the actions de- pendent on them proceed, but not alternating with any obvious elongation of the fibres, and terminating in a much greater and more per- manent shortening of the contracting fibres, than is observed in other muscular organs. Again, in the state of any voluntary muscle, when the distance of its extremities is per- manently shortened (as by an ill-united frac- ture), in that of the sphincter muscles, or of an artery when emptied of blood, we see a ‘permanent contraction, requiring no stimulus to excite it, shewing itself whenever a dis- tending or elongating power is withdrawn, and relaxing only at the close of life. The nume- rous experiments of Dr. Parry on the condition of arteries immediately after death (contained in his Treatise on the Arterial Pulse) afford the most precise information that we have as to this last property. From such facts it appears obvious that three distinct modes of contraction, all strictly vital, may be observed in different textures of the body, or even in the same texture under different circumstances: first, that already con- sidered, to which the term Irritability is strictly applied, and which is best exemplified in the actions of the voluntary muscles and the heart ; secondly, that which may be termed simple Contractility, where contraction is induced by a stimulus, but takes place more slowly, and is nearly or quite permanent; and, thirdly, that which has been accurately described by Dr. Parry and others under the title of Toni- city, which requires no stimulus to call it into action, but takes effect whenever a distending power is withdrawn, and continues until life is extinguished. The second of these forms is seen, not only in the bladder and uterus, but in the arteries under certain irri- tations, perhaps in other textures, and pro- bably also (from certain stimuli) in the fibrin of the blood during coagulation.* The last is clearly, as Dr. Parry’s experiments have shewn, the chief vital endowment of arteries ; and notwithstanding the doubts expressed on the subject by Dr. Bostock, several facts may be stated to show, that it is also an endow- ment of all muscular fibres. Thus, besides the permanent retraction, already noticed, of the fibres of a muscle the fixed extremities of which are approximated, — the retraction of the cut ends of a muscle divided during life, — the state of habitual preponderance of the flexor muscles of the body and limbs (which are the stronger) over the extensors during sleep, j- and the stiffening or “ roideur cadaverique” of the muscles after death, — seem to be clear indica- tions of a tendency to contraction answering * SeePrater’sExperimcntal Inquiries in Chemical Physiology. f See Richerand’s Physiology. CONTRACTILITY. 721 to the definition of Tonicity, not of Irritability. This last phenomenon, as it disappears before putrefaction begins, and as it is variously in- fluenced by causes affecting vital action, is allowed to be a last exertion of vital power. There are evidently slighter modifications or varieties of the powers which we have thus distinguished ; but the distinctions now stated seem to be those which are sufficiently marked to demand separate names. Besides the mus- cular texture, some of the membranes, espe- cially the skin, appear to be endowed with a certain degree of vital contractile power, al- though not with true Irritability. It is remark- able, that the greatest degree of contraction seen in muscular fibres, is in those which pos- sess the property of simple Contractility rather than Irritability, viz. in the bladder and uterus more than in the intestines, and in these more than the heart. „ III. As to the conditions, necessary to the maintenance of the contractile powers of living parts, it is in the first place obvious, that they are always dependent on the maintenance of the organization of these parts themselves. When the muscles waste, as from rheumatic inflammation, cr from the poison of lead, as in colica pictonum, or when their texture is gra- dually altered, as by inflammation or in cer- tain organic diseases occasionally affecting them, or more rapidly relaxed and injured by over-distension, they lose their contractile power more or less completely; and their power is likewise gradually diminished in old age, as their texture partakes of the gradually increasing rigidity. Like all other vital actions, the contractions of moving parts are more immediately depen- dent on the maintenance of a certain tempe- rature, varying in the different tribes of ani- mals,— in all the warm-blooded (in the state of activity) probably confined within the de- grees of 60 and 120 of Fahrenheit. They are dependent also on the regular supply of arterial Blood. The experiments of Stenon and others have shewn, that the pow'er of muscles is rapidly extinguished w'hen the ar- teries supplying them are tied. It has gene- rally been supposed, since the time of Bichat, that venous blood, when it penetrates muscular fibres, is equally or even more rapidly noxious to them, than the denial of the supply of arterial blood; but the experiments of Dr. Kay* have shewn, that the contractile power of mus- cles, when failing from this latter cause, may be restored by the influx of venous blood, al- though in a less degree than by arterial, — • and Dr. Marshall Hall has observed, that in hybernating animals whose respiration is sus- pended, the flow of venous blood through all the textures continues, and keeps up a certain degree of muscular power ; so that the venous blood can only be regarded as less powerful in maintaining the irritability of muscles than arterial blood (probably because it is incapable * Edin. Med. and Surg. Journal, vol. xxviii. and Treatise on s-hyxiu, cli. iii. of affording them nourishment), not as posi- tively deleterious to them. The act of healthy Nutrition, by arterial blood, is therefore the main condition of the vital power of muscles, as of all other living solids. And it is im- portant to remember that this vivifying in- fluence of the living blood on the solids is evidently reciprocal ; for when any of the vessels containing blood lose their vitality, as from injury, the blood then coagulates, as if drawn from the body. There is a remarkable difference which has been long observed, in the different classes of animals, and even in the different states of the same animals, as to the consumption of oxygen by the blood on one hand, and the indications of muscular power on the other. The activity of muscular power (as indicated by the rapi- dity of the circulation and the energy of vo- luntary muscular exertions) appears to be, in general, in direct proportion to the amount of action between the air and the blood, being greatest in birds, greater in the mammalia than in reptiles or fishes; and greater in insects, where air is freely admitted into the interior of the body, and applied to the blood, than in the Zoophyta, or even the Mollusca, where there is less exposure of the blood to the air ; and again, being greater in perfect animals than in eggs or pup®, and greater in animals in a state of activity than in those in a state of torpor or hybernation. But on the other hand, the endurance of the muscular power, or tenacity of life, in whatever manner the vital principle is depressed or extinguished, is generally in the inverse ratio of the activity of muscular contractions, and of the amount of mutual action between the air and the blood. Thus the tenacity of life in reptiles and fishes is well known to be greater than in mammalia or birds, — in some of the lower classes, par- ticularly the infusory animalcules, much greater than in any of the higher; in very young ani- mals greater than in adults; and in hyberna- ting animals, in eggs, and pup®, greater than in any perfect animals. Dr. Marshall Hall has observed, that in some of the lower classes of animals, such as Reptiles, the degree of muscular contraction induced by stimuli, as well as its duration, is greater than in the warm-blooded animals ; and he has hence been led to lay down as a general principle the reverse of what has com- monly been stated, viz. that the Irritability of muscular fibres is inversely as the quantity of Respiration. But this proposition seems to be too generally, if not incorrectly, expressed. It seems an unnecessary innovation in language, to assert that the irritability of muscular fibres is inversely as the activity of muscular con- tractions, or that the irritability in insects, where the blood is fully exposed to the air, is less than in the Zoophyta, where there is much less provision for respiration. In fact, the vital powers of contractile parts vary so much in different organs, even of the same animal, that it may be doubted whether any other general proposition can be laid down as CONTRACTILITY. 722 to its connexion with respiration, than that of the greater activity of muscular action, on the whole, in those animals where there is much exposure of the blood to the air, and the greater endurance or tenacity of life where there is little. The question, how far the Nervous System furnishes one of the conditions necessary to the maintenance of the contractile power of muscles, has long engaged the attention of physiologists, and been the occasion of much erroneous medical theory ; but in the present state of the science, need not occupy much of our attention. The doctrine of Cullen and many other systematic writers, that the muscles derive re- gular supplies of Irritability or vital power, through the nerves, from the larger masses of the nervous system, seems to be now pretty generally abandoned, although the terms Ner- vous Influence or Energy are still suffered to retain, in the language of many medical writers, a vague and indefinite meaning, derived from that apparently erroneous theory. When we remember, that after the nerves of a muscle are cut, the muscle continues irritable under stimuli applied to itself, or to the portions of nerves below the section, as long as it retains its organization unim- paired,— that section of the nerves leading to the heart has in very numerous experiments been found to produce little or no ettect on its movements, — that these movements continue for hours after the head has been cut off], or even (as was first shewn by Dr.Wilson Philip) after both brain and spinal cord have been removed from the body, provided that the flow of the blood through the lungs is maintained by means of the artificial respiration, — that in hybernating animals (as Dr. M. Hall* has ascertained) when respiration is at a stand, the regular movements of the heart may con- tinue for nine hours after the gradual but com- plete destruction of the whole brain and spinal cord, — and that there are many instances on record, of the human foetus having come to a full size (implying long-continued and regular- action of the heart), where neither brain nor spinal cord existed,! — it seems impossible to maintain the purely hypothetical proposition, that the irritability of muscles is dependent on an influence or energy. continually flowing to them from the brain or spinal cord;J and * Philosophical Transactions, 1832 t See Brachet’s Recherches sur le Systeme Ner- veaux, p. 36 & seq. 1 Mr. J W. Earle, in a “ New Exposition of the Functions of the Nerves,” has attempted to revive this theory. He trusts chiefly to an experiment, in which the irritability of muscles, exhausted by repeated irritation, was not recovered after their nerves had been cut. But this experiment is incon- clusive, because the muscles had become inflamed and disorganized. — (See p. 70 and 71 of his work.) This experiment has been lately repeated in Edin- burgh, with precautions to prevent the inflam- mation of the muscles, and the result was the reverse of that obtained by Mr. Earle.— See Trans- actions of British Association, 1834. the only question that can remain is, whether the irritation of muscles is always effected through the medium of nerves, i. e. whether every stimulus which excites contraction in a muscle first acts on some of the nervous fibrils which enter it, and by exciting them throws the muscular fibres into action. An ex- periment of Brachet * has been thought to furnish evidence of the dependence of the heart’s actions on the cardiac plexus of nerves, but is so liable to fallacy, and so much op- posed to the experience of others, on the effect of injuries of the cardiac nerves, that the in- ference seems to have been generally dis- trusted. Without presuming to decide absolutely on a question which still divides the opinions of physiologists, and without entering on various arguments which have been stated as furnishing probable evidence either on the one side or the other, we may observe, — 1 . That the safe logical rule in such cases, is “ Affirmantibus incumbit probatio;” and therefore it does not appear philosophical to teach, that the con- traction of all muscles, on stimuli being ap- plied to themselves, is owing to the inter- vention of nerves, until that intervention be proved. 2. That if the contraction of all muscles were excited through nerves, we might expect to find all muscles supplied with nerves, the mechanical irritation of which, in the li- ving or newly killed animal, should excite that contraction. But it has been already observed, that in the case of the involuntary muscles, physical irritation of the nerves en- tering them (if strictly confined to the nerves) has very generally been found quite ineffectual for that purpose. This seems pretty clearly to indicate, that the power of exciting muscular fibres to contraction is an endowment peculiar to the nerves of the voluntary muscles, or at least enjoyed by them in a much greater de- gree than by others, and designed, not to render these muscles irritable, but merely to subject their irritability to the dominion of the Will. The observation of Fontana on this subject, made as early as 1775, and in perfect accord- ance with the statements of Haller previously, and of many other physiologists subsequently, may still be quoted as more conclusive than any other which has since been brought for- ward. “ If you open the chest of an animal, (a cold-blooded one answers best for the ex- periment) and stimulate as you please the nerves going to the heart, that muscle will neither accelerate its movements if it be moving, nor resume them if it be at rest, — even although it be prone to immediate con- traction on its own fibres being touched. The nerves of the heart, therefore, are in no sense the organs of the movement of this muscle, as they are of other muscles. This experiment is certain, and the inference direct. It would be a contradiction to assert that the movements of the heart take place through the intervention of * Eoc. cit. p. 125. CONTRACTILITY. 723 nerves, when experiment shews that nerves cannot excite these movements.” IV. In regard to the laws, by which the vital powers of contractile parts may be regu- lated, we have probably much to learn ; but three sets of facts have been observed, which may at present be regarded as general laws in this department of physiology. 1. Notwithstanding what has been said of the contractility of muscles being independent of any influence continually flowing to them from the brain or spinal cord, it is well ascer- tained that in a living and entire animal, where all the functions of the body are, for wise and important purposes, made liable to change, from changes in the nervous system, the con- tractile power of various moving parts is sub- ject to increase or diminution from physical causes acting in these larger masses of the ner- vous system, just as they are from various acts and affections of Mind, the effects of which may be said to be imitated by those physical causes. Thus in the experiments of Le Gallois, of Dr. Wilson Philip, of Flourens, and others, suddenly crushing any large portion, either of the brain or spinal cord, has been found uni- formly to depress or even extinguisli the power of the heart ; the well-known fatal effect often ob- served from sudden violent injury of the epi- gastrium in the human body, has been ascribed with probability to the injury of the great semi- lunar ganglion ; and the depression of the heart’s action which attends Concussion, and which is the immediate cause of death in the most quickly fatal cases of that kind, is also generally regarded as an impression, made ori- ginally on the nervous system, and immediately transmitted to the heart. On the other hand, slighter and more continued physical irritations of the nervous system appeared in many expe- riments, especially of Dr. Wilson Philip, to augment the irritability of the heart. It is true that, in all these cases, some have supposed the effects of the violence to be on the organs of circulation directly, and not through the inter- vention of the nerves; but when it is remem- bered, that some of those injuries, which are the most rapidly fatal to the heart’s actions, (such as the pushing of a probe along the spinal canal,) do not necessarily imply any great violence to the body at large ; and further, that precisely similar effects on the heart’s ac- tion (both increase and diminution) often result from mental emotions and passions, which cer- tainly act first on the nervous system, the ac- count which we give of the mode of action of these causes appears to be sufficiently con- firmed. One cause, acting primarily on the nervous system, which seems to have a peculiar de- pressing effect on the heart’s action, is, sudden re- moval of the pressure to which the brain had previously been subjected. The effect of this on the heart has been repeatedly seen in surgi- cal operations ; and this seems to be an essen- tial part of the pathology of seveial cases of syncope, particularly of that which results, either from bloodletting in the erect posture, or from tapping in ascites. It is very remarkable that the heart, which is so strictly an involuntary muscle, and so little liable to excitation by stimuli applied to its nerves, is much more liable than the voluntary muscles both to sudden increase and to diminution, or even total loss, of vital power from such causes as we have now considered. But a little reflection will shew, that the direct stimulation of a muscle, and the increase or diminution of its irritability, are perfectly distinct cases. And we may approxi- mate, at least, to an explanation of the peculiar liability of the heart (and probably of other involuntary muscles) to the influence of such causes acting through the nervous system, as augment or depress the vital power, when we remember two facts : 1 . that the causes which act in this way are very generally such as are applied to large portions of the brain or spinal cord ;* and 2. that the arrangements of the ganglionic nerves are such as to place the heart and other organs supplied from the ganglia, in connexion with the whole extent of the cerebro- spinal axis, and hardly with any individual part of it more than another. 2. There are various external agents, by the application of which the vital power of con- tractile parts, and especially of the heart, — the main agent in the circulation, — may be altered or even destroyed. It is increased, not only by moderate increase of the Temperature in which living parts are kept, and of the quantity of arterial blood sent to them, but also by Elec- tricity applied in a low degree of intensity, and by various articles of diet and medicinal agents, such as the various preparations of Alcohol ; and it is diminished, or even suddenly extin- guished often by the same agents applied in excess, (as in the case of Lightning when most rapidly fatal,) and still more remarkably by certain Poisons, such as the upas antiar, tobacco, digitalis, arsenic, and hydrocyanic acid. It is still doubtful through what medium these poi- sons act on the vital power of the heart ; but it is certain that the effect which they produce on that power is the immediate cause of the death resulting from them.f In cases of the most sudden death produced by such causes acting in the utmost inten- sity, the contractile power in the voluntary muscles, as well as in the heart, has been found to be very much diminished or even nearly ex- tinguished; and it is very important to observe, that in such cases the property of coagulation in the blood is likewise lost; which seems clearly to indicate (what various other facts confirm) that tins change in the blood is de- pendent on the existence in that fluid of a certain degree of the same vital properties, to which we give the name of Contractility as ex- isting in the solids. 3. The contractile power of living parts is liable to much alteration from the degree in * See Dr. Wilson Philip’s Experimental Inqui- ries, &c. ch. ii. and iv. f The terms Stimulant and Sedative are applied most correctly to those agents which thus exalt or depress the vital actions of the circulating system. 724 CRANIUM. which it is itself exercised. The immediate effect of frequently repeated stimulation of a voluntary muscle, whether by physical or mental stimuli, in a living or newly killed animal, is gradual diminution or ultimate extinction, or what is usually called Exhaustion of its Irri- tability ; which is gradually restored when the stimulation is discontinued and the muscle is at rest. But the theoretical conclusions which have been drawn from this fact have greatly exceeded the legitimate inferences. It is by no means clear that such increased action of involuntary muscles, as results from causes of the kinds just mentioned, which exalt or increase their contractile power, is necessarily followed by any corresponding depression. On the con- trary, in the case of violent exercise, in many instances of mental agitation and excitement, and in the course of certain febrile and inflam- matory diseases, we see the heart’s action greatly and permanently increased, without evidence of any subsequent loss of power which can reasonably be ascribed merely to the cir- cumstance of increased action. It is true that the effect of many stimulating substances, such as alcohol, is first to excite, and after atime to weaken or depress, the actions of the heart and circulating system ; but as we know that an equal or greater degree of excite- ment from exercise, from exciting passions of mind, or from inflammatory disease, may exist without producing any such subsequent de- pression, we ought to regard the loss of power which follows the excessive use of such sub- stances, as an ulterior effect of these substances themselves, rather than as the result of the mere circumstance of previous increased action.* Although, therefore, we consider all exertions of the irritability of muscles as necessarily im- plying intervals of relaxation, and are aware of the exhaustion of irritability by excessive sti- mulation, yet we do not see that the operation of those agents which augment the vital power, particularly of the involuntary muscles, is ne- cessarily followed by a corresponding loss of power. Further, it has been often alleged that the vital power of Irritability is not only expended or exhausted by excessive action, but likewise increased or accumulated by rest. But there is no evidence whatever that rest does more than merely restore the power that had been lost by previous exertion. A muscle or set of muscles which has been weakened by excessive excitement, and regained its power by rest, may remain quiescent for an indefinite time thereafter, and will not only not continue to gain power, but will gradually lose, after a time, that which it had previously possessed. The idea of the accumulation of Irritability by long-continued inaction has been thought to be supported by the fact, that the stimulating effect of Heat on all vital action, is greatest when it is applied after long-continued Cold. But this seems manifestly to be owing to the * See Gregory’s Conspectus, art. De Remediis Slimulantibus. principle that the stimulating effect of heat on vital action is proportioned, not merely to the temperature that may be applied, but chiefly to the degree of change of temperature under- gone in a given time; of which point many illustrations might be given, and which neces- sarily implies that the effect of Heat must be much increased by its being applied after Cold. Another law, which may be deduced from observation of repeated exertion of living con- tractile parts, is of great importance both in physiology and pathology ; viz. that the ulti- mate effect of such repeated exertion, with sufficient intervals of repose, is to augment both the bulk and strength of muscular fibres, and facilitate the subsequent excitation of vital action, whether in voluntary or involuntary muscles. This is seen in the state of hyper- trophy of the muscular fibres of the arms of labourers, of the legs of dancers, — of the heart, in those who have disease of the valves of the aorta, — of the bladder, in those who have disease of the prostate gland or stricture of the urethra; and is in fact only a. part of a more general law, — that the habitual exertion (within limits consistent with health) of all vital powers, is naturally attended with an increased flow of blood to the organs exerting those powers, and with an increase of their nutrition. And the counterpart of this is seen in the very slow and gradual, but ultimately extreme dimi- nution, not only of the vital properties, but of the bulk and characteristic appearance, of mus- cular parts which have been, from any cause, kept very long in a state of absolute inaction. According to the observation of Andral, the structure of muscles may in these circum- stances be so altered, that they become ulti- mately hardly distinguishable from cellular texture. The act of Nutrition, and therefore the organization of muscular fibres, as well as of other living parts, is manifestly intended by nature to be, in a certain degree, dependent on the exertion of their own vital power; and one effect of that exercise of vital power is to solicit or attract the living fluid to the part concerned in it, in a manner which the re- searches of physiologists have not yet satisfac- torily elucidated. ( W. P. Alison.) CRANIUM (in anatomy) Gr. xganor; Fr. Crane; Germ. Hirnschadel ; Ital. Cranio. The cranium is the protective investment of the brain, on which it is moulded, and the form of which, in warm-blooded animals, it represents. It also incloses and protects the organ of hearing. In cold-blooded animals there is not this adjustment of the surfaces of the brain and its case; but, although in them the parietes of the cranium are expanded beyond the limits of the brain,'* the principle of formation is neverthe- * Thus, according to Desmoulins the area of a vertical section of the brain in the European tor- toise is nearly one-third less than the area of the cranial cavity ; and in Fishes, whether osseous or cartilaginous, the disproportion is constantly still greater. — Ed. CRANIUM. 725 less the same; and a glance at the several classes of vertebraled animals will demonstrate that security for the brain is the grand aim of the contrivance, and that the modification it sustains in the case of Fishes and Reptiles is for the purpose of carrying into effect some additional design. Considering the cranium as a capsule for the brain, its form is necessarily determined by the extent to which that organ is developed in the several classes of animals ; while, at the same time, the nature of its organization is in harmo- nious correspondence with their habits, and with the external circumstances by which they are surrounded. By pursuing this inquiry from the lowest to the highest animals, it will be per- ceived that, as respects both form and struc- ture, additions are made in proportion as the endowments are of a more and more exalted character; and further, that these successive changes of structure are the changes which the human skull itself experiences in its progress from a fetal to an adult condition The rudimentary part of the most elaborate cranium is a sac consisting of two membranes and an intervening gelatinous fluid ; in the next step of the formative process, this gelati- nous fluid gives place to cartilage. A deposi- tion of earthy matter in this cartilaginous nidus gives it firmness, but breaks up the sac into isolated ununited patches. These isolated patches coalesce in definite numbers, and thus establish a secondary and less numerous divi- sion of ununited parts; these, in their turn, approach and combine with each other, form- ing a solid case of bone; and lastly, this solid case resolves itself into two tables of different structure, and a still further differing connect- ing medium. In each and all of these states through which the crania of the Mammalia pass there is presented to us a type of the skull in some lower animal. In Fishes the cranium is little more than a tubular continuation of the spine through the head to contain a similar prolongation of the medulla spinalis. These, however, are not in contact. A mass of reticulated membrane, holding in its cells a gelatinous fluid, forms the real superior investment of the brain ; while the superjacent parietes are designed to afford an extensive origin to the muscles of the body; and as these muscles increase, so does the sur- face of their attachment. For this purpose it is that the ossific deposits remain ununited, that, by being simply in juxtaposition, or at most over- lapping each other, they may unfold them- selves, and thereby admit of the head being at all times in proportion to the rest of the body. In Reptiles the skull is still further deve- loped. It is charged more with earthy than with animal matter ; and this being loosely distributed, tough spongy bones are the result. The tardiness of their circulation does not favour the combination of the individual por- tions, and the bones are therefore for the most part loose, although some of them unite by a species of anchylosis in the direction in which defence is required. In Birds the character both of form and structure is greatly changed ; light, fragile, and compact, it is (by reason of the high state of vitality which prevails) so rapidly and com- pletely ossified over its entire surface as to afford no evidence, or but a very slight one, of its original subdivision. In conformity with the development of the brain, it extends itself backwards, to each side, and upwards as well as forwards, thus constituting a considerable portion of the entire head. In Mammiferous animals the skull is more compact than that of Reptiles and more diffuse than that of Birds. Its elementary portions unite so as to form a determinate number of bones which are either dovetailed together by the interlacement of crooked processes with which their edges are liberally studded, or flow into each other so as to exhibit no trace of their junction. Its structure is made up of two osseous lamellae, called an inner and an outer table, which are united by an areolar ossific tissue, termed diplu'e, that adds greatly to the defensive properties of the skull. TheCranium (in human anatomy) is a hollow bone of an ovoid figure ; elongated from be- hind forwards ; narrower before than behind ; compressed on the anterior part of its sides ; surmounting the face and spine, and projecting considerably beyond the latter. It contains in its parietes the organs of hearing, and contributes to form the orbits, the nostrils, and the face. The dome-like upper portion is termed the calvaria, and the lower part is the base. The former presents the synciput in front, the occiput behind, the vertex or bregma, (fipexp.cc, from irrigo,) above, and the temples on the sides. Placed at the summit of the body and des- tined to contain the brain, the skull is pierced at its base by numerous foramina for the trans- mission, 1st, of the nerves which establish the communication between the brain and other organs ; and 2dly, of the vessels which supply the brain and its membranes. From the inferior surface of the cranium, be- tween its anterior and middle thirds, there de- scend two columns which limit posteriorly the boundaries of the face ; so that it is anteriorly to these columns that it contributes to form the orbits and the nose, and consequently there the bones which enter into the composition of the face are fixed to it. Hence the surface of that part is very irregular, presenting, in addition to the foramina, depressions and elevations, sulci and processes indicative of the articulation of bones and the lodgement of other organs. Posteriorly, between its middle and posterior thirds, the base of the cranium overtops the spine, and a great opening there establishes the continuity of the vertebral canal with the inte- rior of the skull ; and the muscles which move the head and maintain its equipoise being at- tached around, but especially behind this open- ing, the skull is strongly marked in that direc- tion. The intermediate space or middle third is above the pharynx, offering, centrally, a plain surface to form the roof of that cavity, and, 726 CRANIUM. laterally, rough surfaces and processes for the attachment of muscles concerned in deglutition, also some of the foramina already referred to, for the transmission of the vessels and nerves of the throat to and from the interior of the skull, as well as the surfaces on which the lower jaw moves. The upper surface of the base conforming to the base of the brain, there are larger depres- sions on it for the anterior and middle lobes; a deep pit or cavity for the cerebellum, and in the centre a broad sulcus, which glides into that pit, for the medulla oblongata, as well as strong ridges and processes to afford attachment to the membranous partitions which severally exist between the cerebrum and cerebellum, the he- mispheres of the former and the lobes of the latter organ. Thebonesinto which the cranium is separable or of which it is immediately formed, are eight, viz. the sphenoid , th e frontal, the ethmoid, the occipital, the two temporal, and the two parietal. The first named bone is so placed as to be in connexion with all the others, and to have them grouped around it ; so that the frontal (F , fig. 370) and ethmoid are in its front, the Fig. 370. occipital (O, fig. 372) is behind it, the two temporal (T, fig. 370) are on its sides, and the two parietal (P, fig. 370) are above it. The sphenoid bone (from crtpriv, cuneus, os sphenoidale; Germ. Sphenoidal-knochen, Keil- knochen ) comprehends the quadrilateral mass which forms the centre of the frame-work, the anterior ribs which supportthe frontal and partly the lateral domes, and the depending pillars which form the boundaries of the face ; it extends to each temple, is behind and in part forms the orbits and the nose, and is also behind but in close connexion with the bones of the face. The central portion is called the body, and the diverging processes are named alae majores and alae minores. The body is of a quadrilateral figure, hollow and divided by a partition into two chambers {the sphenoidal cells, s, fig. 371), which open through the medium of the posterior ethmoidal cells into the superior meatus of the nose. On its upper surface is a deep depression ( ephip- pium, sella turcica, fossa pituitaris ) for the lodge- ment of the pituitary gland. The posterior bor- der of this depression presents a crest, the comers of which are slightly tumid, ( posterior ephip- pial, or clinoid processes,) for the attachment of the tentorium, and this crest is prolonged down- wards and backwards under the name of the basilar process, to join the process of the same name of the occipital bone; on each side there is a depression (sulcus caroticus ) for the reception of the internal carotid artery, and which also marks the situation of the cavernous sinus. On its under surface may be seen, on the median line, the processus azygos ( rostrum ), which is wedged into the base of the vomer, and on each side of it a line indicating the articulation of the two plates of which the vomer is formed. Still more out- wardly there is a groove which is converted into a canal by the application against it of the in- ferior orbitary or sphenoidal process of the pala- tine bone. Fig. 371. The anterior surface exhibits the openings of the sphenoidal cells, having, between them, and apparently a continuation of their septum, a prominent ridge which articulates with the ver- tical plate of the ethmoid, and, below them, the triangular curved processes denominated the turbinated processes of the sphenoid bone. Ex- ternally to these foramina and turbinated pro- cesses on each side is a rough line for the arti- culation, in its two superior thirds, of the orbital plate of the ethmoid, and, in its inferior third, of the orbitar process of the palatine bone. To the outer side of this rough line is a smooth surface which contributes to the formation of the orbit. The posterior surface is rough, quadrilateral, and at an early age becomes indissolubly united to the basilar process of the occipital bone {d, fig. 371); for which reason Scemmerring and Meckel have regarded as one, the occi- pital and sphenoid bones, and as such have described it under the name of os basilare. This surface is bounded superiorly by the basilar process before mentioned, which is CRANIUM. 727 placed with such a degree of obliquity, that it may be questioned whether it be on the posterior or superior surface of the body of the bone. It is smooth, slightly concave, and on its edges may often be seen the commencement of the sulci basilares for the lodgement of the basilar sinuses. The alee majores are those large curved pro- cesses, which, stretching outwards, forwards, and upwards, contribute to form the middle fosste of the skull, the orbits, and the temples. The upper surface of each ala, that which in part forms the middle fossa of the base of the skull, is concave from side to side, and still more so from behind forwards. On it are seen (though not so distinctly) the digital impres- sions which mark the lodgement of convo- lutions of the brain on the cerebral surface of the other bones of the skull. Close to the spot where it departs from the body of the bone there is a sulcus directed forwards, and ter- minating in a round hole (foramen rotundum ) for the exit of the superior maxillary branch of the par trigeminum or fifth pair of nerves. More outwardly, and behind the plane of the posterior edge of the body of the bone, is a large oval opening (foramen ovale ), di- rected downwards and slightly outwards for the transmission of the inferior maxillary branch of the par trigeminum and the entrance of the ascending pharyngeal artery, which then be- comes a meningeal vessel. Behind this fora- men is another (the foramen spinale ), which is very small, and affords entrance to the middle meningeal artery. On the inferior surface are seen the pterygoid processes descending from the great wing where it joins the body of the bone, to afford a resist- ing surface against which the bones of the face may be grouped. Anterior to these processes is the termination of the foramen rotundum, the opening of which is directed somewhat out- wards, and from which there passes, outwards and upwards, a groove (sulcus temporalis) for a deep temporal branch of the superior maxil- lary nerve. Behind the pterygoid processes, and extending from the base of the internal to the extremity of the wing, is the sulcus Eusta- chiunus, which lodges part of the Eustachian tube, and on the outer side of this sulcus are seen successively the foramen ovale and the foramen spinale. Immediately behind the lat- ter opening, and overhanging the Eustachian tube, is the styloid process, to which the inter- nal lateral ligament of the lower jaw is attached. On the outer side of the pterygoid processes is a plain surface forming part of the zygomatic fossa, and bounded externally by a crest, which marks the division between the zygomatic and the temporal fossae, and which intervenes be- tween the superior attachment of the external pterygoid and the inferior attachment of the temporal muscles. The pterygoid processes consist of two plates, with a triangular separation interi- orly, and they are called the external and the internal pterygoid processes or plates. The external is broader, thinner, and is directed more outwardly than the internal ; its outer surface, which also looks a little forwards, gives attachment to the external pterygoid, its inner to the internal pterygoid muscles. The internal is nearly vertical ; it is pierced longi- tudinally at its base by the canalis Vidianus for the passage of the vessel and nerve which bear that name; at its inferior extremity there is a hook (the hamular process ), which acts as a pulley for the tensor palati muscle, the attachment of which to the outer side of the internal pterygoid process is shewn by a sul- cus which is most evident at the base (fossa navicularis ) ; to its anterior edge is applied a thin plate of the palatine bone, thus sepa- rating it from the superior maxillary, and to its posterior edge is affixed the aponeurotic origin of the superior constrictor of the pha- rynx. The concavity between the two pro- cesses is the fossa pteryguidea which is occu- pied by the internal pterygoid muscle, and the notch at the lower part (the hiatus pala- tinus) is filled up by the pterygoid process of the palatine bone. The external surface of each ala is continu- ous with the inferior; it is concave from before to behind, and convex from above downwards ; it contributes to the formation of the temporal fossa, and the continuation of the sulcus tem- poralis is evident at its anterior part (S, fig. 373). The anterior surface forms the major part of the external wall of the orbit, is oblong, di- rected forwards and inwards, and is narrower at its extremities than in its middle. The superior border of the great wing sepa- rates the orbital from the cerebral surface ; it presents a sharp smooth edge on its inner half, and a rough irregular surface on its outer half ; it is convex, and its convexity is directed up- wards, forwards, and inwards. The sharp internal half concurs with the ala? minores to form the sphenoidal fissure, which will be de- scribed with those processes. The external rough half becomes broader as it passes out- wards, so as to produce a triangular indented surface, the outer edge of which is prolonged at the expense of the inner table in such a manner that it overlaps the frontal bone which is affixed on it, and this prolongation is con- tinued without the indented surface, so as to grasp the anterior inferior spinous process of the parietal bone. The external border is nearly the reverse of the former. It is concave, and looks outwards and backwards, and it is articulated in its entire extent to the squamous portion of the temporal bone, by which it is overlapped in its anterior third, and receiving and supporting it in its two posterior thirds ; the former at the expense of its outer table, the latter at that of the in- ternal. The posterior border is applied against the outer side of the petrous portion of the tem- poral bone, and extends from the body of the sphenoid to the posterior extremity of the ex- ternal border. Idle junction of these two bor- ders forms the spinous process, which is received 728 CRANIUM. into the angle of the petrous and squamous portions of the temporal bone. The laxator tympani muscle arises from this process, and the styloid process before described descends from it. The angle which exists where this border departs from the body, in part forms the foramen lacerum anterius, an opening which, in the recent skull, is closed by cartilage. The anterior border consists of two portions which join with each other at an angle. Of these the upper is indented, separates the or- bital from the temporal surface, and articulates with the malar bone. The inferior portion is smooth, and forms with the palatine and supe- rior maxillary bone, the Jissura lacera orbitalis inferior. The ala minores are on the upper and an- terior part of the body of the bone ; they ex- tend outwards over the superior borders of the greater wings, and, gradually tapering, they at last end in a point. The upper surface of each ala minor is smooth, and partly forms the anterior fossae of the skull. The processus ethmoidulis is a thin lamina somewhat triangular in form, prolonged for- wards on the median line to articulate with the cribriform plate of the ethmoid bone. Passing backwards from this process, there is a slightly elevated line separating the depressions which on each side receive the olfactory nerves, and terminated posteriorly by a tubercle ( processus olivaris ) marking the decussation of the optic nerves, and having upon it a transverse depression for the lodgement of their com- missure. This depression terminates on each side in the foramen opticum for the passage of the optic nerve and the ophthalmic artery, in such a manner that the lesser ala appears to arise by two roots, one above and the other below the foramen. From the sides of the processus ethmoidalis there pass the two transverse spi- nous processes, being the anterior serrated mar- gins of the wings; they are articulated to the orbitar processes of the frontal bones, and sometimes join by their extremities the great wings; thereby, in such a case, converting the superior orbital fissure into a foramen without the aid of the frontal bone. The posterior margins of the alae minores are smooth and less sharp than the anterior ; they are pro- longed backwards and inwards, so as to form on each side a short and thick triangular pro- cess, the apex being directed backwards, called the anterior ephippial (anterior clinoid) pro- cess, to which the cornua of the lunated margin of the tentorium are attached. The inferior surface of each ala minor forms the posterior part of the orbit. On it is seen the opening of the optic foramen, and under- neath it, between the smaller and the greater wings, the Jissura lacera orbitalis superior. This fissure is completed into a foramen by the articulation of the frontal bone to the sphenoid, when it appears as an elongated triangular opening directed from below up- wards and from within outwards. Thus is formed the foramen lacerum orbitale superius, which allows to emerge from the skull the third, fourth, the ophthalmic division of the fifth, and the sixth pair of nerves, and to enter from the orbit the ophthalmic veins. The articulations then of this bone are, to the ethmoid, by the ethmoidal process and the fore part of the body; to the frontal, by the transverse spinous processes, and the summits of the great wing; to the parietal, by the tips; to the temporal, by the external and posterior borders, and to the malar, by the anterior bor- ders of the same wings ; to the occipital, by the basilar process ; to the palatine, by the ptery- goid processes and adjacent part of the body ; and to the vomer, by the azygos process. The sphenoid bone is developed by nu- merous points of ossification, some of which coalesce before the others appear ; and during the period of intra-uterine life the union of these parts is so rapid, that, at birth, the bone con- sists but of three parts, one central, compre- hending the body and smaller wings, and two lateral, each involving a great wing and its cor- responding pterygoid processes. So early as the third month there appear six points^of ossification, two in the great wings, two in the internal pterygoid processes, and two in the smaller wings. During the fourth, fifth, and sixth months six points are esta- blished in the body, one on each side the median line, afterwards another between these and the corresponding greater wing, and ulti- mately another between the optic foramen and those already existing. During the sixth month also a deposit appears between the optic fora- men and the olivary process. In the course of the seventh month the six points of ossification in the body run into each other ; in the next month a coalition takes place between those in the pterygoid processes and those in the greater wings, and shortly afterwards a similar union occurs between the point in the small wing and that near the optic foramen. To- wards the termination of the ninth month the two smaller wings are associated together, which then become attached to the already formed body, and thus constitute at birth the three pieces which exist at that epoch. In the early period of extra-uterine life these three portions unite into one, the great wings acquire a more determined curvature than they at first possessed, the pterygoid pro- cesses lose their striated appearance, and ex- hibit more completely their fossa; but it is not until after the lapse of years that the ab- sorbing process, which, commencing in the centre of the body, developes the sinuses, is terminated, so that during childhood there is not only an absence of these sinuses, but of the openings leading from them and of the tur- binated processes which are fixed to their front. 2. Th eJ'rontalbone( os frontis, corona ; Germ. das Stirnbein,) (F, Jig. 370, 373,) is situated at the anterior part of the cranium, forming part of the vault and part of the base, but considerably more of the former than it does of the latter. It comprises the two anterior ovoidal domes and the anterior portion of the longitudinal curved rib of the general frame- CRANIUM. 729 work, which will be afterwards more fully ex- plained. The convexity of these domes is turned outwards and forwards in such manner that the circumference may abut against the longitu- dinal rib internally ; and, behind against the anterior rib in the base and a portion of the circumference of the lateral dome in the vault. That portion which is in the base is, as it were, pressed upwards to increase the space of the orbit, but not so much so as, at first sight, might appear; for on the external surface of the junction of the two portions there is an extraordinary development of the bone, which projecting over the face destroys the uniformity of surface and causes the orbitar portion to appear more elevated than it is in reality, and even to pass backwards at right angles with the other. Fig. 372. The external surface of the frontal portion in its upper two-thirds is smooth, of an equa- ble convexity and directed backwards ; its inferior third is more vertical, and its convexity is interrupted by prominences. On the me- dian line it exhibits evidence of its original division into two parts, and this generally by a slight ridge, although in some instances there is a linear depression of equal indistinctness. This line is terminated by the nasal prominence, which has immediately above it a smooth tri- angular surface ( glabella ), and below it a rough notch for the articulation of the nasal and superior maxillary bones. From the centre of this notch there is a projection ( pro- cessus nasalis ), on the fore part of which are fixed the nasal bones, and to its back part, which is grooved, the ethmoid bone is ap- plied. On either side of the median line there is, at about the distance of an inch where the middle joins with the lowest third of the bone, th e frontal eminence ( eminent ia frontalis, pro- cessus primi genii ), which marks the centre of ossification, and the prominence of which is inversely as to the age of the subject. Be- low this eminence, bounding the glabella, and inclining downwards and inwards towards the nasal prominence (with which, in fact, it is ultimately confounded), is a pyramidal protu- berance, varying very much in distinctness in VOL. I. different individuals, (processus frontalis,) more evident below than above, and indicating the situation of the frontal sinus. There is a slight depression underneath and to the outer side of this process, and, finally, the super- ciliary ridge terminates the frontal portion of the bone. This ridge is more prominent at its outer than at its inner side ; its extreme points are called external and internal angular pro- cesses, to the former of which the malar bone is articulated, to the latter the os unguis; at the junction of its inner and middle thirds there is a hole (foramen supra orbitarium ), or otherwise a notch, for the passage of the frontal branch of the ophthalmic vessels and of the ophthalmic division of the fifth pair of nerves. Behind the external angular process there is a depression (fossa temporalis) which forms part of the temporal fossa ; a part of the temporal muscle is attached to it, and it is bounded above by a line (linea temporalis) which is continuous with the outer margin of the external angular process, and to which is attached the temporal aponeurosis. Fig. S78. The posterior or cerebral surface of the frontal bone is concave, is marked by depres- sions which correspond with the convolutions of the brain, and by sulci for the lodgement of the arteries of the dura mater, and is conti- nuous inferiorly with the orbitar portion ; cor- responding to the eminentiae frontales there are two depressions, and on the median line there is a sulcus ( sulcus longitudinalis ) for the re- ception of the longitudinal sinus, on the edges of which sulcus may sometimes be seen the fossa; Pacchionii for the glands of the same name. This sulcus as it descends is generally replaced by a dense crest, which projects con- siderably into the cavity of the cranium ; to it and to the edges of the sulcus, the falx cerebri is attached ; and at its lowest point it is bifid, so that, by its being applied against a similar bifurcation of the processus cristatus of the ethmoid bone, it contributes to form the fora- men caecum. 3 B no CRANIUM. The orbitin' portion by its upper surface supports the anterior lobes of the brain, and its under surface forms the root of the orbits. It is divided into two processes by a longitu- dinal notch, which corresponds to the roof of the nose. The orbitar process of either side is convex in both directions on its upper surface, and •the mammillary eminences and digital im- pressions formed by the intergyral spaces and convolutions of the brain are of a decided character. On its under surface it is concave and triangular, the base being directed for- wards; at its anterior and outer part there is a fossa (fossa luchrymalis ) for the lachrymal gland, and which is overhung by the external orbitar process ; at its anterior and inner part, near to the internal orbitar process, and be- tween it and the foramen supra-orbitarium, there is a small pit (fossa trochlear is ) to which is fixed the cartilaginous pulley in which plays the tendon of the superior oblique muscle of the eye; at the middle of its inner edge there is a notch, which, applied to a similar notch of the ethmoid bone, constitutes the foramen orbitarium internum anticum, through which pass the ethmoidal twig of the ophthalmic branch of the fifth pair of nerves, and the an- terior ethmoidal branch of the ophthalmic artery; and a little behind this there is another notch, which by a like contrivance forms a hole (the foramen orbitarium internum posticum ) for the passage of the posterior ethmoidal branch of the ophthalmic artery and corres- ponding vein. The notch which is between the orbitar pro- cesses is the hiatus cthmoidalis (incisura ethmoidulis ), and in the cranium it is filled up by the cribriform plate of the ethmoid bone. Its longitudinal is twice the length of its trans- verse diameter ; anteriorly, it is bounded by the notch which, in part, forms the foramen coecum and the posterior surface of the nasal process ; posteriorly, it is open ; and its sides are bounded by the commutual edges of the orbitar processes, the tables of which are sepa- rated in such a manner as to communicate with the ethmoidal cells and close them at the upper part, and at the anterior part of the notch to communicate also with the frontal sinuses. The frontal sinus is formed by the separation of the two tables of which the l one is com- posed, and by the absorption of the diploe ; they are usually separated by a septum, and they communicate on each side with the mid- dle meatus of the nose in the manner indi- cated above. The posterior and upper border of the bone as far down as the posterior extremity of the inferior margin of the fossa temporalis, is arti- culated to the parietal bones; and it will be remarked that rather more than the middle third of it advances upon and secures those bones at the expense of their outer table, while the inferior portions of it are in their turn grasped by each parietal bone respectively, the outer table of the latter advancing, at this part, upon the inner table of the former. Behind the external angular process, be- tween the temporal fossa on the one band and the orbitar process on the other, there is a triangular rough surface which is implanted on a similarly-disposed surface of the great wing of the sphenoid bone. The posterior margin of this surface is in apposition with the edge of the thin extremity of the small wing of the sphenoid, to which also is articulated the re- maining portion of the posterior border of the orbitar process ; but with this difference, that, while in the former instance the edges are plain and simply applied to each other, in the latter the margins are denticulated, the sphenoid overlapping the frontal so as to render the roof of the orbit secure. Thus the frontal bone articulates by the pos- terior borders of its two portions, with the parietal and sphenoid ; by the inner edges of its orbitar processes, with the ethmoid ; by its nasal process, with the nasal ; by its internal angular process, with the lachrymal ; by the surface between the nasal and internal angular processes, with the superior maxillary ; and by its external angular process, with the malar bones. This bone in the foetus, and for nearly two years after birth, consists of two pieces, the first deposit in each being at the prominence already indicated. From this point the ossific matter radiates, and approaching that from the opposite side, the two combine so as to form on the median line a suture which is speedily effaced. Nevertheless it occasionally happens that complete union does not take place, and then the suture persists through life. The ethmoid bone nbpo;, cribrum, osethmoideum; Germ. Et/nnoidal-knochen) com- pletes that portion of the base of the cranium, anterior to the sphenoid, which is not supplied by the frontal. It is however devoted less to the skull than to the face, with many of the bones of which it is connected; and it con- tributes greatly to form the nostrils and their septum, as well as both of the orbits. As an element of the cranium it is very simple, being merely a plate connecting the two orbitar processes of the frontal bone, and having on its median line a ridge, which joins the frontal spine before, to the body of the sphenoid bone behind. This plate is the cri- briform plate or process; it is notched poste- riorly where it receives the ethmoidal process of the sphenoid bone, the apex of which pro- cess is applied to the posterior extremity of the central ridge. Advancing forwards, this ridge quickly springs upwards as a pyramidal pro- cess (the crista, galli, or processus cristatus ), to which the falx cerebri is attached ; its pos- terior edge is long and oblique, its anterior is shorter, more vertical, and it terminates in- feriorly in two slightly divergent plates, so as to form by their articulation with the frontal bone \heforurncn ccccum. On each side of the crista galli, more especially towards the fore- part, the cribriform plate is channelled for the reception of the olfactory nerves, and each channel is perforated by numerous foramina for the transmission of the ramifications CRANIUM. 731 of the olfactory nerves (foramina cribrosa ). These openings are variable in their number, and differ from each other in their size and modes of termination ; those nearest the crista galli are the largest, and of them one or two of the anterior ones are very considerable; the smallest are situated on the outer edge of the cribriform plate, and both of these sets are the orifices of canals which terminate, the former about the root and upon the sides of the septum, the latter on the outer wall of the nose; those which are intermediate and in the centre of the channel, are complete foramina, and open on the opposite surface of the plate. Immediately in front of the inner set of fora- mina, there is, between the crista galli and cribriform plate, a fissure which gives passage to the ethmoidal nerve and vessels. From the under surface of the cribriform plate and at right angles with it, there descend, on the median line, the nasal lamella, and, on each side, a cellular mass which partly forms the outer wall of the nostril and the inner wall of the orbit. The nasal lamella, or vertical plate, forms the upper portion of the septum narium ; it is immediately underneath the crista galli, and becomes gradually thinner as it descends ; its anterior border is rough, thicker above than below, and articulates, first, with the nasal process of the frontal bone, and, secondly, with the nasal bones themselves ; its posterior border is also rough and is articulated to the crest on the fore part of the sphenoid bone ; its inferior border is, in its posterior half, thin and inclined downwards and forwards to be articulated to the vomer, and, in its anterior half, somewhat thicker and rougher, and in- clined downwards and backwards to be arti- culated with the triangular cartilage of the nose; its sides are plain, and exhibit sulci which are continuous with the foramina that open on its root. On each side of this lamella and between it and the lateral masses there is a space which is encroached upon in the middle more than it is above or below, and a portion of the cribri- form plate forms its roof. The lateral masses are delicate in their struc- ture and complicated in their arrangement. Each consists of a number of cells ( cellulee ethmoidales ), which are divided by a partition into an anterior and a posterior set, with the former of which the frontal sinus communi- cates, and with the latter the sphenoidal. The outer surface of each lateral mass is compact and smooth, and constitutes the greater portion of the inner wall of the orbit. This is the orbitar process or os planum, which articulates above with the frontal bone, below with the superior maxillary and palate bones, behind with the sphenoid, and in front with the la- chrymal. On its upper border are seen the two notches which assist the frontal in forming the anterior and posterior orbital foramina. The inner surface of this cellular mass, that which looks towards the nasal lamella, is ren- dered irregular by two curved processes (the superior and middle turbinated processes ), of which tire upper one is smaller, delicate, re- gular in its curve, and is seen only on the posterior half of the wall; the other is larger, more spongy, and extends the entire length of the wall. Both of them are convex on the side next the cavity of the nostril, and concave on that which looks towards the cells ; but the inferior is also at its lower edge again curled in such a manner as to offer a convexity on both of its surfaces. Between the two turbinated pro- cesses there is a triangular space (the sitperior meatus ) the apex of which is directed forwards, and in which there is an opening commu- nicating with the posterior ethmoidal cells. Underneath the middle turbinated process, and bounded by its concavity on the one hand and the cells on the other, is the middle meatus ; into which open the anterior ethmoidal cells, and the tubular communication with the frontal sinus, called infundibulum. The connexions of this bone are, behind to the sphenoid ; in front to the frontal and nasal bones; laterally by its upper borders to the orbitar processes of the frontal, by its under borders to the same-named processes of the superior maxillary and palate bones, and by its anterior border to the lachrymal ; by the under edge of its middle vertical plate to the vomer and triangular cartilage; and by the anterior extremity of the outer surface of the middle turbinated process to the inferior tur- binated bone. The ethmoid is the most tardy in its deve- lopment of all the bones of the cranium. The lateral masses exhibit each of them an ossific deposit about the middle period of intra- uterine life, but neither the cells nor turbinated processes are much developed at birth, at which time also the central portion is carti- laginous. The ossification of this part pro- ceeds from above downwards, so that the crista galli is completely formed while the lower part of the nasal lamella is yet cartila- ginous. During infancy the cribriform plate becomes narrower, curved, and as it were compressed ; the nasal lamella advances for- wards; and the spaces between the septum and outer walls are considerably increased. The occipital bone ( os occipitis; Germ. Occi- pital-knochen, Hinterhaupts-knochen ,) is situ- ated behind the sphenoid, and forms the pos- terior part of the base of the cranium and the contiguous projection of the occiput. Its figure is that of a lozenge with its anterior angle truncated, and is so curved as to be generally concave on one surface and convex on the other. The inferior and anterior half of it is situated between the two temporal bones ; the superior and posterior half is be- tween the posterior margins of the two pa- rietal. At its anterior part it is pierced by a large elliptical foramen (the foramen magnum ), through which there pass, from the skull, the medulla spinalis and its membranes, the sinus venosus and the spinal arteries ; and, into the skull, the vertebral arteries, the posterior me- ningeal arteries, and the nervus accessorius. On the cerebral surface the internal crucial 3b 2 732 CRANIUM. spine divides it into four fossa:, the two supe- rior of which are the/iwiYf cerebri for the pos- terior lobes of the cerebrum, the two inferior, the Jos ?cc cerebelli, for the hemispheres of the cerebellum; the former being marked by the convolution of the brain, they are not so smooth as those which lodge the cerebellum. The lower limb of the crucial spine is prominent, and arises by a bifid root from the margin of the foramen magnum; the upper limb is grooved for the reception of the longitudinal sinus, and to its borders the septum cerebri is attached ; this groove is mostly directed to one side or the other, and generally to the right ; to the lateral limbs the tentorium is fixed, and the grooves which are on them contain the lateral sinuses. At the point where the trans- verse bisects the vertical portion of the crucial spine, it is very prominent, is called the inter- nal occipital protuberance, and marks the situ- ation of the torcular Herophili. In front of the foramen magnum, ascending obliquely towards the sphenoid bone, and nar- rowing in its ascent, is the upper surface of the basilar process, which is concave from side to side for the lodgement of the pons Varolii and medulla oblongata, and exhibits on each margin a depression (the sulcus basilaris ) for the basilar or inferior petrosal sinus. On either side of the foramen magnum is a groove which advances from without inwards, and from behind forwards, and lodges the ter- mination of the lateral sinus. The anterior extremity of this groove turns downwards and forms a large notch (th e fossa jugularis ), which is bounded on the outer side by a strong rough process (the processus jvgularis ), and on the inner side by a smooth oval eminence which is situated between it and the sulcus basilaris, and below which is the orifice of the foramen condyloidcum anticum for the passage of the motor lingua nerve. The external convex surface, in that part which is behind the foramen magnum, is di- vided into an inferior rough, and a superior smooth, triangular portion. The division be- tween the two is marked by a curved line (the superior occipital ridge ), which abuts on the petrous masses of the temporal bones, and exhibits in its centre the tuberose process, or the external occipital tubercle, to which the ligamentum nucha is attached. From the ridge next to the tubercle the occipito-frontalis and trapezius muscles arise, and, still more outwardly, the splenius capitis and the sterno- cleido-mastoideus are attached. From the tu- bercle to the foramen magnum extends a longitudinal spine, which is bisected in its middle by a second curved line (the inferior occipital ridge), and constitutes, thereby, the external crucial spine. On each side of the spine and between the two ridges, there is a considerable rough depression for the attach- ment of the complexus, and, to the outer side of it, one which is smoother, for the traehelo- mastoideus. Between the inferior ridge and the foramen magnum, there are on either side of the longitudinal spine, indications of the attachment, in succession, of the recti capitis postici minores et majores and of the obliquus capitis superior. On the outer side of this region is the sulcus occipitalis, which runs backwards and upwards between the surfaces of attach- ment of the trachelo-mastoideus and the com- plexus, and is formed by the occipital artery. Underneath the anterior half of the margin of the foramen magnum are the condyloid pro- cesses, two elongated articulating eminences, convex in both directions, wider in the middle than at either end, inclined from above down- wards, from behind forwards, and from with- out inwards, and having their internal edges below the level of the external. On the inner side of each process is a rough surface for the attachment of the odontoid ligament ; on the outer side is a ridge (the processus lateralis ) which ends in the jugular process, and gives insertion to the rectus capitis lateralis; ante- riorly is the anterior orifice of the anterior condyloid foramen ; and posteriorly there is a depression in which is sometimes seen a fora- men (foramen eondyloideumposticum ) through which a vein of the scalp communicates with the terminal portion of the lateral sinus. In front of the foramen magnum is the under surface of the basilar process, which, by reason of the superior thickness of its an- terior extremity, is not so oblique as it appears on its upper surface. There is a slight tuber- cle on the middle line to which is fixed the middle constrictor of the pharynx, and behind it, on both sides, a transverse line for the su- perior constrictor, between which and the foramen are depressions caused by the recti capitis antici majores et minores. The superior angle of this bone is applied on the junction of the two parietal, and the serrated borders which extend from it to the lateral angles are articulated to the posterior borders of the same bones. The upper angle itself and more than half of the borders pro- ceeding from it, overlap the parietals, but in the remainder of their extent the latter bones overlap the occipital ; in each case the arrange- ment being the same as that which exists be- tween the parietal and the frontal bones. From the lateral angles to the jugular pro- cesses, a rough but not denticulated border articulates it to the posterior border of the mastoid portion of the temporal bone. Im- mediately in front of the jugular process is the fossa jugularis, which forms, in common with the temporal bone, the foramen jugulare or foramen lacerum posticum in basi cranii, through which emerge the jugular vein, the pneumo-gastric, glosso-pharyngeal, and spinal accessory nerves. The rest of the border from the fossa jugularis to the anterior angle is in apposition with the petrous portion of the temporal bone, but the quantity of cartilage between them is too large to admit of there being any fixed articulation at this part. The anterior angle itself is truncated and presents a rough quadrilateral surface, which articulates, and, indeed, consolidates itself, at an early period of life, with the basilar process and body of the sphenoid bone. This union is so complete and so similar to the union CRANIUM. 733 which takes place beween the several elements of the bones of the cranium, that Soemmering and Meckel have described the two as one bone, under the name of us basilare or osspheno- occipitale. The connexions of this bone are few and simple, being, in its superior half, with the parietals ; in its inferior half, with the tem- porals ; at its anterior extremity, with the sphenoid ; and, by its condyles, with the atlas. At birth this bone is separable into four dis- tinct portions, one being in front, one behind, and one on each side of the foramen magnum, the border of which is, consequently, not then completed. The anterior and two lateral por- tions are formed by the extension of ossific matter from one point of deposit in each ; but that posterior to the foramen is produced from many points, in the number of which ana- tomists are not agreed. The ossification com- mences in the lower part, at some distance from the foramen, by one point on each side of the median line ; and before they have completely approached each other, two ana- logous deposits appear in the upper part, which coalesce before the upper and lower pieces are joined. This occurs during the fourth month, at which time the inferior and broad part dis- plays on each side another point of ossification on a level witli the spot where the process first commenced; in the fifth month the whole of these are consolidated into one piece. It often happens, however, that other deposits are formed, especially in the upper part ; and frequently they refuse to merge into the others, continuing then to be distinct through life as separate small bones having their own serrated margins to articulate with the adjoining struc- tures. The lateral pieces (those which comprehend the condyles, and lateral and jugular pro- cesses) commence their formation about the fourth month ; and the anterior piece is the last in the order of development. The temporal bone (os temporum ; Germ, das Schlajenbein.) One is situated on each side of the sphenoid and lower half of the occipital bone ; they complete the base of the cranium and form the inferior part of the sides of the vault. For the purposes of description it is usually divided into three portions; one, strong and compact, in the base and between the middle and posterior fossae, the petrous ; a second, tumid and less dense, behind the ear, the mastoid; and a third rising from the former two, thin and scaly, situated in the temple, the squamous. The petrous portion is an elongated, pyra- midal mass, of which two of the surfaces enter into the formation of the cavity of the cranium, and the third is underneath. It is situated on a line which, if prolonged, would extend from behind the ear to the opposite external angular process of the frontal bone; but it is limited by the body of the sphenoid. It occupies the space between the posterior border of the ala ' major of the sphenoid and the basilar process of the occipital bone, in the angle of which its free extremity is impacted. In its substance is contained the labyrinth of the ear. Of the two surfaces which are in the cra- nium, one is superior, the cerebral; the other is posterior, the cerebellar. On the cerebral surface near its middle, is a smooth, convex, and transverse elevation (the processus semicircularis ), produced by the su- perior semicircular canal of the labyrinth ; immediately in front of this is a depression on which the Gasserian ganglion lies ; more out- wardly and running lengthwise, is a faint sulcus (the sulcus Vidianus ), which terminates at a small opening (the hiatus Fallopii ) for the entrance of the Vidian nerve into the aque- ductus Fallopii. On the cerebellar surface is seen the foramen auditorium internum, the superior and posterior part of the margin of which is more prominent than the anterior, which, in fact, degenerates into a sulcus. It is the commencement of a canal (the meatus auditorius internus ) into which pass the acoustic and facial nerves, and the bottom of which is divided by a ridge into two unequal depressions; the upper one being the/ossf/fa parva, in which is the orifice of the aqueduct of Fallopius for the exit of the facial nerve ; the lower one being the fossula magna, in which are several minute perforations for the acoustic nerve. Behind the foramen audi- torium is an indistinct slit, which is the ter- mination of the aqueductus vestibuli ; above and rather anterior to this slit is a triangular orifice for the entrance of vessels; and below it, extending to the foramen lacerum posticum, is a slight groove. Between the cerebral and cerebellar surfaces there is a sharp ridge on which there is a groove (the sulcus petrosas ), more evident pos- teriorly than anteriorly ; to the ridge is attached the tentorium ; the groove lodges the petrosal sinus. The under surface is divided into two parts by a sharp, prominent ridge, which has on either side of it a considerable fossa. That on its outer side is the fossa parotidea for the upper part of the parotid gland ; that on its inner side is a thimble-like depression (the fossa jugular is ), which forms with the occipital bone the foramen lacerum posterius. In this bone, however, it is not so wide as it is in the occipital; from which it results that the fora- men is imperfectly divided into two parts — the anterior for the nerves, the posterior for the vein ; and it is the latter organ which is lodged in the fossa jugularis of the temporal bone. The fossa parotidea is limited, above and in front, by a fissure ( thefssura Glasseri ), which penetrates to the tympanum and gives exit to the chorda tympani and entrance to the laxator tympani muscle; behind, by the external auditory process. The margin of the foramen auditorium externum, which is ellip- tical, has its long diameter vertical, and is the commencement of the meatus auditorius externus ; a tube which is curved a little downwards, is more expanded at its extre- mities than in its middle, and terminates at 734 CRANIUM. the membrana tympani, in front, by a sulcus which is situated on the border between the cerebral and under surfaces, and passes back- wards, between the petrous and squamous portions as a canal (the canalis Eustachianus), which is divided by a lamina of bone, called the processus cochleariformis, into two parts, the inferior of which contains the Eustachian tube, and the superior the tensor mein bran® tympani muscle. Immediately behind the fossa jugularis there is a rough surface, for the articulation of the jugular process of the occi- pital bone; and to the outer side of this sur- face is the foramen stylo-mastoideum for the exit of the facial nerve. In front of and close to this foramen, and between it and the jugular fossa, is the long pointed process (the styloid process ) for the attachment of the stylo-maxil- lary and stylo-hyoid ligaments, and the stylo- pharyngeus, stylo-glossus and stylo-hyoideus muscles ; this process is embraced on the outer side at its root by a portion of the ridge separating the parotid and jugular fossa; that portion is called the vaginal process. In front of the fossa jugularis are two foramina ; one very large, the foramen caroticum ; the other very small, to the inner side of the former and nearly on the margin between this and the cerebellic surfaces, being the termination of the aqueduct of the cochlea. The foramen caro- ticum is the inferior opening of the canalis caroticus , a canal which exists in the bone, and consists of two parts that are at right angles with each other — the inferior, short, vertical, and extending upwards from the fo- ramen caroticum into the substance of the bone; the superior, horizontal, running length- wise, and extending to the end of the petrous process : in this canal there pass the carotid artery to the cavity of the cranium, and a filament of the nervus abducens, as well as one of the Vidian, to the neck. A rough sur- face is observed anterior to the foramen caro- ticum for the attachment of the levator palati and the tensor tympani muscles. The outer and posterior extremity of the petrous is confounded with the mastoid and squamous portions ; the inner and anterior is open, and the bone is so much removed at its upper part (to allow the carotid artery to pass upon the body of the sphenoid) that it there appears more like a deep groove than a tube. This is filled up in the recent subject by a plate of cartilage, but in the dried skull, when this cartilage has been removed, there is found an opening, between the sphenoid bone and this extremity of the temporal, which is called the foramen lacerum anticum. The mastoid portion is situated at the outer end of the petrous, and behind and below the squamous. It is of a nipple-like shape, with an upper horizontal denticulated border, with which the posterior inferior angle of the pari- etal bone articulates ; and with a posterior semi- circular border which is joined to the occipital : in both directions it is overlapped by the bones to which it is joined, except at the lower part, where it is applied to the occipital by a sort of harmonic suture. On its inner surface there is a deep, semi- circular sulcus (the concavity looking back- wards) which traverses its entire length ; it receives the lateral sinus from the parietal bone and transmits it to the lower part of the occi- pital : there is generally observed in it a fo- ramen (the foramen mastoideum ), through which a vein of the scalp communicates with the sinus. Its outer surface is roughened and gives attachment to the sterno-cleido-mastoideus, and sometimes to the trachelo-mastoideus ; it terminates below in the mammillary eminence, called the mastoid process, behind and to the inner side of which are two grooves — the one nearest to the process (the sulcus digastricus ) very evident, for the attachment of the digas- tricus ; the other nearly on the articulating edge (sulcus occipitalis), less distinct, for the occi- pital artery. The squamous portion rises upwards from the mastoid, and part of the outer border of the petrous portions; it has a semicircular mar- gin which embraces the parietal and sphenoid bones. Its internal surface, which is concave, con- tributes to form the middle fossa of the cra- nium, and exhibits strongly the depressions and elevations which correspond to the con- volutions of the brain, and to the spaces between them. At its anterior part, and com- mencing at the angle between it and the pe- trous process, there is a groove which runs upwards and divides into other grooves, some of which pass backwards; these are formed by the middle meningeal artery and its branches. The external plate of its border is prolonged upwards, in such a manner that this surface is surmounted by a rough articulating line, of considerable breadth, which is applied on the outside of the parietal and partly on the sphe- noid bone. The external surface is slightly convex, is smooth, and there may be often seen indica- tions of deep branches of the temporal artery having passed over it. It forms in part the temporal fossa, and the temporal muscle is attached to it. At its lower part, a process (the zygomatic process ) passes transversely outwards, and is then twisted on itself in a di- rection forwards, after the fashion of the ribs at their angles ; so that the surface of the process which would have been superior becomes internal, and that which would have been in- ferior becomes external. This process has two roots, an anterior or transverse and a pos- terior or longitudinal. The former is a convex elongated eminence, situated transversely and in front of a fossa (the fossa articularis ), in which the condyle of the lower jaw is placed. This root is the eminentia articularis, on which the condyle, with its inter-articular cartilage, is thrown when the jaw is depressed. The pos- terior root has itself two origins, which cir- cumscribe the external auditory foramen ; and it flows into and joins the anterior, just when that root is altering its direction. Be- tween the squamous process, and that part of the zygomatic process which is between the CRANIUM. 735 tvvo roots, there is a groove in which play the posterior fibres of the temporal muscle. The fossa articularis, which is between the roots, is bounded behind by the Glasserian fissure before mentioned; it forms, with the adjoining fossa parotidea, the glenoid cavity. The zygomatic process extends forwards about an inch from its anterior root ; being, therefore, convex externally and concave internally. Its upper border gives attachment to the temporal fascia; its inferior (which is about half the length of the superior) to the masseter muscle. Its external surface is covered by the integu- ment, and its internal forms the outer boun- dary of the temporal fossa, in which is situ- ated the temporal muscle. The extremity of the zygomatic process forms a point, on account of the under margin being bevelled and den- ticulated to articulate with the malar bone. The circumference of the squamous process is sharp, in all that part which is above the level of the zygomatic process, and denticu- lated, at the expense of its outer table, in the rest of its extent ; so that it rests on the sphe- noid bone. The connexions of this bone and the me- chanical effects which result from its position, will be readily understood. Its petrous por- tion being wedged between the basilar process of the occipital bone, which serves it as a fulcrum, and the ala major of the sphenoid, which binds it against that fulcrum ; the in- ferior part of its squamous process resting on, and being sustained by the sphenoid bone, while its mastoid process is braced in by the posterior inferior angle of the parietal, and by the occipital bone — the fronting squamous margin will effectually resist the lateral thrust of the parietal; the more so that a limited yielding movement is allowed at the fulcrum. The zygomatic process advancing forwards to the malar bone, will, with its fellow of the opposite side, give stability to the several bones of the face ; and, in common with the pterygoid processes of the sphenoid bone, maintain the integrity of the various arches which they form. It is also connected with the lower jaw. This bone is developed from six points of ossification : viz. one for each of the three great divisions, and one each for the zygomatic and styloid processes and the auditory canal. At birth it consists of four pieces, the squa- mous (a), mastoid (c), petrous, and an in- Fig. 374. complete bony ring (d), to which the mem- brane of the tympanum is attached. The bony ring is the first to join, by its upper part, the squamous ; after which it is consolidated with the petrous, and then extends itself out- wards and backwards to form the meatus auditorius externus, and all the four pieces are then united. In infancy the bone sustains great changes; the squamous process from being straight becomes curved ; the zygomatic process recedes from the squamous and in- creases the space between them ; the mastoid portion becomes more tumid, is developed upwards and backwards, and sends forth the nipple-like process which gives to it its name. The eminentia articularis and fossa articularis from an oblique assume a transverse direction, and become, the one more concave, the other more convex. The styloid process, though ossified in its middle, is frequently, to an ad- vanced age, connected with the bone by carti- lage only. The parietal bone (os parietale; Germ, die Scheitelbeineocler Seitenbeine) (Jig. 372, 373 P) constitutes with its fellow the greater portion of the vault of the skull, and forms with it a sort of bridge, the corners of which on each side are fixed, the one on the great wing of the sphenoid, the other on the mastoid process of the temporal bone, the squamous process of which braces in the intervening space. The external surface oilers in its centre a prominence which marks the spot at which ossification commenced ; and it marks also the widest part of the skull. Below this is a semicircular line (the linea temporalis), to which are attached the temporal fascia and muscle ; still more inferiorly is a plane surface occupied by the temporal muscle; and be- tween it and the lower border, is a lunated articular portion with converging striae, to be applied against the squamous portion of the temporal bone. Near the posterior part of the bone and a little removed from its upper border is the foramen parietale, for the passage of a vein to the longitudinal sinus. The inner surface exhibits the usual indi- cations of the convolutions of the brain, and also arborescent sulci, which mainly proceed from the anterior inferior angle, of the bone, and are directed upwards and backwards to the fossa parictulis, which answers to the pa- rietal prominence on the outer surface ; these sulci lodge the branches of the middle menin- geal artery. Along the upper border is a de- pression, which, with a similarly disposed edge of the other bone, forms a groove for the lodgement of the longitudinal sinus, and hence is termed sulcus longitudinalis ; near to it are sometimes seen small depressions (fossa Pacchionii ) for the granulations of the dura mater, called glandul* Pacchionii externae. The borders are of various lengths; the superior is the longest, the inferior is the shortest, and the anterior is longer than the posterior. The superior is united to the same border of the opposite bone by the regular interchange of serrations of the outer table ; the anterior and posterior reverse the arrange- 736 CRANIUM. ment which obtains in the frontal and occipital bones ; that is, they are overlapped in the upper part, while in the lower they overlap those bones ; the inferior is sharp, and merely terminates the articular surface already al- luded to. The angles contained within these borders are the frontal (which is nearly a right angle) formed by the superior and anterior borders ; the occipital (more obtuse) by the superior and posterior borders ; the mastoidal, truncated and articulated with the mastoid process of the temporal bone ; and the spinous (acute) re- ceived on the tip of the great wing of the sphenoid, and intervening between the tem- poral and frontal bones. The mastoidal angle is, on its inner surface, traversed by a sulcus (the eulcus lateralis ) to lodge the lateral sinus and to transmit it from the occipital to the temporal bone. The spinous angle is deeply grooved on its inner surface by the sulcus spinosus for the middle meningeal artery, or the arteria spinalis durs matris ; this groove has its place frequently supplied by a canal, then called canalis spinosus. Its connexions are with its fellow above ; the temporal and sphenoid below ; the frontal before ; and the occipital behind. The parietal, like each half of the frontal bone, is developed from the protuberance ; and from this point the ossific matter radiates to- wards its several borders. While this process is going on, the part above and the part below the centre form a considerable angle with each other; but this is much effaced when the edges have arrived at their destination, espe- cially when the squamous process of the tem- poral quits its vertical for its curved position. Articulation of the cranial bones. — These several bones are locked together so as to form the envelope of the brain, and the mode by which their secure adherence to each other is effected, differs in the summit, on the sides, and in the base of the cranium. In the calvaria they are united either by the overlapping or by the dove-tailing of their edges, or else by the two modes combined. The inner table does not proceed so far as the external, and the latter being jagged with pro- cesses which have no definite form, but which are either tortuous, or narrower at their fixed than at their free extremity, the outer tables are immovably joined by the fixation of the processes of each side into the spaces of the other. By this means the inner tables of the two bones are brought nearly into contact, a thin lamina only of cartilage intervening ; so that on looking into the vault, but little more than a plain line will be noticed. Here, however, there is no overlapping of the outer tables; but the only instance of it is in the junction of the two parietals on the median line, by which, in effect, they form but one bone. On the sides of the skull there is a mere overlapping of the descending by the ascending portions, and to accomplish this, and yet maintain uniformity of surface, those parts of the outer tables which project beyond the inner are pared off or thinned in opposite directions. Thus the squamous processes of the temporal bones and the great wings of the sphenoid rise upwards from a fixed basis and form a wall which is bevelled off on the inner edge of its outer plate, so as to receive the parietal and frontal bones, the outside of which sustains a corresponding bevelling, by which arrangement they are prevented from being thrust outwards. The articulation of the anterior and the posterior with the middle portion of the calvaria, is a modification of the two preceding; that is, the outer table is partly bevelled and partly denticulated. The frontal and occipital bones are symmetrical and single, while there are two parietal ; and, though these are well united by their mutual interchange of denticulation, they are yet more firmly consolidated by the extension of the frontal and occipital bones on the frontal and occipital angles of the parietals, and on their borders to some distance from those angles ; each symmetrical bone thereby forming a spe- cies of cramp on the parietals. The edges, however, of the outer tables are not pared to a sharp ridge, but there is left sufficient to be fashioned into processes to maintain the secu- rity of the skull in a longitudinal direction. The parietals being thus firmly secured above and below, the intervening portion of then- edges is competent to act as girders themselves, and, in fact, we find that the lower part of their anterior and posterior borders overlap the corresponding portions of the frontal and occi- pital bones respectively. In the base of the cranium the bones are placed in simple contact, and are so disposed that forces, descending from above, will neces- sarily drive them closer to each other. To understand this rightly, we must suppose the sphenoid and occipital to form (which, in fact, they do) but one bone at an early period of life. The temporal bone is placed alongside the occipital, in such a way that the petrous process is wedged into the angle between the basilar process of the occipital, and the great wing of the sphenoid ; while the latter, again, is wedged into the angle between the petrous and squamous processes of the temporal bone. It has been said that on the upper surface of the outer margin of the great wing, rests the lower part of the squamous process ; in case of force descending through the parietal bone this will be the fulcrum, and the lever (the squamous process) being directed outwards, the mastoid and petrous processes will neces- sarily be squeezed more forcibly against the occipital bone and its basilar process. The peculiar appearance presented by the articulations on the outer surface of the cal- varia, has procured for them the name of sutures, a term which is applied frequently to the joinings in the base, although they are essentially different in appearance and in fact. Those which are situated in the calvaria, and to which the name is more suitable, are the coronal, lambdoidal, and sagittal sutures. The coronal suture extends between the two great wings of the sphenoid bone across the upper part of the skull, and connects the fron- CRANIUM. tal to the two parietal bones (fig. 373, a). The lambdoidal (o) consists of two diverging lines formed by the articulation of the posterior border of the two parietals with the superior- half of the occipital; and extends from the superior to the lateral angles of that bone. The sagittal is the line of union between the parietals themselves, and runs longitudinally from the superior part of the lambdoidal to the centre of the coronal suture. On each side of the skull is the squamous suture (fig. 373, e); it has none of the serrated characters of the other sutures, but is an arched line ex- tending- from the great wing of the sphenoid to the mastoid process of the temporal bone, and traversing so much of the border of its squamous process as embraces the parietal bone. The squamous suture and the lambdoidal suture are connected by a short transverse line formed by the articulation of the mastoid angle of the parietal bone with the mastoid process of the temporal, and which is called addita- mentum sutura. squamosee (fig. 373, g). From the lateral angle of the occipital bone to its jugular process, that is, from the termination of the lambdoidal suture (where it is joined by the before-mentioned supplement of the squa- mous suture) to the jugular foramen, there is a line formed by the posterior border of the mastoid process and the occipital bone termed additamentum sutura lambdoidalis. The transverse frontal suture (fig. 373 , a) is situated transversely, but forms several angles in its course. It extends from one external angular process of the frontal bone to the other; commencing at either angle, after uniting that angle to the malar bone, it enters the orbit, and unites the frontal bone to the great wing and to the small wing of the sphe- noid ; it then passes out of the other side of the orbit, joining the same bone to the eth- moid, lachrymal, nasal process of the superior maxillary and nasal bones themselves ; enters the orbit of the opposite side and retires from it, articulating the frontal to bones analogous to those in the other orbit. Other sutures are occasionally enumerated, such as the sphenoidal, which entirely sur- rounds the sphenoid bone; and the ethmoidal, which bounds the cribriform plate of the eth- moid bone. Both of these, so far as they deserve the name of sutures, are comprehended in the transverse frontal suture. The articulations of the temporal with the occipital, sphenoid, and parietal bones have been designated as the petro-occipital, petro- sphenoidal, spheno-temporal, and spheno-pari- etal sutures ; but, with the exception of the last, (which is squamous, and truly a part of that suture,) they are not sutures. It ought further to be remarked that, while the bones of the calvaria are much thinner than those of the base, they are comparatively thicker in their borders to allow of that serra- tion from which the term suture is derived. To study, in combination with each other, the facts enumerated in the foregoing descrip- tion, it is necessary to take a survey of the 737 external and internal surfaces of the skull itself. For this purpose the external surface may be divided into four regions : the superior, the inferior, and the two lateral. The superior region extends from the nasal process of the frontal bone to the occipital protuberance, and is bounded on each side by the linea temporalis; a curved line, which, commencing at the external angular process of the frontal bone, passes backwards, traverses the parietal below its protuberance, and is re- ceived on the extreme point of the root of the zygomatic process of the temporal bone. To proceed from before to behind, there are, on the median line, the nasal process and the rough notch for the articulation of the nasal bones ; the nasal protuberance ; the glabella bounded laterally by the frontal processes; the line indicating the junction of the two foetal portions of the frontal bone ; the centre of the coronal suture; the whole length of the sa- gittal suture, with the foramen parietale on each side of it; the superior angle of the occipital bone ; a part of the occipital bone itself; and, lastly, the occipital protuberance. Laterally, and on each side, there are the frontal process, the superciliary ridge, the depression between them, and the supra-or- bitary foramen ; the frontal protuberance ; the coronal suture ; the parietal protuberance ; the lambdoidal suture ; and so much of the side of the occipital bone as is above the transverse ridge. The inferior region extends from the pos- terior part of the nasal process to the occipital protuberance, and is circumscribed by a line, continuous with the extremities of the supe- rior curved ridge of the occipital bone, and passing on the outside of the mastoid and in the direction of the zygomatic process of the temporal bone, to the crest which is on the temporal process of the great wing of the sphe- noid. The facts to be here noticed are nu- merous, and, to facilitate their enumeration, this region may be divided into three parts, one anterior to the pterygoid processes of the sphenoid bone, one posterior to the articu- lating processes of the occipital bone, and a middle one between these two. The anterior division contributes to form the nose and the orbits. For the first, there may be observed on the median line, the nasal lamella of the ethmoid bone, articulated, in front, to the nasal process of the frontal, and, behind, to the creit in front of the body of the sphenoid. On the same line, but below and behind this, is the azygos process, and inferior part of the body of the sphenoid, with the channels to form, with the vomer, the palatine canals. On either side of the nasal lamella is the slit for the ethmoidal nerve and vessels ; the cribriform plate and its foramina; and the space which assists to form the nares. More laterally, and still passing from before back- wards, is the internal angular process of the frontal bone, to unite with the lachrymal ; the cellular mass of the ethmoid, with its turbi- nated processes on one of its sides, and the 738 CRANIUM. orbitar plate on the other; the junction of this mass to the body of the sphenoid ; the turbi- nated process of the same bone, and, some- times, the opening into its sinus; the articular surface for the palate bone; and, lastly, the base of the pterygoid process exhibiting the anterior orifice of the Vidian canal. Still more outwardly is the part which forms the orbit, concave, and broader before than behind. To the fore part there are, on the outer side, the lachrymal fossa ; on the inner side the trochlear fossa, and, near to it, the orbitar orifice of the supra-orbitary foramen. Further back there is on the inner side a por- tion of the transverse suture between the frontal and ethmoidal bones, containing the two internal orbitar foramina ; and, to the outer side, another portion of the same suture between the frontal and sphenoid. A third, shorter portion connects the two preceding, and unites the frontal to the small wing of the sphenoid. Behind this there are in succession the foramen opticum ; the foramen lacerum orbitale superius ; the foramen rotundum ; and, lastly, the sulcus temporalis leading from the last foramen, and being behind the orbitar process of the sphenoid bone. The middle division offers in its centre the basilar process of the occipital bone, and the line of its junction with the sphenoid. On it are seen the indications of the attachment of the pharyngeal and anterior recti muscles. Its posterior edge forms a segment of a circle to assist in forming the foramen magnum. On either side, and from before backwards, are the external and internal pterygoid pro- cesses, with the fossa navicularis, fossa ptery- goidea, and hiatus palatinus between the two processes; the posterior orifice of the Vidian canal ; the foramen lacerum anterius ; the under surface of the petrous process of the temporal bone, with, on one side, the line of its junction with the basilar process, and, on the other, the line of its junction with the sphenoid bone, the Eustachian sulcus occu- pying the latter; behind the foramen lacerum anterius is the rough surface for the origin of the levator palati and tensor tympani muscles; the inferior orifice of the carotid canal ; the opening of the aqueduct of the cochlea; and, lastly, the foramen lacerum posterius. More outwardly, and pursuing the same direction, are the under surface of the great wing of the sphenoid bone; its line of union with the temporal ; the processus articularis ; the fossa articularis ; the Glasserian fissure ; the fossa parotidea ; and, lastly, the rough inferior bor- der of the foramen auditorium externum. On the inner edge of this plane, and to the outer side of the sulcus Eustachianus, there are, successively, the foramen ovale ; the foramen spinale ; the styloid process ; the spinous pro- cess, which is wedged into the Glasserian fis- sure; the crest between the fossa parotidea and the foramen lacerum posterius ; the vagi- nal process and the styloid process. The posterior division exhibits, on the me- dian line, the foramen magnum ; the longi- tudinal spine bisecting the inferior curved ridge, and having, on each side, below that ridge, rough depressions for the attachment of the posterior recti muscles, and above that ridge, still stronger and larger marks of the attachment of the complexus ; and, lastly, the inferior aspect of the occipital protuberance. To the extreme outside and passing from behind forwards, there are the termination of the superior occipital ridge; the additamentum suturae lambdoidalis ; the posterior part of the mastoid portion of the temporal bone dis- playing the foramen mastoideum ; the sulcus occipitalis on one hand, the mammillary pro- cess of the mastoid portion of the temporal bone on the other, and the sulcus digastrieus between the two ; and, lastly, the foramen stylo-mastoideum at the bottom of the sulcus digastrieus. Midway, and between the me- dian and outer portions of this region, and still passing from behind forwards, there are, the superior occipital ridge, the inferior occipital ridge, and between them the marks of the attachment of the splenius capitis and trachelo- mastoideus ; the oblique surface into which the obliquus capitis superior is inserted ; the posterior condyloid fossa, containing the pos- terior condyloid foramen whenever it exists ; the condyle itself ; the anterior condyloid fossa and foramen ; and, lastly, to the outside of the condyle, the processus lateralis. The lateral region (fig. 373) is oval, and its boundaries have already been stated. Its sur- face, lengthwise, is undulated, being convex behind, where the temporal and parietal form it; and concave in front, where the temporal and sphenoidal enter into its composition. Pro- ceeding from above downwards, and com- mencing with the linea temporalis, we have so much of the parietal and frontal bones as are below that line, with the inferior extremity of the coronal suture between them; next, the sutura squamosa between the parietal and temporal bones, and part of the transverse suture between the frontal and sphenoid ; below this, the squamous process of the tem- poral bone, and, in front of it, the temporal process of the sphenoid with the line of arti- culation between them. These parts form the fossa temporalis, which is limited inferiorly, on the sphenoid by a crest which divides it from the jugal fossa belonging to the face, and on the temporal by a groove on the upper part of the two roots of the zygomatic process, in which play the posterior horizontal fibres of the temporal muscle. Passing from behind forwards, there will be observed at the lower boundary of this region, the additamentum suturte squamosa; ; the base of the mastoid process ; the foramen auditorium externum ; and, lastly, the zygomatic process of the tem- poral bone articulating anteriorly with the malar bone. The interior of the cranium presents through- out its entire extent more or less evidence of the adaptation of its surface to the convolutions of the brain. The base is bounded, in front by the fora- men ccecum ; behind, by the centre of the internal crucial spine; and, in its circumfe- CRANIUM. 739 rence, by a line passing on each side along the outer border of the orbitar process of the frontal bone, the junction of the parietal and sphenoid; the parietal and temporal bones; and the lateral limb of the internal crucial spine of the occipital. It is placed obliquely downwards and back- wards, and consists of three principal divisions or platforms — the posterior being the lowest, the anterior the highest; and the middle, on a plane between the two. The anterior division is called the anterior fossa, and sustains the anterior lobes of the brain. It is concave in the middle and con- vex on each side; it is limited, anteriorly by the merging of the orbitar processes into the general mass of the frontal bone, and poste- riorly by the posterior margin of the alae mi- nores. On the median line, from before back- wards, we encounter the foramen ccecum ; the crista galli; the ethmoidal process of the sphenoid bone ; and, lastly, the smooth sur- face of that bone on which the olfactory nerves repose. On either side of the crista galli is the processus cribrosus, with its foramina, and slit for the ethmoidal nerve and vessels ; more outwardly, is the transverse suture uniting this process to the frontal bone, and in it may be seen the internal orifice of the anterior internal orbitar foramen. From hence outwards, is the orbitar process of the frontal bone, somewhat arched, and displaying, more evidently than in the rest of the skull, the digital impressions of the brain ; behind this is the transverse suture uniting it to the small wings of the sphenoid bone ; and, lastly, there is the upper surface of the small wings themselves. The middle fossa consist of two large fossae laterally, and one, which is smaller, centrally. This latter is the pituitary fossa; in its front is the olivary, and, behind it, is the basilar process ; on its sides are the sulci carotici, and its corners are bounded by the ephippial or clinoid processes. In front of the olivary process is the groove on which the optic nerves decussate ; and between it and the anterior ephippial processes of each side is the foramen opticum. The lateral fossae are very deep and of an irregular triangular figure, the base of which is directed outwards. Anteriorly they are bounded by the small wings of the sphenoid bone, and posteriorly by the ridge which se- parates the cerebral from the cerebellar surface of the petrous portion of the temporal bone. Each is formed, anteriorly and internally, by the great wing of the sphenoid ; posteriorly, by the cerebral surface of the petrous process; and, externally, by the squamous process of the temporal bone. In it are seen the lines of junction between these parts, and the sulci formed by the spinous artery of the dura mater. At its anterior boundary there is the foramen lacerum orbitale superius ; and behind it, inclining gradually outwards, there are in suc- cession, the foramen rotundum, the foramen ovale, the foramen spinale, the sulcus Vidi- anus, the hiatus Fallopii, the depression for the Gasserian ganglion, and the processus semi- circularis. To the inner side of this range, and on a level with the foramen ovale, is the foramen lacerum anterius. The posterior division extends from the basilar process of the sphenoid bone to the internal tubercle of the occiput. Its margin is of a triangular figure, with its base curved and directed backwards. The petrosal ridges form the sides of the triangle, and the lateral limbs of the internal crucial spine, its base. On the median line and passing backwards we observe the superior sulcated surface of the basilar process, with a groove on each side for the basilar sinus ; the foramen magnum with the anterior condyloid foramina near its ante- rior part; and, lastly, the inferior limb of the internal crucial spine, separating the two great cerebellar fosste. Each of the latter is bounded, above and to the outside, by a broad groove for the lateral sinus, which groove passes from the occipital bone to the mastoid angle of the parietal, from thence to the mastoid process of the temporal (where the mastoid foramen opens into it), and, ulti- mately, to the occipital bone again, where it turns forwards to the foramen lacerum pos- terius. In this groove is seen the terminal^ of the lambdoidal suture, and the additamer/tum suturae squamosse and the additamentum su- turae lambdoidalis cross it ; the principal portion of the latter being seen in the cere- bellar fossa. Anteriorly, and above the fora- men lacerum posterius, is the cerebellar surface of the petrous process of the temporal bone ; exhibiting the openings of the meatus audi- torius interims and of the aqueduct of the vestibule; and, on the ridge which separates this from the cerebral surface, the groove for the petrosal sinus. The calvaria possesses in its centre a dense curved rib, which extends through the roof from the anterior to the posterior part of the base, but which is more evident at its extre- mities than in its middle, where it is generally marked by a groove for the longitudinal sinus. The frontal spine commences it, and its ter- mination is the superior limb of the internal crucial spine ; the intermediate portion (where it is masked) is the sagittal suture. On each side, and from before backwards, we notice in succession the frontal depression ; the coro- nal suture; the parietal depression, and several arterial sulci running towards it from below ; part of the lambdoidal suture ; and, lastly, the cerebral fossa of the occipital bone. On each side of the sagittal suture are the fossae Pacchioni, and, near its back part, the foramen parietale. A comparison of the external and internal surfaces of the cranium establishes the fact that there is a general correspondence of the two as far as regards those parts which are in contact with the periphery of the brain. But, between the several divisions of that organ, there are developed on the inside of the skull very large ribs and processes which destroy the particular correspondence of the two surfaces. CRANIUM. 740 Nevertheless, this does not impair our ability to deduce the internal capacity of the cranium from an examination of its exterior; since the diploe between the two plates, in the spaces intermediate to these ribs, seldom varies more than one or two lines in its thickness. In a skull of ordinary capacity, the length, measuring from the frontal spine to the longi- tudinal sulcus, is five inches and a half; its width, between the bases of the petrous pro- cesses of the temporal bones, four inches and a half; between the parietal fossae, five inches; and between the extremities of the alee mi- nores, three inches and three quarters : its depth, from the foramen magnum, four inches and a half, from the ephippium three inches and a quarter; and, from the front of the olivary process, two inches and three quarters. But observation proves to us that there is little dependence to be placed on these measure- ments ; scarcely any two skulls agree in their diameters, for where one exceeds in a given direction, it may fall short in some other. To this conclusion we shall be led by the ex- amination of skulls, not only of members of the same community but even of persons con- nected by the closest ties of consanguinity. While, however, there is any doubt about the matter, it is not to mixed communities we should have recourse in our search for facts ; but rather to the well-authenticated skulls of such tribes as inhabit parts of the globe re- mote from each other, and whose manners and customs have, to the best of our belief, re- mained stationary from time immemorial ; for by this procedure we shall avoid the confusion arising from a mixture of different races of men whose respective dispositions have been modified by intermarriage. The skulls of a North American Indian and a Hindoo will be good examples to shew how the diameters will vary. By making a longi- tudinal section of each, we shall find, by ap- plying a line between a spot about five-eighths of an inch above the root of the nose, and another about three-eighths of an inch above the superior angle of the occipital bone, that there is considerably more space above the line in the Hindoo than there is in the American Indian, while the distance to the foramen magnum is much greater in the latter than in the former. Again, if we make the usual ho- rizontal section, it will be manifest that in breadth the Indian will exceed the Hindoo by nearly, and, sometimes, more than an inch, although the latter has the advantage in length. In the Negro, which, in length, is equal to the Hindoo, the space above the line in a vertical section is not absolutely, much less relatively, so great towards the frontal bone as in the shorter skull of the Indian; while towards the posterior part of the parietals it is much greater, and in its breadth it falls but little short of it. These three aboriginal types will suffice to shew the endless varieties which must prevail in mixed communities, and to satisfy us that the forms of skulls are as numerous as the diversified modifications of character with which the Creator has endowed the human race. Several naturalists have sought to establish an analogy between the cranium and the ver- tebrae, and have imagined that they had dis^ covered in the one a type of the other; in other words, that the cranium is neither more nor less than a gigantic vertebra which has been submitted to some necessary modifications. In this sense the ephippium and basilar por- tion of the occipital bone represent the body of a vertebra; the foramen magnum, the ver- tebral foramen ; the longitudinal spine of the occipital bone, the spinous process ; the ex- panded portion of the bone as far as the mas- toid portion of the temporals, the vertebral plates ; the mastoid processes themselves, the transverse processes ; the eminence above the anterior condyloid foramina and the condyles themselves, the superior and inferior oblique processes ; and the notch behind the condyles and the jugular notch, the notches which form the conjugal foramina.* Others again regard the cranium as com- posed of several vertebrae more or less com- plete, which are so associated as to meet the exigencies of the highly developed summit of the medulla spinalis. The resemblance, how- ever, of many of the parts to a vertebra is so imperfect as to admit of the greatest license, as respects both the fixing of the number and the apportioning of the parts which severally belong to them. The alteration of position, too, to which they are necessarily subject to enable them to accord with the change in direc- tion which the nervous matter sustains, casts much confusion on the subject, and prevents the mind from recognizing, at once, a similarity which would be more apparent if they con- tinued to be superimposed on each other as they are in the spine instead of being arranged at right angles with it.f The occipital bone certainly offers no dif- ficulty to the detection of an analogy between it and a vertebra; and we readily discern in it a body ; a foramen ; two transverse, four arti- cular, and one spinous process ; and four notches. These have already been pointed out, and it is sufficient here to observe, that, in this bone apart from the others, the basilar process alone will represent the body, and the lateral processes will be the type of the trans- verse processes of the vertebra. By removing the bones of the face and taking the sphenoid in conjunction with the frontal bone, we shall (if we place the body 8 This was Dumeril’s theory. — See Consid. gen. sur l’Analogie entre tous les os et les muscles du tronc des animaux. — Magasin Encyclopedique, 1808, t. lii. t The celebrated Goethe was among the first to adopt this idea. He admitted the existence of three vertebrae in the cranium, (7,ur Naturwis- senschaft iiberhaupt, &c. Stuttg. 1817-24.) The further development of it occupied the attention of O’Ken, Spix, Meckel, Geoffroy St. Hilaire, and Carus. — See Meckel, Anat. Desc. & c. t. i. p. 631, and Carus, Anat. Comp, par Jourdain, t. iii. Introduction. — Ed. CRANIUM. 741 of the sphenoid bone vertically) at onoe per- ceive the same analogy to exist. If, when they are thus placed, we look at the cerebral surface, we shall recognize the body in that of the sphenoid ; the vertebral plates in the small wings of the sphenoid, and two halves of the frontal bone ; the foramen in the space cir- cumscribed by these last ; the transverse processes in the two great wings of the sphe- noid ; and the notches in the lacerated orbitar foramina, and the angles between the body of the sphenoid and posterior margin of its great wings. If we look at it in front, it will not require any great stretch of the imagination to recognize the four articulating processes in the pterygoid processes of the sphenoid bone and the external angular processes of the frontal. The temporal and the parietal bones toge- ther represent another vertebra, situated be- tween the former two. By looking at the base of the skull held vertically, and abstract- ing in the mind the occipital bone, we can (under favour of the license allowed to, or taken by anatomists) see in the two petrous portions of the temporal bones, if they were brought into contact, a type of the body of a vertebra; and in those parts of them which contribute to form the anterior and posterior- lacerated foramina, we observe a resemblance to those notches which form in the vertebra, as they do here, conjugal foramina. The arti- cular eminences of the temporal bones give us no bad notion of the transverse processes, while the zygomatic processes above (still holding the skull vertically) and the part which projects behind the mastoid processes below, will indicate the four oblique or arti- culating processes. Lastly, the squamous pro- cesses of the temporal and the whole of the parietal bones represent the vertebral plates, and the space enclosed by them, the vertebral foramen. Development of the cranial bones. — The progressive development of the bones of the cranium has been pointed out in their separate descriptions ; but there are some general facts which regard its formation as an entire organ which merit further notice. The cranium of the fcetus presents, like all other organs, a rude outline of the shape it is destined to assume; and, at the earliest pe- riod at which it is noticed, its walls are com- pletely membranous, being formed by the dura mater and pericranium so united as to render it impossible to separate them without injury. Very early points of ossification are developed in this membranous envelope, whence osseous radii shoot out, so that the several points enlarge towards each other, and ultimately coalesce or are united by suture. Unlike other bones of a similar character the opposite surfaces are not of similar den- sity. The surface secreted by the vessels of the dura mater contains less animal matter than that which is produced from the vessels of the pericranium ; and it is, therefore, of a more dense and brittle character ; so much so, that, when the contiguous bones approximate, the edges of the inner table are simply in juxta-position, a slight layer of cartilage alone separating them. Hence, in the interior of the skull, the sutures are plain lines ; or, if at all irregular, there is no interchange of substance between them. Not so, however, with the external. By reason of the greater quantity of animal matter which it possesses, and the more diffuse character of its texture, a prin- ciple of toughness is conferred on it which admits of its being dove-tailed with the same table of other bones. The base takes precedence of the calvaria in the commencement and completion of its ossification. With the exception of its most prominent points, and the ethmoid bone, it is completely ossified at birth; while, between the bones of the calvaria, there are conside- rable membranous interspaces, so as to allow of these bones being squeezed together, or to overlap each other, at the period of parturition. The ossific matter departing from the Dro- tuberances of the (c>d,Jigs. 374,375) and radiating to- wards the circum- ference of these bones, it follows that the angles will be incomplete when the rest of the bone is formed. On this account it is that, at the four angles of each pa- rietal bone, there is a membranous spot which the ossific matter has not reached, when, in other parts, it is joined to the surrounding bones. These spaces are called fontanelles ; two of them are situated on the median line and superiorly ; and two others inferiorly and in each lateral region. The posterior superior fontanelle is triangular, and is found between the superior angle of the occipital bone, and the occipital angles of the two parietal. The anterior superior fontanelle ( a , Jig. 376), by reason of Fig. 376. the frontal bone being formed in two parts, is of a lozenge shape ; and it is between those two parts and the frontal an- gles of the parietal bones that it occurs. These two fontanelles are conse- quently at the extremities of the sagittal suture. The inferior fontanelles are found, the anterior ( a , fig. 375) between the spinous angle of the parietal, and the great wing of the sphenoid bone ; the posterior ( b , Jig. 375) between the mastoid angle of the first-named bone and the mastoid process of the temporal. These two fontanelles are, therefore, situated at the extremities of the squamous suture. frontal and parietal bones Fig. 375. 742 CRANIUM. Fig. 377. In infancy the rela- tive proportion of the cranium to the face is much greater than in adult life; and this causes the foramen magnum to appearto be situated much further forward, in the infe- rior region of the base, than it is when the face is more expanded. The lower part of the occiput is flattened, the superior is very projecting, and, altogether, the cranium has a character of rotundity which is speedily exchanged for the oval form which prevails in the adolescent age. When the sutures have become conjoined, and the cranium is constituted a defensive in- vestment of the brain in virtue of its mechan- ism, the internal table (the tabula vitrea ) is secreted in greater abundance, and the diplbe between it and the outer table is rendered more manifest. The spongy tissue of the sphenoid bone is absorbed and the sinuses formed ; but it is not until a period nearly coeval with puberty, that those of the frontal bone are developed. It is not until the diplbe is fully formed that we can demonstrate those venous canals with which that structure has been shown to abound by the researches of Chaussier, Dupuytren, and Breschet (figs. 187, 188, p. 436). Mechanical adaptation of the cranium,. — It will now be noticed that the properties of the cranium, those on which its defensive qualities are founded, differ in the several periods of life ; but that, nevertheless, there is in each as perfect an adaptation of it to these purposes as seems consistent with the schemes of Provi- dence in the creation of a finite being. The pressure which the brain has to sustain during the process of parturition, is directed solely to that part which is not essential to life ; the condition of the bones of the calvaria ad- mits of the volume of the hemispheres being diminished at the time the foetus is ushered into the world. Not so the base ; the parts which it is destined to protect require to be maintained in all their integrity, and the ex- tent to which it has acquired solidity is such as to forbid the encroachment of the parietes on parts which are essential to the continuance of life, and which are highly intolerant of pres- sure. In infantile life, also, protection is afforded on the same principle. The bones of the calvaria are notoriously capable of sustaining indentations, and afterwards, by their resili- ency, of regaining their normal form. The preponderance, too, of the organic over the inorganic texture, blunts the force which may be applied, and resists its transmission to the parts below. But there is an addition even to these provisions, a mechanical disposition of the bones highly favourable to resistance. At the back, on the sides, and in front— opposed in every direction from which force may pro- ceed— are the summits of ovoidal domes, and, as the ossific matter radiates from these summits to the circumference, the force will be received on one extremity of a bundle of diverging lines, and that which would sever the structure if it fell on any other point, here falls compa- ratively innoxious. Hence it is that the cen- ters of ossification are so much more projecting during infancy than in afterlife; for, although the mechanical contrivance abides through the whole term of existence, it is not, when asso- ciated with other means, of that predominating character which we observe in youth. The manner in which the cranium (when fully formed) defends the brain, differs widely from the preceding. In proportion as its several parts become consolidated, and the relation between its animal and earthy consti- tuents is reversed, so its power of deadening or neutralizing the vibrations which pass through it, is diminished. It is here on its general shape and the disposition of its parts that its protective properties depend. It has been already stated that the bones of the cranium are so fashioned as to concur in the production of an egg-like cavity ; and that their margins are so arranged as to enable them to bind and be bound by each other, in such a manner that if one bone be taken away the whole will have a tendency to separate. This ovoid form ensures (much better than any other which has no fixed basis or point of resistance beyond itself) the transmission of the vibrations which are distributed from any spot on which force may be applied. Assuming that the skull involved the pro- perties of an arch, its defensive power has by some been attributed to the circumstance of its being of that figure. An arched form, how- ever, would serve it only in the case of force descending from above ; it would not provide resistance to those severe shocks which are communicated from below, as in jumping, nor protect it from blows that might arrive on its sides. But the cranium is not an arch, for there are neither piers on which the extremities of that arch could rest, nor abutments to resist their lateral thrust. Supposing a barrel to be sawed lengthwise, and the edges to be connected by a base, if the centre be applied on a column, (the proportion of which to the base is the same as that of the spine to the width of the skull,) it is manifest that, since the extremities of the arch are received on the ends of two long levers which have a common fulcrum, an inconsiderable force would have a tendency to sever them at their junction. On the other hand, if the barrel were entire, force would be transmitted through the parietes to a point exactly opposite to that on which it impinged, if it were not dissipated in its transit. Such a degree of force however might be applied, that its vibrations, distributed at the moment of its application, might pass through the entire walls, and, accumulating at one spot, by their intensity cause the fracture of the part. The natural mode of providing against this occur- CRANIUM. 743 rence would be to strengthen the part in which (from tlie situation of the organ) these vibra- tions might, in general, be expected to concur; and this is the contrivance adopted in the cra- nium, for in the centre of its base there is a qua- drilateral portion (the body of the sphenoid bone) of characteristic massiveness and strength. It does not however augment uniformly in its substance from above downwards. The matter is accumulated in dense lines or ribs, which pass to a common centre, and constitute thereby a peculiar skeleton or frame-work of surpassing strength, which admits of the intro- duction of a lighter and more fragile structure in the intervening spaces, and resists the shocks that arrive through the spine, from behind or from above. This frame-work is situated almost entirely in the base; the only part which is in the calvarium being a longitudinal curved line, formed by the ethmoidal process of the sphe- noid bone, the crista galli of the ethmoid, the spine of the frontal, the thickened commutual margins of the parietals, and the superior limb of the internal occipital spine. Independently of this curved rib, the calvarium consists of four ovoidal domes, two on each side; formed, the anterior by the corresponding half of the frontal bone, and the posterior by the parietal. The summits of these domes are their centres of ossification, and their bases abut, partly on the longitudinal rib, and partly on the frame- work in the base. The part to which all the forces tend is the body of the sphenoid bone. From its posterior corners there pass backwards two ribs, (the petrous processes of the temporal bones,) which terminate on the extremities of an arch, (the lateral limbs of the internal crucial spine of the occiput,) which is placed horizontally, and the convexity of which is turned back- wards. This arch and the two ribs which connect it to the centre are in the line in which the oc- ciput would strike the ground in falling back- wards ; and they further form the brim of the pit which contains the cerebellum, so that the vibrations of force pass in the interstice between that organ and the cerebrum. From each side of the body of the sphenoid bone there stretches forwards, outwards, and upwards towards the temples, a curved rib, (the anterior part of the great wing,) and, from the anterior part of the body, a transverse rib which overlays the former. These and the posterior lateral ribs, all of which depart from a common centre, constitute the frame-work of the base which sustains the ovoidal domes of the calvaria. The frontal dome is placed with its summit (the frontal depression) looking backwards, downwards, and inwards; its mar- gin is received, interiorly on the whole length of the anterior transverse, and on the extremity of the anterior lateral curved rib; towards the middle line, on so much of the longitudinal rib as extends to the parietal bones ; and supe- riorly, it is applied against a portion of the base of the parietal dome. It is against these parts that it thrusts, whenever it receives a shock on its summit. The parietal dome is placed with its summit (the parietal depression) looking downwards and inwards. Below, it is received on the extremities of the lateral ribs ; above, it thrusts against the remainder of the longitudinal rib ; behind, it falls on the corresponding portion of the horizontal arch ; and, in front, it antagonizes the frontal. It is by the bases of these domes thus thrusting against a solid frame-work, that the cranium is endowed with the power of re- sisting lateral shocks whether they approach from before or behind ; and it is not, as some allege, simply by the mobility of the head, that it withstands blows, which, if it were fixed, would fracture it. There yet remains to be noticed an impor- tant part of this skeleton or frame-work ; that which bears upon the spine, and resists the force transmitted through it. At the bottom of the pit containing the cerebellum, there is an elliptical opening (the foramen magnum), the margin of which is very dense; this opening is provided underneath with two tubercles (the articulating processes), by which it rests on the vertebral column ; from these tubercles a curved rib on each side (the lateral process of the oc- cipital bone and the mastoid of the temporal) extends upwards and outwards to the extremity of the posterior lateral rib ; the segment of the margin of the opening which is anterior to the tubercles, is prolonged upwards and forwards, in the form of a broad pillar (the basilar pro- cess), to the back part of the common centre ; the segment which is behind the tubercles sends off, at its back part, a spine (the inferior limb of the internal crucial spine), which ends at the centre of the horizontal arch, at the point where the superior longitudinal rib terminates; and this point of confluence of the forces from below, from above, and from behind, is strength- ened by a nodule (the internal occipital protu- berance). The frame-work of the cerebellar cavity is thus connected with that of the general cavity; anteriorly, to the body of the sphenoid bone; posteriorly, to the tubercle of the occi- pital ; and, laterally, to the extremities of the petrous processes of the temporal bones. In both of them it will be seen that they occupy spaces between the grand divisions of the ner- vous matter, which latter is, therefore, removed from the chance of sustaining injury by shocks, much more completely than it could have been had the parietes been submitted to a progres- sive augmentation of substance from above downwards. As it is, the spaces in which the nervous matter reposes are thin and frequently diaphanous ; and, were they situated in un- protected parts, would be perforated by the slightest force. During a considerable period of life the sub- ject enjoys additional protection from the slight yielding of the bones, and from the cartilage which intervenes especially at the base. Pres- sure applied on the vertex would tend to disjoin the parietal bones from each other, and from the frontal and occipital bones. This the pe- culiar nature of the articulations forbids, and the longitudinal rib chiefly, and the expanded 744 CRANIUM. portion of the bones themselves in part, convey the force downwards, the former forwards through the median line of the ethmoid to the front of the sphenoid, and backwards through the superior and inferior limbs of the crucial spine of the occiput, traversing the foramen magnum, and passing through the basilar process to the back of the sphenoid bone : the latter forwards through the frontal bone to the small and great wings, and, through them, to the body of the sphenoid ; and backwards through the parietal and occipital to the lateral limbs of the crucial spine. The parietals convey it down the sides to the great wing of the sphenoid and the mas- toid process of the temporal bone, from which it is transmitted to the common centre ; and the slight rotation which is permitted to the temporal bone, (and which has already been alluded to,) materially tends to break the force in its transit. Nor is there any imperfection in this apparent inclination of the parietals to an outward divergence, for the squamous process of the temporal bone which overlaps each be- tween its two fixed points is strongly supported on its outer side by the temporal muscle. Abnormal conditions of tiie cranium. Most of the abnormal conditions of the cra- nium are dependent on circumstances con- nected with the evolution of the brain, and are mostly acquired after birth ; the only con- genital variations being those in which there is a total or a partial privation of its parietes. There is no vestige of it, or, indeed, of the head itself, in the true acephalous foetus; but, whenever the medulla oblongata is present, the base of the cranium is developed, and often- times there are found rudimentary portions of the other bones (false acephal'ui and anence - plialia ) . The parietal or occipital bones, and some- times all of them are imperfect in that mal- formation termed encephalocele, which, in some cases, is analogous to spina bifida, and, in others, to hernia cerebri. When serous fluid constitutes the tumour, the deficiency of the bones is considerable, owing to the arrestation of the formative process; but when the brain protrudes, their development continues in such a way as to embrace the root of the tumour, and then the calvaria, flattened and in contact with the base, exhibits an opening through which the hernia escaped. The cranium is said to be, at times, insuffi- ciently evolved ; the evolution of its parts being accelerated and their coalescence prematurely effected, so that the ossific capsule is formed before the brain has attained its full growth. It is, however, most probable that in this as in other cases it adapts itself to the brain, and that it is on an imperfect development of that organ that the smallness of the cranium is de- pendent ; but varieties of this description which are connected with deficiences of mental en- dowment will scarcely admit of enumeration. The parietes of the cranium may be preter- naturally thin, without this being dependent on disease; but they are most obviously in that condition in hydrocephalus, in which affection, however, there are two opposite states of the skull. When the disease occurs in infancy, and persists for any length of time, the bones of the calvaria usually become thin and pellucid ; the spaces between them are of great extent ; and the deposition of the inorganic texture is arrested in such a way that instead of bones we have frequently little more than a membrano- cartilaginous lamina, and some- times not even that; for instances have been known in which the upper part of the head has been covered by membrane only. This suspension of action, however, is in some instances only temporary. The deposition of ossific matter becomes then more rapid and abundant than under ordinary circumstances ; the points of deposit are more numerous than usual ; and a skull of gigantic dimensions and of peculiar and premature hardness is pro- duced. It has been sufficiently explained that the several ossific elements of the cranium unite in definite numbers to produce the bones which we have been occupied in describing. Never- theless, it not unusually happens that some of these elements, or, otherwise, adventitious de- posits of a similar character, which manifest themselves, do not flow into and combine with the other elements of the bone in which they occur; but, on the contrary, each in itself forms the centre of an ossific process, and the bone thus formed (be it large or small) articu- lates by its circumference to the parts with which it comes into contact. These adven- titious pieces are commonly known under the name of ossa Wormiana, because it is supposed that they were first described by Wormius, a physician at Copenhagen in the seventeenth century;* they are also called ossa triquetra, triangularia, ossa suturarum, ossa supranume- raria. They vary in situation, number, and size. In general they are situated in the lambdoidal suture ; they are, however, met with in the sagittal, occasionally in the coronal, and (though rarely) in the squamous suture. One of the most remarkable is that which sometimes replaces the superior angle of the occipital bone, called by Blasius os triangulare or epac- tale. Bertin describes one in the situation of the anterior fontanelle. It is by a process analogous to the pre- ceding that the occipital bone occasionally presents a suture between the upper and under halves of its posterior portion. The elements of those two parts combine among themselves, and the pieces resulting from their union ap- proach, and, instead of forming the continuous bone, as we usually see it, they are associated by means of an additional suture. An anomaly of not very unusual occurrence is the permanence of the suture uniting the two halves of the frontal bone, and which is seldom apparent beyond the second year of extra-uterine life. * Vid. 01. Wormii et ad eum doctorum virfim epistolss, t. i. Hafnise, 1728. CRANIUM. 745 There are but few skulls which are perfectly symmetrical, although the variation of one side from the other is generally so slight that the eye does not at once detect it. In numerous cases, however, the want of symmetry forcibly obtrudes itself; sometimes one half is considerably larger than the other ; and in other cases it appears to be thrown out of position, as though, during the time that the parietes were soft, pressure had been applied in front and behind, and, by a sort of rotatory movement, it had been drawn back on one side and pushed forward on the opposite. There does not appear to be an absolute uniformity among the skulls of this description saving that the projections are always situated diagonally with respect to each other ; that is, if it be twisted to the right, the right half of the frontal bone will be in advance of the left; while the posterior part of the left parietal, and the corresponding side of the occipital bone, will project behind the right. This is by far the most prevalent variation, but, occasionally, the left half of the frontal bone is in advance, and, in such instances, the posterior increase will be on the right side. The change which takes place in advanced age can scarcely be accounted an anomaly. At that period the skull is much more an entire bone than it is in the earlier epochs. The sutures are to a certain extent effaced, and a mere line indicates the former disjunction of the bones. It is on the interior of the skull that these sutures are first effaced, and on the exterior the order of obliteration is from the summit to the base. It has been affirmed that the volume of the skull diminishes in old age, and that it is susceptible of change, in different directions, after the bones are locked together. It is, however, certain that its external con- figuration is somewhat altered, for the promi- nences formed by the centres of ossification of the parietal and frontal bones become flattened and undistinguishable from the rest of the parietes; which, as old age sets in, become thinner than they were previously. This change, however, is but temporary, for, in extreme old age, the skull is thicker and more porous than at any antecedent period of life. This hyper- trophy is produced by the recession of the inner from the outer table, and the conversion of some part of the substance of each into a thin spongy tissue ; the diplde itself sustaining an analogous alteration, by the enlargement of its cells, and the thinning of the plates which form their walls. Occasional instances occur in which the skull is of inordinate thickness, and this, appa- rently, without its being connected with the age of the subject. The late Mr. Joshua Brookes had some sections of a skull, found in a church- yard in Lancashire, of nearly three quarters of an inch in thickness; and specimens have been seen of more than an inch. In some of them the diplde is perfect, the augmentation being in the two tables ; in others, and indeed in the majority of specimens, the two tables and the diplde are confounded together in one thick mass of matter, which is of an ivory hardness. It is not improbable that we might justly refer this VOL. I. condition, as well as some other peculiarities of the cranium, to inflammation of the bone itself, or of its investing membranes. That exostosis is the product of a limited periostitis admits of but little dispute, and it is very likely that those cases of hyperostosis in which there is a uniform deposit of bone, only mark the effect of a more diffused and general inflammation ; the more so, since we meet with these local and general deposits, as well on the inner, as on the outer table of the skull, and for the existence of which it would otherwise be impossible to account. When they occur on the inner table, the func- tions of the brain are usually more or less dis- turbed, although it would appear that the mental manifestations are not always implicated. In the skull of an idiot of advanced age, examined several years since by the writer of this article, there was a uniform deposition to the extent of nearly a quarter of an inch ; and in a recent autopsy of a young girl, he found the entire syncipital region very irregular in its surface, from being studded with variously-sized nodules, the bases of which flowed into and were lost in each other. This girl was of feeble intellect, and the victim of epilepsy. In the examination of a body at the Hotel Dieu, by Mr. King, that gentleman discovered on the petrous portion of the tem- poral bone a tumour which he had not been led to expect by any indication of suffering which appeared during life This tumour had the volume of a marble or pistol-bullet, was cel- lular in its structure, and perfectly smooth on its surface ; a depression exactly corresponding to it was found on the under surface of the middle lobe of the brain, but its substance and membranes had their normal characters. The cranium is oftentimes found in the oppo- site state of atrophy, in which the balance be- tween deposition and absorption seems to have been disturbed, so much to the prejudice of the former, that the walls are sometimes not much thicker than a piece of paper. When- ever the two textures maintain their usual pro- portion, this atrophy may be regarded as a natural abnormal state; but those cases in which either the inorganic or animal element preponderates, and a fragility or softening of the bone is thereby established, must be referred to some constitutional affection in which the rest of the osseous system has participated, and the influence of which it will not fail to exhibit. In addition to exostosis and hyperostosis, the cranium sustains other pathological changes as the effects of inflammation. Previously to the establishment of osteitis, whether from a common or specific cause, mercurial or syphilitic, there is found that stasis of the blood which always precedes inflam- mation. The sanguineous complexion of the diplde in cases of erysipelas testifies that this engorgement may be produced by increased action in the neighbouring teguments. It has already been stated that hypertrophy of the cranium may be regarded as a termina- tion of osteitis. When inflammation is limited in its action and of long duration, it is probable that the ossific element is poured into the cells 3 c 746 REGIONS AND MUSCLES OF THE CRANIUM. of the diploe so as to effect their obliteration ; but when it is of a more vivid character, the opposite effect of softening (the precursor of ulceration) takes place, and both the outer and inner tables are rendered friable. This fre- quently occurs to a great extent in the mastoidal cells, especially in children ; and as, in them, the posterior portion of the meatus auditorius internus possesses an unclosed fissure, the dis- charge which is consequent on the destruction of the cells is allowed an exit, before the mem- brana tympani is destroyed ; although that, as well as the whole of the internal ear, is fre- quently involved in the ravages of the disease — then, however, having passed into another ter- mination of osteitis, viz. ulceration. Adhesion can take place only where the cra- nium has experienced a lesion from a mechani- cal cause; and it is altogether prevented if the solution of continuity be great. The edges of a wound, produced by a cutting instrument penetrating more or less perpendicularly to the surface of the bone, do not approximate; but they are united by an interposing callus as in the case of a common fracture, and the line formed by it is always visible in the same way as the cicatrix which persists after the ad- hesion of soft parts. When a piece of the outer plate is elevated by a cutting instrument passing very obliquely to the surface of the bone, and the scalp is not detached, it will, on being immediately re-applied, unite with the surface from which it has been raised ; and, if it be altogether removed, the reparation will be effected in the same way as in other parts, viz. by the granulation and cicatrization of the cut surface. When there is loss of substance of the entire thickness of the bone, whether that loss be pro- duced by mechanical or pathological causes, granulations spring up from the dura mater; the edge of the opening becomes very thin ; the surface cicatrizes and produces the appear- ance of a dense fibrous membrane, the circum- ference of which is attached to the margin of the hole and the adjacent pericranium. Caries, which is analogous to ulceration of the soft parts, and is, in fact, an ulcerative ab- sorption of bone, attacks the cranium in com- mon with the rest of the osseous system ; but it always first appears on one of the two tables, and not on the diploe, although ultimately the entire thickness is, in some cases, involved. Indeed, when it commences on the inner table, it is only by the extension of the ulcerative pro- cess through the substance of the bone, that the suppurative collection can be emancipated. In this affection the pericranium is sometimes enormously thickened and almost inseparably attached to the rough biscuit-like surface of the bone beneath. In other cases, especially in those in which the ulcerative process has been provoked by mercury, it is in irregular patches; the pericranium is unattached and the denuded surface is of a dark colour. Necrosis, or mortification of the bone, is of frequent occurrence ; but not in the way usually implied by that term. Whether it be the sub- stance of the bone, or merely its outer lamina which is deprived of its vitality, the reparation is not by a fresh deposition of bone, nor is it coeval with the separation of the necrosed part, as in the long bones ; but it is a subse- quent action (such as has been already pointed out) which is established to supply the loss. Considerable portions of the frontal and parietal bones may thus be thrown off and the deficiency provided for by the granulations of either the subjacent diploe or the dura mater. Medullary sarcoma sometimes manifests itself in the cranium. It appears to commence in the diploe by a deposition of tuberculous matter, which softens, and which in that state may be mistaken for pus; the inorganic ele- ment is withdrawn ; the accumulation con- tinues and advances towards both tables, which in turn submit to the same change of structure; and, ultimately, atumour is formed, the capsule of which is constituted, on the one side by the pericranium, and, on the other, by the dura mater. In this tumour the knife detects spiculae of bone interspersed throughout its substance, and the edge of the opening which is left in the skull after maceration, is studded with irregular projecting points. For the Bibliography, see Osseods System. (J. Malyn.) CRANIUM, REGIONS AND MUSCLES OF THE, (Surgical Anatomy.) — If a line be drawn on the skull from the external angular process of the frontal bone, backwards along the rough line on that and the parietal bone, which indicates the attachment of the temporal fascia, be continued downwards and backwards parallel and a little external to the occipito- mastoid suture, and then be carried forwards along the inferior surface of the occipital bone to end just behind the foramen jugale, and a little internal to the stylo-mastoid foramen, — this line, with another similar one on the other side, will include an oblong region which has very natural limits both before and behind. Ante- riorly this region is limited on each side by the anterior margins of the roof of the orbit, in the centre by the line of articulation of the frontal bone with the nasal and superior maxil- lary, posteriorly by the superior curved line of the occipital bone, and on each side by the mastoid process. To this oblong region may be appropriately given the designation occipito- frontal region ^ The line which thus limits laterally the region just named circumscribes another region which occupies nearly the whole lateral surface of the cranium, and which is called the temporo- parietal region. This region passes into the base of the cranium, and may be limited below and within by a line from the styloid process external to the glenoid cavity, as far as the spheno-maxillary fissure * r Blandin makes five cranial regions — occipito- frontal , temporal , auricular , mastoid , and the region of the base of the cranium : the last is quite out of the reach of the surgeon, and therefore is excluded from consideiation in the present article. Velpeau has three regions, — the frontal, temporo- REGIONS AND MUSCLES OF THE CRANIUM. 747 I. Occipito-frontal region. — ' The anterior and posterior boundaries of this region are suffi- ciently obvious on the integuments, the eye- brows forming the anterior, the posterior being constituted by a line extending as far as the mastoid process on each side of the occipital protuberance corresponding to the insertion of the superficial muscles of the back of the neck, which protuberance can be felt through the integuments. The lateral limits, however, are not so distinct; in the living subject, however, when the temporal muscle is rendered tense, a distinct line of demarcation is felt along the upper margin of this muscle, extending down- wards and backwards nearly as far as the mas- toid process. We proceed to examine the several structures which are presented to the anatomist as he pursues the dissection of this region. 1. Integument. — It is in this region that we can best examine the general characters of the integument of the cranium, commonly known under the name of scalp (Fr. cuir chevelu). The greatest part of it is remarkable for the more or less luxuriant growth of hair from it,* the nature of which, it is hardly necessary to observe, differs materially in the male and in the female. In the natural state about two- thirds or three-fourths of the scalp are covered with hair, the anterior third or fourth, — namely, the skin of the forehead, — being uncovered. In front the hairs terminate abruptly on the frontal region ; behind they terminate less ab- ruptly, and descend in general to a variable distance on the posterior part of the neck, becoming finer and more downlike as they descend. The natural direction of the hairs is at right angles with that portion of the scalp from which they grow; consequently the dif- ference of direction of the hairs depends upon the differences in the aspects of those regions. This is most obvious in that part of the head which is called the crown, which in most per- sons inclines downwards and backwards to a greater or less extent. Such, however, is the parietal, and oecipito-mastoid. The advantages to be derived from the subdivision of the body into so many small regions as is adopted by the French anatomists, are by no means obvious. I decidedly prefer a subdivision which is indicated by certain naturally prominent points or landmarks, which will, 1 think, in general be found to map out regions not too limited nor too numerous, nor yet too comprehensive. * We cannot resist the temptation of transcribing the following passage from Gerdy, which is not devoid of some national characteristics. “ La surface superieure de la tete est arrondie et ovo'ide. Elle est couverte par les cheveux qui en cachent les formes, lui donnent, par la soupplesse et le contraste de leur couleur, une sorte de beaute dif- ficile a exprimer, et fournissent au gout delicat des femmes l’ornement le plus gracieux et le plus se- duisant par les masses legeres, les guirlandes flex- ueuses, les boucles arrondies qu’elles en composent, et par les mille arrangemens que suggere a leur imagination Famour ou Fart de plaire. Mais la tete.^se depouillant avec l’age, de la chevelure qui l’embellisait, ne presente plus dans la vieillesse qu une surface nue et luisante, ou Fon entrevoit quelquefois la trace des sutures frontales et parie- tales.” influence of art in the arrangement of the hair, that it is difficult to meet with “ a head of hair” — to borrow the phrase from the hair- dresser,— where the growth is perfectly na- tural. There is an obvious difference in the nature of that portion of the scalp from which hairs grow, and that which is naturally bald : the former is much thicker and denser, owing, no doubt, to a larger developement of the fibres of the corion, and to the great magnitude of the hairs which pierce it. It is at the posterior part of the occipito-frontal region that the hairs are strongest, and that portion of the scalp very rarely becomes bald. 2. Subcutaneous tissue. — Subjacent to the integument is a dense and lamellated cellular tissue, with little fat, and such as does exist deposited in small pellets, much more nume- rous in the posterior part of the region. This cellular membrane is very intimately connected with those parts of the scalp especially from which hairs grow ; it is much more loose and less adipose in the frontal region ; it also ad- heres pretty closely to the subjacent aponeurotic expansion of the occipito-frontalis muscle. The bulbs of the hairs are lodged in it. The firm adhesion of this cellular membrane on the one hand to the skin, and on the other to the subjacent aponeurosis, is sufficient to ac- count for the great pain and danger which at- tend punctured wounds of the scalp, in conse- quence of the non-extensibility of the membrane and the tension which a very slight degree of swelling consequently gives rise to. 3. Muscles. — If the scalp and subcutaneous tissue be divided by a transverse incision over the vertex, and the flaps carefully dissected off, — one as far as the eyebrows, the other to the superior curved line of the occipital bone, the occipito-frontalis muscle is brought into view. Anteriorly and inferiorly we find the few fibres of the orbicularis palpebrarum muscle overlap- ping the occipito-frontalis just above the mar- gin of the orbit. Occipito-frontalis ( epicranius , Albin. : de- scribed by some anatomists as two distinct muscles, the frontal and occipital). This is an expanded digastric muscle occu- pying the whole of this region. The two bellies of which the muscle is composed are united in the centre by a broad aponeurotic expansion. The anterior belly corresponds to a great part of the frontal bone, and the posterior to a part of the occipital. Very frequently the fibres are weak and pale, so that the dissector finds it difficult to trace out the extent and attachments of the muscle ; and, moreover, even in its most developed state it is a thin muscle, so that great care is required for the accurate dissection of it. The anterior belly of this muscle, or that which is by some called the frontal, consists distinctly of two lateral portions united by a narrow triangular slip of aponeurosis. Each portion is connected inferiorly to the integu- ment of the eyebrow through the intervention of cellular membrane, and slightly overlapped by the superior fibres of the orbicular muscle of the eyelids, and commingled with some of the 3 c 2 748 REGIONS AND MUSCLES OF THE CRANIUM. fibres of die last named muscle, as well as of the corrugatov supercilii. The aponeurotic slip before alluded to, situated in the middle line, forms the internal boundary of each la- teral portion. On the outside the fibres gra- dually shorten and extend a very short distance into the temporal region, over the temporal fascia. Each portion presents a convex margin above, which is inserted into the thin tendinous aponeurosis, which extends over the middle portion of the occipito-frontal region, correspond- ing to the posterior margin of the frontal bone, the fronto-parietal suture, internal portions of the parietal bones, the sagittal and lambdoidal sutures and part of the occipital bones, but se- parated from them by the pericranium and by some fine cellular tissue which connected the aponeurosis to the last-named membrane. This aponeurosis is called the cranial or epicranial aponeurosis : in some instances its fibrous cha- racter is very distinct in all its extent ; but very frequently it is most manifest in its posterior third or half, the anterior part being little more than condensed cellular membrane, excepting near to the fleshy fibres of the frontal portion of the muscles, where the aponeurotic structure again becomes manifest. On the sides this aponeurosis gradually degenerates into cellular membrane without leaving any defined margin. The aponeurosis in its whole extent adheres closely to the superjacent subcutaneous cellular tissue and to the subjacent pericranium through the intervention of a fine cellular membrane already referred to. Proceeding from before backwards, we find that this aponeurosis ends in affording insertion to the fibres which form the posterior belly of the muscle. This portion of the muscle, also called the occipital muscle, consists likewise of two lateral portions which are attached inferiorly to the ex- ternal part of the superior curved line of the occipital bone, and to the mastoid portion of the temporal. . The fibres are parallel and nearly vertical, inclining a little inwards, and are inserted, as already described, into the pos- terior margin of the epicranial aponeurosis. The attachment of the muscle to the occipital bone is immediately above that of the sterno- mastoid and splenins muscles. On the sides the fibres gradually disappear over the mastoid portion of the temporal bone, and the fleshy belly of the muscle lies immediately over the pericranium, some cellular membrane only in- tervening; its adhesion to the skin, however, is less intimate than that of the frontal portion. This muscle is evidently destined to act upon the integuments of the cranium : its influence is most apparent upon the skin of the forehead and eyebrows ; it distinctly raises the latter, and throws the former into transverse wrinkles. Under its influence the whole scalp may be made to move backwards and forwards, but the occipital portion of the muscle cannot create, as the frontal does, wrinkles in its corresponding integument, owing to the less firm adhesion of the muscle to it. Subjacent to the anterior portion of the occi- pito-frontal is is the corrvgalor supercilii muscle. It lies cn the inner half or third of the orbital margin of the frontal bone. By its inner extre- mity it is attached to the internal angular pro- cess of the frontal bone; the fibres pass thence outwards, inclining a little upwards, and are inserted into the integument of the eyebrow, being mixed with the orbicularis and occipito- frontalis muscle. This muscle evidently can depress the eyebrow, and acting in conjunction with its fellow, throw the integuments into vertical wrinkles, approximating the eyebrow’s, and occasioning the act of frowning. This muscle lies on the supra-orbital nerve and vessels. 4. Nerves. — The anterior part of the occi- pito-frontal region is freely supplied with nerves from those branches of the ophthalmic portion of the fifth which originate within the orbit. Of these the supra-orbital is the largest: imme- diately after its emergence from the supra-or- bital foramen this nerve divides into a series of branches which pass up on the forehead, some adhering to the pericranium, others distributed to the muscle, and others becoming subcu- taneous. Here, too, we find ramifications of the supra-trochleator or internal frontal nerve, chiefly distributed in the internal portion of the muscle. At the external part of this frontal region we find some filaments of the portio dura. In the posterior or occipital region the principal nerves are derived from the cervical plexus; the auricular and mastoid branches of this plexus distribute their filaments here; and we also find ramifications from the posterior branch of the first cervical nerve, accompany- ing the subdivisions of the occipital artery. 5. Arteries. — In front we have ramifications of the supra-orbital and superficial temporal freely anastomosing with each other; and deeper-seated, a few branches of the deep temporal, distributed to the pericranium. In the occipital region we have the occipital, often of considerable size, and the posterior auricular also sends some of its ramifications to anastomose with the occipital branches. Both in front and behind, the arteries of oppo site sides inosculate with each other on the middle line. 6. Veins. — Small veins accompany most of the arteries; but the most remarkable vein is one which is situated in the frontal region nearly on the middle line ; it is the frontal vein, or vena preparata , sometimes replaced by two or three. Velpeau advocates the re- vival of the ancient practice of bleeding from this vein in head affections. It carries the blood, as he observes, from all the anterior part of the head to the root of the nose, whence he argues that venesection practised on this vessel would empty the whole of the scalp. How often in practice do we see manifest advantage from cupping the temples or some region of the scalp, when little or no benefit had been derived from other modes of practising the detraction of blood 1 7. Lymphatics. — The lymphatics are very few7, and pass into the parotid ganglions, or those behind the ear or in the superior part of the neck. 8. Pericranium. — This fibrous tissue, pos- REGIONS AND MUSCLES OF THE CRANIUM. 749 sessing the same properties as the periosteum in other parts of the body, is, in a practical point of view, not the least interesting structure which is to be found in this region. It is largely supplied with blood, more especially in early life. We have already noticed its adhesion to the superjacent aponeurosis ; it adheres to the bone by cellular membrane, and is easily raised from it by dissection in all points except where there are sutures. This membrane is not unfvequently the seat of peri- ostitis and of nodes. II. Temporo-purietal region. — The lateral boundary of the occipito-frontal region consti- tutes the superior limit of this region, and a line drawn from the external angular process of the os frontis backwards and a little down- wards along the zygoma to the mastoid process of the temporal bone, limits it inferiorly. The integument and subcutaneous cellular membrane of this region differ but little from the same structures in the occipito-frontal re- gion. The former is finer and not so thick as in the middle and posterior parts of the last- named region. The hairs are oblique, some directed forwards, others backwards towards the occiput, and others downwards overlap- ping the ears. Here the hairs first begin to grow grey, whence the denomination tempura has been applied to these regions, grey hairs marking the inroads of time. The skin of this region, however, is naturally bald for a consi- derable portion in front of the ear, and for the distance of about an inch immediately behind and above it. The subcutaneous cellular tissue is very loose in front of the ear, but behind it in the vicinity of the mastoid process, it is more dense, and hence the scalp is much less move- able over that process, and immediately be- hind the ear. The epicranial aponeurosis is confounded with this subcutaneous tissue in the superior part of this region. Temporal fascia. — Subjacent to the cellular expansion is a fibrous membrane of consider- able strength, which stretches from the zygoma below to the curved line above and behind which limits the temporal fossa on the frontal, parietal, and temporal bones. It is very thick and strong, composed of white interlacing fi- bres, firmly attached to the points of bone referred to, and giving attachment by the greater part of its deep surface to the fibres of the temporal muscle. In front and below, however, for a short space, some adipose cel- lular membrane intervenes between the muscle and the fascia. Along the margin of the zy- goma, especially in front, the fascia is divisible into two laminae, which pass down, one in- ternal, the other external to the bone, and become incorporated with periosteum: by their separation above the zygoma they leave a tri- angular space which is in general filled with cellular tissue more or less adipose. Muscles. — Some fibres of the occipito- frontalis extend more or less into this region, according to the state of developement of the muscle. Here too we find the three auricular muscles immediately subjacent to the subcu- taneous cellular tissue. (See Ear ) Under the temporal fascia and adhering to its deep surface is the fleshy portion of the temporal muscle, attached to almost the whole of the fossa. Behind, the mastoid process is enveloped by the tendinous insertion of the sterno-mastoid muscle. Nerves.— zThe nerves of this region are very numerous. The subcutaneous ones are derived from the portio dura and the superficial tem- poral or auricular of the fifth, and posteriorly from the mastoid and digastric branches of the portio dura, as well as some from the ascending branches of the cervical plexus. The deep- seated nerves in the temporal fossa are the deep temporals from the inferior maxillary, and the temporal filament of the orbitar branch of the superior maxillary. Arteries. — The superficial arteries are nu- merous and important. They are derived from the trunk of the superficial temporal, which enters this region by passing over the zygoma in front of the tragus, crossed over by the anterior auris muscle. After it has passed the zygoma it inclines forwards, and is a little more distant from the ear than when on the zygoma. In all this course it may be felt distinctly, although it is pretty firmly bound down by the subcutaneous tissue and epicranial aponeurosis, which are here conjoined. A little more than an inch above the zygoma it divides, and we trace its anterior branch forwards towards the frontal region, which it enters and anastomoses with the supra-orbital. The posterior branch passes upwards and backwards, winding over the ear, and anastomoses with ramifications from the occipital artery. It is in one or other of these branches that arteriotomy is generally performed, in preference to opening the trunk of the artery. The middle branch of the temporal artery pierces the fascia, and enters the substance of the tem- poral muscle, anastomosing with the deep temporals. The posterior part of this region is supplied from branches of the occipital and posterior auris. Veins. — Veins accompany almost all the arteries : there are none worthy of any special notice. Lymphatics . — These vessels likewise accom- pany the arteries, and enter the ganglions in the neighbourhood of the ear, and those of the neck. Pericranium. — The pericranium does not differ from that of the occipito-frontal region, except perhaps in firmer adhesion to the squa- mous portion of the temporal bone. It affords insertion to the fibres of the temporal muscle. This region presents more surgical interest than the former one; it is more fre- quently the seat of operation (arteriotomy, and in its posterior part, that of opening the mastoid cells); and in consequence of the number of its arteries and nerves, and the great strength of the temporal fascia, wounds in this region are of a more dangerous kind. Fractures here are also liable to be complicated with a wound of the middle meningeal artery, part of the course of which corresponds to this region. ( R. B. Todd.) 750 CRUSTACEA. CRUSTACEA. Eng. Crustaceans; Germ. Krustenthiere ; Fr. Crustaces — This is the name given to a class of articulated animals, the type of which we have in the common crab and lobster, and which is essentially distin- guished by the conformation of the organs of circulation, of respiration, and of locomotion. The body of these animals is articulated ; that is to say, it is divided into rings, for the most part very distinct and partially move- able; their integuments are of considerable consistency, being either homy or calcareous, and form a kind of external skeleton ; their extremities are also articulated, arranged in a double series, and constitute antennos, jaws, limbs, (ambulatory, natatory, or prehensile, the most common number of which is five or seven pairs,) and other appendages ; their nervous system is ganglionic, situated partly in front of the alimentary canal, and partly behind and below the intestine ; their blood is colourless, and put into motion by an aortic and dorsal heart; their respiration is almost invariably aquatic, and is accomplished by means of branchiae, or the skin only ; to conclude, the sexes are distinct, and the organs of genera- tion double. Great and striking analogies occur between the Crustacea, the Insecta, and the Arachnida; so that it was long the custom to associate the whole of the animals now comprised in these three classes, under the single name of In- secta, or Insects. Brisson and Lefranc de Berkhey proposed, it is true, to separate the Crustacea, but the classifications of these writers not being based upon organic charac- ters of sufficient consequence, did not receive the general assent of naturalists, and it is only since the beginning of the present century that the necessity of separating the annulosa into certain distinct classes has been universally acknowledged. This result was mainly due to the anatomical inquiries of Cuvier, and this great naturalist was even the first who established a class among the invertebrate series of animals for the reception of those having bloodvessels, a ganglionic spinal cord, and articulated extremities, characters which, at the present time, still suffice to distinguish the Crustacea from the greater number of other animals. It is more especially in the general confor- mation of the body, in the structure of the extremities, and in the organization of the ner- vous system, that the Crustacea resemble the Insects and Arachnidans. The apparatus of vegetative life in these different animals pre- sents numerous and important differences. Thus Insects, instead of breathing by means of bran- chiae, and possessing a vascular system like the Crustacea, breathe by means of tracheae, and have no bloodvessels; and Arachnidans, which, like the Crustacea, have a heart more or less perfect, and distinct vessels for the circulation of their blood, have an aerial respiration ef- fected either by the medium of tracheae or of pulmonary sacs. The whole of the Crustacea are evidently formed after one and the same general type ; still, numerous and extensive varieties of struc- ture are observed among these animals ; and when compared one with another, their orga- nization is found to become more and more complicated in proportion as we rise in the series comprised by the group; it is farther found that the lower links of this kind of chain re- present, to a certain extent, the different phases through which the more perfect Crustaceans pass during the period of their embryonic ex- istence. This diversity of organization affords the grounds by which naturalists are guided in their distribution of the Crustaceans into orders and families. The natural arrangements of these animals that have been followed, are consequently ob- served to vary with the extent of knowledge of their structure possessed. It were tedious to enter upon the consideration of the different sys- tems which have been successively proposed for their classification; in order to aid the mind in the comprehension of the anatomical details into which we shall have to enter in the course of this article, it will be enough for us to pre- sent at once those divisions which appear to indicate most truly the differences and resem- blances subsisting between the various mem- bers of the class;* and to do this in the most compendious manner, and to exhibit the clas- sification which thence ensues, we shall present them to the reader in the shape of a synoptical table. * See Histoire Naturelle des Crustaces, par M. Milne Edwards, vol. i. p. 231. CRUSTACEA. 751 752 CRUSTACEA. § 1 . Of the skin 01 • tegumentary skeleton, and of the organs of locomotion. In the definition which has been given of the Crustacea, one of the most important cha- racters was derived from the nature and dispo- sition of their tegumentary system. And it is from this point that we shall start in laying before our readers a detailed account of the peculiarities of organization presented by this class of animals. By pursuing this course all the subsequent parts of the present article will appear clearer, the disposition of the internal organs, their forms, their mutual relations, &c. being in a great number of instances readily explicable by the various modes of confor- mation of the modified skin, which in this class performs the important office of the in- ternal skeleton among the Vertebrata. In some Crustacea the skin always con- tinues soft, but in the greater number it presents a great degree of solidity, and forms a solid casing, within which are included the whole of the soft parts. This difference in the condition of the tegumentary envelope is generally found to coincide with the pre- sence or absence of particular organs for the purposes of respiration ; and in fact it is easy to understand that in those species in which this important function is performed by the surface of the body at large, the integument required to be membranous, whilst in those in which the covering is of stony hardness, a con- dition which renders it incompetent to expose the blood to the contact of the atmospheric air dissolved in water, respiration can only be performed by the medium of organs especially contrived and set apart for the purpose. When the tegumentary envelope of the Crus- tacea is studied among the more elevated indi- viduals of the class, it is found to possess a somewhat complex structure ; parts may be distinguished in it comparable to those which are known to constitute the integument of the Vertebrata. Among the Brhchyura, for in- stance, the integument consists of a corium and an epidirmis with a pigmentary matter of a peculiar nature destined to communicate to the latter membrane the various colours with which it is ornamented. The corium or dermis, as among the Verte- brata, is a thick, spongy, and very vascular mem- brane; on its inner surface it is intimately con- nected with a kind of serous membrane, which lines the parietes of the cavities in the Crus- tacea in the same manner as the serous mem- branes line the internal cavities among the Ver- tebrata ; these two membranes, divided in the latter order by the interposition of muscular and bony layers, which cover and protect the great cavities, become closely united when these layers disappear, as they do in the Crus- tacea in consequence of the important changes that take place in the conformation of the ap- paratus of locomotion. The corium, again, among the Crustacea, is completely covered on its outer surface by a membranous envelope unfurnished with blood- vessels, and which must be held in all respects as analogous to the epidermis of the higher animals. It is never found in the properly membranous state, save at the time of the Crus- tacea casting their shell ; at this period it is interposed between the corium and the solid covering, ready to be cast off, and has the appearance of a pretty dense and consistent membrane, in spite of its thinness. It forms, as among animals higher in the scale, a kind of inorganic lamina, applied to the surface of the corium, from which it is an exudation. After the fall of the old shell, it becomes thicker and very considerably firmer, owing to the deposi- tion or penetration of calcareous molecules within its substance, as well as by the addition of new layers to its inner surface. The degree of hardness finally acquired, however, and the amount of calcareous matter deposited within it, vary considerably; in many members of the class it remains semi-corneous, in a condition very similar to that of the integuments of in- sects, with which, moreover, it corresponds very closely in point of chemical composition; in the higher Crustaceans, again, its composi- tion is very different: thus, whilst chitine in combination with albumen is the principal element in the tegumentary skeleton of some species, this substance scarcely occurs in the proportion of one or two-tenths in the carapace of the Decapods, which, on the contrary, con- tains sixty and even eighty per cent, of phos- phate and carbonate of lime, the latter sub- stance particularly occurring in considerably larger proportions than the former.'* With regard to the pigmentum, it is less a membrane or reticulation than an amorphous matter diffused through the outermost layer of the superficial membrane, being secreted like this by the corium. Alcohol, ether, the acids, and water at 212° Fahr. change it to a red in the greater number of species; but there are some species in which it may be exposed to the action of these different agents without under- going any perceptible change.-) The epidermic layer hardened in different degrees is the part which mainly constitutes the tegumentary skeleton of the Crustacea. In its nature it is obviously altogether different from that of the internal skeleton of the Verte- brata; still its functions are the same, and this physiological resemblance has led naturalists to speak of these two pieces of organic mecha- nism, so dissimilar in their anatomical rela- tions, under the common name of skeleton. The tegumentary skeleton of the Crustacea consists, like the bony skeleton of the Verte- brata, of a great number of distinct pieces, connected together by means of portions of the epidermic envelope which have not become hardened, in the same way as among the higher animals certain bones are connected by cartilages, the ossification of which is only accomplished in extreme old age. On the varieties which these pieces present in their • Clievreul and Geoffroy, Journal Complemen- taire du Diction, des Sciences Medicales, Avril 1820. Milne Edwards, Hist. Nat. des Crustaccs, t. i. p. 10. t Lassaigne, Journal d. Plrarmacic, t. vi. p. 174. CRUSTACEA. 753 number, their form, their relations, &c. depend the differences that occur in the conformation of the solid frame-work, the anatomical study of which is now about to engage our atten- tion. The most prominent feature in the external skeleton of the Crustacea is common to the whole grand division of articulated animals, and consists in the division of this envelope into a series of segments or rings, connected in suc- cession one with another, and supporting tu- bular appendages, also divided into segments, and arranged endwise. This peculiar structure is met with among the whole of the Crustacea ; but when the frame-work of these animals is examined more narrowly, variations are disco- vered so extensive and so numerous, that the mind is almost led to regard it as consisting of elements essentially different. Yet this is not so; and in pursuing the study, aided by the means of investigation developed in the pro- gress of the philosophy of the natural sciences, very opposite results are elicited, — results which are replete with interest and instruction in regard to the mysteries of nature in her creative energies. Now these methods of investigation may be reduced to two : — the first, which studies crea- tures at their full growth, after having ar- ranged them according to the natural order which follows from the investigation of their organization : the second, which studies each creature, but the more perfect in preference, in the series of successive evolutions which constitute the different phases of the em- bryonic state and of extra-uterine life ; for it is a demonstrated fact that these two series, so distinct, so widely separated in appearance, are in reality connected by links So inti- mate, that the one is, in certain respects, the permanent reproduction of the other, which is the continual repetition of the first in one and the same individual. By studying in this relative or comparative manner the skeleton of the Crustacea, we suc- ceed in reducing to common principles the mode of conformation, apparently so various, of this apparatus, in the different groups formed by these animals. A remarkable tendency to uniformity of composition is every where re- cognizable, and all the varieties are explicable in a general way by the laws in conformity with which the development of these animals takes place. During the period of embryonic life the body is seen becoming divided into rings more and more numerous, and more and more unlike one another. The same tendency to diversity in the organization is also found in the types of which the series of Crustaceans consists; and in both instances the differences are readily seen to depend on various modifications undergone by parts originally similar. It is farther referable to one of the most general laws of organiza- tion, viz. the tendency which nature shows to perfect functions by subdividing the work to be done, and throwing it upon a greater number of special organs. And we observe, in fact, among the most inferior animals that the different seg- ments into which the body is divided are so completely repetitions of one another, that they all act precisely in the same manner ; they severally include the elements necessary to the display of the vitality distinctive of the entire system to which they belong, so that they may be dissevered without any function whatsoever being therefore the less completely performed in either of the detached portions. Many Annelidans present instances of this uniformity of composition. As we rise, how- ever, in the scale of beings, the different seg- ments of the body are found to become more and more unlike, both as regards their func- tions and their conformation. This law is also visibly manifested among the Crustaceans, whether they be studied at the various epochs of their embryonic state or compared together, examples being selected from the different groups of which this portion of the animal series consists. In either case a well-marked tendency to subdivision of the physiological operations is conspicuous; and in proportion as the divers acts, the aggregate of which constitutes the life of the individual, become attached to a particular system or place, the parts to which different functions are apportioned, acquire forms more dissimilar and more appropriate to their peculiar uses. When we come to treat of the evolution of the embryo of the Crustacea, we shall have occa- sion to revert to this subject, but it is neces- sary so far to hint at it in this place, inasmuch as the conclusions which have been mentioned will often supply us with means of explaining those difficulties that are encountered when we seek to render comparative the study of the different constituent parts of the external ske- leton of the articulated series of animals. The frame-work or solid parts of the Crus- tacea consist, as we have said, of a series of rings. The number of these rings may vary, but this happens to a much less extent than on a superficial view we might be led to conclude. By calling in to our aid the principles of ob- servation and of comparison pointed out above, we have found that in every member of this class of animals the normal number of seg- ments of the body is twenty-one. But a very few instances of a larger number oc- curring are known, and it seldom happens that the number falls short of that which has been indicated. Occasionally, it is true, one or more rings prove abortive, and are never developed ; but in general their apparent ab- sence depends entirely on their intimate union one with another, and other obvious indica- tions of their existence may be discovered. By-and-by we shall find that in the embryo these segments are formed in succession from before backwards, so that, when their evolution is checked, the later rather than the earlier rings are those that are wanting ; and in fact it is generally easy to see in those specimens of full-grown crustaceous animals whose bodies present fewer than twenty segments, that the anomaly depends on the absence of a certain number of trie most posterior rings of the body. 754 CRUSTACEA. The Loemodipods, the Entomostraca, and the Ilaustellate Crustacea present us with instances of this condition, which calls to mind one of the stages through which the embryo of the higher species, whose development is the most complete, is known to pass. Each segment of the body, when it attains its normal condition, consists of two distinct ele- ments : the central or annular portion, and cer- tain appendices which it supports. The central or annular portion of the seg- ments of the tegumentary skeleton presents, in its most simple state, the appearance of a com- plete ring, but instead of a single piece it is requisite to count in its composition no fewer than eight, as has been demonstrated by the inquiries of M. Audouin on the structure of the thorax of insects,* inquiries the results of which are immediately and almost wholly applicable to the Crustacea so nearly allied to the insects in their organization. Each ring is divided first into two arcs, the one superior or dorsal, the other inferior or ventral, and each arc may present as many as four Elementary pieces. Two of these pieces by being united in the me- Fig. 378. t t s s Theoretical figure illustrating the composition of the tegumentary skeleton of Crustacea. D, Dorsal arc ; t, t, tergal pieces ; e, e, epimeral pieces ; V, ventral arc ; s, s, sternal and epistemal pieces ; P, insertion of the extremities. dian line constitute the tergum (Jig. 378, D) ; the superior arc is completed on either side by two other pieces, known under the name of flancs or epimeral pieces (Jig. 378, e). The inferior arc presents in its composition an exact counter- part of the superior. Two of the four pieces into which it may be resolved constitute the sternum , situated in the median line, and are flanked by the two episternums. The two arcs thus composed, instead of cohering by their edges, leave a space for the insertion of the lateral appendages or extremities which eorre- Fig. 379. Anterior portion of the body of an Amphipoda. t, tergum of the fourth thoracic ring ; e, epimera of the same ring. spond with them. It is true, indeed, that we have no instance of any single ring which exhi- bits the whole of these pieces distinct from one another ; in general several are anchylosed so * Annales des Sc. Nat. tom. i. as to appear but one; yet the comparative study of the apparatus in the different members of the class at large, leaves no doubt of their existence severally. Fig. 380. Thorax of an Atelecyclus seen from below, a, sternal pieces of the second thoracic ring ; b, epistemal piece of the corresponding ring ; c, epi- meral pieces ; d, apodemata, which run from the sternum to the epimera, and separate the inser- tions of the extremities ; e, antipenultimate ring of the thorax presenting the orifices of the female reproductive organs. It frequently happens that the tegumentary membrane is folded so as to penetrate more or less deeply the interior of the ring among the different organs which fill the cavity. These folds, which may become solid laminae by being impregnated with calcareous salts, have received the name of apodemata, and always proceed from the lines of conjunction of the different pieces, or of the different rings with one another. We shall have occasion to revert to this part of our subject very shortly. Fig. 381. Thorax of the 31a. j a Squinado, shewing the apode- mata which form septa between the sternum and the epimeral pieces of the thoracic rings. The structure of the ring once investigated in the manner we have done, let us now pro- ceed to inquire in what manner the different rings by the modifications they undergo, and by the divers modes of union they present, give rise to the variety of forms we observe among the Crustaceans. By general consent and usage, three regions are recognized in the bodies of these animals, — a head, a thorax, and an abdomen; and from this custom we shall not depart, although we must avow that these denominations are only derived from very clumsy views, and are calculated to convey false impressions in regard to the nature and composition of the parts so named, by leading the mind to liken them to the grand divisions entitled head, thorax, and abdomen in the Vertebrata. Nevertheless, with the ex- ception of the objectionable names, the division of the body into three regions is not less a fact as regards the organization of the Crustaceans ; and the one-and-twenty rings of which, as we have said, their body consists in the type to which every member of the class may be re- ferred, are generally found divided into three CRUSTACEA. 755 Fig. 382. rings ; c, abdomen composed also of seven dis- tinct rings. equal series of seven, each of which may be held as corresponding with one of the three regions. This law of composition is observed to obtain not only among the more simple species, where the rings generally resem- ble each other most closely, but its influence may be remarked among the most complicated also, and amidst exceptions and contradictions in appearance the most obvious. The head or cephalic region includes the principal organs of sense as among the Vertebrata, the com- mencement of the apparatus subservient to digestion, and the appendages destined to seize and masticate the food. The thorax, strictly speaking, forms no cavity distinct from the pre- ceding, but is its continuation ; the part espe- cially designated thorax, however, is that which is included from front to back between the head and the beginning of the abdomen, and is formed by the rings to which the extremities serving for locomotion are attached. This mid- dle portion of the general cavity of the body contains almost the whole of the viscera. As to the abdomen, it succeeds the last of the thoracic rings, distinguishable by the presence in it of the orifices of the male organs of gene- ration ; the appendices attached to it do not commonly attain any considerable size, and do not serve in a general way as organs of locomo- tion ; to conclude, nothing is found in its inte- rior save muscles and the terminal portion of the intestinal canal, the anal orifice of which exists in the last of the abdominal series of rings. These three portions of the tegumentary ske- leton are not always equally distinct, and their respective limits may even vary, for we occa- sionally observe two or three of the foremost thoracic rings detaching themselves, as it were, from this region to which they properly belong, to join or blend with the cephalic rings ; and the same thing may be said in regard to the segments of which each of the remaining divi- sions of the body consists; we in fact know of no specimen of a Crustacean in which the whole of the rings are moveable upon one another ; a certain number of them always appear to be- come consolidated, and this union is frequently so intimate that all traces of its existence are obliterated, so that the section of the body which results from this aggregation of rings appears to consist of no more than a single piece, and on a cursory view might be held to be constituted by a simple ring. The shape and size of these compound rings varies also, circumstances which evidently depend on the unequal development of the different pieces of which they severally consist. This consolidation of the rings occurs with increasing frequency as we rise in the scale of Crustaceans, and approach those the organiza- tion of which is most complex ; yet there are a considerable number of species which form ex- ceptions to this rule. The consolidation of the rings also shows a tendency to take place in the same order in which the different segments of the tegumentary skeleton appear in the em- bryo, that is to say from before backwards : thus it is generally complete as regards the cephalic rings; it is more frequent as regards the foremost than the hindmost thoracic rings ; and it but rarely occurs among the abdominal rings. The differences which present themselves in the dimensions and forms of the different rings of the tegumentary skeleton, and which concur so essentially in producing varieties in the ge- neral form of the Crustaceans, also show a ten- dency to become greater and greater as we as- cend in the series of these animals, and com- monly influence the cephalic rings in a degree greater than those of the divisions situated more posteriorly. To conclude, it is also among the most ele- vated Crustaceans that the tegumentary skeleton is complicated in the greatest degree by the evolution of apodemata in the interior of the rings ; and further, it is in the cephalo-thoracic portion of the skeleton only that these laminae are encountered. A few examples will render these general rules more readily appreciated. In the earlier periods of evolution of the embryo of the river-crab, the whole of the rings, which are even then apparent, are of the same form and dimensions, and the segments, which only appear at a later date, are at first similar to what these rings were in the beginning. This state of uniformity in the composition of the whole of the constituent rings of the tegumentary skeleton, which is invariably tran- sient in the embryo, is not observed as a permanent feature in any perfectly developed Crustacean ; still there are several of these ani- mals which are but little removed from it. In the Branchipods, for instance, the body consists of a long series of rings, having, with the ex- ception of the very first, as nearly as possible the same form and the same dimensions. In the Amphipods (fig. 382) the want of resemblance between the different rings of the body becomes much more remarkable: the first seven become so completely united that they form a single piece, in which no trace even of the lines of consolidation remains, and the conical segment which constitutes the head grows much more slowly than the rest of the body, so that the re- lative dimensions become smaller and smaller as regards the head in proportion as the animal approaches the adult age. The seven rings of the thorax, on the other hand, continue per- 756 CRUSTACEA. fectly distinct, and differ but little from one another; and the seven abdominal rings, in like manner, remain moveable, and only differ from those of the thorax as they do from one another by a relatively inferior degree of deve- lopment. In the majority of the Isopods the structure of the tegumentary skeleton is essen- tially the same as in the Amphipods ; but there occurs a greater inequality of development be- tween the thoracic and the abdominal rings, most of the latter remaining more or less in a rudimentary state. In the Apus and the Nebalia we conti- nue to find the rings of the thoracic and abdo- minal portions of the tegumentary skeleton nearly equal in size and similar in form; but the cephalic section, instead of presenting the same conformation as these two portions of the body, constitutes superiorly an immense shield, which extends over the rings of the thorax and conceals them. This dorsal shield or buckler, which is denominated Carapace by zoologists, also occurs among the whole of the Podoph- thalmians, and more than all besides conspires to give to these animals their distinguishing peculiarities of shape. Inquiries, of which it would be tedious to give a detailed account in this place, have led us to discover that the carapace of these Crustaceans is neither more nor less than the superior arc of the third or fourth cephalic ring, enormously developed, and which in attaining its large dimensions laps over and modifies the conformation of a greater or smaller number of the neighbouring rings.* In the generality of the Stomapods the cara- pace does not quite cover and conceal the two first cephalic rings, which indeed continue dis- tinct and moveable; but in the whole of the Decapods these rings cohere with one ano- ther and with the following ones, and unite more and more intimately under the carapace, which then covers the whole of the head as well as the thorax. In the Macroura the anterior extremity of the carapace only extends over the ophthalmic or first cephalic ring ; but in the Brachyura it bends around this ring so as to include it, and to go to unite underneath with the next segment. As we ascend in the series of Crustaceans, we observe the carapace en- croaching more and more upon the thorax. In the Squillae the three last cephalic and three first thoracic rings are nearly lost by becoming blended with those to which the carapace be- longs ; they scarcely retain any mobility, and protected above by this shield, unite intimately, and remain imperfect in their tergal portions ; the four last rings of the thorax continue, on the contrary, free, and are in almost every particular similar to those of the abdomen. In the Mysis this union of the cephalic shield with the seg- ments of the thoracic division of the tegumen- tary skeleton is carried further, for there are not more than two of these rings which remain distinct. But it is in the Decapods that the carapace attains its greatest development, and * See my Hist. Nat. des Crustaces, t. i. p. 23. that its influence upon the evolution of the thoracic segments is carried the farthest. In these animals the framework of the body does not appear at first sight to consist of more than two portions, the one anterior, formed by the carapace, and representing the cephalic and thoracic segments conjoined ; the other poste- rior, formed by the abdomen. In reality, the first fourteen rings of the body are covered by this enormous buckler, and are so intimately conjoined as to have lost all their mobility ; the whole of the thoracic segments thus hidden below the carapace, are connected with it in their superior part, they are only joined with one another underneath and laterally ; and their tergal parts having, in consequence of this, be- come useless, are no longer to be found, being in some sort replaced by the great cephalic buckler; thus the whole of these rings, in con- formity with this arrangement, are imperfect and open above. Hitherto we have not been able to deter- mine whether the carapace of the Podophthal- mia is formed at the expense of the third or of the fourth ring of the tegumentary skeleton ; but we have the strongest reasons to conclude that this buckler is neither more nor less than the dorsal arc of one or other of these cephalic rings, and not of the two conjointly. In fact we czn here demonstrate a composition analo- gous to that which we have already pointed out as characteristic of every arc, whether supe- rior or inferior, of the different rings in their state of complete development, to wit, a tergal portion and two lateral or epimeral pieces. In following the embryo of the River-crab in its progressive stages of development, Rathke* observed the carapace to be formed of three pieces, which at length became consolidated so as to form but one. In many of the Deca- pods it is even easy to perceive this structure or composition in the carapace of adults, inas- much as there exist lines marking the conjunc- tion, and accurately indicating the respective limits of the different pieces of which this great dorsal plate is composed. The general form of the carapace depends in great measure on the relative development of these different pieces; in the Macroura the tergal portion of the carapace extends but a short way backwards, whilst the lateral or epimeral pieces reach as far as the begin- ning of the abdomen, and being no longer kept at a distance by the tergum, meet in the median line of the back, and are there con- joined. In the Brachyura, on the contrary, the tergal portion is that which is especially deve- loped, so that it constitutes the whole of the upper part of the carapace, whilst the lateral pieces, thrust outwards and underneath, only form a narrow band above the bases of the ex- tremities. It is also in consequence of modifications analogous to those on which the existence of the carapace depends, that in other Crustacea the * Untersucliungen ueber die Bildung dcs Fluss- krebses, &c. Tr. iu Annales des Sciences Nat. t. 20. CRUSTACEA, 757 tegumentary skeleton presents the most singular forms : thus among the Limmadia and the Cypris, the pieces which are analogous to the epimeral or lateral pieces of this cephalic buckler, acquire a great extension, whilst the tergal portion of the arc to which they belong continues rudimentary or proves entirely abor- tive, so that they constitute two large valves covering the whole body of the animal, and bearing considerable resemblance to the shells of certain acephalous Mollusks. The dorsal lamina; which in the Pandams form appendices on the back similar to Elytra, and those which in the Anthostomata form a kind of sheath around the posterior part of the body, are also formed by the anomalous development of cer- tain parts of both the dorsal and ventral arcs of the two posterior thoracic rings. The inferior arcs of the thoracic rings of the tegumentary skeleton of the Decapoda, by their intimate union, form a kind of ventral shield, named sternal plastrum, upon which lines of conjunction indicate the respective limits of the greater number of the segments, as well as of the sternal and episternal pieces of which these are composed. In the Decapoda Macroura and Anomoura, this plastrum is in general very narrow, but in the Brachyura it is expanded to such a degree as frequently to con- stitute a great and nearly circular disc. In the whole of these Crustaceans, the lateral pieces of the thoracic rings are conjoined, like those of the inferior arc of the same segments, and form on either side of the middle portion of the body a septum which is covered by the cara- pace, and which is known among anatomists under the name of the vault of the Jiancs. In the Macroura this septum is nearly vertical, but in the Brachyura it is oblique, or even almost horizontal. Fig. 383. Lateral portion of the thorax of a Decapod. a, the epimeral pieces united to form the vault of the flancs ; b, the sternum ; c, the apodeinata rising from the sternum and separating the in- sertions of the legs. It is among those Crustaceans the thoracic rings of whose tegumentary skeleton blend or become consolidated in this manner, and ac- quire dimensions so considerable, that the struc- ture of this portion of the frame-work also exhi- bits the utmost extent of complication, in con- sequence of the existence of large apodernata in their interior. These septa are of two kinds ; the one, styled sternal apodernata, arise from the lines of consolidation of the thoracic sternal pieces; the other, named epimeral apodernata, Fig. 384. Vertical section of a portion of the thorax of one of the Brachyura. a, sternum, with a sternal apodema rising from it; b, epimera from the inner surface of which an epimeral apodema descends to join the sternal apodema, and thus form a septum between the thoracic cells. arise in a similar manner from the epimeral pieces of the same rings. They are met with among the Macroura and Anomoura, as well as among the Brachyura ; but it is among these last that they acquire their highest development; their direction, vertical to the internal planes of the rings, and the unions of those that rise from the inferior aspect or floor with those that des- cend from the arched superior surface, give rise to the most singular combinations and forms, too multifarious to admit of description in an article of the extent of that in which we are engaged, but the final effect of which is the establishment of cells, divided from one an- other by vertical septa, and corresponding to each ring, and further intersected in the direc- tion of their height, in a certain number of species, and divided into two stages by means of horizontal reduplications. It is within these different cells that the muscles and principal vessels of the thorax are lodged in the Brachyura ; holes left at the con- junctions of these laminte admit of the com- munication of the cells two and two, either through the vertical septa or through the hori- zontal floors which divide the superposed cells, and it is by means of these holes of conjunc- tion that the anastomoses of the vessels of one ring take place with those of the neighbouring ring, as we shall see presently. In the Macroura, again, this structure does not occur, in consequence of which other means of communication between the vessels of the different segments require to be established, the nature of which we shall also have to inves- tigate before long. Generally speaking, the disposition of these cells and of the septa which form them varies considerably in the Brachyura and the Macroura. Certain pro- longations from the superior and internal angle of the sternal apodernata, by their union in the median line, after bending from before back- wards, even form a longitudinal canal, which extends through almost the whole length of the thorax. This is the sternal canal, destined to lodge the ganglionic nervous cord, and to serve as the chief venous reservoir. It has long been admitted as an axiom in animal physics, that when any particular part of the body acquires a very high degree of de- velopment, certain other parts stop short of their ordinary state of evolution, as if the former had obtained their unusual increment at the cost 758 CRUSTACEA. Fig. 385. Thorax of the Astacus Flumatilis, showing the d is- position of the apodemata and the thoracic cells. of the latter. This rule, which has been dis- cussed by M. GeofFroy St. Hilaire under the title of la loi de balancemeiit organique, or law of organic equivalents, is found to apply in the present instance ; for the Crustacea in which the cephalic portion of the tegumentary skele- ton is developed in the greatest degree, (viz. the Brachyura) present the abdominal portion of the body of very small dimensions; whilst, on the other hand, in the Macroura, or those species in which the abdominal portion of the body arrives at its maximum of develop- ment, and performs a very important office in the business of locomotion, the cephalic por- tion is relatively greatly inferior in size. With regard to its disposition the abdomen is simple enough; the rings of which it con- sists are in general moveable upon one another, and even when they are consolidated, present no apodemata projecting from their interior. It is also deserving of remark that the elementary pieces of the different rings are not very distinct, and sometimes even appear to be partially wanting. Let us now go on to examine the portion of the tegumentary skeleton belonging to the extremities or that portion of the external skeleton of the Crustacea which may be re- garded as an appendage to the more essen- tial covering of the head, thorax, and ab- domen. The Crustacea present this invariable cha- racter, that the whole of the appendages belong exclusively to the inferior arc of their tegu- mentary rings, a point in which they resemble the Arachnidans, and differ like these from Insects, in which one or two of the thoracic rings generally present a pair of extremities supported by the superior arcs, as in the An- neiidans, in which the dorsal segment of each of the rings almost always carries a pair of extremities fashioned in the same manner as those belonging to the ventral arcs.* We have already said that a pair of appendages ought to be found attached to each ring ; but it very frequently happens that many of the pairs are completely checked in their develop- * Vide Annelida, p. 167. ment, or that the forms they assume, in har- mony with the uses they serve, render them liable to be mistaken. It is very dif- ferent in the embryo ; here, in fact, as among the simplest forms of the series, the whole of the extremities are at first similar; and it is only in consequence of ulterior develop- ments that each pair finally assumes diver- sities of form and character in relation with the various functions to which they are espe- cially destined. In its most perfect state of development, the extremity in the Crustacean consists of three principal parts : the stem (a), which is the most Fig. 386. essentia! and most constant part, formed of a variable number of articulations ; the palp (5), an appendage which is detached from one of the three first articulations of the stem, but almost always from the first; and the whip (fouet ) (c), which is sent off above and to the outer side of the palp. It but rarely happens, however, that these three organs exist simultaneously ; occa- sionally not more than one of them can be demonstrated ; and sometimes the whole three are altogether wanting. Fig. 387. First cephalic ring of the Sqtiilla separated from the rest of the head, and bearing one of the ocular peduncles. The first ring presents no appendages except in the very highest Crustaceans, and even then they are simple in their composition, and never exhibit more than the stem, which arises from a more remote check to their development dating from about the commencement of their embryonic evolution ; these are the ocular pe- duncles. The second and third pairs of extremities constitute the antenna. These are wanting in a certain number of the inferior species, and even in those among which they occur, they vary considerably in their structure : they may for instance present one only, or two, or the whole of the three elements of which we have spoken. But as the three first pairs of ap- CRUSTACEA. 759 Fig. 388. a, second thoracic ring of theSquilla; b, one of the small antennaj. pendages belong especially to the function of sensation, and as we shall have to revert to these at a later period, and give an ample de- scription of their structure, we shall not enter upon this subject farther at present. Fig. 389. Third and fourth cephalic rings of the Squilla : a, carapace ; b, one of the posterior antennae ; c, one of the mandibles. The eleven pairs of appendages which suc- ceed are variously apportioned between the functions of digestion and locomotion, to which last the five hindmost pairs are entirely dedi- cated in the Decapods. In other Crustacea, again, the first pair only is set apart in an especial manner for the office of mastication, all the others then serving for locomotion, and this pair is in consequence very generally de- scribed under the name of mandibles; very commonly one and even two other pairs are added to this first pair, and these are desig- nated jaws or maxilla. In the majority of instances, moreover, the three succeeding pairs assist the three preceding; and as they are frequently more especially apportioned to loco- motion, the two last in particular, whilst in some cases they serve for the two functions at one and the same time, they have been de- signated by anatomists and naturalists the maxillary limbs ( pieds-machoirs ): these we shall describe when we come to speak of the apparatus of digestion. As to the five pairs which we have already mentioned as essentially ambulatory (see fig. 382), they present in the Brachyura no more than a simple stem, composed of six articulations ; whilst in the Astacus and allied genera, we find a flabelliform appendage or whip, dedicated especially to the purposes of respiration, and in the Peneoe the three sorts of appendages existing simultaneously. By- and-by, when speaking of respiration, we shall see how it happens that in a great number of these animals the whip of the thoracic extremities assumes a vesicular structure, and becomes the organ of this important function. The same peculiarity is observed in the appendages of the abdominal extremities of a great number of species ; but among the members of the most elevated tribes, these appendages are but very slightly developed, and appear to have no other use than to attach the eggs along the in- ferior surface of the abdomen. Fig. 390. Abdomen of the female Maja Squinado. a, the abdominal appen- dages. We shall not at present enter upon the con- sideration of the forms of the thoracic and abdominal extremities, having it in view to take up the subject when we come to examine these appendages as the organs of prehension, and as fulfilling important offices in locomotion. Before quitting the study of the tegumen- tary skeleton, to go on to that of the extre- mities considered especially as the organs of locomotion, we think it necessary to say a few words upon the moult or process by which the tegumentary covering of the whole of the Crus- tacean is cast off and renewed. The necessity for this operation is a con- sequence of the very nature of the envelope : like every other epidermic covering, the pro- duct of secretion, the shell of the Crustacea is closed in on every side, and can only increase in thickness, so that all growth would be pre- vented in the body of these animals were they denied the power of freeing themselves from time to time of their prison. Accordingly they have this power ; and as might have been ex- pected the shell is cast by so much the more frequently as the animal is younger, inasmuch 7fc>0 CRUSTACEA. as the growth is then most rapid; as many as eight changes of the tegumentary envelope have been observed to take place in the course of seventeen days in the young Daphnia; whilst in adult Crustacea the change is not in general effected oftener than once a year. Reaumur watched the phenomenon through its whole course, and has noted it with all its details as it occurs in the Astacus Jluviatilis.* 1 1 takes place in this species towards the end of summer or beginning of autumn. A few days of fasting and sickness precede it, during which the carapace becomes loosened from the corium to which it adhered, and which im- mediately begins to secrete a new one, soft and membranous at first, but soon becoming harder and harder, and finally completely cal- careous. In this way the animal before long finds itself free from all connexion with its old envelope, and it has only to make its escape. This last operation is announced by symptoms of inquietude. The creature rubs its legs one against another, and then throwing itself upon its back begins to shake itself, puffs itself out, so as to tear the membrane which connects the carapace with the abdo- men, and to raise the carapace itself. After sundry intervals of rest and agitation of longer or shorter duration, the carapace is raised com- pletely ; the animal extricates its head, its eyes, and its antennae. The operation of freeing its extremities appears to be the most difficult, and would even be impossible did not the solid covering of these parts split longitudi- nally ; but in spite of every assistance, it not unfrequently happens that the animal leaves one or two of its limbs impacted within the old sheath, and occasionally even perishes through inability to escape completely from its shell. The abdomen is the last division of the body which clears itself of the old enve- lope. All the parts of the tegumentary ske- leton which had only been separated from one another, without however having undergone any softening, or fracture, or separation, fall one upon another in resuming their old posi- tions, so as to represent the complete external form of the creature with the whole of its solid internal as well as external parts; even the eyes, the antennae, and the thoracic cells formed by the sternal and epimeral apodemata, may be distinguished. The operation now described does not in general occupy more than half an hour in the performance ; and only two or three days, or even no more than four-and-twenty hours are required to convert the soft and membranous envelope with which the corium or naked body of the animal is surrounded, into a firm calcareous covering similar to the one which has just been got rid of. The new envelope presents the same appendages as the former one, even the same hairs ; but these, instead of being con- tained within the old ones, as Reaumur ima- gined, exist ready formed in the new envelope, but turned in towards the interior, like the fingers of a glove turned in upon themselves. * Memoircs de 1’A.cademie des Sciences, 1718. There are some species, such as the Crabs and the Brachyura generally, in which the carapace presents a considerable expansion on either side, forming two large compartments in which the greater mass of the thoracic vis- cera is contained. Under these circumstances it would be impossible for the animal to escape from its dorsal covering by the relatively in- considerable opening which this part presents on its inferior aspect. This renders it neces- sary that the carapace, instead of being cast off by simply rising in a single piece, should give way and separate in some direction or another, and this it does by splitting along the curved lines, extending on either side from the mouth to the origin of the abdomen, in the course of which the epimeral pieces cohere with the dorsal one.*' The time occupied in the business of throw- ing off the shell varies considerably in dif- ferent species ; it is also dependent on at- mospheric influences. It is the same also, in regard to the number of days necessary to give to the new epidermic layer the consistency of the old tegumentary covering. A general remark, however, and one which is applicable to the whole of the species that have been duly observed, especially those that are found along the shores of France, is this, — that the period which precedes as well as that which follows the change of the shell is one of rest- lessness and evident illness. The muscles of these creatures are then flaccid, the flesh is soft and watery, and as food they are rejected as tasteless and held unwholesome. This would not appear to be the case with the Land-crab, however, according to the statements of several travellers, who inform us that the flesh of this species is never in greater perfection than during the season of the moult. A phenomenon, which has some analogy with the renovation of the tegumentary skeleton, but which is much more curious, is the repro- duction of the legs of these animals. Most Crustacea cast off their claws very easily and without apparent pain ; the separation always takes place in a determinate point near the basis of the member (in the second articula- tion), and is soon followed by the formation of a cicatrice, from the surface of which sprouts out a small cylindrical appendage ; this shortly after presents distinct articulations, and re- sembles in miniature the organ it is destined to form, but its growth is slow, and it does not for some time attain its full size. If one of the limbs be severed in any other part, the wound continues to bleed, and no renovating process begins unless the animal, by a violent muscular contraction, succeeds in breaking off the stump in the articulation above mentioned. The kind of solid sheath formed by the tegumentary skeleton of the Crustacea, and which includes in its interior the whole of the viscera and other soft parts of these ani- mals required to be so constructed as not to oppose locomotion; consequently there exist, * Collinson, Phil. Trans. 1746 and 1751 ; Hist. Nat. des Crustaces, t. i. p. 56. CRUSTACEA. 761 either between the different rings of the body or the various constituent elements of the limbs, articulations destined to admit of mo- tion to a greater or less extent, between these different pieces. The structure of these arti- culations is of the most simple kind ; the moveable piece rests upon that which precedes it by two hinge-like joints situated at the two extremities of a line perpendicular to the plane in which the motion takes place. In the in- ternal portion of the edge of the moveable piece comprised between the joints, there exists a notch of greater or less depth, destined to admit of flexion, whilst on the opposite or external side, the same edge generally glides under that of the preceding piece. This kind of articulation, whilst it is the most favourable to precision of movement and to strength, has tire disadvantage of admitting motion in one plane only; therefore the whole of the rings of the body, the axis of motion being entirely parallel, cannot move save in a vertical plane ; but nature has introduced a kind of corrective of this disadvantage in the structure of the limbs, by changing the directions of the arti- cular axes, whence ensues the possibility of general motions being performed in every di- rection. Between the two fixed points two opposed empty spaces are observed, left by the rings severally, and destined to admit of the occurrence of motions of flexion and ex- tension. The tegumentary membrane which fills it never becomes encrusted or calcareous, but always continues soft and flexible. The tegumentary skeleton, of which we have thus taken a summary view, supplies the apparatus of locomotion with fixed points of action as well as with the levers necessary to motion. The immediate or active organs of this apparatus are the muscles, the colour of which is white, and the structure of which presents no peculiarity worthy of notice. They are attached to the pieces which they are re- quired to move either immediately, or by the intermedium of horny or calcareous tendons, which are implanted upon the edge of the segment to which they belong. To the fixed point they are most commonly at- tached immediately. Their structure is sim- ple, and each segment, in fact, as has al- ready been said, being contrived to move in one fixed and determinate plane, the mus- cles which communicate motion to it, can constitute no more than two systems anta- gonists to each other, the one acting in the sense of flexion, by which the segment moved is approximated to that which precedes it, the other in the sense of extension, by which the segment is brought into the position most remote from the centre of motion. The mus- cles that produce these opposite effects, as might have been concluded, are found im- planted into the opposite arms of the lever upon which their energy is expended. The motions in flexion tend universally to bring the extremities and the different rings towards the ventral aspect of the body ; it is consequently upon this aspect that the flexor muscles are inserted, and these are in general VOL. i. the more powerful. On the contrary, and in accordance with the nature of the motion pro- duced, it is upon the superior or dorsal aspect of the segments that the extensor muscles are attached. In the trunk the two orders of mus- cles generally form two distinct layers, the one superficial, the other deep ; the former thin and sometimes absent, the second, on the contrary, very powerful wherever powerful motions are required. The muscles generally extend from the arc above to the one immediately below, passing for the most part from the anterior edge of the upper to the anterior edge of the lower segment. The extent and the direction of the flexion of which any segment is sus- ceptible, depend on the size of the inter- annular spaces above or below the ginglymoid points ; and as these spaces are in general of considerable magnitude on the ventral aspect, whilst the superior arcs are in contact and can only ride one over another in a greater or less degree, it is only downwards that the body can be bent upon itself ; while upwards, or in the sense of extension, it can hardly in general be brought into the horizontal line. Thus far what has been said applies more especially to the rings of the body, but the extremities present nothing that is essentially different either as regards the mode in which the tubular segments are articulated to one another, or as regards the mode in which the muscles are inserted. Each of these indeed having but one kind of motion, and even that very limited in its extent, nature has aided the deficiency, as has been stated, by increasing the number . of articulations, by which extent of motion is conferred, and in varying the direction of the articular axes, an arrangement by which the animal obtains the ability of moving in every direction, but at the expense both of power, ra- pidity, and precision in its motions. Each seg- ment of a limb encloses the muscles destined to move that segment which succeeds it, un- less it be too short and weak for this end, in which case the muscles themselves have their origin at some point nearer to the median plane of the body. As a general law the muscles are observed to be more powerful in proportion as they are nearer to the centre, which is to be explained by the fact that each motion they then communicate is transmitted to a larger portion of a limb, to a lever longer in that sense in which it is disadvantageous to the power. Occasionally, however, the two last segments of a member are converted into a sort of hand, and in this case the penul- timate segment sometimes includes a mus- cular mass which may surpass in power the same system in the whole of the limb besides. Those muscles that put an extremity generally into motion, are attached to the sides of the thoracic cavity, and the apodemata supply them with surfaces of insertion of great extent and very favourably situated as regards their action. They occupy the double rank of cells formed by these laminae; but they %’ary too much in their mode of arrangement to admit of our saying any thing general upon this head. The motions of translation, or from place to 3 D 762 CRUSTACEA. place, the only kind upon which it seems neces- sary to say anything here, are effected in two modes, either by the alternate flexion and ex- tension of the trunk, or by the play of the limbs. In those Crustacea which are formed essen- tially for swimming, the posterior part of the body is the principal agent in enabling the animal to change its place ; but here the mo- tions, instead of being lateral, are vertical ; and instead of causing the creature to ad- vance they cause it to recede : it is by bend- ing the abdomen suddenly downwards, and bringing it immediately under the sternum, that it strikes the water, and consequently by darting backwards that the animal makes its way through that liquid. From what has now been said it maybe imagined that the Crustacea whose conformation is the best adapted for swimming, have the abdomen relatively largely developed, and this is, in fact, what we always observe; the Amphipoda and Decapoda ma- croura are examples ; whilst, in the walking Crustacea, such as the Crabs, the Caprella, the Oniscus, &c. this portion of the body attains but very insignificant dimensions. In the swimming Crustacea the appendages of the penultimate segment of the abdomen also become important organs of locomotion, inasmuch as they for the most part terminate in two broad horizontal plates, which, with the last segment, also become lamelliform, con- stitute an extensive caudal fin arranged in the manner of a fan. We have already said that the thoracic ex- tremities alone constitute true ambulatory limbs. When destined for swimming only, their segments are lamelliform, and the palp, as well as the stem, contributes to form the kind of oar which each of them then con- stitutes. The Copepoda supply us with in- stances of thoracic extremities particularly destined for swimming, and a corresponding structure is observed in certain Podophthalmia, such as the Mysis. (See fig. 386.) To conclude, this stemmatous portion of the thoracic extremities, whilst it still preserves the general form which we have assigned it, is modified in some cases to serve for walking as well as swimming, or to aid the animal as an instrument for burrowing with facility, and making a cavity for shelter among the sand. Thus in the Decapods that burrow, the last seg- ment of the tarsus assumes a lanceolated form, and in the swimming Braehyura, the same segment, especially of the last pair of extre- mities, appears entirely lamellar. We have only further to add that in a great number of species one or several pairs of the thoracic extremities are modified so as to become instruments of prehension; some- times it is the last segment of the limb which, acquiring more than usual mobility, bends in such a manner as to form a hook with the preceding segment ; sometimes it is this penul- timate segment which extends below or by the side of the last, so as to form a kind of im- moveable finger with which it is placed in opposition. In the first instance these instru- ments are denominated subcheliform claws, in the second chelte simply, or cheliform claws. We shall revert to these organs when we come to treat of the apparatus of digestion. § 2. Apparatus of Sensation. A. Nervous System. — When endeavouring to form as accurate and complete an idea as possible of the tegumentary skeleton of the Crustacea, we began by studying" it in its suc- cessive states of development in the embryo, and then compared the various stages of transition in which it met our observation, with the permanent conditions in which it finally remains in the organic series, classed in conformity with the structural affinities of the different genera. In the study of the nervous system, upon which we are now about to enter, the same mode of proceeding will lead us to analogous results. The deep situation of the nervous system, and the transparency of the filaments and various masses which compose it, are each obstacles to its observation until it has arrived at a somewhat advanced stage of development. It was, in fact, only after the sternal canal had begun to appear under the form of an enlarge- ment, edged by a double series of tubercles, which prove to be the rudiments of the motor muscles of the extremities, that Rathke* was able to catch a sight of the earliest traces of the nervous system in the Astacus fluviatilis, and even this was no more than the portions be- longing to the head and thorax. All that can be seen then amounts to very little ; in the part behind the mouth, eleven pairs of whitish spots are arranged in two longitudinal series perfectly distinct from one another, and situated on either side of the mesial plane. It is otherwise easy to perceive that a pair of these spots corres- ponds to each ring, setting out from, but in- cluding those of the mandibles. Neither the oesophageal cords nor the cephalic ganglions are then distinct. At a later period these rudiments of the nervous system undergo remarkable modifica- tions. The six first ganglions of each series approach those that are symmetrical with them severally, so as to become united along the median line, and, at length, to form a simple chain of ganglions corresponding to the six rings, whose appendages are the mandibles and the five pairs of maxillary extremities. The ganglions, on the contrary, which corres- pond to the five posterior thoracic rings, continue to form a double series. During this time the sternal canal is evolved so as to surround the nervous system with a firm and solid sheath. At a period of the incubation still farther ad- vanced, that is to say, during the time which elapses from the birth of the young Crustacean to that at which it attains its full growth, new and important changes take place. First, the four most anterior oesophageal tubercles, in other words, those which correspond to the mandibles, to the jaws, and to the first pair of maxillary limbs, become united, by approach- ing one another along the mesial line, so * Untersucliungen iiber die Bildung des Fluss- krebses. CRUSTACEA. 763 as finally to constitute a single continuous mass only. The same tiling happens in re- gard to the fifth and sixth, which soon form no more than a single ganglion. As to the other pairs they always remain completely distinct, and some way parted from one another. Thus the study of the gradual evolution of the nervous system in the Astacus fluviatilis, al- though by no means belonging to the type in which this system is most completely developed, presents us with three distinct and successive facts, which we shall find reproduced in the most perfect manner in the natural series of genera, and which will put us into a position to give a satisfactory explanation of those very striking variations in the organization which we shall encounter. These are, in the first place, the isolated for- mation of the nervous centres, independently one of another. We now acknowledge this independence of the several organs at the moment of their appearance, and their ulterior conjunction is one of the most interesting and important facts with which modern science has been enriched ; it constitutes the law of centri- petal development , as it has been established by M. Serres. In the second place a tendency to conjunc- tion by a motion transversely. Lastly, a second motion in the line of the axis of the body, the effect of which is the concentration definitively of a greater or smaller number of nervous centres primarily indepen- dent of one another. The Talitrus exhibits in the Fig. 391. most striking manner the first of a the three dispositions which we b have mentioned from the mo- ment at which the nervous sys- — tern appears. In this genus, in fact, we perceive on either side ss of the median line a ganglionic chain, formed by the conjunc- ^ tion of the nervous centres, extremely simple in their struc- ture, and flattened and some- what lozenge-shaped in their gs outline.* There are thirteen pairs thus constituted, cones- * ponding to the thirteen seg- ments which enter into the com- 9 position of the whole body. The two nuclei of each pair com- “ municate together, in the same manner as each pair is con- 1 nected with that which succeeds, and with that which precedes it, by means of medullary cords in "" the first instance, and longitu- system , 3 T or the lahtrus. dinal cords m the second. In ... ,, . , . , . . a, cephalic san- all essential particulars each pair 0.);a : j is a counterpart of any and dullary cords every other pair, without even uniting the first excepting the cephalic ganglion, and second pair and it is with difficulty that the ofSanSlia- * Vide Recherches Anatomiques sur le Systeme Nerveux. des Crustaces, parM M. Audouin et Milne Edwards, Annales des Sciences Naturelles, tom. 14. thoracic pairs are seen to be in a slight degree larger than the others. At a somewhat greater distance forward from the oesophagus, too, than usual, we observe the cephalic ganglion, which sends branches to the antennas and eyes, and the nervous cords by means of which it commu- nicates with the ganglions of the first thoracic rings. These cords, having the oesophagus inter- posed between them, are held a little farther apart than the other branches, which establish com- munications between the different succeeding pairs of ganglions in the longitudinal direction. Already in the Oniscus asellus * and in the Cy- amus cetif we find the ganglionic cord, double in its middle portions, simplified at its opposite extremities in such wise that the ganglions of the first and of the last pairs are single. This commencement of approximation coincides in other respects with an incipient approximation in the longitudinal direction, for, to the four- teen segments of which the whole body consists, we find no more than ten pairs of ganglions apportioned. This tendency to centralization is still more conspicuous in the Phyllosoma.J Here we discover the two cephalic nuclei united by their internal angle, without, however, their state of doubleness being thereby obscured. It is the same with the first pair of thoracic ganglions, from which they are separated by the whole length of the great oval lamina which supports the cephalic appendages and is traversed lengthwise by the nervous filaments which embrace the oesophagus. The ganglions of the second pair, although rudimentary, are still united immediately, as are those of the third pair also. Those of the six suc- ceeding pairs, on the contrary, Fig. 392. only communicate by means of a transverse but thick and short commissure, so that it gives to the connexion established be- tween the nuclei of the several pairs, the appearance of a more immediate conjunction than ac- tually exists. To conclude, the abdom inal gangl ions are perfectly distinct, and those of the several pairs are only connected by means of extremely slender fila- ments. In the Cymothoa the union of the medullary nuclei in the trans- verse direction is complete, and all we perceive is a single series extended along the median line through the whole length of the body. This is similar to the nervous system of the Talitrus conjoined longitudinally; with this difference, that the longitudinal filaments uniting the ganglion have continued distinct, as if to testify, by their doubleness, to the mode of formation of the single ganglionic cord. * Cuvier, Lecons d’Anatomie comparee, t. ii. p. 314. t Treviranus, Vermischte Schriften anatomiseher und physiologischev inhalts. Band 2. Heft I. f Audouin et Edwards, loc. cit. ~ 3 D 2 Nervous system of the Cymothoa . 764 CRUSTACEA. But it is move especially in the types which still ask our attention, that we perceive the system of centralization pushed yet farther by the actual conjunction of the nuclei, which we have hitherto only seen approximated to one another, Fig. 393. Nervous system of the Astactis Marinus , or Sphinx Ligustri . in consequence of their gliding or encroaching, as it were, upon the median line. The Lobster ( Astacusmarinus ) (fig- 39 3) pre- sents us with another step in the system of cen- tralisation. Here, in fact, the longitudinal cords of communication are entirely consolidated along the median line through the whole of the abdomen, although they are still to be found double in the thorax. Moreover, the first thoracic ganglion (f<), and the last of the abdominal series of ganglions (a6), are conspicuously formed by the reunion of several distinct ner- vous centres, in the way we have already indi- cated as happening, although in a minor degree and less perfectly, in the Amphipoda and the Isopoda. Before we pass, however, to the con- sideration of more complicated systems, we shall pause a moment to describe somewhat at length the one which we have but just mentioned, the more as it is among the number of those which have been most attentively studied. The cephalic ganglion ( g',J>g ■ 393), situated above the base of the internal antennae, is of con- siderable size, and appears to be simple ; it gives origin to five pairs of nerves and to two cords, which connect it with the rest of the ganglionic nervous system. The first of these pairs (o)arises from its anterior edge : this is the optic pair, which, after having penetrated the peduncles of the eyes, increase in size, and traverse a mem- branous diaphragm, which may be likened to the sclerotic coat. The second pair of nerves correspond to the ocular motors ; they run parallel to the pre- ceding pair, and are distributed to the muscles of the eyeball. The third pair proceed to the internal anten- nae (6) ; but before they enter these appendages they send off a branch to the muscles which move them. A like ramification is sent off from the principal trunk to each of the rings of which these antennae are composed, and the nerve ends by becoming bifurcated, in order to penetrate the two filaments in which the an- tennae terminate. The fourth pair of nerves (e) are distributed to the tegumentary membranes of the anterior extremity of the animal. Behind the fourth a fifth pair is seen ( d ), which proceeds anteriorly to the fourth pair almost immediately after its origin, sends one branch to the cake-like organ of doubtful function which covers the ear, a second branch to the organ of hearing itself, and finally terminates in a trunk of considerable size, which traverses the external or second antenna through its entire length. A sixth pair is destined to establish con- nexions between the cephalic ganglion and the first of the thoracic ganglions, after having sur- rounded the oesophagus ; but instead of ap- pearing as simple nervous cords through their whole length, as in types which we have hitherto studied, each -of them presents an enlargement in its middle, which is neither more nor less than a ganglion, from which there is sent off, first, a nerve that proceeds to the mandibles (f); next, a gastric nerve (g), of large size, which gives many filaments to the coats of the stomach, and finally anastomoses with CRUSTACEA. 765 the corresponding cord of the opposite side ; after this the two form a single nerve, which by-and-by presents an enlargement having the appearance of a small median ganglion, and then remounts upon the dorsal aspect of the stomach to ramify there, and ultimately to lose itself upon the intestine (A). Behind the stomach a transverse cord (i) is seen, which connects the two nervous filaments, and appears to be the cord of communication be- tween the ganglion of which mention has just been made, pushed backwards, in the same way as the ganglions themselves have been kept apart, to wit, by the resistance of the oesophagus, interposed at the time when that process is going on by which the pairs gene- rally are approximated in the course of the median line. The first of the thoracic nervous masses (t1) is oval-shaped, and gives origin to ten pairs of nerves, five of which issue from the anterior aspect. The first run to the mandibles and to their muscles; the second to the auditory apparatus ; the third to the first jaw, the fourth to the second jaw ; the fifth to the cells of the flancs, to the muscles and neighbouring inte- guments ; the sixth and seventh arise from the inferior aspect of the nervous mass to proceed to the maxillary feet; the nerves of the eighth pair are extremely slender, and are distributed to the muscles of the thorax ; the two succeed- ing pairs belong to the third pair of maxillary extremities; lastly, two cylindrical cords arise from the posterior extremity of this nervous centre, and connect it with the second thoracic ganglion, giving origin themselves in their passage to a pair of extremely minute filaments, which run to be distributed to the muscles of the thorax. This first thoracic nervous mass represents, therefore, the five pairs of ganglions which follow the mandibular ring, and must be viewed as resulting from the concentration of the five pairs of medullary nuclei belonging to the five rings which bear the accessory masticatory or- gans. In the adult Lobster the different ele- mentary constituents are not traceable, and the whole mass appears to be composed of no more than two ganglions closely connected in the medianplane; but in a species very nearly allied, namely, the River-crab ( Astacus Jluviatilis), very obvious traces of the existence of several medullary nuclei can always be demonstrated in its interior. The five pairs of ganglions that follow ( t~ — t6), and that belong to the five last thoracic rings, have, on the contrary, continued distinct ; although simple, these nervous centres still exhibit manifest indi- cations of their composition severally by two nuclei ; from either half we have a cord of communication sent off, similar to those which we have already pointed out as exist- ing between the first and second thoracic ganglions ; the whole of these inter-ganglionic cords are in contact along the median line, except the penultimate or antepenultimate pairs, which are separated from one another by the sternal artery, in the same manner as those of the head are kept asunder for the pas- sage of the cesophagus. Each of these five thoracic ganglions sends two pairs of nerves to the ambulatory extre- mities which correspond to them severally. Of these two nerves, the posterior and larger sends branches to the basilar articulations of the extremities; the anterior, again, distributes twigs to the muscles of the flancs; the two soon anastomose, and form a single trunk before penetrating into the extremity itself, which then traverses the whole limb, send- ing a branch to the muscles of each arti- culation. The abdominal ganglions (a1 — a6) are smaller than the preceding ones, and are connected by simple longitudinal cords. They also supply two pairs of nerves, the one destined to the muscles of the abdomen, the other to the ap- pendages of the ring with which it corresponds. As in the thorax, nervous fibres, distributed to the median and superior part of the abdomen, are observed proceeding from the cords which establish a communication between one gan- glion and another. The last ganglion («6), which appears to be made up of the medullary nuclei be- longing to the sixth and seventh segments of the abdomen, gives origin to four pairs of nerves, which run to the penultimate articu- lation of the abdomen, and to the last, which is of a flattened form, and along with the ap- pendages of the former constitutes the kind of horizontal oar which terminates this part of the body. Such is the nervous system in the Lobster. If we study it in the Palemon, we shall find precisely the same elements, but with a still higher degree of centralization, for the ganglia of the three lowest thoracic rings are conso- lidated into one, and situated much forwards, so that the nerves to which they give origin have to pursue a very oblique course, in order to reach the parts to which they are distributed respectively. The ganglion of the second pair is isolated ; that of the first pair of ambulatory extremities blends and is confounded with that of the third pair of maxillary limbs. The five anterior pairs of oesophageal ganglions, in fine, are united into a single nervous centre. There are consequently, properly speaking, no more than four medullary masses in the whole length of the cephalo-thoracic portion of the Palemon ; and even these are very close to one another, and all but united, their longi- tudinal commissures being thick and simple, and bearing as close a resemblance to constric- tions in a single nucleus as to bands of communication between distinct nuclei. The fourth of these four ganglions presents a longi- tudinal cleft through its centre, a structure which is easily explained by the presence at this point of the sternal artery, which existed there before the ganglia became conjoined in the course of the median line, and necessarily opposed a merely mechanical obstacle to their entire union. In the Palinurus the whole of the thoracic 766 ganglia, strictly speaking, are united into a single mass of a greatly elon- gated form, and presenting a little way back, like the fourth ganglion of the Palemon, a cleft for the trans- mission of the sternal artery. The transition Fig. 394. CRUSTACEA. Fig. 395. X V Cephah-tJwracic por- from the Deca- poda Macroura to the Brachyura takes place by the Iiomola, and certain Anomou- ra,* in which the constantly in- creasing concen- tration of the thoracic nervous centres coincides with the almost rudimentary state of the abdominal ganglionic sys- tem, which is here reduced to a kind of median trunk without en- largements. This, too, is the disposition tion of the nervous presented by the system of the Pali- nervous system niirus Vulgaris. in the Carcinus moenas among the Brachyura, with this difference only, that the medullary nuclei are rather closer to one another, and more intimately connected.f The tho- racic ganglion has the form of a ring, the cir- cumference of which gives origin to the nerves of the thoracic appendages. The single abdomi- nal cord is in its rudimentary state, in obvious relation with the abdomen itself, and therefore reduced to very insignificant dimensions. It is in the Maja,J in fine (fig. 395), that the nervous system is found in its highest degree of centralization ; for the elements of which the two masses there encountered are composed, are so intimately conjoined, that no trace can be found of their ever having existed indepen- dently, although among neighbouring genera several of them may still be discovered isolated- ly. The cephalic ganglion (a) is a sufficiently faithful counterpart of that of the Lobster. The nervous cords (g) which connect this first portion of the system with the thoracic portion also present the same arrangement as in the Lob- ster; there are similar mandibular nerves, a like gastric pair, the same transverse band (g) behind the oesophagus, &c. But the thoracic ganglion (Z), instead of the ring which it presents in the * Vide Rech. sur 1’organiz. et la classific. des Crustaces Decapodes par M. Milne Edwards ; An- nates des Sciences Naturelles, t. xv. t Cuvier, Lemons d’Anatomie Comparee, t. ii. p. t Audouin et Edwards, loc. cit. Nervous system of the Maja Squinado. a, cephalic ganglion ; b, optic nerves ; c, oculo- motor nerves ; d, nerves of the antennulae ; e, fourth pair of nerves belonging to the integuments ; f, nerves of the exterior antennas ; g, medullary cords uniting the cephalic and thoracic ganglions ; g' , transverse cord ; h, mandibular ganglion ; h' , small nerve belonging to the muscles of the mandible ; i, stomato-gastric nerve ; k, lateral branches of the stomato-gastric nerves ; l, tho- racic ganglion ; m, nerves of the maxillae ; n, nerves of the first pair of legs ; o, abdominal nerve ; p, cells of the Danes ; q, arch of the flancs. Carcinus mcenas, here appears as a solid circu- lar and flattened nucleus giving origin to the whole of the nerves of the thorax and abdo- men, which radiate from it to the number of nine pairs, and one azygous nerve situated in the median plane. There is nothing very remarkable in the distribution of these nerves, unless it be that several pairs, and among the number the first and second, are distributed simultaneously to several rings, which proclaims that in the species which engages us the work of con- centration has extended from the ganglions to the nervous cords. Any farther detail in addition to what has now been said would contribute little to our essential knowledge of the nervous system. We have traced it from its commencement in CRUSTACEA. 767 a series of independent centres, and we have seen these becoming successively conjoined in a greater and greater degree, as if in obedience to a law of attraction, whose tendency was to collect these various nuclei from every part of the body towards a common centre. This dis- position to centralization has, in its turn, given a satisfactory explanation of the most remark- able differences observed in the disposition of the ganglions and of the nervous cords among the different types of the class, however dissimilar these may be one from another. We may, therefore, here conclude, as has been done already in my work especially devoted to this subject, that the nervous system of the Crustacea consists uniformly of medullary nuclei (ganglions ), the normal number of which is the same as that of the members or rings of the body, and that all the modifica- tions encountered, whether at different periods of the incubation, or in different species of the series, depend especially on the approximation, more or less complete, of these nuclei, (an ap- proximation which takes place from the sides towards the median line as well as in the longi- tudinal direction,) and to an arrest of develop- ment occurring in a variable number of the nuclei. In a paper upon the nervous system of the Lobster recently published,'* Mr. Newport mentions an interesting fact hitherto overlooked by anatomists. He found that the double ganglionic chain of this Crustacean is composed of two orders of fibres, forming distinct and superposed fasciculi or columns, which the author designates columns of sensation and of motion, following the analogy which he be- lieved he had traced between these fasciculi and the anterior and posterior columns of the spinal cord of the higher animals. The fas- ciculi here indicated are but indistinct in the interganglionic cords, but become extremely apparent in the ganglions themselves, for these enlargements belong exclusively to the inferior or sensitive fasciculi, and the superior or motor fasciculi pass over their dorsal surface without penetrating their substance at all. Before going on to the study of those organs the object of which is the application, if we may be allowed the expression, of the nervous system to the perception of the existence of outward objects, and of those in which the reaction designated volition is immediately effected, that is to say, the organs of the senses and the muscles, it may be as well to say a word upon the general functions of the nervous system itself in its different parts. The experiments made by M. Audouin and me, with a view to solve the principal problems which may be proposed on this subject, have confirmed the inductions to which we had been led hy views arrived at a priori wholly from anatomical researches, of which the preceding- may be regarded as the summary. Thus : — * On the Nervous System of the Sphinx ligustri, &c. by G. Newport, Philos. Transact. 1834, pt. ii. p. 406. lstly, The nervous is the system which en- tirely presides over the sensations and motions. 2dly, The nervous cords are merely the organs of transmission of the sensations and of volition, and it is in the ganglions that the power of perceiving the former and of pro- ducing the latter resides. Every organ sepa- rated from its nervous centre speedily loses all motion and sensation. 3dly, The whole of the ganglions have analogous properties : the faculty of determin- ing motions and of receiving sensations exists in each of these organs; and the action of each is by so much the more independent as its development is more isolated. When the ganglionic chain is nearly uniform through its whole length, it may be divided without the action of the apparatus being destroyed in either portion thus isolated, — always under- stood, that both are of considerable size ; because when a very small portion only is isolated from the rest ' of the system, this appears too weak, as it were, to continue its functions, so that sensibility and contractility are alike speedily lost. But when one portion of the ganglionic chain has attained a develop- ment very superior to that of the rest, its action becomes essential to the integrity of the functions of the whole. It must not be imagined, however, from this that sensibility and the faculty of exciting muscular contractions are ever completely con- centrated in the cephalic ganglions, and it seems to us calculated to convey a very inaccurate idea of the nature and functions of these ganglions to speak of them under the name of brain, as the generality of writers have been led to do, seduced by certain inconclu- sive analogies in point of form and position. It is nevertheless to be remarked that in these animals an obscure tendency to the centra- lization of the nervous functions is observable in the anterior portion of the ganglionic chain ; because if in the Lobster, for instance, it be divided into two portions, as nearly equal as possible, by severing the cords of communica- tion between the ganglions belonging to the first and second thoracic rings, sensibility, and especially mobility, are much more quickly lost in the posterior than in the anterior half ; and this disproportion is by so much the more manifest as the division is performed more posteriorly; still there is a great interval between this first indication and the concen- tration of the faculties of perception and of will in a single organ — the brain, of which every other portion of the nervous system then becomes a mere dependency. B. Organs of the senses. — Do the five senses exist, and to what degree of development have they attained in the Crustacea ? Such is the question we have now to consider, and which we shall sometimes find ourselves in a condition to answer from the simple inspection of the various organs of special application. Thus we discover almost at once that the sense of general touch is obtuse, and can convey to the animal no other but confused 768 CRUSTACEA. notions of the existence and of the resistance of the bodies with which it finds itself in immediate relationship by its external surface. To be satisfied of this, it is enough to consider for a moment the hard and unyielding nature of the general tegumentary envelope over every point of the body except the articulations, — - parts which on other grounds are obviously inadequate to exercise any sense whatever. Nevertheless, in front of the head there are certain special organs which all the observa- tions I have had an opportunity of making upon the organization of these animals lead me to regard as parts more particularly destined to be the seat of the sense of touch. These organs are the antennae,. — those slender fila- ments, possessed of a great degree of flexibility, of motility, and of sensibility. M. de Blain- ville was led to regard these organs as the seat of the sense of smell ; but direct and conclusive experiment has satisfied us that the destruction of the antennae has no influence whatever on the exercise of the sense, of smell : and we are on the same grounds'' in- duced to believe them destined to the exer- cise of the sense of touch of considerable delicacy, unless we would imagine them as the instruments of some quite peculiar sense the existence of which would be purely hypothetical. The number and disposition of these organs varies extremely. Some of the Crustaceans at the very bottom of the series are wholly without antennae, or are furnished with them in a merely rudimentary state. Some species have no more than a single pair; the normal number, however, is two pairs. In speaking of the tegumentary skeleton, we have said to which of the rings these appendages belong; we shall only say farther here, that they may be inserted on the superior or on the inferior surface of the head according to the respective development of the different pieces of which this segment is composed. They do not differ less widely in their form and composition, and under this double point of view present modi- fications analogous to those which we have specified as occurring in the extremities. The Crustaceans, like almost all other animals, make a selection of matters in especial relation- ship with the state of their organs of nutrition ; they must therefore be endowed with the sense of taste. With reference to the seat of this faculty, which perchance is the mo- dification of sensibility the least remote front the sense of touch, it appears to reside in the Crustacea, as it does obviously in the majority of animals, in that portion of the tegumen- tary membrane which lines the interior of the mouth and oesophagus ; but the dispo- sition of the parts there presents no peculiarity worthy of especial notice. The Crustaceans perceive the existence of bodies at a distance by the medium of odorous particles emitted from these bodies. Many of the known habits of these animals, and the certainty with which they are attracted by baits placed in close traps from which the light is excluded, do not allow us to entertain any doubts upon this point; but we are reduced to conjecture when we are required to point out the precise seat of the organ of smell. The horny appendages named antennae are certainly not it, as M. de Blainville imagined ;* and the opinion of M. Rosen thal,f who ascribes the function to a cavity which he discovered at the base of the first pair of antennae, requires to be supported by direct experiment. Hearing, at least in a great number of species, resides in a particular apparatus per- fectly well known. It (Jig. 396) is found in the inferior surface Fig. 396. of the head, behind the an- tennae of the second pair, or upon the first basilar articu- lation of these antennae them- selves} (jig. 396, «}. It con- sists in the River-crab of a small bony tubercle pierced at its summit by a circular opening, upon which is stretched a thin elastic membrane, which Scarpa has compared to that of the tym- panum, or of the fenestra ovalis of the ves- tibule in the higher animals. Behind this membrane there ' is a membranous vesicle filled with fluid, into which a branch of the antennary nerve is observed to plunge. Above this organ there is another of a glandular appearance, the intimate relations of which with the apparatus we have just described might lead to the belief that it was not un- connected with the sense of hearing. In the Palinurus it communicates with an opening which is pierced through the centre of the membrane that closes the auditory tubercle in front. The membrane in the greater number of the Brachyura is replaced by a small moveable os- seous disc, which in the Maja and some others presents a pretty broad bony plate ( fig. 397) at Fig. 397. Auditory disc of the Maja Squinado separated from the rest of the apparatus. its posterior edge, detaching itself at right angles and running upwards towards the glan- dular organ already mentioned. Near its base this lamellar prolongation is pierced with a large oval opening, over which there is stretched a thin and elastic membrane which might be named the internal auditory * Principes d’anatomie comparee, t. i. p. 338 et ,339. f Reil’s Archiv. und Treviranus’s vermischte Schriften, 2ter Band. 2tes Heft. $ Minasi, Dissertazioni di timpanetti del’udito scoperti nel Granchio paguro. Scarpa, De striictura fenestras rottmdte, &c. Anat. observ. 4to. Matin. 1772; Anat. Disq. de Audita et Olfactu, fol. Tiein. 1789. Cuvier, Lemons d’anatomie comparee, t. ii. Milne Edwards, Histoire natuielle des Crustaces, t. i. p. 121. CRUSTACEA. 769 membrane, near to which the auditory nerve appears to terminate. This small bony lamina, which is moved by minute muscular fasciculi, recals in some measure the stapes of the human ear. Under the anterior edge of the external opening of the ear which is closed by this bony disc (fig. 398 ), is seen a small Fig. 398. Auditory apparatus of the Maja in its natural position, showed by removing the carapace and the vis- cera. lamina parallel to the internal auditory mem- brane ; and when the anterior muscle of the ossiculum contracts so as to bring, in a slight measure, the whole of this little apparatus forwards, the membrane of which mention has just been made rests upon the bony prolonga- tion, and is made tense in a continually in- creasing degree; and from the experiments of M. Savart we know that all increase in the tension of thin membranes lessens their dispo- sition to be thrown intovibration ■* consequently in undergoing such a modification, the kind of tympanum described must serve to moderate sounds of too great intensity, in their passage to the acoustic nerve. In other respects it is evident that the mechanism described pre- sents the most forcible analogies with what we observe in the human ear, and that the ossiculum auditus here stands in lieu of the chain of small bones which exists in the organ of hearing arrived at its highest point of de- velopment. The presence of the long rigid stem formed by the antennae of the second pair, and its immediate communication with the organ of hearing cannot, it might have been presumed a priori, be unimportant as regards the per- ception of sound ; and this is found to be the case in fact;f for from the beautiful experiments of M. Savart we learn that the addition of a rigid stem is sufficient to render certain vibra- tions perceptible, which, without this kind of conductor, are altogether inappreciable. The auditory apparatus of the Crustacea con- sequently consists essentially of a cavity full of fluid, to which a nerve adapted to perceive sonorous impulses is distributed ; which ele- mentary and essential apparatus is assisted in * Recherches sur les usages de la membrane du tympan et de l’oreille externe. Journal de Physio- logic de Magendie, t. iv. t Strauss - Druckheim, Considerations generates sur l’anatomie des Crustaces, p. 419. its functions by certain special organs, such as elastic membranes and rigid stems, calculated by their nature to vibrate under the action of sonorous undulations. We have still to speak of the organ of sight. With the exception of certain parasitic species, the faculty of perceiving the existence of ex- ternal objects by the medium of light is pos- sessed by the whole class of Crustacea, and is found dependent on a particular organ of a con- siderably complicated structure situated in the head, towards its anterior aspect, superiorly or on the sides. Even the exception which has been made is merely accidental, as it were ; for in the earliest periods of their existence the parasitic Crustacea also possess eyes, and it is only as an effect of the kind of meta- morphosis which these animals experience that the organs of vision disappear. The eyes in insects are simple or compound ; but this division is inadequate to give us any proper idea of the various forms under which these orgaus present themselves to our observa- tion in the Crustacea, and into the study of which we shall, therefore, enter with some attention to detail.* The least complex form under which the eyes of the Crustacea occur is that which has been designated under the name of Stemmata, smooth eyes or simple eyes. The structure of these does not differ essentially from that ob- served among the higher animals. We distin- guish, in the first place, a transparent cornea, smooth and rounded, which is in fact nothing more than the general tegumentary mem- brane modified in a particular point. The internal aspect of this cornea is in immediate contact with a crystalline lens, generally of a spherical form ; this, again, is in contact poste- riorly with a gelatinous mass analogous to the vitreous humour, and this mass in its turn is in contact with the extremity of the optic nerve. A layer of pigmentum thick and of a very deep coloqr, envelopes the whole of these parts, lining the internal wall of the globe of the eye up to the point at which the cornea begins to be formed by the thinning of the tegumentary envelope become transparent. This is what we observe in a limited number of the Crustacea, among which we may mention the Limuli, the Cyamae, and the Apus. The number of these simple eyes never exceeds two or three. A step in the complexity of the organ of sight is presented to us in the eyes of the Nebalia, Branchipus, and Daphnia. In these, behind the cornea, which externally presents no trace of divisions, a variable number of small crystalline lenses and vitreous humours are found, each included in a kind of sac or pigmentary cell, and terminating by coming * On the structure of the eyes, vide Swammer- dam, in the Collection Academique, partieetrangere, t. v. p. 170. Cavolini, Memoria sulla generazione dei Pesci et Dei Granchi. Strauss, op. cit. J. Midler, Zur vergleichenden Pbysiologie des Gesichtsinnes etc. Ann. des Sciences Naturelles, t. 17. Milne Edwards, Hist. Nat. des Crustaces, t. i. p. 114. 770 CRUSTACEA. immediately into contact with the optic nerve. These eyes are obviously made up by the con- junction of several stemmata under a common cornea. The Apus, besides its pair of simple eyes, presents another compound pair, behind and at some distance from these. The Amphihoe Prevostii and some other Edriophthalmians present the transition from the form last described to that of truly com- pound eyes, having distinct facets. The cornea in these is formed of two transparent laminae, the external of which is smooth and without divisions, whilst the internal is divided into a variable number of hexagonal facets, each of which is a distinct cornea, superposed upon such a conical crystalline lens, as we shall have occasion immediately to describe when speaking of compound eyes properly so called , or eyes with simple facets. In these the two membranes, external and internal, the union of which constitutes the cornea, present simultaneously the division into facets, each of which forms anteriorly an ocular compartment proper to it. These facets, always hexagonal in insects, are of various forms in the Crustacea: thus in the Astacus fluviatilis, the Peneae, the Galatliece, and the Scyllari, they are square (fig. 399), whilst the Paguri, the Phyllosoma, the Fig. 399. Squill®, the Gebiae, the Calli- anassae, and the Crabs, have them hexagonal (fig. 400). The crys- talline that succeeds them imme- diately is of a conical form, and is followed by a vitreous humour Fig. 400. having the appearance of a gelati- nous filament, adhering by its base to the optic nerve. Each of the columns thus formed is, more- over, lodged within a pigmentary cell, which likewise covers the bulb of the optic nerve. But the most remarkable circumstance is, that the large cavity within which the whole of these parallel columns, every one of which is in itself a perfect eye, are contained, is closed posteriorly by a membrane, which ap- pears to be neither more nor less than the middle tegumentary membrane, pierced for the passage of the optic nerve ; so that the ocular chamber at large results from the sepa- ration at a point of the two external layers of the general envelope. Fig. 401. Longitudinal section of the Eye of the Lobster. The gelatinous or vitreous elongated pro- cesses which succeed the conical crystallines have been looked upon by several anatomists as ramifications of the optic nerve; but we do not imagine that they are so in reality. In the Lobster, for instance, we have even seen the surface of the bulb isolated from the masses in question, divided into compartments. corresponding to those of the cornea itself, and lined with a layer of pigmentum perfectly distinct. The most remarkable modification of facetted eyes consists in the presence of a kind of sup- plementary lens, of a circular shape and set within the cornea in front of each proper crys- talline lens {fig. 402). These small lenticular bodies exist independently, and are perfectly distinct from the small corneal facets. In some cases they might be mistaken (in the Idoteas, for example, where they may be perceived singly, and with their distinct circular forms), and the incau- tious observer led to conclude that the cor- neal facets are merely these lenticular bodies so much enlarged that their hexagonal or square forms result from their agglomeration in a point; but there are Crustacea, such as the Callianass®, in which these two elements of the external cornea may be perfectly dis- tinguished, the lenticular body being of insig- nificant dimensions and occupying the centre of the corneal facet only (fig. 402). In general, however, the diameter of the lenticular body is equal to that of the corneal facet itself, so that their edges blend. Farther, the lenticular bodies are most commonly evolved in the sub- stance of the cornea ; but there are cases in which, under favourable circumstances, they may be detached from it. Although the existence of these different modifications must not be understood as being exclusive, inasmuch as there are certain Crus- tacea which exhibit more than one of them at the same time, for instance, stemmata and compound eyes, the latter only are the species of visual organ encountered in the great ma- jority of cases. Their general number is two ; but these are occasionally united, so as to form a single mass, and make the animal appear at first sight as if it had but a single eye. This peculiarity of organization can even be followed in the Daphnise, in the embryo of which the eyes are first seen isolated; with the progress of the development, however, they are observed gradually to approach each other, and finally to become united. Stemmata are always immoveable and sessile; the com- pound eyes with smooth corneoe, however, although in the majority of cases they present the same disposition, now and then occur moveable : sometimes they are supported by a pedicle, moveable in like manner, and pro- vided with special muscles. The eyes with facets present the same modifications, and even supply important charac- ters in classifying these animals : thus in the Edriophthalmia the eyes are always immoveable and sessile, (fig. 403,) whilst in the Decapo- da and the Stomapoda (fig. 404) they are sup- ported upon moveable Fig. 402. CRUSTACEA. 771 Fig. 404. stems of very various lengths, and which every consideration leads us to view as the limbs or appendages of the first cephalic ring. It some- times even happens (Jig. 404) that in these animals, between the outer edge of the cara- pace and the base of the antennae, there occurs a furrow or cavity within which the eyes may be withdrawn or laid flat, so as to be out of the way of injury ; this groove or cavity is generally spoken of under the name of the orbit. § 3. Apparatus of Nutrition. In the study of this apparatus we shall have to consider successively the organs of digestion, of circulation, of respiration, and of secretion. A. Apparatus of digestion. — The organs concerned in the digestion of the food among the Crustacea may be divided into three orders, according to the functions they fulfil, to wit, 1st, the apparatus for the prehension and mastication of the food ; 2nd, the alimen- tary canal ; 3rd, the various secreting organs associated with the intestine. The Crustacea are divided into two grand sections in conformity with their habits and the nature of their food : — the masticators , which generally live apart from their prey, pursue it, and seize it in proportion as they are admonished by their wants or appetite to do so ; and the suckers, considerably fewer in number, and which in their state of perfect growth live almost invariably attached to their prey without executing any other motions than such as are performed by the latter. The masticating Crustacea being the highest in point of organization, wre shall commence our description with them,* and we shall even select for our particular consideration the spe- cies among these which have the class of organs about to be investigated of the most complex structure, namely, the Decapoda brachyura. In these animals the mouth is constantly situated on the inferior surface of the cephalic portion of the body. Two lips close it anteriorly and posteriorly ; the upper Up or labrum [a, fig. 405) is a median piece in the form of a simple fold, and the lower Up or languette (c) is for the most part bifid. Be- tween these two pieces and on their sides are the mandibles, (fig. 406,) appendices of the fourth cephalic ring, modified so as to serve for mastication. As in the whole tribe of articu- * On this subject consult Savigny Memoires sur les Animaux sans Vertebres, Ire fascicule ; La- treille, Hist. Nat. des Crustaces et Insectes, & c. ; Cuvier, Regne Animal ; Desmarest, Considerations sur les Crustaces ; Milne Edwards, Hist. Nat. des Crustaces, t. i. p. 61. Fig. 405. Masticatory Organs of the Phyllosomu. a, upper lip ; b, mandibles ; c, lower lip ; d, maxillaj. Fig. 406. lated animals, these organs act laterally, and not upwards and downwards in the line of the axis of the body as in the vertebrate series univer- sally. They do not vary much in point of form among the Decapoda; in almost every one of these they are seen pos- sessed of a principal part terminated by a cutting edge, or a sur- face adapted for tritu- ration ; and an appendage which appears to fasten the food and keep it steady during the process of mastication. The mandible itself, which is of extreme hardness, appears to be neither more nor less than the basilar piece of the member or appendage, of great strength and toothed. The articulated palp which it supports, in this mode of viewing the structure, would turn out to be a mere continuation of the stem (tige), and not a proper palp, as its name seems to imply, but which it has only acquired from its resem- blance to the appendage to which the term of right belongs. Such is the structure of the mouth among a certain number of the inferior Crustacea; but among those to which we now turn our atten- tion, we remark an addition of as many as five pairs of modified appendages situated behind the under lip, and all subservient to the pre- hension and the mastication of the food. The two first (figs. 406 and 407) are the most con- stant; and even when we get low in the series, and they have lost their special functions, they can still be traced, although of course only in a rudimentary state. When well developed they are without palps and are designated by the name of jaws. The three other pairs, again, soon cease to appear as part of the implements of digestion, in order to show them- selves among the instru- ments of locomotion ; sometimes, however, they seem to serve for both kinds of function, a circumstance which has 772 CRUSTACEA. led to their ordinary denomination of maxil- lary limbs ox feet (jigs. 408, 409, 410.) Fig. 408. amounts to three pairs, and in the Phyllo- soma to two pairs only. To conclude, the Limuli, a group of Crusta- ceans of the most singular conformation, are at the bottom of the scale in this respect ; for in them (fig. 411) the anterior ambulatory extre- mities themselves surround the mouth, and their basilar articulations perform the office of jaws. The organs of which we have just made mention, are, according to the modifications they undergo, adapted in a more or less espe- cial manner to seize, to hold fast, and to comminute the alimentary matters upon which the animal lives. Moreover the thoracic ex- tremities in many species are themselves calcu- lated to accomplish one or all of these offices with various degrees of success, according to their form, their extent, and the mode in which The forms and dimensions of these organs vary considerably, and are obviously in harmony with their uses ; they are by so much the shorter and flatter as they are more peculiarly appor- tioned to the oral apparatus, a disposition which is nowhere more conspicuously displayed than among the short-tailed De- capods, in which they resemble horny laminae, armed with teeth or serrae of various sizes, and supporting an articulated palp (b, Jig. 408) as well as a flabelliform or whip -shaped appendage (c), which penetrates into the interior of the branchial cavity. The last pair of all (fig. 410) presents Fig. 410. Fig. 411. Limulus polyphemus, (ventral aspect.) , carapace ; b, frontal portion of the carapace ; c, thorax ; d, chelifera •, e, f, g, li, i, j, legs, the basilar portions of which surround the mouth and act as mandibles ; l, under-lip ; m, branchial or lamelliform appendages; n, mouth. itself under the shape of two thin and much expand- ed laminae which serve as a kind of broad operculum to cover the whole of the oral apparatus. Starting from this complication of structure, the greatest in the series, we shall see the ap- paratus degenerating by successive degrees, at the same time that in any given group its com- position presents much less of constancy or regularity. The Sergestes among the Decapods have one pair of maxillary feet fewer than the highest number; the Edriophthalmians have no more than a single pair, whilst in the Thysanopoda and the generality of the Sto- mapoda the number of oral appendages they are terminated. The most favourable disposition to these ends is observed in the lobsters, crabs, &c.; in a woi;d in a very great number both of the short and long-tailed De- capods, in which the anterior thoracic extre- mities terminate in pincers, of greater or less strength, armed with teeth and sharp hooks which give them increased powers of pre- hension. This form results mainly from the state of extreme development in which the pe- nultimate articulation frequently occurs, and its assumption of the shape of a finger, by the prolongation of one of its inferior angles. Against the finger-like process thus produced, which is of great strength and quite immove- able, the last articulation can be brought to bear with immense force, as it is put into mo- tion by a muscular mass of great size, and in relation with the extraordinary size of the pe- CRUSTACEA. 773 i ! Fig. 412, Ventral aspect of the cephalo thoracic portion of the Dichelestion. a, trunk or sucker ; b, maxilla?. Fig. 413, The trunk or sucker magnified, a, thelabrum; b, the mandibles. Fig. 414